ACI 546.3R-14 Guide to Materials Selection for Concrete Repair

Guide to Materials Selection for Concrete RepairReported by ACI Committee 546

AC

I 546

.3R

-14

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First PrintingJune 2014

ISBN: 978-0-87031-895-5

Guide to Materials Selection for Concrete Repair

Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI.

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This document provides guidance on the selection of materials for concrete repair. An overview of the important properties of repair materials is presented as a guide for making an informed selection of the appropriate repair materials for specific applications and service conditions.

Keywords: cementitious; cracks; epoxy; materials; methacrylate; polymer; polyurethane; repair; surface sealer; silica fume; test methods; waterproofing.

CONTENTS

CHAPTER 1—INTRODUCTION AND SCOPE, p. 21.1—Introduction, p. 21.2—Essential steps of concrete repair, p. 31.3—Objective, p. 31.4—Scope, p. 31.5—Current industry issues and concerns, p. 4

CHAPTER 2—NOTATION AND DEFINITIONS, p. 42.1—Notation, p. 42.2—Definitions, p. 4

CHAPTER 3—PROPERTIES OF CONCRETE REPLACEMENT AND OVERLAY MATERIALS AND THEIR IMPORTANCE, p. 5

3.1—General, p. 53.2—Volume stability, p. 53.3—Mechanical properties, p. 73.4—Constructibility characteristics, p. 123.5—Aesthetic properties, p. 123.6—Factors affecting durability, p. 123.7—Chemical composition, p. 163.8—Summary tables, p. 16

CHAPTER 4—CONCRETE REPLACEMENT AND OVERLAY MATERIAL SELECTION, p. 16

4.1—Concrete, p. 194.2—Silica-fume concrete, p. 194.3—Polymer-modified concrete, p. 204.4—Magnesium-ammonium-phosphate-cement concrete

(MAPCC), p. 204.5—Polymer concrete, p. 204.6—Mortars, p. 214.7—Types of concrete replacements and overlays, p. 22

John S. Lund, Chair David W. Whitmore, Secretary

ACI 546.3R-14

Guide to Materials Selection for Concrete Repair

Reported by ACI Committee 546

James Peter BarlowMichael M. Chehab

Marwan A. DayeMichael J. GarlichPaul E. Gaudette

Timothy R. W. GillespieYelena S. GolodFred R. GoodwinHarald G. Greve

Ron HeffronRobert F. Joyce

Lawrence F. Kahn

Brian F. KeaneBenjamin Lavon

Kenneth M. LozenJames E. McDonald

Myles A. MurrayJay H. Paul

Richard C. Reed*

Johan L. SilfwerbrandJoe Solomon

Michael M. SprinkelRonald R. StankieJoseph E. Tomes

David A. VanOckerAlexander M. Vaysburd

Kurt WagnerPatrick M. Watson

Mark V. Ziegler

Subcommittee MembersYogini S. DeshpandeFloyd E. Dimmick Sr.

Peter A. LipphardtWilliam F. McCannShreerang N. Nabar

Paul H. ReadLouis M. Wenick

Consulting MembersPeter Emmons

Noel P. MailvaganamKevin A. MicholsRichard Montani

Don T. Pyle

*Editor and subcommittee Chair.

ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.

ACI 546.3R-14 supersedes 546.3R-06 and was adopted and published June 2014.Copyright © 2014, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

1Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=yuyuio, rtyru


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4.8—Deep concrete replacements and overlays, p. 224.9—Shallow concrete replacements and overlays, p. 254.10—Thin overlays, p. 264.11—Aggressive environments and exterior applications,

p. 26

CHAPTER 5—PROPERTIES OF CRACK REPAIR MATERIALS AND THEIR IMPORTANCE, p. 26

5.1—General, p. 265.2—Types of crack repair materials, p. 275.3—Properties of rigid crack repair materials, p. 275.4—Properties of elastomeric crack repair materials, p.

295.5—Properties of flexible crack repair materials, p. 325.6—Other considerations, p. 335.7—Summary tables, p. 33

CHAPTER 6—CRACK REPAIR MATERIALS SELECTION, p. 33

6.1—General, p. 336.2—Crack repair materials and procedures, p. 386.3—Epoxy resin, p. 386.4—Methacrylates, p. 396.5—Polyurethane chemical grout, p. 406.6—Polyurethane sealant, p. 416.7—Silicone sealant, p. 426.8—Silyl-terminated polyether sealant, p. 426.9—Polysulfide sealant, p. 436.10—Flexible epoxy resin, p. 436.11—Polyurea, p. 436.12—Strip-and-seal systems, p. 436.13—Grouts, p. 446.14—Selection of crack repair materials, p. 44

CHAPTER 7—PROPERTIES OF SURFACE SEALERS, ANTI-CARBONATION COATINGS, AND TRAFFIC-BEARING ELASTOMERIC COATINGS AND THEIR IMPORTANCE, p. 45

7.1—General, p. 457.2—Properties of surface sealers, p. 457.3—Properties of anti-carbonation coatings, p. 507.4—Properties of traffic-bearing elastomeric coatings, p.

517.5—Summary tables, p. 53

CHAPTER 8—SURFACE SEALER, ANTI-CARBONATION COATING, AND TRAFFIC-BEARING ELASTOMERIC COATING MATERIALS SELECTION, p. 57

8.1—General, p. 578.2—Surface sealers, p. 578.3—Anti-carbonation coatings, p. 598.4—Traffic-bearing elastomeric coatings, p. 608.5—Selecting surface sealers and anti-carbonation coat-

ings, p. 61

CHAPTER 9—OTHER MATERIALS USED IN CONCRETE REPAIR, p. 61

9.1—General, p. 619.2—Reinforcing steel coatings, p. 619.3—Embedded galvanic anodes, p. 629.4—Concrete bonding agents and techniques, p. 639.5—Crystalline pore blockers, p. 639.6—Surface-applied, penetrating corrosion inhibitors, p.

64

CHAPTER 10—REFERENCES, p. 65Authored documents, p. 68

APPENDIX A—CURRENT INDUSTRY ISSUES AND CONCERNS, p. 69

A.1—Material test methods and reporting of test data, p. 70

A.2—Curing repair materials and manufacturers’ reported test results, p. 70

A.3—Product limitations and warnings, p. 71A.4—Standardized industry acceptance, p. 71A.5—Repair material bond, p. 71A.6—Corrosion reduction, p. 71A.7—Structural repairs, p. 72A.8—Ongoing developments, p. 72

CHAPTER 1—INTRODUCTION AND SCOPE

1.1—IntroductionConcrete is inherently a durable material, but its dura-

bility under any given set of exposure conditions varies with concrete mixture proportions; the presence and positioning of reinforcement; and the detailing, placing, finishing, curing, and protection it receives. In service, it may be exposed to conditions of abrasion, moisture cycles, cycles of freezing and thawing, temperature fluctuations, reinforce-ment corrosion, and chemical attack, resulting in deteriora-tion and potential reduction of its service life.

As the concrete industry develops and grows, concrete repair is frequently required; however, with the increasing number and age of concrete structures, frequent deferral of maintenance, and increased public awareness of dete-rioration and maintenance needs, repair is becoming a major focus of design and construction activities. Although concrete repair is traditionally as much an art as a science, engineers and contractors typically do not receive much formal training in techniques for repair and the performance of repair materials applied to concrete. Personal experience is beneficial, but takes time to accumulate and can be costly in terms of failed repairs. Although this is changing, there is still too little information available to reliably predict the serviceability and durability of repairs. Concrete repairs that fail prematurely result in economic loss and usually require additional repairs.

Due to a greatly expanded repair market, new materials and repair methods are being introduced at an increasing rate to the construction market. At the same time, due to changing environmental and building codes and other regu-

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lations, many existing, well-proven products are being refor-mulated into essentially new products that have limited track records. The user might not be informed of these changes.

It is often difficult for a specifier to find the appropriate data to systematically evaluate a product for a given repair situation. Often, test data are unavailable or, if available, are either not presented in useful or appropriate terms or presented in a manner that makes comparison with other competing materials difficult. One example is the use of nonstandard or modified test methods.

Although there are many competent repair materials avail-able commercially, there are also unsubstantiated claims of suitability and success. Even the highest-quality materials do not perform as expected if they are used inappropriately.

ACI 546R is the first ACI publication devoted entirely to the subject of concrete repair. Its principle emphasis is on techniques for concrete repair with limited information on selecting repair materials. The physical properties of repair materials govern their performance in service and, as a result, the appropriate selection of these materials for a given repair is at least as important to a successful, long-lasting repair as is using the proper procedures and work-manship. This guide is the second in a series of documents prepared by Committee 546 to aid the user in specifying and executing typical concrete repairs.

1.2—Essential steps of concrete repairThe success of concrete repairs depends on determining

the cause and extent of concrete distress or deterioration and developing a repair strategy to address the problem. Typical steps in a systematic repair are to:

a) Conduct a condition survey with a scope consistent with the perceived condition of the structure and the owner’s repair objectives, performed by qualified individuals, to document and evaluate visible and concealed deterioration, distress, defects, and damage, as well as potential future deterioration and distress;

b) Determine the cause of the damage or deterioration necessitating the repair—for example, mechanical damage such as impact or abrasion; design, detailing, or construc-tion deficiencies; chemical damage such as alkali-aggregate reaction; physical damage related to cycles of freezing and thawing or thermal movements; corrosion of the steel rein-forcement caused by improper placement; carbonation of the concrete; or chloride ingress into the concrete to the reinforcing steel;

c) Assess the application and service conditions to which the concrete repair material is, or will be, exposed;

d) Determine the repair objectives, including desired service life;

e) Select a repair strategy, including consideration of an appropriate protection system in conjunction with future maintenance, in terms of what is required to preserve or protect the structure and repairs, and what actual mainte-nance is likely to be available.

Once the concrete to be repaired is evaluated and the cause of distress established, details of the proposed repair are developed. This includes evaluating and determining the

required physical properties of repair materials, followed by the appropriate selection of available repair materials. Selec-tion is usually based on the ability of the material to conform to repair constraints and objectives as defined in this guide, including consideration of cost and availability.

The repair is then implemented, including protective systems if designed as part of the repair. Refer to ACI 546R, where these steps are discussed in further detail.

1.3—ObjectiveThe objective of this guide is to provide guidance for the

materials selection for concrete repair, including:a) Identification of common repair materials;b) Discussion of relevant material properties;c) Lists and discussion of test procedures for measuring

these properties;d) Recommendations of minimum test values or perfor-

mance levels;e) Discussion of the importance of specific material proper-

ties for various repair applications and service environments.

1.4—ScopeThis guide discusses material selection for several types of

repairs and materials used in their repair:a) Concrete replacements, categorized on the basis of the

depth and orientation of repair;b) Overlays, categorized on the basis of their thickness;c) Crack repairs, categorized on the basis of crack stability,

crack width, and other service conditions;d) Surface sealers and traffic-bearing elastomeric coat-

ings, categorized on the basis of their water and chloride ion permeability;

e) Anti-carbonation coatings, categorized on the basis of their carbon dioxide diffusion;

f) Reinforcing steel coatings, embedded galvanic anodes, concrete bonding agents and procedures, crystalline pore blockers, and surface-applied, penetrating corrosion inhibi-tors, categorized on their ability to alter and improve various concrete properties.

1.4.1 Concrete replacement and overlay materials discussed in this guide include:

a) Portland or blended cement-based mortar and concrete;b) Portland or blended cement-based silica-fume mortar

and concrete;c) Portland or blended cement-based polymer-cement

mortar and concrete;d) Magnesium-ammonium-phosphate-cement mortar and

concrete;e) Polymer-based mortar and concrete.1.4.2 Crack repair materials discussed in this guide

include:a) Epoxy resin;b) Methacrylate resin;c) Polyurethane chemical grout;d) Polyurethane sealant;e) Silicone sealant;f) Silyl-terminated polyether sealant;g) Polysulfide sealant;


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h) Flexible epoxy resin;i) Polyurea;j) Strip and seal systems, including preformed flexible

sheets;k) Polymer grout;l) Polymer-cement grout;m) Cementitious grout.1.4.3 Surface sealer materials discussed in this guide

include:a) Silanes;b) Siloxanes;c) Acrylics;d) Epoxies;e) Linseed oil.1.4.4 Anti-carbonation coating materials discussed in this

guide include:a) Acrylics;b) Methacrylate coating;c) Polymer-modified cementitious materials.1.4.5 Traffic-bearing elastomeric coating materials

discussed in this guide include:a) Polyurethane systems;b) Polyurethane-epoxy composite systems;c) Polyurea systems.1.4.6 Reinforcing steel coating materials discussed in this

guide include:a) Modified cementitious materials;b) Epoxies;c) Zinc-rich products.1.4.7 Concrete bonding materials and procedures

discussed in this guide include:a) Preparing a clean, dry substrate;b) Preparing a saturated surface-dry substrate;c) Prepare a saturated surface-dry substrate with scrub

coat of paste from replacement material;d) Acrylic bonding agents;e) Epoxy bonding agents.1.4.8 Crystalline pore blockers and surface-applied, pene-

trating corrosion inhibitors—These are proprietary products with undisclosed ingredients. This guide discusses these materials on a generic performance basis.

1.4.9 Summary tables of test methods and test values—Tables 3.8a and 3.8b present summaries of available test methods and typical test values for concrete replacement and overlay materials; Table 4.7 presents a selection guide for these materials. Tables 5.7a and 5.7b present summaries of available test methods and typical test values for crack repair materials; Table 6.14 presents a selection guide for these materials. Tables 7.5a, 7.5b, and 7.5c present summaries of available test methods and typical test values for surface sealers, anti-carbonation coatings, and traffic-bearing elas-tomeric coatings; and Tables 8.5a and 8.5b present selection guides for surface sealers and anti-carbonation coatings.

1.4.10 Safety cautions—Repair material specifiers and users should be aware that many repair materials have to be handled with care to avoid potential harm to workers and the environment. Health and safety practices have to be estab-lished appropriate to the specific circumstances involved

with material use. The applicability of all regulatory limita-tions have to be determined when selecting repair materials, and material selection and use have to comply with all appli-cable laws and regulations.

1.4.11 Special repair and service environments—This guide covers concrete repair materials for common types of concrete construction. Special repair and service envi-ronments may require repair materials with enhancement of particular properties. For the repair of environmental or mass-concrete structures, underwater repairs, and other special repair and service environments, refer to the recom-mendations of other ACI publications (including those of ACI Committee 350 and ACI 546.2R), industry organiza-tions, and material manufacturers for specific guidance in repair material selection.

1.5—Current industry issues and concernsAppendix A includes a discussion of a number of current

industry issues and concerns, including:a) Material test methods and reporting of test data;b) Curing of repair materials and manufacturers’ reported

test results;c) Product limitations and warnings;d) Standardized industry acceptance;e) Repair material bond;f) Corrosion reduction;g) Structural repairs; andh) Ongoing developments.

CHAPTER 2—NOTATION AND DEFINITIONS

2.1—NotationThere are no notations used in this guide.

2.2—DefinitionsACI provides a comprehensive list of definitions through

an online resource, “ACI Concrete Terminology,” http://www.concrete.org/Tools/ConcreteTerminology.aspx. Defi-nitions provided herein complement that source.

basic portland-cement concrete—a composition of port-land cement, fine and coarse aggregates, and water.

concrete replacement—the removal and replacement of damaged or deteriorated concrete, including partial-depth as well as full-depth repairs that are sometimes informally called patches.

electrical resistivity—the resistance of a material to the flow of electrical charge in the presence of a voltage poten-tial between two points.

permeability—the ability of a material to transmit or resist the penetration of water and water-borne chemicals. This definition differs from that in ACI Concrete Termi-nology in that the ability to transmit or the resist the penetra-tion of gases is not included.

surface sealer—material applied to the concrete surface to reduce moisture and chemical penetration into the concrete member. Surface sealers may achieve limited penetration into uncracked concrete, but are either too brittle or applied in a coating too thin to bridge moving cracks or cracks that





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may form in the concrete after the material application. Surface sealers are differentiated from sealers, as defined in ACI Concrete Terminology, in that surface sealers may or may not prevent the penetration of gaseous media, be colorless, or be absorbed by the concrete, and commonly are visible on the concrete surface.

traffic-bearing elastomeric coating—material applied to the concrete surface to greatly reduce moisture and chem-ical penetration to the concrete member and that is suited for exposure to pedestrian and vehicular traffic. Elasto-meric coatings have some flexibility so they are capable of bridging narrow cracks that experience some movement and some cracks that might form in the concrete after the elasto-meric coating application.

volume stability—initial and long-term changes in the linear dimensions or volume of a material after placement.

working time—elapsed time from completion of mixing until the material becomes too stiff or otherwise unusable.

CHAPTER 3—PROPERTIES OF CONCRETE REPLACEMENT AND OVERLAY MATERIALS AND

THEIR IMPORTANCE

3.1—GeneralCompatibility between the properties of concrete replace-

ment and overlay materials and the properties of the intended substrate is an important consideration. For example, in many concrete replacement applications, the properties of repair materials, such as the coefficient of thermal expansion and creep, should be similar to those of the substrate. In contrast, the success of many crack repair applications depends on repair materials that have significantly different properties, such as high elasticity and low modulus of elasticity, from that of the substrate, and which will perform better than the base concrete in the service environment. Regardless, it is necessary to identify the repair material properties and the substrate properties before an approach to the repair is deter-mined (McDonald et al. 2002).

Many properties of replacement materials, overlay mate-rials, and the existing concrete are time-dependent. In cases where material properties are specified, the corresponding age of the materials should be noted. A conclusion from Alberta Transportation’s 1987 concrete replacement testing program was that the durability of concrete replacement materials correlated better with long-term physical proper-ties—for example, 1 year or more after placement, rather than shorter-term physical properties (24-hour and 28-day properties) (Gurjar 1987).

Most test methods cited in this guide are performed at standard conditions at room temperature in many cases, with standard-sized specimens, so reported properties may not reflect the actual properties of the repair material in various-sized repairs in service conditions.

Chapter 3 discusses properties of concrete replacement and overlay materials, and test methods used to evaluate them. Some test methods are not specifically applicable for certain replacement or overlay materials, or replacement or overlay installations, but are useful for comparison. Because

descriptions of the various test methods are brief, referenced standards should be reviewed for details. Material manufac-turers should provide test data based on ASTM standards and other standardized test methods. ACI 364.3R and ICRI 320.3R describe many relevant properties and appropriate modifications to standardized test methods suitable for cementitious replacement materials. Refer to Appendix A for further discussion regarding modifications to standard test methods.

3.2—Volume stabilityVolume stability properties affect compatibility of the

repair material with the substrate concrete. Substrate concrete is usually relatively stable, with minimal residual creep and shrinkage deformations. The substrate concrete, however, may experience some volume instability for various reasons, including thermal expansion and contraction from seasonal environmental changes. It is desirable for any shrinkage or expansion of the repair material to occur before the repair material has reached its final set, while creep is high. If this is not possible with some repair materials, consideration should be given to accommodating differential movements in some manner in the repair design, such as use of control joints, curing, avoidance of reentrant corners, avoidance of high length-to-width ratio configurations, or treatment of anticipated cracks.

Most cementitious materials undergo early shrinkage within the first few hours to days after application. Non-cementitious materials, such as those with polymeric binders, tend to be more stable with little or no shrinkage after hardening. These materials, however, are subject to greater volume changes due to temperature variations. Significant changes in repair material volume can cause high shear stresses at the interface, debonding from the substrate concrete, and cracking of the repair material. Stresses created in the repair material by restrained contraction and expan-sion may be reduced by using repair materials with a lower modulus of elasticity or a higher rate of creep. Expansion of the repair material may be resisted by providing restraint or confinement, such as by keying it into the substrate concrete. Cracking of the repair material to relieve restrained shrinkage should be anticipated, and further repairs may be needed.

Six test methods are used to evaluate volume stability of concrete, mortar, and cementitious materials:

1) ASTM C1572) ASTM C157, as modified by ICRI 320.3R3) ASTM C5964) ASTM C8065) ASTM C8276) ASTM C1581ASTM C157, ASTM C596, and ASTM C806 are test

methods that involve monitoring the length of test specimens over time under different curing conditions. A restraining cage with an embedded steel rod is used in ASTM C806 to restrain the specimen expansion. ASTM C827 is a test method that involves monitoring the height of cylindrical test specimens until the specimens harden. ASTM C1581 is a test procedure that involves measuring the strains and observing





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cracking in donut-shaped specimens with inner steel rings. The primary use of these test methods is to provide a rela-tive comparison of various materials when tested in the same fashion. Actual shrinkage experienced in the field will likely differ from shrinkage reported from tests; harsh laboratory test conditions sometimes yield higher shrinkage than that which actually occurs in the field.

3.2.1 ASTM C157—The curing and comparator reading regimen in this test method is not applicable for repair mortars and concretes. The test specimens are approximately 11-1/4 in. (285 mm) long and vary in cross section from 1 in. (25 mm) square for mortar specimens to 3 or 4 in. (75 or 100 mm) square for concrete specimens. Initially, the test speci-mens are stored in a moist room for 24 hours, demolded, and placed in lime-saturated water for a minimum of 15 minutes for mortar specimens and 30 minutes for concrete speci-mens. Initial length comparator measurements are taken. The specimens are stored in lime-saturated water until they have reached an age of 28 days, when another set of length comparator measurements are made. After these measure-ments, the specimens are stored in either lime-saturated water or in a drying room, and length comparator measure-ments are taken at 4, 7, 14, and 28 days (drying room storage only), and 8, 16, 32, and 64 weeks, including the initial 28-day curing period. The length change, in percent, at any age is calculated. Typical shrinkage strains range from 0.02 percent expansion to –0.12 percent shrinkage. The length comparator setup is shown in Fig. 3.2.1.

Neither curing regimen is representative of field condi-tions for most repair mortars because the initial length-comparator measurement is made at 24 hours, neglecting volume changes that occur within the first 24 hours; exten-sive wet curing is used, and the specimens are not restrained. In field conditions, bonding repair materials to the substrate concrete provides restraint to shrinkage and an increased

exposed surface area, such as shallow or long slender repair geometries, can significantly increase shrinkage.

When testing shrinkage-compensating mortars, unreal-istic curing conditions and inappropriate comparator reading schedules could lead to misleadingly low values of drying shrinkage. It is critical that the demolding time, curing condi-tions, and comparator reading schedule are understood when interpreting test results. For example, if the initial measure-ment is recorded while the material is still expanding, the ultimate drying shrinkage appears less than it actually is; the net length change (expansion less shrinkage) during the test, therefore, should be used as the value for drying shrinkage.

The specimen size has a significant effect on shrinkage results. Different-sized specimens have different surface-to-volume ratios, which will affect the rate of shrinkage (Hansen and Mattock 1966). A 1 in. (25 mm) square spec-imen shrinks more quickly than 3 or 4 in. (75 or 100 mm) square specimens. If larger specimens are used, it may be appropriate to consider shrinkage at 16 weeks instead of 28 days. Comparison of shrinkage results should always be made using the same specimen dimensions, curing regimen, and storage conditions.

3.2.2 ASTM C157 as modified by ICRI 320.3R—ICRI 320.3R describes a modification of ASTM C157 and makes recommendations for reporting properties appropriate for cement-based repair materials. The standard test specimen is 3 in. (75 mm) square by 11-3/4 in. (300 mm), so the same surface area-to-volume ratio exists for mortar, extended mortar, and concrete. Non-polymer-cement materials are cured in a moist room for 24 hours, or for 2 hours after final setting time for rapid-hardening materials, and then demolded. Initial comparator readings are made based on final setting time as an indicator of development of suffi-cient strength to handle the bar. Polymer-cement mate-rials are covered with polyethylene film immediately after casting, and demolded after 24 hours, or 2 hours after final setting time for rapid-hardening materials, in accordance with ASTM C1439. Initial comparator readings are made. The specimens are stored in a drying room or a water tank, and comparator readings are made at 3, 7, 14, 28, and 56 days. Measurements continue until 90 percent of the ulti-mate drying shrinkage or moisture expansion, as determined by ASTM C596, is attained.

3.2.3 ASTM C596—Length change during drying is deter-mined for flowable mortar containing hydraulic cement and graded standard sand. Test specimens are 1 in. (25 mm) square by approximately 11-1/4 in. (285 mm). Specimens are moist cured for 24 hours, demolded, and cured in lime-saturated water for 48 hours. Length comparator measure-ments follow. The specimens are then stored in air for 25 days, and length comparator measurements are made after 4, 11, 18, and 25 days of air storage. Typical shrinkage strains range from –0.05 to –0.15 percent. In general, shrinkage values more negative than –0.10 percent are considered too high for concrete repair (Vaysburd et al. 1999). Some repair materials have shrinkage values more negative than this criterion, and may be inappropriate for use in applications where shrinkage may be an issue.

Fig. 3.2.1—Length comparator with standard calibrating rod (ASTM C157). (Photo courtesy of BASF Construction Chemicals, LLC.)





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3.2.4 ASTM C806—This test method is typically used for comparative evaluation of expansive cements using a prescriptive mortar mixture. It is inappropriate for use with repair mortars because the test specimens are cured under water continuously for 28 days while repair mortars are usually exposed to air drying within 1 week after placement. Test specimens are 2 in. (50 mm) square by 10 in. (250 mm) long. A restraining cage, including a steel rod, is cast with the specimen. Immediately after casting, the specimens are covered with polyethylene sheets. After 6 hours, the speci-mens are demolded. The specimens are then cured in lime-saturated water for 28 days. Comparator measurements are made after 7 and 28 days, and the length change is calcu-lated. A typical value for expansion is 0.06 percent under the conditions of this test.

3.2.5 ASTM C827—The early-age movements of cylin-drical specimens of cementitious mixtures of paste, grout, mortar, and concrete are measured. Depending on the maximum-size aggregates, specimen size varies from 2 in. (50 mm) diameter by 4 in. (100 mm) high to 6 in. (150 mm) diameter by 12 in. (300 mm) high. Immediately after molding the specimens, an indicator ball is partially embedded in the top of each specimen. The test specimen is placed between a projected light source and a magnifying lens system, and movements of the ball are enlarged optically and measured on a wall chart. Measurements are made at 5-minute inter-vals for the first 90 minutes, at 10-minute intervals for the next hour, and at 20-minute intervals thereafter until the mixture has hardened. The change in height of the specimen is then calculated.

3.2.6 ASTM C1581—This test measures the strains in a cylindrical specimen cast around a steel ring on a smooth, nonabsorbent, nonbonding surface, shown in Fig. 3.2.6. The specimens have an inside diameter of 13 in. (330 mm), an outside diameter of 16 in. (405 mm), and a height of 6 in. (150 mm). Unless otherwise specified, the specimens are wet cured for 24 hours and then demolded, leaving the instrumented inner steel ring in place. The top surface is then sealed with paraffin wax or adhesive aluminum-foil tape. As the repair material shrinks, strain is transferred to the steel ring, which is fitted with strain gauges. Strains are measured every 30 minutes maximum, and the specimens are visually inspected every 3 days maximum. The specimens are moni-tored for at least 28 days after initiation of drying, unless cracking occurs prior to 28 days. The age at cracking is indi-cated when the strain suddenly decreases.

The test is intended to give a relative indication of when cracking due to restrained shrinkage may occur for different repair materials. The results provide a comparative measure of a material’s tendency to crack, which is affected by a combination of several material properties, including drying shrinkage, modulus of elasticity, tensile strength, strain capacity, and creep. Temperature changes and coarse aggre-gate effects are not considered.

3.3—Mechanical propertiesMechanical properties affect repair material interactions

with the substrate concrete. It is essential that the repair

material remain bonded to the concrete. It is also important that the repair material has mechanical properties compat-ible with those of the substrate concrete to ensure that the materials act as one and no material failure occurs. If some properties of the repair material are greatly different from those of the substrate concrete, such as the coefficient of thermal expansion, other properties should compensate for these differences for the repair to perform successfully. For example, a lower modulus of elasticity will reduce the stresses due to differing thermal movements. Usually it is not necessary, or even desirable, for the repair material to have some mechanical properties, such as compressive strength, tensile strength, or bond strength, substantially in excess of the substrate concrete, as any subsequent failures would simply occur in the weaker substrate concrete adja-cent to the repair.

3.3.1 Elasticity—Elasticity is a material property that causes the material to recover its original size and shape after an applied deformation or force is removed. Elasticity is primarily important for materials intended to bridge active cracks, such as some crack sealants and surface coatings. Elasticity is typically quantified by measuring the elonga-tion of a material in tension, as in ASTM D638, discussed in 5.3.2.

3.3.2 Static modulus of elasticity—If the repair is not structural (not intended to share load with the substrate concrete), then it is typically desirable that the repair mate-rial have a modulus of elasticity lower than that of the substrate concrete, so it can more readily accommodate future movements within the repair material and at the inter-face between the repair material and substrate concrete. A lower modulus is particularly desirable if the repair material has volume stability or thermal compatibility properties that differ significantly from those of the substrate concrete. If a repair is intended to share load with the existing structure (structural repair), it is desirable for the moduli of elasticity of both materials to match as closely as possible. If the repair material has a higher modulus of elasticity, it will attract more of the applied load; if the repair material has a lower modulus of elasticity, it will deform under stress and transfer load into the substrate. Significant deviations can lead to uneven load distribution and system failure.

Fig. 3.2.6––Schematic of ASTM C1581 ring test specimen. (Reprinted with permission from ASTM C1581.)





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Two ASTM test methods typically used to measure the modulus of elasticity of repair materials are:

1) ASTM C4692) ASTM C580In ASTM C469, a molded cylindrical specimen or a

drilled core specimen is loaded in compression and the axial deformation measured. Load-deformation data is plotted and a chord modulus of elasticity is calculated for a stress corresponding to 40 percent of the ultimate load. The test setup is shown schematically in Fig. 3.3.2a. In ASTM C580, a square-bar beam specimen is loaded at midspan in flexure and the midspan deflection is measured. Load-deflection data are plotted and a secant modulus of elasticity is calculated for a deflection that is 50 percent of the maximum deflection. The test setup is shown schematically in Fig. 3.3.2b. The results reported in stress units (psi or MPa).

3.3.3 Coefficient of thermal expansion—In situations where temperature is not controlled, such as in exterior and some interior applications, it is desirable for the repair mate-rial to have a coefficient of thermal expansion similar to that of the substrate concrete, so the two materials behave simi-larly under daily and seasonal temperature variations. If the coefficients vary significantly, the differential movements due to temperature fluctuations could affect the perfor-

mance of the repair and should be accounted for in the repair design. The coefficient of thermal expansion for concrete typically ranges from 0.000002 to 0.000008/°F (0.000004 to 0.000014/oC), depending primarily on the aggregate type.

Four test methods are used to determine the coefficient of thermal expansion.

1) ASTM C5312) ASTM D6963) ASTM C8844) United States Army Corps of Engineers (USACE)

CRD-C 39ASTM C531 and D696 and USACE CRD-C 39 are test

methods in which the coefficient of thermal expansion is measured by determining the change in length of a mate-rial at constant humidity between two different tempera-tures: 73°F and 210°F (23°C and 100°C) in ASTM C531; and –22°F and +86°F (–30°C and +30°C) in ASTM D696. Results are reported as strain per unit temperature change. ASTM C884 is a test method where thermal compatibility between concrete and an epoxy resin overlay is determined by a similar approach. In this case, a concrete substrate with an epoxy-resin overlay is cycled through a temperature range between 77°F and –6°F (25°C and –21ºC) five times. If the epoxy resin overlay debonds from the concrete or there are horizontal cracks in the concrete near the interface, the epoxy resin system fails the test.

3.3.4 Creep—Because many repairs are not subjected to significant compressive forces, compressive creep may not be a significant property of repair materials. Creep can be important in reducing stress induced in the repair mate-rial due to restraint of shrinkage strains or factors, such as thermal movement or the application of live loads.

Two ASTM test methods are used to evaluate compressive creep:

1) ASTM C5122) ASTM C1181Both tests are suitable for testing repair materials.In ASTM C512, creep is determined by placing a material

under a sustained stress, usually not more than 40 percent of the compressive strength at the age of loading, measuring the resultant strain over time, and reducing the strain by measured strains from unloaded control specimens, which

Fig. 3.3.2b—Schematics of flexural test setups.(Courtesy of BASF Construction Chemi-cals, LLC.)

Fig. 3.3.2a—Schematic of ASTM C469 test setup.(Courtesy of BASF Construction Chemicals, LLC.)





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account for strains due to shrinkage. To determine the complete creep behavior of a repair concrete, test specimens are loaded at ages of 2, 7, 28, and 90 days, and 1 year. The creep strains are measured at specified intervals in the first year. Results are reported as percent strain at a given age for a given sustained stress. Creep may be determined for materials of different ages and under different curing regi-mens; however, variation from standard conditions should be explicitly reported. Figure 3.3.4 shows schematics of a typical creep test setup.

In ASTM C1181, test specimens are conditioned for 7 days and are then tested for 35 days. A test stress is selected and applied to the specimen, and the specimen deflection is measured. The specimen is then unloaded and placed in an oven at a selected temperature for 24 hours, after which the specimen is allowed to cool at 73°F (23°C) for 24 hours. The specimen is then reloaded to the selected stress and the deflection measured. This heating, cooling, loading, and deflection measurement cycle is repeated five times, with subsequent heating periods of 24, 72, and 48 hours, and 7 and 28 days. Creep is expressed as a graph of strain versus time in the oven.

Tensile creep is a significant property for repair materials. Tensile creep can reduce the cracking of repair materials by relaxing the tensile stress over time. No commonly accepted, standardized test method is available for measuring tensile creep, and there is no consensus regarding a correlation between tensile and compressive creep (Pigeon and Bisson-nette 1999; Iriya et al. 1999, 2000; Beaudoin 1982).

3.3.5 Bond strength—Bond strength, or adhesion, relates to the ability of the two materials to act as one. This section addresses bond between the repair material and substrate concrete only.

A repair material should have sufficient bond strength to the substrate concrete so it does not separate from the substrate concrete. It is desirable for the bond strength to be larger than the minimum requirements so that any reductions due to field-application conditions are not as critical. Bond

strengths that exceed the tensile strength of either the repair material or the substrate will induce failure in the weaker material if sufficient interface stresses result from shrinkage, thermal movement, or other factors.

Seven test methods are used to measure bond strength:1) ASTM C8822) ASTM C1042 (withdrawn 2008)3) ASTM C1404 (withdrawn 2010)4) CSA A23.2-6B5) ASTM C15836) ICRI 210.37) Michigan Department of Transportation (MDOT)

Direct Shear Bonding TestIn these test methods, bond strength is usually inferred

from the measured slant shear, direct tension, or direct shear test values, because failure rarely occurs at the bond line. Failures that occur away from the bond line imply that the bond strength is greater than the failure load in the test. When failure occurs at the bond line in direct tension tests, the measured tensile force is the actual bond strength. While ASTM C1042 and C1404 have been withdrawn, some mate-rial manufacturers still report bond strengths based on these procedures.

Slant shear bond tests (ASTM C882 and C1042) measure the resistance to sliding between the repair material and concrete substrate along an inclined surface. The interface is subjected to combined shear and compressive stress. The measured bond strength may be influenced by the compres-sive strength of the substrate concrete and the surface rough-ness of the bonding surface. Direct tension bond tests (ASTM C1404, CSA A23.2-6B, ASTM C1583, and ICRI 210.3) are more appropriate for repair applications because they apply a single mode of stress and direct tension at the bond inter-face. The ASTM C1404 test is a laboratory test for adhesive systems, while the CSA A23.2-6B, ASTM C1583, and ICRI 210.3 tests use a cored specimen drilled through the repair material into the substrate. The latter three tests are suitable for field and laboratory evaluations. ASTM C1583 and ICRI

Fig. 3.3.4—Schematic of ASTM C512 creep loading. (Reprinted with permission from ASTM C512) and spring-loaded creep frame (Courtesy of BASF Construction Chemicals, LLC).





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210.3 test procedures were introduced in 2004 and have had limited time for industry use. The MDOT direct shear bonding test measures the shear applied along the interface between the repair material and sawn substrate concrete.

ASTM C882 and C1042 are slant shear bond tests specifi-cally for epoxy-resin and latex bonding systems, and are the most commonly reported test results. These tests involve casting a 3 x 6 in. (75 x 150 mm) right cylinder of substrate mortar or concrete using a dummy section to form a planar bonding surface that is 30 degrees off the longitudinal axis of the cylinder. The bonding surface is prepared by sand-blasting or diamond sawcut (ASTM C1042 only), the bonding material is applied, and the test material is cast on top of the test specimen to complete the 3 x 6 in. (75 x 150 mm) right cylinder. At the appropriate age, the test specimen is loaded to failure in compression. The stress at fracture is determined by dividing the ultimate load by the elliptical area of the bonding surface to determine the bond strength. If the specimen does not fail at the bond line, the bond strength is considered to be at least the resulting failure stress. The substrate strength, porosity, surface roughness, moisture content, and other factors should be considered in evaluating values determined from these tests. Tests are shown schematically in Fig. 3.3.5a.

ASTM C1404 is a direct tension test procedure that involves cutting a 3 x 6 in. (75 x 150 mm) concrete cylinder in half, creating a planar bonding surface perpendicular to the longitudinal axis of the cylinder. The cut surface is rubbed with abrasive paper, the adhesive being tested is applied to the cut surface, and a mortar overlay is applied, completing the 3 x 6 in. (75 x 150 mm) right cylinder. Steel pipe nipples are attached to the specimen, the nipples are screwed into pipe caps, the pipe caps are attached to the test machine, and the specimen is loaded to failure in direct tension. Stress at frac-ture is determined by dividing the ultimate load by the cross-sectional area of the cylinder. If the specimen does not fail at the bond line, bond strength is at least the stress at fracture.

CSA A23.2-6B, ASTM C1583, and ICRI 210.3 are test procedures that involve coring through a concrete replace-

ment or overlay material into the substrate concrete; adhering with epoxy a rigid plate or a machined, standard pipe cap with a minimum outside diameter of 2 in. (50 mm) to the core surface; and pulling along the core axis to failure at a rate of approximately 15 to 23 lb (70 to 100 N) per second. The procedure is shown schematically in Fig. 3.3.5b. The failure type and load are recorded, and the failure load is reported in terms of psi (MPa).

Direct tension values below 100 psi (0.69 MPa) most likely indicate a serious problem with the repair material bond. As the direct tension bond strength approaches 200 psi (1.4 MPa), the bond interface strength begins to approach the tensile strength of the concrete substrate, which is a limiting value of the overall repair (Knab et al. 1989).

The MDOT Direct Shear Bonding Test is a direct shear test that is performed with a 4 in. (100 mm) cube or a cast or cored cylinder. For cube specimens, substrate concrete is cast into a cube and a 1 in. (25 mm) thick section is sawn from one face. The resulting surface is cleaned and veri-fied to have a uniform profile, and the test material is cast onto the substrate to reform a 4 in. (100 mm) cube. The cube is then secured in a test machine and direct shear force is applied to the bonding surface. Stress at failure is deter-mined by dividing the ultimate load by the area of bonding surface. A similar procedure is used with a right cylinder. A cored cylinder can be used to test in-place materials. Direct shear bond strengths of 300 to 500 psi (2.1 to 3.4 MPa) are generally considered to be adequate (Knab et al. 1989). The test setup is shown in Fig. 3.3.5c.

3.3.6 Compressive strength—Three test methods are used to measure compressive strength:

1) ASTM C392) ASTM C1093) ASTM C579Compressive strength is determined by applying an

increasing axial compression load until the specimen is unable to support additional load. The ultimate load is divided by the cross-sectional area to determine the ulti-mate failure stress (psi or MPa). ASTM C39 tests cylindrical

Fig. 3.3.5a—Schematic of ASTM C882 and C1042 slant shear tests. (Courtesy of BASF Construction Chemicals, LLC.)

Fig. 3.3.5b—Schematic of direct tension bond test setup (CSA A23.2-6B). (Courtesy of BASF Construction Chemi-cals, LLC.)





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concrete specimens that are 4 x 8 in. (100 x 200 mm) or 6 x 12 in. (150 x 300 mm). ASTM C109 tests 2 in. (50 mm) mortar cubes. ASTM C579 tests right cylinders 1 x 1 in. (25 x 25 mm) for materials with aggregates less than 1/16 in. (1.6 mm) in size; 2 in. (50 mm) cubes for materials with aggregates from 1/16 to 0.4 in. (1.6 to 10 mm) in size; and 2 in. (50 mm) minimum diameter right cylinders, with a height twice the diameter, for materials with aggregates larger than 0.4 in. (10 mm). A schematic of the test setup is shown in Fig. 3.3.6. Usually, it is desirable to have a compressive strength similar to that of the substrate concrete, but at least 4000 psi (28 MPa). The fracture pattern of the specimens should also be documented according to ASTM C39.

3.3.7 Tensile strength—Three test methods are used to measure tensile strength:

1) ASTM C3072) ASTM C4963) USACE CRD-C 164Tensile strength of cementitious materials is usually deter-

mined by a splitting tensile test (ASTM C307 and C496). The splitting tensile test applies a compressive force along the axis of an unconfined cylinder supported on its side, causing it to split along its axis, as shown schematically in Fig. 3.3.7a. Results are reported in stress (psi or MPa) and are normally of greater magnitude than direct tensile

strength measurements (USACE CRD-C 164). Direct tensile strength measurements provide a true indication of the tensile strength of the material because the tensile stress is applied perpendicular to the failure plane. The direct tension test setup is shown schematically in Fig. 3.3.7b.

3.3.8 Flexural strength and modulus of rupture—Five test methods are used to measure the flexural strength of different repair materials:

1) ASTM C782) ASTM C2933) ASTM C3484) ASTM C5805) ASTM D790Flexural strength is determined by casting a beam spec-

imen of a given material and testing it in bending. Tests use concrete beams supported at their ends with either one (ASTM C293, C348, C580, and D790) or two (ASTM C78) loading points, as shown schematically in Fig. 3.3.2b. The one-point loading at midspan creates the maximum tensile stress at a single cross section where the load is applied, whereas the two-point loading at the third points produces the maximum tensile stress over the middle third of the specimen, making the test less susceptible to scatter due to non-uniform material or the presence of large aggregate at the loading point. Tests have shown that the flexural strength from third-point loading could be approximately 75 psi (0.52 MPa) less than that obtained from center-point loading (Portland Cement Association 1995). The resulting flexural strength is reported in stress units (psi [MPa]).

Fig. 3.3.5c––MDOT direct shear bonding test setup. (Cour-tesy of Wiss, Janney, Elstner Associates, Inc.)

Fig. 3.3.6––Schematic of compression test setup (ASTM C39; C109; C579). (Courtesy of BASF Construction Chemi-cals, LLC.)

Fig. 3.3.7a—Schematic of splitting tension test setup (ASTM C307; C496). (Courtesy of BASF Construction Chemicals, LLC.)

Fig. 3.3.7b—Schematic of direct tension test setup (USACE CRD-C 164). (Courtesy of BASF Construction Chemicals, LLC.)





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3.3.9 Significance of compressive, tensile, and flexural strengths—Compressive and flexural strengths are normally not the limiting properties in the performance of repair mate-rials but may be used as general indicators of the material quality. Usually it is desirable for these properties to meet or slightly exceed those of the substrate concrete (as measured at the time of the repair, not as originally specified). Higher tensile strength could be beneficial in reducing cracking due to restrained shrinkage and thermal contraction.

3.4—Constructibility characteristicsConstructibility characteristics are those material proper-

ties that affect or limit the installation or application of the repair material for varying field conditions, such as overhead or formed and poured repairs and hot or cold weather work.

3.4.1 Cohesiveness—The cohesiveness of a repair mate-rial is its ability to remain intact or not segregate during its application. Cohesiveness of repair material is important for the ease of construction and uniformity of repair. For example, in concrete replacements on vertical and overhead surfaces, a more cohesive material can be applied in thicker lifts with less chance of internal separations or debonding before setting.

3.4.2 Viscosity—The measured value of viscosity is affected by factors such as the method of measurement (viscometer or rheometer geometry), temperature, and the rate of applied shear strain. Materials with low viscosity flow more freely than those with higher viscosity. In general, low-viscosity materials are used to repair cracks and penetrate into concrete pores. Flowable, self-consolidating materials are also available for concrete replacements.

3.4.3 Working time—Factors such as ambient and material temperature, mixing ratio, and mass of material can signifi-cantly affect the amount of time available for the applicator to spread the material. Consequently, it is difficult to test for and report working time in a meaningful manner. A material may be unworkable before initial set occurs, so that working time is less than or equal to initial set time.

3.4.4 Environmental considerations—Repair material should be suitable for the specific repair application environ-ment. For example, some environmental limitations at the time of construction include the air and concrete tempera-tures, amount of moisture on the substrate concrete surface, relative humidity, wind speed, if the repair area is in direct sunlight or shade, and anticipated climatic conditions that occur before the repair material reaches its final set. The choice of specific repair materials and their corresponding properties depends on actual construction conditions. In some cases, the construction conditions are modified to fit the properties of the repair materials chosen.

3.5—Aesthetic propertiesThe appearance of repair materials is important in some

circumstances.3.5.1 Surface texture—Generally should match that of the

adjacent material.

3.5.2 Color—Generally should match that of the adjacent material, unless the repair is not visible, such as after the application of a coating.

3.5.3 Aging—Some repair materials will change appear-ance as they age due to weathering, exposure to ultraviolet light, drying, or curing.

3.5.4 Moisture absorption—The appearance of repair material may change when it gets wet, and it may return to its original appearance as it dries. Changes in appearance may be different from the adjacent concrete.

3.6—Factors affecting durabilityService conditions can place various demands on the

repair material, possibly requiring the repair material to have enhanced properties for long-term durability. Conditions can include exposure to moisture, temperature variations, chem-icals, and mechanical wear.

3.6.1 Resistance to freezing and thawing—Some repair materials, including concrete, are susceptible to deterioration when exposed to cycles of freezing and thawing in a saturated condition. The expansion and migration of water can generate destructive internal pressures unless measures such as air entrainment are taken to provide the needed durability.

Three test methods are used to evaluate resistance to cyclic freezing and thawing:

1) ASTM C6662) ASTM C6723) ASTM C672 as modified by ICRI 320.2RDurability of material in freezing environments is evalu-

ated in bulk by ASTM C666, or as a surface scaling effect by ASTM C672 and modified by ICRI 320.2R. The approach in ASTM C666 is to expose concrete or a cementitious mate-rial to freezing-and-thawing cycles and record the change in dynamic modulus of elasticity and mass loss of the speci-mens. ASTM C672 relies on a visual inspection of surface damage caused by freezing-and-thawing cycles of a ponded salt solution, while the ICRI 320.2R modification includes measuring the mass loss of the scaled material to quantify the amount of scaling.

ASTM C666—This test method includes two procedures. Procedure A is with both freezing and thawing in water, and Procedure B is with freezing in air and thawing in water. Procedure A is the most commonly used because it is more easily automated. A complete test consists of 300 freezing-and-thawing cycles, unless the relative dynamic modulus of elasticity of the specimen first reaches 60 percent of the initial value. A durability factor, as calculated in the test procedure, which is greater than 80, is generally considered to represent a material that will be durable under freezing-and-thawing conditions. If this test is not carried out to 300 cycles, the total number of cycles should be reported. ASTM C666 is considered a severe test method; some materials that fail the test may not fail under harsh service conditions.

ASTM C672—This test method, commonly called the salt scaling test, is appropriate for materials exposed to freezing-and-thawing cycles in conjunction with deicing salt expo-sure. A 4 percent solution of calcium chloride is ponded on the specimen surface and subjected to cyclic freezing and





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thawing. Each cycle lasts 24 hours and, generally, 50 cycles are sufficient to evaluate a surface. Test results use a subjec-tive visual scale of 0 to 5, with 0 indicating no scaling and 5 indicating severe scaling. Refer to Fig. 3.6.1 for a schematic of the test setup.

ICRI 320.2R provides a modification of ASTM C672 that is often used to eliminate subjectivity of the standard test. The modification involves collecting, drying, and weighing the scaled material to quantify the mass loss from surface deterioration after every 10 cycles. A value less than 0.16 lb/ft2 (0.8 kg/m2), after 50 cycles, usually denotes acceptable performance.

As durability of the concrete surface improves with age, the age of test specimens when initially exposed to the freezing-and-thawing cycling is critical to interpreting the results. ASTM C672, with or without the ICRI 320.2R modi-fication, has been found to be a severe test method; some materials that fail the test may not fail under harsh service conditions. ASTM C672, with or without the ICRI 320.2R modification, has also been found to be sensitive to surface finishing techniques (Johnston 1993). Conducting the test on a formed versus finished face of a specimen can significantly affect the results.

3.6.2 Permeability—The permeability of a repair mate-rial is important in environments where the repair mate-rial or substrate concrete is vulnerable to moisture-related deterioration such as freezing-and-thawing damage of satu-rated concrete, corrosion of embedded reinforcing steel, alkali-aggregate reactions, or sulfate attack. Permeability is particularly sensitive to the age of the material being tested. Generally, permeability decreases as the cementitious material hydrates or as the level of carbonation increases. Tests should always indicate the specimen age at the time of the test.

Five test methods are used to measure permeability:1) American Association of State and Highway Transpor-

tation Officials (AASHTO) T2592) ASTM C15433) AASHTO T2774) ASTM C12025) ASTM C642The permeability of concrete or mortar is sometimes deter-

mined by its resistance to chloride ion penetration. AASHTO T259 consists of ponding a sodium chloride solution on the top surface of slab specimens for 90 days and measuring the chloride-ion content at different levels within the concrete.

The results can be used to compare different concretes and repair materials. ASTM C1543 is similar to AASHTO T259, except that it does not have a specific test period. AASHTO T277 and ASTM C1202 were developed to provide an indi-cation of a material’s resistance to chloride-ion ingress in a shorter period of time, which is typically 6 hours. In this procedure, a constant voltage is applied across a cylindrical specimen with ionic solutions on both sides of the specimen, and the total electrical current measured. The test does not actually measure the chloride-ion penetration but rather the electrical resistance of the immersed sample. As a result, the test results are influenced by the electrical resistivity of the test material and its permeability. ASTM C642 is a quick and economical method to approximate the permeable void content of concrete.

AASHTO T259 and ASTM C1543 consist of a 3 percent sodium chloride solution ponded on top of a concrete slab specimen for 90 days or longer. After 90 days, the concrete is sampled and analyzed to determine the chloride-ion content at various levels below the surface. In ASTM C1543, the testing entity may select a test period longer than 90 days. The findings are reported in percent chloride ions relative to the concrete or cement mass in the specimen, based on acid-soluble chloride. A schematic of the test setup is shown in Fig. 3.6.2a. AASHTO T259 requires 90 days to perform and ASTM C1543 usually requires at least 90 days to perform; the results can be used to compare different concretes and repair materials. Care should be taken to ensure that compar-ative tests are performed in the same manner; in particular, the test duration should be the same, the concrete should be sampled in the same manner for chloride testing, and the same chloride-ion test procedure should be used for all of the samples.

In the AASHTO T277 and ASTM C1202 procedure a cylindrical test specimen is placed in the test apparatus with a sodium chloride solution on one side and a sodium hydroxide solution on the other side, as shown in Fig. 3.6.2b(a). A constant voltage of 60 V is applied across the test specimen for 6 hours and the total electrical current passed is measured. In-progress tests are shown in Fig. 3.6.2b(b). The total charge passed, measured in coulombs (C), is taken as the measure of the permeability of the material. Gener-ally, moderate-water-to-cementitious-material-ratio (w/cm) concrete (0.4 to 0.5) has values of 2000 to 4000 C; low-w/cm concrete (less than 0.4) has values ranging from 1000 to

Fig. 3.6.1—Schematic of ASTM C672 freezing-and-thawing test setup. (Courtesy of BASF Construction Chemicals, LLC.)

Fig. 3.6.2a—Schematic of AASHTO T259 and ASTM C1543 test setup. (Courtesy of BASF Construction Chemicals, LLC.)





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2000 C, and silica fume and polymer-cement concrete have values ranging from 100 to 1000 C (Whiting 1981).

Values obtained from AASHTO T277 and ASTM C1202 give an indication of a cementitious material’s ability to resist the penetration of chloride ions, but the measured values should be interpreted with caution. Because the electrical current is measured, the electrical resistivity and permeability of the specimen will influence test results. To accurately predict chloride-ion permeability, the results of this test procedure should be correlated with the results of the long-term ponding test procedure described in AASHTO T259 or ASTM C1543. These tests are not suitable for testing steel fiber-reinforced concrete or other materials that influ-ence the electrical conductivity of the material. Although the results are reported quantitatively, test values for properly conducted tests on the same material by different laborato-ries may differ by as much as 51 percent (ASTM C1202).

ASTM C642 is used to determine absorption after immersion, absorption after immersion and boiling, dry bulk density, bulk density after immersion, bulk density after immersion and boiling, apparent density, and volume of permeable pore space or voids. Boiling may result in increased values of absorption and bulk density. This method can provide an indirect indication of the permeability of cementitious paste repair materials. Permeable pore space data from this method should be supplemented by the other methods discussed in this section to provide a true indication of permeability. The volume of the permeable void result is affected by the material’s porosity and damage to applied materials, such as cracking.

3.6.3 Alkali-aggregate reactions—Some aggregates are susceptible to deleterious expansive reaction with other components of the repair material, particularly with alkali in portland cement or chemicals introduced by the environ-ment. These aggregates can be identified based on previous service records or with one or more of the test methods described herein. It is preferable not to use reactive aggre-gates in environments where deleterious reactions could occur. If they are used, steps should be taken to avoid the deleterious reactions, such as modifying the repair mate-rial mixture composition or protecting the material from the environment. Protection from the environment can be provided by water-repellent and waterproofing coatings. Relative humidity greater than 85 percent in the concrete has been shown to promote alkali-aggregate reactions (Stark 1991).

The five test methods used to evaluate alkali-aggregate reactivity potential are:

1) ASTM C2272) ASTM C12603) ASTM C12934) ASTM C2895) ASTM C295ASTM C227, C1260, and C1293 all test the potential for

alkali reactivity between a particular aggregate and cement by storing samples of the combined materials in prescribed conditions and monitoring the change in length over time. In ASTM C227, the specimens are conditioned for 1 day, then supported over water in a sealed container at 100°F (38°C) for 12 days, and then stored at 73°F (23°C) for 1 day. In ASTM C1260, the specimens are conditioned for 2 days and then stored in a 1 N solution of sodium chloride for 14 days. The ASTM C1293 procedure is similar to that of ASTM C227, except that ASTM C1293 is intended to assess the effects of a pozzolan or slag in the specimen and the dura-tion of the test is 12 or 24 months. Materials with a length change of 0.05 percent or less are considered to have a high resistance to alkali-silica attack. ASTM C289 evaluates the reactivity of a particular aggregate by soaking the aggregate for 24 hours in a 1 N sodium hydroxide solution at 176°F (80°C). This method may not reliably predict the reactivity in concrete because the aggregates are tested in an alkali solution that is much different than in a concrete environ-ment, and should only be used for initial screening. ASTM C295 describes a petrographic procedure to characterize aggregates, identify aggregate types that are susceptible to alkali-aggregate reaction, and identify other deleterious properties of aggregates that can harm the concrete. Addi-tional discussion is found in ACI 221.1R and CSA A864.

3.6.4 Electrical resistivity—Corrosion is an electrochem-ical process. Therefore, if corrosion of embedded reinforcing steel is a concern, the electrical resistivity of the repair mate-rial is important, particularly for concrete replacements. Depending on the method of corrosion protection, a high or low value of this property may be desirable. Cathodic protec-tion systems, both impressed current and galvanic, generally require a lower value (approximately 300 ohm-cm) than the higher resistance value (1000 to 15,000 ohm-cm) desired in

Fig. 3.6.2b—AASHTO T277 and ASTM C1202 rapid chlo-ride permeability test: (a) test specimen; and (b) test in progress. (Courtesy of BASF Construction Chemicals, LLC.)





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conventional repairs (ASTM C1202). Refer to ACI 222R for further guidance. One indication of the resistivity of a repair material can be obtained from AASHTO T277 or ASTM C1202, as discussed in 3.6.2.

3.6.5 Abrasion resistance—Many repairs are subjected to abrasion in service. The abrasion can be from wind-blown debris, mechanical contact, or other sources. In particular, vehicular traffic and abrasion on hydraulic structures are aggressive types of abrasion. Repair materials should have suitable abrasion resistance for their service environment.

Four test methods are used to measure abrasion resistance:1) ASTM C7792) ASTM C9443) ASTM C4184) ASTM C1138MThese procedures measure surface resistance to different

types of abrasive actions. The tests are intended to deter-mine variations in the surface properties of concrete affected by mixture proportions, finishing, and surface treatment. They provide relative results between concretes but are not intended to provide a quantitative measure of the service life that may be expected from a specific surface.

ASTM C779 includes three procedures for determining the relative abrasion resistance of horizontal concrete surfaces based on depth of wear measurements. The three procedures differ in the type and degree of abrasive force they impart. Procedure A uses revolving disks with No. 60 silicon carbide grit that slide and scuff the concrete surface in a circular path. Procedure B uses dressing wheels riding in a circular path to abrade the concrete surface by impact and sliding friction. Procedure C uses rapidly rotating ball bearings in a race and under load to impart high-contact stresses, impact, and sliding friction to a concrete surface. Procedures A and B are run for 30 minutes when depth-of-wear readings are taken. Procedure C is run for 20 minutes or until a maximum wear depth of 0.12 in. (3.0 mm) is reached, with depth of abrasion measurements taken at least every 50 seconds. A test-in-progress is shown in Fig. 3.6.5. ASTM C944 is a test procedure where rotating cutters are applied to the concrete surface under a normal load of 22 or 44 lb (98 or 197 N) for three 2-minute periods. After each period, the weight loss of the specimen is determined.

ASTM C418 determines the abrasion-resistance charac-teristics of a concrete surface when subjected to the impinge-ment of air-driven silica sand using specified pressures, abrasive, and sandblasting equipment. Wear is determined volumetrically by filling the eroded cavity with a weighed quantity of putty. Comparative data between samples make it possible to rank abrasion resistance.

ASTM C1138M determines the relative resistance of concrete to underwater abrasion by simulating the abrasive action of waterborne particles such as silt, sand, gravel, and other solids. A 12 in. (300 mm) diameter by 4 in. (100 mm) tall test specimen is immersed 6-1/2 in. (163 mm) under water in a steel pipe. A rotating mixing paddle propels 70 Grade 1000 chrome-steel grinding balls, graded from 1/2 to 1 in. (13 to 25 mm) in diameter, at the sample surface. The

loss in mass is measured every 12 hours for a test period of 72 hours.

3.6.6 Resistance to chemical attack—Repair materials may be exposed to various chemicals in the service environ-ment. The long-term performance of the repair may depend on the proper selection of repair material and possibly on the use of an appropriate protective barrier. In many environ-ments, it may be important that the barrier be free of pinholes and holidays. Some repair materials may be damaged by a solvent-based barrier material. Detailed discussions of resis-tance to chemical attack are found in ACI 201.2R and PCA IS001 (Portland Cement Association 2007). In addition, a number of materials and solutions that are aggressive to concrete are listed in PCA IS001.

Aggressive chemicals can be loosely categorized as sulfates, inorganic and organic acids, alkaline solutions, salt solutions, solvents, and others.

Portland-cement mortar and concrete could experience a destructive expansive reaction when exposed to sulfates in groundwater or from other sources. ASTM C1012 evalu-ates the susceptibility of a cement mortar to sulfate attack by measuring the length change of a specimen over a period of 12 or 18 months while immersed in a sodium sulfate solution. The length comparator setup is shown in Fig. 3.2.1. Results are presented as percent length change at a given time of exposure. A material with a length change of 0.05 percent or less is considered to have high resistance to sulfate attack.

Acids are those materials with a pH below 7. They react with concrete and cement-based repair materials to form compounds that are water-soluble. Acids could also attack

Fig. 3.6.5—Measuring depth of wear during ASTM C779 abrasion test. Note disks (Procedure A) and dressing wheels (Procedure B) at top of machine. (Courtesy of CTL Group.)





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carbonate aggregates (limestone and dolomite). The effect of an acid is influenced by its concentration and chemical type, length of exposure, and temperature.

Alkaline solutions are those materials with a pH above 7. They are less aggressive than acids to portland-cement-based materials, but may react with other types of repair materials, depending on concentration, chemical type, tempera-ture, and the chemical composition of the repair material. Hydrated cement is alkaline, so most repair materials have at least some resistance to high-pH environments. Strong concentrations of sodium or potassium alkalis can induce alkali-silica reactions if susceptible aggregates are present.

Salt solutions can be slightly acidic or alkaline and, depending on the chemical composition, might attack concrete and concrete repair materials. Salt scaling is one form of chemical attack (Taylor 1990).

Several solvents are aggressive to polymeric materials and others slowly attack concrete. A more common problem is previous solvent contamination of the substrate concrete, which can adversely affect the bond of the repair material.

Other chemicals are aggressive to concrete and repair materials. Extremely soft or purified water could slowly leach the calcium from cement-based concrete and mortar.

3.7—Chemical composition3.7.1 Repair material chemistry—Repair products are

sometimes independently tested for comparison with competitive products, for product approval purposes, or to ensure the chemical formulation is not significantly changed.

3.8—Summary tablesAs concrete mixtures may include different types of port-

land cement, different gradations and types of fine and coarse aggregates, and different mixture proportions, the replace-ment concrete properties can vary significantly. Table 3.8a presents a brief summary of the test procedures described in detail in this chapter, including typical test values for basic portland-cement replacement concrete.

Where recommended test values are given in Table 3.8a, they represent the minimum values recommended by Committee 546 for typical repair materials used in successful repairs and are not necessarily applicable for all conditions. For most of the tests, Committee 546 has indicated if the test is recommended for evaluating repair materials. Some recommended test methods are not appropriate for certain repair materials or repair applications. Some are useful for comparing different materials.

Basic portland-cement replacement concrete may be modified in a variety of ways:

a) Substituting various hydraulic cements;b) Including chemical admixtures;c) Including mineral admixtures such as fly ash, silica

fume, and natural pozzolans;d) Including polymer modifiers;e) Including or substituting slag cement;f) Including fiber reinforcement;g) Substituting a polymer for portland cement;

h) Omitting the coarse aggregate to create various replace-ment mortars.

There are an unlimited number of variations for basic portland-cement concrete. In general, the same test proce-dures are used to evaluate most replacement and overlay materials. Table 3.8b lists principle material properties that may change when additives and substitutions are made to basic portland-cement concrete. Although some typical values are presented, numerical values vary greatly and only trends in material properties are presented. For addi-tional information, refer to ACI 225R for types of hydraulic cements, the influence of admixtures, and the influence of cement on properties of concrete; ACI 212.3R for chemical admixtures; ACI 232.2R for fly ash; ACI 234R for silica fume; ACI 232.1R for natural pozzolans; ACI 548.3R for polymer-modified concrete; ACI 233R for slag cement; ACI 544.1R for fiber reinforcement; and ACI 548.1R for polymer concrete.

CHAPTER 4—CONCRETE REPLACEMENT AND OVERLAY MATERIAL SELECTION

Every repair application places different demands on repair materials. Repair materials, therefore, should have suitable properties to meet the demands throughout the intended life of the repair. All repair materials have limitations, and the material specifier and user should select the materials with the highest likelihood of good, long-term performance. Table 3.8a provides a summary of the test methods available for comparing the properties of replacement and overlay materials. Material cost is often the deciding factor among comparable materials. While life-cycle cost is a better comparator between alternate repair materials, life-cycle costs are often unavailable or approximate at best, leaving the repair specifier with a choice based on the initial cost of the materials and their application for materials with antici-pated similar durability.

Many of the proprietary products for concrete repair that are available commercially are blends of several types of materials. Because these materials are proprietary, a list of their ingredients is usually unavailable to the specifier, except possibly in terms of generic materials. Prior experi-ence with specific products and the results of independent testing of products are useful in evaluating such products. In this regard, many State and Canadian Provincial Depart-ments of Transportation (DOT) maintain lists of approved proprietary concrete repair materials. These lists provide useful input to the specifier and user of products that have been found satisfactory by those agencies. Because repair products may be reformulated and their physical properties altered over time, some DOTs, such as the Alberta Transpor-tation, Canada, periodically update their approval lists based on regular retesting. The American Association of State Highway and Transportation Officials (AASHTO) main-tains a Product Evaluation List Management System, APEL, (http://www.ntpep.org/Pages/APEL.aspx) (accessed March 28, 2014), where the findings of evaluations of new, propri-etary, or both new and proprietary engineered transportation products are voluntarily posted.





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Table 3.8a—Summary of available test methods and test values for portland-cement replacement concreteDescription Test method Typical value Recommended value* Recommended test

3.2—Volume stability

Length change – concrete† ASTM C1570.02 percent (expansion) to–0.05 percent (shrinkage)

Less negative than (–0.05 percent) (shrinkage)

No; curing and comparator reading regi-mens not representative of field condi-tions of repair mortars and concretes.

Drying shrinkage – mortar† ASTM C596 0.05 to 0.15 percent < 0.10 percent YesRestrained expansion ASTM C806 0.06 percent Refer to 3.2 Yes

3.3.2—Modulus of elasticityASTM C469 1,000,000 to 5,500,000 psi (6.8 to 38 GPa)

Refer to 3.3.3Yes

ASTM C580 300,000 to 3,000,000 psi (2.1 to 21 GPa) Yes

3.3.3—Thermal expansion†

ASTM C531 0.000014/°F (0.000025/°C)

Refer to 3.3.3

YesASTM D696 0.000014/°F (0.000025/°C) Yes

USACE CRD-C 39 0.000006/°F (0.0000108/°C) YesASTM C884 Qualitative test Yes

3.3.4—CreepASTM C512 0.000000001/psi (0.000000007/KPa)

Refer to 3.3.4Yes

ASTM C1181 — Yes3.3.5—Bond strength

Slant shear bondASTM C882 1 day – 400 to 1000 psi (2.8 to 6.9 MPa)

7 days – 1000 to 1800 psi (6.9 to 12 MPa)28 days – 2000 to 3000 psi (14 to 21 MPa)

Committee 546 does not have a recommended value for this test.

No; results are highly dependent on compressive strength of substrate and

roughness of bonding surface.ASTM C1042

Direct tensile bond

ASTM C14041 day – 70 to 150 psi (0.48 to 1.0 MPa)7 days – 150 to 250 psi (1.0 to 1.7 MPa)28 days – 250 to 300 psi (1.7 to 2.1 MPa)

Refer to 3.3.5

YesCSA A23.2-6B YesASTM C1583 Yes

ICRI 210.3 Yes

Direct shear bond MDOT1 day – 150 to 300 psi (1.0 to 2.1 MPa)7 days – 300 to 400 psi (2.1 to 2.8 MPa)28 days – 400 to 600 psi (2.8 to 4.1 MPa)


No, test apparatus not commonly avail-able and test not commonly performed.

3.3.6—Compressive strength† ASTM C39 28 days – 3000 to 10,000 psi (21 to 70 MPa)Similar to substrate

YesASTM C109 28 days – 4000 to 12,000 psi (28 to 85 MPa) Yes

3.3.7—Tensile strength†

ASTM C307 — — YesASTM C496 400 to 1800 psi (2.8 to 12 MPa) > 400 psi (2.8 MPa) Yes

USACECRD-C 164

200 to 600 psi (1.4 to 4.1 MPa) > 400 psi (2.8 MPa)Committee 546 does not have a recom-

mendation for this test.

3.3.8—Flexural strength†

ASTM C78 28 days – 1200 psi (8.3 MPa)Committee 546 does not have a recommended value for this test.

YesASTM C293 28 days – 500 to 1200 psi (3.4 to 8.3 MPa) YesASTM C348 28 days – 1500 psi (10 MPa) YesASTM C580 7 days – 2400 psi (17 MPa) Yes

3.6.1—Resistance to freezing and thawing† ASTM C666 28 days – 80 to 100 DF at 300 cycles > 80 DF Yes

Scaling resistance

ASTM C67228 days — 0 to 5 visual rating at 50 to 300

cycles< 2 Yes

ASTM C672 modified by ICRI

320.2R


Yes

3.6.2—Permeability

90-day pondingAASHTO T259

0.42 percent at 0.5 in. (13 mm)0.15 percent at 1.0 in. (25 mm)


Yes

ASTM C1543 No

Rapid chloride permeabilityAASHTO T277

28 days – 4000 to 5000 C 4000 C‡ YesASTM C1202 Yes

Absorption after immersion ASTM C642 4 to 6 percent < 6 percent YesVolume of permeable pore space

ASTM C642 5 to 12 percent < 12 percentCommittee 546 does not have a recom-


3.6.3—Alkali-aggregate reaction

ASTM C227 Refer to 3.6.3 < 0.1 percent YesASTM C1260 Refer to 3.6.3 < 0.1 percent YesASTM C1293 Refer to 3.6.3 < 0.1 percent Yes

ASTM C289 Refer to 3.6.3 Refer to 3.6.3No; may not reliably predict aggregate

reactivity in concrete.ASTM C295 Refer 3.6.3 Refer to 3.6.3 Yes

3.6.5—Abrasion resistanceASTM C779 Procedure A

0.004 to 0.1 in. (0.1 to 2.5 mm) at 30 min.0.008 to 0.2 in. (0.2 to 5.1 mm) at 60 min.

Refer to 3.6.5 Refer to 3.6.5

3.6.6—Sulfate resistance ASTM C1012 0 to 0.2 percent < 0.1 percent Yes*The recommended values are minimum values recommended by Committee 546 for typical repair materials used in successful repairs and are not necessarily applicable for all conditions.†Material properties based on a specific modification to a test method discussed in this chapter.‡Committee 546 recommends that test results be correlated with test results from AASHTO T259 or ASTM C1543.





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Table 3.8b—Summary of changes in material properties of basic portland-cement replacement and overlay concrete when adding various admixtures, polymer modifiers, and pozzolans; using other cements; or removing coarse aggregates

Modification to basic portland-cement concrete Effects on propertiesVarious hydraulic cements (slag cement is discussed separately

below)

Reduce heat of hydration; reduce set time; increase early strength; reduced drying shrinkage; expansive or shrinkage compensating; improve sulfate resistance.

Chemical admixtures

Air-entrainingImproved workability; improved durability in freezing-and-thawing, deicing, sulfate, and alkali-reactive environments; reduced compressive strength.

Accelerating Accelerated set and early-strength development; increased creep and drying shrinkage.Water-reducing, mid-range

water-reducingReduce water content at least 5 percent (5 to 10 percent for mid-range); reduced permeability; increased strength.

Water-reducing and set-retarding

Reduce water content at least 5 percent and delay set time;reduced permeability; increased strength.

High-range water-reducingReduce water content by at least 12 to 40 percent, increase slump, decrease placing time, and increase flowability; reduced permeability; increased strength.

Flowing concrete Slump greater than 7-1/2 in. (190 mm) while maintaining cohesive nature (ASTM C1017); reduced permeability.

Self-consolidating concreteReduced construction time and labor; improved formed surface finish; increased strength, shrinkage, and creep; reduced permeability and improved durability.

Very high early strengthReduced set/working time; Strategic Highway Research Program (SHRP) SHRP-C-363 defines very high-early strength material as 2000 psi (13.8 MPa) minimum compressive strength 6 hours after mixing; durability factor of 80 percent after 300 freezing-and-thawing cycles in accordance with ASTM C666, Procedure A.

Extended set control Used to stop or severely retard cement hydration process.

Shrinkage-reducingIncreased set time; reduce drying shrinkage by 30 to 50 percent; reduced strength, thermal cracking, and slab curling; increased susceptibility to freezing-and-thawing deterioration.

Corrosion-inhibitingSignificantly reduce rate of steel corrosion and extend time of onset of corrosion; reduced or increased compressive strength; may distort results of ASTM C1202 and AASHTO T277.

Lithium May affect set/working time; minimize deleterious expansion from alkali-silica reaction.Permeability-reducing: For non-

hydrostatic conditions.Water-repellent surface, reduced water absorption;Can affect finishing properties, consistency, compressive strength, freeze and thawing resistance, and shrinkage.

Permeability-reducing: For hydrostatic conditions.

Reduced permeability, increased resistance to water penetration under pressure;Can affect finishing properties, consistency, compressive strength, freezing-and-thawing resistance, and shrinkage.

BondingIncreased bond, tensile, and flexural strength; decreased compressive strength; latex may cause excessive entrained air; some polymers may decompose and sofn in the presence of moisture.

Rheology- and viscosity-modi-fying; Anti-washout

Increased cohesiveness; reduced segregation and bleeding; used as pumping aid, for concrete to be pumped underwater; reduced loss of cementitious material due to washout.

Supplementary cementitious materials

Fly ashReduced water demand; reduction in portland cement; increased air-entraining admixture demand; improved workability; slower rate of reac-tion; reduced permeability and alkali-aggregate reactivity; improved sulfate resistance; discoloration of concrete.

Silica fumeIncreased water demand; increased air-entraining admixture demand; decreased workability;increased cohesiveness; reduced bleeding; increased plastic shrinkage cracking; darker color; increased compressive and bond strength; increased electrical resistivity; reduced perme-ability; increased resistance to alkali-silica reaction; sulfate and chemical attack; increased abrasion resistance.

Natural pozzolansImproved workability and finishing; reduction in portland cement; increased cohesiveness; increased set time; reduced permeability; increased strength at later ages; improved resistance to alkali-silica reaction in minimum dosages; too little natural pozzolan may actually increase detrimental effects of alkali-silica reaction; improved resistance to sulfate attack.

Slag cementImproved workability; increased set time; reduced early rate of heat generation; reduced strength at early ages; increased strength at later ages; lighter in color; reduced permeability and potential expansion due to alkali-silica reaction; improved sulfate resistance.

Polymer modifiersExcessive amounts of entrained air unless antifoam agent is used; improved workability; increased set time; increased tendency for plastic-shrinkage cracking; lower compressive strength; increased bond and tensile strength; reduced permeability; improved resistance to freezing and thawing; may improve impact strength and abrasion resistance.

Fiber reinforcement

Steel fibersReduced slump and workability; tendency for fibers to ball; increased number of smaller-width shrinkage cracks;improved post-cracking ductility; increased compressive, direct tension, shear and torsion, flexural, and flexural fatigue strength; improved toughness and resistance to flexural impact loading.

Synthetic fibersReduced workability; reduced average width of shrinkage cracks; improved post-cracking ductility; improved resistance to impact, fatigue strength, and flexural toughness.

Polymer concreteIncreased safety concerns during construction; typically less contractor familiarity with materials and installation procedures; reduced cure time; reduced weight; increased tensile, flexural, compressive, and bond strengths; reduced modulus of elasticity; increased coefficient of thermal expansion; reduced permeability; improved chemical resistance.

Portland-cement mortarIncreased drying shrinkage; may be modified by substituting various hydraulic cements or polymers; or including chemical admixtures, mineral admixtures, polymer modifiers, slag cement and fiber reinforcement, or both; effects on properties are similar to those discussed for concrete above.





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The materials most commonly used for concrete replace-ments and overlays are:

a) Portland or blended cement-based concrete;b) Portland or blended cement-based, silica-fume concrete

(silica-fume concrete), sometimes with fiber reinforcement;c) Portland or blended cement-based, polymer-modified

concrete;d) Magnesium-ammonium-phosphate-cement concrete

(MAPCC);e) Polymer-based concrete (polymer concrete);f) Portland or blended cement-based mortar (cement

mortar);g) Portland or blended cement-based, silica-fume mortar

(silica-fume mortar), sometimes with fiber reinforcement;h) Portland or blended cement-based, polymer-modified

mortar;i) Magnesium-ammonium-phosphate-cement mortar

(MAPCM);j) Polymer-based mortar (polymer mortar).Before any repairs are undertaken, it is essential to follow

the assessment steps (1.2) to achieve satisfactory results.

4.1—ConcreteConcrete is composed of portland or blended cement, fine

and coarse aggregates, and water. Admixtures are frequently used to entrain air, accelerate or retard hydration, improve workability, reduce mixture water requirements, increase strength, or alter other freshly mixed and hardened prop-erties of concrete. Pozzolanic materials, such as some fly ashes, may be used in conjunction with portland cement for economy or to affect specific properties, such as reduced early heat of hydration, increased later-age strength develop-ment, reduced permeability, or increased resistance to alkali-aggregate reaction and sulfate attack.

Concrete proportions should be carefully selected to provide the necessary characteristics for the specific appli-cation, such as workability, density, strength, durability, or resistance to deterioration under the expected exposure conditions (ACI 211.1). To minimize drying shrinkage, repair concrete should have the lowest possible water content, the smallest paste volume, and the largest coarse aggregate size and highest coarse aggregate content that are feasible. Shrinkage-reducing admixtures or shrinkage-compensating cements may also be considered when propor-tioning a concrete mixture. According to ACI 201.2R, frost-resistant, air-entrained, normalweight concrete should have a maximum w/cm of 0.45 for thin sections and 0.50 for all other structures. Mixing, transporting, placing, and curing should follow the guidance of ACI 213R, ACI 304R, ACI 304.1R, ACI 304.2R, ACI 304.6R, and ACI 308R.

Many properties of rebuild and overlay concrete such as modulus of elasticity and coefficient of thermal expansion are typically of similar magnitude to those of the substrate concrete. Entrained air can be incorporated into the repair concrete to provide resistance to freezing and thawing. The quality of concrete, particularly its permeability and enhanced corrosion protection of embedded reinforcement, is frequently improved by reducing the w/cm to 0.40 or less in

conjunction with using a high-range water-reducing admix-ture. This type of concrete is called low-w/cm concrete.

A concrete or mortar repair will usually contract due to plastic and drying shrinkage, cooling, and autogenous volume changes. If this contraction is restrained through bond to a stable substrate, tensile strains develop in the repair material. When these strains exceed the tensile strain capacity of the hardened concrete, cracks develop. This cracking may require further repair or future maintenance because of the possibility of ingress of deleterious materials, loss of bond to substrate, edge spalling of the crack under traffic conditions, or aesthetic objections. Drying shrinkage can be minimized with appropriate mixture proportioning, such as maximizing the size of coarse aggregates compatible with the depth of the application. Plastic shrinkage cracking can be minimized with timely application of curing mate-rials. Some admixtures, such as accelerating admixtures, may increase the repair material shrinkage and the resulting cracking. While properly proportioned concrete has good durability, other repair materials, such as polymer concrete and magnesium-ammonium-phosphate concrete, are more resistant to certain types of chemical attack. Ready mixed concrete being placed is shown in Fig. 4.1.

4.2—Silica-fume concreteSilica fume, a by-product of the ferrosilicon industry, is

a highly pozzolonic material used to enhance mechanical and durability properties of concrete. Silica-fume concrete is conventional concrete with silica fume and a high-range water-reducing admixture added. Typical silica fume dosage ranges from 5 to 10 percent replacement of cement by mass.

Silica-fume concrete has properties similar to, but gener-ally stronger than, conventional concrete, including higher bond strength. It also has lower permeability and provides increased protection against corrosion of embedded rein-forcement. It is more resistant to attack by some chemicals and to the abrasive action of waterborne solids in hydraulic structures with high flow rates in confined areas (ACI 234R).

Silica-fume concrete is more cohesive and has less bleed water than conventional concrete. Consequently, it is more difficult to finish and, without proper protection during placement and timely curing, more susceptible to plastic

Fig. 4.1—Ready mixed concrete being placed. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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shrinkage cracking than concrete with a moderate w/cm. The potential for cracking of restrained concrete repairs, with and without silica fume, should be recognized. Any variations in concrete materials, mixture proportions, and construction practices that minimize shrinkage or reduce temperature differentials should be considered. Cracking due to restrained shrinkage or temperature movements may necessitate further repair. Silica-fume concrete has a gray to black color and may not blend in well with the appearance of the adjacent existing concrete (ACI 234R).

4.3—Polymer-modified concretePolymer-modified concrete is a portland or blended

cement-based concrete with polymer modifiers added. Typical polymer modifiers include styrene butadiene, acrylic, vinyl acetate-ethylene, styrene acrylic, and epoxy. Generally, the polymer modifier is added at the rate of 10 to 20 percent by mass of cement. The w/cm for concrete with a latex modifier is normally 0.30 to 0.40, including the water in the latex, and 0.25 to 0.35 for concrete with an epoxy modifier.

Compared with conventional concrete, polymer-modified concrete has increased flexural and bond strength, reduced permeability, and provides increased protection against corrosion of embedded reinforcement (Mindess and Young 1981). Polymer-modified concrete is more difficult to place and finish than conventional concrete, and has a relatively short working time—approximately 15 to 30 minutes—before the dispersed polymer begins to coalesce. Although it can still be worked after the polymer has begun to coalesce, the beneficial properties of the polymer modification will be significantly reduced. The mixture should never be retem-pered. The manufacturers’ instructions may not recognize the constructibility limitations as described above (ACI 548.1R).

Because of the short working time, polymer-modified materials should be batched and mixed on site. When a concrete mixer is used on small repairs, batch sizes should be restricted to quantities that can be placed and finished within the working time. A longer mixing time may result in a marked increase in total air content, which can result in a significant reduction in the compressive strength. Because the manufacturer may or may not add a defoaming agent to the polymer, they should be consulted for the recommended mixing procedures and times. Mobile mixers are frequently used where large quantities of polymer-modified concrete are required. It is recommended that air content tests be performed.

Polymer-modified concrete is normally moist cured for 1 to 2 days, followed by air-drying. While the drying shrinkage of concrete is not increased by the addition of polymers, polymer-modified concrete is more sensitive to plastic shrinkage if curing material is not applied as soon as practical. Concrete modified with styrene butadiene or some epoxies will exhibit color change when exposed to ultravi-olet light (ACI 548.1R and 548.3R).

4.4—Magnesium-ammonium-phosphate-cement concrete (MAPCC)

MAPCC is concrete in which magnesium-ammonium-phosphate is substituted for the portland or blended cement. It has excellent bond strength, low drying shrinkage, rapid strength gain, and low permeability (Popovics and Rajen-dran 1987; Popovics et al. 1987).

Because the binder is not based on portland cement, surface preparation, application, and curing requirements are different. MAPCC should not be applied over a carbon-ated substrate; that is, one with a pH that is no lower than 10 because low bond strength may result. The pH of the substrate should be tested before application. MAPCC hardens rapidly and generates ammonia and large quantities of heat during curing. Aggregates are used for large or deep placements to control the exothermic reaction; however, the aggregates should not contain carbonate minerals to avoid an undesirable chemical reaction with the binder. Placement procedures should avoid trapping ammonia gas within the MAPCC. The only necessary curing is a light application of curing compound in extreme drying conditions, such as direct sunlight, strong winds, high temperatures, or low humidity. Moist curing is not recommended.

MAPCC is used for specialized applications. The rapid strength gain and volume stability make this repair mate-rial a good option for fast-turnaround applications and for long, slender repairs. Hot and cold weather formulations are available. MAPCCs are excellent for cold weather applica-tions. As long as the mixing water is above freezing, the exotherm as the product sets, as well as the ammonia in the product, prevent product freezing. Lower temperatures will slow strength development. Typically, the drying shrinkage of MAPCC is less than that of other rapid-setting repair materials. Contamination of MAPCC with other hydraulic cement or contaminated mixing water may result in low strength, rapid stiffening, and poor performance. The speci-fier and user should consult with the material manufacturer for specific material properties to determine the applicability and use of the material.

4.5—Polymer concretePolymer concrete is one in which an organic polymer

serves as the binder. Polymers typically used include epoxy, polyester, furan, vinyl ester, or methyl methacrylate. Portland cement, however, is sometimes used as a filler (ACI 548.1R).

Polymer concrete may have low shrinkage as it cures, good bond strength to the substrate concrete, high tensile and flexural strength, low permeability, increased protec-tion against corrosion of embedded reinforcing steel, and good resistance to chemical attack (ACI 548.1R). It also sets quickly, reducing the down time of the repair area. Because of the rapid setting time, however, it should be batched on site (Concrete Society 1976).

The cure time of polymer concrete is directly related to the polymer type and other agents used, concrete substrate temperature, air temperature, and temperature attained by the mixed polymer. While polymer concrete generally sets much more quickly than portland-cement-based concrete,





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low temperatures or an inappropriate polymer selection may significantly increase the set time. Conversely, high temper-atures may reduce the working time below acceptable levels.

Polymer concrete has a significantly higher coefficient of thermal expansion than the substrate concrete, and in situa-tions where the temperature of the service environment is not controlled, the aggregates in the polymer concrete mixture should be carefully graded and proportioned to minimize the distance between the aggregate particles, decreasing the coefficient of thermal expansion (Sprinkel 1983); preplacing the aggregates results in tightly packed aggregate. It is desir-able to place polymer concrete near the midrange of service temperatures to reduce cracking and internal stress caused by long-term thermal stress cycles. In many instances, however, some cracking should be anticipated, and further repair may be needed.

Polymer concrete can also have a modulus of elasticity significantly different from the substrate concrete. Many polymer concretes have a lower modulus of elasticity that can be beneficial in reducing stresses that develop from other differences in the material properties, particularly the coefficients of thermal expansion. This, however, may also make this material inappropriate for structural repairs.

Most polymers used in polymer concrete soften when heated. Their mechanical properties change significantly beyond their heat deflection temperatures (HDT). Although the HDT varies for each formulation, for those systems used in concrete construction, it generally ranges from 60 to 160°F (16 to 71°C). The polymer formulation may need to be adjusted to achieve proper curing at higher temperatures. Some polymers may soften when exposed to high tempera-tures in fires, or solvents in surface coatings and sealers.

General construction workers usually are not experienced in working with polymer concrete and will require special training. Moisture in the aggregates or on the concrete surface adversely affects polymer concrete. Special clean-up solvents are necessary; these solvents may be hazardous materials that require special disposal procedures. Special safety equipment and precautions may be necessary due to fumes and flammability of some materials. Polymer concrete usually does not blend in with the appearance of the adjacent existing concrete (ACI 548.1R).

Because the properties of polymer concrete are signifi-cantly different from those of the substrate concrete, and because polymer concrete has higher material and installa-tion costs, it is commonly used only for repairs with unusual requirements or in demanding environments where the enhanced properties of polymer concrete are desired.

4.6—Mortars4.6.1 Cement mortar—Cement mortar generally consists

of portland cement, fine aggregate, and water, and may contain other ingredients such as admixtures. Cement mortar is frequently mixed in small batches at the site; therefore, it may be difficult to maintain uniform characteristics. Because of the absence of coarse aggregate, higher water volume, higher cement content, and the higher paste-aggregate ratio, cement mortar shrinks more than concrete, often resulting

in more cracking, and further repair may be needed. Water-reducing admixtures, expansive agents, and other modifiers are sometimes used to reduce shrinkage. The coefficient of thermal expansion is dependent on aggregate content, type, and size, and on the cement content; therefore, some differ-ences in thermal properties between mortars and concrete are likely (Neville 1996).

4.6.2 Prepackaged repair mortars—Prepackaged repair mortars are also commercially available. Hydraulic cement and other ingredients, including fine aggregate, dry admix-tures, and, frequently, proprietary ingredients, are blended in a production plant and then packaged, commonly into several sizes of containers. Prepackaged materials may offer more consistent and predictable work-site performance. Addi-tional potential advantages include, but are not limited to:

a) Better mixture and quality control at the work site—Commonly, only water is added at the work site.

b) Quality control—During production, most manu-facturers inspect and test their materials to confirm that the material meets their product specifications before the material leaves the plant. Some manufacturers are certi-fied by the International Organizations for Standards (ISO), which means that their production processes and procedures are documented and consistent with this documentation. Note, however, that ISO certification indicates a product is produced consistently, but does not imply that it is a good product.

c) Performance-based materials—Mixture proportions, often including admixtures or proprietary ingredients, are designed to meet specific needs, such as approval for contact with potable water (NSF certification), resistance to freezing and thawing, fast set, abrasion resistance, and low shrinkage.

d) Data readily available—Performance test results are usually available from the manufacturers. Product data sheet information provides benchmarks for the applicator and specifier to compare with on-site testing; however, differ-ences in test methods may create difficulties comparing properties between materials. Modified test procedures can also produce misleading performance expectations.

e) Those mixtures that can be extended with coarse aggregate to create concrete for repairing deeper sections—The extended mixtures will have properties more similar to concrete rather than mortar.

These prepackaged materials have a limited shelf life, and generally should not be used after the expiration of this limit.

4.6.3 Silica-fume mortar—Silica-fume mortar is cement mortar with silica fume added. Silica fume increases the bond strength and cohesiveness of mortar. Silica-fume mortar also has increased compressive and tensile strength, reduced permeability, increased electrical resistivity charac-teristics, and is also more resistant to chemical attack. Again, the absence of coarse aggregate causes increased shrinkage and greater tendency to crack.

The potential advantages outlined in 4.6.2 resulting from the use of prepackaged materials apply, plus the benefits associated with the incorporation of silica fume into a repair mortar. Site-added silica fume may be difficult to adequately disperse.





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4.6.4 Polymer-modified mortar—Polymer-modified mortar consists of cement mortar with a polymer modi-fier added. Compared with cement mortar, polymer-modi-fied mortar has excellent bond strength and cohesiveness, improved resistance to freezing and thawing, reduced permeability, increased electrical resistivity, and improved resistance to chemical attack. As with any mortar, increased shrinkage and cracking should be expected because of the absence of coarse aggregate and higher water and cement contents. Refer to 4.3 for further discussion of the effects of using a polymer modifier.

Prepackaged repair mortars containing a dry polymer are widely used. The potential advantages of prepackaged mate-rials are reviewed in 4.6.2.

Polymer may also be introduced through a second compo-nent as a liquid dispersion. This liquid, which contains polymer, water, and usually other additives, may be propor-tioned such that a specified volume of dispersion is mixed with a bag of prepackaged repair mortar to produce the repair material.

4.6.5 Magnesium-ammonium-phosphate-cement mortar (MAPCM)—MAPCM is mortar in which magnesium-ammo-nium-phosphate cement is used in place of portland cement, usually for specialized repairs such as those requiring rapid strength development, low shrinkage, application in below-freezing conditions, or very high bond strength. Refer to 4.4 for further discussion of its use.

4.6.6 Polymer mortar—Polymer mortar consists of a polymer binder and fine aggregate. Polymer mortar has good volume stability; relatively high compressive, tensile, and bond strengths; good resistance to freezing and thawing; low permeability; high electrical resistivity; and good chemical resistance characteristics. It also sets quickly, allowing the repair area to be returned to service in a short time.

As in the case of polymer concrete, the curing time of polymer mortar is directly related to the polymer and other agents used, as well as the concrete substrate temperature, air temperature, and temperature attained by the mixed polymer. While polymer mortar generally sets much more quickly than portland cement mortar, low temperatures or the selection of a polymer not intended for the specific repair application may significantly increase the set time.

The coefficient of thermal expansion and modulus of elas-ticity of polymer mortars can vary significantly from those of the substrate concrete. Differential strains between the repair mortar and substrate concrete, due to high exothermic reactions of some polymer compositions and differences in the coefficients of thermal expansion and moduli of elas-ticity, can cause cracking and even debonding of repairs (ACI 548.5R). Such cracking and debonding of repairs may require further repair.

Polymers used in polymer mortar soften when heated, such as when exposed to fire, and harden when cooled. Their mechanical properties change significantly beyond their heat deflection temperature (HDT). Although the HDT is different for each formulation, for those systems used in concrete construction it generally ranges from 60 to 160°F

(16 to 71°C). The polymer formulation may require adjust-ment to achieve proper curing at higher temperature.

Concrete construction workers are often inexperienced working with polymer mortar and will require special training. Moisture in the aggregate or on the substrate concrete surface adversely affects most polymer mortars. Special clean-up solvents are necessary. Special safety equipment and precautions may be necessary due to fumes and flammability of some materials. Polymer mortar usually does not blend in with the appearance of the adjacent existing concrete.

4.7—Types of concrete replacements and overlaysBased on typical repair thicknesses and common methods

for applying these materials, the following sections on concrete replacements and overlays are divided into three categories: 1) deep concrete replacements (including full depth replacement) and overlays; 2) shallow concrete replacements and overlays; and 3) thin overlays. For the purposes of distinguishing repair materials in this guide, deep concrete replacements and overlays are thicker than 3/4 to 1 in. (19 to 25 mm) and the repair materials include coarse aggregate; shallow concrete replacements and overlays are at least 1/16 to 1/8 in. (1.6 to 3.2 mm) thick and less than 3/4 to 1 in. (19 to 25 mm) thick, and the repair materials include fine aggregate only; and thin overlays are essentially thick coatings less than 1/16 to 1/8 in. (1.6 to 3.2 mm) thick. Table 4.7 provides a list of the materials commonly used for each repair category, along with a summary of the favorable and unfavorable properties of the various materials relative to repair categories.

It is usually difficult to achieve repairs that match the color and texture of the surrounding concrete. If the finished appearance is critical, special measures such as using white cement, tinting the repair mixture, using proprietary mate-rials, or applying a surface treatment should be considered.

4.8—Deep concrete replacements and overlaysDeep concrete replacements and overlays, defined for

the purposes of this guide as thicker than 3/4 to 1 in. (19 to 25 mm), are commonly constructed with repair materials that include fine and coarse aggregates. For deep concrete replacements and overlays, top surface (horizontal) applica-tions have different requirements from overhead and vertical applications (4.8.1 and 4.8.2).

4.8.1 Top surface (horizontal) applications—Materials used for deep concrete replacements and overlays in top surface applications include concrete, silica-fume concrete, polymer-modified concrete, MAPCC, and polymer concrete (Table 4.7). Concrete is the most commonly used mate-rial, primarily because of low cost, ease of construction, and adequate compatibility with the substrate concrete. Silica-fume concrete is only moderately more expen-sive than conventional concrete and is used for protective overlays and concrete replacements in applications where its enhanced properties are desirable. Polymer-modified concrete is used for protective overlays and, less frequently, for concrete replacements due to its higher cost and rela-





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tively short time before set. MAPCC is used for concrete replacements in situations where its cost premium is offset by special repair requirements, such as minimum downtime. Polymer concrete is used for concrete replacements and overlays in situations where its cost premium and differing properties from the concrete substrate are offset by special repair requirements, such as minimum downtime or resis-tance to chemical attack. Figure 4.8.1 shows a concrete overlay placement.

4.8.2 Vertical and overhead applications—For vertical and overhead applications, two primary concerns for repairs that are not formed are adherence to the substrate and cohe-siveness of the repair material during its application and curing to resist the pull of gravity. Also, because vertical and overhead concrete replacements are commonly not exposed to as aggressive an in-service environment as top surface replacements, their durability properties are often less crit-ical. An exception is in environments where reactive gasses,

Table 4.7—Repair material selection guide for concrete replacements and overlays and overlaysFavorable properties* Unfavorable properties* Remarks

1. Deep concrete replacements and overlaysA. Top surface applications

Concrete 2,3,7,8 1,9,10,11 Most commonly usedLow-w/cm concrete 2,3,7,8 1,11 Improved durabilitySilica-fume concrete 2,3,4,5,8,9,10,11 1,7 Significantly improved durability

Polymer-modified concrete 2,3,4,5,8,9,10,11 1,7 Significantly improved durabilityPolymer concrete 1,2,†4,5,8,9,10,11 1,2,†3,7,12 Significantly improved durability; used in special situations

MAPCC 1,2,3,4,5,6,9, 10 11Good durability, good dimensional stability, rapid setting. Used where quick application is desired. Not commonly

used for overlaysB. Vertical and overhead applications

Concrete 2,3,8 1,4,5 Form-and-cast, preplaced aggregate, and shotcrete applications

Silica-fume concrete 2,3,4,5,6,8,9,10,11 1,7 Form-and-cast and shotcrete applicationsPolymer-modified concrete 2,3,4,5,6,8,9,10,11 1 Form-and-cast and shotcrete applications

Polymer concrete 4,5,6,8,9,10,11 1,3,7,12 Form-and-cast and preplaced aggregate applicationsCement mortar 2,3 1 Shotcrete and occasionally trowel-applied applications

Silica-fume mortar 2,3,4,5,6,9,10,11 1,7 Shotcrete and occasionally trowel-applied applicationsPolymer-modified mortar 2,3,4,5,6,7,9,10,11 1 Trowel-applied applications and shotcrete

Polymer mortar 4,5,6,8,9,10,11 1,3,12 Trowel-applied applications2. Shallow concrete replacements and overlays

Cement mortar 2 1,3,8 Poor durability; used in relatively benign applicationsSilica-fume mortar 2,4,5,6,8,9,10,11 1,3 Improved durability; commonly used

Polymer-modified mortar 2,4,5,6,8,9,10,11 1,3 Improved durability; commonly used

Polymer mortar 4,5,6,8,9,10,11 1,2,3,12 Good durability; used in special situations or as the applica-tion gets thinner

MAPCM 1,2,3,4,5,6,9,10 11 Good durability, good dimensional stability, rapid setting3. Thin overlaysCement mortar — 1,3,8 Sometimes used

Silica-fume mortar 4,6,8,9,11 1,3 Good durabilityPolymer-modified mortar 4,6,8,9,11 1,3 Good durability

Polymer mortar 4,5,6,8,9,11 1,2,3,12 Good durability*Key code to favorable and unfavorable material properties:1 – Volume stability.

Mechanical properties:2 – Modulus of elasticity3 – Coefficient of thermal expansion4 – Bond strength5 – Tensile strength

Construction characteristics:6 – Cohesiveness7 – Ease of construction

External and chemical environment factors:8 – Resistance to freezing and thawing9 – Permeability10 – Electrical resistivity11 – Resistance to chemical attack12 – Low heat deflection, or glass transition, temperature†For polymer concrete, a lower modulus of elasticity than the substrate concrete’s is beneficial in relieving differential stresses between the repair material and the substrate concrete, but is undesirable for structural repairs.





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chemicals, and high humidity or water are present, such as in wastewater treatment plants, chemical plants, pulp and paper mills, and parking garages. Refer to 4.11 for further discus-sion of repairs in aggressive environments. Frequently, repair materials with improved bond are high-quality mate-rials with improved durability characteristics as well.

One distinguishing characteristic of the repair is the construction method. Common construction methods are form-and-cast, preplaced aggregate, high-velocity place-ment with pneumatic pressure (shotcrete), and trowel-applied (4.8.2.1 through 4.8.2.4).

4.8.2.1 Form-and-cast repairs—In form-and-cast repairs, the repair area is formed and the repair material placed by gravity flow (Fig. 4.8.2.1a) or pumping through an opening in the form or a hole in the substrate concrete. It can also be placed by dry packing (Fig. 4.8.2.1b). Materials used for form-and-cast repairs include concrete, silica-fume concrete, polymer-modified concrete, and polymer concrete

(Table 4.7). Again, concrete is often used, particularly for vertical concrete replacements where less resistance to gravity is necessary due to low cost, ease of construction, and adequate compatibility with the substrate concrete. Silica-fume concrete or polymer-modified concrete is frequently substituted for concrete due to their increased bond strengths. As vertical and overhead repairs are more labor intensive and frequently have smaller repair quantities, the cost premium for polymer-modified concrete is often not a controlling factor. Because form-and-cast repairs are self-curing while the forms remain in place, plastic shrinkage and drying shrinkage cracking are normally reduced. Polymer concrete is used only in special situations where its good bond strength and durability characteristics offset its cost, differing properties from the concrete substrate, and special construction training requirements. It also requires special form surfacing because of its strong adhesion to a wide range of materials. For more information on form-and-pour techniques, refer to ACI RAP-4; for more information on form-and-pump techniques, refer to ACI RAP-5.

4.8.2.2 Preplaced-aggregate concrete repairs—In the preplaced-aggregate concrete procedure, the formed removal area is filled with coarse aggregate, and a cement-sand grout (usually with admixtures) or a resinous material is then injected into the form from the lowest point, resulting in a concrete or a polymer concrete repair. Preplaced-aggre-gate concrete contains a higher percentage of coarse aggre-gate than concrete that is formed and cast (ACI 304R and 304.1R).

Because coarse aggregate is preplaced and the grout or resin is pumped under pressure, segregation is seldom a problem and virtually all substrate voids should be filled with grout or resin. Drying shrinkage of preplaced-aggregate concrete is less than one-half that of conventional concrete because of point-to-point contact of the coarse aggregate. The cement-sand grout may have a relatively high water content to yield a pumpable grout. This high water content can have an adverse effect on some of the cured material properties, such as permeability and porosity. Preplaced-aggregate, polymer concrete has a coefficient of thermal

Fig. 4.8.1—Placement of concrete overlay. (Courtesy of Euclid Chemical Company.)

Fig. 4.8.2.1a—Form-and-cast concrete placement in vertical patch. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)

Fig. 4.8.2.1b—Form-and-drypack overhead placement. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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expansion similar to cast-in-place concrete due to the point-to-point contact of the coarse aggregate (ACI 304.1R)

Preplaced aggregate repairs require specialized construc-tion skills to install forms with minimal leakage, to place well-compacted coarse aggregate, and to properly inject the grout or resin. Special equipment is needed to pump the grout. The repairs also should be consolidated through external vibration.

Applications with prepackaged materials containing a high-range water-reducing (HRWR) admixture and silica fume made specifically for preplaced-aggregate repairs (Watson 1996), as well as applications with polymer-modi-fied grout, have proven successful.

4.8.2.3 Shotcrete repairs—Shotcrete is mortar or concrete pneumatically projected at high velocity onto a surface (ACI 506R). Shotcrete can contain fiber reinforcement and admixtures. Conventional concrete and mortar, silica-fume concrete and mortar, and polymer-modified concrete and mortar (Table 4.7) can all be placed by shotcreting. All of the shotcrete ingredients can be combined in a mixer (wet mixture), or the solid ingredients can be combined in a mixer and the water added at the shotcrete nozzle (dry mixture). All materials for site-mixed shotcrete should comply with ASTM C1436 and prepackaged shotcrete should comply with ASTM C1480. It is more difficult to add and accu-rately control admixtures with dry-mix shotcrete. Properly placed shotcrete has properties comparable to cast-in-place concrete of similar composition, although the shotcrete oper-ation may reduce the entrained and entrapped air contents. Drying shrinkage and resulting cracking can be a problem with some shotcrete mixtures, largely because of poor sand gradation, too much water, or both, and the absence of aggre-gate coarser than 1/2 in. (13 mm). Fiber reinforcement or welded-wire fabric can be used to help control the cracking. Refer to ACI 506.1R.

Special equipment is required to apply shotcrete, and the skill of the nozzle operator is critical for a satisfactory appli-cation. The shotcreting process generates dust, overspray, and rebound that can disturb adjacent areas and equipment. Rebound should not be incorporated into the repair material. The use of polymer-modified concrete and mortar requires special skill and experience of the nozzle operator, as hard-ened overspray may reduce bond and special surface prepa-ration is required between successive layers (ACI 546R). Figure 4.8.2.3 shows a typical shotcrete placement.

Cement-based concrete and mortar are commonly used for shotcrete because of low cost, ease of construction, and adequate compatibility with the substrate concrete. Silica-fume concrete and mortar are frequently used because of their increased bond strength and cohesiveness compared with cement-based concrete and cement mortar, resulting in increased construction productivity and less rebound waste. Experience has shown that early and thorough wet curing of silica-fume shotcrete is highly desirable to prevent formation of excessive cracks during the curing process. Because of the difficulty in mixing, handling, and cleaning, polymer-modi-fied concrete and mortar are not commonly used for shotcrete.

Proprietary cement mortar can also be placed by low-pres-sure spraying, similar to wet-mix shotcrete, but at a much lower velocity. Refer to ACI RAP-3 for more information.

4.8.2.4 Trowel-applied repairs—In trowel-applied repairs, the repair material is applied directly to the repair location with a trowel (or sometimes by hand). Trowel-applied mate-rials are pressed against the substrate to develop intimate contact without voids. These repairs depend primarily on the adhesive bond between the fresh repair material and the substrate concrete for satisfactory placement. These repairs do not have the benefit of formwork to support the material until it sets, or pneumatic pressure to increase the application pressure and adhesive bond of the applied material. Coarse aggregate is normally not included in the repair material because the coarse aggregate decreases the cohesiveness to the point where the material is weaker than the pull of gravity and falls out of the repair area before the material can set.

Repair materials include cement mortar, silica-fume mortar, polymer-modified mortar, and polymer mortar. Trowel-applied repairs are used for deep concrete replacements only in unusual circumstances, such as when the concrete replacements are limited in size and number or are in rela-tively inaccessible locations. The absence of coarse aggre-gate results in some properties that vary significantly from those of the substrate concrete, such as drying shrinkage, coefficient of thermal expansion, and modulus of elasticity.

4.9—Shallow concrete replacements and overlaysRepair materials for shallow concrete replacements and

overlays, defined for the purposes of this guide as at least 1/16 to 1/8 in. (1.6 to 3.2 mm) thick and less than 3/4 to 1 in. (19 to 25 mm), include fine aggregates only. Concrete replacements and overlays that are at least 3/4 in. (19 mm) in thickness commonly contain some coarse aggregate. Shallow concrete replacements and overlays are differenti-ated from deep concrete replacements and overlays in that repair mortars are generally used in shallow repairs. The materials most commonly used are cement mortar, silica-fume mortar, polymer-modified mortar, MAPCM, and polymer mortar (Table 4.7).

Fig. 4.8.2.3—Shotcrete placement. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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The properties of repair mortars are less compatible with those of the substrate concrete in comparison to concrete mixtures used in deep repairs. Increased shrinkage and cracking are common problems for shallow concrete replacement and overlay materials, which may necessitate further repairs. Polymer repair mortars may have coeffi-cients of thermal expansion sufficiently different from the substrate concrete so that significant thermal stress may develop between the repair mortar and substrate concrete.

Proper mixing, placing, and curing procedures become more important as the repair thickness decreases. Repair mortars are frequently site-batched, making mixture consis-tency and quality more difficult to maintain. The experience of the construction worker becomes more important for achieving a satisfactory application. Timely and adequate curing is critical, except for polymer mortar that does not require curing. Where possible, the addition of even small-sized coarse aggregate (1/4 to 3/8 in. [6 to 10 mm]) can be beneficial to the performance of the repair. Figure 4.9 shows a shallow overlay placement.

Cement mortar is sometimes used for shallow concrete replacements and overlays, but it is susceptible to cracking due to the restraint of shrinkage and higher drying shrinkage. Silica-fume mortar and polymer-modified mortar are commonly used because their increased bond and tensile strengths help to offset the effects of anticipated shrinkage. Their excellent bond and cohesiveness before final set also allow these materials to be placed in thicker lifts for over-head and vertical applications, increasing productivity. Polymer mortar is sometimes used; special attention should be given to mixture proportion and repair details. Thermal incompatibility between polymer mortar and the substrate concrete seldom causes cracking and debonding of concrete replacements, even in situations where service temperature may vary widely. In addition, the excellent bond and tensile strengths and durability characteristics make it a good repair option in most thin repair situations. Refer to ACI 548.1R for additional information of polymer mortars.

4.10—Thin overlaysThin overlays, defined for the purposes of this guide as

less than 1/16 to 1/8 in. (1.6 to 3.2 mm) thick, are applica-

tions that place special requirements on the repair materials, such as more severe effects of surface water evaporation and substrate absorption. Thin overlays are intended primarily to address surface defects and roughness. The materials most commonly used are cement mortar, silica-fume mortar, polymer-modified mortar, and polymer mortar (Table 4.7). As repair materials become thinner, differential behavior with the substrate concrete becomes accentuated, and enhanced repair material properties such as bond and tensile strengths become more important. Proper application, along with timely and adequate curing, is critical to satisfactory repair performance. Construction workers frequently require special training in mixing and placement of repair materials.

Cement mortar is sometimes used for thin overlays; however, it is frequently desirable to use a material with higher bond and tensile strengths to offset differential behavior with the substrate concrete. Silica-fume mortar, polymer-modified mortar, and polymer mortar are commonly used because of their increased bond and tensile strengths, and improved durability characteristics. The dimension stability of polymer mortar also improves its performance. As the repair section becomes thinner, a low modulus of elasticity for polymer mortar will reduce the stresses gener-ated by differential thermal movements; excellent bond and tensile strengths of polymer mortar often offset the gener-ated stresses.

4.11—Aggressive environments and exterior applications

In aggressive environments and exterior applications, the repair approach may include coatings for reinforcing steels exposed in concrete replacement areas (Chapter 9), or surface sealers or coatings on the replacements or on the entire member or structure (Chapters 7 and 8), to improve the structure’s overall durability. Cathodic protection, either active or passive, can also be considered for structures in corrosive environments (ACI 222R). The repair approach should consider the ring anode or halo effect in existing concrete around replacements that were necessitated by corrosion of reinforcement. In chemically aggressive envi-ronments or other unusual applications, a surface sealer, coating, or membrane, or an overlay of silica-fume concrete, polymer-modified concrete, or polymer concrete is some-times used. Refer to ACI 201.2R for a discussion of various ways to improve concrete durability.

CHAPTER 5—PROPERTIES OF CRACK REPAIR MATERIALS AND THEIR IMPORTANCE

5.1—GeneralAs discussed in Chapter 3, compatibility between the

properties of repair materials and intended substrate is an important consideration. For example, the success of many crack repairs depends on repair materials that have signifi-cantly different properties from that of the substrate. An understanding of the repair material and substrate properties is essential to planning the repair approach (McDonald et al. 2002).

Fig. 4.9—Shallow overlay placement. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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Many properties of repair materials and of existing concrete are time-dependent. In all cases where material properties are specified, the corresponding age of the mate-rials should be noted. Many ASTM test methods cited in this guide are performed at standard conditions—essentially room temperature in many cases. Reported properties might not reflect the actual properties of the repair material in service conditions.

This chapter discusses properties of crack repair mate-rials and the test methods used to evaluate them. Some test methods are not specifically applicable to certain repair materials or repair applications, but may be useful for comparing repair materials. The descriptions of the various test methods are necessarily brief. The standards themselves should be consulted for details. Material manufacturers should provide test data based on standardized ASTM and other test methods that contain sufficient details for the published values to be replicated and verified while consid-ering the precision of the method. Refer to Appendix A for further discussion regarding modifications to standard test methods.

5.2—Types of crack repair materialsIn most cases, it is essential that the repair material

remains bonded to the substrate concrete on both sides of the crack for the repair to function properly. It is also impor-tant that the repair material has sufficient strength and flex-ibility to withstand the stresses and movements that occur at the crack. In this guide, crack repair materials are classified as comparatively rigid, comparatively elastomeric, or some-where in between, termed flexible.

Rigid crack repair materials rely on their strength to perform satisfactorily and have relatively little elasticity. Rigid materials can be used to glue the concrete together at the crack, restoring the concrete integrity to some extent. Rigid materials generally cannot accommodate significant crack movement, and either the repair material or the adja-cent concrete is likely to fail if substantial movements occur.

Elastomeric crack repair materials rely on their elasticity to limit stresses in the material to relatively low values. Elas-tomeric materials can be used to repair cracks where some or no crack movement is expected, but are not used to restore the integrity of the concrete.

Flexible crack repair materials have a limited amount of elasticity (although much less than elastomeric materials) and can tolerate small crack movements. Flexible materials are also harder and more tolerant of exposure to surface abrasion than elastomeric materials. As might be expected, different material properties are important for each type of material, and there are sometimes different procedures for testing each type of material.

Rigid repair materials include epoxy resin, methacrylates, cement grout, polymer-modified cement grout, and polymer grout. Important properties of these materials include bond strength; tensile strength and elongation at break; modulus of elasticity; shear, flexural, and compressive strengths; coefficient of thermal expansion; volume stability; viscosity; gel time; water absorption; and heat-deflection temperature.

Elastomeric repair materials include polyurethane grout; polyurethane, silicone, silyl-terminated polyether (STPE), and polysulfide sealant; polyurea; and strip-and-seal systems. Important properties of these materials include adhesion-to-peel strength; tensile strength and elongation at break; cyclic movement capability; elasticity; modulus of elasticity; tear strength; Shore A hardness; tack-free time; artificial weath-ering and staining; and thermal and humidity aging.

Semi-rigid epoxy resins are flexible crack repair material.In addition to repair material properties, the flexibility and

movement of the repaired crack is affected by the member geometry, reinforcement, repair detailing, and other factors. Although elastomeric repair material is used, other factors may limit crack movements and the repaired crack may experience little or no movement. Similarly, although rigid repair material is used, other factors may result in crack movements and the repaired crack may fail.

Other considerations for all three types of materials include repair appearance, installation conditions, and service requirements.

Sections 5.3 through 5.6 discuss the important properties for each type of crack repair material.

5.3—Properties of rigid crack repair materialsMany of the tests used to determine material properties

for rigid crack repair materials are similar to those used for the replacement and overlay repair materials discussed in Chapter 3.

5.3.1 Bond strength—Bond strength (adhesion) is a measure of the force required to separate the repair mate-rial from the substrate concrete on the sides of the crack, which relates to the ability of the two materials to act as one. Crack repair material should have sufficient bond strength so the repair does not separate from the substrate. Preferably, the published bond strength should be larger than the minimum requirement so that any reduction due to field-installation conditions is less critical. Bond strengths that exceed the tensile strength of the substrate will induce failure in the substrate if sufficient interface stresses result from shrinkage, thermal movement, or other factors. Test methods used to determine the bond strength of rigid crack repair materials are the same as those used to determine the bond strength of the cementitious replacement and overlay materials discussed in 3.3.5.

ASTM D4541—This test procedure is similar to the proce-dures of CSA A23.2-6B, ASTM C1583, and ICRI 210.3, all discussed in 3.3.5, except that the ASTM D4541 test procedure does not include drilling a shallow core into the substrate. The procedure consists of adhering a metal loading fixture to a thin coating of the crack repair material with an adhesive and pulling along the axis of the fixture to failure at a maximum rate of 150 psi (1 MPa) per second. The loca-tion of the failure and the failure load are recorded, and the failure load is reported in terms of psi (MPa). Figure 5.3.1 shows the ASTM D4541 test setup.

5.3.2 Tensile strength and elongation—Tensile strength is an indication of the cohesive strength of the repair material. Elongation is an indication of the amount of crack move-





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ment that the repair material can experience prior to failure. Test methods used to determine tensile strength and elonga-tion of rigid crack repair materials are the same as those used to determine the tensile strength and elongation of cementi-tious replacement and overlay materials discussed in 3.3.7.

ASTM D638 is used to determine the tensile properties of plastics, including epoxy resins and polymer grouts. Dumb-bell specimens, commonly with an overall length of 6.5 in. (165 mm), an overall width of 0.75 in. (19 mm), and a thick-ness of 0.16 to 0.28 in. (4 to 7 mm), are machined or cut from sheets of material. The width, thickness, and gauge length are measured on each specimen. Each dumbbell is loaded in tension by a testing machine at a minimum rate of 0.2 in./min. (5 mm/min.), and the load-extension curve is recorded. The tensile strength and percent elongation at break, and the percent elongation at yield if a yield point exists, are calculated. The modulus of elasticity can also be calculated. The ASTM D638 test specimen and test setup are similar to those used in the ASTM D412 test, shown in Fig. 5.4.2a and 5.4.2b.

5.3.3 Compressive strength—Test methods used to deter-mine compressive strength of rigid crack repair materials are the same as those used to determine compressive strength for cementitious replacement and overlay materials discussed in 3.3.6. ASTM D695 is used to determine the compressive strength of plastics, including epoxy resins and polymer grouts, as well as methacrylates. A typical specimen is 0.50 x 0.50 x 2 in. (12.7 x 12.7 x 50.8 mm), or 0.50 in. diameter by 2 in. (12.7 mm diameter by 50.8 mm). The specimen is compressed at a rate of 0.050 in./minute (1.3 mm/minute), and the loads and corresponding deformations recorded. The compressive strength, yield strength, and modulus of elasticity are then calculated. Figure 5.3.3 shows the ASTM D695 test setup with a rectangular prism specimen.

5.3.4 Modulus of elasticity—Normally for a rigid crack repair material, it is desirable that the modulus of elas-ticity of the repair material meets or exceeds that of the substrate concrete, so that the stiffness of the repaired member approaches that of the original uncracked section. Test methods used to determine the modulus of elasticity for cementitious materials are discussed in 3.3.2. ASTM D638, discussed in 5.4.2, is used to determine the tensile modulus

of elasticity for plastics, such as epoxy resins and polymer grouts. ASTM D695 is used to determine the compressive modulus of elasticity for plastics, including epoxy resins and polymer grouts.

5.3.5 Shear strength—Shear stresses are imposed on a crack repair material when concrete on one side of a crack moves parallel to the crack relative to the concrete on the other side of the crack. ASTM D732 is used to determine the shear strength of plastics, including epoxy resin and polymer grout. A 2 in. (50 mm) square or 2 in. (50 mm) diameter disk, 0.050 to 0.500 in. (1.27 to 12.7 mm) thick, is cut from sheet material or molded into this shape. A 1 in. (25 mm) diameter punch is pushed through the specimen at a rate of 0.05 in./min. (1.25 mm/min.), and the load at which the punch clears the specimen thickness is recorded. Shear strength is then calculated.

5.3.6 Flexural strength and modulus of rupture—ASTM D790, discussed in 3.3.8, is used to determine the flexural strength and modulus of rupture of plastics, including epoxy resins and polymer grouts.

5.3.7 Coefficient of thermal expansion—In situations where temperatures are not controlled, such as exterior and some interior applications, it is desirable for the repair mate-rial to have a coefficient of thermal expansion similar to that of the substrate concrete, so the two materials behave simi-larly under daily and seasonal temperature variations. If the coefficients vary significantly, the differential movements due to temperature fluctuations could affect the perfor-mance of the repair and should be accounted for in the repair design. The coefficient of thermal expansion for concrete typically ranges from 0.000002 to 0.000008/°F (0.000004 to 0.000014/°C), depending primarily on the aggregate type. Test methods used to determine the coefficient of thermal expansion are discussed in 3.3.3.

Fig. 5.3.1—ASTM D4541 test setup. (Courtesy of BASF Construction Chemicals, LLC.)

Fig. 5.3.3—ASTM D695 test setup with rectangular prism specimen. (Courtesy of Sika Corporation.)





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5.3.8 Volume stability—For crack repair materials, the primary volume stability concern is initial changes in the linear dimensions or volume of the repair material after placement. Volume stability properties affect compatibility of the repair material with the substrate concrete. The substrate concrete is usually relatively stable, with minimal residual creep and shrinkage deformations. Any shrinkage or expansion of the repair material should occur before the repair material has reached its final set, when creep is high.

Many cementitious materials undergo early shrinkage within the first few hours to days after application. Nonce-mentitious materials, such as those with polymeric binders, tend to be more stable with little or no shrinkage. Signifi-cant changes in the repair material volume can cause high shear stresses at the interface, debonding from the substrate concrete, and cracking of the repair material. Stresses created in the repair material by restrained contraction and expansion may be reduced by using repair materials with a lower modulus of elasticity or a higher rate of creep.

Test methods used to evaluate volume stability of rigid crack repair materials are the same as those used to eval-uate the volume stability of cementitious replacement and overlay materials discussed in 3.2.

5.3.9 Viscosity—Viscosity is the resistance to flow exhib-ited by a fluid. The measured value of viscosity is affected by such factors as the method of measurement (viscom-eter or rheometer geometry), temperature, and the rate and history of applied shear strain. Materials with low viscosity flow more freely than those with higher viscosity. In general, low-viscosity materials are used to repair cracks and pene-trate concrete pores.

5.3.10 Gel time—Gel time is the interval between the beginning of mixing and formation of the gelatinous mass. ASTM C881 is used to determine the gel time for epoxy resins, methacrylates, and polymer grouts. The material components are conditioned to the test temperature, and specified quantities of the components combined and mixed for 3 minutes. The time mixing started is recorded. The material is then transferred to an unwaxed paper cup and monitored for gel time. The time when a soft gelatinous mass forms in the sample center is recorded and the gel time calculated. The gel times for the larger volumes used in construction may vary significantly from the small samples used in this test procedure.

5.3.11 Water absorption—Some epoxy resins experience changes in properties with changes in moisture content. Therefore, the water absorption, or relative rate of absorp-tion of water, could be an important property. ASTM D570 is used to determine the water absorption rate. Test speci-mens, 2.36 in. square by 0.04 in. thick (60 mm square by 1 mm thick), are weighed and then completely immersed on edge in distilled water for 24 hours. The specimens are then wiped off, reweighed, and the water absorption in 24 hours calculated.

5.3.12 Heat-deflection temperature—Some materials, such as epoxy resins and polymer grouts, may soften at elevated temperatures and have reduced properties. ASTM D648 is used to determine the temperature at which a 0.010 in. (0.25

mm) deformation occurs when specimens are subjected to an arbitrary set of testing conditions. A rectangular sample, 5 in. long by 1/2 in. deep by 1/8 to 1/2 in. wide (127 mm long by 13 mm deep by 3 to 13 mm wide), is conditioned, positioned edgewise with the width horizontal as a simple beam, and loaded at midspan to produce a maximum flex-ural stress of 66 psi (0.455 MPa). The specimen is immersed under load in a liquid heat-transfer medium provided with a means of raising the temperature at 3.6°F/min. (2°C/min.). The temperature of the medium is recorded when the spec-imen has deflected 0.010 in. (0.25 mm). The findings from this test procedure provide a reproducible material property that may be used for comparative purposes. Most crack repair materials, however, are loaded in shear, compres-sion, or tension, or some combination of these so that a material property based on flexure is not directly applicable for design or predicting endurance of repaired members at elevated temperatures.

5.4—Properties of elastomeric crack repair materials

Elastomeric crack repair materials rely on their flexibility to expand and contract with crack movements, limiting stress buildups. These repair materials, therefore, are signifi-cantly different from rigid crack repair materials and have different tests for material properties.

5.4.1 Adhesive strength—Adhesive strength is related to the ability of the two materials to act together. The repair material should have sufficient adhesive strength to prevent its separation from the substrate concrete. The adhesive strength should preferably be larger than the minimum requirement so that any reduction due to field-installation conditions is not critical. Adhesive strengths that exceed the tensile strength of the substrate will induce failure in the substrate if sufficient interface stresses result from shrinkage, thermal movement, or other factors.

Three test methods are used to measure adhesive strength:1) ASTM C7942) ASTM D9033) ASTM C1521ASTM C794—This test is used to measure the adhesion

of elastomeric crack repair materials. Slab specimens made with a standardized mortar mixture are cast and cured, and the surfaces roughened, rinsed, and dried. Slab surfaces are primed as recommended by the sealant manufacturer. A bead of sealant at least 4 in. (100 mm) long is then applied to the substrate surface. A wire mesh screen at least 10 in. (250 mm) long is immediately placed on the sealant bead with one end extending beyond the bead, and tapped into the sealant. The sealant is drawn down with a special tool device such that the screen is embedded to a uniform depth of 0.08 in. (2 mm) from the substrate surface. A second bead of sealant is applied over the first bead and the screen, and tooled to achieve a total sealant depth of 0.16 in. (4 mm), with the screen embedded at the approximate mid-depth of the sealant. Excess sealant beyond the edge of the screen is removed. The sealant is cured as recommended by the sealant manufacturer.





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A tensile testing machine is used to pull back the screen at an angle of 180 degrees and a rate of separation of 2 in./min. (50 mm/min.) for approximately 1 minute, and the average peel force and peak force are recorded. It is intended that the sealant separate from the substrate; if the screen breaks or the sealant peels away cleanly from the screen, the test results may not be valid. The peel testing is repeated with samples that have been immersed in distilled water for 7 days.

While this test is useful for comparative purposes, the preparation procedure and curing regimen bear little resem-blance to field conditions.

ASTM D903—This test is used to measure the adhesion of a preformed flexible strip system. Concrete specimens are preconditioned and prepared in accordance with the recom-mendations of the adhesive manufacturer. A preformed flex-ible strip measuring 1 x 12 in. (25 x 305 mm) is bonded for a 6 in. (152 mm) length at one end of the concrete specimen in accordance with the procedure and recommendations outlined by the adhesive manufacturer. The specimens are then conditioned for 7 days at 73°F (23°C), 50 percent rela-tive humidity, unless the adhesive manufacturer specifies otherwise. After conditioning, approximately 1 in. (25 mm) of preformed strip is separated from the concrete specimen and the preformed strip is pulled back at an angle of 180 degrees and at a separation rate of 6 in./min. (152 mm/min.). The peel load is recorded, and the peel strength calculated in terms of load-per-unit width.

ASTM C1521—This practice includes nondestructive and destructive procedures for evaluating installed sealant in joints. Although it is a valuable quality control measure, it is not used by material manufacturers in determining sealant properties, as the results are dependent on actual substrate conditions in the field and are project-specific.

5.4.2 Tensile strength and elongation—Tensile strength is indicative of the repair material’s cohesive strength. Elonga-tion is indicative of the amount of crack movement a repair material can endure prior to failure. Elastomeric crack repair materials have much greater elongation per unit loading than rigid crack repair materials. Ambient temperature conditions may affect the flexibility of some materials.

Three test methods are used for elastomeric crack repair materials, such as rubber or plastic:

1) ASTM D4122) ASTM D6383) ASTM D1623All three of these tests involve stretching dumbbell speci-

mens and measuring tensile forces and elongations. ASTM D412 also includes a procedure for measuring the tensile set of the material. ASTM D638 is discussed in 5.3.2.

ASTM D412—This test method is used to measure the tensile strength and elongation properties of rubber and thermoplastic elastomer materials such as polyurethane and silicone sealant, and strip-and-seal sheets. Dumbbell or ring specimens are cut from injection-molded, 1/8 in. (3.0 mm) thick sheets. The lengthwise direction of the specimens should be parallel to the grain direction if known.

For the dumbbell specimens, overall length varies from 4 to 5-1/2 in. (100 to 140 mm) and the overall width is 5/8

or 1 in. (16 or 25 mm), depending on which die is used. The width, thickness, and gauge length are measured on each specimen. Each dumbbell is pulled apart by a testing machine at a rate of 20 in./min. (500 mm/min.), and the tensile forces at a specified elongation and at the time of rupture are measured. The yield stress, tensile strength at break, and ultimate elongation are then calculated. Tensile set is determined by holding the specimen at a specified elongation for 10 minutes, then releasing the testing machine and allowing the specimen to rest for 10 minutes. The final gauge length is measured and compared to the initial length. Figure 5.4.2a shows an ASTM D412 test specimen and Fig. 5.4.2b the test setup.

Fig. 5.4.2a—ASTM D412 test specimen. (Courtesy of BASF Construction Chemicals, LLC.)

Fig. 5.4.2b—ASTM D412 test setup. (Courtesy of BASF Construction Chemicals, LLC.)





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The typical ring specimen has an inside diameter of 0.64 in. (16 mm) and a radial width of 0.040 in. (1.0 mm). Each ring is mounted between two spindles on the testing machine. The specimen width, thickness, and spindle sepa-ration are measured prior to testing. The specimen is tested in a manner similar to the dumbbell specimens, measuring the distance between the spindles. The stress at a specified elongation, tensile strength at break, and ultimate elongation are then calculated.

Tests values obtained from the dumbbell and ring speci-mens should not be compared unless a correlation has been developed.

ASTM D1623—This test method is used to measure the tensile strength and elongation at break point for rigid cellular plastics, such as polyurethane chemical grout. Dumbbell specimens, which commonly have an overall length of 4-1/4 in. (108 mm) and a minimum mid-length diameter of 1.129 in. (28.7 mm), are molded or machined from blocks of material. The diameter and gauge length are measured on each specimen. Each dumbbell is pulled apart by a testing machine at a minimum rate of 0.05 in./min. (1.3 mm/min.), and the load-extension curve is recorded. The tensile strength at break and percent elongation at break are calculated.

5.4.3 Cyclic movement capability—Cyclic movement capability is the ability of a sealant material to withstand cyclic opening and closing of a crack or joint. ASTM C719 is used to test this capability. A specimen consists of a bead of sealant, 1/2 x 1/2 x 2 in. (12.7 x 12.7 x 50.8 mm), applied between two parallel standardized mortar blocks or glass or aluminum plates, 3 x 1 x 1 in. (75 x 25 x 25 mm). Multi-component sealant samples are cured for 14 days; single-component sealant samples are cured for 21 days. The speci-mens are then immersed in water for 7 days, compressed and heated at 158°F (70°C) for 7 days, released from compres-sion and allowed to cool for 24 hours, and subjected to 10 cycles of compression and extension at a rate of 1/8 in./h (3.2 mm/h). The specimens are then visually examined for any adhesive or cohesive separations. This test method is applicable for any joint movement. While test movements of ±12.5 percent or ±25 percent are most commonly used, the test movements can be adjusted based on the anticipated movement capability of the material being tested. Other specimens are then compressed and heated at 158°F (70°C) for 16 to 20 hours, released from compression and allowed to cool for 2 to 3 hours, and subjected to one extension at a rate of 1/8 in./h (3.2 mm/h) while being cooled down to –15°F (–26.1°C). The specimens are then visually examined for any adhesive or cohesive separations, and the heating and cooling and stretching cycle is repeated nine more times. Figure 5.4.3 shows an ASTM C719 test setup.

5.4.4 Elasticity—Elasticity is the property of a material that causes it to recover its original size and shape after an applied deformation or force is removed. Elasticity is primarily important for materials intended to bridge moving cracks, such as some crack sealants and surface coatings. Elasticity is typically quantified by measuring the elongation of a material in tension, as in ASTM D638.

5.4.5 Modulus of elasticity—Refer to 5.3.4 for a discus-sion of modulus of elasticity.

5.4.6 Tear strength—Tear strength is the maximum force required to cause a cut or nick to grow by tearing of the material. The ASTM D624 test is typically used to determine the tear strength of crack repair materials. A test specimen is prepared and then a defect introduced. The tearing stress is applied at a constant rate of 20 in./min. (500 mm/min.) and the maximum force recorded. The tear strength is then calculated as force-per-unit thickness. Figure 5.4.6 shows the ASTM D624 test setup with a specimen with a defect.

5.4.7 Hardness—The hardness of a crack repair material is an indirect indication of its durability for surface wear. ASTM D2240 is used to determine the material hardness. Twelve types of durometers are discussed in ASTM D2240, including Types A and D. The Shore A or D hardness is the hardness measured by a Type A or Type D durometer. The Shore designation refers to Albert Shore, who developed the durometer in the 1920s.

Specimens are at least 0.24 in. (6.0 mm) thick and sized such that measurements are made at least 0.48 in. (2.0 mm)

Fig. 5.4.3—ASTM C719 test setup. (Courtesy of BASF Construction Chemicals, LLC.)

Fig. 5.4.6—ASTM D624 test setup. Note the defect in the test specimen. (Courtesy of BASF Construction Chemicals, LLC.)





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from any edge. Both Type A and Type D durometers have indentors that are 0.050 in. (1.27 mm) in diameter; a Type A indentor tapers to a tip diameter of 0.031 in. (0.79 mm), whereas a Type D indentor tapers to a point with a radius of 0.004 in. (0.10 mm). The durometers are spring-activated; the Type A durometer applies forces of 0.12 lb (0.55 N) at a hardness reading of 0 and 1.81 lb (8.05 N) at a hardness reading of 100; the Type D durometer applies forces of 0 lb (0 N) at a hardness reading of 0 and 10.0 lb (45 N) at a hard-ness reading of 100. A specimen is placed on the specimen support table. The spring-activated durometer is released, descends at a controlled rate, and applies the presser foot to the specimen. Within 1 second of the cessation of the indentor travel, the maximum reading is recorded. Reliable durometer readings should be between 20 and 90; the hard-ness readings are an inverse function of the indentor travel,

with one hardness point for each 0.001 in. (0.025 mm) of indentor movement. Figure 5.4.7a shows a durometer used in ASTM D2240 testing and Fig. 5.4.7b shows a schematic of the durometer action.

This test is intended for comparison purposes and the results are not related to any fundamental material property. The results are influenced by the elastic modulus and visco-elastic behavior of the material, as well as the geometry of the indentor and applied force.

5.4.8 Tack-free time—The tack-free time is a measure of surface cure time, and may be correlated to the time when the sealant is resistant to damage from construction activities and environmental sources. ASTM C679 is used to deter-mine the tack-free time. The test consists of periodically placing polyethylene film on a sealant sample, weighting the film down with a 1.06 oz. (30 g) weight and, after 30 seconds, removing the film and examining the film for the attachment of any bulk sealant (as opposed to a very thin film of sealant or oil). The tack-free time is the time from when the sealant was applied and tooled, to the time when the film has no bulk sealant attached to it.

5.4.9 Weathering and staining—ASTM C510 is an accel-erated laboratory procedure to determine if a sealant sample will stain the concrete substrate or will change color when exposed to the weather. Slabs made with standardized mortar, 1/4 in. (6 mm) thick, are cast, and a 1/4 in. (6 mm) thick layer of sealant is placed on some of the slabs. After the samples have cured and been conditioned, some of the samples are placed in an accelerated weathering machine and exposed to ultraviolet radiation for at least 100 hours at a sample temperature of 149°F (60°C).

The samples are then visually examined and compared to the samples that did not experience accelerated weathering, and differences in sealant and substrate color are noted. Figure 5.4.9a shows an ASTM C510 test in progress and Fig. 5.4.9b shows a test specimen after testing.

5.4.10 Thermal and humid aging—Some plastics, such as polyurethane grout, will shrink over time when exposed to certain temperature and humidity conditions. ASTM D2126 is used to determine aging effects. Specimens, 4 in. (100 mm) square, are placed in an oven and maintained at a given temperature and relative humidity. The specified tempera-tures range from –100°F to +302°F (–73°C to 150°C), and related relative humidity of ambient, 50 percent, or 97 percent. After 24 hours, 1 week, and 2 weeks, the speci-mens are removed from the oven, allowed to come to room temperature for 2 hours, and the dimensions are measured. These dimensions are compared to the initial dimensions prior to testing, and the percent change is calculated. Figure 5.4.10 shows the ASTM D2126 test setup.

5.5—Properties of flexible crack repair materialsThe properties of flexible crack repair materials are deter-

mined by many of the tests in 5.3 and 5.4. In particular, ASTM D4541 is used to determine bond strength (5.3.1); ASTM D638 is used to determine tensile strength and elon-gation at break (5.3.2); ASTM D790 is used to determine flexural strength (5.3.6); ASTM D695 is used to determine

Fig. 5.4.7b—Schematic of durometer action. (Courtesy of Albright Technologies, Inc.)

Fig. 5.4.7a—Durometer for ASTM D2240 hardness testing. (Courtesy of Rex Gauge Company, Inc.)





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compressive strength (5.3.3); and ASTM D2240 is used to determine hardness (5.4.7).

5.6—Other considerations5.6.1 Repair appearance—Crack repair materials may

affect the appearance of the repaired member. For instance, cracks treated with sealant are usually routed to a width of at least 1/2 in. (13 mm), making the routed crack more visible than the original crack. Sealant is available in a variety of colors so a color best suited to a particular application can be selected. Also, some sealants are prone to pick up dirt, which can adversely affect their appearance. Cracks that are injected with epoxy or polyurethane grout require a surface seal, and injection ports are drilled into the concrete surface. Even if the ports and surface seal are removed after the injec-tion work, the concrete surface is usually marred.

5.6.2 Installation conditions—Crack repair materials should be suitable for the specific repair application environ-ment. They should have the ability to be installed and cured under the specific field conditions. Considerations at the time of installation include the air and concrete temperatures; amount of moisture in the crack and on the crack surfaces; relative humidity and wind speed; whether the repair area is

in direct sunlight or shade; and anticipated climatic condi-tions that occur before the repair material has cured. The choice of specific repair materials and their corresponding properties depends on actual construction conditions, or the construction conditions should be modified to fit the proper-ties of the repair materials chosen.

5.6.3 Service requirements—Service conditions can place various demands on the repair material; the repair material may need to have enhanced properties for long-term dura-bility. Conditions can include exposure to moisture, temper-ature variations, chemicals, and mechanical wear.

5.7—Summary tablesTables 5.7a, 5.7b, and 5.7c present available test proce-

dures described in this chapter and typical test values for rigid crack repair materials, elastomeric crack repair mate-rials, and flexible crack repair materials, respectively. The tables are brief summaries; the text of the chapter should be referred to for additional information. Recommended values listed represent the minimum values recommended by Committee 546 for typical repair materials used for successful repairs. They are not necessarily applicable for all conditions. Some of the recommended test methods listed in the table are not appropriate for certain repair materials or repair applications, and others are useful for comparing different materials.

CHAPTER 6—CRACK REPAIR MATERIALS SELECTION

6.1—GeneralCracks in concrete may be of concern for several reasons,

including that they may:a) Be indicative of a structural problem;b) Be a leakage source of water or other contaminants into

spaces beyond the member;c) Allow the intrusion of moisture, oxygen, chlorides,

carbon dioxide, and other aggressive chemicals and gases into the concrete, resulting in accelerated degradation of the concrete, corrosion of the reinforcing steel, or both;

Fig. 5.4.9a––ASTM C510 test in progress in weathering machine. (Courtesy of BASF Construction Chemicals, LLC.)

Fig. 5.4.9b––ASTM C510 test specimen after testing. (Cour-tesy of BASF Construction Chemicals, LLC.)

Fig. 5.4.10––ASTM D2126 test setup. At left is rectangular prism test specimen and at right is a specimen lowered into oven with weights on top. (Courtesy of Sika Corporation.)





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Table 5.7a—Summary of available test methods and test values for rigid crack repair materials

Description Test methodSpecimen

age Typical value Recommended value* Recommended testEpoxy resin

5.3.1—Bond strength ASTM C882 14 days 1000 to 3000 psi (6.9 to 21 MPa) > 1500 psi (10 MPa) Yes

5.3.2—Tensile strength ASTM D638 7 days 4000 to 8000 psi (28 to 55 MPa) > 5000 psi (35 MPa) Yes

Elongation at break ASTM D638 7 days 1 to 10 percent 1 to 10 percent Yes

5.3.3—Compressive strength ASTM D695 7 days 5000 to 15,000 psi (35 to 103 MPa) > 3000 psi (21 MPa) Yes

5.3.4—Modulus of elasticity

Tension ASTM D638 14 days 200,000 to 600,000 psi (1.4 to 4.1 GPa) 300,000 to 500,000 psi (2.1 to 3.4 GPa) Yes

Compression ASTM D695 7 days 75,000 to 500,000 psi (0.52 to 3.5 GPa) > 150,000 psi (1.0 GPa) Yes

5.3.5—Shear strength ASTM D732 14 days 2500 to 10,000 psi (17 to 69 MPa) > 2000 psi (14 MPa) No

5.3.6—Flexural strength ASTM D790 14 days 5000 to 15,000 psi (35 to 103 MPa) > 1000 psi (7 MPa) No

5.3.10—Gel time ASTM C881 — 5 minutes to 3 hours > 30 minutes Yes

5.3.11—Water absorption ASTM D570 24 hours 0.25 to 1.5 percent < 1 percent Yes

5.3.12—Heat-deflection temperature

ASTM D648 7 days 110 to 160°F (43 to 71°C) > 120°F (49°C) Yes


5.3.2—Tensile strength ASTM D638 500 to 1600 psi (3.4 to 11 MPa)Committee 546 does not have a recommended value for this test.

Committee 546 has no recommendation for this test.


5.3.6—Flexural strength ASTM D790 1 day 2500 psi (17 MPa)Committee 546 does not have a recommended value for this test.


5.3.10—Gel time ASTM C881 — 5 minutes to 1 hour > 10 minutes Yes

Methyl methacrylate

5.3.1—Bond strength ASTM C882 2000 psi (14 MPa)Committee 546 does not have a recommended value for this test.


5.3.2—Tensile strength ASTM D638 7 days 5000 to 8000 psi (35 to 55 MPa)Committee 546 does not have a recommended value for this test.


5.3.3—Compressive strength ASTM D695 7 days 12,000 psi (83 MPa)Committee 546 does not have a recommended value for this test.


5.3.5—Flexural strength ASTM D790 1 day 11,000 to 12,000 psi (76 to 83 MPa)Committee 546 does not have a recommended value for this test.


5.3.10—Gel time — 20 to 30 minutesCommittee 546 does not have a recommended value for this test.


Polymer grout


5.3.2—Tensile strength ASTM D638 14 days 500 to 1500 psi (3.4 to 10 MPa) > 750 psi (5.2 MPa) Yes



Tension ASTM D638 14 days 200,000 to 1,000,000 psi (1.4 to 6.9 GPa) 200.000 to 1,000,000 psi (1.4 to 6.9 GPa) Yes

Compression ASTM D695 7 days 100,000 to 1,000,000 psi (0.69 to 6.9 GPa) > 150,000 psi (1.0 GPa) No

5.3.5—Shear strength ASTM D732 14 days 2000 to 5000 psi (14 to 35 MPa) > 2000 psi (14 MPa) No

5.3.6—Flexural strength ASTM D790 14 days 2000 to 5000 psi (14 to 35 MPa) > 1000 psi (6.9 MPa) Yes

5.3.7—Coefficient of thermal expansion

ASTM C531 —0.000023 to 0.000028/°F (0.000041 to

0.000051/°C)Similar to substrate Yes

5.3.10—Gel time ASTM C881 Immediately 5 minutes to 3 hours > 30 minutes Yes

5.3.12—Heat-deflection temperature

ASTM D648 7 days 110 to 160°F (43 to 71°C) > 120°F (49oC) Yes

Polymer-modified cement grout

5.3.1 Bond strength

Slant shear bondASTM C882 1 day

7 days28 days

400 to 1000 psi (2.8 to 6.9 MPa)1000 to 1800 psi (6.9 to 10 MPa) 2000 to 3000 psi (14 to 21 MPa)


No

ASTM C1042 No

Direct tensile bond ASTM C1404 28 days 250 to 300 psi (1.0 to 1.7 MPa) Refer to discussion Yes

Direct shear bond MDOT1 day7 days28 days

150 to 300 psi (1.0 to 2.1 MPa)300 to 400 psi (2.1 to 2.8 MPa)400 to 600 psi (2.8 to 4.1 MPa)


No





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Table 5.7a—Summary of available test methods and test values for rigid crack repair materials (cont.)

Description Test methodSpecimen

age Typical value Recommended value* Recommended test

5.3.2—Tensile strength

ASTM C307

—

400 to 1800 psi (2.8 to 12 MPa) > 400 psi (2.8 MPa) Yes

ASTM C496 200 to 600 psi (1.4 to 4.2 MPa) > 400 psi (2.8 MPa) Yes

USACE CRD-C 164



Flexural ASTM C580 28 days 300,000 to 3,000,000 psi (2.1 to 21 GPa) Refer to discussion Yes

Compression ASTM C469 28 days 1,000,000 to 5,500,000 psi (6.8 to 38 GPa) Refer to discussion Yes

5.3.3—Compressive strengthASTM C39 28 days 3000 to 10,000 psi (21 to 69 MPa)

Similar to substrateYes

ASTM C109 28 days 4000 to 12,000 psi (28 to 83 MPa) Yes


ASTM C531

28 days

0.00000036/°F (0.00000064/°C)

Refer to discussion

Yes

ASTM D696 0.00000036/°F (0.00000064/°C) Yes

USACE CRD-C 39

0.00000015/°F (0.00000027/°C) Yes

ASTM C884 Qualitative test Yes

5.3.8—Volume stability

Length change ASTM C157 28 days0.02 percent (expansion) to –0.12 percent

(shrinkage)Refer to discussion No

Drying shrinkage ASTM C596 28 days –0.05 to –0.15 percent < –0.10 percent Yes

Restrained expansion ASTM C806 28 days 0.06 percent Refer to discussion Yes

Cement grout

5.3.1—Bond strength

Slant shear bondASTM C882 1 day

7 days28 days

400 to 1000 psi (2.8 to 6.9 MPa)1000 to 1800 psi (6.9 to 10. MPa)2000 to 3000 psi (14 to 21 MPa)


No

ASTM C1042 No

Direct tensile bond ASTM C1404 28 days250 to 300 psi

(1.0 to 1.7 MPa)Refer to discussion Yes

Direct shear bond MDOT1 day7 days28 days

150 to 300 psi (1.0 to 2.1 MPa)300 to 400 psi (2.1 to 2.8 MPa)400 to 600 psi (2.8 to 4.1 MPa)


No

5.3.2—Tensile strength

ASTM C307 400 to 1800 psi (2.8 to 12 MPa) > 400 psi (2.8 MPa) Yes

ASTM C496 200 to 600 psi (1.4 to 4.2 MPa) > 400 psi (2.8 MPa) Yes

USACE CRD-C 164



Flexural ASTM C580 28 days300,000 to 3,000,000 psi

(2.1 to 21 GPa)Refer to discussion Yes

Compression ASTM C469 28 days1,000,000 to 5,500,000 psi

(6.8 to 38 GPa)Refer to discussion Yes

5.3.3—Compressive strengthASTM C39

28 days

3000 to 10,000 psi(21 to 69 MPa)

Similar to substrateYes

ASTM C1094000 to 12,000 psi

(28 to 83 MPa)Yes


ASTM C531

28 days

0.00000036/°F(0.00000064/°C)

Refer to discussion

Yes

ASTM D6960.00000036/°F

(0.00000064/°C)Yes

USACE CRD-C 39

0.00000015/°F(0.00000027/°C)

Yes

ASTM C884 Qualitative test Yes

5.3.8—Volume stability

Length change ASTM C157 28 days0.02 percent (expansion) to –0.12 percent

(shrinkage)Refer to discussion No

Drying shrinkage ASTM C596 28 days –0.05 to –0.15 percent < –0.10 percent Yes

Restrained expansion ASTM C806 28 days 0.06 percent Refer to discussion Yes*The recommended values are the minimum values recommended for typical repair materials used in successful repairs and are not applicable for all conditions.

Note: Materials tested at 73°F (23°C) unless noted otherwise.





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Table 5.7b—Summary of available test methods and test values for elastomeric crack repair materialsDescription* Test method Specimen age Typical value Recommended value† Recommended test

Polyurethane chemical grout5.4.2—Tensile strength ASTM D1623 NoElongation at break ASTM D1623 14 days 25 to 400 percent > 15 percent Yes5.3.4—Shear strength ASTM D732 No5.4.10—Thermal and humid aging

ASTM D2126 14 days 0 to 10 percent < 1 percent Yes

Polyurethane sealant5.4.1—Adhesive strength ASTM C794 21 days 5 to 40 lb (22 to 180 N) > 5 lb (22 N) Yes5.4.2—Tensile strength ASTM D412 21 days 100 to 250 psi (0.7 to 1.7 MPa) 100 to 250 psi (0.7 to 1.7 MPa) NoElongation at break ASTM D412 21 days 400 to 800 percent > 400 percent Yes5.4.3—Cyclic movement ASTM C719 21 days 12.5 to 25 percent 12.5 to 25 percent Yes5.4.6—Tear strength ASTM D624 21 days 50 to 100 lb./in. (8.8 to 18 N/mm) 50 to 100 lb./in. (8.8 to 18 N/mm) No5.4.7—Shore A hardness ASTM D2240 21 days 15 to 50 15 to 50 Yes5.4.8—Tack-free time ASTM C679 NA 7 to 24 hours < 72 hours Yes5.4.9—Weathering and staining

ASTM C510 21 days 500 to 2000 hours > 100 hours Yes

Silicone sealant5.4.1—Adhesive strength ASTM C794 21 days 5 to 25 lb (22 to 111 N) > 5 lb (22 N) Yes5.4.2—Tensile strength ASTM D412 21 days 100 to 300 psi (0.7 to 2.1 MPa) 100 to 300 psi (0.7 to 2.1 MPa) NoElongation at break ASTM D412 21 days 400 to 1000 percent > 400 percent Yes5.4.3—Cyclic movement ASTM C719 21 days 50 to 100 percent 50 to 100 percent Yes5.4.6—Tear strength ASTM D624 21 days 20 to 40 lb/in. (3.5 to 7.0 N/mm) > 50 lb/in. (8.8 N) Yes5.4.7—Shore A hardness ASTM D2240 21 days 5 to 15 5 to 15 Yes5.4.8—Tack-free time ASTM C679 1 to 2 hours < 72 hours Yes5.4.9—Weathering and staining

ASTM C510 21 days 500 to 2000 hours > 100 hours Yes

Silyl-terminated polyether sealant5.4.1—Adhesive strength ASTM C794 21 days 30 to 35 lb (133 to 156 N) > 5 lb (22 N) Yes5.4.2—Tensile strength ASTM D412 21 days 150 to 250 psi (1.0 to 1.7 MPa) 100 to 300 psi (0.7 to 2.1 MPa) NoElongation at break ASTM D412 21 days 300 to 800 percent > 400 percent Yes5.4.3—Cyclic movement ASTM C719 21 days 25 to 50 percent 25 to 50 percent Yes5.4.6—Tear strength ASTM D624 21 days 40 to 70 lb/in. (7.0 to 12 N/mm) > 50 lb/in. (8.8 N) Yes5.4.7—Shore A hardness ASTM D2240 21 days 15 to 30 5 to 15 Yes5.4.8—Tack-free time ASTM C679 0.5 to 2.5 hours < 72 hours Yes5.4.9—Weathering and staining

ASTM C510 21 days — > 100 hours Yes

Polysulfide sealant

5.4.1—Adhesive strength ASTM C794 21 days 20 to 25 lb (89 to 111 N)Committee 546 does not have a recommended value for this test.

Committee 546 has no recom-mendation for this test.

5.4.2—Tensile strength ASTM D412 21 days 125 to 200 psi (0.9 to 1.4 MPa)Committee 546 does not have a recommended value for this test.


Elongation at break ASTM D412 21 days 500 to 550 percentCommittee 546 does not have a recommended value for this test.


5.4.3—Cyclic movement ASTM C719 21 days 25 percentCommittee 546 does not have a recommended value for this test.


5.4.7—Shore A hardness ASTM D2240 21 days 15 to 50Committee 546 does not have a recommended value for this test.


5.4.8—Tack-free time ASTM C679 14 to 24 hoursCommittee 546 does not have a recommended value for this test.

Polyurea

5.3.1—Bond strength ASTM D4541 220 psi (1.5 MPa)Committee 546 does not have a recommended value for this test.


5.4.2—Tensile strengthASTM D412 21 days 2000 psi (14 MPa)



ASTM D638 7 days 650 psi (4.5 MPa)Committee 546 does not have a recommended value for this test.


Elongation at breakASTM D412 21 days 470 percent



ASTM D638 7 days 110 percentCommittee 546 does not have a recommended value for this test.


5.4.5—Modulus of elasticity ASTM D638 21 days 6500 psi (45 MPa)5.4.7—Shore A hardness ASTM D2240 21 days 80 to 90





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d) Be a source of continued concrete deterioration due to wheel traffic causing edge raveling or spalling;

e) Be a trip hazard;f) Be considered unsightly.While the crack itself may or may not be a problem, it is

often the symptom of a condition that is a problem. If left untreated, cracks may eventually lead to the serious degra-dation of the structure or failure of structural components.

Common objectives for crack repairs include (ACI 224.1R):a) Increase the stiffness of cracked components;

b) Improve functional performance;c) Prevent liquid penetration;d) Improve the appearance of the concrete surface;e) Improve durability;f) Prevent development of a corrosive environment at the

reinforcement.Additionally, repairing cracks can:a) Improve hygiene by improving cleanability;b) Reduce gas permeability;c) Reduce sound transmission.

Table 5.7b—Summary of available test methods and test values for elastomeric crack repair materials (cont.)

Description* Test method Specimen age Typical value Recommended value† Recommended testStrip-and-seal system

Sheeting

5.4.2—Tensile strength ASTM D412 21 days 1000 psi (6.8 MPa)Committee 546 has no recom-


Elongation at break ASTM D412 21 days 800 percentCommittee 546 has no recom-

mendation for this test.Adhesive5.3.1—Bond Strength ASTM C882 14 days 1000 to 3000 psi (6.9 to 21 MPa) > 1500 psi (10 MPa) Yes5.3.2—Tensile strength ASTM D638 7 days 2000 to 5000 psi (14 to 35 MPa) > 2000 psi (14 MPa) YesElongation at break ASTM D638 7 days 0.1 to 1 percent > 0.25 percent Yes

5.3.4—Modulus of elasticity ASTM D638 14 days200,000 to 1,000,000 psi (1.4 to

6.9 GPa)200,000 to 1,000,000 psi Yes

5.3.5—Shear strength ASTM D732 14 days 2000 to 5000 psi (14 to 35 MPa) > 2000 psi (14 MPa) Yes5.3.6—Flexural strength ASTM D790 14 days 2000 to 5000 psi (14 to 4.5 MPa) > 1000 psi (6.9 MPa) Yes5.3.3—Compressive strength ASTM D695 7 days 5000 to 15,000 psi (35 to 103 MPa) > 3000 psi (21 MPa) Yes5.3.10—Gel time ASTM C881 20 to 60 minutes > 30 minutes Yes5.3.11—Water absorption ASTM D570 24 hours 0.25 to 1.5 percent < 1 percent Yes5.3.12—Heat-deflection temperature

ASTM D648 7 days 110 to 160°F (43 to 71°C) > 120°F (49°C) Yes

System5.4.1—Adhesion-to-peel strength

ASTM D903 7 days No loss of adhesionCommittee 546 has no recom-

mendation for this test.*MPa rounded to two significant digits.†The recommended values are the minimum values recommended for typical repair materials used in successful repairs and are not applicable for all conditions.Note: Materials tested at 73°F (20°C) unless noted otherwise.

Table 5.7c—Summary of available test methods and test values for flexible crack repair materials

Description* Test methodSpecimen

age Typical value Recommended value† Recommended testFlexible epoxy resin

5.3.1—Bond strength ASTM D4541 180 to 350 psi (1.2 to 2.4 MPa)


Committee 546 does not have a recommendation for this test.

5.3.2—Tensile strength ASTM D638 21 days 450 to 2000 psi (3.1 to 14 MPa)



Elongation at break ASTM D638 21 days 25 to 60 percent Committee 546 does not have a recommended value for this test.


5.3.6—Flexural strength ASTM D790 14 days 95,000 psi (655 MPa) Committee 546 does not have a recommended value for this test.


5.3.3—Compressive strength ASTM D695 7 days 500 to 8000 psi (3.4 to 55.1 MPa)



5.4.7—Hardness Committee 546 does not have a recommended value for this test.


Shore A ASTM D2240 21 days 90 to 95 Committee 546 does not have a recommended value for this test.


Shore D ASTM D2240 21 days 50 to 60 Committee 546 does not have a recommended value for this test.


*MPa rounded to two significant digits.†The recommended values are the minimum values recommended for typical repair materials used in successful repairs and are not applicable for all conditions.Note: Materials tested at 73°F (20°C) unless noted otherwise.





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For repair evaluation, cracks are categorized based on the cause of the crack, width, stability (whether the crack is active or dormant), environmental conditions to which the crack is exposed (if it is wet, actively leaking, or exposed to deleterious chemicals), and structural requirements. Crack widths are measured at the concrete surface. In some instances, the cracks taper and become narrower below the concrete surface. Once the design professional determines the repair requirements, the crack repair material can be selected. Refer to ACI 224.1R, United States Army Corps of Engineers (USACE) EM 1110-2-2002, and ICRI 340.1 for further information regarding the causes, evaluation, and repair of cracks.

6.1.1 Cracks indicative of structural problems—While many cracks are indicative of a structural problem, cracks wider than 0.04 in. (1 mm) often indicate a structural problem in reinforced concrete members and should be eval-uated further. Only a qualified design professional should determine if a crack is indicative of a structural problem that requires repair. Structural cracks are caused by dead loads, applied loads and forces, and other external influences. While crack repair materials that could be part of a structural repair are discussed, the design and detailing of structural repairs is not included in this guide. Note that crack repair materials do not increase the strength of reinforced concrete members, as the members are designed and assumed to be cracked. Some crack repair materials can glue the concrete together at cracks, increasing the stiffness of the repaired member.

6.1.2 Crack widths less than 0.002 in. (0.05 mm)—Cracks less than 0.002 in. (0.05 mm) in width are generally not treated. Very thin cracks may seal themselves by autogenous healing, which occurs when the cement continues to hydrate and carbonates, forming calcium carbonate and calcium hydroxide crystals that can seal the crack. At a minimum, the structure should be inspected periodically to monitor any increase in the crack widths over time, which might be indic-ative of other problems that should be assessed and evalu-ated to determine what repairs, if any, are required.

6.1.3 Cracks wider than 0.002 in. (0.05 mm), but less than 1/4 in. (6.4 mm)—Chapter 6 considers cracks that are less than 1/4 in. (6.4 mm) in width. Cracks that are wider than 1/4 in. (6.4 mm) would probably require special repair proce-dures, possibly including concrete removal and replacement.

6.2—Crack repair materials and proceduresThere are a variety of crack repair materials available to

the specifier. Each material is installed according to one or more specific procedures; some materials penetrate into the crack and others are applied at the surface only. Special mixing heads are available to mix multi-component mate-rials; in particular, these heads are used for crack injection work. In some instances, it may be desirable to construct on-site mockups to verify the compatibility of the repair material with the concrete substrate, to determine if a primer might be necessary, and to demonstrate the finished appear-ance of the repair.

The following crack repair materials, with their most common installation procedures listed, are intended to pene-

trate into cracks and are best suited for cracks no greater than 1/8 in. (3.2 mm) in width:

a) Epoxy resin by pressure injection or gravity feed;b) High-molecular-weight methacrylate by gravity feed;c) Methyl methacrylate by gravity feed;d) Polyurethane chemical grout by pressure injection.The following crack repair materials, with their most

common installation procedures listed, are applied to the crack surface and are well suited for cracks 1/4 in. (6.4 mm) or narrower.

a) Polyurethane sealant by routing and surface application;b) Silicone sealant by routing and surface application;c) Silyl-terminated polyether (STPE) sealant by routing

and surface application;d) Polysulfide sealant by routing and surface application;e) Flexible epoxy resins by routing and gravity feed;f) Polyureas by routing and gravity feed;g) Strip-and-seal systems by surface application.The following crack repair materials, commonly installed

by gravity feed, hand-packing, or pumping, are intended to achieve only partial penetration into cracks and are best suited for cracks wider than 1/8 in. (3.2 mm).

a) Polymer grout;b) Polymer-modified cementitious grout;c) Cementitious grout.Materials that are installed by pressure injection or

gravity feed may also be installed by vacuum pressure injec-tion where a vacuum is maintained on the back side of the concrete member to draw the material into the concrete.

Additional information about each material, such as advantages, limitations, specific applications, and standards, serve to help the specifier determine which of the available materials represents the best choice for a specific repair. This information is summarized in the remainder of this chapter. Refer also to ICRI 340.1 for a discussion of crack repair materials.

6.3—Epoxy resinEpoxies are a generic group of synthetic resins that require

thorough mixing with a hardener or curing agent, usually an amine or a polyamide, to initiate the chemical reaction, which results in their high adhesive strength. ASTM C881 classifies seven types of epoxy resins based on their intended use, viscosity, and temperature limitations. Injection resins are normally classified as Type I—non-load-bearing applica-tions for bonding hardened concrete to hardened concrete, or Type IV—load-bearing applications for bonding hardened concrete to hardened concrete.

6.3.1 Selection—Because of their high bond strength and relatively low viscosity, epoxy resins are widely used for structural bonding and waterproofing repairs. Epoxy resins are available in a wide range of viscosities, moduli, and reac-tion rates, and there are formulations to accommodate many different crack conditions.

Epoxy resins are dependent on their bond to concrete for structural repairs and waterproofing repairs. Without bond, the resins are essentially crack fillers. If dirt or other contam-inants are present in the cracks, the epoxy-resin bond to the





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concrete will likely be reduced, decreasing the effectiveness of the repair. Most epoxy resins marketed to the engineering and construction community will not bond to the concrete in the presence of moisture. Some epoxy resins, however, are moisture-tolerant and will cure in the presence of moisture.

Epoxy resins undergo negligible shrinkage. Most epoxy resins have very limited flexibility and can tolerate only slight or gradual movement at the crack. If large or rapid crack movement occurs, either the epoxy resin will fail in adhesion or cohesion, or the concrete will crack adjacent to the repaired crack.

Ambient-temperature-cured epoxy resins conforming to the requirements of ASTM C881 Type IV have a heat deflec-tion temperature of at least 120°F (50°C). If the repair is intended to increase the stiffness of the cracked member, the repaired member should be evaluated for maximum service temperature conditions, including the effects of fire. Testing of cracked concrete walls repaired with epoxy resin and exposed to fire suggests resin burnout may extend several inches below the concrete surface; the epoxy resin may lose strength during the fire, possibly resulting in a total loss of member strength for stresses perpendicular to the crack; and the remaining epoxy resin may have increased post-fire residual strength due to post-curing. (Plecnik et al. 1982)

Once completed, the crack repair should last indefinitely with no maintenance unless crack movement occurs.

6.3.2 Installation—The resin and hardener should be accurately proportioned and well mixed. Any deviation can result in a material that remains soft or tacky and fails to comply with the specified requirements.

Cracks in top horizontal surfaces that are less than 1/8 in. (3.2 mm) in width are commonly filled by gravity, brushing the epoxy resin into the crack or ponding the resin over the crack. Narrower top surface cracks can be filled by pres-sure injection. Epoxy resins are commonly used to pres-sure-inject cracks. The depth of penetration into the crack is determined by viscosity, pot life, surface tension of the epoxy resin, and injection pressure. An injection cycle consists of injecting material into every injection port in a systematic pattern, commonly from bottom to top on vertical surfaces so that air can escape. Two or three injection cycles are sometimes required to completely fill or waterproof a crack. Figure 6.3.2a and 6.3.2b show epoxy injection repair details. Details on application techniques are beyond the scope of this guide and may be found in ACI 224.1R, ACI RAP-1 and RAP-2, and ICRI 340.1. Experienced application personnel are essential, and special injection equipment is required. If aesthetically objectionable, surface gel and ports may be removed from the surface after the injection work has been completed; even so, the concrete surface is usually still marred from the injection work. The extent of material penetration can sometimes be verified by material coming out the opposite side of the member, although caution should be exercised that the leaking material does not cause injury or property damage. Core samples can be used to observe the depth of material penetration and to test the strength of the repaired concrete.

6.4—MethacrylatesTwo types of methacrylates are used for crack repairs:

high-molecular-weight methacrylates (HMWMs) and methyl methacrylates (MMAs). Both are reactive methyl methacrylic resins; the primary difference in chemistry is that HMWM is composed of larger, more complicated mole-cules with higher molecular weights (molecular weight of at least 150 is arbitrarily designated as high). There is no

Fig. 6.3.2a—Cracks in concrete beam prepared for epoxy injection. (Courtesy of Euclid Chemical Company.)

Fig. 6.3.2b—Epoxy injection in progress. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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standard specification for HMWMs, similar to that for epoxy resins.

6.4.1 Selection—Because of their high bond strength and relatively low viscosities, HMWMs and MMAs are typi-cally used for structural bonding and waterproofing repairs. Methyl methacrylates normally have a somewhat lower viscosity than HMWMs. High-molecular-weight methacry-lates and MMAs are available with a range of moduli and reaction rates, and can be formulated for various application requirements. They can be applied in cold temperatures and will adhere to themselves during recoating.

Two- and three-component HMWM systems are avail-able. Three-component systems are potentially explosive if the components are not mixed in the proper order. Two-component products are much safer. The two-component systems tend to have a shorter shelf life. Methyl methacry-lates are two-component systems.

Methyl methacrylates have a noticeable odor, which is non-toxic, and HMWMs have a less noticeable odor. High-molecular-weight methacrylates typically have a longer cure time than MMAs. Both materials can achieve similar penetration into concrete cracks. Both materials are flam-mable before polymerization; MMAs have a low flash point of approximately 50°F (10°C), and HMWMs have a flash point of approximately 180°F (82°C). Methyl methacrylates, in particular, should not be used in confined spaces or loca-tions subject to open flames. Both materials exhibit a detect-able loss of strength at elevated temperatures, such as when exposed to fire.

6.4.2 Installation—High-molecular-weight methacrylates and MMAs are sensitive to moisture; therefore, the crack surfaces should be dry at the time of application to obtain the required bond. Low viscosities and more forgiving mixing ratios make HMWMS and MMAs easier to mix than epoxy resins. The materials are normally applied by gravity feed to cracks in horizontal surfaces, either by brushing into the cracks, ponding over the cracks, or by flooding the surface. It is not uncommon to require a second application cycle to completely fill or waterproof the crack. Care should be taken

to minimize the damage from material flowing out of the underside of the member. Also, the cured materials are slick, and any material on the surface should be removed by sand-blast or other means, or sand should be broadcast into the material before it cures to improve traction. These materials are seldom pressure injected as their viscosities (typically 10 to 20 cP) are much lower than the viscosities of epoxy resins typically used for injection (100 to 500 cP) (ACI 503.5R). Similar to the injection of epoxy resins, the penetration of the material can be verified by back-side inspection or inspection of core samples. Figures 6.4.2a and 6.4.2b show crack treatment work in progress. Figure 6.4.2c shows the material penetration in a core sample. Refer to ACI RAP-13 for additional information.

6.5—Polyurethane chemical groutAlthough there are other forms of chemical grouts, poly-

urethanes are by far the most common choice of material for crack repairs. Polyurethane chemical grouts consist of a polyurethane resin that reacts with water to form an expan-sive closed-cell foam (hydrophobic types) or gel (hydrophilic types). Hydrophobic polyurethanes are generally recom-mended for applications subject to intermittent wetting and drying; hydrophilic polyurethanes have greater flexibility, but should be maintained continuously wet (USACE EM 1110-1-3500). No standards currently exist for polyurethane chemical grouts.

6.5.1 Selection—Polyurethane chemical grouts are used to repair leaking cracks, including those that are active or leaking a significant amount of water. They are well suited for repairing cracks in tanks used for the storage of liquids, dams, tunnels, sewers, and other water-containment struc-tures. These grouts are not used for structural repairs. Poly-urethane chemical grouts seal cracks by three mechanisms:

1) Bond to the sides of the crack;2) Expansive foaming action that creates a compression

seal;3) Penetration into small voids off the main crack to create

mechanical interlock.

Fig. 6.4.2a—High-molecular-weight methacrylate being spread with a broom. (Courtesy of Virginia Center for Trans-portation Innovation and Research.)

Fig. 6.4.2b—Sand being spread on high-molecular-weight methacrylate crack treatment. (Courtesy of Virginia Center for Transportation Innovation and Research.)





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These grouts are semi-flexible and can tolerate some change in crack width. The grouts have relatively low viscosities and can achieve good penetration into cracks. The reaction time to form the foam may be controlled from a few seconds up to several minutes using different catalyst additives. For example, where a crack is leaking heavily, the polyurethane chemical grout reaction may be highly accel-erated to stop the leak. Finally, these materials typically are unstable when exposed to ultraviolet (UV) light; this is not a concern, however, for crack repairs where the material is not exposed to UV light.

Once injected, the crack repair often performs satisfac-torily, indefinitely, with no maintenance; however, in some instances, reinjection may be necessary at a later time to address new water leakage. Hydrophilic grouts may deterio-rate if subjected to wetting and drying cycles.

6.5.2 Installation—These materials are installed by pres-sure injection, similar to epoxy resins. It is not uncommon to require two or three injection cycles to completely fill or waterproof the crack. A highly skilled work crew is required along with special injection equipment. If aesthetically objectionable, injection gel and ports may be removed from the surface after the injection work has been completed; the concrete surface, however, is usually still marred from the injection work. Similar to the injection of epoxy resins, the penetration of the material can be verified by back-side inspection, if accessible, or inspection of core samples. Figure 6.5.2 shows a crack injected with chemical grout.

6.6—Polyurethane sealantPolyurethane sealants result from a reaction between an

isocyanate group and a hydroxyl group. Typical polyure-thane sealants contain a polymer, fillers, colorants, curing agents, adhesion additives, thixotropic agents, plasticizers, and solvent (Panek and Cook 1992).

6.6.1 Selection—Polyurethane sealants are used to water-proof cracks on top horizontal and vertical surfaces. They are not used for structural repairs. These sealants are available in

one- and two-component varieties. Single-component prod-ucts are ready to use and do not require mixing; however, the color selection may be limited, and sufficient humidity should be present for proper curing. Two-component prod-ucts should be thoroughly mixed before using, and they may cure faster than one-component products in cold environ-ments. There is greater diversity in color choices with two-component sealants, particularly with the use of a color pack as a third component.

Polyurethane sealants generally provide an excellent bond to clean concrete surfaces and do not require a primer unless increased adhesion is required or in situations where the bonding surfaces are not as well prepared as desired. These sealants are suitable for active joints because of their very high elongation properties, due to their ability to relieve the stress at the bond line through controlled internal flow. The sealants work best when crack movements occur perpendic-ular to the crack. Sealant exposed to vehicular traffic should have a Shore A hardness of at least 25.

Polyurethane sealants have excellent resistance to weath-ering and will maintain their original material properties over time. Although the performance of the material is not particularly affected by UV light, the surface of sealant made with aromatic components will tend to chalk, forming a white, dusty deposit under long-term exposure. Certain formulations may be placed in submerged environments, such as cracks in water tanks and reservoirs, because their physical properties are unaffected, even under constant immersion. While the chemical resistance is generally not as good as an epoxy resin, some sealants with enhanced resistance are available. Sealant manufacturers should be consulted regarding the suitability of specific sealants for specific exposures.

Fig. 6.4.2c—Crack penetration verified by coring. (Cour-tesy of Virginia Center for Transportation Innovation and Research.)

Fig. 6.5.2—Polyurethane chemical grout injection. Courtesy of Restruction Corporation.)





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Polyurethane sealants are generally compatible with concrete and will not react with or stain the substrate. Coat-ings may be applied to some polyurethane sealants for a more uniform appearance, particularly on building facades. Dirt pickup can be a problem on coatings applied over poly-urethane sealant; this problem can be minimized by applying a primer over the sealant, as recommended by the coating manufacturer, prior to coating. Polyurethane sealants can provide a service life from 3 to 10 years, at which time they need to be removed and replaced. For optimum performance, polyurethane sealants should have regular inspections and maintenance.

6.6.2 Installation—Proper design of the sealant profile is critical to ensure the sealant performs as specified. Stress buildup in the sealant is minimized with a width-depth ratio of 2:1, with a maximum sealant depth of approximately 1/2 in. (13 mm). The maximum sealant width is generally 1 in. (25 mm), although some products may be applied up to 2 in. (50 mm) or more in width. A minimum sealant width is commonly 1/2 in. (13 mm); therefore, cracks have to be routed to comply with this limitation and the repaired crack is much wider than the original crack.

After routing, it is critical that the concrete surfaces be cleaned by sandblasting, blowing with compressed air, or other means. A bond breaker or backer rod is recommended in the bottom of the crack to provide only end binding of the sealant and allow the sealant to contract vertically when stretched horizontally, similar to a rubber band getting thinner when stretched. The sealant should be tooled imme-diately after application to ensure full contact with the crack edges. These materials do not require a high level of skill to install. Figure 6.6.2 shows sealant being installed in a routed crack.

6.7—Silicone sealantSilicone sealants are based on polymers with back-

bones of alternating silicon and oxygen atoms and carbon-containing side groups. They have different curing mecha-nisms, depending on the end group of the polymer (ASM International 1990). Typically, silicone sealants contain sili-

cone polymers, fumed silica, plasticizers, calcium carbonate fillers, and silanes for adhesion (Panek and Cook 1992).

6.7.1 Selection—Silicone sealants are used to waterproof cracks on vertical surfaces, but are not used for structural repairs. In general, silicone sealants are not intended for exposure to traffic wear and, if installed on top horizontal surfaces, should be recessed and protected from traffic. Some manufacturers, however, offer specialized sealant formulations that are suitable for exposure to traffic. Most silicone sealants are packaged as a single component. They are, however, available in two-component systems.

Silicone sealants commonly have significantly better elon-gation properties than polyurethane sealants, making them suitable for repairing active joints. A primer should be used for good adhesion to concrete. Silicone sealants tend to have poor stress relaxation characteristics and, as a crack widens, stress increases (particularly at the bond line) could result in adhesion loss or tearing of the sealant. With some sealants, oils from the silicone may migrate into porous substrates, such as concrete, resulting in aesthetically unacceptable substrate staining. Non-bleed silicone sealants are available. Silicone sealants are highly resistant to UV light, and do not chalk or change color even when exposed for long periods of time. These sealants may only be overcoated with silicone-based coatings, not with the acrylic coatings commonly used on facades. Silicone sealants are not recommended for immersion, and are not used for sealing cracks in water tanks, reservoirs, or dams. Long-term testing data should always be reviewed before specifying these materials. While they may have longer service life than polyurethane seal-ants, service life typically is five to 15 years, at which time the sealant is removed and replaced.

6.7.2 Installation—Installation of silicone sealants is similar to that for polyurethane sealants (6.6.2).

6.8—Silyl-terminated polyether sealant6.8.1 Selection—Silyl-terminated polyether (STPE) seal-

ants are one- or two-component crack sealants that have properties between those of polyurethane and silicone seal-ants. They are used on vertical surfaces, but are not used for structural repairs. In general, STPE sealants are not intended for exposure to traffic wear and, if installed on top horizontal surfaces, should be recessed and protected from traffic.

The properties of STPE sealants typically compare to those of polyurethane and silicone sealants:

a) Adhesion-to-peel strength—Similar to polyurethane sealants and higher than silicone sealants;

b) Elongation at break—Similar to polyurethane sealants, but less than silicone sealants;

c) Cyclic movement capability—Greater than polyure-thane sealants, but less than silicone sealants;

d) Tear strength—Less than polyurethane sealants, but higher than silicone sealants;

e) Shore A hardness—Less than polyurethane sealants, but higher than silicone sealants;

f) Tack-free time—Less than polyurethane sealants and similar to silicone sealants.

Fig. 6.6.2—Application of sealant in prepared crack. (Cour-tesy of Wiss, Janney, Elstner Associates, Inc.)





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Silyl-terminated polyether sealants are promoted as being more resistant to chalking than polyurethane sealants. Similar to polyurethane sealants, they do not stain adjacent substrates or require a primer, and can be coated soon after installation.

6.8.2 Installation—Installation of STPE sealants is similar to that for polyurethane sealants (6.6.2).

6.9—Polysulfide sealantPolysulfide sealant is a multi-component crack sealant

that is used for many applications unsuitable for other seal-ants, such as submerged conditions and cracks exposed to solvents and chemicals. Typical applications include swim-ming pools, fountains, cooling towers, fuel and chemical storage tanks, wastewater treatment plants, petrochemical plants, and areas with high foot traffic such as malls. Similar to the other sealants, they can be used to waterproof moving cracks, but are unsuitable for structural repairs. In some instances, particularly for submerged cracks, a primer is recommended for enhanced bond. Polysulfide sealant has similar sealant profile and crack preparation requirements to polyurethane sealant.

6.10—Flexible epoxy resin6.10.1 Selection—Flexible epoxy resins are two-compo-

nent systems formulated to provide some elongation capa-bility while still providing the strength and toughness of epoxy resin. Elongations of 25 to 60 percent can be achieved, compared to 1 to 10 percent for rigid epoxy resins discussed in 6.3. Flexible epoxy resins can develop a Shore A hardness of 90 to 95, compared to 15 to 50 for polyurethane, silicone, or polysulfide sealants. Flexible epoxy resins are used in applications where some movement capability is required, but where a harder crack treatment material is needed, such as for cracks and joints in industrial floors with forklift traffic where the flexible epoxy resin helps protect the edges of the cracks and joints from damage. These materials may discolor if exposed to UV light.

6.10.2 Installation—Flexible epoxy resin is installed in a sawcut or routed crack at least 1/8 in. (3 mm) wide by approximately 2 in. (50 mm) deep. The sawcut crack should be completely free of laitance, dust, dirt, debris, and coatings and sealers, and should have no frost or visible moisture. To avoid bonding of the epoxy to the bottom of the sawcut or routed crack, a backer rod may be installed at least 2 in. (50 mm) below the slab surface, or the crack may be “choked off” with a 1/4 in. (6.4 mm) maximum thick layer of clean, dry silica sand at the bottom of the sawcut. Both compo-nents should be accurately batched and thoroughly mixed. The material is commonly installed to within approximately 1/2 in. (13 mm) of the slab surface, and then overfilled with a second pass 60 to 90 minutes later, leaving a slight crown. After the material has cured, the crown is removed flush with the slab surface by shaving or grinding. Figure 6.10.2 shows flexible epoxy being installed in a crack.

6.11—Polyurea6.11.1 Selection—Polyureas have high Shore A hardness,

similar to flexible epoxy resins, but have a substantially larger elongation at break than flexible epoxy resins. Similar to flexible epoxy resins, they are used in applications where some movement capability is required, but where a harder crack treatment material is needed, such as for cracks and joints in industrial floors with forklift traffic where the poly-urea helps protect the edges of the cracks and joints from damage. Similar to flexible epoxy resins, aromatic polyureas may discolor if exposed to UV light; however, formulations of aromatic polyureas are available that are less susceptible to damage from UV exposure.

6.11.2 Installation—The polyurea is installed in a sawcut or routed crack at least 1/8 in. (3 mm) but no more than 1/2 in. (12 mm) wide. The prepared crack surfaces should be clean, sound, and dry; completely free of laitance, dust, dirt, debris, absorbed oils, and coatings and sealers; and should have no frost or visible moisture. The material is intended to completely fill the crack; therefore, backer rods or sand should not be used to reduce the volume of the cavity. Both components should be accurately batched and thoroughly mixed. The material is commonly installed from the bottom up, completely filling and slightly overfilling the crack in one pass. After the material has cured, the crown is removed flush with the slab surface by shaving or grinding.

6.12—Strip-and-seal systemsStrip-and-seal systems consist of a surface-mounted flex-

ible sheet, such as synthetic rubber, that spans over a crack and is adhered to the structure on each side of the crack using a suitable adhesive. These systems are used to waterproof cracks on vertical surfaces. Typically, they are not used on top horizontal surfaces that are exposed to pedestrian or vehicular traffic because of their exposed profile, unless cover plates are included. They are not used for structural repairs. Strip-and-seal systems are designed to be applied to the positive-pressure side of a structure, such that the water pushes the seal against the concrete surface.

Fig. 6.10.2—Application of flexible epoxy in prepared cracks and joints. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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6.12.1 Selection—Strip-and-seal systems have good elon-gation properties, making them appropriate for use on active joints. By adjusting the width of the unbonded flexible strip, the systems can be used for a wide variety of crack widths and movements. Moisture-insensitive epoxy resins may be used as an adhesive on damp surfaces. Some strip-and-seal systems are highly resistant to UV light, and will not chalk or weather. Some systems have a high resistance to aggressive chemicals. Strip-and-seal systems are sometimes effective in stopping leaks that other crack repair materials cannot effec-tively address. Strip-and-seal systems have a service life of 5 to 10 years, at which time they are removed and replaced.

6.12.2 Installation—As the strip-and-seal systems are surface-mounted over the crack and do not extend into the crack, the concrete surfaces on both sides of the crack, but not the crack surfaces, should be clean and sound; free of dust, laitance, grease, curing compounds, sealers, and other contaminants; and free of standing water. The adhesive is batched and mixed, and the flexible sheet is wiped with an activator. The adhesive is then applied to the concrete surfaces on both sides of the crack; the flexible sheet is set in the adhesive and rolled with a hard roller; and a thin layer of adhesive is applied on top of the flexible sheet as a top coat. Generally, these systems do not require any special worker skills or equipment to install.

6.13—GroutsGrouts are flowable mixtures of a binder and, typically,

a fine aggregate such as silica sand. For cement grouts, the binder is portland cement and water, sometimes with admix-tures. The binder for polymer-modified cement grout is port-land cement, water, and a polymer such as acrylic, styrene-acrylic, styrene-butadiene, or a water-borne epoxy resin; sometimes admixtures are also included. The polymer modi-fier should produce mortar that conforms to the requirements of ASTM C1438 Type II mortar. The binder for polymer grout is a polymer, such as an epoxy resin or urethane. For polymer grout, oven-dried silica sand with a grading from 20 to +40 mesh (0.8 to 0.4 mm) is commonly used. No stan-dards exist for cement grouts, polymer-modified cement grouts, or polymer grouts intended for use as crack repair.

6.13.1 Selection—Grouts are commonly used to fill rela-tively wide cracks, at least 1/8 in. (3.2 mm) or wider, in top horizontal surfaces by gravity feed. Due to relatively high viscosities compared to epoxy resins and HMWMs, limited crack penetration is common. For wide cracks on vertical surfaces, a stiff grout may be hand-packed into the cracks. In most cases, grout repairs are fairly superficial. Grouts usually are only crack fillers, and have limited, if any, water-proofing value. They are generally ineffective for structural repairs and at active cracks.

If the crack and crack surfaces can be cleaned of dirt and debris, grouts (particularly polymer grouts) may achieve limited bond to the concrete; however, this cleaning is diffi-cult to perform. Most polymer grouts will not bond to moist concrete surfaces; however, moist concrete surfaces may

be beneficial for bonding polymer-modified cement grout and cement grout. Some polymer grouts, depending on the binder used, are moisture-tolerant and will cure in the pres-ence of moisture.

Polymer grouts have relatively low shrinkage, whereas polymer-modified cement grouts and cement grouts will shrink and perhaps separate from the sides of the crack. Polymer grouts are the most resistant to chemicals and can be designed for fast cure times, but may lose some strength at elevated temperatures. Polymer grouts are also the most costly grouts. Polymer-modified cement grouts have enhanced properties compared to cement grout. Cement grout is the most economical.

6.13.2 Installation—Routing the crack surface may facili-tate initial penetration of the material. Flushing the crack with water or sandblasting the surface of the crack, or both, could also be beneficial. Water, however, should not be used if the repair grout is moisture-intolerant. It is critical to properly proportion and thoroughly mix grout components, particu-larly with polymer grouts. Failure to do so could result in a polymer grout that fails to cure or cures sporadically.

For polymer grouts, pot life or working time may be varied to suit the application. Long pot life enables the applicator to mix and apply larger quantities. Fast-cure products allow rapid turnover; however, care should be taken to mix only sufficient material that may be applied within the specified pot life.

No special equipment is required to apply these materials and the required applicator skill levels are low to moderate.

6.14—Selection of crack repair materialsTable 6.14 summarizes the information in this chapter

regarding suitable applications for the various crack repair materials.

Table 6.14—Repair material selection guide for repair of cracks with widths ranging from 0.002 to 1/4 in. (0.05 to 6.4 mm)

Repair materialCrack

movementMoisture in crack

Note 1Structural bonding

Epoxy resin Dormant Moist or dry YesHigh-molecular-weight methacrylate or methyl

methacrylateDormant Dry Yes

Polyurethane chemical grout

Active or dormant

Actively leaking, wet, or dry No

Polyurethane, silicone, STPE, or polysulfide

sealant

Active or dormant Dry No

Flexible epoxy resin or polyurea

Active or dormant Dry No

Strip-and-seal systems Active or dormant

Crack wet or dry; dry on surface No

Cement, polymer-modified cement, or polymer grouts Dormant Dry or damp No

Note: Not all formulations of a type of repair material may be appropriate for all crack moisture conditions. Specific formulations may need to be selected based on the crack moisture condition.





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CHAPTER 7—PROPERTIES OF SURFACE SEALERS, ANTI-CARBONATION COATINGS, AND

TRAFFIC-BEARING ELASTOMERIC COATINGS AND THEIR IMPORTANCE

7.1—GeneralChapter 7 discusses properties of surface sealers, anti-

carbonation coatings, and traffic-bearing elastomeric coat-ings and test methods used to evaluate them. Some test methods are not specifically applicable for certain repair materials or applications, but may be useful for comparing repair materials. Descriptions of the various test methods are necessarily brief. The standards themselves should be consulted for details. Material manufacturers should provide test data based on standardized ASTM and other test methods that contain sufficient details for the published values to be replicated and verified. Refer to Appendix A for further discussion regarding modifications to standard test methods.

Many properties of repair materials and of existing concrete are time-dependent. In all cases where material properties are specified, the corresponding age of the mate-rials should be noted. The user should note that most ASTM test methods cited in this guide are performed at standard conditions, essentially room temperature. The reported properties may not reflect the actual properties of the repair material in service conditions.

7.2—Properties of surface sealersSurface sealers are intended to significantly reduce water

and, perhaps, chemical penetration into the concrete. To function satisfactorily, the sealer should bond to and remain bonded to the concrete surface. The sealer also should have adequate durability for the service environment to which it is exposed.

7.2.1 Water and chloride ion absorption—Water and chloride ion absorption are measures of the reduction in absorption and, hence, the sealer effectiveness, of treated specimens compared to untreated concrete control speci-mens. These properties are usually primary considerations in selecting a sealer.

Seven test methods used to measure relative absorption are:1) National Cooperative Highway Research Program

(NCHRP) Report 244 (1981), Series I Procedure;2) NCHRP Report 244, Series II Procedure;3) ASTM D6489;4) American Association of State and Highway Transpor-

tation Officials (AASHTO) T259;5) ASTM C1543;6) Strategic Highway Research Program (SHRP)-S-330,

Appendix E;7) ASTM C642.Two other test methods that are sometimes referenced by

manufacturers are ASTM D6904 and ASTM E514.National Cooperative Highway Research Program Report

244 (1981) was a groundbreaking study in 1981 that devel-oped standardized tests for evaluating the effectiveness of surface sealers. The procedures include a quick screening test (Series I and II) that determines reduction in absorption

of water and chloride ions compared to untreated concrete, and a 24-week accelerated weathering test (Series IV) intended to simulate field environments, which determines reduction in chloride ion absorption compared to untreated concrete. The Series II procedure is a fine-tuned version of the Series I procedure, with a shortened test period. The Series II test is still the primary test for evaluating the reduc-tion in water/chloride ion absorption of sealers compared to untreated concrete.

ASTM D6489 is a laboratory test for water absorption of concrete core samples treated with surface sealers.

American Association of State and Highway Transpor-tation Officials T259 is a 90-day ponding test that deter-mines the reduction in chloride ion absorption compared to untreated concrete. ASTM C1543 is a ponding test similar to AASHTO T259; however, this procedure does not specify a specific protocol for applying and curing surface sealers. ASTM C1543 also does not have a specific test time period, although a minimum test period of 3 months is implied.

SHRP-S-330, Appendix E, is a water-absorption test that may be performed in the laboratory or in the field.

ASTM C642 is a procedure for determining the absorp-tion of concrete; some manufacturers have modified the procedure to determine the reduction in absorption of sealers compared to untreated concrete. This test is not specifically intended for surface sealers and bears no resemblance to field environments. ASTM D6904 and ASTM E514 are proce-dures for determining water penetration through coated and uncoated unit masonry due to wind-driven rain. These test methods are not directly applicable to concrete substrates and are not discussed further in this guide.

Chloride ions in concrete may be in the pore water, on the surfaces of aggregates, or bound up in the cement paste. Chlorides ion that are bound up in the cement paste are generally not available to participate in the corrosion of steel embedded in concrete, although the chloride ions may become unbound due to chemical reactions during the life of the concrete. Total chloride ion content, including bound chloride ions, is measured by an acid-soluble method, ASTM C1152; only unbound chloride ions can be measured by a water-soluble procedure, ASTM C1218. The water-soluble chloride ion content will always be less than the acid-soluble content. In determining chloride ion penetration into hardened concrete, water-soluble content might be more appropriate, but the acid-soluble content is more reproduc-ible and less time-consuming to measure and has become more accepted (ACI 222R). For more information about measuring chloride ion content, refer to ACI 222R.

When testing for chloride ion absorption, the initial chlo-ride ion content of the concrete and the C3A content of the binder should be determined. The initial chloride ion content provides a baseline for test results, and the C3A content is an indication of the potential for chloride ion capture in the water-insoluble form.

NCHRP Report 244, Series I Procedure—In this proce-dure, nominal 4 in. (100 mm) concrete cubes are cast. One day after casting, the forms are stripped and the specimens are moist-cured for 7 days. They are then lightly sand-





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blasted, weighed, and air-cured for 21 days. The sealers are applied 28 days after casting, and the specimens are air-dried for 14 days to allow the sealers to cure. The specimens are then immersed in a 15 percent NaCl solution for 21 days; the saturated surface-dry (SSD) weight is measured at 3, 6, 9, 12, 15, 18, and 21 days. The specimens are then air-dried for 24 days, and the weight is measured at 3, 6, 9, 12, 15, 18, 21, 22, 23, and 24 days. The specimens are then split in half, one half is crushed, and the total acid-soluble chloride ion content is determined. Percent weight gains and chloride ion contents are reported. The percent weight gain during the immersion period is calculated. The reduction in the percent weight gain compared to the percent weight gain of untreated concrete is a measure of the effectiveness of the surface sealer. The total chloride ion contents are a measure of the reduction in chloride ion absorption compared to untreated concrete. The depth of penetration of the sealer into the concrete can be measured on the remaining half of the split specimen, as discussed in 7.2.3.

NCHRP Report 244, Series II procedure—This procedure is a fine-tuned version of the Series I procedure with a short-ened test period. After 7 days of moist curing, the specimens are lightly sandblasted, weighed, and then moist-cured for an additional 14 days. Twenty-one days after casting, the speci-mens are air dried for 31 days. The sealer is applied 1, 5, or 21 days into the air drying period and cured until the end of the air-drying period. The specimens are weighed every 7 days during the air-drying period. Fifty-two days after casting, after air-drying, the specimens are immersed in a 15 percent NaCl solution for 21 days; the SSD weight is measured at 3, 6, 9, 12, 15, 18, and 21 days. The specimens are then air-dried for 21 days, and the weight is measured at 3, 6, 9, 12, 15, 18, and 21 days. The specimens are then split in half, one half is crushed, and the total acid-soluble chloride ion content is determined. Percent weight gains and chloride ion contents are reported. The reduction in the percent weight gain compared to the percent weight gain of untreated concrete is a measure of the effectiveness of the surface sealer. The total chloride ion contents are a measure of the reduction in chloride ion absorp-tion compared to untreated concrete.

ASTM D6489—In this procedure, concrete core samples approximately 2.75 in. (70 mm) in diameter by 3 in. (75 mm) in length are extracted from a concrete member that has had a surface sealer applied to its surface. The surfaces of the core samples are cleaned and the samples dried until successive weights after 24 hours vary by no more than 0.2 percent. The sides of the samples are sealed with wax or epoxy. The samples are weighed and then placed upside down, with the sealed end down, on glass rods in a container. The container is filled with water to 2.5 in. (64 mm) above the top of the glass rods, taking care to avoid wetting the tops of the specimens. The specimens are soaked for 48 hours, removing them from the water and weighing them after 24 and 48 hours in immer-sion. The percent absorption is calculated based on the weight of the sample prior to application of the coatings and sealers. Refer to Fig. 7.2.1a for a schematic of the test setup.

AASHTO T259—In this procedure, concrete specimens at least 3 in. (75 mm) thick with a minimum surface area of

27 in.2 (175 cm2) are moist cured for 14 days and then air dried for 28 days. The sealer is applied to the top surfaces of the specimens 21 days after casting, during the air-drying period. For sealers that will be exposed to vehicular traffic, approximately 1/8 in. (3.2 mm) of the specimen top surfaces is abraded off 28 days after casting. Also 28 days after casting, 3/4 in. (19 mm) dams are placed around the tops of the specimens. Forty-two days after casting, after air drying, the tops of the specimens are ponded with 1/2 in. (13 mm) of 3 percent NaCl solution for 90 days. At the end of 90 days, the acid-soluble or water-soluble chloride ion contents are determined 1/16 to 1/2 in. (1.6 to 13 mm) and 1/2 to 1 in. (13 to 25 mm) below the top surfaces of the spec-imens. The reduction in chloride ion absorption compared to untreated concrete is reported. This test procedure is also used to measure the permeability of concrete repair mate-rials, as discussed in 4.6.2. This test is recommended for testing surface sealers, but the long test time period may be considered undesirable.

SHRP-S-330, Appendix E—In this procedure, a water cell is adhered and sealed to the concrete test surface that is clean, dry, and free from grooves, cracks, and irregularities. The concrete test surface should be at least several inches (millimeters) larger than the water cell diameter. For hori-zontal surfaces, the water cell has a 3 in. (75 mm) diameter opening for contact with the concrete surface; for vertical surfaces, the water cell has a 2 in. (50 mm) diameter contact area opening. Water is added to a capillary tube that is attached to the water cell, to a height of approximately 15.75 in. (400 mm). The height of water in the capillary tube is measured every minute for 10 minutes. The sealer is rated as good, moderate, or poor based on the drop in water height in 4 minutes and 10 minutes: good sealers have a drop in water height of 0 to 3/8 in. (0 to 10 mm) in 4 minutes and 0 to 3/4 in. (0 to 20 mm) in 10 minutes; moderate sealers have a drop in water height of 3/8 to 3/4 in. (10 to 20 mm) in 4 minutes and 3/4 to 1.6 in. (20 to 40 mm) in 10 minutes; and poor sealers have a drop in water height of more than 3/4 in. (20 mm) in 4 minutes and more than 1.6 in. (40 mm) in 10 minutes. Figure 7.2.1b shows the SHRP-S-330, Appendix E, test setup.

Fig. 7.2.1a—Schematic of ASTM D6489 test set-up. (Cour-tesy of Wiss, Janney, Elstner Associates, Inc.)





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ASTM C642—In this procedure, concrete specimens consisting of cylinders, beams, or other shapes with a minimum volume of 54.3 in.2 (35,000 mm2) are weighed, dried in an oven at 212 to 230°F (100 to 110°C) for at least 24 hours, coated with a sealer, and then weighed again. The specimens are immersed in water for at least 48 hours and weighed SSD. The specimens are then covered with water and boiled for 5 hours. The specimens are then cooled by natural loss of heat for at least 14 hours to a final temperature of 20 to 25°C (68 to 77°F) and weighed SSD. The reduction in water absorption compared to untreated concrete is deter-mined after immersion and after immersion and boiling.

7.2.2 Water vapor transmission—Water vapor transmis-sion is a measure of the breathability of the sealer. This prop-erty allows water vapor in the concrete to migrate through the sealer rather than building up pressure and possibly debonding the sealer.

Three test methods are used to measure water vapor transmission:

1) NCHRP Report 244, Series I and II procedures;2) Oklahoma Department of Transportation (OKDOT)

OHD L-35 (inactive);3) ASTM D1653 and ASTM E96.In the NCHRP Report 244, Series I procedure, the sealer

is applied to the test specimen, the moisture gain is then measured during 21 days of submersion, and then the subse-quent moisture loss is measured during 24 days of air drying. In the Series II procedure, the sealer is applied to the test specimen, the moisture gain is then measured during 21 days of submersion, and then the subsequent moisture loss is measured during 21 days of air drying. In the OKDOT OHD L-35 procedure, the sealer is applied after the specimen has been submerged in water for 48 hours, and then the subse-quent moisture loss is measured during oven drying until a constant weight is attained. The results of the OKDOT OHD L-35 procedure depend on the ability of the sealer to be applied to an SSD surface. In ASTM D1653 and ASTM E96, the sealer is applied to a substrate and the specimen is sealed to the open mouth of a cup or dish containing desic-cant or water. The cup or dish is placed in a controlled-envi-ronment test chamber for 3 weeks and weighed daily. In all of the procedures, water vapor transmission is determined by the moisture loss during the drying period. Water vapor transmis-sion rates should only be compared to values for other sealers and untreated concrete obtained using the same test procedure.

NCHRP Report 244, Series I and II procedures—These procedures are discussed in 7.2.1. The percent weight loss during the air-drying period is reported. This percent weight loss is a measure of the water vapor permeability of the sealer and is compared to the initial weight of the specimens prior to immersion in the NaCl solution.

OKDOT OHD L-35—In this procedure, nominal 8 x 8 x 2 in. (200 x 200 x 50 mm) concrete specimens are cast and cured for 7 days. The specimens are then oven-dried to a constant weight, cooled to room temperature, and then placed in deionized water for 48 hours. The specimens are brought to an SSD condition and weighed. All six sides of the specimens are then coated with the sealer, and the

specimens weighed. The specimens are then oven-dried to a constant weight, which is recorded. The percent moisture loss is calculated and compared to untreated concrete.

ASTM D1653 and ASTM E96—In the D1653 proce-dure, the sealer is applied to a substrate and the specimens are air-dried for 7 days. The specimens are then tested by Test Method A (Dry Cup Method) or Test Method B (Wet Cup Method). For Test Method A, the specimen is sealed to the open mouth of a cup or dish containing desiccant, with the sealer surface away from the desiccant. The cup or dish assembly is weighed and placed in a test chamber that is maintained at 73°F (23°C) and 50 percent relative humidity (Condition A) or 100°F (38°C) and 90 percent rela-tive humidity (Condition B) for 3 weeks. The cup or dish assembly is weighed daily. For Test Method B, the specimen is sealed to the open mouth of a cup or dish containing water, with the sealer surface toward the water; the water level should be maintained to avoid contact with the sealed surface. The cup or dish assembly is weighed and placed in a test chamber that is maintained at 73°F (23°C) and 50 percent relative humidity (Condition A) or 100°F (38°C) and very low (near zero) relative humidity (Condition C) for 3 weeks. The cup or dish assembly is weighed daily. Figure 7.2.2 shows several types of dishes used in the test.

Fig. 7.2.1b—Schematic of SHRP-S-330, Appendix E, test setup for vertical surfaces. The water cell is attached to the vertical surface. (Courtesy of Transportation Research Board.)

Fig. 7.2.2—Several types of dishes used for ASTM D1653 and ASTM E96. (Reprinted with permission from ASTM E96.)





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The weight change against elapsed time is plotted, and the water vapor transmission rate is the slope of a straight line through the data points. The water vapor transmission rate is compared to rates for other sealers or untreated concrete. The ASTM E96 procedure is similar to, but less specific than, the D1653 procedure.

7.2.3 Depth of penetration into concrete—Depth of pene-tration is a measure of the ability of the sealer to penetrate below the concrete surface. This ability will improve the durability of the sealer if exposed to abrasion.

Two test methods are used to measure the depth of pene-tration into concrete:

1) NCHRP Report 244, Series II procedure;2) OKDOT OHD L-34 (inactive).Both test methods are similar in that the sealer is applied to

the specimen surface, and the specimen is split into sections. The concrete surfaces of the splits are wetted and the depth of non-wettable concrete is observed and measured.

NCHRP Report 244, Series II procedure—This proce-dure is discussed in 7.2.1. The depth of penetration can be determined and measured based on non-wettable concrete on the concrete exposed on the split specimens. Figure 7.2.3 shows the depth of sealer penetration into a concrete cube specimen. The dark area in the middle of the cube shows wet concrete unprotected by the surface sealer and the lighter area around the edges of the cube indicates where the surface sealer has penetrated below the concrete surface and protected the concrete from water penetration.

OKDOT OHD L-34—In this procedure, nominal 8 x 8 x 2 in. (200 x 200 x 50 mm) concrete specimens are cast and cured for 7 days. The specimens are then oven-dried to a constant weight. One of the 8 in. (200 mm) square surfaces is then treated with the sealer and cured. The specimens are then split into four sections and each section is soaked in water for 1 minute. The depth of concrete below the sealed surface that is not wet—indicative of the depth of penetra-tion of the sealer—is observed and measured.

7.2.4 Accelerated weathering—Accelerated weathering testing attempts to simulate the effects of ultraviolet (UV) radiation, moisture, and other environmental conditions on the performance and degradation of the sealer.

Three test methods are used to simulate service conditions:1) NCHRP Report 244, Series IV, southern and northern

exposure procedures;2) ASTM G154.ASTM G154 replaced ASTM G53, which is sometimes

referenced by manufacturers but was withdrawn in 2000. Another test method that is sometimes referenced by manu-facturers is ASTM G156.

NCHRP Report 244, Series IV test procedures are 24-week accelerated weathering tests intended to simulate field envi-ronments, which determine the reduction in chloride ion absorption compared to untreated concrete. The southern exposure procedure aggressively tests the durability of the sealer when exposed to cycles of saltwater ponding and UV light and heat. The northern exposure procedure exposes the sealer to a wider range of environmental conditions, including acid, saltwater, infrared heat, UV light, fresh water rinse, and freezing and thawing. ASTM G154 is a general test method that specifies cyclic exposure to moisture and UV light and heat. ASTM G156 is a subjective description of general components of a weathering test program; is not specifically applicable for testing surface sealers; and is not discussed in detail in this guide.

NCHRP Report 244, Series IV procedures—In these procedures, nominal 5 in. thick by 12 in. square (127 mm thick by 305 mm square) concrete slabs are cast. The slabs may be unreinforced, or some of the slabs may include uncoated reinforcing steels. A 1 in. (25 mm) high dike is attached to the top surfaces of the slabs. The slabs are cured with wet burlap and plastic overnight, and then the forms are stripped and the slabs cured with polyethylene for 21 days. At an age of 18 to 20 days, the top surfaces of the slabs are lightly sandblasted. After the 21 days of moist curing, the slabs are air-dried for 5 days. The four sides of each slab are then coated with two coats of a high-solids epoxy, and the top surface is coated with the sealer. The coatings then cure for 16 days of air drying.

For the southern exposure test, the slabs are then subjected to a weekly cycle of 100 hours of exposure to ponded 15 percent NaCl solution at approximately 60 to 70°F (15.5 to 21.2°C), followed by rinsing with fresh water, and then 68 hours of exposure to 100°F (37.8°C) heat with UV light, for the 24-week test period. For the northern exposure test, the slabs are subjected to a 24-hour test cycle for 5 days each week and stored in a thawed non-test condition for 2 days each week for the 24-week test period. The 24-hour test cycle consists of:

1) Fifteen hour overnight freeze in air at 15°F (–9.4°C) for four nights each week.

2) Two-hour thaw in air at 60 to 70°F (15.6 to 21.1°C).3) Three-hour exposure to UV radiation and infrared heat

at 100°F (37.8°C).

Fig. 7.2.3—NCHRP 244, Series II, cube absorption spec-imen. (Courtesy of Cortec Corporation.)





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4) Three-hour soak period with 15 percent NaCl and 0.02 molar sulfurous acid water solution on test surface (fresh solution daily).

5) Fresh water rinse and drain and repeat from Step 1.The slabs are visually inspected during the 24-week test

period and visible deterioration of the sealer and the concrete is documented. For slabs with embedded reinforcement, corrosion potentials are measured by copper-copper sulfate half-cell weekly for the first 6 weeks and biweekly thereafter. After the 24-week test period, the total acid-soluble chloride ion content is measured approximately 1/2 to 1-1/4 in. (12.7 to 32 mm) below the slab surface. For slabs with embedded reinforcement, the steel is carefully removed from the slabs and the amount of steel surface that is corroded and degree of corrosion are estimated visually. The reduction in chloride ion absorption compared to untreated concrete is reported. Figure 7.2.4 shows an NCHRP Report 244, Series IV test in progress.

ASTM G154—This practice is a general method of exposing specimens to cycles of sunlight and moisture. The practice describes a number of fluorescent lamps and suggests several exposure cycles. Moisture exposure may be by water spray, condensation, or relative humidity. The specific choice of fluorescent lamp, method of moisture exposure, duration of UV and moisture cycles, and number of test cycles is left to the discretion of the evaluator. The specimens are visually inspected periodically during the test to document the sealer performance. ASTM G154 replaced ASTM G53, which was withdrawn in 2000. ASTM G53 is similarly general, but only allows moisture exposure by condensation. This practice is not recommended due to its vagueness.

7.2.5 Chemical analysis—Chemical analysis includes the identification of the active substance and the solvent in the sealer, and the determination of the percent solids or active substance in the sealer and the volatile organic content (VOC) of the sealer.

Two test methods are used to measure the VOC of the sealer:

1) Title 40 Code of Federal Regulation (CFR) Part 60 (40 CFR 60), Appendix A, Method 24;

2) ASTM D5095.In both procedures, the sealer is dispersed in a solvent

or catalyst, and then heated in an oven to release volatile materials. The VOC content is then calculated based on the sample weights before and after heating.

7.2.6 Flame spread and smoke development—The flame spread index and the smoke developed index are compara-tive measures of the performance of a sealer when exposed to fire. ASTM E84 is a test method used to measure these indexes. A concrete specimen that is 23.5 to 25 ft long by 20 to 24 in. wide by 4 in. maximum thickness (7.2 to 7.6 m long by 508 to 610 mm wide by 102 mm maximum thickness) is coated on one surface with the sealer and conditioned at 73°F (23°C), 50 percent relative humidity, to a constant weight. The specimen is placed in a fire test chamber, and exposed to the test fire. The flame spread along the length of the specimen is visually determined versus time, the temper-ature at the exhaust end of the specimen is measured versus time, and the smoke density is measured with a photoelectric cell versus time. The flame spread index is then determined based on the area under the time-flame spread distance plot. The smoke developed index is based on the area under the time-light absorption curve, divided by the area under the time-absorption curve for a red oak calibration sample.

7.2.7 Mold/fungus resistance—Mold resistance is a comparative measure of the resistance of a coating to mold growth. ASTM D3273 is a test method used to measure this property. Test panels 4 x 3 x 1/2 in. (100 x 75 x 12.7 mm) are coated on all surfaces with two coats of the sealer, and the panels conditioned. The test panels are hung vertically in a test cabinet, with the bottoms of the panels approximately 3 in. (75 mm) above the surface of a tray of potting soil to which cultures of three types of mold have been added. The test cabinet is maintained at a temperature of 90.5°F (32.5°C) and a relative humidity of 95 to 98 percent for 4 weeks, and the test panels are visually rated weekly for mold growth using photographic standards.

7.2.8 Other properties—Other material properties that may be useful include construction characteristics, aesthetic features, durability, environmental impact both during installation and service, and ease of reapplication or repair.

Construction characteristics that may be of interest include:a) Flash point and combustibility;b) User safety;c) Storage and handling procedures;d) Environmental limitations, such as temperature,

humidity, and moisture conditions before, during, and after application;

e) Substrate and sealer cure times;f) Bond of subsequently applied materials;g) Overspray damage to vegetation and non-porous

surfaces such as glass, metal, and painted surfaces.An aesthetic feature that may be considered is whether the

sealer cures clear, translucent, or opaque, including if the sealer discolors the concrete. Other considerations are the colorfastness of opaque sealers and the appearance of the sealed concrete surface when wet.

Fig. 7.2.4—NCHRP 244, Series IV testing in progress. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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The durability of the sealer due to exposure to pedes-trian or vehicular traffic may be a concern on top horizontal surfaces.

7.3—Properties of anti-carbonation coatingsAnti-carbonation coatings reduce the penetration of

carbon dioxide into the concrete. To be effective, they should be able to bridge cracks in the concrete substrate and should have good weathering durability, including resistance to UV light. It may be desirable that the coating is breath-able, allowing water vapor to pass through.

7.3.1 Carbon dioxide diffusion—Carbon dioxide diffusion is measured by EN 1062-6. In this procedure, the coating is applied to the substrate and dried in accordance with the manufacturer’s instructions, and then conditioned. The carbon dioxide diffusion is then measured by either Method A or B. In Method A, the test cell is filled with a carbon dioxide absorbent, such as sodium hydroxide, and the test specimen is sealed in the top of test cell, creating a gas-tight enclosure, with the coated side facing upward. The test cell is placed in a test chamber and exposed to a measuring gas containing 10 percent carbon dioxide and 90 percent dry air. The measuring gas is the means of exposing the test specimen to carbon dioxide. The test cell is weighed every 24 hours or at longer intervals, until the mass increase in two subsequent intervals is constant. After the test is completed, the coating thickness is measured optically after the specimen has been broken in half. Carbon dioxide diffusion is then calculated in terms of equivalent air layer thickness; that is, the thick-ness of a static air layer that has the same carbon dioxide diffusion rate, under the same conditions. The Method A test setup is shown in Fig. 7.3.1a.

In Method B, the test specimen is clamped between two halves of a permeation cell, and the two halves are made gas-tight to each other and to the surroundings. A measuring gas stream containing approximately 10 percent carbon dioxide is passed through the side of the permeation cell with the exposed coating; and a carrier gas stream, usually either nitrogen or air free from carbon dioxide, is passed through the other side of the permeation cell. The diffused carbon dioxide in the carrier gas stream is measured by infrared spectrometry or gas chromatography. The test is continued

until a steady state is reached; that is, the carbon dioxide concentration no longer changes with time. Similar to Method A, after the test has been completed, the specimen is broken in half and the coating thickness is measured opti-cally. The carbon dioxide diffusion is then calculated in terms of equivalent air layer thickness. The Method B test setup is shown in Fig. 7.3.1b.

As the absorbent used in Method A will react with humidity from the measuring gas, the measuring gas should be dry. If it is desired to know the carbon dioxide permeability at different humidity levels, Method B should be used.

7.3.2 Water vapor transmission or permeability—Water vapor transmission rate is the steady water vapor flow in unit time through a unit surface area of specimen, under specific conditions of temperature and humidity at each surface. Water vapor transmission rate can be expressed in units of g/h·ft2 (g/h·m2) or as equivalent air layer thickness; that is, the thickness of a static air layer that has the same water vapor transmission rate, under the same conditions. Water vapor permeance is the water vapor transmission rate induced by a unit vapor pressure difference across the spec-imen, expressed in units of Perm (g/Pa·s·m2); permeance is a performance evaluation, not a property of the material. Water vapor permeability is permeance multiplied by the coating thickness, expressed in terms of Perm-in. (g/Pa·s·m).

Two test methods are used to measure water vapor trans-mission through a coating:

1) ISO 7783;2) ASTM E96.ISO 7783—In this procedure, the coating is applied to

a substrate at a thickness recommended by the manufac-turer. The coating is cured for 28 days at 74°F (23°C) and 50 percent relative humidity. The specimen is then condi-tioned with three cycles of 24 hours of storage in water at 74°F (23°C) and 24 hours of drying at 122°F (50°C). The average dry film thickness is calculated based on the amount of non-volatile material used. An aluminum dish is partially filled with a saturated solution of ammonium dihydrogen phosphate, and the specimen is placed on top of the dish, with the coating down. Care should be taken to avoid contact between the solution and the specimen. The saturated solu-tion of ammonium dihydrogen phosphate produces a rela-tive humidity of 93 percent inside the dish. The sample is

Fig. 7.3.1a––EN 1062-6, Method A, test setup.

Fig. 7.3.1b–– EN 1062-6, Method B, test setup.





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weighed and then maintained at a temperature of 74°F (23°C) and a relative humidity outside of the dish of 50 percent. The sample is periodically weighed until the change in mass becomes directly proportional to the time interval, indicating a constant diffusion rate. The water vapor diffu-sion is calculated in terms of equivalent air layer thickness.

The ASTM E96 procedure is explained in 7.2.2.7.3.3 Other properties—Other material properties that

may be of interest include:a) Tensile strength and elongation at break to judge crack

bridging ability. ASTM D412, discussed in 5.4.2, is used to measure these properties;

b) Chemical analysis, particularly the percent solids content and the VOC, as discussed in 7.2.5;

c) Mold/fungus resistance, evaluated by ASTM D3273, which is discussed in 7.2.7;

d) Weathering durability and resistance to UV light.Refer to 7.2.8 for other properties and characteristics that

may be of concern.

7.4—Properties of traffic-bearing elastomeric coatings

Traffic-bearing elastomeric coatings are primarily used to reduce water penetration into top horizontal concrete surfaces. Important properties include the water perme-ability, crack bridging, adhesion to concrete, and durability for exposure to traffic and weather.

7.4.1 Low-temperature flexibility and crack bridging—Two test methods are used to measure low-temperature flex-ibility and crack bridging:

1) ASTM C1305 as modified by ASTM C957 and C836;2) ICC Evaluation Service ES-AC39-12.ASTM C1305 as modified by ASTM C957 and C836—In

this procedure, 1 x 1 x 2 in. (25 x 25 x 50.8 mm) mortar blocks are cast and cured. Two blocks are taped together with the test surface level and sides touching. The total elas-tomeric system, including primer, base coat, top coat, and aggregate, is applied to the test surface, with a minimum cured thickness of 0.020 in. (0.5 mm) excluding the aggre-gate. The test assembly is then cured at room temperature for 14 days followed by 7 days in an oven at 158°F (70°C). After the test assembly cools to room temperature, 6 mm (1/4 in.) wide strips of coating are removed along both sides of the assembly, across the joint. If needed, aluminum angles are adhered to the sides of the assembly for gripping during the test. The test assembly is then preconditioned to –15°F (–26°C) for at least 24 hours, the tape is removed from the blocks, and the assembly is placed in a test machine. The assembly undergoes 10 cycles of stretching to a gap of 1/16 in. (1.6 mm) and closing, at a rate of 1/8 in. (3.2 mm)/h. The assembly is then extended to 1/16 in. (1.6 mm) and the coating is examined for cracking, splitting, pinholes, or other conditions in the area of the joint. The test is performed on five test assemblies, and observed physical changes in the coating are reported. Figure 7.4.1 shows an ASTM C1305 test setup.

ICC ES-AC39-12—In this test method, five specimens are exposed to a temperature of 5°F (2.8°C) for 2 hours.

The specimens are then immediately positioned over a 1 in. diameter by 4 in. long (25 mm diameter by 102 mm long) mandrel, with the weathering side of the specimens outward and bent 180 degrees over the mandrel. The specimens are then observed under 5× magnification and any cracking or crazing is reported. Details of the specimen dimensions, preparation, and curing are left to the discretion of test participants, but are included in the evaluation report.

7.4.2 Adhesion to concrete—Three test methods are used to measure adhesion to concrete:

1) ASTM D4541;2) ASTM C794 as modified by ASTM C957;3) ASTM D903.ASTM D4541 involves adhering a dolly or stud to the

coating surface and using a portable adhesion tester to measure the tension pull-off. The test identifies the weakest part of the coating system, either intra-layer cohesion, inter-layer adhesion, bond to the substrate, or a weak substrate. The test may be performed in the laboratory or in the field as a quality control measure. It is a destructive test that requires patching in the field. ASTM C794 modified by ASTM C957 and ASTM D903 are peel-off tests. In the ASTM C794 procedure, a piece of cloth is embedded in the elastomeric coating, adhered to a substrate, and pulled off the substrate. For ASTM D903, a flexible material is bonded to a flexible or rigid substrate material with the elastomeric coating, and then the flexible material is pulled off the substrate material. The numerical results obtained from each of these proce-dures are for comparison with the results for other materials tested by the same procedure.

ASTM D4541—In this procedure, the concrete or cement mortar substrate is prepared and the coating system applied and cured according to the recommendations of the coating manufacturer. A loading fixture is aligned perpendicular to the surface and secured to the surface of the coating with an adhesive. The coating may be scored around the loading fixture as long as care is taken to prevent microcracking in the coating. The adhesion tester is aligned perpendicular to the surface and connected to the loading fixture. The tester

Fig. 7.4.1––ASTM C1305 test setup. (Courtesy of BASF Construction Chemicals, LLC.)





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applies load to the loading fixture at a rate of less than 150 psi/s (1 MPa/s) so that failure occurs in approximately 100 seconds or less. The failure force is measured and divided by the area of the loading fixture to obtain a failure stress. The average failure stress in psi (MPa) is computed for at least three tests. The failure surface is described for each test. The report should indicate if the coating surface was scored or not. The numerical failure stress is dependent on the specific type of adhesion tester used and on whether the coating was scored or not. Figure 7.4.2a shows an ASTM D4541 test in progress, and Fig. 7.4.2b shows the pull-off results of a test.

ASTM C794 modified by ASTM C957—In this procedure, cement mortar slabs 6 x 3 x 3/8 in. (152 x 76 x 9.5 mm) are cast and cured for 7 days. The surface is then prepared by wet grinding. The base coat of the elastomeric coating, including a primer if specified by the coating manufacturer,

is applied to the clean, dry test surface over a 4 x 3 in. (102 x 76 mm) area, to a thickness slightly greater than that speci-fied by the coating manufacturer or a wet-film thickness necessary to attain a dry-film thickness of 0.020 in. (0.5 mm), whichever is greater. At an interval specified by the coating manufacturer, the base coat is applied to both sides of a 4 x 3 in. (102 x mm) area of a piece of cloth with a putty knife, and the impregnated cloth is pressed into the base coat layer on the mortar slab to a total thickness of the base coat specified by the coating manufacturer or the wet-film thick-ness necessary to attain a dry-film thickness of 0.020 in. (0.5 mm), whichever is greater. Excess material that is squeezed out is trimmed off. The sample is cured for 2 weeks at 74°F (23°C) and 50 percent relative humidity, and then 1 week at 158°F (70°C). After 7 days of curing, the cloth is coated with additional base coat to prevent failure at the cloth. After 3 weeks of curing, two 1 in. (25 mm) wide strips are created by cutting through the sample to the mortar slab. The sample is immersed in distilled or deionized water for 7 days. The specimen is then wiped dry and the ends of the strips are loosened from the mortar slab. The cloth samples are then pulled at 180 degrees in a test machine at a rate of separa-tion of 2 in./min (50.8 mm/min). The specimen is peeled for approximately 1 minute and the average force is recorded in pounds-force (Newtons). If the cloth peels clean from the base coat, the test value is disregarded. The average of four peel tests is reported.

ASTM D903—In this procedure, a 1 x 7 in. (25 x 203 mm) piece of substrate material, presumably made of cement mortar, is conditioned and prepared according to the recom-mendations of the coating manufacturer. A 1 x 12 in. (25 x 305 mm) piece of flexible material, such as metal or rubber, is bonded to the substrate material with the base coat, in accordance with the recommendations of the coating manu-facturer. The specimen is then cured for 7 days at 74°F (23°C) and 50 percent relative humidity. The flexible mate-rial is pulled at 180 degrees in a test machine at a rate of separation of 6 in./min (152 mm/min). The average peel strength is measured. The arithmetic mean of at least 10 test results is reported.

7.4.3 Hardness—Hardness is measured by ASTM D2240, which is discussed in 5.4.7. Hardness is sometimes an indi-cation the durability of the coating when exposed to traffic wear.

7.4.4 Abrasion resistance—Three test methods are used to measure abrasion resistance:

1) ASTM C501 modified by ASTM C957;2) ASTM D4060;3) ASTM D1242, Method A, modified by ICC-ES AC39-12.All three test procedures involve abrading test specimens

under a 2.2 lb (1000 g) normal load with a specified abra-sive for 1000 cycles or some other number of cycles. ASTM C501 modified by ASTM C957 involves casting coating samples, 0.020 in. (0.5 mm) minimum thick and excluding the aggregate, on steel plates and curing the specimens for 14 days at 74°F (23°C) and 50 percent relative humidity, and then 7 days at 158°F (70°C). The specimens are then abraded with a CS-17 abrasion wheel for 1000 cycles. ASTM D4060

Fig. 7.4.2a—ASTM D4541 adhesion test. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)

Fig. 7.4.2b—Results of ASTM D4541 tests, showing failure surfaces in concrete substrate. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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involves applying a uniform coating, at a thickness specified by the manufacturer, on a rigid panel, and curing the coating according to the manufacturer’s instructions. The specimens are then abraded with a CS-17 abrasion wheel for a speci-fied number of cycles. ASTM D1242 is withdrawn, but is still used by some material manufacturers. ASTM D1242, Method A, modified by ICC-ES AC39-12, involves applying a 1/64 in. (0.4 mm) thick coating on the specimen mounting plate and conditioning the specimen at 74°F (23°C) and 50 percent relative humidity for at least 40 hours. The specimen is then abraded for 1000 cycles with No. 80TP aluminum oxide grit that is dropped onto the specimen. In each method, the specimen is weighed before and after the test to deter-mine coating loss. Coating loss is calculated and reported as an abrasive wear index (88/weight loss, expressed as whole number), a wear index (weight loss × 1000/number of abra-sion cycles), or a volume loss (weight loss/coating density). The reported test results can be used to compare the perfor-mance of various repair materials, but the test results have little correlation with actual coating performance under field exposures. Figure 7.4.4 shows an ASTM C501 test setup.

7.4.5 Accelerated weathering—ASTM C957, D822, G152, G153, and G154 can be used to measure the effect of accelerated weathering on elastomeric coatings.

ASTM C957 involves casting and curing a sample of the coating; cutting the coating into dumbbell-shaped speci-mens; exposing some of the specimens to artificial light; and testing the specimens in tension. ASTM D822, G152, G153, and G154 involve applying the coating to a substrate, curing the coating, and then exposing the coating to cycles of light and dark and cycles of moisture consisting of wetting, condensation, or high humidity. ASTM D822 includes the selection of test conditions for accelerated exposure testing in filtered open-flame carbon-arc devices conducted according to the basic principles and operating procedures included in ASTM G152; ASTM G153 includes basic principles and operating procedures for using enclosed carbon-arc light and water apparatus; and ASTM G154 includes basic principles and operating procedures for using fluorescent UV light and water apparatus. ASTM G154 replaced ASTM G53, which was withdrawn in 2000. In all of these test methods, the details of the tests, including specimen size, specimen manufacture and curing, nature of the test cycle exposures, number of test cycles, and interpretation of the test results, are left to the coating manufacturer. The test report should include full information on the test procedure. While all of the test methods can be used to determine degradation of a coating when exposed to the test conditions, comparison of test results from various coating manufacturers is difficult unless the testing is done in parallel with identical parame-ters and conditions. Laboratory test results may not correlate with field performance.

ASTM C957—In this procedure, a free film of the coating material, with a minimum cured thickness of 0.020 in. (0.5 mm), is cast on release paper and cured for 21 days at 74°F (23°C) and 50 percent relative humidity, and then for 7 days at 158°F (70°C). Twenty dumbbell-shaped specimens are then cut in conformance with Die C (5.0 x 1.6 in. [128 x

40 mm] gross dimensions], as stated in ASTM D412. Ten specimens are then exposed to artificial light for at least 500 hours and then allowed to equilibrate for at least 24 hours. The weathered and unexposed specimens are then tested in tension according to ASTM D412, and the tensile strength, elongation, and recovery elongation are measured. The difference in material properties between the weathered and unexposed specimens is an indication of the weathering resistance of the coating.

7.4.6 Other properties—Other material properties that may be useful include other mechanical properties, chemical analysis, and construction characteristics.

Mechanical properties that may be of interest include:a) Tensile strength, elongation, and permanent set, measured

by ASTM D412 as described in 5.4.2.b) Tear resistance, measured by ASTM D1004 or D624

(5.4.6).c) Coating flexibility, measured by ASTM D522.d) Coating water absorption, measured by ASTM D471 or

D570.Chemical analysis includes the identification of the

generic material used in coating, and the determination the solids content and the VOC.

Construction characteristics that may be of interest include:a) Flash point and combustibility;b) User safety;c) Storage and handling procedures;d) Environmental limitations, such as temperature,

humidity, and moisture conditions before, during, and after application;

e) Coating pot life;f) Substrate and coating cure times.Refer to 7.2.8 for other properties and characteristics that

may be of concern.

7.5—Summary tablesTables 7.5a, 7.5b, and 7.5c present available test proce-

dures described in this chapter and typical test values for surface sealers, anti-carbonation coatings, and traffic-

Fig. 7.4.4––ASTM C501 test setup. (Courtesy of BASF Construction Chemicals, LLC.)





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Table 7.5a—Summary of available test methods and test values for surface sealers

Description Test method Specimen age Typical valueRecommended

valueRecom-

mended testSilanes/siloxanes

7.2.1—Reduction in water absorption

NCHRP 244, Series I 42 days

70 to 88 percent compared to untreated concrete85 percent minimum

NCHRP 244, Series II test is preferred.

NCHRP 244, Series II 52 days YesASTM D6489 No specimen age is specified. Yes

AASHTO T259 42 days NoSHRP-S-330, Appendix E No specimen age is specified. Yes

ASTM C642 No specimen age is specified. Yes

Reduction in chlo-ride ion absorption

NCHRP 244, Series I 42 days64 to 97 percent compared to untreated concrete

85 percent mininum


NCHRP 244, Series II 52 days YesAASHTO T259 42 days No

Absorbed chloride ions

AASHTO T259 42 days1/16 to 1/2 in. (1.6 to 12.7 mm); 0.08 lb/yd3 (47 g/m3);

1/2 to 1 in. (12.7 to 25 mm); 0.0 lb/yd3 (0.0 g/m3)No

ASTM C1543 No

7.2.2—Water vapor transmission

NCHRP 244, Series II 52 days 100 percent moisture loss

100 percent moisture loss

Yes

OKDOT OHD L-35 9 days

100 percent moisture loss (Some test procedures report water vapor transmission in terms of percent moisture loss compared to the moisture gain during the sample

conditioning.)

Yes

ASTM D1653, ASTM E96 No specimen age is specified.3.02 grains/ft2/1 hour (2.11 g/m2/1 hour), 100 percent

moisture lossNo

7.2.3—Depth of penetration into concrete

NCHRP 244, Series II 22, 26, 42 days0.4 to 0.6 in. (10 to 15.2 mm)

1/4 in. min. (6.4 mm min.)

Yes

OKDOT OHD L-34 7 days Yes

7.2.4—Accelerated weathering

NCHRP 244, Series IV43 days

No specimen age is specified.14 to 99 percent reduction in absorbed Cl–;

>99 percent water repellency

85 percent min. reduction in absorbed Cl–

Yes

ASTM G154/G53 No

7.2.5—VOC content

40 CFR 60, Method 24<46.7 to 51.1 oz/gal. (350 to 383 g/L)

Consult local authorities

YesASTM D5095 Yes

Acrylics










50 percent minimum




NCHRP 244, Series II 52 days

99 to 100 percent moisture loss (Some test procedures report water vapor transmission in terms of percent moisture

loss compared to the moisture gain during the sample conditioning.)

100 percent moisture loss

Yes

ASTM D1653, ASTM E96 No specimen age is specified. 1 to 11 perms (57 to 629 metric perms) No7.2.3—Depth of penetration into concrete

NCHRP 244, Series II 22, 26, 42 days0 0

Yes



NCHRP 244, Series IV 43 days 0 to 68 percent reduction in absorbed Cl–

50 percent minimum reduc-tion in absorbed

Cl–

Yes

ASTM G154/G53 No specimen age is specified. No chalking, checking, cracking No7.2.5—VOC content

40 CFR 60, Method 2412.4 to 60.1 oz/gal. (93 to 450 g/L)


YesASTM D5095 Yes





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Table 7.5a—Summary of available test methods and test values for surface sealers (cont.)

Description Test method Specimen age Typical valueRecommended

valueRecom-

mended test7.2.6—Flame spread, smoke development

ASTM E84 No specimen age is specified.Flame spread index – 5

Smoked developed index – 5(0 [best] to 200)

Depends on project

requirementsYes

7.2.7—Mold/fungus resistance

ASTM D3273 No specimen age is specified. No growthDepends

on project requirements

Yes

Epoxy










90 percent minimum




NCHRP 244, Series II 52 days

60 to 100 percent moisture loss (NCHRP 244, Table B-29) (Some test procedures report water vapor transmission in

terms of percent moisture loss compared to the moisture gain during the sample conditioning.)

50 percent minimum

Yes

ASTM D1653, ASTM E96 No specimen age is specified. No7.2.3—Depth of penetration into concrete

NCHRP 244, Series II 22, 26, 42 days0 to 1/64 in. (0.5 mm) 0

Yes



NCHRP 244, Series IV 43 days 65 to 93 percent reduction in absorbed Cl-

85 percent min. reduction in absorbed Cl-

Yes

7.2.5—VOC content

40 CFR 60, Method 2446.1 oz/gal. (345 g/L)


YesASTM D5095 Yes

Boiled linseed oil









NCHRP 244, Series I 42 days5 to 15 percent compared to

untreated concrete90 percent minimum




NCHRP 244, Series I 42 days 75 to 85 percent moisture loss (Some test procedures report water vapor transmission in terms of percent moisture loss compared to the moisture gain during the sample

conditioning.)

50 percent minimum


NCHRP 244, Series II 52 days YesASTM D1653, ASTM E96 No specimen age is specified. No






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Table 7.5b—Summary of available test methods and test values for anti-carbonation coatings

DescriptionTest

method Specimen age Typical value Recommended value Recommended testAcrylics

7.3.1—Carbon dioxide diffusion EN 1062-6 No specimen age is

specified.490 to 2130 ft (150 to 650 m)

equivalent air layer 164 ft (50 m) min. Yes

7.3.2—Water vapor transmission or permeability

ISO 7783 No specimen age is specified.

10 in. to 7 ft (0.25 to 2.0 m) equivalent air layer 13.1 ft (4 m) maximum Yes

ASTM E96 No specimen age is specified. 25 Perms (1434 ng/Pa·s·m2)

Committee 546 does not have a recom-

mended value for this test.

Committee 546 does not have a recommendation on the

advisability of using this test method.

Methacrylics7.3.1—Carbon dioxide diffusion EN 1062-6 No specimen age is


equivalent air layer 164 ft (50 m) minimum Yes

7.3.2—Water vapor transmission or permeability

ISO 7783 No specimen age is specified.

5 to 7 ft (1.5 to 2.0 m)equivalent air layer 13.1 ft (4 m) maximum Yes

Polymer-modified cementitious7.3.1—Carbon dioxide diffusion EN 1062-6 No specimen age is


equivalent air layer 164 ft (50 m) min. Yes


Table 7.5c—Summary of available test methods and test values for traffic-bearing elastomeric coatings

Description Test method Specimen age Typical value Recommended value

Recom-mended

testPolyurethanes

7.4.1—Low-temperature flexibility and crack bridging

ASTM C1305 (C957, C836) No specimen age is specified. Pass, no cracking Pass, no cracking Yes

ICC ES-AC39-12 No specimen age is specified. No cracking or crazing—conditioned at 50°F (10°C) No

7.4.2—Adhesion to concrete

ASTM D4541 No specimen age is specified. 275 to 400 psi (1900 to 2760 kPa) 250 psi (1700 kPa) minimum Yes

ASTM C794 (C957) 35 days 10 to 50 pli (18 to 88 N/cm) Committee 546 does not have a recommended value for this test. No

7.4.3—Hardness ASTM D2240 No specimen age is specified. 70 to 90 Shore A45 to 70 Shore D 70 Shore A minimum Yes

7.4.4—Abrasion resistance

ASTM C501 (C957) 21 days <1.8 oz (50 mg)


No

ASTM D4060 No specimen age is specified. 0.35 to 3.5 oz (10 to 100 mg)/1000 cycles No

ASTM D1242 40 hours 0.009 in. (0.23 mm) thick-ness loss No


ASTM D822 No specimen age is specified. Slight chalking Committee 546 does not have a recommended value for this test.

NoASTM G154 Yellowing, no visible effect No

Polyurethane-epoxy composites7.4.2—Adhesion to concrete ASTM C794 (C957) 35 days 50 pli (88 N/cm) Committee 546 does not have a

recommended value for this test. No

7.4.3—Hardness ASTM D2240 No specimen age is specified. 70 to 80 Shore A 70 Shore A minimum Yes7.4.4—Abrasion resistance ASTM D4060 No specimen age is specified. 2.1 oz (60 mg)/1000 cycles Committee 546 does not have a


7.4.5—Accelerated weathering ASTM G154 No specimen age is specified. Yellowing Committee 546 does not have a


Polyureas

7.4.2—Adhesion to concrete

ASTM D4541 No specimen age is specified. <315 to 350 psi (2200 to 2400 kPa) 35 pli (63 N/cm) 250 psi (1700 kPa) minimum Yes

ASTM D903 No specimen age is specified. Committee 546 does not have a recommended value for this test. No

7.4.3—Hardness ASTM D2240 No specimen age is specified. 78 to 80 Shore A50 Shore D 70 Shore A minimum Yes

7.4.4—Abrasion resistance

ASTM C501 (C957) 21 days 2.5 oz (71 mg)0.071 oz (2 mg)/1000 cycles

Committee 546 does not have a recommended value for this test. No

ASTM D4060 No specimen age is specified. NoNote: Materials tested at 73°F (23°C) unless noted otherwise.





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bearing elastomeric coatings, respectively. The tables are brief summaries; the text of the chapter should be referred to for further information. Where recommended values are listed, they represent the minimum values recommended by Committee 546 for typical coating and sealer materials used in successful installations, and are not necessarily applicable for all conditions. Some of the recommended test methods listed in the table are not appropriate for certain materials or applications; some are useful for comparing different materials.

CHAPTER 8—SURFACE SEALER, ANTI-CARBONATION COATING, AND TRAFFIC-

BEARING ELASTOMERIC COATING MATERIALS SELECTION

8.1—GeneralConcrete deterioration frequently is related to contamina-

tion of the concrete, such as from chlorides or carbonation. In many instances, the deterioration process requires the ingress of water to proceed. It is frequently cost-effective to include a surface treatment in a repair program to attempt to reduce future concrete deterioration and maintenance requirements.

Surface sealers and traffic-bearing elastomeric coatings drastically limit water penetration into the concrete. Surface sealers can reduce water penetration by 85 to 95 percent compared to untreated concrete, whereas traffic-bearing elastomeric coatings may even further reduce water penetra-tion. Surface sealers and traffic-bearing elastomeric coatings are used to limit water penetration into existing concrete that is not repaired, in an attempt to reduce or stop ongoing concrete deterioration. They also limit water penetration and improve the durability of concrete repairs. These materials will also reduce the ingress of some water-soluble chemi-cals, such as chloride ions, into the concrete.

Anti-carbonation coatings reduce air and carbon dioxide penetration into the concrete, slowing the progress of carbonation into the concrete. Although anti-carbonation coatings can also reduce water penetration, that is not their primary purpose. Because of this, they may not be as effec-tive as a surface sealer. Anti-carbonation coatings are used on vertical surfaces and horizontal surfaces that are not exposed to pedestrian or vehicular traffic.

The materials discussed in this chapter are suitable for many applications with normal environmental exposures, including exposure to water, chloride ions, mild chemicals, oil, and grease. These materials are generally not suitable for surfaces subjected to hydrostatic head, severe abrasion, or harsh chem-ical exposure. Materials for protecting concrete surfaces in more severe exposures, such as chemical and waste treatment plants, are not specifically discussed, although some of the important material properties may still be relevant.

8.2—Surface sealersSeveral types of surface sealers are discussed in 8.2:a) Silanes;b) Siloxanes;

c) Acrylics;d) Epoxies;e) Linseed oil.Silanes and siloxanes usually penetrate a small depth

into the concrete, while the remaining three types are film-forming. Each type of surface sealer is available in a variety of formulations with differing surface sealing character-istics (National Cooperative Highway Research Program Report 244 1981); for instance, not all silanes are good surface sealers. Consequently, surface sealers should not be specified generically, but the properties of specific products should be reviewed.

A wide range of surface sealer products is available. Surface sealer characteristics and properties that may be important include:

a) Type and concentration of the active ingredient;b) Solvent type;c) Amount of surface sealer applied;d) Molecular size, surface tension, and viscosity;e) Flash point, pot life, ease of application and cleanup,

and cure time;f) Volatile organic content (VOC);g) Reduction in water absorption and vapor transmission

ability;h) Surface color and texture;i) Resistance to UV light and stability under temperature

changes.Some surface sealers penetrate a small depth into the

concrete and others form a film on the concrete surface. Applying more sealer will tend to increase the depth of pene-tration or film thickness and effectiveness of the sealer, espe-cially when multiple applications of smaller dosage are used (Carter 1994). Breathability, however, could be reduced with multiple applications. Some surface sealers are clear and others are tinted.

Surface sealers are commonly applied at a total thickness of 0.010 in. (0.25 mm) or less. Consequently, preparation of the concrete surface is critical to achieve good bond and satis-factory performance of the sealer. Dirt, laitance, and surface contaminants such as curing compounds and previous coat-ings should be removed; the pore structure at the concrete surface should be opened for better sealer penetration; and the surface profiled according to the manufacturer’s instruc-tions for improved sealer adhesion. Surface sealers will not improve a deteriorated, weak, or soft concrete surface, and deficient concrete surfaces will shorten the service life of surface sealers.

Some surface sealers are breathable, allowing water vapor to pass through, whereas others are not. Trapped water vapor can cause accelerated deterioration of the surface sealer and the concrete member. Surface sealers are not intended or promoted to bridge cracks, but some are effective in sealing narrow, non-moving cracks. Cracks that develop in the concrete after a sealer has been applied will likely reflect through the sealer, allowing water or chemicals to penetrate the crack. Surface sealers decrease in effectiveness with time and commonly should be reapplied every 5 to 10 years to remain effective.





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Because the effectiveness of a surface sealer applica-tion depends on the sealer and concrete characteristics and the quality of the sealer application, the only reliable way to determine the effectiveness is to test the concrete after sealing. ASTM D6489 is a procedure for laboratory testing of concrete core samples. The Strategic Highway Research Program (SHRP) SHRP-S-330, Appendix E, test is a field test procedure that consists of adhering a water reservoir to the treated concrete surface, exposing the surface to a column of water, and recording the water absorption. The results of both tests are compared to results from untreated concrete to determine the effectiveness of the surface sealer. These tests can also be performed every few years to evaluate the loss in effectiveness of the surface sealer with time and determine when reapplication might be beneficial. Refer to Chapter 7 for a discussion of these test methods.

8.2.1 Silanes—Silanes are low-molecular-weight compounds of silicon, carbon, oxygen, and hydrogen, applied in pure, 100 percent active silane or diluted with solvent or water. Common concentrations range from 20 to 100 percent. Silanes react with the alkaline concrete and atmospheric humidity to form a hydrophobic layer. Silanes with long alkyl groups that are alkali resistant, such as iso-butyltrialkoxysilane and octyltrialkoxysilane, have good surface sealing properties. Silanes are normally available as solutions with mineral spirits, aromatic hydrocarbon solvents, or water.

8.2.1.1 Selection—Some silanes are good surface sealers that significantly reduce water and chloride penetration into the concrete. Some silanes also have good water vapor trans-mission and will penetrate 1/4 in. (6 mm) or more into the concrete, improving the sealer durability. Thinly-applied surface sealers are solely depended on the durability of the sealer material for abrasion resistance unless some amount of penetration into the concrete substrate is achieved, in which case the abrasion resistance is governed by the quality of the concrete surface. Some silanes have good accelerated weathering performance.

All silanes intrinsically have an appreciable base VOC, based on the silane chemistry and the test method used to determine VOC; this base VOC is the lower limit for the sealer VOC. The VOCs for water-based, “exempt-solvent-based,” and 100 percent solids silane sealers are the base VOC values; the VOCs for “non-exempt-solvent-based” silane sealers will be larger than the base VOC value due to the addition of the non-exempt solvent. The VOC of each silane product should be determined and compared with local environmental limits.

Water-based silanes generally are less effective in reducing water penetration into the concrete. Silane surface sealers are clear. Silanes may need to be reapplied every 5 to 10 years to maintain their sealer characteristics, although good sealer performance has been reported in Sweden after 35 years in service on vertical surfaces (Selander 2010). If the surface sealer is still partially effective, less material will be required for the reapplication.

8.2.1.2 Installation—After preparation of the concrete surface, the silane can be applied with a sprayer, roller,

or brush. A detail coat may be applied at cracks prior to coating the entire member surface, to apply more material and, hopefully, achieve better penetration of material at the cracks. Sometimes a second coat is applied. Silanes require a minimum amount of moisture to react and, because they are breathable, they can be applied to damp concrete. They should not, however, be applied to saturated concrete. Also, generally better penetration into the concrete is attained if the concrete is dry. They should not be applied at temperatures approaching or below freezing. Silanes can be applied to fully carbonated concrete and concrete in desert environments, but the concrete should contain some alkalinity or the silane reac-tion with the concrete is excessively prolonged. Figure 8.2.1.2 shows the spray application of a silane surface sealer.

8.2.2 Siloxanes—Siloxanes, like silanes, are organo-silicons. Several formulations of siloxanes are available, including methyl siloxanes, oligomeric siloxanes, and poly-meric alkyl alkoxysiloxanes. Methyl siloxanes have poor resistance to alkaline environments and are not used to seal concrete surfaces. Oligomeric siloxanes are condensed or partially hydrolyzed molecules, based on methyl silanes, which contain longer-chain alkyl groups like butyl or octyl. Oligomeric siloxanes generally are effective concrete surface sealers. Polymeric alkyl alkoxysiloxanes are long-chain, high-molecular-weight materials. The long-chain alkyl groups in oligomeric siloxanes and polymeric alkyl alkoxysiloxanes are required for effective resistance to the alkaline concrete environment.

Similar to silanes, siloxanes are normally available as solu-tions with mineral spirits, aromatic hydrocarbon solvents, or water. The siloxanes react with atmospheric humidity, with the concrete alkalinity acting as a catalyst, to form a hydro-phobic layer.

8.2.2.1 Selection—Siloxanes are often used in similar situ-ations to silanes. Oligomeric siloxanes, with longer chain alkyl groups than silanes, have good water and chloride ion screening plus good alkali resistance and water vapor trans-mission. Because of the larger molecules, siloxanes gener-ally do not penetrate into concrete as well as silanes. Silox-anes, however, may be preferable for very porous concrete,

Fig. 8.2.1.2––Spray application of a silane surface sealer. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)





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as the less viscous silanes may actually diffuse too deeply into the concrete, reducing the sealing performance. The best siloxane penetration is obtained with mineral spirits or aromatic hydrocarbon solvents. Similar to silanes, the VOCs in solvent-based siloxanes may exceed local limits.

Because siloxanes do not dry as fast as silanes, the applica-tion time increases. Due to less penetration into the concrete, siloxanes may also reduce skid resistance on horizontal concrete surfaces. Siloxanes are less volatile than silanes and may perform better at high temperatures or in very dry conditions. Siloxane surface sealers are clear. Similar to silanes, siloxanes need to be reapplied every 5 to 10 years to maintain their sealer characteristics; if the surface sealer is still partially effective, less material will be required for the reapplication.

8.2.2.2 Installation—Installation concerns are similar to those for silanes discussed in 8.2.1.2.

8.2.3 Acrylics—Acrylic surface sealers are 100 percent active acrylic or water- or solvent-borne materials that form a coating on the concrete surface. A wide variety of acrylic polymers exist, including methyl methacrylate, high-molec-ular-weight methacrylate, and latex modifiers.

8.2.3.1 Selection—Some acrylic surface sealers greatly reduce water penetration into the concrete, and also have good water vapor transmission; solvent-borne and 100 percent active acrylic surface sealers are generally not as breathable as water-borne acrylics. They are avail-able as clear or colored concrete coatings, and have good color retention. Acrylic surface sealers do not penetrate the concrete. Although they have good weathering characteris-tics, they are susceptible to surface abrasion; the rate of UV degradation will vary with the binder type and quality.

8.2.3.2 Installation—Installation concerns are similar to those for silanes discussed in 8.2.1.2. Acrylic surface sealers are not adversely affected by slightly moist surface condi-tions and can be applied to new repairs; they may act as a curing compound to reduce evaporation from the substrate and reduce shrinkage cracking. Sand may need to be broad-cast into coated surfaces exposed to traffic for improved skid resistance. Figure 8.2.3.2 shows the application of an acrylic surface sealer.

8.2.4 Epoxies—Epoxy surface sealers generally consist of two liquid components: an epoxy resin and a hardener. There are many types of epoxy resins and hardeners available.

8.2.4.1 Selection—Some epoxy surface sealers greatly reduce water penetration into the concrete, and some also have good water vapor transmission (NCHRP Report 244). Epoxy surface sealers generally achieve little or no penetra-tion into the concrete, but are relatively durable materials with good resistance to abrasion and many chemicals. They are typically not UV stable and may yellow and chalk over time when exposed to sunlight. Epoxy surface sealers are tinted and many have high VOCs.

8.2.4.2 Application—Two-component epoxy surface sealers should be accurately measured and thoroughly mixed prior to application. Working time varies with the epoxy formulation and ambient temperature conditions. Many epoxy surface sealers should be applied to dry surfaces, but

some formulations will adhere to damp surfaces. Sand may need to be broadcast onto coated surfaces exposed to traffic for improved skid resistance.

8.2.5 Boiled linseed oil—At one time, boiled linseed oil with mineral spirits was the most widely used concrete sealer. Its use has declined as better-performing sealers have become available. Boiled linseed oil is sometimes used for temporarily sealing new concrete construction and as a precoat to enhance the performance of other surface sealers.

8.2.5.1 Selection—Boiled linseed oil reduces water pene-tration into concrete by 20 to 30 percent, compared to 85 to 95 percent of some other sealers. The reduction in chlo-ride ion absorption is even less. Boiled linseed oil has good water vapor transmission, but achieves little or no penetra-tion into the concrete. Boiled linseed oil will tend to darken the concrete surface and has a relatively short service life.

8.2.5.2 Installation—After the concrete surface has been prepared, boiled linseed oil can be applied with a sprayer, roller, or brush. It should not be applied at temperatures approaching or below freezing.

8.3—Anti-carbonation coatingsThere has been increasing awareness of anti-carbonation

coatings in the United States since the mid-1990s. There are still only a small number of anti-carbonation coating products that have been tested and are commercially available. Anti-carbonation coatings can be tinted or clear and are generally not intended for exposure to pedestrian or vehicular traffic.

Three types of anti-carbonation coatings are discussed in 8.3:

a. Acrylics;b. Methacrylates;

Fig. 8.2.3.2––Application of acrylic surface sealer. (Cour-tesy of Wiss, Janney, Elstner Associates, Inc.)





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c. Cementitious-modified polymer.Many acrylic coatings for concrete are available and,

while many may effectively screen carbon dioxide, most have not been tested to demonstrate their effectiveness.

All three materials are good carbon dioxide screens. All have good water vapor transmission, screen water and chlo-ride ions, and good weathering characteristics. The acrylics are elastomeric with some crack bridging ability, opaque, and available in a variety of colors. Both the methacrylates and the cementitious-modified polymer materials are rela-tively brittle. The methacrylates are clear or transparent, and will slightly change the appearance of the concrete. The cementitious-modified polymer coatings are opaque and commonly concrete gray or white, but can be coated for aesthetic quality.

As with all coatings, surface preparation is critical. Usually the concrete surfaces are power washed or sandblasted to remove loose material, surface contaminants, and coatings, and to clean the surface. The prepared surface should be dry for acrylic and methacrylate coatings, but should be satu-rated surface-dry (SSD) for the polymer-modified cementi-tious coating. Acrylic coatings require a primer and are applied in one to three coats, with total thickness ranging from 0.01 to 0.025 in. (0.20 to 0.70 mm). Acrylic coatings can be applied by brush, roller, or spray, and may last 10 to 15 years or longer before maintenance is required.

Some methacrylate coatings also require a primer; meth-acrylate coatings are applied in one or two coats, with a total thickness approaching 0.006 in. (0.14 mm). Methacrylate coatings are also applied by brush, roller, or spray. Mainte-nance, which consists of overcoating, may be desirable after a minimum period of 10 years.

The cementitious-modified polymer coatings are applied to a SSD surface by brush, trowel, or spray to a thickness of 0.08 in. (2 mm). The coatings should be cured similar to other concrete products by either moist curing or applied curing membranes. Care should be taken that the material does not dry out after application. Depending on exposure, mainte-nance may be required after a minimum period of 10 years.

8.4—Traffic-bearing elastomeric coatingsTraffic-bearing elastomeric coatings form a water and

chloride-ion barrier on the concrete surface, and are rela-tively durable when exposed to vehicular and pedestrian traffic and UV light. The coatings consist of several materials applied in layers, including a primer, a water barrier, a wear course, and aggregate for slip resistance. The coating system is applied at total thicknesses ranging from 20 to 30 mils (0.5 to 0.76 mm) to over 100 mils (2.5 mm). The water barrier layer, and sometimes the wear course, is relatively flexible, with some ability to bridge existing moving cracks. Coating systems are also promoted as having the ability to bridge new cracks that form after the coating has been applied, but this is doubtful unless the cracks are very fine. It is generally recom-mended that cracks wider than 1/16 in. (1.6 mm) be routed and filled with elastomeric sealant prior to coating application to provide greater tolerance of crack movements.

As the coatings are relatively thin, they depend on bond with the concrete substrate to perform satisfactorily. Concrete surface preparation is critical and the concrete should be dry. Coatings have temperature and moisture limitations for application. Some coatings have high VOC content and may have noticeable odors during curing. Aggregate should be broadcast into the wear course to achieve satisfactory slip resistance.

The coatings are available in a variety of colors. As the coatings are relatively thin, imperfections and irregulari-ties in the concrete surface will project through the coating and be noticeable. The aggregate type and uniformity of the distribution of the aggregate in the coating surface will also affect the finished appearance.

Three traffic-bearing elastomeric coatings are polyure-thanes, polyurethane-epoxy composites, and polyureas. All three have excellent water-barrier properties, some elas-ticity, good adhesion to concrete, good abrasion resistance, good weathering resistance, and good resistance to expo-sure to fluids from vehicles. The epoxy wear course is more brittle than the polyurethane or the polyurea wear course, and is subject to reflective cracking at cracks in the concrete substrate. These cracks in the epoxy wear course commonly do not extend through the polyurethane water-barrier layer and may not reduce the coating resistance to water penetration.

All three coatings require periodic maintenance, particu-larly in high-traffic areas such as garage entrances, ramps, and traffic aisles. The coatings have thicker, more heavy-duty versions that can be applied in high traffic areas. Snow plows should be equipped with rubber blades, as the coat-ings are susceptible to gouging by snow plows. With limited maintenance every few years, some coatings will perform satisfactorily for 15 or 20 years. It may be desirable to apply another topcoat in 5 to 10 years to cover worn areas and improve the appearance of the coat surface.

The results of laboratory tests are not a good guide for material selection. There are no laboratory tests that accu-rately predict coating durability when exposed to traffic in the field. As coatings are generally expected to last 15 to 20 years with limited maintenance, the best method of selecting a coating is to observe the performance of coating applica-tions after 5 to 10 years in service.

Some coating formulations have been changed from two components to one component, from solvent-based to water-based, and to decrease the cure time and lower VOCs. In some cases, the coating name has not been changed despite the reformulation, and it is sometimes difficult to determine that a coating that has performed satisfactorily for many years has been modified, perhaps in a significant way. Reformula-tions can affect the bond to concrete, the interlayer bond, the wear resistance to traffic, the resistance to UV degradation, or information on the material safety data sheets. If neces-sary, coatings can be analyzed chemically or applied in small mockups prior to full-scale repair installations in an attempt to determine if changes have been made and if the coating is likely to perform satisfactorily. Figure 8.4 shows the appli-cation of a traffic-bearing elastomeric coating.


American Concrete Institute – Copyrighted © Material – www.concrete.orgCopyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=yuyuio, rtyru


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8.5—Selecting surface sealers and anti-carbonation coatings

Tables 8.5a and 8.5b summarize the information in this chapter regarding important material properties for the various surface sealers and anti-carbonation coatings. Within each material category, characteristics can vary widely between individual products, and products should be carefully evaluated.

CHAPTER 9—OTHER MATERIALS USED IN CONCRETE REPAIR

9.1—GeneralSeveral other materials sometimes used in concrete

repairs, including reinforcing steel coatings, galvanic anodes, concrete bonding agents and techniques, crystalline pore blockers, and surface-applied, penetrating corrosion inhibitors are discussed in this chapter.

9.2—Reinforcing steel coatingsEpoxy-coated reinforcing steel has been used in new

construction since 1973 and has continued to be used by many state departments of transportation. Laboratory and field studies have generally shown significant reduc-tion in corrosion activity with epoxy-coated reinforcement compared to uncoated bars (Concrete Reinforcing Steel Institute [CRSI] Bridges 2011).

When epoxy-coated reinforcing steel is exposed in concrete removal areas, damaged coating areas are often found. The damage coating areas are commonly cleaned and recoated with a coating material that is compatible with the existing epoxy coating, frequently a field-applied epoxy. Refer to ACI 364.3T for more information.

As the corrosion of reinforcing steel causes much concrete deterioration and the need for repairs, many repair programs include the coating of uncoated reinforcing steel in repair areas after cleaning by sandblast. Coating materials include cementitious, epoxy, and zinc-rich products. Useful informa-tion in evaluating and selecting coatings includes the level of corrosion protection, bond strength to the reinforcing bars, and durability in a concrete environment. Unfortunately there are no standardized test procedures for any of these material properties. In addition, the coatings are applied in the field during the repair process and the quality of the coating can vary greatly. Finally, it should be determined if the coating has any adverse effect on the repair if it inadver-tently gets on the concrete surface during application. Figure 9.2a shows reinforcing steel being coated with epoxy.

Research by Reed et al. (2003) tested reinforcing bars with six field-applied coating systems in the laboratory for corrosion performance. The coating systems included

Fig. 8.4—Application of traffic-bearing elastomeric coating. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)

Table 8.5a—Material selection guide for surface sealersReduction in water

absorptionWater vapor transmission

Penetrates concrete Clear or tinted UV resistance VOCs

Silane Good Good Yes Clear Good Broad rangeSiloxane Good Good Yes Clear Good Broad rangeAcrylic Good Good No Both Moderate Broad rangeEpoxy Good Fair No Tinted Moderate High

Boiled linseed oil Poor Fair No Clear No data available No data available

Table 8.5b—Material selection guide for anti-carbonation coatingsCarbon dioxide

screeningWater vapor transmission

Water, chloride ion screening Elasticity Color

Weathering resistance Primer

Acrylic Good Good Yes Yes Tinted Good YesMethacrylate Good Good Yes No Clear Good Yes

Polymer-modified cementitious Very good Good Yes No Concrete gray or

white Good No




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one coat of epoxy, one coat of cementitious coating, one coat of a barrier coating, two coats of epoxy, two coats of cementitious coating, and one coat of epoxy over one coat of cementitious coating; uncoated bare bars were also tested for control. The field-applied coatings were generally grossly defective, with as much as approximately one-third of the bar on the underside uncoated. The test bars were cast as top bars in concrete test slabs, 12 in. square by 7 in. thick (300 mm square by 178 mm thick), and electrically connected to uncoated bottom bars. One 24-week test cycle consisted of 12 weeks with 3 days of drying followed by 4 days of saltwater ponding, followed by 12 weeks of continuous salt-water ponding. The 24-week test cycle was repeated four times, for a total test period of nearly 2 years. The corrosion current between the top and bottom reinforcing bars was periodically measured throughout the test period. At the end of the test period, all of the reinforcing bars with two coats of material had less measured corrosion current than the rein-forcing bars with one coat of material, and all of the coated reinforcing bars had less measured corrosion current than the uncoated reinforcing bars. The research concluded that, despite gross imperfections in the coatings, two coats of any

material provided better corrosion protection than one coat of any material, and even one coat of any material provided much better corrosion protection than uncoated bars. Figure 9.2b shows typical shop and field coated reinforcing bars.

9.3—Embedded galvanic anodesGalvanic anodes are discrete elements that are installed

in concrete removal areas as sacrificial elements to protect the reinforcing steel in the remaining adjacent existing concrete from corrosion. Anodes consist of a zinc core in a specialized mortar shell, with protruding connection wires. The sacrificial zinc core corrodes preferentially to the adja-cent reinforcing steel in the existing concrete, protecting the steel. The installation should result in the formation of a complete electrochemical cell with electrical contact between reinforcing steel and the anodes, electrical connec-tivity of the reinforcing bars, and ionic flow between the reinforcing steel and the anodes through the concrete. If the concrete patch or encasement material has a high electrical resistivity, the anodes should be set in a conductive mortar to form the electrical circuit. Refer to ACI RAP-8 for instal-lation information.

Zinc cast in normal portland-cement concrete will form a stable corrosion by-product with a very low corrosion rate and low level of steel protection. To destabilize the corro-sion by-product, or activate the zinc, the zinc anodes should be encapsulated in a specialized mortar, commonly with a high pH (14 to 14.5) (alkali-activated) or containing a halide salt such as chloride (halide-activated), or activated by some other means. Proprietary embedded galvanic anodes include a mortar shell that prevents the zinc from becoming passive.

The anodes that are selected and the anode spacing should be determined on a case-by-case basis based on the steel density ratio (reinforcing steel surface area per square foot of concrete) and the desired level of protection. The specifier should specify an anode size and spacing based on the anode manufacturer’s spacing and service life recommendations.

Anodes are commonly placed around the perimeter of the concrete removal area to reduce corrosion in the adjacent

Fig. 9.2a—Coating reinforcing bars in a concrete removal area. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)

Fig. 9.2b—Coated reinforcing bars: top-shop-coated bar with holiday imperfections circled; middle-top view of field-coated bar; bottom-view of the underside of a field-coated bar with large uncoated areas. (Courtesy of Wiss, Janney, Elstner Associates, Inc.)

Fig. 9.3—Discrete anodes being installed in a concrete removal area. (Courtesy of Vector Corrosion Technologies.)




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existing concrete, called the ring anode or halo effect. Anodes may also be placed throughout the concrete removal area to reduce corrosion in the reinforcing steel in the existing concrete below the surface of the concrete substrate. Figure 9.3 shows anodes being installed in a concrete removal area.

Research performed at the University of Manitoba, Canada, reported that anodes in concrete replacements generated significant galvanic current that resulted in signifi-cant potential and potential decay readings in the immediate vicinity of the anode, within 6 in. (152 mm), but that much smaller changes in potential were noted 12 in. (304 mm) from the anode and little change in potential was noted 18 in. (457 mm) from the anode (CIAS Report 01-1).

For more information on the corrosion of steel in concrete and protection measures, refer to ACI 222R and NACE 01105.

9.4—Concrete bonding agents and techniquesThe bond of replacement and overlay material to the

existing concrete is a critical aspect of a successful repair. Manufacturers of proprietary replacement and overlay materials recommend surface preparation and bonding techniques to use with their materials. There are a number of proprietary materials and non-proprietary materials and techniques that can improve bonding of non-proprietary cementitious replacement and overlay materials to existing concrete. Common bonding agents and procedures include:

a) Clean, dry substrate;b) Saturated surface-dry (SSD) substrate;c) SSD substrate with scrub coat of paste from replace-

ment material immediately before installation of replace-ment material;

d) Proprietary acrylic bonding agents, applied either neat or in a grout;

e) Proprietary epoxy bonding agents.Some important properties and characteristics of bonding

agents and procedures include bond strength of the replace-ment material to the existing concrete, pot life, maximum time before which the replacement material should be installed, thickness of applied bonding agent, necessary remedies if the bonding agent sets or cures before the replacement mate-rials are installed, and long-term performance.

Testing of bond strength is discussed in 3.3.5. It is impor-tant to recognize that bond strength is limited by the quality and strength of the concrete substrate and the replacement or overlay material. Bonding agents and procedures are only effective in increasing the interface bond strength above the strengths of the substrate and replacement or overlay material, such that bond test failures occur away from the bond line.

The bonding material and procedure selected will deter-mine the time period available to apply the bonding material and to place replacement or overlay material. Environmental conditions such as ambient and concrete surface tempera-tures, direct sunlight, and wind will affect the time period. It is extremely important to monitor the thickness of the applied bonding material and the drying, setting, and curing of the material; improper application of the bonding mate-

rial can result in significantly lowered bond strength. Some bonding materials can remain in place and be effective even after they have set or cured, whereas other materials, such as epoxy, should be completely removed and reapplied if they set before the replacement or overlay material is placed.

Some bonding agents, such as neat acrylics, experience decreased bond strength or alkaline hydrolysis, or degra-dation, if the concrete is saturated during service. Some bonding agents may be vulnerable to attack by components of raw or industrial sewage, or other chemical exposures. Figure 9.4 shows the replacement concrete paste being used as a bonding agent.

9.5—Crystalline pore blockersCrystalline pore blockers are topically-applied cement-

based slurries or liquids, with common active ingredients of silicates or silicofluorides. The active ingredient reacts with calcium hydroxide in the cement paste and moisture to form insoluble stable silicate hydrates or calcium silico-fluoride, which increases the density of the surface structure of the concrete. Reaction products decrease the permeability of existing concrete surfaces and fill cracks. Pore blockers essentially enhance some concrete properties, so the effec-tiveness of the repair is limited by the affected properties of the concrete before treatment. Pore blockers may not effec-tively treat new or moving cracks and joints.

9.5.1 Manufacturer’s testing—Laboratory testing reported by material manufacturers indicates that treated samples have reduced water permeability when exposed to 164 to 394 ft (50 to 120 m) of water head (United States Army Corps of Engineers (USACE CRD-C 48; DIN 1048-5)); reduced chloride ion permeability (modified ASTM D1411); and improved resistance to freezing and thawing (ASTM C672). A reported typical rate of penetration of the insoluble reac-tion products into the concrete is 0.08 in. (2 mm) per week.

9.5.2 Transport Research Lab (TRL) CR35 testing—TRL CR35 is an independent evaluation of two liquid pore blockers and three slurries. Before testing, the slurries were removed from the sample surfaces so that the effectiveness of the active ingredients in pore blocking, and not the surface coat effects, were evaluated. Laboratory testing included initial surface absorption (ISA), capillary absorption (CA),

Fig. 9.4—Application of the concrete paste as a bonding agent. (Courtesy of Restruction Corporation.)




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determination of carbonation depth, half-cell potential and chloride penetration, and tests for disruptive reactions.

For the ISA, CA, and carbonation tests, 4 in. (100 mm) cubes of two concrete mixtures were used. Mixture A had a water-cementitious material ratio (w/cm) of 0.45 and was considered a durable concrete; Mixture B had a w/cm of 0.67 and was considered a concrete whose durability might be improved by treatment with a crystalline pore blocker. The pore blockers were applied in accordance with the manu-facturer’s recommendations after the specimens had been cured in a fog room for 7 days and then air dried for 7 days. Following treatment, the specimens were fog cured or air cured for 4, 13, or 48 weeks before testing. After curing, the specimens for ISA and CA were sawn into slices at depths of 3/8 and 1 in. (10 and 25 mm) below the surface, and the ISA and CA tests were performed on each slice so that the effects of the depth of crystal growth could be evaluated. The ISA test consisted of exposing the specimen surface to water under a constant head of 4 in. (100 mm) and measuring the rate of water flow 10, 30, and 60 minutes from the start of the test. The CA test consisted of placing the concrete slices on top of a saturated sponge that was in a tray of water, and measuring the weight gain of the slices 5, 15, 30, 60, and 120 minutes and longer intervals from the time the speci-mens were first brought into contact with the sponge. After 72 hours, the specimens were submerged in water for 2 days to saturate the concrete. For carbonation testing, intact cube specimens were left to carbonate in air for 58 weeks after 4, 13, and 48 weeks of curing.

For the half-cell and chloride penetration testing, 16 in. (400 mm) slabs with two 3/8 in. (10 mm) diameter rein-forcing bars were cast, fog-cured for 7 days, treated with the pore blockers, and then ponded with water for 28 days. The slabs were then ponded with 5 percent sodium chloride solu-tion for 14 days and air dried for 2 to 4 days. The slabs were subjected to five cycles of ponding and air-drying, totaling 70 days of ponding and 109 days total test duration. Half-cell measurements were taken periodically during the test period. At the end of the test period, the slabs were broken up, the chloride ion content of the concrete determined, and the reinforcing bars examined. The chloride ion contents were determined from concrete powder samples taken at depths of 1/8 to 5/8 in. (3 to 15 mm), 5/8 to 1 in. (15 to 25 mm), and 1 to 1-3/8 in. (25 to 35 mm). The powder samples were taken from six holes and combined for each depth range.

There is concern that reaction products from treatment with some pore blockers could chemically disrupt the cement matrix and weaken the concrete. To assess this concern, 4 in. (100 mm) cube specimens were treated with pore blockers and stored in water or a 10 percent solution of liquid silicate for 8 months, and then tested in compression.

TRL CR35 concluded that:a) “The dominant influences on the absorptive behaviour

were found to be the mix proportions and the curing regime of the concrete specimens. The treatments do not appear to have a consistent marked effect, which suggests that they do not modify substantially the pore structure of the concrete. Treat-ment of a moderate quality concrete (cement content 250 kg/

m3, w-c ratio 0.67) did not reduce its absorption such that it could be favourably compared with a good quality untreated concrete (cement content 360 kg/m3, w-c ratio 0.45).”

b) “The capillary absorption and ISA results generally agree closely in terms of relative performances of treated and untreated specimens.”

c) “Carbonation does not appear to be impeded by the application of treatments.”

d) “The time to corrosion of the steel, assessed by half-cell potential measurements, was not increased in comparison with the behaviour of untreated slabs…Chloride penetration after 5 cycles of the ponding regime was similar in treated and untreated slabs.”

e) “There is no indication of any disruptive reaction being reflected in a significant reduction in compressive strength.”

9.5.3 Installation—The pore blocker is applied to clean surfaces with open pore structures as a slurry or liquid by brush, broom, or spray, in one or two coats. The effective-ness of the pore blocker is very dependent on the condition of the existing concrete and application quality, and it is recommended that a trial installation be tested for reduction in permeability prior to full-scale installation. The use of pore blockers should be carefully compared to other perme-ability reduction options, such as surface sealers and traffic-bearing coatings.

9.6—Surface-applied, penetrating corrosion inhibitors

Surface-applied, penetrating corrosion inhibitors (SAPCIs) are chemical substances that migrate from the concrete surface to the level of the reinforcing steel and “decrease the corrosion rate when present in the corro-sion system at suitable concentration, without significantly changing the concentration of any corrosive agent [such as water, oxygen, or chloride ion concentrations]” (ISO 8044). SAPCIs commonly decrease the corrosion rate by adsorbing to the reinforcing steel surface, forming a layer that interferes with the corrosion reactions, or by creating an insoluble oxide or hydroxide layer on the steel surface by shifting the electrochemical potential of the corroding steel (Strategic Highway Research Program [SHRP-S-666]). Common SAPCIs are amines, alkanolamines, and their salts with organic and inorganic acids; monofluorophosphate; and calcium or sodium nitrites (Söylev and Richardson 2008).

To be effective, SAPCIs should penetrate through the concrete in sufficient concentrations to inhibit corro-sion. Factors influencing SAPCI effectiveness include the concrete quality, reinforcing steel cover, current level of chloride contamination or carbonation, and current amount of corrosion by-product on the steel. As might be expected, every concrete structure has one or more unique combina-tions of these factors. Penetration depths up to 3.1 to 4 in. (80 to 100 mm) have been reported (Jones 2011).

9.6.1 Test procedures—Laboratory tests and some field tests have shown some SAPCIs to be effective in reducing reinforcing steel corrosion. Each concrete element, however, should be evaluated individually to determine if conditions are appropriate for an SAPCI to be effective.




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Methods of verifying the presence of an SAPCI on rein-forcing steel samples include scanning electron microscopy, energy dispersive X-ray microanalysis, X-ray photon spec-troscopy, and secondary ion mass spectroscopy. Quaternary-ammonium-compound test sticks can be used to verify the presence of some SAPCIs in concrete powder samples. These test procedures, however, generally indicate the pres-ence of the SAPCI, but not the quantity. Unfortunately, the concrete used in much of the testing by SAPCI manufac-turers has relatively high w/cm, sometimes 0.6 or more, which suggests that the concrete is relatively permeable and easy for the SAPCI to penetrate. In some instances, the w/cm is not even reported. The effectiveness of SAPCIs can be measured with common corrosion measurement techniques, such as half-cell potentials (ASTM C876) and corrosion rate measurements by the linear polarization resistance method (ASTM G59). Again, meaningful assessment cannot be made for several months to a year or more after the SAPCI application.

9.6.2 Installation—Surface-applied, penetrating corrosion inhibitors are applied to clean, dry concrete surfaces. Surface contaminants are removed by light sandblast or waterblast. The SAPCI is then applied by roller, brush, spray, or ponding, and several coats are usually recommended. Vacuum/pres-sure injection has also been used experimentally. At least 1 day is necessary for the SAPCI to penetrate the concrete and the surface to dry. SAPCIs may take several months to a year to penetrate to the level of the reinforcing steel and begin reducing corrosion (Jones 2011), so that verification of the SAPCI penetration and effectiveness cannot be performed for some period of time after application. Figure 9.6.2 shows the application of a surface-applied, penetrating corrosion inhibitor.

CHAPTER 10—REFERENCESACI committee documents and documents published by

other organizations are listed first by document number, full title, and year of publication followed by authored docu-ments listed alphabetically. Include each element of the authored reference, including month and page number(s) where applicable.

American Association of State and Highway Transporta-tion Officials (AASHTO)

T259-02—Standard Method of Test for Resistance of Concrete to Chloride Ion Penetration

T277-07—Standard Method of Test for Electrical Indica-tion of Concrete’s Ability to Resist Chloride Ion Penetration

T334-08-UL—Standard Method of Test for Estimating the Cracking Tendency of Concrete

American Concrete Institute (ACI)201.2R-08—Guide to Durable Concrete211.1-91—Standard Practice for Selecting Proportions for

Normal, Heavyweight, and Mass Concrete (Reapproved 2009)212.3R-10—Report on Chemical Admixtures for Concrete213R-03—Guide for Structural Lightweight-Aggregate

Concrete221.1R-98—Report on Alkali-Aggregate Reactivity

(Reapproved 2008)222R-01—Protection of Metals in Concrete Against

Corrosion (Reapproved 2010)224.1R-07—Causes, Evaluation, and Repair of Cracks in

Concrete Structures225R-99—Guide to the Selection and Use of Hydraulic

Cements (Reapproved 2009)232.1R-12—Report on the Use of Raw or Processed

Natural Pozzolans in Concrete232.2R-03—Use of Fly Ash in Concrete233R-03—Slag Cement in Concrete and Mortar234R-06—Guide for the Use of Silica Fume in Concrete

(Reapproved 2012)304R-00—Guide for Measuring, Mixing, Transporting,

and Placing Concrete (Reapproved 2009)304.1R-92—Guide for the Use of Preplaced Aggregate

Concrete for Structural and Mass Concrete Applications (withdrawn)

304.2R-96—Placing Concrete by Pumping Methods (Reapproved 2008)

304.6R-09—Guide for the Use of Volumetric-Measuring and Continuous-Mixing Concrete Equipment

308R-01—Guide to Curing Concrete (Reapproved 2008)364.3R-09—Guide for Cementitious Repair Material

Data Sheet364.3T-10—Treatment of Exposed Epoxy-Coated Rein-

forcement in Repair503.5R-92—Guide for the Selection of Polymer Adhe-

sives with Concrete (Reapproved 2003)506R-05—Guide to Shotcrete506.1R-08—Guide to Fiber-Reinforced Shotcrete544.1R-96—Report on Fiber Reinforced Concrete (Reap-

proved 2009)546R-04—Concrete Repair Guide546.2R-10—Guide to Underwater Repair of Concrete548.1R-09—Guide for the Use of Polymers in Concrete548.3R-09—Report on Polymer-Modified Concrete548.5R-94—Guide for Polymer Concrete Overlays (Reap-

proved 1998)RAP-1-03—Structural Crack Repair by Epoxy InjectionRAP-2-03—Crack Repair by Gravity Feed with Resin

Fig. 9.6.2—Application of a surface-applied, penetrating corrosion inhibitor. (Courtesy of Virginia Center for Trans-portation Innovation and Research.)




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RAP-3-03—Spall Repair by Low-Pressure SprayingRAP-4-03—Surface Repair Using Form-and-Pour TechniquesRAP-5-03—Surface Repair Using Form-and-Pump TechniquesRAP-8-05—Installation of Embedded Galvanic AnodesRAP-13-10—Methacrylate Flood Coat

ASTM InternationalC39/C39M-14—Standard Test Method for Compressive

Strength of Cylindrical Concrete SpecimensC78-/C78M-10e1—Standard Test Method for Flexural

Strength of Concrete (Using Simple Beam with Third Point Loading)

C109/C109M-13—Standard Test Method for Compres-sive Strength of Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube Specimens)

C157/C157M-08—Standard Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete

C227-10—Standard Test Method for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method)

C289-07—Standard Test Method for Potential Alkali-Silica Reactivity of Aggregates (Chemical Method)

C293/C293M-10—Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Center-Point Loading)

C295/C295M-12—Standard Guide for Petrographic Examination of Aggregates for Concrete

C307-03(2012)—Standard Test Method for Tensile Strength of Chemical-Resistant Mortar, Grouts, and Mono-lithic Surfacings

C348-08—Standard Test Method for Flexural Strength of Hydraulic-Cement Mortars

C418-12—Standard Test Method for Abrasion Resistance of Concrete by Sandblasting

C469/C469M-10—Standard Test Method for Static Modulus of Elasticity and Poisson’s Ratio of Concrete in Compression

C496/C496M-11—Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens

C501-84(2009)—Standard Test Method for Relative Resistance to Wear of Unglazed Ceramic Tile by the Taber Abraser

C510-05a(2011)—Standard Test Method for Staining and Color Change of Single- or Multicomponent Joint Sealants

C512/C512M-10—Standard Test Method for Creep of Concrete in Compression

C531-00(2012)—Standard Test Method for Linear Shrinkage and Coefficient of Thermal Expansion of Chem-ical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes

C579-01(2012)—Standard Test Methods for Compressive Strength of Chemical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes

C580-02(2012)—Standard Test Method for Flexural Strength and Modulus of Elasticity of Chemical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes

C596-09—Standard Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement

C642-13—Standard Test Method for Density, Absorption, and Voids in Hardened Concrete

C666/C666M-03(2008)—Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing

C672/C672M-12—Standard Test Method for Scaling Resis-tance of Concrete Surfaces Exposed to Deicing Chemicals

C679-03(2009)e1—Standard Test Method for Tack-Free Time of Elastomeric Sealants

C719-13—Standard Test Method for Adhesion and Cohe-sion of Elastomeric Joint Sealants Under Cyclic Movement (Hockman Cycle) 1, 2

C779/C779M-12—Standard Test Method for Abrasion Resistance of Horizontal Concrete Surfaces

C794-10—Standard Test Method for Adhesion-in-Peel of Elastomeric Joint Sealants

C806-12—Standard Test Method for Restrained Expan-sion of Expansive Cement Mortar

C827/C827M-10—Standard Test Method for Change in Height at Early Ages of Cylindrical Specimens of Cementi-tious Mixtures

C836/C836M-12—Standard Specification for High Solids Content, Cold Liquid-Applied Elastomeric Waterproofing Membrane for Use with Separate Wearing Course

C876-09—Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete

C881/C881M-10—Standard Specification for Epoxy-Resin-Base Bonding Systems for Concrete

C882/C882M-13a—Standard Test Method for Bond Strength of Epoxy-Resin Systems Used with Concrete by Slant Shear

C884/C884M-98(2010)—Standard Test Method for Thermal Compatibility between Concrete and an Epoxy-Resin Overlay

C944/C944M-12—Standard Test Method for Abrasion Resistance of Concrete or Mortar Surfaces by the Rotating-Cutter Method

C957/C957M-10—Standard Specification for High-Solids Content, Cold Liquid-Applied Elastomeric Water-proofing Membrane with Integral Wearing Surface

C1012/C1012M-13—Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution

C1017/C1017M-13—Standard Specification for Chem-ical Admixtures for Use in Producing Flowing Concrete

C1042-99—Standard Test Method for Bond Strength of Latex Systems Used with Concrete By Slant Shear (with-drawn 2008)

C1138M-12—Standard Test Method for Abrasion Resis-tance of Concrete (Underwater Method)

C1152/C1152M-04(2012)e1—Standard Test Method for Acid-Soluble Chloride in Mortar and Concrete

C1181-00(2012)—Standard Test Methods for Compressive Creep of Chemical-Resistant Polymer Machinery Grouts

C1202-12—Standard Test Method for Electrical Indica-tion of Concrete’s Ability to Resist Chloride Ion Penetration

C1218/C1218M-99(2008)—Standard Test Method for Water-Soluble Chloride in Mortar and Concrete




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C1260-07—Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method)

C1293-08b—Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Silica Reaction

C1305-08—Standard Test Method for Crack Bridging Ability of Liquid-Applied Waterproofing Membrane

C1404/C1404M-98(2003)—Standard Test Method for Bond Strength of Adhesive Systems Used with Concrete as Measured by Direct Tension (withdrawn 2010)

C1436-08—Standard Specification for Materials for Shotcrete

C1438-13—Standard Specification for Latex and Powder Polymer Modifiers in Hydraulic Cement Concrete and Mortar

C1439-13—Standard Test Methods for Evaluating Latex and Powder Polymer Modifiers for use in Hydraulic Cement Concrete and Mortar

C1480/C1480M-07(2012)—Standard Specification for Packaged, Pre-Blended, Dry, Combined Materials for Use in Wet or Dry Shotcrete Application

C1521-13—Standard Practice for Evaluating Adhesion of Installed Weatherproofing Sealant Joints

C1543-10a—Standard Test Method for Determining the Penetration of Chloride Ion into Concrete by Ponding

C1581/C1581M-09a—Standard Test Method for Deter-mining Age at Cracking and Induced Tensile Stress Charac-teristics of Mortar and Concrete under Restrained Shrinkage

C1583/C1583M-13—Standard Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-off Method)

D412-06a(2013)—Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension

D471-12a—Standard Test Method for Rubber Property-Effect of Liquids

D522/D522M-13—Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings

D570-98(2010)e1—Standard Test Method for Water Absorption of Plastics

D624-00(2012)—Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers

D638-10—Standard Test Method for Tensile Properties of Plastics

D648-07—Standard Test Method for Deflection Tempera-ture of Plastics Under Flexural Load in the Edgewise Position

D695-10—Standard Test Method for Compressive Prop-erties of Rigid Plastics

D696-08e1—Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics Between –30°C and 30°C with a Vitreous Silica Dilatometer

D732-10—Standard Test Method for Shear Strength of Plastics by Punch Tool

D790-10—Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insu-lating Materials

D822/D822M-13—Standard Practice for Filtered Open-Flame Carbon-Arc Exposures of Paint and Related Coatings

D903-98(2010)—Standard Test Method for Peel or Strip-ping Strength of Adhesive Bonds

D1004-13—Standard Test Method for Tear Resistance (Graves Tear) of Plastic Film and Sheeting

D1242-95a—Standard Test Methods for Resistance of Plastic Materials to Abrasion (withdrawn 2004)

D1411-09—Standard Test Methods for Water-Soluble Chlo-rides Present as Admixtures in Graded Aggregate Road Mixes

D1623-09—Standard Test Method for Tensile and Tensile Adhesion Properties of Rigid Cellular Plastics

D1653-13—Standard Test Methods for Water Vapor Transmission of Organic Coating Films

D2126-09—Standard Test Method for Response of Rigid Cellular Plastics to Thermal and Humid Aging

D2240-05(2010)—Standard Test Method for Rubber Property-Durometer Hardness

D3273-12—Standard Test Method for Resistance to Growth of Mold on the Surface of Interior Coatings in an Environmental Chamber

D4060-10—Standard Test Method for Abrasion Resis-tance of Organic Coatings by the Tabor Abraser

D4541-09e1—Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers

D5095-91(2013)—Standard Test Method for Determina-tion of the Nonvolatile Content in Silanes, Siloxanes and Silane-Siloxane Blends Used in Masonry Water Repellent Treatments

D6489-99(2012)—Standard Test Method for Determining the Water Absorption of Hardened Concrete Treated With a Water Repellent Coating

D6904-03(2013)—Standard Practice for Resistance to Wind-Driven Rain for Exterior Coatings Applied on Masonry

E84-12c—Standard Test Method for Surface Burning Characteristics of Building Materials

E96/E96M-13—Standard Test Methods for Water Vapor Transmission of Materials

E514/E514M-14—Standard Test Method for Water Pene-tration and Leakage Through Masonry

G53-96—Practice for Operating Light- and Water-Expo-sure Apparatus (Fluorescent UV-Condensation Type) for Exposure of Nonmetallic Materials (withdrawn 2000)

G59-97(2009)—Standard Test Method for Conducting Potentiodynamic Polarization Resistance Measurements

G152-06—Standard Practice for Operating Open Flame Carbon Arc Light Apparatus for Exposure of Nonmetallic Materials

G153-13—Standard Practice for Operating Enclosed Open Flame Carbon Arc Light Apparatus for Exposure of Nonmetallic Materials

G154-12a—Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonme-tallic Materials

G156-09—Standard Practice for Selecting and Character-izing Weathering Reference Materials

Canadian Standards AssociationCSA A23.2-6B-09—Method of Test to Determine Adhe-

sion by Tensile Load




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CSA A864-00 (R2005)—Guide to the Evaluation and Management of Concrete Structures Affected by Alkali-Aggregate Reaction

Code of Federal Regulations (CFR)Title 40 CFR Part 60—Determination of Volatile Matter

Content, Water Content, Density, Volume Solids, and Appendix A, Weight Solids of Surface Coatings, Method 24

DIN Deutsches Institut für Normung e. V.DIN 1048-5, 1991—Testing Concrete; Testing of Hard-

ened Concrete (Specimens Prepared in Mould)

European Committee for StandardizationEN 1062-6:2002—Paints and Varnishes – Coating Mate-

rials and Coating Systems for Exterior Masonry and Concrete – Part 6: Determination of Carbon Dioxide Permeability

ICC Evaluation Service, Inc.ICC ES-AC39-12—Acceptance Criteria for Walking Decks

International Organization for Standardization (ISO)ISO 7783:2011—Paints and Varnishes – Determination of

Water-Vapour Transmission Properties – Cup MethodISO 8044: 1999—Corrosion of Metals and Alloys – Basic

Terms and Definitions

International Concrete Repair Institute (ICRI)210.3-2004—Guide for Using In-Situ Tensile Pull-off

Tests to Evaluate Bond of Concrete Surface Materials320.2R-2009—Guide to Selecting and Specifying Mate-

rials for Repair of Concrete Surfaces320.3R-2012—Guide for Inorganic Repair Material Data

Sheet Protocol340.1-2006—Guide for the Selection of Grouts to Control

Leakage in Concrete Structures

NACE International01105—Sacrificial Cathodic Protection of Reinforced

Concrete Elements—A State-of-the-Art Report (2005)

National Cooperative Highway Research Program (NCHRP)Report 244—Concrete Sealers for Protection of Bridge

Structures (1981)

Oklahoma Department of Transportation (OKDOT)OHD L-34-03—Method of Test for Depth of Penetration

of Concrete by Penetrating Water Repellent Treatment Solu-tions (inactive)

OHD L-35-03—Method of Test for Moisture Vapor Permeability of Treated Concrete (inactive)

Strategic Highway Research Program (SHRP)SHRP-S-330-93—Condition Evaluation of Concrete

Bridges Relative to Reinforcement Corrosion. V. 8, Proce-dure Manual

SHRP-S-363-93—Mechanical Behavior of High Perfor-mance Concretes, V. 3, Very Early Strength Concrete

SHRP-S-666-93—Concrete Bridge Protection and Reha-bilitation: Chemical and Physical Techniques, Corrosion Inhibitors and Polymers

Transport Research Laboratory (TRL)CR35—Crystal Growth Materials as Surface Treatments for

Concrete, Keer, J. G. and Gardiner, G. M.; 01/01/1986; 67 pp.

United States Army Corps of Engineers (USACE)CRD-C 39-81—Test Method for Coefficient of Linear

Thermal Expansion of ConcreteCRD-C 48-92—Standard Test Method for Water PermeabilityCRD-C 164-92—Standard Test Method for Direct Tensile

Strength of Cylindrical Concrete or Mortar SpecimensEM 1110-1-3500-95—Chemical Grouting

Authored documentsAshby, M. F., 1992, Materials Selection in Mechanical

Design, Pergamon Press, London, UK, 311 pp.ASM International, 1990, Engineered Materials Hand-

book, V. 3: Adhesives and Sealants, Metals Park, OH, 893 pp.

Beaudoin, J. J., 1982, “Fibre-Reinforced Concrete,” Cana-dian Building Digest, CBD-223, National Research Council Canada, Institute for Research in Construction.

Carter, P. D., 1994, “Evaluation of Dampproofing Perfor-mance and Effective Penetration Depth of Silane Sealers in Concrete,” Concrete Bridges In Aggressive Environments, SP-151, R. E. Weyers, ed., American Concrete Institute, Farmington Hills, MI, pp. 95-117.

CIAS Report 01-1, 2001, “Galvashield Embedded Galvanic Anodes for Repair of Concrete,” Concrete Inno-vations Appraisal Service (CIAS), American Concrete Insti-tute, Farmington Hills, MI, 23 pp.

Concrete Reinforcing Steel Institute (CRSI), 2011, Bridges, Schaumburg, IL.

Concrete Society, 1976, “Concretes with Dispersed Poly-mers Added,” Polymers in Concrete: Proceedings of the First International Congress on Polymer Concretes, D. H. Cohen, ed., Concrete Construction Publications, Inc., Addison, IL, pp. 179-240.

Gurjar, S., 1987, “Alberta Concrete Patch Evalua-tion Program,” Report No. ABTR/RD/RR-87/05, Alberta Transportation and Utilities, Research and Development, Edmonton, AB, Canada, 69 pp.

Hansen, T. C., and Mattock, A. H., 1966, “Influence of Size and Shape of Member on the Shrinkage and Creep of Concrete,” ACI Journal, V. 69, Feb., pp. 267-290 (reprinted as Bulletin D103 by the Portland Cement Association).

Iriya, K.; Hattori, T.; and Umehara, H., 1999, “Study on the Relationship between Compressive Creep and Tensile Creep of Concrete at an Early Age,” Civil Engineering, No. 33, Japan Society of Civil Engineers, June, pp. 185-198.

Iriya, K.; Negi, T.; Hattori, T.; and Umehara, H., 2000, “Study on Tensile Creep of Concrete at an Early Age,” Civil Engineering, No. 35, Japan Society of Civil Engineers, June, pp. 201-214.




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http://www.din.de/cmd?level=tpl-home&languageid=en

https://www.cen.eu/Pages/default.aspx

http://www.icc-es.org/

http://www.iso.org/iso/home.html

http://www.icri.org/

https://www.nace.org/home.aspx

http://www.trb.org/NCHRP/NCHRP.aspx

http://www.okladot.state.ok.us/

http://www.trb.org/Publications/PubsSHRP2Publications.aspx

http://www.trl.co.uk/

http://www.usace.army.mil/

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Johnston, C., 1993, “Superplasticizers for Concrete Bridge Construction,” Report No. ABTR/RD/RR-93/01, Alberta Transportation and Utilities, Research and Develop-ment, Edmonton, AB, Canada.

Jones, G., 2011, “Taking Control of Corrosion Management Decisions,” Concrete Repair Bulletin, Sept./Oct., pp. 24-31.

Knab, L. I.; Sprinkel, M. M.; and Lane, O. J., 1989, “Preliminary Performance Criteria for the Bond of Portland Cement and Latex Modified Concrete Overlays,” NISTR 89-4156, National Institute of Standards and Technology, Gaithersburg, MD, 102 pp.

McDonald, J. E.; Vaysburd, A. M.; Emmons, P. H.; Poston, R. W.; and Kesner, K. E., 2002, “Selecting Durable Repair Materials: Performance Criteria—Summary,” Concrete International, V. 24, No. 1, Jan., pp. 37-44.

Michigan Department of Transportation (MDOT), “Direct Shear Bonding Test—Qualification Procedure for Prepack-aged Hydraulic Patching Mortars,” 1 p.

Mindess, S., and Young, J. F., 1981, Concrete, Prentice-Hall, Englewood Cliffs, NJ, pp. 624-628.

Neville, A. M., 1996, “Direct Shear Bonding Test—Qual-ification Procedure for Prepackaged Hydraulic Patching Mortars,” Properties of Concrete, fourth edition, John Wiley, New York, 844 pp.

Panek, J. R., and Cook, J. P., 1992, Construction Sealants and Adhesives, third edition, John Wiley, New York, 375 pp.

Pigeon, M., and Bissonnette, B., 1999, “Tensile Creep and Cracking Potential,” Concrete International, V. 21, No. 11, Nov., pp. 31-35.

Plecnik, J. M.; Bresler, B.; Chan, H. M.; Pham, M.; and Chao, J., 1982, “Epoxy-Repaired Concrete Walls Under Fire Exposure,” Journal of the Structural Division, V. 108, Aug., pp. 1894-1908.

Popovics, S., and Rajendran, N., 1987, “Early Age Proper-ties of Magnesium Phosphate-Based Cements under Various Temperature Conditions,” Concrete and Concrete Construc-tion, Transportation Research Record 1110, Washington, DC, pp. 34-44.

Popovics, P. S.; Rajendran, N.; and Penko, M., 1987, “Rapid Hardening Cements for Repair of Concrete,” ACI Materials Journal, V. 84, No. 1, Jan.-Feb., pp. 64-73.

Portland Cement Association, 1995, “Thickness Design for Concrete Highway and Street Pavements,” R. G. Packard, ed., Skokie, IL, 50 pp.

Portland Cement Association, 2007, “Effects of Substances on Concrete and Guide to Protective Treatments,” PCA IS001, Skokie, IL, 24 pp.

Reed, R. C.; Krauss, P.; Sherman, M. R.; and McDonald, D. B., 2003, “Coating Repaired Rebar,” Concrete Construc-tion, Mar., pp. 55-59.

Selander, A., 2010, “Hydrophobic Impregnation of Concrete Structures—Effects on Concrete Properties,” PhD thesis, KTH Royal Institute of Technology, School of Archi-tecture and Built Environment, Department of Civil and Architectural Engineering, Chair of Structural Engineering and Bridges, Stockholm, Sweden.

Shydlowski, L. M., 1998, “Challenges in the Commer-cialization of New Technologies,” Concrete International, V. 20, No. 2, Feb., pp. 25-27.

Silfwerbrand, J., 1990, “Improving Concrete Bond in Repaired Bridge Decks,” Concrete International, V. 12, No. 9, Sept., pp. 61-66.

Söylev, T. A., and Richardson, M. G., 2008, “Corrosion Inhibitors for Steel in Concrete: State-of-the-Art Report,” Construction & Building Materials, V. 22, No. 4, Apr., pp. 609-622. doi: 10.1016/j.conbuildmat.2006.10.013

Sprinkel, M. M., 1983, “Thermal Compatibility of Thin Polymer Concrete Overlays,” Transportation Research Record No. 899, Washington, DC, pp. 64-73.

Sprinkel, M. M., and Ozyildirim, H. C., 1998, “Field Eval-uation of Corrosion Inhibitors for Concrete: Interim Report 1, Evaluation of Exposure Slabs Repaired With Corrosion Inhibitors,” Report No. VTRC 99-IR1, Virginia Transporta-tion Research Council, Charlottesville, VA, 60 pp.

Stark, D., 1991, “The Moisture Condition of Field Concrete Exhibiting Alkali-Silica Reactivity,” Durability of Concrete, Proceedings of the Second CANMET/ACI Inter-national Conference, SP-126, V. M. Malhotra, ed., American Concrete Institute, Farmington Hills, MI., Aug., pp. 973-987.

Taylor, H. F. W., 1990, Cement Chemistry, Academic Press, San Diego, CA, 475 pp.

Vaysburd, A. M.; Emmons, P. H.; McDonald, J. E.; Poston, R. W.; and Kesner, K. E., 1999, “Performance Criteria for Concrete Repair Materials, Phase II Summary Report,” Technical Report REMR-CS-62, U. S. Army Corps of Engi-neers, Mar., 72 pp.

Watson, P. M., 1996, “Preplaced-Aggregate Concrete,” Aberdeen’s Concrete Repair Digest, V. 7, No. 3, June-July, pp. 148-152.

Weiss, J. W.; Yang, W.; and Shah, S. P., 1998, “Shrinkage Cracking of Restrained Concrete Slabs,” Journal of Engi-neering Mechanics, V. 124, No. 7, July, pp. 765-774. doi: 10.1061/(ASCE)0733-9399(1998)124:7(765)

Whiting, D., 1981, “Rapid Determination of the Chloride Permeability of Concrete, Final Report,” Report No. FHWA/ RD-81/119, Federal Highway Administration, Washington, DC, 166 pp.

APPENDIX A—CURRENT INDUSTRY ISSUES AND CONCERNS

Selecting materials for concrete repair is a complex process. New materials and variations in existing technolo-gies appear on a regular basis. Ashby (1992) reported that somewhere between 40,000 and 80,000 different materials are available. Qualities that are desirable for materials used in new construction can be irrelevant or even detrimental in repair materials. Materials that are more rigid, or greatly different in compressive strength or permeability than the concrete being repaired, may not be compatible with the existing structure or with the repair procedure being used, and can contribute to repair failures. The selection of mate-rials used for repair should be based on different criteria than those used for new construction.




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A.1—Material test methods and reporting of test data

For specifiers and applicators to make an informed deci-sion regarding the selection of repair materials, accurate information should be available on the relevant material properties for the materials being considered. This implies that relevant properties should be identified and appropriate test methods used to measure and compare these properties.

Information on material properties is typically furnished by the material manufacturer or supplier; however, different manufacturers frequently report data for similar materials in ways that make the specifier’s and applicator’s decision more difficult and, in some cases, impossible. In some cases, there is no appropriate test method currently approved or even available for certain materials, material properties, or field-application conditions. For instance, there is no standard-ized test method for tensile creep (Neville 1996), which can reduce the buildup of stresses due to restrained shrinkage, thereby possibly reducing cracking in the repair material. Another example is the restrained shrinkage of repair mate-rials. While there are several test methods for measuring the restrained shrinkage of repair materials, very few have been approved by industry organizations. AASHTO has adopted T334, “Standard Method of Test for Estimating the Cracking Tendency of Concrete,” and several other similar test methods are under development (Weiss et al. 1998).

As a result, materials manufacturers and suppliers are left with several options, all of which could result in misleading information for the user:

a) Use existing test procedures that may not be represen-tative of actual repair conditions or may not present their product favorably;

b) Use nonstandard, modified test methods; orc) Develop new test methods.Various manufacturers may modify standard test methods

in different ways, or each may use different, new test methods. In some instances, the modified or new test proce-dures can be developed in such a manner to present certain materials more favorably or to show better performance under certain specific conditions. Specifiers and applicators are then left with reported properties based on different test methods that cannot be compared or evaluated.

Manufacturers sometimes report material test data per standard test methods, but with one or more of the param-eters of the standard test modified. In this case, the testing was basically performed following the general guidelines of the standard test, but some aspect of the test was modified. In most cases, the modification and reasons for it are not described in the data sheet. Given the number of different manufacturers, with each modifying the testing procedures independently, direct comparison based on published test results is often impossible.

One example of a modified test procedure involves a curing regimen followed when testing the length change of a sample material. ASTM C157 describes two curing proce-dures: water cure for 14 days, then air cure for 14 days, or water cure for 28 days. Neither of these curing methods accurately reflects field curing of concrete replacement

materials. On the job site, top concrete replacement may be moist cured for 7 days, but many concrete replacements are moist cured for a short time, or not at all, and then treated with a curing compound. The individual manufacturer typi-cally tests and reports its material using whatever curing regimen the manufacturer recommends for the use of the particular product. Therefore, whenever a particular mate-rial is specified based on given shrinkage data, the specifier most likely does not realize the curing regimen required to achieve the given performance. Actual performance of the material could be quite different under different conditions.

A primary concern is the length of time required for various consensus organizations to review and approve new or modified test methods suited for newly developed materials or for new uses of existing materials. Preferably, professional organizations could be encouraged to expedite their review and approval procedures for repair materials.

A.1.1 Ideally, manufacturers should publish test data using identical testing methods. One publication, ICRI 320.2R, recommends specific modifications to existing standard test methods. ICRI 320.3R is a standard data sheet protocol for repair materials, which evolved from a United States Army Corps of Engineers (USACE) study to develop performance criteria for cement-based repair materials. Until more suitable industry test methods are available, however, Committee 546 recommends that all products be tested following recognized and appropriate test methods, standardized where possible, and the results made available to users. A useful compromise would be for the manufac-turers to publish data from the standard tests in both unmodi-fied and modified forms, indicating specifically the nature of and reason for the modification as appropriate. Alterna-tively, manufacturers could agree on standard modifications to existing test procedures or new tests to be used within that industry. This information would give the specifier and applicator an opportunity to make the best selection of a repair material, and would still allow the manufacturer to present the test results appropriate for the product and appli-cation recommendations.

A.2—Curing repair materials and manufacturers’ reported test results

Curing is beneficial for the development of desirable properties with cementitious materials. ACI 308R discusses the curing of concrete. Adequate curing of repairs can be difficult and is sometimes neglected. In particular, for over-head and vertical repairs, curing methods such as the use of water spray or fog may not be practical, and the applica-tion of certain membrane-forming curing compounds could affect the appearance or properties, or both, of the completed repair. Providing adequate curing of cementitious repairs is a concern for many repair projects and can be a significant problem for architectural concrete repairs. Development of new curing methods and materials for cementitious repair materials is needed, but through proper use of existing methods, it is possible to achieve an effective cure.

Prepackaged repair products usually report hardened properties of the material, such as compressive strength




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and permeability, based on laboratory-cured samples. Field curing of concrete replacements may deviate significantly from laboratory curing conditions, resulting in different material properties. Warnings and clear instructions for curing are needed in application instructions and on pack-ages of repair materials. It would be useful for specifiers and applicators if material properties were reported for labora-tory-cured samples and for samples cured under approxi-mate field conditions.

A.3—Product limitations and warningsGenerally, prepackaged repair materials are marketed for

use within narrow application limits. Most product manufac-turers list some restrictions on where and how their products are to be applied. Limitations may include the depth of the repair or the orientation of the repair (that is, top horizontal, vertical, or overhead). The specifier and the applicator should be aware of these limitations.

Products often contain ingredients that are intended to overcome naturally-occurring limitations of cement-based materials. Product formulations and additives to overcome shrinkage (plastic and drying), to increase initial and final setting time, to provide high early strength, to enhance bond, or to inhibit corrosion are common.

Although there is no current requirement for manufac-turers to disclose the ingredients that make up their products, perhaps there should be. There are no miracle materials; when ingredients are added to enhance a given property, there is usually a corresponding downside. For example, gypsum- or ettringite-forming additives can accelerate set time and early strength gain, but may reduce durability, resulting in poor performance history in moist environments. Some expansive agents, such as ettringite, can expand beyond a desirable limit in moist environments. Some moisture-sensi-tive bonding agents redisperse, and can degrade in a moist environment at pH values greater than 8. In some cases, the specifier or applicator may need special expertise to success-fully use a certain material. These issues become concerns when specifiers and applicators are not adequately informed about the presence or effect of the ingredients in the repair materials.

Prepackaged cementitious repair materials generally absorb moisture and degrade over time, especially in humid climates. Many suppliers do not adequately moisture-proof the containers, nor do they make it easy for the user to deter-mine if the material shelf life has expired, resulting in the possibility that the applied product may not develop to its reported potential properties. Products should be properly packaged, and storage requirements and shelf life should be clearly labeled.

A.4—Standardized industry acceptanceAnother issue facing the concrete repair industry is how

products and materials are brought to market and accepted for widespread use. There are several methods by which the development and acceptance of new technologies to benefit the concrete industry are promoted, including:

a) ACI’s Strategic Development Council.

b) The American Association of State Highway and Trans-portation Officials (AASHTO) Product Evaluation List Management System (APEL) (http://www.ntpep.org/Pages/APEL.aspx) (accessed March 28, 2014), that maintains lists of the findings of evaluations of new or proprietary products.

c) State department of transportations that have processes for the testing and acceptance of new products.

d) Sharing of information, test results, and experiences by website postings, presentations at meetings, and publication of articles.

The burden of additional costs for complete evaluation and approval of new materials, however, has been poorly accepted by the marketplace. “There is no single authority or approval board to validate new technologies. We should rely on the current systems of codes and standards to document industry approval of new technologies and/or application methods…a laborious process that takes 10 years on average to complete” (Shydlowski 1998). It is frustrating for mate-rial manufacturers to create a new product with improved properties and then face industry resistance to its use for many years. On the contrary, there have been failures of new products introduced to the market without adequate testing. Specifiers and applicators are understandably reluctant to try new products when an existing product has been success-fully used for many years. Exaggerated claims by some manufacturers encourage this reluctance. There is a glaring need to accelerate improvements in materials technology and characterization methods.

A.5—Repair material bondMost repairs are bonded to the substrate concrete. There-

fore, the adhesive bond between the repair material and the substrate concrete is critical to the satisfactory performance of the repair; one of the most common causes of repair fail-ures is inadequate bond of the repair material. Some studies have shown that bond is primarily a function of the substrate quality, surface preparation, and application of the repair material (Silfwerbrand 1990). Others argue that the studies have involved small test specimens instead of large repair areas, and that a bonding agent is needed to ensure bond over large areas. Yet the collective experience of Committee 546 is a history of successful repairs without the use of bonding agents. Also, some bonding agents deteriorate the bond when exposed to moisture in service or inhibit the bond when used incorrectly. More information is needed on the key factors to achieve adequate bond under different conditions.

A.6—Corrosion reductionConcrete deterioration due to reinforcing steel corro-

sion is a common reason for performing concrete repairs. The repairs usually do not remove all of the deteriorated concrete, nor do they stop corrosion of the reinforcing steel. Many repair programs do not include a cathodic protection system; thus they extend the service life of a structure but do not stop or eliminate corrosion activity altogether. There are a number of repair options that are intended to reduce corro-sion activity in the concrete replacement or in the existing




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structure away from the concrete replacement, or both. They include:

a) Coating exposed reinforcing steel with materials such as epoxies and polymer-cement-based mortars;

b) Use of embedded galvanic anodes;c) Improving the repair concrete with admixtures, such as

silica fume, a polymer, or a steel corrosion inhibitor;d) Protecting the existing concrete with a surface-applied,

penetrating corrosion inhibitor, a coating, or an overlay.Each of these options has potential benefits, risks, and

associated costs.The use of chemical corrosion inhibitors in concrete repair

was introduced in the early 1990s. The effectiveness and life expectancy of these materials is unknown at this time, and likely vary considerably with different types of inhibitors and site conditions. Users report a wide variation in their effectiveness that presents the question as to what param-eters relate to successful use. Studies of their effectiveness in new concrete at the Virginia Department of Transporta-tion (DOT) (Sprinkel and Ozyildirim 1998) have extended the question to repair materials as well. If manufacturers are adding corrosion inhibitors to prepackaged materials or are selling corrosion inhibitors for topical treatment to the surface of the concrete, the corrosion inhibitor type, recommended uses, constraints, anticipated effectiveness, and quality assurance/quality control measures should be published in their product literature.

Public agencies and private owners spend large sums of money repairing and addressing concrete deterioration due to reinforcing steel corrosion, and much research has been performed to evaluate various repair options. Unfortunately, the results of the research are sometimes conflicting, and all of the repair options have limited effectiveness. Addi-tional research and field trials are needed to further evaluate existing repair options and new materials.

These concerns should not infer that the available products should not be used, only that the specifier and user should be aware of their limitations, as well as their benefits.

A.7—Structural repairsPerhaps the most misused term in the concrete repair

industry today is structural repair. A structural repair is a repair that is intended to satisfy a deflection or strength (load-carrying) requirement of a structural member. Unless the existing loads are temporarily removed from the member, such as by jacking, shoring, or removal of the existing loads, the existing loads are redistributed in the remaining concrete and reinforcement and, at best, the concrete replacement only

shares in additional loads that are applied after the concrete replacement has set. These additional loads are commonly only a fraction of the pre-repair loads; this means that the vast majority of concrete replacements are nonstructural by this definition.

Many repair materials are marketed for structural repairs, which might mean they have different mechanical properties from nonstructural repair materials, such as a higher modulus of elasticity. As discussed in 3.3.2, this may be detrimental for the proper performance of nonstructural repairs.

Repairs that are truly structural in nature are intended to enhance or restore the integrity of a structure and should only be designed by a qualified structural engineer. In this case, the specifier should first ensure that the member to be repaired is unloaded an amount required to achieve the desired structural performance. An appropriate repair mate-rial should then be selected. For structural repairs, a repair material with a modulus of elasticity approximately equal to that of the substrate concrete is generally selected.

A.8—Ongoing developmentsOver the years, the concrete industry has gradually come

to understand that new concrete construction and the repair of existing concrete structures are distinctly different disci-plines. Recognizing the differences in design, materials, and methods is one aspect, and providing qualified profes-sionals and materials of appropriate quality is another. In 1998, a special Technical Activities Committee—Repair and Rehabilitation Committee (TRRC)—was formed by ACI to address the unique issue of repair. The assignment given to the TRRC was to develop and carry out a 5-year strategic plan for repair and rehabilitation within ACI. The mission of the TRRC is to provide leadership and technical guidance within ACI on issues of concrete repair, rehabilitation, main-tenance, protection, and strengthening. A second near-term objective is to survey current ACI committee activities and identify those related to repair and rehabilitation.

The International Concrete Repair Institute (ICRI) is an organization of engineers, material suppliers, and contrac-tors that specialize in concrete repair. This organization has been instrumental in promoting good repair practices and the use of proper repair materials. ACI and ICRI should continue to promote concrete repair as a significant area of concrete practice.

As the concrete repair industry continues to grow and more specialty professionals and suppliers join in, many of these issues and concerns will be addressed.




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As ACI begins its second century of advancing concrete knowledge, its original chartered purpose remains “to provide a comradeship in finding the best ways to do concrete work of all kinds and in spreading knowledge.” In keeping with this purpose, ACI supports the following activities:

· Technical committees that produce consensus reports, guides, specifications, and codes.

· Spring and fall conventions to facilitate the work of its committees.

· Educational seminars that disseminate reliable information on concrete.

· Certification programs for personnel employed within the concrete industry.

· Student programs such as scholarships, internships, and competitions.

· Sponsoring and co-sponsoring international conferences and symposia.

· Formal coordination with several international concrete related societies.

· Periodicals: the ACI Structural Journal, Materials Journal, and Concrete International.

Benefits of membership include a subscription to Concrete International and to an ACI Journal. ACI members receive discounts of up to 40% on all ACI products and services, including documents, seminars and convention registration fees.

As a member of ACI, you join thousands of practitioners and professionals worldwide who share a commitment to maintain the highest industry standards for concrete technology, construction, and practices. In addition, ACI chapters provide opportunities for interaction of professionals and practitioners at a local level.

American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331Phone: +1.248.848.3700Fax: +1.248.848.3701

www.concrete.org



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38800 Country Club Drive

Farmington Hills, MI 48331 USA

+1.248.848.3700

www.concrete.org

The American Concrete Institute (ACI) is a leading authority and resource

worldwide for the development and distribution of consensus-based

standards and technical resources, educational programs, and certifications

for individuals and organizations involved in concrete design, construction,

and materials, who share a commitment to pursuing the best use of concrete.

Individuals interested in the activities of ACI are encouraged to explore the

ACI website for membership opportunities, committee activities, and a wide

variety of concrete resources. As a volunteer member-driven organization,

ACI invites partnerships and welcomes all concrete professionals who wish to

be part of a respected, connected, social group that provides an opportunity

for professional growth, networking and enjoyment.



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ACI 546.3R-14 Guide to Materials Selection for Concrete Repair

Documents

Transcript of ACI 546.3R-14 Guide to Materials Selection for Concrete Repair