ACI 551.1R-14 Guide to Tilt-Up Concrete Construction

Guide to Tilt-Up Concrete ConstructionReported by ACI Committee 551

AC

I 551

.1R-1

4

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

Not for Resale, 06/18/2015 04:18:03 MDTNo reproduction or networking permitted without license from IHS

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First PrintingNovember 2014

ISBN: 978-0-87031-956-3

Guide to Tilt-Up Concrete Construction

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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Tilt-up concrete construction is commonly used in low- to mid-rise building construction. This guide reviews the many issues related to the planning and construction of tilt-up buildings to produce a quality tilt-up project. Major topics include preconstruction planning, foundations, special considerations for slab-on-ground construction, wall panel forming and casting, panel erection, connections and repairing, and painting. This guide also contains sections on sustainability and insulation systems, as well as refer-ences to the relevant codes and standards including updated Occupational Safety & Health Administration (OSHA) safety regulations.

Keywords: forming; finish; inserts; insulation; panel; precast; release agent; sandwich panel; site cast; sustainability; tilt-up.

Jeff Griffin, Chair James R. Baty II, Secretary

ACI 551.1R-14

Guide to Tilt-Up Concrete Construction

Reported by ACI Committee 551

Iyad M. AlsamsamWilliam R. Braswell

Jerry D. CoombsDarryl E. DixonMichael FultonJohn G. Hart

Robert P. Hirsch

Brent E. HungerfordAnthony I. Johnson

Philip S. KopfKimberly Waggle Kramer

James S. LaiJohn W. LawsonEd T. McGuire

Andrew S. McPhersonTrent C. NageleCraig J. OlsonLance Osborne

Jayendra R. PatelJ. Edward SauterNandu K. Shah

Joseph J. SteinbickerJason A. SwagertGerry J. Weiler

Consulting membersHugh Brooks

David L. Kelly

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 551.1R-14 supersedes ACI 551.1R-05 and was adopted and published November 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 repro-duction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

CONTENTS

CHAPTER 1—INTRODUCTION AND SCOPE, p. 21.1—Introduction, p. 2

CHAPTER 2—DEFINITIONS, p. 2

CHAPTER 3––HISTORY, TRENDS, AND SUSTAINABILITY, p. 3

3.1—History of tilt-up construction, p. 3

3.2—Trends, p. 43.3—Sustainability, p. 4

CHAPTER 4—PRECONSTRUCTION PLANNING, p. 6

4.1—Introduction, p. 64.2—Site layout and crane access, p. 64.3—Review of drawings, p. 74.4—Production schedule, p. 74.5—Submittals, p. 74.6—Staging, p. 84.7—Crews, p. 84.8—Panel layout and erection, p. 84.9—Casting beds and stack casting, p. 84.10—Concrete placement and testing, p. 94.11—Panel orientation and bracing, p. 94.12—Safety planning, p. 10

CHAPTER 5—FOUNDATIONS, p. 115.1—Foundation systems, p. 115.2—Continuous footings, p. 115.3—Spread footings, p. 125.4—Foundation walls, p. 125.5—Deep foundations (piles and drilled piers), p. 125.6—Foundation elevation versus bottom of panel eleva-

tion, p. 135.7—Backfill at loading dock high panels, p. 14

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


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CHAPTER 1—INTRODUCTION AND SCOPE

1.1—IntroductionTilt-up concrete construction is a unique form of site-cast

precast construction where building elements commonly referred to as panels are constructed in job-site conditions and set in place within the building design. The conditions of casting location and positioning within the building design, therefore, necessitate tilt-up’s own specialized set of design parameters and construction techniques. Tilt-up panels are generally handled only once. They are lifted or tilted from the casting slab and erected in their final position in one continuous operation.

ACI defines tilt-up as “a construction technique for casting concrete elements in a horizontal position at the job site and then tilting them to their final position in a structure.” ACI 318 further states that tilt-up concrete construction is a form of precast concrete. Several features make the tilt-up construction method unique.

Tilt-up panels serve as many functions for building design as markets in which they are constructed. Panels, or perhaps better described as tilt-up elements are constructed with and without openings, sometimes consisting of only a grid of monolithic beams and columns. Wall panels are found flat, ribbed, curved (with broad to tight radii), and even biaxially curved. Elements have been constructed freestanding and cantilevered, simply supported, and connected in a variety of configurations. Elements have been taller than 96 ft (30 m) (Lucky Street Parking Garage, Hollywood, FL) and building façades have been stacked as high as 138 ft (42 m) (ASU Student Housing, Phoenix, AZ). Not all tilt-up elements are building panels, however. Although the majority produced annually are designed as either load- or nonload-bearing building envelope panels, tilt-up elements have also been featured as signs, monuments and art, walkways, stadium seat supports, spires, tanks, tunnels, and bridges.

1.2––ScopeThis guide presents the basic concepts, techniques, and

procedures used in tilt-up construction. The design of tilt-up wall panels, although not addressed in this guide, is addressed in the companion design guide ACI 551.2R, which is beneficial in content to both licensed design profes-sionals and contractors. This guide includes a brief history of tilt-up concrete and a discussion of planning; foundation and floor slab construction; and wall panel forming, casting, and erection. It briefly describes typical connections used to attach the panels to the rest of the structure, and options for panel finishes are briefly described.

CHAPTER 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 resource.bolster strip––continuous reinforcement support device for wire mesh or mat in a concrete slab or wythe element.cribbing––wood blocking set under crane outriggers to spread the point load over a larger area to prevent damage to the supporting surface.densifier––chemical applied to a concrete surface to fill pores, increasing surface density.elastomeric paint––paint consisting of a polymer with elasticity, generally having low Young’s Modulus and high yield strain compared with other materials that behave as a rubber-like membrane on the concrete surface to span cracks and decrease permeability.hygrothermal analysis––analysis of the movement of heat and moisture through buildings, particularly a building envelope, component, or system.membrane bond breaker––nonchemically active release

CHAPTER 6—CONSIDERATIONS FOR SLAB-ON-GROUND CONSTRUCTION, p. 14

6.1—Temporary construction loads, p. 146.2—Floor slab (casting bed) preparation, p. 146.3—Joints and openings, p. 156.4—Slab closure strips (pour strips), p. 166.5—Floor slab repair, p. 16

CHAPTER 7—WALL PANEL FORMING AND CASTING, p. 17

7.1—Forming, p. 177.2—Architectural treatments, p. 207.3—Reinforcement placement, p. 267.4—Steel embedment plates, p. 277.5—Lifting and bracing inserts, p. 277.6—Concrete placement, finishing, and curing, p. 29

CHAPTER 8—PANEL ERECTION, p. 318.1—Before erection, p. 318.2—Rigging, p. 318.3—Panel erection sequence, p. 318.4—Safety, p. 33

CHAPTER 9—CONNECTIONS, p. 339.1—Design of connections, p. 339.2—Foundation and slab-on-ground connections, p. 339.3—Roof connections and supported floor connections,

p. 359.4—Panel-to-panel connections, p. 379.5—Connections for higher seismic design categories, p.

38

CHAPTER 10—FINISHING AND SEALING, p. 3810.1—Surface preparation, p. 3810.2—Repairs, p. 3810.3—Joints, p. 3910.4—Paints, p. 40

CHAPTER 11—INSULATED PANELS, p. 4111.1—Insulated panels, p. 4111.2––Sandwich panels, p. 4111.3––Insulation, p. 42

American Concrete Institute – Copyrighted © Material – www.concrete.org

2 GUIDE TO TILT-UP CONCRETE CONSTRUCTION (ACI 551.1R-14)



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http://www.concrete.org/Tools/ConcreteTerminology.aspx

http://www.concrete.org/Tools/ConcreteTerminology.aspx

agent that prevents the bond of fresh concrete to the casting surface that dissipates with time.penetrating bond breaker––chemically active release agent that prevents the bond of fresh concrete to the cast-ing surface that requires cleaning methods to remove from substrate.polyisocyanurate––thermoset plastic typically produced as foam and used as rigid thermal insulation.polystyrene––rigid or foamed synthetic aromatic polymer made from the monomer styrene, a liquid petrochemical for use in extruded shapes or insulation boards.polysulfides––sealants designed for joints that need to withstand prolonged immersion in liquids. Typical applica-tions include swimming pools, fountains, cooling towers, fuel and chemical storage tanks, wastewater treatment, and petrochemical plants.reentrant––inward corner of a concrete element that is typically recognized at windows and doors.reveal––longitudinal recess in the surface of a concrete element.spud vibrator––vibrator with a vibrating casing or a vibrating head used to consolidate freshly placed concrete by insertion into the mass. Also commonly referred to as a stinger.thermal transmittance––measure of the rate of heat loss of a building component expressed as watts per square me-ter, per degree Kelvin, W/m2K; U-value is calculated from the reciprocal of the combined thermal resistances of the materials in the element, air spaces and surfaces, also taken into account is the effect of thermal bridges, air gaps, and fixings (commonly known as the U-value).urethanes––thermosetting polymer formed by reacting an isocyanurate with a polyol, used in the manufacture of flex-ible, high-resilience foam seating, caulks, and rigid foam insulation panels.wythe––each continuous vertical section of a concrete wall in monolithic thickness.

CHAPTER 3––HISTORY, TRENDS, AND SUSTAINABILITY

3.1—History of tilt-up constructionAlthough precasting building elements is sometimes

considered an innovative concept in engineering, origins can be traced to as early as 4700 BC to a small village in Jarmo, Iraq, where the villagers made walls for their dwellings from touf, a pressed mud. As cementitious materials became available, the quality and durability of these precast mate-rials improved. The Romans produced pozzolan cement, which they used extensively in their building projects around 25 BC. It was not until the nineteenth century and the development of portland cement that concrete structures became integral to the construction process. By 1890, port-land cement was widely accepted as the standard cementing material.

Early structures using portland-cement concrete were usually cast-in-place. By 1914, cast-in-place concrete rein-

forced with mild steel reinforcing bars was second only to structural steel as a building material.

Some builders in the United States developed an early form of tilt-up construction in which a tilting platform was used. Aiken (1909) described the innovative method where walls for a building were constructed on a structural plat-form, then rotated or tilted upward by means of specially designed mechanical jacks, setting the panel in its final posi-tion. This tilt table method was used on the Jewett Lumber Company in Des Moines, IA, between 1906 and 1912, and on several Army facilities, factory buildings, and churches. The tilt table method was also used on the Memorial United Methodist Church in suburban Chicago. The church construction incorporated decorative precast elements that were embedded in the tilt-up panels (Fig. 3.1a and 3.1b).

Collins (1958) states that railroads during the period before World War I developed a technique for precasting large sections of bridges from reinforced concrete and setting them in place with their heavy cranes. The cranes, however, were mounted on railroad cars and required additional track to be laid to access the site.

The idea of precasting large structural units using rein-forced concrete cast into molds or forms was hastened by World War I. The shortage of steel and labor caused by the war and the subsequent increase in building prices chal-lenged engineers and contractors to develop new methods of building. Most improvements in precasting methods were developed in England and Western Europe. Precast elements, however, were small and easily handled without heavy equipment. In Russia, precast building elements developed using alternative casting methods due to more difficult conditions for fabrication and construction. There, larger sections were constructed using techniques similar to those now used in the United States. Erection was accom-plished with stationary cranes.

In the United States, there was little advancement in the use of precast concrete elements until World War II. Three technological innovations, attributed to this era, made the erection and connection of site-cast elements more practical. The first two of these developments were the heavy-duty

Fig. 3.1a—Front wall panel of Memorial United Methodist Church on tilt table.


GUIDE TO TILT-UP CONCRETE CONSTRUCTION (ACI 551.1R-14) 3



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truck crane and electric-arc welding. The third develop-ment that made site casting of concrete elements a mature industry was transit- or ready-mixed concrete. The ready-mixed concrete concept made quality concrete available to anyone in any quantity on short notice.

As a result of these innovations, the number of buildings constructed with site-cast concrete elements increased signif-icantly. There were construction projects incorporating new technologies and ideas in local areas of the Midwest, Texas, Pennsylvania, and the New England states. The most prog-ress, however, was in southern California during 1945 and 1946. The dollar volume of work using this type of construc-tion in southern California increased dramatically between 1946 and 1952. Other Sun Belt states soon followed.

Numerous surveys conducted by the Tilt-Up Concrete Association (2013) have found that tilt-up concrete is most prevalent in North America, with buildings constructed in every state in the United States, every province in Canada, and in many areas of Mexico. The strongest concentration of tilt-up activity occurs from British Columbia, south along the Pacific coast into Mexico, across the southern United States, and north along the Atlantic coast through Newfoundland. Pockets of strong activity can also be found throughout the Midwest, Plains, and Rocky Mountain states. Strong tilt-up industries have also developed in Australia, New Zealand, and several countries in Central and South America, while locations in Africa, Europe, the Caribbean, and southern Asia have recently been added to the regions where tilt-up is being used.

3.2—Trends3.2.1 Building applications—Tilt-up construction was

first used for large, plain, simple structures—most notably warehouses or distribution centers. This is still a common building type in tilt-up construction. Familiarity with tilt-up by licensed design professionals and the use of the broadening array of innovative finishes, discussed in later sections, have advanced tilt-up for use in many other types of buildings. These include correctional facilities, schools,

multi-story office buildings, retail structures, cold storage buildings, industrial and manufacturing projects, recre-ational facilities, churches, and multi-family housing. Most recently, applications for tilt-up construction have broad-ened to include smaller buildings and single-family residen-tial structures.

3.2.2 Sandwich wall panels––Most model energy codes have minimum thermal performance requirements that can be met or exceeded using insulated sandwich wall panels. Tilt-up sandwich wall panels have been successful for more than half a century in controlling temperatures and increasing the thermal efficiency of tilt-up structures. Current increases in the minimum energy code require-ments and the shift toward sustainable systems have helped sandwich walls grow in popularity and frequency of use. Whether it is schools, offices, correctional facilities, cold storage, or religious buildings, tilt-up sandwich panels can provide the durability, speed of construction, and design flexibility of tilt-up while providing significant R-value and moisture protection. In general, sandwich wall panels are comprised of two layers, or wythes, of concrete separated by a layer of rigid insulation, and are tied together with a series of connectors or fasteners. The performance of the tilt-up sandwich panel, both structurally and thermally, depends on the capacity of the connector and the detailing of the insula-tion layer, as discussed in Chapter 11.

3.2.3 Aesthetics—Economy provided in the tilt-up construction method has combined with the challenge of architectural variety and upscale aesthetics, using creative form and advanced finishes. Engineering creativity and craftsmanship of the construction professional together have delivered building form involving significant amounts of glazing with long spandrel concrete sections (Fig. 3.2.3a), deep recesses and graphics, extensive reveal patterns, complex geometric shapes, and angles and curves both out-of-plane and in-plane. The surface appearance and texture of tilt-up panels has also inspired more upscale architectural finishes. Exposed-aggregate finishes provide natural, durable concrete surfaces with low maintenance (Fig. 3.2.3b). Direct casting onto aggregate placed in a sand bed, sandblasting, power-washing techniques, and chemical retarders are some of the methods used to expose the aggregate in the panel surface to varying depths. These techniques are more dependable than in the past, producing more uniform aggre-gate exposure. Panel elevations fit into a broader variety of traditional community vernacular with thin brick, block, and stone finishes cast into the concrete (Fig. 3.2.3c).

3.3—SustainabilityTilt-up construction offers several key characteristics to

the goal for sustainable construction. By definition, the use of locally available materials to construct energy efficient building elements on-site embodies the essence of sustain-ability. Cement is the only component of a standard panel with high-embodied energy and CO2 output; however, effi-ciencies in the production of cement coupled with the long, low maintenance life of the structure more than compensate for this deficiency.

Fig. 3.1b—Memorial United Methodist Church, Zion City, IL, built circa 1906.





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3.3.1 Carbon footprint reduction—On-site manufac-turing, along with the use of locally available raw materials such as sand, gravel, and water, can significantly contribute to the sustainability of the structure by reducing fossil fuel consumption and emissions related to transporting the mate-rials. On site, the size of tilt-up elements results in fewer lifts, fewer joints, and faster shell construction than many competing construction methods such as masonry, wood, steel, and cast-in-place, further reducing emissions and fuel consumption. Reduced waste of production materials and the ability to recondition unused or outdated buildings further adds to the sustainability of tilt-up by reducing the strain on landfills.

3.3.2 Energy efficiency—Tilt-up construction can be very energy efficient despite the low material R-value of concrete. Thermal mass, inherent in tilt-up and other concrete-based building systems, is largely responsible for structures that require less energy to heat and cool as well as providing greater degrees of comfort for occupants, even when insu-lation is not present. This is particularly true in temperate climates, and those with a dominant cooling load. Where insulation is required by code, or for a specific building program, the negligible concrete R-value of 0.08 ft2-F-hr/BTU-in. = 0.014 m2-C/Watt-mm) is bolstered with many options for continuous insulation on the interior or exterior surface as well as in a configuration known as a sandwich wall construction. Tilt-up insulation systems effectively deliver a building envelope that meets minimum perfor-mance standards, significantly reducing thermal transfer and protecting the interior space conditioning needs. The degree of energy efficiency provided by these insulation system choices combined with the thermal mass can reduce the size of heating and cooling equipment required, further contrib-uting to the sustainability of the system.

Another benefit to energy efficiency and a requirement found in the latest energy codes is a continuous air barrier. The low permeability of a solid concrete tilt-up panel decreases air and moisture infiltration into the structure—one of the major factors in equipment sizing and operation. The International Energy Conservation Code (ICC 2012a) defines such panels as a qualified air barrier envelope compo-nent. Additionally, the size of tilt-up panels results in fewer system joints that must be sealed to meet the continuous air barrier requirements. This results in building envelopes that are much higher in air tightness. The recent development of high emissivity wall coatings can further enhance the perfor-mance of tilt-up buildings in southern climates by reflecting more of the sun’s energy, thus reducing cooling demand and costs.

3.3.3 Longevity—Concrete buildings have a distinct advantage in terms of building life because of the perma-nence and durability of concrete as a building material. Concrete structures have been continually in service since before 150 AD. Change of use is one of the most challenging aspects to the practicality of building life span. Tilt-up building structures, however, offer significant flexibility for modifications to embrace these changes of use and/or occupancy. Panels can be removed, reused, relocated, and

Fig. 3.2.3a—Tilt-up spandrel panels.

Fig. 3.2.3b—Detailed exposed aggregate finish.

Fig. 3.2.3c—Thin brick tilt-up façade.





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modified. Modifications can include both window and door openings. If demolition is required, the wall panels can be crushed, allowing the concrete and steel to be recycled.

3.3.4 Finishes—Tilt-up concrete structures can be painted, unfinished with exposed aggregate, have other materials embedded in the concrete, or left simply as unfinished concrete. Exposed aggregate panels, in particular when executed with retarders and unfinished concrete, provide a low-maintenance surface. The reduction in maintenance and elimination of coatings adds to the sustainable characteris-tics of the system. The use of form liners and the availability of thin brick embedded in the face of panels has further broadened the aesthetic variety for tilt-up, contributing to its use for virtually any building type.

3.3.6 Recycle/reuse/replace—Tilt-up construction employs recycling at several levels. Lumber, if used for side forms, is typically reused several times. When panels are replaced or destroyed, standard methods for recycling steel content as well as the concrete itself can be employed. Recycled concrete can be used as fill under slabs, sidewalks, road base, and as coarse aggregate in concrete mixtures. Careful consideration should be given to the types and source for recycled aggregate that may be used in panels. Cement content can be reduced by supplementary cementi-tious materials such as fly ash, slag cement, and silica fume. These products, formerly directed to landfills, can replace cement content. Recycling reduces direct and indirect costs, and lessens the production of CO2.

3.3.7 Resilience—Tilt-up structures are not subject to attack by termites or other wood destroying organisms. Tilt-up structures have proven to be resilient for forces of nature including tornadoes and hurricanes and the wind born debris produced by these violent storms. As recent as May 2013, tilt-up buildings have withstood the intensity of EF-4 and 5 tornados as seen in Moore, OK. In fact, tilt-up is the building system of choice for many emergency shelters as well as emergency operation centers. Fire stations in Florida and Texas, for instance, are among the building types turning to tilt-up to withstand the intense forces of hurricanes, main-taining safety zones and functional services.

Fire resistance is an important characteristic of tilt-up building envelopes. Due to the height of so many of today’s tilt-up buildings, an average panel thickness of 7 in. (178 mm) is common. Such panel thicknesses are rated at 4-hour fire resistance (ICC 2012b). This is important for separa-tion within larger structures and for buildings, which require distance separations in urban settings. Tilt-up is also used for stair and elevator towers because of its strength and fire-resistive properties.

Resiliency is also expressed in the force-resistance from man-made threats, such as explosives and progressive collapse. Numerous tilt-up structures in Texas, California, District of Columbia, Florida, and Louisiana have been designed for progressive collapse using the structural effi-ciency and redundancy of tilt-up panels. Additionally, tilt-up panels have been studied by the Air Force Research Labora-tory (AFRL-RX-TY-TR-2008-4616) and proven to perform

with substantial resistance to explosive charges without enhanced engineering.

CHAPTER 4—PRECONSTRUCTION PLANNING

4.1—IntroductionPreconstruction planning is essential for the smooth

progression of events in the construction of a tilt-up building. Efficient on-site production operation is important to the economy of tilt-up construction. Successful produc-tion requires organization and planning.

Many projects are developed with a contractor as a member of the design team. This facilitates the coordination of the design with the construction process, thus enabling the coor-dination of construction logistics into the design process. A meeting between the licensed design professionals and contractor can address limitations and concerns such as slab thickness, panel size (height, weight, width, thickness, and configuration), temporary bracing requirements, finishes and reveals, use of new techniques, materials, erection, and crane access. This is of particular importance when team members are not familiar with tilt-up construction. The meeting should also address lead times and other logistical items that may impact the construction schedule.

4.2—Site layout and crane accessDuring preliminary construction planning of the project,

it is important for the contractor to become familiar with the building site. Building location on the site can greatly affect many aspects of construction. Locating the building adjacent to a property line will affect foundation design and construc-tion, panel layout and erection, and panel repairing and painting. A geotechnical engineer should determine the soil bearing capacity and advise of any soil removal or replace-ment requirements in addition to compaction requirements prior to the start of any construction activities.

Crane access in and around the site is critical to a smooth panel erection process. Many owners do not want the crane on the floor slab due to potential slab damage. As a result, many specifications restrict the crane to the building exte-rior or to an uncast strip of floor. If panel erection is to proceed from outside the building perimeter, the area should be graded smooth and compacted so no soft spots or ruts impede the crane’s progress. Utility trenches into or around the building may restrict crane access. Lateral clearance around the building should also be sufficient to allow the crane to maneuver. This is especially critical in urban areas.

All overhead power lines within potential reach of cranes or other equipment should be carefully evaluated. The contractor should consult OSHA 29 CFR 1926.1408 for required safe working distance based on the voltage, or deenergize and ground the overhead power lines within the operating reach of construction equipment. Proximity to airports can even require special permits for panel erection activities. Early planning for these situations is critical to be the least disruptive to surrounding property owners.

If crane access around the building is limited, some or all of the panels may have to be erected from within the





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building perimeter. The panel erection crane is typically much heavier than a framing erection crane. Consequently, if the panel erection crane is required to drive on the slab, the slab edge may need to be thickened where the crane enters and exits the building. Slab recesses or other obstructions may also restrict crane access. Panel size, weight, and lift distance will dictate the required crane size. The crane’s operation manual provides guidance on maximum reach. A general rule of thumb is that the crane’s rated capacity should be three times the maximum panel weight.

The slab should be investigated wherever construction loads are to be placed, including loading applied from tempo-rary wind bracing. If the crane is going to be placed on the slab during erection, the subgrade and the building slab must be able to withstand the loads applied during erection or slab damage will occur. The loads will vary depending on crane location and weight of the tilt-up panels. Also, placement of crane outriggers near slab corners, edges, and control and construction joints can contribute to floor damage. Timber cribbing should be placed under outriggers to distribute the load. For structural slabs, including those supported on deep foundations, the Engineer of Record should be made aware if the erection crane is going to be placed on these slabs. A licensed design professional should review this temporary construction loading condition.

For buildings with large plan areas, it may be beneficial to cast only the perimeter bay of the floor slab, which is enough to form and cast panels. This has the advantage of casting the majority of the slab after the panels and roof have been erected and casting in a relatively controlled environment. This staging can avoid placing large construction loads on the slab. Proper planning is required to designate traffic access in and out of the building and to areas of the slab that are to be cast.

Planning should consider which panels are to be used to allow the crane to exit the building. If the framing erection crane is scheduled to place the closure panel(s) into its final position, it should have the capacity to do so.

4.3—Review of drawingsConstruction planning should involve a thorough review

of the architectural and structural drawings. The contractor should ensure that the design intent is fully understood. Structural drawings should be compared with the architec-tural drawings to make sure reveals, chamfers, openings, and other items are not in conflict and can be constructed as intended without impeding on design concrete cover. Discrepancies, or areas in doubt, should immediately be brought to the attention of the licensed design professionals. If a more efficient design is visualized, it also should be brought to the attention of the licensed design professionals before commencement of construction.

When calculating the lifting stresses, the licensed design professional assumes an unreinforced panel and adds the needed steel to address the stresses. If the engineer of record has designed the same quantity and size of reinforcement in the same plane (location) the added reinforcement may not

be required but should be confirmed by the licensed design professional completing the lifting and bracing design.

All necessary information should be assembled for panel forming, casting, and erection. This information includes panel dimensions, opening dimensions, reinforcing, embed-ment plates, connections, architectural features, and similar items.

4.4—Production scheduleAs with all construction projects, the contractor often uses

a flow chart, Gantt chart (bar graph), or other visual form of planning depicting all stages and steps in the process, including the sequence in which they should proceed; the items that are dependent on other phases before they can proceed; lead time; the time period for completion; and the manpower, resources, and materials required for each task. The task of putting this schedule together can highlight problem or critical areas and provide a visual depiction of the entire process. The production schedule should be coor-dinated with overall building occupancy schedule.

Planning should also include scheduling of subcontractor start times and logistics for materials ordering. On large warehouse buildings, panel forming, casting, and erection may progress simultaneously with roof framing. Failure to account for these activities can produce inefficiency or even a safety hazard.

4.5—SubmittalsPanel shop drawing submittals should include at least the

following (Fig. 4.5):a) Openings and reveal locationsb) Reinforcing steel, including concrete coverc) Lift and brace insert locations and product informationd) Embedmentse) Panel dimensions, including thicknessf) Panel weight and concrete strength at time of lifting

It is also suggested that panel shop drawings include section cuts, the depth and shape of rustication, and the types and locations of panel finishes (including form liners and thin brick).

Material submittals should include at least the following:a) Concrete mixture proportion and substantiated 28-day compressive strength (prescriptive concrete requirements, if any; water-cementitious material ratio; air content and minimum lifting compressive or flexural strength)b) Bond breakers and curing compounds to check compatibilityc) Form liners, reveal detailsd) Grouting and repairing materialse) Aggregate samples if exposed aggregate is usedf) Any other materials integrated into the panelg) Reinforcing supportsh) Finishes and coatings

Thorough construction planning also involves the concrete supplier, who should be aware of approved mixture proportions including flexural and compressive strengths, and quantities of concrete required for each series of panel castings.





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If specifications require it, or if the architect has special finishing requirements such as exposed aggregate, a sample panel should be made for approval. This mock-up panel should be a minimum of 32 ft2 (3.0 m2), using the same materials and methods proposed for the finished building. This panel will serve as the basis for acceptance and help to establish the range of acceptable finishes on other panels.

Submittals should be approved before commencement of any aspect of the work that is influenced by the respective material or work item.

4.6—StagingJob-site staging can begin when most of the submittals

have been approved. Staging involves selection of locations for support structures and materials storage, fabrication areas, and paths for movement of materials and heavy equip-ment such as concrete trucks, cranes, and concrete convey-ance equipment.

All planning should be done with safety as an underlying goal. Essential items should be placed in areas that will not be affected by rain or other adverse weather. In winter condi-tions, provisions for removal or depositing of snow may be advisable.

4.7—CrewsCrew size, productivity, and tasks should be carefully

planned. Crew tasks should be sequenced to avoid over-running production of the preceding crew. Typical crews include floor preparation, panel layout, forming, reinforce-ment, inspection, concrete, preerection, erection layout, lift and brace preparation, erection, and grouting or repair. To reduce manpower, personnel from one crew can staff other crews. If several tilt-up operations occur simultaneously, additional personnel may be required.

4.8—Panel layout and erectionOne of the more important items to discuss during

preconstruction planning is the panel-casting and erection

sequence. Additionally, the contractor should determine if there is sufficient slab area to cast the panels and maneuver equipment during construction. A planning session to review these items should be held early in the planning phase and should include the superintendent, concrete subcontractor, panel crane operator, and framing erector if the closure panel will be set. A typical casting and erection sequence plan is shown in Fig. 4.8a. The plan shows where panels are to be formed and cast, as well as their final erected posi-tions. Crane access through the building and the panel erec-tion sequence are also shown. Crane size and access in and around the building, including whether or not the crane is permitted on the slab, and site layout greatly affect the panel casting layout.

Figure 4.8b shows variations in the forming locations for panels near a corner, based on decisions such as temporary casting slabs, stack casting and crane access, size, or reach capacity. A proper layout plan should provide enough space between the panel being erected and panels yet to be erected to attach temporary braces to the slab. Corners require added coordination due to the increased brace congestion compared with elsewhere in a building.

A licensed design professional should verify the capacity of the slab to support construction, casting, and bracing loads.

Typically, all panels are erected during one crane mobili-zation. Phasing of panel erection can cost more if there is a second crane mobilization fee. A second crane mobilization, however, could accelerate the schedule by allowing the first phase of panels to be erected before all panels are cast and cured.

To optimize the construction schedule, panels should be cast in nearly the same order as they are to be erected and as close as possible to their final position. Time could be lost if

Fig. 4.5—Typical shop drawing excerpt.

Fig. 4.8a—Casting and erection sequence plan.





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the first panel to be erected is the last panel to be cast, or if the panel is cast too far from where it is to be erected. If panels are cast in the wrong location, they may have to be lifted and temporarily braced while other panels are moved out of the way or they may have to be walked to the correct loca-tion while attached to the crane. In addition to the increased cost and time involved, safety concerns increase each time panels are handled. Lifting insert manufacturers may require increased safety factors if panels are handled more than once. The applied bending stresses from additional handling can also add to durability and performance concerns, which derive from cracks occurring during erection and the possi-bility of damage to the panels. Panels should be arranged so they are erected consecutively. It is difficult to break a panel free when it is cast between two other panels. Lack of plan-ning panel sizes and casting locations may require a larger crane than anticipated or scheduled.

4.9—Casting beds and stack castingIf the required casting area exceeds that available, or if

the floor slab cannot be used for casting, temporary casting slabs at the perimeter should be investigated. The proximity to the floor slab should be planned to minimize crane sets and movements while maintaining the safe maneuver of all panels to their designed location.

Stack casting of panels (Fig. 4.9) can occur on the floor slab (6.2) or on temporary casting slabs (6.2.5). It is recommended that contractors understand the impact of panel configuration

on the stack casting operation. Casting smaller or equal size panels and openings that are easily aligned maximize the effectiveness and simplify the method. However, creativity and experience frequently allow contractors to broaden the application. Additionally, the height of the stack is impor-tant. Maximum height is dependent on many variables and is directly related to the thickness and type of panel (that is, solid or sandwich). The casting surface inside the panel face should be finished to the same quality as the primary casting surface. Formwork should be properly braced if stack casting is required.

4.10—Concrete placement and testingLimited site access for concrete trucks may necessitate the

use of a concrete pump for placement. Panels are often erected within 7 days of being cast. Specified flexural and compres-sive strength tests should be conducted by an accredited testing agency in accordance with ASTM C78/C78M and C39/C39M before erection to verify concrete strengths meet or exceed erection requirements. Tests should be conducted on beams and cylinders cast from the same concrete used in the panels and cured and stored on site in conditions similar to those experienced by the panels. For accurate slump tests, the concrete slump should always be taken at the point of placement (end of chute or hose), not at the hopper, if place-ment equipment is being used. The testing agency should be notified when panels are to be cast so they can fabricate test specimens and perform other on-site quality tests such as slump and air content of the fresh concrete.

4.11—Panel orientation and bracingAnother item to be addressed during preconstruction plan-

ning includes determining whether the panels should be cast inside face-up (more common) or outside face-up, or if they should be braced to the inside or outside of the building. When panels are braced outside of the building, it may be necessary to provide temporary helical ground anchors, or deadman blocks, outside the building to anchor the braces. Exterior bracing will not be possible if the building is located adjacent to a property line or other site geometry restric-tions, such as the grade on or proximity to other buildings or

Fig. 4.8b—Alternative panel forming location.

Fig. 4.9—Stack-cast panels.





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structures on the site, or the proximity of other construction activities. Alternatively, the panel can be lifted and braced in a temporary location with braces initially attached to the outside face of the panel. Additional braces should then be attached to inserts on the inside face. At this point, the panel can be moved to its final position and braced in the normal manner to the floor slab. This will double or triple the time required to erect the panels. Refer to Chapter 8 for panel bracing.

4.12—Safety planningWhile all construction projects require safety planning,

tilt-up construction has specific safety issues that should be addressed. The planning process should include a meeting among the superintendent, crane operator, rigging foreman, and all other personnel involved in the erection process before panel erection begins. Crewmembers should be assigned specific tasks for handling braces and hardware attachment. Only individuals directly involved with the erection process should be near the panel being erected. No one should be permitted to walk under a panel while it is being tilted, on the blind side of the panel when the crane is traveling with it, or between the crane and the panel. The crew should remain alert and look out for the safety of fellow workers.

The rigging foreman, who the crane operator looks to for all signals, should be experienced in handling panels, have received formal training, and be completely familiar with the precise set of hand and arm signals used to communicate with the crane operator. The rigging foreman should be able to demonstrate proper use of all lifting hardware, bracing hardware, and any tools or equipment that may be necessary. Prior to arriving on site, the rigging foreman should review rigging requirements as designed by the licensed design professional responsible for the lifting and bracing design.

CHAPTER 5—FOUNDATIONS

5.1—Foundation systemsFoundations transfer loads from the structure to the soil or

rock supporting the structure. In the case of tilt-up building envelopes, the foundations are loaded with 75 percent of the dead load when the panels are erected. Therefore, it is important to understand the relationship of foundation design to the construction process and the assumptions made in the design process that may or may not fully exist during that process. An understanding of the variations in founda-tion types and how they impact the construction process is equally as important to the tilt-up planning process.

Foundation systems can be categorized as shallow or deep. Shallow foundations bear on a soil layer at a reason-able depth below the surface. These include continuous foot-ings, spread footings, combined footings, and mats. Deep foundations, such as piles and drilled piers, transmit loads by friction or bearing at some depth below the surface. The permissible soil-bearing capacity or pile-load capacity is typically specified in the geotechnical report prepared for the project. The geotechnical engineer is responsible for the selection and design of any foundation element.

Depending on site and building conditions, subgrade preparation may be necessary. This can include excavation and removal of poor soils, compaction of existing soils, or importing engineered fill. The prepared subgrade should be maintained throughout construction as it affects the designed integrity of the supporting slab condition for panel erection.

5.2—Continuous footingsWhere soil conditions are adequate for the use of shallow

foundations, continuous strip footings are typically used to provide support to interior and exterior tilt-up wall panels (Fig. 5.2a, b, and c). The engineer of record determines the continuous footing size and reinforcement. How the panel is set on the footing during erection should always be considered during footing design and construction. Typi-cally, panels will be set on shim packs in two locations temporarily. This is a far greater load than the continuous footing and is designed to support and may subject the footing to cracking if the load is not distributed as promptly

Fig. 5.2a—“At grade” continuous strip footing.

Fig. 5.2b—Dock continuous strip footing.





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as possible with grout (5.6.1 and 5.6.2). Continuous rein-forcement in footings helps to distribute panel loads over weak spots in the subgrade. Heavier reinforcement might be required if the footing should span trenches, drain lines, or other site features. Footing width is inversely proportional to soil capacity, so wider footings are necessary for softer soil conditions. Panels are usually centered on continuous footings unless property lines or other restrictions exist. At a minimum, the bottom of the footing should extend below frost depth in accordance with the geotechnical engineering report and local building codes.

Continuous footings can usually be installed before or after the slab when a portion of the perimeter slab is left out. When the slab has no closure strip, however, the continuous footing should be installed prior to the slab so that the slab can be turned down on top of the footing.

In some instances, the panels are placed directly on a thickened edge cast integral with the slab-on-ground. This is usually an integral beam to accommodate the additional loads created by the direct bearing of the panel. This type of direct bearing can cause cracks in the slab near the junction of the thickened slab edge and slab due to the rotation of the beam when the panel load is applied.

5.3—Spread footingsWhere soil conditions permit, isolated spread footings at

panel joints may be used to provide support for tilt-up wall

panels (Fig. 5.3). Panels are centered on the footing unless property lines or similar restrictions exist and have been accounted for in the design. At minimum, the bottom of the footing should be at or below the foundation embedment depth and also extend below frost depth as required by the geotechnical engineering report and local building codes. Provisions should be made to address frost heave under the unsupported panel edge if it does not extend below frost depth.

Spread footings are typically wider than continuous foot-ings and therefore require placement before the slab, or a generous slab closure strip should be provided.

5.4—Foundation wallsSite conditions or design considerations may necessitate

the use of foundation walls. Because these walls are formed as cast-in-place walls, the formed wall area will require more time, material, and labor than if the same wall area is an integral part of the tilt-up panel. They also reduce the weight from height and occasionally thickness reductions, thus impacting the crane size. The footing is constructed as a continuous element with reinforcement dowels projecting vertically. Typically, reinforcement is placed horizontally and vertically in the center of the foundation walls for at-grade conditions. Using a foundation wall where the exte-rior grade is well below finished floor elevation requires the wall to be designed as a cantilevered retaining wall resisting the backfill pressure and may require reinforcement on both faces or temporary construction bracing. Dowels projecting horizontally from the top of the foundation wall may be required for connection to the floor slab (Fig. 5.4). Panel connections to the slab or foundation walls more commonly found are described in 9.2.

Foundation walls generally favor the use of a perimeter slab closure strip so that the construction of the founda-tion walls can occur at approximately the same time as the construction of the tilt-up panels. Otherwise, the construc-tion of the tilt-up panels should be delayed until the founda-tion walls and slab are complete.

Fig. 5.2c—Continuous foundation elevation.

Fig. 5.3—Spread foundation elevation. Fig. 5.4—Foundation wall system.





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5.5—Deep foundations (piles and drilled piers)Where soil conditions dictate the use of deep foundations,

continuous grade beams on piles or pile caps on groups of piles may be used to provide support to tilt-up wall panels. Grade beams or pile caps are constructed similar to contin-uous strip footings. Panel widths are centered on the contin-uous grade beam or pile cap unless property lines or similar restrictions exist. If piles are centered on the grade beam and not staggered, rotation of the grade beam due to acci-dental misalignment of the as-built components should be prevented by bracing the top of the grade beam to the slab, or by taking other appropriate measures. Floor slabs supported on piles may not be adequate to support construction loads from the panel erection crane. For this reason, panel erection for pile-supported buildings often takes place with the crane located outside the building perimeter.

Foundation systems for drilled piers are similar to those on piles when grade beams or caps are used. If the drilled pier is of sufficient diameter, however, panels may bear directly on the drilled pier without the need for a grade beam or cap.

Because deep foundations require more time to construct than conventional shallow foundations, the process of installing piles or drilled piers should begin well in advance of panel work. The decision to incorporate a slab closure strip is based on whether the slab is at-grade or dock-high and required timing of the slab placement. Dock-high condi-tions and early slab placement generally dictate the use of a slab closure strip while at-grade conditions and delayed slab placement can avoid a slab closure strip and realize the benefits of not having to fill and compact the closure strip as well as having to place and finish the closure strip slab.

5.5.1 Continuous grade beams—When panel widths can be established before foundation construction, the panels can be designed and constructed to span from pier to pier with the piers centered on the panel joints. The purpose of the grade beam then would be to prevent frost heave. The licensed design professional may specify the reinforcement of the grade beam. If panel widths cannot be established before foundation construction, or if drilled pier capacity or size does not permit placement only at panel joints, the grade beam should be designed and constructed to span from pile to pile and provide continuous support to the panels. Contin-uous horizontal reinforcement and reinforcement stirrups should be provided as specified to permit the grade beam to span from pile to pile. Grade beams should be sufficiently wide to allow for staggered or slightly mislocated piles. Pile embedment into the grade beam should be specified by the engineer of record (Fig. 5.5.1).

5.5.2 Individual pile caps—Individual pile caps used to support the panels are usually located under the joint of adja-cent panels. Panel widths should be finalized before foun-dation construction. The pile cap size and reinforcement as well as pile embedment into the cap should be specified by the engineer of record (Fig. 5.5.2). Pile caps can usually accommodate small tolerances of less than 3 in. (75 mm) in pile location. As with individual spread footings, the bottom of the cap should extend below frost depth as required by local building codes. Provisions should also be made to

address frost heave under the unsupported edge of the panel if it does not extend below frost depth.

5.6—Foundation elevation versus bottom of panel elevation

It is common for the contractor and panel engineer to shorten the panel height to accommodate setting or bearing pads and provide for adjustment. This is accomplished by removing panel height from the base of the panel during the shop drawing phase. An adjustment of 1 to 2 in. (25 to 50 mm) is common for continuous footings, spread footings, and piles or piers with grade beams. An adjustment of 1 in. (25 mm) or less is common for foundation walls.

5.6.1 Setting (bearing) pads—Setting or bearing pads are positioned on top of the foundation system to tempo-rarily support the wall panel during the erection and bracing process. Typically, two separate pads are placed 1 to 3 ft (0.3 to 0.9 m) in from each end of the panel to provide the most effective bearing. Although a single pad can be used under the joint of abutting panels, localized shear forces can be

Fig. 5.5.1—Pile/grade beam foundation.

Fig. 5.5.2—Pile and pile cap foundation.





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induced by restraint at the pad, creating a diagonal crack at the panel corner. Additional setting pads composed of plastic shims may be required for wider panels or for panels with openings to evenly distribute the panel weight to the footing. These pads can be placed during or immediately after panel erection. Panel weight alone may account for 75 percent or more of the total load to the footing, so proper distribution of this load is essential (Fig. 5.6.1).

Plastic shims of varying thicknesses are frequently used as bearing pads. These shims allow for adjustment when vertical alignment of the panels is necessary at windows and reveal strips. With excessively high plastic bearing pads, pins or dowels into the footing may have to be added to prevent the panel from sliding off the pads.

5.6.2 Panel grouting—Once the panels are set and aligned, space between the footing and panel should be packed or filled with grout as soon as practical, preferably within 24 to 48 hours, to provide continuous panel support onto the footing. If this space is not grouted, the footing may settle from the point loads if it has not been designed for such loads and damage to the footing or alignment issues in the panels may result. The construction crew may install grout from both sides of the panel to provide full bearing or place flowable grout from one side. Grout typically has a 3000 psi (21 MPa) minimum compressive strength with No. 89 aggregate (ASTM C33/C33M). Although it does not have to be a nonshrink type, the grout should maintain contin-uous bearing. The footing under the panel remains elastic just enough to deflect and close any gap that may develop or exist in the grout joint. The most important aspect of installing the grout is to do so as soon as possible to prevent overload damage to either the panel or the footing as neither is designed for the concentrated loads applied, due to the

full weight supported by the setting pads. Panels should be plumbed within specified tolerances in their final position prior to grouting. Any adjustments to the panel’s position after grouting will disturb the bearing of the panel at the grout joint.

5.7—Backfill at loading dock high panelsFootings for panels used at a loading dock may be located

4 to 6 ft (1.2 to 1.8 m) below floor slab elevation. The floor slab is typically held back 5 to 10 ft (1.5 to 3 m) to allow the panel to be erected onto the footing. The base of the panel may need to be braced before back-filling along dock high panels. The contractor should avoid lateral displacement of the panel due to soil pressures during backfill compaction. The panel may require temporary bracing or welding of the reinforcement dowels (Fig. 5.2b).

CHAPTER 6—CONSIDERATIONS FOR SLAB-ON-GROUND CONSTRUCTION

6.1—Temporary construction loadsBecause tilt-up panels are typically cast directly on the

building floor slab, it is necessary to minimize the possi-bility of temporary construction loads damaging the slab. Loads imposed on the slab by temporary panel braces or stored construction materials such as reinforcement, form materials, aggregate, bond breaker containers, and embed-ment steel are generally not a problem for slabs designed for industrial use. These activities may result in damage to thinner slabs that may be specified for shopping center or office applications, or slabs placed on subgrade with a rela-tively low modulus of subgrade reaction (k value). Braces attached to thin slabs, generally less than 5 in. (125 mm) thick, should be reviewed by the licensed design professional responsible for the bracing design for sufficient capacity of the anchorage to the concrete section. Loads imposed by cranes or concrete trucks are much heavier than most other construction loads and will usually exceed the slab capacity as designed for in-place use. If loads are to be placed on the slab shortly after casting, recognize that early-age concrete strength will be significantly less than the specified 28-day strength.

If panel erection requires the crane be placed on the floor slab, it could be necessary to improve the subgrade or increase the slab thickness and reinforcement. Oftentimes, crane outrigger loads substantially exceed the floor slab capacity, posing a risk of slab cracking or differential move-ment. Under these circumstances, a strip of floor slab can be omitted where the crane will travel during panel erection. This strip of slab is cast after panel erection is completed. Prebid instructions should address crane placement on the slab for panel erection.

6.2—Floor slab (casting bed) preparation6.2.1 General—Placing and finishing the slab should be in

accordance with ACI 302.1R. The floor slab should have a smooth steel trowel finish because the panel face cast against the slab will mirror all imperfections.

Fig. 5.6.1—Panel setting.





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The slab should resist uplift forces imposed by tempo-rary wind braces as defined in ASCE 37 or by the Tilt-Up Concrete Association (2012). For slabs-on-ground less than 5 in. (125 mm) thick, such as those often used in office buildings or shopping centers, a portion of the slab at the temporary wind brace anchorage location will often require thickening, reinforcement, or both, to resist these forces, as determined by a licensed design professional.

On the majority of tilt-up projects, the floor slab is used as a casting bed and, therefore, cast before enclosing the building with the roof system. Take proper precautions during concrete placement to protect against the adverse effects of weather such as wind, temperature extremes, and relative humidity, as recommended in ACI 308.1 and ACI 308R. Because the floor slab is cast during early phases of the project, it can be subjected to traffic and wear from all trades, showing evidence of that activity if care is not taken to minimum these impacts.

6.2.2 Bond breakers—Bond breaker is one of the most critical materials used on a tilt-up project. As the name suggests, the bond breaker will prevent the panel concrete from adhering to the slab. Section 7.1.4 provides an in-depth discussion of bond breakers.

A combination of curing compound and bond breaker material can be used, meeting requirements of ASTM C309. A separate curing compound and bond breaker are also acceptable as long as the products are compatible. Slabs should be cured in accordance with ACI 302.1R, ACI 308.1, and ACI 360R.

Consideration should be given to the removal or cleaning of bond breaker residue remaining on the slab once panels are erected. Contact the bond breaker manufacturer for specific cleaning recommendations. Bond breaker residue on casting slab and wall panel surfaces can be difficult to remove depending on the type of product used and how heavy it was applied. Residue from wax-containing bond breakers is virtually impossible to completely remove, which may result in compatibility concerns with subsequently applied liquid floor treatments, floor coverings, and wall paints and coat-ings. In general, some form of cleaning may be necessary to ensure complete removal of all bond breaker residue.

6.2.3 Sloped floors and utility penetrations—Panels are usually cast on flat surfaces or on floors with constant slope. Areas where compound slopes occur should be avoided for casting panels.

Electrical and plumbing penetrations should be capped at least 0.75 in. (19 mm) below the finished floor level. Utility penetrations above the floor slab interfere with screeding operation and become an obstacle for crane movement. These projections may also become a source of cracks in the slab. It is imperative to coordinate utility penetrations with the slab casting procedures, panel forming, and panel erec-tion sequencing.

6.2.4 Fiber-reinforced floors—Synthetic fiber reinforce-ment can be used in floor slabs for tilt-up buildings. Some fibers may protrude above the surface of the slab, even with the best placing and finishing techniques. These are often easily broken or burned off. Casting of tilt-up panels on

slabs with synthetic reinforcement has not been problematic, either for lifting or finishing. Fibers left projecting from the casting surface, however, will transfer to the tilt-up panel face during casting. Consider removing the projecting fibers if exposed aesthetic impact is a concern. Steel fibers may also be used for floor slabs in tilt-up buildings. There are fewer problems associated with steel fibers projecting above the slab surface because their stiffness and weight ensures that they are worked into the concrete surface during the trowel operation.

6.2.5 Casting beds—Prior to panel layout and forming, verify that the slab area is large enough to cast all panels and allow room for construction equipment to maneuver. A general rule of thumb is that the panel area should not exceed approximately 70 to 85 percent of the floor slab area for casting panels. Otherwise, stack casting or addi-tional temporary casting beds may be required. If temporary casting beds are employed, they may be located outside the main floor slab (Fig. 6.2.5) or in an area where the final floor will be placed at a later date once the panels are erected. Temporary casting beds are typically 3 in. (75 mm) thick and constructed of concrete with 2500 to 3000 psi (18 to 21 MPa) compressive strength. These should be cast on a compacted subgrade, finished, and cured by similar proce-dures used for the floor slab. Casting beds are usually not designed to support loads from the crane. After panel erec-tion, casting beds are usually broken up and hauled away. However, if located correctly, they may be left in place and paved over. Contraction joints in casting beds are optional. Random cracking can be dealt with by filling with latex caulk, depending on crack width and location.

6.3—Joints and openings6.3.1 Joint locations and treatments—Construction and

contraction joints are integral to most floor slab designs and rarely completely eliminated. Because every imperfection on the floor surface is reflected on the panel surface, the contractor should plan for the impact that slab joints may have on the finished surface. There are many options for reducing the effects of mirror images. For example, joints are most

Fig. 6.2.5—Panels formed on casting slab.





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often left untreated or unfilled resulting in fins on the surface of the panel. These can be removed with light grinding. Other options include filling the joints with a removable rubber or plastic strip inserted into the joint (Fig. 6.3.1a), latex caulk (Fig. 6.3.1b), sand, or a drywall compound (Fig. 6.3.1c). Filling with sand or drywall compound are probably the least effective methods because they have an affinity to absorb moisture from the concrete mixture. Also, caulking has a tendency to come up with the panel and not come off cleanly, leaving caulk that requires painting that will eventu-ally fade. The joint, where affected by the caulk or drywall compound, will also be different than the adjacent floor panel area and may be inconsistent or irregular or have a high, fine aggregate concentration. Using tape to cover the joints is not recommended because it will leave a mark on the panel that is difficult to remove or hide behind paint. Because paint or coatings alone will not always eliminate the visual effects of a treated joint, the grinding of fins, or untreated joint impressions on panels should be considered when making this decision. Slab joints left untreated will fill with concrete slurry and require recutting to clean them.

6.3.2 Openings and slab recesses—When space is limited, it may be necessary to cast panels over openings or recesses in the floor slab that are required by other trades. These may be isolated equipment pads, trenches, pits, recessed computer floors, recessed tile areas, or column blockouts. Slab blockouts may be filled with sand to within 2 to 3 in. (50 to 75 mm) from the surface and then topped with a thin concrete layer. After panel erection, the concrete layer is sawcut around the perimeter, chipped out, and discarded or recycled. An alternative method for deep depressions is to use plywood on formwork and level with the slab. Spray the plywood with bond breaker similar to that used on the slab. Support for the plywood should be adequate to prevent sag during construction activity. Use a high quality plyform or finished plywood to minimize the aesthetic impact to the panel surface. The plywood surface may also be depressed 2 or 3 in. (50 to 75 mm) to allow a layer of concrete to be placed on top.

6.4—Slab closure strips (pour strips)Slab closure strips are areas of the slab between the initial

slab pour and erected panels (Fig. 5.2b). These strips will occur wherever the slab is left out from the initial pour, which is most often around the building perimeter where a connec-tion of the panel to footing or slab is to be made. The initial slab pour will usually have reinforcement projecting through the construction joint to be connected to the panel reinforce-ment dowels. For dock conditions, use polyethylene sheeting to minimize the exposed subgrade from erosion during construction. Once panels are erected, braced, and plumbed, the area behind them is backfilled and compacted to the same requirements as the building subgrade. The closure strip is then cast per the drawing requirements with the same materials and methods used for concrete and finishing, and curing procedures used for the initial slab. Slab control joints should continue across the closure strip to the panel. Due to the high length-to-width ratio of the slab closure strips,

Fig. 6.3.1a—Plastic slab joint inserts snapped into joints.

Fig. 6.3.1b—Caulking removal from common slab joint.

Fig. 6.3.1c—Drywall compound applied to floor joints.





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give extra attention to control joint design, as they will differ from the main body of the slab.

6.5—Floor slab repairIf the bond breaker performance is adequate, then minimal

damage should occur to the slab underlying the panel. Avoid the tendency during initial panel lifting to drag the base of the panel along the slab surface before it is lifted clear; panel dragging can cause abrasion damage to the slab and place undue stress load on the panel surfaces. This damage can easily be reduced or eliminated by casting a 1 x 2 strip of lumber or a hard plastic component along the bottom outside edge of the panel. As the panel is lifted, an embedded lumber strip protects the edge, resulting in very little contact between the concrete panel and slab.

Holes in the slab caused by temporary wind brace and form anchors should be repaired (Fig. 6.5a and 6.5b). Various repairing materials are available, which should meet the same strength requirements specified for the slab.

CHAPTER 7—WALL PANEL FORMING AND CASTING

7.1—FormingAs discussed in 4.10, one of the most important plan-

ning items is creating a panel casting and erection sequence plan (Fig. 4.8a) that shows where panels are to be formed; the orientation they are to be formed; their final position in the structure; and their casting and erection sequences. This allows the superintendent, concrete subcontractor, or panel erection subcontractor to plan the sequence of panel construction and erection. The most common method used by contractors to plan the layout of panels is scaled computer aided design (CAD) or computer-generated draw-ings. Another technique is the use of scaled paper cutouts of the panels arranged on a scaled floor plan. Often times, the contractor will use a scale model of a crane with marked boom lengths and capacities with this paper cutout method. Used for decades, it is not as fast as CAD but is a simple method to accurately complete the panel plan. Using either method the lifting capacity at given distances of the selected crane should be known. Panels should be arranged so that they are erected and braced consecutively and bracing will not interfere with erection.

7.1.1 Forming preparations and layout—The slab surface should be clean and free of dirt or other materials. All block outs for columns should be addressed before placement of edge forms. Slab curing chemicals should be thoroughly dry before panel forms are placed. If the slab is cured with a chemical different from the bond breaker, they should be compatible (7.1.4).

All layout elements including architectural features, panel edges, and openings should be marked before setting any forms. Chalk lines are commonly used to mark the loca-tion of panel forms (Fig. 7.1.1). Methods of chalking vary between contractors, such as outside of forms and panel openings. Marking only one side of a form can lead to forming mistakes. Contractors should mark both sides of the form to eliminate confusion over the correct side of the line

Fig. 6.5a—Hole drilled in slab for brace feet bolt.

Fig. 6.5b—Holes in slab from forming cleat attachments.Fig. 7.1.1—Chalk lines marking the location intended for plywood recess.





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to which the form belongs. Be consistent in the method used to avoid confusion. Chalk lines can be sprayed with bond breaker to prevent them from washing away during rain and to reduce fading from foot traffic. Forming tolerances should adhere to the requirements in ACI 117.

7.1.2 Forming materials—Dimension lumber, such as 2 x 6 and 2 x 8, and engineered wood are the most common forming materials. Dimensional lumber is modified to achieve the project needs by cutting down to the desired dimension or using additional pieces as necessary to achieve the required forming thickness. Only straight and true lumber should be used. Sandwich panels are cast with wider-forming material to accommodate the insulation thickness and the additional layer of fascia concrete. To provide the taller form height, striated wood products such as a faced particleboard are more commonly used (Fig. 7.1.2a). Modular aluminum forms as well as steel channels or angles can be used as edge forms as well. These can be effective edge forms but are less common and may offer less dimensional flexibility (Fig. 7.1.2b).

7.1.3 Securing forms—Accurate layout of forms is crit-ical because panel joints are typically only 1/2 to 3/4 in. (13 to 19 mm) wide. Forms are typically secured to form supports spaced 36 to 48 in. (0.9 to 1.2 m) on center if used with nominal 2 in. (50 mm) lumber. Form supports may be constructed on the job from lumber or shop fabricated from a variety of materials including wood, steel angles, or tubing. They can be attached to the floor slab with masonry screws or by drilling small holes and inserting nails, forming spikes, or nylon anchors. Holes in the floor from form attachment anchors should be repaired after erection of the panels. Forms can be attached to the supports in a similar fashion using wood screws or nails (Fig. 7.1.3a). Minor bows in the forming lumber can be corrected with the form supports, although bowing is rare due to the low form pressures created by the thickness of typical panels. Adhesive systems may also be used to secure formwork (Fig. 7.1.3b). Adhesive systems are gaining popularity because the casting slab does not get marred with form holes. Most adhesive systems do, however, cause a slight discoloration where the adhesive is applied.

The joint between the form bottom and slab should be sealed with a chamfer strip, caulk, or both. If concrete paste seeps under the edge form, it will leave a ragged edge that requires additional grinding or repair after panel erection.

It is good practice to lay out forms as continuous panels separated by a common form (Fig. 7.1.3c). Common forms may be of nominal 1 or 2 in. (25 or 50 mm) lumber construc-tion. The advantages of a common form are that fewer form boards are required and any inconsistency in straightness of

Fig. 7.1.2a—Panels formed with engineered wood product.

Fig. 7.1.2b—Aluminum tilt-up panel forms. Fig. 7.1.3a—Typical formwork connection practice.





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the form is in and matches the adjacent panel, assuming the adjacent panel shares the common form. Additionally, the use of a common form allows the contractor to use a double chamfer, which saves time by cutting the chamfer installa-tion time in half and helps to keep the bottom of the form from kicking out. The main disadvantages are the difficulty of securing the common form, the lack of reuse of the lumber and the additional restraint generated during the erection of the panel because the common form cannot be stripped until one panel is erected. In addition, there is no place to wedge the panel free from the casting bed if the need arises due to suction or bond breaker problems.

7.1.4 Bond breakers—Selection and proper application of the bond breaker in conjunction with proper slab finishing and workmanship is critical to the success of any tilt-up project. Bond breakers generally fall into one of two major categories: penetrating or membrane. Penetrating bond breakers should not be used as curing compounds as they do not comply with ASTM C309. Membrane-forming bond breakers do comply with ASTM C309 and can be used as both a curing compound and a bond breaker.

Membrane bond breakers will dissipate over time. Although the rate of dissipation is dependent on a number of environmental factors, it is prolonged in cool, dry, and shaded exposures. If these bond breakers require removal prior to their dissipation, a mechanical or chemical method can be used. A light brushblast or light acid-based chemical appli-cation should be sufficient to remove the remaining product. Penetrating bond breakers do not usually require chemical removal from the tilt-up panel prior to exterior coating, other than pressure washing. They do, however, require chemical removal from the casting surface if subsequent toppings such as chemical hardeners, densifiers, sealers, or epoxies will be applied. When a subsequent topping is specified for the slab and a penetrating bond breaker is to be used, the subsequent topping, such as hardener, densifier, or sealer, should be applied before bond breaker application, if possible. Hardeners and densifiers are most efficient when applied to water-cured slabs, as a preexisting, penetrating bond breaker diminishes their penetration.

Curing compounds; bond breakers; and any chemical hardeners, densifiers, or sealers should be obtained from the same manufacturer. Always use a bond breaker from a single manufacturer. Further, the chosen manufacturer should be consulted on specific compatibility issues among their products. Not all manufactures of subsequent toppings, coatings, or treatments are compatible with bond breakers. Confirm compatibility and manufacturers’ agreement if bond breakers and subsequent toppings, coatings, or treat-ments are used from different manufacturers. Regardless of the bond breaker chosen, the more stringent of the subse-quent topping, coating, or treatment manufacturer’s exterior and interior requirements or bond breaker manufacturer’s requirements for surface preparation should always be followed prior to coating application.

A hard steel-troweled slab finish is a prerequisite for any applied treatments and quality panel surfaces. A higher FF/FL for the casting slab will result in a more consistent panel face with the least risk of shadows and irregularities exposed by sunlight when the panels are vertical. Slabs that are poorly finished or cured, or ones that have low strength at the surface, will exhibit higher permeability, which increases absorption of the bond breaker, reducing its effectiveness. All casting slabs should be cured according to ACI 302.1R, ACI 308.1, and ACI 360R. Most bond breaker manufac-turers recommend their product be applied in two coats after all reveal strips, chamfer strips, and blockouts are installed, but before installation of reinforcement and embedments (Fig. 7.1.4). These coats are sprayed at right angles to each other to ensure complete coverage of the casting slab. A simple test for adequate application is to sprinkle water over the slab once the bond breaker has been applied and allowed to dry. The water should form beads. High concentrations of the material in the form of puddles can cause discolor-ation or a gluing effect or impact the hydration process at the panel face behaving like a retarder. The panel concrete in these areas will not set fully, resulting in a surface that is soft and subject to abrasion during cleaning. If the bond breaker coverage is deemed to be inadequate and a second

Fig. 7.1.3b—Adhesive bracket systems.

Fig. 7.1.3c—Common form separating two panels.





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application is needed, care should be taken to minimize bond breaker overspray covering the reinforcement and embedded items.

7.2—Architectural treatmentsThe development of new finishes, coatings, and construc-

tion techniques, along with improvements in methods for traditional finishes, has given licensed design professionals and contractors many options for aesthetic treatment of tilt-up panels. Aesthetic enhancements are achieved using form liners, applied elements, offset panels, panel shape variations, blockouts, and recesses. Thin brick or block inlays also can be cast with the panel (7.2.7).

Finishes are created using several processes. Color varia-tions of the mixture are created with different cement types, color admixtures (pigments), different coarse and fine aggre-gates, and adjusting the mixture proportioning. Applied finishes offer an even broader opportunity to affect the color with stains, paints, and coatings. Surface texture and appear-ance are developed through various mechanical methods, by special forming techniques, or through application of surface-retarding coatings.

Figure 7.2a illustrates an uncoated panel that gives a natural appearance. Slight variations in color are to be expected and are what give the finish its natural appearance. To limit undue or extreme color variations, cement color, colored admixtures, forming surfaces, release agents, water-cementitious material ratio (w/cm), consolidation proce-dures, fly ash, blast furnace slag cement, course and fine aggregate, and the amount of cement used should be closely controlled.

Textured surfaces can be obtained with the use of form liners, sandblasting, or exposing aggregates (Fig. 7.2b). Form liners should be stiff enough to minimize displace-ment or distortion during concrete placement. An exposed-aggregate finish can be obtained with the use of retarders, sandblasting or waterblasting, mechanical abrasion or bush-hammering, or embedding aggregate in a sand bed prior to casting (Fig. 7.2c). Because coarse aggregate from some

Fig 7.1.4—Applying the bond breaker prior to the installa-tion of any steel reinforcement.

Fig. 7.2a—Uncoated panel finish for a natural appearance.

Fig 7.2b—Panel sand blasting. Note: color/texture change in panel as a result of the sand blasting.

Fig 7.2c—Oyster shells placed in a sand bed.





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sources may have a low hardness and abrade at the same pace or faster than the cement paste matrix, careful evalua-tion of the coarse aggregate is critical if mechanical means is to be used to expose the aggregate.

Architectural treatments resulting in panel thickness reduction should be checked by the licensed design profes-sional and accommodated for by additional thickness if required. Consideration should also be given to the minimum outer wythe thickness for sandwich wall panels. Though not affecting the structural integrity of the tilt-up panel, the manufacturer will have recommendations for the minimum thickness required to develop the pullout capacity of their embedded wythe connectors. In particular, features such as reveal strips, embedded elements, and recesses will impact the intended performance.

7.2.1 Chamfers and corners—Exterior panel edges are usually chamfered (Fig. 7.2.1a), resulting in fewer spalls and a cleaner appearance. Chamfers are normally formed at 45-degree angles and are at least 3/4 in. (19 mm) wide. They are made from wood or a plastic extrusion of vinyl or poly-styrene. Any damage to the chamfer, in particular the leading edges, will result in deformations or ragged edges, so use caution to minimize damage to the softer forming surfaces. Chamfers should be caulked if the joints are not tight.

Panels at building corners can be formed with either butt joints or mitered corners. The butt joint may be the simplest and least expensive to form (Fig. 7.2.1a). The detail shown in Fig. 7.2.1a is much easier to form and less fragile to handle, but far more difficult when the detail is applied to a sandwich panel due to the reentrant section created by the fascia and insulation layers (Fig. 7.2.1b). The mitered corner should be accurately formed because the miter magni-fies any inconsistency (Fig. 7.2.1c). Mitered edges can be formed from an assembly of dimension lumber or by using specially fabricated materials, such as extruded polystyrene shapes or prefabricated metal forms (Fig. 7.2.1d). Mitered corners rarely terminate in a point, which is very difficult to form and erect without damage.

7.2.2 Reveal strips—The simplest method to divide the visual expanse of a large tilt-up panel and hide casting slab irregularities reflected in the panel is to use reveal strips (Fig. 7.2.2a). Reveals may run vertical, horizontal, diag-onal, or circular, and there may be one or several bands on a building (Fig. 7.2.2b and 7.2.2c). Reveals are typically 1/2 to 3/4 in. (13 to 19 mm) deep and 2 to 4 in. (50 to 100 mm) wide with 22.5- or 45-degree beveled sides for ease of stripping. Reveals with square edges (90-degree angles) are not recommended unless they occur at a panel edge or form liner (Fig. 7.2.2d), as they are difficult to strip and may result in poor-quality edges. Chamfers and reveal strips should have a consistent depth and angle. If a reveal is required, its location and subsequent effect on the panel’s structural performance should be considered. The reduction of overall concrete thickness at a reveal weakens the cross section of the concrete panel and may require additional reinforcement or additional panel thickness to achieve the required struc-tural performance.

Fig 7.2.1a—Typical butt joint building corner.

Fig. 7.2.1b—Sandwich panel butt joint.

Fig 7.2.1c—Mitered corner.

Fig. 7.2.1d—Mitered corner formwork.





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Reveals can be fabricated from 1x white pine, poplar, spruce, or fir lumber, or composite lumber. Wood reveals may need to be coated with a sealer to reduce adhesion to concrete and stabilize the wood. The reflection of grain pattern from the wood to the concrete can be a problem. To minimize this condition, a finished lumber or plyform reveal is often used. Reveals can also be made of plastic extrusions of vinyl or polystyrene. A smooth-faced surface is desired, often plastic-coated or naturally formed, to minimize the

bond to the concrete. With any plastic-based component, the use of noncompatible solvents and chemicals should be avoided. As with chamfers, the forming material for reveals is softer and the exposed surfaces subject to damage. Be careful to protect these surfaces to minimize the panel surface finish. The effect of weather and moisture should be considered when choosing the lumber for reveals.

Accurate placement of reveals is important, particularly if the reveal continues from one panel to the next. Loca-tion of the reveals should be marked on the slab with chalk lines and should be fastened, nailed, or adhered to the slab with construction adhesives. Edges of the reveal strip should be caulked with a silicon or latex caulk to produce a clean, crisp edge when needed. Reveal strips should be thoroughly coated with bond breaker after caulking and compatibility of the chemical with the reveal components tested prior to application.

7.2.3 Dimple finish—A dimple surface finish can be used as an accent or to soften the appearance of an entire panel (Fig. 7.2.3a). Although the concept of this treatment is simple, exercise care in its application. The area to receive the dimple finish is outlined or edged by a nominal 2 in. (50 mm) lumber strip, unless the entire panel is to be dimpled, in which case it is then filled to the top of the nominal 2 in. (50 mm) lumber strip with 3/4 to 1 in. (19 to 25 mm) crushed

Fig 7.2.2a—Reveal strip section.

Fig. 7.2.2b—Vertical and horizontal reveals.

Fig. 7.2.2c—Intricate reveal patterns.

Fig. 7.2.2d—Reveals at form liner edge.





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stone (Fig. 7.2.3b). Clear, 6 mil (0.15 mm) (minimum) polyethylene is then stretched over the stone and secured to the nailing strip. All wrinkles and folds in the polyethylene should be stretched out of the area to be cast, unless that is part of the desired effect. A 3/4 in. (19 mm) reveal is then added to the top of the nominal 2 in. (50 mm) lumber strip. Foot traffic or other activities that could dislodge or move the rock or puncture the polyethylene should be avoided. Care should be taken when placing reinforcement for proper location.

For an alternate dimple finish, a dimple formliner may be used (7.2.5).

7.2.4 Exposed-aggregate and stone finishes—Exposed-aggregate finishes can be achieved by using one of the following techniques:a) Exposing the surface aggregate by sandblastingb) Exposing the aggregate by pressure washing, combined with the use of a retarderc) Bush hammeringd) Placing aggregate in a sand bed within the panel forms and casting the concrete onto these aggregates

Exposed-aggregate finishes derive their appearance from crushed graded aggregates, which normally vary between 3/4 and 1-1/2 in. (19 to 38 mm) A colored mortar can also

enhance the finished product. A clean, durable aggregate intended for use in an exposed concrete panel should be used. Aggregates from a reliable and consistent source should be chosen. Aggregates with iron sulphides or other impurities may cause surface discoloration. Some types of aggregates can cause popouts or deteriorate when exposed to alkalinity or freezing-and-thawing cycles. If a specific color aggregate is desired, it should be used throughout the concrete mixture. Some stone may be more expensive than the regular coarse aggregate used in the concrete, which should be considered in the planning and cost-estimating stages. If an expensive aggregate or cement is desired, a special fascia wythe may be an option over using expensive components for the full panel thickness. This fascia wythe, 2 to 3 in. (50 to 75 mm) thick, requires a structural panel backup and adds to the total panel thickness. Adequate bond between the two wythes should be provided and differential shrinkage considered. Shrinkage can be minimized by control of the w/cm, cement content, and placement timing. This same effect could also be achieved by constructing a sandwich panel, which would eliminate any possible concrete compatibility issues that may arise over time. Whichever method is used to obtain an exposed-aggregate finish, or if plain concrete is the desired look, panels should be cleaned and sealed with a nongloss, non-membrane-forming, nonyellowing, penetrating silane/siloxane blend complying with local volatile organic compound (VOC) regulations. The penetrating sealer should impart a breathable water-repellent barrier without changing the appearance of the substrate.

A large-scale panel, a minimum of 4 x 8 ft (1.2 x 2.4 m), should be cast for architect and building owner approval with the provision that aggregate supplier test panels are generally too small to show variations that typically occur in large panels. Rather, supplier test panels are intended to show characteristics of the exposed aggregate finish. Further-more, the cement, casting technique, or curing conditions of the test panel may vary from that used on the subsequently produced full-size panels.

7.2.4.1 Sandblasting—Sandblasting is one typical method to obtain an exposed-aggregate finish. The objective is to abrade the concrete surface to remove the hardened cement matrix surface and expose the underlying aggregate. Light sandblasting will remove approximately 1/16 in. (1.5 mm) of the surface while heavy sandblasting can remove up to 1/2 in. (13 mm), which in turn may require larger coarse aggregate.

Sand or abrasive blasting with or without retarders may change the appearance of aggregates by permanently dulling them. The degree of change will vary depending on aggregate type. Concrete matrix strength will affect the final appearance and ease of sandblasting. Concrete matrix strength in each panel should be approximately the same when it is sandblasted. Ideally, concrete should be less than 14 days old. Diameter of the venturi nozzle, air pressure, and type of sandblast sand used should be determined by a trial procedure on concrete similar to that used in the actual tilt-up panel. Once the sand is selected, the source and particle size should not be altered during the course of the project.

Fig. 7.2.3a—Dimple finish.

Fig. 7.2.3b—Formed dimple finish.





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The degree of uniformity is generally in direct proportion to the depth of exposure; therefore, the deeper the sandblast exposure, the greater the uniformity. A brush or light sand-blast finish may appear acceptable on a small sample, but uniformity on a large panel is difficult to obtain. To mask some nonuniformity or to allow for variation in the depth of exposure of the sandblasted surface, reveal strips can be used to divide the surface into smaller areas (Fig. 7.2b).

When casting panels that are to be sandblasted, the contractor should be prepared to give extra attention to the concrete placement, crack control, and the prevention of other irregularities to the surface. The sandblasting process will round the edges of all cracks and increase their visibility.

The sandblasting operator should use an aerial lift (Fig 7.2b) or have scaffolding sufficient to maintain a consistent angle and constant distance from the concrete surface being blasted to obtain the best results. Sandblasting is generally more uniform if the nozzle is moved in a circular motion rather than only vertically and horizontally. Wet sand-blasting may be required for conformance with environ-mental regulations.

Sandblasted surfaces are normally classified as:a) Brush—Removes the cement matrix and exposes the fine aggregate—no projection of the coarse aggregate from the matrixb) Light—Sufficient to expose fine aggregate and occasional exposure of coarse aggregate reveal 1/16 in. (1.5 mm)c) Medium—Sufficient to expose coarse aggregate with a slight reveal—maximum aggregate reveal 1/4 in. (6 mm)d) Heavy—Sufficient to generally expose and reveal the coarse aggregate to a maximum projection of 1/3 the maximum size of coarse aggregate diameter with a reveal of 1/4 to 1/2 in. (6 to 13 mm) and a surface that is rugged and uneven

Careful selection of coarse aggregate is critical if a mechanical means is being used to expose the aggregate. This will provide greater uniformity and reduce sandblasting time. When sandblasted surfaces are required, only 100 percent plastic, pointed chairs should be used to support the reinforcing steel. Plastic tips on steel chairs can come off, resulting in rust stains on the panel. The deeper the sand-blast, the more coarse aggregate is required in the mixture proportion. Deep exposure of coarse aggregate requires a finer abrasive to obtain uniform results.

7.2.4.2 Pressure washing—Pressure washing, in combina-tion with the retarder, gives similar results to sandblasting by stopping the hydration process of the cement paste at the surface, and then removing the cement and fine aggregate on the panel surface to expose the coarse aggregate below. Proper retarder application and concrete placement are crit-ical to obtaining a uniform appearance with exposed-aggre-gate finishes. Once the panel forms are placed, the retarder is applied to a properly sealed casting surface, eliminating the possibility that the retarder is absorbed by the casting surface. The retarder should be checked for compatibility with the curing compound, sealer, or both. Care should be taken to obtain a constant concentration of retarder that will result in uniform aggregate exposure. Select a retarder with

an etch depth compatible with the size of aggregate used. Protection from the elements should be provided during the time period after the retarder has been applied until concrete is placed because the retarder is activated by water. Joints and cracks should be covered or filled to prevent the absorp-tion of retarder or moisture from the concrete mixture. The material, however, should not have an affinity for water. Care should also be taken when installing panel reinforce-ment, lifting inserts, and other items to avoid scraping the retarder off the casting surface.

Concrete should be deposited as close as possible to its final position in the panel and not moved about with the vibrator. Otherwise, segregation may occur, resulting in a nonuniform surface finish. Once panels have been cast, the edges should be protected in the event of rain to prevent the retarder from being diluted by the precipitation.

After the panel has been lifted into place, the retarded surface is removed by light sandblasting or waterblasting. Aggregate exposure should begin as soon as possible to within 2 to 3 hours after lifting because the retarded surface will start to harden from ultraviolet exposure. Use light etch retarders in combination with medium or deep sandblasting of exposed surfaces to minimize time and labor. Proper procedures and trained personnel are critical in obtaining desirable results.

7.2.4.3 Bush-hammering—Another type of exposed aggregate surface, though less common than sandblasting, is produced by bush-hammering. Bush-hammered surfaces are produced by pneumatic tools fitted with a bush-hammer, comb, chisel, or multiple-pointed attachment. The type of tool is determined by the final surface desired. Bush-hammering is normally applied to well-graded mixtures with softer aggregates such as dolomite and marble. Most bush-hammering will remove 3/16 in. (5 mm) of surface mate-rial. Bush-hammering works best with 4000 psi (28 MPa) and higher concrete. To minimize loosening of the aggregate during hammer operations, a minimum concrete age of 14 days is recommended. Bush hammering at corners tends to cause damage unless special care is taken. Corners should be completed with hand tools rather than pneumatic hammers.

7.2.4.4 Sand bed—The sand bed method involves hand-placing aggregates on a 2 to 3 in. (50 to 75 mm) sand bed within the forms. A low slump sand/cement grout is then placed over the aggregates. This method has been success-fully used with maximum sizes of coarse aggregate up to 6 in. (150 mm). These larger aggregates should be hand placed in the sand. Large stone has also been used successfully in sand bed casting (Fig. 7.2.4.4a) including thin slices of facing stone, flagstone, limestone, and rounded river rocks.

The best results are obtained with dry masonry sand as the sand bed. The color of the sand should be consistent with the aggregates used in the concrete to avoid a mottled appear-ance. Sand is usually spread to a depth of 40 to 50 percent of the stone diameter, but depth is dependent on the amount of exposure desired. All aggregate to be exposed should be of uniform size and gradation for best results. However, smaller aggregate needs to be worked in to fill voids.





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Special care should be taken to ensure that adequate aggregate density is obtained around edges, corners, and openings. This may require special tamping tools in these areas. After aggregate distribution has been obtained, the aggregate is pushed or hand tamped into the sand bed. The aggregate can be rolled into the sand bed using a weighted, smooth-face roller. Once a final adjustment in sand thick-ness has been made, a fine spray of water is then used to settle the sand around the aggregates. Excessive use of water from a normal nozzle may disturb the aggregate bedding and promote cement migration into the sand bed. The grout mixture is then placed over the aggregate. The surface is mechanically roughened prior to setting to aid in bonding with the structural wythe.

Reinforcement should then be placed in its proper posi-tion within the structural wythe of the concrete portion of the panel. Chairs maintain this position similarly to a normal reinforcement placement. When placed on top of the stones or grout bed (Fig. 7.2.4.4b), however, the varia-tion in aggregate thickness may make it difficult to maintain the proper location. The licensed design professional should be consulted for possible adjustments to the reinforcement design to account for these variations.

With smaller aggregates or if a specific color of mortar is desired, a 2 to 3 in. (50 to 75 mm) cement and sand grout can be placed over the aggregate and allowed to harden to ensure that the aggregate is not dislodged when the structural wythe concrete is placed. Provisions should be made to cure the grout. A curing compound should not be used as a bonding agent to ensure bond with the concrete. The grout surface should also be raked to promote bonding with the concrete.

After the tilt-up panels have been erected, the sand is hand brushed or removed with water under low pressure, 1000 psi (7 MPa) or less.

7.2.5 Form liners—Manufactured form liners are often used to produce a special finish or create geometric shapes. They can be used as an accent on a portion of the panel or for the entire panel. Form liners are available in a variety of materials and patterns (Fig. 7.2.5a). Liners designed for a single use, manufactured from polystyrene or vacuum-formed plastic, are most common on tilt-up projects. There are, however, also multi-use form liners made out of high-density plastic or rubber.

Corrugated siding, metal decking, and other commonly available materials have been successfully used as form liners, and other common materials like roughhewn wood impart interesting surface textures (Fig. 7.2.5b).

7.2.6 Surface applied features—Accent features are used extensively in construction because of their relatively low price and the ability to form complex shapes on the panel surface. These systems consist of cementitious coatings over a base material or shape usually consisting of a rigid or foam plastic shape.

Accent features and their finishing systems are used in conjunction with tilt-up construction, either directly on the tilt-up panel or in conjunction with tilt-up and other forms of construction. Applications should be limited to fascia and feature elements that are less susceptible to damage from ground level such as projectiles and vandalism, unless a system is selected with a higher durability. Affixed features that cross tilt-up joints can be damaged due to the movement of the panel. Care should be taken to address this move-ment. Simple reveals and patterns can be easily applied to

Fig. 7.2.4.4a—Hand-placed stone finish.

Fig.7.2.4.4b—Flagstone concrete casting. Fig. 7.2.5a—Form liner finishes.





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the panel, depending on the coatings used. Combining these multiple elements can add new dimensions to the finished building.

7.2.7 Thin cast brick/block—Thin cast bricks and blocks are now widely used in tilt-up construction as architectural features or to create an architectural style (Fig. 7.2.7a). Thin bricks are used over the entire panel or an accent portion of the panel. Thin bricks come in all colors and textures and can be cast in the same types of courses as applied brick. The brick area is laid out in the panel with special care to be taken to keep the running pattern constant across panel joints. Further, special return bricks are manufactured for window and door openings so that the brick feature is constant (Fig. 7.2.7b). Form liners or a snap system can be used as the brick template. Both systems incorporate the mortar joint into the system and provide a pattern to place the thin bricks into. The thin bricks are scored on the back to allow for a mechanical bond with the concrete. The front of the thin brick can be waxed or nonwaxed. The waxed front helps keep any mortar flow from sticking to or staining the brick face (Fig. 7.2.7c). A hot water pressure washer is needed to remove the wax from the brick face.

7.3—Reinforcement placementThe engineer of record will determine the size, number, and

spacing of reinforcement for the in-place wall panel. In most cases, another licensed design professional with the lift and brace insert manufacturer or retained by the contractor will provide the lifting analysis of the stresses created by lifting and temporary bracing of the panel. This engineer may also stipulate additional reinforcement to resist these forces. ACI 318 governs the placement of reinforcement (deformed bar and welded wire) including cover, lap lengths, and spacing. Steel reinforcement location is critical to the performance of the panel, and all instructions and information relating to it should be precisely followed (Fig. 7.3). Refer to ACI 117 for reinforcement placement tolerances.

Fig. 7.2.5b—Rough wood exterior finish.Fig. 7.2.7a—Thin brick application.

Fig. 7.2.7b—Special detailing options at corners.

Fig. 7.2.7c—Erected panels with thin brick prior to washing.





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7.4—Steel embedment platesSteel embedment plates (Fig. 7.4) are used to attach the

panel to other building components, such as roof or floor framing members, or for panel-to-panel connections and panel-to-foundation connections. They are fabricated from plate steel with lugs, headed studs, or weldable deformed bar anchors welded to the back. The embedment plate should be exposed to facilitate ease of attachment. The plates may be either flush with the surface or recessed. In structures where appearance is a factor, or where a highly corrosive envi-ronment is anticipated, a recessed embedment is preferred because it can be concealed. Galvanized or stainless steel embedment plates should be used in corrosive environments if they are to be exposed.

Welding is the most frequent form of connection to an embedment plate. It gives maximum flexibility and allows greater latitude to adjust for variations in height or dimen-sion. All welding should be performed by certified welders and in accordance with AWS D1.1/D1.1M and AWS D1.4/D1.4M. Bolting can also be used but requires the use of

slotted attachment members to account for dimensional variations.

Steel embedment plates may be either galvanized or the exposed surface may be painted to minimize rusting. The embedded portion should not be painted. Welded areas should be touched up with paint or galvanizing paint. Contract documents often direct the presetting of embeds. If not restricted, however, embed plates may be preset or placed in the concrete prior to initial set, following the provi-sions of ACI 301. Consultation with the panel design engi-neer is recommended before proceeding with wet-setting.

7.5—Lifting and bracing insertsInserts are required for lifting the panels and for the connec-

tion of temporary braces. Lifting inserts are the attachment points of the crane to the panel through the rigging. Bracing inserts are the attachment points of pipe braces that hold the panels in place until the roof diaphragm and floor connec-tions are made and the licensed design professional approves their removal.

Lifting and bracing inserts are usually selected and supplied by the hardware manufacturer based on panel dimensions and configuration. The supplier analyzes each panel to determine the number and location of lifting inserts required. These requirements are a function of the panel weight and stresses encountered during its lifting. The lifting hardware manufacturer typically provides the lifting analysis and lifting insert details along with any additional requirements like strongbacks. Special or odd-shaped panels may require strongbacks. Strongbacks may be required to prevent panel cracking during lifting due to deflection and should be installed as detailed by the licensed design profes-sional for the lifting design.

Many factors are involved in the design of the lifting inserts. They include:a) Panel size, thickness, and weightb) Insert typec) Panel shaped) Concrete compressive and flexural strengths at time of lifte) Panel reinforcementf) Panel openingsg) Panel finishh) Panel lifting options, for example, edge or face lift

Concrete flexural strengths should be equal to or greater than the lifting strength before panels are lifted. Higher-strength or high early-strength concrete can be used if early panel erection is desired. Inserts properly sized for antici-pated loading, panel thickness, and other characteristics should be provided along with drawings detailing the exact location for the inserts and any additional reinforcement requirements. Lifting inserts should be installed to a plan location tolerance of ±1 in. (±25 mm) unless otherwise spec-ified by the supplier.

Inserts are supplied with a void form material designed to prevent concrete from filling the insert during casting opera-tions (Fig. 7.5a). Infill pieces are usually made of plastic and have nubs that project after the troweling or finishing opera-tion so that the insert can be easily located.

Fig. 7.3—Reinforcement and shop drawings critical to panel layout.

Fig. 7.4—Embedment plates set and tied to steel prior to concrete placement.





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All lifting inserts used today can be connected to the rigging apparatus with a ground-release mechanism. This allows the insert to be disconnected at the appropriate time without the need to climb ladders (Fig. 7.5b), as was the method of the past.

The supplier of the bracing inserts analyzes each panel to also determine the required number and location of these inserts. These requirements are a function of the construc-tion period wind load applied to the project and capacity of the braces available to the project as well as the brace foot anchorage condition. The calculated wind load may be increased either as desired for greater protection or as required based on the time of the year.

Braces are attached to panel inserts before lifting (Fig. 7.5c). After the panel has been erected and before the crane is released, the braces are attached to the floor slab, or temporary anchoring devices such as helical ground anchors or deadmen. Floor attachments may be either cast-in or post-drilled (Fig. 7.5d). Manufacturer’s instructions should be explicitly followed regarding attachment capacity based on slab thickness, edge distance, and other parameters. Helical ground anchor systems are an alternative to slab-based anchors for attachment of the wind load bracing system. They are installed into the surrounding grade (Fig. 7.5e) at designed locations and the braces are attached to the exposed anchor heads. The braces are attached to the exposed heads of the anchors. Deadmen are premade or cast-in-place concrete blocks wholly or partially buried into the grade to provide attachment of the braces (Fig. 7.5f). Bolts and inserts should

Fig. 7.5a—Brace insert and lifting insert.

Fig. 7.5b—Releasing lifting clutch from inserts.

Fig. 7.5c—Panel braces attached prior to lifting.

Fig. 7.5d—Brace foot bolted to the floor slab.





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be compatible and from the same manufacturer. A deviation in threads, length, or strength could cause the insert or the bolt to fail when subjected to load.

7.6—Concrete placement, finishing, and curingBefore placement of the concrete, the location of inserts,

embedments, and other critical components should be checked. The floor slab may be misted with water to provide cooling unless a retarder is used.

7.6.1 Pumping—Pumping is becoming increasingly popular for placement of concrete (Fig. 7.6.1). It has several advantages, including easier and quicker placement, espe-cially on difficult sites and if pumped from the outside of the building perimeter, the slab is not damaged due to concrete trucks.

Pumped concrete requires special considerations to mini-mize shrinkage and resulting cracks. A concrete mixture proportion formulated for pumping with appropriate aggre-gate size, w/cm, additives, maximum allowable slump measured at point of placement, and minimum hose size (preferably at least 5 in. [125 mm] system reduced to 4 in. [100 mm] diameter) should be selected. Additional informa-

tion may be found in ACI 304.2R on the requirements for placing concrete with pumps.

When pumping, the height of drop should be kept to a minimum. The fresh concrete placement should always be directed into an area of previously placed concrete. This method absorbs the impact of pumping and minimizes abra-sion of the bond breaker (or retarder for an exposed-aggre-gate panel) and aggregate segregation. Concrete placement should progress across the panel beginning at one corner.

7.6.2 Bucket—A crane with a bucket is still used on some projects. The bucket has few moving parts and no pumps. Placement with a bucket also has the advantages of placing concrete where it is needed and works well on difficult or tight sites. No special mixtures are required. It can be unwieldy, is slower than pumping, and requires a crane and operator to transport the bucket. Placement should follow the same procedures previously outlined for pumping.

7.6.3 Direct chute placement—Direct chute placement of concrete (Fig. 7.6.3) is the most economical and depend-able method of placement if the site conditions and building layout are favorable. Access to at least two sides of the panel is required. If access from the interior of the building is desirable, a decision should be made as to whether concrete truck traffic on the slab is permissible or if sections of the slab should be omitted until the panels are cast.

7.6.4 Placement sequence—Regardless of the concrete placement method used, it should proceed from one edge of the panel to the opposite side, not from the perimeter to the center, or vice versa. The concrete should not abrade the bond breaker or retarders from the slab during place-ment. Use a shovel, piece of plywood, or other surface to

Fig. 7.5f—Brace foot to cast-in-place deadman.

Fig. 7.6.1—Pumping operation.

Fig. 7.5e—Brace feet attached to helical ground anchors.





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slow the first concrete volume to be placed. Freshly placed concrete can then be used to break the impact from the chute or nozzle (Fig. 7.6.4). Concrete should be placed as close as is practical to its final location. It is acceptable to rake concrete short distances. The vibrator should not be used to move concrete.

If a common form is used between panels, concrete should be evenly distributed on both sides of the form to reduce the chances of form movement.

7.6.5 Consolidation—Vibration is critical to ensure consolidation around reinforcement, inserts, and embed-ments, and to get a proper finish on the panel. A spud vibrator is the method most commonly used (Fig. 7.6.5a). The tubular end of the vibrator should be positioned as close to parallel with the slab as possible and pulled through the concrete without coming into contact with the slab (Fig. 7.6.5b). An attachment to hold the end of the vibrator can be fabricated if one is not available. The vibrator should be drawn through each successive deposit of fresh concrete into the previous placement to ensure adequate blending. The vibrator can also be placed in contact with the forms to

ensure flow at the edges. Secondary vibration will promote the flow of concrete between reinforcement if two layers are used. The use of vibrating screeds is another popular consol-idation method currently in use with supplementary spud vibrators at embedments (Fig. 7.6.5c). Refer to ACI 309R for further information. A single-person, gas-operated truss screed vibrator provides considerable ease with which strike off and vibration become a one-person, one-step operation.

7.6.6 Finishing and curing—Interior finish of the panels is often an owner’s preference. If the panels are to be left exposed, a hard trowel finish may be desired. (Hard trowel finish is required if panels are to be stack cast.) Many times, a float finish is all that is required, especially when the interior is to receive insulation or a furred wall with drywall finish.

For concrete to develop the desired properties for strength and durability, it should be properly cured. ACI 308.1 discusses proper curing procedures.

Fig. 7.6.3—Concrete placement operation direct from chute.

Fig. 7.6.4—Concrete placement maintained in fresh concrete.

Fig. 7.6.5a—Spud vibrator for vibration around inserts, embeds, and reinforcement.

Fig. 7.6.5b—Spud vibrator moved through concrete.





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CHAPTER 8—PANEL ERECTION

8.1—Before erectionAny errors or miscalculations occurring during the plan-

ning stages will become obvious when the panels are erected. Panels cast in the wrong location, crane inaccessibility to the site or portions of the site, panels stack cast in the wrong order, an inexperienced crane operator or crew, or inadequate crane size will severely hinder the erection process. Safety procedures are critical to the erection process and should be reviewed in a safety meeting before panel erection.

8.1.1 Planning review—The panel erection process should be reviewed before the start of panel erection. A preerec-tion meeting should take place between the controlling contractor and the steel or panel erection contractor. This meeting confirms the panel layout and sequence. If panel erection is from the outside of the building, careful atten-tion to the crane movement should be in place accounting for power lines, roads, excavations, and other obstacles. The casting and erection sequence plan should be reviewed to verify that all panels have been cast and are in their correct locations. Items that have changed from the original plan should be addressed.

8.1.2 Panel preparation—Panel preparation includes removing formwork, locating and cleaning out lifting and brace inserts, testing each lifting insert with the lifting hard-ware, attaching braces, and cleaning debris from around and on the panels. Any standing water around the panels and within openings should be removed. Standing water flows between the casting surface and panel face, which results in additional loading needed to break the bond. The addi-tional loading can result in damage to the panel and create a dangerous situation for the erection crew. Locations of lifting and brace inserts should be checked with the erec-tion manual. It is good practice to clean out blockouts for framing connections before erecting panels because of the easy access. Attachment of shelf angles and beam seats to embedded plates is also easier at this stage.

Panel concrete strengths, both flexural and compressive, should be determined according to ASTM C78/C78M and C39/C39M procedures before erection. These strengths are obtained from tests performed by the testing agency in accor-dance with ASTM E329 on the cylinder and beam specimens fabricated during casting of the panels. Field tests should be performed by an ACI Certified Concrete Field Technician. The erection manual should specify the strengths needed for lifting panels. Panel erection should not occur until strengths are equal to or above the requirement stated previously.

8.1.3 Site preparation—Ground conditions where cranes are placed to lift panels should be verified for adequate support. The controlling contractor should consult the geotechnical engineer to determine ground conditions are adequate to support the crane’s weight and load as required by OSHA 29 CFR 1926.1402.

8.1.4 Footing preparation—Several items are required to prepare footings for panel erection. Setting pads should be properly located both in plan and elevation. Grout setting pads (Fig. 8.1.4a) require sufficient time to reach their speci-fied strength and, therefore, plastic shim stacks are the more common method of setting elevation of the supported panel base (Fig. 8.1.4b). High spots in continuous footings should be ground down to allow panels to bear on the setting pads.

Fig. 8.1.4a—Grout setting pads prepared for panel placement.

Fig. 8.1.4b—Panels being set on plastic shim stacks.

Fig. 7.6.5c—Vibrating screed or strike-float vibrates final surface.





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If the panel bears on a high spot in the footing, the panel may not be plumb and the footing may be overloaded.

8.2—RiggingAll rigging should be sized and verified that it will support

the intended loads per the minimum safety factor of 5 based on ultimate loads in compliance with OSHA 29 CFR 1926.704. All applications of the rigging should be used in accordance with the manufacturer’s recommendations. Cable lengths and rigging layout should be compatible with the lifting design (Fig. 8.2).

8.3—Panel erection sequencePanel erection should progress in one continuous and

smooth operation. The rigging should first be inspected for proper alignment after the rigging and lifting hardware have been attached to the panel and the slack has been taken out of the cables, but before initial loading of the inserts. If the cables twist or the hardware tries to rotate, the lift should be halted and the hardware realigned. Lifting inserts should not be subjected to a significant amount of side loading unless they are specifically designed for that purpose. The lifting hardware manufacturer’s recommendations should be followed at all times.

The crane operator applies force to the panel through the rigging until the load gauge reaches the weight of the panel and rigging. The erection team should make sure that the panel has broken free of anticipated suction, created when the center of the panel moves prior to the edges as the panel begins to flex, to avoid applying excessive force to lifting hardware. Additional suction forces such as bond breaker failures and water between the casting surface and panel face can cause damage to tilt-up panels during erection, including breaking of the tilt-up panel.

If the panel does not readily break free from the casting surface, use wedges and pry bars to help release the panel. As the panel rotates and lifts off the slab, crewmembers should support the free end of the braces above the slab so the braces do not bind or hang up on other panels or construction materials. The crane operator should lift the panel without dragging the bottom edge along the slab or striking any previously erected panels.

Once the panel is set on the setting pads, it can be roughly plumbed with the crane before attaching the braces to the slab. A 4 ft (1.2 m) level may be sufficiently accurate for this initial plumbing. Adjustments in the plane of the panel are accomplished by adding or removing plastic shims at the setting pads. A transit is often used to verify that the vertical edges of the first panel set are plumb. Subsequent panels can be adjusted relative to the first panel by providing a uniform joint width between panels. Minor panel adjustments in or out can be accomplished with the brace’s threaded adjusting mechanism, enabling the brace to be lengthened or short-ened after it is attached to the slab and the rigging released.

The tilt-up contractor can make minor vertical adjust-ments until the panels are grouted or the roof and floor diaphragm framing is erected. Once the panel is grouted and connected at its base, its position cannot be adjusted. If a panel supports another panel, which is often called a span-drel or lintel panel, the supporting panel should be vertically straight before spandrel panel erection.

8.3.1 Temporary bracing of panels—Typically, the licensed design professional designing the lifting inserts will also design the temporary panel bracing. The number, size, and placement of the braces are based on wind loads and panel location and size with a minimum of two braces per panel (Fig. 8.3.1). If knee braces are required, lateral bracing with intermittent X-bracing is also needed to reduce the brace’s

Fig. 8.2—Rigging arrangements.





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unsupported length. If a strip of floor slab is left out until the panels are erected, deadmen for anchoring the braces may be required until permanent connections are made. The crane should not be released from the panel until the licensed design professional’s bracing recommendations have been satisfied. The Tilt-Up Concrete Association’s (2012) wind bracing guidelines or ASCE 37 should be used.

It is good practice to have lifting and bracing equipment on-site in addition to what is designed for the panel erec-tion and bracing process, in the event that the primary hard-ware is missing, damaged, or malfunctions. This emergency equipment often includes special lifting plates that can be anchored to the panel face when an embedded lifting insert is mislocated or knocked over during panel casting. The lifting plate is bolted to the panel as near as possible to where the insert should have been located. The plate and connection bolts should have the same load capacity as the cast-in lifting inserts and should be specified or otherwise approved by the licensed design professional providing the lifting design. Other equipment may include additional braces for replace-ment of braces damaged in shipment or staging.

8.3.2 Stack casting panels—When panels are cast atop one another, additional time is required for panel erec-tion. Forming lumber below the top panel erected should be removed before erecting the next panel. Lifting inserts should be located and cleaned out and panel braces attached. This process will often double the time required to erect these panels. In addition, the crane operator should exercise caution when lifting stacked panels because the crewmem-bers supporting the braces may have to walk over the panel on which the panel being erected was cast.

8.3.3 Panel connections—After the panel is shimmed and plumbed, it should be grouted as soon as possible and connected at the base as shown on the structural drawings. The tilt wall contractor should verify the locations of embed-ment plates for permanent connections. Any discrepancies should be brought to the engineer of record’s attention for immediate resolution.

8.3.4 Panel brace maintenance—Panel brace connections at the floor and panel should be checked daily and tightened in accordance with the manufacturer’s recommendations.

Because wind vibration may work connectors loose, connec-tion bolts should be checked and torqued daily.

8.3.5 Brace removal—Panel braces should remain in place until the panel is fully connected to the roof diaphragm to stabilize the building structure. The engineer of record should verify when temporary wind braces can be removed.

8.4—SafetyIn addition to safety issues discussed in Chapter 4, special

attention should be given to the quality of the crane and rigging. OSHA 29 CFR 1926.1402 requires that the crane owner be responsible for documenting inspections. Annual, monthly, and daily inspections should be readily available for review by the controlling contractor, which means they are to be kept with the crane at all times while it is on site.

Qualifications of the operators should be reviewed. Items such as crane access and crane support, quality control of placement, attachment of lifting inserts to lifting hardware, and rigging should also be monitored.

CHAPTER 9—CONNECTIONS

9.1—Design of connectionsThis chapter introduces typical connections to the licensed

design professional and contractor who are new to tilt-up. It does not recommend one connection over another nor is it all-inclusive. The details shown are pictorial repre-sentations of connections that have been successfully used in the construction of uninsulated and insulated sandwich wall panels. This detailing is shown to illustrate the proper structural, as well as thermal, connection between building elements. Commonly, the licensed design professionals are responsible for designing and detailing connections while the contractors are responsible for proper execution. All permanent connections should be made before the removal of the temporary wind braces, or as directed by the engineer of record. Several references are available on connection design and construction for tilt-up buildings (PCI 1999; PCA 1987; Weiler 1986; Lemieux et al. 1998).

9.2—Foundation and slab-on-ground connectionsMost tilt-up panels are connected to the floor slab with

bent reinforcement dowels cast into the panel and lapped with reinforcement cast into the floor slab closure strip (Fig. 9.2a). Dowels can also be drilled and epoxied into the panel. Welded embedment plates are another option (Fig. 9.2b) and eliminate the need for the slab closure strip. In many cases, if the panel is anchored to the floor slab, connections to the footing are not required except for grout under the panels. Additionally, use of a thickened slab edge is not required in many cases, and often depends on construction sequence or contractor preference.

Where a positive connection to the foundation is required, foundation connections can be made by dowel between the footing and panel, to the slab (Fig. 9.2c) or providing a keyway (Fig. 9.2d). Alternatively, use a welded embedment plate connection or a field-drilled mechanical connection (Fig. 9.2e and 9.2f). Corrosion protection should be added

Fig. 8.3.1—Temporary panel bracing.





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to all connection elements exposed to potentially corrosive environments. If analysis shows tension forces are present at the base of the panel, a reinforcement bar or dowel can be projected from the footing and spliced to the panel rein-forcement (Fig. 9.2g). Embed plates with dowels can also be provided on both sides of the panel and welded to corre-sponding embeds in the footing (Fig. 9.2h).

Steel embed plates cast into sandwich walls are very often the same used in uninsulated panels (Fig. 9.2i); however, the insulation may have to be thinned locally to accommodate embed sizes. Sandwich wall panels placed on foundation walls are set on shims beneath the interior bearing wythe only; the grout joint between shims should also be limited to the area beneath the structural wythe only, allowing the nonstructural exterior concrete wythe to expand and contract as needed. A closed-cell backer rod and caulk should be used to impede the penetration of moisture and debris along this horizontal joint.

When sandwich walls are attached to the floor with a threaded dowel (Fig 9.2j), care should be taken to assure that the reinforcing bar or doweling extending out from the sandwich wall is contained within the interior-bearing wythe only. Insulation removal is typically unnecessary and will reduce the thermal efficiency of the wall panels.

Fig. 9.2a—Panel to slab dowel connection.

Fig. 9.2b—Panel to slab welded plate connection.

Fig. 9.2c—Slab dowel connection.

Fig. 9.2d—Keyway dowel connection.

Fig. 9.2e—Welded plate connection.





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9.3—Roof connections and supported floor connections

Roof and supported floor connections usually consist of embedment plates with headed studs or reinforcing bars. A continuous angle or seat angle is welded to the embedment. Seat angles can also be attached to the panel with expansion or adhesive bolt fasteners. A recessed pocket with an embed-ment angle or plate is commonly used for heavy loads such as joist girders, although embeds on the face of the panel can also be used to support girders (Fig. 9.3a to 9.3g).

Wood roof systems and hybrid systems, which usually use a combination of wood sheathing and subpurlins with steel joists and girders, are also common in some areas, particu-larly in the western states. These systems often use wood ledgers attached with anchor bolts to the wall for support of wood subpurlins and wood sheathing attachment.

Where joist connections occur at a panel joint, a slip detail that allows for panel shrinkage and thermal expansion should

Fig 9.2h—Welded plate and dowel connection.

Fig. 9.2i—Sandwich panel welded plate connection.

Fig 9.2j—Sandwich panel threaded dowel connection.

Fig. 9.3a—Chord angle.

Fig. 9.2f—Field-drilled plate connection.

Fig. 9.2g—Foundation dowel connection.





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be considered, particularly if the condition occurs at succes-sive panel joints. One common method is to weld a seat or plate to an embed on one side of the joint, and provide cast bolts in horizontal slotted holes on the opposite panel.

An advantage of tilt-up, sandwich walls is the ability to extend the exterior concrete wythe beyond the interior, concrete-bearing wythe. This condition allows the wall and roof insulation to be made continuous at the roof and wall

Fig. 9.3b—Seat angle for joist.

Fig. 9.3c—Pocket for joist girder.

Fig. 9.3d—Steel beam connection plate.

Fig. 9.3e—Glulam beam seat.

Fig. 9.3f—Wood joist ledger.

Fig. 9.3g—Hollow core plank ledge.





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intersection (Fig. 9.3h). Joists being set on sandwich walls can bear directly on top of the interior concrete wythe or be pocketed (Fig. 9.3i to 9.3k), thus allowing for a more effec-tive insulation transition at the roof line, which is considered critical to the overall building envelope.

9.4—Panel-to-panel connectionsIn the past, it was common practice to connect all panel

joints with rigid embedment plates welded together. Subse-quent panel shrinkage and other panel movement resulted in cracking or even total failure of these connections. Many licensed design professionals avoid panel-to-panel connec-tions except where required to meet structural require-ments for wind or seismic loads (Fig. 9.4a). Joint alignment is seldom an issue, except in outside corners where panel bowing can result from temperature variations due to differ-ential sun exposure.

When a licensed design professional requires a panel-to-panel connection, they should provide some degree of

Fig. 9.3i—Sandwich panel joist pocket connection.

Fig. 9.3j—Sandwich panel tall parapet joist pocket connection.

Fig. 9.3k—Sandwich panel low roof termination.

Fig. 9.4a—Panel joint connection.

Fig. 9.4b—Alternate panel joint connection.

Fig. 9.4c—Reinforcing bar chord splice.

Fig. 9.3h—Sandwich panel roof deck connection.





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ductility to accommodate panel shrinkage and thermal expansion and contraction. For this purpose, reinforcing bar anchors are preferred over short, headed studs. When a rigid connection is required (for example, chords and shear walls), however, welding of these connections should be delayed as long as possible to allow for the majority of panel shrinkage to occur. This reduces the risk of cracking around the embeds (Fig. 9.4b and 9.4c). Recessed embeds (Fig 9.4c) should be used with caution, as they tend to cause unwanted panel cracks because of the reduced concrete section and strain created around the embeds. Rigid panel connections, however, can be provided at corner conditions without significant risks of cracking (Fig. 9.4d and 9.4e). All welding should be performed by a certified welder using welding procedures specified in AWS D1.1/D1.1M or AWS D1.4/D1.4M for reinforcing steel.

Panel-to-panel connections for sandwich panels will typi-cally be made within the interior concrete wythe, allowing insulation to extend the panel edges. Panel joints are typi-cally sealed on the inside and outside with backer rod and caulk to protect from moisture intrusion and provide for a clean interior finish (Fig. 9.4f). In cases where a fire-rated joint is required, mineral wool, along with fire-rated backers and caulks, may be specified (Fig. 9.4g). Where special moisture issues are of concern, poly-sheeting and spray urethanes may be placed within the joint (Fig. 9.4h).

9.5—Connections for higher seismic design categories

In areas of high seismic activity, connection design and construction are especially critical to the integrity of the structure. Wall anchorage to the roof structure is very impor-tant, as this is the typical area of failure in seismic events. Careful attention should be given to the chords, drag struts, and collectors.

CHAPTER 10—FINISHING AND SEALING

10.1—Surface preparationBefore the repair of any blemishes on wall panels, they

should be thoroughly cleaned of all bond breakers, form release agents, oils, dust, mold, and mildew. Any repair

Fig. 9.4d—Overlap corner connection.

Fig. 9.4e—Mitered corner panel to panel joint.

Fig. 9.4f—Typical panel joint sealant.

Fig. 9.4g—Fire-rated panel joint detail.

Fig. 9.4h—Insulated and vapor-protected panel joint detail.





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material applied over the bond breaker and most paints will not adhere to the panel surfaces with their presence. Bond breaker manufacturers provide recommendations for removal of their product and coatings manufacturers provide the required surface preparation for their product. Power washing, detergent washing, or wet blasting may be required. After drying, concrete should change color to a relatively uniform gray. If heavy applications of bond breaker are present, additional cleaning may be necessary.

Panel joints should also be thoroughly cleaned. The same factors that can prevent paint adhesion can also prevent caulk or other joint sealants from adhering to the panel.

10.2—RepairsOnce panels are cleaned, surface defects can be repaired.

Almost every blemish in the floor slab or casting bed will appear on the panel surface. Floor slab construction and contraction joints, column blockouts, utility blockouts, and any cracks or voids should be filled or concealed before casting the panels (6.3.1 and 6.3.2).

Concrete panels cast over unfilled floor joints will have fins projecting from the panel surface (Fig. 10.2a). These fins should be ground smooth after panels are erected. A rubbing stone generally works best for this operation, but power grinding may also be necessary. Filling joints before panel casting can greatly reduce the amount of repair required. Refer to 6.3.1 for joint treatments. Fins left along panel edges and reveal strips should be knocked off with a rubbing stone.

Formed edges around doors and windows usually require the most repairs, but care in forming these edges can elimi-nate much of this work. Caulking around formed edges and reveal strips can also reduce the amount of subsequent repairing and finishing (7.1.3).

The repairing or patching process involves filling bugholes, cracks, or honeycombed areas on the panel surface and exposed edges. Repair material is often hydraulic cement or a specially manufactured patching compound. The repair material should be applied to a dampened surface with a rubber trowel and then scraped off flush. Steel trow-eling the repair material when it begins to dry will produce a smooth surface. The repair material should also be allowed to cure sufficiently before painting. When a textured paint is to be used, small imperfections in the panel surface can be ignored.

Cracks in concrete tilt-up panels are typically caused by either shrinkage or lifting and generally do not affect the structural integrity of the panel. If the w/cm of the concrete mixture is too high or the panels are improperly cured, cracking will occur due to restrained drying shrinkage. Cracking can also occur at corners of openings (Fig. 10.2b) or where contraction caused by drying shrinkage is restrained. For example, wide spandrel panels rigidly attached to the supports can crack diagonally at or near the support, unless the design allows for some stress relief; for example, with the use of bolts in slotted holes. Cracks occurring during lifting usually occur at locations in the panel with reduced section opening locations or reveals or at the lifting inserts.

Causes of cracks during lifting include low concrete strength; mislocation of lifting inserts, whether by design or construc-tion; improper rigging configuration; or poor bond breaker performance. The crack width determines the repair type. Small cracks, less than 0.013 in. (0.33 mm), can be grouted as previously described or filled with latex caulk by pressing it in by hand. Caulk should be compatible with the paint to be used. Elastomeric paint or quality primer can sometimes be used to span the crack. The engineer of record should examine all large or structural cracks wider than 0.013 in. (0.33 mm) before any repair is attempted. Usually the crack can be repaired by pressure injection with a structural epoxy performed by a qualified applicator.

Cracking in the exterior panel face of sandwich panels may also occur if the two layers of concrete become monolithic, resulting from holding the insulation back from the panel edge(s). During the curing process, the restraint created by these monolithic areas further induces shrinkage cracking. A sandwich panel, however, is also designed to maintain unique temperature differences on opposing sides of the wall and, therefore, will have large temperature differen-tials between the inside and outside concrete layers. Uncon-

Fig. 10.2a—Floor joint ridge.

Fig. 10.2b—Reentrant corner crack.





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strained relative movement, due to temperature differentials alone, can often be as great as 1/4 in. (7 mm). When full-thickness concrete connections exist, cracking and bowing can result from the restraint.

Therefore, insulation should not be interrupted by any monolithic concrete sections or restraints of any kind. However, at a minimum the two layers of concrete should be separated by insulation on three full edges to reduce the likelihood of restraint cracking.

10.3—JointsMany water infiltration problems are traced to failed

joints between panels. Caulking may become brittle and crack from expansion and contraction, or the sealant may pull away from the panel. The latter may be due to improper preparation of the panel edge. Dirt, grease, paint, or form release agent not cleaned from the panel edge will prevent proper adhesion of the sealant. As mentioned in 10.1, power washing, wire brushing, grinding, chemical cleansing, and sandblasting may be required to prepare the surface.

Polyurethanes, polysulfides, silicones, and some specially formulated acrylics are used as joint sealants for buildings. Polyurethane and silicone sealants are most commonly used in tilt-up construction. Also, many types of polyure-thane do not require the panel surface to be primed. For best results, use a sealant that conforms to ASTM C920 for Type S (single-component) or Type M (multi-component); Grade NS (nonsagging when applied between 40 and 122°F [4 and 50°C]); and Class 25, which withstands a 25 percent increase or decrease in joint width.

At each sealant location, a foam backer rod of the appro-priate size for the gap between the panels and the caulk is set to the appropriate depth (Fig. 10.3a). Surface preparation and installation requirements should follow the manufactur-er’s recommendations and include backer rod type, size and placement depth, conditions that warrant the use of a primer, and temperature range for optimum application.

Joint sealants should not be installed in panel joints smaller than 0.25 in. (6 mm) or larger than 2.5 in. (63 mm). The sealant depth (thickness) should be half of the width of the joint and no less than 0.25 in. (6 mm) or more than 0.5 in. (13 mm) thick. Closed cell backer rods are preferred with most sealants and required with urethane sealants. The backer rod should be 25 to 50 percent larger than the joint. Installation procedures for installing joint sealants should follow guidelines published by the Sealant, Waterproofing and Restoration Institute (2013).

Most paint coatings and sealers do not adhere well to seal-ants. The recommended method for installing joint sealants in painted concrete panels is to install the sealant prior to painting (Fig. 10.3b), choosing a sealant to match the paint. Another method is to first install the backer rod halfway into the joint in a manner that protects the joint face at the adhe-sion plane of the sealant. After the panels are painted, push the backer rod in to the appropriate depth and install sealant.

Do not install sealants in panel joints prior to attaching panels permanently to the structure and adding roof, roof top

units, and roof loads. Panels can shift and tear or damage the sealant.

Types of panel joint treatments are:a) Exterior only––Joints comprised of backer rod and sealant that only provide protection from the exterior elements; the backer rod and sealant extend from the bottom of the panel to the top (including the top and back of parapets) in a single, uninterrupted lineb) Exterior and interior––Joints comprised of backer rod and sealant on both faces of the concrete wall panel to protect from the exterior elements while maintaining a cleaner interior environment; the backer rod and sealant extend fully from the bottom of the panel or exposure to the top (including the top and back of parapets) in uninterrupted linesc) Two-stage (pressure equalized)––Joints most often used in insulated wall panels that are based on rain screen principles and comprised of two stages of backer rod and caulk; one placed within the exterior, concrete wythe, and the other at the intersection of insulation layer and the interior concrete

Fig. 10.3a—Backer rod inserted to panel joint.

Fig. 10.3b—Sealant applied over backer rod to exterior panel joint.





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wythe. These joints are unique because the space between the stages is vented and drained to the exterior.

In cases where a fire-rated joint is required, mineral wool, other fire-rated backers, or both, and fire-rated sealants may be specified (Fig. 9.4g). In cases where thermal or moisture issues are of concern, poly-sheeting and spray urethanes and precompressed foam fillers may be placed within the joint to offer additional protestation (Fig. 9.4h).

Do not install sealants off of ladders. Follow OSHA 29 CFR 1926.501. When installing sealants below grade, comply with OSHA 29 CFR 1926.651. Do not install seal-ants on panels that have not been permanently attached to the structure unless temporary shoring has been reviewed by a licensed design professional.

10.4—PaintsRecommendations of ACI 515.1R should be followed

when painting tilt-up panels. Painting should proceed after the panels have been cleaned and allowed to dry a sufficient period of time to allow as much excess water as possible to leave the panel. Any dirt or dust blown onto the panels from other construction operations should be removed with wire brushes or compressed air before painting. Panel pH, moisture content, and surface preparation should be checked before painting for conformity to the paint manufactur-er’s recommendations. Generally, a pH value of 7 to 10 is preferred.

Paint systems should consist of a primer coat and at least one finish coat. The primer coat should be approximately 3 mils (0.08 mm) thick and each finish coat should be 1.5 to 2 mils (0.04 to 0.05 mm), with the total paint thickness equal to 5 mils (0.13 mm) minimum. Application of paint may be by either sprayer or roller, as recommended by the coating manufacturer.

The prime coat may be either latex- or solvent-based. Solvent-based primers are more effective as an adhesion promoter, but their use and production have all but been eliminated due to the more stringent federal VOC laws. Many contractors recommend a 100 percent acrylic latex topcoat. Use of alkyd- and oil-based paint has declined because they contain esters that react with alkalis in the concrete to form water-soluble soaps. As a result, these paints have a strong tendency to blister and lose adhesion, which is also known as burning. Acrylic coatings will not burn, but they may allow efflorescence to migrate through the paint. The paint and joint caulk should also be compatible or the paint may not adhere to the concrete surface. Some caulks are produced in different colors to match the paint color.

A popular option for the exterior treatment is the use of elastomeric paint systems. These are largely primerless multiple coats that achieve the desired thickness systems, and specially formulated to provide a weatherproof coating over cured concrete surfaces. Their advantages are savings in resources, time, and money from reduction of surface preparation, including patch, rub, and surface cleaning during the construction process. The systems are available in several finishes including smooth, fine, coarse, and extra coarse, which enhances the aesthetics of the building with

color variety and texture. The systems are environmentally friendly due to an extremely low VOC content and are resis-tant to fading, even in darker colors. Their use also facilitates vapor impermeance of the building envelope environments where significant temperature and humidity differential occurs between the building interior and exterior (such as a refrigerated structure or warm, humid climates).

CHAPTER 11—INSULATED PANELS

11.1—Insulated panelsTilt-up panels can be insulated with either interior applied

systems or through use of sandwich panels. Several forms of applied insulation systems are available. These systems may be acceptable where a less durable interior finish is accept-able and where fire and moisture are not of concern. All inte-rior systems isolate the thermal mass inherent in concrete from the conditioned space, reducing the benefits of thermal mass.

Interior systems are boards or blankets of fiberglass, mineral wool, polyisocyanurate, or polystyrene. They may also be metal-skinned panels with insulation cores. The first two types, fiberglass and mineral wool, are typically backed with some form of vapor-resistant coating. The coatings range from a thin flexible plastic or paper liner to a rigid plastic or metallic board. The insulation strips are usually secured with some type of spline or cap that is attached to the wall. The systems are inexpensive, quick to install, and can be applied after the building is erected. By code, plastic insulation should be covered by a thermal barrier to reduce fire spread and smoke development. When using sand-wich wall panels, the interior concrete layer serves as the thermal barrier so no additional protection to the insulation is required.

11.2––Sandwich panelsSandwich panels consist of an inner and outer wythe

of concrete with an insulating material in between. These panels may be fully composite, partially composite, or noncomposite. In fully composite sandwich panels, the two concrete wythes are structurally linked to perform as a single unit. Partially composite sandwich panels display some composite behavior between the concrete wythes. Noncomposite panels have two wythes that behave structur-ally independent.

11.2.1 Fully composite sandwich panels—sandwich panels constructed so that the two layers of concrete are rigidly connected together as an integral unit using reinforcement or monolithic concrete. The entire panel thickness behaves structurally similar to a solid or uninsulated concrete panel. Where the concrete layers are connected monolithically with concrete or significantly with steel reinforcement, large thermal bridges are created, resulting in increased thermal conductivity or reduced insulating value. Fully composite systems are subject to bowing brought about by differential thermal expansion rates on the interior and exterior wythes constrained by the rigid connections.





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11.2.2 Partially composite sandwich panels––sandwich panels constructed so that insulation extends fully between the two layers of concrete with rigid connections between the layers. The rigid connections permit the total panel thick-ness to have a structural capacity greater than the individual concrete wythes but less than the same thickness as an unin-sulated panel. The interior and exterior wythes of concrete are allowed to move relatively independently of one another in response to thermal changes, reducing the potential for bowing. Partially composite sandwich panels are most often created with nonconductive structural connections that elim-inate or substantially reduce thermal bridging.

11.2.3 Noncomposite sandwich panels—These are sand-wich panels constructed with one structural wythe and another architectural or nonstructural wythe separated fully by continuous insulation. They are the most commonly used form of tilt-up sandwich panels. Systems use fiber composite, steel, or plastic injection-molded connectors pushed through the insulating material and into the still fresh concrete below. Some fiber composite systems use uniformly spaced connec-tors that are inserted into predrilled holes or placed between insulation sheets. These systems are recognized as being thermally efficient.

The inner concrete wythe is typically designed to carry the structural loads for the panel. The outer wythe is usually thinner (2 to 3 in. [50 to 75 mm]) and serves primarily as an exterior skin to protect the insulation. The minimum recom-mended exterior wythe thickness of a sandwich wall panel is 2 in. (50 mm), plus the depth of any reveal, rustication, or architectural feature. Therefore, if incorporating a 3/4 in. (19 mm) architectural reveal, the minimum exterior concrete thickness is 2.75 in. (69 mm). The nonstructural, exterior concrete layer of a sandwich wall panel is typically cast first with the connectors installed while the concrete remains in a plastic state. This concrete wythe is typically reinforced with welded wire mats (ACI 318-11, 14.3). The mats are posi-tioned on plastic bolster strips or chairs. A working slump of 5 to 7 in. (125 to 175 mm) is recommended to ensure proper consolidation around the connectors. Additionally, maximum aggregate size is 3/4 in. (19 mm) and 3000 to 4000 psi (20.7 to 27.6 MPa) concrete is typical.

11.3––InsulationThe insulation thickness for sandwich wall panels is

a function of the desired R-value and interior condition including ambient, cooler, and freezer. Ambient facilities, where the interior space will remain at room temperature, typically requires 2 in. (50 mm) of insulation, whereas coolers require 3 to 4 in. (75 to 100 mm) and freezers use 6 in. (150 mm) or more.

To achieve a high R-value and consistent thermal and moisture protection, edges of the insulation layers should remain in contact along their entire length, separating the two layers of concrete. If the insulation is not continuous, thermal bridges occur, resulting in a loss of thermal integrity and increasing the likelihood for moisture migration.

Several types of insulation are used successfully in concrete sandwich panels. The most common type is

extruded polystyrene, although expanded polystyrene and polyisocyanurate are also used in sandwich wall designs. These insulations are widely used because of their avail-ability of thickness and rigidity, as well as durability and ease of cutting during the construction process. However, the physical and insulating properties of each are different.

11.3.1 Expanded polystyrene (EPS or beadboard) is manufactured by compressing expanded polystyrene beads under heat and pressure into a large block that is then sliced into sheets. Densities of 1 to 1.5 lb/ft3 (16 to 24 kg/m3) are common with R-values of 3.7 to 4.2 ft2·°F·hr/Btu per in. (0.026 to 0.03 m2•K/W per mm) of thickness. EPS has a relatively low moisture absorption and permeability but will strongly adhere to the concrete. The effects of differential thermal expansion between the inner and outer concrete wythes should be considered, particularly in large panels.

11.3.2 Extruded polystyrene (XPS) is closed-cell and manufactured to a specified sheet thickness. It has greater and more uniform density with better physical properties compared with EPS. Moisture absorption and permeability are lower, the R-value is higher (5 per in.), and adhesion to concrete is reduced if not eliminated over time. XPS is also stronger and less compressible than EPS. Because sand-wich tilt-up panel construction involves walking on top of the insulation during the placement operation, the higher-strength XPS boards resist breakage and are preferred over EPS, even though the initial price is higher.

11.3.3 Polyisocyanurate (PIR) insulations are closed-cell and also manufactured to a specified sheet thickness. It has density and physical properties similar to XPS insulation. When the product is covered with a trilaminate polyester or aluminum foil facer, however, the moisture absorption and permeability rates are lower than XPS, but the R-value is higher (6.5 ft2·°F·hr/Btu per in. [0.124 m2•K/W per mm]).

11.3.4 Other types of insulation used in sandwich panel construction include polyurethanes and mineral wool boards. Because of the high moisture absorption properties of these types of insulation, they should not be considered unless there is an integral and impervious facing material, like that of a polyisocyanurate. Moisture absorbed from the concrete into the insulation can adversely affect the insula-tion properties and the concrete.

CHAPTER 12––REFERENCESACI committee documents and documents published to

other organizations are listed first by document number and year of publication followed by authored documents listed alphabetically.

American Concrete InstituteACI 117-10—Specification for Tolerances for Concrete

Construction and Materials and CommentaryACI 301-10—Specifications for Structural ConcreteACI 302.1R-04—Guide for Concrete Floor and Slab

ConstructionACI 304.2R-96—Placing Concrete by Pumping MethodsACI 308.1-11—Specification for Curing ConcreteACI 308R-01—Guide for Curing Concrete





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http://www.concrete.org/

ACI 309R-05—Guide for Consolidation of ConcreteACI 318-11—Building Code Requirements for Structural

Concrete and CommentaryACI 360R-10—Guide to Design of Slabs-on-GroundACI 515.1R-79—A Guide to the Use of Waterproofing,

Dampproofing, Protective, and Decorative Barrier Systems for Concrete (Inactive)

ACI 551.2R-10—Design Guide for Tilt-Up Concrete Panels

Air Force Research LaboratoryAFRL-RX-TY-TR-2008-4616—Precast/Prestressed

Concrete Experiments–Series 1 (V. 1)

ASTM InternationalASTM C33/C33M-13—Standard Specification for

Concrete AggregatesASTM C39/C39M-12—Standard Test Method for

Compressive Strength of Cylindrical Concrete SpecimensASTM C78/C78M-10—Standard Test Method for Flex-

ural Strength of Concrete (Using Simple Beam with Third-Point Loading)

ASTM C309-11—Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete

ASTM C920-11—Standard Specification for Elastomeric Joint Sealants

ASTM E329-11—Standard Specification for Agencies Engaged in Construction Inspection, Testing or Special Inspection

American Society of Civil EngineeringASCE 37-10—Design Loads on Structures During

Construction

American Welding SocietyAWS D1.1/D1.1M:2008—Structural Welding Code SteelAWS D1.4/D1.4M:2011—Structural Welding Code–

Reinforced Steel

Occupational Health & Safety Administration (OSHA)29 CFR 1926.501-1995—Safety and Health Regulations

for Construction, Fall Protection

29 CFR 1926.651-1994—Safety and Health Regulations for Construction, Excavations

29 CFR 1926.704-1988 (89) —Requirements for precast concrete

29 CFR 1926.1402-2010—Safety and Health Regula-tions for Construction, Cranes & Derricks in Construction, Ground Conditions

29 CFR 1926.1408-2010—Safety and Health Regulations for Construction, Cranes & Derricks in Construction, Power Line Safety (up to 350kv) – Equipment OperationsAuthored documents

Aiken, R., 1909, “Monolithic Concrete Wall Building—Methods, Construction and Cost,” ACI Journal Proceed-ings, V. 5, No. 1, Jan., pp. 83-105.

Collins, F. T., 1958, Building With Tilt-Up, Know-How Publications, 160 pp.

International Code Council, 2012a, “International Energy Conservation Code,” ICC, Washington, DC, 90 pp.

International Code Council, 2012b, “International Building Code,” ICC, Washington, DC, 690 pp.

Lemieux, K.; Sexsmith, R.; and Weiler, G., 1998, “Behavior of Embedded Steel Connectors in Concrete Tilt-Up Panels,” ACI Structural Journal, V. 95, No. 4, July-Aug., pp. 400-411.

PCA, 1987, “Connections for Tilt-Up Wall Construction,” EB110.01D, Portland Cement Association, Skokie, IL, 39 pp.

PCI, 1999, PCI Design Handbook for Precast and Prestressed Concrete, fifth edition, Precast/Prestressed Concrete Institute, Chicago, IL, 630 pp.

Sealant, Waterproofing and Restoration Institute, 2013, “Sealants: The Professionals Guide,” SWAI, 75 pp.

Tilt-Up Concrete Association, 2012, “Tilt-Up Concrete Association’s Guideline for Temporary Wind Bracing of Tilt-Up Concrete Panels During Construction,” Tilt-Up Concrete Association, Mount Vernon, IA, Dec., 11 pp.

Tilt-Up Concrete Association, 2013, http://www.tilt-up.org/resources/wind_bracing.php (accessed August 12, 2014).

Weiler, G., 1986, “Connections for Tilt-Up Construction,” Concrete International, V. 8, No. 6, June, pp. 24-28.





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http://www.wpafb.af.mil/AFRL/

http://www.astm.org/

http://www.asce.org

http://www.aws.org/w/a/

https://www.osha.gov/

http://www.tilt-up.org/resources/wind_bracing.php

http://www.tilt-up.org/resources/wind_bracing.php

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.

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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 551.1R-14 Guide to Tilt-Up Concrete Construction

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Transcript of ACI 551.1R-14 Guide to Tilt-Up Concrete Construction