Controlling Water Vapour in Concrete Floors - Property Care ...

Moisture Mitigation – Controlling water vapour in

concrete floors

PCA International Conference 2019

© KÖSTER BAUCHEMIE AG

http://www.kb-ag.de/cm/

Where does water vapour in floors come from?


H2O




Coarse aggregate

Mortar (paste + sand)

Paste

(cementitious materials +

water)



Hydration of the cement




Admixtures


An admixture is a material other than

water, aggregates, hydraulic cement and

fiber reinforcement, used as an ingredient

of a cementitious mixture to modify its

freshly mixed, setting or hardened

properties and that is added to the batch

before or during its mixing.

Classifications for admixtures include:

⚫ Air-entraining

⚫ Accelerators

⚫ Retarders

⚫ Water-reducing (superplasticizers)

⚫ SCMs (fly ash)



Lightweight Aggregate Issues


Drying Normal Weight vs Lightweight Concretes

50

55

60

65

70

75

80

85

90

95

100

6-May 20-May 3-Jun 17-Jun 1-Jul 15-Jul 29-Jul 12-Aug 26-Aug 9-Sep 23-Sep 7-Oct 21-Oct 4-Nov

Date

rela

tive

hum

idity

at 5

0 m

m, %

lightweight aggregate

concrete

normal weight

concrete

length of time to dry to 75% internal relative

humidity is approximately double



Old Slabs:


• Water Vapour can

enter the slab even if

no contact with ground

water

• May have no under-

slab vapour barrier

• Existing vapour barrier

may be damaged or

degraded

• RH Testing should be

carried out prior to

installing a new floor

covering



New Slabs


• Should have DPM or WPM

• Concrete drying rate normally

25mm per 1 to 2 months

• A slabs dries from the surface

first, so may look dry but still

contain a lot of water

• Air-conditioning systems can

increase the vapour drive

• Flooring manufacturers

guidelines should be checked

• Concrete should be tested


Slab drying hmk rev2.ppt

How does water vapour harm flooring systems?





No floor covering

Water can pass through concrete

Can introduce higher humidity levels into

building

Can lead to efflorescence




New Floor Covering

Lower Permeability than concrete

Relative Humidity of Concrete will increase

Damage to wooden floors

Mycobacterial growth

Floor coatings and adhesives debond

Alkali Silica Reaction




Water can condense within the

surface layer of the concrete

Development of High Alkalinity

Caused by Potassium, Calcium

and Sodium within concrete

Form Hydroxides

This condensate is very high

PH (up to PH14)

Very aggressive to adhesives

and floor coatings




Blister Formation

Highly Alkaline condensate

Attacks floor coatings, primers, adhesives

“Osmotic Blisters” form

Typically with 3 to 6 months

Blisters are liquid filled

Highly Alkaline liquid (up to PH14)


How can water vapour problems be controlled?


If test results indicate an elevated water vapour level in the concrete something needs to be

done. Drying out of the slab may take several months. The moisture mitigation system blocks

rising water vapour, and prevents the final flooring from coming into contact with the high

alkalinity which develops in the concrete.

Moisture

Mitigation

System




• ASTM F3010-13 Standard Practice for Resin based

membrane-forming moisture mitigation systems for

use under resilient floor coverings

• No equivalent British or European Standard

• Covers the situations where a vapour control systems

may be required

• The type of formulations that can successfully be

used for these applications (2 part, 100% solids, resin

based)

• The surface preparation required

• Maximum vapour permeability permitted

• Treatment of cracks and expansion joints

• Designed for bonded floor build-ups




Standard Fast Set Ultra Fast

Set

Overcoating 12 hours 4-5 hours 3 hours

VOC Zero Zero <10g/L

Vapour diffusion

resistance

144,960µ 172,718µ 135,296µ

Sd value at 400g/sq.m. 52.2m 62.2m 48.7m

RH of Concrete Up to 100%

Layers True one coat system

Withstands Alkalinity Up to ph 14

Concrete cure time Application to green concrete after

Min. 7 days

VOC = any organic compound having an initial boiling point less than or equal to 250 °C

measured at a standard atmospheric pressure of 101.3 kPa - VOC Solvents Emissions Directive


µ = 26,000

µ = 150mm

µ = 144,960

µ = 100



Vinyl flooring at 1.5mm thick = sd 39m

Adhesive at 1mm thick = sd 0.15m

Concrete at 150mm thick = sd 15m

Less than half the water vapour passing

through the concrete can escape through

the flooring.

Vapour Control at 0.4mm = sd 58m

Reduces the water vapour to a level that

the floor covering can cope with.

The thickness of the Vapour Control is

calculated according to the flooring type

and thickness


Concrete testing and analysis – Relative Humidity Testing


ASTM F 2170

Hole drilled to 40% of the

slabs thickness

20% for upper levels

Probes are placed into

boreholes, reading taken after

24h hours (ASTM F 2170)

Good indicative reading can

be obtained after 1 hour

3 tests for 1st 100 sq.m.

Various manufacturers

Borehole size 18mm


Concrete testing and analysis – What else to look for?


New Concrete

• The mix design can be

reviewed and evaluated for

problematic ingredients

• Topically applied curing

compounds can act as bond

breakers

• Confirm which vapour barrier

was used under slab

• Visual check for other

problems such as drying

cracks or excessive power

floating


Concrete testing and analysis – What else to look for?


Old Concrete

• Reliable information is not

normally

available

• Problematic ingredients in mix.

• Substances that effect bonding

may have been introduced

• 50mm diameter by 50mm deep

cores need to be taken

• Core samples are sent to an

independent lab

• Pull-off strength min. 1.5n/mm2


Concrete testing and analysis – Test Report


The four tests normally requested are:–

• Ion Chromatography – looking for contaminants such

as sodium and/or potassium rich metasilicate residues

and sulphate-rich surface precipitates and excess

chloride salts

• Thin-section Petrographic analysis – used to find out if

ASR (Alkali Silicate Reaction) or sulphate degradation

is present

• X-Ray defraction analysis – determines the mineral

constituents of the concrete

• Infrared Spectroscopy – determines if there are

organic contaminants (oil or grease) in the concrete

and at what concentrations.


Surface preparation – The third pillar


Material

Low viscosity

Excellent bond to

concrete

Excellent

resistance to water

vapour

Resistant to high

alkalinity

Knowhow

When is it

needed?

When it shouldn’t

be used?

Interpreting tests

How much to use

How to avoid

problems

Surface

Preparation

Creates a “key” for

the entire floor

Effects the

quantities needed

Prevent unsightly

imperfections

Saves time


Surface preparation – Shot-blasting


Shot-blasting with “wheel

abrader”

• Delivers a consistent CSP

value

• Relatively easy to operate

• Provides nearly dust-free

operation

• Provides an ideal surface

for coating adhesion

• Does not clog concrete

pores


Surface preparation – Shot-blasting



Surface preparation - Grinding


Other methods

• Diamond grinding at edges

• Diamond grinding of high spots

• Removal of old coatings

• Make sure all dust is removed from

the surface

• Always shot-blast as the final stage


Surface preparation : Joints and cracks


• Joints can be stabilised

against curl relaxation

• Use low viscosity high

strength Epoxy (sand can

be added)

• Do not use elastic

materials or cement based

patching compounds

• Widen narrow cracks

• Seal all leaks through crack

injection, before structural

repair

• Do not fill movement joints


Application of the moisture mitigation system


Mix with a jiffy type mixer for 3 minutes at 400 rpm

Slowly pour all of Part B into the large component “A” drum.




IMMEDIATELY after mixing, Pour the material onto the

substrate




• Spread using 2mm

notched squeegee

• Material usage between

300 and 500g/m2

depending on

specification

• Coverage rates can vary

depending on surface

condition and porosity

• Two person application -

one person pours while

the other spreads




• Lightly back-roll fresh

material with a phenolic,

short nap roller

• Ensure uniform

coverage

• Works material into

pores

• Helps de-air material

• Extension poles used to

give a longer reach




• Application finished, just

wait to cure

• Keep area clear with no

foot traffic while curing

• Standard – 12 hours

• Fast Set – 4 to 5 hours

• Ultra Fast Set – 3 hours

• Direct overcoating with

resin floors possible for

48 hours


Alternatives for light-duty applications


• Alternative without Shot blasting

• Waterproofing, vapour barrier and screed within

10mm build-up

• Remove old coatings, fix cracks

• Additional ”primer layer” Sealing slurry or ultra low

viscosity epoxy

• Vapour Reduction Layer (higher consumption)

• Primer then 8-10mm high strength, self–levelling

screed

• Makes floor “future proof” for many different floor

coverings

• All components must be used, including screed

• Only for smaller areas, on larger areas it is more

economical to shot-blast



Screeds and floor finishes


Moisture Mitigation – Controlling water vapour in

concrete floors

PCA International Conference 2019



Controlling Water Vapour in Concrete Floors - Property Care ...

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