Defining Surface Defects on Concrete Horizontal Slabs, Surface Treatments and the Remediation

of these Surface Defects

W.R. MEADOWS, INC.

Cementitious Technology

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Lets start with the basics:

DefinitionsCement = Powder

Cement + Water = PastePaste + Sand = Mortar

Mortar + Stone = Concrete

A chemical reaction takes places when the water is mixed with the cement

The chemical reaction starts a crystal-type growth in the cement

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BAD WATER

GOOD WATER

The Water to Cement Ratio Controls Strength. As the W/C ratio increases, compressive strength decreases, by

as much as 50%.Severe environments ACI 201.2R – 0.45 w/c

0500

100015002000250030003500400045005000

Strength

w/ c 0.4w/ c 0.5w/ c 0.6

Properties Effected by Water to Cement Ratio & Curing

• Compressive Strength• Tensile Strength• Flexural Strength• Abrasion Resistance• Freeze-Thaw Resistance• Scaling Resistance• Porosity• Cracking

Durable Concrete

• ACI 201.2R-08, “Guide to Durable Concrete”

– Outlines procedures to design and place durable concrete.

Some Common Concrete Flatwork Surface Issues

• Surface Scaling• Popouts• Dusting• Delamination

Surface scaling

• ACI 201.1R, “Guide for Conducting a Visual Inspection of Concrete in Service” defines scaling as:– local flaking or peeling away of the near-surface

portion of hardened concrete or mortar. Which can vary from light to very severe with loss of coarse particles greater than 20 mm (7/8”).

Surface Scaling – Typical Causes• Inadequate or no air entrainment. (Concrete with

proper entrained air will still scale for the following reasons)

• Improper Curing• Deicing salts on newly placed concrete or excessive

deicing salts on concrete with poor surface strengths.

• Concrete finished while bleeding or over worked.• High degree of freezable water content (late

season pours)

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Surface Scaling – Application Hints During Concrete Placement

• Ensure proper air-entrainment for environment.

• Do not use de-icing salts on new concrete, or excess de-icing salts on old concrete.

• Do not perform any finishing operations with water present on surface.

• Cure the concrete.• Seal the concrete.

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Popouts

• ACI 201.1R, “Guide for Conducting a Visual Inspection of Concrete in Service” defines popouts as:– The breaking away of a small portions of a

concrete surface due to localized internal pressure that leaves a shallow, typical conical, depression with a broken coarse aggregate at the bottom.

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Surface Popouts – Typical Causes

• Use of non durable aggregates.• Improper curing.• High degree of freezable water content.• Popouts may occur without freezing and thawing

– Again, caused by internal pressures, but not by freezing and thawing / deicing salts, but by some deleterious reaction between the aggregate and cement alkali.

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Surface Popouts – Application Hints During Concrete Placement

• Ensure that the aggregate is suitable for the environment.

• Properly cure the concrete.• Seal the concrete.• Avoid sealing if reactive aggregate is known.

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Dusting

• ACI 201.1R, “Guide for Conducting a Visual Inspection of Concrete in Service” defines dusting as:

– The development of a powdered material at the surface of hardened concrete.

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Dusting – Typically Causes

• Any finishing operation performed too early.• Use of additional water on the surface.• Inadequate ventilation.• Insufficient curing.• Inadequate protection from freezing.

Dusting – Application Hints During Concrete Placement

• Allow concrete time to adequately bleed.• Do not use additional water to finish surface.• Ensure proper ventilation of heaters.• Properly cure the concrete.• Do not apply when temperature is expected

below freezing.

Delamination

• ACI 201.1R, “Guide for Conducting a Visual Inspection of Concrete in Service” defines delamination as:– A separation along a plane parallel to a surface, as

in the case of a concrete slab, a horizontal splitting, or separation with in the slab in a plane roughly parallel to, and generally near, the upper surface. [from the base slab by a thin layer of water or air].

Delamination – Typical Causes

– Finishing the concrete too early prior bleeding or when the concrete is still bleeding.

– Over working and/or densifying the surface during the finishing operation.

– Cool sub-grade or concrete, retards or delays bleeding.

– Air content is too high for application.– Rapid drying of surface which causes the concrete

to appear ready for finishing.

Delamination – Application Hints During Concrete Placement

• Allow the concrete sufficient time to bleed.• Be wary of concrete that appears ready for

final finishing before expected.• Use accelerators in cold weather.• Do not use air-entrained concrete on hard

troweled floors.• Protect from rapid drying.

Preventive Chemical Treatments

• Curing Compounds• Linseed Oil Treatments• Curing and Sealing Compounds• Penetrating Sealers• Silicates (Floor Hardeners)

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Curing Per ACI 201.2R-6• Will ensure strength development of paste at

surface.• Will also decrease the porosity of concrete,

thereby lowering content of freezable water.• Help maintain a concrete RH below 85 percent

• Adequate curing will ensure that proper minimum strength development of concrete is achieved.– 500 PSI single freeze episode– 3,600 PSI multiply freeze episodes

Curing Compounds• Applied after bleeding and final finishing. • ASTM C 309 (ACI 308)

– Type I (Non-pigmented)– Type II (White pigmented)

• Class A – No vehicle restriction• Class B – Resins • Application rate – 200 sq. ft. / gal.• Film Dries in as little 4 hours.

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If the cement does not get enough water, the reaction stops and the concrete will not reach its

designed strength. ACI 201.2R – Min. 3,600 PSI

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

Strength

DesignedStrength

Strengthw/ o propercuringRapidmoistureloss

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Linseed Oil Treatments

• Linseed penetrating and anti-scaling compound – is a specification-grade formulation of boiled

linseed oil in mineral spirits specifically compounded to prevent the scaling of concrete. This type of penetrating compound is recommended by many state Departments of Transportation for prolonging the life cycle of concrete exposed to water, de-icing salts and other destructive materials.

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Curing & Sealing Compounds

• ASTM C 1315 – Acrylic / Styrene Acrylic• Passive protective barrier

– Minimum 25% Solids Content– Typically do not yellow– Reduces (per ACI 201.2R) the amount of freezable

water in the matrix and the salt content.– Enhances appearance.– Can be used as a curing compound.

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Penetrating Sealers

• Governing Specification– NCHRP 244– ALBERTA Ministry of Transportation Specification

• Common Chemistries– Silane– Siloxane

Penetrating Sealers

• Chemical protective barrier– Water-based or solvent-based– Typically is applied at 100 – 200 sq. ft./gal.– Penetrates in to concrete / long lasting

• Up to 5mm (3/16”)

– Allows moisture to evaporate while keeping moisture from / chlorides out.

Penetrating Sealers

• High degree of protection from freezable water and reduces salt content

• Reduces water intrusion up to 90%• Reduces chloride penetration up to 99%

• Passes scaling resistance per ASTM C 672 on non-air entrained concrete

• Little or no affect on surface appearance• Highly breathable

SilicatesFloor Hardener & Densifier

• Eliminates dusting in most cases.• Penetrates and chemically reacts with the soft

weak layer of concrete (Dust) to form a hard & Dense, highly abrasion resistant surface.

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Normal 3-6 mm

SilicatesFloor Hardener & Densifier

• Sodium based– Existing concrete, must be washed off.

• Lithium based– Fresh concrete, may be left on.

• Increases abrasion resistance by over 50 Percent.

• Reduces staining.• Polishes, thereby increasing reflectivity.

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UNTREATED

TREATED AND BURNISHED

And if all else fails...Restore

• Polymer Modified Cementitious Thin Overlay Repair Mortars

• Self-leveling Cementitious Toppings• Concrete Polishing

POLYMER MODIFIED CEMENTITIOUS THIN OVERLAY REPAIR MORTARS

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Self-Leveling Cementitious Toppings

• Characteristics of a standard self-leveling underlayment, but are true wearing surfaces.

• Specialized Cement Technology• Typically interior applications.• Highly architectural.

Application of a SL Topping

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Floor Polishing

• Restore: Scaling, Dusting & Delaminations• Mechanically removes the deteriorated layer

of concrete.• Used with Floor Hardeners, leaves a dense

wear resistant surface.

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Metal bond

Resin bond

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Summarize

• Read and follow ACI 201.2R-08, “Guide to Durable Concrete”

• Do not finish concrete too early, this may cause– Scaling, dusting, delamination, popouts

• Properly curing concrete may eliminate– Scaling, dusting & popouts

• Sealing the concrete may eliminate– Scaling, dusting & popouts

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Summarize

• If you don’t– Properly finish the concrete

• And– Cure the concrete

• Or – Seal the concrete in harsh environments

• You will be repairing the concrete.

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Thank You

THANK YOU