Concrete scaling, referred to as "spalling" by masons, can be caused by contact with salt or de-icing chemicals, over-mixing of wet concrete, poor curing methods, weak aggregate and exposure to subfreezing temperatures while wet. Scaling or spalling results in thin peeling or crumbling layers of concrete coming off the surface, and a dusty look and feel to the texture. Address minor scaling as soon as possible to salvage the concrete. Concrete with severe scaling is not salvageable and requires replacement. Signs of severe scaling include crumbling, scaling beyond 1/2-inch deep and exposed reinforcement wire or re-bar.
Things You'll Need
- Dust mask
- Protective eyewear
- Power drill or masonry grinder
- Wire brush attachment
- Power washer or sandblaster
- Stiff broom
- Epoxy-based concrete bonding agent
- Bucket, trough or wheelbarrow
- Curing compound
Don a dust mask, protective eyewear and gloves.
Use a power drill with a wire brush attachment to grind scaling off smaller areas or use a power washer to blast scaling off larger surfaces. Contractors and masons use a masonry grinder with a wire brush attachment to grind the surface of the concrete and expose nonscaling concrete or use a sandblaster to remove a scaling surface.
Sweep the area with a stiff broom to remove all concrete dust and debris. If you own a leaf blower, you can follow up with that to remove remaining dust.
Mix concrete in a bucket, trough or wheelbarrow with water according to the directions on the bag. Mixed, wet concrete will have a thick pastelike consistency. If the scaled section is very large, you may want to purchase ready-mixed concrete from a concrete delivery company.
Paint the surface with an epoxy-based concrete bonding agent. An epoxy-based bonding agent will help to seal exposed concrete layers and allow bonding of newly poured concrete. Have the concrete ready for pouring after the epoxy-bonding agent application, depending on the brand of epoxy-bonding agent, you will have 20 to 30-minutes to add new concrete and achieve a good bond.
Pour the concrete immediately over the still-wet epoxy-based bonding agent on the surface.
Smooth the concrete with a trowel and spread curing compound on the surface as soon as the water on the surface loses its water sheen. Shake a thin, even layer over the entire surface or use a liquid curing compound and spray on the surface with a sprayer in a thin, even layer.
Allow a minimum of 48 to 72 hours for concrete to harden before walking on the surface and seven days before driving on the surface. Concrete requires 28 days to fully cure, which typically marks the completion of the hydration process--the chemical reaction--between the water and Portland cement, the key ingredient in concrete.
Tips & Warnings
- Apply concrete sealer to 30-day cured concrete to help prevent scaling.
- Do not pour concrete in below freezing temperatures, or if you expect freezing temperatures to occur during the curing period.
- "Masonry"; Time Life Editors; 1977
- "The Contractor's Guide To Quality Concrete Construction"; American Concrete Institute; 2005
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