How to repair concrete spalling
Concrete spalling is concrete that has had the top protective layer removed and has broken up, flaked, or become pitted.
It occurs when water that soaks into the concrete has no way to drain, usually due to precipitation combined with freeze/thaw cycles that cause the concrete slab to expand and contract. In addition, it can be caused by corrosion of the steel reinforcement bars or other metal, such as pipes or handrails, that are embedded in the concrete. Left unrepaired, the concrete spalling area can crack and sections can break away.
Concrete spalling can be prevented when concrete is poured by mixing the concrete with the correct amount of water – too much can weaken the concrete – and by allowing enough time for the concrete to cure. Sealing concrete can also help prevent concrete spalling.
Preparing the concrete
Avoid making repairs to concrete spalling unless the outside temperature is between 50 and 85 degrees F. Thoroughly clean the area to be repaired of all dirt, grime and loose stones using a pressure washer.
Rough up the surface with a wire brush so the mixture will maintain a stronger hold. If there are any deep depressions in the surface, fill them so they are more level with the area to be repaired. Allow any filled areas to dry completely before beginning the repair.
Repairing the concrete spalling
Polymer-modified concrete is ideal for the repair of concrete spalling as it excellent bond and tensile strengths. Mix the polymer-modified concrete per the package instructions. Be careful not to over-work, over-finish, or over-water the mixture.
Pour the mixture on the area to be repaired (no wider than 1 foot) and spread it with a squeegee. Then before the repair dries, use a trowel or edger to smooth the edges of the repair. Allow the repair to dry for 24 hours or as recommended by the manufacturer. If the surface is still uneven when the repair is completely dry, cover the area with another layer of the repair material.
For larger repairs, such as a sidewalk or driveway, make the repair in small sections approximately 1-foot wide. Polymer-modified concrete dries quickly and the surface can harden before you can smooth it. Pour the repair material, squeegee and smooth the repaired area before moving on to the next area to be repaired. Use weather stripping in joints to keep the repair material out of them.
With the right mix of polymer-modified concrete, correct application, and proper curing time, this repair should last a lifetime.
Tools and materials
- 3500 psi pressure washer
- safety glasses
- waterproof gloves
- cement broom
- edging tool
- wire brush
- polymer-modified concrete
- weather stripping