Figure 1 - chisel expanding crack in concrete slab for repair
- Using a cold chisel, as shown in Figures 1 and 2 and a hammer, chisel the crack in a manner that will create a inward angle cut or depression below the crack. This gives the filler a better area for bonding.
Figure 2 - Cold chisel
- Using an electric drill with a wire wheel attachment or a wire brush, as shown in Figure 3, remove all loose debris from the crack. A hose or power washer can also be used to remove debris from inside the crack. If water is used for cleaning, ensure the crack is completely dry prior to using the concrete patch patching material.
Figure 4 - Filling crack in concrete slab
Use a vinyl or acrylic reinforced patching compound, as shown in Figure 4. Read and follow the manufacturer's instructions. Use a trowel to fill the crack with the compound and then feather the edges with the trowel and a brush. Try to get the patching compound as flush to the surface of the concrete as possible.
Variation when repairing a large crack:
Figure 5 - Filling extra wide crack in concrete slab
Follow the instructions for a small crack as previously defined. Place sand into the crack and compress as best you can. The sand should be about 0.5 inch from the surface of the concrete slab, as shown in Figure 5. Use a pre-formulated concrete repair product available from any DIY home improvement center or hardware store. Make sure that the product has a concrete fortifier in its blend. Use a trowel to fill the crack and feather to the previous concrete surface appropriately.