Is It Possible to Patch Cracks in a Cement Driveway?

Surface Preparation

• To determine the extent and size of the cracks, remove grass and weeds growing up through the concrete with a spade, weed eater or lawn-edging tool. Remove the decaying concrete from the cracks with a chisel and hammer, taking care to dig below the surface to expose the subterranean damage and make the crack wider beneath the surface than on top to give the patch strength and stability. Brush away the loose particles with a wire brush and sweep the entire driveway with a stiff broom to remove all the loose dirt and gravel. A garden hose with a strong spray attachment and good water pressure or a compressed air cleaning tool can also be used.

Washing and Debris Removal

• After the initial surface preparation, thoroughly wash the concrete by applying detergent and working it into the cracks and crevices with a broom or brush. Rinse the driveway with highly pressurized water until the runoff is clear and let the surface area dry. When the driveway is completely dry, use a shop vacuum cleaner to extract all the dirt from the cracks, as any remaining dirt will compromise the crack repair. A compressed air tool is not recommended for this step as it will blow dirt onto the surface of the freshly cleaned concrete.

Small Crack Repair

• Small cracks can be eradicated by one of two methods. To fix them with a patching compound, treat the crack and surrounding area with a primer or bonding adhesive to make the patching compound adhere to the surface. Roughly work the primer or adhesive into the surface with an old paintbrush and let it dry before applying the compound. Apply the patching compound in thin layers, letting each layer dry completely before proceeding with the next until the crack is filled. Sand the finished patch to match the rest of the driveway surface. If the cracks are very fine, they can be repaired with cement based paint and paste. Make thin cement paint with cement and water and brush the crack. Let it dry and apply the paste, made from one part cement, three parts sand and enough water to make a thick mixture. Apply the mixture to the patch and proceed as with the compound.

Filling Larger Cracks

• Cracks with widths in excess of 1/8 inch wide and depths more than 1/2 inch require foam backer rods to repair. After preparing and cleaning the surface, force the flexible rods down into the cracks about 1/4 inch deep and fill them with patching compound. Smooth the surface with a trowel, let it set for two or three hours and cover it with a sheet of industrial mil plastic. Keep the plastic in place with rocks or bricks and let the patch cure for a week, misting it daily to keep it slightly damp. Sand the finished surface as necessary.