Many homeowners pour a concrete slab as a pad for a driveway, patio, garage floor or a base for a shed. Concrete offers a stable and secure base for construction and acts as an area to park cars on, entertain on or relax on. Large cracked depressions, sunken areas or other damage from a large fallen object or the result of no room for contraction or expansion are all reasons to try to patch the hole in concrete rather than to remove and replace the concrete slab. Accidents or improper installation can cause severe damage to a concrete driveway, concrete garage floor, basement floor or patio and ruin the look of the area. Large holes or damage in concrete is also dangerous because they can be the cause of a trip and fall accident. It is much less expensive to patch a concrete slab than it is to break it up, remove it and pour new concrete.
Isolating the Damage
Put on a hard hat, safety glasses and a dust mask.
Break the damaged area of concrete up with a sledge hammer or rent a jack hammer.
Break the concrete up into smaller manageable pieces that you can easily lift and carry away. Jack hammers can be rented at tool rental stores, home improvement stores and hardware stores. If you choose to break the concrete with a jack hammer wear ear protection.
Preparing the Damaged Area for a Patch
Remove the broken pieces from the hole by hand or scoop them out with a coal shovel.
Use a cold chisel and a hammer to chisel the edges of the hole and slope them towards the center. A cold chisel is a chisel designed to be used on masonry surfaces.
Use a wire brush to rough up the edges of the hole and to break away any loose pieces of concrete.
Use a shovel to dig the hole about 4 inches below the bottom part of the remaining concrete.
Pack the dirt in the hole down with a tamper or use the end of a 2 by 4 piece of lumber.
Add crushed stone to the hole. Use enough to make it even with the bottom of the concrete slab.
Cut wire reinforcing mesh to closely fit the inside of the hole.
Lay the wire reinforcing mesh over the crushed stone.
Pouring the Patch
Mix concrete according to the directions on the ready mix bag or be ready for a pour if you are using pre-mixed cement from a truck.
Coat the edges of the hole with an epoxy concrete bonding agent.
Add concrete to the hole beginning at the epoxy coated edges. The concrete needs to be added to the hole while the epoxy is still wet.
Make the concrete slightly higher than the existing concrete.
Use a 2 by 4 piece of lumber that is long enough to fit across the entire hole. Lay the 2 by 4 down and push it across the hole to remove excess concrete from the patch.
Allow the concrete to begin to harden, sprinkle with water and cover the patch with plastic to keep the moisture in.
Curing the Patch
Every day for a week, check the patch to make sure it has not dried out, sprinkle with water as needed and keep it covered.
Remove the plastic and allow three days for the concrete to cure before using.