Basement floors are almost always made of concrete. Fixing cracks in your basement floor is little different than fixing cracks in any other concrete slab. Ideally, you want to discover the cause of the shift in your basement floor that led to the crack in the first place, but in many cases this simply isn't possible. Be certain, however, that you stop any water leaks that might be undermining your basement slab. Redirect snow and rain runoff away from your home to prevent possible erosion of the ground beneath your slab. The process for repairing cracks depends on their size.
Scrub a hairline with the wire brush. Clean everything out of the crack and remove any loose pieces of concrete, using a wet-dry vacuum.
Wash the crack with a degreaser or soap and water to remove any grease, oil or other contaminants that might prevent the new concrete from adhering. Allow the area to dry thoroughly.
Squeeze a bead of concrete filler into the crack. Smooth and feather it with a small trowel.
Inspect the crack after one hour. Add more cement filler if the filler has sagged into the crack. Smooth and feather the material with the trowel. Let the repair dry throughly.
Place a chisel at a 45-degree angle on the edge of a crack that is wider than 1 inch. Strike the chisel with a hammer, chipping off 1/8 to 1/4 inch on each side of the crack. This will ensure there is no loose concrete along the edges of the crack.
Brush the crack with the wire brush. Clean the crack completely with a wet/dry vacuum. Wash the area with degreaser to remove any grease or oil. Allow it to dry thoroughly.
Put on a pair of goggles. Mix concrete and water in a plastic bucket, according to the manufacturer's instructions.
Fill the crack with the concrete. Smooth and feather the material with your trowel. Allow the concrete to sit for one hour. Add more concrete if necessary to make the floor level. Smooth and feather the concrete with the trowel.
Spray the new concrete with water from a spray bottle at least twice a day. Do not walk on the new concrete for 14 days, allowing it to completely cure.