Repair Concrete Slab Patio
The technique for patching cracks will depend on the size of the crack. Narrow Cracks. Remove any loose debris from the crack and surrounding area with a wire brush and broom. Narrow cracks can be filled with a masonry crack filler that comes in a cartridge designed to be used in a caulking gun. Or you can fill the cracks with a vinyl concrete patching compound applied and smoothed with a putty knife. Vinyl concrete patching compound does not require the use of a bonding agent. Wide Cracks.
Use a small sledgehammer and chisel to undercut the edges of the crack. Undercutting the crack makes it wider at the base than at the surface, providing a mechanical method of 'keying' the patch in place for a more secure and permanent repair. Clean the area in and around the crack with a wire brush and broom. Wash the area with a stream of water. Mix vinyl patching compound as directed by the manufacturer and trowel the compound into the cracks. Tamp the mixture to remove air pockets.
If you use patching mortar instead of vinyl patching compound, either mix it with bonding agent instead of water or coat the edges of the surface to be repaired with bonding agent. Smooth the mixture with the trowel. When the patch has set (see manufacturer's instructions for the patch compound you are using), smooth or brush the surface to match the surrounding area.
Repair Concrete Slab Floor
In the past, when a concrete patio or driveway started to show serious signs of aging, using a jackhammer or bringing in a bulldozer were the only repair options.