The concrete floor in your garage is susceptible to cracking just like a driveway or walkway. Once cracks develop, it is necessary to patch them quickly to prevent moisture from getting under the concrete. Repairing cracked concrete on a garage floor requires filling the crack with an epoxy that expands and contracts with the concrete. The epoxy works much like an expansion joint in concrete. Epoxy fillers and patching cement are available at home improvement centres and hardware stores.
Brush the crack on both sides with a stiff steel bristle brush. This removes any loose cement that could interfere with the repair. Sweep the crack and the area around the crack with a broom to remove debris. Vacuum the crack out with a wet/dry vacuum, if you have one available.
Fill the crack with epoxy filler and a caulking gun. Squeeze the filler into the depth of the crack along the entire length. Continue filling the crack with the epoxy filler until it is even with the floor surface.
Spread the epoxy evenly at the surface with a trowel. Allow the epoxy filler to cure completely. Usually 24 hours is ample time for curing.
Dip a trowel into the bucket of patching cement and spread the cement evenly across the length of the crack. Trowel the cement smooth and allow it to cure 24 hours before driving your car over the patch.