Things You'll Need
Concrete floor grinder
Paddle bit drill attachment
A well-finished concrete floor should be comfortable to use as well as strong and durable. During finishing, the floor is leveled and smoothed with a surface that you can walk across on your bare feet. With years of use though, a concrete floor will wear down, with the once smooth surface becoming roughened or damaged. Slab repair followed by grinding the surface smooth can help, but to regain the smoothness of the slab without unsightly repair patches you'll have to apply an overlay as well. By placing a thin overlay of concrete over the roughened slab, you can create an entirely new, smooth surface that also conceals any repair work necessary to remove the rough patches.
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Sweep the floor with a push broom to remove any loose dirt or debris. Wash away any ingrained dirt with a damp mop using a pH-neutral cleanser and warm water. Rinse away any cleanser residue with clean water and then allow the concrete to dry completely.
Find any damaged areas in the concrete, such as cracks or flakes and spalled areas. Remove any shards of concrete by breaking away the shards with a cold chisel and hammer. Place the tip of the chisel at the base of the shard and strike the chisel head with the hammer to cut through the shard. Clean any debris from the damaged areas with a wire brush and then remove the debris.
Brush the sides of the damaged area with epoxy gel and allow the epoxy to dry. It serves as a bonding agent between the concrete and the patching material.
Fill the damaged areas with epoxy resin to the surface level of the surrounding concrete floor. Use a putty knife to fill the crack or hole in the concrete, and then level the top of the resin with the floor using the knife. Allow the patch to dry overnight.
Check the plane of the floor using a leveling bar. Place the bar flat against the surface of the floor and then drag the bar over the concrete. Look under the bar as you drag it for dips or high areas in the concrete. Mark the areas with a piece of chalk for leveling.
Lower high spots to the level of the floor surrounding it by grinding the high area down with a concrete grinder. Turn the grinder on and run it over the high areas using a small circular motion to grind the rise down to the same level as the rest of the floor.
Texture the surface of the floor by lightly running the grinder over the entire floor in rows. Remove any grinding residue with the push broom.
Mix the self-leveling compound with water in a large bucket, using an electric drill with a paddle-bit attachment. Mix the compound to the consistency of oatmeal. Pour the compound onto the floor, filling the marked dips in the floor first, and then applying a layer about a ½-inch thick on the floor's surface. Spread the compound evenly over the floor with a squeegee. Wait four hours before stepping onto the smoothed new floor surface. Wait a full 48 hours for the surface to cure completely before putting the floor to normal use.
Wear long protective clothing, including work gloves, a face mask and safety goggles during the repair process to protect from concrete shards and harmful chemicals in the overlay material.