How to Seal Concrete Floor Cracks While It's Wet

Slip on a pair of chemical-resistant rubber gloves and safety goggles before preparing a mixture of 1 tablespoon tri-sodium phosphate, or TSP, and 1/2 gallon warm water. Stir the ingredients until the TSP powder is completely dissolved.

Dampen a plastic bristled brush with the mixture and wipe down the cracked area to remove any grease, grime, efflorescence and loose mortar. Rinse away the TSP with plain water.

Place a chisel into the crack and gently tap it with a hammer to remove any loose cement or mortar. Continue to gently chisel away the crack until it is approximately 1/4 inch wide. Wipe away the loose mortar and cement with a separate plastic bristled brush.

Mix the hydraulic cement according to the package directions in a plastic container. Do not mix any more than you can use in 15 minutes as the cement begins to dry very quickly.

Wet the crack with plain water, if it isn’t already damp, and begin to pack in the hydraulic cement with a pointed trowel. Continue to work the hydraulic cement into the crack until it is completely full. Smooth the excess cement with the trowel immediately.

Allow the hydraulic cement to cure until according to the package directions, or at least 24 hours, before sealing the patched concrete. Using a natural-bristled paintbrush, cover the area with a thin layer of concrete sealant.

Allow the first layer of sealant to cure for at least 12 hours before applying a second and, if necessary, third coat of the product.