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Repair cracks in concrete

Whether it is on the patio, in the garage or across the driveway, cracked concrete looks unsightly and if left unattended will only crack and crumble even more.


Proper maintenance of concrete floors often involves crack repair. Cracks in a concrete floor are caused by a number of factors including temperature changes, changes in moisture levels, stress loads (such as heavy traffic or heavy objects), ground or building movement, the hydration process of the concrete slab when it is curing, or poorly placed control joints. Cracks can also be caused when a concrete slab is poured on an unstable surface.

Cosmetic cracks in floors are generally easy to repair. It is important to repair cracks, because if left unrepaired they will spread and cause the concrete to become unstable. If not repaired before applying new coatings, such coatings will fracture along joints or cracks that are not properly addressed. For example: ceramic tiles applied to a cracked surface will eventual fracture across the tiles or break along grout lines.

Repair small cosmetic cracks in concrete

1. Use a cold chisel and a hammer to get rid of any large pieces in the crack. Hold the chisel at an angle and pound with the hammer to chisel out the crack. This is called 'keying' the hole to make the base or inside of the crack bigger than it is at the surface. Keying helps the new patching material bond with the old crack.

2. Once you've keyed the crack, it's important to clean up and get rid of dust and debris. Use a whisk broom then vacuum the crack thoroughly.





3. If you're mixing a concrete patch see the table below. High-strength concrete should be used for precast items such as flagstones, and heavy-duty floors such as workshops. Medium-strength concrete is suitable for light-duty floors,paths, patios and steps, driveways and carport floors. Mix according to the guidelines and then trowel the patch into the crack. Check the cracks in a few minutes to see whether the filler has settled. You may have to add some more if it doesn't look tight. Use a trowel to smooth out the cracks. Allow the filler to cure overnight or at least the duration recommended by the manufacturer. Then check it again to see if any additional patch is needed.

4. After patching the concrete, it's a good idea to seal it. Concrete easily absorbs stains, and sealing will prevent that. There are more than a few products available for concrete sealing, but a heavy-duty water-based polyurethane is a good choice.