How to Repair Cracked Concrete

July 19, 2013

Concrete is a very strong building material that can cope with large amounts of stress, but it is possible for it to be damaged. However, there are several methods that can be used to repair damaged concrete. The technique that is chosen will depend on the extent and location of the crack.

Narrow concrete cracks are easier to repair than those that are wider, as long as the correct techniques are followed. Loose debris should be removed using a wire brush, and then the area should be washed using either a bucket of water or a hose. This will remove any remaining dust. Extremely narrow cracks, sometimes called hairline cracks, should be repaired by using a patching compound. This needs to be applied and smoothed over using a putty knife, to ensure that the surface remains level. If the patching compound that has been chosen is vinyl-based, then a bonding agent does not need to be applied over the top.

Slightly wider cracks can be filled by using a masonry filler that is applied using a caulking gun. It is easier to apply to small cracks than a patching compound would be, filling the crack accurately and effectively, with very little wastage.

Wide concrete cracks are more difficult to seal, but they must be repaired in order to maintain the safety and structural integrity of the building or other construction. Cracks allow water to seep in and will eventually lead to greater problems. The crack should initially be widened as the first step in the repair process. Using a hammer and chisel on the edges of the crack will help to create a more stable surface on which the concrete patch can be fixed. This will ensure that the patch remains in place and provides a long term solution to the damage. Once this has been done, the area should be cleaned using a wire brush, to remove any small pieces of loose concrete, and a damp cloth to remove dust. This is important because those small fragments will prevent the new concrete from adhering firmly.

Once the surface is clean, the concrete patching compound can be applied. A trowel should be used to fill the crack with the compound and ensure that the surface is smooth. You should also try to prevent any air bubbles from forming. Sealing it, once it is dry, would also be advisable, to reduce the risk of the patch absorbing any liquids or stains.

Epoxy injection is another method of sealing cracks in concrete, and is used when it would be difficult to apply the repair compound in any other way. The cleaning and preparation of the surface should take place as for the other methods. Epoxy injection can be used on cracks that are 0.05mm in width or greater, but if further movement is likely to occur, this method may not be suitable.