Concrete repair is a vital aspect of any construction project, whether it’s reforming the edge of a residential concrete step or injecting a crack. A successful repair must be structurally sound, meet a specific design load and resist weathering over time. It should also be cost effective and easy to implement. Choosing the right concrete repair materials and procedures is crucial. Contractors should also consider the location of a repair, as well as its environment and any restrictions. For example, some repairs require material that sets quickly to limit downtime and others need to be durable for traffic or abrasion resistance.

The first thing a contractor should do before any concrete repair is to evaluate the issue. This includes inspecting the problem area and taking notes or photos. Contractors should also prepare the repair area by cleaning it with a pressure washer, using a wire brush to remove debris and delaminated concrete. It’s also important to make sure that the surface is free of oil, moss and dirt, which can inhibit proper bonding.

If the issue is sinking concrete, contractors should consider a polyurethane product such as PolyLevel. This system is injected beneath the sinking slab through tiny ports and expands into a structural foam that compacts the soil. It’s fast, noninvasive, aesthetically pleasing and doesn’t retain moisture. It’s also more efficient than the traditional method of concrete lifting, which involves drilling holes and inserting epoxy, says ICRI.

Before any repairs are made, the contractor must select a suitable repair material. Depending on the situation, this may be a cement mix, quick-setting nonshrink mortar or concrete, an elastomeric sealant or even polymer concrete. Choosing the right repair material should take into consideration factors such as its viscosity, elasticity, water resistance, freeze-thaw resilience and thermal expansion/contraction characteristics. It should also be compatible with the existing concrete and have a good chemical resistance.

Once the repair material is selected, the contractor should follow the manufacturer’s instructions to properly prepare and place the material. For example, for a cracked concrete repair, a backer rod should be stuffed into the crack to provide support and prevent the formation of thin shrinkage joints that could weaken the repair. The backer rod should be a diameter slightly larger than the width of the crack. It’s also a good idea to saw cut the repair site at an angle, which will mechanically lock the patch to the existing concrete and minimize the development of early-age shrinkage cracks.

When the patch is poured, a technique called “feathering” should be used to lightly blend the wet concrete into the surrounding dry concrete. Contractors should also use a tool to level the surface once it’s reached its proper height, and a trowel to create a smooth finish. For safety, it’s always wise to have a hammer and chisel nearby for chipping off any excess concrete. It’s also important to monitor the concrete repair over time, and perform any necessary maintenance as soon as possible to avoid further damage.