Concrete Crack Repair: Understanding Why Concrete Cracks & How to Fix It

Concrete Crack Repair: Understanding Why Concrete Cracks & How to Fix It

Concrete crack repairs are sure to pop up on your ‘to do’ list at some point. After all, concrete is notorious for cracking. Luckily, there are things you can do to ensure longer lasting results and fewer concrete cracks. Starting with hiring an experienced professional to take care of repairs. It’s important to approach concrete crack repair carefully to prevent causing additional damages and deterioration. There are a variety of techniques used to patch cracks, and the method utilized should vary based on the surface you are working on, the extent of cracking, and if it is a walkable surface.

Why Does Concrete Crack?

Understanding why concrete cracks can help you proactively protect it against damages. There’s no way to 100% prevent concrete from cracking, as cracking is a natural part of the ageing process. Current technology has not produced concrete that is completely crack-free. That’s because by nature concrete expands and shrinks based on temperatures, humidity levels, and moisture. Concrete is prone to shrinking, which is the most common cause of cracks in young concrete surfaces. Irregular cracks are common and don’t necessary signal any underlying issues, although they can be unsightly.

To help reduce cracks, pressure on concrete is relieved by creating pre-planned cracks—technically known as control joints. As a result, when concrete shrinks, most cracks should occur in the control joint as opposed to throughout the slab.

Even with solid control joints, concrete is still prone to crack and freeze-thaw cycles are a leading reason why. When moisture seeps into concrete surfaces, it freezes and thaws with temperature fluctuations—concrete freezes around 18 degrees F. As this occurs, concrete is put under pressure as it expands. When temperatures creep back up around 35 degrees, moisture vaporizes and shrinks, reducing pressure on concrete. This continuous cycle puts pressure on concrete and leads to cracks, pits, and scaling.

The sun is another contributor to concrete cracks. Intense rays from the sun cause concrete to heat up and expand. When the sun disappears for the night, concrete reduces in size.

Repairing Wide Cracks Vs. Small Cracks

Different methods are applied for repairing wide cracks versus smaller or narrower cracks. Wider cracks must be undercut with a small sledgehammer and chisel. Further widening the crack helps produce a keyed surface to apply the concrete patch. All debris must be removed from the crack using a wire brush, vacuum, and damp cloth. Even the smallest particles can prevent proper adhesion. When ready, the properly mixed concrete patch is applied and smoothed out. It is recommended to seal surfaces after patching a crack, this helps prevent stains from absorbing into concrete.

Repairing small cracks is an easier task but one that should not go ignored. You don’t need to remove any excess concrete. Instead, simply remove debris from the existing crack. Hose out the area and let it dry before proceeding. A masonry crack elastomeric filler can be used to fill in smaller cracks. Filler must be properly applied and smoothed out.

Preventing Future Concrete Cracks

There is no way to prevent all concrete cracks, but there are some things you can do to reduce the risk of more severe cracking, and at least slow the progression of cracks.

  • Apply a solid acrylic silicone solvent-based sealant to concrete about once a year (frequency depends on traffic, exposures, etc.)
  • Have cracks repaired as soon as possible so they don’t have a chance to expand. Cracks also make it easier for moisture to seep inside and increase the damaging effects of freeze/thaw cycles. A variety of techniques are used to seal and stabilize cracks including applying an epoxy injection, routing, or dry packing.
  • Regularly clean concrete surfaces to prevent a buildup of abrasive chemicals and debris.