4 methods to repair active cracks in concrete

The four most efficient methods to repair active cracks in concrete are presented below.

Active cracks, which can be hazardous, frequently appear in concrete structures. Those cracks may be stress-induced or can be triggered by freeze-thaw cycles or thermal expansion. They can propagate and expand over time posing severe threats for the stability of constructions.

The restoration of those structural flaws is critical but it is also a challenging task. Four optimal techniques to address the issue are the following: 

1. Drilling and Plugging through Crack

This method includes drilling a 50-70mm hole near the crack. This hole must be large enough to cut across the crack along its full length and is filled with grout. The purpose of this technique is to prevent the crack from propagating further in the concrete. This approach is cost- and time-effective.

If the priority is to make the structure more water resilient, then the cavity is filled with a waterproof material of low modulus.

2. Stitching of Cracks

The second practice that can be utilized to repair crack is stitching. In this technique, holes are drilled across the crack and then metallic wires are passed through the holes' ends which are anchored with grout. In this way, stress is distributed within concrete rather than concentrating in the crack plane.

3. External Pre-stressing

This technique involves the sealing of flexural cracks in reinforced concrete. It is used to prevent cracks from widening by adding compressive force to alleviate the tensile stresses.

4. Flexible Sealing

Last but not least, flexible sealing is a method that utilizes a bond breaker while the crack is filled with backup material.

Whichever method is selected, if the strength of the structural component must be restored, an expansion joint near the repaired crack should also be installed to avoid the occurrence of new cracks.