How to Repair Hairline Cracks?

In this article, we will discuss how to repair hairline cracks on concrete surfaces.

Concrete is a composite material that is composed of a mixture of fine and coarse aggregates bonded together with biding material which hardens over time.

The binding material mostly includes fluid cement paste, lime putty, lime, etc.

Hairline cracks are seen on the freshly poured concrete. The presence of hairline crack is due to the phenomenon of plastic shrinkage. These cracks are very small- about 0.003 inches (0.08 mm) in width and can be very shallow that look like a single hair.

The line crack can be observed in walls, plaster, ceiling, etc.

  A. How to Repair Hairline Cracks?  

The stages used in the rehabilitation of hairline cracks in concrete are noted below:

1. Cleaning of Crack

This is the first and earliest phase in the repair of hairline cracks in the concrete. A check of the crack is carried out and if any oil or stains have infiltrated the crack and have discolored the concrete, the stains will have to be managed before fixing the crack.

2. Selection of Sealant

The sealant is used as a filler material that is infiltrated into the crack. The perfect sealant must maintain low surface tension and low viscosity. These two characteristics permit the liquid sealer to move deeply into the crack.

Crack repair materials for concrete are usually polymer-modified cement grouts, silicone or latex caulking, or epoxies. Polymer-modified cement grout is the typical material utilized to seal pinholes and voids in concrete at the time of manufacture. If cracks occur before the concrete is filled, this is usually the material utilized to repair them.

3. Application of Sealant

The selected sealer is applied on the substrate by using a squeegee and/or in combination with a roller. The use of sealant must be done for a minimum of 5-10 minutes to make sure of penetration.

4. Curing

Proper curing must be ensured to complete the hardening of the sealant. The warmer the temperature, the faster the curing, the lower the temperature, and the longer it will take.