Causes, Prevention & Repair for Hairline Cracks

Posted by County Supplies on November 18th, 2019

Hairline cracks are most commonly noticed in the freshly placed concrete. It occurs due to the phenomenon known as plastic shrinkage. As its name, Hairline Cracks, these are very small, just about 0.03 inches.

What are the main causes of hairline cracks in concrete?

The main causes of hairline cracks in concrete are as follows:

• Plastic shrinkage
• Rapid depletion of moisture
• Water loss due to formwork or aggregate.
• Bleeding & sedimentation
• Negligence of the workers during construction.
• Alkali-Aggregate reactions.
• Type and the amount of cement and supplementary materials used
• The type and dosage of chemical admixtures.

How can hairline cracks be prevented in the concrete?

Some of the methods that can be used for preventing hairline cracks in the concrete are as follows:

• Fog nozzles can be used to saturate the air above the surface area.
• Plastic sheets can be used to cover the surface of the final finishing operations.
• Wind breakers can be used to lessen the wind velocity.
• Sun shades can be used so as to reduce the amount of temperature on the surface.
• Before placing the concrete, dampen the formwork and subgrade so as to ensure that excess of water is removed.
• Microfibers can be used so as to increase the tensile capacity of the plastic concrete.
• Curing process should be started as soon as plastic concrete is applied.

How can repair of hairline cracks be done in the concrete?       

• Cleaning of Crack: Inspection of the crack has to be taken place and check if any stains have been penetrated, then it has to be addressed. Inspection is the first step in the wall crack repair.
• Selection of Sealant: Sealant is used as a filler materials for filling the concrete in wall cracks. The best type of sealant must have low surface tension and low viscosity. These two features of the sealant allows the cracks to be penetrated deeply in the cracks.
• Application of Sealant: The sealant that you selected must be applied using a squeegee or with roller. The process must be carried on for 5-10 minutes so as to ensure that the sealant is deeply penetrated in the cracks. 
• Curing: It is important that proper caring is ensured so as to harden the sealant applied. Curing plays an important role in cracked wall repair. Remember that the temperature must be lower as possible so as hardening takes place at a faster rate.