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Hairline cracks are ordinarily observed in freshly placed concrete and their occurrence is owed to the phenomenon of plastic shrinkage. As the proper noun implies, these cracks are very pocket-sized- about 0.003 inches (0.08mm) in width and can be very shallow.

Fig 1: Hairline cracks in Concrete

Contents:

  • Causes of Hairline Cracks in Concrete
  • Prevention of Hairline Cracks in Concrete
  • Repair of Hairline Cracks in Concrete
    • ane. Cleaning of Crack
    • ii. Pick of Sealant
    • 3. Application of Sealant
    • four. Curing
  • ** Precautions

Causes of Hairline Cracks in Concrete

The main crusade backside the generation of hairline cracks in physical is plastic shrinkage which is the rapid depletion of moisture from the fresh concrete within its plastic state.

The causes for these cracks to show upwards can exist due to the variations in air temperature, physical temperature, relative humidity and wind velocity at the surface of the concrete. These factors can cause high rates of evaporation in either hot or common cold weather.

The other factors that accelerate the chances of hairline cracks are:

  1. Water loss due to absorption by subgrade, formwork or aggregate.
  2. Bleeding and sedimentation
  3. Poor workmanship and negligence
  4. Brine-Amass reactions.
  5. Type and content of Portland cement and supplementary cementitious materials (wing ash, silica fume,etc.)
  6. Type and dosage rate of chemical admixtures.
  7. Structure operations like screeding and finishing operations.

Prevention of Hairline Cracks in Concrete

There are many methods and techniques to prevent this type of scissure in example of rapid loss of moisture due to hot weatherand dry winds.

  1. Utilise of fog nozzles to saturate the air to a higher place the surface.
  2. Use of plastic sheeting to comprehend the surface betwixt the final finishing operations.
  3. Use of wind breakers to reduce the windvelocity, sunshades to reduce the surface temperature are too helpful.
  4. Dampen the subgrade and formwork, ensuringthat any backlog h2o is removed prior to placing concrete
  5. Applying a sprayable evaporation retardant
  6. Use of microfibers in the concrete mixture toincrease the tensile chapters of the plastic concrete.
  7. Starting of curing processas soon equally possible later on finishing.

Repair of Hairline Cracks in Concrete

The steps involved in the repair of hairline cracks in concrete are as follows:

1. Cleaning of Cleft

This is the showtime and foremost step in the repair of hairline cracks in the concrete. Inspection of the crack is done and if any oil or stains have penetrated the crack and have discoloured the concrete, the stains will have to be addressed earlier repairing the crack.

ii. Selection of Sealant

The sealant is a filler material that is penetrated into the scissure. The platonic sealant must have low surface tension and low viscosity. These two characteristics allow the liquid sealer to penetrate securely into the crack.

Crevice repair materials for concrete are often polymer-modified cement grouts, silicone or latex caulking, or epoxies. Polymer-modified cement grout is the typical textile used to fill pinholes and voids in concrete during industry. If cracks occur before the concrete is sealed, this is oftentimes the material used to repair them.

three. Awarding of Sealant

The selected sealer is practical on the substrate by using a squeegee and/or in combination with a roller. The application process must be carried out for at least 5-10 mins to ensure penetration.

iv. Curing

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

** Precautions

Repairing hairline cracks can be challenging because making the cracks vanish takes skill, forbearance, exercise and a good heart for colour matching. I definition of a hairline crack is a crack that hasn't opened up.

That means at that place is very petty room to fill it with anything simply a very low-viscosity liquid. Since about hairline cracks don't affect the structural integrity of a countertop, sealing and concealing the crack are the main goals of a repair.

Read More: Causes and Types of Cracks in Masonry Buildings and their Repair Methods