That means there is very little room to fill it with anything but a very low-viscosity liquid. One definition of a hairline crack is a crack that hasn't opened up. Repairing hairline cracks can be challenging because making the cracks vanish takes skill, forbearance, practice and a good eye for colour matching. The warmer the temperature, faster the curing, lower the temperature, the longer it will take. Proper curing must be ensured to complete hardening of sealant. The application process must be carried out for at least 5-10 mins to ensure penetration. The selected sealer is applied on the substrate by using a squeegee and/or in combination with a roller. If cracks occur before the concrete is sealed, this is often the material used to repair them. Polymer-modified cement grout is the typical material used to fill pinholes and voids in concrete during manufacture. These two characteristics allow the liquid sealer to penetrate deeply into the crack.Ĭrack repair materials for concrete are often polymer-modified cement grouts, silicone or latex caulking, or epoxies. The ideal sealant must have low surface tension and low viscosity. The sealant is a filler material that is penetrated into the crack. 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 before repairing the crack. This is the first and foremost step in the repair of hairline cracks in the concrete. The steps involved in the repair of hairline cracks in concrete are as follows: 1. Starting of curing processas soon as possible after finishing.Use of microfibers in the concrete mixture toincrease the tensile capacity of the plastic concrete.Applying a sprayable evaporation retardant.Dampen the subgrade and formwork, ensuringthat any excess water is removed prior to placing concrete.Use of wind breakers to reduce the windvelocity, sunshades to reduce the surface temperature are also helpful.Use of plastic sheeting to cover the surface between the final finishing operations.Use of fog nozzles to saturate the air above the surface.There are many methods and techniques to prevent this type of crack in case of rapid loss of moisture due to hot weatherand dry winds. Prevention of Hairline Cracks in Concrete Construction operations like screeding and finishing operations.Type and dosage rate of chemical admixtures.Type and content of Portland cement and supplementary cementitious materials (fly ash, silica fume,etc.).Water loss due to absorption by subgrade, formwork or aggregate.The other factors that accelerate the chances of hairline cracks are: These factors can cause high rates of evaporation in either hot or cold weather. The causes for these cracks to show up can be due to the variations in air temperature, concrete temperature, relative humidity and wind velocity at the surface of the concrete. The main cause behind the generation of hairline cracks in concrete is plastic shrinkage which is the rapid depletion of moisture from the fresh concrete within its plastic state. Prevention of Hairline Cracks in Concrete.
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