Quality worthy of time
Quality worthy of time

Chemical admixtures for concrete

Admixtures for concrete roads and airfields. Pore-forming (air-entraining) admixtures (2)

Admixtures for road construction are preferably used for production of concrete mixes of enhanced frost resistance and water impermeability. These admixtures are classified as air-entraining agents and plasticizers and refer to the category of surfactants. The class of air-entraining admixtures was discovered by chance in the late 30-s, when it was discovered that road slabs produced in New-York state and containing some types of cement turned out to be more frost resistant and watertight compared to concrete slabs containing other cements. The analysis showed, that in the course of cement grinding, substances containing fish and animal fats and calcium stearate were added producing air-entraining action. Since that time, air entrainment has become a significant factor in increas

Accelerating and retarding admixtures (2)

Under normal humidity conditions, the rate of hardening of concrete to optimum strength is about 28 days. However, builders often cannot wait so long. If the time of concrete gaining its grade strength should be reduced as much as possible, special chemical compounds, called accelerators, are used. Accelerators multiply increase the rate of concrete hydration and can be used also at low ambient temperatures. Thanks to their use, the terms of putting the facility into operation can be significantly reduced. How to accelerate the setting of concrete There are two most common methods to accelerate the setting of concrete – its isothermal heating and the use of accelerators. Isothermal heating is effective, but is associated with significant financial costs. This method invol

Antifreeze admixtures (3)

Admixtures for winter concreting are special synthetic compounds used for concrete works in cold seasons. Due to their application concrete mix fully retains its properties at ambient temperatures from +5 0С to -25 0С and below. Admixtures for winter concreting also: accelerate concrete setting time; make it more plastic and workable; increase the bulk density of concrete; increase its water and corrosion resistance. Application of special admixtures is more expedient and cost effective compared to steam or electric heating of concrete. The costs for acquiring these compounds are about 1.5 times lower than the costs of heat and electricity that the contractor has to bear. Thanks to modern admixtures the co