There are a variety of types of admixtures that can be used to improve or alter the properties of concrete. These admixtures can reduce the water content of cement, increase workability, delay setting time, retard bleeding, and enhance the strength of concrete.

During the mix design and construction process, various admixtures are added to the concrete mixture in order to adjust its properties. These admixtures are classified according to their functions, which include corrosion inhibition, shrinkage reduction, alkali-silica reactivity reduction, workability enhancement, bonding, damp proofing, and coloring.

types of admixtures

Air-entraining admixtures encourage microscopic air bubbles to form and stabilize these bubbles during the mixing of fresh concrete. These bubbles increase the fluidity of the mixture and significantly increase the resistance of the resulting concrete against freezing-thawing damage and deicing chemicals.

Water reducing, retarding, and super plasticizing admixtures lower the water content of cement and reduce the setting time of concrete. They also maintain workability with a decreased water-cement ratio.

Retarding admixtures are added to concrete in situations where cement sets too fast and creates problems such as poor bonding between surfaces, discontinuities in structure, and voids. These admixtures include calcium sulphate, gypsum, starch, cellulose products, common sugar, salts of acids, and other water-reducing agents.

Gas-forming chemical admixtures, such as aluminium powder, activated carbon, and hydrogen peroxide, help to produce lightweight concrete and strengthen bonds between reinforcing bars and grout. They reduce or eliminate settling and are useful for grouting under machine bases.