Invented in 1930 Air Entraining Cement is used for all types of concrete specially to improve resistance to freezing when exposed to water and deicing chemicals.
This cement is made by mixing a small amount of an air-entraining agent with ordinary Portland cement clinker at the time of grinding. The different types of air entraining agents are as follows
(a) Alkali salts of wood resins.
(b) Synthetic detergents of the alkyl-aryl sulphonate type.
(c ) Calcium lignosulphate derived from the sulphite process in paper making.
(d) Calcium salts of glues and other proteins obtained in the treatment of animal hides.
In powder, or in liquid forms these agents are added to the extent of 0.025–0.1 per cent by weight of cement clinker. There are other additives including animal and vegetable fats, oil and their acids could be used. Wetting agents, aluminium powder, hydrogen peroxide could also be used. Air-entraining cement will produce at the time of mixing, tough, tiny, discrete non-coalesceing air bubbles in the body of the concrete which will modify the properties of plastic concrete with respect to workability, segregation and bleeding. It will
enrich the properties of hardened concrete with respect to its resistance to frost action. Airentraining agent can also be added at the time of mixing ordinary Portland cement with rest of the ingredients.
