Abstract
Surface-active agents as chemical admixtures are widely used in concrete industry to improve the properties of fresh concrete. By the introduction of admixtures, the use of high strength concrete with low water content became popular, and the durability of concrete structures was largely improved. The most frequently used admixtures are (1) water-reducing and setretarding admixtures to reduce the water requirement of concrete or retard the set, or both [these include ligninsulfonic acid, hydroxylcarboxylic acids, carbohydrates, polyols, and the salts], (2)air-entraining admixtures to introduce a system of small air bubbles into the fresh concrete dung mixing [these are anionic surface-active agnets]. A new group of water-reducing admixtures, termed superplasticizers, has been introduced in the last few years [these are naphthalenesulfonic acid, specific ligninsulfonic acid, and polycarboxylic acid]. They are about twice as effective as the conventional admixtures.
