Admixture

Chemical admixture is a type of chemical compound that is added to concrete, mortar, or grout during the mixing process to modify its properties. Chemical admixtures are used to improve the workability, strength, durability, and other properties of the construction material. They are commonly used in the construction industry to enhance the performance of concrete and other building materials.

1. Plasticizers: The basic components are lignosulphonates, and their derivatives; acid of hydroxylated carboxylic acids, and their derivatives; and carbohydrates. When these components are combined in the right formula & proportions, makes plasticizing admixture which gives higher strength to the concrete by reducing water content by 5-12% keeping the same workability.

2. Super Plasticizers: Compounds used here include sulfonated naphthalene formaldehyde condensate, sulfonated melamine formaldehyde condensate, acetone formaldehyde condensate, and polycarboxylate ethers. Higher strength can be achievable by reducing water content by 12-30% keeping the workability the same as before.

3. Retarders: Main components are gypsum, sugar, dextrins, hydroxylated carboxylic acids or their salts, etc. A retarder is used to slow down the process of hydration so that concrete remains plastic and workable for a longer time.

4. Accelerator: Accelerating admixtures contain the following components: nitrates and nitrites, formates; carbonates; diethanolamine (DEA); triethanolamine (TEA); triisopropanolamine (TIPA); bromides; fluorides; alkali hydroxides, etc. They are added to concrete to speed up the onset of strength so that formwork may be removed earlier.

5. Air Entraining Agents: Air entraining admixture usually contains rosin resin, alkyl sulfonate, aliphatic alcohol sulfonate, protein salt, and petroleum sulfonate, among which rosin resin is widely used. This admixture is used to reduce the bleeding, and permeability of the concrete during placement.