Additives for construction are a chemical compound that has a small share of cement and concrete but can significantly improve certain properties of concrete.
They only need to be blended in cement and concrete, which can generally reduce the amount of water added; improve the strength and durability of concrete; change the flowability of concrete and increase its operability; and save building materials and reduce engineering costs. .
The variety of additives is sensitive and the functions are different. However, there are mainly: water reducing agents, air entraining agents (AE agents, air entraining agents), retarders, accelerators, early strength agents, antifreeze agents, expansion agents, water repellents, anti-cracking agents, and composite additives.
(1) Water reducing agent is a kind of surfactant, which has many branches of molecular structure, short molecular group of hydrophobic group and strong polarity. Divided into common reducer and superplasticizer. The ordinary water reducing agent refers to an admixture having a general water reducing enhancement effect while maintaining the consistency of the concrete. Main ingredients: lignosulfonate, alkali lignin, sodium sulfonate humate, etc. Superplasticizer refers to an additive that has a significant water-reducing effect under the condition that the consistency of the concrete is constant. The main components are: methylnaphthalenesulfonate, naphthalenesulfonate, polynaphthalenesulfonate, β-naphthalenesulfonic acid formaldehyde condensate sodium salt, Gumalon-indene resin, sulfonated melamine formaldehyde resin, etc.
(2) Air entraining agent refers to an admixture capable of introducing a large amount of finely distributed fine bubbles in concrete to reduce the segregation of concrete, improve workability, and significantly improve the durability against frost. Main ingredients: rosin soap, rosin hot polymer, sodium alkyl sulfonate, sodium alkylbenzene sulfonate, linear alkyl sulfonate, lauryl sulfate, protein material, higher fatty alcohol derivative, AE minus Aqueous agent, sulfonated alkyl succinate, and the like.
(3) Early strength agent is an additive that can improve the early strength of concrete and has no significant effect on the late strength. Can be applied to projects under a variety of temperature conditions. Main components: chloride, thiosulfate, calcium chloride, ferric chloride, magnesium chloride and other chlorides, alcohol amines, potassium hydroxide, sodium hydroxide, formic acid and methyl salt, carbonate, aluminum cement, Sintered alum and so on.