Definition and classification of concrete admixture

definition-and-classification-of-concrete-admixture

 

According to the national standard GB8075, the definition of admixture is: concrete admixture is a substance mixed in the process of mixing concrete to improve the performance of concrete, and the mixing amount is not more than 5% of the cement quality (except in special circumstances).

 

Concrete admixtures are classified into four categories according to main functions:

1. Additives to improve the rheological properties of concrete mixture. Include various water reducing agents, air entraining agents and pumping agents. Water reducing agent has the characteristics of increasing concrete fluidity and improving workability. Such as polycarboxylic acid superplasticizer

● Super water reducing effect for cement and gypsum based material applications

● Low dosage compared to traditional water reducing agent

● High dispersion, fluidity and workability

● Improvement of early and final strength of cement based system

 

2. Additives to adjust the setting time and hardening performance of concrete. Include retarder, early strength agent and accelerator. Retarders can prolong the setting time of concrete and reduce the hydration heat. Such as Protein gypsum retarder, tartaric acid, tartar potassium sodium and so on.

Early strength agent can improve the early strength of concrete, reduce the dosage of cement and shorten the curing time. Such as calcium chloride and sodium chloride.

 

3. Admixtures to improve the durability of concrete. Include air entraining agent, waterproof agent and rust inhibitor. For example, polypropylene fiber can improve the crack resistance, temperature-induced microcracking, leakage resistance, impact resistance and seismic performance of cement or concrete.

 

4.Admixtures to improve other properties of concrete. Include defoamer, air entrainer, expansion agent, antifreeze, colorant, adhesive, etc.