The use of concrete admixtures

In the preparation process of concrete, mortar and paste, a small amount (not more than 5% of the amount of cement) can change the performance of concrete, mortar or paste, called concrete admixture. Adding appropriate admixtures to concrete can improve the quality of concrete, improve the performance of concrete, reduce the water consumption of concrete, save cement, reduce costs and speed up the construction progress. With the progress of technology, admixtures have become the fifth necessary materials in addition to cement, coarse aggregate, admixtures and water. Admixtures are an important measure to optimize the design of concrete mix ratio and improve the durability of concrete. Therefore, the newly revised "hydraulic concrete construction Code" (DL/T5144-2001) emphasizes that an appropriate amount of admixtures must be added to hydraulic concrete. Concrete admixtures can be divided into the following four categories according to their main functions: admixtures that improve the variable performance of concrete mixing. Including ordinary water reducing agent and high efficiency water reducing agent, air entraining agent and pumping agent. Admixtures for adjusting the setting time and hardening properties of concrete. Including retarding agent, early strength agent and accelerating agent. Admixtures to improve durability of concrete. Including air entraining agent, water repellent agent and rust inhibitor. Admixtures to improve other properties of concrete. Including expansion agent, antifreeze, coloring agent and so on. The commonly used admixtures of hydraulic concrete are mainly water reducing agents, retarding agents, air entraining agents and various compound admixtures, such as retarding water reducing agents or retarding high efficiency water reducing agents, early strength water reducing agents, air entraining water reducing agents, according to special needs, but also mixed with other types of admixtures, such as pumping agents, water repellent agents, antifreeze and so on. GB8076-1997 "Concrete admixture", DL/T5100-1999 "hydraulic concrete admixture technical regulations" and other national and industry standards have strict requirements for the performance indicators and technical regulations of these admixtures, which can be selected according to the different needs of concrete.