Setting retarder refers to an admixture that delays the setting time of commercial concrete without significant influence on the later strength. Its main components are hydroxyl compounds, hydroxycarboxylates and their derivatives, and high sugar lignosulfonates.
Because of its water reducing effect, it is also called retarding water reducing agent. In addition, some inorganic salts such as zinc chloride, borate, and various phosphates also have a retarding effect. It is mainly suitable for continuous pouring of commercial concrete, mass commercial concrete, precast commercial concrete and pumped commercial concrete under high temperature, and its mixing amount is mostly 0.1% to 1% of cement consumption.
Characteristics of retarder
① It can reduce the release rate of heat of hydration of commercial concrete products.
As we all know, the early strength development of commercial concrete is closely related to the occurrence of cracks in commercial concrete. Early hydration is too fast and the temperature changes too quickly, which will easily cause cracks in commercial concrete, especially large-volume commercial concrete. Because the internal temperature of commercial concrete is not easy to spread, the temperature difference between inside and outside is large, which leads to the occurrence of commercial concrete cracks. Affected the quality of commercial concrete.
② It can reduce the slump loss of commercial concrete.
Practice has shown that the use of retarders containing lemon, sodium tripolyphosphate, sucrose and other ingredients can significantly extend the initial setting time of commercial concrete, and at the same time, the time interval between the initial setting and final setting of commercial concrete is also shorter, which reduces The slump loss of coagulation degree is not affected without affecting the early strength growth of commercial concrete. It has good application value, and there are more and more opportunities to be used in commercial concrete construction.