Research on using waste gypsum as cement retarder

The research on using waste gypsum from producing concrete admixture as cement retarder is presented. The results show that though the waste gypsum used independent can affect the setting time and the strength of cement, the waste gypsum mixed with natural gypsum is used as cement eretarder, and the content of SO3 is controlled correctly, the qualified cement can be produced in inherent technology conditions, and the high performance concrete can be made with this cement.