Gypsum in cement is mainly used to delay the setting time of cement, which is conducive to concrete mixing, transportation and construction. If there is no gypsum in cement, concrete will set rapidly in the mixing process, resulting in no mixing and construction.
The action of gypsum:
1.Gypsum reacts with cement tricalcium aluminate to produce ettringite, which prevents tricalcium aluminate hydration and plays a retarding role in coagulation.
2. Gypsum reacts with cement tricalcium aluminate to produce ettringite, so that cement has a dense empty structure and give cement with high strength.
3. Gypsum reacts with cement tricalcium aluminate to produce ettringite,which can make the cement produce continuous expansion effect to compensate for the cold shrinkage cracks of the structure in the late stage, so as to extend the service life of the structure.
