Influence Mechanism of Gypsum Crystal Types on Physical Properties of Portland Cement

The influence of gypsum crystal types on physical properties of Portland cement was studied by the series of design experiments that the anhydrite substituted varying proportions of gypsum with the help of the X ray powder diffractometer(XRD) and the scanning electron microscope(SEM),and its mechanism was studied too.The result was revealed that the difference of gypsum structures caused the difference of cement strength,and the cement strength of anhydrite was better than the gypsum.The formed needlelike ettringites in the dosed anhydrite hydrated cement have no effect on the cement strength,but are good for compactness of hydrated cement.But the formed columnar ettringites were thicker and bigger in the dosed gypsum hydrated cement than the anhydrite hydrated cement,which caused the bigger capillarycrack,and then caused that the dosed gypsum cement strength is lower.