Study on desulfurized gypsum used as cement retarder

The effects of desulfurized gypsum, heat-treated desulfurized gypsum and hydrogen peroxide modified desulfurized gypsum on the setting time of Portland cement were studied. The results showed that when the content of desulfurized gypsum after 80 °C heat treatment was 4% of Portland cement, the initial setting time was 136min, and the final setting time was 196min, which met the requirements of cement. Compared with natural gypsum, the retarding effect of desulfurized gypsum on Portland cement is more significant at the same dosage. The desulfurized gypsum treated with hydrogen peroxide can improve the stability of cement. When the proportion of desulfurized gypsum and natural gypsum is 1:1 and the content is 3%, it has a better retarding effect on Portland cement.