Study on phosphogypsum as cement retarder

The phosphate especially soluble phosphate in the phosphogypsum can overly retard the setting process of the cement. In this paper two kinds of solidified phosphogypsum are prepared. When they had cured 6 d and merged in water for 24 d , They had a compressive strength above 2.0 MPa. They could be added in the cement easy and steadily. Cement prepared with solidified phosphogypsum as retarder had similar setting time as cement prepared with natural gypsum and higher strength than them.