Combined Use of Phosphoric Acid Modified Steel Slag and Protein Material for Retarding of Β-Semi-Hydrous Gypsum

Building gypsum has the disadvantage of short setting time and fast hardening characteristics. Based on the systematic experiments, a combined retarding system of phosphoric acid modified steel slag (3%, gypsum-based) and protein-based material (Sika 200P 0.005%, gypsum-based) is proposed. The initial setting time of gypsum is prolonged to 206 min and the final setting time is 221 min. The retarding effect for desulfurization building gypsum is significantly better than Sika 200P, and the cost is greatly reduced.