Effect of Soluble Phosphorus on the Mechanical Properties of α-Hemihydrate Gypsum

Preparation of α-hemihydrate gypsum crystal is an approach for utilization of phosphogypsum (PG), but the soluble phosphorus impurities in PG have a crucial influence on the performance of α-hemihydrate gypsum. In this article, different forms of soluble phosphorus (H3PO4, H2PO4− and HPO42−) on the setting time and mechanical properties of α-hemihydrate gypsum were studied, and the influence mechanism was clarified by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results show that the low-content of soluble phosphorus could prolong the initial setting time and final setting time of α-hemihydrate gypsum. The soluble phosphorus has a negative effect on the mechanical strength of α-hemihydrate gypsum; especially when the content of soluble phosphorus exceeded 0.1