Abstract：The cement retarder (phosphogypsum) was ultra-fine processed by superheated steam powdered jet mill.The phosphogypsum (PG₀) and superfine phosphogypsum (PG₃₅) which mass fraction were 4%were mixed in cement clinker (C) to prepare a cement-based material respectively.And the effect of ultrafine phosphogypsum as retarder on the properties of cement-based materials were studied.The particle size and moisture content of phosphogypsum after ultra-fine processed are significantly reduced, and the setting time of cement-based materials prepared from superfine phosphogypsum conforms GB175-2007.The compressive strength for 28 d of cement hardenite with superfine phosphogypsum is significantly increased.The porosity is decreased by 11.32%and the rate of hydration heat release is accelerated.XRD and SEM analysis show that the hydration products of PG₀-C and PG₃₅-C cements are Ca (OH) ₂and C-S-H gels.However, the ettringite is also formed in the hardenite of PG₃₅-C cement, which results in a much denser microstructure of the hardenite.

Keywords：superheated steam powdered jet mill; superfine phosphogypsum powder; retarder; cement-based materials