磷建筑石膏的物化性能及水化特性

Physical and chemical properties and hydration characteristics of building phosphogypsum

采用热分析仪、SEM、XRD和氮吸附等分析测试方法,系统研究了磷石膏经水洗预处理与直接煅烧制备的磷建筑石膏的物化性能与水化过程。结果表明:磷建筑石膏颗粒为层板状结构、呈多粒级分布、疏松多孔、内含许多狭缝,导致较高的需水量;难溶杂质主要为石英、硬石膏、磷酸氢钙和硫化铁,其中磷酸氢钙在半水石膏颗粒中均匀分布,以固溶体形式存在,水化过程中逐渐释放导致pH值降低。磷石膏未经水洗预处理制备的磷建筑石膏凝结时间短、水化结晶粗大、硬化体孔径粗化、强度偏低。

Thermal analyzer,SEM,XRD and BET were used to characterize the physical and chemical properties of building phosphogypsum and its hydration process.The results indicate that the particles of building phosphogypsum are distributed in multiple gradations and are laminate structure containing many pores and slits which can be responsible for its high water requirement.The insoluble impurities in building phosphogypsum are mainly quartz,anhydrite,calcium hydrogen phosphate and iron sulfide.Moreover,calcium hydrogen phosphate is uniformly distributed among hemihydrate gypsum particles presenting as solid solution,which is gradually released during hydration,resulting in the decrease of pH in solution.Building phosphogypsum prepared by phosphogypsum without the pretreatment of water wash sets fast and the final gypsum crystal are coarse leading to loose microstructure with lower strength.