Influence of Preparing Methods on the Properties of Anhydrite from Phosphogypsum

• 作 者: Huang Tao Peng Xiaoqin Wang Shuping Zhuang Ruiwen Qiu Feng
• 机 构: College of Material Science and Engineering, Chongqing University, Chongqing 400045, China;Sichuan R
• 出 处: The 14th International Congress on the Chemistry of Cement (
• 发表日期: 2015年8期
• 关键词: Phosphogypsum Anhydrite Preparing Method Hydration process

　　To reduce the negative influence of organic substance and P2O5 on crystal lattice, phosphogypsum was calcined into anhydrite at high temperature.The properties of anhydrite which were influenced by preparing methods,including calcining conditions and preparing procedure, were studied.The calcining conditions were consisted of calcining temperature (500~900℃), reacting time (0~4 h) and calcining methods.The latter one adopted in this study mainly included calcining from room temperature to the target temperature and calcining at the target temperature directly.Different preparing procedures, calcining before grinding (CG) and grinding before calcining (GC) were involved.The properties of anhydrite were expressed by flowability and specific surface area.The microstructure of the anhydrite were discussed by XRD, SEM and IR.Finally, the dissolution rate and hydration process of anhydrite, as well as physical performance of hardened plasters were also investigated.Results showed that direct calcining at 900℃ and reacting for 40 min were the optimum calcining condition as considering perfect flowability and practicability.And the specific surface areas of anhydrite-CG3 (prepared by calcining before 3 min grinding) and anhydrite-G30C (prepared by 30 min grinding before calcining) were similar.Whether under the action of chemical activators or not, the dissolution rate of anhydrite-CG3 was faster than the one of anhydrite-G30C.With chemical activators of alum 3.1 wt% and potassium sulfate 0.7 wt%, the initial setting time was appeared after the minimum resistivity of anhydrite-CG3 plaster but opposite for anhydrite-G30C plaster.Although dry compressive strengths of the hardened plasters were both higher than 30 MPa, 1 day compressive strength of anhydrite-CG3 hardened plaster was almost two times of the one of anhydrite-G30C hardened plaster, due to more amount of crystal nuclei providing by faster dissolution rate in hydration process.The different kinds of anhydrite could be used in different purposes.