净化磷石膏做水泥缓凝剂研究

Research on the Preparation of Cement Retarder by Purifying Phosphogypsum

为节约天然石膏资源和提高磷石膏综合利用率,选用净化磷石膏作为水泥缓凝剂,对其进行性能优化和力学强度研究。结果表明,净化磷石膏的最佳洗涤工艺温度为60℃,液固比为3∶1,搅拌时间为15 min,洗涤3次,添加0.5%生石灰陈化5 d再蒸养作为水泥缓凝剂。水泥试件的最佳配比为70%熟料、25%粉煤灰、5%水泥缓凝剂,试件的28 d抗折、抗压强度分别为8.45、49.49 MPa。X射线衍射(XRD)、扫描电镜(SEM)、傅里叶红外光谱(FT-IR)分析表明,掺入净化磷石膏后,其中的球形二氧化硅晶体与水化硅酸钙(C-S-H)凝胶、Ca(OH)_(2)晶体相互交缠填充形成一个坚固的网络,使其接近天然石膏作为水泥缓凝剂的力学性能。

In order to save natural gypsum resources and improve the comprehensive utilization rate of phosphogypsum,purified phosphogypsum was selected as cement retarder,its properties and mechanical strength were investigated.The results showed that the optional washing process of purifying phosphogypsum was the temperature of 60℃,liquid-solid ratio of 3∶1,stirring time of 15 min,washing three times,adding 0.5% quicklime aging for 5 days and then steaming as cement retarder.The optimal ratios of cement specimens were 70% clinker,25% fly ash and 5% cement retarder.The 28 d flexural strength and compressive strength of the specimen were 8.45 MPa and 49.49 MPa,respectively.The XRD,SEM and FT-IR analysis showed that the spherical silica crystal,C-S-H gel and Ca(OH)_(2) crystal were intertwined and filled together to form an indestructible network after the addition of purified gypsum,which was close to the mechanical properties of natural gypsum as cement retarder.