磷石膏复合胶凝材料配比优化及浸出机制

Ratio Optimization and Leaching Mechanism of Phosphogypsum Composite Cementitious Material

为实现磷石膏的大宗化利用,以磷石膏、生石灰和矿渣微粉制备矿井充填材料,开展正交试验,研究其抗压强度、塌落度、扩散度、凝结时间和孔溶液pH,采用扫描电镜阐述水化机理,通过毒性浸出试验评价环境相容性。结果表明:当磷石膏掺量为25%、生石灰掺量为6%、矿渣微粉掺量为64%,灰砂比为1∶3时,3 d、7 d、14 d、28 d抗压强度分别达1.57,2.86,4.03,7.49 MPa,塌落度为26.8 cm,扩散度为69.5 cm。随着磷石膏掺量的增加,凝结时间逐渐增加,孔溶液pH不断减小;随着水化龄期增长,孔溶液pH增大。磷石膏胶凝材料主要水化产物为C-S-H凝胶和钙矾石,水化产物紧密包裹、联合细化毛细孔,阻隔污染物PO_(4)^(3-)和F^(-)溶出,充填体具有良好的环境相容性。

In order to realize the bulk utilization of phosphogypsum,mine filling materials were prepared with phosphogypsum,quicklime and slag powder,and orthogonal tests were carried out to study the compressive strength,slump,diffusivity,setting time and pH of pore solution.The hydration mechanism was elaborated by scanning electron microscopy,and the environmental compatibility was evaluated by toxic leaching test.The results show that when the content of phosphogypsum is 25%,the content of quicklime is 6%,the content of slag powder is 64%,and the cement-sand ratio is 1:3,the compressive strength of 3 d,7 d,14 d and 28 d is 1.57,2.86,4.03 and 7.49 MPa respectively,the slump is 26.8 cm,and the diffusivity is 69.5 cm.With the increase of phosphogypsum content,the setting time increases gradually,and the pH of pore solution decreases continuously.With the increase of hydration age,the pH of pore solution increases.The main hydration products of phosphogypsum gelling material are C-S-H gel and ettringite,and the hydration products closely wrap and jointly refine the capillary pores,blocking the dissolution of pollutants PO_(4)^(3-) and F^(-),and the filler has good environmental compatibility.