掺和料对磷石膏复合胶凝材料性能影响研究

研究主要掺和料矿粉及水泥单掺和复掺对磷石膏复合胶凝材料力学性能及耐水性能的影响,并通过扫描电镜(SEM)、压汞法(MIP)探究影响机理。结果表明,水泥掺量为0~20%、矿粉掺量为0~40%时,水泥和矿粉的单掺对磷石膏抗压强度有负面影响,但可有效提升软化系数。水泥及矿粉复掺时,可显著提高磷石膏软化系数,使软化系数达到0.65以上;当水泥掺量为5.58%,矿粉掺量为20.00%时,磷石膏复合胶凝材料抗压强度达到最大值16.50 MPa;水胶比由0.6降低至0.3,可制备抗压强度为32.50 MPa,软化系数为0.87的高强耐水磷石膏复合胶凝材料。由SEM结果可知,水泥及矿粉的水化产物包覆在石膏晶体表面,可显著提升其耐水性;由MIP结果可知,矿粉与水泥复掺可增加小孔(3~50 nm)比例及孔弯曲度,大幅降低平均孔径,改善孔径分布,增加基体致密度,进而提升抗压强度。

Investigation on Effect of Admixture to the Performance of Phosphogypsum Composite Binders

The influence of slag,cement and slag-cement on mechanical properties and water-resistance of phosphogypsum composite binders were investigated,and the influence mechanism were explored using SEM and MIP.The results indicated that 0-20%cement or 0-40%slag has a negative effect on the compressive strength of phosphogypsum,but can effectively improve the softening coefficient of phosphogypsum.When cement and mineral powder are mixed,the softening coefficient of phosphogypsum can be significantly increased,and the softening coefficient reaches more than 0.65;when cement content is 5.58%and slag content is 20%,the compressive strength of phosphogypsum composite binders reache the maximum value of 16.50 MPa.By reducing the water-binder ratio from 0.6 to 0.3,phosphogypsum composite binders with compressive strength of 32.5 MPa and softening coefficient of 0.87 can be prepared.SEM tests indicated that the hydration products of cement and slag would cover the surface of gypsum and improve its water-resistance.MIP tests indicated that cement-slag could increase the micropore ratio and tortuosity of phosphogypsum,reduce average pore diameter,improve pore diameter distribution,increase the density of matrix,and significantly improve the compressive strength of gypsum.