低浓度拜耳赤泥充填材料制备及水化机理

Preparation and hydration mechanism of low concentration Bayer red mud filling materials

针对矿山充填中拜耳法赤泥利用率较低或低浓度赤泥充填材料存在强度低、泌水量高、易收缩等问题,研究粉煤灰添加比例、脱硫石膏、石灰及激发剂对赤泥充填材料早期强度及体积稳定性的影响,采用扫描电子显微镜-能谱仪(SEMEDS)和X射线衍射(XRD)分析手段探讨赤泥基充填材料的水化机理.结果表明,脱硫石膏促进钙矾石的生成,石灰促进粉煤灰火山灰效应,激发剂可以加快赤泥-粉煤灰水化反应进程,三者协同作用提高赤泥充填体强度.充填材料28 d抗压强度3.35 MPa,且初始及60 min流动度在200 mm以上.微观实验表明,硬化体水化产物为钙矾石、硬柱石、硅铝酸盐凝胶类矿物,水化产物通过填充孔隙,提高浆体强度.赤泥基充填材料固体废弃物利用率达到92%,无泌水,无沉缩,具有较高的经济价值和环保价值.

Red mud is a solid waste produced in the process of bauxite refining alumina,with high alkali content,and its treatment methods are mainly stacking and ocean dumping,which not only occupy a large amount of cultivated land and pollute land and water sources,but also have high safety risk.The preparation of red mud-based filling materials to fill the underground goaf can improve the utilization rate of mineral resources and reduce the harm of red mud to the environment,which has the effect of killing two birds with one stone.In view of the problems of low utilization rate of bayer red mud in mine filling system,low strength,bleeding and shrinkage in filling materials slurry with low concentration,the effects of the addition ratio of fly ash,desulfurization gypsum,lime and initiator on the early strength and volume stability were studied in this paper.Scanning electron microscope-energy dispersive spectroscope(SEMEDS)and X-ray diffraction(XRD)were used to analyze the hydration mechanism of the filling materials.The results show that when the ratio of red mud to fly ash is 4∶6,the mechanical properties of the filling material are the best.Desulfurized gypsum promotes the formation of ettringite.Lime promotes the pozzolanic effect of fly ash.The composite activator can accelerate the hydration process of red mud and fly ash.All of this enhance the red mud backfill strength.The filling materials 28 d compressive strength is 3.35 MPa,and the initial and 60 min fluidity are above 200 mm.Microscopic test results show that the hydration products of hardened paste are ettringite,lawsonite,silica aluminate gel,which fill the pores and improve the strength of slurry.Through adding activator,activating red mud activity and designing low concentration filling material,it is the direction of mass and green utilization of red mud,desulfurization gypsum and other solid wastes.The utilization ratio of solid waste of red mud filling materials reaches 92%,no bleeding,no shrinkage,and has high economic value and environmental value.