Abstract:Red mud contains a lot of valuable metallic iron, and iron concentrate can be recovered by the process of reduction roasting-magnetic separation, but at the same time, some magnetic separation tailings will be produced which are difficult to treat. Alkali-activated geopolymer grouting material (CRT-S) was prepared from red mud reduction roasting-magnetic separation tailings and blast furnace slag at different roasting temperatures. The results show that the grouting materials of CRT-S geopolymer at different roasting temperatures are in accordance with the expression results of Herschel-Buckley model with R2 of 0.99 above after fitting. The mechanical properties are the highest at roasting temperature of 700 ℃ with the fluidity of 24.5 cm, initial coagulating time of 120 min, final coagulating time of 380 min, final bleeding rate of 2.6%, and compressive strength at 7 d and 28 d of 9.9 MPa and 18.6 MPa, respectively. Three-dimensional CT shows that its pores and cracks are small, and its heat release rate and final heat release amount are high under the evolution of heat flow. The microstructure of CRT-S geopolymer grouting material is lamellar structure. XRD and FT-IR show that the hydration products of CRT-S geopolymer grouting material are mainly C—S—H. Red mud reduction roasting-magnetic separation tailings are applied in underground grouting engineering to solve its difficult problems and achieve the purpose of multi-angle, batch and deep comprehensive utilization of red mud and its reduction roasting-magnetic separation tailings.