Performance and Microstructure of Alkali-Activated Red Mud-Based Grouting Materials Under Class F Fly Ash Amendment

From the perspective of sustainable development and environmental protection, the environmental friendly substitute of ordinary grouting materials is needed to be proposed. In this paper, we prepared a high-performance and low-cost grouting materials from red mud, granulated blast furnace slag (GBFS) and class F fly ash (FFA). In order to determine the optimal raw materials property, we investigated the effect of FFA dosages on red mud–GBFS grouts system. The results showed that 10% of FFA content could improve the 90-day compressive strength of grouts by 15.4%; fluidity and volume stability were also improved considerably. But when the FFA content is overmuch, it would result in some negative effects, such as longer setting time and higher bleeding rate. According to the mineral phase analysis, the effects of FFA mainly attributed to the physical properties before 28 days, such as ball effect, filling effect and micro-aggregate effect, and the pozzolanic effect of FFA influenced the long-term performance chiefly. Above all the results in this study, the optimum dosage of FFA is 10%.