Analysis of Calcined Red Mud Properties and Related Mortar Performances

Abstract

Red mud (RM) is a low-activity industrial solid waste, and its utilization as a resource is currently a hot topic. In this study, the micro characteristics of red mud at different calcination temperatures were analyzed using X-ray diffraction and scanning electron microscopy. The performance of calcined red mud was determined through mortar strength tests. Results indicate that high-temperature calcination can change the mineral composition and microstructure of red mud, and increase the surface roughness and specific surface area. At the optimal temperature of 700°C, the addition of calcined red mud still leads to a decrease in mortar strength, but its activity index and flexural coefficient increase by 16.2% and 11.9% with respect to uncalcined red mud, reaching values of 0.826 and 0.974, respectively. Compared with the control group, the synergistic activation of calcined red mud with slag can increase the compressive and flexural strength of the mortar by 12.9% and 1.5%, reaching 8.7 and 62.4 MPa, respectively. Correspondingly, the activity index and flexural coefficient of the calcined RM and GGBS (Ground Granulated Blast furnace Slag) mixtures also increase to 1.015 and 1.130, respectively.