Preparation of ceramsite from low-silicon red mud (LSRM): Effects of Si–Al ratio and sintering temperature

Low-silicon red mud (LSRM) is a complex red mud with an extremely low silicon content, hence, it difficult to directly prepare ceramsite from LSRM. To circumvent this problem, supplementary sintering materials (SSMs) are used to regulate the Si–Al ratio of the LSRM, thereby improving its physical properties. The influence of the Si–Al ratio and sintering temperature on the physical properties of SSM-assisted LSRM was investigated in this study. The results revealed that as the increase of sintering temperature, the apparent density (AD) and particle strength (PS) of ceramsite exhibited an initial increase followed by a subsequent decrease, the water absorption (WA) exhibited a declining trend. The increase in the Si–Al ratio led to a continuous decrease in the AD and PS of ceramsite, but the WA first decreased and then increased slightly. In addition, the sintering temperature and Si–Al ratio significantly influenced the microstructure of ceramsite, which is closely related to the internal liquid viscosity and the air pressure inside ceramsite during sintering. At a sintering temperature of 1120 °C and an Si–Al ratio of 1.376, ceramsite was prepared with an AD of 1064 kg/m3, WA of 1.33%, and a PS of 5.54 MPa, and it possessed a relatively uniform pore distribution and good environmental performance.