Influence of Bayer Red Mud on the Operational and Mechanical Characteristics of Composite Cement Mortar

Abstract

The aim of this study is to enhance the value and utilization of red mud generated in the Bayer process by pre-paring composite cement mortars. The effects of two different types of Bayer red mud with varying physical and chemical characteristics on the fluidity, mechanical strength, mineral composition, and microstructure of the composite cement mortar were systematically evaluated. The results showed that the optimal addition of red mud A was 10 wt%, while it was 20 wt% for red mud B. The mechanical properties of the composite cement mortar met the standards for P·O42.5 cement. Furthermore, the composite mortar with the addition of red mud B showed higher flexural and compressive strengths compared to the composite mortar with red mud A. This improvement is attributed to the smaller particle size of red mud B, which filled the micro-pores and increased the compactness of the cement stone, as well as its higher content of Na2O, K2O, and other free alkalis, which resulted in more obvious alkali activation, accelerating the hydration of the active minerals in the slurry.