Synthesis process-based mechanical property optimization of alkali-activated materials from red mud: A review

Repeated red mud (RM) stockpile accidents have sounded an alarm that a healthy alumina industry requires secure RM disposal. Unfortunately, the flawed mechanical properties of RM-based alkali-activated materials (RM-AAM) with bulk RM incorporation have impeded the ideal large-volume, low-risk utilization of RM and the provision of sustainable binders for communities. By reviewing a wide range of studies, this work provides insights into establishing a mature synthesis technique for optimizing the mechanical properties of RM-AAM. Brief evaluations of the nature and the current RM-AAM synthesis systems were conducted. The following emphasis is on addressing the influence characteristics and mechanisms of the known RM-AAM synthesis factors, including RM pre-activation, precursor composition, alkali activator property, preparation process treatment, and curing regime, on the mechanical properties of RM-AAM. Further optimization suggestions on each aspect of the synthesis process and the final complete set of synthesis technology that could best enhance the mechanical properties of RM-AAM were proposed. The general limitations of current research on developing a mature RM-AAM synthesis technique were identified, along with possible solutions.