Characterization of red mud and its utilization in preparing alternative cementitious materials: a review

Red mud-the residue generated during alumina production from bauxite—has become a major challenge to the sustainable development of the bauxite refining industry due to its massive stockpiles and significant environmental risks. Currently, red mud utilization faces dual challenges: continuously increasing discharge volumes and an extremely low recycling rate. Previous reviews have identified the building materials sector as the most promising avenue for large-scale red mud utilization. However, most of these studies have focused primarily on its application in traditional cement and concrete production. With the cement industry transitioning toward a low-carbon future, various alternative cementitious materials (ACMs) have been developed and explored as potential replacements for ordinary Portland cement (OPC). In this context, there is an urgent need for a comprehensive review of the progress in utilizing red mud for ACMs, particularly in novel low-carbon clinkers, alkali-activated materials, geopolymers, phosphate cements, and solid waste–based cementitious systems. This work systematically summarizes the effects of red mud on hydration processes, phase assemblages, microstructure development, and performance characteristics within specific ACM systems. The goal is to provide a comprehensive overview of red mud utilization in ACMs and to identify the most promising strategies for the safe and effective disposal of the rapidly growing global red mud stockpiles. The literature indicates that, unlike the adverse alkali effects observed in OPC, red mud shows considerable potential in the production of low-carbon, high-ferrite clinkers. Moreover, when optimally incorporated into non-sintered ACMs, red mud can enhance performance, although concerns regarding heavy metal leaching and radiological risks remain. Notably, the application of red mud in solid waste–based cementitious materials appears particularly promising, offering both high incorporation capacity and long-term stability.