Study on the utilization of red mud (bauxite waste) as a supplementary cementitious material: Pathway to attaining sustainable development goals

Concrete is the second most consumed material on our planet. However, traditional concrete production releases much CO2 and is not eco-friendly. Cement, one of the prime concrete-making materials, is manufactured using an energy-intense process and is not eco-friendly. Researchers have been investigating using certain materials to replace cement in concrete, retaining its strength simultaneously. Red Mud (RM) is a waste the alumina industry generates, and its disposal is a huge challenge. It consumes a lot of space, and its high alkali content makes it unsafe for the environment. Several types of research are being carried out to find how RM can effectively alleviate the use of ordinary Portland cement (OPC) in concrete, thus providing a greener construction material. This review highlights the effect of using RM in varying proportions on the fresh, mechanical, thermal, durability, and microstructural properties of cementitious materials. Using RM up to certain levels positively impacts the compressive strength of the mixes. The durability properties, such as the resistance to chloride migration, freezing-thawing action, and alkali-silica reactions, also improve using RM. The microstructural studies reveal the formation of a higher amount of hydration products and densification of the matrix upon RM addition. In terms of the leaching characteristics, RM has a good potential to stabilize and solidify heavy metals, majorly cadmium. The review has calculated and summarized the overall environmental, mechanical, and economic performance. This review shows that RM can effectively replace around 10-20% of cement, where the replacement levels also depend on the RM source.