A review on the utilization of red mud for the production of geopolymer and alkali activated concrete

Abstract

The production of ordinary Portland cement releases many greenhouse gases, which have led to adverse environmental changes such as global warming and climate change. These phenomena have invigorated the utilization of various industrial waste products to synthesize geopolymer materials and alkali-activated binders (AAB) to alleviate OPC's use in construction and building materials. Red Mud (RM) is one such harmful radioactive waste material generated as a by-product in aluminum production by Bayer's process. This article highlights RM's utilization of materials such as fly ash, ground granulated blast furnace slag, silica fume, metakaolin, refuse mudstone, and rice husk ash to synthesize geopolymer and AAB samples. The heavy metal ions present in the raw materials in their weak acid-soluble and reducible fraction were in their residual and oxidizable fractions in the geopolymer, providing better stability and curing a severe threat to the environment. The freeze�thaw results showed that the mass-loss rate of the geopolymer was less than that of concrete. The geopolymer samples exhibited activity concentration levels well within the prescribed limit. Studies also include the analysis of Fe's role in the ettringite structure using the M�ssbauer spectra analysis. Besides, an overview of the recent advances in the use of RM for geopolymer synthesis has been presented in terms of hardened, fresh, and thermal properties and geopolymer and AAB's microstructure analysis. The effect of ambient curing, heat treatment, elevated temperature curing, and autoclave curing has been briefly outlined, along with the impact of the RM fraction in the geopolymer samples. The research findings revealed that the RM-based geopolymer and AAB manifested similar properties to OPC concrete for various civil engineering applications. � 2021 Elsevier Ltd