Factors affecting the mechanical properties and microstructure of geopolymers from red mud and granite waste powder: A review

Geopolymer offers many advantages over OPC such as excellent mechanical strength, better durability, thermal resistance, and excellent stability in acidic and alkaline environments. Compared to other industrial by-products such as fly ash, slag, rice husk ash, silica fume, kaolin, etc., red mud (RM) from alumina production and granite waste powder (GW) from granite quarries are less utilized for geopolymer synthesis. This study presents a review of the research papers that utilize RM and GW to produce geopolymer binder and mortar. The parameters such as setting time and workability, influence of factors such as types of alkaline activator, concentration of alkaline activators, molar ratios of different chemical compounds, liquid to solid ratio, fine aggregate to binder ratio, curing conditions, addition of plasticizer and other additives on the mechanical and microstructural behaviour of RM and GW geopolymers are summarized in this paper. The durability and thermal behavior of RM geopolymers are also discussed. The potential usage of RM and GW for geopolymer synthesis points towards the requirement for further investigations on the mix proportioning and combinations of these two raw materials with other pozzolanic materials resulting in novel, energy-efficient, low-cost construction processes and products. • Review on geopolymer binder and mortar from red mud and granite waste powder is presented. • Mechanical properties and microstructure are elaborated. • Durability, thermal behaviour and environmental compatibility of red mud geopolymer are discussed.