Effect of Fly Ash characteristics, sodium-based alkaline activators, and process variables on the compressive strength of siliceous Fly Ash geopolymers with microstructural properties: A comprehensive review

Geopolymer concrete (GPC) exhibits enhanced performance compared to conventional concrete across various dimensions. These include decreased CO2 emissions, elevated mechanical strength, improved thermal insulation, greater fire resistance, the valorization of industrial wastes and increased efficiency in energy conservation and production costs. This review focuses on the impact of 11 factors such as class F Fly Ash (FA) characteristics (fineness, SiO2/Al2O3 ratio, and iron content), sodium-based alkaline activators parameters such as molarity of sodium hydroxide (SH), Silicate Modulus (SM) of sodium silicate (SS) solution, ratio of SS/SH solution, alkaline liquid to binder ratio, water to binder (w/b) ratio, H2O/Na2Oequivalent, and process variables such as heat curing temperature and heating duration on the compression strength of low calcium (class F or siliceous) FA-based geopolymers (GP). Existing literature explicitly indicates that the molarity of NaOH solution is the primary strength parameter that significantly affects the compression strength of the GPC, among other factors. The range of alkaline activator parameters and heat curing temperature contingent on the SiO2/Al2O3 ratio of FA moreover accurately the reactive SiO2/Al2O3. Among all factors, one of the crucial parameter is the water content because of its importance in geopolymerization; the additional water released during the chemical reaction has to be considered in the mix design. The aforementioned eleven parameters are analysed and reported in the development of the compressive strength. •Physical, chemical, morphological, and mineralogical properties of class F FA are exhibited.•A pseudo-ternary diagram of FA is constructed by incorporating the principal oxide composition together with alkalis.•The influence of 11 distinct factors on the compressive strength of FA-GP is elucidated.•The potential impact of numerous unexplored factors on the efficacy of FA-GP are suggested as further research endeavours.