Fire resistance characteristics of geopolymer concrete for environmental sustainability: a review of thermal, mechanical and microstructure properties

Cement production produces more CO2 released into the environment, worsening global warming. Certainly, a more sustainable approach and a thorough investigation of the conventional concrete alternatives have thus become necessary. Geopolymer materials possess comparable or higher durability and strength than concrete-based ordinary materials and have become preferred testing materials for designers of various projects, such as buildings, bridges, and tunnels. The geopolymer materials used in the civil engineering structures should also be fire resistant up to the required duration of time, considering the sustainability issues. Therefore, the present study reviews and discusses the characteristics of geopolymer materials after exposure to high temperatures, such as thermal conductivity, weight loss, thermal expansion, thermodynamics, mechanical strength, and microstructural properties. Features and properties of application-based geopolymer materials after exposure to fire are also discussed. The literature review shows that the thermal characteristics of geopolymer materials (GPM) are superior to conventional materials, i.e., OPC concrete. At elevated temperatures, the previous studies found that the geopolymer mortars demonstrate degradation in tensile and bending strengths yet lower bond and compressive strength degradation than OPC mortar. For temperatures ranging from 30 to 700 °C, the bond strength of GPM on concrete is comparable to, if not superior to, that of commonly used mortar for repair work. The microstructural damage at high temperatures occurred due to dehydration and dehydroxylation, as well as thermal incompatibility between geopolymer paste and aggregates; those were the major causes of strength loss in geopolymer mortar. This article also provides the scope for future research on the fire-resistant properties of geopolymer materials required in civil engineering structures for sustainable development.