Eco-friendly fibre reinforced geopolymer concrete: A critical review on the microstructure and long-term durability properties

The environmental impact caused by the production process of ordinary Portland cement (OPC) concrete is a major challenge that requires demanding solutions in the construction sector. In the process of substituting OPC concrete production, the development of geopolymer concrete (GPC) is considered as the major breakthrough. However, research works related to durability of fibre reinforced geopolymer in several corrosive environments, i.e., sewage conveyer concrete pipeline, wastewater treatment, and offshore structures is limited compared to other types of concrete structures, and which is essential to estimate the long-term performance of concrete structure in extensive engineering applications. This review paper analyzes and discusses the mechanical and durability related properties of GPC containing various supplementary binding materials together with organic or synthetic fibres exposed to chloride salt, acid, and sulfate solution. Significant findings have concluded that the better long-term performance of geopolymer concrete is explained than OPC concrete, the durability mechanism is greatly affected by the calcium content. The fly ash/slag based geopolymer concrete geopolymer concrete specimens immersed in MgSO4 didn’t indicate a certain dimensional change in the first 120 d exposure, except that of salt deposition. Whereas, the conventional ordinary Portland cement, showed a 0.0184% expansion. Further, alkali activated slag mortar shows an approximate of 12 mm chloride penetration compared to the 10 mm depth of concrete specimens with a 25 w.t % fly ash replacement. Increasing the cement content from 10% to 20% had no significant effect on the properties of fly-ash based geopolymer concrete with crumb rubber and steel fibre subjected to normal and acid environmental exposure, considering the chemical reaction of sulfuric acid and calcium, and this chemical reaction led to the destruction of C-S-H bonds and production of different gypsums. The impact of fiber on the long-term behavior of geopolymer concrete have been highlighted. At last, potential recommendations and notable challenges have been forwarded for further studies on the durability of GPC.