Durability of low‑calcium fly ash based geopolymer concrete culvert in a saline environment

This study reports the investigation of the durability of a low-calcium fly ash based geopolymer concrete (GPC) mix in a saline lake environment. Core specimens from the GPC and Ordinary Portland Cement (OPC) concrete structures underwent durability assessment including in-situ carbonation, chloride and sulphate ingress, microstructural characterization and porosity analysis. It was found that the particular GPC mix design studied was more vulnerable to carbonation and the deterioration effects due to chloride and sulphate ingress in GPC were higher than OPC concrete after 6 years of exposure. According to FT-IR and XRD analysis, there was no evidence of carbonation reaction products remaining in GPC. This indicates that the carbonation products dissolved when in contact with water, which caused high porosity of the concrete surface thereby facilitating more diffusion into the concrete. This study revealed that the development of a durable geopolymer concrete mix design for aggressive environments requires appropriate consideration of binder chemistry and preliminarily durability property testing to avoid premature deterioration. •Rate of chloride ingress in fly ash based geopolymer concrete is high in aggressive environment.•Geopolymer concrete shows less carbonation resistance compared to Portland cement concrete.•Reinforcement bars embedded in geopolymer concrete is more prone to corrosion compared to OPC concrete.