Durability performance of fly ash-based geopolymer concrete buried in saline environment for 10 years

Abstract

Durability of geopolymer concrete is an important property for its application in construction sector; however, it is less explored. In this study, the long-term durability of fly ash-based geopolymer concrete (GPC), exposed in a severe salt lake environment with the buried and fully saturated condition for 10 years, is investigated. The outcome of chloride and sulphate attack on the durability behaviour of GPC was compared to ordinary Portland cement (OPC) concrete at the same exposure conditions. The results of this study reveal that the GPC has an adverse effect of chloride transportation with higher chloride diffusion coefficient and the lower binding capacity, compared to OPC concrete. The sulphate penetration of GPC was also greater than OPC concrete, however, its detrimental effect has been found more pronounced in OPC concrete due to the gypsum formation resulting in the softening of its matrix. The pH measurement indicated that the GPC has the neutral to mild alkalinity with the pH range of 7.0–8.0, whereas OPC concrete showed between 12.0 and 12.5. The mineralogical and morphological changes within the microstructure as a result of long term exposure in the buried saline environment were also studied by FT-IR and SEM/EDX analysis.