Macro and microstructural evolution of low-calcium fly ash-based geopolymer mortar exposed to sulphuric acid corrosion
Piumika W. Ariyadasa, Allan Manalo, Weena Lokuge, Vasantha Aravinthan, Andreas Gerdes, Jonas Kaltenbach, Beatriz Arévalo Galván
Abstract
This article reports an investigation of the behaviour of a low-calcium fly ash-only geopolymer (FAGP) mortar in comparison to Ordinary Portland Cement (OPC) mortar and a commercially available geospray mortar (P-GP) under laboratory-induced sewer conditions. An aggressive sewer condition was simulated by an accelerated corrosion rate, with mortar specimens immersed in 0.5pH sulphuric acid at a controlled temperature of 40 °C for 31 days. The macro and microstructural evolution of the specimens was analysed through visual observations, mass changes, and SEM coupled with EDS, XRD, and MIP analysis. OPC exhibited a 49 % mass loss attributed to the loss of the gypsum layer formed during the acid attack. The mass reduction in the low-calcium FAGP was only 6 %, which was 42 % lower than that of OPC, indicating that calcium-bearing hydrates in the cementitious binder systems are susceptible to sulphuric acid corrosion. The acid-resistant properties of FAGP mortar suggest its suitability for sewer rehabilitation applications.