Durability of Geopolymer Mortar Based on Waste-Glass Powder and Calcium Aluminate Cement in Acid Solutions

Abstract

The aim of this study is to investigate the durability of geopolymer mortars based on waste-glass powder (WGP) and calcium aluminate cement (CAC) exposed to acid attack. Geopolymer specimens were prepared by a combination of WGP and CAC activated by an aqueous solution of sodium hydroxide and sodium silicate and were cured under hydrothermal conditions. The prepared specimens were immersed in sulfuric and hydrochloric acid solutions (pH=1) for 6 months, and their residual compressive strength and several key durability parameters were assessed and compared to those of portland cement and high alumina cement mortars as control specimens. Microstructural and compositional changes in the geopolymer samples were studied using scanning electron microscopy, X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy. The results showed that the acid resistance of geopolymer mortar against both acid solutions was comparable to the control mortars, as indicated by the relatively lower strength loss and lower mass change. The microstructure of the geopolymer after acid exposure, however, possessed significant microcracks in the near-surface region, leading to a higher porosity and a lower strength. XRD results revealed the formation of gypsum crystals due to the reaction between sulfuric acid and calcium from the geopolymer gel.