Sulphuric acid resistance of ground ferronickel slag blended fly ash geopolymer mortar

Abstract

This study presents an investigation on the sulphuric acid resistance of geopolymer mortar made using different proportions of ground ferronickel slag (GFNS) with fly ash. The changes in mass, visual appearance, compressive strength and microstructure of the geopolymer mortars were evaluated after immersion in 3% sulphuric acid solution for up to one year. It was found that geopolymer mortar containing 75% GFNS showed better sulphuric acid resistance than the neat fly ash geopolymer mortar. The strength loss after 12 months of acid exposure were 43.67, 31.05, 24.15 and 22.54% in mortars using 0, 25, 50 and 75% GFNS, respectively. The improvement of acid resistance of fly ash-GFNS geopolymer is ascribed to the formation of N-M−A−S−H gel which reduced the ingress of sulphuric acid by providing a more compact microstructure. Moreover, the lower deterioration of fly ash-GFNS geopolymer compared to neat fly ash geopolymer is considered to be due to the formation of lower amount of expansive gypsum in the fly ash-GFNS geopolymer as shown in the QXRD analysis.