Effect of calcium carbide residue on the sulphate resistance of metakaolin-based geopolymer mortars

Abstract

Sulphate resistance is an essential indicator for assessing the durability of geopolymer mortars. This study investigates the effects of calcium carbide residue (CCR) addition on the sulphate resistance of metakaolin-based geopolymer mortar via strength tests. The influence of NaOH concentration and NaOH/Na2SiO3 mass ratios on the compressive strengths was investigated. The prepared geopolymer mortars, with and without CCR, were cured at room temperature, and their durability was evaluated in a 5 % magnesium sulphate solution. The durability of the optimum geopolymer mix was compared with Ordinary Portland Cement mortar. The results indicated that the optimum 7-day compressive strength for geopolymers with and without CCR was achieved at 10 M NaOH with a NaOH/Na2SiO3 mass ratio of 1:2. The addition of CCR resulted in an increase in compressive strength by 26.12 % compared to the geopolymer without CCR. The sulphate resistance of geopolymer material with CCR was lower than those without CCR but higher than OPC-based mortar, which recorded a reduction in strength of about 3.2 % after sulphate exposure. The findings indicate that CCR addition to metakaolin-based geopolymer can produce high compressive strength with enhanced sulphate resistance compared to the OPC.