Experimental Investigation on the Durability of Metakaolin-Based Geopolymer Concrete in Aggressive Environments

Abstract

Abstract The properties and performance of geopolymer concrete have been evaluated in numerous studies in recent decades. One of the fields of study is the evaluation of the durability of geopolymer concrete in aggressive environments. In this study, the influence of four experimental factors, including curing temperature (T), the weight ratio of sand to metakaolin (S/M), aggressive environment type (AE), and aggressive environment exposure time (Et) were investigated on the durability and mechanical properties of metakaolin-based geopolymer concrete (MGPC). Moreover, 5% sulfuric acid solution, 5% sodium chloride solution, and Persian Gulf seawater were used as aggressive environments. Response surface methodology (RSM) was implemented to statistically design and analyze the experiments. Mathematical models were derived for the prediction of residual compressive strength (RFc), weight changes (∆W), and compressive strength changes (∆Fc) of MGPC. The analysis of variance showed that all four factors had a significant effect on the responses, while only AE-S/M and AE-ET factors had an interaction. Design-Expert software (DX7) was employed for the optimization of design factors. Results revealed that the use of the optimum weight ratios of S/M (2.52, 2.07, and 1.29) at a curing temperature of 46 °C and an exposure time of 56 days led to RFc values of 34.12, 43.60, and 44.15 for sulfuric acid, sodium chloride, and Persian Gulf seawater aggressive environments, respectively. These results, which are higher than the minimum required compressive strength of concrete, along with the ∆Fc and ∆W values, confirm the acceptable durability of MGPC.