Durability Assessment of Metakaolin-Based Geopolymer Mortars Incorporating Microsilica under Accelerated Curing in Acidic Environments

Document Type : Research Paper

Authors

1 Department of Civil Engineering, La.C., Islamic Azad University, Lahijan, Iran

2 Department of Civil Engineering, La.C., Islamic Azad University, Lahijan, Iran.

3 Department of Civil Engineering, Ahrar ins, Rash, , Iran

Abstract

In recent decades, the adverse environmental impacts associated with Ordinary Portland Cement (OPC) production have encouraged researchers to investigate sustainable and environmentally friendly alternatives such as geopolymer materials. One of the main challenges in the application of geopolymer mortars is the evaluation of their performance in aggressive environments, particularly acidic conditions. In this study, the effect of incorporating microsilica at weight replacement levels of 5%, 10%, 15%, and 20% as a partial substitute for metakaolin in geopolymer mortar was investigated. Sodium hydroxide was employed as the alkaline activator at two molar concentrations of 6 M and 12 M, and all specimens were subjected to an accelerated curing regime. To assess durability, the specimens were immersed in a sulfuric acid solution with a pH of 1 for 28 days after the initial curing period. The compressive strength test results indicated that increasing the microsilica replacement level and the sodium hydroxide concentration effectively enhanced the 28-day compressive strength. Replacing 20% of the binder with microsilica at a molarity of 12 M increased the compressive strength by more than 55% and the flexural strength by more than 37% compared with the sample without microsilica. Furthermore, the results demonstrated that the incorporation of microsilica significantly improves the durability of geopolymer mortars and minimizes the reduction in compressive strength caused by acidic exposure. These findings highlight the potential application of geopolymer mortars in aggressive environments.

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References

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