Comparison of pore structure in alkali activated fly ash geopolymer and ordinary concrete due to alkali-silica reaction using micro-computed tomography

Alkali-Silica reaction (ASR) is a deleterious chemical reaction in concrete and manifests itself through pore structure changes. Alkali activated fly ash geopolymer concrete is a new type of green concrete that forms binder through alkali activated materials without using Portland cement. However, due to the alkali solution used, alkali activated fly ash geopolymer concrete is naturally susceptible to ASR. In this paper, ASR effect is traced through pore distribution and its change with time through micro-computed tomography (Micro-CT). Through Micro-CT images, it is found that ASR in fly ash geopolymer concrete is less severe than its ordinary Portland cement concrete counterpart, since the pore distribution in fly ash geopolymer concrete is more uniform and does not change with time, while increasing sizes of pores are found in the ordinary Portland cement concrete.