Impact of aggregate mineralogy and exposure solution on alkali-silica reaction product composition and structure within accelerated test conditions

•Systematic study of ASR products regarding chemistry, morphology, and structure.•Aggregate mineralogy and exposure solution affect chemistry of gel products.•Structure of gel varies significantly depending on aggregate mineralogy.•Structure of gel is influenced by local environment in which alkali-silica gel forms. Electron microscopy, chemical X-ray microanalysis, and Raman microscopy was used with expansion measurements of mortar bars in a systematic fashion to determine the impact of aggregate composition and exposure variations on alkali-silica reaction (ASR) products’ chemistry and structure. The results show that aggregate mineralogy plays a large role in the composition and structure of ASR products as does the local environment in which ASR products form. Additionally, solution exposure composition, a factor relevant to relating laboratory measurements to field performance, has a significant impact on ASR product chemistry but limited impact on structure, or at least on coordination of SiO2 in ASR products.