Effect of calcium and lithium on alkali-silica reaction kinetics and phase development

This study aims to investigate the influence of lithium and calcium content on the alkali-silica reaction kinetics and phase formation processes at atomic scales. The atomic structure of the reacted ASR gels was analyzed with the Pair Distribution Function (PDF) measurement. The analysis results can explain the expansion potential difference of gels with different chemical composition. The in situ PDF characterizations of the samples containing lithium compounds identified the formation of the Li-Si phase, and thus both the alkali-silica reaction and the reaction between dissolved silica and Ca(OH)(2) were suppressed. The alkali-silica reaction kinetics was further indicated with the changes of Si-O peak intensity. The amorphous structure of the generated Li-Si phase was confirmed with in situ XRD tests. The results strongly support the formed amorphous Li-Si phase can act as a surface barrier for silica dissolution, and thus prohibit both the alkali-silica reaction and pozzolanic reaction in hardened concrete.