The study ofα-quartz reactivity towards alkali–silica reaction by X-ray powder diffraction

The present study is a contribution to the understanding of α-quartz reactivity towards the alkali–silica reaction (ASR), based on the use of X-ray powder diffraction (XRPD) line broadening. In particular the relationship between α-quartz structural disorder and its potential alkali reactivity towards ASR was investigated by combining traditional and advanced analytical techniques. Two aggregates were characterised by means of optical, physical and chemical analyses. Their potential alkali-reactivity was then tested by the ultra-accelerated mortar-bar test (RILEM AAR-2). Moreover a full profile analysis by XRPD was performed to extract the microstructural features (crystallite size and microstrain) of α-quartz in two aggregates, revealing its degree of structural order. By comparing the mortar bar results with those from the XRPD analysis, a correlation between α-quartz microstructural features and its reactivity towards ASR is highlighted, even if the microstructural features of α-quartz were not the only parameter to be considered.