Alkali–silica reaction (ASR) is one of the most important deterioration mechanisms in concrete leading to substantial damages of structures worldwide. Synchrotron-based micro-X-ray diffraction (micro-XRD) was
employed to characterize the mineral phases formed in micro-cracks of concrete aggregates as a consequence
of ASR. This high spatial resolution technique enables to directly gain structural information on ASR products
formed in a 40-year old motorway bridge damaged due to ASR.
Micro-X-ray-fluorescence was applied on thin sections to locate the reaction products formed in veins within
concrete aggregates. Micro-XRD pattern were collected at selected points of interest along a vein by rotating
the sample. Rietveld refinement determined the structure of the ASR product consisting of a new layered framework similar to mountainite and rhodesite.
It is conceivable that understanding the structure of the ASR product may help developing new technical
treatments inhibiting ASR.