Quantification of deformation and cracking processes of an aggregate due to alkali-silica reaction using digital volume correlation from X-ray CT images

This study aims to provide insights into the location of expansion due to alkali-silica reaction (ASR) by quantifying deformations during the early stage of expansion of a single reactive andesite aggregate embedded within cement paste. One-month time-lapse microstructural information was obtained by performing global (low-resolution) and local (high-resolution) X-ray computed tomography (CT) on the specimens. Highresolution scans were used to measure displacement fields using mechanics-informed digital volume correlation (DVC). The CT images revealed the formation of cracks inside the aggregate along its surface after 14 days, followed by crack opening and propagation. The DVC results showed outward-directed displacements from the inner surface of the aggregate, indicating the presence of expansive sites on the surface, even when no crack was observed in the CT images. After cracking, large displacements developed in the direction perpendicular to the cracks. The mechanisms of ASR expansion pressure generation, which explain the observed deformation and crack changes, are discussed in relation to previous propositions.