Anisotropy mechanism of alkali-silica reaction at the material scale: From expansion behavior to mechanical property degradation

This study aimed to elucidate the anisotropic relationships among expansion, cracking, and mechanical properties in compression caused by the alkali-silica reaction (ASR) under applied stress using mesoscale modeling based on a 3D-rigid body spring model. A concrete model consisting of a composite phase of aggregate and mortar was used, and the ASR expansion was reproduced by considering two mechanisms of generation of swelling pressure. Consequently, both the difference in the expansion models and the creep of the aggregate affected the anisotropy of expansion and cracking. It was thus suggested that the creep of the aggregate should be considered when discussing ASR expansion because the accumulation of swelling pressure caused a significantly high compressive stress in the aggregate. Furthermore, the expansion cracks under restraint exhibited an orientation parallel to the restraint direction, which resulted in the anisotropy of the compressive properties. The cracks perpendicular to the loading axis caused a significant reduction in the compressive properties compared with the parallel cracks. Consequently, the indices related to expansion alone are insufficient to estimate the change in compressive properties owing to ASR under restraint conditions.