Mechanism exploration of crack orientation influence on compression fracture behavior of ASR-affected concrete under multiaxial restraint using DIC analysis

Although crack anisotropy has been shown to significantly influence the compressive behavior of alkali–silica reaction (ASR)-deteriorated concrete, an insufficient understanding of the underlying mechanism hinders the accurate modeling of ASR-affected concrete under restrained conditions. This study investigates the relationship between compressive fracture process and pre-existing ASR-induced cracks in different orientations to address the critical gap regarding the influence of crack orientation. The specimens subjected to ASR under varying restraint conditions were tested under compression in different directions at comparable volumetric expansion levels. A digital image correlation analysis was employed to characterize the fracture behavior during loading. The loading-induced crack was observed to propagate along the pre-existing crack in parallel-crack-dominant specimens whereas they additionally formed perpendicular to the pre-existing cracks in orthogonal-crack dominant specimens. Furthermore, both qualitative and quantitative analyses illustrated a causal chain in which stress concentrations around the orthogonal cracks initiated minor perpendicular cracks under loading, which in turn facilitated crack bridging and induced an additional strength reduction in the orthogonal-crack-dominated specimens. Based on the analysis, the model for compressive strength reduction was improved with integrating the negative influence of orthogonal cracks. These findings can enhance the reliability of performance prediction for ASR-affected structures under complex restraint and loading conditions.