Influence of orthogonal and parallel cracks on the post-peak compressive response of ASR-deteriorated concrete: experimental evaluation and mechanism interpretation

This study experimentally investigated the influence of crack anisotropy on the post-peak compressive response of alkali–silica reaction (ASR)-affected concrete under three restraint conditions. At comparable expansion levels, specimens were loaded in compression along directions either orthogonal or parallel to the dominant crack orientation. Specimens with cracks predominantly orthogonal to the loading direction exhibited greater post-peak ductility, with higher fracture energy and lower stiffness degradation rate. In contrast, specimens dominated by cracks parallel to the loading direction exhibited more brittleness. Notably, orthogonal cracks were shown to have opposite effects on pre-peak and post-peak compressive responses. Mechanistic investigation suggests that the enhanced ductility in orthogonal-crack-dominant specimens is associated with lateral confinement arising from interactions between pre-existing and loading-induced cracks. Comparisons with non-ASR specimens and prior studies further reveal that orthogonal-crack-dominant specimens exhibit a distinctive failure pattern and post-peak response, which are underrepresented in existing ASR models. These findings clarify post-peak behavior and underlying mechanisms, providing valuable insights for improving ASR modeling and assessing the collapse risk of ASR-deteriorated concrete members under compression.