Static and fatigue performance of the interface between the epoxy resin and cement asphalt mortar for CRTS II slab track

Epoxy resin (ER) has been extensively adopted for the repair of interface debonding in the China railway track system (CRTS) II slab track. In this study, the static and fatigue performance of the cement asphalt mortar (CAM) - ER interface in CRTS II slab tracks were explored through three-point bending tests for the first time. The former was evaluated by tracking the static interface behavior and analyzing the static failure mode. The latter was thoroughly investigated by analyzing its fatigue failure modes, S - N curves, probabilistic fatigue life assessment, fatigue evolution behavior, and fatigue damage modeling. Results indicate that the static failure process of the interface includes three stages of microcrack-free, rapid accumulation of microcracks and rapid propagation of macroscopic cracks, accounting for 64 %, 26 %, and 10 % of the static loading process, respectively. The static and fatigue failure modes of CAM-ER interface both primarily fail in the mode of mortar failure. The fatigue life of the CAM-ER interface exceeds that of the CAM-concrete slab (CS) interface, which exhibits great variability. Incorporating the Weibull distribution, a probabilistic estimation model of CAM-ER interface was established and can well predict interface fatigue life under various stress levels. During fatigue loading, the interface residual strain and fatigue damage both increase in an inverted S-shaped pattern, which is caused by the rapid initiation and progressive accumulation of microcracks and the rapid propagation of macrocracks. Considering these evolution characteristics of the interface damage, a generalized interfacial fatigue damage model for various stress levels was developed to quantitatively study the fatigue damage process of CAM-ER interface.