Damage Process of Roller-Compacted Concrete Based on Combined Action of Freeze-Thaw and Triaxial Compression

Roller-compacted concrete (RCC) structures are often destroyed by coupling damage of freeze-thaw and complex loads in cold conditions, resulting in degradation of the mechanical properties of the RCC. In this study, the failure process of freeze-thaw RCC in the triaxial compression test and the law of crack development were studied through a combination of tests and the discrete-element method (DEM). The results showed that the freeze-thaw damage degree of the RCC presents three different stages: (1) growth, (2) slow growth, and (3) rapid growth phases. It was found that 125 cycles can be regarded as a critical point of RCC freeze-thaw damage, beyond which the damage degree increases sharply. With the increasing number of freezing-thawing cycles, the brittle failure weakened and the failure patterns became increasingly severe. The cracks on the failure surface mainly passed through the cement mortar and interfacial transition zone, whereas the coarse aggregate was rarely damaged. The peak strain was regarded as the critical point for the damage of freezing-thawing cycles coupled with triaxial compression. Before the peak strain, microcrack growth of the RCC was not obvious, and the coupling damage was relatively weak. As the microcrack approached the peak strain, it grew rapidly and the coupling damage increased remarkably.