Meso-Scale Failure of Freezing-Thawing Damage of Concrete under Uniaxial Compression

In this study, discrete element PFC3D software was used to simulate the uniaxial compression of C30 concrete specimen models after freezing-thawing damage. Based on the thickness of the freezing-thawing damage layer of the concrete and the uniaxial compression test, the meso-parameters of cement mortar in concrete and the meso-parameters of weak interface between the cement mortar and coarse aggregate under different freezing-thawing cycles were calibrated. The axial compression deformation produced in the experiment was compared with the axial displacement of particles obtained by numerical simulation to verify the accuracy of the model and the selected meso-parameters. Based on the numerical model, the effects of freeze-thaw damage on the mechanical properties of concrete were studied from the perspectives of the contact force between particles, crack development, and concrete cracking, and the characteristics of meso-scale failure of concrete model after freezing-thawing damage were analyzed. The results show that the stress-strain curves obtained by uniaxial compression simulation in the PFC3D-based numerical model of freezing-thawing concrete are consistent with the test results. During the uniaxial compression process in the freezing-thawing concrete model, the contact force at different stage points between the particles, crack development, and the number of cracked concrete fragments quantitatively reflected the degree of meso-scale concrete failure. With increasing numbers of freeze-thaw cycles, the failure severity of the model increased with obvious penetrating cracks, which is consistent with the failure pattern obtained by physical experiments. Therefore, numerical experiments can be used to study the meso-scale failure modes of concrete.