Modeling and fracture behavior of mesoscale concrete considering actual aggregate shapes and placement domain shapes

The establishment of meso-concrete models under complex boundary conditions still faces great challenges at present. In this study, a numerical framework for constructing concrete meso-structures in irregularly placement domains is developed based on the dot matrix idea. In addition, a solution to quickly obtain numerous 3D aggregates with realistic morphology as well as 2D cross-section aggregates is proposed. On this basis, wedge splitting (WST) tests with different coarse aggregate contents are conducted and the numerical results agree well with experimental results. The fracture mechanism of the wedge splitting specimen was then investigated by analyzing the contact force chain and crack evolution. Finally, parametric analysis was used to investigate the impact of aggregate and mortar strength on the fracture characteristics of WST specimens. The results show that the numerical framework has good robustness. Tensile stress is the driving force for crack extension in WST specimens, the area of the pure tensile stress zone and the distance between the front end of the pure tensile stress zone and the crack tip decreases as the crack extension length increases. With the increase of coarse aggregate content, the deflection effect of the crack is intensified, the crack path becomes more tortuous, and the fracture zone range also increases. The mechanical properties of concrete and the crack extension path are significantly influenced by the strength of the mortar and the aggregate, but the aggregate does not contribute as much to the overall strength of the concrete structure as the mortar matrix does.