Influence of mesoscale heterogeneous and initial defects on the fracture of cement-treated base materials

•Mesoscale heterogeneous DEM model was established by randomization methods.•The material random field and initial defects were introduced to characterize the heterogeneous.•Nanoindentation test was adopted to capture the actual micromechanical distribution of mortar.•A half-normal distribution was used to construct the material random field of mortar.•Discrete Fracture Network was utilized to characterize the microscopic initial defects. To investigate the mesoscopic fracture of heterogeneous cement-treated base (CTB) materials, a mesoscale numerical model was established through discrete element method (DEM) and randomization algorithm. The proposed model was composed of aggregate, mortar, interface transition zone (ITZ), pores and initial defects. Combined with nano-indentation test, a half-normal distribution function was used to characterize the micromechanical heterogeneity of mortar and ITZ. A discrete fracture network (DFN) was used to characterize the initial microscopic defects in mortar hardening. Then the heterogeneous DEM model and DFN were integrated, and mechanical properties of CTB and failure mechanism were investigated on meso-level. The influence of material random field and microscopic initial defects on cracking behavior was further studied. The simulation results showed that the failure of CTB was mostly due to the accumulation of damage at mesoscopic level. Material heterogeneity results in stress concentration and induces microcracks. Initial defect was negative to structural strength but would increase the allowable failure deformation. The random particle model combined with microscopic initial defects could better characterize the mesoscopic cracking process of CTB materials. The present research provided a new numerical method for investigating the progressive failure process and the failure mechanism of cement-treated composites.