A user-defined micromechanical model was developed to investigate the fracture mechanism of asphalt concrete(AC)using the discrete element method(DEM).A three-dimensional(3D)AC beam was built using the “Fish” language provided by PFC3D and was employed to simulate the three-point bending beam test at two temperature levels:-10°C and 15°C.The AC beam was modeled with the consideration of the microstructural features of asphalt mixtures.Uniaxial complex modulus test and indirect tensile strength test were conducted to obtain material input parameters for numerical modeling.The 3D predictions were validated using laboratory experimental measurements of AC beams prepared by the same mixture design.Effects of mastic stiffness,cohesive and adhesive strength on AC fracture behavior were investigated using the DEM model.The results show that the 3D DEM fracture model can accurately predict the fracture patterns of asphalt concrete.The ratio of stress at interfaces to the stress in mastics increases as the mastic stiffness decreases;however,the increase in the cohesive strength or adhesive strength shows no significant influence on the tensile strength. A user-defined micromechanical model was developed to investigate the fracture mechanism of asphalt concrete (AC) using the discrete element method (DEM). A three-dimensional (3D) AC beam was built using the “Fish” language provided by PFC3D and was employed to simulate the three-point bending beam test at two temperature levels: -10 ° C and 15 ° C. The AC beam was modeled with the consideration of the microstructural features of asphalt mixtures. Uniaxial complex modulus test and indirect tensile strength test were conducted to obtain material input parameters for numerical modeling. The 3D predictions were validated using laboratory experimental measurements of AC beams prepared by the same mixture design. Effects of mastic stiffness, cohesive and adhesive strength on AC fracture behavior were investigated using the DEM model The results show that the 3D DEM fracture model can accurately predict the fracture patterns of asphalt concrete. The ratio of stress at interfaces to the stress in mastics增加 as the mastic stiffness; however, the increase in the cohesive strength or adhesive strength shows no significant influence on the tensile strength.