The interface behaviour between layers of a composite pavement is analysed using DEM simulations of a direct shear test. Bituminous and cement pavement materials are modelled by cohesive grain assemblies with standard size distributions. The contact model uses a Coulomb elastic-plastic law associated with tension and shear limit strengths. According to the strength value of the contact bond, cohesive or frictional interfaces are simulated. Depending on the fine particles content, several interface grading are considered. The macroscopic shear strength of the interface results to be more dependent on the binder resistance in the case of the fine grading than in the coarse one. The analyses of the contact forces network along the interface exhibit a better mobilisation of the cohesive forces in the case of the fine interfaces. Inversely, in the case of the coarse interface, compression and frictional forces bring a higher contribution to the macroscopic shear resistance
