Discrete element visco-elastic modelling of a realistic graded asphalt mixture

The Discrete Element Model has been used here to simulate constant strain rate uniaxial compression tests for a realistic asphalt mixture comprising graded aggregates. A numerical sample preparation procedure has been developed to represent the physical specimen. A parallel bond model has been used in the elastic modelling to give moment resistance at the contacts. Uniaxial constant strain rate loading and unloading tests have been simulated. The effects of the normal to shear contact stiffness ratio on the bulk properties, the parallel bond radius, the number of particles and their positions, and the loading speed have been investigated. A modified Burger's model has been used to introduce time-dependent contact stiffness with the ability to transmit moment and torsion. Two-ball clumps have been used to investigate the effect of particle shape. The effect of Burger's model parameters, the ratio of normal to shear Burger's model parameters, the bond radius multiplier, the friction coefficient and the bond strength distribution in the viscoelastic simulations have been investigated. Constant strain rate uniaxial compression tests have been undertaken in the laboratory where the axial stress–strain response has been measured for comparison with the numerical modelling results. The modified Burger's model has proved to be useful and ready for simulating uniaxial constant strain rate and creep tests in the laboratory.