Discrete Modelling of 2PB Complex Modulus Test of Hot Asphalt Mixes Using Irregular Aggregates

Asphalt mixtures are complex multiphase materials showing a viscoelastic behavior. In order to assess the mechanical response under traffic of these materials, a typical practice is to perform a complex modulus test. An alternative to laboratory characterization is to simulate numerically the complex modulus test by means a discrete approach. Classical discrete approaches are able to reproduce the mechanical performances of asphalt mixtures, but show some difficulties to model non-spherical particles. In this work, the complex modulus test is reproduced numerically for an asphalt mixture by 3D simulations carried out with the LMGC90 code. A viscoelastic contact law is used to handle the interaction between particles with irregular shapes. The numerical aggregates were generated using the particle size distribution (PSD), the flakiness index (FI), and statistic data of actual aggregates, without using complex imaging technics. Experimental and numerical testing campaigns were conducted for the complex modulus test on trapezoidal samples in a two-point bending (2PB) configuration. The numerical model was able to reproduce the mechanical performances obtained during the experimental tests, regarding the viscoelastic properties of the material. The influence on the mechanical performances of particle shape considering irregular aggregate was analyzed. The proposed model can be used to simulate the mechanical response of road structure under traffic loading concerning rutting, crack propagation and fatigue damage.