Numerical Simulation of the Physical Processes Inducing Moisture Damage in Asphaltic Mixes

In countries that suffer from large amounts of rainfall, the asphalt wearing surfaces of the roads are often constructed of open graded asphalt mixes. The high permeability of these wearing surfaces ensures a fast drainage of the water away from the surface, thus increasing road safety. This water infiltration has, however, a negative effect on the material characteristics of the individual components of the asphalt and damages the bond between the components, leading to premature separation of the aggregates from the mix (raveling). Insight into the different phenomena that cause raveling will lead to better asphalt mix design and better road maintenance strategies. For this reason a finite element program named RoAM is developed as a subsystem of the 3D Computer Aided Pavement Analysis system (CAPA-3D) developed by the group of Mechanics of Structural Systems at Delft University of Technology in the Netherlands. This paper focuses on simulation of the degrading mechanical performance of an aggregate-mastic interface region on micro-scale, due to the combined action of moisture diffusion and mechanical loading. The proposed numerical model is shown capable of simulating the phenomenon of aggregate stripping in an asphaltic mix. Issues associated with this simulation and the ongoing experimental effort for the determination of the associated material parameters are discussed.