Microstructural analysis of porous asphalt concrete mix subjected to rolling truck tire loads

Porous asphalt concrete (PAC) course is best known for its noise reduction and improved wet skid resistance characteristics. Nevertheless, the use of PAC is associated with reduced lifetimes and high maintenance costs, mainly owing to various distress mechanisms such as raveling. Therefore, it is necessary to have a better understanding of the stress states associated at the micromechanical level, that is, at the mastic-aggregate interfacial zone and the mastic itself. For this purpose, it is necessary to develop micromechanical finite element (FE) models that are composed of realistic asphalt mix meshes with different phases that are subjected to rolling wheel loads. A framework is presented to develop a three-dimensional FE model capable of simulating a rolling wide-base truck tire over an asphalt pavement surface. From results of FE simulations, the stress states at the mastic and mastic-aggregate interfacial layer were studied. For the analyzed surface of the PAC mix, it was observed that the mastic phase registered high stress states compared with the mastic-aggregate interfacial phase, suggesting that the sample may experience a cohesive failure in the long run. The developed methodology also provides a tool to analyze the influence of tire operating conditions such as tire inflation pressures and loads on the stress states of asphalt mixes. Finally, the micromechanical stress response of PAC mix was compared with that of other conventional asphalt mix designs, and it was found that the magnitude of stresses developed in the mastic of PAC are higher compared with the conventional asphalt mix designs.