An Irreversible Cohesive Crack Model for Estimating the Fatigue Life of Asphalt Mixtures

Fatigue cracking is one of the main distresses in flexible pavements. Depending on the nature of loading and the structure of pavement, the cracks inside the asphalt pavements can be reflective, top down or thermal types which can be initiated due to traffic cyclic loads of moving vehicles or thermal stresses induced by daily or seasonal temperature variations. Fracture mechanics is one of the suitable methods for characterizing the fatigue characteristics of asphalt pavements. In this research, using the Laser Scanning Detection (LSD) system as a tool for inspecting the crack forming in the asphalt mixtures, an irreversible damage-based cohesive crack model is employed to simulate the crack propagation and estimate the total fatigue life of asphalt concrete mixtures. The suggested framework provides a hysteresis traction separation law which considers material’s degradation during the cyclic loads. In the experimental part of this paper, two different asphalt mixtures with two air void ratios were tested under uniaxial fatigue loading and the dynamic modules of the tested asphalt were determined versus number of cyclic loads. It was shown that the cohesive crack finite element modeling results were in good agreement with other fatigue criteria as well as the laboratory fatigue tests.