Fatigue Crack Propagation Model of Asphalt Concrete Based on Viscoelastic Fracture Mechanics

A fatigue crack propagation model of asphalt mixtures is developed on the basis of viscoelasticity and fracture mechanics. The fatigue model is extended from the generalized J-integral model proposed previously by the authors to consider the effects of temperature and air void. Laboratory fatigue crack propagation tests for three different asphalt mixtures are performed at various loading conditions, air voids, and temperatures. The test results indicate that the J-integral could take care of the loading magnitude and frequency dependence of the crack speed but could not consider temperature dependence completely. The air void and temperature effects on crack propagation in asphalt mixtures are investigated. Generally the crack propagation of the asphalt mixtures is developed more quickly at high temperatures and large air voids. Finally, the generalized J-integral model is extended by employing a regression function to take care of the temperature and air void effects. The resulting model could provide a reasonable prediction of fatigue crack propagation lives of the asphalt mixtures under various loading and temperature conditions.