An energy based crack growth model is developed in this study to simulatethe propagation of top-down cracking in asphalt pavements. A viscoelasticfracture mechanics approach, generalized J integral, is employed to modelthe crack growth of asphalt concrete. Laboratory fatigue crack propagation tests for three different asphalt mixtures are performed at various loadlevels, frequencies and temperatures. Disk-shaped specimens with a properloading fixture and crack growth monitoring system are selected for the tests. It is observed from the tests that the crack propagation model basedon the generalized J integral is independent of load levels and frequencies, while the traditional Paris law model based on stress intensity factoris dependent of loading frequencies. However, both models are unable to take care of the temperature dependence of the mixtures. The fatigue crack propagation model proposed in this study has a good agreement between experimental and predicted crack growth lives, which implies that the energy based J integral could be a better parameter to describe fatigue crack propagation of viscoelastic materials such as asphalt mixtures.
Abstract