Comparing of Fatigue Damage Defining Ways of Asphalt Mixtures

Vehicles move on asphalt pavements repeatedly at high frequency and the stress due to temperature changing also acts on asphalt pavements repeatedly at low frequency. Many defining ways on fatigue damage have been used to study fatigue damage developing law of asphalt mixtures. But comprehensive comparing should be done between different fatigue damage defining ways. Laboratory low frequency fatigue tests and high frequency fatigue tests of asphalt mixtures were developed with Material Test System (MTS-810). The damage developing laws within fatigue life of asphalt mixtures were analyzed respectively with fatigue damage defining ways based on strain amplitude, residual strain, dynamic modulus and dissipated energy. The results show that fatigue damage developing process based on different defining ways are different from each other and the critical damage values are also different from each other. The analyzing results show that the fatigue damage developing curve based on dissipated energy defining way is quite distinct from the others. So it is best to define fatigue damage with dissipated energy and fatigue damage defining ways based on strain amplitude, residual strain, dynamic modulus are not appropriate to express fatigue damage.