Laboratory evaluation of strain controlled fatigue criteria in hot mix asphalt

The fatigue lives of hot mix asphalt are affected by the test method and the loading mode. In the strain controlled mode, the 50% reduction in initial stiffness is widely used by asphalt professionals. Also, different approaches based on dissipated energy concept have been used to define the fatigue life of hot mix asphalt mixtures. In this research study, the 50% reduction in initial stiffness, Energy Ratio and Rate of Dissipated Energy Change approaches are used to depict fatigue life and compared with the observed failure point in beam fatigue test. The beam fatigue tests were conducted in accordance with AASHTO T321 using 1000 microstrain and semi sinusoidal loading at 10 Hz. The results show that the 50% reduction in initial stiffness underestimates fatigue life of hot mix asphalt mixtures. According to the tests results, the fatigue life corresponding to 65% reduction in initial stiffness is close to the observed failure point.