Characterization of Interface Failure Envelope and Shear Fatigue Life of Airfield Asphalt Mixtures

Abstract

Adequate interface shear resistance is crucial to ensure continuous transfer of traffic loading to underlying layers for airfield pavements. Engineers often rely on interface shear strength (ISS) measured through simple monotonic testing, which provides a rough estimate of the interface bonding strength but does not provide insights into interface properties influenced by complex stress states. This study aims to characterize the interface failure envelope and fatigue life of airfield asphalt mixtures using a new test protocol. The failure envelope of the asphalt mixture is characterized with the cohesion strength and friction angle. The fatigue test method adopts actual stress states experienced in airfield pavements under moving aircraft tire loads. A displacement-based new failure criterion was proposed for determination of fatigue life as a function of confining stress. This failure criterion not only eliminates the limitations of traditional methods for interface shear fatigue testing but also reduces the variability in results and shortens the test turnaround time. The results show that although two stress states yield the same stress ratio, the stress state with lower confining stress is more critical to interface failure than that with higher confining stress. The shear fatigue life is found to correlate well with the ISS.