Understanding the damage mechanism of asphalt binder under controlled-stress fatigue loads in dynamic shear rheometer

摘要

Fatigue damage is one of the major distresses of asphalt binder. Most of the previous studies have focused on the crack growth in asphalt binder while cracking is not the only type of damage that occurs during fatigue process, which means that the damage mechanism of asphalt binder under fatigue loads is not well understood. This study characterized and compared the fatigue damage features of asphalt binder under controlled-stress time sweep tests with different amplitudes of fatigue loads. Cohesive failure appearances of all the involved asphalt binder were collected and employed to analyze the failure process. These failure appearances showed that there were primarily two types of pattern in the failure appearance: factory roof morphology and the wave-shaped pattern. Factory roof morphology was related to the cracking of asphalt binder, and the wave-shaped pattern was linked to the plastic flow of asphalt binder. Combining the failure appearance and the collected rheological properties proved that two types of damage occurred in asphalt binder in the time sweep test: elastic damage and plastic flow damage. The former and the latter one respectively dominated the failure process of asphalt binder under small-and large-amplitude fatigue loads. During the elastic damage process, phase angle of asphalt binder held constant while the complex shear modulus kept decreasing. During the plastic flow damage process, obvious variations on both complex shear modulus and phase angle can be observed. It addition, it was found that the profile of the failure surface was concave rather than horizontal, which proved the non-negligible effect of normal force on the cracking behavior of asphalt binder.(c) 2021 Elsevier Ltd. All rights reserved.