Mechanistic Characterization of Fatigue Damage Process and Failure Predictions of Asphalt Binders

To better understand the fatigue damage characteristics of asphalt binders in a whole process, an energy-based mechanistic (EBM) approach was employed. A damage density is used to quantify the damage in the material. Two kinds of asphalt binders were tested using a time sweep fatigue test at three temperatures and three strain levels. Two separation points divide the damage process of the asphalt binder into three stages, including the (1) edge flow stage, (2) Mode III cracking stage, and (3) Mode II cracking stage. The separation points on the damage density versus loading cycle curve are defined as the load cycles corresponding to the peak values of dissipated pseudostrain energy (DPSE) and phase angle. At the end of the third stage, a fatigue failure point is defined at the load in which the phase angle reaches its lowest value and starts to oscillate. The accumulated DPSE at the failure point is defined as fatigue energy consumption (FEC). The FEC is proven to be a reliable characterization indicator for the material resistance to the fatigue damage in asphalt binders. The ratios between the accumulated DPSE at the two separation points to the FEC are material constants and independent of environmental and load conditions, such as temperatures and strain levels. Based on this characteristic, a method to predict the FEC of an asphalt binder is proposed.