Investigation of Toughening Mechanism of Virgin Asphalt by Blending with Waste Battery Powder

Waste battery powder (WBP) can effectively enhance the service performance of virgin asphalt with sol–gel structures; however, its toughening mechanism for sol–gel virgin asphalt still lacks rigorous mechanical characterization. Therefore, the objective of this study is to investigate the toughening of WBP-modified asphalt based on the mechanical parameter of cracking area. First, a 12% content of WBP was incorporated into the sol–gel 70# virgin asphalt to prepare WBP-modified asphalt and its fatigue performance was evaluated through linear amplitude, non-damage, and damage time sweep tests. Then, energy–mechanics balance equations were used to establish a cracking area model. Furthermore, the asphalt cracking area was employed to quantify its induced damage and determine the representative rate for the cracking damage process (kcd). Finally, the activation energy for cracking damage (Eacd) was used to quantify the difficulty of the cracking damage process. The scanning electron microscope test was employed to examine the microstructure of WBP-modified asphalt and the Eacd and microscopic morphology of WBP-modified asphalt were analyzed to reveal the toughening effect of WBP on virgin asphalt. The results showed that WBP-modified asphalt exhibits three nonlinear cracking stages, with a lower cracking rate than virgin asphalt. Its cracking damage generally increases over time, and the damage evolution parameter β serves as kcd. The micro-grooves and wrinkles of WBP improve bonding to asphalt, increasing the Eacd of sol–gel 70# virgin asphalt from 10.6 to 23.88 kJ·mol−1, thus achieving toughening. In summary, the fatigue damage process of WBP-modified asphalt can be characterized by the kinetic parameters β and Eacd.