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 (k_cd). Finally, the activation energy for cracking damage (E_acd) 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 E_acd 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 k_cd. The micro-grooves and wrinkles of WBP improve bonding to asphalt, increasing the E_acd 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 E_acd.