Innovative Utilization of Waste Zanthoxylum Seed: Enhancing Rheological and Thermal Stability of Rejuvenated Asphalt Binder

The limited stability and antiaging performance of traditional asphalt rejuvenators hinder the effective use of reclaimed asphalt pavement in hot mix asphalt. This study investigates Zanthoxylum seed oil (ZSO), derived from agricultural waste, as a rejuvenator and antioxidant for long-term aged asphalt. Using Pen60/80 asphalt as the control, asphalt binders at different service life stages are simulated using a rolling thin-film oven and pressure aging vessel. The physical, rheological, and molecular structure properties of virgin, aged, rejuvenated, and rejuvenated aged binders are evaluated using the Dynamic Shear Rheometer, Bending Beam Rheometer, and Fourier-Transform Infrared Spectroscopy (FTIR). The results show ZSO significantly enhances the viscoelastic properties of aged asphalt through a softening effect rather than substantial molecular structure repair. The phase angle increase stabilizes between 0.2% and 0.7% when the ZSO content exceeds 8%, but further increases in concentration accelerate strain accumulation and reduce permanent deformation resistance. The optimal ZSO dosage for long-term aged Pen60/80 asphalt is 8%–9% (by mass of aged asphalt), which improves fatigue and low-temperature properties while maintaining rutting resistance comparable with virgin asphalt. Asphalt rejuvenated with ZSO, characterized by a lower activation energy, shows reduced thermal oxidative sensitivity and improved thermal cracking stability during aging, with a low-temperature performance decay rate at 68% of virgin asphalt. In addition, the FTIR analysis indicates that the aging pattern of carbonyl in the binder matches rheological property degradation. In conclusion, ZSO demonstrates remarkable effectiveness in enhancing the performance and antiaging capacity of aged asphalt, highlighting its potential for asphalt rejuvenation.