Abstract

This study investigates an optimised pyro-rejuvenator (PR), derived from the pyrolysis of waste tyres, as a novel agent for self-healing asphalt. A multi-scale approach, encompassing chemical, microstructural, and mechanical evaluations, was employed to assess the effectiveness of the pyro-rejuvenator. The PR was incorporated into long-term aged bitumen (PAV) at dosages of 3 wt. % and 6 wt. %, with chemical changes analysed using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and chemical fractionation (SARA). The self-healing performance of the treated and unaged bitumen was evaluated through fatigue-healing-fatigue tests using a dynamic shear rheometer (DSR) and tensile tests under static conditions. Additionally, the PR's efficacy was compared with a commercial rejuvenator. Results showed that PR's high content of alkenes and aromatics (e.g., limonene: 32.9 %, cymene: 20.65 %) facilitated the restoration of the maltenic fraction in bitumen and enhanced chemical interactions with the treated material. These compounds also promoted the pepticising effect on the "bee-like" structures, leading to a more homogeneous microstructure. Under optimal conditions (6 wt. % PR dosage and 30 degrees C), a fatigue healing index of 30 % was achieved, comparable to virgin bitumen (31 %). In tensile tests at 25 degrees C after 12 h, the healing index matched that of the commercial rejuvenator. These findings highlight the potential of pyro-rejuvenators as a sustainable and effective solution for the functional restoration of aged bitumen.