Abstract

The progressive ageing of bitumen in road construction, driven by environmental and traffic conditions, presents a significant challenge in pavement engineering. This ageing process reduces the lifespan of the asphalt roads and their intrinsic self-healing capabilities to seal cracks. To address this issue from a waste valorisation perspective, the present study proposes using a pyro-rejuvenator (PR), obtained by pyrolysis of waste tyres and optimised by thermal fractionation, as a novel rejuvenating agent for aged asphalts. The effects of the PR at different dosages (3 %, 6 %, and 9 % wt. of bitumen) on the chemical, rheological, and self-healing properties of long-term aged bitumen (PAV) were evaluated. In this study, a commercial rejuvenator (CR) was also used at equivalent dosages for comparison. The effect of the type and content of the rejuvenators on the PAV-aged bitumen samples was evaluated through chemical properties. This analysis included the change in the carbonyl (C = O) and sulfoxide (S = O) functional groups in bitumen molecules by FTIR-ATR tests. Additionally, rheological tests using a Dynamic Shear Rheometer (DSR) on bitumen samples were also carried out to evaluate changes in the dynamic shear modulus (|G*|) and phase angle (delta) through frequency-temperature sweep tests. A methodology was also developed to quantify the self-healing capability of modified bitumen by measuring the recovery of the |G* | in fatigue DSR tests. The results indicate that the addition of PR up to 6 % wt.: i) restored the changes in the carbonyl and sulfoxide functional groups of a PAV-aged bitumen to levels between a short-term aged bitumen (RTFO) and an unaged state; ii) promoted the restoration of the |G* | and delta of the PAV-aged bitumen to levels comparable to an unaged bitumen, and iii) promoted the healing of the PAV-aged sample. In conclusion, this research highlights the potential of the pyro-rejuvenator as a sustainable solution for improving the rheological and self-healing properties of aged bitumen. These findings also support its use as an alternative additive to enhance the chemo-mechanical properties of aged bitumen, particularly in mixtures with high Reclaimed Asphalt Pavement (RAP) content, among other applications.