Asphalt pyro-rejuvenators based on waste tyres: An approach to improve the rheological and self-healing properties of aged binders

Abstract

Waste Tyres (WT) are a significant fraction of industrial waste and a source of environmental hazards withlimited valorisation. To reduce this problem, currently there is a growing interest in valuing the WT throughpyrolysis to obtain multifunctional liquids to improve the rheological and self-healing properties of aged binders.This research provides a comprehensive study on using WT mixtures as precursors for asphalt rejuvenators bymeans of pyrolysis and distillation processes. To this end, WT polymeric fractions from light (WT-L) and miningtrucks (WT-M) were used as feedstock and characterised for compositional and thermal properties. Additionally,micropyrolysis coupled with gas chromatography/mass spectrometry (Py-GC-MS) was used to identify the majorproducts in pyrolysis vapours, to elucidate the reaction maps describing thermal degradation of WTs and topredict the feasible reaction conditions. The pyrolysis liquids were produced after a screening of reaction conditionsand subjected to distillation, following a response surface model to produce an optimised pyrorejuvenator.The results showed that the pyrolytic rejuvenator obtained through pyrolysis at 465 ◦C anddistillation cutting at 160–200 ◦C is mainly composed of hydrocarbons and aromatic substances (95.5%), with asignificant proportion of limonene (33.71%). Furthermore, the pyrolytic rejuvenator exhibited highly desirablephysical properties in the context of its application and excellent oxidative stability (85.7%). Otherwise, it wasdetermined that bitumen mixtures with 3%–6% doses of pyro-rejuvenator improved the viscosity, softeningpoint, and penetration of aged binders, restoring their physical properties to the virgin state. In conclusion, pyrorejuvenatorscan be successfully used as a promising solution to produce more durable and sustainable pavementswith improved rheological and healing properties.