Evaluating Rheological and Mechanical Properties of Asphalt Binders and Mixes with Waste EPDM Rubber and Pyro-Oil Composites

Pyrolysis is increasingly acknowledged as a sustainable process for converting waste plastic and tire rubber into pyro-oils, addressing the environmental challenges faced by India and other countries in the disposal of these materials. A significant quantity of high-quality ethylene-propylene-diene-monomer (EPDM) rubber, widely used in nontire rubber components, roofing membranes, and sealing applications, becomes available after its use/service life. Exploring diverse applications for pyro-oils and EPDM rubber is crucial for their effective integration into waste management strategies. Whereas tire and plastic pyro-oils improve the fatigue and low-temperature performance of asphalt binders, they can adversely affect high-temperature performance. However, using pyro-oils and EPDM rubber modifiers in composite or hybrid modifications may lead to improvements across a broader temperature range. This study explored the use of discarded EPDM rubber and waste tire pyro-oil and plastic pyro-oil for individual and composite asphalt binder modification. Four binder modification formulations were explored: (1) individual addition of modifiers, (2) sequential addition of EPDM rubber and pyro-oils for composite modification, (3) modification with a heat-pretreated composite, and (4) modification with a microwave-pretreated composite. Various modified binders formulated were first examined for storage stability, rutting, fatigue, and cracking properties and then were used to fabricate dense-graded asphalt mixes, which were assessed for their mechanical performance in terms of rutting, fatigue, cracking, moisture damage, and raveling resistance. Asphalt mixes with binders individually modified with pyro-oils suffered from premature rutting failure. In contrast, the mix with EPDM rubber-modified binder was found to be challenging with respect to fatigue and low temperature/thermal cracking. Asphalt mixes with binders modified using heat-pretreated composites delivered the most synergistic performance, outperforming the control mix by 86% in the Grey relational analysis, which considered all tested parameters. This highlights the significance and benefits of composite modification of asphalt binders through the incorporation of EPDM rubber and pyro-oils.