Performance and Interaction Mechanisms of Bitumen Modified with Devulcanized Rubber-Recycled Polymer Composites

The accumulation of end-of-life tires and post-consumer polyolefin waste is a growing environmental burden, and their reuse as bitumen modifiers offers a sustainable, large-volume outlet in road construction. This study investigated paving-grade bitumen modified with four pre-compounded, partially devulcanized rubber (DVR)-recycled-polymer composites, differing in polymer type and, for two of the systems, in styrene–butadiene–styrene (SBS) chain architecture (linear or radial), added at 9–15 wt.%. The modified binders were characterized by penetration, softening point, elastic recovery, force ductility, low-temperature brittleness, and dynamic shear rheometry (DSR), together with FTIR, TGA, and fluorescence microscopy. All four composites improved binder stiffness, elasticity, and high-temperature rheology relative to the unmodified bitumen, with the two SBS-containing systems performing best overall. At the highest modifier content, the best-performing composite roughly halved the penetration and raised both the softening point and the higher critical temperature or rutting parameter by approximately 28–30 °C, while also markedly improving elastic recovery and low-temperature flexibility relative to the base bitumen. These findings indicate that SBS-containing devulcanized-rubber/recycled-polymer composites are promising sustainable modifiers for producing high-performance bituminous binders from waste-derived materials.