Synergistic Effects of Devulcanized Rubber, Polyethylene, and Fumed Silica on the Rheological and Structural Stability of Bitumen

This study examines the influence of virgin polyethylene (vPE), recycled polyethylene (rPE), and Aerosil (A) on the performance of bitumen binders modified with partially devulcanized rubber (DVR). The experimental program included morphology analysis, determination of devulcanization degree, dynamic viscosity measurements, shear stress-shear rate analysis, load-displacement (<i>F-</i>Δ<i>l</i>) testing, storage-stability evaluation, ring and ball softening point (R&B), penetration (<i>P</i>), and elastic recovery (<i>ER</i>) testing. The results show that DVR-rPE-modified bitumen binders exhibit 20-35% higher viscosity and up to 25% greater elongation at the break compared to DVR-vPE-modified bitumen systems, indicating more effective interaction with the bitumen matrix. The incorporation of Aerosil increased viscosity ca. 1.5-2 times for DVR-rPE and DVR-vPE-modified systems, respectively. Meanwhile, top and bottom differences in R&B decreased by a factor of 1.6-5 for DVR-rPE and DVR-vPE-containing composites, respectively, demonstrating significant enhancement in structural stability during storage. Mechanical testing further revealed that DVR-rPE + A binders absorbed 10-20% more deformation energy and consistently maintained ER values above 70-80%, corresponding to a higher elastic recovery grade at 25 °C. Overall, the DVR-rPE + A system provided the most balanced improvements in rheological, mechanical, and thermal properties, confirming its potential for use in high-performance, thermally stable, and environmentally sustainable bituminous materials for pavement applications.