Abstract
Abstract
The growing demand for cost-effective and sustainable asphalt binder modification has increased interest in waste-derived polymers in hybrid systems. Ethylene-propylene-diene monomer (EPDM) recovered from end-of-life rubber offers a potential route to reduce reliance on commercial modifiers such as styrene-butadiene-styrene (SBS), yet EPDM–SBS interactions remain insufficiently studied. This research evaluates the viscoelastic behavior of EPDM-SBS hybrid binders and identifies performance-optimized formulations using rheological modeling and numerical optimization. Dynamic Shear Rheometer frequency sweeps (0.1–10 Hz) were performed at 40–80 °C to develop master curves, which were fitted with the Christensen-Anderson (CA) and Cross models. EPDM, despite being a waste material, markedly increased complex modulus and viscosity, particularly in the presence of SBS. Hybrid binders showed lower crossover frequency, longer relaxation times, and reduced crossover stress compared with single-modifier binders, indicating a more elastic response under long-term loading. Both models closely matched the experimental data (R2 > 0.99). Response Surface Methodology indicated temperature as the primary driver of
G
*/sinδ, followed by SBS and EPDM contents. Overall, within the investigated high-to-intermediate temperature rheological domain, waste EPDM showed potential to partially reduce SBS demand while maintaining favorable binder-level viscoelastic and flow characteristics.