Effects of Elvaloy and Polyphosphoric Acid on the High-Temperature Performance of Asphalt Binders

This study investigates the effects of Elvaloy and polyphosphoric acid (PPA) as alternative modifiers to the commonly used styrene–butadiene–styrene (SBS) polymer on the rheological and mechanical properties of bituminous binders and hot mix asphalts. A 50/70 penetration grade bitumen obtained from the TÜPRAŞ Batman refinery was used as the base binder, which was modified using three different Elvaloy + PPA combinations (0.8% + 2%, 0.9% + 1%, and 1% + 0%). The rheological behavior of the modified binders was evaluated by Dynamic Shear Rheometer (DSR) tests at temperatures ranging from 52 °C to 88 °C. The results revealed that Elvaloy and PPA significantly improved the rutting resistance (G/sin δ)* and elastic response of the binders compared with the neat bitumen. Each 6 °C temperature increase caused approximately a 50% reduction in the rutting parameter, but the modified binders maintained higher stiffness values, particularly E1 and E2 formulations, which met the 1000 Pa specification limit up to 82 °C. The phase angle (δ) increased with temperature for all binders, yet the modified ones exhibited lower δ values, confirming enhanced elasticity due to PPA’s effect. Overall, the combined use of Elvaloy and PPA demonstrated a synergistic improvement in binder performance, providing a technically efficient and economically viable alternative to SBS for asphalt pavements subjected to high thermal loads and heavy traffic conditions.