Influence of Asphalt Binder Source and Polymer Type on the Performance and Fractional Composition of Asphalt Binders

The performance enhancement achieved through polymer modification depends on both the chemical composition of the base asphalt binder and the intrinsic characteristics of the modifying polymer. This study investigated the combined influence of asphalt binder source and polymer type on the engineering performance and fractional composition of asphalt binders produced from three Iraqi refineries (Dora, Nasiriyah, and Mosul). Styrene-butadiene-styrene (SBS) and ethylene-vinyl acetate (EVA) were incorporated at dosages of 2–6% by weight of binder. The binders were characterized using conventional physical tests, Energy-Dispersive X-ray (EDX) analysis, storage stability, Performance Grading (PG), Multiple Stress Creep Recovery (MSCR), Linear Amplitude Sweep (LAS), SARA fractionation, and statistical analysis. The results demonstrated that asphalt binder source significantly influenced the engineering performance and SARA fraction distribution of both unmodified and polymer-modified binders. Among the base binders, the Mosul binder exhibited the highest stiffness and rutting resistance, whereas the Dora binder contained the highest aromatic content. SBS modification produced substantially greater improvements than EVA, increasing the high-temperature grade from PG 70-x to PG 100-x and PG 106-x, whereas EVA improved the binders only to PG 76-x. SBS also reduced the non-recoverable creep compliance by up to 74%, while both polymers improved VECD-predicted fatigue life, although their relative effectiveness depended on the binder source. Overall, the findings demonstrate that optimizing polymer-modified asphalt binders requires simultaneous consideration of both the base-binder source and polymer characteristics to achieve superior high-temperature and fatigue performance.