Mechanical alterations of bitumens with different crude oil origins through polymer modification

Hot mix asphalt (HMA) performance is significantly influenced by the chemical variability of bitumen, which is closely linked to crude oil origin. These source-dependent variations also affect the response of bitumen to polymer modification. This study investigates the mechanical performance of asphalt mixtures produced using two bitumens with the same penetration grade but obtained from different refineries (Turkey–Batman and Iraq–Lanaz), modified with two styrene-based polymers: styrene-butadiene-styrene (SBS) and styrene-ethylene-butadiene-styrene (SEBS). Polymer-modified binders (2%, 3%, and 4%) were prepared and evaluated through Marshall stability, indirect tensile strength (ITS), stiffness modulus (ITSM), fatigue, and dynamic creep tests. The results demonstrated that bitumen origin plays a decisive role in both binder behavior and mixture performance. SEBS modification produced superior stability and deformation resistance in mixtures with Iraqi bitumen, whereas SBS modification provided the highest stability and stiffness improvement in mixtures with Batman bitumen. Fatigue and creep analyses indicated that SEBS-modified mixtures, particularly with 3% SEBS, achieved the longest fatigue life and highest resistance to permanent deformation. Overall, the study highlights that the interaction between binder origin and polymer type critically governs the performance of polymer-modified asphalts, and that optimal polymer dosage varies depending on the source characteristics of the bitumen.