Jaleel, Mustafa MohammedAlbdairi, MustafaAlmusawi, Ali2025-07-062025-09-182025-07-062025-09-1820252673-7108https://doi.org/10.3390/constrmater5020040https://hdl.handle.net/20.500.12416/14560Albdairi, Mustafa/0009-0002-6673-363XIraq's extreme summer temperatures pose critical challenges to pavement durability, as conventional asphalt mixtures often fail under prolonged thermal stress. This paper provides a comparative evaluation of the high-temperature performance of unmodified (40/50 penetration grade) and polymer-modified (PG 76-10) asphalt mixtures for the asphalt course layer. Marshall stability, flow, and stiffness were measured at elevated temperatures of 60 degrees C, 65 degrees C, 70 degrees C, and 75 degrees C after short-term (30 min) and extended (24 h) conditioning. Results show that while both mixtures experienced performance degradation as the temperature increased, the polymer-modified mixture consistently exhibited superior thermal resistance, retaining approximately 9% higher stability and 28% higher stiffness, and displaying 18% lower flow deformation at 75 degrees C compared to the unmodified mixture. Stability degradation rate (SDR), stiffness degradation rate (SiDR), and flow increase rate (FIR) analyses further confirmed the enhanced resilience of PG 76-10, showing nearly 39% lower FIR under thermal stress. Importantly, PG 76-10 maintained performance within specification thresholds under all tested conditions, unlike the conventional 40/50 mixture. These findings emphasize the necessity of adapting mix design standards to regional climatic realities and support the broader adoption of polymer-modified asphalt binders to enhance pavement service life in hot-climate regions like Iraq.eninfo:eu-repo/semantics/closedAccessPolymer-Modified Bitumen (PMB)Marshall StabilityHigh-Temperature PerformancePg76-1040/50 BitumenAsphalt PavementStiffnessArticle10.3390/constrmater50200402-s2.0-105009333070