Performance evaluation of hot-climate asphalt binders modified with different nano materials

Asphalt pavements form the backbone of modern transportation systems due to their cost-effectiveness, structural adaptability, and ease of maintenance; however, their long-term performance is often compromised by binder aging, oxidation, and thermal stresses that lead to cracking and rutting. This study investigates the effects of Titanium Dioxide, Carbon Nanotubes, and Natural Graphite Oxide (NGO) on the rheological and mechanical properties of asphalt binders under the hot-climate conditions of Najaf, Iraq. The base binder (PG 70–16) was modified with varying dosages of nanomaterials (1–7% TiO 2 , 0.5–2% CNT, and 0.2–1% NGO) and evaluated through Rotational Viscosity, Dynamic Shear Rheometer (DSR), Multiple Stress Creep Recovery, and Bending Beam Rheometer tests, alongside Scanning Electron Microscopy. Results indicated that nanomaterial modification significantly enhanced binder stiffness, elasticity, and temperature susceptibility, increasing the performance grade by about +6 °C to PG 76–16. The optimal dosages—5% TiO 2 , 1.5% CNT, and 0.5% NGO provided the best balance between rutting resistance, fatigue life, and flexibility. TiO 2 and CNT reduced non-recoverable creep compliance (Jnr) by 20–25% and 10–15%, respectively, while improving recovery (R) by up to 10%. Fatigue performance improved by 12–15% with CNT and 8–12% with NGO, and low-temperature stiffness at −12 °C decreased by 45% for TiO 2 and 10–15% for NGO, reducing cracking potential. Although viscosity increased moderately (up to 18%), all binders remained below the 3000 mPa·s limit, ensuring acceptable workability. SEM analysis confirmed uniform nanoparticle dispersion at optimal contents, while higher dosages led to agglomeration and reduced performance. Overall, CNTs provided the greatest reinforcement, TiO 2 offered balanced performance, and NGO enhanced flexibility, confirming nanomodification as a practical, cost-effective strategy for improving asphalt binder durability and pavement performance in hot-climate regions such as Iraq. Results indicated that nanomaterial modification significantly enhanced binder stiffness, elasticity, and temperature susceptibility, increasing the performance grade by about +6 °C to PG 76-16. TiO 2 (5 %) and CNT (1.5 %) reduced non-recoverable creep compliance (Jnr) by 20–25 % and 10–15 %, respectively, while increasing recovery (R) by up to 10 %. Fatigue performance improved by 12–15 % with CNT and 8–12 % with NGO. Low-temperature stiffness at −12 °C decreased by 45 % for TiO 2 and 10–15 % for NGO.