In the present study, ethylene‐vinyl acetate (EVA) and crumb rubber (CR) were used as bitumen modifiers. The experiment was designed by response surface methodology (RSM) at different levels of modifier additives based on the central composite design (CCD). Next, the Superpave protocol was followed to evaluate the modified bitumen performance at different temperatures compared with the unmodified bitumen. In this regard, to evaluate at high temperatures, a dynamic shear rheometer (DSR) test was performed, and G^∗/sinδ index was examined on bitumen samples after aging. Besides, the bending beam rheometer (BBR) test was performed to evaluate the low‐temperature behaviour of the modified bitumen according to the SHRP standard based on the creep stiffness and creep rate. The optimal combination of additives was evaluated using RSM and analysis of statistical values to improve the performance properties of bitumen at high and low temperatures. Moreover, based on the DSR and BBR test results, 5.6% of EVA and 3.9% of CR were selected as the optimal values for the modified bitumen behaviour at the high and low temperatures of the mixture.

Low-temperature cracking is a significant concern in asphalt pavements, especially in regions exposed to moisture with varying acidity from surface runoff. This study investigated whether nano-iron oxide (Fe₂O₃) and nano-aluminum oxide (Al₂O₃) can enhance the cracking resistance of hot-mix asphalt (HMA) under such environmental stresses. PG 58–22 bitumen was modified with 0.5% and 1% of the nanomaterial by weight. The modified mixtures were evaluated using semi-circular bending (SCB) and Pull-Off tests to assess fracture energy (FE), fracture toughness (FT), cohesion (CP), and adhesion (AP). Moisture conditioning at pH levels of 5, 6, 7, 8, and 9 simulated the effects of acidic and alkaline environments. Exposure to non-neutral moisture significantly reduced the fracture, adhesive, and cohesive properties of unmodified HMA. In contrast, both nanomaterials improved performance across all parameters, with nano-Al₂O₃ demonstrating superior results compared to nano-Fe₂O₃. The nanomaterials also enhanced the m-value of bitumen, indicating improved stress relaxation capacity at low temperatures. Increasing the nanomaterial content from 0.5% to 1% led to further improvements, particularly under extreme pH conditions. Statistical analysis confirmed that aggregate type, bitumen modification, and environmental conditions significantly affected FE, FT, CP, and AP parameters. The only exception was CP, which was not significantly influenced by aggregate type. The combination of limestone aggregate and 1% nano-Al₂O₃ was identified as the most effective in mitigating low-temperature cracking. These findings suggest nano-Al₂O₃ and nano-Fe₂O₃ as promising modifiers for enhancing pavement durability, reducing moisture sensitivity, and improving the longevity of asphalt surfaces exposed to challenging environmental conditions.