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<p>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.</p>

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Effects of Nano-Iron Oxide and Nano-Aluminum Oxide on the Low-Temperature Cracking Potential of HMA Exposed to Acidic and Alkaline Environments

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年9月15日

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  • Gholam Hossein Hamedi,
  • Mohammad Hosein Dehnad,
  • Munadhil Ali Hasan

摘要

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.