Abstract: In order to reveal the mechanism of nano-ZnO modifier improving the physical properties of asphalt, the molecular dynamics simulation technology was used to simulate nano-ZnO modified asphalt. The asphalt molecular model was constructed by the representative compounds of four fractions of asphalt, combined with the test results of element content of matrix asphalt and the relative content of four fractions. Models of nano-ZnO with different particle sizes and nano-ZnO/asphalt blends were built according to the morphological characteristics of nano-ZnO. The interaction between nano-ZnO and asphalt molecules was calculated by molecular dynamics method, and the diffusion properties of nano-ZnO in asphalt were analyzed. Moreover, the influence of nano-ZnO on physical modulus and the molecular structure of asphalt was investigated. According to the molecular dynamics simulation results, the modification mechanism of nano-ZnO modified asphalt was revealed. Research results show that when the simulation temperature is about 150 ℃, the van der Waals interaction and non-bonding interaction of nano-ZnO/asphalt blends reach the maximum, whose architecture is the most stable. Nano-ZnO particles increase the bulk modulus, shear modulus and elastic modulus of asphalt system and improve the high temperature performance of asphalt, so as to improve the shear resistance of asphalt. Meanwhile, nano-ZnO enlarges the centroid distance between asphaltenes and resins system molecules, alleviates of the accumulation of strong polar fractions, strengthens the ductility of branched chains between molecules and increases the compactness of asphalt structure, which contributes to a more stable colloidal structure and better physical properties of asphalt.

Key words: highway engineering; nano-ZnO; asphalt molecular model; molecular structure; physical properties; molecular dynamics

摘要： 为揭示纳米ZnO改性剂对沥青物理性能改善的机理，采用分子动力学模拟技术对纳米ZnO改性沥青进行模拟研究。借助沥青四组分代表性化合物，结合沥青的元素含量、四组分相对含量试验结果构建了沥青分子模型。根据纳米ZnO形貌特点，构建了不同粒径的纳米ZnO簇团模型及纳米ZnO/沥青共混体系模型。采用分子动力学方法计算了纳米ZnO与沥青分子间的相互作用，分析了纳米ZnO在沥青中的扩散性能，研究了纳米ZnO对沥青物理模量及沥青分子结构的影响，根据分子动力学模拟结果揭示了纳米ZnO改性沥青的改性机理。研究结果表明：模拟温度为150 ℃左右时，纳米ZnO/沥青共混体系的范德华相互作用和非键接相互作用达到最大值，体系结构最稳定；纳米ZnO颗粒增大了沥青体系的体积模量、剪切模量和弹性模量，改善了沥青的高温性能，从而提高了沥青的抗剪切能力；同时，纳米ZnO增大了沥青质与胶质体系分子间的芳环质心距离，减缓了强极性组分的堆积，加强了支链在分子间的延展性，增加了沥青结构的致密性，从而促使沥青具有更稳定的胶体结构、更好的物理性能。

关键词: 道路工程;纳米ZnO;沥青分子模型;分子结构;物理性能;分子动力学