沥青微观结构组成研究进展

为了进一步促进沥青微观组成结构的发展, 综述了国内外沥青化学组成、微观结构理论、数值模拟与试验研究方法; 介绍了沥青四组分物理化学性能, 蜡与杂原子对沥青微观结构的影响; 综合沥青胶体理论与改进的Yen模型对沥青微观结构进行了研究; 分析了沥青微观组成结构研究中常用的分子动力学与相场法; 总结了凝胶渗透色谱、红外光谱、小角散射技术、显微技术等方法在沥青微观结构的研究进展。研究结果表明: 沥青应被视为一个化学连续体, 沥青中各类分子的摩尔质量、氢碳比、极性等, 按饱和分、芳香分、胶质、沥青质的顺序递变, 主碳链大于C40的蜡可以视为沥青质组分, 沥青中的氧、氮、硫杂原子以特征官能团的形式存在于沥青质、胶质、芳香分等极性较强的组分中, 是沥青分子结构组成的关键参数之一, 也与沥青-集料的黏附性能密切相关; 沥青的胶体状态是沥青黏弹行为的微观结构基础, 改进的Yen模型可以对沥青胶体理论进一步解释, 即沥青质浓度低于纳米聚集体的临界浓度时, 沥青表现为溶胶结构, 当沥青质浓度逐渐高于纳米聚集体的临界浓度时, 沥青中出现团簇与絮凝, 沥青微观结构由溶胶结构向凝胶结构转变; 沥青微观结构中广泛采用的模拟方法包含分子动力学与相场法, 但2个模拟方法均对沥青的微观结构进行了一定程度简化, 以微观结构模拟为基础的沥青多尺度仿真方法仍面临着巨大的挑战; 结合沥青化学成分、沥青胶体理论与流变特征建立完整的力学本构关系将是沥青材料科学的重要发展方向之一。 

Research progress of bitumen microstructures and components

To further promote the development of bitumen microstructures and components, the research progresses of bitumen chemical component, microstructure theory, simulation, and experimental methods were summarized. The physical and chemical properties of four components of bitumen, and the influence of wax and heteroatoms on bitumen microstructure were investigated. The bitumen microstructure was studied by combining bitument colloid theory and modified Yen model. The molecular dynamics and phase-field method commonly used in bitumen microstructure research were analyzed. The research progress of gel permeation chromatography, infrared spectroscopy, small angel scattering technology, microscopy technique in the study of bitumen microstructure was summarized. Research results show that bitumen should be regarded as a chemical continuum system. The molar mass, hydrogen to carbon ratio, and the polarity of molecules in bitumen gradually change in the order of saturate, aromatic, resin, and asphaltene. Waxes with a main carbon chain greater than C40 can be regarded as asphaltene components. The oxygen, nitrogen, and sulfur heteroatoms of bitumen exist in the form of characteristic functional groups in the polar components such as asphaltenes, resins, and aromatics, which are key parameters of bitumen molecular structure and are closely related to the adhesion properties of bitumen-aggregates. The colloidal state of bitumen is the microstructural basis of the viscoelastic behavior of asphalt. The modified Yen model can further explain the bitumen colloid theory. When asphaltene concentration is lower than the critical concentration of nano-aggregates, bitumen microstructure turns to the sol. When asphaltene concentration is gradually higher than the critical concentration of nano-aggregates, clusters and flocculation appear in bitumen, and bitumen microstructure changes from sol to gel. The molecular dynamics and phase-field method are widely used to simulate bitumen microstructure, but both two simulation methods simplify bitumen microstructure, there is still existing a huge challenge in the multi-scale simulation method based on microstructure simulation. One of the important development directions in bitumen material science is to combine bitumen chemical composition, bitumen colloid theory, and rheology characteristics to establish a complete mechanical constitutive relationship.