基于分子动力学的相变沥青物理力学性能研究

Study on Physical and Mechanical Properties of Phase Change Asphalt Based on Molecular Dynamics

相变材料可以显著提升沥青的调温能力,减少路面温度病害。为从分子层面研究相变材料对沥青力学性能及调温能力的影响,通过分子动力学模拟技术对沥青四组分(饱和分、芳香分、胶质、沥青质)建模,使用四组分平均分子结构模型构建了沥青分子结构模型并验证了其可靠性;进一步构建了沥青与相变材料共混体系模型,并对共混体系与沥青体系的力学性能参数、扩散系数、内聚能密度等参数进行对比。研究结果表明:通过沥青四组分平均分子结构“组装”的沥青分子模型具有合理性,能够真实体现沥青材料特性;相变材料的加入使得沥青体系的力学参数在一定程度上都有所提高,其中:体积模量提高了约36%,剪切模量提高了约17%,弹性模量提高了约8%;相变材料能提高沥青质的扩散速度,但对胶质、芳香分、饱和分的扩散能力有一定的削弱作用;相变材料使得沥青体系的内聚能密度增大,沥青的热稳定性得到加强;相变材料可以使沥青在吸收相同能量的情况下温度变化更小,有效发挥了对沥青温度的调控作用。

PCM(Phase Change Materials)can significantly improve the temperature regulation abili-ty of asphalt binder.It can reduce road diseases caused by temperature changes.In order to study the ef-fect of PCM on the mechanical properties and temperature regulation ability of asphalt from the molec-ular level,the SARA fractions(saturates,aromatics,resins,asphaltenes)of asphalt binder was modeled by molecular dynamics simulation technology.The molecular structure model of asphalt binder was constructed by using SARA average molecular structure models.Further more,the blending model of asphalt and PCM was constructed.Then,the reliability of the asphalt model was verified.And the me-chanical properties parameters,diffusion coefficient,cohesive energy density and other parameters were compared between the above two models.The results showed that:the molecular model of as-phalt binder was reasonable and could truly reflect the characteristics of asphalt binder,the addition of PCM could improve the mechanical parameters of asphalt binder,e.g.the bulk modulus,shear modulus and elastic modulus increased by 36%,17%and 8%,respectively;PCM increased the diffusion rate of asphaltenes,but decreased the diffusion coefficients of resins,aromatics and saturates;PCM increased the cohesive energy density of asphalt binder and enhanced the thermal stability of asphalt binder;PCM made the temperature change of asphalt binder smaller under the condition of absorbing the same energy,and effectively played the control ability of asphalt temperature.