基于分子动力学模拟的胶粉改性沥青自愈合性能研究

Research on self-healing properties of crumb rubber modified asphalt based on molecular dynamics simulation

采用沥青十二分子模型和丁苯橡胶(SBR)分子模型,建立了基质沥青和胶粉改性沥青自愈合模型,并利用分子动力学模拟研究了不同温度下沥青自愈合过程中沥青分子的运动规律和扩散行为。从密度、扩散系数、内聚能密度和相对浓度多个指标评价了沥青分子和胶粉改性沥青模型的自愈合能力。研究结果表明,胶粉改性沥青自愈合模型的密度达到稳定的时间早于基质沥青。两个模型自愈合扩散系数随着温度的升高而增大。在各温度条件下,胶粉改性沥青整体扩散系数较大,说明胶粉的添加能显著增大沥青的扩散系数,自愈合性能较基质沥青更好。从相对浓度的变化来看,沥青的自愈合可以分为扩散、接触、相互融合三个阶段,胶粉改性沥青模型的相对浓度数值趋近为1的时间早于基质沥青自愈合模型。该计算结果与密度、均方位移具有一致性,都说明胶粉改性沥青自愈合效果好于基质沥青。

Self-healing models of base asphalt and crumb rubber modified asphalt were built using the asphalt 12 molecular model and the styrene-butadiene rubber(SBR)molecular model,and molecular dynamics simulations were used to investigate the motion rule and the diffusion behaviour of asphalt molecules during asphalt self-healing process at different temperatures.The self-healing ability of the asphalt molecules and the crumb modified modified asphalt model was evaluated in terms of density,mean square displacement,cohesive energy density and relative solubility.The results of the research showed that the time of density of the self-healing model of crumb rubber modified asphalt reached stability earlier than that of the self-healing model of base asphalt.The self-healing diffusion coefficients of the two models increased with increasing temperature.The overall diffusion coefficient of the crumb rubber modified asphalt is larger under all temperature conditions,indicating that the addition of crumb rubber can significantly increase the diffusion coefficient of asphalt,and the self-healing performance is better than that of the base asphalt.From the change of relative concentration,the self-healing of asphalt can be divided into three stages of diffusion,contact,and mutual fusion,and the time of relative concentration value of the model of crumb rubber modified asphalt tends to 1 earlier than the model of base asphalt self-healing.This calculation result has consistency with the density and mean square displacement,which all indicate that the self-healing effect of crumb rubber modified asphalt is better than that of the base asphalt.