Cao Wei, Fini Elham
School of Civil Engineering, Central South University, Changsha 410075, China.
School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287, USA.
Polymers (Basel). 2022 Jul 19;14(14):2916. doi: 10.3390/polym14142916.
Oxidative aging is an inevitable environmental factor that accelerates asphalt pavement deterioration. This study employed a molecular dynamics simulation to investigate the impact of aging on asphalt cement from the perspectives of thermodynamic properties, and diffusion and adhesion characteristics. Results indicate that aging increased bulk density from 1.008 to 1.081 g/cm and cohesive energy density by 15.6%, which was attributed to the promoted molecular polarity and intermolecular attractiveness. The enhanced molecular interactions also reduced molecular mobility, which led to an increase in the glass transition temperature by 30 K, suggesting that aging diminished the resistance of asphalt to thermal cracking. Simulations of the diffusion behaviors across different temperatures demonstrated that the Arrhenius relationship described well the temperature dependence of the diffusion coefficient, and that aging considerably slowed down the diffusion process as represented by Arrhenius prefactor , which dropped by 38.2%. The asphalt-aggregate adhesion was assessed using layered models with and without a water interlayer of different thicknesses. The adhesion was enhanced upon aging due to the significantly improved electrostatic interactions at the interface. Evaluation of the residual adhesion with the presence of interfacial water suggested that aging would raise the moisture susceptibility of asphalt pavement. The increase in molecular polarity was considered to be highly responsible for these aging consequences, and was thus further investigated via the electrostatic potential surface and dipole moment.
氧化老化是加速沥青路面劣化的一个不可避免的环境因素。本研究采用分子动力学模拟，从热力学性质、扩散及粘附特性等角度研究老化对沥青胶结料的影响。结果表明，老化使体积密度从1.008 g/cm增加到1.081 g/cm，内聚能密度增加了15.6%，这归因于分子极性和分子间吸引力的增强。增强的分子相互作用也降低了分子流动性，导致玻璃化转变温度升高30 K，这表明老化降低了沥青抵抗热裂的能力。不同温度下扩散行为的模拟表明，阿伦尼乌斯关系很好地描述了扩散系数与温度的关系，并且老化显著减缓了扩散过程，表现为阿伦尼乌斯前因子降低了38.2%。使用有无不同厚度水夹层的分层模型评估沥青与集料的粘附性。老化后粘附性增强，这是由于界面处静电相互作用显著改善。对存在界面水时残余粘附性的评估表明，老化会提高沥青路面的水敏感性。分子极性的增加被认为是造成这些老化后果的主要原因，因此通过静电势表面和偶极矩进一步进行了研究。
