基于分子动力学模拟的再生剂-老化沥青扩散机理

采用Materials Studio(MS)分子动力学模拟软件对再生剂-老化沥青扩散体系进行研究.以沥青四组分试验为基础,选取12种分子模型构建再生剂分子组、复合水老化沥青分子组和复合紫外老化沥青分子组.针对在不同模拟时间、模拟温度和沥青成分条件下的老化沥青扩散体系进行模拟,得到扩散体系的扩散系数.结果 表明:随着模拟时间的延长,再生剂在老化沥青扩散体系中的扩散系数变小,同时在复合紫外老化沥青扩散体系中的扩散系数小于复合水老化沥青扩散体系;随着扩散温度的增加,扩散系数增速逐渐变缓;再生剂中油性成分(芳香分和饱和分)的扩散系数大于极性成分(胶质和沥青质),芳香分由于多为链状且相对分子质量较小,其扩散速率在4种组分中最快.

Diffusion Mechanism of Regenerant Aged Asphalt Based on Molecular Dynamics Simulation

In order to further understand the diffusion mechanism of regenerant in aged asphalt.Based on the four component test of asphalt, 12 kinds of molecular models were selected to construct the regeneration agent molecular group, composite water aging asphalt molecular group and composite UV aging asphalt molecular group.The MSD (mean square displacement) curve of the aging asphalt diffusion system was obtained by simulating the aging asphalt diffusion system under different simulation time, simulation temperature and asphalt composition, and its diffusion coefficient was calculated.The results show that with the increase of the total simulation time, the diffusion coefficient of the regenerant in the aged asphalt diffusion system becomes smaller, while the diffusion coefficient of the UV aged asphalt diffusion system is smaller than that of the water aged asphalt diffusion system, and with the increase of the diffusion temperature, the increase speed of the diffusion coefficient gradually slows down.This shows that the diffusion coefficient does not increase with the increase of diffusion temperature, but the diffusion process continues, while the diffusion rate slows down. When the four components of the regenerant diffuse in the aged asphalt, the diffusion coefficients of aromatic phenol and saturated phenol are larger than those of gum and asphaltene, and the diffusion speed of aromatic phenol is the fastest among the four components, because most of them are chain and small molecular weight molecules.