水分在泡沫温拌沥青中的分子动力学研究

摘要

To study the microcosmic effect of moisture in the foamed warm mix asphalt,a representative four-component molecular structure of asphalt was selected.The water content of 0,1%,2% and 3% were studied by the molecular dynamics simulation respectively. We studied the glass transition temperature,free volume fraction and diffusion coefficient of water molecules in the FWMA.The interaction energy between water molecules and asphalt molecules was also simulated and analyzed.The results showed that the glass transition temperature of FWMA was lower than that of matrix asphalt. The free volume fraction gap of FWMA system with different water content was shown small. At the same time,the diffusion coefficient of water molecules in FWMA increased with the rise of water content.When the content of water was 3%,the diffusion coefficient of water molecules in the FWMA increased obviously. We found the interaction between water molecules and asphalt molecules could be analyzed which indicated that there was an exclusion between water molecules and asphalt molecules,besides the FWMA system was unstable.The electrostatic force between the water molecules and the asphalt molecules played a dominant role when studied the non-bond interaction energy of FWMA system,and which growed with the increase of the water content in the system.%为考察水分对泡沫温拌沥青的微观作用,选择具有代表性的沥青四组分分子结构,采用分子动力学模拟方法,研究了含水率分别为0、1%、2%、3%的基质沥青和泡沫温拌沥青体系玻璃化转变温度、自由体积分数、水分子的扩散系数;同时,也模拟分析了水分子与沥青分子之间的相互作用能.研究表明,与基质沥青相比,水分的添加使得泡沫温拌沥青的玻璃化转变温度下降,不同含水率的泡沫温拌沥青体系自由体积分数差距较小.同时,在泡沫温拌沥青中,随着含水率的增加水分子在泡沫温拌沥青中的扩散系数不断增大,当含水率为3%时,水分子在泡沫温拌沥青中的扩散系数上升得较为明显.水分子与沥青分子进行相互作用过程中,水分子与沥青之间存在着排斥作用,泡沫温拌沥青体系不稳定.此外,通过对泡沫温拌沥青体系的非键相互作用能分析得出,水分子与沥青分子之间静电力起主导作用,且随着体系含水率的增加而增大.