基于分子动力学的泡沫沥青-集料界面黏附性研究

Adhesion of Foamed Asphalt⁃Aggregate Interface Based on Molecular Dynamics

为了揭示泡沫沥青与集料的界面微观黏附特性,基于分子动力学(MD)模拟方法,采用4组分12分子沥青分子模型并向其中加入水分子来模拟泡沫沥青,分别分析了含水率、温度对泡沫沥青黏聚性的影响以及含水率、集料类型、集料表面潮湿和水分子扩散对泡沫沥青-集料界面黏附性的影响,并应用统计学方法分析了含水率、温度和时长对泡沫沥青中水分子扩散的影响。结果表明:水的加入会增加沥青大分子之间的距离,使沥青分子间作用力减弱,降低泡沫沥青黏性,提高泡沫沥青的玻璃化转变温度;当泡沫沥青含水率(<1%)较低时,泡沫沥青-集料界面黏附性有所增强,当含水率(>1.6%)较高时,水会从泡沫沥青中溢出与集料结合,使沥青-集料界面黏附性降低;集料表面潮湿情况下,碱性集料与泡沫沥青的界面黏附性优于酸性集料与泡沫沥青的界面黏附性,并且随着泡沫沥青中含水率的增加,界面黏附性并不会减弱,反而会得到一定的增强;含水率对水分子扩散的影响无显著性规律,而温度和时长对水分子的扩散具有显著影响,随着时长增加,水分子扩散逐渐减弱,最终达到动态平衡,温度越高,水在沥青中的扩散越快,对泡沫沥青-集料界面黏附性产生不良影响。

To reveal the micro-scale interfacial adhesion properties of foamed asphalt and aggregate, based on molecular dynamics(MD) simulation method, the 4-component 12-molecule asphalt molecular model was employed and water molecules was added into it to simulate foamed asphalt, then the influence of the water content and temperature on the foamed asphalt cohesion was analyzed, also, the effect of water content,aggregate type, aggregate surface humidity and the diffusion of water molecules on the foamed asphalt-aggregate interface adhesion was investigated in this study. The effects of water content, temperature and simulation duration on the diffusion of water molecules in foamed asphalt were analyzed by statistical method. The results showed that the addition of water can increase the distance among asphalt macromolecules, weaken the intermolecular force of asphalt and reduce the viscosity of foamed asphalt. Moreover, the introduction of water can increase the glass transition temperature of the foamed asphalt. When the moisture content(<1%) of the foamed asphalt was relatively low, the foamed asphalt-aggregate interface adhesion was enhanced, additionally, when it was relatively high(>1.6%), the water can overflow from the foamed asphalt and combine with the aggregate, so as to reduce the interface adhesion of foamed asphalt-aggregate. Under the wet condition of the aggregate surface, the interface adhesion between the alkaline aggregate and the foamed asphalt was better than that between the acidic aggregate and the foamed asphalt. Also, with the increase of the moisture content of the foamed asphalt, the interface adhesion cannot be weakened, but it can be enhanced to a certain extent. The moisture content showed no significant effect on the diffusion of water molecules, while the temperature and simulation duration performed an important effect on it. As simulation duration increased, the diffusion of water molecules gradually weakened and finally reached a dynamic equilibrium. The higher the temperature, the faster the diffusion of moisture in the foamed asphalt, which can cause an adverse effect on the foamed asphalt-aggregate interface adhesion.