有机蒙脱土改性沥青抗老化性及其分子模拟试验

Experiment of Aging Resistance and Molecular Simulation of Organic Montmorillonite Modified Asphalt

为延长沥青路面的使用寿命,延缓沥青因光氧造成的老化,探究了不同类型有机蒙脱土(OMMT)对改性沥青抗老化性能的影响。采用扫描电镜和X射线衍射仪对OMMT的微观结构进行表征;并采用傅立叶变换红外光谱仪、全自动比表面和孔径分布分析仪及同步热分析仪对OMMT的官能团、微孔结构及热稳定性进行了评价。将OMMT应用于基质沥青,对其流变性能进行研究;同时采用3种不同的老化方式探究不同类型的OMMT对改性沥青的影响。最后采用分子动力学法从微观层面上对OMMT改性沥青的物理老化现象进行模拟,分析沥青分子在运动过程中分子间的相互作用关系。研究结果表明:有机基团通过离子交换进入蒙脱土层间,提高了层间的吸附能力;沥青混合料拌合温度下OMMT拥有较好的热稳定性,初始分解温度大于200℃;其中双十八烷基二甲基氯化铵(DDAC)OMMT和十八烷基二甲基苄基氯化铵(ODBA)OMMT制备出的改性沥青均表现出较好的高温抗变形能力。OMMT层间结构越大和苄基的存在均可以提高对沥青分子的约束能力,阻碍沥青分子间的相对运动;同时较大层间的OMMT更易产生剥离结构,可有效阻隔紫外线及氧气分子进入沥青,减缓沥青老化。ODBA-OMMT改性沥青的抗老化性能最佳,DDAC-OMMT改性沥青次之,Na-OMMT改性沥青最差。分子动力学模拟物理老化后的OMMT改性沥青分子状态相对活跃,DDAC-OMMT改性沥青相对自由体积增长最大,ODBA-OMMT改性沥青分子的迁移率最高。研究结果为合理选择OMMT改性剂,增强改性沥青的抗老化性能提供了参考和理论支撑。

To prolong the service life of asphalt pavement and delay the aging of asphalt caused by light and oxygen.This paper explores the effect of different types of organic montmorillonite(OMMT)on the aging resistance of modified asphalt.The microstructure of OMMT was characterized by scanning electron microscope and X-ray diffraction.The functional groups,microporous structure,and thermal stability of OMMT were evaluated by Fourier transform infrared spectrometer,Automatic specific surface and pore size distribution analyzer,and Synchronous thermal analyzer.OMMT was applied to matrix asphalt to study its rheological properties.At the same time,the aging resistance of OMMT modified asphalt was evaluated by three different aging methods.Finally,the physical aging phenomenon of OMMT Modified asphalt was simulated by the molecular dynamics method from the micro-level,and the interaction relationship between asphalt molecules in the movement process was analyzed.The results show that organic groups enter the montmorillonite layer through ion exchange,which improves the adsorption capacity between layers.OMMT has good thermal stability at the mixing temperature of asphalt mixtures,and the initial decomposition temperature is above 200℃.The modified asphalt prepared by dioctadecyl dimethyl ammonium chloride(DDAC)-OMMT and octadecyl dimethyl benzyl ammonium chloride(ODBA)-OMMT showed excellent high-temperature deformation resistance.The larger the interlayer structure of OMMT and the existence of the benzyl group can improve the binding ability to asphalt molecules and hinder the relative movement between asphalt molecules.At the same time,OMMT with a larger interlayer is more likely to produce a stripping structure,which can effectively block ultraviolet and oxygen molecules from entering asphalt and slow down asphalt aging.ODBA-OMMT modified asphalt has exhibited anti-aging performance,followed by DDAC-OMMT modified asphalt and Na-OMMT modified asphalt.After molecular dynamics simulation of physical aging,the molecular state of OMMT modified asphalt is relatively active.The relative free volume growth of DDAC-OMMT modified asphalt is the largest,and the molecular mobility of ODBA-OMMT modified asphalt is the highest.The research results provide reference and theoretical support for the OMMT modifier to be reasonably chosen and the aging resistance of modified asphalt to be enhanced.