纳米尺度沥青微观结构特征演化分析

Analysis of Nanoscale Evolution Features of Microstructure of Asphalt

为研究老化引起的沥青纳米尺度微观结构演化特征,建立微观结构演化特征与宏观尺度性能衰变之间的相关关系,分别选取实验室老化和现场老化回收的沥青样本为研究对象,利用原子力显微技术(AFM)和动态剪切流变试验(DSR),对沥青表面微观结构的演变特性和宏观性能的衰变规律进行了研究。研究结果表明:老化对沥青表面微观结构形貌有显著影响,未老化沥青和短期老化(RTFOT)沥青样本表面形貌中存在典型的"蜂相结构",长期老化(PAV)和铣刨料(RAP)中抽提回收的沥青样本其表面形貌仅呈现一些褶皱似的凸起和亮白色斑点;在纳米尺度,老化改变了沥青纳米级相态的空间分布特性,降低了相态之间表面高度差异,表面高度以及表面粗糙度指标可以量化这种空间分布的特征;宏观尺度上,沥青样本黏弹特性发生显著变化,复数剪切模量升高,相位角降低,这种流变响应可以表征老化引起的流变性能的演变。基于此,提出了沥青纳米级形貌特征和流变性能相关关系的量化表征模型。

To investigate the evolution features of nanoscale microstructure of asphalt resulting from aging and establish the correlation between the evolution features of microstructure and the decay of macroscale performance,taking asphalt samples aging in the laboratory and field as research objects,the evolution features of microstructure in the surface of asphalt were investigated by atomic force microscopy（AFM）.In addition,dynamic shear rheological（DSR）test was applied to measure the decay law of rheological properties.The results show that aging has a significant effect on the microstructure.The typical bee-shaped structures are observed in the microstructures of original asphalt and RTFOT-asphalt,while the asphalt samples extracted from PAV and RAP show some wrinkle-like projections and bright white spots in their surfaces.At the nanoscale,aging is found to alter the spatial variations and reduce the nanoscale height differences among different phases.The surface microstructure evolution could be characterized and quantified by surface height or surface roughness parameter.At the macroscale,viscoelastic properties of asphalt change significantly such as the increasing complex shear modulus and thedecreasing phase angle.The rheological response could represent the evolution of the rheological properties initiated from aging.Based on these,models that could quantize the correlation between surface microstructure features and rheological properties are proposed.