冻融循环作用下沥青混合料界面粘结退化的细观力学机理研究

The interface between asphalt and aggregate is the key factor to the performance of bituminous pavement. Aiming at the freezing-thawing cycle and deicing salt erosion damage as well as destory of bituminous pavement in northern cold areas. On the basis of thermodynamica and micromechanics, the interface between asphalt and aggregate will be studied.The interface adhesion property and change rule of asphalt and aggregate will be studied by surface free energy measurement experiment after freezing and thawing cycle.The digital image correlation method will be used to measure the strain distribution of interface in the process of bond degradation and unstick under freezing -thawing cycle and loading. The microscopic damage degree will be described and the damage equation of interface will be established based on the changing of strain and stress.The micro-hardness change、 crack emerge and expansion rule of asphalt and aggregate interface will be explored based on nanoindentation tests and scanning electron microscopy observation. It will analyze the bond degradation performances of interface in freezing -thawing cycle on the basis of the mesoscopic mechanical properties and the microstructure of interface.In addition, it will explore the correlation between the bond degration and mesoscopic damage of interface and try to find out the interface bond degration and failure mechanism under freezing-thawing and deicing salt erosion conditions.The project has local characteristics, and in the meantime, it is important for a deep understanging of the asphalt mixture mechanical behaves on both macro and micro as well as research methods.

沥青与骨料界面的粘结性能是影响沥青路面结构性能的关键因素。本项目针对北方寒冷地区沥青路面在冻融循环及除冰盐侵蚀作用下的损伤和破坏问题，基于热力学和细观力学原理，以沥青与骨料界面为研究对象，通过沥青及骨料的表面自由能测试实验，研究冻融循环作用下沥青与骨料的粘结性能及变化规律；通过数字图像相关方法测量冻融循环及荷载作用下界面粘结退化、脱粘过程中界面的应变分布，基于粘结退化过程中应变、应力变化描述界面细观损伤程度，建立界面损伤演化方程；通过纳米压痕实验及扫描电镜观测，研究界面区域的微观硬度及模量变化，揭示界面在粘结退化过程中裂纹的萌生和发展规律，基于界面的细观力学性能和细观结构特征研究冻融循环条件下界面粘结退化特性；探索界面粘结退化与界面细观损伤间的相关性，揭示冻融循环条件下沥青混合料界面粘结退化、失效机理。该项目既有地区特点，同时对于深入了解沥青混合料的宏、细观力学行为和研究方法具有重要意义。

沥青与骨料界面的粘结性能是影响沥青路面抗裂性能的关键因素。本项目针对北方寒冷地区沥青路面在冻融循环及除冰盐侵蚀作用下的损伤和破坏问题，基于热力学和细观力学原理，以沥青与骨料界面为研究对象，通过沥青及骨料在冻融循环及盐侵蚀作用下的粘附性实验,沥青、骨料及沥青与骨料界面细观结构特征实验，沥青与骨料界面细观力学特性实验，以及沥青-骨料界面粘结退化机理研究，得到冻融循环作用下沥青与骨料的粘结及界面力学性能变化规律。研究发现，冻融循环是影响沥青混合料界面开裂的重要因素。盐晶体存在于沥青与骨料的界面处和孔隙中，这些晶粒会刺破沥青膜，破坏沥青的粘结性；沥青混合料的起裂点大多数位于沥青砂浆与骨料的界面处，少数位于沥青砂浆处，裂纹的走向是沿着骨料的边缘也就是界面发展的。胶浆、骨料与界面处水平应变EXX曲线随时间经历三个阶段：EXX稳定上升期、EXX突变期和EXX释放期，微裂纹的形成时间是水平应变EXX突变的时间，宏观裂纹形成的时间是EXX释放并趋于零的时间点。EXX可以作为裂尖位置与裂缝发展的判断指标。盐冻融循环作用下，沥青种类对混合料断裂韧度的影响最显著，冻融循环次数次之，除冰盐浓度影响最小；盐冻破坏过程中，中低浓度的除冰盐对沥青混合料的抗裂性影响比较显著；项目基于粘结退化过程中应变、应力变化描述界面细观损伤程度，揭示了界面在粘结退化过程中裂纹的萌生和发展规律，建立了界面粘结退化与界面细观损伤间的相关性，揭示了冻融循环条件下沥青混合料界面粘结退化、失效机理。研究结论对于沥青混合料的设计和指导工程应用有重要的科学意义和实用价值。