半柔性路面材料界面区力学表征及开裂机理研究

Semi-flexible pavement materials are still in a state that the material design is disjointed with material destruction. The interfacial zone of the material is the key part of stress generation and concentration. This project carried out these research based on the interface zone to study the cracking of the mixture: The atomic force microscopy (AFM) is applied to study the micro-structural indexes such as adhesion, dissipation energy and elastic modulus of aggregate-asphalt binder interface and cement mortar-asphalt mortar interface area. And a constitutive equation of stress intensity coefficient in interface area is established. The whole process of crack generation and expansion is studied by means of mechanics and traceability to establish the fracture model of interface crack. The three-dimensional numerical model of the material is established by X-ray CT non-destructive scanning. And the mechanical response of the supercomputer is studied by using the supercomputer to study its cracking mechanism. Based on these study a kind of organic material affinity cement mortar is designed and the design method of anti-cracking semi-flexible pavement materials is raised. The research results will help to improve the design level of semi-flexible pavement materials, provide economic and durable pavement materials for special road sections, and improve the overall service level of the road network.

半柔性路面材料仍处于材料设计与材料破坏相脱节的状态。材料内部界面区是应力产生与集中的关键部位，本项目基于界面区研究混合料的开裂问题：采用原子力显微镜（AFM）从微观层面研究集料-沥青胶浆界面、水泥砂浆-沥青胶浆界面区域的粘附力、耗散能和弹性模量等微观力学指标，建立界面区应力强度系数的本构方程；采用力学推导溯源的手段研究裂缝产生与扩展的全过程，建立界面裂纹曲折破坏模型；利用X-ray CT无损扫描建立材料的三维数值模型，借助超级计算机得到不同工况下的力学响应，研究其开裂机制；设计有机材料亲和型水泥砂浆，形成体积稳定型抗裂半柔性路面材料的设计方法。研究成果有助于提高半柔性路面材料的设计水平，为特殊路段路面设计提供经济耐用的路面材料，提高路网的整体服务水平。

以多尺度分析的手段研究半柔性路面（SFP）材料界面区的开裂机制，分析半柔性材料界面区域的裂缝产生与发展过程，有助于提高SFP材料的设计水平。本项目使用直接拉拔试验及数字图像分析技术对比剖析不同龄期下三种沥青与两种不同水灰比砂浆的花岗岩-沥青-砂浆试件界面抗拉强度及交互情况，发现界面抗拉强度排序与沥青的针入度大小的联系；采用原子力显微镜PF-QNM模式对沥青-砂浆过渡区进行观察，通过观测区域杨氏模量、黏附能、耗散能的变化，统计得沥青-砂浆界面过渡区范围；对沥青-砂浆界面进行黏附模拟，发现沥青与砂浆黏附能为负值，即四组分沥青与水化硅酸钙为互相排斥，随着温度的升高这种排斥能增加；通过对温拌再生沥青混合料基体的SFP的进行有限元模拟，进一步验证了温拌再生SFP材料的可行性，发现了半柔性材料内部的界面结构在荷载作用下的变形抵抗作用，减缓材料内部的应力扩展；研究基于工程水泥基复合材料（ECC）制备的ECC-SFP材料，研究发现随着ECC材料的加入，ECC-SFP材料实现了一定程度的自愈合。项目研究结果表明，考虑提高界面的抗变形能力可增强半柔性材料的抗开裂能力。