ABSTRACT

Bitumen is the primary binder of asphalt covering most of the roads in the world. The origin of the primary oil, the refinery treatment, the specific chemical structure, and the natural or induced chemical modifications determine the mechanical properties of bitumen. Aging affects the time evolution of its thermo-rheological behaviour. Numerous studies have suggested that the particular local microstructure of bitumen affects its rheological properties including ‘bee’ – patterned structures. We have used scanning probe microscopy to distinguish between surface effects and bulk properties. Using scanning probe microscopy we conclude that the ‘bee’ structures exist at the surface only and do not occur in the bulk. In particular, they are not observed on freshly fractured surfaces. A special technique was used to chisel off the bitumen surface. The material relaxes and the ‘bee’ structures disappear from the surface. This proves that the ‘bees’ are formed as a thin surface layer. Improved recycling will thus have to rely on chemical treatment of aged and used bitumen rather than on intentional modifications to the surface microstructure which is merely a surface effect. The bitumen surface microstructure can nevertheless be seen as a fingerprint of the overall bitumen properties to a certain degree.

摘要

沥青是覆盖世界上大部分道路的主要沥青粘合剂。初级油的来源、炼油厂处理、特定的化学结构以及天然或诱导的化学改性决定了沥青的机械性能。老化影响其热流变行为的时间演变。大量研究表明，沥青特定的局部微观结构会影响其流变特性，包括“蜜蜂”——图案结构。我们使用扫描探针显微镜来区分表面效应和体积特性。使用扫描探针显微镜，我们得出结论，“蜜蜂”结构仅存在于表面，不会大量存在。特别是，在新断裂的表面上没有观察到它们。一种特殊的技术被用来凿掉沥青表面。材料松弛，“蜜蜂”结构从表面消失。这证明了“蜜蜂”是作为一个薄的表面层形成的。因此，改进回收将不得不依赖于老化和使用过的沥青的化学处理，而不是对表面微观结构的有意修改，这仅仅是一种表面效应。然而，沥青表面微观结构在一定程度上可以被视为整体沥青性能的指纹。