Analysis of Bitumen Properties during Ageing Using Atomic Force Microscopy

It is well-known that bituminous materials age during exposure to sunlight, heat and oxygen. This ageing process causes both the properties of the bitumen and the behavior in a typical asphalt mixture to change. Depending on the level of ageing, the bitumen or asphalt may become unsuitable for its intended application. Various methods exist for the analysis and characterization of ageing of bitumens. In this paper a potential alternative method that has not received much attention yet as an ageing characterization method is discussed. The Atomic Force Microscope (AFM) is a device that is used on a daily basis by scientists working specifically in the nanotechnology field. The AFM allows various properties of a sample to be investigated, including the surface morphology. Researchers have investigated the AFM as a method for evaluating properties of bituminous binders. During previous work the author has evaluated the effect of artificial laboratory ageing on the surface morphology of a specific binder. In this paper the general ageing process is summarized and the AFM technique for characterizing the surface morphology of bitumen samples, both neat and treated with TiO₂, are discussed. Data from various laboratory aged and field aged samples are presented.