SURFACE ENERGY STUDY OF PAVING ASPHALTS BY AFM

摘要

The micro- and nano-scale surface features and adhesive properties of eight asphalts were investigated by different atomic force microscopy techniques. Specifically, surface energies of asphalts prepared as micron thickness thin films were measured by force microscopy based on a Johnson-Kendell-Roberts contact mechanics approach to measure work of adhesion. The shape and magnitude of force curves measured for different asphalts indicated that the pull-off force was crude oil source dependent. Results from this study also indicated that scatter in surface energy measurements was likely dependent on the micro-structural features of the asphalt at the surface interface. Phase imaging of asphalt surfaces showed surface undulation features covering several square microns of surface area, and were spaced apart from other features by comparable distances. Furthermore, frictional force measurements indicated that two distinct phases of material could be detected at the surface interface based on feature hardness. These studies would appear to indicate that asphalts constitute a complex material with variable properties of adhesion. Future work will entail deciphering the results presented here to better characterize the adhesive nature of asphalt as a glue in pavement.