| In this study, pull-off experiments were conducted on asphalt surfaces, the materials usedin this study included asphalt AAA, AAD and AAM from the Strategic Highway ResearchProgram (SHRP), they are varied in crude source, chemical composition and elementalanalysis.The objective of this thesis is to collect and analyze atomic force microscope (AFM)force displacement curves to measure work of adhesion/cohesion. And then the data will beanalyzed to determine the surface energy and dissipative components of the overall work ofadhesion for the test asphalts.In this study, experiments on asphalt surface included the effects of loading force, dwelltime, pull-off rate, temperature and different spots on the sample surface. The result shows thecantilever work was significantly affected by the temperature and separation rate, but theeffects of the other control variables were found to be relatively insignificant.So experiments based on AFM wereused to study the work of adhesion and adherenceenergy of asphalt as a function of pull-off rate and temperature.We show fracture energy as afunction of separation rate and temperature for three SHRP core asphalts representative ofdifferent crude sources, from force versus time plots recorded during fracture the total fractureenergy as well as the thermodynamic and reversible components can be derived. In the roomtemperature, for AAA sample the measured surface energy is about30mJ/m2, for AADsample, the measured surface energy is nearly28mJ/m2, for AAM sample, themeasuredsurface energy is around42mJ/m2, these results were pretty close to the surface energy Miknismeasured using NMR imaging, this means our experiments are reasonable.The result indicates that the stability of AAA and AAD are better than AAM. And theadherence energy of AAA is larger than AAD shows that AAA has a better flexibility, thit isspeculated that AAA may be a better fracture resistant asphalt compared to AAD and AAM. |
