ESEM Microstructural and Physical Properties of Virgin and Laboratory Aged Bitumen
The physical and microstructural properties of four straight run asphalt binders were examined and compared in virgin state and in after short term aging (RTFOT) and long-term (PAV) laboratory aging. RTFOT aging was conducted at 123, 143 and 163 °C. Physical testing parameters included penetration and softening point. Selected binders came from four different sources with same penetration grade. They all showed an increase in stiffness with aging, and RTFOT temperatures. The microstructural evolution of the binder was examined by Environmental Scanning Electron Microscopy (ESEM) on aged binders at 123 and 163 °C. The physical transformation corresponded to an evolution in the binders’ ‘fibril’ microstructure under ESEM as a result of electron beam exposure, with the microstructure getting denser with PAV aging. The asphalt binders showed varied ESEM ‘fingerprints’ and aged in different ways. The ESEM properties generally showed to evolve with the physical properties, although this was not the case for all of the binders due to their unique aging characteristics.
KeywordsAsphalt binder Aging Environmental Scanning Electron Microscopy (ESEM) Microstructure Penetration Softening point
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