Utilising fluorescence spectroscopy and optical microscopy to investigate bitumen long-term ageing

Abstract

Linking the chemical composition of bitumen to its microstructure is challenge due to its complexity, viscoelasticity and sensitivity to high energy input. Therefore, fluorescence spectroscopy combined with fluorescence microscopy are promising tools, as they are capable to link the materials fluorescence behaviour to its respective microstructural features. Herein, these techniques were coupled with dark-field microscopy to gain insight on the chemical composition of these auto fluorescent microstructural features and their changes during long-term-ageing (LTA). The results show that upon LTA a loss in fluorescence intensity goes in line with a shift to higher emission wavelength. While the overall intensity decreases during ageing the density and number of fluorescent particles increases. Dark-field microscopy confirms that these fluorescent particles show particle light scattering, proving that on the micro-scale bitumen is a non-homogeneous material.