How infrared and fluorescence spectroscopy can shed new light on the characterization of bitumen and its ageing processes

Abstract

A combination of chromatography and spectroscopy was applied to characterize the chemical peculiarities of bitumen and analyse thermally induced ageing processes. Therefore, a bitumen sample was short-term and long-term aged followed by a polarity-based fractionation. Subsequently, the fractions and the base binder were analysed by infrared (IR) and fluorescence spectroscopy. IR provided the possibility to track the fate of carboxylic acids and quinolones and the evolution of ketones and sulfoxides during oxidative ageing. Information on abundant aromatic structures and the effect of ageing on certain molecular classes was obtained with fluorescence spectroscopy. It was shown that shifts to higher emission wavelengths correlate to the polarity of the fractions and the ageing state. Solid-state measurements of the resins revealed characteristic signals of porphyrins and how they are affected during ageing. Here we evaluate the impact of different ageing conditions with the perspective to improve the understanding of complex chemical ageing in bitumen.