Aging behaviour and mechanical characterisation of maltenes and asphaltenes

Abstract

The analysis of bitumen is challenging due to its complex and ever-changing chemical composition. Fractionation techniques based on solu-bility and polarity properties facilitate the examination process, sheddingmore light on composition, structure and aging behaviour. However, theseseparation experiments are often performed post-aging, making it diffi-cult to understand the behaviour and mechanical properties of individualsubfractions. Hence, the focus of this study was to separate maltenes andasphaltenes in large quantities and age them at various temperatures (80,130 and 180°C), followed by analysis with chemical and mechanical meth-ods. Results showed that both maltenes and asphaltenes display viscoelas-tic properties: maltenes are more viscous, while asphaltenes are more elas-tic compared to the base binder. Maltenes aged at 180°C became extremelystiff with a nearly temperature-independent phase angle, while asphaltenesaged at 130°C exhibited the stiffest and most elastic behaviour. Decompo-sition of sulfoxides at high temperatures was observed for both fractions,while additional decarboxylation occurred in the asphaltenes. During theaging of the maltenes, a significant amount of asphaltenes were formed,which most likely originated from both the aromatics and resins fraction.Furthermore, no major discrepancies between oxidation products in bitu-men and in the maltenes were detected, indicating that asphaltenes mightnot crucially influence the qualitative aging process. This study demon-strated a possible approach for obtaining bituminous subfractions in largequantities, allowing for a detailed analysis of their mechanical and agingproperties.