Investigating bitumen long-term-ageing in the laboratory by spectroscopic analysis of the SARA fractions

Abstract

Ageing is an omnipresent phenomenon that affects all materials in earth’s atmosphere including roads. The material most prone to ageing within an asphalt road is its organic binder, i.e. bitumen. The quality and chemical composition of bitumen can be affected by the crude oil source and refinery process. Hence, they can show differences in long-term performance and ageing susceptibility, even when being within the same specification class.To investigate long-term-ageing (LTA) in the laboratory, three binders from different crude oil sources, but within the same specification class, were aged with two different laboratory LTA procedures, chemo-mechanically investigated, separated into four SARA fractions and analyzed with FTIR spectroscopy. The results revealed that a clear differentiation between ageing methods and crude oil source can be obtained by chemo-mechanical correlation as well as on the molecular level (SARA fractions). While standard laboratory ageing (Pressure Ageing Vessel – PAV) reaches a similar ageing level for each binder, the second LTA method (Viennese Binder Ageing – VBA) leads to different ageing levels for the samples and is therefore a more suitable tool to distinguish ageing susceptibility. The fractions mainly show the formation of carbonyls and sulfoxides as well as a slight increase in certain sections of the fingerprint area. By combining these techniques, we aim at achieving a thorough investigation on the molecular level and link it to the binder level. This should help us to detect differences in ageing susceptibility, crude oil origin and refinery processes.