Evaluating the ageing degrees of bitumen by rheological and chemical indices

The ageing of bitumen is an inevitable phenomenon which is still challenging
to be characterised. This paper aims at evaluating the ageing
degrees of bitumen comprehensively. There were six types of bitumen
being aged to five levels for comparing purposes and multiple rheological
tests by a DSR as well as chemical test for the SARA (saturates, aromatics,
resins and asphaltenes) properties of bitumen were carried out. The critical
temperatures, G-R parameter and nonrecoverable-compliance-based ageing
indices were proposed to evaluate the ageing degrees of bitumen in
terms of low-, intermediate- and high-temperature performance of bitumen,
respectively. Also, a novel ageing evaluation index based on the integration
of modulus of master curves was employed and modified, which
can evaluate the ageing degrees of bitumen accurately in terms of the
whole range of temperature. Finally, the chemical ageing index were analysed
and was confirmed to have strong linear relationship with rheological
indices of bitumen.