State of the art: Multiscale evaluation of bitumen ageing behaviour

•Multiscale evaluations of the effect of ageing on bitumen were reviewed.•The bulk performance of bitumen is closely related to the micro even nano properties.•Chemical parameters can be used to characterise the rheological performance of bitumen.•Inter-hierarchy scale should be combined within the research of bitumen ageing. Ageing is a common phenomenon that seriously affects the performance and service life of asphalt pavements. In this paper, multiscale evaluations of bitumen ageing behaviour were reviewed to better understand the bitumen ageing mechanism and thereby contribute to future anti-ageing and binder rejuvenation work in this area. The paper initially looks at conventional as well as bespoke ageing methods before concentrating on bitumen ageing evaluation at different scales ranging from macro, meso, micro to nano scale. This is done by introducing the application of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) in thermal indices; thin-layer chromatography-flame ionization detector (TLC-FID), gel permeation chromatography (GPC) and Fourier infrared spectrometer (FTIR) in components and functional groups; atomic force microscopy (AFM), optical spectroscopy and fluorescence spectroscopy (FM) in microstructural analysis; and, finally, nuclear magnetic resonance (NMR), time-of-flight secondary ion mass spectrometry (TOF-SIMS) and molecular dynamic simulations at the nanoscale. This review paper highlights the intricate correlations between the different hierarchical scales of bitumen ageing and the importance of a multiscale approach to provide a more comprehensive study and understanding of the ageing of bitumen.