Impact of reactive oxygen species on bitumen aging – The Viennese binder aging method

Utilising fluorescence spectroscopy and optical microscopy to investigate bitumen long-term ageing

“…The second laboratory LTA method was the Viennese Binder Ageing (VBA) method (Mirwald et al, 2020), a newly developed method to simulate bitumen field ageing in the laboratory in a more realistic manner. This is achieved by directly inducing two types of reactive oxygen species (ROS), ozone (O 3 ) and nitrogen oxides (NO X ), into the ageing atmosphere, which can be found in the troposphere, near the pavement surface (Atkinson, 2000).…”

“…A high ROS concentration (O 3 : 12 g m −3 and NO X : ∼ 1.2 g m −3 ) was selected for the ageing procedure to maximise the oxidation potential of the ROS, inducing as much ageing as possible at said temperature and duration. The choice of temperature can be justified, as no thermal ageing occurs at +80°C (Mirwald et al, 2020), also maximising the ageing rate as much as possible, without inducing any thermal ageing or altering the reactions that could occur at too high temperatures (Petersen, 2009). Furthermore, it needs to be kept in mind that the current VBA setup simulates nighttime ageing, as no UV or visible light is present during ageing.…”

“…Furthermore, by combining spectroscopy and microscopy, the spectral information can be linked to the surface morphology. Previous work using a confocal laser scanning microscope (CLSM) (Bearsley et al, 2004;Handle et al, 2016;Lu et al, 2005) or incidental fluorescence microscopy (Mirwald et al, 2019(Mirwald et al, , 2020 have provided insight on the microstructure of bitumen and have found correlation to spectral information. However, no direct correlation of unmodified bitumen fluorescence spectra and its surface was reported.…”

“…Bitumen usually shows a lower-fluorescent matrix with small highly fluorescent particles embedded. First studies showed that a trend between ageing and mean fluorescence intensity could be observed, while particle number and density can change with ageing state (Mirwald et al, 2020). In addition to fluorescence microscopy, other optical microscopic techniques have been used to characterise bitumen.…”

“…This study combines fluorescence spectroscopy and optical fluorescence and dark-field microscopy in the quest to obtain information on the ageing process from a perspective other than FTIR spectroscopy and link it to its respective microstructural features. Therefore, two different laboratory LTA procedures, a standard Pressure Ageing Vessel (PAV) procedure and the newly developed Viennese Binder Ageing method (VBA) (Mirwald et al, 2020), were compared to a 5 years field aged sample in order to gain insight on how well the laboratory ageing procedures are able to mimic the ageing behaviour from the field. The application of fluorescence and dark-field microscopy should provide answers how the microstructure changes during ageing.…”