Impact of UV–Vis light on the oxidation of bitumen in correlation to solar spectral irradiance data

Abstract

The ageing behavior of bitumen is a complex phenomenon which is tackled by many studies in the laboratory and on the field. While ageing parameters like temperature, moisture, reactive gasses or UV light have been utilized in the laboratory, the impact of visible light has not been addressed yet. Thus, this study investigates the impact of UV–visible light in the range of 365–770 nm on the oxidation behavior of bitumen. Furthermore, a correlation to solar spectral data was conducted, which should link the ageing experiments run in the lab to the conditions on earth’s surface. FTIR spectroscopy on the sample surfaces was conducted to determine the extent of ageing. The results show that when considering solar spectral data, blue light in the range of 405 nm contributes significantly towards oxidation of bitumen. Additionally, an unexpected, characteristic oxidation profile shows higher oxidation levels around light in the blue (405 nm) and green (525 nm) wavelength ranges. This provides first evidence on how visible light can cause significant oxidation for bitumen in asphalt pavements. The obtained knowledge can be used to better understand which parameters contribute towards the ageing process in the field and to provide suitable solutions for laboratory ageing.