Effect of UV radiation on asphalt functional groups through FTIR and entropy weight method

Ultraviolet (UV) ageing is an important factor that affects the service performance of asphalt pavement. However, transformation of the functional groups of asphalt under UV radiation remains to be studied as the ageing mechanism of asphalt could be better understood by studying its functional groups. In this study, asphalt was aged using three wavelength bands of UV light. The changes in the characteristic functional groups of the asphalt before and after UV treatment were analysed using Fourier transform infrared spectroscopy. The entropy weight method was used to calculate the counts of interconversion. The results showed that the carbonyl index of asphalt increased after UV ageing, while the methylene, aromatic, aliphatic and sulfoxide indices decreased. After the asphalt was aged by UV light, the C–C, C–H and C=C bonds in the asphalt material were converted into C=O and S=O bonds were converted into sulfur dioxide. The results of this work could be used to simulate asphalt molecules in order to better understand the performance and properties of asphalt.