Laboratory Study on Ultraviolet Radiation Aging of Bitumen

The effects of ultraviolet (UV) radiation on degradation of bitumen have received much attention from both academic and industrial points of view. However, quantitative evaluations of bitumen photo-oxidation in pavements have apparently not been determined. In this study, the effects of photo-oxidation of bitumen were investigated by exposing pressed thin films of bitumen. The data for thermal aging only were compared with corresponding data for photo-oxidation from exposure to UV radiation. The levels of aging were evaluated by following increases in the carbonyl functional group, and increases in viscosity. The results indicated that both thermal and UV aging occurred during exposure in the UV radiation oven test for thin bitumen films of both unmodified and SBS-modified bitumen. UV aging had a significant effect on bitumen properties, particularly when the bitumen film thickness was less than 150 μm. Results also showed that the level of UV irradiation intensity had a significant influence on the level of photo-oxidation of the bitumen.