Effect of Heat, Oxygen, and UV Light Coupled Aging on Chemical Properties of Bitumen

The properties of bitumen can deteriorate under environmental aging. In this study, heat-, oxygen-, and ultraviolet (UV) light-induced aging of bitumen was carried out using an environmental coupled aging simulator. The effects of aging were analyzed by saturate, aromatic, resin, and asphaltene (SARA) fractionation, Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. The results showed that the change rates of asphaltenes and resins of styrene-butadiene-styrene (SBS)-modified bitumen were about half those of virgin bitumen, effectively slowing the bitumen aging. SBS modifier slowed the transition of fractions. Carbonyl and sulfoxide indexes under thermal-oxygen aging conditions were 2-3 times higher than under thermal aging conditions. The contents of carbonyl and sulfoxide were relatively stable under thermal aging conditions without oxygen. Heat, oxygen, and UV light coupled aging decreased Har values by as much as 20.74% but increased Hβ+Hγ by only 5.90%. Higher temperature (70°C) contributed significantly to the reduction of hydrogen atoms in aromatic rings of bitumen. The carbonyl index was the most sensitive to bitumen aging among six chemical evaluation indexes. The combination of heat and oxygen could significantly aggravate bitumen aging. UV light had the least effect on chemical properties of bitumen when coupled with two other environmental factors.