Effect of Thermal Oxygen Conditions on the Long-Term Aging Behavior of High-Viscosity Modified Bitumen

High-viscosity modified bitumen is affected by a complex thermal oxygen environment during long-term service. However, the existing standard long-term thermal oxygen aging test cannot fully simulate the effect of different thermal oxygen conditions on the aging of high-viscosity modified bitumen. In this study, on the basis of the standard pressure aging vessel test, high-viscosity modified bitumen was aged under different oxygen conditions through adjusting test parameters. Then, the analysis of the complex moduli, phase angles, and creep and recovery properties was conducted to evaluate the rheological properties of high-viscosity modified bitumen before and after aging. Moreover, gel permeation chromatography was performed to evaluate the molecular size distribution of high-viscosity modifiers during aging. The results indicate that aging improves the modulus of high-viscosity modified bitumen and changes the phase angle of that. Temperature, pressure, and time are the factors affecting the high-temperature sensitivity and viscoelastic properties of high-viscosity modified bitumen. With respect to the creep and recovery property, different high-viscosity modified bitumen exhibits different aging characteristics with the change of thermal oxygen conditions. Gel-permeation-chromatography results directly illustrate that thermal oxygen conditions influence the degradation of high-viscosity modifiers at the initial stage of long-term aging, which is the key factor affecting the rheological properties of high-viscosity modified bitumen.