Effect of Thermal Oxygen Aging on Rheological Properties and Chemical Structure of Lignin-Modified Asphalt

In recent years, lignin has received increasing attention due to its wide availability, low cost, renewability, and potential for improving the performance of asphalt pavement. The purpose of this study is to investigate the rheological properties and microscopic mechanism of modified asphalt by using different types of lignin. The effects of different aging durations on the rheological properties, as well as the chemical and morphological changes of different lignin-modified asphalts, were analyzed using dynamic shear rheometer (DSR), Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). The results of the rheological tests demonstrated that the addition of lignin had a positive effect on the permanent deformation of the asphalt matrix and significantly improved the rutting resistance of the asphalt at high temperatures, with the most significant change observed in enzymatic lignin. The addition of lignin improves certain fatigue resistance and good fatigue life. The chemical test results indicate that lignin, as a blending agent, can compensate for the molecular weight changes caused by the aging of the matrix asphalt when degrading, maintaining a balanced distribution of molecular weight, which is the main mechanism of resistance to thermal oxidation aging of lignin-modified asphalt.