Research on Molecular Weight Distribution and Rheological Properties of Bitumen during Short-Term Aging

Abstract

In recent years, asphalt pavements have been widely used due to their desirable properties: safety, smoothness, and durability. However, the aging of bitumen during its service period is inevitable, so the performance of asphalt pavement will decline. Thus, it is necessary to investigate the aging mechanism systematically to offer a new way of illustrating changes during the aging process, and the investigation of the short-term aging mechanism could be a first step. This study explored the variations of rheological properties and molecular weight distribution during the aging process, and the data obtained by gel permeation chromatography (GPC) were analyzed by principal component analysis. The experiments in this research include preparing aged bitumen samples under five aging temperatures and six aging durations, and then tests were performed using a dynamic shear rheometer (DSR), bending beam rheometer (BBR), and GPC. The results indicate that the aging increased complex modules (G*), creep stiffness (S), and fatigue resistance index (Nf) but decreased phase angle (δ) and m-values. In addition, the transformation from medium molecular size to large molecular size was found to be the most significant phenomenon during the aging process. Moreover, during the aging process of bitumen, the molecular weight distribution index polydispersity index was found to have the best correlation with rheological properties.