Investigation of SARA Fractions Transformations and Molecular Weight Distribution During Adhesion of Crumb Rubber Modified Asphalt Binder and Aggregates

The adhesion behavior between crumb rubber (CR) modified asphalt binder and aggregate interface is more complicated due to the incorporation of crumb rubber. This paper focuses on the changes in the interfacial chemical structure and the SARA fractions transformations during the adhesion of the CR modified asphalt binder to the aggregate. A new iso-mass layered extraction process was proposed to obtain different layers of CR modified asphalt binder on the aggregate surface. Afterwards, the SARA fractions and molecular weight distribution of each layer of binder was studied by gel chromatography (GPC) test, SARA four-component separation test and thin layer chromatography-flame ionization detection (TLC-FID). The results show that the changes in interfacial structure and molecular weight distribution due to the adhesion process continue from the innermost layer to the third elution layer on the aggregate surface. From the outermost layer to the eluted layer near the aggregate surface, the asphaltene content increases significantly, the saturate content decreases significantly, the resin content decreases slightly, and the aromatic fraction content varies insignificantly. Additionally, the closer to the adhesion contact surface between the aggregate and the CR modified asphalt binder, the higher the number of macromolecules, which reaches a maximum in the innermost layer.