Interaction mechanism and cohesion strength of colloid structure of reclaimed asphalt modified by rubberized binder on aggregate surface

Abstract

Asphalt mixture performance is attributed to morphological interlocking and physiochemical interaction between binder and aggregate. Many studies fostered the adhesion and bonding characteristics of many binders without conferring the interfacial interaction. To realistically understand the binder cohesion strength, this study investigates the impact of interfacial interaction on the binder colloid structure. An innovative experimental method was developed using the pull-off and gel permeation chromatography tests to investigate the binder/aggregate interface interaction from molecular and mechanical standpoints. The results showed success for the developed method to pursue the mechanism of the binder/aggregate interface interaction and evaluate the resulting molecular diffusion. Two mechanisms were distinguished for molecular diffusion, depending on the percentage of light components. The abundant light components can mobilize the heavy fractions, whereas binder colloids with limited light components have a molecular diffusion for light fractions only. The binder film portion near the aggregate surface has higher cohesion strength than the upper portion, where a strong correlation was proven between the decrease in the cohesion strength and the molecular diffusion due to the interfacial interaction. A robust prediction model with R2 of 0.90 was developed for the binder cohesion strength, where both the molecular composition and the molecular mobility due to interfacial interaction have significant impacts. As the accretion of heavy fractions strengthens the cohesion strength, the molecular diffusion mechanism, which mobilizes the heavy fractions toward the interface, further improves the cohesion strength of the binder film portion near the interface.