Characterization of the Interaction Effect of Crumb Rubber Modified Binders Using HP-GPC

There have been many studies investigating the properties of crumb rubber modified (CRM) binders, but few that have attempted to quantify the specific effects that the addition of crumb rubber has on asphalt binders. The writers previously identified two major effects that crumb rubber has on binders: interaction effect (IE) and particle effect (PE). The IE results from the diffusion of the light fractions of the binder into the rubber particles and the PE is due to the addition of particulate matter to the binder. This study focused on providing a further explanation of the IE by characterizing 36 CRM and three base binders using high-pressure gel permeation chromatography (HP-GPC). Comparison of the molecular size distributions of the different binders verified that the IE is, in fact, due to the diffusion of lighter binder fractions into the rubber particles. Additionally, the IE may provide a simple means to determine the compatibility of binders with crumb rubber.