Characterization of Recycled Aged RAP Binders Containing Crumb Rubber Modifier Using Gel Permeation Chromatography

The recycling of hot-mix asphalt pavements containing a crumb rubber modifier (CRM) has been an area of interest since CRM was first used in asphalt paving materials over 40 years ago. Studies on the recycling of rubberized asphalt concrete materials have focused mainly on the mixture properties at the location of in-field paving. However, for the long-term performance characterizations, there is a need to investigate the aging properties of rubberized binders and the subsequent recycling properties of these aged rubberized binders. To address this issue, the previous research was conducted to identify performance properties of recycled aged CRM binders using Superpave binder test methods. The research results indicated that the recycled aged CRM binders can result in satisfactory binder performance meeting current Superpave binder requirements. This paper presents a limited study that uses gel permeation chromatography (GPC) to characterize the aging process of recycled aged CRM binders as a function of binder source and RAP binder percentage. In addition, performance properties of the binders at three aging states (i.e., original, RTFO residual, and RTFO+PAV residual) were correlated with the large molecular size (LMS) values from the GPC results. The results indicated that the compositional changes of recycled aged CRM binders are well reflected by the GPC parameter (i.e., LMS), and the performance properties from Superpave binder tests have good correlations with the corresponding LMS values. In addition, the empirical prediction models for long-term performance properties were developed using the GPC parameter and physical properties of the binders. The predicted values showed a high correlation with the performance properties of G(*)sin delta and stiffness of binders.