Fundamental investigation of the interaction mechanism between new and aged binders in binder blends

Abstract

Determining the permissible amount of reclaimed asphalt pavement (RAP) in new pavement mixes is a design challenge for pavement practitioners due to the limited understanding regarding the interaction between the aged and unaged binders in these mixtures. In this study, the solubility related molecular interactions of blended binders comprising of aged-unaged fractions was evaluated using an extension of the Hansen Solubility Parameter (HSP) model. Virgin binder was blended with aged binders from two different sources, at proportions of 15%, 30%, and 50%. These binder blends were evaluated using a method of titrations to identify their internal stability and relative extents of intermolecular interactions in terms of dispersive forces, hydrogen bonding, and polar interactions. The results implied that small proportions of aged binders have limited effect on the original stability of the unaged binders. Further Fourier transform infrared spectroscopy and gel permeation chromatography tests revealed that the oxidative elements in the blended binders increased with the increasing percentage of aged binders. It is theorized that these fractions will affect the polydispersity of the molecules through increased molecular associations. It is advised that incorporation of higher RAP contents in mixtures should ideally involve some consideration of the chemistries of the intermixing binders.