| The incorporation of conventional reclaimed asphalt pavement (RAP) in hot-mix asphalt (HMA) pavements has become routine in many states around the United States and many other countries all over the world. In addition, the recycling of crumb rubber modified (CRM) materials has been an area of interest since CRM was first used in asphalt paving materials over 40 years ago. Previous research on the recycling of rubberized asphalt concrete (RAC) materials have been limited and focused mainly on the mixture properties at the location of in-field paving. However, for the long-term performance characterizations, it is needed to investigate the aging properties of rubberized binders and the subsequent recycling properties of these aged rubberized binders.; This research investigated the recycling of aged CRM binders, and the objectives of this study included: (1) evaluating the interaction effects of CRM binders as a function of various blending treatments in the laboratory; (2) evaluating the binder properties of artificially long-term aged CRM binders and CRM mixtures; (3) evaluating the properties of aged CRM binders rejuvenated using either a commercial rejuvenator or a softer binder; (4) evaluating the properties of recycled aged CRM binders and identifying the performance properties and compositional changes.; The following conclusions were drawn based on the laboratory investigation: (1) the interaction conditions for CRM binders were found to have significant effect on the binder properties; (2) after subjecting to the long-term aging, the asphalt mixtures with the control and CRM modified binders had statistically insignificant difference in aging level; (3) the aged CRM binders could be recycled up to a targeted PG grade using rejuvenating agents; (4) the performance properties of recycled aged CRM binders showed satisfactory results meeting current Superpave binder requirements, and selected Superpave binder properties at each aging state correlated well with the large molecular size (LMS) values of recycled aged CRM binders. |
