Improving the Selection of Virgin Binders for Recycled Hot Mixtures in Ontario

ABSTRACTThe design of Recycled Hot Mixtures (RHM) in the United States is based on the guidelines provided by the National Cooperative Highway Research Program (NCHRP) Report 452. However, the extreme climatic characteristics in Canada require a validation on the selection of the virgin binders especially for Superpave Surface layer mixtures. This paper shows the results of a laboratory characterization of twelve conventional Superpave 12.5 mm mixtures, four of them with high Reclaimed Asphalt Pavement (RAP) content. Thermal Stress Restrained Specimen Test (TSRST) was conducted on triplicate samples for each mixture, and also the continuous grades for the binders were obtained. The findings were compared with the recent guidelines provided by the NCHRP Report 752. Dynamic modulus was performed and used to determine the critical temperatures of the blended binder without extraction. The analyses suggest that the virgin binder could be selected based on the critical temperature of the climate zone and the RAP content, and that the use of softer binders could not guaranty that the mixtures have the desired performance to low temperature cracking.