REJUVENATOR DIFFUSION IN BINDER FILM FOR HOT-MIX RECYCLED ASPHALT PAVEMENT

In hot-mix recycling of bituminous mixes a rejuvenator is commonly used to restore the aged asphalt cement to a condition that resembles that of virgin asphalt cement. The type and amount of rejuvenator to be used are generally determined from a characterization of the recovered weathered binder. However, the extent to which the salvaged bitumen will be softened by the recycling agent during the hot-mix operation, and hence the characteristics of the rejuvenated binder and the resulting performance of the recycled pavement, has not been widely reported. An investigation was undertaken to determine the extent to which certain types of rejuvenators diffuse into the hardened asphalt film coating the aggregate and affect its properties during a specified period of time. A partial extraction technique that had the effect of dividing the asphalt film into microlayers was used. The binder recovered from each microlayer was characterized by means of consistency tests. This technique was used to evaluate the consistency distribution of the binder film around the aggregate in (a) the extracted mix containing recycled asphalt pavement (RAP) only; (b) the extracted mix containing RAP and a rejuvenator; and (c) the extracted mix containing RAP, virgin aggregate, and a rejuvenator.