Effects of Rejuvenation and Aging on Binder Homogeneity of Recycled Asphalt Mixtures

Despite the well-recognized benefits of recycling milled asphalt pavement material, some remaining challenges limit the reclaimed asphalt pavement (RAP) content in asphalt mixtures. Rejuvenators are frequently used to enhance the properties of the aged binder in asphalt mixtures containing RAP. The blending process between the rejuvenator and the aged binder continues to be a source of performance uncertainty, especially for high-RAP mixtures. This study investigates the diffusion of a rejuvenator into RAP binder and the effect of aging and blending procedures on the homogeneity of the rejuvenated binder. A staged extraction method was used to separate the different layers within the asphalt film that covers the aggregates. Each layer was characterized by its rheological properties measured by a dynamic shear rheometer. Results showed that the rejuvenator was initially mostly absorbed by outer binder layers but continued to diffuse into inner layers as time elapsed. Aging also affects outer layers more intensely. A homogeneity index is introduced to quantify the consistency of the binder.