Evaluation ofin situRAP binder interaction in asphalt mastics using micromechanical models

In this article the mastic level structure of asphalt concrete containing reclaimed asphalt pavement (RAP) materials is investigated using the principles of micromechanics. Locally sourced RAP material was screened and sieved to separate the coated fines (smaller than 0.075 mm) from the remaining sizes. These binder coated fines were mixed with virgin filler at proportions commensurate with 0, 10, 30, 50 and 100% RAP dosage levels. Asphalt mastics were prepared with these blended fillers and a PG 64-22 binder at a filler content of 27% by volume. Temperature–frequency sweeps were conducted on the resulting composites as well as the constituents, virgin binder, solvent extracted RAP binder. The results from the experiments showed an expected increase in stiffness with increase in dosage levels. These results were also used to model the hypothesised structure of the composite. The study presented discusses the applicability of Herve and Zaoui model to predict the blended mastic composite and to quantify the amount of blending between RAP binder and newly added asphalt binder. It is found that as the RAP dosage level increases the amount of blending that occurs, as a proportion of the total RAP binder decreases.