Evaluation of binder blending on warm mix asphalt recycling

It is still a challenge to produce recycled asphalt mixtures with increased contents of reclaimed asphalt pavement (RAP) without compromising field performance. On hot and warm recycling, the RAP binder is activated, but the amount that truly interacts with the fresh binder is unknown. The present study describes the application of a staged extraction laboratory procedure to evaluate the homogeneity of the binder film in two plant-produced warm mixtures, one containing 25% RAP and the other without RAP (control mixture). The “layers” of binder obtained through the procedure were tested in the Dynamic Shear Rheometer. Results showed a progressive variation of the parameters for the 25% RAP mixture, which was not observed for the control mixture. The procedure was useful to determine binder homogeneity in recycled mixtures, which can be related to the degree of blending between RAP and fresh binders, providing useful information to ensure adequate field performance.