UC Pavement Research Center
Available online at: https://doi.org/10.1080/14680629.2019.1588777
Hung, Shawn S., Mohamed Elkashef, John T. Harvey, David Jones (2019) Development of an Alternative Test Approach for Binder Blending Charts with Fine Aggregate Matrix Mix Testing. Road Materials and Pavement Design 20 (1)
Binder blending charts are used to determine the selection of virgin binder grade of asphalt mixes containing more than 25% reclaimed asphalt pavement (RAP) as part of the Superpave volumetric mix design procedures. However, the extraction and recovery of RAP binder used as part of the binder blending charts process is expensive, hazardous, and poses potential threats to human health and the environment due to the solvents used. An alternative two-phase approach was developed in this study that uses fine aggregate matrix (FAM) mix testing with the help of predictive models. The first phase is to determine the predictive model fitting parameters using the results of virgin binders and virgin FAM mixes. The second phase involves using these model-fitting parameters along with the predictive models to estimate the performance grade of the binders within the FAM mixes containing RAP. The predicted performance grades are compared with the actual performance grade of the RAP/virgin binder blend. The results indicate that the proposed approach can be used to estimate the intermediate and low PG temperatures of the blended binder within the FAM mixes containing RAP with an acceptable accuracy compared to the blending charts approach. The use of FAM mixes also allows consideration of the blending of the RAP and virgin binders, compared with solvent extraction which results in complete blending.
Keywords: RAP binder blending, binder blending charts, Hirsch model, fine aggregate matrix mix testing