Evaluation of the Combined Effects of Recycled Asphalt Pavement (RAP), Recycled Asphalt Shingles (RAS), and Different Virgin Binder Sources on Performance of the Blended Binder for Mixes with Higher Percentages of RAP and RAS
Principal Investigator: John Harvey
| University of California, Davis
Research Team: Zia Alavi, Yuan He, and David Jones | University of California, Davis
As virgin material sources become increasingly scarce, and the volume of pavement material that is routinely recycled increases, it becomes more desirable to use significantly higher amounts of RAP and RAS for pavement construction.
The California Department of Transportation (Caltrans) has recently increased the allowable RAP content to 25 percent in asphalt mixes. Caltrans-industry-academia task group has proposed increasing the RAP and RAS percentages to allow binder replacement up to 40 percent. Virgin binders from different sources blend differently with the age-hardened oxidized binder in RAP and RAS. There are concerns that depending on the source of the virgin binder, the rheological properties of the blended binder could vary appreciably that will result in highly variable cracking performance.
The University of California Pavement Research Center has proposed and studied a methodology to evaluate the effect of RAP and RAS without extraction and recovery by testing of the fine aggregate matrix (FAM) using solid torsion bar fixture with the dynamic shear rheometer (DSR).
The specific objective of this study investigates the effect of different binder sources used in California by conducting a small laboratory study and measuring the rheological properties of the blended binders without extraction and recovery of the aged binder.