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
This report summarizes the main findings from a project funded by the National Center for Sustainable Transportation (NCST) to investigate the use of higher percentages of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) as a replacement for a percentage of the virgin binder in new asphalt mixes in California. The research focused on testing procedures that do not first require chemical extraction and recovery of the age-hardened asphalt binders from the RAP and RAS. Five different asphalt binders covering two performance grades (PG 64-16 and PG 58-22) and sourced from three California refineries were evaluated in this study. The influence of two different percentages of RAP (25 and 40 percent by binder replacement) and one percentage of RAS (15 percent by binder replacement) were evaluated through partial factorial asphalt binder testing and full factorial fine aggregate matrix (FAM) mix testing. The effect of a petroleumbased rejuvenating agent added to selected mixes (with 40 percent RAP and 15 percent RAS) was also investigated. Testing was limited to the intermediate temperature properties of the mixes (i.e., 4°C to 40°C). Based on the findings from this study, FAM mix testing is considered to be a potentially appropriate procedure for evaluating the properties of blended asphalt binder in mixes containing relatively high quantities of RAP and RAS. Further testing on a wider range of asphalt binder grades, asphalt binder sources, and RAP and RAS sources is recommended to confirm this conclusion and to develop models for relating binder properties determined from FAM mix testing to those determined from conventional performance grade testing. Chemical analyses of blended binders may provide additional insights for interpreting test results and warrant further investigation.