Development of characteristic-based guidelines to determine maximum allowable reclaimed asphalt pavement content in polymer-modified asphalt mixture. Issue 8 (3rd July 2022) - Park, Bongsuk
ABSTRACT: Current Florida Department of Transportation specifications limit reclaimed asphalt pavement (RAP) usage to 20% in polymer-modified asphalt (PMA) mixtures, because aged and brittle RAP binder may reduce benefits of polymer modification. Previous studies indicated RAP binder stiffness and RAP gradation were important characteristics related to RAP mixture cracking performance. This study focused on developing guidelines to determine maximum RAP content in PMA mixtures based on these RAP characteristics. Eight RAP sources covering a broad range of RAP binder stiffness and RAP gradation were used to assess the effect of these RAP characteristics on cracking performance. The interstitial component fracture energy (FEIC ) which is correlated well with mixture fracture energy (FEmix ) was employed as a surrogate for FEmix to assess all RAP mixture combinations, and FEIC was determined by the IC direct tension test. FEmix obtained from Superpave indirect tensile tests was used to evaluate findings from FEIC results. Finer RAP and stiffer RAP was more detrimental to cracking resistance, indicating characterising RAP binder stiffness and RAP gradation was necessary to increase the current maximum RAP content in PMA mixture. Developed guidelines allowed up to 40% RAP depending on RAP characteristics and were validated by the way of full mixture testing.