The interaction among polymers, aged binder from reclaimed asphalt pavement (RAP), and recycling agents (RA) is still a concern for the asphalt industry. Therefore, laboratory and field performance of six plant-produced polymer-modified (PM) mixes containing up to 40% RAP and RA included in a pilot project were evaluated in this study. The base binder performance grade (PG) specified for the control mix with no RAP/RA for this study was PG64-28M. A softer base binder (PG58-34M) was used for all other RAP mixes to reduce the need for RA dosage. In this study, the RA dosages for the RAP mixes were selected during the job mix formula (JMF) by restoring the high PG of the extracted binders containing RAP compared to the control mix. The extracted binder test results obtained during construction indicated that a softer binder might have been used for the control mix with no RAP instead of the specified PG64-28M binder. The laboratory AC mix results indicated a somewhat similar performance for the RAP mixes. The stiffer RAP mixes showed greater strain sensitivity in the flexural fatigue test than the softer mixes. The mainline mix with 23% RAP and no RA exhibited slightly lower fracture cracking resistance than other mixes. The mixes with RAP also showed higher rutting resistance in the laboratory than the control mix with no RAP. The comparison between the extracted binder and mix frequency sweep results indicated that both had similar rankings and trends, indicating good diffusion of the RAP and virgin binders, except for the mix with 40% RAP and RA. The field survey conducted after 34 months (2.8 years) of service indicated that all test sections (with and without RAP/RA) are in very good condition.
Rahman et al. (Fri,) studied this question.