Performance of High RAP Pavement Sections in NH

This report summarizes the University of New Hampshire (UNH) results of test pavements used to determine the effect of using higher amounts of Recycled Asphalt Pavement (RAP) in Hot Mix Asphalt (HMA). The New Hampshire Department of Transportation (NHDOT) has allowed RAP in HMA for over 20 years but has limited use to 15-20% of the mix. This study evaluated the changes in performance due to increased amounts of RAP as well as evaluating the impact of bumping the binder grade (to a softer binder) for higher RAP contents. The pavements tested were in place for approximately three years. Long-term performance was not evaluated. Binder testing included PG grade, shear modulus master curve, and the multiple stress creep recovery test. Mixture testing included complex modulus, flow numbers, Hamburg Wheel tracking, and fatigue. Test results for both binder and mixes using PG 58-28 demonstrated expected results with high RAP contents having a stiffer modulus, better rutting performance, and lower fatigue resistance. The PG 52-34 binder had unexpected trends. Testing did not include determining the presence of binder additives. The results of this project support the practical limitation of 1% total recycled binder (TRB) in NHDOT surface mixtures.