Performance Based Specifications for High Performance Thin Overlay Mixtures Incorporating Reclaimed Asphalt Pavement

A pilot specification for high performance thin overlay (HiPO) mixtures utilizing a highly modified asphalt binder (HiMA) was developed by State Department of Transportation (DOT) agencies in the Northeast Pavement Preservation Partnership (NEPPP), the Pennsylvania Asphalt Pavement Association (PAPA), academia, and industry. The pilot specification allows the incorporation of Reclaimed Asphalt Pavement (RAP) in the mixture. Also, it addresses surface preparation, material properties, tack coat, mixture design requirements, RAP testing requirements, and mixture performance criteria in terms of reflective cracking, thermal cracking, fatigue cracking, and rutting. The National Center for Pavement Preservation (NCPP) published and posted the pilot specification on the AASHTO Transportation System Preservation Technical Services Program (AASHTO TSP2) web site. In 2011, the state transportation agencies of Minnesota (MN), New Hampshire (NH), and Vermont (VT) placed demonstration projects of the HiPO mixture incorporating up to 25% RAP. This paper presents the evaluation of the laboratory performance of plant produced mixtures from field project of three state DOTs (MN, NH, and VT). Based on the evaluation of the mixtures and field observations, recommendations were provided to refine the pilot specification. It was recommended to put more emphasis on the testing of the RAP materials, as it showed a significant impact on the performance of the mixtures. Furthermore, surface preparation of the existing pavement impacted the performance of the HiPO mixture. Finally, to make the specifications universal, alternative tests were proposed.