Production of HMA mixtures with higher percentages of RAP is gaining more attention as a way to save money and more efficiently utilize existing resources. Many state agencies and contractors are very comfortable using RAP percentages of 10-15%. However, questions about low temperature performance and the need to bump binder grades limit the amount of HMA produced with greater than 15-20% RAP in many areas of the northeast US. A previous study presented at the 2010 TRB Annual Meeting performed an evaluation of extracted binder properties for various batch-plant-produced HMA mixtures containing 0-25% RAP. The general conclusion was that binder bumping was not necessary at the 20% RAP level for the mixtures evaluated. The pooled-fund study proposed herein will expand on the initial work by including higher RAP percentages, drum and batch plants, and mixture testing. Testing of plant-produced mixtures will allow for evaluation of blending and the impact of higher RAP percentages on material properties and performance. Mixture testing will also be expanded to evaluate moisture susceptibility of the mixtures containing RAP. The proposed work will complement an ongoing FHWA evaluation being conducted by the North Central Superpave Center, and other research projects across the country.

The objectives of this research are to: 1. Evaluate the performance of plant-produced RAP mixtures in terms of low temperature cracking, fatigue cracking, and moisture sensitivity in the laboratory and the field 2. Establish guidelines on when it is necessary to bump binder grades with RAP mixtures 3. Provide further understanding of the blending that occurs between RAP and virgin binder in plant-produced mixtures

The URL for the draft scope-of-work is provided below. The scope will be modified upon identification of project partners. The research plan is broken down into two phases. Phase I will focus on evaluating the effects of binder grade and plant type on the properties of mixtures with various percentages of RAP. Phase II will be geared towards evaluating the amount of blending that occurs between the virgin and RAP binders. The testing and results of Phase I will be used to inform the testing matrix and final plan to be developed for Phase II. Contractors from participating states will be asked to provide plant-produced mix for testing. Table 2 in the draft scope-of-work shows a summary of producers that have already volunteered to participate in this study and detail on the mixtures they are willing to produce. Additional producers will be solicited to ensure that at least one producer from each participating state is represented.

The draft scope and budget assumes a minimum of six to seven states participating. A total commitment of $90,000 per state is requested. Commitments may be spread over a three (3) year period. Target participants include states located in the Northeast Asphalt User/Producer Group (NEAUPG) region, Virginia, and NC. Initial stages of work will proceed in CY 2010 based on current commitments.