The use of reclaimed asphalt pavement (RAP) has become part of the daily practice in the construction of hot mix asphalt pavements. Besides the cost savings on materials, the use of RAP represents an environmentally positive method of recycling. Significant experimental work has been performed in the lab to evaluate the asphalt mixtures modified with RAP materials. However, the performance of pavements built with RAP is very hard to come by. Many pavements have been built in Minnesota and around the United States using RAP, but very few have been monitored closely to provide useful performance data. Questions remain about the viability of using RAP in a wearing course. A recently completed NCHRP study investigated many issues related to using RAP in HMA pavements. Some of the issues examined concerning RAP include: . Variability of the RAP materials . Extent of blending between RAP and virgin binders . Binder PG Grade and blending charts . Superpave mix design incorporating RAP . Other issues not necessarily covered in the above study include RAP processing, fractionated RAP, temperature gradients in the mixtures prepared with RAP during the laydown and compaction process, and correct softening agents. It will be desirable to determine the material properties of the asphalt mixtures by performing laboratory tests. The RAP mixtures from this proposed study would likely be tested with the Simple Performance Test for input into the M-E Design Guide. The RAP mixtures would also be tested for their low temperature fracture characteristics as part of a separate proposed pooled fund study (Investigation of Low Temperature Cracking in Asphalt Pavements ¿ Phase II). Moisture sensitivity testing specified by AASHTO T283 and at much lower temperatures is also of interest. The University of Minnesota recently completed two studies involving RAP. The first was aimed toward investigating the effect of various types and percentages of RAP on asphalt binder and asphalt mixture properties. This is a first step in the more complex process of developing a rational design for asphalt mixtures containing RAP that may change Mn/DOT current specifications. The second project looked into developing a simple test that could be used to obtain asphalt binder properties that are required in developing blending charts to select the appropriate percentage of RAP. The results of these studies also need to be verified with field sections. Related studies include: . LRRB 826: Appropriate Use of RAP Based on Field Performance (Mn/DOT) . LRRB 788: Recycled Asphalt Pavement (RAP) Effects on Binder and Mixture Quality (University of Minnesota) . LRRB 783: Development of Simple Asphalt Test for Determination of RAP Blending Charts (University of Minnesota) . SPR-3(045): Use of Reclaimed Asphalt Pavement Under Superpave Specifications (Becky McDaniel) . NCHRP 9-12: Incorporation of Reclaimed Asphalt Pavement in the Superpave System (Becky McDaniel) . NCHRP 9-39: Procedure for Determining Mixing and Compaction Temperatures of Asphalt Binders in Hot Mix Asphalt (NCAT) . RMRC Project 37: Simulating Plant Produced RAP Mixtures in the Laboratory for Mix Design (Jo Daniel) . RMRC Project 9 - Properties of Asphalt Mixtures Containing RAP (Jo Daniel) The majority of current and former research projects using RAP are based on laboratory material characterization and mix design. The research proposed in this pooled fund study seeks to validate many of the previous findings with field performance data. There is a lot of anecdotal evidence of existing pavements containing RAP, but this research would provide a controlled field experiment in which valuable results could be obtained. This work should lead to the development of new specifications related to RAP or further implement the usage of existing specifications.

The main idea of the project is to monitor several sections built at the Minnesota Road Research Facility (MnROAD) specifically to study RAP under controlled testing conditions. The sections may contain identical structural designs and hot mix asphalt mix designs, with the only variable being the percentage of RAP in each of the mixes. The final scope and work plan for the study will be developed by the participating states. The Minnesota Department of Transportation specifies the maximum amount of RAP allowed in a mix based on pavement layer and traffic level. Mn/DOT wishes to determine if the present limits on RAP are justified. This pooled fund study is strictly to perform the RAP research on newly built test sections at MnROAD, and its funding will come from Mn/DOT and other participating states. The funding for the construction of new test sections will be obtained separately from Mn/DOT and other partners.

This project may consist of the following activities: . Work Plan: The work plan for this pooled fund study will ultimately be developed by the participating organizations. This will include selecting materials and mix designs for the reconstruction of three cells at MnROAD. Variables that may be included in the mix designs are the percentage of RAP, source of RAP, and PG grade of the added binder. . Instrumentation Design: Thermocouples, strain gages, etc. . General Testing & Monitoring: Monitor the pavement performance over time on each test section. Monitoring activities will include FWD tests, rutting measurements, distress surveys, ride measurements, and analysis of pavement sensor data. . Special Testing & Monitoring: Obtain samples for laboratory testing on asphalt binders and mixtures. Of particular interest is the bending beam rheometer test on beams of asphalt mixtures developed as part of an earlier study. These tests will help to fully characterize the pavement materials and predict the field performance. . Design Guide Modeling & Validation: The material properties for HMA layers containing RAP will be modeled in the new mechanistic-empirical design procedure. . Pooled Fund Travel: Money for each state to travel to discuss the progress of the study. . Data Analysis & Reports: Work done under a research contract will develop interim and final reports that document the findings of this study.

Mn/DOT along with other participating states are asked to contribute $15,000 per year for 5 years to fund the research proposed in this pooled fund study. The Minnesota Department of Transportation (as the lead agency) along with other partners will provide approximately $400,000 in initial construction funding outside of this pooled fund study to construct the pavement test sections containing RAP.