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INVESTIGATION OF RECYCLED ASPHALT PAVEMENT ( RAP ) MIXTURES Final Report

This report presents the results of a study on recycled asphalt pavement (RAP) mixtures. The report includes a literature review on RAP and a summary of past research. The research focuses on the use of resilient modulus and complex modulus testing to compare mixtures compacted with only virgin materials to those compacted with varying amounts of RAP. The additional of RAP makes the mixture stiffer, as evidenced by an increase in resilient modulus and complex modulus measurements, according to the research. The addition of RAP also decreases the mixture phase angle, which corresponds to an increase in the elastic properties and a decrease in the viscous mixture properties. The report includes recommendations regarding the proper temperatures and loading frequencies for use in the complex modulus test. It also gives the percentage of RAP and the respective asphalt binder grade necessary to yield the stiffness similar to a virgin mixture. This report represents the results of research conducted by the authors and does not necessarily represent the views or policies of the Minnesota Department of Transportation. This report does not contain a standard or specified technique. (RAP) Mixtures project. The objectives of this report were to: 1. Describe the RAP material used in the project. 2. Describe the test methods used and the results obtained from the testing. 3. Provide conclusions and recommendations relating to the amount of RAP and the asphalt binder grade which should be used to achieve properties similar to a virgin asphalt concrete mixture. The RAP material was characterized in a number of ways. Asphalt content was determined by the ignition oven method. RAP aggregate gradation was determined before and after the asphalt binder was removed by solvent extraction. A dynamic shear rheometer (DSR) was used to determine the RAP binder Superpave performance grade after solvent extraction The properties of the RAP aggregate were also evaluated by determining the specific gravity, absorption, and fine aggregate angularity (FAA). Samples were compacted in the laboratory using a Superpave gyratory compactor. The samples contained from 0 to 40 percent RAP from either MnDOT District 6 or District 8, and either PG 58-28, PG 52-34 or PG 46-40 virgin asphalt binder. RAP material was blended with virgin aggregate such that all samples tested had approximately the same gradation. Samples were tested for resilient modulus, complex modulus, and moisture sensitivity. The resilient modulus test provides a measure of the elastic properties of …