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Develop a Laboratory Mixing Procedure For Hot Mix Asphalt Containing RAP Materials
AdvisorHajj, Elie Y.
Civil and Environmental Engineering
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AbstractThe use of reclaimed asphalt pavement (RAP) has become more prevalent with the rising costs of virgin materials and the recent push to develop more environmentally friendly and sustainable roadways. The use of RAP decreases the costs of constructing new pavements by limiting the amount of virgin materials required. For this reason there is a significant amount of research being conducted to examine the effects of using high amounts of RAP in the new HMA mixtures. The primary objective of this study is to develop a mixing procedure for the laboratory that best simulates the plant-produced samples after their mixing and production process. Three distinct methods for incorporating the RAP material into the mixing process will be examined and compared to the plant produced samples provided by Granite Construction. The general descriptions of the three methods are as follows:Method A: The virgin aggregate, the virgin asphalt binder and the RAP material will all be heated to the appropriate mixing temperature as dictated by the virgin asphalt binder grade. Method B: The virgin aggregate will be superheated in accordance with NAPA's recommendations from Information Series 123. The virgin asphalt binder will be heated to the appropriate temperature dictated by the performance grade. The RAP material will be dried and added at the ambient temperature.Method C: The virgin aggregate is superheated in accordance with NAPA's recommendations from Information Series 123. The virgin asphalt binder will be heated to the appropriate temperature dictated by the performance grade. The RAP material will be moisturized to the appropriate moisture content and added at the ambient temperature.To be able to determine which method of incorporating the RAP material into the laboratory mixing process will produce the mixture that most closely simulates the plant-produced mixture several characteristics will be analyzed. This thesis will examine the mixing temperatures over the duration of the mixing process for each method. This will provide insight into how effectively the virgin aggregate is transferring heat to the RAP material. Additionally a short term oven aging analysis will help determine the appropriate aging time in the laboratory the replicate the aging experience by the plant-produced mixtures. To assess the different aging levels, the asphalt binder will be extracted from the plant-produced and laboratory-produced mixtures and graded according to the Superpave performance grading system. Lastly, compacted samples will be created for each mixing method as well as for the plant-produced laboratory-compacted mixtures to conduct an analysis of the volumetric properties and dynamic modulus.