Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration. AbstractThis regional pooled fund project was conducted to investigate the performance of Superpave asphalt mixtures incorporating RAP. This study was closely coordinated with a national study on the same topic (NCHRP 9-12, Incorporation of Reclaimed Asphalt Pavement in the Superpave System). Specifically, this regional project looked at typical materials from the North Central United States to determine if the findings of NCHRP 9-12 were valid for Midwestern materials and to expand the NCHRP findings to include higher RAP contents.Three RAP materials from Indiana, Michigan and Missouri were evaluated. Mixtures were designed and tested in the laboratory with each RAP, virgin binder and virgin aggregate at RAP contents up to 50%. The laboratory mixtures were compared to plant produced mixtures with the same materials at the medium RAP content of 15-25%. Binder and mixture tests were performed.Briefly, the results showed that mixtures with up to 50% RAP could be designed under Superpave, provided the RAP gradation and aggregate quality were sufficient. In some cases, the RAP aggregates limited the amount of RAP that could be included in a new mix design to meet the Superpave volumetric and compaction requirements. Linear binder blending charts were found to be appropriate in most cases. In general, increasing the RAP content of a mixture increased its stiffness and decreased its shear strain, indicating increased resistance to rutting. It is important to consider the RAP aggregate gradation and quality in the mix design, since a poor aggregate structure could reduce mixture stiffness and ultimately performance.Provided the RAP properties are properly accounted for in the material selection and mix design process, Superpave mixtures with RAP can perform very well. Key WordsReclaimed Asphalt Pavement, RAP, recycling, Superpave, hot mix asphalt, rutting The objectives of this regional project, then, were to:• Expand the research conducted under NCHRP 9-12 to examine more materials, particularly those common to the North Central region, • Investigate higher proportions of RAP in the mixtures, and • Focus on mixture properties and the effects of RAP on those properties. The objectives were addressed by comparing mixtures produced in the laboratory with different proportions of RAP and virgin materials. Three RAP sources were investigated at RAP contents up to 50%. Indiana, Michigan and Missouri provided RAP and virgin materials for use in the study. For each RAP source, a laboratory mix was also compared to a plant-produced mix with the same RAP content. Binder and mixture tests were performed following protocols established in NCHRP 9-12.. FindingsThe study demonstrated that acceptable Superpave mixtures can be designed with up to 50% RAP. Aggregate quality and gradation in the RAP material may limit the amount of RAP that can be incorporated.Linear blending charts, as recommended in NCHRP 9-12, were found to be a...

The influence of reclaimed asphalt pavement (RAP) content on the mixture and recovered binder properties of plant-produced hot-mix asphalt (HMA) was examined by studying the complex moduli of RAP mixtures and binders. RAP was added at 15%, 25%, and 40% levels to HMA with PG 64-22 and at 25% and 40% levels to HMA with PG 58-28 binder. In addition, control mixture samples with PG 64-22 and no RAP were also collected and tested for comparison. Compacted specimens were tested to determine the complex dynamic moduli (|E*|) at three temperatures. Complex shear moduli (|G*|) of the binders recovered from these HMA samples, RAP samples, and original binders were determined at the same test temperatures. Low-temperature creep compliance and indirect tensile strength of the mixtures were also determined, and these results were used to estimate the critical cracking temperature of the pavement. Statistical analysis indicated that there were no differences in mean strength and |E*| of the mixtures at the 15% and 25% RAP levels. Some differences between the control mixture and the 40% RAP mixtures were found only at the higher test temperatures.

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Prepared in cooperation with the Federal Highway Administration and the Indiana Department of Transportation. AbstractThis report presents the results of an investigation of the performance of a variety of materials added to asphalt binders and mixtures to change their properties, particularly with respect to rutting and cracking. The approach included a field trial of seven polymer and particulate modifiers, supplemented by laboratory characterization of the materials used in the field. The modifiers evaluated included PAC, Novophalt, Multigrade asphalt cement, polyester fibers, Neoprene, SBR and asphalt rubber. The field trial showed that different modifiers do yield different performance. Modifiers are not essential to ensure that the pavement will not rut. None of the mixtures evaluated here exhibited appreciable rutting. Dramatic differences were noted in the cracking behavior, however. Newly developed laboratory tests were able to identify binders that would be more prone to cracking. All of the materials evaluated did change the properties of the binders or mixtures in some way.Some of the modifiers, however, were more effective at modifying the properties to provide improved field performance in a cost effective manner. 17.