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...
Peridotite xenoliths entrained in magmas near the Alpine fault (New Zealand) provide the first direct evidence of deformation associated with the propagation of the Australian-Pacific plate boundary through the region at ca. 25–20 Ma. Two of 11 sampled xenolith localities contain fine-grained (40–150 mm) rocks, indicating that deformation in the upper mantle was focused in highly sheared zones. To constrain the nature and conditions of deformation, we combine a flow law with a model linking recrystallized fraction to strain. Temperatures calculated from this new approach (625–970 °C) indicate that the observed deformation occurred at depths of 25–50 km. Calculated shear strains were between 1 and 100, which, given known plate offset rates (10–20 mm/yr) and an estimated interval during which deformation likely occurred (<1.8 m.y.), translate to a total shear zone width in the range 0.2–32 km. This narrow width and the position of mylonite-bearing localities amid mylonite-free sites suggest that early plate boundary deformation was distributed across at least ~60 km but localized in multiple fault strands. Such upper mantle deformation is best described by relatively rigid, plate-like domains separated by rapidly formed, narrow mylonite zones.
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