Utilization of Cold Central Plant Recycled Asphalt in Long-Life Flexible Pavements

Long-life flexible pavements are well documented and used widely across the U.S. Found in every climate zone and traffic classification, long-life pavements do not experience deep structural distresses such as bottom-up fatigue cracking or substructure rutting. Full-scale test sections, built in 2003 at the National Center for Asphalt Technology (NCAT) Test Track, provided the basis for an optimized design approach that utilizes strain distributions for long-life thickness design. These sections, containing only virgin materials, were subjected to 30 million standard axle loadings with excellent performance in terms of rutting, cracking, and roughness. In 2012, three new sections were built at the Test Track using cold central plant recycled asphalt materials as the base layer. These layers, made from nearly 100% reclaimed asphalt pavement (RAP), supported hot mix asphalt layers that also included RAP with one section featuring in-place stabilization of the existing aggregate base. This paper provides a direct comparison between the sets of sections to compare and contrast their performance histories and structural characterization, and consider their economic and environmental impacts. None of the recycled sections are exhibiting any surface deterioration, despite heavy trafficking, and the section with a stabilized base is exhibiting lower strains than established long-life pavement thresholds. The economic analysis suggested that the recycled sections can deliver similar performance at a lower average structure normalized section cost than the non-recycled sections. Furthermore, the section with the stabilized base and 76% recycled material is likely a long-life pavement and can potentially outperform the sections with no recycled content.