Abstract
Cold in-place recycling (CIR) is a viable pavement rehabilitation technique that recycles 100% of the reclaimed asphalt pavement (RAP) in place, without the addition of heat. One of the barriers to the use of CIR has been the lack of a suitable mixture design procedure. Researchers at the University of Rhode Island have shown that Superpave® mix design technology is applicable to CIR mixtures if the mix design compactive effort [number of compaction revolutions or gyrations (Ndesign)] can be established for the Superpave gyratory compactor (SGC). The two objectives of the present project were to determine the mix design compactive effort (Ndesign) with the SGC required to match the field densities of CIR mixtures and to evaluate the effect of sample compaction before and after breaking of the emulsion on the Ndesign compactive effort. RAPs from seven CIR projects were obtained, as was asphalt emulsion from each project. Samples were compacted with the SGC by use of the mix water and emulsion content from the field. The change in density with the number of compaction revolutions was monitored, and the Ndesign required to match the field density was determined. The effects of RAP physical properties, such as RAP gradation, the percentage of flat and elongated particles, aggregate gradation, and angularity, on Ndesign were evaluated. RAP shape, as measured by the percentage of flaky pieces, was found to influence the compacted field density. The Ndesign compactive effort for CIR mix design was also established.