Flexible Pavement Recycling Techniques: A Summary of Activities

Abstract

Cold in-place recycling (CIR) involves the recycling of the asphalt portions (including hot-mix asphalt and chip, slurry, and cape seals, as well as others) of a flexible or composite pavement with asphalt emulsion or foamed asphalt as the binding agent. Full-depth reclamation (FDR) includes the recycling of the entire depth of the pavement and, in some cases, a portion of the subgrade with asphalt, cement, or lime products as binding agents. Both processes are extensively utilized in Illinois. This project reviewed CIR and FDR projects identified by the Illinois Department of Transportation (IDOT) from the Transportation Bulletin and provided comments on pavement designs and special provisions. The researchers evaluated the performance of existing CIR/FDR projects through pavement condition surveys and analysis of falling weight deflectometer data collected by IDOT. They also reviewed CIR/FDR literature and updated/modified (as appropriate) previously provided inputs concerning mix design, testing procedures, thickness design, construction, and performance as well as cold central plant recycling (CCPR) literature related to design and construction. The team monitored the performance of test sections at the National Center for Asphalt Technology and Virginia Department of Transportation. The researchers assisted IDOT in the development of a CCPR special provision as well as responded to IDOT inquiries and questions concerning issues related to CIR, FDR, and CCPR. They attended meetings of IDOT’s FDR with the Cement Working Group and provided input in the development of a special provision for FDR with cement. The project’s activities confirmed that CIR, FDR, and CCPR techniques are successfully utilized in Illinois. Recommendations for improving the above-discussed techniques are provided.