Performance-Related Tests and Specifications for Cold In-Place Recycling: Lab and Field Experience

Cold in-place recycling (CIR) is a cost-effective treatment for deteriorated pavements, and a recent FHWA policy statement recommends recycled materials be considered for all paving projects. A survey of 38 state departments of transportation by the Rocky Mountain User Producer Group found that many routinely use the technique, but there are some problems with performance reliability, specifically pointing to the lack of a uniform, defined design procedure, and problems with raveling, thermal cracking, compaction problems, low early strength and extended curing time. Other agencies are reluctant to try CIR because of those problems. Much recent asphalt research focuses on lessening risks of early pavement failures through the use of performance type specifications. When an improved technology for emulsion cold in-place recycling was developed, researchers also developed performancerelated test methods to improve the reliability of the process and give agencies more confidence in trying CIR. A laboratory raveling test run on Superpave Gyratory Compactor prepared samples simulates the raveling that can occur on the newly recycled pavement, and is used as part of an engineered design process as well as specifying raveling resistance and early strength. The Indirect Tensile Test developed for Superpave design is modified to design and specify CIR resistance to thermal cracking. The data from these tests for numerous projects is given, and compared for a side-by-side trial of the new CIR and conventional methods. Since 2000, over 1280 lane-kilometers of pavements in 17 states have been successfully recycled using the new performance-related specifications.