Selection Guidelines for In-Place Recycling Projects

Abstract

Information on the type, extent, and project features of hot in-place recycling (HIR), cold in-place recycling (CIR), and full-depth reclamation (FDR) was collected through an online survey of state agencies and in-place recycling contractors. Agency and contractor responses were compared, and guidelines were developed for the most appropriate traffic, climate, and geometric features of projects. Preferences for materials, mix design methods, structural design considerations, and wearing courses were summarized. Findings showed that FDR projects could be constructed in all regions, whereas CIR and HIR would require careful consideration when constructed in either hot and wet or cold and wet climates. Agencies were found to overuse HIR and CIR on roadways with low traffic volume (annual average daily traffic lower than 5,000); these roadways may have inadequate support for recycling equipment. Geometric features were more likely to restrict the use of HIR than the use of either CIR or FDR. Most agencies required the contractor to design recycled mixes. The benefits of in-place recycling included reduced use of natural materials, reduced fuel consumption, reduced emissions, and briefer lane closures. Barriers to increased use were lack of specifications, competing industries, unsuccessful experiences, lack of experienced contractors, and lack of project selection criteria.