I-81 In-Place Pavement Recycling Project

During the 2011 construction season, the Virginia Department of Transportation (VDOT) completed an in-place pavement recycling project to rehabilitate a section of pavement on I-81 near Staunton, Virginia. The project consisted of a 3.66-mile section of southbound I-81 in Augusta County. VDOT employed three in-place pavement recycling techniques and a unique traffic management plan to accomplish the work. The recycling processes included full-depth reclamation (FDR), cold in-place recycling (CIR), and cold central-plant recycling (CCPR). This project marked the first time in the United States that these three recycling techniques were combined in one project on the interstate system. Materials for both the CIR and CCPR were produced using hydraulic cement and foamed asphalt. A combination of hydraulic cement and lime kiln dust was chosen for the FDR process. The purpose of this research portion of this construction project was threefold: (1) to allow VDOT personnel to gain experience with the specific laboratory mix designs, field evaluation, and quality assurance procedures; (2) to characterize the structural properties of the materials used in the recycling project; and (3) to document the performance of the entire rehabilitated section during its initial 3-year service period. Various laboratory tests were conducted on materials collected before, during, and after construction to characterize the materials. These tests included gradation, resilient modulus, indirect tensile strength, dynamic modulus, and flow number. Additional tests to document the performance of the project included ride quality testing and rut-depth measurements collected via a traffic-speed profiler; pavement layer thickness measurements by ground penetrating radar; and structural capacity measurements by the falling weight deflectometer. From the results of this study, the combined structural layer coefficient for the CCPR and FDR materials was calculated as 0.37. The structural layer coefficient for the CIR material was calculated as 0.39. The structural layer coefficient for the CCPR material was calculated to have a likely range of 0.37 to 0.44. Laboratory testing showed that the performance of the CCPR and CIR materials is expected to be similar. The field performance tests demonstrated that the section of pavement rehabilitated by the three in-place recycling methods continues to perform well after nearly 3 years of high-volume interstate traffic. This study recommends that VDOT pursue in-place recycling where it is most suitable. The study also recommends that VDOT consider increasing the structural layer coefficients used in the design for recycled materials. Further, VDOT should continue to monitor the performance of the I-81 project and other in-place recycling projects in an effort to develop long-term performance data. Finally, the study recommends that VDOT consider using long-term lane closure strategies similar to those employed in this project on other major pavement rehabilitation projects.