Pavement Structural Monitoring of CCPR and FDR Using Non-Destructive Testing Methods

Abstract

Cold Central Plant Recycling (CCPR) and Full Depth Reclamation (FDR) are pavement recycling techniques that provide a sustainable option for pavement construction and rehabilitation. However, these methods are not commonly implemented on high-volume routes due to the need for more detailed information on their field performance and the interactions between material properties and environmental conditions. This dissertation aims to document and evaluate the performance of semi-rigid pavement structures with CCPR and FDR layers through multi-year monitoring, including data collected using three nondestructive testing methods: the falling weight deflectometer (FWD), the traffic speed deflectometer (TSD), and embedded pavement instrumentation. The analysis includes three pavement sections from the NCAT Test Track (N3, N4, and S12) and two instrumented segments (Segment II and Segment III) on Interstate 64 in Virginia. The first study characterized CCPR and FDR materials by calculating in-situ moduli for three full-scale pavements on the NCAT Test Track, with a focus on the moduli of individual layers using linear and viscoelastic software. FWD data were collected at the beginning of three research phases (2012, 2015, and 2018). The results showed that the section including CCPR and FDR (S12) exhibited the lowest overall deflections compared to sections with only CCPR (N3 and N4). Deflections decreased over time, indicating increased pavement stiffness. Additionally, low deflection and estimated strain levels suggest that fatigue cracking is unlikely. The second study reports measured pavement responses, including strains and stresses, for two recycled sections on Interstate 64 subjected to actual environmental and traffic-loading conditions. Pavement structures were also modeled using layered-elastic software to compare measured and calculated responses. The results indicate that the pavement sections exhibited low strain, pressure, and deflection, suggesting a long structural life. Instrumentation remained generally functional after five years and may continue to provide valuable performance data. The third study assesses the functional and structural performance of two recycled pavement segments on Interstate 64 in Virginia. Structural performance was evaluated using calculated structural condition indexes and deflection velocity data from TSD. Deflection velocity profiles were compared with estimated values from 3D-Move software under various modulus scenarios. The scenarios that most closely matched observed data were further compared with measured pavement responses from in-situ instrumentation under loading conditions similar to those of the TSD rear axle. The findings demonstrate that both recycled pavement structures maintain good functional condition and favorable structural behavior after several years of service. Collectively, these studies advance understanding of pavement structural behavior under loading and environmental conditions, highlight the potential of recycled materials in flexible pavements on high volume routes, and promote innovation in pavement engineering. The results support the consideration of similar design approaches, including recycled-material foundations, when existing pavements require deep repair or reconstruction.