The main objective of this research is to determine the in-place properties of pavement cross-sections containing recycled materials common to the New England region, and to relate changes in those properties to variations in temperature and moisture. The study will focus primarily on obtaining field data from base layers (as opposed to asphalt surface layers) that have been constructed with different types of unbound or bound recycled layers such as full depth reclamation (with or without stabilizing additives), plant mix recycled asphalt pavement (PMRAP), or foamed asphalt. The research team will work with the NETC advisory board members to identify appropriate field sites where the pavement design is clearly documented and where pavement performance can be linked to factors such as traffic loadings, moisture regimes and freeze-thaw effects. Laboratory testing will also be included to complement the analysis of in-place test data and instrumentation monitoring.
The importance of testing reclaimed layers with Falling Weight Deflectometer, evaluating the response at the different times of the year, and utilizing good practices during mix design and construction have been emphasized by multiple researchers. Based on their conclusions, the following testing and analysis plan is proposed for the study. In order to accomplish this research, five tasks have been established and are broken into two Phases.
Progress/Accomplishments Through March 31, 2015
- The research team began testing on the two existing sites in NH. The Warren Flats site was tested on February 21 and on March 21. On both dates, thermistor data suggests that there was some temporary thawing down to about 5 inches beneath the top of pavement. In between those temporary thawing events, there have been refreezing events. Based upon forecast air temperatures and cumulative thawing indices, it is anticipated that the current thawing event (beginning March 28) is likely to continue with minimal or no refreezing. The first Kancamangus testing will thus likely be during early thaw conditions; frozen conditions will be tested in 2015. Testing of both the Warren Flats and Kancamangus sites will continue through the next quarter, to capture stiffness data during the thaw-weakened period as well as the recovery period. The research team has also been working with the ME DOT to identify an appropriate location for instrumentation on the PMRAP Waterford/Norway project.
- Identification and partial instrumentation of two new sites in ME.
- Instrumentation and testing of soils samples from the two new ME sites. ME Instrumentation Sites: The site located in Waterford, ME on Rt 118 was instrumented last quarter and the paving was completed over the summer. The site located on Rt 122 in Auburn ME was instrumented on August 21, 2014 once the full-depth reclamation with emulsion was done and before the surface layer was placed. The post for the data logger at this site will be installed in the coming quarter and data collection will begin. Field and Lab Tests for ME sites: During drilling operations for instrument installation, standard penetration testing (SPT) was conducted, and samples were obtained for laboratory testing. In the lab, sieve analysis and moisture content determination were performed on each sample, and then each sample was classified according to the USCS and AASHTO classification systems.
- The instrumentation of the Auburn, ME site on Rt. 122 was completed and ME DOT conducted baseline FWD testing for the two sites. The research team contracted with Mr. Bob Eaton to have data loggers installed at the three NH Kancamagus sections to collect hourly temperature in the pavements through the winter and spring thaw period. The research team has also contracted with CRREL to conduct the FWD testing on the Warren Flats and Kancamagus sections during the winter and 2015 spring thaw and recovery season. ME DOT has generously agreed to conduct the FWD testing at the two ME locations during the winter and 2015 spring thaw and recovery season. The proposed plan for the FWD testing is listed below: Fall baseline (completed) 2. Frozen condition (Jan/early Feb) 3. Pre-thaw (late Feb/early March) 4. Weekly during thaw and early recovery 5. Bi-weekly through recovery 6. Early July
- If possible, early thaw and refreeze events will also be captured. The research team will be monitoring the temperature data and air temperatures to determine the appropriate timing for the FWD teams to begin the weekly testing to capture the spring thaw. The research team held a web conference with the technical committee on December 5th to discuss the project status and plans. Additional questions were received after the meeting from TC member David Kilpatrick and the research team sent a response to all TC members on December 22nd.
- This quarter (January to March 2015) has been focused on FWD testing at the NH and ME sites. The research team has been analyzing the temperature data to determine the appropriate timing for FWD tests at all sites, and several sets of FWD tests have been conducted at each site.
- The data logger at the Waterford site was replaced and the issue with the thermistor string at Warren Flats was resolved. Currently, all four sites are collecting and transmitting data as expected.
Technical Committee Members
- Dale Peabody (Chairperson ), Maine Department of Transportation
- Laurence (Larry) Andrews, Massachusetts Highway Department
- Denis M. Boisvert, New Hampshire Department of Transportation
- Jeffrey DiFilippo, Rhode Island Department of Transportation
- David J. Kilpatrick, Connecticut Department of Transportation