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MnROAD | NRRA | Structure & Teams | Flexible Team

Mix Rejuvenator Test Sections (Phase 3)

Status: In development

Project objectives

Asphalt rejuvenators are used to incorporate higher amounts of Reclaimed Asphalt Pavement (RAP) in Hot Mix Asphalt (HMA) without detrimentally impacting the long-term performance of the pavement. Rejuvenating agents (RAs) are relatively new in the HMA industry and there are many different products marketed to transportation agencies. However, most of these products have limited field and laboratory test data available to support their effectiveness over time. Several recent research efforts have shown that some products, while effective immediately after production, show rapid decrease in effectiveness with aging. Therefore, there is a need for a better understanding of how various RAs perform over time through both laboratory and field evaluations to help guide engineers on appropriate usage of these materials.

The National Road Research Alliance (NRRA) Flexible Team constructed field test sections as part of a mill and overlay project on Trunk Highway 6 (TH6) located in Emily, MN in August of 2019. These field sections include wearing courses with 40% RAP that incorporate seven different RA products, with the dosage determined by the supplier to meet a target extracted and recovered performance grade (PG) of XX-34. In addition to the RA test sections, there are control sections with 40% RAP and 30% RAP (the maximum level allowed on remainder of this project). Mixtures and binders were sampled at the time of production. A range of mixture tests on the plant produced mixtures were conducted by NRRA members. Field cores were taken shortly after construction and every subsequent year and field performance data has been collected yearly.

The ongoing NRRA project “Long-term Testing and Analysis on Asphalt Mix Rejuvenator Field Sections” (MnDOT Contract 1036343 WO1) has conducted binder and mixture characterization and performance testing on the plant produced materials, field cores collected each year, and plant mixtures that were conditioned in the laboratory at two long-term aging levels. After three years in service, there have not been significant changes observed in the laboratory measured properties of the field cores nor has any substantial distress been observed in the field sections. Additional monitoring and testing of field cores from the sections is needed to fully evaluate the effectiveness of the seven RA products over time and evaluate their performance as compared to the control mixtures.

Project tasks

Task 1: Testing and analysis of field cores

Field cores taken each year will be subject to complex modulus and fatigue testing using the small specimen geometry to continue to track the material property changes occurring in the field and to allow for comparison to laboratory aged conditions evaluated in the initial project. The results will also be used to conduct the pavement evaluation of the test sections in Task 3.

  • Deliverable: A summary of the results from the testing conducted on the field core specimens and discussion in context with the previous years’ results will be included in the annual report each year.

Task 2: Binder testing and analysis

Binder extraction and recovery from the top ½” of the field cores will be conducted using ASTM D7906 procedure (toluene extraction and rotovap recovery). Rheological characterization of the recovered binders will include G* frequency sweeps to develop complex modulus and phase angle master curves, determine continuous PG temperatures and calculate and various rheological indices (e.g. binder Glover-Rowe parameter, ΔTc and R-value). Chemical characterization will include SARA analysis to determine the typical four fractions of asphalt binders and the FTIR test to evaluate the functional groups within the binder samples.

  • Deliverable: A summary of the results from the testing conducted on the field core specimens and discussion in context with the previous years’ results will be included in the annual report each year.

Task 3: Field performance data and analysis

Field performance data for the field sections will be collected from MnDOT and summarized for comparison with the laboratory measured properties over time. Pavement evaluation of each test section will be conducted using the as-built section information, actual traffic, local climate information, and measured material properties from the Task 1 testing each year. Pavement evaluation will be conducted using the FlexPAVE™ software.

  • Deliverable:: A summary of the field performance and pavement evaluation results discussion in context with the previous years’ results will be included in the annual report each year.

Task 4: Reporting

The research team will prepare quarterly reports for the duration of the project. Annual reports that summarize the results of additional testing and analysis conducted under Tasks 1-3 will be prepared. A presentation of the results to date will be given to the TAP and/or through the NRRA Research Pays Off webinar series or at the Minnesota Transportation Conference annually. The research team will prepare a draft final report, following MnDOT publication guidelines, to document project activities, findings, and conclusions. The report will also include any recommendations for further testing and monitoring of the sections. The draft final report will be submitted six weeks prior to the contract end date for review by the TAP. A TAP meeting will be scheduled approximately one month prior to the contract end date for presentation of the results and to facilitate the discussion of the draft report. The report will then be updated to incorporate TAP comments and feedback.

  • Deliverable: Quarterly reports, annual reports and presentations, final report.

Project team

Email the Project Team
Principal Investigator:
Jo Sias, University of New Hampshire, jo.sias@unh.edu
Technical Liaison: Michael Vrtis, MnDOT, michael.vrtis@state.mn.us
Project Technical Advisory Panel (TAP): Contact us to join this TAP

  • Brian Hill, Illinois DOT
  • Raquel Moreas, NCAT
  • Dylan Specht, Illinois DOT
  • Hassan Tabatabaee, Cargill
  • Michael Vrtis, MnDOT (TL)
  • Fan Yin, NCAT

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