Towards the Development of Pavement-Specific Structural Synthetic Fibers
Status: Contract development
The application of synthetic fibers can reduce the fatigue cracking and faulting of thin concrete pavements and overlays. Currently available synthetic fibers used in concrete pavements are mainly polyolefin-based. Previous studies suggest that any fibers can plastically elongate and pullout from the concrete when crack widths are wide enough, thus becoming ineffective in transferring wheel load across adjacent sawn or cracked slabs. The purpose and effectiveness of reinforcement is holding concrete across differing crack widths. The goal of this proposed study is to better understand existing polyolefin fiber performance against the abovementioned plastic elongation and pullout to eventually further increase the life of concrete pavements and overlays. This study will be conducted in two phases. This proposal is for the first phase, which has the two following objectives: (i) determining the forces induced on the fibers because of vehicular and environmental loads when used in concrete pavements; (ii) identifying those characteristics that can most easily be changed in both or either the concrete and fibers for the purpose of improved performance of thin concrete pavements and overlays. Once the first phase is completed, the next phase will deal with the designing and testing of the pavement specific concrete mixture and fibers.
Task 1: Initial Memorandum on Expected Research Benefits and Potential Implementation Steps
- Scheduled date for task final approval: May 31, 2021
- Deliverable: Task 1 Memo
Task 2: Quantifying the forces on the fibers because of vehicular and environmental loads when used in concrete pavements
The objective of the Task 2 is to understand and quantify the forces exerted on to the fibers when used in pavements. This task will be performed with the help of the finite element modeling and field data (temperature gradient, environment-, and load-induced strains, crack width movement, falling weight deflectometer data) collected from the NRRA 2017 FRC pavement sections. Finite element models of thin concrete overlays and pavements will be developed to understand the forces induced on to the fibers because of the vehicular and environmental loads at different seasons. Figure 5 shows an example of a FEM model of short paneled thin concrete pavements. The distress data collected from the abovementioned project revealed that structural fibers can reduce faulting by increasing the load transfer between the slabs. The trends of joint faulting, International Roughness Index (IRI), and joint load transfer with respect to the ESAL for the abovementioned FRC project will be studied to determine the desired load transfer contribution of fibers so that the cumulative faulting at the design ESAL does not exceed the maximum allowable limit. It may be worth mentioning that the maximum allowable faulting for the short-paneled pavements and overlays will be less than that is recommended for the conventional pavements, because of a greater number of transverse joints in the former. The IRI data will be useful in determining the maximum allowable faulting for the short-paneled pavements and overlays.
- Scheduled date for task final approval: October 31, 2021
- Deliverable: Task 2 report
Task 3: Identifying the desired properties of fibers and concrete for pavement applications
The objective of the Task 3 is establishing the desired properties of fibers and concrete for pavement applications. In this task, an ongoing laboratory investigation (at UMD) will be extended to understand the influence of fibers’ physical and mechanical properties on the behaviors of the fiber reinforced concrete (FRC). Fibers’ physical properties include equivalent diameter, length, geometry, aspect ratio, etc. The mechanical properties include the stress-strain behavior, elastic and plastic strains at failure, modulus of elasticity, and lateral stiffness, and pullout of individual fibers. A test setup will be built for testing individual fibers. Individual fiber’s properties will be correlated with the properties of the FRC produced with the respective fiber. Two types of tests will be conducted on the FRC: (i) post-crack tensile test, and (ii) joint performance test. Figure 6 shows a photograph of a test setup developed at UMD for studying the post-crack tensile behavior of FRC. Figure 6 (see work plan, linked below) also shows load vs. crack width plots for five different concrete mixes prepared with five structural synthetic fiber types, with varied geometries. It can be seen that the peak load, as well as the post-peak behaviors, varies with the fiber geometries, indicating the different crack creep and post-crack toughening behaviors. Figure 7 shows a photograph of the joint performance test. In addition to the fiber properties, the other significant variables for this test will be the crack creep, fiber distribution, and orientation. Commercially available fibers with various physical and mechanical properties will be considered for this task. However, as the currently available fibers probably exhibit limited residual elastic strain (< 20%), some correlations might necessarily be extrapolated. The base concrete mixture design for this task will be decided jointly by the PI, industry partners, and the technical advisory panel members emphasizing the required paste volume to coat the fibers and aggregates. However, working with the concrete mixture proportions at MnROAD would allow for some intended correlations between field observations and laboratory data. The work would establish a control FRC mixture compared to two or more mixtures changing the fiber length and dosage and changing the concrete mixture proportions. The outcome of this task will provide statistically verified correlations between the properties of fibers and concretes. These correlations will be useful to show other desired properties of fibers and concretes for pavement application. For example, these correlations will answer to the question like what optimum length and dosage affecting residual elastic strain do the fibers possess so that the plastic elongation and fiber pullout is less than a certain maximum allowable value which will ensure better post-crack and joint load transfer performances..
- Scheduled date for final report approval: May 31, 2022
- Deliverables: Task 3 report
Task 4: Draft Final Report
The final Report will be a comprehensive report including the scope of the work, literature review, works completed in Tasks 5.2 and Task 5.3, conclusions and recommendations. The final report will be prepared, following MnDOT publication guidelines, to document project activities, findings and recommendations. This report will be reviewed by the Technical Advisory Panel (TAP), updated by the PI to incorporate technical comments, and then approved by the Technical Liaison before this task is considered complete. If possible, a TAP meeting will be scheduled to facilitate the discussion of the draft report.
- Scheduled end date: November 30, 2022
- Deliverables: Final report and recommendations to NRRA Technical Transfer Committee
Task 5: Editorial review and publication of final report
During this task, the approved report will be processed by MnDOT’s contract editors. The editorial review will ensure it meets publication standards. The PI will work with the editor to address editorial comments, so this task must be finished while the contract is still active.
- Scheduled end date: January 31, 2023
- Deliverables: Final report and recommendations for technology transfer
Task 6: Benefits and implementation plan
Review of research report and development of an implementation plan.
- Scheduled end date: June 30, 2023
- Deliverables: Implementation plan
Principal Investigator: Manik Barman, Ph.D., University of Minnesota - Duluth, email@example.com
Co-PIs: Bill Coursen, FORTA Corporation, firstname.lastname@example.org; Gerald Welch, FORTA Corporation, email@example.com; Clifford MacDonald, MSCE, FACI, Vigilant Enterprise, LLC, firstname.lastname@example.org
Technical Liaison: David Lim, CalTrans, email@example.com
Project Technical Advisory Panel (TAP) – Email the TAP
Email us to join this TAP
- Tim Andersen, MnDOT
- Tom Burnham, MnDOT
- Rob Golish, MnDOT
- David Lim, Caltrans (TL)
- Maria Masten, MnDOT
- Angel Mateos, UC-Berkley
- Mike Radler, The Dow Chemical Company
- Peter Taylor, Iowa State CP Tech Center