IPRF Project FAA-01-G-002-2

Improved Concrete Overlay Design Parameters for Airfield Pavements


Current trends in pavement design philosophy rely on increasingly sophisticated analytical modeling coupled with correlations with laboratory, accelerated trafficking, and in-service tests. Overlay design philosophy has tended to lag behind this trend, and much of today's airfield overlay design still relies on empirical relations developed in the 1950s. The FAA has developed an improved rigid pavement overlay design methodology based on layered elastic theory, but its performance correlations are based upon accelerated traffic tests largely conducted in the 1940s and 1950s before analytical models such as layered elastic theory were easily solvable in practice. Consequently, material characterization and data collection from these old tests do not necessarily provide the desired information for use with more modern analytical models. The FAA is now in the process of developing an advanced pavement design procedure based on finite element modeling which requires modeling data far more detailed than ever envisioned in these older tests.


This research shall develop an experimental design for a large-scale, accelerated testing program at the FAA National Airfield Pavement Test Facility (NAPTF) or other locations in order to get performance data on concrete overlays to support modern analysis based on layered elastic theory and finite element analysis methods. The overlays to be considered will be rigid overlays with various potential degrees of nominal bonding over rigid and flexible pavements that carry aircraft with single wheel loads greater than 30,000 lbs. The analytical models to be considered will be layered elastic theory and finite element analysis techniques that include finite element models throughout the pavement structure and hybrid finite element models that model the critical layers (e.g., the overlay and base pavement) with finite elements that are then coupled with simplified representations of underlying materials (e.g., Winkler foundation of springs). This overall program will concentrate on structural behavior of overlays under aircraft loading, but it should attempt to include environmental contributions such as temperature and moisture extremes that clearly effect overlay behavior.

Task 1. Identification of Critical Design Parameters.

This task will result in the identification of the parameters that affect overlay pavement performance and rank them in order of importance.

It is expected that the person that is preparing the proposal will be intimately familiar with airfield overlay design philosophy and methodology. Hence, an exhaustive general state-of-the-art literature review and summary should not be necessary to accomplish this phase. Any literature review will be focused on specific issues needed to fully develop critical design parameters. The FAA empirical overlay design equations, layered elastic design method, and the evolving finite element design methodology will be included as candidate design procedures; but additional design methodologies besides these can and should be considered. Critical information needed to assess, validate, refine, or develop these design concepts shall be the critical design parameters. Critical overlay design parameters that will be considered for evaluation shall, as a minimum, be:

    1. Effect of varying stiffness and material properties of the overlay, support conditions of base or fill material, and subgrade materials.
    2. Impact of existing pavement condition.
    3. Impact of joints and cracks in existing pavement and performance of the overlay.
    4. Interface conditions and effects on performance (how they should be modeled).
    5. Effect of progressive fatigue cracking in different levels on stress conditions and performance.

Task 2. Develop Experimental Design and Test Program.

In this task, the proposer will develop a detailed testing plan to test and find critical values for the parameters identified and approved by the Project Technical Panel in Task 1.

Using the critical test parameters defined in Task 1, carry out a critical assessment of the identified critical parameters and compare those parameters to the testing capability of the FAA National Accelerated Pavement Test Facility (NAPTF). Develop a recommended experimental plan for accelerated traffic testing at NAPTF, or other facilities, that will result in the data collection needed to develop and validate improved airport concrete overlay design procedures. This includes understanding and including in the experimental plan only requirements and material specifications that can be readily used at the NAPTF, or other facilities. There are always more variables and requirements than funding so the proposal must fully develop the recommended experimental design and subsequently assign a priority to each test item.

Each test item will thoroughly identify the parameters which are being investigated, provide complete details on all materials, dimensions, construction requirements, traffic, quality control/quality assurance, evaluation tests, and instrumentation, as well as design details for why the test item was selected and what it is expected to accomplish. Each test item will include an analysis plan that details how the data will be analyzed and how it will contribute to improving overlay design methods. Finally, each test item will have an estimated cost and budget. Ideally, there will be a testing program and budget for both a "minimum testing program" and an "optimized testing program."

Task 3. Technical Report.

The proposer will provide a final report summarizing the work performed, providing a summary of the critical design parameters, and providing the test item details. The main emphasis of this report will be the final detailed testing plan.


The test plan will be a "roadmap" to gather performance data on concrete overlays to be used with modern analytical models and overlay designs. Note that the design solution envisioned using this information is one that will predict pavement performance as well as develop a pavement thickness.

It is anticipated that "roadmap" will include, as a minimum, the following items:

    1. Draft contract documents for the construction of the large-scale test sections.
    2. Instrumentation plan.
    3. Schedule for construction and testing phases.
    4. Post-testing and evaluation plan.
    5. Estimated costs for the entire program.


1. The technical panel believes that "pumping" is not a major concern for most overlays. However, it is recognized as a significant cause of rigid pavement distress. The views of the people preparing the proposal are requested and should be included in the proposal.

2. After the technical panel completes the evaluation of proposals, each of the proposals will be rank ordered. The organization, group, or individual that is ranked as the first and second choice for the recommendation to award will be asked to make a presentation to the project technical panel. The Principal Investigator and one other person from each entity ranked first and second choice will participate in an interview to discuss the project details, goals, and objectives. The IPRF will reimburse the expenses (up to 2 people) to make this presentation at a location yet to be determined in Skokie, IL. The interview will occur within a 30-day window subsequent to the proposal submittal deadline.

3. The investigator will be responsible for preparing and submitting quarterly reports that describe the progress of the research effort. Reports will be due in the offices of the IPRF on the last day of the fiscal year quarter (i.e., last day of March, last day of June, last day of September, and the last day of December). The reports will be two pages maximum in a format that will be specified. Due to the short time frame of the project, two quarterly reports will be used as review and approval points by the technical panel.

4. The research team must spend sufficient time at the NAPTF to thoroughly understand the capabilities of the facility and the conditions under which construction and data collection must be undertaken. At that same time, it is expected that the contractor will become intimately familiar and cognizant with the current FAA design procedures in order that the detailed test procedure is compatible with the test facility and addresses the gaps in the current procedures.

PROJECT DIRECTOR: James W. Mack, P.E., (717) 441-3506, jmack@pavement.com

Have Questions?
Contact Jim Lafrenz, Cooperative Agreement Programs Manager Phone: 202-842-1010

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