The current Federal Aviation Administration (FAA) pavement overlay design procedure described in Chapter 4 of FAA Advisory Circular 150/5320-6D uses a thickness deficiency approach to determine the required thickness of hot mix asphalt (HMA) overlays. This approach requires an assessment of the structural condition of the existing pavement. Considerable variability and subjectivity is allowed in this evaluation process. The new FAA overlay thickness design procedure contained in draft AC 150/5320-6E makes use of the Structural Condition Index (SCI) to provide a more objective measure of the existing pavement condition in HMA overlays of existing rigid pavements. However, a similar method is not available to assess the condition of existing HMA pavement to be overlayed. Although nondestructive pavement testing (NDT) is allowed, guidelines for integration of NDT data into the layered elastic methodology and appropriate input parameters for the existing pavement are needed. A review of the entire overlay design procedure is needed to ensure that the most economical, fundamentally sound overlay structure is provided.

Objectives

The objective of this study is to provide a comprehensive document that gives the practicing airport designer guidelines to evaluate existing pavement in the overlay design procedure. Preparation of this document requires knowledge of the Federal Aviation Administration's present and proposed overlay design procedures and extensive knowledge of other pavement design and evaluation procedures. The primary emphasis of the completed document shall be on overlays on existing asphalt concrete surfaces. In addition, the entire FAA proposed elastic layer overlay design procedure shall be reviewed, recommended revisions provided and comments on procedure enhancements be given.

The following information is provided to insure that the proposals address the critical elements of the research and keep within the scope of the proposed project:

1. Current and proposed FAA pavement design procedures are to be the basis of the research. Advisory Circular 150/5320-6D and Draft Advisory Circular 150/5320-6E may be obtained from http://www.f aa.gov/airports_airtraffic/airports/resources/advisory_circulars. The FAARFIELD 1.1 computer program may be obtained from: http ://www.faa.gov/airports%5Fairtraffic/airports/construction/design%5Fsoftware/.
2. Standard material properties and inputs as required in FAA design procedures are assumed to be consistent with FAA AC 150-5370-10B or appropriate technical bulletins.
3. In this research, Portland cement concrete (PCC) pavement structure elements shall only be considered when it is not the surface of the existing pavement.
4. Evaluation of existing pavement structure may include non-destructive tests, laboratory tests and visual surveys. Visual distress survey elements shall conform to ASTM D5340 definitions. No laboratory or field evaluations are anticipated in this project.
5. The research shall consider types and warrants for pre-treatment activities prior to overlay and the corresponding revisions in input parameters.
6. Recommendations for changes to the FAARFIELD computer program may result from this research effort, but access to the source code and actual revisions to the program are outside the scope of the project.

1. Propose rational procedures for assigning modulus values to represent the existing pavement layers in the FAARFIELD design procedures.
2. Recommend a systematic approach to account for the lower quality and/or distressed condition of the existing pavement. This may include penalty factors such as reduced moduli or layer thicknesses, or penalties applied to the cumulative damage factor (CDF), but technical justifications must be provided for whatever approach is used.
3. Address all realistic modes of failure (i.e., rutting, fatigue, reflective cracking, etc.).

Product

The contractor shall develop and deliver to AAPTP a final technical report addressing the existing FAA pavement evaluation and overlay design procedures based on elastic layer analysis. The document should provide the contractor's recommendations for incorporating these procedures into the existing draft advisory circular 150/5320-6E and proposed enhancements to the FAARFIELD program. In addition, a stand-alone guide document to assist practicing engineers shall be developed as per task 5 below. These products shall be developed by addressing and documenting the following tasks:

Task 1 -- Conduct a review of overlay design procedures and practices for airfields. This will include FAA, PCASE, Asphalt Institute (M.S. 11), and others.

Task 2 -- Conduct a sensitivity analysis on the FAARFIELD overlay design methodology that includes input parameters for the existing pavement structure and other factors.

Task 3 -- Identify methods for assessing existing HMA pavement condition, limiting values, and possible alternative corrective actions. Assess what values should be used for the FAA overlay design procedures to best handle the appropriate conditions of existing or modified pavements.

Task 4 -- Provide an interim report presenting work to date and the future course of action that is being considered. The report is expected to be presented to the technical panel at a mutually agreed upon location 6-8 months after award. At the time of this meeting Tasks 1 and 2 should be completed and initial work started on Task 3.

Task 5 -- Revise work per technical panel's comments and concerns. Complete draft report, guidelines and submit for the technical panel review. Draft products shall consist of a document providing details of the research and recommendations and a stand alone guide to assist practicing engineers in assessing the existing pavement condition. The technical panel will provide comments within one (1) month after receiving drafts.

Task 6 -- Prepare a presentation detailing research completed and project products. This presentation shall be in Microsoft PowerPoint format and suitable for a one-hour presentation.

Task 7 -- Revise report and guidelines and submit final products. Camera-ready copy of the final documents and electronic copy in press-quality PDF format shall be submitted under this task.

All written documentation will be prepared using Microsoft Word unless otherwise stated. All reports will be the property of the AAPTP and Auburn University and will be supplied in a format that complies with the FAA's Section 508 requirements for electronic documents.

Proposal Evaluation Criteria

The proposal will be evaluated on the following criteria:

1. Understanding of project requirements, scope and complexity;
2. Merit of the proposed research approach;
3. Experience of team members in asphalt technology, airport pavements design, and elastic layer design;
4. Level of effort and cost effectiveness of budget proposal.

Reporting Requirements

Progress Reports

Quarterly progress reports (2 hard copies and an electronic copy in Microsoft Word format) are required from the research agency and are to be prepared on the basis of calendar quarters. The research agency will mail the report directly to the AAPTP and will e-mail each of the members of the technical review panel a copy of the progress report. Each report will include a cover letter and the following:

1. a clear and complete description of the work performed on each task during that quarter;
2. an outline of the work to be accomplished during the next quarter;
3. a description of any problem(s) encountered or anticipated that might affect the completion of the project within the time and fiscal constraints recommended;
4. potential solutions to problems identified in (c) if any exist.

Report Format

The formats for the Interim and Final reports are provided under "Research Process."

Contractual Information

Funds Available: $150,000

Contract Time: 18 months (includes 1 month for AAPTP to review and for the contractor to revise the final report.)

Staff Responsibility: Monte Symons, 334-844-4964, symonmg@auburn.edu

Proposals Due: March 15, 2008

Submit Proposals To: AAPTP, 277 Technology Parkway, Auburn, AL, 36830

Authorization to Begin Work: April 15, 2008 -- estimated