Proposals Due August 1, 2006
Airfield Asphalt Pavement
Technology Program (AAPTP)
Reflective cracking is a major concern on hot mix asphalt airport pavement overlays. When asphalt overlays are placed over jointed or severely cracked rigid and flexible pavements, cracks reflect to the surface in a relatively short period of time. These reflective cracks require maintenance to prevent the generation of loose aggregates and creation of roughness that may be detrimental to aircraft operations and to prevent water from penetrating into underlying materials and damaging or weakening the pavement structure. There have been numerous attempts to development methods to prevent reflective cracking in the past. It is the consensus opinion that no product or process (other than removal or rubblization) will totally prevent reflective cracking. At best, the use of materials and procedures that are presently available only delay or limit the severely of the reflective cracks. Many new and existing materials and methods are being aggressively marketed with only limited performance data. This performance data often has not been adequately evaluated and/or independently documented for decision makers to determine what products are best suited for different situations. There are on going studies aimed at developing a comprehensive model for reflective cracking. It is not the purpose of this project to investigate or develop reflective crack modeling. This project will provide the Federal Aviation Administration (FAA) and others with guidance and recommendations on the appropriate use of materials and procedures to improve resistance and/or delay reflective cracking on pavements overlaid with hot mix asphalt materials.
The objective of this study is to develop technical guidance on the selection of materials and procedures to resist, control or delay reflective cracking on hot mix asphalt (HMA) airfield pavements. It is not the intent to evaluate and endorse specific products in this research. Proprietary products and procedures may be evaluated but should be stated in terms of basic approach and characteristics to the maximum extent possible. In general, the project shall maximize use of categorized groups of existing products by function, properties, materials and most appropriate for specific airport situations as the primary element for investigation and recommendations.
The project includes literature review and field performance elements. The literature review shall consist of gathering information on past and present materials and procedures that are presently used in reflective crack mitigation efforts. The great amount of performance information has been documented on highway pavements and this should be included in the literature review. The majority of the verification of the performance shall be directed towards information on products/processes used on HMA airport pavements. Although laboratory tests will be addressed for each category of products or approaches, no direct laboratory testing is envisioned in this project. The investigator is encourage to initially contact manufactures and suppliers of the various crack mitigation products to determine the application locations.
The guidance and recommendations must consider but not be limited to the following:
Specific conditions for application of these products to airfield pavements should consider the following:
The initial effort of this study will be to gather and evaluate literature related to reflective cracking and determine materials and procedures that have significant promise to retard or prevent reflective cracking. Methods and products that appear to have the most potential will be identified, evaluated and discussed in the final report. It is suggested that the types of reflective cracking mitigation methods and procedures be grouped into the following categories: (1) crack control methodologies, (2) thin interlayer of grids, fabrics and composite products, (3) stress absorbing layers, (4) conventional HMA overlay mixtures with specially designed properties and materials and (5) others. These are intended as a starting point and may be changed or adjusted as the research may require. The report shall include a mechanism for identifying and classifying potential for reflective cracking and a logical process to evaluated products and procedures for application at a particular site. In addition, the final product shall provide a reasonable estimate of the time period when reflective cracking is expected to occur for each category of mitigation methodology.
The final product recommendations and guidance shall be developed by addressing the following tasks:
Task 1 -- Review existing literature on products and processes used to prevent or mitigate reflective cracking on highway and airfield pavements and the mechanisms that describe reflective cracking.
Task 2 -- Collect and evaluate field performance of categories of crack mitigate applications on airfield pavements.
Task 3 -- Identify and provide recommended laboratory tests that assess key properties of the materials used for mitigation of reflective cracking strategies.
Task 4 -- Compare and contrast the different categories of crack mitigation strategy applications and provide benefits and potential issues with each strategy.
Task 5 -- Develop preliminary report for the technical panel's review and comments. This report shall include status of work to date and present the information into an organized process that provides logical, non-bias decisions for selecting reflective cracking mitigation strategies. This report is expected approximately 8 months from the contract starting date. If requested by the researcher or the technical panel, a meeting may be held within 30 days of receiving the preliminary report to comments and discussion on the preliminary report. Such a meeting will be at the researcher's location.
Task 6 -- Revise guidelines on the technical panel comments and discussion and develop specifications to use the crack mitigation strategies on airport pavements.
Task 7 -- Post final draft for 30 days for general public review and comments.
Task 8 -- Provide final report with public comments in appendices. Camera ready copy of the final report and an electronic copy in press quality PDF format shall be submitted under this task.
All written documentation will be prepared using Microsoft Word. 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.
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:
The formats for the Interim and Final reports are provided under "Research Process."
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, firstname.lastname@example.org
Proposals Due: August 1, 2006
Submit Proposals To: AAPTP, 277 Technology Parkway, Auburn, AL, 36830
Authorization to Begin Work: September 1, 2006 -- estimated
Maintained by Linda Kerr