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FAA Airport Safety Technology R&D

September 2013

REDAC Recommendations

(7) Finding: Regarding Pavement Design and Evaluation (RPD 145), the Subcommittee believes that the FAA has addressed our recommendations from our Fall 2012 meeting on a conceptual level. These recommendations included (1) definition of the term “40-year design life” and (2) description of project success criteria. This said the Subcommittee would like to see refinement and embellishment of these definitions as the project proceeds. There was also a desire to have opportunities for more robust industry participation of the project by subject matter experts (SME) in both asphalt & Portland cement concrete design.

Recommendation: The Subcommittee recommends forming a SME advisory panel with selected members of the Subcommittee and the Airfield Pavement Working Group that can collaborate with the FAA project team directly in its refinement and execution of the RPD 145 work plan, leaving the subcommittee free to focus on the higher level aspects of the pavement research program.

FAA Response:  The FAA is in agreement with the recommendations and will have a Subject Matter Expert (SME) advisory panel in place consisting of a concrete Industry representative (Gary Mitchell), an asphalt Industry representative (Monte Symons), both Mitchell and Symons are also members of the Subcommittee, two Airport Authority Representatives (Scott Murrell – PANY/NJ & Kathy Masters - AHJIA), and an Airports Consultants Council representative (Dean Rue – CH2M Hill). Several of these representatives are also members of the FAA Pavement Working Group. The panel will collaborate with the FAA project team headed by Jeffrey Gagnon

FAA Update:  The SME Group is currently made up of the following:

1.Jeff Gagnon (ANG-E262)	2. David Brill (ANG-E262)	3. Greg Cline (AAS-100)	4. Joe Herbert  (APP-500)

5. Gary Mitchell –(ACPA)	6. Monte Symons (AI)		7. Scott Murrell (PANY/NJ) 	8. John Rone (HJAIA )	

9. Dean Rue (CH2M Hill)

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FAA Airport Safety Technology R&D

September 2013

REDAC Recommendations

(9) Finding: The Subcommittee encourages the National Airport Pavement Test Facility (RPD 138) project to continue investigating high strength concrete effects on pavement fatigue life. The current research results indicate that high strength (e.g., flexural strength of approximately 1000 psi) PCC surface layers perform as well or better than medium strength PCC surface layers (e.g., flexural strength of 750 psi) assuming that the PCC layers are of the same thickness. While these results provide evidence that the FAA’s flexural strength design limits can be relaxed provided pavement section thicknesses are held constant, they do not address the important relationship between pavement strength and pavement thickness. The Subcommittee believes that the significant benefit of using higher strength materials lies in being able to reduce construction costs through the use of thinner PCC surface layers. Many local areas are able to achieve higher strength concrete with normal construction practices. Making use of this phenomenon is logical and can help reduce construction cost.

Recommendation: The Subcommittee recommends the FAA continue research on the effects of higher strength concrete on concrete pavement fatigue life by investigating the pavement life when reducing pavement thickness proportionally to the increase pavement strength. Until such research is completed, relaxation in maximum flexural strength limits for PCC surface layers should be conditioned on the retention of “conventional” PCC surface layer thicknesses.

FAA Response:  The FAA will continue to investigate high strength concrete effects on pavement fatigue life through both laboratory fatigue tests and full-scale studies considering the relationship between concrete flexural strength and thickness. We will seek to obtain further validation for relaxed upper flexural strength limits from field studies at airports where the design slab thickness is intentionally less than would be allowed given the current maximum design flexural strengths, but is nevertheless consistent with high concrete strengths normally achieved in the field. We will prefer projects where high flexural strength is achieved conventionally, without relying on excessive cement content, additives, or other extraordinary means.