National Airport Pavement Test Facility Update

1. National Airport Pavement Test Facility Update Airport Pavement Working Group Don Barbagallo April 24, 2012

2. Acknowledgement • This presentation overview represents the work of many individuals including: • FAA Pavement Group • SRA International • Gemini Technology • McQueen Associates

3. Current Ongoing Projects at NAPTF • Construction Cycle 5 (Flexible Pavement). • Construction Cycle 6 (Rigid Pavement). • High Tire Pressure Testing on HMA. • Reflective Cracking of HMA Overlay Testing. • Alkali-Silica Reactivity Slabs. • Single Wheel Module Instrumentation. • Engineered Material Arresting System (EMAS) Testing. • Runway Friction Test. • Upgrades to the Test Vehicle. • Future Tests.

4. Post Traffic Testing • CC5 examines the effect of multiple gear configurations on low strength subgrade flexible pavement life.

5. CC5 TRENCH AREA

6. CC5 TRENCH SUBGRADE CHARACTERIZATION Nuclear Density LWD Profiles CBR Measurement

7. Preliminary CC 5 Trench Findings CBR Summary

8. CC 6 Rigid Pavement • CC6 tests to determine the effect of concrete flexural strength on rigid pavement life (AC 150/5320-6E) specification. North Asphalt Stabilized Base South Econocrete Base MRS 1 = 500 psi TFS Total Passes = 17,500 @ 45K MRS 2 = 750 psi TFS Total Passes = 20,000 @ 45 + 13,529 @ 52K + 5,200 @70K MRS 3 = 1000 psi TFS Total Passes = 20,000 @ 45K + 11,000 @ 52K + 7,729 @ 70K

9. CC6 Rigid Pavement Tests • Dr. David Brill & Mr. Josh Davis will present update on CC6 testing.

10. HMA High Tire Pressure Tests • Ran tests over the winter of 2010/11. • Rutting failure in the PG 64-22 mix. • Will continue testing the PG 76-22 mix at 17 ºF higher temperature than for the PG 64-22 mix. • High temperature can only be achieved during the summer. • Delayed because of CC6 testing. • Plan to partially groove section of heated pavement vs unheated pavement.

11. Reflective Cracking Test Rig • Goal: Develop design guidance for asphalt overlay of concrete pavements based upon full scale testing. • AC 150/5320 - 6D purely empirical solution • AC 150/5320 – 6E FAARFIELD does not address problem. • Cracking of asphalt overlays is a complex problem. • Environmental temperature expansion/contraction. • Thermal induced warping • Load induced fatigue

12. Reflective Cracking Test Rig

13. Reflective Cracking Test Rig • Environmental temperature change simulation. • Interface temperature 32F • Movement = Sinusoidal 0 to 15 mils • Total Cycle Time = 6 minutes • Total # of cycles completed to date ≈ 2600 • Instrumentation includes: • Strain gages: concrete, asphalt, and surface • LVDT’s measuring concrete movement • Thermistors • Crack length monitored with photos. • Dr. Hao Lin of Gemini Technologies will present data.

14. Alkali-Silica Reactivity Testing • Indoor, outdoor, & control slabs. • Periodic dosing with potassium acetate solution whenever slabs dry out; about every 6 - 8 weeks. • On–going testing of slabs continues with little visual evidence of ASR. • Planned grooving of slabs to expose aggregate to potassium acetate.

15. Single Wheel Module Instrumentation Wheel Encoder Bending, Shear, & Torque Strain Gages

16. EMAS Testing • Work performed under a CRDA between the FAA and Zodiac Aerospace (formerly ESCO). • Comparison testing of new block design. • Additional tests planned for May 2012.

17. Aircraft Tire Friction Braking Testing • Measure forces and friction coefficient for snow covered surface. • Single wheel module with locked wheel

18. Aircraft Tire Friction Strain Gage Ave Vertical Force Ave Horizontal Force Sliding Friction Coefficient : µ ≈0.13

19. Planned Facility Upgrades • Replace fiber optic data communication line – SPUs to control room. • Add wireless access point for east end of building. • Charging station for electric vehicles. • 200,000 lb in-ground scale to facilitate calibration of test vehicle wheel loads.

20. Test Vehicle Projects* • Study to upgrade vehicle traction drives to incorporate dynamic braking. • Procure and install hydraulic oil heating system. • On-going load control system upgrade - Delta controllers and digital servo valves. * Ryan Rutter to further discuss

21. Future NAPTF Schedule Continue Traffic CC6. Finish testing on CC5 HMA sections that were suspended due to cold weather. Remove/reinistallHMA overlay on reflective cracking rig. Plan and construct CC7 on the low-strength subgrade. Proposed testing to look at overload on flexible pavements. CC7 to also look at perpetual HMA pavements.

22. Future NAPTF Schedule (continued) • Repave the HTP pavement with warm-mix asphalt in conjunction with CC7 HMA construction. • CC8 concrete pavement test planning beginning. • Joint design – load transfer of dowels for thick slabs on moderate strength subgrades. • Joint design – sinusoidal keyways vs. dowels. • As-built slab strength vs. predicted slab strength. • Slab aspect ratios.