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FAA Airport Pavement Technology Program

FAA Airport Pavement Technology Program. Testing and preliminary data analysis from flexible pavements on low-strength subgrade (Construction Cycle Three (CC3)). Current work and plans for next rigid pavement test items. Low-Strength SG Flexible Replacement – Fall 2002.

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FAA Airport Pavement Technology Program

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  1. FAA Airport PavementTechnology Program • Testing and preliminary data analysis from flexible pavements on low-strength subgrade (Construction Cycle Three (CC3)). • Current work and plans for next rigid pavement test items. 1

  2. Low-Strength SG Flexible Replacement – Fall 2002 Thicknesses are based on 55,000 lb wheel load on 3 CBR subgrade. 5-in thick 8-in thick 16-in (40-cm) thick 24-in (60-cm) thick 34-in (85-cm) thick LFC1 43-in (110-cm) thick LFC2 LFC3 LFC4 Target Repetitions to Failure 6-Wheel 200 770 3,500 11,000 4-Wheel 370 2000 11,800 36,400 2

  3. Low-Strength SG Rework 3

  4. Design Methodology • LEDFAA with 2-layer subgrade. • Vary Poisson’s Ratio with subgrade strength: • Poisson’s Ratio = 0.82 – 0.1 * (logESG/145). • Improve behavior of failure model at low departure levels: • log v = – 2.301 – 0.1607 log CF(Super-Heavy Aircraft Study). 4

  5. Design Conditions • Reworked subgrade CBR = 3 • Existing subgrade CBR = 5.5 • Wheel load = 55,000 lbs • Dual spacing = 54 inches (4- and 6-wheel) • Tandem spacing = 57 inches (4- and 6-wheel) 5

  6. LFC3 – Reworked Subgrade = 3 CBR 6

  7. Variation of Asphalt Modulus with Temperature (Witczak) 7

  8. Variation of Pavement Life with Temperature – LFC3, from LEDFAA 350-600 and 1200-2100 8

  9. Testing Schedule • September 3: started. • September 4: stopped testing on LFC1. • September 6: 990 passes. • September 12: stopped testing on LFC2 at 3,168 passes. • September 13 and 16: 2 test pits in LFC2. • September 17: tried MWHGL wander on LFC3 and 4. • September 18: increased load to 65,000 and continued testing on LFC3 and 4 with old wander. • October 18: stopped at 23,826 passes. 9

  10. Asphalt Temperatures 10

  11. Pavement at 19,500 Passes 11

  12. North, 6-Wheel Track 12

  13. South, 4-Wheel Track 13

  14. Rut Depths from Straightedge Tried different wander. Then increased load to 65,000 lbs 14

  15. Rut Depths from Straightedge Tried different wander. Then increased load to 65,000 lbs 15

  16. LFC3 - Upheaval on North Track 16

  17. LFC3 - Upheaval on South Track 17

  18. Laser Profiler – 21.5 ft Span, 8 in Range 18

  19. Transverse Profile – LFC3 ~1,000 Pass Intervals 19

  20. Failure Criteria for Flexible Design • From MWHGL Report. • A pavement was considered failed when either of the following conditions occurred: • Surface upheaval of the pavement adjacent to the traffic lane reached 1 in. or more. • Surface cracking occurred to the point that the pavement was no longer waterproof. 20

  21. Rut Depths from Profiles 21

  22. Uplift from Profiles 22

  23. Rut Depth from Profiles 23

  24. Uplift from Profiles 24

  25. Uplift from Profiles 25

  26. Rut Depth from Profiles - Extrapolated 26

  27. CC3 and CC1-MFC Compared to MWHGL 27

  28. MWHGL DT Test Item B-747 gear, 60,000 lb wheel loads, failed at 420 passes. 28

  29. Layered Elastic Strain 29

  30. Starting Excavation of Trench 30

  31. Current Proposal for Rigid Reconstruction (1) • 15 ft x 15 ft (4.5 m x 4.5 m) slabs. • 3-Part optimized mix. • 28-day wet burlap cure. • Transverse joints doweled. 31

  32. Current Proposal for Rigid Reconstruction (2) • Looked at decreasing strength and increasing thickness: • Rounded intermediate aggregate, no significant decrease. • 30%, and 50% Class C flyash replacement in a two-part mix (batched 1/13/03), significant decrease at 50%. 32

  33. PCC Beam Strengths 33

  34. PCC Cylinder Strengths 34

  35. Flexural vs. Compressive 35

  36. Current Proposal for Rigid Reconstruction (3) • One more batch at 70% flyash replacement. • 15 ft x 15 ft x 11 in thick test slab on existing PCC. Will measure. • Vertical displacement of corners. • Horizontal strains. • Temperature through depth. • Relative humidity through depth. 36

  37. Current Proposal for Rigid Reconstruction (4) • Three test items on medium-strength subgrade: • Existing econocrete subbase. • Aggregate subbase. • Slab-on-subgrade. • Rebuilding medium strength subgrade to depth of 3 feet. Target strength is 7 CBR. Half finished. 37

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