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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
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

low strength sg flexible replacement fall 2002
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

design methodology
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

design conditions
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

testing schedule
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

rut depths from straightedge
Rut Depths from Straightedge

Tried different wander. Then increased load to 65,000 lbs

14

rut depths from straightedge1
Rut Depths from Straightedge

Tried different wander. Then increased load to 65,000 lbs

15

failure criteria for flexible design
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

mwhgl dt test item
MWHGL DT Test Item

B-747 gear, 60,000 lb wheel loads, failed at 420 passes.

28

current proposal for rigid reconstruction 1
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

current proposal for rigid reconstruction 2
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

current proposal for rigid reconstruction 3
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

current proposal for rigid reconstruction 4
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