FAA Airport Pavement Technology Program

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.

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
200
11,000
770
3,500
6-Wheel
4-Wheel
370
2000
11,800
36,400
3
Low-Strength SG Rework
4
Design Methodology

• LEDFAA with 2-layer subgrade.
• Vary Poissons Ratio with subgrade strength
• Poissons 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).

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)

6
LFC3 Reworked Subgrade 3 CBR
7
Variation of Asphalt Modulus with Temperature
(Witczak)
8
Variation of Pavement Life with Temperature
LFC3, from LEDFAA
350-600 and 1200-2100
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.

10
Asphalt Temperatures
11
Pavement at 19,500 Passes
12
North, 6-Wheel Track
13
South, 4-Wheel Track
14
Rut Depths from Straightedge
Tried different wander. Then increased load to
65,000 lbs
15
Rut Depths from Straightedge
Tried different wander. Then increased load to
65,000 lbs
16
LFC3 - Upheaval on North Track
17
LFC3 - Upheaval on South Track
18
Laser Profiler 21.5 ft Span, 8 in Range
19
Transverse Profile LFC3 1,000 Pass Intervals
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.

21
Rut Depths from Profiles
22
Uplift from Profiles
23
Rut Depth from Profiles
24
Uplift from Profiles
25
Uplift from Profiles
26
Rut Depth from Profiles - Extrapolated
27
CC3 and CC1-MFC Compared to MWHGL
28
MWHGL DT Test Item
B-747 gear, 60,000 lb wheel loads, failed at 420
passes.
29
Layered Elastic Strain
30
Starting Excavation of Trench
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.

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.

33
PCC Beam Strengths
34
PCC Cylinder Strengths
35
Flexural vs. Compressive
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.

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.