o’hare modernization project reflective cracking and improved performance of grooved asphalt july...
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O’Hare Modernization Project
Reflective Cracking and Improved
Performance of Grooved Asphalt
July 20th, 2006
Research Overview
Hyunwook Kim, Research Assistant
William G. Buttlar, Associate Professor
Imad Al-Qadi, Professor
Outline
• Project Overview
• FE Fracture Model of Reflective Cracking
• Evaluation of Grooved Asphalt
• Conclusion and Discussion
• Future Plan
Project Overview
• Project initiated in January, 2006.
• Goals:– Model reflective cracking of HMA overlays
– Evaluate binder properties to design materials that are more resistant to cracking, including the evaluation of environmental effects that impact distress mechanisms
– Evaluate stability of grooves in HMA surface
FE Fracture Model ofReflective Cracking
Task Outline
• Explore new methods/materials to reduce maintenance and/or to delay reflective cracking at O’Hare.
• Study mechanisms of reflective cracking w/ new lab tests and models
• Evaluate/inform design methods
Mechanism of Reflective Cracking
• Can begin to occur as soon as the first winter after construction
• Can decrease the serviceability of the overlay
• Can cause the acceleration of other pavement distresses such as the weakening of subgrade and aggregate layers through water infiltration, stripping in HMA layers, and loss of subgrade support.
Key Factors to be Considered
• Overlay and interlayer properties, bonding
• Load transfer efficiency in underlying PCC
• Subgrade support
• Structural condition of the underlying slabs
• Fracture mechanisms (crack initiation and
propagation)
• Critical gear loading condition
• Other boundary conditions
FE Fracture Modeling
Reflective Crack
Subgrade
Subbase
PCC
AC Overlay
Boeing 777
3-D Field
2-D Model
• 2-D FE modeling is a reasonable approximation of the 3D geometry for the purpose of studying the fracture behavior of airport overlay systems.
Model Dimension
36 ft (10.97 m)
Boeing 777-200
2D Model Description--Loading
57 in 57 in
21.82 in
13.64 in
55in
One Boeing-777 200 aircraft:• 2 dual-tridem main gears • Gear width = 36 ft• main gear (6 wheels; 215 psi)• Gross weight = 634,500 lbs (287,800
kg)• Each gear carries 47.5% loading
= 301,387.5 lb
• Boeing777-200: larger gear width (36 ft = 432 in)• The 2nd gear is about 2 slabs away from 1st gear
57 in
55in
225 in
Gear 1
6.82 in
225 in
240 in
432 in
57 in
16.32 in
Note: Dimensions not drawn to scale
Gear 255in
1 Slab 2 Slab 3 4
2D Model Description--Loading
Geometry and Loading
Concrete Slabs
ESubbase = 40 ksi; = 0.20
k = 200 pciSubgrade
Subbase
18 in
8 in
AC Overlay 5 in EAC = 200 ksi; AC = 0.350.5 in0.2 in
EPCC = 4,000 ksiPCC = 0.15
Cross section
Loading Positions
Transverse Joint = 0.5in
Longitudinal Joint = 0.5in
240 in
225 in
Top view CL
Traffic Direction
A
B
C
Air Temperature Profile
2001 - 2002 2002 - 2003
* Weather Station * Weather Station
Temperature Profile - Coolest
A critical cooling event ~ January 30, 2004
2003 - 2004
On the AC surface2.2 °F(-16.6° C) at 4:00am
At the bottom of AC22.7 °F(- 5.2° C) at 7:00am
At the bottom of PCC31.5 °F(- 0.3° C) at 7:00am
10:00am – 7:00am (22 hours)
Lowest air temperature: 4:00am
January 30 – 31th, 2004
* EICM Analysis* Weather Station
-25
-20
-15
-10
-5
0
0 5 10 15 20 25 30 35
Temperature (°F)
De
pth
(in
ch)
10:00am 01/30
11:00am 01/30
12:00am 01/30
14:00pm 01/30
-25
-20
-15
-10
-5
0
0 5 10 15 20 25 30 35
Temperature (°F)
De
pth
(in
ch)
14:00pm 01/30
16:00pm 01/30
22:00pm 01/30
04:00am 01/31
Pavement Temperature Profiles
Warming
Cooling
AC Overlay
PCC
5”
18”
Different positions – Both gear loadings
R1
R0
R4L4
FE Model Description - 1
CZM
Crack Tip
FE Model Input
• Elastic properties– Young’s modulus (E)– Poisson’s ratio (ν)
• Viscoelastic properties– Creep compliance
• Fracture properties– Fracture energy (Gf)
– Tensile strength (St)
• The others– Layer thickness– LTE– Subgrade support– Thermal coefficient– Friction between PCC
and granular subbase– Gear loading time (e.g.,
0.1 sec = 50 mph)– Pavement temperature
profiles (EICM)
Temperature Loading Only
Temperature Loading Only
Temperature + Gear Loading (R0)
Temperature + Gear Loading (Ro)
- Cracking with Lower Fracture Properties and Heavy Loading -
Summary
• 2-D FE fracture modeling can be used to study reflective cracking mechanisms based on fracture properties.
• Typical asphalt overlay configurations at ORD will be studied this Fall, to evaluate current design and material methodologies.
• The current model suggests cracking potential at the crack tip in the bottom of the AC overlay; however the underlying PCC thickness limits predicted cracking rates.
Evaluation of Grooved Asphalt:
Literature Review
Improvement of Asphalt Grooves Evaluate/ improve stability of grooves in HMA surfaces
Understanding the mechanism of groove collapse
Develop a simple torture test to evaluate pavement groove stability and evaluate lab samples and field samples from O’Hare
Conduct pavement modeling to evaluate mechanisms of groove collapse and methods to mitigate this phenomenon
Make recommendations for improved groove performance – Geometry – Materials – Mix design
FAA HMA Groove Standards • Grooves reduce effects hydroplaning• Transverse grooves are common on runways• Standard dimensions are ¼ deep by ¼ wide at 11/2
centers (1)
Figure 1 Grooving on HMA runway: 5-year old saw-cut grooves at Volk Field Air National Guard Base in Wisconsin (2)
1. AC 150/5320-12C (1997); “Measurement, Construction, and Maintenance of Skid-resistant Airport Pavement Surfaces.”
Federal Aviation Administration.
2. Duval, J.; and Buncher, M. (2004). “Superpave for Airfields.” Presented for the 2004 FAA Worldwide Airport Technology
Transfer Conference, Atlantic City, NJ.
Performance of HMA Grooves
Allen and Quillen (3) evaluated the effects of aircraft loading and climatic conditions on grooved asphalt R/Ws.• Problems identified:
Grooves were severely damagedduring 180º turns
In the large aggregate asphaltsections, the ½ and ¾ inch aggregatestend to break loose from the groove
The paper recommends that
groovingshould be performed only in asphaltwith aggregates less than 3/8 inches.
3. Allen, C. R.; and Quillen, J. W. (1969): “Problem Areas Associated with the Construction and Operation of the Landing Research Runway at NASA Wallops Station.” Pavement Grooving and Traction Studies, NASA SP-5073, Paper No. 8.
4. McGuire, R.C.; (1969): “Report on Grooved Runway Experience at Washington National Airport.” Pavement Grooving and
Traction Studies, NASA SP-5073, Paper No. 19.
Damaged grooves by Convair 990 during 180º turns at Wallops Station (3)
McGuire(4) evaluated different groove patterns at 6 airports and The grooves were monitored for four seasons
Performance of HMA Grooves
5. Emery, S. J. (2005). “Bituminous Surfacing for Pavements on Australian Airports.” 24th Australia Airports Association Convention, Hobart
6. Emery, S. J. (2005). “Asphalt on Australian Airports.” Australia Asphalt Paving Association Pavement Industry Conference, Surfers Paradise, Queensland.
7. Mosher, L.G. (2002): “Results from studies of Highway Grooving and Texturing of State Highway by several state Highway
Departments. Pavement Grooving and Traction Studies, NASA SP-5073, Paper No. 27.
• Groove collapse was caused by slow moving, heavy aircraft and groove collapse was common at runway/taxiway crossings (5, 6)
• Mosher (7) concluded that asphalt binder is a critical parameter
Mechanism of Groove Collapse– Involves viscous flow. – Microscopic analysis of asphalt which has deformed into
the groove shows the binder still covers the aggregates suggesting a cohesion (or stiffness) rather than adhesion failure
– It was suggested that groove closure is related to a property of the binder that changes with time of loading and age
– Since most airfield pavements are designed to resist environmental effects (rutting is of secondary concern), the binder plays a critical role in rutting behavior
– Therefore binder viscosity/stiffness may be critical to groove closure
Mechanism of Groove Collapse
• Mechanism of groove edge breakage – It was suggested that groove edge breakage is caused
by horizontal stresses induced by aircraft tires.– It was reported that horizontal stresses could be up to
500 kPa – Repeated application of this level of stress on the
unsupported edge of the groove could lead edge failure– Examination of the broken edge asphalt shows that the
aggregates were still covered with binder indicating cohesion failure.
– Thus groove closure and groove edge breakage (groove collapse) are dependent on asphalt viscosity/stiffness.
Summary
• Need to visit O’Hare airfields to study groove collapse and deformation characteristics (August ?)
• Must investigate groove performance as a function of groove pattern, HMA mix design and binder grade
• Currently developing an experimental test for understanding the phenomenon of groove collapse
• Numerical modeling (DEM) will be developed and compared with the laboratory testing and field performance.
Thank You !!
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