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OHare 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
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Outline

• Project Overview
• FE Fracture Model of Reflective Cracking
• Evaluation of Grooved Asphalt
• Conclusion and Discussion
• Future Plan

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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

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FE Fracture Model ofReflective Cracking
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Task Outline

• Explore new methods/materials to reduce
  maintenance and/or to delay reflective cracking
  at OHare.
• Study mechanisms of reflective cracking w/ new
  lab tests and models
• Evaluate/inform design methods

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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.

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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

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FE Fracture Modeling
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Model Dimension

• 2-D FE modeling is a reasonable approximation of
  the 3D geometry for the purpose of studying the
  fracture behavior of airport overlay systems.

3-D Field
2-D Model
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2D Model Description--Loading
36 ft (10.97 m)

• 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

Boeing 777-200
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2D Model Description--Loading

• Boeing777-200 larger gear width (36 ft 432 in)
• The 2nd gear is about 2 slabs away from 1st gear

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Slab 3
1
Slab 2
Gear 1
Gear 2
55in
55in
57 in
57 in
240 in
432 in
16.32 in
6.82 in
225 in
225 in
Note Dimensions not drawn to scale
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Geometry and Loading
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Air Temperature Profile
Weather Station
Weather Station
2001 - 2002
2002 - 2003
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Temperature Profile - Coolest
Weather Station
EICM Analysis
At the bottom of PCC 31.5 F(- 0.3 C) at 700am
At the bottom of AC 22.7 F(- 5.2 C) at 700am
On the AC surface 2.2 F(-16.6 C) at 400am
2003 - 2004
1000am 700am (22 hours) Lowest air
temperature 400am January 30 31th, 2004
A critical cooling event January 30, 2004
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Pavement Temperature Profiles
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Warming
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Cooling
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FE Model Description - 1
Different positions Both gear loadings
R4
L4
R1
R0
CZM
Crack Tip
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FE Model Input

• Elastic properties
• Youngs modulus (E)
• Poissons ratio (?)
• 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)

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Temperature Loading Only
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Temperature Loading Only
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Temperature Gear Loading (R0)
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Temperature Gear Loading (Ro)- Cracking with
Lower Fracture Properties and Heavy Loading -
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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.

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Evaluation of Grooved AsphaltLiterature
Review
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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 OHare
• 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

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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.

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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 damaged
• during 180º turns
• In the large aggregate asphalt
• sections, the ½ and ¾ inch aggregates
• tend to break loose from the groove
• The paper recommends that grooving
• should be performed only in asphalt
• with aggregates less than 3/8 inches.

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

• 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.

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Performance of HMA Grooves

• 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

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.
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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

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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.

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Summary

• Need to visit OHare 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.

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Thank You !!