Effect of Deicing and Anti-Icing Chemicals on HMA Airfield Runways

1
Effect of Deicing and Anti-Icing Chemicals on HMA
Airfield Runways

• D. Christensen, J. Mallela, D. Hein, E. Kalberer,
  M. Farrar, and R. Bonaquist
• FAA Worldwide ATT Conference, April 2010

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Introduction

• Some evidence that deicing/anti-icing chemicals
  (DIAICs) can cause or contribute to premature
  failure of HMA runways
• Purpose of this presentation is to summarize
  recent research on effect of DIAICs on HMA
  airfield runways

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Background Deicing vs. Anti-icing

• Deicing is the removal of existing ice and/or
  snow from the runway
• Anti-icing is application of chemicals to prevent
  buildup of ice and/or snow on the runway
• Anti-icing is also performed on airplanes in
  specific locations, using similar chemicals

4
Background Chemicals

• For aircraft deicing, ethylene and propylene
  glycol most commonly used
• Potassium acetate most commonly used airfield
  pavement DIAIC
• Other chemicals used include sodium acetate,
  potassium formate and sodium formate
• Recent shift away from glycols and urea

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Background Problems

• In the 1990s airfields in Norway and Sweden
  switched from urea to potassium acetate and
  potassium formate
• Problems later observed in HMA runways
  softening, stripping, degradation, disintegration

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Summary of Previous Research Scandinavia, Canada

• High temperatures probably needed to cause
  DIAIC-related damage
• Chemical mechanism not clear DIAICs might attack
  asphalt-aggregate bond, and/or soften asphalt
  binder
• Damage tends to be more severe for HMA with
  softer binders, higher air voids

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Approach in AAPTP 5-3

• Develop laboratory test and evaluate
  DIAIC-related damage (if any) in the laboratory
• Perform airfield site visits, evaluate possible
  DIAIC-related damage, take specimens for testing
  in laboratory
• Develop recommendations

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Lab Testing Aggregates

• Virginia diabase, 9.5-mm
• Virginia Limestone, 9.5-mm
• Mississippi chert/gravel, 12.5-mm
• Virginia siliceous gravel, 12.5-mm
• Pennsylvania greywacke sandstone, 9.5-mm

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Lab Testing Binders

• PG 58-28
• Two PG 64-22s
• One PG 76-22, polymer modified

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Lab Testing DIAICs

• Propylene glycol
• Sodium formate
• Sodium acetate
• Potassium acetate
• All as 2 solutions in water

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Immersion/Tension (IT) Test

• Similar to AASHTO T 283
• Gyratory specimens/cores
• No vacuum saturation
• 4 days in 2 DIAIC solution at 60 C
• Control 4 days water at 60 C
• Tensile strength ratio

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Four Experiments with IT Test

• Aggregate effects
• Five aggregates
• Single PG 64-22 binder
• Binder effects
• Three aggregates
• Four different binders
• Air Voids and hydrated lime effects

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Aggregate Effects Experiment
The PA sandstone and MS chert/gravel are highly
AS reactive
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Binder Effects Experiment
This confirmed that softer binders are more
susceptible to DIAIC-related damage.
15
Air Voids/Hydrated Lime Expt. Virginia Gravel/PG
64-22
There is possibly some slight DIAIC damage at 7
air voids
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Air Voids/Hydrated Lime Effects Mississippi
Chert/PG 64-22
Lower air voids reduce DIAIC-related damage
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Air Voids/Hydrated Lime Expt. Mississippi
Chert/PG 58-28
In this case, HL also seems to reduce damage
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Other Laboratory Testing Surface Tension and
Density

• As found by other researchers, DIAICs reduce the
  surface tension of water
• DIAICs can also increase the density of water
• Decreased surface tension and increased density
  could aggravate moisture damage

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Site Visits

• Four airfields Boston Logan Colorado Springs
  Boise, Idaho and Friedman in Hailey, Idaho
• Inspection of HMA damage
• Photographs
• Cores
• Laboratory tests on cores

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Boston Logan
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Friedman Airport
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IT Test on Field Cores Water and2 Potassium
Acetate Solution
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Conclusions

• The IT test successfully demonstrated
  DIAIC-related damage in the laboratory for one
  aggregate (Mississippi chert)
• Significant DIAIC-related damage was not observed
  in mixes made using four other aggregates and in
  testing of field cores using the IT test

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Conclusions

• It appears that DIAIC-related damage is not a
  widespread problem in North America
• DIAIC-related damage, when it does occur, appears
  to be an acceleration of moisture damage, and can
  be treated in the same wayadditives, careful
  compaction to low/normal air voids

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Conclusions

• The IT test appears promising, but lack of a
  large number of susceptible mixes made complete
  evaluation problematic
• Additional research on the IT test would be
  useful, to confirm its effectiveness in
  identifying mixes susceptible to DIAIC-related
  damage

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Acknowledgments

• Support of the AAPTP program
• Monte Symons
• Co-authors at ARA and WRI
• Laboratory personnel