Asphalt Pavement Patching

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Highway Noise Issues
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Public is Demanding Quieter Pavements!
Governors Derby Breakfast, Louisville, KY
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Presentation Outline

• Quantifying Noise
• Measuring Pavement Noise
• Mitigation Methods
• Comparison of Pvmt. Surfaces
• Arizonas Quiet Pavements

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How Do We Quantify Noise?
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How Do We Quantify Noise?
The Decibel Scale
Discomfort
Conversation
Hearing Threshold
Pain Threshold
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Increasing the Decibel Level by 10 Doubles the
Sound Intensity
The Decibel Scale
Conversation
Chain Saw
Train
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75 Decibels
The individual is exposed to a combined total 78
Decibels
75 Decibels
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The Decibel Scale
A reduction of 3 dB(A) is like doubling the
distance from the noise.
67 dB(A)
50 ft
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The Decibel Scale
A reduction of 3 dB(A) is like doubling the
distance from the noise.
67 dB(A)
- 3 dB(A) 64 dB(A)
100 ft
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A 3dB(A) reduction corresponds to

• doubling the distance
• reducing traffic volume by 50
• reducing traffic speed by 25

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• FHWA - Noise Abatement Criteria
• 67 dB(A)
• this is not an absolute value or design
  standard, only a level where noise mitigation
  must be considered
• For new construction or reconstruction
• (ISO 11819-1)

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Side-Line Measurements

• Statistical By-pass Method (ISO 11819-1)

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Close-proximity (CPX) Method
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NCAT Close Proximity Noise Trailer
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Comparison of CPX versus Side-Line
MeasurementsIndianapolis - September 2003
Offset 23 dB(A)
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What Can Be Done to Mitigate Pavement Noise?

• Distance
• Obstructions
• Noise Walls
• Earth Berms
• Trees/ Shrubs
• Control at the Source with Pavement Surface

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Controlled Through Distance
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Controlled Through ObstructionsAverage 1 dBA
for each 2 ft of Wall Above Line of Sight
Wall 10 above LOS
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Noise Walls
Effective only for those in line-of-sight.
Does not reduce noise at source.
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Sound or Noise Walls
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Noise Barrier Effectiveness Must Justify Expense

• Walls
• top 10 States in 1998 spent over 1.3M per mile
• do nothing to eliminate the noise at the source
• Earth Berms
• require a lot of land if very high
• Vegetation
• takes a long time to develop
• 200 thick would only achieve a 10 dB reduction

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Controlling At the Source
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Pavement / tire noise has been studied for well
over 30 years and several large databases have
been compiled in the last decade. NCHRP
Synthesis 268 is a summary of the research
findings of this extensively studied topic.
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Conclusions In general, when dense-graded
asphalt and PCC pavements are compared, the
dense-graded is quieter by 2 to 3 dB(A)
A 3dB(A) reduction corresponds to - doubling
the distance - reducing traffic volume by
50 - reducing traffic speed by 25
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Conclusions Open-graded asphalt shows the
greatest potential for noise reduction for passby
noise. Reduction when compared to dense-graded
asphalt ranged from 1 to 9 dB(A).
A 9dB(A) reduction corresponds to - a
reduction in traffic noise by almost 50!
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I-64 Noise Study in Louisville

• By Local Engineering Firm
• Readings taken before and after B/S Overlay
• A 4-6 decibel reduction between old PCC and new
  asphalt

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OGFCs Reduce Noise, Eliminate Hydroplaning,
Increase Wet Friction, and Minimize Spray
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I-74 in Ohio Driving on Dense HMA onto OGFC then
back onto Dense HMA
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Texas Highway Driving on Dense Graded Mix then
onto OGFC
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Is It Cost Effective?

• A decrease of 2 dB means a reduction of five feet
  in wall height or for a mile of pavement a
  reduction of 528,000 (Average of 20/sf)

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Summary Effect of Pavement Surface

• OGFC is the quietest surface type. (Wayson, NCHRP
  Synthesis 268)
• SMA has also proven to be a quiet surface.
  (Wisconsin DOT, 1993)
• Dense graded HMA surfaces are quieter than PCC
  pavements. (Hibbs and Larson, Report
  FHWA-SA-96-068, May 1996)

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Arizona DOT Uses ARFC to Provide Quiet Pavements

• ADOT is Spending 34M to Overlay PCCP in the
  Phoenix Metropolitan
• The ARFC is Minus 9.5mm 9-9.5 Binder
• 12.5 mm Thick When Used on Flexible Pavement
• 25 mm Thick When Used on PCCP
• ADOT Uses Pavement Type (ARFC) as a Noise
  Mitigation Strategy (4 dBA)

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(No Transcript)
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Recorded Noise Levels from CPX
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Recorded Noise Levels from CPX
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Summary

• Highway noise very important to public
• Small changes in dB(A) level very noticeable
• reduction of 3dB(A) like doubling distance or
  halving traffic
• Sound barriers expensive and not very effective
• Controlling Noise at the Source is Best Option
• Dense HMA 2-4dB(A) quieter than PCC
• OGFCs 1-9dB(A) quieter than Dense HMA