Benefits of Modified Asphalts

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Benefits of Modified Asphalts

• John Duval, P.E.
• Oregon Asphalt Conference
• March 8, 2006

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Modified Binder Use to Increase

• It is likely that modified binders represent as
  much as 15 of the total annual tonnage of
  asphalt binder used in the United States this
  percentage is expected to increase in the coming
  decade
• NCHRP Report 9-10 (2001)

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AI Member Companies
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Overview

• Commonly used asphalt modifiers?
• What is the benefit of asphalt modifiers?
• PG PLUS Specifications
• The Path to PG PLUS Specifications
• How did other states arrive there?
• FinallyA way to Quantify the Benefit of Modified
  Asphalt Binders
• Summary/Recommendations

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Types of Asphalt Modifiers
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Extenders

• Sulfur
• Lignin

Sulfur Extended Asphalt?
Extenders are typically cheaper than asphalt and
replace asphalt binder
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Fibers

• Natural
• Rock Wool
• Cellulose
• Man-Made
• Polypropylene
• Polyester
• Fiberglass

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Polymers

• Elastomers
• Plastomers
• Combinations

• poly ? mer
• many parts

Image courtesy Infrapave
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Elastomers

• Natural Latex Rubber
• Synthetic Latex
• Styrene-butadiene (SB)
• Block Copolymer
• Styrene-butadiene-styrene (SBS)
• Reclaimed Rubber

Image courtesy Injectec.com
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Plastomers
PVC Pipe

• Polyethylene
• Polypropylene
• Ethyl-vinyl-acetate (EVA)
• Polyvinyl-chloride (PVC)

Image courtesy slpipe.com
EVA is a plastic that is used to create stiffer
insoles for your shoes
Image courtesy cyclingfitness.com
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Others

• Oxidants / Antioxidants
• Hydrocarbons
• Asphalt Blending (from different Crude Oils)
• Lake Asphalt
• Recycling/Rejuvenating Oils
• Antistrip Agents
• Lime
• Liquid (Amines)

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Polyphoshoric Acid (PPA)

• PPA is a liquid mineral polymer
• PPA be used alone or in conjunction with polymers
• PPA can improve high temperature stiffness
• PPA modification does not oxidize the asphalt
  binder
• Care should be taken to avoid neutralization of
  amine-based liquid antistrip chemicals

IS-220
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Why are Asphalt Modifiers being used?
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Plastic Deformation (Rutting)
SR2 near Wenatchee, WA
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Low Temperature Cracking
SR2 near Davenport, WA
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Performance Graded Asphalt

• Grading System Based on Climate

PG 70-22
Performance Grade
Average 7-day max pavement design temp
Min pavement design temp
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PG Binder Grades
PG 64-22 Probably Unmodified
PG 70-28 Probably Modified
TEMPERATURE ºC
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PG PLUS Specifications
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Agency Perspective

• Many Highway Agencies have developed PG PLUS
  specifications
• The intent is to ensure that the preferred
  modifier is used

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Industry Perspective

• Encourage Agencies to use performance
  specifications
• This allows suppliers to innovate and compete in
  the marketplace to earn a profit

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States with PG PLUS Specs
ER-Elastic Recovery FD-Force Ductility TT-Toughnes
s Tenacity PA-Phase Angle
Source Asphalt Institute ER 215 (2005)
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Research on Modified Binders

• NCHRP 9-10 (Prof. H. Bahia)
• FHWA Accelerated Loading Facility
• European Studies
• Industry Research
• State DOT research
• Nevada DOT I-80 Study (Prof. P. Sebaaly)
• Nevada DOT Construction Variability Study (Prof.
  P. Sebaaly)

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Nevada DOT (2003)
SourceSebaaly et al. RR 1393-5, (2003)
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The Path to PG PLUS(Its shorter than you might
think)
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Courtesy of Tennessee DOT
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Courtesy of Tennessee DOT
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Mississippi DOT
PG 76-22 or PG82-22 and shall be made by adding
a polymer modifier to a PG 67-22 or lower grade
asphalt. Polymer shall be SBS, SBR, or equal
approved by Engineer. Mississippi DOT Std Spec
Section 702.02 We make the suppliers start with
the PG 67-22, then modify that to get the PG
76-22. Jimmy Brumfield, Mississippi DOT Polymer
adds between 3 to 5 per ton of mix, which
increases the cost of mix to about 38 to 42 per
ton. Working with Polymers, Better Roads, 2004
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FinallyA way toQuantify the Benefitof Modified
Asphalt Binders
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Quantifying the Effects of PMA for Reducing
Pavement Distress

• This study (published in Feb 2005) uses national
  field data to determine enhanced service life of
  pavements containing polymer modified binders
  versus conventional binders. The data is from a
  variety of climates and traffic volumes within
  North America.

IS 215
ER 215
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Study Objectives

• Quantify the effect of using PMA as compared to
  conventional-unmodified HMA mixtures in terms of
• Increasing pavement life
• Reducing occurrence of distresses
• Identify conditions that maximize effect of PMA
  to increase HMA pavement overlay life.

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Field Test Sections

• FHWAs LTPP
• SPS-1 SPS-5 SPS-6 SPS-9
• GPS-1 GPS-2 GPS-6 GPS-7
• M.T.Ontario Modifier Study
• Accelerated Pavement Tests
• FHWA ALF
• NCAT Test Track
• California HVS Studies
• Ohio Test Road
• Corp of Engineers

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Locations of Test Sections- PMA and Unmodified
Companion
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Companion SectionsMontana
HMA Overlay (w/ PMA)
HMA Overlay
HMA
HMA
Soil-Aggregate Base
Soil-Aggregrate Base
Soil-Aggregate Base
Soil-Aggregate Base
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Companion SectionsMontana
HMA Overlay (w/PMA)
HMA Overlay
HMA
Soil-Aggregrate Base
HMA
Soil-Aggregate Base
Soil-Aggregate Base
Soil-Aggregate Base
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Direct Comparisons Rutting
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Distress Comparisons Transverse Cracking
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Distress Comparisons Fatigue Cracking
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Mechanistic-Empirical Analysis

• Use M-E distress prediction models from new 200x
  Pavement Design Guide for
• Fatigue Cracking
• Rutting
• Damage indices computed using factorial cell
  specific calibration
• Compare damage indices to actual distress
  measurements for both PMA and unmodified sections

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Summary of Expected Increase in Service Life,
Years, Based on M-E Damage Based Analysis
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Summary of Expected Increase in Service Life,
Years, Based on M-E Damage Based Analysis
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Generic LCCA Strategy/ Timeline and Revised PMA
Timelines Based on Results
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Life Cycle Cost Analysis
Initial Construction
Net Present Value
Rehabilitation
Maintenance
0
Salvage
Time
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(No Transcript)
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EXAMPLE 1, Unmodified All Layers
Yr. Activity Cost, NPW, 0 10
Base 668K 668K 2.5 Binder 2 Wearing 10 2
mill/fill 87K 58K 1 patching (not on
shoulders) 18 2 mill 285K 141K 3
patching scratch 2.5 Binder 2
Wearing (incl. shoulders) 28 Same as
yr.10 87K 29K 34 Same as yr.18
285K 75K Annual Maint (1.8K/yr) 73K 33K Tot
al NPW 1,005K

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EXAMPLE 2, Modified Wearing Course (top 2,
including shoulders)
Yr. Activity Cost, NPW, 0 10
Base 682K 682K 2.5 Binder 2
Wearing 18 2 mill 298K 147K 3
patching scratch 2.5 Binder 2
Wearing (incl. shoulders) 34 Same as yr.18
298K 79K Annual Maint (1.8K/yr) 73K 33K Tot
al NPW 941K

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EXAMPLE 3, Perpetual Pavement Modified Wearing
Course (top 2) and Bottom 4 of Base (incl.
shoulders)
Yr. Activity Cost, NPW, 0 10
Base 709K 709K 2.5 Binder 2
Wearing 18 2 mill/fill 141K 70K (incl.
shoulders) 34 Same as yr.18 141K 37K Annual M
aint (1.8K/yr) 73K 33K Total NPW 849K

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Quantifying the Benefit
Pavement Type Initial Cost Change
NPV Savings 1) Unmodified 669K
- 1,005K - (resurface yr.10
and 28, structural overlay yr.18 and 34) 2)
Modified Wearing 682K 2.0 941K
6.5 (structural overlay yr.18 and 34) 3)
Modified Wearing Base 709K 6.0 849K
15.5 (Perpetual Pavement resurface yr. 18
and 34)
Cost to use PMA equates to approx. 1 of initial
cost per inch modified
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Summary/Recommendations

• Modifiers can improve high and low temperature
  properties of asphalt binders
• We are still waiting for a PG PLUS test that is
  blind to the modifier
• AI ER 215 provides a sound method to measure the
  benefit of modified asphalts in order to make
  decisions based on lowest lifecycle cost.

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Summary/Recommendations

• ODOT should study the cost and benefit of
  modified asphalt mixes in Oregon
• Laboratory assessment of rut susceptibility using
  Asphalt Pavement Analyzer
• Field studies of full-scale modified asphalt
  sections subjected to actual traffic

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Thank you