benefits of modified asphalts john duval, p.e. oregon asphalt conference march 8, 2006
TRANSCRIPT
Benefits of Modified Asphalts
John Duval, P.E.
Oregon Asphalt Conference
March 8, 2006
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)
AI M
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ies
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?
• Finally—A way to Quantify the Benefit of Modified Asphalt Binders
• Summary/Recommendations
Types of Asphalt Modifiers
Extenders
• Sulfur• Lignin
Extenders are typically cheaper than asphalt and replace asphalt binder
Sulfur Extended Asphalt?
Fibers
• Natural– Rock Wool– Cellulose
• Man-Made– Polypropylene– Polyester– Fiberglass Fibers can be used to increase
asphalt stiffness, but are primarily used to control
“drain-down” in open-graded mixtures
Polymers
• Elastomers• Plastomers• Combinations
poly mer
“many parts”
Imag
e co
urte
sy In
frap
ave
Elastomers
• Natural Latex Rubber• Synthetic Latex
– Styrene-butadiene (SB)
• Block Copolymer– Styrene-butadiene-
styrene (SBS)
• Reclaimed Rubber
Imag
e co
urte
sy In
ject
ec.c
om
Plastomers
• Polyethylene• Polypropylene• Ethyl-vinyl-acetate
(EVA)• Polyvinyl-chloride
(PVC)
EVA is a plastic that is used to create stiffer
insoles for your shoes
PVC Pipe
Ima
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ourt
esy
slp
ipe.
com
Image courtesy cyclingfitness.com
Others
• Oxidants / Antioxidants
• Hydrocarbons– Asphalt Blending (from
different Crude Oils)– Lake Asphalt– Recycling/Rejuvenating Oils
• Antistrip Agents– Lime– Liquid (Amines)
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
Why are Asphalt Modifiers being used?
Plastic Deformation (Rutting)
SR2 near Wenatchee, WA
Low Temperature Cracking
SR2 near Davenport, WA
Performance Graded Asphalt
Grading System Based on Climate
PG 70-22
PerformanceGrade
Average 7-daymax pavementdesign temp
Min pavementdesign temp
PG Binder Grades
00 1010 2020 3030 4040 5050 6060-10-10-20-20-30-30-40-40 7070 8080
PG 64-22
PG 70-28
The Rule of 90
PG 64-22 Probably Unmodified
PG 70-28 Probably Modified
This is the
benefit of the
modifier
TEMPERATURE ºCTEMPERATURE ºC
PG PLUS Specifications
Many Highway Agencies have developed PG PLUS specifications
The intent is to ensure that the preferred modifier is used
Agency Perspective
Industry Perspective
Encourage Agencies to use performance specifications
This allows suppliers to innovate and compete in the marketplace
to earn a profit
ER-Elastic RecoveryFD-Force DuctilityTT-Toughness & TenacityPA-Phase Angle
States with PG PLUS Specs
PG + modifierPG
ER
SB/SBS Required
ER & PA
PA
PA
ER
SB/SBS Required
ER & TT
ER
ER & FD
FD & ER
ER
Ductility
Ductility, TT & ER
ER & PA
ER
ER
ER
ER
FD
ER
ER
TT & DT
PA ER & TT
ER
Source: Asphalt Institute ER 215 (2005)
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)
Nevada DOT (2003)
Sou
rce:
Seb
aaly
et
al.
RR
139
3-5,
(20
03)
The Path to PG PLUS(Its shorter than you might think)
Cou
rtes
y of
Ten
ness
ee D
OT
Cou
rtes
y of
Ten
ness
ee D
OT
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
Finally—A way toQuantify the Benefit
of Modified Asphalt Binders
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.
ER 215
IS 215
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.
Field Test Sections
• FHWA’s 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
Locations of Test Sections- PMA and Unmodified Companion
Not all sites located on map.
Companion Sections—Montana
HMA Overlay (w/ PMA)
HMA
Soil-Aggregrate Base
Soil-Aggregate Base
HMA Overlay
HMA
Soil-Aggregate Base
Soil-Aggregate Base
Companion Sections—Montana
HMA Overlay (w/PMA)
HMA
Soil-Aggregrate Base
Soil-Aggregate Base
HMA Overlay
HMA
Soil-Aggregate Base
Soil-Aggregate Base
Direct Comparisons – Rutting
00.20.40.60.8
11.21.41.61.8
2
0 0.2 0.4 0.6 0.8 1 1.2
Rut Depths on PMA Sections, inches
Ru
t D
epth
s o
n C
om
pan
ion
S
ecti
on
s, in
ches
Distress Comparisons – Transverse Cracking
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
450.0
500.0
0.0 100.0 200.0 300.0 400.0 500.0
Transverse Cracking - PMA Sections, ft.
Tra
nsv
erse
Cra
cki
ng
- C
om
pan
ion
S
ect
ion
s, f
t.
Distress Comparisons – Fatigue Cracking
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
0.00 20.00 40.00 60.00 80.00
Fatigue Cracking - PMA Sections, %
Fa
tig
ue
Cra
cki
ng
- C
om
pan
ion
S
ect
ion
s, %
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
Summary of Expected Increase in Service Life, Years, Based on M-E Damage Based Analysis
Site Factor Condition Description Added Life
Foundation
Non-expansive, coarse soils 5-10
Expansive and plastic soils (PI>35) 2-5
Frost Susceptible in cold climate 2-5
Water Table & Drainage
Deep 5-10
Shallow; adequate 5-8
Shallow; inadequate 0-2
Existing Pavement Condition
HMAGood 5-10
Poor-extensive cracking 1-3
PCCGood 3-6
Poor-faulting & cracking 0-2
Summary of Expected Increase in Service Life, Years, Based on M-E Damage Based Analysis
Site Factor Condition Description Added Life
Climate; Temp. Fluctuations
Hot Hot Extremes 5-10
Mild 2-5
Cold Cold Extremes 3-6
Traffic, Truck Volumes
Low
Intersections 5-10
Thoroughfares 3-6
Heavy Loads 5-10
Moderate 5-10
High 5-10
Generic LCCA Strategy/ Timeline and Revised PMA Timelines Based on Results
PMA Surface 2-4 in.
RM RM RM
HMA OL
HMA OL
Years 5 10 15 20 25 30 35 40
Conv. Struct.
RM RM RM RM
Mill-Fill
HMA OL
Mill-Fill
HMA OL
PMA Full Depth
RM RM RM
Mill-Fill
Mill-Fill
Life Cycle Cost Analysis
Time
NetPresentValue
Initial Construction
Rehabilitation
Maintenance
Salvage0
Present Worth Analysis (ln/mi) for -- LCC Unmodified)14.5-inch section
Interest
4
Year Construction Item and/or Material Quantity Unit Cost/Unit Current Price PW
0 10" HMA Base ( 3 - 10 EAL) 14080 sy 19.10$ $268,928 $268,9280 2.5" HMA Binder (3 - 10 EAL) 14080 sy 4.78$ $67,302 $67,3020 2" HMA Wearing (3 - 10 EAL) 14080 sy 3.94$ $55,475 $55,4750 10" HMA Base (0.3 - 3 EAL) 8212 sy 19.10$ $156,849 $156,8490 2.5" HMA Binder (0.3 - 3 EAL) 8212 sy 4.78$ $39,253 $39,2530 2" HMA Wearing (0.3 - 3 EAL) 8212 sy 3.94$ $32,355 $32,3550 Maint. & Protection of Traffic @2.3% 1 ls $14,264 $14,264 $14,2640 Mobilization @5.5% 1 ls $34,109 $34,109 $34,109
10 Deep Patch 1% (mainline) 141 sy 36.00$ $5,076 $3,42910 Mill 2" (mainline) 14080 sy 1.40$ $19,712 $13,31710 2" hma overlay (mainline) 14080 sy 3.94$ $55,475 $37,47710 Maint. & Protection of Traffic @2.3% 1 ls 1,846.05$ $1,846 $1,24710 Mobilization @5.5% 1 ls 4,414.48$ $4,414 $2,982
$0 $018 Mill 2" 22292 sy 1.40$ $31,209 $15,40618 Deep Patch 3% (mainline) 422 sy 36.00$ $15,192 $7,49918 #60 scratch course 422 ton 36.00$ $15,192 $7,49918 2.5" hma overlay (binder) 14080 sy 4.78$ $67,302 $33,22218 2" hma overlay (wearing) 14080 sy 3.94$ $55,475 $27,38418 #60 scratch course 246 ton 36.00$ $8,856 $4,37218 2.5" hma overlay (binder) 8212 sy 4.78$ $39,253 $19,37718 2" hma overlay (wearing) 8212 sy 3.94$ $32,355 $15,97118 Maint. & Protection of Traffic @2.3% 1 ls $6,091 $6,091 $3,00718 Mobilization @5.5% 1 ls $14,566 $14,566 $7,190
$0 $028 Same Scenario as Year 10 1 ls $86,524 $86,524 $28,854
$0 $034 SameScenario as Year 18 1 ls $285,492 $285,492 $75,242
$0 $020 Total Annual Maintenance ($1825/yr) 40 yr 1,825.00$ $73,000 $33,316
$0 $0 Total Present Worth $1,005,328
EXAMPLE 1, Unmodified All Layers
Yr. Activity Cost,$ NPW,$
0 10” Base 668K 668K2.5” Binder2” Wearing
10 2” mill/fill 87K 58K1% patching(not on shoulders)
18 2” mill 285K 141K3% patchingscratch2.5” Binder2” Wearing(incl. shoulders)
28 Same as yr.10 87K 29K
34 Same as yr.18 285K 75K
Annual Maint ($1.8K/yr) 73K 33K
Total NPW:1,005K
Present Worth Analysis (ln/mi) for --LCC Modified Surface)14.5-inch section
Interest
4
Year Construction Item and/or Material Quantity Unit Cost/Unit Current Price PW
0 10" HMA Base ( 3 - 10 EAL) 14080 sy 19.10$ $268,928 $268,9280 2.5" HMA Binder (3 - 10 EAL) 14080 sy 4.78$ $67,302 $67,3020 2" HMA Wearing (3 - 10 EAL) 14080 sy 4.48$ $63,078 $63,0780 10" HMA Base (0.3 - 3 EAL) 8212 sy 19.10$ $156,849 $156,8490 2.5" HMA Binder (0.3 - 3 EAL) 8212 sy 4.78$ $39,253 $39,2530 2" HMA Wearing (0.3 - 3 EAL) 8212 sy 4.48$ $36,790 $36,7900 Maint. & Protection of Traffic @2.3% 1 ls $14,541 $14,541 $14,5410 Mobilization @5.5% 1 ls $34,771 $34,771 $34,771
$0 $018 Mill 2" 22292 sy 1.40$ $31,209 $15,40618 Deep Patch 3% (mainline) 422 sy 36.00$ $15,192 $7,49918 #60 scratch course 422 ton 36.00$ $15,192 $7,49918 2.5" hma overlay (binder) 14080 sy 4.78$ $67,302 $33,22218 2" hma overlay (wearing) 14080 sy 4.48$ $63,078 $31,13718 #60 scratch course 246 ton 36.00$ $8,856 $4,37218 2.5" hma overlay (binder) 8212 sy 4.78$ $39,253 $19,37718 2" hma overlay (wearing) 8212 sy 4.48$ $36,790 $18,16018 Maint. & Protection of Traffic @2.3% 1 ls $6,368 $6,368 $3,14318 Mobilization @5.5% 1 ls $15,228 $15,228 $7,517
$0 $034 SameScenario as Year 18 1 ls $298,469 $298,469 $78,662
$0 $020 Total Annual Maintenance ($1825/yr) 40 yr 1,825.00$ $73,000 $33,316
$0 $0 Total Present Worth $940,824
EXAMPLE 2, Modified Wearing Course (top 2”, including shoulders)
Yr. Activity Cost,$ NPW,$
0 10” Base 682K 682K2.5” Binder2” Wearing
18 2” mill 298K 147K3% patchingscratch2.5” Binder2” Wearing(incl. shoulders)
34 Same as yr.18 298K 79K
Annual Maint ($1.8K/yr) 73K 33K
Total NPW: 941K
Present Worth Analysis (ln/mi) for --LCC Modified Surface & 4"Base)14.5-inch section
Interest
4
Year Construction Item and/or Material Quantity Unit Cost/Unit Current Price PW
0 4" HMA Modified Base ( 3 - 10 EAL) 14080 sy 8.76$ $123,341 $123,3410 6" HMA Base ( 3 - 10 EAL) 14080 sy 11.46$ $161,357 $161,3570 2.5" HMA Binder (3 - 10 EAL) 14080 sy 4.78$ $67,302 $67,3020 2" HMA Wearing (3 - 10 EAL) 14080 sy 4.48$ $63,078 $63,0780 4" HMA Base (0.3 - 3 EAL) 8212 sy 8.76$ $71,937 $71,9370 6" HMA Base ( 3 - 10 EAL) 8212 sy 11.46$ $94,110 $94,1100 2.5" HMA Binder (0.3 - 3 EAL) 8212 sy 4.78$ $39,253 $39,2530 2" HMA Wearing (0.3 - 3 EAL) 8212 sy 4.48$ $36,790 $36,7900 Maint. & Protection of Traffic @2.3% 1 ls $15,115 $15,115 $15,1150 Mobilization @5.5% 1 ls $36,144 $36,144 $36,144
$0 $018 Mill 2" 22292 sy 1.40$ $31,209 $15,40618 2" hma overlay (wearing) 14080 sy 4.48$ $63,078 $31,13718 2" hma overlay (wearing) 8212 sy 4.48$ $36,790 $18,16018 Maint. & Protection of Traffic @2.3% 1 ls $3,015 $3,015 $1,48818 Mobilization @5.5% 1 ls $7,209 $7,209 $3,559
$0 $034 SameScenario as Year 18 1 ls $141,301 $141,301 $37,240
$0 $020 Total Annual Maintenance ($1825/yr) 40 yr 1,825.00$ $73,000 $33,316
$0 $0 Total Present Worth $848,734
EXAMPLE 3, Perpetual Pavement: Modified Wearing Course (top 2”) and Bottom 4” of Base (incl. shoulders)
Yr. Activity Cost,$ NPW,$
0 10” Base 709K 709K2.5” Binder2” Wearing
18 2” mill/fill 141K 70K(incl. shoulders)
34 Same as yr.18 141K 37K
Annual Maint ($1.8K/yr) 73K 33K
Total NPW: 849K
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
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.
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
Thank you