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)

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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?

• 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”

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Elastomers

• Natural Latex Rubber• Synthetic Latex

– Styrene-butadiene (SB)

• Block Copolymer– Styrene-butadiene-

styrene (SBS)

• Reclaimed Rubber

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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

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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)

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The Path to PG PLUS(Its shorter than you might think)

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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

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

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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.

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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, %

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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

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