national research in binder technology

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER

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National Research in Binder Technology

Rocky Mountain Asphalt Conference February 24, 2011

Denver, CO

Jack Youtcheff


Outline

• Research Topics• Asphalt compatibility• Fatigue Testing• Asphalt Aging and Embrittlement

• 4.75 mm Overlay

• Summary and Future Direction


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Asphalt Compatibility - Objectives

• Address use of RAP, RAS, bio-asphalts, …– Understand the chemical composition of these

materials and how they inter-relate• Calculate asphalt and asphalt component solubility

parameters• Describe phase behavior of asphalts, components, and

additives


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ESI EVA

Photomicrographs of ESI and EVA


7

0

3.00

6.00

9.00

12.00

AAD AAG AAK AAM

Calculated Solubility Parameters for Asphalt Fractions So

lubi

lity

Para

met

er

Parent Asphalt

δ Strong Acidsδ Neutrals


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ALF Fatigue Experiment

Laboratory Scale Tests

BinderRheology

Full-ScaleALF

Performance

As-BuiltAs-Designed


7 Asphalt Binders

CR-AZ----70-22

1

PG70-22Control

2

AirBlown

3

SBSLG

4

CR-TB

5

TP

6

PG70-22+Fibers

7

PG70-22

8

SBS64-40

9

AirBlown

10

SBSLG

11

TP

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Fatigue Cracking Data for 100 mm HMA Pavements

Lane 2

Control

100K

Lane 3

Air Blown

100K

Lane 4

SBS LG

300K

Lane 5

CR-TB

100K

Lane 6

TP

200K

Lane 1

CR-AZ

300K

Lane 7

Fiber

300K


Binder Parameters for Fatigue Cracking


Fatigue – Critical Tip Opening Displacement

W = 30 mm

40 mm

CTOD is a measure of strain tolerance in the presence of a crack


Crack Tip Opening Displacements

L2 Control L3 Airblown L4 SBS L5 CRTB L6 RET0.0

30.0

60.0

90.0

Laboratory Aged Binder

13.7 10.8

66.0

14.826.1

Strain Rate = 50 mm/min T = 25oC


• PG specs control the way asphalt binders are bought and sold

• Identified more discriminating asphalt binder test for fatigue cracking


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ALF Embrittlement Study

Laboratory Scale Tests

BinderRheology

Full-ScaleALF

Performance

As-BuiltAs-Designed

Chemistry With accelerated aging


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Embrittlement Issues

• How to identify and characterize asphalt embrittlement

• How to determine/predict impact of aging on asphalt and asphalt components and their fatigue performance


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Ongoing: Accelerated Aging


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Top Down and Bottom Up Cracking in Terminal Blended CR Aged Test Section


Change in Fatigue Performance Ranking

UnagedUnaged AgedAgedBest

1 CR-AZ Fiber Best

1 2 Fiber Terpolyme

r2

3 SBS-LG SBS-LG 3

4 Terpolymer

CR-AZ 4

5 CR-TB CR-TB 5

6 Control Control 6

7 Worst

Air Blown Air Blown 7 Worst


CTOD decrease during accelerated aging

Strain Rate = 50 mm/min T = 25oC

Western Research Institute Activities

• Improve the Global Aging System (GAS) Model

• FHWA ALF Original Binder and Aged + Unaged Cores have been sent to WRI

Analytical Methods Being Evaluated• Fourier Transform Infrared Spectroscopy (FTIR)

– Solution and ATR

• Differential Scanning Calorimetry (DSC)• Glass Transition Profiles

• Nuclear Magnetic Resonance Spectroscopy• Aromaticities and Structural Features

• On-Column Precipitation and Re-Dissolution• Asphaltene Determinator• Waxphaltene Determinator

• Dynamic Shear Rheometry• Master Curve

• Linear Amplitude Sweep Test (LAST)

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ALF Core Slices for Phase 1

Ambient Aged Core Accelerated Aged Core

FTIR ATR Absorbance for Functional Groups

All of the functional groups of interest increase with aging

DSC Analyses Results

Glass transition width increases with aging

Asphaltene Determinator Separation

STEP GRADIENT TIMES Solvents at 2 mL/minHeptane: 0 minCyclohexane: 15 minToluene: 25 min CH2Cl2:MeOH: 35 min

•10 uL 20% Solution (2 mg) •250 x 7 mm column, 40-60 mesh PTF•ELS and 500 / 700 nm Absorbance Detectors

Lloydminster Residuum AAAAsphaltene Subfractions


Ability of pavement preservation

• Chip Seal?• Slurry Seal?

Thin HMA Overlay– 4.75mm Superpave


44 foot test section

22 foot Inlay section


4.75mm HMA Contents

12.5mm

19mm

25mm

9.5mm

4.75mm

2.36mm

Virgin Asphalt BinderPG 76-22

Extracted BinderPG 82-22


A B

C D

A:B = Effect of Aging on Conventional HMA

B:D = Effect of “New” unaged 4.75mm on Aged Pavement

Lane 8Control 70-22


A B

C D

A:B = Effect of Aging on Conventional HMA

B:D = Effect of “Old” Aged 4.75mm on Aged Pavement

Lane 10 Air Blown


Summary – 4.75 mm Mix

• 4.75 mm mix shows promise. The unaged section remains crack free (though the aged section has cracked).

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Summary

• Presented a chemo-mechanical approach to addressing asphalt embrittlement

• Oxidation has a significant and variable effect on modified asphalts.

• New tools for characterizing asphalt binders and additives are being developed and evaluated– Asphalt Solubility Parameter Calculator

– CTOD potential binder fatigue parameter

– Chemical markers for monitoring binder aging

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Future Work

• Develop program for predicting phase behavior of asphalt components and additives.

• Explain performance of aged fiber and CR AZ sections.

• Look into potential of chemical markers as pavement preservation/maintenance tools– Timing of treatment

– Extent of treatment

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Acknowledgements

• TFHRC: Nelson Gibson, Audrey Copeland, Terry Arnold

• SES: Adrian Andrescieu• Penn State University:Paul Painter, Michael

Coleman• WRI: John Schabron, Ron Glaser, Fred Turner

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Questions ?

[email protected]

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