Asphalt Binder Characteristics Affecting Durability Cracking

Mike Anderson

11th Arizona Pavements/Materials ConferenceNovember 19-20, 2014Tempe, AZ

Acknowledgments

• TPF-5(153) Optimal Timing of Preventive Maintenance for Addressing Environmental Aging in Hot-mix Asphalt Pavements

• MN, MD, OH, TX, WI, LRRB• Thomas J. Wood, Lead Agency Contact

• Airfield Asphalt Pavement Technology Program (AAPTP) Project 06-01

• Techniques for Prevention and Remediation of Non-Load-Related Distresses on HMA Airport Pavements

• AAPTP sponsors and research panel

• Member Companies of the Asphalt Institute

Team

• Asphalt Institute• AMEC

• Doug Hanson, Researcher• Consultant

• Gayle King, Researcher

Concept

Year

Dura

bilit

y Pa

ram

eter

Critical Range

Cracking

Non-Cracking

General Concept

• In-service aging leads to oxidation and loss of flexibility at intermediate and low temperatures

• Block-cracking• when environmental (non-load) conditions

create thermal stresses that cause strain in the asphalt mixture that exceeds the failure strain

General Concept

• In-service aging leads to oxidation and loss of flexibility at intermediate and low temperatures

• Preventing or mitigating distress• identify a property of the asphalt binder or

mixture that sufficiently correlates with its flexibility

• provide a procedure to monitor when flexibility reaches a state where corrective action is needed

Asphalt Durability

• A durable asphalt: • has physical properties necessary for desired initial

product performance, and• is resistant to change in physical properties during

long-term, in-use environmental aging

Petersen, J.C., “Chemical Composition of Asphalt as Related to Asphalt Durability-State of-the-Art”, TRR. 999, 1984

Asphalt Oxidation

Vallerga: Age-Embrittlement

Raveling Block Cracking

Witczak and Mirza: Global Aging Model (1995)

Depth

Stiffness

Asphalt Oxidation

• Physical Changes – Ductility• Block cracking severity related to ductility at 60ºF

(15ºC) – Kandhal (1977)• “Low-Temperature Ductility in Relation to Pavement

Performance”, ASTM STP 628, 1977• Loss of surface fines as ductility = 10 cm• Surface cracking when ductility = 5 cm • Serious surface cracking when ductility < 3 cm

1981 CA Durability Study

0

4

8

12

16

0 20 40 60Aging Time, Months

Kemp, et.al.Sacramento (62.9C), 7-9% Air Voids, Non-Absorptive Aggregate

Valley

LA Basin

Santa Maria

Abso

lute

Vis

cosi

ty R

atio

, (A

ged/

Orig

inal

)

Rate of Aging

0

5,000

10,000

15,000

20,000

25,000

Original RTFO PAV

AAG

AAK

AAM

G*

(Pa)

, 60C

, 10

rad/

s

Rate of Aging (Normalized – Original)

0

5,000

10,000

15,000

20,000

25,000

Original RTFO PAV

AAG

AAK

AAM

G*

(Pa)

, 60C

, 10

rad/

s

More Recent Aging Research

• Texas A&M Research (Glover, et.al.)• 2005• “Development of a New Method for Assessing

Asphalt Binder Durability with Field Evaluation”• Build on work by Kandhal suggesting block

cracking and raveling is related to low binder ductility after aging

• Identified rheological parameter related to ductility

Dynamic Shear Rheometer

• Mastercurve at 15°C• 8-mm parallel plate• 5, 15, and 25°C• Frequency sweep (0.1 to

100 rad/s)• Obtain Texas A&M

parameter at 0.005 rad/s• G′/(η′/G′)• Related to ductility at

15°C and 1 cm/min.

Ductility and DSR Parameter

(Glover et.al., 2005)

AAPTP 06-01

• Lab Study• Asphalt Binder Study

• Various aged conditions• Asphalt Mixture Study

• Various aged conditions• Field Study

• Limited validation of lab findings• Asphalt binder and mixture tests

Asphalt Binders

• Three asphalt binders representing different expected aging characteristics

• Selected based upon the relative relationships between low temperature stiffness (S) and relaxation (m-value)

• West Texas Sour (PG 64-16)• 3.1°C m-controlled

• Gulf Southeast (PG 64-22)• 1.3°C m-controlled

• Western Canadian (PG 64-28)• 0.6°C S-controlled

BBR: Gulf-Southeast (GSE)

-40

-30

-20

-10

0 20 40 60 80

Tem

pera

ture

, °C

PAV Aging Time, Hrs

Tc,S(60)

Tc,m(60)

Effect of PAV Aging Time on ∆Tc

- 6.0

0.0

6.0

12.0

0 20 40 60 80

PAV Aging Time, Hrs

WTXGSE WC

Diffe

renc

e Be

twee

n Tc

,m a

nd T

c,S

(°C)

Mastercurve Procedure

y = 0.035x -0.670

R² = 0.853

0

2

4

6

8

10

12

1E-04

Duct

ility

at 1

5°C,

1cm

/min

(cm

)

G′/(η′/G′) at 15°C, 0.005 rad/s (MPa/s)

WTX GSE WC

1E-03 1E-02 1E-01

Relationship between ∆Tc and Ductility

y = 7.77e-0.27x

R² = 0.74

0

2

4

6

8

10

12

-2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0Duct

ility

at 1

5°C,

1 c

m/m

in (c

m)

Difference Between Tc,S(60) and Tc,m(60), °C

WTX GSE WC

Relationship between G′/(η′/G′) and ∆Tc

1E-07

1E-05

1E-03

1E-01

-6.0 0.0 6.0 12.0

Difference Between Tc,m(60) and Tc,S(60), °C

WTXGSEWC

G′/(

η′/G

′), M

Pa/s

Effect of Aging

1E+03

1E+05

1E+07

1E+09

0 45 90Phase Angle, degrees

G*, P

a

Glover-Rowe Parameter

Rowe: Prepared Discussion to M. Anderson paper - AAPT 2011

Ductility15C, 1 cm/min

Glover-Rowe0.005 rad/sec

Damage Onset:Early Raveling

5 180 kPa

Damage Visible:Surface cracking

3 600 kPa

Gʹ / ( ) = G*ω((cos δ)2/ sin δ)ηʹGʹ

Rowe: Prepared Discussion to M. Anderson paper - AAPT 2011

0 hr PAV

20 hrPAV

40 hrPAV

80 hrPAV

3.5

4

4.5

5

5.5

6

6.5

7

0 10 20 30 40 50 60 70 80 90

log G*(Pa)

Phase Angle

WTXGSEWC

No BlockCracking

BlockCracking

Glover-Rowe Plot in Black Space:DSR on Aged Binders (15°C; 0.005 rad/s)

Field Validation

• Three general aviation (GA) airport projects representing four in-service pavements

• Roundup (Montana)• Upper layer representing the new pavement (Roundup

Top)• Lower layer representing the older pavement (Roundup

Bottom)• Clayton (New Mexico)

• Some low-severity longitudinal cracking and raveling • Conchas Lake (New Mexico)

• Some low-to-moderate severity raveling was identified over most of the paved area

• Pavement surface appeared slightly oxidized

Relationship between G′/(η′/G′) and ΔTc (with Field Cores)

1E-01

-6.0 -3.0 0.0 3.0 6.0 9.0 12.0

Difference Between Tc,m(60) and Tc,S(60), °C

Recovered

1E-03

1E-04

1E-05

1E-06

1E-07

1E-02G′/(η′/G′),

MPa

/s

West Texas SourGulf SoutheastWestern Canadian

Summary – AAPTP 06-01 Research

• Past research• Some relationship between ductility (conducted at

an intermediate temperature) and the durability of an asphalt pavement

• Texas A&M research validated through identification of DSR parameter, G′/(η′/G′), at 15°C and 0.005 rad/s

Summary – AAPTP 06-01 Research

• Current research• Confirmed relationship of Texas A&M DSR

parameter, G′/(η′/G′), at 15°C and 0.005 rad/s, to ductility

• Identified similar parameter through BBR testing, ΔTc, which quantifies the difference in continuous grade temperature for stiffness and relaxation properties

• Parameters appear to quantify the loss of relaxation properties as an asphalt binder ages

Summary – AAPTP 06-01 Research

• Field Studies• Four sections from three GA pavements in

Montana and New Mexico• Findings generally matched the lab studies, with

the newer pavements having values of G′/(η′/G′) and ΔTc that indicated less aging and more flexibility than the older pavements

Concept

0 2 4 6Year

G′/

(η′/

G′)

or Δ

Tc

Critical Range

Cracking

Non-Cracking

9E-04 MPa/s or 2.5°C

TPF-5(153)

• Laboratory and Field Evaluation of MnROAD and Other Test Sections

• Critical fracture parameters monitored throughout the life of the pavement

• Appropriate remedial action can be taken as the critical limit is approached

• Simple tests to be used for field monitoring purposes

• physical properties from simple tests correlated to crack predictions from DC(t) or other more sophisticated fracture tests.

MnROAD Low Volume Road

MnROAD Cell 24

24A (2008)

24B (2009)

24C (2010)

24D (2011)

24E (2012)

24F (2013)

CRS-2PCRS-2P

CRS-2PCSS-1

MnROAD Cores: Recovered Binder Testing

• Extraction/Recovery• Centrifuge extraction

using toluene/ethanol• Recovery using

Rotavapor

• 2 Cores (150-mm diameter x 12.5-mm thickness)

• ~50 grams asphalt

12.5-mm

Mid (B)Top (A)

Bottom (C)

MnROAD Cores: Binder Testing

• Each Layer• DSR Temperature-Frequency Sweep

• Three temperatures (5, 15, 25°C) using 8-mm plates

• Rheological mastercurves for modulus (G*) and phase angle (δ)

• BBR• Tc determined to the nearest 0.1°C for S(60) and m(60)• Difference in Tc (ΔTc)

MnROAD Cell 24: Effect of Layer Depth

1.0E-05 3.0E-05 5.0E-05

6.25

23.75

41.25

G′/(η′/G′) at 15°C, 0.005 rad/s, MPa/s

24A Non Travel24B Non Travel24F Non Travel

Aver

age

Laye

r Dep

th, m

m

Witczak and Mirza: Global Aging Model (1995)

Depth

Stiffness

Binder Testing

• Linear Amplitude Sweep (LAS) Test• DSR Test

• Frequency Sweep (0.1 – 30 Hz)• Continuous Oscillation at 10 Hz with Linearly-Increasing

Strain from 0.1 to 30%• Viscoelastic Continuum Damage (VECD) analysis to get

reduction in G*sin δ• Cycles to failure as a function of strain

Nf = AγB

LAS Frequency Sweep

y = 3.013E+06x5.654E-01

R² = 9.976E-01

1.00E+05

1.00E+06

1.00E+07

1.00E+08

0.1 1.0 10.0 100.0Frequency, Hz

LAS: Frequency Sweep at 16°C

C24A Non-Travel Top

Power (C24A Non-Travel Top)

LAS Strain Sweep

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

0 2 4 6 8 10 12 14 16

Effe

ctiv

e Sh

ear S

tres

s [P

a]

Effective Shear Strain [%]

Amplitude Sweep

Aging as a Function of Depth and Time:LAS Slope (B)

2.800

2.900

3.000

3.100

3.200

3.300

3.400

3.500

3.600

3.700

3.800

C24A Top C24A Mid C24A Bot

|LAS

Slo

pe (B

)|

2010

2011

Aging as a Function of Depth and Time:LAS Nf (2%)

-

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

C24A Top C24A Mid C24A Bot

LAS

Nf (

2%)

2010

2011

Effect of Aging (Conceptual)

0.0E+00

2.0E+06

4.0E+06

6.0E+06

8.0E+06

1.0E+07

1.2E+07

1.4E+07

1.6E+07

0 2 4 6 8 10Year

Nf

ESALs

MnROAD Cell 24: Aging Profile

Spec Limit

1E-05

1E-04

1E-03

1E-022008 2010 2012 2014

G′/(

η′/G

′) at

15°

C a

nd 0

.005

ra

d/s,

MPa

/s

Summary

• Effects of Aging• Increase stiffness• Decrease flexibility

• Surface Cracking

Thanks!R. Michael (Mike) Anderson, P.E.Director of Research and Laboratory ServicesAsphalt Institute2696 Research Park Dr.Lexington, KY 40511-8480859.288.4984 office859.422.1301 FAXmanderson@asphaltinstitute.orgwww.asphaltinstitute.org