Developments in IntermediateTemperature Binder Specifications Fatigue

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Developments in Intermediate-Temperature Binder
Specifications (Fatigue)

• Carl Johnson, Haifang Wen, Wilfung Martono,
• Hussain Bahia
• UW-Madison
• Dept. of Civil Environmental Engineering

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What is fatigue damage?
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Performance Grading Superpave PG HT-LT
Thermal Cracking
Fatigue Cracking
Rutting
Workability
G.sin d
Traffic speed, Traffic volume
RTFO
PAV
Testing Temperatures, C
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Superpave Binder SpecificationsAcceptable Limits
to Resist Failures
S300MPa
mgt0.3
Gsind5 MPa
Flash Point For safety
Modulus
PAV-aged
RTFO
h 3.0 pa-s
G/sind.001, .0022 MPa
Unaged
Temperature
LT
IT
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PG-grading system
t
tmax
g
gmax

• Assumes thin asphalt pavement thickness/weak
  structure ? strain-controlled condition
• Less dissipated energy less damage
• ? reduce G.sin (d)

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Evaluation of CurrentBinder Fatigue Parameter
Gsind
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Gsin d of Binders vs. Mixture NfPacific Coast
AUPG Study Results (Monismith et al.)
G.sin d of binders
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Do binders affect fatigue of pavements ?

• If not, why bother testing binders!

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Binder Effect on Mixture Fatigue Life
Change Due to Binder
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Significantly Less Fatigue of HMA by Use of
Polymer Modified Binders(H. Von Quintus AMAP
Meeting 2/2004
80 less Fatigue Cracking
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Problem Statement

• So binders are important for fatigue.
• What is wrong with G sin d ?
• Measured in Linear Visco-elastic
• Damage not considered
• Non-linearity not considered
• Could not correlate with mixture fatigue nor
  field fatigue.

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Possible Solutions

• Binder Fatigue test-NCHRP Study
• Time sweep test (DSR)
• Surrogate (accelerated) binder test
• R-master curve, m, DTT, others

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Binder Fatigue Test

• Use test protocols that simulate traffic
• (cyclic loading until we can see damage)

tmax
Stress
?max
Strain
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Binder Fatigue Test Time sweep
G
LVE Limit
Initial G
95 of LVE G
50 of LVE G
N cycles
No / Low damage accumulation
Non-Linear Region High damage accumulation
G.sin(d) range
Nf Binder Fatigue life
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Binder Fatigue testing Different binders of same
PG grade
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Possible Solutions Binder Fatigue Test

• NCHRP 9-10 Report 459
• Based on ratio of dissipated energy
• Np20 as fatigue indicator
• Non-linearity considered
• Damage considered

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Binder Nf vs Mixture Nf Much better correlation !
R2 gt 80
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Possible Solutions Binder Fatigue Test

• However, binder fatigue test is
• Time-consuming,
• Not very repeatable,
• Failure criteria not simple to define

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Research Progression

• FHWA ETG (2003 2006)
• Surrogate (accelerated) binder testing
• Stress sweep- Dissipated pseudo-strain energy
  (WR1, WR2)- (with help from TTI- E. Masad)
• Difficulty in execution
• Failure criteria not defined
• Paper in session 523
• DTT
• Operational difficulties
• Modeling to account for temp effect is very
  difficult
• Machine not serviced anymore

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FHWA Turner Fairbanks RC Group Strain Sweep

• Shenoy (2002) low strain levels were a cause of
  Gsin d inadequacies.
• Proposed specification parameter is based on
  modulus values at 25 strain
• Temperature at which Gs has a value of 1 MPa
  at 25 strain is designated Te
• Intermediate temp spec is written as
• The lower the TIS, the better the ranking.

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Research Progression

• Asphalt Research Consortium
• (2007 to date)
• 1. Binder monotonic shear test ( DSR)
• Constant strain rate in DSR
• 2. Fundamental characterization of binder fatigue
• Visco-elastic continuum damage (VECD) mechanics
• Target Characteristics independent of external
  conditions, temperature, and test type

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Monotonic Test- Background

• For asphaltic mixture,
• Wen and Kim (2002)- NC State Univ.
• Fracture energy from IDT test correlated well
  with fatigue performance of mixes at WesTrack.
• Roque et al. (2005) Univ. of Florida, DCSE.
• F. Perez et al. (2006)- Polytech of Catalonia-
  Spain, Maximum strain in a monotonic test
• For binders
• Investigate monotonic test using DSR on binders
  with known field performance

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Proposed Binder Fatigue Test

• Fracture energy for mixtures (Wen and Kim, 2002)
  
• Area under the stress-strain curve up to the peak
  stress

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Monotonic Binder Test Following Dissipated Creep
Strain Energy (DCSE), Roque et al.
DCSE
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LABORATORIO DE CAMINOS
Félix E. Pérez Jiménez, Rodrion M. Recasens,
Adriana Martínez Universidad Politécnica de
Cataluña
Nomograph for determining the mixture fatigue law
from the direct tensile test
ITT
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Binder Monotonic Test Using DSR

• Test procedures (C. Johnson and H. Wen)
• Apply constant strain-rate
• Stop the test after the peak stress is reached

Shear Stress
Strain
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Sample of Asphalt Failing in Monotonic Shear


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Initial Validation Alf Binders -Experimental
Design
100 mm
560 mm
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Monotonic Test Using DSR

• Used three strain rates
• 30 per min.
• 45 per min.
• 60 per min.
• Test temperature 19?C (ALF Control)
• Three replicates for each binder
• Test time less than 30 minutes

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Monotonic Testing Constant Strain Rate
30/min(3 replicates)- Fracture energy
Binder Fracture Energy (Pa) form DSR- Monotonic
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Monotonic Binder Test Strain at Peak Stress 30
60 / min
Strain at Peak Stress, (30 /min)
Strain at Peak Stress, (60 /min)
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Considering pavement Structure
AC 3
Granular Base
Granular Subbase
AC 6
Subgrade
Granular Base
Granular Subbase
Subgrade
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Effect of Pavement Structure on Fatigue Strain
in binder testing
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2. Fundamental Characterization

• Use monotonic test to predict effect of traffic
  volume and pavement structure
• Apply VECD to the monotonic tests results
• Collaborate with FHWA group studying fatigue of
  mixtures. (Gibson Kutay)

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Binder- Monotonic Test
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Fundamental CharacterizationBinder Testing
C, Material Integrity
S, Damage Intensity
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Selection of Yield Energy Level
Binder Yield Energy, YE (Pa)
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Cracking in ALF vs. Simulated Nf (50 Gi) of
Binders
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Typical Values of Yield Energy
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Proposed Limits for Yield Energy, MPa
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Simplified Proposed Limits for Yield Energy, MPa

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How would it fit in Specification Table? Yield
Energy, MPa
Test Temp oC
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Can use SN instead of Thick Int. Temp
8 C
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Monotonic Test Procedure
YE, MPa
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Grade shifting for Traffic speed and volume- PG
64-22
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Findings

• The monotonic test can lead to a simple
  specification parameter
• Both Yield Energy and strain at maximum stress
  correlated well with field performance
• Need to study repeatability
• Need further validation LTPP
• Define limits on YE and Temperature

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Acknowledgments

• Texas AM group
• Eyad Masad, Dallas Little and Ahmit Bhasin
• Y. R. Kim and H. J. Lee
• Richard Kim and Jo Daniel
• Felix Perez group (UPC)
• FHWA Group
• E. Kutay and N. Gibson

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Comparison of Monotonic and Binder Fatigue Test
Binder Fatigue Test
Binder Monotonic Test