Compact Tension Testing of Asphalt Binders at Low Temperatures

1
Compact Tension Testing of Asphalt Binders at
Low Temperatures

• Michelle A. Edwards and Simon A.M. Hesp
• Queens University
• Kingston, Ontario, Canada
• Transportation Research Board
• 85th Annual Meeting, January 2006

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Acknowledgments

• Government
• Ontario Ministry of Transportation Highway
  Innovations Funding Program (2003-2005)
• NCHRP Innovations Deserving Exploratory
  Analysis (IDEA 84 and 104)
• Natural Sciences and Engineering Research Council
  of Canada (NSERC 2002-2006)
• Industry
• Imperial Oil of Canada and E.I. du Pont Canada
• Individuals
• Serban Iliuta

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Project Objectives

• Develop New Low Temperature Binder Test
• Easy to Use
• Compatible with Existing Direct Tension Equipment
• Reproducible
• Accurate (i.e., fundamentally sound)

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Current Binder Specification
Bending Beam Rheometer
BBR DATA
T1
e, m/m
T2
Time, s

• AASHTO M320 Specification
• Creep Stiffness, S(2 hr)lt300 MPa (after Readshaw,
  1972)
• Relaxation Ability, m(2 hr)gt0.3

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Deficiencies of AASHTO M320

• Reversible Aging is Ignored
• Age Hardening (1930s), Steric Hardening (1950s),
  Physical Aging (1970s), Physical Hardening
  (1990s), Isothermal Hardening, Reversible
  Hardening (2000s)
• It is of little use to measure creep with
  accurate instruments and thermostats if one
  ignores the ageing effect. (Struik (1978, p.
  29))
• Large Variations for Fracture Energies in Brittle
  and Ductile State are Ignored
• 5 J/m2 lt Gf lt 400 J/m2
• 1 kJ/m2 lt we lt 25 kJ/m2 0.1 MJ/m3 lt wp lt 2 MJ/m3

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Variations in Fracture Energy
5 wt SBS in Cold Lake 300/400 Gf 58 J.m-2
5 wt SBS in Cold Lake 300/400 Gf 400 J.m-2
T -32oC and Rate 0.01 mm/s Photographs
courtesy of S. Iliuta, 2006.
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Fracture Energy Master Curves
Ductile State Ductile-to-Brittle Brittle
State Transition ?
8.0
PG 64-34 PG 52-34
Plastic Works
6.0
log G
Essential Works
f
4.0
Brittle Energies
2.0
0.0
-6.0
-3.0
0.0
3.0
6.0
log Reduced Rate
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Specimen Geometry and Size

• Specimen widths B 12.5, 18.75, and 25 mm
• Specimen height W 25 mm
• Notch depths a/W 0.2, 0.4, and 0.6

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Test Fixtures and Set Up
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Why Plane Strain Toughness?
P
B
syy
sXX
sZZ
B
CRACK
a
W
Y
P
X
z
See T.L. Anderson, Fracture Mechanics, 1995
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Reproducibility
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Effect of Razor Sharpening
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Plane Strain Fracture Toughness
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Validation of ASTM Approach(AAG-2 5 SBS at
22oC)
Gf, c (Unotched Uunnotched)/BWf
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Generalized Locus Method
?,? AAN at 16oC/22oC ?,? AAG-2 5 SBS at
22oC/28oC
Jf -1/B dU/da
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Ductile-to-Brittle Transitions
Gf ? (655-5) and ? (655-6) df ?
(655-5) and ? (655-6)
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Conclusions

• Compact tension test is fast and reproducible.
• Fracture in binders involves significant energy
  dissipation away from the crack tip yield zone.
• Some polymer modified binders show a significant
  increase in brittle state fracture properties
  over straight run binders.
• Significant differences can exist between the
  limiting stiffness and limiting fracture
  temperatures of a given binder.

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Further Work

• Evaluation of New Pavement Trials
• Highway 655 Low Temperature Trial
• Constructed in 2003
• Seven Test Sections SBS, oxidized, RET, control
• Highway 417 Overlay Trial
• Construction in 2006
• Seven Test Sections SBS, RET, control
• Highway 655 Fatigue Trial
• Construction in 2007
• Eight Test Sections SBS, RET, PET PP Fibers,
  PPA

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Questions