Role of Binders in Asphalt Mixture Performance

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Role of Binders in Asphalt Mixture Performance

• H. Bahia
• The University of Wisconsin-Madison
• Annual Meeting of
• The Canadian User-Producer Group for Asphalt
• Montréal , Quebec, November 21, 2004

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Why do we need to discuss binder effect on
mixtures?

• Pavements are built with Asphalt Mixtures, not
  binders !
• We select binders before mixture is even
  designed.
• This requires understanding the range of binder
  effects on specific mixture behaviors.
• Effective binder specification should probably be
  based on a scale of mixture behavior.

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A Very Complex Material Asphalt Rocks Air
Voids
Very, very complex composite
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Advanced Technology Combined Digital Image/
X-Ray
New Tools
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We Can determine Film Thickness Distribution
Can be very Precise
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Film Thickness Distribution
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Not a new Topic Empirical Binder toMixture
Stiffness relations

• Hukelom and Klomp Relations 50s -60s
• where n f(Sb)
• Bonnaures relations 70s
• If Sb is between 5.0 MPa and 1.0 GPa
• If Sb is between 1.0 GPa and 3.0 GPa
• 
  

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Most Recent Models AASHTO 2002 and after

• Witczak et al. (1976 2001)
• Last 25 years. The latest version of this model
  is based on 1,429 mixture testing data on 149
  asphalt mixtures.
• Included in The 2002 AASHTO Design guide
• D.W. Christensen, Pellinen, and Bonaquist (2003)

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AASHTO 2002 Dynamic Modulus /E/Phase Angle, ?
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AASHTO 2002 (Witczak et al.) Model for Plastic
Strain (ep) All Data log ep c1 c2 log N
c3 log No4 c4 log No200 c5 log temp
C6 log th_ei c7 log Va c8 log vfa c9
log th_fr c10 log Dev_st c11 log visc_t
c12 (log N)2c13 (log No4) 2 c14 (log
thei) 2 c15 (log Va) 2 c16 (log temp) 2
c1 22.083, c2 0.5083, c3 38.131,
c4 -11.297, c5 44.16, c6 -111.539, c7
0.4515, c8 0.6739, c9 3.5783, c10
0.7, c11 0.0825, c12 0.0349, c13
-12.456, c14 5.69, c15 31.219, c16
-10.468
R2 71.8 Se/Sy 0.537 N 4995
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Measured Mixture and Binder Rheology
Mixture
Binder
E, MPa
Reduced Frequency, Hz
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Binder and mixture Phase angle - ? -master curves
Binder
Mixture
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Sensitivity to temperature Ratio of G at 46C
to G at 52C (f0.1Hz)
5
PG82 (SBSr)
PG82 (PE)
PG82 (ss)
PG82 (SBR)/(SBSl)
PG76 (ET)
PG76 (oxd)
PG58 (SBSl)
PG58 (SB)
PG58 (oxd)
4
52C
3
Binder Change per 6C 2.3
/G
1.6
46C
2
G
0.6
Mix Change per 6 C 1.4
1
0
Aggregate Type
Binder
AI Coarse
AI Fine
NCAT Coarse
NCAT Fine
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Sensitivity to Traffic Speed Ratios of G at
10 Hz to G at 0.1 Hz (T52C)
40
PG82 (SBSr)
PG82 (PE)
PG82 (ss)
PG82 (SBR)/(SBSl)
PG76 (ET)
PG76 (oxd)
35
PG58 (SBSl)
PG58 (SB)
PG58 (oxd)
30
25
0.1Hz
Binder Change per 100Hz 18
/G
20
8
10Hz
G
15
10
Mix Change per 100 Hz 5
4
5
0
Aggregate Type
AI Coarse
AI Fine
NCAT Coarse
NCAT Fine
Binder
AI Coarse
AI Fine
NCAT Coarse
NCAT Fine
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Effect of Traffic Speed Ratios of G at 10 Hz
to G at 0.1 Hz (TIT)
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PG82 (SBSr)
PG82 (PE)
PG82 (ss)
PG82 (SBR)/(SBSl)
PG76 (ET)
PG76 (oxd)
PG58 (SBSl)
PG58 (SB)
PG58 (oxd)
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Binder Change per 100Hz 7.0
0.1Hz
/G
6
10Hz
G
Mix Change per 100 Hz 3.0
5
2
0
Binder
AI Coarse
AI Fine
NCAT Coarse
NCAT Fine
Aggregate Type
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Sensitivities to Temperature and Traffic Speed

• Mixture sensitivity to temperature is lower than
  binder. Changing grade from PG-58 to PG-64
  results in
• Binder G increase by 230
• Mix G/E increase by only 40
• Mixture sensitivity to traffic speed is also
  lower than binder. Increasing speed from 0.5 mph
  to 50 mph results in
• Binder G increase by 1800 (52 C), 700 (25 C)
• Mix G/E increase by only 500 (52C), 300 (25C)

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Mixture vs. Binder (G)
Crushed Limestone
Gravel
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Simplified Binder to Mixture Relationships
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The Best Simplified Relationship

• Analyses of data (9 binders and 36 mixtures)
  indicate that the best model is
• Mix G 720 (G of Binder)0.50
• This model could be used for estimating binder
  effects in pavement analysis and design of layer
  thickness.
• It should allow revision of binder grading to
  effective grades.

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How do binders affect mix damage

• 1.Rutting
• 2.Fatigue

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Flexible Pavement Failures. 1. RUTTING
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Mixture Rutting (log-log plot)
Permanent Strain
Number of Cycles
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Normal Scale
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Evaluation of Binder Effect on Mixture Rutting
Average of All Aggregates
0.5
Mix 0.201 Binder C
0.45
2
0.4
R
0.6821
Mixture rutting slope S
0.35
0.3
0.25
0.2
0
0.1
0.2
0.3
0.4
Binder rutting slope, (1/Kpa)
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Longitudinal Cracking In the Wheel Path
Alligator cracking
Fatigue
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Mixture Fatigue Response
Stiffness (Mpa)
Number of Cycles
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Binder only Fatigue Test Results (DSR)
G, Pa
400000
20000
Number of Cycles in the DSR
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Correlation between Binder Mixture Fatigue
Lives
350000
300000
250000
Mix 0.198 Binder C
200000
150000
2
R
0.8412
100000
50000
0
-50000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
No. of Cycles at 50 G (Mixture) Average
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Findings from Damage Testing

• Rutting Resistance
• On average, the rule of 5 to 1 applies
• 100 change in binder resistance could results in
  only 20 change in mixture rutting resistance.
• Fatigue Resistance
• Surprisingly, the same rule of 5 to 1 can be
  applied
• 100 change in fatigue life of binders results in
  20 change in fatigue life of mixtures.
• Aggregate type and gradation can have significant
  influence on rutting and fatigue.

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• Moisture Damage !

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Adhesion Measurement
Schematic of Piston
Specimen Preparation
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Binder Cohesion TestingConcept of Tack Test

• The relationship between the stress (f) and the
  time (t) when the plates move from d0 to d1  

• f stress applied
• t duration
• ? viscosity of adhesive
• a radius of specimen
• d0 initial thickness of adhesive layer
• d1 thickness after time interval t  

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Hamburg Wheel Tracking Test

• Asphalt
• B1 Original PG 58-28 (RTFO)
• B2 PG 64-28 Chemically Treated (RTFO)
• B3 PG 64-28 w/ Elvaloy (RTFO)
• B4 PG 64-34 w/ Elvaloy (RTFO)
• B5 PG 70-28 w/ Elvaloy (RTFO)
• Aggregate Limestone and Granite
• Testing Results and Pictures Provided by Mr.
  Reinke of the MTE Services, Inc.

Condition at 50C
Test at 50C
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HWT Test Results
Polymer
Base
Acid
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Linear Model Predicting the HWT Test results from
Adhesion and Cohesion of Binder
Study will be Published in2005 tRB
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In summary

• There are tools today to estimate relative effect
  on mixture
• Effective binder specification should be based on
  a scale of mixture behavior.

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Thank You for this Opportunity Questions !