Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Evaluating Mixing of RAP and New Binders in Plant Mixes Ramon Bonaquist, Ph.D., P.E. Chief Operating Officer Advanced Asphalt Technologies, LLC
Advanced Asphalt Technologies, LLC
“Engineering Services for the Asphalt Industry”
Evaluating Mixing of RAP and New Binders in Plant Mixes
Ramon Bonaquist, Ph.D., P.E.Chief Operating Officer
Advanced Asphalt Technologies, LLC
Advanced Asphalt Technologies, LLC
“Engineering Services for the Asphalt Industry”
Results From Recent Laboratory Efforts• Evaluate Plant Produced Mixtures
– RAP Contents of 25 % or More– 5% Recycled Asphalt Shingles
Advanced Asphalt Technologies, LLC
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Acknowledgements• Agencies
– Maryland State Highway Administration– Pennsylvania Department of Transportation
• Suppliers/Producers– NuStar Asphalt Refining, LLC– Aggregate Industries – Edgemoor Materials of Maryland, Inc.– F.O. Day Company, Inc.– Independence Construction Materials– Reliable Contracting Company, Inc.
Advanced Asphalt Technologies, LLC
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AASHTO M323 Design Guidance
• Combined New and RAP Aggregates– Gradation– Angularity– Flat and Elongated
• Binder Grade Changes– < 15 % RAP, no grade change– 15 -25 % RAP, use one grade softer– > 25 % RAP, use blending chart
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Issues
• AASHTO M323 Recommendations Assume Complete Mixing of New and Recycled Binder
• AASHTO M323 Does Not Address RAS Binders– Blending Chart Analysis Not Applicable– Much Different Rheology than Paving Binders
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Mixture Homogenity
• How Well Does the RAP/RAS Binder Mix with the New Binder?– Black Rock– Complete Mixing
• Process Specific– Plant Type– Plant Operations– RAP/RAS Processing
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One Tool
• Dynamic Modulus – Test Is Highly Sensitive to
Binder Stiffness• Assess Degree of Mixing of
New and Recycled Binders
– Relatively Easy to Perform with the Asphalt Mixture Performance Tester (f.k.a. SPT)
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Simple Performance Test System
• Rugged– 5 Years in FHWA
Mobile Asphalt Lab• Technician Friendly
– Automated Testing Cell– Easy to Install
Instrumentation– Standard Software
• Testing and Analysis• Data Quality
• Reasonable Cost
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How?• Perform Dynamic Modulus Tests on Plant
Produced Mixture– Plant Mixed Condition
• Recover Binder, Test and Estimate Dynamic Modulus Using Predictive Model– Fully Blended Condition
• Compare Measured and Estimated Mixture Modulus
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Mix Modulus Testing
• Representative Plant Mixture• AMPT Modulus Master Curve
Procedure– Replicate Specimens
PG 58-XX and softer PG 64-XX & PG 70-XX PG 76 –XX and stifferTemperature°C
LoadingFrequenciesHz
Temperature°C
LoadingFrequenciesHz
Temperature°C
LoadingFrequenciesHz
4 10, 1, 0.1 4 10, 1, 0.1 4 10, 1, 0.120 10, 1, 0.1 20 10, 1, 0.1 20 10, 1, 0.135 10, 1, 0.1,
and 0.0140 10, 1, 0.1,
and 0.0145 10, 1, 0.1,
and 0.01
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Recovered Binder Testing
• Partial Master Curve– Frequency Sweep 0.1 to 100 rad/sec– 10, 22, 34, and 46 °C
• Christensen Anderson Model2log2log
1)(*
R
R
r
cgGG
−
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡
⎟⎟⎠
⎞⎜⎜⎝
⎛+=
ωω
ω
where:G*(ω) = complex shear modulusGg = glass modulus assumed equal to 1GPaωr = reduced frequency at the reference temperature, rad/secωc = cross over frequency at the reference, rad/secR = rheological index
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Example Partial Master Curve
1.E+00
1.E+02
1.E+04
1.E+06
1.E+08
1.E+10
1.E-04 1.E-02 1.E+00 1.E+02 1.E+04
Reduced Frequency at Tr (20°C), rad/sec
G*,
Pa10°C 22°C 34°C 46°C Model
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Hirsch Model
⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢
⎣
⎡
+⎟⎠⎞
⎜⎝⎛ −
−+⎥
⎦
⎤⎢⎣
⎡⎟⎠
⎞⎜⎝
⎛+⎟
⎠⎞
⎜⎝⎛ −=
binder
cbindercmix
GVFAVMA
VMAPVMAxVFAGVMAPE
|*|3000,200,4100
1
1000,10
|*|3100
1000,200,4|*|
where:
58.0
58.0
|*|3650
|*|320
⎟⎠⎞
⎜⎝⎛+
⎟⎠⎞
⎜⎝⎛ +
=
VMAGxVFA
VMAGxVFA
Pbinder
binder
c
VMA = Voids in mineral aggregates, %VFA = Voids filled with asphalt, %|G*|binder = shear complex modulus of binder, psi
Binder Modulus and Mix Volumetrics
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Good Mixing
1
10
100
1000
10000
4 C
, 10
Hz
4 C
, 1 H
z
4 C
, 0.1
Hz
20 C
, 10
Hz
20 C
, 1 H
z
20 C
, 0.1
Hz
40 C
, 10
Hz
40 C
, 1 H
z
40 C
, 0.1
Hz
Testing Condition
Dyn
amic
Mod
ulus
, ksi
Measured Estimated for Complete Mixing
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Poor Mixing
1
10
100
1000
10000
4 C
, 10
Hz
4 C
, 1 H
z
4 C
, 0.1
Hz
20 C
, 10
Hz
20 C
, 1 H
z
20 C
, 0.1
Hz
40 C
, 10
Hz
40 C
, 1 H
z
40 C
, 0.1
Hz
Testing Condition
Dyn
amic
Mod
ulus
, ksi
Measured Estimated for Complete Mixing
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Estimate Effective Binder Grade
• Measure Dynamic Modulus of Plant Mixture
• Solve Hirsch Model Backward to Determine the Modulus of the Binder
• Compare to PG Grade Requirements
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Hirsch Model
⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢
⎣
⎡
+⎟⎠⎞
⎜⎝⎛ −
−+⎥
⎦
⎤⎢⎣
⎡⎟⎠
⎞⎜⎝
⎛+⎟
⎠⎞
⎜⎝⎛ −=
binder
cbindercmix
GVFAVMA
VMAPVMAxVFAGVMAPE
|*|3000,200,4100
1
1000,10
|*|3100
1000,200,4|*|
where:
58.0
58.0
|*|3650
|*|320
⎟⎠⎞
⎜⎝⎛+
⎟⎠⎞
⎜⎝⎛ +
=
VMAGxVFA
VMAGxVFA
Pbinder
binder
c
VMA = Voids in mineral aggregates, %VFA = Voids filled with asphalt, %|G*|binder = shear complex modulus of binder, psi
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Standard Grades
1
10
100
1000
10000
100000
1000000
1.0E-03 1.0E-01 1.0E+01 1.0E+03 1.0E+05 1.0E+07
Reduced Frequency at 20 C, rad/sec
Bin
der G
*, kP
a PG 64-22PG70-22
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RAP Mix 1
1
10
100
1000
10000
100000
1000000
1.0E-03 1.0E-01 1.0E+01 1.0E+03 1.0E+05 1.0E+07
Reduced Frequency at 20 C, rad/sec
Bin
der G
*, kP
a
PG 64-22PG70-22From Mixture
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RAP Mix 2
1
10
100
1000
10000
100000
1000000
1.0E-03 1.0E-01 1.0E+01 1.0E+03 1.0E+05 1.0E+07
Reduced Frequency at 20 C, rad/sec
Bin
der G
*, kP
a
PG 64-22PG70-22From Mixture
Advanced Asphalt Technologies, LLC
“Engineering Services for the Asphalt Industry”
Summary
• Mixture Design Assumes Complete Mixing of RAP and New Binders– How do you design for 50% mixing?
• Production QC Must Address Mixing– Increasing Importance as Recycled Binder
Content Increases– Recycled Binder Stiffness Increases
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Summary
• Dynamic Modulus Provides A Tool• HMA Producers
– Evaluate Process to Improve Mixing• Fractionation• Plant Mixing Times• Post Mixing Storage
• Agencies– Accept Producers Process– Approach to Estimating Binder Grade Without
Extraction Extraction/Recovery
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Questions?