Evaluating Mixing of RAP and New Binders in Plant MixesAASHTO M323 Design Guidance • Combined New and RAP Aggregates ... chart . Advanced Asphalt Technologies, LLC “Engineering

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




Results From Recent Laboratory Efforts• Evaluate Plant Produced Mixtures

– RAP Contents of 25 % or More– 5% Recycled Asphalt Shingles



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.



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



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



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



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)



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



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



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


Temperature°C


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



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



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



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



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



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



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



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



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



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


Bin

der G

*, kP

a

PG 64-22PG70-22From Mixture



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


Bin

der G

*, kP

a

PG 64-22PG70-22From Mixture



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



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



Questions?

Documents

Evaluating Mixing of RAP and New Binders in Plant MixesAASHTO M323 Design Guidance • Combined New and RAP Aggregates ... chart . Advanced Asphalt Technologies, LLC “Engineering