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COMPATIBILITY OF RAP AND
VIRGIN BINDER
2012 Arizona Pavements/Materials Conference
October 31, 2012
Michael Harnsberger
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Introduction
• Early in the 20th Century, it became apparent that
asphalt performance varied
• Derived from different crude sources
• Even asphalts of the same grade
• Classification methods developed
• Composition based
• Rheology based
• Crude oil methods adapted
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Introduction
• Asphalt behaved as a colloidal system (Traxler)
• Asphaltenes dispersed in maltene solvent
• Asphalts classified as sol or gel
• Sol asphalts are more compatible
• Lower asphaltene content
• Gel asphalts are less compatible
• Higher asphaltene content
• Many asphalts are intermediate
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Methods for Estimation of
Compatibility
• Asphaltene dispersibility index
• Asphaltene filtering rate
• Asphaltene compatibility index (Branthaver)
• Relative viscosity (v. asphalt/ v. maltenes)
• Ratios of fractions (Corbett, Rostler, Schweyer, Traxler)
• Heithaus parameters
• pa – peptizability of the asphaltenes
• po – peptizability of the maltenes
• P – state of peptization
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Composition and Compatibility
Heithaus Test
Solution of asphalt in toluene titrated with heptane;
Must match
Solvent power of petrolenes
Dispersibility of asphaltenes
Altgelt and Harle
“Thickening power” of asphaltenes related to degree of
association
Degree of association of asphaltenes controlled by
solvent power of petrolenes
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Effect of Compatibility on Blending
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Effects of Crossblending
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Asphalt Characterization
• Methods developed to separate asphalt components
(maltenes)
• Rostler Method
• Corbett-Swarbrick method ASTM D4124
• Clay-gel
• Size-exclusion chromatography (GPC) (whole asphalt)
• Ion-exchange chromatography (whole asphalt)
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Composition Fraction Comparison
Rostler Corbett Function
Paraffins Saturates Gel
2nd Acidaffins Naphthene
Aromatics
Fluidity
1st Acidaffins Solvent
Nitrogen Bases Polar Aromatics Dispersant
Asphaltenes Asphaltenes Thickener
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What is Compatibility?
Operational Definition of Compatibility
• Mixing of two or more similar materials gives expected
results
Incompatibility
• Mixing of two or more similar materials gives unexpected
results
• Softer than expected
• Stiffer than expected
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Aging
What happens when asphalts age?
• Saturates – little oxidation/ little change
• Aromatics – some oxidation/ small change
• Oxidation products move to Resins
• Resins – considerable oxidation
• Oxidation products move to Asphaltenes
• Asphaltenes – increase
• Molecular associations increase
• Asphalt aging decreases with pavement depth
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RAP and Virgin Binder
• Virgin and RAP asphalts mix --- Degree?
• Age of RAP affects blending
• Some components more “available”
• Adsorption effects of RAP aggregate
• Solubility “Power” of virgin asphalt
• Is compatibility of virgin and RAP an issue?
• Depends
• Compatibility depends on solubility
• Combined binder rheology will be a function of
compatibility
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RAP Compatibility Work
• Lab blends of virgin and RAP @ 0,15 & 50%
• 2 asphalts of different composition
• 4 RAP; MB, SC, IA, & CA
• Rheology
• Heithaus parameters
• Separation methods, etc.
• Evaluation of NCSPC plant-mix samples
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Virgin Asphalt RAP Blends
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Virgin Asphalt RAP Blends
0.E+00
1.E+07
2.E+07
3.E+07
4.E+07
5.E+07
6.E+07
7.E+07
8.E+07
0 20 40 60 80 100
G*,
Pa,
0C
, 10r
ad/s
ec
Percent Manitoba RAP
AAA/Manitoba 0°C
1.00E+07
2.00E+07
3.00E+07
4.00E+07
5.00E+07
6.00E+07
7.00E+07
8.00E+07
0 20 40 60 80 100
G*,
Pa,
0C
, 10
rad
/se
c
Percent Manitoba RAP
AAC/Manitoba 0°C
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Virgin Asphalt RAP Blends
0.E+00
1.E+04
2.E+04
3.E+04
4.E+04
5.E+04
6.E+04
7.E+04
8.E+04
0 20 40 60 80 100
G*,
Pa,
60
C, 1
0 ra
d/s
ec
Percent S. Carolina RAP
AAA/SC RAP 60°C
0.E+00
1.E+04
2.E+04
3.E+04
4.E+04
5.E+04
6.E+04
7.E+04
8.E+04
0 20 40 60 80 100G
*, P
a, 6
0C
, 10
rad
/se
cPercent S. Carolina RAP
AAC/SC RAP 60°C
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Virgin Asphalt RAP Blends
0.0E+00
2.0E+07
4.0E+07
6.0E+07
8.0E+07
1.0E+08
1.2E+08
1.4E+08
1.6E+08
1.8E+08
0 20 40 60 80 100
G*,
Pa,
0C
, 10
rad
/se
c
Percent S. Carolina RAP
AAA/SC RAP 0°C
0.0E+00
2.0E+07
4.0E+07
6.0E+07
8.0E+07
1.0E+08
1.2E+08
1.4E+08
1.6E+08
1.8E+08
0 20 40 60 80 100G
*, P
a, 0
C, 1
0 ra
d/s
ec
Percent S. Carolina RAP
AAC/SC RAP 0°C
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NCSC Plant Mix Study
• 5 contractors produced 6 RAP mixes
• PG 64-22 with 0, 15, 25, and 40% RAP
• PG 58-28 with 25 and 40% RAP
• Mix Testing
• Dynamic modulus and Low Temp IDT
• Binder extracted and graded
• Samples of binder sent to WRI for
compatibility (4 of 5)
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Mix Properties vs. Compatibility
4.20
4.30
4.40
4.50
4.60
4.70
4.80
4.9015
20
25
30
1A-0% 1B-15% 1C-25% 1D-40% 1E-25% 1F-40%
AF
T, P
valu
e
Sti
ffn
ess, G
Pa
Stiffness
AFT, P value
64-22 58-28
Stiffness data from: Investigation of Low and High Temperature Properties
of Plant-Produced RAP Mixtures Phase II, McDaniel and Huber
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3.80
3.90
4.00
4.10
4.20
4.30
4.40
4.50
4.60
4.70
4.80
4.90
5.00
5.1010
15
20
25
30
2A-0% 2B-15% 2C-25% 2D-40% 2E-25% 2F-40%
AF
T, P
valu
e
Sti
ffn
ess, G
Pa
Stiffness
AFT, P value
Mix Properties vs. Compatibility
64-22 58-28
Stiffness data from: Investigation of Low and High Temperature Properties
of Plant-Produced RAP Mixtures Phase II, McDaniel and Huber
-22.1 -21.9 -21.8 -21.3 -24.1 -23.3
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3.20
3.30
3.40
3.50
3.60
3.70
3.80
3.90
4.00
4.10
4.2020
25
30
35
3A-0% 3B-15% 3C-25% 3D-40% 3E-25% 3F-40%
AF
T, P
valu
e
Sti
ffn
ess, G
Pa
Stiffness
AFT, P value
Mix Properties vs. Compatibility
64-22 58-28
Stiffness data from: Investigation of Low and High Temperature Properties
of Plant-Produced RAP Mixtures Phase II, McDaniel and Huber
-22.5
-21.8
-21.4
-20.3
-21.3
-24.5
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4.40
4.50
4.60
4.70
4.80
4.90
5.00
5.10
5.20
5.30
5.4015
20
25
30
4A-0% 4B-15% 4C-25% 4D-40% 4E-25% 4F-40%
AF
T, P
valu
e
Sti
ffn
ess, G
Pa
Stiffness
AFT, P value
Mix Properties vs. Compatibility
64-22 58-28
Stiffness data from: Investigation of Low and High Temperature Properties
of Plant-Produced RAP Mixtures Phase II, McDaniel and Huber
-20.5
-20.8
-20.5
-19.6 -24.2 -23.3
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Comments
• Lab binder blending study using rheology and compatibility
will hopefully provide more insight
• Lab tests must correlate to plant mixing
• Goals of this are:
• Better understanding of RAP/Virgin blending
• Quick material evaluation method to determine the amount of
RAP/RAS blending with new asphalt
• If oil prices rise, asphalt crude sources/blends are sure to
change
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Acknowledgements
• This work performed under FHWA Contract DTFH61-07-H-0009
Asphalt Research Consortium
• WRI – Troy Pauli, James Beiswenger
• North Central Superpave Center & Heritage Research
• Becky McDaniel and Gerald Huber