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Solvent Extraction-Recovery Procedures and their Effect on Recovered Asphalt Properties
OAPC-CPATT Study Findings
Amma Wakefield, MASc, PEng.Canadian Regional Engineer
Asphalt Institute
OAPC Fall SeminarNovember 29, 2018
Introduction
Asphalt binders specified based on their properties in an original state
• Performance Graded by AASHTO or ASTM
What about properties of in-situ asphalt mixtures?
• Research
• Forensic investigation
• Correct asphalt used in production
• Evaluate properties of blended asphalt binder (RAP or RAS)
Introduction
What options do we have to determine in-situ asphalt properties?
• Performance testing of asphalt mixture
• Physical properties of recovered asphalt• Since early 1900’s
Challenges with Recovered Binder Testing
• The choice of procedure and solvent can have an impact on the resulting physical properties of the recovered asphalt binder
• Physical properties test results of recovered binders have much higher variability compared to unrecovered binders
• The effect of solvent extraction on polymer modified binders and impact on physical properties is still being investigated
Research Objectives
1. Compare physical properties and testing variability of original (tank) asphalt to recovered asphalt
2. Compare laboratory aging and field aging through chemical analysis of functional groups of asphalt
3. Provide alternative methods of assessing the quality of plant produced asphalt mixes: performance testing
Challenges with Recovered Binder Testing
• The choice of procedure and solvent can have an impact on the resulting physical properties of the recovered asphalt binder
• Physical properties test results of recovered binders have much higher variability compared to unrecovered binders
• The effect of solvent extraction on polymer modified binders and impact on physical properties is still being investigated
NCHRP Project 09-12: RAP in Superpave System
Project Goal:
To develop guidelines for incorporating RAP in the Superpave System.
Part of research evaluated effect of different extraction-recovery procedures and solvents on high temperature properties of recovered asphalt binders
Two RAP Sources: Kentucky and Florida
NCHRP Project 09-12: RAP in Superpave System
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
Procedure-Solvent
G*/s
in δ
at
64 C
, k
Pa
Centrifuge
Abson
TCE
Centrifuge
Rotovapor
Toluene
SHRP
Rotovapor
TCE
SHRP
Rotovapor
Toluene
Kentucky RAP
NCHRP Project 09-12: RAP in Superpave System
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
Procedure-Solvent
G*/s
in δ
at
64 C
, k
Pa
Centrifuge
Abson
TCE
Centrifuge
Rotovapor
Toluene
SHRP
Rotovapor
TCE
SHRP
Rotovapor
Toluene
Kentucky RAP
NCHRP Project 09-12: RAP in Superpave System
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
Procedure-Solvent
G*/s
in δ
at
64 C
, k
Pa
Centrifuge
Abson
TCE
Centrifuge
Rotovapor
Toluene
SHRP
Rotovapor
TCE
SHRP
Rotovapor
Toluene
Kentucky RAP
Abson recovery method susceptible to experiencing incomplete solvent removal thereby lowering the measured stiffness.
NCHRP Project 09-12: RAP in Superpave System
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
Procedure-Solvent
G*/s
in δ
at
64 C
, k
Pa
Centrifuge
Abson
TCE
Centrifuge
Rotovapor
Toluene
SHRP
Rotovapor
TCE
SHRP
Rotovapor
Toluene
Kentucky RAP
NCHRP Project 09-12: RAP in Superpave System
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
Procedure-Solvent
G*/s
in δ
at
64 C
, k
Pa
Centrifuge
Abson
TCE
Centrifuge
Rotovapor
Toluene
SHRP
Rotovapor
TCE
SHRP
Rotovapor
Toluene
Kentucky RAP
NCHRP Project 09-12: RAP in Superpave System
Cartridge filter in SHRP rotavapor toluene procedure may remove more fine aggregate from the effluent
SHRP rotavapor uses lower temperature and higher vacuum which could help minimize hardening during the recovery process
Most specifications don’t identify one extraction-recovery method.
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
Procedure-Solvent
G*
/sin
δa
t 6
4 C
, k
Pa
Centrifuge
Abson
TCE
Centrifuge
Rotovapor
Toluene
SHRP
Rotovapor
TCE
SHRP
Rotovapor
Toluene
Challenges with Recovered Binder Testing
• The choice of procedure and solvent can have an impact on the resulting physical properties of the recovered asphalt binder
• Physical properties test results of recovered binders have much higher variability compared to unrecovered binders
• The effect of solvent extraction on polymer modified binders and impact on physical properties is still being investigated
Single lab repeatability
(d2s%) of G*/sinδ
0.0
20.0
40.0
60.0
80.0
100.0
120.0
2002 2004 2006 2008 2010 2012 2014 2016 2018
d2
s%
Year
Abson
Rotavapor
RTFO
AASHTO re: source proficiency sample. This graph is an analysis of the variability in testing using summary report data collected from 2003 to 2017.
The data shows single lab repeatability following the two recovery procedures and for an unrecovered binder marked by RTFO.
Research Objectives
1. Compare physical properties and testing variability of original (tank) asphalt to recovered asphalt
2. Compare laboratory aging and field aging through chemical analysis of functional groups of asphalt
3. Provide alternative method of evaluating quality of plant produced asphalt mixes: performance testing
Sample A - Terminal
Sample B – Tank Asphalt
Sample C – Plant Mix (Performance Testing)
Sample D – Job Site (Recovered)
Sampling Plan Review
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
5 5
6 0
6 5
7 0
7 5
8 0
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
P G H ig h T e m p e r a t u r e
P G G r a d e , R A P C o n te n t
PG
Hig
h
Te
mp
(o
C)
T a n k A s p h a lt
8 mixes sampled4 – 5 testing labs
Solvent: TCEAbson & Rotavapor
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
5 0
6 0
7 0
8 0
9 0
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
P G H ig h T e m p e r a t u r e
P G G r a d e , R A P C o n te n t
PG
Hig
h
Te
mp
(o
C)
T a n k A s p h a lt
R e c o v e r e d P la n t M ix
61.6 – 63.5
70.3 – 72.8
71.3 – 75.7
68.0 – 75.572.1 – 77.8 77.4 – 81.2
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
5 0
6 0
7 0
8 0
9 0
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
P G H ig h T e m p e r a t u r e
P G G r a d e , R A P C o n te n t
PG
Hig
h
Te
mp
(o
C)
T a n k A s p h a lt
R e c o v e r e d P la n t M ix
Gas Chromatographic Distillation (GCD) to determine presence of TCE or Toluene.
Results highlighted in redshow samples contaminated with TCE or Toluene based on GCD analysis.
Ash Content
• Test established in Ontario to determine inorganic content in asphalt cement
• Implemented by MTO “to prevent over-modification of AC with Re-Refined/Recycled Engine Oil Bottoms (REOB).”1
• What about inorganic aggregate fines in recovered asphalt from plant produced mix?
1Modi et al. Innovative Testing of Ontario’s Asphalt Materials. CTAA 2016
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
0
1
2
3
4
5
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
A s h C o n t e n t
P G G ra d e s a n d R A P C o n te n t
As
h
Co
nte
nt
(%)
T a n k A s p h a lt
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
0
1
2
3
4
5
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
A s h C o n t e n t
P G G ra d e s a n d R A P C o n te n t
As
h
Co
nte
nt
(%)
T a n k A s p h a lt
R e c o v e r e d A s p h a lt
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
0
1
2
3
4
5
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
A s h C o n t e n t
P G G ra d e s a n d R A P C o n te n t
As
h
Co
nte
nt
(%)
T a n k A s p h a lt
R e c o v e r e d A s p h a lt
S p e c if ic a t io n 0 .6
Challenges with Recovered Binder Testing
• The choice of procedure and solvent can have an impact on the resulting physical properties of the recovered asphalt binder
• Physical properties test results of recovered binders have much higher variability compared to unrecovered binders
• The effect of solvent extraction on polymer modified binders and impact on physical properties is still being investigated
Literature search of solvent extraction-recovery procedures with polymer modified asphalts
Asphalt Institute
• Modify Rotavapor procedure using toluene
• Does not have stabilizers that can cause problems with modified asphalts
Switzerland
• Most solvents showed little difference in elasticity except with dichloromethane
Belgium
• Some polymer modified asphalt lost their elasticity after recovery
• TCE resulted in higher variability in test results
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
0
2 0
4 0
6 0
8 0
1 0 0
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
M S C R P e r c e n t R e c o v e r y
P G G ra d e s a n d R A P C o n te n t
MS
CR
%
Re
c
@ 3
.2k
Pa
T a n k A s p h a lt
R e c o v e r e d A s p h a lt49.0 – 74.3
75.7 – 93.8
75.1 – 94.4
15.0 – 56.0
72.6 – 92.0
58.2 – 76.6
5 8 -3 4
1 5 R
7 0 -2 8
0 R
7 0 -2 8
1 5 R
0
2 0
4 0
6 0
8 0
1 0 0
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
M S C R P e r c e n t R e c o v e r y
P G G ra d e s a n d R A P C o n te n t
MS
CR
%
Re
c
@ 3
.2k
Pa
T a n k A s p h a lt
R e c o v e r e d A s p h a lt
Results highlighted in redshow samples contaminated with TCE or Toluene based on GCD analysis.
7 0 -2 8
0 R
7 0 -2 8
1 5 R
0
5
1 0
1 5
2 0
2 5
T a n k A s p h a lt a n d R e c o v e r e d A s p h a lt
C r it ic a l T ip O p e n in g D is p la c e m e n t
P G G ra d e s a n d R A P C o n te n t
dt,
CT
OD
(m
m)
T a n k A s p h a lt
R e c o v e r e d A s p h a lt
Research Objectives
✓Compare physical properties and testing variability of recovered asphalt to original (tank) asphalt
2. Compare laboratory aging and field aging through chemical analysis of functional groups of asphalt
3. Provide alternative method of evaluating quality of plant produced asphalt mixes: performance testing
Review: MTO HWY 655 Research Findings
Tank AC (Laboratory Aged) Properties
Recovered AC (Field Aged) Properties
PG Grading properties relate to cracking performance, if lab aging can match field aging.
Review: Asphalt Cement Properties
Asphalt is composed of extremely large number of organic molecules
Can be grouped into various molecular types and fractions:
• Saturates; Aromatics; Resins; Asphaltenes
Reacts with oxygen from environment
Oxidation/aging process changes the concentrations of these fractions
Aging Index
Absorbance AI =Toluene Soluble Asphaltenes
Resins
Absorbance AI was calculated using data from SAR-AD® on asphalt binders collected after various stages of aging:
• RTFO lab-aged binder
• 20hr PAV lab-aged binder
• 40hr PAV lab-aged binder
• Plant Mix (Recovered binder from plant produced mix, sampled on construction site)
Bland-Altman Plots: Aging Index
Purpose: Measure agreement between methods
• Methods of aging asphalt binder
1
Aging methods:
• Plant/Field aged mix
• Lab RTFO aged
• Lab 20hr PAV aged
• Lab 40hr PAV aged
2
How well do these methods agree?
• Compare Aging Index (AI) of lab aging methods to field aging.
3
Bland Altman Plots
Absorbance AI of the plant mix (i.e. recovered binder from plant produced mix) compared to Absorbance AI of lab-aged binders.
Smaller differences (i.e. Bias closer to zero) suggest the two methods are producing similar results.
Plant aging index vs. RTFO aging index
Plant aging index vs. 20hr PAV aging index
Plant aging index vs. 40hr PAV aging index
Lab aging getting close to field aging as difference approaches zero.
Research Objectives
✓Compare physical properties and testing variability of recovered asphalt to original (tank) asphalt
✓Compare laboratory aging and field aging through chemical analysis of functional groups of asphalt
3. Provide alternative method of evaluating quality of plant produced asphalt mixes: performance testing
Phase 3 – to be continued…
Summary
• The choice of procedure and solvent can have an impact on the resulting physical properties of the recovered asphalt binder
• During recovery aggregate fines remains in the recovered asphalt that will affect the physical properties
Summary
• d2s% values on recovered asphalt binder are approximately 4-7 times greater than the same values measured on unrecovered asphalt binder.
• Technical competence in performing extraction-recovery procedures important in obtaining repeatable, valid test results
• Users should exercise caution when comparing values of recovered asphalt binder to test criteria and variability derived for unrecovered (virgin) asphalt binder.
Solvent Extraction-Recovery Procedures and their Effect on Recovered Asphalt Properties
OAPC-CPATT Study Findings
Amma Wakefield, MASc, PEng.Canadian Regional Engineer
Asphalt Institute
OAPC Fall SeminarNovember 29, 2018