Solvent Extraction-Recovery Procedures and their Effect on ... Recovered PG... · Rotavapor RTFO...

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

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


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


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.


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


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

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


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




PG

Hig

h

Te

mp

(o

C)


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




PG

Hig

h

Te

mp

(o

C)


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


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

(%)


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


A s h C o n t e n t


As

h

Co

nte

nt

(%)


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


A s h C o n t e n t


As

h

Co

nte

nt

(%)



S p e c if ic a t io n 0 .6

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


M S C R P e r c e n t R e c o v e r y


MS

CR

%

Re

c

@ 3

.2k

Pa


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


M S C R P e r c e n t R e c o v e r y


MS

CR

%

Re

c

@ 3

.2k

Pa



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


C r it ic a l T ip O p e n in g D is p la c e m e n t


dt,

CT

OD

(m

m)



Research Objectives

✓Compare physical properties and testing variability of recovered asphalt to original (tank) asphalt



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


Phase 3 – to be continued…

Summary


• 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

Solvent Extraction-Recovery Procedures and their Effect on ... Recovered PG... · Rotavapor RTFO...

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Transcript of Solvent Extraction-Recovery Procedures and their Effect on ... Recovered PG... · Rotavapor RTFO...