COMPATIBILITY OF RAP AND

VIRGIN BINDER

2012 Arizona Pavements/Materials Conference

October 31, 2012

Michael Harnsberger

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

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

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

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

Effect of Compatibility on Blending

Effects of Crossblending

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)

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

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

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

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

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

Virgin Asphalt RAP Blends

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

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

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

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)

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

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

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

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

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

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