characterizing pma performance with pg plus tests · characterizing polymer modified asphalt...

Characterizing Polymer Modified Asphalt Performance with PG Plus Tests

2020 OAPC Asphalt Symposium

Presented by: Mike Aurilio

June 16, 2020

1

2

Physical Properties of PMA

Stiffness

▪ Increases▪ Improves rutting resistance▪ Can improve fatigue cracking resistance

Response to Loading

▪ More elastomeric▪ No longer purely ductile/brittle▪ Improves cracking resistance

Coil- speedwaymotors.comPavement Distresses- pavementinteractive.com

3

Styrene-Butadiene-Styrene

SBS Structure- polymerdatabase.com

Linear Radial

▪ Thermoplastic- Rubber▪ Good solubility in asphalt (Hildebrand

parameters are similar)▪ Glass Transition Temperature (Tg) of -90˚C

Butadiene Styrene

4

PMA Compatibility

▪ Good compatibility causes swelling of SBS chains (increase in volume fraction)▪ Good compatibility causes increase in stiffness and elastomeric properties

Asphalt Cement Chemistry

▪ Different crude sources result in asphalt with different chemistries

▪ Increase in aromatic fraction can improve compatibility

SBS Microstructure

▪ Molecular weight can effect dispersion in asphalt

▪ Styrene content can effect level of swelling

Cross-linking Agents

▪ Generally improve SBS stability

▪ Can improve quality of polymer network

Images- Planche, Elwardany, Adams, Rovani, Boysen, “Compatibility in Asphalt – A moving Target with Sources, Modifications and Aging”, TRB Annual Meeting, January 13, 2020

Increasing Compatibility

5

How much SBS do we need?

0 – 2%

▪ Small increase in stiffness

▪ Not enough to improve elastomeric properties

2 - 4%

▪ Asphalt continuous phase

▪ Noticeable improvement to elastomeric properties

4 - 6%

▪ Co-continuous phases

▪ Possibility of instability?

6 - 8%

▪ Polymer continuous phase

▪ Great performance but expensive

Perf

orm

ance

incr

ease

s as

co

nce

ntr

atio

n in

crea

ses

Images- Planche, Elwardany, Adams, Rovani, Boysen, “Compatibility in Asphalt – A moving Target with Sources, Modifications and Aging”, TRB Annual Meeting, January 13, 2020

PMA Master Curve

6

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E-06 1.0E-05 1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05

Co

mp

lex

Mo

du

lus

(Pa)

Reduced Frequency (Hz)

58-28 0% SBS

58-28 2% SBS A

58-28 4% SBS A

58-28 2% SBS B

58-28 4% SBS B

Low TemperatureHigher Frequency

High TemperatureLower Frequency

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E-07 1.0E-05 1.0E-03 1.0E-01 1.0E+01 1.0E+03 1.0E+05

Co

mp

lex

Mo

du

lus

(Pa)

Reduced Frequency (Hz)

Self-Healing Asphalt Cement Unaged Self-Healing Asphalt Cement PAV 58-28 0% SBS Unaged 58-28 0% SBS PAV

Aging Master Curve

7

PMA Black Space Diagram

8

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

0 20 40 60 80 100

Co

mp

lex

Mo

du

lus

(Pa)

Phase Angle (˚)

58-28 0% SBS58-28 2% SBS A58-28 4% SBS A58-28 2% SBS B58-28 4% SBS B

High TemperatureLower Stiffness

Intermediate TemperatureHigher Stiffness

Experimental Design

9

5 Asphalt Cements:

▪ PG 58-28▪ PG 64-28▪ PG 52-34▪ PG 58-28B▪ PG 52-34B

2 SBS Sources:

▪ SBS A▪ SBS B

Concentrations:

0, 1, 2, 3 and 4%

Low Strain Amplitude Cracking Tests:

▪ DENT▪ ΔTc / ExBBR▪ Glover-Rowe Parameter▪ Cross-Over Temperature

Large Strain Amplitude Cracking Tests:

▪ Linear Amplitude Sweep (LAS)▪ Asphalt Binder Cracking Device

(ABCD)

20 Hour PAVRTFO

Large Strain Amplitude Rutting Test:

▪ MSCR

0

10

20

30

40

50

60

70

80

90

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Pe

rce

nt R

eco

ve

ry (

%)

Percent Polymer (%)

58-28 SBS A 58-28 SBS B

64-28 SBS A 64-28 SBS B

52-34 SBS A 52-34 SBS B

Percent Recovery vs Percent Polymer

-10

0

10

20

30

40

50

60

70

80

90

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Perc

en

t R

ecovery

(%

)

Percent Polymer (%)

PG 58-28 SBS A PG 58-28 SBS B

PG 52-34 SBS A PG 52-34 SBS B

58-28B SBS A 58-28B SBS B

52-34B SBS A 52-34B SBS B

Percent Recovery vs Percent Polymer

11

0.0

5.0

10.0

15.0

20.0

25.0

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

CT

OD

(m

m)

Percent Polymer (%)

Average CTOD 58-28 SBS A Average CTOD 58-28 SBS B

Average CTOD 64-28 SBS A Average CTOD 64-28 SBS B

Average CTOD 52-34 SBS A Average CTOD 52-34 SBS B

DENT (Average CTOD) vs Percent Polymer

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

CT

OD

(m

m)

Percent Polymer (%)

Average CTOD PG 58-28 SBS A Average CTOD PG 58-28 SBS B

Average CTOD 58-28B SBS A Average CTOD 58-28B SBS B

58-28 DENT (CTOD) vs Percent Polymer

13

-28 MTO PMA Minimum

-28 MTO Unmodified Minimum

0.0

5.0

10.0

15.0

20.0

25.0

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

CT

OD

(m

m)

Percent Polymer (%)

Average CTOD PG 52-34 SBS A Average CTOD PG 52-34 SBS B

Average CTOD 52-34B SBS A Average CTOD 52-34B SBS B

52-34 DENT (CTOD) vs Percent Polymer

14

-34 MTO Minimum

Fatigue Indicator (ε6 ) vs Percent Polymer and Recovery

15

0

100

200

300

400

500

600

700

800

900

0 2 4

Str

ain

Am

plit

ude (

µm

/m)

Percent Polymer (%)

PG 58-28 SBS A

PG 64-28 SBS A0

100

200

300

400

500

600

700

800

900

1000

0 25 50 75

Str

ain

Am

plit

ude (

µm

/m)

Percent Recovery (%)

Logarithmic!64-28 500 µm/m: 2,500,00064-28 700 µm/m: 200,000Results of individual tests

Fatigue Indicator (ε6 ) vs DENT (CTOD)

16

0

200

400

600

800

1000

0 1 2 3 4 5 6 7 8 9 10

Str

ain

Am

plit

ude (

µm

/m)

CTOD (mm)

PG 58-28 SBS A

PG 64-28 SBS A

CTOD: 2.3 mmΕ6: 621.2 µm/m

CTOD: 3.2 mmΕ6: 798.7 µm/m

CTOD: 3.5 mmΕ6: 314.2 µm/m

CTOD: 9.2 mmΕ6: 620.9 µm/m

Bending Beam Rheometer

17

▪ Used to determine Low Temperature Grade, ΔTc, Low Temperature Limiting Grade and Grade Loss▪ Does not characterize SBS modified asphalt very well▪ Extended conditioning times does not change shortcomings with measurement

0.29

0.3

0.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

0 1 2 3 4 5

M-V

alu

e

Percent Polymer (%)

58-28 SBS A

58-28 SBS B

64-28 SBS A

64-28 SBS B

52-34 SBS A

52-34 SBS B

ΔTc = Tc,S - Tc,m

Tc,S – Stiffness Critical TemperatureTc,m – m-Value Critical Temperature

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0% 1% 2% 3% 4%

ΔTc

Percent Polymer (%)

58-28 SBS A 58-28 SBS B 64-28 SBS A 64-28 SBS B 52-34 SBS A

52-34 SBS B 52-34B SBS A 52-34B SBS B 58-28B SBS A 58-28B SBS B

ΔTc vs Percent Polymer

18

Dynamic Shear Rheometer

19

▪ Measures phase angle, modulus (stiffness) with constant shear strain and single frequency• High temperature grade does not predict rutting resistance well• Intermediate temperature grade does not predict cracking resistance well

Glover-Rowe Parameter

▪ Taken from master curve data at reference temperature of 15˚C and frequency of 0.005 rad/s

▪ Damage zone calculated using:

G∗ (cosδ)2/sinδ = 180 kPa

G∗ (cosδ)2/sinδ = 600 kPa or 450 kPa

Cross-Over Temperature

▪ Temperature at which the phase angle of PAV aged material reaches 45°

▪ Phase Angle:• 0˚ = purely elastic• 45˚ = transition between more viscous and

more elastic behaviour• 90˚ = purely viscous

Black Space Diagrams- Close Ups!

20

58-28 64-28 58-28B

52-34 52-34B

Phase Angle Decreases

Phase Angle Increases

Black: 0% SBSGreen: 2% SBSPurple: 4% SBS

Y-Axis: Complex ModulusX-Axis: Phase Angle

Glover-Rowe Parameter vs Percent Polymer

21

10

12

14

16

18

20

22

24

0% 1% 2% 3% 4%

Cro

ss-O

ver

Tem

pe

ratu

re (

°C)

Polymer Concentration

58-28 SBS A 58-28 SBS B

64-28 SBS A 64-28 SBS B

58-28B SBS A 58-28B SBS B

Cross-Over Temperature vs Percent Polymer

22

0

2

4

6

8

10

12

14

16

0% 1% 2% 3% 4%

Cro

ss-O

ver

Tem

pe

ratu

re (

°C)

Polymer Concentration

52-34 SBS A 52-34 SBS B52-34B SBS A 52-34B SBS B

Cross-Over Temperature vs Percent Polymer

23

Linear Amplitude Sweep

24

𝑁𝑓 = 𝐴 𝛾𝑚𝑎𝑥𝐵

Viscoelastic Continuum Damage Model (VECD)

• Number of Cycles to Failure

Fracture Mechanics Approach

• Fatigue Resistance Energy Index (FREI)

▪ Part 1: Frequency Sweep- gives initial binder properties▪ Part 2: Amplitude Sweep- cyclic loading ramps up from 0.1% to 30% applied strain

• Binder begins to crack at edge of sample▪ AASHTO TP 101

▪ Two approaches to data analysis:

𝐹𝑅𝐸𝐼 =𝐽𝑓−𝜏𝑚𝑎𝑥

𝐺0.5𝜏𝑚𝑎𝑥

⋅ 𝛾0.5𝜏𝑚𝑎𝑥

2

LAS (Number of Cycles to Failure) vs Percent Polymer

25

y = 98563x + 504358-28 SBS A R² = 0.99

y = 94293x + 504358-28 SBS B R² = 0.9827

y = 66997x + 382858-28B SBS B R² = 0.9877

y = 72473x + 382858-28B B SBS A R² = 0.9393

y = 69443x + 398064-28 SBS A R² = 0.9829

y = 68867x + 398064-28 SBS B R² = 0.8612

3000

4000

5000

6000

7000

8000

9000

10000

0% 1% 2% 3% 4% 5%

Nu

mb

er o

f C

ycle

s to

Fai

lure

Percent Polymer (%)

58-28 SBS A 58-28 SBS B 58-28B SBS A

58-28B SBS B 64-28 SBS A 64-28 SBS B

LAS (Number of Cycles to Failure) vs Percent Polymer

26

y = 143557x + 508752-34 SBS A R² = 0.9816

y = 140060x + 508752-34 SBS B R² = 0.9893

y = 130663x + 454552-34B SBS A R² = 0.9831

y = 108590x + 454552-34B SBS B R² = 0.9451

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

0% 1% 2% 3% 4% 5%

Nu

mb

er o

f C

ycle

s to

Fai

lure

Percent Polymer (%)

52-34 SBS A 52-34 SBS B

52-34B SBS A 52-34B SBS B

LAS (FREI) vs Percent Polymer

27

y = 71.333x + 3.258-28 SBS A R² = 0.7907

y = 70x + 3.258-28 SBS B R² = 0.717

y = 16.333x + 1.264-28 SBS A R² = 0.8038

y = 22.333x + 1.264-28 SBS B R² = 0.9212

y = 29x + 1.7658-28B SBS A R² = 0.7994

y = 45x + 1.6558-28B SBS B R² = 0.931

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0% 1% 2% 3% 4% 5%

Fati

gue

Res

ista

nce

En

erg

y In

dex

Percent Polymer (%)

58-28 SBS A 58-28 SBS B 64-28 SBS A

64-28 SBS B 58-28B SBS A 58-28B SBS B

LAS (FREI) vs Percent Polymer

28

y = 66x + 5.952-34 SBS A R² = 0.4594

y = 49.333x + 5.952-34 SBS B R² = 0.3635

y = 28.333x + 4.752-34B SBS A R² = 0.3229

y = 12x + 4.752-34B SBS B R² = 0.0916

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0% 1% 2% 3% 4% 5%

Fati

gue

Res

ista

nce

En

erg

y In

dex

Percent Polymer (%)

52-34 SBS A 52-34 SBS B52-34B SBS A 52-34B SBS B

Asphalt Binder Cracking Device

29

▪ ABCD critical temperature based on modulus, phase angle, thermal coefficient of contraction and failure strength of binder

▪ Proposed to replace Direct Tension Test▪ Sample is cooled at constant rate of -10˚C until cracking occurs

▪ AASHTO TP 92

Elwardany, Planche and King, “A Tale of Two Deltas: Toward a Universal “Blind” Framework for Asphalt Durability”, TRB Annual Meeting, January 13, 2020

Tf = Tc,S - Tcr(BBR) (ABCD)

y = -127.5x - 34.11758-28 SBS B R² = 0.9643

y = -90x - 31.73364-28 SBS B R² = 0.999

y = -95x - 39.16752-34 SBS B R² = 0.9991

y = -127.5x - 32.48358-28B SBS B R² = 0.9938

y = -90x - 38.53352-34B SBS BR² = 0.9838

-46

-44

-42

-40

-38

-36

-34

-32

-30

0% 1% 2% 3% 4% 5%

AB

CD

Cra

ckin

g Te

mp

erat

ure

(°C

)

Polymer Concentration (%)

58-28 SBS B 64-28 SBS B 52-34 SBS B 58-28B SBS B 52-34B SBS B

ABCD (Tcr )vs Percent Polymer

30

2.5

3.5

4.5

5.5

6.5

0% 1% 2% 3% 4% 5%

ΔTf

(°C

)

Polymer Concentration (%)

58-28 SBS B

64-28 SBS B

52-34 SBS B

58-28B SBS B

52-34B SBS B

ABCD (ΔTf )vs Percent Polymer

31

Unmodified Asphalt Rankings

32

52-3452-34B58-2858-28B ≈ 64-28

ΔTc Cracking Resistance MoreLess

Cross-Over Temperature Cracking Resistance MoreLess

52-3452-34B58-2858-28B64-28

LAS Cracking Resistance MoreLess

52-3452-34B58-2858-28B ≈ 64-28

ABCD Cracking Resistance MoreLess

52-3452-34B58-2858-28B64-28

Rankings are relative to each other, not definitive measures of performance

Conclusions

33

▪ SBS polymer modified asphalt has a fundamentally different behaviour than unmodified asphalt• It is more elastomeric than purely ductile

▪ Low strain tests and parameters which operate in the linear viscoelastic region seem to be unable to characterize SBS modified asphalt well

• High temperature grade, low temperature grade, DENT, ΔTc / Extended BBR, Cross-Over temperature

▪ Large strain tests produce conditions more comparable to the strains observed in pavements and seem to improve characterization of SBS polymer modified asphalt• MSCR, LAS (VECD or fracture mechanics approach) and ABCD

Recommendations

34

Simpler Binder Characterization

▪ Single specification across Ontario would be optimal

▪ AASHTO M 332 would increase simplicity of rutting characterization

▪ MSCR is suitable for evaluating SBS concentration▪ Ash content is suitable for limiting REOB

▪ More frequent?• Increasing simplicity could allow for

resources to be reallocated to more frequent testing if desired

Mixture Characterization

▪ Best form of characterization▪ Will require multiple years of coordinated work

from industry and owners▪ Gives understanding of final product performance▪ Has been shown to be sensitive to mix and binder

properties

Improved Binder Cracking Characterization?

▪ If necessary, a large strain amplitude cracking test would likely be better suited to characterizing cracking performance for all types of asphalt

Thank You!

35

Contact Information:

Mike Aurilio(289) 260-2934maurilio@yellowline.ca

Research Partners: