Arizona Update on Multiple Stress Creep Recovery and ......Ryan Stevens Civil Engineer II, City of...

Arizona Update on Multiple Stress Creep Recovery and AASHTO M332 Evaluation

PCCAS Committee Meetings Reno, NV, October 21, 2015

Shane Underwood, Ph.D. Assistant Professor, School of Sustainable Engineering and the Built Environment Civil, Environmental, and Sustainable Engineering Arizona State University

Ryan Stevens Civil Engineer II, City of Phoenix

Jeff Stempihar, Ph.D., P.E. Research Assistant Professor Arizona State University

Dharminder Paul Pal, P.E. Bituminous Engineer, Arizona Department of Transportation

1

Overview

Background on ADOT efforts Agency questions ASU study to address these

questions Experiences and findings Next steps

2

Background RMAUPG meeting and

presentation from John D’Angelo in 2007-2008

Dan Anderson, ADOT asphalt lab supervisor • ADOT central lab began

testing using the MSCR test in 2008 and test has been performed almost continuously since.

• AASHTO TP 70 & AASHTO T 350

3

Background Database

• 342 binder samples • 5 state suppliers • 10 binder grades (4 primary and 6

in a more limited capacity) • Mostly non-modified • WCTG asphalts (x 21)

Tested with three different instruments • 2008-2012 Malvern (2) • 2013-2014 Anton-Paar (1)

Test temperatures • Standard M320 high temperature

grade • High temperature grade -6 and -

12 (limited subset) 4

Agency Questions Are manufacturer supplied calculations accurate? Are there any biases in results obtained from

different instruments? Does the method detect the presence of Arizona

modifiers? What would be the result of a change to the

AASHTO M332 grading system? • How variable would the materials appear to be under this system? • What grades would the current state binders receive under the new

system? • What would this change mean for suppliers (number of grades

required throughout the state, control protocols, delivered product, etc.)?

• Would this change yield paving materials with better value?

5

ASU Study Objective To evaluate the Arizona Department of

Transportation (ADOT) Multiple Stress Creep Recovery (MSCR) test database and provide ADOT with the necessary information to answer their questions and participate in regional MSCR/ AASHTO M332 task groups.

6

Study Methodology Review of MSCR data

• Verify calculations • Check for equipment biases

AASHTO M332 shadow grade assessment • Calculate differences in MSCR and regular DSR

(|G*|/sin δ) parameters over time by supplier • Determine the traffic grade of each binder at the

standard high temperature. Multi-grade assessment

• Evaluate relationship between traffic grade and test temperature changes

State-wide specification impacts 7

8

Disclaimer: We are using data from binders produced under the M320 system to “guess” at what would occur with binders produced under a M332 system

MSCR Test

9 Source: Gierhart, 2013

AASHTO T 350 Repeated shear

creep and recovery loading at level exceeding the

viscoelastic limit of the material

cε pε

rε

Source: Anderson, M., A.I.

( )3.2 3.2

c rnrJ

ε ε−=

( )3.2 100c p

c

Rε ε

ε

−= ×

10

MSCR Test

0

20

40

60

80

100

0 0.5 1 1.5 2

R3.

2 (%

)

Jnr@3.2kPa

Modified

Unmodified

11

MSCR Test

AASHTO M332 The AASHTO M332 binder grade was

determined for each binder at AASHTO M320 high temperature grade.

Traffic (ESALS, millions)

AASHTO M332 Grade

Orig. Binder DSR @

64°C

RTFO MSCR @ 64°C PAV Binder DSR @

25°C Jnr3.2(kPa-1) Jnr%Diff

Standard (<10m) PG64S-22

|G*|/sinδ ≥ 1.0(kPa)

≤ 4.5

≤ 75%

|G*|sinδ ≤ 5000(kPa)

Heavy (10~30m) PG64H-22 ≤ 2.0

|G*|sinδ ≤ 6000(kPa)

Very Heavy (>30m) PG64V-22 ≤ 1.0

Extreme (>30m+sitting) PG64E-22 ≤ 0.5

12

0

1

2

3

4

5

0 1 2 3 4 5

J nr3

.2(k

Pa-1

) -AD

OT

Jnr3.2 (kPa-1) - ASU

MalvernB

MalvernA

Verifying Manufacturer Calculations

13

0

20

40

60

80

100

0 20 40 60 80 100

J nrd

iff (%

) -AD

OT

Jnrdiff (%) - ASU

Original Calculation

Corrected Calculation

Verifying Manufacturer Calculations

14

[ ]3.2 0.1

0.1

100nr nrnrdiff

nr

J JJ

J−

= ×

Shadow Grade Assessment

15

1.E-1

1.E+0

1.E+1

1/1/2008 9/17/2009 6/4/2011 2/18/2013 11/5/2014

J nr3

.2 (k

Pa-1

)

Sample Date

I J K

PG 76S-16

PG 76V-16

PG 76H-16

PG 76E-16

Current Grading Results (Orig.)

16

Current Grading Results (RTFO)

17 1.E-1

1.E+0

1.E+1

1/1/2008 5/15/2009 9/27/2010 2/9/2012 6/23/2013 11/5/2014

|G*|/

sin δ

(kPa

)

I J K

Parameter Comparison

18

1.E-1

1.E+0

1.E+1

1/1/2008 5/15/2009 9/27/2010 2/9/2012 6/23/2013 11/5/2014

|G*|/

sinδ

(kPa

)

I J K

1.E-1

1.E+0

1.E+1

1/1/2008 9/17/2009 6/4/2011 2/18/2013 11/5/2014

J nr3

.2 (k

Pa-1

)

Sample Date

I J K

PG 76S-16

PG 76V-16

PG 76H-16

PG 76E-16

Shadow Grade Assessment Grade Supplier % by Traffic Grade

Fail S H V E

PG 76-16 I – 92 8 – – J – 91 9 – – K – 100 – – –

PG 70-10 K 5 95 – – – L – 97 3 – –

PG 64-22

I – 100 – – – J – 100 – – – K – 100 – – – L – 96 4 – –

PG 64-16

I – 71 29 – – J – 90 10 – – K – 100 – – – L – 100 – – –

PG 58-22 J – 47 29 24 L – – 57 37 6 19

Shadow Grade Assessment

0

1

2

3

4

5

1/1/2008 9/17/2009 6/4/2011 2/18/2013 11/5/2014

J nr3

.2 (k

Pa-1

)

Sample Date

I J K L MPG 58S-22

PG 58H-22

PG 58V-22PG 58E-22

20

Shadow Grade Assessment Apparent Relative Variability between T350 and T315

0

1

2

3

4

5

J nr3

.2(k

Pa-1

)

I J K

0

1

2

3

4

5

|G*|/

sinδ

(kPa

)

I J K

CV = 0.22 CV = 0.21 CV = 0.12

CV = 0.24 CV = 0.19 CV = 0.09

AASHTO T350 (MSCR) AASHTO T315 (|G*|)

21

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0 0.1 0.2 0.3 0.4 0.5 0.6

CV

of J

nr3.

2Pa

ram

eter

CV of |G*|/sinδ Parameter

PG 76-16 PG 70-22TR+PG 70-22 PG 70-10PG 64-28 PG 64-22PG 64-16 PG 58-22

Shadow Grade Assessment Apparent Relative Variability between T305 and T315

22

Multi-Grade Assessment Current Issue Identified

Since the grade of a binder in the M332 system is based on both temperature and climate a single binder can have multiple grades depending on the temperature tested.

Example • A binder has a Jnr3.2 = 3.5 kPa-1 at 64°C

PG 64S-22 • The same binder has a Jnr3.2 = 1.8 kPa-1 at

58°C PG 58H-22 23

Multi-Grade Assessment Temperature-Traffic Interaction Effect - Method

WCTG binders and subset of AZ binders (total of 38) tested at same high temperature as before plus temperatures of 6 and 12° less.

Additional set of 8 binders tested at different intermediate temperatures in order to evaluate stiffness change

24

Multi-Grade Assessment Intermediate Temperature Effects

25

Multi-Grade Assessment

0

0.2

0.4

0.6

0.8

1

0 3 6 9 12 15

Nor

mal

ized

Jnr

3.2

Para

met

er

Delta T (°C)

( )( )

0

3.2 0.1622

3.2

nr TT

nr T

Je

J− ×∆∆ =

26

Multi-Grade Assessment

0.0

1.0

2.0

3.0

4.0

0 3 6 9 12 15

Delta T (°C)

PG76-16 (I) PG76-16 (K)PG76-16 (M) PG70-22 (I)PG70-22 (I2) PG70-22 (K)PG70-22 (M) PG70-10 (K)Average

( )( ) ( ) ( )

0

2

2

* sin0.009 0.100 1

* sin

0.99998

T

T

GT T

G

R

δ

δ∆ = ∆ + ∆ +

=

27

Nor

mal

ized

Fat

igue

Par

amet

er

Multi-Grade Assessment All Binder Grades

No. Samples %S %H %V %E %Fail

Original Traffic Grade* 342 75.7 14.9 6.7 2.3 < 1.0

Traffic Grade at 6°C Temperature Drop 342 0.0 44.4 37.1 13.2 5.3

Traffic Grade at 12°C Temperature

Drop 342 0.0 0.0 9.1 64.5 26.4

28

*Excluding PG 58-22: N = 281; S = 85.8%, H = 8.9%; V = 2.8%, E = 2.1%, F < 1%

Multi-Grade Assessment Reality Check

29

Multi-Grade Assessment Only Relevant Grades

No. Samples %S %H %V %E %Fail

Original Traffic Grade 258 79.1 14.0 5.8 0.8 < 1.0

Traffic Grade at 6°C Temperature Drop 100 0 34.0 43.0 11.0 3.3

Traffic Grade at 12°C Temperature

Drop 31 0 0 6.5 83.9 9.7

30

*Excluding PG 58-22: N = 197; S = 94.4%, H = 5.1%; V = 0.0%, E = 0.0%, F < 1%

POLYMER MODIFIED SYSTEMS DETECTION AND BEHAVIOR

31

Materials

32

Group Binder Grade Samples Sample #

A PG 76-22TR+ 10 1-10 PG 70-22TR+ 13 11-23

B

PG 76-22TR+, 76 4

24-27 28-31 PG 76-22TR+, 70

PG 76-22TR+, 64 32-35 PG 70-22TR+, 70 7 36-42 PG 70-22TR+, 64 43-49

C

PG 76-28 3 50-52 PG 76-22 2 53-54 PG 70-34 1 55 PG 70-28 5 56-60 PG 70-22 5 61-65 PG 64-34 2 66-67 PG 64-28 4 68-71

TR+ Specification Composition

• Minimum 8% crumb rubber Wright Process

• Minimum 2% SBS polymer • 97.5% minimum solubility in TCE

Rheology • Conforms to AASHTO M320 • Minimum 55% elastic recovery at 25°C • Softening point (54° or 60° min) • Maximum phase angle at high temperature

grade = 75°

33

1.E-2

1.E-1

1.E+0

1.E+1

0 5 10 15 20 25

Jnr@

3.2k

Pa

Sample Number

PG76-22TR+ (Group A)

PG70-22TR+ (Group A)

S

H

V

E

Results AZ TR+ Binders

34

1.E-2

1.E-1

1.E+0

1.E+1

23 28 33 38 43 48 53

Jnr@

3.2k

Pa

Sample Number

PG76-22TR+, 76 PG76-22TR+, 70PG76-22TR+, 64 PG70-22TR+, 70PG70-22TR+, 64

S

H

V

E

Results AZ TR+ Binders at Multiple Temperatures

35

1.E-2

1.E-1

1.E+0

1.E+1

49 54 59 64 69 74

Jnr@

3.2k

Pa

Sample Number

PG 76-28 PG 76-22 PG 70-34 PG 70-28

PG 70-22 PG 64-34 PG 64-28

S

H

V

E

Results Alternative Modified Systems

36

0

20

40

60

80

100

0 1 2 3 4 5

R3.

2 (%

)

Jnr3.2 (kPa-1)

PG 76-22 TR+PG 70-22 TR+PG 76-16PG 70-22PG 70-10WCTG

Modified

Unmodified

Detection of Polymer Modification

PG 70-22ER

PG 70-22 PG 64-28

37

0

20

40

60

80

100

0 1 2 3 4 5

R3.

2 (%

)

Jnr3.2 (kPa-1)

PG 70-16 (PG 76-16)

PG 64-16 (PG 76-16)

PG 64-22 (PG 70-22)

PG 64-10 (PG 70-10)

WCTG

Modified

Unmodified

Detection of Polymer Modification

PG 70-22

PG 64-28

PG 70-22ER

38

0

20

40

60

80

100

0.00 0.50 1.00 1.50 2.00

R3.

2 (%

)

Jnr@3.2kPa

PG76-22TR+, 76 PG70-22TR+, 70PG76-22TR+, 70 PG76-22TR+, 64PG70-22TR+, 64

Modified

Unmodified

39

Results AZ TR+ Binders at Multiple Temperatures

Grading System in Arizona

Currently ADOT purchases asphalt in one of 8 grades • Major (3) = PG 76-

16, PG 70-10, and PG 64-22

• Minor (4) = PG 70-22, PG 64-28, PG 58-28, and PG 58-22

• Very Minor (1) = PG 64-16

40

Grading System in Arizona

Strict adherence to M332 would require 13 different asphalt grades • Major (3) = PG 70H-10,

PG 70S-10, and PG 64S-22

• Minor (7) = PG 76S-16, PG 70S-16, PG 64H-22, PG 64S-16, PG 64S-10, PG 58H-22, and PG 58S-22

• Very Minor (3) = PG 70H-16, PG 64H-10, and PG 64S-28 41

Summary

ADOT has tested more than 300 individual binder samples and confirmed that most non-modified binders are “Standard” under their current high temperature grade.

General rule of thumb for these binders is that every single drop in high temperature grade will result in a one traffic grade bump. 42

Summary

A strict implementation of AASHTO M332 for Arizona would result in 13 different asphalt grades with PG 70H-10, PG 70S-10, and PG64S-22 accounting for approximately 75% of the binder used.

Next steps forward • Verification of potential for MSCR based

grading to yield better value. • Adjustment and reduction of potential binder

grades through engineering judgment.

43

Thank You

44

Shane.Underwood@asu.edu; JStempihar@azdot.gov