arizona update on multiple stress creep recovery and ......ryan stevens civil engineer ii, city of...
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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
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 (%
)
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
