Understanding the MSCR Test and
its Use in the PG Asphalt Binder
Specification
R. Michael Anderson, Asphalt Institute
31 August 2011
MSCR Webinar
• Webinar Objectives
– Understand why the MSCR test is needed to
characterize the performance of asphalt
binders
– Understand how the test is performed
– Understand how and why the MSCR test
values – Jnr, %Recovery, and Stress
Sensitivity – are used
– Understand how the proposed specification
works
Acknowledgments
• DTFH61-08-H-00030
– Cooperative Agreement between the FHWA
and the Asphalt Institute
• John Bukowski, AOTR
• John A. D’Angelo
• Asphalt Binder ETG
• Member Companies of the Asphalt
Institute
– Technical Advisory Committee
How Asphalt Behaves
• Behavior is affected by :
– Temperature
– Time of Loading
– Age of pavement or service life
60C
1 hour
25C
1 hour
10 hours
Pavement Behavior – High
Temperature
• Permanent Deformation
• Mixture is Plastic
– wheel path rutting
– shoving at intersections
• Depends on
– asphalt cement (some)
– mineral aggregate (some)
– volumetric proportioning (some)
Testing of Asphalt Cements
• Characteristics of Asphalt Cements
– Consistency
• term used to describe the viscosity or degree of
fluidity of asphalt at any particular temperature
• varies with temperature
– necessary to define an equivalent temperature or an
equivalent consistency when comparing temperatureconsistency characteristics of asphalt cements
Viscosity
• Absolute Viscosity
– ASTM D2171; AASHTO T202
– Conducted at 60°C (140°F)
– Uses partial vacuum to induce flow through
capillary tube
• Kinematic Viscosity
– ASTM D2170; AASHTO T201
– Conducted at 135°C (275°F)
– Uses gravity to induce flow through capillary tube
Viscosity
Asphalt Cement
• Viscosity Graded Asphalt
– 60°C (140°F) selected to simulate in-service
temperature of asphalt pavements
– 135°C (275°F) selected to simulate mixing
and laydown temperature for HMA
Problems with Previous Systems
• Penetration
– empirical measure of viscous and elastic effects
• Viscosity
– viscous effects only
• No Low Temperature Properties Measured
• Problems Characterizing Modified Asphalt
Binders
– Specification proliferation
• Long Term Aging not Considered
Apparent Viscosity, P
Problems with Previous Systems
32,000
PBA-6A
30,000
28,000
26,000
24,000
22,000
20,000
0.00
0.50
1.00
Shear Rate, s-1
1.50
PG System Concept
“the values of the specification criteria that
warrant against distress are independent of
temperature, but the values must be obtained
at different temperatures according to climate.”
This implies test measurements at
temperatures and loading rates consistent
with conditions existing in the pavement.
Superpave Binder Testing
• Performance-Based Physical Properties Measured by
–
–
–
–
Rotational Viscometer (RV) (high temps)
Dynamic Shear Rheometer (DSR) (high, intermediate temps)
Bending Beam Rheometer (BBR) (low temps)
Direct Tension Tester (DTT) (low temps)
- 22
20
64
Pavement Temperature (oC)
135
Performance Grades
Performance-Related Requirements
•
Shearing resistance to resist traffic loads
– Upper specification temperature
– G*/sin  1.00 kPa Tank
– G*/sin  2.20 kPa RTFOT residue
Grade-Bumping: Used to Increase
Rutting Resistance (AASHTO M 323)
The SHRP PG Binder Tests
•
Dynamic Shear Rheometer (DSR),
AASHTO T315
–
for determining the modulus (stiffness) of
asphalt binders at intermediate and upper
pavement temperatures.
Dynamic Shear Rheometer
• Test procedure results in complex
modulus and phase angle
– Specification test is conducted at 10 rad/s
– Temperature range from 3°C to 88°C
• Parallel plate geometry
• Valid for linear viscoelastic materials
– Materials with moduli that are independent of
applied stress or strain
• Particles must be < 250 microns
DSR Test Fundamentals
• Asphalt binder is
placed between two
parallel plates
• Upper plate it is
rotated with respect
to lower plate
• Cyclical rotation A-B-A-C-A-B-A-C-A, etc.
• Maximum stress and strain in each
direction are measured
Elastic:  = 0 deg
max
Viscous:  = 90 deg
max
Applied
Shear
Stress
time
max
max
Resulting
Shear
Strain
time
time lag converts to 
Viscoelastic: 0 <  < 90°
Applied
Shear
Stress
max
time
G* =
max

max
max
360tf
 = 2p
Resulting
Shear
Strain
time
Asphalt A
Asphalt B
G*
Viscous Part
(G′′)
Viscous Part (G′′)
G*

Elastic Part
(G′)

Elastic Part (G′)
Viscous Part (G′′)
sin  =
G*
Shortcomings of G*/sin 
• G*/sin  as a High Temperature Parameter
– Properties determined in Linear Viscoelastic
(LVE) region
• No damage behavior
– Rutting is a non-linear failure
– Polymer-modified systems engaged in non-linear region
• Characterizes stiffness
– Related to rutting
Effect of Phase Angle
1.00
Sin 
0.98
0.96
0.94
0.92
0.90
60
65
70
75
80
Phase Angle, degrees
85
90
ALF Study - 7 Asphalt Binders
AZ
PG
CRM
Air
TX
SBS
TP
70-22
---Blown
TBCR
Control
70-22
PG
70-22 PG
SBS Air
SBS TP
+
70-22 64-40 Blown
Fibers
1
7
2
3
4
5
6
8
9
10
11
12
Relationship between G*/ sinδ
and ALF rutting
12
10
y = -7.4519x + 10.956
R2 = 0.1261
G*/sin d 64C
8
6
4
Existing SHRP specification has poor
relationship to rutting for modified systems.
2
0
0
0.1
0.2
0.3
0.4
rutting inches
0.5
0.6
0.7
0.8
NCHRP 9-10
• NCHRP 9-10 Asphalt Binders
–
–
–
–
–
–
–
–
–
PG 82-22 SBS-radial
PG 82-22 Polyethylene-stabilized
PG 82-22 Steam Distilled
PG 82-22 SBR-low molecular weight
PG 76-22 Ethylene Terpolymer
PG 76-22 Oxidized
PG 58-40 SBS-linear
PG 58-40 SB Di-block
PG 58-40 Oxidized
NCHRP 9-10 Binders
Excerpt from NCHRP Report 459, Characterization of Modified
Asphalt Binders in Superpave Mix Design
Kentucky 70-22 Study
October 2001
Kentucky 70-22 Study
• Kentucky PG 70-22 Study (1996)
– Evaluate PG 70-22 asphalt binders produced by
different methods
•
•
•
•
SBS (2)
SBR
Gel
Select Crude
– I-64 near Winchester
• Duplicate 1-mile test sections using each asphalt binder
• Asphalt binder and mixture testing
Effect of Binder G*/sin  on Mixture
Permanent Shear Strain
25000
RSCH @58C, microstrain
20000
y = 19270.79e-0.09x
R2 = 0.42
15000
10000
5000
0
0.00
2.00
4.00
6.00
RTFO G*/sin , 70C
8.00
10.00
PG Grading Alone Does Not Always
Predict Performance
• Study of the two mixes with the same
aggregate structure, but different binders.
PG 63-22 modified, no rutting
PG 67-22 unmodified, 15mm rut
AASHTO M320 and PolymerModified Binders
• Why doesn’t AASHTO M320 properly
characterize polymer-modified binders?
– Current spec, G* and δ are measured in the
linear viscoelastic range.
– For neat asphalts, flow is linear and not sensitive
to the stress level of the test.
– For polymer-modified binders, the response is not
linear and sensitive to the stress level of the test.
The polymer chains can be rearranged
substantially as the stress increases.
AASHTO M320 and PolymerModified Binders
• What happened as a result of the inability to
properly characterize polymer-modified
binders?
– Most states began requiring additional tests to the
ones required in AASHTO M320
• These mostly empirical tests are commonly referred to
as “PG Plus” tests
• These tests are not standard across the states –
difficult for suppliers
• Even some of the tests that are the most common, e.g.
Elastic Recovery, are not run the same way from state
to state
States with a “PG Plus”
Specification
*
*
*
PG Plus Spec
No PG Plus Spec
NCHRP 9-10:
High Temperature Testing
• Repeated Shear Creep
– Analogous to mixture test (RSCH)
– Performed in DSR
•
•
•
•
Controlled shear stress (i.e., 25 Pa or 300 Pa)
100 cycles
1-second load, 9-second rest per cycle
High test temperature (HT-?)
– Response: permanent shear strain (p) or strain slope
Perm. Shear Strain, %
Repeated Shear Creep
14
12
Recoverable shear strain
10
8
Instantaneous
shear strain
6
Permanent
shear strain
4
2
0
0
2
4
6
Time, seconds
8
10
NCHRP 9-10
Excerpt from NCHRP Report 459, Characterization of Modified
Asphalt Binders in Superpave Mix Design
NCHRP 9-10
Jnr = 0.105 /0.3 kPa
= 0.35 kPa-1
Rec = (0.125 – 0.105)/0.125
= 16%
Jnr = 0.075 /0.3 kPa
= 0.25 kPa-1
Rec = (0.125 – 0.075)/0.125
= 40%
γpeak
γnr
Jnr = 0.045 /0.3 kPa
= 0.15 kPa-1
Rec = (0.125 – 0.045)/0.125
= 64%
Excerpt from NCHRP Report 459, Characterization of Modified
Asphalt Binders in Superpave Mix Design
Perm. Shear Strain, %
Repeated Shear Creep
NCHRP 9-10: PG 82 Binders
Repeated Shear Creep (70C, 300Pa)
14
12
10
8
6
4
2
0
Ox
PE-s
SBS-r
0
200
400
600
Time, seconds
800
1000
NCHRP 9-10: Relationship of Binder
RCR to Mixture Rutting
Excerpt from NCHRP Report 459, Characterization of Modified
Asphalt Binders in Superpave Mix Design
Problem Statement
• Provide Users a High Temperature Binder Spec
Blind to Modification
• Provide Users with alternatives to the empirical
Superpave Plus tests
– Elastic Recovery
– Ductility/ Force Ductility
– Toughness and Tenacity
• Approach: Develop AASHTO/ASTM Standard
Practice for Superpave Plus Specifications
– DSR
• Multiple Stress Creep Recovery
High Temperature Specification
Parameter Related to Rutting
• Any new specification must be blind to
modification.
• A new specification must identify the
rutting potential of all binder types under
multiple conditions.
• Binders are stress sensitive and different
mix tests apply different stress conditions.
Multiple Stress Creep Recovery Test
• Performed on RTFO-aged Binder
• Test Temperature
– Environmental Temperature
– Not Grade-Bumped
• 10 cycles per stress level
– 1-second loading at specified shear stress
• 0.1 kPa
• 3.2 kPa
– 9-second rest period
Standard Test Procedure
developed for AASHTO
Multiple Stress Creep Recovery
• The test method is detailed in AASHTO TP70
• The test uses the same Dynamic Shear
Rheometer (DSR) as required in M320
• Only minor software changes are need to run
the MSCR test
• The test uses the creep and recovery method
to measure the percent recovery and nonrecoverable creep compliance (Jnr)
Multiple Stress Creep Recovery
Definitions:
Creep and recovery – a standard test protocol whereby a
specimen is subjected to a constant load for a fixed time
period and then allowed to relax (recover) at a zero load
for a fixed time period
Percent Recovery – A measure of how much the sample
returns to its previous shape after being repeatedly
stretched and then relaxed
Non-Recoverable Creep Compliance (Jnr) – a measure
of the amount of residual strain left in the specimen after
repeated creep and recovery, relative to the amount of
stress applied
Multiple Stress Creep Recovery Test
• Calculate Non-recoverable Creep
Compliance (Jnr)
– Non-recoverable shear strain divided by
applied shear stress
• “J” = “compliance”
• “nr” = “non-recoverable”
• Calculate Recovery for each Cycle, Stress
– Difference between strain at end of recovery
period and peak strain after creep loading
Perm. Shear Strain, %
MSCR
14
12
Recoverable shear strain
10
8
Instantaneous
shear strain
6
Non-recoverable (permanent)
shear strain
4
2
0
0
2
4
6
Time, seconds
8
10
MSCR – Non-Recoverable Compliance
(Jnr)
Jnr =
80
Unrecovered Shear Strain
Applied Shear Stress
70
Strain, %
60
50
Cycle 3 Unrecovered
(permanent) strain
40
Cycle 2 Unrecovered
(permanent) strain
30
20
Cycle 1 Unrecovered
(permanent) strain
10
0
0
5
10
15
20
25
Time, seconds
30
35
40
MSCR – Non-Recoverable Compliance
(Jnr)
0.1 kPa Shear Stress
0.80
0.70
Jnr =
Strain
0.60
Unrecovered Shear Strain
Applied Shear Stress
0.50
Jnr =
0.40
0.197
= 1.97 kPa-1
0.1 kPa
0.30
0.20
0.197
0.10
Cycle 1 Unrecovered
(permanent) strain
0
0
5
10
15
20
25
Time, seconds
30
35
40
Normalized Creep and Recovery Cycles
for a Neat PG 70-22 @ 0.1 kPa and 70ºC
40.0
Normalized strain [%]
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
0.00
20.00
40.00
60.00
Time [s]
80.00
100.00
Normalized Creep and Recovery Cycles
for a Neat PG 70-22 @ 3.2 kPa and 70ºC
1400
Normalized strain [%]
1200
1000
800
600
400
200
0
0.0
20.0
40.0
60.0
Time [s]
80.0
100.0
Normalized Creep and Recovery Cycles
for a PMA PG 70-28 @ 0.1 kPa and 58ºC
7
6
Normalized strain%
5
4
3
2
1
0
0
20
40
60
Time s
80
100
Normalized Creep and Recovery Cycles
for a PMA PG 70-28 @ 3.2 kPa and 58ºC
200
Normalized strain %
150
100
50
0
0
20
40
60
time s
80
100
MSCR Calculations: Jnr
Meas. Pts.
Time
[s]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0.1
0.2
0.3
0.4
0.5
0.6
0.701
0.801
0.901
1.001
1.101
1.201
1.301
1.401
1.501
1.601
1.701
1.801
1.901
2.001
Shear Stress Strain
[Pa]
[%]
100
2.69374
100
4.93844
100
6.80793
100
8.44763
100
9.9813
100
11.3947
100
12.7678
100
14.0523
100
15.3203
100
16.5372
1.911E-23
15.1257
0
13.9755
0
13.2543
0
12.6937
0
12.2402
0
11.8613
0
11.5305
0
11.2409
0
10.9871
0
10.7647
0 = initial strain
r = strain at the end of recovery
10 = total strain at 10 seconds
τ = applied shear stress, kPa
10 = (r – 0)/100
10
Jnr =
95
96
97
98
99
100
9.5
9.6
9.701
9.801
9.901
10.001
0
0
0
0
0
0
6.59212
6.57239
6.55293
6.53421
6.51511
6.49638
τ
MSCR Calculations: Jnr
Meas. Pts.
Time
[s]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0.1
0.2
0.3
0.4
0.5
0.6
0.701
0.801
0.901
1.001
1.101
1.201
1.301
1.401
1.501
1.601
1.701
1.801
1.901
2.001
95
96
97
98
99
100
9.5
9.6
9.701
9.801
9.901
10.001
Shear Stress Strain
[Pa]
[%]
100
2.69374
100
4.93844
100
6.80793
100
8.44763
100
9.9813
100
11.3947
100
12.7678
100
14.0523
100
15.3203
100
16.5372
1.911E-23
15.1257
0
13.9755
0
13.2543
0
12.6937
0
12.2402
0
11.8613
0
11.5305
0
11.2409
0
10.9871
0
10.7647
0
0
0
0
0
0
6.59212
6.57239
6.55293
6.53421
6.51511
6.49638
0 = initial strain = 0 for 1st cycle
r = strain at the end of recovery
10 = total strain at 10 seconds
τ = applied shear stress, kPa
10 = (r – 0)/100 = (6.49638 – 0)/100
10 = 0.0649638
τ = 100/1000 = 0.1 kPa
10
Jnr =
τ
=
Jnr = 0.650 kPa-1
0.0649638
0.1
MSCR Calculations
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
MSCR Calculations: Jnr
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
Jnr = non-recoverable strain at the end
of the cycle divided by applied stress
MSCR Calculations: Jnr
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
Jnr =
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
10 (not expressed as a %)
Stress (expressed in kPa)
MSCR Calculations: Jnr
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
Jnr =
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
2.89698%
100%
100 Pa
1000 Pa/kPa
= 0.289698
MSCR Calculations: Recovery
Meas. Pts.
Time
[s]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0.1
0.2
0.3
0.4
0.5
0.6
0.701
0.801
0.901
1.001
1.101
1.201
1.301
1.401
1.501
1.601
1.701
1.801
1.901
2.001
95
96
97
98
99
100
9.5
9.6
9.701
9.801
9.901
10.001
Shear Stress Strain
[Pa]
[%]
100
2.69374
100
4.93844
100
6.80793
100
8.44763
100
9.9813
100
11.3947
100
12.7678
100
14.0523
100
15.3203
100
16.5372
1.911E-23
15.1257
0
13.9755
0
13.2543
0
12.6937
0
12.2402
0
11.8613
0
11.5305
0
11.2409
0
10.9871
0
10.7647
0
0
0
0
0
0
6.59212
6.57239
6.55293
6.53421
6.51511
6.49638
0 = initial strain
c = strain at the end of creep
1 = total strain at 1 second
r = strain at the end of recovery
10 = total strain at 10 seconds
1 = c – 0
10 = r – 0
1 – 10
Recovery = 100 x
1
MSCR Calculations: Recovery
Meas. Pts.
Time
[s]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0.1
0.2
0.3
0.4
0.5
0.6
0.701
0.801
0.901
1.001
1.101
1.201
1.301
1.401
1.501
1.601
1.701
1.801
1.901
2.001
95
96
97
98
99
100
9.5
9.6
9.701
9.801
9.901
10.001
Shear Stress Strain
[Pa]
[%]
100
2.69374
100
4.93844
100
6.80793
100
8.44763
100
9.9813
100
11.3947
100
12.7678
100
14.0523
100
15.3203
100
16.5372
1.911E-23
15.1257
0
13.9755
0
13.2543
0
12.6937
0
12.2402
0
11.8613
0
11.5305
0
11.2409
0
10.9871
0
10.7647
0
0
0
0
0
0
6.59212
6.57239
6.55293
6.53421
6.51511
6.49638
0 = initial strain = 0 for 1st cycle
c = strain at the end of creep
r = strain at the end of recovery
1 = c – 0 = 16.5372 – 0 = 16.5372
10 = r – 0 = 6.49638 – 0 = 6.49638
Recovery = 100 x
16.5372 – 6.49638
16.5372
Recovery = 60.7%
MSCR Calculations: Recovery
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
Recovery = ratio of recoverable strain
to total strain
MSCR Calculations: Recovery
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
Recovery =
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
1 - 10
1
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
x 100%
MSCR Calculations: Recovery
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
Recovery =
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
5.65359 – 2.89698 x 100% = 48.8%
5.65359
Stress Sensitivity Parameter
Jnr, diff =
(Jnr, 3.2kPa - Jnr, 0.1kPa)
x 100 ≤ 75%
Jnr, 0.1kPa
For polymer-modified binders, the strain response is not
linear and sensitive to the stress level of the test. The
polymer chains can be rearranged substantially as the stress
increases. This parameter is a check on the phenomenon.
MSCR Calculations
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
c
215.2849
329.1282
439.8686
550.9107
662.9821
775.9253
889.6097
1003.761
1118.101
1232.409
1
185.0663
184.0163
184.589
185.3816
186.0347
186.3401
186.525
186.6063
186.5684
186.388
r
145.1119
255.2796
365.5291
476.9474
589.5852
703.0847
817.1547
931.5326
1046.021
1160.374
-1
10
Recovery Jnr, kPa
114.8933
37.9
0.359
110.1677
40.1
0.344
110.2495
40.3
0.345
111.4183
39.9
0.348
112.6378
39.5
0.352
113.4995
39.1
0.355
114.07
38.8
0.356
114.3779
38.7
0.357
114.4884
38.6
0.358
114.353
38.6
0.357
39.2
0.353
3,200
0
30.21859
145.1119
255.2796
365.5291
476.9474
589.5852
703.0847
817.1547
931.5326
1046.021
MSCR Calculations
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
Stress
Cycle
1
2
3
4
5
6
7
8
9
10
Average
100
0
0
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
c
5.724265
9.060554
12.20788
15.26679
18.27734
21.25832
24.21541
27.14828
30.06472
32.9752
1
5.724265
5.689118
5.68006
5.670252
5.66398
5.66407
5.6629
5.65705
5.65105
5.65359
r
3.371436
6.52782
9.596538
12.61336
15.59425
18.55251
21.49123
24.41367
27.32161
30.21859
-1
10
Recovery Jnr, kPa
3.371436
41.1
0.337
3.156384
44.5
0.316
3.068718
46.0
0.307
3.016822
46.8
0.302
2.98089
47.4
0.298
2.95826
47.8
0.296
2.93872
48.1
0.294
2.92244
48.3
0.292
2.90794
48.5
0.291
2.89698
48.8
0.290
46.7
0.302
c
215.2849
329.1282
439.8686
550.9107
662.9821
775.9253
889.6097
1003.761
1118.101
1232.409
1
185.0663
184.0163
184.589
185.3816
186.0347
186.3401
186.525
186.6063
186.5684
186.388
r
145.1119
255.2796
365.5291
476.9474
589.5852
703.0847
817.1547
931.5326
1046.021
1160.374
-1
10
Recovery Jnr, kPa
114.8933
37.9
0.359
110.1677
40.1
0.344
110.2495
40.3
0.345
111.4183
39.9
0.348
112.6378
39.5
0.352
113.4995
39.1
0.355
114.07
38.8
0.356
114.3779
38.7
0.357
114.4884
38.6
0.358
114.353
38.6
0.357
39.2
0.353
3,200
0
30.21859
145.1119
255.2796
365.5291
476.9474
589.5852
703.0847
817.1547
931.5326
1046.021
Stress Sensitivity =
Jnr,3.2 – Jnr,0.1
Jnr,0.1
Stress Sensitivity =
0.353 – 0.302
0.302
Stress Sensitivity =
0.17
MSCR and Rutting
• What is the relationship of Jnr to Rutting?
– The relationship was determined with many
field and lab studies using many modified and
neat binders.
– During Specification development many
stress levels where evaluated in the test.
Relationship between G*/ sinδ
and ALF rutting
12
10
y = -7.4519x + 10.956
R2 = 0.1261
G*/sin d 64C
8
6
4
Existing SHRP specification has poor
relationship to rutting for modified systems.
2
0
0
0.1
0.2
0.3
0.4
rutting inches
0.5
0.6
0.7
0.8
Relationship between Jnr and ALF
Rutting 25.6kPa
2.5
Jnr = (4.74*Rut Depth) - 1.17
R2 = 0.82
2
1.5
Jnr
MSCR can adjust for field
conditions and has excellent
relations to performance.
1
0.5
0
0
0.1
0.2
0.3
0.4
0.5
ALF Rutting, in
0.6
0.7
0.8
Effect of Binder G*/sin  on Mixture
Permanent Shear Strain
25000
RSCH @58C, microstrain
20000
y = 19270.79e-0.09x
R2 = 0.42
15000
10000
5000
0
0.00
2.00
4.00
6.00
RTFO G*/sin , 70C
8.00
10.00
Effect of Binder Jnr on Mixture
Permanent Shear Strain
25000
y = 8633.20e0.58x
R² = 0.71
RSCH @58C, microstrain
20000
15000
10000
5000
0
0.00
0.20
0.40
0.60
0.80
1.00
Jnr @3.2kPa, 64C (kPa-1)
1.20
1.40
Jnr @ 3.2kPa (1/kPa)
Mississippi I55: 6-Year Rutting
Compared to Jnr 3.2 kPa
4
y = 0.29x + 0.13
2
R = 0.75
3
2
1
0
0
2
4
6
Rut Depth, mm
8
10
12
Hamburg Rut Testing: MnROAD Mixes
Tested at Multiple Temperatures
Jnr 12.8 kPa
14.0
PG 58-28
12.0
PG 58-34
PG 58-40
Jnr kPa-1
10.0
y = 0.4416x - 0.5205
R2 = 0.93
8.0
6.0
4.0
2.0
0.0
0
5
10
15
20
rut mm
25
30
35
High Temperature Binder
Criteria
• Linear binder tests will not correlate with high
temperature mixture failure tests unless the
binder is a viscous fluid at those temperatures
• To accurately address mix failure, non-linear
binder properties have to be evaluated
• Creep & Recovery testing of the binder at
different stress levels is needed to describe
binder properties in the non-linear range
Effect of Jnr on Rutting
• Reducing Jnr by half typically reduced rutting by
half
• This effect is seen on ALF sections and
Hamburg Rut Testing
– But most importantly this is seen on the Mississippi
I-55 sections.
Determination of Specification
Criteria
• The existing binder specification works very well
for neat binders.
• The grading for neat binders should not change.
• Establish new Jnr criteria based on response of
neat binders at their continuous grade temp.
• Evaluate the binders near the end of their linear
range. Most neat binders remain linear up to 3.2
kPa stress.
Neat PG58-28 at Multiple
Temperatures
3
30
2.5
25
58C
64C
70C
Neat binders are typically linear
up to 3.2 kPa or higher
Jnr
2
20
1.5
15
1
10
0.5
5
0
10
100
1000
Stress Pa
10000
100000
Evaluation of Straight-Run Binders
Sample ID
Name
Grade
true grade
ALF 6727
Control
70-22
72.7-74.2
72.7
4.39
BBRS3
straight
64-22
66.1-27.3
66.1
4.18
MN county rd 112
neat Valero
58-28
60.8-33.4
60.8
3.68
MN county rd 112
neat Citgo
58-28
59.5-29.8
59.5
5.30
MN county rd 112
AshlandM
58-28
60.7-31.4
60.7
4.30
Minn Road
straight
58-28
61.8-30.8
61.8
3.03
Miss I-55
CSL
67-22
68.3-25.1
68.3
2.67
Shandong
straight
64-22
64.4-23.5
64.4
4.44
BBRS3
straight
70-22
71.4-24.8
71.4
4.81
BBRS3
straight
58-28
61.3-30
61.3
4.00
MD project
straight
64-28
64.8-29.6
64.8
4.59
average
Temp
Jnr 3.2kPa
4.13
MSCR
• Polymer modified binders have shown
significant sensitivity to the applied stress.
• The existing SHRP binder specification
does not identify this issue.
SBS PG 70-28 SBS
1
0.9
9
58C
64C
70C
76C
72C calc
0.8
8
7
0.7
Jnr
0.6
6
Compliance values increase with
temperature and stress. The rate of
increase with stress increases with
increased temperature.
0.5
5
0.4
4
0.3
3
0.2
2
0.1
1
0
10
100
1000
Stress Pa
10000
100000
Variations in Temp sensitivity
3.2kPa
3
30
70-28 SBS
2.5
25
y = 4E-17x8.9845
R2 = 0.9979
70-28 Elvaloy
PG 58-28
70-28 SBS-El
Jnr
2
20
1.5
15
PG 70-22
Neat binders have similar temp.
sensitivity modified binder do not.
y = 8E-19x9.6024
R2 = 1
1
10
y = 2E-22x11.437
R2 = 0.9999
y = 6E-27x13.808
R2 = 0.996
0.5
5
y = 1E-19x9.7667
R2 = 0.9999
0
55
60
65
70
Temp C
75
80
Effect of Temp and Stress on Jnr
• In neat binders a grade bump by temperature will
more than double the Jnr value.
• Some neat binders will maintain their compliance
value well beyond the 3.2 kPa stress.
• M320 Grade bumping (increasing PG grade
temperature) have forced suppliers to use very soft
base binders and high degree of polymer
modification to meet wide temperature ranges and
the 2.2 kPa for the RTFOT.
• This has made some polymers very stress sensitive.
Grade Bumping Recommendation
• All testing should be done at the environmental
grade temperature – one shift factor does not work
for all polymer-modified asphalt binders.
• The standard grade should be based on the Jnr
value of existing neat binders (4.0 kPa-1).
• For high traffic, the Jnr value should be reduced by
half at the grade temperature to 2.0 kPa-1
• For very high or standing traffic, the Jnr value should
be reduced by half again to 1.0 kPa-1
• For extreme traffic (high volume, slow or standing),
the Jnr value should be reduced by half again to 0.5
kPa-1
Purpose of the Stress Sensitivity
Requirement
• Stress sensitivity requirement limits the
change in compliance Jnr with stress level
to less than on full grade change.
• The stress sensitivity requirement is an
additional safety factor if the pavement
experiences higher than expected
temperatures and or higher loading.
Stress Sensitivity of the ALF
Binders
64-40 64C
Jnr kPa-1
2.0
AB 64C
1.8
SBS LG
1.6
control 64C
1.4
Elvaloy 64C
TBCR 64C
1.2
1.0
0.8
0.6
0.4
0.2
0
.010
0.1
1.0
Stress kPa
10.0
100
Effect of Temperature and
Stress on Jnr
• Some binders are very sensitive to stress showing large
increases in compliance with increased stress level.
• These same binders are very often more sensitive to
temperature changes also showing large increases in
compliance with increased temperature.
• The 3.2 kPa stress level in the MP 19 spec was a
compromise where there was good correlation to field
performance, but lab testing at higher temperatures and
accelerated loading at higher stress levels correlated
better to rutting.
New High Temperature Binder
Specification
• AASHTO MP19
– The new specification is based on the nonrecoverable compliance (Jnr) of the binder
– All testing should be done at the pavement
environmental grade temp to reflect response at
actual operating temperatures
– The test should be run at two stress levels 0.1 and 3.2
kPa for ten cycles at each level.
– Low temp BBR and DTT remain unchanged
AASHTO MP19
Original
DSR G*/sinδ
Min 1.0
64
RTFOT
64 Standard
MSCR3.2 <4.0
64 Heavy
MSCR 3.2<2.0
64 Very heavy
MSCR3.2 <1.0
64
64
[(MSCR3.2 –
MSCR 0.1)/
MSCR 0.1] < .75
64
PAV
S grade
DSR G*sinδ
Max 5000
28
25
22
19
16
H & V grade
DSR G*sinδ
Max 6000
28
25
22
19
16
Low temp BBR and DTT remain unchanged
AASHTO MP19
• Grades
– Based on Climatic Temperature
• High and Low Pavement Temperature
– Traffic Designation
•
•
•
•
“S” – Standard
“H” – Heavy
“V” – Very Heavy
“E” – Extreme
New PG Grading System (MSCR)
• Environmental grade plus traffic level
designation; i.e. PG 64-22E
– Four traffic levels
• S = Standard:
• H = Heavy:
• V = Very Heavy:
• E = Extreme:
< 10 million ESALs and
standard traffic loading
10 – 30 million ESALs or
slow moving traffic loading
> 30 million ESALs or
standing traffic loading
> 30 million ESALs and
standing traffic loading
New High Temperature
Specification
• PG 64 (Standard, Heavy, Very Heavy,
Extreme) based on traffic
– PG 64-xxS
– PG 64-xxH
– PG 64-xxV
– PG 64-xxE
Jnr =< 4.0
Jnr =< 2.0
Jnr =< 1.0
Jnr =< 0.5
AASHTO MP19
• PG 64-22V asphalt binder
– What do I need to test?
– What are the temperatures and criteria?
PG 64-22V Asphalt Binder
• Original (Unaged) Binder
– COC Flash Point
• Must be ≥ 230°C
– Rotational Viscosity @ 135°C
• Must be ≤ 3 Pa-s
– DSR (AASHTO T315)
• G*/sin  must be ≥ 1.00 kPa @ 64°C
PG 64-22V Asphalt Binder
• RTFO Aged Binder
– RTFO Mass Change
• Must be ≤ 1.00%
– DSR (AASHTO TP70)
• Jnr must be ≤ 1.0 kPa @ 64°C
• Stress Sensitivity must be ≤ 0.75
PG 64-22V Asphalt Binder
• PAV Aged Binder
– DSR (AASHTO T315)
• G*sin  must be ≤ 6000 kPa @ 25°C
– BBR (AASHTO T313)
• S(60) must be ≤ 300 MPa @ -12°C
• m(60) must be ≥ 0.300 @ -12°C
AASHTO MP19
• Grades
– Within same climatic grade all test
temperatures stay same
– PG 64-22_
•
•
•
•
Original DSR @ 64°C
RTFO MSCR @ 64°C
PAV DSR @ 25°C
BBR @ -12°C
Criteria changes
depending on
traffic designation
Grade Bumping with MP19
• Without temperature bumping how is the binder
grade adjusted for traffic?
• Can the existing LTPPBind software still be used
for grade bumping?
LTPPBind 3.1 can still
be used for binder
selection.
The unadjusted grade
is the New S grade.
PG 58S
LTPPBind 3.1 can still
be used for binder
selection.
As the temperature is
adjusted for speed or
traffic instead of
bumping with temp
bump to H, V, or E.
In this case PG58V
MSCR: What is % Recovery?
• MSCR Jnr addresses the high temperature
rutting for both neat and modified binders,
but many highway agencies require
polymers for cracking and durability.
• The MSCR % Recovery measurement can
identify and quantify how the polymer is
working in the binder.
MSCR %Recovery:
Validate Polymer Modification
100
90
80
High elasticity
% recovery
70
y = 29.371x-0.2633
60
50
40
30
20
Poor elasticity
10
0
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
Jnr kPa
2
2.1
MSCR %Recovery:
Validate Polymer Modification
100
90
80
% recovery
70
60
50
40
Minimum value for
Jnr .125 to .25
grade
Minimum value
for Jnr .5 to 1
grade
Minimum value for Jnr
1 to 2 grade
30
20
y = 29.371x-0.263
10
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1
Jnr 1/kPa
MSCR %Recovery:
Table of Minimum Values
Minimum % Recovery for Measured Jnr values
Jnr @ 3.2 kPa
Minimum % Recovery
2.0 - 1.01
30%
1.0 - 0.51
35%
0.50 - 0.251
45%
0.25 - 0.125
50%
Validate Polymer Modification
100
Recovery = 29.37*(Jnr-0.26)
Recovery, %
80
60
High Elasticity
40
20
0
0.00
Low Elasticity
0.50
1.00
Jnr, kPa-1
1.50
2.00
Validate Polymer Modification
PG 76-22 Binders: MSCR3200
110
Rec3200 @ 64C, %
100
90
y = 29.82x -0.39
R² = 0.54
80
70
60
50
40
Recovery = 29.37*Jnr-0.26
30
20
0.00
0.10
0.20
0.30
Jnr @ 64C, kPa-1
0.40
0.50
0.60
Blending of Binders and Polymers:
MSCR Study
• PG 64-22 Base asphalt
• 4 % SBS polymer
– Radial
– Linear
• 0.5% PPA
• 2 blending temperatures
Polymer Network Affects
Response
800
4 binders same base asphalt all
with 4% SBS polymer. 2 with .5%
PPA all have different properties.
700
600
% strain
500
400
300
LC P4 70C
LOP 4P 70C
LC 4 70C
LOP 4 70C
200
100
0
0
2
4
6
time s
8
10
Fatigue Evaluation
ASTM 4760 4-point Flexural Fatigue
Cycles*Stiffness Analysis
200C Test Temperature
1.00E+07
DLSI-4 PG 64-22V
DLSI-2 PG 64-22V
Cycles to Failure, (Nf)
1.00E+06
ER = 68%
MSCR Recovery = 30.8%
1.00E+05
ER = 65%
MSCR Recovery = 24.7%
y = 8.69E+20x-5.60E+00
R² = 9.33E-01
1.00E+04
y = 3.44E+25x-7.27E+00
R² = 9.53E-01
1.00E+03
300
400
500
600
700
800
Microstrain
900
1,000
1,100
1,200
Implementation Activities
• User-Producer Groups
– Task Force participation
– Coordination of round-robin testing
• Conducting testing for individual user
agencies
Implementation Assistance
• Educational
– FHWA Technical Brief
• FHWA‐HIF‐11‐038
– Asphalt Institute
• Guidance Document, “Implementation of the
Multiple Stress Creep Recovery Test and
Specification”
• Guidance Document, “Using the MSCR Test with
the AASHTO M320 Specification”
• www.asphaltinstitute.org
– Engineering/MSCR Information
Implementation
• Telephone survey in 2010 and since
indicate that there are barriers to state
MSCR implementation
– Inadequate DSR equipment/software
– Lack of resources to perform transitional tests
– Lack of guidance from suppliers and other
states
– Uncertainty about effect on binder supply and
modification
Survey Results - Barriers
• 9 of 14 states said biggest barrier was
concerns over correlation between existing
PG Plus and new MSCR criteria
• Comment:
– Satisfied with the PG 76-22 polymer modified
binder performance. There is a perception
that moving to MSCR test may result in lower
polymer loading and reduction in binder
performance.
Survey Results - Training
• 11 of 14 states said they could use some
type of training
– 8 requested classroom training
– 9 requested laboratory training
– Comments:
• More important than training is keeping abreast of
progress around the country
• Internet based training would be preferred since
travel is restricted
Implementation
Recognize that the refineries that serve your state
may also serve bordering states.
This may be a good reason to work with other
states to implement regionally
Note that every Performance Grade may not
equate to a distinct MSCR grade - for example, the
current polymer loading in both a PG 70-22 and
PG 76-22 may be high enough that both grade to a
“PG 64-22 E”
Implementation
Some agencies may be reluctant to implement
MSCR fully, since the names by which they refer
to binder types will necessarily change.
“PG 64-22 H” instead of “PG 70-22,” for a possible
example
AI’s “Guidance on the Use of the MSCR Test with
the AASHTO M320 Specification.”
High PG Map (98%)
Recommended Testing
Temperature (M320 Grade)
TABLE 1: Recommended MSCR Testing Temperature (based on M320 Grade)
2
Grade
PG 46-28
States
1
PG 52-28
PG 52-34
3
4
PG 58-22
PG 58-28
PG 58-34
9
25
12
PG 64-10
PG 64-16
PG 64-22
PG 64-28
PG 64-34
1
4
38
31
7
PG 67-22
5
PG 70-10
PG 70-16
PG 70-22
PG 70-28
PG 70-34
2
3
22
22
4
PG 76-16
PG 76-22
PG 76-28
PG 76-34
1
30
12
2
PG 82-16
PG 82-22
PG 82-28
1
6
2
1
2
3
4
5
6
3
46
X
MSCR Test Temperature1, °C
52
58
64
67
70
X
X
X4
4
X
X
X
X4
X5
X4
X
X
X
X5
X
X
X
X4
X5
X4
X
X5
X
5
X4
X
X4
X5
X
X5
X6
X
X5
X6
All MSCR testing is performed on the asphalt binder after RTFO-aging.
AASHTO M320 Table 1. “Premium” grades (defined as those grades where
the temperature differential is 92 degrees or greater) are shown in red.
Number of states listing the grade in the Asphalt Institute binder specification
database (www.asphaltinstitute.org).
Test at either 52°C or 58°C depending on the climate of the project. Users can
test at both temperatures if desired.
Test at either 58°C or 64°C depending on the climate of the project. Users can
test at both temperatures if desired.
Test at either 64°C or 70°C depending on the climate of the project. Users can
test at both temperatures if desired.
Implementation
Importantly, AI recommends that if the MSCR test is
implemented to evaluate the delayed elastic response of
binders, then other PG Plus tests with a similar purpose such as Elastic Recovery, Force Ductility, and Toughness
and Tenacity tests - should be eliminated.
If you are conducting side-by-side testing for a while as a
precaution, keep in mind that these types of tests give
much more simplified results with a much higher degree of
error than the MSCR, so agencies should not expect a
strong correlation between them and MSCR results.
Why MSCR?
• Why Use the MSCR Test and Spec?
– Non-recoverable creep compliance, Jnr, is
better correlated with pavement rutting than
G*/sin δ
• The high temperature parameter is truer to the
intent of the PG specification, that it be blind to
method of modification
Why MSCR?
• Why Use the MSCR Test and Spec?
– MSCR Recovery can be used to identify
elastomeric modification, thereby eliminating
the need for many PG-Plus tests like Elastic
Recovery
• Much quicker test
• Not directly tied to performance
Asphalt Institute TAC
• Position of the Technical Advisory
Committee of the Asphalt Institute.
– “It is AI’s opinion that the MSCR test and
specification represent a technical
advancement over the current performancegraded (PG) asphalt binder specification,
AASHTO M320, which will allow for better
characterization of the high temperature
performance-related properties of an asphalt
binder.”
Thanks!
Contact Information:
R. Michael (Mike) Anderson, P.E.
Director of Research and Laboratory Services
Asphalt Institute
859.288.4984 office
[email protected]
www.asphaltinstitute.org