2 IAC2014 MSCR mike anderson

Introduction to the Multiple‐Stress Creep‐
Recovery (MSCR) Test and its Use in the PG Binder 
Specification
Mike Anderson, Asphalt Institute

54th Annual Idaho Asphalt Conference
Moscow, Idaho
23 October 2014


Acknowledgments
• DTFH61‐08‐H‐00030 and DTFH61‐11‐H‐00033
• Cooperative Agreements between the FHWA and 
the Asphalt Institute
• John Bukowski, AOTR (00030)
• Michael Arasteh, AOTR (00033)

• Asphalt Binder ETG
• John D’Angelo

• Member Companies of the Asphalt Institute
• Technical Advisory Committee


Discussion
• Why do we need a new high temperature 
parameter?
• How does the MSCR test work?
• How do MSCR results (Jnr) relate to rutting?
• How can MSCR Recovery be used and what 
does it indicate?

• How does the specification work?
• What educational and implementation 
activities are going on?


DSR Operation: AASHTO T315
Spindle
Position

One cycle
is complete...

B
A

A
A
C
B

A

C

Time


Shortcomings of G*/sin δ
• G*/sin δ 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


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


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
10

Recoverable shear strain

8
Instantaneous
shear strain

6
4

Permanent
shear strain

2
0
0

2

4

6

Time, seconds

8

10


Repeated Shear Creep

Perm. Shear Strain, %

NCHRP 9-10: PG 82 Binders
Repeated Shear Creep (70C, 300Pa)
14
12
10
8
6
4
2
0
0

2

4

6

Time, seconds

8

10

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


Multiple‐Stress Creep‐Recovery (MSCR) Test:
AASHTO T350
• 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


MSCR 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
10

Recoverable shear strain

8
Instantaneous
shear strain

6
4

Non-recoverable (permanent)
shear strain

2
0
0

2

4

6

Time, seconds

8

10


MSCR – Non‐Recoverable Compliance (Jnr)

80

Jnr =

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


Relationship between Jnr and ALF Rutting
Jnr‐25.6 
2.5

Jnr = (4.74*Rut Depth) - 1.17
R2 = 0.82

Jnr

2
1.5

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


Mississippi I55: 6‐yr rutting
Jnr‐3.2
4
3.5
3
2.5
2
1.5
1
0.5
0

binder
Ultrapave
Styrelf
GTR 80
Sealoflex
Multigrade
Cryo Rubber
Control

0
18

mod
SBR

SB
SBS

2

true grade
70-27
77-29
75-29
82-27
72-24
75-28
70-24

6 yr
rut mm
4.5
2
1.5
3
5
7
11

4

Jnr 3.2 kPa
70C
1.7
0.44

1.21
0.19
2.13
1.62
3.5

6

y = 0.2907x + 0.1297
2
R = 0.7499

8

10

12


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


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
3.2 kPa Shear Stress
0.80

Recovery = 100% * 

0.70

Peak Strain – Unrecovered Strain 
Peak Strain

Strain

0.60
Recovery = 100% * 

0.50

0.300 – 0.197
0.300

= 34.3% 

0.40
0.30

0.300

0.20

0.197
Cycle 1 Unrecovered 
(permanent) strain 

0.10
0

0

5

10

15
20
25
Time, seconds

30

35

40

MSCR Recovery:
Validate Polymer Modification
100

The curve stops at J nr = 2 kPa-1. J nr values greater than 2 kPa-1
are not required to have any minimum value of %Recovery.

90
80
Recovery, %

70

Significant
High elasticity

Elastic Response

60
50
40
30
20
10
0 elasticity
Poor
0.00

0.50

1.00
Jnr , kPa-1

1.50

2.00


MSCR Recovery:
Validate Polymer Modification
100

The curve stops at Jnr-3.2 = 2.00 kPa-1 and 0.1 kPa-1. Jnr-3.2
values greater than 2.00 kPa-1 are not required to have any
minimum Rec-3.2 value. Jnr-3.2 values less than 0.10 kPa-1
are required to have a minimum Rec-3.2 value of 55%.

90
80

Rec-3.2, %

70

High elasticity

60

Significant Elastic Response

50
40
30
20
10
0 elasticity
Poor
0.00

0.50

1.00
Jnr-3.2, kPa-1

1.50

2.00


Table for MSCR % Recovery: Minimum Values
Minimum % Recovery for Measured Jnr values
Jnr @3.2 kPa, kPa‐1

Recovery 

> 2.00

n/a

≤ 2.00

≥ 30%

≤ 1.00

≥ 35%

≤ 0.50

≥ 45%

≤ 0.25

≥ 50%

≤ 0.10

≥ 55%


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

Recovery = 29.37*Jnr-0.26

40
30
20
0.00

0.10

0.20

0.30
Jnr @ 64C, kPa-1

0.40

0.50

0.60