Regional Implementation of
the MSCR Test
Pennsylvania Asphalt Pavement
Association
54th Annual Conference
Hershey, PA
January 30, 2014
Gregory A. Harder, P.E.
Past MSCR Presentations
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Development of Standard Practice for Superpave Plus Specifications - J. D'Angelo –
2005 – Burlington, VT
Binder and Mixture ETG Update - J. D'Angelo – 2006 – Wilmington, DE
FHWA Pavements Program - What's Happening - J. D'Angelo – 2007 – Mystic, CT
Current Status for Multiple Stress Creep Recovery October 9, 2008 - K. Mooney –
2008 – Atlantic City, NJ
Asphalt Mixture and Binder Expert Task Group Update - J. Bukowski – 2008 –
Atlantic City, NJ
Update on National Issues - ETG Activity - J. Bukowski – 2009 – Portland, ME
MSCR Test - A New High Temp Spec - J. D'Angelo – 2009 – Portland, ME
Update on National Issues - ETG Activity - J. Bukowski – 2010 – Saratoga, NY
Binder Grade Selection Using the MSCR Specification - J. D'Angelo – 2010 –
Saratoga, NY
Update on National Issues - ETG Activity - J. Bukowski – 2011 – Providence, RI
Regional Implementation of the MSCR Test – G. Harder – 2012 – Philadelphia, PA
MSCR Implementation
The use of polymer modified
binders has grown tremendously
over the past several years
However, the most widely used
binder specification in the U.S.,
AASHTO M 320, was based on a
study of neat (unmodified)
binders, and may not properly
characterize polymer modified
binders
Why doesn’t M 320 properly characterize
polymer-modified binders?
• Current spec, G* and δ are measured in the
linear visco-elastic range.
• For neat binders, flow is linear(strain increases
in a constant proportion to stress) and therefore
not sensitive to the stress level of the test.
• For polymer-modified binders, the response is
not linear and very sensitive to the stress level of
the test. The polymer chains can be rearranged
substantially as the stress increases.
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
Why Do We Need New Binder Test?
• PG Binders
– Most Common “Neat” Binder Grades
• PG 64-22
Works OK for neat binders
• PG 67-22
– Most Common “Modified” Binder Grade
• PG 76-22
Doesn’t work as well for modified binders
What happened as a result of M 320’s inability to
fully characterize polymer-modified binders?
• Most states began requiring additional tests
to the ones required in AASHTO M 320
• 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
ER Information and Test Time
• The Elastic Recovery Test is an excellent tool to
establish the presence of polymer modification.
– It takes about 4 hours to prepare and test
samples for this information.
• However, it is a poor tool to evaluate the rutting
performance of polymer-modified binders.
– The MSCR test can use the same sample
already being run in the DSR to give more
information in a few extra minutes.
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
Multiple Stress Creep Recovery Test
• Calculate Recovery for each Cycle, Stress
– Difference between strain at end of recovery
period and peak strain after creep loading
• Calculate Non-recoverable Creep
Compliance (Jnr)
– Non-recoverable shear strain divided by
applied shear stress
• “J” = “compliance”
• “nr” = “non-recoverable”
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
ALF Loading
• The pavement was heated to a constant
64ºC.
• The FHWA ALF uses an 18,000 lbs wheel
load with no wheel wander.
• The speed is 12 MPH.
– This is a extreme loading condition far more
sever than any actual highway.
Relationship between G*/ sinδ
and ALF rutting
12
10
y = -7 .4 5 1 9 x + 1 0 .9 5 6
2
R = 0 .1 2 6 1
G */s in d 6 4 C
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
ru ttin g in c h e s
0 .5
0 .6
0 .7
0 .8
Relationship between Jnr and
ALF rutting
25.6kPa
2.5
y = 4.7357x - 1.1666
R2 = 0.8167
2
MSCR can adjust for field
conditions and has excellent
relations to performance.
Jnr
1.5
1
0.5
0
0
0.1
0.2
0.3
0.4
ALF Rutting in
0.5
0.6
0.7
0.8
Miss I-55 6yr rut Jnr 3.2 kPa
4
3.5
3
2.5
2
1.5
1
0.5
0
y = 0.2907x + 0.1297
R2 = 0.7499
0
2
4
6
8
10
12
New PG Grading System (MSCR)
AASHTO MP-19
• Environmental grade plus traffic level designation; i.e.
PG 64E-22
– Based on Climatic Temperature
• High and Low Pavement Temperature
– Traffic Designation
• “S” – Standard:
• “H” – Heavy:
• “V” – Very Heavy:
• “E” – Extreme:
< 10 million ESALs and
standard traffic loading
10 – 30 million ESALs or
slow moving traffic
> 30 million ESALs or
standing traffic
> 30 million ESALs and
standing traffic
New PG Grading System (MSCR)
Requirements
•S = Standard:
Jnr ≤ 4.5 kPa-1
•H = Heavy:
Jnr ≤ 2.0 kPa-1
•V = Very Heavy:
Jnr ≤ 1.0 kPa-1
•E = Extr. Heavy:
Jnr ≤ 0.5 kPa-1
AASHTO M320
• Grades
– As an example, following Table 1…
• Kentucky’s climate requires a PG 64-22 to meet
high and low pavement design temperatures
• PG 64-22 is a standard, unmodified asphalt binder
grade
• For Very Heavy (slow and/or very high volume)
traffic, Kentucky “grade bumps” to a PG 76-22
asphalt binder
• PG 76-22 is a modified asphalt binder grade
– Kentucky requires ER ≥ 75%
AASHTO M320
• Grades
– As an example, following Table 1…
• Although a PG 76-22 is specified, Kentucky
recognizes that the pavement temperature never
gets that hot
– Original DSR (T315): G*/sin d ≥ 1.00 kPa @ 76°C
– RTFO DSR (T315): G*/sin d ≥ 2.20 kPa @ 76°C
• Grade bumping is a way to get a stiffer asphalt
binder at the expected high pavement temperature
AASHTO MP-19
• Grades
– As an example, following MP-19…
• Kentucky’s climate requires a PG 64-22 to meet high
and low pavement design temperatures
• PG 64-22S is an unmodified asphalt binder grade that
can be used for Standard (normal speed, normal
volume) traffic conditions
• For Very Heavy (slow and/or very high volume) traffic,
Kentucky requires a PG 64-22V asphalt binder
• PG 64-22V is a modified asphalt binder grade
– Particularly if MSCR Recovery requirement is added
AASHTO MP-19
• Grades
– As an example, following MP-19…
• Instead of increasing the test temperature as in M320, Kentucky recognizes that the pavement
temperature never gets that hot and adjusts criteria
– Original DSR (T315): G*/sin d ≥ 1.00 kPa @ 64°C
– RTFO MSCR (TP70): Jnr ≤ 1.0 kPa-1 @ 64°C
• Get a stiffer asphalt binder at the expected high
pavement temperature
NEAUPG
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Tasked by steering committee
Formed Implementation Team
Mission statement, description, target
audience, opportunities, obstacles, strategies,
and goals identified
Performed round robin testing
All states participated in pooled fund, each will be
obtaining/using the same Malvern DSR
States agreed to specify both MP 19 Jnr requirements
and MP 70 MSCR Recovery requirements beginning
January 2014
(H, V, and E grades only – S grades remain M320)
MSCR Implementation Team
Goals
MSCR % Recovery validates
polymer modification
100
AASHTO TP 70
90
80
y = 29.371x-0.2633
% recovery
70
% Recovery above the line means
asphalt binder is modified with an
acceptable elastomeric polymer
60
50
40
30
20
Below line - not modified with an elastomeric polymer
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
MODIFIED GRADES IN THE NORTHEAST
CURRENT GRADE –
M320
NEW GRADE – MP-19
PG 76-22
PG 64E-22
PG 76-28
PG 64E-28
PG 70-28
PG 64V-28
PG 64-22P
PG 64V-22
PG 58-34
PG 58H-34
WHAT IS CURRENTLY BEING SUPPLIED?
MSCR DATA - PG 76-22
100
GRADE
64E
%Rec @ 3.2 kPa tested at 64C
90
GRADE
64H
GRADE
64V
80
70
60
SUPPLIER 1
50
SUPPLIER 2
SUPPLIER 3
40
SUPPLIER 4
SUPPLIER 5
30
20
10
0
0
0.5
1
Jnr @ 3.2 kPa tested at 64C
1.5
2
MEDOT
CURRENT GRADE –
BASE – 58C
M320
NEW GRADE –
MP-19
PG 58-28
PG 58S-28
PG 58-34
PG 58H-34
PG 64-28(PPA)
PG 58H-28
PG 70-28
PG 58V-28
PG 76-28
PG 58E-28
Will be specifying for modified grades on Jan. 1,
2014 – PG 58V-28[PG 70-28] – little to no use of PG
58-34 – not sure yet on PG 64-28 (PPA modified)
NHDOT
CURRENT GRADE –
BASE – 58C
M320
NEW GRADE –
MP-19
PG 64-28
PG 58H-28
PG 64-28(PPA)
PG 58H-28
PG 70-28
PG 58V-28
PG 76-28
PG 58E-28
Use a very limited amount of modified grades but
will implement PG 58V and PG 58E grades on Jan.
1, 2014
NJDOT
CURRENT GRADE –
BASE – 64C
M320
NEW GRADE –
MP-19
PG 64-22
PG 64S-22
PG 76-22
PG 64E-28
Will be specifying MSCR for PG 76-22 effective
Jan.1, 2014 – not sure if it will be PG 64V-22 or PG
64E-22
DelDOT
CURRENT GRADE –
BASE – 64C
M320
NEW GRADE –
MP-19
PG 58-28
PG 58S-28
PG 64-22
PG 64S-22
PG 70-22
PG 64H-22
PG 76-22
PG 64E-22
Will implement on Jan. 1, 2014 if suppliers want to
MDSHA
CURRENT GRADE –
BASE – 64C
M320
NEW GRADE –
MP-19
PG 58-22
PG 58S-22
PG 58-28
PG 58S-28
PG 64-22
PG 64S-22
PG 64-28
PG 64H-28
PG 70-22
PG 64H-22
PG 76-22
PG 64E-22
Working on software upgrade to test for MSCR – will
collect data for information – implementation of
MSCR possible in 2014
VT-AOT
CURRENT GRADE –
BASE – 58C
M320
NEW GRADE –
MP-19
PG 52-34
PG 52S-34
PG 58-28
PG 58S-28
Currently running MSCR on 75% of the full set
testing – base temperature will be 58C – but will test
at 52C for those mixtures containing high RAP – all
projects for 2014 have been bid – have been using
MSCR on emulsion residue
CTDOT
CURRENT GRADE –
BASE – 58C
M320
NEW GRADE –
MP-19
PG 58-28
PG 58S-28
PG 64-22
PG 64S-22
PG 76-22
PG 64E-22
Limited amount of PG 76-22 polymer modified is
used - currently running test and collecting data –
considering allowing substitution of MP-19 grades in
2014 with full implementation for all grades possible
in 2015
Mass
CURRENT GRADE –
Highway
M320
BASE – 58C
NEW GRADE –
MP-19
PG 52-34
PG 52S-34
PG 64-28
PG 64S-22 or
PG 58H-28
PG 64-28 Rubber
PG 64?-28
PG 64-28 SBR
PG 64?-28
Currently discussing internally – want to talk with
industry this winter as to how to move forward – no
implementation on Jan.1 – hope to have better idea
of direction in early 2014
NYSDOT
BASE –
58/64C
CURRENT GRADE –
M320
NEW GRADE –
MP-19
PG 58-34
PG 58H-34
PG 64-22
PG 64S-22
PG 64-22P
PG 64V-22
PG 70-22
PG 64H-22
PG 76-22
PG 64E-22
Full implementation MP-19 for all grades in 2014 –
actual date yet to be determined
RIDOT
CURRENT GRADE –
BASE – 64C
M320
NEW GRADE –
MP-19
PG 64-28
PG 64S-28
PG 70-28
PG 64V-28
PG 76-28
PG 64E-28
Already implemented PG 64V-28 and PG 64E-28
PennDOT
BASE –
58/64C
CURRENT GRADE –
M320
NEW GRADE –
MP-19
PG 58-28
PG 58S-28
PG 64-22
PG 64S-22
PG 76-22
PG 64E-22
Have been collecting data - will allow a substitution
of PG 64E-22 for PG 76-22 in 2014
Binder Grade Substitution
PG 64E-22 = PG 76-22
Thanks