1. Regional Implementation of the MSCR Test
Pennsylvania Asphalt Pavement Association
54th Annual Conference
Hershey, PA
January 30, 2014
Gregory A. Harder, P.E.

2. Past MSCR Presentations
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, 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

3. 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

4. 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.
The slide show continues with the second and third bullet items.
Neat asphalts behave in a linear fashion, where the strain increases in a constant proportion to the stress.
In polymer-modified binders, the strain does not always increase in a linear fashion. At higher stress levels, the polymer chains can be substantially rearranged, resulting in non-linear behavior.

5. PG Grading Alone Does Not Always Predict Performance
Study of the two mixes with the same aggregate structure, but different binders.
PG modified, no rutting
PG unmodified, 15mm rut
Furthermore, PG grading alone does not predict performance, especially when comparing neat and modified binders.

6. Why Do We Need New Binder Test?
PG Binders
Most Common “Neat” Binder Grades
PG 64-22
PG 67-22
Most Common “Modified” Binder Grade
PG 76-22
Works OK for neat binders
Doesn’t work as well for modified binders
Like I said previously, the SEAUPG states decided to adopt the Performance Grade (PG) binder grading system back in the mid 1990s. Each of the states decided to adopt a series of binder grades for use in their states, depending on various factors.
Probably the most common grades used in the SE are as follows:
the most common “neat” or unmodified binders were PG and PG
the most common “modified” grade is PG 76-22
Over the last 17 years, the PG system has served us pretty well. There is no doubt that we have come a long ways with this approach. So how does the specification working…click…the current PG grading system works well for the neat binders. However…click…experience and research has shown that the current PG does not work as well for modified binders. This was recognized from the start so many states decided to adopt additional tests (commonly referred to as “PG Plus” tests) like Elastic Recovery, phase angle or force ductility to ensure that the modifiers were present in the binder.

7. 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

8. States with a “PG Plus” Specification
No PG Plus Spec

9. 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.
ER - Pour, cool, trim, load, pull, wait, measure

10. 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

11. 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”

12. ALF Study - 7 Asphalt BindersAZ
CRM
----
70-22 PG
70-22
Control
Air
Blown
SBS TX
TBCR TP PG
70-22 +
Fibers PG
70-22
SBS
64-40
Air
Blown
SBS TP
An Accelerated Load Facility (ALF) at Turner-Fairbanks Highway Research Center conducted rut testing on mixes incorporating 7 different binder types. They then tried to correlate the binder performance as measured by Superpave binder testing and MSCR testing to the observed rutting. 1 2 3 4 5 6 7 8 9 10 11 12

13. 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.

14. Relationship between G*/ sinδ and ALF rutting
As you know, the coefficient of determination, R2, is a measure of how well future outcomes can be predicted by a model, “0” being unable to reliably predict performance and “1” being a perfect predictor of performance. The Superpave binder grading, at an R2 of , is a poor predictor of modified binder rutting in this ALF study.
Existing SHRP specification has poor relationship to rutting for modified systems.

15. Relationship between Jnr and ALF rutting 25.6kPa
MSCR can adjust for field conditions and has excellent relations to performance.
On the other hand, the MSCR Jnr, at an R2 of , is a reliable predictor of modified binder rutting in this ALF study.

16. Miss I-55 6yr rut Jnr 3.2 kPa

17. 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: < 10 million ESALs and
standard traffic loading
“H” – Heavy: 10 – 30 million ESALs or
slow moving traffic
“V” – Very Heavy: > 30 million ESALs or
standing traffic
“E” – Extreme: > 30 million ESALs and
NO MORE GRADE BUMPING

18. 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

19. AASHTO M320 Grades As an example, following Table 1…
Kentucky’s climate requires a PG to meet high and low pavement design temperatures
PG is a standard, unmodified asphalt binder grade
For Very Heavy (slow and/or very high volume) traffic, Kentucky “grade bumps” to a PG asphalt binder
PG is a modified asphalt binder grade
Kentucky requires ER ≥ 75%

20. AASHTO M320 Grades As an example, following Table 1…
Although a PG is specified, Kentucky recognizes that the pavement temperature never gets that hot
Original DSR (T315): G*/sin d ≥ °C
RTFO DSR (T315): G*/sin d ≥ °C
Grade bumping is a way to get a stiffer asphalt binder at the expected high pavement temperature

21. AASHTO MP-19 Grades As an example, following MP-19…
Kentucky’s climate requires a PG 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

22. AASHTO MP-19 Grades As an example, following MP-19…
Instead of increasing the test temperature as in M-320, Kentucky recognizes that the pavement temperature never gets that hot and adjusts criteria
Original DSR (T315): G*/sin d ≥ °C
RTFO MSCR (TP70): Jnr ≤ °C
Get a stiffer asphalt binder at the expected high pavement temperature

23. NEAUPG 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)
NY MP 19 on all grades including S, recovery H, V, and E grades only

24. MSCR Implementation Team

25. Goals

26. MSCR % Recovery validates polymer modification
AASHTO TP 70
% Recovery above the line means asphalt binder is modified with an acceptable elastomeric polymer
Plotting the % recovery can show the presence of an elastomeric polymer, as outlined in Appendix X2 of AASHTO TP 70.
Below line - not modified with an elastomeric polymer 26

27. 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

28. WHAT IS CURRENTLY BEING SUPPLIED?

29. MEDOT
BASE – 58C
CURRENT GRADE – 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 – not sure yet on PG (PPA modified)

30. NHDOT
BASE – 58C
CURRENT GRADE – M320
NEW GRADE – MP-19
PG 64-28
PG 58H-28
PG 64-28(PPA)
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

31. NJDOT
BASE – 64C
CURRENT GRADE – M320
NEW GRADE – MP-19
PG 64-22
PG 64S-22
PG 76-22
PG 64E-28
Will be specifying MSCR for PG effective Jan.1, 2014 – not sure if it will be PG 64V-22 or PG 64E-22

32. Will implement on Jan. 1, 2014 if suppliers want to
DelDOT
BASE – 64C
CURRENT GRADE – 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

33. MDSHA
BASE – 64C
CURRENT GRADE – 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

34. VT-AOT
BASE – 58C
CURRENT GRADE – 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

35. CTDOT
BASE – 58C
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
Limited amount of PG 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

36. Mass Highway
BASE – 58C
CURRENT GRADE – M320
NEW GRADE – MP-19
PG 52-34
PG 52S-34
PG 64-28
PG 64S-22 or
PG 58H-28
PG Rubber
PG 64?-28
PG SBR
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

37. 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

38. Already implemented PG 64V-28 and PG 64E-28
RIDOT
BASE – 64C
CURRENT GRADE – 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

39. 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 in 2014

40. Binder Grade Substitution
PG 64E-22 = PG 76-22

41. Thanks