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

• 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

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

MSCR Implementation

• 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.

Why doesn’t M 320 properly characterize polymer-modified binders?

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• PG 67-22

– Most Common “Modified” Binder Grade• PG 76-22

Works OK for neat binders

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

PG Plus Spec

No PG Plus Spec

States with a “PG Plus” Specification

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

AZCRM----70-22

1

PG70-22Control

2

AirBlown

3

SBS

4

TXTBCR

5

TP

6

PG70-22+Fibers

7

PG70-22

8

SBS64-40

9

AirBlown

10

SBS

11

TP

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.

y = -7.4519x + 10.956

R2 = 0.1261

0

2

4

6

8

10

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

rutting inches

G*/

sin

d 6

4C

Relationship between G*/ sinδ and ALF rutting

Existing SHRP specification has poor relationship to rutting for modified systems.

Relationship between Jnr and ALF rutting25.6kPa

y = 4.7357x - 1.1666

R2 = 0.8167

0

0.5

1

1.5

2

2.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

ALF Rutting in

Jn

r

MSCR can adjust for field conditions and has excellent relations to performance.

Miss I-55 6yr rut Jnr 3.2 kPa

y = 0.2907x + 0.1297

R2 = 0.7499

0

0.5

1

1.5

2

2.5

3

3.5

4

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: < 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

standing traffic

NO MORE G

RADE BUMPING

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 M-320, 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• 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

y = 29.371x-0.2633

0

10

20

30

40

50

60

70

80

90

100

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 kPa

% r

eco

ve

ryMSCR % Recovery validates polymer modification

% Recovery above the line means asphalt binder is modified with an acceptable elastomeric polymer

Below line - not modified with an elastomeric polymer

AASHTO TP 70

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

MODIFIED GRADES IN THE NORTHEAST

0 0.5 1 1.5 20

10

20

30

40

50

60

70

80

90

100

MSCR DATA - PG 76-22

SUPPLIER 1

SUPPLIER 2

SUPPLIER 3

SUPPLIER 4

SUPPLIER 5

Jnr @ 3.2 kPa tested at 64C

%R

ec

@ 3

.2 k

Pa

te

ste

d a

t 6

4C

GRADE 64E

GRADE 64V

GRADE 64H

WHAT IS CURRENTLY BEING SUPPLIED?

MEDOTBASE – 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 58-34 – not sure yet on PG 64-28 (PPA modified)

NHDOTBASE – 58C

CURRENT GRADE – 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

NJDOTBASE – 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 76-22 effective Jan.1, 2014 – not sure if it will be PG 64V-22 or PG 64E-22

DelDOTBASE – 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

MDSHABASE – 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

VT-AOTBASE – 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

CTDOTBASE – 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 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 Highway

BASE – 58C

CURRENT GRADE – M320

NEW GRADE – MP-19

PG 52-34 PG 52S-34

PG 64-28 PG 64S-22 orPG 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

NYSDOTBASE – 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

RIDOTBASE – 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

PennDOTBASE – 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