Presentation on theme: "Regional Implementation of the MSCR Test Pennsylvania Asphalt Pavement Association 54 th Annual Conference Hershey, PA January 30, 2014 Gregory A. Harder,"— Presentation transcript:
Regional Implementation of the MSCR Test Pennsylvania Asphalt Pavement Association 54 th 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, VTDevelopment of Standard Practice for Superpave Plus Specifications Binder and Mixture ETG Update - J. D'Angelo – 2006 – Wilmington, DEBinder and Mixture ETG Update FHWA Pavements Program - What's Happening - J. D'Angelo – 2007 – Mystic, CTFHWA Pavements Program - What's Happening Current Status for Multiple Stress Creep Recovery October 9, K. Mooney – 2008 – Atlantic City, NJCurrent Status for Multiple Stress Creep Recovery October 9, 2008 Asphalt Mixture and Binder Expert Task Group Update - J. Bukowski – 2008 – Atlantic City, NJAsphalt Mixture and Binder Expert Task Group Update Update on National Issues - ETG Activity - J. Bukowski – 2009 – Portland, MEUpdate on National Issues - ETG Activity MSCR Test - A New High Temp Spec - J. D'Angelo – 2009 – Portland, MEMSCR Test - A New High Temp Spec Update on National Issues - ETG Activity - J. Bukowski – 2010 – Saratoga, NYUpdate on National Issues - ETG Activity Binder Grade Selection Using the MSCR Specification - J. D'Angelo – 2010 – Saratoga, NYBinder Grade Selection Using the MSCR Specification Update on National Issues - ETG Activity - J. Bukowski – 2011 – Providence, RIUpdate on National Issues - ETG Activity 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 modified, no rutting PG unmodified, 15mm rut
Why Do We Need New Binder Test? PG Binders –Most Common “Neat” Binder Grades PG PG –Most Common “Modified” Binder Grade PG 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 (J nr ) –Non-recoverable shear strain divided by applied shear stress “J” = “compliance” “nr” = “non-recoverable”
ALF Study - 7 Asphalt Binders AZ CRM PG Control 2 Air Blown 3 SBS 4 TX TBCR 5 TP 6 PG Fibers 7 PG SBS Air Blown 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.
Relationship between G*/ sinδ and ALF rutting Existing SHRP specification has poor relationship to rutting for modified systems.
Relationship between Jnr and ALF rutting 25.6kPa MSCR can adjust for field conditions and has excellent relations to performance.
Miss I-55 6yr rut Jnr 3.2 kPa
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 GRADE BUMPING
New PG Grading System (MSCR) Requirements S = Standard: J nr ≤ 4.5 kPa -1 H = Heavy: J nr ≤ 2.0 kPa -1 V = Very Heavy: J nr ≤ 1.0 kPa -1 E = Extr. Heavy: J nr ≤ 0.5 kPa -1
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%
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 ≥ °C –RTFO DSR (T315): G*/sin ≥ °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 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 ≥ °C –RTFO MSCR (TP70): J nr ≤ 1.0 kPa 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
MSCR % 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 76-22PG 64E-22 PG 76-28PG 64E-28 PG 70-28PG 64V-28 PG 64-22PPG 64V-22 PG 58-34PG 58H-34 MODIFIED GRADES IN THE NORTHEAST
WHAT IS CURRENTLY BEING SUPPLIED?
MEDOT BASE – 58C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 58-28PG 58S-28 PG 58-34PG 58H-34 PG 64-28(PPA)PG 58H-28 PG 70-28PG 58V-28 PG 76-28PG 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)
NHDOT BASE – 58C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 64-28PG 58H-28 PG 64-28(PPA)PG 58H-28 PG 70-28PG 58V-28 PG 76-28PG 58E-28 Use a very limited amount of modified grades but will implement PG 58V and PG 58E grades on Jan. 1, 2014
NJDOT BASE – 64C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 64-22PG 64S-22 PG 76-22PG 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
DelDOT BASE – 64C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 58-28PG 58S-28 PG 64-22PG 64S-22 PG 70-22PG 64H-22 PG 76-22PG 64E-22 Will implement on Jan. 1, 2014 if suppliers want to
MDSHA BASE – 64C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 58-22PG 58S-22 PG 58-28PG 58S-28 PG 64-22PG 64S-22 PG 64-28PG 64H-28 PG 70-22PG 64H-22 PG 76-22PG 64E-22 Working on software upgrade to test for MSCR – will collect data for information – implementation of MSCR possible in 2014
VT-AOT BASE – 58C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 52-34PG 52S-34 PG 58-28PG 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 BASE – 58C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 58-28PG 58S-28 PG 64-22PG 64S-22 PG 76-22PG 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
Mass Highway BASE – 58C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 52-34PG 52S-34 PG 64-28PG 64S-22 or PG 58H-28 PG RubberPG 64?-28 PG SBRPG 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 58-34PG 58H-34 PG 64-22PG 64S-22 PG 64-22PPG 64V-22 PG 70-22PG 64H-22 PG 76-22PG 64E-22 Full implementation MP-19 for all grades in 2014 – actual date yet to be determined
RIDOT BASE – 64C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 64-28PG 64S-28 PG 70-28PG 64V-28 PG 76-28PG 64E-28 Already implemented PG 64V-28 and PG 64E-28
PennDOT BASE – 58/64C CURRENT GRADE – M320 NEW GRADE – MP-19 PG 58-28PG 58S-28 PG 64-22PG 64S-22 PG 76-22PG 64E-22 Have been collecting data - will allow a substitution of PG 64E-22 for PG in 2014