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 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 = -7.4519x + 10.956 R2 = 0.1261 G*/sin d 64C 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 rutting inches 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 • • • • • • 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
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