Grading Asphalt Binders with the Multiple Stress Creep Recovery Test AASHTO TP-70 and MP-19 “The Future is Coming” Karl Zipf DelDOT February 2014 WARNING Brief History of the Test • DTFH61-08-H-0003 – Cooperative Agreement between the FHWA and the Asphalt Institute • John A. D’Angelo (FHWA) • Asphalt Binder ETG • Member Companies of the Asphalt Institute – Technical Advisory Committee • The present test methods for asphalt binder grading do not adequately characterize rutting or polymer-modified asphalts (PMA). • The current PG System (AASHTO M-320) is blind to modification and requires PG plus tests such as Elastic Recovery to characterize PMA binders. • The PG system was supposed to reduce rutting but over the past decade and a half it has not The New Asphalt Binder Test • Uses the DSR which labs already have. • Runs the sample 10 times. Load and relax. MSCR Test Data • The test gives two values which are the basis of the standards, TP-70 and MP-19. • Jnr – Nonrecoverable creep compliance for 10 cycles at a creep stress of 3.2 kPa • % Average Recovery at a creep stress of 3.2 kPa The New Asphalt Binder Test What’s in a Name • SHRP (Sharp) – Strategic Highway Research Program • ISTEA (Ice Tea) – Intermodal Surface Transportation Equality Act • TWG (Twig) – Technical Working Group • MSCR (???) – Multiple Stress Creep Recovery “MASCAR” • Sounds like NASCAR “Massacre” • Like in the Boston Massacre “Mascara” • Both asphalt and mascara are black “Muskrat” • Multiple Stress Creep Recovery Test Jnr Limits are Based on Rut Data • The Jnr (Nonrecoverable Compliance) correlated to rut depth in the ALF track, field studies and lab tests. • The Jnr will used to determine the binder grade. • Jnr works for both modified and nonmodified binders. MSCR % Recovery & Modification • Many processes will stiffen and binder but not all make them elastic. • The % Recovery is used to characterize the elasticity from polymer modification. • A polymer curve was developed based on data from available PMA binders. Polymer Modification Curve • Currently in TP-70, will move to MP-19 Elastic Response TP-70 X2.1 Curve 90 80 70 y = 29.37x-0.263 % Recovery 3.2 kPa 60 50 Passing Percent Recovery 40 30 Failing Percent Recovery 20 10 0 0 0.2 0.4 0.6 0.8 1 Jnr 3.2 kPa 1.2 1.4 1.6 1.8 2 So Far So Good • Two key values for the MSCR test • These will determine the binder grade and whether it can be called a PMA binder. –Jnr –% Recovery So how do you grade a binder? Like PG System, Grade Based on LTPP Climate Temperature Looks Familiar • USDA Plant Hardiness Zone Map Northeast States LTPP High, Low and USDA M-320 & MSCR Nomenclature • Right now it now it looks like the PG System • The BIG change is that everything is based on the LOCAL high temperature environment. • Our environment is 64C and our standard grade, like the PG system is PG 64-22. • Other grades, PG 70, and PG 76 will be tested at 64C as PG 64(something), based on the Jnr. • Binder name becomes state/region dependent. MSCR and Low Temperature • The low temperature tests and nomenclature will not change with MSCR. • It still uses the BBR results. • The mid temperature criteria, the 8 mm DSR test, will have 6000 kPa as a cutoff for the stiffer grades, since for DelDOT the test temp will be 25C. MP-19 Grades at 64C • • • • • • • • • Jnr = 2.0 – 4.0 = PG 64S-22 “Standard” = PG 64-22 Jnr = 1.0 – 2.0 = PG 64H-22 “Heavy” = PG 70-22 Jnr = 0.5 – 1.0 = PG 64V-22 “Very Heavy” = PG 76-22 Jnr = 0.25 – 0.5 = PG 64E-22 “Extreme” = PG 76-22 Note MP-19 uses “High” & “Heavy” interchangeably Standard “S” = traffic < 10 million ESALs, > 70 km/h Heavy “H” = traffic 10-30 million ESALs, 20-70 km/h Very Heavy “V” = traffic > 30 million ESALs, < 20km/h Extreme “E” > 30 million ESALs, < 20km/h, toll plazas Polymer Curve & DelDOT Data Where the New Grades Fall at 64C When Will DelDOT See MP-19? • The FHWA is pushing the MSCR test ASAP. • The Asphalt Institute is pushing the MSCR test. • The NEAUPG (Northeast Asphalt UserProducer Group) is reviewing a limited regional implementation for maybe 2014. • NEAUPG will be polymer curve in 2014, and non-PMA in a future year. • SEAUPG will consider it in 2015, central USA later, and west coast probably not at all. • National implementation date is unknown. DelDOT M-320 vs MP-19 Grades • • • • • • • PG 58-28 = PG 58S-28, Jnr 2.0 – 4.5 58C PG 64-22 = PG 64S-22, Jnr 2.0 - 4.5 64C PG 64-28 = PG 64S-28, Jnr 2.0 – 4.5 64C PG 70-22 = PG 64H-22, Jnr 1.0 – 2.0 64C No Grade = PG 64V-22, Jnr 0.5 – 1.0 64C For 2014 ? PG 76-22 = PG 64E-22, Jnr < 0.5 64C and meet polymer elasticity curve. DelDOT and PG 76-22 as MSCR 64V 64E NEAUPG & PMA • From Maine to Maryland there will probably be two standard grades, PG 58S & PG 64S. • NYDOT will switch over all grades around Sept 2014 to MP-19. MSCR and RAP • Like the PG System, M-320 the MSCR spec, MP-19 is based on 100% virgin binders. • RAP is stiff, Jnr 0.1 - 0.2, but not elastic so will fail the polymer curve. • RAP affects the low temperature properties, and these rules have not changed, and it is the low temperature where one sees failure. August 2014 • The MSCR Test AASHTO TP-70 will be a full standard AASHTO T-350 • The MSCR Binder Grading AASHTO MP-19 will be a full standard, AASHTO M-322. The End (Not really. There will probably be more next year.) Questions? Implementing a New Standard
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