Grading Asphalt Binders with theMultiple Stress Creep Recovery TestAASHTO TP-70 and MP-19
The Future is ComingKarl ZipfDelDOT February 2014
Brief History of the TestDTFH61-08-H-0003 Cooperative Agreement between the FHWA and the Asphalt Institute John A. DAngelo (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 TestUses the DSR which labs already have.Runs the sample 10 times. Load and relax.
MSCR Test DataThe 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
Whats in a NameSHRP (Sharp) Strategic Highway Research ProgramISTEA (Ice Tea) Intermodal Surface Transportation Equality ActTWG (Twig) Technical Working GroupMSCR (???) Multiple Stress Creep Recovery
MASCARSounds like NASCAR
MassacreLike in the Boston Massacre
MascaraBoth asphalt and mascara are black
MuskratMultiple Stress Creep Recovery Test
Jnr Limits are Based on Rut DataThe 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 non-modified binders.
MSCR % Recovery & ModificationMany 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 CurveCurrently in TP-70, will move to MP-19
So Far So GoodTwo key values for the MSCR testThese 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 FamiliarUSDA Plant Hardiness Zone Map
Northeast StatesLTPP High, Low and USDA
M-320 & MSCR NomenclatureRight now it now it looks like the PG SystemThe 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 TemperatureThe 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 64CJnr = 2.0 4.0 = PG 64S-22 Standard = PG 64-22Jnr = 1.0 2.0 = PG 64H-22 Heavy = PG 70-22Jnr = 0.5 1.0 = PG 64V-22 Very Heavy = PG 76-22Jnr = 0.25 0.5 = PG 64E-22 Extreme = PG 76-22Note MP-19 uses High & Heavy interchangeablyStandard S = traffic < 10 million ESALs, > 70 km/hHeavy H = traffic 10-30 million ESALs, 20-70 km/hVery Heavy V = traffic > 30 million ESALs, < 20km/hExtreme 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 User-Producer 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 GradesPG 58-28 = PG 58S-28, Jnr 2.0 4.5 58CPG 64-22 = PG 64S-22, Jnr 2.0 - 4.5 64CPG 64-28 = PG 64S-28, Jnr 2.0 4.5 64C PG 70-22 = PG 64H-22, Jnr 1.0 2.0 64CNo Grade = PG 64V-22, Jnr 0.5 1.0 64CFor 2014 ?PG 76-22 = PG 64E-22, Jnr < 0.5 64C and meet polymer elasticity curve.
DelDOT and PG 76-22 as MSCR64V64E
NEAUPG & PMAFrom 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 RAPLike 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 2014The MSCR Test AASHTO TP-70 will be a full standard AASHTO T-350The MSCR Binder Grading AASHTO MP-19 will be a full standard, AASHTO M-322.
(Not really. There will probably be more next year.)
Implementing a New Standard