Introduction to the Multiple‐Stress Creep‐ Recovery (MSCR) Test and its Use in the PG Binder  Specification Mike Anderson, Asphalt Institute 54th Annual Idaho Asphalt Conference Moscow, Idaho 23 October 2014 Acknowledgments • DTFH61‐08‐H‐00030 and DTFH61‐11‐H‐00033 • Cooperative Agreements between the FHWA and  the Asphalt Institute • John Bukowski, AOTR (00030) • Michael Arasteh, AOTR (00033) • Asphalt Binder ETG • John D’Angelo • Member Companies of the Asphalt Institute • Technical Advisory Committee Discussion • Why do we need a new high temperature  parameter? • How does the MSCR test work? • How do MSCR results (Jnr) relate to rutting? • How can MSCR Recovery be used and what  does it indicate? • How does the specification work? • What educational and implementation  activities are going on? DSR Operation: AASHTO T315 Spindle Position One cycle is complete B A A A C B A C Time Shortcomings of G*/sin δ • G*/sin δ as a High Temperature Parameter • Properties determined in Linear Viscoelastic (LVE)  region • No damage behavior • Rutting is a non‐linear failure • Polymer‐modified systems engaged in non‐linear region • Characterizes stiffness • Related to rutting Effect of Phase Angle 1.00 Sin  0.98 0.96 0.94 0.92 0.90 60 65 70 75 80 Phase Angle, degrees 85 90 Effect of Binder G*/sin  on Mixture Permanent Shear Strain 25000 RSCH @58C, microstrain 20000 y = 19270.79e-0.09x R2 = 0.42 15000 10000 5000 0.00 2.00 4.00 6.00 RTFO G*/sin  , 70C 8.00 10.00 High Temperature Testing • Repeated Shear Creep • Analogous to mixture test (RSCH) • Performed in DSR • • • • Controlled shear stress (i.e., 25 Pa or 300 Pa) 100 cycles 1‐second load, 9‐second rest per cycle High test temperature (HT‐?) • Response: permanent shear strain (p) or strain  slope Perm Shear Strain, % Repeated Shear Creep 14 12 10 Recoverable shear strain Instantaneous shear strain Permanent shear strain 0 Time, seconds 10 Repeated Shear Creep Perm Shear Strain, % NCHRP 9-10: PG 82 Binders Repeated Shear Creep (70C, 300Pa) 14 12 10 0 Time, seconds 10 Binder B (PG 70‐22ER): Jnr‐3.2 at 64°C (all data) 0.700 0.600 Jnr, 3.2 0.500 0.400 0.300 0.200 0.100 Lab 10 11 12 13 14 15 16 Effect on Repeatability (r) and Reproducibility (R)? Binder B: Jnr‐3.2 w/ Lab 5 w/o Lab 5 Average 0.333 0.311 1s (within lab) 0.018 0.013 d2s (within lab) 0.049 0.035 d2s% (within lab) 14.8% 11.4% 1s (between labs) 0.086 0.035 d2s (between labs) 0.241 0.097 d2s% (between labs) 72.3% 31.3% Multi‐Lab Precision Estimates: AI ILS Studies ILS ETG 2009 NEAUPG 2010 SEAUPG 2011 NEAUPG 2012 PCCAS 2013 Multi‐Lab Rec‐3.2 Multi‐Lab Jnr‐3.2 18.1% 18.7% 9.8% 7.6% 17.3% 22.0‐42.6% 33.7% 28.0% 33.0% 36.0% Multi‐Lab Precision Estimates: AI ILS Studies with AMRL PSP Data ILS ETG 2009 NEAUPG 2010 SEAUPG 2011 NEAUPG 2012 PCCAS 2013 AMRL PSP (2009‐2011) (2012‐2013) Multi‐Lab Rec‐3.2 Multi‐Lab Jnr‐3.2 18.1% 18.7% 9.8% 7.6% 17.3% 22.0‐42.6% 33.7% 28.0% 33.0% 36.0% 27.4% 14.5% 45.1% 30.1% AMRL PSP Analysis 60.0% AMRL d2s% 50.0% 40.0% 30.0% Jnr‐3.2 20.0% Rec‐3.2 10.0% 0.0% 2009 2010 2011 Year 2012 2013 Jnr‐Recovery Curve 100 90 The curve stops at Jnr-3.2 = 2.00 kPa-1 and 0.1 kPa-1 Jnr-3.2 values greater than 2.00 kPa-1 are not required to have any minimum Rec-3.2 value Jnr-3.2 values less than 0.10 kPa-1 are required to have a minimum Rec-3.2 value of 55% 80 Rec-3.2, % 70 60 50 40 30 20 10 0.00 0.50 1.00 Jnr-3.2, kPa-1 1.50 2.00 Jnr‐Recovery Curve 100 90 The curve stops at Jnr-3.2 = 2.00 kPa-1 and 0.1 kPa-1 Jnr-3.2 values greater than 2.00 kPa-1 are not required to have any minimum Rec-3.2 value Jnr-3.2 values less than 0.10 kPa-1 are required to have a minimum Rec-3.2 value of 55% 80 Rec-3.2, % 70 60 50 40 30 E-AI D E D64 B C C64 B70 A-AI A 20 10 0.00 0.50 1.00 Jnr-3.2, kPa-1 1.50 2.00 Repeatability and Reproducibility Estimates MSCR Rec-3.2 8.0% 17.3% 2013 PCCAS ILS MSCR  Rec‐3.2 ER Binder A 32.6 87.4 Binder A‐AI 39.1 Binder B 59.7 Binder C 57.3 Binder D 73.1 R&B  SP Ductility (O) Ductility (R) 91.4 49.7 T&T  T&T  Toughness Tenacity 78.4 86.2 138.7 81.2 68.7 141.0 120.3 MSCR, ER tests performed on RTFO-aged binder Binder E 90.7 187.0 and Tenacity tests performed on 79.2 72.9 R&B Softening79.0 Point, Toughness original binder Ductility tests performed on both original and RTFO-aged binder Binder E‐AI 79.8 PCCAS 2013 ILS • Summary • Analysis of MSCR results after outlier removal  indicated similar precision as in other studies • High variability seen with Binder A • Test results indicate highly stress‐sensitive binder • Meets M332 criterion for PG64V‐28 • Meets Elasticity Evaluation by Jnr‐Recovery curve • Some improvement in variability noted when aging  was conducted by a single lab (AI) • Expected response since there is some inherent  variability in RTFO procedure PCCAS 2013 ILS • Summary • PG‐Plus tests not correlated directly with MSCR  Rec‐3.2 • ER directionally correlated for 3 of 4 binders • Binder A indicated high ER value with low MSCR Rec‐3.2 • All binders plot above the Jnr‐Recovery curve Why MSCR? • Why Use the MSCR Test and Spec? • Non‐recoverable creep compliance, Jnr, is better  correlated with pavement rutting than G*/sin δ • The high temperature parameter is truer to the intent  of the PG specification, that it be blind to method of  modification Why MSCR? • Why Use the MSCR Test and Spec? • MSCR Recovery can be used to identify  elastomeric modification, thereby eliminating the  need for many PG‐Plus tests like Elastic Recovery • Much quicker test • Not directly tied to performance Summary • Industry Actively Involved • Asphalt Institute Technical Advisory Committee • Participation in UPG Meetings • Supportive of Elimination of PG Plus Tests • Replacing ER, other similar tests, with MSCR  Recovery • Recovery‐Jnr curve • Supportive of Using Jnr instead of G*/sin δ • Modified asphalts in particular • M332 Grade Names • Remains an issue for some Thanks! Contact Information: R Michael (Mike) Anderson, P.E Director of Research and Laboratory Services Asphalt Institute 859.288.4984 office manderson@asphaltinstitute.org www.asphaltinstitute.org ... SBR SB SBS true grade 70 -27 77 -29 75 -29 82- 27 72- 24 75 -28 70 -24 yr rut mm 4.5 1.5 11 Jnr 3 .2 kPa 70C 1.7 0.44 1 .21 0.19 2. 13 1. 62 3.5 y = 0 .29 07x + 0. 129 7 R = 0.7499 10 12 Effect of Binder Jnr... Validate Polymer Modification PG 76 -22 Binders: MSCR 320 0 110 Rec 320 0 @ 64C, % 100 90 y = 29 .82x -0.39 R² = 0.54 80 70 60 50 Recovery = 29 .37*Jnr-0 .26 40 30 20 0.00 0.10 0 .20 0.30 Jnr @ 64C, kPa-1 0.40... ≤ 75% “S” Grade: Jnr-3 .2 ≤ 4.5 kPa-1 “H” Grade: Jnr-3 .2 ≤ 2. 0 kPa-1 “V” Grade: Jnr-3 .2 ≤ 1.0 kPa-1 “E” Grade: Jnr-3 .2 ≤ 0.5 kPa-1 64 -40 AASHTO M3 32 PG 64 -10 -16 -22 -28 -34 -40 PAV-Aged Binder