Understanding the Performance of Modified Asphalts in Mixtures NCHRP 90-07, 07, TPF 5(019)

Transcription

1 Understanding the Performance of Modified Asphalts in Mixtures NCHRP 90-07, 07, TPF 5(019) Thomas Harman Materials & Construction Team Leader, R&D Federal Highway Administration

2 United States National Highway System A $1 trillion investment/priceless national asset The way nearly all products move Inter-modal link to sea air air rail Permits our high quality of life & economic growth

3 United States National Highway System NHS is over 160,000 miles of pavement most over 35 years old $59 billion shortfall to maintain condition Safety tied to pavement condition Customer/User expectations Safer pavements Smoother ride Quieter pavements Reduced delay & congestion

4 Annual HMA Investment $15 Billion 500 M tons of HMA 30 M tons of binder

5 Traffic congestion Up 400% on the rise! Compared with 1970: Up 132% Up 90% Up 63% Up 32% Up 6% 1970 Americans Drivers Vehicles Miles Ton Miles Highways Traveled

6 Following current congestion trends: More than 8 hours per day! About 80 hours per year! More than $250 per year per American! Hrs / Day When Roads are Congested Driver Time Lost in Rush Hour Cost of Congestion

7 Extra Vehicle Operating Cost per Year Due to Poor Pavement Condition $ 41.5 Billion / year! $500 $450 $400 $350 $300 $250 $200 $150 $100 $50 $0 $222 $432 $23 AVERAGE HIGH LOW STATE Averages The Road Information Program (TRIP) April 2001

8 But Things are Improving 2002 Report on Conditions and Performance of the NHS 86.0% with acceptable ride quality Up from 82.5% in 1993 A trend reversal Most of the improvement on higher order highways What we are doing we are doing better!

9 Get In Structural Stay In Get Out Stay Out Materials Construction

10 Outline Superpave Binder ETG Direction Preliminary FHWA ALF Results Next Steps Goal - Right materials provide the best performance!

11 Production Rutting Fatigue Cracking Thermal Cracking DTT RV DSR BBR Time No aging RTFO - aging PAV - aging

12 Superpave Binder Specification Rutting, Fatigue, and Low-Temp. Cracking WHEN WHAT HOW WHERE Construction Early (RTFO) Late (+PAV) Safety Pumpability Rutting Flash Point Rot Visc G * / sin δ 230 min 3 Pa-s max T(high) Rutting G * / sin δ T(high) Fatigue Low Temp G * sin δ BBR/DTT T(inter) T CR

13 Superpave 2002 Asphalt Binder Implementation Status Implemented In Progress Undetermined

14 Superpave Plus Elastic recovery Forced ductility Toughness and tenacity Phase angle Method (mode and dose) Combinations Number of States As is Modified PG Grade Specifications

15 Superpave Performance Grading PG 58 PG 58 High Pav. Temp. 50% Reliability PG 70 PG 64 PG 58 PG 52 PG 46 PG 40 PG <34

16 Adjusting Model for Performance Degree Days Frequency and Damage vs. Temperature Frequency Damage Frequency, Hours Damage Pavement Temperature, C

17 Superpave Binder Specification Short Term Aging - NCHRP?

18 Superpave Binder Specification Rutting Shear Stress, kpa? Shear Stain, mm/mm G * / sin δ

19 Superpave Binder Specification Fatigue Strain γ max? τ max Stress G * sin δ

20 Superpave Binder Specification Long Term Aging? Little Research Using Microwave Technology

21 Superpave Binder Specification Low Temperature Cracking (Thermal Fatigue)? R&D

22 Superpave II PG based on Degree Days WHEN WHAT HOW WHERE Construction Early (GRF, TX) Late (PAV) Safety Pumpability Rutting Flash Point Rot Visc f (G * δ) 230 min 3 Pa-s max T(high) Rutting f (G * δ) T(high) Fatigue Low Temp f (G * δ)dt DT ABCD T(inter) T CR

23 Relationships TRB Superpave Committee -Binder ETG -Mix/Aggregate ETG TPF 5(019) / SPR 2(174) Technical Working Group TWG Collaborative Researchers Laboratory Study ALF Loading Response Data Industry Support Output Validation/Calibration Data, Specification Recommendations

24 Not Yet TPF-5(019) SPR-2(174) Technical Working Group (TWG) Meeting December 5-6, 2002 (17 States, 29 Industry Partners/Collaborative Researchers)

25 Final Test Matrix AZ CRM PG Control Air Blown SBS TX TBCR T-P PG PG SBS Air Blown Fibers SBS T-P

26 FHWA 0.45 Power Chart 12.5 mm Nominal Maximum Size Mix Designs 100 Superpave 12.5mm NMS Coarse Graded Pb = 5.3 % PG Ndes = 75 Percent Passing Sieve Size, mm Arizona CRM 12.5mm NMS Coarse Graded Pb = 7.1 % PG with 17% CRM Percent Passing FHWA 0.45 Power Chart 12.5 mm Nominal Maximum Size Moderate Traffic Mix Sieve Size, mm

27 ALF Testing Status Lane Rutting Test Fatigue Test Completed Test Shakedown Test *Initial Strain Measurements: 100% Complete *Rutting Tests: Shakedown Tests Complete (5, 9) *Rutting Tests: 5 of 12 Lanes Complete *Fatigue Tests: Shakedown Test Complete (1)

28 ALF - Laboratory Preliminary Results

29 Rut Dep th, m m FHWA ALF TBCR SBS / SBS / Air Blown Ter-Polymer Control AZ CRM ,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 ALF Passes, 45kN (10kip) at 64C

30 Preliminary ALF Results 19.5 ALF Rutting after 40,000 Passes at 64 C, (mm) mm AZ CR E-T TBCR PG Air Blown SBS Asphalt Binder

31 FHWA ALF LO G ( R utting w ithin A C lay er, in) TBCR: y = x , R 2 = 0.98 SBS 64-40: y = x , R 2 = 0.98 SBS 64-40: y = x , R 2 = 0.98 Air Blown: y = x , R 2 = 0.99 T-Polymer: y = 0.157x , R 2 = 1.00 Control: y = x , R 2 = 0.99 AZ CR: y = x , R 2 = 0.99 TBCR SBS SBS Air Blown T-Polymer Control AZ CR Linear (SBS 64-40) Linear (TBCR) Linear (T-Polymer) Linear (AZ CR) Linear (Control) Linear (SBS 64-40) Linear (Air Blown) LOG (ALF Passess - 45kN(10 kips) at 64 C)

32 FHWA ALF 0.35 Slop e: Log(Rutting)/Log(Passes) TBCR SBS SBS Air Blown T-Polymer Control AZ CR

33 French PRT, Rut Depth at 60,000 / 74 C, m m R 2 = 0.17 Preliminary ALF Data TB CR E-T AZ CR PG AB SBS ALF Rut Depth at 40,000 Passes, 64 C

34 Ham burg, W heel Passes to 20m m at 64 C 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 R 2 = 0.23 Preliminary ALF Data TBCR E-T AZ CR AB PG SBS ALF Rut Depth at 40,000 Passes, 64 C

35 RSCH, G * at 10 Hz / 74 C, MPa 60,000 55,000 50,000 45,000 40,000 35,000 30,000 25,000 20,000 R 2 = 0.76 Preliminary ALF Data TBCR E-T AZ CR AB PG SBS ALF Rut Depth at 40,000 Passes, 64 C

36 RSCH Cycles to 2% CPSS, 74 C 2,500 2,000 1,500 1, R 2 = 0.86 Preliminary ALF Results TB CR AZ CR AB AZ CR PG SBS ALF Rut Depth at 40,000 Passes, 64 C

37 Significance Superpave Shear Tester Repeated Shear at Constant Height to 2% Cumulative Permanent Shear Strain Tracks ALF Rutting Performance RSCH Cy cles to 2% CPSS, 74 C Preliminary ALF Results 2,500 R 2 = ,000 E-T 1,500 AZ CR 1,000 PG TB CR AB 0 AZ CR ALF Rut Depth at 40,000 Passes, 64 C

38 Superpave Performance Tests Dynamic Modulus, E* Flow Time Flow Number Repeated Creep Ongoing Testing

39 Binder Specification Parameters Preliminary Results

40 High Temperature Parameters G* /sin radians (Superpave) G* /(1-(1/tanδ (1/tanδ radians (Shenoy) % γ acc Repeated 300 Pa (Bahia) 0.01 radians/s, LSV (Dongre /D Angelo) η ~0 radians/s, ZSV (Rowe) MVR,, 1.225kg load, cc/10min (Shenoy)

41 High Spec. Temperature, T HS G* /sin δ = 2200 Pa (Superpave) G* /(1-(1/tanδ (1/tanδ sinδ)) = 50 Pa (Shenoy) % γ acc No Criterion (Bahia) η = 250 Pa-s,, LSV (Dongre /D Angelo) η 0 = 250 Pa-s,, ZSV (Rowe) MRV = 50 cc/10min (Shenoy)

42 High-Temperature Performance I-80, Nevada Same gradation - different binders. PG modified No rutting PG unmodified 15mm of rutting

43 High Temperature (Rutting) Repeated Creep Recovery Test PG Neat AC S train, ( % ) PG Modified Time, (seconds)

44 Repeated Creep Test Results Two binders of Same PG-Grade Grade B 6281 (PG74-28) B 6289 (PG74-31) Limited Recovery, AB ALF, 15.7mm, s=0.24 Strain (mm/mm) Time (s) Higher recovery, T-P ALF, 8.8mm, s=0.15

45 Repeated Creep Test Results Two binders of Different PG-Grades Grades B 6280 (PG71-38) Strain (mm/mm) B 6286 (PG79-28) SBS ALF, 19.5mm, s= Time (s) TBCR ALF, 8.8mm, s=0.15

46 Summary of Findings To Date Preliminary Results Current specification does not adequately identify the benefits of modifiers RSCH tracks ALF rutting performance A wide range of high specification temperature parameters are being evaluated

47 What s Next Fatigue Testing Two Temperatures Rutting Testing 7 Lanes Additional Sections TBD Superpave SPT E*, Creep Beam Fatigue Low-Temp Study ABCD, DT, T CR

48 Superpave II 2005/6 PG based on Degree Days WHEN WHAT HOW WHERE Construction Early (GRF, TX) Late (PAV) Safety Pumpability Rutting Flash Point Rot Visc f (G * δ) 230 min 3 Pa-s max T(high) Rutting f (G * δ) T(high) Fatigue Low Temp f (G * δ)dt DT ABCD T(inter) T CR

49 Binder Specification Direction To better handle neat asphalts To address modifiers To do it faster, better, and more economical! *** RULES *** TESTS NEED TO BE: EASY TO SET UP EASY TO PERFORM EASY TO ANALYZE

50

51