What is on the Horizon in HMA. John D AngeloD Federal Highway Administration

Transcription

1 What is on the Horizon in HMA John D AngeloD Federal Highway Administration 1

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3 Development of Standard Practice for Superpave Plus Specifications Use of DSR in Place of ER and Ductility 3

4 Why Superpave Plus Specs. The existing specifications do not identify the performance characteristics of modified binders. The existing specifications do not have a criteria for fatigue or durability. Agencies look to other tests to identify modifiers Elastomeric polymer modifiers are desired 4

5 State DOT s s Specifying Polymer PG (PG+) Ductility ER ER Ductility, TT & ER TT & DT ER & TT ER ER PA ER & FD ER & TT ER & PA ER ER ER FD ER SB/SBS Required PG + modifier PG ER ER SB/SBS Required FD & ER ER ER & PA PA PA ER-Elastic Recovery FD-Force Ductility TT-Toughness & Tenacity PA-Phase Angle 5

6 Toughness & Tenacity 6

7 Elastic Recovery AC doesn t recover SB modified AC recovers 7

8 Proposed MSCR TEST Protocol 3200 Pa Creep Stress 100 Pa 1 10 time Creep Strain time 8

9 What criteria? % recovered strain Creep 1st cycle 70C 1000 Pa (Peak Strain - recovered Strain)/Peak Strain % strain control Elvaloy Stylink AB time 9

10 PG SBS 83% recovery 100Pa PG SBS 100Pa 64C 5.00E E E E E+01 Strain % 2.50E E+01 Series1 1.50E E E E E E E E E E E E E E E+02 time s 10

11 PG SBS 21% recovery 3200Pa PG SBS 3200Pa 64C 2.50E E E+03 Strain % Series1 1.00E E E E E E E E E E E E E E+02 time s 11

12 % recovery 100Pa 4% SB, 19% oil, PG 67-28, recovery 100 Pa, 67C 3.50E E E+01 Strain % 2.00E E+01 Series1 1.00E E E E E E E E E E E E E E+02 time s 12

13 % recovery 3200Pa, 75% ER 4% SB, 19% oil, PG 67-28, recovery 3200 Pa, 67C 1.20E E E+02 Strain % 6.00E+02 Series1 4.00E E E E E E E E E E+02 Time 2 13

14 Findings to date The DSR MSCR percent strain recovery criterion can replace the FD, ER, or T&T. 14

15 Future Steps Analyze available MSCR percent recovered strain data to finalize creep stress level and test protocol Where available, show relationships with existing ER, FD, Duct., and T&T data 15

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17 Superpave Gyratory Compactor Calibration Making Superpave Consistent 17

18 Eight Different Models 18

19 Standard Method of Test for Preparing and Determining the Density of Hot-Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor AASHTO Designation: T

20 4. APPARATUS 4.1Superpave Gyratory Compactor The compactor shall tilt the specimen molds at an external angle of or an average internal angle of in accordance with AASHTO. The compactor shall gyrate the specimens mold at a rate of gyrations per minute 20

21 Internal Angle of Gyration Internal Angle of Gyration Development of the FHWA Dynamic Angle Validator (DAV) Wireless Unit Drop into mold either before or after adding mix 21

22 Average Dynamic Internal Angle DAV on Top to measure α T DAV on Bottom to measure α B 22

23 Internal Angle of Gyration DAV Validate Differences in SGCs Demonstrated that internal angle of gyration could be different even though external angle was the same. Calibration Potentially time-intensive intensive Up to 1 day for a calibration Affected by mixture stiffness Requiring recalibration for different mix types 23

24 Forces Acting in a Mold During Gyratory Compaction 24

25 Mechanical Simulation of an Asphalt Mixture RAM RAM Rapid Angle Measurement Device (Pine) 25

26 RAM Operations Increasing Ring Diameter = Increasing Mix Eccentricity/Stiffness 26

27 Mechanical Simulation of an Asphalt Mixture HMS HMS Hot-Mix Simulator (TestQuip) 27

28 1.300 Comparison of Internal Angle Using Mechanical Mix Simulation Devices Avg Internal Angle (deg) Pine G1 Pine 125x Brovold Troxler 4140 Troxler 4141 SGC RAM (44 mm) HMS (21 deg) OLD DOME HMS (21 deg) NEW DOME DAV with Mix 28

29 Conclusions Recommend 22-mm (233 N-m) N to set angle Difference at higher eccentricity limit no greater than degrees for most SGC models Use 25-mm (265 N-m) N to set angle for other model? No consistent significant difference in internal angle as a function of mold temperature Initial results showed no consistent relationship between internal angle measured with RAM and HMS Modification to HMS dome has significantly improved relationship 29

30 National Cooperative Highway Research Program 30

31 9-29: Simple Performance Tester for Superpave Mix Design Evaluation of 1st-article SPTs from Shedworks/IPC and Interlaken complete. Single-replicate measurement COV: dynamic modulus 13%, flow time 33%. Advanced Asphalt Technologies (November 2005) 31

32 Performance Tester 32

33 Dynamic Modulus E* σ 0 ε 0 = dynamic stress = recoverable axial strain E * = σ0 ε 0 Phase Angle φ Load 75 ~ 125 µε Displacement ƒ Loading Frequency 33

34 Flow Number Test (Fn) Dynamic Creep Repeated Load STRESS STRAIN TIME Flow Number Applied Stress (kpa) 600 (87 psi) Temperature ( C)( 54 Failure limits CYCLES 10,000 cycles or 5% strain Flow Number: : number of load repetitions at which shear deformation occurs under constant volume 34

35 Flow Number Test (Fn) Load on for 0.1 sec, off for 0.9 sec 50,000 Flow Number Axial Strain Secondary Flow Constant Volume Tertiary Flow Nonrecoverable Deformation 0 Load Cycles

36 Slope of Accumulated Microstrain Curves Total Accumulated Microstrain Mix Design 4.9% Mix Design 5.4% Mix Design 5.9% 2 per. Mov. Avg. (Mix Design 4.9% ) 2 per. Mov. Avg. (Mix Design 5.4%) 2 per. Mov. Avg. (Mix Design 5.9%) Total Cycles Slope of curve indicates progression of material into Tertiary Flow 36

37 9-33: A Mix Design Manual for Hot Mix Asphalt Update method in AI Manual SP-02: Simple performance test(s). As-delivered M-E E design guide performance models and software. New volumetric criteria. Framework for integrated mix and structural design. Advanced Asphalt Technologies, LLC (August 2006) 37

38 1-40:Facilitating the Implementation of the Guide for the Design of New and Rehabilitated Pavement Structures Conduct a thorough review of the Guide Organize and convene workshops Develop a concise user s s guide Provide technical support 38

39 FHWA Design Guide Implementation Team (DGIT) To support & educate State highway agencies and industry in development & implementation of Mechanistic-Empirical Pavement Design Facilitating Implementation of Mechanistic-Empirical Pavement Design 39

40 FHWA DGIT Workshops Past Workshops Introduction to the DG 8* Traffic 2 Alaska Current Materials 11* Traffic 2 Future Hawaii Climatic Inputs 4 Local Calibration *Webcast available Workshop Locations 40

41 Additional Workshops Planned 1-Day Climatic Inputs for M-E M Pavt Design Under development by DGIT Pilot: February 2006 Purpose: : educate Pavt Designers on obtaining climatic inputs through EICM Local Calibration for M-E PDG models Awaiting deliverables from NCHRP 1-40 A,B Planned for Winter 2007 Purpose: discuss Sensitivity of inputs & calibration, educate Pavt Designers & Pavement Managers 41

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43 Intelligent Compaction GPS antenna GPS reference station (Trimble) BW 174 Asphalt Manager equipped with BCM05 and GPS 43

44 What is intelligent compaction? Automatic adjustable compaction equipment Usage of Continuous Compaction Control, CCC Selection of the most suitable equipment 44

45 GPS / positioning with reference station 45

46 At the mix plant are there other process that can be part of a QA program? 46

47 In line viscometer for verification of binder 47

48 Computer recordation 48

49 QA of the Future The QA will all be tied to Internet. Direct down load of info to the owner. Posting of data immediately to all parties. Faster review and resolution of discrepancies. 49

50 Questions 50