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NCAT Pavement Test Track

Research Findings from the NCAT Test Track APAI Winter Conference Indianapolis , December 14, 2010. NCAT Pavement Test Track. 1.7 mile oval asphalt track 45 experimental test sections, each 200 ft. long

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NCAT Pavement Test Track

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  1. Research Findings from the NCAT Test TrackAPAI Winter ConferenceIndianapolis, December 14, 2010

  2. NCAT Pavement Test Track • 1.7 mile oval asphalt track • 45 experimental test sections, each 200 ft. long • A pooled-fund project with test sections sponsored by highway agencies and businesses to evaluate specific materials and/or pavement design strategies • Realistic traffic applies 10 million ESALs in each two year cycle • Currently 60% complete with the 4th cycle 2

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  4. 4

  5. Lab Testing 5

  6. Test Track Research Findings • Fine and coarse Superpave mixes perform similarly • Modified binders cut rutting approximately 50%, densify less under traffic, enable high binder content • Aggregate specification assessments • F&E for SMA & OGFC • Polishing prone aggregates • Elimination of Restricted Zone • Gravel performs well in SMA & OGFC

  7. Test Track Research Findings • Benefits of OGFC: safety, noise, smoothness • Lowering Ndesign is O.K. • High RAP content mixes perform well • Criteria for Lab Performance Tests • Air voids • Asphalt Pavement Analyzer • Flow Number • Energy Ratio for top-down cracking

  8. Test Track Research Findings • Mechanistic pavement models validated and calibrated • Measured vs. predicted HMA tensile stresses • Seasonal effects on pavement layers • Compressive stresses in unbound layers • Transfer functions for strain damage • Field fatigue threshold • Validation of pavement temperature models • Traffic wander • Speed vs strain / load pulse

  9. 2006 Indiana Low QC Voids Study 9

  10. 2006 Indiana Low QC Voids Study 10

  11. Track Layout 11

  12. 2009 Thinner Structural Test Sections 12

  13. Perpetual Pavement on Soft Clay 1400 1200 10” 1000 0.0335*Temperature N8 Strain = 21.487e 800 2 R = 0.96 Tensile Microstrain 600 N8 N9 0.0298*Temperature N9 Strain = 11.496e 400 2 R = 0.9217 14” 200 0 0 20 40 60 80 100 120 140 Mid-Depth Temperature, F

  14. 200 175 150 125 100 IRI (inches per mile) 75 50 25 0 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 MESALs N8 N9 Perpetual Pavement on Soft Clay Visible Cracks on Pavement Surface Cracks appear on surface

  15. Perpetual Pavement on Soft Clay • 14” pavement looks great after 16.2 million ESALs • 10” pavement recently rehabilitated for 2nd time • In need of 1st rehabilitation after 10 million ESALs • 5” mill/inlay failed again after 3.5 million ESALs • 1.6 million ESALs on 5-3/4” high polymer inlay 15

  16. Perpetual Pavements • 24 inch perpetual (original) Track foundation • Designed with ‘93 Guide for MANY cycles • Two 9 inch thick structural sections in 2003 • ‘93 Guide predicted failure near 10M ESALs • 26.2M ESALs to date (perpetual expectation) • 15 inches of wasted (excess) thickness? • 14 inches required on N9 soft subgrade 16

  17. Layer Coefficient Recalibration 18.5% Thinner

  18. Layer Coefficient Recalibration • Technology has improved since AASHO Road Test • Need to recalibrate coefficients • Increase a1 from 0.44 to 0.54 based on all structural sections on the Track • 18.5 percent thinner structural designs • Alabama saving $25M to $50M annually 18

  19. 2009 Group Experiment (+)

  20. 2009 Group Experiment (+)

  21. High RAP Mixes on the NCAT Test Track • 2006: • 45% RAP surface mix with four different virgin binder grades • 2009: • 2006 high RAP sections continued • 45% RAP surface mix from Mississippi • 50% RAP HMA & 50% RAP WMA in structural sections

  22. Group Experiment – High RAP (N10 & N11) Control HMA Section 50% RAP Section 50% RAP WMA Section

  23. PFC Surface Cracks (Tack Method) 23

  24. PFC Surface Cracks (Tack Method) • 2006 crack susceptible dense Superpave mix • Surface cracks after 1.9M ESALs (Rehab at 5.6M) • 2009 PFC surface placed with conventional tack • Surface cracks after 2.2M (cracking/pumping at 6.2M) • 2009 bonded PFC surface placed with spray paver • Surface cracks after 4.1M (very good at 6.2M) 24

  25. PFC Surface Permeability

  26. PFC Surface Noise

  27. SBS vs GTR Mill/Inlay: Rutting SBS GTR

  28. Pavement Preservation (S13)

  29. Temperature Reduction (S13)

  30. Reflective Cracking (S13)

  31. Web Performance Reports 31

  32. www.pavetrack.com

  33. Profiler Certification Program 33

  34. National WMA Certification Program • 9.5 mm coarse granite PG67-22 mix (TSR ≈ 0.3!) • Laboratory performance of plant produced mix • Flow number, dynamic modulus, APA • IDT, overlay tester, bond strength, PG grading • TSR, stripping via boiling, Hamburg (aged & unaged) • Field performance on Pavement Test Track • Hot-mix control, immediate traffic (1 year thereafter) • Weekly rutting, roughness, macrotexture • Final report within 18 months of commitment 34

  35. Thank Youwww.NCAT.us

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