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Oklahoma’s Test Section at NCAT Track AMAP 12 th Annual Conference Western Crown Center Hotel

Oklahoma’s Test Section at NCAT Track AMAP 12 th Annual Conference Western Crown Center Hotel Kansas City, MO February 16, 2011. Kenneth Ray Hobson, P.E. – Bituminous Engineer. Topics. Test Sections – N8 and N9 History of Performance N8 Repairs Success vs. Failures Use of Knowledge.

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Oklahoma’s Test Section at NCAT Track AMAP 12 th Annual Conference Western Crown Center Hotel

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  1. Oklahoma’s Test Section at NCAT Track AMAP 12th Annual Conference Western Crown Center Hotel Kansas City, MO February 16, 2011 Kenneth Ray Hobson, P.E. – Bituminous Engineer

  2. Topics • Test Sections – N8 and N9 • History of Performance • N8 Repairs • Success vs. Failures • Use of Knowledge

  3. OK Sections

  4. OK Sections

  5. 2006 N8 and N9 History Perpetual Pavement Design • N8 and N9 on Soft Clay Subgrade • N8: 10" HMA • N9 : 14" HMA • RBL Bottom Lift for Both • N9 - Successful • N8 - Cracked

  6. 2009 N8 and N9 History Retard Cracking • N9: Continue Traffic • N8: Mill and Replace Top Two Lifts • N8: Retard Cracking by Two Fabrics

  7. N8 Reflective Cracking to Retard

  8. N8 Cracking at 2.7 MESALs

  9. Microstrain Comparison

  10. More Distress at 3.4 MESALs

  11. June 16, 2010 Repair

  12. Terminal Distress at 3.8 MESALs

  13. Observed Shear

  14. End of Section

  15. Shear Plane

  16. End of Section

  17. Reflective Crack

  18. Preliminary Forensic Results

  19. Additional Forensic Results

  20. Final Forensic Results

  21. N8 Repair Two • Forensics Showed Extensive Subgrade Deformation • Significant Repair Needed • Use Design Similar to N7 (7.5% SBS) • Make Sublot 3 Similar to Sublot 1 • 9.5 mm NMS and Add Binder • Similar to RBL Concept

  22. 2009 Group Experiment (+)

  23. N8 Repair Two Details • NTSS-1HM Tack Coats 0.07 gal/SY • Average Mill Depth of 5.8" • Bottom Two Lift Total Thickness 4.7" • N8-1 Like N7-1, 1.2" Thick • N8-3 Like N8-1 Except 0.2% Binder Added • N8-2 Like N7-2, 19 mm NMS

  24. N8 Repair Two Details • N8-1 3.2% Air Voids, 91.4% Density • N8-2 4.9% Air Voids, 94.2% Density • N8-3 2.1% Air Voids, 94.3% Density

  25. Matt After Rain

  26. Matt on 1/21/2011

  27. Improved IRI and MTD

  28. Use of Knowledge • Use Repair Concept on Interstate • NTSS-1HM Tack Coats 0.07 gal/SY • Use PG88-22 Binder for Top 3 Lifts • Top and Bottom Lifts (1 and 3) • Use Superpave 9.5 mm NMS • Lift below Top Lift: Superpave 25 mm NMS • Use 50 SGC Gyrations for 9.5 mm NMS • 2.0% Air Voids for Lift 3 (RBL Concept)

  29. Spring 2012 Repair SiteI-40 Mile Posts 102-104

  30. Acknowledgements • Dr. R. Buzz Powell, P.E. • Kraton Polymers LLC • Jeff Dean, Pavement Engineer ODOT • AMAP

  31. Questions? • khobson@odot.org • http://pavetrack.com • Subscribe Dixie Contractor • Fournier, Paul. Failed Test Track Section Repaired. Dixie Contractor. Vol. 84 Number 12, Dec. 2010 • ODOT 2009 Standard Specifications

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