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Alaska Concrete Summit

Join us at the Alaska Concrete Summit on December 5, 2012 in Anchorage, AK to learn about studded tire wear and abrasion resistance, utility cuts and their impact on pavement performance, and the benefits of diamond grinding. Gain insights from experts in the field and discover recommendations for mix designs and repair procedures. Don't miss this opportunity to improve your concrete pavement knowledge!

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Alaska Concrete Summit

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  1. Alaska Concrete Summit December 5, 2012 Anchorage, AK Jim Powell, P.E. Executive Director American Concrete Pavement Association, Northwest Chapter

  2. Alaska Concrete Summit • Studded tire wear and abrasion resistance • Utility cuts and pavement performance • Diamond grinding

  3. Studded Tire Wear • Significant source of pavement damage • Primary source of surface damage for PCCP • Can result in noticeable ruts in 10 years or less • Can be mitigated

  4. Studded Tire Wear • Primary mechanism of damage is impact • Experience indicates slower wear rate at slower driving speeds • Wear rates range from 0.05 mm/year per million studded vehicles to 0.5 mm/year per million studded vehicles

  5. Studded Tire Wear • Wear rate ranges from 0.05 to 0.5 mm/yr per million studded vehicles • Average wear rate in WA is 0.1 mm/year per million studded vehicles • At 50,000 ADT and 50% stud use this equals 0.012”/year • 20 years to 0.25” rut • At 0.5 mm/year that is 4 years to 0.25” rut • At 0.05 mm/year that is 40 years to 0.25” rut

  6. Studded Tire Wear • Material properties affecting studded tire wear • Aggregate hardness • Aggregate gradation • Paste hardness

  7. Canadian Study • Evaluated the effects of aggregate type, w/c ratio, and silica fume • A very low water cement ratio (0.30) can make the concrete nearly as abrasion resistant as a very high quality granite or trap rock

  8. Norway Study • Showed that high strength concrete (100 Mpa) exhibits the same abrasion resistance as massive granite

  9. Washington State Experience • SPS 2 test sections • 500 psi, 650 psi, and 900 psi flexural strengths • 500 psi and 650 psi mixes showed significant wear after 5 years • 900 psi still shows tine marks after 15 years • Seems to support Canadian and Norwegian results

  10. Mix Designs Recommendations • Well graded, hard aggregates • High cement content • Low water cement ratio • High compressive strength, >= 10,000 psi

  11. Removing Ruts • Diamond Grinding

  12. Diamond Grinding

  13. What is Diamond Grinding? • Removal of thin surface layer of hardened PCC using closely spaced diamond saw blades • Results in smooth, level pavement surface • Longitudinal texture with desirable friction and low noise characteristics • Frequently performed in conjunction with other CPR techniques, such as full-depth repairs, dowel bar retrofit, retrofit edgedrains

  14. Advantages of Diamond Grinding • Costs substantially less than AC overlays ($2.50 - $12 per square yard) • Enhances surface friction and safety • Can be accomplished during off-peak hours • Grinding of a rough area does not require grinding of adjacent areas • Blends patching and other surface irregularities into a consistent, identical surface

  15. Pavement Problems Addressed • Faulting at joints and cracks • Built-in or construction roughness • Polished concrete surface • Wheelpath rutting • Unacceptable noise level • Permanent upward slab warping • Inadequate transverse slope

  16. Faulted Joints

  17. Utility Cuts in Concrete Pavements • We can’t use concrete because it is difficult to restore when cut • City of Seattle Study

  18. City of Seattle Study • Looked at pavement performance over utility cuts to develop cost schedule • Found significant reduction in pavement condition on asphalt pavements with utility cuts • Asphalt cuts typically require frequent patching and thicker overlays

  19. City of Seattle Study • Found no reduction in pavement condition rating in concrete streets with utility cuts • Policy requires that any intact panel be replaced entirely • No panel can be left in three pieces • Patch constitutes 1 piece • Effectively requires either full panel or half panel replacement

  20. City of Seattle Study • Policy effectively ensures that repairs in PCCP pavements restore the load transfer and structural integrity of the pavement

  21. Repair Procedures

  22. . Partial Depth Repairs • Repairs deterioration in the top 1/3 of the slab. • Generally located at joints, but can be placed anywhere surface defects occur. . . . . .

  23. Partial-Depth Patch Layout 2 - 6 in. min. 2 - 6 in. min. Patch Spall 2 in. (min.) - t/3 (max.) t

  24. Partial DepthConcrete Removal • Sawing and chipping • Carbide milling • Transverse • Longitudinal

  25. Sawing & Chipping

  26. Point Bearing Pop out & Breakage Joint Closure Debonding Expansion Expansion

  27. Full-Depth Patching • Purpose • Restore structure • Restore ride • Used for • Joint/crack deterioration • Broken slabs • Corner breaks

  28. Full-Depth Patching • Joint Deterioration • Spalling (below surface) • Cracking

  29. Full-Depth Patching Corner Breaks Transverse Cracks

  30. Load Transfer Jointed Pavements: Patch 12 in. c-c typ. spacing Top View Optional Dowels 12 in. typ. d/2 Side View Remove loose material and fill any depressions with concrete

  31. Load Transfer Utility Patches: Utility Trench Good Practice 9-10 in. rim Utility Trench Poor Practice

  32. Placement of Bond-Breaking Board

  33. Completed patch combined with diamond grinding

  34. QUESTIONS?

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