Alaska Concrete Summit

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

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

4. 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

5. 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

6. 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

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

8. 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

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

10. 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

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

12. Removing Ruts • Diamond Grinding

13. Diamond Grinding

14. 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

19. 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

20. 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

21. Faulted Joints

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

24. 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

25. 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

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

27. Repair Procedures

28. . 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. . . . . .

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

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

31. Sawing & Chipping

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

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

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

39. Full-Depth Patching Corner Breaks Transverse Cracks

40. 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

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

45. Placement of Bond-Breaking Board

48. Completed patch combined with diamond grinding

49. QUESTIONS?