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Concrete Overlay Performance in Nebraska

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A presentation given during the 39th Annual NCPA Concrete Paving Workshop. By Brandon Varilek, P.E., PMP, NDOT

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Concrete Overlay Performance in Nebraska

  1. 1. Concrete Overlay Performance in Nebraska Brandon Varilek, P.E., PMP Pavement Design Engineer
  2. 2. PCC Overlay Performance in NE • Terminology • NDOT Project Design & Performance • Historical; 40’ - 60’s • Modern; 80’s – Today • Lessons Learned • Future of PCC Overlays
  3. 3. Terminology • Whitetopping Vs. Concrete Overlay • Bonded vs. UnBonded • Designed as part of pavement struct • Must behave as monolithic pavement • Bonding critical • Preventative Maintenance/Minor Rehab • Add structural capacity and eliminate surface distress of a good pavement • Thickness (T): 2” - 6” • Joints: 3’-8’ (1.5xT) over HMA Match joints over PCC 2014 Guide to Concrete Overlay
  4. 4. Terminology • Bonded vs. UnBonded • Designed as new structure on stable base • Acts as independent structure • Bonding to HMA not needed “structurally” but beneficial • Adds some load carrying capacity • Holds slabs together in absence of ties • Bonding to underlying concrete not allowed • Use HMA or Geotextile to avoid matching joints • Minor/Major Rehab • Restore structural cap. to a deteriorated pavement • Thickness (T): 4”-11” • Joints: 1.5xT for T<6”* 2xT for T>6” up to 15’ 2014 Guide to Concrete Overlay *CPTech Recommendation revised between 2008 & 2014 Guide to Concrete Overlay
  5. 5. • Hwy 6, Lincoln – Greenwood & Greenwood - Chalco • Base: 1929/1930 9”-6”-9” x 20’ PCC • PCC Overlay: 1948 & 1952 • 10 mi of 6” x 24’ RCP (wire mesh) • 2.8 mi of 5-6” x24’ RCP on 1.5” Bit mat • Resurfaced w/HMA in 1972,1985 or 1991 • 24-40 yr life (some correlation) • Hwy 6, “B” Street in McCook • Base: 1931 9”-7”-9” x 20’ PCC • PCC Overlay: 1964 • 0.5 mi of 5” RCP on 1.5” Granular FC • Reconstructed with PCC in 2001/2006 • 37-42 yr life “Historical” PCC Overlays (40’s – 60’s)
  6. 6. “Modern” PCC Overlays (1980’s) • Hwy 81 • Belvidere N&S, Hebron N, Strang S • 600 – 900 Trucks • Base ~ 6-8” HMA milled var. depth • PCC Overlay: 1982 & 1985 • 16.3 mi of 9” Unbonded* (non-doweled) PCC • Random 12-19’ Joints • 33-36 yrs old • Significant PCC Repairs present • Ready for resurfacing 2017 2017
  7. 7. “Modern” PCC Overlays (1990’s) • Hwy 2, Ansley – Mason City • 400 Trucks • Base~10” HMA milled var. depth • PCC Overlay: 1991 • 5.9 mi of 9” Unbonded (non-doweled) PCC • 16.5’ Joints • Resurfaced w/HMA in 2017 • 26 yr life • Significant maintenance required • Significant ASR Deterioration 1995 2016
  8. 8. “Modern” PCC Overlays (2000’s) • Hwy 50, Tecumseh North • 600 Trucks • Base: 1952 8”-6’-8”x22’ PCC • PCC Overlay: 2001 • 1500’ of 110mm (4.5”) Bonded PCC overlay • Milled PCC • Matched joints • Included fibers and 3’ widening • Will be removed in 2023 • 22 yr life • Repaired multiple times • Significant cracking, de-bonding
  9. 9. “Modern” PCC Overlays (2000’s) • Hwy 2, Berwyn – Ansley • 325 Trucks • Base ~11” HMA milled 0”-6” • PCC Overlay: 2003 • 5.7 mi of 8” Unbonded (doweled) PCC • 16.5’ Joints • 15 years old – Good condition • Slight ASR Staining? • May need Silane Sealer 2003 2016 2003
  10. 10. “Modern” PCC Overlays (2000’s) • Hwy 20, In O’Neill • 600 Trucks • Base ~ 11” HMA milled 4” • PCC Overlay: 2008 • 0.6 mi of 8” Unbonded (doweled) PCC • 16.5’ Joints • 10 years old, excellent condition • Few cracked slabs 2008 2017
  11. 11. “Modern” PCC Overlays (2000’s) • Hwy 30 • 1) Paxton - Sutherland • 2) Cozad – Lexington • Includes Darr Spur • 3) Gothenburg West • 4) Roscoe – Paxton • 5) Sutherland – Hershey • 175-275 Trucks • Base:1930’s 9-7-9”x20’PCC+1950’s 8”x2’ PCC + 4-6”HMA • Exceptions: Darr Spur, Roscoe – Paxton (Full depth HMA) 514 3 2 North Platte
  12. 12. Hwy 30 Concrete Overlays • Paxton – Sutherland - 2010 • 12 mi of 5” Unbonded PCC, on milled surface • 6’x6’ joints, No Tie Bars, Shld: 2.5” HMA • Cozad – Lexington - 2013 • 12.4 mi of 5” Unbonded PCC on milled surface • 6’x6’ joints, No Tie Bars, Shld: 2.5” HMA • Gothenburg West - 2015 • 11.9 mi of 6” Unbonded PCC on 1” new HMA • 12’x12’ joints, Tied CL, Shld: 3”-2” HMA • Significant stripping in cores • Roscoe – Paxton - 2016 • 11.5 mi of 6” Unbonded PCC on milled surface • 9’x12’ joints, Tied CL, Shld: 2” HMA • HMA base, Joints shortened to 9’ based on 2014 Guide* • Sutherland – Hershey - 2018 • 7 mi of 5” Unbonded PCC on milled surface • 6’x6’ joints, No Tie Bars, Shld: 6” PCC *2014 CPTech Guide to Concrete Overlay Cozad - Lexington
  13. 13. Hwy 30 PCC Overlays Cozad – Lexington 2017 Darr Spur 2017Paxton – Sutherland 2017 Roscoe – Paxton 2017 • Paxton – Sutherland –8yrs • Cozad – Lex. & Darr Spur–5yrs • Gothenburg West – 3yrs • Roscoe – Paxton – 2yrs • Sutherland – Hershey – N/A • Excellent condition Gothenburg West 2017
  14. 14. Hwy 30 Concrete Overlays • More details • Constructed 1 lane at a time, closed road conditions • Opposing lane used for local access and construction equip. • Construction equip limited to 1 dir, and not on shoulders • Min 1” HMA required between slabs,including PCC repr • Paid for PCC in CY (max 110%) and Placement in SY • Cross-Slope/Supers corrected w/milling and/or HMA • Why Hwy 30? • Parallels I-80 – Convenient Detour • Composite provides solid base to minimize PCC depth • ML: 5” PCC vs. Traditional 4” HMA • Existing HMA provides bond breaker between slabs • HMA allows milling to limit grade raise/shld costs Cozad - Lexington
  15. 15. • Lessons Learned - Hwy 30 • Center Lane tie bars difficult to install when paving 5”x12’ • Sufficient manpower/equipment critical for timely sawing of thin pavements • Test strip can identify problems with sawing, tie bar placement • Required sealing of joints prior to traffic • Milled 1’ beyond PCC edge to allow inspection/clean-out of trench • Need to look into isolated drainage issues • Lessons Learned – All • Thin, 4.5” Bonded Overlay test section performed poorly • ~30 mi of 8-9” Unbonded PCC overlays have performed very well • Neglecting material defects (ASR) • ~ 50 mi of 5-6” Unbonded Overlays are performing well but <8yrs old Concrete Overlay Performance in Nebraska
  16. 16. Concrete Overlay Performance in Nebraska Future of PCC Overlays in NE • Hwy 30, Sutherland – Hershey - 2018 • Continue to look for good candidates • Detour route, good base, ability to minimize grade raise through milling Sources • NDOT Archives & Pavement Management • CP Tech Guide to Concrete Overlays, May 2014
  17. 17. Questions?

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