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Concrete Overlay Performance in Nebraska
- 1. Concrete Overlay Performance in Nebraska Brandon Varilek, P.E., PMP Pavement Design Engineer
- 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. 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. 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. • 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. “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. “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. “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. “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. “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. “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. 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. 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. 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. • 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. 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. Questions?
Editor's Notes
- Photos at 297.06
- Photos at 297.06
- 2016 Photo @ 291.96
- Paxton – Sutherland - 2010 ML: Mill 2.5”, 5” Unbonded PCC, 6’x6’ joints, No Tie Bars Shld: 2.5” HMA Cozad – Lexington - 2013 ML: Mill 2.5”, 5” Unbonded PCC , 6’x6’ joints, No Tie Bars Shld: 2.5” HMA Gothenburg West - 2015 ML: Mill 5”, 1” HMA, 6” Unbonded PCC 12’x12’ joints, Tied CL Shld: Mill 1”, 3”-2” HMA Significant stripping in cores Roscoe – Paxton - 2016 ML: Mill 6”, 6” Unbonded PCC , 9’x12’ joints, Tied CL Shld: Mill 2”, 2” HMA HMA base, Joints shortened to 9’ based on 2014 Guide* Sutherland – Hershey - 2018 ML: Mill 3”, 5” Unbonded PCC , 6’x6’ joints, No Tie Bars Shld: 6” PCC
- 30-2(138), Paxton – Sutherland, 61461 30-3(116), Cozad – Lexington, 61468 30-2(140), Gothenburg West, 61467 30-2(139), Roscoe – Paxton, 61462 30-2(143), Sutherland – Hershey, 61568
- G Thayer: pay by the SY (plan) and CY (maximum 110%) to cut the risk of the contractor as we mill is to depth but the top of surfacing is to grade yet they have to meet thickness requirements so they have to establish a paving model. It was from industry conversation prior to our first project.