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
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
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.