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Two-Lift Paving

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A presentation given during the 39th Annual NCPA Concrete Paving Workshop. By Gary Fick, NCPTC

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Two-Lift Paving

  1. 1. TWO-LIFT PAVING NEBRASKA CONCRETE PAVING WORKSHOP 2018 Gary Fick
  2. 2. Two-Lift Paving • Portland cement concrete pavement • Bottom lift commonly uses less expensive materials • Top lift uses highly durable materials • Constructed wet-on-wet 3” top lift 6” bottom lift MnRoad 2010 Ref. SHRP2 R-21, Rao, et.al
  3. 3. Two-Lift Paving • Motivation/Benefits – Economics – Sustainability – Life cycle costs
  4. 4. Two-Lift Paving • Achieving durability goals at the lowest life cycle cost • Driven by locally available materials – Lower quality aggregates in the bottom lift – Recycled aggregates in the bottom liftIncreased use of recycled, reclaimed and by-product materials in the bottom lift – High quality durable aggregates in the top lift
  5. 5. Two-Lift Paving • Is it experimental? Ref. Gillen JRCP circa 1960
  6. 6. Two-Lift Paving • Standard practice for Austria • Specialized projects in: – Switzerland – Belgium, – the Netherlands – France – Germany Ref. SHRP2 R-21, Rao, et.al
  7. 7. Two-Lift Paving • US experience – Numerous test sections and pilot projects – Mid 1980’s to 2016 Ref. SHRP2 R-21, Rao, et.al
  8. 8. Two-Lift Paving I-90 Illinois • Illinois Tollway • 2013 – 2015 construction • 37 miles – ±1,500,000 yd2 • $800,000,000 Ref. Wenberg
  9. 9. Two-Lift Paving I-90 Illinois • 11 ¼” to 13” thick two-lift JCP – Bottom lift 8 ¼” to 10” thick • 15% to 50% fractionated recycled asphalt pavement (FRAP) • Ternary cement blend – portland cement, fly ash & slag (max. 50% replacement) – Top lift 3” standard IDOT mix Ref. Ozinga & Wenberg
  10. 10. Two-Lift Paving I-90 Illinois • Cost savings of approximately $10 per yd2 • Not all savings were attributable to the two- lift design – Reduced number of dowels (wheelpath only) – Use of DBI – Highly competitive bidding market Ref. Gillen
  11. 11. Two-Lift Paving I-90 Illinois • Not practical for all locations – Ramps – Gaps • Larger plant sites needed • Concrete uniformity is critical • Top lift placed within ±30 minutes Ref. Wenberg
  12. 12. Two-Lift Paving Design • Design using PavementME • Example designs provided in SHRP2 R-21 report – Composite Pavement Systems Volume 2: PCC/PCC Composite Pavements Ref. SHRP2 R-21, Rao, et.al
  13. 13. Two-Lift Paving Properties • Average compressive strength • Example from MnRoad section constructed in 2010 – Bottom lift • RCA with 40% fly ash ≈ 4,500 psi • Std. aggregate with 60% fly ash ≈ 4,800 psi – Top lift (exposed aggregate) ≈ 5,500 psi Ref. SHRP2 R-21, Rao, et.al
  14. 14. Two-Lift Paving Construction • European example PROCESS OVERVIEW 1) Equipment: 3 unit paving train consisting of: 1) SP 1500 w/ DBI – bottom layer 2) SP 1500 – top layer 3) TCM 1800 – application of surface retarder 4) 2 Wire brush/broom Vehicles 2) Crew and operational tasks 1) 3 operators 2) 2 excavator operators - bottom layer spreading and charging 2nd layer hopper/conveyor 3) Concrete discharge coordinator 4) DBI operator 5) 2 finishers 6) 2 wire brush vehicle operators Courtesy Wirtgen
  15. 15. Two-Lift Paving Construction • European example Courtesy Wirtgen
  16. 16. Courtesy Wirtgen Two-Lift Paving Construction
  17. 17. Courtesy Wirtgen
  18. 18. Two-Lift Paving Construction • US Example – I-70 Abilene, KS – Dual drum plant with 4 bins – Both mixtures produced from one plant – Color coded cards for each mixture Courtesy Koss Construction Company
  19. 19. Two-Lift Paving Construction • US Example – I-70 Abilene, KS – Spreader – Paver – Spreader – Paver – Texture/Cure
  20. 20. Two-Lift Paving Construction • US Example – I-70 Abilene, KS • Stiff bottom layer Courtesy Koss Construction Company
  21. 21. Two-Lift Paving Construction • US Example – I-70 Abilene, KS Courtesy Koss Construction Company
  22. 22. Two-Lift Paving • Conclusions – Potential use where aggregate resources are deficient and/or have limited supply – Increased use of recycled, reclaimed and by- product materials in the bottom lift – Design and construct the top lift for long-term durability – Exposed aggregate surface finish is feasible – Thorough LCCA should be performed
  23. 23. Questions and Discussion HAPPY HAPPY HAPPY

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