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

1. TWO-LIFT PAVING
NEBRASKA CONCRETE PAVING WORKSHOP
2018
Gary Fick

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. Two-Lift Paving
• Motivation/Benefits
– Economics
– Sustainability
– Life cycle costs

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. Two-Lift Paving
• Is it experimental?
Ref. Gillen
JRCP circa 1960

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. Two-Lift Paving
• US experience
– Numerous test sections and pilot projects
– Mid 1980’s to 2016
Ref. SHRP2 R-21, Rao, et.al

8. Two-Lift Paving I-90 Illinois
• Illinois Tollway
• 2013 – 2015 construction
• 37 miles – ±1,500,000 yd2
• $800,000,000
Ref. Wenberg

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. 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. 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. 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. 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. 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. Two-Lift Paving Construction
• European example
Courtesy Wirtgen

16. Courtesy Wirtgen
Two-Lift Paving Construction

17. Courtesy Wirtgen

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. Two-Lift Paving Construction
• US Example – I-70 Abilene, KS
– Spreader
– Paver
– Spreader
– Paver
– Texture/Cure

20. Two-Lift Paving Construction
• US Example – I-70 Abilene, KS
• Stiff bottom layer
Courtesy Koss Construction Company

21. Two-Lift Paving Construction
• US Example – I-70 Abilene, KS
Courtesy Koss Construction Company

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. Questions and Discussion
HAPPY
HAPPY
HAPPY