A Two-Lift concrete Paving (2LCP) workshop was organized as a part of the Texas Department of Transportation (TxDOT) project 0-6749: Feasibility Study of Two-Lift Concrete Paving (2LCP). This workshop was conducted at the J. J. Pickle Research Campus (PRC), The University of Texas at Austin, Austin, TX on May 23rd, 2013. Dr. Jiong Hu, Texas State University, Research Supervisor, and Dr. David Fowler, The University of Texas at Austin, Co-Research Supervisor, co-chaired the workshop. The workshop offered the option of attending in person or remotely through webinar. Fifty-one attendees were present remotely or in person; 28 in person and 23 persons remotely.

1. Two Lift Concrete Composite
Pavements
Shreenath Rao, Ph.D., P.E.
Two‐Lift Paving Workshop
Austin, TX – May 23, 2013

2. Two Lift Concrete Paving‐
A Forgotten Practice
Popular back in the 50’s, 60’s and 70’s when the
Tollway was originally built

3. Tollway Requires 100% Recycling of Concrete
and Asphalt Pavements with Reconstruction
In Base Aggregates In New Asphalt Mixes

4. Plenty of Coarse FRAP to be Left for
Concrete – How do we Reuse it?

5. Composite Pavement Field Trials
Initiated in 2010
 Asphalt‐over‐concrete
composite ramps built
 6.5 bag fly ash mix with
20 percent black rock
placed
 Compressive strengths
> 3500 psi in three days
 Flexural Strengths >650
psi in seven days

6. Black Rock Ternary Mixes Researched
 Further processing of FRAP to
remove agglomerated
sand/asphalt particles was not
necessary
 A ternary concrete design with a
cement factor of 6.2 obtained
specified strength properties
with up to 50% of the coarse
aggregate replaced with FRAP
 Durability of concrete will be
adequate for composite
pavement applications

7. Composite Pavement Research Performed
 Further evaluated black
rock concrete mixes for
fresh, hardened and
durability properties
 Developed better
predictive models of the
field performance for 2‐lift
composite concrete
pavements using recycled
materials

8. Why Go Back to the Old Paving Methods?

9. Making Concrete Greener and Ultimately
Cheaper For Both Lifts
Optimize
gradation and
reduce cement
content
Replace Virgin
Aggregate with
Recycled
Replace portland
cement with SCM’s

10. Bottom Lift Concrete Options / Requirements
As Currently Specified
 Optimized Gradations
 15% to 50% Coarse FRAP
(Black Rock)
 0% to 85% Coarse RCA
 Ternary Mixes Required
 Blended Cements Allowed
Being Researched
 Use of Coarse FRAP from
IDOT mix sources
 Use of Lower Quality Virgin
Aggregates
 Use of Aged / Oxidized
Steel Slag FRAP

11. Options to Improve Top Lift Performance
 Reduced Permeability, Mitigate ASR Concerns,
and Improve Durability with Optimized Ternary
Mixes
 Reduce Noise and Improve Surface Friction with
Exposed Aggregate Finish
 Better Control on Smoothness
 Pervious Concrete Possible for Future
Permeable Pavements
 Photocatalytic Cements Can Be Used

12. Specifications For Composite Pavements
 Materials
Top Lift Concrete Designs either Standard Class PV, or
Optimized Ternary Performance Based Mixes with
Virgin Aggregate.
Bottom Lift Concrete Designs only Optimized Ternary
Performance Based Mixes with some Recycled
Aggregate.

13. Construction Methods
 Removal and
Reprocessing of Old
Pavements
RCA for reuse as
PGE or coarse
aggregate for
concrete
RAP Millings for reuse as
coarse aggregate for
concrete, FRAP for new
asphalt mixes, or for capping
stone

14. Specifications For Composite Pavements
 Equipment
 All in accordance with
IDOT Standards

15. Test Strips to be Constructed for All Types
of Placements (single and double lane)

16. Single Lift Placements vs. Two Lift

17. Dowel Alignment Tolerances

18. Consolidation to be Monitored

19. Two Slip Form Pavers / Two Belt Placers

20. One Slip Form Paver / Two Belt Placers

21. Envelope Outside Edges of Bottom Lifts

22. Finishing / Curing / Opening to Traffic

23. Economic Benefits of Greener Concrete
’04 – ’09 JPCP Bid Prices
 > 3,000,000 Sq. Yds. of JPCP
Built System‐wide
 11.25” JPCP ‐ $61.00/SY
 12” JPCP ‐ $65.00/SY
 13” JPCP ‐ $70.00/SY
’13 Composite Bid Prices
 > 700,000 Sq. Yds. to be
built on I‐90 in 2013
 11.25”– $40.66/SY
 12” ‐ $45.92/SY
 13” ‐ $49.70/SY
23

24. Prime contractor: Applied Research Associates, Inc.
Sub contractors: University of Minnesota
Minnesota Department of Transportation
University of California at Davis
University of Pittsburgh
Key Staff: Darter, Rao, Khazanovich, Von Quintus,
Harvey, Signore, Wu, Worel, Clyne, Watson,
Vandenbossche, Tompkins, Vancura
Duration: ~48 months
SHRP2 R21 Composite Pavement Systems SHRP2 R21 Composite Pavement Systems
Acknowledgements: FHWA MCL; Illinois Tollway, CS McCrossan

25. 2007 2008 2009 2010 2011
Phase 1
2012
Phase 1 (completed May 2008)
• State of the practice
Phase 2 (completed May 2009)
• Identify failure mechanisms and other factors the influence
performance.
• Develop draft performance models
• Research plan to evaluate critical design parameters
• European report
Phase 3 (completed April 2012)
• Construct experimental sections
• Refine and validate performance models
• Develop design procedures, guidelines, and construction
specifications
• Research plan for future validation an refinement of models
• Training materials to aid in implementation
Phase 2 Phase 3
SHRP2 R21 Composite Pavement Systems SHRP2 R21 Composite Pavement Systems

26. PCC/PCC HMA/PCC
SHRP2 R21 Composite Pavement Systems SHRP2 R21 Composite Pavement Systems
http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=2173

27. Thank You
1st Paver: Lower
JPCP Layer
2nd Paver:
Upper PCC Layer