Two Lift Concrete Composite 
Pavements 
Shreenath Rao, Ph.D., P.E.
Two‐Lift Paving Workshop
Austin, TX – May 23, 2013
Two Lift Concrete Paving‐
A Forgotten Practice
Popular back in the 50’s, 60’s and 70’s when the
Tollway was originally bui...
Tollway Requires 100% Recycling of Concrete 
and Asphalt  Pavements with Reconstruction
In Base Aggregates In New Asphalt ...
Plenty of Coarse FRAP to be Left for 
Concrete – How do we Reuse it?
Composite Pavement Field Trials 
Initiated in 2010
 Asphalt‐over‐concrete 
composite ramps built
 6.5 bag fly ash mix wi...
Black Rock Ternary Mixes Researched
 Further processing of FRAP to 
remove agglomerated 
sand/asphalt particles was not 
...
Composite Pavement Research Performed
 Further evaluated black 
rock concrete mixes for 
fresh, hardened and 
durability ...
Why Go Back to the Old Paving Methods?
Making Concrete Greener and Ultimately 
Cheaper For Both Lifts
Optimize
gradation and
reduce cement
content
Replace Virgin...
Bottom Lift Concrete Options / Requirements
As Currently Specified
 Optimized Gradations
 15% to 50% Coarse FRAP 
(Black...
Options to Improve Top Lift Performance 
 Reduced Permeability, Mitigate ASR Concerns,  
and Improve Durability with Opti...
Specifications For Composite Pavements
 Materials
Top Lift Concrete Designs either Standard Class PV, or 
Optimized Tern...
Construction Methods
 Removal and 
Reprocessing of Old 
Pavements
RCA for reuse as
PGE or coarse
aggregate for
concrete
R...
Specifications For Composite Pavements
 Equipment
 All in accordance with 
IDOT Standards
Test Strips to be Constructed for All Types 
of Placements (single and double lane)
Single Lift Placements vs. Two Lift
Dowel Alignment Tolerances
Consolidation to be Monitored
Two Slip Form Pavers / Two Belt Placers
One Slip Form Paver / Two Belt Placers
Envelope Outside Edges of Bottom Lifts
Finishing / Curing / Opening to Traffic
Economic Benefits of Greener Concrete
’04 – ’09 JPCP Bid Prices
 > 3,000,000 Sq. Yds. of JPCP 
Built System‐wide
 11.25”...
Prime contractor: Applied Research Associates, Inc. 
Sub contractors: University of Minnesota
Minnesota Department of Tran...
2007 2008 2009 2010 2011
Phase 1
2012
Phase 1 (completed May 2008)
• State of the practice
Phase 2 (completed May 2009)
...
PCC/PCC HMA/PCC
SHRP2 R21 Composite Pavement Systems SHRP2 R21 Composite Pavement Systems 
http://apps.trb.org/cmsfeed/TRB...
Thank You
1st Paver: Lower
JPCP Layer
2nd Paver:
Upper PCC Layer
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Two-Lift Paving - Agency Viewpoints

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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.

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Two-Lift Paving - Agency Viewpoints

  1. 1. Two Lift Concrete Composite  Pavements  Shreenath Rao, Ph.D., P.E. Two‐Lift Paving Workshop Austin, TX – May 23, 2013
  2. 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. 3. Tollway Requires 100% Recycling of Concrete  and Asphalt  Pavements with Reconstruction In Base Aggregates In New Asphalt Mixes
  4. 4. Plenty of Coarse FRAP to be Left for  Concrete – How do we Reuse it?
  5. 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. 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. 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. 8. Why Go Back to the Old Paving Methods?
  9. 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. 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. 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. 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. 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. 14. Specifications For Composite Pavements  Equipment  All in accordance with  IDOT Standards
  15. 15. Test Strips to be Constructed for All Types  of Placements (single and double lane)
  16. 16. Single Lift Placements vs. Two Lift
  17. 17. Dowel Alignment Tolerances
  18. 18. Consolidation to be Monitored
  19. 19. Two Slip Form Pavers / Two Belt Placers
  20. 20. One Slip Form Paver / Two Belt Placers
  21. 21. Envelope Outside Edges of Bottom Lifts
  22. 22. Finishing / Curing / Opening to Traffic
  23. 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. 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. 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. 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. 27. Thank You 1st Paver: Lower JPCP Layer 2nd Paver: Upper PCC Layer

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