Construction of Crack Free Concrete Bridge Decks TPF5051

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Construction of Crack Free Concrete Bridge Decks
TPF-5(051)

• Richard L. McReynolds, P.E.
• Engineer of Research

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Approval Process for Transportation Pooled Fund
Projects

• Solicitation requests are evaluated as received
  by technical area Bureau Chief(s), myself, Chief
  of Transportation Planning, Division Director and
  Asst. Sec. and STE.
• Typically reviews and approvals of funding are
  completed within a week or two of initial receipt
  using e-mail.
• With KS as lead state Work plan and project cost
  estimate are prepared for internal review. KDOT
  commitment is determined. Same approvals as above
  are then required before solicitation is posted.

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Current TPF Project Participation

• FFY 2005 funds obligated to 19 projects.
• FFY 2006 funds currently obligated/ committed to
  19/20 projects.
• FFY 2007 funds committed to 17 projects to date.

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Pooled Fund Project Budgets
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TPF Projects as Lead Agency

• Currently KS is Lead State on 6 active projects.
• To date since May 2000, 3,184,898 has been
  placed under contract on these projects.
• Most contracted with KSU and KU.
• Three are nearing completion.
• One is ongoing with an annual program.
• A 7th project has been completed except for final
  close out by the FHWA Finance Office.

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Construction of Crack Free Concrete Bridge Decks
TPF-5(051)

• University of Kansas
• Dr. David Darwin, Co-PI
• Dr. JoAnn Browning, Co-PI
• Ken Hurst, Engineering Manager, State Bridge
  Office, KDOT Project Monitor
• 15 states FHWA have contributed to date
• 950,000 contract
• 9/1/2002 to 3/30/2008

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Project Benefits to Participants

• With a 60K contribution, each state has an
  option of having the KU research team meet with
  their personnel to discuss and evaluate their
  designs and materials specifications.
• Team makes recommendations to reduce cracking.
• Team on site during construction of a control and
  test bridge to observe and do testing.
• Team will perform periodic crack surveys after
  construction.
• Materials testing also being done at KU to
  evaluate basic related materials properties.

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Low Cracking - High Performance Concrete (LC-HPC)
Bridge Decks

• By
• David Darwin, JoAnn Browning, Will D.
  Lindquist, Heather K. McLeod, and Swapnil
  Deshpande
• University of Kansas

2006 Concrete Bridge Conference Reno, Nevada May
7-10
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Research supported by

• 15 State DOTs Delaware, Kansas, Idaho, Indiana,
  Michigan, Minnesota, Mississippi, Missouri,
  Montana, New Hampshire, North Dakota, Oklahoma,
  South Dakota, Texas, Wyoming
• FHWA
• Lead state Kansas

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Outline

• Project scope
• Why were using LC-HPC
• Specifications for LC-HPC decks
• Progress and where were going

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20 Bridges
Project Scope

• So far
• 13 planned for Kansas
• 2 planned for South Dakota

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Selection of Bridges

• Composite steel girder bridges
• Full-depth slabs
• Removable forms
• Matching bridges to serve as a control where
  possible

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Why LC-HPC?

• Chlorides
• Cracks

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76 mm (3 in.)
Off cracks
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On cracks
76 mm (3 in.)
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Specifications
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Overall Approach

• Low cement water contents
• Low slump
• High strength is not always good
• Low evaporation rate
• Construction methods and materials matter
• More early cracking means more total cracking

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LC-HPC

• 1 inch Max Size Aggregate
• Optimized Aggregate Gradation
• Cement Content lt 535 lb/yd3
• Air Content of 8 11/2
• Max w/c ratio of 0.42
• Improved curing
• Controlled temperature

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Thermal Cracking

• Rule of Thumb Cracking will result when the
  temperature of the concrete deck exceeds the
  temperature of the girders by more than 20 C
  (36 F).

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Thermal Cracking

• PennDOT1 15 C (27 F)
• KsDOT 14 C (25 F)

1 Pennsylvania Department of Transportation,
Prevention of Cracks in Concrete Bridge Decks
Summary Report, Report No. 89-01, March 1996.
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Alternatives to Pumping

• Concrete Buckets
• Conveyor Belts

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Consolidation Requirements

• Vertically mounted internal gang vibrators

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Finishing
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Machine Fogging
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Early Wet Burlap Cure within 10 minutes
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Curing

• 14 days wet cure with burlap, soaker hoses, and
  plastic
• Followed by curing compound to slow the rate of
  evaporation

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Trial Slab

• To demonstrate implementation of the specialized
  process and address problems before bridge deck
  casting.
• Process
• Contractor
• Ready Mix Plant
• Inspectors

NO SUPRISES
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Progress and where were going

• Two LC-HPC and four control bridges constructed
• First crack surveys completed
• Three more LC-HPC bridges scheduled for this
  spring.

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Testing low shrinkage mix designs

• Fly ash
• Slag
• Silica fume
• Shrinkage reducing admixtures

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Average Free Shrinkage (Drying Only). 535 lb/yd3
Type I/II Cement
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Average Free Shrinkage (Drying Only). 535 lb/yd3
Type I/II Cement w/cm 0.42, 23.26 paste
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Average Free Shrinkage (Drying Only). w/cm
0.42, 23.26 paste
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Average Free Shrinkage (Drying Only). w/cm
0.42, 23.26 paste
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Questions?