Precast Deck Panels

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Precast Deck Panels The Future Belongs to
Those Who Prepare for it Today - Malcolm X
The future is here. Its just not widely
distributed yet William Gibson
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Why is Bridge Division so dedicated to the use of
precast deck panels?

• The National Bridge Inventory and Purdue
  University have identified the primary source of
  bridge deterioration as being the deck slab.

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Factors that Affect Structural Service Life
As you can see, the majority of factors that
affect the structural service life of a bridge
are directly related to the deterioration of the
deck and its components.
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Deterioration Profile
Once crack formation has been initiated in
concrete deck slabs, advanced chloride
penetration occurs and the rate of deterioration
is greatly increased. The longer initial crack
formation can be delayed, the longer the service
life of the deck will be.
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Primary Cause of Crack Propagation

• Corrosion of the steel reinforcement in the deck
  due to chloride penetration at crack locations,
  together with freeze thaw action, cause cracks to
  widen and propagate.

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What causes crack initiation in CIP concrete
decks in the first place?

• Composite CIP decks become locked in with the
  supporting girders as soon as the deck concrete
  sets. Shortening of the deck due to temperature
  change and concrete shrinkage due to moisture
  loss is resisted by the much stiffer underlying
  girders. This resistance puts the deck in
  tension. The resulting affect is the formation
  of cracks in the deck as a way for it to
  effectively relieve itself from that tension.

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So how can we prevent crack initiation in CIP
Decks?

• We cant. But there is another option.
• PRECAST DECK PANELS

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Why are Precast Deck Panels less prone to crack
initiation?

• Shrinkage and temperature changes due to
  hydration are already essentially completed
  before the deck is installed and made composite
  with the supporting girders.
• Use of high performance concrete reduces deck
  porosity and infiltration of chlorides.
• Prestressing puts the deck concrete in
  compression and virtually eliminates the
  potential for cracking.

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All this sounds great, but exactly how much is it
going to cost me?

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The 3 variables controlling the optimal usage of
financial resources

• Initial Cost
• Maintenance Cost
• Life Expectancy

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Initial Costs

• Cast-in-Place Deck Slabs 20/ft2

• Precast Deck Slabs 28/ft2

Lifecycle Maintenance Costs (Includes Crack
sealing and overlays)

• Cast-in-Place Deck Slabs 15/ft2

• Precast Deck Slabs 9/ft2

Life Expectancy

• CIP Deck 20 to 30 Years

• Precast Deck 50 Years

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Lifecycle Cost Comparison of a CIP Deck vs. a
Precast Deck for the Pacific Street Project
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Summary of the 50 Year Lifecycle Costs for a CIP
deck vs. a Precast deck as applied to the Pacific
Street Project(All values are in 2007 dollars)

• Precast Deck
• Initial Construction - 586,093
• Deck Replacement -
• 0
• Maintenance
• 166,006
• Overlays
• 25,667
• Total Lifecycle Cost
• 777,766

• CIP Deck
• Initial Construction - 418,638
• Deck Replacement -
• 418,638
• Maintenance
• 143,385
• Overlays
• 167,456
• Total Lifecycle Cost
• 1,148,117

D 370,351 in Lifecycle Savings by using a
Precast Deck!
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NDOR has been awarded 160,000 towards
implementation of Rapid Construction Methods to
be applied to the Pacific Street project
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Is the extra initial cost of the precast deck
covered by the delta costs awarded to the State
by the FHWA?

• The engineers estimate for the delta cost
  associated with substitution of a Precast Deck in
  place of a CIP Deck is 167,455 only 7,500
  over the delta funds awarded.

YES!
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So the only question left is..