DECK PROTECTION SYSTEMS FOR POSTTENSIONED SEGMENTAL CONCRETE BRIDGES

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DECK PROTECTION SYSTEMS FOR POST-TENSIONEDSEGMENT
AL CONCRETE BRIDGES

• Michael M. Sprinkel, P.E.Associate
  DirectorVirginia Transportation Research Council

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INTRODUCTION

• Post-tensioned segmental concrete bridge
  construction is economical for many applications.
• The economy increases as the number of segments
  increases.
• Concern cost effective repair if chlorides reach
  critical reinforcement in the superstructure.
• A deck protection system is required to prevent
  the infiltration of chloride ions.

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OBJECTIVE
The objective of this paper is to compare
conventional and new deck protection systems for
post-tensioned segmental concrete bridges.
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Conventional Deck Protection Systems

• Thin bonded hydraulic cement concrete overlay
• Waterproof membrane overlaid with asphalt

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New Deck Protection Systems

• Thin bonded epoxy concrete overlay
• Monolithically cast concrete
• Low permeability concrete segments

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Thin Bonded Hydraulic Cement Concrete Overlay
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Waterproof Membrane Overlaid With Asphalt
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Thin Bonded Epoxy Concrete Overlay
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Monolithically Cast Concrete
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Low Permeability Concrete Segments
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Thin Bonded Hydraulic Cement Concrete Overlay
complex, expensive, high risk of failure

• High bond strength often a problem
• Low permeability easily obtained
• Few cracks often a problem
• Good skid resistance, ride quality, and surface
  appearance typically not a problem

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Thin Bonded Concrete Overlay milling surface of
segments causes fractures that result in low bond
strength
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Thin Bonded Concrete Overlay poor consolidation
of bottom of 3-in thick overlay causes low bond
strength
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Thin Bonded Concrete Overlay shrinkage cracks
reduce protection and increase risk of
delamination of overlay
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Waterproof Membrane Overlaid With Asphalt
complex, expensive, high risk of failure

• Waterproof membrane must be carefully constructed
  so that it does not leak
• Asphalt must be appropriate mixture
• Asphalt overlay must be properly compacted
• New membrane and overlay after 15 years

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Thin Bonded Epoxy Concrete Overlay simple, low
cost, low risk of failure

• Shot blast concrete surface
• Place two layers of epoxy and aggregate
• 15 to 30 year life
• Easy to repair and replace
• Spall is not a major problem because of 0.25-in
  thickness

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Thin Bonded Epoxy Concrete Overlay 2 layers of
epoxy and broadcast aggregate provide 0.25-in
wearing, protective surface
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Monolithically Cast Concrete simple, low cost,
low risk of failure

• Extra concrete is placed as segment is
  constructed
• Extra concrete removed years later when
  contaminated with chloride
• New thin bonded overlay placed after removing
  chloride contaminated concrete

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Low Permeability Concrete Segments simple, low
cost, low risk of failure

• Low permeability concrete is placed as segment is
  constructed
• Concrete does not become contaminated with
  sufficient chloride to cause corrosion for more
  than 100 years
• Separate deck protection system not required

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Permeability,1 year, concrete deck mixtures,
coulombs (AASHTO T277)Ref. 1 Ozyildirim, TRR
1610, 1998
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Time to Corrosion of 1970 Concrete and 2003 Low
Permeability Concrete Ref. 2 Pyc, VTRC 00-R16,
2000
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Low Permeability Concrete

• The use of a protection strategy other than
  casting the segments with low permeability
  concrete is difficult to justify.

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Construction Steps Required For Deck Protection
Systems
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Construction Steps Required For Deck Protection
Systems
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Cost Data For Deck Protection Systems

• Average values based on bid tabulations between
  1999 and 2002 obtained from the Virginia
  Department of Transportation bridge office. Bid
  data is for many types of bridges with concrete
  decks (cast in place concrete on beams,
  prestressed box beams, prestressed slabs,
  post-tensioned segmental).

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Cost of Deck Protection Systems,/yd2
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Conclusions

• Use of low permeability concrete in segments is
  the most practical and economical deck protection
  system. Concretes with low water to cement
  ratios and pozzolans or slag should provide a
  service life of more than 150 years.
• Monolithic concrete is practical and economical
  when a sacrificial concrete cover is required.

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Conclusions

• Thin epoxy overlays are practical when an
  impermeable overlay is required. Low cost and
  ease of maintenance make it ideal for
  post-tensioned segmental concrete bridges.
• Use of thin bonded hydraulic cement concrete
  overlays and waterproof membranes overlaid with
  asphalt should be reduced. These protection
  systems are the most complicated and expensive
  and come with a high risk of failure.

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Thank You

• www.VirginiaDOT.org/vtrc