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Durability of Post-Tensioned Structures

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					Durability of Post-Tensioned
         Structures
     Grout Specifications
    Durability Design Details
        Durability and Post-
            Tensioning
 Extremely durable         moisture, Cl-, CO2
  when properly
  constructed
                                 concrete
 Crack control
                          duct              grout
 Multiple protection
  levels

 The grout is the last
level of protection for
      the strand                            strand
    Purpose of Grout
 Corrosion protection
 Bond
      Properties
   Fluidity
   Bleed
                    Bleed
   Segregation
   Set Time
   Strength
   Permeability
   Volume Change
   Corrosion
    Protection
         Bleed in Grouts
                                   Bleed

 Bleed water is
  trapped in duct
 Higher vertical rises
  = higher pressures      Intermediate lense
  and more bleed
  water
 Strand promotes
  bleed by wicking
            Bleed Lenses
 Voids
 Loss of protective
  environment

                           9 ¾” bleed
                             column




    Intermediate lense
        Keys to a Good Grout
   Completely fills duct
   Low permeability
   Appropriate bleed resistance
   Careful use of admixtures




         Many admixtures help one grout property
                while degrading another
         Tasks under WO-81

 Literature review and summary of current
  practice
 Development of specification language,
  details, and revisions to PennDOT
  publications
 Scope includes
  –   Grouting (materials, procedures, venting)
  –   Durability details (anchorage, duct material)
  –   Inspection/repair
  –   Training of personnel

				
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posted:8/21/2012
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