1. Durability of Post-Tensioned Structures Grout Specifications Durability Design Details

2. Durability and Post-Tensioning
Extremely durable when properly constructed
Crack control
Multiple protection levels
moisture, Cl-, CO2
concrete
duct
grout
The grout is the last level of protection for the strand
strand

3. Purpose of Grout
Corrosion protection
Bond

4. Properties Fluidity Bleed Segregation Set Time Strength Permeability
Volume Change
Corrosion Protection
Bleed

5. Bleed in Grouts Bleed water is trapped in duct
Higher vertical rises = higher pressures and more bleed water
Strand promotes bleed by wicking
Intermediate lense
Bleed lenses form as a result of the separation of water from the cement. Ducts with vertical rises will typically experience more bleed due to the increased pressure within the grout column. Intermediate bleed water lenses may form in tall vertical ducts, leaving a void through the cross-section of the duct exposing the tendon. This sedimentation process is accentuated by the addition of seven-wire strand. The spaces within the individual twisted wires that form the strand are large enough to allow easy passage of water but not cement.

6. Bleed Lenses Voids Loss of protective environment 9 ¾” bleed column
Intermediate lense

7. Keys to a Good Grout Completely fills duct Low permeability
Appropriate bleed resistance
Careful use of admixtures
Detailed description of bleed lense formation and result. Exposed strand at high points in low vertical rise ducts. Possible completely exposed strand in areas for large piers.
Many admixtures help one grout property
while degrading another

8. 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