I-99 HPC Initiative: Upcoming Work

Phase II Testing  25 Phase II Mixes –Control, silica fume, fly ash, slag, ternary, Aquron, Ipanex  Phase II Testing –Freeze-thaw, scaling, ASR, Cloride ion permeability, shrinkage, abrasion  Continued corrosion testing

Revised Scope  Delay in bridge construction for I-99 section C-10 (15 single spans) –Focus on lab testing and best practices guide –Development of instrumentation plan  New HPC projects –Districts 9-0 and 4-0 HPC decks for summer 2002  New grouting specifications and details for Post-Tensioning

HPC Decks – Summer 2002  Kernville viaduct, Johnstown, District 9-0 –3300 ft –multi-span, curved composite bridge  District 4-0 –Approximately 500 ft

Tasks for Summer HPC Decks  Review mix designs  Review casting sequence  Review quality control data during casting  Log of construction practices  Evaluate placing and curing techniques to improve concrete quality  Instrumentation  Companion slabs

Instrumentation  Temperature  Strain  Deflections  Corrosion monitoring embedment surface sister bar

Durability of Post-Tensioned Structures Grout Specifications Durability Design Details

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

Purpose of Grout  Corrosion protection  Bond

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

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

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