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EVALUATING CHLORIDE PERMEABILITY EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUT USED TO SEAL OF A CHEMICAL GROUT USED TO SEAL LEAKS IN POSTLEAKS IN POST--TENSIONING DUCTS: AN TENSIONING DUCTS: AN
ACCELERATED TEST METHODACCELERATED TEST METHOD
Presented by Jack Tinnea,Presented by Jack Tinnea,
PO Box 22349PO Box 22349Seattle, Washington 98122Seattle, Washington 98122206/328206/328--7872 7872 www.tinnea.net
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 1 of 32
The Project – The Need
The old Woodrow Wilson Bridge crosses the Potomac River between Washington, D.C. and Alexandria, VirginiaThe old bridge, completed in 1961, reached its design capacity of 75,000 vehicles per day within eight years of entering serviceToday the bridge carries almost three times that initial design traffic capacity
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 2 of 32
The Project – The Need
The new Woodrow Wilson Bridge will double the number of traffic lanes, removing one of the largest traffic bottlenecks in the country.The new bridge will have a higher clearance reducing drawbridge openings about 70%The new bridge will have the option to replace HOV lanes with mass transitTotal costs are approximately $2.5 billion
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 3 of 32
The Project – The Neighborhood
Arlington Memorial Bridge
New Woodrow Wilson Bridge
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 4 of 32
The Bridge – Support
Pile Cap
Arches
Roadway
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 5 of 32
The Bridge – Support
Pile Cap
PedestalArch
Roadway
Generalized Bridge Support Elevation
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 6 of 32
The Bridge – PT Anchorage
Pile Cap
Pedestal
Precast Segments
Restrained by PT
PT Strands
PT Loop Anchors
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 7 of 32
The Bridge – PT Anchorage
Plan Elevation
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 8 of 32
The Bridge – Construction
Pedestals
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 9 of 32
The Bridge – Construction
PT Loop Anchor Ducts in Pile Cap
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 10 of 32
The Bridge – Construction
PT Loop Anchor
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 11 of 32
The Bridge – Construction
Pedestal Forms
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 12 of 32
The Bridge – Construction
Ducts Exiting Pile Cap
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 13 of 32
The Bridge – Construction
Pedestal reinforcementPT ducts visible within the cageLighter ducts are the loops for the first segmentDarker ducts are the loop anchors extending down into the pile cap
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 14 of 32
The Problem – Leaks
Joints in post-tensioning ducts allowed brackish Potomac River to seep into the ductsPost-tensioning strands were not yet in place
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 15 of 32
The Problem – Likely Site
Cold Joint Below MHW
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 16 of 32
The Problem – Solution
The water was pumped outPlugs were set in the ducts above and below the suspected jointsThe joints were injected with an acrylic gelThe plugs were removed and the ducts were flushed with clean water, dried, and no leaks
The UnknownThe chloride permeability of the gel
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 17 of 32
Test Method – The Basis
Based on the Post-Tensioning Institute’s (PTI) Accelerated Corrosion Test Method (ACTM)Appendix B of the PTI “Specification for Grouting of Post-Tensioned Structures”Used 1000 hours as test time limit per Florida Department of Transportation Standard Specification 938-6
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 18 of 32
Test Method –Specimen Design
Based on PTI’s ACTMPVC tubes were filled with the same grout used on-site with post-tensioning strands in the center of the tubes3½-inches of PVC removedArtificial cracks cut at exposed area midpoint Figure 1
9"
4½"
3½"
1"
7-W irePost-tensioningStrand
Clear PVCTubing
ExposedGroutSurface(Diameter ≅ 1")
End Cap
Cut 'Crack'
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 19 of 32
Test Method – Fabrication
Specimens After Assembly and Grouting
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 20 of 32
Test Method – Fabrication
Cutting “cracks” in specimens using masonry saw0.012 and 0.025-in. diamond jeweler’s blades were usedProfile showing “crack”before filling with gel
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 21 of 32
Test Method – Injecting Cracks
Sections of the PVC tube were used to form injection damsEach half of the dam was fitted with a port and tubeThe gel was injected from belowCrack after injection
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 22 of 32
Test Method – Curing
The specimens were cast and cured 10-days in the PVC tubesAfter removing the center section of PVC, the specimens were water-cured for 5 daysThe cracks were cut and the specimens were water-cured for an additional 13 days (28 total)Prior to injecting, the cracks were thoroughly rinsed with clean water.
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 23 of 32
Test Method – ACTM
The specimens were placed into large beakers containing a 3% NaCl solutionConnections were through a multiplexer to a potentiostat.Specimens were polarized to +200 mV relative to a SCE reference electrodeSpecimens were considered to “pass” if they did not corrode for 1000 hours
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 24 of 32
Test Method – ACTM
Final Test Cell Assembly
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 25 of 32
Test Method – ACTM
Test Cells and Potentiostat
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 26 of 32
Test Method – ACTM
Under Test After Removal
ExpandingGel
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 27 of 32
Test Method – ACTM
When cutting the “cracks” we tried to leave a thin layer, 0.025-in, of grout surrounding the tendonIf the tendon was not well centered, steel could be exposed to gelIn that case failure was quickly apparent.
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 28 of 32
Test Method – ACTM
The nominal resistivity of the cementitious grout is 10,000 ohm-cmThe resistivity of the gel was much lower, less than 150 ohm-cmIf the gel was in immediate contact with the steel tendon it effectively short-circuited the testLeaving a thin layer of grout completely encapsulating the tendon evaluated the grout’s ability to resist chloride ion penetration.
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 29 of 32
Findings
Specimens that had a very thin layer of grout around the strands showed no signs of corrosionThis was after the 1000 hours of anodic polarization
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 30 of 32
Conclusions
The gel itself was able to resist the flow of chloride ions to pass a 1000-hour ACTMThe acrylic gel has a pH of about 7.4 whereas the grout has a pH of about 12.3. This is a difference of 5 orders of magnitudeSuch a difference in pH with the difference in resistivity can cause a differential corrosion cellIt was recommended that the strands and the acrylic gel were not to come into contact
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 31 of 32
Special Thanks
Tinnea & Associates extends our thanks toParsons CorporationMaryland State Highway AdministrationFederal Highway Administration
and to you,for your interest
2006 PTI TECHNICAL CONFERENCE-SESSION-6 EVALUATING CHLORIDE PERMEABILITY OF A CHEMICAL GROUTIN POST-TENSIONING DUCTS: AN ACCELERATED TEST METHOD
JACK TINNEA
© COPYRIGHT POST-TENSIONING INSTITUTE, ALL RIGHTS RESERVED Page 32 of 32