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Prestressed ConcreteOnline self-study

Post-Tensioning Tendons: Grout, Corrosion and Inspection

1 PDH · about 60 minutes · Course no. BR-P03 · Instructor: Michael Craig, PE

About the instructor

Michael Craig, PE is Senior Vice President and Southeast Director at Strinteg Corporation, leading bridge inspection and structural engineering across eight states and Puerto Rico. In 27+ years he has inspected over 4,000 structures and completed 3,000+ load ratings and 160+ load tests. He has managed repair and preservation design for complex bridges, including cable-stayed bridges. He holds PE licenses in twelve states, DC and Puerto Rico, SPRAT Level 1, and FAA Part 107 credentials.

Bonded post-tensioning carries much of the load in segmental box girders, spliced girders, cast-in-place box girders and PT substructures. The tendons are hidden inside ducts, so the steel is protected only by the grout, the duct and the concrete around them, and failures are usually found late. This course follows two public FHWA sources. The first is the Post-Tensioning Tendon Installation and Grouting Manual, FHWA-NHI-13-026 (Corven and Moreton, Version 2.0, May 2013), which covers components, grout materials, grouting practice and corrosion protection. The second is Guidelines for Sampling, Assessing, and Restoring Defective Grout in Prestressed Concrete Bridge Post-Tensioning Ducts, FHWA-HRT-13-028 (Theryo, Hartt and Paczkowski, October 2013, with the January 2014 errata), which covers inspecting tendons in existing bridges, grout sampling, grading and restoration. Code and specification references are quoted as these sources state them; confirm against current editions. Worked numbers are labeled illustrative.

⬇ Download study guide (PDF)

Learning objectives

  • Describe PT system components
  • Explain grout voids and segregation
  • Identify tendon inspection methods
  • Apply lessons from tendon failures

Outline

  1. Why post-tensioning tendons need special attention
  2. Tendon components: strand, bar and anchorages
  3. Ducts, inlets, outlets and couplers
  4. Grout: what good grout must do
  5. How grout voids and bleed form
  6. Layers of corrosion protection
  7. Fallacies the failures exposed
  8. Lessons from forensic studies of newer grouts
  9. Construction quality: the first inspection
  10. Inspecting existing tendons: the four-step process
  11. Risk-based selection of tendons
  12. Where to look: strategic sampling locations
  13. How to open a tendon and what to record
  14. Grading tendons and choosing actions
  15. Restoring openings, NDT and monitoring
  16. Open the course (21 screens, 2 knowledge checks)
  17. Final quiz — 10 questions, 70% to pass

References

  1. FHWA, Post-Tensioning Tendon Installation and Grouting Manual, FHWA-NHI-13-026, 2013
  2. AASHTO, LRFD Bridge Design Specifications, 9th Edition, 2020
  3. Theryo, T.S., Hartt, W.H., Paczkowski, P., Guidelines for Sampling, Assessing, and Restoring Defective Grout in Prestressed Concrete Bridge Post-Tensioning Ducts, FHWA-HRT-13-028, Federal Highway Administration, October 2013 (amended January 7, 2014).
  4. PTI/ASBI M50.3-12, Guide Specification for Grouted Post-Tensioning, and PTI M55.1-12, Specification for Grouting of Post-Tensioned Structures (as cited in FHWA-NHI-13-026).