Bond Performance of Post-tensioning Tendons with Corrosion Inhibitor

Details

• Creators:
  Consolazio, Gary R. ; Hamilton, H. R. (Trey) ; Yumnam, Mahesh
• Corporate Creators:
  University of Florida. Dept. of Civil and Coastal Engineering
• Corporate Contributors:
  Florida. Department of Transportation. Research Management Center
• Subject/TRT Terms:
  Adhesive Bond Strength Concrete Structures Corrosion Protection Flexural Strength Girders Grout Material Tendons Posttensioning
• Publication/ Report Number:
  P0260410-P0260749
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final Report
• Corporate Publisher:
  Florida. Department of Transportation
• Abstract:
  Corrosion of steel tendons in post-tensioned bridge girders can lead to section loss and, if left unaddressed, may result in strand rupture and a corresponding reduction in girder strength. In the state of Florida, a number of remedial measures have been explored and implemented to address such issues, including the use of corrosion inhibitors to mitigate strand corrosion. Impregnation of corrosion-inhibiting fluids into grouted post-tensioned tendons has been shown to be effective in reducing strand corrosion. However, the impregnation of these fluids may also have the potential to adversely affect the bond between steel tendons and the surrounding grout. Past studies involving pull-out tests of unstressed strands in grout have indicated that a reduction in bond strength may result from the use of corrosion-inhibiting fluids. However, relatively little research has been carried out to determine the effect that such fluids may have on the flexural performance of full-scale post-tensioned concrete bridge girders.
  
  In this study, full-scale experimental flexural tests of post-tensioned concrete beams with grouted tendons were performed to directly evaluate the extent to which impregnation with a corrosion-inhibiting fluid might affect either the strength level performance (nominal flexural strength) or the service level performance (crack severity) of such beams. Variables that could potentially influence the bond condition between tendon and grout, due to the presence of corrosion inhibitor, were incorporated into the experimental test program. These variables included tendon size (6-, 12-, and 19-strands), tendon profile (straight, draped), grout type (prepackaged, plain cement, legacy), duct type (metal, plastic), age of corrosion inhibitor impregnation at the time of testing (0.5 months to 2.5 months), and the beam condition when initially impregnated (uncracked, cracked). Five groups of beams were tested under four-point bending to evaluate both strength level nominal flexural resistance and service level crack behavior.
  
  At the strength load level, test results and corresponding analyses indicated negligible differences (less than 2%) between the nominal flexural resistances of newly constructed beams treated with corrosion-inhibiting fluid and the nominal flexural resistances of corresponding untreated control beams. In regard to service load levels, a “cracking load” level was defined in this study as the applied load that produced a calculated tensile stress of 12√fc , at the extreme tension fiber, consistent with the ACI 318 definition of a cracked section. This higher stress level was selected to ensure that cracking would be observed while remaining reasonably aligned with AASHTO LRFD serviceability limits, which typically allow 6√fc , under Service III conditions. At the defined cracking load level, treatment with corrosion inhibiting fluid produced negligible changes in observed patterns of crack spacing and crack frequency. Conversely, alternate analyses of beam cracking produced mixed results wherein a limited number of tests indicated that impregnation of corrosion-inhibiting fluid was associated with moderately increased crack severity. It must be noted, however, that the presence of an adequately impregnated volume of corrosion-inhibiting fluid into a tendon could presumably protect such a tendon from any increased exposure risk that was associated with increased cracking.
  
  
• Format:
  PDF
• Funding:
  BED31-977-07
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:79084f866537930e8cae8cb3944a96144d43d6f0d5a950e795e0dd61035b53ea4387b577655b0d0c5aece23ab0f3b7e2360b885d45c04cc1989ecf133e418abf
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/90506/dot_90506_DS1.pdf
• File Type:
  [PDF - 13.74 MB ]