Thresholds

Details

• Alternative Title:
  FHWA Special Study: Post-Tensioning Tendon Grout Chloride ; Thresholds
• Creators:
  Lee, Seung-Kyoung ; Zielske, James
• Corporate Creators:
  Rutgers University. Center for Advanced Infrastructure and Transportation
• Corporate Contributors:
  United States. Department of Transportation. Federal Highway Administration. Office of Infrastructure Research and Development
• Subject/TRT Terms:
  • Grout
  • Grouting
  • Tendons (Materials)
  • Posttensioning
  • Chloride threshold, Chloride, Corrosion initiation, Corrosion propagation, Seven-wire strand, Post-tensioning, Grout, Accelerated corrosion testing, Sulfate ions
• Publication/ Report Number:
  FHWA-HRT-14-039
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Corporate Publisher:
  United States. Department of Transportation. Federal Highway Administration. Office of Infrastructure Research and Development
• Abstract:
  "Elevated levels of chloride were recently discovered in a commercially available pre-bagged grout product made for ; post-tensioned (PT) tendons. Chloride concentrations were reported to be as high as 5.27 percent by weight of cement. ; These numbers exceed the current limits set by all of the domestic and international regulatory committees. For ; example, the chloride limits for prestressed concrete imposed by American Concrete Institute committees are either ; 0.06 percent water-soluble chloride by weight of cement or 0.08 percent acid-soluble chloride by weight of cement. ; Chloride threshold is defined as a minimum chloride concentration needed to induce corrosion. However, there is ; limited information reported in the literature pertaining to actual chloride threshold of seven-wire PT strands. For this ; reason, the Federal Highway Administration sponsored a 6-month accelerated corrosion testing program to determine ; chloride threshold(s) of PT strands exposed to chloride-contaminated grout. ; Based on the test results obtained through the 6-month accelerated corrosion testing program and subsequent autopsy ; of the specimens, two chloride threshold values were determined for the PT strands fully encased in normal grout. The ; first threshold is 0.4 percent chloride concentration by weight of cement, which is the lowest amount needed to initiate ; corrosion of strands. At this threshold, rust spots can be formed, and a small number of pits start to form beneath some ; of the rust spots. The second critical chloride threshold is found in association with corrosion propagation. At this ; threshold, corrosion starts to intensify in terms of the number of pits and pit depth. Test data and autopsy results ; obtained in this study indicated that 0.8 percent chloride by weight of cement is the critical threshold. Once chloride ; concentration exceeds the critical threshold, significant corrosion damage can occur rapidly, and structural integrity of ; the PT bridges may be compromised in the near future. The actual deterioration rate will be influenced by many ; factors. These threshold values are applicable to normal grout condition only. They may not be adequate in other ; conditions such as carbonated grout, segregated grout, duct cracks, grout voids filled with water with or without ; chloride ions, or free sulfate ions in contact with the strands. In these circumstances, corrosion should start below the ; proposed threshold values."
  More +
• Format:
  PDF
• Funding:
  DTFH61-08-C-00005
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/27468/dot_27468_DS1.pdf
• File Type:
  [PDF - 14.00 MB]
• Collection(s):
  Federal Highway Administration ; US Transportation Collection
• Main Document Checksum:
  urn:sha-512:72d8e5eca5b0fbfd38d3e1b1fa69bb78277510cf334dae6982a2d7a1e01feb00c9497a7c1f02c8440e9c38906d38c2c305518a177367ef9beb16fdd2d2862293