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Vertical Electrical Impedance Scanner for Concrete Bridge Deck Assessment without Direct Rebar Attachment

Bridge decks in marine areas and cold regions experience rapid and widespread steel corrosion due to the presence of elevated concentrations of salts that are either naturally present in the marine environment or deliberately applied in cold regions for safety. Over time, salts can diffuse through the concrete cover, after passing through any overlays that may be applied to the deck surface, and initiate corrosion of the steel reinforcement. Because corrosion at an early stage occurs internally where it is not visible, visual inspection alone is not adequate to evaluate the protection against chloride ingress that is offered to steel reinforcement. By the time delamination and spalling of the concrete occur, rehabilitation is costly and often involves traffic disruption to perform the necessary repairs. Because early intervention, before concrete cracking has occurred, is the most cost-efficient bridge deck management approach, a device for measuring the quality of protection offered to the steel reinforcement on bridge decks was needed. Among the many techniques available for assessing the condition of concrete bridge decks, vertical electrical impedance (VEI) measurements have been shown to provide a quantitative measure of the protection offered to the steel reinforcement against chloride ingress. However, major limitations to using VEI in the field have been the following: (1) The need to directly connect to the steel reinforcement to perform a VEI measurement and then to drag a wire from this direct connection to the measurement location; (2) Single-channel probes mounted to small carts that had limited data collection speed and exposed the operator to potential traffic hazards; (3) Lack of established measurement protocols and standards across different bridge deck conditions and overlay types to establish validation of the technique; and (4) Lack of robust mapping techniques for presenting spatial variations in VEI measurements on a bridge deck. All these limitations were successfully addressed during the development of the multi-channel VEI scanner. The key to success was the theoretical and practical development of a large-area electrode (LAE) to replace the direct tapped connection to steel reinforcement. Investigating this LAE concept in the field, extensive testing of the VEI scanner was performed on multiple concrete bridge decks, with and without overlays, that were constructed using both uncoated and epoxy-coated reinforcing steel in Utah and Nebraska in 2018. VEI scanning of full traffic lanes at rates exceeding 1500 ft2/minute was achieved in this project. The VEI scanner is able to operate in conditions where other techniques fail or provide inadequate diagnostic capability. For example, the VEI scanner can successfully scan bridge decks with a variety of different overlay types and can be operated during the day or night. As part of the work performed during the project, specifications for use of the VEI scanner and interpretation of the data were also generated to enable successful commercialization of the technology. Commercial availability of this technique will allow greater diagnostic capabilities, more informed bridge deck rehabilitation planning, and associated cost savings.

  • Record URL:
  • Supplemental Notes:
    • This IDEA project conducted by Brigham Young University, Provo, Utah.
  • Authors:
    • Mazzeo, Brian A
    • Guthrie, W Spencer
  • Publication Date: 2019-8

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 47p
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 01719268
  • Record Type: Publication
  • Report/Paper Numbers: NCHRP IDEA Project 202
  • Files: TRIS, TRB, ATRI
  • Created Date: Oct 11 2019 10:39AM