Galvanic Point Anodes for Extending the Service Life of Patched Areas Upon Reinforced Concrete Bridge Members

The polarization performance of two types of commercial galvanic point anodes for protection of rebar around patch repairs was evaluated. Experiments included measurement of the polarization history of the anode under galvanostatic load, in reinforced concrete slabs, and in field installations. The tests revealed, for both types of anodes, a potential-current function (PCF) indicating relatively little anodic polarization from an open circuit potential at low current levels, followed by an abrupt increase in potential as the current approached an apparent terminal value. Aging of the anodes was manifested by a continually decreasing current output in the concrete tests, and by increasingly more positive potentials in the galvanostatic tests. Those changes reflected an evolution of the PCF generally toward more positive open circuit potentials and, more importantly, to the onset of elevated polarized potentials at increasingly lower current levels. There was considerable variability among the performance of replicate units of a given anode type. Modest to poor steel polarization levels were achieved when coupled with point anodes both in laboratory and field tests. Modeling of a generic patch configuration was implemented with a one-dimensional approximation. The model calculated the throwing distance that could be achieved by a given number of anodes per unit perimeter of the patch, concrete thickness, concrete resistivity, amount of steel and amount of polarization needed for cathodic prevention. The model projections and aging information suggest that anode performance in likely application scenarios may seriously degrade after only a few years of operation, even if a relatively optimistic 100 mV corrosion prevention criterion were assumed. Less conservative criteria have been proposed in the literature but are yet to be substantiated. Other investigations suggest a significantly more conservative corrosion prevention may apply instead. The latter case would question the ability of the point anodes to provide adequate corrosion prevention.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Edition: Final Report
  • Features: Figures; References; Tables;
  • Pagination: 121p

Subject/Index Terms

Filing Info

  • Accession Number: 01146331
  • Record Type: Publication
  • Report/Paper Numbers: BD544-09
  • Contract Numbers: BD544 - 09
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Nov 25 2009 1:29PM