ELECTROCHEMICAL REMOVAL OF CHLORIDES FROM CONCRETE BRIDGE DECKS

The spalling of concrete bridge decks is largely due to corrosion of the top layer of reinforcing steel. This corrosion is induced by chloride ions, which enter the concrete when deicing salt is applied to the deck surface. The construction of many new bridge decks is based on techniques that either prevent penetration of chloride or ensure resistance to chloride-induced rebar corrosion. However, the many salt-contaminated decks that now exist demand attention. Besides costly patching of spalls, only cathodic protection of the steel is currently available as a remedial measure. This paper presents the results of an investigation of an electromigration method for removing chloride from contaminated concrete decks, which prevents rebar corrosion. In this method, the chloride ion moves through and out of the concrete under an electric field applied between the rebar (cathode) and a surface anode. A preliminary laboratory investigation demonstrated the viability of the technique and identified optimum voltage (100 Vdc), treatment time (12 to 24 h), anode material (platinized titanium), surface electrolyte, and chloride fixant. A field trial on a 3 by 6.1-m (10 by 20-ft) section of chloride-contaminated bridge deck was conducted in which laboratory-optimized parameters were used. Under the best conditions, 90 percent of the chloride was removed from the concrete above the rebar; 88 percent was removed from the concrete immediately adjacent to the rebar. Potential measurements have shown that the previously actively corroding rebar became passive after treatment. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 6-15
  • Monograph Title: Bridge decks: corrosion, cathodic protection, and pavement seals
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00156019
  • Record Type: Publication
  • ISBN: 030902577X
  • Files: TRIS, TRB
  • Created Date: Aug 4 1977 12:00AM