Cathodic Protection of Bridges


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Title: Cathodic Protection of Bridges

Author(s): D. G. Manning and H. C. Schell

Publication: Special Publication

Volume: 93


Appears on pages(s): 585-608

Keywords: bridge decks, bridges (structures); cathodic protection; chlorides; corrosion; reinforcing steels; substructures

Date: 9/1/1986

The corrosion of embedded reinforcement caused by the presence of chloride ions in the concrete causes serious deterioration in highway structures. Cathodic protection is the only method presently available of arresting active corrosion. It consists of applying suff icient electrical current to the surface of the reinforcing stee1 to prevent it from discharging ions so that corrosion does not occur. The technology for the cathodic protect ion of steel in concrete is relatively new. Ontario is the only juris diction to use cathodic protection as a routine procedure, and has done so since 1978. The system which is used on bridge decks consists of cast iron anodes positioned in recesses on the deck and a secondary anode of electrically conductive bituminous concrete over the entire deck surface. Current is supplied to the deck anodes by a transformer-rectifier. Research studies were initiated in 1981 to develop a viable method of applying cathodic protection to bridge substructure members. Eight experimental systems were installed in 1982-3, two larger demonstration projects in 1984, and one system in 1985. Several of the systems were found to be effective in stopping the corrosion and work is now underway to improve the long term durability of the components.