Cathodic Protection of Rebars in Old and New Concrete Structures

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Title: Cathodic Protection of Rebars in Old and New Concrete Structures

Author(s): Aladar Tvarusko

Publication: Special Publication

Volume: 128

Issue:

Appears on pages(s): 359-373

Keywords: anodes; cathodic protection; chlorides; corrosion; costs; instruments; reinforcing steels; General

Date: 11/1/1991

Abstract:
Steel reinforcement embedded in concrete is normally passivated in its alkaline environment. In the presence of chlorides, however, the passivating layer is destroyed and the reinforcing bar corrodes, leading to concrete cracking and spalling. Several concrete rehabilitation techniques are available, of which only the cathodic protection (CP) of reinforcing bars was found to stop corrosion regardless of the chloride content of concrete. The CP system consists of reinforcing bars (cathode) connected to the negative terminal of a DC power supply, the positive output of which goes to an anode usually embedded in concrete. This paper describes some properties and applications of a proprietary activated titanium anode mesh and ribbon to a variety of old and new concrete structures: bridges, tunnels, buildings, wharves, piers, offshore platforms. Since its commercial introduction in 1985, 290,000 mý of this anode mesh has been or is being installed all over the world, whereas from 1987 the anode ribbon has been or is being applied to 29,000 mý of concrete surface. The paper addresses also the design and various installation techniques of anodes, as well as the testing, commissioning, and cost of the CP system.