Cathodic Protection for Life Extension of Existing Reinforced Concrete Bridge Elements (2009) / Chapter Skim
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Pages 6-13
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From page 6... ...
IMPRESSED CURRENT CATHODIC PROTECTION SYSTEM Impressed current cathodic protection is achieved by driving a low voltage direct current from a relatively inert anode material through the concrete to the reinforcing steel. Direct current of sufficient magnitude and direction is applied to shut down the anodic reaction and support the cathodic reaction on the steel surface.
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From page 7... ...
Repair Area & Overlay Continuity Bond Reinforcing bars (Cathode) FIGURE 1 Basic layout of an impressed current cathodic protection system.
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From page 8... ...
Several different anodes can be used in the slots and they include platinum niobium wire, carbon fiber, and mixed metal oxide ribbon. The slots are backfilled with an FHWA conductive polymer material when the primary anode is the platinum niobium wire or the carbon fiber.
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From page 9... ...
FIGURE 6 Slotted non-overlay system (Platinum niobium wire anode and FHWA conductive polymer)
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From page 10... ...
No external power source is needed with this type of system and much less maintenance is required. Zinc is more electronegative than low carbon steel, especially in the presence of chloride ions, and is the anode material of choice on reinforced concrete structures.
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From page 11... ...
have also been used inside fiberglass jackets backfilled with cementitious material in non-tidal zones. The activated anodes are available in various shapes and sizes and have zinc at its core surrounded by the proprietary material.
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From page 12... ...
By measuring the current picked up by these probes, one can determine if sufficient current is distributed to monitored areas. SELECTION AND DESIGN OF CATHODIC PROTECTION FOR REINFORCED CONCRETE BRIDGE STRUCTURES The cathodic protection system must be matched to the structure material, its corrosivity (presence of chloride ions or carbonation)
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From page 13... ...
Each zone represents an independent cathodic protection system consisting of anode material, wiring, an external power source (if an impressed current cathodic protection system is used) , connections to the reinforcing steel, and appropriate monitoring devices.
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