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Prestressed concrete cylinder pipe (PCCP) is constructed by circumferentially winding a high strength steel wire, under tension, around a concrete core containing a sheet steel cylinder, which serves as a watertight membrane. The service life of such pipe is generally determined by the ability of this steel prestressing wire to retain its integrity under tension. Corrosion of the steel wire results in pitting, embrittlement, or the dissolution of the iron with a corresponding reduction in cross-sectional area. The result is degradation of the physical strength of the high tensile wire and possible failure of the prestressed concrete cylinder pipe through this mechanism. Pipe affected by this failure mode does not develop leaks as in the case of the steel pipe, but bursts catastrophically. Failure is usually attributed to “wire breaks,” not specifically to corrosion.
For concrete cylinder pipe, the components of the joint are susceptible to stray current corrosion if component low resistance continuity does not exist. This condition can be responsible for failure of the steel prestressing wires if they are not electrically continuous with the other components of the pipe (steel cylinder, bell ring, spigot ring, fittings, and so forth).
This paper presents the potential corrosion problems and causes associated with the metallic components of prestressed concrete cylinder pipe. The difficulties in detecting these problems, because of materials and fabrication practices are discussed, as well as methods that have been used successfully to detect corrosion in buried lines (pipe-to-soil potential profiles, cell-to-cell potential profiles).
The results of a few typical studies are presented as a suggested approach to the investigation and analysis of potential problems involving both galvanic and electrolytic (stray current) corrosion.
prestressed concrete cylinder pipe, steel wire, corrosion, galvanic corrosion, electrolytic corrosion, pipe-to-soil potential profiles, cell-to-cell potential profiles, excavations
Engineering manager, Harco Corporation, Hatboro, PA
President, Openaka Corporation, Denville, NJ