United States Department of Transportation
i
Long-Term Effects of Cathodic Protection on Prestressed Concrete Bridge Components
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1996-11-01
[PDF-2.15 MB]
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Abstract:While cathodic protection effectively reduces or stops ongoing corrosion of reinforcing steel in concrete, applicability of this technology to prestressing steel has been limited because of concerns of possible bond loss and hydrogen embrittlement. Within this context the present research was intended as a comprehensive, multifaceted undertaking to elevate the understanding of prestressed concrete cathodic protection to the same level as for reinforced concrete. The experimental part of the program involved three approaches: 1) constant extension rate tests (CERT) upon straight tendon wire, 2) monitoring of cathodically polarized prestressed beams for both bond loss and hydrogen embrittlement, and 3) concrete block pullout tests involving both tendon and wire. Findings to date include the following: 1) High chromium bearing microalloyed prestressing steel is more susceptible to embrittlement than ordinary steel, and the previously proposed -0.90 v (SCE) lower potential limit is not conservative in this case; 2) Prestressed concrete structures can be qualified for cathodic protection based upon the amount of uniform and localized corrosion wire cross section loss; 3) Loss of bond within the anticipated remaining service life of most prestressed concrete structures should not be a concern provided current density is within the normal range and is not locally concentrated. These and related findings are evaluated within the context of standards for prestressing steel and criteria for cathodic protection.
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