Cathodic protection for reinforced-concrete and prestressed-concrete structures

Abstract

In Japan, concrete structures exposed to marine environments are deteriorating due to corrosion of reinforcement. Since this deterioration advances rapidly and seriously, effective corrosion protection must be considered for both new construction and damage-repair. Cathodic protection is expected to be a practical corrosion protection system for all concrete structures in marine environments In this study, the following were considered for the establishment of high reliability for cathodic protection of concrete structures: (1) developing the criteria for cathodic protection on concrete structures. (2) examining over-protection problem on prestressed-concrete structures. For the laboratory experiments, reinforced and prestressed-concrete speciments were used and the following results obtained: (1) criteria for cathodic protection: -100 mV depolarization is not sufficient for corrosion protection of reinforcements in concrete in marine environments, especially in atmospheric moisture and dry cyclic conditions. Depolarization to 150–200 mV may be necessary to stop the corrosion completely. (2) Cathodic protection on prestressed-concrete structures: the possibility of reduction of strength of a prestressed-concrete strand is found at over-protection-level current density. Additionally, cracking of the concrete along the strands occurred at higher current densities, due to the high pressure of hydrogen evolution.