CORROSION RATE OF STEEL BARS IN REINFORCED CONCRETE UNDER OXIDIZING ENVIRONMENT AND REDUCING ENVIRONMENT

Abstract

 This study aimed at evaluating the corrosion behavior of steel bars in reinforced concrete members constructed under the airtight underground space. Construction works of structures were carried out in the air condition, and structures were initially exposed to oxidizing environment. Structures were afterwards buried in the underground, and the environmental condition surrounding the structures were gradually shifted to the reducing environment. In this study, such environment was experimentally reproduced and corrosion rate of steel bars in concrete were estimated using the various electrochemical methods. As a result, the following conclusions were obtained.
 (1) The corrosion rate in oxidizing environment at temperature of 20°C was 0.001~0.011μA/cm² , and the corrosion rate after being shifted was 0.013~0.056μA/cm² in reducing environment at temperature of 50°C. These values were equivalent to the reported rates by the electrochemical methods so far.
 (2) The accuracy of various polarization methods was greatly influenced by a potential sweep rate.
 (3) "The passive maintaining current method" proposed by the study was very effective so as to evaluate the corrosion rate in reducing environment.