Reinforcement Corrosion Under Simultaneous Diverse Exposure Conditions

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Title: Reinforcement Corrosion Under Simultaneous Diverse Exposure Conditions

Author(s): Sukhir Misra and Taketo Uomoto

Publication: Special Publication

Volume: 126

Issue:

Appears on pages(s): 423-442

Keywords: chlorides; corrosion; cracking (flexural, longitudinal); exposure; reinforced concretes; restraints; stirrups; tests; Materials Research

Date: 8/1/1991

Abstract:
Most studies dealing with the problem of reinforcement corrosion have been carried out using exposure tests in which entire specimens (with their continuous reinforcement) were exposed under uniform conditions. The present paper describes the results of some of the experiments carried out to clarify the characteristics of corrosion occurring under a combination of different conditions. Experiments were carried out by subjecting reinforced concrete specimens to different exposure conditions in the laboratory and a marine exposure site. From the laboratory studies using continuous reinforcing bars in specimens subjected to diverse and simultaneous exposure conditions, it was found that corrosion occurs in those parts of the bars that are exposed to cyclic wetting and drying and at the interface of the submerged and aerially exposed parts. Some aspects of the corrosion monitoring using natural potential measurements under these conditions and the importance of water movement in determining the chloride concentration in concrete are also discussed. From the study of cracked and uncracked reinforced concrete marine environment, it was found that the presence of flexural cracks does marginally accelerate the initiation of corrosion at crack sites. Further, the presence of stirrups in the shear span of these beams was also found to have a significant restraining effect on the initiation and propagation of corrosion-induced longitudinal cracks along the main reinforcing bars. Once the width of these cracks exceeds a certain value, the corrosion of the bars and the widening of such cracks apparently becomes a vicious cycle.