Chloride Corrosion of Reinforcing Steel in Cracked Concrete


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Title: Chloride Corrosion of Reinforcing Steel in Cracked Concrete

Author(s): Kiyoshi Okadaand Toyoaki Miyagawa

Publication: Special Publication

Volume: 65


Appears on pages(s): 237-254

Keywords: chlorides; concrete durability; corrosion; cracking (fracturing); crack width and spacing; marine atmospheres; reinforced concrete; reinforcing steels; water-cement ratio.

Date: 8/1/1980

This paper deals with corrosion of reinforcing steel, the critical problem for the durability of reinforced concrete structures in marine environment. The results of tests using various electrochemical methods are summarized as follows; (1) As the water cement ratio of concrete increases, the natural potential of reinforcing steel becomes less noble and the electric resistance of wet concrete becomes lower due to low permeability which accelerates the corrosion of reinforcing steel. (2) Cracks in reinforced concrete structures make reinforced concrete so heterogeneous as to cause macrocell corrosion of reinforcing steel. (3) According to the experimental method used here, it may be considered that critical crack width is between 0.1 and 0.2 mm. (4) Water cement ratio influences both the macrocell corrosion rate at cracks, and the mechanism of corrosion. (5) It is concluded that the potential difference between macro anode (vicinity of cracks) and cathode (in concrete) is the electromotive force giving rise to the macrocell corrosion. (6) As the ratio of cathodic area to anodic area increases, the macrocell current density and the corrosion rate at cracks becomes larger.