American Society of Civil Engineers


Corrosion of Steel Bars in Cracked Concrete under Marine Environment


by Tarek Uddin Mohammed, (Res. Engr. (Sr.), Port and Airport Res. Inst., Materials Division, 3-1-1 Nagase, Yokosuka, Japan. E-mail: tarek@pari.go.jp), Nobuaki Otsuki, (Prof., Tokyo Inst. of Technol., Dept. of Intl. Development Engrg., 2-12-1 Ookayama, Meguro ku, Tokyo 152, Japan), and Hidenori Hamada, (Chf., Port and Airport Res. Inst., Materials Division, 3-1-1 Nagase, Yokosuka, Japan 239-0826)

Journal of Materials in Civil Engineering, Vol. 15, No. 5, September/October 2003, pp. 460-469, (doi:  http://dx.doi.org/10.1061/(ASCE)0899-1561(2003)15:5(460))

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Document type: Journal Paper
Abstract: This paper deals with the macrocell and microcell corrosion of steel bars in cracked concrete exposed to a marine environment. For this, short-term accelerated laboratory and long-term exposure tests were carried out. Test items include electrochemical and physical evaluations of corrosion, chloride ion content in concrete, and oxygen permeability through concrete. Analyses by scanning electron microscopy and electron probe microanalyzer were also carried out to confirm the deposit in the healed cracks. For an unhealed crack, the portion of the steel bar located at the root of the crack acts as an anode and other portions as a cathode. Also, microcell corrosion at the cracked region is higher than the uncracked region. Macrocell corrosion process and the degree of macro and microcell corrosion are significantly influenced by the water/cement. In a natural marine environment, narrower cracks heal due to the deposition of ettringite, calcite, and brucite in the crack. This reduces the corrosion rate significantly at the cracked region.


ASCE Subject Headings:
Chloride
Coastal environment
Concrete
Corrosion
Cracking
Steel