Corrosion of Steel Bars in Cracked Concrete Made with Ordinary Portland, Slag and Fly Ash Cements

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Title: Corrosion of Steel Bars in Cracked Concrete Made with Ordinary Portland, Slag and Fly Ash Cements

Author(s): Tarek Uddin Mohammed, Toru Yamaji, Toshiyuki Aoyama, and Hidenori Hamada

Publication: Special Publication

Volume: 199

Issue:

Appears on pages(s): 699-718

Keywords: corrosion; cracked concrete; fly ash cement; marine envi-ronment; ordinary portland cement; slag cement

Date: 6/1/2001

Abstract:
Corrosion of steel bars in pre-cracked prism specimens exposed in marine environment for 15-year is presented here. The size of the specimens was 100x100x600 mm. The specimens were made with ordinary Portland, slag (Type A, B and C) and fly ash (Type B) cements. A round steel bar of diameter 9 mm was embedded in each specimen. W/C were 0.45 and 0.55. Crack widths were varied from 0.1 to 5 mm. Chloride-ion concentrations in concrete and corrosion of steel bars were evaluated. Narrower cracks ( < 0.5 mm) heal irrespective of the cement types. Chloride ingress and corrosion of steel bars in concrete are highest for the specimens made with ordinary portland cement and lowest for the specimens made with slag cement of Type C. Locations of the maximum corroded area as well as the deepest corrosion pit are not necessarily at or near the cracked region Wider cracks are not healed and maximum corroded area and deepest corrosion pit are observed at the cracked region. The presence of voids at the steel-concrete interface results in corrosion pits even for chloride-ion concentration less than 0.4% of cement by weight.