Silica Concrete - Protection Against Corrosion of Embedded Steel

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Title: Silica Concrete - Protection Against Corrosion of Embedded Steel

Author(s): 0ystein Vennesland and Odd E. Gjorv

Publication: Special Publication

Volume: 79

Issue:

Appears on pages(s): 719-730

Keywords: carbonation; corrosion resistance; electrical resistance; oxygen; porosity; reinforced concrete; reinforcing steels; silica.

Date: 5/1/1983

Abstract:
The good ability of concrete to protect embedded steel against corrosion is mainly due to the high alkalinity of the pore water of the concrete, which provides a passive, noncorroding state of the embedded steel If this passivity of the steel is broken - either by carbonation or by the presence of chloride ions the corrosion of the steel will mainly be controlled by the electrical resistivity of the concrete and the rate of oxygen transport through the concrete to the steel. The present paper describes a study on how additions of up to 20% condensed silica fume by weight of cement affect the rate of carbonation, electrical resistivity and rate of oxygen transport through water-saturated concrete. It was found that the effect of silica on the parameters studied varied within wide limits, The rate of oxygen transport was only slightly affected while the rate of carbonation was somwhat reduced. The most pronounced effect of silica was found on the electrical resistivity which is increased by up to 190-1600% for cement contents varying from 100 to 400 kg/m3, respectively.