Evaluation of Steel Corrosion in Fly Ash Concrete Containing Chlorides Using Electrochemical Indexes

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Considering the durability of fly ash concrete against the chloride attack, a quantitative evaluation of the rebar corrosion rate in concrete is necessary. In this study, reinforced concrete specimens containing premixed chlorides were prepared, using concrete with cement or fine aggregate partly substituted by fly ash. The corrosion rate of rebar in the specimen was evaluated by the polarization resistance which is an electrochemical corrosion index. The specimens were stored in the wet or dry condition at the temperature of 20 or 40 ºC. As a result, the corrosion rate of rebar was greatly suppressed by admixing fly ash with the increase of the concrete resistivity at the temperature of 20 ºC, while such suppression effect decreased with the rise in temperature to 40 ºC. The suppression effect was remarkable in the cases of fly ash addition as the substitution of fine aggregates. Moreover, the influence of a variation of the chloride content in concrete on the steel corrosion rate was significant when the specimens were stored in the dry condition. The influence of the environment temperature and the chloride content in concrete on the steel corrosion rate measured in this study could be generally evaluated by using an existing equation.