Chloride Exposure of Reinforced Concrete with an Admixed Corrosion Inhibitor: Part I – Time to Corrosion Initiation Neglecting Inhibitor Egress

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Product Number: 51314-3635-SG

ISBN: 3635 2014 CP

Author: William Hartt

Publication Date: 2014

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A first principles based equation from the literature was modified such that the cumulative distribution function (CDF) of Cl- concentration ([Cl-]) in concrete at the reinforcement depth after a given exposure time was calculated by numerical integration. The approach accommodates the fact that surface Cl- concentration (Cs) the effective diffusion coefficient (D) and reinforcement cover (x) each conform to a distribution rather than being discreet. Calculations were performed for a range of mean D Cs and x values. The previously reported limiting [Cl-] for which various dosages of the corrosion inhibitor calcium nitrite (CN) are effective in maintaining reinforcing steel passivity was superimposed upon the CDFs. From probability distributions of first [Cl-] and second Cl- threshold to initiate active corrosion as enhanced by a particular CN addition the percentage of reinforced concrete elements for which active corrosion initiates after specific times and hence inhibitor effectiveness were determined using a Load-Resistance Factor Design type approach. Inhibitor effectiveness in reducing total corrosion is discussed as are scenarios and implications thereof for chlorides and CN being solely in the cement phase as opposed to being uniformly distributed throughout the concrete.Key words: Concrete reinforcing steel corrosion initiation chlorides corrosion inhibitor calcium nitrite.