Protocol for Projecting Time-to-Corrosion of Reinforcing Steel in Concrete Exposed to Chlorides

摘要

A protocol is described whereby time-to-corrosion, T^sub i^, of reinforcing steel in concrete exposed to chlorides was calculated as a distributed, rather than discrete, parameter. The method consists of inputting (1) an average value for surface [Cl-] and the effective diffusion coefficient, (2) the mean and standard deviation of concrete cover over the reinforcement, and (3) a distribution function for the critical Cl- threshold concentration to initiate corrosion, C^sub T^, based upon values previously reported. The calculation result is a cumulative distribution function (CDF) plot of T^sub i^. Example analyses were performed based upon a range of design and material property values of the above parameters for both past and representative, present-day bridge decks and marine bridge substructures. Results for corrosion-resistant reinforcement are compared with those for black bar. It is proposed that reinforced concrete durability should be characterized not simply in terms of the time at which corrosion initiates for a small percentage of the reinforcement, as is normally done, but also by the rate at which active corrosion subsequently begins for the remaining, uncorroded reinforcement. Implications of such an approach are discussed. [PUBLICATION ABSTRACT]