11009 Corrosion Initiation Projection for Reinforced Concrete Exposed to Chlorides – Part II: Corrosion Resistant Bars

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Product Number: 51300-11009-SG

ISBN: 11009 2011 CP

Author: William H. Hartt

Publication Date: 2011

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A companion paper (Part I) introduced a protocol whereby time-to-corrosion, Ti, of reinforcing steel in concrete exposed to chlorides is calculated as a distributed, rather than discrete, parameter. The method consists of, first, considering that identically exposed, electrochemically independent elements comprise the concrete of interest and, second, inputting distribution functions for 1) surface Cl- concentration (Cs), 2) the effective diffusion coefficient (D), 3) concrete cover over the reinforcement (x), and 4) the critical Cl- concentration threshold to initiate corrosion (CT) into a governing equation from which the fraction of elements that have initiated corrosion is calculated for a specific exposure time. Upon repeating the calculation for different times, a cumulative distribution function (CDF) plot of Ti is constructed. In the Part I paper, the protocol was applied to black bar (BB) reinforcement; however, with advent of life-cycle cost considerations and specified bridge design lives of 75-100 years, increased attention has focused during the past one-to-two decades upon corrosion resistant reinforcements (CRR) as an alternative to black and epoxy-coated bars. The present study employed this same governing equation to determine CDF(Ti) trends for selected CRR and project the CDF(Ti) increase that is realized with these CRR compared to BB.

Keywords: Reinforced concrete, corrosion, corrosion resistant reinforcement, critical chloride threshold concentration, time-to-corrosion.