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

摘要

A companion paper (Part I) introduced a protocol whereby time-to-corrosion, Ti, of reinforcing steelin concrete exposed to chlorides is calculated as a distributed, rather than discrete, parameter. Themethod consists of, first, considering that identically exposed, Electrochemically independent elementscomprise 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 equationfrom which the fraction of elements that have initiated corrosion is calculated for a specific exposuretime. Upon repeating the calculation for different times, a cumulative distribution function (CDF) plot ofTi 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 resistantreinforcements (CRR) as an alternative to black and epoxy-coated bars. The present study employedthis 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.