Critical chloride content and its influence on service life predictions

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Abstract
In service life predictions of concrete structures in marine environment, the critical chloride content is a crucial parameter. However, there is a lack of reliable data for this parameter. This paper presents a statistical model for the critical chloride content derived from measurements based on corrosion sensors installed in a 37 years old jetty. For each corrosion sensor location, the chloride content at different sensor rings is found from the chloride profile obtained from detailed profile grinding of the concrete core drilled out before installation of each sensor. The critical chloride content for each sensor location is then obtained by comparing the chloride profile with the sensor reading at the depth of depassivation. Further, the influence of the critical chloride content on the calculated service life is studied. From the probabilistic service life calculations, it is found that the service life increases from 50 to 100 years if the characteristic value of the critical chloride content increases from 0.34 to 0.67% (by weight of cement).