Time-dependent chloride transport models for cracked concrete bridge decks under chloride attack

Abstract

The aims for this study is to develop time-dependent models of chloride diffusion using the survey data of sixteen sites of cracked concrete bridge decks under the influence of chloride attack in form of de-icing salts. This is taken into account, because it is evident that the diffusion of chloride ions through cracked concrete is different from that of uncracked one. The developed models consist of two main models, containing 4 parameters for regression. From the development, the models of chloride diffusion can predict the content of chloride ions through cracked concrete bridge decks in an average sense. Based on the prediction by the developed models, the long-term content of chloride ions near cracked concrete surface is found lower than that near uncracked one, because those chloride ions penetrate deep inside bridge decks. Because of this penetration, the increase of chloride ions near the surface of cracked concrete bridge decks is slower than that of uncracked ones. Moreover, the comparison of the diffusion coefficient indicates that the diffusion of chloride ions through cracked concrete bridge decks is faster than that through uncracked one. Considering the crack-free condition of concrete bridge decks, the available critical value of chloride ions for concrete cracking of 2.0 kg/m3 tends to overestimate the initiation time of concrete cracking. However, the critical chloride value for concrete cracking is here recommended as no more than 0.355 kg/m3 for more conservative condition.