Time-dependent chloride transport models for predicting service life of bridge decks under chloride attack

Abstract

This study aims to propose a set of time-dependent chloride transport models based on the measured data of 16 locations of monolithic concrete bridge decks under the attack of chloride ions in form of de-icing salts. This is carried out due to the shortcomings in the previous study which developed time-independent models containing two regression parameters. In this study, there are four regression parameters to be determined. They are simultaneously calculated using the finite difference formulation embedded with regression analysis. From the study, it is observed that the developed chloride transport model can predict the chloride content in most bridge decks. Although the prediction in some cases falls outside 50% margin of difference, they are on the conservative side. The regression parameters in the surface chloride function calculated here is higher than those in the previous study by two times. Seemingly, the diffusion coefficient in this study is comparable with that in Life-365 program. On the measurement or field survey date, if using the critical chloride value of 0.6 and 1.2 kg/m3, most and 5 of 16 bridge decks, respectively, would have rebar corrosion. However, there would be no concrete cracking if using the critical chloride value of 2.0 kg/m3.