General model for service life analysis of reinforced concrete structures subject to chloride penetration

The conventional procedure for chloride profiles modeling is based only on the diffusion zone considering the solution of Fick's second law of diffusion, however, the extrapolation of this model to the convection zone is not capable to represent the chloride concentrations. Therefore, the present work analyzes the applicability of the Modified Holliday Equation in profiles obtained from field structures built in different parts of the world (composed of different materials and submitted to specific local environmental characteristics). The main goal of this work is to validate the applicability of the Modified Holliday Equation for service life analysis of field reinforced concrete structures subject to chloride penetration. A mathematical proposal for the determination of the peak's chloride concentration position, delimiting the convection and diffusion zones, is also part of the scope of this work. The results showed that the empirical model based on the Modified Holliday Equation is capable of representing the chlorides concentration considering both, the data from the convection zone and the diffusion zone. Furthermore, in many analyzed cases, a better statistical fit between the proposed model and the chloride profile concentrations was obtained, when compared to the modeling through the solution of Fick's second law. The mathematical proposal presented for the peak determination has shown to be simple and efficient in cases where there are, at least, three neighboring points, forming a sharp peak in the profile. Finally, the results attested to the possibility of applying the Modified Holliday Equation to represent chloride concentration of field structures in different marine aggressive zones, in order to predict the service life of these structures in a more accurate way.