Chloride profile modeling contemplating the convection zone based on concrete structures present for more than 40 years in different marine aggressive zones

A new empirical chloride profile model contemplating the convection zone based on concrete structures present for more than 40 years in tidal, splash and marine atmosphere zone, under natural degradation, is presented in this paper. Concrete cores were extracted from different structures in order to determine the chloride concentration by X-Ray Fluorescence Spectroscopy technique for chloride profile analysis. The concrete characterization was performed through physical and mechanical tests. Chloride profiles that presented a peak of maximum chloride concentration were analyzed by two methodologies: First, through the Second Fick's Law solution and, secondly, through a new approach through the Modified Holliday Equation, aiming to contemplate chloride concentrations present in the convection zone using the same variables of the first method. The results showed that in the diffusion zone, both methodologies presented a strong correlation in order to represent chlorides concentrations, even admitting more advanced structure ages, however, in the convection zone, only the Modified Holliday Equation was able to represent the chloride concentrations of the profiles. Through the analysis performed, it was concluded that it is possible to represent the chloride concentration contemplating the convection zone through a simple empirical model using the apparent diffusion coefficient, structure age and chlorides concentration at the peak as variables. (C) 2018 Elsevier Ltd. All rights reserved.