As chlorides penetrate into the concrete, some of them are physically and chemically bound to the cement matrix. Therefore, only free chloride ions can promote the further penetration. Also, only free chloride ions are responsible for steel depassivation and initiation of the reinforcement corrosion. This effect needs, therefore, to be included in our predictions. The simplest way to do this is to consider binding as a linear phenomenon. Some authors suggested, however, that this assumption is not suitable for a wide range of chloride concentrations. Therefore, non-linear binding isotherms (mainly Freundlich and Langmuir) are often used. First trials with the both nonlinear and linear binding have been performed, and here are the results!
