In this chapter, the use of the models developed in Chapters 10 and 11 is extended to interpret the results from simple diffusion tests in which no voltage is applied. The general approach used was to solve the Nernst–Planck equation numerically for two physical ideal states that define the possible conditions under which chlorides will move through concrete. These conditions are named here as voltage control and current control. For each condition, experiments and simulations were carried out in order to establish the importance of electrical variables such as voltage and current in modelling chloride transport in concrete.