Analysis of chloride migration in concrete based on multicomponent medium theory

An analytic description of chloride migration in concrete has been carried out using multicomponent medium equations. These equations have made it possible to quantify flow of ions CI'', take into account both effects of their adsorption taking place on the pore walls and interactions of accompanying sodium ions as well. The process is being analyzed according to the multicomponent medium theory, on the basis of the equations of mass balances, electric charge, momentum and energy, and entropy inequality. These relations have been reduced to the flow equation, in which the concentration change rate of the process components as related to the concentration gradient of ions CI'' has been quantified. The material properties of the concrete have been expressed by determinant diffusion coefficient. In order to quantify numerical values of the determinant diffusion coefficient a converse task of the diffusion equation has been formulated. The relationships obtained have made it possible, in a theoretically justified manner, to average the changing in time process variables, to take into account boundary conditions, to quantify non stationary influences and the formations of chemically bounded chlorides, and to determine concentration difference range in which calculation results of diffusion coefficient of chloride ions are stable. The example-like calculations have been carried out using the experimental data published. The solution has shown usefulness of the deduced relations for generalization and interpretation of the results of the experimental researches.