Physicochemical processes and mathematical modeling of concrete chlorination

TitlePhysicochemical processes and mathematical modeling of concrete chlorination
Publication TypeJournal Article
Year of Publication1996
Papadakis VG, Fardis MN, Vayenas CG
JournalChemical Engineering Science

Corrosion of steel bars in concrete may start when the concentration of free chlorine ions in the liquid phase of the pores exceeds a certain threshold level causing depassivation of the bars. The physicochemical processes of diffusion of Cl− in the aqueous phase of the pores, their adsorption and binding in the solid phase of concrete and their desorption therefrom are described by a nonlinear partial differential equation for the concentration of Cl− in the aqueous phase, from which that of Cl− bound in the solid phase can be computed algebraically. A simple yet accurate enough approximate analytical solution is also proposed, based on the assumption of the formation of a “chlorination front” where all the absorption and binding of Cl− takes place, and beyond which no effects of the ingress of Cl− from the environment are felt. Model parameters are identified through fitting to experimental results. Parametric studies allow identification of the relative importance of the various geometric, physicochemical and environmental exposure parameters.

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