Sulfate transfer through concrete: Migration and diffusion results

This paper presents a study on the effect of sulfate ions on concrete. The sulfate attack is approached in two different ways: results in natural diffusion are compared to migration results. Both sodium sulfate and magnesium sulfate are used as test agents. The comparison is presented in terms of concentration profiles and amounts of sulfate reacting with the cementitious matrix, together with mechanical resistances. It is shown that the electrical field has impact on the transfer of sulfate: when Mg2+ is used as the counter-ion, the penetration depth proves to be larger in migration than the depth obtained with sodium sulfate. It is the opposite case in natural diffusion. A possible explanation could be found in the kinetics of brucite formation. Finally, the combination of magnesium sulfate with the electrokinetic technique results in significant mechanical strength losses after 6 months of test, while natural diffusion attacks lead to a much smaller loss.