Diffusion of Chloride Ions in the Pastes and Mortars Containing Ground Granulated Blast Furnace Slag

The chloride corrosion is one of the seriously harmful processes leading to the destruction of concrete structure. Aparat from the chemical attack on the concrete cover, the chloride ions show their aggressive action on the steel reinforcing elements. The high resistance of slag cementitious materials has been proved in many earlier works. In the presented study the authors give a confrontation of results on the durability of Portland cement, slag cement with 60% granulated blast furnace slag and alkali activated slag cement. The mortars were stored in NaCl, MgCl 2 and CaCl 2 solutions respectively. Aparat from the strength tests, the phase composition studies using XRD and SEM were carried out. The effective diffusion coefficients of Cl - ions, originating from NaCl, MgCl 2 or CaCl 2 , were measured for the Portland cement and slag mortars. The significantly higher corrosion resistance of slag cementitious mortars has been thus proved. It has been also shown that the rate of corrosion process was closely correlated with the type of accompanying cation in chloride solution. The progress of corrosion was the most evident in the presence of Mg 2+ ion, the slowest corrosion was observed in the presence of sodium.