Intensity of Mass Transfer Processes in Concrete with Inhibitors in Chloride Corrosion

Abstract

The article presents the results of a study of the effect of alkaline and alkaline-earth metal nitrates added to concrete cement stone on the intensity of mass transfer processes occurring during corrosion in a highly aggressive liquid chloride-containing medium. The studies were carried out on samples of cement stone from Portland cement of the CEM I 42.5 N brand with W/C = 0.3 in a 2 % MgCl2 solution. As inhibitory additives, KNO3 NaNO3, Ca(NO3)2, Zn(NO3)2, Mg(NO3)2 were introduced into the cement mixture in an amount of 0.5 % by weight of cement. When additives of nitrates of alkaline or alkaline-earth metals are introduced into the cement mixture at the stage of concrete production, the rate of mass transfer corrosion processes decreases by 1.5 times. It was found that inhibitors do not have a significant effect on the change in the strength of concrete cement stone during chloride corrosion. The mass transfer indicators (coefficients of mass conductivity and mass transfer, the density of the flow of the transferred components) were determined, according to which the periods of reaching the limiting concentration of chloride ions at the surface of steel reinforcement in concrete during corrosion in 2 % MgCl2 solution were calculated. To achieve such concentration of chloride ions at the surface of steel reinforcement in concrete without an inhibitory additive, it will take 174 days, in concrete with 0.5 % KNO3 additive – 260 days.