Analysis of changes in the electrical parameters of cement composites under the simultaneous action of direct current and chloride ions

Purpose. The aim of this study is to investigate changes in the electrical parameters of cement composites subjected to the simultaneous action of direct electric current and chloride ions, as well as to establish the patterns of variation in electrical conductivity and equivalent electrical resistance during long-term ion electromigration. Methodology. Experimental studies were carried out on cement-sand mortars. Cylindrical specimens were exposed to a 0.35 mol/L sodium chloride solution and to water under conditions of forced passage of a pulsed direct current through the specimens with continuous monitoring of current intensity and voltage. The state of the system was evaluated based on the analysis of current intensity, voltage, and the calculation of equivalent electrical resistance according to Ohm’s law. Findings. The presence of chloride ions was found to significantly increase the electrical conductivity of the cement composite. The stabilized current intensity in specimens exposed to the NaCl solution was approximately 38 mA, whereas in the specimens stored in water it was only about 7.4 mA. Accordingly, the equivalent electrical resistance decreased from approximately 4050 Ω to 785 Ω. During long-term exposure, an initial increase in current intensity followed by its gradual decrease was observed, indicating an increase in system resistance caused by chloride ion migration and their partial binding by cement hydration products. Originality. The study established the regularities of changes in current intensity and equivalent electrical resistance under the influence of electromigration processes and chloride binding within the porous structure of cement stone. New data were obtained on the manifestation of polarization processes in cement composites under cyclic electrical loading. Practical value. The obtained results can be used to assess the durability of concrete and reinforced concrete structures operating under chloride-containing environments and stray current conditions typical of transport infrastructure facilities, bridges, tunnels, and hydraulic engineering structures.