Performance of Manganese Oxide Reference Electrode for Concrete Monitoring with Inner Alkaline Electrolytes

Abstract

Manganese oxide electrode (MnO2) is a promising reference electrode imbedded in concrete for long-term health monitoring of concrete structure. The MnO2 electrodes made of the high purity graphite powders, the MnO2 powders and Ca (OH)2 powders mixed with the inner alkaline electrolytes such as saturated Ca (OH)2 solution or synthetic concrete pore solution are manually assembled. The rejection ratios, reproducibilities, stabilities and the effects of temperature and NaCl concentration in outer electrolyte (synthetic concrete pore solution) on potentials of the MnO2 electrodes are comparatively experimented. And then the comprehensive properties of the MnO2 electrodes are analyzed based on their potentials relative standard error (PRSE). Though the relative high rejection ratio of MnO2 electrode is induced by the manual method, the following results and conclusions can be drawn. Firstly the MnO2 electrodes express good performances with little potential fluctuations in outer synthetic concrete pore solution. Secondly the potentials under condition of certain temperature or certain NaCl concentration, the reproducibilities and stabilities of MnO2 electrodes are influenced by their inner alkaline electrolytes. Especially the potential of the MnO2 electrode with the inner saturated Ca (OH)2 solution in outer electrolyte with high NaCl concentration is more outstandingly stable than the one with the inner synthetic concrete pore solution. The third the MnO2 electrode with inner synthetic concrete pore solution has better comprehensive property than the one with inner saturated Ca (OH)2 solution when the temperature is less than 50 °C or the NaCl concentration is not greater than 0.1 mol/L in outer electrolyte.