Preparation And Performance Of All-solid Chloride Ion Sensor For Concrete

Chloride is one of the major causes of corrosion in reinforced concrete. The rapid and accurate measurement of chloride ions distribution in concrete structure can provide an important scientific evidence for correct assessment and prediction of concrete durability and rehabilitation of damaged structures. The traditional method of detection is time-consuming, operation-complicated and destructive. In this paper, a solid chlorine ion sensor was studied based on the electrochemical principle, using MnO₂ electrode and Ag/AgCl/rGO electrode as reference electrode and work electrode, respectively. And it can be used for in situ monitoring of chloride ion concentration in concrete.MnO₂ solid reference electrode with three-layer structure was assembled by combining gel electrolyte, foam concrete, and electrolytic manganese dioxide（EMD） material which was prepared by electrolytic oxidation method. The electrochemical test shows that the potential fluctuation of electrodes was less than 10 mV after immersed in simulated pore solution for 279 days. Meanwhile, the electrode was proved to have a low charge transfer resistance, large exchange current density and excellent performance in electrode polarization resistance. The temperature coefficient of the electrode is 0.68 mV/℃. In the pH range of 9–13.5, the electrode potential will decrease by 1.8 mV with the pH increase by 0.1, but the decrease is smaller than the theoretical value. It is interesting that the electrode potential shows no response to chloride and corrosion inhibitor.Secondly, we prepared Ag/AgCl/rGO composite by hydrothermal method. The morphology analysis indicates that the diameter of the Ag nanoparticles was less than 50 nm, and attached on the reduced graphene oxide layer evenly.Then the composite was spread on silver, compressed to be Ag/AgCl/rGO electrode. We tested the electrochemical performance of the electrode in simulate pore solution. The potential fluctuation is less than 3 m V during 180 days, chloride ion response relationship good linearity, the corrosion current density is large, indicating the electrode polarization resistance is better. The temperature coefficient is 0.41 mV/℃. What’s more, the electrode potential is almost immunity from pH.Finally, we also wrapped the Ag/Ag Cl/r GO electrode by the non-woven cloth coated with polyvinyl alcohol gel electrolyte and then embedded in mortar. The mortar was maintained in simulated pore solution which contained different concentration of chloride ion. During the curing period, the open circuit potential of the electrodes was found to be stable and exhibit a good linearity to log [Cl-]. When low content of sulfide and amine corrosion inhibitors was admixed in the mortar, the potential fluctuation of the Ag/Ag Cl electrode is small. It indicates that the electrode has strong anti- interference capacity.