Hybrid cement composite-based sensor for in-situ chloride monitoring in concrete structures

In this paper, we present a rugged cementitious composite sensor for monitoring chloride ingress in concrete structures. The sensor is in the form of an electrochemical double-layer, consisting of a chloride ion-selective functionalized graphene film sandwiched between two cementitious composites. The cementitious composite chloride sensor was subjected to different chlorides concentrations and electrochemical impedance spectroscopy (EIS) measurements were conducted to characterize its response. The effect of the pore solution and the independent impact of temperature and humidity on the sensor's response were also quantified. The experimental results showed that the sensor successfully measured chlorides concentration changes with good sensitivity. The sensor's response was not affected by temperature and humidity and showed good reversibility and stability. However, the pH of the pore solution affected the sensor's response to chlorides and a sensor calibration equation that considers pH is proposed. The characterization work presented herein provides a base for the development of such chloride sensing method, which can provide useful information for chloride diffusion models updating and health monitoring of the concrete structures subjected to sodium chloride.