Electrical impedance behaviour of carbon fibre reinforced cement-based sensors at different moisture contents

Carbon fibre reinforced cement-based sensors offer a potential low-cost and high-performance alternative to externally applied sensors for health monitoring of concrete structures. This paper focuses on the moisture dependence of bulk conductivity for carbon fibre reinforced cement-based sensors with fibre contents 0.1–1.5 vol%. Under two-point AC impedance spectroscopy at frequencies 1 Hz–10 MHz, the electrode polarization (EP) process, an electrical double layer polarization process (EDLP), and the bulk Maxwell-Wagner type interfacial polarization process (MWP) were identified. While reducing the saturation degree from 100 % to 0 %, the fractional change of bulk conductivity (FCS) underwent three different stages, which consists of a non-linear stage at 100–80 % saturation, a linear stage at 80–20 % saturation, and a final stage at 20–0 % saturation. The results gave insights into the stability of cement-based sensors under field conditions, and the underlying mechanisms of behaviour. From this, a route towards appropriate use of cement-based sensors in mechanical sensing and potentially moisture sensing without further external measures can be realised.