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

Strain Monitoring of Concrete Using Carbon Black-Based Smart Coatings

“…where R bulk is the resistance value corresponding to the ionic conduction of the interconnected pores in parallel with the electronic conduction through the conductive filler [138] [Ω], L is the distance between the pair of chosen electrodes or gauge length [m], and A is the cross-section of the specimen [m 2 ]. Moreover, selecting the cusp point for AC applications limits the moisture influence and thus the contribution of ionic conduction in the electrical response of the coatings.…”

“…Therefore, the capacitance contribution to the AC electrical response-represented by the imaginary part of the impedance-was limited to its minimum by choosing the frequency of the cusp point and, thus, making the measured resistance less dependent on any moisture variation. In this study, electrical tests on smart cement were conducted with the aim of maintaining the system's inner moisture at a constant 90% saturation degree, a condition identified in analogous studies as optimal for enhancing low-resistance and high strain-sensing capabilities [138,140]. This specific moisture level not only aligns with best practices for smart cement production but also addresses the challenge of water theft, when water is drawn into the concrete substrate from the coating after application and full curing.…”

“…The electromechanical tests involved only AC measurements to assess the coating's electrical response to flexural load due to its higher reliability and equipment precision. Due to the electrode's configuration [135]) and (b) capacitive/resistive components in the equivalent circuit of cement-based conductive composites (adapted from [138]).…”

Electrochemical Impedance Spectroscropy Study on the Behavior of Reinforced Concrete Elements under Loading

“…Several fillers have been tested that provide ductility [20] but also electrical conductivity due to the nature of the fillers employed: carbonbased and metal-based fillers (carbon fibers, carbon black, carbon nanotubes, graphite, graphene, steel slag, metal oxide, steel fiber, and nickel powder). When the filler concentration lies close to the percolation threshold (Figure 9a), any deformation of the material results in changing the spacing of the conductive filler, with associated changes in the measured resistivity [20,27,40].…”

“…The importance of water content in self-monitoring devices was less studied [24][25][26], perhaps due to the poor understanding of the water contribution to the overall capacitance of the system [27]. Thus, this review focuses mainly on this aspect.…”