Electrical properties of cement mortars incorporating MWCNTs using electrochemical impedance spectroscopy: Experimental study and efficient modelling approach

This study investigates the electrical properties of cement mortars incorporating multi-walled carbon nanotubes (MWCNTs), with a focus on how moisture content and nanotube concentration influence impedance characteristics. Electrochemical impedance spectroscopy (EIS) was used to analyze two types of mortars: a standard composition containing 450 g of cement and a superplasticiser (C0), and a high-cement-content mix with 675 g of cement and no admixtures (C5). MWCNTs were added in concentrations of 0.05 %, 0.10 %, and 0.20 % by weight of cement. Samples were tested at various moisture levels ranging from 2 % to 8 % by sample weight. The results showed that increasing moisture content significantly reduced electrical resistance in both mortar series, with the effect being more pronounced in the C0 series. The influence of MWCNT content on electrical parameters was less consistent; however, the C5 series exhibited a stronger interaction between nanotube content and humidity, resulting in greater overall sensitivity. The C5 series may be better suited for applications requiring high sensitivity to moisture variation, whereas the C0 series may be more appropriate where a stable and predictable electrical response is desired. To interpret these observations, six principal electrical conduction paths within the composite were proposed, each affected differently by moisture and nanotube content. Based on this framework, a simplified equivalent circuit was developed, comprising a resistor representing the pore solution in series with a parallel combination of a resistor and a constant-phase element. This simplified model effectively captures the material's electrical response across a wide range of frequencies and moisture conditions, providing a practical tool for simulating its behaviour. • EIS method assessed cement mortars' electrical performance with MWCNT. • Three MWCNT dosages, two cement-to-aggregate ratios were analysed. • Electrical resistivity, capacitance studied under varying moisture content. • Practical predictive model for electrical performance of cement mortars was derived. • The proposed simplified model aligned well with experimental results.