Experiments and micromechanical modeling of electrical conductivity of carbon nanotube/cement composites with moisture

Carbon nanotube (CNT)/cement composites have been proposed as a multifunctional material for self-sensing and traffic monitoring due to their unique electric conductivity which changes with the application of mechanical load. However, material constituent and environmental factors may significantly affect the potential application of these materials. Therefore, it is necessary to understand an influence of material constituent such as porosity and dispersion of CNT and environmental factor such as moisture on the electrical conductivity of CNT/cement composite. This paper investigates the effect of moisture on the effective electrical conductivity of CNT/cement composites. To prepare the specimens, multi-walled carbon nanotubes (MWCNTs) are well dispersed in cement paste, which is then molded and cured into cubic test specimens. By drying the specimens from the fully saturated state to the fully dry state, the effective electrical conductivity is measured at different moisture contents. As the water in the specimen is replaced by air voids, the electrical conductivity significantly decreases. Different ratios of MWCNTs to cement have been used in this study. Micromechanical models have been used to predict the effective electrical conductivities. A comprehensive model is proposed to take into account the effects of individual material phases on the effective electrical conductivity of CNT/cement composites with moisture effect.