A study of the effects of MWCNTs on the fresh and hardened state properties of 3D printable concrete

Much research in 3D concrete printing focuses on material design and testing new additives to improve performance. However, there are very few examples of studies using carbon nanomaterials to improve mechanical performance and create smart mortars with self-sensing capabilities. 3D concrete printing is a new technology that focuses on optimizing the building industry, a composition able to monitor structural health can provide important insights into stress levels and microcrack concentration in critical structural parts. In this study, multi-walled carbon nanotubes (MWCNTs) were embedded in a printable concrete, and its self-sensing ability was investigated. Four compositions with different concentrations of MWCNTs were prepared to assess the porosity distribution and mechanical properties in the fresh and hardened states. To evaluate the self-sensing ability of the material, the change in conductivity was measured using a resistivity meter with a four-point Wenner probe, while the material was tested under compression and tension. The results showed that porosity, strongly influenced by the distribution of nanomaterials in the matrix, had a significant effect on the fresh and hardened state behavior and self-sensing ability of the compositions, and the composition with better self-sensing capabilities was the one with a MWCNTs content of 0.5% per binder content.