Incorporation and Characterization of Multi-walled Carbon Nanotube Concrete Composites for 3D Printing Applications

Being 3D concrete printing (3DCP) a relatively new technology, there is a constant need for development, not only in hardware but also in the materials we currently use. The use of nanomaterials, notably carbon nanotubes, in concrete and cement mixes is not new, but it is a novelty in 3DCP.
This paper investigates the effect on the fresh and hardened state properties of adding multi-walled carbon nanotubes (MWCNTs) to a printable concrete mix. Cement composites reinforced with MWCNTs may exhibit an irreversible change in resistivity when subject to damage or microstructural changes caused by strain or stress. Research also points to an improvement in flexural and compressive strength and lower shrinkage for CNT-cement mortars. The combined electrical and mechanical properties of these mixtures are of interest in crack self-detection for structural health monitoring. In this paper, two commercial solutions of MWC-NTs dispersed in water were used to determine their effect on a cement mortar suitable for 3D printing. Three different mixes were prepared: a reference mix, a mix with 0.05% of MWCNTs per binder content and a mix with 0.1% of MWCNTs per binder content. Higher percentages of carbon nanotubes resulted in a decrease in flowability and mechanical properties due to the difficulty in dispersing the nanotubes.
The results show that one of the two batches of MWCNTs used performed better overall than the other and the mix with 0.05% of MWCNTs per binder content revealed a better performance both in the fresh and hardened state than the mix with 0.1% of MWCNTs.