Influence of carbon nanotubes on printing quality and mechanical properties of 3D printed cementitious materials

This paper presents the impact of incorporating carbon nanotubes (CNTs) into the 3D printing of cementitious materials, along with the effective dispersion of CNTs. Compared to the control mix, adding CNTs with superplasticizer significantly enhanced the printing quality by reducing the error in height of two-layers from 38% to 30% and an 81% enhancement in the buildability. Moreover, rheology properties revealed shear-thinning behaviour with lower viscosity, resulting in improved flowability. The progressive increase in CNT concentrations up to 0.2% yielded a noteworthy improvement in the mechanical properties. At 28 days, the incorporation of 0.2% CNTs resulted in a significant increase in the flexural strength, compressive strength, and Young's modulus by 99%, 72%, and 43%, respectively, compared to the mix containing silica fume. Microstructural investigation of the CNT-cement matrix revealed nanoscale crack bridges formed by CNTs, reinforcing the cementitious material and improving its mechanical properties. •Printing quality, buildability and rheology were improved by adding 0.2% carbon nanotubes (CNTs) compared to the control mix.•The flexural strength increased by 99% at 28 days with the addition of 0.2% CNTs compared to a mix containing silica fume.•Adding 0.2% CNTs enhanced compressive strength and Young's modulus by 72% and 43%at 28 days compared to a mix involving SF.•Nanoscale crack bridges formed by CNTs were observed in the scanning electron microscope images.