Methylcellulose stabilized multi-walled carbon nanotubes dispersion for sustainable cement composites

Multi-walled carbon nanotubes (MWCNTs) are promising nanoreinforcing materials owing to the superior mechanical properties. Dispersion of MWCNTs is the key to achieving a desirable reinforcing effect, especially in cementitious mixtures, where dispersion is challenging due to high ionic strength. In this study, methylcellulose (MC) is used to stabilize the dispersion of MWCNTs with a constant mass concentration of 0.08 wt% in sustainable ternary cementitious blends of OPC, FA and SF. The effect of different MC dosages on MWCNTs dispersion in a simulated alkaline environment is investigated via UV-vis-NIR spectrometry. The influences of MC on fluidity, bleeding rate, density, wave velocity, porosity, compressive strength, elastic modulus of cementitious blends with w/c of 0.6 were studied. The results showed that MC could significantly improve the stability of MWCNT dispersion in alkaline environment via the viscosity effect. It was found that an optimal concentration of 0.18 wt% MC addition in MWCNT suspension performed the best for improvement of MWCNT dispersion. The MC is effective in improving consistency and reducing bleeding in the cement pastes. An appropriate range of MC (0.10 ∼ 0.20 wt%) is required to achieve optimum enhancing effect of MWCNTs and strength properties of MWCNT-cementitious composite.