A comprehensive investigation of the rheology of cement pastes containing multi-walled carbon nanotubes

Abstract

Multi-walled carbon nanotubes (MWCNTs) have gained increasing attention for their potential applications in cement-based materials due to their excellent mechanical, electrical, and thermal properties. While numerous studies have explored their effects on the mechanical properties of cementitious systems, a comprehensive understanding of their impact on rheological behavior remains limited. This study investigates the influence of MWCNTs content (0–0.5 %) on the static and dynamic yield stress, viscosity, thixotropy, and viscoelasticity of cement paste, as well as the impact of MWCNTs on cement hydration. Experimental results demonstrate that MWCNTs induce remarkable rheological modifications: (1) Static yield stress escalates from 19.46 Pa to 32.59 Pa (67.5 % increase) and dynamic yield stress rises from 7.37 Pa to 18.77 Pa (154.7 % enhancement) at 0.5 % MWCNTs, attributable to synergistic nano-filling and network-forming effects; (2) A distinctive rheological transition from thixotropic to rheopectic behavior occurs, with viscosity recovery rate reaching 87.17 % at 0.5 wt%, indicating superior structural reconstruction capacity through time-dependent structural reorganization; (3) Viscoelastic analysis reveals that MWCNTs also improve the viscoelastic stability of cement pastes, especially under high stress. Notably, MWCNTs incorporation reduces chloride diffusion coefficient by 63 % while maintaining negligible influence on hydration kinetics.