Study of rheological properties of carbon nanotube-reinforced ultrafine cement grouting materials

In this study, three different diameters of multi-walled carbon nanotubes (MWCNTs) dispersed by polyvinyl pyrrolidone (PVP) were used to reinforce superfine cement grouting materials. The effect of MWCNTs and PVP on the rheological properties of grouting material were accordingly studied. It was found that the yield stress (τ₀) and plastic viscosity (η) decreased slightly when PVP content was low and increased when PVP content increased. The effect of MWCNT diameter on τ₀ was not found to be clear but was more significant on η. The smaller the MWCNT diameter, the quicker η increased. It was also found that the thixotropic ring area increased as the MWCNT content increased. The addition of PVP and MWCNTs caused an increase in the number of entanglement points in different scales, which was the main reason for the viscosity and thixotropy increase. Therefore, the rheological properties of superfine cement grouting material should be adjusted when MWCNTs are added as a reinforcing component. Owing to the wrapping of PVP on cement particles, which isolates the contacting part between water and cement particles, it slows down the hydration rate of cement and thus slows down the fluidity loss of the slurry.