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Mechanical properties and microstructure of reactive powder concrete with multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) have received increasing attention as prominent candidates to reinforce cement-based composites. In this study, the combination of ultrasonication and surfactants was used to disperse uniformly MWCNTs in aqueous solution. Especially, the surfactants were proportionally composed of sodium dodecyl benzene sulfonate (SDBS) and polyvinyl pyrrolidone (PVP). Reactive powder concrete samples with different MWCNTs content were prepared, and their mechanical performance and microstructure were also evaluated. The results show that the synergistic effect, provided by anionic SDBS and nonionic PVP, is effective to achieve stable dispersion of MWCNTs. The flexural strength and compressive strength were increased by 8.5% and 15.4%, respectively, when 0.10 wt% MWCNTs were added. Moreover, scanning electron microscope (SEM) revealed that the uniform dispersion of MWCNTs in matrix was further confirmed, and the porosity of cement composites with the addition of MWCNTs was decreased measured by mercury intrusion porosimetry (MIP) results. MWCNTs can reduce internal drawbacks and restrain cracks propagation at nanoscale level, thus improving the microstructure and mechanical properties.