Cement Paste Modified by Nano-Montmorillonite and Carbon Nanotubes

This paper investigates the coupled effect of functionalized multi-walled carbon nanotubes (MWCNTs-COOH), nanomontmorillonite (NM), and sodium dodecylbenzene sulfonate (SDBS) anionic surfactant on compressive and flexural strengths of cement paste. The response surface methodology (RSM) was used to optimize the content of the two nanomaterials and surfactant, and to analyze the effect of their interactions on the mechanical properties and microstructural characteristics of the paste. Test results indicate that the simultaneous use of NM and MWCNTs can lead to a 30% gain in compressive strength and a 40% increase in flexural strength. Using analysis of variance (ANOVA), it was possible to predict the optimal weight percentage of nanomaterials. Atomic force microscope observations showed that the use of NM and MWCNT can reduce the surface roughness of cement paste and refine porosity, thus reducing the risk of cracking at the cement matrix and improving the homogeneity of the microstructure. Keywords: central composite design (CCD); multi-walled carbon nanotubes (MWCNTs); nano-montmorillonite (NM); response surface methodology (RSM); sodium dodecylbenzene sulfonate (SDBS); strength.