Effect of highly dispersed carbon nanotubes on the flexural toughness of cement-based composites

Multi-walled carbon nanotubes (MWCNTs) modified by anionic gum arabic have been incorporated into Portland cement pastes to investigate the effect on flexural toughness. The flexural toughness of the cement composites were investigated, and the results showed that the addition of treated nanotubes significantly improved both the fracture energy and flexural toughness index of Portland cement pastes. The porosity and pore size distribution of the composites were measured using mercury intrusion porosimetry, and the results indicate that cement paste containing MWCNTs had lower porosity and a more uniform pore size distribution. The microstructure of samples was investigated using field emission scanning electron microscopy. This showed that MWCNTs act as bridges across cracks and voids and form a network that transfers the load in tension.