Reinforcement of surface-modified multi-walled carbon nanotubes on cement-based composites

Multi-walled carbon nanotubes (MWCNTs) play an important role in various kinds of composites. MWCNTs with different concentrations were incorporated into cement-based composites to improve the toughness and fracture resistance of the composites. The effect of different concentrations of MWCNTs on the mechanical properties of the cement-based composites was investigated. Results show that the flexural strength and compressive strength increase significantly. The microstructure of the MWCNTs in hardened cement was observed and analysed by field emission scanning electron microscopy. The reinforcing mechanisms of cement-based composites by MWCNTs were also discussed, and the conclusion is that the improvement can be correlated to energy-dissipating processes owing to crack bridging, network filling and MWCNTs pull out at the crack tips. The porosity and pore size distribution of the composites were measured using mercury intrusion porosimetry, and the results indicate that cement-based composites containing MWCNTs have lower porosity and more concentrated pore size distribution.