Fabrication and fracture toughness properties of carbon nanotube-reinforced cement composite

Multi-walled carbon nanotube (MWNT) reinforced cement composites (MWFRCs) were prepared with surfactant dispersion, ultrasonic treatment, and subsequently high-speed shear mixing processes. These MWFRCs were characterized in the fracture toughness property with single edge notch bend method. As found, the addition of nanotubes improves the stress-intensity factor (K_IC), critical crack mouth opening displacement (δ_C) and flexural strength (σ_s) of the cured nanocomposite, significantly. The maximal enhancement arrives up to 56.4%, 119.4%, and 54.8%, compared to the baseline, respectively. These achievements are mainly attributed to the superior pulling-out effect of dispersed and tough MWNT fiber upon the notched cracks. Incorporation of acid-treated MWNT balances the σ_s, K _IC, and δ_C values. Additional nanophase carbon black mixed into the above MWFRC further increases the corresponding fracture toughness, while additional short carbon fiber shows a negative effect.