Mechanical properties of Portland cement mortar containing multi-walled carbon nanotubes at elevated temperatures

Addition of nanomaterials to Portland cement mortars could potentially enhance their properties. It has been previously reported that addition of multi-walled carbon nanotubes (MWCNTs) to mortars can lead to considerable improvement in the mechanical properties of the binder paste. In this study, the effect of the addition of MWCNTs at the ratios of 0-0.15 wt% of Portland cement on the compressive, tensile, and flexural strength; and resistance to the elevated temperature of Portland cement mortar was evaluated. The specimens were heated up at the elevated temperatures (200-800 °C) and accordingly, the mass loss and compressive strength were determined. The microstructure of the samples was analyzed by petrography. The obtained results showed that the mortar samples containing MWCNT acquired higher mechanical strength and resistance to the elevated temperatures, in comparison with the ordinary mortar samples. The mortar containing solely 0.1 wt% MWCNT showed an increase in the compressive, tensile, and flexure strength by 35, 8 and 11.2%, respectively. Moreover, the residual compressive strength after heating showed significant improvement. Petrography image analyses also indicated that the porosity of the cement paste was reduced, whereas the cement paste became denser and more stable due to the addition of MWCNT.