The characteristics of alkali-activated slag mortar containing multi-walled carbon nanotubes at elevated temperature

The effect of the addition of different concentrations (0, 0.05, 0.10 and 0.15 wt%) of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and microstructure of alkali-activated slag (AAS) mortars at temperatures of 23, 200, 400, 600 and 800°C was investigated. To investigate the strength parameters of the specimens, the mechanical strength and mass loss of the specimens at ambient temperatures and after exposure to elevated temperatures were determined. Petrographic image analysis was also conducted to analyse the microstructures of the specimens. The Matlab image processing toolbox was used to calculate the pore area of the samples at room temperature. The results showed that the addition of MWCNTs improved the mechanical properties of the AAS mortars at both ambient and elevated temperatures: the compressive and flexural strengths of the mortars were improved by up to 69% and 85%, respectively. At 400°C, the compressive strength increase of the specimens compensated for the deterioration rate of about 3% mass loss. This temperature should be considered the maximum tolerable degree for AAS mortars.