Residual impact resistance behavior of concrete containing carbon nanotubes after exposure to high temperatures

Abstract

Multi-walled carbon nanotubes (MWCNTs) have not only high strength and toughness, but also good thermal stability and thermal conductivity. By investigating the failure patterns and fractal index (i.e., impact crushing fractal dimension Df) of MWCNTs reinforced concrete (MC), this paper explored the effect of MWCNTs on impact resistance of concrete after exposure to high temperature. Results showed that after exposure to high temperature, Df increased with the increase of strain rate and temperature. However, compared with plain concrete (PC), MC had relatively few fragments, low Df value, enormous energy consumption, and high residual dynamic compressive strength. The variation of Df essentially depends on the development of cracks and compactness of concrete. It is precisely because the strengthening and thermal conductivity of MWCNTs on the matrix, which effectively alleviated the thermal cracking and impact crushing, thus improving the thermal resistance and impact resistance of concrete. Moreover, the pore fractal dimension (Dp) of concrete after exposure to high temperatures were also investigated and compared with Df. The results noted that the change trend of Dp and Df of MC and PC were completely opposite. The Dp of MC was larger than that of PC, but its Df was smaller than that of PC.