Evaluation of pore deterioration of carbon nanotubes reinforced concrete exposed to high temperatures based on CT technique

In this study, the pore deterioration of multi-walled carbon nanotubes (MWCNTs) reinforced concrete specimens exposed to high temperatures was investigated by X-ray computed tomography (CT) technique from the mesoscopic level. Meanwhile, the effects of MWCNTs on mechanical properties and micromorphology of concrete were evaluated by a uniaxial compressive test and scanning electron microscope (SEM) test as auxiliary support. The results show that adding MWCNTs to concrete could delay the propagation of microcracks and have a specific impact on the formation of pore networks in concrete exposed to high temperatures, so as to reduce the possibility of cracking and spalling of specimens and improve their residual mechanical properties. In addition, considering the influence of different cooling systems on the concrete after high temperature, it is found that the spray cooling system is conducive to optimize the pore structure distribution and improve the residual strength of concrete specimens exposed to high temperature, while natural cooling and quench cooling will further deepen the deterioration of pore and mechanical properties of the specimens.