Study on microstructure evolution mechanism of concrete containing carbon nanotubes subjected to different heating-cooling regimes: Experiments and molecular dynamics simulation

High temperatures and subsequent cooling regimes cause irreversible damage to the microstructure of concrete, posing a non-negligible risk to its macroscopic properties . This study investigated the micro-structural evolution mechanism of concrete containing multi-walled carbon nanotubes (MWCNT concrete) underwent different heating-cooling regimes through micro-experiments and molecular dynamics simulations. The experimental results showed that the weight, micromorphology, microporosity and hydration product changed depending on the rising temperature and variable cooling regimes, and MWCNT positively contributed to these changes, leading to a 6.9 % increase in hydration and a 17.23 % reduction in microstructure pyrolysis . The simulation revealed that the increase of total potential energy value and internal repulsive force caused by high temperature was the intrinsic cause of deterioration of concrete. The quench cooling after high temperature effectively promoted the rehydration after high temperature due to the stronger degree of water diffusion and greater water mobility. The addition of MWCNT improved the high temperature resistance of concrete by attracting Ca 2 + , promoting hydration, enhancing the electronegativity of C 3 S and system stability . • The effect of MWCNT on multi-level microevolution of concrete was studied. • The relationship between C-S-H and compressive strength was established. • C 3 S and C-S-H with CNT models under different heating-cooling regimes were proposed.