The effect of pre-dehydrated magnesium-silicate-hydrate on the properties of the castables bonded with hydrable magnesium carboxylate

This study investigates the effect of pre-dehydrated magnesium-silicate-hydrate (PMSH) on the properties of HMC-bonded castables (HMCC), aiming to enhance the medium-temperature mechanical performance of HMCC through the structural memory characteristics of PMSH. The results indicate that adding M-S-H-300 (PMSH treated at 300 degrees C) improves the mid-temperature mechanical properties of HMCC. Specifically, the cold modulus of rupture (CMOR) for the samples 300MSH increases by 605.9 % at 500 degrees C and 582.6 % at 800 degrees C compared to control samples due to the excellent thermal stability of M-S-H-300 and a 38.3 % improvement in castable sintering performance. Additionally, M-S-H-300 improves the thermal shock resistance and setting properties of HMCC, extending the castable's setting time by 19 %. The conductivity test results indicate that the addition of M-S-H-300 inhibits the ionization of HMC, thereby delaying its hydration process. Castables with M-S-H-300 demonstrate higher CMOR and residual strength ratio before and after thermal shock. Further testing reveals that adding M-S-H-300 increased the castable's elastic modulus by 482.6 % and fracture toughness by 35.6 % after sintering at 1500 degrees C, enhancing resistance to microcrack propagation during thermal shock. Furthermore, adding M-S-H-300 reduces the aspect ratio of HMC hydration products, optimizing microstructure and reducing porosity. However, this modification slightly decreases the mechanical properties of the green body.