Improving the mechanical property of the castables bonded with hydratable magnesium carboxylate by incorporating MgO fumes.

Previous studies have indicated that hydratable magnesium carboxylate (HMC) exhibits potential as an MgO‐based binder, but its limited medium‐temperature strength has hindered its widespread industrial application. In this study, the incorporation of MgO fumes into castables is intended to react with microsilica to form magnesium–silicate–hydrate (M–S–H), and the synergistic effect of HMC and M–S–H is anticipated to improve the mechanical properties of castables at intermediate temperatures. The effects of MgO fumes on the properties of HMC‐bonded castables were comprehensively investigated. The results demonstrate that incorporating MgO fumes into castable serves multiple functions. The ionized MgOH+ from MgO fumes hinders the hydration process of HMC, prolonging the final setting time from 13 to 98 min and improving the workability of castables. The incorporation of MC‐1100 enhanced mechanical properties at medium temperature due to the synergistic effects of brucite, HMC, and M–S–H. Specifically, the CMOR increased 20% after sintering at 800°C. Furthermore, adding MC‐1100 increases the residual strength rate of castable by 10% compared to those without MgO fumes. This can be attributed to enhanced spinel formation resulting from adding MgO fumes that improves elastic modulus and reduces elastic strain energy generation during thermal shock, thus increasing crack propagation resistance. [ABSTRACT FROM AUTHOR]