Microstructure evolution of hydration products and strength change of hydratable alumina‐bonded castables below 1250°C

Abstract There have been reports that strength of hydratable alumina (HA)‐bonded castables without silica fume drops significantly at 600°C and decreases substantially again at 1000°C. But the strength variation of the HA‐bonded castables during the intermediate temperature range has not been investigated and elaborated from the perspective of phase evolution and microstructural change in the castables. In this work, the relationship between the change in the strength of castables and the microstructural characteristics of the HA‐bonded castables was investigated. The phase and microstructure evolution of HA‐bonded castables between 110°C and 1250°C were investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). It has been found that strength drops of the HA‐bonded castables during heating process do not mainly happen at the temperature at which HA hydrates decompose, but at the temperature at which the structure of dehydrated HA hydrates disintegrates.