Chuanyin Zhang

Effect of B2O3 on Volume Stability and Strength of Corundum-based Castables

Abstract Calcium aluminate cements (CAC) with 0.21 wt% B2O3 and without B2O3 were used as binders of corundum-based castables. The properties of the castables with and without B2O3 after heat treatment at 110 °C, 1,100 °C and 1,450 °C were investigated, with emphasis on studying the effect of B2O3 in CAC on the volume stability and high temperature strength of the castables. It is found that a very small amount (about 0.01 wt%) of B2O3 introduced by the cement alleviates the expansion of the castables after firing at 1,450 °C and decreases the high-temperature strength of castables as the presence of B2O3 should generate liquid phase.

Hydration Behavior of Calcium Alumina Cements with Different Amounts of Impurities

The influence of impurities such as SiO2 and F2O3 on the hydration behavior of calcium aluminate cement (CAC) was studied in this work. The hydration of the cement was characterized by the exothermic profile of cement pastes, and the dissolution-precipitation rate of the cement aqueous suspension was evaluated by electrical conductivity measurement. In order to analyze the resulting hydration products, the cement hydration was terminated via the freeze-vacuum drying method at the designated times. Then the phase development and microstructure evolution during cement hydration were investigated by XRD and SEM, respectively. The results indicate that the hydration rate is faster when the cement contains a higher amount of impurities. It is proposed that the higher hydration rate of the cement is probably related to the lattice imperfection of the main calcium aluminates in CAC.