The effect of nano-alumina addition on the properties of high-alumina low-cement self-flowing refractory castables

In this study, the effect of nano-alumina addition on the properties of high-alumina low-cement self-flowing refractory castables was studied. For this reason, the reactive alumina in the refractory castable composition was substituted by nano-alumina powder. Then, the self-flow characteristics such as; self-flow value and working time of high-alumina low-cement refractory castables were studied. Besides, the physical and mechanical properties, phase composition and microstructure of these refractory castables were studied after drying at 110 °C and firing at 1250 and 1450 °C. The results showed that the nano-alumina addition has a great effect on the self-flow characteristics and mechanical strength of these refractory castables. With addition of nano-alumina particles, the self-flow value and working time tends to decrease due to high surface area of nano-alumina particles. By use of 1 wt.% nano-alumina content in the castable composition, the alumina self-flowing castable with adequate working time can be obtained according to standard values of self-flowing castables. The decrease in porosity and, increase in mechanical strengths after drying is obtained by adding nano-alumina. The phase analysis and microstructure evaluations showed that CA6 phase can be form at lower temperatures (1250 °C) with the addition of nano-alumina. CA6 platy formation leads to increase of porosity in the microstructure. But, the because of bonding behavior of platy CA6, the mechanical strengths are considerably increased after firing.