Parameters influencing the characteristics of the nano-bonded aluminosilicate based refractory castables

Abstract

Replacing calcium aluminate cement as hydraulic binder by silica sol as sol-gel binder for refractory castables is known to reduce drawbacks of hydraulic binders but still comprehensive information regarding the effect of various raw materials and additives are required. In this research bauxite, andalusite and argellite were chosen as aluminosilicate aggregates and silica sol as binder and the effect of citric acid, micro silica and cement as setting agent were investigated for different compositions. Mechanical strength of the obtained castables at different temperatures of 110, 1000 and 1400°C were probed for various compositions. Finally based on the maximum mechanical strength of 342.5 and 241 Kg/cm² at 110°C, workability and flowability of the castables, optimum compositions were selected. The used amounts of citric acid, micro silica and cement for bauxite optimized composition were 0.04%, 2% and 1% while there were 0.02%, 0% and 1%, respectively for andalusite based one. The effect of sol-gel binder on the corrosion resistance of the optimized compositions was investigated in contact with molten sodium silicate using static cup test. Bauxite based castables showed mechanical strength higher than andalusite ones, while the later exhibited better corrosion resistance which related to the intrinsic characteristics of the used aggregates.