|Abstract||Ever-increasing demand and application of unshaped refractories replacing shaped ones have inspired the scientists and manufacturers to investigate these materials in depth for further improving the quality and performance. Among different bonding materials of castables calcium aluminate cement (CAC) is most common, but presence of CaO in cement results in low melting phases on reaction with Al2O3 and SiO2 of the refractory systems, resulting in poor hot properties. To avoid the crisis, decrease in cement content and use of alternate bonding system were widely experimented. Among alternate bonding, sol-gel technique has opened a new horizon in bonding system for refractory technologists. The principle behind sol gel bonding is the formation of a 3-dimensional network (gel) of particles that surrounds the refractory materials and which on subsequent heating develop strength by formation of ceramic bonding through sintering.
In the present work, four different sol systems has been developed that generates refractory oxides on firing, like alumina, mullite and spinel and these sols are used as sole binder in high alumina castable system containing no cement. High alumina castable with two different particle size distribution coefficients has been studied by using the developed sols. The castable are processed conventionally and evaluated at different temperatures for the various refractory properties. Phase analysis and microstructural development are also studied to investigate the reasoning of the properties development. These synthetic sol based castable compositions are further compared with commercially available silica sol and cement containing compositions processed under exactly similar conditions.