Effect of Filler material replacement on the properties of high alumina conventional castables

Abstract

The demand for the monolithic refractories as compared to their shaped counterparts have been increasing over the years due to their distinct advantages like comparable durability, low cost and relatively easy installation procedure. Several attempts are being made in the optimization of the properties of these products. Among monolithics, refractory castables are the major ones which have replaced significant fraction of shaped refractories in the furnace lining. Among the castables, high alumina based castables are the most important type. This work focuses on the study of the properties of the conventional high alumina based refractory castables, firstly due to the reduction in the percentage of cement by reactive alumina and secondly due to the replacement of cement by micro-silica in the composition. The reduction in the percentage of cement improved the thermo-mechanical property which was indicated by the HMOR values and the incorporation of the micro-silica in the composition resulted in the development of good mechanical strength to the castables and also improved their thermo-mechanical properties. The improvement in mechanical properties and HMOR values for microsilica castables was definitely due to mullite formation. However as the microsilica content was only 4%, the fraction of mullite that formed on firing was also less. Therefore, though the enhancement was distinct but it was only by about 25%.