Nanometric zirconia-mullite precursors are synthesized through sol-gel route. Incorporation of these precursors in low cement castable refractories improves the bulk density, compressive strength and thermal shock resistance through formation of integrated matrix of castable at high temperature. In the present investigation, white tabular alumina aggregate, calcium aluminate cement bond material, microsilica, microfine alumina and nanometric zirconia-mullite precursors are used in the formulation. The important properties like bulk density, apparent porosity, linear change, cold crushing strength before and after thermal spalling of castables are studied. Phases are identified by X-ray diffraction analysis. SEM study has been used to analyze the integrated matrix of the castables. © 2010 Taylor and Francis Group, LLC.