This study aims at in situ formation of sintered cordierite-mullite nano-macro composites having high technological properties using waste silica fume, calcined ball clay, calcined alumina, and magnesia as starting materials. The starting materials were mixed in different ratios to obtain different cordierite-mullite composite batches in which the cordierite contents ranged from 50 to 100 wt.%. The batches were uni-axially pressed at 100 MPa and sintered at 1350, 1400 and 1450 degrees C to select the optimum temperature required for cordierite-mullite nano-macro composites formation. The formed phases were identified by X-ray diffraction (XRD) pattern. The sintering parameters in terms of bulk density (BD) and apparent porosity (AP) were determined. The microstructure of composites has been investigated by scanning electron microscope (SEM). Cold crushing strength (CCS) of the sintered batches was evaluated. The result revealed that the cordierite-mullite nano-macro composites were in-situ formed at 1400 degrees C. The batch containing 70 wt.% cordierite showed good physical and mechanical properties. (c) 2012 Elsevier Ltd. All rights reserved.