Plate product of ceramic material and process for the manufacturing thereof

A process for manufacturing plates of ceramic material starting from natural stone material of natural origin having a flexural strength higher than 300 kg/sq.cm. or from a granulation of a ceramic material, the following steps:

• (a) preparation of a ceramic mixture comprising a binding phase and a granulate having particles of maximum size consistent with a thickness of a final compacted plate, said granulate being obtained from natural stone materials having a widely variable granule size and selected from the group consisting of feldspars, porphyry, granites and quartz materials, or from a granulation of ceramic materials, and said binding phase consisting of powders of ceramic materials moistened with a moistening agent and mixed with an inorganic water based binder, the ratio between granulate and binding phase being between 0.35 and 0.55 by volume, and the maximum size of the granules being less than 1/3 of the thickness of the final compacted plate or tile, and said moistening agent being sodium silicate in an aqueous solution and/or another refractory binder in an aqueous solution;
• (b) molding into a form of a plate in the form of a tile of the mixture thus prepared in step (a) and distributing or compacting the mixture onto a molding support, by a simultaneous application of a vibration action and of a pressing action onto the distributed mixture, the pressure being at least 0.5 kg/sq. cm., and subjecting the mixture throughout the molding to a vacuum of at least 40 mbar of residual pressure;
• (c) drying the molded product at a temperature lower than that of ceramic firing and for a time period of at least two hours;
• and
• (d) firing of the molded and dried product at a temperature of between 1000.degree. C. and 1300.degree. C. for the time necessary to obtain a plate of ceramic material having the properties characteristic of these materials.