Abstract: To manufacture in thin structure, easily and at low cost. By forming a foaming glaze layer on the surface of a base material made of ceramics, the product strength is assured in a base material formed densely, and the heat insulation in the foaming glaze layer is assured, and after applying a foaming glaze on a base material or a formed body adjusted to be formed as base material, and by baking the glazed material at temperature higher than the melting and foaming point of the foaming glaze and at temperature lower than the softening temperature of the base material, dimensional changes of base layer (base material) at the time of baking are suppressed, and strict management during manufacture is not needed.

Abstract: The invention provides a process for producing a ceramic product for use as a construction material. According to the process of the invention, 2 to 50% by weight, based on the total weight, of sludge ashes containing 0.3 to 0.8 mole of CaO in Seger formula, 0.1 to 0.5 mole of MgO in Seger formula, and 0.2 mole or more of P.sub.2 O.sub.5 in Seger formula is added to a ceramic raw material. A desired percentage can be selected from the range of 2 to 50% to produce a ceramic product with desired properties. Also, according to the invention, a molded body can be fired at a temperature lower than a temperature used to fire a molded body with no sludge ashes to produce a ceramic product which is comparable to a ceramic product produced by firing the latter molded body. That is, according to the invention, a molded body can be fired at a temperature of 900.degree. to 1,200 .degree. C. to produce such a ceramic product.

Abstract: A process for producing a ceramic product using sludge ashes comprises the steps of (i) mixing at least ashes obtained by burning a sludge which has been obtained by the treatment of sewage and a plastic ceramic raw material to prepare a first body, (ii) mixing at least a plastic ceramic raw material and a fusible material to prepare a second body, (iii) supplying the first and second bodies into a matrix of a molding machine such that the first and second bodies form a lower, larger layer and an upper, smaller layer which covers the lower layer, respectively, (iv) molding the whole of the first and second bodies into an object with a desired shape, and (v) firing the molding to produce a two-layer ceramic product.