Aqueous curable molding compositions based on inorganic ingredients and process for the production of molded parts

A process for the production of molded parts from molding compositions which comprises preparing a flowable or press-moldable composition containing 1.3-10 parts by weight of a water-free oxide mixture with contents of amorphous SiO.sub.2 and aluminum oxide and 0.7-2.5 parts by weight of K.sub.2 O or 0.55-1.5 parts by weight of Na.sub.2 O per 1 part by weight of dissolved SiO.sub.2 or equivalent amounts of the sodium oxide being used for equivalent amounts of the potassium oxide, as well as optionally inert fillers, by

• (a) mixing the oxide mixture containing silicon dioxide and aluminum oxide into an aqueous solution of at least one alkali silicate selected from the group consisting of sodium silicate and potassium silicate which alkali silicate solution is admixed, with at least one solid or dissolved alkali hydroxide selected from the group consisting of sodium hydroxide and potassium hydroxide;
• or
• (b) dissolving amorphous, aqueous silicic acid in an aqueous solution of at least one alkali hydroxide selected from the group consisting of sodium hydroxide and potassium hydroxide to obtain an aqueous silicate solution thereof, and adding the oxide mixture, or
• (c) mixing amorphous, aqueous silicic acid with at least one alkali hydroxide selected from the group consisting of sodium hydroxide and potassium hydroxide or its aqueous solution, and reaction of the proportion of silicic acid to be dissolved to the resulting alkali silicate solution, and adding the oxide mixture, and filling this composition into molds, venting, optionally press-molding, and curing.