The invention relates to the use of a composition which contains A) 55 to 90 wt-% of aluminum oxide, B) 5 to 35 wt-% of a sodium compound which has a solubility in water of =< 300 g/l at pH 7 and 20 DEG C and which can be thermally converted practically exclusively to sodium oxide as the only solid, C) 0 to 15 wt-% of a magnesium compound and/or a lithium compound selected from the group which consists of: magnesium oxide, magnesium carbonate, magnesium nitrate, lithium oxide, lithium carbonate, lithium nitrate, and D) 0 to 30 wt-% zirconium dioxide, for producing a ceramic molded product by extrusion.