Abstract: A premixed material is obtained by tempering a castable refractory powder composition comprising refractory aggregate, fine refractory powder, alumina cement, a dispersing agent and an alumina cement hydration stopper with water. The hydration stopper is acidic in a state of an aqueous solution. The amount of the hydration stopper is controlled such that the premixed material has a pH of 2 to 7. Immediately after adding and mixing an alumina cement hydration starter to the premixed material, the resultant mixture is cast into a mold. The addition of the hydration starter can be carried out 5 days or more after the production of the premixed material.

Abstract: A premixed material is obtained by tempering a castable refractory powder composition comprising refractory aggregate, fine refractory powder, alumina cement, a dispersing agent and an alumina cement hydration stopper with water. The hydration stopper is acidic in a state of an aqueous solution. The amount of the hydration stopper is controlled such that the premixed material has a pH of 2 to 7. Immediately after adding and mixing an alumina cement hydration starter to the premixed material, the resultant mixture is cast into a mold. The addition of the hydration starter can be carried out 5 days or more after the production of the premixed material.

Abstract: The cement-free, castable refractory composition for producing dense cast refractories according to the present invention comprises 70-98 weight % of refractory aggregate regulated to have a particle size of 10 mm or less, 2-30 weight % of ultrafine refractory powder having a particle size of 10 &mgr;m or less, and 0.01-1.0 weight % (outer percentage), based on 100 weight % of the refractory aggregate+the ultrafine refractory powder, of a dispersing agent. The cement-free, castable refractory composition tempered with water or other tempering liquids to have a castable flowability or the factory-premixed, cement-free, castable refractory composition is conveyed to a gunning nozzle by a pump, and a coagulant is added to the tempered refractory material together with compressed air in the nozzle to carry out gunning.

Abstract: The method for wet-gunning a castable refractory composition includes the steps of (a) preparing a cement-free, castable refractory composition comprising 70-98 weight % of refractory aggregate having a particle size of 10 mm or less, 2-30 weight % of ultrafine refractory powder having a particle size of 10 .mu.m or less, and 0.01-1.0 weight % (outer percentage) of a dispersing agent, and further a thickener (in the case of factory premixing); (b) premixing the cement-free, castable refractory composition with water in situ or in a factory to provide an in-situ premixed or factory-premixed, water-containing refractory material having a castable fluidity; (c) conveying the in-situ premixed or factory-premixed, water-containing refractory material to a gunning nozzle by a pump; (d) adding 0.

Abstract: The castable refractory material comprising as binders, per 100 parts by weight of solid components, (a) 10-30 parts by weight of water-inactive, fine refractory powder, which is a mixture of fine refractory powder having an average diameter of 0.2-0.6 .mu.m and fine refractory powder having an average diameter of 1-10 .mu.m at a ratio of 1:2-2:1; (b) 2-7 parts by weight (as an effective amount) of alumina cement having an average diameter of 3-8 .mu.m, cement clinker minerals thereof comprising CaO.Al.sub.2 O.sub.3 and CaO.2Al.sub.2 O.sub.3, with 12CaO.7Al.sub.2 O.sub.3, if any, in such an amount that a diffraction intensity index of the 12CaO.7Al.sub.2 O.sub.3 at a lattice plane distance D of 2.68 .ANG. is 1 or less assuming that the diffraction intensity index of the CaO.Al.sub.2 O.sub.3 at a lattice plane distance D of 2.96 .ANG. is 100; and (c) 0.4-3 parts by weight of fine amorphous silica powder having an average diameter of 0.5 .mu.