Castable refractory compositions comprising zeolithic microstructures and uses thereof

1. A dry refractory particulate composition comprising:

5% to 95% by weight of an aggregate,

1% to 8% by weight of a silica fume,

0.1% to 1.5% by weight of a hydratable alumina,

0.1% to 1% by weight of a calcium source, and

0.01% to 1% by weight of a dispersant,

wherein the aggregate is not a hydratable alumina or a silica fume;

wherein the calcium source is selected from calcium aluminate cement, Portland cement, hydrated lime, calcium sulfate, calcium acetate, calcium chloride, calcium chlorate or mixtures thereof;

wherein the calcium aluminate cement and Portland cement have a particle size of up to 80 microns, and the hydrated lime, calcium sulfate, calcium acetate, calcium chloride, calcium chlorate have a particle size of up to 200 microns,

wherein the calcium oxide content is no greater than 0.3% by weight, and

wherein all percentages by weight are based on the total dry weight of the dry refractory composition.

2. The dry refractory particulate composition of claim 1 , wherein a green body obtained therefrom has a green crushing strength of at least 6 MPa.

3. The dry refractory particulate composition of claim 1 , wherein the aggregate is selected from alumina, aluminosilicate, zirconia, zircon, magnesia, olivine, chromium oxide or chrome ores, spinel, silicon carbide, or mixtures thereof.

4. The dry refractory particulate composition of claim 1 , wherein the dispersant is selected from polyphosphate, polycarboxylate, polycarboxylate ether, polynaphthalene, polymelamine, polyglycol, lignosulfonate, and citric acid.

5. The dry refractory particulate composition of claim 1 , wherein the hydratable alumina has a BET surface area in the range of 200 to 350 m 2 /g and/or a median particle size, d 50 , in the range of 3 to 10 μm as measured by laser diffraction using a Microtrac SRA 150.

6. The dry refractory particulate composition of claim 1 , wherein the hydratable alumina includes rho alumina.

7. The dry refractory particulate composition of claim 1 comprising no more than 1.0% by weight of organic binder.

8. The dry refractory particulate composition of claim 1 , wherein the silica fume has a BET surface area in the range of 8 to 25 m 2 /g and/or a median particle size, d 50 , in the range of 0.25 to 0.8 μm as measured by sedimentation using a Sedigraph III.

9. The dry refractory particulate composition of claim 1 , further including up to 0.1% by weight of a setting acceleration agent selected from lithium carbonate, lithium hydroxide, calcium aluminate, sodium silicate, sodium aluminate, calcium hydroxide, sodium nitrate, sodium nitrite or mixtures thereof.

10. The dry refractory particulate composition of claim 1 , further including a setting retardation agent selected from citric acid, sodium citrate, boric acid, oxalic acid, or mixtures thereof.

11. The dry refractory particulate composition of claim 1 , having a working time ranging from 30 to 240 min and/or having a setting time ranging from 1 to 12 hours, at 20° C. measured using UltraTest IP-8.

12. The dry refractory particulate composition of claim 1 , having a total amount of bonded water lower than 0.7% as measured by water released between 110° C. and 800° C.

13. The dry refractory particulate composition of claim 1 , having a drying aptitude with a degree of unidirectional drying higher than 30% after 5 hours as measured in a moisture tight cylindrical mould, wherein the mould is heated to 500° C. on an open face.

14. The dry refractory particulate composition of claim 1 , further comprising:

5% to 50% by weight silicon carbide, and

up to 10% by weight carbon.

15. The dry refractory particulate composition of claim 14 , further comprising 1% to 10% by weight carbon.

16. The dry refractory particulate composition of claim 14 , wherein the carbon is selected from carbon black, pitch, petroleum pitch, graphite, coke, solid hydrocarbon having a carbon residue of at least 5% by weight after coking, asphalts, and mixtures thereof.

17. The dry refractory particulate composition of claim 14 , further comprising up to 5% by weight of an antioxidant.

18. The dry refractory particulate composition of claim 17 , wherein the antioxidant is selected from aluminium nitride, aluminium oxy-nitride, boron carbide, zirconium carbide, calcium carbide, a metal and mixtures thereof; wherein the metal is selected from the group consisting of aluminium, silicon, magnesium, iron, chromium, zirconium, or an alloy thereof.