FIRE-RESISTANT CALCIUM SULPHATE-BASED PRODUCTS

Abstract

The present invention provides calcium sulphate-based product having reduced shrinkage after exposure to high temperatures, the product comprising gypsum, a pozzolan source (e.g. in an amount between 4-27 wt %) and a metal salt additive (in an amount between 0.5 and 10 wt %). The pozzolan source may be selected from a kaolinitic clay material, fly ash, rice husk ash, diatomaceous earths, volcanic ashes and pumices, micro-silica, silica fume and silicone oil. The metal salt additive may be a metal salt which decomposes between a temperature of 300-500° C. to yield a metal oxide, e.g. magnesium nitrate.

Claims

1. A calcium sulphate-based product comprising gypsum, a pozzolan source and a metal salt additive wherein the gypsum is provided in an amount between 65 and 98 wt % (based on the weight of the gypsum, pozzolan source and metal salt) and wherein the metal salt is selected from calcium nitrate and salts of magnesium, copper, zinc, iron or aluminum.

2. A calcium sulphate-based product according to claim 1 wherein the pozzolan source is included in an amount between 4 and 27 wt % (based on the weight of the gypsum, pozzolan source and metal salt).

3. (canceled)

4. A calcium sulphate-based product according to claim 1 wherein the metal salt additive is included in an amount between 0.5 and 10 wt % (based on the weight of the gypsum, pozzolan source and metal salt).

5. (canceled)

6. (canceled)

7. (canceled)

8. (canceled)

9. (canceled)

10. A calcium sulphate-based product formed from drying an aqueous slurry containing calcined gypsum, a pozzolan source and a metal salt additive wherein the calcined gypsum is provided in the slurry in an amount between 60 and 95 wt % (based on the weight of the calcined gypsum, pozzolan source and metal salt) and wherein the metal salt is selected from calcium nitrate and salts of magnesium, copper, zinc, iron or aluminum.

11. A calcium sulphate-based product according to claim 10 wherein the pozzolan source is included in the slurry in an amount between 5 and 30 wt %.

12. (canceled)

13. A calcium sulphate-based product according to claim 10 wherein the metal salt additive is included in the slurry in an amount between 1 and 15 wt %.

14. (canceled)

15. A calcium sulphate-based product according to claim 1 wherein the wt % of pozzolan source and wt % metal salt are equal.

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. A calcium sulphate-based product according to claim 1 wherein the pozzolan source is selected from a kaolinitic clay material, fly ash, rice husk ash, diatomaceous earths, volcanic ashes and pumices, micro-silica, silica fume and silicone oil.

21. A calcium sulphate-based product according to claim 1 where the metal salt additive is a metal salt which decomposes between a temperature of 300-500° C. to yield a metal oxide.

22. (canceled)

23. A calcium sulphate-based product according to claim 1 wherein the metal salt is a nitrate, a carbonate, a hydrogen carbonate, a sulphate, a hydroxide or chloride.

24. A calcium sulphate-based product according to claim 1 wherein the metal salt is magnesium nitrate.

25. A calcium sulphate-based composition for use in forming a calcium sulphate-based product by drying an aqueous slurry of the calcium sulphate-based composition, the calcium sulphate-based composition comprising calcined gypsum, a pozzolan source and a metal salt, wherein the calcined gypsum is provided in the composition in an amount between 60 and 95 wt % (based on the weight of the calcined gypsum, pozzolan source and metal salt) and wherein the metal salt is selected from calcium nitrate and salts of magnesium, copper, zinc, iron or aluminum.

26. A calcium sulphate-based composition according to claim 25 wherein the pozzolan source is included in an amount between 5 and 30 wt %.

27. (canceled)

28. A calcium sulphate-based composition according to claim 25 wherein the metal salt additive is included in an amount between 1 and 15 wt %.

29. (canceled)

30. A calcium sulphate-based composition according to claim 25 wherein the wt % of pozzolan source and wt % metal salt are equal.

31. (canceled)

32. (canceled)

33. (canceled)

34. (canceled)

35. A calcium sulphate-based composition according to claim 25 wherein the pozzolan source is selected from a kaolinitic clay material, fly ash, rice husk ash, diatomaceous earths, volcanic ashes and pumices, micro-silica, silica fume and silicone oil.

36. A calcium sulphate-based composition according to claim 25 wherein the metal salt additive is a metal salt which decomposes between a temperature of 300-500° C. to yield a metal oxide.

37. (canceled)

38. A calcium sulphate-based composition according to claim 36 wherein the metal salt is a nitrate, a carbonate, a hydrogen carbonate, a sulphate, a hydroxide or chloride.

39. A calcium sulphate-based composition according to claim 36 wherein the metal salt is magnesium nitrate.

40. A method of forming a calcium sulphate-based product by drying an aqueous slurry comprising a composition according to 25.

41-58. (canceled)

Description

EXAMPLES

[0066] Sample formulations having the amounts of metal salt, pozzolan source and calcined gypsum shown in Table 1 below were prepared (for all but Example 23) by mixing the metal salt with 140 g of water at 40° C. The pozzolan source and calcined gypsum were dry blended and added to the water/salt mixture. The resulting mixture was blended by hand for 30 seconds to form a slurry. For example 23, the silicone oil and metal salt were added to 140 g of water at 40° C. and then the calcined gypsum was added to the solution to form a slurry which was blended by hand for 30 seconds. Wt% amounts (based on the dry ingredients) of each component in the slurry are shown below in brackets.

[0067] The slurry was poured into a cylindrical silicone mould (height 25 mm, diameter 12 mm) and dried overnight (minimum 12 hours) at 40° C.

TABLE-US-00001 TABLE 1 Summary of sample formulations Pozzolan Metal source/g salt/g Sample Stucco/g (wt %) (wt %) (wt %) Control 1 200 0 0 Control 2 180 (90)  20 (10)  0 Kaolin Control 3 140 (70)  60 (30)  0 Kaolin Control 4 200 (91)  0 20 (9)  Control 5 200 (93)  0 16 (7)  Control 6 200 (92)  0 19 (8)  Control 7 200 (91)  0 20 (9)  Control 8 200 (91)  0 20 (9)  Control 9 180 (90)  20 (10)  0 Rice husk ash Control 10 180 (90)  20 (10)  0 Silicone oil Control 11 180 (90)  20 (10)  0 Micro-silica Control 12 180 (90)  20 (10)  0 Diatomaceous earth Example 1  180 (81.8) 20 (9.1)  20 (9.1) Mg nitrate (hexahydrate) Kaolin Example 2  140 (63.6)  60 (27.3)  20 (9.1) Mg nitrate (hexahydrate) Kaolin Example 3  180 (89.1) 20 (9.9)  2 (1.0) Mg nitrate (hexahydrate) Kaolin Example 4  195 (96.5)  5 (2.5)  2 (1.0) Mg nitrate (hexahydrate) Kaolin Example 5  195 (95.1)  5 (2.4)  5 (2.4) Mg nitrate (hexahydrate) Kaolin Example 6  180 (87.8) 20 (9.8)  5 (2.4) Mg nitrate (hexahydrate) Kaolin Example 7  190 (92.7) 10 (4.9)  5 (2.4) Mg nitrate (hexahydrate) Kaolin Example 8  180 (83.3) 20 (9.3)  16 (7.4) Cu nitrate (tetrahydrate) Kaolin Example 9  140 (64.8)  60 (27.8)  16 (7.4) Cu nitrate (tetrahydrate) Kaolin Example 10  180 (82.6) 20 (9.2)  18 (8.3) Ca nitrate (tetrahydrate) Kaolin Example 11  140 (64.2)  60 (27.5)  18 (8.3) Ca nitrate (tetrahydrate) Kaolin Example 12  180 (81.8) 20 (9.1)  20 (9.1) Fe (III) nitrate (nonahydrate) Kaolin Example 13  140 (63.6)  60 (27.3)  20 (9.1) Fe (III) nitrate (nonahydrate) Kaolin Example 14  180 (81.8) 20 (9.1)  20 (9.1) Al nitrate (nonahydrate) Kaolin Example 15  140 (63.6)  60 (27.3)  20 (9.1) Al nitrate (nonahydrate) Kaolin Example 16  180 (81.8) 20 (9.1)  20 (9.1) Zn nitrate (hexahydrate) Kaolin Example 17  140 (63.6)  60 (27.3)  20 (9.1) Zn nitrate (hexahydrate) Kaolin Example 18  180 (89.1) 20 (9.9)  2 (1.0) Mg chloride (hexahydrate) Kaolin Example 19  195 (96.5)  5 (2.5)  2 (1.0) Mg chloride (hexahydrate) Kaolin Example 20  195 (95.1)  5 (2.4)  5 (2.4) Mg chloride (hexahydrate) Kaolin Example 21  180 (87.8) 20 (9.8)  5 (2.4) Mg chloride (hexahydrate) Kaolin Example 22 180 (82)  20 (9)   20 (9)  Mg nitrate (hexahydrate) Rice husk ash Example 23 180 (82)  20 (9)   20 (9)  Mg nitrate (hexahydrate) Silicone oil Example 24 180 (82)  20 (9)   20 (9)  Mg nitrate (hexahydrate) Micro-silica Example 25 180 (82)  20 (9)   20 (9)  Mg nitrate (hexahydrate) Diatomaceous earth

Linear Shrinkage

[0068] Linear shrinkage was measured using a Netzsch dilatometer. The samples were heated to 1000° C. at a rate of 5° C./min. The shrinkage was measured in-situ using a transducer having a resolution of 8 nm.

[0069] The dilatometer results are shown in Table 2.

TABLE-US-00002 TABLE 2 Pozzolan Metal Stucco/wt % source/wt % salt/wt % in slurry in slurry in slurry (wt % in (wt % in (wt % in Shrinkage (%) Sample product) product) product) 500° C. 750° C. 900° C. 950° C. 1000° C. Control 1 100 0 0 −1.8 −3.6 −7.13 −18 Off scale Control 2   90(91.4)  10(8.6) 0 −1.59 −2.50 −3.10 −5.11 −8.03 Control 3   70(73.5)   30(26.5) 0 −1.6 −2.7 −3.46 −6.48 −8.59 Control 4   91(92.2) 0   9(7.8) −0.02 −0.12 −0.17 −2.84 −6.51 Control 5   93(93.7) 0   7(6.3) −0.24 −1.54 −12/9 Off Off scale scale Control 6   92(92.6) 0   8(7.4) −0.26 −2.84 −9.05 −9.08 −9.1 Control 7   91(92.2) 0   9(7.8) −0.6 −0.7 −3.6 −7.7 −12.3 Control 8   91(92.2) 0   9(7.8) −0.7 −0.4 −0.4 −0.9 −3.5 Control 9   90(91.4)  10(8.6) 0 −1.7 −2.6 −3.5 −7.7 −10.4 Control   90(91.4  10(8.6) 0 −1.3 −2.2 −2.4 −3.2 −4.6 10 Control   90(91.4)  10(8.6) 0 −2.0 −3.4 −4.8 −9.4 −11.7 11 Control   90(91.4)  10(8.6) 0 −1.8 −2.6 −3.5 −6.2 −8.5 12 Ex. 1 81.8(84.2) 9.1(7.9) 9.1(7.9) −0.13 0.02 0.04 −0.13 −0.69 Mg(NO.sub.3).sub.2 Ex. 2 63.6(67.5) 27.3(24.4) 9.1(8.1) −0.22 −0.23 −0.7 −1.52 −1.85 Mg(NO.sub.3).sub.2 Ex. 3 89.1(90.7) 9.9(8.5) 1.0(0.8) −1 −1.11 −1.36 −3.34 −6.07 Mg(NO.sub.3).sub.2 Ex. 4 96.5(97.1) 2.5(2.1) 1.0(0.8) −1.25 −1.41 −1.42 −2.19 −12.4 Mg(NO.sub.3).sub.2 Ex. 5 95.1(95.9) 2.4(2.1) 2.4(2.1) −0.74 −0.61 −0.77 −1.3 −12.8 Mg(NO.sub.3).sub.2 Ex. 6 87.8(89.5) 9.8(8.4) 2.4(2.1) −0.18 0.022 0.16 −0.24 −1.45 Mg(NO.sub.3).sub.2 Ex. 7 92.7(93.8) 4.9(4.2) 2.4(2.1) −0.32 −0.068 0.13 −0.39 −6.95 Mg(NO.sub.3).sub.2 Ex. 8 83.3(85.6) 9.3(8.0) 7.4(6.4) −0.19 −0.03 −0.29 −0.04 −1.49 Cu(NO.sub.3).sub.2 Ex. 9 64.8(68.6) 27.8(24.8) 7.4(6.6) −0.47 −0.38 −0.52 −0.99 −1.5 Cu(NO.sub.3).sub.2 Ex. 10 82.6(84.9) 9.2(8.0) 8.3(7.2) −0.3 −0.01 −0.3 −0.24 −0.72 Ca(NO.sub.3).sub.2 Ex. 11 64.2(68.0) 27.5(24.6) 8.3(7.4) −0.49 −0.52 −0.04 −0.52 −1.01 Ca(NO.sub.3).sub.2 Ex. 12 81.8(84.2) 9.1(7.9) 9.1(7.9) −0.75 −0.64 −0.92 −1.0 −1.42 Fe(NO.sub.3).sub.3 Ex. 13 63.6(67.5) 27.3(24.4) 9.1(8.1) −0.47 −0.34 −0.42 −0.68 −0.99 Fe(NO.sub.3).sub.3 Ex. 14 81.8(84.2) 9.1(7.9) 9.1(7.9) −0.78 −0.5 −0.32 −0.3 −0.36 Al(NO.sub.3).sub.3 Ex. 15 63.6(67.5) 27.3(24.4) 9.1(8.1) −0.82 −0.93 −0.79 −0.80 −0.79 Al(NO.sub.3).sub.3 Ex. 16 81.8(84.2) 9.1(7.9) 9.1(7.9) −0.47 −0.31 −0.86 −2.07 −4.43 Zn(NO.sub.3).sub.2 Ex. 17 63.6(67.5) 27.3(24.4) 9.1(8.1) −0.05 0.1 −0.07 −0.6 −0.87 Zn(NO.sub.3).sub.2 Ex. 18 89.1(90.7) 9.9(8.5) 1.0(0.8) −0.5 −0.4 −0.07 −1.2 −1.4 MgCl.sub.2 Ex. 19 96.5(97.1) 2.5(2.1) 1.0(0.8) −0.58 −0.63 −2.64 −7.4 −8.69 MgCl.sub.2 Ex. 20 95.1(95.9) 2.4(2.1) 2.4(2.1) −0.49 −1.45 −5.51 −8.89 −10.61 MgCl.sub.2 Ex. 21 87.8(89.5) 9.8(8.4) 2.4(2.1) −0.3 −0.3 −0.5 −0.1 −0.1 MgCl.sub.2 Ex. 22   82(84.2)   9(7.9)  9(7.9) −0.04 −0.04 −0.15 −1.85 −4.23 Mg(NO.sub.3).sub.2 Ex. 23   82(84.2)   9(7.9)  9(7.9) −0.95 −1.42 −1.38 −1.52 −1.95 Mg(NO.sub.3).sub.2 Ex. 24   82(84.2)   9(7.9)  9(7.9) −0.41 −0.31 −0.2 −0.7 −8.8 Mg(NO.sub.3).sub.2 Ex. 25   82(84.2)   9(7.9)  9(7.9) −0.03 −0.01 −0.02 −0.07 −1.92 Mg(NO.sub.3).sub.2

[0070] The results show that a combination of pozzolan source and a metal salt can help reduce shrinkage after exposure to elevated temperatures. Results are most pronounced when greater than 5 wt % of pozzolan source is used in the slurry (greater than 4 wt % in the product) and when greater than 1 wt % metal salt is used in the slurry (greater than 0.5 wt % in the product). Results where an equal amount of pozzolan source and metal salt are used are particularly pronounced.