WO2017089899A1

WO2017089899A1 - Chemically activated cement using industrial waste

Info

Publication number: WO2017089899A1
Application number: PCT/IB2016/001859
Authority: WO
Inventors: Ramkumar Natarajan; Satheesh Kumar Kartheesan Thiyagarajan
Original assignee: Eko Tech4Trans Pvt. Ltd.
Priority date: 2015-11-26
Filing date: 2016-11-16
Publication date: 2017-06-01
Also published as: CA2913306A1

Abstract

A process and product of an activated cement composition comprising: industrial waste such as ground granulated blast furnace slag, cement kiln dust, lime kiln dust, and Class C fly ash having a specific surface area between 2500-7000 cm²/gram and/or high alumina cement; an alkali metal hydroxide; an alkali metal salt of hydro carboxylic acid and/or a source of alkali salt of hydro carboxylic acid; alkali metal fluoride; alkali metal chloride such as MgCl₂, NaCI and KCI, preferred is MgCl₂; a retarder such as an alkali metal phosphate and/or an alkali metal stannate; and nano alkali metal carbonate that does not require clinkering and can be used for a broad range of applications.

Description

CHEMICALLY ACTIVATED CEMENT USING INDUSTRIAL WASTE

FIELD OF THE INVENTION

This invention relates to process and composition of producing high performance cement using industrial wastes, more specifically, cements incorporating fly ash.

BACKGROUND OF THE INVENTION

Disposal of industrial waste such as Ground Granulated Blast Furnace Slag (GGBFS), Cement Kiln Dust, Fly Ash, etc have been a major problem and concern for the industry. The above industrial wastes have alkali metal oxides like lime, silica, alumina, iron, etc., the combination of which react with calcium to produce pozzolans. Ordinary Portland Cement (OPC) having ingredients required for concrete, mortar and stucco is obtained by grinding Portland cement clinkers and Calcium Sulphate to form a hydraulic material that hardens by reacting with water and forms water resistant product. However, the process to make Portland cement clinkers requires heating the raw materials to sintering temperatures. Large amounts of C0₂ are released in the making of such preparation which have deleterious effects on the environment. It is estimated that the production of OPC utilizes 2% of all the global energy used and 5% of industrial energy consumed.

Moreover, the production of a single ton of OPC results in the production of at least 3/4 ton of green house gases (of which C0₂ accounts for ½ ton) is emitted that is a major pollutant that spoils the environment. The OPC so produced has several drawbacks like cracks due to shrinkage, expansion because of sulfate attack, expansion due to the presence of alkalis in the aggregates etc.

Fly ash is a pozzolan. Class C fly ash contains silica, aluminium and calcium in combinations which makes it cementitious and self hardening and has been used as a strengthening additive in Portland cement. Class C fly ash is sub-bituminous and has higher sulphur content. The chemical attributes of the Class C fly ash are defined in ASTM C-61 8 which a person of ordinary skilled in the art is knowledgeable about. Adding water to Class C fly ash causes it to harden, but the same does not have significant strength. Similarly, when Class C fly ash is mixed with Portland cement there are limitations to the quantity that can be added.

US Patent No. 4,997,484 as well as US Patent No. 7,288,148 disclose a composition of fly ash with acid-base reacting system utilizing the combined effect of citric acid and alkali hydroxide or metal carbonate. The composition does not exhibit the required working time and releases lot of heat during the setting of the cement which, in turn, causes durability issues.

US Patent No. 8,016,937 discloses a composition containing industrial pozzolan powder with a neutral pH activator without the use of any hydrocarboxylic acids like citric acid or metal carbonate or alkali metal stannate or alkali metal chloride in a weight proportion greater than 50% of total activator content of its cement composition and less than 30% by weight content of acidic activator in association with 95 parts of Class C fly ash to achieve high strength in short time. The use of increased percentage alkali metal salt of citric acid to achieve setting not only results in increasing the cost of the final cement but also results in the quick setting of the cement creating several drawbacks, for example quick loss of slump associated with such setting. As a result, the present invention cannot be used for many applications except for rapid concrete repairs. Some of the drawbacks of the prior art include: cements having quick setting time and hence limited applications; the use of hazardous alkalis such as potasium hydroxide; the quick loss of flowability resulting in difficult placement; the inability to use Class C fly ash having low amount of calcium oxide; the creation of expansive forces during setting making the cement self stressing; the difficulty in using fly ashes having high water absorption; and the high cost.

The inventors after years of trials have surprisingly and unexpectedly discovered that with the use of alkali metal stannate or alkali metal chloride or alkali metal phosphate along with alkali metal salt of hydro carboxylic acid in the cement composition, the working time of the cement can extend beyond three hours depending on the composition of the fly ash. This enables the cement to be used for normal construction uses.

Despite the prior art, there still exists a need for a workable, practical and economical cement composition having increased percentage of fly ash which can be manufactured by simple powder blending process.

SUMMARY OF THE INVENTION

More specifically, this invention relates to a process and product of an activated cement composition comprising: industrial waste such as ground granulated blast furnace slag, cement kiln dust, lime kiln dust, and Class C fly ash having a specific surface area between 2500-7000 cm²/gram and/or high alumina cement; an alkali metal hydroxide; an alkali metal salt of hydro carboxylic acid and/or a source of alkali salt of hydro carboxylic acid; alkali metal fluoride; alkali metal chloride such as MgCl₂, NaCl and KG, preferred is MgC^; a retarder such as an alkali metal phosphate and/or an alkali metal stannate; and nano alkali metal carbonate that does not require clinkering and can be used for a broad range of applications. Preferably, the required surface area of the industrial byproducts can be obtained by mechanical grinding followed by classification of same.

According to one aspect of the present invention, there is provided a rapid setting hydraulic cement composition comprising: an industrial byproduct containing calcium oxide ranging from 10 to 50 wt %; optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal oxide; and

- an alkali metal carbonate.

According to one aspect of the present invention, there is provided a rapid setting hydraulic cement composition comprising:

an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %;

- optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal oxide;

an alkali metal carbonate; and

an high alumina cement.

According to one aspect of the present invention, there is provided a controlled setting hydraulic cement composition comprising:

an industrial byproduct containing calcium oxide ranging from 10 to 50 wt %; optionally, an alkali metal hydroxide;

- an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

a retarder selected from the group consisting of: an alkali metal phosphate an alkali metal stannate, alkali metal titanate and combinations thereof;

an alkali metal chloride; and

optionally, an alkali metal carbonate.

an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %;

optionally, an alkali metal hydroxide;

- an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal chloride;

optionally, an alkali metal carbonate; and

- an high alumina cement

According to one aspect of the present invention, there is provided a rapid setting hydraulic cement composition for use in concrete road repair comprising: - an industrial byproduct containing calcium oxide ranging from 10 to 50 wt %;

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal oxide;

- an alkali metal carbonate; and

a sand (such as quartz sand).

According to one aspect of the present invention, there is provided a rapid setting hydraulic cement composition for use in concrete road repair comprising:

- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %;

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal oxide;

an alkali metal carbonate;

- an high alumina cement; and

a sand (such as quartz sand).

- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %;

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

a retarder selected from the group consisting of: an alkali metal phosphate an alkali metal stannate, and combinations thereof;

- an alkali metal chloride;

optionally, an alkali metal carbonate; and

a sand (such as quartz sand).

According to an object of the present invention, there is provided a cement composition comprising fly ash and the use of an activator such as a fluoride. Preferably, the fluoride is sodium fluoride.

According to a preferred embodiment of the present invention, there is provided a cement composition comprising fly ash and retarders to prevent a sudden loss in flowability. Preferably, the cement composition of the present invention uses chlorides as retarders as they are cheaper than borates or tartrates. According to a preferred embodiment of the present invention, the cement composition comprising fly ash has an extended working time through the use of low cost retarders such as magnesium chloride. According to an object of the present invention, there is provided a cement composition comprising fly ash and a retarder selected form the group consisting of: alkali metal phosphate, alkali metal stannate and a combination thereof.

According to an object of the present invention, there is provided a cement composition comprising fly ash and which does not require the use of harsh alkalis.

According to a preferred embodiment of the present invention, there is provided a cement composition comprising fly ash having low calcium oxide in combination with calcium aluminate cement.

According to a preferred embodiment of the present invention, there is provided a cement composition comprising fly ash whereby the self stressing nature thereof is prevented or limited by using of quartz sand powder as additive.

According to a preferred embodiment of the present invention, there is provided a cement composition comprising fly ash having high water absorption which is ground and classified and mixed with water reducing agents such as polycarboxylate ethers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for the use of industrial waste such as fly ash to prepare both rapid setting cement composition and controlled setting cement composition.

Preferably, the rapid setting hydraulic cement composition for use in concrete road repair comprising;

- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %;

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal oxide;

an alkali metal carbonate;

a granular material such as sand (preferably quartz sand) and water.

Preferably, the composition further comprises an high alumina content cement when the calcium oxide content in the industrial byproduct is less than 10%.

Preferably as well, the controlled setting hydraulic cement composition comprising:

an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %; optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

- an alkali metal chloride;

optionally, an alkali metal carbonate;

a granular material such as sand (preferably quartz sand) and water.

According to a preferred embodiment, the cement composition has a setting time ranging between 3 minutes to 5 hours depending on the composition chosen.

The industrial byproducts containing lime may be selected from the group of Class C fly ash, Ground Granulated Blast Furnace Slag (GGBFS), Cement Kiln Dust or Lime Kiln Dust. According to a preferred embodiment, Class F fly ash can used in combination with any one of Ground Granulated Blast Furnace Slag (GGBFS), Cement Kiln Dust and Lime Kiln Dust. Preferably, the composition of the present invention will be free of portland cement but may require the addition of up to a maximum of 20% by weight of the composition of calcium aluminate cement in certain cases when the Aluminum Saturation Index (AS1) of the fly ash measured by the formula ASI= (Al₂0₃)/(CaO+MgO+Na₂0+K₂0) increases beyond 0.9.

Industrial waste having calcium oxide in the range of 5-50% having a specific surface area between 2500- 7000 cm²/g is preferably present in an amount ranging from 80 to 95% by weight of the total composition; quartz sand powder is preferably present in an amount ranging from 0.1 to 20% by weight of the total composition; alkali metal oxide is preferably present in an amount ranging from 0.1 to 5% by weight of the total composition; nano alkali metal carbonate is preferably present in an amount ranging from 0.1 to 4% by weight of the total composition; alkali metal of hydrocarboxylic acid is preferably present in an amount ranging from 0.1 to 7% by weight of the total composition; alkali metal fluoride is preferably present in an amount ranging from 0.1 to 5% by weight of the total composition; alkali metal phosphate is preferably present in an amount ranging from 0.1 to 7% by weight of the total composition; alkali metal chloride is preferably present in an amount ranging from 0.1 to 3% by weight of the total composition; hydrocarboxylic acid is preferably present in an amount ranging from 0. 1 to 5% by weight of the total composition; alkali metal stannate is preferably present in an amount ranging from 0.1 to 4% by weight of the total composition and/or alkali metal titanate is preferably present in an amount ranging from 0.1 to 4% by weight of the total composition.

The surface area of the unclassified fly ash used ranged from 2000- 4000 cm²/gram. The classified fly ash preferably has a surface area ranging from 3300 to 4000 cm²/gram. It is preferable to use fly ash within those particle size ranges as uniform particle size distribution is preferable for the performance of the cement.

It is understood that the cements according to the present invention can be used to make concretes by the addition of various types of aggregates commonly used in the field. The purposes disclosed herein are understood to be examples of the breadth of use the present invention can be applied and should not be construed to be limited to such.

The following examples are included to illustrate the present invention and are not to be considered limiting thereof. In each of the examples, the amount of water was carefully controlled, as would be understood by the person of ordinary skill in the art, to ensure an efficient mixing and reaction and also to ensure that the cement created was of sufficient strength. The person skilled in the art will understand the scope of the invention is defined by the claims appended hereto. Example 1

A cementitious composition was prepared according to the following composition:

Classified Class C - Ash - 923g

Sodium Citrate - 55g

Lime Powder - 20 g

Lithium Carbonate - 2 g

Quartz Sand (3mm Size) - 1000 g

Water - 320 ml

All the powder components were mixed first and water was then added and mixed in a mixer. Then sand was then added and the resulting mixture was mixed for another 10 minutes.

Cubes of 70.6 mm were cast, their setting times were recorded and the hardness was measured. The final setting time was 10 minutes. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 1 are listed below:

2 Hrs - 15 Mpa

24 Hrs - 20 Mpa

3 days - 21.4 Mpa

7 days - 24.8 Mpa

28 days - 28.9 Mpa

Example 2

A cementitious composition was prepared according to the following composition:

Classified Class C -Fly Ash - 903 g Sodium Citrate - 55 g

Lime Powder - 20 g

Lithium Carbonate - 2 g

MgCl₂ - 20 g

Sand - 1000 g

Water - 320 ml

The final setting time was 2 hours. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 2 are listed below:

2 Hrs - 13 Mpa

24 Hrs - 22 Mpa

3 days - 26.4 Mpa

7 days - 28.9 Mpa

28 days - 34 Mpa

Example 3

A cementitious composition was prepared according to the following composition:

C - Ash - 903 g

Sodium Citrate - 55g

Lime Powder - 20g

Lithium Carbonate - 2g

Citric Acid- 20g

Sand - l OOO g

Water - 360 ml

The final setting time was 24 minutes. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 3 are listed below:

2 Hrs - 12.4 Mpa

24 Hrs - 19.8 Mpa

3 days - 22.4 Mpa

7 days - 26 Mpa

28 days - 30 Mpa

Example 4

A cementitious composition was prepared according to the following composition:

Ash - 710 g

Sodium Citrate - 64g

Lime Powder- 24g

Lithium Carbonate - 2g Calcium Aluminate Cement - 200g

Sand - lOOOg

Water - 325 ml The final setting time was 15 minutes. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 4 are listed below:

2 Hrs - 20 Mpa

24 Hrs - 30 Mpa

3 days - 34.4 Mpa

7 days - 38.7 Mpa

28 days - 42.3 Mpa

Example 5

A cementitious composition was prepared according to the following composition:

C - Ash - 710 g

Sodium Citrate - 64 g

Lime Powder - 24 g

Lithium Carbonate - 2 g

Calcium Aluminate Cement - 200g

Sand - lOOOg

Water - 325 ml

The final setting time was 15 minutes. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 5 are listed below:

2 Hrs - 4 Mpa

24 Hrs - 15 Mpa

3 days - 17 Mpa

7 days - 22 Mpa

28 days - 27 Mpa

Example 6

A cementitious composition was prepared according to the following composition:

C - Ash - 903 g

Sodium Citrate - 55g

Lime Powder - 20 g

Nano Calcium Carbonate - 20 g (Particle size between 5 to 10 microns)

Lithium Carbonate - 2g

Sand - 1000 g Water - 340 ml

The final setting time was 12 minutes. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 6 are listed below:

2 Hrs - 9 Mpa

24 Hrs - 16 Mpa

3 days - 20.4 Mpa

7 days - 22.9 Mpa

28 days - 26.4 Mpa

Example 7

A cementitious composition was prepared according to the following composition:

C - Ash - 900 g

Sodium Citrate - 55g

Lime Powder- 30g

Lithium Carbonate - 2 g

Mono Ammonium Phosphate - 10 g

Sand - 1000 g

Water - 335 ml

The final setting time was 2 hours. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 7 are listed below:

4 Hrs - 13 Mpa

24 Hrs - 28.4 Mpa

3 days - 27.5 Mpa

7 days - 32 Mpa

28 days - 38.9 Mpa

Example 8

A cementitious composition was prepared according to the following composition:

C - Ash - 903 g

Sodium Citrate - 55g

Lime Powder - 20g

Lithium Carbonate - 2g

Mono Potasium Phosphate - lOg

Sand - l OOO g

Water - 385 ml The final setting time was 2 hours. The cement hardness was monitored and recorded over a range of time of up to 4 weeks. The results of the hardness testing for example 8 are listed below:

24 Hrs - 21.5 Mpa

3 days - 25 Mpa

7 days - 34 Mpa

28 days - 37.6 Mpa

Example 9

A cementitious composition was prepared according to the following composition:

C - Ash - 923 g

Sodium Fluoride -55 g

Lime Powder - 20 g

Lithium Carbonate - 2 g

Sand - 1000 g

Water - 450 ml

The final setting time was 20 minutes. The cement hardness was monitored and recorded of time of up to 4 weeks. The results of the hardness testing for example 9 are listed below:

2 hrs - 5 Mpa

24 hrs - 9.4 Mpa

3 days - 13.2 Mpa

7 days - 17.1 Mpa

28 days - 19.8 Mpa Example 10

A cementitious binder was prepared according to the following composition:

Classified Class C - Ash - 903 g

Sodium Citrate - 55g

Lime Powder - 20 g

Lithium Carbonate - 2 g

Sodium Stannate - 20 g

Quartz Sand (3mm Size) - 1000 g

Water - 320 ml

The final setting time was 4 hours. The cement hardness was monitored and recorded of time of up to 4 weeks. The results of the hardness testing for example 10 are listed below:

24 Hrs - 18 Mpa

3 Days - 23.2 Mpa Days - 26 Mpa Days- 32 Mpa

Claims

1. A rapid setting hydraulic cement composition comprising:

an industrial byproduct containing calcium oxide ranging from 10 to 50 wt % by weight;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

optionally, an alkali metal hydroxide; and

an alkali metal carbonate.

2. A rapid setting hydraulic cement composition comprising:

an industrial byproduct containing calcium oxide ranging from 5 to 50 wt % by weight;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

optionally, an alkali metal hydroxide;

an alkali metal carbonate; and

a high alumina cement.

3. A controlled setting hydraulic cement composition comprising:

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal chloride; and

optionally, an alkali metal carbonate.

4. A controlled setting hydraulic cement composition comprising:

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal chloride;

a high alumina cement; and

optionally, an alkali metal carbonate.

5. A rapid setting hydraulic cement composition for use in concrete road repair comprising :

- an industrial byproduct containing calcium oxide ranging from 10 to 50 wt % by weight;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

optionally, an alkali metal hydroxide;

an alkali metal carbonate; and

a granular material containing fine rock and mineral.

6. A rapid setting hydraulic cement composition for use in concrete road repair comprising :

- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt % by weight; an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

optionally, an alkali metal hydroxide;

an alkali metal carbonate;

a high alumina cement; and

a granular material containing fine rock and mineral.

7. A controlled setting hydraulic cement composition comprising:

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal chloride;

optionally, an alkali metal carbonate; and

a granular material containing fine rock and mineral.

8. A controlled setting hydraulic cement composition comprising:

optionally, an alkali metal hydroxide;

an alkali metal salt of an hydrocarboxylic acid or an alkali metal fluoride;

an alkali metal chloride;

optionally, an alkali metal carbonate;

a high alumina cement; and

a granular material containing fine rock and mineral.

9. The composition according to any one of claims 1 to 8 wherein the industrial byproduct containing calcium oxide is selected from the group consisting of: Class C fly ash; ash; ground granulated blast furnace slag; cement kiln dust; lime kiln dust; and high alumina cement.

10. The composition according to claim 9 wherein the industrial byproduct containing calcium oxide is fly ash.

1 1. The composition according to claim 10 wherein the industrial byproduct containing calcium oxide is Class C fly ash.

12. A use of the composition according to claim 1 , 2, 5, and 6 as a quick setting grout.

13. A use of the composition according to claim 1 , 2, 5, and 6 for concrete road repairs.

14. A use of the composition according to claim 3, 4, 7 and 8 in precast components.

15. A use of the composition according to claim 3, 4, 7 and 8 in concrete masonry units.

16. A use of the composition according to claim 3, 4, 7 and 8 as tile adhesive.

17. A use of the composition according to claims 3, 4, 7 and 8 for various construction use.

18. The composition according to any one of claims 5, 6 and 9 to 1 1, where the granular material is sand.

19. The composition according to claim 7 to 1 1 , where the granular material is sand.

20. The composition according to claim 18 or 1 , wherein the sand is quartz sand.

21 . The composition according to any one of claims 1 to 1 1 and 18 to 20, wherein the industrial waste having calcium oxide content in the range of 5-50% by weight and a specific surface area between 2500- 7000 cm²/g is present in an amount ranging from 80 to 95% by weight of the total composition.

22. The composition according to any one of claims 1 to 1 1 and 18 to 21, wherein the granular material is present in an amount ranging from 0.1 to 20% by weight of the total composition.

23. The composition according to claim 22, wherein the granular material is quartz sand powder.

24. The composition according to any one of claims 1 to 1 1 and 1 8 to 23, wherein the alkali metal hydroxide is present in an amount ranging from 0.1 to 5% by weight of the total composition.

25. The composition according to claim 24, wherein the alkali metal hydroxide is calcium hydroxide.

26. The composition according to any one of claims 1 to 1 1 and 18 to 25, wherein the nano alkali metal carbonate is present in an amount ranging from 0.1 to 4% by weight of the total composition.

27. The composition according to claim 26, wherein the nano alkali metal carbonate is selected from the group consisting of: lithium carbonate, calcium carbonate and combinations thereof.

28. The composition according to any one of claims 1 to 1 1 and 18 to 27, wherein alkali metal of hydrocarboxylic acid is present in an amount ranging from 0.1 to 7% by weight of the total composition.

29. The composition according to claim 28, wherein alkali metal of hydrocarboxylic acid is sodium citrate.

30. The composition according to any one of claims 1 to 1 1 and 18 to 29, wherein the alkali metal fluoride is present in an amount ranging from 0.1 to 5% by weight of the total composition.

31 . The composition according to claim 30, wherein the alkali metal fluoride is sodium fluoride.

32. The composition according to any one of claims 1 to 1 1 and 1 8 to 31 , wherein the alkali metal phosphate is present in an amount ranging from 0.1 to 7% by weight of the total composition.

33. The composition according to claim 32, wherein the alkali metal phosphate is selected from the group consisting of: potassium phosphate, ammonium phosphate.

34. The composition according to any one of claims 1 to 1 1 and 18 to 33, wherein alkali metal chloride is present in an amount ranging from 0.1 to 3% by weight of the total composition.

35. The composition according to claim 34, wherein alkali metal chloride is selected from the group consisting of: MgCl₂, NaCl and KG.

36. The composition according to claim 35, wherein alkali metal chloride is MgCl₂.

37. The composition according to any one of claims 1 to 1 1 and 18 to 36, wherein the hydrocarboxylic acid is preferably present in an amount ranging from 0.1 to 5% by weight of the total composition.

38. The composition according to claim 36, wherein the hydrocarboxylic acid is citric acid.

39. The composition according to any one of claims 1 to 1 1 and 18 to 38, wherein the alkali metal stannate is present in an amount ranging from 0.1 to 4% by weight of the total composition.

40. The composition according to claim 39, wherein the alkali metal stannate is sodium stannate.