ENVIRONMENTALLY FRIENDLY CEMENT AND PRODUCTION METHOD THEREOF

Abstract

An environmentally friendly cement comprises (1) an active filler comprising waste materials composed of a thermal insulation wool and a waste thereof; (2) an inert filler comprising metakaolin and an aggregate optionally selected from cement, fine sand, gravel, waste to be solidified, and organic resin; and (3) an aqueous solution of sodium metasilicate as an alkaline compound. A method for producing the environmentally friendly cement comprises mixing ingredients (1) and (3) and ingredients (2) and (3) respectively to obtain a slurry A and a slurry B respectively; mixing the slurry A and B; and hardening the final slurry, whereby elements silicon and aluminum in the ingredient (1) are dissolved out in the basic solution of the ingredient (3), and a closed framework structure is formed by bonding silica and alumina as tetrahedrons. The environmentally friendly cement has excellent fire tolerance, heat insulation, acid and alkaline resistance, and mechanical properties.

Claims

1. An environmentally friendly cement, comprising (1) an active filler, comprising waste materials composed of a thermal insulation wool and a waste thereof; (2) an inert filler, comprising metakaolin and an aggregate optionally selected from cement, fine sand, gravel, waste to be solidified including furnace slag, and organic resin; and (3) an aqueous solution of sodium metasilicate as an alkaline compound.

2. The environmentally friendly cement according to claim 1, wherein the thermal insulation wool and the waste thereof used in the ingredient (1) have a SiO.sub.2/Al.sub.2O.sub.3 ratio of 7.0-9.5.

3. The environmentally friendly cement according to claim 1, wherein the metakaolin in the ingredient (2) has a SiO.sub.2/Al.sub.2O.sub.3 ratio of 1.5-2.3.

4. The environmentally friendly cement according to claim 1, wherein the sodium metasilicate in the ingredient (3) has a SiO.sub.2/Na.sub.2O ratio of 1.0-2.5.

5. The environmentally friendly cement according to claim 1, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

6. The environmentally friendly cement according to claim 2, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

7. The environmentally friendly cement according to claim 3, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

8. The environmentally friendly cement according to claim 4, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

9. A method for preparing an environmentally friendly cement comprising a mixture of (1) an active filler, comprising waste materials composed of a thermal insulation wool and a waste thereof; (2) an inert filler, comprising metakaolin and an aggregate optionally selected from cement, fine sand, gravel, waste to be solidified including furnace slag, and organic resin; and (3) an aqueous solution of sodium metasilicate as an alkaline compound, the method comprising the steps of (a) mixing the ingredient (1) with the ingredient (3), to obtain a first slurry; then mixing the ingredient (2) with the ingredient (3), to obtain a second slurry; subsequently, mixing the first slurry with the second slurry, to obtain a final slurry; and then hardening the final slurry; and then hardening the finally mixed slurry.

10. The method for producing an environmentally friendly cement according to claim 9, wherein the thermal insulation wool and the waste thereof used in the ingredient (1) have a SiO.sub.2/Al.sub.2O.sub.3 ratio of 7.0-9.5.

11. The method for producing an environmentally friendly cement according to claim 9, wherein the metakaolin in the ingredient (2) has a SiO.sub.2/Al.sub.2O.sub.3 ratio of 1.5-2.3.

12. The method for producing an environmentally friendly cement according to claim 9, wherein the sodium metasilicate in the ingredient (3) has a SiO.sub.2/Na.sub.2O ratio of 1.0-2.5.

13. The method for producing an environmentally friendly cement according to claim 9, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

14. The method for producing an environmentally friendly cement according to claim 10, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

15. The method for producing an environmentally friendly cement according to claim 11, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

16. The method for producing an environmentally friendly cement according to claim 12, wherein the SiO.sub.2/Na.sub.2O ratio in the final environmentally friendly cement is in the range of 2.5-4.0.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 shows the reaction mechanism of geopolymer.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

[0029] According to a first objective of the present invention, an environmentally friendly cement is provided, which comprises (1) an active filler, comprising waste materials composed of a thermal insulation wool and a waste thereof; (2) an inert filler, comprising metakaolin and an aggregate optionally selected from cement, fine sand, gravel, waste to be solidified such as furnace slag, and organic resin; and (3) an aqueous solution of sodium metasilicate as an alkaline compound.

[0030] According to another objective of the present invention, a method for producing an environmentally friendly cement is provided, that is, producing an environmentally friendly cement comprising a mixture of (1) an active filler, comprising waste materials composed of a thermal insulation wool and a waste thereof; (2) an inert filler, comprising metakaolin and an aggregate optionally selected from cement, fine sand, gravel, waste to be solidified such as furnace slag, and organic resin; and (3) an aqueous solution of sodium metasilicate as an alkaline compound. The method comprises the steps of: (a) mixing the ingredient (1) with the ingredient (3), to obtain a first slurry, then mixing the ingredient (2) with the ingredient (3), to obtain a second slurry, and subsequently, mixing the first slurry with the second slurry, to obtain a final slurry, whereby the elements silicon and aluminum in the ingredient (1) are dissolved out in the basic solution of the ingredient (3), and then a closed framework structure is formed by bonding silica and alumina as tetrahedrons to each other. In this way, an environmentally friendly cement having excellent fire tolerance, heat insulation, acid and alkaline resistance, and mechanical properties is obtained.

[0031] The ingredients are described in detail below.

[0032] (1) Active Filler

[0033] The active filler useful in the present invention includes waste materials such as thermal insulation wool used in industry and a waste thereof, and especially thermal insulation wool used in reacting furnaces in factories and power plants and a waste thereof.

[0034] The thermal insulation wool in the active filler of the present invention may be for example perlite wool, rock wool, corundum wool, and other industrial waste, for example, industrial waste from fuel electric plant and/or nuclear power plant of Taiwan Power Company. The perlite wool contains about 50-70% of silica, with the balance being alumina. The rock wool contains silica and alumina at a ratio of about 1:1. The corundum wool is composed essentially of alumina. Therefore, the thermal insulation wool is rich in the silicon and aluminum elements needed for the geopolymer, thus being extremely suitable for being used as a material for geopolymer.

[0035] (2) Inert Filler

[0036] The inert filler mainly plays a role of “filling”, to reinforce the properties of the geopolymer. For example, an aggregate such as cement, fine sand, gravel, waste to be solidified such as furnace slag, and organic resin may be used to increase the strength. The inert additive may also be any materials with filling property or with fire tolerance, thermal insulation, porosity, and other properties, to increase the particular applications of the geopolymer.

[0037] The environmentally friendly cement and the preparation method thereof according to the present invention are characterized in thatthe inert filler needs to contain metakaolin, because metakaolin can effectively provide the ingredients needed by, and increase the mechanical strength of the geopolymer. Kaolin is a clay mineral, and often found in the weathered layer of igneous rock and metamorphic rock. Kaolin has a chemical composition of Al.sub.4[Si.sub.4O.sub.10].(OH).sub.2, and is a silicate mineral with a triclinic layered structure; and the fundamental building block is formed by bonding 1:1 silica tetrahedron to alumina octahedron via oxygen, and connected by hydrogen bonding theretween. After kaolin is dehydrated at a high temperature (generally between 600-800° C.), Al is transitioned from an octahedrally coordinated position in kaolin to a tetrahedrally coordinated position in metakaolin. Therefore, metakaolin is of a structure with long-range disorder and short range existing as silica tetrahedron, and thus has a greatly increased activity. However, when kaolin is thermally treated at an excessively high temperature (above 800° C.), the activity is lost because the internal structure is completely destroyed (burn). Additionally, the incomplete solid structure easily causes unstable chemical properties, which allows the material to have a high activity.

[0038] The metakaolin used in the environmentally friendly cement and the preparation method thereof according to the present invention has a SiO.sub.2/Al.sub.2O.sub.3 ratio of 1.5-2.3, and preferably 1.7-1.9.

[0039] (3) Aqueous Solution of Sodium Metasilicate as Alkaline Compound

[0040] The sodium metasilicate has a SiO.sub.2/Na.sub.2O ratio of 1.0-2.5, and preferably 1.5-1.8. Since sodium metasilicate has a high water solubility (of about 50 g/mL) and contains Si ingredient, sodium metasilicate is used as an alkaline compound in the method for preparing the environmentally friendly cement according to the present invention, which may provides Si ingredient to the cement to be produced, thus improving the shaping ability of the cement and reducing the formation of white efflorescence of the finish product cement caused by the education of NaHCO.sub.3/Na.sub.2CO.sub.3 ingredient.

EXAMPLE

[0041] The present invention is described in further detail with reference to examples below. However, the examples are provided for exemplification, instead of limiting the scope of the present invention.

[0042] In the examples below, the description is given by way of example in which commercially available thermal insulation wool is used as an active material. Because the material of the commercially available thermal insulation wool is the same as that of the spent thermal insulation wool, if the effect of the present invention can be achieved with the commercially available thermal insulation wool, the effect of the present invention can also be achieved with the spent thermal insulation wool in place of the commercially available thermal insulation wool.

Example 1

[0043] Preparation method: basic geopolymerization

[0044] Materials:

[0045] Thermal insulation wool: perlite wool purchased from ISOLITE Industry Co., Ltd (Japan)

[0046] Metakaolin: metakaolin powder (25 kg/package) purchased from the manufacture catalogue of IMERYS Performance Minerals Inc (France).

[0047] Sodium metasilicate: sodium metasilicate powder (25 kg/package) purchased from the manufacture catalogue of Santos Inc (Taiwan).

[0048] Production procedure of the environmentally friendly cement

[0049] (A) Extraction of Thermal Insulation Wool

[0050] 1. The perlite thermal insulation wool was pulverized and sieved to obtain a powder with a particle size of less than the hole of Mesh No. 18.

[0051] 2. 1,250 g of sodium metasilicate (SiO.sub.2/Na.sub.2O=1.5-1.8) was weighed, added to 2,500 mL of water, stirred uniformly until it was fully dissolved, to formulate a solution WG.

[0052] 3. 75 g of pulverized and sieved perlite thermal insulation wool (SiO.sub.2/Al.sub.2O.sub.3=7.9-8.7) was weighed, added to 200 mL of the solution WG, and stirred for 30-60 min at a constant speed of 300 rpm at normal temperature (25° C.), to extract SiO.sub.2 and a small amount of Al.sub.2O.sub.3 contained in the perlite thermal insulation wool. In this manner, a first slurry was obtained.

[0053] (B) Formulation of Slurry Containing Inert Filler

[0054] 1,000 g of metakaolin (SiO.sub.2/Al.sub.2O.sub.3=1.7-1.9) was added, added to 2,300-1,900 mL of the solution WG, and uniformly mixed by uniformly stirring for 30-60 min at a rotation speed of 300 rpm. In this manner, a first slurry B was obtained.

[0055] (C) Formulation of Environmentally Friendly Cement

[0056] The first slurry was uniformly mixed with the second slurry, and then 1,000 g of metakaolin was added to adjust the SiO.sub.2/Na.sub.2O ratio in the mixed slurry to 4.31 and adjust the SiO.sub.2/Al.sub.2O.sub.3 ratio to 3.06, and stirred for 15-30 min at a constant speed of 300 rpm. The mixed slurry that was uniformly stirred was filled to a mold, and stood to harden and shape the slurry. In this way, the environmentally friendly cement of Example 1 was obtained.

Example 2

[0057] The steps in Example 1 were repeated, except that the ratio of the ingredients was changed as shown in Table 1; and the SiO.sub.2/Na.sub.2O ratio in the mixed slurry was adjusted to 4.43, and the SiO.sub.2/Al.sub.2O.sub.3 ratio was adjusted to 3.14, to obtain the environmentally friendly cement of Example 2.

Example 3

[0058] The steps in Example 1 were repeated, except that the ratio of the ingredients was changed as shown in Table 1; and the SiO.sub.2/Na.sub.2O ratio in the mixed slurry was adjusted to 4.66, and the SiO.sub.2/Al.sub.2O.sub.3 ratio was adjusted to 3.31, to obtain the environmentally friendly cement of Example 3.

Test Example

[0059] The environmentally friendly cements obtained in Examples 1 to 3 was evaluated for compressive strength, dissolution rate, weatherability, radiotolerance, water resistance, free water, fire tolerance, and bacterial resistance.

[0060] 1. Uniaxial Compressive Strength

[0061] The test was conducted according to ASTM-C39. The product is accepted if the compressive strength is higher than 15 kgf/cm.sup.2.

TABLE-US-00001 TABLE 1 Thermal Sodium Compressive Example insulation metasilicate Metakaolin Water strength No. wool (g) (g) (g) (mL) SiO.sub.2/Na.sub.2O SiO.sub.2/Al.sub.2O.sub.3 (kgf/cm.sup.2) 1 75 1,250 2,000 2,500 4.31 3.06 86 2 150 1,250 2,000 2,500 4.43 3.14 89 3 300 1,250 2,000 2,500 4.66 3.31 85 * The volume of 300 gthermal insulation wool is roughly equal to that of 2,000 gmetakaolin.

[0062] 2. Dissolution Rate Test

[0063] The dissolution rate test was carried out following a standard method for testing the dissolution rate of a solidified form, that is, the America Nuclear Society ANS 16.1 “Determination of dissolution rate of low level radioactive solidified form by a short test procedure”. The various dissolution rate indices of the solidified form should be greater than 6. The test result is shown in Table 2.

TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Average Time (ppm) (ppm) Index  2 h 5.342 14.35 9.273 9.65 5.2  7 h 3.371 6.392 5.816 5.19 5.6 24 h 1.527 5.304 3.709 3.51 6.5 48 h 1.304 4.252 5.283 3.61 6.2 72 h 2.229 1.401 5.186 2.94 6.3 96 h 2.603 1.169 3.353 2.38 6.3 120 h  1.014 1.616 1.827 1.49 6.6 456 h  0 0 0 0 — 792 h  0 0 0 0 —
Average dissolution time=6.1

[0064] 3. Weatherability Test

[0065] Weather resistance test was carried out by placing the test sample in a weatherability tester, and then changing the temperature and humidity in the tester according to the set conditions in steps 00-08, in which 30 cycles of the steps 00-08 were performed. The result denotes the weatherability after exposure to an extreme environment for 30 years. The result is shown in Table 3 below.

TABLE-US-00003 TABLE 3 Step HH:MM Temperature ° C. Humidity % 00 0:05 25 60 01 1:00 25 60 02 0:20 60 90 03 1:00 60 90 04 0:40 25 60 05 1:00 25 60 06 0:40 −10 0 07 1:00 −10 0 08 0:20 25 60
Time setting: HH (hr), MM (min), for example, 1:40 is 1 hour and 40 minutes.

[0066] 4. Free Water

[0067] The test was conducted according to ANSI/ANS55.1. The product is accepted if the free water content is less than 0.5% of the volume of the solidified form, and the pH value of free water is above 6. According to the visual examination results of the environmentally friendly cements obtained in Examples 1-3, no free water is produced on all of the environmentally friendly cements, suggesting that the environmentally friendly cement produced according to the present invention meets the requirement.

[0068] 5. Water Resistance

[0069] The compressive strength of the test sample was tested 90 days after being immersed in water. The compressive strength may be an index of water resistance, and the product is accepted if the compressive strength is higher than 15 kgf/cm.sup.2. The result is shown in Table 4 below.

TABLE-US-00004 TABLE 4 Compressive strength No (kgf/cm.sup.2) 1 84 2 87 3 81

[0070] In addition, since the environmentally friendly cement of the present invention is a cement-like material, and composed exclusively highly basic (9<pH<11) inorganic materials, the environmentally friendly cement undoubtedly has a fire tolerance, and may be directly judged to have a bacterial resistance according to its highly basic inorganic composition.

[0071] It can be known from the results above that by virtue of the environmentally friendly cement and the preparation method thereof according to the present invention, a route is found for the waste thermal insulation wool that is previously useless and should be discarded and properly disposed, such that the waste that is previously discarded is converted into a material of economic benefit. For the environmentally friendly cement and the preparation method thereof according to the present invention, the treatment procedure is simple, safe, and low in cost, thus being applicable to solve the existing problem of wastes stored in Taiwan Power Company, and of great value in industry.