Geopolymer composition and its hardened product

Abstract

To provide a geopolymer composition having excellent workability and mechanical properties in an obtained cured product, as well as excellent stability of its quality, and to provide the cured product thereof.SOLUTION: A geopolymer composition comprises: metakaolin with an average particle size D50 of 3 to 12 μm on a piece count basis, and a vitrification ratio of 92% or higher; and an aqueous alkaline activator solution. A cured product thereof is also provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to geopolymer compositions and cured products thereof. [Background technology]

[0002] The geopolymer method, which uses geopolymer compositions to obtain hardened products, is being researched as an alternative technology to the conventional production of hardened cement because it produces less carbon dioxide and can effectively use industrial by-products as raw materials. Such geopolymer compositions contain a filler containing aluminum and silicon, and an alkali source that activates and hardens the filler.

[0003] Fillers used in geopolymer compositions are mainly industrial by-products such as fly ash, blast furnace slag, sewage incineration sludge, etc. For example, Patent Document 1 describes a geopolymer composition made from a filler, preferably fly ash, blast furnace slag, sewage incineration sludge, etc., an alkali activator, and aggregate.

[0004] However, since the quality of such industrial by-products is unstable, the geopolymer compositions obtained using them have problems such as unstable workability and the quality of the hardened product, for example, mechanical strength. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-239446 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a geopolymer composition and a cured product thereof that have excellent workability and mechanical properties in the resulting cured product, as well as excellent quality stability. [Means for solving the problem]

[0007] In order to solve the above problem, according to one aspect of the present invention, the number-based average particle diameter D 50 A geopolymer composition is provided, which contains metakaolin having a particle size of 3 to 12 μm and a vitrification rate of 92% or more, and an aqueous alkali activator solution.

[0008] In the geopolymer composition of the present invention, the content of the alkaline activator in the alkaline activator aqueous solution is 10 to 60 mass %, and the amount of the alkaline activator aqueous solution relative to 100 mass parts of the metakaolin is preferably 70 to 140 mass parts.

[0009] The geopolymer composition of the present invention may further contain an aggregate, and in that case, the amount of the aggregate is preferably 200 to 700 parts by mass relative to 100 parts by mass of the metakaolin.

[0010] According to another aspect of the present invention, there is provided a cured product of the geopolymer composition of the present invention. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a geopolymer composition and its cured product that have excellent workability and mechanical properties in the resulting cured product, as well as excellent quality stability. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing the relationship between the average particle size D50 of metakaolin and the flow value in the geopolymer compositions (1 to 5) shown in the examples. [Figure 2] 1 is a graph showing the relationship between the vitrification rate of metakaolin in geopolymer compositions (1 to 5) shown in the examples and the compressive strength of the hardened product. [Figure 3]1 is a graph showing the relationship between the content ratio of an alkaline activator aqueous solution to metakaolin and the flow value in geopolymer compositions (6 to 11) shown in the examples. [Figure 4] 1 is a graph showing the relationship between the content ratio of an aqueous alkaline activator solution to metakaolin in geopolymer compositions (6 to 11) shown in the examples and the compressive strength of the hardened product. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes embodiments of the present invention. However, although the embodiments described below are subject to various limitations that are technically preferable for carrying out the present invention, the scope of the invention is not limited to the following embodiments. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower and upper limits.

[0014] [Geopolymer composition] The geopolymer composition of the present invention has an average particle size D 50 The composition contains metakaolin (hereinafter also referred to as metakaolin (A)) having a particle size of 3 to 12 μm and a vitrification rate of 92% or more, and an aqueous solution of an alkaline activator.

[0015] As described above, the geopolymer composition contains a filler containing aluminum and silicon (hereinafter simply referred to as "filler") and an alkali source that activates and hardens the filler. In the geopolymer composition of the present invention, metakaolin (A) is contained in the geopolymer composition as a filler. The aqueous alkali activator solution also functions as an alkali source.

[0016] The geopolymer composition of the present invention may contain optional components other than metakaolin (A) and the alkaline activator aqueous solution, as long as the effects of the present invention are not impaired. Examples of optional components include fillers other than metakaolin (A). The geopolymer composition of the present invention may also contain aggregate as an optional component. Furthermore, other optional components other than bone may also be contained. Each component will be described below.

[0017] <Metakaolin (A)> Metakaolin is a kaolin (chemical composition: Al4Si4O 10 Metakaolin (A) is an amorphous powder that satisfies the following requirements (1) and (2):

[0018] (1) Number-based average particle size D 50 is 3 to 12 μm. (2) The vitrification rate is 92% or more.

[0019] Regarding the requirement of (1), unless otherwise specified, the average particle size D 50 is the average particle size D 50 The average particle size of metakaolin is D 50 However, if the particle size is less than 3 μm, the flow value, which is one of the indicators of workability in geopolymer compositions, is insufficient. 50 However, if the particle size exceeds 12 μm, sufficient flow value cannot be obtained as above. 50 The flow value can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer. The flow value can be measured as a fresh test of the geopolymer composition, for example, using a method in accordance with JIS R 5201.

[0020] Figure 1 shows the average particle size D of metakaolin in each geopolymer composition shown in the examples. 50 2 is a graph showing the relationship between the average particle diameter of metakaolin and the flow value. Considering workability, the flow value needs to be, for example, about 140 mm or more. 50 If the average particle size D of metakaolin (A) is within the above range, the geopolymer composition can achieve a flow value of 140 mm or more. 50 The thickness is preferably in the range of 6 to 11 μm, more preferably in the range of 7 to 10 μm.

[0021] Regarding requirement (2), if the vitrification rate of metakaolin is less than 92%, the cured geopolymer composition will not have sufficient compressive strength. The vitrification rate can be measured, for example, by X-ray diffraction using the following method (I) or (II).

[0022] (I) To measure the vitrification rate of metakaolin, for example, the main peak area S of the crystalline mineral is measured in advance by X-ray diffraction for a sample before heating, and after heating at 1000°C for 2 hours, the sample is slowly cooled at a rate of 1 to 10°C / min, and the main peak area S of the crystalline mineral after heating is determined by X-ray diffraction. Using these S0 and S values, the vitrification rate χ is calculated using the following formula. Vitrification rate χ (%) = 100 × (1-S / S0)

[0023] (II) The vitrification rate (%) of metakaolin can also be calculated by fitting the crystalline portion (peak) and the amorphous portion halo from the X-ray diffraction pattern measured by X-ray diffractometry, and then applying the integrated intensity of each to the following equation:

[0024] Vitrification rate (%) = 100 - (100 × Ic / (Ic + Is)) Ic: Crystalline scattering integrated intensity Is: Amorphous scattering integrated intensity

[0025] In the present invention, method (II) can be preferably used. Figure 2 is a graph showing the relationship between the vitrification rate of metakaolin and the compressive strength in each geopolymer composition shown in the examples. Considering durability, the compressive strength is, for example, 20 N / mm 2 The compressive strength can be measured, for example, by a method conforming to JIS A 1108.

[0026] If the vitrification rate of metakaolin is within the above range, the hardened product of the geopolymer composition will have a strength of 20 N / mm 2The upper limit of the vitrification rate of metakaolin (A) is 100%. The vitrification rate of metakaolin (A) is preferably 92 to 99%, more preferably 94 to 98%.

[0027] In order to activate metakaolin (A), the specific surface area of ​​the powder is increased to 12 m 2 The specific surface area of ​​the powder is preferably a value calculated by the BET method, for example.

[0028] The method for activating metakaolin is not limited, but methods such as pulverization and classification, application of mechanical energy, and thermal spraying can be used.

[0029] Any known method can be used for the pulverization and classification. Pulverization can be performed using a jet mill, a roll mill, a ball mill, or the like. Classification can be performed using a sieve, specific gravity, wind force, wet sedimentation, or the like. These methods can be used in combination as desired.

[0030] Methods for applying mechanical energy include those using a ball media mill, a media-agitated mill, a roller mill, etc. The applied mechanical energy is preferably 0.5 kWh / kg or more and 30 kWh / kg or less to minimize the load while maintaining adequate activation. By setting the energy in this range, depending on the metakaolin used as the raw material, sufficient modification of the crystal structure can be achieved, improving the reactivity of the metakaolin powder at room temperature. Furthermore, recrystallization of minerals such as spinel and mullite in the metakaolin powder can be suppressed, maintaining or improving reactivity at room temperature.

[0031] The thermal spraying method is a thermal spraying technique used for ceramic coating. Examples of the thermal spraying technique include plasma spraying, high-energy gas spraying, and arc spraying. Preferably, the material powder is melted at a temperature of 2000°C to 16000°C, sprayed at a speed of 30 m / s to 800 m / s, and sprayed to a surface having a specific surface area of ​​12 m. 2 / g or more 100m 2It is preferable to make the powder to have a density of 1 / g or less.

[0032] The vitrification rate of the metakaolin (A) can be adjusted, for example, by appropriately adjusting the firing conditions during the preparation. 50 can be adjusted by a conventionally known method such as pulverization and classification. Alternatively, commercially available metakaolin that satisfies the above conditions (1) and (2) may be appropriately selected and used.

[0033] The content of metakaolin (A) in the geopolymer composition is the remainder obtained by subtracting the content of components other than metakaolin (A), as described below, from the total amount of the geopolymer composition.

[0034] <Other fillers> The geopolymer composition of the present invention may contain fillers other than metakaolin (A) as long as the effects of the present invention are not impaired. Other fillers are not limited to fillers containing aluminum and silicon, and include, for example, fly ash, blast furnace slag, sewage incineration sludge, incineration ash, rice husk ash, clinker ash, zeolite, etc. Among these, JIS-standardized fly ash and blast furnace slag are preferred.

[0035] Fly ash is a fine ash recovered from exhaust gas in a dust collector, among the coal ash by-products produced during coal combustion at coal-fired power plants and other facilities. It is primarily composed of silica (SiO2) and alumina (Al2O3), and is classified into classes I to IV in JIS A 6201 based on particle size and flow value. Classes I and II, which have fine particle size and high reactivity, are preferred.

[0036] Blast furnace slag is a by-product of producing pig iron in a blast furnace, and is preferably JIS A 6206 compliant, with CaO, SiO2, Al2O3, and MgO as its main components.

[0037] The proportion of the other fillers relative to the total amount of metakaolin and the other fillers is, for example, preferably 50% by mass or less, and more preferably 30% by mass or less.

[0038] As an additive to the geopolymer composition, metal ions other than those eluted from the filler (e.g., Al 3+ , Si 4+ Solutions containing metal salts, solids such as complexes, and fillers with different metal ion contents can be added in any ratio. In addition, by adding this additive at any timing from before the hardening of the geopolymer composition begins to during hardening, it is possible to control the strength of the geopolymer composition.

[0039] Furthermore, by using metal salts, complexes, or fillers with different solubilities or metal ion contents, it is possible to control the amount of metal ions leached out and thereby control the hardening time of the geopolymer composition.

[0040] <Alkaline activator aqueous solution> The alkaline activator aqueous solution is prepared by dissolving an alkaline activator in water. Examples of the alkaline activator include alkali metal salts and alkali metal silicates. Examples of the alkali metal salts include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of the alkali metal silicates include lithium silicate, sodium silicate, and potassium silicate. These may be used alone or in combination of two or more.

[0041] Among these, sodium silicate is more preferably used because of its availability, etc. Commercially available sodium silicate products include sodium silicate Nos. 1 to 3, sodium silicate No. 4, and sodium metasilicate Nos. 1 and 2 according to JIS standard (K1408).

[0042] Alkali metal silicates are generally represented by the molecular formula MO·nSiO (M represents an alkali metal), and refer to compositions in which n is in the range of 0.5 to 4.0, or mixtures thereof. n is preferably in the range of 0.7 to 3.0, and more preferably in the range of 1.0 to 2.0. n can be adjusted as desired by mixing the above-mentioned alkali metal silicate with an alkali metal hydroxide, such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. The alkali metal hydroxide can be used in either a solid or aqueous solution form.

[0043] The content of the alkaline activator in the alkaline activator aqueous solution is preferably 10 to 60 mass%, more preferably 15 to 50 mass%, and further preferably 20 to 45 mass%. The molar ratio of the alkaline activator to water in the alkaline activator aqueous solution, alkaline activator / water, is preferably 0.1 or more, and more preferably in the range of 0.15 to 0.23.

[0044] The amount of the alkaline activator aqueous solution per 100 parts by mass of metakaolin in the geopolymer composition is preferably 70 to 140 parts by mass, more preferably 80 to 120 parts by mass. The amount of the alkaline activator per 100 parts by mass of metakaolin is preferably 7 to 84 parts by mass, more preferably 8 to 72 parts by mass.

[0045] <Aggregate> The geopolymer composition may optionally contain aggregate, which can be used to make concrete or mortar.

[0046] The aggregate can be any aggregate commonly used in concrete and mortar. It is classified into fine aggregate and coarse aggregate depending on particle size, natural aggregate and artificial aggregate depending on origin, and lightweight aggregate, normal aggregate and heavy aggregate depending on density. One type of aggregate can be used alone, or two or more types can be used in combination.

[0047] The content of the aggregate in the geopolymer composition is preferably 200 to 700 parts by mass as the amount of aggregate relative to 100 parts by mass of metakaolin (A).

[0048] The content of aggregate in the geopolymer composition can be adjusted appropriately depending on the application. For example, when using the geopolymer composition as mortar, the content of aggregate is preferably 200 to 450 parts by mass, more preferably 250 to 380 parts by mass, per 100 parts by mass of metakaolin (A). When using the geopolymer composition as concrete, the content of aggregate is preferably 300 to 700 parts by mass, more preferably 350 to 600 parts by mass, per 100 parts by mass of metakaolin (A).

[0049] <Other optional ingredients> In addition to the aggregate, the geopolymer composition may contain various admixtures and additives as optional components, as long as they do not impair the effects of the present invention. Examples of other optional components include fluidizers, shrinkage reducing agents, rust inhibitors, waterproofing agents, setting retarders, antifoaming agents, dust reducing agents, pigments, calcium carbonate powder, etc.

[0050] The geopolymer composition may contain a reinforcing material as an optional component. The reinforcing material may be, for example, an iron-containing material. The shape of the reinforcing material may be, for example, short fiber, spherical, rod-like, or three-dimensional. It is preferable to use a plurality of steel fiber materials formed into short fibers. The mixing ratio of the steel fiber material to the geopolymer composition is preferably 0.5 to 2 vol%, more preferably 0.5 to 1 vol%.

[0051] When a geopolymer composition contains an iron-containing reinforcing material, the iron component contained in the reinforcing material is incorporated as a metal component into the polymerization reaction of the geopolymer composition during the hardening process (described below). This iron component and the silicon component contained in the geopolymer composition are chemically bonded together when the composition hardens. This results in a strong bond between the geopolymer composition and the reinforcing material, improving the durability of the entire geopolymer structure. The aggregate used as a raw material for the geopolymer composition may also contain iron. In this case, the compressive strength of the geopolymer composition can be improved.

[0052] The geopolymer composition of the present invention is preferably obtained by mixing the essential components consisting of the metakaolin (A) and the alkaline activator aqueous solution described above and the optional components to be blended as needed, preferably in the above content ratio.

[0053] The method for mixing each component may be a method of adding and mixing all components at the same time, or a method of adding and mixing components sequentially. When the geopolymer composition contains aggregate, for example, a method may be used in which metakaolin (A) and an aqueous alkali activator solution are first mixed, and then the aggregate is added and mixed, or a method may be used in which metakaolin (A) and an aggregate are first mixed, and then the aqueous alkali activator solution is added and mixed. In this case, other optional components may be added first or later.

[0054] The equipment used for mixing is not particularly limited, and examples include various mixers such as a forced twin-screw mixer used for mixing concrete. As for mixing conditions, the temperature is not particularly adjusted, and the mixture is typically carried out at room temperature (15 to 25°C). The mixing time is adjusted appropriately so that the mixture is uniform throughout.

[0055] (Physical properties of geopolymer compositions) The geopolymer composition of the present invention preferably has a flow value of 140 mm or more, more preferably 150 mm or more, and particularly preferably 160 mm or more, measured under the following conditions in a fresh test, for example, according to a method conforming to JIS R5201. The flow value can be measured specifically using a mortar flow tester (manufactured by Maruto Seisakusho). The flow value was determined based on the average value of the maximum diameter and the diameter perpendicular to the maximum diameter in the 15-hit flow after 15 drops.

[0056] [Cured geopolymer composition] The hardened geopolymer composition of the present invention can be obtained by treating (curing) the geopolymer composition obtained as described above at a predetermined temperature for a predetermined time. The hardening of the geopolymer composition occurs when the filler is activated by an alkaline activator, and the silicon and metal components contained in the filler are polymerized.

[0057] The curing conditions may be underwater curing or sealed curing. The curing temperature is, for example, about 5 to 90°C, preferably about 15 to 75°C. The curing time is adjusted appropriately depending on the temperature. For example, at room temperature of about 5 to 35°C, the curing time is preferably about 1 to 14 days, more preferably about 2 to 10 days. At high temperatures of about 35 to 90°C, the curing time is preferably about 3 hours to 10 days. A period of 6 hours to 7 days is more preferable.

[0058] (Physical properties of the cured product) The compressive strength of the cured product of the geopolymer composition of the present invention, measured, for example, by a method according to JIS A 1108, is 20 N / mm 2 It is preferable that the resistance is 24N / mm or more. 2 More preferably, it is 30N / mm 2 More preferably, it is equal to or greater than this. [Example]

[0059] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C).

[0060] [Examples 1-5] Average particle size D as shown in Table 1 50 Geopolymer compositions 1 to 5 were produced by mixing five types of metakaolin MK1 to MK5 with different vitrification rates, an aqueous alkali activator solution, and aggregate in the amounts shown in Table 1. The aqueous alkali activator solution was GP1 (product name: manufactured by Toso Sangyo Co., Ltd., an aqueous solution of sodium silicate:water (molar ratio) = 0.11:1, density 1.40 g / cm). 3 ) was used as the aggregate. Standard sand (Toyoura standard sand, density 2.56 g / cm) was used as the fine aggregate. 3 ) was used.

[0061] The geopolymer composition was produced by adding metakaolin, an aqueous alkali activator solution, and aggregate to a mixer (approximately 5 liters, manufactured by Maruto Seisakusho) and kneading them under the mixing conditions shown in Table 1 to obtain a geopolymer composition. In the mixing conditions in Table 1, "H" indicates that the rotation speed of the device was set high, and "L" indicates that the rotation speed of the device was set low. Of the resulting geopolymer compositions, geopolymer compositions 2, 3, and 4 are geopolymer compositions of the present invention (Examples). Geopolymer compositions 1 and 5 are geopolymer compositions outside the scope of the present invention (Comparative Examples).

[0062] (evaluation) For the geopolymer compositions 1 to 5 obtained above, the flow values ​​were measured under the above conditions as fresh tests using a method conforming to JIS R5201. Furthermore, for geopolymer compositions 1 to 5, hardened specimens were prepared by hardening them under the following conditions, and their compressive strengths were measured using a method conforming to JIS A 1108. For the hardened specimens of geopolymer compositions 1 to 5, two cylindrical specimens measuring φ50 mm and H100 mm were used, which were heat-cured (sealed and cured at 70°C for 7 days), and the compressive strength was calculated as the average of the two specimens. The results are shown in the right column of Table 1.

[0063] [Table 1]

[0064] In addition, from the data in Table 1, the average particle size D of metakaolin in the geopolymer compositions (1 to 5) shown in Figure 1 50 We created a graph showing the relationship between the vitrification rate of metakaolin and the flow value, and a graph showing the relationship between the vitrification rate of metakaolin in the geopolymer compositions (1 to 5) shown in Figure 2 and the compressive strength of the hardened product.

[0065] [Examples 6-11] Geopolymer compositions 6 to 11 having the compositions shown in Table 2 were produced in Examples 6 to 11 as follows.

[0066] In geopolymer compositions 6 to 11, metakaolin (A) has an average particle size D shown in Table 1 50 Metakaolin MK3 with a particle size of 9.0 μm and a vitrification rate of 95.8% was used. The alkaline activator aqueous solution and aggregate used were the same as those used in Examples 1 to 5. The composition of each composition was as shown in Table 2. The mixer used was the same as that used in Examples 1 to 5 above.

[0067] Geopolymer compositions 6-8 were produced by adding metakaolin and an aqueous alkali activator solution to a mixer and kneading them at low speed (L) for 60 seconds. Next, aggregate was added to the mixer and kneaded at low speed (L) for 60 seconds (hereinafter, this production method will be referred to as "M-1"). Geopolymer compositions 9-11 were produced by adding metakaolin and aggregate to a mixer and kneading them at low speed (L) for 30 seconds. Next, an aqueous alkali activator solution was added to the mixer and kneaded at low speed (L) for 90 seconds (hereinafter, this production method will be referred to as "M-2"). The paste volume rate (%) including air (2%) was 47% for all compositions.

[0068] (evaluation) Geopolymer compositions 6 to 11 obtained above are all geopolymer compositions of the present invention (Examples). The flow values ​​of geopolymer compositions 6 to 11 obtained above were measured in the same manner as above. Furthermore, for geopolymer compositions 6 to 11, the cured products were prepared in the same manner as above, except that the heat curing conditions were 70°C and sealed curing for 9 hours, and the compressive strength was measured according to a method in accordance with JIS A 1108. The results are shown in the right column of Table 2.

[0069] [Table 2]

[0070] In addition, from the data in Table 2, we created a graph showing the relationship between the content ratio of the alkaline activator aqueous solution to metakaolin in the geopolymer compositions (6 to 11) shown in Figure 3 and the flow value, and a graph showing the relationship between the content ratio of the alkaline activator aqueous solution to metakaolin in the geopolymer compositions (6 to 11) and the compressive strength of the hardened product shown in Figure 4.

Claims

1. Number-based average particle size D ５０ A geopolymer composition containing metakaolin having a particle size of 3 to 12 μm and a vitrification rate of 92% or more, and an alkaline activator aqueous solution.

2. The content of the alkaline activator in the alkaline activator aqueous solution is 10 to 60% by mass, and the amount of the alkaline activator aqueous solution relative to 100 parts by mass of the metakaolin is 70 to 140 parts by mass. The geopolymer composition according to claim 1.

3. The geopolymer composition according to claim 1 or 2, further comprising an aggregate.

4. The geopolymer composition according to claim 3, wherein the amount of the aggregate relative to 100 parts by mass of the metakaolin is 200 to 700 parts by mass.

5. A hardened product of the geopolymer composition according to any one of claims 1 to 4.

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