Co2 absorbing and solidifying material and cement composition

Abstract

Provided is a CO2 absorbing and solidifying material containing an ettringite-generating compound for generating ettringite, wherein the ettringite-generating compound is preferably a combination of a sulfate and at least one among a calcium sulfoaluminate and a calcium aluminate.

Description

CO2 absorption solidification material and cement composition

[0001] The present invention is ２ The present invention relates to an absorbent solidification material and a cement composition.

[0002] CO emitted during the production of concrete products ２ In order to reduce the total amount of cement used, it is effective to reduce the amount of cement used by incorporating large amounts of special additives or industrial by-products (ground granulated blast furnace slag, fly ash, etc.) as cement substitutes, and various research projects are being conducted on this topic.

[0003] On the other hand, CO ２ For example, Patent Document 1 describes a technology that absorbs (fixes) CO during production. ２ Specifically, the method for immobilizing carbon dioxide includes a contacting step of bringing a carbon dioxide-containing gas into contact with a cementitious hardened body to immobilize carbon dioxide contained in the carbon dioxide-containing gas in the cementitious hardened body.

[0004] Japanese Patent Application Laid-Open No. 2020-15659

[0005] However, the fixation method of Patent Document 1 requires that the water content in the carbon dioxide-containing gas be 1.5% or more and that the temperature be 75 to 175°C. ２ There is no disclosure or suggestion of a material that can immobilize the

[0006] From the above, the present invention is a method for producing CO after solidification. ２ CO that can absorb well ２ The object is to provide an absorbent solidification material.

[0007] As a result of intensive research to solve the above problems, the present inventors have come up with the following invention and found that the above problems can be solved.

[0008] [1] CO containing an ettringite-forming compound that forms ettringite ２[2] The CO absorbing and solidifying material according to [1], wherein the ettringite-forming compound is a combination of at least one of calcium sulfoaluminate and calcium aluminate with a sulfate. ２ [3] The CO2 absorbing and solidifying material according to [1] or [2], wherein the ettringite-forming compound is calcium sulfoaluminate and contains auyne as a mineral composition. ２ Absorbent solidification material. [4] Furthermore, γ-2CaO.SiO ２

[0023] The CO according to any one of [1] to [3], which contains powder. ２ [5] The ettringite forming compound and the γ-2CaO.SiO ２ Mass ratio of the powder (γ-2CaO.SiO ２ [4] The CO2 powder / ettringite-forming compound (CO2 powder / ettringite-forming compound) is 5 / 95 to 84 / 16. ２ Absorbent solidification material. [6] Blaine specific surface area value is 1,500 to 8,000 cm ２ / g of CO according to any one of [1] to [5]. ２ Absorbent solidification material. [7] CO ２ 100 parts by mass of the absorbent solidification material was mixed with 50 parts by mass of water, and the mixture was cured for 24 hours. The solidified material was then subjected to CO ２ CO when left standing in a 5% concentration environment for 24 hours ２ [1] to [6], wherein the fixation rate is 25% or more. ２ [8] The CO2 absorbent solidification material according to any one of [1] to [7], which is mixed with cement. ２ [9] The CO absorbing and solidifying material according to any one of [1] to [8]. ２ A cement composition comprising an absorbent solidification material and cement.

[0009] According to the present invention, after solidification, CO ２ CO that can absorb well ２ The above "solidification" refers to a method conforming to JIS R 5201:2015 "Physical Test Methods for Cement" and having a compressive strength of 2.5 N / mm ２ This refers to a state in which:

[0010] Hereinafter, one embodiment of the present invention (the present embodiment) will be described in detail.

[0011] [CO ２ Absorbent solidification material] ２ The absorbing and solidifying material contains an ettringite-forming compound that forms ettringite. ２ Ettringite, which is generated as the absorbent solidification material solidifies, contains carbon dioxide (CO ２ ) by capturing CO ２ is absorbed.

[0012] Specifically, depending on the conditions such as humidity, the produced ettringite is converted into a large amount of CO (1 to 3 moles, 4.2 moles, or 4.6 moles of ettringite) according to any of the following formulas (1) to (3): ２ It is expected to absorb the formula (1): 3CaO·Al ２ O ３ 3CaSO ４ ・32H ２ O + 3CO ２ → 3CaCO ３ +Al ２ O ３ (gel) + 3CaSO ４ ・2H ２ O+26H ２ O Formula (2): 3CaO・Al ２ O ３ 3CaSO ４ ・31.1H ２ O + 4.6CO ２ → 3CaCO ３ +Al ２ O ３ ・10.4H ２ O 1.6CO ２ + 3CaSO ４ ・0.5H ２ O+19.2H ２ O Formula (3): 3CaO・Al ２ O ３ 3CaSO ４ ・30.9H ２ O + 4.2CO ２ → 3CaCO ３ +Al ２ O ３ ・7.9H ２O. 1.2CO ２ + 3CaSO ４ ・2H ２ O+17.0H ２ O

[0013] The ettringite forming compound according to this embodiment is not particularly limited as long as it is a compound that forms ettringite, and examples thereof include calcium sulfoaluminate, calcium aluminate, calcium fluoroaluminate, calcium chloroaluminate, alinite, Na ２ O・8CaO・3Al ２ O ３ , alums, sulfates, etc. Among these, those which exhibit good strength and CO ２ From the viewpoint of the amount of immobilization, a combination of at least one of calcium sulfoaluminate and calcium aluminate with a sulfate is preferred.

[0014] Here, calcium aluminate (CA) according to this embodiment is a mixture of CaO and Al ２ O ３ It is a general term for compounds whose main components are, for example, CaO and Al. ２ O ３ Amorphous compounds with CaO.2Al as the main component, ２ O ３ , CaO.Al ２ O ３ , 12CaO・7Al ２ O ３ , 11CaO・7Al ２ O ３ CaF ２ , and 3CaO・3Al ２ O ３ CaF ２ Among these, the CaO / Al of CA is ２ O ３ The molar ratio is preferably in the range of 0.45 to 3, more preferably in the range of 0.8 to 2. ２ O ３ When the molar ratio is 0.45 or more, sufficient early strength development can be obtained.２ O ３ When the molar ratio is 3 or less, sufficient fluidity and usable time can be obtained.

[0015] As mentioned above, calcium aluminate can be used in either crystalline or amorphous form, but amorphous form obtained by quenching a melt in an electric furnace or the like is preferred, and when the amorphous content is 60 mass % or more, excellent short-term strength development is achieved. The amorphous content (amorphous degree) can be determined by powder X-ray diffraction / Rietveld analysis.

[0016] The calcium sulfoaluminate (CSA) according to the present embodiment is produced by calcining and pulverizing raw materials such as lime, sulfate raw materials such as gypsum, and alumina raw materials such as bauxite in a kiln at about 1500°C. ２ O ３ : CaSO ４ The raw materials were mixed in a molar ratio of 3:3:1, fired, and crushed. ２ O ３ CaSO ４ ) is called.

[0017] The fineness of each of calcium aluminate and calcium sulfoaluminate is 3,000 to 9,000 cm in terms of Blaine specific surface area. ２ / g or less, and 4,000 to 7,000 cm ２ It is more preferable that the SiO2 content is 1 / g.

[0018] The sulfates include alkali metal sulfates and alkaline earth metal sulfates. Examples of the alkali metal sulfates include lithium, sodium, potassium, etc., with sodium being preferred. The alkali metal sulfates may be used alone or in combination of two or more.

[0019] Examples of the alkaline earth metal of the alkaline earth metal sulfate include magnesium and calcium, with calcium being preferred. The alkaline earth metal sulfate may be used alone or in combination of two or more. The particle size and grain size of the alkaline earth metal sulfate are not particularly limited, and examples thereof include those having a Blaine specific surface area of ​​4,000 to 8,500 cm. ２ / g. Here, the alkaline earth metal sulfate is preferably calcium sulfate, and examples thereof include anhydrous gypsum (anhydrous calcium sulfate), hemihydrate gypsum (calcium sulfate hemihydrate), and dihydrate gypsum (calcium sulfate dihydrate). Of these, anhydrous gypsum is preferred.

[0020] The amount of sulfate, in anhydrous equivalent, is preferably 7 to 60 parts by mass, more preferably 15 to 58 parts by mass, and even more preferably 20 to 57 parts by mass, per 100 parts by mass of calcium sulfoaluminate. Furthermore, the amount is preferably 40 to 160 parts by mass, more preferably 42 to 157 parts by mass, and even more preferably 45 to 155 parts by mass, per 100 parts by mass of calcium aluminate. When the content of alkaline earth metal sulfate is within the above range, excellent long-term strength development is likely to occur.

[0021] Good strength development and CO ２ From the viewpoint of the amount of immobilization, the ettringite-forming compound is preferably calcium sulfoaluminate and / or calcium aluminate, and contains auyne as a mineral composition. The ettringite-forming compound preferably contains 10 mass% or more of auyne, more preferably 15 mass% or more. The amount of auyne is determined by the ratio of CaO, Al in the raw material, and the like. ２ O ３ , S.O. ３ The upper limit is not particularly limited, but in practice it is 80 mass %.

[0022] The Blaine specific surface area of ​​the ettringite-forming compound is set to 1,500 to 8,000 cm from the viewpoint of fully exerting its function. ２ / g, and 2,000 to 7,000 cm ２It is more preferable that the SiO2 content is 1 / g.

[0023] The formed ettringite may partially decompose and become porous. If this porosity progresses too much, CO ２ Therefore, in this embodiment, the strength of the solidified body formed by the absorbing solidification material may decrease. ２ It is preferable to include γ-2CaO.SiO powder. ２ is CO ２ Reacts with CaCO ３ and SiO ２ It is expected that the strength of the solidified body will be maintained by producing a gel rich in hydroxybenzoates and filling the porous voids.

[0024] Here, γ-2CaO.SiO ２ 2CaO.SiO ２ Among the compounds represented by the formula: ２ and α'-2CaO・SiO ２ , β-2CaO・SiO ２ These are completely different from 2CaO.SiO ２ However, the crystal structure and density are different.

[0025] γ-2CaO.SiO ２ The Blaine specific surface area of ​​the powder is 1,500 to 8,000 cm in order to fully demonstrate its functions. ２ / g, and 2,000 to 7,000 cm ２ It is more preferable that the SiO2 content is 1 / g.

[0026] Ettringite-forming compounds and γ-2CaO.SiO ２ Mass ratio of the powder (γ-2CaO.SiO ２ The mass ratio of the sintered body (aluminum powder / ettringite forming compound) is preferably 5 / 95 to 84 / 16, and more preferably 15 / 85 to 75 / 25. By setting the mass ratio to 5 / 95 to 84 / 16, it is possible to improve the strength development after carbonation and to increase the amount of CO ２ It is possible to fix the

[0027] In this embodiment, CO２ The absorbent solidification material is composed of ettringite forming compound and γ-2CaO・SiO ２ When the powder is included, CO ２ From the viewpoint of achieving good strength and CO2 fixation, the auyne content in the sorbent solidification material is preferably 10% by mass or more, and more preferably 15% by mass or more. The upper limit is not particularly limited, but in practice it is 80% by mass.

[0028] CO of this embodiment ２ In order to fully demonstrate its function, the absorbent solidification material should have a Blaine specific surface area of ​​1,500 to 8,000 cm ２ / g, and 2,000 to 7,000 cm ２ It is more preferable that the SiO2 content is 1 / g.

[0029] Also, CO ２ 100 parts by mass of the absorbent solidification material was mixed with 50 parts by mass of water, and the mixture was cured for 24 hours. The solidified material was then subjected to CO ２ CO when left standing in a 5% concentration environment for 24 hours ２ The fixation rate is preferably 25% or more, and more preferably 30% or more. Here, the fixation rate can be determined by the ratio of the number of moles of reacted CaO to the number of moles of CaO before the reaction (reacted CaO-mol / before the reaction CaO-mol).

[0030] The above CO ２ The absorbent solidification material can be used for various purposes as it is or mixed with other materials, but considering the long-term durability of the solidified body when it is in use and the application of existing technologies related to maintenance and management, it is preferable that it be used for mixing with cement (cement mixing).

[0031] [Cement composition] The cement composition according to this embodiment is a cement composition according to the present invention. ２ Contains absorbent solidification material and cement. ２The content of the absorbing solidification material is preferably in the range of 5 to 90 parts by mass, and more preferably in the range of 30 to 80 parts by mass, relative to 100 parts by mass of cement. Note that the cement composition in this embodiment is a general term for cement, cement paste, mortar, concrete, and concrete composition.

[0032] The cement used in this embodiment is not particularly limited, and examples include various cements such as ordinary, early-strength, extra-early-strength, low-heat, and moderate-heat cements; various blended cements obtained by blending these cements with blast furnace slag, fly ash, silica fume, etc.; environmentally friendly cements (eco-cements) produced using municipal waste incineration ash or sewage sludge incineration ash as raw materials; and commercially available fine particle cements. Various cements and blended cements can also be finely powdered and used. Furthermore, cements prepared by increasing or decreasing the amount of components (e.g., gypsum) normally used in cements can also be used. In this embodiment, ordinary Portland cement or early-strength Portland cement is preferably selected from the viewpoints of heat of hydration, drying shrinkage, and packing properties.

[0033] From the viewpoint of manufacturing costs and strength development, the Blaine specific surface area of ​​cement is set to 2,500 to 7,000 cm ２ / g, and 2,750 to 6,000 cm ２ In this specification, the Blaine specific surface area value is determined in accordance with JIS R 5201 (physical testing methods for cement).

[0034] [Experimental Example 1] <CO ２ Preparation of Absorbent Solidification Material> (Ettringite-forming Compound) Combination of calcium sulfoaluminate (CSA) and sulfate Reagent grade calcium carbonate, reagent grade aluminum oxide, and reagent grade anhydrous gypsum were mixed in a molar ratio of 3:3:1, and the mixture was heat-treated at 1,350°C for 3 hours to produce a material with a Blaine specific surface area of ​​5,000 cm ２ An ettringite-forming compound consisting of calcium sulfoaluminate was prepared. The proportion of auyne in the calcium sulfoaluminate was measured by Rietveld analysis using powder X-ray diffraction. The results are shown in Table 1 below.

[0035] 100 parts by mass of the CSA prepared above and calcium sulfate reagent (powder of anhydrous gypsum) as a sulfate were mixed in the proportions shown in Table 1 to obtain an ettringite-forming compound (Blaine specific surface area: 5,000 cm) consisting of a combination of CSA and a sulfate. ２ / g) was prepared.

[0036] Combination of calcium aluminate (CA) and sulfate: Reagent grade calcium carbonate and reagent grade aluminum oxide were mixed in a molar ratio of 1.0:1.0, heat-treated at 1,350°C for 3 hours, and rapidly cooled to room temperature to obtain a Blaine specific surface area of ​​5,000 cm ２ 100 parts by mass of the prepared calcium aluminate and calcium sulfate reagent (powder of anhydrous gypsum) as a sulfate were mixed in the proportions shown in Table 1 to prepare an ettringite-forming compound (Blaine specific surface area: 5,000 cm) consisting of a combination of CA and a sulfate. ２ / g) was prepared.

[0037] <γ-2CaO・SiO ２ (γC ２ S) Preparation of Powder> Reagent grade calcium carbonate and reagent grade silicon dioxide were mixed in a molar ratio of 2:1, heat treated at 1,400 ° C for 2 hours, and allowed to stand at room temperature to produce a powder with a Blaine specific surface area of ​​4,000 cm ２ / g of γ-2CaO.SiO ２ A powder was produced.

[0038] Ettringite forming compound alone, or Ettringite forming compound and γ-2CaO.SiO ２ The powder was mixed in the ratio shown in the table below. ２ The absorbent solidification materials were prepared and various evaluations were carried out. The results are shown in Table 1 below.

[0039] (Evaluation) <Strength> Mortar with a water / powder ratio of 0.5 and a fine aggregate / powder ratio of 3.0 was molded into a 40 x 40 x 160 mm test piece, and carbonation was started on day 1 of age. The strength was measured after 1, 3, and 7 days of carbonation (JIS R 5201:2015 "Physical Testing Methods for Cement"). The "powder" mentioned above refers to the CSA, CA, gypsum, and γC contained therein. ２The sum of S.

[0040] <CO ２ Content rate, CO ２ Fixation rate> A paste with a water / powder (powder: CSA and gypsum or CA and gypsum) ratio of 0.5 was molded into a 20 x 20 x 80 mm test piece, cured for 24 hours, and the solidified body was then dried at 20°C and 60% RH in a CO ２ After leaving it in a 5% CO concentration environment for 24 hours, ２ By carrying out the treatment (reaction), CO ２ Content rate, CO ２ The immobilization rate was measured.

[0041] where CO ２ The content is CO ２ The treated sample was measured by TG, and the mass loss was calculated from the mass loss from 550 to 850° C. The above-mentioned “powder” refers to the CSA, CA, gypsum, and γC contained therein. ２ CO refers to the sum of S. ２ The fixation rate was calculated as the ratio of the number of moles of reacted CaO to the number of moles of CaO before the reaction (reacted CaO-mol / CaO-mol before the reaction). ２ The fixation rate was calculated as the ratio of the number of moles of reacted CaO to the number of moles of CaO before the reaction (reacted CaO-mol / CaO-mol before the reaction). ２ The amount of CaO in the absorbent solidification material (CaO-mol before reaction) was determined from the ignition loss and XRF. ２ CO after treatment ２ The content was calculated from TG, and the amount of reacted CaO (reacted CaO-mol) was determined.

[0042]

[0043] [Experimental Example 2] Commercially available ordinary Portland cement was used in Experiments No. 1-1 to 1-10 of Experimental Example 1. ２ The solidifying agent was mixed in the ratio shown in the table below to measure the cement composition. The same evaluation as in Experimental Example 1 was carried out except that a cement paste with a water / cement composition ratio of 0.5 was used. The results are shown in the table below.

[0044]

Claims

1. A CO absorption and solidification material containing an ettringite-forming compound that forms ettringite. ２ ​ 2. The CO absorption and solidification material according to claim 1, wherein the ettringite-forming compound is a combination of at least one of calcium sulfoaluminate and calcium aluminate with a sulfate. ２ Absorption and solidification material.

3. The ettringite-forming compound is calcium sulfoaluminate, and the CO ２ absorbent solidifying material according to claim 1, which contains auin as a mineral composition.

4. Further, the CO absorption and solidification material according to claim 1, which contains γ-2CaO·SiO powder. ２ ２ ​ 5. The mass ratio of the ettringite-forming compound to the γ-2CaO·SiO ２ powder (γ-2CaO·SiO ２ powder / ettringite-forming compound) is 5 / 95 to 84 / 16. The CO ２ absorption solidifying material according to claim 4.

6. The CO absorption and solidification material according to claim 1 or 4, wherein the brain specific surface area value is 1,500 to 8,000 cm ２ / g. ２ ​ 7. CO ２ A solidified body obtained by mixing 50 parts by mass of water with 100 parts by mass of the CO absorption solidifying material and curing for 24 hours was placed in an environment with a CO ２ concentration of 5% at 20°C and 60% RH and allowed to stand for 24 hours. The CO ２ immobilization rate is 25% or more. The CO absorption solidifying material according to claim 1 or 4 ２ .

8. The CO absorption and solidification material according to claim 1 or 4, which is mixed into cement ２ ​ 9. The CO according to claim 1 or 4 ２ A cement composition containing an absorption solidifying material and cement.

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