Co2-immobilizing expansive material, cement composition, and concrete composition

Abstract

This CO2-immobilizing expansive material contains an ettringite-forming compound that forms ettringite. The ettringite-forming compound preferably contains free lime as a mineral composition.

Description

CO2 fixation expanding material, cement composition, and concrete composition

[0001] The present invention is ２ The present invention relates to a fixed expansive material, a cement composition, and a concrete composition.

[0002] Reducing cracks in cement and concrete is important from the perspectives of reliability, durability, aesthetics, etc. of products and structures. Therefore, further technological advances in expansive additives that can improve these aspects are desired.

[0003] In addition, 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.

[0004] In this situation, 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.

[0005] Japanese Patent Application Laid-Open No. 2020-15659

[0006] 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 fix the adhesive. There is also no disclosure of an expanding agent.

[0007] From the above, the present invention provides a method for producing a gas having good expansion performance and CO ２ CO with fixation ability ２ The object is to provide a fixed expanding material.

[0008] 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.

[0009] [1] CO containing an ettringite-forming compound that forms ettringite ２ [2] The CO2 according to [1], wherein the ettringite-forming compound contains free lime as a mineral composition. ２ [3] The CO 2 according to [2], containing 10 to 70 mass % of the free lime. ２ [4] The CO2 according to any one of [1] to [3], wherein the ettringite-forming compound contains auyne as a mineral composition. ２ [5] The CO2 composition according to any one of [1] to [4], wherein the ettringite-forming compound contains ternesite and / or gehlenite as a mineral composition. ２ [6] The CO 2 composition according to [5], wherein the content (total content) of the ternesite and the gehlenite in the ettringite-forming compound is 2 to 15 mass%. ２ Fixed expansion material. [7] Blaine specific surface area is 2000 to 6000 cm ２ / g of CO according to any one of [1] to [6]. ２ [8] The CO2 according to any one of [1] to [7], which is mixed with cement. ２ [9] The CO according to any one of [1] to [8]. ２

[10] A cement composition comprising a fixed expansive material and cement.

[11] The CO composition according to any one of [1] to [8]. ２ A concrete composition comprising a fixed expansive material, cement, and aggregate.

[0010] According to the present invention, good expansion performance and CO ２ CO with fixation ability ２ A fixed expanding material can be provided.

[0011] Hereinafter, one embodiment of the present invention (the present embodiment) will be described in detail.

[0012] [CO ２Fixed Expansion Material] CO ２ The fixed expansive material contains an ettringite-forming compound that forms ettringite. ２ In cement compositions and concrete compositions containing fixed expansive materials, ettringite is generated as it solidifies, and carbon dioxide (CO ２ ) by capturing CO ２ is absorbed. ２ The expansion performance of the fixed expansive material allows it to exhibit a good expansion effect. Here, the term "solidification" refers to a condition in which the compressive strength is 2.5 N / mm2 or less in accordance with the method specified in JIS R 5201:2015 "Physical Testing Methods for Cement." ２ This refers to a state in which:

[0013] The aforementioned CO ２ Regarding absorption, depending on the conditions such as humidity, the generated ettringite absorbs a large amount of CO (1 to 3 moles, 4.2 moles, or 4.6 moles of ettringite) according to one 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 3CaSO４ ・30.9H ２ O + 4.2CO ２ → 3CaCO ３ +Al ２ O ３ ・7.9H ２ O. 1.2CO ２ + 3CaSO ４ ・2H ２ O+17.0H ２ O

[0014] 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.

[0015] 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 mainly composed of CaO.2Al 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 Crystalline calcium aluminate, such as CaF2, is one example. ２ O ３The 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.

[0016] 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.

[0017] 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 1300°C to 1600°C. The CSA is not particularly limited, but may be, for example, CaO:Al 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.

[0018] From the viewpoint of expansion coefficient, the ettringite-forming compound preferably contains free lime as a mineral composition. The ettringite-forming compound preferably contains 3 to 80 mass% of free lime, more preferably 15 to 65 mass%. By containing 3 to 80 mass% of free lime, excellent expansion performance can be ensured.

[0019] Furthermore, from the viewpoint of ensuring expansion coefficient and strength, the ettringite-forming compound preferably contains auyne as a mineral composition. The ettringite-forming compound preferably contains 1 to 30 mass% of auyne, more preferably 3 to 25 mass%. By containing 1 to 30 mass% of auyne, it is possible to achieve both excellent expansion performance and strength development.

[0020] Ettringite-forming compounds are efficient CO ２ From the viewpoint of CO fixation, it is preferable that the mineral composition contains ternesite and / or gehlenite. The total amount of ternesite and gehlenite in the ettringite-forming compound is preferably 2 to 15 mass%, more preferably 3 to 10 mass%. By containing ternesite and gehlenite in a total amount of 2 to 15 mass%, CO fixation can be achieved more efficiently. ２ The above content of ternesite can be achieved, for example, by mixing silicon dioxide as a reagent into the raw material.

[0021] 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.

[0022] 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. For example, the alkaline earth metal sulfate may be used in an amount of 1000 to 150 ... 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.

[0023] 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.

[0024] 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 %.

[0025] In addition, good strength and CO ２ From the viewpoint of the immobilization amount, the content of calcium sulfate as a mineral composition in the ettringite-forming compound is preferably 2 to 75 mass%, more preferably 10 to 70 mass%. The mineral composition of free lime, auyne, ternesite, gehlenite, calcium sulfate, etc. in the ettringite-forming compound can be measured by the XRD / Rietveld method.

[0026] The Blaine specific surface area of ​​the ettringite-forming compound is 1,500 to 8,000 cm from the viewpoint of fully exerting its function. ２ / g, and 2,000 to 7,000 cm ２ It is more preferable that the SiO2 content is 1 / g.

[0027] CO of this embodiment ２In order to fully demonstrate its function, the fixed expansive 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 / g, and more preferably 2,000 to 6,000 cm ２ It is more preferable that the SiO2 content is 1 / g.

[0028] From the viewpoint of fully exerting its function, the ettringite-forming compound is ２ The content of the solidified expansive material is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0029] Also, CO ２ 100 parts by mass of the fixed expansive material was mixed with 50 parts by mass of water, and the mixture was cured for 24 hours. The solidified material was then stored at 20°C and 60% RH in a CO ２ CO when left standing in a 5% concentration environment for 24 hours ２ The fixation rate is preferably 9% or more, and more preferably 10% or more. Here, the fixation rate can be determined as 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 fixed expansive material can be used for various purposes as it is or mixed with other materials, but considering the long-term durability of the solidified material when it is in use and the application of existing technologies related to maintenance and management, it is preferable that it be used as a mixture with cement or concrete.

[0031] [Cement composition and concrete composition] The cement composition according to this embodiment is a CO ２ The concrete composition according to this embodiment contains a fixed expansive material and cement. ２ The cement composition in this embodiment includes a fixed expansive material and cement. Note that the cement composition in this embodiment is a general term for cement, cement paste, and mortar.

[0032] CO ２ The content of the fixed expansive material is determined based on the expansiveness and CO per 100 parts by mass of cement.２ From the viewpoint of achieving good immobilization, the amount 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.

[0033] 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 medium-heat cements; various blended cements obtained by blending these cements with blast furnace slag, fly ash, or silica fume; environmentally friendly cements (ecocements) produced using municipal waste incineration ash or sewage sludge incineration ash as raw materials; siliceous materials such as metakaolin and clay calcined ash; and commercially available fine particle cements. Various cements and blended cements can also be finely powdered and used. Furthermore, cements containing components normally used in cement (e.g., gypsum) 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.

[0034] In addition, from the viewpoint of manufacturing costs and strength development, the Blaine specific surface area of ​​cement is 2,500 to 7,000 cm ２ / g, and 2,750 to 6,000 cm ２ In this specification, the Blaine specific surface area is determined in accordance with JIS R 5201 (physical testing methods for cement).

[0035] Examples of fine aggregates used in this embodiment include river sand, mountain sand, land sand, sea sand, silica sand, crushed sand, crushed lime sand, blast furnace slag fine aggregate, recycled fine aggregate, etc. The type and content of the fine aggregate may be selected depending on the target mechanical strength of the hardened concrete body.

[0036] Examples of coarse aggregates used in this embodiment include crushed stone such as andesite, rhyolite, hard sandstone, and limestone, as well as river gravel, mountain gravel, land gravel, blast furnace slag coarse aggregate, and recycled coarse aggregate. The rock type, size, and content of the coarse aggregate may be selected depending on the target mechanical strength of the hardened concrete body.

[0037] In this embodiment, various additives may be contained, such as a water reducing agent, an air entraining agent, a foaming agent, a shrinkage reducing agent, a waterproofing agent, a rust inhibitor, a thickener, a polymer, a water retention agent, a pigment, a water repellent, and an efflorescence inhibitor.

[0038] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0039] [Experimental Example 1] <CO ２ Preparation of fixed expansive material> Calcium carbonate reagent, aluminum hydroxide reagent, calcium sulfate reagent, and silicon dioxide reagent were mixed to obtain the composition shown in Table 1 below, and heat-treated at 1350°C for 3 hours to obtain a solidified expansive material with a Blaine specific surface area of ​​3500 cm ２ / g to prepare an ettringite-forming compound, which was then mixed with CO ２ It was used as a fixed expansion material.

[0040] (Evaluation) <Strength> A composition with a water / powder mass ratio of 0.5 and a fine aggregate / powder mass ratio of 3.0 was molded into a 40 x 40 x 160 mm test piece, and the strength was measured at 1, 3, and 7 days (JIS R 5201:2015 "Physical Testing Methods for Cement"). The ettringite-forming compound was mixed with the powder at 5 mass%. Note that the "powder" refers to the total of the ettringite-forming compound and cement (ordinary Portland cement). Silica sand was used as the fine aggregate. After demolding at 1 day, the test pieces were stored at a temperature of 20°C, humidity of 60% RH, and CO ２ Carbonation curing was carried out under the condition of a concentration of 5%.

[0041] <CO ２ Solid absorption (CO ２ Content rate, CO ２ A paste with a water / powder mass ratio of 0.5 was molded into a 20 x 20 x 80 mm specimen, and after demolding at 1 day old, the specimen was stored at a temperature of 20°C, humidity of 60% RH, and CO ２ The carbonation curing was carried out under the condition of a concentration of 5%. The ettringite-forming compound was mixed with the powder at 6.7 mass%. After that, the test specimens were crushed to 90 μm or less at a predetermined age, and the CO ２ The content was measured. The "powder" mentioned above refers to the total of the ettringite-forming compound and cement (ordinary Portland cement).

[0042] <Expansion> A composition with a water / powder mass ratio of 0.5 and a fine aggregate / powder mass ratio of 3.0 was molded into a 40 x 40 x 160 mm test piece, and the length change rate (JIS A 6202:2017 "Expansive additive for concrete") at ages of 7 and 28 days was measured. After demolding at age 1 day, the test piece was stored at a temperature of 20°C, humidity of 60% RH, and CO ２ Carbonation curing was carried out under the condition of a concentration of 5%. The "powder" mentioned above refers to the total of the ettringite-forming compound and cement (ordinary Portland cement). The ettringite-forming compound was mixed in an amount of 6.7% by mass relative to the powder. Silica sand was used as the fine aggregate.

[0043]

Claims

1. CO containing ettringite-forming compounds that form ettringite ２ Fixed expansion material.

2. The CO2 according to claim 1, wherein the ettringite-forming compound contains free lime as a mineral composition. ２ Fixed expansion material.

3. The CO according to claim 2, containing 10 to 70 mass % of the free lime. ２ Fixed expansion material.

4. The CO2 according to claim 1, wherein the ettringite-forming compound contains auyne as a mineral component. ２ Fixed expansion material.

5. The CO2 according to claim 1, wherein the ettringite-forming compound contains ternesite and / or gehlenite as a mineral composition. ２ Fixed expansion material.

6. The CO composition according to claim 5, wherein the content of the ternesite and the gehlenite in the ettringite-forming compound is 2 to 15 mass %. ２ Fixed expansion material.

7. Blaine specific surface area is 2000 to 6000 cm ２ / g of CO ２ Fixed expansion material.

8. The CO2 of claim 1 mixed with cement. ２ Fixed expansion material.

9. CO according to any one of claims 1 to 8 ２ A cement composition comprising a fixed expansive material and cement.

10. CO according to any one of claims 1 to 8 ２ A concrete composition comprising a fixed expansive material, cement, and aggregate.

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