Non-hydraulic co2-curable solidifying material and carbonation-hardened body

Abstract

To provide a non-hydraulic CO2-curable solidifying material that has enhanced capacity for CO2 absorption and develops high strength.SOLUTION: A non-hydraulic CO2-curable solidifying material comprises γ-2CaO SiO2 and Merwinite as mineral compositions, and contains 2 mass% or more of γ-2CaO SiO2 and 40 mass% or less of Merwinite. It is preferable that the non-hydraulic CO2-curable solidifying material has a particle size allowing at least 40 mass% to pass through a sieve with a 90 μm aperture, and that its Blaine specific surface area is 500 cm2 / g or more and 3000 cm2 / g or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] This invention is a non-hydraulic CO2 refrigerant mainly used in the civil engineering and construction industries. 2 This invention relates to a hardening type solidification material and a carbonated hardened body. [Background technology]

[0002] Concrete uses a large amount of cement as a raw material, so it is CO 2 It is said to be a material with large emissions. This is mainly due to the use of a large amount of fossil fuels to obtain the combustion energy for the furnace in the cement production process, as well as the decarbonation reaction of limestone (CaCO 3 →CaO+CO 2 ) is generated. 2 Reducing emissions has become an important theme as part of measures to combat global warming.

[0003] 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 industrial by-products (ground granulated blast furnace slag, fly ash, etc.) as cement substitutes, and various research projects are currently being conducted on this.

[0004] On the other hand, γ-C 2 S(γ-2CaO SiO 2 By forcibly curing concrete containing non-hydraulic compounds such as belite (also called gamma phase belite) as admixtures, the CO 2 There is a known technology for obtaining highly durable concrete products with a dense surface layer through absorption (for example, Patent Document 1). 2 S does not react with water, CO 2 Reacts with CaCO 3 and SiO 2 These products fill the voids in the cement matrix and dramatically improve the durability of the surface layer of the concrete product. In this case, the CO absorbed by the concrete during the carbonation (salt) curing process is 2The total CO in obtaining concrete products by that amount will be reduced. 2 Emissions will be reduced.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, considering the future efforts towards carbon neutrality, which are attracting more and more attention, materials that can further reduce the cement content have been desired. Also, even when such cement materials are reduced, materials with high strength development ability have been desired.

[0007] The present invention has been made in view of such circumstances, and aims to provide a non-hydraulic CO hardening type solidifying material that improves the CO absorption amount and has high strength development ability, and a carbonated hardened body. 2 absorption amount and has high strength development ability, and a carbonated hardened body. 2

Means for Solving the Problems

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the present inventor has arrived at the following present invention and found that the problems can be solved. That is, the present invention is as follows. [1] As a mineral composition, it contains γ-2CaO·SiO 2 , and melilite, and the γ-2CaO·SiO 2 is contained in an amount of 2% by mass or more, and the melilite is contained in an amount of 40% by mass or less, a non-hydraulic CO 2 hardening type solidifying material. [2] The non-hydraulic CO hardening type solidifying material according to [1], having a particle size such that 40% by mass or more passes through a sieve with an opening size of 90 μm. 2 hardening type solidifying material. [3] The Blaine specific surface area is 500 cm 23000 cm / g or more 2 The non - hydraulic CO described in [1] or [2], which is / g or less 2 Hardening - type solidifying material. [4] The non - hydraulic CO described in any one of [1] to [3], containing electric furnace reduced slag 2 Hardening - type solidifying material. [5] The non - hydraulic CO described in any one of [1] to [4] 2 Carbonated hardened body composed of carbonated hardened product of non - hydraulic CO hardening - type solidifying material.

Advantages of the Invention

[0009] According to the present invention, a non - hydraulic CO 2 Hardening - type solidifying material with improved CO absorption amount and high strength development property, and a carbonated hardened body can be provided. 2

Embodiments for Carrying out the Invention

[0010] [Non - hydraulic CO 2 Hardening - type solidifying material] The non - hydraulic CO hardening - type solidifying material of the present invention 2 contains, as a mineral composition, γ - 2CaO·SiO 2 and melvinite, and contains 2 mass% or more of γ - 2CaO·SiO 2 and 40 mass% or less of melvinite.

[0011] The non - hydraulic CO hardening - type solidifying material of the present invention 2 does not harden by adding water like ordinary hydraulic solidifying materials (hydraulic cement compositions, for example, compositions mainly composed of ordinary cements such as Portland cement), but mainly hardens due to the presence of CO 2 . Since the non - hydraulic CO hardening - type solidifying material hardly reacts with water, it is less likely to cause inhibition of CO absorption by water, and the absorption of CO becomes larger, enabling the effect of reducing CO emission to be exerted. 2 2 2 2

[0012] ​​​​​(γ-2CaO·SiO 2 ) γ-2CaO·SiO 2 refers to 2CaO·SiO 2 which is known as a low-temperature phase and is completely different from the high-temperature phases α-2CaO·SiO 2 and α’-2CaO·SiO 2 , and β-2CaO·SiO 2 . All of these are represented by 2CaO·SiO 2 , but they have different crystal structures and true densities. γ-2CaO·SiO 2 does not have hydraulicity, but γ-2CaO·SiO 2 has the property of absorbing carbon dioxide in the air and hardening, that is, it has air-hardening property.

[0013] (Merwinite) Merwinite is represented by 3CaO·MgO·2SiO 2 (C 3 MS 2 ) and according to Merwinite, a large CO 2 absorption effect is achieved.

[0014] A method for producing a non-hydraulic CO 2 hardening type solidifying material containing 2% by mass or more of γ-2CaO·SiO and 40% by mass or less of Merwinite is obtained by blending CaO raw material, SiO 2 raw material and MgO raw material in a predetermined molar ratio and heat-treating in a temperature range of 1000 °C or higher. Examples of the CaO raw material include calcium carbonate such as limestone, calcium hydroxide such as slaked lime, by-product slaked lime such as acetylene by-product slaked lime, fine powder generated from waste concrete blocks, concrete sludge (dehydrated cake) generated in ready-mix concrete plants and concrete product plants, incineration ash (coal ash, woody biomass, municipal waste incineration ash, sewage sludge incineration ash, paper sludge, etc.), steel slag (converter slag, electric furnace slag, etc.). SiO 2 raw material and MgO raw material in a predetermined molar ratio and heat-treating in a temperature range of 1000 °C or higher. Examples of the CaO raw material include calcium carbonate such as limestone, calcium hydroxide such as slaked lime, by-product slaked lime such as acetylene by-product slaked lime, fine powder generated from waste concrete blocks, concrete sludge (dehydrated cake) generated in ready-mix concrete plants and concrete product plants, incineration ash (coal ash, woody biomass, municipal waste incineration ash, sewage sludge incineration ash, paper sludge, etc.), steel slag (converter slag, electric furnace slag, etc.). SiO 2Examples of raw materials include silica stone, clay, and various silica dusts generated as industrial by-products typified by silica fume and fly ash. Examples of MgO raw materials include magnesium hydroxide, basic calcium carbonate, and dolomite.

[0015] The non-hydraulic CO 2 hardening type solidifying material can use slag containing γ-2CaO·SiO 2 and merwinite. For example, steelmaking slag or stainless steel slag can be used. Among slags, electric furnace reducing slag or stainless steel slag with a high content of γ-2CaO·SiO 2 is preferred.

[0016] The non-hydraulic CO 2 content of γ-2CaO·SiO in the hardening type solidifying material 2 is 2% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more. Also, the content of γ-2CaO·SiO 2 is not particularly limited, but preferably 95% by mass or less, and more preferably 90% by mass or less. If the content of γ-2CaO·SiO 2 is less than 2% by mass, a sufficient CO 2 absorption amount cannot be obtained, and the strength development property of the non-hydraulic CO 2 hardening type solidifying material cannot be obtained.

[0017] Also, the content of merwinite in the non-hydraulic CO 2 hardening type solidifying material is 40% by mass or less, preferably 37% by mass or less, and more preferably 35% by mass or less. Also, the content of merwinite is preferably 3% by mass or more, and more preferably 5% by mass or more. If the content of merwinite exceeds 40% by mass, the initial strength or long-term strength of the non-hydraulic CO 2 hardening type solidifying material decreases.

[0018] The non-hydraulic CO 2 hardening type solidifying material contains γ-2CaO·SiO 2And although it is not particularly limited except for containing melvinite, specifically, CaO, SiO 2 and MgO etc. are the main chemical components, and in addition, Al 2 O 3 , S, Fe 2 O 3 , TiO 2 and MnO etc. may be mentioned. Also, as the mineral composition other than γ-2CaO·SiO 2 and melvinite, gehlenite (2CaO·Al 2 O 3 ·SiO 2 ) is 30 mass% or less (preferably 5 - 30 mass%), periclase (MgO) is 15 mass% or less (preferably 2 - 15 mass%), larnite (β-2CaO·SiO 2 ) is 15 mass% or less (preferably 1 - 15 mass%), spinel (MgO·Al 2 O 3 ) is 25 mass% or less (preferably 10 - 25 mass%), stishovite (SiO 2 ) is 3 mass% or less, cristobalite (SiO 2 ) is 2 mass% or less, bredigite (7CaO·MgO·4SiO 2 ) is 25 mass% or less (preferably 5 - 20 mass%), perovskite (CaO·TiO 2 ) may be contained at 2 mass% or less. When the total of γ-2CaO·SiO 2 and melvinite is less than 100%, these mineral compositions can be included.

[0019] The non-hydraulic CO 2 hardening type solidifying material may be used alone with one kind of slag, or two or more kinds of slag may be used in combination.

[0020] The non-hydraulic CO 2 hardening type solidifying material of the present invention is within the range where the non-hydraulic CO 2 hardening type solidifying material does not show hydraulicity (compressive strength is 10 N / mm2 It may contain hydraulic cement as described below. Examples of the hydraulic cement include Portland cement and blended cement. Examples of the Portland cement include various Portland cements such as ordinary, early-strength, super-early-strength, low-heat, and moderate-heat Portland cements. Examples of the blended cement include various blended cements in which fly ash, blast furnace slag, silica fume, or fine limestone powder is blended with Portland cement. Also, geopolymers cement, sulfoaluminate cement, limestone calcined clay cement (LC3), and carbonated cement that hardens by fixing CO 2 are also mentioned. The content of the hydraulic cement is preferably 35% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less in the non-hydraulic CO 2 hardening type solidifying material. 2 Note that the compression strength of 10 N / mm 2 or less, which is a range not showing hydraulicity, means that after preparing mortar according to JIS R 5201 with the non-hydraulic CO 2 hardening type solidifying material, hand-mixing the mortar for about 3 minutes, putting it into a cylinder container with a diameter of 5 cm and a height of 10 cm, compression molding at 26 MPa, and the compression strength after 5 hours is 10 N / mm 2 or less.

[0021] Also, the particle size of the non-hydraulic CO 2 hardening type solidifying material is preferably such that 40% by mass or more passes through a sieve with an opening of 90 μm, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The particle size of the non-hydraulic CO 2 hardening type solidifying material can be adjusted by performing pulverization and classification. By setting the particle size of the non-hydraulic CO 2 hardening type solidifying material within the above range, the CO 2 absorption amount can be increased.

[0022] The Blaine specific surface area of the non-hydraulic CO 2 hardening type solidifying material is 500 cm 2 ​ / g or more is preferable, and 600 cm 2 / g or more is more preferable, and 700 cm 2 / g or more is even more preferable. Also, the upper limit is 3000 cm 2 / g or less is preferable, and 2500 cm 2 / g or less is more preferable, and 2000 cm 2 / g or less is even more preferable. The Blaine specific surface area of the cement admixture can be adjusted by performing pulverization and classification. By setting the Blaine specific surface area within the above range, the CO 2 absorption amount can be increased.

[0023] The non-hydraulic CO 2 hardening type solidifying material can, depending on the usage mode, within a range that does not substantially inhibit the object of the present invention, use one or more of known and commonly used additives and admixtures used in ordinary cement materials, such as aggregates like sand and gravel, finely ground blast furnace slag, slowly cooled blast furnace slag powder, finely ground limestone, fly ash, silica fume, natural pozzolans such as volcanic ash, expansion agents, quick-setting agents, water reducing agents, AE water reducing agents, high-performance water reducing agents, high-performance AE water reducing agents, defoaming agents, thickening agents, rust preventives, antifreezing agents, shrinkage reducing agents, polymers, setting regulators, clay minerals such as bentonite, and anion exchangers such as hydrotalcite. It is also possible to use artificial calcium carbonate using carbon dioxide as a raw material, aggregate containing artificial calcium carbonate, etc.

[0024] The non-hydraulic CO 2 carbonation of the hardening type solidifying material is, for example, mixing the non-hydraulic CO 2 hardening type solidifying material and water to form a slurry, injecting this into a mold and compacting it. Then, in the range of 20 to 150 °C, for 1 hour to 80 hours, in the range of atmospheric pressure to a pressure about 4 atmospheres higher than the ambient atmospheric pressure, with a relative humidity of 1% or more, CO 2 curing can be carried out by curing under steam with a concentration in the range of 5 to 100% by volume.

[0025] The amount of water used for the non-hydraulic CO 2 hardening type solidifying material is, specifically, for the non-hydraulic CO 2With respect to 100 parts by mass of the hardening type solidifying material, the amount of water is preferably 0 to 60 parts by mass, and more preferably 3 to 60 parts by mass. By being 3 parts by mass or more, sufficient moldability can be obtained, and by being 60 parts by mass or less, strength development and carbonation promotion effect can be made sufficient. Note that the water is not particularly limited, and for example, tap water, groundwater, recovered water from ready-mixed concrete plants, water containing CO 2 and the like can be used.

[0026] The non-hydraulic CO 2 hardening type solidifying materials of the present invention may be produced by mixing each material during construction, or may be partially or entirely mixed in advance. Also, the mixing method of each material and water is not particularly limited, and each material may be mixed during construction, or may be partially or entirely mixed in advance. Also, after mixing a part of the materials with water, the remaining materials may be mixed.

[0027] As a mixing device for mixing each material, any existing device can be used. For example, a tilting drum mixer, an omnimixer, a Henschel mixer, a V-type mixer, a Nauta mixer, etc. can be used.

[0028] (Carbonated hardened body) The carbonated hardened body of the present invention is composed of a carbonated hardened product of the above non-hydraulic CO 2 hardening type solidifying material. The carbonated hardened product is obtained by carbonating and curing the non-hydraulic CO 2 hardening type solidifying material. Carbonation curing in the present invention means performing carbonation treatment on a hardened body produced by mixing the non-hydraulic CO 2 hardening type solidifying material and water in a gas atmosphere containing carbon dioxide gas. Note that the gas atmosphere is not particularly restricted as long as it contains carbon dioxide gas, and may contain gases such as nitrogen, oxygen, hydrogen, argon, and water vapor.

[0029] Also, the carbonated hardened body in the present invention means a hardened body obtained by hydrating and hardening the non-hydraulic CO 2 hardening type solidifying material and further performing carbonation curing.

Example

[0030] Hereinafter, the present invention will be described in more detail using examples and comparative examples. However, the present invention is not limited to the following examples and comparative examples as long as it does not deviate from the gist thereof.

[0031] <Experimental Example 1> Using the electric furnace reduction slag with the content of γ-2CaO·SiO shown in Table 1 2 , and melvinite, a non-hydraulic CO 2 hardening type solidifying material was prepared. Commercial products were used for the electric furnace reduction slag. The mineral composition of the slowly cooled product of the used electric furnace reduction slag is shown in Table 1. Each slowly cooled product of the electric furnace reduction slag was pulverized, and cement (ordinary Portland cement (commercial product)) was mixed so as to be in the ratio shown in Table 2 with respect to the total of the slowly cooled product of the electric furnace reduction slag and cement, to prepare a non-hydraulic CO 2 hardening type solidifying material. The content of γ-2CaO·SiO of the prepared non-hydraulic CO 2 hardening type solidifying material, the Blaine specific surface area, and the passing fraction through a sieve with an opening of 90 μm are shown in Table 2. 2

[0032] Also, as an index indicating non-hydraulicity (non-hydraulic), the compressive strength was measured by the following method. (Non-hydraulic [Compressive Strength]) To 100 parts by mass of the non-hydraulic CO 2 hardening type solidifying material prepared above, 25 parts by mass of water (tap water) was added, and mortar was prepared according to JIS R 5201. After preparation, the mortar was manually mixed for about 3 minutes, then put into a cylinder container with a diameter of 5 cm and a height of 10 cm, and compression molded at 26 MPa. After compression molding for 5 hours, the compressive strength was measured. When the compressive strength is 10 N / mm 2 or less, it is considered non-hydraulic, and when the compressive strength exceeds 10 N / mm 2 it is considered hydraulic.

[0033]

Table 1

[0034] The mineral components of the electric furnace reduced slag used were quantified by mineral composition analysis using powder XRD (Rigaku Corporation, SmartLab Studio II).

[0035] (CO 2 content) Non-hydraulic CO in Test No. 1-1 to 1-21 2 Using hardening solidification material, CO 2 The content of each non-hydraulic CO 2 The hardening solidification material was adjusted to a median particle size of 15 μm to avoid any effects due to particle size. 2 5 g of the hardening solidification material was placed in a polystyrene bottle with a body diameter of 30 mm and a height of 60 mm, and placed in a curing tank at 40°C, 60% RH, and a carbon dioxide concentration of 20% by volume. An equal amount of 2.5 g of water was added appropriately to carbonate the material. After carbonation for one day, the sample was crushed so that it could pass through a sieve with 150 μm openings, and the non-hydraulic CO2 for measurement was measured. 2 A hardening solidification material was used, and the hydration was stopped with acetone and dried at 40°C. 2 The content of each non-hydraulic CO in an Erlenmeyer flask was measured using a coulometer (2000S-CAT model, manufactured by Nippon Ans Co., Ltd.). 2 Add hydrochloric acid (concentration: 3 mol / L) to the hardening solidification material and stir with a stirrer. 2 Gas is introduced into the absorbing solution with nitrogen, and the amount of carbon is measured from the amount of electricity required to maintain the transmittance of the absorbing solution at a constant level. 2 The results were converted into the content ratio, and are shown in Table 2. 2 The content rate of 7.0 mass % or more was determined to be acceptable.

[0036] (Compressive strength [initial strength and long-term strength]) Non-hydraulic CO in Test No. 1-1 to 1-21 2 For hardening solidification materials, water (tap water) is added to non-hydraulic CO 225 parts by mass was added to 100 parts by mass of the hardening type solidifying material and hand-mixed for about 3 minutes. Then, it was put into a cylinder container with a diameter of 5 cm and a height of 10 cm and compression-molded at 26 MPa. After compression molding, before carbonation, the compression-molded body was placed in a container with a relative humidity of 80% for 2 hours. Then, accelerated carbonation curing was carried out in an environment of a temperature of 40 °C, a relative humidity of 50%, a CO 2 concentration of 20%, and an atmospheric pressure of 0.2 MPa, and the compressive strength (initial strength) after 1 day and the compressive strength (long-term strength) after 28 days were measured. The compressive strength was measured according to JIS R 5201. The results are shown in Table 2. The initial strength was 5.5 N / mm 2 or more, and those satisfying both having a long-term strength of 35.0 N / mm 2 or more were considered qualified.

[0037]

Table 2

Industrial Applicability

[0038] The non-hydraulic CO 2 hardening type solidifying material of the present invention can be preferably used particularly in the civil engineering field, the construction field, etc.

Claims

1. As a mineral composition, γ-2CaO·SiO ２ , and contains melilite, The above γ-2CaO·SiO ２ is contained in an amount of 2% by mass or more, and the above melilite is contained in an amount of 40% by mass or less, and it is a non-hydraulic CO ２ hardening type solidifying material.

2. The non-hydraulic CO according to claim 1, having a particle size that passes through a sieve with an opening of 90 μm by 40% by mass or more. ２ Hardening type solidifying material.

3. The brain specific surface area is 500 cm ２ / g or more and 3000 cm ２ / g or less, and the non-hydraulic CO ２ hardening type solidifying material according to claim 1 or 2.

4. The non-hydraulic CO hardening type solidifying material according to claim 1 or 2, containing electric furnace reducing slag. ２ Hardening type solidifying material.

5. The carbonated hardened body made of the carbonated product of the non-hydraulic CO ２ hardening type solidifying material according to claim 1 or 2. ２ which is composed of a carbonated product of a non-hydraulic CO ２ hardening type solidifying material.

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