JP5189262B2 - Carbon dioxide fixed concrete structure - Google Patents

Description

  The present invention relates to a carbon dioxide-fixed concrete structure having a surface that efficiently fixes carbon dioxide in the atmosphere using the reaction of a cement-based material.

Japan's CO ₂ emissions amount to about 1,250 million tons per year, accounting for about 5.1% of the world. The target for reducing CO ₂ emissions in the 1997 Kyoto Protocol is 6% reduction compared to 1990, but the current measure is expected to increase by 7%. There is a need to implement effective measures as soon as possible in related fields centered on the headquarters for the promotion of industrialization.
On the other hand, “strengthening innovative technology development” is one of the pillars of CO ₂ suppression measures, and it stores and immobilizes CO ₂ once exhausted along with technologies such as energy saving and solar power generation. The development of technology is raised. As specific research subjects, marine organisms such as plankton, utilization techniques such as trees, electrochemical techniques, and techniques such as underground sequestration have been proposed, but how efficiently CO ₂ is fixed at low cost. Kaga is in the process of research as a future issue.

Cement concrete used for civil engineering and building structures is gradually cured in the process where calcium hydroxide and calcium silicate hydrate, which are the main chemical components, react with CO ₂ in the atmosphere to produce calcium carbonate. Loss of alkalinity, so-called carbonation / neutralization. Since carbonation / neutralization phenomenon leads to rusting of reinforcing steel in concrete, many techniques for suppressing carbonation have been studied in the past. On the contrary, the present invention proposes a technique for positively fixing CO ₂ to a cement concrete molded body constituting the outer wall of a building by utilizing this reaction.

The carbonation reaction of general concrete can be expressed by the following reaction formula in which calcium hydroxide contained in the hardened cement hydrate reacts with carbon dioxide that has penetrated into the concrete from the atmosphere to generate calcium carbonate.
Ca (OH) ₂ + CO ₂ → CaCO ₃ + H ₂ O
By the above reaction, carbon dioxide in the atmosphere is fixed in the concrete as calcium carbonate, and carbon dioxide in the atmosphere is reduced by immobilization on the concrete molding. Since calcium carbonate in concrete exists as a stable reactant and is extremely difficult to decompose, carbon dioxide remains fixed in the concrete as it is. Such a reaction usually occurs and proceeds when carbon dioxide in the atmosphere gradually permeates and diffuses into the concrete molding and comes into contact with calcium hydroxide contained in the cement hydrate.

Conventionally, a concrete molded body generally used is expressed by the above formula because the microstructure of the concrete is dense, the diffusion coefficient of gas is small, and the penetration rate of carbon dioxide in the atmosphere is extremely slow. Such carbonation progresses very slowly, and it can be said that the characteristic of fixing carbon dioxide in the atmosphere is extremely weak. For example, in general civil engineering concrete, it takes about 50 years for the carbonation reaction to proceed from the surface layer to a depth of about 20 mm, and the amount of carbon dioxide fixed in the concrete is also limited. .
On the other hand, various porous concretes have been proposed for the purpose of imparting water permeability and air permeability to the concrete molding or preventing explosion.

For example, a method of obtaining a porous concrete by adjusting the blending amount of aggregate and cement and maintaining a gap between the aggregates (for example, refer to Patent Documents 1 to 3), lightweight cellular concrete, so-called ALC concrete, etc. A method of entraining a large amount of air into the concrete, a method of mixing a void forming material into the concrete composition, and shrinking or decomposing the void material after curing (see, for example, Patent Document 4), etc. ing. However, in these methods, since the volume of voids formed is large, there is a drawback that mechanical properties such as compressive strength and bending strength of concrete are greatly impaired, and because the void area is large, it is useful for adsorption of carbon dioxide. The increase in concrete surface area cannot be obtained sufficiently, and carbon dioxide has not been fixed effectively, so that no structure with excellent carbon dioxide fixing ability has been realized yet. It is.
In addition, the explosion-resistant concrete composition contains pyrolytic organic fibers in addition to cement and aggregate (see, for example, Patent Document 5), but this composition is exposed to high temperatures. For the first time, fine voids for allowing air and water vapor to permeate are produced, and normally, it does not have a function of permeating and adsorbing carbon dioxide.
JP-A-8-105052 JP-A-9-205875 JP 11-268969 A JP 2003-277164 A JP 2000-143322 A

  The object of the present invention made in consideration of the above problems is that the conventional cement mortar and concrete carbonation reaction have a disadvantage that the penetration rate of gas into the concrete is slow and the progress of the carbonation reaction is very slow. The object is to provide a carbon dioxide-fixed concrete structure having a surface capable of effectively fixing carbon dioxide in the atmosphere.

The present inventors greatly facilitate the penetration of carbon dioxide in the atmosphere into mortar and concrete, and the surface layer of concrete that greatly promotes the carbonation reaction capable of efficiently fixing carbon dioxide, such as buildings such as buildings. things, in Rukoto be applied to civil engineering structures such as dams and piers, it found that can solve the above problems and accomplished the present invention.
That is, the carbon dioxide-fixed concrete structure of the present invention has a diameter of 5 μm to 100 μm composed of water , cement, admixture , aggregate , alkali decomposable resin fine particles having an average particle diameter of 10 μm to 500 μm, and alkali decomposable resin. Of organic fibers having a length of 50 μm to 500 mm, ultraviolet decomposable resin fine particles having an average particle diameter of 10 μm to 500 μm, and organic fibers having a diameter of 5 μm to 100 μm and a length of 50 μm to 500 mm. and at least one and, concrete structures resulting et a cured carbon dioxide immobilization molded body concrete composition containing, in a surface portion of said structure, voids or diameter 10μm diameter 10μm~200μm Cavity pores having a cross section of ˜200 μm, 0.05% by volume to 10% by volume, and carbon dioxide in the atmosphere in the surface layer portion It is provided with a carbon dioxide-fixed molded body for fixing the element, and a reinforcing material selected from a reinforcing bar or steel frame, stainless steel, titanium, nickel, and a ceramic material whose surface is rust-proofed. And

The carbon dioxide-fixed concrete structure includes water, cement, admixture, aggregate, alkali-decomposable resin fine particles having an average particle size of 10 μm to 500 μm, and a diameter of 5 μm to 100 μm and a length composed of an alkali-decomposable resin. Is an organic fiber having an average particle diameter of 10 μm to 500 μm, and an organic fiber having a diameter of 5 μm to 100 μm and a length of 50 μm to 500 mm. After kneading, molding and curing the carbon dioxide-fixed concrete composition for forming a carbon dioxide-containing material, the resin fine particles contained in the concrete composition or the organic fibers composed of the resin are decomposed by alkali or ultraviolet rays to fix the carbon dioxide. What is necessary is just to use what the surface layer part which has a void useful for chemical conversion is formed.
In addition to the decomposable organic material for forming the voids, various compounds having carbon dioxide absorption can be added to the concrete composition for forming a carbon dioxide-fixed molded body.
As a method of placing a carbon dioxide immobilization surface portion made by the composition to the surface of the concrete structure, carbon dioxide immobilization molded body concrete composition capable of forming fine voids as described above and when forming a concrete structure, then pouring directly, by curing, the surface layer portion for carbon dioxide immobilization with air gap may take how to place on the surface of the concrete structure.

As the carbon dioxide-fixed molded body, it is possible to use a prestressed molded body, which is reinforced by a frame body made of PC steel, and by taking such an aspect, It is possible to provide a structural member capable of imparting carbon dioxide fixing ability to a deep part.
In the concrete structure of this invention, it is preferable that the carbon dioxide fixed amount in the surface of the carbon dioxide fixed molded object to be arrange | positioned is 2.0 g / m < ² > or more. Considering that the amount of carbon dioxide immobilized on the surface of a normal concrete structure is 0.30 to 0.40 g / m ² , the concrete structure of the present invention has excellent carbon dioxide immobilization ability. I understand that. The carbon dioxide fixing ability in the structure of the present invention can be further increased by adjusting the amount of fibers mixed in the concrete composition constituting the structure, its characteristics, or the composition of the concrete composition itself. It is.

  Carbonation of cement mortar and concrete is a reaction in which calcium hydroxide generated in the pores of cement hydrate by the hydration reaction of cement reacts with carbon dioxide that has penetrated into the concrete from the atmosphere to form calcium carbonate. Caused by. Since calcium carbonate is a chemically stable compound and is not easily decomposed in concrete under normal environmental conditions, carbon dioxide that has penetrated into the concrete is fixed in the concrete as calcium carbonate.

According to the present invention, in order to accelerate the carbonation reaction of cement hydrate in mortar and concrete, a large number of fine layers are formed on the surface of mortar and concrete so that more carbon dioxide penetrates into mortar and concrete. Since the molded body in which voids are formed is arranged on the structure surface, the air permeability from the concrete surface to the deep part on the surface of the molded body is improved, and the surface area for contacting carbon dioxide inside the concrete is greatly increased. The carbon dioxide in the air can be effectively fixed on the entire surface of the structure. In addition, since the voids in the individually disposed molded bodies are fine and the presence thereof is present in the surface layer portion of the molded body that easily comes into contact with carbon dioxide, the effect is exerted. It is possible to maintain the mechanical characteristics.
In addition, such fine voids are an organic fiber having an average particle diameter of 10 μm to 500 μm and a diameter of 5 μm to 100 μm and a length of 50 μm to 500 mm made of an alkali decomposable resin in the concrete composition. an average particle size of the ultraviolet degradable resin particles of 10 m to 500 m, and easily by the diameter made of an ultraviolet-decomposable resin is 5 m to 100 m, a length to contain at least one of organic fibers 50μm~500mm Can be formed.

  In the present invention, by the method of forming fine voids in the concrete by means as described above, the amount of carbon dioxide permeated is increased without greatly reducing the amount of cement in the concrete and without impairing the mechanical properties of the concrete. It became possible to make it. The size of such fine voids is preferably a void having a diameter of 10 μm to 200 μm or a hollow hole having a cross section of the same diameter, and 0.05% to 10% with respect to the concrete volume in the surface layer portion. .

  ADVANTAGE OF THE INVENTION According to this invention, the carbon dioxide fixed concrete structure which has the surface which can fix the carbon dioxide in air | atmosphere effectively can be provided. According to such a concrete structure, since carbon dioxide in the atmosphere can be effectively fixed continuously from the construction, it is useful for reducing carbon dioxide in the atmosphere.

The concrete structure of the present invention is obtained by curing a concrete composition containing water, cement, admixture, and aggregate on the surface thereof, and has a void in the surface layer portion, and in the surface layer portion, carbon dioxide in the atmosphere is obtained. A carbon dioxide-immobilized molded body capable of immobilizing carbon is arranged.
The concrete structure in the present invention is a structure having a surface in contact with the atmosphere, and at least a part of the surface of the structure in contact with the atmosphere is made of a carbon dioxide-fixed molded body, specifically, For example, a detached house, a building or the like, a bridge pier, a dam, a retaining wall, a civil engineering structure such as sloped concrete, a concrete paving stone, a fence, or a concrete object, etc. It refers to what is satisfied.

Hereinafter, the carbon dioxide fixed molded body used in the present invention and the arrangement method thereof will be sequentially described.
Carbon dioxide immobilization molded body can immobilize carbon dioxide in the atmosphere, which is disposed on the surface of the concrete structure of the present invention, the surface layer portion, the bore hole having voids or cross-section of the same diameter with a diameter of 10 m to 200 m, It is provided in the range of 0.05 volume% to 10 volume%. The voids are alkali-decomposable resin fine particles having an average particle diameter of 10 μm to 500 μm, organic fibers having a diameter of 5 μm to 100 μm, a length of 50 μm to 500 mm, and ultraviolet decomposition having an average particle diameter of 10 μm to 500 μm. At least one organic fiber having a diameter of 5 μm to 100 μm and a length of 50 μm to 500 mm made of a fine resin fine particle and an ultraviolet-decomposable resin is contained in the concrete composition, and is exposed to an alkaline atmosphere after the concrete is cured. These resins are formed by decomposing and reducing the volume by natural light or artificially irradiating ultraviolet rays. The size and density (abundance) of the voids can be easily adjusted by the size of the resin fine particles to be contained or the organic fibers made of the resin, the added amount, and the like.
The effect of the present invention is achieved by the presence of voids and cavity holes in the surface layer portion. The surface layer referred to in the present invention refers to a range of about 0 to 100 mm in the depth direction from the surface in the cross section of the concrete molded body, that is, a depth range of 100 mm from the outermost surface in contact with the atmosphere. The effect of the present invention can be achieved by having such voids and hollow holes. The voids may exist uniformly up to a further deep part of the molded body, but may be formed only in the vicinity of the surface in the depth direction. When the strength of the concrete molded body itself is maintained by a reinforcing material such as steel or a frame material, there is a gap to the bottom of the molded body. Depending on the position of the structure, carbon dioxide gas on the back surface Immobilization can also be expected.

The resin forming these voids is not particularly limited as long as it has a characteristic of being reduced in volume or extinguished by irradiation under ultraviolet light or by irradiation with ultraviolet rays, but is an aliphatic polyester that is rapidly hydrolyzed by alkali. Preferred examples include biodegradable resins such as polyacrylic acid, polyethylene terephthalate that is hydrolyzed by alkali, polypropylene resins that are decomposed by ultraviolet irradiation, and acrylic resins.
In particular, aliphatic polyester has sufficiently high fiber strength and good handling properties before being mixed into a concrete composition, but it is mixed into a concrete composition and cured to form a cement-based molded body. Is formed, it is particularly preferable from the viewpoint that the resin constituting the fiber is hydrolyzed and reduced in molecular weight, gasified, and forms good voids in the molded body.

First, an aliphatic polyester resin will be described as an example of the resin having hydrolyzability in such an alkaline atmosphere.
The aliphatic polyester resin used in the present invention may be either a homopolymer resin or a copolymer resin, but is preferably a homopolymer resin obtained by self-condensation polymerization and / or ring-opening polymerization. As such a homopolymerized aliphatic polyester resin, various known resins can be used, and more specifically, selected from the group consisting of polylactic acid, polyglycolic acid, poly-3-hydroxybutyrate and polycaprolactone. At least one is preferred.
Any of the above exemplified homopolymerized aliphatic polyester resins is known as a biodegradable resin, but is preferably used in the present invention because it is easily hydrolyzed and reduced in molecular weight under an alkaline atmosphere.

Further, in the present invention, a copolymerized aliphatic polyester resin having two or more structural units of each resin in a polymer molecule, or a copolymerized aliphatic polyester resin having a structural unit of each resin and other structural units. Can also be used.
Among these resins, polylactic acid using lactic acid obtained by fermentation as a raw material is particularly preferable from the viewpoints of economy, carbon neutrality, and effects.
In the present invention, these aliphatic polyester resins may be used singly or in combination of two or more kinds as resin fine particles and organic fiber materials.

In the case of forming voids, the aliphatic polyester resin is used after being formed into a fiber shape or a fine particle shape by a known method such as emulsion polymerization, granulation or spinning. In the case of forming into an organic fiber, the spinning method is not particularly limited, and an arbitrary method can be appropriately selected from known methods conventionally used in spinning thermoplastic resins. Moreover, you may extend | stretch a spinning fiber by a well-known method as needed. A resin molded into a fiber form is preferable because it forms a long and narrow continuous void inside the concrete, so that the effect of the present invention is improved as compared with an indeterminate or fine particle resin.
In addition, the aliphatic polyester resin has other properties within the range in which the object of the present invention is not impaired in order to improve moldability, spinnability, and physical properties other than alkali hydrolyzability in the case of fibers. These thermoplastic resins such as polyethylene, polypropylene, polyvinyl alcohol, polyacetal, aromatic polyester, polystyrene, polyamide, etc. may be used in combination, and known additives such as plasticizers may be added as appropriate.

  The organic fiber for a cement-based molded body of the present invention made of such a material has hydrolyzability in an alkaline atmosphere. Therefore, when mixed with a cement compound to form a cement-based molded body, The resin constituting the fiber is hydrolyzed by exposure to an alkali atmosphere inherent in cement hydrate. For example, when polylactic acid fibers are used, the volume is reduced and voids are formed by leaving the cement hydrate for a certain period, specifically, 9 weeks or more.

When blending an aliphatic polyester resin into a concrete composition, from the viewpoint of effects, the fine particles preferably have an average particle size in the range of 10 to 500 μm, more preferably 20 to 200 μm.
The organic fiber preferably has a diameter of 5 to 100 μm and a length of 50 μm to 500 mm, more preferably a diameter of 10 to 50 μm and a length of 1 to 15 mm, still more preferably a diameter of 15 to 25 μm and a length of 5 -10 mm.
The particle diameter of the fine particles and the shape of the organic fiber can be measured by a conventional method using an image taken with an electron microscope or a high magnification optical microscope.

In the present invention, the carbon dioxide-fixed molded body applied to the surface of the concrete structure contains fine particles or organic fibers made of the aforementioned alkali-decomposable or ultraviolet-decomposable resin, water, cement, admixture, and aggregate. It is a molded article obtained by curing a concrete composition. The blending amount of resin fine particles or organic fibers in the concrete composition is in the range of 0.02 to 2.0% by volume with respect to the total amount of the composition in consideration of the workability of the concrete and the strength of the structure. Is preferable, more preferably 0.05 to 1.0% by volume, and still more preferably 0.1 to 0.5% by volume.
The cement molded body is a concrete composition comprising water, cement, an admixture, an aggregate, and a chemical admixture, and the weight ratio of various materials is appropriately adjusted according to the intended use of the formed cement-based molded body. be able to.

In the concrete composition, from the viewpoint of improving the carbon dioxide immobilization ability, fine powder or adsorbent that can adsorb carbon dioxide (hereinafter referred to as carbon dioxide adsorbing material as appropriate), calcium oxide (CaO) fine powder, etc. Additives can be included.
Here, as the fine powder or adsorbent capable of adsorbing carbon dioxide that can be blended in the concrete composition, slag containing γ-2CaO · SiO ₂ is preferably mentioned. Examples of such slag containing γ-2CaO · SiO ₂ include stainless steel slag and steelmaking slag. The slag is required to be Blaine specific surface area of 3000 cm ² / g or more, and more preferably in the range of 4000~10000cm ² / g. The specific surface area of slag can be measured by the brane method described in JIS R 5201 or by a method using a laser diffraction particle size meter.
When the slag is used as a carbon dioxide adsorbing substance, it is preferably in the range of 15 to 45% by mass with respect to the cement content contained in the concrete composition. Is expressed and has excellent mechanical properties.

Other preferable examples of the fine powder or adsorbent capable of adsorbing carbon dioxide include fine powder selected from the group consisting of zeolite fine powder, silica gel fine powder, alumina fine powder, and crustacean fine powder. Among these, zeolite fine powder and crustacean fine powder are preferable. Since crustaceans contain a large amount of calcium, when they are made fine powder, they exhibit excellent carbon dioxide adsorption ability.
The particle size of these fine powders is preferably about 1 μm to 3 mm, more preferably 10 μm to 1 mm.
When these fine powders are used as a carbon dioxide adsorbing substance, the content thereof is preferably in the range of 5 to 30% by mass with respect to the content of cement contained in the concrete composition. In this range, a remarkable carbon dioxide absorption effect is exhibited, and there is no concern of affecting the mechanical properties of the concrete molded body.

As the CaO fine powder that can be used in the present invention, one containing CaO and having a brain specific surface area of 2000 cm ² / g or more is used.
As the fine powder mainly composed of CaO, a powder obtained by pulverizing quick lime, lime-based expansion material, or the like into a fine powder having a Blaine specific surface area of 2,000 cm ² / g or more can be used. Such a fine powder can be used as an admixture as well as a lime-based admixture.
Blaine specific surface area of fine powder required to be at 3000 cm ² / g or more, and more preferably in the range of 3000~4000cm ² / g.
The CaO fine powder is preferably contained in the concrete composition in the range of 0.5 to 2.0% by volume. In this range, excellent carbon dioxide adsorption ability is expressed, and the mechanical properties of the molded article are also excellent. .

There is no restriction | limiting in particular as a cement used for the concrete composition which is a raw material of a molded object in this invention, According to the use of the cement-type molded object formed, it can select suitably from various cements. As the cement, ordinary Portland cement, moderately hot Portland cement, low heat Portland cement, blast furnace cement, fly ash cement, and the like can be used.
There is no restriction | limiting in particular as said admixture, According to the use of the cement-type molded object formed, a kind and usage-amount can be suitably selected from various cement and the admixture for concrete. As the admixture, blast furnace slag fine powder, fly ash, silica fume and the like can be generally used.
Moreover, there is no restriction | limiting in particular in the kind and quantity of aggregate, According to the use of the molded object formed, the kind and mixing ratio of aggregate can be selected suitably.

In the cement-based molded article of the present invention, various additives usually added to the cement-based molded article, for example, water reducing agents, air entraining agents, antifoaming agents, and the like can be appropriately mixed.
The weight ratio of water and cement in the cement molded body can be appropriately selected according to the use of the cement-based molded body to be formed. In order to promote the carbonation reaction with carbon dioxide in the atmosphere, The weight ratio of water to the binder is preferably 30% to 70%, more preferably 40% to 65%.

The carbon dioxide-fixed molded article of the present invention is kneaded with a concrete composition for forming a carbon dioxide-fixed molded article containing fine particles or organic fibers made of a degradable resin for forming voids, molded, cured, It can be produced by decomposing the resin fine particles or the organic fibers made of the resin contained in the concrete composition with alkali or ultraviolet rays to form a surface layer portion having voids useful for fixing carbon dioxide.
When exposed in an alkaline atmosphere, the resin gradually decomposes (/ volume reduction) from the surface area of the molded body in contact with the alkali, and voids are formed. By controlling the characteristics of the alkaline atmosphere and the contact conditions with the alkaline atmosphere, a void can be formed only in the surface layer portion of the concrete molded body. In addition, by placing concrete containing void-decomposable resin on the surface of a molded body made of a concrete composition that does not contain void-decomposable resin and curing it to form voids, only on the surface layer A molded body having voids can also be formed.
Thus, although the space | gap should just be formed in the surface layer part concerned at the fixation of a carbon dioxide at least, it may be uniformly formed to the further deep part of concrete.

  Carbon dioxide gradually permeates from the openings in the surface layer having such voids, and reacts with calcium hydroxide, which is a reaction product of cement hydration in the concrete composition, to form calcium carbonate. Carbon dioxide is fixed.

The size and shape of the gap formed in the surface layer portion can be detected by observing the cross section of the molded body with an electron microscope. The porosity can be measured with a mercury intrusion porosimeter or the like.
The concrete composition for forming a carbon dioxide-fixed molded body used here has a faster carbonation reaction with carbon dioxide in the atmosphere than conventional cement-concrete compositions, and is fixed as calcium carbonate in the cement molded body. In addition to the effect of increasing the amount to be formed, it is possible to obtain a molded product having the same mechanical properties as the conventional one.
From the viewpoint of the effect, the amount of carbon dioxide fixed on the surface of the carbon dioxide fixed molded body constituting the concrete structure of the present invention is preferably 2.0 g / m ² or more, and more preferably 4.0 g / m. ² or more.

Next, a method for arranging the molded body thus obtained on the surface of the concrete structure will be described.
As a preferred method, when a concrete structure is constructed, a method using the concrete composition capable of forming a surface layer portion excellent in carbon dioxide fixing ability as described above is used as a raw material.
That is, the carbon dioxide fixing molded body concrete composition Da設, by curing, intended to build a concrete structure formed by arranging the surface layer portion for carbon dioxide immobilization with air gap to the surface is there. At this time, the entire structure may be composed of such a concrete composition for forming a carbon dioxide-fixed molded body. However, a general concrete composition is used for the portion of the foundation that is not exposed to the atmosphere, and the atmosphere is exposed to the atmosphere. You may shape | mold only the surface to contact with such a concrete composition for carbon dioxide fixed molded object formation.
This method is suitable for constructing large-scale civil engineering structures such as piers and dams.

The carbon dioxide-fixed molded article used in the present invention achieves efficient fixation of carbon dioxide mainly by promoting carbonation. Because of its rapid nature, rebars and steel frames used in the structure should be selected from materials that are difficult to oxidize and those that have been rust-proofed with excellent durability .
That is, as a reinforcing material in the molded body, when using a reinforcing steel or steel, Ru used as the surface was rust. Examples of the rust prevention treatment include a known method, for example, surface coating with a resin-based material such as an epoxy resin. Further, instead of the iron material, a metal material such as stainless steel, titanium, or nickel that is not easily oxidized, or a ceramic material may be embedded as a reinforcing material .
Furthermore, it is also a preferable aspect that a reinforcing fiber selected from the group consisting of carbon fiber, stainless steel fiber, and vinylon fiber is dispersed and mixed in the concrete composition.

In the present invention, as a method for estimating the carbon dioxide fixing ability of the carbon dioxide fixing panel, the method described in the specification of Japanese Patent Application No. 2005-145628 previously proposed by the applicant of the present application can be applied.
That is, depending on the carbon dioxide fixing ability of the carbon dioxide-fixed molded body used for the concrete structure, the time when the molded body is in contact with the atmosphere is from T ₀ at the time of occurrence to T _S at the end of fixation such as at the time of dismantling. More specifically, the carbonation depth c of the concrete gas-absorbing material at the elapsed time t from the time T ₀ is expressed as the carbonation rate equation c = Further, carbon dioxide is expressed as dc (depth from the surface), where S is the area of the boundary surface s between the already carbonized region and the non-carbonized region in the carbon dioxide fixed molded body used for the structure. A) The density of carbon contained in the volume portion when it has progressed by a is defined as a, and the gas absorption amount W when the carbonation depth c is reached is expressed as W (c) = ∫ (a × S) dc. Greenhouse gas absorption within a specified time from both methods It is intended to estimate the amount.

Carbonation of concrete is also commonly referred to as neutralization reaction but, as its carbonation (neutralization) rate equation can be used c = A × t ^n, called the root law. Here, c is the reaction amount, A is the carbonation rate coefficient, and t is the elapsed time. N is a constant determined experimentally, and generally n = 0.5.

The carbonation rate coefficient A in the carbonation rate equation c = A × t ^0.5 has been studied variously in the past, but simply, A _Q depending on the water cement ratio (W / C), A constant R depending on other factors, which can be expressed as A = A _Q × R, where R is a constant called a carbonation rate, A _{P is} a coefficient due to the attribute of concrete, and A is a coefficient due to the finishing material. _{If the} coefficient according to the classification of _S and the environment (temperature and humidity, carbon dioxide concentration) is A _E , R = A _P × A _S × A _E.

For the A _Q, for example, the following formula 1 are known when experimentally a W / C ≧ 0.6, also Equation 2 is known when a W / C ≦ 0.6 (Kishitani, “Durability of Reinforced Concrete” published by Kashima Construction Technology Research Institute, 1963).

[Formula 1]
A _Q = {(W / C) −0.25} / [0.3 × {1.15 + 3 (W / C)}] ^0.5

[Formula 2]
A _Q = {4.6 × (W / C) −1.76} / √ (7.2)
In addition, if the above-mentioned W (c) = ∫ (a × S) dc is used, it is possible to measure the amount of greenhouse gas absorbed in a concrete structure of an arbitrary shape. The amount of absorption per unit surface area can also be obtained by setting / S = ∫adc.
Thus, the carbon dioxide fixing ability in the concrete structure of the present invention can be estimated and used for the design.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited to these description.
(Experimental example: Formulation of concrete composition)
Water / cement composition ratio by blending organic fiber made of degradable resin in the amount shown in Table 1 below into 100 parts by mass of cement composition containing ordinary Portland cement and water, sand and crushed stone (aggregate). A concrete composition having a (W / C ratio) of 55% was prepared.
For comparison, instead of alkali-decomposable organic fibers, general building materials are blended with non-degradable organic fibers used as reinforcing materials, and concrete compositions are prepared with the same mixing amount for comparison. As an example.

[Materials used]
Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement), density 3.16 g / cm ³
Water: tap water Sand: Kisarazu mountain sand, surface dry density 2.59 g / cm ³ , water absorption 1.61%, coarse particle rate 2.60
Crushed stone: Crushed stone from Hachioji, surface dry density 2.65 g / cm ³ , water absorption 0.40%,
Coarse grain ratio 6.60
AE water reducing agent: Tupole EX20 (manufactured by Takemoto Yushi Co., Ltd.)
Antifoaming agent: AFK-2 (manufactured by Takemoto Yushi Co., Ltd.)

Organic fiber:
1) Fiber obtained by melt spinning polylactic acid resin (described as PLA fiber in the table, the same applies hereinafter), fiber diameter 20 μm, length 10.0 mm
2) Fiber obtained by melt spinning polypropylene resin (described as PP fiber in the table, the same applies hereinafter), fiber diameter 48 μm, length 10.0 mm

[Concrete composition]
Table 1 shows the composition of the concrete composition. Details of each material used in the table are as described above. In Table 1 below, W / C represents the water / binder ratio.

[Construction of building with concrete composition]
Using the concrete composition described in Table 1, a predetermined amount of predetermined organic fibers corresponding to each of the water, cement, fine aggregate, coarse aggregate, comparative example, and example are mixed with a predetermined amount (forcing 2 A shaft mixer (capacity 55 L) was added and kneaded for 3 minutes. At this time, appropriate amounts of AE water reducing agent and antifoaming agent were added and adjusted so that the amount of air in the kneaded concrete would be a constant value (4.5% by volume).
With this concrete composition, a five-story building with the scale shown in Table 2 below will be constructed. FIG. 1 is a plan view of the first floor portion of the building, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. The floor slab 10 is constituted by a floor portion 10A of a dwelling unit, a balcony 10B, and an external corridor 10C, and is supported by beams 14 passed between pillars 12 arranged at four corners of each dwelling unit. The other floors are the same plan view as shown in FIG.

[Capacity to fix carbon dioxide in concrete structures]
The total formwork area described in Table 2 above is the total area of the formwork required when placing the floor slab 10, the column 12, and the beam 14. Therefore, the total area of the formwork is substantially equal to the surface area of the concrete molded body for constructing the floor slab 10, the column 12, and the beam 14. The amount of carbon dioxide absorbed on the surface of the concrete molded body is estimated to be 3.54 kg / m ² .
This carbon dioxide immobilization ability was measured as follows.
The concrete compositions of the above examples were kneaded, placed in a mold, molded, and after curing, the neutralization depth was measured by JIS A 1153 (Concrete accelerated neutralization test method).
The amount of carbon dioxide fixed was determined by accelerating neutralization in the same way as in the neutralization depth test. After accelerated neutralization, the test specimen was pulverized with a ball mill and screened for those passing through a # 200 sieve. The amount of carbon in the powder sample was measured using a differential thermogravimetric analyzer (TAS-200 manufactured by Rigaku Corporation). It calculated | required by converting into the amount of carbon dioxide with respect to the area of the carbonation surface of a test body from the carbon content of the sample.
The measurement results of Examples and Comparative Examples are shown in Table 3 below.

The neutralization depth of JIS A 1153 under accelerated environmental conditions with a carbon dioxide concentration of 5.0% is equivalent to about 100 times in the atmosphere when outdoors and about 25 times when indoors (The Architectural Institute of Japan: Reinforced concrete) Guidelines for Durable Design and Construction of Buildings (Draft) / Explanation, March 2004) Assuming that the service period of the structure is 50 years, the fixed carbon dioxide equivalent to 50 years is the accelerated material age shown in Table 3 It can be estimated that the promotion material age is 26 weeks for outdoor use and the promotion material age is 104 weeks for indoor use, corresponding to 50 years.
The total amount of carbon dioxide immobilized on the surface of the concrete structure of the present invention calculated from this value and the formwork area is 37.6 tons during the 50-year service period.
As shown in Table 3, the carbon dioxide immobilization amount of the normal concrete composition in the comparative example is 0.73 kg / m ² , and the concrete structure of the present invention is compared with the surface of the normal concrete composition. It was confirmed that carbon dioxide was immobilized at a high efficiency of 4 times or more.
From this, it can be seen that the concrete structure of the present invention is excellent in carbon dioxide fixing ability.

It is a top view which shows the aspect of the building of Example 1 which is an example of the carbon dioxide fixed concrete structure of this invention. It is sectional drawing which shows the aspect of the building of Example 1. FIG.

Explanation of symbols

10 Floor slab 12 Column 14 Beam

Claims (3)

Water , cement, admixtures, and aggregates, alkali-degradable resin fine particles having an average particle diameter of 10 μm to 500 μm, organic fibers having an average diameter of 5 μm to 100 μm and a length of 50 μm to 500 mm, average particles For forming a carbon dioxide-fixed molded article containing ultraviolet decomposable resin fine particles having a diameter of 10 μm to 500 μm and organic fibers composed of an ultraviolet decomposable resin having a diameter of 5 μm to 100 μm and a length of 50 μm to 500 mm. A concrete structure obtained by kneading, molding, and curing a concrete composition, and an organic fiber made of resin fine particles or resin contained in the concrete composition by alkali or ultraviolet rays on a surface layer portion of the structure Decomposed and formed with a gap of 10 μm to 200 μm in diameter or a cross section of 10 μm to 200 μm in diameter The cavity holes, Ri Na surface portion is formed to have a useful gap for the immobilization of the carbon dioxide with 0.05 volume% to 10 volume%, carbon dioxide in the atmosphere immobilized in said surface layer portion, and, A carbon dioxide-fixed concrete structure provided with a reinforcing material selected from a reinforcing bar or steel frame, stainless steel, titanium, nickel, or a ceramic material whose surface is rust-proofed . The carbon dioxide-fixed concrete according to claim 1 , wherein the concrete composition for forming a carbon dioxide-fixed molded body further contains a reinforcing fiber selected from the group consisting of carbon fiber, stainless steel fiber, and vinylon fiber. Structure. The carbon dioxide fixed concrete structure according to claim 1 or 2 , wherein the carbon dioxide fixed amount on the surface of the carbon dioxide fixed concrete structure is 2.0 kg / m ² or more.

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