Method for manufacturing cement hardened body for stabilizing carbon dioxide

Abstract

To provide a method for manufacturing a cement hardened body for stabilizing carbon dioxide, capable of rapidly permeating a carbon dioxide-absorbing liquid containing a carbon dioxide-absorbing agent to a deeper part of the cement hardened body.SOLUTION: A method for manufacturing a cement hardened body for stabilizing carbon dioxide includes: injecting a carbon dioxide-absorbing liquid containing a carbon dioxide-absorbing agent into an inside of the cement hardened body at a pressure higher than atmospheric pressure; and causing the cement hardened body to support the carbon dioxide-absorbing agent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a hardened cement product for fixation of carbon dioxide. [Background technology]

[0002] In order to prevent global warming, there is a worldwide demand for a reduction in carbon dioxide (hereinafter, also referred to as "CO2") emissions. In the field of construction materials, methods have been proposed for reducing the amount of CO2 generated during concrete production by reducing the amount of cement, as well as technologies related to concrete that can fix (absorb) CO2 (see, for example, Patent Document 1).

[0003] A known technique for accelerated fixation of CO2 in newly constructed concrete is, for example, the technique described in Patent Document 2. The technique described in Patent Document 2 accelerates carbonation from the surface of a concrete structure by placing a concrete structure in which carbonation has not progressed, such as newly constructed concrete, in a high-concentration CO2 gas environment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4822373 [Patent Document 2] JP 2014-51422 A Summary of the Invention [Problem to be solved by the invention]

[0005] When carrying out the carbonation treatment, it is necessary to cover the concrete structure with sheets or other materials to prevent CO2 gas from leaking outside. This method is not necessarily easy depending on the shape of the concrete structure, and there is a risk of CO2 gas leaking outside. In addition, if the pH inside the concrete structure decreases due to carbonation, there is also the issue of an increased risk of corrosion of the reinforcing bars buried inside.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for producing a hardened cement body for fixation of carbon dioxide, which is capable of quickly permeating a carbon dioxide absorbing liquid containing a carbon dioxide absorbent deep into the hardened cement body. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following aspects. [1] A method for producing a hardened cement body for fixation of carbon dioxide, comprising injecting a carbon dioxide absorbing liquid containing a carbon dioxide absorbent into the hardened cement body at a pressure higher than normal pressure, thereby causing the hardened cement body to support the carbon dioxide absorbent. [2] The method for producing a hardened cement product for carbon dioxide fixation according to [1], wherein the pressure is less than 0.4 MPa. [3] The method for producing a hardened cement product for carbon dioxide fixation according to [1], wherein the pressure is 0.4 MPa or more. [4] The method for producing a hardened cement product for fixation of carbon dioxide according to any one of [1] to [3], wherein the carbon dioxide absorbing liquid contains carbonate ions or bicarbonate ions derived from carbon dioxide. [5] The method for producing a carbon dioxide fixation hardened cement body according to any one of [1] to [4], further comprising injecting a carbon dioxide absorbing liquid containing a carbon dioxide absorbent into the hardened cement body through an injection port formed in advance in a thickness direction from a surface of the hardened cement body. [6] The method for producing a hardened cement body for fixation of carbon dioxide according to [5], wherein the injection port is a small hole formed by drilling the hardened cement body in the thickness direction. [7] The method for producing a hardened cement body for fixation of carbon dioxide according to [5], wherein the injection port is a pore formed when the cement composition is hardened to form the hardened cement body. Effect of the Invention

[0008] According to the present invention, it is possible to provide a method for producing a hardened cement body for fixation of carbon dioxide, which is capable of quickly permeating a carbon dioxide absorbing liquid containing a carbon dioxide absorbent into the inner part of the hardened cement body. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective view showing a low-pressure injection method in a manufacturing method for a hardened cement for fixation of carbon dioxide according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a syringe used in a low-pressure injection method in a manufacturing method for a hardened cement for fixation of carbon dioxide according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing an injection device used in a high-pressure injection method in a manufacturing method for a hardened cement body for carbon dioxide fixation according to one embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view showing a method for forming an injection port in the hardened cement body in the method for producing the hardened cement body for fixation of carbon dioxide according to one embodiment of the present invention. [Diagram 5] FIG. 2 is a perspective view showing a method for forming an injection port in the hardened cement body in the method for producing the hardened cement body for fixation of carbon dioxide according to one embodiment of the present invention. [Figure 6] FIG. 2 is a graph showing the relationship between the time elapsed from the start of injection of the aqueous solution (injection time) and the amount of the aqueous solution injected into the hardened cement body in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Method of manufacturing hardened cement for carbon dioxide fixation] A method for producing a hardened cement body for fixation of carbon dioxide according to one embodiment of the present invention includes injecting a carbon dioxide absorbing liquid containing a carbon dioxide absorbent into the hardened cement body at a pressure higher than normal pressure, thereby causing the hardened cement body to support the carbon dioxide absorbent. In this specification, the term "supported" refers to the carbon dioxide absorbent being attached to both or either one of the interior and the surface of the hardened cement body. In this specification, the hardened cement body functions as a so-called carrier.

[0011] "Hardened cement body" The hardened cement product is a hardened product of a cement composition containing cement and water. In this specification, the term "cured product" refers to a product that has cured to the extent that it does not deform when pressed with a finger. The hardened cement material is preferably concrete.

[0012] "Cement Composition" The cement composition contains cement and water. Examples of the cement composition include concrete (ready mixed concrete), mortar (paste mortar), and cement milk (cement paste). In this specification, concrete refers to a mixture of cement, fine aggregate (sand), and coarse aggregate (gravel (crushed stone)), mixed with water. In this specification, mortar refers to a mixture of cement and fine aggregate (sand) kneaded with water. In this specification, cement milk refers to cement mixed with water only. In this specification, cement refers to a powder that is made primarily from limestone, clay, silica, iron oxide raw materials, etc., and hardens through a chemical reaction with water. In this specification, fine aggregate refers to sand with a diameter of 5 mm or less. In this specification, coarse aggregate refers to gravel (crushed stone) having a diameter of more than 5 mm, and the diameter of the coarse aggregate is preferably 25 mm or less.

[0013] The mixing ratio of cement, fine aggregate, and coarse aggregate in concrete can be appropriately determined depending on the strength required for the concrete. The mixing ratio of cement, fine aggregate, and coarse aggregate is preferably, for example, 1 part cement, 2 to 3 parts fine aggregate, and 4 to 6 parts coarse aggregate by mass ratio.

[0014] The mixing ratio of cement to fine aggregate in the mortar can be appropriately determined depending on the strength required for the mortar. The mixing ratio of cement to fine aggregate is preferably, for example, 1 part cement to 2 to 4 parts fine aggregate by mass ratio.

[0015] "Carbon dioxide absorbing liquid" The carbon dioxide absorbing liquid is a liquid containing a carbon dioxide absorbent capable of absorbing carbon dioxide and a solvent. When the carbon dioxide absorbent is a liquid, the carbon dioxide absorbing liquid does not need to contain a solvent described later.

[0016] The content of the carbon dioxide absorbent in the carbon dioxide absorbing liquid is, for example, preferably 0.01% by mass or more, more preferably 1% by mass or more, and even more preferably 5% by mass or more, based on the total mass of the carbon dioxide absorbing liquid. When the content of the carbon dioxide absorbent is equal to or more than the lower limit, the amount of carbon dioxide that can be fixed can be further increased.

[0017] Examples of the solvent contained in the carbon dioxide absorbing liquid include water and organic solvents such as ethanol. As the solvent, water is preferable because it is difficult to volatilize at room temperature and easily dissolves the carbon dioxide absorbent. These solvents may be used alone or in combination of two or more.

[0018] The content of the solvent is, for example, preferably 25% by mass or more and 99.99% by mass or less, more preferably 50% by mass or more and 99% by mass or less, and even more preferably 75% by mass or more and 95% by mass or less, based on the total mass of the carbon dioxide absorbing liquid. When the content of the solvent is equal to or more than the lower limit, the amount of the carbon dioxide absorbing liquid impregnated into the cement composition can be increased. When the content of the solvent is equal to or less than the upper limit, the content of the carbon dioxide absorbent can be increased. Therefore, the amount of carbon dioxide that can be fixed can be increased.

[0019] The viscosity of the carbon dioxide absorbing liquid at 25° C. is, for example, preferably 20 mPa·s or less, and more preferably 5 mPa·s or less. When the viscosity of the carbon dioxide absorbing liquid at 25° C. is equal to or more than the lower limit, the carbon dioxide absorbing liquid can be easily injected into the hardened cement body. The viscosity of the carbon dioxide absorbing liquid at 25°C can be obtained, for example, by setting the temperature of the measurement target to 25°C, using the No. 2 rotor of a B-type viscometer at a rotation speed of 60 rpm, and reading the value 30 seconds after the rotor starts to rotate.

[0020] The pH of the carbon dioxide absorbing liquid at 20° C. is, for example, preferably 7.0 or more, more preferably 8.5 or more, and even more preferably 10.0 or more. When the pH of the carbon dioxide absorbing liquid at 20° C. is equal to or more than the lower limit, the rate of absorbing carbon dioxide can be further increased. The upper limit of the pH of the carbon dioxide absorbing liquid at 20° C. is not particularly limited, but is set to, for example, 14.0 in consideration of ease of handling. The pH of the carbon dioxide absorbing solution at 20°C can be measured by adjusting the measurement target to 20°C and using a pH meter (for example, compact pH meter LAQUAtwin (registered trademark) pH-22B manufactured by Horiba, Ltd.).

[0021] The carbon dioxide absorbing liquid may contain carbonate ions or bicarbonate ions derived from carbon dioxide. The higher the content of carbonate ions or bicarbonate ions, the more carbon dioxide can be fixed in the hardened cement material for fixation of carbon dioxide during production of the hardened cement material for fixation of carbon dioxide. The content of carbonate ions or bicarbonate ions is, for example, preferably 0.2% mol or more, and more preferably 0.5% mol or more, based on the molar equivalent of nitrogen atoms in the carbon dioxide absorbent. The method for making the carbon dioxide absorbing liquid contain carbonate ions or bicarbonate ions is not particularly limited, but for example, a method of bubbling carbon dioxide gas to dissolve it in the carbon dioxide absorbing liquid, or a method of adding dry ice (solid state) to the carbon dioxide absorbing liquid, etc., can be used.

[0022] "Carbon dioxide absorbent" The carbon dioxide absorbent is contained in the hardened cement body for carbon dioxide fixation and absorbs carbon dioxide in the atmosphere. Therefore, the carbon dioxide in the atmosphere is taken in by the hardened cement body for carbon dioxide fixation, and the carbon dioxide concentration in the atmosphere is reduced. In other words, the carbon dioxide in the atmosphere can be fixed in the hardened cement body for carbon dioxide fixation. The carbon dioxide absorbent may be a solid or a liquid at room temperature and pressure. In this specification, "normal temperature" refers to the standard temperature of the atmosphere, for example, 15° C. to 25° C. "Normal pressure" refers to the standard pressure of the atmosphere, for example, 1 atmosphere (1013 hPa).

[0023] The carbon dioxide absorbent may be, for example, an alkaline compound. Here, the term "alkaline compound" refers to a compound that has a pH of greater than 7 when dissolved in water. The alkaline compound may be an inorganic compound, an organic compound, or a mixture thereof. Examples of inorganic alkaline compounds include calcium hydroxide, magnesium hydroxide, sodium silicate, potassium silicate, lithium silicate, lithium nitrite, and calcium nitrite. Examples of the organic alkaline compound include arginine, lysine, urea, sodium acetate, potassium acetate, and amine compounds. It is preferable that the carbon dioxide absorbent is one that is less likely to cause a decrease in pH when reacting with CO2. The carbon dioxide absorbent may be used alone or in combination of two or more kinds.

[0024] Examples of the amine compounds include aliphatic amines and aromatic amines. As the amine compound, an aliphatic amine is preferred since it is easily soluble in water. Examples of the aliphatic amine include alkylamines and alkanolamines. Examples of alkylamines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, and butylamine. Examples of alkanolamines include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), monoisopropanolamine (MIPA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), N-methylethanolamine (MMEA), and N-methyldiethanolamine (MDEA).

[0025] The amine compound may be any of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium salt, and may have a cyclic structure. In addition to the above, examples of amine compounds include dicyclohexylamine (DCHA), dimethylcyclohexylamine (DMCHA), polyetheramine (PEA), diglycolamine (DGA), 2-amino-2-methyl-1-propanol (AMP90), n-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), pyrrolidine, piperidine, piperazine, morpholine, and the like. These amine compounds may be used alone or in combination of two or more.

[0026] Amine compounds have the effect of inhibiting corrosion of steel materials such as carbon steel. Therefore, when the hardened cement body is reinforced concrete, amine compounds can inhibit corrosion of reinforcing bars in the reinforced concrete. It is generally known that when reinforced concrete absorbs carbon dioxide, neutralization progresses and there is a risk of corrosion of the reinforcing bars due to a decrease in pH. By supporting an amine compound on the hardened cement body, the risk can be reduced. From the above viewpoints, amine compounds are preferable as carbon dioxide absorbents.

[0027] The content of the carbon dioxide absorbent in the hardened cement for carbon dioxide fixation is preferably 1 part by mass or more, and more preferably 5 parts by mass or more, per 100 parts by mass of cement contained in the hardened cement for carbon dioxide fixation. When the content of the carbon dioxide absorbent in the hardened cement for carbon dioxide fixation is equal to or more than the lower limit, the amount of carbon dioxide that can be fixed can be further increased. The content of the carbon dioxide absorbent in the hardened cement material for fixation of carbon dioxide can be adjusted by the type of the hardened cement material, the type of the carbon dioxide absorbent, or a combination thereof.

[0028] In the method for producing a carbon dioxide fixation hardened cement body of the present embodiment, a carbon dioxide absorbing liquid containing a carbon dioxide absorbent is injected into the hardened cement body at a pressure higher than normal pressure (0.1 MPa) to cause the hardened cement body to support the carbon dioxide absorbent.

[0029] Methods for injecting a carbon dioxide absorbent into hardened cement include a low-pressure injection method and a high-pressure injection method.

[0030] In the low-pressure injection method, for example, as shown in FIG. 1, a number of syringes 100 are arranged at equal intervals on the surface 1a of the hardened cement body 1, and the carbon dioxide absorbing liquid is injected into the inside of the hardened cement body 1 from the outlet 101a at the tip of the injection washer 101 of the syringe 100.

[0031] As the syringe 100, as shown in FIG. 2, one that includes an injection washer 101, a cylinder 102, a pressure rubber 103, a ring 104, and a stopper 105 is used.

[0032] When injecting the carbon dioxide absorbent into the hardened cement body using syringe 100, syringe 100 is positioned so that outlet 101a of injection washer 101 faces and contacts surface 1a of hardened cement body 1.

[0033] The interval (pitch) at which the syringes 100 are arranged on the surface 1a of the hardened cement body 1 is preferably 300 mm or more, more preferably 500 mm or more, and even more preferably 1000 mm or more. When the interval at which the syringes 100 are arranged is equal to or more than the lower limit, the efficiency of the operation of injecting the carbon dioxide absorbent into the hardened cement body is improved. The interval at which syringes 100 are arranged refers to the distance between the centers of discharge ports 101 a of injection washers 101 .

[0034] In the low pressure injection method, the pressure of the carbon dioxide absorbing solution when injecting the carbon dioxide absorbent into the hardened cement body is 0.1 MPa or more and less than 0.4 MPa.

[0035] When the carbon dioxide absorbent is injected using the syringe 100, the carbon dioxide absorbent is injected into the hardened cement body by the elastic force of the pressurized rubber 103. In addition, the elastic force of the pressurized rubber 103 adjusts the pressure of the carbon dioxide absorbing liquid.

[0036] In the high-pressure injection method, for example, as shown in FIG. 3, a nozzle 201 of an injection device 200 is placed on the surface 1a of the hardened cement body 1, and the carbon dioxide absorbing liquid is injected into the inside of the hardened cement body 1 from the outlet 201a at the tip of the nozzle 201.

[0037] As the injection device 200, as shown in FIG. 3, one equipped with a nozzle 201, a pressurized tank 202, and a compressor 203 is used.

[0038] The nozzle 201 and the pressurized tank 202 are connected via a liquid supply pipe 204. A valve 205 is provided in the middle of the liquid supply pipe 204. The pressurized tank 202 and the compressor 203 are connected via an air supply pipe 206 and a barometer 207.

[0039] When the carbon dioxide absorbent is injected into the hardened cement body using the injection device 200, the nozzle 201 is positioned so that the discharge port 201a faces and contacts the surface 1a of the hardened cement body 1.

[0040] The interval (pitch) at which the nozzles 201 are arranged on the surface 1a of the hardened cement body 1 is preferably 300 mm or more, more preferably 500 mm or more, and even more preferably 1000 mm or more. When the interval at which the syringes 100 are arranged is equal to or more than the lower limit, the efficiency of the operation of injecting the carbon dioxide absorbent into the hardened cement body is improved. The interval at which the nozzles 201 are arranged refers to the distance between the centers of the outlets 201a of the nozzles 201 at a location on the surface 1a of the hardened cement body 1 where the nozzles 201 are next arranged on the surface 1a of the hardened cement body 1 after the nozzles 201 are arranged at any location on the surface 1a of the hardened cement body 1 and the carbon dioxide absorbent is injected from the nozzles 201 into the hardened cement body.

[0041] In the high pressure injection method, the pressure of the carbon dioxide absorbing liquid when injecting the carbon dioxide absorbent into the hardened cement body is 0.4 MPa or more. If the pressure of the carbon dioxide absorbing liquid is 0.4 MPa or more, the carbon dioxide absorbent can be injected into the hardened cement body using the injection device 200 described above.

[0042] In injecting the carbon dioxide absorbent using the injection device 200, compressed air produced by the compressor 203 is sent into the pressurized tank 202 containing the carbon dioxide absorbing liquid 300, and the compressed air pressurizes the carbon dioxide absorbing liquid 300. Next, when the valve 205 is opened, the carbon dioxide absorbing liquid 300 is pushed out by the compressed air, and the carbon dioxide absorbent is injected into the hardened cement body 1 from the nozzle 201.

[0043] In the method for producing a hardened cement body for fixation of carbon dioxide according to the present embodiment, it is preferable to inject a carbon dioxide absorbing liquid containing a carbon dioxide absorbent into the hardened cement body from an injection port that is formed in advance in the thickness direction from the surface of the hardened cement body.

[0044] The injection port may be a small hole formed by drilling a hole in the thickness direction of the hardened cement body. When the pores are formed by drilling the hardened cement body, the interval (pitch) of the pores on the surface of the hardened cement body is preferably 300 mm or more, more preferably 500 mm or more, and even more preferably 1000 mm or more. When the interval of the pores is equal to or more than the lower limit, the efficiency of the operation of injecting the carbon dioxide absorbent into the hardened cement body is improved. The pore spacing refers to the distance between the centers of the pores.

[0045] When forming pores by drilling holes in the hardened cement body, the depth of the pores is not particularly limited, but is appropriately determined according to the dimensions of the hardened cement body. The deeper the pores are, the more the carbon dioxide absorbing liquid can reach the inside of the hardened cement body.

[0046] When forming pores by drilling into the hardened cement body, the diameter (inner diameter) of the pores is not particularly limited. However, since the smaller the diameter of the pores, the smaller the depth that can be drilled, the diameter should be determined appropriately according to the dimensions of the hardened cement body.

[0047] An example of a method for drilling holes in the hardened cement body in the thickness direction is to drill holes in the hardened cement body from the surface thereof in the thickness direction thereof with a hammer drill or the like.

[0048] Injection of the carbon dioxide absorbing liquid into the hardened cement body through small holes formed by drilling the hardened cement body can be applied to both the low pressure injection method and the high pressure injection method.

[0049] The injection port may be a pore formed when the cement composition is hardened to form a hardened cement body.

[0050] When injection ports are formed during molding of the hardened cement body, the interval (pitch) of the injection ports on the surface of the hardened cement body is preferably 300 mm or more, more preferably 500 mm or more, and even more preferably 1000 mm or more. When the interval of the injection ports is equal to or more than the lower limit, the efficiency of the operation of injecting the carbon dioxide absorbent into the hardened cement body is improved. The spacing between the injection ports means the distance between the centers of the injection ports.

[0051] A method for forming an injection port in a hardened cement body will be described with reference to Figs. As shown in FIG. 4, when pouring concrete, a formwork 400 is used in which an embedding material (foam material or the like) 401 is placed on the inner bottom surface 400a. After pouring a cement composition into this formwork 400, the cement composition is hardened to obtain a hardened cement body 5. Next, the hardened cement body 5 is taken out of the formwork 400, and then the embedding material 401 is removed to obtain the hardened cement body 5 having a large number of injection ports 6 provided at predetermined intervals, as shown in FIG.

[0052] According to the manufacturing method for carbon dioxide fixation hardened cement body of the present embodiment, the carbon dioxide absorbing liquid containing the carbon dioxide absorbent is injected into the inside of the hardened cement body at a pressure higher than normal pressure, so that the carbon dioxide absorbing liquid containing the carbon dioxide absorbent can penetrate deeper into the hardened cement body at an early stage.

[0053] According to the method for producing a carbon dioxide fixation hardened cement body of the present embodiment, the carbon dioxide absorbing liquid can be diffused deeper into the hardened cement body, so that CO2 can be fixed inside the hardened cement body more quickly than in a method in which the carbon dioxide absorbing liquid is applied to the surface of the hardened cement body and the hardened cement body is impregnated with the carbon dioxide absorbing liquid.

[0054] According to the manufacturing method for carbon dioxide fixation hardened cement body of this embodiment, when CO2 is released from the carbonate ions or bicarbonate ions contained in the carbon dioxide absorbing liquid and fixed in the hardened cement body, the carbon dioxide absorbing liquid injected into the hardened cement body becomes able to absorb new CO2 to that extent. In other words, the carbon dioxide absorbing liquid containing CO2 injected into the hardened cement body functions as the carbon dioxide absorbing liquid after injection into the hardened cement body, and continuously exerts the effect of promoting fixation of CO2.

[0055] According to the method for producing a hardened cement body for carbon dioxide fixation of this embodiment, the risk of CO2 gas leakage can be significantly reduced compared to a conventional method in which the hardened cement body is left in a high-concentration CO2 gas environment and carbonation is promoted from the surface of the hardened cement body.

[0056] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. EXAMPLES

[0057] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to these examples.

[0058] [Example 1] As a carbon dioxide absorbent, an aqueous solution A containing 10 mass % N-methyldiethanolamine (MDEA) was prepared. Aqueous solution A was filled into the syringe shown in FIG. A number of the syringes were placed at equal intervals on the surface of a concrete wall, as shown in Figure 1. The pressure of the aqueous solution A was adjusted to 0.2 MPa using the elasticity of the pressure rubber of the syringe, and the aqueous solution A was injected into the hardened cement body from the outlet at the tip of the injection washer of the syringe. The time elapsed from the start of injection of Aqueous Solution A (injection time) and the amount of Aqueous Solution A injected per syringe into the hardened cement paste were investigated. The results are shown in Figure 6.

[0059] [Example 2] Aqueous solution A was injected into the hardened cement body in the same manner as in Example 1, except that the pressure of the aqueous solution A was set to 0.3 MPa. The time elapsed from the start of injection of aqueous solution A (injection time) and the amount of aqueous solution A injected into the hardened cement paste were investigated. The results are shown in Figure 6.

[0060] [Comparative Example] The injection method of lithium nitrite solution is well known as a repair method for reinforced concrete structures with rebar corrosion. In this method, a lithium nitrite solution of about 40 mass % close to the saturation concentration is injected into the reinforced concrete structure. This solution is called solution B. In the same manner as in Example 1, the aqueous solution B was injected into the inside of the concrete wall. The time elapsed from the start of injection of Solution B (injection time) and the amount of Solution B injected into the hardened cement paste were investigated. The results are shown in Figure 6.

[0061] From the results shown in FIG. 6, it was found that aqueous solution A containing N-methyldiethanolamine required a larger injection amount into the concrete wall than aqueous solution B containing lithium nitrite. [Explanation of symbols]

[0062] 1 Hardened cement 100 Syringes 200 Injection device 201 Nozzle 202 Pressurized Tank 203 Compressor

Claims

1. A method for producing a hardened cement body for fixation of carbon dioxide, comprising: injecting a carbon dioxide absorbing liquid containing a carbon dioxide absorbent into the hardened cement body at a pressure higher than normal pressure, thereby causing the hardened cement body to support the carbon dioxide absorbent.

2. 2. The method for producing a hardened cement material for fixation of carbon dioxide according to claim 1, wherein the pressure is less than 0.4 MPa.

3. 2. The method for producing a hardened cement product for fixation of carbon dioxide according to claim 1, wherein the pressure is 0.4 MPa or more.

4. The method for producing a hardened cement product for fixation of carbon dioxide according to claim 1, wherein the carbon dioxide absorbing liquid contains carbonate ions or bicarbonate ions derived from carbon dioxide.

5. 2. The method for producing a carbon dioxide fixation hardened cement body according to claim 1, further comprising the step of: injecting a carbon dioxide absorbing liquid containing a carbon dioxide absorbent into the hardened cement body through an injection port that is formed in advance in a thickness direction from a surface of the hardened cement body.

6. The method for producing a hardened cement body for fixation of carbon dioxide according to claim 5, wherein the injection port is a small hole formed by drilling the hardened cement body in a thickness direction.

7. 6. The method for producing a hardened cement body for fixation of carbon dioxide according to claim 5, wherein the injection port is a pore formed when the cement composition is hardened to form the hardened cement body.

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