Carbon dioxide fixation method and method for manufacturing an existing concrete structure equipped with a carbon dioxide fixation unit

Abstract

To provide a carbon dioxide gas fixation method that can fix a carbon dioxide gas without breaking an existing concrete structure, and to provide a method for manufacturing an existing concrete structure including a carbon dioxide gas fixation part.SOLUTION: A carbon dioxide gas fixation method includes: a boring step of boring at least one or more holes having a predetermined length toward an inside from a surface of an existing concrete structure; and a carbon dioxide gas source supply step of supplying a carbon dioxide gas source into the holes, where the carbon dioxide gas is fixed to at least inner surfaces of the holes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide fixation method and a method for manufacturing an existing concrete structure equipped with a carbon dioxide fixation section. [Background technology]

[0002] Concrete may contain unhydrated cement. When unhydrated cement is present in concrete, the strength of the concrete can be improved by introducing water or steam into the concrete, causing the unhydrated cement to react with the water.

[0003] Furthermore, for example, Patent Document 1 describes a method for increasing the strength of concrete in which a gas or liquid that reacts with cement hydrate to form a solid is prepared to an appropriate concentration that has a strength-increasing effect depending on the gas or liquid, and is allowed to penetrate into voids in the concrete of all or the surface layer of a concrete structure to generate a reaction product between the cement hydrate and the gas or liquid, which fills the voids in the concrete of all or the surface layer of the concrete structure and densifies the structure. In Patent Document 1, a gas such as sulfur dioxide or a liquid such as a sulfuric acid solution is reacted with cement hydrate to generate a reaction product that densifies the structure, thereby increasing the strength of the entire concrete without relying on strength amplification due to the hydration of unhydrated cement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-15869 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a carbon dioxide gas immobilization method capable of immobilizing carbon dioxide gas without destroying an existing concrete structure, and a method for manufacturing an existing concrete structure equipped with a carbon dioxide gas immobilization section. [Means for solving the problem]

[0006] [1] A carbon dioxide fixation method comprising a hole drilling step of drilling at least one hole having a predetermined length from the surface toward the interior of an existing concrete structure, and a carbon dioxide source supplying step of supplying a carbon dioxide source to the hole, thereby fixing carbon dioxide on at least the inner surface of the hole. [2] The carbon dioxide fixation method according to [1] above, wherein in the carbon dioxide source supply step, the humidity in the hole is 40% RH or less and 60% RH or less, and the carbon dioxide source is at least one of a gaseous and solid carbon dioxide source. [3] The carbon dioxide fixation method according to [1] above, wherein in the carbon dioxide source supplying step, the humidity in the hole is 20% RH or less, and the carbon dioxide source contains a liquid carbon dioxide source. [4] The carbon dioxide fixation method according to any one of the above [1] to [3], wherein in the hole-making step, the holes are made while water is being poured onto the existing concrete structure. [5] The carbon dioxide fixation method according to any one of the above [1] to [4], further comprising a humidity control step of controlling the humidity in the hole, which is carried out before the carbon dioxide source supply step. [6] The carbon dioxide fixation method according to [5] above, wherein in the humidity adjustment step, a dry gas having a humidity lower than that of the holes is supplied to the holes. [7] The carbon dioxide fixation method according to the above [5], wherein the pressure in the hole is reduced in the humidity adjustment step. [8] The method for immobilizing carbon dioxide gas according to any one of the above [1] to [7], wherein the carbon dioxide gas source is injected into the hole in the carbon dioxide gas source supplying step. [9] The carbon dioxide fixation method according to [7] or [8] above, wherein in the hole drilling step, a plurality of holes are drilled, in the humidity adjustment step, at least one of the plurality of holes is depressurized, and in the carbon dioxide source supply step, the carbon dioxide source is pressurized into at least one of the holes other than the hole depressurized in the humidity adjustment step.

[10] The carbon dioxide fixation method according to any one of the above [5] to [9], wherein the humidity adjustment step and the carbon dioxide source supply step are repeated.

[11] The carbon dioxide fixation method according to any one of the above [1] to

[10] , further comprising a filling step, which is carried out after the carbon dioxide source supply step, of filling the holes with an immobilization substance that fixes carbon dioxide.

[12] The method for immobilizing carbon dioxide gas according to any one of the above [1] to

[11] , wherein the diameter of the hole is 5 mm or more and 100 mm or less.

[13] The method for immobilizing carbon dioxide gas according to any one of the above [1] to

[12] , wherein the length of the hole is 200 mm or more.

[14] A method for fixing carbon dioxide gas according to any one of the above [1] to

[13] , wherein the amount of the carbon dioxide gas source supplied in the carbon dioxide gas source supplying step is adjusted based on at least one of the pH of the holes opened in the hole-opening step and the pH of the concrete powder produced in the hole-opening step.

[15] A method for manufacturing an existing concrete structure equipped with a carbon dioxide fixation section, comprising: a hole drilling step of drilling at least one hole having a predetermined length from the surface toward the interior of the existing concrete structure; and a carbon dioxide source supplying step of supplying a carbon dioxide source to the hole, wherein a carbon dioxide fixation section that fixes carbon dioxide is provided on at least the inner surface of the hole. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a carbon dioxide immobilization method that can immobilize carbon dioxide without destroying an existing concrete structure, and a method for manufacturing an existing concrete structure equipped with a carbon dioxide immobilization section. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a flowchart showing an example of the carbon dioxide gas fixation method of the first embodiment. [Figure 2] FIG. 2 is an overall view showing an example of an existing concrete structure used in the carbon dioxide fixation method of the first embodiment. [Figure 3] FIG. 3 is a perspective view showing an example of a hole-making step in the carbon dioxide gas fixation method of the first embodiment. [Figure 4] FIG. 4 is a perspective view showing an example of a humidity adjustment step (drying) in the carbon dioxide fixation method of the first embodiment. [Figure 5] FIG. 5 is a perspective view showing another example (decompression) of the humidity adjustment step in the carbon dioxide gas fixation method of the first embodiment. [Figure 6] FIG. 6 is a perspective view showing an example of the carbon dioxide gas source supplying step in the carbon dioxide gas fixation method of the first embodiment. [Figure 7] FIG. 7 is a perspective view showing an example of a carbon dioxide gas immobilization section formed by the carbon dioxide gas immobilization method of the first embodiment. [Figure 8] FIG. 8 is a perspective view showing an example of the filling step in the carbon dioxide gas fixation method of the first embodiment. [Figure 9] FIG. 9 is a perspective view showing an example in which a protection section is installed on an existing concrete structure in the carbon dioxide fixation method of the first embodiment. [Figure 10] FIG. 10 is a perspective view showing an example of the humidity adjustment step (decompression) in the carbon dioxide fixation method of the second embodiment. [Figure 11] FIG. 11 is a perspective view showing an example of the carbon dioxide gas source supplying step in the carbon dioxide gas fixation method of the second embodiment. [Figure 12] FIG. 12 is a perspective view showing an example of a carbon dioxide gas immobilization section formed by the carbon dioxide gas immobilization method of the second embodiment. [Figure 13] FIG. 13 is a perspective view showing an example in which a protection section is installed on an existing concrete structure in the carbon dioxide fixation method of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a detailed description will be given based on an embodiment.

[0010] As a result of extensive research, the inventors have focused on the recent need to reduce carbon dioxide (carbon dioxide, CO2) in the atmosphere in order to curb climate change, and have conducted extensive research into reducing carbon dioxide in the atmosphere. As a result of their extensive research, the inventors have discovered a way to immobilize carbon dioxide without destroying existing concrete structures, and have completed the present invention based on this finding.

[0011] The carbon dioxide fixation method of the present invention includes a hole drilling step of drilling at least one hole having a predetermined length from the surface toward the inside of an existing concrete structure, and a carbon dioxide source supplying step of supplying a carbon dioxide source to the hole, thereby fixing carbon dioxide at least on the inner surface of the hole.

[0012] The method of the present invention for manufacturing an existing concrete structure equipped with a carbon dioxide fixation section includes a hole drilling step of drilling at least one hole having a predetermined length from the surface toward the inside of the existing concrete structure, and a carbon dioxide source supplying step of supplying a carbon dioxide source to the hole, and provides a carbon dioxide fixation section in which carbon dioxide is fixed on at least the inner surface of the hole.

[0013] (First embodiment) FIG. 1 is a flowchart showing an example of the carbon dioxide gas fixation method of the first embodiment. FIG. 2 is an overall view showing an example of an existing concrete structure used in the carbon dioxide gas fixation method of the first embodiment. FIG. 3 is a perspective view showing an example of a hole drilling step in the carbon dioxide gas fixation method of the first embodiment. FIG. 4 is a perspective view showing an example of a humidity adjustment step (drying) in the carbon dioxide gas fixation method of the first embodiment. FIG. 5 is a perspective view showing another example of a humidity adjustment step (depressurization) in the carbon dioxide gas fixation method of the first embodiment. FIG. 6 is a perspective view showing an example of a carbon dioxide gas source supply step in the carbon dioxide gas fixation method of the first embodiment. FIG. 7 is a perspective view showing an example of a carbon dioxide gas fixation section formed in the carbon dioxide gas fixation method of the first embodiment.

[0014] Although Fig. 2 shows an example in which the existing concrete structure is a building, the existing concrete structure may also be a civil engineering structure such as a dam. Fig. 2 shows an overall view of the existing concrete structure, while Figs. 3 to 7 and Figs. 8 to 13, which will be described later, show enlarged views of the existing concrete structure. Figs. 3 to 13 also show some parts in transparent view.

[0015] As shown in Fig. 1, the carbon dioxide immobilization method of the first embodiment includes a hole drilling step and a carbon dioxide source supplying step. Then, in the existing concrete structure 1 that has been subjected to the carbon dioxide source supplying step, carbon dioxide is immobilized at least on the inner surface of the hole 10. As shown in Fig. 2, the existing concrete structure 1 in which carbon dioxide is immobilized is, for example, an existing concrete structure in the air.

[0016] In the hole drilling step constituting the carbon dioxide fixation method, as shown in FIG. 3, at least one hole 10 having a predetermined length is drilled from the surface toward the inside of the existing concrete structure 1. The hole 10 is a cavity. For example, the hole 10 is drilled by boring using a drill. When the hole drilling step is completed, at least one hole 10 is provided in the existing concrete structure 1.

[0017] Here, an example is shown in which hole 10 is drilled in the outer wall of existing concrete structure 1, but the part of existing concrete structure 1 in which hole 10 is drilled is not particularly limited. Also, an example is shown in which hole 10 does not penetrate existing concrete structure 1, but hole 10 may penetrate existing concrete structure 1. Also, an example is shown in which hole 10 is in a non-coring form, but hole 10 may be in a coring form.

[0018] In order to increase the amount of carbon dioxide gas fixed in the existing concrete structure 1, it is preferable to drill a plurality of holes 10 in the existing concrete structure 1, as shown in Fig. 3. In this case, when the drilling step is completed, a plurality of holes 10 are formed in the existing concrete structure 1. For example, as shown in Fig. 3, the plurality of holes 10 are independent and do not communicate with each other.

[0019] The lower limit of the diameter of the hole 10 formed in the existing concrete structure 1 is preferably 5 mm or more, more preferably 20 mm or more, and the upper limit is preferably 100 mm or less, more preferably 50 mm or less. When the diameter of the hole 10 is equal to or greater than the above-mentioned lower limit, the carbon dioxide gas source can be easily supplied to the hole 10 in the carbon dioxide gas source supplying step. When the diameter of the hole 10 is equal to or less than the above-mentioned upper limit, the structural strength of the existing concrete structure 1 having the hole 10 can be sufficiently maintained.

[0020] The length of the hole 10 formed in the existing concrete structure 1 is preferably 200 mm or more, and more preferably 1000 mm or more. If the length of the hole 10 is 200 mm, the hole 10 can be drilled during the drilling process while reliably avoiding rebar (not shown) in the existing concrete structure 1 that is located further inside than the hole. Furthermore, if the length of the hole 10 is 200 mm or more, it becomes possible to measure the compressive strength of a sample of the existing concrete structure 1 that can be collected by drilling the hole 10 in order to investigate the strength of the existing concrete structure 1. Furthermore, since the amount of carbon dioxide gas fixed in the existing concrete structure 1 can be increased as the hole 10 becomes longer, the hole 10 may penetrate the existing concrete structure 1.

[0021] When the existing concrete structure 1 has a plurality of holes 10, the compressive strength of the existing concrete structure 1 is 24 N / mm 2 For ordinary concrete structures with a compressive strength of about 40 N / mm, the thickness is preferably 500 mm or less, more preferably 150 mm or less. 2 In an existing concrete structure 1 having a size of about 100 mm, the interval d1 between the holes 10 is preferably 200 mm or less, and more preferably 100 mm or less. The interval d1 between the holes 10 is the shortest interval between the edge of a hole and the edge of multiple adjacent holes, as shown in Figure 3. If the interval d1 between the holes 10 is within the above range, the amount of carbon dioxide gas fixed in the existing concrete structure 1 can be further increased.

[0022] In this way, the interval d1 between the holes 10 can be set appropriately depending on the compressive strength of the existing concrete structure 1. When the interval d1 between the holes 10 is within the above range, the holes 10 may communicate with each other depending on their diameters.

[0023] Furthermore, in terms of ease of processing and processing accuracy of the holes 10, it is preferable to drill the holes 10 while pouring water on the existing concrete structure 1 in the drilling step. In this case, water may be present in the formed holes 10.

[0024] 1 and 4 to 5, the carbon dioxide gas fixation method of the first embodiment preferably further includes a humidity control step, which is carried out before the carbon dioxide gas source supply step, of controlling the humidity of the hole 10. The humidity of the hole 10 refers to the humidity at the opening of the hole 10.

[0025] For example, if at least one gaseous or solid carbon dioxide source is supplied to hole 10, whose humidity has been controlled to 40% RH or less and 60% RH or less in the humidity adjustment step, in the carbon dioxide source supply step described in detail below, the carbon dioxide fixation rate increases, allowing carbon dioxide to be fixed in an even shorter time and further increasing the amount of carbon dioxide that can be fixed. The shorter time and larger amount of carbon dioxide fixation using a carbon dioxide source in this state improves as the humidity of hole 10 approaches 50% RH. Therefore, when at least one gaseous or solid carbon dioxide source is supplied to hole 10, it is preferable to control the humidity of hole 10 to 40% RH or less and 60% RH or less in the humidity adjustment step, and it is most preferable to control the humidity of hole 10 to 50% RH.

[0026] Furthermore, if a carbon dioxide gas source containing a liquid carbon dioxide gas source is supplied to hole 10, the humidity of which has been controlled to 20% RH or less in the humidity adjustment step, in the carbon dioxide gas source supply step, the carbon dioxide gas source penetrates throughout hole 10 in a short time, allowing carbon dioxide gas to be immobilized in an even shorter time and further increasing the amount of carbon dioxide gas that can be immobilized. The shorter the time and the larger the amount of carbon dioxide gas immobilization using a carbon dioxide gas source in this state, the lower the humidity of hole 10. Therefore, when a carbon dioxide gas source containing a liquid carbon dioxide gas source is supplied to hole 10, it is preferable to control the humidity of hole 10 to 20% RH or less in the humidity adjustment step, more preferably to control the humidity of hole 10 to 10% RH or less, and most preferably to control the humidity of hole 10 to 0% RH.

[0027] When a plurality of holes 10 are provided in the existing concrete structure 1, it is preferable to subject all of the plurality of holes 10 to the humidity conditioning process in order to shorten the time required for fixing carbon dioxide gas and increase the amount of carbon dioxide gas.

[0028] As an example of the humidity adjustment step, as shown in FIG. 4, it is preferable to supply a dry gas having a humidity lower than the humidity of the hole 10 to the hole 10. Humidity control using such a dry gas is easily performed. In order to control the humidity of the hole 10 to a predetermined value or less in a short time, it is preferable to pressurize the dry gas into the hole 10. Furthermore, in terms of ease of handling and workability, it is preferable that the dry gas is dry air. In particular, when a gaseous carbon dioxide source is supplied to the hole 10 in the carbon dioxide source supply step, it is preferable that the dry gas contains carbon dioxide.

[0029] As another example of the humidity control process, it is preferable to reduce the pressure in the hole 10, as shown in Figure 5. Humidity control by such reduction in pressure can be easily performed. For example, a suction pump is used. When the pressure in the hole 10 is reduced, the pressure in the hole 10 becomes lower than the pressure outside the existing concrete structure 1 (atmospheric pressure). Therefore, in the carbon dioxide gas source supplying process performed after reduction in pressure, the carbon dioxide gas source can be supplied throughout the entire hole 10 in a short period of time. The lower the pressure in the hole 10, the better.

[0030] In the carbon dioxide source supplying step, which is performed after the hole drilling step, or after the humidity adjustment step if the carbon dioxide fixation method includes the humidity adjustment step, a carbon dioxide source is supplied to the holes 10, as shown in Figure 6. When multiple holes 10 are provided in the existing concrete structure 1, it is sufficient to supply the carbon dioxide source to at least one or more holes 10, but it is preferable to supply the carbon dioxide source to all of the multiple holes 10 in order to efficiently increase the amount of carbon dioxide fixated in the existing concrete structure 1 in a short period of time.

[0031] Here, the existing concrete structure 1 hardens by forming calcium hydroxide, CSH, etc. as a result of the reaction between cement and water. The calcium hydroxide and CSH that make up the existing concrete structure 1 are contained in large amounts inside the existing concrete structure 1, and have the ability to react with carbon dioxide to become calcium carbonate.

[0032] After drilling holes 10 in the existing concrete structure 1, when a carbon dioxide source is supplied to the holes 10, calcium hydroxide and CSH contained in large amounts inside the existing concrete structure 1 react with the carbon dioxide supplied from outside the existing concrete structure 1. In this way, the carbon dioxide can be fixed in the existing concrete structure 1.

[0033] When carbon dioxide reacts with calcium hydroxide and CSH and is fixed in the existing concrete structure 1, carbon dioxide fixing portions 20 are formed in the existing concrete structure 1, as shown in FIG. 7. The carbon dioxide fixing portions 20 are formed at least on the inner surface of the holes 10. Furthermore, when the carbon dioxide supplied to the holes 10 is also supplied to a plurality of micropores (not shown) that are smaller than the holes 10 and exist within the existing concrete structure 1, the carbon dioxide fixing portions 20 are formed not only on the inner surface of the holes 10 but also inside the existing concrete structure 1 excluding the inner surface of the holes 10. The type and distribution of the carbon dioxide fixing portions 20 depend on the type of carbon dioxide source supplied to the holes 10, etc.

[0034] In this way, in the carbon dioxide fixation method of the first embodiment, carbon dioxide can be fixed in the existing concrete structure 1 without destroying the existing concrete structure 1. For example, in the carbon dioxide fixation method of the first embodiment, the existing concrete structure 1 is not demolished. In other words, in the carbon dioxide fixation method of the first embodiment, the existing concrete structure 1 is not discarded as waste material.

[0035] In addition, generally, during the drilling process of drilling the hole 10 in the existing concrete structure 1, the inside of the hole 10 becomes moist. Therefore, in the carbon dioxide source supplying process, when the carbon dioxide source is at least one of a gaseous and a solid carbon dioxide source, the humidity of the hole 10 is preferably 40% RH or less and 60% RH or less, and most preferably 50% RH. The term "at least one of a gaseous and a solid carbon dioxide source" refers to a gaseous carbon dioxide source, a solid carbon dioxide source, or a mixture of a gaseous and a solid carbon dioxide source. When the humidity of the hole 10 is within the above range, the carbon dioxide fixation rate increases, allowing carbon dioxide to be fixed in a shorter time and the amount of carbon dioxide that can be fixed to be further increased. In particular, as the humidity of the hole approaches 50% RH, the time required for carbon dioxide fixation and the amount of carbon dioxide that can be fixed improve.

[0036] Furthermore, in the carbon dioxide gas source supply step, when the carbon dioxide gas source is a carbon dioxide gas source containing a liquid carbon dioxide gas source, the humidity of the hole 10 is preferably 20% RH or less, more preferably 10% RH or less, and most preferably 0% RH. When the humidity of the hole 10 is within the above range, the carbon dioxide gas source penetrates throughout the entire hole 10 in a short time, so that the carbon dioxide gas can be immobilized in an even shorter time and the amount of carbon dioxide gas that can be immobilized can be further increased. The lower the humidity of the hole, the shorter the time for immobilizing the carbon dioxide gas and the greater the increase in the amount.

[0037] Furthermore, in the carbon dioxide gas source supplying step, the lower limit of the temperature of the hole 10 through which the carbon dioxide gas source is supplied is preferably 10°C or higher, more preferably 40°C or higher, and the upper limit is preferably 100°C or lower, more preferably 60°C or lower. The temperature of the hole 10 refers to the temperature of the opening of the hole 10. If the temperature of the hole 10 is equal to or higher than the lower limit, the carbon dioxide gas can be immobilized in an even shorter time, and the amount of carbon dioxide gas that can be immobilized can be further increased. If the temperature of the hole 10 is equal to or lower than the upper limit, the temperature can be easily controlled.

[0038] Furthermore, in the carbon dioxide gas source supplying step, if the carbon dioxide gas source is injected into the hole 10, the carbon dioxide gas source can be supplied in a short time throughout the entire hole 10. Therefore, the carbon dioxide gas can be immobilized in an even shorter time, and the amount of carbon dioxide gas that can be immobilized can be further increased.

[0039] In the carbon dioxide source supplying step, the form of supplying the carbon dioxide source to the hole 10 is not particularly limited and can be selected appropriately depending on the type of carbon dioxide source, the condition of the existing concrete structure 1, etc. For example, the carbon dioxide source may be supplied to the hole 10 continuously, intermittently, or only once.

[0040] The type of carbon dioxide gas source supplied to hole 10 is not particularly limited as long as it can immobilize carbon dioxide gas in the existing concrete structure 1. From the viewpoints of being able to efficiently immobilize carbon dioxide gas in the existing concrete structure 1, ease of handling of the carbon dioxide gas source, and ease of availability, it is preferable to use a solid, liquid, or gaseous carbon dioxide gas source as listed below.

[0041] The solid carbon dioxide gas source is preferably dry ice or crushed dry ice. Also, the solid carbon dioxide gas source is preferably a microorganism that continuously emits carbon dioxide gas under a specific environment, such as cyanobacteria.

[0042] Liquid carbon dioxide gas sources are preferably CO2-dissolved water, CO2-saturated solution, CO2 nanobubble water, etc. Also, liquid carbon dioxide gas sources are preferably aqueous solutions of alkali carbonates such as K2CO3 solution, Na2CO3 solution, NaHCO3 solution, Li2CO3 solution, Ca(HCO3)2 solution, KHCO3 solution, and NH4HCO3 solution. Also, liquid carbon dioxide gas sources are preferably dry ice or carbon dioxide gas dissolved in water.

[0043] The gaseous carbon dioxide source is preferably carbon dioxide gas, a mixed gas containing carbon dioxide gas, or various exhaust gases. The various exhaust gases are preferably exhaust gas from a thermal power plant, exhaust gas from a boiler, or exhaust gas containing carbon dioxide emitted in the manufacturing process of other products. Furthermore, the humidity and temperature of the exhaust gas may be adjusted, and the adjusted exhaust gas may be used as the gaseous carbon dioxide source.

[0044] Only one carbon dioxide gas source may be used, or two or more carbon dioxide gas sources may be used in combination. When two or more carbon dioxide gas sources are used in combination, the multiple carbon dioxide gas sources may be used as a mixture, or each carbon dioxide gas source may be used separately.

[0045] In the carbon dioxide source supplying step, the carbon dioxide concentration in the hole 10 into which the carbon dioxide source is supplied is preferably 2% or more, more preferably 20% or more, and even more preferably 80% or more. The carbon dioxide concentration in the hole 10 is the carbon dioxide concentration at the opening of the hole 10. When the carbon dioxide concentration in the hole 10 is 2% or more, the carbon dioxide can be immobilized in an even shorter time and the amount of carbon dioxide that can be immobilized can be further increased. With regard to shortening the time required for immobilizing carbon dioxide and increasing the amount, the carbon dioxide concentration in the hole 10 is preferably 2% or more, and this improves as the carbon dioxide concentration in the hole 10 increases.

[0046] In addition, in order to sufficiently fix carbon dioxide gas in the existing concrete, it is preferable to repeat the humidity adjustment step and the carbon dioxide gas source supply step.

[0047] 1 and 8, the carbon dioxide gas immobilization method of the first embodiment preferably further includes a filling step, which is carried out after the carbon dioxide gas source supply step, of filling the holes 10 with an immobilization substance 30 that immobilizes carbon dioxide gas. The immobilization substance 30 may be filled in the entire holes 10 as shown in FIG. 8, or may be filled in only a part of the holes 10.

[0048] In terms of the ability of the immobilization substance 30 to efficiently immobilize carbon dioxide gas, it is preferable that the immobilization substance 30 be a cement-containing liquid obtained by solid-liquid separation of concrete waste containing unsolidified cement fine particles into a cement-containing liquid containing at least a portion of the unsolidified cement fine particles and a solid content.

[0049] This cement-containing liquid contains calcium and calcium in the cement particles. When the carbon dioxide gas source supplied into the hole 10 in the carbon dioxide gas source supplying step or carbon dioxide gas supplied from outside the existing concrete structure 1 enters the immobilizing substance 30 filled in the hole 10, the calcium in the cement-containing liquid that constitutes the immobilizing substance 30 reacts with the carbon dioxide gas to form calcium carbonate. In this way, the immobilizing substance 30 filled in the hole 10 of the existing concrete structure 1 can immobilize carbon dioxide gas. In this way, when the carbon dioxide gas immobilization method of the first embodiment includes the filling step, the amount of carbon dioxide gas immobilized in the existing concrete structure 1 can be further increased.

[0050] Furthermore, as shown in FIG. 9 , a protective unit 40 that covers the opening of the hole 10 may be provided on the existing concrete structure 1. The protective unit 40 is attached to the existing concrete structure 1 by bolts (not shown) or the like. A bolt hole (not shown) formed on the surface of the existing concrete structure 1 for inserting a bolt is much smaller than the hole 10. The protective unit 40 is provided so as to be able to open and close the opening of the hole 10, or is provided so as to be detachable from the existing concrete structure 1. The opening of the hole 10 can be appropriately opened and closed by the protective unit 40 in the carbon dioxide source supplying process, humidity control process, and filling process, depending on the condition of the existing concrete structure 1, the type of carbon dioxide source, and the like. Similarly, the timing for installing the protective unit 40 on the existing concrete structure 1 can be appropriately set depending on the condition of the existing concrete structure 1, the type of carbon dioxide source, and the like. Note that, although an example in which one protective unit 40 is installed for one hole 10 is shown here, one protective unit 40 may be installed for multiple holes 10.

[0051] Next, a method for manufacturing an existing concrete structure equipped with the carbon dioxide gas immobilization section of the first embodiment will be described.

[0052] The method for manufacturing an existing concrete structure equipped with a carbon dioxide gas immobilization unit can be manufactured by the above-mentioned carbon dioxide gas immobilization method. Therefore, this manufacturing method includes the above-mentioned hole drilling step and carbon dioxide gas source supply step. It may also include the above-mentioned humidity adjustment step and filling step.

[0053] By carrying out the carbon dioxide source supplying step, the existing concrete structure 1 can be provided with a carbon dioxide immobilization section 20 in which carbon dioxide is immobilized at least on the inner surface of the hole 10, as shown in Fig. 7. In this way, an existing concrete structure 1 in which carbon dioxide is immobilized can be manufactured.

[0054] (Second embodiment) Fig. 10 is a perspective view showing an example of a humidity adjustment step (depressurization) in the carbon dioxide fixation method of the second embodiment. Fig. 11 is a perspective view showing an example of a carbon dioxide source supply step in the carbon dioxide fixation method of the second embodiment. Fig. 12 is a perspective view showing an example of a carbon dioxide fixation section formed in the carbon dioxide fixation method of the second embodiment. Fig. 13 is a perspective view showing an example of a protection section installed in an existing concrete structure in the carbon dioxide fixation method of the second embodiment.

[0055] In the embodiments described below, the same components as those in the carbon dioxide fixation method and the method for manufacturing an existing concrete structure equipped with a carbon dioxide fixation section of the first embodiment are given the same symbols, and duplicate explanations will be omitted or simplified.

[0056] The carbon dioxide fixation method of the second embodiment is basically the same as the carbon dioxide fixation method of the second embodiment except for the humidity adjustment step and the carbon dioxide source supply step, so the different configurations will be mainly described here.

[0057] As shown in Figure 10, an existing concrete structure 1 has a plurality of holes 10. In the humidity control process, at least one or more holes 10a (also referred to as decompression hole 10a) of the plurality of holes 10 are decompressed. Then, as shown in Figure 11, in the carbon dioxide source supplying process, a carbon dioxide source is injected into at least one or more holes 10b (also referred to as carbon dioxide source supply hole 10b) other than hole 10a decompressed in the humidity control process. Here, an example is shown in which the decompression process is performed on three holes 10a located on the lower side of the existing concrete structure 1, and the carbon dioxide source supplying process is performed on three holes 10b located on the upper side of the existing concrete structure 1.

[0058] As described above, the multiple holes 10 formed in the existing concrete structure 1 during the hole drilling process are not interconnected. However, the multiple holes 10 may be connected to each other via multiple micropores (not shown) that are smaller than the holes 10. Therefore, as shown in FIG. 10, by depressurizing the depressurization hole 10a during the depressurization process, the carbon dioxide gas source supply hole 10b can also be depressurized via the multiple micropores (not shown). Then, as shown in FIG. 11, by injecting a carbon dioxide gas source into the carbon dioxide gas source supply hole 10b during the carbon dioxide gas source supply process, as shown in FIG. 12, a carbon dioxide gas immobilization section 20 can be easily formed in a short time on at least the inner surface of the carbon dioxide gas source supply hole 10b. As a result, carbon dioxide immobilization in the existing concrete structure 1 can be achieved in an even shorter time. Furthermore, as shown in FIG. 13, a protective section 40 may be provided in the existing concrete structure 1 to cover the openings of the depressurization hole 10a and the carbon dioxide gas source supply hole 10b.

[0059] It is preferable that the decompression hole 10a and the carbon dioxide gas source supply hole 10b are adjacent to each other in order to decompress the carbon dioxide gas source supply hole 10b in a short time by decompressing the decompression hole 10a. Also, in order to decompress the carbon dioxide gas source supply hole 10b in a short time and sufficiently fix the carbon dioxide gas in the existing concrete, it is preferable to repeat the decompression step and the carbon dioxide gas source supply step, or to carry out the decompression step and the carbon dioxide gas source supply step simultaneously.

[0060] (Third embodiment) The carbon dioxide fixation method of the third embodiment is basically the same as the carbon dioxide fixation method of the first embodiment except for the carbon dioxide source supply step, so the different configuration will be mainly described here.

[0061] In the third embodiment, at least one of the pH of the hole 10 drilled in the drilling process and the pH of the concrete powder generated in the drilling process is measured. The distribution and amount of calcium hydroxide and CSH in the existing concrete structure 1 can be indirectly determined from the pH value. The pH of the hole 10 refers to the pH of the inner surface of the hole 10. The pH of the concrete powder refers to the concrete powder generated from the existing concrete structure 1 when the hole 10 is drilled in the drilling process, and the concrete powder contains water. The pH is measured using, for example, a pH meter or a pH indicator such as phenolphthalein solution.

[0062] Then, the amount of carbon dioxide source supplied in the carbon dioxide source supplying step is adjusted based on at least one of the pH of the hole 10 and the pH of the concrete powder. For example, if the pH is above 12, the amount of carbon dioxide source supplied in the carbon dioxide source supplying step is increased, and if the pH is 12 or less, the amount of carbon dioxide source supplied in the carbon dioxide source supplying step is decreased.

[0063] Furthermore, for example, if the pH is above 12.5 and the torque for drilling holes 10 is large, the existing concrete structure 1 has a large amount of cement and the compressive strength of the existing concrete structure 1 is high, so the spacing d1 of holes 10 is made smaller. If the pH is 12.5 or less and the torque for drilling holes 10 is small, the existing concrete structure 1 may be made of blended cement and the compressive strength of the existing concrete structure 1 is low, so the spacing d1 of holes 10 is made larger. If the pH is 12.5 or less and the torque for drilling holes 10 is large, the existing concrete structure 1 may be made of blended cement and the compressive strength of the existing concrete structure 1 is high, so the spacing d1 of holes 10 is made intermediate between the above.

[0064] In this way, the supply amount of the carbon dioxide source and the interval d1 of the holes 10 are adjusted based on at least one of the pH of the holes 10 and the pH of the concrete powder, thereby making it possible to further improve the efficiency of immobilizing carbon dioxide in the existing concrete structure 1. In other words, while measuring the pH, the supply amount of the carbon dioxide source and the interval d1 of the holes 10 that are efficient for immobilizing carbon dioxide can be adjusted as needed.

[0065] Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept and scope of the claims of the present disclosure, and can be modified in various ways within the scope of the present disclosure. [Explanation of symbols]

[0066] 1 Existing concrete structures 10 holes 10a Pressure reduction hole 10b Carbon dioxide gas supply hole 20 Carbon dioxide fixation unit 30 Immobilization substance 40 Protection Department

Claims

1. a drilling step of drilling at least one hole having a predetermined length from the surface of the existing concrete structure toward the interior thereof; a carbon dioxide gas source supplying step of supplying a carbon dioxide gas source to the hole; and When at least one of the pH of the hole drilled in the hole drilling step and the pH of the concrete powder produced in the hole drilling step is higher than 12, the amount of carbon dioxide gas source supplied in the carbon dioxide gas source supplying step is increased, and when the pH is 12 or less, the amount of carbon dioxide gas source supplied in the carbon dioxide gas source supplying step is decreased; A method for immobilizing carbon dioxide gas, wherein carbon dioxide gas is immobilized at least on the inner surfaces of the holes.

2. 2. The carbon dioxide fixation method according to claim 1, wherein in the carbon dioxide source supply step, the humidity in the hole is 40% RH or more and 60% RH or less, and the carbon dioxide source is at least one of a gaseous carbon dioxide source and a solid carbon dioxide source.

3. 2. The carbon dioxide fixation method according to claim 1, wherein in the carbon dioxide source supplying step, the humidity in the hole is 20% RH or less, and the carbon dioxide source includes a liquid carbon dioxide source.

4. 4. The method for immobilizing carbon dioxide gas according to claim 1, wherein the carbon dioxide gas source is injected into the hole in the carbon dioxide gas source supply step.

5. a drilling step of drilling at least one hole having a predetermined length from the surface of the existing concrete structure toward the interior thereof; a carbon dioxide gas source supplying step of supplying a carbon dioxide gas source to the hole; and When at least one of the pH of the hole drilled in the hole drilling step and the pH of the concrete powder produced in the hole drilling step is higher than 12, the amount of carbon dioxide gas source supplied in the carbon dioxide gas source supplying step is increased, and when the pH is 12 or less, the amount of carbon dioxide gas source supplied in the carbon dioxide gas source supplying step is decreased; A method for manufacturing an existing concrete structure equipped with a carbon dioxide gas immobilization section, in which a carbon dioxide gas immobilization section in which carbon dioxide gas is immobilized is provided at least on the inner surface of the hole.

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