WO2022118731A1 - コンクリートへの二酸化炭素の固定方法、およびコンクリートを含むコンクリート構造体 - Google Patents

コンクリートへの二酸化炭素の固定方法、およびコンクリートを含むコンクリート構造体 Download PDF

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WO2022118731A1
WO2022118731A1 PCT/JP2021/043177 JP2021043177W WO2022118731A1 WO 2022118731 A1 WO2022118731 A1 WO 2022118731A1 JP 2021043177 W JP2021043177 W JP 2021043177W WO 2022118731 A1 WO2022118731 A1 WO 2022118731A1
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Prior art keywords
concrete
gas injection
carbon dioxide
injection hole
gas
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PCT/JP2021/043177
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English (en)
French (fr)
Japanese (ja)
Inventor
裕介 藤倉
智洋 藤沼
サンジェイ パリーク
Original Assignee
株式会社フジタ
学校法人日本大学
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Application filed by 株式会社フジタ, 学校法人日本大学 filed Critical 株式会社フジタ
Priority to JP2022566875A priority Critical patent/JPWO2022118731A1/ja
Publication of WO2022118731A1 publication Critical patent/WO2022118731A1/ja
Priority to JP2024225482A priority patent/JP2025031847A/ja

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/62—Carbon oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/81—Solid phase processes
    • B01D53/82—Solid phase processes with stationary reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
    • B28B11/24—Apparatus or processes for treating or working the shaped or preshaped articles for curing, setting or hardening
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/50—Carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/02—Selection of the hardening environment
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C3/00—Structural elongated elements designed for load-supporting
    • E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
    • E04C3/20—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of concrete or other stone-like material, e.g. with reinforcements or tensioning members
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C3/00—Structural elongated elements designed for load-supporting
    • E04C3/30—Columns; Pillars; Struts
    • E04C3/34—Columns; Pillars; Struts of concrete other stone-like material, with or without permanent form elements, with or without internal or external reinforcement, e.g. metal coverings
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
    • E04G21/02—Conveying or working-up concrete or similar masses able to be heaped or cast
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04—Lining with building materials
    • E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor

Definitions

  • One of the embodiments of the present invention relates to a method of fixing carbon dioxide to concrete contained in a concrete structure, and a concrete structure to which this method is applied.
  • Concrete is mainly composed of cement hydrate, aggregate, water, and additives, due to its excellent mechanical properties, weather resistance, ease of handling, economy, etc., social production base, economy. It is widely used in various fields as one of the important structural materials for creating a foundation. Cement is known to emit large amounts of carbon dioxide during its manufacture, which is cited as one of the causes of the greenhouse effect. Therefore, in order to contribute to solving this problem, for example, in Patent Document 1, when constructing a structure containing concrete (hereinafter referred to as a concrete structure), carbon dioxide is brought into contact with ready-mixed concrete before the concrete is hardened to form carbon dioxide. A method of fixing carbon to concrete is disclosed. Patent Document 2 discloses an effective method for designing a concrete structure for promoting the absorption of carbon dioxide into concrete.
  • One of the tasks of the embodiment of the present invention is to provide a method for efficiently fixing carbon dioxide to concrete.
  • one of the embodiments of the present invention is to provide a method for fixing carbon dioxide to concrete contained in an existing concrete structure.
  • one of the embodiments of the present invention is to provide a concrete structure obtained by applying the above method.
  • One of the embodiments of the present invention is a method of fixing carbon dioxide to concrete. This method involves forming a gas injection hole in the concrete contained in the concrete structure, introducing a gas containing carbon dioxide into the gas injection hole, and capping one end of the gas injection hole after the gas introduction. Includes enclosing gas in gas inlets.
  • One of the embodiments of the present invention is a concrete structure.
  • This structure includes a first concrete and a second concrete.
  • the second concrete has a different composition from the first concrete, is surrounded by the first concrete, and extends in the first direction toward the inside of the first concrete.
  • the first concrete includes a first zone in contact with the second concrete and a second zone surrounding the first zone.
  • the concentration of calcium carbonate in the first zone decreases continuously as the distance from the interface between the first concrete and the second concrete increases in the second direction perpendicular to the first direction.
  • the concentration of calcium carbonate in the second zone is constant in the second direction.
  • One of the embodiments of the present invention is a concrete structure.
  • This structure includes concrete having a bottomed hole or a through hole extending in the first direction.
  • the concrete includes a first zone that constitutes the side wall of the bottomed hole and the through hole, and a second zone that surrounds the first zone.
  • the concentration of calcium carbonate in the first zone decreases continuously as the distance from the sidewall increases in the second direction perpendicular to the first direction.
  • the concentration of calcium carbonate in the second zone is constant in the second direction.
  • drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the actual embodiment, but the drawings are merely examples and limit the interpretation of the present invention. It's not something to do.
  • elements having the same functions as those described with respect to the above-mentioned figures may be designated by the same reference numerals and duplicate description may be omitted.
  • a structure is exposed from another structure means an aspect in which a part of one structure is not covered by another structure, and is not covered by another structure.
  • the portion also includes an embodiment covered by yet another structure.
  • concrete refers to concrete that does not show fluidity because the hydrate produced by the reaction of cement, which is one of the raw materials, with water is hardened.
  • ready-mixed concrete also called ready-mixed concrete.
  • a concrete structure containing hardened concrete is used as a substrate for fixing carbon dioxide. That is, carbon dioxide is brought into contact with the concrete contained in the concrete structure to fix carbon dioxide (carbonation of concrete).
  • the existing concrete structure may be, for example, a pillar or a foundation beam of a building, a pier or a pier of a bridge, a dike or a breakwater installed in a river or a harbor, a wave-dissipating block, or a lining concrete used for a road or a tunnel. good.
  • it may be a movable property (concrete product) containing concrete such as a square or U-shaped concrete block or a gravel stone.
  • FIG. 1A shows a schematic perspective view of the concrete structure 100.
  • the concrete structure 100 shown here schematically represents all or part of various concrete structures, and as described above, the type, shape, and use of the concrete structure are not limited.
  • a gas injection hole 104 is formed in the concrete 102 constituting the concrete structure 100.
  • the gas injection hole 104 may be a through hole penetrating the concrete structure 100 from the surface of the concrete 102 to the opposite surface (FIG. 1B), and one end thereof is closed. It may be a bottomed hole (Fig. 1C).
  • the gas injection hole 104 may be formed so as to extend linearly, or may include a bent shape (not shown). Further, as shown in FIGS. 2A and 2B, a plurality of gas injection holes 104 may be provided.
  • the extending directions of the plurality of gas injection holes 104 may be the same as each other, or the extension direction of at least one gas injection hole 104 may be different from that of the other gas injection holes 104.
  • the stretching direction of all the gas injection holes 104 may be perpendicular to the outer surface of the concrete structure 100, or as shown in FIG. 2B, some or all of the gas injection holes 104 may have an extension direction. , May be stretched in a direction inclined with respect to the outer surface of the concrete structure 100.
  • a plurality of gas injection holes 104 may intersect. That is, the gas injection holes 104 may be formed in a network in the concrete 102.
  • the surface on which the gas injection hole 104 is provided is not limited to the surface perpendicular to the horizontal plane, but may be a surface parallel to the horizontal plane (for example, the upper surface of the concrete structure 100), and the gas injection hole may be a surface inclined at an angle of less than 90 ° from the horizontal plane. 104 may be provided.
  • the cross-sectional area of the gas injection hole 104 that is, the opening area of the gas injection hole 104 on the outer surface of the concrete 102 can be arbitrarily set.
  • the diameter may be 1 mm or more and 100 mm or less or 2 mm or more and 150 mm or less, and the opening area is 0.785 mm 2 or more 78. It may be 5 cm 2 or less or 3.14 mm 2 or more and 177 cm 2 or less.
  • the gas injection hole 104 may be formed from the outer surface of the concrete 102 toward the inside by using a drill such as a vibration drill or a hammer drill.
  • the gas injection hole 104 may be formed at the same time as the concrete structure 100 is formed. Specifically, a formwork 150 for determining the shape of the concrete structure 100 is produced (FIG. 3A). At this time, one or more core materials (cores) 152 for forming a space corresponding to the gas injection hole 104 in the concrete 102 are arranged in the formwork 150 (FIGS. 3A and 3B). The core material 152 may be provided so that a part thereof is exposed from the mold 150. The shape of the core material 152 may be determined in consideration of the shape of the gas injection hole 104, may be a linear rod shape, or may be partially or wholly bent. Further, the core material 152 may be a hollow tube or may not be hollow (solid).
  • the material contained in the core material 152 is not limited, and may be, for example, a metal material such as aluminum, iron, or stainless steel, wood, or resin.
  • the resin may be a fiber reinforced plastic compounded with fibers such as glass fiber and carbon fiber.
  • a release agent (release agent) or a curing retarder may be applied to the outer surface of the core material 152. By applying a mold release agent or a curing retarder, the core material 152 can be easily removed from the concrete 102 to form the gas injection hole 104, as will be described later.
  • Ready-mixed concrete 154 contains at least water and cement, but aggregates such as sand, gravel, boulders, rocks, crushed stones, crushed sand, AE agents (bubble dispersants) fluidizers, thickeners, It may contain an additive such as a quick-setting agent.
  • the structure 100 is formed by hardening the ready-mixed concrete 154 and removing the formwork 150. Further, by removing the core material 152, the gas injection hole 104 can be formed in the concrete structure 100 (FIG. 5).
  • the core material 152 does not necessarily have to be removed. For example, when the gas injection hole 104 is formed in a network shape, it may be difficult to remove the core material 152. In such a case, a porous material or a tubular core material 152 having a fine opening may be used, and carbon dioxide and the concrete 102 may be brought into contact with each other via the core material 152.
  • a gas containing carbon dioxide is supplied to the gas injection hole 104, and the carbon dioxide is brought into contact with the side wall of the gas injection hole 104.
  • a carbon dioxide supply source 120 is connected to one end (injection port) of the gas injection hole 104 via a carbon dioxide line 122, and a gas containing carbon dioxide is introduced into the gas injection hole 104 (FIG. 6A). ..
  • the same number of carbon dioxide supply sources 120 as the gas injection holes 104 may be used, and the carbon dioxide supply sources 120 corresponding to the respective gas injection holes 104 may be connected.
  • a well or branched carbon dioxide line 122 may be used to connect a smaller number of carbon dioxide sources 120 to the gas injection holes 104 than the number of gas injection holes 104.
  • the carbon dioxide line 122 is provided with a pressure gauge 124 and / or a flow meter 125 for measuring the pressure of the gas containing carbon dioxide introduced into the gas injection hole 104 (that is, the pressure in the gas injection hole 104). May be good.
  • connection method between the carbon dioxide line 122 and the gas injection hole 104 can be arbitrarily selected, and the tip of the carbon dioxide line 122 may be simply inserted into the gas injection hole 104.
  • an adapter 110 having an opening having a female screw structure is attached to the injection port, and the tip of the carbon dioxide line 122 has a male screw structure that meshes with the female screw structure.
  • the joint 126 may be attached. By screwing the joint 126 into the adapter 110, the carbon dioxide line 122 can be reliably connected to the gas injection hole 104.
  • a resin O-ring (or packing) 112 may be provided between the adapter 110 and the concrete 102 in order to prevent leakage of a gas containing carbon dioxide.
  • the other end is capped to contain the gas containing carbon dioxide, thereby preventing the leakage of the gas containing carbon dioxide and more effectively.
  • the discharge port may be sealed with an adhesive tape, an elastic body such as rubber, or, as shown in FIGS. 6B and 7A, an acrylic resin, an epoxy resin, a polyester resin, a polyimide resin, or the like.
  • the gas injection hole 104 may be sealed with a plate 106 containing the resin of the above or a metal material such as iron, stainless steel, or aluminum. Fiber reinforced plastic may be used as the resin.
  • the plate 106 may be fixed by using bolts or screws, or simply a plate 106 that matches the shape of the discharge port may be inserted into the discharge port. Alternatively, the plate 106 may be fixed using an adhesive, an adhesive tape, or the like. Further, as shown in FIG. 8A, in order to improve the airtightness of the gas injection hole 104, the discharge port is closed with a packing 108 containing an elastic body such as rubber, and the plate 106 is sandwiched between the packing 108 and the concrete 102. May be provided.
  • the gas containing carbon dioxide may be pure carbon dioxide (for example, a purity of 99% or more) or a mixed gas of carbon dioxide and another gas.
  • a mixed gas When a mixed gas is used, other gases include air, oxygen, nitrogen and the like.
  • the concentration of carbon dioxide in the mixed gas can be arbitrarily set, but it is preferably higher than the concentration of carbon dioxide contained in the atmosphere (about 420 ppm) in order to efficiently bring the concrete 102 into contact with carbon dioxide.
  • the carbon dioxide concentration may be set from any concentration of 1% by volume or more and 100% by volume or less, 10% by volume or more and 50% by volume, or 10% by volume or more and 20% by volume or less.
  • the carbon dioxide supply source 120 may have a function of supplying a gas containing carbon dioxide to the gas injection hole 104, and examples thereof include a cylinder and a tank of the gas containing carbon dioxide as shown in FIG. 6A.
  • the carbon dioxide supply source 120 is connected to a regulator (not shown), and the gas containing carbon dioxide is regulated.
  • the gas emitted from these facilities, or Purified carbon dioxide obtained by performing dedusting, desulfurization, denitration, etc. on the exhaust gas may be used. In this case, since these facilities function as the carbon dioxide supply source 120, the cost for transporting carbon dioxide is reduced, and further emission of carbon dioxide due to the transport is prevented.
  • the gas containing carbon dioxide may be introduced so that the pressure in the gas injection hole 104 is higher than 0 MPa and lower than 2 MPa.
  • a vacuum pump 130 such as a rotary oil pump or a dry pump is connected to the carbon dioxide line 122 to connect the gas injection hole.
  • a gas containing carbon dioxide may be introduced.
  • a compressor or the like may be used.
  • the gas containing carbon dioxide may be introduced constantly or intermittently during the period in which carbon dioxide is fixed.
  • the carbon dioxide line 122 may be removed from the gas injection hole 104, the injection port may be closed, and the gas injection hole 104 may be closed.
  • the injection port may be closed with an adhesive tape, or an elastic body such as rubber may be inserted into the injection port to seal the injection port.
  • the gas injection hole 104 may be sealed by using a cap 114 having a male screw structure that meshes with the adapter 110.
  • a densitometer 128 for measuring the carbon dioxide concentration may be provided inside the gas injection hole 104 (for example, the side wall of the gas injection hole 104 or the cap 114), and the carbon dioxide concentration may be measured periodically. This makes it possible to monitor changes in carbon dioxide concentration.
  • a water supply source 140 may be provided to supply water into the gas injection hole 104 via the carbon dioxide line 122 (FIG. 6A).
  • the water supply source 140 may include a heating device and a cooling device for controlling the temperature of the supplied water.
  • a gas containing carbon dioxide may be supplied from the carbon dioxide supply source 120 to the water supply source 140, and the water containing carbon dioxide may be supplied to the gas injection hole 104.
  • a hygrometer 129 for measuring humidity may be provided inside the gas injection hole 104 (for example, the side wall of the gas injection hole 104 or the cap 114), and the humidity may be measured periodically (FIG. 7B). This makes it possible to monitor changes in humidity.
  • the inside of the gas injection hole 104 may be depressurized by using a vacuum pump 130 in order to remove a part of the water in the gas injection hole 104. After that, the gas containing carbon dioxide may be supplied into the gas injection hole 104.
  • the contact time between the concrete 102 and the gas containing carbon dioxide depends on the length, cross-sectional area (that is, the volume of the gas injection hole 104) and temperature of the gas injection hole 104, and the concentration of carbon dioxide in the gas containing carbon dioxide. For example, it may be 1 hour or more and 20 years or less, 1 day or more and 10 years or less, 10 weeks or more and 5 years or less, and 1 year or more and 3 years or less.
  • the control device 142 may be used to supply carbon dioxide and water. Carbon dioxide and water are supplied to the control device 142 from the carbon dioxide supply source 120 and the water supply source 140, respectively.
  • the control device 142 includes a mechanism (for example, a blower pump or the like) for supplying a gas containing carbon dioxide to the gas injection hole 104.
  • the control device 142 may further prepare a gas containing carbon dioxide having an appropriate humidity by using the supplied water and carbon dioxide, and may be configured to supply this gas to the gas injection hole 104. Alternatively /
  • the control device 142 may be configured so that the temperature of the gas containing carbon dioxide supplied to the gas injection hole 104 can be controlled. By imparting such a function to the control device 142, a gas containing carbon dioxide can be supplied into the gas injection hole 104 at a temperature and humidity at which a large carbon dioxide fixation rate can be obtained.
  • a gas containing carbon dioxide may be circulated between the control device 142 and the gas injection hole 104.
  • the control device 142 includes a mechanism for recovering the gas discharged from the gas injection hole 104, which is exemplified in a circulation pump or the like, and supplying the gas to the gas injection hole 104 again.
  • the control device 142 is configured to measure the concentration and humidity of carbon dioxide contained in the gas discharged from the gas injection hole 104, and appropriately add carbon dioxide or water to the gas based on the obtained data. May be. As a result, the inside of the gas injection hole 104 can be constantly placed under the condition that the optimum carbon dioxide fixation rate can be obtained.
  • repair concrete 103 may be newly placed in the gas injection holes 104 of the concrete structure 100 in which carbon dioxide is fixed. Specifically, as shown in FIGS. 9A to 9C, the gas injection hole 104 is filled with ready-mixed concrete and hardened. In the concrete structure 100, the repair concrete 103 extending inside the concrete 102 is surrounded by the concrete 102. The area of the cross section of the repair concrete 103 (the cross section perpendicular to the direction in which the repair concrete 103 is stretched) is the same as or substantially the same as the opening area of the gas injection hole 104, for example, 0.785 mm 2 or more and 177 cm 2 or less. ..
  • the repair concrete 103 may be cast in the entire gas injection hole 104, or may be cast only in a part of the injection port side, although not shown. By placing the repair concrete 103, the structural strength lost by forming the gas injection hole 104 can be compensated, and the aesthetic appearance of the concrete structure 100 can be maintained.
  • the compositions of the concrete 102 and the repair concrete 103 may differ from each other.
  • the concentration of calcium carbonate is higher in the former, and conversely, the concentration of calcium hydroxide is higher in the latter.
  • the concrete 102 has a relatively high calcium carbonate concentration, and has a first zone 102a (a zone surrounded by a chain line in FIG. 10A) constituting the side wall of the gas injection hole 104, and a calcium carbonate concentration. Is lower than that of the first zone 102a and will have a second zone 102b (the outer zone of the circle) surrounding the first zone 102a. The first zone 102a and the second zone 102b are in contact with each other.
  • the concrete 102 in the first zone 102a, in the direction perpendicular to the y direction, that is, in any direction in the xz plane (see, for example, arrow a in FIG. 10A), the concrete 102.
  • the concentration of calcium carbonate decreases continuously as the distance from the side wall of the gas injection hole 104 increases.
  • the concentration of calcium carbonate in the concrete 102 continuously increases as the distance from the interface between the repair concrete 103 and the concrete 102 increases.
  • the zone where this increase is stopped and the concentration of calcium carbonate is constant or substantially constant is the second zone 102b.
  • the concentration of calcium carbonate in the repair concrete 103 is constant or substantially constant.
  • the concentration of calcium hydroxide in the concrete 102 in any direction in the xz plane is determined by the gas injection hole 104. It increases continuously as the distance from the side wall increases.
  • the concentration of calcium hydroxide in the concrete 102 continuously decreases as the distance from the interface between the repair concrete 103 and the concrete 102 increases.
  • the concentration of calcium hydroxide becomes constant or substantially constant.
  • the concentration of calcium hydroxide in the repair concrete 103 is constant or substantially constant.
  • the calcium carbonate concentration plot with respect to the distance from the outer surface can show three stages.
  • the first stage corresponds to the second zone 102b from the outer surface to the interface between the first zone 102a and the second zone 102b, here with calcium carbonate.
  • the concentration of calcium hydroxide is constant or substantially constant.
  • the second stage corresponds to the first zone 102a after passing through the interface between the first zone 102a and the second zone 102b and then reaching the interface between the first zone 102a and the second zone 102b again.
  • the concentration of calcium carbonate continuously increases and then decreases continuously, and the concentration of calcium hydroxide continuously decreases and then continuously increases.
  • the third stage corresponds to the second zone 102b, which secondly passes through the interface between the first zone 102a and the second zone 102b and then reaches the outer surface of the concrete structure 100, here with calcium carbonate.
  • the concentration of calcium hydroxide is constant or substantially constant.
  • the concrete 102 of the concrete structure 100 can come into contact with carbon dioxide at an extremely high concentration as compared with the carbon dioxide concentration in the atmosphere in the gas injection hole 104. Therefore, the carbon dioxide introduced into the gas injection hole 104 can efficiently come into contact with the concrete 102. Further, by sealing the gas injection hole 104, leakage of carbon dioxide is prevented, and high safety during work can be ensured.
  • Cement which is the raw material of concrete 102, releases a large amount of carbon dioxide during its production.
  • the concrete 102 fixes a large amount of carbon dioxide. Therefore, the method for fixing carbon dioxide according to the embodiment of the present invention can contribute to the reduction of carbon dioxide in the atmosphere and the suppression of global warming.
  • the concrete 102 can have a high concentration of calcium carbonate produced by the reaction between calcium hydroxide generated by hydration of cement and carbon dioxide, the density of the concrete 102 increases by immobilizing carbon dioxide. As a result, the compression strength increases.
  • the inventors have confirmed that when carbon dioxide of about 20% (60 kg / m 3 ) of cement is fixed, the compressive strength of concrete increases by about 8% to 10%. Therefore, by applying this carbon dioxide fixation method, it is possible to increase the strength of the existing concrete structure 100.
  • a method of fixing carbon dioxide to concrete a method of placing and contacting hardened concrete in a curing tank filled with carbon dioxide, a method of bringing carbon dioxide into contact with the surface of hardened porous concrete, and ready-mixed concrete.
  • There are known methods such as supplying carbon dioxide into a mold for pouring concrete structure and contacting the concrete structure with the atmosphere.
  • the method using a curing tank requires a curing tank for accommodating concrete for fixing carbon dioxide, and cannot be applied to buildings such as buildings, pillars, and tunnels.
  • a means for sealing the concrete surface is required, so that it is not realistic to apply it particularly to a large concrete structure.
  • the type, size, shape, use, and construction site are not particularly restricted. It can be applied to various existing concrete structures 100. Further, since it is not necessary to use new cement except for the step of filling the repair concrete 103, there is almost no need to directly or indirectly utilize the step of producing cement that generates a large amount of carbon dioxide. This means that not only does it not need to create a new reaction substrate to fix carbon dioxide, but there is a huge amount of reaction substrate on the ground. Therefore, it can be said that the carbon dioxide fixing method according to one of the present embodiments can fix an extremely large amount of carbon dioxide and is useful as an effective tool for suppressing global warming.
  • the method for fixing carbon dioxide according to one of the embodiments of the present invention can be applied to various concrete structures 100.
  • the concrete structure 100 can be applied even if it is a tunnel, and carbon dioxide is used by using the concrete (tunnel lining concrete) 102 constituting the inner wall of the tunnel. Carbon can be fixed.
  • a plurality of gas injection holes 104 are formed in the concrete 102, and a gas containing carbon dioxide is supplied to the gas injection holes 104.
  • the stretching direction of the gas injection hole 104 is arbitrary, and may be a vertical direction (z direction) or may be inclined from the vertical direction.
  • the gas injection hole 104 may be formed so as to be parallel to the normal of the inner wall of the tunnel or to be inclined from the normal. Further, the gas injection hole 104 may be a through hole penetrating the concrete 102 or a bottomed hole. Even if the gas injection hole 104 is a through hole, the discharge port is a bedrock or ground in contact with the concrete 102, so that the discharge port does not have to be closed when supplying gas containing carbon dioxide.
  • the method for fixing this carbon dioxide can be applied to the reinforced concrete constituting columns and beams.
  • a gas injection hole 104 is provided so as to avoid reinforcing bars 160 (see FIG. 13A) constituting column main bars, lateral reinforcing bars, and the like (FIG. 13B).
  • Concrete is alkaline, but when it reacts with carbon dioxide to produce calcium carbonate, it gradually acidifies.
  • carbon dioxide When concrete is acidic, the reinforcing bars are corroded, and the expansion of the reinforcing bars due to the corrosion may induce deterioration such as cracking or breakage of the concrete. Therefore, when the concrete structure 100 including the reinforcing bar is used, it is preferable that carbon dioxide is not fixed to the concrete located in the vicinity of the reinforcing bar.
  • the reinforcing bar is not arranged in the center of the concrete structure 100, but is arranged in a zone relatively close to the outer surface.
  • the reinforcing bar 160 is arranged so as to cut off the central portion of the concrete structure, and the concrete 102 is constructed so as to embed the reinforcing bar 160.
  • the reinforcing bars 160 the reinforcing bars (column main bars) parallel to the extending direction of the columns are arranged so as to surround the central axis of the columns, and the reinforcing bars extending in the horizontal direction called lateral reinforcing bars are the columns. Arranged so as to surround the main bar.
  • the portion outside the reinforcing bar is called cover concrete.
  • a protective tube 162 may be provided to cover the portion of the side wall of the gas injection hole 104 made of the cover concrete.
  • the protective tube 162 can be provided on the inlet side and / or the outlet side of the gas injection hole 104, and its end reaches the outer surface of the concrete structure 100. Therefore, a portion of the side wall covered by the protective tube 162 reaches one end (inlet or outlet) of the gas inlet 104. Although not shown, a portion of the protective tube 162 may protrude outward from the gas injection hole 104.
  • the length L of the protective tube 162 in the direction in which the gas injection hole 104 extends is preferably equal to or larger than the thickness of the cover concrete. More specifically, the length L of the protective tube 162 is the shortest distance D from the reinforcing bar 160 located inside the innermost part of the concrete structure 100 to the outer surface of the concrete 102, and the maximum length of the cross section of the reinforcing bar 160. It is preferably the same as or more than the sum S of (for example, the diameter d of the cross section). Alternatively, the length L is preferably selected from the range of 2 times or more and 5 times or less or 1.5 times or more and 3 times or less of the sum S.
  • the material contained in the protective tube 162 there are no restrictions on the material contained in the protective tube 162, and for example, metal materials such as iron, aluminum, and stainless steel, resins such as epoxy resin, silicone resin, and acrylic resin, and wood may be used.
  • resins such as epoxy resin, silicone resin, and acrylic resin, and wood may be used.
  • an epoxy-based adhesive or an acrylic-based adhesive may be applied to the injection port and the discharge port side of the gas injection hole 104 so as to have a length of L, and cured to form a protective tube 162.
  • the side wall exposed from the protective tube 162 selectively contacts carbon dioxide. Will be done.
  • carbon dioxide fixation carbonation
  • carbonation is started from the side wall exposed from the protective tube 162, and then carbonation proceeds from the side wall to the inside of the concrete 102.
  • FIG. 14 it is possible to prevent the first zone 102a in which carbon dioxide is fixed from expanding to the reinforcing bar 160, and the second zone in which carbon dioxide is not fixed (that is, not carbonated) can be prevented.
  • Reinforcing bar 160 can be held in the zone 102b of. Since the reinforcing bar 160 is included in the second zone 102b, it is possible to prevent corrosion of the reinforcing bar 160 and deterioration of the concrete 102 due to the corrosion.
  • the repair concrete 103 may be placed after the protective tube 162 is removed, or the protective tube 162 may be placed while remaining in the gas injection hole 104.
  • the concrete structure 100 includes a protective tube 162, which covers at least a portion of the surface of the repair concrete 103.
  • Example 1-1 Fabrication of Concrete with Gas Injection Hole
  • a formwork with an internal volume of 100 mm ⁇ 100 mm ⁇ 400 mm was prepared, and a metal rod having a cross section diameter of 9 mm and a length of 400 mm was arranged parallel to the longitudinal direction of the formwork.
  • the metal rod was placed so as to pass through the center of the cross section perpendicular to the longitudinal direction of the internal volume of the formwork.
  • Ready-mixed concrete was placed in this formwork.
  • Ready-mixed concrete was prepared by using ordinary Portland cement manufactured by Taiheiyo Cement Co., Ltd. so that the unit water amount was 170 kg / m 3 and the unit cement amount was 340 kg / m 3 (water cement ratio 50%).
  • FIG. 15 A schematic perspective view of the concrete 102 is shown in FIG. As shown in FIG. 15, the concrete 102 had a volume of 100 mm ⁇ 100 mm ⁇ 400 mm, and had a through hole parallel to the longitudinal direction as a gas injection hole 104.
  • a carbon dioxide cylinder was connected to one end (injection port) of the carbon dioxide fixation gas injection hole 104 via a rubber hose, and carbon dioxide was continuously supplied to the gas injection hole 104 at a pressure of 0.1 MPa. After the supply of carbon dioxide, the concrete was cut and the liquid property of the pore solution having a cross section perpendicular to the longitudinal direction was evaluated. The liquid property was evaluated by spraying a cross section with a 1% ethanol solution of phenolphthalein as an indicator and confirming the presence or absence of coloration of the indicator.
  • 100 Concrete structure
  • 102 Concrete
  • 102a First zone
  • 102b Second zone
  • 103 Repair concrete
  • 104 Gas injection hole
  • 106 Plate
  • 108 Packing
  • 110 Adapter
  • 112 ⁇ Ring
  • 114 Cap
  • 120 Carbon dioxide source
  • 122 Carbon dioxide line
  • 124 Pressure gauge
  • 125 Flow meter
  • 126 Joint
  • 128 Densitometer
  • 129 Humidity gauge
  • 130 Vacuum pump
  • 140 Water source
  • 142 Control device
  • 150 Formwork
  • 152 Core material
  • 154 Ready-mixed concrete
  • 160 Reinforcing bar
  • 162 Protective tube

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JP2023040557A (ja) * 2021-09-10 2023-03-23 鹿島建設株式会社 炭酸ガス固定化方法および炭酸ガス固定化部を具備する既設コンクリート構造物の製造方法
EP4051474A4 (en) * 2019-12-10 2023-12-06 Carbicrete Inc. SYSTEMS AND METHODS FOR HARDENING A FINISHED CONCRETE PRODUCT
JP2024062647A (ja) * 2022-10-25 2024-05-10 日本コンクリート株式会社 セメント硬化体の製造方法、及びセメント硬化体

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JPS63156168A (ja) * 1986-12-20 1988-06-29 多川工業株式会社 鉄筋コンクリ−ト造りの建築物の室内解体工法
JPH04290540A (ja) * 1991-03-19 1992-10-15 Hitachi Ltd 炭酸ガスの海洋への封入投棄方法及びシステム
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EP4051474A4 (en) * 2019-12-10 2023-12-06 Carbicrete Inc. SYSTEMS AND METHODS FOR HARDENING A FINISHED CONCRETE PRODUCT
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JP2023040557A (ja) * 2021-09-10 2023-03-23 鹿島建設株式会社 炭酸ガス固定化方法および炭酸ガス固定化部を具備する既設コンクリート構造物の製造方法
JP2024062647A (ja) * 2022-10-25 2024-05-10 日本コンクリート株式会社 セメント硬化体の製造方法、及びセメント硬化体

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