Method for constructing dome-shaped structure

Abstract

To allow concrete used in a dome-shaped structure to fully absorb carbon dioxide.SOLUTION: A method for constructing a dome-shaped structure 100 comprises the processes of: making a first membrane 10 self-supporting by injecting gas between the first membrane 10 formed in a dome-shape and a floor surface 1; spraying concrete onto an inner surface of the self-supporting first membrane 10; placing a second membrane 14 inflated by gas injection into an inner space 4 facing a sprayed surface 25a formed by being sprayed with concrete; and supplying carbon dioxide gas into a gap between the sprayed surface 25a and the second membrane 14. The concrete contains a carbon dioxide gas-binding admixture that can chemically bond with the carbon dioxide gas.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for constructing a dome-like structure. [Background technology]

[0002] Patent Document 1 discloses a method for producing precast concrete that has absorbed a large amount of carbon dioxide by carbonation curing a solidified concrete mixture that contains an admixture that can chemically bond with carbon dioxide gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-168436 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to reduce carbon dioxide emissions, it is desirable to use a concrete mixture capable of absorbing a large amount of carbon dioxide, as described in Patent Document 1, in various structures. However, in order to absorb a large amount of carbon dioxide into concrete, a curing tank filled with carbon dioxide is required, and it is not realistic to install a huge curing tank capable of accommodating a relatively large structure, such as a structure cast in situ. Even if it were possible to install equipment equivalent to a curing tank, in order to sufficiently absorb carbon dioxide into concrete, it would be necessary to prepare carbon dioxide gas in an amount greater than the amount to be absorbed, and if the amount of carbon dioxide gas that is left surplus without contributing to the curing of concrete increases, there is a risk that the expected effect of reducing carbon dioxide emissions will not be achieved.

[0005] An object of the present invention is to provide a construction method that can allow the concrete used in a dome-shaped structure to sufficiently absorb carbon dioxide. [Means for solving the problem]

[0006] The present invention is a method for constructing a dome-shaped structure, comprising the steps of: making the first membrane self-supporting by injecting gas between a first membrane formed in a dome shape and a floor surface; spraying concrete onto the inner surface of the self-supporting first membrane; placing a second membrane expanded by injecting gas in a space facing the sprayed surface formed by spraying the concrete; and supplying carbon dioxide gas into the gap between the sprayed surface and the second membrane, wherein the concrete contains a carbon dioxide-binding admixture that can chemically bond with carbon dioxide gas. Effect of the Invention

[0007] According to the present invention, carbon dioxide can be sufficiently absorbed into the concrete used in the dome-shaped structure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view showing an example of a dome-shaped structure constructed by a construction method according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the dome-shaped structure shown in FIG. [Diagram 3] 1 is a flowchart showing the procedure of a method for constructing a dome-shaped structure. [Figure 4] FIG. 13 is a diagram showing a process of making the first film body self-supporting. [Diagram 5] FIG. 13 is a diagram showing a process of spraying shotcrete onto the first membrane body. [Figure 6] FIG. 13 is a diagram showing a step of placing a second membrane body. [Figure 7] FIG. 2 is a diagram showing a process of performing carbonation curing. [Figure 8] FIG. 13 is a diagram showing a modified example of the second membrane body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a method for constructing a dome-shaped structure according to an embodiment of the present invention will be described with reference to the drawings.

[0010] First, a dome-shaped structure 100 constructed by a method for constructing a dome-shaped structure according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of the dome-shaped structure 100 taken along line AA in Figure 2, and Figure 2 is a plan view of the dome-shaped structure 100.

[0011] The dome-shaped structure 100 is a building constructed on a floor surface 1 that has been leveled with concrete pavement or the like, and mainly comprises a cylindrical wall portion 2 formed vertically on the floor surface 1, a ceiling portion 3 formed in a convex shape pointing vertically upward, and an entrance / exit portion 5 for entering and exiting an internal space 4 surrounded by the wall portion 2 and the ceiling portion 3.

[0012] Here, the term "dome-shaped" means that the shape of the ceiling portion 3 is not flat along a horizontal plane, but the cross-sectional shape of the ceiling portion 3 in the vertical direction is a substantially arc-shaped shape that protrudes upward, and the diameter of the ceiling portion 3 gradually increases as it goes vertically downward. In the example shown in Figures 1 and 2, the planar shape of the dome-shaped structure 100 is circular, but as long as the cross-sectional shape of the ceiling portion 3 is a substantially arc-shaped shape, the planar shape is not limited to a circle, and may be an ellipse, an oval, or a rectangle with rounded corners.

[0013] Moreover, the dome-shaped structure 100 may be composed only of a hemispherical ceiling portion 3 without including the wall portion 2. Moreover, two or more entrances 5 may be provided, and the wall portion 2 and the ceiling portion 3 may be appropriately provided with ventilation openings and windows.

[0014] 1, the wall 2 and ceiling 3 of the dome-shaped structure 100 have a laminated structure and are mainly composed of a first membrane 10 disposed on the outside and a sprayed concrete section 20 (concrete) formed on the inside of the first membrane 10. If necessary, a heat insulating material or fiber-reinforced mortar may be sprayed onto the inner surface of the first membrane 10 in order to maintain the shape of the first membrane 10 when the sprayed concrete section 20 is sprayed.

[0015] The first membrane 10 is a sheet material made of polyvinyl chloride (PVC), and is formed in advance into a dome shape having portions corresponding to the wall portion 2 and the ceiling portion 3 by cutting and pasting the sheet material. The first membrane 10 formed into a dome shape functions as a formwork that guides the shape of the sprayed concrete portion 20 sprayed on the inner side to a dome shape. Note that the material of the first membrane 10 is not limited to polyvinyl chloride, and any material may be used as long as it has flexibility that allows it to stand on its own under air pressure, strength that is not damaged even when concrete is sprayed on the inner side, and waterproofness that prevents rainwater from entering, as described below.

[0016] The sprayed concrete section 20 is formed by spraying concrete multiple times to a thickness of approximately 30 to 50 mm, and will ultimately have a thickness of approximately 100 to 700 mm depending on the size of the dome-shaped structure 100 (planar diameter 10 to 60 mm).

[0017] 1, the shotcrete section 20 has a two-layer structure consisting of a first shotcrete 21 formed by being sprayed onto the first membrane body 10, and a second shotcrete 25 formed by being sprayed onto the first shotcrete 21. In other words, when the shotcrete section 20 is sprayed onto the first membrane body 10, the concrete being sprayed is changed from the first shotcrete 21 to the second shotcrete 25 midway through.

[0018] Furthermore, inside the sprayed concrete portion 20, reinforcing bars 22 are arranged along the first membrane body 10 to reinforce the strength of the concrete structure.

[0019] The main binder of the concrete composition of the first shotcrete 21 is Portland cement such as ordinary Portland cement (OPC). The Portland cement is not limited to ordinary Portland cement, and other types of Portland cement, such as high-early-strength Portland cement and moderate-heat Portland cement, may be used.

[0020] Moreover, ground granulated blast furnace slag (BFS) is preferably mixed as a mineral admixture into the binder of the concrete composition of the first shotcrete 21. Ground granulated blast furnace slag has a smaller amount of carbon dioxide emitted during its manufacturing process, the so-called CO2 emission unit (CO2 emission coefficient), which is about 1 / 30th of that of Portland cement, so it is possible to reduce the amount of carbon dioxide emitted in the construction of the dome-shaped structure 100 by increasing the proportion of ground granulated blast furnace slag contained in the binder of the concrete composition.

[0021] The ground granulated blast furnace slag is a fine powder as specified in JIS A 6206:2013 "ground granulated blast furnace slag for concrete" and its type is classified according to the specific surface area (cm 2 / g), any of the ground granulated blast furnace slag may be used in this embodiment.

[0022] Furthermore, the binder of the concrete composition of the first shotcrete 21 may be blast furnace cement, which is a mixed cement in which ground granulated blast furnace slag and a cement material such as ordinary Portland cement are mixed in advance.

[0023] The main binder of the concrete composition of the second shotcrete 25 is Portland cement such as ordinary Portland cement (OPC), but it differs from the first shotcrete 21 in that it contains dicalcium silicate γ phase (γ: γ-C2S) as an admixture.

[0024] The dicalcium silicate γ phase is a carbon dioxide-binding admixture that can chemically bond with carbon dioxide, and as described below, when the second shotcrete 25 is subjected to carbonation curing, it functions to fix carbon dioxide (carbon dioxide) as calcium carbonate in the second shotcrete 25. The generation of calcium carbonate in this way densifies the surface layer of the second shotcrete 25, and as a result, the strength of the shotcrete portion 20 is improved.

[0025] As a carbon dioxide-binding admixture capable of chemically bonding with carbon dioxide, in place of or in addition to the dicalcium silicate gamma phase, blast furnace slag, steelmaking slag, copper slag, fly ash, sewage sludge incineration ash, biomass combustion ash, silica fume, rice husk ash, slaked lime, quicklime, natural pozzolan, etc. may be used.

[0026] To further reduce the amount of carbon dioxide emissions involved in the construction of the dome-shaped structure 100, it is preferable to include ground granulated blast furnace slag (BFS) as an admixture in the concrete composition of the second shotcrete 25, as in the first shotcrete 21. In particular, by increasing the proportion of ground granulated blast furnace slag, the alkali concentration at the start of curing becomes relatively low, which allows carbonation to proceed quickly when carbonation curing is performed.

[0027] The mass ratio (mixture ratio of concrete composition) of the total binder (powder) amount of the second shotcrete 25 is set to about 15-30% ordinary Portland cement, 30-50% ground granulated blast furnace slag, and 30-50% gyrosilicate calcium silicate, taking into consideration various properties such as hardening speed after spraying, carbonation depth after carbonation curing, and compressive strength after carbonation curing. In addition, the water-powder ratio (W / P) is set to about 40%, and the air content is set to about 4-6%, so that sufficient fluidity and adhesion are exhibited when spraying. Note that these mixes are merely examples, and the mix is ​​not limited to these. In addition, the mix of the first shotcrete 21 is a mix that does not contain gyrosilicate calcium silicate, compared to the mix of the second shotcrete 25.

[0028] Here, as described above, the second sprayed concrete 25 contains, as an admixture, a carbon dioxide-binding admixture that can chemically bond with carbon dioxide, and by carrying out carbonation curing as described below, the vicinity of the sprayed surface (surface) becomes neutral or acidic, while the portion close to the first sprayed concrete 21 is maintained alkaline.

[0029] When the reinforcing bars 22 are placed in the second sprayed concrete 25 which contains neutral or acidic parts in this manner, the reinforcing bars 22 become prone to corrosion and rust, which may reduce the adhesion between the reinforcing bars 22 and the concrete and result in a lack of sufficient reinforcing effect.

[0030] Therefore, the first shotcrete 21 containing an alkaline component is sprayed onto the area where the reinforcing bars 22 are arranged. In other words, the reinforcing bars 22 are arranged within the area where the first shotcrete 21 is sprayed. The alkaline component of the first shotcrete 21 can be increased by increasing the proportion of Portland cement.

[0031] The spraying thickness of the first shotcrete 21 is set so as to cover the reinforcing bars 22 by a predetermined thickness, while the spraying thickness of the second shotcrete 25 is set to be a predetermined thickness thicker than the carbonation depth (e.g., 15 to 30 mm) formed on the surface side that comes into contact with carbon dioxide gas during carbonation curing. Note that if treatment to prevent moisture from penetrating into the second shotcrete 25 or anti-rust treatment has been applied to the reinforcing bars 22, the reinforcing bars 22 may be provided within the second shotcrete 25.

[0032] Next, a method for constructing the dome-shaped structure 100 having the above-mentioned configuration will be described with reference to Figures 3 to 7. Figure 3 is a flow chart showing the procedure of the construction method, and Figures 4 to 7 show each step of the construction work in order.

[0033] First, in step S11, a step of making the first membrane body 10 stand on the floor surface 1 by itself is carried out.

[0034] Specifically, after the outer edge 11 of the first membrane body 10 is fixed to the floor surface 1, air (gas) is injected from a blower 31 between the first membrane body 10 and the floor surface 1 as shown in Fig. 4. By injecting air between the first membrane body 10 and the floor surface 1, the first membrane body 10 expands upward due to the air pressure and becomes self-supporting.

[0035] To the inner surface of the free-standing first membrane body 10, a heat insulating material or fiber reinforced mortar is sprayed as necessary in order to maintain the shape of the first membrane body 10.

[0036] Next, in step S12, a step of spraying the first shotcrete 21 onto the inner surface of the free-standing first membrane body 10 is carried out.

[0037] When spraying the first shotcrete 21 onto the inner surface of the first membrane body 10, the reinforcing bars 22 are arranged in advance along the inner surface of the first membrane body 10, and the first shotcrete 21 is sprayed by a spraying device 32 so as to cover the reinforcing bars 22 to a predetermined thickness, as shown in Fig. 5. Fig. 5 also shows the state in which the second shotcrete 25 is sprayed by the spraying device 32.

[0038] When the spraying of the first shotcrete 21 is completed, the next step S13 is carried out, in which the second shotcrete 25 is sprayed onto the inner surface of the first shotcrete 21 that has hardened to a certain extent.

[0039] Specifically, as shown in FIG. 5, the second shotcrete 25 is sprayed onto the inner surface of the first shotcrete 21 by a spraying device 32 so as to achieve a preset spray thickness.

[0040] After the spraying of the second shotcrete 25 is completed, carbonation curing of the second shotcrete 25 is then carried out.

[0041] Carbonation curing is a curing method carried out to forcibly fix carbon dioxide in the second sprayed concrete 25 containing the above-mentioned carbon dioxide-binding admixture, and is carried out in a state where the sprayed surface 25a, which is the inner surface of the second sprayed concrete 25, is exposed to a relatively high concentration of carbon dioxide.

[0042] Here, as shown in Figure 5, in order to expose the sprayed surface 25a of the second sprayed concrete 25 sprayed onto the inner surface of the first sprayed concrete 21 to carbon dioxide, it is necessary to fill the internal space 4 facing the sprayed surface 25a with a relatively high concentration of carbon dioxide.

[0043] However, even if the entire internal space 4 is filled with a relatively high concentration of carbon dioxide, the only carbon dioxide that is fixed in the second shotcrete 25 is that present in the immediate vicinity of the sprayed surface 25a, and most of it is released or recovered without being fixed in the second shotcrete 25.

[0044] This may result in an increase in surplus carbon dioxide that does not contribute to the carbonation curing of the second shotcrete 25, and as a result, the expected effect of reducing carbon dioxide emissions may not be achieved.

[0045] Therefore, in this embodiment, in order to reduce the amount of excess carbon dioxide during carbonation curing, carbon dioxide is mainly filled in the vicinity of the sprayed surface 25a of the second shotcrete 25.

[0046] Specifically, before carbonation curing, a step of placing the second membrane body 14 in the internal space 4 (space) to which the sprayed surface 25a of the second shotcrete 25 faces is carried out in step S14.

[0047] The second membrane body 14 is a sheet material such as polyvinyl chloride (PVC) like the first membrane body 10, and is formed in a bag shape having a bottom surface 15 that is fixed to the floor surface 1, as shown in Fig. 6. Specifically, the second membrane body 14 is formed so that when air is injected into it from the blower 31 and it expands, its outer shape becomes a dome shape similar to the outer shape of the first membrane body 10.

[0048] In step S14, the second film body 14 is carried into the internal space 4, and then the bottom surface 15 is first fixed to the floor surface 1 by a fixing device (not shown). If carbon dioxide gas (carbon dioxide) supplied to the internal space 4 in the carbonation curing process described later gets between the bottom surface 15 and the floor surface 1, the amount of carbon dioxide gas that does not contribute to the carbonation curing will increase, so the second film body 14 is fixed so that the bottom surface 15 comes into contact with the floor surface 1 as much as possible.

[0049] When air is injected from the blower 31 into the second membrane body 14 whose bottom surface 15 is fixed to the floor surface 1 in this manner, the second membrane body 14 bulges upward, and as shown in Fig. 6, a gap of a predetermined size, for example, 300 to 900 mm, is formed between the sprayed surface 25a of the second shotcrete 25 and the outer surface of the second membrane body 14. The gap formed between the sprayed surface 25a and the second membrane body 14 becomes the gap through which carbon dioxide gas is supplied in the carbonation curing process described below.

[0050] Furthermore, since the second membrane body 14, like the first membrane body 10, becomes self-supporting due to air pressure, there is no need to work at heights when installing the second membrane body 14, so the installation work can be carried out safely and quickly.

[0051] In addition, an air exhaust valve 33 capable of exhausting the air inside the second membrane body 14 to the outside is connected to the second membrane body 14, and the opening degree of the air exhaust valve 33 and the amount of air injected from the blower 31 into the inside of the second membrane body 14 are appropriately adjusted so that the internal pressure of the second membrane body 14 becomes a predetermined magnitude. By maintaining the internal pressure of the second membrane body 14 constant in this manner, the external shape of the second membrane body 14 is stabilized, and as a result, the size of the gap formed between the blowing surface 25a and the second membrane body 14 is maintained constant.

[0052] Note that a plurality of spacers may be arranged at a predetermined interval on the spray surface 25a so that the size of the gap formed between the spray surface 25a and the second membrane body 14 is constant. The spacer is, for example, a rod-shaped member made of resin, and is installed with one end fixed to the reinforcing bar 22 and the other end protruding a predetermined length from the spray surface 25a toward the internal space 4. By providing such spacers at a plurality of locations, the spacers prevent the second membrane body 14 from contacting the spray surface 25a.

[0053] Also, it may be possible to monitor at a plurality of locations whether the size of the gap formed between the spray surface 25a and the second membrane body 14 is a predetermined size. For example, distance sensors capable of measuring the distance between the spray surface 25a and the second membrane body 14 may be installed at a plurality of locations to monitor the gap between the spray surface 25a and the second membrane body 14. The distance sensor is attached, for example, to a bolt or bracket (not shown) having one end tied to the reinforcing bar 22 and the other end extending into the internal space 4.

[0054] In addition, a through hole penetrating the first membrane body 10 and the sprayed concrete section 20 may be formed as a monitoring window, allowing a worker to visually check the condition of the second membrane body 14, such as whether the second membrane body 14 is in contact with the sprayed surface 25a, through the monitoring window.

[0055] In this way, by positioning the dome-shaped second membrane body 14 in the internal space 4 facing the sprayed surface 25a, the space through which carbon dioxide gas can flow is limited to the gap formed between the sprayed surface 25a and the second membrane body 14, and therefore, as described below, the amount of carbon dioxide gas filled in the internal space 4 when carbonation curing of the second sprayed concrete 25 is performed can be reduced.

[0056] Once the placement of the second membrane body 14 in the internal space 4 is completed, a carbonation curing step is carried out in the following step S15.

[0057] As shown in FIG. 7, carbonation curing is performed by appropriately operating a carbon dioxide gas supplying device 34 that supplies carbon dioxide gas into the internal space 4, an air conditioner 38 that adjusts the temperature and humidity of the air containing carbon dioxide gas in the internal space 4 and circulates the air, and a control valve 35 that can exhaust the air in the internal space 4 to the outside.

[0058] The carbon dioxide gas supplying device 34 has a portable cryogenic container (LGC) (not shown) filled with liquid carbon dioxide, a vaporizer (not shown) that vaporizes the liquid carbon dioxide, and an solenoid valve (not shown) that can adjust the supply flow rate of the carbon dioxide gas vaporized by the vaporizer, and is configured to be able to supply carbon dioxide gas to the gap between the spraying surface 25a and the second membrane body 14.

[0059] In addition, a carbon dioxide gas supplying device 34 including a portable ultra-low temperature container and a vaporizer is installed outside the dome-shaped structure 100, and a duct pipe through which carbon dioxide gas flows from the carbon dioxide gas supplying device 34 to the internal space 4 is installed penetrating the first membrane body 10 and the part of the sprayed concrete section 20 near the floor surface 1 so as to open near the floor surface 1.

[0060] The control valve 35 is a valve device such as a solenoid valve whose valve opening degree can be adjusted, and is installed in an exhaust duct 36 that is installed to communicate between the internal space 4 and the outside of the dome-shaped structure 100. The exhaust duct 36 opens in the internal space 4 near the top of the internal space 4, and the flow rate of air that flows through the exhaust duct 36 and is exhausted from the internal space 4 is adjusted by the control valve 35.

[0061] The air conditioner 38 has an air outlet 38a installed near the top of the internal space 4, a pair of air inlets 38b installed on the floor surface 1 around the second membrane 14, and a main body 38c that adjusts the temperature and humidity of the air containing carbon dioxide gas sucked in from the air inlets 38b and supplies the air containing carbon dioxide gas whose temperature and humidity have been adjusted to the air outlet 38a. The main body 38c is installed outside the dome-shaped structure 100, and a duct pipe connecting the main body 38c and the air outlet 38a and a duct pipe connecting the main body 38c and the air inlets 38b are installed penetrating the first membrane 10 and the shotcrete section 20.

[0062] Components installed in the internal space 4, such as the exhaust duct 36, the air outlet 38a, the air inlet 38b, and the ducts connecting the air outlet 38a and the air inlet 38b to the main body 38c, are attached to bolts or brackets (not shown) having one end tied to the reinforcing bar 22 and the other end extending into the internal space 4 before the second membrane body 14 is inflated.

[0063] In step S15, first, the internal space 4 is filled with carbon dioxide gas.

[0064] Specifically, when the control valve 35 is open, carbon dioxide gas is gradually supplied from the carbon dioxide gas supply device 34 to the lower side of the internal space 4, and air having a smaller specific gravity than carbon dioxide gas is exhausted to the outside through the exhaust duct 36 that opens near the top of the internal space 4. Note that an exhaust blower may be installed at the outlet of the exhaust duct 36 to quickly exhaust the air within the internal space 4.

[0065] When the carbon dioxide concentration detected by a carbon dioxide concentration sensor (not shown) installed near the top of the internal space 4 reaches a predetermined concentration, the control valve 35 is closed and the supply of carbon dioxide from the carbon dioxide gas supply device 34 is temporarily stopped. The carbon dioxide concentration sensor may be installed at the outlet of the exhaust duct 36 to detect the concentration of carbon dioxide exhausted through the exhaust duct 36.

[0066] Once the air present in the internal space 4 has been replaced with carbon dioxide gas, the air environment in the internal space 4 is then adjusted by the air conditioner .

[0067] Generally, the carbonation rate of concrete varies depending on temperature and humidity, and there exists an air environment with optimal temperature and humidity for carbonation. In addition, the second shotcrete 25, which is the subject of carbonation curing, is structured to ensure the rigidity of the dome-shaped structure 100 together with the first shotcrete 21, so carbonation, which affects the rigidity of the second shotcrete 25, must be performed uniformly.

[0068] For this reason, in this embodiment, in order to make the environment within the internal space 4, particularly the environment in the gap between the spray surface 25a and the second membrane body 14, uniform, the air conditioner 38 adjusts the temperature and humidity of the air containing a high concentration of carbon dioxide to optimal conditions for carbonation, and circulates the air containing a high concentration of carbon dioxide.

[0069] Specifically, the air conditioner 38 is operated automatically or manually so that the detection values ​​of temperature and humidity sensors (not shown) installed at multiple locations within the interior space 4 are within a predetermined range centered on a temperature of 50 degrees and a humidity of 50%.

[0070] In this manner, the environment within the internal space 4 is adjusted by the air conditioner 38, whereby the carbonation curing of the second shotcrete 25 is started.

[0071] Carbonation curing is carried out for a predetermined period (e.g., 28 days), during which the temperature and humidity in the internal space 4 are adjusted to be constant (e.g., temperature 50 degrees, humidity 50%) by the air conditioner 38, and the carbon dioxide concentration in the internal space 4 is adjusted to be constant (e.g., 80%) by the carbon dioxide gas supply device 34 and control valve 35.

[0072] The carbon dioxide concentration in the internal space 4 gradually decreases as the carbon dioxide solidifies in the second sprayed concrete 25, so that the carbon dioxide concentration detected by a carbon dioxide concentration sensor not shown is maintained at a predetermined concentration (e.g., 80%), the solenoid valve of the carbon dioxide supply device 34 is automatically or manually operated to supply carbon dioxide into the internal space 4, while the opening of the control valve 35 is adjusted, and the air in the internal space 4 with the reduced carbon dioxide concentration is exhausted through the exhaust duct 36.

[0073] During the carbonation curing, the internal pressure of the second film body 14 is also adjusted appropriately so that the size of the gap formed between the spray surface 25a and the second film body 14 is maintained constant.

[0074] After a predetermined carbonation curing period has elapsed, the carbon dioxide in the internal space 4 is collected by the carbon dioxide gas supplying device 34, and the carbonation curing is completed. The carbon dioxide in the internal space 4 may be replaced with air and released to the outside of the dome-shaped structure 100.

[0075] After the carbonation curing is completed, the second membrane body 14, the carbon dioxide gas supply device 34, and the air conditioner 38 that were installed for the carbonation curing are sequentially removed, and the through holes through which duct pipes, etc. were inserted are backfilled or expanded to create openings, completing the construction of the dome-shaped structure 100 as shown in Figure 1.

[0076] As described above, the construction of the dome-shaped structure 100 is completed through each process including the carbonation curing process that is carried out especially after the second membrane body 14 is placed in the internal space 4.

[0077] According to the above embodiment, the following effects are achieved.

[0078] According to the above-mentioned method of constructing the dome-shaped structure 100, concrete containing a carbon dioxide-binding admixture is sprayed onto the inner surface of the first membrane body 10 formed into a dome shape, and then the second membrane body 14 inflated with air is placed in the internal space 4 facing the sprayed surface 25a, and carbon dioxide is supplied into the gap formed between the sprayed surface 25a and the second membrane body 14, thereby carbonation curing the second sprayed concrete 25.

[0079] In this way, by positioning the second membrane body 14 in the internal space 4 facing the sprayed surface 25a, the space into which carbon dioxide can flow is limited, making it possible to reduce the amount of carbon dioxide required when performing carbonation curing of the second sprayed concrete 25.

[0080] This prevents the increase of excess carbon dioxide gas that does not contribute to the carbonation curing of the second sprayed concrete 25, making it possible for the concrete to absorb sufficient carbon dioxide even in a relatively large structure such as the dome-shaped structure 100, and as a result, the amount of carbon dioxide emissions associated with the construction of the dome-shaped structure 100 can be reduced.

[0081] Furthermore, according to the above-mentioned method for constructing the dome-shaped structure 100, the carbon dioxide gas is adjusted to be uniformly distributed in the gap formed between the sprayed surface 25a and the second membrane 14, so that the surface layer of the second shotcrete 25 is uniformly densified by calcium carbonate produced by carbonation curing. Since the strength of the shotcrete portion 20 is improved by densifying the surface layer of the second shotcrete 25 in this way, the rigidity of the dome-shaped structure 100 can be improved as a result.

[0082] In addition, the following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the above embodiment, or to combine the configurations described in the different modified examples below.

[0083] In the above embodiment, the reinforcing bar 22 is disposed inside the sprayed concrete portion 20, but if the strength of the concrete skeleton is sufficient, the reinforcing bar 22 may not be disposed. Instead of the reinforcing bar 22, a reinforcing bar made of carbon fiber or glass fiber may be disposed inside the sprayed concrete portion 20. When storing a storage object (such as coal) with a low moisture content and relatively dry inside the dome-shaped structure 100, the reinforcing bar 22 may also be disposed inside the second sprayed concrete 25, since there is a low risk of moisture entering the second sprayed concrete 25. In addition, the reinforcing bar made of carbon fiber or glass fiber can be disposed inside the second sprayed concrete 25, regardless of the moisture content or dryness of the storage object stored inside the dome-shaped structure 100. When the reinforcing bar is formed of carbon fiber or glass fiber, there is no risk of rust or the like occurring even inside the second sprayed concrete 25, which may be acidic inside.

[0084] In the above embodiment, the shotcrete section 20 has a two-layer structure of the first shotcrete 21 and the second shotcrete 25. Alternatively, the shotcrete section 20 may be composed of only the second shotcrete 25. In this case, it is preferable to use reinforcing bars made of carbon fiber or glass fiber, rather than reinforcing bars 22.

[0085] In the above embodiment, the exhaust duct 36, the duct pipe connecting the main body 38c of the air conditioner 38 to the outlet 38a, and the duct pipe connecting the main body 38c of the air conditioner 38 to the inlet 38b are arranged in the internal space 4 along the sprayed surface 25a of the second shotcrete 25. Alternatively, these ducts may be arranged outside the dome-shaped structure 100 along the outer surface of the first membrane 10. By configuring the ducts to be arranged outside the dome-shaped structure 100 in this way, it is possible to perform the installation work of the ducts in parallel with the work inside the dome-shaped structure 100, for example, the spraying work of the second shotcrete 25, and therefore the construction period of the dome-shaped structure 100 can be shortened.

[0086] In the above embodiment, the steps S13 to S15 are performed only once. Alternatively, the steps S13 to S15 may be repeated, and concrete containing a carbon dioxide-binding admixture capable of chemically bonding with carbon dioxide may be sprayed onto the inner surface of the second shotcrete 25 after carbonation curing has been completed, to perform carbonation curing. By repeating the steps S13 to S15 in this manner to expand the carbonation region in the concrete, the amount of carbon dioxide absorption can be increased and the rigidity of the dome-shaped structure 100 can be improved.

[0087] In the above embodiment, the outer shape of the second membrane body 14 disposed in the internal space 4 is dome-shaped similar to the outer shape of the first membrane body 10. Alternatively, the second membrane body may be an assembly 116 in which a plurality of spheres 114 inflated with air (gas) and having different diameters are assembled into a substantially dome shape, as in the modified example shown in Fig. 8. In this case, the carbon dioxide gas supplied into the internal space 4 in the carbonation curing process is mainly supplied to the gap between the spray surface 25a and the assembly 116 (second membrane body).

[0088] In this manner, when the aggregate 116 is arranged in the internal space 4 facing the sprayed surface 25a, as in the above embodiment, the space into which the carbon dioxide gas supplied to the internal space 4 can flow during the carbonation curing process is restricted, and as a result, it is possible to reduce the amount of carbon dioxide gas required when performing the carbonation curing of the second sprayed concrete 25.

[0089] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. [Explanation of symbols]

[0090] 100 Dome-shaped structure 1. Floor surface 4. Internal space (space) 10...First membrane 14...Second membrane 20···Sprayed concrete section (concrete) 21. First sprayed concrete 22 Reinforcement 25...Second sprayed concrete 25a···Spray surface 116...Aggregation (second membrane body)

Claims

1. A method for constructing a dome-shaped structure, comprising the steps of: a step of injecting gas between a dome-shaped first membrane and a floor surface to make the first membrane self-supporting; spraying concrete onto an inner surface of the free-standing first membrane; a step of placing a second membrane body inflated by injecting gas into a space facing the sprayed surface formed by spraying the concrete; supplying carbon dioxide gas into the gap between the spray surface and the second film body; The concrete contains a carbon dioxide-binding admixture capable of chemically bonding with the carbon dioxide. A method for constructing a dome-like structure.

2. The outer shape of the second membrane body inflated by injecting gas is a dome shape similar to the outer shape of the first membrane body. A method for constructing the dome-shaped structure according to claim 1.

3. The concrete includes at least a first sprayed concrete sprayed on the first membrane side and a second sprayed concrete sprayed on the sprayed surface side, The carbon dioxide gas binding admixture is contained only in the second sprayed concrete. A method for constructing the dome-shaped structure according to claim 1 or 2.

4. A reinforcing bar is provided in the area where the first shotcrete is sprayed, and the reinforcing bar is not provided in the area where the second shotcrete is sprayed. A method for constructing a dome-shaped structure according to claim 3.

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