Carbonation curing method

Abstract

To provide a carbonation curing method capable of quickly and uniformly making an inner surface of lining concrete the target curing environment.SOLUTION: A carbonation curing method for lining concrete placed as a lining of a tunnel is provided. The method comprises the steps of: forming a curing surface in an arch shape by planar material 1 that shields curing gas containing carbon dioxide at a position separated from an inner peripheral surface of lining concrete F by a predetermined distance; supplying curing gas with adjusted relative humidity and temperature from one supply side base 31 of a curing surface formed in an arch shape to a curing space 10 between the curing surface and the inner peripheral surface and discharging the curing gas from the other discharge side base 32; and continuously supplying and discharging the curing gas for a predetermined period of time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for carbonation curing of lining concrete cast as a tunnel lining. [Background technology]

[0002] A technology has been developed to manufacture carbonated concrete, which is dense and has excellent chemical stability, by carbonation curing concrete in which a special admixture, γ-2CaO·SiO2 (a type of belite), has been used to partially replace ordinary Portland cement, and its application to precast components and factory products has been put to practical use (see Patent Document 1). On the other hand, in order to apply carbonated concrete to cast-in-place concrete, a curing method that suits the characteristics of various structures is required.

[0003] Furthermore, Patent Document 2 describes that by supplying a gas containing carbon dioxide during the curing of the lining concrete of a mountain tunnel, the carbon dioxide can be fixed in the ordinary concrete as calcium carbonate.

[0004] Generally, for lining concrete, ordinary concrete is poured using a center formwork, and after the form is removed the day after pouring, the required wet curing is carried out. In Patent Document 2, a curing cart that can move in the extension direction of the tunnel is used, and the curing cart is placed on the inner peripheral side of the lining concrete to form an enclosed space, and carbon dioxide is supplied to the enclosed space to fix the carbon dioxide during curing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5504000 [Patent Document 2] Patent Publication No. 2022-18281 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method disclosed in Patent Document 2, gas containing carbon dioxide is supplied from the top (apex) of the lining concrete and discharged from the base on both sides near the bottom of the tunnel. Patent Document 2 does not aim at carbonation curing, and only requires that carbon dioxide be fixed in the lining concrete, so it does not pay attention to the concentration distribution of carbon dioxide in the curing space.

[0007] However, as will be described later, the carbon dioxide supply method described in Patent Document 2 is not suitable for carbonation curing because carbon dioxide, which is heavier than air, tends to collect toward the base and it is not possible to achieve a uniform carbon dioxide concentration over the entire inner surface of the lining concrete.

[0008] Therefore, an object of the present invention is to provide a carbonation curing method that can quickly and uniformly create a target curing environment on the inner surface of the lining concrete. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the carbonation curing method of the present invention is a carbonation curing method for lining concrete cast as a tunnel lining, and is characterized by comprising the steps of: forming an arch-shaped curing surface at a position spaced a predetermined distance from the inner circumferential surface of the lining concrete to block curing gas containing carbon dioxide; supplying the curing gas, the relative humidity and temperature of which have been adjusted, from one base of the arch-shaped curing surface to a curing space between the curing surface and the inner circumferential surface and discharging the curing gas from the other base; and continuing the supply and discharge of the curing gas for a predetermined period of time.

[0010] Here, the relative humidity of the curing gas to be supplied is preferably adjusted to 80% or less. Furthermore, the carbon dioxide concentration of the curing gas to be supplied is adjusted to a value of 5% or more and 80% or less, and the temperature of the curing gas is adjusted to a value of 5° C. or more and 50° C. or less, and the temperature and concentration of carbon dioxide in the curing gas and the flow rate of the curing gas are measured at the base side where the supply is performed and at the base side where the discharge is performed, thereby making it possible to calculate the amount of carbon dioxide fixed in the lining concrete.

[0011] In order to maintain the predetermined distance, a plurality of spacers may be arranged in the curing space. Furthermore, it is preferable that the height of the spacers is 200 mm or less. The curing space may be closed by arranging an elastic body on the edge of the curing surface. Effect of the Invention

[0012] In the carbonation curing method of the present invention thus configured, a curing gas containing carbon dioxide with adjusted relative humidity and temperature is supplied from one base of the curing surface to the curing space between the arch-shaped curing surface and the inner peripheral surface of the lining concrete, and is discharged from the other base.

[0013] This makes it possible to quickly and uniformly create the desired curing environment on the inner surface of the lining concrete. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic overview of a carbonation curing method according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram illustrating an apparatus used in the carbonation curing method of the present embodiment. [Diagram 3] FIG. 1 is an explanatory diagram showing an enlarged view of the protective space. [Figure 4] FIG. 11 is an explanatory diagram illustrating an example of the arrangement of spacers. [Diagram 5] 11 is an explanatory diagram illustrating a configuration of a blocking process around a base portion. FIG. [Figure 6] 1 is a flowchart illustrating steps of a carbonation curing method according to an embodiment of the present invention. [Figure 7] FIG. 13 is an explanatory diagram showing the analysis results of a carbonation curing method serving as a comparative example. [Figure 8] FIG. 1 is an explanatory diagram showing an analysis result of a carbonation curing method according to an example of the present embodiment. [Figure 9] FIG. 1 is an explanatory diagram showing the analysis results of the optimal carbonation curing method of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram that shows a schematic overview of the carbonation curing method of the present embodiment.

[0016] The carbonation curing method of this embodiment is intended for lining concrete F that is cast in situ in tunnels such as mountain tunnels. The lining concrete F is cast in situ using a center form, and is carbonation cured after the center form is removed.

[0017] The carbonated concrete used in the carbonation curing method of the present embodiment is, for example, concrete in which a special admixture γ-2CaO·SiO2 (a type of belite) is substituted for part of ordinary Portland cement (see Patent Document 1).

[0018] To carry out carbonation curing, a curing space 10 is formed along the inner peripheral surface F1 (see FIG. 3) of the lining concrete F, and the curing space 10 is filled with a curing gas containing a high concentration of carbon dioxide.

[0019] 1, the curing space 10 is formed in an arch shape in the circumferential direction TY of the tunnel when seen across the tunnel, and is formed in the shape of an arc plate with a certain width in the extension direction TX of the tunnel. A curing gas containing carbon dioxide, the concentration, relative humidity and temperature of which have been adjusted by a curing gas circulating device 2, is supplied to the curing space 10 from a supply side base 31, which is one base of the arch shape when seen across the tunnel.

[0020] The curing gas supplied from the supply-side base 31 to the curing space 10 diffuses in the extension direction TX and the circumferential direction TY of the curing space 10, passes through the top end (apex) of the tunnel, and is discharged from the discharge-side base 32, which is the other base. The discharged curing gas is then recovered by the curing gas circulator 2 and sent back to the supply-side base 31.

[0021] Fig. 2 is an explanatory diagram illustrating the configuration of the apparatus used in the carbonation curing method of the present embodiment. The lower half of Fig. 2 illustrates the configuration as seen from a cross-sectional view of the tunnel, and the upper half shows a development of the curing space 10.

[0022] After the removal of the lining concrete F is completed and the center formwork (not shown) has moved to the next section, a curing cart 12 is set on the inner surface F1 side of the lining concrete F. The curing cart 12 is capable of traveling on the bottom surface T1 of the tunnel, and moves behind the center formwork.

[0023] The curing cart 12 is equipped with multiple arch-shaped frames 11 for supporting the planar material 1 that will become the curing surface in an arch shape. The frames 11 are made of steel material such as H-shaped steel processed into an arch shape such as a horseshoe shape or semicircular shape when viewed across the tunnel, and are mounted on the curing cart 12 at intervals in the extension direction TX of the tunnel. For example, the length of the curing cart 12 in the extension direction TX, in which the frames 11 are arranged at intervals of 1.5 m, is about 10 m.

[0024] The planar member 1 supported from below by the frame 11 is a sheet or plate made of a material that blocks carbon dioxide. For example, a waterproof sheet or an FRP (fiber reinforced plastic) plate can be used.

[0025] In addition, a curing gas circulating device 2 and piping 23 for supplying a curing gas containing a high concentration of carbon dioxide are mounted on the curing cart 12. One end of the piping 23 extending from the curing gas circulating device 2 is connected to an air supply port 21 opened in the sheet-shaped material 1, and the other end of the piping 23 is connected to an exhaust port 22 opened in the sheet-shaped material 1.

[0026] The air supply port 21 is provided in the vicinity of an edge of the sheet material 1 on the tunnel entrance side of the supply side base 31 in the extension direction TX, for example. In contrast, the air exhaust port 22 is provided in the vicinity of an edge of the sheet material 1 on the tunnel face side (excavation surface side) of the discharge side base 32 in the extension direction TX.

[0027] In short, as shown in the cross-sectional view of the tunnel in the lower half of Fig. 2, an air supply port 21 is provided in one base part (31) connected to the curing space 10, and an exhaust port 22 is provided in the opposing base part (32). Also, as shown in the development view in the upper half of Fig. 2, an exhaust port 22 is provided in a position diagonally opposite to the air supply port 21. By arranging the air supply port 21 and the exhaust port 22 in this way, the curing gas can be diffused quickly and evenly in the curing space 10.

[0028] In the curing space 10, environmental measurement sensors 4 are arranged to measure the concentration of carbon dioxide in the curing gas (curing gas concentration), relative humidity, temperature, etc. For example, the environmental measurement sensors 4 are arranged at the air supply port 21 and the exhaust port 22. In addition, a plurality of environmental measurement sensors 4 are arranged at intervals in the extension direction TX at the top end (vertex) of the curing space 10.

[0029] 3 is an explanatory diagram showing an enlarged view of the curing space 10. As shown in this figure, a spacer 13 is interposed between the inner peripheral surface F1 of the lining concrete F and the curing surface of the sheet-shaped material 1 to maintain a predetermined distance in the curing space 10.

[0030] The height of the spacer 13 can be any height, such as 30 mm, 50 mm, 100 mm, or 200 mm. The appropriate thickness for the curing space 10 will be described later. The spacer 13 can be made of steel, FRP, rubber, plastic, mortar, spring, or the like. The shape of the spacer 13 is preferably a shape that does not impede the flow of air during curing, such as a circular, elliptical, or streamlined shape. In addition, the contact area between the spacer 13 and the inner circumferential surface F1 of the lining concrete F is very small compared to the contact area between the entire inner circumferential surface F1 and the curing gas, so there is no problem of locally slowing down or becoming uneven in carbonation near the contact surface between the spacer 13 and the inner circumferential surface F1.

[0031] 4 is an explanatory diagram illustrating an example of the arrangement of the spacers 13 in a development view of the curing space 10. The spacers 13 are attached, for example, to the surface of the sheet material 1 at a position where the frame 11 is arranged. A plurality of spacers 13 are arranged at intervals in the extension direction TX and the circumferential direction TY.

[0032] The curing space 10 must be kept filled with the curing gas for a specified period of time, and therefore must be an airtight space. As described above, on the tunnel center side of the curing space 10, a curing surface is formed by the sheet material 1 parallel to the inner surface F1 of the lining concrete F, which prevents leakage of the curing gas.

[0033] On the other hand, if nothing is placed at the end of the curing space 10, which is the tunnel entrance side and the face side, an arch-shaped opening will result. Therefore, arch-shaped elastic bodies (not shown) are placed at the edges on both sides of the extension direction TX of the sheet material 1 to close the opening. For example, an air frame that injects gas to expand into an arch shape is placed.

[0034] Furthermore, elastic bodies are also placed on the edges of the sheet material 1 that becomes the supply side base 31 and the discharge side base 32 to prevent leakage of the curing gas. Fig. 5 is an explanatory diagram illustrating an example of a configuration for blocking the periphery of the bases (31, 32). The periphery of the bases (31, 32) of the curing space 10 can be blocked by a rectangular suction pad 5 whose longitudinal direction is the extension direction TX. The suction pad 5 can be made of an elastic body such as rubber.

[0035] For example, a suction tube 52 with a suction port 51 at its tip is built into the suction pad 5 that closes the opening of the base (31, 32). When the suction port 51 is brought into contact with the inner circumferential surface F1 of the lining concrete F and sucked by the suction tube 52, the suction port 51 comes into close contact with the inner circumferential surface F1, and the suction pad 5 can be firmly fixed to the edge of the sheet material 1.

[0036] By providing a sealing structure that prevents the curing gas from leaking into the tunnel interior, not only is the loss of carbon dioxide reduced and the curing efficiency improved, but the leakage of carbon dioxide into the tunnel interior can be prevented, maintaining a safe working environment inside the tunnel.

[0037] Next, the carbonation curing method of the present embodiment will be described with reference to the flow chart shown in FIG. Below, we will explain the construction of a mountain tunnel using the NATM method as an example.

[0038] When constructing a tunnel using the NATM method, excavation is carried out while spraying quick-setting sprayed concrete onto soft ground or ground with developed cracks from the rear of excavation equipment such as breakers and backhoes, or heavy machinery such as wheel loaders (Step S1).

[0039] In addition, steel supports are installed at intervals along the tunnel's semi-cylindrical excavation surface in the extension direction TX, and the ground is supported by spraying concrete. After confirming that the ground displacement has converged, a waterproof sheet is placed along the excavation surface.

[0040] A movable center form is placed on the tunnel interior side of the waterproof sheet, and cast-in-place concrete (carbonated concrete) is poured to construct the lining concrete F (Step S2). The lining concrete F is constructed in the shape of an arc plate, for example, with a thickness of about 30 cm to 50 cm. The center form can generally be removed the next day, so it is moved toward the next section on the tunnel face side (Step S3).

[0041] In the section where the center formwork has been moved and the inner peripheral surface F1 of the lining concrete F has been exposed, the curing cart 12 is moved and set on the side of the inner peripheral surface F1 of the lining concrete F (step S4). As shown in Fig. 2, the curing cart 12 has an arch-shaped curing surface formed in the cross-sectional view of the tunnel by the sheet material 1 supported by the frame 11, so that a curing space 10 covering the inner peripheral surface F1, for example, with a thickness of about 50 mm to 200 mm, can be formed. For example, the sheet material 1 together with the frame 11 can be pushed up with a jack or the like, and the frame 11 can be lowered until it is separated by a predetermined distance from the position where it is in close contact with the inner peripheral surface F1, thereby forming a curing space 10 of a desired thickness.

[0042] An air frame is placed on both edges of the extension direction TX of the curing space 10 formed by the sheet material 1, and air is injected into the air frame to inflate it, thereby performing a closing process. Also, a rubber suction pad 5 or the like is placed on the edge of the sheet material 1 on the tunnel base (31, 32) side of the curing space 10, thereby performing a closing process. In this way, the curing space 10 is sealed.

[0043] After sealing the curing space 10, the curing gas circulating device 2 is operated to send the curing gas containing a high concentration of carbon dioxide into the curing space 10 (step S5). The curing gas circulating device 2 adjusts the carbon dioxide concentration (CO2 concentration), relative humidity and temperature of the curing gas and supplies the curing gas toward the air inlet 21, and also re-adjusts the concentration of the curing gas discharged from the exhaust outlet 22 and circulates it.

[0044] In short, the curing gas sent into the curing space 10 not only decreases in concentration as carbon dioxide is absorbed by the lining concrete F, but also increases in relative humidity due to moisture discharged from the concrete surface due to carbonation. The carbonation reaction of concrete increases in speed as the carbon dioxide concentration increases, but the reaction rate drops significantly when the relative humidity exceeds 80%. For this reason, the concentration and relative humidity of the curing gas recovered by the curing gas circulator 2 are readjusted, and it is preferable to supply a curing gas with a low relative humidity in anticipation of an increase in the relative humidity in the curing space 10. This makes it possible to approach the target values ​​(target curing environment) of the carbon dioxide concentration, relative humidity, and temperature required on the concrete surface (inner circumferential surface F1).

[0045] For example, the curing gas sent from the curing gas circulation device 2 is adjusted to a constant temperature of 5°C to 50°C, a given relative humidity of 80% or less, and a given carbon dioxide concentration of 5% to 80%. Here, the higher the concentration of carbon dioxide in the curing gas, the faster the carbonation reaction, the lower the relative humidity, the faster the penetration of the curing gas into the depths of the lining concrete F, and the higher the temperature, the faster the carbonation reaction. Since the carbon dioxide concentration in the atmosphere is about 0.04%, a carbon dioxide concentration of 5% is a 100-fold concentration difference, and the specific gravity difference is sufficient. For this reason, it is preferable to adjust the temperature of the curing gas to a constant value of 20°C to 50°C, the relative humidity to 50% or less, and the carbon dioxide concentration of the curing gas to 60% to 80%. It is further preferable to adjust the temperature to a constant value of 40°C to 50°C, and the relative humidity to 40% or less.

[0046] As shown in Fig. 2, the environmental measurement sensors 4 are installed at the air inlet 21, the exhaust port 22, and near the top of the curing space 10, so that the carbon dioxide concentration, temperature, relative humidity, etc. in the curing gas are monitored at each location while carbonation curing is performed (step S6). By monitoring the curing gas concentration at each location in the curing space 10, it is possible to confirm whether the carbonation curing is performed in an environment where the curing gas of the desired concentration is uniformly dispersed. Furthermore, by setting the concentration of carbon dioxide in the curing gas supplied at the air inlet 21 to a constant value (e.g., 80%) and the temperature to a constant value (e.g., 50°C), and continuously measuring the concentration and flow rate of carbon dioxide in the curing gas at the exhaust port 22 during the carbonation curing period, the amount of carbon dioxide fixed in the lining concrete F by carbonation curing (CO2 fixed amount) can be calculated and recorded as an actual measurement value.

[0047] On the other hand, in order to keep the carbon dioxide concentration of the curing gas supplied from the curing gas circulation device 2 constant, high technology and a large amount of cost are required. Therefore, when the carbon dioxide concentration in the curing gas supplied from the air inlet 21 cannot be kept substantially constant, the flow rate, temperature and carbon dioxide concentration of the curing gas sent from the curing gas circulation device 2 are continuously measured not only at the exhaust port 22 but also at the air inlet 21. In this way, it becomes possible to calculate the amount of carbon dioxide in the curing gas supplied from the curing gas circulation device 2 to the curing space 10 and the amount of carbon dioxide in the curing gas discharged from the curing space 10. Then, the difference obtained by subtracting the amount of carbon dioxide in the curing gas discharged from the curing space 10 from the amount of carbon dioxide in the curing gas supplied to the curing space 10 is calculated as the amount of carbon dioxide fixed in the lining concrete F by carbonation curing (fixed CO2 amount), and can be recorded as an actual measurement value.

[0048] The supply of the curing gas is continued for a predetermined time, and the carbonation curing is completed. After the carbonation curing is completed, the curing gas containing carbon dioxide is collected from the curing space 10, and the airtight state by the air frame and the suction pad 5 is released, and the curing cart 12 is moved to the next curing section (step S7).

[0049] Next, the action of the carbonation curing method of the present embodiment will be described. In the carbonation curing method configured in this manner, a curing gas containing carbon dioxide whose concentration, relative humidity and temperature have been adjusted is supplied from a supply-side base 31, which is one of the bases of the arch, to the curing space 10 between the curing surface formed by the sheet materials 1 arranged in an arch shape and the inner peripheral surface F1 of the lining concrete F, and the curing gas is discharged from the discharge-side base 32, which is the other opposite side.

[0050] Here, Fig. 7 to Fig. 9 show the results of airflow analysis performed by changing the thickness of the curing space 10 and the positions of the air inlet and exhaust port. Here, the supply flow rate of the curing gas is 6 (m 3 / min) and the diameters of the air intake and exhaust ports were also set to 300 mm. Note that no suction was performed on the exhaust port side, and natural exhaust was used.

[0051] First, Fig. 7 showing the analysis results of the carbonation curing method as a comparative example will be described. In the comparative example, similar to Patent Document 2, the curing gas was supplied from the top end (vertex) of the lining concrete and discharged from the base on both sides near the tunnel bottom (see white arrows). In the comparative example, the thickness of the curing space was set to 100 mm.

[0052] Figure 7(a) shows the distribution of carbon dioxide (CO2) concentration 5 minutes after the start of curing gas supply, and Figure 7(b) shows the distribution of CO2 concentration 10 minutes after the start of curing gas supply. As can be seen from this figure, 5 minutes after the start of curing gas supply, there is a large variation in concentration between the top and base, and even after 10 minutes, the low CO2 concentration near the top has not improved. This is thought to be because carbon dioxide is heavier than air and tends to collect at the base.

[0053] 8 and 9 are explanatory diagrams showing the analysis results of the carbonation curing method of this embodiment. That is, the curing gas is supplied from the supply side base 31 and discharged from the discharge side base 32.

[0054] First, the results of Fig. 8, in which the thickness of the curing space 10 was set to 100 mm, the same as in the comparative example, will be described. Fig. 8(a) shows the distribution of the CO2 concentration 5 minutes after the start of the supply of the curing gas, and Fig. 8(b) shows the distribution of the CO2 concentration 10 minutes after the start of the supply of the curing gas.

[0055] As can be seen from this figure, five minutes after the curing gas was supplied, the area with low CO2 concentration spreads in the curing space 10 from the top end to the discharge side base 32, although not as much as in the comparative example. However, after 10 minutes, it can be seen that the distribution of CO2 concentration becomes almost uniform throughout the entire curing space 10.

[0056] On the other hand, Fig. 9 shows the analysis results of the carbonation curing method of this embodiment in which the thickness of the curing space 10 is narrowed to 50 mm. Fig. 9(a) shows the distribution of CO2 concentration 5 minutes after the start of the supply of the curing gas, and Fig. 9(b) shows the distribution of CO2 concentration 10 minutes after the start of the supply of the curing gas.

[0057] When the curing gas is supplied from the supply-side base 31 to the curing space 10 having a thickness of 50 mm and discharged from the discharge-side base 32, a nearly uniform distribution of the CO2 concentration is achieved about 5 minutes after the start of the curing gas supply, and after 10 minutes, the distribution of the CO2 concentration is uniform throughout the entire curing space 10.

[0058] By using the carbonation curing method of this embodiment in this way, the vicinity of the inner circumferential surface F1 of the lining concrete F can be quickly and uniformly brought into a target curing environment. When carbonation curing carbonated concrete, it is desirable to make the curing space 10 into a curing environment with a relative humidity of a predetermined value (for example, 60%, preferably 50%, and more preferably 40%) or less so that the large amount of water vapor generated by the hydration reaction does not fill the pores in the lining concrete F and prevent the permeation of the curing gas (carbon dioxide) into the depths of the lining concrete F. For this reason, it is preferable to adjust the relative humidity of the curing gas supplied to the air inlet 21 to a value lower than the target value.

[0059] Furthermore, by continuously measuring the concentration and flow rate of carbon dioxide not only at the exhaust port 22 of the discharge side base 32 but also at the intake port 21 of the supply side base 31, the fixed amount of carbon dioxide can be calculated and recorded as an actual measurement value even if the carbon dioxide concentration of the supplied curing gas is any value between 5% and 80%.

[0060] Regarding the temperature of the curing gas supplied, in the case of a tunnel being excavated, only the minimum necessary ventilation is performed, so the temperature inside the tunnel is expected to be around 20°C, which is close to the temperature of the natural ground. After the tunnel is penetrated, the temperature inside the tunnel is expected to drop to around 5°C due to the supply of fresh air from outside the tunnel. On the other hand, if there is no air flow around the curing space, the air temperature around the curing space may rise to around 50°C due to the heat of hydration of the concrete. In light of the above, the temperature of the curing gas supplied from the curing gas circulation device 2 can be set to any value in the range of 5°C to 50°C inclusive in order to keep the temperature of the curing gas constant while suppressing energy consumption due to heating and cooling.

[0061] Furthermore, by arranging a plurality of spacers 13 between the inner peripheral surface F1 of the lining concrete F and the curing surface of the sheet-shaped material 1, the curing space 10 can be maintained at a constant thickness (predetermined distance). As shown in Fig. 2, by arranging the positions of the air inlet 21 and the exhaust outlet 22 at positions on the diagonal of the curing cart 12, even if the height of the spacer 13 is set to 100 mm, for example, a curing environment with a roughly uniform distribution of carbon dioxide concentration can be created as shown in the analysis result of Fig. 8. In particular, by setting the height of the spacer 13 to 50 mm or less, a curing environment with a uniform distribution of carbon dioxide concentration can be created in a short time as shown in the analysis result of Fig. 9.

[0062] Furthermore, by placing elastic bodies such as air frames or rubber suction pads 5 on the edges of the sheet material 1 to make the curing space 10 a sealed space, it is possible to prevent the curing gas containing high concentrations of carbon dioxide from leaking out of the curing space 10, allowing for efficient carbonation curing and maintaining a safe working environment inside the tunnel.

[0063] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0064] For example, in the above embodiment, the carbonated concrete described in Patent Document 1 is used as an example, but the present invention is not limited to this, and the present invention can be applied to any cast-in-place concrete for which carbonation curing is effective. [Explanation of symbols]

[0065] 1: Surface material (curing surface) 10:Curing space 13: Spacer 31: Supply side base (one side base) 32: Discharge side base (other base) 5: Suction pad (elastic material) F: Lining concrete F1: Inner surface

Claims

1. A method for carbonation curing of lining concrete cast as a tunnel lining, comprising the steps of: forming an arch-shaped curing surface at a position spaced a predetermined distance from an inner peripheral surface of the lining concrete to block a curing gas containing carbon dioxide; supplying the curing gas, the relative humidity and temperature of which have been adjusted, from one base of the arch-shaped curing surface into a curing space between the curing surface and the inner circumferential surface, and discharging the curing gas from the other base; and continuing the supply and discharge of the curing gas for a predetermined period of time.

2. 2. The carbonation curing method according to claim 1, wherein the relative humidity of the curing gas supplied is adjusted to 80% or less.

3. 3. The carbonation curing method according to claim 2, characterized in that a carbon dioxide concentration of the curing gas supplied is adjusted to a value of 5% or more and 80% or less, a temperature of the curing gas is adjusted to a value of 5°C or more and 50°C or less, and the amount of carbon dioxide fixed in the lining concrete is calculated by measuring the temperature and concentration of carbon dioxide in the curing gas and a flow rate of the curing gas at the base side where the curing gas is supplied and at the base side where the curing gas is discharged.

4. 4. The carbonation curing method according to claim 1, further comprising disposing a plurality of spacers in the curing space to maintain the predetermined distance.

5. 5. The carbonation curing method according to claim 4, characterized in that the height of the spacer is 200 mm or less.

6. The carbonation curing method according to claim 4, characterized in that the curing space is closed by placing an elastic body on the edge of the curing surface.

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