Carbonation curing method

Abstract

This invention provides a carbonation curing method that allows for carbonation curing of the back side of the lining concrete. [Solution] This is a method for carbonation curing of lining concrete F, which is poured on the inner surface side of a waterproof sheet F1 as a tunnel lining. The method further includes the steps of: arranging elongated carbon dioxide supply paths 1, which extend in the direction of tunnel extension, at intervals along the circumferential direction TY of the tunnel, on the inner surface of the waterproof sheet; forming lining concrete by pouring cast-in-place concrete to cover the waterproof sheet and the carbon dioxide supply paths; and supplying a curing gas containing carbon dioxide to the carbon dioxide supply paths.

Description

Technical Field

[0001] The present invention relates to a carbonation curing method for shotcrete concrete placed on the inner surface side of a waterproof sheet as a tunnel lining.

Background Art

[0002] A technique has been developed to produce carbonated concrete that is dense and has excellent chemical stability by carbonation curing concrete in which a special admixture γ-2CaO·SiO2 (a type of belite) is substituted for a part of ordinary Portland cement, and its application to precast members and factory products has been put into practical use (see Patent Document 1). On the other hand, in order to apply carbonated concrete to in-situ concrete, a curing method according to the characteristics of various structures is required.

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

[0004] In general mountain tunnel construction, ordinary concrete is placed using a center formwork on the inner peripheral surface of a waterproof sheet that covers the sprayed concrete applied to the excavation surface of the natural ground. After demolding on the day after placement, the required wet curing is carried out.

[0005] In Patent Document 2, a curing trolley that can move in the tunnel extension direction is used. The curing trolley is placed on the inner peripheral surface side of the shotcrete concrete to form a sealed space, and carbon dioxide is supplied to this sealed space to fix carbon dioxide during curing.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] However, supplying carbon dioxide from the inner surface of the tunnel lining concrete does not allow for carbonation curing of the back side (waterproofing sheet side) of the tunnel lining concrete. In other words, while carbon dioxide emitted from vehicles passing through the tunnel during its operation can promote carbonation on the inner surface of the tunnel lining concrete, such passive carbonation cannot be expected on the back side of the tunnel lining concrete that is in contact with the waterproofing sheet.

[0008] Therefore, the present invention aims to provide a carbonation curing method that can cure the back side of lining concrete by carbonation. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a carbonation curing method for lining concrete cast on the inner surface side of a waterproof sheet as a tunnel lining, comprising the steps of: arranging a long carbon dioxide supply path extending in the direction of extension of the tunnel at intervals in the circumferential direction of the tunnel with respect to the inner circumferential surface of the waterproof sheet; forming the lining concrete by casting concrete so as to cover the waterproof sheet and the carbon dioxide supply path; and supplying a curing gas containing carbon dioxide to the carbon dioxide supply path.

[0010] Here, the carbon dioxide supply path can be configured to be formed in a strip shape using a nonwoven fabric. Furthermore, the nonwoven fabric can be configured to surround a drain material located in the center. The nonwoven fabric can be formed from polyester fibers.

[0011] Furthermore, the curing gas can be supplied from one end of the carbon dioxide supply path in a state where the relative humidity, temperature, and carbon dioxide concentration are adjusted. The carbon dioxide supply path can also be formed to have a circumferential width of approximately 100 mm to 300 mm and a height of approximately 5 mm to 50 mm.

[0012] Furthermore, the carbon dioxide supply path can also be configured such that a moisture-permeable and waterproof resin film layer is placed adjacent to the nonwoven fabric. In addition, the carbon dioxide supply path can be formed in a strip shape using a moisture-permeable and waterproof sheet. Preferably, the moisture-permeable and waterproof sheet is provided so as to surround the drain material located in the center. [Effects of the Invention]

[0013] In the carbonation curing method of the present invention configured as described above, elongated carbon dioxide supply paths are arranged at intervals in the circumferential direction of the tunnel on the inner surface of the waterproof sheet, and cast-in-place concrete is poured to cover the carbon dioxide supply paths to form the lining concrete.

[0014] Then, a curing gas containing carbon dioxide is supplied to the carbon dioxide supply pathway. This makes it possible to perform carbonation curing on the back side of the lining concrete that is in contact with the waterproof sheet. [Brief explanation of the drawing]

[0015] [Figure 1] This is an explanatory diagram showing an overview of the carbonation curing method of this embodiment. [Figure 2] This is a schematic perspective view illustrating the carbonation curing method of this embodiment. [Figure 3] This is a diagram illustrating the layout of carbon dioxide supply pathways. [Figure 4] This is a cross-sectional view at position AA shown in Figure 3. [Figure 5] This is an explanatory diagram illustrating the piping of a curing gas circulation system that utilizes the joints in the lining concrete. [Figure 6] A diagram for explaining the details of the carbon dioxide supply path, where (a) is a longitudinal sectional view cut in the extending direction of the tunnel, and (b) is a transverse sectional view cut in the circumferential direction of the tunnel. [Figure 7] An explanatory diagram showing the results of experimentally verifying the performance of materials that can be used for the non-woven fabric part of the carbon dioxide supply path. [Figure 8] An explanatory diagram showing the results of experimentally verifying the performance of materials that can be used for the drain material of the carbon dioxide supply path. [Figure 9] A flowchart for explaining the steps of the carbonation curing method of the present embodiment. [Figure 10] A diagram for explaining the details of the carbon dioxide supply path of Example 1, where (a) is a longitudinal sectional view cut in the extending direction of the tunnel, and (b) is a transverse sectional view cut in the circumferential direction of the tunnel. [Figure 11] An explanatory diagram of the experimental results for comparing the carbonation depth due to differences in the configuration of the carbon dioxide supply path. [Figure 12] An explanatory diagram for explaining the relationship between the drainage of excess water in concrete and the carbonation depth. [Figure 13] An explanatory diagram for explaining the relationship between the water-cement ratio of concrete and the carbonation depth.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are explanatory diagrams schematically showing the outline of the carbonation curing method of the present embodiment.

[0017] The carbonation curing method of the present embodiment targets the in-situ cast lining concrete F in tunnels such as mountain tunnels. The lining concrete F is provided by casting carbonated concrete in-situ using a center formwork against the inner peripheral surface of the waterproof sheet F1 that covers the sprayed concrete sprayed on the excavation surface of the natural ground.

[0018] The carbonated concrete used in the carbonated curing method of this embodiment is, for example, concrete in which a special admixture γ-2CaO·SiO2 (a type of beelite) is substituted for a portion of ordinary Portland cement (see Patent Document 1), but is not limited thereto, as will be described later.

[0019] To perform carbonation curing, a carbon dioxide supply path 1 is formed along the waterproof sheet F1 on the back side of the lining concrete F, and this carbon dioxide supply path 1 is filled with a curing gas containing a high concentration of carbon dioxide.

[0020] As shown in Figures 1 and 2, the carbon dioxide supply path 1 is formed in a long, elongated shape extending along the tunnel's extension direction TX, and multiple paths are arranged at intervals along the tunnel's circumferential direction TY.

[0021] The parallel carbon dioxide supply paths 1 are connected by pipes 21 as appropriate, and a curing gas containing carbon dioxide whose concentration, relative humidity, and temperature have been adjusted by a curing gas circulation device 2 is supplied.

[0022] The curing gas circulation device 2 is a device capable of adjusting the carbon dioxide (CO2) concentration in the curing gas and supplies the curing gas to the carbon dioxide supply path 1 via piping 21. Here, piping 21 only needs to be a path for transporting the curing gas, and can be either a hose or a pipe.

[0023] The curing gas circulation device 2 supplies curing gas to the supply side piping 21, and also recovers the curing gas that has flowed through multiple carbon dioxide supply paths 1 and been discharged from the exhaust side piping 21, and discharges the reconditioned curing gas as needed.

[0024] The curing gas circulation device 2 is equipped with a mechanism for adjusting the concentration and temperature / humidity, as well as a mechanism for adjusting the pressure to increase or decrease it. Valves 22 are provided in the supply and exhaust piping 21 of the curing gas circulation device 2 to adjust the pressure of the curing gas in the carbon dioxide supply path 1 or to stop circulation and allow it to accumulate.

[0025] Figure 3 is an unfolded diagram illustrating the arrangement of carbon dioxide supply pathways 1. Specifically, it shows an example of multiple parallel carbon dioxide supply pathways 1 arranged by unfolding the back surface of the lining concrete F into a planar shape. Figure 4 is a cross-sectional view taken at position AA shown in Figure 3.

[0026] The carbon dioxide supply path 1 is formed such that the length of the tunnel in the extension direction TX is, for example, about 10m. The length of this carbon dioxide supply path 1 can be determined in accordance with the section length (length of the centering formwork) when carbonated concrete is poured in place at once during tunnel construction.

[0027] On the other hand, the width of the circumferential TY of the tunnel for carbon dioxide supply path 1 is formed to be approximately 100 mm to 300 mm. Furthermore, the height of carbon dioxide supply path 1 (the amount of projection toward the center of the tunnel) is formed to be approximately 5 mm to 50 mm in height relative to a typical lining concrete F of, for example, a thickness of approximately 300 mm to 500 mm, as shown in Figure 4.

[0028] The carbon dioxide supply path 1 can be attached to the waterproof sheet F1, for example, by bonding the waterproof sheet F1 and the carbon dioxide supply path 1 together with double-sided tape. Furthermore, the carbon dioxide supply path 1 can also be clipped to a fin-shaped welded section formed by heat-welding the side edges of waterproof sheets F1 adjacent to each other in the tunnel extension direction TX.

[0029] In the example configuration shown in Figure 3, the curing gas (CO2) supplied from pipe 21 to one end of the carbon dioxide supply path 1 on the far right flows through the carbon dioxide supply path 1 along the extension direction TX and reaches the other end.

[0030] Then, the curing gas is supplied to the adjacent carbon dioxide supply path 1 through piping 21 connected to the end of the adjacent carbon dioxide supply path 1. Repeating this process, the curing gas (CO2) discharged from the left end of the carbon dioxide supply path 1 is recovered by the curing gas circulation device 2, as shown in Figure 2, and after its concentration, relative humidity, and temperature are adjusted, it is supplied again to the right end of the carbon dioxide supply path 1.

[0031] Figure 5 is an explanatory diagram illustrating the piping 21 of a curing gas circulation system 2 that utilizes the joints F2 of the tunnel lining concrete F. The tunnel lining concrete F is constructed in units of a predetermined length (section length) using centering formwork. Therefore, joints F2 are created between adjacent tunnel lining concrete F, F in the tunnel extension direction TX. These joints F2 can be used to construct piping 21 that supplies curing gas (CO2) to the carbon dioxide supply path 1.

[0032] Figure 6 is a diagram illustrating the details of the carbon dioxide supply route 1, where Figure 6(a) is a longitudinal section of the tunnel cut along the extension direction TX, and Figure 6(b) is a transverse section of the tunnel cut along the circumferential direction TY.

[0033] The carbon dioxide supply path 1 illustrated in Figure 6 is formed in a long, strip-like shape by a drain material 12 located in the center and a nonwoven fabric section 11 that surrounds the drain material 12.

[0034] The nonwoven fabric portion 11 is formed from a nonwoven fabric of organic synthetic fibers and is required to have the property of preventing cement paste from entering the drain material 12 before the cast-in-place concrete hardens. Furthermore, after the cast-in-place concrete hardens, it is required to have the property of allowing the curing gas carbon dioxide (CO2) to pass through easily.

[0035] Figure 7 is an explanatory diagram showing the results of experimental verification of the performance of materials usable in the nonwoven fabric section 11 of the carbon dioxide supply path 1. Materials A and D used in the experiment are both nonwoven fabrics made from polyester (PET) fibers. Although PET fiber material was used in this experiment, other materials can also be used.

[0036] Material AD is based on the weight (g / m²). 2 The materials differ in thickness (mm). Material A, which has the greatest thickness and weight, has a high ability to prevent cement paste from penetrating, but its ability to allow carbon dioxide (CO2) to pass through was not sufficiently high.

[0037] In contrast, material B, despite being only 0.3 mm thick, was able to ensure the function of preventing cement paste from penetrating, and sufficient performance in terms of carbon dioxide (CO2) permeability was also confirmed.

[0038] On the other hand, the performance required of the drain material 12 is to function as a space-holding material that can maintain a space sufficient to allow curing gas to pass through under the lateral pressure and pressurized filling pressure acting during concrete placement. The treatment of the drain material 12 after curing is complete will be described later.

[0039] Figure 8 is an explanatory diagram showing the results of an experiment that confirmed the performance of materials usable as drain material 12 in the carbon dioxide supply path 1. The thickness shown in these experimental results represents the thickness when a 0.3 mm thick nonwoven fabric is layered on top of and below each material.

[0040] Materials a and b used in this experiment are nonwoven fabrics made from high-density polyethylene (HDPE). Both materials a and b showed minimal thickness reduction under pressure, confirming that they have sufficient space retention performance after pressurization.

[0041] On the other hand, material c is a molded plastic sheet with a textured surface. Material d is a molded polypropylene sheet with a textured surface. Even with materials whose rigidity is enhanced by these shapes, sufficient space retention performance can be ensured.

[0042] Next, the carbonation curing method of this embodiment will be explained with reference to the flowchart shown in Figure 9. The following explanation will use the excavation work of a mountain tunnel using the NATM method as an example.

[0043] When constructing a tunnel using the NATM method, excavation is carried out by spraying rapid-setting shotcrete onto soft ground or ground with well-developed cracks from behind excavation equipment such as breakers and backhoes, and heavy machinery such as wheel loaders (Step S1).

[0044] Furthermore, steel supports are installed at intervals in the extension direction TX along the semi-cylindrical excavation surface of the tunnel, and the ground is further supported by spraying with shotcrete. Then, a waterproof sheet F1 is placed along the shotcrete (step S2).

[0045] After positioning the waterproof sheet F1 along the sprayed concrete, the carbon dioxide supply path 1 is attached to the inner surface of the waterproof sheet F1 with double-sided tape. Additionally, the carbon dioxide supply path 1 is clipped to the welded joints between the side edges of waterproof sheets F1 adjacent to each other in the tunnel extension direction TX.

[0046] Alternatively, multiple carbon dioxide supply paths 1 can be pre-attached in parallel to one side of the inner perimeter of the waterproof sheet F1, and then placed together with the waterproof sheet F1.

[0047] On the tunnel interior side of the waterproof sheet F1, a movable centering formwork is placed, and the lining concrete F is constructed by pouring cast-in-place concrete (carbonated concrete) (Step S3). The lining concrete F is constructed in a semi-cylindrical shape with a thickness of, for example, 30 cm to 50 cm.

[0048] While the centering formwork can generally be removed the following day, the carbonation curing with curing gas from step S4 onward can be carried out without being affected by the timing of the centering formwork's movement.

[0049] In order to carbonate-cur the lining concrete F, in step S4, the curing gas circulation device 2 is set up as shown in Figure 2, and piping 21 is installed to connect it to the carbon dioxide supply path 1. Then, by operating the curing gas circulation device 2, curing gas containing a high concentration of carbon dioxide is sent to the carbon dioxide supply path 1 (step S5).

[0050] The curing gas circulation device 2 adjusts the carbon dioxide concentration (CO2 concentration), relative humidity, temperature, and pressure of the curing gas and supplies it to the supply side piping 21. It also readjusts the concentration of the curing gas discharged from the exhaust side piping 21 and circulates it. Additionally, the valve 22 is operated as needed to adjust the internal pressure and circulation state within the carbon dioxide supply path 1.

[0051] In short, the curing gas supplied to the carbon dioxide supply path 1 not only decreases in concentration as carbon dioxide is absorbed by the lining concrete F, but its relative humidity also increases due to moisture released from the concrete surface through carbonation. The carbonation reaction of concrete proceeds more rapidly at higher carbon dioxide concentrations, but the reaction rate decreases significantly when the relative humidity exceeds 80%RH. For this reason, the concentration and relative humidity of the curing gas recovered by the curing gas circulation device 2 are readjusted, but it is preferable to supply curing gas with a low relative humidity in anticipation of the increase in relative humidity within the carbon dioxide supply path 1.

[0052] For example, the curing gas supplied from the curing gas circulation device 2 is adjusted to a constant temperature of 5°C to 50°C, a relative humidity of 80% RH or less, and a carbon dioxide concentration of 5% to 80%. By bringing these values ​​closer to the optimal values, the carbonation reaction can be accelerated. For example, the temperature of the curing gas is adjusted to around 50°C or lower, and the relative humidity is adjusted to 40% RH to 50% RH. In addition, the carbon dioxide concentration of the curing gas is adjusted to 60% to 80%.

[0053] Although not shown in the diagram, environmental measurement sensors are installed at multiple locations in the supply air piping 21, exhaust air piping 21, and carbon dioxide supply path 1, and carbonation curing is performed while monitoring the concentration of carbon dioxide in the curing gas, temperature, relative humidity, etc. at each location (step S6).

[0054] By monitoring the curing gas concentration at various points in the carbon dioxide supply path 1, it is possible to confirm whether carbonation curing is being carried out in an environment where curing gas of the desired concentration is supplied. Furthermore, by setting the carbon dioxide concentration in the curing gas supplied through the supply side piping 21 to a constant value (e.g., 80%) and the temperature to a constant value (e.g., around 50°C), and continuously measuring the carbon dioxide concentration and flow rate in the curing gas through the exhaust side piping 21 during the carbonation curing period, the amount of carbon dioxide fixed to the lining concrete F by carbonation curing (CO2 fixation amount) can be calculated and recorded as an actual measured value.

[0055] On the other hand, maintaining a constant carbon dioxide concentration in the curing gas supplied from the curing gas circulation device 2 requires advanced technology and significant expense. Therefore, if the carbon dioxide concentration in the curing gas supplied on the supply side cannot be kept approximately constant, the flow rate, temperature, and carbon dioxide concentration of the curing gas supplied from the curing gas circulation device 2 are continuously measured on both the exhaust and supply sides. This allows for the calculation of the amount of carbon dioxide in the curing gas supplied from the curing gas circulation device 2 to the carbon dioxide supply path 1 and the amount of carbon dioxide in the curing gas discharged from the carbon dioxide supply path 1. The difference between the amount of carbon dioxide in the curing gas supplied to the carbon dioxide supply path 1 and the amount of carbon dioxide in the curing gas discharged from the carbon dioxide supply path 1 is calculated as the amount of carbon dioxide fixed in the lining concrete F by carbonation curing (CO2 fixation amount), and this can be recorded as a measured value.

[0056] The carbonation curing process is completed by continuing to supply the curing gas for a predetermined time. After the carbonation curing is complete, the curing gas circulation device 2 is moved to the next curing section (step S7). Note that carbonation curing can be continued for an extended period; in this case, a different curing gas circulation device 2 will be set up in the next construction section.

[0057] Furthermore, after the carbonation curing is complete, the carbon dioxide supply path 1 is filled with a hardening agent such as cement grout to achieve a density similar to that of the lining concrete F. In other words, after the curing is complete, measures are taken to ensure that the required performance of the lining concrete F, such as material and structural properties, is satisfied by filling the drain material 12, which has been functioning as a space-holding material, with grout.

[0058] Next, the operation of the carbonation curing method of this embodiment will be explained. In this carbonation curing method, elongated carbon dioxide supply paths 1 are placed at intervals along the circumferential direction TY of the tunnel relative to the inner surface of the waterproof sheet F1, and cast-in-place concrete is poured to cover the carbon dioxide supply paths 1 to form the lining concrete F.

[0059] Then, a curing gas containing carbon dioxide is supplied to the carbon dioxide supply path 1. This allows for carbonation curing of the lining concrete F on the back side where it is in contact with the waterproof sheet F1.

[0060] In other words, carbon dioxide is not naturally supplied to the back side of the lining concrete F even while the tunnel is in use, so carbonation does not progress there. However, by providing a carbon dioxide supply path 1 and performing carbonation curing from the back side of the lining, the amount of CO2 fixed increases, which can lead to the widespread use of environmentally friendly concrete.

[0061] Furthermore, when carbonation curing is performed from the interior side of the lining concrete F, equipment to seal the carbon dioxide gas is necessary to ensure safety. In contrast, if carbonation curing is performed from the rear side of the lining concrete F, the concrete around the carbon dioxide supply path 1 and the waterproof sheet F1 are in close contact and sealed. As long as the outflow treatment around the supply and exhaust sides is properly carried out, the possibility of carbon dioxide gas leakage becomes extremely low, and safe carbonation curing can be performed with relatively minimal equipment. [Examples]

[0062] In this embodiment 1, a carbon dioxide supply path 1A, which has a different configuration from the carbon dioxide supply path 1 described in the above embodiment, will be described with reference to Figures 10-13. Note that parts that are the same or equivalent to those described in the above embodiment will be described using the same terms or reference numerals.

[0063] In the carbon dioxide supply path 1A described in Example 1, a moisture-permeable and waterproof resin film layer is placed adjacent to the nonwoven fabric. The moisture-permeable and waterproof resin film layer is formed from a porous film such as a polyethylene resin film.

[0064] A porous film is a perforated resin sheet, and its numerous holes are large enough to prevent moisture from passing through, thus ensuring waterproofing. On the other hand, the numerous holes can allow gases such as moisture to pass through, and can also allow curing gases (CO2) to pass through.

[0065] In this embodiment 1, the carbon dioxide supply path 1A is formed in a long, strip-like shape by a drain material 12 located in the center, a nonwoven fabric portion 11A surrounding the drain material 12, and a porous film portion 111 which is a resin film layer covering the surface of the nonwoven fabric portion 11A.

[0066] Here, the porous film portion 111 may be positioned at the boundary between the nonwoven fabric portion 11A and the lining concrete F, or at the boundary between the nonwoven fabric portion 11A and the drain material 12. In other words, it is sufficient that it covers either the front or back side of the nonwoven fabric portion 11A.

[0067] In this embodiment 1, we will explain using a breathable and waterproof sheet having moisture permeability and waterproofing properties, in which a nonwoven fabric portion 11A and a porous film portion 111 are laminated. A breathable waterproof sheet refers to a sheet that meets the quality specified in the Japanese Industrial Standard "JIS A 6111:2016 Breathable Waterproof Sheet".

[0068] The quality of the breathable waterproof sheet used in the carbon dioxide supply path 1A of this embodiment 1 is preferably one that meets the performance requirements of "Breathable Waterproof Sheet B for Exterior Walls" as specified in "JIS A 6111:2016". The breathability (water permeability resistance) of "Breathable Waterproof Sheet B for Exterior Walls" is 0.13 (m 2 The pressure is less than or equal to s·Pa / μg. Furthermore, the waterproofing performance ensures that moisture can be blocked even under water pressure of 10 kPa or more.

[0069] An example of a product that meets these quality standards is "Super Airtex KD30" (Fukubi Chemical Industry Co., Ltd.). "Super Airtex KD30" is a two-layer breathable waterproof sheet consisting of a polyethylene resin film with numerous perforations and a polyester nonwoven fabric.

[0070] Figure 11 illustrates the results of an experiment conducted to compare the carbonation depth under different configurations of the carbon dioxide supply pathway. In this figure, "No Sheet" shows the carbonation depth (mm) when a rectangular prism made of carbonated concrete measuring 8 × 8 × 16 cm was subjected to a 3-day carbonation curing period with a curing gas supply from the bottom at a temperature of 50°C, a relative humidity of 40% RH, and a CO2 concentration of approximately 90%.

[0071] On the other hand, the "nonwoven fabric" case shows the carbonation depth (mm) when carbonation curing was performed under the same conditions as the "no sheet" case, with only the PET fiber nonwoven fabric shown as material C in Figure 7 attached to the bottom surface of the test specimen.

[0072] The "breathable waterproof sheet" case shows the carbonation depth (mm) when a breathable waterproof sheet that meets the performance requirements of "Breathable Waterproof Sheet B for Exterior Walls" as defined in "JIS A 6111:2016" is attached to the bottom surface of the test specimen and subjected to carbonation curing under the same conditions as the "no sheet" and "nonwoven fabric" cases.

[0073] The carbonation depth achieved through carbonation curing is naturally greatest in the "sheet-free" case, where there are no obstacles to contact with carbon dioxide. This was the expected result, and the experiment was conducted to establish a baseline for comparison.

[0074] On the other hand, in the case where a nonwoven fabric was attached to the bottom surface of the test specimen and carbonation curing was performed, although the carbonation depth was shallower than in the case without the sheet, it was clear that carbonation was progressing. The experimental results shown in Figure 11 are the results of 3 days of carbonation curing, and it is possible to increase the carbonation depth by extending the curing period.

[0075] Furthermore, in the case where a "breathable waterproof sheet" was attached to the bottom surface of the test specimen and carbonation curing was performed, the carbonation depth was shallower than in the case without the sheet, but it was significantly deeper than in the case with nonwoven fabric, indicating that the influence of interposing the sheet on the curing surface was minimized.

[0076] Therefore, we will examine the differences between the case of "nonwoven fabric" and the case of "breathable waterproof sheet." Figure 12 is an explanatory diagram illustrating the relationship between the drainage of excess water from concrete and the carbonation depth.

[0077] If a nonwoven fabric acting as a drain material is placed on the surface of carbonated concrete, as shown in Figure 12, excess water (bleeding water) generated when the concrete hardens will be drained away by the nonwoven fabric.

[0078] When excess water is drained, the apparent water-cement ratio decreases, as shown on the right side of Figure 12, and the strength of the densified concrete is increased. Figure 13 shows the relationship between the water-cement ratio of the concrete and the carbonation depth.

[0079] Figure 13 shows the results of the carbonation depth (mm) after 3 days of carbonation curing for three types of carbonated concrete with different water-cement ratios (W / P). As can be seen in Figure 13, the "W / P40" with the lowest water-cement ratio had the shallowest carbonation depth, while the "W / P50" with the highest water-cement ratio had the deepest carbonation depth. In other words, it is thought that the lower the water-cement ratio and the denser the concrete, the more difficult it is for carbon dioxide to penetrate into the interior of the concrete, resulting in a shallower carbonation depth.

[0080] These experimental results suggest that when a breathable waterproof sheet is placed in contact with the surface of carbonated concrete, the drainage of excess water is prevented by the waterproofing properties of the sheet, thus reducing the likelihood of concrete densification and preventing it from becoming an inhibitory factor in carbonation.

[0081] Furthermore, the breathability of the moisture-permeable waterproof sheet allows curing gas to pass through, enabling carbon dioxide (CO2) in the curing gas supplied by the carbon dioxide supply path 1A to reach the lining concrete F through the moisture-permeable waterproof sheet.

[0082] In the carbon dioxide supply path 1A of Example 1 configured in this way, a porous film portion 111, which is a resin film layer having moisture permeability and water permeability, is arranged adjacent to the nonwoven fabric portion 11A.

[0083] The porous film portion 111 may be a separate sheet from the nonwoven fabric portion 11A, covering either the surface or back surface of the nonwoven fabric portion 11A, or it may be manufactured as a breathable waterproof sheet in which the porous film portion 111 and the nonwoven fabric portion 11A are laminated.

[0084] In either case, if a waterproof porous film portion 111 is placed adjacent to the nonwoven fabric portion 11A, it is possible to prevent the drainage of excess water from the adjacent carbonated concrete (lining concrete F) and suppress densification that makes it difficult to carbonate.

[0085] Furthermore, if the porous film portion 111 has moisture permeability, it can allow curing gas containing carbon dioxide (CO2) to pass through, so that carbonation can be efficiently promoted in the lining concrete F, which has suppressed densification, through carbonation curing.

[0086] Furthermore, the other configurations and effects are substantially the same as those of the above-described embodiment, so their explanation will be omitted.

[0087] While embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and examples, and any design modifications that do not depart from the spirit of the present invention are included in the present invention.

[0088] For example, the above embodiment was described using the case of using carbonated concrete described in Patent Document 1 as an example, but the present invention is not limited to this, and can be applied to any concrete that is cast in place in which carbonation curing is effective.

[0089] Furthermore, although the above embodiments and Example 1 described carbon dioxide supply paths 1 and 1A equipped with drain material 12, the invention is not limited thereto. For example, a carbon dioxide supply path can also be created by simply forming a nonwoven fabric or a breathable waterproof sheet into a thick strip.

[0090] Furthermore, while the first embodiment described the use of a two-layer breathable waterproof sheet, the invention is not limited to this. For example, a breathable waterproof sheet can be used that is made of a single-layer material of high-density polyethylene fiber nonwoven fabric, and whose breathability and waterproofing properties are ensured by adjusting the weight of the nonwoven fabric and pressing it.

[0091] Even with these breathable waterproof sheets, the breathability (water permeability resistance) of "Exterior Wall Breathable Waterproof Sheet A" as defined in "JIS A 6111:2016" is 0.19 (m 2 There are products that meet the performance requirements of (s·Pa / μg) or less. For example, "Tyvek" (manufactured by DuPont) falls into this category. [Explanation of symbols]

[0092] 1,1A: Carbon dioxide supply pathway 11,11A: Non-woven fabric part 111: Porous film portion (resin film layer) 12: Drain material F: Lining concrete F1: Waterproof sheet TX: Direction of tunnel extension TY: Circumferential direction of the tunnel

Claims

1. A method for carbonation curing of lining concrete that is poured on the inner side of a waterproof sheet as part of the tunnel lining, The process involves arranging, at intervals in the circumferential direction of the tunnel, elongated carbon dioxide supply paths extending in the direction of extension of the tunnel, on the inner surface of the waterproof sheet, The process of forming the lining concrete by pouring cast-in-place concrete to cover the waterproof sheet and the carbon dioxide supply path, A carbonation curing method characterized by comprising the step of supplying a curing gas containing carbon dioxide to the carbon dioxide supply path.

2. The carbonation curing method according to claim 1, characterized in that the carbon dioxide supply path is formed in a strip shape by a nonwoven fabric.

3. The carbonation curing method according to claim 2, characterized in that the nonwoven fabric is provided so as to surround the drain material located in the center.

4. The carbonation curing method according to claim 2 or 3, characterized in that the nonwoven fabric is formed of polyester fibers.

5. The carbonation curing method according to claim 1 or 2, characterized in that the curing gas is supplied from one end of the carbon dioxide supply path in a state in which the relative humidity, temperature, and carbon dioxide concentration are adjusted.

6. The carbon dioxide supply path is formed such that its circumferential width is 100 mm to 300 mm and its height is 5 mm to 50 mm, as described in claim 1 or 2.

7. The carbonation curing method according to claim 2 or 3, characterized in that a resin film layer having moisture permeability and waterproofing properties is arranged adjacent to the nonwoven fabric.

8. The carbon dioxide supply path is formed in a strip shape by a breathable waterproof sheet having breathability and waterproofing properties, as described in claim 1.

9. The carbonation curing method according to claim 8, characterized in that the breathable waterproof sheet is provided so as to surround a drain material located in the center.

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