Curing method for poured concrete in tunnels and curing system used therefor

Abstract

To provide a method for curing concrete poured in a tunnel, which can surely maintain the wet state of the concrete surface and can solve the problems of the reduction in compressive strength of the concrete after curing and the occurrence of cracks, and a curing system used therefor. [Solution] A perforated conduit 4 is laid along a water-retaining curing sheet 3 that is in contact with the surface of the poured concrete 2 in the tunnel, and a pressing means 5 is arranged on the back side of the water-retaining curing sheet 3, filling it with gas inside to bring the surface of the water-retaining curing sheet 3 into contact with the surface of the poured concrete 2. The perforated conduit 4 is laid in the longitudinal direction of the tunnel and on the surface side of the water-retaining curing sheet 3, with the liquid ejection holes of the perforated conduit 4 facing the surface of the poured concrete 2.

Description

[Technical Field]

[0001] The present invention relates to a method for curing concrete poured for tunnels and a curing system used therefor. [Background technology]

[0002] For example, when constructing a tunnel (lining concrete) by pouring concrete, water evaporates from the surface of the concrete during curing, resulting in the loss of moisture needed for the hydration reaction, which can lead to a decrease in the compressive strength of the cured concrete or the occurrence of cracks.

[0003] To prevent this, it has been proposed to lay a water-retaining curing sheet made of nonwoven fabric or synthetic resin on the surface of the concrete while it is curing, thereby reducing the amount of water that evaporates from the surface of the concrete while it is curing (see, for example, Patent Documents 1 to 3), or to lay a perforated conduit along the water-retaining curing sheet that is in contact with the surface of the poured concrete in a tunnel, and to provide a pressing means on the back side of the water-retaining curing sheet that presses the surface of the water-retaining curing sheet against the surface of the poured concrete by filling the inside with gas (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-61184 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-245526 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-14734 [Patent Document 4] Japanese Patent Application Publication No. 10-102773 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology proposed in Patent Document 4 involves using a water-retaining curing device to lay and contact a water-retaining curing sheet on the surface of the concrete being cured, and supplying water to the water-retaining curing sheet through a perforated conduit, thereby moistening the water-retaining curing sheet and maintaining the wet state of the concrete surface without the need for frequent watering.

[0006] The present invention aims to provide a method for curing concrete poured into tunnels and a curing system for use therein, which allows the concrete surface to be reliably kept moist while enjoying the advantages of the water-retaining curing sheets and water-retaining curing devices used in the conventional curing of poured concrete in tunnels, thereby eliminating the problems of reduced compressive strength and cracking of the concrete after curing. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides a method for curing poured concrete in tunnels, which comprises laying a perforated conduit alongside a water-retaining curing sheet that is to be abutted against the surface of the poured concrete in the tunnel, and arranging a pressing means on the back side of the water-retaining curing sheet by filling the interior with gas so that the surface of the water-retaining curing sheet abuts against the surface of the poured concrete. In this method, water or water containing silicate is supplied from the perforated conduit to bring the water-retaining curing sheet into a moist state containing water or water containing silicate, and then the interior of the pressing means is filled with gas so that the surface of the water-retaining curing sheet abuts against the surface of the poured concrete.

[0008] In this case, before supplying water or water containing silicate from the perforated conduit, the inside of the pressing means on the side of the tunnel is filled with gas so that the surface of the water-retaining curing sheet abuts against the surface of the poured concrete on that side of the tunnel, and then water is supplied from the perforated conduit to make the water-retaining curing sheet moist and wet, and then the inside of the pressing means above the side of the tunnel is filled with gas so that the surface of the water-retaining curing sheet abuts against the surface of the poured concrete.

[0009] Furthermore, in order to achieve the above-mentioned object, the curing system used in the method for curing poured concrete in a tunnel of the present invention comprises laying a perforated conduit along a water-retaining curing sheet that is in contact with the surface of the poured concrete in the tunnel, and arranging a pressing means on the back side of the water-retaining curing sheet to press the surface of the water-retaining curing sheet against the surface of the poured concrete by filling the inside with gas, and is characterized in that the perforated conduit is laid in the longitudinal direction of the tunnel and on the surface side of the water-retaining curing sheet.

[0010] In this case, the perforated conduit can be laid so that the liquid ejection holes face the surface of the poured concrete.

[0011] Furthermore, by supplying water or water containing silicate through the perforated conduit, the water-retaining curing sheet can be brought into a moist state containing water or water containing silicate.

[0012] Furthermore, by supplying a liquid containing at least one of a concrete surface curing agent, a concrete shrinkage reducing agent, and a concrete surface impregnating agent from the perforated conduit, the water-retaining curing sheet can be made wet by containing the liquid.

[0013] Furthermore, by arranging multiple curing carts equipped with the water-retaining curing sheets, perforated conduits, and pressing means in a line, and supplying water or water containing silicate from the perforated conduit of the curing cart at the front in the direction of movement, the water-retaining curing sheets can be made moist by containing water or water containing silicate, and by supplying a liquid containing at least one of a concrete surface curing agent, a concrete shrinkage reducing agent, and a concrete surface impregnating agent from the perforated conduit of the curing cart at the rear in the direction of movement, the water-retaining curing sheets can be made moist by containing the liquid.

[0014] Furthermore, by using a sheet material containing silicate as the water-retaining curing sheet, the water-retaining curing sheet can be brought into a moist state containing water containing silicate.

[0015] The water-retaining curing sheet may be made of a strip-shaped sheet material sewn together so that the sewing direction is the longitudinal direction of the tunnel.

[0016] The water-retaining curing sheet may be made up of, from the surface side, at least a sheeting, a nonwoven fabric, and a waterproof layer.

[0017] The perforated conduit may be laid along the surface of the sheeting of the water-retaining curing sheet or between the sheeting and the nonwoven fabric. [Effects of the Invention]

[0018] The method for curing poured concrete for tunnels and the curing system used therein of the present invention make it possible to reliably maintain the concrete surface in a moist state, thereby eliminating the problems of reduced compressive strength and cracking of the concrete after curing. [Brief explanation of the drawings]

[0019] [Figure 1]FIG. 1 is an explanatory diagram showing an example in which the tunnel poured concrete curing system of the present invention is applied to the curing of poured concrete (lining concrete) in a tunnel constructed using a center (arch lining formwork). [Figure 2] This is a cross-sectional view showing a curing cart used in the curing system for poured concrete in the same tunnel. [Figure 3] FIG. [Figure 4] This is a side cross-sectional view showing a curing cart used in the curing system for poured concrete in the same tunnel. DETAILED DESCRIPTION OF THE INVENTION

[0020] Below, an embodiment of the method for curing poured concrete for tunnels and the curing system used therein of the present invention will be explained using an example of curing poured concrete (lining concrete) for a tunnel constructed using a center (arch lining formwork).

[0021] As shown in Figures 1 to 4, the tunnel concrete curing system of the present invention involves laying a perforated conduit 4 along a water-retaining curing sheet 3 that is in contact with the surface of poured concrete 2 in a tunnel constructed using a center 1, and disposing a pressing means 5 on a curing cart 6 that fills the back side of the water-retaining curing sheet 3 with gas to bring the surface of the water-retaining curing sheet 3 into contact with the surface of the poured concrete 2.

[0022] The curing cart 6 is equipped with support structures that are independently formed to unit lengths L6 (10.5 m in this embodiment) whose longitudinal length is the same as the length L1 of the center 1 (10.5 m in this embodiment), and multiple curing carts 6 (three in this embodiment) are arranged in a row so that they can move on rails 7 together with the center 1. This allows the poured concrete 2 constructed using the center 1 and then removed from the form to be cured in sequence using multiple curing carts 6.

[0023] The curing cart 6 has support frames 61, 62 attached to the support structure, and multiple air tubes (balloons) as pressing means 5 are curved into an approximately horseshoe shape and arranged side by side, with the water-retaining curing sheet 3 placed on the outside so that the back side of the water-retaining curing sheet 3 is supported by the pressing means 5.

[0024] The perforated conduit 4 is laid in the longitudinal direction of the tunnel, on the surface side of the water-retaining curing sheet 3, and with the liquid ejection holes of the perforated conduit 4 facing the surface of the poured concrete 2. As a result, as will be described later, when a liquid such as water is supplied from the perforated conduit 4 before the surface of the water-retaining curing sheet 3 is brought into contact with the surface of the poured concrete 2, the liquid can be impregnated into the water-retaining curing sheet 3 without flowing off, and the water-retaining curing sheet 3 can be brought into a moist state in which it is uniformly saturated with the liquid. The number of perforated conduits 4 is determined according to the size of the curing cart 6, and is laid around the top of the curing cart 6, taking into consideration the gravity of the liquid ejected from the liquid ejection holes of the perforated conduits 4 flowing down. Specifically, in this embodiment, a total of five perforated conduits 4 are laid on the center line, within a range of ±5 to 10° from the center line, and within a range of ±25 to 30° from the center line, and further, if necessary, a total of seven perforated conduits 4 are laid within a range of ±50 to 60° from the center line. This allows the entire surface of the water-retaining curing sheet 3 in contact with the surface of the poured concrete 2 to be uniformly moistened by the liquid supplied from the liquid outlet holes of the perforated conduit 4, specifically water or water containing silicate.

[0025] The water-retaining curing sheet 3 is made of a strip-shaped sheet material (e.g., width: 1.1 m) sewn (longitudinal stitching) so that the sewing direction is the longitudinal direction of the tunnel (e.g., width: 20 m, length: length of the curing cart 6). This allows the liquid sprayed out from the liquid spray holes of the perforated conduit 4 to be dispersed horizontally along the sewn seams of the water-retaining curing sheet 3, thereby making it possible to uniformly moisten the entire surface of the water-retaining curing sheet 3 that is in contact with the surface of the poured concrete 2.

[0026] The water-retaining curing sheet 3 is made up of, from the surface side, sheeting (a woven fabric made of coarsely thick yarns, which has better breathability than plain woven fabric), nonwoven fabric, and a waterproof layer (laminate layer and reinforcing fabric). It is also possible to use a material that has a certain strength as a single layer for the waterproof layer. This prevents the nonwoven fabric from being worn away by the sheeting, making the water-retaining curing sheet 3 durable, and combined with the provision of a reinforcing fabric in the waterproof layer, the water-retaining curing sheet 3 can be repeatedly laid and placed against the surface of poured concrete 2 using mechanical equipment.

[0027] When sheeting is used as the material that forms the surface of the water-retaining curing sheet 3, the perforated conduit 4 can be laid along the surface of the sheeting of the water-retaining curing sheet 3, or between the sheeting and the nonwoven fabric.

[0028] As proposed by the present applicants in Patent Document 3, a curing sheet is formed by laminating a water-impermeable film portion onto the surface of a water-retaining portion made of nonwoven fabric, and is impregnated with water containing silicate as a modifier to densely modify the surface of poured concrete. The water-retaining portion of the curing sheet impregnated with the silicate-containing water is then attached to the surface of poured concrete to cure the concrete. When the curing sheet dries, the silicate creates a bond between the curing sheet and the concrete, preventing the curing sheet from accidentally peeling off from the surface of the curing concrete. By maintaining the curing sheet in close contact with the surface of the curing concrete for a long period of time, the curing sheet prevents and reduces the amount of water that would otherwise evaporate and dissipate from the surface of the curing concrete, allowing the surface of the curing concrete to remain moist for a long period of time. This, combined with the absence of residue on the surface of the concrete that would affect the concrete structure, allows for the construction of a high-quality concrete structure.

[0029] Therefore, in the tunnel concrete pouring system of the present invention, a water-retaining curing sheet 3, specifically a sheet material in which silicate is contained in the nonwoven fabric of the water-retaining curing sheet 3, is used, and by supplying water as a liquid from a perforated conduit 4, the water-retaining curing sheet 3 is made to be in a moist state containing water containing silicate, thereby achieving the same effect as the technology proposed in Patent Document 3.

[0030] Furthermore, by supplying water containing silicate from the perforated conduit 4, the water-retaining curing sheet 3 can be made moist with water containing silicate, even if a sheet material that does not contain silicate is not used for the nonwoven fabric of the water-retaining curing sheet 3, and the same effect as the technology proposed in Patent Document 3 can be achieved. Even when water containing silicate is supplied from the perforated conduit 4, a sheet material in which silicate is contained in the nonwoven fabric of the water-retaining curing sheet 3 can be used.

[0031] The liquid supplied from the perforated conduit 4 contains water containing silicate as well as at least one of a concrete surface curing agent, a concrete shrinkage reducing agent, and a concrete surface impregnating agent, thereby making the water-retaining curing sheet wet with the liquid. Here, the concrete surface curing agent, concrete shrinkage reducing agent, and concrete surface impregnating agent will be explained. 1.Concrete surface curing agent It penetrates the surface of the concrete and prevents water from evaporating (drying) from the surface of the concrete. Specifically, it is as follows: Polyalkylene glycol (Knox's "Conclic Ace" (registered trademark)) Special surfactant (Knox's "Kirekku Eco" (product name)) Water-dispersible polyester (Kao Corporation's "New Track SK" (product name)) 2.Concrete shrinkage reducing agent These are used to suppress the drying shrinkage of concrete, and specifically, they are as follows. Alkylene oxide adduct of lower alcohol ("Crack Saver" (trade name) manufactured by Pacific Materials Corporation) 3.Concrete surface impregnation agent It prevents the penetration of chloride ions and other substances that are harmful to concrete, and specifically, it is as follows. Silane / siloxane-based (Daido Paint Co., Ltd.'s "Aquaseal" (registered trademark)) This improves the density of the concrete after curing and reduces cracks, allowing for the construction of high-quality concrete structures.

[0032] When multiple curing carts 6 are arranged in a line, water or water containing silicate can be supplied from the perforated conduit 4 of the first curing cart 6 at the front of the cart in the direction of movement, for example, to bring the water-retaining curing sheet 3 into a moist state containing water or water containing silicate, and liquid containing at least one of a concrete surface curing agent, a concrete shrinkage reducing agent, and a concrete surface impregnating agent can be supplied from the perforated conduits 4 of the second and third curing carts 6 at the rear of the cart in the direction of movement, for example, to bring the water-retaining curing sheet 3 into a moist state containing the liquid, thereby allowing the effects of each agent to be enjoyed.

[0033] When curing poured concrete in a tunnel using this tunnel pouring concrete curing system, the inside of the pressing means 5 is filled with gas so that the surface of the water-retaining curing sheet 3 abuts against the surface of the poured concrete 2, and then a liquid (water, water containing silicate, a liquid containing at least one of a concrete surface curing agent or a concrete shrinkage-reducing agent and a concrete surface impregnating agent) is supplied from the perforated conduit 4 to bring the water-retaining curing sheet 3 into a wet state containing the liquid.In this case, the water-retaining curing sheet 3 is brought into a wet state containing the liquid by supplying a liquid (water, water containing silicate, a liquid containing at least one of a concrete surface curing agent or a concrete shrinkage-reducing agent and a concrete surface impregnating agent) from the perforated conduit 4, and then a gas is filled inside the pressing means 5 so that the surface of the water-retaining curing sheet 3 abuts against the surface of the poured concrete 2. As a result, after the water-retaining curing sheet 3 is moistened, tension is applied to the water-retaining curing sheet 3 by filling the inside of the pressing means 5 with gas, so that the surface of the water-retaining curing sheet 3 can be brought into a wrinkle-free state and brought into contact with the surface of the poured concrete 2, thereby eliminating the problem of wrinkles occurring on the surface of the water-retaining curing sheet 3 when the surface of the dry water-retaining curing sheet 3 is brought into contact with the surface of the poured concrete 2.

[0034] In addition, the pressing means 5 is divided in the circumferential direction, and the divided pressing means 5 can be selectively filled with gas. Before supplying liquid from the perforated conduit 4, the gas is filled into the pressing means 5 on the side of the tunnel, which is less likely to cause wrinkles on the surface of the water-retaining curing sheet 3, so that the surface of the water-retaining curing sheet 3 is brought into contact with the surface of the poured concrete 2 on the side of the tunnel. Thereafter, liquid (water, water containing silicate, liquid containing at least one of a concrete surface curing agent or a concrete shrinkage reducing agent and a concrete surface impregnating agent) is supplied from the perforated conduit 4, and the water-retaining curing sheet 3 is kept in a wet state containing the liquid. After the tunnel is put into this state, gas can be filled into the inside of the pressing means 5 above the side of the tunnel so that the surface of the water-retaining curing sheet 3 comes into contact with the surface of the poured concrete 2. As a result, when liquid is supplied from the perforated conduit 4, the excess curing water that drips down is received by the water-retaining curing sheet 3 at a position on the side of the tunnel and absorbed by the water-retaining curing sheet 3, preventing the dripping curing water from wetting the tunnel roadbed and turning it into mud.

[0035] Next, the results of a demonstration test on the method for curing concrete poured for tunnels and the curing system used therein according to the present invention will be shown.

[0036] [Curing water and its supply volume] As the curing water supplied from the perforated conduit 4, water (purified water) or a silicate aqueous solution (water containing silicate) prepared by dissolving silicate (potassium silicate) in water (purified water) was used. The amount of curing water supplied is 1 curing cart 6 (area of ​​water-retaining curing sheet 3: 210 m) when the water-retaining curing sheet is dry (when using for the first time or when not used for about a week after the last use). 2 ) was set at 150 liters per In addition, when the curing cart 6 is moved and set up (three times), the sheet is kept wet, so one curing cart 6 (area of ​​water-retaining curing sheet 3: 210 m) is used for each movement and setting. 2 ) was set at 100 liters per This prevents excess curing water from dripping down and wetting the tunnel roadbed, turning it into mud, and combined with the use of nonwoven fabric with high water retention properties for the water-retaining curing sheet 3, it is possible to reduce the amount of water that needs to be supplied and also to reduce the size of equipment such as water tanks.

[0037] [Basic composition of Water Retaining Curing Sheet 3] The water-retaining curing sheet 3 used was a four-layer sheet having, from the surface side, a sheeting, a nonwoven fabric, and a waterproof layer (laminate layer and reinforcing fabric) as shown in Table 1.

[0038] [Table 1]

[0039] [Curing method] Curing was carried out using the method shown in Table 2. Here, seven-day curing refers to the fact that in actual tunnel construction where a tunnel is constructed using a center tunnel, the lining concrete is often poured three times (three spans) per week, and in such cases, three curing carts 6 are used to move and install each span, resulting in a curing period of seven days.

[0040] [Table 2]

[0041] [Test Results] The results of the demonstration test are shown in Table 3. Here, the compressive strength is the compressive strength test value obtained by curing using the curing method shown in Table 2 and then leaving the material to stand at a temperature of 20°C and humidity of 60% for 28 days (the compressive strength test was conducted in accordance with JIS A 1108. The test specimens were cylindrical specimens (diameter 100 mm, height 200 mm), with three specimens per case, and the average value was used as the test result).The air permeability coefficient is the surface layer air permeability test value of the concrete using the Trent method (a test that indicates the density of the concrete (a smaller value indicates a denser concrete)).

[0042] [Table 3]

[0043] From the test results of the demonstration test shown in Table 3, it was confirmed that No. 3 and No. 4 (embodiments of the method for curing concrete poured into tunnels and the curing system used therein of the present invention), especially No. 4, which used water containing silicate as the curing water supplied from the perforated conduit 4, had good compressive strength and density of the concrete after curing compared to other curing methods. This is thought to be because, by applying the method of curing concrete poured in tunnels and the curing system used therein of the present invention to the curing of concrete, the moisture necessary for the hydration reaction was supplied at an early age, and the hydration reaction was sufficiently promoted in the same way as in underwater curing.

[0044] The above describes the method for curing concrete poured into tunnels and the curing system used therein according to the present invention, based on its embodiments. However, the present invention is not limited to the embodiments described in the above examples, and the configuration can be changed as appropriate within the scope of the spirit of the present invention. [Industrial Applicability]

[0045] The method for curing concrete poured into tunnels and the curing system used therein of the present invention have the advantages of the water-retaining curing sheets and water-retaining curing devices used in conventional curing of concrete poured into tunnels, while also making it possible to reliably maintain a moist state on the concrete surface, thereby eliminating the problems of reduced compressive strength and cracking of concrete after curing. Therefore, the method is useful in a wide range of applications, including curing concrete poured into tunnels (lining concrete) constructed using a center (arch lining formwork). It can be widely and suitably used for curing poured concrete. [Explanation of symbols]

[0046] 1 Center (arch lining formwork) 2. Cast concrete 3. Water-retaining curing sheet 4 Perforated conduit 5 Pressing means 6. Protective cart 61 Support frame 62 Support Frame 7 Rail

Claims

1. A method for curing poured concrete in a tunnel, which involves laying a perforated conduit alongside a water-retaining curing sheet that is to be abutted against the surface of the poured concrete in the tunnel, and arranging a pressing means on the back side of the water-retaining curing sheet by filling the inside of the sheet with gas to bring the surface of the water-retaining curing sheet into abutment against the surface of the poured concrete, characterized in that water is supplied from the perforated conduit to make the water-retaining curing sheet wet, and then the inside of the pressing means is filled with gas to bring the surface of the water-retaining curing sheet into abutment against the surface of the poured concrete.

2. A method for curing poured concrete in a tunnel as described in claim 1, characterized in that the water-retaining curing sheet is made moist and contains water containing silicate by supplying water containing silicate from the perforated conduit.

3. 3. A method for curing poured concrete in a tunnel as claimed in claim 1 or 2, characterized in that before supplying water or water containing silicate from the perforated conduit, the inside of the pressing means on the side of the tunnel is filled with gas so that the surface of the water-retaining curing sheet abuts against the surface of the poured concrete on that side of the tunnel, and then water is supplied from the perforated conduit to make the water-retaining curing sheet wet, and then gas is filled inside the pressing means above the side of the tunnel so that the surface of the water-retaining curing sheet abuts against the surface of the poured concrete.

4. A curing system for poured concrete in a tunnel in which a perforated conduit is laid along a water-retaining curing sheet that is placed in contact with the surface of the poured concrete in the tunnel, and a pressing means is arranged on the back side of the water-retaining curing sheet by filling the inside with gas to bring the surface of the water-retaining curing sheet into contact with the surface of the poured concrete, characterized in that the perforated conduit is laid in the longitudinal direction of the tunnel and on the surface side of the water-retaining curing sheet.

5. 5. A curing system for poured concrete in a tunnel according to claim 4, wherein the perforated conduit is laid so that the liquid jet holes face the surface of the poured concrete.

6. 6. A curing system for poured concrete in a tunnel according to claim 4 or 5, characterized in that the water-retaining curing sheet is kept moist by supplying water from the perforated conduit.

7. A curing system for poured concrete in a tunnel as described in claim 6, characterized in that by supplying water containing silicate from the perforated conduit, the water-retaining curing sheet is made moist and contains water containing silicate.

8. A curing system for poured concrete in a tunnel as described in claim 4 or 5, characterized in that a liquid containing at least one of a concrete surface curing agent, a concrete shrinkage reducing agent, and a concrete surface impregnating agent is supplied from the perforated conduit to make the water-retaining curing sheet wet and containing the liquid.

9. 6. The tonnage machine according to claim 4 or 5, characterized in that a plurality of curing carts, each equipped with the water-retaining curing sheet, perforated conduits and pressing means, are arranged in a line, and water or water containing silicate is supplied from the perforated conduit of the curing cart at the front in the direction of movement to make the water-retaining curing sheet wet by containing water or water containing silicate, and a liquid containing at least one of a concrete surface curing agent, a concrete shrinkage reducing agent and a concrete surface impregnating agent is supplied from the perforated conduit of the curing cart at the rear in the direction of movement to make the water-retaining curing sheet wet by containing the liquid. Nel's curing system for poured concrete.

10. A curing system for poured concrete in a tunnel as described in claim 4 or 5, characterized in that the water-retaining curing sheet is made of a sheet material containing silicate, thereby making the water-retaining curing sheet moist and containing water containing silicate.

11. A curing system for poured concrete in a tunnel as described in claim 4 or 5, characterized in that the water-retaining curing sheet is made of a strip-shaped sheet material sewn so that the sewing direction is in the longitudinal direction of the tunnel.

12. 6. A curing system for poured concrete in a tunnel according to claim 4 or 5, characterized in that the water-retaining curing sheet comprises, from the surface side, at least a sheeting, a nonwoven fabric and a waterproof layer.

13. 13. A curing system for poured concrete in a tunnel according to claim 12, wherein the perforated conduit is laid along the surface of the water-retaining curing sheet.

14. 13. A curing system for poured concrete in a tunnel according to claim 12, wherein the perforated conduit is laid between the sheeting of the water-retaining curing sheet and the nonwoven fabric.

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