Concrete curing sheet

Abstract

To provide a concrete curing sheet that is resistant to damage on both its surface and back. [Solution] This concrete curing sheet 10 is constructed by laminating a cotton fabric 1, a cotton nonwoven fabric 2, a synthetic resin film 3, and a reinforcing fabric 4 in that order from the surface side. The cotton fabric 1 is a plain weave fabric using spun cotton yarn as the warp and weft. The cotton nonwoven fabric 2 is a spunlace nonwoven fabric made of cotton fibers. The synthetic resin film 3 is a polyethylene film. The reinforcing fabric 4 is a plain weave fabric using polyethylene flat yarn as the warp and weft. This concrete curing sheet 10 is used to moist-cur the tunnel lining concrete by covering a trolley equipped with a pressing means and a water-guiding means.

Description

Technical Field

[0001] The present invention relates to a concrete curing sheet for wet-curing concrete for tunnel lining or the like.

Background Art

[0002] As a method for wet-curing concrete for tunnel lining or the like, a method described in Patent Document 1 has been conventionally known. In this method, after placing lining concrete in a tunnel, in a method for wet-curing the lining concrete, a curing sheet (expressed as a water-retaining sheet in Patent Document 1) is brought into contact with the surface of the lining concrete, and on the back surface of this curing sheet (the surface of the curing sheet that is not in contact with the lining concrete is referred to as the back surface. Also, the surface of the curing sheet that contacts the lining concrete is referred to as the front surface), a pressing means including a hollow body that can be inflated by introducing a gas such as air is provided. And a water guiding means for guiding and supplying water to the curing sheet is provided separately. This method can wet-cure the concrete for a long time by simply operating the pressing means and the water guiding means, so that the wet curing sheet is pressed against the surface of the lining concrete. Such a wet-curing method has an advantage that it can efficiently prevent drying cracks on the concrete surface. The curing sheet, the pressing means, and the water guiding means are generally placed on a trolley.

[0003] Once the wet curing described above is completed in the preceding section where the tunnel lining concrete has been laid, the pressing means and water supply means are released, and the trolley is moved to the subsequent section where the lining concrete has been laid, where wet curing is carried out. Even when the pressing means are released, the curing sheet and the lining concrete do not necessarily separate, and may stick together due to the surface tension of water, etc. When the trolley is moved in such a case, friction occurs between the lining concrete and the surface of the curing sheet. It has been known for the use of nonwoven fabric as a concrete curing sheet (Patent Document 1). In addition, it is known that a concrete curing sheet is made of a laminate of cotton nonwoven fabric and a synthetic resin film, in which the cotton nonwoven fabric is the surface of the curing sheet (Patent Document 2). When these are applied to the above curing method in a tunnel, the nonwoven fabric is prone to fraying, damage, breakage or tearing (hereinafter collectively referred to as "damage, etc.") when the trolley is moved, which has the disadvantage of making wet curing difficult in many sections. Furthermore, Patent Document 1 describes using ordinary fabric instead of nonwoven fabric as a concrete curing sheet, but ordinary fabric has the disadvantage of insufficient water retention. In addition, it has been proposed to provide a protective sheet such as spunbond nonwoven fabric on the surface of the nonwoven fabric to protect the surface (Patent Document 3). However, such protective sheets also have insufficient water retention, and when applied to the above curing method inside a tunnel, they still have the disadvantage of being prone to damage. Moreover, in the case of the above curing method inside a tunnel, the back surface of the curing sheet is repeatedly subjected to external force by a pressing means. As a result, the synthetic resin film that constitutes the back surface of the curing sheet is prone to damage.

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-102773 [Patent Document 2] Japanese Patent Publication No. 2018-71295 [Patent Document 3] Japanese Patent Publication No. 2017-36657 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a concrete curing sheet that is less susceptible to damage to both the surface and back surface of the curing sheet, even when applied to the above-mentioned curing method inside a tunnel. [Means for solving the problem]

[0006] The present invention solves the above problem by arranging specific fabrics on the surface and back of a curing sheet made of laminated nonwoven fabric and synthetic resin film. Specifically, the present invention relates to a concrete curing sheet used in a concrete wet curing method in which gas is introduced into a hollow body of a pressing means including a hollow body provided on the back of the curing sheet to expand it, thereby bringing the surface of the curing sheet into close contact with a concrete surface. The concrete curing sheet is laminated in the following order from the surface side: a cotton fabric using cotton spun yarn as warp and weft threads, a cotton nonwoven fabric mainly composed of cotton fibers, a synthetic resin film, and a reinforcing fabric.

[0007] The concrete curing sheet 10 according to the present invention is constructed by laminating, from its surface side, a cotton fabric 1 using spun cotton yarn as the warp and weft threads, a cotton nonwoven fabric 2 containing cotton fibers, a synthetic resin film 3, and a reinforcing fabric 4 in that order.

[0008] Cotton fabric 1 is woven using spun cotton yarn for both the warp and weft. The basis weight of cotton fabric 1 is 100-200 g / m 2The thickness of the cotton fabric 1 is preferably about 250 to 450 μm. The tensile strength of the cotton fabric 1 is preferably about 350 to 600 N / 5 cm width in both the warp direction (also called the MD direction) and the weft direction (also called the CD direction). Furthermore, the elongation of the cotton fabric 1 is preferably about 3 to 15% in both the warp direction and the weft direction. Spun cotton yarn is obtained by spinning cotton fibers, and its cross-section is approximately circular. Cotton fibers have excellent water absorption and water retention properties, making them suitable for wet curing in contact with concrete surfaces. The cotton count of the spun cotton yarn is preferably in the range of 15 to 50 count. The weave structure of the cotton fabric 1 is preferably a plain weave structure. This is because the plain weave structure has superior morphological stability compared to other weave structures. The warp density and weft density of the cotton fabric 1 are preferably in the range of 20 to 70 threads / inch. Good strength, stretchability, and water retention can be obtained within this range of thickness, weave density, and plain weave structure. A specific example of cotton fabric 1 is a plain weave fabric made from 20-count spun cotton yarn with a warp density of 40 threads / inch and a weft density of 33 threads / inch. The water retention capacity is approximately 100-300 g / m². 2 That is the case.

[0009] Cotton nonwoven fabric 2 is mainly composed of cotton fibers, which are intertwined or bonded together. Specifically, a so-called spunlace nonwoven fabric can be used, which is made by opening a cotton mass of 50-100% cotton fibers and 50-0% polyester staple fibers using a carding machine, and then passing the resulting fiber web through a water-flow entanglement device to entangle the fibers. The basis weight of cotton nonwoven fabric 2 is 80-150 g / m². 2 It is preferable that the water retention capacity is within a certain range. Such a cotton nonwoven fabric 2 can supply water to the cotton fabric 1 through the water absorption and water retention properties of the cotton fibers themselves, and the water retention properties that allow a relatively large amount of water to be retained in the gaps between the cotton fibers. A specific example of the cotton nonwoven fabric 2 is a spunlace nonwoven fabric made of 100% by mass of cotton fibers. The degree of water retention is 300 to 500 g / m². 2 That is the case.

[0010] The synthetic resin film 3 is intended to prevent water contained in the cotton nonwoven fabric 2 and cotton fabric 1 from evaporating from the back of the protective sheet. Specifically, polyolefin films such as polyethylene film and polypropylene film, or polyester film, are used. The thickness of the synthetic resin film 3 is approximately 50 to 150 μm. A specific example of the synthetic resin film 3 is a polyethylene film with a thickness of 100 μm.

[0011] The reinforcing fabric 4 is intended to prevent tearing or rupture of the concrete curing sheet 10 when it is stretched over a trolley with an arched upper structure, and conventionally known fabrics are used. Specifically, fabrics such as flat yarn fabrics and gauze are used. Flat yarn fabrics are woven using flat yarn as both warp and weft threads. Flat yarn is made of synthetic resin, and specifically, polyolefins such as polyethylene and polypropylene, or polyester are used. The cross-section of the flat yarn is long-sided, with a thickness of about 0.05 to 0.20 mm and a width of about 1 to 6 mm. The weave structure is generally preferably plain weave, because plain weave has superior shape stability compared to other weave structures. The weave density of the flat yarn fabric 4 is preferably such that no gaps are formed between the warp and weft threads. If gaps are formed, the warp or weft threads tend to shift during use, making them more susceptible to damage. Furthermore, if gaps are formed, water can easily pass through, and if damage occurs to the synthetic resin film 3, water retained by the cotton fabric 1 and cotton nonwoven fabric 2 tends to leak out more easily. A specific example of the flat yarn fabric 4 is a polyethylene flat yarn with a thickness of 0.15 mm and a width of approximately 3 mm, woven in a plain weave structure with a warp density of 5 threads / inch and a weft density of 5 threads / inch. The gauze is woven from spun yarn, monofilament yarn, or multifilament yarn. Yarns with a thickness of about 20 to 40 count are used, and these are woven with a warp density and weft density of about 30 to 80 threads / inch. The yarn material is preferably polyolefin such as polyethylene or polypropylene, or polyester.

[0012] It is preferable that the cotton nonwoven fabric 2 and the reinforcing fabric 4 are joined and integrated by a synthetic resin film 3. The cotton nonwoven fabric 2 and the reinforcing fabric 4 joined and integrated by the synthetic resin film 3 will be referred to below as "cotton nonwoven fabric 2, etc." The preferred method for joining and integrating them is the extrusion lamination method. The extrusion lamination method involves extruding molten synthetic resin through a T-die between the cotton nonwoven fabric 2 and the reinforcing fabric 4, pressing them together, and then cooling them. The molten synthetic resin through the T-die forms the synthetic resin film 3 and also adheres and joins the cotton nonwoven fabric 2 and the reinforcing fabric 4 together. The basis weight of the cotton nonwoven fabric 2, etc. is 150-300 g / m². 2 Preferably, the thickness of the nonwoven cotton fabric 2 is about 300 to 700 μm. Furthermore, the tensile strength of the nonwoven cotton fabric 2 is preferably about 200 to 1000 N / 5 cm width in both the MD and CD directions. In addition, the elongation of the nonwoven cotton fabric 2 is preferably about 3 to 15% in both the MD and CD directions.

[0013] Cotton fabric 1 may be used simply by overlapping it with cotton nonwoven fabric 2, etc., or by overlapping and joining them together. Furthermore, the concrete curing sheet 10 used when wet curing the tunnel lining concrete is a large sheet, with a length of about 10m in the longitudinal direction of the tunnel and a length of about 10 to 30m corresponding to the inner circumference of the tunnel. Cotton fabric 1 and cotton nonwoven fabric 2, etc. are generally supplied in rolls as long pieces with a width of about 1 to 2m. Therefore, in order to make a concrete curing sheet 10 of a size applicable to the tunnel lining concrete, it is necessary to connect the widths of cotton fabric 1 and cotton nonwoven fabric 2, etc. to make it wider. Specifically, in order to make the width of the concrete curing sheet 10, which is made by overlapping cotton fabric 1 and cotton nonwoven fabric 2, etc., to match the length corresponding to the inner circumference of the tunnel, about 5 to 30 sheets will need to be connected. Also, in order to make the width of cotton fabric 1 and cotton nonwoven fabric 2, etc., to match the length in the longitudinal direction of the tunnel, about 5 to 10 sheets will need to be connected. One method of connection is to overlap the widths of the cotton fabric 1 and the cotton nonwoven fabric 2, etc., and sew them together with a sewing machine or the like. Figure 2 is a schematic plan view of a concrete curing sheet 10 whose width has been widened by overlapping and sewing both ends to match the length of the inner circumference of the tunnel, and the seams 5 created by sewing are visible.

[0014] A method for wet-curing the lining concrete of a tunnel's inner wall using the concrete curing sheet 10 according to the present invention will be described. First, a trolley that can move inside the tunnel is prepared. The trolley has an arch structure at the top and is equipped with a pressing means including a hollow body and a water supply means for supplying water to the concrete curing sheet 10. A perforated pipe, which is part of the water supply means for supplying water to the cotton fabric 1 or cotton nonwoven fabric 2, may be attached to the surface of the concrete curing sheet 10. Then, the concrete curing sheet 10 according to the present invention is stretched over the trolley so that the reinforcing cloth 4 is placed on the trolley side and the cotton fabric 1 is placed on the outside, covering the trolley. As shown in Figure 2, the concrete curing sheet 10 is wide and therefore difficult to transport as is. Therefore, the concrete curing sheet 10 is transported by being rolled up or folded in an accordion shape from both ends in the inner circumferential direction of the tunnel to the center. When the concrete curing sheet 10 is in a rolled-up state, after it is attached to the arch top of the trolley, unrolling it will cause the sheet to automatically or semi-automatically (including partially manually) fall to the left and right, covering the trolley. When the concrete curing sheet 10 is folded in an accordion-like state, after it is attached to the arch top of the trolley, it will cover the trolley by being pulled by strings or the like attached to both ends of the concrete curing sheet 10 in the direction of the inner circumference of the tunnel. If the cotton fabric 1 and cotton nonwoven fabric 2 of the concrete curing sheet 10 according to the present invention have the above-mentioned suitable range of strength and elongation, they will be less likely to break under the tensile force when they fall automatically or when they are pulled. Furthermore, the above work may also be performed inside the tunnel. In this case, the concrete curing sheet 10 will be inserted into the gap between the vicinity of the arch top of the trolley and the lining concrete. This gap is about several tens of centimeters, and specifically it may be about 40 centimeters. However, if the concrete curing sheet 10 according to the present invention has the above-mentioned suitable thickness, it can be easily inserted into this gap even when rolled up or folded.

[0015] The trolley is moved and stopped in the preceding section where the tunnel lining concrete has been laid (tunnel lining concrete is usually laid every 10 meters; therefore, this section is also approximately 10 meters long). After stopping, air is blown into the hollow body, which is the pressing means, causing it to expand and the cotton fabric 1 of the concrete curing sheet 10 to come into close contact with the lining concrete surface. The sheet is then cured in this state for a predetermined period. Water is supplied to the cotton nonwoven fabric 2 and the cotton fabric 1 by the water supply means at any point, such as before air is blown into the hollow body, immediately after air is blown into the hollow body to expand it, or when water shortage is detected during curing. The curing period is also arbitrary, but generally 7 days is sufficient. With the above steps, the curing of the lining concrete in the preceding section is completed.

[0016] Here, an example of a method for supplying water to cotton fabric 1 and cotton nonwoven fabric 2 using a water supply means will be described. The cross-section of the inner wall of a tunnel generally consists of side walls and an upper arch. The side walls are generally perpendicular to the road, and the arch is generally parallel to the road. Therefore, if water is supplied to the arch, the water in the arch will be guided to the side walls by gravity through the cotton fabric 1 and cotton nonwoven fabric 2, so the water supply means will mainly be installed in the arch. In some cases, a perforated pipe is used as the water supply means installed in the arch, and water is supplied by spraying it out of the holes. In this case, the water sprayed out of the holes will be guided in the longitudinal direction of the arch due to the water absorption of the cotton fabric 1 and cotton nonwoven fabric 2, and will also be guided to the side walls by gravity. The concrete curing sheet 10 according to the present invention consists of a cotton fabric 1, a cotton nonwoven fabric 2, a synthetic resin film 3, and a reinforcing fabric 4 from the surface side. Water passes through the cotton fabric 1 and the cotton nonwoven fabric 2, and then passes through the side walls in the longitudinal direction of the arch and by gravity. However, if the concrete curing sheet 10 is sewn as shown in Figure 2, the seams 5 created by the sewing may partially block the water flow. In such cases, it is preferable to make the seams 5 parallel to the longitudinal direction of the tunnel to facilitate water flow in the longitudinal direction of the arch. By facilitating water flow in the longitudinal direction of the arch and allowing water to spread throughout the entire arch, the water in the arch will pass through the cotton fabric 1 and the cotton nonwoven fabric 2 by gravity and reach the side walls. As the water travels from the arch to the side walls, it is blocked by the seams 5 which are provided parallel to the longitudinal direction of the tunnel, but the degree of this blockage is weaker than the water flow by gravity, so the water in the arch reaches the side walls well.

[0017] Once the curing of the leading section is completed, the pressing means and the water guiding means are released. As a result, the air in the hollow body of the pressing means escapes, and the hollow body shrinks. Subsequently, the trolley is moved to the trailing section of the constructed lining concrete. Then, the lining concrete in the trailing section is cured in the same manner as described above. Such curing is carried out for each section, and the curing of all the lining concrete constructed in the tunnel is completed. When moving the trolley from the leading section to the trailing section, the surface of the cured lining concrete and the surface of the cotton fabric 1 of the concrete curing sheet 10 may rub against each other. However, since the cotton fabric 1 is composed of cotton spun yarn and has a plain weave structure, damage and the like are less likely to occur compared to non-woven fabric. Further, the back surface of the concrete curing sheet 10 is formed of the reinforcing cloth 4, and damage and the like are less likely to occur compared to the synthetic resin film 3 even when an external force is applied by the pressing means.

Advantages of the Invention

[0018] When the wet curing of the tunnel lining concrete is carried out using a trolley on which the pressing means and the water guiding means as described above are placed, if the concrete curing sheet according to the present invention is used, damage and the like are less likely to occur on the concrete curing sheet and it has excellent durability. Therefore, the effect of being able to continuously carry out wet curing in a large number of sections is achieved.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic side view of a concrete curing sheet according to an example of the present invention. [Figure 2] It is a schematic plan view of a widened one with both ends of the concrete curing sheet according to an example of the present invention overlapped and sewn.

Explanation of Reference Numerals

[0020] 1 Cotton fabric 2 Cotton non-woven fabric 3 Synthetic resin film 4 Reinforcing cloth 5 Seam 10 Concrete curing sheet

Claims

1. A concrete curing sheet used in a method of wet curing concrete, wherein a pressing means including a hollow body provided on the back of the curing sheet is expanded by introducing gas into the hollow body, thereby bringing the surface of the curing sheet into close contact with the concrete surface, the concrete curing sheet being laminated in the following order from the surface side: a cotton fabric using cotton spun yarn as warp and weft threads, a cotton nonwoven fabric mainly composed of cotton fibers, a synthetic resin film, and a reinforcing cloth.

2. The concrete curing sheet according to claim 1, wherein the reinforcing fabric is a flat yarn fabric using flat yarn as both the warp and weft threads.

3. The concrete curing sheet according to claim 1, wherein the concrete surface is the concrete surface of the tunnel lining.

4. The concrete curing sheet according to claim 1, wherein a cotton nonwoven fabric and a reinforcing fabric are joined and integrated by a synthetic resin film, and a cotton fabric is layered on top of the cotton nonwoven fabric.

5. The concrete curing sheet according to claim 3, wherein the seams of the concrete curing sheet are parallel to the longitudinal direction of the tunnel.

6. The concrete curing sheet according to claim 1, wherein both the cotton fabric and the reinforcing fabric are of a plain weave structure.

7. The concrete curing sheet according to claim 1, wherein the cotton nonwoven fabric contains 50% by mass or more of cotton fibers, and the cotton fibers are entangled with each other.

8. The concrete curing sheet according to claim 7, wherein the cotton nonwoven fabric is composed of 100% by mass of cotton fibers.

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