Concrete curing sheet

Abstract

To provide a curing sheet capable of not only curing hardened concrete, but also improving the quality of concrete through discharge of redundant water before hardening.SOLUTION: A concrete curing sheet 10 is disposed on an inner face 1a of a formwork 1 for concrete placement. The curing sheet 10 comprises a permeable layer 11 facing a concrete placement space 1c, a water shielding layer 13 having impermeability, facing the inner face 1a, and a water retaining layer 12 having water absorbability, disposed between the permeable layer 11 and the water shielding layer 13. The permeable layer 11 is composed of a woven fabric 20 or a porous sheet 30 made of preferably thermoplastic resin, allowing water to pass through in the thickness direction, and inhibiting or restricting water from passing in-plane direction orthogonal to the thickness direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a curing sheet used for curing poured concrete. [Background technology]

[0002] Concrete needs to be cured so that it remains moist for a certain period of time after being poured. If it dries out, the hydration reaction of the cement will not proceed, and quality cannot be ensured. For this reason, it is known to lay a curing sheet containing a water-retaining layer over the concrete during curing (see Patent Document 1). The curing sheet keeps the surface of the concrete moist. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-071283 A Summary of the Invention [Problem to be solved by the invention]

[0004] The curing sheet in the above-mentioned patent document is applied when the poured concrete has hardened and been demolded, so it does not contribute to improving the quality of the concrete between pouring and demolding. For example, it does not drain excess water from fresh concrete when poured. In addition, when the curing sheet is peeled off from the concrete after curing is complete, if fibers from the curing sheet remain on the surface of the concrete, it will look bad. In view of the above circumstances, the present invention has as its main or first object to provide a curing sheet that not only cures hardened concrete but also contributes to improving the quality of concrete by draining excess water before hardening, etc. Furthermore, the second object is to provide a curing sheet that does not leave fibers or the like on the surface of concrete after it is finally peeled off. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides a concrete curing sheet provided on an inner surface that defines a concrete pouring space in a formwork for pouring concrete, A permeable layer facing the concrete pouring space; an impermeable water shielding layer facing the inner surface; A water retaining layer having self-absorbency and sandwiched between the water permeable layer and the water impermeable layer; The water-permeable layer has holes that allow water to pass through in the thickness direction, and prevents or restricts water passage in an in-plane direction perpendicular to the thickness direction.

[0006] When the concrete curing sheet is stretched over the inner surface of a concrete casting formwork and concrete is poured into the concrete pouring space, excess water in the concrete can permeate the permeable layer in the thickness direction. The excess water is prevented or restricted from flowing in the in-plane direction within the permeable layer. Therefore, the excess water flows almost uniformly in the thickness direction of the permeable layer. This ensures that excess water can be drained from fresh concrete during and immediately after pouring, accelerating the hardening of the concrete and densifying the concrete to improve its quality. The excess water that permeates the permeable layer is absorbed and retained in the water-retaining layer. By preventing or restricting the flow in the in-plane direction, water can be retained almost evenly throughout the entire water-retaining layer. The water-retaining layer is self-absorbent, so it can retain water stably. Furthermore, the water shielding layer prevents moisture from escaping. After the concrete hardens, it is wet cured using water stored in the water-retaining layer. As a result, the quality of the concrete can be improved, and the main object or the first object can be achieved.

[0007] The water-permeable layer is preferably made of a woven fabric or a porous sheet of a thermoplastic resin. This allows the permeable layer to reliably allow water to pass through in the thickness direction while preventing or restricting water passage in the in-plane direction. Furthermore, it is possible to prevent fibers and the like from remaining on the surface of the concrete after the curing sheet is peeled off, thereby achieving the second object.

[0008] It is preferable that a drainage layer that allows water to pass in the in-plane direction is interposed between the water permeable layer and the water retaining layer or between the water retaining layer and the water impermeable layer. As a result, any excess water that cannot be retained by the water retention layer due to an excessive amount of water can be discharged by flowing in the in-plane direction through the drainage layer.

[0009] It is preferable that an end of the concrete curing sheet protrudes from the formwork to form a water receiving portion for receiving water. During curing after the concrete has hardened, water is sprayed onto the water spray receiver. The sprayed water is absorbed into the water-retaining layer, which ensures that the water-retaining layer is kept in a water-retaining state, ensuring wet curing of the concrete. If the curing sheet includes a drainage layer, the water flows in-plane through the drainage layer, allowing curing equivalent to flood curing to be achieved, further improving the quality of the concrete.

[0010] It is preferable that the water permeable layer, and therefore the concrete curing sheet, be able to maintain a tight adhesion with the concrete poured in the concrete pouring space during and after the formwork is removed, and be able to be peeled off from the concrete after it is removed. This allows the formwork to be removed during the concrete curing process. When removing the formwork, the concrete curing sheet is peeled away from the formwork, while the concrete curing sheet is left on the surface of the concrete. Therefore, the concrete can continue to be cured by the concrete curing sheet even after removal of the formwork. From another perspective, early removal of the formwork can shorten the construction period. After that, at any time, preferably after the required curing period using only the concrete curing sheet has ended, the concrete curing sheet can be peeled away from the concrete and removed.

[0011] The water-retaining layer has a thickness of 0.1 mm to 3.0 mm and a basis weight of 50 g / m 2 ~500g / m 2 , density 0.1g / cm 3 ~1.0g / cm 3 It is preferable that: The thickness of the water impermeable layer is preferably 1.0 mm or less. It is preferable that the total thickness of the concrete curing sheet is 10 mm or less.

[0012] The water impermeable layer is preferably a thermoplastic resin film containing a weathering agent, which can prevent the water impermeable layer from being deteriorated or altered by sunlight or the like during the curing period.

[0013] The water retaining layer preferably contains water-absorbent fibers or water-absorbent polymers, which can ensure the water retention of the water retaining layer and further enhance the moisture absorption and release properties. Effect of the Invention

[0014] According to the present invention, excess water can be evenly drained from unhardened concrete, and hardened concrete can be evenly wet cured, thereby improving the quality of the concrete. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a concrete pouring site where concrete is being poured into a formwork provided with a concrete curing sheet according to a first embodiment of the present invention and cured. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the concrete curing sheet. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of the circle III in FIG. [Figure 4] Fig. 4(a) is an enlarged plan view showing one embodiment of the water-permeable layer of the concrete curing sheet, and Fig. 4(b) is an enlarged plan view showing another embodiment of the water-permeable layer of the concrete curing sheet. [Diagram 5] FIG. 5 is a cross-sectional view of a concrete pouring site showing the curing process using only the concrete curing sheet after removal of the form. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a concrete curing sheet according to a second embodiment of the present invention. [Figure 7]FIG. 7 is a cross-sectional view of a concrete pouring site where concrete is being poured into a formwork provided with a concrete curing sheet according to the second embodiment and cured. [Figure 8] FIG. 8 is an enlarged cross-sectional view of the circle VIII in FIG. [Figure 9] FIG. 9 is a graph showing the results of Example 2 and the Comparative Example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. <First embodiment (FIGS. 1 to 5)> Fig. 1 is a schematic diagram of a concrete pouring site. There are no particular limitations on the concrete pouring site, and examples include construction sites for bridge abutments, piers, retaining walls, tunnels, dams, buildings, and various other concrete structures. A concrete pouring formwork 1 is installed at the concrete pouring site. A concrete pouring space 1c is defined by an inner surface 1a of the formwork 1. Concrete 2 is poured into the pouring space 1c.

[0017] As shown in FIG. 1, a concrete curing sheet 10 is provided on an inner surface 1a of the formwork 1. As shown in Fig. 2, the concrete curing sheet 10 includes a water permeable layer 11, a water retaining layer 12, and a water impermeable layer 13. The water permeable layer 11, the water retaining layer 12, and the water impermeable layer 13 are laminated in this order from the side of the concrete pouring space 1c. The thickness direction of each layer 11, 12, and 13 is aligned with the lamination direction of the layers 11, 12, and 13. The water permeable layer 11 and the water retaining layer 12, and the water retaining layer 12 and the water impermeable layer 13 are respectively joined by bonding with an adhesive or fusion bonding.

[0018] As shown in FIG. 3, the water-permeable layer 11 faces the concrete pouring space 1c and is in contact with the concrete 2. The water-permeable layer 11 allows water to pass through in the thickness direction (permeation of water) and prevents the permeation of solids such as cement and aggregates. Furthermore, the water-permeable layer 11 prevents or restricts water from passing through in the in-plane direction perpendicular to the thickness direction (stacking direction). In other words, water is hardly able to flow in the in-plane direction inside the water-permeable layer 11.

[0019] Specifically, as shown in Fig. 4(a), the water-permeable layer 11 is composed of a woven fabric 20 made of thermoplastic resin fibers 21. The mesh of the woven fabric 20 forms through-holes 23 that allow water to pass through in the thickness direction. The size of the mesh, i.e., the through-holes 23, is preferably large enough to allow the passage of water but prevent the passage of concrete particles. Examples of the thermoplastic resin include polypropylene (PP) and polyethylene terephthalate (PET).

[0020] As shown in Fig. 4(b), the water-permeable layer 11 may be composed of a porous sheet 30. The porous sheet 30 is made of a thermoplastic resin such as PP or PET, and has a large number of small holes 33 formed therethrough in the thickness direction. The holes 33 serve as water passages in the thickness direction. The size of the holes 33 is preferably large enough to allow the passage of water and prevent the passage of concrete particles. By pouring the concrete 2 into the pouring space 1c, the permeable layer 11 is bonded in close contact with the concrete 2. The permeable layer 11, and therefore the curing sheet 10, can maintain close contact with the concrete 2 during and after the formwork 1 is removed (FIG. 5), and can be forcibly peeled off from the concrete 2 after removal from the formwork.

[0021] The water-impermeable layer 13 shown in Fig. 2 is made of impermeable resin or rubber. For example, the water-impermeable layer 13 is made of a thermoplastic resin film such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET). Preferably, the thermoplastic resin film constituting the water-impermeable layer 13 contains a weather-resistant agent. More preferably, the material of the water-permeable layer 13 is linear low-density polyethylene (LLDPE) containing a weather-resistant agent. Examples of weather-resistant agents include known ultraviolet absorbing agents and antioxidants. Preferably, the thickness of the water impermeable layer 13 is 1.0 mm or less. If the thickness of the water impermeable layer 13 exceeds 1.0 mm, it becomes costly and uneconomical.

[0022] As shown in FIG. 3, the waterproof layer 13 is in contact with the inner surface 1 a of the formwork 1 . An adhesive layer for attaching the waterproof layer 13 to the formwork 1 may be provided on the surface of the waterproof layer 13 facing the formwork 1. The adhesive layer is preferably peelable from the formwork 1.

[0023] 2, the water retaining layer 12 is sandwiched between the water permeable layer 11 and the water shielding layer 13. The water retaining layer 12 is thicker than the water permeable layer 11 and the water shielding layer 13. The water retaining layer 12 has self-absorbency. Having self-absorbency means that the water retaining layer has the ability to absorb water into the water retaining layer itself, thereby exhibiting water absorbency. The water retaining layer 12 may be a nonwoven fabric carrying a water-absorbent polymer or a nonwoven fabric made of natural fibers. The water-absorbing polymer may be an acrylic resin. The water-absorbing polymer may be in the form of particles. Examples of materials for the nonwoven fabric on which the water-absorbent polymer is carried include chemical fibers such as polyester, polypropylene, and polyethylene. Methods for supporting the polymer include sandwiching the granular water-absorbent polymer between two sheets of nonwoven fabric, placing the granular water-absorbent polymer in a bag made of nonwoven fabric, and fixing the granular water-absorbent polymer to fibers of nonwoven fabric or the like by fusion or adhesion. Natural fibers include cotton, silk, pulp, hemp, and wool. The water retention layer 12 may include water-absorbent fibers such as SAF.

[0024] Preferably, the water retaining layer 12 has a thickness of 0.1 mm to 3.0 mm and a basis weight of 50 g / m 2 ~500g / m 2 , density is 0.1g / cm 3 ~1.0g / cm 3 It is. If the thickness of the water retaining layer 12 is less than 0.1 mm, the water retention capacity is insufficient due to the insufficient water absorption amount of the water retaining layer 12. If the thickness of the water retaining layer 12 exceeds 3.0 mm, it is costly and uneconomical. The weight of the water retaining layer 12 is 50 g / m 2 If the concrete pouring pressure is less than 500 g / m, the water retention layer 12 will be crushed, and uniform water retention will not be achieved. In addition, the water retention capacity (retention force) of the curing sheet 10 when installed vertically will be insufficient, resulting in insufficient water retention capacity. 2 If it exceeds this value, workability will deteriorate and there is a risk of the concrete peeling off under its own weight after the formwork 1 is removed. The density of the water retaining layer 12 is 0.1 g / cm 3 If the density of the water-retaining layer 12 is less than 1.0 g / cm, the water-retaining layer 12 will be crushed by the pouring pressure of the concrete, and uniform water-retaining capacity cannot be reproduced. In addition, when the curing sheet 10 is installed vertically, the water-retaining capacity (retention force) is insufficient, resulting in insufficient water-retaining capacity. 3 If it exceeds this value, roll forming is not possible and productivity is poor.

[0025] Preferably, the total thickness of the concrete curing sheet 10 is 10 mm or less. If the total thickness exceeds 10 mm, it will have a large effect on the shape and dimensions of the concrete structure.

[0026] As shown in Fig. 1, for example, the upper end of the curing sheet 10 placed on the formwork 1 protrudes from the formwork 1 to form a water sprinkler receiving portion 10d. Preferably, the water sprinkler receiving portion 10d is folded and placed over the upper end surface of the formwork 1, and is fastened to the formwork 1 with fasteners such as staples or nails (not shown). The water permeable layer 11 in the water sprinkler receiving portion 10d forms the outer surface (upper surface) of the water sprinkler receiving portion 10d. The water shielding layer 13 in the water sprinkler receiving portion 10d faces the upper end surface of the formwork 1. Furthermore, the lower end of the protective sheet 10 is folded along the bottom surface of the formwork 1 to form a discharge path 10e. The end face of the discharge path 10e faces the outside of the formwork 1.

[0027] The concrete curing sheet 10 is used as follows. A protective sheet 10 is attached to the inner surface 1a of the formwork 1, and the formwork 1 is assembled. The upper end of the protective sheet 10 is a water receiving portion 10d, and the lower end of the protective sheet 10 is a discharge path 10e.

[0028] Next, concrete 2 is poured into the space 1c within the formwork 1. The amount of water in the concrete 2 when poured is set to be greater than the amount required for hardening. This increases the fluidity of the concrete 2, improving pouring workability. The permeable layer 11 contacts the concrete 2 in the space 1c. The surplus water exceeding the required amount seeps out from the concrete 2 into the permeable layer 11 and permeates the permeable layer 11 in the thickness direction. Since the permeable layer 11 is composed of the woven fabric 20 or the porous sheet 30 having the through holes 23, 33, the permeability in the thickness direction can be reliably ensured. On the other hand, the permeability of the water in the in-plane direction in the permeable layer 11 is prevented or restricted, so that the water flows almost uniformly in the thickness direction of the permeable layer 11. This allows excess water to be reliably drained from the fresh concrete 2 during and immediately after pouring, accelerating the hardening of the concrete 2, while at the same time densifying the concrete by reducing the water-cement ratio W / C, improving the quality. Solid components such as cement and aggregate in the concrete 2 cannot permeate the permeable layer 11, and so outflow can be prevented.

[0029] Excess water that permeates the water permeable layer 11 in the thickness direction is absorbed and retained in the water retaining layer 12. Because the flow of water in the in-plane direction in the water permeable layer 11 is prevented or restricted, water can be retained evenly throughout the entire water retaining layer 12. For example, if the formwork 1 and the curing sheet 10 are arranged vertically, the excess water can be prevented from flowing downward in the water permeable layer 11 due to gravity. This makes it possible to prevent water from concentrating in the lower part of the water retaining layer 12, and to prevent a shortage of water retention in the upper part of the water retaining layer 12. Moreover, the water retentive layer 12 has self-absorbency and can stably retain water. For example, water absorbed in the upper part of the water retentive layer 12 does not fall due to gravity or the like. Therefore, water can be retained evenly in both the upper and lower parts of the water retentive layer 12. Furthermore, the water shielding layer 13 can prevent the dissipation of water.

[0030] After the concrete 2 hardens, it is further cured for a certain period of time to ensure quality. During the curing period, moisture in the water retentive layer 12 can permeate through the water permeable layer 11 in the thickness direction and be supplied to the concrete 2. This allows the concrete 2 to be kept moist and improves its quality. Since water is evenly retained throughout the water retentive layer 12, the concrete 2 can be moist cured without bias. Furthermore, during the curing period, water may be sprayed onto the water-spraying receiving portion 10d on the formwork 1 (see the second embodiment).

[0031] After the concrete 2 has hardened, the formwork 1 may be removed during the curing period. At this time, the fasteners (not shown) between the sprinkler receiving portion 10d and the formwork 1 are removed, the curing sheet 10 is peeled off from the formwork 1, and the formwork 1 is removed, while the curing sheet 10 is left on the surface of the concrete 2 as shown in FIG. 5. This allows the concrete 2 to continue curing even after it has been removed from the form. From another perspective, this allows the concrete 2 to be removed early. This, combined with the promotion of hardening due to the above-mentioned drainage of excess water, can shorten the construction period. Even after demolding, the concrete 2 can be wet cured due to the water retention of the water retentive layer 12. As a result, the quality of the concrete 2 can be sufficiently improved.

[0032] Thereafter, at any timing, preferably after the required curing period using only the curing sheet 10 has ended, the curing sheet 10 is peeled off from the concrete 2. The surface of the curing sheet 10 that comes into contact with the concrete 2 is formed of a permeable layer 11 made of a thermoplastic resin fiber woven fabric or a porous resin sheet, so it can be peeled off cleanly. For example, it is possible to prevent fibers originating from the curing sheet from remaining on the surface of the concrete 2. Therefore, the surface of the concrete 2 can be finished neatly.

[0033] Next, another embodiment of the present invention will be described. In the following embodiments, the same components as those in the above-described embodiment will be denoted by the same reference numerals in the drawings and the description thereof will be omitted. <Second embodiment (FIGS. 6 to 8)> As shown in FIG. 6, in a concrete curing sheet 10B according to the second embodiment, a drainage layer 14 is interposed between a water permeable layer 11 and a water retaining layer 12. The drainage layer 14 is made of, for example, a nonwoven fabric or a sponge-like porous resin with continuous pores. The drainage layer 14 is permeable to water in the in-plane direction (the direction perpendicular to the stacking direction of the layers 11 to 14). That is, the drainage layer 14 allows water to flow in the in-plane direction inside the drainage layer 12. At least the drainage layer 14 has higher water permeability in the in-plane direction than the water permeable layer 11. The thickness of the drainage layer 14 is greater than that of the permeable layer 11 and the water impermeable layer 13 .

[0034] In the second embodiment, when the concrete 2 is poured, the excess water that cannot be retained by the water retaining layer 12 flows in the in-plane direction of the drainage layer 14 and can be discharged to the outside, for example, through the drainage channel 10e. 7, water is continuously or appropriately sprayed onto the water sprinkler receiving portion 10d during curing after the concrete 2 has hardened. Specifically, for example, a water sprinkler nozzle 3 is installed above the concrete pouring formwork 1. Water w is supplied from the water sprinkler nozzle 3 to the water sprinkler receiving portion 10d. Watering may be carried out continuously, or may be carried out intermittently at regular or irregular intervals.

[0035] As shown by the bold arrowed line in FIG. 8, the water w from the watering nozzle 3 flows from the watering receiver 10d in the in-plane direction within the drainage layer 14, spreading over a wide area of ​​the curing sheet 10B, while a portion Wa is supplied to the concrete 2 via the water permeable layer 11. Another portion Wb of the water w is absorbed by the water retention layer 12, which keeps the water retention layer 12 in a water-retaining state. This allows the concrete 2 to be stably wet-cured. Furthermore, curing comparable to that of flooded curing can be performed. As a result, the concrete 2 can be reliably produced with high quality. Of the sprayed water W, the water that is not absorbed by the water retaining layer 12 or the like is drained from the drainage path 10e (FIG. 7).

[0036] Even after removal from the form, the curing sheet 10B is left in place for further curing. During the period of curing using only the curing sheet 10B, the concrete 2 can be wet cured due to the water retention of the water retentive layer 12. Furthermore, even after removal from the form, water is appropriately sprayed onto the water spray receiving portion 10d. In this way, the concrete 2 can be reliably wet cured even after removal from the form, and can be cured in a state close to flood curing. As a result, the quality of the concrete 2 can be sufficiently improved.

[0037] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the water receiving portion 10d or the discharge passage 10e may be omitted. The drainage layer 14 may be provided between the water retaining layer 12 and the water shielding layer 13, instead of between the water permeable layer 11 and the water retaining layer 12. The drainage layer 14 may be provided between the water permeable layer 11 and the water retaining layer 12, and between the water retaining layer 12 and the water shielding layer 13. The present invention is not limited to cast-in-place concrete, but can also be applied to the production of precast concrete. EXAMPLES

[0038] The present invention is not limited to the following examples. Several samples of the water retaining layer of the curing sheet were prepared as Example 1. The content of superabsorbent fiber (SAF) in the water retaining layer was 0%, 10%, 15%, and 50% by weight relative to the base fiber (PE / PET) for each sample. The width (short side dimension) of each sample was 200 mm. The length (longer dimension) of each sample was 100 mm. The thickness of each sample was 0.8 mm to 2.0 mm. Each sample was clamped between two transparent acrylic plates. Gaskets were provided at both ends of each sample in the width direction to prevent water leakage. Each sample was placed with its longitudinal direction vertical, and water was supplied into the sample from its upper end.

[0039] In the samples containing 0%, 10%, and 15% SAF, water reached the bottom of the sample and leaked out during the water supply period, confirming that water had permeated the entire water-retaining layer. The sample with SAF 50% absorbed water up to the middle in the vertical direction, but the absorption did not progress downward from there. It was thought that the water was stopped by swelling. The moisture retention of the samples after a certain time had elapsed since the end of water supply roughly corresponded to the SAF content. EXAMPLES

[0040] As Example 2, a number of samples of a concrete curing sheet having substantially the same structure as that of the first embodiment (FIG. 2) were prepared. The content of superabsorbent fiber (SAF) in the water-retaining layer was 0% and 15% for each sample, expressed as a weight ratio to the matrix fiber (PE / PET). Hereinafter, the example of the sample with 0% SAF will be referred to as "Example 2A", and the example of the sample with 15% SAF will be referred to as "Example 2B". The permeable layer of each sample was a water-permeable resin sheet (product name "Filter Sheet Tough") manufactured by Fujimori Sangyo Co., Ltd. These samples were attached to the inner surface 1a of the formwork 1, and concrete 2 was poured into the concrete pouring space 1c. Then, the concrete 2 was cured until it hardened.

[0041] Furthermore, Comparative Example A was a case where no curing sheet was used (only the formwork), and Comparative Example B was a case where only the permeable layer made of the water-permeable resin sheet "Filter Sheet Tough" was used as the curing sheet. In parallel with the implementation of Examples 2A and 2B, concrete of the same composition as in Examples 2A and 2B was poured and cured under the same conditions.

[0042] The curing period for Examples 2A and 2B and Comparative Examples A and B was 7 days. In both Examples 2A and 2B and Comparative Examples A and B, water was not supplied to the concrete and water was not sprinkled on the curing sheet during the curing period (see the second embodiment).

[0043] For each concrete after curing, the surface layer air permeability coefficient was measured by a surface layer air permeability test (Trent method). The measurement results are shown in Figure 9. As is clear from the figure, according to Examples 2A and 2B, the surface layer air permeability coefficient can be made lower than that of Comparative Examples A and B, specifically, by 0.01 × 10 -16 m 2 It was therefore confirmed that the present invention can densify the concrete surface and produce good concrete. It was also confirmed that the curing sheet has a water-retaining layer such as SAF, which provides a curing effect. [Industrial Applicability]

[0044] The present invention can be applied to curing of concrete in concrete structures such as bridge piers, retaining walls, tunnels, and buildings. [Explanation of symbols]

[0045] 1. Concrete pouring formwork (formwork) 1a Inner surface 1c Concrete pouring space 2. Concrete 3. Watering nozzle 10,10B Concrete curing sheet 10d Water receiver 10e Exhaust channel 11 Permeable layer 12 Water retention layer 13 Water impermeable layer 14 Drainage layer 20 Woven fabric 23 Mesh (through hole) 30 Perforated Sheet 33 Through hole w water

Claims

1. A concrete curing sheet provided on an inner surface defining a concrete pouring space in a form for pouring concrete, A permeable layer facing the concrete pouring space; an impermeable water shielding layer facing the inner surface; A water retaining layer having self-absorbency and sandwiched between the water permeable layer and the water impermeable layer; the water-permeable layer has holes that allow water to pass through in the thickness direction, and prevents or restricts water from passing through in an in-plane direction perpendicular to the thickness direction, and the upper end of the concrete curing sheet protrudes from the upper end surface of the formwork, with the water-permeable layer facing upward and the water-shielding layer facing the upper end surface, and is folded and placed over the upper end surface to form a water-spray receiving portion that receives water.

2. 2. The concrete curing sheet according to claim 1, wherein the permeable layer is made of a woven fabric or a porous sheet of a thermoplastic resin.

3. 3. The concrete curing sheet according to claim 1, wherein a drainage layer that allows water to pass in an in-plane direction is interposed between the water permeable layer and the water retaining layer or between the water retaining layer and the water impermeable layer.

4. A concrete curing sheet as described in any one of claims 1 to 3, characterized in that the lower end of the concrete curing sheet is folded along the bottom surface of the formwork to form a water drainage path, and the end face of the drainage path faces outside the formwork.

5. A concrete curing sheet as described in any one of claims 1 to 4, characterized in that the permeable layer can maintain a close contact with the concrete poured in the concrete pouring space during and after the formwork is removed, and can be peeled off from the concrete after the formwork is removed.

6. The water retaining layer has a thickness of 0.1 mm to 3.0 mm and a basis weight of 50 g / m ２ Up to 500 g / m ２ , density 0.1g / cm ３ ~1.0 g / cm ３ The concrete curing sheet according to any one of claims 1 to 5, characterized in that the thickness of the waterproof layer is 1.0 mm or less, and the total thickness of the concrete curing sheet is 10 mm or less.

7. 7. The concrete curing sheet according to claim 1, wherein the water impermeable layer is a thermoplastic resin film containing a weathering agent.

8. The concrete curing sheet according to any one of claims 1 to 7, characterized in that the water retaining layer contains water-absorbent fibers or water-absorbent polymers.

Images