JP7610972B2 - Concrete curing sheet - Google Patents

Description

The present invention relates to a curing sheet used to cure poured concrete.

Concrete needs to be cured so that it remains moist for a certain period of time after being poured. If it dries out, the cement hydration reaction 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.

JP 2018-071283 A

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, its 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.

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.

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 is drained from fresh concrete during and immediately after pouring, accelerating the hardening of the concrete and densifying the concrete to improve its quality. 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 the 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.

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.

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.

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.

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.

The water retaining layer preferably has a thickness of 0.1 mm to 3.0 mm, a basis weight of 50 g/m ² to 500 g/m ² , and a density of 0.1 g/cm ³ to 1.0 g/cm ³ .
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.

It is preferable that the water-shielding layer is a thermoplastic resin film containing a weathering agent. This can prevent the water-shielding layer from deteriorating or changing in quality due to sunlight during the curing period.

It is preferable that the water-retaining layer contains water-absorbent fibers or water-absorbent polymers. This ensures the water retention of the water-retaining layer and also enhances the moisture absorption and release properties.

According to the present invention, excess water can be evenly drained from unhardened concrete, and hardened concrete can be evenly wet cured, improving the quality of the concrete.

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. FIG. 2 is an enlarged cross-sectional view of the concrete curing sheet. FIG. 3 is an enlarged cross-sectional view of the circle III in FIG. 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. FIG. 5 is a cross-sectional view of a concrete pouring site showing a curing process using only the concrete curing sheet after removal of the form. FIG. 6 is an enlarged cross-sectional view of a concrete curing sheet according to a second embodiment of the present invention. FIG. 7 is a cross-sectional view of a concrete pouring site where concrete is poured into a formwork provided with a concrete curing sheet according to the second embodiment and curing is being performed. FIG. 8 is an enlarged cross-sectional view of the circle VIII in FIG. FIG. 9 is a graph showing the results of Example 2 and the Comparative Example.

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. The concrete pouring site is not particularly limited, 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.

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 shielding layer 13. The water permeable layer 11, the water retaining layer 12, and the water shielding 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 shielding layer 13 are bonded to each other by bonding with an adhesive or fusion bonding, etc.

As shown in FIG. 3, the 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, and prevents the passage 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 (layering direction). In other words, water is hardly able to flow in the in-plane direction inside the water-permeable layer 11.

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 and prevent the passage of concrete particles.
Examples of the thermoplastic resin include polypropylene (PP) and polyethylene terephthalate (PET).

As shown in Fig. 4(b), the water-permeable layer 11 may be composed of a perforated sheet 30. The perforated sheet 30 is made of a thermoplastic resin such as PP or PET, and is formed with a large number of small holes 33 penetrating the sheet 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.

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 weathering agent. More preferably, the material of the water permeable layer 13 is linear low density polyethylene (LLDPE) containing a weathering agent. Examples of the weathering agent 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 is costly and uneconomical.

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.

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 made of 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.
Examples of the supporting method include a method of sandwiching the granular water-absorbent polymer between two sheets of nonwoven fabric, a method of placing the granular water-absorbent polymer in a bag made of nonwoven fabric, or a method of fixing the granular water-absorbent polymer to fibers of nonwoven fabric or the like by fusion, adhesion, or the like.
Natural fibers include cotton, silk, pulp, hemp, and wool.
The water retention layer 12 may include water-absorbent fibers such as SAF.

Preferably, the water retaining layer 12 has a thickness of 0.1 mm to 3.0 mm, a basis weight of 50 g/m ² to 500 g/m ² , and a density of 0.1 g/cm ³ to 1.0 g/cm ³ .
If the thickness of the water retaining layer 12 is less than 0.1 mm, the water retention capacity is insufficient due to insufficient water absorption of the water retaining layer 12. If the thickness of the water retaining layer 12 exceeds 3.0 mm, it is costly and uneconomical.
If the basis weight of the water-retaining layer 12 is less than 50 g/ ^m2 , 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, the water-retaining capacity (retentive force) is insufficient when the curing sheet 10 is installed vertically, resulting in insufficient water-retaining capacity. If the basis weight of the water-retaining layer 12 exceeds 500 g/ ^m2 , the workability will be poor and there is a risk of peeling off under its own weight after the formwork 1 is removed.
If the density of the water-retaining layer 12 is less than 0.1 g/ ^cm3 , the water-retaining layer 12 will be crushed by the pouring pressure of concrete, and uniform water-retaining capacity cannot be reproduced. In addition, the water-retaining capacity (retention force) is insufficient when the curing sheet 10 is installed vertically, resulting in insufficient water-retaining capacity. If the density of the water-retaining layer 12 exceeds 1.0 g/ ^cm3 , roll molding is not possible, resulting in poor productivity.

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.

As shown in Fig. 1, for example, the upper end of the curing sheet 10 installed 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 fixed 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 curing sheet 10 is folded along the bottom surface of the formwork 1 to form a discharge passage 10e. The end face of the discharge passage 10e faces the outside of the formwork 1.

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.

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 and improves 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, and also densifying the concrete by reducing the water-cement ratio W/C, improving the quality.
Solid components in the concrete 2, such as cement and aggregate, cannot permeate the permeable layer 11 and are prevented from flowing out.

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, when 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, so it can retain water stably. 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.

After the concrete 2 has hardened, 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 spray receiving portion 10d on the formwork 1 (see the second embodiment).

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 water 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 formwork. 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.

After that, at any time, 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 curing sheet 10 can be peeled off cleanly because the contact surface with the concrete 2 of the curing sheet 10 is formed of a permeable layer 11 made of a woven thermoplastic resin fiber fabric or a porous resin sheet. For example, it is possible to prevent fibers from the curing sheet from remaining on the surface of the concrete 2. Therefore, the surface of the concrete 2 can be finished neatly.

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 10</b>B 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). In other words, 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 .

In the second embodiment, when the concrete 2 is poured, there is too much excess water to be retained by the water retention layer 12, and the excess water can flow in the in-plane direction through the drainage layer 14 and 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.

As shown by the bold arrow in Figure 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, with a portion Wa being 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 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 through a drainage passage 10e (FIG. 7).

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.

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.

The present invention is not limited to the following examples.
As Example 1, a number of samples of the water retaining layer of the curing sheet were prepared. The content of the 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 between 0.8 mm and 2.0 mm.
Each sample was clamped between two transparent acrylic plates. Packing was 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.

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

As Example 2, a number of samples of a concrete curing sheet having a structure substantially similar to that of the first embodiment (FIG. 2) were prepared.
The content of the superabsorbent fiber (SAF) in the water retention layer was 0% or 15% for each sample in terms of weight ratio to the base 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.

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.

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).

The surface layer air permeability coefficient of each concrete after curing 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 could be made lower than that of Comparative Examples A and B, specifically, it could be made 0.01 x ^10-16 m2 or ^less . Therefore, it was confirmed that according to the present invention, the concrete surface can be densified and good concrete can be obtained. It was confirmed that the curing effect can be obtained by the curing sheet having an SAF or other water retentive layer.

The present invention can be applied to concrete curing work in concrete structures such as bridge piers, retaining walls, tunnels, and buildings.

1. Concrete pouring formwork (formwork)
1a Inner surface 1c Concrete casting space 2 Concrete 3 Sprinkler nozzle 10, 10B Concrete curing sheet 10d Sprinkler receiver 10e Drainage channel 11 Permeable layer 12 Water retaining layer 13 Water shielding layer 14 Drainage layer 20 Woven fabric 23 Mesh (through hole)
30 Perforated sheet 33 Through hole w Water

Claims (8)

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 . The concrete curing sheet according to claim 1, characterized in that the permeable layer is made of a woven fabric or a porous sheet of thermoplastic resin. The concrete curing sheet according to claim 1 or 2, characterized in 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. 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 . The concrete curing sheet according to any one of claims 1 to 4, characterized in that the permeable layer can maintain a tight 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. The concrete curing sheet according to any one of claims 1 to ⁵ , characterized in that the water retaining layer has a thickness of 0.1 mm to 3.0 mm, a basis weight of 50 g/ ^m2 to 500 g/ ^m2 , and a density of 0.1 g/ ^cm3 to 1.0 g/cm3, the water impermeable layer has a thickness of 1.0 mm or less, and the total thickness of the concrete curing sheet is 10 mm or less. The concrete curing sheet according to any one of claims 1 to 6, characterized in that the water impermeable layer is a thermoplastic resin film containing a weathering agent. 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.

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