JP7398322B2 - How to build concrete structures - Google Patents

Description

The present invention relates to a method of constructing a concrete structure.

BACKGROUND ART As a construction method for constructing concrete structures such as bridges and dams, the construction method described in Patent Document 1 is newly being used. In this method, a formwork for concrete pouring is installed, and a non-permeable, highly water-repellent curing sheet is pasted on the inner surface of the formwork before concrete is poured. After the concrete is poured, the formwork will be removed, but the curing sheet will remain on the concrete side. This curing sheet covers the poured concrete as it is, allowing the concrete to cure for a long period of time without ever being exposed to the outside air.

Patent No. 5698304 JP2015-206215

In the above method, if it takes 5 days from pouring concrete to demolding the formwork, the strength of the poured concrete will be 20N/ ^mm2 or more, and the adhesive force between the curing sheet and the formwork will be about 250g. For example, it has been confirmed that curing sheets remain on the concrete during demolding. On the other hand, for early demolding, for example, if you try to demold the day after concrete is poured, the strength of the poured concrete is about 5N/ ^mm2 , and the adhesive force between the curing sheet and the formwork should not be less than 50g. Therefore, the curing sheet tends not to remain properly on the concrete during demolding. However, when attaching the curing sheet to the formwork with adhesive, etc., it is necessary to adjust the adhesive force and amount (thickness) of the adhesive so that the adhesive force between the curing sheet and the formwork is 50g or less instead of 250g. Therefore, early demolding using the above method was difficult. Furthermore, even if the adhesive strength between the curing sheet and the formwork could be reduced to 50g or less, the curing sheet attached to the formwork would easily wrinkle due to the decrease in adhesive strength, and the curing sheet would separate from the formwork during construction. There is a risk that it may come off.

The present invention has been made in order to solve the above-mentioned problems, and provides a concrete structure that can realize early demolding in a method of pouring concrete into formwork etc. to which a curing sheet is attached. The purpose is to provide a method for building things.

A method for constructing a concrete structure according to the present invention includes a formwork structure including at least a plate-like member having a large number of through holes, and a formwork structure having an impermeable curing sheet and the curing sheet attached to the plate-like member. an installation step in which the formwork assembly is installed at a predetermined location so that the curing sheet is located on the concrete pouring side in a three-dimensional structure; a placing step in which concrete is poured so that the concrete is in contact with the curing sheet of the formwork assembly; The method includes a demolding step of demolding at least a part of the formwork structure after pouring concrete, and a curing process of leaving a curing sheet on the surface of the concrete to cure the concrete for a predetermined period after the demolding process. The diameter of the many through holes in the plate member is 10 mm or less, and the center pitch of the many through holes is 20 mm or less.

In this method of constructing a concrete structure, a curing sheet is attached to a plate-like member having a large number of through holes. In this case, the contact area when attaching the curing sheet to the formwork structure can be suitably reduced by the amount of the through holes. As a result, compared to adjusting the adhesive force of the curing sheet to the formwork etc. using adhesive alone, it is now easier to adjust the overall adhesive force, and the adhesive force of the curing sheet to the formwork structure can be adjusted more easily. Even in the case of early demolding, where the force must be kept to a low value of 50 g or less, the curing sheet can be reliably left behind in the concrete. Moreover, in this method of constructing a concrete structure, the diameter of the many through holes of the plate member used is 10 mm or less, and the center pitch of the many through holes is 20 mm or less. In this construction method, a plate-like member with many holes faces the concrete pouring surface through a curing sheet, but the many through-holes in the plate-like member used are smaller than the specified hole diameter and within the specified diameter. By setting the pitch to be less than or equal to the center pitch, it is possible to suppress the formation of unevenness due to the holes of the plate member being directly transferred to the surface of the poured concrete. Therefore, according to this construction method, it is possible to suppress the formation of unevenness and achieve a clean concrete surface, while also realizing early demolding of the formwork. In addition, the "adhesive force" here is measured by the following method. First, the curing sheet to be measured is cut into strips with a width of 3 cm and a length of 20 cm, and the strip-shaped curing sheet is attached to a formwork structure (plate-like member, etc.) using an adhesive or the like. Thereafter, the weight required to peel the curing sheet from the formwork structure is measured using a scale, and this is taken as the adhesive strength.

In addition, in this concrete structure construction method, a perforated plate member is used as the member to which the curing sheet is attached, so air pockets and wrinkles that occur in the curing sheet are removed by the lateral pressure of the poured concrete. It becomes possible to remove it naturally using the part (through hole). Therefore, according to this construction method, the transfer of wrinkles and the like formed on the curing sheet to the concrete surface is also suppressed, so that an even more beautiful concrete surface can be obtained. Furthermore, in this construction method, the individual adhesive strength in each adhesive area (area other than the through-holes) of the curing sheet can be maintained high, so it is possible to make it difficult for the curing sheet to peel off. Note that this construction method can be applied not only to construction methods for constructing large and medium-sized concrete structures such as bridges and dams, but also to construction methods for concrete structures such as precast concrete.

In the above method for constructing a concrete structure, it is preferable that the plate member has a porosity of 10% or more and 40% or less. By setting the porosity of the plate member to 40% or less, it is possible to further suppress irregularities formed on the concrete placement surface and make them less noticeable. On the other hand, when the plate member has a porosity of 10% or more, the curing sheet can be more reliably left in the concrete during demolding.

In the method for constructing a concrete structure described above, it is preferable that the diameter of the many through holes in the plate member is 5 mm or less, and the center pitch of the many through holes is 10 mm or less. In this case, the unevenness formed on the concrete placement surface can be further suppressed and made less noticeable (see FIGS. 9 and 10).

In the method for constructing a concrete structure described above, the demolding step may be performed at least 12 hours and within 24 hours after the completion of the pouring step. According to this construction method, even in the case of early demolding, the curing sheet can be reliably left on the concrete side, making it possible to achieve early demolding.

In the method for constructing a concrete structure described above, the formwork structure further includes a formwork for concrete pouring, and a preparatory step of pasting a curing sheet on the plate member fixed to the pouring surface of the formwork. Further, in the preparation step, it is preferable to remove air pockets remaining in the curing sheet attached to the plate-like member. In this case, wrinkles in the curing sheet caused by air pockets remaining in the curing sheet are further suppressed from being transferred to the poured concrete, making it possible to obtain an even more beautiful concrete surface.

In the method for constructing a concrete structure described above, the plate member is a punched metal, and the punched metal may be used as a formwork. It is also possible to use a construction method that uses a structure in which punched metal is fixed to a formwork such as plywood as a formwork structure, but by using punched metal as it is as formwork, the number of parts used can be reduced, and the number of man-hours and costs can be reduced. It can be further reduced. Note that the plate-like member may be punched metal, resin mold, or plywood. In the case of punched metal, rigidity can be easily ensured, and in the case of resin molds, the work can be reduced due to their light weight.

According to the present invention, early demolding of the formwork can be realized in a method of pouring concrete into a formwork structure to which a curing sheet is attached.

FIG. 1 is a flowchart showing a method for constructing a concrete structure according to this embodiment. FIG. 2 is a cross-sectional view showing the construction method shown in FIG. 1 in order. FIG. 3 is a cross-sectional view sequentially showing the construction method shown in FIG. 1 following FIG. 2. FIG. 4 is a plan view showing an example of punched metal used in the construction method shown in FIG. 1. FIG. 5 is an enlarged plan view of a part of the punched metal shown in FIG. 4. FIG. FIG. 6 is a schematic diagram showing the contact angle of the surface of the curing sheet to water used in the construction method shown in FIG. 1. FIG. 7 is a schematic perspective view for explaining the preparation process in the construction method shown in FIG. 1. FIG. 8 is a diagram showing a process chart for explaining early demolding in this construction method. FIG. 9 is an image showing an example of the pouring surface of a concrete specimen manufactured by this construction method (Example 1). FIG. 10 is an image showing another example of the pouring surface of the concrete specimen manufactured by this construction method (Example 2). FIG. 11 is an image showing a pouring surface of a concrete specimen manufactured by a construction method according to a comparative example.

Hereinafter, a method for constructing a concrete structure according to an embodiment of the present invention will be described with reference to the drawings. In the description, the same reference numerals may be used for the same elements or elements having the same function, and redundant description will be omitted.

FIG. 1 is a flowchart showing a method for constructing a concrete structure according to this embodiment. As shown in FIG. 1, the method for constructing a concrete structure according to the present embodiment includes a preparation step (step S1) in which a curing sheet is attached to a formwork for concrete pouring via punching metal, and a step in which the curing sheet is attached. an installation step (step S2) in which the molded formwork is installed, a pouring step (step S3) in which concrete is poured on the side of the formwork to which the curing sheet is attached, and the formwork is demolded after pouring the concrete. This method includes a demolding process (step S4) and a curing process (step S5) in which a curing sheet is left on the concrete surface to cure the concrete structure when the formwork is demolded.

Next, the method for constructing a concrete structure according to this embodiment will be described in more detail with reference to FIGS. 2 and 3. 2 and 3 are cross-sectional views sequentially showing the construction method shown in FIG. 1. First, as shown in FIG. 2(a), a formwork 10 for pouring concrete, punching metal 20, and curing sheet 30 are prepared. The formwork 10 for concrete pouring is a plywood formwork that has a pouring surface 10a and has a rectangular shape when viewed from above (when viewed from the right side to the left side in Fig. 2) (Fig. 7 ). The formwork 10 is composed of, for example, a wooden formwork, but may also be a steel formwork. The formwork 10 and the punching metal 20 constitute a formwork structure K1.

The punching metal 20 is a metal plate having a back surface 20a on the formwork 10 side and a surface 20b on the curing sheet 30 side, and has a rectangular shape when viewed from above. The punching metal has a thickness of, for example, about 2 mm to 5 mm. As shown in FIG. 4, the punching metal 20 is provided with a large number of through holes 20c that penetrate from the front surface 20b toward the back surface 20a. The through hole 20c is provided according to a predetermined rule. For example, the through holes 20c may be provided in a staggered pattern, or may be provided in a straight line (lattice pattern) both vertically and horizontally. In the example shown in FIGS. 4 and 5, the through holes 20c are provided in a staggered manner, and as shown in FIG. 5, the center of one through hole 20c and the center of two vertically adjacent through holes 20c are The connecting angle A may be 60 degrees or 45 degrees.

The hole diameter D of the through hole 20c of the punching metal is, for example, 10 mm or less, preferably 5 mm or less, and more preferably 3 mm or less. Further, the center pitch P of the through holes 20c of the punching metal 20 in the vertical and horizontal directions is 20 mm or less in any direction. The center pitch P of the through holes 20c is preferably 10 mm or less, more preferably 5 mm or less. The center pitch P here is the distance between the centers of adjacent through holes 20c. Further, the porosity of the punching metal 20 is preferably 40% or less, more preferably 35% or less or 30% or less. Note that the perforation ratio of the punching metal 20 is preferably 10% or more in consideration of the ability of the curing sheet 30 to remain in the poured concrete. The open area ratio here indicates the ratio (%) of the total area of the large number of through holes 20c in the planar direction to the total area of the punching metal 20 in the planar direction.

The curing sheet 30 is a non-water permeable resin sheet that has a back surface 30a on the punching metal 20 side and a casting surface 30b on the concrete placement side, and has a rectangular shape when viewed from above. The curing sheet has a thickness of, for example, about 0.02 mm to 2.0 mm. As the curing sheet 30, it is preferable to use a thermoplastic resin sheet. Examples of thermoplastic resins used here include olefin resins such as low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymers, and olefin thermoplastic elastomers; polyamide; polyethylene terephthalate; polycarbonate; polyvinyl chloride. , vinyl chloride resins such as chlorinated polyvinyl chloride and polyvinylidene chloride; fluorine resins, and the like. Note that as the curing sheet 30, it is preferable to use an olefin thermoplastic elastomer. The olefinic thermoplastic elastomer is an ethylene-propylene copolymer or a melt mixture or polymerization reaction product of polypropylene and ethylene-propylene rubber, such as "Prime TPO (registered trademark)" manufactured by Prime Polymer Co., Ltd., Nippon Polypro Co., Ltd. Examples include "Nucon (registered trademark)" manufactured by the company, "Cataroy" manufactured by Sun Allomer Co., Ltd., and "Zelas (registered trademark)" manufactured by Mitsubishi Chemical Corporation.

Although the curing sheet 30 is not particularly limited to this, a highly water-repellent sheet whose contact angle with water on the casting surface 30b (surface) on the concrete side of the curing sheet 30 is 50 degrees or more may be used. It is preferable to adopt it. Specifically, the contact angle θ of the surface of the curing sheet 30 with water is preferably 69 degrees or more, more preferably the contact angle θ is 80 degrees or more, and the contact angle θ is 90 degrees or more. It is even more preferable. Here, the "contact angle θ" is the angle between the tangent of the droplet and the solid surface (the surface of the curing sheet 30), as shown in FIG. 6(a), and is expressed by the following equation (1). It is indicated by.

γS: Surface tension of solid γL: Surface tension of liquid γSL: Interfacial tension between solid and liquid

The "contact angle θ" can be measured, for example, by the θ/2 method. Specifically, as shown in FIG. 6(b), the radius r and height h of the droplet are determined. Then, the contact angle θ can be determined from the following equations (2) and (3).

Subsequently, when the preparation shown in FIG. 2(a) is completed, the punching metal 20 is placed on the casting surface 10a of the formwork 10, and screws etc. The punching metal 20 is fixed to the formwork 10 by attachment means (not shown). The punching metal 20 has the same size in the planar direction as the casting surface 10a of the formwork 10, and the four corners of the punching metal 20 and predetermined locations along the long and short sides of the punching metal 20 are shaped using screws or the like. It is attached to the frame 10. As will be described later, once the punching metal 20 is attached to the formwork 10, the formwork 10 (also referred to as "formwork structure K1") to which the punching metal 20 is attached may be used repeatedly.

Subsequently, as shown in FIGS. 2(c) and 7, a curing sheet 30 is attached to the surface 20b of the punching metal 20 fixed to the casting surface 10a of the formwork 10 (also referred to as "formwork assembly K2"). To tell). An adhesive having a predetermined adhesive force is provided in advance at a predetermined thickness on the back surface 30a side of the curing sheet 30, and thereby the curing sheet 30 is attached to the punching metal 20. The curing sheet 30 is formed to be slightly smaller than, for example, the size of the punching metal 20 in the plane direction, and is coated with double-sided adhesive along the peripheral portions 30c to 30f where the periphery (four sides) of the punching metal 20 is exposed. Attach tape (not shown). Thereby, the edges (peripheral portions 30c to 30f) of the curing sheet 30 can be reliably attached to the punching metal 20 without peeling off. These double-sided adhesive tapes function as a leaving tape for leaving the curing sheet 30 on the concrete C side when demolding the formwork 10 and the like. Through the above preparation step S1, the formwork assembly K2 is assembled. Note that in the above explanation, one curing sheet 30 is attached to one formwork 10, but the invention is not limited to this, and a plurality of curing sheets 30 may be attached so that their edges overlap. It may be wrapped and attached to one or more formworks 10.

Subsequently, when the formwork assembly K2 is assembled, the formwork assembly K2 is installed at a predetermined location so that the curing sheet 30 of the formwork assembly K2 is located on the concrete pouring side (installation step S2). For example, when constructing a rectangular parallelepiped-shaped concrete structure, four formwork assemblies K2 are prepared, a pair of formwork assemblies K2 are arranged so as to face each other in the long side direction, and a pair of formwork assemblies K2 are arranged so as to face each other in the long side direction, and the short side direction perpendicular to the long side direction A pair of formwork assemblies K2 are arranged so as to face each other. At this time, the curing sheets 30 of each formwork assembly K2 are arranged so as to face inward (concrete pouring side) so as to face the curing sheet 30 of the opposing formwork assembly K2. As a result, all sides of the rectangular parallelepiped concrete are covered with the curing sheet 30 when it is poured.

Subsequently, when the installation of the formwork assembly K2 is completed, as shown in FIG. S3). After that, when the compaction of the concrete C is completed, the concrete C is cured for about 1 to 10 days, for example, for about 1 to 10 days, or about 1 to 3 days in the case of early demolding, with the formwork 10 still in place. Let it harden.

Subsequently, when the poured concrete C hardens, the formwork 10 to which the punching metal 20 is fixed is demolded together with the punching metal 20, as shown in FIG. 3(b) (demolding step S4). . At this time, although the curing sheet 30 is pasted to the punched metal 20, it is not pasted to the many through-holes 20c, so it can be easily removed from the punched metal 20 and placed on the concrete with double-sided adhesive tape. It is left on the C side. In addition, as early demolding, this demolding process S4 may be performed 12 hours or more and within 24 hours after the completion of the above-mentioned casting process S3. Even in this case, the curing sheet 30 can be reliably left in the concrete because the punching metal 20 is used with a hole diameter, hole area ratio, center pitch, etc. below a predetermined value.

Subsequently, when demolding of the formwork 10 is completed, as shown in FIG. 3(c), the hardened concrete structure Ca is cured as is with a curing sheet 30 (curing step S5). The curing using the curing sheet 30 may be continued for 28 days or more after the formwork 10 is removed from the mold, or may be continued for 91 days or more after the formwork 10 is removed from the mold. Furthermore, it is of course possible to continue curing until the concrete structure Ca is delivered (for example, one year or more after demolding). In this way, by continuing to cure the concrete for a long period of time without ever exposing it to the outside air, the strength and durability of the concrete structure Ca can be dramatically increased and its quality can be improved. When curing for a predetermined period is completed, the curing sheet 30 is removed from the concrete structure Ca and discarded, thereby completing the concrete structure Ca.

On the other hand, once the use of the formwork 10 is completed, the surface 20b on the pouring side is cleaned as a formwork structure K1 without removing the punching metal 20. Then, another curing sheet 30 is attached again using an adhesive or double-sided adhesive tape to obtain a structure similar to that of the formwork assembly K2, which can be used for another concrete pouring. In this case, cleaning and scraping of the casting surface 10a of the formwork 10 can be simplified, so that workability can be improved.

As described above, in the method for constructing a concrete structure according to the present embodiment, the curing sheet 30 is attached to the formwork 10 with the punched metal 20 having a large number of through holes 20c sandwiched therebetween. In this way, since the punching metal 20 having a large number of through holes 20c is provided between the curing sheet 30 and the formwork 10, the relationship between the curing sheet 30 and the formwork 10 (more specifically, the punching metal 20) is The contact area can be suitably reduced by the amount of the through hole 20c. As a result, the adhesion between the curing sheet 30 and the formwork 10 (punched metal 20) can be adjusted more easily than when adjusting the adhesion between the curing sheet and the formwork using adhesive alone. Even in the case of early demolding, in which the adhesive force between the curing sheet 30 and the formwork 10 needs to be suppressed to a low value of 50 g or less, the curing sheet 30 can be reliably left in the concrete.

Moreover, in this concrete structure construction method, the hole diameter D of the many through holes 20c of the punching metal 20 used is set to 10 mm or less, and the center pitch P of the many through holes is set to 20 mm or less. In this construction method, the punching metal 20 having a large number of through holes 20c faces the concrete placement surface through the curing sheet 30, but the punching metal 20 used has a large number of through holes 20c with a diameter smaller than a predetermined hole diameter. By setting the pitch to be larger than the predetermined center pitch or less, it is possible to prevent the holes of the punched metal 20 from being directly transferred to the surface of the concrete that has been placed, thereby preventing the formation of irregularities. Therefore, according to this construction method, it is possible to suppress the formation of unevenness and achieve a clean concrete surface, while also realizing early demolding of the formwork. The "adhesion between the curing sheet and the formwork structure" referred to herein is measured by the following method. First, a curing sheet to be measured is cut into strips with a width of 3 cm and a length of 20 cm, and the strip-shaped curing sheet is attached to a formwork structure (punched metal 20) using an adhesive or the like. Thereafter, the weight required to peel the curing sheet from the formwork structure is measured using a scale, and this is taken as the adhesive strength.

In addition, since the punching metal 20 is used between the formwork 10 and the curing sheet 30, the air pockets and wrinkles that occur in the curing sheet 30 are removed by the lateral pressure of the poured concrete. can be removed naturally (by its own weight). Therefore, according to this construction method, the transfer of wrinkles and the like formed on the curing sheet 30 to the concrete surface is also suppressed, so that the concrete surface can be made even more beautiful.

In the method for constructing a concrete structure according to the present embodiment, the perforation ratio of the punched metal 20 may be 10% or more and 40% or less. When the perforation ratio of the punching metal 20 is 40% or less, the unevenness formed on the concrete C placement surface can be further suppressed and made less noticeable. On the other hand, since the perforation ratio of the punching metal 20 is 10% or more, the curing sheet 30 can be left in the concrete C more reliably during demolding.

In the method for constructing a concrete structure according to the present embodiment, the hole diameter D of the many through holes 20c of the punching metal 20 may be 5 mm or less, and the center pitch P of the many through holes 20c may be 10 mm or less. . In this case, the unevenness formed on the concrete C placement surface can be further suppressed and made less noticeable.

The method for constructing a concrete structure according to the present embodiment further includes a preparation step S1 of pasting a curing sheet 30 on the punching metal 20 fixed to the casting surface 10a of the formwork 10, and this preparation step S1 In this case, air pockets remaining in the curing sheet 30 attached to the punching metal 20 may be removed. In this case, wrinkles in the curing sheet 30 caused by air pockets remaining in the curing sheet 30 are further suppressed from being transferred to the poured concrete, making it possible to obtain an even more beautiful concrete surface.

In the method for constructing a concrete structure according to the present embodiment, the demolding step S4 may be performed at least 12 hours and within 24 hours after the completion of the pouring step S3. According to this construction method, it is possible to realize such early demolding. Note that the demolding step S4 may be performed within 22 hours, within 20 hours, or within 18 hours from the end of the casting step S3.

Here, early demolding by the above-mentioned construction method will be further explained with reference to FIG. 8. As shown in Figure 8(b), in normal concrete construction, after assembling the formwork and pouring concrete, the compressive strength of the concrete required for removing the formwork and shoring (for example, 5 N/mm ² ), and after that, the formwork could not be removed due to the need to continue moist curing (for example, 3 to 12 days, depending on the average temperature, concrete material, etc.) Treatment is often continued. For this reason, with conventional construction methods, it may take eight days, for example, to form one concrete body. Furthermore, after demolding the formwork, it is necessary to clean and scrub the formwork.

On the other hand, as shown in Figure 8(a), this method uses the same method as the assembly of the formwork and the pouring of concrete, but the curing sheet can be left in the formwork as it is, so Even without a frame, so-called wet curing can be performed using this curing sheet. Therefore, in this construction method, the formwork can be quickly removed after the compressive strength of the concrete reaches the level required for removing the formwork and shoring (for example, 5 N/mm ² for the side surface of the column). Furthermore, as described above, since the punching metal 20 is used, the curing sheet 30 can be reliably left on the concrete. As described above, according to this construction method, demolding can be performed immediately after pouring (for example, within one day), and for example, it takes about 3.5 days to form one concrete body. In other words, it is possible to construct concrete structures at more than twice the pace compared to conventional construction methods. Furthermore, with this construction method, the curing sheet is attached to the formwork in advance, making it difficult for slag stains to stick to it, thereby reducing the time required for cleaning.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments and can be applied to various embodiments. For example, in the embodiment described above, the punching metal 20 is used as the plate-like member having a large number of through holes, but a resin formwork or plywood (wooden formwork, etc.) plate having the same hole configuration as the punching metal 20 A shaped member may also be used. When using a resin formwork, the work can be reduced because it is lightweight. Further, in the embodiment described above, the formwork structure K1 in which the punching metal 20 is fixed to the formwork 10 is used, but since the punching metal 20 is made of metal and has rigidity, the punching metal 20 has the function of the formwork 10. You may also have it played. That is, the above construction method may be performed without using the formwork 10 and forming the formwork structure K1 made of only the punched metal 20. In this way, when the punching metal 20 is used as the formwork 10 as it is, the number of members can be reduced and the number of man-hours and costs can be further reduced. In addition, as the formwork 10, a formwork such as a center may be used. Further, for example, the method for manufacturing a concrete structure described above can be applied not only to a construction method for constructing large concrete structures such as bridges and dams, but also to precast concrete.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples.

First, as Example 1, four wooden forms, four punched metal sheets, and four curing sheets were prepared. The dimensions of each wooden formwork were 900 mm x 1800 mm x 10 mm. The dimensions of each punched metal were 900 mm x 1800 mm x 2 mm. The punching metal used had through holes arranged in a staggered manner, a hole diameter D of 5 mm, a center pitch P of 10 mm, and an open area ratio of 22.6%. The dimensions of the curing sheet are 880 mm x 1800 mm x 0.2 mm, and it is made of polypropylene and is a "Beautiful Sheet" (trade name of Kajima Corporation and Sekisui Molding Industry Co., Ltd. (registered trademark of Kajima Corporation)). ” resin sheet was used.

Next, as shown in FIG. 7, a punching metal and a curing sheet were attached to each wooden formwork in this order (the punching metal was fixed to the formwork with screws) to form four sets of formwork assemblies. Then, the formwork assembly was installed at a predetermined position so that a rectangular parallelepiped-shaped concrete specimen could be formed.

Thereafter, a concrete material obtained by mixing the concrete materials listed in Table 1 below in the proportions shown in Table 2 is poured into the formwork, and after the concrete has solidified, the formwork is removed and the concrete is prepared. A specimen (equivalent to a concrete structure) was obtained.

As Example 2, a concrete specimen was obtained with the same configuration and conditions as in Example 1, except that the configuration of the punching metal used was changed. In the punching metal used in Example 2, the through holes were arranged in a staggered manner, the hole diameter D was 3 mm, the center pitch P was 5 mm, and the open area ratio was 32.6%.

As a comparative example, a concrete specimen was obtained with the same configuration and conditions as in Example 1, except that the configuration of the punching metal used was changed. In the punched metal used in the comparative example, the through holes were arranged in a staggered manner, the hole diameter D was 20 mm, the center pitch P was 30 mm, and the open area ratio was 40.3%.

In all of the construction methods using punched metal according to Example 1, Example 2, and Comparative Example, although the strength of the concrete was about 5 N/ ^mm2 (21 hours after pouring), the mold was demolded. Therefore, the curing sheet was securely left on the concrete using double-sided adhesive tape. In other words, it was confirmed that early demolding could be performed.

Further, concrete surfaces of concrete specimens obtained by the method using punched metal according to Example 1, Example 2, and Comparative Example are shown in FIGS. 9 to 11. As shown in Figure 11, in the method using punched metal in the comparative example, traces of the through holes of the punched metal were clearly formed on the surface of the manufactured concrete specimen, and the unevenness was easily formed. It was in a state where it was possible to recognize it. On the other hand, in the construction method using punched metal having the configurations shown in Examples 1 and 2, there are no traces of the through holes of the punched metal left on the surface of the manufactured concrete specimen, and moreover, the unevenness is easy to touch. The unevenness was slightly noticeable (Example 1), or the unevenness was not noticeable even by touch (Example 2). In other words, by setting the hole diameter of the punching metal to 10 mm or less and the center pitch of the holes to 20 mm or less, more preferably, by setting the hole diameter to 5 mm or less and the center pitch of the holes to 10 mm or less, the unevenness can be improved. It was confirmed that it was possible to achieve early demolding of the formwork while suppressing the formation of concrete and creating a clean concrete surface.

10... Formwork, 10a... Casting surface, 20... Punching metal, 20a... Back surface, 20b... Front surface, 20c... Through hole, 30... Curing sheet, 30a... Back surface, 30b... Casting surface, 30c to 30f... Circumferential portion , A... Angle, C... Concrete, Ca... Concrete structure, D... Hole diameter, K1... Formwork structure, K2... Formwork assembly, P... Center pitch.

Claims (6)

A formwork structure including a plate member having a large number of through holes and a formwork for concrete pouring, and a formwork assembly including an impermeable curing sheet and the curing sheet attached to the plate member. an installation step of installing the formwork assembly at a predetermined location so that the curing sheet is located on the concrete pouring side;
a placing step of placing concrete so that the concrete is in contact with the curing sheet of the formwork assembly;
a demolding step of demolding at least a part of the formwork structure after pouring the concrete;
a curing step of leaving the curing sheet on the surface of the concrete after the demolding step and curing the concrete for a predetermined period,
The plurality of through holes of the plate-like member penetrate the plate-like member from the front surface of the plate-like member toward the opposite back surface,
The hole diameter of the large number of through holes of the plate member is 10 mm or less, and the center pitch of the large number of through holes is 20 mm or less,
In the formwork assembly, the plurality of through holes are in contact with the formwork on the front side and in contact with the curing sheet on the back side,
A method for constructing a concrete structure, wherein the demolding step is performed within 24 hours after the completion of the pouring step . The method for constructing a concrete structure according to claim 1, wherein the plate member has a porosity of 10% or more and 40% or less. The method for constructing a concrete structure according to claim 1 or 2, wherein the diameter of the many through holes of the plate member is 5 mm or less, and the center pitch of the many through holes is 10 mm or less. The demolding step is performed 12 hours or more after the completion of the casting step.
A method for constructing a concrete structure according to any one of claims 1 to 3. It further comprises a preparation step of pasting the curing sheet on the plate - like member fixed to the casting surface of the formwork, and in the preparation step, the curing sheet is pasted on the plate-like member. The method for constructing a concrete structure according to any one of claims 1 to 4, comprising removing residual air pockets. The method for constructing a concrete structure according to any one of claims 1 to 5, wherein the plate member is punched metal, resin formwork, or plywood.

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