JP2021186998A - Method for producing precast concrete member, and precast concrete member - Google Patents

Abstract

To provide a method for producing a precast concrete member, when a precast concrete member is formed by spraying concrete, capable of easily securing the smoothness of the member surface.SOLUTION: A method for producing a precast concrete member having a cavity at the central part of the cross-section comprises a mounting step S2 where a reinforcing cage composed of a main reinforcement and a shear reinforcement is mounted on the upper face of a bottom plate, a concrete spray step S4 where concrete is sprayed to a partition material arranged so as to be stored at the inside of a reinforcing cage from the outside of the reinforcing cage to form an open cross-section concrete layer in which the face of the bottom plate side is released and a leveling step S5 where the surface of the concrete layer is leveled. In the mounting step S2, the reinforcing cage is mounted in such a manner that the main reinforcement is made parallel to the plate face of the bottom plate. Further, the partition material is arranged in such a manner that the bottom plate side is opened.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for manufacturing a precast concrete member and a precast concrete member.

When constructing concrete structures, the precast method may be used to shorten the construction period. The precast method is a cast-in-place method that requires on-site formwork installation, concrete placement and curing, and formwork demolding because the construction is completed simply by arranging and fixing the precast members in place. In comparison, it is easier to work in the field. Further, in the half precast method in which a part of the cross section is precast, in addition to reducing the amount of concrete placed at the site, it is possible to omit or reduce the formwork, support member and the like.
Precast members are generally formed by placing concrete in a formwork in a factory, a manufacturing yard, or the like. Therefore, it took time and effort to assemble the formwork, compact the concrete, and remove the formwork. As a method different from the general method for manufacturing a precast member, a concrete member may be formed by sprayed concrete that develops a predetermined strength at an early stage. For example, Patent Document 1 discloses a method for manufacturing a concrete product that forms a molded body by spraying concrete on a molding die surface to a predetermined thickness.
However, the method for manufacturing a concrete product in Patent Document 1 is to manufacture the concrete product in an upright state by a spraying method, and since concrete is sprayed over the entire outer peripheral surface of the tubular member, the concrete product is manufactured in a horizontally placed state. There is no idea of doing it. Further, a method of manufacturing a concrete product using a centrifugal molding device in a factory or the like is also disclosed, but it is not adopted for manufacturing in a construction site because a special device is required.
Further, in Patent Document 2, a beam having a U-shaped cross section is formed by spraying concrete from below on a grid-like connecting material (net material) bound to the outside of a reinforcing material to a predetermined thickness. The method of constructing the skeleton to be constructed is disclosed.
However, the skeleton construction method of Patent Document 2 is to construct the skeleton itself by spraying, and does not show the construction method of the precast member. In addition, it is necessary to maintain the beam and slab in a state of being supported by the support work until a predetermined strength is developed so that the beam and the slab do not bend after being placed at the site. Even in the skeleton construction method of Patent Document 2, it is necessary to provide a support in advance so that the beams and slabs do not bend after spraying. I can't.

Special Publication No. 60-30244 Japanese Unexamined Patent Publication No. 2018-193794

An object of the present invention is to propose a method for manufacturing a precast concrete member, which enables a precast concrete member having a cavity in a cross section to be manufactured horizontally in a construction site by spraying concrete, and further. The challenge is to propose precast concrete members that can be manufactured in a short period of time and at low cost compared to the conventional construction method.

The method for manufacturing a precast concrete member of the present invention for solving the above problems is to manufacture a precast concrete member having a cavity in the center of a cross section at a construction site, and is a reinforcing bar cage composed of a main bar and a shear reinforcing bar. Was placed on the upper surface of the bottom plate, and concrete was sprayed from the outside of the reinforcing bar cage onto the partition material arranged so as to fit inside the reinforcing bar cage, and the surface on the bottom plate side was released. It includes a spraying step of forming a concrete layer having an open cross section and a leveling step of leveling the surface of the concrete layer. In the pre-described step, the reinforcing bar cage is placed horizontally so that the main bar is parallel to the plate surface of the bottom plate, and the partition material has a substantially U-shaped cross section (for example, U-shaped, V-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, U-shaped, Arrange in a character shape, a C shape, etc.) so that the bottom plate side is open (so as to be substantially n-shaped). The "bottom plate" is a plate material provided at a place where a precast concrete member is manufactured.
According to the method for manufacturing a precast concrete member, since the precast concrete member is formed by spraying concrete, a precast concrete member having a cavity in the center of a cross section can be easily manufactured in a construction site without requiring a large formwork or the like. Moreover, it can be manufactured at an early stage. Further, since the main bar is laid horizontally and manufactured horizontally, even when a long member such as a column or a beam is manufactured, a large-scale scaffolding or a support member is not required. That is, according to the method for manufacturing a precast concrete member of the present invention, it is possible to omit or reduce the labor and cost required for installing and removing formwork, scaffolding, support members, etc., which is shorter and cheaper than the conventional method. Precast concrete members can be manufactured.

In the spraying step, it is desirable to spray concrete in a state where a pair of stoppers parallel to the main bar are arranged below the reinforcing bar cage. By doing so, a concrete layer having an open cross section can be formed. Further, in the leveling step, it is desirable to level the surface of the concrete layer by moving the scraper along a guide installed in parallel with the finished surface of the concrete layer. By doing so, the surface of the concrete layer can be easily smoothed.
Further, the method for manufacturing the precast concrete member may further include a second spraying step of spraying concrete downward from a nozzle inserted into the space inside the partition material. In the second spraying step, concrete is sprayed with the stopper removed to close the concrete layer having an open cross section formed in the spraying step to form a closed cross section. By doing so, it becomes possible to manufacture a tubular member with the main bar tilted sideways. When manufacturing a tubular member with the main bar upright, it is necessary to install scaffolding and support members, but when manufacturing a tubular member with the main bar laid down sideways, the scaffolding and support member can be manufactured. Since it can be reduced or omitted, the precast concrete member can be manufactured easily and inexpensively.

The precast concrete member of the present invention has a cavity in the center of the cross section, and a partition material for forming the cavity is left inside, and the reinforcing bar cage placed on the bottom plate has a cavity. From the outside, a concrete layer made of concrete sprayed on the partition material is formed. According to such a precast concrete member, it can be easily manufactured by spraying sprayed concrete toward a partition material. Further, since the partition material made of wire mesh is provided, the bondability on the joint surface is improved when concrete is poured inside.

According to the method for manufacturing a precast concrete member of the present invention, the precast concrete member can be manufactured horizontally in a construction site by spraying concrete. Further, the precast concrete member of the present invention can be manufactured in a short time and at low cost as compared with the conventional method.

It is a perspective view which shows the beam which concerns on 1st Embodiment. It is a flowchart which shows the manufacturing method of the precast concrete member of 1st Embodiment. It is a figure which shows each process of the manufacturing method of the precast concrete member of 1st Embodiment, (a) is a perspective view of an assembly process, (b) is a perspective view of a partition process, (c) is a front view of a spraying process. Is. (A) is a perspective view which shows the leveling process of the manufacturing method of the precast concrete member of 1st Embodiment, and (b) is a perspective view which shows the precast concrete member. It is a perspective view which shows the pillar of the 2nd Embodiment. It is a flowchart which shows the manufacturing method of the precast concrete member of 2nd Embodiment. It is a figure which shows each process of the manufacturing method of the precast concrete member of 2nd Embodiment, (a) is a perspective view of an assembly process, (b) is a perspective view of a partition process, (c) is a front view of a spraying process. Is. It is a figure which shows each process of the manufacturing method of the precast concrete member which follows | It is a perspective view. It is a figure which shows the precast concrete member of the 2nd Embodiment, (a) is a perspective view, (b) is a plan view.

<First Embodiment>
In the first embodiment, a manufacturing method for manufacturing the precast concrete member 1 in the construction site, which is used when the beam B is formed by the half precast method, will be described. FIG. 1 is a perspective view of a beam B formed by a half precast method.
As shown in FIG. 1, the beam B is formed by a precast concrete member 1 having a U-shaped cross section having a cavity in the center and cast-in-place concrete 2 cast inside and on the upper surface of the precast concrete member 1. ing. The precast concrete member 1 is a so-called half precast member.
FIG. 2 shows a flowchart of a method for manufacturing the precast concrete member 1. As shown in FIG. 2, the method for manufacturing the precast concrete member 1 includes an assembly process S1, a mounting process S2, a partitioning process S3, a spraying process S4, and a leveling process S5.

The assembly step S1 is a step of assembling the reinforcing bar basket 3. FIG. 3A shows the assembly process S1. As shown in FIG. 3A, the reinforcing bar cage 3 of the present embodiment has a main bar 31 arranged along the axial direction of the beam B and a stirrups (shear reinforcing bar) intersecting (orthogonal) with the main bar 31. It is formed by assembling with 32. The stirrups 32 of this embodiment have a phylum shape. J-shaped hooks are formed at both ends of the stirrups 32 by bending the tips inward. The shape of the stirrups 32 may be appropriately determined according to the cross-sectional shape of the beam B. Further, the shape of the end portion of the stirrups 32 is not limited, and may be, for example, a hook shape.

The mounting step S2 is a step of mounting the reinforcing bar cage 3 on the upper surface of the bottom plate S as shown in FIG. 3A. The reinforcing bar basket 3 is placed on the bottom plate S via the spacer 5 so that the end portion of the stirrups 32 is on the lower side. The reinforcing bar basket 3 is placed so that the main reinforcing bar 31 is parallel to the plate surface of the bottom plate S. In the mounting step S2, the cover thickness control spacer 51 is attached to the side surface and the upper surface of the reinforcing bar cage 3. The cover thickness management spacer 51 has a height equivalent to the cover thickness required for the reinforcing bar cage 3. Here, the "bottom plate S" in the present specification is a flat plate installed at a place where the precast concrete member 1 is manufactured.

FIG. 3B shows the partition step S3. As shown in FIG. 3B, the partition step S3 is a step of arranging the partition member 4 along the inner surface of the reinforcing bar cage 3. The partition material 4 of the present embodiment is made of a corrugated sheet. The partition member 4 has a substantially U-shape, and is arranged in an n-shape so that the bottom plate S side opens. The partition member 4 is detachably attached to the reinforcing bar basket 3. The structure for attaching the partition member 4 to the reinforcing bar cage 3 is not limited, and may be fixed via bolts or may be locked to a hook-shaped locking member, for example. A release agent (release agent) may be applied to the surface of the partition material 4 (the surface in contact with concrete).

FIG. 3C shows the spraying step S4. The spraying step S4 is a step of forming the concrete layer 6 as shown in FIG. 3C. The concrete layer 6 is formed by spraying concrete on the partition material 4 from the outside of the reinforcing bar cage 3. The concrete is sprayed until the cover thickness control spacer 51 (see FIG. 3B) is filled so that the reinforcing bar cage 3 can secure a predetermined cover thickness. In addition, concrete shall be sprayed on the lower sides of both ends of the reinforcing bar cage 3. That is, concrete is also sprayed on the gap between the bottom plate S and the reinforcing bar cage 3. Before spraying concrete on the lower sides of both ends of the reinforcing bar cage 3, a pair of stoppers 7 and 7 parallel to the main reinforcing bar 31 are arranged below the reinforcing bar cage 3 at intervals (FIG. 3 (c)). reference). The stopper 7 has, for example, a prismatic wood having a length equal to or longer than the length of the reinforcing bar cage 3 (the length of the main bar 31) and a height equal to or higher than the spacer 5 (required cover thickness) (for example, the length of the reinforcing bar 31). You can use the pier). In the present embodiment, the stopper 7 is arranged inside the both ends of the reinforcing bar cage 3. When spraying concrete on the lower side of the reinforcing bar cage 3, the concrete is sprayed from the outside of the reinforcing bar cage 3 toward the stopper 7. The stopper 7 prevents concrete from entering the lower part of the reinforcing bar cage 3, and the concrete layer 6 has an open cross section with the lower surface open (the bottom plate S side is released). The timing of arranging the stopper 7 is not limited as long as it is before the concrete is sprayed, and for example, the stopper 7 may be arranged in the mounting step S2 or the partitioning step S3.

FIG. 4A shows the leveling step S5. The leveling step S5 is a step of leveling (flattening) the surface of the concrete layer 6 as shown in FIG. 4A. In the leveling step S5, first, the guide 8 is installed around the reinforcing bar cage 3 sprayed with concrete. The guide 8 is installed in parallel with the main bar 31 (finished surface of the concrete layer 6). In the present embodiment, the guide 8 is arranged along the corners and the lower ends of the reinforcing bar cage 3 sprayed with concrete. That is, the upper and lower two-stage guides 8 are arranged on the left and right sides of the reinforcing bar cage 3. The guide 8 is supported by a bottom plate S or a support column 81 erected on a work surface (for example, a floor surface) on which the bottom plate S is installed. The guide 8 is arranged with a predetermined distance from the reinforcing bar cage 3. In the present embodiment, the distance between the reinforcing bar cage 3 and the guide 8 is the total value of the cover thickness and the scraper 9. That is, the guide 8 is arranged at a position spaced from the finished surface of the concrete layer 6 by the thickness of the scraper 9. After installing the guide 8 in a predetermined position, the scraper 9 is moved along the guide 8 to scrape off excess concrete to level the surface of the concrete layer 6. The scraper 9 is moved along the upper surface and the side surface of the reinforcing bar cage 3 (precast concrete member 1) sprayed with concrete.

After the surface of the concrete layer 6 is leveled and the concrete is cured, the partition member 4 is removed to complete the precast concrete member 1 having a U-shaped cross section. FIG. 4B shows the precast concrete member 1. As shown in FIG. 4B, the precast concrete member 1 of the present embodiment has corrugated irregularities formed on the inner surface, and therefore has high bondability with the cast-in-place concrete 2.
Further, according to the method for manufacturing the precast concrete member 1 of the present embodiment, the surface of the concrete can be easily smoothed by moving the scraper 9 along the guide 8.
Further, since the precast concrete member 1 is formed by spraying concrete, it can be manufactured easily and at an early stage without requiring a large-scale formwork or the like. Since only the partition member 4 of the core portion is arranged as the formwork, it is possible to reduce the trouble of installing and removing the formwork.
In addition, since it is manufactured with the main bar 31 lying down, it does not require a large-scale scaffolding or support member, and it is possible to omit or reduce the labor and cost required for installing and removing the formwork, scaffolding, support member, etc. It will be possible.
Further, since no special device other than the spraying machine is required, the precast concrete member 1 can be manufactured in a relatively small space, and by extension, it can be carried out on the site of the site.

<Second embodiment>
In the second embodiment, a method for manufacturing the precast concrete member 1 used in the case of forming the pillar P by the half precast method will be described. FIG. 5 is a perspective view of the pillar P formed by the half precast method. As shown in FIG. 5, the pillar P is formed of a square tubular precast concrete member 1 having a cavity in the center and a cast-in-place concrete 2 cast inside the precast concrete member 1.
FIG. 6 shows a flowchart of a method for manufacturing the precast concrete member 1 of the second embodiment. As shown in FIG. 6, the method for manufacturing the precast concrete member 1 includes an assembly process S1, a mounting process S2, a partitioning process S3, a first spraying process S4, a leveling process S5, and a second spraying process S6.

FIG. 7A shows the assembly process S1. The assembly step S1 is a step of assembling the reinforcing bar basket 3. As shown in FIG. 7A, the reinforcing bar cage 3 of the present embodiment has a main bar 31 arranged along the axial direction of the beam B and a band bar (shear reinforcing bar) intersecting (orthogonal) with the main bar 31. It is formed by assembling with 33. The reinforcing bar cage 3 of the present embodiment has a square cylinder shape, and the band bar 33 has a frame shape. The shape of the band 33 is not limited, and may be, for example, an annular shape.

The mounting step S2 is a step of mounting the reinforcing bar basket 3 on the bottom plate S as shown in FIG. 7A. The reinforcing bar cage 3 is placed on the bottom plate S via the spacer 5 so that the main reinforcing bar 31 is parallel to the plate surface of the bottom plate S. Further, in the mounting step S2, the cover thickness control spacer 51 is attached to the side surface and the upper surface of the reinforcing bar cage 3. The cover thickness management spacer 51 has a height equivalent to the cover thickness required for the reinforcing bar cage 3.

FIG. 7B shows the partition step S3. As shown in FIG. 7B, the partitioning step S3 is a step of arranging the partitioning material 4 along the inner surface of the reinforcing bar cage 3. The partition material 4 of the present embodiment is made of a wire mesh having a length equivalent to that of the reinforcing bar cage 3 and having a width equivalent to the peripheral length of three of the four inner side surfaces of the reinforcing bar cage 3. It is desirable that the wire mesh constituting the partition material 4 has a mesh smaller than that of the aggregate of the concrete (sprayed concrete) to be sprayed in the first spraying step S4. The partition member 4 has three surfaces (upper surface and both side surfaces) other than the lower surface of the four inner surfaces of the reinforcing bar cage 3 so that the lower surface (bottom plate S side) opens (so as to form an n-shape). To fix.

FIG. 7C shows the first spraying step S4. The spraying step S4 is a step of forming the concrete layer 6 as shown in FIG. 7 (c). The concrete layer 6 is formed by spraying concrete on the partition material 4 from the outside of the reinforcing bar cage 3. The concrete is sprayed until the cover thickness control spacer 51 is filled so that the reinforcing bar cage 3 can secure a predetermined cover thickness. In addition, concrete shall be sprayed on the underside of the reinforcing bar cage 3. That is, concrete is also sprayed on the gap between the bottom plate S and the reinforcing bar cage 3. A pair of stoppers 7 and 7 parallel to the main bar 31 are arranged below the reinforcing bar car 3 at intervals, and the concrete sprayed on the lower side of the reinforcing bar car 3 is applied to the stopper 7 from the outside of the reinforcing bar car 3. Blow towards. By doing so, a concrete layer 6 having an open cross section made of sprayed concrete having an open lower surface (an opening 61 is formed) is formed on the outside of the partition member 4. The stopper 7 is, for example, a prismatic wood having a length equal to or longer than the length of the reinforcing bar cage 3 (the length of the main bar 31) and a height equal to or higher than the spacer 5 (required cover thickness). For example, a crosspiece) may be used. Further, the timing of arranging the stopper 7 is not limited as long as it is before the concrete is sprayed, and for example, the stopper 7 may be arranged in the mounting step S2 or the partitioning step S3.

FIG. 8A shows the leveling step S5. The leveling step S5 is a step of leveling the surface of the concrete layer 6 as shown in FIG. 8A. In the leveling step S5, first, the guide 8 is installed around the reinforcing bar cage 3 sprayed with concrete. Since the details of the guide 8 are the same as those shown in the first embodiment, detailed description thereof will be omitted. After the guide 8 is installed at a predetermined position, the scraper 9 is moved along the guide 8 to scrape off excess concrete to level the surface of the concrete layer 6. The scraper 9 is moved along the upper surface and the side surface of the reinforcing bar cage 3 (precast concrete member 1) sprayed with concrete.

8 (b) and 8 (c) show the second spraying step S6. In the second spraying step S6, the concrete layer 6 having an open cross section formed in the first spraying step S4 is closed to form the concrete layer 6 having a closed cross section. The second spraying step S6 is performed after the surface-leveled concrete layer 6 is cured and the stopper 7 is removed as shown in FIG. 8 (b). After the stopper 7 is removed, as shown in FIG. 8C, concrete is sprayed downward from the nozzle N inserted into the space inside the partition member 4, so that the opening 61 of the concrete layer 6 is seconded. It is closed by sprayed concrete 62. By doing so, the precast concrete member 1 having a cavity in the center of the cross section is manufactured. A partition member 4 is left inside (inner surface) of the precast concrete member 1.

Since the precast concrete member 1 of the present embodiment is provided with a wire mesh (partition material 4) on the inner surface, the precast concrete member 1 has high bondability with the cast-in-place concrete 2.
Further, according to the method for manufacturing the precast concrete member 1 of the present embodiment, the partition material 4 made of wire mesh is used as a side formwork and does not need to be removed, so that the labor of demolding can be omitted.
Since the operation and effect of the method for manufacturing the precast concrete member 1 of the second embodiment is the same as that shown in the first embodiment, detailed description thereof will be omitted.

Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-mentioned components can be appropriately changed without departing from the spirit of the present invention.
For example, in the first embodiment, a corrugated sheet is used as the partition material 4, and in the second embodiment, a wire mesh is used as the partition material 4, but the material constituting the partition material 4 is not limited to the corrugated sheet. However, it may be, for example, a flat plate or a sheet.
Further, the timing of installing the partition member 4 may be before or after the reinforcing bar basket 3 is placed on the bottom plate S. That is, the mounting step S2 may be performed after the assembly step S1 or after the partitioning step S3.
Further, in the above-described embodiment, the case where the partition material 4 is detachably provided on the inner surface of the reinforcing bar cage 3 or fixed to the inner surface of the reinforcing bar cage 3 in the partitioning step S3 has been described. It suffices to be arranged so as to fit inside, and it is not always necessary to attach it to the reinforcing bar basket 3. For example, a substantially U-shaped partition member 4 may be provided in the space inside the reinforcing bar car 3 with a gap from the inner surface of the reinforcing bar car 3.
Further, in the above embodiment, the reinforcing bar cage 3 is assembled and then placed on the spacer 5, but the reinforcing bar may be assembled on the spacer 5. That is, the assembly step S1 and the mounting step S2 may be performed at the same time.
In the above embodiment, the scraper 9 is used to smooth the surface of the upper surface of the precast concrete member 1, but the upper surface of the precast concrete member 1 may be finished with a trowel.

1 Precast concrete member 2 Cast-in-place concrete 3 Reinforcing bar cage 31 Main bar 32 Stirrup bar (shear reinforcing bar)
33 band reinforcement (shear reinforcement)
4 Partition material 5 Spacer 6 Concrete layer 7 Stopper 8 Guide 9 Scraper B Beam N Nozzle P Pillar S Bottom plate S1 Assembly process S2 Mounting process S3 Partition process S4 Spraying process (first spraying process)
S5 leveling process S6 second spraying process

Claims (4)

It is a manufacturing method of a precast concrete member that manufactures a precast concrete member having a cavity in the center of a cross section at a construction site.
A mounting process in which a reinforcing bar cage consisting of a main bar and a shear reinforcing bar is placed on the upper surface of the bottom plate,
A spraying step of spraying concrete from the outside of the reinforcing bar cage onto the partition material arranged so as to fit inside the reinforcing bar cage to form a concrete layer having an open cross section with the surface on the bottom plate side open.
The concrete layer is provided with a leveling step of leveling the surface of the concrete layer.
In the pre-described step, the reinforcing bar cage is placed horizontally so that the main bar is parallel to the plate surface of the bottom plate.
A method for manufacturing a precast concrete member, wherein the partition material has a substantially U-shaped cross section and is arranged so that the bottom plate side is open. In the spraying step, concrete is sprayed in a state where a pair of stoppers parallel to the main bar are arranged below the reinforcing bar cage.
The precast according to claim 1, wherein in the leveling step, the surface of the concrete layer is leveled by moving the scraper along a guide installed in parallel with the finished surface of the concrete layer. Manufacturing method of concrete members. It is further equipped with a second spraying process in which concrete is sprayed downward from a nozzle inserted into the space inside the partition material.
2. The second aspect of the present invention is described in claim 2, wherein concrete is sprayed with the stopper removed to close the concrete layer having an open cross section formed in the spraying step to form a closed cross section. How to manufacture precast concrete members. A precast concrete member having a cavity in the center of the cross section.
A partition material for forming the cavity is left inside,
A precast concrete member, characterized in that a concrete layer made of concrete sprayed on the partition material is formed from the outside of a reinforcing bar cage placed on a bottom plate.

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