JP3830484B2 - Formwork and method for producing concrete structure - Google Patents

Description

The present invention relates to a mold used when a concrete structure is manufactured by filling a cement-based mixed material into a mold and a method for manufacturing a concrete structure using the mold.

The fiber-reinforced cement-based mixed material, which is one of the cement-based mixed materials, is designed by blending cement, silica fume, pozzolanic reactive particles, sand, etc. based on the closest packing theory, so the water / cement ratio is 20 to In order to avoid separation resistance from fibers that are very small as 22% and mixed in a large amount, high separation resistance is retained. Therefore, when kneading a fiber-reinforced cement-based mixed material, a large amount of entrapped air, that is, the bubble diameter naturally formed during kneading is large and irregular, so it does not contribute to the improvement of workability, rather This leads to a decrease in compressive strength. In addition, even after completion of the kneading, these entrapped air remains. Therefore, after the fiber reinforced cementitious mixed material is placed in the mold, the air remaining inside the material rises during the primary curing (36 to 48 hours at 20 to 30 ° C.). Then, it remains on the lower surface of the mold, and after removing the mold, surface bubbles tend to remain on the surface of the member in a crater shape.

In addition, since fiber-reinforced cementitious mixed materials contain a large amount of cement and silica fume, condensation starts due to the hydration reaction of the cement, and self-shrinkage of 500 to 800μ occurs when the strength develops. It has been known. In high-strength concrete having a compressive strength of 150 N / mm ² or more, such self-contraction is a big problem.
As measures against the self-shrinking material, methods such as mixing an expansive admixture or mixing a shrinkage reducing agent have been taken.

In Patent Document 1, as a method of preventing cracking of concrete after placing, a method of applying concrete shrinkage reducing agent to the formwork surface and placing the concrete in contact with the coated surface is disclosed.
Moreover, in patent document 2, the invention regarding the formwork which stuck the film formed with the alkali decomposable substance is disclosed for the purpose of enabling the diversion of the formwork.
Japanese Patent Laid-Open No. 11-256819 JP 10-217223 A

The conventional method for manufacturing a concrete structure has the following problems.
<1> Among the cement-based mixed materials, particularly fiber-reinforced cement-based mixed materials have very little moisture and require about 20 hours for setting, and it is difficult to finish the surface while leveling after placing. . Further, since bubbles formed on the surface are generated not only on the lower surface of the mold but also on the leveled surface that has been cast, it is difficult to level the cast surface flatly.
<2> Self-shrinkage is a problem in high-strength concrete, but when reinforcing steel bars and formwork constrain self-shrinkage, the above-mentioned restraint against self-shrinkage occurs when the cementitious mixed material hardens and develops strength. This causes problems such as tensile stress and cracks.
<3> When a method such as mixing an expansive admixture or a shrinkage reducing agent is used as a countermeasure from the material side of self-shrinkage, ettringite produced by these materials has a compressive strength of 20 to 30%. Decrease the degree. Furthermore, since the pore voids of the cementitious matrix tend to increase, the resistance to salt permeation and moisture intrusion may be reduced, resulting in a problem that durability performance is significantly reduced.
<4> When a method such as mixing an expansive admixture or a shrinkage reducing agent is used as a countermeasure from the material side of self-shrinkage, such material costs are expensive, resulting in a problem of rising construction costs. .

  In order to solve the above problems, the form of the present invention is a form for a concrete structure having a box-shaped cross section having an overhang made of a fiber-reinforced cement-based mixed material, and the form is An upper frame for molding the upper surface of the concrete structure, an inner frame for molding the inner side of the box part of the concrete structure, and an outer frame for molding the overhanging part of the concrete structure and the outer side of the box part. The inner frame is composed of a plate material made of wood, steel, aluminum alloy or plastic and a deformation following sheet provided on the entire surface of the plate material, and the outer frame is made of wood, steel, aluminum alloy or plastic And a deformation following sheet attached to a portion of the plate corresponding to the projecting portion of the concrete structure, and the deformation following sheet is composed of a film layer and a soft board. Use It can also be.

  Further, a deaeration sheet is attached to the surface of the inner wall of the inner frame for forming the box part bottom plate, and the deaeration sheet has a two-layer structure of an air intake sheet and a perforated film layer. Can also be used.

The upper frame includes a plate material made of wood, steel, aluminum alloy, or plastic, and a deaeration sheet having a three-layer structure of a film layer, an intake sheet, and a perforated film layer provided on the surface of the plate material. Degassing comprising a two-layer structure consisting of a plate material, a deformation tracking sheet comprising a film layer and a soft board provided on the surface of the plate material, and a suction sheet and a perforated film layer provided on the surface of the deformation tracking sheet A formwork characterized by comprising a sheet can also be used.

  Also, a method for producing a box-shaped cross-section concrete structure having an overhang, wherein the mold according to any one of the above is used and the fiber reinforced cementitious mixed material is filled into the mold and produced. The concrete is characterized by comprising a container for molding a concrete structure using the mold, filling the container with a fiber-reinforced cement-based mixed material, and installing the upper frame as a lid for the container. Structure fabrication methods can be used.

The method for producing a formwork and a concrete structure of the present invention can obtain at least one of the following effects by means for solving the above-described problems.
<1> By using a formwork provided with a degassing sheet, for example, in the production of a concrete structure using an ultra-high-strength fiber-reinforced cement-based mixed material, a solid and smooth finished surface can be created.
<2> By using a mold with a degassing sheet, the entire surface, including the finished surface, can be covered with the mold, so that even a concrete structure with a complicated shape can be manufactured with high accuracy. It becomes.
<3> The degassing sheet is for removing bubbles generated from, for example, a fiber-reinforced cementitious mixed material, and the cement paste is blocked by a perforated film. Therefore, the possibility that the degassing sheet is clogged in the cementitious mixed material is extremely low, and the mold having the degassing sheet can be diverted and is economical.
<4> By using the formwork provided with the deformation following sheet, generation of internal stress due to self-shrinkage can be prevented. Therefore, it is possible to prevent the occurrence of internal defects and internal cracks due to internal stress.
Since the <5> deformation following sheet protects the surface with a film, the formwork provided with the deformation following sheet can be diverted and is economical.

<1> Configuration of Formwork The formwork 1 of the present invention is a degassing sheet comprising a plate material 2 and a three-layer structure of a film layer 311, an intake sheet 312 and a perforated film layer 313 provided on the surface of the plate material 2. The mold 11 is composed of 31 (see FIG. 1). As another example of the mold 1, a mold 12 including a plate 2 and a deformation following sheet 4 including a film layer 41 and a soft board 42 provided on the surface of the plate 2 is manufactured. (See FIG. 3). Furthermore, the plate 2, the deformation following sheet 4 comprising the film layer 41 and the soft board 42 provided on the surface of the plate 2, and the air intake sheet 321 and the perforated film layer provided on the surface of the deformation following sheet 4 It is also possible to manufacture a mold 13 composed of a degassing sheet 32 having a two-layer structure 322 (see FIG. 4).
Details of the deaeration sheet 3 and the deformation following sheet 4 will be described later.
The plate member 2 is a known board conventionally used as a mold, and a board made of wood, steel, aluminum alloy, plastic, or the like can be used.

The main purpose of using the form 11 configured by attaching a degassing sheet 31 to be described later to the plate material 2 is the container configured by the mold 11 (or the container configured by the mold 11 and the plate 2). This is for effectively degassing the bubbles 7 inside the fresh cementitious mixed material 5 filled in (1).
On the other hand, the main purpose of using the mold 12 configured by pasting the deformation follow-up sheet 4 to be described later on the plate 2 is the container (or the mold 12 and the plate 2 formed of the mold 12). When the fresh cementitious mixed material 5 filled in the container self-shrinks, the deformation of the deformation following sheet 4 relaxes the constraint of the cemented mixed material 5 and controls the generation of cracks. .
Further, the main purpose of using the mold 13 formed by attaching the deformation following sheet 4 and the degassing sheet 32 to be described later to the plate material 2 is to effectively degas the bubbles 7 inside the cementitious mixed material 5. It is possible to perform both control of cracks that may occur due to self-shrinkage of the cement-based mixed material 5.
When the cement-based mixed material 5 to be used is, for example, a high-strength cement-based mixed material or a fiber-reinforced cement-based mixed material, generation of tensile stress due to restraint of reinforcing steel bars, formwork, etc. against the self-shrinkage, and cracks resulting therefrom The occurrence of was a big problem. The present invention provides a new formwork 1 in which a conventional formwork is configured to cope with such a problem.

The cement-based mixed material 5 filled in the vessel constituted by the mold 1 of the present invention includes a wide variety of materials such as high-strength cement, high-fluid cement, and fiber-reinforced cement-based mixed material in addition to ordinary cement. Especially, when using a fiber reinforced cementitious mixed material, the performance of the mold 1 is effectively exhibited.
Here, as the fiber-reinforced cement-based mixed material, for example, cement, pozzolanic reactive particles (for example, fine silica powder, fly ash, blast furnace slag, lime powder, etc.), silica fume, silica sand or sand having a particle size of 6 mm or less, Cement-based matrix mixture composed of at least one high-performance water reducing agent and water and fibers having a diameter of 0.05 to 0.3 mm and a length of 8 to 16 mm (chemical fibers such as metal fibers or vinylon fibers) ) Can be used as a fiber-reinforced cement-based mixed material obtained by mixing about 1 to 4% by volume.

<2> Deaeration Sheet The deaeration sheet 3 includes a film layer 311, an intake sheet 312, and a perforated film layer 313 as shown in FIG. 1, and an intake sheet 321 and a film layer as shown in FIG. 4. 322 may be configured. However, the deaeration sheet 32 composed of the intake sheet 321 and the film layer 322 is preferably used when the deformation following sheet 4 is added as a formwork component.
Hereinafter, the deaeration sheet 31 having a three-layer structure of the film layer 311, the intake sheet 312 and the perforated film layer 313 will be described.

The perforated film layer 313 is formed with a plurality of fine holes 33. Here, the diameter of the hole 33 is about 10 to 100 μm, and the number of the holes 33 can be about 10 to 20 / cm ² . The reason why the hole diameter is preferably in the above numerical range is that the bubbles 7 in the cementitious mixed material 5 can be easily degassed, and the cemented mixed material 5 enters the hole 33 and is difficult to be demolded. This is due to preventing this. In particular, when a fiber-reinforced cement-based mixed material is used as the cement-based mixed material 5, the possibility that the cement-diameter matrix mixture enters the hole 33 by setting the diameter of the hole 33 within such a numerical range is extremely low. At the same time, since the amount of water in the cement diameter matrix mixture is small, it is considered that there is almost no possibility of water dehydrating from the holes 33.
FIG. 2 shows a situation where the bubbles 7 in the cementitious mixed material 5 are deaerated from the holes 33.

An air intake sheet 312 is attached to the surface of the perforated film layer 313. The air intake sheet 312 is a sheet for sucking the air bubbles 7 that have passed through the holes 33 of the perforated film layer 313 and may be made of any material that can absorb and retain air. The air intake sheet 312 can be made of, for example, a nonwoven fabric or paper containing a synthetic fiber as a component. By providing such a perforated film layer 313 on the surface of the mold 11 in contact with the cement-based mixed material 5, the above-described degassing effect can be expected, and it can be easily made from the cement-based mixed material 5 after curing when the mold 11 is demolded. In addition, the effect that the mold 11 can be removed can be expected. If the mold can be removed without damaging the perforated film layer 313, the form 11 can be diverted.
The thickness of the air intake sheet 312 is preferably manufactured to about 0.5 to 1.5 mm, for example. This is to ensure that the intake performance is ensured but not excessively thick.
The perforated film layer 313 can be made of, for example, a polyester resin.

The film layer 312 is a sheet interposed between the plate material 2 and the intake sheet 312. The film layer 312 may be made of the same material as the perforated film layer 313.
When the amount of deaeration is small, it is not necessary to provide a hole in the film layer 312. However, when the amount of deaeration is large, it is preferable to prepare a plurality of holes having a hole diameter of, for example, about 5 to 10 μm.

<3> Deformation Tracking Sheet The deformation tracking sheet 4 includes a film layer 41 and a flexible board 42. Integration of the plate material 2 and the deformation following sheet 4 is performed by attaching a soft board 42 to the surface of the plate material 2 and attaching a film layer 41 to the surface of the soft board 42.
The soft board 42 can be manufactured to a thickness of about 5 to 10 mm using, for example, a polystyrene material. Note that the thickness (t) of the soft board 42 is t = (5 to 5) based on the range length (L) assumed to be self-shrinking of the concrete structure 6 to be manufactured and the strain (ε) due to self-shrinking. 10) It can be calculated by × L × ε.
By providing the film layer 41 on the surface of the soft board 42, when a fiber-reinforced cement-based mixed material is used as the cement-based mixed material 5, it is possible to prevent metal fibers from being pierced into the soft board 42 and causing damage. Can do.

The deformation following sheet 4 relaxes the restraint stress generated by the self-shrinkage in the deformation following sheet 4 by applying the deformation following sheet 4 to all locations of the plate 2 that can be assumed to restrain the self-shrinkage of the cementitious mixed material 5. It is possible to control cracks that may occur during primary curing of the cement-based mixed material 5.

Hereinafter, examples using the mold of the present invention will be described with reference to FIGS.

In this embodiment, a box-shaped cross-section bridge girder is shown as the concrete structure 6 (see FIG. 6). When manufacturing such a box-shaped cross-sectional structure, even if the cement-based mixed material 5 is constrained by the plate material 2 serving as the outer frame, the internal stress is obtained by providing the mold frame 12 with the deformation following sheet 4 on the inner frame. Can be made minute. Here, it is preferable to provide the mold 13 provided with the deformation following sheet 4 and the deaeration sheet 32 on the inner frame of the bottom plate of the box-shaped cross section. This is because it is necessary to deaerate the bubbles 7 in the bottom plate portion. On the other hand, by providing the mold 11 with the degassing sheet 31 on the upper frame of the upper floor slab of the box-shaped cross section, it is possible to degas the bubbles 7 on the side wall of the box-shaped cross section and the bubbles 7 on the upper floor slab. It becomes.

The Example concerning the manufacturing method which manufactures a concrete structure using the formwork 1 of this invention is shown.
In production, a container for forming the concrete structure 6 using the plate material 2 or the mold 1 is configured. Such containers vary depending on the shape of the structure to be manufactured. In addition to the polygonal shape shown in the first embodiment, a rectangular shape, a cylindrical shape, or the like is assumed. The combination of the mold 1 and the plate material 2 to be used is preferably determined in consideration of the location where deaeration is necessary and the location where the deformation needs to be followed as described above.
When the cement-based mixed material 5 is filled into the vessel from above via a treme pipe such as a hose, the ceiling of the vessel is in an open state. Therefore, the cemented mixed material 5 is filled in the molded vessel, and the ceiling of the vessel is installed with the mold 11 or the mold 13 provided with at least the degassing sheets 31 and 32 as a lid. FIG. 5 shows a situation where the bubbles 7 are moving toward the ceiling when the formwork 11 is installed on the ceiling of the vessel.

In the above manufacturing method, after the cement-based mixed material 5 is filled, the cement-based mixed material 5 in the vicinity of the ceiling of the vessel is preferably leveled so as to be substantially flat before the mold 11 or the mold 13 is installed as a lid. .
When a fiber-reinforced cement-based mixed material is used as the cement-based mixed material 5, it is extremely difficult to finish the ceiling surface of the ceiling. Therefore, when the placement of the fiber-reinforced cement-based mixed material reaches a predetermined level, the surface is roughened so that the surface is substantially flat, and after the leveling, the mold 11 or 13 is installed as a lid. To do.
The predetermined level of placement of the fiber reinforced cementitious mixed material described above is such that when the mold 11 or 13 is covered, the lower surfaces of the molds 11 and 13 are in contact with the fiber reinforced cementitious mixed material. It is height. Therefore, when the lid of the mold 11 or 13 is placed on the fiber reinforced cementitious mixed material, the flat surface of the mold 11 or 13 is placed by placing a weight on the upper surface of the mold 11 or 13. By uniformly contacting the fiber reinforced cementitious mixed material, the bubbles 7 can be easily removed through the degassing sheets 31 and 32, and a flat finished surface can be formed.
Here, when roughening, although not shown, it is effective to use a leveling device in which a vibrator is attached to a V-shaped or U-shaped leveling bar. By using such a leveling device, surface finishing can be performed in a short time.

The perspective view which showed the Example of the formwork of this invention. Sectional drawing explaining the condition where the air bubbles in a cement-type mixed material are absorbed by the air intake sheet through the hole of a perforated film. The perspective view which showed the Example of the formwork of this invention. The perspective view which showed the Example of the formwork of this invention. Explanatory drawing explaining the condition which installed the formwork of this invention as a lid | cover after filling a cement-type mixed material in a container. Sectional drawing which showed the Example of the concrete structure. Sectional drawing which expanded the A section of FIG. Sectional drawing which expanded the B section of FIG. Sectional drawing which expanded the C section of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Formwork 2 ... Plate material 3 ... Deaeration sheet 31 ... Deaeration sheet 311 ... Film layer 312 ... Air intake sheet 313 ... Perforated film layer 32 ... Desorption Air sheet 321 .. Air intake sheet 322 .. Perforated film layer 4... Deformation following sheet 41... Film layer 42 .. soft board 5... Cement-based mixed material 6. object

Claims (4)

A formwork for a concrete structure with a box-shaped cross section having an overhang made of a fiber reinforced cementitious mixed material,
The mold frame includes an upper frame that molds the upper surface of the concrete structure, an inner frame that molds the inside of the box portion of the concrete structure, an overhang portion of the concrete structure, and an outer frame that molds the outside of the box portion. Composed of
The inner frame is composed of a plate material made of wood, steel, aluminum alloy or plastic, and a deformation following sheet provided on the entire surface of the plate material,
The outer frame is composed of a plate material made of wood, steel, aluminum alloy or plastic, and a deformation following sheet attached to a portion corresponding to the projecting portion of the concrete structure of the plate material,
The deformation following sheet is composed of a film layer and a soft board,
Formwork.   A degassing sheet is attached to the surface of the deformation following sheet of the inner frame forming the box bottom plate,
  The said deaeration sheet | seat was comprised from the two-layer structure of the suction sheet | seat and the perforated film layer, The formwork of the said Claim 1 characterized by the above-mentioned. The upper frame is
  It comprises a plate material made of wooden or steel or aluminum alloy or plastic, and a deaeration sheet comprising a three-layer structure of a film layer, an intake sheet and a perforated film layer provided on the surface of the plate material,
  Or, from the plate material, a deformation following sheet comprising a film layer and a soft board provided on the surface of the plate material, and a deaeration sheet comprising a two-layer structure of an air intake sheet and a perforated film layer provided on the surface of the deformation following sheet. The formwork according to claim 1 or claim 2, wherein the formwork is configured. Production of a concrete structure with a box-shaped cross section having an overhanging portion, which is produced by using the formwork according to any one of claims 1 to 3 and filling the formwork with a fiber-reinforced cement-based mixed material. A method,
  Configure a container for molding a concrete structure using the mold,
  Filling the vessel with fiber reinforced cementitious mixed material,
  The upper frame according to claim 3 is installed as a lid of the vessel,
  How to make concrete structures.

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