JP2002339479A - Method of forming explosion preventive concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming concrete that can prevent an explosion by arranging thermoplastic resin fibers in appropriate positions in the concrete with simple work. SOLUTION: After main reinforcements 2, outer peripheral reinforcements 3 and core reinforcements 4 constituting a column are built up, organic fibers 5 are locked to the outer peripheral reinforcements 3 at prescribed spaces so as to partially hang down. A form is then installed, and unhardened concrete is poured into the vicinity of the center part in the form. The organic fibers 5 are washed away toward the form along the flow face of the concrete and embedded in the state of the end parts of the organic fibers 5 reaching the form. When heated by a fire or the like, the organic fibers 5 melt and evaporate, and are diffused from the surface of the concrete to form a large number of pores in the covering concrete. Moisture evaporated in the concrete is discharged to the outside from these pores. The pressure inside the concrete is thereby suppressed from becoming higher to prevent the explosion. The organic fibers 5 may be locked to filamentous members or a mesh member, and these members may be fastened to the reinforcements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming concrete capable of preventing a so-called explosion, in which a surface layer explosively separates and scatters when a concrete member is strongly heated in a fire or the like. It is.

[0002]

2. Description of the Related Art In recent years, high-strength concrete having higher compressive strength than commonly used concrete is sometimes used for high-rise buildings and apartment houses. Since high-strength concrete has a large design standard strength, the amount of concrete used in a building decreases. For this reason, the height of the building is increased and the degree of freedom of the plan is improved, and the demand for high-strength concrete is expected to further increase in the future.

[0003] On the other hand, when a pillar or a wall of a building made of concrete is strongly heated by a fire, the water contained in the concrete rapidly rises in temperature, evaporates, and the volume of the water expands. For this reason, it is known that the inside of the concrete becomes high pressure and the concrete surface peels and scatters, that is, a so-called explosion occurs. In particular, since high-strength concrete has a dense structure, if the water inside the concrete expands in volume due to heating, the inside of the concrete tends to become high in pressure. Therefore, high-strength concrete is more likely to explode than ordinary concrete.

[0004] In order to prevent such explosion of concrete, a method of applying a fireproof coating to the concrete surface to reduce the external heat effect, or providing a reinforcing member such as a steel plate or a spiral streak on the concrete surface to provide an internal pressure And the like have been proposed. However, these methods require a lot of time and cost to apply the refractory coating and the reinforcing member. Moreover, since the concrete cross section increases, the merit of using high-strength concrete is reduced.

On the other hand, JP-A-11-79807, JP-A-7-252901, and JP-A-7-102661
Japanese Patent Application Publication No. JP-A-2005-64131 discloses a technique for preventing explosion by embedding thermoplastic resin fibers in concrete. The thermoplastic resin fibers embedded in the concrete are melted by being strongly heated, and further vaporize and dissipate.
Thereby, many small holes are formed in the concrete, and the vaporized moisture in the concrete is discharged to the outside through the small holes. For this reason, even in the case of high-strength concrete having a dense structure, internal pressure is released, and explosion is unlikely to occur.

[0006]

However, the above prior art has the following problems. JP-A-11-79
The technique described in Japanese Patent Publication No. 807 discloses a method in which short fibers of a thermoplastic resin or a mesh cut to a predetermined size is kneaded and cast into concrete. In this technique, thermoplastic resin fibers are arranged in an arbitrary direction in concrete. Therefore, even if the thermoplastic resin fibers are melted and vaporized in the event of a fire, not all of them form small holes communicating with the surface of the concrete member. Therefore, the water vapor cannot efficiently move to the concrete surface and is hardly released to the outside.
In addition, the explosion occurs mainly in a portion called cover concrete from the reinforcing steel bar to the concrete surface. When thermoplastic resin fibers are mixed into the entire concrete, an appropriate amount or more of thermoplastic resin fibers is required. Also,
The technique described in Japanese Patent Application Laid-Open No. Hei 7-252901 is a technique in which a sheet formed by projecting a large number of pin-shaped bodies made of a low melting point resin is pasted on the inner surface of a mold, and the pin-shaped bodies are embedded in concrete to be cast. It is. In this technology, the pin-shaped body is supported by the formwork, so when casting concrete,
The pin-shaped body is knocked down by the flowing uncured concrete, and cannot penetrate into the concrete. For this reason, the water vapor inside the concrete is hardly released to the outside of the concrete. Further, Japanese Patent Application Laid-Open No. Hei 7-102661 discloses that a net made of a cord-like member knitted with a fiber is wound around a placed reinforcing bar, and a plurality of cord members branched from the net are extended to a formwork for fastening or forming. This is a technique of penetrating and supporting a frame, and casting concrete so as to embed these string members. However, fastening or penetrating the string member into the mold is not preferable from the viewpoint of workability and economy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to dispose thermoplastic resin fibers at appropriate positions inside concrete by a simple operation to prevent explosion. It is an object of the present invention to provide a method for forming explosion-proof concrete.

[0008]

Means for Solving the Problems To solve the above-mentioned problems, the invention according to claim 1 is characterized in that after a reinforcing steel to be embedded is arranged below the surface of a concrete member, the reinforcing steel is cut to a predetermined length. A step of locking the resin fiber so that a part thereof hangs down; a step of assembling a formwork outside the reinforcing bar; and a step of charging uncured concrete into the concrete member from the reinforcing bar and flowing toward the formwork surface. And a step of curing and curing the uncured concrete.

When the uncured concrete is poured into the concrete member from the reinforcing bar, the uncured concrete flows toward the formwork surface, and the hanging portion of the thermoplastic resin fiber is uncompressed toward the formwork surface. It is washed away by hardened concrete. Then, the thermoplastic resin fibers are arranged between the reinforcing bar and the formwork surface along the flow surface of the concrete. By setting the length of the thermoplastic resin fiber to an appropriate length equal to or greater than the distance between the reinforcing bar and the formwork surface, the end of the thermoplastic resin fiber reaches the formwork surface. When the concrete member is heated at a high temperature during a fire, the thermoplastic resin fibers in the concrete member are melted, and when further heated, are vaporized and released from the surface of the concrete member. Then, the portion where the thermoplastic resin fibers are disposed becomes a gap, and a number of small holes penetrating from the reinforcing bar in the concrete member to the surface are formed. On the other hand, the water in the concrete member is also heated and vaporized to become steam. This water vapor is released to the outside of the concrete member through the small holes. For this reason, even if the water in the concrete member expands in volume due to evaporation, the pressure in the concrete member is unlikely to increase,
Explosion of the concrete member can be prevented. In addition, the appropriate amount and length of thermoplastic resin fibers can be arranged almost uniformly only in the cover concrete section from the reinforcing bar that is liable to explode to the formwork surface, so that explosion is prevented economically and efficiently. can do.

[0010] The invention according to claim 2 is a step of arranging a reinforcing bar to be embedded under the surface of the concrete member at a predetermined position; Fixing a member or a string-shaped member to the reinforcing bar, assembling a formwork on the outside of the reinforcing bar, charging uncured concrete into the concrete member from the reinforcing bar, and flowing toward the formwork surface. And a step of curing and curing the uncured concrete.

Since the thermoplastic resin fibers are locked to a thread-like member or a string-like member, by fastening this string-like member to the assembled rebar, a large number of thermoplastic resin fibers can be quickly removed. Can be arranged. For this reason, by previously fixing the thermoplastic resin fiber to the thread-like member or the string-like member at a factory or the like, the work time on site can be shortened, and the work can be made more efficient.

According to a third aspect of the present invention, there is provided a step of arranging a reinforcing bar to be embedded under a surface of a concrete member at a predetermined position, and a plurality of thermoplastic resin fibers cut to a predetermined length are engaged so as to partially hang down. Fixing the member to the rebar, assembling a formwork outside the rebar, charging unhardened concrete from the rebar to the inside of the concrete member, and flowing toward the formwork surface; Curing the uncured concrete and curing the uncured concrete.

In this method, the thermoplastic resin fibers are previously locked to a mesh member at a factory or the like, and the mesh member is fastened to, for example, a reinforcing bar, so that a large number of thermoplastic resin fibers can be formed at once. Fibers can be placed. For this reason, work efficiency is significantly improved.

According to a fourth aspect of the present invention, in the method for forming explosion-proof concrete according to the fourth aspect, the mesh member has a lattice-like warp and a weft, and at least one of them is arranged at intervals. Is set to be larger than the size of the coarse aggregate contained in the uncured concrete.

The arrangement interval of at least one of the warp and the weft contained in the mesh member is larger than the size of the coarse aggregate contained in the uncured concrete. For this reason, when the uncured concrete is poured into the concrete member from the reinforcing bar, the uncured concrete flows toward the formwork surface, and the coarse aggregate in the uncured concrete is also meshed with the reinforcing bar. It can pass through the mesh of the member. Therefore, the composition of the cover concrete between the reinforcing bar and the formwork surface and the concrete at the center portion are not biased, and a uniform concrete can be obtained as a whole.

According to a fifth aspect of the present invention, in the method for forming explosion-proof concrete according to the fourth aspect, the mesh member has a lattice-like warp and a weft, and at least one of these arrangement intervals is provided. Is set to 20 mm or less.

By setting the arrangement interval of at least one of the warp yarn and the weft yarn of the net-like member to 20 mm or less, an appropriate amount of organic fibers can be arranged at a sufficiently dense interval in the cover concrete portion, so that it is effective. Explosion can be prevented.

According to a sixth aspect of the present invention, in the method for forming explosion-proof concrete according to the first, second, or third aspect, the thermoplastic resin fiber may be a reinforcing bar, a thread-like member, a string-like member, or a net-like material. The interval between the members is 10m
m to 50 mm, and in the vicinity of the protruding corner of the cross section of the concrete member to be buried, the spacing is made smaller than the locking interval near the flat surface.

In general, in the vicinity of the protruding corner, water vapor in the concrete member easily escapes, and explosion hardly occurs. In the above method, the thermoplastic resin fibers are sparsely arranged near the protruding corner where the explosion is unlikely to occur, and densely arranged near the flat surface, whereby the explosion can be effectively prevented in the entire concrete member. .

According to a seventh aspect of the present invention, in the method for forming explosion-proof concrete according to the first, second or third aspect, the length L of the hanging portion of the thermoplastic resin fiber is equal to the length of the concrete member. T is the rebar cover thickness
Where: t + 5 mm ≦ L ≦ t + 30 mm

In this method, since the length of the thermoplastic resin fiber hanging down is appropriately set, when the concrete fiber is flushed toward the formwork surface by the flow of the concrete, the tip reaches the formwork surface, The surplus length appears on the surface of the concrete, and the finish of the surface is less likely to deteriorate.

[0022]

FIG. 1 is a schematic sectional view showing an example of a column formed by the method for forming explosion-proof concrete according to the first aspect. In this pillar, a plurality of main reinforcements 2 are arranged in the concrete 1 at intervals of 80 mm to 150 mm in the vertical direction, and the outer reinforcements 3 and the core reinforcements 4 are combined at intervals of 80 mm to 150 mm in the horizontal direction. Shear reinforcement is located. Then, a large number of organic fibers 5 having a predetermined length are locked to the outer peripheral streaks 3.
Extends slightly obliquely downward toward the surface of the pillar, and the tip is almost exposed to the surface.

The method of forming the above pillars will be described with reference to the drawings. As shown in FIG. 2, after assembling the main muscle 2, the outer circumferential muscle 3 and the core muscle 4, the organic fibers 5 are fixed to the outer circumferential muscles 3 at predetermined intervals so that a part of the organic fibers 5 hang down. I do.
The organic fibers 5 are, as shown in FIG.
It is possible to reduce the amount of the organic fibers 5 to be disposed at the corners of the concrete member where the explosion hardly occurs in the concrete member. Next, as shown in FIG.
Unhardened concrete 7 adjusted to have appropriate fluidity is poured near the center of the formwork by a concrete pump or a concrete bucket. This allows
The uncured concrete 7 flows radially toward the formwork 6.

FIG. 5 shows the organic fiber 5 when concrete is charged.
It shows the behavior of. FIG. 5A shows a state before the surface of the cast concrete 7 rises and a part of the organic fiber 5 reaches the hanging portion. When the flow surface of the concrete 7 reaches the organic fiber 5 as shown in FIG. 5B, the hanging portion of the organic fiber 5 is pushed down toward the formwork 6 along the flow surface of the concrete 7.
Then, as shown in FIG. 5 (c), when the end of the organic fiber 5 reaches the mold 6 and the concrete 7 flows from the central part, as shown in FIG. Is embedded in the cover concrete portion between the outer peripheral reinforcement 3 and the formwork 6 while keeping the gradient along the flow surface. Then, after the uncured concrete 7 is cured and sufficiently cured, the form 6 is removed.

The organic fibers 5 are heated in the event of a fire, melt and evaporate to form voids in the concrete. As the material, a fiber having a low melting point, evaporating after melting and leaving no embers is selected. . For example, polypropylene resin fiber, vinylon fiber, polyethylene fiber, acrylic fiber, and the like can be used. The organic fiber 5 has a diameter of 0.1
mm to 1.0 mm can be used,
It is desirable to set it to 0.2 mm to 0.5 mm. Also,
So that one end of the organic fiber 5 reaches the concrete surface,
It is desirable to set an appropriate length equal to or more than the thickness of the cover concrete from the outer peripheral bar 3 to the concrete surface, that is, 5 mm to 30 mm longer than the thickness of the cover concrete. The amount of the organic fiber 5 used is suitably about 0.02% to 0.2% of the volume of the cover concrete.
The amount used depends on the shape and arrangement of the organic fibers 5.

When the pillar is heated rapidly in a fire,
The organic fibers 5 arranged in the cover concrete portion are melted and vaporized by heating. Since the end of the organic fiber 5 reaches the concrete surface, the vaporized organic fiber 5 is diffused from the concrete surface, and a number of small holes reaching the concrete surface are formed in the cover concrete portion. Moisture vaporized in the concrete by heating passes through the small holes and is discharged to the outside of the concrete member. For this reason, even if the water in the concrete member expands in volume due to evaporation, the pressure in the concrete member is unlikely to increase,
Explosion of the concrete member can be prevented. Further, since the organic fibers 5 are arranged at substantially uniform intervals only in the fogging portion where the explosion easily occurs, the explosion can be efficiently and economically prevented.

After the outer fiber 3 is assembled as described above, the organic fiber 5 is locked to the outer fiber 3 in addition to the outer fiber 3 beforehand. May be assembled. Thereby, the working time at the construction site can be reduced. Further, as shown in FIG.
, A large number of organic fibers 13 can be arranged in a short time.

FIG. 7 is a schematic perspective view showing the locked state of organic fibers in the method for forming explosion-proof concrete according to the second aspect. The organic fibers 23 are joined so as to branch off from the string-like members 24 at intervals of about 10 mm to 50 mm, and as shown in FIG. The organic fibers 23 are arranged by locking so as to be wound around 21. FIG.
As shown in (b), a string-shaped member 24 having the organic fibers 23 locked therein may be stretched in the vertical direction and locked to the outer peripheral streaks 22. It is desirable that the organic fiber 23 be bound to the string-like member 24 by being tied or twisted in a factory or the like, whereby the work on site can be made more efficient and the work time can be shortened.

After arranging the organic fibers 23, a formwork (not shown) is provided, and uncured concrete is poured into the center of the formwork, so that the organic fibers 23 are similar to those shown in FIG. The organic fibers 23 are washed away by the concrete, and the ends of the organic fibers 23 reach the formwork, and are uniformly arranged in the cover concrete portion. When heated by a fire, the organic fibers 23 melt and vaporize, forming small holes reaching the concrete surface, thereby preventing explosion. In addition, the same thing as the pillar shown in FIG. 1 is used for the main reinforcement 21, the outer peripheral reinforcement 22, and the organic fiber 23.

FIG. 8 shows a third, fourth or fifth aspect of the present invention.
It is a schematic perspective view which shows the locking state of the organic fiber in the formation method of the explosion-proof concrete concerning this. This organic fiber 3
1 is connected to a warp 32a of the mesh member 32 as shown in FIG. 8 (a), and the mesh member 32 is wound around the assembled outer peripheral line 33 as shown in FIG. 8 (b). To stop. In addition, the organic fiber 31 and the outer peripheral stripe 3
3 is the same as the column shown in FIG.

The mesh member 32 has a lattice-shaped warp yarn 32a and a weft yarn 32b, and the warp yarn 32a and the weft yarn 32a.
The arrangement interval of b or one of the arrangement intervals is larger than the size of the coarse aggregate contained in the unhardened concrete. For this reason, when the uncured concrete is put into the concrete member from the reinforcing bar, the coarse aggregate in the uncured concrete also passes through the mesh and reaches the form. Therefore, the whole concrete has the same composition, and almost uniform strength can be obtained. In addition, the arrangement interval of at least one of the warp yarn 32a and the weft yarn 32b is equal to or less than 20 mm, and the organic fibers 31 can be arranged at a desired interval in the cover concrete portion.

As shown in FIG. 9, the organic fiber 41 shown in FIG. 8 may be one in which the organic fiber 41 is engaged with both the warp yarns 42a and the weft yarns 42b of the mesh member 42.

[0033]

As described above, according to the method for forming explosion-proof concrete of the present invention, a proper amount and length of thermoplastic resin can be applied only to the rebar and the cover concrete section up to the formwork surface by a simple operation. The fibers can be arranged almost uniformly. The thermoplastic resin fibers are arranged so as to reach the surface of the member from inside the concrete. For this reason, when the concrete member is heated in a fire, the thermoplastic resin fibers disposed in the concrete member are melted and vaporized, and a number of small holes are formed in the cover concrete member, which communicate with the concrete surface. Then, the moisture in the concrete member is vaporized by heating, and is released through the hole to the outside of the concrete member, so that explosion can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a pillar formed by the method for forming explosion-proof concrete according to claim 1.

FIG. 2 is a schematic cross-sectional view showing a locked state of organic fibers in the method for forming explosion-proof concrete according to claim 1.

FIG. 3 is a schematic perspective view showing a locked state of organic fibers in the method for forming explosion-proof concrete according to claim 1;

FIG. 4 is a schematic diagram illustrating a method for placing concrete.

FIG. 5 is a schematic view showing behavior of organic fibers at the time of placing concrete.

FIG. 6 is a schematic perspective view showing another example of the locked state of the organic fibers.

FIG. 7 is a schematic perspective view showing an organic fiber locked state in the method for forming explosion-proof concrete according to claim 2;

FIG. 8 is a schematic perspective view showing a locked state of organic fibers in the method for forming explosion-proof concrete according to claim 3, 4 or 5.

FIG. 9 is a schematic perspective view showing another example of a mesh member to which organic fibers are bonded in the method for forming explosion-proof concrete according to claim 3, 4, or 5.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Concrete 2, 21, 34 Main bar 3, 12, 22, 33 Perimeter bar 4 Rebar 5, 13, 23, 31, 41 Organic fiber 6 Formwork 7 Unhardened concrete 24 String member 32, 42 Mesh member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // (C04B 28/02 C04B 16:06 Z 16:06) 111: 20 111: 20 111: 28 111: 28 F term (reference) 2E001 DE01 DH39 EA01 FA02 FA03 GA06 GA07 HA01 HA05 JD04 KA05 LA10 2E164 AA02 AA05 4G012 PA24 PC15 PE04

Claims (7)

[Claims] After arranging a reinforcing bar to be embedded below the surface of a concrete member, a step of locking a thermoplastic resin fiber cut to a predetermined length to the reinforcing bar so that a part thereof hangs down, and forming a mold outside the reinforcing bar. A step of assembling a frame, a step of introducing uncured concrete from the rebar to the inside of the concrete member and flowing it toward the formwork surface, and a step of curing and curing the uncured concrete. Method of forming explosion-proof concrete. 2. A step of arranging a reinforcing bar to be embedded under a surface of a concrete member at a predetermined position, and a step of fixing a thread-like member or a string-like member in which a number of thermoplastic resin fibers cut to a predetermined length are locked so that a part thereof hangs down. Fastening the reinforcing bar to the reinforcing bar, assembling a formwork outside the reinforcing bar, charging unhardened concrete from the reinforcing bar inside the concrete member, and flowing toward the formwork surface; Curing the hardened concrete and hardening the hardened concrete. 3. A step of arranging a reinforcing bar to be embedded under a surface of a concrete member at a predetermined position, and fixing a mesh member, which is formed by cutting a plurality of thermoplastic resin fibers cut to a predetermined length so that a part thereof hangs down, to the reinforcing bar. Attaching, forming a formwork outside the reinforcing bar, charging uncured concrete from the reinforcing bar inside the concrete member, and flowing toward the formwork surface, curing the uncured concrete. And curing the concrete. 4. The mesh member has a lattice-like warp yarn and a weft yarn, and an arrangement interval of at least one of the warp yarn and the weft yarn is set to be larger than the size of the coarse aggregate contained in the uncured concrete. The method for forming explosion-proof concrete according to claim 4. 5. The explosion according to claim 4, wherein the mesh member has a warp yarn and a weft yarn in a lattice shape, and an arrangement interval of at least one of them is set to 20 mm or less. How to form preventive concrete. 6. The interval at which the thermoplastic resin fibers are locked to a reinforcing bar, a thread-like member, a string-like member, or a mesh-like member is 10 minutes.
5 mm to 50 mm, and in the vicinity of the protruding corner of the cross section of the concrete member to be buried, the distance is less than the locking interval in the vicinity of the flat surface. The method for forming the explosion-proof concrete described in the above. 7. The length L of the hanging portion of the thermoplastic resin fiber is t + 5 mm ≦ L ≦ t + 30 mm, where t is the cover thickness of the reinforcing bar of the concrete member. The method for forming the explosion-proof concrete according to claim 2 or 3.