JP4852018B2 - How to build concrete columns - Google Patents

Description

  The present invention relates to a method for constructing a concrete pillar.

  There are cases where wet curing is performed while preventing drying of the casting surface by spraying water on the concrete placing surface or by laying a ridge or sponge soaked with water (for example, Patent Document 1). If this kind of wet curing is performed on high-strength concrete having a small water binder ratio, the supplied water may be added to the concrete, leading to a decrease in strength and the like.

  As a curing method that does not supply water, as disclosed in Patent Document 2, Patent Document 3, and the like, the upper surface (placed surface) of concrete is covered with a curing sheet made of a hygroscopic material, and this curing sheet is covered with breathing water. There is known a curing method that keeps the placing surface wet by absorbing water. Patent Document 3 also discloses a curing method in which a curing sheet made of a plastic film having no hygroscopic property is laid on the placing surface.

JP 2006-183264 A JP 2000-336931 A JP-A-6-172060

If the design standard strength is up to about 60 N / mm ² , the casting surface is covered with the breathing water that has floated on the casting surface, so that the casting surface is not immediately dried. When ultra-high-strength concrete exceeding 100 N / mm ² , the breathing water hardly occurs because the water binder ratio is kept low, and the casting surface starts to dry immediately after casting. The concrete stiffens before the bubbles (entrapped air or entrained air) near the placement surface are completely removed, and the bubbles remain in the vicinity of the placement surface. When passing concrete, if bubbles (cavities) remain in the vicinity of the casting surface, it will cause a decrease in strength. Therefore, it is necessary to remove the thin-film concrete that covers the bubbles. Since it is super-high strength, it takes a lot of labor and time for the removal work.

  Such a problem can be solved by preventing the casting surface from drying, but the curing method of Patent Document 1 for supplying water to the casting surface is not suitable for ultra-high-strength concrete as described above. It is. Although it is conceivable to spread the curing agent on the placement surface, not only the effect is insufficient, but also the strength of the placement surface may be reduced.

  On the other hand, if the placement surface can be covered with a curing sheet without a gap as in the curing methods of Patent Documents 2 and 3, drying of the placement surface can be prevented, and the problem of strength reduction due to water addition is also eliminated. However, if it is not firmly suppressed, it will be easily turned up by the wind or the like, and the placement surface may be exposed. In addition, if a curing sheet made of a hygroscopic material (polymer absorbent material) is laid on the casting surface of ultra-high-strength concrete that generates almost no breathing water, it absorbs moisture near the casting surface more than necessary. There is also a possibility of inhibiting the strength expression in the vicinity of the installation surface.

By the way, super high-strength concrete whose design standard strength exceeds 100 N / mm ² is often applied to concrete columns such as high-rise buildings. It is unsuitable for curing the casting surface of concrete columns where the main reinforcement stands. However, it is necessary to process the curing sheet according to the position and thickness of the column main reinforcement in order to cover the placement surface of the concrete column without any gaps. However, it takes time to process the curing sheet, and the curing sheet is overlaid. This is because the casting surface has been dried by this time.

From this point of view, the present invention is a method for constructing a concrete column made of concrete having a design standard strength of 100 N / mm ² or more, and it is possible to easily and reliably suppress drying of the casting surface. And it aims at providing the construction method of the concrete pillar which a bubble does not remain easily in the vicinity of a casting surface.

In the present invention that solves such a problem, immediately after placing concrete having a design standard strength of 100 N / mm ² or more, a dry or wet open-cell sponge is laid on the casting surface. In addition, the concrete is cured in a state in which movement of the sponge (particularly lateral movement) is restricted by the columnar reinforcing bars protruding from the placement surface, and the lower surface of the sponge is in contact with the placement surface. And

According to the concrete column construction method of the present invention, since the evaporation of moisture from the casting surface is suppressed by the sponge brought into contact with the casting surface, the casting surface is not stiff immediately after the casting, Bubbles rising near the placement surface will escape from the placement surface. That is, according to the present invention, it is difficult for bubbles (cavities) to remain in the vicinity of the casting surface, and therefore it is possible to omit or simplify the operation of removing the thin-film concrete covering the bubbles. If the setting surface is covered with a curing sheet made of a plastic film that is difficult to pass air, air may remain between the setting surface and the curing sheet, and a crater-shaped recess may be formed on the setting surface. However, according to the present invention, air that has escaped from the concrete is absorbed by the open cells (cavities) in the sponge, so that it is difficult to form a crater-like recess, and thus a smooth casting surface is obtained. It becomes possible.
The “dried state” means a state shipped from the factory, stored in a normal room without getting wet with rainwater, etc. A state in which the sponge is dehydrated, in other words, a state in which water is contained so that water does not drip from the sponge when the sponge is lifted into the air.

  Further, in the present invention, the movement of the sponge is restrained by using the columnar main bars, so that it is difficult for the sponge to turn up. Therefore, it is ensured that the lower surface of the sponge is in contact with the placement surface. Can be maintained.

  Furthermore, according to the present invention for covering the sponge in a dried state or a wet state, moisture is not added to the concrete, so there is no possibility of causing a decrease in strength and the like, and plenty of water is included. Unlike the conventional curing method of laying a water-absorbing curing sheet in a wet state, the moisture contained in the curing sheet is not absorbed into the concrete, so there is a decrease in strength near the placement surface and the occurrence of cracks. There is no fear. By the way, if the sponge contains excessive water enough to dripping water, the tendency of the sponge to adhere to the placement surface increases, and in some cases, the sponge adheres firmly to the placement surface and the sponge is removed. Some of them may be peeled off and remain on the casting surface. In this case, it is necessary to remove the sponge.

  In the present invention, it is desirable that the movement of the sponge is restrained by reducing the column main reinforcement into the sponge. This makes it possible to hold the sponge firmly, so that even when a strong wind blows, the sponge does not turn up, ensuring that the lower surface of the sponge is in contact with the placement surface. Can be maintained.

The sponge is divided into at least one outer sponge disposed on at least one of the inner sponge head region formed outside of the core region is arranged in a core region surrounded by said post main reinforcement of several It is . If the sponge is divided, it is possible to easily and quickly cover the surface of the concrete column where a plurality of column main reinforcements stand.

Incidentally, the outer sponge, that Soo interposed between arranged frame body so as to surround the pillar main reinforcement of multiple said pillar main reinforcement. If it does in this way, movement will also be restrained also about an outside sponge. In addition, when the upper surface of the mold and the casting surface are flush with each other, the outer sponge may be surrounded by a frame-like body separate from the column mold.

  Although there is no restriction | limiting in the material of the said sponge, etc., it is desirable to consist of a flexible urethane foam whose foaming magnification is 30-50 times. If it is a flexible urethane foam, it has the degree of flexibility that can be easily deformed by human power while maintaining the shape of its own, so even if it is pushed in between the column main muscles The lower surface can be brought into contact with the placement surface, and the processing and handling are facilitated, so that the work efficiency is improved.

  In the case where the sponge is made of flexible urethane foam, it is not preferable that the thickness of the sponge is less than 30 mm because the sponge is easily turned up and the amount of water transpiration is increased. On the other hand, if it exceeds 50 mm, it becomes bulky and difficult to handle, so the thickness of the sponge is preferably 30-50 mm.

According to the present invention, when a concrete column is constructed using concrete having a design standard strength of 100 N / mm ² or more, it is possible to easily and reliably suppress drying of the concrete placing surface, and Air bubbles hardly remain in the vicinity of the installation surface.

(First embodiment)
The concrete column construction method according to the first embodiment, which is a reference embodiment, is a method for constructing a precast concrete column made of ultra-high strength concrete having a design standard strength of 100 N / mm ² or more.

In many cases, the ratio of the water binder of the concrete having a design standard strength of 100 N / mm ² or more is 25% or less. Although there is no restriction | limiting in the concrete mixing | blending of such concrete, For example, a high performance water reducing agent and water and a powder containing cement, a pozzolanic reaction particle, and an aggregate so that a water binder ratio may be 25% or less. It is obtained by mixing 0.5 to 3.5 kgf / m ^{3 of} polypropylene fiber or ethylene vinyl alcohol fiber having a shape with a diameter of 10 to 100 μm and a length of 5 to 20 mm in a cement-based matrix obtained by mixing be able to. Concrete with such a composition has high fluidity but hardly separates materials, and can carry aggregates and cement paste to every corner of the mold without vibration compaction. In many cases, it has a self-filling property. Incidentally, the pozzolanic reaction particles are particles made of, for example, silica fume, fly ash, blast furnace slag, a compound selected from kaolin derivatives, precipitated silica, volcanic ash, silica sol, and the like. The maximum particle size of the aggregate is preferably 20 mm or less.

The concrete column construction method according to the present embodiment will be described in detail with reference to FIG.
In the concrete column construction method according to the present embodiment, as shown in FIG. 1A, first, a plurality of column main bars (rebars) T, T,. And a column mold K that molds the side surface of the column around the column main bars T, T,..., And then the design standard strength is 100 N / mm ^2. Fresh concrete C blended as described above is placed in the column mold K. As described above, since the concrete C has a self-filling property, vibration compaction is unnecessary. In the present embodiment, the upper surface (hereinafter referred to as “placement surface”) J of the concrete C is positioned below the top end of the column mold K.

  When the concrete C is placed, the sponge S in a dried state (containing no moisture) or a wet state is possible without performing finishing work (roughening, etc.) on the placement surface J. Immediately lay on the placing surface J (see FIG. 1B). When laying the sponge S, the lower surface of the sponge S is brought into contact with the placement surface J while restraining the movement of the sponge S by the column main bars T, T,... Protruding from the placement surface J (see FIG. 3). . In addition, it is desirable that the laying operation of the sponge S is performed within a few minutes after the concrete C is placed.

  The sponge S is an open-cell sponge member. Although there is no restriction | limiting in the material etc. of sponge S, in this embodiment, it consists of an ether type flexible urethane foam whose expansion ratio is 30-50 times. The thickness of the sponge S is not limited, but if it is less than 30 mm, it will be easy to turn up and the amount of transpiration will increase, and if it exceeds 50 mm, it will be bulky and difficult to handle. Is desirable.

  As shown in FIG. 2B, the sponge S includes an inner sponge S1 disposed in a core region J1 (see FIG. 2A) surrounded by a plurality of columnar main bars T, T,. The outer sponge S2 is divided into a square-shaped (annular) fogging area J2 (see FIG. 2A) formed outside the core area J1.

  The inner sponge S1 has a planar shape similar to the planar shape of the core region J1 having a rectangular shape in plan view, and the area of the upper surface and the lower surface of the inner sponge S1 is larger than that of the core region J1. Therefore, when the inner sponge S1 is laid on the core region J1, the column main bars T, T,... Are reduced to the outer peripheral portion of the inner sponge S1, and the movement of the inner sponge S1 is restricted by the column main bars T, T,. become. That is, the inner sponge S1 comes into contact with the core region J1 of the placing surface J in a state where movement is restricted by the columnar main bars T, T,. The inner sponge S1 of the present embodiment has a moderate flexibility even though it is a planar shape obtained by enlarging the planar shape of the core region J1, so that when the inner sponge S1 is laid on the core region J1, The outer peripheral portion of the sponge S1 enters between the adjacent column main bars T, T, and the placing surface J (band-like region J3) located between the column main bars T, T is also covered with the inner sponge S1. When the column main reinforcement T is reduced in the outer peripheral portion of the inner sponge S1, the outer peripheral surface of the inner sponge S1 is brought into contact with the outer peripheral surface of the column main reinforcement T by a local restoring force generated in the portion where the column main reinforcement T is reduced. It will be in close contact.

  The outer sponge S2 has a planar shape that is substantially similar to the planar shape of the fogging area J2, but is divided into two pieces S21 and S21 that are L-shaped in plan view in this embodiment. The width dimension of each side of the outer sponge S2 is larger than the width dimension of the cover region J2 (that is, the cover thickness of the column main reinforcement T), and the area of the upper surface and the lower surface of the outer sponge S2 is larger than that of the cover region J2. It is getting bigger. Therefore, when the outer sponge S2 is disposed in the cover region J2, the column main bars T, T,... Are reduced in the inner peripheral portion of the outer sponge S2, and the column mold K is in close contact with the outer peripheral portion. That is, since the outer sponge S2 is sandwiched in a compressed state in the width direction by the column mold K and the column main bars T, T,..., The movement is restricted, and in this state, It will be in contact with the covering area J2 of the placing surface J. When the column main muscle T is reduced in the inner peripheral portion of the outer sponge S2, the inner peripheral surface of the outer sponge S2 becomes the outer periphery of the column main muscle T due to the local restoring force generated in the portion where the column main muscle T is reduced. It will be in close contact with the surface.

  When curing the concrete C with the sponge S in contact with the casting surface J, some amount of moisture contained in the upper layer of the concrete C is absorbed by the lower part of the sponge S, but evaporates and dissipates. And the wet state of the placing surface J is maintained so that the strength expression of the concrete C is not impaired. That is, it is possible to prevent the upper layer of the concrete C from being dried, and to prevent the occurrence of “stiffness” of the concrete C and plastic cracks due to the drying.

  And as shown to (a)-(c) of FIG. 4, until the fluidity | liquidity of concrete C is impaired from immediately after placement, the entrapd air entrained in the inside of concrete C is bubble A and However, for a while after the placement, the sponge S prevents “stiffness” in the upper part of the concrete C, so the bubbles A can reach the placement surface J, The air in the bubble A that has reached the placement surface J escapes from the placement surface J without staying there. That is, if the concrete C is cured while the sponge S is in contact with the placement surface J, bubbles are unlikely to remain in the vicinity of the placement surface J. Moreover, since air that has escaped from the casting surface J is absorbed by the cavities (open cells) in the sponge S, a crater-like recess is hardly formed on the casting surface J. In addition, in (a)-(c) of FIG. 4, illustration of the column main reinforcement T is abbreviate | omitted.

  Although the time required for discharging the bubbles A varies depending on the properties of the concrete C, in many cases, it is about 30 to 120 minutes after the completion of placing. In addition, in order to advance the hydration reaction of the concrete C in the vicinity of the casting surface J, it is left for about one day until the concrete C reaches the demolding strength. Moreover, when performing roughening etc. on the placement surface J, or when confirming the appearance of the placement surface J, the sponge S may be temporarily removed.

  As described above, according to the method for constructing a concrete column according to the present embodiment, since it is difficult for bubbles to remain in the vicinity of the casting surface J, the removal work of the thin-film concrete covering the bubbles is omitted or simplified. It becomes possible. In addition, since the air that has escaped from the concrete C is absorbed by the cavities (open cells) in the sponge S, it becomes difficult to form a crater-like recess in the placement surface J, and as a result, a smooth placement surface. J can be obtained.

  Moreover, if the sponge S in a dried state or a wet state is covered on the placing surface J as in the present embodiment, moisture is not added to the concrete C, resulting in a decrease in strength or the like. Unlike conventional curing methods that lay a water-absorbing curing sheet with plenty of water, the moisture contained in the curing sheet is not absorbed into the concrete. There is no risk of strength reduction or cracking in the vicinity of the installation surface J.

  In addition, when the movement of the sponge S is restrained using the columnar main bars T, T,... As in this embodiment, it is difficult for the sponge S to turn up. The state in contact with J can be reliably maintained. In particular, in the present embodiment, the column main bars T, T,... Are reduced in the outer peripheral portion of the inner sponge S1, so that drying / reduction in a narrow portion (band-like region J3) between the adjacent column main bars T, T is performed. Stiffness can also be prevented.

  Further, as in this embodiment, when the sponge S is divided into a plurality of pieces (pieces S21, S21 of the inner sponge S1, outer sponge S2), the placement surface J on which the plurality of columnar main bars T, T,. It becomes possible to cover easily and quickly. Incidentally, the inner sponge S1 is restrained from the front, rear, left and right by the column main bars T, T,... Surrounding it, and the outer sponge S2 is front, rear, left and right by the column main bars T, T,. Therefore, the positions of the inner sponge S1 and the outer sponge S2 do not shift even if a strong wind blows or a worker or the like makes a mistake.

  Moreover, since the specific gravity of the sponge S is about 50 to 1/100 of the specific gravity of the concrete C, the sponge S is placed even if the sponge S is placed on the placement surface J of the concrete C in a fresh state. Therefore, even if the concrete C is hardened in a state where the sponge S is placed on the placing surface J, it can be removed easily and quickly.

  In addition, what is necessary is just to change suitably the shape etc. of each piece in the case of forming sponge S by a several piece according to the cross-sectional shape of a concrete pillar, or a bar arrangement state.

  For example, as shown in FIG. 5A, a plurality (two in the drawing) of pieces S11 and S11 may be combined to form the inner sponge S1, or four pieces S22, S22, ... may be combined to form the outer sponge S2.

  Further, for example, as shown in FIG. 5 (b), it is surrounded by column main bars (herein referred to as “outer column main bars”) T, T,. When a plurality of column main bars (herein referred to as “inner column main bars”) T ′, T ′,... Are arranged in the core region, the inner sponge S1 is connected to the inner column main bars T ′, T ′. ,... Formed between a rectangular piece S12 arranged in a rectangular region, the outer column main bars T, T,... And the inner column main bars T ′, T ′,. You may divide | segment into the L-shaped piece S13, S13 arrange | positioned at a shape (annular) area | region.

  In addition, the planar shape of the sponge S can be appropriately changed according to the cross-sectional shape of the concrete column. For example, although illustration is omitted, when the concrete pillar has a circular cross-sectional shape, the inner sponge S1 may be formed into a circular shape in plan view and the outer sponge S2 may be formed into a ring shape (annular shape).

(Second embodiment)
The method for constructing a concrete column according to the second embodiment, which is an embodiment of the present invention, is a method in which precast column members made of ultra-high strength concrete having a design standard strength of 100 N / mm ² or more are joined in the field. How to build a pillar. In addition, although there is no restriction | limiting in particular in the construction method of a precast pillar member, It is desirable to utilize the construction method of the concrete pillar which concerns on 1st embodiment.

  In the second embodiment, as shown in FIG. 6A, first, the precast column member 1 on the lower floor is erected, and the precast beam members 2 and 2 are disposed above the upper end surface of the precast column member 1. Place. The precast beam member 2 is positioned on the side of the column main bars T, T,... Protruding from the upper end surface of the precast column member 1.

  Thereafter, a frame-shaped body W (see FIG. 8) having a square shape in plan view (see FIG. 8) is disposed so as to surround the plurality of columnar main bars T, T,... Secure to the top surface of The frame-shaped body W may be integrally molded, or may be a combination of L-shaped or linear frame components that can be separated.

Subsequently, as shown in FIG. 6B, ultra high strength concrete C having a design reference strength of 100 N / mm ² or more is placed on the upper end surface of the precast column member 1.

  When the concrete C is cast to a predetermined height (in this embodiment, the same height as the upper surface of the precast beam member 2), as shown in FIG. 6C, the concrete C is dried (does not contain moisture). State) or wet sponge S is laid on the casting surface J as quickly as possible, and the movement of the sponge S is restrained by the column main bars T, T,. The concrete C is cured with the lower surface of S in contact with the casting surface J. As in the first embodiment, the sponge S is divided into an inner sponge S1 and an outer sponge S2, but the outer sponge S2 has a frame-like body W and columnar muscles T, T,. It is pinched by.

  When the concrete C is cured while the sponge S is in contact with the casting surface J, “stiffness” in the upper layer of the concrete C is prevented as in the first embodiment. Bubbles rising in the vicinity of J escape from the casting surface J and are absorbed by the sponge S.

  Thereafter, the sponge S and the frame-like body W are removed, and a concrete column is constructed when the upper floor precast column member 1 is erected on the setting surface J of the hardened concrete C as shown in FIG. It will be. Incidentally, an insertion hole 1a into which the column main bars T, T,... Protruding from the placement surface J are formed is formed at the lower end of the upper floor precast column member 1.

  As described above, according to the method for constructing a concrete column according to the present embodiment, as in the case of the first embodiment, since it is difficult for bubbles to remain in the vicinity of the placement surface J, a thin film covering the bubbles. It is possible to omit or simplify the work of removing the concrete. In addition, since the air that has escaped from the concrete C is absorbed by the cavities (open cells) in the sponge S, it becomes difficult to form a crater-like recess in the placement surface J, and as a result, a smooth placement surface. J can be obtained.

  Moreover, if the sponge S in a dried state or a wet state is covered on the placing surface J as in the present embodiment, moisture is not added to the concrete C, resulting in a decrease in strength or the like. Unlike conventional curing methods that lay a water-absorbing curing sheet with plenty of water, the moisture contained in the curing sheet is not absorbed into the concrete. There is no risk of strength reduction or cracking in the vicinity of the installation surface J.

  In addition, if the movement of the sponge S is restrained using the columnar bars T, T,... And the frame-like body W, it is difficult for the sponge S to turn up due to strong winds. In addition, the state where the lower surface of the sponge S is in contact with the placement surface J can be maintained.

  In addition, when using what combined several frame structural material as a frame-shaped body, it is not necessary to join frame structural materials. As shown in FIG. 9, the frame-shaped body may be configured by separating the adjacent frame members W1, W1.

In addition, in this embodiment, although the construction method of the concrete pillar using the precast pillar member 1 was illustrated, it is not the meaning which limits the application range of this invention. Although not shown in the drawings, the technical idea described above can also be applied to the case where a concrete column is constructed by passing over ultra-high strength concrete having a design standard strength of 100 N / mm ² or more.

  In the present embodiment, the case where the sponge S is directly brought into contact with the columnar main bars T, T,... To restrain the movement of the sponge S by the columnar main bars T, T,. ,... May be constrained to move the sponge S through the hoop muscles.

(A), (b) is a perspective view for demonstrating the construction method of the concrete pillar which concerns on 1st embodiment. It is a top view for demonstrating the construction method of the concrete pillar which concerns on 1st embodiment, (a) is a figure which shows the state before laying sponge, (b) is the state after laying sponge. FIG. It is the BB sectional view taken on the line of (b) of FIG. (A)-(c) is typical sectional drawing for demonstrating the effect | action of the construction method of the concrete pillar which concerns on 1st embodiment. (A) And (b) is a top view for demonstrating the modification of sponge. (A)-(c) is sectional drawing for demonstrating the construction method of the concrete pillar which concerns on 2nd embodiment. FIG. 7 is a cross-sectional view illustrating a process following FIG. It is also a plan view. It is a top view which shows the modification of a frame-shaped body.

Explanation of symbols

C Concrete J Casting surface J1 Core area J2 Cover area T Column main bar S Sponge S1 Inner sponge S2 Outer sponge K Column form W W Frame

Claims (2)

Immediately after placing concrete with a design standard strength of 100 N / mm ² or more, a dry or wet open-cell sponge is laid on the casting surface, and the column protrudes from the casting surface Constraining the movement of the sponge with the main reinforcement, and a concrete pillar construction method for curing the concrete in a state where the lower surface of the sponge is in contact with the placement surface,
The sponge is divided into at least one inner sponge disposed in a core region surrounded by a plurality of columnar main bars and at least one outer sponge disposed in a cover region formed outside the core region. And
A method for constructing a concrete column, wherein the outer sponge is sandwiched between a frame-like body arranged so as to surround a plurality of column main bars and the column main bars.   2. The method for constructing a concrete pillar according to claim 1, wherein the movement of the sponge is restrained by reducing the pillar main reinforcement into the sponge.

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