JP2004232233A - Concrete structure and method of constructing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-strength concrete structure which forms a building of high space-using efficiency while suppressing construction costs, and to provide a method of constructing the concrete structure. <P>SOLUTION: The concrete structure 1 is formed of high-strength concrete 2 and an outer shell precast concrete form 3 arranged around the same. The precast concrete form 3 is lower in design strength than the concrete 2. To construct the concrete structure 1, precast concrete having predetermined design strength is used as a form 3, and the high-strength concrete 2 which has higher design strength than the predetermined design strength is poured in the form 3, and the form 3 is left as a face material of the high-strength concrete 1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【表２】

【００１４】
表１において、Ｗ・Ｃ・Ｓ・Ｇ・Ｍは、それぞれ、水・セメント・細骨材・粗骨材・減水剤を示している。各調合材料は一般的なコンクリートに使用されるもので構わない。
【００１５】
表２において、Ｗ・Ｃ・Ｓ１・Ｓ２・Ｇ・ＳＦは、それぞれ、水・セメント・細骨材１（市原産山砂）・細骨材２（相模川水系陸砂）・粗骨材・混和剤（粉体シリカフューム）を示している。表中のＢは結合材であり、セメントと粉体シリカフュームの総量によって示される。さらに、結合材に対して１．５％の割合で高強度のコンクリートを得るための芳香族系減水剤（高性能ＡＥ減水剤）も調合されている。
【００１６】
以上の構成を備えた本実施例の柱によれば、建築物からの軸力を高強度コンクリートによるコアコンクリートが受け止めて建築物の高層化を可能としつつ、火災によりこの柱の表面が高温に曝された場合には、爆裂しやすいコアコンクリートが爆裂しにくい強度のコンクリートでできた外殻ＰＣａで覆われているため、コアコンクリートの表面で爆裂が起きたとしても、その被害が柱の外部に及ばないようになっている。また、外殻ＰＣａが実質的に柱表層とコアコンクリート表面との間に介在する断熱材として機能し、外部の熱がコアコンクリートにまで伝わらず、爆裂自体を防止する効果もある。したがって、建築物の高層化と爆裂による被害防止とを低い建築コストで達成することができる。なお当然のことではあるが、本発明は柱に限らず梁など、他のコンクリート構造体に適用することが可能である。
【００１７】
【発明の効果】
本発明のコンクリート構造体によれば、高強度コンクリートによる建築物の高層化と、高強度コンクリートによる火災時の爆裂現象による被害防止とをともに達成することができる。また、かぶりを厚くする必要がないので、建築物の空間利用効率も向上する。さらに、この構造体の構築に当たっては、外殻プレキャストコンクリート型枠内に高強度コンクリートを打設し、型枠を残置する工法が採用でき、工期の短縮や建築コストの低減も期待できる。
【図面の簡単な説明】
【図１】本発明の実施例に係るコンクリート構造体である柱の破断斜視図である。
【図２】上記柱における水平面での断面図である。
【符号の説明】
１ 柱
２ コアコンクリート
３ 外殻プレキャストコンクリート型枠[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a concrete structure, and more particularly to a technique for preventing a burst phenomenon in which concrete explosively bursts when a high-strength concrete structure is heated violently by a fire or the like.
[0002]
[Prior art]
When a floor or a wall of a concrete building is rapidly heated by a fire, a concrete explosion phenomenon occurs, and a concrete mass splatters violently around, which may cause serious damage. It is considered that this explosion phenomenon is often caused mainly by moisture contained in the concrete member. That is, when the concrete member is rapidly heated locally, the internal moisture may evaporate and an enormous vapor pressure may be accumulated. This vapor pressure is related to the thermal expansion of the concrete itself, and explosion occurs at the cover portion of the concrete as in a so-called steam explosion. Therefore, the explosion phenomenon tends to occur in a high-strength concrete structure having a low water content. This explosion phenomenon causes the cover portion of the concrete to be lost, exposing the reinforcing steel, and ultimately lowering the strength of the concrete structure itself, resulting in structural collapse.
[0003]
In order to prevent the explosion phenomenon, it is usually possible to cope by increasing the cover thickness. Even if the fogging part is somewhat lost due to the explosion, the strength of the structure is sufficiently maintained. In addition, various attempts have been made to prevent the explosion phenomenon itself in high-strength concrete.For example, a heater is provided inside a concrete structure to forcibly dry the concrete, and water itself, which is the main cause of the explosion, is removed from the concrete. (For example, refer to Patent Document 1), or cast concrete into a high-strength concrete driving form in which plastic fibers are kneaded to construct a concrete structure (for example, refer to Patent Document 2). The technology is known.
[0004]
[Patent Document 1]
JP-A-5-105549
[Patent Document 2]
JP-A-8-189080
[Problems to be solved by the invention]
However, if the fogging portion is made thick to prevent the strength from being reduced by the explosion phenomenon, the cross section of the structure naturally increases. Therefore, a building constructed by the structure has a significantly reduced space utilization efficiency. Further, the various explosion phenomena prevention techniques described above have problems in that the construction period is prolonged and construction costs related to construction costs and material costs are increased.
[0007]
Therefore, an object of the present invention is to provide a high-strength concrete structure capable of constructing a building having higher space utilization efficiency while suppressing construction costs, and a method of constructing the same.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a concrete structure comprising a high-strength concrete and an outer shell precast concrete formwork having a design standard strength lower than that of the concrete.
[0009]
Further, in the method of constructing a concrete structure, a precast concrete having a predetermined design standard strength is used as a mold, and high-strength concrete having a design standard strength higher than the predetermined standard strength is poured into the mold. A method of constructing a concrete structure in which the formwork is left as a surface material of the high-strength concrete is also included in the scope of the present invention.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the concrete structure of the present invention is a pillar. FIG. 1 shows a partially cutaway perspective view of the column 1, and FIG. 2 shows a horizontal sectional view of the column 1. The pillar 1 is composed of a surface material 3 made of a hollow square tubular precast concrete, and a core concrete 2 cast in a hollow portion of the surface material 3. As a construction procedure of the pillar 1, first, a precast concrete formwork 3 is built, and concrete is poured into the formwork 3 to obtain a core concrete 2. The formwork 3 is left as it is and used as the surface material 3 of the core concrete 2. That is, it is an outer shell precast concrete form (outer shell PCa).
[0011]
In this pillar 1, the outer shell PCa3 has a built-in streak 5, and the main streak 4 stands upright along the inner wall slightly apart from the hollow inner wall surface of the formwork 3. In this example, the thickness of the outer shell PCa3 is about 70 mm, and the cover thickness of the core concrete 2 is about 10 mm. Of course, the present invention is not limited to this configuration, and a form in which the stirrups are looped around the main streaks may be used, or a form in which the main streaks and the stirrups are built in the outer shell PCa.
[0012]
A characteristic point of this pillar is that the design standard strength (Fc) of the outer shell PCa3 is, for example, 50 to 70 (N / mm ² ) of general concrete, whereas the core concrete 2 is, for example, High strength concrete of about 80 to 150 Fc. In this embodiment, the outer shell PCa3 is Fc60, and the core concrete 2 is Fc100. Table 1 shows the mixing ratio of the outer shell PCa3, and Table 2 shows the mixing ratio of the core concrete 2.
[0013]
[Table 1]

[Table 2]

[0014]
In Table 1, W, C, S, G, and M indicate water, cement, fine aggregate, coarse aggregate, and water reducing agent, respectively. Each compounding material may be used for general concrete.
[0015]
In Table 2, W, C, S1, S2, G and SF are water, cement, fine aggregate 1 (mountain sand from Ichigen), fine aggregate 2 (Sagami River water-based land sand), coarse aggregate, Shows an admixture (powder silica fume). B in the table is a binder and is indicated by the total amount of cement and powdered silica fume. Further, an aromatic water reducing agent (high-performance AE water reducing agent) for obtaining high-strength concrete at a ratio of 1.5% with respect to the binder is also prepared.
[0016]
According to the pillar of the present embodiment having the above configuration, the core force of the high-strength concrete receives the axial force from the building, thereby enabling the building to be high-rise. When exposed, the core concrete, which is easy to explode, is covered with an outer shell PCa made of concrete that is hard to explode, so even if an explosion occurs on the surface of the core concrete, the damage will not occur outside the pillar. Less. Further, the outer shell PCa substantially functions as a heat insulating material interposed between the surface layer of the pillar and the surface of the core concrete, so that external heat is not transmitted to the core concrete, and there is also an effect of preventing explosion itself. Therefore, it is possible to achieve high building and prevention of damage due to explosion at a low building cost. Needless to say, the present invention is not limited to columns, but can be applied to other concrete structures such as beams.
[0017]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the concrete structure of this invention, it can achieve both the high-rise building of a building by high-strength concrete, and the damage prevention by the explosion phenomenon at the time of fire by high-strength concrete. In addition, since it is not necessary to increase the cover, the space utilization efficiency of the building is improved. Further, in constructing this structure, a construction method in which high-strength concrete is poured into the outer shell precast concrete formwork and the formwork is left can be adopted, and shortening of the construction period and reduction of construction cost can be expected.
[Brief description of the drawings]
FIG. 1 is a cutaway perspective view of a pillar as a concrete structure according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the column in a horizontal plane.
[Explanation of symbols]
1 Pillar 2 Core concrete 3 Shell precast concrete formwork

Claims (2)

A concrete structure comprising a high-strength concrete and an outer shell precast concrete formwork having a design reference strength lower than that of the concrete. The method for constructing a concrete structure according to claim 1, wherein a precast concrete having a predetermined design reference strength is used as a mold, and high-strength concrete having a design reference strength higher than the predetermined reference strength is formed in the form. A method for constructing a concrete structure, comprising: casting and leaving the formwork as a surface material of the high-strength concrete.

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