JPH07279312A - Concrete filler member - Google Patents

Abstract

PURPOSE:To enhance the durability and stiffness by filling a steel pipe with a high strength concrete containing short fibers in a specific share by weight. CONSTITUTION:A high strength concrete is prepared from water, cement, fine aggregate, and coarse aggregate, whereto an AE agent, AE water reducing agent or a high performance AE water reducing agent is added according to necessity. To concrete, short fibers of steel, etc., are added in a content by volume of 0.5-3%, preferably 1-3%, still more favoarbly 1-2.5% so that a concrete filler member 1 is provided. A steel pipe 2 is filled densely with this concrete filler member 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete filling member in which a steel pipe is filled with concrete, and particularly to a structural member having high yield strength and high toughness in a super high-rise building or other large building. The present invention relates to a concrete filling member that is advantageously used as

[0002]

2. Description of the Related Art In recent years, the construction of super high-rise buildings or other large-scale buildings has become more and more popular, but in such large-scale buildings, the structural members, especially columnar structural members, namely, Since the stress acting on the column member becomes very large, it is necessary to increase the cross-sectional dimension thereof. However, if the cross-sectional dimension of the pillar member is increased, the weight of the pillar member increases, which further increases the stress. Therefore, it is important to reduce the cross-sectional size of the pillar member to reduce its own weight. Therefore, recently, there has been a tendency that a concrete filling member in which concrete is filled in a steel pipe is widely used as a column member having high yield strength and high toughness even if the cross-sectional dimension is small.

In such a concrete filling member, the compressive force acting in the axial direction is borne by the concrete filled in the pipe alone or jointly with the steel pipe, and a circle generated when the compressive force acts. The steel pipe bears the tensile force in the circumferential direction so that the steel pipe exhibits high yield strength and high toughness in a three-dimensional stress state. in this way,
Concrete filling members are characterized by the fact that concrete, which is weak against tensile force but extremely strong against compressive force, and steel pipes having the opposite characteristics exert their respective advantages and complement each other's shortcomings. Have. Further, the steel pipe constituting the concrete filling member has an advantage that it can be conveniently used as a concrete driving mold.

[0004]

In a concrete-filled member having such excellent properties, it is desired to further improve the excellent mechanical properties as described above. There is an increase in the strength of the concrete filled inside the pipe. This is intended to improve the yield strength of the concrete filling member by using high-strength concrete having a compressive strength of about 300 to 1000 kgf / cm ² as the concrete to be filled inside the pipe. However, since concrete is not originally rich in toughness and has a high strength, the toughness generally tends to decrease. Therefore, it is necessary to increase the strength of the concrete filled inside the pipe by increasing the strength of the concrete-filled member. It has the drawback that it does not necessarily lead to toughness, and also loses its high yield strength over time. That is, since the deformation capacity of steel pipe is much larger than that of concrete, the steel pipe is greatly deformed under the action of high stress, whereas the filled high-strength concrete cannot be deformed and is cracked finely. As a result, it becomes impossible to follow the deformation of the steel pipe, a gap is created between the two, and the three-dimensional stress state cannot be maintained. For this reason, there has been a problem that the high proof stress possessed by the initial concrete filling member decreases sharply with time.

[0005]

As a result of various studies to solve the above-mentioned problems, the present inventor has found that 0.5 to 3% by volume of short fibers is added to the high-strength concrete to be filled inside the conduit. As a result, the deformation capacity (elongation capacity) of concrete can be improved without impairing the compressive strength of concrete, and as a result, concrete-filled members in which such concrete is filled in steel pipes have both high yield strength and high toughness. It was found that it can be held for a long time.

Therefore, an object of the present invention is to provide a concrete filling member which has both high yield strength and high toughness and can maintain these characteristics for a long time, and the inside of a steel pipe is filled with concrete. In the concrete filling member, the concrete is a high-strength concrete containing 0.5 to 3% by volume of short fibers based on the concrete, and relates to the concrete filling member.

In the present invention, high strength concrete means concrete having a compressive strength of about 300 to about 1000 kgf / cm ² , preferably 400 to 800 kgf / cm ² , and concrete having such a compressive strength. Any concrete can be used provided that it consists of water, cement, fine aggregate and coarse aggregate,
Further, in addition to these, an AE agent for the purpose of improving the workability and durability of concrete,
Examples thereof include those to which an AE water reducing agent or high-performance AE water reducing agent has been added, and those to which silica fume or fly ash has been added for the purpose of increasing the strength and durability of concrete.

Water, cement, fine aggregate and coarse aggregate used as constituent components of such high strength concrete,
As the necessary auxiliary agent such as AE agent, AE water reducing agent, and high-performance AE water reducing agent, any of those conventionally used in the technical field of the present invention can be used. As the water, for example, not only tap water, fresh water such as river water and lake water, but also seawater can be used as long as it is a reinforced concrete structure. Examples of the cement include Portland cement, blast-furnace cement, silica cement, fly ash, and other inorganic powders such as blast-furnace slag and fly ash, as well as those having a pozzolanic reaction such as stone powder and silica fume, which are used alone or in combination of two kinds The above is used in combination.

As the fine aggregate, it is possible to use an aggregate that passes through a 10 mm mesh sieve and 85 mm% or more of a 5 mm mesh sieve, and as a coarse aggregate, 5 mm.
It is possible to use an aggregate that stays on the screen at 85% by weight or more.

Examples of the AE agent include sulfonic acid hydrocarbons and natural resin acid salts. Examples of the AE water reducing agent include a lignin sulfonic acid compound, a polyol complex, and an oxycarboxylic acid salt.

Examples of the high-performance AE water-reducing agent include naphthalenesulfonic acid formalin highly condensed products, melaminesulfonic acid formalin highly condensed products, polycarboxylic acid salts and the like.

In the present invention, the short fiber means a reinforcing material of concrete or mortar processed from various materials as raw materials and processed into a discontinuous fiber shape, which has an action of remarkably improving the toughness of the concrete filling member. Have. In the present invention, any of the conventionally known short fibers can be used, and examples thereof include steel fibers, polypropylene fibers, glass fibers, carbon fibers, aramid fibers, vinylon fibers, and polyethylene fibers. Medium, steel fibers, carbon fibers, vinylon fibers or aramid fibers are preferred, and steel fibers are particularly preferred. These short fibers can be used alone or in combination of two or more.

These short fibers are linear and can have a shape in which their cross-sections or end portions are modified, and their thickness (the length of the longest portion of the cross-sectional area) is generally 0.2 to 0.8.
mm, preferably 0.3-0.6 mm, and the length is generally 20-40 mm, preferably 25-30 mm
Is.

It is preferable that these fibers are uniformly dispersed in concrete in a linear, three-dimensional random orientation state, and the short fibers are dispersed in such a state.
For example, it is carried out by mixing with a concrete material using an omni mixer or the like.

In the present invention, the short fibers are contained in concrete in a volume ratio of 0.5 to 3%, preferably 1 to 3%, and particularly preferably 1 to 2 based on the concrete (including short fibers). 0.5% is added. If the addition amount is less than 0.5% by volume, the effect of sufficiently improving the toughness of the concrete filling member cannot be obtained, while if it is more than 3% by volume, the short fibers are uniformly dispersed in the high strength concrete. Becomes difficult, and the homogeneity of the concrete filled in the pipe is impaired,
In the present invention, the addition amount of the short fibers contained in the concrete is set to 0.5 to 3% based on the concrete. The volume of short fibers means the volume ratio of short fibers contained in concrete.

As the steel pipe, any of those conventionally used in the technical field of the present invention can be used, and its component composition, shape, size and the like are not limited, but a square steel pipe or a round steel pipe is preferable. Particularly preferably, a square steel pipe or a round steel pipe having a cross-sectional area of 5,000 to 30,000 cm ² is used.

In the concrete filling member of the present invention, the high-strength concrete containing short fibers is densely filled in the steel pipe with as little voids as possible. It is desirable to fully exert the condition, and for that purpose, the consistency of the concrete before hardening is appropriately adjusted, and the fluidity and filling property of the concrete before hardening are sufficiently enhanced, and then it is filled into the steel pipe. It may be preferable to do so. In order to improve the fluidity of concrete, for example, an AE water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent, fly ash or the like is used.

The concrete filling member of the present invention comprises, for example, water, cement, fine aggregate, coarse aggregate and short fibers,
In addition, a high-strength concrete containing short fibers is manufactured by mixing the necessary auxiliary agents, and the steel pipe is filled with the high-strength concrete and then cured.

[0019]

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples.

Example 1 Water, cement, fine aggregate having a particle size of 5 mm or less, particle size 5 to 20
mm coarse aggregate and an AE water-reducing agent as a ligninsulfonic acid compound or an aromatic aminosulfonic acid compound, and short fibers as a steel fiber (steel material: carbon steel, shape: linear, length: 30 mm, thickness: 0. 6 mm), the present concretes 1 to 4 containing uncured short fibers and comparative concrete samples 1 to 2 containing uncured short fibers having a water-cement ratio, a fine aggregate ratio and a mixing ratio shown in Table 1. Were prepared by mixing them using a pan-type forced kneading twin-screw mixer.

[0021]

[Table 1] The slump value and air content of these concretes were measured and the results are shown in Table 2.

[0022]

[Table 2] Thereafter, these concretes 1 to 4 of the present invention and comparative concretes 1 to 2 were respectively given an outer diameter of 114.3 mm,
After being filled in a round steel pipe (steel material: carbon steel) having a thickness of 3.2 mm, standard curing is performed for 28 days, and concrete 1 is filled in the round steel pipe 2 as shown in FIG. Filling members 1-4 and comparative concrete filling members 1 and 2 were produced.

Then, as shown in FIG.
Was installed, a load was applied to the concrete filling members via the loading plate 4, and the load and the displacement were measured to examine the yield strength and toughness of these concrete filling members. .

The measured values obtained as a result are shown in FIG. 3 as a graph showing the relationship between the load P and the displacement S of each filling member. As is clear from FIG. 3, both the maximum proof stress and the deformation capacity (toughness) of the concrete filling members 1, 2 and 3, 4 of the present invention are larger than those of the comparative concrete filling members 1 and 2, respectively. It can be seen that the filling member is a structural member superior in both yield strength and toughness to the comparative concrete filling member containing no short fibers.

Example 2 The concrete 1 of the present invention used in Example 1 was filled in a round steel pipe having an outer diameter of 318.5 mm and a thickness of 6.9 mm and allowed to cure in air for 6 months. The filling member was cut as shown in FIG. 4 and the filling state of the concrete was visually observed. As a result, no void was found in the steel pipe, and it was found that the concrete of the present invention had a sufficient filling property.

[0026]

As is clear from the above description, according to the present invention, there is provided a concrete filling member having both high yield strength and high toughness and capable of maintaining these characteristics for a long time, and particularly A structural member is provided that is advantageous for building high-rise buildings or other large buildings.

[Brief description of drawings]

FIG. 1 is a partially cutaway vertical sectional view of a concrete filling member in which a steel pipe is filled with concrete.

FIG. 2 is a schematic diagram showing a method for measuring the yield strength and toughness of a concrete filling member.

FIG. 3 is a graph showing the relationship between the load and the displacement of the filling member.

FIG. 4 is a schematic diagram showing a cutting direction of a concrete filling member according to a second embodiment.

[Explanation of symbols]

 1 Concrete 2 Steel pipe 3 Displacement meter 4 Loading plate

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Claims (3)

[Claims] 1. A concrete filling member in which concrete is filled inside a steel pipe, wherein the concrete is high-strength concrete containing 0.5 to 3% by volume of short fibers based on the concrete. A concrete filling member characterized by the above. 2. The concrete filling member according to claim 1, wherein the short fibers are steel fibers. 3. The concrete filling member according to claim 1, wherein the short fiber content is 1 to 3% by volume.