JPH0449005A - Concrete filling member - Google Patents

Abstract

PURPOSE:To obtain a concrete filling member, which increases the adhesion of a steel pipe and cured concrete and improves integrality while having high toughness and high resistance, by adding a water-soluble thickening agent and an AE water reducing agent to concrete. CONSTITUTION:Any water-soluble thickening agents which have been used can also be employed as a water-soluble thickening agent, methyl cellulose, anionic polyacrylamide and hydroxyethyl cellulose are preferable among them, and it is important that the content of the water-soluble thickening agent is 0.2-0.5kg/m<2>. The AE water reducing agent is contained by 0.3-1.5kg/m<2>, vibrating compaction is to some extent executed on placing or no cavity and honeycomb is generated in the inside even when no vibrating compaction is carried out, the inside of a steel pipe can be filled with the title filling member, and execution if facilitated extremely.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a concrete filling member in which hardened concrete is filled inside a steel pipe, and in particular to a concrete filling member that is advantageously used as a structural member of a skyscraper. It is related to.

[Prior Art] In recent years, the construction of skyscrapers and other large-scale skyscrapers has become more and more popular, but in such skyscrapers, the stress acting on their structural members is enormous. Therefore, it is important to reduce the weight of this structural member. Therefore, concrete-filled members, in which the inside of a steel pipe is filled with concrete, are now widely used as column members that have high toughness and high yield strength even if their cross-sectional dimensions are small. In such a concrete-filled member, the internal filling concrete bears solely or mainly the bearing capacity against the compressive force acting in the axial direction, and the tensile force against the circumferential direction tensile force generated when this compressive force is applied is borne by the steel pipe. Concrete is weak against tensile force but strong against compressive force, and steel has the opposite properties. In addition to having the characteristics that each exhibits its strengths and compensates for their weaknesses, it also has the advantage that the steel pipes surrounding the concrete can be conveniently used as formwork.

[Problem to be solved by the invention]

In order for a composite member such as this concrete-filled member to exhibit the excellent mechanical strength mentioned above, there must be sufficient adhesion between the hardened concrete inside and the surrounding steel pipe, and the bond between the two must be strong. It is desirable to ensure excellent integrity, but when manufacturing concrete filling members by pouring concrete inside steel pipes, ■ It is important to avoid breathing in the concrete filled inside the steel pipes. This breathing reduces the adhesion between the hardened concrete and the steel pipe, making it difficult to achieve the desired integrity between the two, and also causes separation of coarse aggregate in the concrete. , causing variations in the strength of the hardened concrete in the axial direction, resulting in a partial decrease in the compressive strength of the hardened concrete itself, and therefore a decrease in the strength of the concrete filling member. When press-fitting concrete and pouring concrete into the side pipe at once, if the steel pipe is long, the distance that the concrete must move within the steel pipe becomes longer, causing aggregate separation in the concrete. This causes variations in the strength of the hardened concrete in the axial direction, leading to a decrease in the strength of the concrete filling member as described above, and as shown in FIG. When 1° of concrete is filled into a 2° steel pipe in which the joining bracket 6 protrudes from the inner surface of the steel pipe or the diaphragm 4 is provided to prevent the concrete from sinking, the flow rate of the concrete increases. Since the strength and filling properties are not necessarily sufficient, voids 7 or 8 are formed around these brackets 6 or diaphragms 4, especially on their lower surfaces, respectively, and these voids reduce the cross-sectional dimension of the hardened concrete, reducing the strength of the concrete filling member. The problem was that it caused

[Findings based on research]

Therefore, as a result of various studies in view of the above-mentioned problems, the inventor of the present invention found that: ■ 0.2
When using concrete containing a water-soluble thickener at a mixing ratio of ~0.5 kg/rd, water: 152 kg/ITf, cement: 346 kg/ITf, sand with a particle size of 5w or less:
841kg#rf and coarse aggregate with particle size 5-205m+:
Water-soluble thickener to be included in concrete with a blending ratio of 967 kg/n: Methylcellulose blending ratio (
How does the breathing rate 2B (%) (this breathing rate is expressed as the amount of breathing water relative to the amount of mixed water) change with respect to the standing time (days: D) after kneading when M) is varied in various ways? As can be seen in Figure 4, which is a graph of the results, breathing in this concrete is significantly suppressed, preventing the decrease in adhesion between the steel pipe and hardened concrete and the separation of coarse aggregate in the concrete caused by breathing. As a result, the above-mentioned insufficient integrity in the concrete filling member and the axial quality variations of the concrete, and hence the strength loss, are avoided; ■ Concrete containing water-soluble thickeners as mentioned above; ■ This concrete is highly viscous and has improved resistance to material separation, making it difficult for aggregate separation to occur even if the concrete moves over a long distance during pouring. ■ This concrete already has high fluidity and Although it has filling properties, it has a filling property of 0.3 to 1.5. AE of the compounding ratio of kg/m! When more water is added, the fluidity and filling properties are further improved, filling concrete to every corner without leaving any voids inside the steel pipe, which has a complex inner shape with protruding protrusions or diaphragms. What can be done: ■ If the amount of water-soluble thickener contained in concrete is less than 0.2 kg/m3, the occurrence of breathing and the separation of coarse aggregate will not be satisfactorily suppressed; If it exceeds m, the occurrence of breathing and the separation of coarse aggregate will be suppressed, but the compressive strength of hardened concrete may actually be lower than that of concrete to which no water-soluble thickener has been added. , decrease, and ■ If the amount of AEfIi water agent added to concrete is less than 0.3 kg/bo, the above-mentioned further improvement effect on fluidity and filling properties cannot be obtained; It was found that if the weight exceeds 1.5 kg/bo, aggregate separation or abnormal coagulation may occur.

[Means to solve the problem]

The present invention was invented based on the above knowledge, and in a concrete filling member consisting of a steel pipe and hardened concrete filled inside the steel pipe, the adhesive force between the steel pipe and the hardened concrete is increased to integrate the two. (1) Concrete filling in which hardened concrete generated by hardening of concrete is filled inside a steel pipe. In the member, the concrete has a content of 0.2 to 0
．． A concrete filling member characterized by containing a water-soluble thickener at a mixing ratio of 5 kg/rff, and (2) a steel pipe filled with hardened concrete produced by hardening the concrete. In the concrete filling member, the concrete has a content of 0.2 to 0.
．． A water-soluble thickener with a blending ratio of 5 kg/rrf and 0
．． This invention relates to a concrete filling member characterized by containing an AE water reducing agent at a mixing ratio of 3 to 1.5 kg/nl.

[Detailed description of the invention]

As mentioned above, water-soluble thickeners prevent the occurrence of breathing in concrete, thus reducing the adhesion of concrete to steel pipes, and the separation of coarse aggregate, thus preventing variations in compressive strength in the axial direction of hardened concrete. This water-soluble thickener has the effect of improving the fluidity and filling properties of concrete, and any water-soluble thickener conventionally used in the technical field of the present invention can be used. For example, methyl cellulose, anionic polyacrylamide and hydroxyethyl cellulose are each preferably used, and two or more of these thickeners can also be used in combination.

The content of water-soluble thickener is 0.2 to 0.5 kg/m3
It is important that The unit of this content means the weight of the thickener added to a mixture of water, cement, fine aggregate, and coarse aggregate, ie, one volume of concrete.

As the steel pipe, any steel pipe of any shape and size that is conventionally used in the technical field of the present invention and made of steel materials of any composition can be used, such as square steel pipes and round steel pipes. is conveniently used.

Furthermore, if necessary, the AEI water agent added to the concrete of the present invention has the effect of appropriately adjusting the slump flow value of the concrete and further improving the fluidity and filling properties of the concrete. Concrete containing AE water reduction within the scope of the present invention can be filled into the inside of a steel pipe without forming any cavities or slabs even if some or no vibration compaction is applied at the time of pouring. This makes construction extremely easy.

As this AEfi water agent, AE water reducing agents that have been conventionally used in the technical field of the present invention can also be adopted, but for example, geninsulfonic acid compounds, highly condensed triazine compounds, anionic compounds, oquine carboxylic acid compounds, etc. Compounds etc. are preferably used.

〔Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

Example 1 Using fine aggregate with a particle size of 5 square meters or less, coarse aggregate with a particle size of 5 to 20 square meters, and a lignin sulfonic acid compound as an AE water reducing agent, the water-cement ratio and fine aggregate as shown in Table 1 were used. Invention concretes 1 to 4 (containing methyl cellulose) and comparative concretes 1 to 2 (not including methyl cellulose) having the aggregate ratio and blending amount were manufactured, respectively, and the slump value and air content of these concrete samples were determined. measure,
Then each of these concretes was made to have a diameter of 318.5
After filling a round steel pipe with a thickness of 6.9 mm, it was allowed to cure for 28 days, and as shown in Fig. Concrete filling members 1 to 4 of the present invention and comparative concrete filling members 1 to 2 were manufactured.

Next, in order to investigate the adhesion strength between the hardened concrete and the steel pipe in these concrete filling members, the amount of slippage (■) between the hardened concrete and the steel pipe was determined to be 0.05.0.10 using a displacement needle and a strain gauge attached to the steel pipe. .0
．． 15. Adhesion stress degree (kgf/cd) and maximum adhesion stress degree (kgf/cj) when 0.20 and 0.25.
) was measured.

Table 1 shows the slump value and air amount measured as described above, while Table 2 shows the values of adhesion stress and maximum adhesion stress for various amounts of slip.

From the results shown in Table 2, it can be seen that the degree of adhesion stress and the degree of maximum adhesion with respect to the amount of sliding of the concrete filling members 1 to 4 of the present invention are the same as the degree of adhesion stress and the degree of maximum adhesion with respect to the amount of sliding of filling members 1 to 2 of the present invention. greater than the stress level,
The concrete filling members (1 to 4) of the present invention are composite members with greater adhesion strength between the internal concrete and surrounding steel pipes and superior integrity than the comparative concrete filling members 1 to 2 (conventional concrete filling members). I understand that.

Example 2 Inventive concrete 1 and comparative concrete 1 produced in Example 1 were put into a 600 mm x 450 mm x 1800 mm formwork and allowed to cure for 28 days, and then the lower end of the hardened concrete after demolding from 20C11,6 respectively
The compressive strength of each core specimen of diameter 100 cm x height 200 cm collected at 01,100 CI, 140 cm and 1801 apart positions was measured by the uniaxial compressive strength test method,
The results are shown in the form of a graph of the compressive strength of the core specimen: S (kgf/cd) against the core sampling height: h (am).
Shown in the figure.

From the graph a for the concrete 1 of the present invention and the graph b for the comparative concrete 1 shown in FIG. 2, it can be seen that in the comparative concrete 1, as the core collection height h increases, the occurrence of breathing and coarse aggregate separation and the consolidation effect cause the concrete to While the compressive strength of
In Invention Concrete 1, the compressive strength of the core specimen does not decrease even when the core sampling height increases, and a high compressive strength that is almost uniform from the bottom end to the top end of the filled concrete is maintained. It can be seen that in No. 1, breathing and separation of aggregate are prevented, and a concrete filling member with excellent strength can be formed without any variation in strength in the axial direction.

〔Effect of the invention〕

As is clear from the above description, according to the present invention,
This suppresses the occurrence of breathing and the separation of aggregate in the concrete filled into the steel pipes, improves the adhesion between the steel pipes and hardened concrete, and makes the quality uniform in the axial direction, and therefore the strength, as a result of the overall We provide concrete filling members with high toughness and high yield strength as
It is possible to provide a structural member particularly suitable for the construction of skyscrapers.

[Brief explanation of drawings]

FIG. 1 is a partial longitudinal cross-sectional side view showing a concrete-filled column manufactured by the present invention or the prior art, and FIG. 2 is a diagram showing the relationship between the height of the internal concrete and the compressive strength of the concrete-filled member by the present invention and the prior art. Graph, 3rd
The figure is a vertical cross-sectional view to show the voids that occur when conventional concrete is filled inside a steel pipe with various protrusions on the inner surface, and Figure 4 shows that the breathing rate of concrete changes over time as water solubility increases. In Figure 0, which is a graph showing how it changes with the amount of adhesive added, 1, 1...concrete, 2.2...a pipe.

Claims (2)

[Claims] (1) In a concrete filling member in which the inside of a steel pipe is filled with hardened concrete generated by hardening of concrete, the concrete is 0.2 to 0.
．． A concrete filling member characterized by containing a water-soluble thickener at a mixing ratio of 5 kg/m^3. (2) In a concrete filling member in which the inside of a steel pipe is filled with hardened concrete generated by hardening of concrete, the concrete is 0.2 to 0.
．． A water-soluble thickener with a blending ratio of 5 kg/m^3 and 0.
A concrete filling member characterized by containing an AE water reducing agent at a mixing ratio of 3 to 1.5 kg/m^3.