JP2006137630A - Concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete, whose self-shrinkage is suppressed, and which develops a compression strength of ≥100 N/mm<SP>2</SP>. <P>SOLUTION: The concrete contains at least cement, a pozzolanic fine powder, an inorganic powder, a fine aggregate, a water reducing agent, water, and an expandable admixture. The inorganic powder comprises an inorganic powder A, which has a Blaine specific surface area of 5,000-30,000 cm<SP>2</SP>/g, and an inorganic powder B, which has a Blaine specific surface area of 2,500-5,000 cm<SP>2</SP>/g. The concrete contains one or more kinds of fibers selected from the group consisting of a metal fiber, an organic fiber, and a carbon fiber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a concrete that suppresses self-shrinkage and exhibits a compressive strength of 100 N / mm ² or more.

Conventionally, concrete having excellent mechanical properties (compressive strength, bending strength, etc.) has been developed.
Patent Document 1 below discloses inorganic particles A (for example, silica dust) having a particle size of 0.05 to 0.5 μm, particles B (for example, Portland cement) having a particle size of 0.5 to 100 μm and at least one order larger than the particle A, and surface activity. A concrete is disclosed that includes a dispersant and an additional material C (selected from the group consisting of sand, stone, fibers, etc.). The concrete exhibits a compressive strength of 100 N / mm ² or more by setting the water / binder ratio to 0.2 or less.

Japanese Patent Publication No. 60-59182

  However, the concrete described in Patent Document 1 causes a problem that self-shrinkage increases. If the self-shrinkage increases, there is a high possibility that cracks will occur when the concrete is hardened. Therefore, it has been desired to develop a method for suppressing the self-shrinkage.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a concrete that suppresses self-shrinkage and exhibits a compressive strength of 100 N / mm ² or more.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved if the concrete is a combination of specific materials, and the present invention has been completed.

That is, the present invention is concrete comprising at least cement, pozzolanic fine powder, inorganic powder, fine aggregate, water reducing agent, water and an expandable admixture (Claim 1). With such a concrete structure, self-shrinkage is suppressed and a compressive strength of 100 N / mm ² or more can be expressed. Moreover, it can be excellent in durability. Furthermore, since it has self-fluidity, operations such as casting and molding can be easily performed.
In the present invention, the inorganic powder may be composed of an inorganic powder A of Blaine specific surface area 5000~30000cm ² / g, the Blaine specific surface area 2500~5000cm ² / g and inorganic powder B (claim 2) . Thus, by using two kinds of inorganic powders having different brain specific surface areas, it is possible to further improve the workability of concrete, the development of strength after curing, and the durability.
The concrete can include one or more kinds of fibers selected from the group consisting of metal fibers, organic fibers, and carbon fibers (Claim 3). Thus, by including a metal fiber etc., the bending strength after breaking, a fracture strength, etc. can be improved.

According to the present invention, there is provided a concrete that suppresses self-shrinkage and exhibits a compressive strength of 100 N / mm ² or more.

Hereinafter, the present invention will be described in detail.
Examples of the cement used in the present invention include various Portland cements such as ordinary Portland cement, early-strength Portland cement, medium heat Portland cement, and low heat Portland cement.
In the present invention, when it is intended to improve the early strength of concrete, it is preferable to use early-strength Portland cement. It is preferable to use an agent.

Blaine specific surface area of the cement, preferably ^{2500~5000cm 2 / g, 3000~4500cm 2 /} g is more preferable. If the value is less than 2500 cm ² / g, the hydration reaction becomes inactive and the strength development after curing is reduced. If it exceeds 5000 cm ² / g, it takes time to grind the cement. In addition, since the amount of water for obtaining a predetermined fluidity increases, there is a drawback that strength development after curing is reduced.

Examples of the pozzolanic fine powder include silica fume, silica dust, fly ash, slag, volcanic ash, silica sol, and precipitated silica.
In general, silica fume and silica dust have a BET specific surface area of 5 to 25 m ² / g and do not need to be pulverized, and thus are suitable as the pozzolanic fine powder of the present invention.
BET specific surface area of the pozzolanic substance fine powder is preferably ^{5~25m 2 / g, 5~15m 2 /} g is more preferable. If the value is less than 5 m ² / g, there are disadvantages such as reduced strength development after curing, and if it exceeds 25 m ² / g, the amount of water for obtaining a predetermined fluidity increases, There are disadvantages such as later deterioration in strength.
The blending amount of the pozzolanic fine powder is 5 to 50 parts by mass, preferably 10 to 40 parts by mass with respect to 100 parts by mass of cement. When the blending amount is outside the range of 5 to 50 parts by mass, there are disadvantages such as the workability of the concrete is decreased, the self-shrinkage is increased, and the strength development property after curing is decreased.

As the fine aggregate, river sand, land sand, sea sand, crushed sand, silica sand and the like, or a mixture thereof can be used.
In the present invention, it is preferable to use a fine aggregate having a maximum particle size of 2 mm or less, and a fine particle having a maximum particle size of 1.5 mm or less from the viewpoint of fluidity of the concrete, strength development after hardening, durability and the like. More preferably, aggregate is used.
The amount of fine aggregate is preferably 50 to 250 parts by weight with respect to 100 parts by weight of cement, from the viewpoint of workability of concrete, self-shrinking, strength development after hardening and durability, 80 to 200 parts by weight. More preferably, it is part by mass.

Examples of the inorganic powder include slag, limestone powder, feldspar, mullite, alumina powder, quartz powder, fly ash, volcanic ash, silica sol, carbide powder, and nitride powder. Among these, slag, limestone powder, and quartz powder are preferably used in terms of cost and quality stability after curing.
The inorganic powder preferably has a Blaine specific surface area of 2500 to 30000 cm ² / g, more preferably 4000 to 20000 cm ² / g, and a Blaine specific surface area larger than that of cement. If the Blaine specific surface area of the inorganic powder is less than 2500 cm ² / g, the difference in Blaine specific surface area with the cement will be small, resulting in reduced workability of the concrete and reduced strength development after curing. If it exceeds 30000 cm ² / g, there are drawbacks such as difficulty in obtaining materials because of the time required for pulverization, and deterioration of workability of concrete.

Since the inorganic powder has a larger Blaine specific surface area than cement, the inorganic powder has a particle size that fills the gap between the cement and the pozzolanic fine powder. Can be improved.
The difference in the specific surface area of the brain between the inorganic powder and the cement is preferably 1000 cm ² / g or more, and more preferably 2000 cm ² / g or more, from the viewpoint of workability of the concrete, strength development after hardening, and durability.
The blending amount of the inorganic powder is preferably 5 to 55 parts by weight, more preferably 10 to 50 parts by weight with respect to 100 parts by weight of cement, from the viewpoint of workability of concrete, self-shrinkage, strength development after hardening and durability. preferable.

In the present invention, two different inorganic powders A and B can be used in combination as the inorganic powder.
In this case, the inorganic powder A and the inorganic powder B may use the same type of powder (for example, limestone powder) or different types of powder (for example, limestone powder and quartz powder).
The inorganic powder A has a Blaine specific surface area of 5000 to 30000 cm ² / g, preferably 6000 to 20000 cm ² / g. Moreover, the inorganic powder A has a larger Blaine specific surface area than the cement and the inorganic powder B.
When the specific surface area of the inorganic powder A is less than 5000 cm ² / g, the difference in the specific surface area of the brane with the cement or the inorganic powder B is reduced, and the concrete work is compared with the case where the above-mentioned one kind of inorganic powder is used. The effect of improving the property, the strength development property after hardening, and the durability are reduced, and since two kinds of inorganic powders are used, it takes time to prepare the material, which is not preferable. When the specific surface area of the branes exceeds 30000 cm ² / g, it takes time to grind, so that there are drawbacks such as difficulty in obtaining materials and reduced workability of concrete.

In addition, the inorganic powder A has a grain size that fills the gap between the cement and the inorganic powder B and the pozzolanic fine powder because the inorganic powder A has a larger Blaine specific surface area than the cement and the inorganic powder B. Thus, the workability of concrete, the strength development after hardening and the durability can be further improved.
The difference in the specific surface area of the brain between the inorganic powder A and the cement and the inorganic powder B (in other words, the difference in the specific surface area of the brain between the inorganic powder A and the larger one of the cement and the inorganic powder B). From the standpoint of improving the workability, strength development after curing, and durability, 1000 cm ² / g or more is preferable, and 2000 cm ² / g or more is more preferable.

The inorganic powder B has a Blaine specific surface area of 2500 to 5000 cm ² / g. The difference between the Blaine specific surface area of the cement and the inorganic particles B is preferably at least 100 cm ² / g, workability of the concrete, from the viewpoint of strength development and durability after curing, more 200 cm ² / g and more preferably .
If the Blaine specific surface area of the inorganic powder B is less than 2500 cm ² / g, workability of the concrete is decreased, strength development after curing has drawbacks such as a decrease, and when it exceeds 5000 cm ² / g, the Blaine specific Since the numerical value of the surface area approaches that of the inorganic powder A, the effect of improving the workability of the concrete, the strength development after hardening, and the durability is reduced as compared with the case of using the above-mentioned one kind of inorganic powder. Since seed inorganic powder is used, it takes time to prepare the material, which is not preferable.
In addition, the difference in the Blaine specific surface area between the cement and the inorganic powder B is 100 cm ² / g or more, so that the filling property of the particles constituting the concrete is improved, the workability of the concrete, the strength development after hardening and the durability The sex can be further improved.

The blending amount of the inorganic powder A is preferably 50 parts by mass or less, more preferably 5 to 45 parts by mass with respect to 100 parts by mass of cement. The blending amount of the inorganic powder B is preferably 40 parts by mass or less, more preferably 5 to 35 parts by mass with respect to 100 parts by mass of cement. When the blending amount of the inorganic powder A and the inorganic powder B is outside the above numerical range, the effect of improving the workability of concrete, the strength development property and durability after curing, compared to the case of using the one kind of inorganic powder. This is not preferable because the preparation of the material takes time because two kinds of inorganic powders are used.
In addition, 5-55 mass parts is preferable with respect to 100 mass parts of cement, and, as for the total amount of inorganic powder A and inorganic powder B, More preferably, it is 10-50 mass parts.

As the water reducing agent, a lignin-based, naphthalenesulfonic acid-based, melamine-based, or polycarboxylic acid-based water reducing agent, an AE water reducing agent, a high-performance water reducing agent, or a high-performance AE water reducing agent can be used. Among these, it is preferable to use a high performance water reducing agent or a high performance AE water reducing agent having a large water reducing effect, and it is more preferable to use a polycarboxylic acid-based high performance water reducing agent or a high performance AE water reducing agent.
The blending amount of the water reducing agent is preferably 0.1 to 4.0 parts by mass, more preferably 0.1 to 1.0 part by mass in terms of solid content with respect to 100 parts by mass of cement. If the blending amount is less than 0.1 parts by mass, kneading becomes difficult and there are disadvantages such as the workability of concrete being extremely lowered. If the blending amount exceeds 4.0 parts by mass, material separation and significant setting delay may occur, and strength development after curing may decrease.
The water reducing agent can be used in a liquid or powder form.

Examples of the expandable admixture include lime-based expandable materials and calcium sulfoaluminate-based expandable materials. The fineness of the expandable admixture is preferably 2000 cm ² or more in terms of Blaine specific surface area. When the Blaine specific surface area of the expandable admixture is less than 2000 cm ² , the effect of reducing the self-shrinkage becomes small. The fineness of the expandable admixture is more preferably 3000 to 8000 cm ² / g from the viewpoints of cost, concrete workability, and self-shrinkage reduction.
The amount of the expandable admixture is preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass with respect to 100 parts by mass of cement. When the amount of the expandable admixture is less than 1 part by mass, the effect of reducing the self-shrinkage is reduced. If it exceeds 15 parts by mass, the workability of the concrete will be lowered, and the strength development after curing may be lowered.

In the present invention, the expandable admixture, major minerals _{3CaO · SiO 2 -2CaO · SiO 2} -CaO- gap material, 3CaO · SiO ₂ -CaO- gap material, 2CaO · SiO ₂ -CaO- gap material or It is preferable to use a mixture of pulverized clinker composition and gypsum which is CaO-interstitial material and contains CaO crystals in an amount of 50 to 92% by mass, or a mixture of pulverized clinker composition and quick lime and gypsum. .

Clinker composition in the mixture comprises at least CaO crystal and the gap material as a major minerals may or may not be included include alite (3CaO · SiO ₂₎ and / or belite (2CaO · SiO ₂₎ clinker The composition is pulverized and contains 50 to 92% by mass of CaO crystals. By containing at least CaO crystals and interstitial substances as the main mineral, the effect of reducing the self-shrinkage of the concrete can be obtained without impairing workability. When the CaO crystal in the clinker composition is less than 50% by mass, the effect of reducing the self-shrinkage of the concrete is reduced. When the CaO crystal in the clinker pulverized product exceeds 92% by mass, the workability of the concrete deteriorates. The interstitial substances are similar to the minerals that fill the space between alite and belite in cement clinker minerals. Specifically, calcium ferrite minerals such as 2CaO · Fe ₂ O ₃ and 3CaO · Al ₂ O ₃ etc. Calcium aluminate minerals such as 6CaO ・ Al ₂ O ₃・ Fe ₂ O ₃ , 4CaO ・ Al ₂ O ₃・ Fe ₂ O ₃ , 6CaO ・ 2Al ₂ O ₃・ Fe ₂ O ₃ etc. is there.

  The type of gypsum in the mixture is not limited, and anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum can be used, but anhydrous gypsum is preferable. The amount of gypsum in the mixture is appropriately 5 to 50 parts by mass with respect to 100 parts by mass of the clinker composition when the mixture is a two-component system of the clinker composition and gypsum. Moreover, when a mixture is a ternary system of a clinker composition, quicklime, and gypsum, 5-50 mass parts of gypsum is suitable with respect to 100 mass parts of total amounts of a clinker composition and quicklime. When the amount of gypsum in the mixture is less than the above range, the effect of reducing the self-shrinkage of the concrete is reduced. When the blending amount of gypsum is larger than the above range, there is a concern that the concrete may cause a decrease in strength due to expansion cracks.

When the mixture is a ternary system of clinker composition and quicklime and gypsum, the kind of quicklime is not limited, and quicklime such as soft calcined quicklime, medium calcined quicklime, hard calcined quicklime, and extremely hard calcined quicklime can be used. From the viewpoint of workability of concrete, it is preferable to use quick lime having a coarse titration test value of 650 ml or less by the coarse titration test method using 4N-hydrochloric acid of the Japan Lime Association, and more preferably 400 ml or less.
The amount of quicklime is suitably less than 400 parts by weight with respect to 100 parts by weight of the clinker composition, that is, less than 80% by weight of quicklime in the total amount of the clinker composition and quicklime. If the amount of quicklime in the mixture is greater than the above range, the workability of the concrete will be reduced.

The brane specific surface area of the above mixture is preferably 3500 cm ² / g or more, and more preferably 4000 to 8000 cm ² / g from the viewpoint of workability of concrete, self-shrinkage, cost, and the like. When the Blaine specific surface area of the mixture is less than 3500 cm ² / g, the effect of reducing the self-shrinkage of the concrete is reduced.
The blending amount of the above mixture is preferably 1 to 10 parts by mass with respect to 100 parts by mass of cement in view of workability of concrete, self-shrinkage, strength development after curing, and the like.

  The amount of water is preferably 10 to 35 parts by mass, more preferably 12 to 30 parts by mass with respect to 100 parts by mass of cement. If the amount of water is less than 10 parts by mass, kneading becomes difficult and the workability of the concrete is extremely lowered. When the amount of water exceeds 30 parts by mass, strength development after curing decreases.

In the present invention, it is preferable to blend one or more fibers selected from the group consisting of metal fibers, organic fibers, and carbon fibers into the concrete from the viewpoint of greatly increasing the bending strength, fracture strength, etc. of the concrete.
A metal fiber is mix | blended from a viewpoint which raises the bending strength etc. after hardening significantly.
Examples of metal fibers include steel fibers, stainless fibers, and amorphous fibers. Among these, steel fibers are excellent in strength and are preferable from the viewpoint of cost and availability. The dimension of the metal fiber is preferably 0.01 to 1.0 mm in diameter and 2 to 30 mm in length from the viewpoint of preventing material separation of the metal fiber in the concrete and improving the bending strength after curing. More preferably, the length is 0.05 to 0.5 mm and the length is 5 to 25 mm. The aspect ratio (fiber length / fiber diameter) of the metal fiber is preferably 20 to 200, more preferably 40 to 150.

The shape of the metal fiber is preferably a shape that imparts some physical adhesion (for example, a spiral shape or a waveform) rather than a straight shape. If it is in a spiral shape or the like, the stress is secured while the metal fibers and the matrix are pulled out, so that the bending strength is improved.
Preferable examples of metal fibers include, for example, interfacial adhesion to a matrix of a cementitious hardened body made of steel fibers having a diameter of 0.5 mm or less and a tensile strength of 1 to 3.5 GPa and having a compressive strength of 120 N / mm ^2. The strength (maximum tensile force per unit area of the adhesion surface) is 3 N / mm ² or more. In this example, the metal fiber can be processed into a corrugated or helical shape. Moreover, the groove | channel or processus | protrusion for resisting the motion (longitudinal slip) with respect to a matrix can also be attached on the surrounding surface of the metal fiber of this example. The metal fiber of this example has a metal layer having a Young's modulus smaller than the Young's modulus of the steel fiber on the surface of the steel fiber (for example, one or more selected from zinc, tin, copper, aluminum, etc.) It is good also as what provided.

  The blending amount of the metal fiber is preferably 4% or less, more preferably 0.5 to 3%, and particularly preferably 1 to 3% by volume percentage in the concrete. If the blending amount exceeds 4%, the unit water amount increases in order to ensure fluidity and the reinforcing effect of the metal fiber is not improved even if the blending amount is increased. Therefore, it is not preferable because so-called fiber balls are easily formed.

The organic fiber and the carbon fiber are blended from the viewpoint of increasing the breaking strength after curing.
Examples of the organic fiber include vinylon fiber, polypropylene fiber, polyethylene fiber, and aramid fiber. Among these, vinylon fibers and / or polypropylene fibers are preferably used in terms of cost and availability.
Examples of the carbon fiber include PAN-based carbon fiber and pitch-based carbon fiber.
The dimensions of the organic fibers and carbon fibers are preferably 0.005 to 1.0 mm in diameter and 2 to 30 mm in length from the viewpoint of preventing material separation of these fibers in the concrete and improving the breaking strength after curing. More preferably, the diameter is 0.01 to 0.5 mm and the length is 5 to 25 mm. Further, the aspect ratio (fiber length / fiber diameter) of the organic fiber and the carbon fiber is preferably 20 to 200, more preferably 30 to 150.

  The blending amount of the organic fiber and the carbon fiber is preferably 10.0% or less, more preferably 1.0 to 9.0%, and particularly preferably 2.0 to 8.0% by volume percentage in the concrete. If the blending amount exceeds 10.0%, the unit water amount increases to ensure fluidity and the like, and even if the blending amount is increased, the fiber reinforcing effect is not improved. Since it becomes easy to produce a fiber ball, it is not preferred.

  In the present invention, from the viewpoint of increasing the toughness after curing, it is preferable to blend fibrous particles or flaky particles with an average particle size of 1 mm or less into concrete. Here, the particle size of the particle is the size of the maximum dimension (particularly, the length of the fibrous particle). Examples of fibrous particles include wollastonite, bauxite, mullite, and examples of flaky particles include mica flakes, talc flakes, vermiculite flakes, and alumina flakes. The blending amount of the fibrous particles or flaky particles is preferably 35 parts by mass or less, and 5 to 25 parts by mass with respect to 100 parts by mass of cement, from the workability of concrete, strength development after curing, durability and toughness. Is more preferable. In addition, it is preferable to use a fibrous particle having a needle-like degree represented by a length / diameter ratio of 3 or more from the viewpoint of increasing toughness after curing.

The concrete kneading method is not particularly limited. For example, (1) materials other than water and water reducing agent are mixed in advance to prepare a premix material, and the premix material, water and water reducing agent are prepared. (2) Prepare a powdery water reducing agent, mix materials other than water in advance, prepare a premix material, and add the premix material and water to the mixer. A method of charging and kneading, (3) a method of individually charging each material into a mixer, and kneading can be employed.
The mixer used for kneading may be of any type used for ordinary concrete kneading. For example, a rocking mixer, a pan type mixer, a biaxial kneading mixer, or the like is used.
The concrete curing method of the present invention is not particularly limited, for example, conventional means such as air curing, wet air curing, underwater curing, heating accelerated curing (steam curing, autoclave curing), or a combination thereof. Should be done.

  In addition, the concrete of the present invention is a flow measured without performing the falling motion 15 times in the method described in “JIS R 5201 (Cement physical test method) 11. Flow test” because of the workability of the concrete. The value is preferably 220 mm or more, and more preferably 240 mm or more.

Hereinafter, the present invention will be described by way of examples.
[1. Materials used]
The following materials were used.
(1) Cement; Low heat Portland cement (manufactured by Taiheiyo Cement)
; Blaine specific surface area 3200cm ² / g)
(2) Pozzolanic fine powder; silica fume (BET specific surface area 10 m ² / g)
(3) Inorganic powder; quartz powder (Blaine specific surface area 7500cm ² / g)
(4) Fine aggregate: quartz sand (maximum particle size 0.6mm)
(5) Water reducing agent; Polycarboxylic acid-based high-performance water reducing agent (6) Water; Tap water (7) Metal fiber; Steel fiber (diameter: 0.2 mm, length: 15 mm)
(8) expandable admixture;
A: "Expan" (manufactured by Taiheiyo Materials, lime-based expansion material)
B: "Expan Hyper" (manufactured by Taiheiyo Materials Co., Ltd., lime-based expansion material)
C: Limestone, quartzite, clay, and iron raw materials are mixed so as to have the mineral composition shown in Table 1, and the mixture is baked in a rotary kiln at a firing temperature of 1300-1600 ° C and a residence time of 60-120 minutes to produce a clinker. , which was ground to a Blaine specific surface area of 5000 cm ² / g, said a clinker composition 100 mass parts, anhydrous gypsum (Blaine specific surface area of 6500cm ² / g) 10 parts by mass a mixture of.

Low heat Portland cement 100 parts by weight, silica fume 31 parts by weight, quartz powder 35 parts by weight, silica sand 110 parts by weight, high performance AE water reducing agent 1.0 part by weight (solid content with respect to cement), water 28 parts by weight and expansive admixture shown in Table 2 The material was put into a pan type mixer and kneaded for 12 minutes to prepare concrete.
The length change test of each concrete was conducted. The change in length was measured according to “JIS A 6202”. The curing was allowed to stand at 20 ° C. for 48 hours, then demolded, and steam-cured at 90 ° C. for 48 hours. The results are shown in FIG.

  From FIG. 1, it can be seen that the self-shrinkage is remarkably suppressed in the concrete of the present invention as compared with the concrete not containing the expandable admixture.

Low heat Portland cement 100 parts by weight, silica fume 31 parts by weight, quartz powder 35 parts by weight, silica sand 110 parts by weight, high performance AE water reducing agent 1.0 part by weight (solid content with respect to cement), water 28 parts by weight and expansive admixture C (compounding) The amount shown in Table 3) was put into a pan type mixer and kneaded for 12 minutes to prepare concrete.
The length change test of each concrete was conducted. The length change was measured according to “JIS A 6202”. The curing was allowed to stand at 20 ° C. for 48 hours, then demolded, and steam-cured at 90 ° C. for 48 hours. The results are shown in FIG.

  From FIG. 2, it can be seen that the concrete of the present invention has suppressed self-shrinkage compared to the concrete not including the expandable admixture.

  In the method described in “JIS R 5201 (Cement physical test method) 11. Flow test”, the flow values of the concretes with the blending numbers 1, 3, and 4 were measured without performing 15 drop motions. As a result, the flow value of the concrete 1 was 265 mm, the flow value of the concrete 3 was 260 mm, and the flow value of the concrete 4 was 270 mm.

Concretes of the above blending numbers 1, 3 and 4 were filled in a mold of φ10 × 20 cm, allowed to stand at 20 ° C. for 48 hours, and then steam-cured at 90 ° C. for 48 hours. Compressive strength of the cured resin (average pieces of 3), in one of the concrete in the concrete 205N / mm ^2, 3 in the concrete 200 N / mm ^2, 4 was 200 N / mm ^2.

It is a figure which shows the length change test result of each concrete manufactured in the Example. It is a figure which shows the length change test result of each concrete manufactured in the Example.

Claims (3)

Concrete comprising at least cement, pozzolanic fine powder, inorganic powder, fine aggregate, water reducing agent, water, and expandable admixture. Inorganic powder, the Blaine specific surface area 5000~30000cm ² / g of the inorganic powder A and concrete according to claim 1, wherein comprising an inorganic powder B of Blaine specific surface area 2500~5000cm ² / g. The concrete according to claim 1 or 2, comprising one or more fibers selected from the group consisting of metal fibers, organic fibers, and carbon fibers.

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