JP2001220201A - Fiber reinforced concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultra high strength concrete hardened material excellent in a flexural strength, a tensile strength and a toughness. SOLUTION: A fiber reinforced concrete containing at least a cement, a pozzolanic fine powder, aggregates having particle diameters of <=2 mm, water, a water reducing agent, an organic fiber and a modified-shape steel fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high-strength hardened concrete, particularly fiber-reinforced concrete, which is excellent in bending strength and tensile strength and also excellent in toughness.

[0002]

2. Description of the Related Art Conventional steel fiber reinforced concrete has a small interfacial bond strength between steel fiber and concrete serving as a matrix as compared with fiber strength, and the fiber reinforcing effect has not always been sufficiently exhibited. Further, even if the steel fiber is formed into a so-called irregular shape such as indentation or bending, the bonding strength can be increased, but the matrix is destroyed when the fiber is pulled out, and the load that the fiber bears rapidly decreases. Therefore, there is a problem that the toughness of the fiber reinforced concrete is reduced.

[0003]

SUMMARY OF THE INVENTION The present invention improves the strength of the matrix of fiber-reinforced concrete and exerts the good interfacial adhesion characteristics of deformed steel fibers, thereby providing excellent bending strength and tensile strength, and furthermore, toughness. An object of the present invention is to provide an ultra-high-strength concrete hardened body excellent in quality.

[0004]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, at least cement, pozzolanic fine powder, aggregate having a particle size of 2 mm or less, water, water reducing agent, organic fiber The cured product of the composition containing the modified steel fiber and the modified steel fiber was found not only to have excellent bending strength and tensile strength, but also to have excellent toughness, and thus completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The type of cement used in the present invention is not limited. Various portland cements such as ordinary Portland cement, early-strength Portland cement, medium heat Portland cement, low heat Portland cement, and mixed cements such as blast furnace cement and fly ash cement can be used.

In the present invention, it is preferable to use an early-strength Portland cement in order to improve the early strength of concrete, and to use a medium-heat Portland cement or a low-heat Portland cement in order to improve the fluidity of concrete. It is preferred to use

The pozzolanic fine powder includes silica fume, silica dust, fly ash, slag, volcanic ash,
Silica sol, precipitated silica and the like. Generally, in silica fume and silica dust, the average particle size is 1.
Since it is 0 μm or less and it is not necessary to grind, it is suitable as the pozzolanic fine powder of the present invention.

By blending pozzolanic fine powder,
Due to the microfiller effect and the cement dispersing effect, the concrete is densified and the compressive strength is improved. on the other hand,
When the amount of the pozzolanic fine powder increases, the unit water amount increases.
It is preferably 5 to 50 parts by weight based on parts by weight.

In the present invention, an aggregate having a particle size of 2 mm or less is used. Here, the particle size of the aggregate is 85% (weight).
It is a cumulative particle size (an aggregate larger than 2 mm may be included). If the particle size of the aggregate exceeds 2 mm, the strength decreases. It is preferable to use an aggregate having a maximum particle size of 2 mm or less, more preferably an aggregate having a maximum particle size of 1.5 mm or less, from the viewpoint of the separation resistance of the concrete, the strength after hardening, and the like.

[0010] Aggregates include river sand, land sand, sea sand, crushed sand,
Silica sand, and mixtures thereof, can be used. The amount of the aggregate is preferably 50 to 250 parts by weight based on 100 parts by weight of cement, from the viewpoint of workability and separation resistance of concrete, strength after curing and resistance to cracks, and the like.
80 to 180 parts by weight are more preferred.

As the water reducing agent, a lignin-based, naphthalenesulfonic acid-based, melamine-based, 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 them, it is preferable to use a high performance water reducing agent or a high performance AE water reducing agent. The amount of the water reducing agent to be added is 0.5 to 4.0 parts by weight in terms of solid content with respect to 100 parts by weight of cement in view of the fluidity and separation resistance of concrete, the strength after hardening, and the cost. preferable.

In the present invention, the water / cement ratio is preferably from 10 to 30%, more preferably from 15 to 25%, from the viewpoint of the fluidity and separation resistance of concrete, the strength and durability of the cured product, and the like.

In the present invention, from the viewpoint of increasing the bending strength, tensile strength and toughness of the cured product, the composition contains deformed steel fibers and organic fibers. By mixing organic fibers, the strength of the matrix holding the deformed steel fibers is improved, so that even after cracks are generated by bending and tensile loads, the deformed steel fibers bear the load without breaking the surrounding matrix Therefore, dramatically high bending strength, tensile strength and toughness can be obtained.

The deformed steel fiber is a steel fiber having a so-called deformed shape, such as indentation, in which the cross-sectional shape of the fiber is periodically changed or the fiber is bent into a corrugated shape. And the bonding strength with the adhesive. The deformed steel fiber has a diameter of 0.01 to 1.0 mm and a length of 2
It is preferably 30 mm. If the diameter is less than 0.01 mm, the strength of the fiber itself is insufficient, and the fiber tends to be cut when subjected to tension. If the diameter exceeds 1.0 mm, the number of pieces with the same blending amount decreases, and the flexural strength of concrete decreases. If the length exceeds 30 mm, fiber balls tend to be formed during kneading. If the length is less than 2 mm, the adhesive strength to the matrix is reduced and the bending strength is reduced.

[0015] The compounding amount of the deformed steel fiber is preferably less than 4% of the concrete volume after setting, more preferably 3.5%.
Is less than. The content of the deformed steel fiber is determined from the viewpoint of fluidity and bending strength of the cured product. In general, as the content of the deformed steel fiber increases, the bending strength improves, but on the other hand, the unit water amount also increases in order to ensure fluidity. In addition, it is also possible to use together with a deformed steel fiber and a metal fiber such as a normal steel fiber or an amorphous fiber.

The organic fibers include vinylon fiber, polypropylene fiber, polyethylene fiber, aramid fiber, carbon fiber and the like. The organic fiber has a diameter of 0.005 to 0.5.
Those having a length of 5 mm and a length of 2 to 15 mm are preferred. The content of the organic fibers is preferably less than 10% of the concrete volume after setting, more preferably less than 7%.

In the present invention, from the viewpoint of increasing the packing density of the cured product, it is preferable to include an inorganic powder having an average particle size of 3 to 20 μm, more preferably 4 to 10 μm. As the inorganic powder, quartz powder, limestone powder, Al
Oxide powder such as ₂ O ₃ , carbide powder such as SiC, SiN
And the like, and among them, quartz powder is preferable in terms of cost and quality stability of the cured product. Examples of the quartz powder include quartz, amorphous quartz, and opal and cristobalite silica-containing powders. The amount of the inorganic powder is preferably 50 parts by weight or less, more preferably 20 to 35 parts by weight, based on 100 parts by weight of cement, from the viewpoint of the fluidity of the concrete, the strength of the hardened body, and the like.

In the present invention, from the viewpoint of increasing the toughness of the cured product, it is preferable to include fibrous particles or flaky particles having an average particle size of 1 mm or less. Here, the particle size of a particle is the size of its maximum dimension (in particular, its length for fibrous particles). Examples of the fibrous particles include wollastonite, bauxite, and mullite, and examples of the flaky particles include mica flake, talc flake, vermiculite flake, and alumina flake. The blending amount of the fibrous particles or flaky particles is preferably 35 parts by weight or less, more preferably 10 to 25 parts by weight, based on 100 parts by weight of cement, from the viewpoint of the fluidity of the concrete, the strength and the toughness of the cured product. From the viewpoint of enhancing the toughness of the cured product, it is preferable to use fibrous particles having a needleiness expressed by a length / diameter ratio of 3 or more.

In the present invention, the method for kneading concrete is not particularly limited. The apparatus used for kneading is not particularly limited, and a conventional mixer such as an omni mixer, a pan-type mixer, a biaxial kneading mixer, and a tilting mixer can be used.

The fiber-reinforced concrete of the present invention can be manufactured by molding, curing and hardening the kneaded concrete. The molding method is not particularly limited, and can be performed by a conventional molding method such as cast molding. Also, the method of curing the concrete is not particularly limited, and may be room temperature curing, steam curing, or the like.

[0021]

Hereinafter, the present invention will be described with reference to examples.
The present invention is not limited to these examples.

In Examples and Comparative Examples described below, materials used and test methods other than fibers are as follows. (Materials used) 1) Cement; Low heat Portland cement (manufactured by Taiheiyo Cement Corporation) 2) Pozzolanic fine powder; Silica fume (average particle size 0.7 μm) 3) Aggregate: 2: 1 of silica sand 4 and silica sand 5 Weight ratio) mixture 4) high performance AE water reducing agent; polycarboxylic acid high performance AE water reducing agent 5) water; tap water 6) quartz powder (average particle size 7 μm) 7) fibrous particles; wollastonite (average length) 0.3mm length, length / diameter ratio 4)

(Test Method) Materials other than fibers were put into a biaxial kneading mixer at once and kneaded. After the fluidity was developed, the fibers were added and kneaded again. Thereafter, concrete was poured into a formwork, placed at 20 ° C. for 48 hours, steam-cured at 90 ° C. for 48 hours, and provided with a specimen having a diameter of 5 cm, a height of 10 cm and a specimen of 4 cm long, 4 cm wide and 16 cm long. Specimens were molded, and the former was used for measurement of compressive strength, and the latter was used for measurement of four-point bending strength and breaking energy. In addition, the flow test method of the re-kneaded concrete was measured according to “JIS R 5201 (Physical test method of cement) 11. Flow test”. However, the measurement was performed without performing the falling motion 15 times.
Further, the fracture energy was obtained by dividing the integrated value of the load-displacement at the load point until the load decreased to 10% of the maximum load after the load became the maximum load in the four-point bending strength test, divided by the cross-sectional area of the test specimen. The value was adopted.

Example 1 (Fibers used) The fibers were vinylon fibers (diameter: 0.04 m).
m, length: 6 mm) and indented deformed steel fibers (diameter: 0.2 mm, length: 15 mm). (Blending conditions) Low heat Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 120 parts by weight High-performance AE water reducing agent; 1 part by weight (solid content) Water / cement ratio; 22% steel fiber; 2% by volume vinylon fiber; 0.8% by volume in concrete The flow values, compressive strength, flexural strength and breaking energy were measured using these materials according to the test methods described above. The results of these measurements are shown in Table 1.

Example 2 (Fiber used) Aramid fiber (diameter: 0.012)
mm, length: 6 mm) and corrugated deformed steel fiber (diameter: 0.1 mm, length: 12 mm) were used. (Blending conditions) Low heat Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 120 parts by weight High-performance AE water reducing agent; 1 part by weight (solid content) Water / cement ratio; 22% steel fiber; 2% of volume aramid fiber; 0.5% of volume in concrete These materials were used to measure the flow value, compressive strength, flexural strength and breaking energy according to the test method described above. The results of these measurements are shown in Table 1.

Example 3 (Used fiber) The fiber was carbon fiber (diameter: 0.007 m).
m, length: 6 mm) and indented deformed steel fibers (diameter: 0.5 mm, length: 25 mm). (Blending conditions) Low heat Portland cement; 100 parts by weight Silica fume; 32.5 parts by weight Aggregate: 120 parts by weight Quartz powder: 30 parts by weight Wollastonite: 24 parts by weight High-performance AE water reducing agent: 1 part by weight (solid content) Water / cement ratio; 22% steel fiber; 3% of volume in concrete Carbon fiber; 0.5% of volume in concrete Using these materials, flow values, compressive strength, flexural strength according to the above test method And the breaking energy were measured. The results of these measurements are shown in Table 1.

Comparative Example 1 The fiber was a steel fiber which had not been deformed (diameter: 0.1 mm).
2 mm, length: 15 mm) only. The test was conducted under the same blending conditions as in Example 1 except that the fiber amount was set to 2% of the volume in the concrete, and the flow value, the compressive strength, the bending strength, and the breaking energy were measured. The results of these measurements are shown in Table 1.

Comparative Example 2 The fiber was a deformed steel fiber (diameter: 0.1 m) processed into a corrugated shape.
m, length: 12 mm). The test was performed under the same blending conditions as in Example 2 except that the fiber amount was set to 2% of the volume in the concrete, and the flow value, the compressive strength, the bending strength, and the breaking energy were measured. The results of these measurements are shown in Table 1.

Comparative Example 3 Fibers were indented deformed steel fibers (diameter: 0.1 mm).
5 mm, length: 25 mm). The test was performed under the same blending conditions as in Example 3 except that the fiber amount was 3% of the volume in the concrete, and the flow value, the compressive strength, the bending strength, and the breaking energy were measured. The results of these measurements are shown in Table 1.

[0030]

[Table 1]

From Table 1, it can be seen that in all of the examples, the flexural strength and the breaking energy are significantly higher than those of the corresponding comparative examples, even though the concrete has substantially the same flow value and compressive strength. From that
It can be seen that the concrete matrix portion is significantly strengthened.

[0032]

According to the present invention, since the strength of the matrix holding the deformed steel fibers is improved, the deformed steel fibers can be loaded without breaking the surrounding matrix even after cracks are generated by bending and tensile loads. , A remarkably high bending strength, tensile strength and toughness can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 14:48) C04B 14:48) D 103: 32 103: 32

Claims (5)

[Claims] 1. A fiber reinforced concrete comprising at least cement, fine pozzolanic powder, aggregate having a particle size of 2 mm or less, water, a water reducing agent, organic fibers and deformed steel fibers. 2. The deformed steel fiber has a diameter of 0.01 to 1.0 m.
The fiber reinforced concrete according to claim 1, wherein m and the length are 2 to 30 mm. 3. The organic fiber has a diameter of 0.005 to 0.5 m.
The fiber-reinforced concrete according to claim 1 or 2, wherein the fiber-reinforced concrete is at least one fiber selected from vinylon fiber, polypropylene fiber, polyethylene fiber, aramid fiber, and carbon fiber having a length of 2 to 15 mm. 4. The fiber reinforced concrete according to claim 1, wherein the composition contains an inorganic powder having an average particle size of 3 to 20 μm. 5. The fiber-reinforced concrete according to claim 1, wherein the composition contains fibrous particles or flaky particles having an average particle size of 1 mm or less.