JP2014001092A - Endpoint hook type steel fiber for hydraulic material reinforcement, hydraulic material, and hydraulic material hardening body - Google Patents

Abstract

Disclosed is a double-end hook-type steel fiber for reinforcing a hydraulic material capable of forming a cured body excellent in compressive strength, tensile strength and toughness, a cured hydraulic material and a cured hydraulic material using the same.
A straight portion, a first hook portion bent from both ends of the straight portion so as to have an angle with the straight portion, and a straight portion formed by bending an end portion of the first hook portion. A second hook portion that is parallel to each other, the diameter (φ) of the steel fiber is 0.10 mm or more and 0.50 mm or less, and the length (l ₁ ) of the second hook portion is 1 mm or more ( l ₁ / φ) is 5 or more and 25 or less, the bending height (h) of the first hook portion is 0.3 mm or more, (h / φ) is 2 or more and 10 or less, and the first hook portion and the second hook portion The radius of curvature (r1) formed by the inner surface of the bent portion of the hook portion and the radius of curvature (r2) formed by the straight portion and the first hook portion are (r1 / φ) of 3 or more and 10 or less, (r2 / R1) is a double-end hook-type steel fiber for reinforcing a hydraulic material having a ratio of 1.5 to 10.
[Selection] Figure 1

Description

  The present invention relates to a double-end hook-type steel fiber for reinforcing a hydraulic material, a hydraulic material containing the double-end hook-type steel fiber, and a hydraulic material cured body obtained by curing the hydraulic material.

Hydraulic materials applied to civil engineering and building structures, especially hydraulic materials such as cement, mortar and concrete, are used for various purposes. Hardened materials of hydraulic materials have a high compressive strength, so that It is used widely. However, the cured hydraulic material is not sufficient in tensile strength with respect to excellent compressive strength, and in a structure such as concrete, it is designed in a usage mode that bears only the compressive force and does not bear the tensile force. It was general.
For the purpose of improving the strength against tensile stress, conventionally, a steel material for reinforcement is mixed with a hydraulic material, and in order to further improve resistance to pulling force, a deformed steel fiber such as corrugated steel is used. Techniques have been proposed in which fibers (for example, see Patent Document 1), S-shaped steel fibers (for example, see Patent Document 2), both-end deformed fibers (for example, see Patent Document 3), and the like as reinforcing materials.

  In recent years, improvements have been made to improve the compressive strength of hardened hydraulic materials typified by hardened concrete. In particular, the ratio of water to binder in the hydraulic material, that is, concrete is taken as an example. And a mass ratio (hereinafter, referred to as a water / binder ratio) of a material that hydrates in concrete such as cement, silica fume, blast furnace slag, fly ash, and the like. Various techniques have been proposed to increase the strength by reducing the mass (based on the mass, in particular). This is because when the water / binder ratio is reduced, the distance between the particles is reduced, and the hydrated product is precipitated and filled in the liquid phase portion, so that the structure becomes dense and concrete with high compressive strength is obtained. It is thought that it is.

If a high-strength cemented body is obtained, the column cross section of the structure can be reduced and the load area of the column load can be increased, which is useful for the construction of high-rise structures. , It will be possible to increase the spacing between the pillars of the building, it will be possible to increase the degree of freedom in the floor plan of the building, a great merit is born. On the other hand, higher resistance to tensile stress is required.
When the compressive strength of the cured hydraulic material is high, for example, when the compressive strength is 60 N / mm ² or more, there are cases where effective reinforcement cannot be achieved even if steel fibers that are conventionally used are used as they are.

JP-A-7-53247 JP 2001-220190 A JP 2005-170715 A

Usually, it is considered that the reinforcing fiber such as steel fiber exerts the reinforcing effect because the stress acting on the cured body is dispersed in the reinforcing fiber through the adhesive force.
As a result of detailed examinations by the present inventors, when the tensile stress increases and the deformation of the cured body proceeds, if the strength of the cured body is not sufficiently high, the reinforcing fibers escape while breaking the cured body. Although there is a tendency, when the water binder ratio is small and the compressive strength of the hardened hydraulic material is 60 N / mm ² or more, the hardened body is not destroyed, and the steel fibers themselves are pulled out by plastic deformation. For this reason, it has been found that conventionally known steel fibers cannot provide sufficient resistance to tensile stress.
The problems of the present invention in consideration of these problems are preferably used and formed for a hydraulic material having a small water / binder ratio, such that the compressive strength of the cured hydraulic material is 60 N / mm ² or more. Another object of the present invention is to provide a reinforcing fiber for a hydraulic material that improves not only the compressive strength of the cured hydraulic material but also the strength against tensile stress.
Another object of the present invention is a hydraulic material using the above-mentioned reinforcing fiber for hydraulic material of the present invention, and a cured hydraulic material that is excellent in both compressive strength and tensile strength obtained by the hydraulic material. Is to provide.

As a result of intensive studies, the inventors of the present invention have found that when the strength of the hardened hydraulic material is high, the frictional resistance and the plastic deformation energy during the removal of the reinforcing steel fibers while plastically deforming effectively act to increase the hydraulic properties. The present inventors have found that the above problems can be solved by improving the compressive strength, tensile strength, and toughness of the cured material, and optimizing the shape and strength of the steel fiber.
That is, the configuration of the present invention is as follows.
<1> A straight portion, a first hook portion bent at an angle with the straight portion from both ends of the straight portion, and an end portion of the first hook portion are bent in a direction away from each other. A double-ended hook-type steel fiber having a second hook portion parallel to the straight portion,
The diameter (φ) of the steel fiber is 0.10 mm or more and 0.50 mm or less,
The length (l ₁ ) of the second hook part is 1 mm or more, and the ratio (l ₁ / φ) of the diameter (φ) of the steel fiber to the length (l ₁ ) of the second hook part is 5 or more. 25 or less,
The bending height (h) of the first hook portion, which is the distance between the straight portion and the second hook portion, is 0.3 mm or more, and the diameter (φ) of the steel fiber and the bending height of the first hook portion. The ratio (h / φ) to (h) is 2 or more and 10 or less,
The radius of curvature of the R portion formed by the inner surface of the bent portion of the first hook portion and the second hook portion is defined as r1, and the inner surface of the bent portion of the straight portion and the first hook portion is formed by R. Both ends hook for hydraulic material reinforcement where r1 / φ is 3 or more and 10 or less and r2 / r1 is 1.5 or more and 10 or less when the radius of curvature of the part is r2 and the diameter of the steel fiber is φ Shaped steel fiber.

<2> The double-end hook-type steel fiber for reinforcing a hydraulic material according to <1>, wherein the total length (l _a ) of the double-end hook-type steel fiber is 6 mm or more and 50 mm or less.
<3> The relationship between the length (l ₂ ) of the straight part of the hook-type steel fiber at both ends and the length (l ₁ ) _{2 of} the second hook part satisfies the following formula <1> or <2> Both ends hook type steel fiber for hydraulic material reinforcement as described in 1.
(Formula) 6 × l ₁ <l ₂
<4> The double-end hook-type steel fiber for reinforcing a hydraulic material according to any one of <1> to <3>, wherein the tensile strength of the steel fiber constituting the double-end hook-type steel fiber is 2000 MPa to 5000 MPa.

<5> Cement, aggregate, water, and a water-binding material containing 0.5% by volume or more and 5.0% by volume or less of the double-end hook-type steel fiber according to any one of <1> to <4>. A hydraulic material having a ratio of 0.1 to 0.3 on a mass basis.
<6> A cured hydraulic material obtained by curing the hydraulic material according to <5> and having a compressive strength of 60 N / mm ² or more and a tensile strength of 10 N / mm ² or more.

  The hydraulic material in the present specification is a concept including cement, mortar, and concrete, and typically includes cement, aggregate, hydratable material, and water, and has a water / binder ratio ( Concrete compositions having a mass standard) of 0.1 or more and 0.3 or less are mentioned. The hardened hydraulic material is obtained by mixing a concrete composition and a cement composition, putting them in a formwork, and curing them. A hardened body is shown. In addition, when forming a high intensity | strength hardening body, in addition to normal curing, the steam curing which cures a hardening body in the temperature range of 70 to 100 degreeC for 2 hours to 72 hours, the temperature range of 100 to 400 degreeC It is also a preferred embodiment to carry out by appropriately combining one or more of high temperature curing and the like heated for 2 hours to 72 hours.

By using the reinforcing steel fibers of the present invention, the water / binder ratio is 0.1 or more and 0.3 or less by weight, compressive strength is in the range of ^{60N / mm 2 ~400N / mm 2} , and Moreover, a hydraulic material cured body excellent in strength and toughness against tensile stress can be formed, and such a hydraulic material cured body is also useful as a structural member such as a building.
The operation of the present invention is not clear, but is considered as follows.
In the both-end hook type steel fiber of the present invention, by setting the diameter of the steel fiber within the above range, the resistance against plastic deformation is ensured, the length (l ₁ ) of the second hook portion is sufficiently set, and the steel fiber The ratio (l ₁ / φ) of the diameter (φ) of the steel and the length (l ₁ ) of the second hook part is in the range of 5 to 25, the diameter (φ) of the steel fiber and the bending of the first hook part By setting the ratio (h / φ) to the height (h) to 2 or more and 10 or less and setting the radius of curvature to a specific range, the frictional resistance at the contact portion and the energy associated with the plastic deformation of the fiber are efficient. Can be obtained. In addition, when the steel fiber is pulled out, if it is accompanied by plastic deformation, there is a phenomenon that the strength lowers as the material before the plastic deformation occurs. To do. As a result, a large pulling resistance is obtained, the toughness is hardly reduced, and even a small amount of addition is considered to improve both the compressive strength and tensile strength of the cured hydraulic material. . In particular, it is effective for improving the tensile strength. The tensile strength here refers to the maximum value in terms of stress-strain relationship.

According to the present invention, the cured hydraulic material cured body suitably used for a hydraulic material having a small water / binder ratio such that the compressive strength of the cured hydraulic material is 60 N / mm ² or more. Reinforcement fibers for hydraulic materials that improve not only the compressive strength but also the strength and toughness against tensile stress are provided.
Moreover, by using the reinforcing fiber for hydraulic material of the present invention, a hydraulic material and a cured hydraulic material that is excellent in both compressive strength and tensile strength obtained by the hydraulic material are provided.

It is a schematic front view which shows an example of the both-ends hook type steel fiber of this invention. It is a schematic sectional drawing which shows the state in which the both ends hook type | mold steel fiber of this invention was contained in the hydraulic material hardening body. It is a graph which shows the relationship between the tensile stress and tensile strain by the tensile test of the hydraulic material hardening body of an Example and a comparative example. It is a schematic sectional drawing which shows the preparation aspect of the sample for a drawing test of the hydraulic material hardening body of an Example and a comparative example.

Hereinafter, the double-end hook type steel fiber for reinforcing a hydraulic material of the present invention, a hydraulic material containing the double-end hook type steel fiber, and a hydraulic material cured body obtained from the hydraulic material will be described in detail.
[Hook type steel fiber for both ends of hydraulic material reinforcement]
The both-ends hook type steel fiber for hydraulic material reinforcement of this invention is demonstrated using figures.
FIG. 1 is a front view showing an embodiment of a double-end hook type steel fiber 10 for reinforcing a hydraulic material according to the present invention.
A double-end hook-type steel fiber for reinforcing a hydraulic material according to the present invention (hereinafter referred to as a double-end hook-type steel fiber as appropriate) 10 is a steel fiber, and forms a straight portion 12 and an angle with the straight portion 12 at both ends. Both ends having first hook portions 14A and 14B bent in this manner and second hook portions 16A and 16B which are parallel to the straight portion by bending the end portions of the first hook portions 14A and 14B away from each other. Hook type steel fiber.

The steel fibers constituting the both-end hook type steel fibers 10 of the present invention are required to have a diameter (φ) of 0.10 mm or more and 0.50 mm or less. When the diameter (φ) is less than 0.10 mm, it is difficult to ensure the processing accuracy, so it is difficult to obtain the necessary reinforcing effect. When the diameter (φ) exceeds 0.50 mm, the strength is further improved. Since the effect cannot be expected and the molding process becomes difficult, neither is preferable.
Further, the length (l ₁ ) of the second hook portions 16A and 16B parallel to the straight portion 12 needs to be 1 mm or more, and when the diameter (φ) is 0.30 mm or more, it is 2.5 mm or more. preferable. If the length is too short, the resistance to tensile stress decreases. Although there is no restriction | limiting in particular in the upper limit of length, From a viewpoint of workability | operativity at the time of mixing with a hydraulic material, it is preferable that it is 5 mm or less.
As shown in FIG. 1, the length (l ₁ ) of the second hook portions 16A and 16B is the distance from the bent position of the first hook portions 14A and 14B to the end portions of the second hook portions 16A and 16B. Point to.
Moreover, the ratio (l ₁ / φ) of the diameter (φ) of the steel fiber and the length (l ₁ ) of the second hook portions 16A and 16B is 5 or more and 25 or less, and the diameter (φ) is 0.30 mm or more. In some cases, it is preferably 6.5 or more and 15 or less.

Furthermore, the bending height (h) of the first hook portions 14A and 14B, which is the distance between the straight portion 12 and the second hook portions 16A and 16B, needs to be 0.3 mm or more, and the diameter (φ) is 0. In the case of 30 mm or more, it is preferably 0.8 mm or more. Although there is no restriction | limiting in particular in the upper limit of height (h), From a viewpoint of making uniform mixing easy when mixing with a hydraulic material, it is preferable that it is 3 mm or less. As shown in FIG. 1, the bending height h indicates the distance between the center line of the steel fiber in the second hook portions 16 </ b> A and 16 </ b> B and the center line of the steel fiber in the straight portion 12.
Here, the ratio (h / φ) between the diameter (φ) of the steel fiber and the bending height (h) of the first bent portions 14A and 14B is required to be 2 or more and 10 or less, and 3 or more and 6 or less. It is preferable that
The radius of curvature of the R portion formed by the inner surfaces of the bent portions of the first hook portions 14A, 14B and the second hook portions 16A, 16B is r1, and the straight portion 12 and the first hook portions 14A, 14B When the radius of curvature of the R portion formed by the inner surface of the bent portion is r2, and the diameter of the steel fiber is φ, r1 / φ is 3 to 10, and r2 / r1 is 1.5 to 10 It is as follows.

The double-end hook type steel fiber of the present invention has a total length (l _a ), that is, the distance from the end of one second hook portion 16A to the end of the other second hook portion 16B is 6 mm or more and 50 mm or less. It is preferably 15 mm or more and 40 mm or less.
By setting the total length within the above range, resistance to tensile stress is further improved, and generation of cracks when subjected to tensile stress is more effectively suppressed.
Moreover, it is preferable that the relationship between the length (l ₂ ) of the straight portion 12 of the hook-type steel fiber 10 at both ends and the length (l ₁ ) of the second hook portions 16A and 16B satisfies the following formula.
(Formula) 6 × l ₁ <l ₂
In the balance of both lengths, the length (l ₁ ) of the second hook parts 16A, 16B has the length of the above ratio with respect to the length (l ₂ ) of the straight line part 12, so that the shape of the hook Works more effectively, the pull-out resistance in the hydraulic material is further improved, and the resistance to tensile stress of the cured hydraulic material is improved.

The tensile strength of the steel fiber (element wire) constituting the both-end hook type steel fiber 10 of the present invention is preferably 2000 MPa or more and 5000 MPa or less. The higher the strength of the strand is, the more effective as the reinforcing fiber, but the upper limit is set to 5000 MPa in consideration of workability and the like. From such a viewpoint, the tensile strength of the strand is 3000 MPa or more. It is more preferable. The tensile strength of the steel fibers that make up the hook-type steel fibers at both ends is in accordance with the JSCE-E101-2007 appendix (normative) “Tensile Strength Test Method for Steel Fibers” of the Japan Society of Civil Engineers. Is going.
In the loading test, a universal testing machine model 55R1125 manufactured by Instron was used, and the displacement speed was tested by pulling at a crosshead speed of 0.2 mm / min. The average value of the five test results was taken as the test value. In this standard, it was fixed with a flat plate chuck. Steel fibers with a diameter of about 0.2 mm or less were often broken near the chuck when tested using a flat plate chuck. Use an air capstan type thread clamp (manufactured by Shimadzu Corporation). The fiber fixing portion was provided at a position half a round around the cylindrical portion with respect to the pulling direction and tested so as not to break at the grip portion.
In order to achieve such a tensile strength, for example, JIS G 7305 "Spring Steel Wire-Part 2: Cold-drawn Carbon Steel is used as the material of the steel fiber (element wire) constituting the hook-type steel fiber at both ends. JIS G 7306 "Spring Steel Wire-Part 3: Oil Temper Wire (ISO Specification)", JIS G 3522 "Piano Wire", JIS G 3521 "Hard Steel Wire", etc. Is preferred.
Further, the first hook portion and the second hook portion are formed into the preferable shape by adjusting a coiling machine for precision spring machining. When producing in large quantities, you may manufacture with the gear type shaping | molding apparatus etc. which are shown by Unexamined-Japanese-Patent No. 5-337727.

  The both-end hook type steel fiber surface may be subjected to chemical or physical surface treatment such as primer treatment or surface roughening treatment for the purpose of improving adhesion to a hydraulic material described later.

[Hydraulic material]
The hydraulic material including the both-end hook-type steel fiber 10 of the present invention is not particularly limited as long as it has hydraulic properties, and representative examples thereof include cement, mortar, and concrete. Especially, when it applies to the concrete composition which requires high intensity | strength and toughness, the addition effect of the both ends hook type steel fiber 10 is high. This is because when the strength of the hardened body is a certain level or more, the pull-out resistance effect of the hook-type steel fibers 10 at both ends is more effectively exhibited.
The hydraulic material of the present invention includes cement, aggregate, water, and both-end hook-type steel fibers of the present invention, and the content of both-end hook-type steel fibers is 0.5 volume% or more and 5.0 volume% or less. Preferably, it is 1.0 volume% or more and 4.0 volume% or less.
If the content is less than 0.5% by volume, the effect of improving the strength against tensile stress of the obtained cured product cannot be obtained sufficiently, and if it exceeds 5.0% by volume, the uniform dispersibility and the fluidity of the hydraulic material are lowered. Any of these regions is not preferable because a region with insufficient strength may be locally generated.
FIG. 2 is a schematic cross-sectional view schematically showing a cured hydraulic material 18 containing the both-end hook-type steel fiber 10 of the present invention. By having the hook portion in the steel fiber, even when tensile stress is applied, the pulling resistance from the hydraulic material cured body 18 as a matrix is remarkably improved.

Among the hydraulic materials, a hydraulic material capable of forming a high-strength cured body having a water / binder ratio of 0.1 to 0.3 on a mass basis is preferable. Hereinafter, unless otherwise specified, the water / binder ratio is expressed on a mass basis.
An example of the hydraulic material includes cement, aggregate, silica fume, water, and the above-mentioned both-end hook type steel fiber of the present invention at a predetermined content, and the water / binding material ratio (mass basis) is 0.1 or more and 0. Preferably, the cement composition is .3 or less.

(Each component of hydraulic material)
Hereinafter, materials used for the cured hydraulic material of the present invention will be described.
(Water / Binder ratio)
The cement composition (which may be a concrete composition further including a coarse aggregate as an aggregate) used in the production of the hardened cement of the present invention has a water / binder ratio of about 0.5. However, from the viewpoint that a high-strength cured body can be formed, the water / binder ratio is preferably 0.1 or more and 0.3 or less.
In addition, it contains at least other binders such as silica fume, including water and cement. Depending on the purpose, aggregates such as fine aggregates and coarse aggregates, water reducing agents, etc. Containing.
The binder in the present invention includes cement, which is a main component of a hardened cement body, and fine powder (solid content) involved in the effect of the hardened cement body such as silica fume, slag, fly ash and the like generally used with cement. is there. Note that aggregates and surfactants added to improve fluidization are not included in the binder in the present invention.

(cement)
There is no restriction | limiting in particular in the cement used for manufacture of the cement hardening body of this invention, According to the objective, it can select suitably from various cements. As the cement, known cements such as ordinary Portland cement, moderately hot Portland cement, low heat Portland cement, and early-strength Portland cement can be suitably used. Preferably, low heat Portland cement is good.
Portland cement containing silica fume in advance may be used. Portland cement containing silica fume is also available as a commercial product, for example, trade name: silica fume cement super, silica fume cement, manufactured by Taiheiyo Cement Co., Ltd .: silica fume premix cement, and the like.

(Silica fume)
The cement composition used for producing the hardened cement body of the present invention may contain silica fume.
The silica fume used preferably can be used in either powder or granular form. As the silica fume, generally used ferrosilicon or silica fume (average particle size: 0.1 μm to 0.2 μm) by-produced during the production of metal silicon is preferable.
In addition, the particle diameter of the silica fume in this specification uses the value calculated by calculating the specific surface area by the BET method and assuming that the particle density and the particles are spherical from the specific surface area.

  As content of a silica fume, it is preferable that it is 5 mass%-35 mass% in all the binders in a cement composition, and it is more preferable that it is 10 mass%-30 mass%. In order to contain 5% by mass to 35% by mass of silica fume in the total binder, 5% by mass to 35% by mass of cement as the binder may be replaced with silica fume. When the content of silica fume is within the above range, the fluidity improving effect and the strength improving effect are sufficiently exhibited.

(Other binders)
When producing the hardened cement body of the present invention, as long as the effects of the present invention are not impaired, other binders are appropriately selected according to the intended use of the cement composition to be prepared and used in an appropriate amount. May be.
Examples of other binders include silica fine powder obtained by finely pulverizing crystalline silica, slag such as blast furnace slag fine powder, limestone fine powder, fly ash and the like.

(aggregate)
The cement composition for producing the hardened cement body of the present invention contains an aggregate. The aggregate is preferably a fine aggregate, and may be a concrete composition containing a fine aggregate and a coarse aggregate. The strength of the hardened cement body is further improved by further containing coarse aggregate.
(Fine aggregate)
For fine aggregates, high-quality and solid natural sand, crushed sand and processed sand are used. The type and content of fine aggregates can be selected as appropriate according to the strength of the target cement hardened body, but when crushed sand or processed sand is used, the one with treated corners or one with adjusted particle size Etc. are effective.
(Coarse aggregate)
In the case of using a coarse aggregate in addition to the fine aggregate as the aggregate, a good quality and solid coarse aggregate may be used. The maximum size of the coarse aggregate requires a particle size (maximum particle size) of 20 mm or less, and preferably the maximum size is 15 mm or less. About a rock kind, what is necessary is just to select suitably according to the target intensity | strength from general things, such as a hard sandstone, andesite, and rhyolite. By using a coarse aggregate for the cement composition forming the cement hardened body, a concrete composition is obtained, and the strength of the obtained hardened body is further improved. In addition, the term “cement composition” in the present specification is used to include a “concrete composition” further including a coarse aggregate as an aggregate.

(Other ingredients)
The cement composition used in the hardened cement body of the present invention may further contain other components usually used in concrete compositions such as a water reducing agent and a retarder depending on the purpose.
The hardened cement body of the present invention can be obtained by curing a cement composition appropriately containing each component as described above and performing the following specific curing.

[Hardened hydraulic material]
The hydraulic material cured body of the present invention is obtained by curing the hydraulic material containing the both-end hook-type steel fibers of the present invention.
Since the hydraulic material cured body of the present invention contains the above-mentioned double-end hook type steel fiber of the present invention in the range of 0.5% by volume or more and 5.0% by volume or less, the obtained cured body has a compressive strength of 60 N / mm ² or more, and the tensile strength is hydraulic material cured product having excellent strength and toughness that is 10 N / mm ² or more. The compressive strength of the cured body is more preferably 120 N / mm ² or more, and the tensile strength is 12 N / mm ² or more.
The compressive strength is adjusted by a method of adjusting the composition of the hydraulic material, for example, adjusting the water / binder ratio, or using an appropriate curing accelerator or water reducing agent. The tensile strength is adjusted by adjusting the content of the double-end hook type steel fiber of the present invention. Specifically, for example, in the case of a cement composition having a water / binder ratio of about 0.1 to 0.2, the content of both-end hook-type steel fibers is 1.0% by volume to 4.0% by volume. If the cement composition has a water / binder ratio of more than 0.2 and not more than 0.3, the content is preferably 1.5% by volume or more and 4.0% by volume or less. .

(Method for producing a cured hydraulic material)
In order to manufacture the cement hardened body of the present invention, cement, aggregate, water and various additives used in combination as required are mixed and made uniform, then both end hook type steel fibers are added and further mixed, What is necessary is just to carry out by putting in a mold and making it harden | cure and forming a cement molding. The formed cement molded body is cured as necessary to obtain a cured body having sufficient strength.
Mixing can be performed by a conventional method. First, a slurry of a hydraulic material is prepared. That is, it is a method of preparing a slurry by putting cement, aggregate, water, and optionally added silica fume and other additives into a mixer and mixing them. In addition, first, the aggregate may be mixed, then cement and additives may be added and mixed, and then water may be added and mixed to adjust the slurry. 50% by mass to 90% in the total binder The slurry may be prepared by kneading mass% and water to adjust the slurry, and then adding and mixing the remaining binder.
After adjusting the slurry, a double-end hook type steel fiber is added in an amount of 0.5 vol% to 5.0 vol% in accordance with the purpose of the hydraulic material and mixed to obtain a cement composition.
The prepared slurry is put into a mold and cured to form a cement molded body. Since the hydraulic material according to the present invention has the above-described configuration, it is useful for forming a high-strength cured body having a water / binder ratio of 0.1 to 0.3. After the slurry-like cement composition is put into the mold, a process such as defoaming may be further performed according to a conventional method.
The cement composition thrown into the mold is cured with self-heating to form a cement molded body. The cured cement molded body thus obtained is cured to improve the strength.

The applicable curing method is not particularly limited, and a general curing process applied when forming a cement or concrete hardened body may be performed.
There is no particular limitation on the curing process, and any curing may be performed, for example, standard curing performed in water, wet sand, or saturated steam maintained at a temperature of 20 ± 3 ° C., or water performed in water. Curing, high temperature, for example, a method in which a cement molded body is steam-cured in a temperature range of 70 ° C. to 100 ° C. for 2 hours to 72 hours, and is heated at a heating temperature of 100 ° C. to 400 ° C. for 2 hours to 72 hours. And autoclave curing, which is a steam curing under high pressure.
The curing process may be performed at any timing as long as the cement molded body is cured, or may be performed immediately after curing, or may be performed after elapse of time, for example, after the self-heated molded body is cooled to room temperature. Well, after producing a large number of molded bodies, a plurality of molded bodies may be cured together.

Steam curing is performed by a conventional method. For example, steam produced by a boiler can be introduced into a curing tank through an introduction pipe, a temperature sensor is installed in the tank, and the temperature in the tank is set. Steam curing performed by opening and closing the steam supply valve so as to become a temperature history is the most common, but as another steam curing method, after taking measures that the molded body does not dry extremely, for example, Examples of the method include heating by attaching a sheet heating element or the like that generates heat by energization to the surface of the molded body, and steam curing may be performed by such a method.
The cured hydraulic material containing both-end hook-type steel fibers for reinforcement of the present invention exhibits a more stable and practically sufficient strength and toughness through the curing process performed as desired, and is suitably used for various structural materials. Is done.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited to these description.
In the following examples, examples in which a cement composition is used as a hydraulic material will be given.
(Example 1, Comparative Example 1)
[Cement composition]
(Materials used)
Cement: Silica fume cement super (trade name: manufactured by Mitsubishi Ube, density 3.01 g / cm ³ , 17.5% by mass of low heat Portland cement, which is a base cement, replaced with silica fume)
Water: Tap water Fine aggregate: Mikawa silica sand (particle size D50 212 μm, density 2.6 g / cm ³ )
Admixture: SSP-104: (Brand name: Takemoto Yushi Co., Ltd., solid content 30%)
Steel fibers such as double-end hook-type steel fibers will be described later.
Table 1 below shows the composition of the cement composition applied to the production of the cured hydraulic material of the present invention.
* In Table 1 below, the moisture contained in the admixture was a part of water, and the solid content was divided by the unit volume.
** The amount of steel fiber added (volume%) was divided by the outer volume of the matrix portion of the hydraulic material.

[Manufacture of double-end hook type steel fiber A for hydraulic material reinforcement]
Steel fibers having the shapes shown in Table 2 below were molded by adjusting a coiling machine for precision spring machining.
[Steel fiber for comparative reinforcement]
Shinko Building Materials Co., Ltd., Shinko Fiber Doramix (trade name: RC-80 / 30-BP)
[Measurement of shape of reinforcing steel fiber]
The fiber diameter (φ) of the steel fiber is a value obtained by measuring the shape of a total of 20 positions at both ends of the steel fiber arbitrarily extracted with a microscope (manufactured by Keyence Corporation: Digital HF microscope VH-8000). In addition, the shape of the steel fiber such as the total length, the length of the first hook part, the radius of curvature, the bending angle, and the bending height is drawn using the microscope shape measurement function and the center line of the fiber is drawn on the obtained image. The original measured value is used. Specifically, for the straight portion of the steel fiber, the center point in the diametric direction of the fiber is obtained in the vicinity of the start point and end point of the straight portion, and the center line is drawn by connecting the two points, and the bent portion has three points in the diametric direction. The center point described above was obtained, a circle passing through this was obtained, and the radius of the circle was defined as the radius of curvature. Here, l ₁ is the distance from the tip to the center of the first bend. l ₂ is the distance from the center of the second bent portion from the tip to the symmetrical point of the opposite end. Table 2 shows average values of 10 measurement results.

[Measurement of tensile strength of strands forming reinforcing steel fibers]
Moreover, the tensile strength of the strand which forms a both ends hook type | mold steel fiber was measured with the following method.
Displacement using the universal testing machine model 55R1125 manufactured by Instron Co., Ltd. The speed was tested by pulling at a crosshead speed of 0.2 mm / min. Fibers with flat chuck for fixing, of the total length 30mm fibers, gripping the both ends 12.5mm chuck was measured intensity at the points corresponding to the central portion 5mm straight portion l ₂ of the steel fibers. Data that caused slipping at the gripping part or early breakage at the gripping part was excluded, and one new test was added, and the average value of the five test results was taken as the strength. In addition, about five strands before processing the hook-type steel fiber manufactured on the basis of the present invention, a tensile test was performed using an air capstan type thread gripper which is less likely to break at the chuck portion. Was 3120 MPa, which was confirmed to be equivalent to the processed double-end hook-type steel fiber, and it was confirmed that the base material strength of the steel fiber could be measured by this method.

(1. Preparation of hydraulic material)
About the cement composition described in Table 1, water, cement, and aggregate were weighed in an amount such that the amount of kneading was 5 L with the ratio shown in Table 1, and an omnimixer (OM-10E manufactured by Chiyoda Machinery Co., Ltd., capacity 10 L) ) And kneaded under the following conditions.
(1) In an omnimixer, add the entire amount of cement and fine aggregate, empty kneading for 30 seconds, add water, stir for 3 minutes at low speed (speed: 150 rpm), scrape off, and further for 5 minutes at medium speed ( (Speed: 300 rpm).
The double-end hook type steel fiber of the present invention is put into the omni mixer containing the kneaded slurry, and again kneaded in the omni mixer for 2 minutes (speed: 300 rpm) to prepare a slurry. The hydraulic material of Example 1 Adjusted.

Since the comparative steel fibers were bundled with paste-like fibers, they were washed with alkaline water in advance before being put into the omni mixer, unwound one by one, washed with tap water and dried.
The hydraulic material of Comparative Example 1 was prepared by the same method and procedure except that a comparative steel fiber was used instead of the double-end hook type steel fiber.

(2. Molding of hardened hydraulic material)
The hydraulic material (steel fiber-mixed cement composition) of Example 1 and Comparative Example 1 was put into a dumbbell-shaped test body for a tensile test. For compressive strength, it was put into a steel mold having a diameter of 5 cm and a height of 10 cm.
For the tensile test, a cured body having a fixed holding portion at the top and bottom of the test body and having a tensile test section having a thickness of 3 cm, a width of 3 cm, and a length of 8 cm at the center of the test body was prepared. The fixed holding part is tapered with a gradient of 15/40 from the part of thickness 3cm, width 6cm length 8.5cm and the tensile test part in the center, so that there is no sudden change in cross section It was used.
This is left to stand for 5 to 7 days to be naturally cured, taken out from the mold, heated at a rate of temperature increase of 15 ° C./hour, maintained at a maximum temperature of 90 ° C. for 24 hours, and cooled at 15 ° C./hour to form a molded product. Got. Then, it stored in the room | chamber interior of 20 degreeC60RH% until test material age.

(3. Compressive strength test of hardened hydraulic material)
On the 14th day of age, the compressive strength of the obtained cured hydraulic material (cured cement) was measured according to JIS A 1108 (2006).
The compressive strength of the cured hydraulic material of Example 1 is 245 N / mm ² , and the compressive strength of the cured hydraulic material of Comparative Example 1 is 242 N / mm ^2, which is equivalent compressive strength. confirmed.
(4. Tensile strength test of hardened hydraulic material)
On the 14th day of age, the dumbbell-shaped specimen was fixed with a jig, and the tensile load was measured with a high-precision universal testing device (Autograph AG-250kN: manufactured by Shimadzu Corporation). The tensile load was obtained by dividing the tensile load by the cross-sectional area (30 mm × 30 mm), and the maximum value was taken as the tensile strength. The displacement meter is attached via a jig so that the displacement at the position of the tensile test part 80 mm in the center of the test body can be measured, and the tensile strain is obtained by dividing the displacement during the test by the distance between the gauge points of 80 mm. It was.
FIG. 3 is a graph showing the relationship between tensile stress and tensile strain of a cured hydraulic material by a tensile test. The result of the hardening body using the steel fiber A of Example 1 is indicated by a solid line, and the result of the hardening body using a comparative steel fiber that is a commercial product is indicated by a broken line.

The hydraulic material cured body of the present invention using the both-end hook type steel fiber A of Example 1 has an initial crack at about 8 N / mm ² , but hardens with subsequent deformation. The tensile strain was about 1% and the tensile strength was about 14 N / mm ² . Even at 2% strain, it can bear a tensile stress of about 12 N / mm ² .
On the other hand, the hydraulic material cured body of Comparative Example 1 using comparative steel fibers cracked at about 6 N / mm ² , and after that, some hardening was observed with the progress of tensile strain, but at about 1% strain. The tensile strength was about 10 N / mm ² . At 2% strain, the tensile stress is about 9 N / mm ² .
From the above results, the hydraulic material cured body using the double-end hook type steel fiber of the present invention is equivalent in compressive strength to the cured body using the comparative steel fiber that is a conventional product, but the tensile stress degree at the same strain point is It is about 30% larger than the cured body of Comparative Example 1. From this, it became clear that the hardened body using the steel fiber according to the present invention has extremely excellent tensile performance and toughness as a cement material.

(Examples 2-5, Comparative Examples 2-9)
[Cement composition]
The materials used for blending the cement composition are the same as those in Example 1 and Comparative Example 1 except that the steel fiber A and the comparative steel fiber are not added. The composition of the cement composition is shown in Table 3 below.
* In Table 3 below, the moisture contained in the admixture was a part of water, and the solid content was divided by the unit volume.

[Manufacture of hook-type steel fibers for reinforcing hydraulic materials]
For the production of steel fibers, a coiling machine used for precision spring machining was used. Both-end hook-type steel fibers B, C, D and E (Examples 2 to 5) of the present invention and both-end hook-type steel fibers outside the scope of the present invention (Comparative Example Steel Fibers 2, 3, 5, 6, 7 and 8) Was made.
Further, as a test hardened body, a straight fiber not subjected to hook processing (comparative steel fiber 4), a commercially available both-end hook-type steel fiber (commercially available comparative steel fiber used in Comparative Example 1), The test hardened body using this was evaluated as Comparative Example 4 and Comparative Example 5, respectively.
As for the shape of steel fiber manufactured by coiling machine and commercially available steel fiber, 10 pieces are randomly selected from each steel fiber, and a total of 20 shapes at both ends are made into a microscope (manufactured by Keyence Corporation: Digital HF microscope VH-8000). The shape measurement method is the same as in Example 1 and Comparative Example 1.
The shape of the obtained reinforcing steel fiber is shown in Table 4 below.

(Pullout test)
Using each of the obtained reinforcing steel fibers, the resistance to pulling out the reinforcing steel fibers from the cured hydraulic material was measured and used as a measure of the toughness of the reinforcing steel fiber-containing cured body.
As shown in Table 3, the hydraulic material has a water / binder ratio of 0.12 (that is, a water content of 12% by mass with respect to the total amount of water and the binder). Here, the reinforcing steel fiber is not mixed into the hydraulic material, but a test body is produced in which the two steel fibers are bridged perpendicularly to the surface assuming cracks. The stress to be borne during the process was evaluated. The shape of the test body and the mold forming the test body is shown in FIG.
As the pair of molds 20A and 20B forming the test body, those having a thickness of 25 mm, the cured hydraulic material 18 having the shape shown in FIG. 4, ie, there are fan-shaped hook portions at both ends, and between the both ends In the center part, a straight part having a width of 25 mm and a length of 80 mm was used. A balsa material 24 of 25 mm × 25 mm was attached to the molds 20A and 20B so that the molds 20A and 20B were divided into two equal parts. Two steel fibers 10 are attached to the balsa material 24 in a state in which the balsa material 24 is vertically penetrated. The steel fiber 10 is located at a height of 12.5 mm from the bottom of the formwork. The balsa material 24 is adjusted so as to have the same length on both sides at positions that are 7.5 mm from the side surfaces.
The hydraulic material is kneaded by the same method and procedure as the hydraulic material preparation method of Example 1 and Comparative Example 1 except that it does not have a step of feeding reinforcing steel fibers, and the kneaded hydraulic material is converted into the steel described above. The molds 20 </ b> A and 20 </ b> B in which two fibers 10 are arranged are filled, and the molds 20 </ b> A and 20 </ b> B are fixed with bolts 22. At the same time, the hydraulic material was put into a steel mold having a diameter of 5 cm and a height of 10 cm for measuring the compressive strength.
The hydraulic material in the mold or the mold is allowed to stand for 5 to 7 days to be naturally cured, heated at a rate of temperature increase of 15 ° C./hour, and heated to maintain a maximum temperature of 90 ° C. for 24 hours. The temperature was lowered over time to obtain a cured hydraulic material. Then, it took out from the mold and stored in a room at 20 ° C. and 60 RH% until the test material age.
On the 14th day of age, the compressive strength of the obtained cured hydraulic material (cured cement) was measured according to JIS A 1108 (2006). The hardened hydraulic material was common to any test body in which any steel fiber was embedded, and the compressive strength of the hydraulic material was 251 N / mm ² .
On the 14th of the material age, the fan-shaped portion of the test body (hardened body) in which the steel fiber for reinforcing resistance evaluation is embedded is fixed to the chuck of a high-precision universal testing device (Instron model 55R1125). A tensile test jig capable of being attached was attached, the test specimen was pulled at a rate of 0.5 mm / min, and the load required when the steel fiber was pulled out was measured. Moreover, a part of the balsa material 24 of the partition plate was cut off, and a clip gauge (manufactured by Tokyo Sokki Co., Ltd.) was attached to measure the pull-out amount of the steel fiber. Divide the maximum load value by the cross-sectional area of the steel fiber to obtain the stress level acting on the steel fiber for reinforcement, and further calculate this stress level as the tensile strength of the base material (hardened hydraulic material) of the steel fiber for reinforcement. In other words, the amount of stress that can be applied to the potential strength of the reinforcing steel fiber was calculated. Further, from the relationship between the load at the time of drawing and the amount of pull-out, it was evaluated whether or not the fiber was broken at the time of drawing.
At this time, a stress degree / strength of 0.85 or more and a steel fiber for reinforcement not broken was evaluated as “good” as having practically sufficient performance, and the stress degree / strength was 0.85. The case of less than or the case where the steel fiber was broken was evaluated as x.
The results are shown in Table 5 below.

When the double-end hook type steel fibers B, C, D, or E of Examples 2 to 5 were used, the drawing stress (described as “stress degree” in Table 5) obtained by dividing the drawing load by the area of the fiber was 2626 N / mm. ^{From 2} to 3250 N / mm ² , it can be seen that the steel fiber has a stress of 85% or more of the tensile strength of the strand of the fiber, and can effectively resist the tension. Moreover, it pulled out without fracture, suggesting that it is effective in improving toughness.
On the other hand, in Comparative Examples 2 to 5, the drawing stress obtained by dividing the drawing load by the area of the fiber was 1435 N / mm ² to 2578 N / mm ² , and only a stress of less than 85% of the tensile strength of the strand was obtained. The performance of steel fibers has not been utilized. Accordingly, the straight comparative reinforcing steel fiber 4 has a low drawing stress, and even if it has a hook-shaped shape on both ends, the steel fiber having a shape outside the range of the present invention also has a low drawing stress compared to the embodiment. I understand that.
Further, in Comparative Examples 6 to 9, although the pulling stress is high, the steel fiber is not broken at the very initial stage of the pulling process, and the stress that can be borne at a stretch is lowered, so that the toughness cannot be improved.

  From the above results, it was confirmed that a high tensile resistance and a high toughness can be imparted to the hydraulic material only when the hydraulic material using the both-end hook type steel fiber of the present invention is used. It is clear that the reinforcing double-end hook type steel fiber of the present invention shows a remarkably high tensile performance by using the same amount of reinforcing steel fiber as in the hydraulic material used in Example 1, for example. Therefore, the hydraulic material cured body of the present invention using the reinforcing steel fiber of the present invention has extremely excellent tensile performance as a cement-based material.

10 Double-end hook-type steel fibers for reinforcing hydraulic materials (both-end hook-type steel fibers)
12 straight portions 14A, 14B first hook portions 16A, 16B second hook portions 18 cured hydraulic material

Claims (6)

A straight portion, a first hook portion that is bent from both ends of the straight portion so as to have an angle with the straight portion, and an end portion of the first hook portion that is bent away from each other. A hook-type steel fiber having both ends having a parallel second hook portion,
The diameter (φ) of the steel fiber is 0.10 mm or more and 0.50 mm or less,
The length (l ₁ ) of the second hook part is 1 mm or more, and the ratio (l ₁ / φ) of the diameter (φ) of the steel fiber to the length (l ₁ ) of the second hook part is 5 or more. 25 or less,
The bending height (h) of the first hook portion, which is the distance between the straight portion and the second hook portion, is 0.3 mm or more, and the diameter (φ) of the steel fiber and the bending height of the first hook portion. The ratio (h / φ) to (h) is 2 or more and 10 or less,
The radius of curvature of the R portion formed by the inner surface of the bent portion of the first hook portion and the second hook portion is defined as r1, and the inner surface of the bent portion of the straight portion and the first hook portion is formed by R. Both ends hook for hydraulic material reinforcement where r1 / φ is 3 or more and 10 or less and r2 / r1 is 1.5 or more and 10 or less when the radius of curvature of the part is r2 and the diameter of the steel fiber is φ Shaped steel fiber. 2. The double-end hook type steel fiber for reinforcing a hydraulic material according to claim 1, wherein the total length (l _a ) of the double-end hook type steel fiber is 6 mm or more and 50 mm or less. The water according to claim 1 or 2, wherein a relationship between a length (l ₂ ) of the straight portion of the both-end hook-type steel fibers and a length (l ₁ ) of the second hook portion satisfies the following expression. Both ends hook type steel fiber for reinforcing hard materials.
(Formula) 6 × l ₁ <l ₂   The tensile strength of the steel fiber which comprises the said both ends hook type steel fiber is 2000 MPa or more and 5000 MPa or less, The both ends hook type steel fiber for hydraulic material reinforcement of any one of Claims 1-3.   The cement-to-aggregate, water, and the double-end hook-type steel fiber according to any one of claims 1 to 4 are contained in an amount of 0.5% by volume or more and 5.0% by volume or less. A hydraulic material having a reference value of 0.1 to 0.3. A cured hydraulic material obtained by curing the hydraulic material according to claim 5 and having a compressive strength of 60 N / mm ² or more and a tensile strength of 10 N / mm ² or more.