JP7228473B2 - High-strength concrete containing steel fibers and its preparation method - Google Patents

Description

The present invention relates to high-strength concrete with steel fibers and a method for preparing the same.

Mixing steel fibers into the high-strength concrete that constitutes RC beams is effective in increasing the cycle period of RC buildings due to cracking during earthquakes and in suppressing reduction in yield strength due to edge crushing during extreme earthquakes. In particular, if the amount of steel fiber added can be increased to about 1.0% by volume, the performance as a member can be remarkably improved. However, if the amount of steel fiber added is increased, advanced technology will be required for the formulation design.
In general, the standard design strength of high-strength concrete constituting RC beams is 60 N/mm ² or less (36 to 60 N/mm ² ).

Concrete containing about 1.0% by volume of steel fibers includes ultra-high-strength concrete (Patent Document 1) with a water binder ratio of 25% or less assuming a design standard strength of 100 N/mm ² or more, or a water binder ratio of 20% or less. of explosion-resistant concrete (Patent Document 2) has been proposed.

Japanese Patent No. 6432811 Japanese Patent No. 4071983

When the water binder ratio is low as in Patent Documents 1 and 2, the unit cement amount is as large as 800 kg/m ³ or more, and the viscosity of the concrete is high. can be sufficiently secured.
However, when the design standard strength is 60 N/mm ² or less (36 to 60 N/mm ² ), the water binder ratio is high, so the unit cement amount is as small as 700 kg/m ³ or less, and the viscosity of the concrete is low. Therefore, when about 1.0% by volume of steel fibers are mixed, sufficient material separation resistance of concrete cannot be ensured, and material separation may occur. In particular, material separation is conspicuous at a design standard strength of 36 to 48 N/mm ² (unit cement amount of 500 kg/m ³ or less).

The present invention has been made in view of the above circumstances, and has a steel fiber containing steel fiber with a design standard strength of 60 N / mm ² or less that ensures material separation resistance even though the steel fiber content is high, and has excellent workability. It is an object of the present invention to provide high-strength concrete and its preparation method.

The present invention has the following aspects.
[1] Containing cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber, with a water binder ratio of 30 to 60% by mass, and a mixing ratio of the steel fiber exceeding 0.50% by volume 2 A steel fiber-containing high-strength concrete having a volume % or less,
The chemical admixture contains either or both of a high performance water reducing agent and a high performance AE water reducing agent and a thickening agent,
A steel fiber-containing high-strength concrete having a unit coarse aggregate bulk volume of 0.3 to 0.5 m ³ /m ³ .
[2] The steel fiber-containing high-strength concrete of [1], wherein the steel fibers have a diameter of 0.15 to 0.9 mm and a length of 12 to 32 mm.
[3] The steel fiber-containing high-strength concrete of [1] or [2], which has a plastic viscosity of 60 to 85 Pa·s at 20±5°C.
[4] Cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber are blended, the water binder ratio is 30 to 60% by mass, and the steel fiber mixing ratio is over 0.5% by volume. 1. A method of preparing high strength concrete with steel fibers of 2% by volume or less, comprising:
Using at least one or both of a high performance water reducing agent and a high performance AE water reducing agent as the chemical admixture and a thickener,
The target value _V'bG of the unit coarse aggregate bulk volume of the steel fiber-containing high-strength concrete is calculated by the following formula (1), and the blending amount of the coarse aggregate is set so as to achieve the target value _V'bG . , a method for preparing high-strength concrete with steel fibers.
V′ _bG =V _bG −(K _S ·2r _G /3r _F −1)·V _F /G _S (1)
Here, V' _bG represents the target value (m ³ /m ³ ) of the unit coarse aggregate bulk volume of the steel fiber-containing concrete,
V _bG is a standard value range of unit coarse aggregate bulk volume (m ³ /m ³ ) of base high-strength concrete and indicates a number of 0.53 to 0.65 (m ³ /m ³ ). ,
K _S is an influence coefficient and indicates a number from 1.0 to 1.35,
r _G indicates the radius (mm) of the coarse aggregate calculated from the total coarse aggregate surface area obtained from the particle size distribution of the coarse aggregate, assuming that the coarse aggregate is spherical,
r _F represents the radius (mm) of the steel fiber calculated assuming that the steel fiber has a cylindrical shape,
_VF indicates the mixing ratio (% by volume) of the steel fibers,
_GS indicates the actual volume ratio (volume %) of the coarse aggregate.
[5] The method of mixing high-strength concrete containing steel fibers according to [4], wherein the steel fibers have a diameter of 0.15 to 0.9 mm and a length of 12 to 32 mm.
[6] The steel fiber of [4] or [5], wherein the blending amount of the thickener is set so that the plastic viscosity of the steel fiber-containing high-strength concrete at 20 ± 5 ° C. is 60 to 85 Pa s. Mixing method for high-strength concrete.

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide a high-strength concrete containing steel fibers having a design standard strength of 60 N/mm ² or less, which ensures material separation resistance even though the steel fiber content is high, and which has excellent workability, and a method for mixing the same. .

46-0.60-0-SP1 is a photograph showing evaluation results of material separation resistance. 37-0.58-0-SP1 is a photograph showing evaluation results of material separation resistance. 28-0.56-0-SP1 is a photograph showing evaluation results of material separation resistance. 46-0.60-80-SP4 is a photograph showing evaluation results of material separation resistance. 46-0.60-80-SP4' is a photograph showing evaluation results of material separation resistance. 46-0.60-80-SP1 is a photograph showing evaluation results of material separation resistance. 46-0.40-80-SP3 is a photograph showing evaluation results of material separation resistance. 46-0.40-80-SP4 is a photograph showing evaluation results of material separation resistance. 46-0.40-80-SP2 is a photograph showing evaluation results of material separation resistance. 37-0.30-80-SP4 is a photograph showing evaluation results of material separation resistance. 28-0.30-80-SP4 is a photograph showing evaluation results of material separation resistance.

The following term definitions apply throughout the specification and claims.
"Concrete" includes fresh and hardened concrete.
"Water binder ratio" indicates the ratio (mass %) of water to the total mass of binders in fresh concrete.
A "binder" is a material that hydrates in concrete, such as cement, silica fume, slag, fly ash, and the like.
“High-strength concrete” refers to concrete having a design strength of 36 N/mm ² or higher.
"Ratio of steel fiber content" indicates the ratio (volume %) of the volume of steel fiber to the total volume of high-strength concrete used as the base of high-strength concrete containing steel fiber.
"Base high-strength concrete" refers to concrete having the same composition as the steel-fiber-containing high-strength concrete except that it does not contain steel fibers (the remainder of the steel-fiber-containing high-strength concrete after removing the steel fibers).

(High-strength concrete containing steel fibers)
The steel fiber-containing high-strength concrete of the present invention (hereinafter also referred to as "this concrete") contains cement, water, coarse aggregate, fine aggregate, a chemical admixture, and steel fibers.
The present concrete may further contain other components other than these.

As the cement, moderate heat Portland cement and low heat Portland cement are preferable because of their low heat of hydration.

The content of water is such that the water binder ratio is 30 to 52% by mass. The lower the water binder ratio, the higher the compressive strength. A water binder ratio of 30 to 52% by mass can achieve a design strength of 36 to 60 N/mm ² . When the design strength is 36-48 N/mm ² , the water binder ratio is preferably 37-52% by mass.

Coarse aggregates include hard sandstone crushed stone, andesite crushed stone, rhyolite crushed stone, and the like.
The surface dry density of coarse aggregate is, for example, 2.55-2.7 g/cm ³ .
The coarse grain ratio of the coarse aggregate is, for example, 6 to 6.6.

The maximum dimension of coarse aggregate is typically 20 mm or less. The maximum size of the coarse aggregate is the nominal size of the smallest size sieve through which 90% by mass or more of the coarse aggregate passes.
As coarse aggregate having a maximum dimension of 20 mm or less, for example, coarse aggregate having a maximum dimension of 20 mm, coarse aggregate having a maximum dimension of 15 mm, coarse aggregate having a maximum dimension of 13 mm, and the like are commercially available.

The content of coarse aggregate is such that the unit coarse aggregate bulk volume of the concrete is 0.3 to 0.5 m ³ /m ³ . The unit coarse aggregate bulk volume is preferably 0.33 to 0.43 m ³ /m ³ . When the unit coarse aggregate bulk volume is 0.3 m ³ /m ³ or more, the material separation resistance is excellent.
The actual volume ratio of coarse aggregate in the present concrete is, for example, 58% by volume, more preferably 58 to 64% by volume.

Examples of fine aggregates include crushed sand, mountain sand, land sand, and the like.
The surface dry density of fine aggregate is, for example, 2.55 to 2.7 g/cm ³ .

The chemical admixture contains at least one or both of a high performance water reducing agent and a high performance AE water reducing agent (hereinafter collectively referred to as "high performance (AE) water reducing agent") and a thickener. .
If necessary, the chemical admixture may contain other chemical admixtures to the extent that the effects of the present invention are not impaired.

Advanced (AE) water reducing agents are used to improve the workability of the concrete.
Definitions of high performance water reducing agent and high performance AE water reducing agent are as per JIS A 6204.
Examples of high-performance water reducing agents include those containing polycarboxylic acid ether as the main component and those containing polycaribonic acid copolymer as the main component.
High-performance AE water reducing agents include, for example, those containing polycarboxylic acid as a main component.

A thickener is used for the purpose of increasing the viscosity of the concrete and increasing the material separation resistance.
Any thickening agent may be used as long as it can be mixed with concrete. One example of a thickening agent is primarily cellulosic.

The advanced (AE) water reducer and the thickener may be provided separately in the formulation of the present concrete, and an advanced (AE) water reducer containing thickener (hereinafter "thickener containing high performance ( AE) water-reducing agent”) may be used in the preparation of the present concrete. Preferably, it is provided in the concrete formulation as a thickener-containing advanced (AE) water reducer.

Commercially available products can be used as thickener-containing advanced (AE) water reducing agents. Commercially available thickener-containing superplasticizers include, for example, "Mighty 21-V" manufactured by Kao Corporation. Commercially available thickener-containing high-performance AE water reducing agents include, for example, "Master Glenium 6520" manufactured by BASF Japan.

The content of each of the high performance (AE) water reducing agent and the thickening agent can be appropriately selected according to the types of the high performance (AE) water reducing agent and the thickening agent so that the desired effects can be obtained.
The total content of the high performance (AE) water reducing agent and the thickener or the content of the thickening agent-containing high performance (AE) water reducing agent is, for example, in terms of solid content, 0.3 to the mass of cement It is about 0.9% by mass.

Examples of the steel material that constitutes the steel fiber include ordinary steel material, stainless steel, etc., and those having alkali resistance are preferable.
Moreover, from the viewpoint of rust prevention, it is preferable that the surface of the steel material is plated with zinc.
Examples of the shape of the steel fiber include hook type, straight type, wave type, and the like. The hook type is preferable in terms of improving the adhesion between concrete and steel fibers and improving the toughness of concrete.
As the steel fibers, for example, those commercially available as steel fibers for steel fiber reinforced concrete can be used.

The length of the steel fibers is preferably 12-32 mm, more preferably 24-32 mm. If the length of the steel fibers is within the above range, the dispersibility of the steel fibers in the fresh concrete and the bending toughness of the hardened concrete are more excellent. The length of the steel fiber is measured with a vernier caliper or the like.
The diameter of the steel fibers is preferably 0.15-0.9 mm, more preferably 0.38-0.75 mm. The diameter of the steel fiber is measured with a vernier caliper or the like.

In the present concrete, the mixing ratio of steel fibers is preferably more than 0.5% by volume and 2% by volume or less, more preferably 0.7 to 1.2% by volume. When the content of steel fibers exceeds 0.5% by volume, the concrete has excellent toughness and crack resistance. If the steel fiber content is 2% by volume or less, sufficient material separation resistance can be ensured.

Examples of other components include binders other than cement (silica fume, slag, fly ash, etc.), organic fibers (polyolefin fibers such as polypropylene fibers and polyethylene fibers, polyvinyl alcohol fibers, polyacetal fibers, etc.). be done.
Organic fibers are commonly used to impart blast resistance to concrete having a low water binder ratio. Since the concrete has a high water-binder ratio of 30% by mass or more, it typically does not contain organic fibers.

This concrete must be mixed with cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber to satisfy the prescribed water-binder ratio, steel fiber mixing ratio, unit coarse aggregate bulk volume, etc. It can be prepared by blending other ingredients according to.

The plastic viscosity of the present concrete at 20±5° C. is preferably 60 to 85 Pa·s, more preferably 65 to 75 Pa·s. If the plastic viscosity is 60 Pa·s or more, the material separation resistance is more excellent. If the plastic viscosity is 85 Pa·s or less, workability is more excellent.
The plastic viscosity is measured by the measuring method described in Examples below.
The plastic viscosity can be adjusted by adjusting the blending amount of the thickener.

The present concrete preferably has an increase rate of plastic viscosity calculated by the following formula (2) of 10 to 20%, more preferably 13 to 17%. If the plastic viscosity increase rate is 10% or more, the material separation resistance is more excellent. If the rate of increase in plastic viscosity is 20% or less, workability is more excellent.
Increase rate of plastic viscosity (%) = (P1-P2) / P2 × 100 (2)
Here, P1 indicates the plastic viscosity (Pa s) of this concrete at 20 ± 5 ° C,
P2 indicates the plastic viscosity (Pa·s) at 20±5° C. of a comparative product obtained by replacing the high efficiency (AE) water reducing agent and thickener of the present concrete with the high efficiency (AE) water reducing agent.
The rate of increase in plastic viscosity can be adjusted by adjusting the blending amount of the thickener.

Since the present concrete described above contains an advanced (AE) water reducing agent and a thickening agent as chemical admixtures, and has a unit coarse aggregate bulk volume of 0.3 to 0.4 m ³ /m ³ , The water binder ratio is as high as 30 to 60% by mass, and the steel fiber mixing ratio is as high as more than 0.5% by volume and 2% by volume or less, while ensuring sufficient material separation resistance and excellent workability. Moreover, since the water-binder ratio is 30 to 60% by mass, a design standard strength of 36 to 60 N/mm ² can be achieved. Furthermore, since the content of steel fibers is as high as more than 0.5% by volume and not more than 2% by volume, the toughness and crack resistance are excellent.

(Method for mixing high-strength concrete containing steel fibers)
The method of mixing high-strength concrete containing steel fibers of the present invention (hereinafter also referred to as "the present mixing method") comprises mixing cement, water, coarse aggregate, fine aggregate, a chemical admixture, and steel fibers, A method for mixing steel fiber-containing high-strength concrete having a binder ratio of 30 to 60% by mass and a steel fiber content of more than 0.5% by volume and not more than 2% by volume.
Other ingredients may be blended with cement, coarse aggregate, fine aggregate, chemical admixtures, and steel fibers.

In this mixing method, the target value _V'bG of the unit coarse aggregate bulk volume of steel fiber-containing high-strength concrete is calculated by the following formula (1), and the blending amount of coarse aggregate is adjusted so as to achieve this target value _V'bG . set.
V′ _bG =V _bG −(K _S ·2r _G /3r _F −1)·V _F /G _S (1)
Here, V′ _bG represents the target value (m ³ /m ³ ) of the unit coarse aggregate bulk volume of the steel fiber-containing high-strength concrete,
V _bG is a standard value range of unit coarse aggregate bulk volume (m ³ /m ³ ) of base high-strength concrete and indicates a number of 0.53 to 0.65 (m ³ /m ³ ). ,
K _S is an influence coefficient and indicates a number from 1.0 to 1.35,
r _G indicates the radius (mm) of the coarse aggregate calculated from the total coarse aggregate surface area obtained from the particle size distribution of the coarse aggregate, assuming that the coarse aggregate is spherical,
r _F represents the radius (mm) of the steel fiber calculated assuming that the steel fiber has a cylindrical shape,
_VF indicates the mixing ratio (% by volume) of the steel fibers,
_GS indicates the actual volume ratio (volume %) of the coarse aggregate.

The range of _VbG was set based on the Architectural Institute of Japan: Concrete Mixing Design Guidelines and Commentaries, and the Architectural Institute of Japan: High-strength Concrete Construction Guidelines and Commentaries.
Cement, coarse aggregate, fine aggregate, chemical admixtures, steel fibers and other components are as described above.
The preferable range of water binder ratio and steel fiber mixing ratio is the same as above.
The preferred blending amounts of fine aggregates, chemical admixtures, etc. are the same as described above.
The volume fraction of coarse aggregate is measured according to JIS A 1104.
In this mixing method, it is preferable to set the blending amount of the thickener so that the plastic viscosity or the increase rate of the plastic viscosity at 20±5° C. of the obtained high-strength concrete containing steel fibers is within the preferred range described above. .

In the present preparation method described above, at least an advanced (AE) water reducing agent and a thickening agent are used as chemical admixtures, and the coarse bone is adjusted to the target value V' _bG calculated by the above formula (1). In order to set the blending amount of the material, the water binder ratio is as high as 30 to 60% by mass, and the steel fiber mixing ratio is as high as more than 0.5% by volume and 2% by volume or less, but sufficient material separation resistance is achieved. It is possible to prepare high-strength concrete containing steel fibers with excellent workability. In addition, the steel fiber-containing high-strength concrete obtained has a water-binder ratio of 30 to 60% by mass, so that a design standard strength of 36 to 60 N/mm ² can be achieved. Furthermore, since the content of steel fibers is as high as more than 0.5% by volume and not more than 2% by volume, the toughness and crack resistance are excellent.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these.
Table 1 shows the materials used.

(Test example 1)
In this test example, the formulation of steel fiber-containing high-strength concrete (design standard strength Fc: 36 to 60 N/mm ² ) in which steel fibers are mixed at a mixing ratio of 1.0% by volume was investigated.

<Preparation of high-strength concrete containing steel fibers>
Table 2 shows the formulation of the steel fiber-filled high-strength concrete. The compound name consists of "W/C--unit coarse aggregate bulk volume (m ³ /m ³ )--mixed amount of steel fiber (kg/m ³ )--type of chemical admixture".
W/C is the mass ratio of water (W) to cement (C) and corresponds to the water binder ratio. W/C was set assuming a design standard strength of 36 to 60 N/mm ² . A mixed amount of steel fibers of 80 kg/m ³ corresponds to a mixed rate of 1.0% by volume. "SP amount" is a ratio (% by mass) to 100% by mass of cement (C).
In Table 2, "slump or slump flow" indicates the target slump or target slump flow, and "air amount" indicates the target air amount. "s/a" indicates the fine aggregate ratio.

At the time of preparation, as a guideline for an appropriate unit coarse aggregate bulk volume, the target value _V'bG of the unit coarse aggregate bulk volume is calculated by the following formula (1), and the coarse bone is adjusted so that this target value _V'bG is obtained. The amount of material to be added was set.
V′ _bG =V _bG −(K _S ·2r _G /3r _F −1)·V _F /G _S (1)
The definitions of V _bG , K _S , r _G , r _F , V _F and G _S are as described above.
Table 3 shows the values of V _bG , K _S , r _G , r _F , V _F and G _S adopted in this formulation and the calculated value of V′ _bG .

<Kneading>
For kneading, a twin-screw forced kneading mixer (manufactured by Pacific Machinery Co., Ltd., Model SD-55) with a nominal capacity of 0.055 m ³ was used. Cement (C) and fine aggregate (S) were added and dry kneaded, then water (W) and chemical admixture (SP) were added and kneaded to obtain mortar. Next, coarse aggregate (G) was added and kneaded to obtain high-strength concrete. Further, steel fibers (ST) were added and kneaded for 120 seconds to obtain steel fiber-containing high-strength concrete.

<Evaluation>
Fresh concrete properties (slump, slump flow, flow time (50 cm and stop), air content, concrete temperature, plastic viscosity (20±5° C.), material separation resistance) and hardening for each formulation of high-strength concrete with steel fibers. Concrete properties (compressive strength (age: 28 days), elastic modulus (age: 28 days), flexural toughness coefficient (age: 28 days), autogenous shrinkage in sealed curing (age: 91 days)) were evaluated.
JIS A 1101 for slump, JIS A 1150 for slump flow and flow time, JIS A 1128 for air content, JIS A 1156 for concrete temperature, JIS A 1160 for material separation resistance, JIS A 1160 for compressive strength, JIS A 1108 for elastic modulus A 1149, flexural toughness modulus was evaluated according to JSCE-G552-2013.
The plastic viscosity is determined by measuring the relationship between the rotational speed and torque of the rotor blades of the rotary blade viscometer, and measuring the relationship between the rotation speed and torque of the high-strength concrete that serves as the base before the steel fibers are added. (Reference: Hiroki Kazumi, Hiroshi Kasai, Katsumi Yanagida, Yasuhiro Kameda, "Experimental study on measuring method of flow characteristics of high-strength concrete using rotary vane viscometer", Concrete Engineering Paper Vol. 1, No. 1, pp. 133-141, 1990.1).
Autogenous shrinkage is described in Japan Concrete Institute: Superfluid Concrete Research Committee Report (II), pp. 209-210, 1994.5 [Appendix 1] (tentative name) In accordance with the self-shrinkage test method for high-flow concrete, the embedded strain gauge KM-100BT manufactured by Tokyo Sokki Kenkyusho is placed in a 10 x 10 x 40 cm test piece. The autogenous contraction strain was measured by placing it in the central part.
Table 4 shows the evaluation results. 1 to 11 show the evaluation results of material separation resistance (state of fresh concrete after slump flow test) of each formulation other than 46-0.30-80-SP2.

As shown in Table 4, formulations (46-0.40-80-SP4, 46-0.40-80- SP2, 46-0.30-80-SP2, 37-0.30-80-SP4, 28-0.30-80-SP4) are high-strength steel fiber containing steel fibers that ensure material separation resistance and have good workability. Concrete was achieved.

<Discussion>
"Influence of Unit Coarse Aggregate Bulk Volume"
A formulation with a water-cement ratio of 46.0% by mass, which is considered to be the easiest to separate materials with a low concrete viscosity, was examined.
46-0.60-0-SP1 contains no steel fibers, has a water-cement ratio of 46.0% by mass, and a unit coarse aggregate bulk volume of 0.60m ³ /m ³ . 46-0.60-80-SP1 is a formulation of 46-0.60-0-SP1 with 1% by volume steel fiber. In 46-0.60-80-SP1, as shown in FIG. 6, the slump collapsed and the coarse aggregate separated.
46-0.60-80-SP4 and 46-0.60-0-SP4' are formulations in which the superplasticizer of 46-0.60-80-SP1 is changed to a thickener-containing superplasticizer. be. As shown in FIG. 4, when the amount of the chemical admixture used was small, the materials were not separated, but the slump was small and the workability was poor. On the other hand, as shown in FIG. 5, when the amount of the chemical admixture used was forcibly increased in order to improve workability, the slump collapsed and the coarse aggregate separated.
From the above, it was not possible to realize a high-strength concrete containing steel fibers with good workability while securing material separation resistance with a unit coarse aggregate bulk volume of 0.60 m ³ /m ³ .

"Influence of high performance AE water reducing agent"
46-0.40-80-SP3 is a blend that contains 1% by volume of steel fiber, has a unit coarse aggregate bulk volume of 0.40 m ³ /m ³ , and uses a high performance AE water reducing agent as a chemical admixture. be. As shown in FIG. 7, the mortar seeped out around the slump and separated.
From the above, even if the unit coarse aggregate bulk volume is 0.40 m ³ /m ³ , a general high-performance AE water reducing agent can produce high-strength concrete containing steel fibers that ensures material separation resistance and has good workability. could not be realized.

"Influence of Types of Thickener-Containing Advanced (AE) Water-Reducing Additives"
46-0.40-80-SP4 and 46-0.40-80-SP2 contain 1% by volume of steel fiber, the unit coarse aggregate bulk volume is 0.40m ³ /m ³ , and the thickener content is high. Performance (AE) formulations differing only in type of water reducer. As shown in FIGS. 8 and 9, all of these formulations provide a slump with good workability that ensures material separation resistance.
From the above, even if the brand of the thickener-containing high performance (AE) water reducing agent is changed, high-strength concrete containing steel fibers that ensures material separation resistance and has good workability could be realized.

<Summary>
The findings obtained in this study are shown below.
・By reducing the bulk volume of coarse aggregate using the above formula (1) and using a thickener-containing high performance (AE) water reducing agent, the material separation resistance is secured and workability is good. We were able to achieve high-strength concrete. Also, the type of thickener-containing advanced (AE) water reducer had no effect.
• Reducing the unit coarse aggregate bulk volume resulted in material segregation unless a thickener-containing advanced (AE) water reducer was used.
・Even if a thickener-containing superplasticizer is used, material separation occurs unless the coarse aggregate bulk volume is reduced.

Claims (7)

Containing cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber, the water binder ratio is 30 to 60% by mass, and the mixing ratio of the steel fiber is more than 0.50% by volume and 2% by volume or less. A steel fiber-containing high-strength concrete that is
The chemical admixture contains either one or both of a high performance water reducing agent and a high performance AE water reducing agent, and a thickening agent, and the sum of the high performance water reducing agent, the high performance AE water reducing agent and the thickening agent is 0.85 to 1.40% by mass with respect to the mass of the cement,
Steel fiber containing unit coarse aggregate bulk volume, which is the value obtained by dividing the unit coarse aggregate amount by the surface dry density of the coarse aggregate and further dividing by the solid volume ratio , is 0.3 to 0.5 m ³ /m ³ High-strength concrete. A high-strength concrete containing steel fibers according to claim 1, except that it contains fly ash. The steel fiber-containing high-strength concrete according to claim 1 or 2, wherein the steel fibers have a diameter of 0.15 to 0.9 mm and a length of 12 to 32 mm. The steel fiber-containing high-strength concrete according to any one of claims 1 to 3, which has a plastic viscosity of 60 to 85 Pa·s at 20 ± 5°C. Cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber are blended, the water binder ratio is 30 to 60% by mass, and the mixing ratio of the steel fiber is more than 0.5% by volume and 2% by volume. 1. A method of formulating steel fiber-filled high-strength concrete comprising:
Using at least one or both of a high performance water reducing agent and a high performance AE water reducing agent as the chemical admixture and a thickener,
The target value _V'bG of the unit coarse aggregate bulk volume of the steel fiber-containing high-strength concrete is calculated by the following formula (1), and the blending amount of the coarse aggregate is set so as to achieve the target value _V'bG . , a method for preparing high-strength concrete with steel fibers.
V′ _bG =V _bG −(K _S ·2r _G /3r _F −1)·V _F /G _S (1)
Here, V′ _bG represents the target value (m ³ /m ³ ) of the unit coarse aggregate bulk volume of the steel fiber-containing high-strength concrete,
V _bG is a standard value range of unit coarse aggregate bulk volume (m ³ /m ³ ) of base high-strength concrete and indicates a number of 0.53 to 0.65 (m ³ /m ³ ). ,
K _S is an influence coefficient and indicates a number from 1.0 to 1.35,
r _G indicates the radius (mm) of the coarse aggregate calculated from the total coarse aggregate surface area obtained from the particle size distribution of the coarse aggregate, assuming that the coarse aggregate is spherical,
r _F represents the radius (mm) of the steel fiber calculated assuming that the steel fiber has a cylindrical shape,
_VF indicates the mixing ratio (% by volume) of the steel fibers,
_GS indicates the actual volume ratio (volume %) of the coarse aggregate. The method for mixing steel fiber-containing high-strength concrete according to claim 5 , wherein the steel fiber has a diameter of 0.15-0.9 mm and a length of 12-32 mm. 7. The steel fiber-containing high-strength concrete according to claim 5 or 6 , wherein the blending amount of the thickener is set so that the plastic viscosity of the steel fiber-containing high-strength concrete at 20±5° C. is 60 to 85 Pa s. formulation method.

Images