JP6414350B1 - Concrete composition and method for producing concrete composition - Google Patents

Abstract

[Problem] To provide a concrete composition that is excellent in cost effectiveness and environmental load reduction, has a high level of material separation resistance and / or impact deformation resistance, and has excellent workability. A JA funnel of fly ash paste containing cement and pulverized fly ash obtained by pulverizing fly ash raw powder, wherein the pulverized fly ash includes 50 parts by mass of water with respect to 100 parts by mass of pulverized fly ash. A concrete composition having a time in the range of 17 to 27 seconds. [Selection figure] None

Description

  The present invention relates to a concrete composition and a method for producing a concrete composition.

The performance required for concrete is largely classified into workability, strength and durability. Among them, the index indicating the performance of concrete is representative and general of slump or slump flow belonging to workability and compressive strength belonging to strength. Moreover, since the compressive strength of concrete greatly depends on the water-cement ratio, if this compressive strength is set appropriately, the durability that also largely depends on the water-cement ratio is secured. If the durability cannot be satisfied by the water cement ratio alone, the type of cement may be selected according to the required performance.
On the other hand, since the slump or slump flow has become too typical and general as an index indicating workability, there is a case where the workability is judged only by the numerical value. In practice, material separation resistance and / or impact deformation resistance belonging to workability are also important indicators of concrete performance. The material separation resistance and / or impact deformation resistance are greatly related to the viscosity of concrete, but if the fluidity is increased too much in order to improve the workability, the material separation resistance and / or the impact deformation resistance. Decreases. When material separation occurs, which is a phenomenon in which the coarse aggregate is separated from the mortar portion, strength and durability are lowered. In addition, when the degree of deformation of the concrete composition with respect to impact increases, the material separation resistance decreases. That is, material separation resistance and / or impact deformation resistance are not only related to workability, but also related to improvement in strength and durability.

In order to ensure the material separation resistance and / or impact deformation resistance of concrete, it is necessary to examine the materials used and the composition. As a measure to ensure material separation resistance and / or impact deformation resistance, it is to use as much fine powder as cement as possible. And it is to use the fine particles such as fine aggregate as much as possible within the allowable range.
However, there is a limit to the amount of powder or fine particles used, and the amount necessary for ensuring material separation resistance and / or impact deformation resistance may not be used. Therefore, in order to ensure material separation resistance and / or impact deformation resistance, if the powder and fine particles cannot be supplemented, admixtures such as blast furnace slag fine powder, limestone fine powder, fly ash and silica fume are used. There is a case.
Thus, in order to increase the material separation resistance of concrete, it has been proposed to mix a material containing powder, fine particles and admixture in a balanced manner as a concrete material (see, for example, Patent Document 1). On the other hand, a technique has been proposed in which viscosity is chemically imparted with a special admixture such as a thickener and an inseparable admixture in water to increase material separation resistance (see, for example, Patent Document 2).

JP 2014-114176 A Japanese Patent Laid-Open No. 2005-281888

As described above, in order to ensure the material separation resistance and / or impact deformation resistance of concrete, it is a basic means to appropriately contain powder and fine particles. However, increasing the material separation resistance and / or impact deformation resistance with powder and fine particles may lead to a decrease in workability due to increased viscosity. Further, increasing the material separation resistance and / or impact deformation resistance while securing a fine cement amount may develop problems of temperature cracking and self-shrinkage due to an increase in the cement amount.
Therefore, it is considered to be advisable to include admixtures such as silica fume and special admixtures such as thickeners and non-separable admixtures in water. However, these admixtures and special admixtures are very expensive materials, and if they are included only for securing material separation resistance and / or impact deformation resistance, there is a problem that they are not cost effective. is there.

  Therefore, the present invention aims to provide a concrete composition which is excellent in cost effectiveness and environmental load reduction, ensures a high level of material separation resistance and / or impact deformation resistance, and has excellent workability. To do.

  As a result of intensive studies to achieve the above object, the present inventor considers cost-effectiveness and environmental load reduction, and blends pulverized fly ash obtained by pulverizing fly ash raw powder so as to have specific physical properties. Thus, the present inventors have found that a material composition resistance and / or impact deformation resistance at a high level can be secured and a concrete composition excellent in workability can be provided, and the present invention has been conceived. That is, the present invention is as follows.

[1] containing cement and pulverized fly ash obtained by pulverizing fly ash raw powder;
A concrete composition, wherein the pulverized fly ash has a JA funnel flow time of 17 to 27 seconds in a fly ash paste containing 50 parts by mass of water with respect to 100 parts by mass of pulverized fly ash.
[2] containing cement and ground fly ash obtained by grinding fly ash raw powder,
When the pulverized fly ash stirs the mixture of the pulverized fly ash and water by “9.2.3 Mechanical kneader” of JIS R5201, the current flowing through the mechanical kneader is maximum. A concrete composition having a water powder mass ratio of 23 to 27% when the mixture becomes.
[3] containing cement and crushed fly ash obtained by pulverizing fly ash raw powder,
The pulverized fly ash is a concrete composition in which the specific gravity only after pulverization is increased by 1.5% or more and 3.0% or less with respect to the specific gravity before pulverization.
[4] The concrete composition according to any one of [1] to [3], wherein the pulverized fly ash has a loss on ignition of 3% by mass to 10% by mass.
[5] The concrete composition according to any one of the above [1] to [4], wherein the amount of the pulverized fly ash is 20 kg or more and 150 kg or less per 1 m ³ of the volume of the concrete composition.
[6] The concrete composition according to any one of [1] to [5], further including at least one selected from an admixture and a special admixture.
[7] The cement according to any one of [1] to [6], wherein the cement is at least one selected from the group consisting of ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, and low heat Portland cement. Concrete composition.
[8] A method for producing a concrete composition containing cement and pulverized fly ash obtained by pulverizing fly ash raw powder,
A step of pulverizing the fly ash raw powder into the pulverized fly ash so that the specific gravity only after pulverization is increased by 1.5% or more and 3.0% or less with respect to the specific gravity before pulverization;
The manufacturing method of the concrete composition including the process of mix | blending the said cement and the said grinding | pulverization fly ash.
[9] The method for producing a concrete composition according to the above [8], wherein the fly ash raw powder has a loss on ignition of 3% by mass to 10% by mass.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in cost effectiveness and environmental impact reduction, can ensure the material separation resistance and / or impact deformation resistance in a high level, and can provide the concrete composition excellent in workability.

The concrete composition according to the embodiment of the present invention contains cement and pulverized fly ash obtained by pulverizing fly ash raw powder, and the pulverized fly ash contains 50 parts by mass of water with respect to 100 parts by mass of pulverized fly ash. The fly ash paste contained has a JA funnel flow time in the range of 17 to 27 seconds.
In this specification, the JA funnel flow-down time refers to a flow-down time measured using a grouting flow cone of MIC-363-0-03 in accordance with “PC Grout fluidity test method” of JSCE-F531.
In this specification, the JA funnel flowing time of fly ash paste containing 50 parts by mass of water with respect to 100 parts by mass of fly ash may be described as “JA funnel flowing time” or “JA funnel flowing time of fly ash paste”. is there.

In the present specification, “pulverized fly ash” refers to a pulverized fly ash powder. In the present specification, the pulverized fly ash is not necessarily required to be obtained by pulverizing all the individual particles contained in the fly ash raw powder. Even if the particles are included without being crushed even after being pulverized, when the fly ash raw powder is pulverized, it is referred to as pulverized fly ash.
As a pulverizing apparatus for performing the pulverization process, a ball mill, a vibration mill (vibrating the container and transmitting the vibration to the medium (ball and rod) inside the container to make the powder finer), and the like can be used. The pulverization of the fly ash raw powder is such that the obtained pulverized fly ash has a JA funnel flow time of 17 to 27 seconds in a fly ash paste containing 50 parts by mass of water with respect to 100 parts by mass of the pulverized fly ash. .

  When the pulverized fly ash contained in the concrete composition has a JA funnel flow time of fly ash paste in the range of 17 to 27 seconds, the concrete composition containing the pulverized fly ash is excellent in fluidity and suitable. While having viscosity and improving workability, it is possible to ensure high material separation resistance by appropriate fluidity. The material separation resistance can be indirectly evaluated by the rebound reduction effect, and the impact deformation resistance of the concrete composition can also be evaluated by the rebound reduction effect. The rebound reduction effect can be evaluated as the rebound reduction effect is larger and the material separation resistance and / or impact deformation resistance is better as the number of spreads measured by the test method described in the examples is larger. If pulverized fly ash has a JA funnel flow time of fly ash paste of less than 17 seconds, the fluidity of the concrete composition containing pulverized fly ash increases, the viscosity decreases too much, and conversely, the workability is improved. May decrease. On the other hand, if the pulverized fly ash has a JA funnel flow time of fly ash paste longer than 27 seconds, the fluidity may be lowered and the workability may not be improved.

The pulverized fly ash having a JA funnel flow time of 17 to 27 seconds in a fly ash paste containing 50 parts by mass of water with respect to 100 parts by mass of pulverized fly ash has improved workability and high material separation resistance. From the viewpoint of ensuring, when the pulverized fly ash is stirred by the “9.2.3 Mechanical kneader” of JIS R5201, the mixture of the pulverized fly ash and water is added to the mechanical kneader. The thing whose water powder mass ratio of the said mixture when the flowing electric current becomes the maximum is 23 to 27% is preferable.
Moreover, the pulverized fly ash in which the JA funnel flow time of fly ash paste containing 50 parts by mass of water with respect to 100 parts by mass of pulverized fly ash is in the range of 17 to 27 seconds has improved workability and high material separation resistance. From the viewpoint of securing, it is preferable that the specific gravity only after grinding is increased by 1.5% or more and 3.0% or less with respect to the specific gravity before grinding.

  A concrete composition according to an embodiment of the present invention contains cement and pulverized fly ash obtained by pulverizing fly ash raw powder, and the pulverized fly ash is a mixture of the pulverized fly ash and water according to JIS R5201. The water powder mass ratio of the mixture is 23 to 27% when the current flowing through the mechanical kneader becomes the maximum when stirring by "9.2.3 Mechanical kneader". is there.

  When each of the current values to be energized when stirring with “9.2.3 Mechanical kneader” of JIS R5201 is measured for a mixture in which the ratio of water to 1000 g of pulverized fly ash is changed, the current value is The maximum value is shown in a mixture in which a certain amount of water is added to 1000 g of pulverized fly ash. In the present specification, the ratio of the mass of water to the mass of pulverized fly ash in the mixture in which the current value passed through the kneader for mechanical kneading is maximized is the “water powder mass ratio at the maximum current value”. May be described.

  The water powder mass ratio at the maximum current value is a numerical value specific to the target powder. The water powder mass ratio at the maximum current value can also be defined as the restricted water ratio, and is recognized as a numerical value specific to the powder. The restrained water ratio represents the mass of water restrained by the powder. When the current value supplied to the “9.2.3 Mechanical kneader” of JIS R5201 is maximized, it does not depend on the type of the stirrer and the operation status (low speed or high speed) of the stirrer. When water is gradually added to the powder and the current value applied to the mechanical kneader during stirring is measured, the current value shows a peak at a certain water powder mass ratio. At this time, the operation of the paddle of the mechanical kneader does not change, and it cannot be discriminated at all. The water powder mass ratio at which the stirring torque is maximum can be identified only by a change in the current value. The water powder mass ratio at the maximum current value can be measured, for example, by the method described in Examples described later.

  When the pulverized fly ash is kneaded and stirred with the pulverized fly ash and water using “9.2.3 Mechanical kneader” of JIS R5201, the mechanical kneader is energized. When the mass ratio of the water powder that maximizes the current value is 23 to 27%, the pulverized fly ash adsorbs water appropriately, and the concrete composition containing the pulverized fly ash is excellent in fluidity and moderate. It is possible to improve workability by having a good viscosity. When the pulverized fly ash kneads and stirs the pulverized fly ash and water, the pulverized fly ash having a water powder mass ratio that maximizes the stirring torque is 23 to 27% because it adsorbs water appropriately. The concrete composition containing this fly ash can ensure high material separation resistance and / or impact deformation resistance. When the pulverized fly ash is kneaded and stirred with the pulverized fly ash and water with the mechanical kneader, the mass ratio of the water powder that maximizes the current applied to the mechanical kneader is If it is less than 23%, the amount of water restrained by the pulverized fly ash is small, and if shot concrete is taken as an example, the rebound increases and the rebound reduction effect tends to decrease. When the pulverized fly ash is kneaded and stirred with the pulverized fly ash and water with the mechanical kneader, the mass ratio of the water powder that maximizes the current applied to the mechanical kneader is If it exceeds 27%, the amount of water restrained by the pulverized fly ash increases, and in addition to the decrease in fluidity in the fresh state at the beginning of kneading, the viscosity increases while absorbing too much water. Rebound increases and impact deformation resistance required for rebound reduction decreases.

In addition, when the pulverized fly ash and water are kneaded and agitated using “9.2.3 Mechanical kneader” of JIS R5201, the current applied to the mechanical kneader is maximized. The pulverized fly ash having a water powder mass ratio of 23 to 27% has a JA funnel flow time of fly ash paste from the viewpoint of improving workability and ensuring high material separation resistance and / or impact deformation resistance. It is preferable that it is the range of 17 to 27 seconds.
Further, when the pulverized fly ash and water are kneaded and stirred using the kneader for mechanical kneading, the water powder mass ratio that maximizes the current applied to the kneader for mechanical kneading is 23 to 27. % Crushed fly ash has a specific gravity of 1.5% only after pulverization relative to the specific gravity before pulverization from the viewpoint of improving workability and ensuring high material separation resistance and / or impact deformation resistance. It is preferable that it is increased by 3.0% or less.

  The concrete composition according to the embodiment of the present invention contains cement and pulverized fly ash obtained by pulverizing fly ash raw powder, and the pulverized fly ash has a specific gravity of 1 only after pulverization relative to the specific gravity before pulverization. Increased by 5% or more and 3.0% or less. In the present specification, the rate of increase in the specific gravity only after pulverization relative to the specific gravity before pulverization of fly ash may be referred to as “increase rate in specific gravity of tsutsuka”.

When the increase rate of the specific gravity of the pulverized fly ash is less than 1.5%, sufficient material separation resistance and / or impact deformation resistance cannot be ensured. Further, when the increase rate of the specific gravity of the pulverized fly ash exceeds 3.0%, the fluidity and workability deteriorate. In view of the above, the pulverized fly ash preferably has a specific gravity increased only by 1.6% or more and 2.9% or less after pulverization with respect to the specific gravity before pulverization, and is preferably 1.7% or more and 2.9%. % Is more preferable, and more preferably 1.8% or more and 2.7% or less.
In this specification, “Mitsukasa specific gravity” means a powder (fly ash) to be measured in a cylindrical stainless steel container having a diameter of 8 cm ± 0.5 cm and a height of 8 cm ± 0.5 cm. ) Is apparently filled and then the apparent density of the powder in the container after 70 times of dropping by the flow table defined in JIS R5201: 2015 is applied. Specifically, for example, it can be measured by the method described in the examples described later.

Note that the pulverized fly ash in which the specific gravity after pulverization is increased by 1.5% or more and 3.0% or less with respect to the specific gravity before pulverization is improved in workability and high material separation resistance and / or From the viewpoint of securing impact deformation resistance, it is preferable that the JA funnel flow time of the fly ash paste is in the range of 17 to 27 seconds.
In addition, pulverized fly ash in which the specific gravity after pulverization is increased by 1.5% or more and 3.0% or less with respect to the specific gravity before pulverization is improved in workability, high material separation resistance and / or impact. From the viewpoint of ensuring deformation resistance, when the pulverized fly ash and water are kneaded and agitated using “9.2.3 Mechanical kneader” of JIS R5201, the mechanical kneader It is preferable that the water powder mass ratio that maximizes the current value to be energized is 23 to 27%.

It is preferable that the pulverized fly ash has a specific gravity of 1.06 to 1.13 g / cm ³ . When the specific gravity of the pulverized fly ash is 1.06 to 1.13 g / cm ³ , the concrete composition containing the pulverized fly ash has excellent fluidity and moderate viscosity to improve workability. In addition, it is possible to ensure high material separation resistance and / or impact deformation resistance.

  The ignition loss of the pulverized fly ash is preferably 3% by mass or more and 10% by mass or less from the viewpoint of ensuring sufficient workability. The ignition loss of pulverized fly ash is more preferably 3% by mass or more and 9% by mass or less, and further preferably 3% by mass or more and 8% by mass or less. The ignition loss can be measured by the method described in Examples described later. The mechanism by which the loss on ignition of pulverized fly ash contributes to workability is not clear, but if the loss on ignition of pulverized fly ash is 3% by mass or more and 10% by mass or less, this pulverized fly ash and cement are included. Appropriate viscosity is imparted to the concrete composition, and sufficient workability is obtained. The pulverized fly ash having the ignition loss within the above range can be substantially obtained by pulverizing the fly ash raw powder having the ignition loss within the above range.

The kind of cement contained in the concrete composition is not particularly limited, and is preferably at least one selected from the group consisting of ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, and low heat Portland cement.
The blending amount of cement in the concrete composition is preferably 300 kg or more and 420 kg or less, more preferably 320 kg or more and 400 kg or less, and further preferably 340 kg or more and 380 kg or less per 1 m ³ of the volume of the concrete composition. .

The concrete composition can further contain, for example, water, fine aggregate, coarse aggregate, admixture and the like as a constituent material. The fine aggregate has a particle size of 5 mm or less. For example, known aggregates such as river sand, mountain sand, land sand, crushed sand, sea sand, and quartz sand can be used. The coarse aggregate has a particle size of more than 5 mm. For example, known aggregates such as gravel and sandstone crushed stone can be used.
The blending amount of fine aggregate in the concrete composition is preferably 850 kg or more and 1050 kg or less, more preferably 875 kg or more and 1025 kg or less, and 900 kg or more and 1000 kg or less per 1 m ³ of the volume of the concrete composition. Further preferred.
The blending amount of the coarse aggregate in the concrete composition is preferably 600 kg or more and 900 kg or less, more preferably 650 kg or more and 850 kg or less, and more preferably 700 kg or more and 800 kg or less per 1 m ³ of the volume of the concrete composition. Further preferred.

The concrete composition preferably further contains at least one selected from admixtures and special admixtures. It is preferable to contain the admixture and the special admixture in a range suitable for cost effectiveness and environmental load reduction.
Examples of the admixture include blast furnace slag fine powder, limestone fine powder and silica fume.
Special admixtures include thickeners and non-separable admixtures in water.
Examples of the thickener include cellulose thickeners such as methylcellulose; biopolymer thickeners such as water-soluble polysaccharides; and acrylic thickeners such as acrylic polymers.
Examples of the water inseparable admixture include a cellulose admixture mainly composed of a cellulose-based water-soluble polymer; and an acrylic admixture mainly composed of a polyacrylamide-based water-soluble polymer.

The blending amount of the pulverized fly ash in the concrete composition is 20 kg or more and 150 kg or less per 1 m ³ of the volume of the concrete composition from the viewpoint of ensuring high material separation resistance and / or impact deformation resistance and sufficient workability. Preferably there is. The blending amount of the pulverized fly ash is more preferably 30 kg or more and 140 kg or less, and further preferably 40 kg or more and 130 kg or less.

  The ignition loss of the fly ash raw powder is preferably 3% by mass or more and 10% by mass or less from the viewpoint of ensuring sufficient workability. The ignition loss of the fly ash raw powder is more preferably 3% by mass or more and 9% by mass or less, and further preferably 3% by mass or more and 8% by mass or less. The ignition loss can be measured by the method described in Examples described later. When the loss on ignition of the fly ash raw powder is 3% by mass or more and 10% by mass or less, a pulverized fly ash having high material separation resistance can be obtained.

The specific surface area of the fly ash raw powder is preferably 3000 cm ² / g or more 3700cm ² / g or less. The specific surface area of the fly ash raw flour, more preferably not more than 3100 cm ² / g or more 3500 cm ² / g. The specific surface area can be measured by the method described in Examples described later. If the specific surface area of the fly ash raw powder is not more than 3000 cm ² / g or more 3700 cm ² / g, the effect of improving material separation resistance due to the use by grinding is obtained.

  The fly ash raw powder whose ignition loss is in the above range is, for example, ash discharged from a thermal power plant, and is produced by pulverized coal combustion. As fly ash raw powder, the fly ash dropped from the combustion gas of the combustion boiler when passing through the air regenerator or the economizer, the fly ash collected by the electric dust collector, and dropped to the furnace bottom of the combustion boiler Including ash.

  The concrete composition according to the embodiment of the present invention is preferably used for shotcrete. The shotcrete refers to concrete used for a method of compressing concrete containing a concrete composition and water, and spraying the compressed composition from a nozzle tip to a predetermined location using a compressed air. In the concrete spraying method, the aggregate bounces back due to the impact of the sprayed concrete, the planned amount of concrete is not sprayed, and the loss of the concrete amount is called rebound, and the rebound reduction effect is The sprayed concrete can withstand the impact, the aggregates will not bounce back, and concrete close to the planned amount can be sprayed, which means that the loss of concrete is small. A concrete composition having a rebound reducing effect has little separation between aggregates and components other than aggregates (cement, fly ash, etc.), that is, high material separation resistance. Moreover, the concrete composition which has a rebound reduction effect does not bounce off the aggregate, and has high impact deformation resistance. By confirming the superiority or inferiority of the rebound reduction effect of shotcrete, the superiority or inferiority of material separation resistance or impact deformation resistance can be indirectly evaluated.

  A preferred example of a method for producing a concrete composition according to an embodiment of the present invention is a method for producing a concrete composition containing cement and pulverized fly ash obtained by pulverizing a fly ash raw powder, and the specific gravity is determined only before pulverization. The pulverized fly ash is pulverized into a pulverized fly ash, and the cement and the pulverized fly ash are mixed so that the specific gravity increases only by 1.5% or more and 3.0% or less after pulverization. Compounding.

In the step of pulverizing the fly ash raw powder to obtain a pulverized fly ash, various pulverization methods can be employed in which the specific gravity of the pulverized fly ash is within the above range.
As a pulverizing apparatus for producing pulverized fly ash, a ball mill, a vibration mill (vibrating the container and transmitting vibration to the medium (ball and rod) inside the container to make the powder finer), etc. it can.
When the ball mill is used as the pulverizer, the rotation speed of the mill is preferably 45 rpm or more and 75 rpm or less, more preferably 50 rpm or more and 70 rpm or less, and further preferably 55 rpm or more and 65 rpm or less. The pulverization time when using a ball mill is preferably 3 minutes or longer and 15 minutes or shorter, more preferably 3 minutes or longer and 12 minutes or shorter, and further preferably 3 minutes or longer and 10 minutes or shorter.

  In the step of blending cement and pulverized fly ash, a concrete composition can be prepared by blending cement, pulverized fly ash and other constituent materials in a required mixing ratio and mixing them with a mixer or the like.

The concrete composition according to the embodiment of the present invention produces a concrete kneaded material by kneading the solid material and water contained in the concrete composition, but preparing a solid material contained in the concrete composition in advance. This may be mixed with water to form a concrete kneaded material, and is not particularly limited as long as it can be uniformly kneaded even if all the solid materials and water contained in the concrete composition are mixed at once.
The amount of water used for kneading can be changed depending on the type and blending of the materials used, so it is not uniquely determined, but the water cement ratio is 50% by mass or more and 70% by mass or less. It is more preferable that it is 55 mass% or more and 65 mass% or less.
Moreover, there is no limitation in kneading conditions, the kind of kneading machine, etc., it is possible to use a conventional kneading machine.
The obtained concrete kneaded material can be subjected to curing such as steam curing and underwater curing to obtain concrete.

  According to the concrete composition of the present invention, a high level of material separation resistance can be ensured by blending pulverized fly ash obtained by pulverizing fly ash raw powder so as to have specific physical properties. And since the material composition resistance of the concrete composition is high, the workability of the concrete composition is excellent, and the work efficiency can be improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples.

(Materials used)
・ Cement: Ordinary Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.)
・ Water: Tap water ・ Fine aggregate: Mountain sand ・ Coarse aggregate: Sandstone crushed stone ・ Fly ash (FA): (1) to (15) shown below
(1) Type II ash (JIS A 6201: 2015 Concrete fly ash type II conforming product (classified product), specific surface area 3570 cm ² / g, loss on ignition 2.75% by mass)
(2) Raw powder A (fly ash raw powder, domestic thermal power plant, specific surface area 3410 cm ² / g, loss on ignition 6.21% by mass)
(3) Raw powder A-1 minute pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder A for 1 minute)
(4) Raw powder A-2 minutes pulverized FA (crushed fly ash obtained by pulverizing raw powder A for 2 minutes)
(5) Raw powder A-3 minutes pulverized FA (crushed fly ash obtained by pulverizing raw powder A for 3 minutes)
(6) Raw powder A-4 minutes pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder A for 4 minutes)
(7) Raw powder A-5 minutes pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder A for 5 minutes)
(8) Raw powder A-10 minutes pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder A for 10 minutes)
(9) Raw powder A-20 minutes pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder A for 20 minutes)
(10) Raw powder A-30 minutes pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder A for 30 minutes)
(11) Raw powder B (fly ash raw powder, domestic thermal power plant, specific surface area 3120 cm ² / g, loss on ignition 5.89% by mass)
(12) Raw powder B-2 minutes pulverized FA (crushed fly ash obtained by pulverizing raw powder B for 2 minutes)
(13) Raw powder B-5 minutes pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder B for 5 minutes)
(14) Raw powder B-10 minutes pulverized FA (crushed fly ash obtained by pulverizing raw powder B for 10 minutes)
(15) Raw powder B-20 minutes pulverized FA (ground pulverized fly ash obtained by pulverizing raw powder B for 20 minutes)

In addition, the specific surface area of the fly ash raw powder was calculated | required based on the "8.1 specific surface area test" prescribed | regulated by JISR5201: 2015.
The ignition loss of the fly ash raw powder was determined according to JIS A 6201: 2015 fly ash for concrete (975 ° C., 15 minutes ignition). Further, the loss on ignition of the pulverized fly ash was determined by the above method, and it was confirmed that the loss on ignition of the fly ash raw powder before pulverization was the same.

(Crushing fly ash raw powder)
The pulverization of fly ash raw powder uses a tilting ball mill having a drum with a capacity of 100 liters. The balls to be thrown are chrome steel balls of φ10 mm (about 3.5 kg / piece), and the balls are thrown into the fly ash raw powder (weight ratio, maximum 10% fly ash raw powder)
100 kg of balls against g). After the balls were thrown, the mill was placed in a horizontal position, and the mill was rotated at 60 rpm for the predetermined time to perform pulverization.

  (1) Type II ash, (2) Raw powder A, (3) to (10) Each ground fly ash of raw powder A, (11) Raw powder B, and (12) to (15) Raw powder B The following measurements were performed on crushed fly ash.

(Measurement of specific gravity)
The fly ash to be measured was ground and filled into a cylindrical stainless steel container having a diameter of 8.0 cm and a height of 8.0 cm, and the lid was covered with a plastic plate. Next, the container filled with this fly ash was dropped and moved 70 times using a flow table defined in “12.2 Measurement of Flow Value” of JIS R5201: 2015 “Physical Test Method for Cement”. . Then, the volume and weight of the fly ash in the said container after this falling motion were measured, the apparent density (bulk density) was calculated, and this was made into the specific gravity.

(Mitsukasa specific gravity increase rate)
The specific gravity of fly ash raw powder before grinding is defined as d1, the specific gravity of crushed fly ash after grinding is defined as d2, and the rate of increase in the specific gravity of crushed fly ash relative to the fly ash raw powder is measured by the following formula (1). did.
Increase rate of specific gravity of crushed fly ash (%) = (d2−d1) / d1 × 100 (1)

(JA funnel flow time)
1500 g of fly ash to be measured and 750 g of water (50 parts by mass of water with respect to 100 parts by mass of fly ash) were kneaded and stirred to prepare a fly ash paste. The kneading of fly ash and water was performed in accordance with “9.4.1 Cement paste kneading” in JIS R5201: 2015 “Cement physical test method”. About the obtained fly ash paste, the flow-down time (seconds) was measured using a grout flow cone of MIC-363-0-03 in accordance with “PC grout fluidity test method” of JSCE-F531.

(Water powder mass ratio at maximum current value)
JIS R5201 “9.2.3 Mechanical kneader” stirs and kneads a plurality of mixtures having different water / powder mass ratios, and measures the current flowing through the mechanical kneader. Specifically, water is added little by little to 1000 g of fly ash, and each time water is added, the current flowing through the mechanical kneader as the mixture having different water-powder mass ratio is changed as needed. taking measurement. The current flowing through the mechanical kneader is measured by using one of the two single-phase power cables of the mechanical kneader as a current measuring device (product name: Memory HiCorder MR8870, Hioki). Denki Co., Ltd.), and when the mixture was stirred, the current flowing through the mechanical kneader was measured, and among the different types of water powder mass ratios, the mechanical kneading mixture was measured. The water powder mass ratio when the current flowing through the machine was the maximum was measured as the water powder mass ratio at the maximum current value. The mechanical kneader can be energized with a maximum current of 500 amperes (A).
As an example of the measurement of the water powder mass ratio at the maximum current value, Table 1 against 1000 g of the above fly ash (1) type II ash (JIS A 6201: 2015 fly ash type II compliant product (classified product)) Table 1 shows the measured values of the electric current supplied to the mechanical kneader after each of the mixtures with the amount of water added was stirred with the mechanical kneader. Moreover, when each fly ash (2) to (15) is measured in the same manner as the fly ash (1) II seed ash, the water powder at the maximum value of the current passed through the mechanical kneader. The mass ratio is shown in Table 2.

As shown in Table 1, fly ash (1) type II ash (JIS A 6201: 2015 fly ash for concrete type II compliant product (classified product)) mixture in which the ratio of water to 1000 g was changed (Reference Examples 1 to 14) Was measured with “9.2.3 Mechanical kneader” of JIS R5201 to measure the current value that was energized. As a result, when the amount of water added to 1000 g of fly ash (1) II seed ash in Reference Example 9 is 220 g and the water powder mass ratio is 22%, the current value that is passed through the mechanical kneader is A maximum of 3.81 amps (A) was shown. That is, the mass ratio of the water powder at the maximum current value of fly ash (1) II seed ash is 22%.
In the same manner as in Reference Examples 1 to 14 shown in Table 1, each fly ash (2) to (15) was stirred and kneaded with the above-mentioned mechanical kneader for the mixture with the water / powder mass ratio changed. By measuring the current value energized in the kneader, the water powder mass ratio at the maximum current value can also be measured for each fly ash (2) to (15).

  (1) Type II ash, (2) Raw powder A, (3) to (10) Each ground fly ash of raw powder A, (11) Raw powder B, and (12) to (15) Raw powder B Table 2 shows the measured specific gravity of the pulverized fly ash, the increase rate of the specific gravity, the JA funnel flow time, and the water powder mass ratio at the maximum current value.

(Manufacture of concrete composition)
(Examples 1-8 and Comparative Examples 1-12)
Using each fly ash, concrete compositions of Examples and Comparative Examples were produced with the formulations shown in Table 3.

  Furthermore, the following tests were conducted on each concrete composition manufactured with the formulation shown in Table 3. The results are shown in Table 3.

(slump)
About each concrete composition manufactured with the mixing | blending shown in Table 3, slump (cm) was measured based on JIS A1101: 2014 "the concrete slump test method."

(Number of spreads)
About the concrete composition manufactured with the mixing | blending shown in Table 3, the test based on DIN1048 which is a German industrial standard was done as an evaluation test of material separation resistance. This test evaluates material separation resistance at a high level required for shotcrete, and the rebound reduction of shotcrete can be indirectly evaluated by this test value. Moreover, the impact deformation resistance required for rebound reduction can also be evaluated by this test.
The outline of this test method is as follows. After measuring the slump (cm) according to the JIS A 1101: 2014 concrete slump test method, the operation of lifting and dropping one side of the slump plate by 4 cm is repeated. By repeating this dropping operation, the number of times when the concrete flow reached 60 cm (the number of times of spreading) was measured. As the number of times of spreading increases, the material separation resistance and / or impact deformation resistance as sprayed concrete is excellent, and the evaluation is effective for reducing rebound.
In Table 3, “impossible to measure” means that the concrete did not flow in the first drop operation, but was crushed, the concrete flow could not be observed, and the number of expansions could not be measured. ing.

  From the results shown in Table 3, the concrete compositions of Examples 1 to 8 have a JA funnel flow time of fly ash paste in the range of 17 to 27 seconds, have excellent fluidity, and have an appropriate viscosity. It became possible to improve property, and the frequency | count of spreading increased compared with the concrete composition of Comparative Examples 1-4 and 6-12.

  Moreover, according to the results shown in Table 3, the concrete compositions of Examples 1 to 8 were subjected to kneading and stirring of the pulverized fly ash and water using JIS R5201 “9.2.3 Kneader for mechanical kneading”. The mass ratio of the water powder that maximizes the current applied to the kneader for mechanical kneading is 23 to 27%, and the pulverized fly ash in the concrete composition adsorbs water appropriately, and this pulverized fly ash The concrete composition containing No. 1 was excellent in fluidity and had an appropriate viscosity, and the number of times of spreading increased compared to the concrete compositions of Comparative Examples 1 to 4 and 6 to 12.

  Further, according to the results shown in Table 3, the increase rate of the specific gravity of the crushed fly ash obtained by pulverizing for 4 minutes and 5 minutes with the raw powder A is 2.7%, and 3 minutes and 10 minutes with the raw powder A. The increase rate of the specific gravity of the crushed crushed fly ash is 1.8%, the increase rate of the specific gravity of the crushed fly ash pulverized for 5 minutes using the raw powder B is 1.9%, The increase rate of the specific gravity of the crushed fly ash that was pulverized for 10 minutes was 2.9%, and the concrete compositions of Examples 1-8 using these crushed fly ash were Comparative Examples 1-4 and 6-6. The number of spreads increased compared to 12 concrete compositions.

  Thus, since the concrete composition of Examples 1-8 increased the frequency | count of expansion compared with the concrete composition of Comparative Examples 1-4 and 6-12, it is thought that the rebound reduction effect as shotcrete became large. Therefore, it can be said that the material separation resistance and / or the impact deformation resistance is excellent.

As shown in Table 3, in the concrete compositions of Comparative Examples 2 to 4 and 10 using fly ash raw powder and type II ash, the number of expansions of the concrete composition of Comparative Example 1 not using fly ash varies greatly. The rebound reduction effect was considered to be small.
In addition, as shown in Tables 3 and 4, the concrete composition of Comparative Example 5 in which the blending amount of the fly ash raw powder is larger than that of Comparative Example 4, the amount of water restrained by the fly ash raw powder increases. The fluidity in the fresh state at the beginning of the kneading was remarkably lowered and the viscosity was low, so it did not flow in the first place, and the number of spreads could not be measured.

As shown in Table 3, the concrete compositions of Comparative Examples 6, 7 and 11 containing pulverized fly ash having a JA funnel flow time longer than 27 seconds had decreased fluidity. It is considered that the pulverized fly ash used in Comparative Examples 6, 7, and 11 was not greatly different from the physical properties of the fly ash raw powder, and the quality improvement effect by pulverization could not be obtained.
As shown in Table 3, the concrete compositions of Comparative Examples 8, 9, and 12 containing ground fly ash having a JA funnel flow time of less than 17 seconds had high fluidity. It is considered that the pulverized fly ash used in Comparative Examples 8, 9, and 12 had a JA funnel flow time as short as less than 17 seconds and an insufficient viscosity.

As shown in Table 3, the concrete compositions of Comparative Examples 6, 7, and 11 including pulverized fly ash having a water powder mass ratio at a maximum current value exceeding 27% are large, and water constrained by pulverized fly ash is used. The amount increases, the fluidity decreases in the fresh state at the beginning of kneading, and the viscosity increases. On the other hand, water is absorbed too much and rebound increases, and the number of times of expansion does not increase as much as in Examples 1 to 8, reducing rebound. The impact deformation resistance required for this was reduced.
As shown in Table 3, the concrete compositions of Comparative Examples 8, 9 and 12 including the pulverized fly ash having a small water powder mass ratio of less than 23% at the maximum current value are the amount of water restrained by the pulverized fly ash. Less, the fluidity in the fresh state at the beginning of kneading is increased, and the viscosity is decreased, so the rebound is increased, the number of spreads is not increased as much as in Examples 1 to 8, the rebound reduction effect is decreased, and the material separation resistance And / or impact deformation resistance decreased.

  According to the present invention, by blending pulverized fly ash obtained by pulverizing fly ash raw powder so as to have specific physical properties, high material separation resistance and / or impact deformation resistance can be ensured, and workability is improved. It is possible to provide an excellent concrete composition.

Claims (10)

Containing cement and pulverized fly ash obtained by pulverizing fly ash raw powder having a loss on ignition of 3% by mass or more and 9% by mass or less ,
A concrete composition, wherein the pulverized fly ash has a JA funnel flow time of 17 to 27 seconds in a fly ash paste containing 50 parts by mass of water with respect to 100 parts by mass of pulverized fly ash. Containing cement and pulverized fly ash obtained by pulverizing fly ash raw powder having a loss on ignition of 3% by mass or more and 9% by mass or less ,
When the pulverized fly ash stirs the mixture of the pulverized fly ash and water by “9.2.3 Mechanical kneader” of JIS R5201, the current flowing through the mechanical kneader is maximum. A concrete composition having a water powder mass ratio of 23 to 27% when the mixture becomes. Containing cement and pulverized fly ash obtained by pulverizing fly ash raw powder having a loss on ignition of 3% by mass or more and 9% by mass or less ,
The pulverized fly ash is a concrete composition in which the specific gravity only after pulverization is increased by 1.5% or more and 3.0% or less with respect to the specific gravity before pulverization.   The specific surface area of the fly ash raw powder is 3000 cm ² / G or more 3700cm ² The concrete composition of any one of Claims 1-3 which is / g or less.   The specific gravity of the crushed fly ash is 1.06-1.13 g / cm ³ The concrete composition according to any one of claims 1 to 4, wherein The concrete composition according to any one of claims 1 to 5 , wherein a loss on ignition of the pulverized fly ash is 3% by mass or more and 9 % by mass or less. The concrete composition according to any one of claims 1 to 6 , wherein an amount of the pulverized fly ash is 20 kg or more and 150 kg or less per 1 m ³ of the volume of the concrete composition. The concrete composition according to any one of claims 1 to 7 , further comprising at least one selected from an admixture and a special admixture. The concrete composition according to any one of claims 1 to 8 , wherein the cement is at least one selected from the group consisting of ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, and low heat Portland cement. A method for producing a concrete composition comprising cement and pulverized fly ash obtained by pulverizing fly ash raw powder having an ignition loss of 3% by mass or more and 9% by mass or less ,
A step of pulverizing the fly ash raw powder into the pulverized fly ash so that the specific gravity only after pulverization is increased by 1.5% or more and 3.0% or less with respect to the specific gravity before pulverization;
The manufacturing method of the concrete composition including the process of mix | blending the said cement and the said grinding | pulverization fly ash.