KR102202545B1 - Cement composition, method for producing the same, and method for producing fly ash for cement composition - Google Patents

Abstract

It maintains its properties as an admixture material such as improved fluidity and contributes to strength development, does not remove coarse powder by classification, so that all of the raw material fly ash obtained from coal-fired power plants can be used as a blending material. It provides a cement composition that can contribute, a method for producing the same, and a method for producing a fly ash for a cement composition.
It is a cement composition comprising cement and fly ash, wherein the fly ash content is 30 mass% or less, and the fly ash satisfies the following formula (I) in a particle size distribution on a volume basis.
0.24<(D50-D10)/(D90-D50)≤0.5 (I)
(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.)

Description

Cement composition, method for producing the same, and method for producing fly ash for cement composition

The present invention relates to a cement composition using fly ash, a method for producing the same, and a method for producing a fly ash for a cement composition.

Fly ash is fine particles obtained by recovering fine particles floating in a high-temperature air stream among burned ash generated when pulverized coal is burned by a boiler of a coal-fired power plant. Pozzolan, which is composed of silicon dioxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) contained in fly ash as main components, reacts with calcium hydroxide (Ca(OH) ₂ ) contained in cement to form hydrates, Contributes to the development of long-term strength of the cured product. This reaction is called a pozzolanic reaction. Since the pozzolanic reaction proceeds gently, the heat of hydration can be suppressed, and fly ash is used as a material for mixing concrete or mortar (for example, Patent Document 1). In addition, fly ash containing a large number of spherical particles is used as a material for admixing concrete or mortar in order to improve workability (for example, Patent Document 2).

In fly ash, pulverized coal is burned in a boiler, and burned ash floating in a boiler furnace is exposed to high temperature to melt, and in the process of being cooled, spherical particles formed into spheres by surface tension, It contains unburned carbon in a relatively coarse and porous shape. The spherical particles in the fly ash are vitrified by melting the surface of the particles. It is considered that the relatively coarse and porous unburned carbon contained in the fly ash has a large particle diameter, so that combustion of the burnt ash does not proceed and does not become spherical particles. Coarse and porous unburned carbon in fly ash inhibits the ball bearing effect of spherical particles, decreases fluidity, and causes a decrease in strength.

In addition, if the amount of coarse and porous unburned carbon in the fly ash is large, when the fly ash is used as a blended material, the AE agent added to adjust the amount of air is adsorbed to the unburned carbon, and the amount of AE agent added increases. In some cases, it leads to an increase in manufacturing cost.

The quality of fly ash used as an admixture material for concrete or mortar is specified in JIS A6201:2015 "Fly ash for concrete". Fly ash from which coarse and porous unburned carbon is removed by classification to meet the degree of powder specified in JIS A6201:2015 "Fly Ash for Concrete" is used as an admixture material for concrete or mortar.

Japanese Unexamined Patent Application Publication No. 2004-292307 Japanese Unexamined Patent Application Publication No. 2011-132111

Coarse powder containing classified unburned carbon generated at the time of production of standardized fly ash is used as industrial waste for landfill disposal or as a clay substitute material for cement production raw materials.

As the amount of power generation in coal-fired power plants increases, the amount of fly ash generated in coal-fired power plants also increases. It is required to effectively utilize all of the fly ash generated in a coal-fired power plant without removing a part of the fly ash with an increased amount of production.

Therefore, in the present invention, all of the raw material fly ash obtained from a coal-fired power plant, etc., can be used as a blending material, without removing coarse powder by maintaining properties as a blended material such as improvement of fluidity and contributing to strength development. , An object of the present invention is to provide a cement composition capable of contributing to long-term strength development, a method for producing the same, and a method for producing a fly ash for a cement composition.

In order to achieve the above object, the inventors of the present invention conducted a thorough study, and as a result, in the particle size distribution based on the volume of particles contained in fly ash and fly ash, when the following formula (I) is satisfied, the fluidity and strength are expressed. The present invention was completed by discovering that all of the raw material fly ash obtained from a coal-fired power plant or the like can be used as a blended material, and that long-term strength development can also be contributed, without impairing the properties as a blended material such as sex. That is, the present invention is as follows.

[1] A cement composition comprising cement and fly ash, wherein the fly ash content is 30% by mass or less, and the fly ash satisfies the following formula (I) in a volume-based particle size distribution.

0.24<(D50-D10)/(D90-D50)≤0.5 (I)

(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.)

[2] The cement composition according to [1], wherein the fly ash content is 12% by mass or more.

[3] The cement composition according to [1] or [2], wherein the amount of amorphous phase in the fly ash is 55% by mass or more with respect to the total amount of the crystalline and amorphous phases in the fly ash.

In addition, in this specification, the amorphous phase amount (mass %) in fly ash means a value obtained by subtracting the amount (mass %) of unburned carbon from the amorphous phase amount (mass %) obtained by Rietveld analysis described later.

[4] The cement composition according to any one of [1] to [3], wherein the amount of Fe in the amorphous phase of the fly ash is 3.5% by mass or more and 10% by mass or less.

[5] The cement composition according to any one of [1] to [4], wherein the amount of unburned carbon in the fly ash is 3% by mass or more and 15% by mass or less.

[6] The cement composition according to any of the above [1] to [5], wherein the fly ash has a blaine specific surface area of 3000 cm ² /g or more and 4500 cm ² /g or less.

[7] The cement composition according to any of [1] to [6], wherein the amount of unburned carbon in the cement composition exceeding 212 µm is 1.5% by mass or less.

[8] The cement composition according to any one of [1] to [7], wherein a mass ratio of unburned carbon having a particle diameter exceeding 212 µm to the unburned carbon in the fly ash is 35% or less.

(9) Raw material fly ash is classified, the classified coarse fly ash having a particle diameter of 45 µm or more is crushed, and the particle size ratio of the following formula (I) is satisfied in a volume-based particle size distribution. Method for producing a fly ash for cement composition mixing and crushed fly ash.

0.24<(D50-D10)/(D90-D50)≤0.5 (I)

(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.)

(10) Raw material fly ash is classified, the classified coarse fly ash is pulverized with a particle diameter of 45 µm or more, and the raw material fly ash and the crushed fly ash are mixed so as to satisfy the following formula (I) in the particle size distribution based on the volume. , A method for producing a cement composition in which the mixed fly ash is blended to be 30% by mass or less based on the total amount of the cement composition.

0.24<(D50-D10)/(D90-D50)≤0.5 (I)

(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.)

[11] The method for producing a cement composition according to [10], wherein the mixed fly ash is blended in an amount of 12% by mass or more with respect to the total amount of the cement composition.

[12] The method for producing a cement composition according to [10] or [11], wherein the amount of the amorphous phase in the mixed fly ash is 55% by mass or more with respect to the total amount of the crystalline and amorphous phases in the mixed fly ash.

[13] The method for producing a cement composition according to any one of [10] to [12], wherein the amount of Fe in the amorphous phase of the mixed fly ash is 3.5% by mass or more and 10% by mass or less.

According to the present invention, it is possible to use all of the fly ash of raw materials obtained in a coal-fired power plant, etc. as a blended material that does not impair its properties as a blended material such as improved fluidity and contributes to strength development, and does not remove coarse powder by classification. In addition, it is possible to provide a cement composition capable of contributing to long-term strength development, a method for producing the same, and a method for producing a fly ash for a cement composition.

Hereinafter, the present invention will be described.

One embodiment of the present invention is characterized in that it contains cement and fly ash, the fly ash content is 30% by mass or less, and the fly ash satisfies the following formula (I) in a particle size distribution based on volume. It is a cement composition.

0.24<(D50-D10)/(D90-D50)≤0.5 (I)

(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.)

Fly ash

Fly ash produced in a coal-fired power plant or the like contains spherical particles spheroidized by surface tension in the process of melting and cooling the burnt ash and unburned carbon having a relatively coarse and porous shape.

Ratio of (D50-D10)/(D90-D50) in volume-based particle size distribution

The fly ash contained in the cement composition satisfies the above formula (I) in the particle size distribution on a volume basis. The formula (I) is obtained by subtracting the particle diameter D50 (median diameter) corresponding to the cumulative frequency 50% from the particle diameter D90 corresponding to the cumulative frequency 90% from the small diameter side in the particle size distribution based on the volume of the fly ash. The ratio of the value obtained by subtracting the particle diameter D10 corresponding to the cumulative frequency of 10% from the small diameter side from the above D50 is shown.

As shown in Formula (I), when the ratio represented by (D50-D10)/(D90-D50) in the volume-based particle size distribution of the fly ash exceeds 0.24 and is 0.5 or less, The particle size distribution shows a distribution close to a normal distribution that is symmetrical left and right centering on the particle diameter D50 (median diameter), and more specifically, the right side (the particle side larger than the particle diameter D50) shows a slightly broader shape distribution. In addition, when the ratio represented by (D50-D10)/(D90-D50) in the volume-based particle size distribution of fly ash exceeds 0.24 and is 0.5 or less, the volume-based particle size distribution shows a sharp shape distribution. The fly ash contained in the cement composition has a ratio represented by the above formula (I) in the particle size distribution based on the volume, so that the amount of coarse powder in the fly ash decreases, resulting in a large amount of coarse and porous unburned carbon. It is possible to suppress a decrease in fluidity and strength development, thereby maintaining good fluidity and strength development of a cement composition in which fly ash is mixed.

In the present specification, the particle size distribution based on the volume of the fly ash can be measured using a laser diffraction scattering type particle size distribution measuring device (for example, Microtrac MT2000, manufactured by Nikiso Corporation).

When the ratio represented by (D50-D10)/(D90-D50) of the formula (I) exceeds 0.5 in the particle size distribution of the fly ash contained in the cement composition, on a volume basis, the proportion of small particles contained This increases, the setting time of the cement composition becomes short, and workability may fall. In addition, when the ratio of (D50-D10)/(D90-D50) of the formula (I) is 0.24 or less in the particle size distribution of the fly ash contained in the cement composition on a volume basis, coarse particles are The contained ratio increases, the fluidity|liquidity falls, and the strength expression property may fall.

The ratio ((D50-D10)/(D90-D50)) of the value obtained by subtracting the particle diameter D50 from the particle diameter D50 to the value obtained by subtracting the particle diameter D50 from the particle diameter D90 is preferably 0.25 or more and 0.49 or less, and more preferably 0.26 It is not less than 0.48, and more preferably not less than 0.27 and not more than 0.47.

The particle diameter D50 is preferably 17 to 26 µm, more preferably 18 to 25 µm. Fly ash in which the particle diameter D50 is in the range of 17 to 26 μm and the relationship between the particle diameter D50, the particle diameter D10 and the particle diameter D90 satisfies the above formula (I) in the particle size distribution based on the volume, has a small amount of coarse powder in the fly ash. In addition, it is possible to suppress a decrease in fluidity and strength development caused by a large amount of coarse and porous unburned carbon, and maintain good fluidity and strength development properties of a cement composition in which fly ash is mixed.

The particle diameter D10 is preferably 4 to 12 µm, more preferably 5 to 10 µm. Further, the particle diameter D90 is preferably 50 to 69 µm, more preferably 52 to 68 µm. In the particle size distribution based on the volume, the fly ash having the particle diameter D10 and the particle diameter D90 satisfying the above formula (I) with respect to the particle diameter D50 exhibits a decrease in fluidity and strength caused by a large amount of coarse and porous unburned carbon. It is possible to suppress deterioration of the property and maintain good fluidity and strength development of a cement composition in which fly ash is mixed.

Fly ash content in cement composition

The fly ash content in the cement composition is 30 mass% or less, preferably 29 mass% or less, more preferably 25 mass% or less, preferably 5 mass% or more, and more preferably 10 mass% or more. And more preferably 12% by mass or more.

When the fly ash content in the cement composition exceeds 30% by mass, the fly ash content in the cement composition increases, and the cement content in the cement composition becomes relatively small. When the amount of cement in the cement composition is small, the strength of the cured product may decrease due to a decrease in strength due to a decrease in the content of cement than the effect of the strength development of the fly ash due to the pozzolanic reaction. When the content of fly ash in the cement composition is 5% by mass or more, by adding fly ash satisfying the above formula (I) to the cement composition, it is possible to maintain good fluidity and strength development properties of the cement composition. In addition, if the fly ash content in the cement composition is 12% by mass or more, the setting time can also be lengthened, and workability at the time of construction can be improved.

Amorphous phase in fly ash

As for the fly ash contained in the cement composition, it is preferable that the amount of amorphous phase in the fly ash is 55% by mass or more with respect to the total amount of the crystalline phase and the amorphous phase in the fly ash. The amorphous phase in the fly ash contains a lot of pozzolanic components (SiO ₂ , Al ₂ O ₃ ) that cause a pozzolanic reaction, and the pozzolanic reaction can further improve the strength expression of a long-term age of 28 days or 91 days of age. . Silicon (Si), aluminum (Al), and iron (Fe) contained in fly ash are amorphous phases containing these elements, crystalline quartz (SiO ₂ ), cristobalite (SiO ₂ ), mullite (3Al ₂ O ₃₎ 2SiO ₂ , in this specification, it may be referred to as mullite (3:2)), hematite (Fe ₂ O ₃ ), and magnetite (Fe ₃ O ₄ ). The crystalline phase in the fly ash does not react with pozzolanism and does not contribute to the strength development of an organ. If the amount of amorphous phase in the fly ash contained in the cement composition is 55% by mass or more with respect to the total amount of the crystalline and amorphous phases in the fly ash, the pozzolanic components (SiO ₂ , Al ₂ O ₃ ) present in the amorphous phase in the fly ash are By reacting with calcium hydroxide (Ca(OH) ₂ ) produced by hydration, calcium silicate hydrate (CSH) can be sufficiently produced, and the strength expression properties of an organ can be further improved. The amount of amorphous phase in the fly ash is more preferably 58% by mass or more, and still more preferably 59% by mass or more with respect to the total amount of the crystalline phase and the amorphous phase in the fly ash. Fly ash having an amorphous phase amount of 100% by mass hardly exists, and the amorphous phase amount in the fly ash is preferably 98% by mass or less, and more preferably 95% by mass or less with respect to the total amount of the crystalline phase and amorphous phase in the fly ash.

Measurement of the amount of the crystalline phase and the amorphous phase in the fly ash can be measured using a Rietvelt analysis with a powder X-ray diffraction apparatus. As the powder X-ray diffraction apparatus, for example, D8 Advance (manufactured by Bruker AXS (Bruker AXS)) can be used. As the basic measurement conditions, the measurement conditions described in Examples to be described later can be applied.

In addition, for Rietbelt analysis, TOPAS Ver. 4.2 (Bruker AXS (manufactured by Bruker AX)) can be used, and as Rietvelt analysis conditions, the conditions described in Examples described later can be applied. Examples of the mineral to be analyzed include quartz, mullite (3:2), anhydrous gypsum, limestone, magnetite, hematite, and titanium dioxide (only a sample added as an internal standard substance).

The amount of crystal phase and amorphous phase by Rietveld analysis of fly ash can be measured specifically by the method of Examples.

In the present specification, the amorphous phase amount (mass%) in fly ash is a value obtained by subtracting the amorphous phase amount (mass%) in fly ash by the following equation (1) by the Rietveld analysis Say.

Amorphous phase amount (mass%) in fly ash = Amorphous phase amount (mass%) by Rietveld analysis-Unburned carbon amount (mass%) (1)

As for the amount of unburned carbon, the amount of loss on ignition measured in accordance with JIS A6201 "Fly Ash for Concrete" was taken as the amount of unburned carbon (mass%) in the fly ash.

Fe content in the amorphous phase of fly ash

As for the fly ash contained in the cement composition, it is preferable that the amount of Fe in the amorphous phase of the fly ash is 3.5% by mass or more and 10% by mass or less. The amount of Fe in the amorphous phase of fly ash is related to the hydration activity after 28 days of age in the amorphous phase, and if the amount of Fe in the amorphous phase of fly ash is 3.5% by mass or more and 10% by mass or less, the hydration reaction after 28 days of age is related to the long term. Since the calcium silicate hydrate (CSH) produced by the pozzolanic reaction is more easily densified from the point that it is easy to proceed gently, the long-term strength development is more likely to be improved. The larger the amount of Fe in the amorphous phase of fly ash is, the more preferable it is, but usually, there are few cases where the amount of Fe in the amorphous phase of fly ash exceeds 10% by mass. In the fly ash contained in the cement composition, the amount of Fe in the amorphous phase of the fly ash is more preferably 3.6% by mass or more, and still more preferably 3.7% by mass or more.

In the chemical composition of fly ash, the main components are SiO ₂ (about 60 to 80 mass%) and Al ₂ O ₃ (about 20 mass%), in the process of heating, melting and cooling during combustion in a coal-fired power plant, In fly ash, a SiO ₂ -Al ₂ O ₃ system amorphous phase (glass phase) and a crystalline phase (mullite (3:2), quartz, etc.) are formed. In the cooling process, it is presumed that the more rapid cooling causes the atomic order of the crystal phase in the fly ash to be more deformed, and the hydration activity of the amorphous phase (glass phase) becomes more active. In the cooling process, when slow cooling, when there is an impurity Fe, etc. in the liquid phase that becomes mullite (3:2), SiO ₂ -Al ₂ O ₃ amorphous phase (glass phase) having the same composition as the composition of mullite Fe is randomly present in it, and the deformation of the amorphous phase (glass phase) increases. In general, when the activity of the amorphous phase (glass phase) increases, the strength development is increased in a relatively short period, but when the deformation of the amorphous phase (glass phase) increases due to the presence of Fe, the hydration activity is maintained gently over a long period of time. Therefore, it is estimated that it contributes to the strength improvement of the long term strength.

The amount of Fe in the amorphous phase of fly ash can be calculated by the following formula (2) by a fluorescence X-ray analysis method and Rietveld analysis. As described above, the amorphous phase amount (mass%) of fly ash is the amount of unburned carbon (mass%) in the fly ash from the amorphous phase amount (mass%) by Rietveld analysis of fly ash according to the above equation (1). It is the subtracted value.

Fe amount in the amorphous phase of fly ash (% by mass) = [{(a) Total amount of Fe in fly ash (fluorescent X-ray analysis value)-((b) Total amount of Fe in hematite and magnetite determined by Rietveld analysis)}/ ((c) Amorphous mass (mass%) obtained by Rietveld analysis-(d) Unburned carbon amount (mass%))] × 100 (2)

In the above formula (2), (a) the total amount of Fe in fly ash is the amount of Fe in terms of oxide measured in accordance with JIS R5204 ``Method for Fluorescent X-ray Analysis of Cement'' (Iron (III): Fe ₂ O ₃ ) It can be calculated by converting the amount of Fe by the following formula (3) from the measured value 1 of.

(a) Total amount of Fe in fly ash (% by mass) = measured value 1×2Fe/Fe ₂ O ₃ (111.6/159.7) (3)

In the above formula (2), (b) the amount of Fe in hematite and magnetite determined by Rietbelt analysis is the measured value of hematite 2 and the measured value of magnetite measured by Rietveld analysis by the method of Examples described later. It can be calculated by the following formulas (4) and (5) from 3, and is the total amount of the amount of Fe in hematite and the amount of Fe in magnetite.

(c-1) Fe amount (mass%) in hematite = measured value 2×2Fe/Fe ₂ O ₃ (111.6/159.7) (4)

(c-2) Fe amount (mass%) in magnetite = measured value 3×3Fe/Fe ₃ O ₄ (167.4/231.5) (5)

The amount of unburned carbon in fly ash

The amount of unburned carbon in the fly ash is preferably 3% by mass or more and 15% by mass or less, more preferably 3% by mass or more and 14.8% by mass or less, and still more preferably 3% by mass or more and 14.5% by mass or less.

When the amount of unburned carbon in the fly ash is 15% by mass or less, the fly ash satisfies the formula (I) in the particle size distribution on a volume basis, whereby the cement composition can maintain good fluidity and strength development. If the amount of unburned carbon in the fly ash is too large, even when the proportion of the coarse unburned carbon in the fly ash is small, the unburned carbon having a porous shape may lower the strength development property. Although it is preferable that the amount of unburned carbon in the fly ash is small, the fly ash obtained in a coal-fired power plant usually contains 3% by mass or more of unburned carbon unless some unburned carbon is removed by classification or the like. As described above, in the present specification, the amount of unburned carbon in the fly ash was measured in accordance with JIS A6201 ``fly ash for concrete'', and the loss on ignition was measured as (d) the amount of unburned carbon in the fly ash (mass%). .

Blaine specific surface area of fly ash

The blast specific surface area of the fly ash is preferably 3000 cm ² /g or more and 4500 cm ² /g or less, more preferably 3100 cm ² /g or more and 4400 cm ² /g or less, and more preferably 3200 cm ² /g or more and 4300 cm ² /g or less.

If the specific surface area of the fly ash is in the range of 3000 cm ² /g or more and 4500 cm ² /g or less, the effect of fly ash maintaining the ball bearing effect, which is a characteristic of fly ash, and having a particle size distribution satisfying the above formula (I) Thereby, good fluidity can be maintained and good strength development can be maintained.

Mass ratio of unburned carbon with particle diameter exceeding 212㎛ to unburned carbon in fly ash

It is preferable that the mass ratio of unburned carbon having a particle diameter exceeding 212 µm (unburned carbon/unburned carbon having a particle diameter exceeding 212 µm) to the unburned carbon in fly ash is 35% or less. The mass ratio of the unburned carbon in the fly ash with a particle diameter exceeding 212 µm to the unburned carbon is more preferably 34% or less, still more preferably 33% or less, and even more preferably 32% or less.

If the mass ratio of the unburned carbon with a particle diameter exceeding 212 μm to the unburned carbon in the fly ash is 35% or less, the mass ratio of the coarse and porous unburned carbon contained in the cement composition when fly ash is used in the cement composition This is small, and a decrease in fluidity and a decrease in strength development can be suppressed. The smaller the mass ratio of unburned carbon with a particle diameter of more than 212 µm to the unburned carbon in fly ash (unburned carbon/unburned carbon having a particle diameter of 212 µm) is less, but in the particle size distribution based on volume, the formula (I ), the mass ratio of unburned carbon having a particle diameter exceeding 212 µm (unburned carbon/unburned carbon having a particle diameter exceeding 212 µm) to the unburned carbon in the fly ash is usually 5% or more.

The amount of unburned carbon (mass%) in the fly ash exceeding 212 µm in particle diameter is in accordance with JIS Z8801-1 "Test sieve-Part 1: Metal mesh". , It can be calculated|required as the amount (mass %) of unburned carbon exceeding 212 micrometers in particle diameter in fly ash.

The mass ratio of unburned carbon exceeding 212 µm in the cement composition

It is preferable that the amount of unburned carbon exceeding 212 µm in the cement composition is 1.5% by mass or less. The amount of unburned carbon in the cement composition having a particle diameter exceeding 212 µm is more preferably 1.4% by mass or less, still more preferably 1.3% by mass or less, and even more preferably 1.2% by mass or less.

When the amount of unburned carbon exceeding 212 µm in the cement composition is 1.5% by mass or less, there are few coarse and porous unburned carbons in the cement composition, and a decrease in fluidity and a decrease in strength development can be suppressed. The smaller the amount of unburned carbon in the cement composition exceeding 212 μm, the more preferable, but in the case of fly ash that satisfies the above formula (I) in the particle size distribution on a volume basis, unburned carbon having a particle diameter exceeding 212 μm in the cement composition The amount is usually 0.05% by mass or more.

The amount of unburned carbon in the cement composition exceeding 212 µm in particle diameter is, according to Equation (7) described later, in terms of the fly ash content (mass%) in the cement composition, and the amount of unburned carbon in the fly ash exceeding 212 µm (mass%) ) Multiplied and divided by 100 can be calculated as the amount of unburned carbon in the cement composition exceeding 212 µm (mass%).

Method for producing fly ash for cement composition

In the method for producing a fly ash for a cement composition according to an embodiment of the present invention, a raw material fly ash is classified, the classified coarse fly ash having a particle diameter of 45 μm or more is crushed, and the following formula (I ), raw fly ash and crushed fly ash are mixed.

0.24<(D50-D10)/(D90-D50)≤0.5 (I)

(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.)

The raw material fly ash may satisfy the numerical value of the loss on ignition of type I, type II, or type IV fly ash described in JIS A6201:2015 "Fly ash for concrete".

As a method of classifying coarse powdered fly ash having a particle diameter of 45 µm or more from raw material fly ash, a sieve, a wind classifier or the like can be used, for example. The classified coarse fly ash having a particle diameter of 45 µm or more can be pulverized using a grinder such as a jet mill, a ball mill, or a bead mill. When fly ash with a particle diameter of 45 µm or more is crushed, coarse and porous unburned carbon is crushed mainly. If coarse and porous unburned carbon contained in fly ash with a particle diameter of 45 μm or more can be crushed, even when the crushed fly ash and raw fly ash are mixed and the mixed fly ash is used in the cement composition, coarse and porous unburned carbon It is possible to suppress a decrease in fluidity and a decrease in strength development properties caused by the inclusion.

cement

The kind of cement used in the cement composition is not particularly limited, and usually Portland cement, crude steel Portland cement, medium heat Portland cement, low heat Portland cement, and the like can be used.

Method for preparing cement composition

In the method for producing a cement composition in an embodiment of the present invention, raw material fly ash is classified, and the classified coarse fly ash having a particle diameter of 45 μm or more is pulverized, and the following formula (I) is satisfied in the particle size distribution on a volume basis. This is a method for producing a cement composition in which raw material fly ash and crushed fly ash are mixed, and the mixed fly ash is blended to be 30% by mass or less based on the total amount of the cement composition.

0.24<(D50-D10)/(D90-D50)≤0.5 (I)

(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.)

In the method for producing a cement composition, as a method for classifying coarse fly ash having a particle diameter of 45 µm or more from the raw material fly ash, similarly to the method for producing a fly ash for cement composition, for example, a sieve or a wind classifier can be used. The classified coarse fly ash having a particle diameter of 45 µm or more can be pulverized, for example, using a pulverizer such as a jet mill, a ball mill, or a bead mill, in the same manner as the method for producing a fly ash for a cement composition. The pulverized fly ash is mixed with the raw material fly ash so as to satisfy the above formula (I) in the particle size distribution based on the volume, and the mixed fly ash is 30% by mass or less based on the total amount of the cement composition. By blending, a cement composition can be prepared.

Fly ash obtained by mixing raw material fly ash and crushed fly ash is blended so that it is preferably 29% by mass or less, more preferably 25% by mass or less, and preferably 5% by mass or more with respect to the total amount of the cement composition. , More preferably 10% by mass or more, and still more preferably 12% by mass or more. When the fly ash content in the cement composition is 12% by mass or more, the setting time is also long, and a cement composition having good workability during construction can be obtained.

The amount of the amorphous phase in the fly ash obtained by mixing the raw material fly ash and the crushed fly ash is preferably 55% by mass or more with respect to the total amount of the crystalline phase and the amorphous phase in the mixed fly ash. If the amount of amorphous phase in the mixed fly ash is 55% by mass or more with respect to the total amount of the crystalline and amorphous phases in the mixed fly ash, the amount of pozzolanic components (SiO ₂ , Al ₂ O ₃ ) contained in the amorphous phase is large, due to the pozzolanic reaction. By reacting with calcium hydroxide (Ca(OH) ₂ ) produced by hydration of the surrounding cement particles, it is easy to produce calcium silicate hydrate (CSH), and a cement composition that is easy to improve long-term strength development can be obtained. The amount of amorphous phase in the mixed fly ash is more preferably 58% by mass or more, still more preferably 59% by mass or more, preferably 98% by mass or less, and more preferably with respect to the total amount of the crystalline phase and amorphous phase in the fly ash. Is 95% by mass or less. The measurement of the amount of amorphous phase in the mixed fly ash can be specifically measured by the method used in the examples.

It is preferable that the amount of Fe in the amorphous phase of the fly ash obtained by mixing raw material fly ash and crushed fly ash is 3.5% by mass or more and 10% by mass or less. The amount of Fe in the amorphous phase of fly ash is related to the hydration activity after 28 days of age in the amorphous phase, and if the amount of Fe in the amorphous phase of fly ash is 3.5% by mass or more and 10% by mass or less, the hydration reaction after 28 days of age is related to the long term. Since the calcium silicate hydrate (CSH) produced by the pozzolanic reaction is more easily densified from the point that it is easy to proceed gently, the long-term strength development is more likely to be improved. In the fly ash contained in the cement composition, the amount of Fe in the amorphous phase of the fly ash is more preferably 3.6% by mass or more, and still more preferably 3.7% by mass or more.

The cement composition may contain admixtures other than fly ash. Examples of admixtures include blast furnace slag powder, limestone powder, quartz powder, and gypsum.

Example

Next, the present invention will be described in detail by examples, but the present invention is not limited at all by these examples.

Manufacture of fly ash

Fly ash of Preparation Examples 1 to 7, Reference Preparation Example 1, and Comparative Preparation Examples 2 to 6 were prepared as follows.

(Reference Manufacturing Example 1)

Fly ash obtained from a coal-fired power plant was used as raw material fly ash.

Of the raw material fly ash, about 30% by volume with respect to the total amount of the raw material fly ash is classified and removed by a mesh sieve method with a sieve of 45 µm, and a fly ash that satisfies the conditions specified in Class II of fly ash for concrete in JIS A6201 is manufactured. did. In Table 2, the ratio of fly ash used with respect to raw material fly ash is shown as "the ratio of use of fly ash to raw material".

(Production Examples 1 to 7)

The raw material fly ash was classified into a coarse powder of 45 μm or more using a turbo classifier (TC-15N, manufactured by Nisshin Engineering Co., Ltd.). The classified coarse fly ash was pulverized using a pin-type pulverizer (free pulverizer, M-2 type, manufactured by Nara Machinery Co., Ltd.) to obtain crushed fly ash. In the volume-based particle size distribution measured using a laser diffraction scattering type particle size distribution measuring device (Microtrac MT2000, manufactured by Nikiso Corporation), raw material fly ash and disintegrated fly ash were prepared so as to satisfy the following formula (I). By mixing, the mixed fly ash of Production Examples 1-7 was obtained.

0.24<(D50-D10)/(D90-D50)≤0.5 (I)

In Formula (I), D10, D50, and D90 represent particle diameters corresponding to 10% of the cumulative frequency, 50% of the cumulative frequency, and 90% of the cumulative frequency from the small diameter side of the fly ash, respectively.

Table 1 shows the amount of loss on ignition measured by the method described later, D10, D50, and D90 of the fly ash of Production Examples 1 to 7. The loss on ignition was made into the amount of unburned carbon in fly ash. In addition, the ratio represented by (D50-D10)/(D90-D50) of Formula (I) is shown in Table 2. In Table 2, in the fly ash of Production Examples 1 to 7, there is no fly ash removed from the raw material fly ash, and all of the raw material fly ash is used. )" was expressed as 100%.

(Comparative Manufacturing Examples 2 to 6)

The raw material fly ash was classified into a coarse powder of 45 μm or more using a turbo classifier (TC-15N, manufactured by Nisshin Engineering Co., Ltd.). The classified coarse fly ash was pulverized using a pin-type pulverizer (free pulverizer, M-2 type, manufactured by Nara Machinery Co., Ltd.) to obtain crushed fly ash. In the volume-based particle size distribution measured using a laser diffraction scattering type particle size distribution measuring device (Microtrac MT2000, manufactured by Nikiso Corporation), represented by (D50-D10)/(D90-D50) of formula (I) Raw material fly ash and crushed fly ash were mixed so that the ratio became the value shown in Table 2, and the fly ash of Comparative Production Examples 2-6 was obtained.

Table 1 shows the amount of loss on ignition measured by the methods described later and D10, D50, D90 of the fly ash of Comparative Production Examples 2 to 6. In addition, the ratio represented by (D50-D10)/(D90-D50) of the fly ash of Comparative Production Examples 2 to 6 is shown in Table 2. In Table 2, in the fly ash of Comparative Production Examples 2 to 6, no fly ash was removed from the raw material fly ash, and all of the raw material fly ash was used, so the ``use ratio of fly ash to the raw material'' was 100 Expressed in (%).

Analysis of fly ash

The following measurements were performed about the fly ash of Production Examples 1-7, Reference Production Example 1, and Comparative Production Examples 2-6. The results are shown in Table 2.

(Measurement of Blaine Specific Surface Area)

In accordance with the measurement method of the blasting method (specific surface area) of JIS A6201 "Fly Ash for Concrete", the blast specific surface area of the obtained fly ash was measured.

(Measurement of crystalline phase and amorphous phase amount (mass%) in fly ash)

The measurement of the amount of the crystalline phase and the amorphous phase (mass%) in the fly ash was measured by a Rietveld analysis method using an internal standard substance with a powder X-ray diffraction apparatus. As the powder X-ray diffraction apparatus, D8 Advance (manufactured by Bruker AXS (Bruker AX)) was used. Measurement conditions, internal standard substances, and Rietveld analysis conditions were described below.

Measuring conditions

X-ray tube: Cu

Tube voltage: 40kV

Tube current: 40mA

Measurement range of diffraction angle 2θ: start angle 5°, end angle 70°/75°

※ When rutile type titanium dioxide is added as an internal standard substance, if the end angle is set to 70°, the peak shape of titanium dioxide around 70° cannot be obtained correctly. For this reason, for the sample to which titanium dioxide was added, the end angle was set to 75°.

Step Width: 0.025°/step

Counting time: 60sec./step

Internal standard material: rutile type titanium dioxide

Rietvelt analysis conditions

Rietvelt analysis software: TOPAS Ver.4.2 (manufactured by Bruker AXS (Bruker AX))

Zero point correction: none

Correction of the height of the sample surface: Yes

Minerals to be analyzed: Quartz, mullite (3:2), anhydrous gypsum, limestone, magnetite, hematite, titanium dioxide (only samples added as internal standards)

Selective orientation function of the hematite phase: The selective orientation of the hematite phase is assumed to occur on the diffraction line of the (110) plane near the diffraction angle 2θ = 35.5°, and the initial value of the coefficient is set to 1 using the March Dollase function. Did. Regarding the magnetite phase, it was assumed that no selective orientation occurred.

The procedure for measuring crystal phases such as magnetite and hematite in fly ash and amorphous material is described below.

(i) As internal standards, fly ash (Sample 1) to which 20% by mass of rutile type titanium dioxide was added, and fly ash (Sample 2) to which no internal standard substance was added were prepared.

(ii) Fly ash (Sample 2) to which no internal standard substance was added was measured using a powder X-ray diffraction apparatus, and a powder X-ray diffraction pattern of the obtained fly ash (Sample 2), quartz of the mineral to be analyzed Each theoretical profile of mullite (3:2), anhydrous gypsum, limestone, magnetite, and hematite is fitted, and quantitative analysis of each analysis target mineral contained in fly ash is performed, and each analysis target is performed by analysis software. The amount of minerals (mass%) was calculated. For magnetite and hematite, the amounts (mass%) of magnetite and hematite in coal ash were calculated only from fly ash (Sample 2) to which no internal standard substance was added.

For the quantitative analysis of magnetite and hematite, sample 2 without the addition of an internal standard material was used, with a peak near the diffraction angle of magnetite and hematite 2θ = 35.5° to 35.6° and the diffraction angle of rutile titanium dioxide 2θ = 36.1 This is because the peak near ° is close. Particularly, when rutile titanium dioxide having a small particle diameter and a small crystallite size is used as an internal standard material, broadening of the peak occurs, and the vicinity of the bottom of the peak near the diffraction angle 2θ = 36.1° of the rutile titanium dioxide is magnetite, hema This is because it greatly affects the quantified value when it overlaps with the tight peak (overlap), particularly when the content of magnetite or hematite is small.

(iii) The fly ash (Sample 1) to which the internal standard substance rutile type titanium dioxide was added was measured using a powder X-ray diffraction apparatus, and the powder X-ray diffraction pattern of the obtained fly ash (Sample 1) and the analysis object Each of the mineral quartz, mullite (3:2), anhydrous gypsum, limestone, hematite, magnetite, and titanium dioxide was fitted to each theoretical profile and contained in the fly ash (sample 1) to which the internal standard material was added. Quantitative analysis of the analysis target mineral was performed, and the amount (mass%) of each analysis target mineral was calculated by the analysis software.

(iv) From the quantitative value of the rutile type titanium dioxide in Sample 1, the total amorphous phase amount G _total (mass%) containing unburned carbon was calculated by the following (A) formula.

Total amorphous phase G _total =100×(YX)/{Y×(100-X)/100} (A)

However, in formula (A), X is the addition amount (20 mass %) of an internal standard substance, and Y is Rietvelt analysis value (mass %) of rutile type titanium dioxide.

(v) After quantifying the total amorphous phase from the content (mass%) of the crystalline phase of the mineral to be analyzed in Sample 1, from the content (mass%) of the mineral to be analyzed in Sample 2, the total amorphous phase was determined by the following (B) equation. The content of the crystal phase was calculated taking into account.

Crystalline phase (considering total amorphous phase G _total ) = Crystalline phase (Sample 2 analysis value)×(100-G _total )/100 (B)

However, in Equation (B), G _total is the analyzed value of Sample 1 and the total amorphous quantitative value (%) obtained by Equation (A).

(vi) Specifically, the value obtained by subtracting the unburned carbon content (mass%) in the fly ash from the total amorphous phase amount G _total (mass%) calculated by the following equation (1) is obtained in the fly ash. It was set as the amorphous upper amount G _FA (mass %). As for the amount of unburned carbon, the loss on ignition measured in accordance with JIS A6201 "fly ash for concrete" was taken as the unburned carbon content (mass%) in fly ash.

Amorphous phase amount G _FA (mass %) in fly ash = Total amorphous phase amount G _total (mass %)-unburned carbon content (mass %) (1)

(Measurement of Fe amount (mass%) in the amorphous phase of fly ash)

The amount of Fe in the amorphous phase of the fly ash was calculated by the following formula (2) by a fluorescence X-ray analysis method and Rietveld analysis.

Fe amount in the amorphous phase of fly ash (% by mass) = [{(a) Total amount of Fe in fly ash (fluorescent X-ray analysis value)-((b) Total amount of Fe in hematite and magnetite determined by Rietveld analysis)}/ ((c) Amorphous mass (mass%) obtained by Rietveld analysis-(d) Unburned carbon amount (mass%))] × 100 (2)

In the above formula (2), (a) the total amount of Fe in fly ash is the amount of Fe in terms of oxide measured in accordance with JIS R5204 ``Method for Fluorescent X-ray Analysis of Cement'' (Iron (III): Fe ₂ O ₃ ) It can be calculated by converting the amount of Fe by the following formula (3) from the measured value 1 of.

(a) Total amount of Fe in fly ash (% by mass) = measured value 1×2Fe/Fe ₂ O ₃ (111.6/159.69) (3)

In the above formula (2), (b) the amount of Fe in hematite and magnetite determined by Rietbelt analysis is the measured value of hematite 2 and the measured value of magnetite measured by Rietveld analysis by the method of Examples described later. It can be calculated from 3 by the following formulas (4) and (5), and is the total amount of the amount of Fe in hematite and the amount of Fe in magnetite.

(c-1) Fe amount (mass%) in hematite = measured value 2×2Fe/Fe ₂ O ₃ (111.6/159.69) (4)

(c-2) Fe amount (mass%) in magnetite = measured value 3×3Fe/Fe ₃ O ₄ (167.4/231.5) (5)

(Amount of unburned carbon in fly ash (mass%))

As for the amount of unburned carbon in fly ash, the amount of loss on ignition measured in accordance with JIS A6201 "fly ash for concrete" was taken as (d) the amount of unburned carbon in fly ash (mass%).

(Amount of unburned carbon exceeding 212 μm in particle size (% by mass))

The amount (mass%) of unburned carbon in the fly ash having a particle diameter exceeding 212 µm is in accordance with JIS Z8801-1 "Test sieve-Part 1: Metal mesh". Can be calculated as the amount of unburned carbon (mass%) exceeding 212 µm in particle diameter in fly ash.

(The mass ratio (%) of unburned carbon exceeding 212 µm in particle diameter to unburned carbon in fly ash)

The mass ratio of unburned carbon having a particle diameter exceeding 212 µm in fly ash (unburned carbon/unburned carbon having a particle diameter exceeding 212 µm) to the amount of unburned carbon in the fly ash was calculated by the following formula (6).

Unburned carbon with particle diameter exceeding 212 μm/unburned carbon (%) = Unburned carbon with particle diameter exceeding 212 μm in fly ash (mass%) ÷ Unburned carbon in fly ash (mass%)×100 (6)

Cement composition

(Examples 1 to 7, Reference Examples 8 to 10)

The fly ash produced in Production Examples 1 to 7 was mixed with the usual Portland cement at the blending ratio shown in Table 2 to prepare the cement compositions of Examples 1 to 7 and Reference Examples 8 to 10.

(Comparative Examples 1-6)

The fly ash prepared in Reference Preparation Example 1 and Comparative Preparation Examples 2 to 6 were mixed with ordinary Portland cement at the blending ratio shown in Table 2 to prepare the cement compositions of Comparative Examples 1 to 6.

For the obtained cement composition, the mass ratio (%) of unburned carbon having a particle diameter exceeding 212 µm in the cement composition, fluidity, mortar compressive strength, and setting time were measured. The measurement method is described below. In addition, the measurement results are shown in Table 2.

(The amount of unburned carbon in the cement composition exceeding 212 µm (mass%))

The amount of unburned carbon (mass%) exceeding 212 µm in the cement composition was calculated by the following formula (7).

The amount of unburned carbon in the cement composition exceeding 212 µm (mass %) = the content of fly ash in the cement composition (mass %) × the amount of unburned carbon in the fly ash exceeding 212 µm (mass %) ÷ 100 (7)

(Liquidity: Evaluation of mortar liquidity)

Using the cement composition in which the fly ash of each of the Examples and Comparative Examples was mixed, in accordance with JIS R5201 "Physical Test of Cement", without using an admixture, at each temperature of 20°C and 30°C, A flow test was performed and the flow value of the mortar was measured. In the case of an environmental temperature of 20°C, a mortar having a flow value of 180 mm or more was evaluated as having good fluidity, and a mortar having a flow value of less than 180 mm was evaluated as having low fluidity. When the environmental temperature was 30°C, the mortar having a flow value of 165 mm or more was evaluated as having good fluidity, and the mortar having a flow value of less than 165 mm was evaluated as having low fluidity.

(Condensation test)

JIS R5201 "Physical Test Method of Cement", except that the temperature of the test chamber for preparing and testing a sample for measurement was set to 30±2°C using a cement composition mixed with fly ash of each Example and Comparative Example. In conformity with "Annex A (regulation) condensation test" A mortar with a starting time of 110 minutes or more and a setting of 160 minutes or more was evaluated as having a long setting time. A mortar with a starting time of less than 110 minutes and a setting of less than 160 minutes was evaluated as having a short setting time.

(The compressive strength of mortar at 3 days old, 28 days old and 91 days old)

Using the cement composition in which the fly ash of each of the Examples and Comparative Examples was mixed is used, "11. In accordance with the "strength test", the mortar compressive strength was measured at the age of 3 days, age of 28 days and age of 91 days. Mortars having a compressive strength of ²² N/mm ² or more at the age of 3 days were evaluated as having high initial compressive strength, and a mortar having a compressive strength of mortar at the age of 3 days of less than ²² N/mm ² was evaluated as having low initial compressive strength. Further, mortars having a mortar compressive strength of 50 N/mm ² or more at 28 days old were evaluated as having high compressive strength, and mortars having a mortar compressive strength at 28 days old of less than 50 N/mm ² were evaluated as having low compressive strength. A mortar compressive strength of 75 N/mm ² or more at the age of 91 days was evaluated as having high compressive strength in a long term. The mortar compressive strength at the age of 91 days was less than 75 N/mm ² was evaluated as having low long-term compressive strength.

As shown in Table 2, the cement compositions of Examples 1 to 8 using the fly ash of Preparation Examples 1 to 5 in which the ratio of (D50-D10)/(D90-D50) exceeds 0.3 and is 0.5 or less, at 20°C. A flow value of 180 mm or more and a flow value of 165 mm or more at 30° C. were good, and both the mortar compressive strength at the age of 3 days and the mortar compressive strength at the age of 28 days showed high values. In addition, the cement compositions of Examples 1 to 7 also had a high mortar compressive strength of 76.3 N/mm ² or more at 91 days old, and the long-term strength development was further improved.

In the cement composition of Example 7, the fly ash content of Production Example 4 in the cement composition was as few as 11% by mass, so the fluidity and compressive strength were good, but the setting time was short.

The cement composition of Reference Example 8 uses the fly ash of Preparation Example 5, and since the amount of Fe in the amorphous phase of the fly ash of Preparation Example 5 is as small as 3.3% by mass, the strength development of a long-term age of 28 days or 91 days of age It was degraded.

The cement composition of Reference Example 9 uses the fly ash of Preparation Example 6, and the fly ash of Preparation Example 6 has a blast specific surface area of 2800 cm ² /g and contains a relatively large amount of coarse powder, age 28 days or 91 days. The strength expression of the organ of the body was decreased.

The cement composition of Reference Example 10 uses the fly ash of Production Example 7, and the fly ash of Production Example 7 has a small amount of amorphous phase in the fly ash of 51.5% by mass, so the strength of the organs at 28 days old or 91 days old was expressed. The castle has declined.

As shown in Table 2, the fly ash of Reference Manufacturing Example 1, which is the same as the fly ash II class specified in JIS A6201 ``fly ash for concrete,'' is about 30% by volume of raw fly ash in order to meet the standards of JIS. The fly ash must be removed, the ratio of fly ash to the raw material is 70%, and all of the raw fly ash is not effectively used.

As shown in Table 2, in Comparative Example 1, the ratio of (D50-D10)/(D90-D50) of the fly ash of Reference Preparation Example 1 used for the cement composition was as low as 0.17, and the mortar compressive strength at the beginning of 3 days of age. , The mortar compressive strength at the age of 28 days and the mortar compressive strength at the age of 91 days are both relatively high values, but both the flow value at 20°C and the flow value at 30°C are reference values for evaluation (20°C: 180 Mm or more, 30°C: 165 mm or more) was not satisfied, and the fluidity was lowered.

As shown in Table 2, in Comparative Example 2, the ratio of (D50-D10)/(D90-D50) of the fly ash of Comparative Production Example 2 used for the cement composition was as small as 0.18, and the particle diameter relative to the amount of unburned carbon in the fly ash The mass ratio of unburned carbon exceeding 212 μm (unburned carbon/unburned carbon exceeding 212 μm in particle diameter) is larger than 35%, and there are many coarse and porous shapes of unburned carbon, resulting in poor fluidity, and aged 28 days. Alternatively, the strength development of organs aged 91 days was decreased.

As shown in Table 2, the fly ash of Comparative Production Example 3 used in Comparative Example 3 was the same as the fly ash used in Production Example 4, the blaine specific surface area, and the ratio of (D50-D10)/(D90-D50). , The fly ash content in the cement composition exceeded 30% by mass, and the fluidity was good, but the compressive strength at the initial stage of 3 days old was lowered, and the mortar compressive strength at 28 days old was also lowered.

As shown in Table 2, in Comparative Example 4, the ratio of (D50-D10)/(D90-D50) of the fly ash of Comparative Production Example 4 used in the cement composition was as small as 0.19, and there were relatively large amounts of coarse and porous unburned carbon. Because it is contained, the fluidity at 20°C and the fluidity at 30°C were lowered, the mortar compressive strength at the age of 28 days was also low, and the mortar compressive strength at the age of 91 days was also decreased.

As shown in Table 2, in Comparative Example 5, the ratio of (D50-D10)/(D90-D50) of the fly ash of Comparative Production Example 5 used in the cement composition was as small as 0.14, and the particle diameter in the cement composition exceeded 212 μm. Since the amount of unburned carbon is also large at 1.6% by mass, a large amount of coarse and porous unburned carbon is contained, the fluidity at 20°C and the fluidity at 30°C are also lowered, and the mortar compressive strength at the age of 28 days is also lowered.

As shown in Table 2, in Comparative Example 6, the ratio of (D50-D10)/(D90-D50) of the fly ash of Comparative Production Example 6 used for the cement composition was greater than 0.51 and 0.5, and the specific surface area of the blade was 4650 cm. ^It was large at ² /g, and a large number of relatively small particles were contained in the fly ash, and the fluidity at 20°C and the fluidity at 30°C were lowered. Moreover, the setting time at 30 degreeC was also shortened.

According to the present invention, a fly ash that maintains properties as a blended material such as improved fluidity and contributing to strength development, without removing part of the fly ash whose generation amount is increasing as the amount of power generated in a coal-fired power plant increases. Using, it is possible to provide a cement composition that can contribute to long-term strength development, a method for producing the same, and a method for producing a fly ash for a cement composition.

Claims (13)

Cement and fly ash are included, the fly ash content is 30 mass% or less, the fly ash satisfies the following formula (I) in the particle size distribution on a volume basis, and the amount of amorphous phase in the fly ash is the fly ash 55% by mass or more and 75.1% by mass or less with respect to the total amount of the crystalline and amorphous phases in the fly ash, the amount of Fe in the amorphous phase of the fly ash is 3.5% by mass or more and 10% by mass or less, and the specific surface area of the fly ash is 3000 cm ² /g or more and 4500 cm ² /g or less, and the amount of unburned carbon in the fly ash is 3% by mass or more and 15% by mass or less.
0.25≤(D50-D10)/(D90-D50)≤0.47 (I)
(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.) The method of claim 1,
A cement composition having a fly ash content of 12% by mass or more. The method according to claim 1 or 2,
The cement composition, wherein the amount of unburned carbon exceeding 212 µm in the cement composition is 1.5% by mass or less. The method according to claim 1 or 2,
A cement composition, wherein a mass ratio of unburned carbon having a particle diameter exceeding 212 µm in the fly ash to unburned carbon in the fly ash is 35% or less. Raw material fly ash is classified, the coarse powder fly ash having a particle diameter of 45 μm or more is crushed, and the whole amount of raw fly ash and crushed fly ash are mixed so as to satisfy the following formula (I) in the particle size distribution based on volume, The amount of amorphous phase in the mixed fly ash is 55% by mass or more and 75.1% by mass or less with respect to the total amount of the crystalline and amorphous phases in the mixed fly ash, and the amount of Fe in the amorphous phase of the mixed fly ash is 3.5% by mass or more and 10% by mass or less. A method for producing a fly ash for cement composition, wherein the blended fly ash has a specific surface area of 3000 cm ² /g or more and 4500 cm ² /g or less.
0.25≤(D50-D10)/(D90-D50)≤0.47 (I)
(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.) Raw material fly ash is classified, the coarse powder fly ash having a particle diameter of 45 μm or more is crushed, and the whole amount of raw fly ash and crushed fly ash are mixed so as to satisfy the following formula (I) in the particle size distribution based on volume, The amount of amorphous phase in the mixed fly ash is 55% by mass or more and 75.1% by mass or less with respect to the total amount of the crystalline and amorphous phases in the mixed fly ash, and the amount of Fe in the amorphous phase of the mixed fly ash is 3.5% by mass or more and 10% by mass or less. The method for producing a cement composition, wherein the blended fly ash has a specific surface area of 3000 cm ² /g or more and 4500 cm ² /g or less, and the blended fly ash is blended to be 30 mass% or less based on the total amount of the cement composition.
0.25≤(D50-D10)/(D90-D50)≤0.47 (I)
(In the formula, D10, D50, and D90 represent particle diameters corresponding to 10% cumulative frequency, 50% cumulative frequency, and 90% cumulative frequency from the small diameter side of fly ash, respectively.) The method of claim 6,
A method for producing a cement composition, wherein the mixed fly ash is blended in an amount of 12% by mass or more based on the total amount of the cement composition. delete delete delete delete delete delete