AU2017396650A1 - Method for producing coal ash, coal ash, and cement composition - Google Patents

Method for producing coal ash, coal ash, and cement composition Download PDF

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AU2017396650A1
AU2017396650A1 AU2017396650A AU2017396650A AU2017396650A1 AU 2017396650 A1 AU2017396650 A1 AU 2017396650A1 AU 2017396650 A AU2017396650 A AU 2017396650A AU 2017396650 A AU2017396650 A AU 2017396650A AU 2017396650 A1 AU2017396650 A1 AU 2017396650A1
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coal ash
crushing
value
lightness
mass
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AU2017396650B2 (en
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Kenji MIYAWAKI
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Sumitomo Osaka Cement Co Ltd
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Sumitomo Osaka Cement Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
    • B02C17/04—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls with unperforated container
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
    • B02C17/14—Mills in which the charge to be ground is turned over by movements of the container other than by rotating, e.g. by swinging, vibrating, tilting
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
    • C04B18/10—Burned or pyrolised refuse
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02—Treatment
    • C04B20/026—Comminuting, e.g. by grinding or breaking; Defibrillating fibres other than asbestos
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • C04B28/08—Slag cements
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/24—Cements from oil shales, residues or waste other than slag
    • C04B7/28—Cements from oil shales, residues or waste other than slag from combustion residues, e.g. ashes or slags from waste incineration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Food Science & Technology (AREA)
  • Combustion & Propulsion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Civil Engineering (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)
  • Processing Of Solid Wastes (AREA)
  • Crushing And Grinding (AREA)
  • Soil Conditioners And Soil-Stabilizing Materials (AREA)
  • Medicines Containing Plant Substances (AREA)
  • Detergent Compositions (AREA)

Abstract

Provided is coal ash and a method for producing same, wherein coal ash containing a large amount of unburned carbon can be used without undergoing classification, and the uniformity of the mixing of cohesive soil during soil improvement can be improved. The method for producing coal ash comprises pulverizing coal ash having an ignition loss of 3.5 mass% or more such that the ratio (Lg/Lp) of the lightness (Lg value) of pulverized coal ash to the lightness (Lp value) of unpulverized coal ash is 0.9 or less.

Description

SPECIFICATION
Title of Invention
METHOD OF PREPARING COAL ASH, COAL ASH, AND CEMENT COMPOSITION
Technical Field [0001]
The present invention relates to a method of preparing coal ash, coal ash, and a cement composition.
Background Art [0002]
Cohesive soil has an extremely small particle diameter and is hardened. Therefore, it is difficult to mix and agitate cohesive soil with a solidification material, in soil improvement. In order to solve the problem, for example, a method of using a special agitator, a method of increasing water content to improve uniformity with a solidification material, or a method of using a dispersant acting on soil particles in combination with solidification material milk may be used.
[0003]
On the other hand, the safety of a nuclear power plant is questionable, and the operating ratio of a coal-fired power plant increases. Therefore, the efficient use of coal ash produced in the operation of a coal-fired power plant becomes an issue.
Fly ash that accounts for most of coal ash is used as an admixture of concrete. However, the quality of fly ash is defined in detail by JIS, and a process such as classification is required to maintain a certain level of quality. For example, coarse powder or the like removed by classification is landfilled.
In this case, it is difficult to say that coal ash is efficiently used.
[0004]
In addition, it is known that unburned carbon in coal ash has an adverse effect (for example, admixture adsorption) during concrete manufacturing, and various methods are disclosed regarding a method of removing unburned carbon (for example,
Patent Literature Nos. 1 to 3).
Prior art Literature
Patent Literature [0005] [Patent Literature No. 1]
Publication No. H08-026740 [Patent Literature No. 2]
Publication No. Hll-011999 [Patent Literature No. 3]
Japanese Laid-open Patent
Japanese Laid-open Patent
Japanese Laid-open Patent
Publication No. 2007-054773
Summary of Invention
Problems to be solved [0006]
However, in the methods disclosed in Patent Literature Nos .
to 3, there are problems such as necessity of new equipment, high running costs, or low classification efficiency.
[0007]
In addition, in a case where an additive such as coal ash is mixed with a solidification material to realize the efficient use of the coal ash, the amount of the solidification material can be reduced. Therefore, cost reduction such as a reduction in the amount of sludge can be expected.
However, in a case where the processing target is soil such as cohesive soil, as described above, it is difficult to mix and agitate the soil with a solidification material. Therefore, solidification materials which are currently known have problems such as an increase in cost or low efficiency. From the viewpoint of efficient use of coal ash, it is preferable to use the entire amount of coal ash. In addition, in a case where a technique can improve uniformity during mixing in improvement of cohesive soil through a simple process without requiring a process such as removal of unburned carbon, the technique is extremely significant but is not currently known.
[0008]
Therefore, an object of the present invention is to provide coal ash, a method of preparing the same, and a cement composition containing the coal ash, in which the coal ash containing a large amount of unburned carbon can be used without performing a process of classification and in which uniformity during mixing in improvement of cohesive soil can be improved.
Solution to Problems [0009]
The present inventors performed a thorough investigation in order to achieve the object and found that, even in a case where coal ash having a high ignition loss, which may have an adverse effect for concrete manufacturing, is used, the coal ash obtained by crushing the coal ash in a predetermined range can improve uniformity during mixing in improvement of cohesive soil. That is, the present invention is as follows.
[0010] [1] A method of preparing coal ash comprising:
crushing coal ash having an ignition loss of 3.5 mass% or higher such that a ratio (Lg/Lp) of a lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower.
[2] The method of preparing coal ash according to [1], in which the coal ash is crushed such that the ratio (Lg/Lp) of the lightness (Lg value) after crushing to the lightness (Lp value) before crushing is 0.6 or higher.
[3] The method of preparing coal ash according to [1] or [2] , in which the coal ash is crushed such that a ratio (Vg/Vp) of a content (Vg) of particles having a particle diameter of μιη or more in the coal ash after crushing measured by a laser diffraction particle size analysis method to a content (Vp) of the particles having a particle diameter of 45 μιη or more in the coal ash before crushing measured by the analysis method is 0.85 or lower.
[0011] [4] Coal ash, in which after crushing, an ignition loss is 3.5 mass% or higher, a content of particles having a particle diameter of μιη or more measured by a laser diffraction particle size analysis method is 20 vol% or higher and 45 vol% or lower, a
Blaine specific surface area is 3200 cm2/g or higher and 4200 cm2/g or lower, and a lightness (Lg value) is 25.0 or higher and
50.0 or lower, and a ratio (Lg/Lp) of the lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower.
[5] The coal ash according to [4], in which the ignition loss is 8.0 mass% or lower.
[0012] [6] A cement composition including:
the coal ash according to [4] or [5]; and cement.
[7] The cement composition according to [6], in which the cement is at least one selected from the group consisting of normal Portland cement, high early strength
Portland cement, moderate heat Portland cement, and low-heat
Portland cement.
[8] The cement composition according to [6] or [7], in which a content of the coal ash is higher than 5 mass% and 40 mass% or lower with respect to a total amount of the cement composition .
Effects of Invention [0013]
According to the present invention, coal ash, a method of preparing the same, and a cement composition containing the coal ash can be provided, in which the coal ash containing a large amount of unburned carbon can be used without performing a process of classification and in which uniformity during mixing in improvement of cohesive soil can be improved. As a result, the entire amount of coal ash produced from a coal-fired power plant can be used as a raw material, and the work efficiency in soil improvement can be improved.
Mode for carrying out the Invention [0014] [Method of Preparing Coal Ash and Coal Ash] (1) Method of Preparing Coal Ash
A method of preparing coal ash according to an embodiment of the present invention comprises : crushing coal ash having an ignition loss of 3.5 mass% or higher such that a ratio (Lg/Lp) of a lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower .
[0015]
According to the present invention, in a case where predetermined crushing is performed on coal ash having an ignition loss of 3.5 mass% or higher to use the crushed coal ash in improvement of cohesive soil, coal ash (improved coal ash) capable of improving mixing properties with cohesive soil can be manufactured.
Here, the ignition loss is proportional to the amount of unburned carbon in the coal ash, and ignition loss being 3.5 mass% or higher indicates that the amount of so-called unburned carbon is high. By performing the predetermined crushing on coal ash having a high ignition loss, at least a part of unburned carbon contained in particles of the coal ash is exposed to the particle surface sides. As a result, mixing properties between cement particles and clay particles can be improved by the coal ash. The unburned carbon exposed to the particle surfaces of the coal ash by crushing exhibits the same property as unburned carbon in powder particles present before crushing, and the property is hydrophobicity. That is, the amount of unburned carbon exposed to the particle surfaces of the coal ash by the predetermined crushing is higher than that before crushing.
Therefore, hydrophobicity is further improved. For example, in a case where a mixture of cement and the coal ash is used as a solidification material, excessive water absorption is not exhibited during cement mixing due to the hydrophobic unburned carbon exposed to the particle surfaces. As a result, dispersibility between clay particles and cement particles in improvement of cohesive soil having high water content can be efficiently improved.
[0016]
The ignition loss of the coal ash relates to the content of unburned carbon, and it can be presumed that, in a case where the ignition loss of the coal ash is high, the content of unburned carbon in the coal ash is also high. Accordingly, in a case where the ignition loss of the coal ash is lower than 3.5 mass%, the absolute content of unburned carbon exhibiting hydrophobicity is low. Therefore, dispersibility of clay particles cannot be improved. The ignition loss of the coal ash is preferably 3.5 mass% or higher and 9.0 mass% or lower and more preferably 6.0 mass% or higher and 9.0 mass% or lower. The ignition loss can be measured by a method described below in Examples.
[0017]
The coal ash having an ignition loss of 3.5 mass% or higher is, for example, ash produced from a coal-fired power plant, and is produced by burning pulverized coal. Examples of the coal ash are: coal ash that is collected from combustion gas of a combustion boiler by falling when the combustion gas passes through an air preheater, an economizer, or the like; fly ash that is collected by an electrical dust collector; and coal ash that falls to a furnace bottom of a combustion boiler.
[0018]
The coal ash having an ignition loss of 3.5 mass% or higher is crushed by, for example, a crusher such that a ratio (Lg/Lp) of a lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower. As a result, unburned carbon contained in coal ash particles is exposed.
As the crusher, a ball mill or a vibration mill (that refines powder by applying vibration to a container and transmitting the vibration to media (balls and rods) in the container) can be used.
[0019]
For crushing, first, the lightness (Lp value) of the coal ash before crushing is measured, and the ratio (Lg/Lp) of the lightness (Lg value) of the coal ash after crushing to the lightness (Lp value) of the coal ash before crushing is adjusted to be 0.9 or lower. Regarding the coal ash to be crushed, the entire amount of the coal ash may be crushed, or a part of the coal ash may be crushed. In addition, a mixture of the crushed coal ash and the non-crushed coal ash may be used as the coal ash after crushing. Even in a case where a part of the coal ash is crushed and a mixture of the crushed coal ash and the non-crushed coal ash is used as the coal ash after crushing, the coal ash has to be crushed such that a ratio (Lg/Lp) of a lightness (Lg value) of the mixed coal ash containing the crushed coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower.
Here, the lightness of coal ash relates to blackness and is an index mainly indicating the abundance of unburned carbon exposed to the surface. In a case where Lg/Lp, which is the ratio before and after crushing, is higher than 0.9, unburned carbon contained in the coal ash is not sufficiently present on the surface. As a result, in a case where a mixture of the coal ash and cement is used as a solidification material, dispersibility between clay particles and cement particles cannot be efficiently improved.
Lg/Lp is preferably 0.6 or higher and 0.9 or lower, and more preferably 0.6 or higher and 0.85 or lower. In a case where
Lg/Lp is 0.6 or higher, crushing of spherical particles can be suppressed as much as possible, and deterioration in fluidity can be suppressed.
The lightness of the coal ash can be measured by a method described below in Examples.
[0020]
In addition, particles having a particle diameter of 45 μιη or more contain a large amount of non-spherical particles, and from the viewpoints of improving fluidity by crushing and pulverizing the particles to expose spherical particles contained therein, it is preferable that the coal ash is crushed such that a ratio (Vg/Vp) of the content (Vg; vol%) of particles having a particle diameter of 45 μιη or more in the coal ash after crushing measured by a laser diffraction particle size analysis method to the content (Vp; vol%) of the particles having a particle diameter of 45 μιη or more measured in the coal ash before crushing by the analysis method is 0.85 or lower. It is more preferable that the coal ash is crushed such that the ratio (Vg/Vp) is 0.6 or higher and 0.80 or lower. Particles having a particle diameter of 45 μιη or more in the coal ash may be crushed, and the crushed coal ash may be mixed with the non-crushed coal ash to be used as the coal ash after crushing.
[0021]
As described above, the coal ash capable of improving dispersibility of clay particles can be easily obtained by performing the predetermined crushing. That is, the entire amount of coal ash produced from a coal-fired power plant can be used as a raw material, there are no problems such as necessity of new equipment or high running costs, and the work efficiency in soil improvement can be improved.
[0022] (2) Coal Ash:
In coal ash according to an embodiment of the present invention, after crushing, an ignition loss is 3.5 mass% or higher, the content of particles having a particle diameter of μιη or more measured by a laser diffraction particle size analysis method is 20 vol% or higher and 45 vol% or lower, a
Blaine specific surface area is 3200 cm2/g or higher and 4200 cm2/g or lower, and a lightness (Lg value) is 25.0 or higher and
50.0 or lower, and a ratio (Lg/Lp) of the lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower.
[0023]
In a case where the ignition loss of the coal ash is lower than 3.5 mass%, the absolute content of unburned carbon exhibiting hydrophobicity is low. Therefore, dispersibility of clay particles can be improved. The ignition loss of the coal ash is preferably 3.5 mass% or higher and 9.0 mass% or lower and more preferably 6.0 mass% or higher and 9.0 mass% or lower.
[0024]
In a case where the content of particles having a particle diameter of 45 μιη or more measured by a laser diffraction particle size analysis method in the coal ash is lower than 20 vol%, the amount of non-spherical particles is low, and the effect of exposing unburned carbon particles by crushing to improve dispersibility deteriorates. In a case where the content of particles having a particle diameter of 45 μιη or more is higher than 45 vol%, the amount of non-spherical particles is high, and fluidity deteriorates or hydration activity of the coal ash itself deteriorates.
The content of particles having a particle diameter of 45 μιη or more is preferably 20 vol% or higher and 45 vol% or lower and more preferably 23 vol% or higher and 43 vol% or lower.
[0025]
In a case where the Blaine specific surface area of the coal ash is lower than 3200 cm2/g, hydration activity deteriorates, and a predetermined strength may not be obtained.
In a case where the Blaine specific surface area of the coal ash is higher than 4200 cm2/g, fluidity deteriorates.
The Blaine specific surface area is preferably 3200 cm2/g or higher and 4200 cm2/g or lower and more preferably 3300 cm2/g or higher and 4000 cm2/g or lower.
[0026]
In addition, in a case where the lightness (Lg value) of the crushed coal ash is lower than 25.0, the amount of unburned carbon increases, the coal ash becomes more black, and there is a color difference between the coal ash and the surrounding soil in soil improvement. In a case where the lightness (Lg value) of the crushed coal ash is higher than 50.0, the amount of unburned carbon exposed is low. Therefore, in a case where the crushed coal ash is mixed with cohesive soil, superior fluidity cannot be obtained, and uniform mixing may not be performed.
The lightness of the coal ash is preferably 30.0 or higher and 50.0 or lower and more preferably 35.0 or higher and 45.0 or lower.
[0027]
In a case where the ratio (Lg/Lp) of the lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is higher than 0.9, unburned carbon contained in the coal ash is not sufficiently present on the surface. As a result, in a case where a mixture of the coal ash and cement is used as a solidification material, dispersibility between clay particles and cement particles cannot be efficiently improved.
The ratio is preferably 0.6 or higher and 0.9 or lower and more preferably 0.6 or higher and 0.85 or lower.
[0028]
The coal ash according to the embodiment of the present invention can be prepared by the method of preparing coal ash according to the embodiment of the present invention. In order to prepare the coal ash of the embodiment of the present invention, a crusher such as a ball mill or a disk mill is used, and it is preferable to measure a particle diameter distribution, a
Blaine specific surface area, and a color difference after crushing to check whether or not predetermined physical property values are obtained.
[0029]
It is preferable that the coal ash of the embodiment of the present invention is used for a cement composition described below and can also be used for other various applications by utilizing the properties thereof.
[0030] [Cement Composition]
A cement composition of an embodiment of the present invention comprises: the coal ash of the embodiment of the present invention; and cement.
The kind of the cement is not particularly limited, and is preferably at least one selected from the group consisting of normal Portland cement, high early strength Portland cement, moderate heat Portland cement, and low-heat Portland cement.
[0031]
It is preferable that the content of the coal ash is preferably higher than 5 mass% and 40 mass% or lower with respect to the total amount of the cement composition. By setting the content of the coal ash to be higher than 5 mass% and 40 mass% or lower, the cement composition can be used as a solidification material. Preferably, the content is 25 mass% or higher and 35 mass% or lower.
[0032]
In order to obtain the cement composition, in addition to the coal ash and the cement, for example, gypsum, blast furnace slag, limestone powder, or burned lime can be mixed. In order to mix the components, for example, a V-type mixer, a vibrating mixer, a pan mixer, or a planetary centrifugal mixer can be used.
[0033]
The cement composition of the embodiment of the present invention is used preferably as a cement-based solidification material and more preferably as a cement-based solidification material for improvement of cohesive soil.
In a case where the cement composition is used as a cement-based solidification material for improvement of cohesive soil, the amount of water (mixing water) used for mixing is preferably 80 parts by mass or more and 120 parts by mass or less and more preferably 85 parts by mass or more and 110 parts by mass or less with respect to 100 parts by mass of the cement composition.
Examples [0034]
Next, the present invention will be described in more detail with Examples but is not limited to the Examples.
[0035] (Preparation of Coal Ash A to F)
Each of coal ash A to F produced from a coal-fired power plant in Japan was crushed by a test ball mill (inner volume:
100 L) . The degree of crushing was adjusted by checking powder physical properties by a laser diffraction particle size analyzer, a Blaine specific surface area measuring device, and a color difference meter.
The coal ash properties (ignition loss, amount of carbon,
ΜΤ-45μΚ, ratio between ΜΤ-45μΙ1 values before and after crushing,
Blaine specific surface area, L value, and ratio between L values before and after crushing) of the coal ash A to F before and after crushing are shown in the following Table 1.
[0036] [Table 1]
Before Crushing After Crushing
Ignition Loss (mass%) Amount of Carbon (mass%) MT-45qR (vol%) (Vp) Blaine specific surface area (cm2/g) L Value (Lp Value) MT-45qR (vol%) (Vg) Blaine specific surface area (cm2/g) L Value (Lg Value) MT-45qR Ratio (Vg/Vp) L Value Ratio (Lg/Lp)
Coal Ash A 4.10 3.54 37.6 3370 48.0 24.8 3450 44.0 0.66 0.89
B 5.26 4.51 36.3 3620 41.2 25.8 3710 36.0 0.71 0.87
C 6.21 5.39 40.6 3410 38.0 26.6 3520 30.0 0.66 0.79
D 6.21 5.39 40.6 3410 38.0 35.5 3460 36.2 0.87 0.95
E 8.80 7.70 45.6 3790 35.8 36.5 4050 29.0 0.80 0.81
F 8.80 7.70 45.6 3790 35.8 41.0 3850 34.0 0.90 0.95
[0037]
The coal ash properties were obtained as follows.
(1) Ignition Loss:
The ignition loss was measured according to JIS A 6201 Fly
Ash for use in Concrete (ignition loss at 975°C for 15 minutes) .
(2) Amount of Carbon:
The amount of carbon was measured by a carbon/sulfur analyzer for solid materials (EMIA-320V, manufactured by Horiba
Ltd.) .
(3) MT-45qR (content of particles having a particle diameter of 45 μιη or more) :
ΜΤ-45μΒ was measured by a laser diffraction particle size analyzer (MICROTRAC MT-3300EX, manufactured by Nikkiso Co.,
Ltd.) . The content (Vp; vol%) of particles having a particle diameter of 45 μιη or more in the coal ash before crushing was measured by a laser diffraction particle size analysis method, and the content (Vg; vol%) of particles having a particle diameter of 45 μιη or more measured in the coal ash after crushing was measured by the analysis method. Based on the measured values, a ratio (Vg/Vp; ΜΤ-45μΒ ratio) of the content (Vg; vol%) of particles having a particle diameter of 45 μιη or more measured by a laser diffraction particle size analysis method in the coal ash after crushing to a content (Vp; vol%) of the particles having a particle diameter of 45 μιη or more measured by the analysis method in the coal ash before crushing was obtained.
[0038] (4) Blaine Specific Surface Area
The Blaine specific surface area was measured according to JIS R5201 Physical Testing Methods for Cement.
(5) Color Difference (L value):
The lightness (L value) defined by the International
Commission on Illumination (CIE) was measured by a color difference meter (CR-300) manufactured by Konica Minolta Japan,
Inc. The lightness (Lp value) of the coal ash before crushing and the lightness (Lg value) of the coal ash after crushing were measured. Based on the measured values, the ratio (Lg/Lp; L value ratio) of the lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing was obtained.
[0039] (Mixing Test for Examples and Comparative Examples) g of each of the coal ash A to F after crushing, 70 g of cement (normal Portland cement, manufactured by Sumitomo
Osaka Cement Co., Ltd.), and 100 g of mixing water were sufficiently uniformly mixed by a hand mixer to prepare cement milk. The cement milk and 1 L (wet density: 1.846 g/cm3) of kaolin (manufactured by Kishida Chemical Co., Ltd.) as cohesive soil were added together into a planetary centrifugal mixer and were mixed with each other to prepare a specimen according to
JGS 0821-2009 Practice for Making and Curing Stabilized Soil
Specimens without Compaction.
The details of mixing (water content: 35 mass%) are shown in Table 2 below.
[0040]
The coal ash E and the coal ash F were formed of the same sample and were different in the degree of crushing. The same shall be applied to the coal ash G and the coal ash H.
[0041]
After mixing, mixing properties between the solidification material and the cohesive soil were evaluated by a vane shear test. In the vane shear test, a vane blade welded to a stainless steel plate (0.5 cmx3 cm) in a vertical direction was attached to a tip of a torque driver (manufactured by Tohnichi
Mfg. Co., Ltd.) and was inserted into the sample to measure a maximum torque (refer to Table 2 below). Based on the measured maximum torque, a vane shear resistance value was obtained. The results are shown in Table 2 below. In addition, evaluation indices (refer to the following description) based on the resistance values are also shown.
G (good): vane shear resistance value<10.0 kN/m2
Av (average) : 10.0 kN/m2<vane shear resistance value<12.0 kN/m2
P (poor)X: vane shear resistance value>12.0 kN/m2 [0042] [Table 2]
Coal Ash Crushing L Value Ratio (Lg/Lp) Mixing Test (g) Vane Shear Resistance Value
Kaolin Cement Coal Ash Mixing Water Maximum Torque (CN-m) Value (kN/m2) Evaluation
Example 1 C Crushed 0.79 1846 70 30 100 9.3 7.5 G
Example 2 B Crushed 0.87 1846 70 30 100 10.9 8.8 G
Example 3 A Crushed 0.89 1846 70 30 100 11.4 9.2 G
Example 4 C Crushed 0.79 1846 70 30 90 10.5 8.5 G
Example 5 E Crushed 0.81 1846 70 30 100 8.0 6.5 G
Comparative Example 1 C Not Crushed 1.00 1846 70 30 100 16.1 13.0 P
Comparative Example 2 B Not Crushed 1.00 1846 70 30 100 16.7 13.5 P
Comparative Example 3 A Not Crushed 1.00 1846 70 30 100 19.3 15.6 P
Comparative Example 4 D Crushed 0.95 1846 70 30 100 15.8 12.8 P
Comparative Example 5 E Not Crushed 1.00 1846 70 30 100 14.7 11. 9 Av
Comparative Example 6 F Crushed 0.95 1846 70 30 100 12.6 10.2 Av
[0043]
It was found from a comparison between Examples 1 to 3 and and Comparative Examples 1 to 3 and 5 that, for Examples 1 to 3 and 5 containing the crushed coal ash, the vane shear resistance values were low, and mixing properties were good.
As can be seen from Example 4, even in a case where the water content was lower than that of Example 1, good mixing properties were obtained. In Comparative Examples 4 and 6, the degree of crushing was lower than that of Examples 1 and 5, and mixing properties were insufficient.
Industrial Applicability [0044]
According to the present invention, coal ash that is increasingly produced as the power generation amount increases in a coal-fired power plant can be efficiently used, and uniformity during mixing in improvement of cohesive soil can be improved.

Claims (7)

1. A method of preparing coal ash comprising:
crushing coal ash having an ignition loss of 3.5 mass% or higher such that a ratio (Lg/Lp) of a lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower.
2. The method of preparing coal ash according to claim
1, wherein the coal ash is crushed such that the ratio (Lg/Lp) of the lightness (Lg value) after crushing to the lightness (Lp value) before crushing is 0.6 or higher.
3. The method of preparing coal ash according to claim
1 or 2, wherein the coal ash is crushed such that a ratio (Vg/Vp) of a content (Vg) of particles having a particle diameter of
45 μιη or more in the coal ash after crushing measured by a laser diffraction particle size analysis method to a content (Vp) of the particles having a particle diameter of 45 μιη or more in the coal ash before crushing measured by the analysis method is 0.85 or lower.
4. Coal ash, wherein after crushing, an ignition loss is 3.5 mass% or higher, a content of particles having a particle diameter of
45 μιη or more measured by a laser diffraction particle size analysis method is 20 vol% or higher and 45 vol% or lower, a
Blaine specific surface area is 3200 cm2/g or higher and 4200 cm2/g or lower, and a lightness (Lg value) is 25.0 or higher and
50.0 or lower, and a ratio (Lg/Lp) of the lightness (Lg value) of the coal ash after crushing to a lightness (Lp value) of the coal ash before crushing is 0.9 or lower.
5. The coal ash according to claim 4, wherein the ignition loss is 8.0 mass% or lower.
6. A cement composition comprising:
the coal ash according to claim 4 or 5; and cement.
7. The cement composition according to claim 6, wherein the cement is at least one selected from the group consisting of normal Portland cement, high early strength
Portland cement, moderate heat Portland cement, and low-heat
Portland cement.
The cement composition according to claim 6 or 7, wherein a content of the coal ash is higher than 5 mass% and 40 mass% or lower with respect to a total amount of the cement composition .
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