KR102241949B1 - Mixed cement - Google Patents

Abstract

A mixed cement containing coal ash and maintaining its properties as an admixture of coal ash and high in strength development in a short term is provided.
With respect to the total amount of coal ash and Portland cement _{, 20 to 40% by mass of coal ash with a SiO 2} content of 55 to 60% _{by mass and a mass ratio of SiO 2} /Al ₂ O ₃ of 2.3 to 2.7, and 60 to 80% by mass of Portland cement It is a mixed cement containing 100 to 300 mg/kg of trialkanolamine having three straight-chain alkanol groups having 3 or less carbon atoms.

Description

Mixed cement

The present invention relates to a mixed cement in which coal ash is mixed.

With the increase in the amount of power generation in coal-fired power plants, the amount of coal ash generated is increasing. Although most of the coal ash becomes industrial waste, it is difficult to secure a disposal site for industrial waste, and because environmental regulations are also being strengthened, effective use of coal ash is required. The coal ash discharged from a thermal power plant is classified into fly ash and clinker ash, and fly ash refers to the ash of fine powder collected by a dust collector among coal ash generated when coal is burned in a coal-fired power plant. Clinker ash refers to the crushed coal ash that has fallen into a water tank at the bottom of a boiler in a red heat state with a crusher. About 90% of coal ash is fly ash.

From the viewpoint of effective use of coal ash, fly ash cement in which fly ash is used as a mixture of coal ash is manufactured and sold. The quality of some fly ash used as a cement admixture is specified in JIS A6201 "Fly Ash for Concrete". In this specification, coal ash refers to fly ash.

Coal ash contains pozzolans containing silicon dioxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) as main components. The pozzolan in the coal ash reacts _{gently with calcium hydroxide (Ca(OH) 2} ) produced by the hydration reaction of cement (pozzolan reaction) to generate a hydrate, and contributes to the strength development of the cured product for a long period of time. On the other hand, in order to supplement the strength development of the cured product at short-term age, as a strength enhancer, a composition comprising a reaction product obtained by reacting glycerin and formaldehyde, or in the group consisting of manose, galactose, talos, ribose, and erythrose A composition containing a specific amount of one or more selected compounds has been proposed (Patent Documents 1 and 2).

Japanese Unexamined Patent Application Publication No. 2014-189417 Japanese Unexamined Patent Application Publication No. 2014-237577

Since the mixed cement using coal ash as an admixture material has little hydraulic property at short-term age in the coal ash itself, the short-term strength development property of 3 days old age is lowered. In order to supplement the short-term strength development properties, even when a conventional strength enhancer is used, a sufficient improvement effect of the short-term strength development properties cannot be obtained depending on the component contained in the coal ash used as an admixture and the amount of coal ash mixed.

Accordingly, an object of the present invention is to provide a mixed cement containing coal ash and maintaining its properties as an admixture of coal ash and having high strength development in a short term.

The present inventors have conducted a study example in order to achieve the above object a result, the mass ratio of silica (SiO ₂₎ for the content and the alumina (Al ₂ O _3), the silica (SiO ₂₎ Among the pozzolanic contained in coal ash (SiO ₂ /Al ₂ O ₃ ), it was found that mixed cement containing coal ash in a specific range of these, while maintaining the properties of coal ash as an admixture, could obtain a mixed cement with high strength development in a short term, and the present invention Finished. That is, the present invention is as follows.

[1] With respect to the total amount of coal ash and Portland cement, 20 to 40% by mass of coal ash with a _{SiO 2} content of 55 to 60% _{by mass and a mass ratio of SiO 2} /Al ₂ O _{3 of 2.3 to 2.7, and 60 to of Portland cement.} A mixed cement containing 80% by mass and containing 100 to 300 mg/kg of trialkanolamine having three linear alkanol groups having 3 or less carbon atoms.

[2] The mixed cement according to [1], wherein the trialkanolamine is triethanolamine.

[3] The mixed cement according to [1] or [2], wherein the sum _{of the SiO 2} content and the Al ₂ O _{3 content in the coal ash is 70 to 82% by mass.}

[4] The mixed cement according to any one of [1] to [3], wherein the content _{of Fe 2} O _{3 in the coal ash is 5.0 to 8.0% by mass.}

[5] Mixing according to any of the above [1] to [4], wherein the mass ratio of the amount of iron content in the crystal phase contained in the coal ash to the amount of iron content in the coal ash (the amount of Fe in the crystal phase/the amount of Fe in the coal ash) is 0.10 to 0.17. cement.

[6] The mixed cement according to any one of [1] to [5], wherein the content of an insoluble residue (insol) in the coal ash is 75 to 87% by mass.

[7] The mixed cement according to any one of [1] to [6], wherein the coal ash blaine specific surface area is 2500 to 4000 cm ^{2 /g.}

[8] The mixed cement according to any one of [1] to [7], comprising 25 to 35% by mass of the coal ash and 65 to 75% by mass of Portland cement.

Advantageous Effects of Invention According to the present invention, it is possible to provide a mixed cement containing coal ash and maintaining its properties as an admixture of coal ash and having high short-term strength development.

Hereinafter, the present invention will be described.

In an embodiment of the present invention, with respect to the total amount of coal ash and Portland cement, 20 to 40% by mass of coal ash having a _{SiO 2} content of 55 to 60 mass% and _{a mass ratio of SiO 2} /Al ₂ O _{3 of 2.3 to 2.7, and Portland} It is a mixed cement composition containing 60 to 80% by mass of cement and 100 to 300 mg/kg of trialkanolamine having three straight-chain alkanol groups having 3 or less carbon atoms.

〔Coal ash〕

The coal ash has a SiO ₂ content of 55 to 60 mass% and a SiO ₂ /Al ₂ O ₃ mass ratio of 2.3 to 2.7. It is preferable that the coal ash is produced in a coal-fired power plant.

When coal ash is used as a cement admixture, the mechanism is not clear, but the mass ratio of the content _{of SiO 2 , one of the main components of pozzolan, and the main components of pozzolan (SiO 2} , Al ₂ O _{3 ) (SiO 2} /Al ₂ O ₃₎ ), for example, contributes to the short-term intensity development at 3 days of age.

It is known that pozzolan in coal ash reacts _{gently with calcium hydroxide (Ca(OH) 2} ) produced by the hydration reaction of cement (pozzolan reaction) to generate hydrates, and contributes to the strength development of a cured product for a long period of time.

In the mixed cement of the present disclosure, the hydration reaction of Portland cement contained in the mixed cement is accelerated by the chelate action of trialkanolamine having three straight-chain alkanol groups having 3 or less carbon atoms. It is estimated that a pozzolanic reaction between calcium hydroxide (Ca(OH) ₂ ) produced by the hydration reaction and pozzolanic components (Al ₂ O ₃ , SiO ₂ ) in coal ash occurs, thereby improving the short-term strength development. In addition, when cations (for example, calcium ions (Ca ²⁺ ) or aluminum ions (Al ³⁺ )) in Portland cement are masked by the chelate action of the trialkanolamine, the equilibrium state of the hydration reaction of the mixed cement is Because of holding, it is estimated that the cation contained in the pozzolan component (SiO ₂ , Al ₂ O _{3) in the coal ash becomes easy to react.} The mixed cement of the present disclosure promotes the hydration reaction of Portland cement in an early stage by the chelate action of the trialkanolamine, and the resulting calcium hydroxide (Ca(OH) ₂ ) and the pozzolanic component (Al _It is estimated that the pozzolanic reaction with 2 O ₃ and SiO ₂ ) is also promoted at an early stage, and is considered to contribute to the improvement of the strength development property in a shorter period.

In the present specification, _{chemical components such as SiO 2} , Al ₂ O ₃ , and Fe ₂ O _{3 in} coal ash refer to values measured in accordance with JIS R5204 "Method for Fluorescent X-ray Analysis of Cement".

The SiO ₂ content in the coal ash is 55 to 60 mass%, preferably 55.0 to 59.5 mass%, and more preferably 55.0 to 59.0 mass%. When the SiO ₂ content in the coal ash is less than 55.0 mass%, the SiO ₂ content, which is one of the pozzolanic components contained in the coal ash, is too small, and the mixed cement containing coal ash may not exhibit the desired long-term strength development. When the SiO ₂ content in the coal ash exceeds 60.0% by mass, the _{content of Al 2} O ₃ is relatively small, and the mass ratio of _{SiO 2} /Al ₂ O ₃ exceeds 2.7 due to the high _{SiO 2 content contained in the coal ash.} do. The SiO ₂ content contained in the coal ash is correlated with the content of other components contained in the coal ash, for example, Al ₂ O ₃ , Fe ₂ O ₃ , CaO, MgO, etc. contained in the coal ash, and the SiO ₂ content in the coal ash As this increases, the content of other components tends to decrease relatively.

The mass ratio of SiO ₂ /Al ₂ O ₃ in coal ash is 2.3 to 2.7, preferably 2.30 to 2.65. When the mass ratio of SiO ₂ /Al ₂ O _{3 in} the coal ash exceeds 2.7, _{the content of silica (SiO 2} ) in the coal ash is large, and the content of alumina (Al ₂ O ₃ ) decreases, and the trialkanolamine Even if calcium ions or aluminum ions in the mixed cement are masked due to the chelate action, since there are few aluminum ions contained in the pozzolanic component of coal ash, the pozzolanic reaction is not accelerated at an early stage, and it becomes difficult to increase the short-term strength development.

The sum of the SiO ₂ content and the Al ₂ O ₃ content in the coal ash is preferably 70 to 86 mass%, more preferably 72.0 to 82.0 mass%, and still more preferably 75.0 to 81.5 mass%. A more preferable lower limit of the sum of the SiO ₂ content and the Al ₂ O _{3 content in the coal ash is 75.37% by mass. When the sum of the SiO 2} content and the Al ₂ O ₃ content in the coal ash contained in the mixed cement is 70 to 82% by mass, a gentle pozzolanic reaction contributing to long-term strength development and a chelate action of the trialkanolamine The hydration reaction of Portland cement is accelerated. When the cation in Portland cement is masked by the chelate action of the trialkanolamine, the mixed cement maintains the equilibrium state of the hydration reaction of the mixed cement, so the pozzolanic component (SiO ₂ , Al ₂ O ₃ ) in the coal ash The cation contained in it becomes easy to react. In the mixed cement, pozzolanic components (Al ₂ O ₃ , SiO ₂ ) contained in the coal ash react with calcium hydroxide (Ca(OH) ₂ ) produced by the hydration reaction of Portland cement in a relatively early stage, thereby promoting the pozzolanic reaction. As a result, it is thought that it contributes to the improvement of the short-term strength development.

As for the coal ash, the Fe ₂ O ₃ content is preferably 5.0 to 8.0 mass%, and more preferably 5.1 to 7.9 mass%. The Fe ₂ O ₃ content in the coal ash, the mechanism contributing to the short-term strength development of, but are not clear, the Fe ₂ O ₃ content in the coal ash is 5.0 ~ 8.0% by weight, contained in the SiO ₂ content, and coal ash contained in the coal ash In relation to the content of other components other than _{SiO 2 , such as Al 2} O ₃ , Fe ₂ O ₃ , CaO, MgO, etc. in _{coal ash, the mass ratio of SiO 2} /Al ₂ O ₃ tends to be 2.3 to 2.7, It is estimated that the mass ratio of SiO ₂ /Al ₂ O ₃ tends to be a preferable range contributing to short-term strength development.

The mass ratio (the amount of Fe in the crystal phase/the amount of Fe in the coal ash) of the amount of iron in the crystal phase (the amount of Fe in the crystal phase) contained in the coal ash to the amount of iron in the coal ash (the amount of Fe in the coal ash) is preferably 0.10 to 0.17, more Preferably it is 0.110 to 0.170. The mass ratio of the amount of iron in the crystalline phase contained in the coal ash to the amount of iron in the coal ash (the amount of Fe in the crystalline phase/the amount of Fe in the coal ash) is an index indicating the mass ratio between the amount of crystalline phase and the amount of amorphous phase contained in the coal ash. In the present specification, the amount of Fe in the crystalline phase is obtained by the method of measuring the crystalline phase and the amorphous phase (mass%) in the coal ash described in Examples to be described later, and the total amount of amorphous phase including unburned carbon G _total ( It refers to the amount of Fe in the crystalline phase calculated by considering the mass %). In the present specification, "the _{amount of Fe in the crystalline phase calculated in consideration of the total amorphous phase amount G total} (mass%) including unburned carbon" is also referred to as "the amount of Fe in the crystal phase".

If the amount of Fe in the crystal phase/the amount of Fe in the coal ash is 0.10 to 0.17, the amount of iron in the crystal phase is relatively small, in other words, the amount of crystal phase that does not contribute to the pozzolanic reaction in the coal ash is relatively small, and alumina (Al ₂ O _{3) that contributes to the pozzolanic reaction.} ) Or silica (SiO ₂ ). When the amount of Fe in the crystalline phase/the amount of Fe in the coal ash exceeds 0.17, it is assumed that the content of the crystalline phase in the coal ash increases, and the amorphous phase which is relatively easy to contribute to the pozzolanic reaction decreases. As a crystal phase in coal ash, for example, quartz or cristobalite (SiO ₂ ), mullite (3Al ₂ O ₃ ·2SiO ₂ or 2Al ₂ O ₃ ·SiO ₂ ), hematite (Fe ₂ O ₃ ), magnetite (Fe ₃ O ₄ ) and the like.

When the mass ratio of the amount of Fe in the crystalline phase and the amount of Fe in the coal ash is 0.17 or less, which indicates an index of the amount of crystallized phase in the coal ash and the amount of amorphous phase, the amount of amorphous phase in the coal ash is small, and the amount of amorphous phase is relatively large. In the mixed cement, if the mass ratio of the amount of Fe in the crystal phase of the coal ash contained in the mixed cement / the amount of Fe in the coal ash is 0.17 or less, the hydration reaction of Portland cement is promoted at a relatively early stage by the chelate action of the trialkanolamine, resulting in calcium hydroxide. (Ca(OH) ₂ ) is produced, and a pozzolanic reaction between the calcium hydroxide (Ca(OH) ₂ ) and the pozzolanic components (Al ₂ O ₃ , SiO ₂ ) contained in the amorphous phase occurs, resulting in short-term strength development. It is estimated to be improved. In addition, since the mixed cement maintains the equilibrium state of the hydration reaction of the mixed cement when the cations in Portland cement are masked by the chelate action of the trialkanolamine, the pozzolanic components (SiO ₂ , Al ₂ O _The cation contained in 3) becomes easy to react, and the reactivity of the pozzolanic reaction, which reacts relatively gently, is promoted even at an early stage, and is considered to contribute to the improvement of short-term strength development. As for the mass ratio of the amount of Fe in the crystalline phase and the amount of Fe in the coal ash, the smaller the value is, the more the amorphous phase is, in other words, the pozzolanic component contained in the coal ash (Al ₂ O ₃ , SiO ₂ ) increases, and a pozzolanic reaction is liable to occur. Usually, the mass ratio of the amount of Fe in the crystalline phase in the coal ash/the amount of Fe in the coal ash is 0.10 or more.

Coal ash has an insoluble insol content of preferably 75 to 87 mass%, more preferably 75.5 to 86.5 mass%. It is thought that the crystalline phase and the amorphous phase (glass phase) constituting silicic acid and silicate are included in the insoluble residue in the coal ash. The mechanism by which the insol in the coal ash contained in the mixed cement contributes to the short-term strength development is not clear. When the insoluble residue (insol) in the coal ash contained in the mixed cement is 75.0 to 87.0% by mass, the amorphous phase containing _{pozzolanic components (Al 2} O ₃ , SiO _{2) contributing to the pozzolanic reaction contained in the coal ash is relatively large.} Mixed cements, by including coal ash and the tree alkanolamine of the mass ratio of the content and the SiO ₂ / Al ₂ O ₃ of SiO ₂ a preferred range, with gentle pozzolanic reaction contributing to the long-term strength development of a relatively early Even at the stage, pozzolanic components (Al ₂ O ₃ , SiO ₂ ) contained in coal ash react with calcium hydroxide (Ca(OH) ₂ ) produced by the hydration reaction of Portland cement, promoting the pozzolanic reaction, resulting in short-term strength development. It is speculated that it can increase.

In this specification, the insoluble residue in the coal ash refers to the insoluble residue measured in accordance with the method described in JIS R5202 "Cement Chemical Analysis".

Coal ash, its blast specific surface area, preferably 2500 to 4000 cm ² /g, more preferably 2600 cm ² /g or more, more preferably 2700 cm ² /g or more, even more preferably 2800 to 4000 cm ² / g.

When the blast specific surface area of the coal ash is large, the activity increases, and in a relatively early stage, the pozzolanic components (Al ₂ O ₃ , SiO ₂ ) contained in the coal ash are produced by the hydration reaction of Portland cement (Ca(OH) _{2 ).} ) And easy to react. If the blast specific surface area of coal ash is 2500~4000cm ² /g, coal ash and Portland cement can be uniformly mixed, and the chelating action of the trialkanolamine is alumina (Al ₂ O ₃ ), which is a pozzolanic component in Portland cement and coal ash. In addition, the pozzolanic reaction proceeds at a relatively early stage, and short-term strength development can be improved.

In this specification, the blast specific surface area of coal ash refers to a value measured in accordance with JIS R5201 "Physical Test Method of Cement".

It is more preferable that the coal ash is contained in the mixed cement in an amount of 20 to 40 mass% and 25 to 35 mass% with respect to the total amount of the coal ash and Portland cement. If the amount of coal ash is contained in less than 20% by mass relative to the total amount of coal ash and Portland cement in the mixed cement, the amount of coal ash is too small, and the coal ash cannot be effectively used. In the mixed cement, when coal ash is contained in an amount exceeding 40% by mass relative to the total amount of coal ash and Portland cement, the amount of coal ash having little hydraulicity at short-term age is too large, and the short-term strength development property of the mixed cement decreases. do. In the mixed cement, based on the total amount of coal ash and Portland cement, the trialkanolamine is contained in an amount of 100 to 300 mg/kg and 20 to 40% by mass of coal ash, and the amount of coal ash and SiO ₂ is 55 to 60% by mass. If _{the mass ratio of SiO 2} /Al ₂ O ₃ is 2.3 to 2.7, it can contribute to the improvement of short-term strength development.

〔Portland Cement〕

The kind of Portland cement contained in the mixed cement is not particularly limited. As Portland cement, portland cement, crude steel Portland cement, medium heat Portland cement, low heat Portland cement, and the like are mentioned.

In the mixed cement, it is preferable to contain 60 to 80 mass% of Portland cement and 65 to 75 mass% with respect to the total amount of coal ash and Portland cement. With respect to the total amount of coal ash and Portland cement, if the content of Portland cement is less than 60% by mass, a hardened product having the desired strength cannot be obtained because the amount of cement is small, and when the content of Portland cement exceeds 80% by mass, mixing The amount of coal ash contained in the cement is small, and the coal ash cannot be used effectively.

[Trialkanolamine]

The mixed cement contains 100 to 300 mg/kg, preferably 150 to 250 mg/kg, of trialkanolamine having three straight-chain alkanol groups having 3 or less carbon atoms with respect to the total amount of coal ash and Portland cement. The trialkanolamine promotes the hydration reaction of Portland cement by a chelate action on Portland cement, so that calcium hydroxide (Ca(OH) ₂ ) is produced in a relatively early stage, and also the chelating action of the trialkanolamine It is assumed that the pozzolanic component of the coal ash also reaches alumina (Al ₂ O ₃ ), and calcium hydroxide (Ca(OH) ₂ ) produced by the hydration of Portland cement and the pozzolanic component (Al ₂ O ₃ , SiO ₂ ) in the coal ash It becomes easier to react than this, and the pozzolanic reaction proceeds at a relatively early stage, and it is thought that it can contribute to short-term strength development. If the content of the trialkanolamine is less than 100mg/kg with respect to the total amount of coal ash and Portland cement, the chelating action of the trialkanolamine is too small, and the hydration reaction of the Portland cement becomes slow, thereby enhancing the short-term strength expression. There are cases where you can't. Even if the content of the trialkanolamine exceeds 300 mg/kg with respect to the total amount of coal ash and Portland cement, a chelating action appropriate for the content does not occur, and the hydration reaction of Portland cement cannot be further promoted.

Trialkanolamine has three linear alkanol groups having 3 or less carbon atoms, and specifically, examples thereof include trimethanolamine, triethanolamine, and tripropanolamine. Among them, triethanolamine is preferable. For Portland cement that does not contain coal ash, triisopropanolamine and triethanolamine use triisopropanolamine, for example, the short-term strength (e.g., mortar strength) of 3 days of age may increase.

On the other hand, in the case of a mixed cement containing 20 to 40 mass% of coal ash, the effect of short-term strength enhancement is greater when triethanolamine is used than when triisopropanolamine is used. In the case of using triethanolamine, the mechanism by which the contribution to the improvement of the short-term strength development of the mixed cement containing coal ash increases is not clear, but the reaction with the _{pozzolan components (Al 2} O ₃ , SiO _{2) contained in the coal ash is not clear.} It is thought that this is because the hydration reaction of Portland cement is accelerated at a rate that is likely to occur, and calcium hydroxide (Ca(OH) _{2) is produced by an appropriate chelate action of triethanolamine.}

[Production of mixed cement]

Mixing cement, based on the total amount of fly ash and Portland cement, SiO ₂ containing 55 to 60% by weight also SiO ₂ / Al ₂ O and the _three fly ash weight ratio of 2.3 ~ 2.7 20 ~ 40% by weight, Portland cement 60 It can be prepared by mixing -80% by mass, and mixing 100-300 mg/kg of trialkanolamine having three straight-chain alkanol groups having 3 or less carbon atoms.

The mixed cement can be used as a mixed cement composition by mixing admixtures other than coal ash and Portland cement. Examples of the admixture 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.

Coal ash analysis

The coal ash of Examples 1 to 9 was analyzed. The analysis of the chemical component of coal ash was measured in accordance with JIS R5204 "Method of Fluorescent X-ray Analysis of Cement". From the results of the analysis of the chemical composition of the coal ash, _{the total value of silica (SiO 2} ) and alumina (Al ₂ O ₃ ) contained in the coal ash, and the mass ratio of silica to alumina (SiO ₂ /Al ₂ O ₃ ) were calculated. .

The boron (B) and fluorine (F) in the coal ash of Examples 1 to 9 were measured in accordance with the Cement Association standard test method (JCAS I-53).

In addition, the ignition loss (ig.loss) and the insoluble residue (insol) in the coal ash refer to the insoluble residue of the coal ash measured in accordance with JIS R5202 "Cement Chemical Analysis". In addition, the blast specific surface area of coal ash was measured according to JIS R5201 "Physical test method of cement". Table 1 shows the results.

In addition, when the amorphous phase of each coal ash was measured by the method described later, the amorphous phase amount of the coal ash of Examples 1 to 6 was in the range of 66.7 to 68.2 mass%. The amorphous phase amount of coal ash of Examples 7 to 9 was in the range of 60.5 to 61.9 mass%. The amorphous phase amount (mass %) in each coal ash of Examples 1 to 9 is shown in Table 1. _{The amorphous phase amount G FA} (mass %) in the coal ash in Table 1 is a value obtained by subtracting the unburned carbon amount (mass %) of the coal ash from the total amorphous phase amount G _{total (mass %) by Rietveld analysis of the coal ash.} The method of measuring the amount of crystalline phase and amorphous phase (mass %) in coal ash is described below.

(Measurement of the amount of crystalline and amorphous phases (% by mass) in coal ash)

The measurement of the amount (mass %) of the crystalline phase and the amorphous phase in the coal 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 (manufactured by Bruker AXS)) 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 in the vicinity of 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

Rietbelt 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 1 using the March Dollase function. Did. Regarding the magnetite phase, it was assumed that no selective orientation occurred.

The procedure for measuring a crystalline phase and an amorphous phase such as magnetite and hematite in coal ash is described below.

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

(ii) A powder X-ray diffraction pattern of the obtained coal ash (Sample 2) by measuring the coal ash (Sample 2) without the addition of an internal standard substance using a powder X-ray diffraction apparatus, and the minerals to be analyzed, such as quartz and mullite. , Anhydrous gypsum, limestone, magnetite, and hematite are fitted with each theoretical profile, and quantitative analysis of each analysis target mineral contained in coal ash is performed, and the amount (mass%) of each analysis target mineral is determined by the analysis software. Calculated. For magnetite and hematite, the amounts (mass%) of magnetite and hematite in the coal ash were calculated only from coal ash (Sample 2) to which no internal standard substance was added.

Sample 2 without an internal standard substance added to the quantitative analysis of magnetite and hematite is the 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 in the vicinity of ° is close. In particular, when rutile-type titanium dioxide having a small particle diameter and a small crystallite size is used as an internal standard material, peak broadening occurs, and the vicinity of the bottom of the peak near the diffraction angle 2θ = 36.1° of rutile-type 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) Fly ash (Sample 1) to which rutile type titanium dioxide, which is an internal standard, was added, was measured using a powder X-ray diffraction apparatus, and the powder X-ray diffraction pattern of the obtained coal ash (Sample 1), and the mineral to be analyzed, Each theoretical profile of quartz, mullite, anhydrous gypsum, limestone, hematite, magnetite, and titanium dioxide was fitted, and a quantitative analysis of each mineral to be analyzed contained in coal ash (Sample 1) added with an internal standard substance was performed. , By analysis software, the amount (mass %) of each analysis target mineral was calculated.

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

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

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

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

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) The value obtained by subtracting the unburned carbon content (mass%) in the coal ash from _{the total amorphous phase amount G total} (mass%) calculated by the equation (A) by the following equation (1) is calculated as the amorphous phase _{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 coal ash.

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

The mass ratio of the amount of iron content in the crystal phase contained in the coal ash to the amount of iron content in the coal ash of Examples 1 to 9 (the amount of Fe in the crystal phase/the amount of Fe in the coal ash) was calculated as follows.

(i) The amount of Fe in the coal ash is the following formula (2) from the measured value 1 of the _{amount of iron content in terms of oxide (iron (III): Fe 2} O ₃ ) measured in accordance with JIS R5204 "Method for Fluorescent X-ray Analysis of Cement" ) Was calculated by converting the amount of iron content.

Iron content in coal ash (Fe amount in coal ash) = measured value 1×2Fe/Fe ₂ O ₃ (111.6/159.7) (% by mass) (2)

(ii) The amount of iron content in the crystalline phase contained in the fly ash is _{calculated by taking into account the total} amount of amorphous phase G total (mass %) including unburned carbon contained in the fly ash, and the amount of hematite in the crystalline phase (mass %) is a measured value 2 The content (mass%) of the magnetite in the crystal phase calculated in consideration of the _total amount of amorphous phase G total (mass%) containing unburned carbon was taken as the measured value 3, and was calculated by the following formula (3).

Iron content (Fe amount) in the crystalline phase considering _{the total amorphous phase amount G total} including unburned carbon contained in coal ash _{= [measured value 2×{2Fe/Fe 2} O ₃ (111.6/159.7)}}) + [measured value 3× {3Fe/Fe ₃ O ₄ (167.4/231.5)}] (3)

(iii) Iron in the crystalline phase taking into account the amount of iron in the coal ash obtained by the above formula (2) (the amount of Fe in the coal ash) and the total amount of amorphous _{phase G total including unburned carbon contained in the coal ash obtained by the above formula (3)} From the amount (the amount of Fe in the crystal phase), the mass ratio of the amount of Fe in the crystal phase (the amount of Fe in the crystal phase/the amount of Fe in the coal ash) was obtained in consideration of the _{total amount of amorphous phase G total including unburned carbon with respect to the amount of Fe in the coal ash.} The results are shown in Tables 1 and 2.

(Examples 1 to 8 and Comparative Examples 1 to 6)

Usually Portland cement, examples 1 to 9, and a kind of additive selected from the group consisting of triethanolamine (TEA), triisopropanolamine (TIPA), and diethylene glycol (DEG), in the formulation shown in Table 2, mixed cement Was prepared. The content of coal ash is a mixing ratio of 100% by mass of the total amount of coal ash and ordinary Portland cement. In addition, the addition amount of a kind of additive selected from triethanolamine (TEA), triisopropanolamine (TIPA) and diethylene glycol (DEG) is the addition amount (mg/kg) per 1000 kg of the total amount of coal ash and normal Portland cement. In Table 2, with respect to the coal ash used in the mixed cement, _{the chemical composition amount (mass%) of silica (SiO 2} ) and alumina (Al ₂ O ₃ ), the mass ratio of silica to alumina (SiO ₂ /Al ₂ O ₃ ), Fe _The mass ratio of the amount of Fe in the crystal phase/the amount of Fe in the coal ash in consideration of the chemical component amount (% by mass) of 2 O _{3 and the total amorphous phase amount G total} ^{including unburned carbon, and the specific surface area of the blast (cm 2} /g) were described.

Mortar strength

^{For the mixed cements of Examples 1 to 8 and Comparative Examples 1 to 6, the mortar compressive strength (N/mm 2} ) at the age of 3 days was determined according to the "11 strength test" of JIS R5201 "Physical Test Method of Cement". Measured. The mortar compressive strength at the age of 3 days of the mortar specimen using the mixed cement in which the coal ash content of Comparative Example 6 is 25% by mass was 1.00, and the relative values of the mortar strength of Examples 1 to 8 and Comparative Examples 1 to 6 were calculated. did.

In addition, for some examples and comparative examples, in accordance with JIS R5201 ``11 Strength Test'' of ``Physical Test Method of Cement'', mortar compressive strength (N/mm ² ) of 28 days old or 91 days old was measured. Then, the mortar compressive strength of the 28-day-old mortar specimen using the mixed cement of Comparative Example 6 was 1.00, and the relative values of the mortar strength of Examples 6 to 8 and Comparative Example 3 were calculated. Further, the mortar compressive strength of the mortar specimen using the mixed cement of Comparative Example 6 at the age of 91 days was 1.00, and the relative values of the mortar strength of Examples 6 to 8 and Comparative Example 3 were calculated. Table 2 shows the results.

As shown in Table 2, _{the mixed cements of Examples 1 to 6 in which the SiO 2} content is 55 to 60 mass% and the _{coal ash content of the SiO 2} /Al ₂ O ₃ mass ratio of 2.3 to 2.7 is 25 mass% are comparative examples. The relative values of the mortar strength at the age of 3 days with respect to 6 (coal ash content 25% by mass, additive 0 mg/kg) were 1.14 or more, respectively, and short-term strength development was improved.

In addition, _{the mixed cement of Examples 1 to 6 in which the SiO 2} content is 55 to 60 mass% and the _{coal ash content of the SiO 2} /Al ₂ O ₃ mass ratio is 2.3 to 2.7 is 30 mass%, Comparative Example 6 (coal ash content 25 The relative value of the mortar strength at the age of 3 days with respect to mass% and additive 0 mg/kg) was 1.06 or more, respectively, and it was confirmed that short-term strength development properties were improved.

The mixed cement of Examples 1 to 6 in which the SiO ₂ content is 55 to 60% _{by mass and the coal ash content of the SiO 2} /Al ₂ O ₃ is 2.3 to 2.7 is 35% by mass, Comparative Example 6 (coal ash content of 25% by mass , Additive 0 mg/kg), the relative values of the mortar strength at the age of 3 days were 0.98 or more, respectively, and the short-term strength development was improved.

In addition, the mixed cements of Examples 6 to 8 having a coal ash content of 25% by mass were all compared to the relative value of the mortar strength at the age of 28 days and the age of 91 days to Comparative Example 6 (coal ash content of 25% by mass, additive 0 mg/kg). The relative value of the mortar strength was 1.15 or more, and the coal ash contained in the mixed cement also maintained the characteristic contributing to the long-term strength development.

In addition, the SiO ₂ content and _{the mass ratio of SiO 2} /Al ₂ O ₃ meet the above range, contain 200 mg/kg of triethanolamine (TEA), and the amount of Fe in the crystal phase considering _{the total amorphous phase amount G total including unburned carbon} The mixed cements of Examples 1 to 8 using coal ash in the range of 0.10 to 0.17 in the mass ratio of the Fe content in the coal ash were comparative examples in any case of 25% by mass, 30% by mass, and 35% by mass of coal ash content. 6 (coal ash content 25% by mass, additive 0 mg/kg), the relative value of the mortar strength at the age of 3 days is that the coal ash content of the mixed cements of Comparative Examples 1 to 5 is 25% by mass, 30% by mass, and 35% by mass. It was larger than each relative value of, and the short-term strength development was improved. As shown in Table 1, the coal ash of Examples 1 to 6 in which the mass ratio of the amount of Fe in the crystal phase _{including the total amount of amorphous phase G total including unburned carbon/the amount of Fe in the coal ash is in the range of 0.10 to 0.17 contains unburned carbon.} Compared to the coal ash of Examples 7 to 8, where the mass ratio of Fe content/Fe content of coal ash exceeded 0.17 in the crystalline phase considering the total amorphous _{phase amount G total , the amorphous phase amount G FA} in the coal ash was higher than that of the coal ash.

On the other hand, as shown in Table 2, the mixed cement of Comparative Examples 1 to 3 using coal ash in which the _{SiO 2} content exceeds 60 mass% and _{the mass ratio of SiO 2} /Al ₂ O _{3 exceeds 2.7,} In any case of the coal ash content of 25% by mass, 30% by mass, and 35% by mass, the relative values of the mortar strength at the age of 3 days with respect to Comparative Example 6 (coal ash content of 25% by mass, additive 0 mg/kg) are respectively less than 1.14, It was low to less than 1.06 and less than 0.98, and the short-term strength development property was not improved compared with the mixed cement of Examples 1-6.

In addition, the mixed cement of Comparative Example 3 having a coal ash content of 25% by mass was the relative value of the mortar strength at the age of 28 days and the mortar strength at the age of 91 days with respect to Comparative Example 6 (coal ash content of 25% by mass, additive 0 mg/kg). The relative value was 1.09, and the coal ash contained in the mixed cement also retained the characteristic contributing to the long-term strength development, but compared with Examples 6 to 8, the long-term strength development was slightly lowered.

As shown in Comparative Examples 4 and 5 of Table 2, _{even when coal ash having a SiO 2} content of 55 to 60 mass% and _{a mass ratio of SiO 2} /Al ₂ O ₃ of 2.3 to 2.7 is used, as an additive, triisopropanolamine ( TIPA) or diethylene glycol (DEG), the chelating action of the additive to ordinary Portland cement is not appropriate, and the mixed cement of Comparative Examples 4 and 5 has a coal ash content of 25% by mass, 30% by mass, and 35%. In any case of mass%, the relative values of the mortar strength at the age of 3 days with respect to Comparative Example 6 (coal ash content 25 mass%, additive 0 mg/kg) were less than 1.14, less than 1.06, and less than 0.98, respectively, and short-term strength expression The property was not improved compared to the mixed cement of Examples 1-6.

As shown in Comparative Example 6 in Table 2, _{even when coal ash having a SiO 2} content of 55 to 60 mass% and _{a mass ratio of SiO 2} /Al ₂ O ₃ of 2.3 to 2.7 is used, or an additive is not used, As the coal ash content increased to 25% by mass, 30% by mass, and 35% by mass, the relative value of the mortar strength at the age of 3 days with respect to Comparative Example 6 (coal ash content 25% by mass, additive 0 mg/kg) decreased. Since coal ash itself has almost no hydraulicity at a short-term age, it is estimated that the more coal ash is, the lower the relative value of the mortar strength at the age of 3 days decreases.

Advantageous Effects of Invention According to the present invention, it is possible to effectively use coal ash whose generation amount is increasing with an increase in the amount of power generation in a coal-fired power plant, has high short-term strength development, and provides a mixed cement containing coal ash having a specific component. can do.

Claims (8)

With respect to the total amount of coal ash and Portland cement _{, 20 to 40% by mass of coal ash with a SiO 2} content of 55 to 60% _{by mass and a mass ratio of SiO 2} /Al ₂ O ₃ of 2.3 to 2.7, and 60 to 80% by mass of Portland cement And, triethanolamine contains 100 to 300 mg/kg, and the mass ratio of the amount of iron in the crystal contained in the coal ash to the amount of iron in the coal ash (the amount of Fe in the crystal phase/the amount of Fe in the coal ash) is 0.10 to 0.17, JIS R5202 A mixed cement having an insoluble residue (insol) content of 75.5 to 86.5 mass% in the coal ash measured in accordance with "Cement Chemical Analysis". The method of claim 1,
_{The mixed cement, wherein the sum of the SiO 2} content and the Al ₂ O ₃ content in the coal ash is 75.37 to 86% by mass. The method according to claim 1 or 2,
_{The mixed cement, wherein the content of Fe 2} O ₃ in the coal ash is 5.0 to 8.0% by mass. The method according to claim 1 or 2,
A blended cement with a blast specific surface area of 2500-4000 cm ^{2 /g of coal ash.} The method according to claim 1 or 2,
A mixed cement containing 25 to 35% by mass of the coal ash and 65 to 75% by mass of Portland cement. delete delete delete