AU2021242720A1 - Cement clinker, cement composition, and cement clinker production method - Google Patents

Abstract

Provided are a cement clinker and a cement composition which can be reduced in heat of hydration and are excellent in short term strength development. A cement clinker in which the proportion of C

Description

DESCRIPTION TITLE OF INVENTION CEMENT CLINKER, CEMENT COMPOSITION, AND CEMENT CLINKER PRODUCTION METHOD

Technical Field

[0001]

The present invention relates to a cement clinker and

a cement composition, especially ordinary Portland cement.

Background Art

[0002]

From the viewpoint of suppressing cracks in concrete,

a cement composition having a low heat of hydration is

required. For example, according to "Common Specifications

for Civil Engineering Work (revised in April 2019)" (Kanto

Regional Development Bureau, Ministry of Land,

Infrastructure, Transport and Tourism), Vol. 2 "Materials",

Section 6 "Cement and Admixtures", 2-2-6 -2 "Cement", and

table 2-2-18 "Quality of ordinary Portland cement",

regarding the heat of hydration of cement, control target

values of 350 J/g or less at 7 days of age and 400 J/g or

less at 28 days of age are shown.

[0003]

In recent years, various wastes and by-products

containing a large amount of Al, such as coal ash and

construction-generated soil, have been used as cement raw

materials. However, when these wastes and by-products are

used, the amount of C 3 A in a mineral composition of a cement

clinker increases, and the heat of hydration increases. In

a case where the wastes and by-products are used as raw

materials of the cement clinker, the amount used is

currently limited.

[0004]

As a method for reducing the heat of hydration of a

cement composition, a method for controlling the mineral

composition of C 3 S and C 3 A to a low mineral composition such

as moderate heat Portland cement and low heat Portland

cement, or a method for mixing with a blast furnace slag is

known (for example, Non Patent Literature No. 1 and Non

Patent Literature No. 2).

[0005]

Non Patent Literature No. 3 reports an influence of

TiO 2 and MgO, which are trace components in a cement

clinker, on a mineral composition and physical properties

of cement. Non Patent Literature No. 3 discloses that as a

MgO content increases, an aluminate phase (C 3 A) tends to

decrease and heat of hydration tends to decrease, and

furthermore, the more the total content of MgO and TiO 2 , the smaller the heat of hydration tends to be.

Citation List

Non Patent Literature

[00061

[Non Patent Literature No. 1] "C & C Encyclopedia

Basic Explanation of Cement and Concrete Chemistry",

published by Cement Association, July 1996, pp. 17-18

[Non Patent Literature No. 2] "Common Knowledge of

Cement", published by Cement Association, January 2007, pp.

13-15

[Non Patent Literature No. 3] Keiji Chabayashi et

al., "Effects of TiO2 and MgO on clinker mineral

composition and physical properties of cement", Cement and

Concrete Proceedings, vol. 66 (2012), pp. 211-216

Summary of Invention

Technical Problem

[0007]

As in Non Patent Literature No. 3, it is also possible

to reduce the heat of hydration by the content of MgO and

TiO 2 in the clinker. However, various trace components are

introduced into the clinker actually produced, which is

derived from industrial waste and by-products. In Non

Patent Literature No. 3, no consideration is given to an influence of other trace components on physical properties such as heat of hydration.

[00081

The present invention has been made in view of above

problems, and an object of the present invention is to

provide a cement clinker capable of reducing heat of

hydration and a cement composition containing the cement

clinker cement composition.

Solution to Problem

[00091

In actual cement clinker manufacture and cement

manufacture, a mineral composition and a physical property

of cement are affected by various trace components in

addition to MgO and TiO 2 , manufacture conditions, or the

like. As a result of investigating a relationship between

heat of hydration and a clinker having different

manufacture conditions such as a blending amount of a trace

component, the inventors of the present application focused

on a chemical component in a mineral composition of the

clinker. As a result, it was found that particularly a

content of a trace component in an aluminate phase (C3 A)

greatly affects the heat of hydration, and the present

invention was completed.

[0010]

That is, in order to solve the above problems, the

present invention provides the following <1> to <5>.

<1> A cement clinker including: 3CaO•SiO2 in a

proportion, calculated by Bogue formula, of 50% to 75% by

mass; 2CaO•SiO2 in a proportion, calculated by Bogue

formula, of 5% to 25% by mass; 3CaO•Al2O3 and

4CaO•Al2O3•Fe2O3 in a total proportion, calculated by Bogue

formula, of 15% to 22% by mass; MgO; TiO 2 ; MnO; and ZnO, in

which Formula (1) is satisfied.

CMg-C3A X CTi-C3A X CMn-C3A X CZn-C3A 0 . 00 10 . . . (1)

In Formula (1),

CMg-C3A represents a content rate (% by mass) of MgO in

3CaO•A1203,

CTi-C3A represents a content rate (% by mass) of TiO 2 in

3CaO•A1203,

CMn-C3A represents a content rate (% by mass) of MnO in

3CaO•A1203, and

CZn-C3A represents a content rate (% by mass) of ZnO in

3CaO•Al2O3.

<2> The cement clinker according to <1>, in which a

content rate of Fe203 in 3CaO•Al2O3 is less than 6.32% by

mass.

<3> The cement clinker according to <1> or <2>, in

which the content rate of TiO 2 is less than 0.24% by mass.

<4> A cement composition including: the cement clinker according to any one of <1> to <3>; and gypsum.

<5> A method for manufacturing a cement clinker,

including: a step of blending raw materials; and a step of

calcining the raw materials blended, in which a cement

clinker after calcining contains 3CaO-SiO2 in a proportion,

calculated by Bogue formula, of 50% to 75% by mass,

2CaO•SiO2 in a proportion, calculated by Bogue formula, of

5% to 25% by mass, 3CaO•Al2O3 and 4CaO•Al2O3•Fe2O3 in a total

proportion, calculated by Bogue formula, of 15% to 22% by

mass, MgO, TiO 2 , MnO, and ZnO, and Formula (1) is

satisfied.

CMg-C3A X CTi-C3A X CMn-C3A X CZn-C3A 0 . 0010 . . . (1)

In Formula (1),

CMg-C3A represents a content rate (% by mass) of MgO in

3CaO•A1203,

CTi-C3A represents a content rate (% by mass) of TiO 2 in

3CaO•A1 2 03 ,

CMn-C3A represents a content rate (% by mass) of MnO in

3CaO•A1203, and

CZn-C3A represents a content rate (% by mass) of ZnO in

3CaO•Al 20 3 .

Advantageous Effects of Invention

[0011]

According to the present invention, it is possible to obtain a cement clinker capable of reducing heat of hydration. When using the cement clinker of the present invention, a cement composition having low heat of hydration can be obtained.

Description of Embodiments

[0012]

Hereinafter, a cement clinker and a cement composition

of the present invention will be described in detail. The

notation of the numerical range of "AA to BB" in the

present specification means "AA or more and BB or less".

[0013]

[Cement clinker]

The cement clinker of the present invention includes:

3CaO•SiO2 in a proportion, calculated by Bogue formula, of

50% to 75% by mass; 2CaO-SiO2 in a proportion, calculated by

Bogue formula, of 5% to 25% by mass; 3CaO•Al2O3 and

4CaO•Al2O3-Fe2O3 in a total proportion, calculated by Bogue

formula, of 15% to 22% by mass; MgO; TiO 2 ; MnO; and ZnO, in

which Formula (1) is satisfied.

CMg-C3A X CTi-C3A X CMn-C3A X CZn-C3A 0. 0010 . . . (1)

In Formula (1),

CMg-C3A represents a content rate (% by mass) of MgO in

3CaO•A1203,

CTi-C3A represents a content rate (% by mass) of TiO 2 in

3CaO•A1 2 03

, CMn-C3A represents a content rate (% by mass) of MnO in

3CaO•A1203, and

CZn-C3A represents a content rate (% by mass) of ZnO in

3CaO•Al2O3.

The cement clinker of the present invention is

preferably used for ordinary Portland cement.

[0014]

The cement clinker of the present invention is a main

composition forming a cement composition, and is

manufactured by blending limestone (CaO component), clay

(A12 0 3 component and SiO 2 component), silica stone (SiO 2

component), an iron oxide raw material (Fe203 component),

and the like and calcining. The cement clinker of the

present invention may contain industrial waste or the like

such as coal ash, construction-generated soil, blast

furnace slag, converter slag, by-product gypsum, and

municipal waste incineration ash, as raw materials.

The cement clinker of the present invention contains

3CaO-SiO2 (abbreviation: C 3 S), 2CaO-SiO2 (abbreviation: C 2 S),

3CaO-Al2O3 (abbreviation: C 3A), and 4CaO-Al2O3-FeO3

(abbreviations: C 4AF). The cement clinker is formed of main

minerals of alite (C 3 S) and belite (C 2 S) and an interstitial

phase or the like of an aluminate phase (C 3 A) and a ferrite

phase (C 4 AF) existing between crystals of the main minerals.

[0015]

Proportions of C3S, C 2 S, C 3 A, and C 4 AF in the cement

clinker are determined from proportions of CaO, SiO 2 , A1 2 0 3

, and Fe203, measured by JIS R 5204:2019 "Analysis method for

cement by X-ray fluorescence" in cement clinker, by a

calculation called Bogue formula in a field of cement

chemistry (for example, see "Science of Cement", translated

by Masaki Daimon, Uchida Old Tsuruno (1989), p. 11).

[0016]

<Proportion of 3CaO-SiO2 (C3 S)>

The proportion of the 3CaO-SiO2 calculated by the

Bogue formula in the cement clinker of the present

invention is 50% to 75% by mass. When the proportion of the

3CaO'SiO2 calculated by the Bogue formula is less than 50%

by mass, a strength of concrete or mortar expressed by the

cement clinker may decrease in some cases. When the

proportion of the 3CaO'SiO2 calculated by the Bogue formula

is larger than 75% by mass, heat of hydration of a cement

composition may become too high in some cases. The

proportion of the 3CaO'SiO2 calculated by the Bogue formula

is preferably 50% to 70% by mass, more preferably 55% to

70% by mass, and still more preferably 55% to 67% by mass.

[0017]

<Proportion of 2CaO-SiO2 (C 2 S)>

The proportion of the 2CaO-SiO2 calculated by the

Bogue formula in the cement clinker of the present

invention is 5% to 25% by mass. When the proportion of the

2CaO'SiO2 calculated by the Bogue formula is less than 5% by

mass, the proportion of the 3CaO-SiO2 becomes high as a

result, and the heat of hydration of a cement composition

may become too high in some cases. Also, when the

proportion of the 2CaO'SiO2 calculated by the Bogue formula

becomes more than 25% by mass, a short-term strength of

concrete or mortar expressed by a cement composition may

become too low in some cases. The proportion of the

2CaO'SiO2 calculated by the Bogue formula is preferably 10%

to 25% by mass, more preferably 11% to 23% by mass, and

still more preferably 12% to 22% by mass.

[0018]

<Total proportion of 3CaO-Al2O3 (C 3 A) and

4CaO-Al 2 0 3 -FeO3 (C 4AF)>

A total proportion of the 3CaO-Al2O3 and the

4CaO-Al2O3-FeO3 calculated by the Bogue formula in the

cement clinker of the present invention is 15% to 22% by

mass. When the total proportion of the 3CaO-Al2O3 and the

4CaO-Al2O3-FeO3 calculated by the Bogue formula is less than

15% by mass, since the amount of a liquid phase generated

during calcining of cement clinker is reduced, a solid

phase-liquid phase reaction due to liquid phase

intervention may not proceed rapidly, and the cement clinker may be insufficiently calcined in some cases. In addition, since dust is scattered during cement kiln and radiant heat from a burner is blocked, the cement clinker may not be calcined efficiently in some cases. In addition, when the total proportion of the 3CaO-A1203 and the

4CaO-Al2O3-FeO3 calculated by the Bogue formula is more than

22% by mass, since poor operation is likely to occur, and

at the same time and production of calcium silicate

minerals that contribute to strength is reduced, the

strength of a cement composition using the cement clinker

of the present invention may be reduced in some cases. In

addition, heat of hydration of a cement composition may

become too high in some cases. The total proportion of the

3CaO-Al2O3 and the 4CaO-Al2O3-FeO3 calculated by the Bogue

formula is preferably 17% to 22% by mass, more preferably

18% to 22% by mass, and still more preferably 18% to 20% by

mass.

[0019]

<Proportion of 3CaO-A1203 (C 3 A)>

The proportion of the 3CaO-A1203 calculated by the

Bogue formula in the cement clinker of the present

invention is preferably 5.5% to 12.5% by mass, more

preferably 7% to 12% by mass, and still more preferably 8%

to 11% by mass. When the proportion of the 3CaO-Al2O3

calculated by the Bogue formula is within the above range, a decrease in viscosity of the liquid phase generated during calcining of the cement clinker is suppressed, and granulation of the cement clinker is appropriately proceeded, because it is possible to suppress a layer pressure in a clinker cooler from becoming inconsistent due to a reduction in a particle size of the cement clinker and to reduce the heat of hydration. When the layer pressure in the clinker cooler is not constant, interference with quenching of cement clinker may occur in some cases.

[0020]

<Proportion of 4CaO-Al2O3-FeO3 (C 4AF)>

The proportion of the 4CaO-Al2O3-FeO3 calculated by the

Bogue formula in the cement clinker of the present

invention is preferably 8.5% to 12.5% by mass, more

preferably 9.0% to 11.5% by mass, and still more preferably

9.5% to 11.0% by mass. When the proportion of the

4CaO-Al2O3-FeO3 calculated by the Bogue formula is within

the above range, the strength exhibited by the cement

composition can be further increased and the heat of

hydration can be further reduced.

[0021]

<Trace components>

The cement clinker of the present invention contains

MgO, TiO 2 , MnO, and ZnO, as trace components. Each content

of the MgO, the TiO 2 , and the MnO is measured in accordance with JIS R 5204:2019 "Analysis method for cement by X-ray fluorescence". The content of the ZnO is measured in accordance with JCASI-53: 2018 "method for quantifying trace components in cement".

The MgO is introduced into the cement clinker, for

example, by using a slag containing a large amount of MgO

as a raw material for the cement clinker.

The TiO 2 is introduced into the cement clinker, for

example, by using titanium gypsum or fly ash as a raw

material for the cement clinker.

The MnO is introduced into the cement clinker by

using, for example, a blast furnace slag and a converter

slag as raw materials for the cement clinker.

The ZnO is introduced into the cement clinker, for

example, by using municipal waste incineration ash as a raw

material for the cement clinker.

[0022]

<Content of MgO>

In the present invention, the content of the MgO in

the cement clinker is preferably 0.50% to 2.00% by mass,

more preferably 0.80% to 1.80% by mass, and still more

preferably 0.95% to 1.60% by mass. When the content of the

MgO is within the above range, the cement clinker can be

calcined well and hydration expansion during hardening of

concrete or mortar can be suppressed.

[0023]

In the cement clinker of the present invention, each

content rate (% by mass) of the MgO, the TiO 2 , the MnO, and

the ZnO in 3CaO-Al2O3satisfies the following formula (1).

CMg-C3A X CTi-C3A X CMn-C3A X CZn-C3A 0. 0010 . . . (1)

CMg-C3A: Content rate (% by mass) of MgO in 3CaO•Al2O3

CTi-C3A: Content rate (% by mass) of TiO 2 in 3CaO•Al2O3

CMn-C3A: Content rate (% by mass) of MnO in 3CaO•Al2O3

CZn-C3A: Content rate (% by mass) of ZnO in 3CaO•Al2O3

In formula (1) , CMg-C3A, CTi-C3A, CMn-C3A, and CZn-C3A each

represent a content rate of each component contained in C 3 A

in an actual cement clinker. Formula (1) can be obtained by

multiple regression analysis.

[0024]

The CMg-C3A, the CTi-C3A, the CMn-C3A, and the CZn-C3A can be

determined by the following steps. First, the cement

clinker is subjected to a predetermined treatment, and a

composition image of the cement clinker particle is

observed with an electron probe microanalyzer (EPMA). In

the composition image, each mineral is specified based on

the following characteristics.

(a) C3S: Polygonal particle, light gray, and tens of

pm in size

(b) C2S: Elliptical particle, dark gray, and tens of

pm in size

(c) C 3 A: Amorphous structure found between particles

identified as C 3 S and C 2 S, dark gray, several pm to a dozen

pm in size

(d) C 4AF: Amorphous structure found between particles

identified as C 3 S and C 2 S, white, several pm to a dozen pm

in size

A characteristic X-ray analysis is performed on the

C 3 A specified in accordance with the above index using an

electron probe microanalyzer (EPMA), and the content rates

(% by mass) of the MgO, the TiO 2 , the MnO, and the ZnO in

the C 3 A are determined. In the present invention, the

characteristic X-ray analysis is performed on a plurality

of points in a region specified as the C 3 A in the

composition image, and a point where 1.35 < (CaO content

rate)/(Al 2 0 3 content rate + Fe203 content rate) < 2.2 is

satisfied is adopted as an analysis point. Then, each

average of the measured value of each component at the 20

analysis points is defined as CMg-C3A, CTi-C3A, CMn-C3A, or CZn

C3A.

[0025]

When satisfying Formula (1), a cement clinker having a

low heat of hydration can be obtained. The following two

points can be considered as the reason for this.

Formula (1) represents that the contents of the MgO,

the TiO 2 , the MnO, and ZnO in the C 3 A are small. It is presumed that when the amount of the trace components in the C 3 A is small, activity of the C3 A decreases, and as a result, the heat of hydration is reduced. From the viewpoint of reducing the heat of hydration, a left side of

Formula (1) is preferably 0.0008 or less. On the other

hand, the left side of Formula (1) is preferably 0.0001 or

more from the viewpoint of securing the activity of the C3 A

to some extent and preventing a delay in setting time of

mortar or concrete.

[0026]

Furthermore, a case where the trace components in the

C 3A satisfy Formula (1) means that a relatively large amount

of Mg, Ti, Mn, and Zn are dissolved in other phases. It is

considered that when Mg, Ti, Mn, and Zn are dissolved in

the C 4 AF, Al is easily incorporated into C 4 AF, and

precipitation of the C 3 A becomes relatively small, because

the heat of heat of hydration is reduced.

Although the MnO and the ZnO are extremely trace

amount of components in general Portland cement clinker, it

is considered that an influence of the heat of hydration on

the reduction of the relative precipitation amount of the

C 3 A or a crystal structure in the C 3 A cannot be ignored.

[0027]

In the present invention, the content rate of the

Fe203 in the 3CaO-Al2O3 (C 3 A) (hereinafter, may be referred to as "CFe-C3A" in some cases) is preferably less than 6.32% by mass. The CFe-C3A is obtained from analysis using an electron probe microanalyzer (EPMA), as the CMg-C3A or the like. Specifically, a characteristic X-ray analysis is performed on the C3 A specified by the above steps, using an electron probe microanalyzer (EPMA), and the content rate

(% by mass) of the Fe203 in the C 3 A is determined. Moreover,

an average of the measured value of each component at 20

analysis points is defined as CFe-C3A.

Minerals in an actual cement clinker are formed by

solid-dissolving other components with respect to the main

components of each phase due to the influence of the above

mentioned trace components or manufacture conditions. Most

of the Fe203 is contained in the C 4 AF, but some is also

solid-dissolved in the C 3 A, the C 3 S, and the C2S. Here, it

is presumed as a case where, in a range of a mineral

composition represented by Bogue formula, as the content

rate of the Fe203 contained in the C 3 A, which is an

interstitial phase of actual minerals, is small, the C3 A is

difficult to precipitate and the C 4 AF is easy to

precipitate. That is, the Fe203 and the A1 2 0 3 in the cement

clinker are easily consumed for the precipitation of the

C 4 AF, which leads to a relative reduction in the proportion

of the C3 A in the cement clinker. As described above, when

the content rate of the Fe203 in the C 3 A is less than 6.32% by mass, the precipitation of the C 3 A, which causes an increase in the heat of hydration is suppressed, and an effect of reducing the heat of hydration can be obtained.

The content rate of the Fe203 in the C 3 A is more preferably

6.00% by mass or less, still more preferably 5.90% by mass

or less, and particularly preferably 5.80% by mass or less.

[0028]

In the present invention, the CTi-C3A (content rate of

TiO 2 in C 3 A) is preferably less than 0.24% by mass. As the

content rate of the TiO 2 in the C 3 A decreases, the content

of the Fe203 in the C 3 A also tends to decrease. Therefore,

the proportion of the C4 AF in the cement clinker tends to

increase relatively, and the proportion of the C4 AF tends to

decrease. When the CTi-C3A is within the above range, the

precipitation of the C 3 A can be suppressed and the heat of

hydration can be reduced.

[0029]

The chemical composition of the cement clinker in the

actual minerals can be adjusted by the chemical composition

of the cement clinker, the calcination conditions (heat

history) at the time of manufacturing the cement clinker,

and the like.

[0030]

In order to make it easier to satisfy Formula (1), for

example, each content rate of the A1 2 0 3 , the Fe203, the MgO, the TiO 2 , the MnO, and the ZnO in the cement clinker preferably satisfies Formula (2).

CA1203 X (33.06) + CFe203 X (-8.12) + CMgO x (-48.08)

+ CTi02 X (-163.60) + CMnO x (-390.81) + CZnO x (104.60) <

42.9 ... (2)

In Formula (2), CA1203 is the content rate (% by mass)

of the A1 2 0 3 , CFe203 is the content rate (% by mass) of the

Fe203, CMgO is the content rate (% by mass) of the MgO, CTiO2

is the content rate (% by mass) of the TiO 2 , and CMnO is the

content rate (% by mass) of the MnO, and CznO is the content

rate (% by mass) of the ZnO. The CA1203, the CFe203, the CMgO,

the CTi02, and the CMnO are measured in accordance with JIS R

5204:2019 "Analysis method for cement by X-ray

fluorescence", and the CznO is measured in accordance with

JCAS 1-53:2018 "method for quantifying trace components in

cement". Formula (2) can be obtained by multiple regression

analysis.

[0031]

A coefficient of each section on a left side of

Formula (2) corresponds to contribution of the component to

the heat of hydration. The formula (2) means that the

mineral composition of the interstitial phase changes due

to a combined action of the MgO, the TiO 2 , the MnO, and the

ZnO which are the trace components. In Formula (2), since

the coefficients of the MnO and the ZnO, which are extremely trace amount of components, are high in general

Portland cement clinker, it can be said that the MnO and

the ZnO also affect the composition proportion of minerals

in the interstitial phase. In the present invention, when

the chemical composition of the cement clinker satisfies

Formula (2), it becomes easy to satisfy Formula (1).

[0032]

The calcining conditions include a calcining

atmosphere, a calcining temperature, a cooling rate, and

the like. For example, in a case where the calcining

atmosphere is in a reduced state, in a case where the

calcining temperature is high, or in a case where the

cooling rate is quenching, Formula (1) can be easily

satisfied.

[0033]

[Method for manufacturing cement clinker]

A clinker of the present invention can be

manufactured, for example, as follows.

As a clinker raw material, those containing at least

Mg, Ti, Mn, and Zn, in addition to Ca, Si, Al, and Fe are

used. As long as the raw material contains the above

elements, any form thereof such as an elemental substance,

an oxide, a carbon oxide can be used and mixtures thereof

can be used. Examples of natural raw materials include

limestone, clay, silica stone, and iron oxide raw materials. Examples of industrial raw materials include waste raw materials containing the above elements, a blast furnace slag, fly ash, and the like. Regarding a mixing proportion of the clinker raw materials, the composition of the components corresponds to a target value of the Bogue formula, and the raw material blending is determined as in

Formula (1) in the cement clinker after calcining. For

example, the raw materials are blended because the chemical

composition of the cement clinker satisfies Formula (2).

[0034]

Then, the clinker raw material mixed in a composition

so as to obtain the targeted clinker is calcined under a

predetermined calcining condition and cooled. Firing is

usually performed using an electric furnace, a rotary kiln,

or the like. Examples of a calcining method include a

method including: a first calcining step in which a clinker

raw material is heated and calcined at a predetermined

first calcining temperature for a first calcining time; a

temperature raising step of raising a temperature, after

the first calcining step, from the first calcining

temperature to a predetermined second calcining temperature

over a predetermined temperature raising time; and a second

calcining step of heating and calcining, after the

temperature raising step, at the predetermined second

calcining temperature for a second calcining time. The temperature and time of each step can be set to obtain the cement clinker after calcining which satisfies Formula (1).

For example, the clinker can be manufactured in a manner

that the clinker raw material is heated at a calcining

temperature of 9500C to 11000C (first calcining

temperature) for 30 to 60 minutes (first calcining time) to

perform calcining (first calcining step), and then

temperature is raised to 14200C to 14800C (second calcining

temperature) over 30 to 60 minutes (temperature raising

time) (temperature raising step), and the clinker raw

material is further heated at 14200C to 14800C for 15 to 45

minutes (second calcining time) to perform calcining

(second calcining step), and then a calcined product is

quenched.

[0035]

[Cement composition]

The cement composition of the present invention

contains the cement clinker and gypsum. The Blaine's

specific surface area of a mixture of the cement clinker

and the gypsum is preferably 3000 cm 2 /g or more and 3400

cm 2 /g or less, and more preferably 3100 cm 2 /g or more and

3300 cm 2 /g or less.

<Gypsum>

A proportion of the gypsum in the cement composition

of the present invention is preferably 0.5% to 2.5% by mass, and more preferably 1.0% to 1.8% by mass in terms of

SO 3 equivalent. When setting the proportion of the gypsum

to the range, drying shrinkage of the cement composition

can be made appropriate, and strength exhibited by the

cement composition can be increased. A proportion of SO 3 in

the gypsum can be measured in accordance with JIS R

5202:2010 "Chemical analysis method for Portland cement". A

proportion of the mass of the gypsum converted to SO 3 in the

cement composition can be determined from a blending amount

of the gypsum and the proportion of the SO 3 contained in the

gypsum.

As the gypsum, any of anhydrous gypsum, hemihydrate

gypsum, and dihydrate gypsum can be used.

[00361

<Other components>

Fly ash, blast furnace slag, silica fume, or the like

can be further added to the cement composition of the

present invention in order to control fluidity, a hydration

rate, or strength development. Further, an AE water

reducing agent, a high-performance water reducing agent, or

a high-performance AE water reducing agent, particularly a

polycarboxylate-based high-performance AE water reducing

agent, can be added to the cement composition of the

present invention.

[0037]

[Mortar and concrete]

Cement milk can be prepared by mixing the cement

composition of the present invention with water, mortar can

be prepared by mixing with water and sand, and concrete can

be manufactured by mixing sand and gravel. Further, when

producing the mortar or the concrete from the cement

composition, a blast furnace slag, fly ash, or the like can

be added.

Examples

[0038]

Hereinafter, the present invention will be described

in more detail with reference to examples. However, the

present invention is not limited to the following examples.

1. Measurement and evaluation

1-1. Clinker composition

A chemical composition (content rate of each

component) in cement clinkers of Examples and Comparative

Examples was measured in accordance with JIS R 5204:2019

"Analysis method for cement by X-ray fluorescence" and JCAS

1-53:2018 "Quantification method for trace components in

cement". A mineral composition was calculated from the

obtained mass proportions of CaO, SiO 2 , A1 2 0 3 , and Fe203 by

using the following Bogue formula. Results are shown in

Table 1.

C3S = (4.07 x CaO) - (7.60 x SiO 2 ) - (6.72 x A1 2 0 3 ) -

(1.43 x Fe203)

C2 S = (2.87 x SiO2) - (0.754 x C 3 S)

C3 A = (2.65 x A1 2 0 3 ) - (1.69 x Fe203)

C4AF = 3.04 x Fe203

Further, the value on the left side of Formula (2) was

calculated using the obtained content rate of each

component. Results are shown in Table 2.

[00391

1-2. EPMA measurement

The cement clinker of Examples and Comparative

Examples was pulverized to a particle size of about 1 to 2

mm to adjust the particle size. The obtained particles were

embedded in an epoxy resin, and then the resin surface was

mirror-polished. After the mirror polishing, carbon vapor

deposition was performed on the resin surface to produce a

sample for EPMA measurement.

An EPMAJXA-8200 manufactured by JEOL Ltd. was used as

a measuring device, and a structure image of the cement

clinker particles on the mirror surface of the sample was

observed under the following conditions. In the structure

image, each mineral was specified based on the

characteristics of above (a) to (d).

<EPMA structure image observation conditions>

Acceleration voltage: 15 kV

Irradiation electric current: 3.0 x 10-8 A

[0040]

Characteristic X-ray analysis was performed on a

region identified as the C 3 A under the following conditions,

and a MgO content rate (% by mass), a TiO 2 content rate (%

by mass), a MnO content rate (% by mass), a ZnO content

rate (% by mass), and a Fe203 content rate (% by mass) in

the C 3 A were determined.

<EPMA structure image observation conditions>

- Acceleration voltage: 15 kV

Irradiation electric current: 3.0 x 10-8A

- Beam diameter: Approximately 1 pm

- Correction calculation method: Oxide-ZAF method

The analysis was performed on a plurality of cement

clinker particles in the sample, the content rates (% by

mass) of each component at a total of 20 analysis points

were obtained, and an average value thereof was calculated

as CMg-C3A, CTi-C3A, CMn-C3A, Czn-C3A, and CFe-C3A in C 3 A.

Furthermore, the value on the left side of Formula (1) was

calculated from the obtained content rate of each

component. Results are shown in Table 2.

[0041]

In addition, a characteristic X-ray analysis was

performed on the region specified as the C 4 AF under the same

conditions as above, and the content rate of the Fe203 in

the C 4 AF (% by mass) was determined. In the present invention, a point where a range within 0.8 < (CaO content rate)/ (A1 2 0 3 content rate + Fe203 content rate) < 1.35 was satisfied was adopted as an analysis point, and an average at the 20 analysis points was defined as CFe-C4AF. Results are shown in Table 2.

[0042]

1-3. Powder X-ray diffraction measurement

For the cement clinker of Examples and Comparative

Examples, X-ray diffraction measurement was performed using

a powder X-ray diffractometer (X'Part Power, manufactured

by Panalysis Ltd.) under measurement conditions of a

measurement range: 20 = 100 to 70°, a step size: 0.0170,

scan speed: 0.1012°/s, voltage: 45 kV, and an electric

current: 40 mA to obtain an X-ray diffraction profile.

With respect to the obtained X-ray diffraction

profile, cement clinker minerals were quantified using

software for crystal structure analysis (X'Part HighScore

Plus version 2.1b, manufactured by Panalysis Ltd.) provided

in the powder X-ray diffractometer. The cement clinker

minerals to be analyzed are set to C 3 S-M1 (Ml phase), C 3 S-M3

(M3 phase), C 2 S-a'H (a'H phase), C 2S-@ (p phase), C3A-cubic

(cubic crystal), C3A-ortho (orthorhombic crystal), and C 4AF.

A proportion (% by mass) of each mineral of the cement

clinker was obtained using an analysis function of Rietveld

method installed in the software, in accordance with Joint experiment procedure manual 2 of document "Report C-12 of

Cement Chemistry Expert Committee, Examination of

differences in clinker mineral content due to difference in

measurement methods, Part 2, Chapter 4, Examination of

Quantification by Powder X-ray Diffraction/Rietveld

Analysis". In addition, a total proportion of each mineral

is 100% by mass, and the content rate of the C 3 A (CC3A, % by

mass) and the content rate of the C 4 AF (CC4AF, % by mass) in

each of Examples and Comparative Examples was obtained.

Results are shown in Table 2.

[0043]

1-4. Measurement of heat of hydration

For the cement of Examples and Comparative Examples,

the heat of hydration at 7 days of age and 28 days of age

was measured in accordance with JIS R 5203:2015 "Method for

measuring heat of hydration of cement (heat of dissolution

method)". As reference values, the heat of hydration at 7

days of age was set to 350 J/g, and the heat of hydration

at 28 days of material was set to 400 J/g. Those having a

heat of hydration equal to or less than the reference value

at both 7 days of age and 28 days of age were evaluated as

"A", and those exceeding the reference value at any of the

ages were evaluated as "C". Results are shown in Table 2.

[0044]

1-5. Mortar compressive strength

For mortar specimens obtained from the mortar of

Examples and Comparative Examples, a compressive strength

at 3 days of age was measured in accordance with JIS R

5201:2015 "Physical testing methods for cement". Results

are shown in Table 2.

[0045]

2. Preparation of cement composition

2-1. Clinker

As raw materials for the cement clinker, calcium

carbonate (manufactured by Kishida Chemical Co., Ltd.,

reagent first grade, CaCO3), silicon dioxide (manufactured

by Kanto Chemical Co., Ltd., reagent first grade, SiO 2 ),

aluminum oxide (manufactured by Kanto Chemical Co., Ltd.,

reagent first grade, A1 2 0 3 ), iron oxide (III) (manufactured

by Kanto Chemical Co., Ltd., reagent special grade, Fe203),

basic magnesium carbonate (manufactured by Kishida Chemical

Co., Ltd., reagent special grade, 4MgCO3-Mg(OH)2-5H20),

sodium carbonate (manufactured by Kishida Chemical Co.,

Ltd., special grade, Na2CO3), potassium carbonate

(manufactured by Kanto Chemical Co., Ltd., reagent first

grade, K 2 CO 3 ), calcium sulfate dihydrate (manufactured by

Kishida Chemical Co., Ltd., reagent first grade,

CaSO4-2H20), titanium dioxide (manufactured by Kanto

Chemical Co., Ltd., reagent special grade, TiO 2 ), tricalcium

phosphate (manufactured by Kishida Chemical Co., Ltd., reagent first grade, Ca3(PO4)2), manganese oxide

(manufactured by Kanto Chemical Co., Ltd., Cica first

grade, MnO2), and zinc oxide (manufactured by Kanto Chemical

Co., Ltd., reagent special grade, ZnO) were used.

[0046]

The raw materials blended with varying the blending

amount were put into an electric furnace and calcined at

10000C for 30 minutes. Then, a temperature was raised from

10000C to 14500C over 45 minutes, and further calcined at

14500C for 30 minutes. Then, the calcined product was

quenched by taking the calcined product into an atmosphere

to prepare cement clinkers of Examples 1 to 9 and

Comparative Examples 1 and 2.

[0047]

2-2. Preparation of cement composition

Semi-hydrated gypsum (manufactured by Kanto Chemical

Co., Inc., semi-hydrated gypsum, model number: 07108-01

(calcined gypsum deer first grade) with SO 3 equivalent

amount of 1.5% by mass) was blended with the prepared

cement clinker. The compound was pulverized with a ball

mill because the Blaine's specific surface area value

became in a range of about 3200 ± 200 cm 2 /g to prepare

cement compositions of Examples 1 to 9 and Comparative

Examples 1 and 2.

[0048]

2-3. Preparation of mortar

Mortar was adjusted from the cement compositions of

Examples and Comparative Examples in accordance with JIS R

5201:2015 "Physical testing methods for cement". The

obtained mortar was cast into three metal molds having a

size of 40 mm x 40 mm x 160 mm, and after 24 hours, the

mortar was demolded to prepare three specimens. Thereafter,

the specimen was cured in water at 200C until 3 days of age

to obtain mortar specimens of each of Examples and

Comparative Examples.

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Claims (5)

1. A cement clinker comprising:

3CaO•SiO2 in a proportion, calculated by Bogue

formula, of 50% to 75% by mass;

2CaO•SiO2 in a proportion, calculated by Bogue

formula, of 5% to 25% by mass;

3CaO•Al2O3 and 4CaO•Al2O3•Fe2O3 in a total proportion,

calculated by Bogue formula, of 15% to 22% by mass;

MgO;

TiO 2 ;

MnO; and

ZnO,

wherein Formula (1) is satisfied,

CMg-C3A X CTi-C3A X CMn-C3A X CZn-C3A 0 • 0010 ... (1)

in Formula (1),

CMg-C3A represents a content rate (% by mass) of MgO in

3CaO•A1203,

CTi-C3A represents a content rate (% by mass) of TiO 2 in

3CaO•A1203,

CMn-C3A represents a content rate (% by mass) of MnO in

3CaO•A1203, and

CZn-C3A represents a content rate (% by mass) of ZnO in

3CaO•Al2O3.

2. The cement clinker according to claim 1,

wherein a content rate of Fe203 in 3CaO•Al2O3 is less

than 6.32% by mass.

3. The cement clinker according to claim 1 or 2,

wherein the content rate of TiO 2 is less than 0.24% by

mass.

4. A cement composition comprising:

the cement clinker according to any one of claims 1 to

3; and

gypsum.

5. A method for manufacturing a cement clinker,

comprising:

a step of blending raw materials; and

a step of calcining the raw materials blended,

wherein a cement clinker after calcining contains

3CaO•SiO2 in a proportion, calculated by Bogue

formula, of 50% to 75% by mass,

2CaO•SiO2 in a proportion, calculated by Bogue

formula, of 5% to 25% by mass,

3CaO•Al2O3 and 4CaO•Al2O3•Fe2O3 in a total

proportion, calculated by Bogue formula, of 15% to 22% by

mass,

MgO,

TiO 2

, MnO, and

ZnO, and

Formula (1) is satisfied,

CMg-C3A X CTi-C3A X CMn-C3A X CZn-C3A : 0 01 ... (1)

in Formula (1),

CMg-C3A represents a content rate (% by mass) of MgO in

3CaO•A1203,

CTi-C3A represents a content rate (% by mass) of TiO 2 in

3CaO•A1 2 03 ,

CMn-C3A represents a content rate (% by mass) of MnO in

3CaO•A1203, and

CZn-C3A represents a content rate (% by mass) of ZnO in

3CaO•Al2O3.