JP2021160985A - Cement composition and cement composition production method, and durability-enhancing admixture - Google Patents

Abstract

To provide a cement composition suppressing expansion with DEF even when there is a large content of an admixture, and having sufficient compressive strength development in a high temperature environment.SOLUTION: Provided is a cement composition containing cement clinker, gypsum and an admixture. The admixture includes inorganic powder including an amorphous phase, and limestone. The inorganic powder has a chemical composition including CaO, SiO2 and Al2O3, and on the basis of the total amount of the inorganic powder, the amount of CaO is 6.0-40.0 mass%, the amount of SiO3 is 35.0-75.0 mass%, and the amount of Al2O3 is 14.0-25.0 mass%. The content of the admixture based on the total amount of the cement clinker, the gypsum and the admixture is 2.0-30.0 mass%, the content of the inorganic powder is 1.0-29.0 mass%, and the content of the limestone is 1.0-10.0 mass%.SELECTED DRAWING: None

Description

The present disclosure relates to a cement composition, a method for producing the same, and a mixture for improving durability.

From the viewpoint of preventing global warming and reducing carbon dioxide, it is desired to increase the content of the mixture in the cement composition instead of the cement clinker that emits a large amount _{of CO 2 during production.} As the mixing material, an inorganic powder having excellent reactivity when used together with a cement composition has been used. These inorganic powders contain a large amount of amorphous substances, and for example, blast furnace slag and fly ash are used. However, in order to further expand the use of the mixed material, it is also desired to expand the options of the available inorganic powders.

Examples of inorganic powders that have not been used as a mixing material so far include crushed coal gasified slag. Coal gasification slag is a non-crystalline inorganic powder having a large amount of CaO solidified by melting ash in coal after combustion in integrated coal gasification combined cycle power generation. Integrated coal gasification combined cycle power generation is more efficient than conventional coal-fired power generation and _{emits less CO 2} , so it is expected to become widespread in the future. However, at the same time, it is necessary to consider effective utilization measures for coal gasification slag produced as a by-product. Patent Document 1 discloses that a cement composition containing 40% by mass of belite and fly ash and / or coal gasified slag powder improves strength development and flow value at room temperature. However, the manifestation of strength in a high temperature environment when using coal gasified slag powder is unknown.

In recent years, in relation to the durability of hardened cement, delayed ettringite formation (DEF) in concrete structures and secondary products of steam curing under high temperature environment and deterioration of hardened cement due to DEF have been regarded as problems. (For example, Non-Patent Document 1). DEF refers to the following ettringite regeneration phenomenon. First, as represented by the heat generation of the initial high-temperature curing and cement compositions, that the temperature inside the concrete is increased significantly, in the original ettringite to be initially generated _{(3CaO · Al 2 O 3 ·} 3CaSO 4 · 32H 2 O Decomposition of compound) occurs. After that, when water is supplied during the operation of concrete, a phenomenon occurs in which ettringite is regenerated. Further, it is known that ettringite expands with crystallization, and DEF causes expansion of the cured body structure, causing serious deterioration such as cracks in concrete.

As a measure for suppressing DEF, Non-Patent Document 2 reports that by adding 25% by mass of coal ash (fly ash), expansion can be suppressed even under conditions where DEF is likely to occur. However, there is no document that describes the effect of inorganic powder containing a large amount of amorphous material such as coal gasified slag powder on DEF in a mixed material other than slag and fly ash.

Japanese Unexamined Patent Publication No. 11-139860

Yuichiro Kawabata, Hiromichi Matsushita, "Study on DEF expansion in concrete cured at high temperature", JSCE Proceedings E2 (Material / Concrete Structure), 2011, Vol. 67, No. 4, p. 549-563 Shingo Asamoto et al., "Study on the effect of carbonate ions on delayed ettringite formation", Annual Proceedings of Concrete Engineering, 2016, Vol. 28, No. 1, p. 819-824

The present disclosure provides a cement composition and a method for producing the same, which suppresses expansion associated with DEF even when the content of the mixed material is large and has sufficient compressive strength development in a high temperature environment. The purpose. The present disclosure is also intended to provide a durability-enhancing mixture that can be used to produce cement compositions such as those described above.

One aspect of the present disclosure contains cement clinker, gypsum, and a mixture, wherein the mixture contains an inorganic powder containing an amorphous phase and limestone, and the inorganic powder is CaO, SiO ₂ It _{has a chemical composition containing Al 2} O ₃ and, based on the total amount of the above inorganic powder, the amount of CaO is 6.0 to 40.0% by mass, the _{amount of SiO 3} is 35.0 to 75.0% by mass, and The _{amount of Al 2} O ₃ is 14.0 to 25.0 mass%, and the content of the mixed material based on the total amount of the cement clinker, the plaster and the mixed material is 2.0 to 30.0 mass. %, The content of the inorganic powder is 1.0 to 29.0% by mass, and the content of the limestone is 1.0 to 10.0% by mass.

The cement composition contains a cement clinker, gypsum, an inorganic powder having a specific chemical composition and containing an amorphous phase, and limestone in a specific composition, and therefore contains an admixture, but DEF. It is possible to prepare a hardened cement product that suppresses the expansion associated with the above and has excellent compressive strength in a high temperature environment.

The content of the inorganic powder based on 100% by mass of the mixed material may be 5.0 to 95.0% by mass. When the content of the mixed material is within the above range, the CO ₂ reduction effect at the time of cement production and the compressive strength of the hardened cement can be sufficiently compatible with each other.

The chemical composition of the inorganic powder may further contain MgO, and the amount of MgO based on the total amount of the inorganic powder may be 5.0% by mass or less. When the amount of MgO is within the above range, excellent strength development can be obtained.

The chemical composition of the inorganic powder _{may further contain SO 3, and the amount of SO 3 based on} the total amount of the inorganic powder may be 1.0% by mass or less. When the _{amount of SO 3} is within the above range, the expansion of the hardened cement material due to DEF can be suppressed.

The brain specific surface area of the inorganic powder ^{may be 2000 to 10000 cm 2} / g. When the brain specific surface area of the inorganic powder is within the above range, the expansion of the hardened cement material due to DEF can be further suppressed.

The amount of the amorphous phase in 100% by mass of the inorganic powder may be 80.0 to 100.0% by mass. When the amount of the amorphous phase in the inorganic powder is within the above range, the reactivity can be enhanced and excellent strength development can be obtained.

The inorganic powder may contain a pulverized product of coal gasified slag. When the inorganic powder contains a pulverized product of coal gasified slag, the effect of suppressing the expansion of the hardened cement product associated with DEF and the excellent strength development can be obtained.

The cement clinker is a _{C 3} S amount calculated by the Bogue formula from 35.0 to 75.0 wt%, _{C 3} A content may be 8.0 to 15.0 wt%. When the cement clinker has the above-mentioned mineral composition, the amount of waste used as the clinker raw material can be increased. In addition, the expansion of the hardened cement body due to DEF can be suppressed.

Based on the total amount of the cement clinker and the gypsum content of the gypsum may be from 0.5 to 3.0 wt% with SO ₃ amount conversion. When the content of gypsum is within the above range, it is possible to sufficiently secure the pot life while suppressing the generation of DEF.

The cement clinker _{contains SO 3} and R _{2 O, and the amount of SO 3} is 0.10 to 2.0% by mass and the _{amount of R 2} O is 0.10 to 2.0 in 100% by mass of the cement clinker. It may be% by mass. When the _{amount of SO 3 and the} amount of R ₂ O in the cement clinker are within the above ranges, it is possible to further increase the amount of waste used during firing of the cement clinker, and it can be obtained from the cement composition containing the cement clinker. DEF in the hardened cement product can be further suppressed.

The cement composition further contains a curing accelerator, and the content of the curing accelerator is 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the total amount of the cement clinker, the gypsum and the mixture. It's okay. When the curing accelerator is contained and the content thereof is within the above range, the curing promoting effect can be sufficiently exerted, and the promotion of coagulation and the decrease in fluidity can be suppressed.

Based on the total amount of the inorganic powder, the amount of CaO in the amorphous phase of the inorganic powder is 6.0 to 40.0% by mass, and the _{amount of SiO 2} is 35.0 to 75.0% by mass. , Al ₂ O ₃ amount may be 14.0 to 25.0% by mass. When the chemical composition of the inorganic powder is the chemical composition in the amorphous phase, the effect of suppressing the expansion of the hardened cement product associated with DEF and the excellent strength development can be obtained.

One aspect of the present disclosure comprises a step of mixing a cement clinker, a plaster, and a mixing material, wherein the mixing material contains an inorganic powder containing an amorphous phase and limestone, and the inorganic powder is CaO. , SiO ₂ and Al ₂ O _3, and based on the total amount of the above inorganic powder, the amount of CaO is 6.0 to 40.0% by mass, and the _{amount of SiO 3} is 35.0 to 75.0% by mass. % And Al ₂ O ₃ amount is 14.0 to 25.0% by mass, and in the above step, the content of the above-mentioned mixture based on the total amount of the above-mentioned cement clinker, the above-mentioned plaster and the above-mentioned mixture is 2. Cement so that the content of the inorganic powder is 1.0 to 29.0% by mass and the content of limestone is 1.0 to 10.0% by mass. Provided is a method for producing a cement composition, which comprises mixing clinker, the plaster and the mixture.

The method for producing the cement composition includes a step of having a cement clinker, gypsum, an inorganic powder having a specific chemical composition and containing an amorphous phase, and limestone in a specific composition, and is an admixture. However, it is possible to produce a cement composition capable of suppressing expansion due to DEF and preparing a hardened cement product having excellent compressive strength in a high temperature environment.

One aspect of the present disclosure is a durability-enhancing mixed material containing an inorganic powder containing a non-crystalline phase and limestone, and the inorganic powder has a chemical composition containing _{CaO, SiO 2} and Al ₂ O _3. and, based on the total amount of the inorganic powder, CaO amount is 6.0 to 40.0 wt%, SiO ₃ weight 35.0 to 75.0 wt%, and _Al 2 _{O 3} amount is from 14.0 to 25 It is 0.0% by mass, and the content of the inorganic powder is 1.0 to 29% by mass and the content of the limestone is 1 when the total amount of cement clinker, gypsum and the durability improving mixture is 100% by mass. Provided is a durability-enhancing mixed material used by blending with cement clinker and gypsum so as to have a content of .0 to 10.0% by mass.

Since the above-mentioned durability-enhancing mixed material contains a specific inorganic powder and limestone and is mixed and used in a predetermined blending ratio with cement clinker and gypsum, the above-mentioned cement composition can be easily produced. can do.

According to the present disclosure, it is possible to provide a cement composition and a method for producing the same, which suppresses expansion due to DEF and has sufficient compressive strength development in a high temperature environment even when the content of the mixed material is large. .. The present disclosure also provides a durability-enhancing mixture that can be used to produce the cement compositions described above.

Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. In the following description, when "X to Y" (X and Y are arbitrary numbers) is described, it means "X or more and Y or less" unless otherwise specified.

One embodiment of the cement composition comprises a cement clinker, gypsum, and a mixture.

The content of the gypsum in which the total content of the cement clinker, the gypsum and the mixed material is 100% by mass may be 0.5 to 3.5% by mass in terms of _{SO 3.} When the content of gypsum is within the above range, the generation of DEF associated with the hardening of the cement composition can be further reduced. When the content of gypsum is within the above range, the compressive strength of the hardened cement prepared by using the cement composition can be further improved.

The mineral composition of cement clinker can be calculated by the Bogue formula. Here, the Bougue formula is a formula widely used as a formula for calculating the content of major minerals in cement clinker from the content ratio of chemical composition. By using the Bogue formula shown below, the cement clinker in the tricalcium silicate (indicated by _{3CaO · SiO 2, C 3 S} .), Dicalcium silicate (. Indicated by _{2CaO · SiO 2, C 2 S} ), and it is possible to calculate the content of tricalcium aluminate (3CaO _· Al ₂ O 3, shown in C3A.). In addition, "%" in the following formula means "mass%". The chemical formula represents the content ratio (mass%) of each compound indicated by the chemical analysis value by JIS R 5204 "Fluorescent X-ray analysis method of cement".

<Bogue type>
C ₃ S [%] = (4.07 × CaO [%])-(7.60 × SiO ₂ [%])-(6.72 × Al ₂ O ₃ [%])-(1.43 × Fe ₂ O ₃ [%])-(2.85 x SO ₃ [%])
C ₂ S [%] = (2.87 x SiO ₂ [%])-(0.754 x C ₃ S [%])
C ₃ A [%] = (2.65 x Al ₂ O ₃ [%])-(1.69 x Fe ₂ O ₃ [%])
C ₄ AF [%] = 3.04 × Fe ₂ O ₃ [%]

The lower limit of _{C 3} S content in the cement clinker is preferably not less than 35.0 mass%, more preferably not less than 40.0 mass%, still more preferably at least 45.0% by weight, particularly preferably It is 50.0% by mass or more. When _{the lower limit of the amount of C 3} S is within the above range, the initial strength in hardening of the cement composition can be further improved. The upper limit of the _{C 3} S content in the cement clinker is preferably not more than 75.0 wt%, more preferably not more than 70.0 wt%, further preferably not 65.0 mass% or less, even more It is preferably 60.0% by mass or less, and particularly preferably 55.0% by mass or less. By the upper limit of the C 3 _S content is within the above range, more suppress heat generation during curing of the cement composition can suppress the decomposition of the ettringite, it is possible to further suppress the occurrence of DEF. Incidentally, _{C 3} S content is also difficult preparation of cement clinker it exceeds 75.0 mass%.

The lower limit of C _{3 A} content in the cement clinker, although it is preferably 8.0 wt%, more preferably at least 9.0 wt%, more preferably not less than 9.5 mass%, particularly preferably Is 10.0% by mass or more. By the lower limit of C 3 _A content within the above range, it is possible to produce waste by-products usage cement composition having an increased coal ash such as a cement clinker raw material. The upper limit of the _{C 3} A content in the cement clinker, although 14.0 mass% or less, preferably not more than 13.0 wt%, more preferably not more than 12.0 wt%, more preferably 11. It is 0% by mass, particularly preferably less than 10.5% by mass. C ₃ A content may be appropriately adjusted within the above range, for example, be from 8.0 to 14.0 wt%. By the upper limit of the C ₃ A content within the above range, moderate the production of ettringite due to hardening of the cement composition _{(3CaO · Al 2 O 3 ·} 3CaSO 4 · 32H compound represented by the ₂ O) Can be. Further, it is possible to further reduce the increase in the adiabatic temperature rise during curing of the cement composition, suppress the decomposition of ettringite, and further suppress the expansion of the hardened cement due to DEF.

_{The amount of C 3} A and the amount of C ₃ S in the present specification are obtained using the chemical analysis value of cement clinker measured according to the method described in JIS R 5204 “Fluorescence X-ray analysis method of cement”. It means the value calculated by the formula.

Cement clinker may contain _{SO 3} and R _{2 O.}

The amount of SO ₃ in the cement clinker is preferably 0.10 to 2.00% by mass, more preferably 0.25 to 1.60% by mass, still more preferably 0.25 to 1.60% by mass, based on 100% by mass of the cement clinker. It is 0.30 to 0.70% by mass. When the _{amount of SO 3} is within the above range, the amount of waste used at the time of firing the cement clinker can be further increased, and the DEF in the hardened cement obtained from the cement composition containing the cement clinker is further suppressed. can do.

The amount of SO ₃ in the cement clinker means the chemical analysis value of the cement clinker measured according to the method described in JIS R 5204 “X-ray fluorescence analysis method of cement”.

_{R 2} O content in the cement clinker, based on 100% by weight cement clinker, preferably 0.10 to 2.00 wt%, more preferably from 0.20 to 1.60 wt%, more preferably Is 0.25 to 1.25% by mass, and particularly preferably 0.30 to 0.70% by mass. By R 2 _O content is within the above range, it is possible to further increase the amount of waste to be used for cement clinker firing, more the DEF in the cement cured body obtained from the cement composition containing the cement clinker It can be suppressed.

R _{2 O} content in the cement clinker, with a chemical analysis of the cement clinker, as measured in accordance with the method described in JIS R 5204 "fluorescent X-ray analysis method cement" means a value calculated from the following equation do. Incidentally, R 2 _O amount as a total amount of alkali in the cement, are used like the quality standards.
R ₂ O [%] = Na ₂ O [%] +0.658 × K ₂ O [%]

As the gypsum, for example, dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum can be used. One type of gypsum may be used alone, or a plurality of types of gypsum may be used in combination. The content of gypsum in the cement composition, the total content of the cement clinker and the gypsum as 100 mass%, converted to SO _3, preferably 0.5 to 3.0 wt%, more preferably 0 It is .7 to 2.5% by mass, more preferably 0.9 to 2.0% by mass, and particularly preferably 1.1 to 1.6% by mass. When the content of gypsum is within the above range, it is possible to sufficiently secure the pot life while suppressing the generation of DEF. When the content of gypsum is within the above range, the compressive strength of the hardened cement product can be improved.

The mixture contains at least an inorganic powder containing an amorphous phase and limestone. By containing the above-mentioned inorganic powder as a mixed material, it contributes to suppressing the expansion of the hardened cement product due to DEF and improving the compressive strength after long-term high-temperature curing. By containing limestone as a mixed material, _{it contributes to the reduction of CO 2} emissions during cement production and the improvement of the compressive strength of the hardened cement after high temperature curing.

The total content of the mixed materials in the cement composition is preferably high from the viewpoint of low carbonization, while it is desirable to be low from the viewpoint of improving the physical properties (for example, compressive strength) of the hardened cement. desirable. The content of the mixed material in the cement composition is 2.0 to 30.0% by mass based on the total amount of the cement clinker, the gypsum and the mixed material, but is preferably 4.0 to 25. It is 0% by mass, more preferably 5.5 to 20% by mass, further preferably 6.5 to 15.0% by mass, and particularly preferably 7.5 to 12.5% by mass. When the content of the mixed material is within the above range, the CO ₂ reduction effect at the time of cement production and the compressive strength of the hardened cement can be sufficiently compatible with each other.

The inorganic powder has a chemical composition containing _{CaO, SiO 2} and Al ₂ O _3. The chemical composition of the inorganic powder may further contain, for example, MgO, SO _{3 and the like in addition to CaO, SiO 2} and Al ₂ O _3. The chemical composition of the inorganic powder, based on the total amount of the inorganic powder, CaO amount is 6.0 to 40.0 wt%, SiO ₃ weight 35.0 to 75.0 wt%, and _Al 2 _{O 3} amount Is 14.0 to 25.0% by mass. With the above composition, an excellent DEF suppressing effect and a sufficient compressive strength at the time of high temperature curing can be obtained.

The amount of CaO is preferably 7.0 to 35% by mass, more preferably 8.0 to 30.0% by mass, and further preferably 10.0 to 25.0% based on the total amount of the above-mentioned inorganic powder. It is by mass%, more preferably 12.0 to 20.0% by mass, and particularly preferably 14.0 to 18.0% by mass.

The _{amount of SiO 2} is preferably 40.0 to 70.0% by mass, more preferably 45.0 to 65.0% by mass, still more preferably 50.0 to 50.0% by mass, based on the total amount of the inorganic powder. It is 60.0% by mass.

The _{amount of Al 2} O ₃ is preferably 15.0 to 24.0% by mass, more preferably 16.0 to 22.0% by mass, still more preferably 17.2% by mass, based on the total amount of the above-mentioned inorganic powder. It is 0 to 21.0% by mass, and particularly preferably 18.0 to 20.0% by mass.

When MgO is contained in the chemical composition of the inorganic powder, the amount of MgO is preferably 5.0% by mass or less, more preferably 0.2 to 4.5% by mass, based on the total amount of the inorganic powder. Yes, more preferably 0.4 to 4.0% by mass, and particularly preferably 0.6 to 2.0% by mass.

_{When SO 3} is contained in the chemical composition of the inorganic powder, the _{amount of SO 3} is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, based on the total amount of the inorganic powder. It is more preferably 0.6% by mass or less, and particularly preferably 0.4% by mass or less. It is lower SO ₃ content of the inorganic powder is good in terms of DEF suppressed.

The inorganic powder containing a large amount of amorphous material is more preferable. The amount of the amorphous phase in 100% by mass of the inorganic powder is preferably 80.0 to 100.0% by mass, more preferably 85.0 to 100.0% by mass, and further preferably 90.0. It is 100.0% by mass, and particularly preferably 95.0-100.0% by mass. The above-mentioned chemical composition is preferably a composition in an amorphous phase.

Blaine specific surface area of the inorganic powder is preferably 2000~10000cm ² / g, more preferably 3000~10000cm ² / g, and more preferably 3500~8000cm ² / g, particularly preferably 4000~6000cm ^{It is 2} / g. If the brain specific surface area of the inorganic powder is low, the effect of suppressing DEF is low, and if the brain specific surface area is too high, handling may be poor. The brain specific surface area can be adjusted, for example, by classifying and crushing an inorganic powder. Further, the crushed inorganic powder and the classified inorganic powder may be mixed and adjusted. The classification of the inorganic powder can be performed by, for example, air classification, electrostatic classification, sieving classification, gravitational field classification, centrifugal force field classification, and the like. The method for pulverizing the inorganic powder is not particularly limited, and for example, equipment such as a ball mill, a jet mill, a rod mill, a blade mill, and a vertical mill can be used.

“Brain specific surface area” as used herein means a value measured according to the method described in JIS R 5201: 2015 “Physical test method for cement”.

As the inorganic powder, for example, a crushed product of coal gasified slag discharged from a coal-fired power plant can be preferably used. Coal gasification slag is non-crystalline inorganic particles with a large amount of CaO that are solidified by melting ash in coal after combustion in integrated coal gasification combined cycle power generation. The coal gasification slag may be pulverized by using, for example, a ball mill, a jet mill, a rod mill, a blade mill, a vertical mill, or the like, and the coal gasification slag powder can be obtained by pulverization. The coal gasified slag may be pulverized at the same time as limestone, cement clinker, etc., or may be pulverized separately.

As the inorganic powder other than the crushed product of coal gasification slag, for example, as a power generation boiler fuel for a coal-fired power plant, coal, which is the main fuel, and biomass fuel derived from wood chips, coconut shells, sewage sludge, etc. are co-fired. Examples include ash obtained in some cases. In addition, natural pozzolan such as volcanic ash, clinker ash, chlorine bypass dust and the like can also be used.

Even if the material cannot be used alone, it may be used as long as the components are adjusted by mixing and pulverizing and the above requirements for the inorganic powder are satisfied. For example, even if the amount of material such as coal gasified slag powder, biomass combustion ash, natural pozolan, clinker ash, chlorine bypass dust, coal ash, and blast furnace slag fine powder alone cannot be used as the above-mentioned inorganic powder, it is mixed and crushed. , Can be used as an inorganic powder by adjusting the components.

The lower limit of the content of the inorganic powder is preferably 5.0% by mass or more, more preferably 12.5% by mass or more, still more preferably 35.0% by mass, based on 100% by mass of the mixed material. % Or more, and particularly preferably 60.0% by mass or more. The upper limit of the content of the inorganic powder is preferably 95.0% by mass or less, more preferably 92.5% by mass or less, still more preferably 90.0% by mass, based on 100% by mass of the mixed material. % Or less, particularly preferably 87.5% by mass or less. The content of the inorganic powder can be appropriately adjusted within the above range, and may be, for example, 5.0 to 95.0% by mass based on 100% by mass of the mixed material. The content of the inorganic powder is within the above range, and the effect of suppressing DEF can be improved by containing a large amount of the inorganic powder. By containing an appropriate amount of limestone, it contributes to the improvement of strength after high temperature curing.

The content of the inorganic powder is 1.0 to 29.0% by mass, preferably 3.0 to 20.0% by mass, based on the total amount of the cement clinker, the plaster and the mixture. Yes, more preferably 5.5 to 15.0% by mass, still more preferably 5.0 to 9.0% by mass.

As the limestone, for example, commercially available limestone powder and powder containing calcium carbonate as a main component such as cold water stone powder can be used. The limestone preferably contains one that conforms to the small amount of mixed components described in JIS R 5210 "Portland cement".

The brain specific surface area of limestone is preferably 2500 to 10000 cm ² / g, more preferably 4000 to 9000 cm ² / g, and ^{even more preferably 6000 to 8000 cm 2} / g. When the brain specific surface area of limestone is 2500 cm ² / g or more, the reactivity of the cement composition can be improved. When the brain specific surface area of limestone is 10,000 cm ² / g or less, deterioration of handleability can be suppressed.

The content of limestone is preferably low from the viewpoint of suppressing DEF, while it is desirable to be high from the viewpoint of low carbon dioxide including reduction _{of CO 2 generation in the production of cement composition.} The content of limestone is 1.0 to 10.0% by mass, preferably 2.0 to 9.0% by mass, based on the total amount of the cement clinker, the gypsum and the mixture. It is more preferably 2.4 to 12.5% by mass, and even more preferably. It is 5 to 10.0% by mass. When the content of limestone is within the above range, heat generation due to hydration of the cement composition can be reduced, decomposition of ettringite can be further suppressed, and the strength of the hardened cement can be further increased. When the content of limestone is within the above range, the initial and long-term strength development of the hardened cement product can be further improved.

A mortar composition or a concrete-forming composition can be produced by adding a fine aggregate, a coarse aggregate, water and / or an admixture, a curing accelerator, or the like to the above-mentioned cement composition. The mortar and concrete formed by using the above-mentioned cement composition can exhibit excellent adiabatic temperature rise suppression, strength enhancement, and DEF suppression effects.

As the fine aggregate, the fine aggregate specified in JIS A 5005 “Crushed stone and sand for concrete” can be used. Examples of the fine aggregate include river sand, land sand, sea sand, crushed sand, silica sand, hard blast furnace slag fine aggregate, blast furnace slag fine aggregate, copper slag fine aggregate, electric furnace oxidized slag fine aggregate and the like. Be done. As the fine aggregate, one type may be used alone, or a plurality of types may be used in combination. The content of the fine aggregate in the above-mentioned cement composition may be, for example, 50 to 500 parts by mass with respect to 100 parts by mass of the total amount of the above-mentioned cement clinker, the above-mentioned gypsum and the above-mentioned mixture.

As the coarse aggregate, the coarse aggregate specified in JIS A 5005 “Crushed stone and sand for concrete” can be used. Examples of the coarse aggregate include gravel, crushed stone, blast furnace slag coarse aggregate, and electric furnace oxidized slag coarse aggregate. As the coarse aggregate, one type may be used alone, or a plurality of types may be used in combination. The content of the coarse aggregate in the above-mentioned cement composition is preferably 50 to 500 parts by mass with respect to 100 parts by mass of the total amount of the above-mentioned cement clinker, the above-mentioned gypsum and the above-mentioned mixed material.

Examples of water include tap water, distilled water, deionized water and the like. The content of water in the above-mentioned cement composition is preferably 20 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the total amount of the cement clinker, the gypsum and the mixture. By setting the water content in the cement composition within the above range, it is possible to sufficiently secure predetermined fresh properties (fluidity, air content, etc.) and moldability, and the compressive strength of the obtained hardened cement product can be sufficiently ensured. It is also possible to sufficiently suppress a decrease in durability and durability.

Examples of the admixture include an AE agent, a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, a fluidizing agent, a defoaming agent, a shrinkage reducing agent, a coagulation accelerator, a coagulation retarder, and an increase. Examples include thickeners. As the admixture, one type may be used alone or a plurality of admixtures may be used in combination depending on the required performance. The content of the admixture in the above-mentioned cement composition is preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the total amount of the above-mentioned cement clinker, the above-mentioned gypsum and the above-mentioned mixture.

Examples of the curing accelerator include potassium sulfate, sodium sulfate, lithium sulfate, anhydrous gypsum, fresh lime, slaked lime, calcium nitrite, calcium nitrate, calcium chloride, alkali aluminate, alkali carbonate, triethanolamine, triisopropanolamine, and methyl. Examples thereof include diethanolamine, diethanolisopropanolamine, calcium formate, maleic anhydride, calcium rodaneate, CSH nanoparticles, calcium thiocyanate and the like. As the curing accelerator, one type may be used alone, or a plurality of types may be used in combination.

The content of the hardening accelerator in the above-mentioned cement composition is preferably 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the total amount of the above-mentioned cement clinker, the above-mentioned plaster and the above-mentioned mixture, and more preferably. Is 3.0 to 15.0 parts by mass, more preferably 6.0 to 10.0 parts by mass or less. When the content of the curing accelerator is within the above range, the curing promoting effect can be sufficiently exerted, and the promotion of coagulation and the decrease in fluidity can be suppressed.

The brain specific surface area of the above-mentioned cement composition is preferably 3000 to 5000 cm ² / g, more preferably 3100 to 4500 cm ² / g, and further preferably 3150 to 4000 cm ² / g. When the brain specific surface area is 3000 cm ² / g or more, the strength development at the time of demolding is improved, and when it is 5000 cm ² / g or less, the initial hydration heat generation is lowered and the DEF can be further suppressed.

The mixed material in the above-mentioned cement composition can be used to improve the durability of the hardened cement body by itself, and can be said to be a durability-enhancing mixed material. The durability-enhancing mixture contains an inorganic powder containing an amorphous phase and limestone. The inorganic powder has a _{chemical composition containing CaO, SiO 2} and Al ₂ O _3, and the amount of CaO is 6.0 to 40.0% by mass and the _{amount of SiO 3} is 35. Based on the total amount of the inorganic powder. _{The amount of Al 2} O ₃ is 0 to 75.0% by mass, and the amount of Al 2 O 3 is 14.0 to 25.0% by mass. The durability-enhancing mixed material has a content of the inorganic powder of 1.0 to 29% by mass, where the total amount of the cement clinker, gypsum and the durability-improving mixed material is 100% by mass, and contains the limestone. It is used by blending with cement clinker and gypsum so that the amount is 1.0 to 10.0% by mass.

The above-mentioned cement composition can be produced, for example, by the following method. One embodiment of the method for producing a cement composition includes a step (mixing step) of mixing a cement clinker, gypsum, and a mixing material. The mixed material contains an inorganic powder containing an amorphous phase and limestone, and the inorganic powder has a _{chemical composition containing CaO, SiO 2} and Al ₂ O _3, and is based on the total amount of the inorganic powder. CaO amount is 6.0 to 40.0 wt%, SiO ₃ weight 35.0 to 75.0 wt%, and _Al 2 _{O 3} amount is 14.0 to 25.0 wt%, in the step, The content of the mixed material based on the total amount of the cement clinker, the plaster and the mixed material is 2.0 to 30.0% by mass, and the content of the inorganic powder is 1.0 to 29.0% by mass. The cement clinker, the plaster and the mixture are mixed so that the content of the limestone is 1.0 to 10.0% by mass.

The mixing order of the various components in the mixing step may be appropriately adjusted, for example, the cement clinker and gypsum may be mixed first to prepare the base cement, and then the mixed material may be mixed, and the cement clinker, gypsum and mixed material may be mixed. May be mixed at once. The mixing step may also serve as a crushing step of crushing various components. For example, the above-mentioned production method may include a mixing step in which cement clinker, gypsum, and a mixing material are put into a crusher and mixed and crushed. Since the mixing step is a step of mixing and pulverizing the cement clinker, gypsum, and the mixed material, it is possible to produce a cement composition excellent in the effect of suppressing DEF.

Mixing of various components in the mixing step may be performed using, for example, a mixer such as a pan-type mixer, a tilting mixer, or a ribbon mixer.

Although some embodiments have been described above, the present disclosure is not limited to the above embodiments. In addition, the contents of the description of the above-described embodiments can be applied to each other.

Hereinafter, the contents of the present disclosure will be described in more detail with reference to Examples and Comparative Examples. However, the present disclosure is not limited to the following examples.

[Preparation of base cement (mixture of cement clinker and gypsum)]
Table 1 shows the base cements (NC1 to NC3) used in Examples and Comparative Examples described later. For the base cements (NC1 to NC3), first add dihydrate gypsum to the cement clinker without adding a small amount of admixture, and then use a ball mill to make ^{the brain specific surface area 3300 ± 100 cm 2 / g.} Prepared by crushing. _{The amount of dihydrate gypsum was adjusted and added so that the total amount of SO 3} in the base cement was 1.9% by mass ± 0.1% by mass.

Table 1 shows the brain specific surface area of the base cement, the chemical composition, and the mineral composition of the cement clinker calculated by the Bougue formula. The brain specific surface area of the base cement was determined based on JIS R 5201 “Physical test method for cement”. The chemical composition of the base cement and the mineral composition of the cement clinker were analyzed based on the fluorescent X-ray analysis method of JIS R 5204 "Fluorescent X-ray analysis method of cement". Simultix 12 manufactured by Rigaku Co., Ltd. was used for fluorescent X-ray analysis.

[Inorganic powder (coal gasification slag: IGCC slag)]
Tables 2 and 3 show the inorganic powders (IG1 and IG2) used in Examples and Comparative Examples described later. The inorganic powder was used after crushing the same coal gasified slag collected from a thermal power plant with a ball mill.

[Lime stone]
Table 2 shows the limestone (CC) used in Examples and Comparative Examples described later. As the limestone, a 325 mesh product (for passing through a 45 μm sieve) manufactured by Ube Material Industries Ltd. was used. The 325 mesh product has a specific surface area of 7470 cm ² / g, a calcium carbonate content of 90% by mass or more, an aluminum oxide content of 1.0% by mass or less, and a small amount of JIS R 5210: 2019 "Portland cement". The one suitable for the mixed component was used.

[Blast furnace slag fine powder]
Tables 2 and 3 show the blast furnace slag fine powder (BS) used in Examples and Comparative Examples described later. As the blast furnace slag fine powder (BS), a commercially available blast furnace slag fine powder (brain specific surface area 4180 cm ² / g) was used.

Table 2 shows the brain specific surface area and chemical composition of the mixed materials (inorganic powder, limestone, and blast furnace slag fine powder). The brain specific surface area was determined based on JIS R 5201 “Physical test method for cement”. The chemical composition was analyzed based on the fluorescent X-ray analysis method of JIS R 5204 "Fluorescent X-ray analysis method for cement". Simultix 12 manufactured by Rigaku Co., Ltd. was used for fluorescent X-ray analysis.

Table 3 shows the ratio of the chemical composition in the amorphous phase based on the amorphous amount of the mixed material (inorganic powder and blast furnace slag fine powder) and the total amount of the mixed material. Since no peak corresponding to the crystal quality was observed in the inorganic powder (coal gasification slag) by X-ray diffraction measurement, it was judged that the total amount was an amorphous phase (amorphous amount was 100% by mass). Blast furnace slag is assumed from the peaks other than gypsum was observed in X-ray diffraction measurement, the SO ₃ component and all gypsum derived, non by subtracting the weight ratio of gypsum The crystal mass was determined. As the X-ray diffractometer, D2PHASER (Bruker AXS Co., Ltd.) was used.

[Fine aggregate]
In the DEF test and activity index measurement, standard sand for cement strength test of Cement Association (one company) was used as the fine aggregate.

(Examples 1 to 6, Comparative Examples 1 to 6, and Reference Example 1)
A cement composition was prepared by mixing and pulverizing cement, inorganic powder (coal gasification slag), limestone, and blast furnace slag fine powder in the blending ratio (mass%) shown in Table 4.

Using each cement composition prepared in Examples and Comparative Examples, a DEF test and a measurement of compressive strength were performed.

[DEF test]
(Preparation of mortar composition)
First, the cement compositions prepared in Examples and Comparative Examples were mixed with standard sand for cement strength test of the Cement Association (one company) as a fine aggregate and water, and JIS R 5201: 2015 " A mortar composition was prepared according to the method described in "Physical test method for cement". The composition of the mortar composition is shown in Table 5.

(DEF test)
In the DEF test, potassium sulfate was added as a curing accelerator to the above-mentioned mortar composition _{, adjusted so that the total amount of SO 3} in the cement composition was 6% by mass, and further, the preparation at a high temperature of 90 ° C. was performed. The curing was carried out under conditions in which DEF was likely to occur. This is because when there is no increase in the high-temperature curing and SO ₃ amount, there may be a case that does not cause expansion due DEF, in order to observations made easy, was adjusted as described above.

More specifically, first, a curing accelerator was added to the mortar composition, and then kneading and molding were performed. Next, the mold was placed in a constant temperature bath in a sealed state, cured at 20 ° C. for 4 hours, raised to 90 ° C. over 2 hours, and held at 90 ° C. for 12 hours. After 12 hours, the temperature was lowered to 20 ° C. over 4 hours, and the mixture was cured at 20 ° C. for 2 hours. Then, it was demolded to obtain a cured mortar.

The cured mortar prepared by the above method was cured in water in a constant temperature room at 20 ° C., and the amount of change in length of three cured mortars was measured at each level. The method for measuring the amount of change in length is based on the description in JIS A 1129-3: 2010 "Measuring method for measuring the change in length of mortar and concrete", using a dial gauge, and underwater curing based on the base length at the time of demolding. The cured mortar was taken out of the water on the 7th, 14th, and 28th days of the age of the material, and every 28 days thereafter, and the amount of change in length was measured. The amount of change in length was measured at 6 locations on the front and back of the three cured mortars, and the average value was taken as the amount of change in length of the target cured mortar. The value obtained by dividing the obtained amount of change in length by the interval of the strain gauge (100 mm) is defined as the expansion coefficient of the cured mortar, and the cured mortar at 112 days of age of the underwater curing material is according to DEF and DEF according to the following criteria. The degree of suppression of expansion of the cured mortar was evaluated. The results are shown in Tables 6 and 7.
A: The expansion coefficient of the cured mortar is 0.05% or less.
B: The expansion coefficient of the cured mortar is more than 0.05% and 0.10% or less.
C: The expansion coefficient of the cured mortar is more than 0.10% and 0.25% or less.
D: The expansion coefficient of the cured mortar is more than 0.25%.

(Measurement of compressive strength)
The compressive strength of each cured mortar was measured in accordance with the description of JIS R 5201: 2015 “Physical test method for cement”. To prepare a cured mortar for measuring compressive strength, first, the mortar composition prepared with the formulations shown in Tables 3 and 4 is kneaded as mortar in a constant temperature room at 35 ° C. and molded, and the mold is moistened. It was stored in a box and cured for 24 hours. After curing for 24 hours, the mold was removed to obtain a cured mortar. The obtained cured mortar was cured in water in a constant temperature room at 35 ° C. until the age of 28 days, and then the compressive strength was measured. Each cured mortar was evaluated according to the following criteria. The results are shown in Tables 6 and 7.
A: The compressive strength is 55 MPa or more.
B: The compressive strength is 53 MPa or more and less than 55 MPa.
C: The compressive strength is 52 MPa or more and less than 53 MPa.
D: The compressive strength is 50 MPa or more and less than 52 MPa.
E: Compressive strength is less than 50 MPa.

As shown in Table 6, it was confirmed that by satisfying the requirements of the cement composition according to the present disclosure, the effect of suppressing expansion associated with DEF and the compressive strength can be sufficiently compatible in practical use. First, the compositions of Comparative Examples 1 to 3 shown in Table 6 and the mortar compositions of Examples 1 to 3 have the same base cement in NC1 as shown in Table 5, and the total amount of the admixtures is the same. The content is also common with 10% by mass. On the other hand, the compositions of Comparative Examples 1 to 3 and the mortar compositions of Examples 1 to 3 differ in the type and composition ratio of the admixture. As shown in Table 6, from the results of the compositions of Comparative Examples 1 to 3 and the mortar compositions of Examples 1 to 3, when the admixture was only limestone, the expansion associated with DEF could not be suppressed (Comparative Example 2). It was confirmed that the compressive strength decreased when the admixture was only inorganic powder (Comparative Example 3), and it was confirmed that the inorganic powder and limestone must be used in combination as the admixture. From the results of Comparative Example 1 and Example 2, it can be confirmed that by including the inorganic powder having a specific chemical component as a mixed material, the effect of suppressing expansion associated with DEF and the compressive strength can be sufficiently compatible in practical use.

As shown in Table 7, it was confirmed that even when the base cement is NC2, the tendency is the same as when the base cement is NC1. When different samples of base cement are compared with the same mixed material (for example, comparison of Comparative Examples 2 and 6 or Examples 1 and 4), the expansion coefficient associated with DEF differs depending on the type of base cement, and the base the larger the C _{3 S} content and the C _{3 a} content of cement, the tendency of expansion rate increases due to the DEF was confirmed. Also, as the C 3 _A content is large, it tends to decrease compressive strength at 35 ° C. was observed. From this, it was confirmed that it is desirable to adjust the composition according to the type of base cement and the degree to which the effect of suppressing expansion associated with DEF and the compressive strength are required.

Comparative Example 4 was a sample in which 5% by mass of limestone was added to simulate ordinary Portland cement specified in JIS R5201, but the expansion coefficient associated with DEF was large. Further, when the limestone was increased to 10% by mass, or when the blast furnace slag fine powder was added to 5% by mass of the limestone, an increase in the expansion coefficient associated with DEF was observed. On the other hand, it was confirmed that all the samples of the examples had a high DEF suppressing effect and had sufficient compressive strength.

Comparing Reference Example 1 and Example 2, the same cement clinker and the same composition are used, but the expansion coefficient associated with DEF differs depending on the coal gasification slag used. It was confirmed that the higher the brain specific surface area of the coal gasified slag, the smaller the expansion rate associated with DEF.

According to the present disclosure, a cement composition capable of suppressing expansion due to DEF and providing a hardened cement body having excellent compressive strength in a high temperature environment even when the content of the mixed material is large and its production. A method can be provided. The present disclosure also provides a durability-enhancing mixture that can be used to produce the cement compositions described above.

Claims (14)

With cement clinker
With plaster
Containing with the mixture,
The mixed material contains an inorganic powder containing an amorphous phase and limestone.
The inorganic powder has a _{chemical composition containing CaO, SiO 2} and Al ₂ O _3, and the amount of CaO is 6.0 to 40.0% by mass and the _{amount of SiO 3} is 35. Based on the total amount of the inorganic powder. The _{amount of Al 2} O ₃ is 14.0 to 25.0 mass%, and the amount is 0 to 75.0 mass%.
Based on the total amount of the cement clinker, the gypsum and the mixture.
The content of the mixed material is 2.0 to 30.0% by mass, and the content is 2.0 to 30.0% by mass.
The content of the inorganic powder is 1.0 to 29.0% by mass, and
A cement composition having a limestone content of 1.0 to 10.0% by mass. The cement composition according to claim 1, wherein the content of the inorganic powder based on 100% by mass of the mixed material is 5.0 to 95.0% by mass. The chemical composition of the inorganic powder further comprises MgO.
The cement composition according to claim 1 or 2, wherein the amount of MgO based on the total amount of the inorganic powder is 5.0% by mass or less. The chemical composition of the inorganic powder further comprises _{SO 3 and}
The cement composition according to any one of claims 1 to 3, _{wherein the amount of SO 3 based on} the total amount of the inorganic powder is 1.0% by mass or less. The cement composition according to any one of claims 1 to 4, wherein the inorganic powder has a specific surface area of 2000 to 10000 cm ^{2 / g.} The cement composition according to any one of claims 1 to 5, wherein the amount of the amorphous phase in 100% by mass of the inorganic powder is 80.0 to 100.0% by mass. The cement composition according to any one of claims 1 to 6, wherein the inorganic powder contains a pulverized product of coal gasified slag. The cement clinker is _{C 3} S amount calculated by the Bogue formula from 35.0 to 75.0 wt%, _{C 3} A content is from 8.0 to 14.0 wt%, claims 1-7 The cement composition according to any one of the above. Based on the total amount of the gypsum and the cement clinker, the content of the gypsum is 0.5 to 3.0 mass% converted to SO _3, as claimed in any one of claims 1-8 Cement composition. The cement clinker _{contains SO 3} and R ₂ O and contains
In the cement clinker to 100 mass%, a SO ₃ weight 0.10 to 2.00 wt%, and _{R 2} O content is 0.10 to 2.00 wt%, any one of claims 1 to 9 The cement composition according to one item. Further contains a curing accelerator,
The invention according to any one of claims 1 to 10, wherein the content of the curing accelerator is 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the total amount of the cement clinker, the gypsum and the mixture. Cement composition. Based on the total amount of the inorganic powder, the amount of CaO in the amorphous phase of the inorganic powder is 6.0 to 40.0% by mass, and the _{amount of SiO 2} is 35.0 to 75.0% by mass. , The cement composition according to any one of claims 1 to 11, wherein the amount of _{Al 2} O _{3 is 14.0 to 25.0% by mass.} A step of mixing cement clinker, gypsum, and a mixture material is provided.
The mixed material contains an inorganic powder containing an amorphous phase and limestone.
The inorganic powder has a _{chemical composition containing CaO, SiO 2} and Al ₂ O _3, and the amount of CaO is 6.0 to 40.0% by mass and the _{amount of SiO 3} is 35. Based on the total amount of the inorganic powder. The _{amount of Al 2} O ₃ is 14.0 to 25.0 mass%, and the amount is 0 to 75.0 mass%.
In the step, the content of the mixed material based on the total amount of the cement clinker, the gypsum and the mixed material is 2.0 to 30.0% by mass, and the content of the inorganic powder is 1.0 to 3. A method for producing a cement composition, wherein the cement clinker, the gypsum and the mixed material are mixed so that the content of the limestone is 29.0% by mass and the content of the limestone is 1.0 to 10.0% by mass. A durability-enhancing mixed material containing an inorganic powder containing an amorphous phase and limestone.
The inorganic powder has a _{chemical composition containing CaO, SiO 2} and Al ₂ O _3, and the amount of CaO is 6.0 to 40.0% by mass and the _{amount of SiO 3} is 35. Based on the total amount of the inorganic powder. The _{amount of Al 2} O ₃ is 14.0 to 25.0 mass%, and the amount is 0 to 75.0 mass%.
Assuming that the total amount of cement clinker, gypsum and the durability improving mixture is 100% by mass, the content of the inorganic powder is 1.0 to 29% by mass, and the content of the limestone is 1.0 to 10.0% by mass. A durability-enhancing mixed material used in combination with cement clinker and gypsum so as to be%.