Cement composition and method for producing the same

Abstract

To provide a cement composition with excellent sulfate resistance even when the content of C3A is large.SOLUTION: A cement composition of the invention comprises a mixture of cement and gypsum powder, or a mixture of ground cement and gypsum powder, wherein: the cement satisfies a hydraulic hardness ratio of 2.18 to 2.30, a silicic acid ratio of 2.40 to 2.54, and an iron ratio of 1.74 to 1.90; the cement composition satisfies a tricalcium aluminate content of 8.0% by mass or more when calculated by using the Borg formula, a Blaine specific surface area of 3500 to 3850 cm2 / g, a total gypsum and gypsum powder content in the cement satisfies 2.4 to 2.9% by mass in terms of SO3; a gypsum powder content satisfies 0.4 to 0.9% by mass in terms of SO3; and the gypsum powder satisfies such that the proportion of powder having a particle size of 50 μm or more satisfies 10% by mass or more and the proportion of powder having a particle size of 200 μm or more satisfies less than 10% by mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement composition and a method for producing the same. [Background technology]

[0002] In soil containing sulfates, there is a problem that cementitious hardened materials such as concrete are deteriorated by the sulfates. Patent Document 1 describes a highly sulfate-resistant cement composition comprising a composition of cement and limestone powder in a mass ratio of 5:95 to 100:0, to which 1 to 10 parts by mass of a formalin condensate salt of naphthalenesulfonic acid, 0.005 to 0.1 parts by mass of a thickener, and / or 5 to 30 parts by mass of fine silica powder, fly ash, or ground granulated blast furnace slag, per 100 parts by mass of the composition, is added. Furthermore, Patent Document 2 describes a cement composition characterized by containing a cement additive containing calcium carbonate, gypsum, and silica fume. Furthermore, Patent Document 3 discloses a mixed cement mainly composed of ground granulated blast furnace slag and Portland cement, in which the mixing ratio of ground granulated blast furnace slag having an alumina content of 12 to 17.5 mass% is set to 10 to 60 mass%, and the mixed cement is added with a cement having a specific surface area of ​​7,000 cm 2 The paper describes a sulfate-resistant cement characterized by containing 2 to 4 mass % of gypsum, calculated as SO3, with a sulfate content of 2 to 4 mass % or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-331459 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-227549 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-201656 Summary of the Invention [Problem to be solved by the invention]

[0004] "JIS R 5210:2019 (Portland cement)" specifies that sulfate-resistant Portland cement must contain 4% or less of tricalcium aluminate (hereinafter also referred to as "C3A") by mass. An object of the present invention is to provide a cement composition that has excellent sulfate resistance even when the C3A content is high (specifically, 8.0 mass % or more). [Means for solving the problem]

[0005] As a result of intensive research by the present inventors to solve the above problems, the present inventors have discovered a cement composition comprising a mixture of cement or a ground product of said cement, which satisfies the respective numerical ranges of hydraulic modulus (HM) of 2.18 to 2.30, silica modulus (SM) of 2.40 to 2.54, and iron modulus (IM) of 1.74 to 1.90, and gypsum powder, wherein the tricalcium aluminate content is 8.0 mass% or more and the Blaine specific surface area is 3,500 to 3,850 cm 2 / g, the total content of gypsum and gypsum powder in the cement satisfies the respective numerical ranges of 2.4 to 2.9 mass% in terms of SO3, and the content of gypsum powder satisfies the respective numerical ranges of 0.4 to 0.9 mass% in terms of SO3, and the gypsum powder satisfies the respective numerical ranges of 10 mass% or more of powder having a particle size of 50 μm or more and 10 mass% or less of powder having a particle size of 200 μm or more, and the present inventors have completed the present invention. That is, the present invention provides the following [1] to [6]. [1] A cement composition comprising a mixture of cement and gypsum powder, or a mixture of crushed cement and gypsum powder, wherein the cement satisfies the respective numerical ranges of hydraulic modulus (HM) 2.18 to 2.30, silica modulus (SM) 2.40 to 2.54, and iron modulus (IM) 1.74 to 1.90, and the cement composition has a tricalcium aluminate content calculated using the Bogue formula of 8.0 mass% or more and a Blaine specific surface area of ​​3,500 to 3,850 cm 2 / g, the total content of gypsum in the cement and the gypsum powder in SO3 equivalent is 2.4 to 2.9 mass% and the content of the gypsum powder in SO3 equivalent is 0.4 to 0.9 mass%, respectively, and the gypsum powder satisfies the following numerical ranges: a proportion of powder having a particle size of 50 μm or more is 10 mass% or more, and a proportion of powder having a particle size of 200 μm or more is 10 mass% or less.

[0006] [2] The cement composition according to [1], wherein the cement is ordinary Portland cement. [3] The cement composition according to [1] or [2], wherein the gypsum powder satisfies the numerical range of 7 mass % or more of powder having a particle size of 50 to 100 μm. [4] The cement composition has a compressive strength of 30 N / mm2 at 3 days, measured in accordance with JIS R 5201:2015 (physical testing method for cement). 2 The cement composition according to any one of the above [1] to [3]. [5] A method for producing the cement composition according to any one of [1] to [4] above, comprising a mixing step of mixing the cement with the gypsum powder, or grinding the cement to obtain a ground product of the cement, and then mixing the ground product with the gypsum powder to obtain the cement composition. [6] In the mixing process, the Blaine specific surface area of ​​the cement is 3,400 cm 2 / g or less, the cement is pulverized to obtain a pulverized product of the cement, and then the pulverized product and the gypsum powder are mixed to obtain the cement composition. [5] The method for producing a cement composition according to [Effects of the Invention]

[0007] The cement composition of the present invention has a high C3A content (specifically, 8.0 mass % or more) yet has excellent sulfate resistance. DETAILED DESCRIPTION OF THE INVENTION

[0008] The cement composition of the present invention is a cement composition comprising a mixture of cement and gypsum powder, or a mixture of crushed cement and gypsum powder, in which the cement satisfies the respective numerical ranges of a hydraulic modulus (HM) of 2.18 to 2.30, a silicate modulus (SM) of 2.40 to 2.54, and an iron modulus (IM) of 1.74 to 1.90, and the cement composition has a tricalcium aluminate content calculated using the Bogue formula of 8.0 mass% or more and a Blaine specific surface area of ​​3,500 to 3,850 cm. 2 / g, the total content of gypsum and gypsum powder in the cement is 2.4 to 2.9 mass% in terms of SO3, and the content of gypsum powder is 0.4 to 0.9 mass% in terms of SO3. The gypsum powder satisfies the following numerical ranges: the proportion of powder having a particle size of 50 μm or more is 10 mass% or more, and the proportion of powder having a particle size of 200 μm or more is 10 mass% or less. A detailed explanation is provided below.

[0009] Examples of cement that can be used in the present invention include various types of Portland cement such as ordinary Portland cement and high-early-strength Portland cement, mixed cement such as blast-furnace cement and fly ash cement, ecocement, etc. These may be used alone or in combination of two or more. Among these, ordinary Portland cement is preferred from the viewpoint of easy availability of cement and obtaining a cement composition having a tricalcium aluminate content of 8.0 mass % or more. The Blaine specific surface area of ​​cement is determined by the ease of availability and the adjustment of the Blaine specific surface area of ​​the cement composition (3,500 to 3,850 cm 2 / g), it is preferable to use a temperature of 3,400 cm 2 / g or less, more preferably 3,000 to 3,300 cm 2 / g, particularly preferably 3,100 to 3,250 cm 2 / g.

[0010] In the present invention, the Blaine specific surface area of ​​the cement composition is adjusted (3,500 to 3,850 cm2 In order to facilitate the adjustment of the solubility (to 0.1g / g), a ground cement obtained by grinding the cement may be used instead of the above-mentioned cement. When using ground cement, the Blaine specific surface area of ​​the cement is preferably 3,400 cm 2 / g or less, more preferably 3,000 to 3,300 cm 2 / g, particularly preferably 3,100 to 3,250 cm 2 / g.

[0011] The tricalcium aluminate (3CaO·Al2O3; also referred to as the aluminate phase) content of the cement is 8.0% by mass or more, preferably 8.5% by mass or more, and more preferably 9.0% by mass or more. If the content is less than 8.0% by mass, the strength development of the cement composition (particularly the strength at 3 and 7 days) will be reduced. Furthermore, the cement composition of the present invention (having the above content of 8.0% by mass or more) can be produced using common materials (e.g., ordinary Portland cement). From the viewpoints of ease of production and improved sulfate resistance, the above content is preferably 15.0% by mass or less, more preferably 12.0% by mass or less, and even more preferably 10.0% by mass or less. The alite (3CaO·SiO2; also referred to as "C3S") content of the cement is preferably 53.0 to 70.0 mass%, more preferably 55.0 to 67.0 mass%, and particularly preferably 58.0 to 65.0 mass%, from the viewpoints of sulfate resistance, strength development, fluidity, etc. of the cement composition. The belite (2CaO·SiO2; also referred to as "C2S") content of the cement is preferably 6.0 to 18.0 mass%, more preferably 7.5 to 16.0 mass%, and particularly preferably 9.0 to 14.0 mass%, from the viewpoints of sulfate resistance, strength development, fluidity, etc. of the cement composition. The content of the ferrite phase (4CaO·Al2O3·Fe2O3; also referred to as "C4AF") in the cement is preferably 5.0 to 15.0 mass%, more preferably 7.0 to 12.0 mass%, and particularly preferably 8.0 to 10.0 mass%, from the viewpoints of the sulfate resistance of the cement composition and ease of production.

[0012] The content of each element such as tricalcium aluminate in cement can be calculated from the results of chemical analysis of the cement using the following Borg's formula. (1) Tricalcium aluminate = (2.65 × Al2O3) - (1.69 × Fe2O3) (2) Alite = (4.07 × CaO) - (7.60 × SiO2) - (6.72 × Al2O3) - (1.43 × Fe2O3) - (2.85 × SO3) (3) Belite = (2.87 × SiO2) - (0.754 × C3S) (4) Ferrite phase = (3.04 × Fe2O3)

[0013] The hydraulic modulus (HM) of the cement is 2.18 to 2.30, preferably 2.19 to 2.28, and more preferably 2.20 to 2.25. If the hydraulic modulus (HM) does not satisfy the above range, the sulfate resistance and strength development of the cement composition will be reduced. If the hydraulic modulus is less than 2.18, the early strength development of the cement composition will be reduced. If the hydraulic modulus exceeds 2.30, the heat of hydration will be greater. The silicate content (SM) of the cement is 2.40 to 2.54, preferably 2.41 to 2.53, and more preferably 2.42 to 2.52. If the silicate content (SM) does not satisfy the above range, the sulfate resistance and strength development of the cement composition will be reduced. Furthermore, if the silicate content is less than 2.40, the heat of hydration of the cement composition will be large. If the silicate content exceeds 2.54, it will be difficult to increase the amount of waste used as a raw material. The iron content (IM) of the cement is 1.74 to 1.90, preferably 1.74 to 1.80, and more preferably 1.74 to 1.75. If the iron content (IM) does not satisfy the above range, the sulfate resistance and strength development of the cement composition will be reduced. If the iron content is less than 1.74, the early strength development will be reduced. If the iron content is 1.90 or more, the heat of hydration will be large.

[0014] The hydraulic ratio, silica ratio, and iron ratio of cement can be calculated using the following formulas. Hydraulic rate=(CaO-0.7×SO3) / (SiO2+Al2O3+Fe2O3) Silicate ratio = SiO2 / (Al2O3+Fe2O3) Iron rate=Al2O3 / Fe2O3 (The chemical formula in the above formula represents the content (mass%) of the compound represented by the chemical formula in the cement.)

[0015] The content of MgO in the cement is preferably 1.30 mass % or more, and more preferably 2.00 to 4.00 mass %, from the viewpoint of further improving the sulfate resistance and strength development of the cement composition. Furthermore, from the viewpoint of further improving the sulfate resistance and strength development of the cement composition, the content of P2O5 in the cement is preferably 0.47 mass% or less, more preferably 0.15 to 0.40 mass%, and even more preferably 0.20 to 0.30 mass%.

[0016] Examples of the gypsum in the gypsum powder include powders of natural gypsum dihydrate, flue gas desulfurization gypsum, phosphate gypsum, titanic gypsum, hydrofluoric gypsum, etc. These may be used alone or in combination of two or more. Examples of the form of gypsum include gypsum dihydrate, gypsum hemihydrate, and anhydrous gypsum. The gypsum powder may be a powder consisting of only one type of form, or may be a powder containing two or more types of forms. The gypsum powder satisfies the following numerical ranges: the proportion of powder having a particle size of 50 μm or more is 10 mass% or more (preferably 13 to 80 mass%, more preferably 20 to 70 mass%, particularly preferably 30 to 55 mass%), and the proportion of powder having a particle size of 200 μm or more is 10 mass% or less (preferably 8 mass% or less, more preferably 5 mass% or less, and most preferably 2 mass% or less). If gypsum powder having a particle size distribution that does not satisfy the above numerical ranges is used, the sulfate resistance of the cement composition will decrease. The proportion of the gypsum powder having a particle size of 50 to 100 μm is preferably 7 mass% or more, more preferably 10 to 60 mass%, even more preferably 20 to 50 mass%, and particularly preferably 30 to 40 mass%. When a gypsum powder having a particle size distribution satisfying the above numerical range is used, the sulfate resistance of the cement composition is further improved. In this specification, the particle size value is a value corresponding to the size of the sieve openings.

[0017] The D50 (median diameter) of the gypsum powder is preferably 10 to 70 μm, more preferably 12 to 65 μm, from the viewpoint of further improving the sulfate resistance of the cement composition. D50 (median diameter) refers to the specific particle size at which, when a powder or granular material is divided into particles smaller than a specific particle size (aggregates of small particle sizes) and particles larger than that particle size (aggregates of large particle sizes), the aggregates of these small particle sizes and the aggregates of large particle sizes are equal in volume (for example, 50% by volume of each). In this specification, the "median diameter" is based on volume and can be obtained by creating a cumulative volume distribution using a laser diffraction / scattering particle size distribution analyzer or a sieving method in accordance with "JIS Z 8815-1994 (General rules for sieving test methods)."

[0018] The content of gypsum powder contained in the cement composition is 0.4 to 0.9 mass%, preferably 0.45 to 0.85 mass%, and more preferably 0.5 to 0.85 mass%, calculated as SO3. If gypsum powder having a particle size distribution in which the content does not satisfy the above numerical range is used, the sulfate resistance of the cement composition will decrease. In this specification, the term "gypsum powder" does not include gypsum contained in cement.

[0019] The tricalcium aluminate content of the cement composition, calculated using the Bogue formula, is 8.0% by mass or more, preferably 8.3% by mass or more, and more preferably 8.6% by mass or more. If the content is less than 8.0% by mass, the strength development of the cement composition (particularly the strength at 3 days and 7 days) will be reduced. Furthermore, the cement composition of the present invention (having the above content of 8.0% by mass or more) can be produced using common materials (e.g., ordinary Portland cement). From the viewpoints of ease of production and improved sulfate resistance, the above content is preferably 15.0% by mass or less, more preferably 12.0% by mass or less, and even more preferably 10.0% by mass or less.

[0020] The Blaine specific surface area of ​​the cement composition is 3,500 to 3,850 cm 2 / g, preferably 3,510 to 3,840 cm 2 / g, more preferably 3,510 to 3,830 cm 2 / g. The specific surface area is 3,500 cm 2 If the specific surface area is less than 3,850 cm / g, the sulfate resistance and strength development of the cement composition will be reduced. 2 If the content exceeds 1 / g, the sulfate resistance of the cement composition decreases.

[0021] The total content of gypsum and gypsum powder in the ground cement is 2.4 to 2.9 mass%, preferably 2.45 to 2.85 mass%, and more preferably 2.5 to 2.8 mass%, calculated as SO3. If the content is less than 2.4 mass%, calculated as SO3, the usable time before hardening of the cement composition (the time during which good fluidity can be maintained) will be shortened. If the amount exceeds 2.9 mass%, the strength development of the cement composition will be reduced.

[0022] The compressive strength of the cement composition at 3 days, measured in accordance with "JIS R 5201:2015" (physical testing method for cement), is preferably 30 N / mm 2 More preferably, 32N / mm 2 More than 35N / mm 2 That's all.

[0023] Examples of methods for producing the cement composition of the present invention include a method including a mixing step of mixing cement and gypsum powder, or grinding cement to obtain ground cement, and then mixing the ground cement with gypsum powder to obtain the cement composition. If the Blaine specific surface area of ​​the cement used is, for example, 3,500 to 3,850 cm 2 / g, the cement composition of the present invention can be obtained by mixing with gypsum powder without pulverization. The Blaine specific surface area of ​​cement is small (e.g., 3,400 cm 2 / g or less), the Blaine specific surface area of ​​the cement composition is 3,500 to 3,850 cm 2 The cement may be ground to adjust the solubility to 1 / g. For example, in the mixing process, if the Blaine specific surface area of ​​the cement used is 3,400 cm 2 / g or less, the cement may be pulverized to obtain pulverized cement, and then the pulverized cement may be mixed with the gypsum powder. When grinding cement, the grinding means is not particularly limited, and for example, a general grinding means used in cement production, such as a ball mill, can be used. Grinding of cement is appropriately carried out so that the Blaine specific surface area of ​​the resulting cement composition falls within a desired numerical range. Before the mixing step, a classification step may be performed in which the gypsum is pulverized and classified to adjust the particle size distribution of the gypsum powder. The gypsum is pulverized and classified as appropriate so that the resulting gypsum powder has the above-mentioned particle size distribution and the Blaine specific surface area of ​​the cement composition obtained in the mixing step falls within a desired numerical range. [Example]

[0024] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Cement A: Ordinary Portland cement, manufactured by Taiheiyo Cement Corporation, Blaine specific surface area: 3,220 cm 2 / g (2) Cement B: Ordinary Portland cement, manufactured by Taiheiyo Cement Corporation, Blaine specific surface area: 3,190cm 2 / g (3) Cement C: Ordinary Portland cement, manufactured by Taiheiyo Cement Corporation, Blaine specific surface area: 3,810cm 2 / g (4) Gypsum powder 1-4: gypsum dihydrate ground and particle size adjusted The chemical and mineral compositions of cements A to C are shown in Tables 1 and 2. Table 3 also shows the D50 (median diameter) and particle size distribution of gypsum powders 1 to 4 (shown as "Gypsum 1 to 4" in Table 3) measured using a laser diffraction scattering particle size distribution measuring device (manufactured by Microtrackbell, product name "MT3300EX II").

[0025] [Table 1]

[0026] [Table 2]

[0027] [Table 3]

[0028] [Example 1] The type of cement shown in Table 4 was ground, and the ground cement with the Blaine specific surface area of ​​the cement adjusted was mixed with the type of gypsum powder shown in Table 4 to obtain a cement composition such that the gypsum powder content in the cement composition, the total content of gypsum and gypsum powder contained in the ground cement in the cement composition in terms of SO3 (shown as "SO3" in Table 4), the Blaine specific surface area of ​​the cement (shown as "specific surface area" in Table 4), and the tricalcium aluminate content in the cement composition were the respective values ​​shown in Table 4.

[0029] The expansion rate of the resulting cement composition at 14 days was measured in accordance with ASTM C 452 (Standard Test Method for Expansion Potential of Portland Cement Mortar Exposed to Sulfate). The smaller the expansion rate, the better the sulfate resistance. In addition, the compressive strength of the obtained cement composition was measured at ages of 3 days, 7 days, and 28 days in accordance with "JIS R 5201:2015 (Physical testing methods for cement)". As Reference Example 1, the compressive strength of commercially available sulfate-resistant cement was measured in the same manner at ages of 3 days, 7 days, and 28 days.

[0030] [Comparative Example 1] Cement compositions were obtained in the same manner as in Example 1, except that cement compositions were obtained by mixing the types of cement and gypsum powder shown in Table 4. The expansion coefficients and compressive strengths of the obtained cement compositions were measured in the same manner as in Example 1. [Examples 2 to 4, Comparative Examples 2 to 6] A cement composition was obtained in the same manner as in Example 1. The expansion coefficient and compressive strength of the obtained cement composition were measured in the same manner as in Example 1. The results are shown in Tables 4 and 5.

[0031] [Table 4]

[0032] [Table 5]

[0033] From Tables 4 and 5, it can be seen that the expansion coefficients of Examples 1 to 4 (0.031 to 0.0032) are smaller than the expansion coefficients of Comparative Examples 1 to 6 (0.036 to 0.038), and that they are excellent in sulfate resistance. It is also clear that the compressive strengths of Examples 1 to 4 are greater than that of Reference Example 1 (commercially available sulfate-resistant cement).

Claims

1. A cement composition comprising a mixture of cement and gypsum powder, or a mixture of ground cement and gypsum powder, The cement satisfies the following numerical ranges: hydraulic modulus (H.M.) 2.18 to 2.30, silica modulus (S.M.) 2.40 to 2.54, and iron modulus (I.M.) 1.74 to 1.90; The cement composition has a tricalcium aluminate content of 8.0% by mass or more calculated using the Bogue formula and a Blaine specific surface area of ​​3,500 to 3,850 cm ２ / g, the total content of gypsum in the cement and the gypsum powder is SO ３ The content of the gypsum powder is 2.4 to 2.9 mass% in terms of SO ３ The converted amount satisfies the respective numerical ranges of 0.4 to 0.9 mass%, The gypsum powder satisfies the following numerical ranges: a proportion of powder having a particle size of 50 μm or more is 10% by mass or more, and a proportion of powder having a particle size of 200 μm or more is 10% by mass or less. A cement composition.

2. 2. The cement composition of claim 1, wherein said cement is ordinary Portland cement.

3. The cement composition according to claim 1 or 2, wherein the gypsum powder satisfies the numerical range of 7 mass% or more of powder having a particle size of 50 to 100 μm.

4. The cement composition has a compressive strength of 30 N / mm2 at 3 days old, measured in accordance with "JIS R 5201:2015" (physical testing method for cement). ２ The cement composition according to any one of claims 1 to 3, wherein the composition is as described above.

5. A method for producing the cement composition of any one of claims 1 to 4, comprising: A mixing step of mixing the cement and the gypsum powder, or pulverizing the cement to obtain a pulverized product of the cement, and then mixing the pulverized product with the gypsum powder to obtain the cement composition; A method for producing a cement composition, comprising:

6. In the mixing step, the Blaine specific surface area of ​​the cement is 3,400 cm ２ / g or less, the cement is pulverized to obtain a pulverized product of the cement, and then the pulverized product and the gypsum powder are mixed to obtain the cement composition.

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