Cement composition and method for producing cement composition

Abstract

Provided is a cement composition that contains limestone powder and that has excellent strength-expressing characteristics, setting characteristics, and sulfate resistance even while containing the limestone powder.　This cement composition contains fly ash and a mixed cement comprising Portland cement and limestone powder. As calculated values obtained from the Bogue formula, the percentage content of alite is 60-70 mass% and the percentage content of the aluminate phase is 4.9-9.1 mass% in the mixed cement, and the percentage content of Fe2O3 is 15.0-20.0 mass% in the fly ash. The amount of the fly ash is 10-30 parts by mass with respect to 100 parts by mass of the mixed cement.

Description

Cement composition and method for manufacturing the cement composition

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

[0002] When the sulfate concentration in the soil is high, cementitious materials such as concrete deteriorate due to sulfates. For this reason, there is a growing need for mixed cements with excellent sulfate resistance in areas with high sulfate concentrations. For example, as a cement composition with high sulfate resistance, Patent Document 1 describes a 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 naphthalene sulfonic acid formalin condensate salt and 0.005 to 0.1 parts by mass of a thickener and / or 5 to 30 parts by mass of silica fine powder, fly ash or blast furnace slag fine powder are added per 100 parts by mass of the composition.

[0003] Furthermore, various cement compositions have been proposed in which cement admixtures are added to cement. For example, as a fly ash cement that exhibits better initial strength development than conventional fly ash cement and ensures sufficient strength at 28 days of age, Patent Document 2 describes a fly ash cement as a mixed cement made by mixing fly ash with cement, in which C is determined by the Bogue formula as the base cement. ３ S content is 60-71% and C ２ S amount is 1% or more and C ３ S and C ２ The total amount of S is 70-80%, C ３ S / C ２ A fly ash cement is described that uses a cement made by adding gypsum to a clinker mineral composition having an S ratio of 7 to 50 and a high alite content clinker with a free lime content of 1.0 to 4.0% by weight.

[0004] Japanese Patent Publication No. 2004-331459, Japanese Patent No. 4712483

[0005] From the perspective of reducing the usage amount of cement clinker and reducing carbon dioxide emissions during the production of cement clinker, when limestone powder is used as a substitute for cement clinker, there is a problem that the sulfate resistance of a hardened product of a cement composition (e.g., concrete) decreases. An object of the present invention is to provide a cement composition containing limestone powder, which is excellent in strength development, setting property, and sulfate resistance despite containing limestone powder.

[0006] As a result of intensive studies by the present inventor to solve the above problems, a mixed cement composed of Portland cement and limestone powder, wherein the alite content is 60 to 70% by mass and the aluminate phase content is 4.9 to 9.1% by mass, and Fe ２ O ３ content in the fly ash is 15.0 to 20.0% by mass, and the cement composition comprising the fly ash in an amount of 10 to 30 parts by mass relative to 100 parts by mass of the mixed cement can achieve the above object, thereby completing the present invention. That is, the present invention provides the following [1] to [5]. [1] A cement composition comprising a mixed cement composed of Portland cement and limestone powder, and fly ash, wherein, as a value calculated by the Bogue's formula, in the mixed cement, the content of alite is 60 to 70% by mass and the content of aluminate phase is 4.9 to 9.1% by mass, and in the fly ash, Fe ２ O ３ content is 15.0 to 20.0% by mass, and the amount of the fly ash is 10 to 30 parts by mass relative to 100 parts by mass of the mixed cement.

[0007] [2] The cement composition according to [1], wherein the content of magnetite in the fly ash is 2.0 to 10.0% by mass. [3] The cement composition according to [1] or [2], wherein the 45 μm sieve residue of the fly ash is 9.0 to 13.0% by mass, the 50% volume cumulative particle size (D50) is 9.0 to 13.0 μm, and the vitrification rate is 60 to 80%. [4] The cement composition according to any one of [1] to [3], wherein the content of limestone powder in the mixed cement is 5.0 to 15.0% by mass. [5] A method for producing the cement composition according to any one of [1] to [4], wherein the fly ash to be used as a material for the cement composition is the Fe in the fly ash ２ O ３ A selection step in which the fly ash is selected as a material for the cement composition if the fly ash satisfies the condition that the content of is within the range of 15.0 to 20.0 mass%, and the mixed cement and the Fe selected in the selection step ２ O ３ A method for producing a cement composition, comprising a mixing step of preparing the cement composition by mixing fly ash having a content of 15.0 to 20.0% by mass.

[0008] The mixed cement composition of the present invention exhibits excellent strength development, setting properties, and sulfate resistance despite containing limestone powder. Furthermore, by substituting a portion of the cement clinker with limestone powder, the proportion of cement clinker can be relatively reduced, thereby reducing the amount of carbon dioxide emitted during the production of cement clinker.

[0009] The present invention relates to a cement composition comprising a mixed cement consisting of Portland cement and limestone powder, and a cement composition containing fly ash, wherein, as calculated by the Bogue formula, the alite content in the mixed cement is 60 to 70% by mass, the aluminate phase content is 4.9 to 9.1% by mass, and in the fly ash, Fe ２ O ３The content of is 15.0 to 20.0% by mass, and the amount of fly ash is 10 to 30 parts by mass per 100 parts by mass of mixed cement. A detailed explanation follows.

[0010] Portland cement is not particularly limited and can be any of the following: ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, and other types of Portland cement. These may be used individually or in combination of two or more types. The limestone powder content in the mixed cement is preferably 5.0 to 15.0% by mass, more preferably 6.0 to 12.0% by mass, and even more preferably 7.0 to 10.0% by mass. If the above content is 5.0% by mass or more, the amount of limestone powder used can be increased, relatively reducing the amount of cement clinker used, and further reducing the amount of carbon dioxide emitted during cement clinker production. If the above content is 15.0% by mass or less, the strength development of the cement composition can be further improved.

[0011] Alite (chemical formula: 3CaO・SiO) of mixed cement (100% by mass) ２ ; C ３ The content of the aluminate phase (sometimes abbreviated as S) of the mixed cement is 60 to 70% by mass, preferably 62 to 68% by mass, and particularly preferably 64 to 66% by mass. If the above content is less than 60% by mass, the initial strength development of the cement composition deteriorates. If the above content exceeds 70% by mass, the setting properties and sulfate resistance of mortar etc. containing the cement composition deteriorate. In addition, the heat of hydration increases. ２ O ３ ; C ３ The content of (sometimes abbreviated as A) is 4.9 to 9.1% by mass, preferably 5.0 to 8.5% by mass, and particularly preferably 6.0 to 8.0% by mass. If the above content is less than 4.9% by mass, the initial strength development of the cement composition will decrease. If the above content exceeds 9.1% by mass, the sulfate resistance of the cement composition will decrease. In addition, the heat of hydration will increase.

[0012] Belite in blended cement (chemical formula: 2CaO·SiO ２ ; sometimes abbreviated as C ２ S). The content thereof is preferably 5.0 to 10.0% by mass, more preferably 5.5 to 8.0% by mass, and particularly preferably 6.0 to 7.0% by mass. When the content is 5.0% by mass or more, the long-term strength development of the cement composition is further improved. When the content is 10.0% by mass or less, the contents of alite and aluminate phase become relatively large, and the early strength development of the cement composition is further improved. Ferrite phase in blended cement (chemical formula: 4CaO·Al ２ O ３ ·Fe ２ O ３ ; C ４ sometimes abbreviated as AF). The content thereof is preferably 8.8 to 9.4% by mass, more preferably 8.9 to 9.3% by mass, and particularly preferably 9.0 to 9.2% by mass. When the content is 8.8% by mass or more, the amount of waste used as a raw material can be increased. When the content is 9.4% by mass or less, the sulfate resistance of the cement composition is further improved.

[0013] The respective contents of alite (C3S), belite (C2S), aluminate phase (C3A), and ferrite phase (C4AF), which are the mineral compositions of the blended cement contained in the cement composition of the present invention, are calculated based on the results of chemical analysis of Portland cement using the following Bogue formulas (1) to (4), and corrected based on the content of fine limestone powder in the blended cement. (1) C3S (% by mass) = (4.07 × CaO (% by mass)) − (7.60 × SiO2 (% by mass)) − (6.72 × Al2O3 (% by mass)) − (1.43 × Fe2O3 (% by mass)) − (2.85 × SO ３(mass%) (However, in formula (1), the value of "CaO (mass%)" does not include free lime.) (2) C2S (mass%) = (2.87 × SiO2 (mass%)) - (0.754 × C3S (mass%)) (3) C3A (mass%) = (2.65 × Al2O3 (mass%)) - (1.69 × Fe2O3 (mass%)) (4) C4AF (mass%) = 3.04 × Fe2O3 (mass%) The correction due to the limestone fine powder content is calculated by adding (100 - (CaCO) to the values ​​calculated in (1) to (4) above. ３ This is done by multiplying by (mass %) / 100. ３ (Mass %) represents the content of limestone powder in the mixed cement. If the content of fine limestone powder in the mixed cement is unknown, it can be determined as follows: Calcium carbonate (CaCO3) in the mixed cement ３ The content of ) can be determined by first measuring the mass loss around 600°C to 700°C when approximately 30 mg of the sample is heated to 1,000°C in a nitrogen atmosphere at a heating rate of 20°C / min using a high-temperature differential scanning calorimeter (for example, NETZSCH, product name "TG-DTA2000SR"). Then, the ratio of this mass loss to the mass loss of the standard reagent can be used to determine the content of ).

[0014] The specific surface area of ​​the blended cement is preferably 2,000 to 8,000 cm². ２ / g, more preferably 3,000 to 4,000 cm ２ The value is / g. The above Braine specific surface area is 2,000 cm². ２ If the amount is greater than or equal to / g, the strength development of the cement composition will be further improved. The above Blaine specific surface area is 8,000 cm². ２ If the amount is less than / g, the cost of grinding during the production of mixed cement can be reduced.

[0015] Fe of fly ash used in the cement composition of the present invention ２ O ３The content is 15.0 to 20.0% by mass, preferably 16.0 to 19.0% by mass, more preferably 17.0 to 18.0% by mass. When the content is within the above numerical range, the initial strength development property and setting property of the cement composition can be excellently balanced. In addition, when the content is less than 15.0% by mass, the sulfuric acid resistance of the cement composition decreases. In fly ash, the content of magnetite is preferably 2.0 to 10.0% by mass, more preferably 3.0 to 9.0% by mass, still more preferably 4.0 to 8.0% by mass, and particularly preferably 6.0 to 7.0% by mass. When the content is within the above numerical range, the initial strength development property and setting property of the cement composition can be excellently balanced. In addition, when the content is 2.0% by mass or more, the sulfate resistance of the cement composition is further improved.

[0016] In fly ash, SiO ２ content, Al ２ O ３ content, and Fe ２ O ３ The total content is preferably 71.0 to 87.0% by mass, more preferably 71.5 to 84.0% by mass, and particularly preferably 74.0 to 80.0% by mass. When the content is within the above numerical range, the initial strength development property and setting property of the cement composition can be excellently balanced. In addition, when the content is 71.0% by mass or more, the sulfate resistance of the cement composition is further improved. In fly ash, the content of CaO is preferably 3.4 to 18.0% by mass, more preferably 5.0 to 16.0% by mass, and particularly preferably 8.0 to 12.0% by mass. When the content is within the above numerical range, the strength development property and sulfate resistance of the cement composition are further improved.

[0017] The 45 μm sieve residue of fly ash is preferably 9.0 to 13.0% by mass, more preferably 10.0 to 12.5% ​​by mass, and particularly preferably 11.0 to 12.0% by mass. If the 45 μm sieve residue is within the above numerical range, the sulfuric acid resistance of the cement composition is further improved. Furthermore, if the above content is 9.0% by mass or more, the setting start time of the cement composition is shortened, and the setting performance is further improved. The 50% volume cumulative particle size (D50; median diameter) of fly ash is preferably 9.0 to 13.0 μm, more preferably 9.1 to 12.0 μm, and particularly preferably 9.2 to 10.0 μm. If the above 50% volume cumulative particle size is within the above numerical range, the sulfuric acid resistance of the cement composition is further improved. Furthermore, if the above 50% volume cumulative particle size is 9.0 μm or more, the setting start time of the cement composition is shortened, and the setting performance is further improved. In addition, the initial strength development of the cement composition is further improved. The 50% volume cumulative particle size can be obtained by creating a volume cumulative distribution using a commercially available laser diffraction scattering particle size distribution analyzer or by using a sieving method in accordance with "JIS Z 8815-1994 (General Rules for Sieving Test Methods)".

[0018] The L.O.I (loss on ignition) of the fly ash is preferably 1.90% by mass or less, more preferably 0.10 to 1.50% by mass, and particularly preferably 0.30 to 1.00% by mass. If the L.O.I (loss on ignition) is 1.90% by mass or less, the strength development and sulfate resistance of the cement composition are further improved. The vitrification rate of the fly ash is preferably 60 to 80%, more preferably 62 to 79%, and particularly preferably 68 to 72%. If the vitrification rate is within the above numerical range, the initial strength development, setting properties, and sulfate resistance of the cement composition are further improved.

[0019] The specific surface area of ​​fly ash is preferably 2,500 to 8,000 cm². ２ / g, more preferably 3,000-5,000 cm ２ / g, particularly preferably 3,100 to 3,500 cm ２ The value is / g. The above Braine specific surface area is 2,500 cm². ２If the amount is greater than or equal to / g, the strength development of the cement composition will be further improved. The above Blaine specific surface area is 8,000 cm². ２ If the amount is less than or equal to / g, the fluidity of the cement composition is further improved. The amount of fly ash per 100 parts by mass of mixed cement is preferably 10 to 30 parts by mass, more preferably 12 to 25 parts by mass, and particularly preferably 14 to 20 parts by mass. If the above amount is 10 parts by mass or more, the sulfate resistance of the cement composition is further improved. If the above amount is 30 parts by mass or less, the strength development of the cement composition is further improved.

[0020] [Method for manufacturing cement composition] An example of a method for manufacturing the cement composition of the present invention is a method in which fly ash that should be used as a material for the cement composition is used, and the Fe in the fly ash ２ O ３ A selection step involves checking whether the fly ash satisfies the condition that its content is within the range of 15.0 to 20.0% by mass, and if the fly ash satisfies the above condition, selecting the fly ash as a material for the cement composition, and mixing cement and Fe selected in the selection step ２ O ３ The method includes a mixing step of preparing a cement composition by mixing fly ash having a content of 15.0 to 20.0% by mass.

[0021] In the selection process, one or more types of fly ash are prepared to be judged as to whether or not to be used as a material for the cement composition. If the prepared fly ash does not satisfy the above conditions, the fly ash is not selected as a material for the cement composition of the present invention and is used as an admixture for other cements, etc. In the selection process, as the above conditions, Fe in the fly ash ２ O ３ In addition to the content of (i) magnetite, (ii) SiO ２ Al ２ O ３ , and Fe ２ O ３The total content of (iii) CaO content, (iv) 45 μm sieve residue, (v) 50% volume cumulative particle size, (vi) L.O.I (loss on ignition), and (vii) vitrification rate may be examined to see if the conditions are met for at least one of these being within the preferred numerical range for the magnetite content, etc., as described above. In this way, by selecting fly ash that satisfies specific conditions, it is possible to make a cement composition that is excellent in strength development, setting properties, and sulfate resistance, even though it contains limestone powder.

[0022] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The materials used are as follows: (1) Mixed cements A to C; ordinary Portland cement is 93% by mass and limestone powder is 7% by mass, mixed and ground. The mineral composition of the mixed cements, such as alite, calculated using the Borg formula in accordance with "ASTM C 150 Annex A1", is shown in Table 1. (2) Fly ash 1 to 3 (referred to as "FA1 to FA3" in Table 2); details are shown in Tables 2 to 3. The 45 μm sieve residue of the fly ash was measured in accordance with "ASTM C 430". D50 was measured using a laser scattering / diffraction particle size distribution analyzer (Microtrac Bell, product name "MT3300EX II"). Loss on ignition (L.O.I) was measured in accordance with "ASTM C 311". The chemical composition (XRF) of the cement was measured in accordance with ASTM C 114. The Blaine specific surface area (indicated as "Blaine" in Table 1) of the cement and fly ash was measured in accordance with ASTM C 204. The amount of methylene blue adsorbed by the fly ash (indicated as "methylene blue" in Table 2) was measured in accordance with J-CAS I-61. The BET specific surface area of ​​the fly ash was measured by nitrogen adsorption using the BET single-point method with a fluidized specific surface area automatic measuring device (Shimadzu Corporation, product name "Flowsorb 2305").

[0023]

[0024]

[0025]

[0026] [Examples 1-2, Comparative Examples 1-7] To 100 parts by mass of the mixed cement of the type shown in Table 4, 15 parts by mass of the fly ash of the type shown in Table 4 was added and mixed to obtain a cement composition. The physical properties of the obtained cement composition were measured using the following methods. [Measurement of setting (initial setting) time] The initial setting time of the mixed cement composition was measured in accordance with "ASTM C 191". [Measurement of strength] The strength of the mixed cement composition at 3 days of age was measured in accordance with "ASTM C 109". [Measurement of expansion rate] The expansion rate of the mixed cement composition was measured in accordance with "ASTM C 1012". Note that a smaller value for the expansion rate indicates better sulfate resistance. The results are shown in Table 3.

[0027]

[0028] Table 4 shows that when comparing Example 1 with Comparative Examples 1-2 (which use different types of blended cement), the setting start time of Example 1 (135 minutes) is shorter than that of Comparative Examples 1-2 (141-150 minutes), indicating superior setting ability. A similar trend was observed when comparing Example 2 with Comparative Examples 3-4. Furthermore, the strength of Example 1 (28.0 N / mm²) ２ ) is the strength of Comparative Examples 1-2 (23.2-24.8 N / mm²) ２ It can be seen that it is greater than ( ). Strength of Example 2 (25.6 N / mm ２ ) is the strength of Comparative Example 3 (22.8 N / mm²). ２ It can be seen that it is larger than ). Also, it can be seen that the expansion rate of Example 1 (0.076%) is larger than the expansion rate of Comparative Example 2 (0.031%), but smaller than the expansion rate of Comparative Example 1 (0.254%). A similar trend was observed when comparing Example 2 with Comparative Examples 3-4. Comparing Examples 1-2 with Comparative Example 7 (which is the same as Examples 1-2 except for the type of fly ash), the setting start time (150 minutes) and strength (23.4 N / mm²) of Comparative Example 7 were ２ The ), and expansion rate (0.120%) are inferior to those of Examples 1 and 2, respectively, in terms of the time it takes for the start of setting.

Claims

1. A cement composition comprising a mixed cement consisting of Portland cement and limestone powder, and fly ash, wherein, as calculated by the Bogue formula, the alite content in the mixed cement is 60 to 70% by mass, and the aluminate phase content is 4.9 to 9.1% by mass, and the fly ash contains Fe ２ O ３ A cement composition characterized in that the content of is 15.0 to 20.0% by mass, and the amount of fly ash is 10 to 30 parts by mass per 100 parts by mass of the mixed cement.

2. The cement composition according to claim 1, wherein the content of magnetite in the fly ash is 2.0 to 10.0% by mass.

3. The cement composition according to claim 1 or 2, wherein the 45 μm sieve residue of the fly ash is 9.0 to 13.0% by mass, the 50% volume cumulative particle size (D50) is 9.0 to 13.0 μm, and the vitrification rate is 60 to 80%.

4. The cement composition according to claim 1 or 2, wherein the content of the limestone powder in the mixed cement is 5.0 to 15.0% by mass.

5. A method for producing the cement composition described in claim 1, wherein the fly ash to be used as a material for the cement composition is the Fe in the fly ash ２ O ３ A selection step in which the fly ash is selected as a material for the cement composition if the fly ash satisfies the condition that the content of is within the range of 15.0 to 20.0 mass%, and if the fly ash satisfies the condition, the fly ash is selected as a material for the cement composition, and the mixed cement and the Fe selected in the selection step ２ O ３ A method for producing a cement composition, comprising a mixing step of preparing the cement composition by mixing fly ash having a content of 15.0 to 20.0% by mass of the above-mentioned substance.

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