Cement composition and production method thereof

Abstract

To provide a cement composition that exhibits good strength development, even when weathered cement is effectively used, and a production method thereof.SOLUTION: The cement composition comprises cement having a weathering degree of 0.20 to 1.00 mass% and alkanolamine.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] If the conditions for cement are inappropriate during storage in a silo, transportation in an air slide, bagging, storage in a warehouse, etc., it will absorb water vapor from the air and become hydrated, a phenomenon known as weathering. As cement weathers, its strength development decreases, making it difficult to use. Therefore, in order to prevent cement weathering, it is necessary to store it appropriately in a dehumidified environment. However, even if it is stored under appropriate conditions, weathering of cement may be unavoidable due to long-term storage, etc.

[0003] On the other hand, alkanolamines such as triisopropanolamine (TIPA) are commonly used as grinding aids for cement and are known to be effective in developing strength. For this reason, for example, Patent Document 1 proposes a cement composition containing ordinary Portland cement clinker, gypsum, limestone, and an auxiliary containing an alkanolamine. In addition, Patent Document 2 proposes a cement composition in which triisopropanolamine alone or a mixture of triisopropanolamine and diethylene glycol is added to cement containing calcium carbonate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6966012 [Patent Document 2] JP 2023-111356 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes how weathered cement can cause abnormal setting after pouring water, reduced fluidity, and reduced strength of the hardened body, and so reduces the Blaine specific surface area of ​​the cement composition as much as possible to suppress the weathering of the cement (paragraphs 0013 and 0014). Therefore, Patent Document 1 does not intend to use weathered cement. Patent Document 2 uses cement in which 1 to 25 parts by mass of a calcium carbonate-containing material obtained by fixing carbon dioxide in a calcium-containing material is mixed with 100 parts by mass of cement clinker. Weathered cement produces calcium hydroxide through hydration, and as weathering progresses further, it combines with carbon dioxide gas to become calcium carbonate. Since the cement used in Patent Document 2 contains calcium carbonate, it can be considered to correspond to cement that has progressed in weathering, but the degree of weathering is higher than that of cement that has weathered during long-term storage.

[0006] As described above, Patent Documents 1 and 2 do not relate to techniques for effectively utilizing weathered cement. Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a cement composition that exhibits good strength development even when weathered cement is effectively utilized, and a method for producing the same. [Means for solving the problem]

[0007] The present inventors have conducted intensive research to solve the above problems, and as a result have surprisingly found that, although weathered cement (cement with a weathering degree of 0.20 to 1.00 mass%) has been previously believed to reduce strength development, combining weathered cement with an alkanolamine improves strength development, and have thus completed the present invention. That is, the present invention is exemplified as follows.

[0008] [1] A cement composition comprising cement having a weathering degree of 0.20 to 1.00 mass% and an alkanolamine. [2] The cement composition according to [1], wherein the content of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the cement. [3] The cement composition according to [1], further comprising limestone powder, the content of the limestone powder being greater than 0 mass% and not greater than 15 mass% based on the total amount of the cement and the limestone powder. [4] The cement composition according to [3], wherein the content of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the total amount of the cement and the limestone powder. [5] The cement composition according to any one of [1] to [4], wherein the cement has a calcium carbonate content of 0.5 mass% or less. [6] The cement composition according to any one of [1] to [5], wherein the cement has a C3S content of 49.0 to 69.0 mass% and a C2S content of 5.0 to 23.0 mass%. [7] A method for producing a cement composition, comprising mixing cement having a weathering degree of 0.20 to 1.00 mass% and an alkanolamine. [8] The method for producing a cement composition according to [7], wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the cement. [9] The method for producing a cement composition according to [7], further comprising mixing limestone powder, wherein the content of the limestone powder is greater than 0 mass% and not more than 15 mass% based on the total amount of the cement and the limestone powder.

[10] The method for producing a cement composition according to [9], wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the total amount of the cement and the limestone powder.

[11] The method for producing a cement composition according to any one of [7] to

[10] , wherein the cement is weathered cement.

[12] The method for producing a cement composition according to any one of [7] to

[11] , wherein the cement has a calcium carbonate content of 0.5 mass% or less.

[13] A method for producing a cement composition, comprising mixing cement and an alkanolamine, and then weathering the cement to a degree of weathering of 0.20 to 1.00 mass%.

[14] The method for producing a cement composition according to

[13] , wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the cement.

[15] The method for producing a cement composition according to

[13] , further comprising mixing limestone powder, wherein the content of the limestone powder is greater than 0 mass% and not more than 15 mass% based on the total amount of the cement and the limestone powder.

[16] The method for producing a cement composition according to

[15] , wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the total amount of the cement and the limestone powder.

[17] The method for producing a cement composition according to any one of

[13] to

[16] , wherein the weathered cement has a calcium carbonate content of 0.5 mass% or less. Effect of the Invention

[0009] According to the present invention, it is possible to provide a cement composition that exhibits good strength development even when weathered cement is effectively utilized, and a method for producing the same. [Brief description of the drawings]

[0010] [Figure 1] This is the powder X-ray diffraction pattern of the weathered cement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following is a detailed description of the embodiments of the present invention. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements to the following embodiments, which are made based on the ordinary knowledge of those skilled in the art, fall within the scope of the present invention, without departing from the spirit of the present invention.

[0012] A cement composition according to an embodiment of the present invention contains cement having a weathering degree of 0.20 to 1.00 mass % and an alkanolamine. Cement with a weathering degree of 0.20 to 1.00% by mass means weathered cement. This weathered cement usually reduces strength development, but by combining it with an alkanolamine, it is possible to improve strength development. Therefore, it becomes possible to effectively utilize the weathered cement.

[0013] In this specification, the cement composition means paste, mortar, concrete, and raw material compositions used in the preparation of these. In addition, the degree of weathering of cement in this specification [mass %] refers to the value obtained by subtracting the weight loss rate [mass %] due to dehydration of gypsum from the weight loss rate [mass %] up to 500°C in the TG curve obtained by thermogravimetric differential thermal analysis (TG-DTA) of cement. The weight loss rate due to dehydration of gypsum is the weight loss rate at 63 to 163°C. Therefore, the degree of weathering of cement is expressed by the following formula. Weathering degree = (weight loss rate up to 500°C) - (weight loss rate from 63 to 163°C)

[0014] The cement is mainly weathered due to storage in silos or bags, but it can also be weathered intentionally. Methods for intentionally weathering the cement include spraying water inside the mill and increasing the humidity during the process of moving from the mill to the silo. The degree of weathering of the cement thus obtained is 0.20 to 1.00 mass%, preferably 0.30 to 1.00 mass%, more preferably 0.40 to 0.80 mass%, and further preferably 0.50 to 0.70 mass%.

[0015] Although excessive weathering of cement can produce calcium carbonate, the amount of calcium carbonate produced by weathering is small in normal storage or intentional weathering as described above. That is, the content of calcium carbonate produced by weathering of cement is typically 0.5% by mass or less, preferably 0.3% by mass or less, and more preferably 0.1% by mass or less.

[0016] Examples of cement include various Portland cements such as ordinary Portland cement, early strength Portland cement, moderate heat Portland cement, and low heat Portland cement, and ecocement. These may be used alone or in combination of two or more. Among these, ordinary Portland cement is particularly likely to have the effect of improving the strength development of the cement composition because it is easily weathered.

[0017] The cement preferably has a C3S (alite: 3CaO·SiO2) content of 49.0-69.0 mass% and a C2S (belite: 2CaO·SiO2) content of 5.0-23.0 mass%. Cement with such a mineral composition is likely to improve the strength development. The C3A (aluminate: 3CaO·Al2O3) content in the cement is not particularly limited, but is typically 1.0-15.0 mass%. Similarly, the C4AF (ferrite: 4CaO·Al2O3·Fe2O3) content in the cement is not particularly limited, but is typically 3.0-20.0 mass%. Here, the contents of C3S, C2S, C3A and C4AF can be calculated based on the chemical components of the cement using the following Bogue formula. C3S[mass%]=(4.07×CaO[mass%])-(7.60×SiO2[mass%])-(6.72×Al2O3[mass%])-(1.43×Fe2O3[mass%])-(2.85×SO3[mass%]) C2S[mass%]=(2.87×SiO2[mass%])-(0.754×C3S[mass%]) C3A[mass%]=(2.65×Al2O3[mass%])-(1.69×Fe2O3[mass%]) C4AF[mass%]=3.04×Fe2O3[mass%] When the cement is clinker, the C3S content can be calculated based on the chemical composition of the clinker using the following Bogue formula: The C2S, C3A, and C4AF contents can be calculated based on the chemical composition of the clinker using the above Bogue formula. C3S[mass%]=(4.07×CaO[mass%])-(7.60×SiO2[mass%])-(6.72×Al2O3[mass%])-(1.43×Fe2O3[mass%])

[0018] Cement has a Blaine specific surface area of ​​3000 to 8000 cm 2 By controlling the Blaine specific surface area within such a range, it is possible to improve the strength development and fluidity of the cement composition. Here, the Blaine specific surface area of ​​cement can be measured in accordance with JIS R5201:2015.

[0019] Examples of alkanolamines include monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, methylethanolamine, methylisopropanolamine, Nn-butylethanolamine, N-methyldiethanolamine, Nn-butyldiethanolamine, N-methyldiisopropanolamine, diethanolisopropanolamine, ethanoldiisopropanolamine, diisopropanolethanolamine, tetrahydroxyethylethylenediamine, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, tris(2-hydroxybutyl)amine, etc. These may be used alone or in combination of two or more. Among these, the alkanolamine is preferably at least one selected from the group consisting of diethanolisopropanolamine (DEIPA), triisopropanolamine (TIPA), ethanoldiisopropanolamine (EDIPA), N-methyldiethanolamine (MDEA) and Nn-butyldiethanolamine (BDEA), and more preferably triisopropanolamine (TIPA).

[0020] The content of alkanolamine in the cement composition is not particularly limited, but is preferably 0.0050 to 0.0500 parts by mass (50 to 500 ppm), more preferably 0.0100 to 0.0400 parts by mass (100 to 400 ppm), and even more preferably 0.0150 to 0.0300 parts by mass (150 to 300 ppm) relative to 100 parts by mass of cement. By controlling the content of alkanolamine within such a range, the strength development of the cement composition can be stably improved.

[0021] The cement composition according to the embodiment of the present invention may further contain limestone powder in addition to the above components. In recent years, there has been a demand to reduce CO2 emissions even in the cement industry, which involves huge amounts of energy consumption. The use of limestone powder can reduce the cement content, thereby contributing to a reduction in CO2 emissions. The limestone powder may be crushed limestone or may be carbonated powder of fresh concrete sludge or concrete. The content of limestone powder in the cement composition is not particularly limited, but is preferably more than 0 mass% and not more than 15 mass%, more preferably more than 5 mass% and not more than 12 mass%, and even more preferably 8 to 12 mass%, based on the total amount of cement and limestone powder. By controlling the content of limestone powder within such a range, it is possible to suppress a decrease in the strength development of the cement composition.

[0022] When the cement composition contains limestone powder, the content of alkanolamine in the cement composition is not particularly limited, but is preferably 0.0050 to 0.0500 parts by mass (50 to 500 ppm), more preferably 0.0100 to 0.0400 parts by mass (100 to 400 ppm), and even more preferably 0.0150 to 0.0300 parts by mass (150 to 300 ppm) relative to 100 parts by mass of the total amount of cement and limestone powder. By controlling the content of alkanolamine within such a range, the strength development of the cement composition can be stably improved.

[0023] Limestone powder has a Blaine specific surface area of ​​3000 to 10000 cm 2 By controlling the Blaine specific surface area within such a range, it is possible to improve the strength development and fluidity of the cement composition. The Blaine specific surface area of ​​the limestone powder can be measured in accordance with the above-mentioned method.

[0024] In addition to the above-mentioned components, the cement composition according to the embodiment of the present invention may further contain known components within a range that does not impair the effects of the present invention. Examples of known components include admixtures such as gypsum powder, blast furnace slag powder, molten coal slag powder, fly ash, limestone fine powder, siliceous powder, natural pozzolan, calcined clay, and silica fume, grinding aids, admixtures (e.g., water-reducing agents, defoamers, shrinkage-reducing agents, etc.), aggregates (fine aggregates, coarse aggregates), and water.

[0025] The cement composition according to the embodiment of the present invention is not particularly limited and can be produced by a conventional method. For example, the cement composition according to the embodiment of the present invention can be produced by mixing cement having a weathering degree of 0.20 to 1.00 mass% (i.e., weathered cement) and an alkanolamine. Alternatively, the cement composition according to the embodiment of the present invention can be produced by mixing cement (unweathered cement) and an alkanolamine, and then weathering the cement so that the weathering degree is 0.20 to 1.00 mass%. The amount of the alkanolamine to be mixed may be the above-mentioned content.

[0026] The method of adding the alkanolamine is not particularly limited as long as it can be mixed with the cement. For example, when the cement composition is a raw material composition used for preparing paste, mortar, and concrete, an alkanolamine may be added to weathered cement (ground cement clinker) and mixed. When weathered cement clinker is used as a raw material, an alkanolamine as a grinding aid may be added to the cement clinker, which may then be ground and mixed. At this time, other components (e.g., gypsum) may be added to the cement clinker together with the alkanolamine. When unweathered cement clinker is used as a raw material, an alkanolamine as a grinding aid and, if necessary, other components such as gypsum may be added to the cement clinker, which may then be ground and mixed, and the cement may then be weathered. When the cement composition is a paste, mortar, or concrete, the alkanolamine may be added when the components are mixed.

[0027] In addition, when the cement composition according to the embodiment of the present invention contains limestone powder, the limestone powder may be further added and mixed. The amount of the limestone powder may be the content described above. The timing of adding the limestone powder is not particularly limited. For example, when the cement composition is a raw material composition used for preparing paste, mortar, and concrete, alkanolamine and limestone powder may be added to weathered cement and mixed, or limestone powder may be added to weathered cement and then alkanolamine may be further added and mixed. When weathered cement clinker is used as a raw material, limestone, alkanolamine as a grinding aid, and other components such as gypsum as necessary may be added to the cement clinker, and then crushed and mixed. Furthermore, when unweathered cement clinker is used as a raw material, limestone, alkanolamine as a grinding aid, and other components such as gypsum as necessary may be added to the cement clinker, and then crushed and mixed, and then the cement may be weathered. When the cement composition is a paste, mortar, or concrete, the alkanolamine may be added when the components are mixed. EXAMPLES

[0028] The present invention will be described in detail below with reference to examples, but the present invention should not be construed as being limited to these.

[0029] [Raw materials used] Cement N: Ordinary Portland cement (Blaine specific surface area: 3260 cm 2 / g) Cement M: Moderate heat Portland cement (Blaine specific surface area: 3280 cm 2 / g) Cement L: Low heat Portland cement (Blaine specific surface area: 3130 cm 2 / g) Limestone powder (Blaine specific surface area: 5040 cm 2 / g) Triisopropanolamine (TIPA) The chemical composition of each cement and limestone powder is shown in Table 1. Each cement did not contain any admixtures such as limestone, and was produced using diethylene glycol (addition amount: approximately 0.0300 parts by mass per 100 parts by mass of cement) as a grinding aid. The mineral composition of each cement calculated using Bogue's formula is shown in Table 2. The chemical composition was determined by quantitative analysis using an X-ray fluorescence analyzer (ZSX Primus II, manufactured by Rigaku Corporation) in accordance with JIS R5204:2019.

[0030] [Table 1]

[0031] [Table 2]

[0032] [Weathering of cement] The above cements were put into plastic bags and stored at room temperature for 6 and 12 months (cement L was stored for only 6 months) to allow them to weather.

[0033] [Measurement of the degree of weathering of cement] Thermogravimetric differential thermal analysis (TG-DTA) was performed under a N2 gas atmosphere using a Bruker AXS TG-DTA2000SR. The TG-DTA conditions were as follows: Heating rate: 20.0℃ / min N2 gas flow rate: 300mL / min Sample size: approx. 20 mg Measurement temperature range: Room temperature (approx. 26°C) to 1000°C In the TG curve obtained by TG-DTA, the degree of weathering was determined by subtracting the weight loss rate due to dehydration of gypsum (weight loss rate from 63 to 163°C) [mass%] from the weight loss rate up to 500°C [mass%]. The weathering results for each cement are shown in Table 3.

[0034] [Table 3]

[0035] In addition, the presence or absence of calcium carbonate formation was investigated for each of the above-mentioned weathered cements by powder X-ray diffraction (XRD). As a result, no peaks due to calcium carbonate were observed in any of the above-mentioned weathered cements, confirming that calcium carbonate had not formed. For reference, the powder X-ray diffraction patterns of each cement that was weathered (cements N and M were stored at room temperature for 12 months; cement L was stored at room temperature for 6 months) are shown in Figure 1. Some of the peaks due to calcium carbonate overlap with the peaks of the cement minerals, but no peaks specific to calcium carbonate (diffraction angles: peaks at approximately 48.5°, 57.5°, and 65.0°) could be confirmed.

[0036] [Preparation of cement composition] TIPA was added to the above cement and mixed to prepare a cement composition. In this cement composition, the content of TIPA was 0.0100 parts by mass or 0.0300 parts by mass per 100 parts by mass of cement. In addition, limestone powder and TIPA were added to the above cement and mixed to prepare a cement composition. In this cement composition, the content of limestone powder was 10 mass% based on the total amount of cement and limestone powder, and the content of TIPA was 0.0100 mass parts or 0.0300 mass parts based on 100 mass parts of cement. Furthermore, as a comparative cement composition, a cement composition (cement composition not containing TIPA) was prepared by adding limestone powder to the above cement and mixing it. In this cement composition, the content of limestone powder was 10 mass% based on the total amount of cement and limestone powder. For comparison, a sample containing only cement was also prepared. Details of each sample obtained as described above are shown in Table 4.

[0037] [Table 4]

[0038] Using the above cement composition or cement, mortar was prepared in accordance with JIS R5201:2015, and the compressive strength of the mortar was measured at ages of 3 days, 7 days, and 28 days. The results are shown in Table 5.

[0039] [Table 5]

[0040] As shown in Table 5, even when weathered cement was used, the addition of TIPA improved the compressive strength at 28 days (Comparison between No. 1 and No. 2, between No. 3 and No. 4, between No. 5 and No. 6 and No. 7, between No. 8 and No. 9 and No. 10, between No. 15 and No. 16 and No. 17, between No. 18 and No. 19 and No. 20, between No. 21 and No. 22, between No. 23 and No. 24, between No. 29 and No. 30, and between No. 31 and No. 32). In particular, when the cement was ordinary Portland cement (Cement N), all the compressive strengths at 3 days, 7 days, and 28 days were improved (Comparison between No. 1 and No. 2, between No. 3 and No. 4, between No. 5 and No. 6 and No. 7, and between No. 8 and No. 9 and No. 10).

[0041] In addition, when weathered cement was combined with TIPA, the decrease in compressive strength at each age was small even with the addition of limestone powder (comparison between No. 2 and No. 4, No. 6 and No. 9, No. 16 and No. 19, No. 22 and No. 24, No. 30 and No. 32). In addition, when ordinary Portland cement (cement N) was used, the compressive strength at 3 days and 7 days was improved (comparison between No. 2 and No. 4, No. 6 and No. 9). In addition, when moderate-heat Portland cement (cement M) was used, the compressive strength at 3 days, 7 days, and 28 days was improved (comparison between No. 16 and No. 19, No. 22 and No. 24). Furthermore, by increasing the TIPA content, the compressive strength improved at all ages of 3 days, 7 days, and 28 days (comparison between No. 6 and No. 7, comparison between No. 9 and No. 10, comparison between No. 16 and No. 17, comparison between No. 19 and No. 20).

[0042] As can be seen from the above results, the present invention can provide a cement composition that exhibits good strength development even when weathered cement is effectively utilized, and a method for producing the same.

Claims

1. A cement composition comprising a cement having a weathering degree of 0.20 to 1.00 mass % and an alkanolamine.

2. The cement composition according to claim 1, wherein the content of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the cement.

3. The cement composition according to claim 1, further comprising limestone powder, the content of the limestone powder being greater than 0 mass% and not greater than 15 mass% based on the total amount of the cement and the limestone powder.

4. The cement composition according to claim 3, wherein the content of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the total amount of the cement and the limestone powder.

5. The cement composition according to any one of claims 1 to 4, wherein the cement has a calcium carbonate content of 0.5 mass% or less.

6. The cement is C 3 The content of S is 49.0 to 69.0 mass%, 2 The cement composition according to any one of claims 1 to 4, wherein the S content is 5.0 to 23.0 mass%.

7. A method for producing a cement composition, comprising mixing cement having a weathering degree of 0.20 to 1.00 mass % and an alkanolamine.

8. The method for producing a cement composition according to claim 7, wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the cement.

9. The method for producing a cement composition according to claim 7, further comprising mixing limestone powder, wherein the content of the limestone powder is more than 0 mass% and 15 mass% or less with respect to the total amount of the cement and the limestone powder.

10. The method for producing a cement composition according to claim 9, wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the total amount of the cement and the limestone powder.

11. The method for producing a cement composition according to any one of claims 7 to 10, wherein the cement is a weathered cement.

12. The method for producing a cement composition according to claim 11, wherein the cement has a calcium carbonate content of 0.5 mass% or less.

13. A method for producing a cement composition, comprising mixing cement and an alkanolamine, and then weathering the cement to a degree of weathering of 0.20 to 1.00 mass%.

14. The method for producing a cement composition according to claim 13, wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the cement.

15. The method for producing a cement composition according to claim 13, further comprising mixing limestone powder, wherein the content of the limestone powder is more than 0 mass% and 15 mass% or less with respect to the total amount of the cement and the limestone powder.

16. The method for producing a cement composition according to claim 15, wherein the amount of the alkanolamine is 0.0050 to 0.0500 parts by mass per 100 parts by mass of the total amount of the cement and the limestone powder.

17. The method for producing a cement composition according to any one of claims 13 to 16, wherein the weathered cement has a calcium carbonate content of 0.5 mass% or less.

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