hydraulic components

Abstract

To provide a hydraulic composition that uses less cement and reduces CO2 emissions associated with cement production, the composition makes possible to further reduce the emission of CO2 by using calcium carbonate produced by fixing CO2 contained in exhaust gas and the atmosphere.SOLUTION: A hydraulic composition comprising powders containing calcium carbonate, Portland cement, and blast furnace slag, wherein the ratio of the calcium carbonate to the powders is in the range of 20 to 95% by mass. The ratio of Portland cement to the powders is 23 mass% or less, and the ratio of blast furnace slag to the powders is 56 mass% or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a hydraulic composition containing calcium carbonate. [Background technology]

[0002] In order to reduce CO2 (carbon dioxide) emissions, the amount of Portland cement used can be reduced by using industrial by-products such as blast furnace slag as a binder. Blast furnace slag has properties similar to cement, such as latent hydraulic properties, so if the amount of Portland cement used is reduced by using blast furnace slag, the amount of CO2 emitted during the production of Portland cement can be reduced. Concrete materials that use blast furnace slag as a binder are used for a variety of purposes. For example, Patent Document 1 discloses a cement composition containing 20 to 40 mass % of Portland cement and 50 to 80 mass % of blast furnace slag as a cement composition used for ground improvement. Furthermore, Non-Patent Document 1 discloses concrete made using blast furnace cement with a blast furnace slag content of 65% as cast-in-place concrete. Furthermore, Non-Patent Document 2 states that the design standard strength is 100 N / mm 2 The high-strength concrete disclosed in this publication contains 30% Portland cement, 67% blast furnace slag, and 3% silica fume as binders. CO2 is emitted from various places and things, such as coal-fired power plants, vehicles, factories, and waste treatment facilities. For this reason, technology has been developed in recent years to capture CO2 and produce calcium carbonate (carbonate minerals). Calcium carbonate produced by this technology fixes CO2 in the atmosphere and exhaust gases. Therefore, if calcium carbonate is incorporated into hydraulic compositions and solidified, it is possible to reduce CO2 emissions throughout society. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-236073 [Non-patent literature]

[0004] [Non-Patent Document 1] Daijiro Tsuji et al., "Quality of Cast-in-Place Concrete Piles Using High-Content Blast Furnace Slag Cement," Proceedings of the Japan Concrete Institute, Vol. 37, No. 1, pp. 1357-1362, 2015. [Non-patent document 2] Daijiro Tsuji et al., "Construction Experiment of Full-Scale Columns Using 100N / mm2 Class High-Strength Concrete with High-Blast-Furnace Slag Cement," Proceedings of the Japan Concrete Institute, Vol. 36, No. 1, pp. 1702-1707, 2014. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to propose a hydraulic composition that reduces the amount of cement used, thereby reducing CO2 emissions associated with cement production, and that uses calcium carbonate that fixes CO2 from exhaust gases and the atmosphere, thereby further reducing CO2 emissions. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides: Fixing carbon dioxide from exhaust gases or the atmosphere A hydraulic composition containing powders including calcium carbonate, Portland cement, and blast furnace slag, At least one of gypsum and silica fume is included; The ratio of the calcium carbonate to the powder is within a range of 20 to 95% by mass. The ratio of the Portland cement to the powder is 23 mass % or less, and Before The proportion of the blast furnace slag is preferably 56 mass % or less. The content of calcium carbonate in the powder is desirably 70% by mass or less, preferably 50% by mass or less, and more preferably 30% by mass or less. This hydraulic composition uses powdered calcium carbonate (carbonate mineral) that fixes CO2 from exhaust gases and the atmosphere, allowing for long-term fixation of CO2. This means that CO2 emitted throughout society can be stably retained and stored. Furthermore, the use of blast furnace slag, an industrial by-product, contributes to the effective use of resources and reduces the amount of Portland cement used, thereby contributing to a reduction in CO2 emissions. Furthermore, the design standard strength of concrete can be adjusted by adjusting the amount of calcium carbonate used, making the composition suitable for a wide range of applications. [Effects of the Invention]

[0007] According to the hydraulic composition of the present invention, it is possible to reduce the amount of cement used and also to reduce CO2 emissions by using calcium carbonate that fixes CO2 from exhaust gases and the atmosphere. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a graph showing the relationship between the calcium carbonate addition rate and compressive strength based on experimental results. [Figure 2] 1 is a graph showing the relationship between the water-powder ratio and the calcium carbonate addition rate in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this embodiment, a hydraulic composition that reduces CO2 emissions by reducing the amount of Portland cement used will be described. The hydraulic composition of this embodiment contains powders containing calcium carbonate (CaCO3), Portland cement, and blast furnace slag, water, and aggregate. The hydraulic composition is formulated to be able to achieve the required strength even when the amount of Portland cement used is reduced. In addition, expanding agents, silica fume, gypsum, multifunctional admixtures, etc. may be added to the powder to improve strength and durability.

[0010] Calcium carbonate (carbonate mineral) fixes carbon dioxide (CO2) from exhaust gases and the atmosphere. By using calcium carbonate that fixes CO2 from exhaust gases and the atmosphere, it is possible to further reduce CO2 emissions. The ratio of calcium carbonate to the powder is set to 20% by mass or more from the viewpoint of securing the fixed amount of calcium carbonate, and 95% by mass or less from the viewpoint of strength development. The ratio of calcium carbonate in the powder is set according to the design standard strength of the hydraulic composition. For example, for a compressive strength of 60 N / mm 2 If the target is above 30 mass%, the value should be 40 to 60 N / mm 2 If the target is about 50% by mass or less, the value should be 20 to 40 N / mm 2 When the target is about 70 mass % or less, it is desirable to set it to 70 mass % or less.

[0011] Ordinary Portland cement is used as the Portland cement, but other Portland cements such as moderate-heat Portland cement, low-heat Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, sulfate-resistant Portland cement, etc., as specified in JIS R5210 "Portland cement" may also be used. The ratio of Portland cement to the powder should be between 1% and 23% by mass, from the perspective of reducing CO2 emissions. It is desirable to use ground granulated blast furnace slag used in JIS R 5211 "Blast furnace cement" or ground granulated blast furnace slag conforming to JISA 6206 "Blast furnace slag for concrete." The ratio of blast furnace slag to the powder is between 3% and 56% by mass. For example, the expansive material specified in JISA6202 "Expansive materials for concrete" may be used. As the silica fume, for example, powdered silica fume as specified in JISA6207 "Silica fume for concrete" may be used. As the gypsum, for example, gypsum specified in JIS R9151 "Natural gypsum for cement" may be used.

[0012] The hydraulic composition of this embodiment uses calcium carbonate (carbonate mineral) as powder, which fixes CO2 from exhaust gases and the atmosphere, and therefore can fix CO2 for a long period of time. In other words, it is possible to stably retain and store CO2 emitted by society as a whole. In addition, by using blast furnace slag, an industrial by-product, the company contributes to the effective use of resources. In addition, by adding blast furnace slag and calcium carbonate to reduce the amount of Portland cement used, it is possible to reduce CO2 emissions associated with cement production. Furthermore, by adjusting the amount of calcium carbonate used, the design standard strength of the concrete can be adjusted, making it suitable for many uses.

[0013] Below, we estimate the predicted strength, CO2 emissions, and CO2 fixation amounts when part of the powder in the hydraulic composition is replaced with calcium carbonate. In this example, a concrete structure with a design strength of 100 N / mm was used, using cement with a high content of blast furnace slag. 2 High-strength concrete (mixture A) with actual strength of 40N / mm after 28 days 2 Civil engineering concrete (mixture B), design standard strength is 45N / mm 2 For the concrete for cast-in-place piles (mixture C), the predicted strength and amount of CO2 fixed were calculated when part of the powder was replaced with calcium carbonate. Table 1 shows the mix proportions for high-strength concrete (Mix A), civil engineering concrete (Mix B), and cast-in-place pile concrete (Mix C) using high-content blast furnace slag cement as the base mix before replacing some of the powder with calcium carbonate. CO2 emissions were calculated by multiplying the CO2 emissions of each material by its unit weight, based on the Japan Society of Civil Engineers' Environmental Impact Assessment of Concrete (Part 2), Concrete Technology Series. Table 2 shows the CO2 emissions for each material. Here, the CO2 emissions of silica fume were assumed to be 19.6, the same as for fly ash. Furthermore, gypsum was assumed to be natural anhydrous, and its CO2 emissions were assumed to be 16.1, the same as for mined and crushed limestone fine powder, which is manufactured using a similar method.

[0014] [Table 1]

[0015] [Table 2]

[0016] Table 3 shows the mix proportions for this example. In this example, 25%, 50%, 70%, 80%, 90%, and 95% of the concrete powder shown in Table 1 were replaced with calcium carbonate, and the other materials contained in the powder were set at 75%, 50%, 30%, 20%, 10%, and 5%, respectively. That is, in this example, the mix proportions were set without changing the ratios of powders other than calcium carbonate from the basic mix proportions. Furthermore, the volume of the powder was also kept unchanged from the basic mix proportions, and the amounts of water and aggregate (coarse aggregate and fine aggregate) were also kept the same as the basic mix proportions. In the "Mix" column in Table 3, "A," "B," and "C" refer to the base mix proportions (see Table 1), and the numbers such as "25" and "50" indicate the percentage (substitution rate) of calcium carbonate in the powder. In the mix proportions in Table 3, the ratio of Portland cement to powder is 23% by mass for mix proportions "A+25" and "B+25", and 1% by mass for mix proportion "C+95". In addition, the ratio of blast furnace slag to powder is 50% by mass for mix proportion "A+25", and 3% by mass for mix proportion "C+95".

[0017] [Table 3]

[0018] Next, the predicted strength, CO2 emissions, and CO2 fixation amounts for the concrete with the mix shown in Table 3 are calculated. The predicted strength is calculated by experimentally measuring the decrease in compressive strength caused by replacing part of the powder with calcium carbonate, and using the decrease rate of this compressive strength (compressive strength ratio). That is, for a concrete of a given mix, the compressive strength is measured for both cases where part of the powder is not replaced with calcium carbonate and where it is replaced with calcium carbonate, and the ratio of the two compressive strengths (compressive strength ratio) is calculated. The predicted strength for each mix is ​​then estimated using the compressive strength ratio. Table 4 shows the concrete mix used in the experiment to calculate the compressive strength ratio, and the compressive strength ratio calculated from the experimental results. Figure 1 also shows the relationship between the calcium carbonate addition rate and the compressive strength ratio. In the mix shown in Table 4, the cement and fine aggregate mix was changed depending on the amount of calcium carbonate added so that the water-powder ratio (weight ratio) was kept constant (0.5).

[0019] [Table 4]

[0020] As shown in Table 4 and Figure 1, when 25% (mixture D + 25), 50% (mixture D + 50), 70% (mixture D + 70), 80% (mixture D + 80), 90% (mixture D + 90), and 95% (mixture D + 95) of the powder were replaced with calcium carbonate, the compressive strengths were 0.65, 0.34, 0.16, 0.10, 0.05, and 0.02 times that of mix D, which had no calcium carbonate added. In mix D + 99, where 99% of the powder was replaced with calcium carbonate, the specimens did not solidify, and the compressive strength could not be measured. Therefore, it is desirable to use a calcium carbonate content of 95% or less. In this example, the predicted strength of each concrete mix in the example is calculated by multiplying the strength (design standard strength or actual strength at 28 days) of each concrete (mixes A, B, and C) in the basic mix by the compressive strength ratio corresponding to the amount of calcium carbonate added (replacement amount) obtained through experiments. In addition, the amount of CO2 emissions is calculated by summing up the values ​​obtained by multiplying the weight of each material in each formulation by the CO2 emissions for each material shown in Table 2. Furthermore, since the molecular weight of CO2 is 44 out of 100 molecular weight of calcium carbonate, the amount of CO2 fixed is calculated by multiplying the weight of calcium carbonate in each blend by 44 / 100.

[0021] Table 5 shows the predicted intensity, CO2 emissions, and CO2 fixation amounts for this example. As shown in Table 5, the design strength of concrete can be adjusted by adjusting the amount of calcium carbonate added. Furthermore, by replacing part of the powder with calcium carbonate, it is possible to reduce CO2 emissions and increase the amount of CO2 fixed, thereby enabling the stable retention and storage of CO2 emitted by society as a whole. As shown in Figure 2, when the relationship between the water-powder ratio and the calcium carbonate addition rate in this example is plotted on a graph, five zones (predicted strength 80 N / mm 2 Above, 60~80N / mm 2 , 40~60N / mm 2 , 20~40N / mm 2 , 1~20N / mm 2 ) where the predicted strength of mix A and mixes based on mix A is plotted at a water-powder ratio of 20% in Figure 2, the predicted strength of mix B and mixes based on mix B is plotted at a water-powder ratio of 40% in Figure 2, and the predicted strength of mix C and mixes based on mix C is plotted at a water-powder ratio of 50% in Figure 2. Line A in Figure 2 indicates a compressive strength of 80 N / mm 2 Similarly, the lines I to O in Figure 2 show the calcium carbonate addition rate and water-powder ratio that can be expected to achieve a compressive strength of 60 N / mm 2 , 40N / mm 2 , 20N / mm 2 , 1N / mm 2 Figure 2 shows the calcium carbonate addition rate and water-to-powder ratio that can be expected to achieve a compressive strength of 60 N / mm. By using Figure 2, it is possible to set the water-to-powder ratio and calcium carbonate addition rate according to the strength required for the hydraulic composition. For example, 2 More than 80N / mm 2When aiming for a concrete with a compressive strength of less than 40 N / mm, the calcium carbonate addition rate should be set to 20 mass% or more of the powder in order to secure the amount of CO2 fixed, and the calcium carbonate addition rate and water-powder ratio should be set to the area between lines A and B in Figure 2 (water-powder ratio of 24% or less in Figure 2), and a compressive strength of 40 N / mm should be achieved. 2 More than 60N / mm 2 When aiming for concrete of less than 100%, the calcium carbonate content should be set to 20% by mass or more of the powder, and the calcium carbonate content and water-powder ratio should be set so that they fall within the range between lines A and C in Figure 2. Furthermore, in cases where strength is not required as much as in structural concrete, such as in soil improvement materials, the calcium carbonate content can be increased, but from the viewpoint of ensuring sufficient strength, it is preferable to keep the calcium carbonate content at 95 mass% or less.

[0022] [Table 5]

[0023] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be appropriately modified within the scope of the present invention. For example, the materials constituting calcium carbonate, blast furnace slag, expansive agent, hydrated lime, quicklime, fly ash, and Portland cement are not limited to those shown in the above embodiment.

Claims

1. A hydraulic composition containing powders including calcium carbonate that fixes carbon dioxide from exhaust gas or the atmosphere, Portland cement, and blast furnace slag, At least one of gypsum and silica fume is included; A hydraulic composition characterized in that the ratio of the calcium carbonate to the powder is within the range of 20 to 95 mass %.

2. 2. The hydraulic composition according to claim 1, wherein the ratio of the Portland cement to the powder is 23% by mass or less.

3. 3. The hydraulic composition according to claim 1, wherein the ratio of the blast furnace slag to the powder is 56 mass % or less.

4. 4. The hydraulic composition according to claim 1, wherein the proportion of the calcium carbonate in the powder is 70% by mass or less.

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