Manufacturing method of calcium carbonate concrete

Abstract

To provide a method for producing calcium carbonate concrete that can improve the compressive strength of calcium carbonate concrete. [Solution] A method for producing calcium carbonate concrete, comprising: a first step of preparing carbonated mortar powder or carbonated concrete powder by carbonating mortar powder or concrete powder; a second step of injecting the carbonated mortar powder or carbonated concrete powder into a mold and pressurizing the carbonated mortar powder or carbonated concrete powder in the height direction of the mold to form a unit layer consisting of the carbonated mortar powder or carbonated concrete powder; a third step of injecting an aqueous calcium bicarbonate solution into the mold and immersing the unit layer in the aqueous calcium bicarbonate solution to precipitate the calcium carbonate contained inside the unit layer onto the surface of the unit layer; and a fourth step of drying the unit layer and evaporating the aqueous calcium bicarbonate solution in the mold.

Description

Technical Field

[0001] The present invention relates to a method for producing calcium carbonate concrete.

Background Art

[0002] Global warming has become a worldwide problem. In the production of concrete, a large amount of carbon dioxide is emitted. Therefore, in the field of concrete, in order to reduce carbon dioxide, it is required to reduce the amount of cement used or to produce concrete without using cement.

[0003] Consideration has been underway for calcium carbonate concrete (Calcium Carbonate Circulation: CCC) that can be recycled any number of times as construction resources using carbon dioxide and concrete waste and that is carbon neutral (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0007] The present invention has the following aspects. [1] A first step of preparing carbonated mortar powder or carbonated concrete powder by carbonating mortar powder or concrete powder, A second step involves injecting the carbonated mortar powder or carbonated concrete powder into a formwork, and pressurizing the carbonated mortar powder or carbonated concrete powder within the formwork in the height direction to form a unit layer consisting of the carbonated mortar powder or carbonated concrete powder. A third step involves pouring an aqueous calcium bicarbonate solution into the mold, immersing the unit layer in the aqueous calcium bicarbonate solution, and precipitating the calcium carbonate contained inside the unit layer onto the surface of the unit layer. A method for producing calcium carbonate concrete, comprising a fourth step of drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the formwork. [2] The method for producing calcium carbonate concrete according to [1], wherein the third step and the fourth step are repeated in this order two or more times. [3] The method for producing calcium carbonate concrete according to [1] or [2], wherein the second step, the third step, and the fourth step are repeated in this order two or more times. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing calcium carbonate concrete that can improve the compressive strength of calcium carbonate concrete. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram illustrating a method for manufacturing calcium carbonate concrete according to one embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating a method for manufacturing calcium carbonate concrete according to one embodiment of the present invention. [Figure 3]It is a schematic diagram showing a method for manufacturing calcium carbonate concrete according to an embodiment of the present invention. [Figure 4] It is a schematic diagram showing a method for manufacturing calcium carbonate concrete according to an embodiment of the present invention. [Figure 5] It is a schematic diagram showing a method for manufacturing calcium carbonate concrete according to an embodiment of the present invention. [Figure 6] It is a schematic diagram showing a method for manufacturing calcium carbonate concrete according to an embodiment of the present invention. [Figure 7] It is a schematic diagram showing a method for manufacturing calcium carbonate concrete according to an embodiment of the present invention. [Figure 8] It is a schematic diagram showing a method for manufacturing calcium carbonate concrete according to an embodiment of the present invention. [Figure 9] It is a diagram showing the relationship between the pressure during pressurization and the compressive strength of calcium carbonate concrete in Experimental Example 1, Experimental Example 2, and Experimental Example 3. [Figure 10] It is a diagram showing the relationship between the pressurization time and the compressive strength of calcium carbonate concrete in Experimental Example 4, Experimental Example 2, and Experimental Example 5. [Figure 11] It is a diagram showing the relationship between the number of repetitions (cycle number) of repeating the third step, the fifth step, and the fourth step and the compressive strength of calcium carbonate concrete in Experimental Example 6, Experimental Example 2, and Experimental Example 7. [Figure 12] It is a diagram showing the relationship between the number of repetitions (cycle number) of repeating the third step and the fourth step and the compressive strength of calcium carbonate concrete in Experimental Example 8, Experimental Example 9, and Experimental Example 10. [Figure 13] It is a diagram showing the relationship between the compressive strength of calcium carbonate concrete and the combination of the implementation steps of the third step, the fourth step, and the fifth step in Experimental Example 2, Experimental Example 9, and Experimental Example 11. [Figure 14] It is a diagram showing the results of measuring the compressive strength and density of calcium carbonate concrete obtained in Experimental Examples 12 to 14.

Mode for Carrying Out the Invention

[0010] An embodiment of the method for producing calcium carbonate concrete according to the present invention will be described. Note that this embodiment is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[0011] [Method for Producing Calcium Carbonate Concrete] The method for producing calcium carbonate concrete according to an embodiment of the present invention includes a first step of carbonating mortar powder or concrete powder to prepare carbonated mortar powder or carbonated concrete powder, a second step of injecting the carbonated mortar powder or carbonated concrete powder into a mold and pressurizing the carbonated mortar powder or carbonated concrete powder in the height direction of the mold to form a unit layer composed of the carbonated mortar powder, a third step of injecting an aqueous solution of calcium hydrogen carbonate into the mold and immersing the unit layer in the aqueous solution of calcium hydrogen carbonate to precipitate calcium carbonate contained inside the unit layer on the surface layer of the unit layer, and a fourth step of drying the unit layer and evaporating the aqueous solution of calcium hydrogen carbonate in the mold.

[0012] Referring to FIGS. 1 to 8, the method for producing calcium carbonate concrete according to this embodiment will be described. FIGS. 1 to 8 are schematic diagrams showing the method for producing calcium carbonate concrete according to this embodiment.

[0013] "First Step" In the first step, mortar powder or concrete powder is carbonated to prepare carbonated mortar powder or carbonated concrete powder.

[0014] The mortar powder or concrete powder is obtained by mixing cement and aggregate and kneading with water. In this specification, cement refers to a powder that hardens by a chemical reaction with water, mainly using limestone, clay, silica, iron oxide raw materials, etc. as main raw materials.

[0015] Aggregates are materials traditionally used in the manufacture of concrete and asphalt mixtures. Examples of aggregates include gravel and sand originating from rivers and seas; crushed rocks; crushed blast furnace slag, fly ash, and other molten slags from industrial waste; crushed vitrified materials; and crushed inorganic construction waste.

[0016] The aggregate is preferably at least one selected from the group consisting of inorganic particles (including rock aggregates), inorganic fibers, organic fibers, organic particles, metal particles, and metal fibers. Examples of fibers include steel fibers, carbon fibers, glass fibers, basalt fibers (basalt produced by melting and vitrifying basalt), and plastic fibers that are commercially available as materials for mortar or concrete.

[0017] The aggregate may preferably have at least one of carbonite and OH groups on its surface.

[0018] Furthermore, it is preferable that the mortar or concrete used as a raw material for the mortar powder or concrete powder is derived from construction waste.

[0019] The mixing ratio of cement to aggregate in mortar powder or concrete powder can be appropriately determined according to the required strength of the mortar powder. The mixing ratio of cement to aggregate is preferably expressed by mass, for example, 1 part cement to 2 to 4 parts aggregate.

[0020] Substances used to carbonate mortar powder or concrete powder include, for example, those containing calcium carbonate (Ca(HCO3)2) and magnesium carbonate (Mg(HCO3)2).

[0021] The content of the above substance relative to the total mass (100% by mass) of the above substance is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, and most preferably 95% by mass or more.

[0022] In this embodiment, the above-mentioned substance includes cases where it contains both calcium carbonate and magnesium carbonate, cases where it contains calcium carbonate and magnesium carbonate separately, and cases where it is contained as calcium-magnesium carbonate (CaMg(CO3)2).

[0023] The above substance may contain salts other than calcium carbonate or magnesium carbonate. For example, when using seawater as the "water" when carbonating mortar powder or concrete powder, it may contain salts derived from the seawater. Also, when using water containing salts other than calcium carbonate or magnesium carbonate, it may contain those salts.

[0024] The above substance contains a salt other than calcium carbonate or magnesium carbonate, and the salt has CO3 as an anion. 2- It is preferable to include a salt containing the anion CO3. 2- Examples of salts containing these compounds include calcium aluminate hemicarbonate hydrate, calcium aluminate monocarbonate hydrate, barium carbonate, lithium carbonate, iron(II) carbonate, silver carbonate, calcium carbonate hydrate, Cu2(CO3)(OH)2, MnCO3, sodium carbonate, potassium carbonate, calcium monohydrocalcite (CaCO3·H2O), calcium carbonate hexahydrate (CaCO3·6H2O), and mixtures thereof.

[0025] The above substance is CO3 as an anion. 2- Essentially consisting only of salts containing (the salts containing calcium carbonate and magnesium carbonate), or as an anion CO3 2- Preferably, the salt consists only of a salt containing calcium carbonate and magnesium carbonate.

[0026] Here, "essentially" means CO3 as an anion. 2-Other salts besides those containing calcium carbonate and magnesium carbonate (the salt contains at least one of these) may be included, but only in an amount that does not diminish the properties of the calcium carbonate concrete obtained by the calcium carbonate concrete manufacturing method of this embodiment.

[0027] Furthermore, as will be described later, it is preferable that the above-mentioned substance is derived from carbon dioxide in the atmosphere or from carbon dioxide in various industrial exhaust gases. In particular, by deriving the substance from carbon dioxide in various industrial exhaust gases, including carbon dioxide that is released into the atmosphere and dispersed during cement production through calcination, it is possible to contribute to the sequestration of carbon dioxide in the atmosphere.

[0028] A method for carbonating mortar powder or concrete powder comprises: step A, adding particles containing at least one of a Ca source and an Mg source to a first solution containing at least water; step B, dissolving carbon dioxide in the first solution obtained in step A to prepare a second solution containing at least one of calcium carbonate and magnesium carbonate; and step C, adding and mixing mortar powder or concrete powder to the second solution obtained in step B.

[0029] (Process A) In step A, the first solution containing at least water becomes the solvent for the second solution obtained in step B, which contains at least one of calcium carbonate and magnesium carbonate. Examples of the first solution containing at least water include water, a mixed solvent of water and ammonia, seawater, rainwater, etc.

[0030] Particles containing at least one of a Ca source and a Mg source are not particularly limited as long as they contain only a Ca source, only a Mg source, or both a Ca source and a Mg source. The particles may also contain components other than a Ca source or a Mg source.

[0031] The particle size of the particles containing at least one of the Ca source and the Mg source is not particularly limited, as long as a second solution containing at least one of calcium carbonate and magnesium carbonate is obtained by step B.

[0032] Examples of particles containing at least one of a Ca source and an Mg source include those derived from construction waste, rocks, and other industrial by-products (such as blast furnace slag).

[0033] (Process B) In step B, any conventionally known method can be used to dissolve carbon dioxide in the first solution obtained in step A, as long as it can dissolve carbon dioxide in the first solution. Examples of methods for dissolving carbon dioxide include using machines such as bubbling, pore type, pressurized dissolution type, ultrasonic type, swirling liquid flow type, and gas-liquid mixing shear type.

[0034] The carbon dioxide used in process B is preferably derived from atmospheric carbon dioxide or from carbon dioxide in various industrial exhaust gases. In particular, by using carbon dioxide from various industrial exhaust gases, including carbon dioxide that is released into the atmosphere and dispersed during cement production by calcination, the carbon dioxide used in process B can contribute to the sequestration of atmospheric carbon dioxide.

[0035] Step B yields a second solution containing at least one of calcium carbonate and magnesium carbonate.

[0036] Here, the second solution containing at least one of calcium carbonate and magnesium carbonate is not particularly limited as long as it is a solution in which at least one of calcium carbonate and magnesium carbonate is dissolved. For example, it may be a solution in which at least one of calcium carbonate and magnesium carbonate is dissolved, or a liquid in which other substances are suspended or dispersed (e.g., a slurry). Other substances may include substances containing at least one of calcium carbonate and magnesium carbonate, or CO3 as an anion. 2- Salts containing salt are among the examples.

[0037] After mixing the second solution with mortar powder or concrete powder, the solids (powder) are filtered off, and the solids are dried to obtain carbonated mortar powder or carbonated concrete powder, in which the mortar powder or concrete powder has been carbonated.

[0038] "The second step" In the second step, as shown in Figure 1, carbonated mortar powder or carbonated concrete powder 100 is injected into the formwork 10. Next, the carbonated mortar powder or carbonated concrete powder 100 inside the formwork 10 is pressurized in the height direction of the formwork 10 by the piston 20 of the pressurizing device. As a result, as shown in Figure 2, a unit layer 110 consisting of carbonated mortar powder or carbonated concrete powder 100 is formed inside the formwork 10.

[0039] "The third step" In the third step, as shown in Figure 3, a calcium bicarbonate aqueous solution 200 is poured into the mold 10, and the unit layer 110 is immersed in the calcium bicarbonate aqueous solution 200. This causes the calcium carbonate contained inside the unit layer 110 to precipitate on the surface of the particles of the unit layer 110.

[0040] The surface layer of unit layer 110 refers to the region from 10 mm to 50 mm in the depth direction (thickness direction) from the outermost surface of unit layer 110.

[0041] After the third step, the unit layer 110 may be pressurized in the height direction of the mold 10 by the piston 20 of the pressurizing device within the mold 10, similar to the second step (fifth step).

[0042] "The fourth step" In the fourth step, as shown in Figure 4, the unit layer 110 is dried and the calcium bicarbonate aqueous solution 200 in the mold 10 is evaporated.

[0043] In the method for producing calcium carbonate concrete of this embodiment, it is preferable to repeat the third step and the fourth step in that order two or more times. More preferably, the number of repetitions of the third step and the fourth step is three or more, even more preferably six or more, and particularly preferably twelve or more. By repeating the third step and the fourth step in that order two or more times, more calcium carbonate contained inside the unit layer 110 can be precipitated on the surface of the unit layer 110.

[0044] In the method for producing calcium carbonate concrete of this embodiment, it is preferable to repeat the second step, the third step, and the fourth step in this order two or more times.

[0045] For example, as shown in Figure 5, carbonated mortar powder or carbonated concrete powder 100 is poured onto the unit layer 110 formed inside the formwork 10. Next, the carbonated mortar powder or carbonated concrete powder 100 inside the formwork 10 is pressurized in the height direction of the formwork 10 by the piston 20 of the pressurizing device. As a result, as shown in Figure 5, a unit layer 110 (110B) made of carbonated mortar powder or carbonated concrete powder 100 is formed on top of the unit layer 110 (110A) inside the formwork 10 (second step).

[0046] Next, as shown in Figure 6, a calcium bicarbonate aqueous solution 200 is poured into the mold 10, and the unit layers 110A and 110B are immersed in the calcium bicarbonate aqueous solution 200. This causes the calcium carbonate contained inside the unit layers 110A and 110B to precipitate onto the surface of the unit layer 110A and the surface of the unit layer 110B (third step).

[0047] After the third step, the surface of the unit layer 110A and the unit layer 110B may be pressurized in the height direction of the formwork 10 by the piston 20 of the pressurizing device, similar to the second step.

[0048] Next, as shown in Figure 7, the surface of unit layer 110A and unit layer 110B are dried, and the calcium bicarbonate aqueous solution 200 in the mold 10 is evaporated (fourth step).

[0049] As described above, by repeating the second step, the third step, and the fourth step in this order two or more times, calcium carbonate concrete 300 is obtained in which two or more unit layers 110 are stacked, as shown in Figure 8.

[0050] In the method for producing calcium carbonate concrete of this embodiment, the calcium carbonate contained inside the unit layer 110 is precipitated on the surface of the unit layer 110, and two or more unit layers 110 are stacked. As a result, the calcium carbonate functions as a binder at the interface where the unit layers 110 come into contact with each other, thus obtaining calcium carbonate concrete 300 in which the unit layers 110 are firmly bonded together. The obtained calcium carbonate concrete 300 has superior compressive strength compared to conventional calcium carbonate concrete.

[0051] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications are possible within the scope of the gist of the invention as described in the claims. [Examples]

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0053] [Preparation of carbonated mortar powder] The cement, fine aggregate, and water used were those shown in Table 1. The water-cement ratio is shown in Table 2. Calcium carbonate was added to water (the first solution) as particles containing a Ca source. Next, a solution (the second solution) was prepared by dissolving carbon dioxide in water containing calcium carbonate by bubbling. Next, mortar powder was added to the second solution and mixed. Subsequently, the solid component (powder) was filtered off, and the solid component was dried to obtain carbonated mortar powder, which is obtained by carbonating the mortar powder.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Experimental Example 1] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 10 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 10 MPa. The pressurization time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third step, the fifth step, and the fourth step described above were repeated six times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0057] [Experimental Example 2] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 5°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third step, the fifth step, and the fourth step described above were repeated six times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0058] [Experimental Example 3] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 30 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressurizing pressure was set to 30 MPa. The pressurizing time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third step, the fifth step, and the fourth step described above were repeated six times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0059] [Experimental Example 4] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 10 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (5th step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 10 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third step, the fifth step, and the fourth step described above were repeated six times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0060] [Experimental Example 5] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 300 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 300 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third step, the fifth step, and the fourth step described above were repeated six times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0061] [Experimental Example 6] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third step, the fifth step, and the fourth step described above were repeated three times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0062] [Experimental Example 7] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third step, the fifth step, and the fourth step described above were repeated 12 times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0063] [Experimental Example 8] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third and fourth steps described above were repeated three times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0064] [Experimental Example 9] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third and fourth steps described above were repeated six times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0065] [Experimental Example 10] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. The third and fourth steps described above were repeated 12 times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0066] [Experimental Example 11] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 to 24 hours. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature during drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was set to 105°C. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 60 seconds. The third, fourth, and fifth steps described above were repeated six times in this order to obtain calcium carbonate concrete with a height of 5 cm.

[0067] Table 3 shows the pressure during pressurization, pressurization time, the number of times the third and fourth steps are repeated (cycle count), the number of times the third, fifth, and fourth steps are repeated (cycle count), the number of times the third, fourth, and fifth steps are repeated (cycle count), and the cycle contents for Experimental Examples 1 to 11.

[0068] [Table 3]

[0069] [Measurement of compressive strength] The compressive strength of the calcium carbonate concrete obtained in Experimental Examples 1 to 11 was measured. The compressive strength of the calcium carbonate concrete was measured in accordance with JIS A1108:2018 "Test Method for Compressive Strength of Concrete". The results are shown in Figures 9 to 13. Figure 9 shows the relationship between the pressure applied during pressurization and the compressive strength of calcium carbonate concrete in Experimental Examples 1, 2, and 3. From the results shown in Figure 9, it was found that the compressive strength of calcium carbonate concrete improves as the pressure applied during pressurization increases. Figure 10 shows the relationship between pressurization time and the compressive strength of calcium carbonate concrete in Experimental Examples 4, 2, and 5. From the results shown in Figure 10, it was found that the compressive strength of calcium carbonate concrete improves as the pressurization time increases. Figure 11 shows the relationship between the number of repetitions (cycle count) of the third, fifth, and fourth steps described above and the compressive strength of the calcium carbonate concrete in Experimental Examples 6, 2, and 7. It was found that the compressive strength of the calcium carbonate concrete improved as the number of cycles increased. Figure 12 shows the relationship between the number of times the third and fourth steps described above are repeated (cycle count) and the compressive strength of the calcium carbonate concrete in Experimental Examples 8, 9, and 10. It was found that the compressive strength of the calcium carbonate concrete improved as the number of cycles increased. Figure 13 shows the relationship between the compressive strength of calcium carbonate concrete and the combination of the implementation steps of the third, fourth, and fifth steps described above in Experimental Examples 2, 9, and 11. It was found that the compressive strength of the calcium carbonate concrete was improved most when the cycle was performed in the order of the third, fifth, and fourth steps described above. The compressive strength of calcium carbonate concrete is 12 N / mm² as stipulated by the Building Standards Act. 2 It was found that the above can be achieved.

[0070] [Experimental Example 12] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressure during pressurization was 20 MPa. The pressurization time was 60 seconds. The height of the unit layer was 10 cm. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 1 hour. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature used for drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was 105°C. The drying time was 24 hours. The procedure of repeating the second step described above once, followed by the third step, the fifth step, and the fourth step described above, six times in that order, was performed once to obtain a single layer of calcium carbonate concrete with a height of 10 cm.

[0071] [Experimental Example 13] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressurizing pressure was 20 MPa. The pressurizing time was 60 seconds. The height of the unit layer was 1 cm. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 3 minutes. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature used for drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was 105°C. The drying time was 1 hour. The procedure of repeating the second step described above once, followed by the third step, the fifth step, and the fourth step described above, in that order, six times, was repeated until the height exceeded 10 cm, thereby obtaining calcium carbonate concrete with a height of 10 cm.

[0072] [Experimental Example 14] Calcium carbonate concrete was prepared using the same formwork and pressurizing equipment as shown in Figures 1 to 7. The carbonated mortar powder obtained in the above preparation was poured into the mold. Next, the carbonated mortar powder inside the mold was pressurized in the height direction of the mold using the piston of the pressurizing device, forming a unit layer of carbonated mortar powder inside the mold (second step). The pressurizing pressure was 20 MPa. The pressurizing time was 60 seconds. The height of the unit layer was 2.5 cm. Next, a calcium bicarbonate aqueous solution was poured into the mold, and the unit layer was immersed in the calcium bicarbonate aqueous solution (third step). The concentration of calcium bicarbonate in the calcium bicarbonate aqueous solution was 1200 mol / L. The temperature when immersing the unit layer in the calcium bicarbonate aqueous solution was 105°C. The immersion time of the unit layer in the calcium bicarbonate aqueous solution was 5 minutes. Next, the unit layer inside the formwork was pressurized in the height direction of the formwork using the piston of the pressurizing device (fifth step). The pressure during pressurization was set to 20 MPa. The pressurization time was set to 60 seconds. Next, the unit layer was dried and the calcium bicarbonate aqueous solution in the mold was evaporated (fourth step). The temperature used for drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the mold was 105°C. The drying time was 3 hours. The procedure of repeating the second step described above once, followed by the third step, the fifth step, and the fourth step described above, in that order, six times, was repeated until the height exceeded 10 cm, thereby obtaining calcium carbonate concrete with a height of 10 cm.

[0073] [Measurement of compressive strength] The compressive strength of the calcium carbonate concrete obtained in Experimental Examples 12 to 14 was measured. The compressive strength of the calcium carbonate concrete was measured in accordance with JIS A1108:2018 "Test Method for Compressive Strength of Concrete". The results are shown in Figure 14.

[0074] [Density measurement] The density of the calcium carbonate concrete obtained in Experimental Examples 12 to 14 was measured. The density of the calcium carbonate concrete was determined in accordance with JIS A 1107:2012 "Method for sampling cores from concrete and method for testing compressive strength". The results are shown in Figure 14.

[0075] Figure 14 shows the results of measuring the compressive strength and density of calcium carbonate concrete obtained in Experimental Examples 12 to 14. In calcium carbonate concrete obtained by laminating unit layers, it was found that the compressive strength increased towards the lower layers in the thickness direction. Furthermore, it was found that the compressive strength of the calcium carbonate concrete obtained in Experimental Example 13 was higher than that of the calcium carbonate concrete obtained in Experimental Example 14. Furthermore, although the densities of the calcium carbonate concrete obtained in Experimental Example 13 and Experimental Example 14 were greater than the density of the single-layer calcium carbonate concrete obtained in Experimental Example 12, it was found that there was not a significant difference in the densities of any of the calcium carbonate concrete samples. [Explanation of Symbols]

[0076] 10 formwork 20 pistons 100 Carbonated Mortar Powder 110 Unit Layer 200 Calcium bicarbonate aqueous solution 300 Calcium Carbonate Concrete

Claims

1. A first step involves carbonating mortar powder or concrete powder to prepare carbonated mortar powder or carbonated concrete powder, A second step involves injecting the carbonated mortar powder or carbonated concrete powder into a formwork, and pressurizing the carbonated mortar powder or carbonated concrete powder within the formwork in the height direction to form a unit layer consisting of the carbonated mortar powder or carbonated concrete powder. A third step involves pouring an aqueous calcium bicarbonate solution into the mold, immersing the unit layer in the aqueous calcium bicarbonate solution, and precipitating the calcium carbonate contained inside the unit layer onto the surface of the unit layer. A method for producing calcium carbonate concrete, comprising a fourth step of drying the unit layer and evaporating the calcium bicarbonate aqueous solution in the formwork.

2. A method for producing calcium carbonate concrete according to claim 1, wherein the third step and the fourth step are repeated in this order two or more times.

3. A method for producing calcium carbonate concrete according to claim 1 or 2, wherein the second step, the third step, and the fourth step are repeated in this order two or more times.

Images