Carbonate hardened material, granulated aggregate made from carbonate hardened material, and concrete composition using the same

Abstract

This invention provides a carbonate-hardened material with strength suitable for use as an aggregate in concrete. [Solution] One aspect of the present disclosure relates to a carbonate hardened product containing a carbonate and formed by granulation, wherein the coarseness ratio is 3.0 or more.

Description

Technical Field

[0001] The present disclosure relates to carbonate hardened products, granulated aggregates made of carbonate hardened products, and concrete compositions containing such granulated aggregates.

Background Art

[0002] Towards the realization of a carbon-neutral society, technologies related to the storage and immobilization of carbon dioxide (CO2) have attracted attention. If CO2 can be immobilized as carbonate and the carbonate can be used as a construction material such as concrete, a large amount of CO2 can be immobilized, so the establishment of a practical and versatile technology is strongly desired.

[0003] When using carbonate as a concrete material, the appropriate blending amount and required properties vary depending on whether it is used as a powder admixture or as an aggregate. Since most of the constituent materials of concrete are aggregates (fine aggregates or coarse aggregates), if the above carbonate can be used as an aggregate, the contribution to CO2 immobilization can increase in light of the usage amount. Furthermore, in order to popularize such aggregates and contribute to a decarbonized society, it is preferable that they are widely used not only as ordinary concrete but also in special-purpose concrete and secondary products.

[0004] As a technology for producing carbonate that can be used as an aggregate, Patent Document 1 describes a method for producing a carbonated solidified product, characterized by granulating a non-carbonated Ca-containing raw material containing moisture in the presence of carbon dioxide gas and solidifying the raw material in the granulation by a carbonation reaction to obtain a granulated product that is carbonated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] If CO2 can be fixed at the location where the exhaust gas containing CO2 is generated, there is no need for a facility to store CO2, which is more desirable in practical use. There is a demand for the development of carbonates that can be efficiently obtained by such on-site CO2 fixation and have a strength useful for construction materials such as ordinary concrete. However, in the technology of Patent Document 1, improvement was necessary from the viewpoint of the strength as an aggregate of the carbonated solid. Also, in Patent Document 1, carbonation and granulation were carried out simultaneously, and since particle aggregation proceeded during the progress of the carbonation reaction, the amount of CO2 fixed was not sufficient and improvement was necessary.

[0007] An object of the present disclosure is to provide a carbonated cured product that can be suitably used as an aggregate for construction materials such as ordinary concrete.

Means for Solving the Problems

[0008] A preferred embodiment of the present disclosure relates to the following matters.

[0009] 1. A carbonated cured product containing carbonates and obtained by granulation, The carbonated cured product having a coarse grain ratio of 3.0 or more.

[0010] 2. The carbonated cured product according to item 1, wherein the water content is more than 21 parts by mass with respect to 100 parts by mass of the dry mass of the carbonated cured product.

[0011] 3. The carbonated cured product according to claim 1 or 2, wherein, taking 100 parts by mass of the dry mass of the carbonated cured product, 10 parts by mass or more and 60 parts by mass or less of CaCO3 is contained, and 5 parts by mass or more and 20 parts by mass or less of SiO2 is contained.

[0012] 4. The carbonated cured product according to any one of items 1 to 3, wherein the amount of CO2 fixed with respect to the dry mass of the carbonated cured product is 50 kg / t or more and less than 300 kg / t.

[0013] 5. A carbonate cured product as described in any of items 1 to 4, wherein the maximum particle size is 10 mm or less.

[0014] 6. Granulated aggregate consisting of a carbonate hardened product as described in any of items 1 to 5.

[0015] 7. Cement and, Fine aggregate containing the granulated aggregate described in item 6, Coarse aggregate and Water and, A concrete composition containing [the specified element].

[0016] 8. A hardened product of the concrete composition described in item 7. [Effects of the Invention]

[0017] According to one aspect of this disclosure, a carbonate hardened product that can be suitably used as aggregate for construction materials such as ordinary concrete, and a concrete composition using the same can be provided. [Brief explanation of the drawing]

[0018] [Figure 1] This graph shows the relationship between the coarseness ratio and the sieving retention rate of carbonate-hardened material. [Figure 2] This graph shows the relationship between the coarseness ratio and the sieving retention rate of carbonate-hardened material. [Figure 3] This graph shows the relationship between the sieve opening of the carbonate cured product and the percentage of material passing through it. [Figure 4] This graph shows the relationship between the pore size of the aggregate and the cumulative pore volume. [Figure 5] This graph shows the relationship between the pore diameter of the aggregate and the log differential pore volume. [Modes for carrying out the invention]

[0019] The embodiments of this disclosure are described below. However, the embodiments described below are illustrative examples for the purpose of illustrating this disclosure and are not intended to limit this disclosure to the following. In the following description, when "X~Y" (where X and Y are arbitrary numbers) is written, it means "X or greater and Y or less" unless otherwise specified.

[0020] Unless otherwise specified, the materials exemplified herein may be used individually or in combination of two or more. In a composition such as a mixture, the content of each component refers to the total amount of any multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition.

[0021] <Carbonate cured product> The carbonate hardened product of this disclosure is a granulated carbonate hardened product containing a carbonate, preferably having a coarseness ratio of 3.0 or more. The carbonate is preferably an alkaline earth metal carbonate, preferably containing CaCO3 and / or MgCO3, and more preferably containing at least CaCO3. The carbonate hardened product of this disclosure can be suitably used as aggregate (preferably fine aggregate) in construction materials such as concrete. As described later, the carbonate hardened product of this disclosure is a granulated product obtained by granulating a mixture containing calcium carbonate (CaCO3), blast furnace slag, and preferably calcium hydroxide and water. In this specification, the carbonate hardened product is also referred to as "carbonate aggregate" or "granulated aggregate". According to one aspect of this disclosure, a carbonate hardened product having strength useful as aggregate can be provided. According to one aspect of this disclosure, a carbonate hardened product having a good particle size distribution as aggregate can be provided. Furthermore, the carbonate hardened product of this disclosure has a large CO2 fixation amount and can contribute to carbon neutrality.

[0022] In one embodiment, the carbonate cured product preferably contains CaCO3 and SiO2. The CaCO3 content in the carbonate cured product is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, or 20 parts by mass or more, based on 100 parts by mass of the dry mass of the carbonate cured product, and the upper limit may be, for example, preferably 60 parts by mass or less, more preferably 55 parts by mass or less, or 50 parts by mass or less. The SiO2 content in the carbonate cured product is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, or 10 parts by mass or more, based on 100 parts by mass of the dry mass of the carbonate cured product, and the upper limit may be, for example, 20 parts by mass or less, 18 parts by mass or less, or 15 parts by mass or less. SiO2 may exist as a calcium silicate compound or an aluminum silicate compound. The CaCO3 content in the carbonate cured product may be determined, for example, from the mass loss at a heating temperature of 650 to 900°C using a differential thermal-thermogravimetric analyzer (TG-DTA). Furthermore, the SiO2 content can be measured using, for example, an X-ray fluorescence analyzer or an inductively coupled plasma emission spectrometry (ICP-AES) analyzer. In this specification, "dry mass of carbonate aggregate" refers to the mass of the carbonate aggregate after drying at 105°C for 24 hours to remove any adhering water.

[0023] In the presence of Ca(OH)2, when SiO2 is within the above range, the pozzolanic reaction proceeds when a composition containing carbon dioxide and an additive are mixed and granulated, and hydrates are formed, thereby promoting strength development.

[0024] Furthermore, the carbonate cured product may also contain an Al component, which can also contribute to the formation of hydrates.

[0025] In one embodiment, the carbonate cured product may contain CaCO3 and blast furnace slag, and may also contain Ca(OH)2. The CaCO3 content in the carbonate cured product may be, for example, 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more per 100 parts by mass of the dry weight of the carbonate cured product, with an upper limit of, for example, 60 parts by mass or less, 55 parts by mass or less, or 50 parts by mass or less. The blast furnace slag content in the carbonate cured product is not limited, but may be, for example, 30 parts by mass or more, 32 parts by mass or more per 100 parts by mass of the dry weight of the carbonate cured product, or it may be 65 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less. The Ca(OH)2 content in the carbonate cured product is not limited to 2 parts by mass or more, 3 parts by mass or more, per 100 parts by mass of the dry weight of the carbonate cured product, and the upper limit may be, for example, 35 parts by mass or less, 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less.

[0026] The amount of CO2 fixed in the carbonate cured product is not limited, but is preferably 20 kg / t or more, more preferably 50 kg / t or more, and even more preferably 100 kg / t or more, relative to the dry mass of the carbonate cured product, and may be 300 kg / t or less, less than 300 kg / t, or 200 kg / t or less. The amount of CO2 fixed is the mass ratio of CO2 fixed by the carbonation process to the dry mass of the carbonate cured product. The amount of CO2 fixed can be calculated by the method described in the examples. A high amount of CO2 fixed can be achieved according to the manufacturing method of this disclosure. Note that the CO2 fixed by the carbonation process is the CO2 fixed in the raw material during the carbonation process, but if carbonation curing is performed separately after the granulation process, CO2 fixed during curing may also be included. In addition to the method described in the examples, the amount of CO2 fixed may be measured by methods such as barium carbonate back titration as specified in JIS R9011:2006 "Test methods for lime", TOC (total organic carbon) solid sample measurement system, coulometer (inorganic carbon analyzer), TG-MS (thermogravimetric-mass spectrometer), or CS meter (carbon-sulfur analyzer). The carbonate cured products of this disclosure have a large amount of CO2 fixed and can contribute to carbon neutrality.

[0027] In one embodiment, the carbonate cured material has an average fracture load measured in accordance with JIS Z 8841-1993, preferably 50 N or more, but may also be 55 N or more, 60 N or more, or 65 N or more, and the upper limit is not limited, but for example it may be 150 N or less or 120 N or less. Even if at least a portion of the aggregate in a concrete composition is replaced with the carbonate cured material (granulated aggregate) of this disclosure, concrete with practically sufficient strength can be formed.

[0028] Blast furnace slag is a type of granulated blast furnace slag produced by rapidly cooling molten slag discharged from blast furnaces during the steelmaking process with water to create a glassy substance, and then crushing and pulverizing it. Blast furnace slag has latent hydraulic properties and hardens when exposed to alkaline stimuli. Examples of blast furnace slag include the fine blast furnace slag powder for concrete specified in JIS A 6206:2013.

[0029] The coarseness of the carbonate cured product of this disclosure is preferably 3.0 or higher, and may be 3.1 or higher, 3.2 or higher, 3.3 or higher, or 3.4 or higher. The upper limit is not limited, but is preferably 5.0 or lower, more preferably 4.5 or lower, and even more preferably 4.0 or lower. The coarseness can be measured in accordance with the method described in JIS A 1102 "Method for sieving aggregates".

[0030] The inventors of this invention have found that when the coarseness ratio of a carbonate hardened material is 3.0 or higher, it can exhibit strength useful as fine aggregate in construction materials such as ordinary concrete. Carbonate hardened materials with a coarseness ratio of 3.0 or higher can exhibit strength equivalent to or greater than that of commonly used natural aggregates and fine limestone sand, and the strength tends to increase as the coarseness ratio increases. Furthermore, a coarseness ratio of, for example, 5.0 or lower is preferable from the viewpoint of obtaining better fresh properties. It should be noted that commonly used natural aggregates, artificial aggregates such as crushed limestone sand, and artificial lightweight aggregates such as mesalite have a coarseness ratio of less than 3.0.

[0031] The maximum particle size of the carbonate cured product of this disclosure is preferably 10 mm or less, and it passes through a 10 mm sieve.

[0032] It is preferable that the carbonate cured product further contains water. In this specification, the water content per 100 parts by mass of the dry mass of the carbonate cured product is defined as the "moisture content (mass%) of the carbonate cured product." The moisture content of the carbonate cured product can be measured by a method in accordance with JIS A1125:2015 "Test method for moisture content of aggregates and test method for surface moisture content based on moisture content." In one embodiment, the moisture content of the carbonate cured product may be 10% by mass or more, 15% by mass or more, 20% by mass or more, or more than 21% by mass, and the upper limit may be, for example, 35% by mass or less, 30% by mass or less, or 25% by mass or less.

[0033] In one embodiment, when the water content of the carbonate cured product is preferably more than 21% by mass, more preferably 21.5% by mass or more, and even more preferably 22% by mass or more, the correlation between the particle size ratio and strength of the carbonate cured product becomes particularly strong, and the variation in strength with respect to particle size ratio becomes smaller, resulting in more stable quality. The upper limit of the water content of the carbonate cured product is not limited, but may be, for example, 27% by mass or less, 26% by mass or less, or 25% by mass or less. Therefore, carbonate aggregate with a particle size ratio of 3.0 or more and a water content exceeding 21% by mass has stable quality, can exhibit strength useful as fine aggregate, and can be suitably used in construction materials such as concrete.

[0034] In one embodiment, the carbonate hardened material of this disclosure satisfies the standard of JIS A 5308 (Appendix A) in terms of the mass passing percentage at each nominal size, according to JIS A 1102 "Sieving Test Method for Aggregates". Such aggregate has less bias in particle size distribution and can improve the fresh properties of concrete. Furthermore, carbonate aggregate that satisfies the JIS standard can form good concrete even when used as a substitute for ordinary fine aggregate, thus increasing its versatility. In one embodiment, from the viewpoint of easily satisfying the particle size distribution of the JIS standard, the water content of the carbonate hardened material is preferably 10% by mass or more and 35% by mass or less, more preferably 15% by mass or more and 30% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less.

[0035] The carbonate cured product has an average fracture load, measured in accordance with JIS Z 8841-1993, preferably 50 N or more, but may also be 55 N or more, 60 N or more, or 65 N or more. There is no upper limit, but for example, it may be 150 N or less or 120 N or less.

[0036] The carbonate cured product of this disclosure has a strength (sieve residue rate) measured by the sieve residue rate evaluation method described in the examples, preferably 38% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more. The upper limit is not limited, but may be, for example, 95% by mass or less or 90% by mass or less. If the sieve residue rate is within this range, the carbonate cured product can be used as at least a part of the fine aggregate in a concrete composition. Even if at least a part of the fine aggregate in a concrete composition is replaced with the carbonate cured product (granulated aggregate) of this disclosure, concrete with practically sufficient strength can be formed.

[0037] The surface-dry density of the carbonate cured product is not limited, but for example, 1.3 g / cm³. 3 Preferably, it is 1.5 g / cm³. 3 The above is more preferable. A higher surface-dry density is preferable because it can improve the physical properties of the carbonate cured product by reducing the water absorption rate. Furthermore, there is no upper limit to the surface-dry density of the carbonate cured product, but 2.7 g / cm³ is preferable. 3 Below 2.5g / cm 3 The following, or 2.3 g / cm³ 3 The following is also acceptable. If the surface-dry density falls within this range, performance equivalent to that of artificial lightweight aggregate can be obtained. The surface-dry density can be determined in accordance with the method described in JIS A 1109:2020 "Test Method for Density and Water Absorption Rate of Fine Aggregates".

[0038] The carbonate cured products of this disclosure have pores, and the cumulative pore volume of pores with a diameter of 100 nm or less is preferably 0.06 mL / g or more, more preferably 0.08 mL / g or more, even more preferably 0.1 mL / g or more, or 0.12 mL / g or more, and the upper limit is not limited, but is preferably 0.4 mL / g or less, more preferably 0.35 mL / g or less, even more preferably 0.3 mL / g or less, 0.27 mL / g or less, or 0.25 mL / g or less. In this specification, "pores" refers to pores measured by the mercury intrusion method, and the total pore volume and the cumulative pore volume of pores within a specific range of diameters can be measured using a commercially available mercury porosimeter.

[0039] The carbonate cured product of this disclosure has a cumulative pore volume of pores with a pore diameter of 50 nm or less, which is not limited to but preferably 0.05 mL / g or more, more preferably 0.07 mL / g or more, even more preferably 0.09 mL / g or more, or 0.10 mL / g or more, with an upper limit of preferably 0.35 mL / g or less, more preferably 0.30 mL / g or less, and even more preferably 0.25 mL / g or less.

[0040] While carbonate cured materials can be used as aggregates in concrete, they tend to have a higher water absorption rate compared to artificial aggregates such as mesalite. Generally, the higher the water absorption rate, the lower the freeze-thaw resistance tends to be. However, by using carbonate cured materials with a cumulative pore volume of pores smaller than 100 nm or a cumulative pore volume of pores smaller than 50 nm within the above range as aggregates in concrete, concrete with excellent freeze-thaw resistance can be obtained. The carbonate cured materials of this disclosure have a large cumulative pore volume of small sizes within the above range, so water does not enter the pores, thus less affecting freeze-thaw resistance, and as a result, it is presumed that the freeze-thaw resistance of concrete can be improved.

[0041] In one embodiment, the pore distribution of the carbonate cured product preferably has at least one peak at 110 nm or less, and more preferably at 10 to 100 nm. Having pore diameters within this range makes it difficult for moisture to freeze, thus suppressing deterioration due to freeze-thaw cycles.

[0042] In one embodiment, the total cumulative pore volume of the carbonate cured product may be, for example, 0.1 ml / g or more, or 0.12 ml / g or more, and the upper limit may be 0.4 ml / g or less, or 0.35 ml / g or less.

[0043] The particulate matter content of the carbonate cured product is measured in accordance with JIS A 1103 and is not limited, but may be, for example, 9% or less or 8% or less, and the lower limit may be, for example, 0.5% or more or 1.0% or more.

[0044] The water absorption rate of the carbonate cured product is not limited, but is preferably 30% or less, more preferably 25% or less, and the lower limit may be, for example, 1% or more, 2% or more, or 3% or more. The water absorption rate can be determined in accordance with JIS A 1109:2020 "Test method for density and water absorption rate of fine aggregate".

[0045] In one embodiment, the shape of the carbonate aggregate is not limited, but is preferably spherical. In this specification, spherical may be perfectly spherical, approximately spherical, or ellipsoidal. The sphericity of the carbonate aggregate is preferably 0.80 or higher, and more preferably 0.90 or higher. The sphericity is determined by image analysis of the carbonate aggregate obtained with an optical microscope or digital scope, etc. [area of ​​the particle projection cross-section (mm²)] 2 This value is obtained by calculating the ratio of the circumference of a perfect circle with the same area (mm) to the perimeter of the particle projection cross-section (mm), and then taking the average. The spherical shape of the carbonate aggregate makes it easier to obtain good fresh properties in the concrete composition.

[0046] <Method for manufacturing hardened carbonate products> One embodiment of the method for producing a carbonate cured product in this disclosure is: A carbonation process to obtain a composition containing carbon dioxide by bringing a raw material containing a basic compound containing CaO and water into contact with a CO2-containing gas while stirring, The method comprises a granulation step of obtaining a carbonate hardened product by stirring and granulating a mixture containing the carbon oxide composition and an additive (preferably blast furnace slag). In a preferred embodiment, the raw materials contain 15 parts by mass or more of CaO and 30 to 80 parts by mass of water per 100 parts by mass of dry weight.

[0047] The manufacturing method disclosed herein can efficiently fix CO2 on-site from exhaust gas containing CO2, and therefore can contribute to carbon neutrality through CO2 fixation. Furthermore, since it can be manufactured using Beckenbach furnace dust and the like as raw materials, it can also contribute to the formation of a circular economy through the effective utilization of industrial waste.

[0048] (Carbonation process) In the carbonation process, a composition containing carbon oxide is obtained by contacting a raw material containing a basic compound with CaO and water with a CO2-containing gas while stirring. The raw material in the carbonation process contains a basic compound with calcium oxide (CaO) and water. The CaO content is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more per 100 parts by mass of the dry mass of the raw material. The upper limit is not limited and may be 100 parts by mass, but may be, for example, 90 parts by mass or less, 85 parts by mass or less, 80 parts by mass or less, 75 parts by mass or less, 70 parts by mass or less, or 60 parts by mass or less. In this specification, "dry mass of raw material" means the mass after drying the raw material at 105°C for 24 hours to remove any adhering water.

[0049] Multiple basic compounds containing CaO may be present in the raw materials. Examples of basic compounds other than CaO include basic compounds (excluding CaO) that have alkaline earth metals as constituent elements. Mg and Ca are preferred as alkaline earth metals, and Ca is particularly preferred. Examples of basic compounds that have calcium (Ca) as a constituent element include calcium hydroxide (Ca(OH)2), calcium silicate (CaSiO3, Ca2SiO4, Ca3SiO5, etc.), and calcium aluminate (CaAl2O4, Ca3Al2O6, Ca12 Al 14 O 33 Examples thereof include etc. In one aspect, it is preferable to contain Ca(OH)2. Examples of the basic compound having magnesium (Mg) as a constituent element include MgO, Mg(OH)2, etc. Further, examples of the raw material containing these basic compounds include waste materials such as lime calcination dust, cement clinker dust, by-product slaked lime, recycled cement, concrete sludge, and waste concrete, etc. These waste materials can be used as they are, or can be used after being adjusted to the form of CaO or Ca(OH)2 by chemical treatment, heat treatment, etc. Furthermore, even if it is a waste material that does not contain a basic compound, if it contains Ca such as waste gypsum, a basic compound such as CaO or Ca(OH)2 can be prepared by chemical treatment, heat treatment, etc., and this may be used. The content of the basic compound (total content when multiple types are included) is not limited, but for example, it may be 15 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more, and the upper limit may be 100 parts by mass, but for example, it may be 95 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, or 65 parts by mass or less, based on 100 parts by mass of the dry mass of the raw material.

[0050] The raw material may contain one or more other compounds in addition to the above-mentioned basic compounds. Examples of the other compounds include, for example, CaCO3, CaSO4, SiO2, etc.

[0051] In one embodiment, the CaO-containing raw material may include at least one selected from the group consisting of, for example, lime calcination dust, cement clinker dust, by-product slaked lime, recycled cement, concrete sludge, and waste concrete sludge. For example, it is preferable to use lime calcination dust as a raw material. Examples of lime calcination dust include dust collected and recovered by a dust collector in a calcination kiln when calcining limestone. Examples of cement clinker dust include dust contained in the extraction gas of a cement kiln. Examples of by-product slaked lime include by-product slaked lime produced in the acetylene gas production process by the calcium carbide method.

[0052] In one embodiment, the raw materials (preferably lime calcination dust) include CaO, Ca(OH)2, and CaCO2. 3、 The material may contain one or more selected from CaSO4 and SiO2, or all of them. The lower limit of the CaO content per 100 parts by mass of the dry mass of the raw material (preferably lime calcined dust) is preferably 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more, and the upper limit of the CaO content may be 100 parts by mass, but preferably 75 parts by mass or less, 70 parts by mass or less, 65 parts by mass or less, or 60 parts by mass or less.

[0053] When the raw material (preferably calcined lime dust) contains Ca(OH)2, the lower limit of the Ca(OH)2 content per 100 parts by mass of the dry mass of the raw material may be, for example, 0.3 parts by mass or more, 0.5 parts by mass or more, or 1 part by mass or more, and the upper limit of the Ca(OH)2 content may be, for example, 10 parts by mass or less, 8 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less.

[0054] When the raw material (preferably calcined lime dust) contains CaCO3, the lower limit of the CaCO3 content per 100 parts by mass of the dry mass of the raw material may be, for example, 3 parts by mass or more, 5 parts by mass or more, or 10 parts by mass or more, and the upper limit of the CaCO3 content may be, for example, 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less.

[0055] When the raw material (preferably calcined lime dust) contains CaSO4, the lower limit of the CaSO4 content per 100 parts by mass of the dry mass of the raw material may be, for example, 1 part by mass or more, 2 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more, and the upper limit of the CaSO4 content may be, for example, 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less.

[0056] When the raw material (preferably calcined lime dust) contains SiO2, the lower limit of the SiO2 content per 100 parts by mass of the dry mass of the raw material may be, for example, 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more, and the upper limit of the SiO2 content may be, for example, 10 parts by mass or less, or 8 parts by mass or less.

[0057] In one embodiment, the raw material (preferably lime calcined dust) may contain, for example, 20 to 75 parts by mass (preferably 25 to 70 parts by mass) of CaO and 0.3 to 10 parts by mass of Ca(OH)2 per 100 parts by mass of the dry mass of the raw material, and may further contain 5 to 30 parts by mass of CaCO3, 1 to 25 parts by mass of CaSO4 and 1 to 10 parts by mass of SiO2.

[0058] The raw materials in the carbonation process contain water, and the water content per 100 parts by mass of the dry mass of the raw materials (hereinafter also simply referred to as "water content in the raw materials") is preferably 30 parts by mass or more and 80 parts by mass or less. When the water content in the raw materials is within this range, a good carbonation rate, CO2 fixation rate, and CO2 fixation amount can be achieved. Materials other than water, such as basic compounds containing CaO, in the raw materials may be in a dried state before the carbonation process, or they may be in a state containing adhering water without being dried. If the raw materials contain adhering water, the water content in the raw materials includes the amount of that adhering water. The above raw materials can also be called wet powder. According to the inventors' studies, when a long reaction time for carbonation can be secured, it is preferable to have a slurry state as before (for example, a state with 100 parts by mass or more of water per 100 parts by mass of the dry mass of the raw materials). However, in addition to the decrease in the concentration of the raw materials in the slurry, the diffusion of CO2 is rapid and the time efficiency of the carbonation reaction decreases. Therefore, when a reaction in a short time is required, such as for on-site CO2 fixation, the reaction rate may be insufficient. Furthermore, while reducing the water content is desirable for on-site CO2 fixation, the reaction sites for carbonation mediated by water become unevenly distributed. We also found that stirring the raw materials compensates for this, allowing for efficient CO2 fixation in a short time.

[0059] The water content in the raw material may be, for example, 35 parts by mass or more, 40 parts by mass or more, more than 40 parts by mass, 42 parts by mass or more, 43 parts by mass or more, or 45 parts by mass or more per 100 parts by mass of the dry mass of the raw material. By setting the lower limit of the water content in the raw material within the above range, the proportion of water present on the surface of the raw material increases, and the CO2 fixation rate can be further improved. The water content in the raw material may be, for example, 75 parts by mass or less, 70 parts by mass or less, 65 parts by mass or less, 60 parts by mass or less, or 55 parts by mass or less per 100 parts by mass of the dry mass of the raw material. By setting the upper limit of the water content in the raw material within the above range, heterogeneity of CO2 diffusion due to an increase in water in the voids, and the resulting decrease in the CO2 fixation rate can be suppressed. The moisture content in the raw material may be adjusted, for example, by directly adding water.

[0060] The water added in the carbonation process is not particularly limited and may be tap water, treated wastewater, or supernatant water from ready-mix concrete.

[0061] In one embodiment of the present disclosure, when the raw material contains 30 parts by mass or more of CaO per 100 parts by mass of the dry mass of the raw material (for example, when it contains lime calcined dust), the water content is not limited, but preferably more than 40 parts by mass, more preferably 42 parts by mass or more, and preferably 60 parts by mass or less, more preferably 55 parts by mass or less, because this is preferable as it particularly improves the carbonation rate.

[0062] The CO2-containing gas is not particularly limited as long as it contains CO2, and may be exhaust gas containing CO2. Examples of CO2-containing gases include exhaust gas from coal-fired power plants, cement plants, and waste incineration plants. One embodiment of the manufacturing method of this disclosure allows for on-site CO2 fixation and can therefore be implemented at coal-fired power plants, cement plants, and waste incineration plants. The CO2 content in the exhaust gas may be, for example, 1 volume% or more under standard conditions, and may be 3-50 volume%, 5-40 volume%, or 8-30 volume%. These exhaust gases may be used directly, or high-concentration CO2 (e.g., more than 50 volume%) recovered and concentrated from exhaust gas may be used.

[0063] In the carbonation process, the raw materials are brought into contact with CO2 while being stirred. By stirring the raw materials, it is possible to change the contact surface with CO2 over time, thereby further improving the efficiency of CO2 fixation. As mentioned above, in the carbonation process, it is necessary to use the raw materials in a wet powder state from the viewpoint of achieving on-site CO2 fixation. According to the inventors' studies, it has been found that when carbonation is performed in a static state with wet powder, the CO2 fixation rate is significantly inferior.

[0064] The means of stirring the raw materials are not particularly limited, but examples include agitator mixers (ribbon mixers, Nauter mixers, etc.), container mixers (V-type mixers, etc.), mixing and transporting machines (screw feeders, etc.), moving bed reactors (kiln type, etc.), and agitated tank reactors.

[0065] In the carbonation process, the time the raw materials and CO2 are in contact may be adjusted according to the CO2 content in the CO2-containing gas, the shape and size of the container in which the carbonation process is carried out, etc. In the carbonation process, the time the raw materials and CO2 are in contact may be, for example, 3 minutes or more, 5 minutes or more, 6 minutes or more, or 7 minutes or more. By setting the lower limit of the above time within the above range, reaction time can be ensured and the CO2 fixation rate can be further improved. In the carbonation process, the time the raw materials and CO2 are in contact may be, for example, 90 minutes or less, 80 minutes or less, 70 minutes or less, 60 minutes or less, 50 minutes or less, 40 minutes or less, 30 minutes or less, 20 minutes or less, 18 minutes or less, 15 minutes or less, or 12 minutes or less. In order to ensure the above time is long, it is necessary to design a large reactor for fixing the continuously emitted exhaust gas, which is not suitable for on-site manufacturing and tends to increase the manufacturing cost of the carbonate cured product. Therefore, by setting the upper limit of the above time within the above range, carbonate cured products can be manufactured with more practical equipment investment and operating costs. In the carbonation process, the time during which the above raw material and the above CO2 are in contact may be adjusted within the above range, for example, from 3 minutes to 90 minutes.

[0066] In the carbonation process, the amount of CO2 supplied is preferably 1 mole or more per mole of the CaO equivalent of the basic compound, and may be 1.5 moles or more. There is no upper limit, but for example, it may be 3 moles or less, or 2 moles or less. When the amount of CO2 supplied is within the above range, the fixation of CO2 can be made more sufficient, the amount of calcium carbonate can be increased, and the increase in operating costs can be suppressed.

[0067] The carbonized composition obtained in the carbonization process contains carbon oxides such as calcium carbonate and magnesium carbonate, and preferably contains at least calcium carbonate. The carbonized composition may also contain Ca(OH)2 in addition to carbon oxides. In one embodiment, the carbonized composition may contain Ca(OH)2 and / or CaO. The CaO may be present in the raw materials. The Ca(OH)2 may be present in the raw materials, or it may be produced by the reaction of CaO in the raw materials with water. The inclusion of Ca(OH)2 in the carbonized composition allows it to react with additives such as blast furnace slag in the granulation process to form a carbonate hardened product with higher strength.

[0068] The carbonation rate (unit: mass%) of a composition containing carbon dioxide is not limited, but is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more. Furthermore, the carbonation rate of a composition containing carbon dioxide is not limited, but is preferably less than 100% by mass, and may be 98% by mass or less, 95% by mass or less, less than 80% by mass or less, or less than 60% by mass. A carbonation rate of less than 100% by mass is preferable because the remaining CaO, Ca(OH)2, etc., act as stimulants in the granulation process. The carbonation rate is the ratio of the carbonated substance to the total amount of carbonizable substance in the raw material, and specifically represents the ratio (mass%) of basic compounds in the raw material (preferably basic compounds containing alkaline earth metals, more preferably basic compounds containing calcium and / or magnesium) that have been converted to carbon dioxide. In this specification, the carbonation rate can be calculated by the method described in the examples. In the examples, a method for calculating the percentage of a basic compound containing Ca that is converted to calcium carbonate is described. However, if the basic compound containing Mg is included in the raw materials, the carbonation rate can be calculated by replacing calcium with magnesium in the calculation method of the examples. Furthermore, if the basic compound containing both Ca and Mg is included in the raw materials, the carbonation rate for each can be calculated using the calculation method of the examples and then added together to obtain the carbonation rate for the entire composition containing carbon dioxide.

[0069] The CO2 fixation rate in the carbonation process is not limited, but is preferably 10 mol% or more, 20 mol% or more, or 30 mol% or more, and the upper limit may be, for example, 70 mol% or less, 60 mol% or less, 55 mol% or less, or 50% mol or less. The CO2 fixation rate is the ratio of the amount of CO2 gas consumed in the carbonation reaction to the total amount of CO2 gas supplied, and is calculated based on the following formula (i). In formula (i), E represents the content of basic compounds in the raw materials (unit: moles), and F represents the amount of carbon dioxide supplied (unit: moles). If multiple types of basic compounds are present in the raw materials, it is necessary to quantify the unreacted portion in the carbon dioxide, calculate the carbonation rate Z' and CO2 fixation rate for each basic compound, and sum them up. The CO2 fixation rate is calculated by adding up the values ​​for each basic compound. CO2 fixation rate = E x (Z' / F) x 100... Formula (i)

[0070] The carbonation rate and CO2 fixation rate can be adjusted by the water content in the raw materials, the time the raw materials are in contact with CO2, etc. Furthermore, the carbonation rate may also be adjusted by carbonation of other carbonatable substances (e.g., MgO, Ca(OH)2, calcium silicate, etc.) that may be included in the raw materials.

[0071] The carbon dioxide-containing composition obtained in the carbonation process may, in some cases, be temporarily stored in a hopper or the like before the granulation process, or it may proceed directly to the granulation process.

[0072] (granulation process) In the granulation process, a carbonate hardened product is obtained by stirring and granulating a mixture containing the carbon oxide-containing composition obtained in the carbonation process and an additive. The carbonate hardened product is mainly obtained in granular form. The particle shape may be spherical.

[0073] The additives in the granulation process preferably include a latent hydraulic material (preferably blast furnace slag). A latent hydraulic material does not harden simply by mixing with water, but hardens through a hydration reaction when mixed with water in the presence of a stimulant (e.g., alkali, sulfate, etc.), forming a hardened body. Examples of such additives include blast furnace slag and pozzolanic materials (e.g., coal ash, fly ash), and it is preferable to use at least one selected from these, with blast furnace slag being particularly preferable. Other additives besides latent hydraulic materials include polyvinyl alcohol and water glass. The additives may be used individually or in combination of two or more. In the invention of this disclosure, Ca(OH)2 contained in the composition obtained by the carbonation process described above, and / or Ca(OH)2 newly generated from the remaining CaO by adding water, can react with the latent hydraulic material, thereby obtaining a carbonate hardened product with strength suitable for use as aggregate. Thus, by setting the carbonation rate to less than 100% by mass in the carbonation process described above, the hardening reaction can be carried out efficiently without adding any additional stimulants in the granulation process.

[0074] Examples of pozzolanic materials include fly ash and silicate mixtures. As an additive, blast furnace slag is preferable because it is relatively inexpensive and produces little CO2. While other hydraulic materials such as cement compositions containing cement clinker can be used as additives, it is sometimes preferable to avoid using cement clinker due to the high CO2 emissions during its production. When using cement compositions as additives in this disclosure, it is desirable to use those recovered and reused from hardened cement compositions that are no longer needed.

[0075] The mixture in the granulation process preferably contains water in addition to the composition containing carbon dioxide and the additives. The water may originate from the composition containing carbon dioxide or the additives such as latent hydraulic materials, or it may be added from an external source. In this specification, the moisture content of the mixture refers to the total amount of both. As mentioned above, the raw materials used in the carbonation process contain water, but some of this may evaporate due to the heat generated by the carbonation reaction. The water that volatilizes due to this evaporation shall not be included in the moisture content of the mixture. The lower limit of the water content in the granulation process may be, for example, 10 parts by mass or more, 12 parts by mass or more, 15 parts by mass or more, 17 parts by mass or more, 20 parts by mass or more, 21 parts by mass or more, 22 parts by mass or more, 23 parts by mass or more, or more than 23 parts by mass per 100 parts by mass of the dry mass of the mixture. By keeping the lower limit of the amount of water added within the above range, the hardening reaction of the latent hydraulic material can be carried out more sufficiently. The upper limit of the water content may be, for example, 35 parts by mass or less, 30 parts by mass or less, 25 parts by mass or less, or 24 parts by mass or less per 100 parts by mass of the dry mass of the above mixture. Keeping the water content within the above range makes it possible to shorten the time required for stirring and granulation, and to prepare the carbonate hardened product more stably. By adjusting the water content in the granulation process, the strength and particle size of the resulting carbonate hardened product can be adjusted. In this specification, "dry mass of the mixture" means the mass after drying the mixture at 105°C for 24 hours to remove any adhering water.

[0076] As described above, a correlation is observed between the coarseness ratio and strength of the carbonate aggregate. The water content of the carbonate aggregate can be adjusted by adjusting the water content in the mixture during the granulation process. In one embodiment, when the water content per 100 parts by mass of dry mass of the mixture during the granulation process is preferably more than 20 parts by mass, more preferably 23 parts by mass or more, and even more preferably 24 parts by mass or more, the correlation between the coarseness ratio and strength of the carbonate aggregate becomes particularly strong, resulting in less variation in strength relative to the coarseness ratio and providing carbonate aggregate of stable quality. In the granulation process, the upper limit of the water content per 100 parts by mass of dry mass of the mixture is not limited, but may be 27 parts by mass or less, 26 parts by mass or less, or 25 parts by mass or less.

[0077] In one embodiment, a good particle size distribution can be achieved as aggregate by adjusting the water content of the mixture in the granulation process. For example, by setting the water content of the mixture in the granulation process to 21.5 parts by mass or more, 22 parts by mass or more, 24.5 parts by mass or less, 23 parts by mass or less, or less than 23 parts by mass, it becomes easier to obtain a carbonate-hardened product that satisfies the standards of JIS A 5308 (Appendix A).

[0078] The mixture in the granulation process may further contain other materials in addition to the above-mentioned composition containing carbon oxide and additives (preferably latent hydraulic materials, more preferably blast furnace slag). Examples of other materials include binders, dispersants, and water-reducing agents to promote granulation. Examples of water-reducing agents include high-performance water-reducing agents, high-performance AE water-reducing agents, AE water-reducing agents, and fluidizing agents, but water-reducing agents are not essential and may be used as needed. The amount of other components in the mixture is not limited, but may be, for example, 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, or 0 parts by mass per 100 parts by mass of the dry mass of the mixture.

[0079] In the granulation process, a mixture is prepared by mixing the carbon dioxide-containing composition obtained in the carbonation process with an additive and preferably water. The content of the carbon dioxide-containing composition (dry mass) per 100 parts by mass of the dry mass of the mixture is not limited, but is preferably 35 parts by mass or more, may be 40 parts by mass or more, 50 parts by mass or more, and preferably 70 parts by mass or less, and may be 68 parts by mass or less. The content of the additive (preferably a latent hydraulic material, more preferably blast furnace slag) per 100 parts by mass of the dry mass of the mixture is not limited, but is preferably 30 parts by mass or more, may be 32 parts by mass or more, and preferably 65 parts by mass or less, may be 60 parts by mass or less, and may be 50 parts by mass or less. When the blending amounts of the carbon dioxide-containing composition and the additive in the mixture are within the above ranges, the mechanical strength of the carbonate hardened product can be further improved. In this specification, "dry mass of the composition containing carbon dioxide" means the mass of the composition containing carbon dioxide after drying at 105°C for 24 hours to remove any adhering water.

[0080] In the granulation process, a carbonate hardened product is prepared by stirring and granulating a mixture containing the above-mentioned carbon oxide composition, additives, and preferably water.

[0081] In this disclosure, by employing agitation granulation as the granulation method, a carbonate hardened product with excellent mechanical strength can be obtained. Grafting methods are generally known to be wet granulation and dry granulation. Examples of wet granulation include agitation granulation, rolling granulation, fluidized bed granulation, and coated granulation. The reason why agitation granulation yields a hardened product with superior mechanical strength compared to other granulation methods is not entirely clear, but the inventors speculate as follows: (1) First, when granulating a mixture of carbon dioxide and additives, the carbon dioxide itself does not undergo a hydration reaction, making it more difficult to ensure mechanical strength compared to granulating only the additives. In this case, it is considered that sufficient mixing and close contact between the carbon dioxide particles and the additive particles is a condition for superior mechanical strength. (2) Among wet granulation methods, rolling granulation, fluidized bed granulation, and coated granulation are thought to form a layered structure in the resulting hardened product, with multiple layers overlapping. In this granulation process, voids tend to form between layers, making it difficult for the carbon oxide particles and the latent hydraulic material particles to be in close contact. Therefore, it is thought that the formation of mechanically weak defects between some layers may lead to a decrease in the mechanical strength of the hardened body. (3) On the other hand, in the case of agitated granulation, which is a type of wet granulation, the mixture that will be the raw material for the hardened body is stirred and granulated by applying centrifugal compression while homogenizing the system. As a result, a layered structure is unlikely to be formed, and the carbon oxide particles and the additive particles (preferably latent hydraulic material) tend to be sufficiently mixed and in close contact. Therefore, it is thought that the strength of the hardened product obtained by agitated granulation can be improved.

[0082] As described above, stirring granulation allows for the production of dense granules and their hardened products, and continuous production is possible, making it suitable for on-site production of carbonate hardened products. Alternatively, a method involving adding sufficient water to the mixture, pouring it into a mold, and then crushing it after hardening to produce aggregate can also be considered. However, in this case, the amount of water added to homogenize the material tends to be large, making it difficult to obtain high mechanical strength.

[0083] In one embodiment, the granulation process involves mixing a composition containing carbon dioxide, additives, water, and other components, and then stirring and granulating. The granulation time is not limited, but is preferably 1 minute or more, more preferably 3 minutes or more, and may also be 5 minutes or more. For example, it is preferably 30 minutes or less, but may also be 20 minutes or less, 10 minutes or less, or 7 minutes or less. In this specification, "granulation time" refers to the elapsed time from the time water is added to the time stirring is completed while the mixture containing the carbon dioxide composition and additives is being stirred in the stirring device. The mixing order of the components is not limited, but in one embodiment, it is preferable to mix the components other than water before adding water in the granulation process. The stirring device used in the granulation process is not limited, but examples include a three-one motor, Hobart mixer, high-speed mixer, Nauter mixer, etc. The rotation speed of the stirring blades of the stirring device is not limited and may be adjusted as appropriate depending on the capacity of the device, the amount of raw materials added, etc. The temperature during stirring is not limited, but is preferably between 1°C and 50°C, and more preferably above room temperature (e.g., above 10°C) and below 45°C.

[0084] By adjusting the granulation time in the granulation process, the rotation speed of the stirring blades in the stirring device, etc., it is possible to produce carbonate hardened products with a coarseness ratio of 3.0 or higher.

[0085] In the granulation process, the average particle size of the carbonate hardened material may be adjusted to be 0.4 mm or larger. Furthermore, the average particle size may be adjusted according to the intended use of the carbonate hardened material. For example, when using the carbonate hardened material as fine aggregate for concrete (preferably for ordinary concrete), the average particle size is preferably 0.4 mm to 5.0 mm, more preferably 0.6 mm to 3.0 mm, and even more preferably 1.0 mm to 3.0 mm. By setting the average particle size of the carbonate hardened material to these values, it can be suitably used as fine aggregate for concrete.

[0086] In this specification, the average particle size refers to the value measured by the particle size distribution obtained by measuring the particle size distribution using the method described in JIS A 1102:2014 "Test Method for Sieving Aggregates," and determining the particle size volume curve calculated when the mass fraction reaches 50%.

[0087] The method for producing a carbonate cured product according to this disclosure may include other steps in addition to the carbonation step and the granulation step. Examples of other steps include a step to adjust the composition of the above mixture, an analysis step of exhaust gas and carbon oxides, a curing step for the carbonate cured product, and a particle size adjustment step.

[0088] The step of adjusting the composition of the above mixture may be a step of adjusting the composition of the carbon oxide obtained in the carbonation step. It is desirable that the step of adjusting the composition of the above mixture be carried out after the carbonation step and before the granulation step.

[0089] One aspect of this disclosure relates to a granulated aggregate comprising the carbonate hardened material described above. The carbonate hardened material (granulated aggregate) of this disclosure can be used as fine aggregate contained in a concrete composition.

[0090] <Concrete composition> One aspect of this disclosure relates to a concrete composition containing the carbonate hardened material as fine aggregate. The concrete composition comprises cement, fine aggregate containing the carbonate aggregate (granulated aggregate), coarse aggregate, and water.

[0091] The following describes each component constituting the concrete composition of this disclosure. In this specification, "unit amount (kg / m³)" refers to the unit amount (kg / m³). 3 )" means 1m 3 This refers to the amount of each material used when manufacturing concrete. Also, "unit water content" is 1 m³ 3 This refers to the amount of water used when manufacturing concrete.

[0092] <Cement> Examples of cements include ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, sulfate-resistant Portland cement, moderate-heat Portland cement, low-heat Portland cement, blast furnace cement, fly ash cement, silica fume cement, and alumina cement. One type of cement may be used, or two or more types may be used in combination.

[0093] <Fine aggregate> The fine aggregate includes the carbonate hardened product (carbonate aggregate) mentioned above, and may also include other fine aggregates. The other fine aggregates are not particularly limited, and fine aggregates used in the production of ordinary concrete can be used. The fine aggregate is aggregate that passes 100% through a 10 mm sieve and passes 85% or more by mass through a 5 mm sieve. Examples of other fine aggregates include river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, lightweight fine aggregate, blast furnace slag fine aggregate, and limestone fine aggregate. One type of fine aggregate may be used alone, or two or more types may be used in combination. The average particle size of the fine aggregate is preferably, for example, 0.4 mm to 5.0 mm, more preferably 0.6 mm to 3.0 mm, and even more preferably 1.0 mm to 3.0 mm. In this specification, the average particle size refers to the value measured by the particle size distribution obtained by measuring the particle size distribution using the method described in JIS A 1102:2014 "Test Method for Sieving Aggregates," and determining the particle size volume curve calculated when the mass fraction reaches 50%.

[0094] The volume ratio of carbonate aggregate to the total volume of fine aggregate (also referred to as the "volume replacement rate of carbonate aggregate to total fine aggregate," or simply the "volume replacement rate") is not limited to but may be 1% or more, 5% or more, 10% or more, 15% or more, 20% or more, 30% or more, 40% or more, 45% or more, or 50% or more, and the upper limit may be 100%, but may also be 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, or 70% or less. Thus, in the concrete composition of this disclosure, at least a portion of the ordinary fine aggregate is replaced with carbonate aggregate. The concrete composition containing carbonate aggregate of this disclosure can achieve a concrete strength sufficient for practical use.

[0095] The mass ratio of carbonate aggregate to the total mass of fine aggregate (also referred to as "mass replacement rate of carbonate aggregate to total fine aggregate," or simply "mass replacement rate") is not limited to but may be 1% or more, 5% or more, 10% or more, 15% or more, 20% or more, 30% or more, 40% or more, 45% or more, or 50% or more, and the upper limit may be 100%, but may also be 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less. Concrete compositions containing the carbonate aggregate of this disclosure within this range can achieve concrete strength sufficient for practical use.

[0096] The carbonate aggregate used as fine aggregate and its manufacturing method are subject to the description of the carbonate hardened product described above.

[0097] <Coarse aggregate> The coarse aggregate is not particularly limited, and any coarse aggregate used in the production of ordinary concrete can be used. The coarse aggregate is aggregate that remains in a 5 mm sieve by mass at a rate of 85% or more. Examples of coarse aggregate include crushed stone obtained by crushing andesite, rhyolite, hard sandstone, limestone, river gravel, mountain gravel, land gravel, blast furnace slag coarse aggregate, and recycled coarse aggregate. One type of coarse aggregate may be used alone, or two or more types may be used in combination. The average particle size of the coarse aggregate is preferably, for example, 7 to 32 mm, more preferably 8 to 31 mm, and may also be 15 to 25 mm.

[0098] <Water> The water used in the concrete composition is not particularly limited and can be used as long as it does not affect the strength development or fluidity of the concrete, such as tap water, treated wastewater, or supernatant water from ready-mixed concrete.

[0099] <Other ingredients> The concrete composition may contain other components (additives) as long as they do not impair the effects of the present invention. Examples of other components include inorganic fine powders such as gypsum and fly ash, thickeners, defoamers, water-reducing agents, high-performance AE water-reducing agents, AE agents, inks, pigments, dispersants, setting regulators, expansive agents, shrinkage reducing agents, etc. AE water-reducing agents and AE agents are chemical admixtures as defined in "JIS A 6204:2011".

[0100] <Blend amount> The amount of cement in the concrete composition is not limited, but is preferably 180 kg / m³ per unit. 3 The above is more than 200 kg / m 3 That concludes the explanation. Furthermore, while there are no limitations on the amount of cement used in the concrete composition, the unit amount should be 500 kg / m³. 3 It may also be less than 450 kg / m 3 The following may also apply: Alternatively, if the cement composition is further in the realm of high-strength concrete and the carbonate aggregate according to the present invention is used, the upper limit of the cement content may be, for example, 700 kg / m³. 3 It may also be less than 600 kg / m 3 The following is also acceptable.

[0101] The amount of water in the concrete composition is not limited, but is preferably 120 kg / m³ in terms of unit water content. 3 Above, a comfortable 130 kg / m 3 The above is true, and preferably 185 kg / m 3 For the following, a more preferable value is 175 kg / m 3 The following applies:

[0102] The water-cement ratio (W / C) in a concrete composition is not limited, but may be, for example, 20% or more, 30% or more, 40% or more, 50% or more, or 60% or more, or 65% or less, or 60% or less. In this specification, "water-cement ratio (W / C)" is the mass ratio (W / C) of water (W) to cement (C) expressed as a percentage (%). If the concrete composition contains chemical admixtures and the chemical admixtures are added in the form of an aqueous solution, the mass of the chemical admixtures is included in the water (W) when calculating the water-cement ratio (W / C). When the water-cement ratio is within this range, it is easier to obtain concrete with good strength and fluidity.

[0103] The amount of coarse aggregate in the concrete composition is not limited, but for example, preferably 400 kg / m³ per unit. 3 Above, a comfortable 500 kg / m 3 More preferably 600 kg / m 3 The above is sufficient, and preferably 1300 kg / m³ 3 More preferably 1200 kg / m 3 It may be less than or equal to 1100 kg / m³, and more preferably 1100 kg / m³. 3 The following, or 950 kg / m 3 The following is also acceptable.

[0104] The amount of fine aggregate (including carbonate aggregate) in the concrete composition is not limited, but for example, preferably 50 kg / m³ per unit. 3 Above, a comfortable 100 kg / m 3 More preferably 200 kg / m 3 More than 300kg / m 3 More than 400kg / m 3 More than 500kg / m 3 More than 600kg / m 3 More than 700kg / m 3 The above is acceptable, and the upper limit is preferably 1500 kg / m 3 Below 1400kg / m 3 Below 1300kg / m 3 Below 1200kg / m 3 Below 1000kg / m3 Below 900kg / m 3 Below 800kg / m 3 The following is also acceptable.

[0105] The amount of carbonate aggregate used in the concrete composition is not limited, but for example, preferably 50 kg / m³ per unit. 3 Above, a comfortable 100 kg / m 3 More than 120 kg / m 3 The above is sufficient, and more preferably 300 kg / m 3 The above is acceptable. Furthermore, the amount of carbonate aggregate in the concrete composition is not limited, but for example, preferably 1200 kg / m³ per unit. 3 Below, a comfortable 1000 kg / m 3 More preferably, 800 kg / m 3 The following may be true: 700 kg / m 3 Below 500kg / m 3 The following, or 450 kg / m 3 The following is also acceptable.

[0106] <Method for manufacturing concrete compositions> The concrete composition is manufactured by mixing cement, fine aggregate containing the above-mentioned granulated aggregate (carbonate aggregate), coarse aggregate, water, and other additives as needed, in a predetermined mixing ratio, and then kneading the mixture. The mixing order of each component is not limited and can be mixed in any order. Examples of mixers used for mixing include tilting drum mixers, twin-shaft mixers, hand mixers, and Hobart mixers. It is preferable, but not limited, to adjust the temperature of the concrete composition at the end of mixing to, for example, preferably 10°C to 40°C, more preferably 15°C to 35°C. The longer the mixing time of the composition, the larger the flow becomes, and then the flow saturates and becomes almost constant. The mixing time is preferably 3 minutes or more in an environment of 20°C or higher. In a low-temperature environment below 20°C, the mixing time of the concrete composition is preferably 5 minutes or more, and more preferably 6 minutes or more.

[0107] <Hardened concrete> One aspect of this disclosure relates to a hardened product of the above-mentioned concrete composition (hardened concrete). The method for manufacturing the hardened concrete is not limited, but may include a step of molding a mixed concrete composition to obtain a molded body (molding step) and a step of curing the molded body (curing step). The molding method is not particularly limited, and for example, the concrete composition may be poured into a mold (metal, plastic, etc.). Degassing may be performed using a vibrator as needed. With the concrete composition contained in the mold, the molded body is obtained by leaving it for, for example, 1 to 5 days. When using core materials such as reinforcing bars or steel frames, the core materials may be placed in the mold beforehand before pouring in the concrete composition.

[0108] In the curing process, the molded body obtained in the molding process is cured. However, the mold may be removed before curing. There are no particular restrictions on the curing method; any curing method, such as sealed curing or underwater curing, may be used. Curing is preferably carried out until the concrete composition hardens.

[0109] The hardened concrete composition of this embodiment can be used for a variety of applications, including building materials and wave-dissipating blocks, although this is not limited to these uses.

[0110] Although several embodiments have been described above, this disclosure is not limited in any way to the embodiments described above. Furthermore, the descriptions of the embodiments described above are applicable to each other. [Examples]

[0111] The contents of this disclosure will be explained in more detail below with reference to examples. However, this disclosure is not limited to the embodiments described below.

[0112] (Ingredients: Lime calcination dust) Table 1-1 shows the composition of the lime calcined dust (Beckenbach furnace dust, manufactured by Ube Materials Co., Ltd.) used as raw material in the following example. The unit of the numerical values ​​for each composition is "mass%". In Table 1-1, "ig.loss" refers to the loss on ignition and represents the total mass of organic components and water that volatilized when heated at 950°C. "f.CaO" refers to free lime (free CaO).

[0113] [Table 1-1]

[0114] (Blast furnace dust) Table 1-2 shows the composition of the blast furnace slag (manufactured by Chiba Riverment Co., Ltd., product name: Riverment Gx) used in the granulation process in the following example. The unit of each composition value is "mass%". "ig.loss" refers to the loss on ignition and represents the total mass of organic components and water content that volatilized by heating at 950°C.

[0115] [Table 1-2]

[0116] <Example A1> In manufacturing examples A1-1 to A1-7, carbonate-hardened products (also referred to as "carbonate aggregate" or "granulated aggregate") A1-1 to A1-7 were produced by the following carbonation process (a1-1) and granulation process (a1-2).

[0117] (a1-1) Carbonation process (carbonation treatment) In a 5L Hobart mixer (Hobart Japan Co., Ltd., N50), 500g (dry mass) of lime calcination dust (Beckenbach furnace dust) as listed in Table 1 above was mixed with tap water in a ratio of 250g. While stirring, CO2 (carbon dioxide) was passed through at a flow rate of 10L / min for 20 minutes (total CO2 passage volume 200L, CO2 supply volume 8.929 moles) to perform a carbonation treatment and obtain a composition containing carbon oxide.

[0118] (a1-2) Granulation process To the carbon oxide-containing composition obtained in (a1-1) above, blast furnace slag (manufactured by Chiba Riverment Co., Ltd., trade name: Riverment Gx) was added as a hydraulic material to prepare a mixture such that the carbon oxide-containing composition and the hydraulic material were in a dry mass ratio of 65:35.

[0119] 100 parts by mass of the above mixture was weighed out and placed in an 11L high-speed mixer (FS10, manufactured by Earth Technica Co., Ltd.), and mixed for 30 seconds under conditions of agitator rotation speed of 310 rpm and chopper rotation speed of 3000 rpm. Then, tap water was weighed out so that the amount of water added was 23 parts by mass per 100 parts by mass of the dry mass of the mixture, and added to the same high-speed mixer. Granulation was carried out by stirring under the conditions of agitator rotation speed and chopper rotation speed of 3000 rpm as shown in Table 2, for the granulation time shown in Table 2, to obtain a carbonate hardened product. This carbonate hardened product was evaluated as a carbonate granulated aggregate. Note that the granulation time shown in Table 2 is the stirring time from when water was first added.

[0120] <Method for measuring the coarseness ratio of carbonate granulated aggregate> The coarseness of the obtained carbonate aggregate was measured in accordance with the method described in JIS A 1102 "Test Method for Sieving Aggregates". Specifically, the cumulative percentage of sample mass remaining on each sieve with nominal dimensions of 5 mm, 2.5 mm, 1.2 mm, 0.6 mm, 0.3 mm, and 0.15 mm was divided by 100 to determine the coarseness.

[0121] <Method for evaluating the hardness (residual rate after sieving) of carbonate granulated aggregate> The hardness (residual rate on the sieve) of carbonate granulated aggregate was evaluated using the following procedure. (1) From the carbonate granulated aggregate samples that had been cured for 7 days after granulation, only aggregate samples between 2.5 mm and 5.0 mm were sorted using a sieve, and a total of 15 g was set aside for testing. (2) The test sample was spread on a bat and compacted using a 2.45 kg wide roller (using only its own weight, without applying any downward force). The process was repeated 25 times, back and forth. (3) The material was sieved through a 2.5 mm mesh sieve, and the residue (mass) was measured. (4) The sieve residue (mass %) was calculated from the change in mass before and after compaction. (The harder the material, the higher the sieve residue). A larger sieve residue indicates a harder (higher strength) carbonate granulated aggregate.

[0122] Table 2 shows the granulation process conditions for the carbonate aggregates A1-1 to A1-7 obtained above, as well as the results of the coarseness ratio and sieve retention rate of the obtained carbonate aggregates. In the table, "Amount of water added" refers to the parts by mass of water per 100 parts by mass of the total dry mass of the carbon oxide-containing composition and blast furnace slag. "Granulation time" and "Agitator rotation speed" refer to these conditions in the granulation process.

[0123] [Table 2]

[0124] When the carbonate aggregates produced in the above examples A1-1 to A1-7 were measured using a method compliant with JIS A125:2015 "Test method for moisture content of aggregates and test method for surface moisture content based on moisture content", the average moisture content per 100 parts by mass of these carbonate aggregates was 21 parts by mass (moisture content: 21% by mass).

[0125] Figure 1 shows the relationship between the coarseness of the carbonate cured products obtained in manufacturing examples A1-1 to A1-7 and the sieve retention rate. The horizontal axis of Figure 1 represents the coarseness of the particles, and the vertical axis represents the sieve retention rate (mass%), which indicates the strength. The measured values ​​for each example A1 and the regression line are shown. A correlation is observed between the coarseness of the carbonate cured products and the sieve retention rate (strength), and the coefficient of determination (R) of the relationship between the coarseness of the particles and the sieve retention rate (hardness) is shown. 2 The value was 0.7101.

[0126] When the sieve-retaining percentage was measured using commercially available artificial aggregate, fine limestone sand (distributor: Asahi Sangyo Co., Ltd., origin: Higashitani, Fukuoka Prefecture or Tsukumi, Oita Prefecture, grade: crushed limestone sand), it was found to be approximately 45% by mass. Example A1 showed that when the coarseness ratio is 3.0 or higher, it is easier to achieve strength equivalent to or greater than that of the crushed limestone sand.

[0127] <Example A2> In manufacturing examples A2-1 to A2-9, carbonate cured products A2-1 to A2-9 were produced by the following carbonation process (a2-1) and granulation process (a2-2). (a2-1) Carbonation process A composition containing carbon dioxide was produced by the same method as the carbonation step (a1-1) in Example A1 above.

[0128] (a2-2) Granulation process To the carbon oxide-containing composition obtained in (a2-1), blast furnace slag (manufactured by Chiba Riverment Co., Ltd., trade name: Riverment Gx) was added as a hydraulic material to prepare a mixture such that the carbon oxide-containing composition and the hydraulic material were in a dry mass ratio of 65:35.

[0129] 100 parts by mass of the mixture was weighed out and placed in an 11L high-speed mixer (FS10, manufactured by Earth Technica Co., Ltd.), and mixed for 30 seconds under conditions of agitator rotation speed of 310 rpm and chopper rotation speed of 3000 rpm. Then, tap water was weighed out so that the amount of water added was 24 parts by mass per 100 parts by mass of the dry mass of the mixture, and added to the same high-speed mixer. Granulation was carried out by stirring under the conditions of agitator rotation speed and chopper rotation speed of 3000 rpm as shown in Table 3, for the granulation time shown in Table 3, to obtain a carbonate hardened product. This carbonate hardened product was evaluated as a carbonate aggregate in the same manner as in Example A1 above.

[0130] Table 3 shows the granulation process conditions for the carbonate aggregates A2-1 to A2-9 obtained above, as well as the results for the coarseness ratio and sieve retention rate.

[0131] [Table 3]

[0132] When the carbonate aggregates manufactured using the methods described above (A2-1 to A2-9) were measured according to JIS A1125:2015 "Test method for moisture content of aggregates and test method for surface moisture content based on moisture content," the average moisture content per 100 parts by mass of these carbonate aggregates was found to be 22 parts by mass (moisture content: 22% by mass).

[0133] Figure 2 shows the relationship between the coarseness ratio and the sieve retention rate of the carbonate cured products obtained in manufacturing examples A2-1 to A2-9. In Figure 2, the horizontal axis represents the coarseness ratio, and the vertical axis represents the sieve retention rate (mass%), which indicates the strength. The measured value for example A2 and the regression line are shown. A correlation is observed between the coarseness ratio and the sieve retention rate (strength), and the coefficient of determination (R) of the relationship between the coarseness ratio and the sieve retention rate is calculated. 2 The ratio was 0.9031. In Example A2, it was shown that when the coarseness ratio is 3.0 or higher, it is easy to achieve a strength equivalent to or greater than that of commercially available artificial aggregate, limestone fine sand (distributor: Asahi Sangyo Co., Ltd., origin: Higashitani, Fukuoka Prefecture or Tsukumi, Oita Prefecture, grade: crushed limestone sand, sieve retention rate approximately 45% by mass).

[0134] In both Figure 1 (Example A1, moisture content 21% by mass) and Figure 2 (Example A2, moisture content 22% by mass), a correlation was observed between the coarseness ratio and the sieve retention rate (strength), indicating that higher coarseness ratios resulted in stronger carbonate aggregate. In particular, the coefficient of determination in the regression line for Example A2 was close to 1, indicating a stronger correlation between coarseness ratio and sieve retention rate (strength). This suggests that when the moisture content exceeds 21% by mass, the variability in strength relative to the coarseness ratio is smaller, resulting in carbonate aggregate of stable quality.

[0135] The particle size distribution of carbonate aggregates produced in Example A1 (A1-1 to A1-7) and Example A2 (A2-1 to A2-9) was measured. Figure 3 shows the particle size curves representing the relationship between the sieve size used for measurement and the percentage of aggregate passing through. The percentage of aggregate passing through is the mass ratio of aggregate that passed through each sieve. Figure 3 also shows the upper and lower limits of the particle size distribution as defined by the JIS standard (JIS A 5308 (Appendix A)). The particle size curves for Example A1 and Example A2 fall within the range defined by the JIS standard, indicating that they meet the JIS standard. From this, it was confirmed that the carbonate hardened materials produced in Example A1 and Example A2 have a good particle size distribution for use as aggregates in concrete, etc.

[0136] <Example B> (Manufacturing example B1: Manufacturing of carbonate aggregate B1) (b-1) Carbonation process A composition containing carbon dioxide was obtained by carbonizing a 30L ribbon mixer (Dalton Co., Ltd., RM20) into which 10 kg of the aforementioned lime calcined dust (dry mass) and 5 kg of tap water were added and mixed while CO2 (carbon dioxide gas) was passed through at a flow rate of 100 L / min for 30 minutes. The CaCO3 content in the composition containing carbon dioxide was 66.2 parts by mass per 100 parts by mass of the dry mass of the composition containing carbon dioxide. The CaCO3 content in the composition containing carbon dioxide was measured and calculated using the same method as in Example D described below.

[0137] (b-2) Granulation process To the carbon dioxide-containing composition obtained in the carbonization process (b-1) described above, blast furnace slag (manufactured by Chiba Riverment Co., Ltd., trade name: Riverment Gx) was added as a hydraulic material to prepare a mixture such that the carbon dioxide-containing composition and the hydraulic material were in a dry mass ratio of 65:35.

[0138] 100 parts by mass of the above mixture was weighed out and placed in a 118L high-speed mixer (FS100, manufactured by Earth Technica Co., Ltd.), and mixed for 1 minute under conditions of agitator rotation speed of 133 rpm and chopper rotation speed of 3000 rpm. Then, tap water was weighed out so that the amount of water added was 23 parts by mass per 100 parts by mass of the dry mass of the above mixture, and added to the same high-speed mixer, and mixed for 1 minute while adding tap water under conditions of agitator rotation speed of 133 rpm and chopper rotation speed of 3000 rpm. After that, it was stirred and granulated for 3.0 minutes to obtain carbonate hardened product B1. This carbonate hardened product B1 was used as carbonate aggregate (granulated aggregate) (hereinafter also referred to as "carbonate aggregate B1").

[0139] (Manufacturing example B2: Manufacturing of carbonate aggregate B2) Carbonate-hardened product (carbonate aggregate) B2 was manufactured using the same method as for carbonate-hardened product B1, except that the water content in the mixture during the granulation process (b-2) was changed to 22 parts by mass per 100 parts by mass of the dry mass of the mixture.

[0140] The moisture content of the obtained carbonate aggregates B1 and B2 was measured according to the method conforming to JIS A1125:2015 "Test method for moisture content of aggregates and test method for surface moisture content based on moisture content". As a result, carbonate aggregate B1 had a moisture content of 21.5% by mass and carbonate aggregate B2 had a moisture content of 20.6% by mass per 100% dry mass of carbonate aggregate. Furthermore, the SiO2 content of carbonate aggregate B1 (in its raw state) was 11.6 parts by mass and the CaCO3 content was 35.4 parts by mass per 100 parts by mass of dry mass. The SiO2 content of carbonate aggregate B2 (in its raw state) was 11.6 parts by mass and the CaCO3 content was 35.7 parts by mass per 100 parts by mass of dry mass. The SiO2 and CaCO3 content in the carbonate aggregate was calculated from the water content of the carbonate aggregate, the CaCO3 content in the carbon oxide-containing composition, the composition of the raw material lime calcined dust, and the composition of the blast furnace slag.

[0141] The properties of the obtained carbonate aggregates B1 and B2 were measured. Table 4 shows the test method and results. Both carbonate aggregates B1 and B2 had a coarseness ratio of 3.0 or higher.

[0142] [Table 4]

[0143] <Pore size distribution of carbonate aggregate> The pore size distribution was measured for the carbonate aggregates B1 and B2 described above. Specifically, a mercury intrusion porosimeter (Anton Paar Pore Master 60-GT) was used to measure the pore size range from 400,000 to 3.6 nm.

[0144] Figure 4 shows the relationship between pore diameter and cumulative pore volume (the cumulative value obtained by accumulating the volumes of each pore, starting with the largest pore diameter). In the graph of Figure 4, the horizontal axis represents pore diameter (nm), and the vertical axis represents cumulative pore volume (mL / g). Figure 5 shows the relationship between pore diameter and log differential pore volume (dV / d(logD)). In the graph of Figure 5, the horizontal axis represents pore diameter (nm), and the vertical axis represents dV / d(logD)(mL / g). Here, dV represents the differential pore volume, and d(logD) represents the logarithmic difference of pore diameter D.

[0145] (Cumulative pore volume of pores with a diameter of 100 nm or less) When the cumulative pore volume of aggregates with a pore diameter of 100 nm or less was calculated, it was 0.098 mL / g for carbonate aggregate B1 and 0.1108 mL / g for carbonate aggregate B2.

[0146] As shown in Figures 4 and 5, carbonate aggregates B1 and B2 had many fine pores (pore diameters of 10 nm to 110 nm). Aggregates with many such fine pores are less susceptible to water penetration, thus minimizing the impact on freeze-thaw resistance and enabling them to exhibit excellent freeze-thaw resistance.

[0147] <Example C: Preparation and evaluation of concrete test specimens> Concrete test specimens were prepared and evaluated using carbonate aggregates B1 and B2 manufactured as described above. The materials used for the concrete test specimens are as follows: • Cement (C): Blast furnace cement type B (manufactured by UBE Mitsubishi Cement Corporation, density: 3.04 g / cm³) 3 ) • Fine aggregate (S1): Mountain sand (produced in Kimitsu City, Chiba Prefecture, absolute dry density: 2.59 g / cm³) 3 ) and crushed limestone sand (from Hachinohe City, Aomori Prefecture, absolute dry density: 2.69 g / cm³) 3 Mixed sand (mountain sand: crushed limestone sand (mass ratio) = 7:3), fine aggregate (S1) Total oven-dry density: 2.62 g / cm³ 3 • Carbonate aggregate (B1): The carbonate hardened product (B1) produced in the above manufacturing example B1 is used as fine aggregate. • Carbonate aggregate (B2): The carbonate hardened product (B2) produced in the above manufacturing example B2 is used as fine aggregate. • Coarse aggregate (G1): Limestone crushed stone 2005 (produced in Mine City, Yamaguchi Prefecture, absolute dry density: 2.69 g / cm³) 3 , Actual rate: 61%) • Coarse aggregate (G2): Limestone crushed stone 2005 (produced in Hachinohe City, Aomori Prefecture, absolute dry density: 2.69 g / cm³) 3 , Actual rate: 61%) • Water (W): Tap water (Chemical admixture) • AE water-reducing agent (AD): Tupol EX60T (manufactured by Takemoto Oil Co., Ltd.) • AE agent (AE): AE-300 (manufactured by Takemoto Oil Co., Ltd.) • Antifoaming agent (D): AFK-2 (manufactured by Takemoto Oil & Fat Co., Ltd.)

[0148] Table 5 shows the proportions of each component in the preparation of the concrete composition. Examples C1-1 to C1-3 were prepared using carbonate aggregate B1, and examples C2-1 to C2-3 were prepared using carbonate aggregate B2. In Table 5, the proportion of chemical admixtures is expressed as mass % (outside) relative to the mass of cement. Furthermore, the amount of water was adjusted so that the total amount of chemical admixture (aqueous solution) and water (W) in the concrete composition was 55% by mass (W / C) relative to the cement (C).

[0149] In Table 5, "Aggregate Replacement Rate" is the ratio of carbonate aggregate to total fine aggregate, i.e., the ratio of carbonate aggregate (B1 or B2) to the sum of fine aggregate (S1) and carbonate aggregate (B1 or B2), and is calculated using the following formula. Also, s / a(%) represents the volume ratio of the total fine aggregate (including carbonate aggregate) in the total aggregate. Aggregate volume replacement rate (%) = 100 × Volume of carbonate aggregate / (Volume of S1 + Volume of carbonate aggregate) • Bone material volume replacement rate (%) = 100 × Mass of carbonate aggregate / (Mass of S1 + Mass of carbonate aggregate) • s / a(%) = 100 × (Total volume of S1 and carbonate aggregate) / (Total volume of S1, carbonate aggregate, G1 and G2)

[0150] [Table 5]

[0151] In accordance with JIS A 1132:2020 "Method for preparing specimens for concrete strength testing," cylindrical specimens measuring 100 mm (diameter) x 200 mm (height) were prepared. The specimens were subjected to standard curing until the test age (28 days), and their compressive strength, static modulus, and splitting tensile strength were measured using the methods described below. Three specimens of each type were prepared, and their average values ​​were calculated. The results are shown in Table 6.

[0152] (Compressive strength) The compressive strength of the above 28-day-old specimens was measured in accordance with JIS A 1108 "Test Method for Compressive Strength of Concrete".

[0153] (Static elastic modulus) The static elastic modulus of the above 28-day-old specimen was calculated in accordance with JIS A 1149:2017 "Test Method for Static Elastic Modulus of Concrete".

[0154] (Splitting tensile strength test) The splitting tensile strength of the above-mentioned 28-day-old specimens was measured according to the method conforming to JIS A 1113:2018 "Test method for splitting tensile strength of concrete".

[0155] [Table 6]

[0156] The concrete specimens produced with the compositions listed in Table 5 above had a maximum aggregate size of 20 mm and a slump of 12 + 2.5 cm, measured according to JIS A 1101:2020 (Slump Test Method for Concrete). The compressive strength of the concrete specimens listed in Table 5 is the same as the compressive strength of ordinary concrete (18~45 N / mm²) as specified in JIS A 5308:2019 (Ready-Mixed Concrete). 2 ) falls within the range (Table 6). Therefore, it was confirmed that carbonate aggregates B1 and B2 have sufficient strength to be applied to ordinary concrete.

[0157] <Example D> In Examples D1 to D7, carbonate-hardened products (carbonate aggregates) were produced by the following carbonation process (d-1) and granulation process (d-2). (d-1) Preparation of a composition containing carbon dioxide (carbonation process (carbonation treatment)) Compositions D1 to D7 containing carbon dioxide were obtained by carbonization treatment using a 5L Hobart mixer (Hobart Japan Co., Ltd., N50), adding 500g of lime calcination dust (Beckenbach furnace dust) as raw materials as described in Table 1-1 above, and tap water in the proportions described in Table 7. CO2 (carbon dioxide gas) was then passed through the mixture at a flow rate of 10L / min for 20 minutes while stirring (total CO2 volume passed through: 200L, CO2 supply: 8.929 moles). In Table 7, the mass of lime calcination dust (powder) represents the dry mass of the raw material.

[0158] The carbon dioxide-containing composition obtained as described above was transferred to a plastic tray and dried at 70°C for 12 hours. The carbonation rate and CO2 fixation rate were then calculated using the method described later. The results are shown in Table 7.

[0159] (d-2) Manufacturing of hardened carbonate products (granulation process) Compositions D1 to D7 containing carbon oxide were separately prepared by the same manufacturing method as described in (d-1) above. Blast furnace slag (manufactured by Chiba Riverment Co., Ltd., trade name: Riverment Gx, see Table 1-2) was added as a latent hydraulic material to each of the obtained carbon oxide-containing compositions D1 to D7, and mixtures were prepared so that the dry mass ratio of the carbon oxide-containing composition to the latent hydraulic material was 65:35.

[0160] 100 parts by mass of the above mixture was weighed out and placed in an 11L high-speed mixer (FS10, manufactured by Earth Technica Co., Ltd.), and mixed for 30 seconds under conditions of agitator rotation speed of 310 rpm and chopper rotation speed of 3000 rpm. Then, tap water was weighed out so that the amount of water added was 25 parts by mass per 100 parts by mass of the dry mass of the mixture, and added to the same high-speed mixer, and mixed for 30 seconds while adding tap water under conditions of agitator rotation speed of 310 rpm and chopper rotation speed of 3000 rpm. After that, it was stirred and granulated for 4 minutes (granulation time: total 4.5 minutes) to obtain carbonate hardened products D1 to D7 (Table 8). These carbonate hardened products were used as carbonate aggregate. For carbonate hardened products D1 to D7, the amount of CO2 fixed and the average fracture load (curing 7 and 28 days) were measured as follows. The results are shown in Table 8.

[0161] <Method for calculating the carbonation rate of lime calcination dust> The carbonation rate of the lime calcination dust was calculated using the following method.

[0162] First, the total amount of CaO A (mass%) in the lime calcined dust before the carbonation treatment was determined according to JIS R 5202 "Methods for Chemical Analysis of Cement". This total amount of CaO includes calcium oxide (CaO) and calcium hydroxide (Ca(OH)2), which undergo the carbonation reaction, as well as gypsum (CaSO4) and calcium carbonate (CaCO3), which do not contribute to the carbonation reaction. Therefore, the amount of CaO F (mass%) contained in the raw material was calculated by subtracting the amount of CaO derived from CaSO4 and CaCO3 from the total amount of CaO using the following procedure.

[0163] (1) The amount of SO3 B (mass%) is quantified according to JIS R 5202 "Method for chemical analysis of cement". (2) The amount of CaSO4 C (mass%) is calculated using the formula C = B × (136.14 / 80.06). (3) Using a differential thermal-thermogravimetric analyzer (TG-DTA), the mass loss rate D (mass%) from 500°C to 800°C is quantified under conditions of room temperature to 1000°C, heating rate of 10°C / min, and N2 atmosphere. (4) The amount of CaCO3 E (mass%) is calculated using the formula E = D × (100.09 / 44.01). (5) The amount of f.CaO F (mass %) is calculated using the formula F = [A - {C × (56.08 / 136.14) + E × (56.08 / 100.09)}]. "f.CaO" represents free CaO.

[0164] Next, to eliminate the influence of differences in moisture and CO2 content between the samples before and after carbonation treatment, the above-mentioned raw materials were heated at 950°C until a constant weight was reached, and the mass loss G (mass%) was determined. The amount of f.CaO H (mass%) contained in the lime calcined dust of the raw materials heated at 950°C was then calculated using H = {F / (1-G / 100)}.

[0165] Next, the lime calcination dust (Beckenbach furnace dust) was subjected to carbonization treatment, and the amount of CaCO3 J (mass%) in the resulting carbon oxide-containing composition was determined using the following procedure. This was then converted to the amount of CaO L (mass%) contained in the carbon oxide-containing composition heated at 950°C. Furthermore, by subtracting the amount of CaO derived from the CaCO3 contained in the raw material before carbonization from this value, the amount of CaO N (mass%) derived solely from the CaCO3 produced by the carbonization treatment was calculated. The calculation method is described below.

[0166] (6) Using a differential thermal / thermogravimetric analyzer (TG-DTA), the mass loss I (mass%) from 500°C to 800°C is quantified under conditions of room temperature to 1000°C, heating rate of 10°C / min, and N2 atmosphere. (7) The amount of CaCO3 J (mass%) is calculated using the formula J = I × (100.09 / 44.01). (8) Heat the carbon oxide at 950°C until it reaches a constant weight and determine the mass loss K (mass%). (9) The amount of CaCO3 contained in carbon oxide heated at 950°C, converted to CaO equivalent, is calculated in L (mass%) using the formula L = J × (56.08 / 100.09) / (1-K / 100). (10) Based on E and G mentioned above, the amount of CaO M (mass%) derived from CaCO3 contained in the raw material is calculated using the formula M = E × (56.08 / 100.09) / (1-G / 100). (11) Using N=LM, determine the amount of CaO N (mass%) derived solely from the CaCO3 produced by the carbonation treatment.

[0167] Using the values ​​obtained in this way, "amount of f.CaO H contained in the raw material" and "amount of CaO N derived from CaCO3 produced by the carbonation treatment," the carbonation rate X (%), which is the percentage of the f.CaO component that was converted to CaCO3, was calculated using the formula X = (N / H) × 100.

[0168] <Method for calculating the amount of CO2 fixed in carbonate cured products> Since the amount of water and CO2 differs before and after carbonation, first, the amount of CO2 fixed by the carbonation treatment (O, mass%) and the amount of water increased by the quicklime digestion (P, mass%) are determined by external division for the sample before carbonation. Furthermore, by internal division of the amount of CO2 fixed by the carbonation treatment (O), the amount of CO2 fixed by the carbonation treatment (Q, mass%) contained in the sample after carbonation was calculated. The calculation procedure is shown below.

[0169] (12) Based on the amount of f.CaO F and the carbonation rate X mentioned above, the amount of CO2 fixed by the carbonation treatment O (mass%) in the sample before carbonation is calculated using the formula O = F × (X / 100) × (44.01 / 56.08). (13) Based on the amount of f.CaO F and the carbonation rate X mentioned above, the amount of water P (mass %) increased due to the digestion of quicklime is calculated using the formula P = F × (1 - X / 100) × (18.02 / 56.08). (14) Using the formula Q = O / (O + P + 100), the amount of CO2 fixed by the carbonation treatment Q (mass%) in the sample after carbonation is determined.

[0170] (15) As described above, the carbonate aggregate is formed by granulating a mixture of a composition containing carbon dioxide and blast furnace slag in a dry mass ratio of 65:35. Therefore, the amount of CO2 contained in 1 ton of carbonate aggregate was calculated as the amount of fixed CO2 Y [kg / t-dry aggregate] using the formula Y = 650 × (Q / 100) by multiplying the mass (650 kg) of the composition containing carbon dioxide (dry mass) in 1 ton of carbonate aggregate by the value of "amount of CO2 fixed by the carbonation treatment contained in the sample after carbonation Q (mass %)" calculated in (14) above.

[0171] <Method for calculating the CO2 fixation rate of lime calcination dust> The CO2 fixation rate of lime calcined dust after carbonization treatment was calculated based on the following formula. CO2 fixation rate = [(Amount of f.CaO in calcined lime dust (mol) × Carbonation rate (%) / 100) / CO2 supply amount (mol)] × 100 During the ceremony, f.CaO content (mol) of calcined lime dust = 500g × [f.CaO(%)] / [56(g / mol)] = 500g × 49.7 / 100 / [56 (g / mol)] = 4.4375 mol And, As mentioned above, the amount of CO2 supplied (mol) is 8.929 mol.

[0172] Table 7 shows the proportions of lime calcined dust and water in the raw materials during the carbonation process (see (d-1) above), the carbonation rate and CO2 fixation rate after the carbonation process, and the Ca(OH)2 and CaCO3 content in the composition containing the carbon oxide obtained by the carbonation process. The Ca(OH)2 and CaCO3 content after the carbonation process was measured using a differential thermal and thermogravimetric analyzer (STA7300, Hitachi High-Tech Science Corporation) under conditions of room temperature to 1000°C, a heating rate of 10°C / min, and an N2 atmosphere. The Ca(OH)2 content was calculated from the mass loss rate R (mass%) at 300-500°C using the formula R × (74.09 / 18.02). The CaCO3 content was calculated from the mass loss rate S (mass%) at 500-800°C using the formula S × (100.09 / 44.01).

[0173] <Measurement of average fracture load (strength) of carbonate-hardened materials> The carbonate cured products obtained in (d-2) above were tested for strength in accordance with JIS Z 8841-1993 "Granulated materials - Strength testing methods" "3. Strength testing methods for granulated materials". Specifically, the obtained carbonate cured products were sealed in poly bags for 7 days and 28 days, respectively. Then, 20 to 60 carbonate cured products with particle sizes of 2.36 to 4.75 mm were selected and extracted, and the breaking load of each individual particle was measured using a Tensilon universal material testing machine. The arithmetic mean of these values ​​was taken as the average breaking load of the carbonate cured products.

[0174] [Table 7]

[0175] [Table 8] [Industrial applicability]

[0176] The carbonate cured material of this disclosure has strength suitable for use as aggregate in construction materials such as ordinary concrete. In one embodiment, the carbonate cured material of this disclosure has a large CO2 fixation capacity and can contribute to the realization of a carbon-neutral society.

Claims

1. A carbonate hardened product containing carbonates and formed by granulation, A carbonate-cured product with a coarseness ratio of 3.0 or higher.

2. The carbonate cured product according to claim 1, wherein the water content is more than 21 parts by mass per 100 parts by mass of the dry mass of the carbonate cured product.

3. Let the dry mass of the carbonate cured product be 100 parts by mass, CaCO ３ It contains 10 to 60 parts by mass of SiO ２ A carbonate cured product according to claim 1 or 2, comprising 5 parts by mass or more and 20 parts by mass or less of the above.

4. CO2 as a percentage of the dry mass of the carbonate cured product ２ The carbonate cured product according to claim 1 or 2, wherein the amount of fixed material is 50 kg / t or more and less than 300 kg / t.

5. The carbonate cured product according to claim 1 or 2, wherein the maximum particle diameter is 10 mm or less.

6. A granulated aggregate comprising a carbonate hardened product according to claim 1 or 2.

7. cement and Fine aggregate containing the granulated aggregate described in claim 6, Coarse aggregate and Water and, A concrete composition containing [the specified ingredient].

8. A hardened product of the concrete composition according to claim 7.

Images