Material separation reducing agent, powdered cement composition, and hydraulic composition

Abstract

The present invention provides a material segregation reducing agent that can produce concrete with high viscosity and excellent resistance to material segregation regardless of aggregate quality, and that can fix carbon dioxide into concrete, a powdered cement composition containing the material segregation reducing agent, and a hydraulic composition containing the powdered cement composition. [Solution] Contains cement hydrate carbon oxide, with a BET specific surface area of ​​5-100 m² 2 A material segregation reducing agent with a concentration of / g. A powdered cement composition comprising the material segregation reducing agent and cement, wherein the content of the segregation reducing agent in the powdered cement composition is 1 to 50% by mass. A hydraulic composition comprising the powdered cement composition, aggregate, and water.

Description

[Technical Field]

[0001] The present invention relates to a material segregation reducing agent, a powdered cement composition containing the material segregation reducing agent, and a hydraulic composition containing the powdered cement composition. [Background technology]

[0002] In recent years, there has been a growing demand for highly fluid concrete in order to streamline and reduce the labor involved in concrete construction. Highly fluid concrete allows for the uniform filling of concrete without separating the coarse aggregate, even within formwork where reinforcing bars are densely arranged. Depending on the type of material and mix design conditions of highly fluid concrete (hereinafter also referred to as "high-flow concrete"), the viscosity of high-flow concrete may be low. For example, high-flow concrete that requires compaction is more fluid than general concrete, but since the amount of cement contained in high-flow concrete is about the same, the viscosity of high-flow concrete tends to decrease, and a decrease in viscosity increases the risk of material segregation. Patent Document 1 describes a method for producing concrete that has sufficient fluidity and low bleeding, comprising: a first mixing step of mixing all of the cement and primary water, which is part of the mixing water, to obtain a first cement paste; a second mixing step of adding secondary water, which is the remainder of the mixing water, and the admixture to the first cement paste after the first mixing step and mixing to obtain a second cement paste; and a third mixing step of adding all of the aggregate to the obtained second cement paste and mixing.

[0003] On the other hand, reducing carbon dioxide emissions has become a crucial issue in order to curb global warming. Patent Document 2 describes a highly efficient manufacturing method for fixing CO2 to cement hydrate in a short time, which includes a CO2 injection step in which cement hydrate and water are placed in a container, and CO2 is injected into the container while stirring the mixture of cement hydrate and water, and in the CO2 injection step, the CO2 injection rate is 3600 kg / t·h or more and the CO2 injection amount is 600 kg / t or more, and this method fixes CO2 to cement hydrate. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-61593 [Patent Document 2] Japanese Patent Publication No. 2022-156508 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] To reduce the risk of segregation in high-flow concrete, one method of increasing the viscosity of high-flow concrete is to use a thickening agent containing various polymers as a segregation reducer. However, with this method, residual thickening agent in the mixer may affect the viscosity and air content of the concrete in the next batch. Furthermore, if the amount of thickening agent is reduced to a level that does not affect the next batch, the effect of increasing viscosity decreases, increasing the risk of segregation during compaction. There are also problems such as the time-consuming cleaning of the mixer after use and the treatment of wastewater contaminated with thickening agent. Another method involves using large quantities of powdered materials. In this method, increasing the amount of cement used as the powdered material increases the heat of hydration, raising the risk of thermal cracking. Furthermore, it is likely to result in excessive strength, leading to higher material costs and other unreasonable consequences. Additionally, when using mixed materials other than cement or fine mineral powders as the powdered material, the quality of the fresh concrete is heavily influenced by the quality of the powdered material. Furthermore, while selecting appropriate aggregates and increasing the proportion of fine aggregates can ensure resistance to material segregation between mortar and coarse aggregates, the availability of aggregates is regional, and in some locations, high-quality aggregates may be difficult to obtain. Additionally, fluctuations in aggregate quality can increase the risk of material segregation.

[0006] The object of the present invention is to provide a material segregation reducing agent that can produce concrete having high viscosity and excellent resistance to material segregation regardless of the quality of the aggregate, and that can fix carbon dioxide in the concrete, a powdered cement composition containing the material segregation reducing agent, and a hydraulic composition containing the powdered cement composition. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors have found a cement hydrate containing carbon oxide with a BET specific surface area of ​​5 to 100 m². 2 We found that the above objective can be achieved by using a material separation reduction material with a concentration of / g, and thus completed the present invention. In other words, the present invention provides the following [1] to [7]. [1] Contains cement hydrate carbon oxides and has a BET specific surface area of ​​5-100 m² 2 A material separation reducing agent characterized by having a value of / g. [2] A slurry containing the material separation reducing agent described in [1] above and water, wherein the pH is 6.5 to 9.5. [3] A powdered cement composition comprising the material segregation reducing agent and cement described in [1] above, wherein the content of the material segregation reducing agent in the powdered cement composition is 1 to 50% by mass.

[0008] [4] A hydraulic composition comprising the powdered cement composition, aggregate, and water described in [3] above. [5] 1 m of the above hydraulic composition 3 The hydraulic composition according to [4], wherein the mass of the powdered cement composition is 230 to 1,400 kg and the mass of the aggregate is 700 to 2,400 kg. [6] A hydraulic composition comprising the material separation reducing agent slurry, cement, and aggregate described in [2] above. [7] A method for producing the material separation reducing agent described in [1] above, comprising: a slurry preparation step of mixing at least one of cement and cement hydrate with water to obtain a cement hydrate-containing slurry; a carbonation step of contacting the cement hydrate-containing slurry with a carbon dioxide-containing gas to obtain a carbonated slurry containing cement hydrate carbon dioxide; and a drying step of drying the carbonated slurry to obtain a material separation reducing agent containing cement hydrate carbon dioxide, wherein the water solids ratio of the cement hydrate-containing slurry is 100 to 800%. [Effects of the Invention]

[0009] According to the material segregation reducing material of the present invention, concrete and the like containing the material segregation reducing material can be made to have high viscosity and excellent resistance to material segregation regardless of the quality of the aggregate. Furthermore, since concrete and other materials can be made to have excellent resistance to material segregation even without using thickeners or with only a small amount of thickeners, the impact on the next batch due to residual thickeners in the mixer, etc., can be reduced. Furthermore, since carbon dioxide can be fixed within concrete and other materials, carbon dioxide emissions can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] It is a schematic diagram of a manufacturing system for carbonates of cement hydrates.

Embodiments for Carrying out the Invention

[0011] [(1) Material separation reduction material] The material separation reduction material of the present invention contains carbonates of cement hydrates and has a BET specific surface area of 5 to 100 m 2 / g. Cement hydrates are formed by the reaction (hydration) of cement and water. Examples of cement hydrates include 3CaO·Al2O3·3CaSO4·32H2O, 3CaO·Al2O3·CaSO4·12H2O, 3CaO·Al2O3·6H2O, 4CaO·Al2O3·14H2O, 3CaO·2SiO2·3H2O, Ca(OH)2, etc. Examples of cement include various Portland cements such as ordinary Portland cement, early strength Portland cement, medium heat Portland cement, low heat Portland cement, sulfate resistant Portland cement, etc., blended cements such as blast furnace cement, fly ash cement, silica cement, etc., alumina cement, eco cement, etc. These may be used alone or in combination of two or more.

[0012] Cement hydrates are mixtures formed by mixing cement and water, as long as cement hydration occurs. As cement hydrates, cementitious hardened bodies such as waste concrete, waste mortar, fresh concrete sludge, concrete sludge generated by concrete product companies, and offcuts of lightweight foamed concrete may be used. These may be used alone or in combination of two or more. Carbonates of cement hydrates are those obtained by carbonating cement hydrates. In this specification, "carbonation" means absorbing and immobilizing carbon dioxide.

[0013] The BET specific surface area of the material separation reducing material is 5 to 100 m 2 / g, preferably 20 to 95 m 2 / g, more preferably 30 to 90 m 2 / g, still more preferably 40 to 80 m 2 / g, particularly preferably 60 to 75 m 2 / g. When the BET specific surface area is less than 5 m 2 / g, the degree of increase in viscosity of concrete etc. containing a powdery cement composition containing the material separation reducing material is small, and the material separation reducing effect deteriorates. When the BET specific surface area exceeds 100 m 2 / g, the viscosity of concrete etc. containing the material separation reducing material before curing becomes extremely high and the fluidity deteriorates. By using the material separation reducing material of the present invention as a part of the material of the hydraulic composition, it is possible to prevent the material separation of the hydraulic composition.

[0014] [(2) Method for producing material separation reducing material] Examples of the method for producing the material separation reducing material of the present invention include a slurry preparation step of mixing at least one of cement and cement hydrate (hereinafter also referred to as "solid content") and water to obtain a cement hydrate-containing slurry, and a carbonation step of bringing the cement hydrate-containing slurry into contact with a carbon dioxide-containing gas to obtain a carbonated slurry containing a carbonate of cement hydrate, and a drying step of drying the carbonated slurry to obtain a material separation reducing material containing a carbonate of cement hydrate, and the like. In the slurry preparation step, if general cement is used, the BET specific surface area of the material separation reducing material obtained after the drying step can usually be made 5 to 100 m 2 / g. When a cementitious hardened body is used as the cement hydrate, from the viewpoint of making the BET specific surface area of the material separation reducing material within a desired numerical range, a pulverization step of pulverizing at least one of cement and cement hydrate may be provided before the slurry preparation step.

[0015] In the slurry preparation process, the water-solids ratio (the mass ratio of water to solids expressed as a percentage) of the cement hydrate-containing slurry varies depending on the target concentration of the carbonated slurry, but is preferably 100-800%, more preferably 150-500%, and particularly preferably 250-350%. If the water-solids ratio is 100% or higher, the viscosity of the cement hydrate-containing slurry is reduced, improving workability and allowing the cement hydrate-containing slurry to stably absorb and immobilize carbon dioxide. If the water-solids ratio is 800% or lower, the carbonated slurry becomes easier to dry. Furthermore, when the carbonated slurry is used as a slurry containing a material separation reducing agent (described later), the preparation of other materials (e.g., water) becomes easier. Examples of water include tap water, industrial water, supernatant water from ready-mixed concrete, and recovered water as defined in "JIS A 5308:2019 (Ready-Mixed Concrete)."

[0016] There are no particular limitations on the method of supplying carbon dioxide-containing gas to a cement hydrate-containing slurry; one method is to bring the cement hydrate-containing slurry into contact with the carbon dioxide-containing gas. More specifically, one method involves placing a cement hydrate-containing slurry and a carbon dioxide-containing gas in a carbonation tank such that the gas phase consisting of the carbon dioxide-containing gas is positioned above the liquid phase consisting of the cement hydrate-containing slurry, thereby bringing the cement hydrate-containing slurry and the carbon dioxide-containing gas into contact. Furthermore, from the viewpoint of efficient carbonation, it is preferable to supply the carbon dioxide-containing gas while the cement hydrate-containing slurry is flowing.

[0017] Figure 1 is a schematic diagram of a carbonation system 1 for producing cement hydrate carbon dioxide. A storage tank 3 and a carbonation tank 2 contain cement hydrate slurry 9. The carbonation tank 2 is preferably sealed from the viewpoint of efficient carbonation. The cement hydrate slurry 9 is supplied from the storage tank 3 to the carbonation tank 2 via a slurry supply pipe 6 using a pump 5. Carbon dioxide-containing gas is continuously supplied from a carbon dioxide supply device 7 through a carbon dioxide supply passage 8 into the carbonation tank 2, where the cement hydrate slurry 9 and carbon dioxide-containing gas come into contact. The cement hydrate slurry 9 is circulated by moving to the storage tank 3 via a slurry circulation passage 4, and then being supplied again to the carbonation tank 2 from the slurry supply pipe 6. Alternatively, a carbon dioxide supply means (not shown) for supplying carbon dioxide-containing gas to the cement hydrate-containing slurry may be installed, and carbon dioxide-containing gas may be supplied into the cement hydrate-containing slurry.

[0018] In the carbonation process, the carbon dioxide-containing gas supplied to the cement hydrate-containing slurry may consist solely of carbon dioxide (carbonic acid gas), but from the viewpoint of ease of availability, it may also be a gas containing carbon dioxide and other gases (e.g., nitrogen). The proportion of carbon dioxide in the carbon dioxide-containing gas is preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 20% by volume or more, even more preferably 50% by volume or more, even more preferably 80% by volume or more, and particularly preferably 90% by volume or more. If the proportion is 5% by volume or more, the amount of carbon dioxide immobilized in the cement hydrate-containing slurry can be increased. In addition, the time required to prepare the carbonated slurry can be shortened. Examples of carbon dioxide-containing gases include liquefied carbon dioxide, exhaust gas generated in the cement manufacturing process (carbon dioxide concentration: approximately 20% by volume), exhaust gas generated in the steelmaking process (carbon dioxide concentration: approximately 20% by volume), exhaust gas generated in the thermal power generation process (carbon dioxide concentration: approximately 10% by volume), or gas separated and recovered from these exhaust gases (carbon dioxide concentration: approximately 100% by volume).

[0019] In the carbonation process, the supply of carbon dioxide-containing gas is carried out so that the pH of the carbonation slurry is preferably within the range of 5.0 to 11.0, more preferably 5.5 to 10.0, and particularly preferably 6.0 to 9.5. When the carbon dioxide-containing gas is supplied so that the pH is 5.0 or higher, the time required for supplying the carbon dioxide-containing gas is shortened, and the manufacturing efficiency is further improved. When the carbon dioxide-containing gas is supplied so that the pH is 11.0 or lower, a larger amount of carbon dioxide is immobilized in the cement hydrate. Note that supplying carbon dioxide-containing gas lowers the pH of the carbonation slurry. The supply time of carbon dioxide-containing gas necessary to ensure a sufficiently large amount of carbon dioxide is immobilized in the cement hydrate varies depending on the water-solids ratio, the means of supplying the carbon dioxide-containing gas, and the concentration of carbon dioxide in the gas supplied by that means. For this reason, it is preferable to determine the timing of ending the supply of carbon dioxide-containing gas based on the measured pH of the carbonated slurry.

[0020] In the drying process, there are no particular limitations on the method for drying the carbonated slurry, and examples include natural drying, hot air drying, vacuum drying, cooling drying, infrared drying, freeze-drying, and contact drying. These may be performed individually or in combination of two or more methods. In addition, solid-liquid separation of the carbonated slurry may be performed before drying to remove some of the moisture.

[0021] [(3) Slurry containing material separation reducing agent and water] The material separation reducing agent and water-containing slurry (carbonated slurry containing cement hydrate carbon dioxide) of the present invention can be obtained by performing the slurry preparation step and the carbonation step in the method for producing the material separation reducing agent described above, without performing the drying step. The material separation reducing agent and the slurry containing water can be used as materials for a hydraulic composition (described later). By using a slurry containing a material separation reducing agent and water as materials for a hydraulic composition, the amount of water contained in the hydraulic composition (excluding the water contained in the slurry containing the material separation reducing agent and water) can be reduced. Furthermore, the drying process can be omitted from the manufacturing process of the material separation reducing agent. The amount of water contained in the slurry containing the material separation reducing agent and water may be adjusted as appropriate depending on the water-solids ratio of the cement hydrate-containing slurry in the slurry preparation process and the amount of water added to the hydraulic composition. By using the material separation reducing agent and water slurry of the present invention as part of the materials of a hydraulic composition, material separation of the hydraulic composition can be prevented.

[0022] [(4) Powdered cement composition] The powdered cement composition of the present invention contains the material segregation reducing agent and cement described above. The cement used is not particularly limited; the same type of cement used in the material segregation reducing agent described above can be used. The content of the material segregation reducing agent in the powdered cement composition is 1 to 50% by mass, preferably 8 to 45% by mass, more preferably 10 to 35% by mass, and particularly preferably 15 to 30% by mass. If the above content is less than 1% by mass, the viscosity of the hydraulic composition containing the powdered cement composition decreases. If the above content exceeds 50% by mass, the viscosity of the hydraulic composition containing the powdered cement composition before hardening becomes extremely high and the fluidity decreases.

[0023] The powdered cement composition may optionally contain other powdered materials, as long as they do not hinder the objectives of the present invention. Examples of other powdered materials that may be optionally added include various admixtures such as fly ash, silica fume, and blast furnace slag powder. The content of other powdered materials in the powdered cement composition is preferably 30% by mass or less, more preferably 10% by mass or less.

[0024] [(5) Hydraulic composition] An example of the hydraulic composition of the present invention is one comprising the above-mentioned powdered cement composition, aggregate, and water (hereinafter also referred to as the "first hydraulic composition"). The aggregate can consist of fine aggregate alone, or a combination of fine aggregate and coarse aggregate. Natural aggregate, artificial aggregate, or recycled aggregate can also be used. The fine aggregate is not particularly limited and includes, for example, river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, limestone aggregate, slag fine aggregate, lightweight fine aggregate, clinker fine aggregate, and CCU fine aggregate (fine aggregate with carbon dioxide fixed from one or more types selected from recycled aggregate, waste concrete, blast furnace slag, and steelmaking slag). These may be used individually or in combination of two or more types.

[0025] The coarse aggregate is not particularly limited and includes, for example, river gravel, mountain gravel, land gravel, sea gravel, crushed stone, limestone aggregate, slag coarse aggregate, lightweight coarse aggregate, clinker coarse aggregate, and CCU coarse aggregate (coarse aggregate with carbon dioxide fixed from one or more types selected from recycled aggregate, waste concrete, blast furnace slag, and steelmaking slag). These may be used individually or in combination of two or more types. The water used is not particularly limited, and the same type of water used in the slurry preparation process described above can be used. Furthermore, within the limits that do not impede the objectives of the present invention, various admixtures such as AE agents, cement dispersants (water-reducing agents, AE water-reducing agents, high-performance water-reducing agents, or high-performance AE water-reducing agents) may be included as needed.

[0026] First hydraulic composition 1 m 3 The mass of the powdered cement composition is preferably 230 to 1,400 kg, more preferably 240 to 1,000 kg, even more preferably 250 to 800 kg, even more preferably 260 to 500 kg, and particularly preferably 270 to 400 kg. If the mass is 230 kg or more, the strength development of the first hydraulic composition is further improved. If the mass is 1,400 kg or less, the heat of hydration of the first hydraulic composition can be further reduced. First hydraulic composition 1 m 3 The mass of aggregate (total of fine aggregate and coarse aggregate, if included) is preferably 700 to 2,400 kg, more preferably 1,000 to 2,200 kg, even more preferably 1,200 to 2,000 kg, and particularly preferably 1,400 to 1,900 kg. If the above mass is within the above numerical range, the strength development of the first hydraulic composition will be further improved, and the shrinkage rate of the hardened body will be reduced. The fine aggregate ratio of the first hydraulic composition is preferably 40-55%, more preferably 42-53%, and particularly preferably 44-51%, from the viewpoint of workability, moldability, etc. The fine aggregate ratio refers to the volume ratio of fine aggregate to the total amount of fine aggregate and coarse aggregate. The water-to-powder ratio (the mass ratio of water to powder material expressed as a percentage) of the first hydraulic composition is preferably 30-65%, more preferably 40-60%. If the above ratio is 30% or higher, the fluidity of the first hydraulic composition is further improved. If the above ratio is 65% or lower, the strength development of the first hydraulic composition is further improved. The powder material refers to the powdered cement composition and any other powder material that may be added. The first hydraulic composition contains a material separation reducing agent, and therefore exhibits excellent viscosity and resistance to material separation.

[0027] Furthermore, another example of the hydraulic composition of the present invention includes the material separation reducing agent-containing slurry, cement, and aggregate described above (hereinafter also referred to as the "second hydraulic composition"). Such hydraulic compositions also exhibit excellent viscosity and resistance to material separation. The second hydraulic composition may contain water added separately from the water contained in the slurry. Second hydraulic composition 1 m 3 The preferred total mass of cement and material segregation reducing agent, and the preferred amount of aggregate per unit, are, respectively, the first hydraulic composition described above (1 m³). 3 The mass of the powdered cement composition and the mass of the aggregate per unit area are the same. The preferred water-to-powder ratio for the second hydraulic composition is the same as that for the first hydraulic composition. [Examples]

[0028] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Cement A; manufactured by Taiheiyo Cement Corporation, ordinary Portland cement, density: 3.16 g / cm³ 3 (2) Cement B; manufactured by Taiheiyo Cement Corporation, blast furnace cement type B, density: 3.04 g / cm³ 3 (3) Cement hydrate carbon oxide A; dry powder, BET specific surface area: 58.7 m² 2 / g (4) Cement hydrate carbon dioxide B; dry powder, BET specific surface area: 87.3 m² 2 / g (5) Cement hydrate carbon dioxide; dry powder, BET specific surface area: 68.0 m² 2 / g (6) Fine aggregate; mountain sand, surface dry density: 2.59g / cm 3 (7) Coarse aggregate; hard sandstone, crushed stone 2005, surface dry density 2.64 g / cm³ 3 , Actual rate: 59.9% (8) High-performance AE water-reducing agent A (standard type); manufactured by Pozzolith Solutions, product name "Master Glenium SP8SV" (9) High-performance AE water-reducing agent B (delayed type); manufactured by Pozzolith Solutions, product name "Master Glenium SP8RV" (10) High-performance AE water-reducing agent C (delayed type); manufactured by Pozzolith Solutions, product name "MasterEase 8050" (11) AE agent; manufactured by Pozzolith Solutions, product name "MasterAir 202A" (12) Antifoaming agent; manufactured by Pozzolith Solutions, product name "MasterAir 404" The preparation methods for cement hydrate carbon oxides A to C will be described later.

[0029] [Preparation of cementite carbon oxide A] A cement hydrate-containing slurry was prepared by mixing ordinary Portland cement and water in a mass ratio of 1:3 using a hand mixer for 120 seconds. A carbon dioxide-containing gas (carbon dioxide concentration: 99.5 vol%) was supplied from the carbon dioxide supply device 7 shown in Figure 1 through the carbon dioxide supply passage 8 to the carbonation tank 2, into which a cement hydrate-containing slurry was placed. Using a pump 5, the cement hydrate-containing slurry 9 was circulated between the carbonation tank 2 and the storage tank 3, while the cement hydrates in the slurry 9 were carbonated. The pH of the cement hydrate-containing slurry at the end of carbonation was 7.5. After decanting the supernatant water from the carbonated cement hydrate slurry, the residue was dried at 105°C for 24 hours, resulting in a BET specific surface area of ​​58.7 m². 2 We produced cement hydrate carbon oxide A (material separation reducing agent) at a concentration of / g.

[0030] [Preparation of cementite carbon dioxide B] Cement hydrate carbon dioxide B was prepared in the same manner as cement hydrate carbon dioxide A, except that fresh concrete sludge was used instead of ordinary Portland cement, and the solids of the fresh concrete sludge and water (including the water contained in the fresh concrete sludge) were mixed in a mass ratio of 1:3. The pH of the cement hydrate-containing slurry at the end of carbonation was 6.5, and the BET specific surface area of ​​cement hydrate carbon dioxide B (material segregation reducing agent) was 87.3 m². 2 It was / g. [Preparation of cementite carbon dioxide C] Cement hydrate carbon dioxide C was prepared in the same manner as cement hydrate carbon dioxide A, except that ready-mix concrete sludge (different from the one used in the preparation of cement hydrate carbon dioxide B) was used instead of ordinary Portland cement. The pH of the cement hydrate-containing slurry at the end of carbonization was 9.0, and the BET specific surface area of ​​cement hydrate carbon dioxide C (material segregation reducing agent) was 68.0 m². 2 It was / g.

[0031] [Examples 1-5, Comparative Examples 1-3] Concrete was prepared using the types and quantities of materials shown in Tables 1 and 2. Specifically, each component of the powder material, fine aggregate, and coarse aggregate were added to the mixer and dry-mixed for 15 seconds. Next, a mixture of water, a high-performance AE water-reducing agent, and an AE agent was added to the mixer and mixed for 2 minutes. After scraping off the mixture adhering to the inner wall of the mixer, mixing was performed for another minute to prepare the hydraulic composition (concrete). The physical properties of the obtained hydraulic composition were measured or evaluated according to the following methods. (1) Measurement of slump flow The slump flow of the hydraulic composition was measured in accordance with "JIS A 1150:2020 (Slump Flow Test Method for Concrete)". The target value was set at 55 ± 5 cm. (2) Measurement of air volume The air content of the hydraulic composition was measured in accordance with "JIS A 1128:2019 (Test method for air content of flash concrete by pressure - Air chamber pressure method)". The target value was set at 4.5 ± 1.5%. (3) Measurement of gap passage velocity Measurements were taken in accordance with the Japan Society of Civil Engineers standard "Draft Test Method for Void Passability of Concrete under Vibration Using a Box-Type Container (JSCE-F 701-2022)" under flow obstruction R2 conditions. For fresh concrete with a slump flow of 55 cm, a void passage velocity of 40 mm / s or higher satisfies the specified quality considering material segregation resistance and void passability. (4) Presence or absence of material separation The material separation properties of the hydraulic composition after kneading were evaluated visually. The results are shown in Table 2.

[0032] [Table 1]

[0033] [Table 2]

[0034] [Examples 6-7, Comparative Examples 4-5] Concrete was prepared using the types and quantities of materials shown in Tables 1 and 3. Specifically, each component of the powder material, fine aggregate, and coarse aggregate were added to the mixer and dry-mixed for 15 seconds. Next, a mixture of water, a high-performance AE water-reducing agent, and an antifoaming agent, which had been pre-mixed, was added to the mixer and mixed for 3 minutes. After scraping off the mixture adhering to the inner wall of the mixer, mixing was continued for another 2 minutes to prepare the hydraulic composition (concrete). The physical properties of the obtained hydraulic composition were measured or evaluated according to the following method. The results are shown in Table 3. The measurement of air content and whether or not material separation was performed were carried out in the same manner as in Example 1.

[0035] (5) Measurement of slump flow The slump flow of the hydraulic composition was measured in accordance with "JIS A 1150:2020 (Slump Flow Test Method for Concrete)". The target value was set at 70 ± 5 cm. (6) Measurement of filling height Measurements were taken in accordance with the Japan Society of Civil Engineers standard "Filling Test Method for High-Flow Concrete (JSCE-F 511-2018)" under flow impairment R1 conditions. A filling height of 300 mm or more satisfies the quality requirements for the self-filling properties of fresh concrete.

[0036] [Table 3]

[0037] The results in Tables 2 and 3 show that when the material separation reducing agent of the present invention is used (Examples 1-7), the viscosity of the hydraulic composition is appropriately imparted, making material separation less likely to occur. [Explanation of Symbols]

[0038] 1. Carbonation System 2 Carbonation tanks 3. Storage tanks 4. Slurry circulation path 5 pumps 6. Slurry supply pipe 7. Carbon dioxide supply device 8. Carbon dioxide supply channels 9. Cement hydrate-containing slurry

Claims

1. Contains cement hydrate carbon oxides, with a BET specific surface area of ​​5 to 100 m². ２ A material separation reducing agent characterized by having a value of / g.

2. A slurry containing the material separation reducing agent and water according to claim 1, wherein the pH of the material separation reducing agent is 6.5 to 9.

5.

3. A powdered cement composition comprising the material separation reducing agent and cement described in claim 1, A powdered cement composition in which the content of the above-mentioned material segregation reducing agent in the above-mentioned powdered cement composition is 1 to 50% by mass.

4. A hydraulic composition comprising the powdered cement composition, aggregate, and water according to claim 3.

5. 1 m of the above hydraulic composition ３ The hydraulic composition according to claim 4, wherein the mass of the powdered cement composition is 230 to 1,400 kg and the mass of the aggregate is 700 to 2,400 kg.

6. A hydraulic composition comprising a slurry containing a material separation reducing agent, cement, and aggregate as described in claim 2.

7. A method for producing a material separation reducing material according to claim 1, A slurry preparation step involves mixing at least one of cement and cement hydrate with water to obtain a cement hydrate-containing slurry. A carbonation step is performed by contacting the above cement hydrate-containing slurry with a carbon dioxide-containing gas to obtain a carbonated slurry containing cement hydrate carbon dioxide, The above carbonated slurry is dried to obtain a material separation reducing material containing cement hydrate carbon dioxide, A method for producing a material separation reducing agent, wherein the water-solids content ratio of the cement hydrate-containing slurry is 100 to 800%.

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