Hydraulic components, methods for manufacturing hydraulic components, and methods for manufacturing hardened materials.

Abstract

To provide a hydraulic composition with a cement clinker content of 5 mass% or less, containing carbonate, and exhibiting superior compressive strength after curing.SOLUTION: One aspect of the present disclosure is a hydraulic composition that contains cement composed of an alkali activator, granulated blast furnace slag, carbonate, and gypsum, and a promoter. With respect to 100 mass% of the total of the alkali activator, the granulated blast furnace slag, and the carbonate, the content of the alkali activator is 0.1-5.0 mass%, the content of the granulated blast furnace slag is 55.0-94.9 mass%, the content of the carbonate is 5.0-40.0 mass%, and the content of the gypsum in the cement is 2.5-10.0 mass% in terms of SO3. The content of the promoter is 0.2-4.0 pts.mass relative to 100 pts.mass of the cement.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a hydraulic composition, a method for producing a hydraulic composition, and a method for producing a cured product. [Background technology]

[0002] In cement production, significant amounts of CO2 are emitted from fuel combustion and decarbonation of raw materials. In response to the growing demand for measures against global warming, there is a need to reduce these CO2 emissions in cement production. Because a large amount of CO2 is emitted during the preparation of cement clinker, a raw material, cement in which a portion of the cement clinker is replaced with an admixture is being widely considered from the perspective of reducing CO2 emissions.

[0003] It is generally believed that increasing the amount of admixture reduces the compressive strength of the hardened material obtained by the hardening of cement. Therefore, it is important to achieve the desired performance, such as compressive strength, that is suitable for practical use, while adjusting the admixture. Among the admixtures, steel slag, such as blast furnace slag, is expected to enhance the long-term strength of concrete and improve its salt shielding effect. For this reason, research is underway on cement that uses steel slag as an admixture and increases its mixing ratio.

[0004] Blast furnace cement, in which a portion of the cement clinker is replaced with granulated blast furnace slag (BFS), is classified according to the replacement ratio. JIS R 5211:2019 specifies blast furnace cement type B, where the amount of blast furnace slag exceeds 30% by mass but is 60% by mass or less, and blast furnace cement type C, where the amount of blast furnace slag exceeds 60% by mass but is 70% by mass or less. However, there are no regulations for cement with a blast furnace slag content exceeding 70% by mass, and currently, it is believed that such cement cannot exhibit sufficient compressive strength, especially in the initial stages.

[0005] On the other hand, from the perspective of reducing CO2 emissions as mentioned above, research is also being conducted on cement compositions in which the amount of blast furnace slag is even higher than that of blast furnace cement type C (for example, Non-Patent Literature 1). Non-Patent Literature 1 confirms that the cement composition hardens when the amount of cement clinker is 1% by mass or less. However, it is known that this amount needs to be strictly controlled. For example, when the amount of cement clinker exceeds 1% by mass and reaches about 3-5% by mass, it has been confirmed that the hardening reaction of the cement composition does not proceed and the compressive strength drops drastically in the example described in Non-Patent Literature 1. Specifically, 55 N / mm² when the amount of cement clinker is 1% by mass. 2 Depending on the strength, the amount of cement clinker mixed can vary from 1% by mass to 10 N / mm². 2 It has been confirmed that the compressive strength decreases significantly until it reaches a certain strength level.

[0006] Generally, the measurement accuracy in the preparation of cement compositions at the industrial level is said to be at best 1-2 mass%, and as mentioned above, controlling the cement clinker content to 1 mass is not practical. This is one of the reasons why the commercialization of cement compositions with extremely high blast furnace slag content has not progressed. From this perspective, in practical terms, it is appropriate to adjust the composition of blast furnace cement so that the cement clinker content is at least 30 mass, as specified in JIS, and this has become common practice in the industry.

[0007] Furthermore, the reduction of CO2 emissions in cement production has also been investigated by replacing a portion of the admixture used in blast furnace cement type B, in which the amount of blast furnace slag exceeds 30% by mass but is 60% by mass or less, with fine limestone powder (fine calcium carbonate powder) (Non-Patent Literature 2). However, it has been confirmed that as carbonates are used as an admixture and their amount increases, the compressive strength of the hardened body obtained by hardening blast furnace cement type B gradually decreases. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Tokyo Institute of Technology et al., "ECM Cement," a low-carbon cement capable of reducing energy consumption and CO2 emissions by more than 60%, Figure 6, [online], May 2017, NEDO Commercialization Document, [Retrieved January 4, 2022], Internet<URL:https: / / www.nedo.go.jp / hyoukabu / articles / 201705ecm / index.html> [Non-Patent Document 2] Toyoichi Nishida et al., "Development of an environmentally friendly blended cement using fine limestone powder," Journal of Cement and Concrete, 2012, Vol. 66, pp. 375-381. [Overview of the project] [Problems that the invention aims to solve]

[0009] A technology that can suppress a significant decrease in the compressive strength of a hardened body obtained by curing a hydraulic composition in a region with extremely low cement clinker content (for example, a region of 5% by mass or less), and that can produce a hydraulic composition that exhibits stable quality even under industrial-level weighing accuracy, would be useful.

[0010] Furthermore, a technology that can produce hydraulic compositions in which the strength development is not significantly impaired, even when carbonates are incorporated, would be useful.

[0011] This disclosure aims to provide a hydraulic composition containing a cement clinker of 5% by mass or less and a carbonate, which can exhibit excellent compressive strength upon hardening, and a method for producing the same. This disclosure also aims to provide a method for producing a hardened body using the above-described hydraulic composition. [Means for solving the problem]

[0012] This disclosure provides the following [1] to

[16] .

[0013] [1] A cement consisting of an alkali stimulator, granulated blast furnace slag, a carbonate, and gypsum, and an accelerator, wherein based on a total of 100% by mass of said alkali stimulator, said granulated blast furnace slag and said carbonate, the content of said alkali stimulator is 0.1 to 5.0% by mass, the content of said granulated blast furnace slag is 55.0 to 94.9% by mass, and the content of said carbonate is 5.0 to 40.0% by mass, the content of said gypsum in said cement is 2.5 to 10.0% by mass in terms of SO3, and the content of said accelerator is 0.2 to 4.0 parts by mass relative to 100 parts by mass of said cement. A hydraulic composition. [2] The hydraulic composition according to [1], wherein said carbonate comprises calcium carbonate. [3] The hydraulic composition according to [1] or [2], wherein said carbonate comprises a carbonate obtained by immobilizing carbon dioxide contained in exhaust gas. [4] The hydraulic composition according to any one of [1] to [3], wherein said accelerator contains at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts. [5] The hydraulic composition according to any one of [1] to [4], wherein said accelerator contains a salt having a monovalent anion. [6] The hydraulic composition according to any one of [1] to [5], wherein said accelerator contains a calcium salt. [7] The hydraulic composition according to any one of [1] to [6], wherein said accelerator contains at least one selected from the group consisting of nitrites, nitrates and chlorides. [8] The hydraulic composition according to any one of [1] to [7], wherein said alkali stimulator contains at least one selected from the group consisting of Portland cement clinker, slaked lime and quicklime. [9] The hydraulic composition according to any one of [1] to [8], wherein said gypsum contains at least one selected from the group consisting of dihydrate gypsum and hemihydrate gypsum.

[10] The hydraulic composition according to any one of [1] to [9], wherein the basicity of said granulated blast furnace slag is 1.60 to 1.95.

[11] The hydraulic composition according to any one of [1] to

[10] , wherein the aluminum oxide content in the granulated blast furnace slag is 10.0% by mass or more.

[12] A first step of preparing cement by mixing raw materials including an alkaline stimulant, blast furnace granulated slag, carbonate, and gypsum, The process includes a second step of mixing 0.2 to 4.0 parts by mass of an accelerator with 100 parts by mass of the cement, The first step is, Based on a total of 100% by mass of the aforementioned alkali stimulant, the aforementioned blast furnace granulated slag, and the aforementioned carbonate, the amount of the alkali stimulant is adjusted to 0.1 to 5.0% by mass, and the amount of the aforementioned blast furnace granulated slag is adjusted to 95.0 to 99.9% by mass, and A method for producing a hydraulic composition, comprising adjusting the gypsum content in the cement to 2.5 to 10.0% by mass in terms of SO3.

[13] The method for producing the carbonate according to

[12] , comprising calcium carbonate.

[14] The method for producing the carbonate according to

[12] or

[13] , wherein the carbonate comprises a carbonate obtained by fixing carbon dioxide contained in exhaust gas.

[15] The manufacturing method according to any one of

[12] to

[14] , wherein the carbonate comprises at least one selected from the group consisting of alkali metal carbonates and alkaline earth metal carbonates.

[16] A first step of preparing cement by mixing raw materials including an alkaline stimulant, blast furnace granulated slag, carbonate, and gypsum, A second step involves mixing 0.2 to 4.0 parts by mass of an accelerator with 100 parts by mass of the cement to obtain a hydraulic composition. The third step involves blending 50 parts by mass of water with 100 parts by mass of the hydraulic composition, The first step is, Based on a total of 100% by mass of the aforementioned alkali stimulant, the aforementioned granulated blast furnace slag, and the aforementioned carbonate, the amount of the alkali stimulant is adjusted to 0.1 to 5.0% by mass, the amount of the granulated blast furnace slag is adjusted to 55.0 to 94.9% by mass, and the amount of the carbonate is adjusted to 5.0 to 40.0% by mass, and A method for producing a hardened body, comprising adjusting the gypsum content in the cement to 2.5 to 10.0% by mass in terms of SO3.

[0014] One aspect of this disclosure provides a hydraulic composition comprising a cement consisting of an alkali stimulant, granulated blast furnace slag, carbonate, and gypsum, and an accelerator, wherein, based on a total of 100% by mass of the alkali stimulant, granulated blast furnace slag, and carbonate, the content of the alkali stimulant is 0.1 to 5.0% by mass, the content of the granulated blast furnace slag is 55.0 to 94.9% by mass, the content of the carbonate is 5.0 to 40.0% by mass, the content of the gypsum in the cement is 2.5 to 10.0% by mass in terms of SO3, and the content of the accelerator is 0.2 to 4.0 parts by mass per 100 parts by mass of the cement.

[0015] The above-mentioned hydraulic composition is adjusted so that the content of carbonate and gypsum in the cement, as well as the content of the accelerator in the hydraulic composition, are within a predetermined range. As a result, even compositions with a low amount of alkaline stimulants, such as cement clinker, can harden and exhibit sufficient compressive strength. Furthermore, even if the content of the alkaline stimulant changes within 0.1 to 5.0 mass% due to the weighing during the preparation of the above-mentioned hydraulic composition, the occurrence of extreme fluctuations in compressive strength, as seen in conventional methods, is suppressed. The reason for obtaining such effects is not clear. However, it is generally thought that adding an accelerator accelerates the hardening reaction of the hydraulic composition, making it more difficult to control the reaction and leading to greater fluctuations in compressive strength compared to when the reaction proceeds slowly. It is also known that the addition of carbonate reduces the strength development of the hardened hydraulic composition. In light of this common technical knowledge for those skilled in the art, obtaining the above-mentioned effects by adjusting the amounts of carbonate and gypsum and the amount of accelerator is a novel finding that was difficult to anticipate.

[0016] The above carbonate may contain calcium carbonate.

[0017] The carbonates mentioned above may include carbonates obtained by fixing carbon dioxide contained in exhaust gas. By using compounds obtained by fixing carbon dioxide in exhaust gas as the carbonates, the apparent amount of CO2 generated in the production of hydraulic compositions can be further reduced.

[0018] The accelerator described above may contain at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts. By including the accelerator described above, the reactivity of granulated blast furnace slag can be further improved.

[0019] The above-mentioned accelerator may contain a salt having a monovalent anion. By including a salt having a monovalent anion in the accelerator, the influence of differences in the amount of alkaline stimulant can be further reduced.

[0020] The above-mentioned accelerator may contain a calcium salt. By including a calcium salt in the accelerator, the effects of differences in the amount of alkaline stimulant can be further reduced.

[0021] The above accelerator may contain at least one selected from the group consisting of nitrites, nitrates, and chlorides.

[0022] The above-mentioned alkaline stimulant may contain at least one selected from the group consisting of Portland cement clinker, slaked lime, and quicklime. By containing the above-mentioned components in the alkaline stimulant, the hydration reaction of the blast furnace granulated slag can be promoted, and the hardening reaction in the hydraulic composition can be further promoted.

[0023] The above-mentioned gypsum may contain at least one selected from the group consisting of dihydrate gypsum and hemihydrate gypsum. The inclusion of at least one of dihydrate gypsum and hemihydrate gypsum in the gypsum can further promote the initial reaction of the alkali stimulant (e.g., Portland cement clinker) and blast furnace granulated slag.

[0024] The basicity of the above-mentioned blast furnace granulated slag may be between 1.60 and 1.95.

[0025] The aluminum oxide content in the above-mentioned granulated blast furnace slag may be 10.0% by mass or more.

[0026] One aspect of this disclosure provides a method for producing a hydraulic composition, comprising: a first step of preparing cement by mixing raw materials including an alkali stimulant, granulated blast furnace slag, carbonate, and gypsum; and a second step of mixing 0.2 to 4.0 parts by mass of an accelerator with respect to 100 parts by mass of the cement, wherein the first step is adjusted so that the amount of alkali stimulant is 0.1 to 5.0 by mass, the amount of granulated blast furnace slag is 55.0 to 94.9 by mass, and the amount of carbonate is 5.0 to 40.0 by mass, based on a total of 100% by mass of the alkali stimulant, granulated blast furnace slag, and carbonate, and the gypsum content in the cement is adjusted to 2.5 to 10.0% by mass in terms of SO3.

[0027] The above manufacturing method allows for the production of the hydraulic composition described above by adjusting the content of carbonate and gypsum in the cement in the first step and adjusting the content of the accelerator in the second step.

[0028] In the above manufacturing method, the carbonate may contain calcium carbonate.

[0029] In the above manufacturing method, the carbonate may include a carbonate obtained by fixing carbon dioxide contained in exhaust gas. By using a compound obtained by fixing carbon dioxide in exhaust gas as the carbonate, the apparent amount of CO2 generated in the production of the hydraulic composition can be further reduced.

[0030] In the above manufacturing method, the carbonate may include at least one selected from the group consisting of alkali metal carbonates and alkaline earth metal carbonates.

[0031] One aspect of this disclosure provides a method for producing a hardened body, comprising: a first step of preparing cement by mixing raw materials including an alkali stimulant, granulated blast furnace slag, carbonate, and gypsum; a second step of obtaining a hydraulic composition by mixing 0.2 to 4.0 parts by mass of an accelerator with 100 parts by mass of the cement; and a third step of blending 50 parts by mass of water with 100 parts by mass of the hydraulic composition, wherein the first step is adjusted so that the amount of alkali stimulant is 0.1 to 5.0 by mass, the amount of granulated blast furnace slag is 55.0 to 94.9 by mass, and the amount of carbonate is 5.0 to 40.0 by mass, based on a total of 100% by mass of the alkali stimulant, granulated blast furnace slag, and carbonate, and the gypsum content in the cement is adjusted to 2.5 to 10.0 by mass in terms of SO3.

[0032] The above-described method for producing a hardened body involves adjusting the content of carbonate and gypsum in the cement in the first step, and adjusting the content of the accelerator in the second step, thereby enabling the preparation of the hydraulic composition described above. By mixing this with water and standard sand, a mortar capable of exhibiting excellent compressive strength can be produced. [Effects of the Invention]

[0033] According to this disclosure, a hydraulic composition containing a carbonate and having a cement clinker content of 5% by mass or less can be provided, which can exhibit excellent compressive strength upon hardening, and a method for producing the same. According to this disclosure, a method for producing a hardened body using the above-mentioned hydraulic composition can also be provided. [Modes for carrying out the invention]

[0034] 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.

[0035] Unless otherwise specified, the materials exemplified herein may be used individually or in combination of two or more. The content of each component in a composition means 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.

[0036] [Hydraulic composition] One embodiment of the hydraulic composition comprises a cement consisting of an alkaline stimulant, granulated blast furnace slag, carbonate, and gypsum, and an accelerator. In this hydraulic composition, based on a total of 100% by mass of the alkaline stimulant and granulated blast furnace slag, the content of the alkaline stimulant is 0.1 to 5.0% by mass, the content of the granulated blast furnace slag is 55.0 to 94.9% by mass, and the content of the carbonate is 5.0 to 40.0% by mass. The content of the gypsum in the cement is 2.5 to 10.0% by mass in terms of SO3. The content of the accelerator is 0.2 to 4.0 parts by mass per 100 parts by mass of the cement.

[0037] In this specification, "cement" means a powder mainly composed of granulated blast furnace slag, to which an alkaline stimulant is added (and in some cases, a powder further containing gypsum), not limited to cases where the alkaline stimulant contains cement clinker.

[0038] The alkali stimulant is a component that stimulates the hardening reaction of blast furnace granulated slag and promotes the hardening reaction of the hydraulic composition. The alkali stimulant may contain, for example, at least one selected from the group consisting of Portland cement clinker, slaked lime, and quicklime, and may be any one of Portland cement clinker, slaked lime, and quicklime, or it may be Portland cement clinker.

[0039] As the Portland cement clinker, a Portland cement clinker used for preparing various types of Portland cement specified in JIS R 5210:2003 "Portland Cement" may be used. Examples of the above-mentioned various Portland cements include ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and the like. The Portland cement clinker may be a Portland cement clinker used for preparing ordinary Portland cement and high-early-strength Portland cement.

[0040] The mineral composition of Portland cement clinker can be calculated by the Bogue equation. Here, the Bogue equation is a formula widely used as a formula for calculating the content of major minerals in Portland cement clinker from the content ratio of chemical components. By using the Bogue equation shown below, the contents of tricalcium silicate (represented by 3CaO·SiO2, C3S), dicalcium silicate (represented by 2CaO·SiO2, C2S), and tricalcium aluminate (represented by 3CaO·Al2O3, C3A) in Portland cement clinker can be calculated. Note that "%" in the following formulas means "% by mass". The chemical formulas represent the content ratio (% by mass) of each compound indicated by chemical analysis values according to JIS R 5204:2019 "Method for X-ray Fluorescence Analysis of Cement".

[0041] <Bogue式> C3S[%]=(4.07×CaO[%])-(7.60×SiO2[%])-(6.72×Al2O3[%])-(1.43×Fe2O3[%])-(2.85×SO3[%]) C2S[%]=(2.87×SiO2[%])-(0.754×C3S[%]) C3A[%]=(2.65×Al2O3[%])-(1.69×Fe2O3[%]) C4AF[%]=3.04×Fe2O3[%]

[0042] The amount of C3A in Portland cement clinker is preferably 0.5 to 11.0% by mass, more preferably 0.5 to 10.5% by mass, still more preferably 0.5 to 10.0% by mass or less, and particularly preferably 0.5 to 9.5% by mass. When the amount of C3A in Portland cement clinker is within the above range, it is possible to further reduce the amount of gypsum for suppressing the hydration reaction in the hydraulic composition, and the hydration reaction of granulated blast furnace slag can be more sufficiently exhibited.

[0043] The fineness of Portland cement clinker may be adjusted from the viewpoint of further improving the performance of the hydration reaction in the hydraulic composition. The lower limit of the Blaine specific surface area of Portland cement clinker is, for example, 2800 cm 2 / g or more, or 3000 cm 2 / g or more. By setting the lower limit of the Blaine specific surface area of Portland cement clinker within the above range, the hydration reaction with granulated blast furnace slag can be further promoted. The upper limit of the Blaine specific surface area of Portland cement clinker is, for example, 10000 cm 2 / g or less, 5000 cm 2 / g or less, 4000 cm 2 / g or less, or 3500 cm 2 / g or less. By setting the upper limit of the Blaine specific surface area of Portland cement clinker within the above range, the production cost of the hydraulic composition can be reduced, and the CO2 emission in the production of Portland cement clinker can be further reduced. The Blaine specific surface area of Portland cement clinker may be adjusted within the above range, for example, 2800 to 10000 cm 2 / g, 3000 to 5000 cm 2 / g, 3000 to 4000 cm 2 / g, or 3000 to 3500 cm 2 / g.

[0044] For granulated blast furnace slag, for example, a commercially available product may be used, or slag equivalent to granulated blast furnace slag may be prepared by oneself and used.

[0045] The upper limit of the aluminum oxide content (also referred to as Al2O3 content) in granulated blast furnace slag may be, for example, 14.5% by mass or less, or 14.3% by mass or less. Keeping the Al2O3 content in the granulated blast furnace slag within this range helps to further suppress the long-term decrease in strength development of the resulting hydraulic composition. The lower limit of the Al2O3 content in the granulated blast furnace slag may be, for example, 10.0% by mass or more, 11.0% by mass or more, 12.0% by mass or more, or 13.0% by mass or more. Keeping the lower limit of the Al2O3 content in the granulated blast furnace slag within this range allows the latent hydraulic properties of the granulated blast furnace slag to be more fully exhibited. Latent hydraulic properties refer to the characteristic of initiating a hydration reaction by adding an alkaline stimulant. The amount of Al2O3 in the granulated blast furnace slag may be adjusted within the above range, for example, 10.0 to 14.5 mass%, 12.0 to 14.5 mass%, or 13.0 to 14.5 mass%.

[0046] The lower limit of the silicon dioxide content (also expressed as SiO2 content) in granulated blast furnace slag may be, for example, 30.0% by mass or more, 33.0% by mass or more, 34.0% by mass or more, 34.5% by mass or more, or 35.0% by mass or more. By keeping the lower limit of the SiO2 content of granulated blast furnace slag within the above range, a decrease in initial and long-term strength development can be suppressed. The upper limit of the SiO2 content of granulated blast furnace slag may be, for example, 40.0% by mass or less, 38.0% by mass or less, 36.5% by mass or less, or 35.5% by mass or less. By keeping the upper limit of the SiO2 content of granulated blast furnace slag within the above range, a decrease in initial strength development can be suppressed. The SiO2 content of granulated blast furnace slag may be adjusted within the above range, for example, 33.0 to 40.0% by mass, or 34.0 to 35.5% by mass.

[0047] The lower limit of the calcium oxide content (also referred to as CaO content) in granulated blast furnace slag may be, for example, 35.0% by mass or more, 38.5% by mass or more, or 40.0% by mass or more. Having the lower limit of the CaO content in granulated blast furnace slag within the above range can further improve initial strength development. The upper limit of the CaO content in granulated blast furnace slag may be, for example, 45.0% by mass or less, 43.5% by mass or less, 43.0% by mass or less, 42.5% by mass or less, 42.0% by mass or less, or 41.5% by mass or less. Having the upper limit of the CaO content in granulated blast furnace slag within the above range can suppress long-term deterioration of strength development. The CaO content in granulated blast furnace slag may be adjusted within the above range, for example, 38.5 to 45.0% by mass, or 40.0 to 42.5% by mass.

[0048] The lower limit of the magnesium oxide content (also referred to as MgO content) in granulated blast furnace slag may be, for example, 4.0% by mass or more, 5.0% by mass or more, 5.5% by mass or more, 6.0% by mass or more, or 7.0% by mass or more. By keeping the lower limit of the MgO content of granulated blast furnace slag within the above range, a decrease in initial and long-term strength development can be suppressed. The upper limit of the MgO content of granulated blast furnace slag may be, for example, 10.0% by mass or less, 9.0% by mass or less, less than 7.5% by mass, less than 7.4% by mass, less than 7.2% by mass, or less than 7.1% by mass. By keeping the upper limit of the MgO content of granulated blast furnace slag within the above range, a decrease in initial strength development can be suppressed. The MgO content of granulated blast furnace slag may be adjusted within the above range, for example, 4.0 to 10.0% by mass, or 6.0% by mass or more and less than 7.4% by mass.

[0049] The granulated blast furnace slag may also contain other components such as sulfur trioxide (SO3), sodium oxide (NaO2), potassium oxide (K2O), and titanium oxide (TiO2).

[0050] In this specification, the chemical composition of granulated blast furnace slag refers to the value measured in accordance with the description in JIS R 5202:2015 "Methods for Chemical Analysis of Cement".

[0051] The reactivity of granulated blast furnace slag is evaluated using an index called basicity, which is expressed as the value of (CaO + MgO + Al2O3) / SiO2 (the ratio of the total content of calcium oxide, magnesium oxide, and aluminum oxide to the silicon dioxide content in the granulated blast furnace slag). Granulated blast furnace slag can be used with high basicity or low basicity.

[0052] As granulated blast furnace slag, a wide range of materials with a basicity of, for example, 1.60 to 1.95 can be used. Granulated blast furnace slag with a basicity of less than 1.75 is considered to be low-grade slag with low basicity and generally low reactivity, but it can be used as a component of the hydraulic composition disclosed herein.

[0053] The upper limit of the basicity of granulated blast furnace slag may be, for example, 1.95 or less, less than 1.95, less than 1.90, less than 1.85, or less than 1.80. The lower limit of the basicity of granulated blast furnace slag with relatively good reactivity may be, for example, greater than 1.75, or 1.78 or greater. Having the lower limit of basicity within the above range makes it easier to improve the initial strength of the hydraulic composition. The basicity of granulated blast furnace slag can be adjusted within the above range, for example, 1.75 to 1.95, or 1.75 or more and less than 1.80, etc.

[0054] In the hydraulic composition according to this disclosure, blast furnace granulated slag with low basicity can also be used. Blast furnace granulated slag with low basicity is usually not used as low-grade slag because it is difficult to obtain sufficient compressive strength. However, in the hydraulic composition according to this disclosure, the hardening reaction can be sufficiently promoted by incorporating a relatively large amount of gypsum and adjusting the accelerator content, so even the above-mentioned low-grade slag can be used. For such low-grade blast furnace granulated slag, the upper limit of basicity may be, for example, less than 1.75, less than 1.70, or less than 1.65. The lower limit of basicity of low-grade blast furnace granulated slag is not particularly limited, but for example, it may be 1.60 or more, or 1.65 or more. The basicity of low-grade blast furnace granulated slag may be adjusted within the above range, for example, 1.60 or more and less than 1.75.

[0055] The basicity in this specification is a value measured in accordance with the description in JIS A 6206:2013 "Fine Powder of Blast Furnace Slag for Concrete," and specifically refers to the value of (CaO+MgO+Al2O3) / SiO2 (the ratio of the total content of calcium oxide, magnesium oxide, and aluminum oxide to the content of silicon dioxide).

[0056] The Blaine specific surface area of ​​granulated blast furnace slag is, for example, 2500 to 10000 cm². 2 / g, 2500~8000cm 2 / g, 2500~6000cm 2 / g, 2500~5000cm 2 / g, 3000~5000cm 2 / g, 4000~5000cm 2 / g, or 4000-4500cm 2 / g is acceptable.

[0057] In this specification, "Blaine specific surface area" refers to the value measured in accordance with the method described in JIS R 5201:2015 "Physical Testing Methods for Cement".

[0058] The carbonate may include, for example, at least one selected from the group consisting of alkali metal carbonates and alkaline earth metal carbonates, and preferably includes an alkaline earth metal carbonate. Examples of alkali metal carbonates include sodium carbonate. Examples of alkaline earth metal carbonates include calcium carbonate and magnesium carbonate. When the carbonate includes an alkaline earth metal carbonate, it preferably includes calcium carbonate.

[0059] The carbonate may contain heavy calcium carbonate obtained by crushing and classifying limestone, or it may contain light calcium carbonate obtained by reacting carbon dioxide with lime milk, which is obtained by dispersing slaked lime in water. It is preferable to use light calcium carbonate produced using carbon dioxide contained in the exhaust gas of coal-fired power plants, cement kilns, and factories, as this makes it possible to produce a hydraulic composition that reduces CO2 emissions (carbon negative).

[0060] The carbonate content is 5.0 to 40.0% by mass, based on the total amount of cement. A carbonate content of 5.0% by mass or more can further reduce CO2 emissions during the production of the hydraulic composition, while a carbonate content of 40.0% by mass or less can more effectively suppress the decrease in the strength development of the hydraulic composition. The lower limit of the carbonate content may be, for example, 7.0% by mass or more, 10.0% by mass or more, 15.0% by mass or more, or 20.0% by mass or more, based on the total amount of cement. Having the lower limit of the carbonate content within the above range can further reduce CO2 emissions during the production of the hydraulic composition. The upper limit of the carbonate content may be, for example, 35.0% by mass or less, 30.0% by mass or less, or 25.0% by mass or less, based on the total amount of cement. Having the upper limit of the carbonate content within the above range can provide a hydraulic composition with superior strength development.

[0061] The hydraulic composition relating to this disclosure is a so-called low-cement hydraulic composition, having a relatively small content of alkali stimulant in the cement. Specifically, based on a total of 100% by mass of the alkali stimulant, blast furnace granulated slag, and carbonate, the content of the alkali stimulant is 0.1 to 5.0% by mass, the content of the blast furnace granulated slag is 95.0 to 99.9% by mass, and the content of the carbonate is 5.0 to 40.0% by mass.

[0062] In this specification, the content of alkali irritants refers to the value determined by the method described below. Since the detection method differs for the alkali irritants, Portland cement clinker, slaked lime, and quicklime, the content of alkali irritants is determined by performing the following three measurements and calculating their total amounts. First, the content of Portland cement clinker among the alkali irritants is determined. Specifically, a measurement sample is prepared by heating the hydraulic composition at 900°C for 1 hour to crystallize blast furnace granulated slag (glass). Then, X-ray diffraction measurement is performed on the measurement sample, and each crystalline phase in the measurement sample is quantified by the Rietveld analysis method, and the total amount of alite, belite, aluminate phase, and ferrite phase is taken as the content of Portland cement clinker. Next, the content of slaked lime among the alkali irritants is determined. The weight loss of 1 g of the hydraulic composition is measured by thermogravimetric differential thermal analysis (TG-DTA), and the weight loss value around 450-500°C is calculated as the amount of H2O due to the thermal decomposition reaction. The slaked lime content is determined by converting the weight loss values ​​above back to slaked lime (Ca(OH)2) using the respective molecular weights. Finally, the quicklime (CaO) content of the alkali stimulant is determined as follows: CaO is calculated using the Rietveld analysis method described above, and the quicklime content is determined by subtracting the amount of slaked lime (Ca(OH)2) converted to quicklime (CaO) obtained by thermogravimetric differential thermal analysis (TG-DTA) from the calculated value. The total content of the alkali stimulant is determined by summing the contents of Portland cement clinker, slaked lime, and quicklime calculated as described above.

[0063] In this specification, the blast furnace granulated slag content refers to the value determined by the following method. Specifically, first, a measurement sample is prepared by heating the hydraulic material at 900°C for 1 hour to crystallize the blast furnace granulated slag (glass). Then, X-ray diffraction measurement is performed on the measurement sample, and each crystalline phase in the measurement sample is quantified by the Rietveld analysis method. Gehlenite, okermanite, and melvinite are quantified as crystalline phases formed from the crystallization of blast furnace granulated slag, and the total amount of these is taken as the blast furnace granulated slag content. When manufacturing a hydraulic composition oneself, the amount of blast furnace granulated slag added in the manufacturing process (measured value) corresponds to the above content.

[0064] In this specification, the carbonate content refers to the value determined by the method described below. Specifically, the total carbon content in the cement composition is measured using a carbon-sulfur analyzer (C / S meter), and the carbonate content is calculated from the obtained value using the following formula (A). [Carbonate content (mass%)] = 12 ÷ [Total carbon content (mass%)] × [Molecular weight of CaCO3] ... Equation (A)

[0065] In the hydraulic composition relating to this disclosure, the gypsum content in the cement is relatively high from the viewpoint of exhibiting excellent compressive strength. The gypsum content in the cement is 2.5 to 10.0% by mass in terms of SO3. Because the gypsum content is within the above range, even in hydraulic compositions with a low alkali stimulant content, the effect of improving compressive strength due to the hardening of the hydraulic composition by gypsum is exhibited, and even if the alkali stimulant content fluctuates within the above range depending on the conditions with an accelerator prepared in a predetermined amount, extreme fluctuations in compressive strength are suppressed.

[0066] The upper limit of the gypsum content in cement may be, for example, 9.0% by mass or less, 8.0% by mass or less, 7.5% by mass or less, or 7.0% by mass or less, in terms of SO3. By keeping the upper limit of the gypsum content within the above range, the initial and long-term strength development can be further improved. The lower limit of the gypsum content in cement may be, for example, 3.0% by mass or more, 3.5% by mass or more, 4.0% by mass or more, 4.5% by mass or more, 5.0% by mass or more, 5.5% by mass or more, 6.0% by mass or more, or 6.5% by mass or more, in terms of SO3. By keeping the lower limit of the gypsum (SO3) content within the above range, the hydration reaction of the cement can be made more favorable, the fluidity of the hydraulic composition after mixing with water can be further improved, and the initial strength development can be further improved. The gypsum content in cement may be adjusted within the above range, for example, 3.0 to 8.0% by mass, or 6.0 to 7.0% by mass.

[0067] In this specification, the gypsum content refers to the total amount of gypsum components, etc., that are blended into the cement, in addition to the gypsum components that may be contained in the alkali stimulant and blast furnace granulated slag. In this specification, the gypsum content refers to the value determined by the method described below. Specifically, the gypsum content shall be measured in accordance with the SO3 analysis method specified in JIS R 5202:2015 "Methods for Chemical Analysis of Cement".

[0068] For example, dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum can be used. The gypsum may contain at least one selected from the group consisting of dihydrate gypsum and hemihydrate gypsum, or it may be one selected from the group consisting of dihydrate gypsum and hemihydrate gypsum. The gypsum may be gypsum obtained by recycling waste gypsum board.

[0069] The Blaine specific surface area of ​​the above cement is, for example, 2800 to 10000 cm². 2It may be / g. Furthermore, if the alkali stimulant constituting the cement contains Portland cement clinker, the Portland cement clinker, blast furnace granulated slag, and gypsum may be simultaneously crushed to form the cement. When crushed simultaneously, the lower limit of the Blaine specific surface area of ​​the cement may be, for example, 2800 cm². 2 / g or more, or 3000cm 2 It may be 10,000 cm² or more. By setting the lower limit of the Blaine specific surface area of ​​the cement within the above range, the hydration reaction with granulated blast furnace slag can be further enhanced. The upper limit of the Blaine specific surface area of ​​the cement is, for example, 10,000 cm². 2 / g or less, 5000cm 2 / g or less, 4000cm 2 / g or less, or 3500cm 2 It may be less than or equal to / g.

[0070] Accelerators are compounds that accelerate the reaction of granulated blast furnace slag and improve its initial strength.

[0071] The accelerator may contain at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts. The inclusion of alkali metal salts or alkaline earth metal salts in the accelerator can further improve the reactivity of blast furnace granulated slag. The alkali metal salts and alkaline earth metal salts mentioned above are salts other than carbonates.

[0072] The alkali metals mentioned above may be, for example, sodium and potassium, and the alkaline earth metals may be, for example, magnesium and calcium. From the viewpoint of promoting hydrate formation and improving compressive strength, the alkaline earth metal preferably contains calcium, and more preferably calcium. It is thought that calcium hydroxide (Ca(OH)2) eluted from cement clinker contributes to the initiation of the hardening reaction of blast furnace granulated slag, and if the accelerator contains a calcium salt, it can be expected to promote the hardening of the blast furnace granulated slag in the same way as the components eluted from cement clinker. Therefore, if the accelerator contains a calcium salt, a sufficient hardening reaction of blast furnace granulated slag can be expected even in regions where the alkali stimulant content is low, and this effect allows for greater tolerance of fluctuations in the amount of alkali stimulant blended in the hydraulic composition.

[0073] The accelerator may contain a salt having a monovalent anion, and may also contain a calcium salt. The accelerator may contain at least one selected from the group consisting of nitrites, nitrates, and chlorides. Including nitrite in the accelerator can further improve the initial strength during the hardening of the hydraulic composition. Including nitrite in the accelerator can also reduce the amount of heat generated during hydration during the hardening of the hydraulic composition.

[0074] More specifically, accelerators include calcium nitrite, calcium nitrate, calcium chloride, calcium hydroxide, sodium nitrite, potassium nitrite, sodium nitrate, potassium nitrate, sodium chloride, and potassium chloride. Among the compounds mentioned above, the accelerator preferably contains an alkali metal nitrite, more preferably calcium nitrite, and even more preferably calcium nitrite.

[0075] The upper limit of the accelerator content is 4.0 parts by mass or less per 100 parts by mass of the cement, but may be, for example, 3.8 parts by mass or less, 3.6 parts by mass or less, 3.4 parts by mass or less, or 3.2 parts by mass or less. By keeping the upper limit of the accelerator content within the above range, the occurrence of abnormal setting when the reaction of granulated blast furnace slag is excessively accelerated can be more reliably suppressed. The lower limit of the accelerator content is 0.2 parts by mass or more per 100 parts by mass of the cement, but may be, for example, 0.5 parts by mass or more, 1.0 parts by mass or more, 2.0 parts by mass or more, or 3.0 parts by mass or more. By keeping the lower limit of the accelerator content within the above range, the reaction of granulated blast furnace slag can be further accelerated. The accelerator content may be adjusted within the above range, and may be, for example, 0.2 to 4.0 parts by mass or 3.0 to 4.0 parts by mass per 100 parts by mass of the cement.

[0076] In this specification, the accelerator content is determined by performing X-ray diffraction measurements on the powdered composition to be measured and quantifying the accelerator content using the Rietveld analysis method. However, when preparing a hydraulic composition oneself, the accelerator content will be equal to the amount added, so the above analysis is not required.

[0077] The above-mentioned hydraulic composition may further contain other components in addition to cement and accelerators. Examples of other components include silica powder, other inorganic powders containing calcium, fly ash and silica fume, inorganic minerals containing Si and Al, concrete water-reducing agents, and retarders.

[0078] [Method for producing a hydraulic composition] The hydraulic composition described above can be manufactured, for example, by the following method. One embodiment of the method for manufacturing the hydraulic composition includes a first step of mixing raw materials containing an alkaline stimulant, blast furnace granulated slag, carbonate, and gypsum to prepare cement, and a second step of mixing 0.2 to 4.0 parts by mass of an accelerator with 100 parts by mass of the cement.

[0079] In the first step, each component constituting the raw material may be crushed. When crushing is performed in the first step, the order of mixing and crushing is not particularly limited. That is, the various components may be mixed and then crushed, or they may be crushed and then mixed, or the mixing and crushing of the various components may be performed simultaneously. The mixing of the various components in the first step may be performed using a mixer such as a pan mixer, a tilting drum mixer, and a ribbon mixer, or by mixing and crushing using a pulverizer such as a ball mill, a vertical roller mill, and a roller press, or by crushing each of the various components and then mixing them in a mixer such as a mechanical mixer.

[0080] The first step described above includes adjusting the composition of the alkali stimulant, blast furnace granulated slag, and carbonate so that the total amount of the alkali stimulant, blast furnace granulated slag, and carbonate is 100% by mass, the amount of the alkali stimulant is 0.1 to 5.0% by mass, the amount of the blast furnace granulated slag is 55.0 to 94.9% by mass, and the amount of the carbonate is 5.0 to 40.0% by mass, and adjusting the gypsum content in the cement to 2.5 to 10.0% by mass in terms of SO3.

[0081] In the second step, the cement and accelerator are mixed. The mixing method may be the same as or different from that of the first step. Other components may be added in the second step, or in steps other than the first and second steps. Examples of other components include silica powder, other inorganic powders containing calcium, fly ash, and inorganic minerals containing Si and Al.

[0082] The method for producing the hydraulic composition may include other steps in addition to the first and second steps. Examples of these other steps include a step (carbonate preparation step) in which carbon dioxide is brought into contact with a lime milk, which is obtained by dispersing at least one of quicklime and slaked lime in water. The carbon dioxide in the carbonate preparation step may be, for example, contained in exhaust gas, and contact between the lime milk and carbon dioxide may be achieved by bringing the exhaust gas into contact with the carbon dioxide. Examples of such exhaust gas include exhaust gas from coal-fired power plants, cement kilns, and factories. By including a carbonate, such as light calcium carbonate, which has had carbon dioxide contained in the exhaust gas fixed, as the carbonate, or by using exhaust gas as the source of carbon dioxide in the carbonate preparation step, it is possible to reduce the apparent CO2 emissions in the production of the hydraulic composition, and it may even be possible to achieve a negative (carbon negative) result.

[0083] [Method for manufacturing a hardened body] The hydraulic composition described above is suitable as a raw material for preparing hardened bodies such as mortar and concrete. In other words, one embodiment of the method for producing a hardened body includes a step of mixing 50 parts by mass of water with 100 parts by mass of the hydraulic composition described above. In the above production method, in addition to water, a hardened mortar may be produced by mixing with, for example, fine aggregate, coarse aggregate, admixtures, etc.

[0084] The hydraulic composition may be the same as the method for producing the hydraulic composition described above. That is, the method for producing the hardened body may include, for example, a first step of preparing cement by mixing raw materials including an alkali stimulant, granulated blast furnace slag, carbonate, and gypsum; a second step of obtaining a hydraulic composition by mixing 0.2 to 4.0 parts by mass of an accelerator with 100 parts by mass of the cement; and a third step of mixing 50 parts by mass of water with 100 parts by mass of the hydraulic composition. The first step may include adjusting the amount of alkali stimulant to be 0.1 to 5.0 by mass, the amount of granulated blast furnace slag to be 55.0 to 94.9 by mass, and the amount of carbonate to be 5.0 to 40.0 by mass, based on a total of 100% by mass of the alkali stimulant, granulated blast furnace slag, and carbonate, and adjusting the gypsum content in the cement to 2.5 to 10.0% by mass in terms of SO3.

[0085] Examples of water include tap water, distilled water, and deionized water. The amount of water used may be 20 to 100 parts by mass, or 40 to 70 parts by mass, per 100 parts by mass of the hydraulic composition described above.

[0086] Fine aggregate can be any fine aggregate specified in JIS A 5005:2020 "Crushed stone and crushed sand for concrete". Examples of fine aggregate include river sand, land sand, sea sand, crushed sand, silica sand, copper slag fine aggregate, and electric furnace oxidized slag fine aggregate. When using fine aggregate, the amount used may be, for example, 50 to 500 parts by mass, 100 to 300 parts by mass, or 200 to 250 parts by mass per 100 parts by mass of the hydraulic composition described above.

[0087] For coarse aggregate, you can use coarse aggregate as specified in JIS A 5005:2020 "Crushed stone and crushed sand for concrete". Examples of coarse aggregate include gravel and crushed stone. When using coarse aggregate, the amount used may be, for example, 50 to 500 parts by mass, 100 to 300 parts by mass, or 200 to 250 parts by mass per 100 parts by mass of the hydraulic composition described above.

[0088] Fine aggregate and coarse aggregate can be used in combination, in which case the total amount of fine aggregate and coarse aggregate used may be 100 to 300 parts by mass, or 200 to 250 parts by mass, per 100 parts by mass of the hydraulic composition described above.

[0089] Examples of admixtures include air-entraining agents, water-reducing agents, high-performance water-reducing agents, high-performance water-reducing agents, fluidizing agents, defoaming agents, shrinkage reducing agents, setting accelerators, setting retarders, and thickeners. The amount of admixture used may be, for example, 0.01 to 2 parts by mass per 100 parts by mass of the hydraulic composition described above.

[0090] 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]

[0091] The contents of this disclosure will be described in more detail below with reference to examples, comparative examples, and reference examples. However, this disclosure is not limited to the examples described below.

[0092] [Raw materials for hydraulic compositions] The following materials were used as raw materials for the hydraulic composition.

[0093] (Cement clinker) For the cement clinker used, we used the cement clinker commonly used in the preparation of ordinary Portland cement. In Table 1, ordinary Portland cement clinker is referred to simply as "clinker." The chemical composition of the cement clinker was measured in accordance with the description in JIS R 5202:2015 "Methods for Chemical Analysis of Cement." The results are shown in Table 1.

[0094] (plaster) The gypsum used was excreted dihydrate gypsum, a by-product of coal-fired power plants, and anhydrous gypsum used as a reagent. In Table 1, excreted dihydrate gypsum is referred to as dihydrate gypsum. The chemical composition of the gypsum was measured in accordance with JIS R 5202:2015 "Methods for Chemical Analysis of Cement". The results are shown in Table 1.

[0095] (Blast furnace granulated slag) For the granulated blast furnace slag, we used blast furnace slag fine powder without gypsum additive. The chemical composition of the blast furnace slag fine powder was measured in accordance with the description in JIS R 5202:2015 "Methods for Chemical Analysis of Cement". The results are shown in Table 1.

[0096] [Table 1]

[0097] In Table 1, the C / S ratio refers to the value of (CaO content) / (SiO2 content). Furthermore, the ignition loss (also expressed as ig.loss) in Table 1 is the value measured at a heating temperature of 700°C, in accordance with the method described in "5. Method for determining ignition loss" of JIS R 5202:2010, specifically in "5. Cases other than blast furnace cement and blast furnace slag."

[0098] (Carbonate) As the carbonate, light calcium carbonate manufactured by New Lime Co., Ltd. was used. This light calcium carbonate is obtained by reacting carbon dioxide with lime milk, which is obtained by dispersing slaked lime in water. The Blaine specific surface area of ​​the above light calcium carbonate is 18640 cm². 2 It was / g.

[0099] (Promoting agent) An inorganic accelerator was used as the accelerator. Specifically, calcium nitrite monohydrate (hereinafter sometimes referred to as CN), manufactured by Kishida Chemical Co., Ltd., was used.

[0100] [Example 1] Cement was prepared by mixing the following components: 1% by mass of ordinary Portland cement clinker as an alkaline stimulant, 69% by mass of blast furnace granulated slag, 15% by mass of calcium carbonate as a carbonate, and 15% by mass of dihydrate gypsum as a gypsum. Based on the combined amounts of ordinary Portland cement, blast furnace granulated slag, and calcium carbonate, the ordinary Portland cement clinker was 1.2% by mass, the blast furnace cement slag was 81.2% by mass, and the calcium carbonate was 17.6% by mass. The gypsum content in the cement was 6.9% by mass in terms of SO3.

[0101] Next, the hydraulic composition of Example 1 was prepared by adding calcium nitrite monohydrate as an accelerator to 100 parts by mass of cement, so that the accelerator amounted to 2 parts by mass.

[0102] [Example 2] A hydraulic composition was prepared in the same manner as in Example 1, except that the proportions of ordinary Portland cement clinker and blast furnace granulated slag were changed as shown in Table 2.

[0103] [Example 3] A hydraulic composition was prepared in the same manner as in Example 1, except that the proportions of ordinary Portland cement clinker and blast furnace granulated slag, as well as the proportion of accelerators, were changed as shown in Table 2.

[0104] [Comparative Example 1] A hydraulic composition was prepared in the same manner as in Example 2, except that an accelerator was not included.

[0105] [Comparative Examples 2-4] A hydraulic composition was prepared in the same manner as in Example 1, except that the proportions of ordinary Portland cement clinker, blast furnace granulated slag, carbonate (calcium carbonate), and gypsum (dihydrate gypsum) were changed as shown in Table 2.

[0106] [Reference example] As a reference example, a blast furnace cement classified as type B blast furnace cement was prepared. The blast furnace cement prepared in this example had a composition of 26.0% by mass of ordinary Portland cement clinker, 70.0% by mass of granulated blast furnace slag, and 4.0% by mass of dihydrate gypsum (1.9% by mass in terms of SO3).

[0107] [Table 2]

[0108] [Evaluation of hydraulic compositions: Compressive strength] The compressive strength of the hydraulic composition prepared as described above was measured at 7 and 28 days of age according to the method described later. The results are shown in Table 3.

[0109] The compressive strength was evaluated using mortar compositions obtained by blending a hydraulic composition, fine aggregate, and water. Specifically, for each of the hydraulic compositions prepared in the examples, comparative examples, and reference examples, a mortar composition for evaluation was prepared by blending 100 parts by mass of hydraulic composition with 200 parts by mass of sand (standard sand / manufactured by the Cement Association) as fine aggregate and 50 parts by mass of water. The above blending was adjusted so that the ratio of hydraulic composition:sand:water was 100:300:50 (by mass, in accordance with the description in JIS R 5201:2015 "Physical Testing Methods for Cement").

[0110] Mortar hardened bodies were prepared using each of the obtained mortar compositions. First, the above mortar compositions were mixed as mortar in a constant temperature chamber at 20°C and filled into a mold measuring 4cm × 4cm × 16cm (prepared in accordance with the description in JIS R 5201:2015 "Physical Test Methods for Cement"). The mold was stored in a humidity box and cured for 24 hours. After 24 hours of curing, the mold was removed to obtain a hardened mortar body. The obtained hardened mortar body was cured in water for 7 days (age 7 days) in a constant temperature chamber at 20°C. The hardened mortar body after water curing was used as a test specimen, and the compressive strength of the hardened mortar body at 7 days was measured. Similarly, the obtained hardened mortar body was cured in water for 28 days (age 28 days) in a constant temperature chamber at 20°C, and the compressive strength of the hardened mortar body at 28 days was measured. The measurement of compressive strength was performed in accordance with the description in JIS R 5201:1992 "Physical Test Methods for Cement". The results are shown in Table 3.

[0111] [Evaluation of hydraulic compositions: CO2 reduction effect] The CO2 reduction effect of the hydraulic composition prepared as described above was measured according to the method described later. The results are shown in Table 3. The results shown in Table 3 represent the ratio (%) when the CO2 emissions from the production of ordinary Portland cement (a composition having a composition of 96% by mass cement clinker and 4% by mass dihydrate gypsum (1.9% by mass in terms of SO3)) are set to 100.

[0112] More specifically, the CO2 emissions related to the production of the hydraulic composition were calculated as the sum of the CO2 emissions related to the preparation of each component, and the ratio was calculated with the CO2 emissions related to the production of ordinary Portland cement set to 100. In the above calculation, the CO2 emissions related to the preparation of cement and blast furnace granulated slag were the values ​​listed in "Guidelines for Environmental Performance Verification of Concrete Structures (Draft)"; Concrete Library No. 125, 2005, p. 15 (Japan Society of Civil Engineers). The CO2 emissions related to the preparation of cement and blast furnace granulated slag were +766.6 [unit: kg-CO2 / t] and +26.5 [unit: kg-CO2 / t], respectively. Furthermore, the use of recycled gypsum was assumed, and recycled gypsum is a by-product of slaked lime. Therefore, the CO2 emissions related to the preparation of gypsum were set to 0 [unit: kg-CO2 / t]. When using light calcium carbonate as the carbonate, the CO2 emissions associated with the preparation of the carbonate (which can also be considered recovered CO2, as the carbonate consumes CO2 during its synthesis) were calculated using a value of -439.6 [unit: kg-CO2 / t] based on the molecular weight of the chemical components.

[0113] [Table 3]

[0114] As shown in Tables 2 and 3, when comparing the results of a composition without accelerators and containing 3% by mass of ordinary Portland cement clinker (Comparative Example 1), it was confirmed that, as shown in previous research results, the compressive strength decreases significantly when the content of ordinary Portland cement clinker increases to 3% by mass compared to when the content is 1% by mass. Therefore, it was confirmed that industrial development in such a system is difficult.

[0115] On the other hand, as shown in Tables 2 and 3, the amount of ordinary Portland cement clinker was in the low range of 1 to 5% by mass, and despite the presence of carbonate, the compressive strength of the hydraulic compositions prepared in Examples 1 to 3 was found to be comparable to that of a hardened ordinary Portland cement (reference example).

[0116] Furthermore, as shown in Tables 2 and 3, the hydraulic compositions prepared in Examples 1 to 3, by using granulated blast furnace slag and carbonate, exhibit negative apparent CO2 emissions during their production. This confirms that the hydraulic compositions and their manufacturing methods described herein are technologies that enable carbon-negative cement production, a feat not previously possible. [Industrial applicability]

[0117] According to this disclosure, a hydraulic composition containing a carbonate and having a cement clinker content of 5% by mass or less can be provided, which can exhibit excellent compressive strength upon hardening, and a method for producing the same. According to this disclosure, a method for producing a hardened body using the above-mentioned hydraulic composition can also be provided. Furthermore, in this disclosure, by using a compound obtained by immobilizing exhaust gas containing CO2 as the carbonate, it is possible to substantially reduce the amount of CO2 emitted in cement production to zero, and depending on the amount of carbonate used, it may even be possible to make the amount of CO2 emitted in cement production negative (so-called carbon negative).

Claims

1. A cement consisting of an alkaline stimulant, blast furnace granulated slag, carbonate, and gypsum, It contains calcium nitrite, Based on a total of 100% by mass of the alkali stimulant, the granulated blast furnace slag, and the carbonate, the content of the alkali stimulant is 0.1 to 5.0% by mass, the content of the granulated blast furnace slag is 55.0 to 94.9% by mass, and the content of the carbonate is 5.0 to 40.0% by mass. The gypsum content in the cement is SO ３ This is equivalent to 2.5 to 10.0 mass percent. A hydraulic composition wherein the calcium nitrite content is 0.2 to 4.0 parts by mass per 100 parts by mass of cement.

2. The hydraulic composition according to claim 1, wherein the carbonate comprises calcium carbonate.

3. The hydraulic composition according to claim 1 or 2, wherein the carbonate comprises a carbonate obtained by fixing carbon dioxide contained in exhaust gas.

4. The hydraulic composition according to claim 1 or 2, wherein the alkaline stimulant contains at least one selected from the group consisting of Portland cement clinker, slaked lime, and quicklime.

5. The hydraulic composition according to claim 1 or 2, wherein the gypsum contains at least one selected from the group consisting of dihydrate gypsum and hemihydrate gypsum.

6. The hydraulic composition according to claim 1 or 2, wherein the basicity of the granulated blast furnace slag is 1.60 to 1.

95.

7. The hydraulic composition according to claim 1 or 2, wherein the aluminum oxide content in the granulated blast furnace slag is 10.0% by mass or more.

8. The hydraulic composition according to claim 1 or 2, wherein the alkali stimulant comprises Portland cement clinker.

9. The first step involves mixing raw materials, including an alkaline stimulant, blast furnace granulated slag, carbonate, and gypsum, to prepare cement. The process includes a second step of mixing 0.2 to 4.0 parts by mass of calcium nitrite with 100 parts by mass of the cement, The first step is, Based on a total of 100% by mass of the aforementioned alkali stimulant, the aforementioned blast furnace granulated slag, and the aforementioned carbonate, the amount of the alkali stimulant is adjusted to 0.1 to 5.0% by mass, the amount of the aforementioned blast furnace granulated slag is adjusted to 55.0 to 94.9% by mass, and the amount of the aforementioned carbonate is adjusted to 5.0 to 40.0% by mass, and The gypsum content in the cement is SO ３ A method for producing a hydraulic composition, comprising adjusting the amount to 2.5 to 10.0% by mass.

10. The production method according to claim 9, wherein the carbonate contains calcium carbonate.

11. The manufacturing method according to claim 9 or 10, wherein the carbonate includes a carbonate obtained by fixing carbon dioxide contained in exhaust gas.

12. The manufacturing method according to claim 9 or 10, wherein the carbonate includes at least one selected from the group consisting of alkali metal carbonates and alkaline earth metal carbonates.

13. The first step involves mixing raw materials containing an alkaline stimulant, blast furnace granulated slag, carbonate, and gypsum to prepare cement, A second step involves mixing 0.2 to 4.0 parts by mass of calcium nitrite with 100 parts by mass of the cement to obtain a hydraulic composition. The third step involves mixing 50 parts by mass of water with 100 parts by mass of the hydraulic composition, The first step is, Based on a total of 100% by mass of the aforementioned alkali stimulant, the aforementioned blast furnace granulated slag, and the aforementioned carbonate, the amount of the alkali stimulant is adjusted to 0.1 to 5.0% by mass, the amount of the aforementioned blast furnace granulated slag is adjusted to 55.0 to 94.9% by mass, and the amount of the aforementioned carbonate is adjusted to 5.0 to 40.0% by mass, and The gypsum content in the cement is SO ３ A method for producing a cured product, comprising adjusting the amount to 2.5 to 10.0% by mass.

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