Hydraulic composition and method of producing hydraulic composition

Abstract

To provide a hydraulic composition capable of producing a hardened body excellent in compressive strength over a long period of time.SOLUTION: There is provided a hydraulic composition which comprises an alkali activator, a granulated blast furnace slag, cement comprising a gypsum and an accelerator, wherein the SO3 conversion value in the cement is 5.5 to 10.0 mass%, based on 100 mass% of the cement, the content of the alkaline activator is 4.0 to 15.0 mass%, the content of the granulated blast furnace slag is more than 70.0 mass% and 86.0 mass% or less and the content of the gypsum is 10.0 to 15.0 mass%, the gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum and the content of the accelerator is 0.2 to 4.0 pts.mass based on 100 pts.mass of the cement.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to hydraulic compositions and methods for making hydraulic compositions. [Background technology]

[0002] In cement production, large amounts of CO2 are generated during fuel combustion and decarbonation of raw materials, and in response to increasing demands for measures to combat global warming, there is a demand to reduce the amount of CO2 generated in cement production.Since a large amount of CO2 is generated during the preparation of cement clinker, which is the raw material, cement in which part of the cement clinker is replaced with an admixture is being widely studied 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 body obtained by hardening cement. Therefore, it is important to achieve the desired performance, such as practical compressive strength, while blending the admixture. Among admixtures, steel slag, such as blast furnace slag, is expected to increase the long-term strength of concrete and improve its salt-blocking effect. Therefore, research is being conducted on cement that uses steel slag as an admixture and increases its mixing ratio.

[0004] Blast-furnace cement, in which part of the cement clinker is replaced with granulated blast-furnace slag (BFS), is classified according to the replacement ratio. JIS R 5211:2019 specifies two types of blast-furnace cement: Type B, which contains more than 30% but not more than 60% by mass of blast-furnace slag, and Type C, which contains more than 60% but not more than 70% by mass of blast-furnace slag. However, there are no specifications for cement containing more than 70% blast-furnace slag. Currently, cement containing less than 30% blast-furnace slag has unstable compressive strength, making it difficult to use in practice. Meanwhile, research is also being conducted on cement compositions containing an even higher amount of blast-furnace slag than Type C blast-furnace slag, with a view to reducing CO2 emissions (e.g., Non-Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Tokyo Institute of Technology et al., "ECM Cement: A Low-Carbon Cement That Can Reduce Energy Consumption and CO2 Emissions by More Than 60%," Figure 6, [online], May 2017, NEDO Practical Application Document, [Retrieved January 4, 2022], Internet<URL:https: / / www.nedo.go.jp / hyoukabu / articles / 201705ecm / index.html> [Non-patent document 2] Toshio Yonezawa et al., "Energy and CO2 Minimum (ECM) Cement and Concrete System," Concrete Engineering, Japan Concrete Institute, 2010, Vol. 48, No. 9, pp. 69-73 Summary of the Invention [Problem to be solved by the invention]

[0006] If there were a hydraulic composition capable of producing a hardened body exhibiting sufficient compressive strength in a formulation in which the proportion of cement clinker replaced by granulated blast furnace slag is increased even further than in blast furnace cement type C, it would be useful because it would be possible to use it in the same way as before while reducing the environmental impact.

[0007] An object of the present disclosure is to provide a hydraulic composition that can produce a hardened product having excellent long-term compressive strength, and a method for producing the same. [Means for solving the problem]

[0008] According to the investigations of the present inventors, in the region where the replacement ratio of granulated blast furnace slag is extremely high, it is important to make the most of the reaction of the granulated blast furnace slag. It has been found that in conventional hydraulic compositions where the replacement ratio of granulated blast furnace slag is high, a layer of ettringite (a compound represented by 3CaO·Al2O3·3CaSO4·32H2O) is formed to cover the surface of the granulated blast furnace slag particles in the early stage of the hydration reaction, and as a result, the progress of the reaction of the granulated blast furnace slag itself is inhibited, and as a result, the compressive strength of the hardened body is not exhibited to the expected extent even when the reaction time is extended. The present inventors have also found that controlling the amounts of sulfate ions and sulfite ions supplied to the system when hardening a hydraulic composition can prevent ettringite from covering the entire particle surfaces of granulated blast furnace slag, and that as a means for achieving this, reducing the amount of SO3 in cement, using natural anhydrous gypsum or recycled anhydrous gypsum, and further blending a predetermined amount of accelerator can improve compressive strength even in a range where the replacement ratio of granulated blast furnace slag is extremely high. The present disclosure is based on the above findings.

[0009] The present disclosure provides the following [1] to

[11] .

[0010] [1] The cement comprises an alkali activator, granulated blast furnace slag, and gypsum, and an accelerator; The SO3 equivalent value in the cement is 5.5 to 10.0 mass%, Based on 100% by mass of the cement, The content of the alkaline irritant is 4.0 to 15.0% by mass, The content of the granulated blast furnace slag is more than 70.0% by mass and not more than 86.0% by mass, The gypsum content is 10.0 to 15.0% by mass, The gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum, The hydraulic composition has a content of the accelerator of 0.2 to 4.0 parts by mass relative to 100 parts by mass of the cement. [2] The hydraulic composition according to [1], wherein the total alkali content of the gypsum is 0.15% by mass or more. [3] The hydraulic composition according to [1] or [2], wherein the gypsum is recycled anhydrous gypsum. [4] 4. The hydraulic composition according to claim 1, wherein the 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 the accelerator is a salt having a monovalent anion. [6] The hydraulic composition according to any one of [1] to [5], wherein the accelerator contains a calcium salt. [7] The hydraulic composition according to any one of [1] to [6], wherein the 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 the alkaline activator 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 the basicity of the granulated blast furnace slag is 1.60 to 1.95.

[10] The hydraulic composition according to any one of [1] to [9], wherein the content of aluminum oxide in the granulated blast furnace slag is 10.0 mass % or more.

[11] Mixing an alkaline activator, granulated blast furnace slag, and gypsum to prepare cement; Mixing 0.2 to 4.0 parts by mass of an accelerator with respect to 100 parts by mass of the cement, The SO3 equivalent value in the cement is 5.5 to 10.0 mass%, Based on 100% by mass of the cement, The content of the alkaline irritant is 4.0 to 15.0% by mass, The content of the granulated blast furnace slag is more than 70.0% by mass and not more than 86.0% by mass, The gypsum content is 10.0 to 15.0% by mass, The method for producing a hydraulic composition, wherein the gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a hydraulic composition that can produce a hardened product having excellent long-term compressive strength, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following content. In the following description, when it is written "X to Y" (X and Y are arbitrary numbers), it means "X or more and Y or less" unless otherwise specified.

[0013] Unless otherwise specified, the materials exemplified in this specification can be used singly or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0014] One embodiment of the hydraulic composition includes a cement containing an alkali activator, granulated blast furnace slag, and gypsum, and an accelerator. The gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum, and the SO3 equivalent value of the cement is 5.5 to 10.0 mass%.

[0015] Based on 100% by mass of the cement, the content of the alkali activator is 4.0 to 15.0% by mass, the content of the granulated blast furnace slag is more than 70.0% by mass and not more than 86.0% by mass, and the content of the gypsum is 10.0 to 15.0% by mass.

[0016] (Alkaline stimulant) The alkali activator is a component that stimulates the hardening reaction of blast furnace slag and promotes the hardening reaction of the hydraulic composition. The alkali activator may contain at least one selected from the group consisting of Portland cement clinker, slaked lime, and quicklime, may be any one of Portland cement clinker, slaked lime, and quicklime, and may be Portland cement clinker.

[0017] For the Portland cement clinker, the Portland cement clinker used for preparing various Portland cements specified in JIS R 5210:2003 "Portland Cement" can be used. Examples of the various Portland cements include ordinary Portland cement, early-strength Portland cement, medium-heat Portland cement, and low-heat Portland cement. The Portland cement clinker may be the Portland cement clinker used for preparing ordinary Portland cement and early-strength Portland cement.

[0018] The mineral composition of the Portland cement clinker can be calculated by the Bogue formula. Here, the Bogue formula is a formula widely used to calculate the content rate of the main minerals in the Portland cement clinker from the content ratio of the chemical composition. By using the Bogue formula shown below, the contents of tricalcium silicate (3CaO·SiO2, denoted as C3S), dicalcium silicate (2CaO·SiO2, denoted as C2S), and tricalcium aluminate (3CaO·Al2O3, denoted as C3A) in the Portland cement clinker can be calculated. In the following formula, "%" means "mass%". The chemical formula represents the content ratio (mass%) of each compound shown by the chemical analysis value according to JIS R 5204:2019 "Fluorescent X-ray Analysis Method for Cement".

[0019] <Bogue formula> 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[%]

[0020] The C3A content in the Portland cement clinker may be preferably 0.5 to 11.0 mass%, more preferably 0.5 to 10.5 mass%, even more preferably 0.5 to 10.0 mass%, and particularly preferably 0.5 to 9.5 mass%. When the C3A content in the Portland cement clinker is within the above range, it is possible to further reduce the amount of gypsum that inhibits the hydration reaction in the hydraulic composition, and also to more fully exhibit the hydration reaction of granulated blast furnace slag.

[0021] The fineness of the 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 ​​the Portland cement clinker is, for example, 2800 cm 2 / g or more, or 3000cm 2 / g or more. By setting the lower limit of the Blaine specific surface area of ​​the Portland cement clinker within the above range, the hydration reaction with the granulated blast furnace slag can be further promoted. The upper limit of the Blaine specific surface area of ​​the Portland cement clinker can be set to, for example, 10,000 cm 2 / g or less, 5000cm 2 / g or less, 4000cm 2 / g or less, or 3500cm 2 / g or less. By setting the upper limit of the Blaine specific surface area of ​​the Portland cement clinker within the above range, it is possible to reduce the production cost of the hydraulic composition and further reduce CO2 emissions in the production of the Portland cement clinker. The Blaine specific surface area of ​​the Portland cement clinker may be adjusted within the above range, for example, 2800 to 10000 cm 2 / g, 3000-5000cm 2 / g, 3000-4000cm 2 / g, or 3000-3500cm 2 / g.

[0022] The Blaine specific surface area in this specification is a value obtained by the fineness test of JIS R 5201:2015 "Physical Testing Methods for Cement" and measurement using a Blaine air permeability device, and is one of the physical properties that indicate fineness.

[0023] The content of the alkali activator is 4.0 to 15.0% by mass, based on 100% by mass of the cement. The upper limit of the content of the alkali activator may be, for example, 14.0% by mass or less, 13.0% by mass or less, 11.0% by mass or less, or 9.0% by mass or less, based on 100% by mass of the cement. When the upper limit of the content of the alkali activator is within the above range, the rapid reaction of the granulated blast furnace slag due to alkali activating can be further suppressed, and sufficient strength can be exhibited over the long term. The lower limit of the content of the alkali activator may be, for example, 4.5% by mass or more, 5.0% by mass or more, 6.0% by mass or more, or 8.0% by mass or more, based on 100% by mass of the cement. When the lower limit of the content of the alkali activator is within the above range, the initial reactivity of the granulated blast furnace slag can be further improved, and sufficient strength can be exhibited.

[0024] The content of alkaline activator in this specification refers to a value determined by the following method. The alkaline activators, Portland cement clinker, slaked lime, and quicklime, are detected by Rietveld analysis using an internal standard method based on X-ray diffraction measurement of the hydraulic composition powder, quantifying the Portland cement clinker, slaked lime, and quicklime, calculating their total amount, and determining the content of alkaline activator. Specifically, first, either corundum (aluminum oxide) or periclase (magnesium oxide) is used as an internal standard substance, and this is added to the powder whose alkaline activator content is to be determined so that the content is 10% by mass. Next, the powder is wet-pulverized in acetone using an agate mortar to make the particle size as uniform as possible. The acetone is then fully evaporated, and X-ray diffraction measurement is performed. Of the crystalline phases detected in the measurement sample (alite, belite, aluminate phase, ferrite phase, gypsum, sylvite, halite, lime, portlandite, or any one of the internal standards), Rietveld analysis is performed with the internal standard fixed at 10 mass%. Here, the amorphous phase calculated based on the internal standard is treated as glassy granulated blast furnace slag, and the total amount of Portland cement clinker, slaked lime, and quicklime is calculated, and the content of the alkali activator is determined.

[0025] (granulated blast furnace slag) Granulated blast furnace slag is a type of slag with a high vitrification rate, and is a sand-like slag that is crushed by injecting a large amount of pressurized water into the molten slag produced in a blast furnace to rapidly cool it.

[0026] The granulated blast furnace slag may be, for example, commercially available, or slag equivalent to granulated blast furnace slag may be prepared and used.

[0027] The aluminum component in granulated blast furnace slag also serves as a supply source of aluminum used to form ettringite during the hydration reaction of the hydraulic composition. The aluminum oxide content (also referred to as the Al2O3 content) in granulated blast furnace slag may be adjusted to a low value. The upper limit of the Al2O3 content in granulated blast furnace slag may be, for example, 20.0 mass% or less, 17.5 mass% or less, or 15.0 mass% or less. The lower limit of the Al2O3 content in granulated blast furnace slag may be, for example, 10.0 mass% or more, 11.0 mass% or more, 12.0 mass% or more, or 13.0 mass% or more. When the lower limit of the Al2O3 content in granulated blast furnace slag is within the above range, the latent hydraulic properties of the granulated blast furnace slag can be more fully exhibited. Note that latent hydraulic properties refer to the property of initiating a hydration reaction by adding an alkaline activator. The amount of Al2O3 in the granulated blast furnace slag may be adjusted within the above range, for example, 10.0 to 20.0 mass%, 12.0 to 17.5 mass%, or 13.0 to 15.0 mass%.

[0028] Granulated blast furnace slag having a basicity of 1.60 to 1.95 can be widely used. Granulated blast furnace slag having a basicity of less than 1.75 has a low basicity and is generally considered to be a low-grade slag with low reactivity, but it can be used as a component of the hydraulic composition according to the present disclosure containing a predetermined amount of accelerator.

[0029] The upper limit of the basicity of the 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 the granulated blast furnace slag, which has relatively excellent reactivity, may be, for example, more than 1.75 or 1.78 or more. When the lower limit of the basicity is within the above range, it can be easier to improve the early strength of the hydraulic composition. The basicity of the granulated blast furnace slag can be adjusted within the above range, and may be, for example, 1.75 to 1.95, or 1.75 or more but less than 1.80.

[0030] In the hydraulic composition according to the present disclosure, even granulated blast furnace slag with low basicity can be used. Low-basicity granulated blast furnace slag is often avoided as a low-grade slag because it is difficult to obtain sufficient compressive strength. However, in the hydraulic composition according to the present disclosure, the hardening reaction can be sufficiently accelerated by blending a relatively large amount of gypsum and adjusting the content of the accelerator, so even such low-grade slag can be used. The upper basicity limit of such low-grade granulated blast furnace slag may be, for example, less than 1.75, less than 1.70, or less than 1.65. The lower basicity limit of the low-grade granulated blast furnace slag is not particularly limited, but may be, for example, 1.60 or more, or 1.65 or more. The basicity of the low-grade granulated blast furnace slag may be adjusted within the above-mentioned range, for example, 1.60 or more but less than 1.75.

[0031] The basicity (JIS basicity) in this specification is a value measured in accordance with the description in JIS A 6206:2013 "Ground granulated blast furnace slag for concrete," and specifically means 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).

[0032] The fineness of the granulated blast furnace slag may be adjusted in advance from the viewpoint of further improving the performance of the hydration reaction in the hydraulic composition. The Blaine specific surface area of ​​the granulated blast furnace slag is, for example, 2500 to 10000 cm 2 / g, 2500-8000cm 2 / g, 2500-6000cm 2 / g, 2500-5000cm 2 / g, 3000-5000cm 2 / g, 4000-5000cm 2 / g, or 4000 to 55.00 cm 2 / g.

[0033] The content of the granulated blast furnace slag is more than 70.0% by mass and not more than 86.0% by mass, based on 100% by mass of the cement. The upper limit of the content of the granulated blast furnace slag may be, for example, not more than 85.0% by mass, not more than 84.0% by mass, not more than 82.0% by mass, or not more than 80.0% by mass, based on 100% by mass of the cement. When the upper limit of the content of the granulated blast furnace slag is within the above range, the reactivity of the granulated blast furnace slag can be more sufficient. The lower limit of the content of the granulated blast furnace slag may be, for example, not less than 70.1% by mass, not less than 73.0% by mass, not less than 76.0% by mass, or not less than 77.0% by mass, based on 100% by mass of the cement. When the lower limit of the content of the granulated blast furnace slag is within the above range, the latent hydraulic properties of the granulated blast furnace slag can be more fully exhibited.

[0034] The content of granulated blast furnace slag in this specification refers to a value determined by the following method. Specifically, a measurement sample is prepared by heating a hydraulic composition at 900°C for 1 hour to crystallize the granulated blast furnace slag (glass). The measurement sample is then subjected to X-ray diffraction measurement, and the crystalline phases in the measurement sample are quantified by Rietveld analysis to quantify gehlenite, akermanite, and merwinite as crystalline phases formed by crystallization of the granulated blast furnace slag, and the total amount of these is defined as the content of granulated blast furnace slag. When a hydraulic composition is manufactured by one's own manufacturing process, the blending amount (measured value) of granulated blast furnace slag added during the manufacturing process corresponds to the above content.

[0035] (plaster) The gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum. More than 4 million tons of gypsum board are produced and used annually as a major material for building interior materials. From the perspective of reducing the environmental impact by recycling the waste gypsum board generated during its demolition as recycled anhydrous gypsum, it is more preferable to use recycled anhydrous gypsum as the gypsum for the hydraulic composition according to the present disclosure. "Natural anhydrous gypsum" in this specification refers to gypsum powder that can be extracted from natural mines. "Recycled anhydrous gypsum" in this specification refers to gypsum powder prepared from waste gypsum board, excluding by-product gypsum such as desulfurization gypsum and phosphogypsum, and new gypsum powder (e.g., reagent gypsum).

[0036] The gypsum is a component that can also serve as a source of sulfate ions and the like to the reaction system during the hydration reaction, and a higher total alkali content can accelerate the hardening reaction. The lower limit of the total alkali content of the gypsum may be, for example, 0.15% by mass or more, 0.16% by mass or more, 0.17% by mass or more, 0.18% by mass or more, 0.19% by mass or more, 0.20% by mass or more, 0.21% by mass or more, 0.22% by mass or more, or 0.23% by mass or more. The upper limit of the total alkali content of the gypsum may be, for example, 0.40% by mass or less, 0.37% by mass or less, 0.34% by mass or less, 0.31% by mass or less, 0.28% by mass or less, or 0.25% by mass or less. When the upper limit of the total alkali content is within the above range, the local alkali reaction of the granulated blast furnace slag can proceed slowly, and the reaction inhibition associated with ettringite formation due to a rapid reaction can be more sufficiently suppressed. The total alkali content of the gypsum may be adjusted within the above range, for example, 0.15 to 0.40% by mass, or 0.17 to 0.25% by mass.

[0037] The total alkali content in gypsum means a value calculated from the following formula using the chemical analysis value of gypsum measured in accordance with the method described in JIS R 5204:2019 "Fluorescent X-ray analysis method for cement." R2O[%] = Na2O[%] + 0.658 × K2O[%]

[0038] The lower limit of the pH of the gypsum may be, for example, 9.0 or more, 10.0 or more, 10.5 or more, or 11.0 or more. When the lower limit of the pH of the gypsum is within the above range, the reaction of the granulated blast furnace slag can be further promoted. The upper limit of the pH of the gypsum may be, for example, 12.0 or less, 10.0 or less, 8.0 or less, or 7.0 or less. When the upper limit of the pH of the gypsum is within the above range, the reaction of the granulated blast furnace slag can be further promoted.

[0039] The pH of gypsum in this specification means the value measured according to JIS R 9101:2018 "Method for chemical analysis of gypsum."

[0040] The gypsum content is 10.0 to 15.0% by mass, based on 100% by mass of the cement. The upper limit of the gypsum content may be, for example, 14.5% by mass or less, 14.0% by mass or less, 13.0% by mass or less, or 12.5% ​​by mass or less, based on 100% by mass of the cement. When the upper limit of the gypsum content is within the above range, the initial and long-term strength development can be further improved. The lower limit of the gypsum content may be, for example, 10.3% by mass or more, 10.5% by mass or more, 11.0% by mass or more, 11.5% by mass or more, or 12.0% by mass or more, based on 100% by mass of the cement. When the lower limit of the gypsum content is within the above range, the hydration reaction of the granulated blast furnace slag is more favorable, the hardening of the hydraulic composition after mixing with water is promoted, and the early strength development can be further improved. The content of the gypsum may be adjusted within the above range, and may be, for example, 10.0 to 15.0 mass % or 11.0 to 15.0 mass % based on 100 mass % of the cement.

[0041] In the hydraulic composition, the amount of SO3 in the cement detected by X-ray fluorescence analysis may be adjusted to fall within a predetermined range. The amount of SO3 in the cement includes that derived from the alkali activator and granulated blast furnace slag, which are components other than gypsum. Therefore, the amount of SO3 in the cement can be adjusted by adjusting the components used and their amounts.

[0042] The SO3 content of the cement detected by X-ray fluorescence analysis is 5.5 to 10.0 mass% based on the total amount of the cement. When the SO3 content in the cement is within this range, the supply of sulfate ions and the like to the reaction system during the hydration reaction is slower than in conventional hydraulic compositions, the formation of an ettringite film on the particle surfaces of the granulated blast furnace slag is suppressed, the granulated blast furnace slag can be sufficiently reacted, and a hardened body with excellent initial and long-term compressive strength can be produced.

[0043] The upper limit of the SO3 content may be, for example, 10.0 mass% or less, 9.0 mass% or less, 8.0 mass% or less, or 7.0 mass% or less, based on the total amount of the cement. When the upper limit of the SO3 content is within the above range, the resulting hydraulic composition can produce a hardened body with superior initial and long-term compressive strength. The lower limit of the SO3 content may be, for example, 5.5 mass% or more, 6.0 mass% or more, 6.5 mass% or more, or 6.9 mass% or more, based on the total amount of the cement. When the lower limit of the SO3 content is within the above range, the reactivity of the granulated blast furnace slag in a weakly alkaline environment can be further promoted.

[0044] The SO3 content in this specification means a value measured in accordance with the method described in JIS R 5204:2019 "Fluorescent X-ray analysis method for cement."

[0045] (accelerator) The accelerator is a compound that accelerates the reaction of granulated blast furnace slag and improves its early strength.

[0046] The accelerator may contain a monovalent anion or a salt having a monovalent anion. The monovalent anion may be, for example, at least one anion selected from the group consisting of nitrite ion, nitrate ion, chloride ion, formate ion, and acetate ion. For example, when the accelerator contains a nitrite, the early strength of the hydraulic composition during hardening can be further improved. When the accelerator contains a nitrite, the amount of heat generated by hydration during hardening of the hydraulic composition can also be reduced.

[0047] The accelerator may contain at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts. When the accelerator contains an alkali metal salt or an alkaline earth metal salt, the reactivity of the granulated blast furnace slag can be further improved.

[0048] The alkali metal may be, for example, sodium or potassium, and the alkaline earth metal may be, for example, magnesium or calcium. From the viewpoint of promoting hydrate formation and improving compressive strength, the alkaline earth metal preferably contains calcium, and more preferably is calcium. The accelerator may contain, for example, a calcium salt.

[0049] In the hydraulic composition according to the present disclosure, similar to conventional hydraulic compositions containing an alkaline activator such as cement clinker, alkaline activators such as calcium hydroxide (Ca(OH)2) eluted from the alkaline activator are thought to contribute to the initiation of the hardening reaction of granulated blast furnace slag. Similar to the alkaline activator, the accelerator is expected to further accelerate the hardening of granulated blast furnace slag by eluting components containing, for example, calcium. Therefore, when the accelerator contains a calcium salt, a more sufficient hardening reaction of granulated blast furnace slag can be expected even when the amount of alkaline activator is small. This effect allows for greater tolerance of fluctuations in the amounts of each component in the hydraulic composition, making the hydraulic composition according to the present disclosure easier to use.

[0050] Examples of the accelerator include calcium nitrite, calcium nitrate, calcium chloride, calcium hydroxide, sodium nitrite, potassium nitrite, sodium nitrate, potassium nitrate, sodium chloride, potassium chloride, etc. Among the above compounds, the accelerator preferably contains an alkali metal nitrite, more preferably contains calcium nitrite, and even more preferably is calcium nitrite.

[0051] The upper limit of the accelerator content may be, for example, 4.0 parts by mass or less, 3.0 parts by mass or less, 2.0 parts by mass or less, 1.0 parts by mass or less, or 0.8 parts by mass or less, relative to 100 parts by mass of the cement. By keeping the upper limit of the accelerator content within the above range, the occurrence of abnormal setting, which occurs when the reaction of granulated blast furnace slag or the like is excessively promoted, can be more reliably suppressed. The lower limit of the accelerator content may be, for example, 0.2 parts by mass or more, 0.3 parts by mass or more, 0.4 parts by mass or more, 0.5 parts by mass or more, or 0.6 parts by mass or more, relative to 100 parts by mass of the cement. By keeping the lower limit of the accelerator content within the above range, the reaction of granulated blast furnace slag can be further promoted. The accelerator content may be adjusted within the above range, and may be 0.2 to 4.0 parts by mass or 0.3 to 2.0 parts by mass, relative to 100 parts by mass of the cement.

[0052] The content of the accelerator in this specification is determined by subjecting the powdered composition to X-ray diffraction measurement and quantifying the content of the accelerator by Rietveld analysis. When preparing a hydraulic composition by oneself, the content of the accelerator coincides with the blending amount, and therefore the above-mentioned analysis is not required.

[0053] [Method for producing hydraulic composition] One embodiment of a method for producing a hydraulic composition includes mixing an alkaline activator, granulated blast furnace slag, and gypsum to prepare cement (hereinafter sometimes referred to as a first step), and mixing 0.2 to 4.0 parts by mass of an accelerator per 100 parts by mass of the cement (hereinafter sometimes referred to as a second step). The gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum.

[0054] In the first step, each component may be crushed and mixed. 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 the various components may be crushed and then mixed, or 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 mixer, or a ribbon mixer, or may be mixed and crushed using a crusher such as a ball mill, a vertical roller mill, or a roller press, or the various components may be crushed individually and then mixed using a mixer such as a mechanical mixer.

[0055] The SO3 equivalent value of the cement is 5.5 to 10.0 mass%, and the blending ratio of the cement is adjusted so that, based on 100 mass% of the cement, the content of the alkali activator is 4.0 to 15.0 mass%, the content of the granulated blast furnace slag is more than 70.0 mass% and not more than 86.0 mass%, and the content of the gypsum is 10.0 to 15.0 mass%.

[0056] In the second step, cement and an accelerator are mixed. The mixing method may be the same as or different from that in the first step. Other components may be blended in the second step or in a step other than the first and second steps. Examples of other components include silica powder, inorganic powders containing calcium (excluding the above-mentioned admixtures and granulated blast furnace slag), fly ash, silica fume, and inorganic minerals containing Si and Al (excluding aggregates).

[0057] The method for producing a hydraulic composition may include other steps in addition to the first step and the second step. Examples of the other steps include a step of pulverizing a lumpy admixture (pulverizing step), a step of heat-treating the admixture (heat-treatment step), and a step of adjusting the particle size of the admixture (particle size adjusting step). A ball mill or the like can be used for pulverizing in the pulverizing step. In the pulverizing step, the particle size of the admixture may be adjusted to 90 μm or less. In the heat-treatment step, the amount of water adhering to the surface of the admixture is reduced. In the heat-treatment step, a dryer or the like can be used, and the heating temperature can be 100°C or higher and 130°C or lower. In the particle size adjusting step, the particle size of the admixture is adjusted using, for example, a sieve or the like.

[0058] [Method of manufacturing the hardened product] The hydraulic composition described above is suitable as a raw material for preparing hardened products such as mortar and concrete. In other words, one embodiment of a method for producing a hardened product includes a step of blending 50 parts by mass of water with 100 parts by mass of the hydraulic composition described above. In the above-described production method, a hardened mortar may be produced by mixing, in addition to water, fine aggregate, coarse aggregate, admixtures, etc. In the above-described method for producing a hardened product, the hardening time may be about 24 hours, but it is preferable to ensure a relatively long time. The hardening time may be, for example, 48 hours or more, 72 hours or more. During the hardening process, it is preferable to maintain the mortar or the like in a molded state, for example, in a formwork, so as to maintain the shape of the desired hardened product.

[0059] The hydraulic composition may be prepared by the same method as the hydraulic composition described above. That is, one embodiment of a method for preparing a hardened body includes mixing an alkaline activator, granulated blast furnace slag, and gypsum to prepare cement, and blending 50 parts by mass of water with 100 parts by mass of the hydraulic composition containing the cement. The SO3 equivalent value of the cement is 5.5 to 10.0 mass%. Based on a total of 100 mass% of the cement, the content of the alkaline activator is 4.0 to 15.0 mass%, the content of the granulated blast furnace slag is more than 70.0 mass% and not more than 86.0 mass%, and the content of the gypsum is 10.0 to 15.0 mass%, and the gypsum includes anhydrous gypsum. The gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum.

[0060] Examples of water include tap water, distilled water, deionized water, etc. 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.

[0061] The fine aggregate may be one 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 oxidizing slag fine aggregate. When using fine aggregate, the amount of fine aggregate 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.

[0062] The coarse aggregate may be one 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 of coarse aggregate 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.

[0063] Fine aggregate and coarse aggregate can also be used in combination. In this case, the total amount of the 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.

[0064] Examples of the admixture include air-entraining agents, water-reducing agents, air-entraining water-reducing agents, high-performance water-reducing agents, superplasticizers, antifoaming agents, shrinkage-reducing agents, setting accelerators, setting retarders, and thickeners. The amount of the admixture used may be, for example, 0.01 to 2 parts by mass per 100 parts by mass of the above-mentioned hydraulic composition.

[0065] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. Furthermore, the descriptions of the above embodiments can be applied to each other. [Example]

[0066] The present disclosure will be described in more detail below with reference to examples, comparative examples, and reference examples, although the present disclosure is not limited to the following examples.

[0067] [Raw materials for hydraulic compositions] The following materials were used as raw materials for the hydraulic composition.

[0068] (Alkaline stimulant) Cement clinker was used as the alkali activator. The cement clinker used is the type commonly used when preparing ordinary Portland cement. In Table 1, ordinary Portland cement clinker is abbreviated as "OPC." The chemical composition of the cement clinker was measured in accordance with JIS R 5202:2015, "Methods for Chemical Analysis of Cement." The loss on ignition (also abbreviated as ig.loss) was measured at a heating temperature of 700°C in accordance with the method described in "5.2 For Materials Other Than Blast-Furnace Cement and Blast-Furnace Slag" in "5. Methods for Determination of Ignition Loss" of JIS R 5202:2010. The results are shown in Table 1.

[0069] (granulated blast furnace slag) The granulated blast furnace slag used was ground granulated blast furnace slag (JIS basicity: 1.87) without gypsum addition. In Table 1, ground granulated blast furnace slag without gypsum addition is designated "BFS1." The chemical composition of the ground granulated blast furnace slag was measured in accordance with JIS R 5202:2015, "Methods for Chemical Analysis of Cement." The loss on ignition (also abbreviated as ig.loss) was measured at a heating temperature of 700°C in accordance with the method described in "5.2 For Materials Other Than Blast-Furnace Cement and Blast-Furnace Slag" in "5. Methods for Determination of Ignition Loss" of JIS R 5202:2010. The Blaine specific surface area of ​​the granulated blast furnace slag was measured in accordance with the method described in JIS R 5201:2015, "Physical Testing Methods for Cement." The results are shown in Table 1.

[0070] (plaster) The gypsum samples used were recycled anhydrous gypsum prepared from waste gypsum board, natural anhydrous gypsum, hydrofluoric anhydrous gypsum, and dehydrated gypsum dihydrate, a by-product of coal-fired power plants. The chemical composition of the gypsum was measured in accordance with JIS R 5202:2015, "Methods for Chemical Analysis of Cement." The loss on ignition (also abbreviated as ig.loss) was measured at a heating temperature of 700°C in accordance with the method described in "5.2 For Materials Other Than Blast-Furnace Cement and Blast-Furnace Slag" in "5. Methods for Determination of Ignition Loss" of JIS R 5202:2010. The pH was measured in accordance with the method described in JIS R 9101:2018, "Methods for Chemical Analysis of Gypsum." The results are shown in Table 1.

[0071] [Table 1]

[0072] (accelerator) An inorganic accelerator, calcium nitrite monohydrate manufactured by Kishida Chemical Co., Ltd., was used as the accelerator.

[0073] [Example 1] The cement was prepared by measuring and mixing 10% by mass of ordinary Portland cement clinker as an alkaline activator, 77.4% by mass of granulated blast furnace slag powder without gypsum as granulated blast furnace slag, and 12.6% by mass of recycled anhydrous gypsum as gypsum. The amount of SO3 in the cement was 6.9% by mass.

[0074] Next, calcium nitrite monohydrate was measured out as an accelerator so that the amount of accelerator was 2 parts by mass per 10 parts by mass of the cement, and mixed to prepare a hydraulic composition.

[0075] [Examples 2 to 4, Comparative Examples 1 to 2, Reference Examples 1 to 2] Hydraulic compositions were prepared in the same manner as in Example 1, except that the components and blending amounts were changed as shown in Table 2.

[0076] [Table 2]

[0077] <Evaluation of properties of hydraulic composition> The chemical composition, ignition loss, and Blaine specific surface area were measured for each of the hydraulic compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 9. The chemical composition was measured in accordance with the description in JIS R 5202:2015, "Methods for chemical analysis of cement." The ignition loss (also abbreviated as ig.loss) was measured at a heating temperature of 700°C in accordance with the method described in "5.2 For materials other than blast-furnace cement and blast-furnace slag" in "5. Methods for determining ignition loss" of JIS R 5202:2010. The Blaine specific surface area was measured in accordance with the method described in JIS R 5201:2015, "Physical testing methods for cement." The results are shown in Table 3.

[0078] [Table 3]

[0079] <Evaluation of hydraulic composition: compressive strength> The compressive strength of each of the hydraulic compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 9 was measured at ages of 3 days, 7 days, and 28 days according to the method described below. The results are shown in Table 4. In Table 4, the results of Examples 1 and 2 and Reference Example 1 are relative values ​​when the compressive strength of the hardened product obtained by curing the hydraulic composition of Comparative Example 1 is taken as 100, and the results of Examples 3 and 4 and Reference Example 2 are relative values ​​when the compressive strength of the hardened product obtained by curing the hydraulic composition of Comparative Example 2 is taken as 100.

[0080] 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, 300 parts by mass of sand (standard sand / manufactured by the Cement Association) as fine aggregate and 50 parts by mass of water were blended with 100 parts by mass of the hydraulic composition to prepare a mortar composition for evaluation. The blending ratio was adjusted so that the ratio of hydraulic composition:sand:water was 100:300:50 (mass ratio, blending in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement").

[0081] Each of the obtained mortar compositions was used to prepare a hardened mortar. First, the mortar composition was mixed as a mortar in a thermostatic chamber at 20°C and packed into a 4 cm x 4 cm x 16 cm formwork (prepared according to the description in JIS R 5201:2015 "Physical Testing Methods for Cement"). The formwork was stored in a humidity chamber and cured for 24 hours. After 24 hours of curing, the formwork was demolded to obtain a hardened mortar. The obtained hardened mortar was cured in water for 7 days (7-day age) in a thermostatic chamber at 20°C. The hardened mortar after underwater curing was used as a test specimen to measure the compressive strength of the hardened mortar at 3 days of age. Similarly, the obtained hardened mortar was cured in water for 7 days (7-day age) and 28 days (28-day age) in a thermostatic chamber at 20°C, and the compressive strength of the hardened mortar at 7 days of age and 28 days of age was measured. The compressive strength was measured in accordance with the description of JIS R 5201:1992 "Physical testing methods for cement."

[0082] [Table 4]

[0083] As shown in Table 3, it was confirmed that by satisfying the requirements of the hydraulic composition according to the present disclosure, including the use of recycled anhydrous gypsum or natural anhydrous gypsum as anhydrous gypsum, the hydraulic composition is significantly superior in compressive strength compared to hydraulic compositions that do not satisfy the requirements. In the range where the amount of alkaline activator is large, no significant difference as described above in compressive strength depending on the type of anhydrous gypsum is observed, and this is a new finding observed in the range where the amount of alkaline activator is small. [Industrial Applicability]

[0084] According to the present disclosure, it is possible to provide a hydraulic composition that can produce a hardened product having excellent long-term compressive strength, and a method for producing the same.

Claims

1. The cement comprises an alkali activator, granulated blast furnace slag, and gypsum, and an accelerator; The SO 2 content in the cement ３ The converted value is 5.5 to 10.0 mass%, Based on 100% by mass of the cement, The content of the alkaline irritant is 4.0 to 15.0% by mass, The content of the granulated blast furnace slag is more than 70.0 mass% and not more than 86.0 mass%, The gypsum content is 10.0 to 15.0% by mass, The gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum, The content of the accelerator is 0.2 to 4.0 parts by mass per 100 parts by mass of the cement.

2. The hydraulic composition according to claim 1 , wherein the total alkali content of the gypsum is 0.15% by mass or more.

3. 3. The hydraulic composition according to claim 1, wherein the gypsum is recycled anhydrite.

4. The hydraulic composition according to claim 1 or 2, wherein the accelerator contains at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts.

5. 3. The hydraulic composition according to claim 1, wherein the accelerator is a salt having a monovalent anion.

6. The hydraulic composition according to claim 1 or 2, wherein the accelerator contains a calcium salt.

7. 3. The hydraulic composition according to claim 1, wherein the accelerator contains at least one selected from the group consisting of nitrites, nitrates, and chlorides.

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

9. 3. The hydraulic composition according to claim 1, wherein the basicity of the granulated blast furnace slag is 1.60 to 1.

95.

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

11. Mixing an alkaline activator, granulated blast furnace slag, and gypsum to prepare cement; Mixing 0.2 to 4.0 parts by mass of an accelerator with respect to 100 parts by mass of the cement, The SO 2 content in the cement ３ The converted value is 5.5 to 10.0 mass%, Based on 100% by mass of the cement, The content of the alkaline irritant is 4.0 to 15.0% by mass, The content of the granulated blast furnace slag is more than 70.0 mass% and not more than 86.0 mass%, The gypsum content is 10.0 to 15.0% by mass, The method for producing a hydraulic composition, wherein the gypsum is at least one selected from the group consisting of natural anhydrous gypsum and recycled anhydrous gypsum.

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