Powdered hydraulic components

Abstract

To provide a powdery hydraulic composition that has superior handleability, and yields a cured body with superior strength.SOLUTION: A powdery hydraulic composition contains (A) coated fine aggregate that includes fine aggregate and an inorganic binder layer, formed on the surface of the fine aggregate and containing metasilicate hydrate and (B) alumina silica fine powder.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powdery hydraulic composition, a hydraulic slurry, a method for producing a powdery hydraulic composition, and a method for producing a hardened product. [Background technology]

[0002] In recent years, in order to achieve the SDGs, there has been a push to develop environmentally friendly infrastructure from an ESG perspective, and technological development is underway regarding environmentally friendly hydraulic compositions that reduce the amount of CO2 emitted by cement during the firing of calcium carbonate.

[0003] As an example, hydraulic compositions called geopolymers, which are made by hardening ground granulated blast furnace slag containing silicates such as aluminum silicate using an alkaline solution, have been attracting attention.

[0004] Patent Document 1 discloses a geopolymer composition made from a filler, an alkali activator, and an aggregate. Patent Document 2 discloses a geopolymer composition containing ground blast furnace slag and fly ash as powder raw materials, fine aggregate, silica fume, potassium hydroxide or sodium hydroxide as an alkali source, and water, in which the volume ratio of ground blast furnace slag to the powder raw materials: BFS / P is 35 to 80%, the molar ratio of silicon contained in the silica fume to the alkali source: Si / A is 0.05 to 0.35, and the molar ratio of the alkali source to water: A / W is 0.1 to 0.3.

[0005] Non-patent document 1 discloses the definition, materials, mechanisms, challenges, and possibilities of geopolymers. Non-Patent Document 2 discloses a one-component geopolymer that does not use an alkaline solution and is made by blending alumina-silica fine powder, a powdered alkaline compound, and aggregate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-239446 [Patent Document 2] Patent Publication No. 2021-66613 [Non-patent literature]

[0007] [Non-Patent Document 1] Concrete Engineering, Vol. 56, No. 5, pp. 409-414, Japan Concrete Institute, May 2018 [Non-patent document 2] Cement and Concrete Research, Vol. 103, pp. 21-34, Elsevier BV, November 2017 Summary of the Invention [Problem to be solved by the invention]

[0008] If the hydraulic composition for geopolymer can be obtained in powder form, it will be possible to improve the flexibility in terms of handling, etc. For this reason, it is desirable that the compounding raw materials, such as alkaline compounds, are also in powder form. However, when metasilicate hydrate is added as a powdered alkaline compound, there are problems such as a decrease in the strength of the hardened body compared to when it is added as an aqueous solution, and poor handling due to the low fluidity of the powdered metasilicate hydrate. The present invention provides a powdery hydraulic composition which is easy to handle and exhibits good strength after being set. [Means for solving the problem]

[0009] The present invention relates to a powdery hydraulic composition comprising (A) a coated fine aggregate having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate (hereinafter referred to as component (A)), and (B) an alumina-silica fine powder (hereinafter referred to as component (B)).

[0010] The present invention also provides a method for producing a composite concrete mixture, comprising the steps of: (1) mixing a metasilicate hydrate and a fine aggregate at a temperature equal to or higher than the melting point of the metasilicate hydrate to obtain a mixture; (2) a step of cooling the mixture to a temperature below the melting point of the metasilicate hydrate to obtain a coated fine aggregate (hereinafter referred to as component (A)) having a fine aggregate (A) and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate; (3) a step of mixing component (A) with fine alumina-silica powder (B); The present invention relates to a method for producing a powdery hydraulic composition, comprising:

[0011] The present invention also relates to a hydraulic slurry obtained by blending the powdery hydraulic composition of the present invention with water.

[0012] The present invention also provides a method for producing a hydraulic slurry, comprising: (I) mixing the powdery hydraulic composition of the present invention with water; a step (II) of curing the hydraulic slurry to obtain a hardened body; The present invention relates to a method for producing a cured body, including the steps of:

[0013] The present invention also relates to an additive for a powdery hydraulic composition, which comprises a coated fine aggregate having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate. [Effects of the Invention]

[0014] According to the present invention, there is provided a powdery hydraulic composition which is easy to handle and exhibits good strength when set. This invention contributes to the effective use of industrial by-products and waste and the reduction of CO2 emissions, and is therefore thought to be a technology that can contribute to the achievement of SDGs, such as goals 7, 9, 11, 12, and 13, which have been advocated in recent years to realize a sustainable society. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present inventors have found that by combining component (A) and component (B), the handleability of a one-component powdery hydraulic composition is improved, and the strength development is improved when a hydraulic slurry prepared from such a powdery hydraulic composition is made into a hardened product. The reason for this effect is not entirely clear, but is presumed to be as follows. The fine aggregate used in component (A) generally has a porous structure primarily composed of silicate compounds, but the presence of gas (air, water vapor) within the porous structure is thought to limit the infiltration of the inorganic binder into the porous structure due to the surface tension of the inorganic binder and the air pressure within the porous structure. In the present invention, during the process of forming an inorganic binder layer containing metasilicate hydrate on the fine aggregate having a porous structure, the inorganic binder containing metasilicate hydrate infiltrates the porous structure, improving the fluidity of the powder and increasing the contact surface area between the inorganic binder and the fine aggregate. This is thought to result in a stronger bond between the inorganic binder and the fine aggregate during the hardening process, thereby improving the strength development of the hardened body. Furthermore, the alumina-silica fine powder of component (B) tends to aggregate with the metasilicate hydrate due to interparticle forces such as liquid bridging forces, impairing the fluidity of the powder, but the infiltration of the inorganic binder into the fine aggregate used in component (A) reduces the contact area between the metasilicate hydrate and the alumina-silica fine powder, thereby suppressing the decrease in the fluidity of the powder and achieving good fluidity.When preparing a hydraulic slurry by adding water to the powdery hydraulic composition of the present invention, the metasilicate hydrate that has infiltrated the fine aggregate used in component (A) quickly dissolves in water, which allows the reaction with the alumina-silica fine powder of component (B) to proceed smoothly, which is thought to contribute to the development of strength in the set body. However, the mechanism of action of the present invention is not limited to this.

[0016] <Powdered hydraulic composition> The powdery hydraulic composition of the present invention contains a predetermined coated fine aggregate as component (A) and an alumina-silica fine powder as component (B).

[0017] Component (A) has fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate.

[0018] From the viewpoint of the handleability of the powdery hydraulic composition, the angle of repose of component (A) is preferably 35° or less. The angle of repose of component (A) is measured using a repose angle measuring instrument ASK-01 (manufactured by AS ONE Corporation).

[0019] From the viewpoint of improving the handleability of the powdery hydraulic composition and the workability of the hydraulic slurry, it is preferable that component (A) be spherical. Here, the spherical shape of component (A) in this embodiment refers to a round shape like a ball, and more specifically, a sphericity of preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.90 or more, even more preferably 0.95 or more, and even more preferably 0.97 or more. It is preferable from the viewpoint of the workability of the hydraulic slurry that the sphericity of component (A) in this embodiment is equal to or greater than the above lower limit. The upper limit of the sphericity is specifically 1 or less.

[0020] The sphericity of component (A) is determined by analyzing the image (photograph) of the particles taken with an optical microscope or a digital scope (for example, Keyence VH-8000) to determine the area of ​​the projected cross section of the particle and the perimeter of the cross section, and then calculating the projected cross section area (mm 2 The particle diameter can be calculated by dividing the circumference (mm) of a perfect circle with the same area as the particle by the circumference (mm) of the particle's projected cross section, and then averaging the values ​​obtained for any 50 particles.

[0021] The average particle size of component (A) is preferably 0.1 mm or more, more preferably 0.5 mm or more, from the viewpoint of the handleability of the powdery hydraulic composition, and is preferably 5.0 mm or less, more preferably 2.0 mm or less, and even more preferably 1.0 mm or less, from the viewpoint of the handleability of the powdery hydraulic composition. In this embodiment, the average particle size of the component (A) can be measured by the following method.

[0022] (Method for measuring average particle size) If the sphericity of the particle's projected cross section is 1, the diameter (mm) is measured; on the other hand, if the sphericity is less than 1, the major axis diameter (mm) and minor axis diameter (mm) of randomly oriented particles are measured and (major axis diameter + minor axis diameter) / 2 is calculated, and the average value obtained for 100 randomly selected particles is used as the average particle size (mm). The major axis diameter and minor axis diameter are defined as follows: When a particle is stabilized on a flat surface and the projected image of the particle on the flat surface is sandwiched between two parallel lines, the width of the particle at the smallest distance between the parallel lines is called the minor axis diameter, and the distance when the particle is sandwiched between two parallel lines perpendicular to the parallel lines is called the major axis diameter. The major axis diameter and minor axis diameter of a particle can be determined by taking an image (photograph) of the particle using an optical microscope or a digital scope (for example, Keyence VH-8000 model) and analyzing the obtained image.

[0023] The fine aggregate used in component (A) may be natural sand or artificial sand. Examples of natural sand include river sand, land sand, mountain sand, sea sand, lime sand, silica sand, chromite sand, zircon sand, olivine sand, alumina sand, natural lightweight fine aggregate, and crushed sands thereof. Examples of artificial sand include blast furnace slag fine aggregate, ferronickel slag fine aggregate, artificial lightweight fine aggregate, recycled fine aggregate, synthetic mullite sand, SiO2-based artificial sand whose main component is SiO2, Al2O3-based artificial sand whose main component is Al2O3, SiO2 / Al2O3-based artificial sand, SiO2 / MgO-based artificial sand, SiO2 / Al2O3 / ZrO2-based artificial sand, SiO2 / Al2O3 / Fe2O3-based artificial sand, etc. Here, the main component refers to the component that is most abundant among the components contained in the sand. These may be used alone or in combination of two or more.

[0024] From the viewpoint of the workability of the hydraulic slurry, the degree of amorphization of the fine aggregate is preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, and even more preferably 5% or less. The lower limit of the degree of amorphization of the fine aggregate is not limited, but may be, for example, 0% or more, or 1% or more.

[0025] There are various methods for controlling the degree of amorphization of fine aggregate, but it is generally preferable to use a manufacturing method that rapidly cools the molten material. For example, there is a method in which the raw material is melted and rapidly cooled by air-crushing, or a method in which it is treated in a flame and rapidly cooled. In either case, the cooling method may be selected appropriately at various speeds depending on the material and particle size. Another possible method is to amorphize a material that has been crystallized by heat treatment and cooling treatment. Among these, the flame fusion method is preferable, as it allows for easy control of heating and cooling.

[0026] The degree of amorphization of the fine aggregate can be determined by the X-ray diffraction method described below. The fine aggregate was crushed in a mortar and pressed onto an X-ray glass holder of a powder X-ray diffractometer. The powder X-ray diffractometer used was a Rigaku MultiFlex (CuKα radiation source, 40 kV tube voltage, 40 mA tube current) with a scan interval of 0.01°, a scan rate of 2° / min, and slits DS1, SS1, and RS0.3 mm, over the 2θ range of 5° to 90°. A straight line was drawn connecting the X-ray intensities at low and high angles over the 2θ range of 10° to 50°. The area under the line was used as the background. The crystallinity was calculated using the instrument's software and subtracted from 100 to obtain the amorphousness. Specifically, the amorphous peak (halo) and each crystalline component were separated by curve fitting for the area above the background, and their respective areas were determined. The amorphousness (%) was calculated using the following formula: Amorphous ratio (%) = halo area / (crystalline component area + halo area) × 100

[0027] The fine aggregate is preferably spherical from the viewpoint of improving the fluidity of component (A). Here, "spherical" in this embodiment refers to a round, ball-like shape, and more specifically, refers to a fine aggregate having a sphericity of preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.90 or more, even more preferably 0.95 or more, and even more preferably 0.97 or more. It is preferable that the sphericity of the fine aggregate in this embodiment is equal to or greater than the above-mentioned lower limit from the viewpoint of the fluidity of the powdery hydraulic composition. Furthermore, it is also preferable that the sphericity of the fine aggregate in this embodiment is equal to or greater than the above-mentioned lower limit, since the surface becomes smoother, resulting in a better coating state of the inorganic binder layer. The upper limit of the sphericity is specifically 1 or less. The sphericity of the fine aggregate can be measured in the same manner as the sphericity of component (A).

[0028] The average particle size of the fine aggregate is preferably 0.1 mm or more, more preferably 0.5 mm or more, from the viewpoint of the handleability of the powdery hydraulic composition, and is preferably 5.0 mm or less, more preferably 2.0 mm or less, and even more preferably 1.0 mm or less, from the viewpoint of the handleability of the powdery hydraulic composition. The average particle size of the fine aggregate can be measured in the same manner as for the average particle size of component (A).

[0029] Next, the inorganic binder layer of component (A) will be described. The metasilicate hydrate contained in the inorganic binder layer is an inorganic binder. The use of metasilicate hydrate is preferable because it improves the crystallinity of the inorganic binder layer and further turns component (A) into a dry state, resulting in excellent room-temperature fluidity. Furthermore, the use of metasilicate hydrate with a low melting point allows the inorganic binder layer to be formed on the surface of the fine aggregate without dissolving in water. In other words, since there is no need to use an aqueous solution of metasilicate hydrate in the process of producing component (A), the water removal step can be omitted, simplifying the production method.

[0030] From the above viewpoints, the metasilicate hydrate is preferably at least one selected from sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, potassium metasilicate pentahydrate, potassium metasilicate nonahydrate, and magnesium metasilicate pentahydrate, and more preferably at least one selected from sodium metasilicate pentahydrate and sodium metasilicate nonahydrate. The melting points of sodium metasilicate pentahydrate and sodium metasilicate nonahydrate are 72°C and 47°C, respectively.

[0031] The coating amount of the inorganic binder layer in component (A) is, from the viewpoint of the strength development of the hardened body of the hydraulic slurry, for example, 0.05 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the fine aggregate, and from the viewpoint of the handleability of the powdery hydraulic composition, it is, from the viewpoint of the handleability of the powdery hydraulic composition, for example, 10 parts by mass or less, preferably 8 parts by mass or less, and more preferably 6 parts by mass or less, relative to 100 parts by mass of the fine aggregate (A).

[0032] The powdery hydraulic composition of the present invention may contain, relative to 100 parts by mass of the composition, for example, 10 parts by mass or more, further 20 parts by mass or more, or even 30 parts by mass or more of component (A) from the viewpoint of strength development of the set body of the hydraulic slurry, and 90 parts by mass or less, further 80 parts by mass or less, or even 70 parts by mass or less from the viewpoint of handleability of the powdery hydraulic composition.

[0033] Next, the alumina-silica fine powder of component (B) will be described. An example of the alumina-silica fine powder of component (B) is a fine powder containing aluminosilicate (xM2O·yAl2O3·zSiO2·nH2O, where M is an alkali metal). Component (B) dissolves cations such as aluminum and silicon upon contact with an alkaline compound and / or its aqueous solution, and acts as a supply source of these cations.

[0034] The molar ratio of alumina (Al2O3) to silica (SiO2) in component (B) may be, for example, 0.05 or more, or even 0.10 or more, and 1.00 or less, or even 0.50 or less, in terms of the strength development of the hardened body of the hydraulic slurry.

[0035] Suitable examples of the alumina-silica fine powder of component (B) include 1) industrial waste and by-products such as ground granulated blast furnace slag, fly ash, clinker ash, fluidized bed coal ash, ground granulated molten slag from municipal waste incineration ash, red mud, and ground granulated molten slag from sewage sludge incineration ash, 2) natural aluminosilicate minerals such as metakaolin, clays and their fired products, and 3) volcanic ash. Of these, the industrial waste of component 1) is particularly suitable because, compared to the other components, there are no restrictions on the place of origin and it also leads to the effective use of industrial waste resources.

[0036] From the viewpoint of the strength development of the hardened body of the hydraulic slurry, the component (B) is preferably at least one selected from ground granulated blast furnace slag and fly ash. Ground granulated blast furnace slag is a by-product of refining iron in a blast furnace, and is primarily composed of calcium oxide (CaO), silica (SiO2), and alumina (Al2O3), and is specified in JIS A 6206. In the present invention, the ground granulated blast furnace slag particularly used preferably has a CaO content in the range of 30% by mass to 60% by mass. Fly ash is primarily composed of silica (SiO2) and alumina (Al2O3), and is classified into Classes I to IV (JIS A6201) based on particle size and flow value. JIS Classes I and II, which have fine particle size and high reactivity, are suitable. The CaO content in fly ash may be 10.1% by mass or less.

[0037] (B) component is the Blaine specific surface area (cm 2 / g) is, from the viewpoint of the strength development of the set body of the hydraulic slurry, for example, 1,500 or more, preferably 2,000 or more, more preferably 2,500 or more, even more preferably 3,000 or more, and still more preferably 3,500 or more, and from the viewpoint of the handleability of the powdery hydraulic composition, for example, 8,000 or less, preferably 7,500 or less, more preferably 7,000 or less, even more preferably 6,500 or less, and still more preferably 6,000 or less. The Blaine specific surface area of ​​component (B) is measured and calculated using a Blaine air permeability apparatus specified in JIS R 5201.

[0038] The powdery hydraulic composition of the present invention may contain, for example, 5 parts by mass or more, further 10 parts by mass or more, further 20 parts by mass or more, and 60 parts by mass or less, further 50 parts by mass or less, further 40 parts by mass or less of the (B) component per 100 parts by mass of the composition, from the viewpoint of the strength development of the hardened body of the hydraulic slurry.

[0039] In the powdery hydraulic composition of the present invention, the mass ratio (A) / (B) of the content of the component (A) to the content of the component (B) may be, for example, 0.17 or more, further 0.50 or more, further 1.0 or more, and may be 18 or less, further 10 or less, or further 5 or less, from the viewpoint of the strength development of the hardened body of the hydraulic slurry.

[0040] The powdery hydraulic composition of the present invention preferably contains the components (A) and (B) in a total amount of 90 parts by mass or more, further 95 parts by mass or more, and 100 parts by mass or less, per 100 parts by mass of the composition, and the total may be 100 parts by mass, i.e., the powdery hydraulic composition of the present invention may consist of the components (A) and (B).

[0041] The powdery hydraulic composition of the present invention may contain optional components other than components (A) and (B). Examples of optional components include water-reducing agents, air-entraining agents, fluidizing agents, hardening accelerators (alkali stimulants), antifoaming agents, quick-setting additives, shrinkage-reducing agents, hardening retarders, and rust inhibitors. The powdery hydraulic composition of the present invention may contain one or more of these optional components.

[0042] The powdery hydraulic composition of the present invention can optionally contain cement, but the cement content must be carefully determined because it affects the initial setting rate. Furthermore, from the perspective of providing a powdery hydraulic composition with a reduced cement content, a lower cement content is preferable. The powdery hydraulic composition of the present invention optionally contains cement, and the cement content may be less than 30 parts by mass, further 20 parts by mass or less, further 10 parts by mass or less, or even 1 part by mass or less, per 100 parts by mass of component (B). It may also be 0 parts by mass, i.e., no cement is contained. Examples of cement include Portland cement, white Portland cement, blended cement, ecocement, alumina cement, ultra-rapid hardening cement, grout cement, and oil well cement. The powdery hydraulic composition of the present invention may have a Portland cement content within the above-mentioned range relative to component (B).

[0043] The powdery hydraulic composition of the present invention is suitable as a composition for forming a geopolymer. For example, the powdery hydraulic composition of the present invention is mixed with water to obtain a hydraulic slurry, and the hydraulic slurry is hardened to form a geopolymer and a hardened body. The powdery hydraulic composition of the present invention may be a so-called premix, and may also be a premix for geopolymers.

[0044] <Method for manufacturing powdered hydraulic composition> The present invention provides a method for producing a granular composite material, comprising the steps of: (1) mixing a metasilicate hydrate and a fine aggregate at a temperature equal to or higher than the melting point of the metasilicate hydrate to obtain a mixture; (2) a step of cooling the mixture to a temperature below the melting point of the metasilicate hydrate to obtain a coated fine aggregate (hereinafter referred to as component (A)) having a fine aggregate (A) and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate; (3) mixing component (A) with alumina-silica fine powder (B) (hereinafter referred to as component (B)); The present invention relates to a method for producing a powdery hydraulic composition, comprising:

[0045] The matters described for the powdery hydraulic composition of the present invention can be applied as appropriate to the method for producing the powdery hydraulic composition of the present invention. Specific examples and preferred examples of the components (A) and (B) in the method for producing the powdery hydraulic composition of the present invention are also the same as those for the powdery hydraulic composition of the present invention. The method for producing the powdery hydraulic composition of the present invention is suitable as a method for producing the powdery hydraulic composition of the present invention.

[0046] In step (1), metasilicate hydrate and fine aggregate are mixed at a temperature equal to or higher than the melting point of metasilicate hydrate, so that the surface of the fine aggregate is coated with fluidized metasilicate hydrate. Examples of methods for mixing metasilicate hydrate at a temperature equal to or higher than the melting point of metasilicate hydrate include a method in which metasilicate hydrate is added to fine aggregate heated to a temperature equal to or higher than the melting point of metasilicate hydrate, and the fine aggregate and metasilicate hydrate are mixed while melting the metasilicate hydrate [Step (1A)], and a method in which the heated and melted metasilicate hydrate is added to the fine aggregate and mixed [Step (1B)]. Step (1B) is preferred from the viewpoint of shortening the time required for coating.

[0047] From the same viewpoint, it is preferable that the metasilicate hydrate is mixed in step (1) without being previously converted into an aqueous solution, and it is also preferable that step (1) does not include a step of intentionally adding water.

[0048] The mixing conditions, such as the stirring speed and processing time when mixing the fine aggregate and metasilicate hydrate, can be appropriately determined depending on the amount of the mixture to be processed.

[0049] In step (2), the mixture obtained in step (1) is cooled to a temperature below the melting point of the metasilicate hydrate, thereby reducing the fluidity of the metasilicate hydrate and fixing the metasilicate hydrate to the surface of the fine aggregate, thereby forming a metasilicate hydrate layer, i.e., an inorganic binder layer, to obtain a coated fine aggregate [component (A)] having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate.

[0050] In step (3), component (A) obtained in step (2) is mixed with the alumina-silica fine powder of component (B). The method, apparatus, and conditions for mixing components (A) and (B) are not particularly limited, and can be selected appropriately based on the mixing of the powder components.

[0051] <Hydraulic slurry> The present invention relates to a hydraulic slurry obtained by blending the powdery hydraulic composition of the present invention with water. From the viewpoint of the fluidity of the set body of the hydraulic slurry, water can be blended in an amount of, for example, 1 part by mass or more, further 5 parts by mass or more, or even 10 parts by mass or more, relative to 100 parts by mass of the powdery hydraulic composition of the present invention, and from the viewpoint of the strength development of the set body of the hydraulic slurry, water can be blended in an amount of 50 parts by mass or less, further 35 parts by mass or less, or even 20 parts by mass or less.

[0052] The hydraulic slurry of the present invention is suitable as a slurry for forming a geopolymer. By hardening the hydraulic slurry of the present invention, a geopolymer is formed and a hardened body is formed. The hydraulic slurry of the present invention may be a slurry for a geopolymer.

[0053] <Method of manufacturing the hardened body> The present invention relates to a method for producing a hydraulic slurry, comprising: (I) mixing the powdery hydraulic composition of the present invention with water; a step (II) of curing the hydraulic slurry to obtain a hardened body; The present invention relates to a method for producing a cured body, including the steps of:

[0054] In step (I), water can be mixed in an amount of, for example, 1 part by mass or more, further 5 parts by mass or more, or further 10 parts by mass or more relative to 100 parts by mass of the powdery hydraulic composition of the present invention from the viewpoint of the fluidity of the set body of the hydraulic slurry, and 50 parts by mass or less, further 35 parts by mass or less, or further 20 parts by mass or less from the viewpoint of the strength development of the set body of the hydraulic slurry.

[0055] The method, apparatus, conditions, etc. for mixing the powdery hydraulic composition of the present invention with water in step (1) are not particularly limited, and can be appropriately selected from those suitable for preparing a slurry.

[0056] In step (II), the hydraulic slurry obtained in step (I) is cured to obtain a hardened product. The curing in step (II) can be performed under general conditions for obtaining a hardened geopolymer product. In step (II), the curing temperature can be, for example, 20°C or higher, further 30°C or higher, further 40°C or higher, and 80°C or lower, further 70°C or lower. In step (II), the curing time can be, for example, 1 hour or longer and 28 days or shorter.

[0057] <Additive for powdered hydraulic composition> The present invention relates to a powdery additive for hydraulic compositions, which comprises a coated fine aggregate [component (A)] having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate. The matters described for the powdery hydraulic composition of the present invention can be appropriately applied to the additive for powdery hydraulic composition of the present invention.Specific examples and preferred examples of component (A) in the additive for powdery hydraulic composition of the present invention are also the same as those in the powdery hydraulic composition of the present invention. The additive for a powdery hydraulic composition of the present invention is an additive used in a powdery hydraulic composition. The additive for a powdery hydraulic composition of the present invention may be an additive used in a powder composition for forming a geopolymer. The powdery additive for hydraulic compositions of the present invention may be an additive consisting of component (A). [Example]

[0058] The components used in the examples and comparative examples are shown below. Fine aggregate: Mountain sand (produced in Joyo, Kyoto City, surface dry specific gravity 2.54, coarse particle ratio 2.73, amorphousness 1.1%, sphericity 0.86, average particle size 0.6 mm, bone dry condition) Inorganic binder 1: Sodium metasilicate nonahydrate (melting point 48°C, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Inorganic binder 2: Sodium metasilicate pentahydrate (melting point 72°C, manufactured by Sigma-Aldrich Co. LLC) Alumina-silica fine powder 1: Blast furnace slag fine powder (blaine specific surface area: 4,200 cm 2 / g, alumina / silica molar ratio = 0.25) Alumina silica fine powder 2: Fly ash (JIS Type II, Blaine specific surface area: 3,500 cm 2 / g, alumina / silica molar ratio = 0.26) · Tap water (Wakayama City tap water)

[0059] <Example 1 and Comparative Example 1> (1) Preparation of coated fine aggregate (Example) The inorganic binder was heated in a water bath (80°C for 1 hour) to obtain a melt. Next, fine aggregate (80°C) that had been heated to an absolutely dry state was added to a Hobart mixer specified in JIS R 5201, and stirring was initiated at 140 rpm. The inorganic binder melt was added to the hydraulic slurry so that the composition was as shown in Table 1, and the mixture was kneaded at 140 rpm for 5 minutes. The mixture was then allowed to cool naturally to room temperature (20°C), and the coated fine aggregate of the present invention, with an inorganic binder layer formed on its surface, was obtained in a yield of 99.3%. The resulting coated fine aggregate with an inorganic binder layer formed on its surface had an angle of repose of 33.6°, a sphericity of 0.88, and an average particle size of 0.6 mm.

[0060] (2) Preparation of powder hydraulic composition (premix) The coated fine aggregate obtained in (1) and the alumina-silica fine powder were added to a Hobart mixer according to JIS R 5201 so that the hydraulic slurry had the composition shown in Table 1 in parts by mass, and mixed at 140 rpm for 20 seconds to prepare the powder hydraulic composition (premix) of the example. In the comparative example, without using coated fine aggregate, fine aggregate adjusted to an absolute dry state, inorganic binder, and alumina-silica fine powder were each added independently to the hydraulic slurry in the parts by mass shown in Table 1, and mixed at 140 rpm for 20 seconds to prepare a powder hydraulic composition (premix).

[0061] (3) Preparation of hydraulic slurry and its hardened body The powder hydraulic composition (premix) prepared in (2) and tap water were added to a Hobart mixer according to JIS R 5201 in the parts by weight shown in Table 1, and mixed at 140 rpm for 180 seconds to prepare a hydraulic slurry. Next, using the hydraulic slurry immediately after preparation, mortar specimens of φ5 × 10 cm were prepared in accordance with JSCE-F 506, sealed and cured at 20°C for 7 days, and then demolded. A compressive strength test was carried out in accordance with JSCE-G 505, and the unconfined compressive strength (N / mm) was calculated as the average value of n = 2. 2 The results are shown in Table 1.

[0062] <Example 2 and Comparative Example 2> Powder hydraulic compositions (premixes) were prepared in the same manner as in Example 1 and Comparative Example 1, except that the blending components and parts by mass were changed as shown in Table 1, and the uniaxial compressive strength was measured. The results are shown in Table 1.

[0063] [Table 1]

[0064] In Table 1, Examples 1 and 2 showed superior strength development compared to Comparative Examples 1 and 2. This is thought to be because the inorganic binder containing metasilicate hydrate infiltrated into the porous structure of the fine aggregate, increasing the contact surface area between the inorganic binder and the fine aggregate, and thus bonding the inorganic binder and the fine aggregate more firmly during the hardening process, improving the strength of the hardened body.

[0065] <Example 3, Comparative Example 3 and Reference Example 3> (1) Measurement of angle of repose The angles of repose were measured for the powder hydraulic compositions of Example 1 and Comparative Example 1 and the components used in their preparation. That is, the angles of repose of (a) the powder hydraulic composition (premix) of Example 1, (b) the powder hydraulic composition (premix) of Comparative Example 1, (c) the fine aggregate (uncoated), (d) the coated fine aggregate obtained using inorganic binder 1, (e) inorganic binder 1, (f) alumina-silica fine powder 1, and (g) alumina-silica fine powder 2 were each measured using an angle of repose measuring device ASK-01 (manufactured by AS ONE Corporation). The results are shown in Table 2.

[0066] [Table 2]

[0067] In Table 2, the powder hydraulic composition of Example 1 (Example 3-1) exhibited a smaller angle of repose, i.e., superior powder fluidity, compared to the powder hydraulic composition of Comparative Example 1 (Comparative Example 3-1). This is thought to be because the inorganic binder containing bound water infiltrated into the porous structure of the fine aggregate, thereby suppressing a decrease in fluidity due to liquid bridging between powder particles. This is also suggested by the fact that the angle of repose of uncoated fine aggregate alone (Reference Example 3-1) was approximately the same as that of coated fine aggregate (Reference Example 3-2) on the surface of which a layer of inorganic binder 1 used in Example 1 was formed, and that the angle of repose of inorganic binder 1 (Reference Example 3-3) was larger than those of these fine aggregates. Both Example 3-1 and Comparative Example 3-1 were evaluated using powder hydraulic compositions produced using the same amounts of the components of Reference Examples 3-1, 3-3, and 3-5. However, the angle of repose was smaller in Example 3-1, indicating that blending in the form of coated fine aggregate (Reference Example 3-2) leads to improved fluidity.

Claims

1. A powdered hydraulic composition comprising: (A) a coated fine aggregate having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate (hereinafter referred to as component (A)); and (B) an alumina-silica fine powder (hereinafter referred to as component (B)).

2. 2. The powdery hydraulic composition according to claim 1, wherein the metasilicate hydrate is at least one selected from the group consisting of sodium metasilicate pentahydrate and sodium metasilicate nonahydrate.

3. 3. The powdery hydraulic composition according to claim 1, which optionally contains cement, and the content of cement is less than 30 parts by mass per 100 parts by mass of component (B).

4. (1) a step of mixing a metasilicate hydrate and a fine aggregate at a temperature equal to or higher than the melting point of the metasilicate hydrate to obtain a mixture; (2) a step of cooling the mixture to a temperature below the melting point of the metasilicate hydrate to obtain a coated fine aggregate (hereinafter referred to as component (A)) having a fine aggregate (A) and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate; (3) a step of mixing component (A) and component (B) alumina-silica fine powder; A method for producing a powdery hydraulic composition comprising:

5. A hydraulic slurry comprising (A) a coated fine aggregate having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate [hereinafter referred to as component (A)], and (B) a powdered hydraulic composition containing alumina silica fine powder [hereinafter referred to as component (B)], blended with water.

6. A hydraulic slurry as described in claim 5, wherein the metasilicate hydrate is one or more selected from sodium metasilicate pentahydrate and sodium metasilicate nonahydrate.

7. A hydraulic slurry according to claim 5 or 6, optionally containing cement, wherein the cement content is less than 30 parts by mass per 100 parts by mass of component (B).

8. A process (I) of mixing a powdered hydraulic composition containing (A) a coated fine aggregate having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate [hereinafter referred to as component (A)], and (B) an alumina-silica fine powder [hereinafter referred to as component (B)] with water to obtain a hydraulic slurry; (II) a step of curing the hydraulic slurry to obtain a hardened body; A method for producing a hardened body, comprising:

9. A method for producing a hardened body as described in claim 8, wherein the metasilicate hydrate is one or more selected from sodium metasilicate pentahydrate and sodium metasilicate nonahydrate.

10. A method for producing a hardened body as described in claim 8 or 9, optionally containing cement, wherein the cement content is less than 30 parts by mass per 100 parts by mass of component (B).

11. An additive for a powdered hydraulic composition comprising a coated fine aggregate having a fine aggregate and an inorganic binder layer containing metasilicate hydrate formed on the surface of the fine aggregate.

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