Cement composition

Abstract

To provide a cement composition having an excellent bending strength when cured.SOLUTION: The cement composition contains cement and a fibrous or needle-like inorganic filler, in which the product of an aspect ratio [-] of the inorganic filler and a volume of the inorganic filler contained per unit volume [L / m3] is 800 or more. The inorganic filler is preferably one or two or more selected from basic magnesium sulfate, wollastonite, and potassium titanate. A preferable volume of the inorganic filler contained per unit volume is 50 L / m3 or more and 70 L / m3 or less. The inorganic filler preferably has an aspect ratio of 20 or more and 40 or less. The cement composition preferably comprises further silica fume.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to cement compositions. [Background technology]

[0002] Hardened cement products such as concrete are materials that exhibit anisotropy in terms of strength, and generally have a low bending strength relative to their compressive strength. Therefore, cracks may occur in structures containing hardened cement products during their use. These cracks often occur throughout the entire structure, leading to a decrease in the durability of the structure. Therefore, a technology for improving bending strength to reduce cracking is desired.

[0003] Patent Document 1 discloses a multi-layered molded cement hardened body formed from a mixture of cement, pigment, filler, reinforcing material, and water in a predetermined mixing ratio, with the aim of improving strength and dimensional stability.

[0004] Furthermore, Patent Document 2 discloses a cement-based extrusion molded board obtained by extruding molding raw materials containing predetermined amounts of cement, silica sand, fine aggregate, wollastonite, pyrophyllite-containing minerals, reinforcing fibers, thickening agents, and water, with the aim of improving strength and dimensional stability.

[0005] Furthermore, Patent Document 3 discloses a concrete member containing cement, pozzolanic fine particles, aggregate, water, and a plasticizer for the purpose of improving strength and durability, etc. It also discloses that the member can contain acicular particles and metal fibers. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-60727 [Patent Document 2] Japanese Patent Application Publication No. 7-109162 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-233656 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the various hardened cement products described in Patent Documents 1 to 3 are not sufficient in terms of strength development of mortar or concrete.

[0008] Therefore, an object of the present invention is to provide a cement composition that has excellent bending strength when hardened. [Means for solving the problem]

[0009] The present invention provides a cement composition comprising a cement and a fibrous or needle-like inorganic filler, The present invention provides a cement composition in which the product of the aspect ratio of the inorganic filler and the content volume of the inorganic filler per unit volume is 800 or more. [Effects of the Invention]

[0010] According to the present invention, the cured product has excellent bending strength. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention are described below. However, the present invention is not limited to the following embodiments. In the following description, when it is stated that "X to Y[Z]" (X and Y are arbitrary numerical values, and [Z] is a unit added as necessary), it means "X[Z] or more and Y[Z] or less" or "X or more and Y or less" unless otherwise specified. Furthermore, the three states of a substance are based on 1 atmosphere and 20°C, unless otherwise specified.

[0012] The cement composition of the present invention contains cement and a fibrous or needle-like inorganic filler. The cement composition is preferably a hydraulic composition that hardens in the presence of water. Unless otherwise specified, the cement composition of the present invention includes powder that does not contain liquids such as water, cement paste that contains liquids such as water but does not contain aggregate, mortar that contains liquids such as water and contains only fine aggregate as an aggregate, and concrete that contains water, fine aggregate, and coarse aggregate. Furthermore, depending on the context, the cement composition may refer to a pre-hardened composition that has fluidity such as a powder or slurry, or may refer to a hardened composition that has lost fluidity (i.e., a hardened product).

[0013] The cement composition of the present invention contains a fibrous or needle-like inorganic filler, and one of its features is that the relationship between the aspect ratio and the content of the inorganic filler falls within a predetermined range. As described above, typical hardened cement products such as concrete are known to have strength anisotropy, i.e., their flexural strength is low relative to their compressive strength. The present inventors conducted extensive research into eliminating the strength anisotropy of hardened cement products, with the aim of enabling cement compositions to be used in a wide variety of structures. As a result, they discovered that by using an inorganic filler having a predetermined shape, the flexural strength of the hardened product can be increased while sufficiently reducing adverse effects on the intended physical properties of the hardened product, and that the strength anisotropy can be eliminated even when the hardened product of the composition is used alone. In addition, they discovered that the flexural strength of the hardened product can be further improved by adjusting the product of the aspect ratio of the inorganic filler and its content in the cement composition within a predetermined range.

[0014] The present inventors speculate that the reason for this is that the presence of a predetermined amount of inorganic filler suppresses the occurrence of fine cracks and breaks (microcracking) in the hardened product, and that unintentionally formed cracks bypass the filler, thereby mitigating stress concentration at the tip of the crack even if cracks do occur in the cement composition, leading to improved bending strength of the cement composition of the present invention. Furthermore, when a water-soluble inorganic filler is used in the present invention, in addition to the above-mentioned mechanism, the degree of contact between the soluble components of the inorganic filler and the cement hydrate is improved, increasing affinity, and the inorganic filler and cement hydrate are firmly integrated, thereby improving the bending strength of the cement composition.

[0015] The inorganic filler contained in the cement composition is an inorganic compound having a fibrous or needle-like shape in its dry state, and is preferably a powder that is an aggregate of solid particles having the above-mentioned shape. In this specification, "fibrous or needle-like" refers to a shape in which the longitudinal length is sufficiently large compared to the maximum length (i.e., thickness) of the cross section perpendicular to the longitudinal direction, and the cross-sectional shape is an approximately isotropic shape such as a circle at any position. The fibrous shape includes a shape whose thickness changes from one end to the other in the longitudinal direction, and a columnar shape whose length remains almost constant from one end to the other. The needle shape includes a shape whose maximum cross-sectional length decreases continuously or stepwise from the center to the end in the longitudinal direction, and whose apex is formed at at least one end in the longitudinal direction.

[0016] When the ratio (H / D) of the length H (unit: μm) in the longitudinal direction of the inorganic filler to the thickness D (unit: μm) perpendicular to the longitudinal direction of the inorganic filler is defined as the aspect ratio A (unit: no unit. In this specification, the absence of a unit is represented by [-]), the relationship between the aspect ratio A of the inorganic filler and the unit volume 1 m of the cement composition is 3 The inorganic filler content volume B per unit (unit: L / m 3 ) and its product (A × B, unit: L / m 3) is preferably 800 or more, more preferably 1000 to 3000, even more preferably 1100 to 2400, particularly preferably 1200 to 1800, and even more particularly preferably 1200 to 1300. By adjusting the aspect ratio and content of the inorganic filler so as to satisfy such an A×B relationship, the bending strength of the cured product can be efficiently improved.

[0017] Since the inorganic filler used in the present invention has a fibrous or needle-like shape, its aspect ratio A is usually at least 10. From the viewpoint of improving the handleability and dispersibility of the cement composition when mixed, increasing the fluidity of the cement composition when poured, and significantly improving the bending strength of the hardened product, the aspect ratio A of the inorganic filler is preferably 10 to 100, more preferably 20 to 40, even more preferably 22 to 35, and particularly preferably 23 to 28, provided that the above-mentioned A×B relationship is satisfied.

[0018] The aspect ratio of an inorganic filler can be measured, for example, by the following method. Specifically, 10 particles of the inorganic filler to be measured are randomly observed under an electron microscope, and the length along the longitudinal direction and the width perpendicular to the longitudinal direction of each filler particle are measured. Then, from the obtained 10 measurement results, the arithmetic mean of the maximum and minimum measured values ​​of the length along the longitudinal direction is taken as the length of the inorganic filler. Similarly, from the obtained 10 measurement results, the arithmetic mean of the maximum and minimum measured values ​​of the width perpendicular to the longitudinal direction is taken as the width of the inorganic filler. Then, the aspect ratio of the inorganic filler is calculated by dividing the length value of the inorganic filler by the width value of the inorganic filler. Examples of shapes that can satisfy the above-mentioned aspect ratio value include plate-like or scale-like shapes having a pair of main surfaces and side surfaces intersecting these main surfaces. However, these shapes are excluded from the inorganic filler of the present invention because the line segment of the maximum diameter of the main surfaces is the longitudinal direction and the cross section perpendicular to the main surfaces has a highly anisotropic shape such as a rectangle that is long in one direction.

[0019] Since the inorganic filler has a fibrous or needle-like shape, it can also include a continuum of infinite length with substantially no ends. From the viewpoint of improving the handling and dispersibility of the cement composition when mixed, increasing the fluidity of the cement composition when poured, and further improving the bending strength of the hardened product, the length H of the inorganic filler is preferably 1000 μm or less, more preferably 40 μm or less, even more preferably 3 to 35 μm, even more preferably 5 to 35 μm, and even more preferably 6 to 32 μm, provided that the above-mentioned A×B relationship is satisfied. The length H of the inorganic filler can be measured and calculated using the method used in the above-mentioned method for calculating the aspect ratio.

[0020] From the viewpoint of improving the handling property, dispersibility, and fluidity of the cement composition when mixed, while further improving the bending strength of the hardened product, the thickness D of the inorganic filler is preferably 0.1 to 60 μm, more preferably 0.2 to 10 μm, even more preferably 0.3 to 3.0 μm, and even more preferably 0.3 to 1.5 μm, provided that the above-mentioned relationship A × B is satisfied. The thickness D of the inorganic filler can be measured and calculated by the method employed in the above-mentioned method for calculating the aspect ratio.

[0021] Unit volume of cement composition: 1 m 3 The volume B of the inorganic filler per unit area can be changed as appropriate depending on the density of the inorganic filler, but is preferably 30 L / m, provided that the above-mentioned relationship A×B is satisfied. 2 or more, more preferably 30 to 70 L / m 3 , and more preferably 45 to 70 L / m 3 , more preferably 50 to 70 L / m 3 , and more preferably 50 to 60 L / m 3 By adding an inorganic filler in such a range, the bending strength after hardening can be more effectively improved. In addition, the fluidity of the cement composition when poured can be increased, improving the pumpability to the pouring site and the fillability into the formwork, thereby increasing construction efficiency.

[0022] The type of inorganic filler is not particularly limited as long as it satisfies the above-mentioned shape and the above-mentioned relationship between aspect ratio and content volume. Specific examples of inorganic fillers include alkali metal salts or alkaline earth metal salts such as basic magnesium sulfate, potassium titanate, and calcium carbonate; metal oxides such as alumina, zirconia, and ferrite; silicon oxides or carbides such as silica and silicon carbide; minerals such as mica, talc, wollastonite, and boehmite; and inorganic compounds such as glass. These may be used alone or in combination of two or more. It is preferable that each of these inorganic fillers is independently a powdery substance that is an aggregate of solid particles.

[0023] Among these, it is preferable to use one or more inorganic fillers selected from basic magnesium sulfate, wollastonite, and potassium titanate, and it is even more preferable to use basic magnesium sulfate. The use of these compounds as inorganic fillers improves the handling and dispersibility of the cement composition during mixing, improves the fluidity of the cement composition when poured, and further improves the bending strength of the hardened product. Furthermore, these inorganic compounds are advantageous in that they can be easily used as inorganic fillers that easily satisfy the above-mentioned aspect ratio because they tend to form fibrous or needle-like crystals.

[0024] In particular, the use of basic magnesium sulfate as an inorganic filler allows for high adhesion to other materials such as cement, effectively and easily achieving high flexural strength. This is thought to be because, when cement and basic magnesium sulfate are mixed, the basic magnesium sulfate partially dissolves in the cement slurry, causing a chemical reaction that densifies the chemical structure or texture of the cement hydrate around the fibrous crystals of basic magnesium sulfate, thereby modifying the structure to increase flexural strength. In addition, the partial dissolution of basic magnesium sulfate suppresses the decrease in fluidity due to contact between solids during mixing of the cement composition, further improving fluidity and resulting in excellent workability and formwork fillability. Furthermore, by using wollastonite, it is possible to obtain the effect that a cement composition can be easily produced as a substitute for asbestos, while taking into consideration the surrounding environment. Furthermore, by using potassium titanate, the strength of the potassium titanate itself allows the cement composition to be mixed while maintaining its fibrous or needle-like shape during production, which results in fewer fibers being broken during mixing and stirring of the composition, making it easier to obtain the reinforcing effect of the fibers.

[0025] The specific surface area of ​​the inorganic filler is preferably 1 to 30 m 2 / g, more preferably 3 to 25m 2 / g, more preferably 5 to 20m 2 / g. By having such a specific surface area, it is possible to obtain the effect of improving the bending strength while ensuring the fluidity of the cement composition. The specific surface area of ​​the inorganic filler can be measured by, for example, the air permeability method or the BET method.

[0026] The cement composition of the present invention contains cement as described above. Examples of cement that can be used include various types of Portland cement, such as ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement; blended cements, such as blast-furnace cement, silica cement, and fly ash cement; and special cements, such as ecocement and alumina cement. These may be used alone or in combination. These are preferably in powder form. Furthermore, cements specified in, for example, JIS R5210, JIS R5211, JIS R5212, JIS R5213, and JIS R5214 can also be used.

[0027] Of the cements mentioned above, ordinary Portland cement is preferred because it is easily available and has excellent strength development in the hardened product. High-early-strength Portland cement is preferred because it has excellent early strength development in the hardened product and is useful for emergency construction and construction in cold regions. Moderate-heat Portland cement is preferred because it has excellent long-term strength of the hardened product, little drying shrinkage, and resistance to sulfates. Low-heat Portland cement is preferred because it has excellent fluidity during construction, long-term strength of the hardened product, and low heat resistance. Sulfate-resistant Portland cement is preferred because it has excellent fluidity during construction, excellent compressive strength development in the hardened product, and excellent inhibition of MgSO4 leaching when contacted with seawater.

[0028] From the viewpoint of obtaining good setting properties, the mineral composition of the cement is, for example, such that the C3S content is preferably 25.0 to 75.0 mass%, the C2S content is preferably 10.0 to 55.0 mass%, the C3A content is preferably 0.5 to 18 mass%, and the C4AF content is preferably 7.0 to 20.0 mass%. From the viewpoint of improving availability and reducing costs, the mineral composition of the cement is preferably such that, for example, the C3S content is preferably 45.0 to 55.0 mass%, the C2S content is preferably 20.0 to 30.0 mass%, the C3A content is preferably 6.0 to 16.0 mass%, and the C4AF content is preferably 3.0 to 13.0 mass%. From the viewpoint of excellent early strength development and excellent suitability for emergency construction and construction in cold regions, the mineral composition of the cement is, for example, preferably such that the C3S content is 59.0 to 69.0 mass%, the C2S content is preferably 6.0 to 16.0 mass%, the C3A content is preferably 6.0 to 16.0 mass%, and the C4AF content is preferably 6.0 to 16.0 mass%. From the viewpoint of long-term strength, low drying shrinkage, and excellent resistance to sulfates, the mineral composition of the cement is, for example, preferably such that the C3S content is 37.0 to 47.0 mass%, the C2S content is 44.0 to 54.0 mass%, the C3A content is 1.0 to 9.0 mass%, and the C4AF content is 8.0 to 18.0 mass%. From the viewpoint of achieving excellent long-term strength, low heat resistance, and fluidity, the mineral composition of the cement is preferably such that, for example, the C3S content is preferably 23.0 to 33.0 mass%, the C2S content is preferably 48.0 to 58.0 mass%, the C3A content is preferably 1.0 to 8.0 mass%, and the C4AF content is preferably 8.0 to 18.0 mass%. From the viewpoint of achieving excellent fluidity, compressive strength development, and inhibition of MgSO4 leaching in seawater, the mineral composition of the cement is preferably such that, for example, the C3S content is preferably 48.0 to 68.0 mass%, the C2S content is preferably 12.0 to 30.0 mass%, the C3A content is preferably 9.0 to 18.0 mass%, and the C4AF content is preferably 7.0 to 18.0 mass%. The contents of C3S, C2S, C3A and C4AF can be measured in accordance with, for example, JIS R5202.

[0029] Regardless of the type of cement used, the Blaine specific surface area of ​​the cement used is preferably 2500 to 4800 cm 2 / g, more preferably 2800 to 4000 cm 2 / g, more preferably 3000 to 3600 cm 2 / g, particularly preferably 3100 to 3500 cm 2 / g. By setting the specific surface area within this range, the fluidity during application and the compressive strength of the hardened product can be further improved. The Blaine specific surface area of ​​cement can be measured in accordance with JIS R5201.

[0030] The contents of cement and inorganic filler in the cement composition can be changed as long as the inorganic filler satisfies the relationship between the aspect ratio and the content volume described above. However, the content by mass of inorganic filler per 100 parts by mass of cement is preferably 5 to 30 parts by mass, more preferably 7 to 25 parts by mass, even more preferably 7 to 15 parts by mass, and even more preferably 8 to 12 parts by mass. By setting the content in this range, the bending strength after hardening can be more effectively improved. In addition, the fluidity of the cement composition when poured can be increased, improving the ease of pumping to the pouring site and the ease of filling into the formwork, thereby increasing construction efficiency.

[0031] The cement composition may be composed only of the above-mentioned cement and inorganic filler. In this case, the cement composition is a powder that is a mixture of solid particles. Alternatively, in addition to the cement and inorganic filler, materials other than the cement and inorganic filler (hereinafter, also referred to as "other materials") may be further contained. In this case, depending on the type of other materials contained, the cement composition may take the form of a powder that is a mixture of solids, or a liquid that is a mixture of solids and liquid, such as a slurry. Examples of other materials include one or more of silica fume, aggregate, water-reducing agent, antifoaming agent, inorganic powder other than silica fume and inorganic filler, water, and the like.

[0032] From the viewpoints of maintaining a low viscosity of the cement composition to improve fluidity and workability, and of achieving sufficient flexural strength and compressive strength when hardened, thereby obtaining a hardened product with a dense structure and high durability, it is preferable that the cement composition further contains silica fume. Silica fume is a powder containing amorphous SiO2 as its main component, which dissolves in an alkaline solution. For example, a by-product derived from an electric furnace obtained in the production process of ferrosilicon, etc., or a material specified in JIS A6207 can be used. Note that silica fume in this specification is excluded from the inorganic fillers mentioned above.

[0033] The content of silica fume in the cement composition is preferably 1 to 30 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 10 to 15 parts by mass, per 100 parts by mass of cement. By setting the content in this range, it is possible to increase not only the bending strength but also the compressive strength, and as a result, the overall strength of the hardened product is further increased.

[0034] The Blaine specific surface area of ​​silica fume is preferably 10 to 50 m 2 / g, more preferably 12 to 40m 2 / g, more preferably 13 to 25m 2 / g. By keeping the content in this range, the fluidity during application and the strength of the cured product can be further improved. The Blaine specific surface area of ​​silica fume can be measured in accordance with JIS A6207.

[0035] From the viewpoint of increasing the density and obtaining a hardened product with sufficient strength, the cement composition preferably further contains aggregate. Examples of aggregate include fine aggregate and coarse aggregate. Depending on the properties of the target composition, these aggregates can be used in the form of mortar using only fine aggregate, or in the form of concrete using both fine and coarse aggregate.

[0036] Examples of fine aggregates include natural aggregates such as river sand, mountain sand, land sand, and sea sand, artificial fine aggregates such as crushed sand, silica sand, blast furnace slag fine aggregate, ferronickel slag fine aggregate, and electric furnace oxidizing slag fine aggregate, and recycled fine aggregate. Fine aggregates specified in JIS A1102 can also be used as fine aggregates. These can be used alone or in combination. Furthermore, materials used in general building materials can be used as fine aggregates by appropriately adjusting the particle size. Examples of coarse aggregate include river gravel, sea gravel, mountain gravel, crushed stone, crushed slag stone, etc. Coarse aggregates specified in JIS A5005 can also be used. These can be used alone or in combination.

[0037] From the viewpoint of increasing the density and obtaining a hardened product with sufficient strength, the content of the fine aggregate is preferably 50 to 400 parts by mass, more preferably 100 to 300 parts by mass, and even more preferably 150 to 250 parts by mass per 100 parts by mass of cement. From the same viewpoint, when coarse aggregate is contained, the content of the coarse aggregate is preferably 100 to 400 parts by mass, more preferably 150 to 350 parts by mass, and even more preferably 200 to 300 parts by mass per 100 parts by mass of cement.

[0038] From the viewpoint of more easily obtaining a cement composition having the desired fluidity and strength development, it is preferable that the cement composition further contains an admixture. Examples of the admixture include admixtures specified in JIS A6204, specifically various water-reducing agents such as water-reducing agents, high-performance water-reducing agents, and air-entraining water-reducing agents, air-entraining agents, antifoaming agents, shrinkage-reducing agents, fluidizing agents, thickeners, and hardening accelerators. These can be used alone or in combination. The form of the admixture may be, independently of each other, a powder or a liquid dissolved or dispersed in a liquid medium such as water. Of these, it is more preferable to include at least one of various water-reducing agents and antifoaming agents, from the viewpoint of further exerting the above-mentioned effects.

[0039] From the same viewpoint, the content of each admixture is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of cement. From the same viewpoint, the total content of the admixture is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of cement.

[0040] From the viewpoint of achieving stable fluidity during application while also achieving strength development in the hardened product, mortar or concrete, after application, it is preferable that the cement composition further contain an inorganic powder other than cement, silica fume, and inorganic filler. Examples of such inorganic powders include fly ash specified in JIS A6201, ground granulated blast furnace slag, gypsum, limestone or its powder, silica stone or its powder, and other various admixtures. These may be used alone or in combination.

[0041] From the same viewpoint, the content of each inorganic powder is independently preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 1 to 10 parts by mass, relative to 100 parts by mass of cement. From the same viewpoint, the total content of the inorganic powder is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 40 parts by mass, and even more preferably 1 to 30 parts by mass, relative to 100 parts by mass of cement.

[0042] The water that can be used is not particularly limited and may be water that is commonly used in the present technical field, such as tap water, well water, rainwater, distilled water, purified water, or ion-exchanged water.

[0043] From the viewpoint of further increasing the strength of the resulting hardened product, the water-cement ratio (ratio of water mass to cement mass) is preferably 0.1 to 0.6, more preferably 0.15 to 0.5, and even more preferably 0.15 to 0.3.

[0044] The above-mentioned cement composition can be produced by a process of adding and mixing cement, inorganic filler, and, if necessary, other materials in any order, or simultaneously. For example, when producing a cement composition that is a paste containing water, it can be obtained by adding a mixture of solid components other than water to water and further mixing. The mixer used for mixing is not particularly limited, and a chemical mixer, a mortar mixer, a twin-screw forced mixer, a pan mixer, a grout mixer, etc. can be used. When the other ingredients do not contain a liquid such as water, the resulting cement composition is usually a powdery mixture of aggregates of particles of each ingredient. When the other ingredients contain a liquid such as water, the resulting cement composition is usually a liquid, a paste-like mixture, which hardens over time in the presence of water to form a hardened product. When it is a liquid, for example, it can be pumped to the casting site while maintaining its fluidity, filled into a formwork, and hardened after demolding and curing to form a hardened product with the desired dimensions and shape.

[0045] The cement composition of the above embodiment can improve the bending strength of the hardened product and impart isotropic strength to the hardened product. Therefore, it can be suitably used as a material for mortar structures, concrete structures, and the like, which require strength against external forces acting in multiple directions, regardless of the environment during and after construction or the structure of the target structure. In particular, by adjusting at least one of the length, aspect ratio, and content of the inorganic filler within a predetermined range, or by using a specific inorganic compound such as basic magnesium sulfate as the inorganic filler, it is possible to improve the strength of the hardened product and increase the fluidity of the cement composition before hardening. As a result, it is advantageous in that it can be pumped to the pouring site and filled into the formwork during construction, thereby improving workability and handleability. [Example]

[0046] The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples. The following examples were carried out in an environment of a temperature of 20°C and a relative humidity of 60 to 70% RH. In the tables below, columns marked with "-" and blank columns indicate that the substance was not contained, could not be measured, or was not carried out. In the following examples and comparative examples, for the sake of convenience, evaluations are made using mortar containing only fine aggregate as aggregate, but the evaluation results can be similarly applied to concrete.

[0047] [Examples 1 to 6 and Comparative Examples 1 to 79] <1. Preparation of cement composition> Using the materials shown in (1) to (8) below, cement compositions with an air mixing amount of about 2.0% by volume were prepared.

[0048] (1) Cement: Cement raw materials were fired in a kiln and pulverized to prepare Portland cements that met JIS R5201 and were different from ordinary Portland cements in Examples 7 to 10 and Comparative Examples 80 to 82. (2) Inorganic filler: The inorganic fillers used in each example and comparative example are shown in Table 1 below. When the inorganic filler used was fibrous or acicular, the aspect ratio was measured and calculated using the method described above. For inorganic fillers having shapes other than fibrous or acicular, the aspect ratio was not evaluated. The aspect ratios and dimensions of the fibrous or acicular inorganic fillers are shown in Table 2 below.

[0049] [Table 1]

[0050] [Table 2]

[0051] (Other materials) (3) Silica fume: SKW East Asia Co., Ltd., UNISIL MW-YC2, specific surface area 17.6 m 2 / g. (4) Fine aggregate: Ube silica sand No. 6 (surface dry density 2.60 g / cm 3 , coarse grain ratio 1.25). (5) Inorganic powder: fly ash (type I fly ash as specified in JIS A6201). (6) Water reducing agent: Polyether-polycarboxylic acid-based high performance water reducing agent (powder). (7) Antifoaming agent: a nonionic surfactant containing polyoxypropylene and polyoxyethylene. (8) Water (mixing water): Tap water.

[0052] Specifically, water was weighed out as material (8) into a sample container, and a powder mixture of materials (1) to (7) that had been mixed in advance was poured into the container. In Examples 1 to 6 and Comparative Examples 1 to 79, the blending ratios of each material except for the inorganic filler are shown in Table 3 below, and the blending ratios of the inorganic filler are shown in Tables 4 to 6 below, respectively. In Tables 4 to 6, the column marked "Actual" indicates the Examples, and the column marked "Ratio" indicates the Comparative Examples.

[0053] Thereafter, the container containing the materials (1) to (8) was placed in a planetary centrifugal mixer (Thinky Corporation, model ARE-310, maximum load capacity 310 g), and the materials were mixed for about 120 seconds at a revolution speed of 2000 rpm and a rotation speed of 800 rpm to obtain a cement composition as a paste mixture. 3 For samples exceeding this value, the time required for the sample to become fluid also increased, so the mixing time was extended appropriately to obtain the desired paste-like cement composition.

[0054] <2. Evaluation of cement composition> The cement compositions of the Examples and Comparative Examples were evaluated for the following items (i) to (iv).

[0055] (i) Bending strength test of cured product A rectangular columnar specimen was prepared in accordance with JIS A1132-2020 "Method of preparing specimens for concrete strength tests," except that the dimensions of the specimen were changed to 2 cm x 2 cm x 8 cm. This specimen was prepared by filling a formwork with the cement composition of the Example or Comparative Example to the above dimensions, leaving it to stand at 20°C for one day, removing it from the formwork the next day, and then curing it in water at 50°C for six days. The specimens were then subjected to the central point loading method in JIS A1106-2018 "Test method for bending strength of concrete" and a bending strength test was carried out with a span of 60 mm. 2 The higher the value of ) the more excellent the bending strength of the cured product. The results are shown in Tables 4 to 6 below. The bending strength of the hardened cement composition measured by the above method was 33.2 N / mm 2 It was.

[0056] (ii) Fluidity test The mortar zero-pump flow was measured for each of the cement compositions of the Examples and Comparative Examples. The mortar zero-pump flow was measured in accordance with JIS R5201-2015 "Physical Testing Methods for Cement," except that the flow cone was replaced with a cylindrical tube 35 mm in diameter and 35 mm in height, and the measurement was performed under conditions of no drop. The larger the flow (mm) value, the higher the fluidity of the composition before hardening, indicating superior pumpability and formwork filling during construction. The results are shown in Tables 4 to 6 below.

[0057] (iii) Measurement of mixing temperature The temperatures (°C) of the cement compositions of the Examples and Comparative Examples immediately after mixing were measured using a thermometer. This evaluation was conducted to confirm whether excessive temperature increases were observed during mixing of the cement compositions of the Examples and Comparative Examples. The temperature measurement results are shown in Tables 4 to 6 below. In all of the Examples and Comparative Examples, the mixing temperature increased to a degree that did not adversely affect the physical properties of the composition.

[0058] (iv) Density measurement The density (g / cm) of the specimen used for bending strength measurement 3 ) was divided by the measured mass and volume. This evaluation was conducted to confirm that no unintended air inclusion occurred during the production of the cement compositions of the Examples and Comparative Examples. The results are shown in Tables 4 to 6 below. In all of the Examples and Comparative Examples, the density was such that it could be determined that no air was mixed in.

[0059] As shown in Tables 4 to 6 below, the cement compositions of each Example, which use a fibrous or needle-like inorganic filler and set the product of the aspect ratio of the inorganic filler and the filler content volume per unit volume within a predetermined range or more, have improved flexural strength after hardening compared to the Comparative Examples. In particular, Example 1, which uses basic magnesium sulfate as the inorganic filler and sets the filler content volume per unit volume within the above-mentioned preferred range, shows improved flow of the cement composition, high fluidity, and improved workability in pumping the composition and pouring it into formwork, while also achieving high flexural strength after hardening.

[0060] [Table 3]

[0061] [Table 4]

[0062] [Table 5]

[0063] [Table 6]

[0064] [Examples 7 to 10 and Comparative Examples 80 to 82] <1. Preparation of cement composition> Instead of the materials (1) to (8) above, the following materials (a) to (e) were used. A paste-like cement composition with an air mixing amount of approximately 2.0% by volume was prepared in the same manner as in Example 1 above. The blending ratio of each material is shown in Table 7 below, and the blending ratio of the inorganic filler is shown in Table 8 below.

[0065] (a) Cement: Cement raw materials were fired in a kiln and the fired material was pulverized to prepare ordinary Portland cement. (b) Inorganic filler (see Tables 1 and 2): basic magnesium sulfate (trade name "MOS HIGE P", manufactured by Ube Material Industries, Ltd.) or potassium titanate (trade name "TISMOH D", manufactured by Otsuka Chemical Co., Ltd.).

[0066] (Other materials) (c) Fine aggregate: Ube silica sand No. 6 (surface dry density 2.60 g / cm 3 , coarse grain ratio 1.25). (d) Water reducing agent: Polyether-polycarboxylic acid-based high performance water reducing agent (powder). (e) Water (mixing water): Tap water.

[0067] <2. Evaluation of cement composition> The cement compositions of Examples 7 to 10 and Comparative Examples 80 to 82 were evaluated in the same manner as in the Examples and Comparative Examples described above for the above items (i) to (iv). The results are shown in Table 8 below.

[0068] As shown in Table 8 below, the cement compositions of each example, which use fibrous or needle-like inorganic fillers and set the product of the aspect ratio of the inorganic filler and the volume of the filler per unit volume above a predetermined range, have improved bending strength after hardening compared to the comparative examples. The mixing temperature was sufficiently low in all examples and comparative examples. Furthermore, the densities of all examples and comparative examples were such that it was determined that no air was mixed in. In particular, by using ordinary Portland cement in combination with potassium titanate having the physical properties shown in Table 8, the flow of the cement composition is improved and the fluidity is high, which improves the workability of pumping the composition and pouring it into formwork, while also enabling the composition to exhibit high bending strength after hardening.

[0069] [Table 7]

[0070] [Table 8]

Claims

1. cement and a fibrous or needle-like inorganic filler; The aspect ratio [-] of the inorganic filler and the content volume of the inorganic filler per unit volume [L / m ３ ] and the product [L / m ３ ] is 800 or more, the content volume of the inorganic filler per unit volume is 45 L / m 3 or more and 70 L / m 3 or less; The aspect ratio of the inorganic filler is 15 or more and 33 or less.

2. 2. The cement composition according to claim 1, wherein the inorganic filler is one or more selected from the group consisting of basic magnesium sulfate, wollastonite, and potassium titanate.

3. 3. The cement composition according to claim 1, wherein the inorganic filler has a length of 40 μm or less.

4. The cement composition of any one of claims 1 to 3, further comprising silica fume.

5. The cement composition according to claim 4, further comprising one or more inorganic powders selected from the group consisting of fine aggregate, water reducing agent, antifoaming agent, and inorganic powders other than the silica fume and the inorganic filler.

6. Further containing water, 6. The cement composition according to claim 1, wherein the ratio of the mass of water to the mass of cement is from 0.15 to 0.5.

Images