JP2023139504A - Hydraulic composition and its application - Google Patents

Abstract

To solve problems associated with conventional building materials using Portland based cement, magnesium compounds or magnesia-based cement.SOLUTION: This invention relates to a hydraulic composition characterized by containing magnesium oxide, magnesium carbonate, gypsum hemihydrate and a silicate compound, and to a hardened body obtained by curing a mixture of the hydraulic composition with water.SELECTED DRAWING: None

Description

Application for application of Article 30, Paragraph 2 of the Patent Act Published at the 28th Architecture and Building Materials Exhibition 2022 held at the Tokyo International Exhibition Center on March 1, 2020

The present invention relates to a hydraulic composition for use on floors and walls, and its uses.

As inorganic floor finishing and wall finishing materials, materials based on Portland cement are generally used (Patent Document 1), but although these have excellent physical strength, It is known to have the following drawbacks.
・Highly bright finishes such as white or pastel colors are difficult to achieve.
・Easy to crack due to curing shrinkage.
・Efflorescence is likely to occur due to contact with carbon dioxide gas after construction.

Further, as a building material using a magnesium compound, one using basic magnesium carbonate was known in the 1970s to 1980s (Patent Document 2), but it has the following drawbacks.
・A heating process is required, and uncured material cannot be applied and cured at the construction site.
・Difficult to apply to floors due to poor strength.

Furthermore, magnesia cement-based materials using magnesia have existed for a long time and are used as flooring materials with recent patent technology (Patent Document 3), but they have the following drawbacks.
- Due to the influence of the magnesium chloride it contains, metal building materials may be oxidized and corroded.

Special Publication No. 63-11306 Japanese Unexamined Patent Publication No. 53-143627 Patent No. 6389312

The object of the present invention is to solve the problems of conventional building materials using Portland cement, magnesium compounds or magnesia cement.

As a result of intensive research to solve the above problems, the present inventors found that the above problems did not occur by combining magnesium oxide, magnesium carbonate, gypsum hemihydrate, and silicate compounds, and the present invention has been developed. Completed.

That is, the present invention is as follows.
(1) A hydraulic composition characterized by containing magnesium oxide, magnesium carbonate, gypsum hemihydrate, and a silicate compound.
(2) A cured product obtained by curing a kneaded product obtained by kneading the above-mentioned hydraulic composition and water.
(3) A molded article obtained by pouring a kneaded mixture of the above-mentioned hydraulic composition and water into a mold and then curing the mixture.
(4) A method for constructing a floor, which comprises applying a kneaded mixture of the above-mentioned hydraulic composition and water onto a floor surface and then curing the mixture.
(5) A method for constructing a wall, which comprises applying a kneaded mixture of the above-mentioned hydraulic composition and water to a wall surface and then curing the mixture.
(6) A method for producing a molded article, which comprises pouring a kneaded mixture of the above-mentioned hydraulic composition and water into a mold, and then curing the mixture.
(7) A method for constructing a floor, which comprises adhering the molded body to a floor surface.
(8) A method for constructing a wall, which comprises attaching the molded body to a wall surface.

The hydraulic composition of the present invention has excellent reactivity and can secure an appropriate pot life at an ambient temperature of 5°C to 35°C, and at the same time has a fast curing speed, so it has high hardness the next day and is suitable for floor finishing materials. It is suitable as

Further, the hydraulic composition of the present invention can solve the following problems (problems) in conventional materials using Portland cement and alumina cement as hardening bases.
・Available for high brightness finishes in white and pastel colors.
Conventional materials using Portland cement or alumina cement are gray in themselves, so even if white pigment is mixed into this compound, it is not possible to create pure white or bright pastel colors. On the other hand, in the product of the present invention, the main raw materials, magnesium oxide, magnesium carbonate, and gypsum hemihydrate, are all white substances with high brightness. When actually making products such as floor finishing materials, even if aggregates such as silica sand are added to these main raw materials, the whiteness will not be significantly impaired and it will be easy to produce white or pastel-colored cured products. Obtainable.

- Less likely to cause cracks due to curing shrinkage.
In the composition consisting of the main raw materials, magnesium oxide, magnesium carbonate, gypsum hemihydrate, and water, the hydraulic reaction proceeds rapidly, and the crystal growth of gypsum hemihydrate proceeds at the same time, which has the effect of suppressing the volumetric shrinkage associated with hardening. This makes the cured product less prone to cracking.

・After construction, no efflorescence occurs due to contact with carbon dioxide gas.
In conventional materials using Portland cement and alumina cement, a large amount of calcium hydroxide is generated in the hardened material, and when it migrates from the inside of the hardened material to the surface, it reacts with carbon dioxide in the atmosphere. Calcium carbonate is produced and efflorescence occurs. On the other hand, since the product of the present invention is a magnesium-based raw material, it does not produce such an efflorescent substance.

・No ammonia is generated.
Conventional concrete and mortar are known to generate ammonia due to the nitrides in their compounds, and ammonia accelerates the deterioration of art museums and museum collections, so facilities that require ammonia countermeasures. In such cases, measures such as coating the concrete surface are required. The product of the present invention does not contain nitrides and does not generate ammonia, so it is suitable as a finishing material for concrete surfaces.

Furthermore, the hydraulic composition of the present invention, in magnesia-cement-based floor finishing materials, has the effect of attracting water to the surface due to the influence of magnesium chloride, which is one of its main components, and also reduces the sweating phenomenon on metal surfaces. Although it is necessary to take measures such as a protective primer against corrosion, these phenomena do not occur with the developed material, so there is no need for troublesome measures.

Therefore, the hydraulic composition of the present invention is suitable for finishing floors and walls, manufacturing molded objects such as tiles, and the like.

The hydraulic composition of the present invention contains magnesium oxide, magnesium carbonate, gypsum hemihydrate, and a silicate compound.

The above-mentioned magnesium oxide is not particularly limited, but from the viewpoint of physical properties such as the pot life of the obtained hydraulic composition and the strength of the cured product, it is preferable that the magnesium oxide has an average BET specific surface area of 5 to 25 m ² /g, and 10 to 20 m 2 /g. ² /g is more preferable. When using magnesium oxide having the above average BET specific surface area, one with an average BET specific surface area within this range may be used alone, or one with an average BET specific surface area within this range may be used in combination. good. Further, the average particle diameter of magnesium oxide is not particularly limited, but is, for example, 1.0 to 6.0 μm, preferably 3.0 to 4.5 μm. Note that such magnesium oxide may be used by actually measuring the BET specific surface area and average particle diameter of commercially available magnesium oxide, selecting magnesium oxides that meet the above conditions from there, and using them in appropriate combinations. Specifically, such magnesium oxide can be obtained from Kamishima Chemical Industry Co., Ltd., Ako Chemical Industry Co., Ltd., Tateho Chemical Industry Co., Ltd., Kyowa Chemical Industry Co., Ltd., and the like.

The BET specific surface area of magnesium oxide was measured using a flow-type specific surface area automatic measuring device (Flowsorb 2300 model: manufactured by Shimadzu Corporation) in accordance with JIS R1626 (method for measuring the specific surface area of fine ceramic powder using the gas adsorption BET method). ) is the value measured using Further, the average BET specific surface area of magnesium oxide refers to a value obtained by mixing two or more types of magnesium oxides having different BET specific surface areas, and then measuring the BET specific surface area of the mixture using the above gas adsorption BET method. Furthermore, the average particle diameter of magnesium oxide can be determined by placing the sample in a dispersion medium (denatured alcohol) in advance and dispersing the sample for 3 minutes using an ultrasonic dispersion device (UD-201: manufactured by Nippon Seiki Seisakusho Co., Ltd.). This is the average value of the values measured with a Microtrac particle size distribution analyzer (model HRA type: manufactured by Nikkiso Co., Ltd.).

The content of magnesium oxide in the hydraulic composition of the present invention is not particularly limited, but is, for example, 30 to 60% by mass (hereinafter referred to as "%"), preferably 35 to 50%.

The above magnesium carbonate is not particularly limited, but is preferably basic magnesium carbonate. Basic magnesium carbonate is generally expressed by the following formula:
_mMgCO3.Mg ( _OH ) _2.nH2O
(Here, m=3-5, n=3-7)
It is preferably expressed as 4MgCO ₃ .Mg(OH) ₂ .4H ₂ O as the main component. Further, the average BET specific surface area of basic magnesium carbonate is not particularly limited, but is, for example, 10 to 60 m ² /g, preferably 20 to 50 m ² /g. As the basic magnesium carbonate having the above average BET specific surface area, one with an average BET specific surface area within this range may be used, or one with an average BET specific surface area within this range may be used by combining a plurality of average BET specific surface areas. Good too. Furthermore, the average particle diameter of basic magnesium carbonate is not particularly limited, but is 0.5 to 100 μm, preferably 5 to 20 μm. The average BET specific surface area and average particle diameter of basic magnesium carbonate can be measured in the same manner as magnesium oxide.

The mass ratio of magnesium oxide to magnesium carbonate in the hydraulic composition of the present invention is not particularly limited, but is, for example, 3 to 10:1, preferably 5 to 9:1.

The above-mentioned gypsum hemihydrate is also called calcined gypsum and is represented by CaSO ₄ 1/2H ₂ O. Alpha-type and β-type are known for this hemihydrate gypsum, but either one or both types may be used.

The content of gypsum hemihydrate in the hydraulic composition of the present invention is not particularly limited, but from the viewpoint of physical properties such as pot life of the resulting hydraulic composition and strength of the cured product, the content of gypsum hemihydrate is, for example, based on the mass of magnesium oxide. In contrast, it is 6 to 25%, preferably 8 to 20%.

The silicate compound is not particularly limited, and examples thereof include wollastonite, kaolinite, metakaolin, zircon, talc, mica, and pyrogenic silica. Among these silicate compounds, preferred is wollastonite and one or more combinations of silicate compounds other than wollastonite, selected from the group consisting of wollastonite, metakaolin, zircon, and pyrogenic silica. More preferably, one kind or a combination of two or more kinds thereof are used. Wollastonite is made by pulverizing wollastonite, which is a natural inorganic mineral, and is represented by CaSiO ₃ . Since this wollastonite contains a silicic acid component and has an acicular crystal structure, it can also be expected to have an effect on the dimensional stability of the structure of the cured product, so it is preferable to make it essential. Kaolinite is a fine powder of natural koryo stone, and is represented by Al ₄ Si ₄ O ₁₀ (OH) ₈ . Metakaolin is also called semi-calcined kaolin and is represented by anhydrous aluminum silicate, Al ₂ O ₃ .2SiO ₂ . This metakaolin is produced by heating and calcining kaolinite at 700 to 900°C. Zircon (zirconium silicate) is a silicate mineral of zirconium and is represented by _ZrSiO4 . As this zircon, it is preferable to use a pulverized zircon with a particle size of 50 μm or less, and is commercially available, for example, under the trade names of zircon and zircon flour. Talc is a mineral consisting of magnesium hydroxide and silicate, also called talc, and is represented by Mg ₃ Si ₄ O ₁₀ (OH) ₂ . Mica, whose Japanese name is mica, is a silicate mineral consisting of silicon, aluminum, magnesium, potassium, etc., and characterized by its scaly crystal structure. Dry silica is also called fumed silica and is represented by _SiO2 . This dry process silica has a small primary particle size of 50 nm or less, and a plurality of particles are connected in a beaded shape to form a very bulky aggregate, and an effect can be expected with a very small amount of blending.

The content of the silicate compound in the hydraulic composition of the present invention is not particularly limited, but from the viewpoint of physical properties such as pot life of the resulting hydraulic composition and strength of the cured product, for example, 0.1 to 30%, preferably 0.2 to 25%. Especially when the silicate compound contains dry silica, the content of dry silica is as low as 3% or less based on the mass of magnesium oxide, because dry silica is bulky and the viscosity of the material becomes too high when the content is high. It is preferable to do so. Although wollastonite has an acicular shape, it has little effect on the viscosity of the material, and can be blended in an amount of up to about 30% based on the mass of magnesium oxide, which is effective for increasing dimensional stability. In addition, when using wollastonite and one or more types of silicate compounds other than wollastonite in combination as the silicate compound, the mass of wollastonite and silicate compounds other than wollastonite The ratio is 1:0.01-1, preferably 1:0.01-0.8.

In addition to the above-mentioned essential components, the hydraulic composition of the present invention further comprises a filler, a pigment, a water reducing agent, an antifoaming agent, a wetting and dispersing agent, a viscosity modifier, an anti-sag agent, an aqueous resin, and an aggregate. One or more types of compounding agents selected from the group may be included. Basically, these compounding agents may be appropriately blended in amounts suited to the intended use of the hydraulic composition of the present invention.

The above-mentioned filler has the role of adjusting viscosity in workability, providing strength and physical properties of the cured product, and acting as a filler, and includes, for example, calcium carbonate, silica powder, silica sand, barite powder, and the like. Further, the content of the filler in the hydraulic composition of the present invention is not particularly limited, but is, for example, 10% or more, preferably 20 to 70%, and more preferably 30 to 60%.

Examples of the pigments include inorganic pigments, organic pigments, special pigments, and the like. Specific inorganic pigments include natural mineral pigments such as red clay, loess, green clay, malachite, chalk powder, and graphite, and synthetic inorganic pigments such as navy blue, zinc white, cobalt blue, emerald green, viridian, titanium white, and iron oxide. can be mentioned. Specific organic pigments include alkali blue, Lysol red, carmine 6B, disazo yellow, phthalocyanine blue, quinacridone red, isoindolinone yellow, and the like. Specific examples of special pigments include fluorescent pigments, metal powder pigments, pearl pigments, temperature-indicating pigments, and ceramic pigments. Further, the pigment content in the hydraulic composition of the present invention is not particularly limited, but is, for example, 0.1% or more, preferably 0.2 to 2.0%, more preferably 0.4 to 1.5%. It is.

Examples of the water reducing agent include AE agents, water reducing agents/AE water reducing agents, high performance water reducing agents, high performance AE water reducing agents, and the like. Further, the content of the water reducing agent in the hydraulic composition of the present invention is not particularly limited, but is, for example, 0.05% or more, preferably 0.1 to 1.5%, more preferably 0.2 to 1.0%. %.

Examples of the antifoaming agent include mineral oil compounds, polyether compounds, silicone compounds, and the like. Further, these antifoaming agents may be in the form of powder. Further, the content of the antifoaming agent in the hydraulic composition of the present invention is not particularly limited, but is, for example, 0.01% or more, preferably 0.05 to 2.0%, more preferably 0.1 to 1.0%. It is 5%.

Examples of the above-mentioned wetting and dispersing agents include anionic compounds, cationic compounds, nonionic compounds, and polymer compounds. Specific wetting and dispersing agents include aliphatic polycarboxylic acid compounds, aminoamide compounds, phosphate ester compounds, nonionic compounds, acrylic polymers, polyether phosphate ester compounds, and the like. Further, the content of the wetting and dispersing agent in the hydraulic composition of the present invention is not particularly limited, but is, for example, 0.01% or more, preferably 0.02 to 1.0%, more preferably 0.03 to 0.0%. It is 5%.

Examples of viscosity modifiers include urethane-modified polyether compounds, acrylic polymers, amide compounds, polyether phosphate compounds, hydrogenated castor oil compounds, fumed silica compounds, bentonite compounds, and layered silicic acids. Examples include salt compounds. Further, the content of the viscosity modifier in the hydraulic composition of the present invention is not particularly limited, but is, for example, 0.01% or more, preferably 0.02 to 1.0%, more preferably 0.03 to 0.0%. It is 5%.

Examples of the anti-sagging agent include cellulose compounds, starch ester compounds, polyacrylamide compounds, and synthetic polymer compounds. Further, the content of the anti-sagging agent in the hydraulic composition of the present invention is not particularly limited, but is, for example, 0.01% or more, preferably 0.02 to 1.0%, more preferably 0.03 to 0.0%. It is 5%.

Examples of the aqueous resin include re-emulsified powder resin, polymer dispersion, and the like. Examples of re-emulsified powder resins include acrylic resins, vinyl acetate resins, ethylene-vinyl acetate copolymer resins, and the like. Examples of the polymer dispersion include styrene-butadiene rubber latex, acrylic ester emulsion, and ethylene-vinyl acetate emulsion. In addition, since the polymer dispersion is a dispersion of an aqueous resin in water, when it is blended, it may be contained together with water, which will be described separately later. Further, the content of the aqueous resin in the hydraulic composition of the present invention is not particularly limited, but is, for example, 0.5% or more, preferably 1.0 to 10.0%, more preferably 2.0 to 6.0%. %.

Examples of the aggregate include gravel, crushed stone, artificial aggregate, magnetite, barite, iron pieces, expanded slag, and pearlite. Further, the content of aggregate in the hydraulic composition of the present invention is not particularly limited, but for example, it may be 5 parts by mass or more, preferably 10 to 100 parts by mass, or more, based on 100 parts by mass of the hydraulic composition of the present invention. Preferably it is 20 to 80 parts by mass.

A more preferred embodiment of the hydraulic composition of the present invention includes one containing the following components, and a particularly preferred embodiment includes one comprising the following components.
(Composition 1)
Magnesium oxide 30-55 parts by mass Magnesium carbonate 3-15 parts by mass Gypsum hemihydrate 3-10 parts by mass Silicate compound 0.1-30 parts by mass Filler 20-50 parts by mass Compounding agents other than filler 0.5- 5 parts by mass (composition 2)
Magnesium oxide 30-55 parts by mass Magnesium carbonate 3-15 parts by mass Gypsum hemihydrate 3-10 parts by mass Silicate compound 0.1-30 parts by mass Mass ratio of wollastonite and silicate compounds other than wollastonite = 1:0.01~1
Filler: 20 to 50 parts by mass Compounding agents other than filler: 0.5 to 5 parts by mass

The hydraulic composition of the present invention explained above can be kneaded with water to form a kneaded product. The method for preparing the kneaded product is not particularly limited, but examples thereof include a method in which water is added to the hydraulic composition of the present invention and kneaded to prepare a kneaded product. The content of water in the kneaded material is not particularly limited as long as it is enough to cause a hardening reaction, but the total mass ratio of water to the total mass of magnesium oxide, magnesium carbonate, gypsum hemihydrate, and silicate compound is 1. :0.5 to 1.0, preferably 1:0.6 to 0.9.

The above-mentioned kneaded product can be applied to a floor surface, wall surface, etc. and cured to form a cured product, or can be cured in a mold to form a molded product. Curing can be performed at room temperature (5 to 35°C). Further, this kneaded product has an appropriate curing reaction time, for example, a pot life of about 15 to 30 minutes and a curing time of about 15 to 30 hours. Note that the pot life is measured by the method described in Examples, and the curing time is a measure of the time a person can stand on the applied kneaded product.

The cured product or molded product thus obtained preferably has the following properties. A three-point bending test of a test body (molded body) with dimensions of 70 mm x 20 mm x thickness 6.5 mm is 15 MPa or more after 30 days of air drying. Moreover, the three-point bending strength immediately after immersion in water for 7 days after 30 days of air-drying is 9 MPa or more. Furthermore, the compressive strength of the test body (molded body) with dimensions of 12.5 mm x 12.5 mm x height 25.0 mm is 30 MPa or more after 30 days of air drying. Furthermore, a test specimen (hardened product) applied to a concrete plate with a thickness of 3 mm and cured at 20° C. for 30 days had an adhesion of 2.0 N/mm ² or more and an impact resistance of 5 times or more. Note that the three-point bending test, bending strength, compressive strength, adhesiveness, and impact resistance were conducted by the methods described in Examples. Further, the above-mentioned cured product and molded product also have the physical properties described in the effects of the present invention.

The above-mentioned hardened product is used in the terrazzo construction method, in which painted floor materials, colored aggregates and glass pieces are mixed in and polished after hardening, as well as the hardened products of conventional cement compositions, as base treatment materials for painted floors, and as waterproof materials. It can be used as a base preparation material, a repair material for concrete structures, a coating material for interior and exterior walls, etc. Furthermore, the molded product can be used for interior and exterior tiles, boards for building materials, and the like.

In the present invention, among these uses, conventional magnesia cement-based cured materials can reduce strength due to moisture and contact with moisture, sweating phenomenon due to moisture being attracted to the surface, and expansion over a long period of time. It is preferable to use it for floor coatings because it solves problems such as hardness and has excellent quick hardening and workability.

When the above-mentioned cured product is used as a coating floor material, the method of application is not particularly limited, and it is sufficient to simply apply a kneaded product containing the hydraulic composition of the present invention to the floor surface and harden it. The method of applying the kneaded material to the floor surface is not particularly limited, and may be, for example, a trowel, a rake, or the like. In addition, before applying the above-mentioned kneaded product to the floor surface, roughening treatment is performed by polishing the base surface, smoothing treatment if the base surface is uneven, and application of a primer to improve adhesion to the base surface. It's okay. Further, after the kneaded material is applied once or multiple times depending on the condition of the base and cured, a top coat treatment, a sealer treatment, etc. may be performed.

When the above-mentioned hardened product is used as a coating floor material, it has a load-bearing capacity (compressive strength equal to or higher than that of ordinary Portland cement-based or early-strength cement-based flooring materials), so it can be used for forklifts, automated guided vehicles (AGVs), etc. ), impact resistance (can withstand the impact of dropping heavy objects and metal tools, etc.), and abrasion resistance (because of its high surface hardness, it is highly durable even when driven by heavy vehicles). Excellent abrasion resistance against rough running and pallet scraping), crack suppression (general cement-based hardened materials produce cracks due to curing shrinkage, but in the present invention, shrinkage is suppressed during the curing reaction process). (magnesia, which is the main raw material, has a high degree of whiteness, and if an extender pigment such as silica, calcium carbonate, or talc that does not affect the color tone is used), it has a high degree of whiteness. , the resulting cured product has a higher degree of whiteness than a cured product containing ordinary Portland cement as the main curing component). The standard thickness is 3 mm, but by adding aggregate with a large particle size, it is possible to coat it thicker than 20 mm at a time.

Furthermore, the above-mentioned hardened product can be used not only as a flooring material for stores, large commercial facilities, factories, etc., but also as a base treatment material for damaged, chipped, or uneven floors, and as a concrete material for retaining walls, bridge piers, tunnels, etc. It can be used as a repair material for structures, interior wall finishing materials, exterior wall finishing materials, etc. by curing at construction sites, and as molded objects such as molded tiles for interior and exterior wall materials and flooring applications. suitable for

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples at all. In addition, in each composition of Examples, those having the same component name are used.

Implementation example 1
Physical properties of hydraulic composition, molded body and cured body:
A kneaded product was prepared by mixing a hydraulic composition containing the components listed in Table 1 with water. For these kneaded products, we determined the pot life based on the following, measured the strength of the molded product obtained by putting the kneaded product into a mold and hardened it, and evaluated the cracking property of the cured product obtained by curing the kneaded product. Ta. The results are also listed in Table 1.

Among the components listed in Table 1, magnesium oxide was first prepared using three types of commercially available magnesium oxide (Star Mag P manufactured by Kamishima Chemical Co., Ltd.: BET specific surface area 1 to 5 m ² /g, Star Mag U manufactured by Kamishima Chemical Co., Ltd.: BET specific surface area 1 to 5 m 2 /g; The average BET specific surface area of AM-2 (manufactured by Ako Kasei Kogyo Co., Ltd.: 5 to 10 ^{m 2 /} g) was measured by the following method. Thereafter, they were appropriately mixed to prepare magnesium oxide having each average BET specific surface area.

<Average BET specific surface area measurement method>
The average BET specific surface area was measured according to JIS R 1626 (method for measuring specific surface area of fine ceramic powder by gas adsorption BET method) using a flow-type specific surface area automatic measuring device (Flowsorb 2300 model: manufactured by Shimadzu Corporation). It was measured using

<Method for determining pot life>
Immediately after adding water to the hydraulic composition and stirring and mixing for 2 minutes in a room at a temperature of 20° C., the time until the viscosity exceeded 20,000 mPa·s was measured. The viscosity was measured according to JIS Z 8803 (liquid viscosity measurement method) using a BH rotational viscometer model BHII (manufactured by Toki Sangyo Co., Ltd.) at a rotation speed of 20 rpm.

<Method for determining strength of cured product>
In a room at a temperature of 20°C, add a specified amount of water to the hydraulic composition and stir and mix for 2 minutes. Pour the kneaded product into a silicone rubber mold so that the thickness of the kneaded product is about 7 mm, and place it on a flat place. I left it still. After 5 days of curing, the cured molded body was removed from the mold to obtain a molded body having dimensions of 70 mm x 20 mm x thickness 6.5 mm. Furthermore, the molded body was left in the air for 25 days, and after a total of 30 days of air drying, it was immersed in water, and after 7 days, it was taken out of the water, and immediately after that, a 3-point bending test was performed to determine the 3-point bending strength. .

(Test condition)
Testing machine: Autograph model AG-50kNXplus manufactured by Shimadzu Corporation
Test speed: 1mm/min
Distance between fulcrums L: 50mm
Indenter radius: 5mm
Support stand radius: 5mm

(a formula)
σ=(3FL)/(2bh ² )
σ: Bending strength (MPa)
F: Load at failure (N)
L: Distance between fulcrums (mm)
b: Test piece width (mm)
h: Test piece thickness (mm)

<Crackability judgment>
A base board was prepared by coating a flexible board with dimensions of 450 mm x 450 mm with a water-based resin AD-8521 (acrylic styrene emulsion) manufactured by Saiden Chemical Co., Ltd. as a primer and drying it. In a room at a temperature of 20°C, a predetermined amount of water was added to the hydraulic composition and mixed with stirring for 2 minutes, and then a mixture was uniformly applied to the entire surface to a thickness of 3 mm to obtain a cured product. Ta. This was allowed to stand as it was, and after 30 days had elapsed, visual observation was performed to determine the presence or absence of cracks in the cured product.

In composition 9, gypsum hemihydrate accounts for 5.0% of the mass of magnesium oxide, and the occurrence of cracks was confirmed, but in compositions 1 to 8 and composition 10, gypsum hemihydrate accounts for 5.0% of the mass of magnesium oxide. It was 12.5 to 30.0%, and no cracks were observed. In particular, in compositions 2, 3, 6, and 7, the average BET specific surface area of magnesium oxide is in the range of 5 to 25 m ² /g, and the mass ratio of magnesium oxide to magnesium carbonate is in the range of 3 to 10:1, The pot life and the strength of the cured product were well balanced.

Implementation example 2
Physical properties of hydraulic composition and molded object:
A kneaded product was prepared by mixing a hydraulic composition containing the components listed in Table 2 with water. These kneaded products were evaluated in the same manner as in Example 1 to determine the pot life, the strength of the molded product, and the cracking property of the cured product. The results are also listed in Table 2.

Composition 11 does not contain a silicate compound and has a low cured product strength, whereas compositions 12 to 17 contain one or more silicate compounds in a ratio of 0.75 to 25% by weight of magnesium oxide. 0%, and the strength of the cured product was 9 MPa or more.

Implementation example 3
Physical properties of molded body:
A hydraulic composition containing the components listed in Table 3 was mixed with water to prepare a kneaded product, and then a molded product was produced in the same manner as in Example 1. This was subjected to a three-point bending strength test in the same manner as in Example 1 after 10, 20, 30, 50, and 100 days of air-drying in an environment at a temperature of 20° C., and the bending strength was measured. The results are shown in Table 4.

Further, the above-mentioned kneaded product was cast into a silicone mold and then cured to produce a molded product with dimensions of 12.5 mm x 12.5 mm x 25.0 mm in height. Compression tests were conducted in the following manner after 10, 20, 30, 50, and 100 days of air-drying, and the compressive strength was measured. The results are shown in Table 4.

<Compression test>
(Compression test conditions)
Testing machine: Autograph model AG-50kNXplus manufactured by Shimadzu Corporation
Test speed: 1mm/min

(a formula)
σ=F/A
σ: Compressive strength (MPa)
F: Yield point load (N)
A: Cross-sectional area of the test piece before applying stress

It was confirmed that both the bending strength and the compressive strength of the molded body gradually improved as the curing days progressed.

Implementation example 4
Physical properties of cured product of hydraulic composition:
A concrete plate measuring 300 mm long x 300 mm wide x 50 mm thick was installed horizontally, and its surface was sandpapered to remove the fragile surface layer. Emulsion) was applied as a primer and allowed to dry. After drying, the same kneaded material as in Example 3 was applied thereon to a thickness of 3 mm to obtain a cured product. After curing this at 20° C. for 30 days, the test described in Table 5 was conducted using this as a test specimen (base is concrete, upper surface is hardened). The results are also shown in Table 5.

The adhesiveness of the cured product was good. The impact resistance of the cured product also showed good results.

Implementation example 5
Effect of hydraulic composition on iron materials:
A kneaded product similar to that in Example 3 was prepared and poured into a plastic container measuring 100 mm long x 50 mm wide to a depth of approximately 5 mm, and an iron plate 20 mm x 50 mm x 2 mm thick was placed in the container. was installed vertically. When the condition was visually observed after being allowed to stand still for 7 days, no changes such as discoloration were observed.

The hydraulic composition of the present invention can be used for various purposes like conventional cement compositions.
that's all

Claims (15)

A hydraulic composition characterized by containing magnesium oxide, magnesium carbonate, gypsum hemihydrate, and a silicate compound. The hydraulic composition according to claim 1, wherein the magnesium oxide has an average BET specific surface area of 5 to 25 m ² /g. The hydraulic composition according to claim 1 or 2, wherein the magnesium carbonate is basic magnesium carbonate. The hydraulic composition according to any one of claims 1 to 3, wherein the mass ratio of magnesium oxide to magnesium carbonate is 3 to 10:1. The hydraulic composition according to any one of claims 1 to 4, wherein gypsum hemihydrate is present in an amount of 6 to 25% by mass based on the mass of magnesium oxide. The hydraulic composition according to any one of claims 1 to 5, wherein the silicate compound is one or more selected from the group consisting of wollastonite, metakaolin, zircon, and pyrogenic silica. The hydraulic composition according to any one of claims 1 to 6, wherein the silicate compound is present in an amount of 0.1 to 30% by mass based on the mass of magnesium oxide. Furthermore, it contains one or more compounding agents selected from the group consisting of fillers, pigments, water reducing agents, antifoaming agents, wetting and dispersing agents, viscosity modifiers, sag prevention agents, aqueous resins, and aggregates. The hydraulic composition according to any one of claims 1 to 7. A cured product obtained by curing a kneaded product obtained by kneading the hydraulic composition according to any one of claims 1 to 8 and water. A molded article obtained by pouring a kneaded mixture of the hydraulic composition according to any one of claims 1 to 8 and water into a mold and then curing the mixture. A method for constructing a floor, which comprises applying a kneaded product of the hydraulic composition according to any one of claims 1 to 8 and water onto a floor surface and then curing the mixture. A method for constructing a wall, comprising applying a kneaded product of the hydraulic composition according to any one of claims 1 to 8 and water to a wall surface and then curing the mixture. A method for producing a molded article, which comprises pouring a kneaded mixture of the hydraulic composition according to any one of claims 1 to 8 into a mold and then curing the mixture. A method for constructing a floor, comprising affixing the molded article according to claim 10 to a floor surface. A method for constructing a wall, comprising affixing the molded article according to claim 10 to a wall surface.