JP6654964B2 - Cement composition - Google Patents

Description

  The present invention relates to a cement composition.

In recent years, various cement compositions have been proposed which have good fluidity before curing and can exhibit high compressive strength after curing.
For example, Patent Document 1 discloses (A) cement, (B) a fine powder having a BET specific surface area of 5 to 25 m ² / g, and (C) an inorganic powder having a brane specific surface area of 3,500 to 10,000 cm ² / g. , (D) fine aggregate, (E) a water reducing agent, and (F) water, wherein the (D) fine aggregate is 2CaO.SiO ₂ and 2CaO.Al ₂ O _3. · containing SiO _2, relative to 2CaO · _SiO 2 100 parts by weight of a total amount of _{2CaO · Al 2 O 3 · SiO} 2 and _{4CaO · Al 2 O 3 · Fe} 2 O 3 is 10 to 100 parts by weight A cement composition comprising a calcined product is described.
When the fired material contained in the fine aggregate is used in an absolutely dry state, the cement composition has fluidity that can be applied before hardening, and has a high flowability exceeding 250 N / mm ² after hardening. When the fired material contained in the fine aggregate is used in a surface-dry state to exhibit compressive strength, it has good fluidity before curing and has a high compressive strength of 200 N / mm ² or more after curing. It manifests itself and has a small self-shrinkage rate.

JP 2009-227574 A

In Patent Literature 1, as an example in which the flow value was measured at “0 hit”, the mass ratio of water and the binder (mass ratio of water / binder) was 0.135, and the 0 hit flow value was 240 to 242 mm, a cement composition having a compressive strength of 280 N / mm ² , and a mass ratio of water to the binder of 0.135, a zero-hit flow value of 270 to 275 mm, and a compressive strength of 215 N / mm. No. ² is described.
The present invention has a high fluidity (e.g., a 0-hit flow value of 200 mm or more) before curing, and a high compressive strength after curing (e.g., when fine aggregate and coarse aggregate are used as aggregate). It is an object of the present invention to provide a cement composition (mortar or concrete) that expresses 300 N / mm ² or more and 350 N / mm ² or more when only fine aggregate is used as an aggregate.

The present inventor has conducted intensive studies to solve the above problems, and as a result, found that cement, silica fume having a BET specific surface area of 15 to 25 m ² / g, an inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm, and a maximum particle size of Is a cement composition containing aggregate A having a size of 1.2 mm or less, a high-performance water reducing agent, an antifoaming agent and water, wherein cement, the silica fume and the silica fume in a total volume of 100% by volume of the cement, the silica fume and the inorganic powder. The present inventors have found that the above object can be achieved according to the cement composition in which each ratio of the inorganic powder is within a specific numerical range, and completed the present invention.
Further, the present inventors have found that the cement composition can exhibit a compressive strength of 300 N / mm ² or more even when the maximum particle size exceeds 1.2 mm and the aggregate contains aggregate B of 13 mm or less, and completed the present invention. did.

That is, the present invention provides the following [1] to [12].
[1] Cement, silica fume having a BET specific surface area of 15 to 25 m ² / g, inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm, aggregate A having a maximum particle size of 1.2 mm or less, high-performance water reducing agent , A cement composition comprising an antifoaming agent and water, wherein in the total amount of 100% by volume of the cement, the silica fume and the inorganic powder, the proportion of the cement is 55 to 65% by volume, and the proportion of the silica fume is 5 to 5%. 25% by volume, wherein the proportion of the inorganic powder is 15 to 35% by volume.
[2] The cement composition according to the above [1], wherein the cement composition does not contain glass fibers.
[3] The cement composition according to [1] or [2], wherein the amount of water is 10 to 20 parts by mass based on 100 parts by mass of the total amount of the cement, the silica fume, and the inorganic powder.
[4] The cement composition according to any one of [1] to [3], wherein the inorganic powder is at least one selected from the group consisting of quartz powder, volcanic ash, and fly ash.
[5] The cement composition, wherein the cement composition contains one or more fibers selected from the group consisting of metal fibers, organic fibers, and carbon fibers, and a ratio of the fibers in the cement composition is 3% by volume or less. The cement composition according to any one of [1] to [4].
[6] The cement composition according to any of [1] to [5], wherein a ratio of the aggregate A in the cement composition is 20 to 40% by volume.
[7] The cement composition according to any of [1] to [6], wherein the aggregate A has a modified Mohs hardness of 9 or more.
[8] The cement composition according to any one of [1] to [7], wherein the compressive strength after curing is 400 N / mm ² or more.
[9] The flow value before curing is 200 mm or more as a value measured without performing a dropping motion 15 times in the method described in “JIS R 5201 (Physical test method for cement) 11. Flow test”. The cement composition according to any one of the above [1] to [8].
[10] The cement composition according to any one of [1] to [5], wherein the cement composition includes an aggregate B having a maximum particle size of more than 1.2 mm and 13 mm or less.
[11] The cement composition according to [10], wherein the ratio of the total amount of the aggregate A and the aggregate B in the cement composition is 25 to 40% by volume.
[12] The cement composition according to [10] or [11], wherein the compressive strength after curing is 300 N / mm ² or more.

According to the cement composition of the present invention (mortar), high fluidity prior to curing (e.g., 0 beating flow value is more than 200 mm) have, and a high compressive strength after curing (e.g., 350 N / mm ² or more ) Can be expressed. According to the cement composition of the present invention, even a cement composition (coarse) containing coarse aggregate has high fluidity before hardening and high compressive strength (for example, 300N) after hardening. / Mm ² or more).

The cement composition of the present invention includes cement, silica fume having a BET specific surface area of 15 to 25 m ² / g (hereinafter, may be abbreviated as “silica fume”), and inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm. (Hereinafter sometimes abbreviated as "inorganic powder"), a cement composition containing aggregate A having a maximum particle size of 1.2 mm or less, a high-performance water reducing agent, an antifoaming agent and water, wherein cement, silica fume And a total amount of inorganic powder of 100% by volume, wherein the proportion of cement is 55 to 65% by volume, the proportion of silica fume is 5 to 25% by volume, and the proportion of inorganic powder is 15 to 35% by volume.

The type of cement is not particularly limited.For example, various Portland cements such as ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderate heat Portland cement, sulfate-resistant Portland cement, low-heat Portland cement, etc. Can be used.
Above all, from the viewpoint of improving the fluidity of the cement composition, it is preferable to use moderate heat Portland cement or low heat Portland cement.

The BET specific surface area of silica fume is 15 to 25 m ² / g, preferably 17 to 23 m ² / g, particularly preferably 18 to 22 m ² / g. When the specific surface area is less than 15 m ² / g, the strength development of the cement composition is reduced. If the specific surface area exceeds 25 m ² / g, the fluidity of the cement composition before hardening is reduced.

Examples of the inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm include quartz powder (silica powder), volcanic ash, fly ash (classified or pulverized), slag powder, limestone powder, feldspar powder, and mullite. Examples include powder, alumina powder, silica sol, carbide powder, nitride powder, and pulverized emery sand (artificial or natural).
These may be used alone or in combination of two or more.
Among them, it is preferable to use quartz powder or fly ash from the viewpoint of improving the fluidity and strength development of the cement composition.
In the present specification, the inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm does not include cement.

The 50% cumulative particle size of the inorganic powder is 0.8 to 5 μm, preferably 1 to 4 μm, more preferably 1.1 to 3.5 μm, particularly preferably 1.2 μm or more and less than 3 μm. When the particle size is less than 0.8 μm, the fluidity of the cement composition decreases. When the particle size exceeds 5 μm, the strength development of the cement composition is reduced.
In the present specification, the 50% cumulative particle size of the inorganic powder is on a volume basis.
The 50% cumulative particle size of the inorganic powder can be determined using a commercially available particle size distribution analyzer (for example, product name “Microtrac HRA Model 9320-X100” manufactured by Nikkiso Co., Ltd.).
Specifically, a cumulative particle size curve is created using a particle size distribution measuring device, and a 50% cumulative particle size can be determined from the cumulative particle size curve. At this time, 0.06 g of the sample was added to 20 cm ^{3 of} ethanol, which is a solvent for dispersing the sample, and an ultrasonic dispersion device (for example, product name “US300” manufactured by Nippon Seiki Seisaku-sho, Ltd.) was used for 90 seconds. Ultrasonic dispersion is measured.

The maximum particle size of the inorganic powder is preferably 15 μm or less, more preferably 14 μm or less, and particularly preferably 13 μm or less, from the viewpoint of improving the strength development of the cement composition.
The 95% cumulative particle size of the inorganic powder is preferably 8 μm or less, more preferably 7 μm or less, particularly preferably 6 μm or less, from the viewpoint of improving the strength development of the cement composition.

As the inorganic powder, those containing SiO ₂ as a main component are preferable. When the content of SiO ₂ in the inorganic powder is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, the strength expression of the cement composition is further improved. Can be.

In the cement composition of the present invention, the cement ratio is 55 to 65% by volume (preferably 57 to 63% by volume), and the silica fume ratio is 5 to 25% in the total amount of cement, silica fume and the inorganic powder of 100% by volume. % By volume (preferably 7 to 23% by volume), and the proportion of the inorganic powder is 15 to 35% by volume (preferably 17 to 33% by volume).
When the proportion of the cement is less than 55% by volume, the strength development of the cement composition is reduced. When the proportion of the cement exceeds 65% by volume, the fluidity of the cement composition decreases.
When the proportion of silica fume is less than 5% by volume, the strength development of the cement composition is reduced. If the proportion of silica fume exceeds 25% by volume, the fluidity of the cement composition will decrease.
When the proportion of the inorganic powder is less than 15% by volume, the strength development of the cement composition is reduced. When the proportion of the inorganic powder exceeds 35% by volume, the fluidity of the cement composition decreases.

Examples of the aggregate A include river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, natural emery sand, and artificial fine aggregate (for example, slag fine aggregate, fired fine aggregate obtained by firing fly ash, etc.). And artificial emery sand, coarsely crushed alumina or carbide (for example, silicon carbide or boron carbide), recycled fine aggregate, or a mixture thereof.
The maximum particle size of the aggregate A is 1.2 mm or less, preferably 1.1 mm or less, more preferably 1.0 mm or less. When the maximum particle size is 1.2 mm or less, the strength development of the cement composition can be further improved, and a compressive strength of 300 N / mm ² or more (preferably 400 N / mm ² or more) can be exhibited. May be possible.
From the viewpoint of improving the fluidity and strength development of the cement composition, the particle size distribution of the aggregate A is such that the ratio of the aggregate having a particle diameter of 0.6 mm or less is 95% by mass or more and 0.3 mm or less. Is preferably 40 to 50% by mass, and the ratio of aggregate having a particle size of 0.15 mm or less is preferably 6% by mass or less.
The ratio of the aggregate A in the cement composition is preferably 20 to 40% by volume, more preferably 22 to 39% by volume, further preferably 25 to 38% by volume, further preferably 30 to 37% by volume, and particularly preferably. 32 to 36% by volume. When the proportion is 20% by volume or more, the fluidity of the cement composition can be improved, the calorific value of the cement composition decreases, and the shrinkage of the hardened cementitious material decreases. When the ratio is 40% by volume or less, the strength development of the cement composition can be improved.

As the high-performance water reducing agent, a high-performance water reducing agent such as a naphthalenesulfonic acid type, a melamine type, or a polycarboxylic acid type can be used. Among them, a polycarboxylic acid-based high-performance water reducing agent is preferable from the viewpoint of improving the fluidity and strength development of the cement composition.
The amount of the high-performance water reducing agent is preferably 0.2 to 1.5 parts by weight, more preferably 0.4 to 0.4 parts by weight, in terms of solids, based on 100 parts by weight of cement, silica fume and inorganic powder in total. １．２1.2 parts by mass. When the amount is 0.2 parts by mass or more, the water reducing performance is improved, and the fluidity of the cement composition is improved. When the amount is 1.5 parts by mass or less, the strength development of the cement composition is improved.

Commercial products can be used as the defoaming agent.
The compounding amount of the defoaming agent is preferably 0.001 to 0.1 part by mass, more preferably 0.01 to 0.07 part by mass, particularly 100 parts by mass of cement, silica fume and inorganic powder. Preferably it is 0.01 to 0.05 parts by mass. When the amount is 0.001 part by mass or more, the strength development of the cement composition is improved. If the amount exceeds 0.1 parts by mass, the effect of improving the strength development of the cement composition will level off.

The cement composition of the present invention usually does not contain glass fibers from the viewpoint of avoiding a decrease in long-term strength.
In addition, the cement composition of the present invention is a group consisting of a metal fiber, an organic fiber, and a carbon fiber, from the viewpoint of improving the bending strength, the breaking energy, and the like of a hardened body (hardened cementitious body) obtained by hardening the cement composition. It may include one or more fibers selected from the following. The proportion of fibers in the cement composition is preferably 3% by volume or less, more preferably 0.3 to 2.5% by volume, still more preferably 0.4 to 2.3% by volume, particularly preferably 0.5 to 2.5% by volume. 2.0% by volume. When the proportion is 3% by volume or less, the flexural strength, the breaking energy, and the like of the cured product can be improved without lowering the fluidity and workability of the cement composition.

Examples of the metal fiber include a steel fiber, a stainless steel fiber, and an amorphous fiber. Among them, steel fibers are excellent in strength, and are preferable from the viewpoint of cost and availability.
The size of the metal fiber is 0.01 to 1.0 mm in diameter and 2 to 30 mm in length from the viewpoint of preventing material separation of the metal fiber in the cement composition and improving the bending strength of the cured product. It is more preferable that the diameter is 0.05 to 0.5 mm and the length is 5 to 25 mm. Further, the aspect ratio (fiber length / fiber diameter) of the metal fiber is preferably 20 to 200, and more preferably 40 to 150.
Further, the shape of the metal fiber is preferably a shape (for example, a spiral shape or a waveform) that gives some physical adhesive force, rather than a linear shape. In the case of a shape such as a spiral shape, the metal fiber and the matrix secure the stress while being pulled out, so that the bending strength of the cured body is improved.

The organic fiber may be any one that can withstand heating in the method for producing a cementitious cured product obtained by curing the cement composition of the present invention described below, and includes, for example, aramid fiber, polyparaphenylene benzobisoxazole fiber, and polyethylene. Fiber, polyaryt fiber, polypropylene fiber and the like.
Examples of the carbon fiber include a PAN-based carbon fiber and a pitch-based carbon fiber.
The dimensions of the organic fiber and the carbon fiber are 0.005 to 1.0 mm in diameter and 2 to 30 mm in length from the viewpoint of preventing material separation of these fibers in the cement composition and improving the breaking energy of the cured product. It is more preferable that the diameter is 0.01 to 0.5 mm and the length is 5 to 25 mm. The aspect ratio (fiber length / fiber diameter) of the organic fiber and the carbon fiber is preferably 20 to 200, more preferably 30 to 150.

As the water, tap water or the like can be used.
The compounding amount of water is preferably 10 to 20 parts by mass, more preferably 12 to 18 parts by mass, and particularly preferably 14 to 16 parts by mass, based on 100 parts by mass of the total of cement, silica fume and inorganic powder. When the amount is at least 10 parts by mass, the fluidity of the cement composition will be improved. When the amount is 20 parts by mass or less, the strength development of the cement composition is improved.

The flow value of the mortar made of the cement composition (which does not contain the aggregate B described later) before curing was 15 times in the method described in “JIS R 5201 (Physical test method of cement) 11. Flow test”. Is preferably 200 mm or more, more preferably 210 mm or more, and particularly preferably 220 mm or more.
Further, the compressive strength of the cementitious hardened body obtained by hardening the mortar made of the cement composition (containing no aggregate B described later) is preferably 320 N / mm ² or more, more preferably 350 N / mm ² or more. , even more preferably 400 N / mm ² or more, and particularly preferably 450 N / mm ² or more.
The aggregate A has a modified Mohs hardness of 9 or more (preferably 9 to 14, more preferably 9 to 13, still more preferably 10 to 13, and particularly preferably 11 to 13) (for example, natural or artificial). According to a mortar made of a cement composition using (artificial) emery sand, coarsely crushed alumina or carbide, etc. (excluding aggregate B described later), 450 N / mm ² or more (especially emery sand is used) When used, it is possible to develop a compressive strength of 500 N / mm ² or more).

The cement composition of the present invention can include aggregate B having a maximum particle size of more than 1.2 mm and not more than 13 mm.
As the aggregate B, river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, natural emery sand, artificial fine aggregate (for example, artificial emery sand, slag fine aggregate, fly ash, etc. Fired fine aggregate), recycled fine aggregate, river gravel, mountain gravel, land gravel, crushed stone, artificial coarse aggregate (for example, fired coarse aggregate obtained by firing slag coarse aggregate, fly ash, etc.), Recycled coarse aggregate or a mixture thereof is mentioned.
The maximum particle size of the aggregate B is 13 mm or less, preferably 12 mm or less, more preferably 11 mm or less, and particularly preferably 10 mm or less. When the maximum particle diameter is 13 mm or less, the strength development of the cement composition is improved, and for example, a compressive strength of 300 N / mm ² or more can be developed.
Further, the maximum particle size of the aggregate B is a value exceeding 1.2 mm, preferably 3 mm or more, more preferably 5 mm or more, particularly preferably 7 mm or more from the viewpoint of cost reduction and the like.
In this specification, the “maximum particle size” when the maximum particle size of the aggregate B is 5 mm or more refers to the nominal size of the smallest sieve among the sieves through which 90% by mass or more of the entire aggregate B passes. Means the particle size of the aggregate B (generally known as the definition of the maximum particle size of the coarse aggregate).

The minimum particle size of the aggregate B is preferably a value exceeding the maximum particle size of the aggregate A, more preferably 2 mm or more, further preferably 3 mm or more, further preferably 4 mm or more, particularly preferably 5 mm or more (in this case, , Coarse aggregate).
In the present specification, the minimum particle size of the aggregate B refers to the total size of the aggregate B when the size of the aggregate B increases from the smallest particle size to the larger one. Means the particle size of the aggregate B when it reaches 15% by mass.

In the present invention, the ratio of the total amount of the aggregate A and the aggregate B in the cement composition is preferably 25 to 40% by volume, more preferably 30 to 38% by volume, and particularly preferably 32 to 36% by volume. . When the proportion is 25% by volume or more, the calorific value of the cement composition decreases and the shrinkage amount of the cementitious cured product decreases. When the proportion is 40% by volume or less, the strength development of the cement composition can be improved.
The ratio of the aggregate B to the total amount of the aggregate A and the aggregate B is preferably 40% by volume or less, more preferably 30% by volume or less. When the proportion is 40% by volume or less, the strength development (for example, compressive strength) of the cement composition can be improved.
The compressive strength of a hardened cementitious material obtained by hardening a cement composition (for example, concrete) containing the aggregate B is preferably 300 N / mm ² or more, more preferably 320 N / mm ² or more, and particularly preferably 340 N / mm. ² or more.

Hereinafter, a method for producing a cementitious cured product obtained by curing the cement composition of the present invention will be described in detail.
One example of the method for producing a cementitious cured product obtained by curing the cement composition of the present invention is a molding process in which the cement composition is cast into a mold to obtain an uncured molded product, and an uncured molding. The body is sealed or cured in air at 10 to 40 ° C. for 24 hours or more, then released from the mold to obtain a cured molded body at room temperature, and the cured molded body is heated to 70 ° C. to 100 ° C. A heat curing step of performing one or both of steam curing or hot water curing and autoclave curing at 100 to 200 ° C. for 1 hour or more for less than 1 hour, and a heat curing step of obtaining a cured body after heat curing; Is heated at 150 to 200 ° C. for at least 24 hours (excluding heating by autoclave curing) to obtain a cementitious cured body at a high temperature heating step.

[Molding process]
This step is a step of casting a cement composition into a mold to obtain an uncured molded body.
The method of kneading the cement composition of the present invention before casting is not particularly limited. The apparatus used for kneading is not particularly limited, and a conventional mixer such as an omni mixer, a pan-type mixer, a biaxial kneading mixer, and a tilting mixer can be used. Further, the casting (forming) method is not particularly limited.
In addition, the uncured molded body in this step may be made of a cement composition in which bubbles in the cement composition have been reduced or removed. By reducing or removing bubbles in the cement composition, the strength development of the cement composition can be further improved.
As a method of reducing or removing air bubbles in the cement composition, (1) a method of kneading the cement composition under reduced pressure, and (2) a method in which the kneaded cement composition is cast into a mold. A method of defoaming under reduced pressure, (3) a method of pouring the cement composition into a mold, and then defoaming under reduced pressure are exemplified.

[Normal temperature curing process]
In this step, the uncured molded body is sealed at 10 to 40 ° C. (preferably 15 to 30 ° C.) for 24 hours or more (preferably 24 to 72 hours, more preferably 24 to 48 hours), and is sealed or cured in air. Then, it is a step of removing the mold from the mold and obtaining a cured molded body.
If the curing temperature is 10 ° C. or higher, the curing time can be shortened. When the curing temperature is 40 ° C. or lower, the compressive strength of the hardened cementitious body can be improved.
If the curing time is 24 hours or longer, it becomes difficult for defects such as chipping or cracking to occur in the cured molded product during demolding.
In the present step, when the cured molded body has a compressive strength of preferably ^{20 to} 100 N / mm ² , more preferably 30 to 80 N / mm ² , the cured molded body is released from the mold. Is preferred. When the compressive strength is 20 N / mm ² or more, defects such as chipping and cracks are less likely to be generated in the cured molded product upon demolding. When the compressive strength is 100 N / mm ² or less, the cured molded body can absorb water with a small amount of labor in a water absorbing step described later.

[Heating curing process]
In this step, the cured molded article obtained in the preceding step is subjected to steam curing or hot water curing at 70 ° C. or more and less than 100 ° C. (preferably 75 to 95 ° C., more preferably 80 to 92 ° C.) for 1 hour or more. And / or 100 to 200 ° C. (preferably 160 to 190 ° C.) for one hour or more in autoclave curing to obtain a cured product after heat curing.
In this step, when only steam curing or hot water curing is performed, the curing time is preferably 12 hours or more, more preferably 24 to 96 hours, and particularly preferably 36 to 72 hours. When performing only the autoclave curing, the curing time is preferably 2 hours or more, more preferably 3 to 60 hours, and particularly preferably 4 to 48 hours. When performing both steam curing or hot water curing and autoclave curing (for example, after performing steam curing or hot water curing and then performing autoclave curing), the curing time in steam curing or hot water curing is preferably 1 to 72 hours. , More preferably 2 to 48 hours, and the curing time in the autoclave curing is preferably 1 to 24 hours, more preferably 2 to 18 hours.
In this step, if the curing temperature is within the above range, the curing time can be shortened, and the compressive strength of the hardened cementitious body can be improved.
In this step, if the curing time is within the above range, the compressive strength of the cementitious cured product can be improved.

[High temperature heating process]
In this step, the cured product after heating and curing is heated at 150 to 200 ° C. (preferably 170 to 190 ° C.) for 24 hours or more (preferably 24 to 72 hours, more preferably 36 to 48 hours), and heated (autoclave Excluding heating by curing) to obtain a cementitious cured product.
The heating in this step is usually performed under a dry atmosphere (in other words, a state in which water or steam is not artificially supplied).
When the heating temperature is 150 ° C. or higher, the heating time can be shortened. When the heating temperature is 200 ° C. or lower, the compressive strength of the hardened cementitious body can be improved.
If the heating time is 24 hours or more, the compressive strength of the hardened cementitious body can be improved.

[Water absorption process]
Between the room temperature curing step and the heating curing step, a water absorption step of causing the cured molded body obtained in the room temperature curing step to absorb water may be included.
As a method of absorbing water into the cured molded body, there is a method of immersing the molded body in water. Further, in the method of immersing the molded body in water, from the viewpoint of increasing the water absorption in a short time and increasing the compressive strength of the cementitious cured body, (1) immersing the molded body in water under reduced pressure (2) a method in which the molded body is immersed in boiling water, and the water temperature is lowered to 40 ° C. or less while the molded body is immersed; (3) the molded body is immersed in boiling water. A method in which the molded body is taken out of the boiling water after being immersed in boiling water, and then immersed in water of 40 ° C. or lower. (4) The molded body is pressed under pressure. A method of immersing the molded article in water or (5) a method of immersing the molded article in an aqueous solution in which an agent for improving the permeability of water into the molded article is dissolved is preferable.

Examples of a method of immersing the molded body in water under reduced pressure include a method using equipment such as a vacuum pump and a large-sized vacuum container.
Examples of a method of immersing the molded body in boiling water include a method using equipment such as a high-temperature and high-pressure vessel and a hot and cold water tank.
The time for immersing the cured molded body in water under reduced pressure or boiling water is preferably 3 minutes or more, more preferably 8 minutes or more, particularly preferably 20 minutes, from the viewpoint of increasing the water absorption. That is all. The upper limit of the time is preferably 60 minutes, more preferably 45 minutes, from the viewpoint of increasing the compressive strength of the hardened cementitious material.

The water absorption rate in the water absorption step is determined when the cement composition does not contain coarse aggregate (when the cement composition does not contain aggregate B or when the aggregate B in the cement composition does not correspond to coarse aggregate). As a ratio of water to 100% by volume of a cured compact of φ50 × 100 mm, preferably 0.2% by volume or more, more preferably 0.3 to 2.0% by volume, particularly preferably 0.35 to 1.7% by volume. %, And when the cement composition contains coarse aggregate (when the aggregate B in the cement composition corresponds to the coarse aggregate), the ratio of water to 100% by volume of the cured compact of φ100 × 200 mm is as follows: It is preferably at least 0.2% by volume, more preferably from 0.3 to 2.0% by volume, particularly preferably from 0.35 to 1.7% by volume.
When the water absorption is 0.2% by volume or more, the compressive strength of the hardened cementitious body can be further increased.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.
[Materials used]
Materials used are as shown below.
(1) Cement: Low heat Portland cement (manufactured by Taiheiyo Cement Corporation)
(2) Silica fume A: BET specific surface area 20 m ² / g
(3) Silica fume B: BET specific surface area 17 m ² / g
(4) Inorganic powder A: silica powder, 50% cumulative particle size 2 μm, maximum particle size 12 μm, 95% cumulative particle size 5.8 μm
(5) Inorganic powder B: silica stone powder, 50% cumulative particle diameter 7 μm, maximum particle diameter 67 μm, 95% cumulative particle diameter 27 μm
(6) Aggregate A1 (fine aggregate): silica sand (maximum particle size: 1.0 mm, particle size of 0.6 mm or less: 98% by mass, particle size of 0.3 mm or less: 45% by mass, 0%) .15 mm or less particle size: 3% by mass)
(7) Aggregate A2 (fine aggregate): artificial emery sand (manufactured by Uji Denka Kogyo Co., Ltd., modified Mohs hardness: 12) (having a maximum particle size of 1.0 mm and a particle size of 0.6 mm or less: 96% by mass) , With a particle size of 0.3 mm or less: 46% by mass, with a particle size of 0.15 mm or less: 1% by mass, the particle size distribution of which is adjusted)
(8) Polycarboxylic acid-based high-performance water reducing agent: solid content 27.4% by mass, manufactured by Floric, trade name "Floric SF500U"
(9) Defoaming agent: brand name “Master Air 404” manufactured by BASF Japan
(10) Water: tap water (11) Metal fiber: steel fiber (diameter: 0.2 mm, length: 15 mm)
(12) Aggregate B (coarse aggregate): Hard sandstone crushed stone 1005 (particle size: 5 to 10 mm)

[Example 1]
Cement, silica fume A and inorganic powder A were mixed such that each ratio of cement and the like became the ratio shown in Table 1 in a total amount of 100% by volume of the powder raw materials (cement, silica fume A and inorganic powder A). The obtained mixture and the amount of the aggregate A1 in which the ratio of the aggregate A1 in the cement composition was as shown in Table 1 were charged into an omni mixer and kneaded for 15 seconds.
Next, water, a polycarboxylic acid-based high-performance water reducing agent, and an antifoaming agent were charged into the omni mixer in the amounts shown in Table 1, and kneaded for 2 minutes.
After kneading, the kneaded matter adhering to the side wall in the omni mixer was scraped off, and kneading was further performed for 4 minutes.
The flow value of the cement composition after kneading was measured without performing the falling movement 15 times in the method described in “JIS R 5201 (Physical test method of cement) 11. Flow test”. Note that, in this specification, the flow value is referred to as a “zero hit flow value”.

The obtained kneaded material was cast into a cylindrical mold having a diameter of 50 x 100 mm to obtain an uncured molded body. After the casting, the uncured molded body was sealed and cured at 20 ° C. for 48 hours, and then demolded to obtain a cured molded body. The compressive strength at the time of demolding was 50 N / mm ² .
The molded body was immersed in water in a desiccator under reduced pressure for the time shown in Table 2 (described in Table 2 as "under reduced pressure"). In addition, pressure reduction was performed using "Aspirator (AS-01)" manufactured by AS ONE Corporation. The mass of the molded body before and after immersion was measured, and the water absorption was calculated from the measured value.
After immersion, the molded body was subjected to steam curing at 90 ° C. for 48 hours, and then cooled to 20 ° C., and then heated at 180 ° C. for 48 hours without artificially supplying water or steam.
Further, the compressive strength of the obtained cementitious cured product was measured according to “JIS A 1108 (test method for compressive strength of concrete)”. The compressive strength was measured using a 100-ton universal testing machine (hydraulic type) manufactured by Shimadzu Corporation.

[Example 2]
A cement composition and a cured product (molded product) thereof were obtained in the same manner as in Example 1, except that the amount of water per 100 parts by mass of the powder raw material was changed from 13 parts by mass to 15 parts by mass.
In the same manner as in Example 1, measurement of the zero-strike flow value of the cement composition was performed. The compressive strength at the time of demolding was 45 N / mm ² .

[Example 3]
Instead of immersing the molded body after demolding in water in a desiccator under reduced pressure, the molded body is immersed in boiling water (boiling water) for the time shown in Table 2, and the molded body is immersed in water. A cement composition and a cured product thereof were obtained in the same manner as in Example 1 except that the water temperature was cooled to 25 ° C.
In the same manner as in Example 1, calculation of the water absorption rate and measurement of the compressive strength of the hardened cementitious material were performed.
[Example 4]
Instead of immersing the molded body after demolding in water in a desiccator under reduced pressure, except that immersion in boiling water was performed in the same manner as in Example 3, the cement composition and The cured product (molded product) was obtained.
In the same manner as in Example 1, calculation of the water absorption rate and measurement of the compressive strength of the hardened cementitious material were performed.

[Example 5]
A cement composition was prepared in the same manner as in Example 1 except that the amount of silica fume A was changed from 10% by volume to 20% by volume, and the amount of inorganic powder A was changed from 30% by volume to 20% by volume. And a cured product (molded product) thereof.
In the same manner as in Example 1, measurement of a zero-strike flow value and the like were performed. In addition, the compression strength of the molded body at the time of demolding was 50 N / mm ² .
[Example 6]
Instead of immersing the molded product after demolding in water in a desiccator under reduced pressure, except that immersion in boiling water was performed in the same manner as in Example 3, the cement composition and The cured product (molded product) was obtained.
In the same manner as in Example 1, calculation of the water absorption rate and measurement of the compressive strength of the hardened cementitious material were performed.

[Example 7]
A cement composition was prepared in the same manner as in Example 2, except that the amount of silica fume A was changed from 10% by volume to 20% by volume, and the amount of inorganic powder A was changed from 30% by volume to 20% by volume. And a cured product (molded product) thereof.
In the same manner as in Example 1, measurement of a zero-strike flow value and the like were performed. In addition, the compression strength of the molded body at the time of demolding was 45 N / mm ² .
Example 8
Instead of immersing the molded product after demolding in water in a desiccator under reduced pressure, except that immersion in boiling water was performed in the same manner as in Example 3, the cement composition and The cured product (molded product) was obtained.
In the same manner as in Example 1, calculation of the water absorption rate and measurement of the compressive strength of the hardened cementitious material were performed.

[Example 9]
Cement, silica fume A and inorganic powder A were mixed such that each ratio of cement and the like became the ratio shown in Table 1 in a total amount of 100% by volume of the powder raw materials (cement, silica fume A and inorganic powder A). The obtained mixture and the amount of the aggregate A1 in which the ratio of the aggregate A1 in the cement composition was as shown in Table 1 were charged into an omni mixer and kneaded for 15 seconds.
Next, water, a polycarboxylic acid-based high-performance water reducing agent, and an antifoaming agent were charged into the omni mixer in the amounts shown in Table 1, and kneaded for 2 minutes.
After kneading, the kneaded material adhering to the side wall in the omni-mixer was scraped off, and kneading was further performed for 4 minutes. Then, the amount of the metal fiber in the cement composition that became the ratio shown in Table 1 was added to the omni-mixer. It was charged and kneaded for another 2 minutes.
With respect to the obtained cement composition, a 0-hit flow value was measured in the same manner as in Example 1.
In addition, a hardened cementitious product (molded product) was obtained in the same manner as in Example 1 using the obtained cement composition as a material.
About the obtained hardened cementitious product (molded product), the water absorption and the compressive strength were measured in the same manner as in Example 1.
Further, the flexural strength of the obtained cementitious hardened body was measured according to "JSCE-G 552-2010 (Testing method for flexural strength and flexural toughness of steel fiber reinforced concrete)".

[Example 10]
Instead of immersing the molded product after demolding in water in a desiccator under reduced pressure, except that immersion in boiling water was performed in the same manner as in Example 3, the cement composition and The cured product was obtained.
Various physical properties of the cement composition and the cured product thereof were measured in the same manner as in Example 9.

[Example 11]
The amount of water per 100 parts by mass of the powder raw material was changed from 13 parts by mass to 11 parts by mass, and the amount of aggregate A1 was changed from 35.5% by volume to 30.0% by volume. A cement composition and a hardened cementitious material were prepared in the same manner as in Example 1 except that the compounding amount of the agent was changed from 0.69 parts by mass to 0.76 parts by mass, and the molded body was not immersed in water. I got
In the same manner as in Example 1, measurement of the zero-strike flow value of the cement composition was performed. In addition, the compression strength at the time of demolding was 54 N / mm ² .

[Example 12]
Except that the molded body after demolding was immersed in boiling water (boiling water) for the time shown in Table 2, and then cooled until the water temperature became 25 ° C. while the molded body was immersed in water. In the same manner as in Example 11, a cement composition and a cured product thereof were obtained.
In the same manner as in Example 1, calculation of the water absorption and measurement of the compressive strength and the like of the hardened cementitious material were performed.

Example 13
Except that the blending amount of the aggregate A1 was changed from 30.0% by volume to 24.0% by volume, and the amount of the aggregate B in the cement composition was 6.0% by volume. Prepared a cement composition with the same composition as the cement composition of Example 11.
The production of the cement composition was carried out in the same manner as in Example 1, and after kneading each material (powder raw material, aggregate A1, water, polycarboxylic acid-based high-performance water reducing agent, and defoaming agent), the aggregate was further added. B was put into an omni mixer and kneaded for 1 minute.
The cement composition was cured in the same manner as in Example 1 except that the obtained cement composition (kneaded material) was cast into a cylindrical mold having a diameter of 100 x 200 mm and the molded body was not immersed in water. I got a body.
In the same manner as in Example 1, the compressive strength of the cementitious cured product was measured. In addition, the compression strength at the time of demolding was 43 N / mm ² .

[Example 14]
Except that the blending amount of the aggregate A1 was changed from 35.5% by volume to 28.5% by volume, and the amount of the aggregate B in which the ratio of the aggregate B in the cement composition was 7.0% by volume was used. Prepared a cement composition with the same composition as the cement composition of Example 8.
The production of the cement composition was carried out in the same manner as in Example 1, and after kneading the respective materials (powder raw material, aggregate A1, water, polycarboxylic acid-based high-performance water reducing agent, and defoaming agent), Material B was charged into an omni mixer and kneaded for 1 minute.
A cementitious cured product was obtained in the same manner as in Example 8, except that the obtained cement composition (kneaded material) was cast into a cylindrical mold having a diameter of 100 x 200 mm.
In the same manner as in Example 8, the calculation of the water absorption and the measurement of the compressive strength of the hardened cementitious material were performed. In addition, the compression strength at the time of demolding was 37 N / mm ² .

[Example 15]
A cement composition and a cured product (molded product) thereof were obtained in the same manner as in Example 4, except that the aggregate A2 was used instead of the aggregate A1.
In the same manner as in Example 1, the measurement of the 0-hit flow value and the like of the cement composition was performed. In addition, the compression strength at the time of demolding was 47 N / mm ² .

[Example 16]
A cement composition and a cured product thereof (molded product) were obtained in the same manner as in Example 12, except that the aggregate A2 was used instead of the aggregate A1.
When the 0-hit flow value and the like of the cement composition were measured in the same manner as in Example 1, the compressive strength exceeded the measurement limit of the measured value (511 N / mm ² ). In addition, the compression strength at the time of demolding was 55 N / mm ² .

[Comparative Example 1]
Cement, silica fume B and inorganic powder B were mixed such that the proportions of cement and the like in the total amount of powder raw materials (cement, silica fume B and inorganic powder B) were 100% by volume as shown in Table 1. The obtained mixture and the amount of the aggregate A1 in which the ratio of the aggregate A1 in the cement composition was as shown in Table 1 were charged into an omni mixer and kneaded for 15 seconds.
Next, water, a polycarboxylic acid-based high-performance water reducing agent, and an antifoaming agent were charged into the omni mixer in the amounts shown in Table 1, and kneaded for 2 minutes.
After kneading, the kneaded matter adhering to the side wall in the omni mixer was scraped off, and kneading was further performed for 4 minutes.
Using the obtained kneaded material as a material, a cementitious cured product was obtained in the same manner as in Example 1. Various physical properties of the obtained kneaded product (cement composition) and its cured product were measured in the same manner as in Example 1.
Table 2 shows the above results.

From Table 2, it can be seen that according to the cement composition of the present invention (Examples 1 to 16), the 0-hit flow value is 217 mm or more. In addition, the compressive strength of the cementitious cured product obtained by curing the cement composition of the present invention is 350 N / mm ² or more, which is very large.
In addition, the flexural strength of the cement composition containing metal fibers (Examples 9 to 10) was 40 N / mm ² or more, which proved to be large.
In addition, the compressive strength of the cement composition (Examples 15 and 16) using the fine aggregate having a modified Mohs hardness of 12 is 500 N / mm ² or more, which is extremely large.
Furthermore, the compressive strength of the cementitious hardened material obtained by hardening the cement composition containing coarse aggregate (Examples 13 and 14) is 333 N / mm ² or more, which indicates that it is large.
On the other hand, in Comparative Example 1, the compressive strength of the hardened cementitious body was 290 N / mm ^2, which is smaller than Examples 1 to 16.

Claims (5)

Cement, silica fume having a BET specific surface area of 15 to 25 m ² / g, inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm, aggregate A having a maximum particle size of 1.2 mm or less, a high-performance water reducing agent, and defoaming agent and water only contains, and a cement composition containing no coarse aggregate,
In the total amount of 100% by volume of the cement, the silica fume and the inorganic powder, the proportion of the cement is 55 to 65% by volume, the proportion of the silica fume is 5 to 25% by volume, and the proportion of the inorganic powder is 15 to 35% by volume. And
The cement, the silica fume and the amount of the water with respect to 100 parts by mass of the total amount of the inorganic powder is 11 to 15 parts by mass,
The inorganic powder is quartz powder,
A ratio of the aggregate A in the cement composition is 20 to 40% by volume,
Compressive strength of the cement composition after curing is 400 N / mm ² or more;
The flow value of the cement composition before hardening is 200 mm or more as a value measured without performing a dropping motion 15 times in the method described in “JIS R 5201 (Physical test method of cement) 11. Flow test”. cement composition characterized by it. Cement, silica fume having a BET specific surface area of 15 to 25 m ² / g, inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm, aggregate A having a maximum particle size of 1.2 mm or less, and a maximum particle size of 13 mm or less A cement composition comprising an aggregate B that is a coarse aggregate, a high-performance water reducing agent, an antifoaming agent, and water,
In the total amount of 100% by volume of the cement, the silica fume and the inorganic powder, the proportion of the cement is 55 to 65% by volume, the proportion of the silica fume is 5 to 25% by volume, and the proportion of the inorganic powder is 15 to 35% by volume. And
The cement, the silica fume and the amount of the water with respect to 100 parts by mass of the total amount of the inorganic powder is 11 to 15 parts by mass,
The inorganic powder is quartz powder,
A ratio of the aggregate A in the cement composition is 20 to 36% by volume,
The ratio of the total amount of the aggregate A and the aggregate B in the cement composition is 25 to 40% by volume,
A cement composition characterized by having a compressive strength after curing of the cement composition of 300 N / mm ² or more . 3. The cement composition according to claim 1, wherein the cement composition does not contain glass fibers. The cement composition, metal fibers, comprising one or more fibers selected from the group consisting of organic fibers and carbon fibers, the proportion of the fibers of the cement composition is, according to claim 1 to 3 is more than 3% by volume The cement composition according to any one of the above. The cement composition according to any one of claims 1 to 4 , wherein the modified Mohs hardness of the aggregate A is 9 or more.