JP6713347B2 - Cement board and manufacturing method thereof - Google Patents

Description

The present invention relates to a cement board and a method for manufacturing the same.

Hydraulic structures that are exposed to running water or waves containing sand grains (for example, apron parts of sabo dams, spillways, open channels, and surface parts of dikes, etc.), and passage of vehicles and pedestrians, luggage A plate-shaped member having excellent wear resistance is used in the construction or repair of structures that are often transported (for example, pavements, decks, floating floors, etc.).
For example, in Patent Document 1, as a cementitious reinforcing plate capable of improving wear resistance of concrete products, concrete structures, asphalt structures, etc., at least cement, pozzolanic fine powder, and fine aggregate having a particle size of 2 mm or less , A water-reducing agent, and a cured product of a compound containing water.
As a use of the cured product of the above-mentioned mixture described in Patent Document 1, Patent Document 2 describes a reinforcing plate for floor slabs, and Patent Document 3 applies it to an existing concrete pier. The seismic reinforcement panel of is described.

JP, 2003-267764, A JP, 2001-248112, A JP 2001-279933 A

The compressive strength of the compound for the reinforcing plate in the examples described in Patent Documents 1 and 2 described above is 210 to 230 MPa. Moreover, the compressive strength of the compound for earthquake-proof reinforcement panels described in patent document 3 is 170-200 MPa.
In this respect, if there is a cement board having greater compressive strength and excellent in abrasion resistance, water impermeability, freeze-thaw resistance, and salt impermeability, a structure constructed using the cement board The frequency of repairs and reinforcements can be reduced, and when the cement board is used as a reinforcement board, the abrasion resistance, water impermeability, freeze-thaw resistance, and salt barrier of existing structures can be further improved. be able to. Furthermore, it is possible to recover or significantly improve the mechanical performance of the existing structure, which has deteriorated due to aging deterioration or the like.
Therefore, an object of the present invention is to provide a cement board having a large compressive strength and excellent abrasion resistance, water impermeability, freeze-thaw resistance, and salt impermeability.

MEANS TO SOLVE THE PROBLEM As a result of earnestly studying in order to solve the said subject, this inventor has cement, silica fume of BET specific surface area 15-25 m< ² >/g, 50% volume cumulative particle diameter inorganic powder 0.8-5 micrometers, maximum particle. Includes aggregate A with a diameter of 1.2 mm or less, high-performance water reducing agent, defoaming agent, and water, and the ratio of cement, silica fume, and inorganic powder is specified in 100% by volume of the total amount of cement, silica fume, and inorganic powder. It was found that the above object can be achieved by a cement board obtained by curing a cement composition within the numerical range of, and the present invention has been completed.

That is, the present invention provides the following [1] to [11].
[1] A cement plate made of a cementitious hardened material, wherein the hardened cementitious material is cement, silica fume having a BET specific surface area of 15 to 25 m ² /g, and a 50% volume cumulative particle diameter of 0.8 to 5 μm. Inorganic powder, aggregate A having a maximum particle size of 1.2 mm or less, a high-performance water reducing agent, a defoaming agent, and water, and in the total amount of 100% by volume of the cement, the silica fume, and the inorganic powder, A cement board obtained by curing a cement composition having a proportion of 55 to 65% by volume, a proportion of the silica fume of 5 to 25% by volume, and a proportion of the inorganic powder of 15 to 35% by volume. ..
[2] Coarse particles having a particle size of 20 μm or more, which is obtained by polishing the particles constituting the medium heat Portland cement or the low heat Portland cement, and transforming the angular surface portion into a rounded shape, and A fine particle having a particle size of less than 20 μm generated by the polishing treatment, a 50% volume cumulative particle size of 10 to 18 μm, and a Blaine specific surface area of 2,100 to 2,900 cm ² /g. The described cement board.
[3] The cement composition contains one or more fibers selected from the group consisting of metal fibers, organic fibers and carbon fibers, and the proportion of the fibers in the cement composition is 3% by volume or less. The cement board according to [1] or [2].
[4] The cement board according to any one of the above [1] to [3], wherein the cemented hardened product has a compressive strength of 330 N/mm ² or more.
[5] The cement board according to any one of [1] to [3], wherein the cement composition contains aggregate B having a maximum particle size of more than 1.2 mm and 13 mm or less.
[6] The cement board according to the above [5], wherein the hardened cementitious material has a compressive strength of 300 N/mm ² or more.
[7] The cement board according to any one of [1] to [6], wherein the cement board is a wear-resistant board.
[8] The cement board according to any one of [1] to [6], wherein the cement board is a reinforcing board.

[9] A method for producing the cement board according to any one of [1] to [8], wherein the cement composition is cast in a mold to obtain an uncured molded body. A molding step, and a room temperature curing step of obtaining a cured molded article by demolding from the mold after subjecting the uncured molded article to sealing curing or air curing at 10 to 40° C. for 24 hours or more; For the cured molded body, either or both of steam curing or warm water curing at 70° C. or higher and lower than 100° C. for 6 hours or longer, and autoclave curing at 100 to 200° C. for 1 hour or longer, or both, and a cured body after heat curing And a high-temperature heating step of obtaining the cement board by heating the cured product after heating and curing at 150 to 200° C. for 24 hours or more (excluding heating by autoclave curing). A method for manufacturing a cement board, comprising:
[10] The method for producing a cement board according to the above [9], including a water absorption step of allowing the cured molded body to absorb water between the room temperature curing step and the heat curing step.
[11] The method for producing a cement plate according to the above [9] or [10], wherein the cement plate is a wear-resistant plate or a reinforcing plate.

The cement board of the present invention has a large compressive strength, and has abrasion resistance, water impermeability, freeze-thaw resistance, and salt impermeability (for example, chloride ion, sulfate ion, etc. hardly penetrate into the cement board). ) Is excellent.

It is a perspective view showing an example of a cement board of the present invention. FIG. 3 is a front view of an example of a high-speed airflow stirring device, which partially includes a cross section cut in a direction perpendicular to the rotation axis of the rotor. 28 is a side view of a test body b including a concrete beam and a reinforcing plate in Example 28. FIG. It is sectional drawing which shows the state which cut|disconnected the concrete beam shown in FIG. 3 vertically by the AA line about the test bodies (a)-(d) in Example 28.

Cement board of the present invention is a cement board comprising a cementitious hardened body, cementitious cured product, cement, BET specific surface area of 15~25m 2 / ^g silica fume (hereinafter, may be abbreviated to "silica fume" .), an inorganic powder having a 50% volume cumulative particle diameter of 0.8 to 5 μm (hereinafter sometimes abbreviated as “inorganic powder”), and an aggregate A having a maximum particle diameter of 1.2 mm or less (hereinafter, “bone”). Material A"), a high-performance water reducing agent, a defoaming agent and water, and the cement content is 55 to 65 volume% in the total amount of 100 volume% of cement, silica fume and inorganic powder, silica fume. Is a cement composition having a ratio of 5 to 25% by volume and a ratio of inorganic powder of 15 to 35% by volume.

The type of cement is not particularly limited, for example, ordinary Portland cement, early strength Portland cement, ultra early strength Portland cement, moderate heat Portland cement, sulfate resistant Portland cement, low heat Portland cement and other various Portland cement. Can be used.
Above all, it is preferable to use medium heat Portland cement or low heat Portland cement from the viewpoint of improving the fluidity of the cement composition.

Further, from the viewpoint of improving the fluidity of the cement composition and increasing the compressive strength of the hardened cementitious material, as the cement, the particles constituting the medium heat Portland cement or the low heat Portland cement are subjected to a polishing treatment, and are angular. A coarse particle having a particle size of 20 μm or more formed by deforming the surface portion into a rounded shape, and fine particles having a particle size of less than 20 μm generated by the polishing treatment, and having a 50% volume cumulative particle size of 10 to 18 μm, and It is more preferable to use cement having a Blaine specific surface area of 2,100 to 2,900 cm ² /g (hereinafter, also referred to as “cement polishing product”).

The upper limit of the particle size of the coarse particles is not particularly limited, but is usually 200 μm or less in consideration of the general particle size of the cement to be polished, which increases the compressive strength of the cementitious hardened product. From the viewpoint, it is preferably 100 μm or less.
The lower limit of the particle size of the fine particles is not particularly limited, but from the viewpoint of improving the fluidity of the cement composition, and improving the workability in producing a cement plate, preferably 0.1 μm or more, More preferably, it is 0.5 μm or more.

Regarding the cement polishing product, the 50% volume cumulative particle diameter is preferably 10 to 18 μm, more preferably 12 to 16 μm, and the Blaine specific surface area is preferably 2,100 to 2,900 cm ² /g, more preferably Is 2,200 to 2,700 cm ² /g.
When the 50% volume cumulative particle diameter is 10 μm or more, the fluidity of the cement composition is improved. When the 50% volume cumulative particle size is 18 μm or less, the compressive strength of the cementitious hardened body becomes higher.
When the Blaine specific surface area is 2,100 cm ² /g or more, the compressive strength of the cementitious hardened product becomes higher. When the Blaine specific surface area is 2,900 cm ² /g or less, the fluidity of the cement composition is improved.

The above-mentioned polishing treatment may be performed by using a known polishing treatment apparatus capable of polishing particles constituting cement (moderate heat Portland cement or low heat Portland cement). Examples of the polishing apparatus include a commercially available high-speed airflow stirring apparatus (for example, manufactured by Nara Machinery Co., Ltd., trade name "Hybridizer NHS-3 type").
Hereinafter, the high-speed airflow stirring device will be described in detail with reference to FIG.
Cement, which is a raw material, is input from the input port 14 in the upper part of the high-speed airflow stirring device 10 with the opening/closing valve 18 opened. After the charging, the on-off valve 18 is closed.
The injected cement enters the circulation circuit 13 through an opening provided in the middle of the circulation circuit 13, and then enters the collision chamber 17 which is a space for accommodating an object to be treated from an outlet 13b of the circulation circuit 13. ..
After charging the raw material, by rotating the rotor (rotating body) 11 arranged inside the stator 16 which is a fixed body at a high speed, a high-speed airflow is generated by the rotor 11 and the blade 12 fixed to the rotor 11, The cement in the collision chamber 17 is agitated. During the stirring, the particles forming the cement enter the circulation circuit 13 from the inlet 13a of the circulation circuit 13 provided in the collision chamber 17, and the outlet of the circulation circuit 13 provided in the central portion of the collision chamber 17. It is circulated by being charged again into the collision chamber 17 from 13b.
In addition, in FIG. 2, an arrow indicated by a dotted line indicates a flow of particles (including particles constituting cement, and coarse particles and fine particles generated by the polishing treatment).

By stirring, the particles constituting the cement collide with the inner wall surface of the collision chamber 17, the rotor 11 and the blade 12, and the particles constituting the cement collide with each other, whereby the particles constituting the cement are polished, Coarse particles (particles having a particle size of 20 μm or more) in which angular portions of the particle surface are changed to a rounded shape and fine particles (particles having a particle size of less than 20 μm) are generated.

The rotation speed of the rotor 11 is preferably 3,000 to 4,200 rpm, more preferably 3,500 to 4,000 rpm. When the rotation speed is 3,000 rpm or more, the fluidity of the cement composition is improved. When the rotation speed exceeds 4,200 rpm, the effect of improving the fluidity of the cement composition reaches a ceiling. Further, it is difficult for the rotation speed to exceed 4,200 rpm from the viewpoint of the performance of the high-speed airflow stirring device.
The polishing treatment time is preferably 10 to 60 minutes, more preferably 20 to 50 minutes, further preferably 20 to 40 minutes, and particularly preferably 20 to 30 minutes. When the time is 10 minutes or more, the fluidity of the cement composition is improved. When the time exceeds 60 minutes, the effect of improving the fluidity of the cement composition reaches a ceiling.
The obtained polished product (mixture of coarse particles and fine particles) is discharged from the discharge port 15 by opening the discharge valve 19.

The BET specific surface area of silica fume is 15 to 25 m ² /g, preferably 17 to 23 m ² /g, and particularly preferably 18 to 22 m ² /g. If the specific surface area is less than 15 m ² /g, the compressive strength of the cementitious hardened product will decrease. If the specific surface area exceeds 25 m ² /g, the fluidity of the cement composition will decrease.

Examples of the inorganic powder having a 50% volume cumulative particle diameter of 0.8 to 5 μm include quartz powder (silica powder), volcanic ash, and fly ash (classified or crushed), slag powder, limestone powder, feldspar powder, Examples include mullite powder, alumina powder, silica sol, carbide powder, nitride powder and the like.
These may be used alone or in combination of two or more.
Above all, it is preferable to use quartz powder or fly ash from the viewpoint of improving the fluidity of the cement composition and increasing the compressive strength of the hardened cementitious material.
In addition, in the present specification, cement is not included in the inorganic powder having a 50% volume cumulative particle diameter of 0.8 to 5 μm.

The 50% volume cumulative particle diameter of the inorganic powder is 0.8 to 5 μm, preferably 1 to 4 μm, more preferably 1.1 to 3.5 μm, and particularly preferably 1.2 μm or more and less than 3 μm. If the particle size is less than 0.8 μm, the fluidity of the cement composition will decrease. When the particle size exceeds 5 μm, the compressive strength of the hardened cementitious material is reduced.
The 50% volume cumulative particle size of the inorganic powder can be determined using a commercially available particle size distribution measuring device (for example, product name "Microtrac HRA Model 9320-X100" manufactured by Nikkiso Co., Ltd.).
Specifically, a cumulative particle size curve can be created using a particle size distribution measuring device, and the 50% volume 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 Seisakusho Co., Ltd.) was used for 90 seconds. Measure what is ultrasonically dispersed.

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 further increasing the compressive strength of the hardened cementitious material.
The 95% volume cumulative particle diameter of the inorganic powder is preferably 8 μm or less, more preferably 7 μm or less, and particularly preferably 6 μm or less, from the viewpoint of further increasing the compressive strength of the cementitious hardened body.

As the inorganic powder, one containing SiO ₂ as a main component (for example, quartz powder) is 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 cemented hardened product has a higher compressive strength.

In the cement composition, in the total amount of 100% by volume of cement, silica fume and inorganic powder, the proportion of cement is 55 to 65% by volume (preferably 57 to 63% by volume), and the proportion of silica fume is 5 to 25% by volume (preferably Is 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 cement is less than 55% by volume, the compressive strength of the hardened cementitious material is reduced. When the proportion of 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 compressive strength of the cementitious hardened product 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 compressive strength of the hardened cementitious material is lowered. If the proportion of the inorganic powder exceeds 35% by volume, the fluidity of the cement composition will decrease.

As the aggregate A, river sand, land sand, sea sand, crushed sand, silica sand, natural emery sand, artificial fine aggregate (for example, slag fine aggregate, burned fine aggregate obtained by firing fly ash, artificial Examples include (manufactured) emery sand, coarsely pulverized alumina or carbide (for example, silicon carbide, boron carbide, etc.), 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, and particularly preferably 1.0 mm or less. When the maximum particle size is 1.2 mm or less, the compressive strength of the cementitious hardened product becomes high.
From the viewpoint of improving the fluidity of the cement composition and increasing the compressive strength of the cementitious hardened material, the particle size distribution of the aggregate A is such that the proportion of the aggregate having a particle size of 0.6 mm or less is 95% by mass or more, It is preferable that the proportion of the aggregate having a particle diameter of 0.3 mm or less is 40 to 50% by mass, and the proportion of the aggregate having a particle diameter of 0.15 mm or less is 6% by mass or less.
The proportion of aggregate A in the cement composition is preferably 20 to 40% by volume, more preferably 22 to 38% by volume, further preferably 30 to 37% by volume, and particularly preferably 32 to 36% by volume. When the ratio is 20% by volume or more, the amount of heat generated by the cement composition becomes small and the amount of shrinkage of the hardened cementitious material becomes small. When the proportion is 40% by volume or less, the compressive strength of the hardened cementitious material becomes higher.

As the high-performance water reducing agent, a high-performance water reducing agent such as naphthalene sulfonic acid-based, melamine-based, polycarboxylic acid-based can be used. Among them, a polycarboxylic acid-based high-performance water reducing agent is preferable from the viewpoint of improving the fluidity of the cement composition and increasing the compressive strength of the hardened cementitious material.
The blending amount of the high-performance water reducing agent is preferably 0.2 to 1.5 parts by mass, more preferably 0.4 to 0.4 parts by mass, based on 100 parts by mass of the total amount of cement, silica fume and inorganic powder. ~1.2 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 compressive strength of the hardened cementitious material becomes higher.

A commercial item can be used as an antifoaming agent.
The content 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 preferably 0.01 to 0.07 part by mass, relative to 100 parts by mass of the total amount of cement, silica fume and inorganic powder. It is preferably 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. When the amount exceeds 0.1 part by mass, the effect of improving the strength development of the cement composition reaches a ceiling.

The cement composition may contain one or more fibers selected from the group consisting of metal fibers, organic fibers and carbon fibers from the viewpoint of improving the bending strength and fracture energy of the cementitious hardened body. When the cement board of the present invention is used as a reinforcing board for recovering or improving the mechanical performance of an existing structure that has been deteriorated due to aging or the like, the cement composition preferably contains metal fibers.
The proportion of fibers in the cement composition is preferably 3% by volume or less, more preferably 0.3 to 2.5% by volume, and particularly preferably 0.5 to 2.3% by volume. When the ratio is 3% by volume or less, it is possible to improve the bending strength and breaking energy of the hardened cementitious material without lowering the fluidity and workability of the cement composition.

Examples of metal fibers include steel fibers, stainless fibers, and amorphous fibers. Among them, steel fiber is excellent in strength, and is suitable from the viewpoint of cost and availability.
The dimension 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 the material separation of the metal fiber in the cement composition and improving the bending strength of the cementitious hardened body. It is preferable that the diameter is 0.05 to 0.5 mm and the length is 5 to 25 mm. The aspect ratio (fiber length/fiber diameter) of the metal fiber is preferably 20 to 200, more preferably 40 to 150.
Furthermore, the shape of the metal fiber is preferably a shape (for example, a spiral shape or a corrugated shape) that imparts some physical adhesive force, rather than a linear shape. In the case of a spiral shape or the like, the metal fibers and the matrix secure the stress while pulling out, so that the bending strength of the hardened cementitious material is improved.

The organic fiber may be one that can withstand heating in the method for manufacturing a cement plate of the present invention described below, and examples thereof include aramid fiber, polyparaphenylene benzobisoxazole fiber, polyethylene fiber, polyaryto fiber, and polypropylene fiber. To be
Examples of carbon fibers include PAN-based carbon fibers and pitch-based carbon fibers.
The dimensions of the organic fiber and the carbon fiber are 0.005 to 1.0 mm in diameter and 2 in length from the viewpoint of preventing material separation of these fibers in the cement composition and improving fracture energy of the cementitious hardened material. It is preferably ˜30 mm, more preferably 0.01 to 0.5 mm in diameter and 5 to 25 mm in length. 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 water, tap water or the like can be used.
The blending amount of water is preferably 10 to 20 parts by mass, more preferably 11 to 18 parts by mass, and particularly preferably 14 to 16 parts by mass with respect to 100 parts by mass of the total amount of cement, silica fume and inorganic powder. When the amount is 10 parts by mass or more, the fluidity of the cement composition is improved. When the amount is 20 parts by mass or less, the compressive strength of the hardened cementitious material becomes higher.

The flow value before curing of the mortar (which does not include aggregate B described later) composed of the above-mentioned cement composition is 15 times in the method described in "JIS R 5201 (Physical test method for cement) 11. Flow test". The value (hereinafter, also referred to as “0 hitting flow value”) measured without performing the drop motion of is preferably 200 mm or more, more preferably 210 mm or more, and particularly preferably 220 mm or more.
When the flow value is 200 mm or more, workability in manufacturing a cement board can be improved.
The compressive strength of the cementitious cured body formed by curing a mortar made of the cement composition (containing no aggregate B to be described later) is preferably 330N / mm ² or more, more preferably 350 N / mm ² or more , more preferably 370N / mm ² or more, and particularly preferably 400 N / mm ² or more.
The aggregate A has a modified Mohs hardness of 9 or more (preferably 9 to 14, more preferably 10 to 13, and particularly preferably 11 to 13) (for example, natural or artificial (artificial) emery sand, According to the mortar (which does not include the aggregate B described later) made of a cement composition using alumina or a coarsely pulverized carbide, it is possible to set the compressive strength of the cementitious hardened body to 450 N/mm ² or more. it can. In particular, with natural or artificial (artificial) emery sand, the compressive strength of the cementitious hardened body can be set to 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 13 mm or less.
As the aggregate B, river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, natural emery sand artificial fine aggregate (for example, slag fine aggregate, burned fine aggregate obtained by burning fly ash, etc.) , Recycled fine aggregate, river gravel, mountain gravel, land gravel, crushed stone, artificial coarse aggregate (for example, slag coarse aggregate, fired coarse aggregate obtained by firing fly ash, etc., artificial emery sand), recycled Examples thereof include coarse aggregate or a mixture thereof.
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 size is 13 mm or less, strength development of the cement composition is improved, and for example, compression strength of 300 N/mm ² or more can be expressed.
Further, the maximum particle diameter 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 the present specification, the "maximum particle size" in the case where the maximum particle size of the aggregate B is 5 mm or more means the nominal size of the smallest size sieve among the sieves through which 90% by mass or more of the entire aggregate B passes. The particle size of the aggregate B represented by (is generally known as the definition of the maximum particle size of 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, , Which corresponds to coarse aggregate).
In the present specification, the minimum particle size of the aggregate B means the aggregate B as a whole when the particles having the smallest particle size in the aggregate B are accumulated from the smallest particle size to the largest particle size. The particle size of the aggregate B when it reaches 15% by mass.

In the present invention, the ratio of the total amount of aggregate A and aggregate B in the cement composition is preferably 25 to 40% by volume, more preferably 28 to 38% by volume, and particularly preferably 30 to 36% by volume. .. When the proportion is 25% by volume or more, the calorific value of the cement composition becomes small and the shrinkage amount of the cementitious hardened body becomes small. When the ratio 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, and particularly preferably 25% by volume or less. When the ratio is 40% by volume or less, the strength developing property (for example, compressive strength) of the cement composition can be improved.
The compressive strength of a cementitious hardened body obtained by hardening a cement composition containing aggregate B (for example, concrete) is preferably 300 N/mm ² or more, more preferably 320 N/mm ² or more, and further preferably 340 N/mm. ² or more, particularly preferably 360 N/mm ² or more.

Hereinafter, a method for producing a cement board made of a cementitious hardened body obtained by hardening the above-mentioned cement composition will be described in detail.
An example of the method for producing a cement plate of the present invention is a molding step of placing a cement composition in a mold to obtain an uncured molded body, and an uncured molded body at 10 to 40° C. for 24 hours. As described above, the normal temperature curing step of removing the mold from the mold to obtain a cured molded body after the sealing curing or the air curing, and the cured molded body, steam curing or hot water for 6 hours or more at 70° C. or higher and less than 100° C. One or both of curing and autoclave curing at 100 to 200° C. for 1 hour or more to obtain a cured body after heating curing, and a cured body after heating curing at 150 to 200° C. for 24 hours. It includes a high-temperature heating step of heating for at least time (however, excluding heating by autoclave curing) to obtain a cement plate composed of a cementitious hardened product.

[Molding process]
In this step, the cement composition is cast in a mold to obtain an uncured molded body.
The method of kneading the cement composition before performing the casting is not particularly limited. The device used for kneading is also not particularly limited, and a conventional mixer such as an omni mixer, a pan mixer, a twin-screw kneading mixer, or a tilting mixer can be used. Furthermore, the driving (molding) method is not particularly limited.
In addition, the uncured molded body in this step may be made of a cement composition in which air bubbles in the cement composition are reduced or removed. By reducing or removing air bubbles in the cement composition, the strength development of the cement composition can be further improved.
As a method for reducing or removing air bubbles in the cement composition, (1) a method of kneading the cement composition under reduced pressure, (2) before placing the cement composition after kneading in a mold Examples include a method of depressurizing and defoaming, and (3) a method of placing a cement composition in a mold and then depressurizing and defoaming.

[Normal temperature curing process]
In this step, the uncured molded body is treated at 10 to 40° C. (preferably 15 to 30° C.) for 24 hours or more (preferably 24 to 96 hours, more preferably 24 to 72 hours, particularly preferably 24 to 48 hours). ), sealing and curing in air, and then removing from the mold to obtain a cured molded body.
When 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 material (cement plate) can be further increased.
If the curing time is 24 hours or more, defects such as chipping and cracks are less likely to occur in the cured molded body during demolding.
Further, in this step, when the cured molded body develops 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 cracks and cracks are less likely to occur in the cured molded body during demolding. When the compressive strength is 100 N/mm ² or less, the cured molded article can be made to absorb water with less labor in the water absorption step described later.

[Heating and curing process]
In this step, with respect to the cured molded article obtained in the previous step, steam curing or warm water curing at 70°C or higher and lower than 100°C (preferably 75 to 95°C, more preferably 80 to 92°C) for 6 hours or longer, This is a step of performing one or both of autoclave curing at 100 to 200° C. (preferably 160 to 190° C.) for 1 hour or more to obtain a cured product after heat curing.
In this step, when only steam curing or warm water curing is performed, the curing time is preferably 24 hours or more, more preferably 24 to 96 hours, and particularly preferably 36 to 72 hours. When only autoclave curing is performed, the curing time is preferably 8 to 60 hours, more preferably 12 to 48 hours. When performing both steam curing or warm water curing and autoclave curing (for example, after performing steam curing or warm water curing and then performing autoclave curing), the curing time in steam curing or warm water curing is preferably 6 to 72 hours. , More preferably 12 to 48 hours, and the curing time in autoclave curing is preferably 1 to 24 hours, more preferably 4 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 material can be improved.
Further, in this step, if the curing time is within the above range, the compressive strength of the hardened cementitious material 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 longer (preferably 24 to 72 hours, more preferably 36 to 48 hours) (however, autoclave). This is a step of obtaining a cement board made of a cementitious hardened body obtained by hardening the cement composition by heating).
The heating in this step is usually performed in 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 material can be further increased.
If the heating time is 24 hours or more, the compressive strength of the cementitious hardened product can be further increased.

[Water absorption process]
Between the normal temperature curing step and the heat curing step, a water absorption step may be included in which the cured molded body obtained in the normal temperature curing step absorbs water.
Examples of the method of allowing the cured molded body to absorb water include 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 amount and increasing the compressive strength of the cementitious hardened body in a short time, (1) immersing the molded body in water under reduced pressure A method of (2) immersing the molded body in boiling water, and then lowering the water temperature to 40° C. or lower with the molded body immersed, or (3) the molded body Is immersed in boiling water, the molded body is taken out of the boiling water, and then immersed in water at 40° C. or lower, (4) the molded body is pressurized. The method of immersing the molded body in (5) or the method of (5) immersing the molded body in an aqueous solution in which a drug that improves the permeability of water to the molded body is dissolved.

Examples of the method of immersing the above-mentioned molded body in water under reduced pressure include a method of using equipment such as a vacuum pump and a large-sized reduced pressure container.
As a method of immersing the above-mentioned molded body in boiling water, a method of using equipment such as a high-temperature and high-pressure container and a hot water bath can be mentioned.
The time for immersing the above-mentioned molded product in water under reduced pressure or boiling water is preferably 3 minutes or more, more preferably 8 minutes or more, particularly preferably 20 minutes or more from the viewpoint of increasing the water absorption. Is. The upper limit of the time is not particularly limited, but is preferably 60 minutes, more preferably 45 minutes from the viewpoint of further increasing the compressive strength of the cementitious hardened product.

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), the water absorption rate in the water absorption step is The proportion of water with respect to 100% by volume of a cured molded body of φ50×100 mm is 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), as the ratio of water to 100% by volume of the cured molded body of φ100×200 mm, It is preferably 0.2% by volume or more, more preferably 0.3 to 2.0% by volume, and particularly preferably 0.35 to 1.7% by volume.
When the water absorption is 0.2 vol% or more, the compressive strength of the cementitious hardened product can be further increased.

Since the cement board of the present invention is made of a cementitious hardened material having high compressive strength, cracks and the like are unlikely to occur. Moreover, the thickness of the cement board can be reduced, and in this case, the weight of the cement board can be reduced. Further, usually, the higher the compressive strength is, the more excellent the abrasion resistance is. Therefore, the cement plate made of the cementitious hardened body is excellent in the abrasion resistance.
In addition, the grinding depth after 60 minutes, measured according to "ASTM C779" of the cementitious hardened material, is preferably 0.5 mm or less, more preferably 0.4 mm or less, and particularly preferably 0.3 mm. It is below, and the cement board which consists of this cementitious hardened material is excellent in abrasion resistance.

Further, the cement board of the present invention is excellent in water impermeability, freeze-thaw resistance, and salt impermeability.
Furthermore, when the hardened cement material contains fibers, the hardened cement material was measured according to "JSCE-G 552-2010 (bending strength and bending toughness test method of steel fiber reinforced concrete)" of the Japan Society of Civil Engineers. , flexural strength is preferably 20 N / mm ² or more, more preferably 30 N / mm ² or more, particularly preferably 35N / mm ² or more, cement board made of the cementitious cured body has a high bending strength.

Since the cement board of the present invention has high compressive strength and excellent wear resistance, water impermeability, freeze-thaw resistance, and salt impermeability, high compressive strength and excellent wear resistance are required. It is suitable as a member (for example, a wear resistant plate or a reinforcing plate) used for constructing, repairing, or reinforcing a structure.
Specifically, seawater protection plates for coastal areas, apron parts of sabo dams, spillways, open channels, surface parts such as levees, and steel pillars (for lighting, signs, etc.) It can be used for protective plates, pavements, decks, floating floors, etc. that are installed in the vicinity.
Further, the cement board of the present invention can also be used as a reinforcing board for recovering or improving the mechanical performance of an existing structure, which has been deteriorated due to deterioration over time. When the cement board of the present invention is used as a reinforcing board, the mechanical performance of an existing structure can be significantly improved.
In addition, in this specification, a "repair plate" is also included in the "reinforcing plate".
Further, the cement board of the present invention can be fixed to an existing structure by using an adhesive such as an epoxy resin or a bolt.

The shape of the cement board of the present invention is not particularly limited, and may be appropriately determined according to the shape of the structure to be constructed, repaired or reinforced using the cement board, from the viewpoint of versatility, It may be a rectangular (square or rectangular) plate like the cement plate 1 shown in FIG. From the viewpoint of workability and cost, the length of one side of the rectangular cement plate 1 is usually 10 to 200 cm. Further, the thickness of the cement plate 1 is preferably 3 mm or more, more preferably 5 mm or more, particularly preferably 10 mm or more from the viewpoint of wear resistance and strength, and from the viewpoint of improving workability by weight reduction, It is 100 mm or less, more preferably 50 mm or less, and particularly preferably 30 mm or less.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.
[Materials used]
The materials used in Examples 1 to 15 and Comparative Example 1 are as shown below.
(1) Cement: Low-heat Portland cement (manufactured by Taiheiyo Cement)
(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% volume cumulative particle size 2 μm, maximum particle size 12 μm, 95% volume cumulative particle size 5.8 μm
(5) Inorganic powder B: silica powder, 50% volume cumulative particle size 7 μm, maximum particle size 67 μm, 95% volume cumulative particle size 27 μm
(6) Aggregate A1 (fine aggregate): Quartz 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 Particle diameter of less than 15 mm: 3% by mass)
(7) Polycarboxylic acid-based high-performance water reducing agent: solid content 27.4% by mass, manufactured by Floric, trade name "Floric SF500U"
(8) Defoaming agent: manufactured by BASF Japan Ltd., product name "Master Air 404"
(9) Water: Tap water (10) Metal fiber: Steel fiber (diameter: 0.2 mm, length: 15 mm)
(11) Aggregate B (coarse aggregate): crushed hard sandstone 1005 (particle size: 5 to 10 mm)

[Example 1]
Cement, silica fume A and inorganic powder A were mixed so that the respective ratios of cement and the like would be the ratios shown in Table 2 in the total amount 100% by volume of the powder raw materials (cement, silica fume and inorganic powder). The obtained mixture and the aggregate A1 in an amount such that the ratio of the aggregate A1 in the cement composition is the ratio shown in Table 2 were put 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 added to the omni mixer in the amounts shown in Table 2 and kneaded for 2 minutes.
After the kneading, the kneaded material adhering to the side wall inside the omni mixer was scraped off, and the kneading was further performed for 4 minutes.
The flow value of the cement composition after kneading was measured by the method described in "JIS R 5201 (Physical test method for cement) 11. Flow test" without performing 15 drop motions. In addition, in the present specification, the flow value is referred to as “zero hit flow value”.

The obtained kneaded product was cast into a cylindrical mold frame of φ50×100 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 compression strength at the time of demolding was 50 N/mm ² .
This molded product was immersed in water in a desiccator under reduced pressure for the time shown in Table 3 (in Table 3, referred to as "under reduced pressure"). In addition, decompression was performed using "Aspirator (AS-01)" manufactured by AS ONE. The mass of the molded body before and after the immersion was measured, and the water absorption rate was calculated from the obtained measured value.
After the immersion, the molded body was steam-cured at 90° C. for 48 hours, then cooled to 20° C., and then heated at 180° C. for 48 hours.
The compressive strength of the molded body (hardened cementitious body) after heating was measured according to “JIS A 1108 (compressive strength test method for concrete)”.
In addition, a 30×30×6 cm test piece was manufactured in the same manner as the above-mentioned cementitious hardened body (molded body after heating), and the rim depth after 60 minutes was measured in accordance with “ASTM C779”. did.

[Example 2]
Cement composition and cementitious hardened body (molded body after heating) in the same manner as in Example 1 except that the blending 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. Got
In the same manner as in Example 1, the zero strike flow value of the cement composition was measured. 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 3, and then the molded body is kept immersed in water. A cement composition and a cementitious hardened body (molded body after heating) 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, the water absorption was calculated, and the compressive strength of the hardened cementitious material was measured.
[Example 4]
The cement composition and the cement composition were prepared in the same manner as in Example 2 except that the molded product after the mold release was immersed in boiling water in the same manner as in Example 3 instead of being immersed in water in a desiccator under reduced pressure. A cementitious hardened body (molded body after heating) was obtained.
In the same manner as in Example 1, the water absorption was calculated, and the compressive strength of the hardened cementitious material was measured.

[Example 5]
Cement composition in the same manner as in Example 1 except that the mixing ratio of silica fume A was changed from 10% by volume to 20% by volume, and the mixing ratio of inorganic powder A was changed from 30% by volume to 20% by volume. And a cementitious hardened body (molded body after heating) were obtained.
In the same manner as in Example 1, measurement of the 0 shot flow value and the like were performed. The compressive strength during demolding was 50 N/mm ² .

Further, the water permeability of the obtained cementitious hardened body was measured according to the water level permeability test method of “Geotechnical Society Standard JGS 0311-2009 (Soil permeability test method)”. As a result, no water permeation was observed and the water permeability coefficient was "0".
Moreover, the obtained cementitious hardened body was immersed in artificial seawater for 6 months. The artificial seawater was prepared by dissolving each reagent in distilled water in the amounts shown in Table 1. After the immersion, the concentration of chloride ions in the hardened cementitious material was measured using EPMA (manufactured by JEOL Ltd.), and the diffusion coefficient of chloride ions (indicated as "diffusion coefficient" in the table) was calculated. ..
Furthermore, the durability index (300 cycles) of "ASTM C666 75" was used for the obtained cementitious hardened material using the value measured according to "JIS A 1148 (concrete freeze-thawing test method)". Was calculated.
The maximum value of the durability index is 100, and the closer it is to the maximum value, the better the freeze-thaw resistance.

[Example 6]
The cement composition and the cement composition were prepared in the same manner as in Example 5 except that the molded product after the mold release was immersed in boiling water in the same manner as in Example 3 instead of being immersed in water in a desiccator under reduced pressure. A cementitious hardened body (molded body after heating) was obtained.
In the same manner as in Example 1, the water absorption was calculated, and the compressive strength of the hardened cementitious material was measured.

[Example 7]
Cement composition in the same manner as in Example 2 except that the mixing ratio of silica fume A was changed from 10% by volume to 20% by volume, and the mixing ratio of inorganic powder A was changed from 30% by volume to 20% by volume. And a cementitious hardened body (molded body after heating) were obtained.
In the same manner as in Example 1, measurement of the 0 shot flow value and the like were performed. The compressive strength at the time of demolding was 45 N/mm ² .
[Example 8]
The cement composition was prepared in the same manner as in Example 7 except that the molded product after the mold release was immersed in boiling water in the same manner as in Example 3 instead of being immersed in water in a desiccator under reduced pressure. And a cementitious hardened body (molded body after heating) were obtained.
In the same manner as in Example 1, the water absorption was calculated, and the compressive strength and the ground depth of the hardened cementitious material were measured.
Also, in the same manner as in Example 5, the water permeability was measured, and the chloride ion diffusion coefficient and durability index were calculated.

[Example 9]
Cement, silica fume A and inorganic powder A were mixed so that the respective ratios of cement and the like would be the ratios shown in Table 2 in the total amount 100% by volume of the powder raw materials (cement, silica fume and inorganic powder). The obtained mixture and the aggregate A1 in an amount such that the ratio of the aggregate A1 in the cement composition is the ratio shown in Table 2 were put into an omni mixer and kneaded for 15 seconds.
Then, water, a polycarboxylic acid-based high-performance water reducing agent, and an antifoaming agent were added to the omni mixer in the amounts shown in Table 2 and kneaded for 2 minutes, and then the kneaded material adhering to the side wall inside the omni mixer was scratched. It was dropped and kneading was continued for 4 minutes. After that, metal fibers in an amount such that the ratio of the metal fibers in the cement composition was as shown in Table 2 were put into an omni mixer and kneading was further performed for 2 minutes.
With respect to the obtained cement composition, the zero-setting flow value was measured in the same manner as in Example 1.
Further, using the obtained cement composition as a material, a cementitious hardened body (molded body) was obtained in the same manner as in Example 1.
With respect to the obtained cementitious hardened body (molded body), the water absorption and the compressive strength were measured in the same manner as in Example 1.
Furthermore, the bending strength of the obtained cementitious hardened body was measured according to "JSCE-G 552-2010 (Bending strength and bending toughness test method of steel fiber reinforced concrete)".

[Example 10]
The cement composition and the cement composition were prepared in the same manner as in Example 9 except that the molded product after the mold release was immersed in boiling water in the same manner as in Example 3 instead of being immersed in water in a desiccator under reduced pressure. 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.
Also, in the same manner as in Example 5, the water permeability was measured, and the chloride ion diffusion coefficient and durability index were calculated.
[Example 11]
The amount of the high-performance water reducing agent was changed from 0.74 parts by mass to 0.78 parts by mass, the amount of the defoaming agent was changed from 0.02 parts by mass to 0.04 parts by mass, and the mixing ratio of the metal fibers was changed. In the same manner as in Example 10 except that the content was changed from 2% by volume to 2.2% by volume, a cement composition and a cementitious hardened body were obtained.
Various physical properties of the cement composition and the cured product thereof were measured in the same manner as in Example 9.

[Example 12]
The amount of water mixed per 100 parts by mass of the powder raw material was changed from 13 parts by mass to 11 parts by mass, the amount of the aggregate A1 was changed from 35.5% by volume to 30.0% by volume, and high performance water reduction was achieved. The cement composition and the cementitious hardened product 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. Got
In the same manner as in Example 1, the zero strike flow value of the cement composition was measured. The compressive strength at the time of demolding was 54 N/mm ² .

[Example 13]
After the molded body after demolding was immersed in boiling water (boiling water) for the time period shown in Table 3, the molded body was immersed in water and cooled to a water temperature of 25°C. A cement composition and a cementitious hardened body were obtained in the same manner as in Example 12.
In the same manner as in Example 1, the water absorption was calculated, and the compressive strength of the hardened cementitious material was measured.
Also, in the same manner as in Example 5, the water permeability was measured, and the chloride ion diffusion coefficient and durability index were calculated.

[Example 14]
Except that the content of the aggregate A1 was changed from 30.0% by volume to 24.0% by volume and the amount of the aggregate B was 6.0% by volume in the cement composition. A cement composition was produced with the same composition as the cement composition of Example 12.
The production of the cement composition was carried out in the same manner as in Example 1, after kneading the respective materials (powder raw material, aggregate A1, water, polycarboxylic acid type high-performance water reducing agent, and defoaming agent), and further aggregate B was put into an omni mixer and kneaded for 1 minute.
Cementitious hardening was performed in the same manner as in Example 1 except that the obtained cement composition (kneaded product) was cast in a cylindrical mold of φ100×200 mm and the molded body was not immersed in water. Got the body
In the same manner as in Example 1, the compressive strength of the hardened cementitious material was measured. The compressive strength at the time of demolding was 43 N/mm ² .

[Example 15]
Except that the 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 the cement composition was 7.0% by volume. A cement composition was produced with the same composition as the cement composition of Example 8.
The cement composition was produced in the same manner as in Example 1, after kneading each material (powder raw material, aggregate A1, water, polycarboxylic acid-based high-performance water reducing agent, and defoaming agent), and further adding bone. Material B was put into an omni mixer and kneaded for 1 minute.
A hardened cementitious body was obtained in the same manner as in Example 8 except that the obtained cement composition (kneaded product) was cast in a cylindrical mold having a diameter of 100×200 mm.
In the same manner as in Example 8, the water absorption was calculated and the compressive strength of the hardened cementitious material was measured. The compressive strength at the time of demolding was 37 N/mm ² .
Also, in the same manner as in Example 5, the water permeability was measured, and the chloride ion diffusion coefficient and durability index were calculated.

[Comparative Example 1]
Cement, silica fume B and inorganic powder B were mixed so that the respective ratios of cement and the like would be the ratios shown in Table 2 in the total amount 100% by volume of the powder raw materials (cement, silica fume and inorganic powder). The obtained mixture and the aggregate A1 in an amount such that the ratio of the aggregate A1 in the cement composition is the ratio shown in Table 2 were put 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 added to the omni mixer in the amounts shown in Table 2 and kneaded for 2 minutes.
After the kneading, the kneaded material adhering to the side wall inside the omni mixer was scraped off, and the kneading was further performed for 4 minutes.
Using the obtained kneaded product as a material, a cemented hardened 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.
The above results are shown in Table 3.

[Materials used]
The materials used in Examples 16 to 27 and Comparative Examples 2 to 4 are as shown below.
(1) Medium heat Portland cement: Taiheiyo Cement (2) Low heat Portland cement: Taiheiyo Cement (3) Silica fume C: BET specific surface area 14 m ² /g
(4) Silica fume D: BET specific surface area 20 m ² /g
(5) Inorganic powder: silica powder, 50% volume cumulative particle size 2 μm, maximum particle size 12 μm, 95% volume cumulative particle size 5.8 μm (the same as the inorganic powder A used in Examples 1 to 15)
(6) Aggregate A1 (fine aggregate): quartz sand, maximum particle size 1.0 mm, particle size 0.6 mm or less: 98% by mass, particle size 0.3 mm or less: 45% by mass, 0 Particle diameter of 15 mm or less: 3% by mass (the same as the aggregate A1 used in Examples 1 to 15)
(7) Aggregate A2 (fine aggregate): Kakegawa-produced sand (8) Polycarboxylic acid-based high-performance water reducing agent: Solid content 27.4% by mass; manufactured by Floric, product name "Floric SF500U"
(9) Defoaming agent: manufactured by BASF Japan Ltd., product name "Master Air 404"
(10) Water: Tap water (11) Metal fiber: Steel fiber (diameter: 0.2 mm, length: 15 mm)
(12) Aggregate B (coarse aggregate): crushed hard sandstone 1005 (particle size: 5 to 10 mm)

[Manufacturing of polished products of medium heat Portland cement and low heat Portland cement]
Moderate heat Portland cement or low heat Portland cement was polished for 30 minutes at a rotation speed of 4,000 rpm using a high-speed airflow agitator (trade name “Hybridizer NHS-3 type” manufactured by Nara Machinery Co., Ltd.). .. In the polishing treatment, the amount of medium heat Portland cement or low heat Portland cement charged was 800 g per batch. The 50% volume cumulative particle size and the Blaine specific surface area of the medium heat Portland cement or the low heat Portland cement and the polished product of the medium heat Portland cement or the low heat Portland cement were measured. The results are shown in Table 4.
In addition, when a secondary electron image of the polished product was observed using a scanning electron microscope, coarse particles (particles having a particle size of 20 μm or more) of the polished product were found to be medium heat Portland cement particles or low heat Portland cement particles ( Compared to (before polishing), there were few angular surface portions, and the surface portions were deformed into a rounded shape. Further, it was observed that fine particles (particles having a particle size of less than 20 μm) were present in the voids between the coarse particles.

[Example 16]
The low heat Portland cement polishing product, the silica fume D, the inorganic powder, and the aggregate A1 were put into an omni mixer for 15 seconds so that the respective ratios of the low heat Portland cement polishing product etc. were as shown in Table 5. I kneaded it empty.
Then, water, a polycarboxylic acid-based high-performance water reducing agent, and an antifoaming agent were added to the omni mixer in the amounts shown in Table 5 and kneaded for 2 minutes. The amount of the defoaming agent added was 0.02 parts by mass with respect to 100 parts by mass of the powder raw material.
After the kneading, the kneaded material adhering to the side surface of the omni mixer was scraped off, and the kneading was further performed for 4 minutes.
The flow value of the cement composition after kneading was measured by the method described in "JIS R 5201 (Physical test method for cement) 11. Flow test" without performing 15 drop motions.
Further, the cement composition after kneading was cast into a cylindrical mold frame of φ50×100 mm to obtain an uncured molded body. After the casting, the uncured molded body was allowed to stand at 20° C. for 72 hours. Then, the mold was removed to obtain a cured molded body. The compression strength of the molded product at the time of demolding was 52 N/mm ² .
Furthermore, the molded body was steam-cured at 90° C. for 48 hours, then cooled to 20° C., and further heated at 180° C. for 48 hours using a drying furnace.
The compressive strength of the molded body (hardened cementitious body) after heating was measured according to “JIS A 1108 (compressive strength test method for concrete)”. The compressive strength was measured using a 100t universal testing machine (hydraulic type) manufactured by Shimadzu Corporation.

[Example 17]
A cement composition and a cementitious hardened body (molded body after heating) were obtained in the same manner as in Example 16, except that the medium heat Portland cement was used instead of the low heat Portland cement. .. The compressive strength of the molded product at the time of demolding was 55 N/mm ² .
In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured.
[Example 18]
A cement composition and a cementitious hardened body (molded body after heating) were obtained in the same manner as in Example 17, except that the amount of water per 100 parts by mass of the powder raw material was changed from 12 parts by mass to 15 parts by mass. Obtained. The compression strength of the molded product at the time of demolding was 50 N/mm ² .
In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured.

[Example 19]
The molded body after the mold release was immersed in boiling water (boiling water) for 30 minutes, and then cooled while keeping the molded body immersed in water until the water temperature reached 25° C. (“Boiling water” in Table 6). The cement composition and the cementitious hardened body (molded body after heating) were obtained in the same manner as in Example 16 except that steam curing was performed later.
In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured. The compression strength of the cured product exceeded the measurement limit (511 N/mm ² ) of the measuring device.
Further, the mass of the molded body before and after the immersion was measured, and the water absorption rate was calculated from the obtained measured value.
Furthermore, in the same manner as in Example 5, the measurement of the chafing depth and the water permeability, and the calculation of the chloride ion diffusion coefficient and the durability index were performed.

[Example 20]
Cement was prepared in the same manner as in Example 16 except that the molded product after the mold release was immersed in water for 30 minutes in a desiccator under reduced pressure (indicated as "under reduced pressure" in Table 6) and then steam-cured. A composition and a cementitious hardened body (molded body after heating) were obtained.
In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured. The compression strength of the cured product exceeded the measurement limit (511 N/mm ² ) of the measuring device.

[Example 21]
A cement composition and a cement composition were prepared in the same manner as in Example 16 except that the mixing ratio of silica fume D was changed from 10% by volume to 20% by volume, and the mixing ratio of the inorganic powder was changed from 30% by volume to 20% by volume. A cementitious hardened body (molded body after heating) was obtained. The compression strength of the molded product at the time of demolding was 51 N/mm ² .
In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured.
[Example 22]
The cement composition and the cementitious hardened body (molded body after heating) were processed in the same manner as in Example 21 except that the molded body after demolding was immersed in water in a desiccator under reduced pressure for 30 minutes and then steam-cured. ) Got.
In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured. The compression strength of the cured product exceeded the measurement limit (511 N/mm ² ) of the measuring device.

[Example 23]
The cement composition and the cementitious hardened body (molded body after heating) were processed in the same manner as in Example 18 except that the molded body after demolding was immersed in water for 30 minutes in a desiccator under reduced pressure and then steam-cured. ) Got.
In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured.

[Example 24]
The low heat Portland cement polishing product, the silica fume D, the inorganic powder, and the aggregate A1 were put into an omni mixer for 15 seconds so that the respective ratios of the low heat Portland cement polishing product etc. were as shown in Table 5. I kneaded it empty.
Then, water, a polycarboxylic acid-based high-performance water reducing agent, and an antifoaming agent were added to the omni mixer in the amounts shown in Table 5 and kneaded for 2 minutes. The amount of the defoaming agent added was 0.02 parts by mass with respect to 100 parts by mass of the powder raw material.
After the kneading, the kneaded material adhering to the side surface of the omni mixer was scraped off, and the kneading was further performed for 4 minutes. After that, metal fibers in an amount such that the ratio of the metal fibers in the cement composition was as shown in Table 5 were put into an omni mixer and kneading was further performed for 2 minutes.
With respect to the obtained cement composition, the zero impact flow value was measured in the same manner as in Example 16.
Further, using the obtained cement composition as a material, a cemented hardened product (molded product) was obtained in the same manner as in Example 19.
The water absorption rate and the compressive strength of the obtained cementitious hardened body (molded body) were measured in the same manner as in Example 19. The compression strength of the cured product exceeded the measurement limit (511 N/mm ² ) of the measuring device.
Moreover, the bending strength of the obtained cementitious hardened body was measured according to "JSCE-G 552-2010 (Bending strength and bending toughness test method of steel fiber reinforced concrete) of JSCE standard".

[Example 25]
The molded product after demolding was cemented in the same manner as in Example 24 except that steam curing was performed after immersing the molded product in boiling water for 30 minutes instead of immersing it in water in a desiccator under reduced pressure for 30 minutes. A composition and a cementitious hardened body (molded body after heating) were obtained.
Various physical properties of the cement composition and the cementitious cured product (molded product after heating) were measured in the same manner as in Example 24. The compression strength of the cured product exceeded the measurement limit (511 N/mm ² ) of the measuring device.

[Example 26]
The low heat Portland cement polishing product, the silica fume D, the inorganic powder, and the aggregate A1 were put into an omni mixer for 15 seconds so that the respective ratios of the low heat Portland cement polishing product etc. were as shown in Table 5. I kneaded it empty.
Then, water, a polycarboxylic acid-based high-performance water reducing agent, and an antifoaming agent were added to the omni mixer in the amounts shown in Table 5 and kneaded for 2 minutes. The amount of the defoaming agent added was 0.02 parts by mass with respect to 100 parts by mass of the powder raw material.
After the kneading, the kneaded material adhering to the side surface of the omni mixer was scraped off, and the kneading was further performed for 4 minutes. Then, the aggregate B was put into an omni mixer so that the proportion was as shown in Table 5, and kneading was further performed for 1 minute.
The cement composition after kneading was cast into a cylindrical mold of φ100×200 mm to obtain an uncured molded body. After the casting, the uncured molded body was allowed to stand at 20° C. for 72 hours. Then, the mold was removed to obtain a cured molded body. The compression strength of the molded product at the time of demolding was 41 N/mm ² .
Furthermore, the molded body was steam-cured at 90° C. for 48 hours, then cooled to 20° C., and further heated at 180° C. for 48 hours using a drying furnace.
The compressive strength of the obtained cementitious hardened body (molded body after heating) was measured in the same manner as in Example 16.

[Example 27]
In place of the low heat Portland cement polishing product, a medium heat Portland cement polishing product was used, except that the molded product after demolding was immersed in water for 30 minutes in a desiccator under reduced pressure and then steam cured. A hardened cementitious body (molded body after heating) was obtained in the same manner as in Example 26.
With respect to the hardened cementitious material, the water absorption and the compressive strength were measured in the same manner as in Example 19.

[Comparative example 2]
A medium heat Portland cement polishing product, silica fume C, aggregate A2, high-performance water reducing agent, and water were added all at once to the Hobart mixer in the proportions shown in Table 5, and then kneaded at low speed for 12 minutes. Then, a hardened body of the cement composition was obtained in the same manner as in Example 16 except that the cement composition was prepared. In the same manner as in Example 16, the flow value (0 hitting) of the cement composition was measured.
[Comparative Example 3]
Let's prepare a cement composition by throwing in the Hobart Mixer in a batch with the polishing product of medium-high heat Portland cement, aggregate A2, high-performance water reducing agent, and water in the proportions shown in Table 5. However, it was not possible to knead.
[Comparative Example 4]
Medium temperature heat Portland cement, silica fume C, aggregate A2, high-performance water reducing agent, and water were added to the Hobart mixer all at once in the composition shown in Table 5 to prepare a cement composition. I couldn't knead.
The above results are shown in Table 6.

From Tables 3 and 6, the compressive strength of the cementitious hardened bodies of Examples 1 to 13 and Examples 16 to 25 is as high as 350 N/mm ² or more. In particular, the compressive strength of the hardened cementitious body when the cement subjected to the polishing treatment is used (Examples 16 to 25) is 420 N/mm ² or more, which is very large. In addition, in Examples 9 to 11 and Examples 24 to 25 (where the cement composition contains metal fibers), the obtained cementitious cured product has a compressive strength of 454 N/mm ² or more, which is significantly large, and The bending strength is 40 N/mm ² or more.
Further, even when the aggregate B (coarse aggregate) is included (Examples 14 to 15 and Examples 26 to 27), the compressive strength of the cementitious hardened body is 333 N/mm ² or more, which is large. is there.
Further, the hardened cementitious bodies of Examples 1 to 2, 5, 8, 10, 13, 15, and 19 have a grinding edge depth of 0.37 mm or less, which is small.
Furthermore, from the water permeability, the diffusion coefficient of chloride ions, and the durability index of the cementitious hardened bodies of Examples 5, 8, 10, 13, 15, and 19, the obtained cementitious hardened bodies were water-impervious and salt-impervious. , And that the freeze-thaw resistance is excellent.
From these results, it is understood that the cement board of the present invention has a large compressive strength and is excellent in abrasion resistance, water impermeability, freeze-thaw resistance, and salt impermeability.
On the other hand, the compressive strength of the cementitious hardened bodies of Comparative Examples 1 and 2 is 290 N/mm ^2, which is smaller than that of Examples 1-27. Further, it can be seen that the hardened cementitious body of Comparative Example 1 has a fray depth of 0.57 mm, which is larger than that of the Examples. Further, it is understood that the cement compositions of Comparative Examples 3 to 4 cannot be kneaded.

[Example 28]
By the same method as in Example 11, as a molded body (cementoid hardened body) after heating, a longitudinal reinforcing plate of 1,800 mm×horizontal 300 mm×thickness of 20 mm and a longitudinal 1,800 mm×horizontal 150 mm×thickness A 20 mm-thick bottom plate reinforcing plate was manufactured.
Next, an RC concrete beam 20 having the dimensions shown in FIGS. 3 and 4 (the unit of numerical values in FIGS. 3 and 4 is mm) was manufactured. The compressive strength of the concrete 21 forming the beam was 35 N/mm ² . D6SD295 was used as the reinforcing bar 22, and D22SBPD930 was used as the reinforcing bar 23. The cover thickness of the reinforcing bar was 30 mm.
The following test bodies a to d were manufactured using the RC concrete beam 20, the bottom reinforcing plate 24 and the side reinforcing plate 25.
Specimen a: Consists of RC concrete beam 20 only (see FIG. 4(a))
Specimen b: one in which a reinforcing plate 24 for reinforcing the bottom is fixed to the bottom of the RC concrete beam 20 (see (b) of FIGS. 3 and 4).
Specimen c: RC concrete beam 20 to which side reinforcing plates 25 are fixed on both sides (see (c) of FIG. 4)
Specimen d: one in which a bottom plate reinforcing reinforcing plate 24 is fixed to the bottom surface of the RC concrete beam 20, and side surface reinforcing reinforcing plates 25 are fixed to both side faces of the RC concrete beam 20 (see (d) of FIG. 4).
The bottom reinforcing plate 24 and the side reinforcing plate 25 were fixed to the RC concrete beam 20 using an epoxy adhesive and anchor bolts.

The maximum load of each test body was measured using a 200-ton pressure resistance tester. The loading position when measuring the maximum load is as shown in FIG.
As a result, the maximum load of the test body a (which was not reinforced by the reinforcing plate) was 150 kN. On the other hand, the maximum load of the test body b (only the bottom surface is reinforced) is 252 kN, the maximum load of the test body c (only side surfaces are reinforced) is 345 kN, and the test body d (the bottom surface and both side surfaces are reinforced). The maximum load of was 404 kN.
From Example 28, it can be seen that the use of the cement plate of the present invention as a reinforcing plate for a concrete beam significantly improves the mechanical performance of the concrete beam after reinforcement as compared with the concrete beam before reinforcement.

DESCRIPTION OF SYMBOLS 1 Cement plate 10 High-speed airflow agitator 11 Rotor 12 Blade 13 Circulation circuit 13a Circulation circuit inlet 13b Circulation circuit outlet 14 Input port 15 Discharge port 16 Stator 17 Collision chamber 18 Open/close valve 19 Discharge valve 20 RC concrete beam 21 Concrete 22 Rebar (D6SD295)
23 Rebar (D22SBPD930)
24 Bottom Reinforcing Reinforcing Plate 25 Side Reinforcing Reinforcing Plate 26 Anchor Bolt

Claims (11)

A cement board made of a hardened cement material,
The hardened cementitious material is cement, silica fume having a BET specific surface area of 15 to 25 m ² /g, inorganic powder having a 50% volume cumulative particle diameter of 0.8 to 5 μm, and fine aggregate having a maximum particle diameter of 1.2 mm or less. The aggregate A, the high-performance water reducing agent, the defoaming agent, and water, and the ratio of the cement is 55 to 65% by volume in the total amount of 100% by volume of the cement, the silica fume, and the inorganic powder. Of 5 to 25% by volume, and the proportion of the inorganic powder is 15 to 35% by volume, and the proportion of the aggregate A in the cement composition is 20 to 40% by volume. A cement board characterized by being obtained by curing a composition. The above-mentioned cement is a coarse particle having a particle size of 20 μm or more, which is obtained by polishing particles constituting medium-heat Portland cement or low-heat Portland cement, and is obtained by deforming an angular surface portion into a rounded shape; The cement according to claim 1, comprising fine particles having a particle size of less than 20 μm generated by the treatment, having a 50% volume cumulative particle size of 10 to 18 μm, and a Blaine specific surface area of 2,100 to 2,900 cm ² /g. Board. The cement composition contains one or more fibers selected from the group consisting of metal fibers, organic fibers and carbon fibers, and the proportion of the fibers in the cement composition is 3% by volume or less. The cement board according to 2. The cement board according to any one of claims 1 to 3, wherein the cemented hardened product has a compressive strength of 330 N/mm ² or more. The cement composition, see contains aggregate B maximum particle size of less coarse aggregate 13 mm, and the ratio of the total amount of the aggregate A and the bone material B of the cement composition is, 25 It is -40 volume%, The cement board of any one of Claims 1-3. The cement plate according to claim 5, wherein the cemented hardened product has a compressive strength of 300 N/mm ² or more. The cement board according to any one of claims 1 to 6, wherein the cement board is a wear-resistant board. The cement board according to any one of claims 1 to 6, wherein the cement board is a reinforcing board. A method for producing the cement board according to any one of claims 1 to 8, comprising:
A molding step of placing the cement composition in a mold to obtain an uncured molded body,
A room temperature curing step of obtaining a cured molded product by demolding the uncured molded product at 10 to 40° C. for 24 hours or more and then curing it in the mold or in air.
About the above-mentioned hardened molded object, either or both of steam curing or warm water curing at 70°C or higher and lower than 100°C for 6 hours or longer and autoclave curing at 100 to 200°C for 1 hour or longer are performed, and curing after heat curing A heating and curing process to obtain the body,
A high temperature heating step of heating the cured body after the heating and curing at 150 to 200° C. for 24 hours or more (excluding heating by autoclave curing) to obtain the cement board;
A method for producing a cement board, which comprises: The method for producing a cement board according to claim 9, further comprising a water absorption step of allowing the cured molded body to absorb water between the room temperature curing step and the heat curing step. The method for manufacturing a cement plate according to claim 9 or 10, wherein the cement plate is a wear-resistant plate or a reinforcing plate.

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