JP2021155285A - Concrete structure and its manufacturing method - Google Patents

Abstract

To provide a concrete structure having high strength and high endurance.SOLUTION: The present invention relates to a hardened body of a cement composition containing at least cement, silica fume having a BET specific surface area of 15 to 25 m2/g, inorganic powder having a 50% volume cumulative particle size of 0.8 to 5 μm, an aggregate A having the maximum particle size of 1.2 mm or smaller, a high performance water reducing agent, an antifoaming agent, and water, in which with a total amount of the cement, silica fume, and inorganic powder set to 100 vol%, the content of the cement is 55 to 65 vol%, the content of the silica fume is 5 to 25 vol%, and the content of the inorganic powder is 15 to 35 vol%, and the compression strength is 300 N/mm2 or larger.SELECTED DRAWING: Figure 3

Description

The present invention relates to a concrete structure having high strength and high durability, and a method for manufacturing the same.

Conventionally, steel has been widely used for web members such as bridges, but steel has a problem in durability because it may be corroded. On the other hand, although there is an existing technique using ultra-high strength fiber reinforced concrete (for example, Patent Document 1), there are limits to the member thickness and the span length. Moreover, the shape of the fiber used is limited.

Japanese Unexamined Patent Publication No. 2005-23613

Therefore, an object of the present invention is to provide a concrete structure having high strength and high durability, and a method for manufacturing the same.

As a result of diligent studies to solve the above problems, the present inventor has found cement, ^{silica fume having a BET specific surface area of 15 to 25 m 2} / g, an inorganic powder having a 50% volume cumulative particle size of 0.8 to 5 μm, and maximum grains. A cured product of a cement composition containing at least an aggregate having a diameter of 1.2 mm or less, a high-performance water reducing agent, a defoaming agent and water, and the content of each of cement, silica fume and inorganic powder is within a specific range. The present invention has been completed by finding that the concrete structure can achieve the above object. That is, the present invention is a concrete structure or the like having the following configuration.

[1] Cement, silica fume with BET specific surface area of 15 to 25 m ² / g, inorganic powder with 50% volume cumulative particle size of 0.8 to 5 μm, aggregate A with maximum particle size of 1.2 mm or less, high-performance water reduction A cured product of a cement composition containing at least an agent, an antifoaming agent, and water.
Assuming that the total of the cement, silica fume, and inorganic powder is 100% by volume, the content of the cement is 55 to 65% by volume, the content of silica fume is 5 to 25% by volume, and the content of the inorganic powder is 15 to 35% by volume. A concrete structure having a compressive strength of 300 N / mm ^{2 or more.}
[2] The concrete structure according to the above [1], further comprising an aggregate B having a maximum particle size of more than 1.2 mm and 13 mm or less.
[3] The cement is obtained by polishing a moderately hot Portorand cement or a low heat Portorand cement to form an angular surface portion of the cement particles into a rounded shape, and coarse particles having a particle size of 20 μm or more, and the above. The 50% volume cumulative particle size of the polished cement is 10 to 18 μm, and the brain specific surface area of the cement is 2100 to 2900 cm ² / g, which contains fine particles having a particle size of less than 20 μm produced by the polishing treatment. The concrete structure according to [1] or [2].
[4] The above-mentioned [1] to [3], wherein one or more fibers selected from metal fibers, organic fibers, and carbon fibers are contained, and the content of the fibers is 3% by volume or less. Concrete structure.
[5] The concrete structure according to any one of [1] to [4] above, wherein the concrete structure is a web member.
[6] A method for manufacturing a concrete structure, wherein the concrete structure according to any one of the above [1] to [5] is manufactured through at least the following steps (A) to (D).
(A) Molding step of casting the cement composition into a mold to obtain an uncured molded product (B) The uncured molded product is sealed or cured at 10 to 40 ° C. for 24 hours or more. Room temperature curing step (C) The cured molded product is subjected to steam curing or hot water curing at 70 ° C. or higher and lower than 100 ° C. for 6 hours or longer after being medium-cured and then removed from the mold to obtain a cured molded product. , One or both of autoclave curing at 100 to 200 ° C. for 1 hour or more to obtain a cured product after heat curing (D) The cured product after heat curing is 24 at 150 to 200 ° C. High-temperature heating step of obtaining the concrete structure by heating for an hour or longer (excluding heating by autoclave curing) [7] During the normal temperature curing step and the heating curing step, the cured molded body absorbs water. The method for manufacturing a concrete structure according to the above [6], which includes a water absorption step for causing the concrete structure to be formed.

Since the concrete structure of the present invention ^{has a high compressive strength of 300 N / mm 2} or more, the concrete structure can be made thinner, longer spanned, and lighter.
Further, when the concrete structure of the present invention is a web member, the member can be shaped like a plate or a truss.
Further, when prestress is introduced into the concrete structure of the present invention, the weight can be further reduced by connecting with ordinary concrete to form a composite structure.

It is a front view which shows an example of the high-speed airflow agitator which partially includes the cross section cut in the direction perpendicular to the rotation axis of a rotor. It is a cross-sectional view of a composite concrete porridge, (A) is a vertical cross-sectional view in the longitudinal direction, and (B) is a vertical cross-sectional view in the horizontal direction. It is a perspective view of the web member used for the porridge of FIG.

The present invention relates to 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, aggregate A having a maximum particle size of 1.2 mm or less, and high performance. A cured product of a cement composition containing at least a water reducing agent, a defoaming agent, and water, wherein the total of the cement, silica fume, and inorganic powder is 100% by volume, and the content of the cement is 55 to 65% by volume. A concrete structure or the like having a silica fume content of 5 to 25% by volume, an inorganic powder content of 15 to 35% by volume, and a compressive strength of 300 N / mm ^{2 or more.}
Hereinafter, the present invention will be described in detail.

1. 1. Cement The cement used in the present invention is not particularly limited, and for example, various Portland cements such as ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate heat Portland cement, sulfate-resistant Portland cement, and low heat Portland cement. Can be mentioned. Among these, moderate heat Portland cement or low heat Portland cement is preferable because the cement composition has high fluidity.

Further, since the cement used in the present invention has high fluidity of the cement composition and high compressive strength of the concrete structure, it is preferable to polish moderate heat Portland cement or low heat Portland cement to obtain the cement. Coarse particles having a particle size of 20 μm or more in which the angular surface portion of the cement has a rounded shape, and fine particles having a particle size of less than 20 μm produced by the polishing treatment, and 50% volume cumulative particles of the cement. A cement having a diameter of 10 to 18 μm and a brain specific surface area of the cement of ^{2100 to 2900 cm 2 / g.}

The upper limit of the particle size of the coarse particles is not particularly limited, and is preferably 200 μm or less in consideration of the general particle size of the polished cement, and more because the compressive strength of the concrete structure is higher. It is preferably 100 μ or less.
Further, the lower limit of the particle size of the fine particles is not particularly limited, and since the cement composition has high fluidity and workability when manufacturing a concrete structure, it is preferably 0.1 μm or more, more preferably 0. It is 5.5 μm or more.

The 50% volume cumulative particle size of the polished cement is preferably 10 to 18 μm, more preferably 12 to 16 μm, and the specific surface area of the brain is preferably 2100 to 2900 cm ² / g, more preferably 2200 to 2700 cm. ^{It is 2} / g.
When the 50% volume cumulative particle size is 10 μm or more, the fluidity of the cement composition is high, and when it is 18 μm or less, the compressive strength of the concrete structure is higher.
Further, when the specific surface area of the brain is 2100 cm ² / g or more, the compressive strength of the concrete structure becomes higher, and when it is 2900 cm ² / g or less, the fluidity of the cement composition is improved.

The polishing treatment is performed using a known polishing treatment device capable of polishing moderate heat Portland cement or low heat Portland cement, and the polishing treatment device is, for example, a trade name "Hybridizer NHS-3 type" (manufactured by Nara Machinery Co., Ltd.). ) Etc. can be mentioned.
Hereinafter, the high-speed airflow agitator will be described in detail with reference to FIG.

The cement used in the present invention is charged from the inlet 14 at the upper part of the high-speed airflow agitator 10 with the on-off valve 18 open, and the on-off valve 18 is closed.
The charged 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 processed, from the outlet 13b of the circulation circuit 13.
After the cement is charged, the rotor (rotating body) 11 arranged inside the stator 16 which is a fixed body is rotated at high speed, so that a high-speed airflow is generated by the rotor 11 and the blade 12 fixed to the rotor 11. Then, the cement in the collision chamber 17 is agitated. During this stirring, the cement particles enter the circulation circuit 13 from the inlet 13a of the circulation circuit 13 provided in the collision chamber 17, and collide again from the outlet 13b of the circulation circuit 13 provided in the central portion of the collision chamber 17. It is thrown into the chamber 17 and circulates. In FIG. 1, the arrow indicated by the dotted line indicates the flow of cement particles, coarse particles generated by the polishing treatment, and fine particles.

By stirring, the cement particles collide with the inner wall surface of the collision chamber 17, the rotor 11, and the blade 12, and the cement particles collide with each other to polish the cement particles, and the angular portion of the particle surface is rounded. Coarse particles having a particle size of 20 μm or more and fine particles having a particle size of less than 20 μm are produced.

The rotation speed of the rotor 11 is preferably 3000 to 4200 rpm, more preferably 3500 to 4000 rpm. When the rotation speed is 3000 rpm or more,
The fluidity of the cement composition is improved, and when it exceeds 4200 rpm, the effect of improving the fluidity of the cement composition is saturated. Further, due to the performance of the high-speed airflow agitator, it is difficult for the rotation speed to exceed 4200 rpm.
The polishing treatment time is preferably 10 to 60 minutes, more preferably 20 to 50 minutes, still more preferably 20 to 40 minutes, still more preferably 20 to 30 minutes. If the time is 10 minutes or more, the fluidity of the cement composition is improved, and if it exceeds 60 minutes, the effect of improving the fluidity of the cement composition is saturated.
Finally, the obtained polished product (mixture of coarse particles and fine particles) is discharged from the discharge port 15 by opening the discharge valve 19.

2. Silica fume The BET specific surface area of the silica fume used in the present invention is 15 to 25 m ² / g, preferably 17 to 23 m ² / g, and more preferably 18 to 22 m ² / g. If the specific surface area is ^{less than 15 m 2} / g, the compressive strength of the concrete structure is lowered, ^{and if it exceeds 25 m 2} / g, the fluidity of the cement composition is lowered.

3. 3. Inorganic powder 50% volume Inorganic powder with cumulative particle size of 0.8 to 5 μm is quartz powder (silica powder), volcanic ash, slag powder, limestone powder, pebbles powder, mulite powder, alumina powder, silica sol, carbide powder, etc. Nitride powder and one or more classified or crushed fly ash can be mentioned.
Among these, quartz powder or fly ash is preferable because the fluidity of the cement composition is improved and the compressive strength of the concrete structure is increased.
In the present specification, the inorganic powder having a 50% cumulative particle size of 0.8 to 5 μm does not contain cement.

The 50% volume cumulative particle size of the inorganic powder used in the present invention is 0.8 to 5 μm, preferably 1 to μm, more preferably 1.1 to 3.5 μm, still more 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 decreases, and if the particle size exceeds 5 μm, the compressive strength of the concrete structure decreases.
The 50% volume cumulative particle size of the inorganic powder can be determined using a commercially available particle size distribution measuring device such as the product name "Microtrac HRA Model 9320-X100" (manufactured by Nikkiso Co., Ltd.).
^{For the 50% volume cumulative particle size, for example, 0.06 g of the sample is added to 20 cm 3} of ethanol, which is a solvent for dispersing the sample, and an ultrasonic disperser (for example, product name “US300”, Nippon Seiki Seisakusho) is used for 90 seconds. After ultrasonically dispersing using (manufactured by), a cumulative particle size curve of particles in the dispersion liquid is prepared and obtained using a particle size distribution measuring device.

The maximum particle size of the inorganic powder is preferably 15 μm or less, more preferably 14 μm or less, still more preferably 13 μm or less because the compressive strength of the concrete structure becomes higher. Further, the 95% volume cumulative particle size of the inorganic powder is preferably 8 μm or less, more preferably 7 μm or less, still more preferably 6 μm or less because the compressive strength of the concrete structure becomes higher.

The inorganic powder used in the present invention is preferably an inorganic powder containing _{SiO 2 as a main component, such as quartz powder. The content of SiO 2} in the inorganic powder is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. _{When the content of SiO 2} in the inorganic powder is 50% by mass or more, the compressive strength of the concrete structure becomes higher.

4. Cement Content in Cement Composition The cement content in the cement composition used in the present invention is 55-65% by volume, preferably 57-63, with the total of cement, silica fume, and inorganic powder as 100% by volume. Volume%. If the content is less than 55% by volume, the compressive strength of the concrete structure is lowered, and if it exceeds 65% by volume, the fluidity of the cement composition is lowered.
The content of silica fume in the cement composition used in the present invention is 5 to 25% by volume, preferably 7 to 25% by volume, with the total of cement, silica fume, and inorganic powder as 100% by volume. If the content is less than 5% by volume, the compressive strength of the concrete structure is lowered, and if it exceeds 25% by volume, the fluidity of the cement composition is lowered.
The content of the inorganic powder in the cement composition used in the present invention is 15 to 35% by volume, preferably 17 to 33% by volume, with the total of cement, silica fume, and the inorganic powder as 100% by volume. If the content is less than 15% by volume, the compressive strength of the concrete structure is lowered, and if it exceeds 35% by volume, the fluidity of the cement composition is lowered.

5. Aggregate A
The aggregate A used in the present invention is an artificial fine aggregate such as river sand, land sand, sea sand, crushed sand, silica sand, recycled fine aggregate, and fired fine aggregate obtained by firing slag fine aggregate or fly ash. One or more selected from the materials can be mentioned.
The maximum particle size of the aggregate A is 1.2 mm or less, preferably 1.1 mm or less, and more preferably 1.0 mm or less. When the maximum particle size is 1.2 mm or less, the compressive strength of the concrete structure is high.
Since the particle size distribution of the aggregate A improves the fluidity of the cement composition and the compressive strength of the concrete structure, the content of the aggregate having a particle size of 0.6 mm or less is preferably 95% by mass or more. The content of the aggregate having a particle size of 0.3 mm or less is preferably 40 to 50% by mass, and the content of the aggregate having a particle size of 0.15 mm or less is 6% by mass or less.
The content of the aggregate A in the cement composition is preferably 20 to 40% by volume, more preferably 22 to 38% by volume, still more preferably 30 to 37% by volume, and particularly preferably 32 to 36% by volume. When the content is 20% by volume or more, the calorific value of the cement composition is small, and the shrinkage amount of the concrete structure is small, and when it is 40% by volume or less, the compressive strength of the concrete structure is higher.

6. High-performance water-reducing agent The high-performance water-reducing agent used in the present invention is one or more selected from high-performance water-reducing agents such as naphthalene sulfonic acid-based, melamine-based, and polycarboxylic acid-based. Among these, a polycarboxylic acid-based high-performance water reducing agent is preferable because the fluidity of the cement composition is improved and the compressive strength of the concrete structure is increased.
The blending ratio of the high-performance water reducing agent is preferably 0.2 to 1.5 parts by mass, more preferably 0.4 to 1. 2 parts by mass. When the amount is 0.2 parts by mass or more, the water reduction performance is improved and the fluidity of the cement composition is improved, and when the amount is 1.5 parts by mass or less, the compressive strength of the concrete structure is higher.

7. Defoaming agent A commercially available product can be used as the defoaming agent used in the present invention, and the blending ratio of the defoaming agent is preferably 0.001 to 0.1% by mass with respect to 100 parts by mass in total of cement, silica fume, and inorganic powder. Parts, more preferably 0.01 to 0.07 parts by mass, still more preferably 0.01 to 0.05 parts by mass. When the amount is 0.001 part by mass or more, the strength development effect of the cement composition is improved, and when the amount exceeds 0.1 parts by mass, the effect of improving the strength development of the cement composition is saturated.

8. Fiber The cement composition used in the present invention may contain one or more fibers selected from metal fibers, organic fibers, and carbon fibers because the bending strength, breaking energy, and the like of the concrete structure are improved. The fiber content in the cement composition is preferably 3% by volume or less, more preferably 0.3 to 2.5% by volume, and even more preferably 0.5 to 2.3% by volume. When the content is 3% by volume or less, the bending strength, fracture energy, etc. of the concrete structure are improved without lowering the fluidity and workability of the cement composition.

Examples of the metal fiber include steel fiber, stainless steel fiber, and amorphous fiber. Among these, steel fiber is suitable because of its excellent strength, cost, and availability.
The dimensions of the metal fibers are preferably 0.01 to 1.0 mm in diameter and 2 in length because they prevent material separation of the metal fibers in the cement composition and improve the bending strength of the concrete structure. It is ~ 30 mm, more preferably 0.05 ~ 0.5 mm in diameter and 5-25 mm in length. The aspect ratio of the metal fiber (fiber length / fiber diameter) is preferably 20 to 200, more preferably 40 to 150.
Further, the shape of the metal fiber is preferably a spiral shape or a corrugated shape that can impart a physical adhesive force rather than a linear shape. If the shape is spiral or the like, the metal fiber and the matrix secure the stress while pulling out, so that the bending strength of the concrete structure is improved.

The organic fiber may withstand heating in the method for producing a concrete structure of the present invention described later, and examples thereof include aramid fiber, polyparaphenylene benzobisoxazole fiber, polyethylene fiber, polyarite fiber, and polypropylene fiber.
Examples of carbon fibers include PAN-based carbon fibers and pitch-based carbon fibers.
The dimensions of the organic fibers and carbon fibers are preferably 0.005 to 1.0 m in diameter and 2 in length in order to prevent material separation of the fibers in the cement composition and improve the breaking energy of the concrete structure. It is ~ 30 mm, more preferably 0.01 ~ 0.5 mm in diameter and 5-25 mm in length. The aspect ratio of the organic fiber and the carbon fiber (fiber length / fiber diameter) is preferably 20 to 200, more preferably 30 to 150.

9. Water Water or the like can be used, and the mixing ratio of water is preferably 10 to 20 parts by mass, more preferably 11 to 18 parts by mass, still more preferably, with respect to 100 parts by mass of the total of cement, silica fume, and inorganic powder. Is 14 to 16 parts by mass. When the amount is 10 parts by mass or more, the fluidity of the cement composition is improved, and when the amount is 20 parts by mass or less, the compressive strength of the concrete structure is higher.

10. Physical Properties of Cement Composition (Mortar) and Concrete Structure The flow value of the mortar composed of the cement composition (not including aggregate B, which will be described later) before hardening is described in "Physical test method of cement" of JIS R 5201 "Physical test method of cement". In the method described in "11. Flow test", the value measured by omitting the falling motion of 15 times (hereinafter referred to as "0 stroke flow value") is preferably 200 mm or more, more preferably 220 mm or more. When the flow value is 200 mm or more, workability when manufacturing a concrete structure is improved.
The compressive strength of the concrete structure, preferably 300N / 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.

11. Aggregate B
The cement composition of the present invention can contain an aggregate B having a maximum particle size of more than 1.2 mm and 13 mm or less.
Aggregate B is an artificial fine aggregate such as river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, recycled fine aggregate, and fired fine aggregate obtained by firing slag fine aggregate, fly ash, etc. Select from fine aggregates such as river gravel, mountain gravel, land gravel, crushed stone, recycled coarse aggregate, and artificial coarse aggregate such as calcined coarse aggregate made by firing slag coarse aggregate or fly ash. One or more of them can be mentioned.
The maximum particle size of the aggregate B is preferably 13 mm or less, more preferably 12 mm or less, more preferably 11 mm or less, still more preferably 10 mm or less. When the maximum particle size 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 exhibited.
The maximum particle size of the aggregate B is preferably more than 1.2 mm, more preferably 3 mm or more, still more preferably 5 mm or more, and particularly preferably 7 mm or more in order to reduce the cost.
In the present specification, the "maximum particle size" when the maximum particle size of the aggregate B is 5 mm or more is indicated by the nominal size of the sieve having the smallest size among the sieves through which 90% by mass or more of the entire aggregate B passes. Refers to the particle size of the aggregate B (which is 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, particularly preferably 4 mm or more, and extremely preferably 5 mm or more (this is coarse). It corresponds to aggregate.).
In the present specification, the minimum particle size of the aggregate B reaches 15% by mass of the total particle size of the aggregate B when accumulated from the minimum particle size to the maximum particle size in the aggregate B. It refers to the particle size of the aggregate B when it is used.

In the present invention, the total content of the aggregate A and the aggregate B in the concrete structure is preferably 25 to 40% by volume, more preferably 28 to 38% by volume, and further preferably 30 to 36% by volume. .. When the content is 25% by volume or more, the calorific value and the shrinkage amount of the concrete structure are small, and when the content is 40% by volume or less, the strength development of the concrete structure is improved.
The content of the aggregate B with respect to the total of the aggregate A and the aggregate B is preferably 40% by volume or less, more preferably 30% by volume or less, still more preferably 25% by volume or less. When the content is 40% by volume or less, the strength development such as the compressive strength of the concrete structure is improved.
The compressive strength of the concrete structure obtained by hardening the cement composition containing the aggregate B is preferably 300 N / mm ² or more, more preferably 320 N / mm ² or more, still more preferably 340 N / mm ² or more, and particularly preferably. 360 N / mm ² or more.

12. Manufacturing Method of Concrete Structure The manufacturing method manufactures the concrete structure of the present invention through the (A) molding step, (B) normal temperature curing step, (C) heating curing step, and (D) high temperature heating step. How to do it.
Hereinafter, the method for manufacturing the concrete structure will be described separately for the steps (A) to (E). The steps (A) to (D) are essential steps in the present invention, and the steps (E) are arbitrary steps.

(A) Molding Step This step is a step of casting a cement composition into a mold to obtain an uncured molded product. The method of kneading the cement composition before casting and the apparatus used for kneading are not particularly limited, and an omni mixer, a pan-type mixer, a biaxial kneading mixer, a tilting mixer, and the like can be used. Further, the method of casting and molding is not particularly limited. In this step, the strength development of the concrete structure cured by reducing or removing air bubbles in the uncured cement composition is further improved.
Methods for reducing or removing air bubbles in the cement composition include the following methods (i) to (iii).
(I) Method of kneading the cement composition under reduced pressure (ii) Method of defoaming the cement composition after kneading under reduced pressure before placing it in the mold (iii) Method of defoaming the cement composition in the mold A method of defoaming by depressurizing after placing in

(B) Room temperature curing step In this step, the uncured molded product is sealed at 10 to 40 ° C., preferably 15 to 30 ° C. for 24 hours or more, more preferably 24-72 hours, still more preferably 24-48 hours. This is a step of obtaining a cured molded product by removing the mold after curing or curing in the air.
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 concrete structure becomes higher. In addition, the curing time is 24 hours or more, and defects such as chips and cracks are less likely to occur in the cured molded product during demolding.
Further, in this step, the cured molded product is demolded when the compressive strength of the cured molded product is preferably 20 to 100 N / mm ² , more preferably 30 to 80 N / mm ² . When the compressive strength is 20 to 100 N / mm ² or more, defects such as chips and cracks are less likely to occur in the cured molded product during demolding. The compressive strength is 100 N / mm ² or less, and water can be absorbed into the cured molded product with less effort in the water absorption step described later.

(C) Heat Curing Step The step is preferably 70 ° C. or higher and lower than 100 ° C., more preferably 75 to 95 ° C., more preferably 80 to 92 ° C. for 6 hours on the cured molded product obtained in the previous step. In the step of obtaining a cured product after heat curing by performing either or both of the above steam curing or hot water curing and autoclave curing at preferably 100 to 200 ° C., more preferably 160 to 190 ° C. for 1 hour or more. be.
When only steam curing or hot water curing is performed in the step, the curing time is preferably 24 hours or more, more preferably 24-96 hours, still more preferably 36-72 hours. When only autoclave curing is performed, the curing time is preferably 8 to 60 hours, more preferably 12 to 48 hours. When both steam curing or hot water curing and autoclave curing are performed (for example, when steam curing or hot water curing is performed and then autoclave curing is performed), the curing time in steam curing or hot 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 the step, if the curing temperature and the curing time are within the above ranges, the curing time can be shortened and the compressive strength of the concrete structure is improved.

(D) High-temperature heating step In this step, the cured product after heat curing is preferably heated at 150 to 200 ° C., more preferably 170 to 190 ° C. for 24 hours or more, preferably 24 to 72 hours, more preferably 36 to 36 to This is a step of obtaining a concrete structure by heating for 48 hours (excluding heating by autoclave curing).
The heating in this step is usually performed in a dry atmosphere, in other words, in a state where water or water vapor is not artificially supplied. When the heating temperature is 150 ° C. or higher, the heating time can be further shortened, and when the heating temperature is 200 ° C. or lower, the compressive strength of the concrete structure is further improved.
Further, when the heating time is 24 hours or more, the compressive strength of the concrete structure is further improved.

(E) Water Absorption Step The step is an arbitrary step of allowing the cured molded body obtained in the room temperature curing step to absorb water between the room temperature curing step and the heat curing step.
Then, there are the following methods (i) to (v) as a method for causing the cured molded product to absorb water.
(I) Method of immersing the molded body in water under reduced pressure (ii) Method of lowering the water temperature to 40 ° C. or lower while immersing the molded body in boiling water (iii) Immersing the molded body in boiling water After that, a method of taking out the molded body from boiling water and immersing the molded body in water at 40 ° C. or lower (iv) a method of immersing the molded body in water under pressure (v) a drug for improving the permeability of water into the molded body. A method of immersing the molded body in an aqueous solution prepared by

Then, regarding (i) and (ii) above,
(I) As a method of immersing the molded product in water under reduced pressure, there is a method of using equipment such as a vacuum pump and a large decompressing container.
(Ii) As a method of immersing the molded product in boiling water, there is a method of using equipment such as a high-temperature and high-pressure container and a hot and hot water tank. The time for immersing the molded product in water or boiling water under reduced pressure is preferably 3 minutes or longer, more preferably 8 minutes or longer, and further preferably 20 minutes or longer in order to promote water absorption. The upper limit of the immersion time is preferably 60 minutes, more preferably 45 minutes in order to increase the compressive strength of the concrete structure.

The water absorption rate in the water absorption step is 50 mm in diameter and 50 mm in height when the cement composition does not contain coarse aggregate, that is, when the cement composition does not contain aggregate B or aggregate B does not correspond to coarse aggregate. Taking a 100 mm cured molded product as 100% by volume, the content of water in the molded product is preferably 0.2% by volume or more, more preferably 0.3 to 2.0% by volume, and further preferably 0.35 to 50% by volume. It is 1.7% by volume. Further, when the cement composition contains a coarse aggregate, that is, when the aggregate B in the cement composition corresponds to the coarse aggregate, the cured molded body having a diameter of 100 mm and a height of 200 mm is defined as 100% by volume. The content of water in the water is preferably 0.2% by volume or more, more preferably 0.3 to 2.0% by volume, and further preferably 0.35 to 1.7% by volume.
When these water absorption rates are 0.2% by volume or more, the compressive strength of the concrete structure is higher.

13. Characteristics of Concrete Structure The concrete structure of the present invention obtained by the above-mentioned manufacturing method has high compressive strength and is therefore unlikely to crack. Further, the concrete structure can reduce the weight of the member such as reducing the thickness of the member and improve the workability. In addition, since the concrete structure can be made lighter and the span of the bridge can be lengthened, the number of piers can be reduced and the construction cost can be reduced.
Further, the concrete structure of the present invention has excellent wear resistance. For example, the abrasion depth of the concrete structure after 60 minutes, measured according to "ASTM C779", is preferably 0.5 mm or less, more preferably 0.4 mm or less, still more preferably 0.3 mm or less. Is.

Further, the concrete structure of the present invention is excellent in water-shielding property, freeze-thaw resistance, and salt-shielding property (for example, chloride ion, sulfate ion, etc. are difficult to permeate into the web member of the bridge).
Further, the concrete structure of the present invention is excellent in dimensional stability. For example, when a 40 × 40 × 160 mm specimen measured in accordance with JIS A 1129-2: 2010 “Mortar and concrete length change measurement method-Part 2: Contact gauge method” is stored for 6 months. The shrinkage strain of the concrete structure in the above is preferably 10 × 10 ^-6 or less, more preferably 8 × 10 ^-6 or less, still more preferably 6 × 10 ^-6 or less.
Further, the concrete structure of the present invention has a large bending strength. For example, when the concrete structure contains fibers, the bending strength of the concrete structure measured in accordance with JSCE-G 552-2010 "Bending strength and bending toughness test method of steel fiber reinforced concrete" is measured. , preferably 20 N / mm ² or more, more preferably 30 N / mm ² or more, more preferably 35N / mm ² or more.

14. Use of Concrete Structure The concrete structure of the present invention is not limited in the shape of the structural member and the type of the member. For example, it can have any shape such as a panel member, a rod-shaped member, a square member, a tubular member, a box-shaped member, an angle member, and a pipe. Further, these structural members can be used in any combination. Further, the type of the concrete structure of the present invention is not limited. For example, it broadly includes girders, girders, rigid frame structures, bridge girders, etc. of buildings.
Further, the concrete structure of the present invention includes a structure formed in combination with a structural member made of ordinary concrete. Specifically, for example, a structure in which a web member is formed of the concrete structure of the present invention, other structural parts are formed of ordinary concrete, and both members are integrally joined.

Further, a composite prestressed concrete structure can be obtained by using a structural portion formed of ordinary concrete as a prestressed structural portion and integrally joining the structural member formed by the concrete structure of the present invention. A specific example of this structure is that the web member is formed by the concrete structure of the present invention, while the flange portion is formed by ordinary concrete, and both members are integrally joined to form a beam. It is a composite prestressed concrete structure that is being formed.

(A) and (B) of FIG. 2 show an example of a composite prestressed concrete structure. The illustrated structure 20 has a polygonal plate-shaped web member 21 formed by the concrete structure of the present invention, and a plurality of plate-shaped web members 21 are arranged side by side in the longitudinal direction, and upper and lower ends thereof are arranged side by side. Is integrally joined to the flange portion 22 made of ordinary concrete to form a beam. The flange portion 22 made of ordinary concrete is provided with reinforcing bars and is prestressed. By forming high-strength polygonal web members and arranging them side by side to form openings between the web members, the mass of the structure can be significantly reduced.

In the composite prestressed concrete structure shown in FIG. 2, it is necessary that the web member 21 and the flange portion 22 are firmly joined. Therefore, as shown in FIG. 3, a method of forming a tooth-shaped key groove 23 at the upper and lower ends of the web member 21 and engaging and joining with the flange portion (key joining), or a flange at the upper and lower ends of the web member 21. It is advisable to use a method (embedded joining) in which a steel bar that engages with the reinforcement of the portion is provided and this portion is embedded in concrete and joined.

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 Composite concrete porridge 21 Web member (of the present invention) A type of concrete structure)
22 Flange part 23 Keyway

Claims (7)

Cement, silica fume with BET specific surface area of 15 to 25 m ² / g, inorganic powder with 50% volume cumulative particle size of 0.8 to 5 μm, aggregate A with maximum particle size of 1.2 mm or less, high-performance water reducing agent, defoamer A cured product of a cement composition containing at least a foaming agent and water.
Assuming that the total of the cement, silica fume, and inorganic powder is 100% by volume, the content of the cement is 55 to 65% by volume, the content of silica fume is 5 to 25% by volume, and the content of the inorganic powder is 15 to 35% by volume. A concrete structure having a compressive strength of 300 N / mm ^{2 or more.} The concrete structure according to claim 1, further comprising an aggregate B having a maximum particle size of more than 1.2 mm and 13 mm or less. By polishing moderate heat Portland cement or low heat Portland cement, the angular surface portion of the cement particles is formed into a rounded shape with coarse particles having a particle size of 20 μm or more, and the polishing treatment. resulting includes particle size 20μm of less than fine particles, and 50% volume cumulative particle size cement the polishing process 10～18Myuemu, and Blaine specific surface area of the cement is 2100~2900cm ² / g, according to claim 1 or 2. The concrete structure according to 2. The concrete structure according to any one of claims 1 to 3, which contains one or more fibers selected from metal fibers, organic fibers, and carbon fibers, and has a fiber content of 3% by volume or less. The concrete structure according to any one of claims 1 to 4, wherein the concrete structure is a web member. A method for manufacturing a concrete structure, wherein the concrete structure according to any one of claims 1 to 5 is manufactured through at least the following steps (A) to (D).
(A) Molding step of casting the cement composition into a mold to obtain an uncured molded product (B) The uncured molded product is sealed or cured at 10 to 40 ° C. for 24 hours or more. After medium curing, the mold is removed from the mold to obtain a cured molded product. Room temperature curing step (C) The cured molded product is subjected to steam curing or hot water curing at 70 ° C. or higher and lower than 100 ° C. for 6 hours or longer. , One or both of autoclave curing at 100 to 200 ° C. for 1 hour or more to obtain a cured product after heat curing (D) The cured product after heat curing is 24 at 150 to 200 ° C. High-temperature heating step to obtain the concrete structure by heating for more than an hour (excluding heating by autoclave curing). The method for producing a concrete structure according to claim 6, further comprising a water absorption step of causing the cured molded body to absorb water between the normal temperature curing step and the heat curing step.

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