JP2009006541A - Method for producing cement hardened body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a cement hardened body, capable of significantly improving compressive strength by reducing air quantity to 2% or less in a short time. <P>SOLUTION: The method comprises steps of (A) kneading materials including at least cement and water to prepare a kneaded matter with a flow value of 230 mm or more, which is measured without 15 falling motions according to the method described in "JIS R 5201 (physical testing method of cement) 11. flow test"; (B) defoaming the kneaded matter obtained in the step (A) by stirring under reduced pressure; and (C) supplying the defoamed kneaded matter obtained in the step (B) into a form followed by curing and hardening to thereby obtain a cement hardened body. A defoaming device 1 in the step (B) includes a main body including a cylindrical wall part 2a and a tapered wall part 2b, a lid body mounted with a decompression means 4, and a stirring blade 3 for stirring the kneaded matter 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a hardened cementitious material that can significantly improve mechanical properties, particularly compressive strength.

Conventionally, hydraulic compositions (concrete etc.) excellent in mechanical properties (compressive strength etc.) have been developed. For example, Patent Document 1 discloses inorganic solid particles A (for example, silica dust particles) having a particle size of 50 to 0.5 μm and solid particles B (for example, having a particle size of 0.5 to 100 μm and at least one order larger than the particle A). At least 20% by weight of Portland cement), a surface active dispersant (for example, a concrete superplasticizer such as highly condensed naphthalenesulfonic acid / formaldehyde condensate), and additional material C (sand, stone, metal fibers, etc.) A hydraulic composite material is disclosed which is selected from the group consisting of: This hydraulic composite material develops a compressive strength of 100 to 150 N / mm ² after curing.

Further, Patent Document 2, (A) cement 100 parts by weight of the Blaine specific surface area 2,500~5,000cm ² / g and, (B) fine particles 10 to 40 parts by weight of the BET specific surface area 5~25m ² / g And (C) 20-55 parts by weight of inorganic particles having a Blaine specific surface area of 3,000-30,000 cm ² / g and a Blaine specific surface area larger than the cement, and (D) a particle size of 2 mm or less, and A hydraulic composition comprising an aggregate having a particle content of 75 μm or less of 2.0% by weight or less, wherein the aggregate (D) is mixed in the cement (A) and the fine particles (B ) And 30 to 130 parts by weight of the hydraulic composition with respect to 100 parts by weight of the total amount of the inorganic particles (C). A hardened cement body using this hydraulic composition exhibits a compressive strength of about 200 to 220 N / mm ² .

  In the cement kneaded material using the hydraulic material described in Patent Documents 1 and 2, since a relatively large amount of air is mixed during the kneading, at the end of kneading, the kneaded material measured with a mortar air meter The amount of air is about 4-7%. Since the presence of such a large amount of air becomes a factor that inhibits the strength development of the cementitious hardened body, it is desired to reduce the amount of air.

Conventionally, as a method for defoaming a cement kneaded product, for example, a method of defoaming by supplying vibration after supplying the cement kneaded product to a mold (Patent Document 3) is known.
Japanese Patent Publication No. 60-59182 JP 2002-338324 A JP-A-8-151733

When the method of defoaming by applying vibration described in Patent Document 3 described above is applied to a cement kneaded product having a compressive strength of 100 N / mm ² or more, it is measured with a mortar air meter even if vibration is applied for a long time. It is difficult to reduce the amount of air in the kneaded product to 2% or less, and it is also difficult to significantly improve the compressive strength.
In the present invention, even in a cement kneaded product having a compressive strength of 100 N / mm ² or more, the amount of air (measured by a mortar air meter) is reduced to 2% or less in a short time, and the compressive strength is greatly improved. An object of the present invention is to provide a method for producing a hardened cementitious material.

As a result of intensive studies to solve the above-mentioned problems, the inventor stirs and defoams a cement kneaded material having a specific flow value under reduced pressure, and then feeds it into a mold to cure and harden it. Thus, the present inventors have found that the amount of air in the cement kneaded product can be reduced and the compressive strength of the cementitious hardened body can be greatly improved, and the present invention has been completed.
That is, the present invention provides the following [1] to [5].

[1] (A) A material containing at least cement and water is kneaded, and in the method described in "JIS R 5201 (physical test method for cement) 11. Flow test", do not perform the falling motion 15 times. A step of preparing a kneaded product having a measured value of 230 mm or more, (B) a step of stirring and defoaming the kneaded product under reduced pressure, and (C) supplying the defoamed kneaded product into a mold And a step of curing and curing to obtain a cementitious cured body.
[2] The method for producing a hardened cementitious material according to [1], wherein the stirring in the step (B) is performed using only a stirring blade.
[3] The method for producing a hardened cementitious material according to [1] or [2], wherein the stirring in the step (B) is performed under a reduced pressure of −0.09 MPa or more.
[4] Supply of the defoamed kneaded product in the step (C) is as follows: (i) After the supply pipe is disposed so that the lower end is positioned in the vicinity of the bottom surface in the mold, A method of supplying the kneaded material through the supply pipe while maintaining the state where the lower end of the supply pipe is buried in the kneaded product being stored; (ii) supplying a supply plate to the bottom surface of the mold A method of supplying the kneaded material by allowing the kneaded material to flow down on the surface of the supply plate after the lower end is positioned in the vicinity and disposed so as to have an inclination angle with respect to the bottom surface in the mold. The method for producing a hardened cementitious body according to any one of the above [1] to [3], which is carried out by any one of or a combination of two or more.
[5] The method for producing a hardened cementitious material according to any one of the above [1] to [4], wherein the compressive strength of the hardened cementitious material obtained in the step (C) is 100 N / mm ² or more.

According to the method for producing a cementitious hardened body of the present invention, the amount of air in a cement kneaded product (measured value by a mortar air meter) can be reduced to 2% or less in a short time, and as a result, cementum hardening is achieved. The body's compressive strength, flow value, etc. can be greatly increased.
Moreover, the manufacturing method of the cementitious hardened | cured material of this invention can be easily implemented with a simple installation and process.

Hereinafter, the present invention will be described in detail.
In the method described in “JIS R 5201 (physical test method for cement) 11. flow test”, the method for producing a hardened cementitious material according to the present invention includes (A) kneading a material containing at least cement and water. A step of preparing a kneaded product having a measured value of 230 mm or more without performing the falling motion 15 times, (B) a step of stirring and defoaming the kneaded product under reduced pressure, and (C) the defoaming step. Supplying the kneaded material into a mold, curing and curing the mixture, and obtaining a cementitious hardened body.

[Step (A): Kneaded product preparation step]
In the step (A), a material containing at least cement and water is kneaded, and in the method described in “JIS R 5201 (Cement physical test method) 11. Flow test”, 15 falling motions are not performed. This is a step of preparing a kneaded material having a measured flow value of 230 mm or more.
Preferable examples of the material of the kneaded material include those containing cement, fine pozzolanic powder, fine aggregate, water, and a water reducing agent.
Examples of the cement include various Portland cements such as ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, and low heat Portland cement.

In the present invention, in order to improve the early strength after curing, it is preferable to use early-strength Portland cement. On the other hand, when trying to improve the fluidity before curing, it is preferable to use moderately hot Portland cement or low heat Portland cement.
The brane specific surface area of the cement is preferably 2,500 to 5,000 cm ² / g, more preferably 3,000 to 4,500 cm ² / g. When the value is less than 2,500 cm ² / g, the hydration reaction becomes inactive and there is a drawback that the strength of the cementitious cured body is lowered. When the value exceeds 5,000 cm ² / g, it takes a lot of time to grind the cement, and the amount of water for obtaining a predetermined fluidity increases, so that the strength of the cementitious hardened body decreases. There are disadvantages such as.

Examples of the pozzolanic fine powder include silica fume, silica dust, fly ash, slag, volcanic ash, silica sol, and precipitated silica. In general, silica fume and silica dust have a BET specific surface area of 5 to 25 m ² / g and do not need to be pulverized, and thus are preferably used in the present invention.
The BET specific surface area of the pozzolanic fine powder is preferably 5 to 25 m ² / g, more preferably 8 to 15 m ² / g. When the value is less than 5 m ² / g, there is a drawback in that the strength of the cementitious hardened body is lowered because the packing properties of the particles constituting the kneaded product (cement composition) are not dense. When the value exceeds 25 m ² / g, the amount of water for obtaining a predetermined fluidity increases, and thus there is a drawback that the strength of the cementitious cured body is lowered.
The compounding amount of the pozzolanic fine powder is preferably 5 to 40 parts by mass, more preferably 10 to 40 parts by mass with respect to 100 parts by mass of the cement. If the value is outside the range of 5 to 40 parts by mass, the fluidity is lowered, and it takes time to mold the cementitious hardened body, or the amount of air in the kneaded product can be reduced to 2% or less in a short time. There may be inconveniences such as difficulty.

Examples of fine aggregates include river sand, land sand, sea sand, crushed sand, and quartz sand. A fine aggregate may be used individually by 1 type, and may use 2 or more types together.
The proportion of particles of 75 μm or less in the fine aggregate is preferably 2.0% by mass or less, more preferably 1.5% by mass or less. When this value exceeds 2.0 mass%, the fluidity | liquidity of a kneaded material will fall and it may take time to manufacture a cementitious hardened | cured material.
The maximum particle size of the fine aggregate is preferably 2.0 mm or less, more preferably 1.5 mm or less, and particularly preferably 1.0 mm or less, from the viewpoint of improving strength development.
The blending amount of the fine aggregate is preferably 10 to 130 parts by mass with respect to 100 parts by mass of cement from the viewpoints of the fluidity of the kneaded material and the strength of the cementitious hardened body. Further, from the viewpoint of reducing self-shrinkage and drying shrinkage, and reducing the amount of hydration heat, the amount of fine aggregate is more preferably 30 to 130 parts by weight, particularly preferably 100 parts by weight of cement. Is 40 to 130 parts by mass.

Examples of water reducing agents include lignin-based, naphthalenesulfonic acid-based, melamine-based, and polycarboxylic acid-based water reducing agents, AE water reducing agents, high-performance water reducing agents, and high-performance AE water reducing agents. Among these, from the viewpoint of the water reducing effect, a high performance water reducing agent and a high performance AE water reducing agent are preferable, and a polycarboxylic acid-based high performance water reducing agent and a high performance AE water reducing agent are particularly preferable.
The water reducing agent can be used in either liquid or powder form.
The blending amount of the water reducing agent is preferably 0.1 to 4.0 parts by mass, more preferably 0.1 to 2.0 parts by mass in terms of solid content with respect to 100 parts by mass of cement. If the amount is less than 0.1 parts by mass, kneading becomes difficult, fluidity is lowered, and it takes time to produce a hardened cementitious body, and the amount of air in the kneaded product is reduced to 2% or less in a short time. There are drawbacks such as difficulty in reduction. If the amount exceeds 4.0 parts by mass, material separation or setting delay may occur, or the strength of the cementitious hardened body may decrease.

  The amount of water is preferably 10 to 30 parts by mass, more preferably 12 to 25 parts by mass with respect to 100 parts by mass of cement. When the amount is less than 10 parts by mass, kneading becomes difficult, fluidity is lowered, and it takes time to produce a hardened cementitious material, and the amount of air in the kneaded material is reduced to 2% or less in a short time. There are drawbacks such as difficulty. When the amount exceeds 30 parts by mass, the strength and the like of the cementitious hardened body are lowered.

In the present invention, in addition to the materials described above, inorganic particles having a larger Blaine specific surface area than cement can be used. By using the inorganic particles, fluidity, strength after curing, denseness and the like are improved.
Examples of inorganic particles include slag, limestone powder, feldspar, mullite, alumina powder, quartz powder, fly ash, volcanic ash, silica sol, carbide powder, nitride powder and the like. Among these, slag, limestone powder, and quartz powder are preferably used in terms of cost and quality stability after curing.
The Blaine specific surface area of the inorganic particles is preferably more than 2,500 cm ² / g and not more than 30,000 cm ² / g, more preferably 4,000 to 20,000 cm ² / g. When the value is 2,500 cm ² / g or less, the fluidity is lowered, and it takes time to produce a cementitious cured body, and it is difficult to reduce the amount of air in the kneaded material to 2% or less in a short time. There are drawbacks such as. When the value exceeds 30,000 cm ² / g, it takes time and effort to grind, making it difficult to obtain the material, it is difficult to obtain a predetermined fluidity, and it takes time to manufacture a hardened cementitious material. is there.

The inorganic particles preferably have a larger Blaine specific surface area than cement. In this case, the inorganic particles have a particle size that fills the gap between the cement and the pozzolanic fine powder, and high fluidity (for example, self-filling property) can be ensured.
The difference in the Blaine specific surface area between the inorganic particles and the cement is preferably 1,000 cm ² / g or more, more preferably 2,000 cm ² / g or more, from the viewpoint of fluidity before curing and strength development after curing. is there.
The compounding amount of the inorganic particles is preferably 55 parts by mass or less, more preferably 10 to 50 parts by mass with respect to 100 parts by mass of cement. When the value exceeds 55 parts by mass, the mechanical strength and the like of the cementitious hardened body are lowered.

In the present invention, in addition to the materials described above, one or more fibers selected from metal fibers, organic fibers, and carbon fibers can be used. By using metal fibers, the bending strength and the fracture energy after curing are improved. Examples of metal fibers include steel fibers and amorphous fibers. Among these, steel fibers are excellent in strength and are preferable from the viewpoints of cost and availability.
The metal fiber preferably has a diameter of 0.01 to 1.0 mm and a length of 2 to 30 mm.
If the diameter is less than 0.01 mm, the strength of the fiber itself is insufficient, and it is easy to break when subjected to tension. When the diameter exceeds 1.0 mm, the number per the same blending amount decreases, and the effect of improving the bending strength and fracture energy decreases.
On the other hand, when the length is less than 2 mm, the effect of improving the bending strength and fracture energy is lowered. If the length exceeds 30 mm, fiber balls are likely to occur during kneading.
The compounding amount of the metal fibers in the kneaded product is preferably 4.0% by volume or less, more preferably 0.5 to 3.0% by volume.
When the content of the metal fiber is increased, the unit water amount is also increased in order to ensure the workability at the time of kneading. Therefore, the blending amount of the metal fiber is preferably within the above numerical range.

By including organic fibers and carbon fibers, the fracture energy and the explosion resistance after curing are improved.
As the organic fiber, vinylon fiber, polypropylene fiber, polyethylene fiber, aramid fiber, or the like can be used. Among these, vinylon fibers are preferably used from the viewpoints of strength, cost, availability, and the like.
As the carbon fiber, a PAN-based carbon fiber or a pitch-based carbon fiber can be used.
The organic fiber or carbon fiber preferably has a diameter of 0.005 to 1.0 mm and a length of 2 to 30 mm. If the diameter is less than 0.005 mm, the strength of the fiber itself is insufficient, and it is easy to break when subjected to tension. When the diameter exceeds 1.0 mm, the number per the same blending amount decreases, and the effect of improving the breaking energy of the cured body is lowered.
On the other hand, when the length is less than 2 mm, the adhesive force with the matrix is lowered, and the effect of improving the fracture energy and the like is lowered. If the length exceeds 30 mm, fiber balls are likely to occur during kneading.
The amount of organic fiber or carbon fiber in the kneaded product is preferably 10% by volume or less, more preferably 0.5 to 7.0% by volume.
The blending amount of the fiber is determined from the viewpoints of fluidity, fracture energy of the cured body, and explosion resistance. That is, generally, when the fiber content is increased, the fracture energy and explosion resistance are improved, while the unit water amount is increased to ensure fluidity. Therefore, it is preferable that the compounding quantity of organic fiber or carbon fiber exists in said numerical range.

The method for kneading the above materials is not particularly limited. When preparing a paste or mortar, for example, (a) materials other than water and water reducing agents (specifically, cement, pozzolanic fine powder, fine aggregate, and inorganic particles and metal fibers blended as necessary Etc.) are mixed in advance to prepare a premix material, and the premix material, water and a water reducing agent are put into a mixer and kneaded, and (b) a powdered water reducing agent is prepared, except for water. Materials (specifically, cement, pozzolanic fine powder, fine aggregate, water reducing agent, and inorganic particles and metal fibers blended as necessary) to prepare a premix material And a method of adding the premix material and water into a mixer and kneading, and (c) a method of individually introducing each material into a mixer and kneading.
The mixer used for kneading can be a normal type used for kneading concrete. For example, an oscillating mixer, a pan type mixer, a biaxial kneading mixer, and the like can be given.

In this step, the kneaded material containing the above materials is kneaded until the flow value is 230 mm or more, preferably 240 mm or more, more preferably 250 mm or more.
Here, the flow value is a value measured in the method described in “JIS R 5201 (Cement physical test method) 11. Flow test” without performing 15 drop motions (in this specification, It is also referred to as “0 stroke flow value”. If the zero-stroke flow value is less than 230 mm, it is difficult to reduce the amount of air in the kneaded material to 2% or less in a short time in the next step (B).

[Step (B): Defoaming step]
Step (B) is a step of stirring and defoaming the kneaded product under reduced pressure.
Hereinafter, the step (B) will be described with reference to the drawings.
FIG. 1 is a diagram conceptually showing an example of a defoaming device used in the step (B) (partly including a cross-sectional portion).
In FIG. 1, a defoaming device 1 includes a decompression tank 2 for housing the kneaded product obtained in the step (A), and a stirring blade (stirring means) for stirring the kneaded product 5 accommodated in the decompression tank 2. 3) and a decompression means 4 for bringing the inside of the decompression tank 2 into a decompressed state.
The decompression tank 2 includes a cylindrical wall portion 2a and a tapered wall portion 2b that extends continuously downward from the lower end of the cylindrical wall portion 2a and is inclined toward the discharge port 2c. The kneaded material 5 in the decompression tank 2 is defoamed by stirring under reduced pressure in the decompression tank 2, and the amount of air (measured value by a mortar air meter) becomes 2% or less in a short time. The defoamed kneaded product 5 is supplied from a discharge port 2c through a supply pipe 7 provided with an opening / closing valve 6 into a mold (not shown) installed outside.
In addition, defoaming is degassing the air mixed in the kneaded material 5 by kneading.

A preferred example of the stirring means is a stirring blade (see “stirring blade 3” in FIG. 1).
In the present invention, by using only the stirring blade 3 without using a complicated apparatus, the kneaded material 5 accommodated in the vacuum tank 2 can be defoamed until the air amount becomes 2% or less. it can.
In the defoaming apparatus 1 shown in FIG. 1, the stirring blade 3 in which the two-stage rotating blades 3 b and 3 b are provided in the vertical direction is used below the rotating shaft 3 a extending in the vertical direction. The form 3 is not limited to this example. For example, it is possible to use one provided with one or three stages of rotating blades instead of two stages at the lower part of the rotating shaft 3a. Further, the number of blades of the rotary blade 3b is not particularly limited, and may be 2 to 4, for example.
The rotation speed of the stirring blade is preferably 5 rpm or more, more preferably 7 rpm or more, and particularly preferably 9 rpm or more. By setting the number of revolutions to 5 rpm or more, the amount of air in the kneaded product can be reduced to 2% or less under a reduced pressure with a short stirring time.
If the rotation speed of the stirring blade is 30 rpm or more, a mechanism for rotating the stirring blade at a high speed, such as a large motor, is required, which increases the cost and increases the rotation speed of the stirring blade. However, the time required for defoaming is almost the same. Therefore, the rotation speed of the stirring blade is preferably less than 30 rpm, more preferably 20 rpm or less.
The stirring time (defoaming time) of the kneaded product varies depending on the stirring means, but is preferably 30 seconds or more, more preferably 60 seconds or more, and particularly preferably 90 seconds or more.
The upper limit of the stirring time of the kneaded product is not particularly limited, but is preferably 5 minutes, more preferably 4 minutes, and particularly preferably 3 minutes from the viewpoint of the efficiency of the kneading work.
The volume of the kneaded product is preferably 10 to 2000 liters, more preferably 20 to 1500 liters, and particularly preferably 30 to 1000 liters from the viewpoints of the efficiency of the kneading work and the achievement of the target air amount.

The degree of vacuum in the vacuum tank during stirring is preferably −0.09 MPa or more, more preferably −0.095 MPa or more. By setting the degree of vacuum to −0.09 MPa or more, the amount of air in the kneaded product can be reduced to 2% or less in a short time.
Here, the degree of reduced pressure refers to a pressure difference from the pressure when the pressure (atmospheric pressure) in a state where there is no reduced pressure is used as a reference. For example, when the pressure is 0.10 MPa in a state where there is no pressure reduction, the pressure reduction degree of −0.09 MPa or more means that the pressure is 0.01 MPa or less.
A vacuum pump or the like can be used as the decompression means.
The amount of air in the defoamed kneaded material (measured value in accordance with the method defined in “JIS A 1128 (Test method using air pressure of fresh concrete-air chamber pressure method)”; volume ratio (%)) is , Preferably 2.0% or less, more preferably 1.5% or less, particularly preferably 1.0% or less. When the amount of air exceeds 2.0%, the degree of increase in compressive strength due to defoaming tends to remain at 10 to 20%. If the amount of air is 2.0% or less, an increase in compressive strength exceeding 25% can be realized.

[Step (C): Curing step]
Step (C) is a step of supplying the defoamed kneaded material into a mold, curing and curing it, and obtaining a cementitious hardened body.
When discharging the defoamed kneaded material from the decompression tank 2, air is supplied into the decompression tank 2 from an air supply port (not shown) at the top of the decompression tank 2, and the inside of the decompression tank 2 is returned to atmospheric pressure. Then, the kneaded product 5 is discharged to the outside through the supply pipe 7 (see FIG. 1). In order to increase the discharge speed of the kneaded material, air may be pressed into the decompression tank 2 from the air supply port.

As a method for supplying the kneaded material 5 discharged from the decompression tank 2 into the mold, the following method may be used in order to prevent air from entering. 2 and 3 show an example of a method for supplying the defoamed kneaded material into the mold.
As a method of supplying the defoamed kneaded material into the mold, (i) as shown in FIG. 2, after the supply pipe 7 is disposed so that the lower end is positioned near the bottom surface in the mold 8. A method of supplying the kneaded material 5 through the supply pipe 7 while keeping the lower end of the supply pipe 7 buried in the kneaded material 5 being stored in the mold 8, (ii) as shown in FIG. In addition, after the supply plate 9 is disposed so that the lower end is positioned near the bottom surface in the mold 8 and has an inclination angle with respect to the bottom surface in the mold 8, the supply plate 9 is kneaded on the surface of the supply plate 9. Any of the methods of allowing the product 5 to flow down and supplying the kneaded product 5 can be employed. Note that the two methods (i) and (ii) may be used in combination.
In addition, the curing method is not particularly limited, and air curing, steam curing, or the like may be performed.

Compressive strength of cementitious hardened body obtained by the production method of the present invention is preferably 100 N / mm ² or more, more preferably 120 N / mm ² or more, further preferably 140 N / mm ² or more.
Further, the static modulus of elasticity of the cementitious cured body is preferably 40 kN / mm ² or more, more preferably 43kN / mm ² or more, further preferably 45 kN / mm ² or more.
The cementitious cured body obtained by the production method of the present invention preferably has a compressive strength of 25% or more, more preferably compared to a cured body cured without performing the treatment (defoaming treatment) in the step (B). Increase by 30% or more. In addition, the cementitious cured body obtained by the production method of the present invention also improves other mechanical properties such as a static elastic modulus.
Further, according to the production method of the present invention, the flow value of the kneaded product (zero flow value) is increased by the treatment (defoaming treatment) in the step (B) as compared to the kneaded product not subjected to the defoaming treatment. Therefore, the supply work of the kneaded material into the mold becomes easy.

Hereinafter, the present invention will be described by way of examples.
[Materials used]
The following materials were used.
(A) Low heat Portland cement (manufactured by Taiheiyo Cement; Brain specific surface area: 3,200 cm ² / g)
(B) Silica fume (BET specific surface area: 13 m ² / g)
(C) Silica sand No. 5 (maximum particle size: 0.6 mm)
(D) Polycarboxylic acid-based high-performance water reducing agent (e) Tap water (f) Quartz powder (Brain specific surface area: 7,000 cm ² / g)
(G) Steel fiber (diameter: 0.2 mm, length: 15 mm)

[Example 1]
(1) Preparation of kneaded material and properties of the kneaded material 100 parts by mass of low heat Portland cement, 30 parts by mass of silica fume, 30 parts by mass of quartz powder, 110 parts by mass of silica sand, 22 parts by mass of water, and polycarboxylic acid-based high-performance water reducing agent 1 0.0 part by mass (in terms of solid content) was charged into a forced biaxial mixer and then kneaded for 7 minutes to prepare a kneaded product. The obtained kneaded product was subjected to the following measurements.
The amount of air in the kneaded product was measured according to the method specified in “JIS A 1128 (Test Method for Fresh Concrete with Air Pressure—Air Chamber Pressure Method)”. Product name: Measured with an air meter C13).
The flow value of the kneaded product was measured in the method described in “JIS R 5201 (Cement physical test method) 11. Flow test” without performing 15 drop motions. It was poured into (made of steel), pre-positioned at 20 ° C. for 24 hours, and then steam-cured at 90 ° C. for 48 hours to obtain hardened cementitious bodies (3 pieces). The compressive strength and static elastic modulus of the hardened cementitious body (3 pieces) were measured.
In addition, the method (ii) shown in above-mentioned FIG. 2 was used for the supply method of the kneaded material into the mold.
As a result, the kneaded product before the defoaming treatment has an air amount of 6.8%, a flow value of 270 mm, a compressive strength (average value of three) of 210 N / mm ² , and a static elastic modulus. It was 51.8kN / mm ^2.

(2) Defoaming treatment After supplying the kneaded material (volume: 35 liters) into the decompression tank 2 (volume of the internal space of the decompression tank: 70 liters) using the defoaming apparatus 1 shown in FIG. 2 under the atmosphere where the degree of decompression in -2 is -0.09 to -0.093 MPa, the kneaded product is stirred under the condition that the rotation speed of the stirring blade 3 is 9.5 rpm, and the kneaded product is defoamed for 2 minutes. went.
(3) Properties of defoamed kneaded material and cured body thereof After supplying air into the decompression tank 2 shown in FIG. 1 and returning the inside of the decompression tank 2 to atmospheric pressure, the kneaded product 5 is discharged from the decompression tank 2. The properties of the kneaded product 5 discharged from the outlet 2b and defoamed and the properties of the hardened cementitious material obtained by curing the kneaded product 5 were measured by the same method as in (1) above.
As a result, the kneaded product after the defoaming treatment has an air amount of 1.0%, a flow value of 290 mm, a compressive strength (average value of three) of 282 N / mm ² , and a static elastic modulus. It was 58.5 kN / mm ² .
From this result, the properties (air amount, flow value, compressive strength, static elastic modulus) of the kneaded product and the cured product after the defoaming treatment are all improved as compared with the properties of the kneaded product and the cured product before the defoaming treatment. I understand that. In particular, a significant improvement of about 35% was observed in terms of compressive strength.

[Example 2]
Instead of the material of Example 1, 100 parts by mass of low heat Portland cement, 30 parts by mass of silica fume, 110 parts by mass of silica sand, 22 parts by mass of water and 1.0 part by mass of polycarboxylic acid-based high-performance water reducing agent (in terms of solid content) A kneaded material was prepared in the same manner as in Example 1 except that was used.
The properties of the kneaded material before the defoaming treatment were measured in the same manner as in Example 1 except that the static elastic modulus was not measured.
As a result, the kneaded product before the defoaming treatment had an air amount of 6.1%, a flow value of 250 mm, and a compressive strength (average value of three) of 150 N / mm ² .
Further, the above-mentioned kneaded material was subjected to defoaming treatment in the same manner as in Example 1.
The properties of the kneaded product after the defoaming treatment were measured in the same manner as in Example 1 except that the static elastic modulus was not measured.
As a result, the kneaded product after the defoaming treatment had an air amount of 0.8%, a flow value of 272 mm, and a compressive strength (average value of 3 pieces) of 202 N / mm ² .

[Example 3]
Instead of the material of Example 1, 100 parts by mass of low heat Portland cement, 30 parts by mass of silica fume, 30 parts by mass of quartz powder, 110 parts by mass of silica sand, 22 parts by mass of water, 1.0 mass of polycarboxylic acid-based high-performance water reducing agent A kneaded material was prepared in the same manner as in Example 1 except that parts (in terms of solid content) and steel fibers (volume ratio in the kneaded material: 2%) were used.
The properties of the kneaded material before the defoaming treatment were measured in the same manner as in Example 1 except that the static elastic modulus was not measured.
As a result, the kneaded product before the defoaming treatment had an air amount of 5.8%, a flow value of 260 mm, and a compressive strength (average value of three) of 215 N / mm ² .
Further, the above-mentioned kneaded material was subjected to defoaming treatment in the same manner as in Example 1.
The properties of the kneaded product after the defoaming treatment were measured in the same manner as in Example 1 except that the static elastic modulus was not measured.
As a result, the kneaded product after the defoaming treatment is air quantity of 0.8% flow value is 286 mm, compressive strength (average value of this 3) it was 289N / mm ^2.

[Comparative Example 1]
Using the same kneaded material as in Example 1, the kneaded material was supplied to a container having a length of 200 mm × width of 200 mm × height of 500 mm, and the kneaded material was externally used at 240 Hz for 30 minutes using a table vibrator. After applying this vibration, the properties of the kneaded material were measured in the same manner as in Example 1 except that the static elastic modulus was not measured.
As a result, the kneaded material after the vibration was applied had an air amount of 2.8%, a flow value of 274 mm, and a compressive strength (average value of three) of 245 N / mm ² .
From this result, it was found that the amount of air in the kneaded material could not be reduced to 2.0% or less even when the kneaded material was vibrated for a long time (30 minutes).

It is a figure which shows notionally an example of the defoaming apparatus of this invention. It is a figure which shows an example of the means for supplying a kneaded material in a formwork. It is a figure which shows the other example of the means for supplying a kneaded material in a formwork.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Defoamer 2 Depressurization tank 2a Cylindrical wall part 2b Tapered wall part 2c Discharge port 3 Stirring blade 3a Rotating shaft 3b Rotor blade 4 Pressure reducing means 5 Kneaded material 6 Opening valve 7 Supply pipe 8 Formwork 9 Supply plate

Claims (5)

(A) A value obtained by kneading a material containing at least cement and water and measuring 15 times without performing the falling motion in the method described in “JIS R 5201 (Cement physical test method) 11. Flow test”. A step of preparing a kneaded product having a thickness of 230 mm or more,
(B) a step of stirring and defoaming the kneaded product under reduced pressure;
(C) supplying the above-mentioned degassed kneaded material into a mold, curing and curing it, and obtaining a cementitious cured product.   The method for producing a hardened cementitious body according to claim 1, wherein the stirring in the step (B) is performed using only a stirring blade.   The method for producing a hardened cementitious material according to claim 1 or 2, wherein the stirring in the step (B) is performed under a reduced pressure of -0.09 MPa or more.   In the step (C), the defoamed kneaded product is supplied while (i) the supply pipe is disposed in the vicinity of the bottom surface in the mold so that the lower end is positioned and then stored in the mold. A method of supplying the kneaded material through the supply pipe while maintaining a state where the lower end of the supply pipe is buried in the kneaded product, (ii) a lower end of the supply plate near the bottom surface in the mold Any of the methods of supplying the kneaded material by allowing the kneaded material to flow down on the surface of the supply plate after being disposed so as to have an inclination angle with respect to the bottom surface in the mold The method for producing a cementitious hardened body according to any one of claims 1 to 3, which is performed by using one or two or more in combination. The method for producing a hardened cementitious material according to any one of claims 1 to 4, wherein the compressive strength of the hardened cementitious material obtained in the step (C) is 100 N / mm ² or more.

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