JP6211762B2 - Method for producing concrete molded body - Google Patents

Description

  The present invention relates to a method for producing a concrete molded body.

Conventionally, several methods aimed at obtaining a high-strength concrete molded body have been proposed.
For example, in Patent Document 1, a frame is composed of a mold frame in which a dewatering / degassing sheet is affixed to the surface of a barrier plate, and concrete is placed in the frame of the mold with the dehydration / degasification sheet affixing surface inside. A concrete pouring method is described in which a depressurized state is formed inside the dewatering / degassing sheet after being driven.

  Further, for example, in Patent Document 2, prior to producing a lightweight aerated concrete by high-pressure steam curing of a mortar foam, the mortar foam is put in a sealed container and the moisture is reduced to a saturated steam pressure below the foam temperature. In the vacuum deaeration processing method of the lightweight cellular concrete to be evaporated, the vacuum deaeration processing method of the lightweight cellular concrete is characterized in that the end point of the vacuum deaeration processing is set by using the amount of water evaporated from the foam as an index. Has been.

JP-A-4-309663 JP-A-5-105545

  However, the present inventors have found that it is difficult to obtain a concrete molded body having a sufficiently high strength by the conventional methods as described in Patent Documents 1 and 2.

  An object of the present invention is to provide a production method capable of obtaining a concrete molded body having higher strength than conventional ones.

As described above, the present inventor diligently studied the cause of difficulty in obtaining a concrete molded body having a sufficiently high strength by the conventional method, and completed the present invention.
The present invention includes the following (1) to (7) .
(1) A defoaming step [1] for obtaining a defoamed concrete by holding a concrete composition having a water cement ratio adjusted to 14 to 20% in a reduced-pressure atmosphere;
A defoaming step [2] for obtaining defoamed fibers by holding the reinforcing fibers soaked in a cement solution having a water-cement ratio adjusted to 14 to 70% in a reduced-pressure atmosphere;
After placing the defoamed concrete and the defoamed fiber into a mold, it is cured, and a molding step to obtain a high strength concrete molded body ,
The reinforcing fiber is any one of polyvinyl alcohol fiber excluding carbon fiber, polypropylene fiber, nylon fiber, steel fiber, steel cord, polyethylene fiber, glass fiber, alkali-resistant glass fiber, steel fiber, and stainless fiber. A method for producing a concrete compact.
(2) The method for producing a concrete molded body according to (1), wherein the concrete composition further contains an organic synthetic fiber.
(3) The method for producing a concrete molded body according to (1) or (2), wherein the reinforcing fiber does not have a water-repellent organic material on a surface.
(4) The method for producing a concrete molded body according to any one of (1) to (3), wherein the concrete composition includes an admixture and an admixture.
(5) The method for producing a concrete molded body according to any one of (1) to (4), wherein the length of the reinforcing fiber is 0.1 mm or more.
(6) The method for producing a concrete molded body according to any one of (1) to (5), wherein in the defoaming step [2], the reinforcing fiber is in the form of a sheet-like woven fabric.
(7) The defoaming step [1]
This is a step of obtaining a defoamed concrete by obtaining a microwave irradiation time based on the water cement ratio at the time of preparation of the concrete composition, and irradiating the irradiation time and microwave to the concrete composition in a reduced pressure atmosphere. The method for producing a concrete molded body according to any one of (1) to (6) above.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method from which the concrete molded object whose intensity | strength is higher than before can be obtained can be provided.

It is a cross-sectional enlarged photograph of the concrete molding obtained by the manufacturing method of this invention. It is the schematic of the apparatus which can be used in the manufacturing method of this invention. It is a flowchart which shows the example of the operation procedure in the manufacturing method of this invention.

The present invention will be described.
In the present invention, a defoaming step [1] for obtaining a defoamed concrete by holding a concrete composition having a water cement ratio adjusted to 14 to 20% in a reduced-pressure atmosphere, and a water cement ratio adjusted to 14% or more. A defoaming step [2] for obtaining defoamed fibers by holding the reinforcing fibers soaked in the cement solution in a reduced-pressure atmosphere, and curing the defoamed concrete and the defoamed fibers after placing them in a mold. And a molding step for obtaining a high-strength concrete molded body.
Hereinafter, such a method for producing a concrete molded body is also referred to as “the production method of the present invention”.

  According to the production method of the present invention, it is possible to obtain a concrete molded body having a higher bending strength than conventional ones. This molded body has high strength without using a steel material, and when the steel material is not used, the steel material does not corrode due to salt or the like entering from the outside, and is excellent in durability.

<Concrete composition>
First, the concrete composition used in the production method of the present invention will be described.
In the production method of the present invention, the concrete composition means an uncured mixture containing at least cement and water. Therefore, in the present invention, the concrete composition may include general mortar and cement paste.

  In the production method of the present invention, the concrete composition contains cement and water, and may further contain aggregate, admixture, and admixture. Moreover, it is preferable that a concrete composition contains a silica fume as an admixture.

  The concrete composition in the production method of the present invention preferably contains the admixture and the admixture.

  Here, a cement is not specifically limited, For example, a conventionally well-known thing can be used, for example, a Portland cement can be used. Specifically, for example, ordinary Portland cement, early-strength Portland cement, blast furnace cement, low heat Portland cement, intermediate heat Portland cement, and the like can be used.

  Water is not particularly limited, and for example, tap water, ion exchange water, pure water, and the like can be used.

The aggregate is also not particularly limited, and conventionally known aggregates can be used, for example, fine aggregates and coarse aggregates can be used.
As the fine aggregate, land sand, river sand, crushed sand, sea sand, dredged sand, slag fine aggregate, lightweight fine aggregate, heavy fine aggregate, recycled fine aggregate, or a mixed fine aggregate thereof can be used.
As the coarse aggregate, river gravel, mountain gravel, sea gravel, crushed stone, slag coarse aggregate, lightweight coarse aggregate, heavy coarse aggregate, recycled coarse aggregate, or a mixed coarse aggregate thereof can be used.

  The admixture material and the admixture are not particularly limited, and for example, conventionally known ones can be used. For example, an admixture material (solid) such as blast furnace slag fine powder, fly ash, silica fume, limestone fine powder, early-strength expansion material, etc. Can be used. Also, admixtures (liquids) such as water reducing agents, air entraining agents, antifoaming agents, antifoaming agents, foaming agents, thickeners, rust preventives, pigments, etc., are added as long as strength and workability are not impaired Also good. In order to increase the strength, fibers such as metal may be further mixed.

  A concrete composition can be obtained by mixing such cement and water and, if necessary, aggregate, admixture, admixture and the like.

When obtaining the concrete composition used in the production method of the present invention, the mixing ratio of water and cement is adjusted so that the water-cement ratio is 14 to 20%. Here, the water cement ratio is more preferably 19% or less, and further preferably 18% or less. The water cement ratio is preferably 15% or more, more preferably 16% or more, and further preferably 17% or more.
This is because, when the water-cement ratio is within such a range, the compression strength, bending strength, and tensile strength of the concrete molded body obtained by the production method of the present invention tend to be higher.

  In the production method of the present invention, the water-cement ratio means the percentage of the mass ratio of water and admixture to cement ((mass of water + mass of admixture) / mass of cement × 100).

  In the concrete composition in the production method of the present invention, the content ratio of the aggregate is 20 by mass ratio to the total mass of cement and admixture (mass of aggregate / (mass of cement + mass of admixture) × 100). % To 80%, preferably 30% to 70%, more preferably 40% to 60%, and even more preferably about 50%.

  In the concrete composition in the production method of the present invention, the content ratio of the admixture is preferably 1% to 30% in terms of the mass ratio to the mass of the cement (the mass of the admixture / the mass of the cement × 100). It is more preferably ˜15%, more preferably 8% to 12%, and even more preferably about 10%.

  The content ratio of the admixture in the concrete composition in the production method of the present invention is 0 by mass ratio (mass of admixture / (mass of cement + mass of admixture) × 100) with respect to the total mass of cement and admixture. 0.1 to 5% is preferable, 0.5 to 4% is more preferable, 1 to 3% is more preferable, and about 2% is more preferable.

  In the production method of the present invention, the concrete composition preferably contains a water reducing agent as an admixture. This is because the moisture content can be reduced while the fluidity of the concrete composition is maintained, and the tensile strength of the obtained concrete compact tends to be higher.

The concrete composition in the production method of the present invention preferably further contains organic synthetic fibers.
Examples of organic synthetic fibers include PVA (polyvinyl alcohol) fibers and PP (polypropylene). Since the organic synthetic fibers are more easily stretched than carbon fibers and concrete, if the concrete composition contains organic synthetic fibers, the concrete molded body obtained by the production method of the present invention may be cracked. Can be suppressed. Further, the strength of the concrete molded body after yielding is increased, and explosion at the time of destruction can be prevented.

<Production method of the present invention>
Each process with which the manufacturing method of this invention is provided is demonstrated.

[Defoaming step [1]]
In the production method of the present invention, the defoaming step [1] is a step of obtaining defoamed concrete by holding a concrete composition adjusted to a water cement ratio of 14 to 20% in a reduced-pressure atmosphere.

In the defoaming step [1], the water-cement ratio is adjusted within a predetermined range, and the concrete composition obtained by mixing is maintained in a reduced-pressure atmosphere.
For example, after adjusting the water cement ratio within a predetermined range, the concrete composition obtained by mixing using a kneader or the like is charged into a container of a desired mode. Then, the container filled with the concrete composition is put into a sealed container, and the inside of the sealed container is decompressed using a decompression machine (such as a decompression pump), thereby maintaining the concrete composition in a decompressed atmosphere. it can.

  Although the time which hold | maintains the said concrete composition in a pressure-reduced atmosphere is not specifically limited, It is preferable that it is 3-30 minutes, It is more preferable that it is 10-20 minutes, It is further more preferable that it is about 15 minutes.

  The degree of reduced pressure in the reduced-pressure atmosphere is not particularly limited, but is preferably 5 to 60 Torr, more preferably 5 to 40 Torr, and further preferably 5 to 30 Torr.

  When the concrete composition is held in a reduced-pressure atmosphere, the boiling point of water decreases, moisture in the concrete composition becomes water vapor, and moisture is released from the concrete composition. In addition, bubbles containing moisture are released from the inside of the concrete to the outside. As a result, moisture in the concrete is reduced.

Moreover, it is preferable to give vibration to the concrete composition in a reduced pressure atmosphere. For example, vibration can be applied by installing a vibrator in a sealed container, placing a container charged with a concrete composition thereon, and operating the vibrator. When vibration is applied to the concrete composition, the release of bubbles from the inside of the concrete composition is promoted.
Here, a vibration generator or an ultrasonic shaker can be used as the shaker.

In addition, by controlling the moisture content of the surface portion of the concrete composition in a reduced pressure atmosphere to be a certain value or more, the reduced pressure state is achieved so as not to prevent the release of bubbles from the inside of the concrete composition. In particular, the moisture inside the concrete composition can be removed.
The moisture concentration of the surface portion of the concrete composition is controlled to be 15% by mass or more, more preferably 14% by mass or more, more preferably 13% by mass or more, and 12% by mass or more. More preferably. This is because moisture inside the concrete composition can be efficiently removed.

  For example, by measuring the surface resistance value of the concrete composition in a reduced-pressure atmosphere, the moisture concentration on the surface of the concrete composition can be managed so as to be a certain value or more. Specifically, by controlling the surface resistance value of the concrete composition to be 40 kΩ / □ or less, the moisture concentration on the surface of the concrete composition can be controlled to a certain value or more. The surface resistance value is preferably 35 kΩ / □ or less, more preferably 30 kΩ / □ or less, more preferably 25 kΩ / □ or less, and further preferably 20 kΩ / □ or less.

If the resistance of the surface of the concrete composition in the reduced-pressure atmosphere is measured as described above, the moisture concentration of the part is managed, and if the moisture concentration is smaller than the predetermined value, the surface of the concrete composition Parts and the like may be stirred.
When the moisture concentration is smaller than the predetermined value, moisture may be added to the surface portion of the concrete composition using a spray bottle or the like.

In the defoaming step [1], a microwave irradiation time is obtained based on a water cement ratio at the time of producing the concrete composition, and the irradiation time and microwave are irradiated to the concrete composition in a reduced pressure atmosphere. And it is preferable that it is the process of obtaining the said defoaming concrete.
That is, in the defoaming step [1], a microwave irradiation time is obtained based on the water cement ratio at the time of preparing a concrete composition having a water cement ratio adjusted to 14 to 20%, and the concrete composition is subjected to a reduced-pressure atmosphere. It is preferable to be a step of obtaining defoamed concrete by irradiating the concrete composition in a reduced-pressure atmosphere with microwaves for the irradiation time and microwave.

  The microwave irradiation time t (s) is the mass Wam (g) of water (including water such as a water reducing agent) Wa used for the production of the concrete composition, and the mass of water Wb obtained from the target water cement ratio. Wbm (g), heat of vaporization of water (40.8 kJ / mol), mass of 1 mol of water 18 g, output P (W) of the microwave oscillator, and microwave efficiency η (0.6 to 0.7) And is preferably 0.65 (in the case of concrete)), can be determined using the following formula (I).

  Formula (I) ... t = ((Wam-Wbm) × 40800/18) / (P × η)

  Using such formula (I), the microwave irradiation time t is determined based on the water cement at the time of producing the concrete composition. And as above-mentioned, after hold | maintaining the said concrete composition in a pressure-reduced atmosphere, it is preferable to irradiate a microwave for the irradiation time t calculated | required by the said Formula (I) to the said concrete composition in a pressure-reduced atmosphere.

  The concrete composition is held in a reduced-pressure atmosphere for a first predetermined time (for example, about 3 to 20 minutes, preferably 3 to 10 minutes, more preferably 3 to 5 minutes), Thereafter, it is more preferable to irradiate the microwave for the irradiation time t obtained by the above formula (I).

  When the concrete composition is irradiated with microwaves in a reduced-pressure atmosphere, moisture is released from the concrete composition. In addition, bubbles containing moisture are released from the inside to the outside of the concrete composition. As a result, moisture in the concrete composition is reduced.

  Here, the frequency of the microwave is not particularly limited, and for example, a frequency of 900 to 2500 MHz and an output of 100 W to 30 kW can be used.

  Moreover, it is preferable to apply vibration to a container or the like in which the concrete composition is charged while irradiating the concrete composition with microwaves. The method of applying vibration can be the same as described above.

In addition, while controlling the moisture content of the concrete composition more precisely, specifically, by irradiating with microwaves while managing the moisture of the surface portion of the concrete composition to be a certain value or more, the concrete composition The moisture inside the concrete may be efficiently removed without hindering the release of bubbles from the inside of the object.
As described above, the moisture concentration of the surface portion of the concrete composition is controlled while irradiating the concrete composition with microwaves, and is preferably 15% by mass or more, more preferably 14% by mass or more. Preferably, it is more preferable to set it as 13 mass% or more, and it is still more preferable to set it as 12 mass% or more. This is because moisture inside the concrete composition can be efficiently removed.

  For example, in the same manner as described above, by measuring the surface resistance value of the concrete composition, the moisture concentration on the surface of the concrete composition can be managed so as to be a certain value or more.

  When the moisture concentration is controlled by measuring the resistance value of the surface of the concrete composition as described above and the moisture concentration is smaller than the predetermined value, the surface of the concrete composition is the same as described above. A portion or the like may be stirred.

  When the irradiation time t elapses, the microwave irradiation may be stopped, and the vibration and pressure reduction may be stopped together. Here, after the microwave irradiation is stopped, the pressure is reduced for a second predetermined time (for example, about 2 to 5 minutes, preferably 3 to 5 minutes), preferably while continuing the excitation and the pressure reduction. The state may be maintained.

  By such a defoaming step [1], defoamed concrete can be obtained.

[Defoaming step [2]]
In the production method of the present invention, the defoaming step [2] is a step of obtaining defoamed fibers by holding the reinforcing fibers soaked in a cement solution having a water cement ratio adjusted to 14% or more in a reduced-pressure atmosphere.

  The cement solution used in the defoaming step [2] can be obtained by using the cement and water contained in the concrete composition and mixing them so that the water-cement ratio is 14% or more.

The water-cement ratio in the cement solution is preferably 20% or more, more preferably 25% or more, more preferably 30% or more, more preferably 35% or more, and 40% or more. More preferably, it is more preferably 45% or more. The water-cement ratio is preferably 70% or less, more preferably 60% or less, more preferably 50% or less, more preferably 40% or less, and more preferably 30% or less. More preferably.
This is because when the water-cement ratio in the cement solution is in such a range, the bending strength of the concrete molded body obtained by the production method of the present invention tends to be higher.

The cement solution contains cement and water, but may contain others. For example, the concrete composition may contain the aggregate, the admixture, and the admixture.
In the cement solution, the total content of cement and water is preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and 95% by mass or more. More preferably. Moreover, it is preferable that a cement solution consists of a cement, a silica fume, and water substantially.

In the defoaming step [2], the reinforcing fiber is immersed in the cement solution.
As reinforcing fibers, carbon fiber, polyvinyl alcohol (PVA) fiber, polypropylene (PP) fiber, nylon fiber, steel fiber (SF), steel cord (SC), polyethylene (PE) fiber, glass fiber (GRF), alkali-resistant glass Examples include fiber, steel fiber, and stainless fiber.

Among these, it is preferable to use carbon fibers as reinforcing fibers.
The carbon fiber means a fiber composed of carbon by 90% or more by mass ratio.

The form of the reinforcing fiber is not particularly limited.
The length of the reinforcing fiber is preferably 100 mm or less, preferably 30 mm or less, preferably 15 mm or less, and more preferably 5 mm or less. Moreover, it is preferable that it is 0.1 mm or more. In addition, long-fiber reinforcing fibers may be used. For example, long fibers of about 10 cm to several tens of meters may be used, or longer fibers having a longer length may be used. The length of the reinforcing fiber is not particularly limited, and, for example, long fibers having a length of about 8 km may be evenly arranged (twisted) in the concrete molded body. This is because the bending strength of the concrete molded body obtained by the production method of the present invention tends to be higher.

The cross-sectional diameter of the reinforcing fiber is preferably 3 to 15 μm, more preferably 5 to 11 μm, more preferably 6 to 8 μm, and even more preferably 7 μm. This is because the bending strength of the concrete molded body obtained by the production method of the present invention tends to be higher.
In addition, when the cross section of a reinforcing fiber is not circular, the diameter of a cross section shall mean a projected area circle equivalent diameter.

The reinforcing fibers are preferably in the form of a sheet-like woven fabric. For example, a sheet-like woven fabric having a thickness of about 0.01 to 0.1 mm formed by weaving the reinforcing fibers in the vertical direction and the horizontal direction can be mentioned. Moreover, the sheet-like textile fabric of the mass of 50-200 g / m < ² > is illustrated.

  Such reinforcing fibers are immersed in the cement solution. For example, the cement solution is put in a container and the reinforcing fibers are immersed. Then, in a state where the reinforcing fiber is immersed in the cement solution in the container, the reinforcing fiber is put into a sealed container together with the container, and the inside of the sealed container is depressurized using a decompression machine (such as a decompression pump), whereby the reinforcing fiber is decompressed in an atmosphere. Can be held in. Moreover, it is preferable to immerse the reinforcing fiber previously placed in the sealed container in the cement solution in the same sealed container after reducing the pressure first to obtain a decompressed atmosphere.

The sizing agent or sizing agent applied to the surface of the reinforcing fiber often uses a water repellent material. In the present invention, it is preferable to use a hydrophilic material without using the water repellent material. In particular, when the reinforcing fiber is a carbon fiber, the carbon fiber is preferably not coated with a water-repellent organic material such as an epoxy resin. That is, the reinforcing fiber preferably has no water repellent organic material on the surface. This is because the bending strength of the concrete molded body obtained by the production method of the present invention tends to be higher.
The water repellent organic material means a hydrophobic organic material.

  The time for holding the reinforcing fibers in the reduced-pressure atmosphere is not particularly limited, but is preferably 1 to 30 minutes, more preferably 10 to 20 minutes, and further preferably about 15 minutes. If the performance of the decompressor is high, the holding time can be shortened. In addition, when using the general rotary pump etc. which can be pressure-reduced from atmospheric pressure, retention time can be made into about 10 to 20 minutes.

  The degree of reduced pressure in the reduced-pressure atmosphere is not particularly limited, but is preferably 5 to 60 Torr, more preferably 5 to 40 Torr, and further preferably 5 to 30 Torr.

  By holding the reinforcing fibers in a reduced-pressure atmosphere, it is estimated that the cement solution penetrates into the reinforcing fibers when the reinforcing fibers are released and released to atmospheric pressure. And it is estimated that the affinity and adhesion between the reinforcing fiber inside the concrete molded body and the cement in the concrete composition are increased, and the bending strength of the concrete molded body is further increased. In addition, applying vibration when holding in a reduced-pressure atmosphere is effective because it promotes defoaming and prevents cement from solidifying.

  In FIG. 1, the enlarged photograph of the cross section of the concrete molded object obtained by the manufacturing method of this invention is shown. This is a photograph of a cross section of a concrete molded body enlarged by 1000 times using an optical microscope (Keyence Corporation, digital microscope VHX-1000). It can be confirmed that the reinforcing fibers are in close contact with the cement or the like existing in the vicinity thereof.

  A defoamed fiber can be obtained by such a defoaming step [2].

[Molding process]
In the production method of the present invention, the forming step is a step of placing the defoamed concrete and the defoamed fiber into a mold, and then curing to obtain a high-strength concrete molded body.

In the molding step, first, the defoamed concrete and the defoamed fiber are placed in a mold.
The formwork is not particularly limited, and a conventionally known formwork made of a conventionally known material (for example, stainless steel, glass, concrete formwork wood) that is usually used when placing concrete may be used.

  When a sheet-like woven fabric is used as the reinforcing fiber in the defoaming step [2] described above, in the molding step, the sheet-shaped woven fabric (reinforcing fiber) is deformed into an appropriate shape and inserted into the mold, It is preferable to place the defoamed concrete so as to fill the space between the sheet-like fabrics.

  When a string-like reinforcing fiber is used as the reinforcing fiber in the defoaming step [2] described above, in the molding step, for example, a wooden square member equipped with a hanging bracket is attached to a mold made of concrete form wood. After defoaming fibers soaked in a cement solution in a hanging metal fitting, defoamed concrete is placed. The string-like reinforcing fibers are preferably put in a net-like container (such as a colander) and immersed in another container containing a cement solution together with the net-like container for use in the defoaming step [2].

After placing the defoamed concrete and the defoamed fiber into the mold, they are cured by a conventionally known method. For example, standard curing and underwater curing are performed. After performing standard curing without removing the mold, it is preferable to remove the mold and perform underwater curing.
The curing time is not particularly limited, and can be a conventionally known time. For example, standard curing for about 48 hours can be performed. In addition, for example, water curing for about 21 days can be performed.

A concrete molded body can be obtained by such a molding process.
The concrete molded body obtained by such a production method of the present invention has higher bending strength than the conventional one.

The production method of the present invention comprises a sealed container A that can contain the container charged with the concrete composition, a decompressor A that puts the inside of the sealed container A in a reduced pressure state, and a reinforcing fiber immersed therein. It can be carried out by a concrete molded body manufacturing apparatus comprising: a sealed container B that can contain a container containing the cement solution; and a decompressor B that puts the inside of the sealed container B into a decompressed state. .
The sealed container A and the sealed container B may be the same or different.
The decompressor A and the decompressor B may be the same or different.

As such a manufacturing apparatus, the thing of the aspect shown in FIG. 2 can be illustrated.
The apparatus 10 shown in FIG. 2 includes a sealed container 12 and a decompression pump 20. The sealed container 12 is provided with a vacuum gauge 22 and an air valve 24. Here, in the sealed container 12, a container 14 in which the concrete composition 1 is charged and a container 16 in which reinforcing fibers soaked in a cement solution are placed can be installed.

  The sealed container 12 only needs to be able to maintain a reduced pressure state of about 5 to 15 Torr (that is, a reduced pressure state whose vacuum degree is lower than 30 Torr, 40 Torr, and 60 Torr (that is, a reduced pressure state close to atmospheric pressure). It is possible to use an airtight container made of a metal such as stainless steel and glass. Further, inside the sealed container 12, a container 14 into which the concrete composition 1 has been poured and a container 16 into which reinforcing fibers soaked in a cement solution are placed can be installed. The sealed container 12 is provided with an opening capable of maintaining an airtight state after the container 14 is installed. Further, the hermetic container 12 is connected to a decompression pump 20, a vacuum gauge 22, and an air valve 24, and is configured to be able to keep airtight. In addition, when using metal containers, such as stainless steel, for the airtight container 12, it is desirable to provide an observation window so that the state of the concrete composition 1 inside can be observed.

  The container 14 should just be what can insert the concrete composition 1 in the inside, and can use a steel formwork, a wooden formwork, etc. FIG. When producing a precast product in a factory, a steel formwork is desirable from the viewpoint of cost.

  The same applies to the container 16 as long as the reinforcing fiber can be immersed in the cement solution after the cement solution is added.

  The decompression pump 20 is a decompressor and decompresses the inside of the sealed container 12. As the decompression pump 20, a type that operates from atmospheric pressure, such as a diaphragm pump and a rotary pump, can be used. Moreover, as long as it is a pressure reduction machine which can be pressure-reduced to a predetermined value, it is not restricted to said pump, You may use various pressure reduction machines.

  The vacuum gauge 22 measures the pressure in the sealed container 12. The vacuum gauge 22 may be a mechanical pressure gauge such as a Bourdon tube gauge or a diaphragm gauge. As long as the vacuum gauge 22 can measure a pressure of about 5 to 15 Torr from atmospheric pressure, another type may be used.

  The air valve 24 is a so-called vacuum valve, is closed when the inside of the sealed container 12 is brought into a reduced pressure state, and is released when the pressure in the sealed container 12 is returned to atmospheric pressure.

  A concrete molded body can be manufactured by the procedure shown in FIG.

  First, the concrete composition 1 is charged into the container 14, that is, poured into the container 14, and the container 14 into which the concrete composition 1 is poured is placed on the bottom surface in the sealed container 12 (step S 10).

Next, after the air valve 24 is closed, pressure reduction inside the sealed container 12 is started by the decompression pump 20, and the pressure inside the sealed container 12 is reduced to about 20 Torr while confirming the pressure with the vacuum gauge 22 (step S12). ).
By such an operation, the air entrained when producing the concrete composition can be aerated, and the generated water vapor can be discharged from the concrete composition 1. Thereafter, the air valve 24 is opened, and the inside of the sealed container 12 is returned to atmospheric pressure (step S14).

  Next, the cement solution is put into the container 16 and the reinforcing fibers are immersed in the cement solution. Then, the container 16 containing the cement solution in which the reinforcing fibers are immersed is placed on the bottom surface in the sealed container 12 (step S20).

Next, after the air valve 24 is closed, pressure reduction inside the sealed container 12 is started by the decompression pump 20, and the pressure inside the sealed container 12 is reduced to about 20 Torr while confirming the pressure with the vacuum gauge 22 (step S22). ).
By such an operation, the air contained in the reinforcing fiber can be discharged. Thereafter, the air valve 24 is opened, and the inside of the sealed container 12 is returned to atmospheric pressure (step S24).

Next, the defoamed concrete and the defoamed fiber are placed in the mold (step S30).
Then, curing can be performed (step S32) to obtain a concrete molded body.

  An experimental example corresponding to the production method of the present invention will be described.

First, the following raw materials were prepared.
・ Portland cement (model number: ordinary Portland cement, Taiheiyo Cement)
・ Silica fume (model number: Meiko MS610, manufactured by BASF Pozzolith)
・ Silica sand (fine aggregate): Cinnabar No.3, Cinnabar No.5 ・ Water reducing agent (model number: Leobilt SP-8HU, manufactured by BASF Pozzolith)
・ PVA fiber (trade name: RECS100L × 12mm, manufactured by Kuraray Co., Ltd.)
・ Water (purified water)

In the following, for cement: 1000 g,
Silica fume: 100 g (cement ratio: 10%),
Silica sand # 3: 275 g (cement + silica fume weight ratio: 25%)
Silica sand No. 5: 275 g (cement + silica fume weight ratio: 25%),
Water reducing agent: 22 g (weight ratio of cement + silica fume: 2%)
PVA fiber: 11 g (cement + silica fume weight ratio: 1%),
Water: 174.9 g (cement weight + silica fume weight−water reducing agent weight)
The formulation that adds is the basic formulation.

Next, the above raw materials were mixed using a mortar mixer. Specifically, the following operation was performed.
First, cement (2000 g), silica fume (200 g), silica sand No. 3 (550 g), and silica sand No. 5 (550 g) were charged into a mortar mixer based on the above basic composition. And it stirred at low speed (62 rpm) for 1 minute.
Next, water (349.8 g) and a water reducing agent (44 g) were mixed to obtain kneaded water. The resulting kneaded water was put into a mortar mixer, stirred for 1 minute at a low speed (62 rpm), and then stirred for 2 minutes at a high speed (125 rpm).
Next, PVA fiber (22 g) was added and stirred at low speed (62 rpm) for 2 minutes.

In addition, the specification of the mortar mixer (Hobart mixer KC-8, manufactured by Kansai Kikai Seisakusho Co., Ltd.) used here is as follows.
Capacity: About 5L
Rotation speed Low speed: Revolution 62 rpm Auto rotation 141 rpm
High speed: intersection 125rpm auto rotation 284rpm
Free: Revolution 12-180rpm Rotation 27-410rpm
Power supply: AC100 / 110V Power supply facility capacity 2kVA
Weight: about 70kg

  Such an operation was performed to obtain a concrete composition [1].

Next, the obtained concrete composition [1] was put in a plastic container and further put in a polycadicicator. And after sealing, the vacuum pump was operated and evacuation was performed for 15 minutes. Here, the pressure in the polycarbonate detector was adjusted to 30 Torr.
What was obtained by giving such a pressure reduction process to concrete composition [1] is hereafter defoamed concrete [1].

The specifications of the vacuum pump (model number: GLD-051, manufactured by ULVAC) are as shown below.
PUMPING
SPEED: 50 L / min (at 50 Hz), 60 L / min (at 60 Hz)
ULTIMATE
PRES. : 6.7 × 10-2 (Pa)
OIL
CAPACITY: 500 to 800 mL

  The raw materials were mixed as described above, and the operation of obtaining defoamed concrete [1] from the obtained concrete composition [1] was repeated three times to obtain a sufficient amount of defoamed concrete [1].

  Next, a sheet-like reinforcing fiber (BT70-20 100C 50, manufactured by Toray Industries, Inc.) was prepared. And this was cut into the size of 380 mm x 500 mm.

Next, the above-mentioned Portland cement (ordinary Portland cement, Taiheiyo Cement Co., Ltd.) and water (purified water) were mixed so that the water-cement ratio was 25% to 50% to obtain 5 kg of a cement solution.
And this cement solution was put into the container, the cut reinforcing fiber was further put into the container, and the reinforcing fiber was immersed in the cement solution.

Next, a container obtained by immersing reinforcing fibers in a cement solution was placed in a polycadicicator. And after sealing, the vacuum pump was operated and evacuation was performed for 15 minutes. Here, the pressure in the polycarbonate detector was adjusted to 30 Torr.
In addition, the same thing as what was used when adjusting the above-mentioned concrete composition [1] was used for the polycadicicator and the vacuum pump.
The thing after performing such a defoaming process to a reinforcement fiber is also called defoaming fiber [1] below.

Next, defoamed concrete [1] and defoamed fiber [1] were charged into a bending test mold (KC-183A, width 100 × height 100 × length 400 mm, manufactured by Kansai Kikai Seisakusho Co., Ltd.).
Specifically, the following operation was performed.
First, defoamed concrete [1] was placed in a bending test mold to a height of 5 mm from the bottom.
Next, after defoaming fiber [1] deformed to an appropriate shape was charged, defoamed concrete [1] was further placed. Here, defoamed concrete [1] was inserted between the defoamed fibers [1] so as not to leave voids. The defoamed fiber was completely immersed in defoamed concrete [1].
And after covering the outer surface of the mold for bending tests with a lap and performing standard curing for 48 hours, it was removed from the mold, and the obtained specimen was placed in a curing water tank (water temperature 20 ° C. ± 2 ° C.). Underwater curing until day one.
In this way, a concrete compact [1] was obtained.

  Next, with respect to the obtained concrete molded body [1], the bending strength was measured according to the concrete bending strength test method specified in JIS A 1106. As a result, the bending strength was 38.3 MPa.

Next, the concrete composition [1] before being subjected to the above-described decompression treatment was charged into the above-described bending test mold. Reinforcing fibers were not charged. Then, in the same manner as in the case of obtaining the concrete molded body [1], the outer surface of the bending test mold was covered with a wrap and subjected to standard curing for 48 hours, then demolded, and the obtained specimen was cured in a curing water tank. It was put in (water temperature 20 ° C. ± 2 ° C.) and cured under water until the 21st day of age to obtain a concrete molded body [2].
And about the obtained concrete molded object [2], when bending strength was measured like the case of the concrete molded object [1], bending strength was 14.5 MPa.

Next, the defoamed concrete [1] and the reinforcing fiber before being subjected to the above-described decompression treatment were charged into the above-described bending test mold. The charging method was the same as in the case of obtaining a concrete molded body [1].
Then, in the same manner as when the concrete molded body [1] was obtained, the outer surface of the bending test mold was covered with a wrap and subjected to standard curing for 48 hours, then demolded, and the obtained specimen was cured. It put into the water tank (water temperature 20 degreeC +/- 2 degreeC), and it cured underwater until the age of material 21st, and obtained the concrete molded object [3].
Then, when the bending strength of the obtained concrete molded body [3] was measured in the same manner as in the case of the concrete molded body [1], the bending strength was 19.0 MPa.

Next, the above-mentioned defoamed concrete [1] was charged into the above-mentioned bending test mold. Reinforcing fibers were not charged. Then, in the same manner as in the case of obtaining the concrete molded body [1], the outer surface of the bending test mold was covered with a wrap and subjected to standard curing for 48 hours, then demolded, and the obtained specimen was cured in a curing water tank. It was put in (water temperature 20 ° C. ± 2 ° C.) and cured in water until the age of 21 days to obtain a concrete molded body [4].
And about the obtained concrete molded object [4], when bending strength was measured like the case of the concrete molded object [1], bending strength was 16.6 MPa.

DESCRIPTION OF SYMBOLS 1 Concrete composition 10 Apparatus 12 Sealed container 14, 16 Container 20 Depressurization pump 22 Vacuum gauge 24 Air valve

Claims (7)

A defoaming step [1] for obtaining a defoamed concrete by holding a concrete composition having a water-cement ratio adjusted to 14 to 20% in a reduced-pressure atmosphere;
A defoaming step [2] for obtaining defoamed fibers by holding the reinforcing fibers soaked in a cement solution having a water-cement ratio adjusted to 14 to 70% in a reduced-pressure atmosphere;
After placing the defoamed concrete and the defoamed fiber into a mold, it is cured, and a molding step to obtain a high strength concrete molded body ,
The reinforcing fiber is any one of polyvinyl alcohol fiber excluding carbon fiber, polypropylene fiber, nylon fiber, steel fiber, steel cord, polyethylene fiber, glass fiber, alkali-resistant glass fiber, steel fiber, and stainless fiber. about,
A method for producing a concrete compact characterized by the above .   The method for producing a concrete molded body according to claim 1, wherein the concrete composition further contains an organic synthetic fiber.   The method for producing a concrete molded body according to claim 1, wherein the reinforcing fiber does not have a water-repellent organic material on a surface thereof.   The method for producing a concrete molded body according to any one of claims 1 to 3, wherein the concrete composition contains an admixture and an admixture.   The method for producing a concrete molded body according to any one of claims 1 to 4, wherein a length of the reinforcing fiber is 0.1 mm or more.   The method for producing a concrete molded body according to any one of claims 1 to 5, wherein, in the defoaming step [2], the reinforcing fiber is in the form of a sheet-like woven fabric. The defoaming step [1]
This is a step of obtaining a defoamed concrete by obtaining a microwave irradiation time based on the water cement ratio at the time of preparation of the concrete composition, and irradiating the irradiation time and microwave to the concrete composition in a reduced pressure atmosphere. The method for producing a concrete molded body according to any one of claims 1 to 6, wherein: