JP2024000515A - Ultra-high strength concrete pile production method and vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultra-high strength concrete pile production method which can produce an ultra-high strength concrete pile by centrifugal molding.

SOLUTION: As a concrete pile production method, the outer circumference of a pile flask 1 is provided with castings 2 at specified intervals, the lower parts of the castings 2 are supported with runner wheels 3, and centrifugal molding of rotating the flask by the frictional conduction of the runner wheels 3 which are rolled with the castings 2 by a pile molding device 10 is executed. This flask is filled with low slump high strength concrete 4. Then, vibration is applied from the lower parts of the castings 2 by a vibrator 5 to execute centrifugal molding.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention particularly relates to a method for manufacturing ultra-high strength concrete piles using high-strength concrete, and a vibrator.

BACKGROUND ART Concrete piles, which are elongated cylindrical precast concrete structures called "ready-made piles," have conventionally been used for foundation work and the like to be embedded in the foundations of buildings.

This concrete pile is usually manufactured by centrifugal forming method.
The centrifugal force forming method is a manufacturing method that compacts concrete by reducing the apparent water-to-cement ratio (hereinafter referred to as W/C) by dewatering surplus water required for mixing concrete using centrifugal force. The centrifugal force forming method has the advantage that the outer formwork side is extremely dense and highly durable, and there is no need for an inner formwork.

On the other hand, in recent years, the development of admixtures for concrete has made it possible to minimize the amount of water required for mixing, and to produce high-strength concrete with an amount of water so small that it cannot be dehydrated by centrifugal force.

Here, referring to Patent Document 1, a large number of castings are attached to the outer periphery of the formwork at appropriate intervals, the lower part of the casts is supported by a metal runner wheel, and the friction between the casts and the rotating runner wheel is transmitted. In the manufacturing method of concrete pipes by centrifugal force forming, in which the formwork is rotated by centrifugal force, in addition to rotation by a runner wheel, vibration is applied to the formwork by a vibrator from above, and the cemented carbide mixed concrete with zero slump is subjected to centrifugal force. A method of manufacturing a concrete pipe is described, which is formed using a combination of vibration and vibration.
According to this manufacturing method, it is possible to use high-strength concrete made of cemented carbide with zero slump, and it is also possible to manufacture a concrete pipe that is excellent in terms of safety.

Japanese Patent Application Publication No. 06-254831

However, the concrete pipe manufacturing method of Patent Document 1 is a technology for a Hume pipe having a relatively large diameter. This technology could not be applied to elongated cylindrical concrete piles because sufficient vibration could not be applied from above.

The present invention has been made in view of this situation, and aims to solve the above-mentioned problems and provide a method for manufacturing ultra-high strength concrete piles using high strength concrete.

The ultra-high strength concrete pile manufacturing method of the present invention includes installing casts at specific intervals around the outer periphery of a formwork, supporting the lower part of the casts with a runner wheel, and applying frictional conduction between the casts and the rotating runner wheel to form the mold. A method for producing concrete piles by centrifugal force forming by rotating a frame, characterized by filling the cast with high-strength concrete of low slump, applying vibration from the lower part of the cast with a vibrator, and performing centrifugal force forming. do.
In the ultra-high strength concrete pile manufacturing method of the present invention, the vibrator has a gear-like shape in which a plurality of protrusions are formed and the plurality of protrusions rotate while applying pressure from a lower part of the cast according to the rotation of the cast. and a pressing portion that pivotally supports the gear-shaped portion and applies the pressing force.
The ultra-high strength concrete pile manufacturing method of the present invention is characterized in that the vibration is applied only during rotation at a centrifugal acceleration of 10 G or less.
The ultra-high strength concrete pile manufacturing method of the present invention is characterized in that the vibration applies a gravitational acceleration that is 100 to 2000 times the centrifugal acceleration generated during centrifugal force forming.
The ultra-high strength concrete pile manufacturing method of the present invention is characterized in that the high strength concrete has a slump in the range of 0 to 4 cm.
In the ultra-high strength concrete pile manufacturing method of the present invention, the cement used for the high strength concrete is normal cement, early strength cement, moderate heat cement, or low heat cement, and the water binder ratio is 10 to 18%. It is characterized by
In the ultra-high strength concrete pile manufacturing method of the present invention, when the cement is ordinary cement, the amount of cement is 500 to 650 kg/m ³ , the admixture is 100 to 280 kg/m ³ , the water is 100 to 140 kg/m ³ , and the fine aggregate is 500 to 650 kg/m 3 600 kg/m ³ , coarse aggregate 900 to 1200 kg/m ³ , and water reducing agent 10 to 20 kg/m ³ , the water binder ratio is 10 to 18%, and the cement is early strength cement, medium heat cement, Or in the case of low-heat cement, per unit amount of 1 kg/m ³ , cement 500-650 kg/m ³ , admixture 100-280 kg/m ³ , water 100-140 kg/m ³ , fine aggregate 500-600 kg/m ³ , It is characterized by a blend of 900 to 1200 kg/m ³ of coarse aggregate and 10 to 20 kg/m ³ of water reducing agent, and a water binder ratio of 10 to 13%.
In the vibration exciter of the present invention, casts are attached to the outer periphery of a formwork at specific intervals, a lower part of the casts is supported by a runner wheel, and the formwork is rotated by frictional conduction between the casts and the runner wheel that rotates. A vibration exciter used for manufacturing concrete piles by centrifugal force forming, wherein a plurality of protrusions are formed and the plurality of protrusions rotate while applying pressure from a lower part of the cast according to the rotation of the cast. and a pressing portion that pivotally supports the gear-shaped portion and applies the pressing force.

According to the present invention, a method for producing ultra-high-strength concrete piles using high-strength concrete is achieved by filling high-strength concrete with low slump and performing centrifugal force forming while applying vibration from the bottom of the cast with a vibrator. can be provided.

FIG. 1 is a side view of an embodiment of a pile forming device of the present invention. FIG. 1 is a front view of an embodiment of a pile forming device of the present invention. 1 is a photograph showing changes in the high-strength concrete pile according to Example 1 of the present invention depending on the presence or absence of vibration.

<Embodiment>
(Configuration of pile forming device 10)
First, an example of the basic shape and structure of an embodiment of the pile forming apparatus 10 of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic side view, and FIG. 2 is a schematic front view. 1 and 2, components other than the main components are omitted.

The pile forming apparatus 10 according to the present embodiment is an ultra-high strength concrete pile manufacturing apparatus that manufactures piles or poles (hereinafter simply referred to as "concrete piles") using ultra-high strength concrete using the high-strength concrete 4. This is an example.
Hereinafter, in this embodiment, the direction of gravity relative to the ground will be referred to as "down", and the opposite direction will be referred to as "up".
In addition, the distance in the vertical direction from each point on the circumference of the inner surface of the pile formwork 1 to the axis at the shortest distance, that is, the distance in the radial direction of the circumference, is determined in each configuration inside the pile forming device 10. It is called "height". On the other hand, the distance in the direction along the axis of the cylinder (in the axial direction) is referred to as the "length in the axial direction."

The pile formwork 1 is a formwork for ultra-high strength concrete piles according to this embodiment. In this embodiment, the pile formwork 1 is composed of an upper formwork and a lower formwork made of steel, and a reinforcing bar cage for concrete piles (not shown) is arranged inside.

The caster 2 is a steel tire (casting or wheel; hereinafter simply referred to as "caster") that protrudes circumferentially from the circumferential surface of the pile formwork 1 and rotates the pile formwork 1. A plurality of casters 2 are provided at specific intervals of several tens of cm to several meters from a location 50 cm to 1 m from the end of the pile formwork 1 in the axial direction.

The runner wheel 3 is a steel tire or the like that supports the lower part of the caster 2 in pressure contact and rotates the pile formwork 1.
As shown in FIG. 1, the runner wheel 3 rotates in a specific direction by driving the shaft C by a drive unit M such as a motor. Due to the rotation of the runner wheel 3, frictional conduction is transmitted to the caster 2, thereby rotating the connected pile formwork 1.
Here, as shown in FIG. 2, in this embodiment, a pair of left and right runner wheels 3 are provided below the caster 2 to support the caster 2.

High-strength concrete 4 is injected into the inner surface of pile formwork 1 and centrifugally formed.
In this embodiment, the high-strength concrete 4 is poured into the pile formwork 1 by a pumping method or a filling method using a feeding machine (not shown).
The high strength concrete 4 may be low slump concrete. The composition of this high-strength concrete 4 will be described later.

The vibrator 5 is a device that applies vibration from the bottom of the cast 2 during centrifugal force molding.
As shown in FIG. 1, a plurality of vibrators 5 are provided to support the elongated pile formwork 1. Although FIG. 1 shows an example in which the vibrator 5 is provided at every other caster 2 disposed in the axial direction, the vibrator 5 may be provided at all runner wheels or at only a few locations.
Furthermore, as shown in FIG. 2, in this embodiment, the vibrator 5 may be installed at an intermediate position between the runner wheels 3 that support the same caster 2. In addition, in FIG. 1, in order to make the vibrator 5 easier to see, the runner wheel 3 on the front side of the caster 2 with which the vibrator 5 comes in contact is omitted.

The vibrator 5 includes a gear-shaped portion 5a and a pressing portion 5b.

The gear-shaped portion 5a is a rotating member in which a plurality of protrusions are formed in the shape of a gear. The gear-shaped portion 5a is brought into contact with the caster 2 from the lower part of the caster 2 while applying a specific pressure. Therefore, when the caster 2 rotates, the gear-shaped portion 5a rotates while applying pressure to the caster 2 due to friction corresponding to this rotation. As a result, vibration is applied to the contact surface depending on the presence or absence of the protrusion of the gear-shaped portion 5a.

The pressing portion 5b is a member that pivotally supports the gear-shaped portion 5a and applies pressure. In this embodiment, the pressing portion 5b includes a cylinder member that moves up and down using hydraulic pressure or air pressure. Pressure is generated by the stroke of this cylinder member. This pressure may not be such a force as to push up the pile formwork 1 itself, but may be such that the gear-shaped portion 5a contacts the caster 2 and rotates.
The details of this pressing force and the method of calculating the gravitational acceleration of the vibration due to the pressing force will be described later.

(Composition of high strength concrete 4)
Next, an embodiment of high strength concrete 4 of the present invention will be described.
The high-strength concrete 4 according to this embodiment may be, for example, high-strength concrete defined by JIS A 5308.
In this embodiment, the high-strength concrete 4 can be a low-slump high-strength concrete material.

The high-strength concrete 4 according to this embodiment has extremely high viscosity and is used in a state just before it becomes hard concrete like starch syrup.
Specifically, the high-strength concrete 4 according to this embodiment is in a state just before exhibiting high viscosity, that is, has a slump in the range of 0 to 4 cm (hereinafter also referred to as "low slump concrete"). It is characterized by If high-strength concrete 4 is low slump concrete, the unhardened concrete has mortar attached around the aggregate, so it can easily pass through the reinforcing bar cage and be poured into the lower formwork. It is possible. Further, the high-strength concrete 4 can be filled in heaps, and will not overflow from the lower formwork of the pile formwork 1.

Next, a specific configuration of the concrete material used for the high-strength concrete 4 according to this embodiment will be explained.
The high-strength concrete 4 is blended with water, cement, fine aggregate, coarse aggregate, a high-performance water reducing agent, an expanding agent, and the like.

Among these, the water used for the concrete material of this embodiment is not particularly limited, and may be tap water. The pH of the water according to this embodiment is also arbitrary.

As the cement according to this embodiment, ordinary Portland cement (ordinary cement), blast furnace cement, fly ash cement, silica cement, mixed cement thereof, etc. can be used. Among these, the ordinary Portland cement may be, for example, various Portland cements having properties such as moderate heat, low heat, early strength, super early strength, and sulfate resistance. Ordinary Portland cement may have a density of about 3.15 g/cm ³ and a specific surface area of about 3310 cm ² /g, as specified by JIS R 5210, for example.

As the fine aggregate according to this embodiment, general fine aggregate such as crushed sand can be used. This fine aggregate corresponds to JIS A 5005 crushed sand (hard sandstone), and preferably has a density of about 2.62 g/cm ³ . Further, as the fine aggregate, slag-based aggregates such as fine aggregate produced from granulated blast furnace slag, electric furnace oxidized slag aggregate, etc. can also be used.

As the coarse aggregate according to this embodiment, general coarse aggregate such as sandstone can be used. This coarse aggregate corresponds to JIS A 5005 crushed stone 2005 (hard sandstone), for example, and preferably has a density of about 2.67 g/cm ³ .

The high performance water reducing agent according to the present embodiment is a chemical admixture that significantly reduces the unit water amount without affecting the consistency or significantly increases the slump without affecting the unit water amount. The high-performance water reducing agent of this embodiment corresponds to, for example, JIS A 6204, and it is preferable to use, for example, a polycarboxylic acid-based agent having a density of about 1.00 g/cm ³ . Further, in this embodiment, it is preferable that the high-performance water reducing agent is used for internal replacement of water.

The expansion material according to the present embodiment is a powder-like material that expands upon supply of moisture and reduces cracking due to drying shrinkage. Examples of the expanding material of this embodiment include a lime-based expanding material, an ettringite-based (calcium sulfoaluminate-based) expanding material, an ettringite-quicklime composite-based expanding material, and the like. Further, it is preferable that the expanding material conforms to the quality specified by, for example, Japanese Industrial Standards JIS A 6202.

Furthermore, in addition to the above-mentioned expansion materials, it is possible to use admixtures such as pulverized blast furnace slag powder, fly ash silica fume, waterproof materials, crushed stone, and inorganic or organic fibers. In this embodiment, in particular, it is possible to appropriately blend blast furnace slag powder 8000, 10000, 20000 brane, silica fume, etc. Among these, the blast furnace slag powder compliant with JIS A 6206 can be used. Silica fume that conforms to JIS A 6207 can be used. Further, the ratio of this blend can be adjusted as appropriate by those skilled in the art so as to increase the compressive strength.

Next, a specific formulation of the concrete material according to this embodiment will be explained.
In this embodiment, it is preferable that the weight ratio of water, cement, and admixtures, that is, the value of water/(cement + admixtures), be constant, for example, 10 to 30% (wt%). be. If this weight ratio is less than 30%, the absolute amount of water necessary for hydration of cement will be insufficient, making it unsuitable for centrifugal force forming. On the other hand, if this weight ratio is 30% or more, although it is suitable for centrifugal force molding, strength development is insufficient. Furthermore, if this weight ratio is greater than 40%, material separation tends to occur. Furthermore, the fine aggregate percentage (weight %) is also preferably 30 to 50%.
On top of this, ordinary boltland cement 500-1000 kg/m ³ , admixture 0-80 kg/m ³ , fine aggregate 700-900 kg/m ³ , coarse aggregate 800-1200 kg/m ³ , high performance water reducing agent 0. Concrete adjusted to 5 to 4% by weight can be used.

More specifically, as shown in Example 2 below, when ordinary cement is used with a compressive strength exceeding 130 N/mm ² , a high strength admixture is added at a water binder ratio of 10 to 18%. Strength can be obtained by using them together.
Specifically, when using ordinary cement as cement, the amount of cement is 500 to 650 kg/m ³ , the admixture is 100 to 280 kg/m ³ , the water is 100 to 140 kg/m 3 , the fine aggregate is 500 to 600 kg/m ³ , and the coarse bone is 500 to 650 kg/m ³ . It is preferable to mix 900 to 1200 kg/m ³ of material and 10 to 20 kg/m ³ of water reducing agent, and set the water binder ratio to 10 to 18%.
Or, when using early strength cement, medium heat cement, or low heat cement as cement, per unit amount of 1 kg/m ³ , cement 500 to 650 kg/m ³ , admixture 100 to 280 kg/m ³ , water 100 to 140 kg/m 3 m ³ , fine aggregate 500 to 600 kg/m ³ , coarse aggregate 900 to 1200 kg/m ³ , and water reducing agent 10 to 20 kg/m ³ , preferably with a water binder ratio of 10 to 13%. It is.

Note that the air amount of the concrete material according to this embodiment may be adjusted using an air amount adjusting agent such as an AE (Air Entraining) agent. Specifically, in centrifugal force molding, although all air is removed by centrifugal force, for example, an AE agent may be intentionally added to maintain fluidity when fresh. Even in this case, all the air escapes after centrifugal force forming, so there is no reduction in strength due to air.
Examples of the AE agent include various anionic, cationic, nonionic, and amphoteric surfactants. Examples of the anionic surfactant include resin-based, alkylbenzenesulfonic acid-based, and higher alcohol ester-based surfactants. Note that it is also possible to use an AE water reducing agent that has the properties of both an AE agent and a water reducing agent.

In addition, the concrete material according to the present embodiment also contains a fluidizing agent, a retarding agent, a waterproofing admixture, a moisture-proofing admixture, a foaming agent, a thickener, an antifreeze agent, a coloring agent, a workability enhancer, and an anti-corrosion agent. It is possible to appropriately incorporate additives, antifoaming agents, setting regulators, shrinkage reducing agents, cement rapid hardening agents, polymer emulsions, fibers, and the like. Furthermore, substances commonly used in concrete materials, such as zeolite, siliceous fine powder, clay minerals such as calcium carbonate and bentonite, gypsum, and calcium silicate, may be appropriately blended. These formulations may make it possible to produce the above-mentioned high-performance concrete.

Furthermore, the high-strength concrete 4 may be fiber-reinforced concrete, tensile-resistant concrete, expansive concrete, or the like. Among these, vinylon staple fibers, polypropylene staple fibers, acrylic fibers, carbon fibers, inorganic fibers, etc. can also be used as the fibers for fiber-reinforced concrete. The inorganic fibers may be metal fibers.

(Method for manufacturing ultra-high strength concrete piles)
Next, details of a method for manufacturing an ultra-high strength concrete pile using the pile forming apparatus 10 according to the present embodiment will be explained.
In the manufacturing method according to this embodiment, first, a structure such as a welded reinforcing bar cage is placed on the lower formwork of the pile formwork 1, and the above-mentioned high-strength concrete 4 is poured into the structure.
At the time of this charging, it is possible to use either a pump charging method or a filling charging method. Among these, in the pumping method, the high-strength concrete 4 is poured by inserting a long cylindrical pipe into an elongated formwork and pumping it under pressure. Note that, unlike the Hume pipe, in the concrete pile according to the present embodiment, the pile form 1 is not rotated during injection by pumping.
On the other hand, in the loading method, the high-strength concrete 4 is poured onto the lower formwork, and after a predetermined amount has been poured, it is covered with the upper formwork.

At the time of these injections, the high-strength concrete 4 is placed before it exhibits high viscosity, that is, in a state where the slump is in the range of 0 to 4 cm, as described above. Thereby, even when using the filling method, it is possible to pass through the reinforcing bar cage and charge the material into the lower formwork. At that time, as described above, it is also possible to include high-strength concrete 4 in heaps.

Thereafter, the high-strength concrete 4 is compacted by centrifugal force forming. In this embodiment, the pile formwork 1 after charging the high-strength concrete 4 is rotated at high speed by friction transmission between the above-mentioned caster 2 and the rotating runner wheel 3. As a result, using centrifugal force, the material is finally compacted at an acceleration of about 20 to 40 G, and centrifugal force forming is performed to make the concrete material self-supporting or to discharge excess water as sludge water.
Here, since the high-strength concrete 4 according to the present embodiment has a small unit water volume and no surplus water, it is not necessary to discharge sludge water. Specifically, since the high-strength concrete 4 has a small W/C, when sludge water is discharged by centrifugal force forming, it becomes muddy and may form icicles on the inner surface. In order to avoid such a situation, in this embodiment, it is basically preferable to carry out centrifugal force forming so as not to discharge sludge water.

In the centrifugal force forming according to this embodiment, compaction is performed by increasing acceleration in several stages. In this stage, for example, compaction is performed at an appropriate rate of 5G or less, about 15G, and 30 to 35G for low speed rotation, medium speed rotation, and high speed rotation, respectively. This "G" indicates centrifugal acceleration (gravitational acceleration).

Specifically, at low speed rotation (5G or less), the pile formwork 1 is sufficiently filled with concrete. For the low speed rotation according to this embodiment, a range of about 3G to 5G is appropriate. At this time, vibration is applied directly to the caster 2 by the vibrator 5. Thereby, even if it is low slump concrete, it becomes possible to fill the pile formwork 1 sufficiently and uniformly by centrifugal force forming.

The amplitude (total amplitude) of the vibration applied to the caster 2 by the gear-shaped portion 5a of the vibrator 5 during low-speed rotation is preferably set to, for example, 0.5 mm or less.
In this embodiment, this amplitude is controlled by the pressure set on the cylinder member of the pressing part 5b of the vibrator 5. If this pressure is too large, the pile formwork 1 may fall off the runner wheel 3 due to centrifugal force. Furthermore, if the pressing force is too small, vibrations accompanying the rotation of the formwork will not occur or will be too small. By applying appropriate pressure, appropriate vibrations can be applied to the caster 2 through rotation of the gear-shaped portion 5a.
For example, when manufacturing a concrete pile of Φ1200 (maximum diameter) x 15 m (maximum length), the pile formwork 1 and high-strength concrete 4 weigh approximately 30 tons. When seven casts 2 are provided in the pile formwork 1, the load per cast 2 is 30/7=4.5 tons. For this reason, a pressure corresponding to the weight is applied using hydraulic pressure or pneumatic pressure.

Here, when the total amplitude (mm) and frequency (Hz) are given, the vibration acceleration (G) can be calculated using the following formula (1):

Acceleration (G) = {2π x frequency (Hz)} ² x {total amplitude (mm)/2} x 10 ^-3 x {1/9.8} ... Equation (1)

If you want to convert the unit of acceleration into m/s ² , you can multiply the value of acceleration (G) by 9.8.

On the other hand, centrifugal acceleration (m/s ² ) can be calculated using the following formula (2):

Centrifugal acceleration (m/s ² ) = 4π ² N ² l/3600... Formula (2)

Here, N is the rotational speed (rpm), and l is the distance (m) from the center to the center of gravity of the acceleration converter.

Simplifying this equation (2) results in the following equation (3):

Centrifugal acceleration (G) = 1.118 x R x N ² x 10 ^-6 ... Formula (3)

Here, R is the radius of rotation (mm), and N is the number of rotations (rpm).

The centrifugal acceleration (G) can be calculated using equations (1) and (3).
Specifically, the vibration frequency (Hz) is calculated from the outer diameter of the caster 2, the outer diameter of the gear-shaped portion 5a, and the number of protrusions, and the number of contacts of the protrusions when the caster 2 rotates once. On this basis, it is possible to calculate the centrifugal acceleration from the rotational speed (rpm) of the caster 2 during low-speed rotation and the total amplitude (mm), and use this as the gravitational acceleration (G) due to vibration.

In this embodiment, the vibration caused by the vibrator 5 causes a gravitational acceleration (G) caused by vibrations that is approximately 100 to 2000 times the centrifugal acceleration (G) (hereinafter referred to as "centrifugal G") generated during centrifugal force molding. G) (hereinafter referred to as "vibration G") can be added. That is, when the centrifugal G during low-speed rotation is 5 G, it is preferable to add a gravitational acceleration of 500 to 10,000 G as the vibration G.
Here, for example, in a concrete pile with an outer diameter of 1200 mm, the rotation speed of the formwork to obtain 5G is about 100 rpm. Since this is six times the outer diameter of 200 mm of the centrifugal specimen in the example described later, the vibration frequency also increases accordingly. Since the vibration G is proportional to the square of the vibration frequency, it is preferable to apply the vibration G according to the diameter (outer diameter) of the caster 2.

Further, in the present embodiment, in the plurality of vibrators 5, the protrusions of the gear-shaped portions 5a may be aligned to apply vibrations in synchronization.
In this way, by applying vibration at low speed rotation, the high-strength concrete 4 with low slump is reliably filled, and at medium and high speed rotation, the concrete material is made to stand on its own or surplus water is drained as sludge water. be able to. As a result, it becomes possible to centrifugally form densely compacted high-strength concrete 4 inside the pile formwork 1.

After the low speed rotation, the pile form 1 is rotated at a medium speed (approximately 15 G) to eliminate voids in the concrete filled in the pile form 1.
Finally, the pile form 1 is rotated at high speed (30 to 35 G) to make the concrete material self-supporting or to drain excess water as sludge water.

In this embodiment, vibrations are applied only when rotating at 10 G or less, and mainly when rotating at low speeds. On the other hand, when the rotation speed is 10G or more at medium speed or at high speed, no vibration is added. This is because the pile formwork 1 may fall off from the runner wheel 3 if the rotation speed exceeds 15G at medium speed.
Furthermore, if high-speed rotation is applied before applying vibration, the aggregates will engage with each other due to centrifugal G, so even if vibration is applied later at low-speed rotation, the high-strength concrete 4 will not be sufficiently filled. This is because centrifugal force only presses materials such as aggregates in a direction perpendicular to rotation, but does not spread the materials laterally. Vibrations, on the other hand, tend to spread the material laterally. For this reason, it is preferable to apply vibration during low speed rotation.

Furthermore, the concrete of this embodiment may be steam-cured after forming. In this case, it is preferable to adjust steam curing conditions such as preheating time, rising temperature (temperature rise), maximum temperature, holding time, slow cooling method, etc., depending on the target product and formulation conditions.

By configuring as described above, the following effects can be obtained.
Conventionally, concrete piles have been manufactured by centrifugal forming.

On the other hand, in recent years, the development of concrete admixtures has made it possible to produce high-strength concrete. The viscosity of high-strength concrete increases significantly, and when the slump is usually 5 to 10 cm, the viscosity of high-strength concrete becomes so hard that even if you push a shovel into it, it becomes hard like starch syrup and cannot pass through the gaps between reinforcing bars. It was difficult to pour the concrete.
On the other hand, if the slump is in the range of 0 to 4 cm, it is possible to introduce the material before it exhibits high viscosity. However, if such concrete is left as it is, no matter how much centrifugal force forming is performed, it will not be filled into the formwork, resulting in a lumpy state, making it impossible to form high-strength concrete piles.

Conventionally, when the formwork is rotated in centrifugal force forming, gravel or sand is inserted between the formwork and the runner wheel to vibrate it and fill the concrete uniformly into the formwork. known to those skilled in the art.
Furthermore, as described in Patent Document 1, a method of applying vibration by pressing a vibrator against the formwork of the Hume tube has also been known.

However, all of these methods involve adding vibration to the production of Hume pipes, and cannot be applied to concrete piles. This is because concrete piles have an elongated cylindrical shape, and a plurality of casts are formed in the pile formwork for manufacturing the concrete piles.
That is, when vibrating gravel or sand, it is necessary to artificially introduce the gravel or sand between a plurality of casters and the runner wheel at the same time, which is extremely dangerous. Furthermore, there was a possibility of damage to the runner wheels. Furthermore, when pressing a vibrator from above, it was not possible to apply sufficient vibration to the elongated pile formwork.

In contrast, (1) in the ultra-high-strength concrete pile manufacturing method according to the present embodiment, casts 2 are provided at specific intervals around the outer periphery of the pile formwork 1, the lower part of the casts 2 is supported by a runner wheel 3, and the casts are This is a method for producing concrete piles by centrifugal force forming in which a pile formwork 1 is rotated by frictional conduction between a runner wheel 2 and a rotating runner wheel 3. It is characterized by adding vibration by machine 5 and performing centrifugal force forming.

With this configuration, it is possible to densely fill the high-strength concrete 4 with low slump by vibration, and to manufacture a high-quality ultra-high-strength concrete pile.
In addition, by applying vibration directly to the caster 2, there is no need to cause gravel or sand to bite, and damage to the runner wheel 3 can also be prevented.

(2) In the ultra-high strength concrete pile manufacturing method according to the present embodiment, the vibrator 5 is formed with a plurality of protrusions, and the plurality of protrusions press from the lower part of the caster 2 according to the rotation of the caster 2. The ultra-high strength concrete pile manufacturing method according to (1) is characterized in that it comprises a gear-shaped part 5a that rotates while applying pressure, and a pressing part 5b that pivotally supports the gear-shaped part 5a and applies pressure. do.

The vibrator 5 is installed at an intermediate position of the runner wheel 3 configured in this manner, and the gear-like part 5a that is in contact with the cast member 2 rotates to apply vibration, thereby increasing the rotational speed of the vibration. can be easily estimated. Thereby, the vibration G applied to the pile formwork 1 can be easily calculated, and it becomes possible to vibrate reliably and densely fill the high-strength concrete 4.

(3) In the ultra-high-strength concrete pile manufacturing method according to the present embodiment, vibration is applied only when the ultra-high-strength concrete pile according to (1) or (2) is rotated at a centrifugal acceleration of 10 G or less. It is characterized by being a pile manufacturing method.

With this configuration, it is possible to suppress the risk of the formwork popping out at medium speed rotation (15G) or higher. Furthermore, by applying high-speed rotation before applying vibration, it is possible to prevent the aggregates from interlocking with each other due to centrifugal G, and the phenomenon in which materials such as aggregates do not spread even if vibration is applied at low-speed rotation after that can be prevented.

(4) In the ultra-high-strength concrete pile manufacturing method according to the present embodiment, the ultra-high-strength concrete pile according to any one of (1) to (3), in which a vibration G of 100 to 2000 times the centrifugal G is applied by vibration. The present invention is characterized by being a method for manufacturing strong concrete piles.

With this configuration, the concrete material of the high-strength concrete 4 can be sufficiently spread in a direction different from the centrifugal direction, and the high-strength concrete 4 can be densely filled.

Furthermore, conventionally, in the manufacture of concrete cylindrical structures by centrifugal force forming, there are two types of methods for charging concrete into formwork: a pumping method and a filling method.
When pumping something highly viscous, such as high-strength concrete, there was a risk of blockage, making it impossible to pump.
Furthermore, in the pouring method, concrete with a slump of 5 cm to 10 cm is usually used, but because high-strength concrete has high viscosity, it is difficult to pour it through the gaps between reinforcing bar cages.

On the other hand, conventionally, when handling high-strength concrete, it is often handled under a slump flow condition in which the concrete spreads, rather than under normal slump control. Such slump flow concrete is also called self-filling concrete or high-flow concrete, and can self-fill into formwork under its own weight without excessive vibration, and does not separate.
However, when high-strength concrete is used in centrifugal force forming in a state of slump flow, it becomes necessary to use an amount that is 20% to 30% larger than the internal volume of the lower formwork using the filling method. Therefore, there is a problem that it cannot fit into the lower formwork and overflows, so it cannot be used for centrifugal force forming of ultra-high strength concrete piles under slump flow conditions.

On the other hand, (5) in the ultra-high strength concrete pile manufacturing method according to the present embodiment, the high strength concrete 4 has a slump in the range of 0 to 4 cm. It is characterized by being a method for manufacturing ultra-high strength concrete piles.

The concrete for ultra-high strength concrete piles according to the present embodiment configured as described above is a low slump concrete with a slump in the range of 0 to 4 cm, which is on the verge of exhibiting high viscosity. This type of low-slump concrete that has not yet solidified has mortar attached to the aggregate, so it can be easily passed through the reinforcing bar cage and placed into the lower formwork using the filling method. becomes.
Additionally, low slump concrete can be packed in heaps using the filling method, and will not overflow from the lower formwork.

(6) In the ultra-high strength concrete pile manufacturing method according to the present embodiment, the cement used for the high strength concrete 4 is normal cement, early strength cement, moderate heat cement, or low heat cement, and the water binder ratio is The ultra-high strength concrete pile manufacturing method according to any one of (1) to (5) is characterized in that: 10 to 18%.

(7) In the ultra-high-strength concrete pile manufacturing method according to the present embodiment, when the cement is ordinary cement, the high-strength concrete 4 contains 500 to 650 of cement and 100 to 650 of admixture per unit amount of 1 kg/m ³ . 280, water 100-140, fine aggregate 500-600, coarse aggregate 900-1200, and water reducer 10-20, the water binder ratio is 10-18%, and the cement is early strength cement, moderate heat cement, Or in the case of low heat cement, per unit amount of 1 kg/ ^m3 , cement 500-650, admixture 100-280, water 100-140, fine aggregate 500-600, coarse aggregate 900-1200, and water reducing agent 10- 20 and the water binding material ratio is 10 to 13%.

With this configuration, it is possible to manufacture an ultra-high strength concrete pile that meets the concrete pile strength standards.
Here, concrete piles have strength standards of "85N,""105N," and "123N." The standard values of their compressive strengths are 85 N/mm ² , 105 N/mm ² for 105 N, and 123 N/mm ² for 123 N, respectively. Further, the "target" compressive strength in the standard is about 95 N/mm ² for 85N, 115 N/mm ² for 105N, and 130 N/mm ² for 123N. By using the pile forming apparatus 10 according to this embodiment, even when using ordinary cement, the compressive strength of the 105N standard can be satisfied, and by further adjusting the composition as shown in Example 2 described later, 123N standard can also be satisfied. This makes it possible to manufacture high-strength, high-quality concrete piles at low cost.
Furthermore, in order to obtain a concrete pile with a high strength of 150 N/mm ² or more, it is also possible to use early strength cement, moderate heat cement, low heat cement, or the like.

In addition, in the above-mentioned embodiment, although the example in which the vibration exciter 5 is provided with the gear-shaped part 5a was demonstrated, it is also possible to apply vibration from below the caster 2 by other methods. For example, the pressing portion 5b of the vibration exciter 5 may be provided with a smooth cylindrical member or a simple protrusion as the member that contacts the caster 2. In this case, the cylinder member may be directly vibrated pneumatically, hydraulically, or electrically to vibrate the caster 2.
With this configuration, the vibration frequency can be adjusted more finely.

In addition, in FIG. 1 of the above-described embodiment, three vibration exciters 5 are shown as visible, but even if a single vibration exciter 5 is provided, a large number of vibration exciters will be generated according to the number of casters 2. It may also be configured to include a machine 5. Furthermore, although FIG. 1 shows an example in which the vibrator 5 is placed every other one, the vibrator 5 may be provided as many as the number of casters 2. Alternatively, a vibrator 5 that vibrates only the caster 2 at the end of the pile formwork 1 may be provided.
Further, in the above-described embodiment, an example has been described in which vibrations are applied in synchronization with respect to the plurality of vibrators 5, but the vibrations may not be synchronized in order to suppress resonance.

Further, the vibrator 5 may directly apply vibration to the pile formwork 1 instead of applying vibration to the caster 2.
In this case, the pile formwork 1 may have a cylindrical structure different from that of the caster 2. When configured in this way, the pile formwork 1 may be vibrated by forming a gear-shaped protrusion on the cylindrical structure of the caster 2 instead of the gear-shaped portion 5a.

Further, in the above-described embodiment, although it has been described that vibration is applied only during low-speed rotation, vibration with a smaller vibration G than during low-speed rotation may be applied during medium-speed rotation.

Next, the present invention will be further explained by examples based on the drawings, but the following specific examples are not intended to limit the present invention.

A cylindrical centrifugal specimen with an outer diameter of 200 mm, a height of 300 mm, and an inner diameter of 120 mm was prepared based on JIS A 1136, which is a compressive strength test method for centrifugally compacted concrete.

At this time, the outer diameter of the cast member 2 of the pile formwork 1 was 330 mm, and the outer diameter of the gear-shaped portion 5a of the vibrator was 80 mm. The number of protrusions (teeth) on this gear-shaped portion 5a is 18, and when the caster 2 rotates once, the protrusions make contact 74 times. That is, the vibration frequency per one rotation of the formwork is 74.
The conditions in this example are shown in Table 1 below.

Among these, the number of rotations of the gear-shaped portion 5a indicates the number of rotations of the gear-shaped portion 5a per one rotation of the caster 2.
Table 2 below also shows the centrifugal G of this centrifugal specimen (Φ20 x 30 cm), the rotation speed (rpm) of the cast 2 (formwork), the vibration frequency (Hz), the total amplitude (mm), and the vibration G. An example of calculating is shown below.

Here, in this example, the rotation speed of the caster 2 at low speed rotation (5G) is 236 rpm, the frequency at that time is 17523 (Hz), and assuming that the amplitude is 0.001 mm, the vibration G is It becomes 618. That is, a vibration G was generated that was 120 times the centrifugal G generated when centrifugal force was generated, and a force that spread the concrete was applied.
On the other hand, as a comparative example, a specimen with the same centrifugal G and no vibration was also used.

Furthermore, since the diameter of the centrifugal specimen of this example is 20 mm, the load is approximately 30 kg. Including the weight of the formwork, it will be approximately 50 kg. Therefore, when applying air pressure to the cylinder member, setting the pressure of the air compressor in the range of 0.1 MPa to 1 MPa will make it possible to apply an appropriate vibration G without pushing up the entire formwork and causing it to fall off. , is suitable.

The composition of high-strength concrete 4 in this example has a water-cement ratio (W/C (%)) of 18%, and a fine aggregate ratio (S/a), which is the ratio of fine aggregate to the total aggregate volume. %)) was 45%, and the amount of cement was 600 kg. The slump was a low slump of 0 cm, a specified amount was packed into a mold, and centrifugal force forming was performed on a centrifugal tube making machine.
In the centrifugal force molding method, low-speed rotation, which may include vibration, was performed for 30 seconds to 2 minutes. Thereafter, it was rotated at medium speed (15G) and then at high speed (35G).

FIG. 3 shows the state of high-strength concrete 4 after centrifugal force forming. FIG. 3(a) shows the state of the outer surface of the specimen (this example) to which vibration was applied. FIG. 3(b) shows the state of the outer surface of the specimen (comparative example) to which no vibration is applied.
When vibration was applied, the material was filled into the formwork, and the inner surface was also finished beautifully. On the other hand, when no vibration was applied, no filling of the high-strength concrete 4 materials into the pile form 1 was observed, and the pile form 1 was in a stale-like state.

Next, as Example 2, in each composition, cement and other materials were adjusted to further enhance strength development and inner surface properties.
As the cement, ordinary Portland cement, early strength Portland cement, moderate heat Portland cement, and low heat Portland cement (all based on JIS R 5210, manufactured by Taiheiyo Cement Co., Ltd.) were used.
Blast furnace slag powder 8000, 10000, 20000 brane, silica fume, etc. were blended as the admixture. Among these, the blast furnace slag powder used was one compliant with JIS A 6206 (Cerament #8000, Cerament #10000, and Cerament #20000, all manufactured by DC Corporation). The silica fume used was one compliant with JIS A 6207 (imported and sold by Tomoe Kogyo Co., Ltd., made in Egypt).
Hard sandstone-based aggregates conforming to JIS A 5002 were used as the fine aggregate and coarse aggregate (crushed sand for concrete, crushed stone 2005, manufactured by Ryojin Kogyo Co., Ltd.).
A high-performance polycarboxylic acid-based AE water reducing agent compliant with JIS A 6204 was used as the water reducing agent (Reobuild 8000SS, manufactured by Pozolis).
The results are shown in Table 3 below.

In each test example, the cement type "normal" indicates normal cement, "early strength" indicates early strength cement, "moderate heat" indicates moderate heat cement, and "low heat" indicates low heat cement.
Regarding the inner surface condition, "〇" indicates good condition, "△" indicates no smoothness and is wavy, and "x" indicates no smoothness and is not perfectly round.

As a result, when ordinary cement was used as the cement for the concrete of this example, those having a composition whose compressive strength after 7 days exceeded 150 N/mm ² had a wavy inner surface after centrifugal forming. On the other hand, even when ordinary cement was used, concrete with a composition having a compressive strength of up to 130 N/mm ² had good inner surface properties. In addition, for early-strength cement, medium-heat cement, and low-heat cement, the inner surface properties were good regardless of the composition, even if the composition exceeded 150 N/mm ² .
In other words, even a compressive strength of 130 N/mm ² is sufficient strength depending on the application, so if a strength lower than this is acceptable, it is possible to use ordinary cement, early strength cement, moderate heat cement, or low heat cement. . On the other hand, for concrete whose compressive strength must exceed 130 N/mm ² , it is preferable to use early-strength cement, medium-heat cement, or low-heat cement.

Further, the water binder ratio of the concrete of this example was preferably 10 to 18%.
Specifically, in concrete using ordinary cement with a compressive strength of up to 130 N/mm ² , it was preferable that the water binder ratio be up to 18%. Specifically, as shown in Test Example 11, when the unit water volume increased and the water binder ratio exceeded 18%, concrete became easier to handle, but the inner surface properties tended to deteriorate and the strength decreased. . Furthermore, if the water binder ratio is less than 10%, the concrete cannot be kneaded in the first place and the materials will separate, resulting in insufficient inner surface properties and strength.
In addition, for compositions with compressive strength exceeding 150 N/mm ² using early-strength cement, medium-heat cement, or low-heat cement, it is preferable that the water-binder ratio is lower than 18%, and approximately 13%. there were.

To explain more specifically, in concrete using ordinary cement with a compressive strength of up to 130 N/mm ² , per unit amount of 1 kg/m ³ , ordinary cement 500 to 650, admixture 100 to 280, and water 100 to 140, fine aggregate 500 to 600, coarse aggregate 900 to 1200, and water reducing agent 10 to 20, and preferably the water binder ratio is 10 to 18%.
In addition, for concrete with a compressive strength exceeding 150 N/mm ² , per unit amount of 1 kg/m ³ , add 500 to 650 of early strength cement, medium heat cement, or low heat cement, 100 to 280 of admixture, 100 to 140 of water, It is preferable that the fine aggregate is 500 to 600%, the coarse aggregate is 900 to 1200%, and the water reducing agent is 10 to 20%, and the water binder ratio is 10 to 13%.

Note that the configuration and operation of the embodiment described above are merely examples, and it goes without saying that the configuration and operation of the embodiment can be modified and executed as appropriate without departing from the spirit of the present invention.

1 Pile formwork 2 Cast 3 Runner wheel 4 High-strength concrete 5 Vibrator 5a Gear-shaped part 5b Pressing part 10 Pile forming device C Axis M Drive part

Claims (8)

Manufacture of concrete piles by centrifugal force forming, in which casts are provided at specific intervals around the outer periphery of the formwork, the lower part of the casts is supported by a runner wheel, and the formwork is rotated by friction transmission between the casts and the runner wheel that rotates. A method,
Filled with low slump high strength concrete,
A method for manufacturing an ultra-high strength concrete pile, characterized in that centrifugal force forming is performed by applying vibration from the lower part of the cast using a vibrator. The vibration exciter is
a gear-like part in which a plurality of protrusions are formed and the plurality of protrusions rotate while applying pressure from the lower part of the caster according to the rotation of the caster; and a press that pivotally supports the gear-like part to apply the pressure. The ultra-high strength concrete pile manufacturing method according to claim 1, further comprising: a. The ultra-high strength concrete pile manufacturing method according to claim 1, wherein the vibration is applied only during rotation at a centrifugal acceleration of 10 G or less. 2. The ultra-high strength concrete pile manufacturing method according to claim 1, wherein the vibration applies a gravitational acceleration that is 100 to 2000 times the centrifugal acceleration generated during centrifugal force forming. The ultra-high strength concrete pile manufacturing method according to any one of claims 1 to 4, wherein the high strength concrete has a slump in the range of 0 to 4 cm. The cement used for the high strength concrete is normal cement, early strength cement, moderate heat cement, or low heat cement,
The ultra-high strength concrete pile manufacturing method according to claim 5, wherein the water binding material ratio is 10 to 18%. When the cement is normal cement, cement 500-650 kg/m ³ , admixture 100-280 kg/m ³ , water 100-140 kg/m ³ , fine aggregate 500-600 kg/m ³ , coarse aggregate 900-1200 kg/m 3 m ³ and a water reducing agent of 10 to 20 kg/m ³ and a water binder ratio of 10 to 18%,
When the cement is early strength cement, medium heat cement, or low heat cement, per unit amount of 1 kg/m ³ , cement 500-650 kg/m ³ , admixture 100-280 kg/m ³ , water 100-140 kg/m ³ , fine aggregate 500 to 600 kg/m ³ , coarse aggregate 900 to 1200 kg/m ³ , and water reducing agent 10 to 20 kg/m ³ , with a water binder ratio of 10 to 13%. The ultra-high strength concrete pile manufacturing method according to claim 6. Manufacture of concrete piles by centrifugal force forming, in which casts are provided at specific intervals around the outer periphery of the formwork, the lower part of the casts is supported by a runner wheel, and the formwork is rotated by friction transmission between the casts and the runner wheel that rotates. A vibration exciter used for
a gear-shaped part in which a plurality of protrusions are formed and the plurality of protrusions rotate while applying pressure from a lower part of the caster according to the rotation of the caster;
A vibration exciter comprising: a pressing part that pivotally supports the gear-shaped part and applies the pressing force.

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