JPH0365761B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an ultrahigh-speed centrifugal column forming method.

[Conventional technology]

In general, cylindrical concrete products such as concrete piles, pipes, poles, humid pipes, and electric wire pipes are produced by rotating the column formwork at high speed and applying a predetermined centrifugal force to the concrete within the column formwork. It is molded. Specific methods of centrifugal molding include the wheel-tire method in which a cylindrical form is placed on rotating drive wheels, or the wheel-tire method in which the form is placed on a driving belt that runs on a cylindrical form. There is a belt system that rotates the

However, with the wheel-tire method, the formwork tends to vibrate when rotating, making it impossible to apply the necessary centrifugal force.
Concrete materials tend to separate, making it impossible to obtain sufficient compaction effects. For this reason, there is a large difference in the wall thickness of the cylindrical body, resulting in the use of extra concrete, and the inner diameter of the pile etc. becomes small, causing problems in construction such as the hollow excavation method. Also,
During centrifugal molding, a large amount of slag (a water suspension of fine particles) was discharged from the inner surface of the product, making it impossible to fix and solidify the fine particles on the inner surface to form a smooth layer. The belt method also lacked ultra-high-speed rotation technology and there was no demand for such high speeds, so the resulting product had a rough, rough surface with no particulate layer fixed on the inner surface, similar to the wheel-tire method. In the end, no matter which method was used, the centrifugal force applied to the concrete inside the column formwork was about 35G at most, so the compaction of the concrete was insufficient and a large number of pits and unevenness on the inner surface of the hollow were formed. Occurred and the quality was poor.

Furthermore, in order to sufficiently compact the concrete within the column form, it was necessary to rotate the column form for a long time.

[Purpose of the invention]

This invention was proposed in order to solve the above-mentioned conventional problems, and it is possible to centrifugally form cylindrical concrete products such as concrete piles in an extremely short time, eliminate product variations, and improve product accuracy. can be significantly increased,
The purpose of this invention is to provide an ultra-high-speed centrifugal force column forming method that can provide new cylindrical concrete products that have not been possible with conventional methods.

[Structure of the invention]

The above object is achieved by rotating the unhardened concrete raw material of this invention for a certain period of time under a centrifugal force of 60 G or more.

Figure 1 shows a new hollow cylindrical body made of concrete pile manufactured by the method of the present invention, with the concrete layer A, mortar layer B, and paste layer C continuing from the outside to the inside, with ultrafine particles on the inner surface. A solidified layer 2 is formed by solidification.

The ultrafine particles in the hollow cylinder are ultrafine particles in concrete that aggregate on the inner surface of the cylinder during ultrahigh-speed centrifugal molding. Approximately 70% of the particles are less than 50μ in size.
Approximately 30% of the particles are 50μ to 80μ, and the particles aggregate as a water suspension on the inner surface during molding, stick and solidify without flowing out, and have a thickness of 0.3 to 1.5mm and a difference in unevenness of 0.1mm.
Form the following smooth solidified layer. Further, the cylindrical body formed in this manner has a difference in cylinder wall thickness of 2 mm or less at the same time as the coating layer is formed, and has a smooth inner surface. The difference in cylindrical wall thickness of concrete piles using the conventional wheel-tire centrifugal forming method is usually 9 to 15 mm, and the thickness t ₁ , as shown in Fig. 2,
It is expressed as the difference between t ₂ (t ₂ − t ₁ ). Furthermore, the pitt coefficient is 0.1 or less. Here, pits 11 refer to voids or nests formed at the back of coarse aggregate in a concrete pile (see Figure 3a), and the number of pits N per concrete cross-sectional area A (cm ² ) is It is called Pitt coefficient N/A.

Figure 3a shows the concrete pile of the present invention, which has a diameter of 600φ, a cross-sectional area A of 89.3 cm ² , and pits N=4, so the pit coefficient is 0.045.

Note that b in Figure 3 is a concrete pile consisting of a conventional wheel-tire type with a diameter of 600φ and A
= 89.3cm ² , number of pits N = 27, therefore pitt coefficient
It becomes 0.302.

Figure 4 shows an example of an ultra-high-speed centrifugal force column forming machine that can rotate column forming forms under centrifugal force of 60G or more.The configuration is shown in Figures 4 to 6 below. The explanation will be as follows.

The belt-type ultra-high-speed centrifugal force column forming machine has main pulleys 1 and 2 of the same diameter, a sub-pulley 3 that is one size smaller than the main pulleys 1 and 2 (approximately 70 to 80% larger than the main pulleys 1 and 2), and these pulleys. The flat belt 9 is constructed of a flat belt 9, etc., which is stretched between pulleys 1, 2, and 3, and the flat belt 9 is rotated at high speed by rotating the pulleys by the power of a motor or the like.

Main pulleys 1 and 2 have the same diameter, and are one size smaller than main pulleys 1 and 2 (main pulleys 1 and 2 have a diameter of 70~
(approximately 80%) Sub-pulleys 3 are installed at regular intervals in the diametrical direction of these pulleys.

The main pulleys 1 are attached to the shaft 4 at regular intervals in its longitudinal direction. When the shaft 4 is rotated at high speed by the power of a motor or the like, the main pool 1 can be rotated at high speed.

The main pulley 2 and the sub pulley 3 are arranged right side by side with the main pulley 1, and similarly to the main pulley 1, they are installed at regular intervals in the longitudinal direction of the shaft 4.

Further, the main pulley 2 and the sub pulley 3 are attached to bearings 5 and 6, and the distance between the main pulley 2 and the sub pulley 3 can be freely adjusted by shifting the fixed position of the bearing 6 in the horizontal direction of the sub pulley 3. It is considered possible to do so.

Furthermore, a parallel part 7 that continues in the circumferential direction is formed in the central part of the main pulleys 1, 2 and the sub pulley 3, and a tapered part 8 that tapers toward both ends of each pulley is formed on both sides of the parallel part 7. , 8 are formed respectively.

The flat belt 9 is formed by stacking one to a plurality of core materials made of nylon cloth vertically at a certain interval, and covering the surface thereof with a cover rubber to a certain thickness. In the example, three core materials are used.

The nylon cloth used as the core material is a plain weave made of nylon thread or nylon thread and various threads such as vinylon, tetron, and polypropylene.

In such a configuration, when the main pulley 1 is rotated at high speed by the power of a motor or the like via the shaft 4,
The flat belt 9 rotates between the main pulleys 1 and 2 and the sub pulley 3 at high speed (circumferential speed of 500 m/min to 2000 m/min).

Furthermore, when the column forming form 10 is placed horizontally on the flat belt 9 in advance, the column forming form 10 rotates at a high speed that easily exceeds the centrifugal force of 60 G due to the high speed rotation of the flat belt 9. Therefore, the concrete in the column forming form 10 can be centrifugally formed.

In this case, due to the shape of the pulley and the flat belt 9
Due to the structure, even if the rotational speed of the flat belt 9 is greatly increased, there is no danger that the flat belt 9 will meander, generate heat, or break. When centrifugally forming concrete products, column forming 10
The centrifugal force G is divided into 3 to 5 stages. and,
The centrifugal force G is increased step by step until the centrifugal force G is 60G or more for a certain period of time.

Next, to explain an example of a concrete manufacturing method for concrete products, the mixing ratio of concrete is 360 to 400 kg of cement (Portland cement)/
m ³ , fine aggregate 600-750Kg/m ³ , aggregate 900-1200Kg/
^m3 , silica 50~200Kg/ ^m3 , water reducing agent 5~20Kg/ ^m3 ,
Concrete containing 130 to 170 kg/m ³ of water is poured into a column forming form, and centrifugally formed using a belt-type centrifugal force column forming machine under a pressure of 60 G or more for a certain period of time.

Thereafter, it is pre-cured at 60-70°C for about 2-7 hours, and then autoclaved at 180-190°C and 10-12 atmospheres for about 8 hours.

The above-mentioned novel concrete hollow cylinder can be stably obtained by centrifugal forming using a belt-type centrifugal force column forming machine under 60G or more.

This new concrete hollow cylindrical body cannot be obtained at about 35G as in the past.

〔Example〕

Next, the present invention will be explained based on examples of specific manufacturing examples of concrete hollow cylinders.

Portland cement 380Kg/m ² , fine aggregate 700
Kg/m ³ , coarse aggregate 1000Kg/m ³ , silica 120Kg/m ³ ,
A steel pipe form was filled with concrete mixed at a ratio of 12 kg/m ³ of water reducing agent and 150 kg/m ³ of water.

After that, this steel pipe formwork is rotated at high speed by the aforementioned belt-type ultra-high-speed centrifugal force column making machine, and the centrifugal force is increased step by step until the final result is 60G, 70G, 80G,
Centrifugal molding was performed for 3 to 5 minutes at each step of 90G and 100G. Also, for reference, I did the same thing at the 50G stage.

Thereafter, it was pre-cured at 70°C for about 7 hours, and then autoclaved at 180°C and 10 atm for about 8 hours.

Figures 7 to 1 show the compressive strength, pitting coefficient, roundness, and smoothness of concrete for the hollow cylindrical steel tube concrete that was centrifugally formed at each stage.
It is shown in the graph of Figure 0.

[Comparative example]

A steel tube concrete cylindrical hollow body was manufactured by centrifugal molding for a predetermined period of time with only the final stage centrifugal force being 30G and 40G under the same manufacturing method as in the above example.

The compressive strength and other performances of the concrete of the steel pipe concrete cylindrical hollow body are shown in Figures 7 to 10.
Shown in the graph in Figure.

The graph shows that the product according to the present invention is a concrete hollow cylindrical body that has extremely high compressive strength and has extremely small pit coefficient, wall thickness difference, and flatness compared to conventional products.

〔Effect of the invention〕

Since the present invention has the above configuration, it has the following effects.

Since the column formwork is rotated for a certain period of time under a centrifugal force of 60G or more, cylindrical products such as concrete piles can be centrifugally formed in an extremely short time.

Furthermore, since there is no fear that the concrete will shift to one side during the rotation of the column forming form, it is possible to manufacture an extremely ideal perfectly circular concrete product with a uniform concrete thickness and a wall thickness difference of 2 mm or less.

In addition, a coating layer mainly composed of calcium carbonate is formed on the inner peripheral surface of concrete products, and the surface is formed into an extremely flat curved shape with a flatness of 0.1 mm or less, resulting in extremely high product precision and aesthetic appearance. .

In addition, since the concrete can be sufficiently compacted, the pitting coefficient is extremely small.

Furthermore, the occurrence of slag is extremely low,
There is less wastage of materials and manufacturing costs can be reduced.

Moreover, according to the manufacturing method of the present invention, the compressive strength of concrete is further increased.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged cross-sectional view of a concrete pile according to the present invention, Fig. 2 is a diagram illustrating the difference in cylindrical cross section, and Fig. 3 shows pits (a and b) of the concrete pile of the present invention and the conventional concrete pile. Figures 4 and 5 are a front view and plan view of a belt-type centrifugal column making machine for manufacturing concrete piles, Figure 6 is a front view of a pulley, and Figures 7 to 10 are partially enlarged cross-sectional views. The figure is a graph showing the relationship between centrifugal force G, compressive strength, pitt coefficient, wall thickness difference, and flatness. A... Concrete layer, B... Mortar layer, C... Paste layer, D... Ultrafine particle coating layer, 1, 2... Main pulley, 3... Sub-pulley, 4...
...Shaft, 5, 6...Bearing, 7...Parallel part,
8...Tapered portion, 9...Flat belt, 10...Column formwork, 11...Pits.

Claims (1)

[Claims] 1. An ultra-high-speed centrifugal column forming method characterized by rotating concrete raw materials before hardening for a certain period of time under centrifugal force of 60G or more.