JPH1110628A - Mamufacture of concrete cylindrical tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a reduced thickness and light weight concrete cylindrical tube by adding thickener to powder material for concrete, mixing reinforcing short fiber having lower specific gravity than that of the powder material therewith, and centrifugally molding mortal material obtained by preparing so that flow cone bulk height becomes specific value, thereby clearly releasing it from a foam. SOLUTION: Thickener is added to powder material for concrete, reinforcing short fiber having lower specific gravity than that of the powder material is mixed therewith, and mortar material obtained by preparing so that its flow cone height becomes 60 to 70 is centrifugally molded. Viscosity of the mortar material is enhanced by adding the thickener to suppress movement of the mixed fiber. And, an amount of the fiber to be squeezed out by the centrifugal force at the time of centrifugally molding is reduced. And, the fiber is sufficiently retained in matrix to sufficiently develop a strength of the concrete cylindrical tube. And, water holding capacity of the mortar material is enhanced to ensure water content amount necessary to uniformly extend the mortal material. The tube having reduced thickness, light weight, no unevenness in tube thickness and satisfactory quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a concrete cylindrical tube. More specifically, the present invention relates to a method of manufacturing a practical concrete cylindrical tube capable of manufacturing a thin and lightweight concrete cylindrical tube.

[0002]

2. Description of the Related Art Conventionally, concrete cylindrical tubes used for fume tubes and the like have been manufactured by centrifugal molding. Cylindrical pipes with built-in reinforcement as reinforcement
Generally, a reinforcing bar having a diameter of 2 to 3 mm is used, and a concrete cover thickness of about 25 to 30 mm is required to prevent corrosion of the reinforcing bar. For this reason, in the case of a concrete cylindrical pipe into which a reinforcing bar is inserted, the pipe thickness must be at least 5
The thickness is 0 to 60 mm, and there is a problem that it is difficult to reduce the thickness.

Therefore, in order to realize a thin concrete cylindrical tube, for example, a continuous fiber of alkali-resistant glass fiber is used as a reinforcing material instead of a reinforcing bar, and the alkali-resistant glass is provided on the inner surface and the outer surface of the cylindrical tube. A method of burying fiber rovings has been considered. According to this method, a thin and lightweight concrete cylindrical tube of about 10 mm can be manufactured.

[0004]

However, in the above-mentioned method, when a cylindrical tube having an opening is manufactured, the member for the opening is set in a mold and molded, and then the member for the opening is formed after molding. There is a problem that it cannot be removed from the cylindrical tube cleanly. In addition, the above method has a problem that the equipment is large-scale and the cost performance is not good, and is not suitable for practical use.

[0005] As described above, it is desired to realize a manufacturing method which makes it possible to practically manufacture a thin, lightweight concrete cylindrical tube. The present invention has been made in view of the above circumstances, and solves the disadvantages of the conventional production of a concrete cylindrical tube, and is capable of producing a thin, lightweight concrete cylindrical tube. It is an object of the present invention to provide a method for manufacturing a concrete cylindrical tube.

[0006]

The present invention solves the above-mentioned problems by adding a thickener to a concrete powder material and blending reinforcing short fibers having a lower specific gravity than the powder material. The present invention provides a method for producing a concrete cylindrical tube, which comprises centrifugally molding a mortar material adjusted so that the flow cone has a bulkiness of 60 to 70 to produce a concrete cylindrical tube.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method for manufacturing a concrete cylindrical pipe according to the present invention will be described below in more detail. In the method for producing a concrete cylindrical tube according to the present invention, as described above, a thickener is added to a powder material for concrete, and short fibers for reinforcement having a lower specific gravity than the powder material are blended to increase the flow cone bulkiness. Is adjusted by centrifugal molding.

A mortar material premixed with a powder material for concrete forming a matrix of a concrete cylindrical tube as a reinforcing short fiber having a specific gravity smaller than that of the concrete powder, for example, about 2.5 or less, is subjected to centrifugal molding to obtain mixed mortar material. The fibers are squeezed out into the inner space of the cylindrical tube by centrifugal force during molding because the specific gravity is smaller than the powder material for concrete,
Since it is separated and exposed and does not remain in the matrix, poor strength expression is caused.

Further, since the mortar material in which the reinforcing short fibers are premixed has a low water retention capacity, water having a lower specific gravity than the powder material is centrifugally applied to the inner space immediately after being put into the mold. The water is squeezed out before the mortar material is evenly stretched and compacted with the optimum amount of moisture. As a result, molding defects such as an increase in variation in tube thickness occur. The occurrence of the molding failure is also due to the fact that the mortar material itself has low fluidity. That is, although the mortar material has low fluidity, it takes time to expand and spread due to centrifugal force, but water is squeezed into the inner space before the mortar material expands as described above. As a result, the fluidity is further reduced, and the variation in tube thickness is promoted. For this reason, a mortar material prepared by premixing a concrete powder material with a reinforcing short fiber having a lower specific gravity than the concrete powder material has not been used for the production of a concrete cylindrical tube.

The method of manufacturing a concrete cylindrical tube according to the present invention makes it possible to produce a thin, lightweight concrete cylindrical tube of high quality while overcoming the above-mentioned drawbacks by intentionally using the mortar material, and at the same time, to commercialize the tube. Make it possible. Therefore, in the method for manufacturing a concrete cylindrical tube of the present invention,
Add thickener to mortar material with flow cone bulkiness of 60-7
It is adjusted to be 0 and added.

[0011] When the thickener is added, the viscosity of the mortar material is increased, and the movement of the mixed reinforcing short fibers is suppressed.
The amount of reinforcing short fibers squeezed out by centrifugal force applied during centrifugal molding can be reduced. A sufficient amount of the reinforcing short fibers remains in the matrix, and the strength of the concrete cylindrical tube is sufficiently exhibited. In addition, the addition of the thickener increases the water retention capacity of the mortar material, and can secure the amount of water necessary for the mortar material to be uniformly extended.
Water is squeezed out gradually during centrifugal molding, and the mortar material can maintain a sufficient amount of water until it is stretched and spread.

This thickener has a flow cone bulkiness of 60.
It is adjusted to be ~ 70 and added. Here, the flow cone is a conical iron container used in a flow test for measuring the softness of a mortar material specified in JIS R 5201. In the flow test, a flow cone is placed on a flow table, mortar material is packed therein, the flow cone is removed, and then the flow table is moved up and down 15 times at a rate of once a second, and then spread. The flow cone bulk is measured in mm from the mortar material.

When the flow cone has a bulkiness of less than 60, the amount of the thickener to be added is small, and the reinforcing fibers float on the inner surface of the cylindrical tube by centrifugal molding. If it exceeds 70,
The thickener becomes excessive, the fluidity of the mortar material decreases,
It causes molding defects such as variations in tube thickness. The type of the thickener is not particularly limited, but among them, methylose is exemplified as a preferable one. When methylcellulose is used as a thickener, short fibers for reinforcement do not appear on the inner surface of the cylindrical tube after molding, and a clean appearance is obtained. This is because the water retention of the mortar material is increased by the action of methyl cellulose. The amount of water squeezed out during centrifugal molding is further reduced, and more than enough water remains in the matrix, which becomes cement water and hardens on the inner surface of the cylindrical tube, preventing the appearance of short fibers for reinforcement. . Such methylcellulose includes, for example, 65SH-40
00 (manufactured by Shin-Etsu Chemical Co., Ltd.) can be used. A concrete cylindrical tube having no reinforcing short fibers on its inner surface can withstand use as, for example, a gate post. When the inner space of the cylindrical tube is used as a post, the inner surface may be visible, but a concrete cylindrical tube manufactured using methylcellulose as a thickening agent does not have a poor appearance.

As described above, the method for manufacturing a concrete cylindrical tube according to the present invention uses a premix mortar material in which a reinforcing powder having a smaller specific gravity is mixed with a powder material for concrete, and a predetermined amount of By adding the thickening agent, a thin and lightweight concrete cylindrical tube can be manufactured with high quality while suppressing variations in tube thickness. Removal from the mold is performed neatly, the equipment is not large, the cost performance is good, and it is suitable for practical use.

In the method for manufacturing a concrete cylindrical pipe according to the present invention, prior to centrifugally forming the mortar material,
The surface layer can also be formed by mixing 0.5% or less of reinforcing short fibers with a concrete powder material, and putting a mortar material without a thickener into a centrifugal molding machine and performing centrifugal molding. As the amount of the reinforcing short fibers increases, the surface of the produced concrete cylindrical tube has bubble marks. This is because the fibers themselves have air bubbles or the viscosity of the mortar material increases due to the addition of the thickener, so that air is trapped when the fibers are kneaded.
The air bubbles taken into the mortar material remain on the surface of the product without being squeezed out at the time of centrifugal molding, and air bubble marks are formed. Such a bubble mark becomes a problem of poor appearance especially when a patterned cylindrical tube is manufactured.

Therefore, before the mortar material to which the thickener is added is subjected to centrifugal molding, the blending ratio of the reinforcing short fibers is set to 0.5% or less, and the mortar material to which the thickener is not added is charged into a centrifugal molding machine. To form a surface layer. Next, the mortar material to which the thickener is added in a predetermined amount is similarly centrifugally molded, whereby a concrete cylindrical tube having a two-layer structure is produced, and a good appearance having no air bubble mark on the surface can be formed. Mortar materials containing 0.5% or less of reinforcing short fibers that form the surface layer of the cylindrical tube and containing no thickener contain little fiber and have no added thickener. And there are no air bubbles remaining on the surface.

If the amount of the reinforcing short fibers added to the mortar material forming the surface layer exceeds 0.5%, cracks are likely to be generated on the surface. In the method for manufacturing a concrete cylindrical tube of the present invention, a water reducing agent may be added to the mortar material to which the thickener is added in a small amount, for example, about 0.3 to 1.5%. Water is squeezed out of the mortar material at the time of centrifugal molding, and the reinforcing short fibers mixed at that time may be squeezed out by the water. The water reducing agent,
By adding a small amount, it is possible to reduce the amount of water in the mortar material, reduce the amount of water squeezed out during centrifugal molding,
The loss of the reinforcing short fibers from the mortar material is suppressed.
As the water reducing agent, for example, Mighty (manufactured by Kao Corporation) can be used.

Further, in the method for producing a concrete cylindrical tube of the present invention, fine sand having a small particle size and a uniform particle size is used as fine sand used as one component in the powder material for concrete. can do. The use of No. 5 silica sand or the like is effective in improving the fluidity of the mortar material, improving the elongation of the material after being put into the centrifugal molding machine, and suppressing the variation in tube thickness.

[0019]

EXAMPLE 1 Concrete powder material of cement / fine sand = 1/1 (% by weight) was mixed with polyether (NK-5, manufactured by Sanyo Chemical Co., Ltd.).
0) as a thickener, 0.0002 to 0.0010 (% by weight) is added,
After dry mixing with a mixer, the flow value (fluidity) is 1
Water was added so as to be about 60 to 180 (ring size 55φ × 50H) and wet-mixed. Next, 2 to 5% of vinylon short fiber (alkali-resistant glass fiber) is added as a reinforcing fiber, and the mixture is stirred again, and the fluidity of the slurry is adjusted so that the flow cone has a bulkiness in the range of 60 to 70. Materials were made.

While rotating the centrifugal molding machine at a low speed of 350 rpm, the above-mentioned mortar material was charged into the mold of the molding machine. After confirming that the mortar material is uniformly extended in the mold, the rotational speed of the molding machine is increased from 350 rpm (1 min) to 600 r.
pm (2-3min) → 100rpm (10-15min)
Compaction was performed. The formed cylindrical tube is cleanly removed from the mold, and has an outer diameter of 350mmφ, a length of 1800mm, and a thickness of 10-1.
It was 2 mm thin and lightweight. The variation in pipe thickness was suppressed, and a high quality concrete cylindrical pipe was realized. Example 2 Water was added to a concrete / powder material of cement / aggregate = 1/1 (% by weight) so that the flow value (fluidity) became about 160 to 180 (ring size 55φ × 50H), and wet After mixing, vinylon short fibers (alkali resistant glass fibers) having a fiber length of 10 mm or less were added so as to be 0.5% or less. The mortar material was charged into a centrifugal molding machine, and compacted to a thickness of 2 to 3 mm. After removing the water squeezed out of the mortar material accumulated in the mold, the mortar material produced in Example 1 was put into a centrifugal molding machine, and centrifugal molding was performed in the same manner as in Example 1.

The obtained concrete cylindrical tube had a two-layer structure, had no bubble mark on the surface of the surface layer, and had a good appearance with no cracks. Of course, this invention
It is not limited by the above embodiment. It goes without saying that various aspects are possible for details such as the type and the mixing ratio of the concrete powder material and the thickener.

[0022]

As described above in detail, according to the present invention, a mortar material premixed with a reinforcing fiber, which was previously unapplicable, is centrifugally molded to be thin and light, and has no variation in tube thickness. A high quality concrete cylindrical tube can be manufactured. This is expected as a practical production method.

Claims (3)

[Claims] 1. A mortar in which a thickener is added to a powder material for concrete and reinforcing fibers having a lower specific gravity than the powder material are blended to adjust a flow cone bulkiness to 60 to 70. A method for manufacturing a concrete cylindrical tube, comprising centrifugally forming a material to produce a cylindrical tube made of concrete. 2. The method according to claim 1, wherein methylcellulose is used as a thickener. 3. The mortar according to claim 1, wherein a mortar material containing no thickener is first formed by centrifugal molding to form a surface layer. The method for producing a concrete cylindrical tube according to claim 1 or 2, wherein the material is formed by centrifugal molding to produce a concrete cylindrical tube having a two-layer structure.