JPS5814287B2 - Manufacturing method of fiber reinforced concrete laminated pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a fiber-reinforced concrete laminated pipe using metal fibers such as steel fibers and non-metallic fibers such as carbon fibers as concrete reinforcing materials.

In general, concrete pipes are divided into two types: those reinforced with reinforcing bars, asbestos, metal fibers, etc., and those that are not reinforced at all, such as unreinforced concrete pipes, and each type is used differently depending on the purpose and purpose of use. There is.

Among them, the types of reinforced concrete pipes are:
(I) Reinforced concrete pipe manufactured by pouring concrete into a formwork containing reinforcing bars and compacting it using a vibrator, (It) Concrete being poured into a formwork containing reinforcing bars and compacted by centrifugal force. There are reinforced concrete pipes manufactured while compacting, and (1) reinforced concrete pipes manufactured by pouring concrete into a formwork containing reinforcing bars and compacting it by compacting the concrete surface using rolls.

However, all of these conventional reinforced concrete pipes have the drawbacks of being heavy, having low cracking strength, and insufficient wear resistance.

In order to solve this problem, fiber-reinforced concrete pipes are manufactured by reinforcing concrete by mixing metal fibers such as steel fibers, but since the metal fibers have a high specific gravity, concrete that does not harden yet due to centrifugal force is manufactured. This has the major drawback that it separates from the pipe, concentrates and disperses on the outside of the pipe, and is less effective in preventing cracks that occur from the inside of the pipe.

As a countermeasure to this problem, a method is taken in which concrete with a high amount of metal fibers is poured into the formwork in the final step of pouring the concrete into the formwork, but since a large amount of free concrete water comes out on the inner surface of the pipe, it is difficult to crack the concrete. It cannot be used as a preventive measure.

This invention was made in order to solve the above-mentioned conventional problems, and the purpose is to propose a method for manufacturing a concrete pipe that is lighter and has higher strength than existing concrete pipes and has excellent wear resistance. It is.

This invention is a method of manufacturing by mixing and dispersing metal fibers such as steel fibers and non-metallic fibers such as carbon fibers in cement concrete, and subjecting the mixture in an uncured state to a centrifugal molding machine. The method is characterized in that a layer rich in metal fibers is layered on the outer surface of the tube, and a layer rich in non-metal fibers is layered on the inner surface of the tube, using the difference in specific gravity.

In other words, the specific gravity of metal fibers such as steel fibers and non-metallic fibers such as carbon fibers is that the former is heavier and the latter is lighter.
When this uncured concrete mixed with metal fibers and non-metallic fibers is applied to a centrifugal molding machine, most of the metal fibers with heavy specific gravity are concentrated on the outer surface of the tube, forming a layer rich in metal fibers, and Most of the light non-metallic fibers are concentrated on the inner surface of the tube to form a layer rich in non-metallic fibers, making it possible to produce a concrete tube that is highly resistant to cracking and abrasion on both the inner and outer surfaces of the tube.

The metal fibers used in the present invention are not particularly limited as long as they are made of metal fibers and have a higher specific gravity than non-metallic fibers, such as ordinary steel, stainless steel, or steel fibers treated with anti-rust treatment.

In addition, non-metallic fibers include carbon fiber, glass fiber, asbestos,
Any material such as rock wool may be used, but preferably carbon fiber having a low specific gravity is particularly effective.

The metal fibers and the non-metal fibers should have an elastic modulus ratio and a specific gravity ratio of 2 to 6, and both fibers should be placed in concrete or mortar so that the volume ratio is 0.05 to 6. subject to the condition that it be mixed with

The reason why the elastic modulus ratio of the metal fiber and non-metal fiber is limited to 2 to 6 is as follows.

If the elastic modulus ratio of metal fibers and non-metallic fibers is less than 2, it is effective in improving cracking strength, but the toughness and deformability become poor, and if it exceeds 6, the cracking strength and tensile strength due to non-metallic fibers are reduced. , no reinforcement effect on bending strength can be expected.

Further, the specific gravity (ρA) of the steel fiber is 7.87, the specific gravity (ρB) of carbon fiber is 1.4-1.8, the ρB of glass fiber is 2.5, and the ρB of asbestos is 2.4-1.8. 3. -4, ρA/ρ8 was also limited to 2 to 6.

In addition, the volume mixing ratio of the metal fibers and non-metal fibers is set to 0.0.
The reason why it was limited to 5 to 6 was determined from the mixing ratio so that the reinforcing effect of both fibers would be equal.If it is less than 0.05, the improvement effect of metal fibers on cracking strength, tensile strength, and bending strength will be almost gone. , 6, the effect of improving cracking strength, tensile strength, and bending strength by nonmetallic fibers cannot be expected.

Next, one embodiment of the present invention will be described with reference to the drawings.

First, metal fibers a with an elastic modulus ratio and specific gravity ratio of 2 to 6 and non-metal fibers b are mixed so that the volume mixing ratio is in the range of 0.05 to 6, and this is mixed with cement, aggregate, and water. , kneading together with materials forming a matrix such as admixtures.

Concrete and mortar mixed with the metal fibers a and non-metal fibers b are poured into the formwork 1 which is being rotated in the circumferential direction on the rotary support rollers 2.

By this centrifugal forming, the metal fibers a having a high specific gravity are subjected to a larger centrifugal force than the non-metallic fibers b having a lower specific gravity and are concentrated on the outer surface of the tube, forming a layer 3a rich in metal fibers.

At the same time, the nonmetallic fibers b are concentrated on the inner surface of the tube to form a nonmetallic fiber rich mixed layer 3b.

At this time, the metal fiber a receives centrifugal force due to the rotation of the formwork 1.
and non-metallic fiber b are 2 times in the circumferential direction and the tube axis direction with respect to the formwork surface.
Dimensional distribution provides an advantageous orientation for loads from the inner and outer surfaces of the tube after curing, ie, for bending or hoop tensioning applied to the tube.

In addition, both fibers are not completely dispersed and do not form two layers, and a small amount of non-metallic fibers b is also present in the layer 3a rich in metal fibers, and a small amount of metal fibers a is also present in the layer 3b rich in non-metallic fibers. Since these fibers are mixed together, a reinforcing effect that combines both fibers can be expected.

In addition, when manufacturing a reinforced concrete pipe, reinforcing bars may be inserted into the formwork in advance and fiber-mixed concrete and mortar may be added.

As explained above, according to the present invention, metal fibers can be dispersed and mixed in the outer surface of the tube and non-metallic fibers can be mixed in the inner surface of the tube, so that the reinforcing layer is highly resistant to cracking and wear on both the inner and outer surfaces of the tube. In addition, there is no problem of rust caused by the liquid flowing inside the pipe, and high-quality concrete pipes can be manufactured.

In addition, the strength of fiber-reinforced concrete is two to three times higher than that of ordinary concrete, so it is possible to reduce the pipe wall thickness, and when used in conjunction with reinforcing steel, the amount used can be reduced.
A concrete pipe with higher strength and durability can be provided at a lower cost.

[Brief explanation of drawings]

The drawings are explanatory diagrams showing one embodiment of the present invention. In the figure, 1...formwork, 2...rotating support roller, 3a...layer rich in metal fibers, 3b...layer rich in non-metal fibers, a...
...metallic fiber, b...nonmetallic fiber.

Claims (1)

[Claims] 1 Using metal fibers and non-metal fibers with an elastic modulus ratio and specific gravity ratio of 2 to 6 as reinforcing materials, cement concrete is made so that the volume mixing ratio of the metal fibers and non-metal fibers is in the range of 0.05 to 6. By centrifugally forming the concrete, a layer rich in metal fibers is formed on the outer surface of the tube and a layer rich in non-metal fibers is formed on the inner surface of the tube due to the difference in specific gravity between the metal fibers and non-metal fibers. A method for manufacturing a fiber-reinforced concrete laminated pipe, characterized by: