JPS5944550B2 - centrifugal concrete pipe - Google Patents

Description

[Detailed Description of the Invention] Centrifugal concrete pipes have a dense structure that is incomparable to other types of concrete pipes that use vibration or compressive force, so products with high strength and high quality can be obtained.

However, when these concrete pipes are sequentially joined to form a conduit, water may leak from the joints.

That is, as shown in Fig. 3, a so-called Hume tube made by centrifugal force forming has a male part at one end and a female part at the other end, so that both male and female parts of the adjacent pipes to be joined are formed. Normally, a rubber ring is fitted around the outer circumference near the tip of the male part, and this rubber ring is used as a backing material when fitted to the opening of the female part. Since the tube is filled in a compressed state, water is prevented from flowing into and out of the tube.

However, the inner surface of the female opening does not necessarily have a smooth and accurate circumference, and therefore the rubber ring is not compressed uniformly at each part of the circumference, and often the rubber ring is compressed completely (the uncompressed area is localized). Occasionally, this may occur.

As shown in Figure 1, the cross section of a cylindrical body centrifugally formed by a conventional method consists of a large aggregate layer as the outermost layer, with small aggregates intermixed between the aggregates, and these aggregates and A large aggregate layer A in which cement mortar is filled in the gap between the aggregate and the aggregate, followed by a small aggregate layer B in which the size of the aggregate decreases toward the inner layer.
That is, there is a concrete material layer A+B, and a sand layer C1 on the inside, and a very small layer of sand and cement mortar mixed therein, or a dense cement mortar layer consisting almost only of cement.

Each of the above layers forms the substance of concrete 1.
Furthermore, a laitance layer E is formed in the innermost layer in which soft lime with a light specific gravity and other impurities contained in the cement are pressed together with the mixing water in the concrete.

If this is observed in more detail, a sand layer C with relatively few cement particles exists outside the cement mortar layer that forms the innermost layer of the substance of the concrete.

This sand layer differs depending on the concrete mix, but in concrete mixes used for concrete pipes made by the centrifugal force manufacturing method specified by JIS, which are usually referred to as hium pipes, the sand layer is formed by a cement mortar layer, although it also differs depending on the thickness of the member. It is formed about 3 to 15 millimeters outside.

This is because when concrete is compacted by centrifugal force, a large aggregate layer is sequentially formed on the outside due to so-called centrifugation within the wall thickness of the tube, and a cement mortar layer is formed on the innermost layer. Even after the cement mortar layer on the inner wall layer is gradually formed densely by centrifugal force and compacted to the point that the internal kneaded water does not pass through this mortar layer, the water that is squeezed out from the outer layer later remains in the cement mortar layer. It is dammed and eventually accumulates in the next sand layer C, resulting in a water-permeable layer with few cement particles in this area.

This formation of a sand layer with few cement particles is an unavoidable phenomenon in centrifugal concrete pipes, but on the other hand,
The mortar layer on the inner side forms an extremely impermeable layer that does not allow water to pass through due to the strong centrifugal force.

In addition, in the present invention, the thickness of this mortar layer is quite important, but it depends on the size and shape of the aggregate, the ratio of coarse aggregate to fine aggregate, or the amount of aggregate. It can be determined relatively easily based on the relationship with the amount of cement.

Furthermore, the laitance layer E that occurs in the innermost layer of the receiving recess of a concrete pipe has an irregular shape and thickness, and is extremely soft, which is a fatal flaw in joints that require a water-stopping effect. .

For this reason, conventionally, the laitance layer is removed using a wire brush or the like, and this area is filled with cement mortar or a resin mortar that has appropriate adhesive properties and hardens, but usually this laitance layer is completely removed. As a result, the filler cannot firmly adhere to the concrete base material in the pipe wall, and shrinks differently than the main body over a short period of time, causing cracks and eventually peeling. Furthermore, it is extremely difficult to fill the inner circumferential surface of the receptacle to the required smooth and accurate dimensions.

The present invention utilizes the separation phenomenon within the wall thickness of concrete caused by the centrifugal forming described above to overcome the irregular and soft laitance layer on the inner surface of the socket part of the centrifugal concrete pipe and to form a part of the cement mortar layer or even the outer layer. When a part of the concrete material layer is removed by cutting or polishing to form a water-impermeable and dense inner peripheral surface 5, and a joint part as shown in Fig. 4 is constructed, rubber etc. are applied to this part. The purpose of this invention is to provide a centrifugal force concrete pipe that forms a joint between the sealing material 6 of the pipe and the insertion part 7 that prevents water leakage.

To explain the present invention in detail below, as shown in FIG. The formwork 4 is attached removably and placed on a rotating machine via the tires 2, and concrete is poured in while the formwork 4 is rotated at high speed by the rotating machine. was centrifugally formed, and the laitance layer E at the concrete pipe socket, which was generated by the hindlimb centrifugal forming after hardening the concrete through appropriate curing, was removed by grinding with a high-speed rotating grindstone or cutting with a cutting tool, etc. moreover,
Next, remove a part of the cement mortar layer, carve out a smooth finished surface F with this cement mortar layer, and use this cement mortar layer to carve out a smooth finished surface F.
If this is used as the contact surface with a sealing material such as a rubber ring, this cement mortar layer is completely impermeable and will not leak water.

Furthermore, if the above-mentioned finished surface F is further applied to the outer sand layer C, water easily permeates through this layer C, so even if a high-quality sealing material is used, water will seep out, resulting in a joint with complete water-stopping ability. It is not possible to obtain the inner surface of the socket part that constitutes the part.

Therefore, in such a case, if the finished surface y is formed on the outer small aggregate layer B beyond the sand layer C, the small aggregate layer B will have cement mortar filled between the aggregates and will have no water stopping ability. Since the height is high, an inner surface of the socket part that does not leak water can be obtained.

The processing of the socket part is carried out after centrifugal forming and curing. After removing the socket side end plate 1 and formwork 4, the concrete pipe is placed on a rotary machine and is rotated or still. We do what we put in place.

Also, as shown in Fig. 5, the bolts 10 of the formwork, in which the concrete pipe after steam curing is still inserted, are removed.
Either remove only the socket core 8 and rotate the formwork again (while the tire 9 is attached), or if the outer circumference of the concrete pipe maintains a correct circular shape, continue to rotate it. While rotating on the machine, the inner diameter of
In the case of a 0-millimetre Huyum tube with a cutting allowance of about 3 to 5 millimeters, the required time was only about 30 seconds.

In addition, when a humid tube with a diameter of 800 mm was fixed and a high-speed rotating whetstone was used to scrape while rotating along the inner surface of the socket, it took about 2 minutes to shave 5 to 6 millimeters. However, in all cases, the cut surface was extremely smooth, and a dense mortar layer surface with the correct circular shape and diameter was obtained, and in one test of water leakage of the joint constructed with this, the water pressure was 1 kg/
Although the pressure ranged from crA to 6 kg/c4 and the pressurization time was several times longer than the JIS standard, there was no water leakage at all.

Furthermore, as a result of numerous experiments, it was found that during cutting or polishing, when the concrete had not hardened very much, the cut surface was a little rough, but when the concrete had hardened sufficiently, the cut surface was extremely smooth. Ta.

In experiments conducted by the inventors, concrete strength was approximately 175
It was determined that a sufficiently smooth cut surface could be obtained if the cutting surface reached approximately kg/ca (compressive strength) or higher, but of course this is thought to vary depending on the sharpness of the blade and the processing method.

Generally, after centrifugal forming, the tube is taken out of the form after the concrete has hardened through appropriate curing, but when the concrete has reached a strength sufficient for this work, the inner circumferential surface of the socket can be ground to make it sufficiently smooth. A finely cut surface can be obtained.

Also, during many cutting experiments, sometimes the sand layer C is carved out in a small area, but in this case, if you quickly apply a paint that prevents water from passing through, the water pressure 2
It seems that water can be easily stopped at about kg/ctii to 3 kg/crit.

As described above, the present invention involves centrifugally forming a concrete pipe, and then performing appropriate curing to harden the pipe. Furthermore, by cutting or polishing a part of the small aggregate layer beyond the permeable sand layer to form a water-impermeable and precisely smooth inner surface, a sealing material such as a rubber ring can be applied to the entire circumference of the inner surface. It is possible to compress the surface uniformly and completely prevent water leakage.

In addition, conventional internal surface repair using mortar involves manual work and unreliability, the roundness may deteriorate due to mortar sagging, and standing time is required for the mortar to harden. However, since the concrete pipe of the present invention can be obtained by simply mechanically cutting or polishing, high precision can be obtained and the processing time can be shortened.

Furthermore, since conventional concrete pipes have a layer of mortar applied to the socket and inner surface, cracks may occur as the water in the mortar evaporates and hardens after mortar is applied, and the socket body may deteriorate due to differential shrinkage. However, in the concrete pipe of the present invention, the processed surface, that is, the inner surface of the socket part, is made of the same material as the main body, and is processed after appropriate curing and hardening. It is stable, and since no excess moisture is generated during processing, there is no fear of deterioration over time after processing.

Furthermore, since the inner surface of the socket portion is formed by a dense mortar layer or concrete layer compacted by centrifugal molding, it exhibits stable shallow water blocking ability over a long period of time.

Note that a decorative coating may be applied to the inner surface of the tube socket after cutting.

[Brief explanation of the drawing]

Figure 1 is a partially enlarged sectional view of the centrifugal concrete pipe, Figure 2
The figure is a partial vertical sectional view showing an embodiment of the present invention, FIG. 3 is a vertical sectional view of a known pipe joint part, FIG. 4 is a vertical sectional view of a pipe joint part of the present invention, and FIG. FIG. 3 is a partial vertical cross-sectional view of the embodiment. A... Large aggregate layer, B... Small aggregate layer, C
...Sand layer, D...Cement mortar layer, E...Laitance layer, F...Finished surface, 1...Socket side end Board, 2... Tire,
Total: core, 4: formwork.

Claims (1)

[Scope of Claims] 1. A concrete pipe is manufactured by a centrifugal force manufacturing method, and then the pipe is hardened by appropriate curing, and then a light and soft laitance layer, a cement mortar, is formed on the inner surface of the socket part of the limb canal by centrifugal molding. The centrifugal force is characterized in that it exceeds the permeable sand layer and further removes a part of the outer concrete layer by cutting or polishing, etc. to form an accurate and smooth inner circumferential surface of the socket with excellent water-stopping properties. concrete pipe. 2. A concrete pipe is manufactured using the centrifugal force manufacturing method, and after the pipe is hardened by appropriate curing, the light and soft laitance layer generated on the inner surface of the socket of the limb canal is exceeded by centrifugal molding, and a part of the seven-ment mortar layer is formed. A centrifugal force concrete pipe characterized in that a water-impermeable, precise, and precise inner circumferential surface of a socket part is formed by removing parts by cutting or polishing.