JPH03183508A - Centrifugal hollow molded body made of concrete - Google Patents

Abstract

PURPOSE:To improve adhesion to post-placement concrete, by a method wherein light-weight aggregate whose specific gravity is compounded with the concrete as coarse aggregate, the coarse aggregate is raised to an inner circumferential surface of a centrifugal hollow molded body with a difference in specific gravity and the inner circumferential surface of the centrifugal hollow molded body is constituted into a porous state. CONSTITUTION:Light-weight corarse aggregate whose specific gravity is not exceeding 1.5 is compounded with concrete as coarse aggregate in a concrete composition to be loaded into a concrete shuttering device, in a centrifugal hollow molded body which is manufactured by a method wherein the concrete shuttering device is turned by a turning machine and concrete in the concrete shuttering device is compacted with centrifugal force. The centrifugal hollow molded body is constituted so that the coarse aggregate is raised to an inner circumferential surface of the centrifugal hollow molded body with a difference in specific gravity and the inner circumferential surface of the same becomes porous. At the time of centrifugal molding, the cement and fine aggregate whose specific gravity is heavy are gathered to an outer circumferential surface side 7 of a completed product, the coarse aggregate 6, air, water, impurities whose specific gravity is light is raised away to an inner circumferential side 8 of a hollow part and the inner circumferential surface side 8 becomes porous by differing from the outer circumferential surface side 7. With this construction, adhesion to post-placement concrete can be held favorably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a concrete hollow molded body manufactured by a centrifugal molding method.

[Purpose of the invention]

As one of the methods for manufacturing concrete hollow molded bodies, a centrifugal forming method is known in which a formwork device is rotated by a rotary machine and the concrete in the formwork device is compacted by centrifugal force.

The internally hollow concrete preforms produced by this centrifugal forming method have the advantage of having a dense and clean outer surface and almost no need for surface treatment, so they can be used as waste forms for columns in concrete structures. It is also being considered for use as beam material. However, concrete hollow molded bodies made by the centrifugal forming method are compacted considerably not only on the outer peripheral surface but also on the inner peripheral surface, and the adhesion with the post-cast concrete poured into the hollow part during the construction stage is poor, resulting in strong storage. It turned out that there was a problem.

One way to solve these problems is to make reinforcing bars such as barbs protrude inside the concrete centrifugal hollow molded body, and use these protruding reinforcing bars to improve the adhesion with post-cast concrete. However, with this method, during centrifugal molding, barbs etc. must be arranged so that they protrude into the hollow interior, which requires a lot of time and work efficiency, and is also economically disadvantageous. It has the disadvantage of becoming

As a result of various studies in order to solve the problems inherent in such concrete centrifugal hollow molded bodies, the inventor of the present invention found that the specific gravity of the concrete to be charged into the formwork device was 1.5.
By blending the following lightweight coarse aggregate, the coarse aggregate will stand out on the inner circumferential surface of the product after centrifugal forming due to its specific gravity, becoming porous and forming a bond with post-cast concrete. The inventors have discovered that the adhesion is extremely good and that sufficient strength can be obtained without the need for barbage reinforcement, leading to the creation of the present invention.

Therefore, an object of the present invention is to provide a centrifugal hollow molded article made of concrete that has improved adhesion to post-cast concrete.

[Structure of the invention]

In detail, the structure of the present invention for achieving the above object is as follows:
In a centrifugal hollow molded body manufactured by rotating a formwork device with a rotary machine and compacting the concrete inside the formwork device by centrifugal force, coarse aggregate in the concrete composition charged into the formwork device specific gravity as 1
．． A lightweight coarse aggregate of 5 or less is blended, and the coarse aggregate is embossed on the inner peripheral surface of the centrifugal hollow molded body due to the difference in specific gravity, so that the inner peripheral surface of the centrifugal hollow molded body becomes porous. This is a centrifugal hollow molded body made of concrete that is characterized by the fact that, according to the present invention, the inner peripheral surface of the centrifugal hollow molded body is made porous by lightweight coarse aggregate, so it has extremely good adhesion with post-cast concrete. This is the result.

Note that the centrifugal hollow molded body according to the present invention may have a rectangular shape or a circular shape regardless of its cross-sectional shape.

〔Example〕

Hereinafter, a specific configuration of the present invention will be explained in detail based on illustrated embodiments.

Fig. 1 is a perspective view showing one embodiment of the concrete centrifugal hollow formed body of the present invention, Fig. 2 is a partially enlarged sectional view of an arbitrary part of the concrete centrifugal hollow formed body shown in Fig. 1, and Fig. 3 is a It is an explanatory view showing an example of a centrifugal forming machine which manufactures a concrete centrifugal hollow molded object.

In the figure, 1 shows an internally hollow concrete centrifugal hollow molded body manufactured by a centrifugal molding method.

The centrifugal hollow molded body 1 can be manufactured using a centrifugal molding machine as shown in FIG.

That is, in FIG. 3, 2 is a long rotating shaft;
4 is a rotating machine, and 5 is a chain belt that transmits the rotational force of the rotating machine 4 to the rotating shaft 2. 4 is operated, rotational force is transmitted to the rotating shaft 2 via the chain belt 5, and the concrete in the formwork device 3, which is fixed to the outer periphery of the rotating shaft 2, is compacted by the centrifugal force and hardens as shown in Figure 1. A concrete centrifugal hollow molded body 1 can be obtained.

In order to manufacture the concrete centrifugal hollow molded body of the present invention, in addition to the apparatus shown in FIG. It may be a device that is arranged and fixed symmetrically and performs centrifugal molding by rotating a rotating drum, or a formwork device can be set using a rotating disk fixed to the tip of a rotating shaft. Of course, a centrifugal molding machine such as the one shown in FIG.

Accordingly, the present invention provides a centrifugal hollow formed body formed by such a centrifugal forming method, in which lightweight coarse aggregate 6 with a specific gravity of 1.5 or less (for example, Using a material (trade name: Mesalite), the coarse aggregate 6 is made to stand out on the inner peripheral surface side of the centrifugal hollow molded body l due to the difference in specific gravity, making the inner peripheral surface side porous, and then introduced into the hollow part. This is designed to improve adhesion with post-cast concrete.

Note that concrete may be charged into the formwork device 3 in advance before setting it in the centrifugal forming machine, or by rotating the formwork device 3 with the rotating machine 4. It is also possible to put it in while you are in the middle of the day.

Concrete is usually made by mixing cement with a specific gravity of about 3.1, fine aggregate with a grain size of 5 mm or less, coarse aggregate with a grain size of 25 to 5, and water in a predetermined ratio and kneading the mixture thoroughly. However, since the specific gravity of both fine aggregate and coarse aggregate is about 2.6, when this is put into a centrifugal molding machine, the inner circumferential side of the finished product will be hardened and solidified in the same way as the outer circumferential side. There was a problem in that the adhesion with poured concrete deteriorated.

In contrast, in the present invention, lightweight coarse aggregate 6 with a specific gravity of 1.5 or less is used as the coarse aggregate in the concrete composition, so cement and fine aggregate with a high specific gravity are removed from the outer peripheral surface of the finished product during centrifugal forming. At the same time, coarse aggregate 6 with a low specific gravity, air, water, impurities, etc. come to the inner circumference side 8 of the hollow part, and the inner circumference side 8 is porous unlike the outer circumference side 7. This is the result.

Note that the ratios of cement, aggregate, and water used in producing the centrifugal hollow molded body of the present invention are the same as those of conventional methods, and therefore their explanation will be omitted.

As shown below, the centrifugal hollow molded body manufactured by the concrete 1 of the present invention has a porous inner circumferential surface 8, so that it can sufficiently absorb moisture in post-cast concrete. This significantly improves adhesion to concrete.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to maintain good adhesion with post-cast concrete without arranging barbed reinforcements etc. inside the hollow of a centrifugal hollow molded body, and it is possible to maintain good adhesion with post-cast concrete. The field of application can be expanded as beam material, etc.

In addition, since it does not take time and effort to arrange barbs, etc., it can be manufactured at a relatively low cost, and is extremely advantageous economically.

4,

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of a centrifugal hollow molded body made of concrete according to the present invention; 3
The figure is an explanatory diagram showing an example of a centrifugal molding machine for manufacturing a concrete centrifugal hollow molded body. 1: Centrifugal hollow molded body 2: Rotating shaft 3: Formwork device 4: Rotating machine 5: Chain belt 6: Light coarse aggregate 7: Outer peripheral surface side
8: Inner peripheral surface side

Claims (1)

[Claims] In a centrifugal hollow molded body manufactured by rotating a formwork device with a rotary machine and compacting the concrete inside the formwork device by centrifugal force, coarse aggregate in the concrete composition charged into the formwork device specific gravity as 1
．． A lightweight coarse aggregate of 5 or less is blended, and the coarse aggregate is made to stand out on the inner peripheral surface of the centrifugal hollow molded body due to the difference in specific gravity, so that the inner peripheral surface of the centrifugal hollow molded body is formed into a porous shape. Concrete centrifugal hollow molded body.