JP2009068318A - Converting method for long shaft void - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that under the present circumstances a long shaft spiral pipe used as one of void members when constructing a void slab is, finally, embedded within the slab although it is expensive, which means it is left buried and accordingly a unit cost per square meter when constructing the void slab is increased. <P>SOLUTION: An outer periphery of a concrete-retaining air tube on the market is covered with poly-ethylene film, so as to impart lubricating property on the outer surface of the air tube. Accordingly, the air tube, which can easily be pulled out after the concrete is hardened even when the air tube is embedded in the concrete of the void slab, is used as a void member, and also it can be utilized for different purpose. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for constructing a void member installed in a void slab of a reinforced concrete building.

  Conventionally, as a void slab member for a void slab, there are a spherical or box-shaped one made of styrene foam and a long-axis cylindrical thin steel plate (spiral tube), both of which are embedded in concrete, so-called buried state. Used in.

As described above, all of the current void members in the void slab are embedded in the concrete, but these void members are not inexpensive but rather expensive, which increases the m ² unit price of the void slab. In addition, in the case of a long-axis cylindrical spiral tube, it is installed before the upper bar of the slab. It has become a very big problem.
Therefore, in order to solve the former problem, the void member can be diverted first, and in order to solve the latter problem, it can be installed after the upper bar reinforcement work or at the upper bar reinforcement work. It is necessary to use a void member that does not deteriorate the scaffold.

As a result of diligent research, the present inventor has invented a construction method in which the above-described problem, that is, diversion is possible, and work efficiency and safety are ensured by slightly modifying a commercially available air tube.
In general, the size of the slab is 7 to 8 m even in the short side direction, whereas a commercially available air tube is about 5 m at the longest. Therefore, for example, when the span of the slab is 8 m, an air tube having a length of 4 m is installed from both directions. At the time of placing, this air tube having a high coercive pressure due to compressed air is extracted and contracted after solidification of the concrete, and is used after diverting.
However, since this commercially available air tube is originally used as a concrete stopper for splicing, it is relatively hard and has high rigidity, so it cannot be easily pulled out from the solidified concrete. Therefore, the outer periphery of the air tube is covered with a film having a smooth surface such as polyethylene to reduce the resistance when it is pulled out. Regarding work efficiency and safety, since air is introduced into the air tube for the first time after the rebar reinforcement work is completed, the air tube is shrunk until then, and the operator's scaffolding is not deteriorated.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view showing a state in a first stage of work in the construction method according to the present invention. Here, reference numeral 1 is a control panel as a slab mold, reference numeral 2 is a spacer, reference numeral 3 is a lower end line of the slab, and reference numeral 4 is the air tube covered with a polyethylene film of reference numeral 5. I'm not so good. Therefore, there will be no trouble in the rearrangement work of the upper end muscle.
FIG. 2 is a cross-sectional view of the second stage of the construction method. Here, reference numeral 6 denotes an upper end bar of the slab. After the upper bar arrangement work, the air tube of the reference numeral 4 is inflated by being press-fitted as shown in the figure.
FIG. 3 is a cross-sectional view after placing the ready-mixed concrete. Here, reference numeral 7 denotes concrete, and reference numeral 8 denotes a space for extracting air from the air tube after the concrete is solidified. This space will be filled with concrete at a later date, and finally the void slab will be completed.

  If the void slab is constructed by the method according to the present invention as described above, the expensive void member does not have to be lost by burying. That is, this can be diverted by a simple operation of covering the outer periphery of the air tube with a polyethylene film. In addition, the air tube is deflated until the upper bar reinforcement work is completed, and the cylinders are not lined up close to each other as before, so the operator's scaffolding is safe and work efficiency Is also improved.

It is clear that the resistance when the air tube is evacuated and pulled out from the solidified concrete is inversely proportional to the gap between the concrete and the air tube caused by evacuation, that is, the amount of air gap. The experiment was conducted with an outer diameter of 50φ, which is the thinnest and therefore has a large resistance.
The experimental formwork had a rectangular shape with a cross-sectional width of 200 mm, a height of 200 mm, and a length of 4.2 m, and the upper surface was opened and installed horizontally. The air tube having an outer diameter of 50φ and a length of 4.0 m was covered with a polyethylene film and placed at the center of the cross section in the mold in this state, that is, approximately 100 mm below the top of the concrete. However, the air plug side of the air tube was exposed to the outside of the mold by 100 mm from the necessity of air venting and drawing after the concrete solidified. Therefore, only 3.9m of air tube was embedded in the concrete. One week after the placement date, the air tube was pulled out after confirming that the concrete had solidified sufficiently.
First, the air tube was pulled out without venting, but it did not move at all. Next, when it was evacuated and pulled out, the polyethylene film remained in the concrete and could be pulled out without much effort. That is, it was confirmed that the effect of the surface slipperiness of polyethylene and the method according to the present invention are useful and beneficial.

  Sectional view of the first stage of the method according to the present invention   Sectional view of the second stage of the method according to the present invention   Cross section after placing concrete

Explanation of symbols

1. Formwork panel 2. Spacer 3. Lower end of void slab 4. Air tube covered with polyethylene film 5. Polyethylene film 6. Upper end of void slab 7. Concrete 8. Pull-out space

Claims (1)

The present invention is a method for constructing a void slab. Instead of embedding a long-axis spiral tube as in the prior art, a commercially available air tube is used as a void member, and the concrete of the slab is solidified. This is a method of extracting and recovering air from the air tube and diverting it.
This air tube is originally used to stop the concrete at the joint of the concrete, that is, it is made of a hard material so that it can withstand use under harsh conditions. However, it cannot be pulled out easily, so the construction method is characterized in that the outer surface of this tube can be easily pulled out from solidified concrete by covering it with a polyethylene film with high surface smoothness.

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