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Title:
VACUUM MIXING OF CONCRETE
Document Type and Number:
WIPO Patent Application WO/1998/017450
Kind Code:
A1
Abstract:
This invention relates to an apparatus for forcibly reducing air volume of concrete and a method therefor. The apparatus is comprised of an agitator (10) having the concrete therein, a sealable flange (50) blocking an opening for allowing access of the concrete, and a vacuum pump (20) for extracting the air in the agitator (10) through the sealable flange (50) during the rotation of the agitator (10). The method comprises the step of extracting air from the concrete by the vacuum pump (20) during rotation of the sealable agitator (10) and drawing the mixed concrete from the agitator (10) for being supplied to a location for casting.

Inventors:
KANG HEUNG-MOOK (KR)
Application Number:
PCT/KR1997/000189
Publication Date:
April 30, 1998
Filing Date:
October 10, 1997
Export Citation:
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Assignee:
KANG HEUNG MOOK (KR)
International Classes:
B28C5/00; (IPC1-7): B28C5/00; B28C5/42
Foreign References:
US1968691A1934-07-31
GB1478830A1977-07-06
FR998029A1952-01-14
Attorney, Agent or Firm:
Nam, Sang-sun (17th floor #120 Taepyungno 2-G, Chung-ku Seoul 100-102, KR)
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Claims:
CLAIMS
1. An apparatus for forcibly reducing air volume of concrete comprising: a sealable agitator having the concrete therein; and an air extracting means for extracting air embedded in the concrete during the rotation of the agitator; wherein the mixed concrete containing a predetermined volume of the air is supplied to a location for casting.
2. The apparatus for forcibly reducing air volume of concrete according to claim 1, wherein the agitator has an opening which allows access of the mixed concrete into the agitator or extraction of the mixed concrete from the agitator, and further has a sealable flange for blocking the opening.
3. The apparatus for forcibly reducing air volume of concrete according to claim 2, wherein a movement direction of the sealable flange is in line with an extension direction of a rotational shaft of the agitator.
4. The apparatus for forcibly reducing air volume of concrete according to claim 1, wherein the concrete is a cement concrete.
5. The apparatus for forcibly reducing air volume of concrete according to claim 1, wherein the concrete is a cement mortar.
6. The apparatus for forcibly reducing air volume of concrete according to claim 2, wherein the air extracting means is comprised of a vacuum pump, and the air contained in the sealed agitator is extracted through the sealable flange.
7. The apparatus for forcibly reducing air volume of concrete according to claim 6, wherein a pipe is provided between the sealable flange and the vacuum pump, an end of the pipe adjacent to the sealable flange has a rotary joint, thereby the sealable flange is rotated independently of the pipe.
8. The apparatus for forcibly reducing air volume of concrete according to claim 6, wherein an air intake valve is disposed between the vacuum pump and the sealable flange, by which ambient air is supplied before the mixed concrete is drawn out from the agitator.
9. The apparatus for forcibly reducing air volume of concrete according to claim 7, wherein a moisture collector is disposed on the pipe adjacent to the intake port of the vacuum pump, by which moisture contained in the air extracted from the agitator is collected.
10. A method for forcibly reducing air volume of concrete comprising the steps of: drawing concrete into an agitator; sealably blocking a concrete access opening of the agitator; rotating the sealed agitator containing the concrete; extracting air from the concrete for release to ambient air during rotation of the agitator; and drawing the mixed concrete from the agitator for being supplied to a location for casting.
Description:
VACUUM MIXING OF CONCRETE Technical Field The present invention relates to an apparatus for forcibly reducing air volume of concrete and a method therefor. In particular, the present invention relates to an apparatus and a method for forcibly reducing air volume of mixed concrete before drawing the mixed concrete from the agitator for being supplied to a location for casting.

Background Art In conventional concrete mixing, cement, coarse aggregate and fine aggregate are drawn into an agitator with a predetermined ratio under ambient pressure. Water is added to the mixed material for mixing concrete.

Thereafter the concrete mixed in the agitator is casted at a working site and cured.

However, in the conventional concrete mixing apparatus and its method, bubbles form in concrete of the agitator during the mixing process of cement, aggregate, and water. The bubbles remain still during the filling process and curing process, thereby void can occur in the concrete. Therefore, bond strength between cement paste and coarse aggregate is decreased. Further, after the curing honey combs are created on the concrete. That results in visual problem of the concrete.

Also, since the interior of the agitator is exposed to ambient pressure, moisture evaporates from the concrete housed in the rotating agitator. Moisture content of the concrete decreases to shorten the hardening period of the concrete. Therefore, that causes a problem of the decrease of strength of the concrete.

On the other hand, a vacuum mat concrete method is disclosed in U.S.Patent No. 4,203,714, which maintains proper moisture content of the concrete by eliminating air in the concrete. In the vacuum mat concrete method, a vacuum mat blankets a surface of the concrete. Vacuum is applied by vacuum pump to a space defined as a surface of the concrete and a vacuum mat. Atmospheric pressure pushes down the surface of the concrete to extract moisture from the concrete. However, in that method, since vacuum is applied after the process of casting, air volume of the concrete can not be reduced during the mixing process of the concrete.

It is an object of the present invention to provide an apparatus for forcibly reducing air volume of concrete and therefor to solve the above problems.

It is a further object of the present invention to provide an apparatus for forcibly reducing air volume of concrete and therefor actively eliminating air volume of concrete before a casting process, thereby condensing an interior structure for increasing strength of the concrete.

It is a further object of the present invention to provide an apparatus for forcibly reducing the air volume of concrete and therefor preventing evaporation of water from the concrete in the sealable agitator, thereby extending the hardening period of the concrete during the mixing process.

In order to achieve the above objects of the present invention, an apparatus for forcibly reducing the air volume of concrete is comprised of an agitator having the concrete therein, a sealable flange for blocking an access opening of the agitator, and a vacuum pump for extracting the air in the concrete during the rotation of the sealed agitator through the sealable flange.

Further, a method for forcibly reducing the air

volume of concrete is comprised of the steps of drawing concrete into an agitator; sealably blocking a concrete access opening of the agitator; rotating the sealed agitator containing the concrete; extracting air from the concrete for release to ambient air during rotation of the agitator; and drawing the mixed concrete from the agitator for being supplied to a location for casting.

Brief Description of the Drawings Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of an apparatus for forcibly reducing air volume of concrete according to a present invention, Figure 2 is a schematic view showing a drawing-into process of concrete of Figure 1, and Figure 3 is a schematic view showing a drawing-out process of concrete of Figure 1.

Best Mode for Carrying out the Invention Figure 1 illustrates an embodiment of an apparatus for forcibly reducing the air volume of concrete according to the present invention. The apparatus is comprised of an agitator 10 having concrete therein and being rotated by a motor (not shown), and a vacuum pump 20 for extracting the air to the exterior of the agitator 10 in order to enable the atmospheric pressure to convert into a vacuum.

The agitator 10 is the configuration in which a rotation axis of the agitator can vary in a predetermined angle in respect to the ground. An opening 15 is provided

at one end of the agitator 10, through which concrete is drawn into the agitator 10 or drawn out from the agitator 10. A sealable flange 50 further is provided for blocking or opening the opening 15.

The vacuum pump 20 is connected with the sealable flange 50 of the agitator 10 by a pipe 30. A rotary joint 55 is provided at one end of the pipe 30 adjacent to the sealable flange 50. The rotary joint is connected with the pipe independent of the rotation of the sealable flange 50. An air intake valve 40 is installed on the pipe 30 adjacent to the rotary joint 55, by which atmospheric pressure air is introduced into the vacuum agitator 10. A moisture collector 60 is installed on the pipe 30 adjacent to the vacuum pump 20, by which moisture of the air drawn from the agitator 10 is collected.

The air volume reducing apparatus having the same constructed as above is operated as follows.

Concrete is poured into the agitator 10 as shown in Figure 2 to transport the mixed concrete from a batch plant to a casting site or to mix the concrete transported from a batch plant. In other words, the sealable flange 50 is moved along an extension direction of a rotational axis (not shown) of the agitator 10 by an operation of cylinder 58. Further, a hopper 17 is aligned at the opening 15 of the agitator 10 by an operation of cylinder 18 for pouring the concrete into the agitator 10 through the hopper 17.

Further, the hopper 17 is removed from the opening 15 as shown in Figure 3, and the opening 15 is closed by the sealable flange 50. The sealed agitator 10 is rotated by a motor (not shown). Simultaneously, the intake valve 40 is closed, and the air of the agitator 10 remove to the vacuum pump 20 through the pipe 30. The vacuum pump 20 is operated, and the air of the agitator 10 is extracted to the outside of the agitator 10, so the inside of the agitator 10 is below the atmospheric pressure. During the

rotation of the agitator 10, the air embedded in the concrete remains in a space beyond the surface of the concrete. The air content of the concrete as needed, can be satisfied at respective casting sites. Therefore, the interior structure of the concrete is condensed and the strength of the concrete is increased.

In addition, only predetermined air volume remains in the concrete housed in the agitator 10, and surplus air is in the inside-space of the agitator 10, i.e., the vacuum space above the surface of the concrete. Therefore, the evaporation of water from the concrete is prohibited, thereby extending the hardening period of the concrete.

Thereafter, when the air content reaches a predetermined value, the intake valve 40 is opened, and the atmospheric pressure air is intaken into the agitator 10 through the sealable flange 50. Thus, the sealable flange is opened conveniently. Thereafter, the concrete of the agitator 10 is drawn out from the agitator 10 through a shoot 19 for casting at a work site or within a form of secondary concrete product.

The concrete can employ a cement concrete which is utilized at a casting site such as road or dam or a secondary concrete product such as electric pole, high strength pile, or sidewalk curb. Further, a cement mortar can be employed, which is utilized in plaster work or casting a floor of a building.

According to the present invention as described above, since the agitator is configurated in a sealable manner, the air volume of concrete housed in the agitator is reduced by the vacuum pump during the rotation of the agitator and thereafter the concrete is cast, the interior structure is condensed and strength of the concrete is heightened.

Further, since the inside of the agitator is maintained under the vacuum pressure, the evaporation of water embedded in the concrete is prevented, and the hardening period of the concrete is extended.

In addition, when a waterproof agent is added to the mixing concrete housed in the agitator under the vacuum pressure, or in the waterproof work of a frame member, the present invetion provides for the enlargement of the concrete waterproof efficiency.