Concrete pumping method

Abstract

To provide a method for pumping concrete, which reliably pumps concrete without clogging a concrete transport pipe.SOLUTION: Prior to pumping concrete, a plug (12) made of an elastic material and being larger than the inner diameter of a concrete transport pipe is inserted in advance into the concrete transport pipe (6). Next, a predetermined amount of cement paste (13) made by kneading cement and water is placed behind the plug (12). Then, concrete (15) is pumped by a concrete pump to push out the cement paste (13) and the plug (12) together with the concrete (15), and after the plug (12) is discharged from the tip of the concrete transport pipe (6), the concrete (15) is continuously pumped.SELECTED DRAWING: Figure 4D

Description

Technical Field

[0001] The present invention relates to a concrete pumping method for pumping concrete through a concrete transport pipe.

Background Art

[0002] Concrete is pumped to a desired location via a concrete transport pipe. The concrete transport pipe is provided, for example, on a concrete pump truck. The concrete pump truck includes a self-propelled vehicle and various devices mounted on the vehicle, that is, a hopper into which concrete is charged, a concrete pump, a multi-stage boom, and the like. The concrete transport pipe is supported by the boom, and bends and extends as the boom bends and extends. The multi-stage boom is bent and extended to move the discharge port of the concrete transport pipe to a concrete placing point. Concrete is fed into the concrete transport pipe by the concrete pump, that is, pumped. Concrete is discharged from the discharge port. When concrete is pumped through the concrete transport pipe, blockage of the concrete transport pipe is likely to occur. Therefore, conventionally, mortar is pumped prior to concrete pumping, that is, so-called preceding mortar is required. Since the preceding mortar must be discarded after use, this increases costs and wastes resources.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] Patent Document 1 proposes a concrete pumping method that does not use a preceding mortar. The pumping method described in Patent Document 1 uses a spherical plug made of an elastic material. The diameter of the plug is larger than the inner diameter of the concrete transport pipe. Such a plug is placed in the concrete transport pipe prior to pumping the concrete. Then the concrete is pumped using a concrete pump. As the concrete is pumped, the leading edge of the concrete pushes out the plug. Once the plug is discharged from the end of the concrete transport pipe, the concrete pumping is continued. By implementing the concrete pumping method described in Patent Document 1, it is possible to prevent blockage of the concrete transport pipe. [Overview of the project] [Problems that the invention aims to solve]

[0005] The concrete pumping method described in Patent Document 1 is excellent because it allows concrete to be pumped without using pre-filled mortar, resulting in lower costs and efficient resource utilization. However, there are some issues that need improvement. With the concrete pumping method described in Patent Document 1, there is no risk of blockage of the concrete transport pipe when using concrete with general properties, that is, relatively fluid concrete with a slump of 12 cm or more. However, when pumping concrete with a low slump, for example concrete with a slump of 9 cm or less, the plug inside the concrete transport pipe may occasionally become blocked. In other words, there are cases where the concrete cannot be pumped.

[0006] The present invention aims to provide a concrete pumping method that solves these problems. Specifically, the objective is to provide a concrete pumping method that can reliably pump concrete without blocking the concrete transport pipe, regardless of the properties of the concrete, that is, even concrete with a small slump. [Means for solving the problem]

[0007] This invention relates to a concrete pumping method in which concrete is pumped by pressure through a concrete transport pipe. In this invention, prior to pumping the concrete, a plug made of an elastic material and larger than the inner diameter of the concrete transport pipe is placed in the concrete transport pipe beforehand. Then, a predetermined amount of cement paste, which is a mixture of cement and water, is placed behind the plug in the concrete transport pipe. This cement paste should be mixed to have a water-cement ratio that is the same as, or lower than, that of concrete. The system is configured to pump concrete using a concrete pump, pushing out the cement paste and plug along with the concrete, and after the plug is discharged from the end of the concrete transport pipe, the concrete is continuously pumped using the concrete pump.

[0008] The invention described in claim 2 is configured to use a solid, spherical plug. [Effects of the Invention]

[0009] According to this invention, a predetermined amount of cement paste is placed behind the plug, and the concrete is pushed out by a concrete pump, pushing out the cement paste and the plug together with the concrete. In this way, regardless of the properties of the concrete, that is, even if the concrete has a small slump, it is the cement paste that is in contact with and pushing against the plug. Since the cement paste is smooth and has a lubricating effect, there is no risk of the plug becoming blocked in the concrete transport pipe. In other words, concrete can be pumped reliably and stably. and The cement paste has the same or lower water-cement ratio as the concrete being pumped. Therefore, In concrete pumping, there is no need to discard the cement paste that is initially pumped. This is because, since the water-cement ratio is the same or lower, the strength is equal to or greater than that of the concrete, and therefore the cement paste can be mixed with the concrete before placement. Thus, resource waste can be eliminated. [Brief explanation of the drawing]

[0010] [Figure 1]This is a perspective view showing a concrete pump truck equipped with a concrete transport pipe. [Figure 2] This is a front cross-sectional view showing a tapered pipe with a changing diameter, installed upstream of a concrete transport pipe. [Figure 3] Figure (A) is a perspective view of the plug according to this embodiment, and Figure (B) is a perspective view of the plug according to another embodiment of the present invention. [Figure 4A] This is a front cross-sectional view showing a portion of a concrete transport pipe and a plug according to this embodiment placed inside the concrete transport pipe. [Figure 4B] This is a front cross-sectional view showing a portion of a concrete transport pipe, a plug according to this embodiment placed inside the concrete transport pipe, and cement paste. [Figure 4C] This is a front cross-sectional view showing a portion of a concrete transport pipe, a plug according to this embodiment placed inside the concrete transport pipe, and cement paste. [Figure 4D] This is a front cross-sectional view showing a portion of a concrete transport pipe, a plug according to this embodiment placed inside the concrete transport pipe, cement paste, and concrete. [Figure 4E] This is a front cross-sectional view showing a portion of a concrete transport pipe, a plug according to this embodiment placed inside the concrete transport pipe, cement paste, and concrete. [Modes for carrying out the invention]

[0011] The following describes this embodiment. The concrete pumping method according to this embodiment is a method used when pumping concrete using a concrete transport pipe. Although concrete transport pipes can take various forms, the following description will focus on the concrete transport pipe 6 provided in the concrete pump truck 1 shown in Figure 1.

[0012] <Concrete pump trucks and concrete transport pipes> The concrete pump truck 1 is generally composed of a self-propelled vehicle 2, a multi-stage boom 4 installed on the vehicle 2, and a concrete transport pipe 6 installed on the multi-stage boom 4. The multi-stage boom 4 is composed of multiple booms 4a, 4b, ..., and these booms 4a, 4b, ... are rotatably connected to each other so that they can bend and extend freely.

[0013] The concrete transport pipe 6 consists of straight unit pipes 6a, 6a, ... and arc-shaped bent pipes 6b, 6b, ... which are connected to each other. The upstream side of the concrete transport pipe 6 is connected to a concrete pump (not shown), and a tapered pipe 7 with a changing diameter is provided in a part of the upstream section. As shown in Figure 2, the tapered pipe 7 has a smaller diameter d on the downstream side compared to the upstream diameter D, and the diameter changes in a tapered manner. The tapered pipe 7 is provided with an opening 8, into which plugs and cement paste according to this embodiment can be placed, as will be explained later. The opening 8 can be sealed by a lid 9.

[0014] As shown in Figure 1, the concrete transport pipe 6 is supported by multiple stays 10, 10, ... on the multi-stage boom 4. When concrete is poured into the hopper 3 on the vehicle 2 and a concrete pump (not shown) is driven, the concrete is pumped through the concrete transport pipe 6.

[0015] <plug> The plug 12 according to the present embodiment is made of an elastic material such as natural rubber or polyurethane, and is formed into a spherical shape as shown in FIG. 3(A). The diameter of the plug 12 is slightly larger than the inner diameter of the concrete transport pipe 6. Therefore, when the plug 12 is pushed into the concrete transport pipe 6, it elastically deforms and strongly and liquid-tightly adheres to the inner peripheral surface of the concrete transport pipe 6. Due to this strong adhesion, a large sliding resistance acts on the movement of the plug 12 within the concrete transport pipe 6. This large sliding resistance prevents the plug 12 from falling even when the concrete transport pipe 6 is arranged vertically. In order to enable strong adhesion to the inner peripheral surface of the concrete transport pipe 6, it is preferable that the plug 12 is in a densely packed state, that is, it is solid. Even if it is formed to be hollow, it is preferable to form it with a large wall thickness to make it less likely to deform elastically. The entire plug 12 may be formed of an elastic material, or a core made of wood, metal or the like may be provided at the center.

[0016] <Concrete Pumping Method> The concrete pumping method according to the present embodiment will be described. First, prior to pumping concrete, as shown in FIG. 4A, the plug 12 according to the present embodiment is placed into the concrete transport pipe 6. That is, the plug 12 is inserted through the opening 8 of the tapered pipe. Next, as shown in FIG. 4B, cement paste 13 obtained by kneading cement and water is introduced into the concrete transport pipe 6. The cement paste 13 is placed behind the plug 12. The amount of cement paste 13 introduced into the concrete transport pipe 6 may be far smaller than that of conventionally used preceding mortar, for example, 40 L or less. Preferably, 5 to 40 L is introduced, and more preferably 10 to 30 L is introduced. After the cement paste 13 is introduced, the opening 8 is closed with a lid 9 as shown in FIG. 4C.

[0017] A concrete pump (not shown) is driven to pressure-feed concrete 15. Then, as shown in Fig. 4D, the leading end portion of the concrete 15 pushes the cement paste 13, and the cement paste 13 pushes the plug 12. A strong pressure from the concrete pump acts on the plug 12, causing the plug 12 to move downstream within the tapered pipe 7. As the pipe diameter gradually decreases, the plug 12 undergoes elastic deformation and moves while closely adhering tightly within the tapered pipe 7. Eventually, as shown in Fig. 4E, the plug 12 moves within the unit pipe 6a having a constant pipe diameter. The plug 12 deforms into an elliptical shape and tightly adheres to the inside of the concrete transport pipe 6. Since the concrete 15 is pushed out by the concrete pump, even if strong sliding resistance acts on the plug 12, the concrete 15, the cement paste 13 and the plug 12 can be pushed out forcefully.

[0018] When the pressure-feeding of concrete is continued by the concrete pump, the plug 12 is eventually discharged from the tip end of the concrete transport pipe 6. The discharged plug 12 is removed. While being pressure-fed over a long distance by the concrete transport pipe 6, the concrete 15 and the cement paste 13 are mixed to a certain extent. That is, from the tip end of the concrete transport pipe 6, a mixture of the concrete 15 and the cement paste 13 is discharged first. This mixture may be discarded, or may be used, that is, placed. If the water-cement ratio of the cement paste 13 initially charged into the concrete transport pipe 6 is adjusted to be equal to or less than the water-cement ratio of the concrete 15, the mixture can be used without being discarded. This is because it is guaranteed that when the mixture hardens, strength equivalent to or higher than that of the concrete 15 is exhibited. Thereafter, the concrete 15 is pressure-fed in the same manner. [Example]

[0019] <Experiment> An experiment was conducted to confirm that when concrete is pressure-fed by the concrete pressure-feeding method according to the present embodiment, blockage of the concrete transport pipe 6 can be prevented and pressure-feeding can be performed reliably. Experimental setup: A concrete transport pipe 6 was constructed by combining unit pipes 6a, 6a, ... with an inner diameter of 125 mm and bend pipes 6b, 6b, ... to create a total length of 200 m. A tapered pipe 7 was then installed upstream of the concrete transport pipe 6 and connected to a concrete pump. The concrete to be pumped was prepared to have a slump of 9 cm; in other words, concrete with low fluidity was used.

[0020] Experimental Example: Concrete was pumped using the concrete pumping method according to this embodiment. Specifically, a plug 12 according to this embodiment was placed in the concrete transport pipe 6, then cement paste was added, and then the concrete was pumped. The cement paste was adjusted so that the water-cement ratio was the same as that of the concrete being pumped. Experimental results: The experiment was repeated 20 times, and concrete transport pipe 6 was able to pump concrete without ever becoming blocked.

[0021] Comparative example experiment: Concrete was pumped without using cement paste. That is, the plug 12 according to this embodiment was placed in the concrete transport pipe 6, and the concrete was pumped using a concrete pump. Experimental results: After repeating the experiment three times, blockage occurred in concrete transport pipe 6 twice, resulting in failure to pump the concrete. The blockage mainly occurred in bend pipe 6b.

[0022] Experimental Analysis: When the concrete pumping method according to this embodiment was implemented, it was confirmed that even concrete with relatively low fluidity could be reliably pumped without causing blockages. The reason why blockage of the plug 12 within the concrete transport pipe 6 was prevented is thought to be that the cement paste that was directly pressing the plug 12 acted as a lubricant between the plug 12 and the inner surface of the concrete transport pipe 6.

[0023] <Variation> This embodiment can be modified in various ways. For example, the plug 12 according to this embodiment can be modified. Although the plug 12 has been described as spherical, it is not limited to a spherical shape. For example, an ellipsoidal plug 12' may be used, as shown in Figure 3(B). The cement paste 13 can also be modified. Although the cement paste 13 has been described as being mixed only from water and cement, additives may be added. If additives are added to the cement paste 13 to the same concentration as the additives added to the concrete 15 to be pumped, the cement paste 13 can be treated in the same way as the concrete 15. [Explanation of symbols]

[0024] 1. Concrete pump truck 2. Vehicles 4 Multi-stage boom 4a, 4b, 4c boom 6. Concrete transport pipes 6a Unit pipe 6b Bend pipe 7 Tapered tube 8 Opening 9 Lid 10 Stay 12 Plugs 13 Cement Paste 15 Concrete

Claims

1. A concrete pumping method in which concrete is pumped by concrete transport pipes, Prior to pumping the concrete, a plug made of an elastic material and larger than the inner diameter of the concrete transport pipe is inserted into the concrete transport pipe beforehand. A predetermined amount of cement paste, which is a mixture of cement and water, is placed behind the plug of the concrete transport pipe. The cement paste is mixed to have a water-cement ratio that is the same as or less than that of the concrete. The concrete is pumped using a concrete pump to push out the cement paste and the plug together with the concrete. A concrete pumping method comprising continuously pumping the concrete using the concrete pump after the plug has been discharged from the tip of the concrete transport pipe.

2. The concrete pumping method according to claim 1, wherein the plug is solid and spherical.

Images