JP7477954B2 - Concrete pumping method - Google Patents

Description

The present invention relates to a method for pumping concrete.

Fresh concrete before hardening (hereinafter simply referred to as "concrete") is a mixture of cement, water, fine aggregate, coarse aggregate, and admixtures added as necessary, and has both liquid and solid properties. When pumped, the fresh concrete forms a solid plug inside the steel pipe and is pumped while generating friction with the inner wall of the pipe. During this, the coarse aggregate is mainly located in the center of the steel pipe, and the water and cement paste are mainly located on the inner wall side of the steel pipe, and the pumping proceeds while the water, etc. located on the inner wall side buffers the frictional resistance generated during pumping. The pumpability of concrete varies depending on its type. For example, concrete with a low water content or other high viscosity has a high frictional resistance and can lead to clogging of the steel pipe, while concrete with a high water content is prone to separation of solid and liquid, which can easily cause clogging of the steel pipe and a deterioration in the quality of the pumped concrete.

Generally, steel pipes are used to pump fresh concrete (see, for example, Patent Document 1). The steel pipes are connected with joints as necessary to pump fresh concrete to the desired pouring location. Straight steel pipes are about 1, 2, or 3 meters long, and the higher the pressure resistance of the steel pipe, the thicker the pipe wall and the heavier it becomes. For example, a 3-m high-pressure steel pipe weighs about 65 kg. For this reason, multiple people are required to handle one steel pipe at a construction site.

JP 2019-085741 A

When pumping fresh concrete using steel pipes, advance materials are used before pumping begins to maintain lubricity inside the pumping pipe and ensure the quality of the concrete. Advance materials include water, cement paste, and mortar. When pumping high-strength concrete, a similar mix may be used without the coarse aggregate. If pumping of fresh concrete begins without using advance materials, the paste in the fresh concrete will adhere to the inside of the pumping pipe, and the top part of the fresh concrete will gradually become like gravel, increasing frictional resistance and ultimately causing the pipe to become clogged.

The amount of advance material required is determined by the diameter and length of the pumping pipe, and the longer the pumping distance, the more advance material is required. When using advance material, it is pumped first, and once it has been properly pumped, fresh concrete is then pumped. Advance material is mixed into the concrete when pumping begins, and affects the strength and quality of the concrete. For this reason, advance material discharged from the pumping pipe, and concrete mixed with advance material, are discarded.

Although advance materials are necessary to pump fresh concrete without clogging the pumping pipes, the use of advance materials creates the problem of generating a large amount of waste. Therefore, a method for pumping fresh concrete without using advance materials is desired.

The present invention was made in consideration of the above problems, and aims to provide a method for pumping concrete that does not require advance materials.

The inventors conducted extensive research to solve the above problems. As a result, they discovered that the above problems could be solved by using a cylinder made of ultra-high molecular weight polyethylene and a concrete pressure pipe with a specified structure at the end, which led to the completion of the present invention.

That is, the present invention is as follows.
[1]
A step of pumping concrete from one end of one or a plurality of connected concrete pumping pipes having no advance material attached to the inner surface;
a step of visually checking the position of the pumped concrete in the concrete pumping pipe from outside the concrete pumping pipe;
and discharging the concrete from the other end of the concrete pumping pipe.
As the concrete pressure pipe, a concrete pressure pipe made of resin without a metal pipe is used.
Concrete pumping method.
[2]
The pumping pressure of the concrete is 0.01 to 30 MPa.
The method for pumping concrete according to [1].
[3]
The pumping distance of the concrete through the concrete pumping pipe is 10 to 1900 m.
A method for pumping concrete according to [1] or [2].
[4]
The concrete is made by combining cement, coarse aggregate, fine aggregate, water, admixtures, fibers, and powder materials according to the required performance.
The concrete pumping method according to any one of [1] to [3].
[5]
The concrete pumping pipe is a resin cylinder.
The concrete pumping method according to any one of [1] to [4].

The present invention provides a method for pumping concrete that does not require advance materials.

1 is a cross-sectional view of a concrete pumping pipe according to an embodiment of the present invention, taken along the center line of the cylinder. FIG. 13 is a diagram showing an image in which the concrete inside the concrete pumping pipe of this embodiment can be seen when it is in use.

The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this embodiment, and various modifications are possible without departing from the gist of the present invention.

[Concrete pumping method]
The concrete pumping method of this embodiment includes the steps of pumping concrete from one end of one or more connected concrete pumping pipes having no advance material attached to their inner surface, visually checking the position of the pumped concrete within the concrete pumping pipe from outside the concrete pumping pipe, and discharging the concrete from the other end of the concrete pumping pipe, and a concrete pumping pipe made of resin without a metal pipe is used as the concrete pumping pipe.

Traditionally, metal pipes such as steel pipes have been used to pump concrete. This is presumably because the concrete being pumped is heavy and requires a certain amount of pressure to pump, and metal pipes are considered more suitable for safe pumping.

However, it has become clear that metal pipes are not suitable for pumping concrete. For example, each metal pipe is heavy and requires careful handling by multiple workers to avoid accidents. This poses issues in terms of work safety and on-site labor hours.

In addition, because the coefficient of dynamic friction between metal pipes and concrete is relatively high, concrete is usually pumped into metal pipes using advance materials, but the amount of waste advance materials is large, making it impossible to reduce the labor required to use the advance materials, and it is also impossible to reduce the large disposal costs of the advance materials. Furthermore, due to the high coefficient of dynamic friction, the components of the concrete separate during pumping, and the composition of the concrete discharged from the pumping pipe outlet is prone to change. When such changes occur, they have a significant impact on the strength of the building, and concrete with a changed composition must be discarded, further increasing disposal costs.

Furthermore, because it is impossible to see inside a metal pipe, it is not possible to immediately check how far into the concrete pumping pipe the concrete has reached, and it is not possible to notice that the concrete has become clogged and caused a blockage along the way. If such a blockage occurs, not only can the concrete pumping pipe burst, causing an accident, but the concrete pumping pipe, which took a lot of man-hours to place, must be discarded and relocated, which can significantly delay work. Furthermore, if a blockage occurs, the metal pipe may burst suddenly in an unpredictable location, increasing the danger of the work.

In contrast, the concrete pumping pipe of this embodiment uses a concrete pumping pipe made of resin that does not include conventional metal pipes such as steel pipes. By not including metal pipes such as steel pipes, it is possible to realize a concrete pumping pipe that is light and can be handled more safely at the work site, unlike concrete pumping pipes that are heavy and have handling problems.

In addition, the concrete pumping pipe of this embodiment is made of resin, so there is no need to use advance materials. Therefore, not only can the process of using advance materials itself be eliminated, but the costs of using and disposing of advance materials can also be significantly reduced. In addition, separation of the concrete components during pumping can be suppressed, and the costs of disposing of concrete whose composition has changed can also be significantly reduced.

Furthermore, in this embodiment, by using a concrete pumping pipe made of resin, it is possible to ensure visibility of the contents inside the cylinder. As a result, even if concrete gets stuck halfway through the concrete pumping pipe, it is possible to quickly confirm the blockage and prevent burst accidents. Furthermore, when the internal pressure of the resin cylinder increases, it bulges outward to an extent that is immediately noticeable to the naked eye before it breaks. This allows on-site workers to immediately recognize the location of the potential burst and to take appropriate refuge. The concrete pumping method of this embodiment is described in detail below.

[Pressure feeding process]
The pumping process is a process of pumping concrete from one end of one or more connected concrete pumping pipes with no advance material attached to the inner surface. In the method of this embodiment, no advance material is used for pumping. Therefore, concrete is pumped from one end of the concrete pumping pipe with no advance material attached to the inner surface.

The concrete pumping pressure is preferably 0.01 to 30 MPa. The pumping pressure during the pumping process does not need to be constant and may vary within the above range. In addition, the pumping distance of the concrete through the concrete pumping pipe is preferably 10 to 1,900 m. Pumping distances vary depending on the site, but according to the method of this embodiment, concrete can be pumped stably even over such pumping distances.

The type of concrete pumped by the method of this embodiment is not particularly limited, but examples include ordinary Portland cement, high-early-strength Portland cement, extra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, blast-furnace cement, and fly ash cement, fiber-reinforced concrete, lightweight concrete, rich-mix concrete, lean-mix concrete, high-strength concrete, and high-fluidity concrete.

Depending on the type, concrete can be qualitatively classified into those that are easy to pump and those that are difficult to pump, but even within the same type, there are those that are easy to pump and those that are difficult to pump, depending on the composition. The method of this embodiment can be used to pump any type of concrete, since it is possible to pump even those that are difficult to pump without using advance materials. Note that any commonly known concrete can be used, and examples include those that combine cement, coarse aggregate, fine aggregate, water, admixtures, fibers, and powder materials according to the required performance.

[Confirmation process]
The confirmation step is a step of visually confirming the position of the pumped concrete in the concrete pump pipe from the outside of the concrete pump pipe. In this embodiment, by using a concrete pump pipe without a metal pipe, it is possible to ensure the visibility of the contents in the cylinder. As a result, even if concrete is clogged in the concrete pump pipe, it is possible to quickly confirm the blockage and prevent a burst accident. In addition, the confirmation step may be performed by visually confirming the position of the pumped concrete in the concrete pump pipe where it may burst from the outside of the concrete pump pipe. When the internal pressure of the concrete pump pipe used in this embodiment increases, it bulges outward to a degree that can be immediately seen by the naked eye before it breaks. As a result, the workers on site can immediately recognize the position where it may burst and can evacuate appropriately.

[Discharge process]
The discharge process is a process of discharging concrete from the other end of the concrete pumping pipe.

[Concrete pressure pipe]
A concrete pumping pipe made of resin without a metal pipe is used as the concrete pumping pipe. Fig. 1 shows a cross-sectional view of the concrete pumping pipe used in this embodiment cut along the center line of the cylinder. The concrete pumping pipe 10 does not have a metal pipe, but has a cylindrical body 1 made of resin, and may have flanges 2 at both ends for joining with joints. The concrete pumping pipe 10 of this embodiment uses a cylindrical body made of resin, so that the visibility of the contents (concrete 3) inside the cylindrical body can be ensured during use (Fig. 2). The concrete pumping pipe, which is a cylindrical body made of resin, will be described below.

(Resin Composition)
Examples of resins that form the concrete pumping pipe include thermoplastic resins and thermosetting resins. The resins may also contain additives such as ultraviolet absorbers.

Thermoplastic resins are not particularly limited, but examples include polyolefin resins, polyester resins, polyarylates, liquid crystal polyesters, polyvinyl chloride, polyvinyl alcohol, ethylene vinyl acetate, polystyrene, acrylonitrile-butadiene-styrene copolymer resins, acrylonitrile-styrene copolymer resins, polymethyl methacrylate, polyamide resins, polyacetal, polycarbonate, fluorine resins, polyether ether ketone, polyether sulfone, polyphenylene sulfide, etc.

Thermosetting resins are not particularly limited, but examples include phenol resins, urea resins, melamine resins, allyl resins, and epoxy resins.

Among these, thermoplastic resins are preferred from the viewpoints of formability, secondary processability, etc. Furthermore, among thermoplastic resins, polyolefin resins, such as polyethylene and polypropylene, are preferred because they are inexpensive, have excellent chemical resistance, are excellent in processability, and have low hygroscopicity and water absorption properties of the material.

Examples of polyolefin resins include, but are not limited to, homopolymers of ethylene; copolymers of ethylene and one or more α-olefins such as propylene, butene-1, hexene-1, and octene-1; copolymers of ethylene and vinyl acetate, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, and the like; homopolymers of propylene; and copolymers of propylene and one or more α-olefins such as ethylene and butene-1.

Among polyolefin resins, polyethylene is the most preferred because it is inexpensive, has a small coefficient of friction, is easy to process after molding, has excellent chemical resistance, and has low moisture absorption and water absorption properties.

The density of the polyethylene is preferably 890 to 970 kg/ ^m3 , more preferably 910 to 960 kg/ ^m3 , and even more preferably 920 to 950 kg/ ^m3 . When the density is 890 kg/ ^m3 or more, the rigidity of the cylindrical body tends to be improved. Furthermore, when the density is 970 kg/ ^m3 or less, the handleability tends to be improved. Here, the density of the polyethylene can be obtained by measurement by a density gradient tube method (23°C) in accordance with JIS K 7112:1999.

The viscosity average molecular weight of the polyethylene is preferably 1 million to 10 million, more preferably 2 million to 10 million, and even more preferably 3 million to 10 million. By having the viscosity average molecular weight of the polyethylene within the above range, the abrasion resistance is improved and sufficient strength to withstand high pumping pressure tends to be obtained. In this embodiment, polyethylene having the above viscosity average molecular weight is referred to as "ultra-high molecular weight polyethylene."

The viscosity average molecular weight can be determined, for example, by the following method. First, polyethylene is dissolved in decalin (decahydronaphthalene) to prepare a number of solutions with different concentrations. The reduced viscosity (ηsp/C) of each of these solutions is determined in a thermostatic bath at 135°C using an Ubbelohde type viscometer. A linear equation is derived between the concentration (C) and the reduced viscosity (ηsp/C) of the polymer, and the intrinsic viscosity ([η]) is determined by extrapolating to a concentration of 0. The viscosity average molecular weight (Mv) can be determined from this intrinsic viscosity ([η]) according to the following equation.
Mv = 5.34 × 10 ⁴ × [η] ^1.49

In particular, by using ultra-high molecular weight polyethylene as the resin, the coefficient of dynamic friction on the inner surface of the cylinder can be adjusted to about 0.07 to 0.15, and it is possible to create a configuration that can withstand a 25 MPa water pressure resistance test, with a transmittance of 10% or more per 2 mm thick test piece of the cylinder, and a contact angle of 60° or more on the inner surface of the cylinder. This makes the use of advance materials less necessary, makes clogging less likely to occur, and further suppresses fluctuations in the discharged concrete components, while providing sufficient mechanical strength for pumping concrete and improving visibility of the contents. This is a trend.

The raw resin for the concrete pumping pipe may be a mixture of polyethylenes with different densities and/or viscosity average molecular weights, or may be a mixture of polyethylene and a raw resin other than polyethylene.

In addition, the concrete pumping pipe of this embodiment may contain various additives such as heat stabilizers, ultraviolet absorbers, color pigments, and flame retardants added to the resin, as long as the effect of this embodiment is not impaired.

[Appearance]
The cylindrical body of this embodiment is a resin pipe that does not include a metal pipe. The cylindrical body may be made of a resin pipe, such as a multi-layer pipe made of multiple resin layers, a multi-layer pipe made of a single resin layer with an optional inner layer, or a single-layer pipe made of a single resin layer. Among these, a single-layer pipe is preferable.

The outer diameter, inner diameter, and thickness of the cylinder are not particularly limited, so long as they are the sizes used in conventional concrete pumping pipes. For example, the maximum outer diameter R is preferably 100 to 250 mm, more preferably 110 to 240 mm, and even more preferably 120 to 230 mm. The inner diameter r of the cylinder is preferably 70 to 170 mm, more preferably 80 to 160 mm, and even more preferably 90 to 150 mm. By using such a cylinder, it is possible to efficiently pump a relatively large amount of concrete containing various solids of various sizes, and pumping performance tends to be further improved.

Furthermore, the thickness of the cylinder (R-r)/2 is preferably 5 to 20 mm, more preferably 7.5 to 17.5 mm, and even more preferably 10 to 15 mm. By using such a cylinder, the life of the concrete pumping pipe tends to be longer.

The length of the cylinder is not particularly limited as long as it is a size that is used in conventional concrete pumping pipes. For example, the total length Lw of the cylinder is preferably 0.3 to 4 m, more preferably 0.5 to 3.7 m, and even more preferably 0.75 to 3.5 m.

The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples.

<Pressure test method>
Ten concrete pumping pipes of each of the examples and comparative examples were connected to a concrete pump truck with joints, and a concrete pumping test was carried out under the conditions shown in Table 1. Regular concrete was used as the concrete pumped. When a pre-delivered material was used, mortar was used as the pre-delivered material. Prior to pumping the concrete, 1000 kg of the pre-delivered material was introduced into the concrete pumping pipe, and the pre-delivered material was discharged from the other end of the concrete pumping pipe, thereby adhering to the inner surface of the concrete pumping pipe.
Concrete was supplied to the pressure pipe from a pump vehicle, and the pressure-transported state was observed when 200 m ³ was pumped at an initial pressure of 1.5 MPa and a speed of 10 m ³ /h.

<Pressure-feeding state>
The pumping condition was evaluated by checking whether clogging occurred in the pumping pipe before pumping ²⁰⁰ m3 under the conditions shown in Table 1. If no clogging occurred, it was rated "good," and if pumping could not be completed due to clogging, it was rated "clogging:."

<Visual confirmation of concrete passing position>
In the pumping test, the position of the concrete inside the concrete pumping pipe was visually confirmed from outside under clear skies, and visibility was evaluated.

<Leaking>
Under the conditions shown in Table 1, it was confirmed whether leakage of concrete had occurred from the joints, which were the connection parts of the concrete pumping pipe, until 200 ^m3 had been pumped, and an evaluation was made as to whether leakage had occurred or not.

<Characteristics of discharged concrete>
Under the conditions shown in Table 1, it was confirmed whether there was any change in the composition of the discharged concrete until 200 ^m3 was pumped, and the properties of the discharged concrete were evaluated.

<Explosion prediction/bulging>
It was confirmed whether or not swelling occurred in the body of the concrete pumping pipe before pumping ^5,000 m3 under the conditions shown in Table 1. When swelling was visible, pumping was continued and the amount of pumping until the relevant part burst was measured and recorded as the "amount that can be pumped after the body bulge".

Example 1
A cylindrical body was molded by using ultra-high molecular weight polyethylene powder (Sunfine UH910, manufactured by Asahi Kasei Corporation). In this case, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole was used as an ultraviolet absorber. The obtained cylindrical body was used as a concrete pressure pipe. The obtained cylindrical body had a water pressure resistance of 25 MPa, a dynamic friction coefficient of 0.12, a contact angle of 74°, and a transmittance of 52.4% per 2 mm thick test piece of the cylindrical body.

Comparative Example 1
A commercially available steel pipe (manufactured by Linex Corporation, product name Green Line) was used as a concrete pumping pipe in the comparative example. The steel pipe had a water pressure resistance of 25 MPa, a dynamic friction coefficient of 0.52, a contact angle of 50°, and a transmittance of 0% per 2 mm thick cylindrical test piece.

* Waste material quantity: The amount of waste material used prior to pumping concrete.

The concrete pumping pipe of the present invention has industrial applicability at sites where concrete is pumped.

Claims (5)

A step of pumping concrete from one end of one or a plurality of connected concrete pumping pipes having no advance material attached to the inner surface;
a step of visually checking the position of the pumped concrete in the concrete pumping pipe and the state of swelling outward from the concrete pumping pipe from outside the concrete pumping pipe;
and discharging the concrete from the other end of the concrete pumping pipe.
As the concrete pressure pipe, a concrete pressure pipe made of a cylindrical body of ultra-high molecular weight polyethylene resin without a metal pipe is used.
Concrete pumping method. The dynamic friction coefficient of the inner surface of the cylinder is 0.07 to 0.15, the transmittance per 2 mm thick test piece of the cylinder is 10% or more, and the contact angle of the inner surface of the cylinder is 60° or more.
The method for pumping concrete according to claim 1. The pumping pressure of the concrete is 0.01 to 30 MPa.
3. A method for pumping concrete according to claim 1 or 2 . The pumping distance of the concrete through the concrete pumping pipe is 10 to 1900 m.
The method for pumping concrete according to any one of claims 1 to 3 . The concrete is made by combining cement, coarse aggregate, fine aggregate, water, admixture, fiber, and powder materials according to the required performance .
The method for pumping concrete according to any one of claims 1 to 4 .