JP2001262575A - Method of placing underwater concrete using lightweight aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent jumping-out of a lightweight aggregate, in its turn, under water scattering of freash concrete, and to enhance quality of the concrete. SOLUTION: In this method of placing underwater concrete using the lightweight aggregate, first of all, the lightweight aggregate is housed in a meash-like bag body, and is put in a bagged state. Next, the lightweight aggregate of the bagged state is arranged in a prescribed position of an underwater placing area. Next, cement milk is pressurized and injected into clearance among the mutual lightweight aggregates to construct lightweight concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete casting method for constructing an underwater structure such as a footing or caisson of a bridge with underwater concrete using lightweight aggregate.

[0002]

2. Description of the Related Art When building footings or caissons for bridges, so-called underwater concrete is often used. However, if the ground at the construction site is soft, it is necessary to minimize the ground improvement work. It is desirable to make the basic structure such as footing or caisson as light as possible.

On the other hand, in order to reduce the weight of concrete, it is common to use lightweight aggregate.

[0004]

However, when the underwater concrete is cast using the lightweight aggregate, the lightweight aggregate having a small specific gravity rises in the fresh concrete during the casting of the concrete, and when the concrete is lighter than the water, However, there is a risk that the fresh concrete may jump out of the water and float up in the water, and at that time the fresh concrete may fly into the water and pollute the surrounding water area.

[0005] For this reason, the use of underwater concrete using an aggregate is generally inevitable, and as a result, there has been a problem that it is almost impossible to reduce the weight of the foundation structure.

Even if the lightweight aggregate can be prevented from jumping out, it cannot be prevented that the lightweight aggregate is unevenly distributed in the fresh concrete and becomes uneven, and there is room for improvement in quality. Was.

The present invention has been made in view of the above-mentioned circumstances, and provides a lightweight aggregate capable of preventing the light-weight aggregate from flying out and consequently scattering fresh concrete in water, and improving the quality of the concrete. It is an object of the present invention to provide a method of placing used underwater concrete.

[0008]

In order to achieve the above-mentioned object, a method of placing underwater concrete using a lightweight aggregate according to the present invention is characterized in that the lightweight aggregate is formed into a mesh bag. The lightweight aggregate in the bagged state is placed at a predetermined position in the submerged casting area, and then cement milk is injected under pressure into the gap between the lightweight aggregates to reduce the weight of the lightweight concrete. Is to build.

In the method of casting underwater concrete using a lightweight aggregate according to the present invention, first, the lightweight aggregate is stored in a mesh-like bag to be packed.

[0010] The mesh-like bag body is designed so that the stored lightweight aggregate does not jump out due to the buoyancy received from water or cement milk and that the cement milk is smoothly injected under pressure. The size and material strength are appropriately selected. The amount of the lightweight aggregate to be stored is appropriately determined in consideration of the size and shape of the underwater casting area, convenience of handling, and the like.

Next, the lightweight aggregate in a bag-packed state is arranged at a predetermined position in the underwater casting area.

When arranging the packed lightweight aggregate at a predetermined position in the underwater casting area, the lightweight aggregate in the packed state is fixed by a predetermined method such that the buoyancy received from water or cement milk does not allow the lightweight aggregate to float. .

Here, the method of fixing the light-weight aggregate in the bagged state is arbitrary. For example, after all the light-weight aggregates in the bagged state are stacked, a grating or the like is placed on the upper surface thereof, and the grating is molded. A method of fixing them together by fixing them to a frame or putting a weight on the grating, or a method of fixing each of the lightweight aggregates in a bag state to the inner surface of a mold can be considered.

Next, cement milk is injected under pressure into the gaps between the lightweight aggregates to construct lightweight concrete.

In this way, the lightweight aggregate tends to float by receiving buoyancy from the surrounding water before the cement milk is injected and from the cement milk after the cement milk is injected. Since it is fixed at a predetermined position in the underwater casting area in a packed state, it does not float even if such buoyancy acts, and stays at the place where it was originally placed. And because cement milk is pressurized and injected into the gap between such lightweight aggregates and hardens, the constructed lightweight concrete is made of high quality concrete in which the lightweight aggregate is uniformly distributed without uneven distribution. Become.

Further, conventionally, even in a situation where the lightweight aggregate floats in fresh concrete and jumps out into the water due to its lightness, the present invention does not restrict the surrounding cement as described above. Even if it receives buoyancy from milk, it is fixed at a predetermined position in the submerged casting area in a state of being packed in a mesh-like bag, so that the lightweight aggregate does not rise from the initial installation position, and therefore, There is no concern about rising to the top of the cement milk and jumping out of the water from the top.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for placing underwater concrete using lightweight aggregate according to the present invention will be described below with reference to the accompanying drawings. It is to be noted that the same reference numerals are given to components and the like that are substantially the same as those in the conventional technology, and description thereof will be omitted.

FIG. 1 is a construction procedure diagram showing a case where the method of placing underwater concrete using lightweight aggregate according to the present embodiment is applied to placing underwater concrete in a caisson, and FIG. 2 is a mesh used therein. It is the perspective view which showed the shape-like bag body and the lightweight aggregate stored in it.

First, a caisson 1 is installed as shown in FIG. 1 (a) prior to casting underwater concrete using a lightweight aggregate. When installing the caisson 1, the caisson 1 is towed to the site, the caisson installation location is excavated flat in advance, and then the caisson 1 is submerged on the seabed 2 by pouring water into the caisson 1. .

On the other hand, as shown in FIG. 2, the lightweight aggregate 11 used for underwater concrete is housed in a mesh-like bag body 12 and packed into a bag.

The mesh-like bag 12 is made of the stored lightweight aggregate 11.
The size and material strength of the mesh may be selected as appropriate so that the buoyancy received from water or cement milk rises and does not jump out, and the cement milk is smoothly injected under pressure, for example, steel. It is conceivable that the network is made of a net made of FRP or FRP. The mesh bag 12 is preferably set to have an aperture of, for example, about 5 to 10 mm according to the size of the lightweight aggregate 11.

Next, as shown in FIG. 1 (b), the lightweight aggregate 11 packed in the mesh bag 12 is arranged at a predetermined position in the underwater casting area inside the caisson 1.

When the light-weight aggregate 11 in the bag-packed state is arranged at a predetermined position in the submerged casting area, the light-weight aggregate 11 in the bag-filled state is not lifted up by buoyancy received from water or cement milk. After stacking all the lightweight aggregates 11 from the bottom of the caisson 1, press the upper surface with grating or the like, or fix the bottom one to the bottom of the caisson 1, and then interconnect them in the vertical direction to the bottom It is better to stack them sequentially.

Next, as shown in FIG. 3, while the caisson 1 is appropriately drained, cement milk 21 is injected under pressure into the gaps between the lightweight aggregates 11 to construct lightweight concrete.
The injection pipe 22 for injecting the cement milk 21 under pressure is provided with the lightweight aggregate 11 packed in the mesh bag 12.
It is preferred that the pipes be placed at the same time when they are placed at a predetermined position in the underwater casting area inside the caisson 1 so that the cement milk 21 is gradually pulled out as the cement milk 21 is poured.

By doing so, the lightweight aggregate 11 tends to float by the buoyancy from the surrounding water before the cement milk 21 is injected and from the cement milk after the cement milk 21 is injected. Since it is fixed at a predetermined position in the underwater casting area in a state of being packed in the bag-like body 12, it does not float even when such buoyancy acts.
Stay where it was originally placed. Then, the cement milk 21 is injected under pressure into the gap between the lightweight aggregates 11 and hardens.

As described above, according to the method of placing underwater concrete using the lightweight aggregate according to the present embodiment,
Since the lightweight aggregate 11 is fixed at a predetermined position in the submerged casting area in a state where the lightweight aggregate 11 is packed in the mesh-like bag body 12, and the cement milk 21 is injected under pressure in this state, the lightweight aggregate 11
Of the cement milk 21 is prevented.
It will be injected into the gap of the lightweight aggregate 11 remaining at the initial installation position.

For this reason, it is possible to cast light-weight concrete in a state where the light-weight aggregate 11 is not unevenly distributed and is uniformly dispersed, and the quality of the light-weight concrete can be greatly improved.

Further, according to the present embodiment, according to the present embodiment, even if the conventional lightweight aggregate 11 floats in fresh concrete and jumps out into the water due to its light weight, as described above, Even if it receives buoyancy from the surrounding cement milk 21, it is fixed at a predetermined position in the submerged casting area in a state of being packed in the mesh-like bag 12, so that the lightweight aggregate 1
1, there is no possibility of being lifted from the initial installation position.

Therefore, the lightweight aggregate 11 jumps out of the cement milk 21 and the cement milk 21
Underwater, and consequently pollution of surrounding water areas can be prevented beforehand, and as a result, it is also possible to reduce the weight of the foundation structure with underwater concrete using lightweight aggregate.

[0030]

As described above, according to the method for casting underwater concrete using lightweight aggregate of the present invention, it is possible to cast lightweight concrete in a state where the lightweight aggregate is not uniformly distributed and is uniformly dispersed. And the quality of lightweight concrete can be greatly improved.

[0031]

[Brief description of the drawings]

FIG. 1 is a construction procedure diagram showing a state in which underwater concrete is poured into a caisson according to a method of placing underwater concrete using lightweight aggregate according to the present embodiment.

FIG. 2 is a perspective view of a mesh bag used in the casting method according to the embodiment and a lightweight aggregate 11 stored therein.

FIG. 3 is a construction procedure diagram showing a situation in which underwater concrete is poured into a caisson in accordance with the method of placing underwater concrete using lightweight aggregate according to the embodiment.

[Explanation of symbols]

 11 Lightweight Aggregate 12 Reticulated Bag 21 Cement Milk

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeyuki Togawa 4-640 Shimoseito, Kiyose-shi, Tokyo Inside the Obayashi-Gumi Technical Research Institute, Inc. In-house F-term (reference) 2D045 AA04 BA03 BA05 CA11 2D046 DA03

Claims (1)

[Claims] 1. A lightweight aggregate is stored in a mesh-like bag and packed in a bag, and the lightweight aggregate in the bag-packed state is arranged at a predetermined position in a submerged casting area. A method for casting underwater concrete using lightweight aggregates, comprising constructing lightweight concrete by injecting cement milk into the gaps of the concrete under pressure.