JPH07116841B2 - Lightweight prepared concrete method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention requires a large amount of concrete such as a lightweight prepacked concrete construction method, particularly a composite member for an offshore platform, a precast member for civil engineering, and the like. The present invention relates to a lightweight pre-packed concrete construction method suitable for concrete construction that is desirable.

(Prior Art) In recent years, in the production of offshore oil platforms for offshore oil drilling in the Arctic Ocean, the North Sea, etc., there has been proposed a method of constructing using composite members instead of conventional steel or concrete ones. ing. This composite member is constructed by placing concrete as a structural filler in a steel shell that serves as a reinforcing member instead of a reinforcing bar.

In the production of such a composite member, as a method for placing concrete in the steel shell, there is a tremy method of directly filling the steel shell with concrete that has already been kneaded using a tremie pipe, or a rough method in which the steel shell is preliminarily roughened. A pre-packed concrete method is used in which aggregate is packed and mortar is injected later.

The pre-packed concrete method is a method that has been conventionally used to manufacture radiation shields for large-scale underwater structures and nuclear reactors in construction of ports and rivers. When this method is applied to the production of composite members, especially those used for the construction of deep water offshore platforms, it is only necessary to complete the input of coarse aggregate in the dock to maintain the water depth and Since it is possible to perform mortar injection work, there is no need to use a large crane ship, and there are many advantages such as low cost, which is a method that is becoming widespread.

Among structures using such composite members,
For example, in the case of the above-mentioned marine platform, after construction, it is levitated on the ocean and towed to the excavation point by a tugboat, but it is desirable that the whole weight is light in order to reduce the amount of watering at a shallow water depth, For other structures that are desired to be lightweight, it is necessary to use a composite member made of lightweight concrete using lightweight aggregate.

Then, the lightweight concrete is filled in the steel shell of the composite member, and in the prepacked concrete method, the mortar is filled in the steel shell filled with the lightweight coarse aggregate.

(Problems to be solved by the invention) However, when the size of the coarse aggregate is small during the construction of the prepacked concrete, the gap between the coarse aggregates becomes small, so that the injection mortar flows between the coarse aggregates. It has a disadvantage that the construction period as a whole becomes long because it becomes hard and the injection rate needs to be reduced. Therefore, a minimum of 15 mm or more is required as the coarse aggregate used for the pre-packed concrete, and it is better to use the coarse aggregate having a larger size for rapid construction. On the other hand, the conventional lightweight aggregate is 5
It is about 20 mm, which is not preferable from the viewpoint of mortar fluidity. Further, in the case of manufacturing a lightweight aggregate having the above size, there is a drawback that the strength of the aggregate itself is lowered and the strength of the concrete as a whole is lowered even if the filling property of the mortar is improved.

In addition, the conventional prepacked concrete method also uses ordinary concrete or heavy concrete. When using lightweight coarse aggregate, the bulk specific gravity of the lightweight coarse aggregate and the bulk specific gravity of ordinary concrete (mortar) are used. Since the difference in bulk specific gravity between and is large, the mixture of the two causes the lightweight coarse aggregate to float up and cause a separation phenomenon, making it difficult to obtain homogeneous prepacked concrete.Practical application of the prepacked concrete method using lightweight coarse aggregate Not yet successful.

(Means for Solving Problems) Therefore, the inventors of the present invention have solved the above problems and conducted research to obtain an excellent lightweight prepacked concrete, and as a result, a lightweight concrete composed of lightweight coarse aggregate and mortar. The inventors have found that a lightweight prepacked concrete construction method capable of rapid construction can be put into practical use by using a block-shaped lightweight coarse aggregate obtained by molding, and completed the present invention.

That is, the present invention includes (1) filling a block-shaped lightweight coarse aggregate obtained by molding a lightweight concrete composed of lightweight coarse aggregate and mortar into a mold, and then filling a space between the block-shaped coarse aggregates. In the lightweight prepacked concrete construction method characterized by injecting mortar, and (2) the lightweight prepacked concrete construction method described in the above item (1),
In the mold, a sheath pipe having a perforated pipe wall is attached, and a mortar injection pipe having a ring-shaped packer fixed to the outer peripheral surface thereof is inserted in the sheath pipe, and a lightweight coarse aggregate is formed in the mold. The block-shaped lightweight coarse aggregate with a diameter of 20 mm or more obtained by molding a lightweight concrete made of mortar is packed, and then the block-shaped lightweight coarse aggregate is passed from the tip of the injection pipe through a hole in the sheath pipe wall. A lightweight prepacked concrete construction method, characterized in that mortar is injected into the space between the aggregates, the injection and filling is started from below in the mold, and the injection pipe is sequentially pulled up to be upwardly filled. is there.

In the above invention, the mold is preferably a steel shell, and the mortar is preferably a high strength mortar.

Hereinafter, the present invention will be described in more detail.

First, the block-shaped lightweight coarse aggregate obtained by molding a lightweight concrete consisting of the lightweight coarse aggregate and mortar used in the present invention is a large one so that the mortar can be easily injected. The smaller the ratio between the maximum size and the minimum size, the larger the porosity between the coarse aggregates and the faster the injection speed of the mortar. Therefore, the smaller the ratio between the maximum size and the minimum size is, the smaller the ratio. If this is the case, the deviation of the coarse aggregate in the form is small, and a homogeneous lightweight concrete can be obtained. The size of such a block-shaped lightweight coarse aggregate is preferably 20 mm or more.

As a method for obtaining this block-shaped lightweight coarse aggregate, it can be produced by molding a lightweight concrete composed of a normal lightweight aggregate and mortar into an arbitrary shape, for example, a spherical shape or a tetrapot shape.

When a block-shaped lightweight coarse aggregate is manufactured from such lightweight concrete, even though it is a large coarse aggregate, the voids as coarse aggregate are small and the strength of the coarse aggregate itself is small. The overall strength decrease is also small.

In addition, block-shaped lightweight coarse aggregate made of lightweight concrete composed of lightweight coarse aggregate and mortar has a higher bulk specific gravity than the lightweight coarse aggregate itself. A method of pouring mortar into coarse aggregate and placing prepacked concrete, and (2) a block-shaped lightweight coarse bone obtained by molding lightweight concrete composed of lightweight coarse aggregate and mortar as in the method of the present invention Comparing with the method of pouring mortar between materials and placing prepacked concrete, (1) method has a large difference in specific gravity between the bulk specific gravity of lightweight coarse aggregate and the bulk specific gravity of ordinary concrete (mortar). However, when both are mixed, the lightweight coarse aggregate floats up and a large separation phenomenon occurs, and it is difficult to obtain a homogeneous prepacked concrete, whereas according to the method (2), the lightweight coarse aggregate and the mortar are Since the block-shaped lightweight coarse aggregate made of lightweight concrete has a higher bulk specific gravity than the lightweight coarse aggregate itself, the difference in bulk specific gravity between the block-shaped lightweight coarse aggregate and mortar (ordinary concrete) is ( Less than in the case of 1), as a result, no significant separation phenomenon occurs between the block-shaped lightweight coarse aggregate and the mortar,
It becomes easy to obtain homogeneous pre-packed concrete.

Furthermore, when constructing pre-packed concrete using the block-shaped lightweight coarse aggregate, the lightweight coarse aggregate itself, which is originally porous, is all exposed on the surface of the block-shaped lightweight coarse aggregate according to the present invention. However, since the problem of water absorption as coarse aggregate does not increase, it is preferable to obtain the block-shaped lightweight coarse aggregate of the present invention by molding lightweight concrete also in this respect.

The mortar used in the present invention may be a so-called injecting mortar which is used in a conventional prepacked concrete construction method and has a composition such that it has good fluidity, little separation of materials, and no shrinkage. It is preferable to use high-strength mortar for the purpose of improving concrete strength, and the water-binder ratio of high-strength mortar in this case is 30-40.
% Is preferable. As described above, by using the high-strength injection mortar as the mortar, it is possible to reinforce the decrease in strength due to the coarse aggregate having the porous portion, and it is possible to obtain the prepacked concrete that is lightweight and has high strength. However, depending on the strength required for the final prepacked concrete, normal pouring mortar may be used,
The present invention is not limited by the type of mortar used.

The formwork used in the present invention may be of any type as long as it can be filled with the block-shaped lightweight coarse aggregate and can be injected with mortar, for example, a steel shell.

Even when performing a lightweight prepacked concrete construction method using the block-shaped lightweight coarse aggregate according to the present invention having a higher bulk specific gravity than the lightweight coarse aggregate itself, the block-shaped lightweight coarse aggregate and mortar Depending on the difference in bulk specific gravity, the coarse aggregate may rise during mortar pouring, and homogeneous concrete may not be obtained.Therefore, during the construction, the expanded aggregate should be placed on the top of the coarse aggregate packed in the formwork. It is preferable that the block-shaped lightweight coarse aggregate is prevented from rising by using metal, wire mesh or the like.

Next, referring to FIG. 1, which is a cross-sectional view showing the concrete placing condition of the steel partition wall of the marine platform, the light-weight prepacked concrete construction method using the block-shaped lightweight coarse aggregate of the present invention is applied to the marine platform. A case of application will be specifically described as an example.

First, in the steel partition wall formed by the steel shells 1 and 1'as molds, the block-shaped lightweight coarse bone made of lightweight concrete made of lightweight coarse aggregate and mortar by a bucket, a belt conveyor or the like. The material 2 is fed to fill the inside of the partition wall. At this time, when constructing prepacked concrete in which the top of the coarse aggregate is horizontal, that is, the top is horizontal, if a net or the like is put on the top of the coarse aggregate as the above-mentioned means for preventing coarse aggregate from floating. However, in the case of obtaining prepacked concrete having an inclined upper part as in the case of the drawing, the steel shell 1 ″ is applied to the top end of the coarse aggregate as the coarse aggregate floating preventing means and the formwork.

Reference numeral 3 is a sheath pipe having a perforated pipe wall that is attached in advance in the partition wall, and is arranged at an optimum pitch for filling mortar. A vertically movable mortar injection pipe 4 is inserted in the sheath pipe 3, and a ring-shaped packer 5 is fixed to the outer peripheral surface of the pipe 4 immediately above the tip portion thereof. In this state, when mortar is injected from the root of the mortar injection pipe 4 by a mortar pump or the like, the mortar penetrates from the tip of the injection pipe 4 into the space between the block-shaped lightweight coarse aggregates 2 through the hole in the pipe wall of the sheath pipe 3. To go. At this time, since the mortar is dammed by the packer 5, it does not flow backward in the sheath pipe 3.

Reference numeral 6 represents a mortar rise line (boundary line) in the coarse aggregate. Mortar injection is continued while pulling out the mortar injection pipe 4 in accordance with the rise of the mortar rising line, and also pulling out the packer 5 fixed to the outer peripheral surface of the mortar while sliding on the inner peripheral surface of the sheath pipe 3. The mortar is injected while the tip of the mortar injection pipe 4 is always inserted into the mortar for several tens of centimeters or more to construct a lightweight prepacked concrete composite member.

The thus obtained pre-packed concrete was satisfactory in both specific gravity and strength.

(Effect of the invention) As is apparent from the above description, the lightweight prepacked concrete construction method using the block-shaped lightweight coarse aggregate of the present invention is
Using a new block-shaped lightweight coarse aggregate obtained by molding a lightweight concrete consisting of lightweight coarse aggregate and mortar, and by injecting mortar between them, a lightweight aggregate that was previously difficult to use It facilitates the production of prepacked concrete.

And, it is also possible to manufacture lightweight pre-packed concrete with sufficient strength, especially for the construction of underwater concrete and the construction of complicated structures in the atmosphere, in terms of cost and ease. From the point, it is very advantageous.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a concrete placing situation of a steel partition wall portion of an offshore platform according to an embodiment of the present invention. In the figure 1, 1 ', 1 ": Steel shell, 2: Block-shaped lightweight coarse aggregate 3: Saya pipe (perforated), 4: Mortar injection pipe 5: Packer, 6: Mortar rise line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Matsumoto 2-16-1 Kyobashi, Chuo-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Tetsuro Hori 2-16-1 Kyobashi, Chuo-ku, Tokyo Shimizu Construction company (72) Inventor Yoshihiro Takekawa 2-16-1, Kyobashi, Chuo-ku, Tokyo Shimizu construction company (56) Reference JP 61-155561 (JP, A) JP 61- 102966 (JP, A)

Claims (4)

[Claims] 1. A block-shaped lightweight coarse aggregate obtained by molding a lightweight concrete composed of lightweight coarse aggregate and mortar in a formwork, and then mortar is injected into the space between the block-shaped coarse aggregates. A lightweight pre-packed concrete construction method characterized by: 2. The lightweight prepacked concrete construction method according to claim 1, wherein a sheath pipe having a perforated pipe wall is mounted in the mold, and a ring-shaped packer is provided on the outer peripheral surface of the sheath pipe. Insert the fixed mortar injection pipe, and also fill the block with a block-shaped lightweight coarse aggregate with a size of 20 mm or more obtained by molding a lightweight concrete consisting of lightweight coarse aggregate and mortar, Then, the mortar is injected from the tip of the injection pipe through the hole in the wall of the sheath pipe into the space between the block-shaped lightweight coarse aggregates, and injection and filling is started from below in the formwork, and the injection is performed. A lightweight pre-packed concrete construction method characterized by pouring and filling pipes upward while filling them up. 3. The lightweight prepacked concrete construction method according to claim 1 or 2, wherein the formwork is a steel shell. 4. The lightweight prepacked concrete construction method according to any one of claims 1 to 3, wherein the mortar is a high-strength mortar.