JPH0830330B2 - Lightweight prepared concrete method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is applied to a lightweight prepacked concrete construction method, particularly for placing a large amount of concrete such as a composite member for an offshore platform or a precast member for civil engineering. Lightweight prepacked concrete construction method.

(Prior art) Conventionally, as a construction method for placing a large amount of concrete in a short time, prepacked concrete has been used for the production of radiation shields for large-scale underwater structures and nuclear reactors in the construction of ports and rivers. Construction methods have been adopted.

On the other hand, in the production of offshore oil platforms for offshore oil drilling in the Arctic Ocean, the North Sea, etc., it has been conventionally made of steel or concrete, but in recent years, a method of building using composite members has been proposed. There is.

This composite member is constructed by placing concrete as a structural filler in a steel shell that has the role of a reinforcing member instead of a reinforcing bar, and has good followability to the deformation of the steel shell. And the strength of the compressive strength of concrete, which is a member that takes advantage of each material characteristic.

When a marine platform is constructed using this composite member, it has characteristics such as its good watertightness and strong fracture resistance against external forces, and it requires extra work such as arranging the reinforcing bars and demolding the formwork. The use of composite members in offshore platforms is highly preferred because of the advantages of not doing so.

In the production of such composite members, as one of the methods of placing concrete in the steel shell, a method of filling the already-mixed concrete using a tremie pipe (the tremy concrete construction method) was proposed. As another method, a method called a prepacked concrete method in which only concrete aggregate is put into a steel shell and mortar is poured later is also considered.

This pre-packed concrete construction method allows the coarse aggregate to be introduced from the opening during the steel shell assembly in a short period of time, and then the mortar can be injected from the small injection port opened in the steel shell. It has the advantage that work can be performed in parallel. In addition, when building a platform for deep water, the water depth of the dock used for construction is limited to about 10 m or less, so it is generally necessary to place part of the concrete on the sea, but prepacked concrete When using the construction method, only the loading of aggregate is completed within the dock to maintain the water depth, and the work on the sea does not require a large crane ship, only some mortar injection work remains.
It is becoming popular due to its low cost.

(Problems to be Solved by the Invention) However, in the case of a structure that is desired to be lightweight, especially in the case of the above-mentioned offshore platform, after construction, it is levitated to the sea and towed to the excavation point by a tow boat, , It often passes through a place where the water depth is shallow, and it is necessary to reduce the weight of the water to reduce the amount of drinking water, and it is often lightweight concrete using lightweight coarse aggregate.

However, the tremy concrete construction method has a drawback that a part of the concrete needs to be constructed on the ocean when a platform for deep water is constructed, and a large crane ship is used, resulting in high cost.

In addition, in the conventional prepacked concrete construction method, if the diameter size of the coarse aggregate is small, the injected mortar is not filled between the coarse aggregates, so the minimum size of the coarse aggregate is 15
Although it is said that the particle size is required to be mm, the particle size of the lightweight aggregate is generally 20 to 5 mm or 15 to 5 mm and it is difficult to apply as it is. Furthermore, the concrete used in the prepacked concrete construction method is also concrete or heavy concrete having a normal weight, and the prepacked concrete construction method using lightweight coarse aggregate has not yet been put into practical use.

Further, even if the prepacked concrete construction method is carried out using light weight coarse aggregate, the coarse aggregate floats up when the mortar is poured, and homogeneous concrete cannot be obtained.

(Means for Solving Problems) As a result of earnest research in view of the above circumstances, the present inventor succeeded in obtaining a lightweight prepacked concrete construction method using lightweight coarse aggregate.

That is, the present invention packs a lightweight coarse aggregate having a particle size of 20 to 50 mm in a frame, and a lightweight coarse aggregate floating preventing means is provided at the top end of the lightweight coarse aggregate of the frame, and then high strength mortar is added. It is a lightweight prepacked concrete construction method characterized by injecting into the intervals of the lightweight coarse aggregate.

Generally, in pre-packed concrete, the compressive strength of concrete tends to increase as the porosity (porosity) between coarse aggregates increases, but the smaller the ratio of the maximum size to the minimum size of coarse aggregate, the That is, the narrower the particle size range), the larger the porosity between the coarse aggregates, and thus the concrete having high compressive strength can be obtained.

However, the ratio of coarse aggregate used in ordinary pre-packed concrete is about 4: 1, but the particle size of the present invention is 20 to 50 mm and the ratio is about 2: 1. Since the porosity between the materials becomes larger, as a result, concrete having high compressive strength can be obtained.

On the other hand, if the particle size is 20 to 50 mm, the occupancy rate of the lightweight coarse aggregate will increase and the concrete strength will be lowered, but in the present invention, high strength injection mortar (the water binder ratio of the injection mortar is 30 to 40 % Is preferred) to fill the voids between the coarse aggregates to reinforce the decrease in strength and to provide a lightweight, strong, lightweight prepacked concrete.

Next, the reason for defining the particle diameter of the lightweight coarse aggregate in the present invention as 20 to 50 mm is described.When the particle diameter of the lightweight coarse aggregate exceeds 50 mm, the voids inside the coarse aggregate become large, Since the strength of the material itself decreases, the required strength of concrete cannot be obtained, and also when the coarse bone is thrown into the steel shell, it is difficult to insert it uniformly if the coarse aggregate particle size is large. It must be smaller than 50 mm.

If the particle size of the lightweight coarse aggregate is smaller than 20 mm, it becomes difficult for the injected mortar to penetrate into the coarse aggregate gap. In fact, if the minimum size of the coarse aggregate is 15 mm, the injected mortar will penetrate into the gap of the coarse aggregate, but smaller particles will be generated due to cracking of the aggregate during transportation and loading of the coarse aggregate. Since it is unavoidable to mix in, the minimum size of coarse aggregate should be 20 mm.

By the way, in pre-packed concrete using lightweight coarse aggregate, the following phenomenon occurs when mortar is injected.

When the injection mortar flows between the coarse aggregates, the coarse aggregate is porous and absorbs water, so that the water in the injection mortar is absorbed by the coarse aggregate, resulting in a decrease in the fluidity of the injection mortar. .

Since the coarse aggregate has a lower specific gravity than the injected mortar, the coarse aggregate floats up during the injection of the mortar.

Regarding the above points, there is no particular problem during underwater construction, but the flow gradient becomes large during in-air construction, and in an extreme case, an unfilled portion of mortar may eventually occur. This is dealt with by reducing the pre-wetting of the aggregate or the interval between the injection pipes, and by improving the consistency of the injection mortar (reducing the flow value).

The above point can be dealt with by applying a means for preventing the lifting of the lightweight coarse aggregate to the top end of the coarse aggregate with an expanded metal, a wire mesh or the like by the method of the present invention.

According to the present invention, as described above, it is possible to provide a homogeneous and excellent lightweight prepacked concrete in air or water, and it is possible to perform construction of a composite member for an offshore platform, a precast member for civil engineering, etc. is there.

(Example) Using a general lightweight shale lightweight aggregate having physical properties shown in Table 1 and injected mortars ((A) to (H)) shown in Table 2, the prepacked concrete construction method shown in FIG. Lightweight prepacked concrete for structures was manufactured. First
The figure shows a cross-sectional view of a state in which an outer wall portion of an offshore structure is manufactured by the prepacked concrete construction method of the present invention, and a steel outer shell plate 1 which is a frame (formwork) used in the prepacked concrete construction method and an inner shell Lightweight prepacked concrete is formed in the gap with the shell plate 2.

First, the lightweight coarse aggregate 4 in the hopper 5 is dropped and supplied into the gap between the outer shell plate 1 and the inner shell plate 2 from above. At the time of supply, it is preferable to supply the light weight coarse aggregate 4 while sandwiching the light weight coarse aggregate floating prevention net 3 made of, for example, wire mesh at some stage during the supply, but when the supply is completed, the light weight coarse aggregate layer It is advisable that the top end of the uppermost part is restrained by means of coarse aggregate floating prevention means, such as a net fixed to the formwork (1, 2).

Next, branched mortar supply pipes 7-1, 7-2, 7-3, 7 branched from various points in the middle of the mortar supply pipe 7 hanging from above.
The mortar is injected and filled into the gap portion of the lightweight coarse aggregate 4 in the form (1, 2) by -4. The injection and filling of the mortar are sequentially carried out from the lower branch mortar feed section (7-1) to the upper branch mortar feed pipe (7-2, 7-3, and 7-4). For the supply, the main valve 6 of the branch mortar supply pipe 7 is opened, and then the sub valves 6-1 to 6-3.
Are sequentially opened from below. After injecting the mortar 8 from the 7-1 tube to slightly above the height (H ₁ ) of the 7-2 tube, injecting the mortar 8 from the 7-2 tube, 7-3
Inject mortar 8 to slightly above the height of the pipe (H ₂ ), and in the same manner, place mortar in the formwork (1, 2) for all lightweight coarse aggregates 1
4 Fill and fill the gap. At this time, it is preferable to perform the injection of the mortar 8 by wrapping the injection position, because the effect of preventing the breathing and the laitance which start to occur in each layer is exhibited.

If mortar is injected into the gap of the lightweight coarse aggregate 4, there is a risk that the lightweight coarse aggregate 4 may float above the injection mortar 8 due to the difference in specific gravity, but the lightweight coarse aggregate 4 should be fixed with a net 3 or the like. If so, such a problem does not occur, and homogeneous lightweight prepacked concrete can be easily manufactured.

The resulting lightweight concrete is homogeneous,
Its unit volume weight is 1.51 to 1.62t / m ³ , and its compressive strength is about 300k.
It was a pre-packed concrete with excellent properties at g / cm ² .

Table 1 Physical property particle size of lightweight coarse aggregate Specific gravity Actual volume ratio 20 to 50 mm 1.05 to 1.15 55 to 65% (Effects of the Invention) As described above, according to the present invention, it is possible to easily provide an excellent lightweight concrete by a pre-packed concrete construction method that has never been seen before, and the specific gravity, compressive strength, etc. of the lightweight concrete. The physical properties of are also satisfactory.

In particular, when the present invention is used for constructing an offshore platform, it is very advantageous in terms of easiness of construction and satisfactory physical properties of concrete.

[Brief description of drawings]

FIG. 1 shows a cross-sectional view of a state in which an outer wall portion of an offshore structure is manufactured by the prepacked concrete method of the present invention. 1: Outer shell plate, 2: Inner shell plate, 3: Light weight coarse aggregate floating prevention net, 4: Light weight coarse aggregate, 5: Hopper, 6: Main valve, 6-1, 6-2, 6-3, 6-4: Sub valve, 7: Mortar supply pipe, 7-1, 7-2, 7-3, 7-4: Branched mortar supply pipe, 8: Mortar

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tomio Komine 2-16-1 Kyobashi, Chuo-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Yoshihiro Takekawa 2-16-1 Kyobashi, Chuo-ku, Tokyo Shimizu Construction company (72) Inventor Tetsuro Hori 2-16-1, Kyobashi, Chuo-ku, Tokyo Shimizu construction company (56) Reference JP 61-95164 (JP, A) JP 61- 155561 (JP, A)

Claims (4)

[Claims] 1. A lightweight coarse aggregate having a particle size of 20 to 50 mm is packed in a frame, and a lightweight coarse aggregate floating preventing means is provided at the top end of the lightweight coarse aggregate of the frame, and then high strength mortar is added. A lightweight pre-packed concrete method characterized by pouring into the intervals of lightweight coarse aggregate. 2. The lightweight prepacked concrete construction method according to claim 1, wherein the frame is a steel shell. 3. The lightweight prepacked concrete construction method according to claim 2, wherein the frame is a composite member of an offshore platform. 4. The lightweight prepacked concrete construction method according to any one of claims 1 to 3, wherein the high-strength mortar is continuously injected layer by layer.