JPS5952022A - Construction of underwater concrete structure - Google Patents

Abstract

PURPOSE:To maintain the strength of underwater concrete as well as to prevent the occurrence of pollution by a method in which concrete mixed with a thickening agent is placed and concrete without thickening agent is placed below said concrete. CONSTITUTION:A formwork 2 is erected on the foundation 1 to an extent that the upper end of the formwork 2 is slightly exposed from the water surface 3, and a concrete 5 mixed with a thickening agent is placed on the formwork 2 through a tremie tube 4. The tip 7 of the tremie tube 4 is pierced through the concrete 5 and then concrete 6 containing no thickening agent is placed through the tremie tube 4. The resistance of the concrete 5 containing thickening agent against shearing deformation is increased, and therefore, the blow-out of the concrete 6 through the concrete 5 toward the upper part is avoided and the pillar of ordinary concrete 6 can be placed below the viscous concrete 5 having nearly uniform thickness.

Description

[Detailed Description of the Invention] This invention provides an underwater conc IJ with excellent quality and high reliability.
- This relates to a method of constructing a structure.

When constructing a concrete structure underwater, in a river, or in muddy water, when concrete is poured using a tremie pipe, etc., the concrete that is in contact with the water is washed away by the water, and the cement is separated from the concrete and released into the water. This has the disadvantage that the strength of the part is extremely weakened, making the concrete structure unreliable.

In this case, not only the surrounding water area was polluted by the cement dissipated into the water, but also, if there was a fishing area in the surrounding area, a fishing compensation problem occurred, making concrete work extremely difficult.

In addition, if ready-mixed concrete is to be cast in muddy water, such as a 4'1 pile, the strength of the upper part of the concrete that is washed away by water will decrease, so the 50cnL~100cyrt than the height from the edge
It is necessary to pour extra concrete and then chisel off the excess concrete after the concrete has hardened. This chiseling work generates noise, dust, and other pollution, making work in urban areas extremely difficult. was.

Recently, a method has been published to reduce the above-mentioned problems by imparting viscosity to concrete using an admixture and giving the cement the property that it does not separate and escape even in water (Japanese Patent Application Laid-Open No. 57-1991).
However, such thickening agents are generally extremely expensive, and their price is comparable to or higher than that of concrete, so they are not effective in improving the quality of concrete in water. However, it was rarely used in cases where large volumes of concrete were to be poured. In addition, when concrete containing such a thickening agent is placed by free-falling into water, the individual lumps of concrete do not adhere well, so the concrete structure as a whole may be defective. There were some drawbacks that were easy to develop.

This invention overcomes these drawbacks and
The purpose of this invention is to provide a method for constructing concrete structures that has high strength, does not cause pollution, and does not require high costs even if thickeners are used.

This invention is based on the fact that the addition of a thickening agent to fresh concrete has extremely high resistance to shear deformation as a mechanical property; in other words, concrete containing a thickening agent simply has high adhesion between particles. This was done as a result of the discovery that the whole concrete has the property of resisting shear deformation as a whole, and it is possible to cast concrete with a thickening agent added and then pour concrete without adding a thickening agent below it. The present invention relates to a method for constructing an underwater concrete structure in which concrete to which the thickening agent has been added can be uniformly pushed up as a whole by its large resistance to shear deformation.

Next, the construction method of this invention will be explained.

As shown in Figure 1, a mold frame 2 is placed on a base 1 with the upper end facing the water surface 3.
Place the tremie tube 4 in the mold.
Concrete 5 to which a thickening agent has been added is poured. The thickness of the concrete to which this thickening agent has been added is preferably 30 cm or more, preferably 50 cm or more. If this thickness is too thin, this layer will be pierced by the concrete that is subsequently cast below without the addition of a thickening agent, making it impossible to achieve the intended purpose, and must be avoided. .

In this work, if two or more delivery pipes such as tremie pipes and concrete pumps are installed and concrete is placed in parallel, the area to be poured for each tremie pipe, etc. is 30 tons.
T? 2 or less is desirable.

If the pouring area exceeds 50 mm, there is a possibility that the lower concrete without the addition of a thickening agent will break through the upper concrete with the addition of a thickening agent and eject upwards, which must be avoided.

Next, as shown in Fig. 2, the tip 7 of the tremie pipe or concrete pump penetrates the concrete 5 to which a thickening agent has been added and is below it, and concrete 6 to which no thickening agent has been added is poured. However, while pouring concrete 6, be sure to place the tip 7 of the delivery pipe, such as a tremie pipe, on the concrete 6.
It must be ensured that it reaches this layer. If it is poured in this way, the concrete 6 will be placed at the tip 7 of the delivery pipe.
Even if the concrete 5 with the addition of two parts thickening agent tries to rise with uneven thickness after being delivered from the concrete 6, its resistance to shear deformation is extremely high.
The pillars of ordinary concrete 6 can be installed at the bottom of the viscous concrete 5 which has a substantially uniform thickness without breaking through the concrete 5 and spouting out into two parts.

In the above case, a plasticizer (highly condensed doria-syn compound) or 11-1 water reducer c is added to concrete to which a thickening agent has been added.
Cooperation 11 when adding calcium lignin sulfonate)
Immediately after, the fluidity of concrete is significantly improved, but 30
After more than a minute has passed, the effect gradually decreases. In other words, the concrete 5 to which the thickening agent has been added (delivered from a delivery pipe such as a tremie pipe) flows easily and spreads horizontally, but when it is pushed up from the concrete 6 at the bottom, it has little fluidity. Therefore, the concrete 6 at the bottom is the concrete 5 with the thickening agent added.
This is extremely effective in preventing intrusion into the 0 layer.

Examples of the present invention are as follows. Example 1 A construction method of the present invention and a conventional method of pouring ordinary concrete using a tremie pipe on a concrete pile at a location tx with a diameter of 120 cm and a length of 20 m. We applied these methods and compared their effects. The mix of concrete is as shown in Table 1. Polyacrylamide partial hydrolyzate (12% by weight of cement) is added as a thickening agent, and glutaraldehyde (1% of polyacrylamide partial hydrolyzate) is added as a thickening agent.
) is added to concrete.1. After Ot & pouring,
Pile A was made by pouring ordinary concrete down to the pile length, and pile B was made by pouring ordinary concrete over the entire length.

43 days after concrete was placed, a core with a diameter of 10cm and a length of 2m was extracted vertically from the pile head, and a cylindrical specimen with a length of 20cm was cut from it, and a compressive strength test was conducted 46 days after concrete was placed. Ta. The results are shown in Table ≠.

Ordinance Table *- indicates that it is impossible to collect specimens In the construction method of this invention, as is clear from Table →
No deterioration in compressive strength was observed except at a position 15 Cr/L from the top. On the other hand, in conventional construction methods,
Deterioration was observed up to 55 cm at the top. According to this embodiment, the Mononoke according to the present invention has an upper part of only 15C〃L.
It was confirmed that the quality of the concrete was poor only at ~20 cm, but the quality below that was good. In the conventional construction method, 80 crn of concrete was removed from the top of the pile, but according to the present invention, it has become clear that the excess volume on the pile cap can be significantly reduced.

Example 2 Bottom surface 6.27? A rectangular parallelepiped unreinforced concrete structure measuring 6.2 m in length and 12 ffL in height was built in water by removing the top 80 cm using the construction method of the present invention, and the state of cement dissipation was examined.

This structure was constructed by using two concrete pumps with booms and adding 1.5% by weight of polyethylene oxide as a thickening agent to the cement, resulting in a slump of 22. Octn concrete
40tt for F? Slun 7°18 without subsequent addition of thickening agent after pouring. oCnL conch IJ) was poured. As a result, the finished product after removing the mold frame was perfect, and there was no evidence that the cosiclete had been washed out by the water.

As a thickening agent, substantially the same effect can be obtained by using a polyacrylamide-based polymer compound with an alkali metal or alkaline earth metal hypochlorite or hypobromite added, or a water-soluble cellulose derivative. I was able to give you

In this invention, as described above, a thickening agent is added to the concrete, so even if the concrete is placed in water, the cement will separate and escape into the water, causing feces.

Not only does it not reduce the strength of the cleat, but it also does not cause water pollution. Further, in the case of cast-in-place piles, there is no need to lift off much of the upper end, and the noise and dust generated thereby can be reduced.

Moreover, according to this invention, the strength of the structure is sufficiently maintained even though concrete with added thickening agent is used only in a part of the upper end of the structure, so adding expensive thickening agent is not necessary. Therefore, it is possible to use viscous concrete that works effectively at a low cost, and it is not possible to create viscosity using tremie pipes, concrete topsif 0, etc. This has the excellent effect of not having any

[Brief explanation of the drawing]

The drawings show an example of the method for constructing an underwater concrete structure according to the present invention.
Fig. 2 is a side sectional view showing the casting situation of concrete IJ + with a thickening agent added thereto. 1...Foundation, 2...Mold frame, 3...Water surface, 4...
- Tremie pipe, 5... Concrete with added thickening agent, 6... Concrete without adding thickening agent, 7...
Tip of the tube. Patent Applicant Takenaka Construction Co., Ltd. (and 2 others) Representative Patent Attorney Kiyoshi Sakai 1 Figure 2 8-21-1 Ginza, Chuo-ku, Tokyo ■Applicant Sankyo Kasei Kogyo Co., Ltd. Chuo-ku, Tokyo Ginza 3-9-19

Claims (1)

[Scope of Claims] 1. A method for constructing an underwater concrete structure, in which concrete to which a thickening agent has been added is poured, and concrete to which no thickening agent is added is placed below the concrete so as to push up the concrete. 2. Concrete with a thickening agent added is poured to a thickness of 30 cm or more, and concrete without a thickening agent is delivered to the lower part of the concrete using a delivery pipe.
Construction method of underwater concrete structure described in section. 3. The thickening agent is a polyacrylamide-based polymer compound or l? 3. The method for constructing an underwater concrete structure according to claim 1 or 2, wherein ethylene oxide is used. 4. The method for constructing an underwater Funkrete structure according to claim 1 or 2, wherein the thickening agent is a polyacrylamide-based polymer compound with dialdehyde added. 5. Claims 1 or 2, wherein the thickening agent is a polyacrylamide-based polymer compound to which hypochlorite or hypobromite of an alkali metal or alkaline earth metal is added. construction method for underwater concrete structures. 6. The method for constructing an underwater concrete structure according to claim 1 or 2, wherein the thickening agent is a water-soluble cellulose derivative. 7. Claim 1 or 2 in which a fluidizing agent or a water reducing agent is added to the concrete IJ with a thickening agent added.
Construction method of underwater concrete structure as described in section.