JPS6263764A - Reverse casting concrete construction method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a reverse pouring concrete method in which concrete is poured from the top to the bottom.

(Prior art) In the reverse pouring concrete method, it is difficult to make it adhere to the pre-cast concrete at the top because the lower post-cast concrete sinks. Therefore, in most of the reverse pouring methods to date, either the method of injecting grout after the concrete hardens into the gap created at the joint (injection method), or the method of filling the gap with non-shrinkage mortar (filling method). It was dealt with either way.

Both the injection method and the filling method require post-processing after concrete placement, so they are very safe.

This is one of the technical issues that should be improved in terms of economic efficiency. In other words, it is a method that ensures the integration and watertightness of the joint by simply pouring post-cast concrete directly under the pre-cast concrete without any post-treatment as mentioned above (referred to as the direct method). There is a strong desire to develop this, and it has been actively researched.

In the direct reverse concrete method 1 to 1, expanded concrete is used to compensate for settlement and shrinkage after concrete placement. Expandable concrete 1~, which has been considered promising in research to date, is concrete to which aluminum powder is added as an expanding agent.

However, simply adding Alminilla 11 powder to concrete will cause the expansion reaction to begin immediately after pouring and almost end during pouring, making it impossible to eliminate gaps at joints. For this reason, techniques have already been developed for expanding concrete for the reverse pouring method, such as applying surface treatment to aluminum powder so that an effective expansion reaction occurs after pouring. This type of expansive concrete and the reverse concrete construction method using the same are described in detail in, for example, Japanese Patent Application Laid-open Nos. 77065/1982, 135757/1982, and 60650/1980.

(Problem to be solved by the invention) If expanded concrete to which aluminum powder is added (hereinafter treated to delay the expansion reaction unless otherwise specified) is used, ordinary concrete that does not require the use of an expanding agent can be used. Compared to the reverse pouring method using concrete, the gap between pre-cast concrete and post-cast concrete can be made much smaller, and they can be made to stick together almost.

However, even if expanded concrete made of aluminum powder is used, breathing cannot be completely suppressed, and even if pre-cast concrete and post-cast concrete come into close contact with each other due to expansion, a laitance layer due to one reasing is formed between the two. , the adhesive strength was extremely low. Therefore, it has not been a method that can replace the injection method or filling method.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to bring pre-cast concrete and post-cast concrete into close contact, prevent the formation of a laitance layer between them, and ensure sufficient adhesive strength. The object of the present invention is to provide a reverse concrete construction method using a direct method that enables the above-mentioned results.

(Means for Solving the Problems) Therefore, in this invention, aluminum powder whose surface has been treated with IN8 to delay the expansion start time is added as an expansion agent, and a breathing inhibitor such as water-soluble cellulose ether is added. The concrete is placed at least in the part that touches the lower surface of the pre-cast concrete.

(Function) In addition to the aluminum powder swelling agent, a water-soluble cellulose ether breathing inhibitor is added, which not only allows the concrete to expand effectively after pouring, but also increases the viscosity of the concrete and reduces the concentration of the constituent materials of the concrete. Since almost no separation occurs and, as a result, no breathing occurs, the post-cast concrete adheres well to the pre-cast concrete, and no laitance layer is formed.

(Example) Concrete to which the above-mentioned expanding agents and breathing inhibitors have been added need only be poured in the area that contacts the lower surface of the pre-cast concrete, and these expanding agents and breathing inhibitors should be poured in the lower part of the post-cast concrete. It is also possible to pour concrete that has not been added.

Examples of the aluminum powder used as the expansion agent include those with an oxide film formed on the surface to delay the expansion start time (FCl 550), and those with a coating material formed on the surface to delay the expansion start time. Use Chinoku Cellmec) etc.

The appropriate amount of aluminum powder to add varies depending on conditions such as the type of cement used and the construction scale, but an expansion rate of 0.6% or more is required to eliminate gaps in the joints, and for this purpose aluminum powder The amount of addition is about 0.01 to 0.08% based on the weight of cement.

In addition, in order to uniformly disperse aluminum powder in concrete, surfactants (such as Sunflow AD) and cement dispersants for concrete (such as Sunflow P'
Make a suspension of aluminum powder using
Mix this into mortar or concrete.

The addition T of water-soluble cellulose ether as a breathing inhibitor is set to 0.5% (-1ifa ratio) or more of the unit water amount in concrete in order to obtain a sufficient effect. If the amount is less than this, the viscosity of concrete will not increase much due to the addition of water-soluble cellulose ether, and the effect as a breathing inhibitor will not be obtained. Addition of water-soluble cellulose ether changes the expansion characteristics of the concrete due to aluminum powder, so the amount added is determined by taking into consideration the synergistic effect with this.

Various types of cement can be used, such as ordinary Portland cement, Mascon blast furnace Class 8 cement, and Masscon blast furnace Class B cement mixed with fly ash. Coarse aggregate and fine aggregate are added to this as appropriate, and an AE water reducing agent and a fluidizing agent are added as necessary to form a base concrete.

Next, more specific examples of the present invention and comparative test results of strength after construction will be described.

Using four types of concrete, A, B, C, and D shown below, poured concrete specimens having the shapes shown were manufactured. In the figure, 1 is pre-cast concrete, 2 is post-cast concrete, and 3 is a joint.

Concrete A: Only the base concrete in Table 1.

Concrete B: 0.05% (to cement weight M ratio) of aluminum powder (FC1550) is added to base concrete.

Concrete C: Base concrete with 0.5% water-soluble cellulose needle added (ratio of 4 tons to unit water amount).

Concrete D: Base concrete with 0.02% aluminum powder (FCl 550) added and 0.5% water-soluble cellulose ether. However, the fluidizing agent in the base concrete shall be 0%.

Bending strength tests were conducted on specimens using the above four types of concrete. The bending strength test was conducted 4 weeks after pouring concrete 2. For curing, after pouring concrete, it was left in a constant temperature and humidity room under air. In addition, the test was carried out by semi-heating GISA-1106 and loading it at three equal points.

The test results are shown in Table 2 below.

Table 1 (Mixture of base concrete) Table 2 (Bending strength test results) As is clear from the above test results, compared to the case of base concrete alone, B with aluminum powder added as an expanding agent and The strength of all C samples added with water-soluble cellulose ether as a breathing inhibitor was improved.

However, in the case of the embodiment of the present invention using concrete D containing both the above-mentioned expanding agent and the above-mentioned breathing inhibitor,
It has a bending strength about 4 times that of concrete B and C, and the effect of using the above-mentioned expanding agent in combination with the above-mentioned pleasurable agent is clear.

In addition, in the concrete A specimen, gaps due to subsidence of the post-cast concrete were observed, and only the paste was in line contact 1) in the form of veins. The concrete B specimen is 8
There was a small area in the m section where it was not driven in enough, but other than that it was in close contact. The specimen made of Concrete D had a satisfactory appearance (there were no gaps and there was good adhesion).

(Effects of the Invention) As explained in detail above, according to the present invention, aluminum powder subjected to surface treatment to delay the expansion start time is used as an expansion agent, and water-soluble cellulose ether is used as a breathing inhibitor in concrete. By simply adding and pouring, the joint between pre-cast concrete and post-cast concrete will adhere well, and since no laitance layer will be formed at the joint due to breathing, the strength of the joint will be extremely high. , watertightness is also improved.

In other words, the direct reverse concrete construction method can be successfully implemented according to the present invention.

[Brief explanation of the drawing]

The figure is a perspective view of a specimen used in a bending strength test to demonstrate the effects of the present invention. 1... Pre-cast concrete 2...
・・・・・・Post-cast concrete 3・・・・・・・・・Place joint

Claims (1)

[Claims] (1) Concrete made by adding surface-treated aluminum powder to delay the expansion start time as an expansion agent and a breathing inhibitor such as water-soluble cellulose ether is in contact with at least the lower surface of the pre-cast concrete. A reverse concrete construction method characterized by pouring concrete in sections.