JPS6312968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for forming a protective film for protecting concrete and internal reinforcing bars of a concrete structure.

[Prior art]

Concrete structures are generally manufactured by assembling a formwork, arranging reinforcing reinforcing bars inside the formwork, and then pouring concrete into the formwork.

Concrete is strong against compressive loads, and because the internal reinforcing steel supports tensile and bending loads, it has considerable strength against external forces. However, the strength against temperature differences caused by weather, rainwater, seawater, etc. is insufficient, and the durability is particularly markedly reduced in the case of coastal and underwater structures.

The biggest cause of this decrease in durability is the porosity of concrete, which allows moisture to penetrate through the surface and corrode the reinforcing steel inside the concrete. Normally, concrete is alkaline, so oxidative corrosion of reinforcing bars is largely suppressed, but when moisture penetrates into the concrete, carbon dioxide gas in the air neutralizes the concrete, eliminating the anti-corrosion effect mentioned above. In addition, in cold regions, water in concrete freezes, causing damage to the concrete. Furthermore, since the coastal and underwater structures are affected by sea breeze, spray, and seawater in addition to the above-mentioned weather, corrosion of concrete and reinforcing steel is further accelerated.

Conventionally, methods of improving the concrete itself and methods of post-treatment have been adopted as measures to eliminate the above-mentioned drawbacks. The former is a method in which an aqueous vinyl solution or the like is mixed into the concrete or mortar to impart corrosion resistance to the concrete.General concrete is used inside the structure, and this corrosion-resistant concrete is used only on the outside. However, using this method does not change the porosity of the concrete, so it cannot completely prevent water from penetrating through the pores. Particularly in the case of seawater, the content of magnesium sulfide, magnesium chloride, and ammonium bicarbonate is high, so a certain degree of corrosion-resistant concrete cannot cope with the problem.

On the other hand, post-treatment methods for concrete include those using paint and coating with water-impermeable and corrosion-resistant materials. However, paints generally have a thin coating and cannot maintain concrete protection for a long period of time, and in the case of underwater structures, only special paints can be used, and in addition, underwater painting is difficult.

In addition, rubber lining, asphalt, synthetic resin, glass, etc. are used as coating materials, but these have the same problems as painting, such as high cost and difficulty in underwater work.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a method for forming a protective film for concrete structures that is easy to construct and has high durability.

[Summary of the invention]

In order to achieve the above object, the present invention applies an impermeable and corrosion-resistant protective material to the inner surface of the formwork before filling the formwork with concrete, and when the poured concrete hardens and the formwork is removed. A protective film is formed on the concrete surface.

[Embodiments of the invention]

FIG. 1 is a perspective view showing an embodiment in which a support column 1 of a pier is covered with concrete. Normally, a pier is constructed by driving a plurality of steel pipe supports 1 into the sea, passing a steel material (not shown) over the top of each support to form an upper concrete 2, and each support support 1 is also covered with concrete.

For concrete pouring work, first, a plurality of steel members 3 are assembled around the pillar 1 to secure a foothold for the workers. Although only one set of steel members is shown in the figure, multiple sets of these steel members are normally installed above and below as necessary.

A plurality of reinforcing bars 4 are fixed to the outer surface of the column 1, and the reinforcing bars 4 serve to improve the tensile and bending strength of concrete. The reinforcing bar 4 in this embodiment has a large number of bolt studs 4a radially welded to the outer surface of the column 1, but when a plurality of columns 1 are connected, it is necessary to cover all the columns as shown in FIG. A grid-like reinforcing bar 5 is used.

Next, the support 1 is covered with a rectangular cylinder-shaped formwork 6, and the bottom of the formwork 6 is sealed with a seal (not shown). The formwork 6 may be a wooden frame or a metal frame, but a divisible metal frame is often used for pouring work such as piers.

When concrete is made into a square shape as shown in FIG. 1, it is desirable to attach face plates 7 to the four corners of the formwork 6 so that the formwork 6 can be easily removed after the concrete hardens. If there is a possibility that the inner surface of the formwork 6 may adhere to the concrete, a release agent 8 is applied to the inner surface of the formwork 6 as shown in FIG. 3A.

Conventionally, the formwork 6 is filled with concrete at this stage, but in the present invention, a water-impermeable and corrosion-resistant protective material is applied to the inner surface of the formwork 6 to form a protective film 9. This protective film 9 is applied to the formwork 6 or the mold release agent 8.
The material should be lightly attached to the inner surface of the material, preferably water-impermeable and breathable. Protective film 9
The material may be any material as long as it has both water impermeability and corrosion resistance, and adhesive tapes, films, and other resins can be used.

After forming the protective film 9, concrete 10 is filled into the space between the formwork 6 and the pillars 1 and solidified. After the concrete 10 hardens, the formwork 6 is removed as shown in FIG. 3B, and the entire surface of the concrete 10 is covered with the protective film 9. It is desirable to use double-sided adhesive tape or the like for the protective film 9 so that the formwork 6 side has a weak adhesive force and the concrete 10 side has a strong adhesive force.

With this configuration, all of the many fine pores on the surface of the concrete 10 are closed, leaving no room for seawater to penetrate. Furthermore, since this protective film is formed at the same time as the concrete pouring work, the work is extremely easy compared to conventional painting and lining.

Figure 4 shows the pier supports after concrete pouring. In the case of the connecting steel pipe shown in FIG. 2, the protective film can be formed in exactly the same manner. Protective film 9 and concrete 10
If the adhesion between them is sufficient, the face wood 7 shown in
Even if it is removed, it will not cause much trouble in removing the formwork 6.

In the above embodiment, a rectangular cylinder-shaped mold was used, but a cylindrical mold can also be used.
Furthermore, it can be fully applied to general concrete structures, and post-treatment painting work can be omitted.

〔Effect of the invention〕

As mentioned above, in the present invention, before filling the formwork with concrete, an impermeable and corrosion-resistant protective material is applied to the inner surface of the formwork, and when the poured concrete hardens and the formwork is removed, the concrete Since the protective film is formed on the surface, the construction is easy and a highly durable protective film can be obtained.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the construction state of the formwork, Figure 2 is a perspective view of the connecting support, Figures 3A and B are sectional views showing the construction state, and Figure 4 shows the pier after concrete pouring. It is a simplified front view. 1... Pier support, 4, 5... Rebar, 6... Formwork, 8... Mold release agent, 9... Concrete protective film,
10...Concrete.

Claims (1)

[Claims] 1 A method for forming a protective film for a concrete structure in which a formwork is assembled, reinforcing bars are placed, and concrete is poured into the formwork and solidified, the method comprising applying an impermeable and corrosion-resistant protective material to the inner surface of the formwork before filling with the concrete. A method for forming a protective film for a concrete structure, the method comprising applying a coating.