JPH0645969B2 - Crack control method for reinforced concrete - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for suppressing cracking of reinforced concrete by increasing the adhesion strength with reinforced concrete and suppressing cracking of concrete.

<Prior art> Reinforced concrete structures are expected to have an adhesive force between reinforcing steel and concrete in terms of crack resistance and deformation control. However, the current situation is that the adhesive force between the reinforcing bar interface and concrete becomes weak due to insufficient compaction or the tendency of breathing settling by soft concrete to satisfy a large amount of concrete driving plan for the purpose of improving productivity. Was becoming.

<Problems to be solved by the invention> When the adhesive strength between the reinforcing bar and the concrete is low, between the reinforcing bar and the concrete that should suppress cracks in the crack portion of the concrete caused by drying shrinkage, temperature deformation, etc. The slip occurs, and the crack width expands.

In particular, when the structure in which the crack is generated is a wall, the described tendency is strongly exhibited. Further, it is difficult to recover the adhesive force between the concrete and the reinforcing bars by the post-treatment of injecting the epoxy resin after the cracks have been generated in the concrete, or it is difficult to firmly adhere them. New cracks often occur near the repaired part.

The present invention has been made in view of the above circumstances, and its purpose is a place where the adhesion strength with the reinforced concrete is particularly important when constructing a reinforced concrete structure, that is, the adhesion between the rebar and the concrete at specific locations where cracks are likely to occur. It is another object of the present invention to provide a method for suppressing cracking of reinforced concrete, in which the strength is compensated, or the adhesive strength of a portion where voids are likely to be formed at the lower end of the reinforcing bar due to concrete settling during pouring is previously compensated.

<< Means for Solving Problems >> In order to achieve the above object, the method for suppressing cracking of reinforced concrete according to the present invention includes a lower surface position of the reinforcing bar which is intended to secure the adhesive strength between the reinforcing bar and the cast concrete in advance. An injection pipe that leads to the concrete, and then concrete is poured into it, and after this concrete has hardened to some extent, and at an early time when shrinkage cracks do not occur, an adhesive with concrete and rebar as an adherend is applied from the injection pipe to the rebar bottom. Inject and fill the edges.

<Action> After pouring, concrete continues to dry and shrink while hardening and reaching an equilibrium state with the humidity of the outside air. At that time, a void is generated around the reinforcing bar, or a void is generated at the interface of the reinforcing bar due to concrete settling phenomenon immediately after placing or breathing, but the adhesive can be injected into this void by an injection pipe or press-fitted. Therefore, the bond strength between the reinforcing bar and the concrete is ensured, and the integrity with the reinforced concrete is guaranteed.

That is, since the reinforcing bar can adhere the entire surface to the surrounding concrete by eliminating the void portion together with the adhesive force by the adhesive, the capability of the reinforcing bar can be sufficiently transmitted to the concrete.

<Example> Hereinafter, a preferred example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a deformed rebar 1 arranged horizontally. This is the same for the round rope, and although the cracking phenomenon caused by sliding with concrete is completely different, the adhesive force remains the same because it is an important issue.

In such a horizontally arranged reinforcing bar 1, defects such as a water film and voids are formed on the lower surface of the reinforcing bar due to concrete settling and breathing, which greatly affects the bond strength. Further, even when the reinforcing bars 1 are arranged in the vertical direction, air bubbles are generated due to concrete settling on the lower surface of the nose of the deformed reinforcing bars, so that the adhesion rigidity varies depending on the direction in which the reinforcing bars are pulled. The measures may be applied by the same method as in the embodiment.

Reinforcing bar 1 is a horizontal wall bar, and if you rebar this,
An injection pipe 2 is arranged so as to communicate with the lower surface from the outside. The injection pipe 2 may be a vinyl tube having an inner diameter of about 0.5 mm. This is installed at a pitch of about 1 m.

After that, concrete 3 is driven in. Although extremely extreme, the lower surface of the reinforcing bar 1 sinks with the lapse of time after driving, and a slight gap 4 is formed.

After the concrete is poured, the adhesive 5 is injected into the lower surface of the reinforcing bar by the injection pipe 2 at a relatively early time (around one month) when shrinkage cracks do not yet occur.

The adhesive is preferably an epoxy resin adhesive whose hydroxyl group effectively acts on the bond with concrete. Unsaturated polyester resin adhesives are not desirable for concrete immediately after pouring.

FIG. 2 shows the case of the opening 6 of the window provided in the wall, but the injection pipes 2'for injecting the adhesive 5 along the reinforcing bar 7 of the opening are arranged at a constant interval in the horizontal direction and in the vertical direction. Is located at a slightly higher position.

The adhesive 5 is injected from this injection pipe 2 '. Adhesive 5
When is hardened, the reinforcing bars 1 and 7 and the concrete 3 are also firmly adhered to each other through the adhesive 5 also in the gap 4.

<Effect> As described in detail above, according to the crack suppressing method of the reinforced concrete according to the present invention, the injection pipe leading to the lower surface position of the reinforcing bar for ensuring the adhesive strength is arranged in advance to dispose the concrete. Since the adhesive is injected from the injection pipe after driving and waiting for a certain curing period, it has the effect of positively increasing the adhesive force with the reinforced concrete and suppressing the occurrence and expansion of cracks which are a problem in concrete structures. In addition, synthetic resin adhesives generally block moisture after curing, so by selecting an adhesive that blocks moisture after curing, the effect of suppressing corrosion of reinforcing bars can be obtained, and cracks do not easily grow and expand in reinforced concrete structures. You can provide things.

[Brief description of drawings]

1 (a) is a cross-sectional view for explaining the present invention, FIG. 1 (b) is an end view taken along the line AA of FIG. 1 (a), and FIG.
The figure is a side view of the wall opening. 1 ... Horizontally arranged rebar, 2 ... Injection pipe 3 ... Concrete, 4 ... Gap 5 ... Adhesive, 6 ... Opening 7 ... Reinforcing bar

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Koyanagi 4-640 Shimoseito, Kiyose-shi, Tokyo Inside Obayashi Technical Research Institute Co., Ltd. (56) References JP-A-56-22687 (JP, A)

Claims (1)

[Claims] Claims: 1. An injection pipe leading to the lower surface of the reinforcing bar is arranged in advance to ensure the adhesive strength between the reinforcing bar and the cast concrete, and then the concrete is driven in and after the concrete has hardened to some extent, it shrinks. A method for suppressing cracking of reinforced concrete, comprising pouring and filling an adhesive having the concrete and the rebar as an adherend from the pouring pipe to the bottom edge of the rebar at an early stage when cracking does not occur.