JPH0458870B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a method for repairing cracks in concrete that occur immediately after demolding a concrete form.

<<Conventional technology>> Cracks in reinforced concrete exterior walls not only impair the aesthetic appearance, but also cause water leakage caused by rainwater. If these cracks extend to the finishing material, it becomes a major problem from an aesthetic point of view. Therefore, the cracks that can be detected when demolding after pouring concrete are 0.2 mm or more.
For cracks as large as 0.3 mm, resin was injected into the cracks, and for other less noticeable cracks, mortar sealing was performed by applying a mortar-based material.

≪Problems to be solved by the invention≫ However, the repair method of injecting resin into the cracks requires a large amount of construction work, but is not completely effective, and sometimes the drying shrinkage is large when demolding the concrete form. Immediately after, the area adjacent to the repaired area broke again, and the simple method of sealing with mortar often caused cracks to occur again at the same area. In particular, during the short period immediately after concrete is poured, drying shrinkage is severe, and in the case of external walls, atmospheric temperature and humidity changes also act, causing initial cracks to grow (expand).
accompanied by. Conventional repair methods alone are not sufficient for such growing cracks.

The present invention was made in view of the above circumstances, and its purpose is to provide a repair method capable of dealing with a wide range of concrete cracks, including growth cracks.
It is an object of the present invention to provide a convenient method for repairing cracks in concrete, which stops the subsequent growth of cracks and prevents cracks in finishing materials, especially during the construction stage such as demolding of formwork.

<Means for Solving the Problems> In order to achieve the above object, the concrete crack repair method according to the present invention prevents concrete cracks from expanding due to drying shrinkage or temperature changes immediately after demolding the formwork. In a method for repairing cracks in concrete that suppresses cracks, first, long carbon fibers with a small elongation rate are used as vertical fibers and horizontal fibers, and multiple horizontal fibers are strung between a pair of vertical fibers, so that the long carbon fibers are Next, the reinforcing fiber material is inserted into the crack so that the horizontal fibers are along the spreading direction of the crack and the vertical fibers are along the elongation direction of the crack. Then, a curable high-strength resin adhesive is applied to the reinforcing fiber material while filling the cracks from the surface of the reinforcing fiber material to integrate the reinforcing fiber material into the concrete. It is characterized by

≪Operation≫ A reinforcing fiber material made of long carbon fibers with a low elongation rate is attached to the concrete surface with cracks using a hardening high-strength resin adhesive, and this causes the long carbon fibers to By completely integrating with the concrete, it is possible to forcibly restrain the behavior of cracks in the concrete and inhibit the growth of cracks. Specifically, the reinforcing fiber material is constructed in a blind shape by assembling long carbon fibers vertically and horizontally, and the horizontal fibers extend in the direction of crack spread. By covering the crack with the vertical fibers along the direction in which the crack stretches, the tensile strength of the horizontal fibers can suppress the expansion of the crack, and the tensile strength of the vertical fiber can suppress the expansion of the crack. Therefore, it is possible to effectively suppress cracking of a concrete structure that undergoes severe drying shrinkage immediately after demolding the formwork.

<<Example>> Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 to 3.

FIG. 1 is a front view of a reinforcing fiber material 1 used in the present invention. This reinforcing fiber material 1 is made by bundling a plurality of carbon fiber strands according to the required strength to form long carbon fibers with a small elongation rate. A plurality of carbon fibers are laid out at a predetermined interval, and these are connected with two other parallel long carbon fibers that vertically connect the left and right sides of each fiber to form a screen-like structure. For convenience of explanation, the fibers in the horizontal direction are referred to as horizontal fibers 2, and the fibers in the longitudinal direction are referred to as vertical fibers 3. When using this reinforcing fiber material 1, as shown in FIGS. 2 and 3, first, the horizontal fibers 2 are moved along the cracks 5 of the concrete structure 4, specifically in the direction in which the cracks 5 spread. ,
So that the vertical fibers 3 are along the direction of extension of the crack 5,
The reinforcing fiber material 1 is applied and covered. The epoxy resin adhesive 6 is sufficiently applied from the surface thereof, and the epoxy resin adhesive 6 penetrates into the cracks 5 and hardens.

To explain more specifically with reference to FIG. 3, the reinforcing fiber material 1 is determined in principle as follows.

Assume that the wall thickness of the concrete structure 4 is 20 cm, the concrete tensile strength is 15 Kg/cm ² , and the length of the crack 5 is 100 cm. In this case, the limit of the force with which the crack 5 expands can be estimated to be 20 x 15 x 100 = 30000 kg.

Therefore, if the cross-sectional area of the horizontal fiber 2, which is a bundle of seven carbon fiber strands, is 0.77×10 ^-2 cm ² , then this is 5 mm.
If arranged in pitches, there will be 200 pieces with a unit length of 100 cm. In other words, horizontal fibers 2 of 0.77×10 ^-2 cm ² are arranged at a pitch of 5 mm.
When lined up to 100cm, total cross-sectional area as=0.77×10 ^-2 ×
200= ^1.54cm2 .

At this time, if PAN-based high modulus carbon fiber is used, its tensile strength (Kg/cm ² is approximately
Considering 20ton/cm ² is sufficient, so 20ton/cm ² ×as=
It will be 30.8 tons.

A proof stress equivalent to the 30 ton proof stress of the crack 5 mentioned above is ensured, and cracks will not occur again at least at this position. However, it is a prerequisite that the epoxy resin 6 used as the adhesive does not slip.

If cracking does not occur again at this location, there remains a risk that cracking will occur at other locations after a certain period of time after concrete is poured. However, unlike during construction, such as immediately after the formwork is removed, cracks that occur due to tensile stress due to drying shrinkage and temperature changes, like the cracks during construction described above, have a very small degree of expansion and growth, thus destroying the finished material. It's not that big of a deal, so it's not really a problem.

As mentioned above, the fibers used for the reinforcing fiber material 1 are forcibly restraining cracks in concrete, so even if they are materials with extremely high tensile strength, such as glass fibers, they have a high elongation rate. is inappropriate. From this point of view, vinylon fibers such as the trade name "Claron" are also inadequate.

For the reinforcing fiber material 1, select the material and the cross-sectional area of the horizontal fibers and vertical fibers according to the concrete structure to which it is applied, and the width and length when made into a blind shape depending on the length and shape of the crack. All you have to do is decide. It is convenient to form it into a larger size in advance and cut it as necessary for use. The width of the horizontal fiber 2 is approximately 50 mm,
A length of several tens of meters of vertical fiber 3 is wound around a bobbin and cut to a required length on site.

Figure 4 shows a beam 9 integrated with a column 7 and a floor slab 8.
A case is shown in which a wall 10 is attached to a framework of a rigid frame structure that supports a frame, and an opening 11 for a window is formed in the wall 10. Cracks 5 are likely to occur at the corners of openings 11, etc., and if cracks occur before installing or applying finishing materials after demolding the formwork, apply a primer along the cracks 5. Then, the reinforcing fiber material 1 is applied, and the epoxy resin adhesive 6 is filled and applied from the surface thereof. Finally, after the epoxy resin adhesive 6 has hardened, the work is completed by protecting it with mortar or the like to prevent the adhesive from deteriorating.

As described in detail above, since a reinforcing fiber material made of carbon fibers is prepared and used as a restraining material for cracked parts, the adhesive adhesion area is wide, and slippage caused by deterioration of adhesion like embedded reinforcing bars is possible. does not occur. For example, with the conventional technique of injecting epoxy resin into a cracked area, cracks may occur again in the vicinity, and this is also due to the fact that the adhesion to the reinforced concrete is already incomplete and the adhesion has loosened. Compared to just one, it is quite effective. In addition, the reinforcing fiber material can be easily cut with scissors, so
It is easy to process, lightweight, and easy to handle. Since the carbon fibers are simply attached with a hardening high-strength resin adhesive, there is no risk of oxidative corrosion, and there is no problem of rust when used on the outer surface of cracked concrete. Carbon fiber has a low elongation rate and exhibits sufficient power to suppress the growth and expansion of cracks, making it effective for repairing cracks in concrete structures that are subject to severe drying shrinkage after demolding. There is.

≪Effects≫ The concrete crack repair method of the present invention has the following effects:
To prevent concrete cracks from expanding due to drying shrinkage and temperature changes immediately after demolding the formwork,
First, long carbon fibers with a low elongation rate are used as vertical fibers and horizontal fibers, and multiple horizontal fibers are strung between a pair of vertical fibers to prepare a blind-shaped reinforcing fiber material in which these long carbon fibers are arranged vertically and horizontally. Next, the reinforcing fiber material is covered with the crack so that the horizontal fibers are along the direction of crack expansion and the vertical fibers are along the direction of extension of the crack, and then a curable high-strength resin adhesive is applied. By filling cracks from the surface of the reinforcing fiber material and applying it to the reinforcing fiber material, the reinforcing fiber material is integrated into the concrete, so a reinforcing fiber material made of long carbon fibers with a low elongation rate is assembled in a blind shape. is attached to the cracked concrete surface with a hardening high-strength resin adhesive, which allows the long carbon fibers to completely integrate with the concrete and forcibly restrain the behavior of cracks in the concrete. , can inhibit the growth of cracks. In particular, the reinforcing fiber material is constructed in a blind shape by assembling long carbon fibers vertically and horizontally in a vertical and horizontal manner. By covering the crack along the elongation direction of the crack, the tensile strength of the horizontal fibers can suppress the expansion of the crack, and the tensile strength of the vertical fiber can suppress the elongation of the crack. Therefore, it is possible to effectively suppress cracks in a concrete structure that undergoes severe drying shrinkage immediately after demolding the formwork.

[Brief explanation of the drawing]

FIG. 1 is a front view of the reinforcing fiber material, FIG. 2 is a side view when the method of the present invention is implemented, FIG. 3 is a perspective view thereof, and FIG. 4 is a front view showing another embodiment. DESCRIPTION OF SYMBOLS 1... Reinforcement fiber material, 2... Horizontal fiber, 3... Vertical fiber, 4... Concrete structure, 5... Cracks, 6... Epoxy resin adhesive, 7... Column, 8...
...floor slab, 9...beam, 10...wall, 11...opening.

Claims (1)

[Claims] 1. In a concrete crack repair method for preventing concrete cracks from expanding due to drying shrinkage or temperature changes immediately after demolding the formwork, first, long carbon fibers are used as vertical fibers and horizontal fibers. ,
A reinforcing fiber material in the form of a blind is prepared by crossing a plurality of horizontal fibers between a pair of vertical fibers, and then the reinforcing fiber material is prepared such that the horizontal fibers have the above-mentioned cracks. The longitudinal fibers cover the cracks along the extending direction of the cracks, and then a curable high-strength resin adhesive is filled into the cracks from the surface of the reinforcing fiber material. A method for repairing cracks in concrete, which comprises applying the reinforcing fiber material to the concrete to integrate the reinforcing fiber material into the concrete.