JPS63201269A - Method for repairing cracking of concrete - 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 (Field of Industrial Application) 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 due to rainwater. If these cracks extend to the finishing material, it becomes a major problem from an aesthetic point of view. Therefore, the number of cracks that can be noticed when demolding concrete after pouring is 0.2~0.3aw! For large cracks, resin was injected into the cracks, and for other less noticeable cracks, a mortar seal was applied by applying a mortar-based material.

(Problems to be solved by the invention) However, the repair method of injecting resin into cracks requires a large construction process and is not completely effective, and sometimes when demolding concrete formwork, which causes large drying shrinkage. Immediately after, the area adjacent to the repaired area breaks again, and simple methods of sealing the mortar often cause cracks to occur again at the same area. In particular, for a short period of time immediately after concrete is placed, drying shrinkage is severe, and in the case of external walls, atmospheric temperature and humidity changes also act, leading to the growth (expansion) of initial cracks.

Conventional repair methods alone have not been sufficient for such growing cracks.

The present invention has been made in view of the above circumstances, and its purpose is to provide a repair method capable of dealing with a wide range of cracks in concrete, including growth cracks, and in particular to repair subsequent cracks at the construction stage such as formwork removal. To provide a convenient method for repairing cracks in concrete that stops the growth of cracks and prevents cracks in finishing materials.

(Means for Solving the Problems) In order to achieve the above object, the method for repairing cracks in concrete according to the present invention employs blind-like reinforcement in which long carbon fibers with as low elongation rate as possible are assembled vertically and horizontally. A fiber material is prepared, the reinforcing fiber material is applied to the cracks in the concrete, and a hardening high-strength resin adhesive is applied from the surface to the reinforcing fiber material and the cracks.

(Function) High modulus carbon fiber is attached to the cracked concrete surface with adhesive, and this causes carbon tatI! 1 completely integrates with the concrete, forcibly restraining the concrete's behavior and inhibiting the growth of cracks.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front view of a reinforcing fiber material 1 used in the present invention. This reinforcement 41 fiber material 1 is made by bundling a plurality of carbon fiber strands according to the required strength, making them into a certain length, and laying them horizontally at a predetermined interval in the vertical direction. The two sides are connected by two parallel long carbon fibers that connect vertically to create a cage-like structure. For convenience of explanation, the fibers in the horizontal direction are referred to as horizontal fibers 111112, and the FiaM in the vertical direction is referred to as vertical fibers lff3. When using this reinforcing fiber material 1, the reinforcing fiber material 1 is first applied along the cracks 5 of the concrete structure 4, as shown in the side view in FIG. The epoxy resin adhesive 6 is sufficiently applied from the surface thereof, and the epoxy resin adhesive 6 penetrates into the cracks and hardens.

To be more specific 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 (71), the concrete tensile strength is 15 kg/csl, and the length of the crack 5 is 1001. In this case, the limit of the force with which the crack 5 expands is 20 x 15 x 100 = 30.000Kg
It can be estimated that

Therefore, if the cross-sectional area of the weft fiber 2 made of a bundle of 7 carbon fiber strands is 0.77 x 10-2 ci, then if these are arranged in 5-bits, the unit length will be 200 fibers with a unit length of 1001. That is, if the horizontal fibers 2 of 0.77x10-2aI are arranged in 5a+pitch up to 1001, the total cross section f? 4as-0,7
7 x 10-2
K9/cd) is considered to be approximately 20 tons/-, so 20 tons/ai×aS=30.8 tons
become.

A proof stress equivalent to the proof stress 3 Q ton of the crack 5 described 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 material used for reinforcing fiber material 1 forcibly restrains cracks in concrete, so even if the material has a high tensile strength such as glass 1Iff, the elongation rate will be low. High values are inappropriate. From this point of view, vinylon m fibers such as the trade name "Claron" are also inadequate.

Reinforcement! l For the navy blue 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 basket shape according to 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 weft fiber 2 is about 50 #l #1, the width of l II It 3 is several tens of meters, it is wound around a bobbin, and it is cut to the required length on site.

FIG. 4 shows a case where a frame of a rigid frame structure supporting a beam 9 integrated with a floor slab 8 on a pillar 7 has a wall 10, and a frontage 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 the finishing material 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.

(Effects) As described in detail below, the concrete crack repair method of the present invention prepares a reinforcing fiber material made of carbon fibers in the form of blinds, and uses this as a restraining material for the cracked part. The agent has a wide area of adhesion and does not cause slippage due to deterioration of adhesion like embedded reinforcing bars.

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.

Further, since the reinforcing fiber material can be easily cut with scissors, it is easy to process and is light and easy to handle. Since the carbon fibers are simply pasted 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.

[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. 1... Reinforcing fiber material 2... Horizontal fiber 3... Vertical fiber M 4... Concrete structure 5... Cracking 6... Epoxy resin adhesive 7... Column
8... Floor slab 9... Beam
10...Wall 11...Opening

Claims (1)

[Claims] A blind-shaped reinforcing fiber material made of long carbon fibers with the lowest possible elongation rate arranged vertically and horizontally is prepared, the reinforcing fiber material is covered with cracks in the concrete, and the reinforcing fiber material and the cracks are exposed from the surface of the reinforcing fiber material. A concrete crack repair method characterized by filling and applying a hardening high-strength resin adhesive to the cracks.