JPH11148233A - Reinforcing method for reinforced concrete structure of tough resin frp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reinforcing method for a reinforced concrete of tough resin FRP, capable of restricting the separation of a FRP sheet from the concrete surface and improving the bending resistance of the reinforced concrete structure after reinforced. SOLUTION: A carbon fiber sheet is impregnated with tough resin, as impregnating resin, which has an elastic modulus of 1500-2700 Mpa in hardening and an elongation of 2% or more in a time from stress yielding up to rupture after yielding to form a FRP sheet. The sheet is adhered to the concrete surface of a reinforced concrete structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reinforcing fiber sheet impregnated with a tough resin having a specific range of elastic modulus and elongation after yield as an impregnating resin, that is, a tough resin FR.
The present invention relates to a method for reinforcing a reinforced concrete structure by using a tough resin-based FRP, which uses a sheet of P (fiber reinforced plastic) to improve the bending strength of the reinforced concrete structure and has an excellent reinforcing effect.

[0002]

2. Description of the Related Art Epoxy resin F which is a representative of tough resin
The method of reinforcing a reinforced concrete structure by RP has been popular as an effective method of seismic reinforcement in recent years. This reinforcing method is based on an epoxy resin F obtained by impregnating a fiber sheet such as a reinforcing fiber with a two-pack type epoxy resin as an impregnating resin.
This is a method of reinforcing, bending, shearing and toughening concrete by adhering and bonding RP sheets to the concrete surface. In this reinforcing method, improvement of workability and improvement of impregnation of an epoxy resin as an impregnation resin have been development goals. Regarding the performance of the resin carrier for impregnation, strength requirements such as tension, compression and bending are the main development goals. Toughness, which is one of the mechanical properties of epoxy resins, is also a factor that strongly affects the breaking strength of epoxy resin-based FRP. However, no research has been conducted on the effect of the toughness of the epoxy resin focusing on the fracture energy.
There is no research or development on the effect of epoxy resin toughness on the method of reinforcing reinforced concrete structures with P.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an FR
By controlling the toughness of the impregnating resin of the sheet of P and suppressing the peeling of the sheet of FRP from the concrete surface,
An object of the present invention is to provide a method for reinforcing a reinforced concrete structure using a tough resin-based FRP, which suppresses the propagation and development of minute fractures generated in an FRP sheet and improves the bending strength of the reinforced concrete structure as a member to be reinforced.

[0004]

That is, the present invention relates to a toughness wherein the elasticity of the resin alone at the time of curing is from 1500 to 2700 MPa, and the elongation before yielding and breaking after yielding is 2% or more by stress. Provided is a method for reinforcing a reinforced concrete structure by using a tough resin-based FRP that impregnates a fiber sheet for reinforcement with a resin and adheres to a concrete surface of the reinforced concrete structure.

It is preferable that the tough resin is a two-pack type epoxy resin composition.

The above-mentioned reinforcing method is effective in the case of a reinforcing method without forming an FRP hoop.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present invention controls the toughness of an impregnating resin in a reinforced concrete (RC) reinforcing method using FRP to a range different from that of a conventionally used brittle epoxy system or the like, thereby removing the FRP sheet from the concrete surface or the like. To improve the bending strength of the reinforced RC body having cracks.

A preferred example of the method for reinforcing a reinforced concrete structure of the present invention (hereinafter referred to as the reinforcing method of the present invention) is performed as follows. First, the latence layer is removed from the concrete surface of the reinforced concrete structure with a sander, a concrete plane, or the like, and a primer (for example, a one-part or two-part epoxy solvent-diluted primer) is applied. After the primer is dried to the touch, the tough resin used in the reinforcing method of the present invention, whose elastic modulus and yield rate are controlled to specific ranges, is applied to the dried primer surface with a roller brush. Next, a reinforcing fiber sheet, for example, a carbon fiber sheet is stuck, and the above-mentioned tough resin is applied as a resin for impregnation with a roller brush from above the fiber sheet. Further, the fiber sheet is sufficiently handled with a rubber spatula. The fiber sheet is impregnated with the tough resin and defoamed from the tough resin. In this way, a tough resin-based CFRP sheet comprising a fiber sheet and a tough resin is formed on the concrete surface. The amount of the tough resin to be applied is not particularly limited as long as it is an amount sufficient for bonding the fiber sheet. For example, if the basis weight is 500 to 1000 [g / m ² ], the fiber sheet and the concrete are Can be sufficiently adhered. When laminating a plurality of fiber sheets to enhance the reinforcing effect, after impregnating the fiber sheet with the above tough resin,
The following process is repeated in which one fiber sheet is pasted on the fiber sheet, the tough resin is applied on the fiber sheet with a roller brush, impregnated with a rubber spatula, and defoamed. Even when a hoop can be formed by winding a sheet of tough resin-based FRP, such as a bridge girder or a pillar of a building, a hoop cannot be formed by winding a sheet of tough resin-based FRP, such as a beam or a floorboard. Even in this case, the reinforcing method of the present invention can be used. After laminating and adhering the required number of fiber sheets, they are cured and the surface is cured. After the surface has hardened, painting and / or installation of a fire-resistant coating may be performed as necessary.

The tough resin used in the reinforcing method of the present invention is a tough resin having a specific range of elastic modulus and elongation. That is, the elastic modulus when cured with the tough resin alone is 150.
A tough resin having a pressure of 0 to 2700 MPa and an elongation of 2% or more, which exhibits a yield phenomenon due to stress and breaks after yield, is used.

In the reinforcement of a reinforced concrete (RC) structure by FRP, it is important to ensure the adhesion between the sheet of the tough resin-based FRP and the concrete surface not only in the tensile direction but also in the shear direction. The elastic modulus is 1500-2
When the pressure is 700 MPa, the concentration of stress due to the force in the shearing direction between the sheet and the concrete surface is effectively dispersed, and the adhesion between the sheet and the concrete surface is ensured, so that the reinforcing effect is excellent. In addition, since the toughness is high (the energy to break is large), the energy of the shock wave due to the break between the sheet and the concrete surface is effectively absorbed and hardly propagated in the sheet. Can follow large deformation in the direction. On the other hand, if the elastic modulus is more than 2700 MPa, stress is applied to the sheet as seen in an epoxy resin having an elastic modulus of 2700 to 3500 MPa conventionally used as an impregnating resin in a reinforced concrete (RC) reinforcing method by FRP. Concentrated, hard and brittle. On the other hand, if the elastic modulus is too low, less than 1500 MPa, the transmission of stress from the sheet to the reinforced RC body when the external force is applied, that is, the transmission of the reinforcing effect is not sufficient, which is not preferable. The elastic modulus is preferably from 2000 to 2600 MPa.

A cured product of an epoxy resin used as an impregnating resin in a conventional method of reinforcing reinforced concrete does not yield at the time of pulling but breaks at a maximum load at a stretch. The elastic modulus is also 2700-3500 MPa
And it is harder and more brittle than the tough resin used in the reinforcing method of the present invention. On the other hand, in the reinforcing method of the present invention, the toughness resin having a lower elastic modulus when cured with the resin alone than the conventional impregnation resin, and having an elongation to break after yielding of 2% or more is used as the impregnation resin. Thereby, stress concentration is avoided, and the proof strength of the reinforced concrete using the reinforcing method of the present invention exceeds the proof strength of the reinforced concrete reinforced by the conventional reinforcing method using epoxy resin-based CFRP.

The tough resin used in the reinforcing method of the present invention has an elastic modulus of 1500 to 2700 M when the resin alone is cured.
It is not particularly limited as long as it is a tough resin having Pa and an elongation to break after yielding of 2% or more. As a resin having such physical properties, an epoxy resin conventionally used mainly as an FRP matrix resin,
Examples include polyester resins and vinyl esters. Among these, a two-pack type epoxy resin is preferable. Epoxy resin has mechanical strength, electrical properties, adhesiveness, heat resistance,
This is because it has excellent chemical resistance and the like, and has a wide range in which stable performance can be exhibited by reinforcing a reinforced concrete structure that is easily affected by an external environment. To lower the elastic modulus at the time of curing with epoxy resin alone to 1500 to 2700 MPa,
Methods such as mixing a plasticizer or a flexibility imparting agent with the epoxy resin, copolymerizing an oligomer of a rubber skeleton with the epoxy resin, selecting a filler, or compounding an amide wax can be used. In addition, in order to increase the elongation of the epoxy resin from yielding to breaking at the time of curing to 2% or more, select an elastic epoxy as the epoxy resin.
Alternatively, a method of appropriately combining techniques such as lowering the elastic modulus of the epoxy resin can be used.

As the epoxy resin, for example, bisphenol A type epoxy resin, novolak type epoxy resin, bisphenol F type epoxy resin, etc., which satisfy the above conditions, can be used. These may be used alone or in combination of two. Among these, bisphenol A type epoxy resin and bisphenol F type epoxy resin are preferable because they can easily achieve both adhesiveness and workability. In addition, commercially available products can also be used, and Sumiepoxy ELA series manufactured by Sumitomo Chemical Co., Ltd. is preferably mentioned.

[0014] In addition, epoxy resin, if necessary,
Various formulations can be added. Examples of the compound include fillers such as calcium carbonate and talc, inorganic or organic coloring pigments, coloring dyes, reinforcing agents, solvents, plasticizers, and the like.

Examples of the reinforcing fiber sheet used in the reinforcing method of the present invention include a fiber sheet using carbon fiber, aramid fiber, or the like. Among them, carbon fiber sheets are preferable because they are high-strength fibers and have excellent fatigue resistance and heat resistance. As the carbon fiber sheet, a carbon fiber sheet conventionally used in a reinforced concrete reinforcing method by FRP can be used. Such carbon fiber sheet may be commercially available products, for example, Guranokku ^(R) HT300
(35,000 kg / cm ² class, manufactured by Nippon Oil Co., Ltd.).

In the reinforcing method of the present invention, by using a tough resin having the above-mentioned properties, particularly a two-pack type epoxy resin, compared with a resin having no toughness used in a conventional FRP reinforced concrete reinforcing method. In addition, the concrete reinforcing effect is improved in the following points. In the conventional reinforced concrete reinforcement method using FRP, since a hard and brittle epoxy resin is used as the impregnating resin, the limit of cracking and destruction of adhesion to weathered fog concrete (thin layer peeling on the concrete side) is low. On the other hand, in the reinforcing method of the present invention, as shown in Examples described later, 10 to 30%
It is possible to increase the proof stress, and as a result, it is possible to perform reinforcement by effectively utilizing the tensile strength of the reinforcing fiber. In addition, the peeling of the FRP sheet from the concrete surface is suppressed, and it is possible to follow a large shear or tensile elongation which was difficult with the conventional FRP reinforced concrete reinforcing method. Further, when carbon fiber (CF) is used as the reinforcing fiber, the shock wave due to the rupture that occurred in a part of the CFRP (carbon fiber reinforced plastic) sheet is absorbed by the resin and is not directly transmitted to the carbon fiber (CF). The development of transversal cracks (brittle fracture), which is a weak point, is suppressed,
It is also possible to prevent CF breakage that rarely occurs stochastically under a load state lower than expected. In the reinforcing method of the present invention, since the adhesiveness between the sheet of the tough resin-based FRP and the concrete surface is excellent, it is not necessary to form a freshly wound hoop, which is a method of winding the outer circumference of a reinforcing concrete reinforcing bar at least once. In addition, the adhesiveness between the sheet and the concrete surface is ensured, and the reinforcing effect is excellent.

The tough resin system F of the present invention having such an effect
The reinforcement method of the reinforced concrete structure by RP is
The present invention can be used not only as a reinforcing method for forming a hoop of a reinforcing sheet such as a pillar but also for reinforcing a place where a hoop cannot be formed.

[0018]

EXAMPLES Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. (Example 1) Height 25cm, width 15cm, length 180c
m, a concrete beam 1 shown in FIG. 1, wherein four main rebars 2 pass through the concrete in the longitudinal direction, and the abra bars 3 are provided on the outer periphery of these main rebars in a direction substantially orthogonal to the main rebars.
A concrete beam wound with one was used. This beam is set to a distance between supports of 160 cm and a loading width of 20 cm, and is cracked by applying a load until the maximum load is reached. One surface of this beam is coated with a primer (EP201, manufactured by Yokohama Rubber Co., Ltd.) using a roller brush. After the primer is dried to the touch, an epoxy resin (Y-97S, manufactured by Yokohama Rubber Co., Ltd., modulus of elasticity 25400 kgf / cm ² , elongation after yielding 5%) is applied as a resin for impregnation with a roller brush, and then carbon is applied. fiber sheet (Guranokku ^(R) HT300, Nippon Oil Co., Ltd.) one, in the longitudinal direction, stuck only on one surface coated with a primer, the impregnating resin described above is coated again with a roller brush thereon, rubber spatula Then, the carbon fiber sheet was sufficiently squeezed, and the impregnating resin was impregnated into the carbon fiber sheet and defoamed from the resin, thereby preparing a test piece A. The reinforced concrete beam used for the test piece A, which was not damaged and was not reinforced, was referred to as a test piece B. A bending test was performed in advance by the same method as the method in which a crack was introduced, with the side of the specimen A having the sheet attached thereon as the lower surface. The relationship with the amount of deflection was measured. With respect to the test piece B, the relationship between the load and the amount of flexure was measured before cracking. FIG.
2 is a graph schematically showing the relationship between the load and the amount of bending in a bending test performed using a reinforced concrete beam reinforced by the reinforcing method of the present invention. In the figure, point P indicates the limit (yield point) of the elastic range in which the load and the amount of bending are approximately proportional, and the load at this point is the yield load (a in the figure).
That. The point Q indicates that even if a displacement greater than the displacement at the point Q is applied to the reinforced concrete beam, no further bending load is obtained and the concrete beam is destroyed. During,
b). The ratio of the yield load of the specimen A to the yield load of the specimen B was calculated from the measured value as the degree of improvement in the elastic range of the specimen. The ratio of the maximum load of the specimen A to the maximum load of the specimen B was calculated from the measured value as the degree of improvement in the maximum proof stress of the specimen. Table 1 shows the results.

(Comparative Example 1) Epoxy resin was used as the impregnating resin.
(E2500S, manufactured by Konishi Co., Ltd., elastic modulus 31000k
gf / cm^Two, Elongation after yield 0%)
(Granock ^(R)HT300, manufactured by Nippon Oil Corporation)
Specimen C was prepared in the same manner as Specimen A. Also,
The concrete beam before reinforcement was set to the specimen D in the same manner as the specimen B.
Used. Specimens C and D as in Example 1
Then, the yield load and the maximum load were measured and evaluated.

(Example 2) Height 18 cm, width 36 cm,
Specimen E was made in the same manner as Specimen A, except that a 200 cm long concrete beam was used. The reinforced concrete beam used for the test piece E, which did not cause any damage and was not reinforced, was referred to as a test piece F. Yield load and maximum load were measured and evaluated for the test pieces E and F in the same manner as in Example 1.

(Comparative Example 2) Epoxy resin (E2500S, manufactured by Konishi Co., Ltd., elastic modulus 31000k) was used as the impregnating resin.
Specimen G was prepared in the same manner as Specimen E, except that gf / cm ² , elongation after yield was 0%). The same concrete beam as the test body F was used as the test body H. For the test pieces G and H, the elastic limit load and the maximum load were measured and evaluated in the same manner as in Example 1. Table 1 shows the results.

[0022]

[0023]

According to the repair method of the present invention, the upper limit of the range in which the reinforced concrete structure exhibits elasticity is improved by using the impregnating resin having a specific range of elastic modulus and yield rate. In addition, the bending strength of the reinforced concrete structure is improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a reinforcement arrangement of a reinforced concrete beam.

FIG. 2 is a graph schematically showing a relationship between a load applied to a beam and a bending deflection amount caused by the load when a bending test is performed.

[Explanation of symbols]

 1 Reinforced concrete beam 2 Main rebar 3 Abala bar

Claims (3)

[Claims] An elastic modulus at the time of curing is 1500-2700MP.
a, and a tough resin, which yields by stress and has an elongation of 2% or more before breaking after yielding, is impregnated into a reinforcing fiber sheet and adheres to the concrete surface of the reinforced concrete structure. Reinforcement method. 2. The method for reinforcing a reinforced concrete structure by using a tough resin-based FRP according to claim 1, wherein the tough resin is a two-pack type epoxy resin composition. 3. The method for reinforcing a reinforced concrete structure by using a tough resin-based FRP according to claim 1, wherein the reinforcing method is a reinforcing method that does not form a hoop of FRP.