Concrete rear surface reinforcement method and concrete structure

Abstract

To provide technology to suppress damage to rear surfaces of concrete caused by collisions of flying objects.SOLUTION: A concrete rear surface reinforcement method for attaching a fiber sheet 3 to a rear surface 12 of concrete 1 to prevent damage to the rear surface is provided. A process of attaching the fiber sheet 3 to the rear surface 12 of concrete 1 comprises a process of applying a first adhesive 51 to the rear surface 12 of the concrete 1 and a process of affixing the fiber sheet 3 on top of the first adhesive 51. After attaching the fiber sheet 3 to the rear surface 12 of a concrete 101 for testing, a cumulative damage value, which is a cumulative value of collision energy leading to damage to the rear surface, is 7.0 kJ or more, and the collision energy per impact of a flying object 2 is 0.1 kJ or more but less than 7.0 kJ. The concrete 101 for testing has a shape of 1100 mm (length)×1100 mm (width)×150 mm (thickness) and a compressive strength of 24 N / mm2 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for reinforcing the back surface of concrete and a concrete structure (also referred to as a "concrete structure").

Background Art

[0002] When a concrete structure is impacted by a relatively large-mass object such as a falling rock, debris flow, or avalanche at a low speed, overall failure accompanied by large deformations such as flexural failure or shear failure occurs in the concrete. On the other hand, when a relatively small-mass object impacts at high speed, such as a bullet or explosive impact, or an impact by a flying object due to a typhoon or tornado, local failure progresses in the process of surface destruction, penetration, back surface peeling, and penetration of the concrete. Thus, in a concrete member that undergoes high-speed impact with a flying object at a speed of several tens of m / s to several hundreds of m / s, the aspect is completely different from overall failure due to flexural failure or shear failure.

[0003] Conventionally, as a concrete member that undergoes impact by a high-speed flying object, non-porous concrete having a relatively high strength of about 400 N / mm 2 in compressive strength has been studied (Non-Patent Document 1). This concrete has a compressive strength more than 14 times that of ordinary concrete of about 28 N / mm 2 , but the member thickness can only be thinned by about 30%. Also, it is difficult to industrially mass-produce non-porous concrete that allows not even a single defect, and in order to ensure non-porosity, it is also necessary to perform 100% inspection, which is lacking in practicality.

[0004] In another study, it has been reported that although surface local penetration due to an increase in the compressive strength of concrete is somewhat suppressed, no suppression effect on back surface peeling is recognized (Non-Patent Document 2). From the above, although concrete is an indispensable material for mass production, it is clear that increasing the strength of concrete is not a solution for suppressing back surface failure against impact by a high-speed flying object.

[0005] On the other hand, an impact-resistant member for a high-speed flying object using ceramics has also been proposed (Patent Document 1). However, ceramics are expensive materials for mass production, resulting in an excessive economic burden and limited application scope.

[0006] In addition, as a method for preventing the back surface failure of concrete due to the collision of a high-speed flying object, a reinforcement method of attaching a sheet of aramid fiber or carbon fiber to the back surface of the concrete has also been proposed (Non-Patent Document 3). Non-Patent Document 3 shows the generation process of back surface peeling as shown in FIG. 8. FIG. 9 shows an image of an example of back surface peeling. FIG. 9(a) is an example described in Non-Patent Document 3, and FIGS. 9(b) and 9(c) are examples described in Non-Patent Document 4. These are examples where the sheet is not particularly reinforced.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Non-Patent Documents

[0008]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

[0009] In recent years, there have been many reports of damage to shelters due to the impact of volcanic projectiles and damage to buildings due to flying objects in tornadoes. There has been a demand for establishing a method for reinforcing concrete structures such as shelters, protective walls, and buildings. In such disasters, there is a possibility that flying objects (projectiles) may repeatedly collide with the structures. So far, the evaluation of the back surface reinforcement effect for a single collision has been carried out, but the examination regarding the case where the projectile repeatedly collides has not been carried out.

[0010] An object of the present invention is to provide a technique for suppressing the back surface failure of concrete when a projectile repeatedly collides. MEANS FOR SOLVING THE PROBLEMS

[0011] According to the present invention, the following technique is provided. [1] A concrete back surface reinforcement method for preventing back surface failure in which the other surface on the side opposite to one surface of the concrete is damaged by the impact of a projectile on one surface of the concrete, comprising attaching a fiber sheet to the other surface of the concrete, The resin sheet attachment step of attaching the fiber sheet to the other surface of the concrete includes a step of applying a first adhesive to the other surface of the concrete and attaching the fiber sheet from above the first adhesive, Test concrete is prepared as the previous concrete. After attaching the fiber sheet to the other surface of the test concrete, the cumulative value of the collision energy until the projectile collides with one surface and causes the back surface failure, which is the cumulative failure value, is 7.0 kJ or more, and the collision energy per hit of the projectile is 0.1 kJ or more and less than 7.0 kJ, The test concrete has a shape of 1100 mm in length × 1100 mm in width × 150 mm in thickness, and its compressive strength is 24 N / mm 2 or more. Concrete back surface reinforcement method. [2] The resin sheet mounting step further includes a step of applying a second adhesive on the fiber sheet attached to the back surface of the concrete with the first adhesive, the concrete back surface reinforcement method according to [1]. [3] The first adhesive and the second adhesive include at least one of a (meth)acrylic resin-based adhesive and an epoxy resin-based adhesive, the concrete back surface reinforcement method according to [2]. [4] The application amount A of the first adhesive is 100 g / m 2 or more and 1000 g / m 2 or less, The application amount B of the second adhesive is 0 g / m 2 or more and 1500 g / m 2 or less, the concrete back surface reinforcement method according to [2] or [3]. [5] A kg / m which is the application amount of the first adhesive 2 and B kg / m which is the application amount of the second adhesive 2 The ratio B / A of them is 0 or more and 4.0 or less, the concrete back surface reinforcement method according to any one of [2] to [4]. [6] The basis weight of the fiber sheet is 50 g / m 2 or more and 1000 g / m 2 or less, the concrete back surface reinforcement method according to any one of [1] to [5]. [7] The fiber sheet includes a two-directional sheet in which fibers are arranged along each of two axial directions different from each other, or a laminated sheet in which two one-directional sheets in which fibers are arranged along one axial direction are laminated so that the axial directions intersect each other, the concrete back surface reinforcement method according to any one of [1] to [6]. [8] The fiber sheet is an aramid fiber sheet, and it is a concrete back surface reinforcement method according to any one of [1] to [7]. [9] The concrete back surface reinforcement method according to any one of [1] to [8], wherein the cumulative damage value is 10 kJ or more.

[10] When the fiber sheet is attached to the other surface of the test concrete under the following experimental conditions using a high-pressure air type projectile generator, and then the projectile is made to collide with the test concrete three times, no back surface failure occurs. It is a concrete back surface reinforcement method according to any one of [1] to [9]. Experimental conditions: · Apparatus: High-pressure air type projectile generator · Projectile mass: 4.5 kg (Φ 90 mm) · Projectile set speed: 20 m / s, 40 m / s

[11] The collision energy per hit of the projectile is 0.5 kJ or more and less than 1.5 kJ, The concrete back surface reinforcement method according to any one of [1] to

[10] , wherein the cumulative damage value is 15.0 kJ or more.

[12] The collision energy per hit of the projectile is 3.0 kJ or more and less than 4.0 kJ, The concrete back surface reinforcement method according to any one of [1] to

[10] , wherein the cumulative damage value is 25.0 kJ or more.

[13] A concrete structure reinforced using the concrete back surface reinforcement method according to any one of [1] to

[12] .

Effect of the Invention

[0012] According to the present invention, it is possible to provide a technique for suppressing back surface failure of concrete when a projectile repeatedly collides.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0014] <Summary of this Embodiment> In this embodiment, a concrete back surface reinforcement technique will be described. Fig. 1 is a figure showing concrete 1 with a fiber sheet 3 attached to the back surface 12. Fig. 1(a) is a front view, Fig. 1(b) is a side view, and Fig. 1(c) is a rear view. Fig. 2 is an enlarged view of region A in Fig. 1(b). In Fig. 2, the concrete 1 is represented by hatching. Examples of concrete structures (structures) that can adopt the concrete 1 include (1) public facility-related equipment, (2) living infrastructure, communication, and transportation-related equipment, and (3) facilities important for national defense and disaster prevention facilities. More specifically, it is as follows. (1) As public facility-related facilities, for example, schools, research facilities, hospitals, police stations, fire stations, gymnasiums, community centers, government offices, libraries, museums, art galleries, stadiums, etc. can be mentioned. (2) As life infrastructure, communication, and transportation-related facilities, for example, power plants, substations, gas facilities, waterworks, communication bases, broadcasting stations, stations, subways, port facilities, airports, etc. can be mentioned. (3) As facilities important for national defense and disaster prevention facilities, for example, Self-Defense Force garrisons, bases, airfields, nuclear facilities (nuclear reactors, nuclear power plants, nuclear fuel processing facilities, reprocessing facilities, spent fuel storage facilities), shelters, mountain huts, etc. can be mentioned. Note that the above concrete structures are examples, and the present invention is also applicable to concrete structures other than the above.

[0015] The concrete back surface reinforcement technology of the present embodiment is to attach a fiber sheet 3 to the back surface 12 in order to prevent back surface failure, which is a phenomenon in which when a flying object 2 collides with one surface of the concrete 1 (hereinafter referred to as "surface 11"), the other surface on the opposite side of the surface 11 (hereinafter referred to as "back surface 12") is destroyed. Note that the surface 11 and the back surface 12 of the concrete 1 are not particularly distinguished by the structure or the like, but are based on the difference in whether the fiber sheet 3 is attached or not. In other words, the back surface 12 of the concrete 1 refers to the back surface rather than the surface (surface 11) where the flying object 2 collides.

[0016] Prepare a standardized concrete 1 for testing (hereinafter referred to as "test concrete 101"), and attach a fiber sheet 3 to the back surface 12 of the test concrete 101 by the steps described later (see FIGS. 3 and 4). Hereinafter, the test concrete 101 with the fiber sheet 3 attached to the back surface 12 is referred to as "concrete 102 with reinforced back surface".

[0017] Evaluate the cumulative value ES of the destruction cumulative value, which is the cumulative value of the collision energy EA until the flying object 2 collides with the surface 11 of the concrete 102 with the reinforced back surface and reaches back surface failure. That is, when the destruction cumulative value ES is equal to or greater than a predetermined value, it is evaluated that the concrete 1 having the fiber sheet 3 on the back surface 12 and having a certain strength considering back surface failure is constructed. For the evaluation, the following three evaluations of Evaluation Conditions 1 to 3 are performed according to the magnitude of the collision energy EA per hit of the flying object 2. Evaluation Condition 1: The collision energy EA per hit of the flying object 2 is 0.1 kJ or more and less than 7.0 kJ, and the damage accumulation value ES is 7.0 kJ or more. Evaluation Condition 2: The collision energy EA per hit of the flying object 2 is 0.5 kJ or more and less than 1.5 kJ, and the damage accumulation value ES is 15.0 kJ or more. Evaluation Condition 3: The collision energy EA per hit of the flying object 2 is 3.0 kJ or more and less than 4.0 kJ, and the damage accumulation value ES is 25.0 kJ or more. The following will be specifically described.

[0018] In the present embodiment, back surface failure (also referred to as "back surface peeling") refers to a state in which peeling occurs on the back surface 12 due to the collision of the flying object 2 with the front surface 11. For examples of back surface failure, refer to FIGS. 8 and 9 described above.

[0019] <Concrete (test concrete)> The back surface reinforced concrete 102 has test concrete 101 which is concrete 1 standardized for testing, and a fiber sheet 3 attached to the back surface 12 of the test concrete 101. The fiber sheet 3 is attached to the back surface 12 of the test concrete 101 by an adhesive 50 (first adhesive 51, second adhesive 52) in a process described later.

[0020] First, the concrete 1 to which back surface reinforcement is applied will be described. Subsequently, the test concrete 101 and the back surface reinforced concrete 102 will be described.

[0021] In the present embodiment, the concrete 1 is a general term for concrete, mortar, and cement paste. Also, the concrete 1 may be plain concrete or reinforced concrete.

[0022] The concrete 1 may be fiber-reinforced concrete in which short fibers are mixed into the concrete. The short fibers to be mixed may be of one type or a plurality of types. As the short fibers, for example, polypropylene, polyethylene terephthalate, or vinylon can be used. As the size of the short fibers, for example, the fiber diameter can be set to 0.01 mm to 0.1 mm and the fiber length can be set to 10 mm to 30 mm.

[0023] The fiber-reinforced concrete can be expected to have an effect of dispersing the impact when the flying object 2 collides and an effect of suppressing the scattering of concrete pieces. The amount of short fibers used can be, for example, 1 to 5 Vol.% in terms of volume ratio. If it is 1 Vol.% or more, the impact resistance and the prevention of scattering of broken concrete pieces will be sufficient, and if it is 5 Vol.% or less, sufficient performance can be expected.

[0024] From the viewpoint of preventing back surface failure caused by the collision of the flying object 2, the strength level of the concrete 1 is preferably such that the compressive strength is 18 N / mm 2 ~200 N / mm 2 If it is 18 N / mm 2 or more, the impact resistance will be sufficient, and if it is 200 N / mm 2 or less, the production of the concrete slab will be easy, the productivity will be good, and the cost will tend to be low.

[0025] The required compressive strength varies depending on the mass and speed of the flying object 2 that collides, that is, the impact energy per collision. For example, whether to obtain the compressive strength that can withstand one impact under conditions where the impact energy per collision is large, or whether to obtain the compressive strength that can withstand multiple collisions although the impact energy per collision is not so large, the required compressive strength will vary.

[0026] In this embodiment, when assuming conditions such that the impact energy EA per collision of the flying object 2 against the concrete 102 with the fiber sheet 3 attached to the back surface 12 of the test concrete 101 is 0.1 kJ or more and less than 7.0 kJ, and the cumulative damage value ES is 7.0 kJ or more, the compressive strength of the test concrete 101 is 24 N / mm 2 or more.

[0027] The lower limit of the compressive strength is preferably 30 N / mm 2 or more, and more preferably 40 N / mm 2 or more. The upper limit of the compressive strength is not particularly limited, but for example, it is 60 N / mm 2 or less, preferably 55 N / mm 2 or less, and more preferably 50 N / mm 2 or less. The compressive strength is set according to the kinetic energy (impact energy) of the assumed flying object 2. That is, it is set according to how much strength is required for the test concrete 101.

[0028] The test concrete 101 has a rectangular parallelepiped shape with a length of 1100 mm, a width of 1100 mm, and a thickness of 150 mm. One surface defined by the length × width is the front surface 11, and the other surface is the back surface 12.

[0029] <Fiber sheet> The fiber sheet 3 is attached to the back surface 12 of the concrete 1 using an adhesive 50 (the first adhesive 51 and the second adhesive 52 described later). Although details will be described later, the first adhesive 51 is applied as a primer to the back surface 12 of the concrete 1, the fiber sheet 3 is attached, and then the second adhesive 52 is applied as a topcoat as necessary.

[0030] Examples of the fiber sheet 3 include a sheet made of fibers such as aramid fibers and carbon fibers. From the viewpoints of strength and affinity with the adhesive 50, an aramid fiber sheet can be preferably used.

[0031] As the aramid fiber sheet, a sheet of a fabric in which the fibers are arranged in two directions as warp and weft is preferably used. Among them, an isotropic sheet in which the types, thicknesses, and number of filaments of the aramid fibers constituting the warp and weft are the same is particularly preferably used.

[0032] The tensile strength of the fibers constituting the aramid fiber sheet can be, for example, 1 cN / dtex or more and 40 cN / dtex or less. The lower limit is preferably 5 cN / dtex or more, more preferably 10 cN / dtex or more. The upper limit is preferably 35 cN / dtex or less, more preferably 25 cN / dtex or less. By setting the tensile strength of the fibers constituting the aramid fiber sheet within the above range, even when the concrete 1 breaks, it is possible to suppress the broken concrete 1 (or members such as steel bars contained in the concrete 1) from popping out. If the tensile strength is 1 cN / dtex or more, although it depends on the length of the steel bars (steel materials) arranged in the concrete 1, it is possible to sufficiently prevent the popping out when the steel bars break. On the other hand, if the tensile strength is 40 cN / dtex or less, the number of filaments and the thickness decrease in order to achieve such a high tensile strength, and the impregnation of the adhesive 50 proceeds sufficiently.

[0033] The fiber amount of the aramid fiber sheet can be, for example, 50 g / m 2 or more and 1000 g / m 2 or less. The lower limit is preferably 100 g / m 2 or more, more preferably 180 g / m 2 or more. The upper limit is preferably 800 g / m 2 or less, more preferably 650 g / m 2 or less. If the fiber amount is 50 g / m 2 or more, the tensile strength of the aramid fiber sheet is not insufficient. If the fiber amount is 1000 g / m 2 or less, the impregnation of the adhesive 50 proceeds sufficiently and sufficient adhesive strength can be obtained.

[0034] The fiber sheet 3 may be a uniaxial sheet (UD material) formed by arranging fiber bundles in one direction, or a biaxial sheet (cross sheet) formed by weaving fiber bundles as warp and weft in two axes. As the weaving method, there are many patterns in which the warp and weft of a fabric, such as plain weave, twill weave, and satin weave, intersect, but the pattern is not limited. Also, in the case of a biaxial sheet, it may be a sheet (laminated sheet) in which two uniaxial sheets are laminated so that the directions of the fiber bundles are different. Also, in the case of a biaxial sheet, the directions of the fiber bundles may be slightly inclined without being orthogonal. Also, it may be a multi-axial sheet formed by laminating three or more layers by combining uniaxial sheets and biaxial sheets. In the case of a multi-axial sheet, different types of fiber sheets 3 (for example, an aramid fiber sheet and a carbon fiber sheet) may be laminated. From the viewpoint of impregnating the fiber sheet 3 with the adhesive 50, a biaxial sheet woven in plain weave is preferable. That is, the adhesive easily impregnates the unevenness on the front and back surfaces of the fiber sheet 3 formed by plain weave.

[0035] <Areal density of fiber sheet> The areal density (or also referred to as "areal density amount") of the fiber sheet 3 is appropriately set. For example, it can be 50 g / m 2 or more and 1000 g / m 2 or less. The lower limit of the areal density is preferably 100 g / m 2 or more, and more preferably 180 g / m 2 or more. The upper limit of the areal density is preferably 800 g / m 2 or less, and more preferably 650 g / m 2 or less.

[0036] When the areal density is 50 g / m 2 or more, the amount of fibers increases, and the desired strength as the fiber sheet 3 (that is, the strength capable of preventing back surface breakage) can be obtained. Also, since the gaps between the fibers do not become too wide, the amount of the adhesive 50 required to attach the fiber sheet 3 to the concrete 1 does not increase too much, and the curing time does not become long with the increase in the amount of the adhesive 50, improving the workability.

[0037] When the areal density is 1000 g / m 2In the following case, the adhesive 50 can easily penetrate between the fibers, making it easy to obtain the desired adhesiveness.

[0038] <Adhesive (First Adhesive, Second Adhesive)> As the adhesive 50, the first adhesive 51 is used as a primer and the second adhesive 52 is used as a topcoat. The first adhesive 51 and the second adhesive 52 may be of the same type or different types of adhesives. The presence of the first adhesive 51 and the second adhesive 52 causes the first adhesive 51 and the second adhesive 52 to come into contact through the fiber sheet 3, increasing the adhesive strength. When the basis weight of the fiber sheet 3 is small, the application of the second adhesive 52 can be omitted. The case where the basis weight is small means, for example, when the basis weight is 200 g / m 2 The following cases are referred to. When the basis weight of the fiber sheet 3 is small, the interval between the fibers becomes wide as described above. Therefore, when the amount of the first adhesive 51 used increases, the first adhesive 51 may ooze out to the front side of the fiber sheet 3. Therefore, in some cases, the same effect as when using the second adhesive 52, which is a topcoat, can be obtained only by using the first adhesive 51, which is a primer. In such a case, the second adhesive 52 can be omitted.

[0039] As the type of the adhesive 50, an adhesive containing a (meth)acrylic resin ((meth)acrylic resin-based adhesive), an adhesive containing an epoxy resin (epoxy resin-based adhesive), etc. can be used. The (meth)acrylic resin-based adhesive has (meth)acrylic acid or its derivatives (such as methyl methacrylate) as the main component. In the present embodiment, it includes an adhesive containing a methacrylic (MMA) resin (MMA resin-based adhesive). The first adhesive 51 and the second adhesive 52 being of the same type includes, for example, the case where both are acrylic resin-based adhesives of the same type (component), and the case where the components are different but they are different types of (meth)acrylic resin-based adhesives. The first adhesive 51 and the second adhesive 52 may be of any type as long as the desired adhesiveness and workability are realized.

[0040] [(Meth)acrylic Monomer and Its Oligomer] This embodiment contains, as a (meth)acrylic adhesive component, a monofunctional, bifunctional, or trifunctional or higher (meth)acrylic monomer, or a (meth)acrylic oligomer in which a plurality of these (meth)acrylic monomers are bonded. The (meth)acrylic adhesive component is a radically polymerizable component.

[0041] Examples of the (meth)acrylic monomer include (meth)acrylic acid or its derivative, (meth)acrylamide or its derivative, etc., and one or more of them may be mixed and used.

[0042] Examples of the above (meth)acrylic acid derivative include the following.

[0043] (i) A monomer represented by the following formula (1). Z-O-R1(1) (In the formula, Z represents a (meth)acryloyl group, a CH2=CHCOOCH2-CH(OH)CH2O- group, or a CH2=C(CH3)COOCH2-CH(OH)CH2O- group, and R1 represents hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, a benzyl group, a phenyl group, a tetrahydrofurfuryl group, a glycidyl group, a dicyclopentyl group, a dicyclopentenyl group, a (meth)acryloyl group, and an isobornyl group)

[0044] Examples of such a monomer include methyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, glycerol (meth)acrylate, glycerol di(meth)acrylate, isobornyl (meth)acrylate, and (meth)acrylic acid, etc.

[0045] (ii) A monomer represented by the following formula (2). Z-O-(R2O) p -R1(2) (wherein Z and R1 are as described above. R2 is -C2H4-, -C3H6-, -CH2CH(CH3)-, -C4H8- or -C6H 12 -, and p represents an integer of 1 to 25)

[0046] Examples of such monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ethoxyethyl (meth)acrylate, polyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyl oxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, tripropylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate, etc.

[0047] (iii) A monomer represented by the following formula (3).

[0048] [Chemical formula] (wherein Z and R2 are as described above. Z' represents a (meth)acryloyl group, a CH2=CHCOOCH2-CH(OH)CH2O- group or a CH2=C(CH3)COOCH2-CH(OH)CH2O- group, R'2 is -C2H4-, -C3H6-, -CH2CH(CH3)-, -C4H8- or -C6H 12 (-, R3 and R'3 represent hydrogen or an alkyl group having 1 to 4 carbon atoms, q + q' represents an integer of 0 to 20, preferably an integer of 0 to 8. Z and Z' may be the same or different. R2 and R2' may be the same or different. R3 and R'3 may be the same or different.)

[0049] Examples of such monomers include 2,2-bis(4-(meth)acryloxyphenyl)propane, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypropoxyphenyl)propane, 2,2-bis(4-(meth)acryloxytetraethoxyphenyl)propane, and 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane.

[0050] (iv) (Meth)acrylic acid esters of polyhydric alcohols not included in the monomers described in (i), (ii), or (iii) above.

[0051] Examples of such monomers include trimethylolpropane tri(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0052] (v) Urethane prepolymers having a (meth)acryloyloxy group. Such monomers can be obtained, for example, by reacting a (meth)acrylic acid ester having a hydroxyl group, an organic polyisocyanate, and a polyhydric alcohol.

[0053] Examples of the (meth)acrylic acid ester having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0054] Examples of the above-mentioned organic polyisocyanates include toluene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0055] Examples of the above polyhydric alcohol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyester polyol, and the like.

[0056] One or more of the above monomers (i) to (v) can be used. Among these, one or more of the group consisting of (i) and (iii) are preferable, and it is more preferable to use (i) and (iii) in combination, in terms of large adhesiveness and small adhesion strain of the adherend after adhesion. When (i) and (iii) are used in combination, the composition ratio is preferably (i):(iii) = 50 to 95:5 to 50 by mass ratio, and more preferably 60 to 80:20 to 40.

[0057] [Epoxy monomer and its oligomer] This embodiment may contain an epoxy monomer or an epoxy oligomer in which a plurality of these epoxy monomers are bonded as an epoxy adhesive component.

[0058] Examples of the epoxy monomer include bisphenol-based such as bisphenol A-based, bisphenol F-based, bisphenol AD-based, bromine-containing bisphenol A-based; phenol novolak-based, cresol novolak-based, polyphenol-based, linear aliphatic-based, butadiene-based, glycidyl ester type epoxy monomers such as urethane; aliphatic glycidyl ester type epoxy monomers such as hexahydrophthalic acid glycidyl ester, dimer type glycidyl ester, aromatic-based, cycloaliphatic-based; methyl-substituted type epoxy monomers such as ester-based, high molecular weight ether ester-based, ether ester-based, bromine-based novolak-based; heterocyclic type epoxy monomers; glycidyl amine type epoxy monomers such as triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane; linear aliphatic type epoxy monomers such as epoxidized polybutadiene, epoxy soybean oil; cycloaliphatic type epoxy monomers, naphthalene-based novolak type epoxy monomers; diglycidyl oxy naphthalene type epoxy monomers, and the like. These epoxy monomers may be used as a mixture of one or more.

[0059] <Elastomer (B)> In this embodiment, by using the elastomer (B), the toughness of the adhesive composition can be enhanced, and the adhesion and adhesiveness can be improved. Further, it is preferable that the elastomer (B) is soluble in the reactive component (A).

[0060] Examples of the elastomer (B) include one or more selected from the group consisting of methyl (meth) acrylate-butadiene-styrene copolymer (such as MBS resin), butadiene rubber, butadiene-(meth)acrylonitrile copolymer (such as NBR (nitrile rubber)), methyl (meth) acrylate-(meth)acrylonitrile-butadiene-styrene copolymer (such as MABS resin), and other (meth)acrylonitrile copolymers, and modified polyvinyl alcohol. Among them, from the viewpoint of compatibility, one or more selected from the group consisting of butadiene-(meth)acrylonitrile copolymer, methyl (meth) acrylate-butadiene-styrene copolymer, and methyl (meth) acrylate-(meth)acrylonitrile-butadiene-styrene copolymer are preferable, one or more selected from the group consisting of butadiene-(meth)acrylonitrile copolymer and methyl (meth) acrylate-(meth)acrylonitrile-butadiene-styrene copolymer are more preferable, and it is even more preferable to use a combination of butadiene-(meth)acrylonitrile copolymer and methyl (meth) acrylate-(meth)acrylonitrile-butadiene-styrene copolymer. When using a combination of butadiene-(meth)acrylonitrile copolymer and methyl (meth) acrylate-(meth)acrylonitrile-butadiene-styrene copolymer, the combined ratio is preferably butadiene-(meth)acrylonitrile copolymer:methyl (meth) acrylate-(meth)acrylonitrile-butadiene-styrene copolymer = 10-90:10-90, more preferably 25-75:25-75, and even more preferably 40-60:40-60 in a total of 100 parts by mass of butadiene-(meth)acrylonitrile copolymer and methyl (meth) acrylate-(meth)acrylonitrile-butadiene-styrene copolymer.

[0061] The content of the elastomer (B) relative to a total content of 100 parts by mass of the reaction component (A) and the elastomer (B) is preferably 15 to 35 parts by mass, more preferably 15 to 30 parts by mass, and still more preferably 15 to 28 parts by mass. By setting the content of the elastomer (B) to be not less than the above lower limit value, the stress relaxation property becomes good. On the other hand, by setting the content of the elastomer (B) to be not more than the above upper limit value, the coatability becomes good.

[0062] The adhesive composition of the present embodiment may further contain the following components.

[0063] <Polymerization initiator (C)> The adhesive composition of the present embodiment preferably contains a polymerization initiator (C) for reacting the reaction component (A). Among them, as the polymerization initiator (C), a radical polymerization initiator is preferable. As the radical polymerization initiator, an organic peroxide is preferable. The organic peroxide decomposes by heating to generate free radicals, and can promote the curing of the adhesive by causing an addition reaction to the (meth)acrylic monomer and its oligomer. As the organic peroxide, from the viewpoint of improving the storage stability of the adhesive composition of the present embodiment, it is preferable to use one having a decomposition temperature (1-hour half-life temperature) for obtaining a half-life of 1 hour of 100 °C or higher. Examples of the organic peroxide include peroxy esters such as t-butyl peroxybenzoate (half-life temperature for 1 hour: 125°C), t-butyl peroxyacetate (half-life temperature for 1 hour: 121°C), and t-butyl peroxylaurate (half-life temperature for 1 hour: 118°C); peroxy ketals such as 1,1-di(t-butylperoxy)cyclohexane (half-life temperature for 1 hour: 111°C) and 1,1-di(t-hexylperoxy)cyclohexane (half-life temperature for 1 hour: 107°C); and hydroperoxides such as p-menthane hydroperoxide (half-life temperature for 1 hour: 151°C), cumene hydroperoxide (half-life temperature for 1 hour: 188°C), and diisopropylbenzene hydroperoxide (half-life temperature for 1 hour: 173°C). Among these, cumene hydroperoxide is preferred in terms of stability.

[0064] The content of the polymerization initiator (C) is preferably 0.1 to 20 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1.2 to 8 parts by mass with respect to 100 parts by mass of the reaction component (A). By setting the content of the polymerization initiator (C) to be equal to or higher than the above lower limit value, it becomes easier to improve the curing rate. On the other hand, by setting the content of the polymerization initiator (C) to be equal to or lower than the above upper limit value, good storage stability can be maintained.

[0065] [Reducing agent (D)] The reducing agent (D) may be any substance that reacts with the polymerization initiator (C) to generate radicals, and known reducing agents can be used. Examples of the reducing agent (D) include tertiary amines, thiourea derivatives, and transition metal salts.

[0066] Examples of the above tertiary amines include triethylamine, tripropylamine, tributylamine, and N,N-dimethyl-p-toluidine. Examples of the above thiourea derivatives include 2-mercaptobenzimidazole, methylthiourea, dibutylthiourea, tetramethylthiourea, and ethylene thiourea. Examples of the above transition metal salts include cobalt octylate, cobalt naphthenate, copper naphthenate, vanadyl acetylacetonate, and the like. Among these, transition metal salts are preferred in terms of reactivity. Among the transition metal salts, cobalt octylate is more preferred.

[0067] The content of the reducing agent (D) is preferably 0.05 to 15 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the reaction component (A). By setting the content of the reducing agent (D) to be not less than the above lower limit value, the curing rate can be increased. On the other hand, by setting the content of the reducing agent (D) to be not more than the above upper limit value, it is possible to suppress the progress of curing during storage and maintain good storage stability.

[0068] <Hardener or curing accelerator> When the adhesive composition of the present embodiment contains an epoxy monomer and its oligomer, a hardener or a curing accelerator for curing or promoting the effect thereof can be used. As the hardener or curing accelerator, those generally used for curing epoxy resins can be widely used. Examples include acid anhydrides, phenol hydroxyl group-containing resins, phosphorus compounds, imidazole compounds, polyamine compounds, amide compounds, imidazoline compounds, urea-based compounds, organic acid metal salts, Lewis acids, amine complex salts, and the like. Examples of the above acid anhydrides include octenyl succinic anhydride, dodecenyl succinic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrabromophthalic anhydride, hymic anhydride, methylnadic anhydride, trialkyltetrahydrophthalic anhydride, and the like.

[0069] Examples of the phenolic hydroxyl group-containing resin include polyhydric phenol compounds such as phenol novolak resin, cresol novolak resin, aromatic hydrocarbon formaldehyde resin-modified phenol resin, dicyclopentadiene phenol addition type resin, phenol aralkyl resin (Zylok resin), naphthol aralkyl resin, trimethylolmethane resin, tetraphenylol ethane resin, naphthol novolak resin, naphthol-phenol co-condensed novolak resin, naphthol-cresol co-condensed novolak resin, biphenyl-modified phenol resin (a polyhydric phenol compound in which phenol nuclei are linked by bismethylene groups), biphenyl-modified naphthol resin (a polyhydric naphthol compound in which phenol nuclei are linked by bismethylene groups), aminotriazine-modified phenol resin (a polyhydric phenol compound in which phenol nuclei are linked by melamine, benzoguanamine, etc.), and alkoxy group-containing aromatic ring-modified novolak resin (a polyhydric phenol compound in which a phenol nucleus and an alkoxy group-containing aromatic ring are linked by formaldehyde).

[0070] Examples of the phosphorus compound include alkylphosphines such as ethylphosphine and butylphosphine, primary phosphines such as phenylphosphine; dialkylphosphines such as dimethylphosphine and dipropylphosphine; secondary phosphines such as diphenylphosphine and methylethylphosphine; tertiary phosphines such as trimethylphosphine, triethylphosphine, and triphenylphosphine, and phosphate esters.

[0071] The above-mentioned imidazole compounds include, for example, imidazole, 1-methylimidazole, 2-methylimidazole, 3-methylimidazole, 4-methylimidazole, 5-methylimidazole, 1-ethylimidazole, 2-ethylimidazole, 3-ethylimidazole, 4-ethylimidazole, 5-ethylimidazole, 1-n-propylimidazole, 2-n-propylimidazole, 1-isopropylimidazole, 2-isopropylimidazole, 1-n-butylimidazole, 2-n-butylimidazole, 1-isobutylimidazole, 2-isobutylimidazole, 2-undecyl-1H-imidazole, 2-heptadecyl-1H-imidazole, 1,2-dimethylimidazole, 1,3-dimethylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-phenylimidazole, 2-phenyl-1H-imidazole, 4-methyl-2-phenyl-1H-imidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole isocyanurate adduct, 2-methylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1-benzyl-2-phenylimidazole hydrochloride, and the like. The curing agent or curing accelerator may be used alone or in combination of two or more.

[0072] The content of the curing agent is calculated based on the functional group equivalent of the curing agent and the reactive group equivalent of the selected reactive component (A) (for example, the epoxy equivalent in the case of epoxy monomers and their oligomers). Generally, the content of the curing agent or the curing accelerator is preferably 0.1 to 20 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 2 to 8 parts by mass, based on 100 parts by mass of the epoxy monomer and its oligomer. By setting the content of the curing agent or the curing accelerator to be equal to or higher than the above lower limit value, good curing can be obtained. On the other hand, by setting the content of the curing agent or the curing accelerator to be equal to or lower than the above upper limit value, the storage stability of the adhesive layer obtained by the adhesive composition can be improved.

[0073] <Others> In addition to the above components, the adhesive composition of the present embodiment may contain paraffins, antioxidants, polymerization inhibitors, inorganic fine particles, inorganic fillers, ultraviolet absorbers, silicon-based additives, fluorine-based additives, flame retardants, plasticizers, silane coupling agents, organic beads, defoaming agents, anti-fogging agents, colorants, and organic solvents, etc. These various components may be added in any amount according to the desired performance.

[0074] [Method for producing the adhesive] The adhesive composition of the present embodiment can be prepared by uniformly mixing the above various components using a pot mill, ball mill, bead mill, roll mill, homogenizer, super mill, homodisper, planetary mixer, universal mixer, Banbury mixer, kneader, etc. The mixing method is appropriately set according to the raw material components, and various methods can be adopted, such as a method of mixing all the raw material components at once, a method of mixing any components first and then mixing the remaining components at once or sequentially. Also, the settings of the stirring speed, stirring time, temperature, etc. during mixing are appropriately adjusted according to the raw materials.

[0075] [Usage mode] As an embodiment of the present invention in this embodiment, preferably, it can be used as a two-component adhesive composition. For the two-component type, all the essential components of the adhesive composition in this embodiment are not mixed during storage. The adhesive composition is divided into a first agent and a second agent, and a polymerization initiator is stored separately in the first agent and a reducing agent is stored separately in the second agent. The two-component type is preferable in terms of excellent storage stability. In this case, both agents can be applied simultaneously or separately to come into contact and cure, thereby being used as a two-component adhesive composition.

[0076] <Coating amount of the adhesive (first adhesive, second adhesive)> The coating amount of the adhesive 50 is 100 g / m 2 or more and 1500 g / m 2 or less. The lower limit value of the coating amount of the adhesive 50 is preferably 150 g / m 2 or more, and more preferably 200 g / m 2 or more. The upper limit value is preferably 1300 g / m 2 or less, and more preferably 1000 g / m 2 or less.

[0077] The coating amount of the adhesive 50 can be the sum of the coating amounts of the first adhesive 51 and the second adhesive 52. That is, the sum of the coating amount of the first adhesive 51 and the coating amount of the second adhesive 52 is within the range of the coating amount of the adhesive 50 described above. Specifically, the coating amount A of the first adhesive 51 is 100 g / m 2 or more and 1000 g / m 2 or less. The lower limit of the coating amount A of the first adhesive 51 is preferably 150 g / m 2 or more, and more preferably 200 g / m 2 or more. The upper limit is preferably 900 g / m 2 or less, and more preferably 800 g / m 2 or less.

[0078] The coating amount B of the second adhesive 52 is 0 g / m 2 or more and 1500 g / m 2 or less. The lower limit value of the coating amount B of the second adhesive 52 is preferably 50 g / m 2 or more, and more preferably 100 g / m2 The above. The upper limit is preferably 1300 g / m 2 or less, more preferably 1000 g / m 2 or less.

[0079] A kg / m which is the coating amount of the first adhesive 51 2 and B kg / m which is the coating amount of the second adhesive 52 2 The ratio B / A between them is 0 or more and 4.0 or less. The lower limit of the ratio B / A is preferably 0.1 or more, more preferably 0.2 or more. The upper limit of the ratio B / A is preferably 3.0 or less, more preferably 2.5 or less.

[0080] The coating amount A of the first adhesive 51 and the coating amount B of the second adhesive 52 can be appropriately adjusted according to the basis weight of the fiber sheet 3, and can be set as follows, for example. When the basis weight of the fiber sheet 3 is small (for example, 50 to 200 g / m 2 ), the coating amount A of the first adhesive 51 is 100 g / m 2 or more and 600 g / m 2 or less, and the coating amount B of the second adhesive 52 is 0 g / m 2 or more and 600 g / m 2 or less. Further, the total of the coating amount A of the first adhesive 51 and the coating amount B of the second adhesive 52 (that is, the coating amount of the adhesive 50) is 100 g / m as described above 2 or more and 1500 g / m 2 or less, and the ratio B / A is 0 or more and 4.0 or less.

[0081] When the basis weight of the fiber sheet 3 is small, the fiber spacing is wide and the first adhesive 51 may ooze out to the surface of the fiber sheet 3. In such a case, the coating amount of the second adhesive 52 which is a topcoat material is omitted or reduced. On the other hand, even when the basis weight of the fiber sheet 3 is small, if the fiber sheet 3 is thin and has a uniform surface structure, the first adhesive 51 does not necessarily ooze out to the surface of the fiber sheet 3. In such a case, a certain amount of the second adhesive 52 is applied. When the surface of the fiber sheet 3 is uniform, since the necessity of leveling the surface is low, the coating amount of the second adhesive 52 may be small.

[0082] When the basis weight of the fiber sheet 3 is medium (for example, 200 to 500 g / m 2 ), the coating amount A of the first adhesive 51 is 300 g / m 2 or more and 800 g / m 2 or less, and the coating amount B of the second adhesive 52 is 0 g / m 2 or more and 1300 g / m 2 or less. Furthermore, the total of the coating amount A of the first adhesive 51 and the coating amount B of the second adhesive 52 (that is, the coating amount of the adhesive 50) is 100 g / m 2 or more and 1500 g / m 2 or less, and the ratio B / A is 0 or more and 4.0 or less.

[0083] When the basis weight of the fiber sheet 3 is large (for example, 500 to 1000 g / m 2 ), the coating amount A of the first adhesive 51 is 400 g / m 2 or more and 1000 g / m 2 or less, and the coating amount B of the second adhesive 52 is 0 g / m 2 or more and 1500 g / m 2 or less. Furthermore, the total of the coating amount A of the first adhesive 51 and the coating amount B of the second adhesive 52 (that is, the coating amount of the adhesive 50) is 100 g / m 2 or more and 1500 g / m 2 or less, and the ratio B / A is 0 or more and 4.0 or less. For example, when the basis weight of the fiber sheet 3 is large, the fiber interval becomes narrow and the amount of the first adhesive 51 impregnated into the fiber sheet 3 tends to decrease. On the other hand, since the unevenness (specifically, the unevenness of plain weave) of the fiber sheet 3 becomes large, a large amount of resin may be required to level it. Therefore, by increasing the amount of the second adhesive 52 which is a topcoat agent and leveling the unevenness of the fiber sheet 3, the visibility of back surface breakage can be ensured well.

[0084] In the above example, the basis weight of the fiber sheet 3 is divided into three stages, but it is not limited to this, and it may be divided into two stages or four or more stages. Furthermore, the coating amount of the adhesive 50 (the first adhesive 51, the second adhesive 52) may be adjusted according to the unevenness and thickness of the surface of the fiber sheet 3.

[0085] <Collision energy and cumulative damage value> In this embodiment, the projectile 2 collides with the surface 11 of the test concrete 101 whose back surface 12 has been reinforced by the fiber sheet 3, and the cumulative value ES of the collision energy EA up to the back surface failure is evaluated. Assuming that the collision energy (i.e., kinetic energy) of the projectile 2 is not so large, the following three evaluation conditions 1 to 3 are assumed. Evaluation condition 1: The collision energy EA per hit of the projectile 2 is 0.1 kJ or more and less than 7.0 kJ, and the cumulative failure value ES is 7.0 kJ or more. Evaluation condition 2: The collision energy EA per hit of the projectile 2 is 0.5 kJ or more and less than 1.5 kJ, and the cumulative failure value ES is 15.0 kJ or more. Evaluation condition 3: The collision energy EA per hit of the projectile 2 is 3.0 kJ or more and less than 4.0 kJ, and the cumulative failure value ES is 25.0 kJ or more.

[0086] In the case of evaluation condition 1: The cumulative value of the collision energy (i.e., the cumulative failure value ES) until the projectile 2 collides and causes back surface failure is 7.0 kJ or more. That is, when the projectile 2 collides multiple times, if the cumulative failure value ES is less than 7.0 kJ, back surface failure does not occur. When the cumulative failure value ES is equal to or greater than a predetermined value, it is evaluated that the concrete 1 having the fiber sheet 3 on the back surface 12 is constructed so as to have a certain strength considering back surface failure. The lower limit of the cumulative fracture value ES is preferably 10 kJ or more, more preferably 15 kJ or more. The upper limit of the cumulative fracture value ES is not particularly limited, but as a practical value, it is 50 kJ or less, may be 40 kJ or less, or may be 30 kJ or less. For example, when the assumed kinetic energy (impact energy) of the flying object 2 is small, the cumulative fracture value ES is set to "7.0 kJ or more". Also, when the kinetic energy (impact energy) of the flying object 2 is large near a volcano or the like, or when repeated impacts are assumed, it is set to "15 kJ or more". By assigning multiple levels of evaluation ranks according to the cumulative fracture value ES to be set, it becomes easier to determine whether the constructed concrete structure has the required strength.

[0087] In the case of evaluation condition 2: The cumulative value of the impact energy until the flying object 2 collides and causes back surface fracture (i.e., the cumulative fracture value ES) is 15 kJ or more. That is, when the flying object 2 collides multiple times, if the cumulative fracture value ES is less than 15 kJ, back surface fracture will not occur. When the cumulative fracture value ES is equal to or greater than a predetermined value, it is evaluated that the concrete 1 having the fiber sheet 3 on the back surface 12 is constructed so as to have a certain strength considering back surface fracture. The lower limit of the cumulative fracture value ES is preferably 20 kJ or more, more preferably 25 kJ or more. The upper limit of the cumulative fracture value ES is not particularly limited, but as a practical value, it is 50 kJ or less, may be 45 kJ or less, or may be 40 kJ or less. For example, when the assumed kinetic energy (impact energy) of the flying object 2 is small, the cumulative fracture value ES is set to "15 kJ or more". Also, when the kinetic energy (impact energy) of the flying object 2 is large near a volcano or the like, or when repeated impacts are assumed, it is set to "25 kJ or more". By assigning multiple levels of evaluation ranks according to the cumulative fracture value ES to be set, it becomes easier to determine whether the constructed concrete structure has the required strength.

[0088] In the case of evaluation condition 3: The cumulative value of the impact energy (i.e., the destruction cumulative value ES) until the flying object 2 collides and reaches the back surface destruction is 25 kJ or more. That is, when the flying object 2 collides multiple times, if the destruction cumulative value ES is less than 25 kJ, the back surface destruction will not occur. When the destruction cumulative value ES is equal to or greater than a predetermined value, it is evaluated that the concrete 1 having the fiber sheet 3 on the back surface 12 is constructed so as to have a certain strength considering the back surface destruction. The lower limit of the destruction cumulative value ES is preferably 30 kJ or more, and more preferably 35 kJ or more. The upper limit of the destruction cumulative value ES is not particularly limited, but as a realistic value, it is 50 kJ or less, may be 45 kJ or less, or may be 40 kJ or less. For example, when the assumed kinetic energy (impact energy) of the flying object 2 is small, it is set as "25 kJ or more" as the destruction cumulative value ES. Also, when the flying object 2 is close to a volcano or the like and the kinetic energy (impact energy) of the flying object 2 is large or repeated collisions are assumed, it is set as "30 kJ or more". By setting multiple evaluation ranks according to the set destruction cumulative value ES, it becomes easier to determine whether the constructed concrete structure has the required strength.

[0089] Among the above evaluation conditions, evaluation condition 3 is the strictest, and then evaluation condition 2 is strict. Evaluation condition 1 is not the strictest condition among the three evaluation conditions. In this way, by providing multiple indicators with different degrees of strictness of the evaluation conditions, more detailed construction conditions can be proposed according to the facility to be applied. That is, according to the type of facility, the construction location, and the required service life, the optimal construction conditions with no excess or deficiency in the required construction level can be determined.

[0090] <Concrete Back Surface Reinforcement Method> Referring to FIGS. 3 and 4, the concrete back surface reinforcement method will be described. FIG. 3 is a flowchart showing the concrete back surface reinforcement method. FIG. 4 is an image showing the attachment process (especially the attachment state) of the fiber sheet 3 to the concrete 1 in each step of the concrete back surface reinforcement method. In FIG. 4, an example is shown in which the fiber sheet 3 is attached not only to the back surface 12 but also to the side surface and the like.

[0091] The concrete back surface reinforcement method of this embodiment includes a member preparation step S10 and a resin sheet attachment step S20.

[0092] Member preparation step S10: The member preparation step S10 includes a concrete preparation step S11 and a fiber sheet preparation step S12. The order of the concrete preparation step S11 and the fiber sheet preparation step S12 is not particularly limited.

[0093] The concrete preparation step S11 is a step of preparing the concrete 1 to which the fiber sheet 3 is to be attached. The concrete 1 may be a newly constructed concrete structure or an existing concrete structure. At this time, the back surface 12 of the concrete 1 may be coated with a primer or a putty material as a base treatment. By using the same material as the first adhesive 51 as the primer or the putty material, the construction period can be shortened. Note that the base treatment may be performed in the resin sheet attachment step S20 described later.

[0094] The fiber sheet preparation step S12 is a step of preparing the fiber sheet 3 to be attached to the concrete 1. As described above, the fiber sheet 3 is preferably impregnated with a resin (that is, the adhesive 50) and pre-impregnated.

[0095] Resin sheet attachment step S20: The resin sheet attachment step S20 is a step of attaching the fiber sheet 3 to the back surface 12 of the concrete 1, and specifically includes a primer coating step S21, a fiber sheet pasting step S22, and a topcoat coating step S23.

[0096] The primer coating step S21 is a step of applying the first adhesive 51 as a primer to the back surface 12 of the concrete 1 prepared in the member preparation step S10. At this time, on the back surface 12, a coating film of the first adhesive 51 is formed so as to cover at least the region where the fiber sheet 3 is to be attached. The application amount A of the first adhesive 51 is 100 g / m 2 or more and 1000 g / m 2The following is preferable and is adjusted according to the basis weight of the fiber sheet 3.

[0097] The fiber sheet pasting step S22 is a step of pasting the fiber sheet 3 from above the first adhesive 51. It is preferable to attach the fiber sheet 3 before the drying or curing of the first adhesive 51 which is a primer is completed. Thereby, the fiber sheet 3 can be appropriately pasted on the coating film of the first adhesive 51.

[0098] The topcoat application step S23 is a step of applying the second adhesive 52 as a topcoat on the fiber sheet 3 pasted to the concrete 1 with the first adhesive 51. Specifically, application with the second adhesive 52 which is a topcoat is performed so as to cover the first adhesive 51 and the fiber sheet 3, and a coating film of the second adhesive 52 is formed. From the viewpoint of shortening the construction period, it is preferable to complete the pasting of the fiber sheet 3 and the application of the second adhesive 52 before the drying or curing of the first adhesive 51 is completed.

[0099] The application amount B of the second adhesive 52 is 0 g / m 2 or more and 1500 g / m 2 or less, and is adjusted according to the basis weight of the fiber sheet 3, the state of prepreg, and the application amount A of the first adhesive 51. The ratio B / A of the application amount A of the first adhesive 51 to the application amount B of the second adhesive 52 is adjusted to be 0 or more and 4.0 or less.

[0100] <Properties of the concrete with the back surface reinforced> When the back surface reinforced concrete 102 manufactured under the above conditions is tested under the following experimental conditions, back surface failure does not occur. In other words, a preliminary experiment is conducted, and the design is performed so that back surface failure does not occur, and the fiber sheet 3 is constructed on the concrete 1 to be reinforced by the above steps.

[0101] Fig. 5 is a diagram showing the high-pressure air type flying object generating device 90 and the concrete 102 with the back surface reinforced used in the experiment. Fig. 6 is a diagram showing the concrete 102 with the back surface reinforced. Fig. 7 is a diagram of the test flying object 21 (corresponding to the flying object 2) to be launched from the high-pressure air type flying object generating device 90 toward the concrete 1. The high-pressure air type flying object generating device 90 is a device for accelerating the test flying object 21 to a predetermined speed by air pressure and colliding it against the concrete 102 with the back surface reinforced.

[0102] As shown in Fig. 5, the high-pressure air type flying object generating device 90 includes, in order from the upstream side, an air compressor 91, an air chamber 93, a launch tube 94, and a bounce prevention jig 97. A speed sensor 95 is attached to the bounce prevention jig 97. In front of the bounce prevention jig 97, the concrete 102 with the back surface reinforced is fixed to the reaction wall 80 and arranged so that the flying object 2 (high-speed flying object) collides perpendicularly with the center of the surface 11 of the concrete 102 with the back surface reinforced. The maximum capacity of the air compressor 91 is, for example, 4 MPa.

[0103] The air compressed by the air compressor 91 (compressor) is sent into the air chamber 93 and pressurized to a pressure corresponding to the set speed of the test flying object 21. Before pressurization, the test flying object 21 is hydraulically installed in the flying object fixing portion 98 of the air chamber 93. A launch tube 94 is attached to the tip of the air chamber 93, and the compressed air compressed to the set pressure is supplied to the launch tube 94 at a predetermined timing (the timing by the operation or setting by the experimenter).

[0104] The launch tube 94 has an inner diameter (100 mm) slightly larger than the outer diameter of the test flying object 21 and a length of 2200 mm. The test flying object 21 is accelerated to a desired speed inside by the compressed air introduced from the air chamber 93 and launched from the launch port 96. The speed of the launched test flying object 21 is measured by the speed sensor 95. A load cell 81 is installed on the reaction wall 80, and the load when the flying object 2 collides can be measured.

[0105] FIG. 6 shows the back surface reinforced concrete 102 used in the experiment. FIG. 6(a) is a rear view, and FIG. 6(b) is a sectional view taken along line A-A of FIG. 6(a). The back surface reinforced concrete 102 has the test concrete 101 and the fiber sheet 3 attached to the back surface 12.

[0106] The dimensions of the test concrete 101 are 1100 mm × 1100 mm × 150 mm. The compressive strength of the test concrete 101 is 30 N / mm 2 . In order to prevent the fragmentation of the concrete after the impact of the flying object 2, 12 (one body) of D13 reinforcing bars 15 are arranged with a reinforcement ratio of 0.57% (0.49% within the back surface indicator). In the peripheral region of the test concrete 101 (the region where the fiber sheet 3 is not provided), as shown in the figure, a plurality of through holes 16 penetrating from the front surface 11 to the back surface 12 are provided. The through holes 16 are used for screwing and fixing the back surface reinforced concrete 102 to the reaction wall 80.

[0107] The fiber sheet 3 is attached to the back surface 12 of the test concrete 101 by an adhesive 50 (the first adhesive 51 and the second adhesive 52). The area of the fiber sheet 3 to be attached is 830 mm × 830 mm. As the fiber sheet 3 and the adhesive 50 (the first adhesive 51 and the second adhesive 52), the above-described materials can be used.

[0108] As shown in FIG. 7, the test flying object 21 has a tip portion formed in a dome shape and a cylindrical body portion for fixing the tip portion. The tip portion is formed of alloy tool steel with a radius of 90 mm and a length of 55 mm. The body portion is formed of duralumin with a length of 225 mm. The mass of the test flying object 21 is 4.5 kg.

[0109] The launch speed of the test flying object 21, that is, the flying object setting speed when colliding with the concrete 1, is two types: 20 m / s and 40 m / s.

[0110] When the test projectile 21 is collided with the back surface reinforced concrete 102 three times using the high-pressure air type projectile generator 90, if no back surface failure occurs at any of the projectile setting speeds, it can be determined that it has the required strength against the collision of the projectile 2.

[0111] <Summary of this embodiment> [1] A concrete back surface reinforcement method for preventing back surface failure in which the other surface (back surface 12) opposite to the one surface (front surface 11) is damaged by the collision of the projectile 2 on one surface (front surface 11) of the concrete 1, by attaching a fiber sheet 3 to the other surface (back surface 12). The resin sheet attachment step S20 of attaching the fiber sheet 3 to the other surface (back surface 12) of the concrete 1 includes a step of applying a first adhesive 51 (primer) to the other surface (back surface 12) of the concrete 1 (primer application step S21), and a step of attaching the fiber sheet 3 from above the first adhesive 51 (fiber sheet attachment step S22). After attaching the fiber sheet 3 to the other surface (back surface 12) of the test concrete 101, the cumulative value of the collision energy EA up to the back surface failure when the projectile 2 collides with the one surface (front surface 11), the destruction cumulative value ES, is 7.0 kJ or more, and the collision energy EA per hit of the projectile 2 is 0.1 kJ or more and less than 7.0 kJ. The test concrete 101 has a shape of 1100 mm in length × 1100 mm in width × 150 mm in thickness, and its compressive strength is 24 N / mm 2 or more. Concrete back surface reinforcement method. [2] The resin sheet attachment step S20 further includes a step of applying a second adhesive (topcoat) on the fiber sheet 2 attached to the back surface 12 of the concrete 1 with the first adhesive (topcoat application step S23), the concrete back surface reinforcement method according to [1]. [3] The first adhesive and the second adhesive include at least one of a (meth)acrylic resin-based adhesive and an epoxy resin-based adhesive, and the concrete back surface reinforcement method according to [2]. [4] The application amount A of the first adhesive is 100 g / m 2 or more and 1000 g / m 2 or less, The application amount B of the second adhesive is 0 g / m 2 or more and 1500 g / m 2 or less, and the concrete back surface reinforcement method according to [2] or [3]. [5] A kg / m which is the application amount of the first adhesive 2 and B kg / m which is the application amount of the second adhesive 2 The ratio B / A of them is 0 or more and 4.0 or less, and the concrete back surface reinforcement method according to any one of [2] to [4]. [6] The basis weight of the fiber sheet 3 is 50 g / m 2 or more and 1000 g / m 2 or less, and the concrete back surface reinforcement method according to any one of [1] to [5]. [7] The fiber sheet 3 includes a two-way sheet in which fibers are arranged along two axial directions different from each other, or a laminated sheet in which two one-way sheets in which fibers are arranged along one axial direction are laminated so that the axial directions intersect each other, and the concrete back surface reinforcement method according to any one of [1] to [6]. [8] The fiber sheet 3 is an aramid fiber sheet, and the concrete back surface reinforcement method according to any one of [1] to [7]. [9] The cumulative damage value is 10 kJ or more, and the concrete back surface reinforcement method according to any one of [1] to [8].

[10] When the flying object 2 is collided with the standardized concrete 1 three times under the following experimental conditions using a high-pressure air type flying object generator, no back surface failure occurs, and the concrete back surface reinforcement method according to any one of [1] to [9]. Experimental conditions: · Equipment: High-pressure air type projectile generator (National Defense Academy) · Concrete specimen (standardized concrete): 1100mm × 1100mm × 150mm · Projectile mass: 4.5 kg (Φ90mm) · Projectile set speed: 20 m / s, 40 m / s

[11] The collision energy per hit of the projectile 2 is 0.5 kJ or more and less than 1.5 kJ, and the cumulative damage value is 15.0 kJ or more. The concrete back surface reinforcement method according to any one of [1] to

[10] .

[12] The collision energy per hit of the projectile 2 is 3.0 kJ or more and less than 4.0 kJ, and the cumulative damage value is 25.0 kJ or more. The concrete back surface reinforcement method according to any one of [1] to

[10] . A concrete structure (concrete 102 with back surface reinforcement) reinforced by using the concrete back surface reinforcement method according to any one of [1] to

[12] .

Example

[0112] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[0113] The high-pressure air type projectile generator and the concrete with back surface reinforcement (Examples 1 to 6) and the concrete without back surface reinforcement (Comparative Examples 1 to 3) described in FIGS. 5 to 7 above were prepared as concrete specimens, and the projectile 2 was repeatedly collided, and an experiment was conducted to observe the number of collisions until back surface failure and the state of the back surface at that time.

[0114] The outline of the experimental conditions is as follows. In the embodiment, two types of projectile set speeds, 20 m / s and 40 m / s, were described. In this example, as a reference example, an experiment with a projectile set speed of 60 m / s was conducted on Comparative Example 3. · Equipment: High-pressure air type projectile generator (National Defense Academy) · Concrete specimen: 1100 mm × 1100 mm × 150 mm, 28-day compressive strength 30 N / mm 2 (Measured in accordance with JIS A 1108:2018) · Fiber sheet area: 830 mm × 830 mm · Projectile mass: 4.5 kg · Projectile set velocity: 20 m / s (Examples 1 to 3, Comparative Example 1) 40 m / s (Examples 4 to 6, Comparative Example 2) 60 m / s (Comparative Example 3)

[0115] In Examples 1 to 6, a reinforcing fiber sheet was attached to the above concrete specimen. In Comparative Examples 1 to 3, the concrete specimen was used as it was. The specifications of the fiber sheets used in Examples 1 to 6 (test level (fiber sheet reinforcement)) are as shown in Table 1. As the fiber sheets, three types with different basis weights (180 g / m 2 , 330 g / m 2 , 650 g / m 2 ) of two-way aramid fiber sheets were used. Table 2 shows the basis weight, primer, coating amount, and adhesive coating amount (undercoat / topcoat) for each type of two-way aramid fiber sheet. As the primer, a two-component acrylic resin adhesive (product name: Denka DK550-003, manufactured by Denka Co., Ltd.) was used. As the adhesive, a two-component acrylic resin adhesive (product name: Denka Acrysave K, manufactured by Denka Co., Ltd.) was used.

[0116]

Table 1

Table 2

[0117] The concrete specimens of the back surface-reinforced concrete in Examples 1 to 6 were prepared by the concrete back surface reinforcement method described with reference to FIGS. 3 and 4. Specifically, first, as a base treatment, the concrete specimens were subjected to a keren treatment to adjust the substrate of the concrete specimens. Subsequently, a primer was applied to the area where the fiber sheets were to be attached to the concrete specimens. Thereafter, the respective fiber sheets corresponding to Examples 1 to 6 were attached to the areas where the primer was applied, and cured for a predetermined time.

[0118] Using the above-described high-pressure air type flying body generator, the flying bodies were made to collide with the specimens, namely, the obtained back surface reinforced concrete (Examples 1 to 6) and the non-back surface reinforced concrete (Comparative Examples 1 to 3), and the number of collisions causing back surface peeling and the cumulative kinetic energy were calculated.

[0119] The results are shown in Table 3. Also, FIG. 10 shows the state of the back surface after the final number of collisions of Examples 1 to 3 as an image. FIG. 11 shows the state of the back surface after the final number of collisions of Examples 4 to 6 as an image.

[0120] Regarding the specimens of Examples 1 to 6, it was confirmed that back surface peeling could be prevented by fiber sheet reinforcement. In Comparative Examples 1 to 3, no fiber sheet reinforcement was provided, and back surface peeling was confirmed.

[0121] In addition, in all the specimens of Examples 1 to 6, even when the number of collisions was increased, the fiber sheets did not break or peel off, and the center part of the sheet bulged. This is because when the flying body collided multiple times, it was determined that there was a risk that the flying body could not escape from the specimen and the experiment could not be continued, so the subsequent experiments were interrupted. For this reason, although the back surface peeling limit energy could not be directly calculated, it was judged that the probability of breakage and peeling of the fiber sheet was high in the next collision, and the cumulative kinetic energy until the interruption was adopted as a value for evaluation. In addition, the cumulative kinetic energies of Comparative Examples 1 to 3 were 6.3 kJ in Comparative Example 1, 7.2 kJ in Comparative Example 2, and 8.1 kJ in Comparative Example 3. However, the collision energy per impact in Comparative Examples 2 and 3 was 3.6 kJ and 8.1 kJ, respectively. Considering the increase in cumulative kinetic energy when the number of collisions increased by one, the cumulative kinetic energy when back surface peeling occurred was estimated to be less than 7 kJ.

Table 3

Explanation of Symbols

[0122] 1 Concrete 2 Flying object (sometimes referred to as a high-speed flying object) 3 Fiber sheet 11 Surface 12 Back surface 21 Test flying object 51 First adhesive 52 Second adhesive 80 Reaction wall 81 Load cell 90 High-pressure air type flying object generator 91 Air compressor 93 Air chamber 94 Launch tube 95 Speed sensor 97 Anti-rebound jig 101 Test concrete 102 Concrete with reinforced back surface

Claims

1. A concrete back surface reinforcement method for preventing back surface breakage in which the other surface opposite to one surface of the concrete is broken by the collision of a flying object on one surface of the concrete, comprising: The resin sheet attachment step of attaching the fiber sheet to the other surface of the concrete includes a step of applying a first adhesive to the other surface of the concrete and attaching the fiber sheet from above the first adhesive. The concrete is prepared as test concrete, and after attaching the fiber sheet to the other surface of the test concrete, the cumulative value of the collision energy until the flying object collides with the one surface and causes the back surface breakage, i.e., the cumulative breakage value, is 7.0 kJ or more, and the collision energy per hit of the flying object is 0.1 kJ or more and less than 7.0 kJ. The test concrete has a shape of 1100 mm in length × 1100 mm in width × 150 mm in thickness, and its compressive strength is 24 N / mm ２ or more. Concrete back surface reinforcement method.

2. The resin sheet attachment step further includes a step of applying a second adhesive onto the fiber sheet attached to the back surface of the concrete with the first adhesive. The concrete back surface reinforcement method according to Claim 1.

3. The first adhesive and the second adhesive include at least one of a (meth)acrylic resin-based adhesive and an epoxy resin-based adhesive. The concrete back surface reinforcement method according to Claim 2.

4. The coating amount A of the first adhesive is 100 g / m ２ or more and 1000 g / m ２ or less, and The coating amount B of the second adhesive is 0 g / m ２ or more and 1500 g / m ２ or less. The method for reinforcing the back surface of concrete according to claim 2 or 3.

5. Ak g / m, which is the coating amount of the first adhesive ２ and Bk g / m, which is the coating amount of the second adhesive ２ The ratio B / A of the above is 0 or more and 4.0 or less. The concrete back surface reinforcement method according to claim 2 or 3

6. The basis weight of the fiber sheet is 50 g / m ２ or more and 1000 g / m ２ or less. The concrete back surface reinforcement method according to any one of claims 1 to 3.

7. The fiber sheet includes a two-way sheet in which fibers are arranged along two axial directions different from each other, or a laminated sheet in which two one-way sheets in which fibers are arranged along one axial direction are laminated so that the axial directions intersect each other. The concrete back surface reinforcement method according to any one of Claims 1 to 3.

8. The fiber sheet is an aramid fiber sheet. The concrete back surface reinforcement method according to any one of Claims 1 to 3.

9. The cumulative breakage value is 10 kJ or more. The concrete back surface reinforcement method according to any one of Claims 1 to 3.

10. When a flying object is collided with the test concrete to which the fiber sheet is attached three times under the following experimental conditions using a high-pressure air type flying object generator, no back surface breakage occurs. The concrete back surface reinforcement method according to any one of Claims 1 to 3. Experimental conditions: ・ Device: High-pressure air type flying object generator ・ Flying object mass: 4.5 kg (Φ90 mm) ・ Flying object set speed: 20 m / s, 40 m / s

11. The impact energy per hit of the flying object is 0.5 kJ or more and less than 1.5 kJ, The concrete back surface reinforcement method according to any one of claims 1 to 3, wherein the cumulative damage value is 15.0 kJ or more.

12. The impact energy per hit of the flying object is 3.0 kJ or more and less than 4.0 kJ, The concrete back surface reinforcement method according to any one of claims 1 to 3, wherein the cumulative damage value is 25.0 kJ or more.

13. A concrete structure reinforced by using the concrete back surface reinforcement method according to any one of claims 1 to 3.

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