Concrete reinforcing material and concrete reinforced structure

Abstract

To provide a mechanism for improving strength by suppressing an increase in at least one of the volume and mass of a concrete skeleton.SOLUTION: A concrete reinforced structure includes a skeleton including concrete and having a slit hole linearly formed in a surface layer part of the skeleton, and a concrete reinforcing material having a long shape and attached to the slit hole along a longitudinal direction of the slit hole.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The technology disclosed herein relates to concrete reinforcement materials and concrete-reinforced structures. [Background technology]

[0002] Patent Document 1 discloses a reinforcement method that enables observation of cracking progress while suppressing cracking in the surface layer of concrete. In Patent Document 1, a multilayer sheet in which lattice-shaped carbon fibers are woven into a transparent nonwoven fabric substrate is used as a reinforcing material, and this multilayer sheet is adhered to the surface layer of concrete with a transparent adhesive. This makes it possible to observe cracks in the concrete while suppressing cracking. While this multilayer sheet has the advantage of being thin and not significantly increasing the volume of the concrete body, it is subject to significant deterioration due to exposure to the environment, fire damage, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2012-26238 Summary of the Invention

[0004] Therefore, when the bearing strength of concrete has decreased, it is desirable to be able to improve the bearing strength without increasing the volume and mass of the concrete body.

[0005] In view of the above background, the present disclosure employs, for example, the configurations described in the claims. According to the present disclosure, a mechanism is provided for improving the strength of a concrete body by suppressing an increase in at least one of the volume and mass of the concrete body. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0006] [Figure 1]FIG. 1 is a schematic diagram of a stiffener according to one embodiment. [Figure 2] 10(a) to 10(c) are schematic diagrams of a concrete reinforcing material according to another embodiment. [Figure 3A] 1 is a schematic perspective view showing a reinforcing material according to one embodiment and a concrete body having a slit for attaching the reinforcing material. [Figure 3B] 1 is a schematic perspective view of a concrete reinforced structure according to one embodiment; [Figure 4A] FIG. 1 is a schematic perspective view of a tunnel made of reinforced concrete. [Figure 4B] 4B is a schematic perspective view partially showing a concrete reinforcement for reinforcing the tunnel of FIG. 4A and a tunnel provided with a slit for fitting the concrete reinforcement. FIG. [Figure 4C] FIG. 4C is a schematic perspective view of a portion of a tunnel in which the concrete reinforcement of FIG. 4B is installed in the slit. [Figure 5A] 1A is a plan view showing the structure of a slit hole according to one embodiment, and FIG. 1B is a cross-sectional view taken along the line bb. [Figure 5B] 5B is a cross-sectional view taken along the line bb of a reinforced concrete structure obtained by fitting concrete reinforcement materials into the slit holes of FIG. 5A. FIG. [Figure 6] FIG. 10 is a schematic perspective view of a portion of a concrete reinforced structure according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, a concrete reinforced structure, a concrete reinforcing material, and a method for reinforcing a concrete skeleton according to the present technology will be described with reference to the drawings as appropriate. This technology generally involves forming slits in the surface layer of a concrete skeleton and fitting longitudinally elastic concrete reinforcement into the slits to reinforce the concrete skeleton. The reinforced concrete structure obtained in this way is, for example, strengthened without increasing the volume or mass of the original concrete skeleton. The concrete reinforcement functions, for example, like a reinforcing steel member, and can easily add strength to the concrete skeleton. Furthermore, because the concrete reinforcement is not exposed on the surface of the concrete skeleton, deterioration is suppressed.

[0008] (Embodiment 1) [Concrete reinforcement] First, we will explain concrete reinforcement materials. Fig. 1 is a schematic diagram of a concrete reinforcing material 100 according to one embodiment. Figs. 2(a) to 2(c) are schematic diagrams of a concrete reinforcing material 100 according to another embodiment.

[0009] The concrete reinforcement 100 according to this embodiment is an element that reinforces a concrete body (for example, see the concrete cube 6 and concrete body 14 in FIG. 2 described later). The concrete reinforcement 100 is typically long, for example, in the form of a long sheet or plate. The concrete reinforcement 100 has elasticity in at least one direction, typically the longitudinal direction. The concrete reinforcement 100 has, for example, a higher modulus of elasticity (tensile modulus) than the concrete body to be repaired. This concrete reinforcement 100 can function, for example, like a reinforcing bar in reinforced concrete. From this perspective, the concrete reinforcement 100 may also be referred to as a reinforcing bar, a tensioning member, or the like that imparts strength and durability to the concrete body.

[0010] In one embodiment, the concrete reinforcement 100 preferably has a higher elastic modulus than that required for the concrete skeleton 14, for example, it is preferably equal to or higher than the elastic modulus of the concrete skeleton 14 at the time of manufacture. For reference, the tensile elastic modulus of a concrete structure is generally estimated to be equal to or slightly smaller than the compressive elastic modulus. The compressive elastic modulus (Young's modulus) of reinforced concrete is variously defined depending on the design standard strength, etc., but is 3.80 x 10 at a design standard strength of 80. 4 N / mm 2 Above, for PHC piles, 4.00 x 10 4 N / mm 2 That's all.

[0011] In one embodiment, the concrete reinforcement material 100 includes high-elasticity fibers. The concrete reinforcement material 100 is, for example, a woven fabric made of high-elasticity fibers. The woven fabric made of high-elasticity fibers may be, for example, a woven fabric in which untwisted or twisted fiber bundles 1, each consisting of a predetermined number of high-elasticity fibers (e.g., filament yarns), are used as warp yarns and these warp yarns are connected to each other by weft yarns 2, as shown in FIG. 1 . The woven fabric made of high-elasticity fibers may be, but is not required to be, impregnated with a resin material (e.g., a thermosetting resin or a thermoplastic resin) and hardened. The woven fabric made of high-elasticity fibers may be, for example, a fiber-reinforced plastic containing high-elasticity fibers. Note that, in the concrete reinforcement material 100, the multiple fiber bundles constituting the warp yarns are preferably densely connected by weft yarns with almost no gaps, as shown in FIG. 1 . The weft yarns may be any type that can maintain the connection of the multiple fiber bundles, and adjacent weft yarns may be spaced apart. The weft yarns may be arranged at intervals of, for example, 1 to 20 mm (for example, 2 to 15 mm, 3 to 10 mm).

[0012] In this specification, "high modulus" typically refers to a tensile modulus of approximately 100 cN / dtex or greater, for example, a tensile modulus of 200 cN / dtex or greater, preferably approximately 353 cN / dtex (400 g / d) or greater. While not limited thereto, high modulus fibers may have a tensile modulus of 353 cN / dtex or greater, such as 500 cN / dtex or greater, 700 cN / dtex or greater, 900 cN / dtex or greater, 1000 cN / dtex or greater, or 1200 cN / dtex or greater. Furthermore, each fiber bundle constituting the woven fabric may contain, for example, 100 or more high modulus fibers, for example, 10,000 or more high modulus fibers. Examples of such high modulus fibers include, but are not limited to, aramid fibers, carbon fibers, high-density polyethylene fibers, polybenzazole fibers, and glass fibers. The tensile modulus can be measured, for example, in accordance with the test method for chemical fiber tire cords specified in JIS L1017:2002.

[0013] The concrete reinforcement 100 may have a lower density than the concrete mass to be reinforced, for example. The density of the concrete mass is typically about 2.3 g / cm 3 (unreinforced). 3 and for reinforced concrete it is approximately 2.45 g / cm 3 In contrast, the density of high modulus fibers such as resin fibers or carbon fibers is, for example, about 2.25 g / cm 3 or less, for example, about 2 g / cm 3 Below, approximately 1.9g / cm 3 Below, about 1.8g / cm 3 Below, about 1.6g / cm 3 Below, about 1.5g / cm 3 Below, about 1.4g / cm 3 Below, about 1.3g / cm 3 The density of the glass fiber can be, for example, about 2.6 g / cm 3Therefore, the density of the concrete reinforcement 100 made of high modulus fibers is usually lower than the density of the high modulus fibers, and the density of the concrete reinforcement 100 made of a woven fabric of high modulus fibers can be even lower. The density of the concrete reinforcement 100 is, for example, about 2 g / cm 3 Below, approximately 1.9g / cm 3 Below, about 1.8g / cm 3 Below, about 1.6g / cm 3 Below, about 1.5g / cm 3 Below, about 1.4g / cm 3 Below, about 1.3g / cm 3 Below, about 1.2g / cm 3 Below, approximately 1g / cm 3 The following can be adopted: This allows reinforcement to be achieved without excessively increasing the weight of the concrete structure to be reinforced.

[0014] Such a concrete reinforcement material 100 can further include a resin impregnated into the plurality of fiber bundles. By impregnating the plurality of fiber bundles with resin, the plurality of fiber bundles can be integrated, which can improve the ease of handling during, for example, manufacturing, storage, and on-site construction. Furthermore, by coating the surfaces of the plurality of fiber bundles with resin, it is possible to suppress alteration and deterioration of the fiber bundles. This allows, for example, a fabric made of fiber bundles to be formed into a strip or sheet shape.

[0015] There are no particular limitations on the dimensions of the concrete reinforcement 100, such as width, length, and thickness. However, for example, when reinforcing a reinforced concrete skeleton, it is preferable that the width of the concrete reinforcement 100 be smaller than the "cover" dimensions (depth, thickness) of the concrete to be reinforced. From this perspective, the concrete reinforcement 100 may have a width of, for example, about (cover thickness - 1 to 5) mm, and is preferably in the form of a strip or sheet of, for example, 20 mm to 100 mm (typically, 25 mm to 80 mm).

[0016] Furthermore, as shown in Fig. 2, the concrete reinforcement 100 can be formed by combining (e.g., stacking) multiple fiber bundles in the thickness direction depending on the required stress (reinforcing force). For example, the concrete reinforcement 100 may be (a) a two-layer reinforcement (tensioning member) 3 in which two sheets of sheet-like reinforcement (corresponding to the single-layer concrete reinforcement 100) are stacked and integrated, (b) a three-layer reinforcement (tensioning member) 4 in which three sheets are stacked and integrated, or (c) a four-layer reinforcement (tensioning member) 5 in which four sheets are stacked and integrated. Although not specifically shown, the concrete reinforcement 100 may also be formed by stacking five or more sheets (e.g., 10, 20, 50, etc.) of sheet-like reinforcement materials in which five or more sheets are stacked and integrated depending on the required reinforcing strength.

[0017] In such a concrete reinforcing material 100 having a laminated structure, the stacked sheet-like reinforcing materials may be fixed together and integrated with, for example, a resin material. In other words, the concrete reinforcing material 100 having a laminated structure may further include a resin impregnated into each layer of a plurality of fiber bundles. In the concrete reinforcing material 100 having a laminated structure, the same resin is impregnated into adjacent layers of reinforcing material, thereby preventing the interposition of heterogeneous resin layers (e.g., adhesive layers) and suppressing the occurrence of layer separation and a decrease in flexibility, which will be described later.

[0018] However, in one embodiment, the concrete reinforcement 100 having a laminated structure may be fixed by applying a predetermined amount of adhesive between each reinforcement layer (e.g., a woven fabric made of fiber bundles) to the extent that the desired flexibility is obtained.

[0019] The resin contained in the concrete reinforcement 100 may be one that imparts flexibility to the concrete reinforcement 100. Here, "flexibility" with respect to the concrete reinforcement 100 refers to the property of having flexibility and not breaking when bent. In one embodiment, flexibility refers to the property of being able to bend a concrete reinforcement 100 with a thickness of 1 mm at room temperature (e.g., 25°C) with a radius of curvature R of 20 m or less without breaking. "Flexibility" with respect to the concrete reinforcement 100 may mean, for example, having any of the following characteristics: In accordance with JIS K7171:2016, when a three-point bending test is performed on a concrete reinforcement specimen measuring 80 mm x 10 mm x 4 mm, the flexural modulus is, for example, 15 GPa or less (typically, 10 GPa or less, 8 GPa or less, 5 GPa or less). A concrete reinforcement material 100 having a thickness of 1 cm can be bent (curved) at a radius of curvature R of 20 m or less (for example, 10 m or less, 5 m or less, 3 m or less, 1 m or less, 50 cm or less, 30 cm or less, 10 cm or less, 5 cm or less, 3 cm or less) without being damaged. A concrete reinforcement material 100 having a thickness of 1 mm can be bent (curved) at a radius of curvature R of 2 m or less (for example, 1 m or less, 50 cm or less, 30 cm or less, 10 cm or less, 5 cm or less, 3 cm or less, 1 cm or less) without being damaged. The "thickness" of the concrete reinforcing material 100 may be the average thickness measured at three or more points in the longitudinal direction.

[0020] As such a resin, for example, various resin materials that achieve the above-mentioned flexibility in a cured state can be used. Alternatively, a resin in a liquid state (resin composition) that can be impregnated into the fibers or fiber bundles in an uncured state is preferable. While not limited thereto, examples of resins contained in the concrete reinforcement material 100 include flexible epoxy resins, urethane resins, polyesters, polyamides, polycarbonates, polypropylene, polyethersulfone, triacetyl cellulose, polytetrafluoroethylene, thermoplastic elastomers (TPE), and dynamically crosslinked thermoplastic elastomers (Thermoplastic Vulcanizates: TPV). Among these, flexible epoxy resins and urethane resins are preferred from the viewpoints of weather resistance, environmental resistance, and durability.

[0021] The resin composition constituting the flexible resin may include, for example, a base polymer, a curing agent, and a modifying agent including a flexibilizing agent. The flexibilizing agent among the modifiers may be contained in the base polymer and / or the curing agent in the form of a functional group, or may also have other modifying functions (e.g., as a crosslinking agent). The flexible moiety may be contained in any of the base polymer, the curing agent, and the flexibilizing agent. The resin composition may be composed of a monomer, but is not limited thereto, and may be composed of any intermediate reactant. The resin composition may be a resin that has the desired flexibility after curing. The flexible resin will be described below using a flexible epoxy resin as an example. However, those skilled in the art will be able to understand other flexible resins that can be used in the present technology by referring to the description of the flexible epoxy resin below.

[0022] An example of a flexible resin is an epoxy resin having a flexible group introduced therein. The epoxy resin composition constituting this epoxy resin may contain, for example, more than 50% by weight of an epoxy-based base polymer. The epoxy-based base polymer may be selected from various epoxy compounds having two or more epoxy groups in one molecule, for example, from the viewpoint of providing flexibility. The epoxy compound may be, for example, a bifunctional epoxy compound having two epoxy groups in one molecule, or a multifunctional epoxy compound having three or more epoxy groups in one molecule. The epoxy compounds may be used alone or in combination of two or more. In terms of ease of operation when impregnating fibers, in one embodiment, an epoxy compound that is liquid at room temperature (e.g., 25°C) is preferably used.

[0023] In one embodiment, examples of the bifunctional epoxy compound include, but are not limited to, bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin (i.e., an epoxy compound corresponding to a structure in which the aromatic ring of a bisphenol A type epoxy resin is converted to a cycloalkyl ring by hydrogenation), hydrogenated bisphenol F type epoxy resin, biphenyl type epoxy resin, aliphatic type epoxy resin (e.g., polypropylene glycol type epoxy resin), 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and the like.

[0024] In one embodiment, examples of the polyfunctional epoxy compound include, but are not limited to, novolac-type epoxy resins, glycidylamine-type epoxy resins, biphenyl-type epoxy resins, triphenylmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, glycerin-type epoxy resins, trimethylolpropane-type epoxy resins, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, polyglycerol polyglycidyl ether, and the like. The number of epoxy groups contained in one molecule of the polyfunctional epoxy compound is at least 3 or more, and may be 4 or more, or 5 or more. The number of epoxy groups contained in one molecule of the polyfunctional epoxy compound is typically 10 or less, and may be 8 or less, or 6 or less.

[0025] In one embodiment, a bifunctional epoxy compound can be preferably used as the epoxy compound. The use of a bifunctional epoxy compound can be advantageous in imparting suitable elongation to the cured product of the impregnated resin. The bifunctional epoxy compounds can be used alone or in combination of two or more. In one embodiment, an epoxy compound containing a five- or higher-membered carbon ring structure in the molecule can be preferably used as the bifunctional epoxy compound. A cured product of an impregnated resin using a bifunctional epoxy compound with such a structure tends to have high strength and elongation. The five- or higher-membered carbon ring structure can be, for example, a benzene ring, a naphthalene ring, a cyclohexyl ring, etc. Examples of epoxy compounds containing such a carbon ring structure include bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, hydrogenated bisphenol F epoxy resin, biphenyl epoxy resin, etc. In a preferred embodiment, a bisphenol A epoxy resin can be used as the bifunctional epoxy compound. The bisphenol A liquid epoxy resin may have, for example, a mass average molecular weight (Mw) of 300 or more and 600 or less, but is not limited thereto. The mass average molecular weight may be, for example, a value measured by size exclusion chromatography in accordance with JIS K7252-1:2016.

[0026] As the epoxy compound, one or more polyfunctional epoxy compounds can be used in combination with a difunctional epoxy compound or in place of a difunctional epoxy resin. The use of a polyfunctional epoxy compound can improve the strength of the cured product of the impregnated resin. The combined use of a bifunctional epoxy compound and a polyfunctional epoxy compound can produce a cured product of the impregnated resin that exhibits both high strength and elongation. In some embodiments, the polyfunctional epoxy compound can be a polyfunctional epoxy compound having a repeating unit containing an epoxy group (i.e., a polymeric type), and novolac epoxy resins are preferred. Examples of novolac epoxy resins include phenol novolac epoxy resins and o-cresol novolac epoxy resins. The use of novolac epoxy resins can be advantageous for obtaining a sealant sheet that provides a cured product with high strength and excellent elongation. The use of a novolac epoxy resin with a lower molecular weight tends to improve the elongation of the cured product. For example, phenol novolac epoxy resins, which are liquid at room temperature, are preferred.

[0027] Examples of such epoxy compounds include, but are not limited to, the 840 to 850 series, TSR-960, 601, 1650-75MPX, and EXA-4850 series of "EPICLON" products manufactured by DIC Corporation; 871, 872, 872X75, 825, 827, and 828 jER (registered trademark) flexible epoxy resins manufactured by Mitsubishi Chemical Corporation; Epolead GT401 manufactured by Daicel Corporation; and flexible epoxy resins, Quick 5, Bond E series, and microcrack repair primer manufactured by Konishi Co., Ltd.

[0028] The epoxy resin composition may contain, as a modifier, for example, a flexibilizing agent, a crosslinking agent, a curing accelerator, or the like. The flexibilizer is an element capable of imparting flexibility to the cured base polymer, and can be, for example, a compound capable of imparting flexibility to the epoxy resin by adding a modifier or introducing a flexible backbone. Examples of such flexibilizers include, but are not limited to, alkylene ether compounds such as polyglycol diglycidyl ether (DGEPG); linear (acyclic) polycarboxylic acid anhydrides (long-chain fatty acid compounds) formed by polycondensation of polycarboxylic acids such as polyazelaic anhydride and polysebacic anhydride; aromatic compounds such as bisphenol A (BPA); liquid rubbers having functional groups at the terminals such as carboxyl-terminated polybutadiene nitrile rubber (CTBN); and silicone compounds such as modified silicone oil.

[0029] Examples of crosslinking agents include bisphenol A, epichlorohydrin-type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. These may be used alone or in combination of two or more. In one embodiment, a bifunctional crosslinking agent having two crosslinking reactive groups per molecule (e.g., ethylenically unsaturated groups, isocyanate groups, etc.) is used as at least a portion of the crosslinking agent. The use of a bifunctional crosslinking agent facilitates the formation of a flexible crosslinked structure. The bifunctional crosslinking agents may be used alone or in combination of two or more. Examples of bifunctional crosslinking agents include bifunctional monomers such as bifunctional (meth)acrylates, and bifunctional isocyanate compounds. Bifunctional crosslinking agents may be used in combination with trifunctional or higher crosslinking agents. Commercially available epoxy crosslinking agents include "TETRAD-X" and "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc., "Epiclon CR-5L" manufactured by DIC Corporation, "Denacol EX-512" manufactured by Nagase ChemteX Corporation, and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

[0030] As the curing agent, known or conventional curing agents (including, for example, thermal polymerization initiators and photopolymerization initiators) depending on the base polymer used, etc., can be used alone or in appropriate combination of two or more. Examples of such polymerization initiators for epoxy curing agents include phenol-based curing agents, amide-based curing agents, amine-based curing agents, imidazoles, acid anhydride-based curing agents, and organic phosphines. In one embodiment, the curing agent can be a tertiary amine, meta-xylylenediamine, or modified aliphatic polyamine.

[0031] Although not limited thereto, the epoxy compound used in this embodiment is a bisphenol A-type liquid epoxy resin consisting of a polycondensate of 4,4'-isopropylidenediphenol and 1-chloro-2,3-epoxypropane, and a resin composition was used in which this resin composition was mixed with a polyamine-based curing agent in a mass ratio of approximately 1:1 to 10:1. The mixed viscosity of this resin composition was approximately 200 mPa·s or less at room temperature, and the curing time was approximately 35 minutes (25°C). The epoxy compound, when cured by itself, has a compressive strength of, for example, 30 N / mm 2 or more (e.g., 50N / mm 2 More than 70N / mm 2 or more), tensile shear adhesive strength 10N / mm 2 or more (e.g., 15N / mm 2 or more), bending strength 35N / mm 2 or more (e.g., 50N / mm 2 More than 70N / mm 2 or more), tensile bond strength 1.6N / mm 2 or more (e.g., 2N / mm 2 More than 2.5N / mm 2 The system is adjusted to satisfy one or more of the following criteria:

[0032] The resin contained in the concrete reinforcement material 100 according to one embodiment may be, for example, a fiber bundle / fiber woven fabric 1 m from the viewpoint of improving the handling property. 2 The ratio of the fiber bundle / fiber woven fabric per 1 m can be set to approximately 100 g or more, 200 g or more, 300 g or more, or 400 g or more. 2The resin content can be approximately 1000 g or less, 800 g or less, or 600 g or less per kg of fiber bundles / fiber fabric. Furthermore, the resin content of the laminated concrete reinforcement material 100 according to one embodiment can be, for example, approximately 100 g or more, 300 g or more, 500 g or more, 700 g or more, or 900 g or more per kg of fiber bundles / fiber fabric, from the viewpoint of improving handleability. Furthermore, the resin content can be approximately 1500 g or less, 1200 g or less, or 1000 g or less per kg of fiber bundles / fiber fabric, from the viewpoint of optimally exhibiting flexibility. For example, methods such as injection, atmospheric pressure impregnation, vacuum impregnation, and vacuum pressure impregnation can be used to impregnate the fiber bundles / fiber fabric with the resin.

[0033] As described above, the concrete reinforcement 100 has both tensile elasticity and flexibility, making it possible to realize a reinforcement that is easy to handle, for example, during manufacturing, storage, and on-site construction. The concrete reinforcement 100 according to the present technology is provided as a reinforcement having flexibility that allows it to be wound into a roll, for example. The concrete reinforcement 100 according to the present technology is also provided as a reinforcement that can be constructed on curved surfaces such as tunnels, for example. Furthermore, the concrete reinforcement 100 according to the present technology allows, for example, bending of reinforcing bars to be performed manually on-site, making it possible to easily increase anchorage, for example.

[0034] [Methods for strengthening concrete structures] Next, a method for reinforcing a concrete skeleton using the concrete reinforcing material 100 according to the present technology will be described. The method for strengthening a concrete structure 14 according to the present technology generally includes the following steps: (1) A process of forming linear slit holes in the surface layer of a concrete structure; (2) a step of fitting a long concrete reinforcement material along the longitudinal direction of the slit hole; Includes.

[0035] [1. Slit hole forming process] FIG. 3A is a schematic perspective view showing a concrete reinforcing member 100 according to one embodiment and a concrete cube 6 (an example of a concrete skeleton) to be reinforced. The concrete cube 6 to be reinforced is mainly made of concrete. The concrete cube 6 may be made of reinforced concrete with reinforcing bars arranged therein, or may be made of concrete without reinforcing bars. The concrete cube 6 of this embodiment is made of, for example, a cubic concrete mass without reinforcing bars (unreinforced).

[0036] In the slit hole forming process, slit holes 8, 9, and 10 for attaching the concrete reinforcement 100 are formed in the concrete cube 6. The slit holes 8, 9, and 10 are preferably formed along a direction in which the tensile strength of the concrete reinforcement 100 is desired to be increased. For example, one or more slit holes 8, 9, and 10 can be formed in one body. For example, two or more slit holes 8, 9, and 10 can be formed on the same surface of one body or on different surfaces. The multiple slit holes 8, 9, and 10 can be formed in the same direction or in different directions. Furthermore, the shapes of the slit holes 8, 9, and 10 can be suitable for attaching the concrete reinforcement 100 having a shape suitable for imparting the desired strength to the concrete cube 6. The slit holes 8, 9, and 10 can be formed, for example, in a linear or curved shape on the surface portion of the concrete cube 6.

[0037] In the example shown in FIG. 3A, top slit holes 8, side slit holes 9, and bottom slit holes 10 are formed on the top, front, and bottom surfaces of the concrete cube 6, respectively. The top slit holes 8 and bottom slit holes 10 are each formed in a straight line along the X-axis direction of the concrete cube 6, and the side slit holes 9 are formed in a straight line along the Z-axis direction of the concrete cube 6. By forming each of the slit holes 8, 9, and 10 in a straight line, the tensile strength in the direction along the straight line can be effectively increased. Furthermore, by forming slit holes along the X-axis direction separately on the top and bottom surfaces of the concrete cube 6, the tensile strength of the concrete cube 6 in the X-axis direction can be increased with reduced overall uniformity.

[0038] The concrete reinforcement materials 100a, 100b, and 100c used in this embodiment are made of filament yarns with high tensile modulus, and have a strip or tape shape with a substantially rectangular cross section. The density of the concrete reinforcement materials 100a, 100b, and 100c is approximately 1.2 g / cm 3 The slit holes 8, 9, and 10 may be of any size that can accommodate the concrete reinforcement 100 without it protruding, and may be formed, for example, in a shape and size that corresponds to the concrete reinforcement 100 so that the concrete reinforcement 100 fits snugly, or in a shape and size that is slightly larger than the concrete reinforcement 100 so that the concrete reinforcement 100 can be inserted smoothly.

[0039] In one embodiment, the slits 8, 9, and 10 have a groove-like cross section with a substantially rectangular cross section, and their width may be, for example, the thickness of the concrete reinforcement 100a, 100b, and 100c to be attached plus a predetermined clearance. The clearance may be, for example, a gap of 0.1 mm to 1 mm on both sides of the concrete reinforcement 100a, 100b, and 100c. The depth of the slits 8, 9, and 10 may be, for example, the same as the width of the concrete reinforcement 100a, 100b, and 100c.

[0040] In this way, the slit holes 8, 9, and 10 are preferably formed so that their depth dimension is greater than their width dimension. Such slit holes 8, 9, and 10 can be formed (grooved) using, for example, a grinder (e.g., a free-cutting grinding machine). A grinder is also called a groove cutter. This increases the bonding area between the concrete cube 6 and the concrete reinforcements 100a, 100b, and 100c, and reduces the area of ​​the concrete reinforcements 100a, 100b, and 100c exposed to the external environment. As a result, the bearing capacity of the concrete cube 6 can be effectively improved, and deterioration of the concrete reinforcements 100a, 100b, and 100c due to environmental exposure can be suppressed.

[0041] [2. Concrete reinforcement installation process] FIG. 3B is a schematic perspective view of a concrete reinforced structure 200 according to one embodiment. In the concrete reinforcing material fitting step, concrete reinforcing materials 100a, 100b, and 100c are fitted into the slit holes 8, 9, and 10 of the concrete cube 6.

[0042] The concrete reinforcements 100a, 100b, 100c may have dimensions corresponding to the longitudinal dimensions of the slit holes 8, 9, 10, for example. The concrete reinforcements 100a, 100b, 100c can be attached to the slit holes 8, 9, 10 by, for example, applying an adhesive to the surface, inserting the concrete reinforcements 100a, 100b, 100c into the slit holes 8, 9, 10, and allowing the adhesive to harden. Note that the concrete reinforcements 100a, 100b, 100c may be inserted into the slit holes 8, 9, 10 after applying or filling the interior of the slit holes 8, 9, 10 with adhesive. For example, a resin material (e.g., a thermosetting resin or a thermoplastic resin) may be used as the adhesive.

[0043] Here, in order to suitably apply the tension of the concrete reinforcing members 100a, 100b, and 100c to the concrete cube 6, it is preferable that the adhesive has a high adhesive strength to concrete. The adhesive strength after hardening of the adhesive is, for example, 1 N / mm 2 or more in terms of tensile shear bond strength measured in accordance with JIS K6850:1999. 2 More than 3N / mm 2 More than 5N / mm 2 More than 10N / mm 2 or more. In this case, the adherend may be, for example, the surface of concrete made with a standard mix based on the Standard Specifications for Concrete, or the surface thereof cut with a grinder. From the viewpoint of firmly fixing the concrete reinforcement 100 to the slit holes, it is desirable that the adhesive have high hardness. The hardness of the adhesive after curing is, for example, 60 or more, preferably 70 or more, or 80 or more in terms of durometer hardness (HDD) measured in accordance with JIS K7215:1986. Although not limited thereto, examples of adhesives for fixing such concrete reinforcement 100 include thermosetting epoxy resins, saturated polyester resins, thermoplastic polyamide resins, polycarbonate resins, etc.

[0044] The adhesive used to fix the concrete reinforcement 100 to the slit holes is preferably one that has high adhesive strength and good adhesion (e.g., compatibility) with the resin contained in the concrete reinforcement 100. From this perspective, for example, when the resin contained in the concrete reinforcement 100 is an epoxy resin, an adhesive made of an epoxy-based resin can be preferably used. An example of such an epoxy-based resin is an epoxy resin-based adhesive (e.g., Bond E series, manufactured by Konishi Co., Ltd.).

[0045] When the adhesive hardens, it is possible to obtain a concrete reinforced structure 200 in which the concrete reinforcements 100a, 100b, and 100c are integrated with the concrete cube 6 inside the slits 8, 9, and 10. Note that by using an adhesive made of the same resin material as that impregnated into the concrete reinforcements 100a, 100b, and 100c or a compatible resin material, the concrete reinforcements 100a, 100b, and 100c can be more firmly fixed to the concrete cube 6.

[0046] According to the above configuration, by fitting the concrete reinforcements 100a, 100b, and 100c (tensioning members) into the slits 8, 9, and 10 of the concrete cube 6, tension can be applied to the concrete cube 6, and the concrete cube 6 can be easily reinforced. Furthermore, the concrete reinforcements 100a, 100b, and 100c are housed in the slits 8, 9, and 10 of the concrete cube 6. This prevents deterioration of the concrete reinforcements 100a, 100b, and 100c and allows the concrete cube 6 to be reinforced without increasing its bulk. Furthermore, the concrete reinforcements 100a, 100b, and 100c have a lower density than the concrete cube 6, and therefore the concrete cube 6 can be reinforced without increasing its weight before and after repair. Furthermore, the concrete cube 6 can be reinforced without impairing its appearance.

[0047] In the thus obtained reinforced concrete structure 200, the concrete reinforcements 100a, 100b, and 100c impart tensile strength to concrete that is resistant to compression, and can impart, for example, the same strength and tension as conventional reinforcing bars. Therefore, by using the concrete reinforcements 100a, 100b, and 100c, it is possible to obtain a reinforced concrete structure 200 with improved compressive and tensile strength without, for example, eliminating the need for reinforcing bar work, formwork work, and concrete pouring work. This is advantageous in that it can halve the cost and construction period.

[0048] (Embodiment 2) Fig. 4A is a schematic perspective view of a tunnel as a concrete-reinforced structure 200 in one embodiment. For ease of understanding, Fig. 4A shows a cross section of a portion of the tunnel. Fig. 4B is a partial perspective view showing a tunnel (an example of a concrete skeleton) made of reinforced concrete in the process of being reinforced, showing an enlarged portion corresponding to the circled portion in Fig. 4A. Fig. 4C is a partial perspective view showing the reinforcement structure of the tunnel, showing an enlarged portion of the circled portion in Fig. 4A. In this embodiment, the same configurations and effects as those of the first embodiment may not be described again.

[0049] This tunnel is a curved concrete body 7 having a substantially semi-cylindrical shape. In Figures 4A to 4C, the X-axis, Y-axis, and Z-axis correspond to the radial direction, extension direction, and up-down direction of the tunnel, respectively. In this embodiment, the tunnel is reinforced in the Y-axis direction and circumferential direction. For reinforcement, concrete reinforcement materials 100d and 100e made of woven fiber bundles and a gap filling material 13 are used. The concrete reinforcement materials 100d and 100e and the gap filling material 13 used in this embodiment are all strip-shaped or tape-shaped and have approximately the same width and thickness dimensions.

[0050] [1. Slit hole forming process] First, in the slit hole forming step, as shown in FIG. 4B, slit holes 11 and 12 are formed in the curved concrete body 7 from the inside of the tunnel. For example, first, slit hole 11 (an example of a first slit hole) is formed along the tunnel extension direction (Y-axis direction), and then slit hole 12 (an example of a second slit hole) is formed along the circumferential direction. In FIG. 4B, only slit hole 11 along the tunnel extension direction is shown, which is formed at the tunnel top. However, slit holes 11 along the extension direction can be formed not only at the tunnel top but also at multiple positions along the circumferential direction. Similarly, slit holes 12 along the circumferential direction can be formed at multiple positions along the tunnel extension direction. Slit hole 11 and slit hole 12 intersect when viewed in the Z-axis direction and are in communication with each other.

[0051] The widthwise dimensions of the slit holes 11 and 12 correspond to the thickness dimensions of the concrete reinforcement 100d, 100e and the gap filler 13. The depth of the slit holes 12 corresponds to the width dimension of the concrete reinforcement 100e. The depth of the slit holes 11 corresponds to the sum of the width dimensions of the concrete reinforcement 100d and the concrete reinforcement 100e (or the gap filler 13). The depth dimensions of the slit holes 11 and 12 are greater than the widthwise dimensions. However, it is desirable that the depth of the slit holes 11 is the surface layer of the concrete skeleton 14 (i.e., the so-called "concrete cover" portion where no reinforcing bars are arranged). In other words, it is desirable that the depthwise dimension of the slit holes 11 is equal to or less than the cover thickness of the reinforced concrete. This allows construction without damaging the reinforcing bars.

[0052] [2. Insertion process] Next, in the insertion process, first, concrete reinforcement 100d (an example of a first concrete reinforcement) is inserted into slit 11, and then concrete reinforcement 100e (an example of a second concrete reinforcement) is inserted into slit 12. At this time, for example, a predetermined amount of adhesive may be applied to or filled into slits 11 and 12, and then concrete reinforcement 100d and 100e are inserted (engaged). Furthermore, since slit 11 is deeper than concrete reinforcement 100d, after inserting concrete reinforcement 100d into slit 11, by further fitting gap filler 13 into slit 11, concrete reinforcement 100d can be pushed to a predetermined position deep within slit 11. Furthermore, since concrete reinforcement 100e is a woven fabric of fiber bundles in the shape of a strip or tape, it can be easily deformed into an arc shape and inserted along the surface of curved concrete body 7.

[0053] The gap filler 13 is not necessarily required. However, it is useful in that it can push the concrete reinforcement 100d to a predetermined position deep inside the slit hole 11, prevent the concrete reinforcement 100d from being exposed to the environment, and improve the aesthetic appearance of the surface of the curved concrete body 7 after repair. It can also suppress deterioration of the concrete reinforcement 100d due to environmental exposure or fire damage. When the adhesive hardens, a concrete reinforced structure 200 reinforced with the concrete reinforcement 100d, 100e can be obtained, as shown in FIG. 4C, for example.

[0054] In the above configuration, the concrete reinforcement 100d and the concrete reinforcement 100e are arranged in a twisted and crossed state inside the slit holes 11, 12. This increases the tensile strength of the concrete reinforced structure 200 in both the extending direction of the concrete reinforcement 100d and the extending direction of the concrete reinforcement 100e. This allows the concrete skeleton 14 to be reinforced in the desired direction.

[0055] Concrete structures 14 such as tunnels that have been constructed for a long time can deteriorate, causing cracks in the concrete and rust in the reinforcing bars, resulting in a significant decrease in strength (tension). Even in such cases, the above-mentioned method can reinforce the concrete structure without increasing its volume or mass or significantly changing its appearance.

[0056] (Embodiment 3) Fig. 5A shows (a) a plan view and (b) a cross-sectional view along the line bb, illustrating the structure of slit holes 15 and 16 for attaching concrete reinforcement according to one embodiment. Fig. 5B shows (a) a plan view and (b) a cross-sectional view along the line bb of a reinforced concrete structure 200 formed by attaching concrete reinforcement 100g and 100f to the slit holes 15 and 16 of Fig. 5A. In this embodiment, the same configurations and effects as those in the first and second embodiments may not be described again.

[0057] [1. Slit hole forming process] For example, when the concrete body 14 to be reinforced is a large structure (such as a tunnel or a building), preparing concrete reinforcing material of the same length as the dimension in the reinforcement direction of the concrete body 14 is undesirable in terms of manufacturing, management and storage, transportation, workability on site, etc. Therefore, when reinforcing a large concrete body 14, it is advisable to use, for example, connected concrete reinforcing material 100 of a size that is easy to handle.

[0058] In this case, in the slit hole forming step, as shown in FIG. 5A, first slit holes 15 and second slit holes 16 may be formed in concrete body 14 so as to extend in the reinforcement direction and be adjacent to each other by a predetermined distance 17. For example, first slit holes 15 and second slit holes 16 may be substantially parallel and communicate with each other at adjacent portions. To form such slits, for example, first, first slit holes 15 may be formed using a grinder (free grinding grinder) 20 set to a predetermined cutting groove width, and then second slit holes 16 may be formed by moving (offsetting) grinder 20 in the width direction by the groove width. At this time, second slit holes 16 may be formed so that one end of first slit hole 15 and the other end of second slit hole 16 are adjacent to each other by the predetermined distance 17.

[0059] [2. Insertion process] Next, in the insertion step, as shown in FIG. 5B , for example, first concrete reinforcement 100f is inserted into first slit 15, and then second concrete reinforcement 100g is inserted into second slit 12. At this time, for example, it is preferable to apply or fill a predetermined amount of adhesive 19 to slits 11 and 12 before inserting concrete reinforcement 100f and 100g. Also, it is preferable to fit one end of first concrete reinforcement 100f and the other end of second concrete reinforcement 100g into slits 11 and 12 so that they are adjacent to each other by a predetermined distance 18. In the example of FIGS. 5A and 5B , dimension 18 is significantly smaller than dimension 17, but dimension 17 and dimension 18 may be approximately the same.

[0060] Furthermore, a layer of adhesive 19 is interposed between the first concrete reinforcement 100f and the second concrete reinforcement 100g. The first concrete reinforcement 100f and the second concrete reinforcement 100g are connected via this layer of adhesive 19 at a predetermined distance 18. This allows the concrete frame 14 to be continuously reinforced by the first concrete reinforcement 100f and the second concrete reinforcement 100g.

[0061] 5B, the layer of adhesive 19 has a sufficient thickness, but the layer of adhesive 19 may be thick enough to provide a clearance, or the first concrete reinforcement 100f and the second concrete reinforcement 100g may be in contact with each other at least partially or entirely in the area indicated by dimension 18. In this case, the second slit holes may be offset from the first slit holes 15 by a dimension narrower than the groove width. This allows the first concrete reinforcement 100f and the second concrete reinforcement 100g to be more firmly connected to each other.

[0062] In this embodiment, the first slit holes 15 and the second slit holes are parallel, but they do not necessarily have to be parallel as long as they are connected by a predetermined distance 17. Furthermore, the first concrete reinforcement 100f and the second concrete reinforcement 100g are also parallel, but they do not necessarily have to be parallel as long as they are connected by a predetermined distance 18. While not limited to this, the dimension 17 of the connecting portion between the first slit holes 15 and the second slit holes may be, for example, 250 mm to 300 mm. Furthermore, although not limited to this, the dimension 18 of the connecting portion between the first concrete reinforcement 100f and the second concrete reinforcement 100g may be, for example, 200 mm to 250 mm. This allows the first concrete reinforcement 100f and the second concrete reinforcement 100g to be easily and firmly fixed together.

[0063] The grinder 20 may be, for example, a flexible groove grinder equipped with grinding teeth that can freely adjust the groove width. The first slit holes 15 and the second slit holes may be deeper than the width of the first concrete reinforcement 100f and the second concrete reinforcement 100g, and the surfaces of the first concrete reinforcement 100f and the second concrete reinforcement 100g inserted into the first slit holes 15 and the second slit holes may be covered with adhesive 19 to provide an airtight and liquidtight seal. Alternatively, a gap filler may be placed on the surfaces of the first concrete reinforcement 100f and the second concrete reinforcement 100g to cover the first concrete reinforcement 100f and the second concrete reinforcement 100g.

[0064] (Embodiment 4) 6 is a schematic perspective view of a concrete reinforced structure 200 according to one embodiment. In the concrete reinforced structure 200 of this embodiment, at least one end of the concrete reinforcement 100 is curved. Repeated explanations of the same configurations, functions, and effects as those of the above-mentioned embodiments 1 to 3 may be omitted.

[0065] In this embodiment, in the slit hole forming step, at least one end (here, both ends) of the slit hole formed in the concrete skeleton 14 to be reinforced is bent. The bending shape can be determined, for example, in the same manner as the bending method of rebar. As an example, the slit hole can be bent in a substantially U-shape, for example, at 90 degrees, 135 degrees, or 180 degrees, relative to the longitudinal slit hole. In this case, the inner bending radius of the bent portion may be, for example, the inner bending radius when using rebar corresponding to the tensile modulus of the concrete reinforcement material 100. In this example, the slit hole was bent with a curvature radius of approximately 5 cm. However, if it is difficult to form the slit hole using a grinder, at least one end of the slit hole may be inclined in a direction intersecting the longitudinal direction (extension direction) of the slit hole.

[0066] Then, in the insertion process, the concrete reinforcement 100 coated with adhesive is inserted into the formed slit holes. The concrete reinforcement 100 used in this embodiment is, for example, a strip with a total length of approximately 200 m, and is managed in a roll (core diameter of approximately 10 cm). Therefore, in the insertion process, the concrete reinforcement 100 is unwound to a predetermined length on site, cut, and inserted into the slit holes while being curved to fit the slit holes. The ends are bent with a curvature radius of approximately 5 cm to fit the slit holes. For example, epoxy resin can be used as the adhesive. The adhesive then hardens, thereby obtaining the concrete reinforced structure 200 according to the present technology.

[0067] In this concrete reinforced structure 200, at least one end (here, both ends) of the concrete reinforcement 100 is bent. Therefore, for example, when the concrete skeleton expands, a tensile force (tension force) is generated along the concrete reinforcement 100 in this concrete reinforced structure 200. At this time, since at least one end (here, both ends) of the concrete reinforcement 100 is bent, the anchoring force to the concrete skeleton is increased. This allows the concrete skeleton to be reinforced effectively.

[0068] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. The present disclosure discloses any one or any combination of two or more of the features recited in the claims. [Explanation of symbols]

[0069] 100...Concrete reinforcement material (tensioning member), 200...Concrete reinforced structure, 1...Fiber bundle, 2...Weft thread, 3...Two-layer tensioning member, 4...Third-layer tensioning member, 5...Fourth-layer tensioning member, 100a...Top tensioning member, 100b...Side tensioning member, 100c...Bottom tensioning member, 100d...Y-direction tensioning member, 100e...X-direction tensioning member, 100f...L-direction tensioning member, 100g...R-direction tensioning member, 6...Co Concrete cube, 7...concrete curved body, 8...slit hole on top, 9...slit hole on side, 10...slit hole on bottom, 11...slit hole in y direction, 12...slit hole in x direction, 13...gap filling material, 14...concrete body, 15...first slit hole, 16...second slit hole, 17...slit hole dimensions, 18...tensioning member dimensions, 19...adhesive, 20...grinder (free grinding machine)

Claims

1. A concrete structure having linear slit holes formed on a surface of the concrete structure; a concrete reinforcing material having elasticity in a longitudinal direction, the concrete reinforcing material being attached to the slit hole with the longitudinal direction being along the extension direction of the slit hole; A concrete reinforced structure comprising:

2. The concrete reinforcement material contains high-modulus fibers having a longitudinal tensile modulus of 353 cN / dtex or more. The concrete reinforced structure according to claim 1.

3. The concrete reinforcing material includes a plurality of fiber bundles each of which is a bundle of the high elastic modulus fibers, and weft yarns which connect the plurality of fiber bundles in a horizontal arrangement, and has a strip-like shape. The concrete reinforced structure according to claim 2.

4. The concrete reinforcement material further includes a resin impregnated in the plurality of fiber bundles. The concrete reinforced structure according to claim 3.

5. the concrete reinforcement material includes a plurality of the fiber bundles connected in a strip shape; The plurality of connected fiber bundles are stacked and fixed with a resin. The concrete reinforced structure according to claim 3.

6. The concrete reinforcing material includes high-elastic modulus fibers having a longitudinal tensile modulus of 353 cN / dtex or more, and a resin impregnated into the high-elastic modulus fibers, The concrete reinforcement has flexibility. The concrete reinforced structure according to claim 1.

7. The concrete reinforcement is fixed inside the slit hole with an adhesive. The concrete reinforced structure according to claim 1.

8. The slit hole has a depth dimension greater than a width dimension, The concrete reinforcement has a width dimension greater than a thickness dimension, The concrete reinforcement is attached to the slit hole so that the width direction of the concrete reinforcement is along the depth direction of the slit hole. The concrete reinforced structure according to claim 1.

9. The width direction of the slit hole is configured so that a clearance of 0.1 mm to 1 mm is generated on each side between the slit hole and the concrete reinforcement material. The concrete reinforced structure according to claim 1.

10. The concrete structure is made of reinforced concrete, The slit hole is configured so that the dimension in the depth direction is equal to or less than the covering thickness of the reinforced concrete. The concrete reinforced structure according to claim 1.

11. The slit hole has a depth dimension that is equal to or larger than the depth dimension of the concrete reinforcement material, or the concrete reinforcement material and a gap filling material to be placed as needed, The concrete reinforcement material, or the concrete reinforcement material and the gap filling material, are accommodated in the slit holes so as not to protrude from the surface of the concrete skeleton. The concrete reinforced structure according to claim 1.

12. The slit holes include a first slit hole and a second slit hole communicating with the first slit hole, The concrete reinforcement includes a first concrete reinforcement provided inside the first slit hole and a second concrete reinforcement provided inside the second slit hole, The first concrete reinforcement and the second concrete reinforcement are connected at a communicating portion between the first slit hole and the second slit hole. The concrete reinforced structure according to claim 1.

13. The slit holes include a first slit hole and a second slit hole that extend in different directions and communicate with each other, The concrete reinforcement includes a first concrete reinforcement provided inside the first slit hole and a second concrete reinforcement provided inside the second slit hole, The first concrete reinforcement and the second concrete reinforcement are arranged in a twisted and crossed state inside the slit hole. The concrete reinforced structure according to claim 1.

14. A concrete reinforcing material used in a concrete reinforced structure according to any one of claims 1 to 13, A concrete reinforcing material comprising high modulus fibers having a tensile modulus in the longitudinal direction of 353 cN / dtex or more.

15. Forming linear slit holes in the surface layer of a concrete structure; Installing a long concrete reinforcement material along the longitudinal direction of the slit hole; A method for strengthening a concrete structure, including:

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