Repair method for concrete structure

Abstract

To provide a repair method for a concrete structure capable of improving adhesive performance of repair material on a surface of the concrete structure.SOLUTION: A repair method for a concrete structure includes a step S20, a step S40, and a step S50. The step S20 coats a primer including (meth)acrylate having an ethylenically unsaturated double bond or an epoxy resin, and a curing agent, on a surface of the concrete to be repaired. The step S40 bonds a repair material in which a curable composition is coated on or impregnated into a laminated body, onto the primer-coated surface of the concrete after the step S20. The step S50 cures the primer and the curable composition after the step S40.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for repairing a concrete structure. [Background technology]

[0002] Concrete structures have the advantages of being high strength, easy to work with, and inexpensive, so many concrete structures were built in Japan, especially during the period of rapid economic growth.Although concrete structures are highly durable, they can become neutralized over many years of use when carbon dioxide from the atmosphere penetrates into them along with moisture, or can become corroded and expanded by the penetration of sea breezes and chloride ions contained in droplets of antifreeze, leading to cracks.

[0003] As a method for repairing such concrete structures, Patent Documents 1 to 3, for example, disclose a repair method in which a repair material formed by applying or impregnating a laminate with a hardenable composition containing an aqueous silicate solution is attached to the surface of the concrete.

[0004] Fig. 4 is a diagram showing the concrete structure repair methods disclosed in Patent Documents 1 to 3. Fig. 4 shows a state in which a repair material 1010, which is a laminate of two or more layers of sheet-like members impregnated with a hardenable composition, is adhered to a concrete structure 100. Patent Document 3 also discloses a repair method in which a primer is applied to the surface of concrete to improve the adhesion of the repair material, which is a laminate impregnated with a hardenable composition, to the concrete structure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-128908 A [Patent Document 2] Japanese Patent Application Publication No. 2017-186825 [Patent Document 3] Japanese Patent Application Publication No. 2022-081262 Summary of the Invention [Problem to be solved by the invention]

[0006] In the conventional concrete structure repair method described above, there is room for improvement in the adhesion of the sheet to the concrete structure. That is, when the concrete surface is in an excessively dry state, the moisture contained in the hardenable composition is absorbed by the concrete, and the concrete does not harden sufficiently in the hardening process, and the repair material does not exhibit sufficient adhesive strength.

[0007] The present disclosure has been made to solve such problems, and aims to provide a method for repairing a concrete structure that can improve the adhesion of a repair material to the surface of the concrete structure. [Means for solving the problem]

[0008] To achieve the above object, the first disclosed method for repairing a concrete structure comprises an application step, an attachment step, and a curing step. In the application step, a primer containing an ethylenically unsaturated double bond-containing (meth)acrylate or epoxy resin and a curing agent is applied to the surface of the concrete to be repaired. In the attachment step, a repair material formed by applying or impregnating a curable composition to a laminate is attached to the primer-coated surface of the concrete after the application step. In the curing step, the primer and the curable composition are cured after the attachment step.

[0009] Concrete that is excessively dry absorbs moisture rapidly, so simply applying a repair material to the surface of the concrete can result in the moisture contained in the hardenable composition being absorbed by the concrete, and the repair material may not be able to exhibit sufficient adhesive strength due to insufficient hardening.

[0010] In the concrete structure repair method disclosed herein, a primer containing an ethylenically unsaturated double bond-containing (meth)acrylate or epoxy resin and a curing agent is applied before a repair material is applied to the surface of the concrete.

[0011] For example, when an inorganic compound is used as a primer, the inorganic compound itself is hydrophilic and therefore cannot suppress the water absorption of concrete. However, when a (meth)acrylate or epoxy resin containing an ethylenically unsaturated double bond is used as a primer as in the present disclosure, the water absorption of concrete can be suppressed by penetrating into the concrete and forming a film, which can sufficiently promote the hardening of the curable composition and improve the adhesion of the repair material, making it difficult for the repair material to peel off even on concrete structures that are in an excessively dry state.

[0012] The concrete structure repair method of the second disclosure is the concrete structure repair method of the first disclosure, further comprising a drying step, in which the primer is dried after the application step until adhesive strength is developed.

[0013] Generally, water-based repair materials cannot achieve sufficient adhesion with organic substances that have low affinity for water. (Meth)acrylate or epoxy resins containing ethylenically unsaturated double bonds are organic compounds with high affinity for water, but this affinity needs to be improved in order to achieve adhesion. Therefore, strong adhesion can be achieved by drying the primer until it has a higher affinity for water and adhesive strength is developed, and then attaching the repair material.

[0014] The third disclosed method for repairing a concrete structure is the second disclosed method for repairing a concrete structure, in which the pasting process is carried out after the primer has developed adhesive strength in the drying process, but before the primer has completely hardened.

[0015] This allows the repair material to be applied when the primer has a higher affinity with water and adhesive strength is still present before it is completely cured, and then cured together with the curable composition, thereby achieving even stronger adhesion.

[0016] A fourth disclosure of a concrete structure repair method is the concrete structure repair method disclosed in any one of the first to third disclosures, wherein the laminate has a first layer and a second layer. The first layer is in the form of a sheet in which multifilaments are combined in a multiaxial mesh shape. The second layer is in the form of a sheet made of polypropylene spunbond nonwoven fabric. The laminate is arranged in the order of the first layer and the second layer from the surface side of the concrete.

[0017] This allows repairs to be carried out by attaching a repair member, in which the laminate is coated or impregnated with the curable composition, to a concrete structure.

[0018] The fifth disclosed method for repairing a concrete structure is the fourth disclosed method for repairing a concrete structure, wherein the laminate further has a sheet-like third layer formed of glass nonwoven fabric placed on the surface side of the first layer of concrete.

[0019] This allows the repair material to have both strength and adhesion to the concrete.

[0020] A sixth disclosed method for repairing a concrete structure is the method for repairing a concrete structure disclosed in any one of the first to third disclosed methods, further comprising a scraping step of scraping the surface of the concrete before the application step.

[0021] This can further improve the adhesion of the repair material. [Effects of the Invention]

[0022] According to the present disclosure, it is possible to provide a method for repairing a concrete structure that can improve the adhesion of a repair material to the surface of the concrete structure. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing a state in which a concrete structure has been repaired using a repair material (three-layer structure) according to an embodiment of the present disclosure. [Figure 2]FIG. 1 is a diagram showing a state in which a concrete structure has been repaired using a repair material (two-layer structure) according to an embodiment of the present disclosure. [Figure 3] 1 is a flow diagram showing a concrete structure repair method according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a diagram showing a state in which a concrete structure has been repaired using a conventional method for repairing a concrete structure. DETAILED DESCRIPTION OF THE INVENTION

[0024] The concrete structure repair method according to the present disclosure will be described below.

[0025] (Repair material 10, 10') As shown in Fig. 1, a repair material 10 of the present disclosure is used to repair a concrete structure 100. The repair material 10 includes a hardenable composition and a laminate 4 formed by stacking at least two layers of sheet-like members. The laminate 4 and the hardenable composition may exist separately, but during repair, the hardenable composition is impregnated into the laminate 4, as described below.

[0026] As shown in Fig. 1, an impregnating material layer 5 is formed on the surface 100s of a concrete structure 100 to which the repair material 10 is applied. The impregnating material layer 5 is formed by impregnating the concrete structure 100 with a primer, which will be described later. By providing the impregnating material layer 5, the water absorption capacity of the concrete structure 100 can be reduced, and the adhesive strength of the repair material 10 can be improved.

[0027] (Laminates 4, 4´) The laminate 4 of the repair material 10 is formed by laminating two or more layers of sheet-like members.

[0028] For example, the laminate 4 of the repair material 10 shown in Fig. 1 includes a third layer 3 disposed on an impregnating material layer 5 formed on a concrete structure 100, a first layer 1 disposed on the third layer 3, and a second layer 2 disposed on the first layer 1. The third layer 3, the first layer 1, and the second layer 2 are laminated in this order from the concrete structure 100 side.

[0029] Furthermore, the repair material 10 is not limited to the repair material 10 shown in Fig. 1, and may have a configuration such as a repair material 10' shown in Fig. 2. The laminate 4' of the repair material 10' comprises a first layer 1 disposed on the impregnating material layer 5 of the concrete structure 100, and a second layer 2 disposed on the first layer 1. The first layer 1 and the second layer 2 are disposed in this order from the concrete structure 100 side.

[0030] (first layer 1) The first layer 1 is preferably a sheet-like member in which multifilaments are combined in a multiaxial mesh shape. The multifilaments are preferably made using long fibers and preferably have a tensile strength of 150 N or more. The value X represented by formula (1) of the sheet-like member in which multifilaments are combined in a multiaxial mesh shape is preferably 2.0 or more, more preferably 2.5 or more, 2.8 or more, or 3.0 or more.

[0031] X = A × B (1) Here, A represents the tensile strength (kN / 50 mm) of the sheet-shaped member in one direction, and B represents the number of axes of the sheet-shaped member. A can take any value by changing the number of multifilaments per 50 mm. B may range from 2 to 4. Of these, A is preferably 0.75 kN or more, and B is preferably 2 to 3.

[0032] With this configuration, the first layer 1 can fulfill the function of a load-bearing layer that receives concrete pieces that fall from a concrete structure.

[0033] Examples of materials for the first layer 1 include polyester, polyolefin, vinylon, aramid, carbon fiber, and glass fiber. Of these, a vinylon mesh sheet or a glass mesh sheet is preferable. The long glass fibers are preferably glass yarn or roving. Glass yarn is made by twisting glass fibers to form a ply yarn, and roving is made by bundling glass fibers. Examples of weaving methods for the multiaxial mesh include plain weave, twill weave, leno weave, and braided fabric. The weaving direction of the multiaxial mesh may be orthogonal biaxial or more multiaxial woven fabric.

[0034] The thickness of the first layer 1 is preferably 0.1 mm or more and 1.5 mm or less, and more preferably 0.3 mm or more and 1 mm or less.

[0035] The first layer is 50g / m 2 The weight is preferably 60 g / m or more. 2 More preferably, it is 75 g / m or more, and even more preferably, it is 75 g / m 2 That's all.

[0036] By setting the weight per unit area within this range, the tensile strength can be improved, and sufficient bearing capacity of the repair materials 10, 10' can be ensured without causing breakage when concrete pieces fall off.

[0037] The first layer 1 is preferably a triaxial woven fabric with an opening size of 5 mm or more and 25 mm or less. By setting the opening size within this range, the adhesive strength between the second layer 2 and the concrete structure 100 (described later) or between the second layer 2 and the third layer 3 can be improved, ensuring sufficient adhesive strength of the repair materials 10, 10'. In addition, by setting the number of long fibers per unit area of ​​the first layer 1 to an appropriate number, the resistance of the first layer 1 when it breaks through the second layer 2 can be increased, ensuring sufficient strength of the repair materials 10, 10'.

[0038] The first layer 1 has an opening of 5 mm or more and 25 mm or less, and is 50 g / m 2It is more preferable that the first layer 1 is a biaxial woven fabric having a basis weight of 150 N or more. Alternatively, it may be a multiaxial woven fabric having an opening ratio equivalent to that of the biaxial woven fabric. In particular, it is more preferable that the first layer 1 is a sheet-like member of a biaxial or triaxial mesh made by combining multifilaments having a tensile strength of 150 N or more with an opening of 5 mm to 25 mm.

[0039] (Second layer 2) The second layer 2 is preferably a liquid-permeable sheet-like member. The tear strength of the liquid-permeable sheet-like member is preferably 2.0 N or more. By setting the tear strength to 2.0 N or more, the second layer 2 can fulfill the function of a reinforcing layer that increases the resistance when the first layer 1 breaks through the second layer 2.

[0040] The second layer 2 may be in the form of a woven fabric, a nonwoven fabric, or the like. The second layer 2 may be made of a material such as polyester, polyolefin, vinylon, aramid, carbon fiber, or glass fiber. Among these, a polypropylene nonwoven fabric or a glass nonwoven fabric is preferred, and a long-fiber nonwoven fabric is particularly preferred. Glass nonwoven fabric has excellent compatibility with the curable composition, allowing the curable composition to easily penetrate the glass nonwoven fabric, and when the curable composition is cured, the repair material 10, 10' can be firmly fixed to the concrete structure 100. Suitable glass nonwoven fabrics include chopped strand mat, glass paper, and felt.

[0041] When using polypropylene nonwoven fabric, the fibers may be subjected to a hydrophilization treatment to enhance compatibility with the curable composition. The hydrophilization treatment may be carried out by any method known in the art.

[0042] The thickness of the second layer 2 is preferably 0.1 mm or more and 1.0 mm or less, and more preferably 0.15 mm or more and 0.5 mm or less. By setting the thickness within this range, the second layer 2 fulfills its function as a reinforcing layer that increases the resistance when the first layer 1 breaks through the second layer 2, and also has economic advantages, since the amount of the curable composition impregnated into the laminates 4, 4' can be reduced.

[0043] The second layer 2 is 30 g / m 2 It is preferable that the weight is 50 g / m or more. 2 More preferably, it is 60 g / m or more. 2 By setting the weight per unit area within this range, the tensile strength can be improved, and sufficient bearing strength of the repair materials 10, 10' can be ensured without causing breakage when concrete pieces peel off.

[0044] When the repair material 10, 10' has a two-layer structure of a first layer 1 and a second layer 2, or a laminated structure of more than two layers, it is preferable that the first layer 1 is a sheet-like member in which multifilaments are combined in a multiaxial mesh form, and the second layer 2 is a sheet-like member having a tear strength of 2.0 N or more. Furthermore, in the repair material 10, 10', it is preferable that the first layer 1 is a sheet-like member in which multifilaments having a tensile strength of 150 N or more are combined in a multiaxial mesh form with an opening of 5 mm to 25 mm, and the second layer 2 is a sheet-like member having a tear strength of 2.0 N or more. (Third layer 3) The third layer 3 is preferably a liquid-permeable sheet-like member having a porosity of 90% or more, which ensures impregnation of the hardenable composition and thus fulfills the function of an adhesive layer that improves the adhesion between the repair material 10 and the concrete structure 100.

[0045] The third layer 3 may be in the form of a nonwoven fabric. Materials include polyester, polyolefin, vinylon, aramid, carbon fiber, and glass fiber, with polypropylene nonwoven fabric or glass nonwoven fabric being preferred. Glass nonwoven fabric has excellent compatibility with the curable composition, allowing the curable composition to easily penetrate the fabric, and when the curable composition is cured, the repair material 10 can be firmly attached to the concrete structure. Suitable glass nonwoven fabrics include chopped strand mat, glass paper, and felt.

[0046] When a polypropylene nonwoven fabric is used, it is preferable to subject the fiber surface to a surface treatment in order to increase compatibility with the curable composition.

[0047] The thickness of the third layer 3 is preferably 0.1 mm or more and 1.5 mm or less, and more preferably 0.2 mm or more and 0.8 mm or less. When the thickness of the third layer 3 is 0.1 mm or more, the adhesive strength between the repair material 10 and the concrete structure is ensured, and when the thickness is 1.5 mm or less, the amount of the hardenable composition impregnated into the laminates 4, 4' can be reduced, which is economically advantageous.

[0048] When the repair material 10 has a three-layer structure or a laminate structure of more than one layer consisting of a first layer 1, a second layer 2, and a third layer 3, the laminate 4 can use, for example, a glass nonwoven fabric as the third layer 3, a triaxial vinylon mesh as the first layer 1, and a polypropylene spunbond nonwoven fabric as the second layer 2.

[0049] (integrated lamination) The repair material 10, 10', which is composed of at least two laminated sheet-like members, may be integrated by impregnating them with a curable composition, but it is preferable to integrate them in advance, which prevents the sheet members from shifting during application and impregnation.

[0050] The integration can be achieved by mechanical fiber entanglement, chemical bonding, or the like, and examples thereof include fulling, needle punching, chemical bonding, thermal bonding, stitch bonding, and hydroentanglement.

[0051] While Fig. 1 shows a three-layer structure of the repair material 10, the repair material may have four or more layers. Even in the case of four or more layers, it is preferable that the second layer 2 be disposed on the outer side of the first layer 1, counting from the side that contacts the concrete structure 100. This layered structure allows the repair material 10 to have both strength and adhesion to the concrete structure. There is no particular limit to the maximum number of layers in the laminate 4.

[0052] (Curable composition) The hardenable composition is applied to and / or impregnated into the laminate 4, 4'. By applying and / or impregnating the laminate 4, 4' with the hardenable composition and then hardening the hardenable composition, the concrete structure 100 and the repair material 10, 10' can be bonded together. For example, the hardenable composition can be in a liquid form. By bonding the repair material 10, 10', it is possible to prevent concrete pieces from peeling off from the deteriorated portion of the concrete structure 100.

[0053] The hardenable composition contains an aqueous silicate solution and a Hozolan active substance. The aqueous silicate solution is, for example, an aqueous solution of sodium silicate, potassium silicate, lithium silicate, or a mixture thereof. A composition containing an aqueous silicate solution and a Hozolan active substance in this way may be referred to as a "geopolymer" hereinafter. The hardenable composition is usually prepared as a liquid composition.

[0054] In this way, by using an inorganic material in the hardenable composition, the fire resistance of the concrete structure 100 can be ensured without being impaired.

[0055] In geopolymers, the difference in specific gravity between the liquid component consisting of the silicate aqueous solution and the solid component consisting of the pozzolanic active substance is smaller than the difference in specific gravity between the water and cement contained in the cement slurry, so separation of the components in the hardenable composition can be suppressed.

[0056] Such a curable composition preferably has a viscosity of 400 mPa·s or more and 3000 mPa·s or less at 25° C. By adjusting the viscosity to such a level, it is possible to ensure the impregnation into the laminates 4, 4′. It is also possible to prevent the curable composition from dripping when it is applied to the concrete structure 100.

[0057] In particular, when using geopolymers, the pozzolan active substance preferably has an electrical conductivity difference of 0.4 mS / cm or more, more preferably 0.5 mS / cm or more, 0.6 mS / cm or more, or 0.7 mS / cm or more, and even more preferably 0.8 mS / cm or more, 1.0 mS / cm or more, or 1.2 mS / cm or more.

[0058] Such a difference in electrical conductivity ensures sufficient reactivity with the silicate solution and enhances the adhesive strength between the repair material 10, 10' and the concrete structure 100. The electrical conductivity difference here is an index related to the reactivity of the pozzolanic active substance induced by alkaline substances, and refers to the difference in electrical conductivity of the saturated calcium hydroxide solution before and after the addition of the pozzolanic active substance. The electrical conductivity difference is calculated as follows: Following the method described in "Cement Concrete Research, Vol. 19, pp. 63-68, 1989," the electrical conductivity of 200 ml of saturated Ca(OH)2 solution is measured at 40±1°C. Next, 5 g of metakaolin is added, stirred, and the electrical conductivity is measured two minutes later. The difference from the electrical conductivity before the addition is defined as the electrical conductivity difference.

[0059] A pozzolanic active substance is a substance that hardens when water reacts with calcium oxide, calcium hydroxide, aluminum hydroxide, etc. Examples of pozzolanic active substances include silica dust, diatomaceous earth, talc, aerosil, white carbon, kaolin, metakaolin, activated clay, and acid clay. Of these, metakaolin is preferred.

[0060] It is generally preferred that the pozzolan active substance have a silica content of 40% by weight or more when the silica component is converted into SiO2, or an alumina content of 30% by weight or more when the alumina component is converted into Al2O3.

[0061] The pozzolanic active substance is usually in a lump or powder form, and may be used as is in a lump or powder form. Alternatively, the pozzolanic active substance may be activated by a method such as thermal spraying, pulverization / classification, or application of mechanical energy, after which the state of the substance is changed.

[0062] The thermal spraying method is a thermal spraying technique used for ceramic coating. Examples of the thermal spraying technique include plasma spraying, high-energy gas spraying, and arc spraying. Preferably, the material powder is melted at a temperature of 2000°C to 16000°C, sprayed at a speed of 30 m / s to 800 m / s, and sprayed to a surface having a specific surface area of ​​0.1 m. 2 / g or more 100m 2 It is preferable to make the powder to have a density of 1 / g or less.

[0063] Any known method can be used for the pulverization and classification. Pulverization can be performed using a jet mill, a roll mill, a ball mill, or the like. Classification can be performed using a sieve, specific gravity, wind force, wet sedimentation, or the like. These methods can be used in combination as desired.

[0064] Methods for applying mechanical energy include those using a ball media mill, a media agitation mill, a roller mill, etc. The applied mechanical energy is preferably 0.5 kWh / kg or more and 30 kWh / kg or less in order to minimize the load while providing adequate activation.

[0065] The total content of sodium, potassium, lithium, or mixtures thereof derived from the silicate solution in the curable composition, e.g., geopolymer, calculated as M2O (M is sodium, potassium, and lithium) is preferably 5 to 30 wt.%, more preferably 10 to 30 wt.%, based on the dry solids content of the cured product. The content of aluminum derived from the pozzolanic active substance, calculated as Al2O3, is preferably 20 to 40 wt.%, more preferably 25 to 35 wt.%, based on the dry solids content of the cured product.

[0066] Furthermore, the curable composition is one in which the numerical value n, represented by the following formula for an aqueous solution of sodium silicate, potassium silicate, lithium silicate, or a mixture thereof, is preferably 0.4 or more and 1.1 or less, more preferably 0.5 or more and 1.1 or less, and even more preferably 0.5 or more and 1.0 or less.

[0067] n=S / M (S: number of moles of silicon contained in the aqueous solution, M: number of moles of alkali metal contained in the aqueous solution)

[0068] (Other Components of the Curable Composition) In addition to the above components, the curable composition may contain additives known in the art. Examples include fillers, modifiers, dispersants, cure time adjusters, pigments, antioxidants, polymer emulsions, etc. These are not particularly limited, and known additives can be used.

[0069] The filler may be any of those commonly used as a filler. Examples of fillers include carbon, cellulose, mineral fine powder, and synthesized inorganic crystalline powder. Examples of modifiers include various metal salts that can react with aqueous silicate solutions, such as light-burned magnesium oxide and zinc oxide. Examples of polymer emulsions include acrylic rubber, styrene-butadiene rubber, and mixtures thereof.

[0070] These additives can be used in any amount as long as the intended function of the curable composition is not impaired. In particular, the polymer emulsion is preferably blended so that the polymer solids weight is 3% by weight or more and 10% by weight or less based on the total weight of the dry solids of the curable composition. This improves the fluidity of the curable composition, improves the adhesive strength of the cured product, and suppresses drying shrinkage of the cured product.

[0071] The amount of the curable composition impregnated into the laminates 4, 4' is not particularly limited, and is preferably adjusted so that the curable composition is uniformly held throughout the laminates 4, 4' and the entire laminates 4, 4' can be firmly integrated by curing the curable composition. For example, the weight ratio of the curable composition to the laminate (weight of curable composition / weight of laminate) is preferably about 4 to 12, and more preferably 4 to 10.

[0072] Furthermore, for example, a geopolymer containing water glass, latex, metakalion, and blast furnace slag can be used as the hardenable composition. In this case, when a glass nonwoven fabric is used as the third layer 3, a triaxial vinylon mesh is used as the first layer 1, and a polypropylene spunbond nonwoven fabric is used as the second layer 2 in the laminate 4, the hardening time of the hardenable composition is preferably 30 to 300 minutes, more preferably 45 to 240 minutes, from the viewpoint of ensuring time for the hardenable composition to be impregnated into the surface 100s of the concrete structure 100.

[0073] (Impregnated material layer 5) The impregnating material layer 5 is formed by applying a primer containing a (meth)acrylate or epoxy resin containing an ethylenically unsaturated double bond and a curing agent to the concrete structure 100 and impregnating the concrete structure 100. The term (meth)acrylate refers to both acrylate and methacrylate.

[0074] As the (meth)acrylate containing an ethylenically unsaturated double bond, conventionally known compounds can be used, such as (meth)acrylate, hydroxyalkyl (meth)acrylate, alkyl (meth)acrylate, and other (meth)acrylate ester compounds, and epoxy (meth)acrylate, which may be used alone or in combination of two or more.

[0075] As the curing agent for the (meth)acrylate containing an ethylenically unsaturated double bond, a conventionally known curing agent can be used, and examples thereof include organic peroxides such as alkyl hydroperoxides, alkyl peroxy esters, and dialkyl peroxides, which can be used alone or in combination of two or more.

[0076] As the epoxy resin, conventionally known ones can be used, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic type epoxy resin, phenol novolac type epoxy resin, etc., which can be used alone or in combination of two or more.

[0077] As the curing agent for the epoxy resin, conventionally known curing agents can be used, and examples thereof include primary, secondary, and tertiary amines such as aliphatic amines and aromatic amines, imidazoles, phenols, polymercaptans, acid anhydrides, and carboxylic acid compounds, which can be used alone or in combination of two or more.

[0078] From the viewpoint of reducing the water absorption capacity of the concrete by allowing as much primer as possible to penetrate and form a film into the concrete, the solid content of the primer calculated after drying in an oven at 150°C for 60 minutes is preferably 20% by weight or more, and more preferably 30% by weight or more.

[0079] The amount of primer applied is 70g / m 2 More than 300g / m 2 The following is desirable. If it is too little, it will not penetrate the concrete sufficiently and will not be able to suppress water absorption. If it is too much, it may harden while still containing solvent, which may cause a decrease in hardened strength.

[0080] (Method of repairing concrete structures) The concrete structure repair method of the present disclosure can be carried out using the concrete structure repair materials 10, 10' described above.

[0081] FIG. 3 is a flow diagram showing the concrete structure repair method of the present disclosure.

[0082] As shown in FIG. 3, the concrete structure repair method of the present disclosure includes step S10 (scraping step), step S20 (application step), step S30 (drying step), step S40 (affixing step), and step S50 (hardening step).

[0083] (Step S10 (cleaning process)) In step S10, the surface 100s of the concrete structure 100 to be repaired is scraped with a grinder equipped with a concrete grinding blade.

[0084] (Step S20 (coating process)) In step S20, a primer containing a (meth)acrylate or epoxy resin containing an ethylenically unsaturated double bond and a curing agent is applied to the surface 100s of the concrete structure 100 that has been subjected to the cleaning treatment, and the primer is impregnated into the surface 100s of the concrete structure 100.

[0085] The primer can be applied to and impregnated into the concrete structure 100 by, for example, a hand lay-up method in which the primer is applied and impregnated manually using a roller, or by a method in which the primer is applied and impregnated by spraying.

[0086] (Step S30 (drying process)) In step S30, the primer containing the (meth)acrylate or epoxy resin containing an ethylenically unsaturated double bond and the curing agent is dried until adhesive strength is developed. For example, adhesive strength is developed when the applied primer becomes stringy when touched with a finger and then removed. The drying time until adhesive strength is developed varies depending on the formulation, but is generally between 10 and 120 minutes. Note that if step S40 (the application step) described below is performed before adhesive strength is developed (for example, 1 minute after the primer is applied), the curable composition may adhere to the roller when the primer is applied as an undercoat, causing the primer to peel off.

[0087] Furthermore, the drying process ends before the primer is completely hardened. The repair members 10, 10' are attached in the next step S40 (attaching process) before the primer is completely hardened. "Completely hardened" means that there is no resistance when touched with a finger and then removed. In this way, the drying process ends after the primer develops adhesiveness but before it is completely hardened.

[0088] (Step S40 (sticking process)) In step S40, the repair materials 10, 10' are applied to the surface 100s of the concrete structure 100 to which the primer has been applied.

[0089] In the pasting step, the curable composition is applied to the laminates 4, 4', and the laminates 4, 4' are impregnated with the curable composition. For example, after applying the curable composition to the surface 100s of the concrete structure 100, the laminates 4, 4' may be pasted, and the repair material 10, 10' may be pasted by applying the curable composition from above the pasted laminates 4, 4'.

[0090] The laminates 4, 4' may be formed and then impregnated with the curable composition, or the laminates 4, 4' may be formed after impregnation with the curable composition, or the laminates 4, 4' may be formed and then impregnated with the curable composition while being impregnated. Furthermore, the laminates 4, 4' may be impregnated with the curable composition either before or after being attached to the target concrete structure.

[0091] Examples of methods for impregnating the laminates 4, 4′ with the curable composition include (1) a hand layup method in which coating and impregnation are performed manually using a roller, (2) a method of coating and impregnation by spraying, (3) a method in which the thickness of the laminates 4, 4′ is defined using a mold and then the curable composition is coated and impregnated into the laminates 4, 4′ by press-fitting, (4) a method in which the thickness of the laminates 4, 4′ is defined by reducing pressure and then the curable composition is impregnated into the laminates 4, 4′ by reduced pressure injection, (5) a method in which the laminates 4, 4′ are immersed in the curable composition, the laminates 4, 4′ are continuously impregnated with the curable composition, and then the thickness of the laminates 4, 4′ is defined by a roll, and (6) a method in which continuous coating and impregnation are performed by roll transfer. These methods may also be used in combination.

[0092] To improve workability during impregnation and to prevent the impregnated sheets from adhering to each other and to prevent dust from adhering to the impregnated sheets, the front and back surfaces of the laminates 4, 4' may be covered with a resin protective film. This protective film is removed when the laminates are attached to the concrete structure.

[0093] The resulting repair material 10, 10' is applied to the surface 100s of the concrete structure 100 to which a primer has been applied. At this time, it is important to remove any air bubbles that have entered between the repair material 10, 10' and the surface of the concrete structure 100, particularly in order to improve adhesion between the repair material 10, 10' and the surface 100s of the concrete structure 100. A suitable method for removing air bubbles is to use a roll, metal spatula, or the like to expel the air bubbles to the outside of the repair material 10, 10'.

[0094] (Step S50 (hardening process)) In step S50, the curable composition impregnated into the primer and the laminates 4, 4' is cured. In step S50, the primer hardens to form a film on the surface 100s of the concrete structure 100. The curable composition impregnated into the laminates 4, 4' is cured by placing the repair materials 10, 10' in close contact with the concrete structure 100. From the viewpoint of ensuring time for the curable composition to be impregnated into the surface 100s of the concrete structure 100, the curing time of the curable composition is preferably 30 to 300 minutes, more preferably 45 to 240 minutes.

[0095] Because the curable composition of the present disclosure is an inorganic material, the curing time can be adjusted by the amount of water contained. When the curable composition is a geopolymer, the curing time can be adjusted by the content of sodium, potassium, lithium, or a mixture thereof derived from the silicate aqueous solution, the ratio (SiO / MO) of SiO to MO (where M is sodium, potassium, or lithium) derived from the silicate aqueous solution, the difference in electrical conductivity of the pozzolan active substance, the aluminum content, etc. When the hardening of the hardenable composition is complete, the repair materials 10, 10' are fixed to the concrete structure 100, completing the repair of the concrete structure 100. Curing may be performed after the hardening step. From the viewpoint of stabilizing the state after the hardening step, the curing time is preferably 7 to 28 days, and more preferably 14 to 28 days. [Example]

[0096] The concrete structure repair method of the present disclosure will be described below using examples.

[0097] A concrete wall that had been exposed to the outdoors for over 20 years was used as an example of an excessively dry concrete structure. The moisture content of the concrete was measured using a concrete moisture meter (Kett Electric Laboratory, product name: HI-520-2) and was found to be 3.4%.

[0098] Example 1 In step S10, the surface of this concrete was scraped with a grinder equipped with a concrete grinding blade.

[0099] Next, in step S20, a solvent-free epoxy resin primer (MU Matex Co., Ltd., product name: U-Primer EP) was applied in an amount of 150 g / m 2 The mixture was applied to the surface of the concrete that had been scraped using a roller, and impregnated into the deteriorated concrete to form an impregnation layer 5.

[0100] Next, in step S30, the applied primer was left to dry at room temperature for 2 hours.

[0101] The silicate aqueous solution used in the curable composition was prepared by stirring 56 g of No. 3 sodium silicate aqueous solution specified in JIS K 1408, 14 g of 48 wt % sodium hydroxide aqueous solution, 30 g of water, and 10 g of latex (manufactured by Nippon A&L Co., Ltd., product name: SR-151) for 24 hours. 77 g of metakaolin (manufactured by KaMin Co., Ltd., product name: SP-33, electrical conductivity difference: 0.8 mS / cm) as a pozzolanic active substance and 44 g of ground granulated blast furnace slag specified in JIS A 6206 (manufactured by Nippon Steel & Sumikin Cement Co., Ltd., product name: Esment) were mixed with the above aqueous solution to prepare the curable composition.

[0102] Next, glass nonwoven fabric (weight 25g / m 2 , thickness 0.2 mm, porosity 95%), triaxial mesh sheet (basis weight 90 g / m) made of vinylon multifilament 2 , mesh size 8 mm, thickness 0.35 mm, X=3.0) and hydrophilic polypropylene spunbond nonwoven fabric (weight 30 g / m 2 A laminate was prepared by laminating two sheets of paper (0.2 mm thick, tear strength 16 N).

[0103] The glass nonwoven fabric corresponds to the "third layer," and the triaxial mesh sheet corresponds to the "first layer," with a basis weight of 30 g / m. 2 The spunbond nonwoven fabric corresponds to the "first layer."

[0104] Next, in step S40, the sheet-like laminate prepared above, 300 mm x 300 mm, was impregnated with 100 g of a curable composition, and a repair material was applied to the surface of the impregnating material layer 5, which was the surface treatment portion.

[0105] Next, in step S50, the curable composition impregnated into the laminate attached to the surface 100s of the concrete structure 100 was cured to prepare a repair material for the deteriorated concrete structure. Example 2 In step S20 above, a repair material for deteriorated concrete structures was prepared in the same manner as in Example 1, except that an acrylic primer (Toyo Morton Co., Ltd., base agent product name: TM-7416 / hardener product name: CAT-1955) was used as the primer. Example 3 A repair material for deteriorated concrete structures was prepared in the same manner as in Example 2, except that in step S30, the primer was left to stand at room temperature for 15 minutes and dried until adhesiveness appeared on the surface of the primer.

[0106] (Comparative Example 1) In the above step S20, an acrylic emulsion primer (Elephone Chemical Industry Co., Ltd., product name: ER Sealer) was used as the primer, and the drying time in step S30 was set to 2 hours based on the method of use. Except for this, repair materials for deteriorated concrete structures were prepared in the same manner as in Example 1.

[0107] Acrylic emulsion primers are aqueous solutions in which acrylic resin is dispersed in water, and film formation is completed when the water evaporates and the primer dries, so no curing reaction occurs due to a curing agent.

[0108] (Comparative Example 2) A repair material for deteriorated concrete structures was prepared in the same manner as in Example 1, except that in step S20 above, a polyurethane-based primer (Think Chemical Industry Co., Ltd., product name: U-100) was used as the primer, and the drying time in step S30 was set to 2 hours based on the usage method.

[0109] A urethane-based primer is a solution in which a urethane resin is dissolved in a solvent, and film formation is completed when the solvent evaporates and the primer dries, so no curing reaction is involved with a curing agent.

[0110] (Comparative Example 3) In step S20 above, a silicate solution containing 56 g of sodium silicate solution No. 3 specified in JIS K 1408, 14 g of 48 wt % sodium hydroxide solution, and 30 g of water, which had been mixed in advance, was used as a primer, and a repair material for deteriorated concrete structures was prepared in the same manner as in Example 1, except that the drying time in step S30 was set to 2 hours.

[0111] (Adhesion strength evaluation) The adhesive strength of the concrete structure repair materials of each Example and Comparative Example to concrete was evaluated using a simple tensile tester (Technotester R-10000ND) manufactured by the Construction Research Institute. Specifically, concrete walls to which the repair materials prepared in each Example and Comparative Example had been applied were cured outdoors for seven days, and then the adhesive strength was measured according to the standard method of use of the simple tensile tester. Simple tensile tests were performed on three specimens for each Example and Comparative Example, and the average was taken as the adhesive strength. The results are shown in Table 1.

[0112] For example, based on the Metropolitan Expressway Company's Bridge Structure Design Guidelines for Concrete Fragment Peeling Prevention, the adhesive strength is 1.5 N / mm 2 Above 1.5N / mm is considered good. 2 If it is smaller than

[0113] [Table 1] As shown in Table 1, in Examples 1 to 3 in which an epoxy resin or acrylic primer was used, the adhesive strength was 1.5 N / mm 2 As a result, good adhesive strength can be exhibited. [Explanation of symbols]

[0114] 1: First layer 2:Second layer 3:Third layer 4, 4´: Laminate 10, 10´: Repair material 100: Concrete structures 100s: surface

Claims

1. an application step of applying a primer containing an ethylenically unsaturated double bond-containing (meth)acrylate or epoxy resin and a curing agent to the surface of the concrete to be repaired; a bonding step of bonding a repair material obtained by coating or impregnating a laminate with a curable composition containing a silicate aqueous solution and a pozzolan active substance onto the primer-coated surface of the concrete after the coating step; a curing step of curing the primer and the repair material after the attaching step; A method for repairing a concrete structure comprising:

2. After the application step, the method further includes a drying step of drying the primer until adhesive strength is developed. The method for repairing a concrete structure according to claim 1.

3. The attaching step is performed after the primer has developed adhesive strength in the drying step but before the primer has completely hardened. The method for repairing a concrete structure according to claim 2.

4. The laminate is a sheet-like first layer formed by combining multifilaments in a multiaxial mesh shape; a sheet-like second layer formed from a polypropylene spunbond nonwoven fabric; The first layer and the second layer are arranged in this order from the surface side of the concrete. The method for repairing a concrete structure according to any one of claims 1 to 3.

5. The laminate further includes a sheet-like third layer formed of a glass nonwoven fabric and disposed on the surface side of the concrete of the first layer. The method for repairing a concrete structure according to claim 4.

6. The method further includes a scraping step of scraping the surface of the concrete before the application step. The method for repairing a concrete structure according to any one of claims 1 to 3.

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