JP2007246353A - Repair method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a repair method by which the restoration of a cross-section or the like can be performed in a simple and easy manner even without special skill by using a specified mixture. <P>SOLUTION: In the repair method, a face from which a deteriorated part of a concrete structure is removed is coated with a mixture comprising: isocyanates; at least one kind selected from polyols and an alkali metal salt aqueous solution; inorganic powder; and a reaction catalyst, and is thereafter foamed and solidified to be restored. Alternatively, in the repair method, the alkali metal salt aqueous solution is a lithium salt aqueous solution. Alternatively, in the repair method, the foamed and solidified surface is coated with a coating material or pasted with a molding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for repairing a deteriorated concrete structure.

In recent years, maintenance and management of concrete structures have become important, and repair and reinforcement works are increasing. Various methods for repairing and reinforcing concrete structures have been proposed so far.
For example, there is a cross-section repair method in which a portion where concrete has deteriorated due to neutralization or salt damage is removed, and the removed cross-section is repaired with a polymer cement mortar having a new durability. In this cross-section repair method, trowel coating method, spraying method, grout method, etc. are carried out, all of which are constructed by kneading polymer cement mortar, trowel coating method and spraying method without using formwork Now, when the repair depth is deep, it is divided into several layers and repainted.
On the other hand, cross-sectional restoration using a resin mortar in which an acrylic or epoxy resin and an aggregate are mixed is also performed (Patent Documents 1 and 2). These are often used in emergencies because they provide strength early. Further, urethane-based materials having foaming properties are used for stabilization of natural ground in tunnel construction and slope construction, and for filling a cavity on the back of the tunnel (Patent Documents 3 and 4).
JP 2000-063626 A JP 2000-128958 A JP 05-079291 JP 2000-282969 A

However, when repairing degraded parts that do not affect the structural strength, damage of small cross sections due to external forces, repair of small cross sections, or repairs where the repair depth is 30 mm or more, the polymer In order to use cement mortar, it is difficult to perform construction unless it is a worker who has plastering skills, spraying skills, formwork setting skills, etc. Also, the spraying method and grout method have a dedicated construction system and mold. Since it is necessary to install a frame, it was not a simple method. In addition, small cross-section repairs have problems such as a lot of material loss in the construction method using the construction system. Furthermore, resin mortar is a very expensive material and has a problem of poor workability. Urethane-based materials are expensive and often have a high foaming ratio and often have low strength. Therefore, since the construction is in a liquid state that can be pumped, it is difficult to repair the cross section with a large repair depth.
In order to solve the above-mentioned problems, the present inventor provides a repair method that can easily repair a cross section without using special skills by using a specific mixture.

  That is, the present invention provides (1) a mixture containing at least one selected from isocyanates, polyols and alkali metal salt aqueous solutions, inorganic powder, and a reaction catalyst, as a deteriorated part of a concrete structure. (2) The repair method of (1) in which the alkali metal salt aqueous solution is a lithium salt aqueous solution, and (3) The coating material is applied to the foamed and solidified surface. 1) or (2) repair method, and (4) the repair method of (1) or (2), in which a molded product is attached to the foamed and solidified surface.

  By using the repair method of the present invention, repair such as cross-sectional repair of a concrete structure that has been easily deteriorated can be performed without special skills.

  Hereinafter, the present invention will be described in detail.

  The isocyanates of the present invention are not particularly limited, but (1) 4-4′-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (TDI), 1,3-xylylene diisocyanate ( XDI), hexamethylene diisocyanate (HMDI), polymethylene polyphenyl polyisocyanate (polymeric MDI), 1,5-naphthalene diisocyanate (NDI), etc. (2) These isocyanates are converted into water or lower monohydric or polyhydric alcohols. Modified products, (3) terminal isocyanate group-containing urethane prepolymers obtained by reacting these isocyanates with various polyols, and (4) these terminal isocyanate group-containing urethane prepolymers were modified with water or a monohydric or polyhydric alcohol. Things, (5 Use of one or a mixture of two or more of these terminal isocyanate group-containing urethane prepolymer and various isocyanates are possible. Further, one or more of (1) to (5) can be used. Among these, use of polymeric MDI is preferable from the viewpoint of safety and economy.

  The polyols of the present invention form polyurethane foam cured products by reaction with isocyanates, specifically, polypropylene glycol, polyethylene glycol, trimethylol ethane, trimethylol propane, hexamethylene glycol, and castor oil. Ethylene glycol such as alkylene glycol, glycerin, sorbitol, addition products obtained by adding ethylene oxide or propylene oxide to sucrose, and ethylene oxide-propylene oxide copolymer and amines such as ethylenediamine, diethanolamine, triethanolamine and triethylenediamine There are adducts with addition of oxide or propylene oxide. Among these, it is preferable to use an adduct obtained by adding propylene oxide to propylene glycol or ethylenediamine.

  10-200 mass parts is preferable with respect to 100 mass parts of isocyanate, and, as for the usage-amount of polyol, 50-150 mass parts is more preferable. If it is less than 10 parts by mass, the foamed cured product tends to be brittle, and if it exceeds 200 parts by mass, it tends to be too soft.

  The alkali metal salt aqueous solution of the present invention is used for the purpose of improving the strength of the foamed cured product and imparting flame retardancy, and is an aqueous solution of alkali metal carbonates of lithium, sodium and potassium, lithium, sodium and potassium. Alkali metal silicate aqueous solution, lithium, sodium, potassium nitrite aqueous solution and the like. Among these, it is preferable to use lithium silicate or nitrite which is easily available and has an alkali aggregate reaction suppressing effect and an antirust effect.

  50-200 mass parts is preferable with respect to 100 mass parts of isocyanate, and, as for the usage-amount of alkali metal salt aqueous solution, 80-150 mass parts is more preferable. If it is less than 50 parts by mass, it is difficult to impart flame retardancy, and if it exceeds 200 parts by mass, the strength of the cured product tends to decrease.

  In the present invention, the isocyanates and polyols are usually divided into separate containers, and are a two-component type in which the isocyanate side is A liquid and the polyol side is B liquid. They are mixed and used before construction. is there. The aqueous alkali metal salt solution and the reaction catalyst can be mixed in advance on the B liquid side.

  The inorganic powder of the present invention is used for the purpose of improving the strength of the foamed cured product, and specifically, cements, calcium aluminates, fly ash, silica fume, slag, clay minerals, calcium carbonate. , Sand, and mixtures thereof. Among these, cement and sand are preferable in terms of improving strength.

  The amount of inorganic powder used varies depending on whether it is applied thinly with a brush or roller (when the viscosity is reduced) and when applied with a spatula (when the viscosity is increased), but the total of polyols and isocyanates, Or 20-700 mass parts is preferable with respect to a total of 100 mass parts of polyols, isocyanates, and alkali metal salt aqueous solution, and 80-500 mass parts is more preferable. If the amount is less than 20 parts by mass, the effect of improving the strength may not be sufficient. If the amount exceeds 700 parts by mass, the application may not be possible.

  The inorganic powder may be blended at the construction site, and can be mixed and placed in advance on either or both of the liquid A side and the liquid B side. In view of storage stability, it is preferable to mix on site.

  The reaction catalyst of the present invention controls the time from mixing the A liquid and the B liquid to foaming and curing, and includes an amine catalyst, an organometallic catalyst, an inorganic catalyst, and the like. Any of them can be used, but use of an amine-based catalyst is preferable because of its high activity. Examples of amine-based catalysts include ethylenediamine, triethylenediamine, triethylamine, ethanolamine, diethanolamine, and hexamethylenediamine, and mixtures thereof with derivatives or solvents thereof. Examples of the organometallic catalyst include dibutyltin dilaurate, dibutyltin diacetate, and potassium acetate. Examples of the inorganic catalyst include tin chloride.

  Although the usage-amount of a reaction catalyst is not restrict | limited in particular, 0.05-10 mass parts is preferable with respect to 100 mass parts of isocyanates, and 0.2-5 mass parts is more preferable. If it is less than 0.05 parts by mass, the reaction rate is slow and impractical, and if it exceeds 10 parts by mass, the reaction rate tends not to be improved.

  In the present invention, foam stabilizers, flame retardants, solvents, surfactants, thickeners, rust inhibitors and the like can be used in combination as long as the performance of the foam is not impaired.

  The coating material of the present invention is used for the purpose of suppressing the intrusion of water, carbon dioxide gas, and chloride ions that cause deterioration after foaming and curing. For example, (1) Resin-based surface coating materials generally used in repair methods for concrete structures can be used, for example, epoxy resins, acrylic resins, chloroprene resins, etc. (2) silicone-based water repellents (3) Aqueous emulsions such as acrylic, ethylene-vinyl acetate, styrene-butadiene, etc. (4) Inorganic surface coating materials blended with hydraulic materials such as cement, polymer cement mortar, ( 5) Colloidal silica, silicate surface modifiers, and the like.

  The molded product of the present invention is used for the purpose of preventing entry of the above deterioration factors and peeling off after foaming and curing, and is a molded product of metal, resin, cement cured body or the like. For example, (1) vinylon sheet, carbon fiber sheet, aramid fiber sheet, Kevlar fiber sheet, in which fibers are formed into a mesh or sheet, (2) high toughness board formed by mixing a large amount of short fibers into cement mortar, (3) A plate-shaped plastic molding, an FRP board, and the like can be given.

The construction method of the present invention is not particularly limited as long as the missing cross section can be repaired, but the liquid A, liquid B and inorganic powder are put in a bucket etc. at the construction site and kneaded with a rod-shaped object or a hand mixer. Apply evenly to the defect surface using a brush or spatula. Since the time until foam hardening is possible by adjusting the amount of the reaction catalyst, it can be controlled to be appropriate depending on the area to be repaired and the temperature. Usually, foaming starts and hardens several minutes after application. Foaming is adjusted to a level somewhat above the level of the unrepaired area. The expansion ratio can be adjusted by changing the amount of inorganic powder used or the amount of polyol used. For a finer finish, use a saw or grinder to cut off the part beyond the unrepaired part level.
When applying a coating material, it is applied using a brush or a roller after foaming and curing, and when a molded product is attached, it may be fixed with an adhesive or an anchor.

  Examples will be described in detail below.

  To 100 parts by mass of isocyanates, 0.3 parts by mass of reaction catalyst and polyols are added as shown in Table 1, and inorganic powder A is added to 200 parts by mass with respect to 100 parts by mass in total of polyols and isocyanates. The foaming ratio and compressive strength were measured. The results are shown in Table 1.

(Materials used)
Isocyanates: Polymeric MDI, Commercially available polyols: Polypropylene oxide adduct of ethylenediamine, Commercially available reaction catalyst: Hexamethylenediamine, Commercially available inorganic powder A: Lime sand, Maximum particle size 1.2 mm

(Test method)
Foaming ratio: Volume compression strength at the time of maximum foaming with respect to the total volume of liquid A (isocyanates) and liquid B (polyols): After 24 hours of material age, the foamed cured body is formed into a cube of 2 cm long x 2 cm wide x 2 cm high Molding and measuring compressive strength with autograph Curing time: Time from foaming of A and B to maximum foaming

  From Table 1, it can be seen that the repair method of the present invention can provide a repair material having sufficient work (curing) time, high foaming ratio and high strength.

  With respect to 100 parts by mass of isocyanates, 0.3 parts by mass of reaction catalyst, alkali metal salt aqueous solution and polyols are added as shown in Table 2, and inorganic powder is added to polyols and alkali metal salt aqueous solution A or B. The mixture was mixed in an amount of 200 parts by mass with respect to a total of 100 parts by mass with isocyanates, and the same procedure as in Example 1 was performed except that the flame retardancy test was performed. The results are shown in Table 2.

(Materials used)
Alkali metal salt aqueous solution A: lithium silicate aqueous solution, solid content 20% by mass
Alkali metal salt aqueous solution B: lithium nitrite aqueous solution, solid content 40% by mass

(Test method)
Flame retardancy: According to JIS K 7201, a foamed cured sheet having a thickness of 3 mm was prepared and the oxygen index was measured. The case where the oxygen index was 35 or more was evaluated as ◯, the case where it was 8 or more but less than 35 was evaluated as Δ, and the case where it was less than 8 was evaluated as ×.

  From Table 2, it can be seen that the repair method of the present invention can provide a repair material having sufficient work (curing) time, high foaming ratio, high strength, and high flame retardancy.

  As shown in Table 3, 0.3 parts by mass of reaction catalyst, 100 parts by mass of polyols, and inorganic powder A or B are added to 100 parts by mass of isocyanate and polyol, based on 100 parts by mass of isocyanate and polyol. The same procedure as in Example 1 was conducted except that flame retardancy was measured in the same manner as in Example 2. The results are shown in Table 3.

(Materials used)
Inorganic powder B: Ordinary Portland cement

  From Table 3, it can be seen that the repair method of the present invention can provide a repair material having sufficient work (curing) time, high foaming ratio, high strength, and high flame retardancy.

  The same procedure as in Example 1 was performed except that 100 parts by mass of isocyanate and 100 parts by mass of polyol and reaction catalyst were added as shown in Table 4 and flame retardancy was measured in the same manner as in Example 2. . The results are shown in Table 4.

  From Table 4, it can be seen that the repair method of the present invention can provide a repair material having sufficient work (curing) time, high foaming ratio, high strength, and high flame retardancy.

  In the concrete structure, the mixture of Experiment No. 1-6 in Example 1 and Experiment No. 2-9 and 2-15 in Example 2 is applied to the defect portion where the concrete of 30 cm in length × 30 cm in width × 2 cm in depth is removed. Was applied with a spatula to a thickness of 10 to 15 mm. As a result, a foamed cured product was formed at the cross-sectional repaired site that foamed and was lost after several minutes. The curing time, foaming ratio, and compressive strength at that time were measured in the same manner as in Example 1, and the adhesion strength between the foamed cured product and concrete was further measured. The results are shown in Table 5.

(Test method)
Adhesive strength: Drilled to the concrete part with a core drill of φ50 mm, and measured with a Kenken-type adhesion tester.

  From Table 5, it can be seen that the repairing method of the present invention can provide a repair material with sufficient work (curing) time, high foaming ratio, high strength, and high adhesion strength with concrete.

  In the concrete structure, water was sprayed on the defective portion from which the concrete of 30 cm in length × 30 cm in width × 2 cm in depth was removed, assuming water leakage. A mixture of Experiment No. 1-6 of Example 1 and Experiment Nos. 2-9 and 2-15 of Example 2 was applied to the wet surface with a spatula to a thickness of 10 to 15 mm. As a result, a foamed cured product was formed at the cross-sectional repaired site that foamed and was lost after several minutes. The curing time, foaming ratio, compressive strength, and adhesion strength at that time were measured in the same manner as in Example 5. The results are shown in Table 6.

  From Table 6, the repair method according to the present invention can provide a repair material having sufficient work (curing) time, high foaming ratio, high strength, and high adhesion strength to the wet concrete surface. I understand.

A concrete plate having a length of 20 cm, a width of 20 cm, and a thickness of 6 cm was removed from the concrete so that the length was 15 cm, a width of 15 cm, and a depth of 2 cm, and a deficient portion was produced. A mixture of Experiment No. 1-6 in Example 1 and Experiment Nos. 2-9 and 2-15 in Example 2 was applied with a spatula to a thickness of 10 to 15 mm to form a foamed cured body, and a test specimen Was made. On the next day, the specimen was immersed in seawater for 1 month, the foamed cured body was removed, and the internal reinforcing bar state was observed. As a result, in the case of the mixture of Experiment No. 1-6, the reinforcing bars were rusted, and in the case of the other mixtures, rust was not generated.
Therefore, it turned out that a higher rust prevention effect can be provided by using the restoration | repair material which used the alkali metal salt aqueous solution of lithium for the defect | deletion part from which the reinforcing bar is exposed.

  A concrete plate having a length of 20 cm, a width of 20 cm, and a thickness of 6 cm was removed from the concrete so that the length was 15 cm, a width of 15 cm, and a depth of 2 cm, and a deficient portion was produced. A mixture of Experiment No. 1-6 in Example 1 and Experiment Nos. 2-9 and 2-15 in Example 2 was applied with a spatula to a thickness of 10 to 15 mm to form a foam cured body. What applied the various (A, B, C) coating materials shown below was used as a test body, and after 7 days, the test body was immersed in seawater for one month, and then the foamed cured body was removed and the state of internal reinforcing bars was observed. As a result, rust was not generated in the reinforcing bars.

(Materials used)
Coating material A: acrylic coating material, commercial product coating material B: silane-based water repellent, commercial product coating material C: polymer cement-based coating material, commercial product

  Concrete test body 10 cm long × 40 cm wide × 10 cm high (wire mesh installed at a height of 5 cm) The concrete was suspended so that a portion 10 cm wide from the center of the side was 2 cm deep and 2 cm deep. The mixture of Experiment No. 1-6 was applied with a spatula to a thickness of 10 to 15 cm to form a foamed cured product. After that, after attaching the various molded products shown below and observing the situation when loaded and destroyed in the same way as in the bending test, if the molded product is not pasted, break the edge at the interface between the concrete and the cured foam. Although the part of the raised parts peeled off, the ones with the molded products A to C attached had a strong bending shear strength even if the edges were cut at the interface between the concrete and the cured foam. No peeling occurred.

(Materials used)
Molded product A: Biaxial vinylon mesh sheet, acrylic adhesive used for fixing Molded B: FRP plate, acrylic adhesive and anchor bolts used for fixing Molded C: high toughness board, anchor used for fixing Use bolts

  By using the repairing method according to the present invention, it is possible to easily repair a deteriorated concrete structure such as a cross section without having special skills, and thus can be widely applied in the civil engineering and construction fields.

Claims (4)

Applying a mixture containing isocyanate, at least one selected from polyols and alkali metal salt aqueous solutions, inorganic powder, and reaction catalyst to the surface of the concrete structure from which the deteriorated portion has been removed, and then solidifying by foaming Repair method to repair by letting. 2. The repair method according to claim 1, wherein the alkali metal salt aqueous solution is a lithium salt aqueous solution. The repair method according to claim 1 or 2, wherein a coating material is applied to the foamed and solidified surface. The repair method according to claim 1 or 2, wherein a molded product is attached to the foamed and solidified surface.