JP2011011934A - Hydrogel sheet for concrete modification and concrete modification method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogel sheet for concrete modification, capable of efficiently feeding an electrolyte solution to the concrete, and a concrete modification method using the same, whereby the electrolyte solution can be fed into a concrete formed body through a simple method so as to modify the interior of the concrete by the function of the electrolyte solution without causing any great damage to the concrete formed body.SOLUTION: The hydrogel sheet 10 for concrete modification includes a gel sheet having a three-dimensional net structure which includes a water-soluble organic polymer and a water-swellable clay mineral and is impregnated with the electrolyte solution having an ion concentration of ≥0.1-≤15 mol/kg-HO, provided that the weight ratio of the electrolyte solution to the dry gel sheet is 2-100.

Description

  The present invention relates to a hydrogel sheet used for modification of a concrete molded body and a concrete modification method using the same, and is suitable for alkalizing and recovering neutralized concrete inside in a concrete structure or a concrete molded body. The present invention relates to a hydrogel sheet excellent in retention of an alkaline aqueous solution used and a simple concrete reforming method using the hydrogel sheet.

The concrete that constitutes the concrete molded body usually maintains alkalinity, and since the oxidation reaction of steel materials such as reinforcing bars and steel frames is suppressed, rust does not occur and the strength is maintained for a long time. The However, with the passage of time, the alkalinity decreases due to the infiltration of carbon dioxide in the air, and there is concern about the deterioration of the molded product due to the decrease in alkalinity.
In recent years, various technologies have been proposed for the purpose of extending the life of concrete structures or maintaining earthquake resistance and durability from the viewpoint of energy saving or safety maintenance. Specifically, a method of applying to existing structures is desired for the purpose of maintaining long-term and effective rust prevention of steel materials such as reinforcing bars and steel frames arranged in concrete structures. Yes.
Currently, as a generally performed method, there is a method in which a part of surface concrete of a concrete structure having a neutral surface is peeled off, an exposed steel surface is treated with alkali, and then repaired with new concrete. These have the problem that man-hours are required, such as peeling a part of the concrete molded body to a depth that reaches the reinforcing bar.

In contrast, by providing an alkaline electrolyte retention layer and external electrodes on the concrete surface, forming a hole with a depth reaching the steel material existing in the structure, and inserting a conductor there to contact the steel material The steel material itself is energized as an electrode, and an alkaline agent is infiltrated to the vicinity of the reinforcing bar using the electroosmosis principle to suppress the oxidation of the reinforcing bar (for example, refer to Patent Document 1). A method (for example, refer to Patent Documents 2 to 4) for improving the processing efficiency by controlling the temperature condition has been proposed. Even in this method, there is a problem in that holes must be formed in the concrete molded body itself, the molded body needs to be destroyed, and man-hours are required.
Further, as a method for preventing destruction of the molded body, a method has been proposed in which a predetermined region of a concrete molded body is covered and fixed with an alkali-resistant sheet, and an alkaline agent is injected into the fixed sheet so as to penetrate into the concrete surface. (For example, refer to Patent Document 5). However, the concrete molded body contains fine aggregates and coarse aggregates, and since the voids present in the molded body are extremely small, an alkaline agent is applied to a concrete molded body having a fine gap of several nanometers to several tens of nanometers. It was difficult to penetrate.

Japanese Patent Laid-Open No. 5-180661 JP-A-6-24871 JP-A-8-91958 JP-A-7-291767 JP-A-11-79868

An object of the present invention made in view of the above problems is to provide a hydrogel sheet for concrete modification that can efficiently supply an electrolyte solution to concrete.
A further object of the present invention is to supply an electrolyte solution into the concrete molded body by a simple method without damaging the concrete molded body, and the function of the electrolyte solution can neutralize the concrete. A concrete reforming method that can neutralize or neutralize neutralized concrete and suppress deterioration of steel materials and the resulting decrease in strength of concrete compacts due to the neutralization of concrete. There is to do.

The present inventors have solved the above object by using a hydrogel sheet having a micro three-dimensional cross-linking structure, excellent mechanical toughness and flexibility, and excellent retention and release of electrolyte solution. As a result, the present invention has been completed.
That is, the hydrogel sheet for concrete modification of the present invention has a three-dimensional network structure composed of a water-soluble organic polymer and a water-swellable clay mineral, and has an ion concentration of 0.1 to 15 mol / kg-H ₂ O. It is a hydrogel sheet comprising an electrolyte solution 2 to 100 times the dry gel sheet weight.
The hydrogel sheet had a tensile strength measured by a tensile test of 10 kPa or more and 1000 kPa or less, a breaking elongation of 100% or more and 2000% or less, and was subjected to a compression test and was strained to 80%. Since the hydrogel sheet sometimes does not break down, strength and flexibility suitable for practical use can be achieved, and those having such physical properties are preferable.
In addition, as the electrolyte solution, one or more alkali agents selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide are used at an ion concentration of 0.1 mol / kg-H ₂ O to 15 mol / kg-H. It is a preferable embodiment that the alkaline solution is contained within a range of ₂ O or less.
Such a hydrogel sheet may be laminated on a support, or may include a reinforcing material such as a liquid-permeable reinforcing sheet inside the gel sheet.

Moreover, the concrete modification method according to claim 5 of the present invention is a gel sheet having a three-dimensional network structure composed of a water-soluble organic polymer and a water-swellable clay mineral, and an ion concentration of 0.1 mol / kg-H ₂ O. A step of obtaining a hydrogel sheet comprising an electrolyte solution of 15 mol / kg-H ₂ O or less from 2 to 100 times the dry gel sheet weight, a step of closely attaching the hydrogel sheet to the surface of the concrete molded body, It is characterized by having.
In addition, in the concrete modification | reformation method of this invention, it is preferable from the viewpoint of improving the permeability of electrolyte solution to perform the process of drying the surface of the said concrete molded object prior to the process of making the said hydrogel sheet contact | adhere.
Furthermore, it is preferable from a viewpoint of the electrolyte solution retainability to have a step of coating the hydrogel sheet with a water-impermeable sheet after the step of bringing the hydrogel sheet into close contact.
In this modification method, when the electrolyte solution retained by the hydrogel sheet decreases, a step of supplying at least one selected from an electrolyte solution, an electrolyte component, and water to the gel sheet can be performed as desired.

The hydrogel sheet for concrete modification of the present invention uses a gel sheet having a three-dimensional network structure composed of a water-soluble organic polymer and a water-swellable clay mineral, so that the electrolyte solution is stably held in the three-dimensional network structure. be able to. In addition, the hydrogel sheet holding an appropriate amount of the electrolyte solution has moderate strength, flexibility, and surface tackiness. Therefore, the hydrogel sheet is applied to the surface of the concrete molded body, so that the surface of the molded body is stably maintained while maintaining the shape of the sheet. In order to achieve good adhesion to the surface of the formed body without using an adhesive, the electrolyte solution can be supplied to the concrete over a long period of time.
In addition, by using such a hydrogel sheet for modifying concrete, oxidation of the steel solution such that the electrolyte solution, in particular, pH 11 or more effective in suppressing neutralization can be performed without damaging the concrete molded body. Since the alkaline solution that can be suppressed can be supplied from the surface of the concrete compact for a long period of time, it is easy to improve the alkalinity of the neutralized concrete or to improve the concrete such as to suppress neutralization over time. Can be implemented.
The concrete molded body to which the treatment method of the present invention is applied is not particularly limited as long as it is obtained by curing a concrete composition containing water, cement, an admixture, and an aggregate. This includes any structure, civil engineering structures such as dams and piers, concrete partition walls, benches, and objects.

  ADVANTAGE OF THE INVENTION According to this invention, the alkalinity inside the concrete molded object which neutralization advances by the carbonation reaction of the cement hydrate in mortar and concrete can be recovered by a simple method without damaging the molded object. Therefore, the alkaline environment in the concrete is maintained by periodically treating existing buildings and the like. Therefore, the strength reduction due to corrosion of the steel material existing inside is effectively suppressed, and the durability of the concrete molded body can be improved. Furthermore, since it can be modified nondestructively, it can be suitably used for modifying a concrete molded body such as a historical building.

ADVANTAGE OF THE INVENTION According to this invention, the hydrogel sheet for concrete modification | reformation which can supply an electrolyte solution to concrete efficiently can be provided.
Further, by using the hydrogel sheet for modifying concrete according to the present invention, an electrolyte solution can be supplied into the concrete molded body by a simple method without damaging the concrete molded body. The function can suppress the neutralization of the concrete inside, or alkalinize the neutralized concrete, and suppress the deterioration of the steel material and the resulting decrease in the strength of the concrete compact due to the neutralization of the concrete. It is possible to provide a concrete reforming method.

It is a schematic perspective view which shows one aspect | mode of the hydrogel sheet for concrete modification | reformation of this invention which has a reinforcing material in a gel sheet. It is a schematic perspective view which shows one aspect | mode of the hydrogel sheet for concrete modification | reformation of this invention which has a support body sheet as a reinforcing material.

Hereinafter, the present invention will be described in detail.
<Hydrogel sheet for concrete modification>
The hydrogel sheet for concrete modification of the present invention is an electrolyte solution having an ion concentration of 0.1 to 15 mol / kg-H ₂ O on a gel sheet having a three-dimensional network structure composed of a water-soluble organic polymer and a water-swellable clay mineral. Is impregnated with 2 to 100 times the weight of the dry gel sheet.
The gel sheet (dry gel sheet) useful for forming the hydrogel sheet of the present invention has a three-dimensional network structure formed by combining a water-soluble organic polymer and a water-swellable clay mineral. It is an organic-inorganic composite sheet that can stably hold a liquid component, and has excellent retention of an electrolyte solution as a liquid component.

[Gel sheet]
The hydrogel sheet containing an electrolyte component according to the present invention is a method of containing an electrolyte component after polymerizing a water-swellable clay mineral and a raw material monomer constituting a water-soluble organic polymer in an aqueous medium, or water swelling It can be produced by a method of polymerizing a functional clay mineral and a raw material monomer constituting a water-soluble organic polymer in the presence of an electrolyte solution which is a liquid component to be retained.
Examples of such a gel sheet include those obtained by forming an organic / inorganic composite hydrogel described in JP-A-2002-53629 into a sheet, and the sheet-like formed body of the organic / inorganic composite hydrogel described herein is the present invention. It is possible to use it suitably. In addition, a dried body (dried gel sheet referred to in the present invention) obtained by drying the hydrogel sheet is formed in advance, and the dried gel sheet is impregnated with a desired electrolyte solution and retained to obtain the hydrogel sheet of the present invention. You can also.

  The water-soluble organic polymer that constitutes the gel sheet is an organic polymer that dissolves or swells in water, and even if it is a homopolymer consisting of only one type of raw material monomer, it is a copolymer consisting of two or more types of monomers. It may be a coalescence. Such water solubility and water swellability may be achieved under specific polymer concentration, temperature, pressure conditions, coexistence of other additive components, and the like.

The water-soluble organic polymer preferably has an interaction with a water-swellable clay mineral, which will be described later, and has, for example, a functional group capable of forming a hydrogen bond, an ionic bond, a coordinate bond, a covalent bond, etc. with the water-swellable clay mineral. Those are preferred.
Specific examples of such functional groups include amide groups, amino groups, hydroxyl groups, tetramethylammonium groups, silanol groups, and epoxy groups, and organic polymers having one or more of these functional groups are preferable. Can be mentioned. Further, organic polymers having functionality are particularly preferable. For example, polymer properties in an aqueous solution, such as hydrophilicity and hydrophobicity, are slightly lower than before and after LCST (Lower Critical Solution Temperature). Preferable examples include functional organic polymers having characteristics that change greatly depending on changes.

Specific examples of water-soluble organic polymers that can be used for gel sheet formation include acrylamide, N-substituted acrylamide derivatives, N, N-disubstituted acrylamide derivatives, N-substituted methacrylamide derivatives, N, N-disubstituted methacrylamide derivatives, ( Water-soluble organic polymers obtained by polymerizing one or more selected from (meth) acrylic acid and (meth) acrylic acid derivatives. It is also possible to use the above monomer and other organic monomers in combination as long as a uniform organic / inorganic composite hydrogel is formed.
Such water-soluble organic polymers include poly (acrylamide), poly (N-methylacrylamide), poly (N-ethylacrylamide), poly (N-cyclopropylacrylamide), poly (N-isopropylacrylamide), poly (methacrylic). Amide), poly (N-methylmethacrylamide), poly (N-cyclopropylmethacrylamide), poly (N-isopropylmethacrylamide),

Poly (N, N-dimethylacrylamide), poly (N, N-dimethylaminopropylacrylamide), poly (N-methyl-N-ethylacrylamide), poly (N-methyl-N-isopropylacrylamide), poly (N- Methyl-Nn-propylacrylamide), poly (N, N-diethylacrylamide), poly (N-acryloylpyrrolidin), poly (N-acryloylpiperidine), poly (N-acryloylmethylhomopiperazine), Examples include poly (N-acryloylmethylpiperazine), poly ((meth) acrylic acid), poly ((meth) acrylic acid) ester, and the like.

Such a water-soluble organic polymer may be dissolved or swelled not only in water but also in a mixed solvent of water and an organic solvent miscible with water.
Here, the organic solvent miscible with water includes a solvent miscible with water, that is, a solvent that forms a homogeneous phase by mixing with water. Examples of the organic solvent miscible with water include methanol, acetone, Examples include polar solvents such as methyl ethyl ketone and tetrahydrofuran, and a mixed solvent of one or more of these and water can be used. A mixed solvent of water and an organic solvent in such a mixed solvent can be used in place of water for the preparation of the hydrogel sheet, but the mixing ratio of both is within the range in which the water-swellable clay described later can be uniformly dispersed. Can be selected arbitrarily.

The water-swellable clay mineral used in the preparation of the gel sheet is a clay mineral that swells in water and can be uniformly dispersed, and particularly preferably can be uniformly dispersed in water at a molecular level (single layer) or a level close thereto. Examples include layered clay minerals.
Examples of the water-swellable clay mineral that can be used in the present invention include water-swellable smectite and water-swellable mica. Specifically, water-swellable hectorite containing sodium as an interlayer ion, water-swellable montmorillonite. , Water-swellable saponite, water-swellable synthetic mica and the like.
The water-swellable clay mineral needs to be finely and uniformly dispersed in the solution in which the raw material monomer of the water-soluble organic polymer is dissolved from the viewpoint of the suitability for producing the gel sheet. Particularly in the above solution, precipitation of clay minerals occurs, or fine particles without the formation of agglomerates of clay minerals that can be visually confirmed, that is, the solution becomes cloudy, that is, It is preferably in a state of being uniformly dispersed in a thickness of about 1 to 10 layers, and particularly preferably in a thickness of about 1 or 2 layers.

The hydrogel sheet of the present invention holds an electrolyte solution described later as a liquid component. The content of the water-soluble organic polymer and the water-swellable clay mineral at the time of gel sheet production is appropriately adjusted depending on the purpose and the raw material used, and is not necessarily limited, but from the viewpoint of stably holding an alkaline aqueous solution as an electrolyte solution, Water-swellable clay mineral concentration is 1 × 10 ⁻² mol / L-H ₂ O, ˜30 × 10 ⁻² mol / L-H ₂ O, and water-soluble organic polymer concentration is 0.5 mol / L-H ₂ O. It is preferable to use a hydrogel in the range of ˜5 mol / L—H ₂ O.
Moreover, from the viewpoint of imparting suitable flexibility and adhesiveness to the hydrogel sheet when the hydrogel sheet is brought into close contact with the concrete molded body, for example, the water-swellable clay mineral concentration is 1 × 10 ⁻² mol / L−. H ₂ O, it is preferable to use a _{^{~15 × 10 -2 mol / L-}} H 2 O, a water-soluble organic polymer concentration of _{0.5mol / L-H 2 O~3mol /} L-H 2 O hydrogel.

Gel sheet was adjusted by the conditions, the electrolyte solution ion concentration _{0.1mol / kg-H 2 O~15mol /} kg-H 2 O, stable in the range of 2 times to 100 times the weight of the dry gel sheet Since it can hold | maintain, it is useful to this invention.

  Moreover, from the viewpoint of improving the concentration of the electrolyte solution that can be retained, for example, ionic groups containing an acid group or an acid group salt structure such as a sodium salt of a carboxylic acid group or a sodium salt of a sulfonic acid group are described above. It is effective to include the water-soluble organic polymer in a proportion of 3 mol% to 80 mol%.

(Electrolyte solution)
The electrolyte solution contained in the hydrogel sheet is selected depending on the purpose of modifying concrete, the type of the electrolyte component, or the concentration of the electrolyte solution. In the present invention, the ion concentration is alkaline with a pH of 11 or more. it is preferable from the viewpoint of continuous electrolyte supply to the concrete and _{0.1mol / kg-H 2 O~15mol /} kg-H 2 O as _{shown, 0.5mol / kg-H 2 O~10mol} / More preferably, it is in the range of kg-H ₂ O.
The type of the electrolyte component is not particularly limited, but sodium hydroxide, potassium hydroxide, and water are used for the purpose of restoring the alkalinity of concrete that has been carbonized and neutralized, or for suppressing neutralization. contain one or more alkali agent selected from lithium oxide, ion concentration in the aqueous alkaline solution of the alkali agent is used an alkaline aqueous solution is _{0.1mol / kg-H 2 O~15mol /} kg-H 2 O It is preferable. More preferably the concentration of the alkali agent in the aqueous alkaline solution is in the range of _{0.5mol / kg-H 2 O~10mol /} kg-H 2 O.
Moreover, when aiming at the rust prevention of the reinforcement inside concrete, nitrite (for example, lithium nitrite etc.) can be used as an electrolyte component.
The electrolyte component as these concrete modifying materials is usually used as an electrolyte solution in a hydrogel state in an aqueous solution, but as a liquid component, a hydrogel containing an organic solvent that can uniformly dissolve water and the electrolyte material, A solid electrolyte component such as solid sodium hydroxide may be used as it is. In the latter case, it is presumed that the electrolyte component gradually dissolves in the liquid component contained in the hydrogel sheet and penetrates into the concrete molded body from the gel sheet surface.

  At this time, the penetration depth can be improved by adding an auxiliary agent that improves the permeability of the electrolyte component into the concrete. Examples of the auxiliary agent include polyoxyethylene alkyl ether and dialkylsulfosuccinic acid.

  The hydrogel sheet according to the present invention includes a liquid component electrolyte solution in a three-dimensional network formed by combining a water-soluble organic polymer and a water-swellable clay mineral, and is stably held. It is an organic / inorganic composite. Such a hydrogel sheet is a three-dimensional structure obtained by forming a crosslinked structure by combining a water-soluble organic polymer and a water-swellable clay mineral at the molecular level in a liquid component to be included. It is formed including a liquid component in the crosslinked structure.

  The hydrogel sheet comprising the organic / inorganic composite having the liquid component thus obtained can be used as the concrete reforming hydrogel sheet of the present invention in which the electrolyte solution is retained as the liquid component. A hydrogel sheet containing a liquid component such as the above is prepared, stored as a dry body, and impregnated and held with an electrolyte solution at the time of use can be preferably used as the hydrogel sheet of the present invention. The dried gel sheet is in a state in which the liquid component in the three-dimensional crosslinked structure is lost, but since this three-dimensional crosslinked structure is maintained, the electrolyte solution is impregnated and swollen, so These liquid components are absorbed and have a function of stably including them.

From the viewpoint of the effect, the hydrogel sheet of the present invention preferably contains the electrolyte solution in an amount of 2 to 100 times the mass of the dried gel sheet, more preferably 5 to 50 times. It is as follows.
The thickness of the hydrogel sheet of the present invention is not particularly limited, but is preferably 1 mm or more and 100 mm or less, more preferably from the viewpoint of good handleability and the ability to hold the electrolyte in an effective content. Is 3 mm or more and 50 mm or less.

In order to use the hydrogel sheet in the present invention in close contact with a concrete molded body, it is preferable to have strength to withstand practical use and flexibility to achieve shape followability, specifically, a tensile test of the hydrogel sheet. The tensile strength measured by the above is preferably 10 kPa or more and 1000 kPa or less, and more preferably 30 kPa or more and 300 kPa or less. As for flexibility, the tensile elongation at break is preferably 100% to 2000%, more preferably 200% to 1500%.
Furthermore, when the hydrogel sheet is subjected to a compression test, it is preferable that the hydrogel sheet does not break when strained to 80%.
Here, in the tensile test, a gel sheet having a thickness of 5 mm was cut into 10 mm × 70 mm to obtain a measurement sample, and a tensile test apparatus (manufactured by Shimadzu Corporation, tabletop universal testing machine AGS-) in an environment of 24 ° C. and 60% RH. H), and measured under conditions of distance between ratings = 30 mm and pulling speed = 100 mm / min.
In addition, as a compression test, a gel cut out to 10 × 10 × 10 mm is used as a sample, and attached to a tensile testing device (manufactured by Shimadzu Corporation, desktop universal testing machine AGS-H) in an environment of 24 ° C. and 60% RH. Then, strain is applied up to 80% under conditions of a compression speed of 10 mm / min, and the presence or absence of gel breakage is visually confirmed. The gel is broken by observing a strained gel sheet. When the gel is broken or unrecovered after unloading, it is called “breaking”, and the gel is uniform after unloading. Those that maintain the appearance and whose shape is allowed to recover are judged as “not destroyed”.

As long as this condition is satisfied, even when a large area is covered, the sheet does not break or crack during use, and there is little decrease in adhesion.
In addition, even if it does not have the said preferable intensity | strength and a softness | flexibility by itself, required intensity | strength may be achieved by using together the reinforcing material integrated with the hydrogel sheet which is mentioned later.

The hydrogel sheet of the present invention may have a reinforcing material from the viewpoint of improving the strength. The reinforcing material is not particularly limited as long as it has the necessary strength and flexibility, a synthetic resin film, a woven fabric composed of synthetic fibers and natural fibers, a nonwoven fabric, a fiber lump, or a short fiber, Examples thereof include fibers such as long fibers.
Depending on the purpose, the resin film may be a liquid-impermeable film, or may be a porous film having an opening or a mesh-like sheet. Further, not only the sheet-like reinforcing material such as the resin film or the nonwoven fabric, but also the fibers themselves such as long fibers may be dispersed as they are in the gel sheet as the reinforcing material. From the viewpoint of durability, those made of a material having resistance to the electrolyte solution contained in the hydrogel sheet are preferable. For example, when an alkaline aqueous solution is used as the electrolyte solution, the nonwoven fabric formed by entwining the fibers or fusing part of the fibers is more resistant to alkalis than the one in which the fibers are fixed with a binder. It is preferable from the viewpoint. The nonwoven fabric is preferably composed of alkali-resistant fibers, and examples of the alkali-resistant fibers include acrylic, nylon (trade name: polyamide), polyethylene, and polypropylene.

As an aspect of use of the reinforcing material, for example, an aspect of obtaining a high-strength hydrogel sheet having a reinforcing material inside the hydrogel sheet by adhering a mesh sheet or a nonwoven fabric between the two gel sheets is provided. It is done.
FIG. 1 is a perspective view showing one embodiment of a hydrogel sheet for concrete modification having a reinforcing material 12 inside the hydrogel sheet 10.
Although there is no restriction | limiting in particular as a reinforcing material inserted in the inside of a hydrogel sheet, From a viewpoint of the use efficiency of electrolyte solution, a liquid-permeable sheet | seat is preferable and a mesh-like sheet | seat, a nonwoven fabric, etc. are mentioned. The material of the sheet is not particularly limited as long as it satisfies alkali resistance and durability, but is preferably composed of fibers selected from acrylic, polyamide, polyolefin and the like.

Further, for example, by laminating a hydrogel sheet on the surface of an electrolyte solution-impermeable sheet as a support, the tensile strength is remarkably improved due to the support, and the support sheet becomes a protective layer. When the hydrogel sheet is used in close contact with the concrete molded body, loss due to evaporation of the electrolyte solution from the back surface (side not bonded to the concrete molded body) can be suppressed. FIG. 2 is a perspective view showing one embodiment of a hydrogel sheet for concrete modification having a support sheet 14 as a reinforcing material and having a hydrogel sheet 10 laminated on the surface thereof.
As a reinforcing material, a flexible and liquid-impervious sheet is preferable in the case of a use form such as a support, and among them, a polyolefin sheet having excellent alkali resistance is preferable. The thickness of the support sheet is preferably about 10 μm to 300 μm from the viewpoint of the balance between strength and flexibility.

The hydrogel sheet for concrete modification of the present invention is used in close contact with the surface of a concrete molded body. However, in the production of a hydrogel sheet, the hydrogel may be formed into a sheet during synthesis, or the synthesized hydrogel may be used. The sheet may be sliced and formed into a sheet having a predetermined thickness, or the synthesized hydrogel may be crushed and then compressed into a sheet.
Depending on the components of the hydrogel, the surface formed by slicing may have a property with higher adhesion as compared to the molded surface, and a hydrogel sheet exhibiting such properties is used. In this case, it is preferable from the viewpoint of electrolyte solution permeability that the sliced cut surface is used so as to be in close contact with the surface of the concrete molded body.

  In such a hydrogel sheet, the three-dimensional cross-linking structure existing in the hydrogel retains the electrolyte solution. However, by using the hydrogel sheet in close contact with the fine voids on the surface of the concrete molded body, the electrolyte solution is formed into the concrete from the adhesion surface. It gradually penetrates into the body, and the inside of the concrete molded body can be effectively modified with the electrolyte solution. For example, by using an alkaline aqueous solution as the electrolyte solution, it is possible to suppress the neutralization of the inside of the concrete molded body, recover the alkalinity of the neutralized concrete, and the like.

<Concrete reforming method>
Next, the concrete modification method of the present invention using the hydrogel sheet for concrete modification of the present invention will be described.
Concrete modification method of the present invention, the gel sheet having a three-dimensional network structure composed of a water-soluble organic polymer and a water swelling clay mineral, an ion concentration _{0.1mol / kg-H 2 O~15mol /} kg-H 2 A step of obtaining a hydrogel sheet comprising the electrolyte solution of O 2 to 100 times the dry gel weight (hydrogel sheet preparation step), and a step of bringing the hydrogel sheet into close contact with the surface of the concrete molded body (hydrogel sheet adhesion) Step).

[Hydrogel sheet preparation process]
The hydrogel sheet used here is the hydrogel sheet for concrete modification of the present invention, and the step of obtaining the hydrogel sheet is the same as the manufacturing method of the described hydrogel sheet.
The hydrogel sheet according to the present invention is obtained by impregnating a gel sheet having a three-dimensional network structure composed of a water-soluble organic polymer and a water-swellable clay mineral described above with an electrolyte solution to maintain a predetermined amount.
The electrolyte solution used here is appropriately selected according to the purpose of the concrete modification treatment.
Moreover, when producing the hydrogel sheet, by using the electrolyte solution itself as the liquid component of the raw material used for forming the gel, a hydrogel sheet containing the electrolyte solution 2 to 100 times the dry gel sheet weight in one step is obtained. This step is also included in the “step of obtaining a hydrogel sheet” in the present invention.
Moreover, the process of using the existing hydrogel sheet containing liquid components, such as water, and making a solid electrolyte material contain as described in this hydrogel sheet is also included by the hydrogel sheet preparation process in this invention.

[Hydrogel sheet adhesion process]
In this step, a hydrogel sheet containing a predetermined amount of the electrolyte solution is brought into close contact with the surface of the concrete compact to be modified. Since the hydrogel sheet is flexible and excellent in shape followability, it can be suitably used for non-planar concrete molded bodies. Furthermore, by applying and pressing the hydrogel sheet onto the surface of the concrete molded body, the hydrogel sheet follows and adheres to the fine irregularities on the surface of the concrete molded body, and the electrolyte solution contained in the hydrogel sheet becomes finer on the concrete molded body. It gradually penetrates into the gaps by capillarity.
The electrolyte solution held in the hydrogel sheet is held in the three-dimensional network structure of the gel sheet and does not ooze out as a liquid component due to compression or the like. As long as there is a concentration gradient of the electrolyte solution in the pores of the porous concrete molded body and the hydrogel sheet and the concrete molded body, and the capillary phenomenon is not hindered, it gradually permeates over a long period of time. Reforming is achieved.

In the hydrogel sheet adhering step, a known method can be arbitrarily used as a method for stably adhering the hydrogel sheet to the surface of the concrete compact and immobilizing it. Specifically, for example, a method of fixing using a mold, a method of covering with a water-impermeable sheet and fixing to the surface of a concrete molded body with an adhesive tape or the like together with the water-impermeable sheet, and screwing The method etc. are mentioned.
When the hydrogel sheet used in the modification method of the present invention is formed by laminating a hydrogel sheet on a water-impermeable support as described, there is no loss of the electrolyte solution from the back surface, which is preferable. Moreover, what has a reinforcing material inside a hydrogel sheet can be preferably used from a viewpoint of intensity | strength.
In particular, as a concrete modification, even when an alkaline aqueous solution containing a high-concentration alkaline agent is used as an electrolyte solution in order to suppress neutralization or to recover neutralized concrete, the hydrogel sheet of the present invention uses an electrolyte solution. Since it can be stably maintained, there is no concern about the outflow of the alkaline aqueous solution, which is preferable in terms of environment and safety.

[Step of drying the surface of the concrete compact]
As described above, by adhering the hydrogel sheet to the surface of the concrete molded body, the electrolyte solution penetrates into the fine voids of the concrete molded body from the contact surface, and the inside of the concrete is modified. From the viewpoint of improving the permeability, the concrete molded body is preferably in a dry state rather than a wet state in which moisture exists in the voids. From such a viewpoint, it is preferable to first perform a step of drying the surface of the concrete compact to be modified prior to the hydrogel sheet adhesion step.
For example, when the concrete structure in the outdoors is wet with rain, or when the surface is cleaned and wetted with the cleaning liquid, it is desirable to perform the drying step.
There is no particular limitation on the drying conditions and drying means, and a molded body having a relatively small size can be placed in a drying apparatus and dried. Further, in the case of a building or the like, it may be dried by a known method such as drying by applying hot air to the surface or placing an infrared heater near the surface. There is no limitation on the drying conditions, but there is a risk of deteriorating the concrete structure at temperatures exceeding 100 ° C. Therefore, natural drying, hot air in the range of 40 to 880 ° C, blowing air at room temperature (around 25 ° C) The drying temperature condition such as drying is less than 100 ° C., preferably 90 ° C. or less.
When performing a drying process, it is desirable to dry to the depth which needs the process detected beforehand in modification | reformation of a concrete molded object, ie, the concrete depth which is neutralizing.

[Step of coating hydrogel sheet with water-impermeable layer]
In order to suppress the loss of the electrolyte solution contained in the hydrogel sheet, after the hydrogel sheet adhesion step, the back surface of the hydrogel sheet (the surface that does not adhere to the concrete molded body) is covered with a water-impermeable layer, and the moisture back surface It is preferred to prevent evaporation from. In addition, when an alkaline aqueous solution is used as the electrolyte solution, contact with the alkaline aqueous solution from the outside is suppressed by the water-impermeable layer, which is preferable from the viewpoint of safety.
Examples of the coating method using the water-impermeable layer used here include a method of coating with a water-impermeable sheet, and a method of coating a hydrogel sheet by forming a polymer layer having a hydrophobic group. .
The water-impermeable sheet may be appropriately selected from those having weather resistance and strength suitable for the location. For example, a resin sheet made of polyethylene having a thickness of about 50 μm, a metal foil, a wooden plate having a thickness of about 1 mm, etc. Can be used. These may be a single layer or a sheet having a multilayer structure in which different materials are laminated for the purpose of improving water impermeability. The water-impermeable sheet in the present embodiment does not necessarily need to be a hydrophobic sheet, and even if the material itself is hydrophilic like wood, or is porous and water vapor permeable, As long as the required water impermeability is achieved as a whole by the thickness and the layer structure, it can be used in the present invention.
Examples of the polymer having a hydrophobic group used for forming a polymer layer having a hydrophobic group include an acrylic resin, a urethane resin, and an epoxy resin. As a method, a method of coating a hydrogel sheet with these polymer materials, a method of laminating a previously formed polymer layer on one side of the hydrogel sheet, and the like can be employed.

  By bringing the hydrogel sheet for concrete modification of the present invention into close contact with the surface of the concrete molded body, the electrolyte solution held by the hydrogel sheet gradually permeates into the concrete molded body and the concrete is reformed. By adhering the hydrogel sheet over a long period of time, the electrolyte solution penetrates to the deep part inside the concrete molded body, and the modification is performed, but after the hydrogel sheet adhesion process is performed, it is retained in the hydrogel sheet over time. The electrolyte solution is reduced. At this time, the effect can be improved by replacing with a new hydrogel sheet, but at least one selected from an electrolyte solution, an electrolyte material, and water is used for the hydrogel sheet while keeping the hydrogel sheet in close contact with the surface of the concrete molded body. The effect can also be improved by supplying.

[Step of supplying at least one selected from electrolyte solution, electrolyte component and water to hydrogel sheet]
In this step, at least one selected from an electrolyte solution, an electrolyte material, and water is supplied to the hydrogel sheet that is in close contact with the surface of the concrete molded body. The supply of the electrolyte solution or water can be performed by injecting a liquid electrolyte solution or water into the hydrogel sheet, or dropping them into the hydrogel sheet.
The timing of supplying the electrolyte solution or water is arbitrary, and it is specified at regular intervals so as to cope with the decrease in the electrolyte solution or water in consideration of the environment (temperature / humidity, air volume) in which the concrete is reformed. An appropriate amount (for example, 100 ml / m ² · day to 5 l / m ² · day) of an electrolyte solution may be continuously supplied, or the electrolyte in the hydrogel sheet may be visually observed. The electrolyte solution or water may be supplied when the solution is reduced, the thickness of the sheet is reduced, or the appearance is changed.
When supplying the electrolyte material in a solid state, similarly, the solid electrolyte material is inserted into the gel sheet at a predetermined interval, or when the appearance of the hydrogel sheet changes, the solid electrolyte material is It can be performed by a method such as insertion. In the latter case, it is preferable to simultaneously supply a liquid component serving as a solvent, for example, water.
By replenishing the electrolyte solution and the electrolyte material in this manner, the concrete can be effectively modified over a long period of time by performing one hydrogel sheet adhesion step.

In the concrete reforming method of the present invention, the penetration rate of the electrolyte solution such as an alkaline aqueous solution into the concrete molded body inner concrete molded body is determined by the test piece prepared with the concrete composition having the same composition as the concrete molded body. It can be calculated by conducting an experiment, cutting the test piece, performing a color reaction with phenolphthalein, measuring the penetration depth, and dividing by the square root of the contact time. Through such experiments, the penetration rate can be measured in advance, and the necessary contact time with a molded body made of the same concrete composition can be predicted.
In the case of on-site construction, a core is collected from a concrete molded body and a surface color reaction is performed, or a small hole with a predetermined depth is formed using a drill, and the color reaction of the generated powder It is also possible to confirm whether alkalization has progressed to a predetermined depth.

  The concrete molded body is not particularly limited as long as it is formed by curing a concrete composition comprising water, cement, an admixture, an aggregate, and a chemical admixture, and various kinds of concrete compositions having various prescriptions. It can be applied to the molded article.

There is no restriction | limiting in particular as a cement used for the concrete composition which is a raw material of a molded object in this invention, According to the use of the cement-type molded object formed, it can select suitably from various cements. As the cement, ordinary Portland cement, moderately hot Portland cement, low heat Portland cement, blast furnace cement, fly ash cement, and the like can be used.
There is no restriction | limiting in particular as said admixture, According to the use of the cement-type molded object formed, a kind and usage-amount can be suitably selected from various cement and the admixture for concrete. As the admixture, blast furnace slag fine powder, fly ash, silica fume and the like can be generally used.
Moreover, there is no restriction | limiting in particular in the kind and quantity of aggregate, According to the use of the molded object formed, the kind and mixing ratio of aggregate can be selected suitably.

In the concrete molded body to which the method of the present invention can be applied, various additives usually blended in the concrete molded body, for example, a water reducing agent, an air entraining agent, an antifoaming agent and the like can be appropriately blended.
The weight ratio of water and cement in the concrete composition forming the concrete molded body can be appropriately selected according to the use of the concrete molded body to be formed, but the weight ratio of water and binder is 40% or more and 75. % Or less, more preferably 50% or more and 70% or less.

A concrete molded body to which the method of the present invention can be applied can be obtained by kneading, molding and curing the concrete composition. Although the size and shape are arbitrary, from the viewpoint of the effect of maintaining strength by alkalinization, the present invention is applied to a molded body in which steel materials such as reinforcing bars and steel frames are arranged for various purposes such as reinforcing materials and structural materials. It can be said that the effect of is remarkable.
Such molded bodies include not only large structures such as buildings and piers, but also pre-stressed concrete molded bodies, such as decorative moldings such as decorative boards that are reinforced by a frame made of PC steel. The body is also included.

  Since the concrete reforming method of the present invention has the above-described configuration, it can be reformed, in particular alkalized, by allowing the electrolyte solution to penetrate into the concrete molded body without damaging the concrete molded body by a simple method. For this reason, it can be applied to large structures and historical buildings without the need for large-scale equipment, and the strength reduction due to rebar corrosion due to neutralization inside the concrete can be effectively suppressed. Therefore, its application range is wide.

In order to further expand the area of realkalization to the inside of concrete using the hydrogel sheet for concrete modification of the present invention, an electrode is provided on the surface or inside of the hydrogel sheet of the present invention to reach the steel material existing in the structure. A hole with a depth is formed, a conductor is inserted into the hole and brought into contact with the steel. It is possible to take a method of suppressing this. At this time, when a reinforcing material is used in the gel sheet, the reinforcing material itself can be used as an electrode by using a conductive material for the reinforcing material.
Thus, the hydrogel sheet of the present invention can be applied not only to a concrete molded body as it is, but also as an electrolyte supply source in various usage modes.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited to these description.
(Experimental example: Formulation of concrete composition)
A cement composition containing ordinary Portland cement, water, sand, and crushed stone (aggregate), and having a water / cement composition ratio (W / C ratio) of 70%, was prepared.

[Materials used]
Cement: Ordinary Portland cement (Mitsubishi Materials Corporation), density 3.16 g / cm ³
Water: Tap water Fine aggregate 1: Land sand in Kamisu-cho, Kashima-gun, Ibaraki Prefecture, surface dry density 2.62 g / cm ³ , water absorption 2.27%,
Coarse grain ratio 2.53
Fine aggregate 2: Fuzhou city river sand, Fujian, China, surface dry density 2.59g / cm ³ , water absorption 1.60%,
Coarse grain ratio 3.56
Mixing ratio (mass ratio) Fine aggregate 1: Fine aggregate 2 = 80: 20
Coarse aggregate: Crushed stone, Iwafune-cho, Shimotsuga-gun, Tochigi Prefecture, surface dry density 2.66 g / cm ³ ,
Water absorption rate 0.76%, coarse particle rate 6.52
AE water reducing agent standard form (type I)

[Concrete composition]
Table 1 shows the composition of the concrete composition. Details of each material used in the table are as described above. In the following concrete composition, the water / binder ratio is 70.0%, and the fine aggregate ratio is 50.6%.
(Note): In Table 1 below, the amount of admixture is included in the water due to internal substitution.

[Preparation of molded body by concrete composition]
Using the concrete composition shown in Table 1, the above-mentioned water, cement, fine aggregate, and coarse aggregate are put into a predetermined amount of mixer (forced biaxial mixer, volume 3 m ³ ) and mixed for 20 seconds. It was. At this time, an appropriate amount of an admixture (AE water reducing agent) was added and adjusted so that the amount of air in the kneaded concrete became a constant value (4.5% by volume).
A concrete molded body having a width of 10 cm, a length of 40 cm, and a thickness of 10 cm was formed from this concrete composition.

[Pre-neutralization treatment of concrete compacts]
In order to pre-neutralize the concrete molded body, it is left in a chamber with a carbon dioxide concentration of 5.0%, and the neutralization depth from the surface is reduced by a color reaction with phenolphthalein on the cut surface. Neutralization was promoted until it reached about 30 mm.

(Examples 1-3)
[Preparation of hydrogel sheet]
As a water-swellable clay mineral, a water-swellable synthetic hectorite having a composition of [Mg5.34Li0.66Si ₈ O ₂₀ (OH) ₄ ] Na0.66 + (trademark: Laponite XLG, manufactured by Rockwood Corporation (UK)) Used by vacuum drying at 100 ° C. for 2 hours.
N, N-dimethylacrylamide (DMAA) was used as an organic water-soluble monomer capable of forming a water-soluble organic polymer. DMAA was used after removing a polymerization inhibitor using a silica gel column in a volume of 80 ml with respect to 100 ml of DMAA.
As the polymerization initiator, potassium peroxodisulfate (KPS) was diluted with pure water at a ratio of KPS / water = 0.192 / 10 (g / g) to prepare an aqueous solution. As the catalyst, N, N, N ′, N′-tetramethylethylenediamine (TMEDA) was used as it was. As the water, pure water obtained by distilling ion-exchanged water was used. All water was used after bubbling high-purity nitrogen in advance for 3 hours or more to remove oxygen.
A colorless and transparent aqueous solution consisting of 678.4 g of pure water, 30.5 g of Laponite XLG, and 79.2 g of DMAA was prepared in a flat bottom glass container having an inner diameter of 100 mm and a height of 150 mm, the inside of which was replaced with nitrogen. Next, 500 μl of TMEDA and 42.4 g of an aqueous KPS solution were added with stirring to obtain a colorless transparent solution.
A part of this solution was transferred to a glass container of 300 mm × 400 mm × 5 mm, sealed, and allowed to stand at 20 ° C. for 24 hours for polymerization. The operations from the preparation of the solution to the polymerization were all performed in an atmosphere in which oxygen was blocked. After 24 hours, a transparent and uniform cylindrical gel having elasticity and toughness was generated in the glass container, and was taken out from the container. No inhomogeneous or opaque aggregation due to clay minerals or the like was observed in the gel. Using the TG-DTA220 manufactured by Seiko Denshi Kogyo Co., Ltd., the gel obtained was measured according to the moisture content, organic high molecular weight, and clay mineral content measured by raising the temperature to 800 ° C. at 10 ° C./min under air flow. It was found that both were organic / inorganic composite hydrogels having the same composition as the reaction solution. The polymerization yield of the monomers was 99.9% or more.

[Evaluation of Hydrokel Sheet]
1. Tensile strength, tensile elongation at break The hydrogel sheet is cut into 10 mm x 70 x 5 mm to make a measurement sample, and a tensile test device (24-degree 60% RH environment, manufactured by Shimadzu Corporation, tabletop universal testing machine AGS-H) The tensile strength was 100 kPa and the tensile elongation at break was 1500% when measured under the conditions of distance between scores = 30 mm and tensile speed = 100 mm / min.

2. Compression test Two 10% x 10mm x 5mm hydrogel sheets cut into 10mm x 10mm x 10mm samples, and a tensile test device (manufactured by Shimadzu Corporation, desktop type universal) under the environment of 24 ° C and 60% RH It was mounted on a testing machine AGS-H), strained up to 80% under the condition of a compression speed of 10 mm / min, and the presence or absence of destruction of the hydrogel sheet was visually confirmed.
As a result, no breakage was observed in any of the gel sheets used in Examples 1 to 3.
These measurement results are shown in Table 2.

[Preparation of electrolyte-supporting hydrogel sheet]
Two sheets of the hydrogel sheet thus obtained cut out to 100 mm × 400 mm were stacked, 29 parts of lithium hydroxide was added to 300 parts of hydrogel, and the outer periphery was sewn, and used in Example 1. A hydrogel sheet was obtained. Moreover, 48 parts of sodium hydroxide was added to 300 parts of the hydrogel, and the outer periphery was stitched to obtain hydrogel sheets used in Examples 2 and 3. Both are hydrogel sheets holding an electrolyte of 4.6 mol / kg.

3. Liquid content The liquid content [ratio occupied by the electrolyte solution contained in the hydrogel sheet] in the hydrogel sheet was calculated by the following formula. The results are shown in Table 2.
Here, the mass of the electrolyte solution contained in the hydrogel sheet is the same as in Examples 1 to 3, in which the electrolyte component is sandwiched between the hydrogel sheets containing moisture in a solid state and the hydrogel sheet containing moisture. This is a value obtained by dividing the dry mass of the hydrogel sheet from the total mass with the electrolyte component. As in Examples 4 to 10 to be described later, what is used by impregnating the electrolyte solution is the value of the hydrogel sheet after impregnation. It is a value obtained by dividing the dry mass of the hydrogel sheet from the mass.
The [electrolyte solution mass contained in the hydrogel sheet] measures the mass of the hydrogel sheet impregnated with the electrolyte solution mass, and then removes moisture by drying for 15 hours in a hot air dryer at 80 ° C. This is a value obtained by measuring the mass of the hydrogel sheet (dry mass of the hydrogel sheet) and calculating the difference.
(Formula) Liquid content = [Mass of electrolyte solution contained in hydrogel sheet] / [Dry mass of hydrogel sheet]

[Pretreatment of concrete]
The concrete molded body was immersed in water for 15 minutes to absorb water and used for modification (Examples 1 and 2). In Example 3, the concrete molded body was used as it was without absorbing water.
[Concrete property evaluation]
The hydrogel sheets used in Examples 1 to 3 obtained as described above were brought into close contact with the surface of a concrete molded body placed so that the test surface was vertical, and the surface was covered with a polyester sheet, and an adhesive tape It was fixed with and left to stand until the measurement time.
After 4 weeks, the molded body was cut and a 1% by weight phenolphthalein solution was sprayed on the cut surface to confirm the color reaction. In Examples 1, 2, and 3, the depths were 5.3 mm and 14 mm, respectively. Alkaline regions were formed up to .9 mm and 16.4 mm.

(Examples 4 to 10, Comparative Examples 3 and 4)
[Preparation of electrolyte-supporting hydrogel sheet]
The hydrogel sheet prepared in the same manner as in Example 1 was placed in a hot air dryer set at 50 ° C. for 15 hours to obtain a dried hydrogel sheet. 1 part of this dried hydrogel sheet was immersed in 50 parts of an aqueous electrolyte solution containing an electrolyte component having the concentration shown in Table 2 below. When the liquid content shown in Table 2 was reached, the immersion was stopped, and the hydrogel containing the aqueous electrolyte solution A sheet was obtained.
[Evaluation of hydrogel sheet]
In the same manner as in Example 1, a tensile test, a compression test, and a measurement of the liquid content of the hydrogel sheet containing the aqueous electrolyte solution were performed. The results are shown in Table 2 below.

[Pretreatment of concrete]
In Example 7, the concrete compact was immersed in water for 15 minutes to absorb water and used for modification. In Examples 6 and 10, the concrete compact was put into a hot air dryer set at 80 ° C. for 3 days and dried. In Examples 4, 5, 8, 10 and Comparative Examples 3 and 4, the concrete compact was used as it was.
[Concrete property evaluation]
Using these hydrogel sheets, concrete was modified in the same manner as in Examples 1 to 3, and the permeability in the concrete compact was evaluated. The results are shown in Table 2 below.

(Example 11)
[Preparation of electrolyte-supporting hydrogel sheet]
The hydrogel sheet prepared in the same manner as in Example 1 was placed in a hot air dryer set at 50 ° C. for 15 hours to obtain a dried hydrogel sheet. 1 part of this dried hydrogel sheet was immersed in 50 parts of an electrolyte concentration of 1.5 mol / kg-H ₂ O aqueous solution, and when the liquid content was reached, the immersion was stopped to obtain a hydrogel sheet A containing an aqueous electrolyte solution. . Separately, 1 part of the dried hydrogel sheet was immersed in 50 parts of an electrolyte concentration 8 mol / kg-H ₂ O aqueous solution, and when the liquid content reached the hydrogel sheet B containing the aqueous electrolyte solution. Got.
[Evaluation of hydrogel sheet]
In the same manner as in Example 1, the tensile test, compression test, and measurement of the liquid content of the hydrogel sheets A and B containing the aqueous electrolyte solution were performed. The results are shown in Table 2 below.

[Pretreatment of concrete]
In Example 11, the concrete compact was put into a hot air dryer set at 80 ° C. for 3 days and dried.
[Concrete property evaluation]
For the first two weeks, the hydrogel sheet A obtained as described above was brought into close contact with the surface of the concrete molded body placed so that the test surface was vertical, and the surface was covered with a polyester sheet, and an adhesive tape And then left to stand. In 2 weeks, the hydrogel sheet A was removed, and the hydrogel sheet B was replaced with a hydrogel sheet B. The surface was covered with a polyester sheet, fixed with an adhesive tape, and allowed to stand until measurement.
After 4 weeks, the molded body was cut and a 1% by mass concentration phenolphthalein solution was sprayed on the cut surface, and a color reaction was confirmed. As a result, an alkaline region was formed up to 22.0 mm.

(Comparative Example 1)
The alkaline aqueous solution used in Example 4 was applied by applying directly to the surface of a concrete molded body that was not pretreated and was placed so that the test surface was vertical, and was similarly evaluated.
As a result, the alkaline aqueous solution was not retained on the surface of the concrete molded body and therefore hardly penetrated into the concrete. Therefore, the realkalized region depth measured in the same manner as in Example 1 was 1 mm or less. .

(Comparative Example 2)
In place of the dried hydrogel sheet used in Example 4, a non-woven fabric subjected to a hydrophilic treatment (ED-17, 170 g / m ² , manufactured by Japan Vilene Co., Ltd.) was used. The concrete molded body was modified in the same manner as in Example 4 except that it was impregnated into the nonwoven fabric in the amount described in the above and contacted with the surface of the concrete molded body that was not pretreated and was placed so that the test surface was vertical. , Evaluated in the same way.
When the alkaline aqueous solution was brought into contact with the concrete molded body, the alkaline aqueous solution dripped, so that the alkaline aqueous solution could not be retained. Moreover, since there is no adhesiveness to a concrete molded object, fixation to a concrete molded object is difficult, and the clearance gap was formed between the concrete molded object and the nonwoven fabric. Furthermore, although screwing was performed, a gap was formed and sufficient adhesion to the concrete molded body could not be obtained. For this reason, the penetration | permeation by the contact to the concrete molded object of alkaline aqueous solution became inadequate. As a result, the realkalized region depth was 1 mm or less.

(Comparative Examples 5 and 6)
Acrylic container with the surface in contact with the concrete molded body released on the surface of the concrete molded body set so that the test surface is vertical is pressed against the surface of the concrete molded body through rubber for adjusting the surface and fixed. did. In this acrylic container, the alkaline aqueous solution used in Example 4 was sealed, and the solution was placed so as to be in direct contact with the concrete surface and impregnated, and evaluated in the same manner as in Examples 1 to 3.
In Comparative Example 5, the concrete molded body was used as it was without any pretreatment. In Comparative Example 6, the concrete molded body was placed in a hot air dryer set at 80 ° C. for 3 days and dried. used.
After the start of the test, the alkaline aqueous solution gradually leaked from the rubber portion for adjusting the unevenness, and the alkaline aqueous solution sealed in the acrylic container was lost after 3 days. The realkalized region depth measured in the same manner as in Example 1 was 3 mm or less.

(Comparative Example 7)
[Preparation of hydrogel sheet]
Example 1 Instead of the water-swellable clay mineral used in the method for preparing the hydrogel sheet, an organic crosslinking agent (N, N-methylenebisacrylamide) was used in the same manner as in Example 1 except that 1 mol% of DMAA was used. Thus, an organic cross-linked polymer hydrogel (described as “organic cross-linked hydrogel” in Table 2) was prepared.
[Preparation of electrolyte-supporting hydrogel sheet]
The obtained organic crosslinked polymer hydrogel was impregnated with an aqueous electrolyte solution in the same manner as in Example 4 to obtain an electrolyte-retaining hydrogel sheet of Comparative Example 7.
[Evaluation of hydrogel sheet]
In the same manner as in Example 1, a tensile test, a compression test, and a measurement of the liquid content of the hydrogel sheet containing the aqueous electrolyte solution were performed. However, in the tensile test, when the measurement sample was mounted on the testing machine, the sample was destroyed, and no measurement value was obtained. The results are shown in Table 2 below.

[Pretreatment of concrete]
In Comparative Example 7, the concrete molded body was used as it was without pretreatment.
[Concrete property evaluation]
Using the electrolyte-supporting hydrogel sheet using the organic cross-linked hydrogel sheet, an attempt was made to modify concrete in the same manner as in Examples 1 to 3, but the gel sheet was damaged and stuck to the surface of the concrete compact. It was impossible to attach.

As shown in Table 2, according to the concrete reforming method using the hydrogel sheet for concrete modification of the present invention, the electrolyte solution efficiently penetrates into the concrete molded body, and compared with the comparative example, It was confirmed that the reforming was performed up to the inside. As is clear from Example 11, since the electrolyte solution contained in the hydrogel sheet decreases with time, it can be seen that the effect is further improved by replacing the hydrogel sheet.
Moreover, even if it is a case where the hydrogel which concerns on this invention is used from the result of the comparative examples 3 and 4, when content of the electrolyte component hold | maintained at a hydrogel sheet is small (comparative example 3), or holding | maintenance of electrolyte solution It can be seen that when the amount is small (Comparative Example 4), the desired alkali permeability cannot be obtained and the effects of the present invention are not achieved. In Comparative Example 7, an organic cross-linked polymer hydrogel prepared using an organic cross-linking agent was used instead of the water-swellable clay mineral, but practically sufficient strength was not obtained.

10 Hydrogel sheet 12 Internal reinforcement 14 Support sheet

Claims (8)

The gel sheet having a three-dimensional network structure composed of a water-soluble organic polymer and a water swelling clay mineral, dry gel sheet weight ion concentration 0.1mol / _{kg-H 2} O or more 15mol / _{kg-H 2} O following the electrolyte solution A hydrogel sheet for concrete modification, which is held 2 to 100 times as much as the above.   When the tensile strength measured by the tensile test of the hydrogel sheet is 10 kPa or more and 1000 kPa or less, the elongation at break is 100% or more and 2000% or less, and when the hydrogel sheet is subjected to a compression test, strain is applied up to 80%. The hydrogel sheet according to claim 1, which does not break down. The electrolyte solution, sodium hydroxide, potassium hydroxide, and, one or more alkali agent selected from lithium hydroxide, ion concentration 0.1mol / _{kg-H 2} O or more 15mol / _{kg-H 2} O or less The hydrogel sheet according to claim 1 or 2, wherein the hydrogel sheet is an alkaline solution contained within the range of.   The hydrogel sheet according to any one of claims 1 to 3, further comprising a reinforcing material. The gel sheet having a three-dimensional network structure composed of a water-soluble organic polymer and a water swelling clay mineral, dry gel sheet weight ion concentration 0.1mol / _{kg-H 2} O or more 15mol / _{kg-H 2} O following the electrolyte solution A concrete reforming method comprising: a step of obtaining a hydrogel sheet that is held 2 to 100 times the amount, and a step of bringing the hydrogel sheet into close contact with the surface of a concrete molded body.   The concrete reforming method according to claim 5, further comprising a step of drying a surface of the concrete compact prior to the step of bringing the hydrogel sheet into close contact.   The concrete reforming method according to claim 5 or 6, further comprising a step of coating the hydrogel sheet with a water-impermeable sheet after the step of closely contacting the hydrogel sheet.   The concrete reforming method according to any one of claims 5 to 7, further comprising a step of supplying at least one of an electrolyte solution, an electrolyte raw material, and water to the hydrogel sheet.

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