JP7765760B2 - Filler laminate for concrete structure, and concrete structure - Google Patents

Description

The present invention relates to a filler laminate for concrete structures and a concrete structure.

In the past, various fillers have been proposed for joints and cracks in concrete structures. However, adhesion is difficult on complex shapes and wet surfaces, and they are unable to keep up with seasonal expansion and contraction of structures, resulting in problems such as peeling and brittle fracture.

To address these issues, a filler for concrete structures has been proposed, consisting of a polymer hydrogel formed from a polymer of a water-soluble organic monomer and a water-swellable clay mineral (see, for example, Patent Document 1). However, this filler has the problem that, when exposed to the atmosphere, the water evaporates, eventually turning into a brittle material and causing it to peel off from the concrete structure.

Therefore, there was a need for a filler for concrete structures that could maintain flexibility for long periods even under open-air conditions.

WO2017/169002

The problem that this invention aims to solve is to provide a filler laminate for concrete structures that has excellent interlayer adhesion and can maintain excellent flexibility for a long period of time, even when exposed to the atmosphere.

The inventors discovered that the above problems could be solved by using a filler laminate for concrete structures that has a coating film obtained from a water-based paint on an organic-inorganic composite hydrogel layer, and thus completed the present invention.

That is, the present invention provides a filler laminate for concrete structures, characterized by having a coating film (B) obtained from an aqueous paint on an organic-inorganic composite hydrogel layer (A).

The filler laminate for concrete structures of the present invention has excellent interlayer adhesion and can maintain excellent flexibility for a long period of time, making it suitable for use as a filler for concrete structures such as tunnels, roads, bridges, railways, buildings, revetments, and water and sewerage systems, as well as a repair material for these structures.

The filler laminate for concrete structures of the present invention has a coating film (B) obtained from an aqueous paint on an organic-inorganic composite hydrogel layer (A).

The hydrogel layer (A) preferably contains a polymer of a water-soluble organic monomer, a water-swellable clay mineral, and water, as this layer has excellent flexibility.

The polymer of the water-soluble organic monomer is obtained by polymerizing the water-soluble organic monomer. Examples of the water-soluble organic monomer include a monomer having a (meth)acrylamide group, a monomer having a (meth)acryloyloxy group, and an acrylic monomer having a hydroxyl group.

Examples of monomers having a (meth)acrylamide group include acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-cyclopropylacrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, acryloylmorpholine, methacrylamide, N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, N-cyclopropylmethacrylamide, N,N-dimethylaminopropylmethacrylamide, and N,N-diethylaminopropylmethacrylamide.

Examples of monomers having a (meth)acryloyloxy group include methoxyethyl acrylate, ethoxyethyl acrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, methoxymethyl acrylate, and ethoxymethyl acrylate.

Examples of the acrylic monomer having a hydroxyl group include hydroxyethyl acrylate and hydroxyethyl methacrylate.

Among these, from the viewpoints of solubility and the physical properties of the resulting organic/inorganic hydrogel layer, it is preferable to use a monomer having a (meth)acrylamide group, and it is more preferable to use acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, or acryloylmorpholine, and it is even more preferable to use N,N-dimethylacrylamide or acryloylmorpholine, and from the viewpoint of ease of polymerization, N,N-dimethylacrylamide is particularly preferable.

The above-mentioned water-soluble organic monomers may be used alone or in combination of two or more.

If necessary, the polymer of the water-soluble organic monomer can also be copolymerized with other monomers besides the water-soluble organic monomer.

The content of the polymer of the water-soluble organic monomer in the hydrogel layer (A) is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass. A content of the polymer of the water-soluble organic monomer of 1% by mass or more is preferred because it allows for the production of a hydrogel with excellent mechanical properties. On the other hand, a content of the polymer of the water-soluble organic monomer (A) of 50% by mass or less is preferred because it allows for the easy preparation of a hydrogel precursor composition before polymerization.

The water-swellable clay mineral forms a three-dimensional network structure together with the polymer of the water-soluble organic monomer, becoming a component of the hydrogel layer (A).

The water-swellable clay mineral is not particularly limited, but examples include water-swellable smectite and water-swellable mica.

Examples of the water-swellable smectite include water-swellable hectorite, water-swellable montmorillonite, and water-swellable saponite.

Examples of the water-swellable mica include water-swellable synthetic mica.

Of these, from the viewpoint of the stability of the hydrogel precursor composition, it is preferable to use water-swellable hectorite or water-swellable montmorillonite, and it is more preferable to use water-swellable hectorite.

The water-swellable clay mineral may be naturally occurring, synthetic, or surface-modified. Examples of surface-modified water-swellable clay minerals include phosphonic acid-modified hectorite and fluorine-modified hectorite. However, from the viewpoint of the strength and adhesiveness of the resulting organic-inorganic composite hydrogel, it is preferable to use phosphonic acid-modified hectorite.

Examples of the phosphonic acid-modified hectorite that can be used include pyrophosphate-modified hectorite, etidronic acid-modified hectorite, alendronic acid-modified hectorite, methylenediphosphonic acid-modified hectorite, and phytic acid-modified hectorite. These phosphonic acid-modified hectorites may be used alone or in combination of two or more.

The above-mentioned water-swellable clay minerals may be used alone or in combination of two or more types.

The content of the water-swellable clay mineral in the hydrogel layer (A) is preferably 1% by mass or more, and more preferably 2% by mass or more, since this further improves the mechanical properties of the resulting hydrogel. Furthermore, the content of the water-swellable clay mineral in the hydrogel layer (A) is preferably 20% by mass or less, and more preferably 10% by mass or less, since this further suppresses an increase in viscosity of the hydrogel precursor composition.

The hydrogel layer (A) may contain an organic solvent other than water, and since this gives a hydrogel that exhibits little change in mass even under open-to-air conditions and can stably maintain mechanical properties such as substrate adhesion and breaking strength, the volatility is preferably 0.1 ^g or less per 1 cm2 per hour in an open system at 60°C and 1 atmosphere (0.1 g/ ^cm2 hr 60°C 1 atm or less), more preferably 0.05 g or less, and even more preferably 0.01 g or less. Specifically, solvents that are easily miscible with water are preferred, and polyhydric alcohols with a volatility of 0.01 g or less per ^cm² hour in an open system at 60°C and 1 atmosphere, such as glycerin (0.001 g or less/ ^cm² hr, 60°C, 1 atm), diglycerin (0.001 g or less/ ^cm² hr, 60°C, 1 atm), ethylene glycol (0.01 g or less/ ^cm² hr, 60°C, 1 atm), propylene glycol (0.001 g or less/ ^{cm² hr} , 60°C, 1 atm), and polyethylene glycol (0.001 g or less/cm² hr, 60°C, 1 atm), are preferred, with glycerin and diglycerin being more preferred. These organic solvents may be used alone or in combination of two or more. It is also desirable that these organic solvents be uniformly contained in the organic-inorganic hybrid hydrogel of the present invention.

It is important that the mass ratio of water to the organic solvent (water/organic solvent) in the hydrogel layer (A) is 60/40 to 20/80, preferably 50/50 to 30/70, because this results in an organic/inorganic hydrogel that exhibits little change in mass even under atmospheric conditions and is excellent in various physical properties such as substrate adhesion and breaking strength.

A preferred method for producing the hydrogel layer (A) is to polymerize the water-soluble organic monomer in a hydrogel precursor composition containing a mixture of a water-soluble organic monomer, a water-swellable clay mineral, water, and, if necessary, an organic solvent, a polymerization initiator, and a polymerization accelerator, as this method allows for a simple production of a hydrogel having a three-dimensional network structure. The resulting polymer of the water-soluble organic monomer forms a three-dimensional network structure together with the water-swellable clay mineral, becoming a component of the hydrogel.

The polymerization initiator preferably has a solubility in water at 20°C of 50 g/100 ml or more, since it can sufficiently promote the polymerization of the water-soluble organic monomer even in an air atmosphere.

Examples of the polymerization initiator include water-soluble peroxides and water-soluble azo compounds that have a solubility in water at 20°C of 50 g/100 ml or more.

Examples of the water-soluble peroxide include ammonium persulfate, sodium persulfate, and t-butyl hydroperoxide.

Examples of the water-soluble azo compounds include 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 4,4'-azobis(4-cyanovaleric acid).

Among these, from the viewpoint of interaction with the water-swellable clay mineral, it is preferable to use water-soluble peroxides, and it is more preferable to use ammonium persulfate or sodium persulfate.

The polymerization initiators may be used alone or in combination of two or more.

The molar ratio of the polymerization initiator to the water-soluble organic monomer in the hydrogel precursor composition is preferably in the range of 0.01 to 0.1, and more preferably in the range of 0.01 to 0.05, since this allows the polymerization of the water-soluble organic monomer to proceed sufficiently even in an air atmosphere.

Examples of the polymerization accelerator include tertiary amine compounds, thiosulfates, and ascorbic acids.

Examples of the tertiary amine compound include N,N,N',N'-tetramethylethylenediamine and 3-dimethylaminopropionitrile.

Examples of thiosulfates include sodium thiosulfate and ammonium thiosulfate.

Examples of ascorbic acids include L-ascorbic acid and sodium L-ascorbate.

Of these, from the standpoint of affinity and interaction with water-swellable clay minerals, it is preferable to use a tertiary amine compound, and it is more preferable to use N,N,N',N'-tetramethylethylenediamine.

The polymerization accelerators may be used alone or in combination of two or more.

The content of the polymerization accelerator in the hydrogel precursor composition is preferably 0.01 to 1% by mass, and more preferably 0.05 to 0.5% by mass. A content of 0.01% by mass or more is preferred because it efficiently promotes the synthesis of organic monomers for the resulting hydrogel. On the other hand, a content of 1% by mass or less is preferred because it allows the hydrogel precursor composition to be used without agglomerating before polymerization, improving handleability.

The hydrogel precursor composition may further contain an organic crosslinker, a preservative, a thickener, etc., as needed.

The polymerization temperature for the water-soluble organic monomer is preferably 10 to 80°C, and more preferably 20 to 80°C. A polymerization temperature of 10°C or higher is preferred because it allows the radical reaction to proceed in a chain reaction. On the other hand, a polymerization temperature of 80°C or lower is preferred because it allows polymerization without water boiling.

The polymerization time varies depending on the type of polymerization initiator and polymerization accelerator, but is typically between several tens of seconds and 24 hours. In particular, in the case of radical polymerization using heat or redox, the polymerization time is preferably between 1 and 24 hours, and more preferably between 5 and 24 hours. A polymerization time of 1 hour or more is preferred because it allows the polymer of the water-swellable clay mineral and the water-soluble organic monomer to form a three-dimensional network. On the other hand, since the polymerization reaction is nearly complete within 24 hours, a polymerization time of 24 hours or less is preferred.

The coating film (B) is obtained by applying a water-based paint onto the hydrogel layer (A). Because the hydrogel layer (A) has excellent affinity with the water-based paint, the hydrogel layer (A) and the coating film (B) exhibit excellent interlayer adhesion.

The water-based paint is one in which the resin is dissolved or dispersed in an aqueous medium.

The resin is not particularly limited as long as it is used in coating film formation applications, but examples include acrylic resins, urethane-modified acrylic resins, urethane resins, polyester resins, alkyd resins, epoxy ester resins, and epoxy resins. Among these, acrylic resins such as acrylic resins and urethane-modified acrylic resins are preferred because they have excellent affinity with the hydrogel layer (A) and excellent interlayer adhesion. These resins may be used alone or in combination of two or more.

It is also preferable that the resin have hydrophilic groups, as this will further improve solubility and dispersibility in the aqueous medium.

Examples of the hydrophilic group include anionic groups, cationic groups, and nonionic groups.

Furthermore, by introducing crosslinkable functional groups into the resin, it can also be used as a two-component curing water-based paint.

Examples of the aqueous medium include water, hydrophilic organic solvents, and mixtures thereof. However, water or a mixture of water and a hydrophilic organic solvent is preferred due to its excellent affinity with the hydrogel (A).

The hydrophilic organic solvent is preferably a water-miscible organic solvent that is miscible with water without separating, and among these, organic solvents whose solubility in water (number of grams of organic solvent that dissolves in 100 g of water) is 3 g or more at 25°C are preferred. Examples of these water-miscible organic solvents include alcohol solvents such as methanol, ethanol, propanol, butanol, 3-methoxybutanol, and 3-methyl-3-methoxybutanol; ketone solvents such as acetone and methyl ethyl ketone; and glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol dimethyl ether. These water-miscible organic solvents may be used alone or in combination of two or more.

The mass ratio of the resin to the aqueous medium (resin/aqueous medium) in the aqueous coating is preferably 20/80 to 60/40, and more preferably 30/70 to 50/50, as this provides excellent coatability and interlayer adhesion.

The aqueous coating preferably contains a hydrophilic plasticizer, as this further improves interlayer adhesion between the hydrogel layer (A) and the coating film (B).

As the hydrophilic plasticizer, polyol plasticizers such as glycerin, diglycerin, ethylene glycol, propylene glycol, and polyethylene glycol are preferred because they have excellent affinity with the hydrogel layer (A), and of these, glycerin and diglycerin are preferred.

The content of the hydrophilic plasticizer is preferably 1 to 30% by mass of the resin, and more preferably 3 to 20% by mass, as this further improves interlayer adhesion between the hydrogel layer (A) and the coating film (B).

The water-based paint may also contain various additives, such as surfactants, leveling agents, rheology control agents, ultraviolet absorbers, antioxidants, defoamers, light stabilizers, weather stabilizers, heat stabilizers, and pigments, as needed.

The aqueous paint can be applied to the hydrogel layer (A) using various known application methods, but application by brush, spray, or roller is preferred, as this method allows for easy application even to hydrogel layer (A) with a complex shape.

After applying the water-based paint, one method for forming a coating is to cure it at room temperature for about 0.5 to 7 days, but the curing time can also be shortened by heating it to 40 to 80°C.

The amount of the aqueous coating material to be applied is preferably large so that a thick film can be formed, since this provides excellent interlayer adhesion with the hydrogel layer (A) and can further suppress evaporation of water from the hydrogel layer (A). However, since a large amount of application slows down the drying rate, a range of 0.05 to 0.5 kg/ ^m2 is preferred.

A preferred method for producing the filler laminate for concrete structures of the present invention is to inject the hydrogel precursor composition into the gaps or onto the surface of a concrete structure, generate the organic-inorganic composite hydrogel in the gaps or on the surface, and then paint the aqueous paint on top of it, as this allows for easy filling of complex-shaped areas and improves workability at civil engineering and construction sites.

The filler laminate for concrete structures of the present invention has an affinity with concrete, allowing it to penetrate the porous structure through capillary action and adhere tightly.

The filler laminate for concrete structures of the present invention has excellent interlayer adhesion and can maintain excellent flexibility for long periods of time, even when exposed to the atmosphere, making it suitable for use in a variety of industrial materials. For example, it can be used as a filler for concrete structures such as tunnels, roads, bridges, railroad tracks, buildings, revetments, and water and sewerage systems, as well as a repair material for these structures.

The present invention will be described in more detail below using specific examples, but the present invention is not limited to these examples.

(Preparation Example 1: Preparation of Hydrogel Precursor Composition (1))
A flat-bottomed glass container was charged with 40 g of pure water, 63 g of purified glycerin, 4.8 g of phosphonic acid-modified synthetic hectorite ("Laponite RDS" manufactured by BYK Japan K.K.), 20 g of dimethylacrylamide (hereinafter abbreviated as "DMAA"), and 20 mg of N,N'-methylenebisacrylamide, and the mixture was stirred to prepare a uniform, transparent composition (1). The viscosity of this composition (1), after being kept in a thermostatic bath at a water temperature of 25°C, was measured using a Brookfield viscometer ("VISCOMETER TV-20" manufactured by Toki Sangyo Co., Ltd.), and was found to be 50 mPa s.
Next, 12.6 g of purified glycerin and 80 μL of tetramethylethylenediamine (hereinafter abbreviated as "TEMED") were placed in another flat-bottom glass container and stirred to prepare a uniform TEMED solution.
The entire amount of composition (1) was placed in a 200 mL glass beaker, and 0.5 g of sodium persulfate (hereinafter abbreviated as "NPS") was added thereto and stirred until dissolved. The TEMED solution prepared above was then added, and stirring was continued until the mixture was uniformly mixed, thereby preparing hydrogel precursor composition (1).

(Preparation Example 2: Preparation of Hydrogel Precursor Composition (2))
A hydrogel precursor composition (2) was prepared in the same manner as in Preparation Example 1, except that 20 mg of N,N'-methylenebisacrylamide used in Preparation Example 1 was replaced with 0.05 g of polyethylene glycol diacrylate ("Light Acrylate 4EG-A" manufactured by Kyoeisha Chemical Co., Ltd.).

An acrylic emulsion (DIC Corporation's "Burnoc WE-317," non-volatile content: 45% by mass, solvent: water) was used as the water-based paint (1).

A urethane-modified acrylic emulsion (DIC Corporation's "Boncoat HY-364": non-volatile content 45% by mass, solvent: water) was used as the water-based paint (2).

5 parts by mass of glycerin was added to 100 parts by mass of acrylic emulsion (DIC Corporation's "Burnoc WE-317," non-volatile content: 45% by mass, solvent: water) and stirred until uniformly mixed to prepare water-based paint (3).

Example 1
Two mortar plates (70 mm x 70 mm x 20 mm) were arranged so that their flat surfaces were parallel to each other, and two 40 mm-wide polypropylene spacers were inserted between them. The two spacers were spaced 30 mm apart to create a space for filling with hydrogel, and the mortar plates and the spacers were secured together with aluminum tape. 110 g of the hydrogel precursor composition (1) obtained above was poured into this formwork and allowed to stand for 20 minutes to produce an organic-inorganic composite hydrogel. The formwork was then removed to obtain an H-type test specimen. The aqueous coating material (1) obtained above was applied with a brush (application amount: 0.3 kg/m ² ) onto the organic-inorganic composite hydrogel of the H-type test specimen, and the resulting mixture was allowed to stand for 24 hours to obtain a filler layer for concrete structures (1), and a mortar-gel-mortar structure (H-type test specimen) as the concrete structure (1).

[Evaluation of interlayer adhesion]
The H-shaped specimen of the concrete structure (1) obtained above was stretched to 50% elongation at a rate of 5 mm/min, and then returned to 0% elongation (original position) at the same rate. This cycle was repeated five times, and then the specimen was further stretched to 50% elongation. The appearance of the coating film was visually observed, and the interlayer adhesion was evaluated according to the following criteria.
○: No abnormalities ×: Peeling of the coating film is observed

[Flexibility evaluation]
The H-shaped specimens of the concrete structure (1) obtained above were stretched by 50% at a rate of 5 mm/min. The specimens were left for 90 days, and then their condition was visually observed, and their flexibility was evaluated according to the following criteria.
○: No abnormalities ×: The flexibility of the filler laminate is reduced and separation from the mortar is observed

Example 2
The same procedure as in Example 1 was carried out except that the aqueous paint (1) used in Example 1 was changed to the aqueous paint (2), and a mortar-gel-mortar structure (H-type specimen) was obtained as the filler layer for concrete structures (2) and the concrete structure (2), and then each performance was evaluated.

Example 3
A filler layer for a concrete structure (3) and a mortar-gel-mortar structure (H-type specimen) as the concrete structure (3) were obtained in the same manner as in Example 1, except that the hydrogel precursor composition (1) used in Example 1 was changed to the hydrogel precursor composition (2), and then each performance was evaluated.

Example 4
In the same manner as in Example 1, except that the aqueous paint (1) used in Example 1 was changed to the aqueous paint (3), a filler layer for a concrete structure (4) and a mortar-gel-mortar structure (H-type specimen) as the concrete structure (4) were obtained, and then each performance was evaluated.

(Comparative Example 1)
A mortar-gel-mortar structure (H-type specimen) was obtained as a concrete structure (R1) in the same manner as in Example 1, except that the aqueous coating material (1) applied in Example 1 was not applied, and then flexibility was evaluated.

(Comparative Example 2)
A filler layer for concrete structures (R2) and a mortar-gel-mortar structure (H-type specimen) as the concrete structure (R2) were obtained in the same manner as in Example 1, except that the water-based paint (1) used in Example 1 was changed to a solvent-based paint ("Priadeck T-46NX" manufactured by DIC Corporation). Then, each performance was evaluated.

The procedures in the above examples and comparative examples were carried out in a test room at 23°C and 50% RH.

The compositions and evaluation results for Examples 1 to 4 are shown in Table 1.

The compositions and evaluation results for Comparative Examples 1 and 2 are shown in Table 2.

It was confirmed that the filler layers for concrete structures of the present invention in Examples 1 to 4 have excellent interlayer adhesion and can maintain excellent flexibility for a long period of time.

On the other hand, Comparative Example 1 is an example in which no coating film is formed on the organic-inorganic composite hydrogel layer (A), and it was confirmed that flexibility could not be maintained for a long period of time.

Comparative Example 2 is an example in which a coating film obtained from a solvent-based paint is formed on top of the organic-inorganic composite hydrogel layer (A), but it was confirmed that the interlayer adhesion was insufficient and flexibility could not be maintained for a long period of time.

Claims (6)

A method for producing a filler laminate for concrete structures having an organic-inorganic composite hydrogel layer (A) and a coating film (B) obtained from an aqueous paint thereon, the method comprising the steps of injecting a hydrogel precursor composition into gaps in a concrete structure, forming the organic-inorganic composite hydrogel layer (A) in the gaps, and painting the aqueous paint thereon. The method for producing a filler laminate for concrete structures according to claim 1, wherein the organic-inorganic composite hydrogel layer (A) contains a polymer of a water-soluble organic monomer, a water-swellable clay mineral, and water. 3. The method for producing a filler laminate for concrete structures according to claim 2, wherein the organic-inorganic composite hydrogel layer (A) contains a low-volatile solvent whose volatility is 0.1 g or less per ¹ cm2 per hour in an open system at 60°C and 1 atmosphere (0.1 g/ ^cm2 hr 60°C 1 atm or less). The method for producing a filler laminate for concrete structures according to claim 2 or 3, wherein the water-swellable clay mineral includes phosphonic acid-modified hectorite. The method for manufacturing a filler laminate for concrete structures according to any one of claims 1 to 4, wherein the water-based paint contains an acrylic resin. A method for manufacturing a concrete structure, characterized in that gaps are filled with the laminated filler for concrete structures described in any one of claims 1 to 5.