JP7809488B2 - Concrete structure using hardening composition for anti-skinning method - Google Patents

Description

The present invention generally relates to concrete structures in the civil engineering and construction industries that use hardenable compositions to prevent spalling.

Curable compositions (adhesive compositions) have been devised for a variety of uses, and their main components include acrylic, epoxy, and urethane systems, but finding a composition that suits the application is by no means easy. Even if a composition is suitable for one application, it often does not function satisfactorily in another application.

As concrete structures deteriorate over time, spalling can occur from their surfaces. This can be a particularly serious problem when spalling occurs in structures such as bridge structures, building walls, and tunnel interior walls, which are located in areas with heavy pedestrian and vehicular traffic. For this reason, there is a great demand for methods to repair aging concrete structures.

One such repair method is to attempt to reinforce the surface of the concrete structure using a curable composition (adhesive composition).

Patent Document 1 relates to a concrete fragment peeling prevention structure, and is characterized by comprising a transparent primer layer formed by applying a silicone acrylic resin primer containing an amino group-containing acrylic resin and epoxy _silane to the surface of the concrete, and a transparent reinforcing layer formed by applying a transparent polyurea resin coating material on the transparent primer layer, the transparent reinforcing layer containing a non-yellowing isocyanate prepolymer with an NCO weight percentage of 10 to 30% by weight, an alicyclic polyamine, silica sand with an SiO2 content of 90% or more, hydrophilic fine silica, a rheology control agent, a light stabilizer, and an ultraviolet absorber, wherein the silica sand has an average particle diameter D50 (cumulative weight) of 100 to 500 μm, and the silica sand content in the transparent reinforcing layer is 10 to 40% by weight.

Patent Document 2 relates to a transparent primer for application to the surface of concrete structures, characterized by being composed of a bisphenol A liquid epoxy resin, an alkylphenol liquid epoxy resin, a reactive diluent, a polyamidoamine, and an aliphatic modified polyamine.

Japanese Patent Application Laid-Open No. 2017-180081 Japanese Patent Application Publication No. 2018-135257

However, the conventional techniques described in Patent Documents 1 and 2 do not solve the problem of the coating film obtained by applying a hardening composition to a concrete structure deteriorating over time and swelling. The reason for this is thought to be that the surface of aging concrete structures that are the target of repair is porous and easily permeable to water, meaning that the application of the conventional compositions does not provide satisfactory performance.

The inventors have conceived the present invention, which can solve the above problems. Specifically, the present invention provides the following aspects:

Aspect 1.
(a) a radical polymerizable compound,
(b) silica microparticles, and
(c) a reinforcing layer containing a hardened mixture containing a thixotropic agent;
a concrete body to which the reinforcing layer is applied directly or indirectly.

Aspect 2.
2. The concrete structure according to claim 1, wherein the mixture has a viscosity of 600,000 mPa·s or more at 25° C. and 1 rpm.

Aspect 3.
3. The concrete structure according to claim 1, wherein the mixture has a TI value of 6.0 or more at 25°C.

Aspect 4.
A concrete structure according to any one of Aspects 1 to 3, wherein the amount of the (b) silica fine particles is 5 to 12 parts by mass and the amount of the (c) thixotropic agent is 0.5 to 5 parts by mass, relative to 100 parts by mass of the (a) radical polymerizable compound.

Aspect 5.
A concrete structure according to any one of Aspects 1 to 4, wherein the mixture further comprises (d) short fibers, and the reinforcing layer is applied directly to the concrete body.

Aspect 6.
The concrete structure according to any one of aspects 1 to 4, wherein the reinforcing layer is indirectly applied to the concrete body via one or more selected from a sheet and a primer.

Aspect 7.
A concrete structure according to any one of Aspects 1 to 6, wherein the (c) thixotropic agent includes one or more selected from the group consisting of polyether compounds, carboxylic acid amide compounds, hydroxycarboxylic acid amide compounds, urea urethane amide compounds, and polyvinylpyrrolidone.

Aspect 8.
A concrete structure according to any one of Aspects 1 to 7, wherein the viscosity of the (a) radically polymerizable compound at 25°C and 1 rpm is 300 mPa·s or more.

Aspect 9.
A concrete structure according to any one of Aspects 1 to 8, wherein the (a) radical polymerizable compound comprises (a-1) a radical polymerizable monomer and (a-2) a radical polymerizable oligomer.

Aspect 10.
10. The concrete structure according to claim 9, wherein the (a-1) radical polymerizable monomer includes one or more (meth)acrylate monomers.

Aspect 11.
11. The concrete structure of claim 10, wherein the one or more (meth)acrylate monomers include linear (meth)acrylates and cyclic (meth)acrylates.

Aspect 12.
A concrete structure according to any one of Aspects 9 to 11, wherein the (a-2) radically polymerizable oligomer includes one or more urethane (meth)acrylate oligomers.

Aspect 13.
Aspect 13. The concrete structure according to any one of Aspects 9 to 12, wherein an amount of the (a-1) radical polymerizable monomer is 50% by mass or more and 70% by mass or less, based on the total amount of the (a) radical polymerizable compound.

Aspect 14.
A concrete structure according to any one of Aspects 9 to 13, wherein the (a-1) radical polymerizable monomer comprises dicyclopentenyloxyethyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate in a mass ratio of 0.25 to 4:1.

Aspect 15.
The concrete structure according to any one of aspects 1 to 14, wherein the reinforcing layer is a layer formed by applying the mixture to a thickness of 0.3 kg/ ^m² or more and 1.5 kg/ ^m² or less.

Aspect 16.
A step of preparing a first agent including (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (e) a curing catalyst;
preparing a second agent containing (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (f) a radical polymerization initiator;
mixing the first agent and the second agent to obtain a curable composition;
and applying the hardenable composition to the surface of a concrete body.

Aspect 17.
17. The method of claim 16, further comprising the step of (d) mixing short fibers with the first agent or the second agent prior to mixing the first agent and the second agent.

Aspect 18.
A step of preparing a first agent including (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (e) a curing catalyst;
preparing a second agent containing (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (f) a radical polymerization initiator;
mixing the first agent and the second agent to obtain a curable composition;
a step of applying one or more selected from a sheet and a primer to the surface of a concrete body, and then applying the curable composition thereon.

Aspect 19.
(a) a radical polymerizable compound,
(b) silica microparticles, and
(c) A composition containing a thixotropic agent and having a viscosity of 600,000 mPa·s or more at 25°C and 1 rpm.

Aspect 20.
(a) a radical polymerizable compound,
(b) silica microparticles, and
(c) A composition containing a thixotropic agent and having a TI value of 6.0 or more at 25°C.

The concrete structures that can be provided by embodiments of the present invention have a reinforcing layer that prevents the paint film from swelling after construction, resulting in excellent finish and durability.

Embodiments of the present invention are described in detail below, but the present invention is not limited to these embodiments. Note that "parts" and "%" in this specification are based on mass unless otherwise specified. Numerical ranges in this specification include upper and lower limit values unless otherwise specified.

Concrete structures according to embodiments of the present invention are obtained by applying a reinforcing layer to a concrete skeleton. Direct application (i.e., primerless or sheetless) is preferred from the standpoints of cost reduction and work efficiency (shortening construction time and enabling early release). One example of a construction method that can utilize embodiments of the present invention is the Denka One Step Guard construction method provided by Denka Co., Ltd. This construction method may include, for example, the steps of preparing a first agent containing (a) a radically polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (e) a curing catalyst; preparing a second agent containing (a) a radically polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (f) a radical polymerization initiator; mixing the first agent and the second agent to obtain a curable composition; and applying the curable composition to the surface of the concrete skeleton. Furthermore, (d) short fibers may be mixed with the first agent or the second agent to further improve punching load-bearing capacity (punching strength). Prior to mixing the first and second agents, (d) short fibers may be mixed with the first or second agent.
The curable composition according to the present invention is preferably a two-component composition. The two-component composition preferably comprises a first component containing at least (e) a curing catalyst and a second component containing at least (f) a radical polymerization initiator, and the mixture of the first and second components is the composition (cured product) according to the present invention. The blending ratio of the first component to the second component is preferably 25-75:25-75 (mass ratio), more preferably 40-60:40-60 (mass ratio), and even more preferably 50:50 (mass ratio), based on 100 parts by mass of the total of the first and second components. Numerical ranges (e.g., blending amounts) used herein may also refer to numerical ranges relative to the total of the first and second components.

Alternatively, a concrete structure with improved punching load-bearing performance (punching strength) may be obtained by applying the reinforcing layer indirectly to the concrete skeleton (e.g., via a primer layer or undercoat layer). One example of a construction method that can utilize embodiments of the present invention is the Denka NS Guard construction method provided by Denka Company Limited. This construction method may include, for example, the steps of preparing a first agent containing (a) a radically polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (e) a curing catalyst; preparing a second agent containing (a) a radically polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (f) a radical polymerization initiator; mixing the first agent and the second agent to obtain a hardenable composition; and applying one or more selected from a sheet and a primer to the surface of the concrete skeleton and then coating the hardenable composition thereon.

In any of the above methods, the embodiments of the present invention have the excellent effect of suppressing uneven color appearance after application, suppressing swelling of the coating film, and ensuring sufficiently high adhesion strength of the reinforcing layer to the concrete structure.

In this specification, the type of concrete structure (hereinafter also referred to as "base") to which the reinforcing layer is applied is not limited, and may include any type of concrete, mortar, and hardened cement. In particular, the spalling prevention method according to an embodiment of the present invention has the advantage that it can be used to repair concrete structures that have deteriorated and developed numerous microscopic voids on the surface (the surface has become porous), and that it provides an excellent finish and durability. Furthermore, the size of the concrete structure may be arbitrary, and large-area construction is also possible.

The curable composition capable of forming the reinforcing layer according to an embodiment of the present invention contains (a) a radically polymerizable compound, (b) silica microparticles, and (c) a thixotropic agent. That is, the reinforcing layer to be formed may contain a cured product of a mixture containing (a) a radically polymerizable compound, (b) silica microparticles, and (c) a thixotropic agent. In some embodiments of the present invention, the above-described composition itself may also be provided. Preferably, the viscosity of the curable composition at 25°C and 1 rpm may be 600,000 mPa·s or more and 1,500,000 mPa·s or less, more preferably 900,000 mPa·s or more and 1,200,000 mPa·s or less. A viscosity of 600,000 mPa·s or more at 25°C and 1 rpm sufficiently suppresses blistering of the coating film. Furthermore, the T.I (thixotropic index) value of the composition at 25°C is preferably 6.0 or more, more preferably 7.5 or more. By setting the viscosity and thixotropy of the curable composition high in this way, even when the target of application is a dilapidated concrete structure, the curable composition can be impregnated into the concrete structure to an extent that sufficient adhesive strength is obtained, and excessive absorption, which would result in a thin coating film and uneven color appearance, can be prevented. Furthermore, it also solves the problem of coating film deformation and swelling due to the vapor pressure of water vapor that accumulates on the porous surface of a dilapidated concrete structure.

From the perspective of improving workability, the viscosity of the curable composition at 25°C and 1 rpm is preferably 1,500,000 mPa·s or less, and more preferably 1,200,000 mPa·s or less. Similarly, from the perspective of improving workability, the T.I value of the curable composition at 25°C is preferably 10.0 or less, and more preferably 8.0 or less. If the T.I value is 6.0 or more, when applying the adhesive to a concrete structure with a metal trowel or the like, the adhesive spreads well, making workability good and reducing variation in the applied thickness.

The viscosity and TI value can be measured using the method described in JIS Z8803:2011, for example, using a rotational viscometer known in the art. Unless otherwise specified, the TI value in this specification refers to a value measured at 25°C with a rotational speed ratio of 1:10, for example, the ratio of values obtained at rotational speeds of 1 rpm and 10 rpm, and can be expressed by the following formula 1.
TI value = (viscosity measured at 25°C and 1 rpm) / (viscosity measured at 25°C and 10 rpm) ... (Equation 1)

However, such high viscosity and T.I. values are considered to have adverse effects in other applications and are therefore unsuitable for practical use. For example, in spray painting applications, such high viscosity can make it difficult to spray and causes problems such as difficulty in spreading evenly after spraying. Furthermore, even in applications such as repairing cracks in concrete, such high T.I. values are not suitable because they are unable to penetrate fine cracks sufficiently. The viscosity and T.I. values in the embodiments of the present invention were devised by the inventor so that they can be used specifically to prevent spalling of concrete structures.

The curable composition may be a one-part or two-part type, but a two-part type is preferred from the perspective of ease of use at the construction site. In the case of a two-part type, for example, the first part may contain (a) a radically polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (e) a curing catalyst. The second part may contain (a) a radically polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (f) a radical polymerization initiator. In the case of a two-part type, the viscosity and T.I. value of the first and second parts may be measured together as a mixture or individually. It is preferable to measure the viscosity of the first and second parts individually. If measured individually, it is preferable that both the first and second parts have a viscosity of 600,000 mPa·s or greater at 25°C and 1 rpm and a T.I. value of 6.0 or greater at 25°C.

The (a) radically polymerizable compound serves as the base material for the curable composition. The (a) radically polymerizable compound can be any monomer or oligomer having one or more radically polymerizable groups. Examples include vinyl compounds, urethane compounds, epoxy compounds, and (meth)acrylic compounds having radically polymerizable groups. From the perspective of achieving adequate adhesive strength, it is preferable to use a (meth)acrylate monomer and/or oligomer. Furthermore, the viscosity of the (a) radically polymerizable compound is preferably 300 mPa·s or greater at 25°C and 1 rpm.

It is preferable that the (a) radical polymerizable compound contain (a-1) a radical polymerizable monomer and (a-2) a radical polymerizable oligomer in order to efficiently suppress uneven color appearance after application. This is thought to be because, when the monomer and oligomer are compatible, the difference in molecular weight allows the oligomer to suppress excessive absorption of the monomer into the concrete body. To maximize this effect, the molecular weight of the (a-2) radical polymerizable oligomer is preferably in the range of 800 to 50,000, and more preferably 3,000 to 30,000, in terms of weight average molecular weight (Mw). It is preferable that the molecular weight of the (a-1) radical polymerizable monomer be less than 800.

The weight-average molecular weight is a value calculated as a standard polystyrene by gel permeation chromatography (GPC). Specifically, the average molecular weight is determined by using tetrahydrofuran as a solvent, a GPC system (SC-8010 manufactured by Tosoh Corporation) under the following conditions, and creating a calibration curve using commercially available standard polystyrene.
Flow rate: 1.0ml/min
Set temperature: 40℃
Column configuration: One Tosoh "TSK guard column MP (xL)" 6.0 mm ID x 4.0 cm, and two Tosoh "TSK-GELMULTIPORE HXL-M" 7.8 mm ID x 30.0 cm (16,000 theoretical plates), for a total of three (total theoretical plate number: 32,000).
Sample injection volume: 100 μl (sample solution concentration 1 mg/ml)
Liquid delivery pressure: 39 kg/ ^cm2
Detector: RI detector

(a-1) The radical polymerizable monomer can be monofunctional, difunctional, or polyfunctional. Monofunctional radical polymerizable monomers are preferred. Monofunctional (meth)acrylates are preferred as monofunctional radical polymerizable monomers. A monofunctional (meth)acrylate refers to a mono(meth)acrylate having one (meth)acryloyl group.

(a-1) Examples of radically polymerizable monomers include chain (meth)acrylate and cyclic (meth)acrylate monomers.

As a chain (meth)acrylate, a (meth)acrylate having a linear or branched chain structure is preferred. The chain structure preferably has an alkyl group. The chain structure preferably has a hydrocarbon group. The hydrocarbon group may have a substituent. As a chain (meth)acrylate, it is preferred that it does not include a cyclic (meth)acrylate. Examples of linear or branched (meth)acrylates include alkyl (meth)acrylates such as hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicodecyl (meth)acrylate. acrylate, and hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, as well as 2-hydroxyethyl (meth)acryloyl phosphate, 4-butylhydroxy(meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, glycerin di(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and caprolactone-modified 2-hydroxyethyl (meth)acrylate, etc. Among these, one or more members of the group consisting of alkyl (meth)acrylates and hydroxyalkyl (meth)acrylates are preferred, and hydroxyalkyl (meth)acrylates are preferred. Of the hydroxyalkyl (meth)acrylates, 2-hydroxyethyl (meth)acrylate is preferred.

Preferably, the cyclic (meth)acrylate is one having an alicyclic structure or an aromatic structure. The cyclic structure may have a substituent. Examples of alicyclic or aromatic (meth)acrylates include alicyclic (meth)acrylates such as adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, and 1-(1-adamantyl)-1-methylethyl (meth)acrylate, as well as aromatic (meth)acrylates such as nonylphenol EO (ethylene oxide)-modified (meth)acrylate, benzyl (meth)acrylate, methylbenzyl (meth)acrylate, ethylbenzyl (meth)acrylate, propylbenzyl (meth)acrylate, methoxybenzyl (meth)acrylate, and chlorobenzyl (meth)acrylate. Of the aromatic (meth)acrylates, nonylphenol EO (ethylene oxide)-modified (meth)acrylate is preferred. Of these, alicyclic (meth)acrylates are preferred. Of the alicyclic (meth)acrylates, dicyclopentenyloxyethyl (meth)acrylate is preferred.

The amount of (a-1) radically polymerizable monomer is preferably 10% by mass or more and 95% by mass or less, more preferably 35% by mass or more and 85% by mass or less, and most preferably 50% by mass or more and 70% by mass or less, based on the total amount of (a) radically polymerizable compound.

From the perspective of improving adhesive strength, the (a-1) radical polymerizable monomer preferably contains a combination of the above-mentioned linear or branched (meth)acrylate and an alicyclic or aromatic (meth)acrylate, with the blending ratio being in the range of 1:4 to 4:1, and more preferably in the range of 1:2 to 2:1. It is particularly preferred to contain 2-hydroxyethyl (meth)acrylate and dicyclopentenyloxyethyl (meth)acrylate, with the blending ratio being preferably 0.25 to 4 parts by mass of dicyclopentenyloxyethyl (meth)acrylate per 1 part by mass of 2-hydroxyethyl (meth)acrylate, more preferably 0.5 to 3 parts by mass of dicyclopentenyloxyethyl (meth)acrylate, and even more preferably 2 parts by mass of dicyclopentenyloxyethyl (meth)acrylate.

(a-2) The radically polymerizable oligomer is preferably a bifunctional one. The bifunctional radically polymerizable monomer is preferably a bifunctional (meth)acrylate. A bifunctional (meth)acrylate refers to a di(meth)acrylate having two (meth)acryloyl groups.

(a-2) The radical polymerizable oligomer is preferably one or more members selected from the group consisting of urethane (meth)acrylate oligomers and bifunctional polymerizable oligomers having a bisphenol structure, with urethane (meth)acrylate oligomers being more preferred.

As the urethane (meth)acrylate oligomer, a bifunctional (meth)acrylate having a urethane structure is preferred. As the bifunctional (meth)acrylate having a urethane structure, a di(meth)acrylate having a urethane structure and two (meth)acryloyl groups is preferred. Examples of urethane (meth)acrylate oligomers include urethane (meth)acrylates obtained by reacting a polyisocyanate having at least two isocyanate groups per molecule, a polyol having at least two hydroxyl groups per molecule, and a hydroxyl group-containing (meth)acrylate.

Examples of urethane (meth)acrylate oligomers include bifunctional aromatic urethane (meth)acrylate (MIRAMER MU3603 manufactured by MIWON Co., Ltd.) and polybutadiene (meth)acrylate oligomer (NISSO-PB TE2000 manufactured by Nippon Soda Co., Ltd.). Examples of polybutadiene (meth)acrylate oligomers include urethane (meth)acrylates obtained by reacting toluene diisocyanate as the polyisocyanate, polybutadiene with hydroxyl groups at both ends as the polyol, and 2-hydroxyethyl (meth)acrylate as the hydroxyl group-containing (meth)acrylate.

As a difunctional polymerizable oligomer having a bisphenol structure, a difunctional (meth)acrylate having a bisphenol structure is preferred. As a difunctional (meth)acrylate having a bisphenol structure, a di(meth)acrylate having two (meth)acryloyl groups at the end of the bisphenol skeleton via an oxyalkylene structure is preferred. Examples of di(meth)acrylates having two (meth)acryloyl groups attached via an oxyalkylene structure to the terminal of a bisphenol skeleton include 2,2-bis(4-(meth)acryloxyphenyl)propane, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypropoxyphenyl)propane, 2,2-bis(4-(meth)acryloxytetraethoxyphenyl)propane, and 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane. Examples of di(meth)acrylates having two (meth)acryloyl groups attached via an oxyalkylene structure to the terminal of a bisphenol skeleton include MIRAMER M2101 manufactured by MIWON.

The amount of (a-2) radically polymerizable oligomer is preferably 5% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 65% by mass or less, and most preferably 30% by mass or more and 50% by mass or less, based on the total amount of (a) radically polymerizable compound.

(b) Silica microparticles function as a thickener, but are characterized by their interaction with (c) a thixotropic agent, which will be described later. In other words, (b) silica microparticles and (c) a thixotropic agent interact (preferably through hydrogen bonding) to form a network structure, thereby exhibiting structural viscosity, which contributes to achieving the viscosity and T.I. value described above. This finding was arrived at by the inventors after learning that sufficient viscosity and T.I. value cannot actually be achieved by using silica microparticles alone.

A preferred example of the (b) silica microparticles is fumed silica (e.g., AEROSIL (registered trademark) manufactured by Nippon Aerosil Co., Ltd.). Hydrophobic fumed silica is generally preferred for thickening the polar (a) radically polymerizable compound. The size and specific surface area of the (b) silica microparticles are not particularly limited. However, from the viewpoint of achieving both adhesive strength and viscosity/thixotropy, the primary particle diameter of the silica microparticles is preferably in the range of 1 to 100 nm, and the specific surface area by the BET method is preferably in the range of 50 to 200 m ² /g. The primary particle diameter can be determined as the median diameter (d50) in the volume-based particle size distribution using a particle size distribution analyzer employing analytical means such as laser diffraction. From the viewpoint of setting the viscosity and TI value within appropriate ranges, it is preferred that the silica microparticles have good dispersibility in radically polymerizable compounds, particularly radically polymerizable monomers. For example, when a (meth)acrylate monomer is used as the radical polymerizable monomer, among hydrophobic fumed silica, one that has been subjected to a hydrophobic surface treatment (for example, "AEROSIL" manufactured by Nippon Aerosil Co., Ltd.) is preferred.

The amount of (b) silica microparticles is preferably 1 part by mass or more per 100 parts by mass of (a) radical polymerizable compound to improve viscosity and thixotropy, and preferably 20 parts by mass or less to maintain the strength of concrete after application. The amount of (b) silica microparticles is preferably 5 parts by mass or more per 100 parts by mass of (a) radical polymerizable compound to improve viscosity and thixotropy, and preferably 12 parts by mass or less to maintain the strength of concrete after application.

Any (c) thixotropic agent (also called a thixotropic agent) can be used as long as it is capable of interacting with the above-mentioned (b) silica microparticles. From the perspective of ease of handling when preparing the curable composition, it is preferable that the agent be liquid at room temperature (5 to 35°C as defined by JIS Z8703:1983). Examples of (c) thixotropic agents (also called rheology control agents) include polyether compounds, carboxylic acid amide compounds, hydroxycarboxylic acid amide compounds (including polyhydroxycarboxylic acid amide compounds), urea urethane amide compounds, polyvinylpyrrolidone, polysaccharide derivatives (such as guar gum and xanthan gum), benzyl alcohol, xylene, ethanol, turpene, and mixtures of one or more of these.

The amount of (c) thixotropic agent is preferably 0.1 parts by mass or more per 100 parts by mass of (a) radical polymerizable compound to improve viscosity and thixotropy, and preferably 10 parts by mass or less to improve adhesive strength. The amount of (c) thixotropic agent is preferably 0.5 parts by mass or more per 100 parts by mass of (a) radical polymerizable compound to improve viscosity and thixotropy, and preferably 5 parts by mass or less to improve adhesive strength.

When using the curable composition in a primerless or non-sheet system, the curable composition (or any of the components that are mixed to obtain the curable composition) may further contain (d) short fibers. Examples of (d) short fibers that can be used include carbon fiber, aramid fiber, PA6 (nylon 6) fiber, glass fiber, acicular wollastonite, calcium titanate whiskers, calcium carbonate whiskers, and aluminum borate whiskers. The size of the (d) short fibers is preferably 2 to 10 mm in length.

The blending amount of (d) short fibers is preferably 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of (a) radical polymerizable compound. The blending amount of (d) short fibers is preferably 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of (a) radical polymerizable compound.

The curable composition may also contain various additives commonly used in the art, such as (e) a curing catalyst and (f) a radical polymerization initiator. Examples of (e) a curing catalyst and (f) a radical polymerization initiator are listed below.

Curing catalysts react with radical polymerization initiators to generate radicals and accelerate the polymerization of monomers. Examples of curing catalysts include diethylthiourea, dibutylthiourea, ethylenethiourea, tetramethylthiourea, acetylthiourea, mercaptobenzimidazole, benzoylthiourea, N,N-diethyl-p-toluidine, N,N-dimethyl-p-toluidine, N,N-diisopropanol-p-toluidine, triethylamine, tripropylamine, ethyldiethanolamine, N,N-dimethylaniline, ethylenediamine, triethanolamine, cobalt naphthenate, copper naphthenate, zinc naphthenate, cobalt octoate, iron octoate, copper neodecanoate, copper acetylacetonate, titanium acetylacetonate, manganese acetylacetonate, chromium acetylacetonate, iron acetylacetonate, vanadyl acetylacetonate, and cobalt acetylacetonate. Among these, those classified as metal soaps are preferred because of their good surface curing properties. Examples of metal soaps include cobalt naphthenate, copper naphthenate, zinc naphthenate, cobalt octoate, iron octoate, and copper neodecanoate. Of the metal soaps, cobalt octoate is preferred.

The amount of (e) curing catalyst blended is preferably 0.1 parts by mass or more and preferably 15 parts by mass or less per 100 parts by mass of (a) radical polymerizable compound. The amount of (e) curing catalyst blended is preferably 1 part by mass or more and preferably 8 parts by mass or less per 100 parts by mass of (a) radical polymerizable compound.

A radical polymerization initiator generates radicals and initiates the polymerization of monomers. Among radical polymerization initiators, thermal radical polymerization initiators are preferred. Among thermal radical polymerization initiators, organic peroxides are preferred. As a thermal radical polymerization initiator, organic peroxides in particular react with a curing catalyst to generate radicals and initiate the polymerization of monomers. Examples of thermal radical polymerization initiators include organic peroxides such as ketone peroxides, peroxyketals, hydroperoxides, diallyl peroxides, diacyl peroxides, peroxyesters, and peroxydicarbonates, as well as those classified as azo compounds. Examples of organic peroxides include 2-phenyl(2-propyl) hydroperoxide, benzoyl peroxide, dibenzoyl peroxide, dicumyl peroxide, diisopropyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3,3-isopropyl hydroperoxide, t-butyl hydroperoxide, and dicumyl Examples of organic peroxides include benzoyl peroxide, dicumyl hydroperoxide, acetyl peroxide, bis(4-t-butylcyclohexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, isobutyl peroxide, 3,3,5-trimethylhexanoyl peroxide, lauryl peroxide, benzoyl-m-methylbenzoyl peroxide, m-toluoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, and t-butyl peroxybenzoate. Examples of azo compounds include azobisisobutyronitrile. Among organic peroxides, at least one organic peroxide selected from the group consisting of 2-phenyl(2-propyl) hydroperoxide, benzoyl peroxide, benzoyl-m-methylbenzoyl peroxide, m-toluoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, and t-butyl peroxybenzoate is preferred, with 2-phenyl(2-propyl) hydroperoxide being more preferred.

The amount of (f) radical polymerization initiator blended is preferably 0.1 parts by mass or more and preferably 15 parts by mass or less per 100 parts by mass of (a) radical polymerizable compound. The amount of (f) radical polymerization initiator blended is preferably 1 part by mass or more and preferably 8 parts by mass or less per 100 parts by mass of (a) radical polymerizable compound.

A polymerization inhibitor may be added to the curable composition according to an embodiment of the present invention in order to improve long-term storage stability.

The curable composition according to an embodiment of the present invention may contain a silane coupling agent or the like to improve adhesion.

The surface curability of the curable composition according to an embodiment of the present invention can be improved by further blending paraffin.

When forming the reinforcing layer, it is preferable to apply the hardenable composition directly or indirectly to the concrete body at a thickness of 0.3 kg/ ^m2 or more and 1.5 kg/ ^m2 or less, and known devices or tools, such as a metal trowel or spatula, can be used for application.

The present invention will be explained in detail below using examples.

The materials listed below were mixed uniformly at 25°C in the ratios shown in Tables 1 to 3 to obtain the curable compositions of the Examples and Comparative Examples. Unless otherwise specified, equal amounts of the first and second components were mixed.

<Materials used>
(a-1) Radical polymerizable monomer
(a-1-1) Dicyclopentenyloxyethyl methacrylate (Hitachi Chemical Co., Ltd.)
(a-1-2) 2-Hydroxyethyl methacrylate (Mitsubishi Gas Chemical Company, Inc.)
(a-1-3) Nonylphenol EO-modified acrylate ("Aronix M-113" manufactured by Toagosei Co., Ltd.)
(a-2) Radical polymerizable oligomer
(a-2-1) Polyurethane acrylate oligomer (MIWON "MIRAMER MU3603") Weight average molecular weight: 9,000
(a-2-2) Polybutadiene dimethacrylate oligomer (Nisso-PB TE2000 manufactured by Nippon Soda Co., Ltd.) Weight average molecular weight: 2,500
(a-2-3) BisA (bisphenol A) type EO10 modified dimethacrylate oligomer (MIWON "MIRAMER M2101") Weight average molecular weight: 1,000
(b) Silica microparticles: Hydrophobic fumed silica (AEROSIL manufactured by Nippon Aerosil Co., Ltd.) specific surface area 130 m ² /g, primary particle diameter 30 nm
(c) Thixotropic agent: polyhydroxycarboxylic acid amide compound (BYK-405 manufactured by BYK Japan)
(d) Short fiber: PA6 fiber (Toray Industries, Inc. "Tough Binder"), fiber length 5 mm
(e) Curing catalyst: Cobalt octylate (Tokyo Fine Chemical Co., Ltd.)
(f) Radical polymerization initiator: 2-phenyl(2-propyl) hydroperoxide ("Trigonox K-80" manufactured by Nouryon Chemical Industries, Ltd.)

Evaluation method

Viscosity and TI Value: A curable composition (first part) was formulated according to the formulation shown in Tables 1 to 3, excluding (d) short fibers. Within 5 minutes of formulation, the viscosity was measured at 1 rpm and 10 rpm in a 25°C environment using a Brookfield rotational viscometer in accordance with JIS K 7117-1:1999. The Brookfield rotational viscometer used was a "DV2T" model manufactured by Eiko Seiki Co., Ltd., with a rotor No. 7. The viscosity was read 2 minutes after the start of measurement, and the average of three measurements was used. The TI value was calculated using the following formula 1. The results are summarized in Tables 1 to 3.
TI value = (viscosity measured at 25°C and 1 rpm) / (viscosity measured at 25°C and 10 rpm) ... (Equation 1)

Maximum punching load
A 100mm diameter, 55mm ± 3mm deep cut was made in the back of the center of the concrete of a Type 1 U-shaped cover (designated 300 (400 × 600 × 60mm)) specified in JIS A 5372:2016 (Precast Reinforced Concrete Products) using a concrete core cutter. The surface was sanded, and the curable composition of the Example or Comparative Example was applied to the treated surface at 1.0 kg/ ^m² . After curing to form a surface layer, the composition was cured at 25°C and 50% RH for one week to obtain a test specimen. The test specimen was then tested in accordance with JSCE-K 533:2013 (Push-out test method for surface coating materials used to prevent concrete fragment spalling). The maximum load at a displacement of 10mm or more was recorded as the maximum push-out load (kN). The test temperature was 25°C, and the average values of three measurements are listed in Tables 1 to 3. If the maximum punching load is less than 0.5 kN, sufficient peeling prevention performance may not be achieved.

Concrete bond strength
The surface of a concrete slab (300 x 300 x 60 mm) specified in JIS A 5371:2016 (precast unreinforced concrete products) was sanded, and the curable composition of the example or comparative example was applied to the treated surface at 1.0 kg/ ^m². After curing to form a surface layer, the sample was cured for one week at 25°C and 50% RH. An adhesive was then applied to the bonding surface of a steel jig specified in JIS A6909:2014 and bonded to the curable composition surface. After the adhesive cured, a concrete cutter was used to make a cut along the periphery of the steel jig to prepare a test specimen. The adhesion strength of the test specimen was measured in accordance with JSCE-E 545-2007 (Test method for adhesion between continuous fiber sheet and concrete). A BA-800D measuring machine manufactured by Itani Shoki Seisakusho was used. The test temperature was 25°C, and the average values of three measurements are listed in Tables 1 to 3. If the bond strength was 1.5 N/mm ² or more or the concrete base material was destroyed, it was determined that sufficient bond strength was obtained.

Blister resistance
A concrete slab (300 × 300 × 60 mm) specified in JIS A 5371:2016 (precast unreinforced concrete products) was immersed in water for 48 hours. The concrete slab was removed from the water, the surface water was wiped off with a rag, and 1.0 kg/ ^m² of the curable composition of the example or comparative example was applied. Within 5 minutes of application, the slab was placed in a hot air drying oven and cured at 60°C for 1 hour to form a reinforcing layer. The concrete slab with the reinforcing layer was removed from the oven and visually inspected for blistering of the coating. A rating of × (NG) was given for 10 or more blisters with a diameter of 5 mm or greater, △ (moderate) for 4 to 9 blisters, ○ (good) for 3 or fewer blisters, and ◎ (excellent) for no blisters. The results are shown in Tables 1 to 4.

All examples containing the essential components achieved excellent results in maximum punching load, concrete bond strength, and blister resistance.

On the other hand, Comparative Examples 1 to 3, in which no thixotropic agent was added, all showed very poor resistance to blistering.

Furthermore, Comparative Example 4, in which the amount of silica fine particles was increased compared to Comparative Examples 1 to 3 to increase viscosity without adding a thixotropic agent, also had poor blister resistance.

In Comparative Example 5, which contained even more silica microparticles than Comparative Example 4, swelling resistance improved slightly, but the concrete bond strength deteriorated.

In addition, Comparative Example 6, in which a thixotropic agent was added but no silica microparticles were added, also had very poor resistance to swelling.

Claims (19)

(a) a radical polymerizable compound,
(b) silica microparticles, and
(c) a reinforcing layer containing a hardened mixture containing a thixotropic agent;
A concrete structure comprising: a concrete skeleton to which the reinforcing layer is applied directly or indirectly;
The viscosity of the mixture at 25°C and 1 rpm is 900,000 mPa·s or more, and the TI value at 25°C is 7.1 or more and 10.0 or less.
A concrete structure characterized by : 2. The concrete structure according to claim 1, wherein the viscosity of the mixture at 25°C and 1 rpm is 900,000 mPa·s or more and 1,450,000 mPa·s or less . 3. The concrete structure according to claim 1, wherein the TI value of the mixture at 25°C is 7.5 or more and 10.0 or less . The concrete structure according to any one of claims 1 to 3, wherein the amount of the (b) silica fine particles is 5 to 12 parts by mass and the amount of the (c) thixotropic agent is 0.5 to 5 parts by mass, relative to 100 parts by mass of the (a) radical polymerizable compound. The concrete structure described in any one of claims 1 to 4, wherein the mixture further contains (d) short fibers, and the reinforcing layer is applied directly to the concrete body. The concrete structure described in any one of claims 1 to 4, wherein the reinforcing layer is indirectly applied to the concrete body via one or more selected from a sheet and a primer. The concrete structure according to any one of claims 1 to 6, wherein the (c) thixotropic agent comprises one or more selected from the group consisting of polyether compounds, carboxylic acid amide compounds, hydroxycarboxylic acid amide compounds, urea urethane amide compounds, and polyvinylpyrrolidone. The concrete structure described in any one of claims 1 to 7, characterized in that the viscosity of the radical polymerizable compound (a) at 25°C and 1 rpm is 300 mPa·s or more. The concrete structure according to any one of claims 1 to 8, characterized in that the (a) radically polymerizable compound contains (a-1) a radically polymerizable monomer and (a-2) a radically polymerizable oligomer. The concrete structure according to claim 9, wherein the (a-1) radically polymerizable monomer includes one or more (meth)acrylate monomers. The concrete structure according to claim 10, wherein the one or more (meth)acrylate monomers include a chain (meth)acrylate and a cyclic (meth)acrylate. The concrete structure according to any one of claims 9 to 11, wherein the (a-2) radically polymerizable oligomer includes one or more urethane (meth)acrylate oligomers. The concrete structure described in any one of claims 9 to 12, characterized in that the amount of the (a-1) radical polymerizable monomer is 50% by mass or more and 70% by mass or less, based on the total amount of the (a) radical polymerizable compound. The concrete structure according to any one of claims 9 to 13, wherein the (a-1) radically polymerizable monomer contains dicyclopentenyloxyethyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate in a mass ratio of 0.25 to 4:1. The concrete structure according to any one of claims 1 to 14, characterized in that the reinforcing layer is a layer formed by applying the mixture to a thickness of 0.3 kg/m ² or more and 1.5 kg/m ² or less. A step of preparing a first agent including (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (e) a curing catalyst;
preparing a second agent containing (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (f) a radical polymerization initiator;
a step of mixing the first part and the second part to obtain a curable composition having a viscosity of 900,000 mPa s or more at 25°C and 1 rpm and a TI value of 7.1 or more and 10.0 or less at 25°C ;
and applying the hardenable composition to the surface of a concrete body. The method of claim 16, further comprising the step of (d) mixing short fibers with the first agent or the second agent prior to mixing the first agent and the second agent. A step of preparing a first agent including (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (e) a curing catalyst;
preparing a second agent containing (a) a radical polymerizable compound, (b) silica fine particles, (c) a thixotropic agent, and (f) a radical polymerization initiator;
a step of mixing the first part and the second part to obtain a curable composition having a viscosity of 900,000 mPa s or more at 25°C and 1 rpm and a TI value of 7.1 or more and 10.0 or less at 25°C ;
a step of applying one or more selected from a sheet and a primer to the surface of a concrete body, and then applying the curable composition thereon. (a) a radical polymerizable compound,
(b) silica microparticles, and
(c) A composition containing a thixotropic agent, having a viscosity of 900,000 mPa·s or more at 25°C and 1 rpm , and a TI value of 7.1 or more and 10.0 or less at 25°C .