JP7052506B2 - Ground improver composition and its use - Google Patents

Description

The present specification relates to a ground improving agent composition and its use.

Waterglass-based ground improvement agents have been well known as ground improvement agents that are injected into soft ground to improve the ground, and are used for temporary reinforcement during excavation work to build structures. It is widely used for permanent purposes such as ground improvement.

However, it has been pointed out that the gel product obtained from the water glass-based ground improving agent has a problem in terms of durability. In addition, since the chemical solution contains sulfuric acid or phosphoric acid components, there is a concern that deterioration of structures such as concrete may be promoted in the ground.

Examples of the ground improving agent other than the water glass type include an acrylic ground improving agent composed of an aqueous solution containing an acrylic salt. For example, Patent Document 1 describes a composition for an injection material containing a monovalent or divalent metal salt of (meth) acrylic acid, a trivalent metal salt, an oxidizing agent, two or more reducing agents having different reducing powers, and water. The thing is listed. Patent Document 2 discloses a (meth) acrylic acid-based chemical solution containing a monovalent or divalent metal salt aqueous solution of (meth) acrylic acid, an aqueous solution of an aluminum water-soluble salt, and an aqueous solution of bisulfite. Patent Document 3 discloses a ground injection composition containing a (meth) acrylic acid metal salt, a polyvalent metal salt compound other than the (meth) acrylic acid metal salt, an oxidizing agent, a specific reducing agent, and water. ing.

Japanese Unexamined Patent Publication No. 2001-241288 Japanese Unexamined Patent Publication No. 2006-104795 Japanese Unexamined Patent Publication No. 2016-130286

According to the present inventors, the ground improving agents disclosed in Patent Documents 1 to 3 are effective in improving the ground strength and their durability, but depending on the environment in which they are used, a structure such as iron Corrosion was sometimes observed. In addition, for example, in applications such as ground reinforcement for preventing collapse in excavation work of underground pipelines and strengthening of bearing capacity of building foundations, extremely high-strength ground improvement may be required.

The present specification provides a ground improving agent composition and its use, which imparts high gel strength to the extent applicable to the above-mentioned applications and is also excellent in suppressing corrosion of the improved ground.

As a result of diligent studies to solve the above problems, the present inventors use a polyvalent metal salt compound having a basicity of 45% or more in a ground improving agent composition utilizing curing of a (meth) acrylic acid metal salt. As a result, it was found that a gel compound with good strength can be obtained, and that corrosion of various metal elements such as various metal members and structures in the improved ground can be suppressed. Further, it has been found that a gel product having sufficiently high strength can be obtained if it is a ground improving agent composition containing the (meth) acrylic acid metal salt and the polyvalent metal salt compound at a specific concentration. Based on these findings, the present specification provides the following means.

[1] A ground improving agent composition, which is
The following components (A) to (D):
(A) (meth) acrylic acid metal salt (B) polyvalent metal salt compound having a basicity of 45% or more (C) polymerization initiator (D) containing water.
A composition in which the total amount of the component (A) and the component (B) is more than 15% by mass and 40% by mass or less.
[2] The composition according to [1], wherein the polyvalent metal salt compound is an aluminum salt compound.
[3] The composition according to [1] or [2], wherein the pH is 4.0 or more and 9.0 or less.
[4] The composition according to any one of [1] to [3], further comprising α-hydroxy acid or a salt thereof as the component (E).
[5] This is a ground improvement method.
(A) (meth) acrylic acid metal salt (B) polyvalent metal salt compound having a basicity of 45% or more (C) polymerization initiator (D) containing water.
A step of introducing a composition into the ground, wherein the total amount of the component (A) and the component (B) exceeds 15% by mass and is 40% by mass or less.
How to prepare.
[6] The method according to [5], wherein the ground improvement method is an injection solidification method.

The present specification relates to a ground improving agent composition, a ground improving method, and the like. According to the ground improving agent composition disclosed in the present specification (hereinafter, also simply referred to as the present composition), a polyvalent metal salt compound having a basicity of 45% or more is contained together with the (meth) acrylic acid metal salt. In addition, sufficient strength can be imparted to the gel material, and corrosion of metal elements such as iron in the improved ground can be suppressed. From these facts, this composition can be widely applied to various applications from temporary ground reinforcement during excavation work to permanent ground improvement.

The ground improvement method (hereinafter, also referred to as the present method) disclosed in the present specification can produce the same action as that of the present composition.

As used herein, "(meth) acrylic" means acrylic and / or methacrylic, "(meth) acrylate" means acrylate and / or methacrylate, and (meth) acrylamide means acrylamide and / or acrylamide. Or it means (meth) acrylamide.

As used herein, the term "ground improving agent" includes agents used for ground improving for various purposes. Here, "ground improvement" includes, for example, prevention of water leakage, water stoppage, liquefaction suppression, and ground strengthening (reinforcement). , Ground consolidation method, water stoppage method, injection solidification treatment method (or chemical solution injection method), jet grout method, etc.

Hereinafter, embodiments of the present composition, the present method, and the like will be described in detail.

<Ground improving agent composition>
The composition may contain (A) component: (meth) acrylic acid metal salt, (B) component: polyvalent metal salt compound, (C) component: polymerization initiator, and (D) component: water. can.

<(A) component: (meth) acrylic acid metal salt>
Examples of the (meth) acrylic acid metal salt include alkali metal salts such as lithium salt, sodium salt and potassium salt of (meth) acrylic acid; alkaline earth metal salts such as calcium salt and barium salt; magnesium salt and aluminum salt. , Zirconium salt and the like, and only one of these may be used alone, or two or more thereof may be used in combination. Among these, calcium salt and magnesium salt are preferable as the type of metal salt, and magnesium salt is more preferable, in that a gel having good strength and deformation resistance can be obtained.

In preparing this composition, it is preferable to use the (meth) acrylic acid metal salt as an aqueous solution. The concentration at that time is not particularly limited, and can be appropriately set within a range in which (meth) acrylate does not precipitate, that is, a concentration of 45% by mass or less, which is close to saturation. Considering the concentration of the (meth) acrylic acid metal salt in the present composition, for example, it is preferably 2% by mass or more, and particularly preferably 3% by mass or more in the case of an alkaline earth metal salt. It is preferably 4% by mass or more, and more preferably 5% by mass or more. The upper limit concentration can be, for example, 40% by mass or less, for example, 35% by mass or less, for example, 30% by mass or less, and for example, 15% by mass or less. Can be done.

The concentration of the (meth) acrylic acid metal salt in the present composition is not particularly limited, but is preferably, for example, 3.0% by mass or more, for example, 5.0% by mass or more, and for example, 7.0% by mass. % Or more, for example, 10% by mass or more. When the concentration of the (meth) acrylic acid metal salt is 3.0% by mass or more, the strength of the obtained gel is sufficient. Further, the concentration of the (meth) acrylic acid metal salt may be less than 40% by mass, 35% by mass or less, 30% by mass or less, or 25% by mass or less. It may be 20% by mass or less, and may be 15% by mass or less. When the same concentration is less than 40% by mass, it is easy to secure the stability of the ground improvement composition. The range of the concentration of the (meth) acrylic acid metal salt can be set by combining the lower limit concentration and the upper limit concentration thereof, and is, for example, 3.0% by mass or more and less than 40% by mass, and for example, 5. 0% by mass or more and 35% by mass or less, and for example, 5.0% by mass or more and 30% by mass or less, and for example, 7.0% by mass or more and 30% by mass or less, and for example, 7.0% by mass. % Or more and 25% by mass or less. The concentration of the (meth) acrylic acid metal salt in the present composition is also defined by the total amount with the concentration of the polyvalent metal salt compound described later.

<Component (B): Multivalent metal salt compound with a basicity of 45% or more>
The polyvalent metal salt compound is a polyvalent metal salt compound other than the (meth) acrylic acid metal salt, and is a divalent or trivalent or higher polyvalent metal salt compound (hereinafter, also simply referred to as the present polyvalent metal salt compound). .). The polyvalent metal salt compound can act as a cross-linking agent during the polymerization of (meth) acrylic acid.

Regarding the present polyvalent metal salt compound, examples of the divalent metal include, but are not limited to, magnesium, calcium, barium and the like. Examples of the trivalent or higher metal include, but are not limited to, aluminum, zirconium, titanium, cerium and the like. Among these, a trivalent metal salt compound is preferable because it is easy to control the strength of the gel product.

Specific compounds include, for example, aluminum chloride, aluminum nitrate, aluminum sulfate, alum, sodium alum, aluminum acetate, aluminum lactate, polyaluminum chloride (basic aluminum chloride), polyaluminum sulfate (basic aluminum sulfate). , Zirconium acetate, zirconium nitrate, zirconium chloride, zirconium lactate, zirconium carbonate, zirconium oxynitrite, zirconium oxyacetate, zirconium sulfate, zirconium oxysulfate and other zirconium salts, titanium chloride and cerium nitrate, among these are aluminum salts. The compound and the zirconium salt compound are more preferable, and the aluminum salt compound is more preferable.

As the polyvalent metal salt compound, only one of these metal salt compounds may be used alone, or two or more of them may be used in combination.

Further, the polyvalent metal salt compound is preferably a basic salt. By being a basic salt, it can act as a cross-linking agent and effectively improve the corrosion suppressing ability.

For example, among the present polyvalent metal salt compounds, the polyvalent metal salt compound which is a basic salt is represented by the following general formula (1). In this general formula, the basicity (%) of the polyvalent metal compound is represented by n1 / (valence of n1 + n2 × B) × 100 (%).

[M _m (OH) _n1 B _n2 ] _l (1)
(However, M represents a metal having a valence of 2 or more, B represents one kind or two or more kinds of bases, m is an integer of 1 or more, n1 and n2 each represent a number of 0 or more, and M. , OH and B represent stoichiometrically consistent numbers, where l represents an integer greater than or equal to 1.)

Here, polyaluminum chloride suitable as the present polyvalent metal salt compound is represented by the following formula (2). The basicity (%) is represented by n1 / 3 × 100 (%).

[Al (OH) _n1 Cl _n2 ] _l (2)
(However, n2 = 3-n1.)

The basicity of this polyvalent metal salt compound is 45% or more. If the basicity is less than 45%, the corrosiveness of the present composition cannot be suppressed, and it becomes difficult to suppress the corrosion of the base material, underground pipes, piles, etc. existing in the improved ground. In addition, the action as a cross-linking agent is low, and the strength of the obtained gel may not be sufficiently high. The basicity is preferably 50% or more, more preferably 55% or more, further preferably 60% or more, still more preferably 65% or more, still more preferably 70% or more. Further, the basicity is preferably 90% or less. If it exceeds 90%, the stability of the polyvalent metal salt compound is generally lowered and it becomes difficult to obtain it as a water-soluble compound. In addition, it may precipitate due to alkali in the ground and the function as a cross-linking agent may be deteriorated. Preferably, it is, for example, 85% or less.
The range of the basicity of the polyvalent metal salt compound is not particularly limited and can be set by appropriately combining the lower and upper limits described above, but is, for example, 45% or more and 90% or less. Further, for example, it is 50% or more and 85% or less.

The concentration of the polyvalent metal salt compound in the composition is not particularly limited. It is preferably 1.0% by mass or more in terms of the metal oxide contained in the polyvalent metal salt compound, that is, the metal oxide corresponding to the polyvalent metal salt compound, and for example, 2.0 mass. % Or more, for example 3.0% by mass or more, and for example 4.0% by mass or more. When the concentration of the polyvalent metal salt compound is 1.0% by mass or more, the strength of the obtained gel is sufficient and corrosiveness can be suppressed. The concentration of the polyvalent metal salt compound is not particularly limited, but is preferably less than 40% by mass, may be 30% by mass or less, and may be 20% by mass in terms of the corresponding metal oxide, for example. % Or less, 15% by mass or less, or 12% by mass or less. When the concentration of the polyvalent metal salt compound is less than 40% by mass, good permeability to the ground can be ensured. The range of the concentration of the polyvalent metal salt compound can be set by combining the lower limit concentration and the upper limit concentration thereof, but is, for example, 1.0% by mass or more and less than 40% by mass in terms of the corresponding metal oxide. Further, for example, it may be 2.0% by mass or more and 30% by mass or less, and may be 3.0% by mass or more and 20% by mass or less.

<Total concentration of component (A) and component (B)>
The total concentration of the (meth) acrylic acid metal salt as the component (A) and the polyvalent metal salt compound (as converted to the corresponding metal oxide) as the component (B) in the present composition is particularly limited. Although not, it is preferably more than 15% by mass, for example, in consideration of the strength, durability and corrosiveness of the obtained gel. From the viewpoint of the strength of a more suitable gel, the total concentration is also, for example, 16% by mass or more, for example, 17% by mass or more, and for example, 18% by mass or more, and for example. , 20% by mass or more. Although not particularly limited, the total concentration is preferably 40% by mass or less. The total concentration is also, for example, 35% by mass or less, and is, for example, 30% by mass or less, and is, for example, 25% by mass or less, and is, for example, 20% by mass or less. When the total concentration is 40% by mass or less, it is easy to secure the stability of the ground improvement composition. The range of the total concentration can be various concentration ranges obtained by combining these lower and upper limits, respectively, and is, for example, more than 15% by mass and 40% by mass or less, and for example, 15% by mass or more and 35. It is 1% by mass or less, and for example, 16% by mass or more and 30% by mass or less.

<Component (C): Polymerization initiator>
The polymerization initiator is added to polymerize the (meth) acrylic acid metal salt in the present composition, and various known polymerization initiators applied to the (meth) acrylic acid can be used. For example, from the viewpoint of controlling the pot life and the curing time from ground injection to curing (gelation), azo initiators, inorganic peroxides such as peroxodisulfate, percarboxylic acids, and organic peroxides such as hydroperoxides. Peroxides and the like can be used. When an inorganic peroxide and an organic peroxide are used, a reducing agent may be used in combination as appropriate.

As the azo initiator, for example, the decomposition is generally slower than that of the redox-based initiator, and the pot life can be secured, for example, up to several days. Examples of the azo initiator include 2,2'-azobis [2- (imidazolin-2-yl) propane], 2,2'-azobis [2- (imidazolin-2-yl) propane] dihydrochloride, 2, 2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- Methyl-N- (2-hydroxyethyl) propionamide], 4,4'-azobis (4-cyanovaleroic acid) and the like can be mentioned. Among these, 2,2'-azobis [2- (imidazolin-2-yl) propane] and 2,2'-azobis [2- (imidazolin-2-yl) propane] are easy to obtain an appropriate pot life. ] Dihydrochloride is preferred. The azo initiator can be used alone or in combination of two or more.

The inorganic peroxide is not particularly limited, and a known inorganic peroxide can be used. For example, peroxides such as sodium peroxide, sodium perborate, sodium peroxide, calcium peroxide, barium peroxide and hydrogen peroxide, and inorganic persulfate compounds such as sodium persulfate, potassium persulfate and ammonium persulfate. Can be mentioned. The inorganic peroxide can be used alone or in combination of two or more.

As the organic peroxide, there is no particular limitation, and a known inorganic peroxide can be used. Organic peroxides are unaffected by the soil and soil properties, such as the clay and / or cation exchange capacity of the soil, which is believed to be based on the presence and amount of silicon oxide compounds in the ground and soil (A). ) Can promote radical polymerization and curing of polymerizable monomers such as vinyl-based unsaturated monomers, and promote the formation of gels.

The organic peroxide is not particularly limited, but is preferably highly hydrophilic in consideration of the composition of the present composition and the environment in which it is used. From this point of view, for example, an organic peroxide having 15 or less carbon atoms as a whole can be used, and for example, an organic peroxide having 10 or less carbon atoms, or, for example, an organic peroxide having 8 or less carbon atoms. Can be used. The carbon number of the organic peroxide can also be, for example, 2 or more, and can be, for example, 3 or more. The preferred range of the total carbon number of the organic peroxide can be set by appropriately combining the above-mentioned upper limit and lower limit, and is, for example, 2 or more and 10 or less, and for example, 3 or more and 8 or less.

Further, the organic peroxide is preferably hydrophilic, but for example, ketone peroxides, hydroperoxides, percarboxylic acids, diacyl peroxides and the like tend to have high water solubility in general. Among them, hydroperoxides tend to have higher water solubility.

Examples of the organic peroxide include diacyl peroxide, peroxydicarbonate, peroxyester, tetramethylbutylperoxyneodecanoate, bis (4-butylcyclohexyl) peroxydicarbonate, and di (di (4-butylcyclohexyl) peroxydicarbonate. 2-Ethylhexyl) Peroxycarbonate, Butylperoxyneodecanoate, Dipropylperoxydicarbonate, Diisopropylperoxydicarbonate, Diethoxyethylperoxydicarbonate, Diethoxyhexylperoxydicarbonate, Hexyl Peroxy Dicarbonate, Dimethoxybutyl Peroxy Dicarbonate, Bis (3-methoxy-3-methoxybutyl) Peroxy Dicarbonate, Dibutyl Peroxy Dicarbonate, Disetyl Peroxy Dicarbonate, Dimyristyl Peroxy Dicarbonate, 1,1,3,3-tetramethylbutylperoxypivalate, hexylperoxypivalate, butylperoxypivalate, trimethylhexanoyl peroxide, dimethylhydroxybutylperoxyneodecanoate , Amyl Peroxy Neodecanoate, Butyl Peroxy Neodecanoate, t-Butyl Peroxy Neoheptanoate, Amyl Peroxy Pivalate, t-Butyl Peroxy Pivalate, t-Amil Pe Luoxy-2-ethylhexanoate, lauryl peroxide, dilauroyl peroxide, didecyl peroxide, t-butyl hydroperoxide, p-cumyl hydroperoxide, t-amyl hydroperoxide, 1,1,3,3- Hydroperoxides such as tetramethylbutylhydroperoxides, percarboxylic acids such as peracetic acid and perbenzoic acid, methylethylketone peroxides or benzoyl peroxides (benzoylperoxides) and the like can be mentioned. From the viewpoint of water solubility, hydroperoxides such as t-butyl hydroperoxide, p-cumyl hydroperoxide, t-amyl hydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, methyl ethyl ketone peroxide and the like. Ketone peroxides, percarboxylic acids such as peracetic acid and perbenzoic acid, and diacyl peroxides such as benzoyl peroxide are preferred. The organic peroxide may be used alone or in combination of two or more.

(Reducing agent)
The reducing agent that can be used in combination with the inorganic peroxide and the organic peroxide is not particularly limited, and a known reducing agent can be used. Specific examples thereof include thiosulfate compounds such as sodium thiosulfate and potassium thiosulfate, bisulfite compounds such as sodium bisulfite and potassium bisulfite, and hypophosphite compounds such as sodium hyposulfate and potassium hyposulfate. Sulfuric acid compounds such as sodium sulfite and potassium sulfite, hydroxymethanesulfinate such as sodium hydroxymethanesulfinate (longalit), ascorbic acid or a salt thereof such as sodium ascorbate, erythorbic acid or a salt thereof such as sodium erythorsorbate, first. In addition to iron salts and thiourea disulfide, copper sulfate and amines such as diethanolamine, triethanolamine, hydrazine, hydroxylamine, dimethylaminopropionitrile, dimethylaminopropanol, piperazine and morpholin can be mentioned. These reducing agents can be used alone or in combination of two or more.

The concentration and amount of the polymerization initiator should be determined in consideration of the type and concentration of the (meth) acrylic acid metal salt, the type and concentration of the polyvalent metal salt compound, the conditions such as pH and water temperature, and the set values such as the curing time. It may be appropriately selected depending on the intended use of the composition. Further, in the case of a redox-based initiator, a combination of an oxidizing agent and a reducing agent can be appropriately selected.

The concentration of the polymerization initiator (excluding the amount of the reducing agent when the reducing agent is used in combination) in the present composition can be, for example, about 0.1 mM or more and 200 mM or less, and for example, 1 mM or more and 100 mM or less. Yes, and for example, 1 mM or more and 20 mM or less. The concentration of the inorganic peroxide and the organic peroxide in the present composition when a reducing agent is used in combination can be, for example, 0.1 mM or more and 100 mM or less, and for example, 1 mM or more and 100 mM or less. For example, it is 1 mM or more and 20 mM or less. The concentration of the reducing agent in the present composition can be, for example, 1 mM or more and 100 mM or less, and for example, 1 mM or more and 40 mM or less.

<(D) component: water>
The composition contains water. This composition is applied to the ground or the like in the form of an aqueous solution or a suspension. In this composition, water can dissolve or disperse various components and function as a transport medium for these components to the ground. In addition, water can also function as an adjusting agent for pot life and the like. In addition to water, the composition may contain an organic solvent that dissolves and disperses the various components described above, as long as the effects of the composition are not impaired.

The water in the present composition generally corresponds to the residue excluding the component (A) to the component (C) in the present composition and, if necessary, other components described later. The concentration in the composition is not particularly limited, but is, for example, 50% by mass or more, for example, 60% by mass, for example, 70% by mass or more, for example, 80% by mass or more, and the like. Can be.

<Component (E): α-hydroxy acid or a salt thereof>
In addition to the above-mentioned component (A) to component (D), the present composition may contain α-hydroxy acid or a salt thereof as the component (E). In general, the ground improver may be observed to corrode a structure such as iron depending on the pH and other conditions of use. In such a case, when an alkaline compound is added to the ground improving agent to adjust its pH and an attempt is made to suppress corrosion, a precipitate derived from the metal salt compound may be generated. When the ground improving agent contains α-hydroxy acid or a salt thereof, the above-mentioned precipitate is suppressed or reduced.
The α-hydroxy acid is a compound having a carboxylic acid group and at least one hydroxyl group, and the hydroxyl group is bonded to the α-position of the carboxylic acid group. Two or more carboxylic acid groups may be provided. According to the α-hydroxy acid, the formation of precipitates derived from acrylic acid-based metal salts and the like can be suppressed even in the presence of an alkali. The α-hydroxy acid is not particularly limited, and examples thereof include α-hydroxy acids having 2 or more and 8 or less carbon atoms. This is because if the number of carbon atoms exceeds 8, an addition amount is required. The number of carbon atoms of the α-hydroxy acid is, for example, 2 or more and 6 or less, and for example, 4 or more and 6 or less.

Examples of such hydroxy acids include DL-lactic acid, glyceric acid, gluconic acid, pantoic acid, 2-hydroxybutyric acid, 2-hydroxyisobutyric acid, DL-mandelic acid, m-hydroxymandelic acid, leucic acid, citramaric acid and tartron. Acid, pantoic acid, α-phenyllactic acid, benziliden lactic acid, glycolic acid, benzylic acid, benzylglycolic acid, quinic acid, 2-hydroxyvaleric acid, 2-hydroxyisovaleric acid, 2-hydroxycaproic acid, 2-hydroxyenant acid , 2-Hydroxycaprylic acid, α-hydroxyisocaprylic acid, 2-hydroxypelargonic acid, 2-hydroxycapric acid, 2-ethyl-2-hydroxybutyric acid, 2-hydroxy-2-methylbutyric acid, 2-ethyl-2- Hydroxy-3-methylbutanoic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-2,3-dimethylbutanoic acid, 2-hydroxy-2,3,3-trimethylbutanoic acid, 2-hydroxy-3- Methyl valeric acid, 2-hydroxy-2-ethylpentanoic acid, 2-hydroxy-2-methylpentanoic acid, 2-hydroxy-2,4-dimethylvaleric acid, 2-hydroxy-2-propylpentanoic acid, 2-hydroxy- 4-oxopentanoic acid, 2-hydroxy-4-methyl-3-oxopentanoic acid, α-hydroxyisocaproic acid, 2-hydroxy-2-methylhexanoic acid, 3-methyl-2-hydroxyhexanoic acid, 2-hydroxy -3-oxohexanoic acid, 2-hydroxy-4-oxohexanoic acid, 2-hydroxy-5-oxohexanoic acid, 2-hydroxy-2-methylheptanoic acid, 3-methyl-2-hydroxyheptanoic acid, 2-hydroxy Examples thereof include α-hydroxy acid, which is a monovalent carboxylic acid such as -2-methyloctanoic acid, 3-hydroxy-4-methoxymandelic acid, and 4-methoxymandelic acid. Examples thereof include aliphatic α-hydroxy acids such as divalent or higher carboxylic acids such as tartaric acid, citric acid, isocitric acid and DL-malic acid. Of these, α-hydroxy acids, which are divalent or higher carboxylic acids such as citric acid, isocitric acid, and DL-malic acid, are preferable.

The α-hydroxy acid may be in the form of a salt. For example, it may be a salt of an alkali metal such as potassium or sodium.

The concentration of α-hydroxy acid in the present composition is not particularly limited, but the ratio (molar ratio) of the number of moles of α-hydroxy acid to the number of moles of the central metal of the present polyvalent metal salt compound in the present composition is not particularly limited. It can be 0.1 or more. This is because if the molar ratio is less than 0.1, it tends to be difficult to suppress precipitates derived from polyvalent metal salt compounds and the like by contact with alkali. The same concentration is also, for example, 0.15 or more, for example, 0.20 or more, and for example, 0.30 or more. The molar ratio is not particularly limited, but can be 1.0 or less. This is because if it exceeds 1.0, the strength of the gel tends to decrease. The same concentration is also, for example, 0.90 or less, for example, 0.80 or less, for example, 0.70 or less, and for example, 0.60 or less. The range of the same molar ratio can be various concentration ranges obtained by combining these lower and upper limits, respectively, and is, for example, 0.10 or more and 1.0 or less, and for example, 0.15 or more and 0. It is 90 or less, and is, for example, 0.20 or more and 0.60 or less.

<Other ingredients>
Further, the present composition can contain a vinyl-based monomer other than the (meth) acrylic acid metal salt. The vinyl-based monomer used in combination may be either an ionic monomer (anionic monomer or a cationic monomer) or a nonionic monomer, and these may be used in combination. Anionic monomers include (meth) acrylic acid; itaconic acid, itaconic acid monoalkyl ester, maleic acid, maleic acid monoalkyl ester, fumaric acid, fumaric acid monoalkyl ester, citraconic acid, citraconic acid monoalkyl ester, Carboxyl group-containing monomers such as cinnamic acid, itaconic acid anhydride and maleic anhydride and salts or anhydrides thereof; 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, metallicylsulfonic acid, styrene. Sulphonic acid, polyoxyalkylene mono (meth) acrylate sulfate, 2-hydroxyethyl (meth) acryloyl phosphate, phenyl-2-acryloyloxyethyl phosphate, 2-acryloyloxyalkylphosphonic acid and salts thereof (alkali metal salt, alkaline soil). Kind metal salt, ammonium salt) and the like. These monomers may be used alone or in combination of two or more.

Examples of the cationic monomer include tertiary amino group-containing compounds such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide and salts thereof; (Meta) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, (meth) acryloyloxy2-hydroxy A quaternary ammonium base-containing compound such as propyltrimethylammonium chloride can be used. These monomers may be used alone or in combination of two or more.

Examples of the nonionic monomer include (meth) acrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, hydroxyethylacrylamide, vinylpyrrolidone, vinylformamide, vinylacetamide, (meth) acrylic acid-2-hydroxyethyl, and polyoxyalkylene. Examples thereof include mono (meth) acrylate, polyoxyalkylene alkylallyl ether, and glycerin monoallyl ether. These monomers may be used alone or in combination of two or more.

In this composition, in order to improve the strength, dimensional stability and durability of the obtained gel, a water-soluble divinyl monomer such as polyethylene glycol di (meth) acrylate, methylene bisacrylamide and hydroxyethylene bisacrylamide may be used. Further, a cross-linking agent such as N-methylolacrylamide may be blended. The content of these cross-linking agents may be, for example, 30% by mass or less, and for example, 20% by mass or less, based on the (meth) acrylic acid metal salt, from the viewpoint of its effect.

The present composition may contain a basic compound for the purpose of adjusting its pH. The basic compound is not particularly limited as long as it can change the liquid property of the aqueous medium to the alkaline side, and is one or more appropriately selected from various organic basic compounds and inorganic basic compounds. Can be used. For example, it is preferable to use an inorganic basic compound. For example, general alkaline agents such as sodium hydroxide, potassium hydroxide, magnesium hydroxide and the like can be used.

The concentration of the basic compound in the present composition is not particularly limited, but may be added so as to obtain a pH capable of improving corrosion resistance. In order to ensure corrosion resistance in this composition, it is most effective to adjust the pH within a certain range. The concentration of the basic compound for adjusting to a suitable pH of the present composition described above also varies depending on the type of the basic compound and other components to be mixed. Therefore, the amount and concentration of the basic compound used in the present composition are specified in such a pH range or as an effective amount for setting in such a pH range.

The pH of the present composition is preferably in the range of 4.0 or more and 9.0 or less. The pH may be in the range of 5.0 or more and 9.0 or less, or may be in the range of 6.0 or more and 9.0 or less. When the pH of the present composition is 4.0 or more, corrosion resistance tends to be ensured. When the pH is 9.0 or less, the generation of precipitates derived from the metal salt compound can be suppressed or reduced.

In addition, an aggregate may be added as needed to increase or reinforce the composition. As the aggregate, cement, fly ash, diatomaceous earth, calcium carbonate, kaolin, clay, bentonite, pearlite, vermiculite, blast furnace slag, gypsum, silica sand, powder such as pulp and carbon powder, and various fibers can be used. .. If the amount of aggregate used is too large, the fluidity of the composition and the bending strength of the gel may be reduced. Therefore, the mass of the aggregate is preferably 10 times or less the mass of the (meth) acrylic acid metal salt. When the aggregate is settled in the composition, it is preferable to use a settling inhibitor or the like in combination.

In addition to the above, the present composition may contain various components as long as the effects of the present composition are not impaired. For example, other ground improving agents such as known water glass can also be contained. Also, known rust preventives such as quaternary ammonium salts, organic acid amine salts, aromatic compounds, nitrites, alcohols and hexamethylenetetramine, and known defoamers such as silicone-based, mineral oil-based, vegetable oil-based and higher alcohol-based defoamers. One or more selected from foaming agents, known emulsifiers, known metal encapsulants and the like can be appropriately contained.

<Use of this composition>
In this composition, the polymerization reaction proceeds by the polymerization initiator to produce a gel product. Therefore, the present composition can be directly injected into the ground and used for gelling in the ground. According to this composition, a gel product having excellent strength and durability can be obtained, and since corrosiveness is suppressed, corrosion of metal elements in improved soil can be suppressed. Therefore, as a result, a strong gel can be formed in the ground. In addition, this composition is excellent in suppressing corrosion of iron-based structures. Therefore, this composition can be widely applied from primary ground reinforcement during excavation work to permanent use such as ground improvement of building structures.

<Kit for ground improvement>
By including the above-mentioned components (A), (B) and (C), a kit for ground improvement (hereinafter, also referred to as this kit) can be obtained. According to this kit, one or more of these components can be prepared as an aqueous composition such as an aqueous solution and mixed at the time of use to prepare the present composition, or prepared separately (D). The present composition can also be prepared by mixing and / or dissolving the component (A), the component (B) and the component (C) at the time of use using water as a component. After preparing the present composition, various characteristics of the present composition can be exhibited. The kit may also include water as a component (D) and α-hydroxy acid as a component (E).

In addition, when the kit includes the component (A) and the component (C) for preparation at the time of use, the composition can be easily used with a sufficient pot life. That is, since the present composition contains the component (C) which is a polymerization initiator, the kit can overcome the problem caused by the polymerization being started at the same time as the preparation. According to this kit, problems related to manufacturing, distribution, storage, etc., short pot life in ground improvement work, etc. can be solved.

This kit can be provided separately in a manner in which the component (C) does not act on the component (A). That is, in addition to the separation mode of various components for preventing the reaction between the component (A) and the component (C), the form for realizing such separation is not particularly limited. For example, as a form for separation, various components may be separated into two or more packages, or various components may be separated into one package having two or more compartments or storage areas. ..

Alternatively, the composition may be prepared from the kit and injected into the ground via an injection tube prior to ground injection, or one or more components of the kit may be separately injected into the injection tube. The composition may be prepared by injecting and mixing in an infusion tube.

The table below exemplifies some examples of this kit consisting of two agents for the mode of combination of each component in this kit. In the table below, "○" indicates that it is contained, "x" indicates that it is not contained, and "○ / ×" indicates that it may or may not be contained. Further, (a) in the table shows a case where the component (C): polymerization initiator is used alone without using a reducing agent, and (b) shows a case where a reducing agent is further used.

As shown in (a) of the above table, the component (A) and the component (C) are separated so as not to initiate polymerization, and as shown in the same (b), the component (C) and the reducing agent are separated. If the polymerization initiator is separated so as not to be consumed, it is clear that the component (D): water and other components are made into a kit in various embodiments. Further, in the above table, the kit consists of two agents, but it can be divided into three or more agents as long as the combination is such that the initiation of polymerization is suppressed or avoided. Further, water as the component (D) can be contained in any of these agents, or can be prepared as a separate agent.

The content of each component (A) to (C) in this kit is not particularly limited. At the time of preparation, the required amount of each component may be weighed, or it may be weighed in advance so as to have a concentration and pH suitable for the present composition. In addition, it may be subdivided into fixed amounts so that the required amount can be easily measured.

In this kit, for example, it is preferable that each component is measured in advance so as to have the concentration of each component intended in the present composition to be prepared.

Further, the component (A), the component (B) and the component (C) may be appropriately used as a solution with water or the like as the component (D), or may be themselves (powder, liquid or the like). It is appropriately selected according to the handleability, stability, and physical characteristics of each component.

<Ground improvement method>
The ground improvement method disclosed herein can include an introduction step of introducing the composition into the ground. According to this method, the component (A) can be stably polymerized and cured regardless of the properties of the soil to which it is applied, and a gel product having excellent properties can be obtained.

This method can be applied to various ground improvements described above. Specific construction methods include various construction methods already described. The introduction step of the present composition in the present method can be carried out by injecting the present composition into the ground in a known manner according to the application application and the construction method. Generally, by pumping or the like, one or more kinds of liquids to be injected are pumped to the ground through an injection pipe arranged in the ground, separately or while being mixed in the injection pipe or the like. Introduce.

This method is suitable for the injection solidification method (chemical solution injection method). In the injection solidification method (chemical injection method), the composition is permeated into the sand ground, the water existing in the gaps of the sand ground is replaced with the injection agent, and then the injection agent gels to bind the sand ground. It is a ground improvement method that has functions such as water leakage prevention, water stoppage, liquefaction prevention, and ground strengthening. It is a method of injecting a chemical solution from an injection pipe to a required place and solidifying it using a relatively small-scale device. It is a ground improvement method. Since this composition has excellent permeability to the ground, excellent curing rate and gel strength, it can exhibit excellent performance when applied to the injection solidification method (chemical solution injection method).

Hereinafter, the present invention will be specifically described based on examples. The present invention is not limited to these examples. In the following, "parts" and "%" mean parts by mass and% by mass unless otherwise specified.

The evaluation method of the ground improving agent composition will be described below, and then each Example and the like will be described.

[1] Uniaxial Compressive Strength 92 g of each composition was placed in a plastic mold (inner diameter 50 mm), and 298 g of Toyoura sand was added little by little to prepare a sand + composition mixture. Then, it was allowed to stand at 25 ° C. for 3 days or more to be completely cured and taken out to prepare a test piece (sand gel) having a diameter of 50 mm and a height of 85 to 90 mm. This test piece was compressed at 1 mm / min with a compression tester (Type 5566 manufactured by Instron), and the load was measured. The value obtained by dividing the maximum value of the load by the cross-sectional area of the test piece was taken as the compressive strength (unit: kN / m ² ). When the compressive strength exceeds 2000 kN / m ² , it is judged as having sufficient strength and evaluated as “◯”, and when it is less than 2000 kN / m ² , it is judged as having insufficient strength and evaluated as “×”.

[2] Iron Corrosion Rate Put 92 g of each composition in a plastic mold (inner diameter 50 mm), and hang a steel material (SS400) with a length of 50 mm, a width of 15 mm, and a thickness of 2 mm in the mold with a thread to lower the lower end of the steel material. Was arranged so as to be at a height of 2 cm from the bottom surface of the mold. To this, 298 g of Toyoura sand was added little by little to prepare a sand + composition mixture in which a steel material was embedded. Then, it was allowed to stand at 25 ° C. for 3 days or more to be completely cured and taken out to prepare a test piece (sand gel) having a diameter of 50 mm and a height of 85 to 90 mm. This test piece was placed in a 3 L container with a lid, immersed in 2.7 L of deionized water, covered, and allowed to stand. In this state, after standing in a room at room temperature of 25 ° C for 140 days, the test piece is pulled up, the steel material is taken out, sand and rust are removed with a steel brush, dried and weighed, and one month according to the following formula. The weight loss rate per (30 days) was calculated.
Weight reduction rate% = {(Weight of steel before test-Weight of steel after test) ÷ (Weight of steel before test)} × (30 ÷ 140) × 100

<Example 1>
22.8 g of an aqueous solution of polyaluminum chloride (basicity 83%) having a concentration of 23% in terms of Al ₂ O ₃ (5.3% in terms of Al ₂ O ₃ of polyaluminum chloride (PAC)) in 48.1 g of deionized water, concentration 26.3 g (10.5% as magnesium acrylate) of a 40% aqueous magnesium acrylate solution was added and dissolved. Next, 0.228 g of ammonium persulfate was dissolved, and an aqueous solution prepared by dissolving 0.632 g of sodium thiosulfate in 2 g of deionized water was added to prepare the ground improving agent composition of Example 1. As a result of measuring the pH of the ground improving agent composition obtained using a pH meter, the pH was 7.0.

<Examples 2 to 3 and Comparative Examples 1 to 3>
The same operation as in Example 1 was carried out except that the component (A): magnesium acrylate and the component (B): polyaluminum chloride were used as shown in Table 2 below, and various ground improving agent compositions were performed. The thing was prepared. Table 2 also shows the basicity of the polyaluminum chloride used in each example.

<Example 4>
1.8 g of deionized water with 55.0 g of an aqueous solution of polyaluminum chloride (basicity 50%) with a concentration of 10% in terms of Al ₂ O ₃ (5.5% of polyaluminum chloride (PAC) in terms of Al ₂ O ₃ ), concentration 27.5 g (11.0% as magnesium acrylate) of a 40% aqueous magnesium acrylate solution was added and dissolved. Further, 6.52 g of citric acid was added and dissolved, and then 6.27 g of sodium hydroxide was gradually added to adjust the pH to 7.0. Next, 0.228 g of ammonium persulfate was dissolved, and an aqueous solution prepared by dissolving 0.632 g of sodium thiosulfate in 2 g of deionized water was added to prepare the ground improving agent composition of Example 4.

The evaluation results of Examples 1 to 4 and Comparative Examples 1 to 3 are also shown in Table 2.

The following is a supplement to the description in the table.
AAMg: Magnesium acrylate PAC: Polyaluminum chloride αHA / Al: Molar ratio of citric acid to aluminum derived from polyaluminum chloride

As shown in Table 2, all of Examples 1 to 4 were excellent in the characteristics of the gel material (uniaxial compressive strength and iron corrosion rate). That is, it exhibited an extremely high gel strength exceeding 2000 kN / m ² or 3000 kN / m ² and had an excellent corrosion suppressing ability. In particular, when a polyvalent metal salt compound having a higher basicity was used and when citric acid, which is an α-hydroxy acid, was used, excellent corrosion suppressing ability was exhibited.

On the other hand, in Comparative Example 1 in which the concentrations of the (meth) acrylic acid metal salt and the polyvalent metal salt compound were low, a gel having sufficient strength could not be obtained. Further, in Comparative Examples 2 and 3 using a polyvalent metal salt compound having a low basicity, the results were insufficient in terms of the strength of the gel and the ability to suppress corrosion.

This composition can obtain a gel having a very high strength and can have an excellent corrosion suppressing ability. Therefore, it is useful as a ground improving agent composition for various purposes such as for preventing ground liquefaction. For example, it is extremely high in ground reinforcement for preventing collapse in excavation work of underground pipelines and strengthening of bearing capacity of building foundations. It can also be applied to applications that require strong ground improvement. Further, it is useful to apply the ground improving agent composition of the present invention by the injection solidification method (chemical solution injection method) to the ground directly under the existing structure that cannot be moved.

Claims (6)

A ground improver composition,
The following components (A) to (D):
(A) (meth) acrylic acid metal salt (B) polyvalent metal salt compound having a basicity of 45% or more (C) polymerization initiator (D) containing water.
A composition in which the total amount of the component (A) and the component (B) is more than 15% by mass, 30 % by mass or less, and the component (B) is 4.0% by mass or more . The composition according to claim 1, wherein the polyvalent metal salt compound is an aluminum salt compound. The composition according to claim 1 or 2, wherein the pH is 4.0 or more and 9.0 or less. The composition according to any one of claims 1 to 3, further comprising α-hydroxy acid or a salt thereof as the component (E). It ’s a ground improvement method.
(A) (meth) acrylic acid metal salt (B) polyvalent metal salt compound having a basicity of 45% or more (C) polymerization initiator (D) containing water.
A composition in which the total amount of the component (A) and the component (B) exceeds 15% by mass, is 30 % by mass or less, and the component (B) is 4.0% by mass or more is introduced into the ground. Process to do,
How to prepare. The method according to claim 5, wherein the ground improvement method is an injection solidification method.