JPH0967153A - Mixing agent for concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mixing agent for concrete having an excellent preventing effect on reduction of viscosity and excellent fluidity holding property by incorporating an oxyalkylene group-contg. water-soluble vinyl copolymer and a water- soluble salt of unsatd. carboxylic acid (copolymer. SOLUTION: This concrete mixing agent is obtd. by incorporating (A) a copolymer obtd. by polymn. of a monomer expressed by formula I (e.g. methoxypolyethylene glycol) and one or more kinds of monomers selected from compds. expressed by formulae II and III (e.g. acrylic acid), and (B) a single polymer of unsatd. carboxylic acid (e.g. maleic acid) selected from unsatd. monocarboxylic acids and unsatd. dicarboxylic acids, or a water-solulble salt of copolymer or two or more kinds (such as sodium salt of acrylic acid/maleic acid copolymer) as the essential components. In formula I, R1 , R2 are hydrogen or methyl groups, m1 is 0 to 2, AO is a 2-3C oxyalkylene group, (n) is 50 to 300, X is H or a 1-3C alkyl group. In formulae II and III, R3 -R5 are hydrogen, methyl groups, or formula IV, wherein R6 is hydrogen or methyl group, M1 , M2 , Y are each hydrogen, an alkyl metal, etc., and m2 is 0 to 2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a concrete admixture. More specifically, the present invention relates to a concrete admixture which exhibits excellent effects on the viscosity reduction and fluidity and fluidity retention of hydraulic compositions such as cement paste, mortar and concrete.

[0002]

BACKGROUND OF THE INVENTION Among concrete admixtures, typical ones having a great fluidizing effect include naphthalene sulfonic acid formaldehyde condensate (hereinafter referred to as naphthalene type) and melamine sulfonic acid formaldehyde condensation. (Hereinafter, referred to as melamine-based), olefin / maleic acid copolymer (hereinafter referred to as polycarboxylic acid-based), and other high-performance water reducing agents.

Although these admixtures are excellent in dispersibility (fluidity), they have a problem in fluidity retention (called slump loss). Method of compounding reactive polymer or cross-linked polymer into admixture to improve this slump loss [Cement Association published: Cement concrete, No546.Aug, 1992, p.
24] is generally known. By adding these slump retainers, some effects are recognized,
It is not yet sufficient and countermeasures are desired. Regarding the fluidity, the fluidity when concrete is mixed is generally controlled by the slump value or the slump flow (JIS-A 1101 method), but in the actual construction, the effect of viscosity is greater, and the slump and slump are more significant. Some points have been pointed out that cannot be judged by the flow. That is, even if a predetermined liquidity is expressed,
Since the viscosity is high, the handling property of concrete is deteriorated, pumping is difficult, and there are problems such as insufficient filling in the mold. With respect to this decrease in viscosity, sufficient performance cannot be obtained with conventional admixtures, and this tendency is particularly great in the high-strength region where the amount of water is small, and countermeasures are desired.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have found that an admixture which solves the above-mentioned problems, that is, a low viscosity and a predetermined fluidity can be obtained, and the fluidity retention (hereinafter referred to as slump retention). It provides a concrete admixture excellent in.

The present inventors pay attention to the alkylene glycol chain of the polyalkylene glycol monoester monomer in the structure of the water-soluble vinyl copolymer having an oxyalkylene group, and find out the chain length and dispersibility of the alkylene glycol ( As a result of various studies on fluidization performance), it was found that the fluidity and the slump retention are extremely excellent at a specific chain length. Furthermore, by using together an unsaturated carboxylic acid polymer containing no alkylene glycol chain, it has become possible to realize a concrete admixture excellent in viscosity reduction, fluidity and slump retention.

That is, the present invention is a concrete admixture which essentially contains the following components (a) and (b).

Component (a): One or more selected from the monomer (a) represented by the following general formula (A) and the compounds represented by the following general formulas (B) and (C). A copolymer obtained by polymerizing the above monomer (b).

[0008]

Embedded image

(Wherein R ₁ and R _{2 are} hydrogen or a methyl group m ₁ : 0 to the number 2 AO: an oxyalkylene group having 2 to 3 carbon atoms n: the number 50 to 300 X: hydrogen or the carbon 1 3 represents an alkyl group of 3).

[0010]

Embedded image

(Wherein R _{3 to} R _{5 are} hydrogen, a methyl group or
(CH ₂ ) _m2 COOM ₂ R ₆ : hydrogen or a methyl group M ₁ , M ₂ , Y: hydrogen, an alkali metal, an alkaline earth metal, ammonium, an alkylammonium or a substituted alkylammonium m ₂ : represents the number of 0 to 2 . ) Component (b): a homopolymer of an unsaturated carboxylic acid selected from unsaturated monocarboxylic acids and unsaturated dicarboxylic acids or 2
Water soluble salts of one or more copolymers.

Although the mechanism of the effect of the present invention is not clear, it is presumed as follows. The water-soluble vinyl copolymer (a) component containing an alkylene glycol chain adsorbed on the cement surface is excellent in dispersion and dispersion retention due to steric repulsion. However, since the amount of adsorption is small, there are many unadsorbed portions on the cement surface, and the viscosity tends to be high due to friction between particles. It is presumed that the unadsorbed portion is supplemented by using the unsaturated carboxylic acid polymer (b) component having a large carboxyl group content in combination, and the effect of decreasing the viscosity is exhibited.

The component (a) in the present invention is a water-soluble vinyl copolymer having an oxyalkylene group, and in this structure, the chain length and dispersibility (fluidizing performance) of polyalkylene glycol and slump retention are contained. As a result of various studies on the properties, the combined use of the copolymer (B) having a chain length in a specific region and the component (B) is excellent in dispersibility, slump retention and viscosity reduction.

That is, when n in the general formula (A) is in the range of 50 to 300, the dispersibility and slump retention are excellent and n is 100.
The range of -200 is more excellent, and the range of n of 110-150 is extremely excellent. On the other hand, when n is less than 50, the slump retention tends to decrease, and when n exceeds 300, the dispersibility tends to decrease and the viscosity tends to be high.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The concrete admixture of the present invention will be described in detail below. In the copolymer of the component (a) in the present invention, as the monomer represented by the general formula (A), methoxy polyethylene glycol, methoxy polyethylene polypropylene glycol, methoxy polypropylene glycol, ethoxy polyethylene glycol, ethoxy polyethylene polypropylene glycol,
Esterification products and (meth) acrylic compounds of ethoxypolypropylene glycol, propoxypolyethylene glycol, propoxypolyethylenepolypropylene glycol, propoxypolypropylene glycol, etc., one end-capped polyalkylene glycol and (meth) acrylic acid or dehydrogenation (oxidation) reaction product of fatty acid. An ethylene oxide or propylene oxide adduct to a dehydrogenation (oxidation) reaction product of an acid or a fatty acid is used. The average number of moles of polyalkylene glycol added is 110 to 300, preferably 100.
~ 200 mol, more preferably 110-150 mol,
Both additions of ethylene oxide and propylene oxide may be performed by random addition, block addition, alternating addition, or the like.

Examples of the monomer represented by the general formula (B) include acrylic acid, methacrylic acid, crotonic acid and metal salts thereof. Further, as the unsaturated dicarboxylic acid-based monomer, maleic anhydride, maleic acid, itaconic anhydride, itaconic acid, citraconic anhydride, citraconic acid, fumaric acid, or their alkali metal salts, alkaline earth metal salts, Ammonium salts, amine salts, substituted amine salts and the like are used.

As the monomer represented by the general formula (C),
Allyl sulfonic acid, methallyl sulfonic acid, or their alkali metal salts, alkaline earth metal salts, ammonium salts, amine salts, substituted amine salts and the like are used.

The composition ratio of the reaction units of the monomer (a) and the monomer (b) constituting the copolymer in the component (a) in the present invention is monomer (a) / monomer (b). ) = 1/100 to 1
The range of 00/100 (molar ratio) is particularly excellent in fluidity and separation resistance. When the above molar ratio is less than 1/100 and
When it is larger than 100/100, the dispersibility and the slump retention tend to decrease.

The copolymer (a) in the present invention can be produced by a known method. For example, JP-A-59
-162163, Japanese Patent Publication No. 211542, Japanese Patent Publication No. 2-7901, Japanese Patent Publication No. 2-7897, etc. are mentioned.

As the solvent used in the solvent polymerization method,
Examples thereof include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, benzene, toluene, xylene, cyclohexane, n-hexane, aliphatic hydrocarbons, ethyl acetate, acetone and methyl ethyl ketone. Water and primary to quaternary alcohols are preferable in consideration of handling and reaction equipment.

As the water-based polymerization initiator, a water-soluble initiator such as ammonium or alkali metal persulfate or hydrogen peroxide is used. Benzoyl peroxide, lauroyl peroxide or the like is used as a polymerization initiator in solvent polymerization using a solvent other than an aqueous solvent.

It is also possible to use sodium bisulfite, mercaptoethanol or an amine compound as an accelerator in combination with the polymerization initiator, and these polymerization initiators or accelerators can be appropriately selected and used. .

The weight average molecular weight (gel permeation chromatography method / polystyrene sulfonic acid conversion) of the copolymer of the component (a) in the present invention is 3,000 to 500,00.
The range of 0 is preferable, and the range of 5,000 to 100,000 is more preferable. If the molecular weight is too large, the dispersibility tends to decrease, and if the molecular weight is too small, the slump retention tends to decrease.

Further, the copolymer of the component (a) in the present invention may be reacted with another copolymerizable monomer within a range that does not impair the effects of the present invention. For example, acrylonitrile, acrylic ester, acrylamide, methacrylamide, styrene, styrene sulfonic acid, etc. may be mentioned.

The component (b) in the present invention is a water-soluble salt of a homopolymer or a copolymer of two or more kinds of unsaturated carboxylic acids selected from unsaturated monocarboxylic acids and unsaturated dicarboxylic acids. Examples of the saturated monocarboxylic acid include acrylic acid and methacrylic acid, examples of the unsaturated dicarboxylic acid include maleic acid, fumaric acid and itaconic acid, and examples of the water-soluble salts thereof include alkali salts. As an example, a homopolymer of sodium polyacrylate, sodium polymethacrylate, sodium polymaleate,
Copolymers such as acrylic acid and sodium maleate.

The weight average molecular weight (gel permeation chromatography / polystyrene sulfonic acid conversion) of the polymer of component (b) is preferably in the range of 1,000 to 50,000,
3,000 to 10,000 is more preferable. If the molecular weight is too large, the dispersibility tends to decrease and the viscosity tends to increase, and if it is too small, the dispersibility is not sufficiently expressed.

In the present invention, the compounding ratio of the component (a) and the component (b) is (a) component / (b) component = 100/1 to 100 /
50 (solid content weight ratio) is preferable, and the range of (a) component / (b) component = 100/3 to 100/20 is more preferable. In the above blending ratio, (a) component is 100: (b) component is 50
If it exceeds 10, the slump retention property will decrease and the component (a) 10
If the component (b) is less than 1 with respect to 0, the decrease in viscosity is not sufficient.

Further, the component (a) and the component (b) in the present invention are
The amount of components added to concrete is the solid content of cement, and is the total amount of addition of (a) and (b) components.
0.1 to 3.0% by weight is the range of use, 0.2 to 0.5
% By weight is preferably used.

Further, the component (a) and the component (b) in the present invention are
When the components are added, the components (a) and (b) may be added in advance, or they may be added separately, without any limitation.

The concrete admixture of the present invention can be used in combination with other dispersants. The dispersant may be any that is generally used as an admixture for concrete, but it includes naphthalene sulfonate formaldehyde condensate, melamine sulfonate formaldehyde condensate, polycarboxylic acid or its ester or its salt, and purified lignin. Sulfonic acid or its salt, polystyrene sulfonate, cement dispersant having phenol skeleton (for example, formaldehyde co-condensate with other monomer copolymerizable with phenol sulfonic acid), aniline sulfonic acid as main component Cement dispersants (for example, formaldehyde co-condensation products with other monomers capable of co-condensing aniline sulfonic acid) and the like, which are conventionally referred to as high performance water reducing agents, are preferably used.

The concrete admixture of the present invention is used for hydraulic compositions of cement such as civil engineering, construction, secondary products, etc., and is not particularly limited.

The concrete admixture of the present invention can be used in combination with known additives (materials). For example, AE agent, AE water reducing agent, superplasticizer, high-performance water reducing agent, retarder, early strengthening agent, accelerator, foaming agent, water retention agent, thickener, waterproofing agent, defoaming agent, water-soluble agent. Polymers, various surfactants, silica sand,
Blast furnace slag, fly ash, silica fume and the like can be mentioned.

Further, the concrete admixture of the present invention is added to cement pastes and mortars having hydraulic cements as a composition, and various cements constituting concrete, and the content thereof is not limited.

[0034]

EXAMPLES The present invention will be specifically described below, but the present invention is not limited to these examples.

Further, the average molecular weight of the copolymer (A) component (hereinafter referred to as "copolymer (A)") shown in the examples is calculated from the molecular weight by gel permeation chromatography method / sodium polystyrene sulfonate conversion. It is what I asked for.

<Production Example of Copolymer (a)> The contents and symbols of the monomer (a) used for the polymerization in the present invention are shown below. However, EO represents ethylene oxide and PO represents propylene oxide. A-1 Methanol EO / methacrylic acid monoester (EO
Average addition mole number = 55) A-2 Methanol EO / acrylic acid monoester (EO average addition mole number = 90) A-3 Methanol EO / methacrylic acid monoester (EO
Average number of added moles = 115) A-4 Methanol EO / methacrylic acid monoester (EO
Average addition mole number = 135) A-5 Acrylic acid PO / EO block addition product (PO average addition mole number = 10, EO average addition mole number = 180) A-6 Acrylic acid EO / PO addition product (EO average addition mole number) Number =
135, PO average addition mole number = 25) A-7 (comparison) Methanol EO / methacrylic acid monoester (EO average addition mole number = 23) A-8 (comparison) Methanol EO / methacrylic acid monoester (EO average addition mole Number = 350) An example of producing the copolymer (a) is shown below. Production Example 1 (Symbol A-1 in Example) 10 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C in a nitrogen atmosphere. A-
10.30 moles, methacrylic acid 1 mole (molar ratio = 30/10
0), a mixed solution of 7.5 mol of water, 0.01 mol of a 20% ammonium persulfate aqueous solution, and 3 g of 2-mercaptoethanol are simultaneously added dropwise to the reaction system over 2 hours. Next, add 0.03 mol of 20% ammonium persulfate aqueous solution to 30%.
The mixture is added dropwise over a period of 1 minute and aged at the same temperature (75 ° C.) for 1 hour. After aging, the temperature is raised to 95 ° C., 15 g of 35% hydrogen peroxide is added dropwise over 1 hour, and aging is performed at the same temperature (95 ° C.) for 2 hours. After completion of aging, 0.7 mol of 48% sodium hydroxide was added for neutralization to obtain a copolymer having a molecular weight of 35,000.

Production Example 2 (Symbol A-2 in Example) 15 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C. in a nitrogen atmosphere. A-2
0.20 mol, 1 mol of acrylic acid (molar ratio = 20/100), water
A mixture of 15 moles, 0.01 mole of a 20% aqueous solution of ammonium persulfate, and 4 g of 2-mercaptoethanol
Are simultaneously added dropwise to the reaction system over 2 hours. Next, 0.03 mol of a 20% ammonium persulfate aqueous solution is added dropwise over 30 minutes, and the mixture is aged at the same temperature (75 ° C.) for 1 hour. 95 ℃ after aging
The temperature is raised to 12, and 12 g of 35% hydrogen peroxide is added dropwise over 1 hour, followed by aging for 2 hours at the same temperature (95 ° C). After aging, 48
Neutralized by adding 0.7 mol of sodium hydroxide, molecular weight 45,0
A copolymer of 00 was obtained.

Production Example 3 (Symbol A-3 in Example) 15 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C. in a nitrogen atmosphere. A-3
0.35 mol, methacrylic acid 1 mol (molar ratio = 35/100),
A mixture of 15 mol of water, 0.01 mol of a 20% ammonium persulfate aqueous solution, and 4 g of 2-mercaptoethanol are simultaneously added dropwise to the reaction system over 2 hours.
Next, 0.03 mol of a 20% ammonium persulfate aqueous solution is added dropwise over 30 minutes, and the mixture is aged at the same temperature (75 ° C.) for 1 hour. 95 after aging
The temperature was raised to 12 ° C, 12 g of 35% hydrogen peroxide was added dropwise over 1 hour, and the mixture was aged at the same temperature (95 ° C) for 2 hours. After aging, 48
Neutralized by adding 0.7 mol of sodium hydroxide, molecular weight 45,0
A copolymer of 00 was obtained.

Production Example 4 (Symbol A-4 in Example) 10 mol of water was charged into a reaction vessel equipped with a stirrer, and the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C in a nitrogen atmosphere. A-4
0.1 mol, acrylic acid 0.9 mol, sodium methallyl sulfonate 0.1 mol (molar ratio = 10/90/10), water 7.5 mol mixed and dissolved and 20% ammonium persulfate aqueous solution.
01 mol and 4 g of 2-mercaptoethanol are simultaneously added dropwise to the reaction system over 2 hours. Then 20%
0.03 mol of an aqueous ammonium persulfate solution is added dropwise over 30 minutes, and the mixture is aged at the same temperature (75 ° C) for 1 hour. After aging, the temperature was raised to 95 ° C, and 12 g of 35% hydrogen peroxide was added dropwise over 1 hour.
Aged at the same temperature (95 ° C) for hours. After completion of aging, 0.6 mol of 48% sodium hydroxide was added for neutralization to obtain a copolymer having a molecular weight of 45,000.

Production Example 5 (Symbol A-5 in Example) 15 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C. in a nitrogen atmosphere. A-5
0.05 mole, methacrylic acid 1 mole (molar ratio = 5/100),
A mixture of 15 mol of water, 0.01 mol of a 20% aqueous solution of ammonium persulfate, and 1 g of 2-mercaptoethanol were simultaneously added dropwise to the reaction system over 2 hours.
Next, 0.03 mol of a 20% ammonium persulfate aqueous solution is added dropwise over 30 minutes, and the mixture is aged at the same temperature (75 ° C.) for 1 hour. 95 after aging
The temperature was raised to 5 ° C., 5 g of 35% hydrogen peroxide was added dropwise over 1 hour, and the mixture was aged at the same temperature (95 ° C.) for 2 hours. After aging, 48
Neutralized by adding 0.7 mol of sodium hydroxide, molecular weight 47,0
A copolymer of 00 was obtained.

Production Example 6 (Symbol A-6 in Example) 10 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 95 ° C in a nitrogen atmosphere. A-6
0.05 mol, maleic acid monosodium salt 1 mol (molar ratio = 5/100), 90 ° C hot water 15 mol mixed and dissolved
% Mol ammonium persulfate aqueous solution 0.01 mol, and 2-mercaptoethanol 3 g simultaneously into the reaction system
Drop over time. Next, 0.03 mol of a 20% ammonium persulfate aqueous solution is added dropwise over 30 minutes, and the same temperature (95 ° C) for 1 hour
Mature in. After aging, 9% of 35% hydrogen peroxide is added dropwise at 95 ° C over 1 hour, and aging is performed at the same temperature (95 ° C) for 2 hours. After completion of the aging, 0.7 mol of 48% sodium hydroxide was added to neutralize and obtain a copolymer having a molecular weight of 13,000.

Production Example 7 (Symbol A-7 in Example) (Comparative) 5 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C. in a nitrogen atmosphere. A-7
0.3 mol, 1 mol of methacrylic acid (molar ratio = 30/100), mixed and dissolved 5 mol of water, 0.01 mol of 20% ammonium persulfate aqueous solution, and 3 g of 2-mercaptoethanol 3 g
Are simultaneously added dropwise to the reaction system over 2 hours. Next, 0.03 mol of a 20% ammonium persulfate aqueous solution is added dropwise over 30 minutes, and the mixture is aged at the same temperature (75 ° C.) for 1 hour. 95 ℃ after aging
, And 15 g of 35% hydrogen peroxide was added dropwise over 1 hour.
Aged at the same temperature (95 ° C) for 2 hours. After aging, 48%
Add 0.7 mol of sodium hydroxide to neutralize, molecular weight 34,000
To obtain a copolymer of

Production Example 8 (Symbol A-8 in Example) (Comparative) 10 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C. in a nitrogen atmosphere. A-8
0.05 mol, acrylic acid 1 mol (molar ratio = 5/100), water
A mixture of 7.5 mol, 0.01 mol of a 20% ammonium persulfate aqueous solution, and 3 g of 2-mercaptoethanol are simultaneously added dropwise to the reaction system over 2 hours.
Next, 0.03 mol of a 20% ammonium persulfate aqueous solution is added dropwise over 30 minutes, and the mixture is aged at the same temperature (75 ° C.) for 1 hour. 95 after aging
The temperature was raised to 10 ° C., 10 g of 35% hydrogen peroxide was added dropwise over 1 hour, and the mixture was aged at the same temperature (95 ° C.) for 2 hours. After aging, 48
Add 0.7 mol% sodium hydroxide to neutralize, molecular weight 31,0
A copolymer of 00 was obtained.

The contents and symbols of the comparative admixture used in the examples other than the comparative polymer of the copolymer are shown below. Reference symbol NS in the Examples: naphthalene-based admixture (Mighty 15
0: manufactured by Kao Co., Ltd. Table 1 shows the contents and symbols of the (b) component used in the examples.

[0045]

[Table 1]

The concrete evaluation methods of the concrete admixture of the present invention and the comparative admixture are shown below.

<Evaluation as Concrete Admixture> The mixing conditions of concrete are shown in Table 2.

[0048]

[Table 2]

Manufacture of concrete was adjusted by mixing the materials and the concrete admixture by a forced mixer for 3 minutes according to the concrete mix shown in Table 2. The fluidity was adjusted by the addition amount of the admixture so that the slump flow value was 550 ± 50 mm. The amount of air was adjusted to 2% or less with an antifoaming agent (silicon type: Antifoam 013B, manufactured by Dow Corning). Regarding the effect of viscosity reduction (spreading speed),
The time (seconds) until the slump cone was pulled up to reach 500 mm was measured and examined. The slump holding property was evaluated by measuring the slump flow after standing for 1 hour to 2 hours in a static state after preparing the concrete. The results are shown in Table 3.

[0050]

[Table 3]

<Evaluation Results / Effects> As is clear from Table 3, the concrete admixture of the present invention has a higher spreading speed and is excellent in slump holding property as compared with the comparative product. If the concrete admixture of the present invention is added to the cement composition,
Since there is little change in fluidity over a long period of time and the viscosity is low, troubles in workability and construction in terms of transportation are eliminated.

Claims (7)

[Claims] 1. A concrete admixture essentially comprising the following components (a) and (b). Component (a): a monomer (a) represented by the following general formula (A) and one or more types of monovalent compounds selected from compounds represented by the following general formulas (B) and (C) A copolymer obtained by polymerizing the body (b). Embedded image (In the formula, R ₁ and R ₂ : hydrogen or a methyl group m ₁ : the number of 0 to 2 AO: an oxyalkylene group having 2 to 3 carbon atoms n: the number of 50 to 300 X: hydrogen or an alkyl of 1 to 3 carbons Represents a group). Embedded image (In the formula, R _{3 to} R ₅ : hydrogen, methyl group or (CH ₂ ) _{m 2} COOM ₂ R ₆ : hydrogen or methyl group M ₁ , M ₂ , Y: hydrogen, alkali metal, alkaline earth metal, ammonium, alkyl Ammonium or substituted alkylammonium m ₂ represents the number of 0 to _2. ) (b) Component: Homopolymer of unsaturated carboxylic acid selected from unsaturated monocarboxylic acid and unsaturated dicarboxylic acid or 2
Water soluble salts of one or more copolymers. 2. In the component (a), n in the general formula (A) is used.
The concrete admixture according to claim 1, wherein is a number of 100 to 200. 3. The composition ratio of the monomer (a) and the monomer (b) constituting the copolymer in the component (a) is monomer (a) /
The concrete admixture according to claim 1 or 2, wherein the monomer (b) is 1/100 to 100/100 (molar ratio). 4. The concrete admixture according to any one of claims 1 to 3, wherein the copolymer of the component (a) has a weight average molecular weight of 3,000 to 500,000. 5. The unsaturated monocarboxylic acid in the component (b) is selected from acrylic acid and methacrylic acid, and the unsaturated dicarboxylic acid is selected from maleic acid, fumaric acid and itaconic acid. The concrete admixture according to any one of items 1 to 4. 6. The weight average molecular weight of the polymer of component (b) is
It is 1,000-50,000, The concrete admixture according to any one of claims 1 to 5. 7. The composition ratio of (a) component and (b) component is (a) component / (b) component = 100/1 to 100/50 (solid content weight ratio). The concrete admixture according to Item 1.