JPH0940447A - Concrete admixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart a slump holding characteristic to the base itself in a high- temp. region as well by using >=1 kinds selected from a specific copolymer, oxycarboxylic acid or its salt, sugar and sugar alcohol as essential components. SOLUTION: A component (a) is the copolymer formed by polymerizing the monomer expressed by formula I (R1 to 2 is H, methyl; m1 is 0 to 2; AO is a 2 to 3C oxyalkylene; (n) is 50 to 300; X is H, a 1 to 3C alkyl) and >=1 kinds of the monomers selected from the compds. expressed by formulas II, III (R3 to 5 is H, methyl, (CH2 )m2 COOM2 ; R6 is H, methyl; M1 , M2 ; Y is H, an alkali metal, alkaline earth metal, ammonium, alkyl ammonium, substd. alkyl ammonium; m2 is 0 to 2). A component (b) is >=1 kinds of the compds. selected from among the oxycarboxyl acid, such as gluconic acid, glucoheptonic acid and arabonic acid, or its salt, the sugar, which are monosaccharides, oligosaccharides or polysaccharides, and sugar alcohol which is sorbitol. The component (a) and the component (b) are used as the essential components.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a concrete admixture. More specifically, it relates to a concrete admixture for the purpose of improving the deterioration of fluidity over time in a high temperature region where the concrete temperature exceeds 30 ° C.

[0002]

2. Description of the Related Art
Concrete admixtures used for the purpose of improving the fluidity of hydraulic compositions include naphthalene sulfonic acid formaldehyde condensate salt (hereinafter referred to as naphthalene type), melamine sulfonic acid formaldehyde condensate salt (hereinafter referred to as melamine type), Polycarboxylic acid salts (hereinafter referred to as polycarboxylic acid type) and the like are used. However, although these admixtures have excellent fluidity, they have a problem that slump loss (decrease in fluidity over time) is large. A method of blending a reactive polymer or a cross-linked polymer with an admixture to improve the slump loss [Cement Association, Cement Concrete, No546.Aug, 1992, p24] is generally known. By adding these slump retainers, some effects are recognized, but the concrete temperature is 30 ℃.
In the summer season over 10%, it does not show sufficient slump retention, and countermeasures are desired.

[0003]

In order to solve the above-mentioned problems, the inventors of the present invention have made earnest studies and, as a result, have made the base of the admixture itself have a slump-retaining function so that oxycarboxylic acid or its salt or sugar can be used. By using together one or more compounds selected from the group consisting of and sugar alcohols, an admixture having extremely excellent slump retention even in a high temperature region has been completed.

That is, the conventional admixture has no dispersion holding property in the base itself, and it is necessary to add a slump holding agent. This slump-holding agent is hydrolyzed by the alkali in the cement to become a dispersant, which has the effect of preventing a decrease in fluidity, but when it reaches a high temperature, it is hydrolyzed at an early stage,
It no longer functions as a slump retention agent.

Therefore, as in the present invention, the admixture having a slump holding function which prevents aggregation over time becomes effective.
Further, the combined use of one or more compounds selected from the group consisting of oxycarboxylic acids or salts thereof, sugars and sugar alcohols further enhances the slump retention function. Generally, saccharides are known as a retarder, have no dispersing action, and do not show an action as a slump retaining agent. However, they have found that the combined use with the base of the present invention synergistically enhances the slump retention property in a high temperature range.

That is, the present invention is a concrete admixture which essentially contains 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). Component (b): One or more compounds selected from the group consisting of oxycarboxylic acids or salts thereof, sugars and sugar alcohols.

[0007]

Embedded image

(In the formula, R ₁ and R _{2 are} 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 the number of carbon atoms 1 ~ Represents an alkyl group of 3).

[0009]

Embedded image

(Wherein R _{3 to} R _{5 are} hydrogen, a methyl group or
(CH ₂ ) _m2 COOM ₂ R ₆ ; hydrogen or methyl group M ₁ , M ₂ , Y: hydrogen, alkali metal, alkaline earth metal, ammonium, alkylammonium or substituted alkylammonium m ₂ : represents a number of 0 to 2 . )

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The concrete admixture of the present invention will be described in detail below. The component (a) of the present invention is a water-soluble vinyl copolymer having an oxyalkylene group,
In this structure, as a result of various studies on the chain length of polyalkylene glycol and dispersibility (fluidizing performance) and slump retention, by using a copolymer having a chain length in a specific region and (b) component, The dispersibility at high temperature and the slump retention property are enhanced.

That is, when the average added mole number of oxyalkylene groups in the general formula (A) is in the range of 50 to 300, the dispersibility and slump retention are excellent, and the range of 100 to 200 is further excellent, and 110 to 150 The range is extremely good.

The average number of added moles of oxyalkylene groups is 50.
When it is less than 300, the slump retention tends to be low, and when it exceeds 300, the dispersibility and the slump retention tend to be reduced.

In the copolymer (a) used in the present invention, examples of the monomer represented by the general formula (A) include methoxy polyethylene glycol, methoxy polyethylene polypropylene glycol, methoxy polypropylene glycol, ethoxy polyethylene glycol and ethoxy polyethylene polypropylene. Glycol, ethoxy polypropylene glycol, propoxy polyethylene glycol,
An esterification product of a polyalkylene glycol capped with one end alkyl such as propoxy polyethylene polypropylene glycol or propoxy polypropylene glycol and acrylic acid or methacrylic acid, or an ethylene oxide or propylene oxide adduct of acrylic acid or methacrylic acid is used. The average number of moles of polyalkylene glycol added is 110 to 300, and both additions of ethylene oxide and propylene oxide can be used in 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 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 and amine salts are used. .

The reaction units of the monomers (a) and (b) constituting the copolymer (a) in the present invention are monomer (a) / monomer (b) = 1/100 to 100 / A range of 100 (molar ratio) is preferable, and a range of 5/100 to 50/100 is particularly excellent in fluidity and slump retention. When the above molar ratio is less than 1/100 or greater than 100/100, the dispersibility and slump retention tend to decrease.

The copolymer (a) of the present invention can be produced by a known method. For example, JP-A-59-16216
No. 3, Special Fair 2-11542, Special Fair 2-7901, Special Fair 2-78
The solvent polymerization method described in Japanese Patent No. 97, etc. may be mentioned.

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

As the aqueous 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 hydrogen sulfite, mercaptoethanol or an amine compound as a promoter in combination with the polymerization initiator, and these polymerization initiators or promoters can be appropriately selected and used. .

The weight average molecular weight of the copolymer (a) (gel permeation chromatography method / polystyrene sulfonic acid conversion) is preferably in the range of 3,000 to 500,000,
More preferably, it is 100 to 100,000. If the molecular weight is too large, the dispersibility tends to decrease, and conversely, if the molecular weight is too small, the slump retention tends to decrease.

Further, the copolymer (a) in the present invention
May be reacted with another copolymerizable monomer as long as the effects of the present invention are not impaired. For example, acrylonitrile, acrylate, acrylamide, methacrylamide, styrene, styrenesulfonic acid and the like can be mentioned.

Examples of the oxycarboxylic acid as the component (b) in the present invention include gluconic acid, glucoheptonic acid, arabonic acid, malic acid and citric acid. Examples of these salts include inorganic or organic salts such as sodium, potassium, calcium, magnesium, ammonium and triethanolamine. As sugars, monosaccharides such as glucose, fructose, galactose, saccharose, xylose, abitose, repose, and isomerized sugar, oligosaccharides such as disaccharides and trisaccharides, or oligosaccharides such as dextrin, or dextran, etc. Examples include polysaccharides. Moreover, molasses containing these is also included. Furthermore, examples of the sugar alcohol include sorbitol.

In the present invention, the compounding ratio of (a) and (b) is (a) / (b) = 100/1 to 100/50 in terms of solid content weight ratio.
Is preferable, and the range of 100/3 to 100/40 is particularly preferable. If the mixing ratio of (a) and (b) is less than 100/1, sufficient slump retention is not exhibited, and if the mixing ratio of (a) and (b) exceeds 100/50, hardening of the concrete is delayed. Is not preferable.

Further, the addition amount of the components (a) and (b) of the present invention to the concrete is about 0.1 to 3.0% by weight as the total solid component (a) and (b) component with respect to the cement. , 0.2 to 0.5% by weight is preferably used.

When the components (a) and (b) of the present invention are added, a mixture of (a) and (b) in advance may be added, or they may be added separately, and there is no limitation. Not a thing.

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. , Mainly 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 What is conventionally called a high-performance water reducing agent, such as a cement dispersant as a component (for example, a formaldehyde co-condensation product with another monomer capable of co-condensing aniline sulfonic acid), is preferably used.

The concrete admixture of the present invention is used for hydraulic compositions of cements such as civil engineering, construction and secondary products, 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, foaming agent, water retention agent, thickening agent, waterproofing agent, defoaming agent. Examples include water-soluble compositions using agents, water-soluble polymers, defoaming agents, various kinds of surfactants, cement paste mortar, various cements constituting concrete, blast furnace slag, fly ash, silica fume and the like.

[0032]

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

The weight average molecular weight of the copolymer (a) shown in the examples is determined from the molecular weight by gel permeation chromatography method / sodium polystyrene sulfonate conversion.

<Production Example of Copolymer (a)> The contents and symbols of the monomer (a) used in the polymerization of the present invention are shown below. However, EO represents ethylene oxide and PO represents propylene oxide. A-1 Methanol EO / methacrylic acid monoester (EO
Addition mole number = 55) A-2 Methanol EO / acrylic acid monoester (EO addition mole number = 90) A-3 Methanol EO / methacrylic acid monoester (EO
Number of added moles = 115) A-4 Methanol EO / methacrylic acid monoester (EO
Addition mol number = 135) A-5 Acrylic acid PO / EO block adduct (PO addition mol number = 10, EO addition mol number = 180) A-6 Acrylic acid EO / PO adduct (EO addition mol number = 135
, PO addition mole number = 25) A-7 Methanol EO / methacrylic acid monoester (EO
Addition mol number = 102) A-8 (Comparison) Methanol EO / methacrylic acid monoester (EO addition mol number = 350) A-9 (Comparison) Methanol EO / methacrylic acid monoester (EO addition mol number = 23) Below An example of producing the copolymer (ii) is shown. 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-1
0.30 mol, 1 mol of methacrylic acid (molar ratio = 30/100),
7.5 mol of water mixed and dissolved, 0.01 mol of a 20% ammonium persulfate aqueous solution, and 3 g of 2-mercaptoethanol
Are simultaneously dropped into 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. 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 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
Then, 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,
Neutralized by adding 0.7 mol of 48% sodium hydroxide, molecular weight 4
5,000 copolymers were 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
Thus, a copolymer No. 00 was obtained.

Production Example 4 (Symbol A-4 of 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-4
0.1 mol, 0.9 mol of acrylic acid, 0.1 mol of sodium methallylsulfonate (molar ratio = 10/90/10), 7.5 mol of water 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%
An aqueous solution of ammonium persulfate is added dropwise at 0.03 mol 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 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 mol, 1 mol of methacrylic acid (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
Thus, a copolymer No. 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
Drip 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
And mature. After aging, 9 g 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 aging, add 0.7 mol of 48% sodium hydroxide to neutralize,
A copolymer having a molecular weight of 13,000 was obtained.

Production Example 7 (Symbol A-7 in Example) 8 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
0.30 mol, 1 mol of methacrylic acid (molar ratio = 30/100),
A mixture of 8 mol of water and 0.01 mol of a 20% aqueous solution of ammonium persulfate 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
, 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%
Neutralized by adding 0.7 mol of sodium hydroxide, molecular weight 35,000
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 moles, 0.01 mole of a 20% aqueous ammonium persulfate 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
Neutralized by adding 0.7 mole of sodium hydroxide, molecular weight 31,0
Thus, a copolymer No. 00 was obtained.

Production Example 9 (Symbol A-9 of 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-9
0.30 mol, 1 mol of methacrylic acid (molar ratio = 30/100),
A mixture of 5 mol of water, 0.01 mol of a 20% aqueous solution of ammonium persulfate and 2 g of 2-mercaptoethanol are simultaneously dropped into 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
Neutralized by adding 0.7 mol of sodium hydroxide, molecular weight 32,0
Thus, a copolymer No. 00 was obtained.

The contents and symbols of the comparative admixtures used in the examples other than the comparative polymer of the copolymer are shown below. Symbol NS: naphthalene-based admixture (Mighty 150; manufactured by Kao Corporation).

Table 1 shows the contents and symbols of the compound (II) used in the examples.

[0045]

[Table 1]

<Evaluation as Concrete Admixture> Table 2 shows concrete mixing conditions.

[0047]

[Table 2]

The concrete is manufactured by mixing the concrete material and the concrete admixture shown in Table 2 with a tilting mixer at 25 rp.
It was adjusted by kneading for m × 3 minutes. After measuring the slump value,
Further, it was rotated at 4 rpm for 60 minutes, and after 60 minutes, the slump value was measured. The concrete temperature was 32 ° C. The admixture was added so that the initial slump value was 20 ± 1 cm. The slump value was measured by the JIS-A1101 method. The setting speed was determined by collecting mortar in concrete and measuring the setting time by the ASTM-C403 method. The measurement results are shown in Table 3.

[0049]

[Table 3]

<Evaluation Results> As shown in Table 3, the concrete admixture of the present invention exhibits fluidity with a smaller addition amount as compared with the comparative product, and the difference between the slump value immediately after and after 60 minutes is small. That is, it shows an excellent water reducing effect and a remarkable effect in preventing slump loss.

[0051]

When the concrete admixture according to the present invention is added to the cement composition, there is no slump loss even at high temperatures in the summer, so that transport troubles due to pumping are eliminated. Furthermore, since the concrete admixture according to the present invention improves the fluidity of the cement composition, it facilitates the work of filling the formwork, and the concrete admixture according to the present invention has a large water-reducing effect. The application of is also expected.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C04B 24/06 C04B 24/06 A 24/10 24/10 C08K 5/05 C08K 5/05 5 / 09 5/09 C08L 33/14 LHW C08L 33/14 LHW 35/00 LHR 35/00 LHR 41/00 LJZ 41/00 LJZ // C08F 228/00 MNR C08F 228/00 MNR 299/02 MRS 299/02 MRS C04B 103: 32

Claims (9)

[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). Component (b): One or more compounds selected from the group consisting of oxycarboxylic acids or salts thereof, sugars and sugar alcohols. Embedded image (In the formula, R ₁ and R _{2 are} hydrogen or a methyl group m ₁ : the number of 0 to 2 AO: an oxyalkylene group having a carbon number of 2 to 3 n: the number of 50 to 300 X: hydrogen or a carbon number of 1 to 3 Represents an alkyl group.) (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) 2. The concrete admixture according to claim 1, wherein in the component (a), n in the general formula (A) is a number of 100 to 200. 3. The concrete admixture according to claim 1, wherein in the component (a), n in the general formula (A) is a number of 110 to 150. 4. The reaction units of the monomers (a) and (b) constituting the copolymer (a) are monomer (a) / monomer (b) = 1/100 to 100/100. (Mole ratio) The concrete admixture according to any one of claims 1 to 3. 5. The weight average molecular weight of the copolymer (a) is 3,0.
It is 00-500,000, The concrete admixture according to any one of claims 1 to 4. 6. The concrete admixture according to claim 1, wherein the oxycarboxylic acid is gluconic acid, glucoheptonic acid, arabonic acid, malic acid or citric acid. 7. The concrete admixture according to claim 1, wherein the sugar is a monosaccharide, an oligosaccharide or a polysaccharide. 8. The admixture for concrete according to claim 1, wherein the sugar alcohol is sorbitol. 9. The composition ratio of (a) and (b) is (a) /
(B) = 100/1 to 100/50 (solid content weight ratio), The concrete admixture according to any one of claims 1 to 8.