JP4357994B2 - Concrete admixture - Google Patents

Description

  The present invention relates to a concrete admixture.

  In recent years, the strength of concrete has been increased in response to high-rise buildings and large structures. Among them, the requirements for concrete admixture include high water reduction and flowability during construction as well as viscosity reduction during pumping.

  Conventionally, high-performance water reducing agents corresponding to the increase in strength include naphthalene sulfonic acid formalin condensate (naphthalene type), melamine sulfonic acid formalin condensate (melamine type) and the like. Furthermore, in recent years, water-soluble properties such as copolymers of polyalkylene glycol monoester monomers that exhibit excellent dispersibility (slump value) and (meth) acrylic acid and / or dicarboxylic acid monomers. Vinyl copolymers (polycarboxylic acid type) and the like are known. However, although the dispersibility is improved by these water reducing agents, the concrete workability is insufficient because the flowability of the concrete after pumping is poor.

  An object of the present invention is to provide a concrete admixture that is particularly useful in the field of high-strength concrete, has high dispersibility and flowability, and is excellent in concrete workability.

  In order to solve the above-mentioned problems, the present inventor has found that a mixture of copolymers obtained by reacting a specific monomer with a molar ratio within a specific range is effective. Furthermore, as a result of investigation based on this knowledge, among such copolymer mixtures, a mixture of copolymers obtained by changing the molar ratio of monomers during the reaction, or different molar ratios from each other. The inventors have found that a mixture of three or more kinds of copolymers obtained by copolymerization separately is particularly effective and completed the present invention.

  That is, the present invention comprises at least one monomer (A) represented by the following general formula (a) and at least one monomer (B) represented by the following general formula (b). A concrete admixture containing a copolymer mixture obtained by copolymerization, wherein the molar ratio (A) / (B) of the monomers (A) and (B) changes at least once during the reaction. The present invention relates to a concrete admixture [hereinafter referred to as a concrete admixture (I)].

(Where
R ₁ and R ₂ : hydrogen atom or methyl group
m: number from 0 to 2
R ₃ : hydrogen atom or —COO (AO) _n X
p: Number of 0 or 1
AO: C2-C4 oxyalkylene group or oxystyrene group, preferably C2-C3 oxyalkylene group
n: Number from 2 to 300
X: A hydrogen atom or an alkyl group having 1 to 18 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. )

(Where
R _{4 to} R ₆ : a hydrogen atom, a methyl group or (CH ₂ ) m ₁ COOM ₂ , and (CH ₂ ) m ₁ COOM ₂ forms an anhydride with COOM ₁ or other (CH ₂ ) m ₁ COOM ₂ In that case, M ₁ and M ₂ of those groups are not present.
M ₁ and M ₂ : hydrogen atom, alkali metal, alkaline earth metal, ammonium group, alkylammonium group or substituted alkylammonium group
m1: represents a number from 0 to 2. )

In addition, the present invention provides at least one monomer (A) represented by the above general formula (a) and the above general formula (b).
Copolymers of three or more types of copolymers obtained by differentiating the molar ratio of one or more types of monomers represented by (B) with each other within the range of (A) / (B) = 0.02-4. The present invention relates to a concrete admixture containing a polymer mixture (hereinafter referred to as a concrete admixture (II)).

  The present invention further relates to a concrete composition containing at least one of the concrete admixtures (I) and (II) of the present invention.

(Monomer (A))
Monomers (A) represented by the general formula (a) include one-end alkyl-capped polyalkylene glycols such as methoxypolyethylene glycol, methoxypolypropylene glycol, methoxypolybutylene glycol, methoxypolystyrene glycol, and ethoxypolyethylenepolypropyleneglycol ( (Meth) acrylic acid, (half) esterified product with maleic acid, etherified product with (meth) allyl alcohol, and (meth) acrylic acid, maleic acid, ethylene oxide and propylene oxide adducts to (meth) allyl alcohol R ₃ is preferably a hydrogen atom, p is preferably 1, and m is preferably 0. More preferred is an esterified product of alkoxy, particularly methoxypolyethylene glycol and (meth) acrylic acid. The average added mole number of the polyalkylene glycol is preferably in the range of 2 to 300 mol because of excellent fluidity and fluid retention, and more preferably in the range of 2 to 150 mol, and more preferably in the range of 5 to 130 mol.

As the monomer (A), from the viewpoint of obtaining higher dispersibility and flowability, the monomer (A-1) represented by the following general formula (a-1) and the following general formula (a-2) It is preferable to use a monomer (A-2) represented by

(Where
R ₇ : hydrogen atom or methyl group
AO: C2-C4 oxyalkylene group or oxystyrene group, preferably C2-C3 oxyalkylene group
n ₁ : Number from 12 to 300
X _{1 represents a} hydrogen atom or an alkyl group having 1 to 18 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. )

(Where
R ₈ : hydrogen atom or methyl group
AO: C2-C4 oxyalkylene group or oxystyrene group, preferably C2-C3 oxyalkylene group
n ₂ : Number of _{2 to} 290 (however, the relationship with n _{1 in} general formula (a-1) is n ₁ > n ₂ and (n ₁ −n ₂ ) ≧ 10, preferably ≧ 30, more preferably Is ≧ 50.)
X _{2 represents a} hydrogen atom or an alkyl group having 1 to 18 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. )

(Monomer (B))
Monomers (B) represented by the general formula (b) include monocarboxylic acid monomers such as (meth) acrylic acid and crotonic acid, and dicarboxylic acid monomers such as maleic acid, itaconic acid and fumaric acid. Preference is given to monomers, or anhydrides or salts thereof, such as alkali metal salts, alkaline earth metal salts, ammonium salts, and mono-, di-, or trialkyl (2 to 8 carbon atoms) ammonium salts optionally substituted with a hydroxyl group. More preferred is (meth) acrylic acid, maleic acid, maleic anhydride, and still more preferred is (meth) acrylic acid or an alkali metal salt thereof.

[Concrete admixture (I)]
The concrete admixture (I) of the present invention was obtained by reacting the monomers (A) and (B) with a molar ratio preferably in the range of (A) / (B) = 0.02-4. Although it contains a copolymer mixture, the molar ratio (A) / (B) is changed at least once during the reaction. The change in the molar ratio may be an increase, a decrease, or a combination thereof. When the molar ratio is changed stepwise or intermittently, the number of changes is preferably 1 to 10 times, particularly preferably 1 to 5 times. Further, when the molar ratio is continuously changed, any of a linear change, an exponential change, and other changes may be used, but the degree of change is 0.0001 to 0.2, more preferably 0.0005 to 0.1, 0.001 to 0.05 is preferred. The molar ratio (A) / (B) before and after the change is preferably in the range of 0.02 to 4, and both the molar ratio (A) / (B) before and after the change are particularly preferred. It is preferable to be in the range of 0.02 to 4. Further, as described above, there are various modes of changing the molar ratio. In any case, the difference between the maximum value and the minimum value of the molar ratio (A) / (B) in the total copolymerization reaction is at least 0.05. In particular, it is preferably in the range of 0.05 to 2.5.

Such a copolymer mixture can be obtained by a production method having a step of polymerizing by changing the (A) / (B) molar ratio at least once. Specifically, an aqueous solution of the monomer (A) is dropped. There is a method in which the dropping of the monomer (B) is started simultaneously with the start, and dropping is performed for a predetermined time while changing the dropping flow rate (parts by weight / minute) so that the respective molar ratios are within a predetermined range. In this method, monomer (A)
The change amount of the / (B) molar ratio (difference between the maximum value and the minimum value) is preferably 0.05 to 2.5, and more preferably 0.1 to 2. A copolymer mixture obtained by changing the molar ratio even once during the reaction as in this method is obtained from a copolymer obtained by reacting at a constant (A) / (B) molar ratio (A ) / (B) It is presumed to be a mixture of a large number of copolymers having a wide molar ratio distribution.

When the monomer (A-1) and the monomer (A-2) are used as the monomer (A), the average weight ratio between them is (A-1) / (A-2) = 0.1-8 are preferable, More preferably, it is 0.2-2.5, Most preferably, it is the range of 0.4-2. This average weight ratio is an average value of the weight ratios of all monomers used in the reaction. The reaction molar ratio of monomer (A-1) and monomer (A-2) to monomer (B) [(A-1) + (A-2)] / (B) Is preferably in the range of 0.02 to 4, more preferably 0.05 to 2.5, and particularly preferably 0.1 to 2, and particularly preferably the molar ratio before and after the change is within these ranges.

In addition, it is preferable to produce 30% or more, particularly 50 to 100% of the total weight of the monomer by changing the dropping flow rate as described above.

  In the above method, the change in molar ratio or weight ratio may be adjusted by changing the addition rate of all the monomers to be added or by changing the addition rate of only a part of the added monomer. Moreover, the change of dripping speed may be performed continuously, may be performed in steps, and these may be combined. Furthermore, the amount of change may be increased or decreased alternately as well as a unified change of increase or decrease. Monomers to be added may be added individually, or may be sequentially added after preparing two or more monomer mixed solutions having different monomer composition ratios in advance. When dropping individually, it is preferable that the dropping flow rate of the monomer having the largest weight to be added is constant and the dropping flow rate is changed so that other monomers have a predetermined monomer composition. Furthermore, a part of the monomer to be added to the monomer dropping tank is charged, and the remaining monomer is continuously or stepwise changed, and the monomer mixed solution is dropped while being added to the monomer dropping tank. It may be dropped from the tank to the reaction tank. Alternatively, a part of the monomer to be added may be charged into the reactor, and the remaining monomer may be dropped into the reactor and polymerized by changing the flow rate continuously or stepwise.

In the above method, the degree of change in molar ratio or weight ratio is adjusted by measuring the flow rate of the monomer to be supplied with a flow meter, liquid level meter or the like. At that time, the standard for determining the specific degree of change depends on the type of monomer and the charged amount (speed). Generally, when the monomer (A) content is increased, the flowability is improved, and when the monomer (B) content is increased, the dispersibility is improved, and the general formula (a) of the monomer (A) (a) ) Is small, the curing rate is slow and the dispersion retention is low, and if n is large, the curing rate is high and the dispersion retention tends to be high. What is necessary is just to determine a weight ratio.

  The polymerization reaction may be performed in the presence of a solvent. Solvents include water, lower alcohols such as methanol, ethanol, isopropanol, and butanol; aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclohexane; aliphatic hydrocarbons such as n-hexane; acetic acid Examples thereof include esters such as ethyl; ketones such as acetone and methyl ethyl ketone. Among these, water and lower alcohols are preferable from the viewpoint of easy handling and solubility of the monomer and polymer.

  In the copolymerization reaction, a polymerization initiator can be added. Examples of the polymerization initiator include organic peroxides, inorganic peroxides, nitrile compounds, azo compounds, diazo compounds, sulfinic acid compounds, and the like. The addition amount of the polymerization initiator is preferably 0.05 to 50 mol% with respect to the total of the general formula (I), the general formula (II) and other monomers. The dropping of the polymerization initiator is preferably started simultaneously with the monomer. The dropping flow rate may be changed or constant, and may be set so that a desired molecular weight and reaction rate can be obtained.

  In the copolymerization reaction, a chain transfer agent can be added. Examples of the chain transfer agent include lower alkyl mercaptan, lower mercapto fatty acid, thioglycerin, thiomalic acid, 2-mercaptoethanol and the like. In particular, when water is used as a solvent, the molecular weight can be adjusted more stably by adding these chain transfer agents. The chain transfer agent can be mixed with the monomer or dropped separately at the same time as the monomer. The dropping flow rate may be changed or fixed, and may be adjusted so as to obtain a desired molecular weight. The reaction temperature for the copolymerization reaction is preferably 0 to 120 ° C.

  The obtained polycarboxylic acid polymer can be deodorized as necessary. In particular, when a thiol such as mercaptoethanol is used as a chain transfer agent, an unpleasant odor tends to remain in the polymer, and therefore, it is desirable to perform a deodorization treatment.

  The polycarboxylic acid polymer obtained by the above production method can be applied as a dispersant for cement even in an acid form, but from the viewpoint of suppressing ester hydrolysis due to acidity, the salt is obtained by neutralization with an alkali. It is preferable to use the following form. Examples of the alkali include hydroxides of alkali metals or alkaline earth metals, ammonia, mono, di, trialkyl (2 to 8 carbon atoms) amine, mono, di, trialkanol (2 to 8 carbon atoms) amine, and the like. Can be mentioned. When a (meth) acrylic acid polymer is used as a dispersant for cement, partial or complete neutralization is preferred.

  The weight average molecular weight of the polycarboxylic acid polymer obtained by the above production method [gel permeation chromatography method, converted into polyethylene glycol, column: G4000PWXL + G2500PWXL (manufactured by Tosoh Corporation), eluent: 0.2M phosphorus The acid buffer / acetonitrile = 7/3 (volume ratio)] is preferably 10,000 to 200,000, particularly preferably 20,000 to 100,000, in order to obtain sufficient dispersibility as a cement dispersant.

When the concrete admixture (I) of the present invention is obtained by the above method, the average weight ratio of the monomer (A) to the monomer (B) in all the monomers used is (A) / (B ) = 30/70 to 99/1, more preferably 60/40 to 98/2, and particularly preferably 80/20 to 97/3. Further, the monomer (A) as the monomer (A-1) and (A-2
), The average weight ratio of the monomers (A-1) to (A-2) in all the monomers used is (A-1) / (A-2) = 10/90 to 90 / 10, more preferably 20/80 to 80/20.

  Furthermore, copolymerizable monomers such as acrylonitrile, (meth) acrylamide, styrene, alkyl (meth) acrylate (having 1 to 12 carbon atoms which may have a hydroxyl group) ester, styrene sulfonic acid and the like. May be used in combination. These can be used in a proportion of not more than 50% by weight, more preferably not more than 30% by weight, based on all monomers, with 0% by weight being preferred.

  Thus, at least one monomer (A) represented by the above general formula (a) and at least one monomer (B) represented by the following general formula (b) are used together. A method for producing a concrete admixture by polymerization, wherein the molar ratio (A) / (B) of the monomers (A) and (B) is changed at least once during the reaction. The concrete admixture (I) of the present invention is obtained by the production method.

[Concrete admixture (II)]
The concrete admixture (II) of the present invention comprises one or more monomers (A) represented by the general formula (a) and one or more monomers represented by the general formula (b) ( 3) or more, preferably 3 to 10, more preferably 4 to 8 of copolymers obtained by varying the molar ratio of B) with each other within the range of (A) / (B) = 0.02-4. Contains a copolymer mixture of seeds. The copolymer mixture is obtained by mixing three or more types of copolymers that are separately copolymerized. The difference in molar ratio is preferably at least 0.05, more preferably at least 0.1, in particular at least 0.2. The method of obtaining each copolymer is in accordance with the reaction method of the concrete mixture (I) described above, but the (A) / (B) molar ratio is not changed during the reaction.

[Concrete composition]
The concrete composition of the present invention contains at least one of the concrete admixtures (I) and (II) of the present invention, cement, fine aggregate, and coarse aggregate. Moreover, you may contain various additives (materials), such as a high performance water reducing agent, AE agent, a retarder, an antifoamer, a foam agent, a waterproofing agent, and antiseptic | preservative. These are known in the art. Furthermore, you may mix | blend fine powders, such as blast furnace slag, fly ash, a silica fume, and stone powder. The concrete composition of the present invention contains 0.01 to 5.0% by weight (as a solid content) of concrete admixtures (I) and (II) based on cement.
It is particularly preferable to contain 0.05 to 2.0% by weight. The use of the concrete composition is not limited to cellular (lightweight) concrete, heavyweight concrete, waterproof concrete, mortar, and the like.

  According to the concrete admixtures (I) and (II) of the present invention, it is possible to obtain a concrete composition that exhibits a flow distance of 50 cm or more, preferably 70 cm or more under a slump condition of 19 cm. The measuring method of this flow distance is as follows.

<Measurement method of flow distance>
(1) Slump
According to JIS A1101.
(2) Concrete composition (material)
Cement (C): Pacific Portland normal portland cement (specific gravity 3.16)
Fine aggregate (S): Mountain sand from Kimitsu, Chiba Prefecture (specific gravity 2.61)
Coarse aggregate (G): Torigatayama lime crushed stone (specific gravity 2.72)
(W): Tap water mixing ratio, W / C = 40%, s / a [sand / (sand + gravel): volume ratio] = 45.8%, C = 425kg / m 3, W = 170kg / m 3, S = 778kg / m ^3, a G = 960kg / m ^3.
(Preparation method)
The above materials and admixture were kneaded for 90 seconds with a forced biaxial mixer. Adjust the amount of admixture so that the slump value is 18-20cm.
(3) Flow distance (flowability measurement)
As shown in Fig. 1 (a), a concrete composition is placed in a vinyl chloride box 1 having a length of 100 cm, a height of 20 cm, and a width of 20 cm, and a stainless steel funnel 2 having a bottom end closed with a plate at a height of 20 cm. Put 500mL of 3 and drop 500ml at intervals of 10 seconds. When the concrete composition 3 rises to the top of the box 1, measure the distance that flows in the longitudinal direction [Fig. 1 (b)], and use this as the flow distance. . Funnel 2
As shown in Fig. 1 (c), the shape of this is an inverted cone with an upper opening of 14cm in diameter and a lower opening of 7cm in diameter.
The distance from the upper opening to the lower opening is 20 cm. The funnel 2 is installed at the center position (10 cm position) of the short side of the box 1 when the edge of the upper opening is 3 cm away from the short side when viewed from the plane. The position of the lower opening of the funnel 2 is set at a height that matches the height of the box. The measurement is performed twice under the conditions of slump 18 to 19 cm and 19 to 20 cm, and the distance traveled when the slump is 19 cm is calculated.

Reference Examples 1-7 and Comparative Examples 1-3
In this example, the monomers (A) and (B) are added individually and only one of the addition flow rates is changed stepwise.

[I] Monomer Using the monomers (A), (B), and (C) shown in Table 1 as shown in Table 2, concrete admixtures were produced by the following method.

[Ii] Production of concrete admixture 321 parts by weight of water was charged into a glass reaction vessel, and the temperature was raised to 78 ° C. in a nitrogen atmosphere. next,
A mixed solution of 581 parts by weight of a 60% aqueous solution of monomer (A-IV) and 2.5 parts by weight of a 75% aqueous phosphoric acid solution was added dropwise over 90 minutes at a constant flow rate. (BI) 14 parts by weight, 15% ammonium persulfate aqueous solution 20 parts by weight and 2-mercaptoethanol 2.4 parts by weight,
As shown in Table 2, the (A) / (B) molar ratio for each dropping time was changed and dropped for 90 minutes.

Further, the mixture was aged for 60 minutes at the same temperature, 7 parts by weight of 15% ammonium persulfate aqueous solution was dropped in 5 minutes and aged for 120 minutes, and 8 parts by weight of 48% sodium hydroxide aqueous solution was added to obtain a concrete admixture ( Reference Example 1). . Similarly, the concrete admixtures of Reference Examples 2 to 7 and Comparative Examples 1 to 3 in Table 2 were produced (however, the aqueous solution concentration of the charged components was changed as necessary). In addition, the ratio of the monomer C-1 in Reference Example 6 was added for 90 minutes at a constant 1.30 parts by weight / minute.

Reference Example 8
In this example, two mixtures of monomers (A) and (B) were prepared and added sequentially.

A glass reaction vessel was charged with 412 parts by weight of water and heated to 78 ° C. in a nitrogen atmosphere. next,
178 parts by weight of a 60% aqueous solution of the monomer (A-IV) shown in Table 1, 89 parts by weight of an 84% aqueous solution of the monomer (AI) shown in Table 1, and 12.9 parts by weight of the monomer (BI) shown in Table 1 A mixture of 0.6 part by weight, 0.6 part by weight of 75% phosphoric acid aqueous solution and 0.8 part by weight of 2-mercaptoethanol and 5 parts by weight of 15% aqueous ammonium persulfate aqueous solution was added dropwise over 45 minutes, and then the monomers shown in Table 1 (A-IV ) 60% aqueous solution 178 parts by weight, 84% aqueous solution 84% monomer (AI) shown in Table 1, 18.1 parts by weight monomer (BI) shown in Table 1, 75% phosphoric acid aqueous solution 0.6 parts by weight, A mixed solution of 0.9 parts by weight of 2-mercaptoethanol and 6 parts by weight of a 15% aqueous ammonium persulfate solution were added dropwise over 45 minutes. Table 2 shows changes in the (A) / (B) molar ratio and (A-1) / (A-2) weight ratio for each dropping time. After completion of the dropping, the mixture was aged at 78 ° C. for 60 minutes, and then 5 parts by weight of a 15% ammonium persulfate aqueous solution was added dropwise over 5 minutes. The mixture was further aged at 79 ° C. for 120 minutes, and 13 parts by weight of 48% aqueous sodium hydroxide solution was added to obtain a concrete admixture.

* (A) / (B) weight ratio is the average weight ratio of all monomers to be finally reacted (the same applies hereinafter).

Reference examples 9-10
In this example, the dropping rate of the monomer (A-1) is constant, and the dropping rate of other monomers is continuously changed.

[I] Monomer Using the monomers shown in Table 3 as shown in Table 3, concrete admixtures were produced by the following method.

[Ii] Production of concrete admixture 329 parts by weight of water was placed in a glass reaction vessel, and the temperature was raised to 78 ° C. in a nitrogen atmosphere. next,
A mixed solution of 60% aqueous solution of monomer (AI) and 2.6 parts by weight of 75% aqueous phosphoric acid solution was added dropwise over 90 minutes at a constant flow rate. ) The dropping of 7.6 parts by weight, 14 parts by weight of 15% ammonium persulfate aqueous solution and 2 parts by weight of 2-mercaptoethanol was started. At this time, the dropping rate of the aqueous solution of the monomer (AI) is constant at 3.8 parts by weight / minute, and the dropping rate of the monomer (BI) is from 0.39 parts by weight to 1.13 parts by weight / minute, 0.0082 parts by weight / minute. It was dropped at a rate of minutes and dropped for 90 minutes.

Further, the mixture was aged for 60 minutes at the same temperature, and 7 parts by weight of 15% ammonium persulfate aqueous solution was dropped for 5 minutes in 120 minutes, and 6 parts by weight of 48% sodium hydroxide aqueous solution was added to obtain the concrete admixture of Reference Example 9. Similarly, the concrete admixture of Reference Example 10 in Table 3 was produced (however, the aqueous solution concentration of the charged components was changed as necessary).

Comparative Example 4
A copolymer was synthesized in accordance with Reference Example 5 of Japanese Patent Publication No. 2-7901. A glass reaction vessel was charged with 395.5 parts by weight of water and heated to 95 ° C. under a nitrogen atmosphere. Next, a monomer aqueous solution consisting of 140 parts by weight of methoxypolyethylene glycol monomethacrylate (average number of added moles of EO 50), 60 parts by weight of sodium methacrylate and 200 parts by weight of water and 3.0 parts by weight of 5% ammonium persulfate aqueous solution for 2 hours. 5% ammonium persulfate aqueous solution 1.
5 parts by weight were added in 1 hour. Subsequently, the temperature was maintained at 95 ° C. for 1 hour to complete the polymerization reaction, and an aqueous copolymer solution having an average molecular weight of 230,000 was obtained. The viscosity of the obtained copolymer at 25 ° C. and a concentration of 5% was 110 mPa · s. The aqueous solution was used as a concrete admixture.

Comparative Example 5
A polycarboxylic acid copolymer (FC 600 S, manufactured by Nippon Shokubai Co., Ltd.) was used as a concrete admixture.

<Performance evaluation>
About the concrete admixture obtained by Reference Examples 1-10 and Comparative Examples 1-5, the flow distance was measured by the said method. The results are shown in Table 4.

Example 1
A concrete admixture was produced using the monomers shown in Table 1 as shown in Table 5 in the same manner as in Reference Example 1, and the flow distance was measured by the method described above. The results are shown in Table 5. In Table 5, concrete admixtures Nos. 11-1 to 11-5 are ordinary concrete admixtures polymerized at a constant (A) / (B) molar ratio, and concrete admixtures No. 11-6 are: It is an equal mixture of No.11-1 to 11-5. In addition, No. 11-7 is a combination of No. 11-6 and the average weight ratio of the monomer. No. 11-8 is the same as No. 11-7 and the average weight ratio of the monomer. However, it is produced by a process of polymerization while changing the weight ratio depending on the dropping time. As a result, a mixture of three or more copolymers having different molar ratios from a single (A) / (B) molar ratio copolymer further changed the molar ratio at least once during the reaction. It can be seen that the copolymer mixture reacted to have excellent performance.

Schematic showing the method of measuring the flow distance in the examples

Explanation of symbols

1 ... box 2 ... funnel 3 ... concrete composition

Claims (5)

One or more of the monomers represented by the following general formula (a) (A) [hereinafter referred to as the monomer (A)] and one of the monomers represented by the following general formula (b) (B) [hereinafter referred to as monomer (B)] and (A) / (B) = 0 to 0.02-4, and 4 to 8 types of copolymers obtained by different molar ratios. A concrete admixture containing a copolymer mixture of the above, wherein the combination of the monomer (A) and the monomer (B) in the 4 to 8 types of copolymers is the same as each other .

(Where
R ₁ and R ₂ : hydrogen atom or methyl group
m: number from 0 to 2
R _3: hydrogen atom
p : number of 1
AO: C2-C4 oxyalkylene group
n: Number from 2 to 300
X: represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. )

(Where
R _{4 to} R ₆ : hydrogen atom or methyl group
M ₁ and M ₂ : hydrogen atom, alkali metal, alkaline earth metal, ammonium group, alkylammonium group or substituted alkylammonium group
m1: represents a number from 0 to 2. ) The monomer (A) is a monomer (A-1) represented by the following general formula (a-1) and a monomer (A-2) represented by the following general formula (a-2). The concrete admixture according to claim 1, which is a combination.

(Where
R ₇ : Hydrogen atom or methyl group
AO: C2-C3 oxyalkylene group
n ₁ : Number of 12-300
X ₁ : A hydrogen atom or an alkyl group having 1 to 3 carbon atoms
Represents. )

(Where
R ₈ : Hydrogen atom or methyl group
AO: C2-C3 oxyalkylene group
n ₂ : Number of 2 to 290 (however, n in general formula (a-1) ₁ Relationship with n ₁ > N ₂ And (n ₁ −n ₂ ) ≧ 10. )
X ₂ : A hydrogen atom or an alkyl group having 1 to 3 carbon atoms
Represents. ) The concrete admixture according to claim 1 or 2, wherein the copolymer has a (A) / (B) molar ratio different from each other by at least 0.05. A concrete composition containing the concrete admixture according to any one of claims 1 to 3 . The concrete composition according to claim 4, wherein the flow distance is 50 cm or more under the condition of a slump of 19 cm.

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