JPH054845A - Cement admixture - Google Patents

Abstract

PURPOSE:To improve slump loss by using a cement admixture containing a co-condensate prepared by subjecting plural compound shown by specific general formulas and an amino-based polymerization terminator to addition co- condensation with formaldehyde. CONSTITUTION:Given amounts of compounds shown by formula I and formula II (R1 and R2 are 1-6C straight-chain or branched-chain alkyl; X is alkali metal) and an amino-based polymerization terminator shown by formula III, IV, V or VI (X2 and X3 are H, 1-3C alkyl, carboxyl, sulfone or alkali metal; Z1 is H, 1-3C alkyl, -CH2SO3M1 and M1 and M2 are H or alkali metal) are weighed, mixed with water and adjusted to proper concentration and pH. The solution is heated to about 80-90 deg.C, to which 0. 7-5 times as much formalin calculated as formaldehyde as the whole monomer is dripped. The compounds are subjected to addition co-condensation at pH 3-12 for a given time while stirring to give a co-condensate having 1,000-50,000 molecular weight. The co-condensate is used alone as a cement admixture or together with another admixture and mixed with cement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture, and more particularly to a cement admixture such as a water reducing agent and a slump loss inhibitor used in cement compositions such as cement paste, mortar and concrete.

[0002]

2. Description of the Related Art Generally, a hydraulic cement composition gradually loses fluidity with the passage of mixing time (hereinafter, this phenomenon is referred to as slump loss), which causes a problem in workability in construction. In other words, it is known that naphthalene-based and melamine-based admixtures that have been conventionally added as cement dispersants have a large slump loss (Watanabe et al., Building Technology, 8 , N
o.384,71 (1983).).

As a measure against this slump loss, a method of adding a curing retarder such as oxycarboxylate or lignin sulfonate has been proposed (Ando et al., Cement concrete, 430 , 30 (1982).). Depending on the method, the trowel finishing time of the concrete is delayed and the initial strength is lowered, and the slump loss preventing effect has not been sufficiently obtained, and a basic solution has not been reached.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a cement admixture, especially a concrete admixture, which improves the consistency of the cement composition and reduces slump loss. More specifically, when added to the cement composition, the fluidity of the cement composition is improved to increase the water reduction rate, and the cement composition can be transported for a long time without slump loss and pumped. An object is to provide a cement admixture that facilitates.

[0005]

[Means for Solving the Problems] Although the cause of slump loss has not been clarified, the physical agglomeration of cement particles in the cement paste due to the interparticle attractive force progresses, and the fluidity decreases over time. (Hattori, Material, 29 , 240 (1980).).

Therefore, as a result of earnest research based on this inference, the present inventors have increased the adsorption force and adsorption amount of the dispersant to the cement particles, and increased the electrical repulsion force of the cement particle surface to achieve physical cohesion. The inventors have found that the above can be prevented, and have completed the present invention.

That is, in the present invention, a co-condensate obtained by addition cocondensing with formaldehyde by using an amino-based polymerization terminator in combination with a compound represented by the following general formulas (A) and (B) is an essential component. The present invention provides a cement admixture characterized by:

[0008]

[Chemical 9]

[Here, R ₁ means hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms. ]

[0010]

[Chemical 10]

[Wherein R ₂ represents hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms, and X ₁ represents an alkali metal. ].

Examples of the amino-based polymerization terminator used in the present invention include one or more compounds selected from the group of compounds represented by the following general formulas (C), (D), (E) and (F). To be

[0013]

[Chemical 11]

[Wherein X ₂ is selected from the group consisting of hydrogen, an alkyl group having 1 to 3 carbon atoms, a carboxyl group or an alkali metal salt thereof, a sulfone group or an alkali metal salt thereof, a hydroxyl group and a methoxy group, and Y ₁ is It is selected from the group consisting of a carboxyl group or an alkali metal salt thereof and a sulfone group or an alkali metal salt thereof. ]

[0015]

[Chemical 12]

[Wherein X ₃ is selected from the group consisting of hydrogen, an alkyl group having 1 to 3 carbon atoms, a carboxyl group or an alkali metal salt thereof, a sulfone group or an alkali metal salt thereof, a hydroxyl group and a methoxy group, and Y ₂ is It is selected from the group consisting of a carboxyl group or an alkali metal salt thereof and a sulfone group or an alkali metal salt thereof. ]

[0017]

[Chemical 13]

[Wherein Z ₁ is selected from the group consisting of hydrogen, an alkyl group having 1 to 3 carbon atoms and —CH ₂ SO ₃ M ₁ , and M ₁ is hydrogen or an alkali metal. ].

The general formula (F) H ₂ NSO ₃ M ₂ [wherein M ₂ is hydrogen or an alkali metal]. ].

The formaldehyde addition co-condensate used in the present invention enhances the adsorptive power to cement and increases the electric repulsive force on the particle surface, and it is therefore presumed that this can reduce the slump loss.

In general, the adsorption on the cement particles is affected by the functional group in the molecule. The functional groups of the cocondensate of the present invention have one hydroxyl group in phenol, two hydroxyl groups and two sulfonic acid groups in phenolsulfonate, and the amino-based polymerization represented by the above general formulas (C) to (F). Since the terminating agent has at least two functional groups such as amino groups and sulfone groups, it has a total of five or more functional groups. Therefore, it is considered that the addition co-condensate of the present invention strongly adsorbs to the cement particles and increases the charge density on the surface of the particles, so that it exhibits an excellent effect of reducing slump loss. The conventional cement admixture has one functional group of naphthalene type or melamine type, or JP-A-1-11.
The number of phenol / sulfanilic acid cocondensates shown in Japanese Patent No. 3419 is 3, and the cocondensates of the present invention have more functional groups per molecular weight than these. Therefore, the formaldehyde addition co-condensate of the present invention exhibits excellent effects in dispersibility and slump loss prevention as compared with conventional cement admixtures, as will be apparent from Examples described later.

In the present invention, the compounds represented by the above general formulas (A) and (B) are used in combination with an amino-based polymerization terminator to carry out addition cocondensation with formaldehyde.

The compound of formula (A) is a phenol optionally substituted with an alkyl group and is represented by the formula (A) and (B)
R ₁ and R ₂ represent hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms, such as methyl, ethyl, propyl,
Examples include isopropyl, butyl, pentyl, hexyl and the like. The compound of the formula (B) is a phenolsulfonic acid which may be substituted with an alkyl group or an alkali metal salt thereof. The alkali metal salt is not particularly limited, but sodium salt and potassium salt are preferable.

The above general formulas (C) to (F) used in the present invention
The amino-based polymerization terminator selected from the group of compounds represented by is characterized by having a functional group selected from the group consisting of a sulfone group, a carboxyl group, a hydroxyl group and a methoxy group, in addition to the amino group. In the method for producing the addition cocondensation product of the present invention, in the reaction medium of pH 3 to 12, the electrophilic addition reaction of formalin to an aromatic amine is more likely to occur to an amino group rather than an aromatic ring. In this case, a compound having only an amino group will be an amino resin, but in the case of having a functional group such as a sulfone group, a carboxyl group, a hydroxyl group, or a methoxy group in the molecule, the electron density of the nitrogen atom of the amino group is lowered. Therefore, the addition reaction of formalin can be suppressed at the stage of the monomethylolation reaction. Similar to aromatic amines, addition reactions of formalin with aliphatic amines are suppressed by functional groups such as sulfone groups and carboxyl groups. In the present invention, it is presumed that the polymerization termination action is exhibited by the reaction selectivity of the above-mentioned amino-based polymerization terminator.

The amino-based polymerization terminator used in the present invention is water-soluble, and examples thereof include those represented by the above formulas (C) to (F). Specifically, sulfanilic acid, methanilic acid, naphthionic acid, 1-naphthylamine-6-sulfonic acid (clave acid), 1-naphthylamine-5-sulfonic acid (laurent acid), 1-naphthylamine-3,6-disulfonic acid. And N-methyl sulfonated urea, N, N-dimethyl sulfonated urea, compounds having a sulfone group such as sulfamic acid or alkali metal salts thereof, and the alkali metal salts include sodium salt, potassium salt, lithium salt and the like. Is mentioned.

The addition cocondensate of the present invention has an average molecular weight of 1,000.
To 50,000 is preferable, and about 2,000 to 20,000 is more preferable. Ratio Mw of the weight average molecular weight (hereinafter referred to as Mw) and the number average molecular weight (hereinafter referred to as Mn) of components having a molecular weight of 1000 or more in the formaldehyde addition cocondensate used in the present invention
If / Mn is 5.0 or less, it has a sufficient dispersion effect, but 3.
0 or less is more preferable. When Mw / Mn is larger than 5.0, the width of the molecular weight distribution becomes too wide, the amount of the active ingredient suitable for dispersion decreases, and the dispersibility deteriorates. In the present invention, the control of the polymerization rate, and the weight average molecular weight of 1,000 or more components
As the agent for controlling the ratio Mw / Mn of Mw and Mn to be 5.0 or less, the above-mentioned amino-based polymerization terminator is used.

The reactivity of the amino-based polymerization terminator depends on the type and number of functional groups. As the types of functional groups,
Besides the amino group, a sulfone group, a carboxyl group, a hydroxyl group, a methoxy group and the like are suitable, but a sulfone group and a carboxyl group are particularly preferable. With respect to the number of functional groups, the number of functional groups is usually one or more in addition to the amino group to exert a polymerization terminating action, but in the case of sulfone groups, it has one or two, and in the case of other functional groups, it has two or more. Is preferred.

Synthesis ratio (molar ratio) of the amino-based polymerization terminator used in the present invention and the total of the monomers of the general formulas (A) and (B)
Is [amino-based polymerization terminator]: [(A) + (B)] = 0.2:
1.0 to 5.0: 1.0 is good. Even if the amount of the polymerization terminator is naturally out of this range, there is a polymerization termination effect, but in general, when the amount is 0.2 mol or less relative to the total amount of the monomers, a sufficient polymerization termination effect is not expressed, which causes broadening of the molecular weight distribution and Mw. / Mn
Will increase. If it is 5 mol or more, the condensation reaction is controlled and the degree of condensation is difficult to increase.

The synthesis ratio of the monomers represented by the general formulas (A) and (B) is (A) :( B) = 0.1 to 1.0: 0.1 to 1.0
The range is excellent.

The pH range for producing the cocondensate of the present invention is preferably in the range of pH 3 to pH 12, particularly preferably pH 7 to 9. Further, as the amino-based polymerization terminator used in the pH range of 3 to 6, N, N-dimethylsulfonated urea and N-methylsulfonated urea which are compounds of the formula (E) are particularly excellent. If the pH is less than 3, the rate of condensation of the monomer will be remarkably high, so that the polymerization terminating action is difficult to be exhibited. On the other hand, when the pH exceeds 12, the condensation rate of the monomer is low, so that it takes a long time to condense to a predetermined molecular weight. The addition co-condensation reaction of formaldehyde can be carried out in the range of pH 7 to 11 under basic conditions, but considering the efficiency of the methylol addition reaction and condensation reaction, methylolation is carried out at pH 7.5 to pH 8.5, and then A two-step reaction by adjusting the pH, which is a condensation reaction at 9.5 to 11, is preferable.

The formaldehyde used to form these formaldehyde addition co-condensates preferably uses formalin at a concentration of 30-40% by weight in its aqueous solution, the amount of formalin being used is the total monomer for formalin condensation. The optimum amount of formaldehyde is 0.7 to 5 times mol, preferably 0.9 to 2.5 times mol. If the amount of formalin used is less than 0.7 times the molar amount of formaldehyde with respect to all the monomers, the condensation does not proceed so much and the monomer remains in the system. Further, when the amount of formaldehyde is more than 5 times the moles of all the monomers, the width of the molecular weight distribution becomes very wide, and Mw / Mn is
5.0 or higher. As a result, the dispersibility decreases.

As an example of the cement admixture of the present invention, the compound of the above (A), the compound of the above (B), and the following general formula
(C ')

[0033]

[Chemical 14]

[Here, X ₄ means an alkali metal. ] A cocondensate produced by using three components consisting of the compound represented by In this case, the general formula (A), (B)
And the constituent molar ratio of the compound represented by (C ′) is (A): (B):
(C ') = 0.1 to 1.0: 0.1 to 0.5: 0.5 to 1.0. The compound represented by the general formula (C ′) is sulfanilic acid or an alkali metal salt thereof, which is a kind of amino-based polymerization terminator.

The method for producing the addition cocondensate according to the present invention is not particularly limited, and as an example, a synthetic means usually used under basic conditions such as phenol, phenolsulfonic acid, and sulfanyl as an amino-based polymerization terminator is used. For example, there may be mentioned a method of adding formalin to these using an acid, or a method in which phenolsulfonic acid and / or sulfanilic acid is previously added with methylol with formalin and then phenol is added to carry out addition condensation.

An example of the standard method for producing the formaldehyde addition cocondensate of the present invention is shown below, but the present invention is not limited thereto. Measure a predetermined amount of phenol, sodium phenolsulfonate and sodium sulfanilate, which is an amino-based polymerization terminator, and water,
After adjusting the pH (7 to 8.5) and the solid content concentration, the reaction vessel is charged, and formalin (37% formaldehyde aqueous solution) is added dropwise thereto at 80 to 90 ° C for 1 to 3 hours. After the dropping, the mixture is stirred under reflux for 3 to 30 hours. Then cool to 30 ℃, pH 10 ~
Adjust to 11. The cement admixture of the present invention can be obtained by further stirring and cooling under reflux for 3 to 10 hours.

The cement admixture of the present invention can also utilize an oxidation reaction, for example, the oxidation reaction shown in JP-A-60-11257 and JP-A-62-202850. There is no change in the dispersant that has many functional groups.

The cement admixture of the present invention is concrete,
Mortar, used as a dispersant for cement compositions such as cement paste, the addition method is preferably added at the same time as water injection for the purpose of preventing slump loss,
It is also possible to add it immediately after pouring water until the end of kneading, or to the cement mixture once kneaded. The cement admixture of the present invention can also be used as a high performance water reducing agent as a dispersant for secondary products.

When the cement admixture of the present invention is used, it may be used alone or in combination with a known cement admixture. In particular, even if the cement admixture has a large slump loss, the slump loss can be improved by using the cement admixture of the present invention together. The mixing ratio of the cement of the present invention and a known cement admixture can be arbitrarily selected according to the purpose, but if the mixing amount of the cement admixture of the present invention is 5% by weight or less, the slump loss improving effect is not expected so much.
Known cement admixtures that can be used in combination with the cement admixture of the present invention include naphthalene sulfonic acid formaldehyde condensate or a metal salt thereof, alkylnaphthalene sulfonic acid formaldehyde condensate or a metal salt thereof, melamine sulfonic acid formaldehyde condensate or a metal thereof. Examples thereof include salts, ligninsulfonic acid or a metal salt thereof, oxycarboxylic acid or a metal salt thereof, polycarboxylic acid or a metal salt thereof, and the like. Among them, it is preferable to use one or more selected from the group consisting of naphthalene sulfonic acid formaldehyde condensate or a metal salt thereof, melamine sulfonic acid formaldehyde condensate or a metal salt thereof, and lignin sulfonic acid or a metal salt thereof. When the cement admixture of the present invention and the above-mentioned conventionally known cement admixture are used in combination, they may be premixed and used, or may be added separately and used without any particular limitation.

Further, the cement admixture of the present invention is another known cement additive (material) such as a high performance water reducing agent, a fluidizing agent, an AE agent, an AE water reducing agent, a retarder, an early strengthening agent, and an accelerator. , Foaming agents, water retention agents, thickeners, waterproofing agents, rust preventives, coloring agents, antifungal agents, crack reducing agents, polymer emulsions, blast furnace slag, water-soluble polymers, expanding agents, fly ash, silica fume and A sustained release dispersant and a sustained release foaming agent can be used in combination.

[0041]

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

Preparation Example of Cocondensate (1) Phenol (0.1 mol), sodium phenolsulfonate (0.5 mol) and sodium sulfanilate (1.0 mol) were placed in a reaction vessel equipped with a stirrer, and 0.1 N aqueous sodium hydroxide solution and water were added. The solution is adjusted to pH 8.5 and the solids concentration is adjusted to 35% by weight. Next, the temperature of this solution is raised to 85 ° C., and formalin (37% formaldehyde aqueous solution, the same applies below) is added with stirring (as formaldehyde.
2.0 mol), the reaction mixture is stirred under reflux for 8 hours. Then, cool to 30 ° C and adjust the pH with 40% aqueous sodium hydroxide.
After adjusting to 11, stirring under reflux for 12 hours, cooling, and then adding water to adjust the solid content concentration to 25% by weight to obtain the cement admixture of the present invention. Table 1 below shows the contents of the cocondensates Nos. 1 to 7 of the present invention produced according to Production Example (1).

[0043]

[Table 1]

Preparation Example of Cocondensate (2) A reactor equipped with a stirrer was charged with 0.6 mol of meta-cresol, 0.5 mol of sodium phenolsulfonate and 1.0 mol of sodium naphthionate, and 0.1N aqueous sodium hydroxide solution and water were added. The solution of the lever is adjusted to pH 8.5 and the solid content concentration is adjusted to 35% by weight. Next, the solution is heated to 85 ° C., formalin is added with stirring (2.4 mol of formaldehyde), and the reaction mixture is stirred under reflux for 8 hours. Then, the mixture was cooled to 30 ° C., adjusted to pH 11 with a 40% aqueous sodium hydroxide solution, stirred under reflux for 12 hours, cooled, and then water was added to adjust the solid content concentration to 25% by weight. To obtain a cement admixture. Table 2 below shows the contents of the cocondensates Nos. 8 to 10 of the present invention produced according to Production Example (2).

[0045]

[Table 2]

Preparation Example of Cocondensate (3) 0.5 mol of phenol, 0.5 mol of sodium metacresolsulfonate and 1.0 mol of sodium sulfamate were charged into a reaction vessel equipped with a stirrer, and 0.1 N aqueous sodium hydroxide solution and water were added. The leverage is adjusted to pH 8.5 and the solids concentration is 35% by weight. Next, the solution is heated to 85 ° C., formalin is added with stirring (2.0 mol of formaldehyde), and the reaction mixture is stirred under reflux for 8 hours. Then, the mixture was cooled to 30 ° C., adjusted to pH 11 with a 40% aqueous sodium hydroxide solution, stirred under reflux for 12 hours, cooled, and then water was added to adjust the solid content concentration to 25% by weight. To obtain a cement admixture. Table 3 below shows the contents of the cocondensates Nos. 11 to 13 of the present invention produced according to Production Example (3).

[0047]

[Table 3]

Production Example of Cocondensate (4) 0.5 mol of phenol, 0.5 mol of sodium phenolsulfonate and 1.0 mol of sodium sulfanilate were charged into a reaction vessel equipped with a stirrer, and a 0.1 N sodium hydroxide aqueous solution and water were added. The solution is adjusted to pH 8.5 and the solids concentration is 35% by weight. Next, this solution is heated to 85 ° C., formalin is added with stirring (2.0 mol of formaldehyde), and the reaction mixture is stirred under reflux for 5 to 30 hours (first step). Then, cool to 30 ° C, adjust to pH 11 with 40% sodium hydroxide aqueous solution, stir under reflux for 6 hours (second step), and after cooling, add water to adjust the solid concentration to 25% by weight. Adjust to obtain the cement admixture of the present invention. Table 4 below shows the contents of the cocondensates Nos. 14 to 16 of the present invention produced according to Production Example (4).

[0049]

[Table 4]

Production Example of Cocondensate (5) In a reaction vessel equipped with a stirrer, 1.0 mol of phenol, 0.2 mol of phenolsulfonic acid and 6-amino-4-hydroxy-2 were added.
-Prepare 0.2 mol of sodium naphthalene sulfonate and 0.8 mol of N-methyl sulfonated urea, and add 10% aqueous sodium hydroxide solution and water to adjust the pH of the solution to 5.6 and the solid concentration to 35% by weight. Then, the prepared solution is heated to 85 ° C., formalin is added with stirring (2.5 mol of formaldehyde), and the reaction mixture is stirred under reflux for 10 hours. After cooling, add water to adjust the solids concentration to 25.
The cement admixture of the present invention is obtained by adjusting the content to be wt%. Table 5 below shows the contents of the cocondensates Nos. 17 to 19 of the present invention produced according to Production Example (5).

[0051]

[Table 5]

Cement admixture No. 20 and 21 As cement admixture No. 20, 70% by weight of the cocondensate No. 1 obtained in Production Example (1) and a naphthalene-based dispersant (Mighty 150; Kao ( A cement admixture was prepared using 30% by weight (manufactured by K.K.). As the cement admixture No. 21, 50% by weight of the cocondensate No. 3 obtained in Production Example (1) and 50% by weight of a melamine dispersant (Melment; Showa Denko KK) were used. A cement admixture was prepared. The following evaluation was performed using these.

Evaluation as Cement Admixture (1) The mix proportion of concrete was as follows. W / C = 55% S / A = 49% C = 320 kg / m ³ where C is cement, W is water, S is fine aggregate, and A is total aggregate. (2) The materials used are shown below. Cement = Central Portland Cement Fine aggregate = Kinokawa coarse aggregate = Takarazuka crushed stone (3) The mixer used was a tilting type and was kneaded for 3 minutes, then rotated 4 times for 1 minute and stirred for 60 minutes. Table 6 shows the obtained evaluation results.

[0054]

[Table 6]

* Addition amount: solid content% relative to cement * addition amount: solid content relative to cement ** Comparative product A naphthalene-based dispersant (Mighty 150: Kao Corporation) ** Comparative product B-melamine-based dispersant ( (Melment: Showa Denko KK) Evaluation results As shown in Table 6, the admixture of the present invention has a smaller difference between immediately after the slump value and after 60 minutes than the comparative example, and has an excellent water reducing effect and slump loss. It has a remarkable effect on prevention.

[0056]

By using the formaldehyde addition cocondensate of the present invention as a cement admixture, functional groups are adsorbed on the surface of cement particles to increase the charge density and prevent agglomeration over time, thus improving slump loss. To be done.

Claims (6)

[Claims] 1. A co-condensate obtained by addition co-condensing with formaldehyde using a compound represented by the following general formulas (A) and (B) in combination with an amino-based polymerization terminator as an essential component: Cement admixture. [Chemical 1] [Here, R ₁ means hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms. ] [Chemical 2] [Here, R ₂ represents hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms, and X ₁ represents an alkali metal. ] 2. An amino-based polymerization terminator represented by the following general formula (C),
The cement admixture according to claim 1, which is one or more compounds selected from the group of compounds represented by (D), (E) and (F). [Chemical 3] [Wherein X ₂ is hydrogen, an alkyl group having 1 to 3 carbon atoms, a carboxyl group or an alkali metal salt thereof, a sulfone group or an alkali metal salt thereof, a hydroxyl group and a methoxy group, and Y ₁ is a carboxyl group or It is selected from the group consisting of alkali metal salts and sulfone groups or alkali metal salts thereof. ] [Chemical 4] [Wherein X ₃ is hydrogen, an alkyl group having 1 to 3 carbon atoms, a carboxyl group or an alkali metal salt thereof, a sulfone group or an alkali metal salt thereof, a hydroxyl group and a methoxy group, and Y ₂ is a carboxyl group or It is selected from the group consisting of alkali metal salts and sulfone groups or alkali metal salts thereof. ] [Chemical 5] [Wherein Z ₁ is hydrogen, an alkyl group having 1 to 3 carbon atoms and -CH ₂
It is selected from the group consisting of SO ₃ M ₁ and M ₁ means hydrogen or an alkali metal. ] Formula _{(F) H 2 NSO 3 M} 2 [wherein M ₂ is a hydrogen or an alkali metal. ] 3. A cocondensate obtained by addition cocondensation of three components consisting of compounds represented by the following general formulas (A), (B) and (C ′) with formaldehyde as an essential component: Cement admixture. [Chemical 6] [Here, R ₁ means hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms. ] [Chemical 7] [Here, R ₂ represents hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms, and X ₁ represents an alkali metal. ] [Chemical 8] [Here, X ₄ means an alkali metal. ] 4. The constitutional molar ratio of the compounds represented by the general formulas (A), (B) and (C ′) is (A) :( B) :( C ′) = 0.1 to 1.0: 0.1
-0.5: 0.5-1.0 The cement admixture according to claim 3. 5. A method for producing concrete, which comprises using the cement admixture according to claim 1 in combination with another cement admixture. 6. The cement admixture used in combination is one selected from the group consisting of a naphthalene sulfonic acid formaldehyde condensate or a metal salt thereof, a melamine sulfonic acid formaldehyde condensate or a metal salt thereof, and a lignin sulfonic acid or a metal salt thereof. Alternatively, the method for producing concrete according to claim 5, wherein there are two or more kinds.