JPH05213644A - Method for preventing slump loss of cement mixture - Google Patents

Abstract

PURPOSE:To prevent a decrease in flowability by mixing a coploymer of the alkylene oxide-addition monomer and carboxylic monomer shown by specified formulas or the neutralized copolymer as a slump loss preventive agent. CONSTITUTION:From 10 to 80wt.% of an alkylene oxide-addition monomer shown by formula I (X is H or methyl, R is 2-3C alkylenes, R<2> is H or 1-5C alkyls, and (n) is 1 to 100), 20-90wt.% of a carboxylic monomer shown by formula II (M is H, mono- or bivalent metal, ammonium salts or org. amine, and Y is H or methyl) and <=30wt.%, based on the total amt. of the monomers, of a copolymerizable monomer are mixed. A specified amt. of a polymerization initiator is then added to bring about a polymerization reaction, and a copolymer having 50,000-500,000 average mol.wt. is obtained. An aggregate, a water reducing agent and water are mixed into cement to obtain a base concrete, and 0.005-2.5wt.% of the copolymer as a slump loss preventive agent, a cement dispersing agent, etc., are added to the base concrete to obtain a concrete excellent in workability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing slump loss of a cement mixture using a slump loss inhibitor having a cement dispersibility, and more specifically, cement mortar,
Slump of cement mixture using a chemical agent that is added to cement mixture such as concrete to improve its fluidity and prevent deterioration of fluidity over time (hereinafter referred to as slump loss) to improve workability. It relates to a loss prevention method.

[0002]

2. Description of the Related Art Cement compounds such as mortar and concrete have low workability due to a decrease in consistency with the lapse of time after mixing due to a hydration reaction between cement and water. This phenomenon is generally called slump loss.

Slump loss in cement formulations is
In the ready-mixed concrete, there are obstacles such as limitation of transportation time, quality change due to waiting time at the pouring site, poor workability, deterioration of durability due to cold joint, etc. Also, at a secondary concrete product manufacturing plant, etc., when pumping cement mixture was temporarily suspended during lunch break or due to a trouble, and then pumping was restarted, the pumping pressure suddenly increased or the pump clogged. Next to
In addition, after the cement mixture is driven into the mold, if the molding such as compaction is delayed for some reason, problems such as unfilling occur. Therefore, the slump loss in the cement mixture is an important problem that must be solved in the ready-mixed concrete factory, the secondary product manufacturing factory and the like in order to improve the quality control of the cement composition and to improve the workability.

Conventionally, as a measure for preventing slump loss,
The following methods were known.

A) A method of increasing the unit water content of concrete.

(B) A method by post-adding a cement dispersant.

C) A method in which a cement dispersant is repeatedly added.

D) A method in which a setting retarder is added or combined with a cement dispersant.

The above method (a) is a method of increasing the unit amount of water in consideration of the slump loss until the cement compound is placed. However, although the workability can be improved by this, the cured product can be improved. This is accompanied by a quality disadvantage that the durability is reduced due to a decrease in strength and cracking due to drying shrinkage, or an economical disadvantage that the unit cement amount is increased to obtain a predetermined strength.

The method (b) is a temporary measure for improving the fluidity, and the cement dispersant remains locally in the cement mixture even after the purpose of maintaining the slump is finished, and local breathing occurs. As a result, it causes adverse effects such as a decrease in strength.

The method (c) is a method of re-adding the admixture at the time of slump loss, and does not completely prevent slump loss. Moreover, there is a disadvantage in workability and economical efficiency of repeated addition.

In the method (d), a delaying agent such as oxycarboxylic acid salt, lignin sulfonate, dextrin, humic acid or the like is used alone or in combination with a cement dispersant to delay the setting time of the cement mixture and to improve the fluidity. However, in the case of excessive addition, there is a great risk of causing an accident such as strength reduction or curing failure.

As described above, each of the methods has its own drawbacks, which is a problem in practical use.

[0014]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of intensive investigations by the inventors of the present invention, the above-mentioned drawbacks have been improved, and a chemical agent which can be added to a cement composition to enhance its fluidity and prevent slump loss has been obtained. The present invention has been reached by finding that a specific copolymer is effective.

[0015]

That is, the present invention is based on the general formula

[0016]

[Chemical 3]

(Wherein X represents hydrogen or a methyl group, R ¹ represents an alkylene group having 2 to 3 carbon atoms, and R ²
Represents hydrogen or an alkyl group having 1 to 5 carbon atoms, and n is 1
Is a positive integer of -100. ) Alkylene oxide addition monomer (a) represented by the general formula

[0018]

[Chemical 4]

(Wherein, M represents hydrogen, a monovalent metal, a divalent metal, an ammonium group or an organic amine group, and Y represents hydrogen or a methyl group). ) And a monomer (c) copolymerizable with these monomers, the alkylene oxide addition monomer (a) is
Carboxylic acid monomer (b) is 20 to 90 at 80% by weight
% By weight (however, the total of the components (a) and (b) is 100% by weight) and the proportion of the monomer (c) is 30% by weight or less in all the monomers. A slump loss inhibitor comprising a copolymer (A) having an average molecular weight of 50,000 to 500,000 obtained by using the copolymer and / or a copolymer (B) obtained by further neutralizing the copolymer (A) with an alkaline substance. The present invention relates to a method for preventing slump loss of a cement mixture, which comprises mixing with a cement mixture slump-conditioned with a cement dispersant.

[0020]

The monomer (a) used in the present invention is represented by the above-mentioned general formula, for example, unsaturated carboxylic acids such as acrylic acid and methacrylic acid.

[0021]

[Chemical 5]

(Provided that R ¹ , R ² and n are as described above) and obtained by adding ethylene oxide or propylene oxide to the esterified product of a monohydric or dihydric alcohol or the unsaturated carboxylic acid. Examples thereof include esterified compounds, and one or more of these can be used. Further, the addition mole number of the alkylene oxide represented by the above n per carboxyl group of the unsaturated carboxylic acid is appropriately 1 to 100,
It is not preferable to use the monomer (a) added more than that, because the polymerization yield is lowered.

The monomer (b) used in the present invention is represented by the above-mentioned general formula, for example, acrylic acid, methacrylic acid, or a monovalent metal salt or divalent metal salt thereof,
Examples thereof include ammonium salts and organic amine salts, and one or more of these can be used.

The monomer (c) optionally used in the present invention is a monomer copolymerizable with the monomer (a) and the monomer (b) and has, for example, 1 to 20 carbon atoms. Esters of aliphatic alcohol and (meth) acrylic acid; maleic acid, fumaric acid or aliphatic acids having 1 to 20 carbon atoms or glycols having 2 to 4 carbon atoms or addition moles of these glycols Monoesters or diesters with polyalkylene glycols having a number of 2 to 100; unsaturated amides such as (meth) acrylamide and (meth) acrylalkylamide; vinyl esters such as vinyl acetate and vinyl propionate; aroma such as styrene Group vinyls; unsaturated such as vinyl sulfonic acid, allyl sulfonic acid, sulfoethyl (meth) acrylate, styrene sulfonic acid Sulfonic acids and their monovalent metal salts, divalent metal salts, ammonium salts, organic amine salts, and the like, can be used alone or in combination of two or more thereof.

The copolymer (A) is obtained by using the monomer (a), the monomer (b) and the monomer (c) in the above specified ratio. When the ratio is out of the range, that is, when the amount of the monomer (a) is less than 10% by weight in the total amount of the monomer (a) and the monomer (b), the obtained copolymer An unfavorable action such as the retardation of setting is exerted on the polymer. Further, when the amount of the monomer (C) is set to a large amount exceeding 30% by weight based on the total amount of the monomers, the slump loss preventing performance of the resulting copolymer becomes insufficient, which is not preferable. Further, the obtained copolymer (A) and / or (B)
Considering the cement dispersion performance of the copolymer (A)
When obtaining, the amount of the monomer (b) is preferably 20% by weight or more based on the total amount of the monomer (a) and the monomer (b). That is, when the amount of the monomer (B) is less than 20% by weight, the slump loss prevention performance is good but the cement dispersion performance is inferior.

The average molecular weight of the copolymer (A) which is effective as a slump loss preventing agent in the present invention is in the range of 50,000 to 500,000 which is a relatively high molecular weight if the amount of entrained air and the slump loss preventing performance are important. Those are preferable.

To produce the copolymer (A), the above-mentioned monomer components may be copolymerized using a polymerization initiator. The copolymerization can be carried out by a method such as polymerization in a solvent or bulk polymerization.

Polymerization in a solvent can be carried out batchwise or continuously, and the solvent used in this case is water; lower alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol; benzene, toluene, xylene, Examples thereof include aromatic or aliphatic hydrocarbons such as cyclohexane and n-hexane; ethyl acetate; ketone compounds such as acetone and methyl ethyl ketone. At least selected from the group consisting of water and a lower alcohol having 1 to 4 carbon atoms in view of the solubility of the raw material monomer and the resulting copolymer (A) and the feasibility of using the copolymer (A). It is preferable to use one kind. Among the lower alcohols having 1 to 4 carbon atoms, methyl alcohol, ethyl alcohol and isopropyl alcohol are particularly effective.

When carrying out the polymerization in an aqueous medium, a water-soluble polymerization initiator such as ammonium or alkali metal persulfate or hydrogen peroxide is used as the polymerization initiator. At this time, an accelerator such as sodium hydrogen sulfite can be used in combination. For polymerization using lower alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, ethyl acetate or ketone compounds as solvents, peroxides such as benzoyl peroxide and lauroyl peroxide; hydroperoxides such as cumene hydroperoxide; azo Aliphatic azo compounds such as bisisobutyronitrile are used as polymerization initiators. At this time, an accelerator such as an amine compound may be used in combination. Furthermore, when a water-lower alcohol mixed solvent is used, it can be appropriately selected and used from the above-mentioned various polymerization initiators or a combination of a polymerization initiator and an accelerator. The polymerization temperature is appropriately determined depending on the solvent used and the polymerization initiator, but is usually within the range of 0 to 120 ° C.

The bulk polymerization is carried out using a peroxide such as benzoyl peroxide or lauroyl peroxide; a hydroperoxide such as cumene hydroperoxide; an aliphatic azo compound such as azobisisobutyronitrile, etc. It is performed within a temperature range of 150 ° C.

Copolymer (A) thus obtained
Is used as it is as a slump loss preventing agent in the present invention, but if necessary, a copolymer (B) obtained by further neutralizing with an alkaline substance may be used as a slump loss preventing agent in the present invention. . Preferred examples of such alkaline substances include hydroxides, chlorides and carbonates of monovalent and divalent metals; ammonia; organic amines and the like.

The copolymers (A) and / or (B), which are the slump loss preventing agents in the present invention, have excellent slump loss preventing performance, and therefore, when used by mixing with a known cement dispersant, It can be used as a cement dispersant having excellent loss prevention performance.

Examples of the above-mentioned known cement dispersant include naphthalene sulfonate formalin condensate, sulfonate formalin condensate of a mixture containing naphthalene and alkylnaphthalene, melamine sulfonic acid formalin condensate, lignin sulfonic acid, Examples thereof include oxycarboxylic acid, polycarboxylic acid and salts thereof.

Further, the slump loss preventive agent in the present invention is a curing retarder, a curing accelerator, an air entraining agent, a cement wetting and dispersing agent, a waterproofing agent, a defoaming agent, a strength enhancing agent, an expanding agent and other cement admixtures. You may use together.

The addition amount of the slump loss preventing agent in the present invention is preferably 0.005% to 2.5% as the solid content weight% with respect to the cement in the cement mixture. 0.005
If it is less than%, sufficient slump loss prevention performance may not be obtained. On the other hand, if the amount exceeds 2.5%, it may be economically disadvantageous and may cause problems such as delay of setting and excessive amount of entrained air.

The slump loss preventive agent of the present invention can be used in a cement mixture using hydraulic cement such as various portland cements, fly ash cements, various mixed cements and special cements.

The slump loss inhibitor of the present invention is most preferably added to the cement mixture in the form of an aqueous solution, but it may be powder or granules.
When it is used in the form of an aqueous solution, it may be added to the water mixed with the cement mixture, or it may be added after mixing the cement mixture. When used in the form of powder or granules, they can be premixed with cement or components of a cement compound such as aggregate, and then kneaded.

[0038]

EXAMPLES The slump loss prevention method of the present invention will now be described in more detail with reference to reference examples and examples, but the present invention is not limited thereto. still,
Unless otherwise specified,% means% by weight and part means part by weight.

[0039]

Reference Example 1 A glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was filled with water 38
After charging 6.5 parts, the inside of the reaction vessel was replaced with nitrogen while stirring,
Heated to 95 ° C. under nitrogen atmosphere. Then, a monomer aqueous solution consisting of 196 parts of methoxypolyethylene glycol monomethacrylate (average number of moles of ethylene oxide added: 10), 84 parts of sodium methacrylate and 120 parts of water and 9.0 parts of a 5% ammonium persulfate aqueous solution are each used for 2 hours. After the completion of the addition, 4.5 parts of a 5% ammonium persulfate aqueous solution was added over 1 hour. Thereafter, the temperature was kept at 95 ° C. for 1 hour to complete the polymerization reaction to obtain an aqueous solution of the copolymer (1) having an average molecular weight of 170,000. The copolymer (1) obtained had a viscosity of 40 cps at a temperature of 25 ° C. and a concentration of 5%.

[0040]

Reference Example 2 A glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was charged with water 39
5.5 parts was charged, the inside of the reaction vessel was replaced with nitrogen while stirring,
Heated to 95 ° C. under nitrogen atmosphere. Next, a monomer aqueous solution consisting of 140 parts of methoxy polyethylene glycol monomethacrylate (average number of moles of ethylene oxide added: 50), 60 parts of sodium methacrylate and 200 parts of water and 3.0 parts of a 5% ammonium persulfate aqueous solution are each used for 2 hours. After the completion of the addition, 1.5 parts of a 5% ammonium persulfate aqueous solution was further added over 1 hour. After that, the temperature was kept at 95 ° C. for 1 hour to complete the polymerization reaction to obtain an aqueous solution of the copolymer (2) having an average molecular weight of 230,000. The viscosity of the obtained copolymer (2) at 25 ° C. and a concentration of 5% was 110 cps.

[0041]

[Example 1] Ordinary Portland cement (manufactured by Sumitomo Cement Co., Ltd.) as cement, Yodogawa-produced river sand (maximum particle size 5 mm) as fine aggregate, Takatsuki crushed stone (maximum particle size 25 mm) and AE water reducing agent as coarse aggregate As Pozzolis No. 70 is used, the unit cement amount is 320 kg / m ³ , the unit water amount is 169 kg
/ M ³ (water / cement ratio 52.8%), unit fine aggregate 8
83 kg / m ³ , unit coarse aggregate amount 933 kg / m ³ (fine aggregate ratio 48.6%) and unit AE water reducing agent amount 0.8 kg / m ³ , so that the mixing amount is 30 liters Each material was weighed and all materials were put into the tilting mixer. Immediately kneading was performed for 3 minutes, and the total amount of the obtained base concrete having a target slump of 8 cm and a target air amount of 4% was discharged from the mixer. Next, the total amount of the base concrete was returned to the mixer, and the amount of the copolymer (1) obtained in Reference Example 1 was 0.1% based on the solid content of cement and a naphthalenesulfonic acid sodium salt formalin condensate as a cement dispersant. Was added to the mixer in an amount of 0.25% based on the solid content of cement and kneaded for 2 minutes to prepare fluidized concrete.

Immediately after the fluidized concrete was completely discharged from the mixer, the slump and the amount of air immediately after preparation were measured. Next, the whole amount of fluidized concrete was returned to the mixer again, and kneading was continued for a predetermined time at a low speed, and after 30 minutes, 6
The slump after 0 minutes and 90 minutes was measured, and the change with time of the slump was observed.

The compressive strength and setting time of the fluidized concrete obtained were also measured. The results of these measurements are shown in Table 1.

The slump, the amount of air, the compressive strength and the setting time, and the method for sampling the compressive strength specimen are all in accordance with Japanese Industrial Standards (JIS A 1101, 1128, 1108, 62).
04,1132).

[0045]

Example 2 Example 1 was repeated except that the copolymer (2) obtained in Reference Example 2 and the melamine sulfonic acid sodium salt formalin condensate as a cement dispersant were used in the addition amounts shown in Table 1. The same operation was repeated to prepare fluidized concrete, and their slump, air content, compressive strength and setting time were measured. The measurement results are shown in Table 1.

[0046]

Comparative Example 1 A fluidized concrete for comparison was prepared by repeating the same operation as in Example 1 except that the copolymer (1) was not used, and its slump, air content and compressive strength were compared. And the setting time was measured. The measurement results are shown in Table 1.

[0047]

Comparative Example 2 A fluidized concrete for comparison was prepared by repeating the same operation as in Example 2 except that the copolymer (2) was not used in Example 2, and its slump, air content and compression strength were compared. And the setting time was measured. The measurement results are shown in Table 1.

[0048]

[Table 1]

[0049]

The anti-slump loss agent of the present invention is
It consists of a specific copolymer (A) and / or a copolymer (B), but when the average molecular weight of the copolymer (A) and / or (B) is 50,000 to 500,000, various known cement dispersants This makes it possible to prevent a decrease in fluidity over time of the cement mixture adjusted so as to give a predetermined slump, and further increase or decrease the inherent cement dispersibility of a known cement dispersant. Without
Therefore, it is easy to arbitrarily adjust the fluidity of the cement mixture.

Due to the above effects, the slump loss preventive agent of the present invention meets the demand of the customers who demand a cement composition having a small slump loss and a fluidity accurately controlled to a desirable range.

Continued Front Page (72) Inventor Yasuhiro Mori 4-10 Nakanoshima-cho, Suita City, Osaka Prefecture

Claims (1)

[Claims] 1. A general formula: (However, in the formula, X represents hydrogen or a methyl group, R ¹ represents an alkylene group having 2 to 3 carbon atoms, R ² represents hydrogen or an alkyl group having 1 to 5 carbon atoms, and n is 1 to 100. Is a positive integer.) Alkylene oxide addition monomer (a) represented by the general formula: (However, in the formula, M represents hydrogen, a monovalent metal, a divalent metal, an ammonium group or an organic amine group, and Y represents hydrogen or a methyl group.) And a carboxylic acid-based monomer (b) and these. 10% to 80% by weight of the alkylene oxide addition monomer (a) is a monomer (c) copolymerizable with the above monomer.
The proportion of the carboxylic acid-based monomer (b) is 20 to 90% by weight (however, the total of the components (a) and (b) is 100% by weight), and the amount of the monomer (c) is all. Obtained by further neutralizing the copolymer (A) having an average molecular weight of 50,000 to 500,000 and / or the copolymer (A) obtained by using it in a ratio such that the content of the monomer is 30% by weight or less with an alkaline substance. A slump loss preventing method for a cement mixture, comprising mixing a slump loss preventing agent comprising the copolymer (B) as described above with a cement mixture slump-conditioned with a cement dispersant.