JP2006335620A - Cement admixture and extra quick hardening cement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement admixture which can impart high hardening property and improve workability and which can be stored for a long period of time without deteriorating its performances and is suitable for premixing; and an extra quick hardening cement. <P>SOLUTION: The cement admixture contains a powdery cement dispersing agent which is obtained by adding a reducing inorganic compound and a reducing organic compound to a liquid containing, as main components, (A) calcium aluminates, (B) gypsum, (C) lithium carbonate, (D) anhydrous sodium sulfate and (E) a polycarboxylic acid-based polymer having polyalkylene glycol chain, and then drying and pulverizing the resulting mixture. The extra quick hardening cement contains the cement admixture and (G) portland cement. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a ready-mixed cement admixture for imparting rapid hardening to various cement compositions and an ultrafast cement using the admixture.
More specifically, cement admixtures used for early demolding of concrete products, repair work, shortening work periods for emergency work and general work, improving strength development in winter, and improving work quality by improving workability The present invention relates to an ultrafast cement using the admixture.

Conventionally, as a method for accelerating the hardening of a cement composition such as concrete or mortar, there is a method of achieving rapid hardening by adding an admixture mainly composed of calcium aluminate and gypsum and generating ettringite at an early stage. . Further, in order to improve the workability of such a fast-hardening cement composition, a cement dispersant mainly composed of a polycarboxylic acid polymer compound is used.
In recent years, for applications to be pre-prepared (pre-mixed) in fast-hardening cement compositions, liquids containing polycarboxylic acid-based polymer compounds having polyalkylene glycol chains as the main component are reduced inorganic compounds and reducing organics. It has been proposed to use a powdered cement dispersant obtained by adding a compound and then powdered into a dry powder (see Patent Document 1). By preparing the powdered cement dispersant in a quick-hardening cement composition, it became possible to maintain good fluidity (workability) without impairing fast-hardening properties.
Japanese Patent Laid-Open No. 2001-39761

However, even if the above-mentioned pre-prepared product is used, the workability immediately after the compounding is good. However, after the pre-prepared product is stored for a long period of time, problems such as deterioration of workability may occur.
Accordingly, an object of the present invention is to provide a fast-hardening cement composition that can be stored for a long time without deteriorating workability.

  As a result of diligent research to solve the above-mentioned problems, the present inventor, when pre-prepared products are stored for a long period of time, the fast-hardening cement composition has a high reaction activity, and thus reacts with moisture in the air, so The activity has changed over time, the amount of adsorption to the surface of the dispersant has changed, the knowledge that workability has been reduced due to changes in the dispersion effect has been obtained, and further, by blending specific inorganic salts, It has been found that long-term storage is possible without deteriorating the hardness and workability, and the present invention has been completed.

That is, the present invention provides (A) calcium aluminate, (B) gypsum, (C) lithium carbonate, (D) anhydrous sodium sulfate, and (E) a polycarboxylic acid polymer compound having a polyalkylene glycol chain. A cement admixture containing a powdered cement dispersant obtained by adding a reducible inorganic compound and a reducible organic compound to a liquid as a main component and then forming a dry powder.
Moreover, this invention is the super-fast-hardening cement containing this cement admixture and (G) Portland cement.

  The cement admixture of the present invention is a cement admixture suitable for pre-preparation that can impart quick hardening, can further improve workability, and can be stored for a long time without lowering these performances.

(A) Calcium aluminates used in the cement admixture of the present invention impart quick hardening to mortar or concrete. “Calcium aluminate” is a general term for a compound, a solid solution, a vitreous substance or a mixture thereof containing at least CaO and Al ₂ O ₃ as main components. Examples of such calcium aluminates include C ₁₂ A ₇ (12CaO · 7Al ₂ O ₃ ), C ₃ A (3CaO · Al ₂ O ₃ ), C ₁₁ A ₇ · CaF ₂ (11CaO · 7Al ₂ O _3). · CaF ₂ ), NC ₈ A ₃ (Na ₂ O · 8CaO · 3Al ₂ O ₃ ), Erwin (3CaO · 3Al ₂ O ₃ · CaSO ₄ ), CA (CaO · Al ₂ O ₃ ) and CA ₂ (CaO · 2Al ₂ O ₃ ) and alumina cement. A known apparatus such as an electric furnace or kiln can be used for firing the calcium aluminate. A normal pulverizer can be used for pulverization. The calcium aluminates used in the present invention preferably have a Blaine specific surface area of 4000 cm ² / g or more from the viewpoint of imparting quick hardening.
Calcium aluminates are preferably contained in the cement admixture of the present invention in an amount of 30 to 80% by weight, and particularly preferably 40 to 70% by weight.

The (B) gypsum used in the cement admixture of the present invention produces ettringite when used in combination with calcium aluminates, and imparts the action of increasing the short-time strength of fast-hardening mortar or fast-hardening concrete. The gypsum includes anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. From the viewpoint of improving strength for a short time, anhydrous gypsum having a brain specific surface area of 4000 cm ² / g or more is preferable. Moreover, as (B) gypsum, any of chemical gypsum, natural gypsum, waste gypsum board by-products, etc. can be used. A normal crusher can be used for crushing gypsum. The blending amount of gypsum is preferably 20 to 150 parts by weight, particularly preferably 40 to 120 parts by weight, per 100 parts by weight of calcium aluminates.

  (C) Lithium carbonate used in the cement admixture of the present invention accelerates the reaction of calcium aluminates and, when used in combination with gypsum, imparts an effect of increasing the short-time strength of fast-hardening mortar or fast-hardening concrete. Alkali metal carbonates other than lithium, such as sodium carbonate and potassium carbonate, have an effect of increasing strength in a short time, but lithium salt is much more effective, and lithium salt is more effective when used with a retarder. In addition, it is preferable because the pot life can be easily maintained. The blending amount of lithium carbonate is preferably 1 to 15 parts by weight, particularly preferably 3 to 10 parts by weight with respect to 100 parts by weight of calcium aluminates.

(D) Anhydrous sodium sulfate used in the present invention has a function of improving the long-term storage stability of fast-hardening cements and admixtures. Since anhydrous sodium sulfate has a hygroscopic property, pre-mixing it absorbs moisture in the air, prevents the calcium aluminate particle surface from reacting with moisture and changing the reaction activity, and is stored for a long time. Thereafter, the action of the dispersant can be stably maintained. Sodium sulfate contains hydrated salts such as decahydrate and heptahydrate, but heptahydrate is metastable and difficult to use industrially. The effect on sex is not enough.
Further, sodium sulfate has an effect of increasing the sulfate ion concentration in the liquid phase when mortar or concrete is used. When the sulfate ion concentration in the liquid phase increases, competitive adsorption with the cement dispersant described later occurs, and acts as a buffering agent for fluctuations in the amount of adsorption of the dispersant. Therefore, even if the effect of the dispersant fluctuates due to long-term storage, the effect is interfered by the presence of sodium sulfate, and the fluctuation range of the effect can be reduced. However, the effect of sodium sulfate alone is not sufficient for improving long-term storage stability, and must be combined with the hygroscopic effect of anhydrous sodium sulfate.

  The average particle diameter of anhydrous sodium sulfate is preferably 100 μm or less. When exceeding 100 micrometers, a particle size is too coarse and the effect which absorbs the moisture in air falls. The lower limit of the particle size is not particularly defined, but if it is too fine, the dissolution rate will be too high, and the concentration of sulfate ions in the liquid phase will increase before the powder dispersant dissolves. This is not preferable because it may take a long time to mix. A preferable average particle diameter is 5 to 100 μm. In addition, in this specification, the average particle diameter measured 50% passage particle diameter using the laser particle size distribution measuring apparatus, and made this the average particle diameter.

From the viewpoint of long-term storage stability, the amount of anhydrous sodium sulfate is preferably 2 parts by weight or more, particularly preferably 2 to 10 parts by weight, based on 100 parts by weight of calcium aluminates.
Anhydrous sodium sulfate is preferred because it can increase the strength for a short time when used in combination with lithium carbonate. The solubility of lithium carbonate is relatively low as an alkali salt, and it is considered that the strength of lithium carbonate is increased in a short time in order to increase the solubility of lithium carbonate in combination with sodium sulfate and enhance the reaction promoting effect. Considering the strength enhancement for a short time, the amount of anhydrous sodium sulfate added is preferably 50 to 200 parts by weight, particularly 70 to 200 parts by weight with respect to 100 parts by weight of lithium carbonate.

(E) A reductive inorganic compound and a reducible organic compound are added to a liquid mainly composed of a polycarboxylic acid polymer compound having a polyalkylene glycol chain used in the cement admixture of the present invention, and then dried into powder. The powdered cement dispersant obtained by dispersing has the function of improving the workability by dispersing the powder particles in the fast-hardening mortar or fast-hardening concrete.
It is essential that the premix dispersant used for the quick-hardening cement is in powder form. When an aqueous dispersant is used, it cannot be used because the moisture in the dispersant and the fast-hardening component may react and solidify. As powdered dispersants, there are already melamine sulfonic acid-based dispersants and naphthalene sulfonic acid-based dispersants, but these have low dispersion ability and adversely affect fast curing. In addition, polycarboxylic acid-based dispersants are difficult to be powdered, and there is a problem in that rapid hardening and workability are reduced by powdering.
However, a powdery cement dispersant obtained by adding a reducing inorganic compound and a reducing organic compound to a liquid mainly composed of a polycarboxylic acid-based polymer compound having a polyalkylene glycol chain, and then drying the powder. Compared with other dispersants, it is possible to ensure excellent fluidity (workability) with a relatively small amount of use, and further, it has the feature that it does not impede fast curing.

The polycarboxylic acid polymer compound having a polyalkylene glycol chain is not particularly limited. For example, (E ¹ ) a (meth) acrylic acid copolymer having a polyalkylene glycol chain and (E ² ) a polyalkylene glycol chain. (However, in the case of (E ² ), a polyvalent metal salt is excluded) and the like may be used, and these may be used alone or in combination of two or more.

Among these, (E ¹ ) is a (meth) acrylic acid group having a group —COOM (wherein M represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an organic amine) and a polyalkylene glycol chain. A copolymer is mentioned as a preferable thing. Examples of (E ² ) include polyalkylene glycol alkenyl ether-maleic anhydride copolymers (excluding polyvalent metal salts) and the like.

M of the (E ¹⁾ (meth) in groups -COOM acrylic acid copolymer is a hydrogen atom; alkali metals such as sodium and potassium; alkaline earth metals such as calcium and magnesium; ammonium or organic amines are preferred .

Further (E ¹⁾ (meth) as preferred acrylic acid copolymer is present in all the structural units, the structural unit (1) 40 to 80 mole% represented by the following formula (1), the following equation The structural unit (2) represented by (2) is 0.5 to 20 mol%, the structural unit (3) represented by the following formula (3) is 2 to 40 mol% and the following formula (4). A copolymer having the structural unit (4) in a proportion of 0.2 to 15 mol% (total of 100 mol%) is preferable. Particularly, the weight average molecular weight in terms of pullulan measured by gel permeation chromatography is in the range of 15,000 to 100,000. The copolymer having a weight average molecular weight / number average molecular weight ratio (weight average molecular weight / number average molecular weight) in the range of 2 to 7 is preferred.

[In General Formulas (1) to (4), R ¹ , R ² and R ⁴ represent a hydrogen atom or a methyl group, R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X represents —SO ₃ M ² or —O—C ₆ H ₄ —SO ₃ M ³ (wherein M ² and M ³ represent alkali metal, alkaline earth metal, ammonium or organic amine), and A represents oxy A residue obtained by removing a hydroxyl group from a polyether diol having 5 to 109 repeating alkylene units, wherein the oxyalkylene unit comprises only oxyethylene units or both oxyethylene units and oxypropylene units. And M ¹ represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an organic amine. ]

  The above-mentioned copolymer having these structural units (1) to (4) in a predetermined ratio is formed by copolymerizing corresponding monomers.

  As a monomer that forms the structural unit (1) represented by the formula (1), 1) (meth) acrylic acid, 2) alkali metal salt, alkaline earth metal salt of (meth) acrylic acid or There are organic amine salts. Of these, alkali metal salts such as sodium and potassium (meth) acrylic acid are preferred.

  Monomers that form the structural unit (2) represented by the formula (2) include 1) alkali metal salt, alkaline earth metal salt or organic amine salt of methallylsulfonic acid, and 2) p-meta. There are alkali metal salts, alkaline earth metal salts or organic amine salts of ryloxybenzenesulfonic acid. Of these, alkali metal salts such as sodium and potassium of methallyl sulfonic acid are preferable.

  As the monomer that forms the structural unit (3) represented by the formula (3), all of them have 5 to 109 repeating oxyalkylene units, and 1) an alkoxy polyoxy group having 1 to 3 carbon atoms. There are alkylene glycol (meth) acrylates and 2) polyoxyalkylene glycol mono (meth) acrylates. Examples of the above include 1) methoxypolyethylene glycol (meth) acrylate, methoxypolyethylene glycol polypropylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, ethoxypolyethyleneglycol polypropylene glycol ( (Meth) acrylate, ethoxy polypropylene glycol (meth) acrylate, n-propoxy polyethylene glycol (meth) acrylate, n-propoxy polyethylene glycol polypropylene glycol (meth) acrylate, isopropoxy polyethylene glycol mono (meth) acrylate, isopropoxy polyethylene glycol polypropylene glycol (Meta) Acrylate, and the like. Examples of 2) include polyoxyalkylene glycol mono (meth) acrylates such as polyethylene glycol mono (meth) acrylate, polyethylene glycol polypropylene glycol mono (meth) acrylate, and polypropylene glycol mono (meth) acrylate. Of these, methoxypolyethylene glycol methacrylate and polyethylene glycol monomethacrylate, in which oxyalkylene units are only oxyethylene units and the number of repetitions thereof is 26 to 95, are preferred.

  Examples of the monomer that forms the structural unit (4) represented by the formula (4) include methyl acrylate and methyl methacrylate. Of these, methyl acrylate is preferred.

  In the presence of a radical initiator, the above copolymer is a radical copolymerization of the above-mentioned monomers that form the structural units (1) to (4) so as to have a predetermined copolymerization ratio. Is obtained. The radical copolymerization can be carried out by aqueous solution polymerization using water or a mixed solvent of water and a water-soluble organic solvent, and can be carried out continuously or batchwise. For example, first, an aqueous solution having a pH of 4.5 to 6.5 containing 10 to 40% by weight of each monomer as a total amount is prepared. Next, in a nitrogen gas atmosphere, a radical initiator is added to the aqueous solution, and a radical reaction is allowed to proceed at a reaction temperature of 50 to 70 ° C. for 5 to 8 hours to obtain a copolymer. The type of radical initiator to be used is not particularly limited as long as it decomposes at the reaction temperature and generates radicals, but a water-soluble radical initiator is preferably used. Examples of such a water-soluble radical initiator include persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, 2,2-azobis (2-amidinopropane) dihydrochloride, and the like. These can also be used as a redox initiator in combination with a reducing substance such as sulfite or L-ascorbic acid, or an amine.

  The copolymer having the structural units (1) to (4) at a predetermined ratio is combined with a weight average molecular weight (hereinafter simply referred to as a weight average molecular weight) in terms of pullulan by the gel permeation chromatograph and the weight average molecular weight. It is preferable that the ratio to the number average molecular weight (weight average molecular weight / number average molecular weight, hereinafter abbreviated as Mw / Mn) is within a predetermined range. Such molecular weight distribution is controlled by a method known per se, for example, the concentration of each monomer in the polymerization system used for radical copolymerization, the pH of the polymerization system, the reaction temperature of the polymerization system, and the chain transfer to the polymerization system. It can carry out by the method of combining the addition of an agent etc. suitably. In order to obtain a copolymer having a desired molecular weight distribution, it is advantageous to set the pH of the polymerization system to 4.0 to 6.5, and 2-mercaptoethanol and 2-mercaptopropionic acid are added to the polymerization system. It is advantageous to add a chain transfer agent such as 3-mercaptopropionic acid, thioglycolic acid or thioglycerin, but the vinyl monomer which forms the structural unit (2) is itself a chain transfer agent. This can be used as well.

  The copolymer having the structural units (1) to (4) in a predetermined ratio contains 40 to 80 mol%, preferably 45 to 72 mol% of the structural unit (1) in all the structural units. 2) 0.5-20 mol%, preferably 2-16 mol%, structural unit (3) 2-40 mol%, preferably 3-30 mol%, and structural unit (4) 0.2- What has 15 mol%, Preferably it is 1-14 mol% (total 100 mol%) is preferable. The weight average molecular weight is preferably in the range of 15,000 to 100,000, more preferably in the range of 25,000 to 70000. Further, the Mw / Mn is preferably in the range of 2 to 7, particularly preferably in the range of 3 to 6.5.

On the other hand, (E ² ) maleic acid copolymer having an alkylene glycol chain includes methyl polyethylene glycol vinyl ether-maleic anhydride copolymer, polyethylene glycol allyl ether-maleic anhydride copolymer, methyl polyethylene glycol allyl ether- Examples include maleic anhydride copolymer and methyl polyethylene glycol methacrylate-maleic acid copolymer. The number average molecular weight (GPC method, in terms of polyethylene glycol) of the copolymer (E ² ) is preferably 3000 to 200000, and particularly preferably 3000 to 80000.

  Examples of the reducing inorganic compound include sulfites, nitrites, and thiosulfates. These salts are preferably alkali metal salts and alkaline earth metal salts. Addition of the reducing inorganic compound can prevent gelation during the kneading and stirring in the drying step. Although this reason is not clear, it is considered that the reducing inorganic compound deactivates the radical reaction initiator remaining in the polycarboxylic acid copolymer-containing liquid. Therefore, the amount of the reducing inorganic compound added may be determined according to the type and amount of the radical reaction initiator remaining in the mixture, and usually the solid component of the radical reaction initiator used for the synthesis of the polymer compound. However, it is desirable that the amount be equal to or greater than the amount capable of deactivating the oxidizing power of the residual radical reaction initiator below the solid content (mol% value) of the residual radical reaction initiator.

  Further, as the reducing organic compound, amine compounds, particularly alkanolamines are preferable. Specific examples include triethanolamine, diethanolamine, monoethanolamine, isopropanolamine, alkanolamines such as N, N-diethylethanolamine, alkylamines such as sec-butylamine, and diamines such as ethylenediamine. By adding the reducing organic compound, the load on the kneading stirrer is greatly reduced, and the COD value of distilled water discharged during dry powder is reduced (200 mg / L or less).

  The amount of each of the reducing inorganic compound and the reducing organic compound added is 0.01 to 2.5% by weight, particularly 0.5 to 1.5% by weight, based on the solid content of the polycarboxylic acid polymer compound. % Is preferred. The reason why the load of the mixing stirrer in the dry powdering process is reduced by the addition of the reducing organic compound and the COD value of water distilled off during the drying is reduced is that this is a crushing aid. This is presumed to be due to the fact that the polymerization reaction proceeds at a low temperature around room temperature due to the amine effect and unreacted monomers are consumed due to the amine effect.

  In the powdery cement dispersant (E) used in the present invention, in order to improve its hygroscopicity, blocking property, etc., or to reduce measurement error, in addition to the above essential components, in addition to the above essential components, polyalkylene glycol, carbon number 8 ˜22 fatty acids or salts thereof, and inorganic powders may be blended.

  Preferred examples of the polyalkylene glycol include polyethylene glycol having a molecular weight of 1000 to 20000 and polypropylene glycol having a molecular weight of 2000 to 6000. Among these, polyethylene glycol is particularly preferable, and polyethylene glycol having an average molecular weight of 2000 to 4000 is more preferable.

  In addition, the fatty acid having 8 to 22 carbon atoms or a salt thereof may be saturated or unsaturated, and may be linear or branched. Specifically, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, undecylenic acid, Examples include oleic acid, elaidic acid, cetreic acid, erucic acid, brassic acid, and salts thereof. As the fatty acid salt, metal salts such as sodium, potassium, barium, calcium, zinc, aluminum and magnesium are preferable. Of these, stearic acid or a salt thereof is preferable, and calcium stearate is particularly preferable. The blending amount of these polyalkylene glycols and fatty acids having 8 to 22 carbon atoms or salts thereof is 0.2 to 30% by weight of the solid content of the polycarboxylic acid polymer compound having the polyalkylene glycol chain, 0.5 to 20 weight% is especially preferable.

  As the inorganic powder, powders of inorganic salts such as calcium carbonate and calcium silicate, clay mineral powders such as kaolinite and bentonite, or fine powders such as blast furnace slag and fly ash can be used. Such an inorganic powder may be used up to about three times the solid content of the polycarboxylic acid polymer compound.

  The liquid containing the polycarboxylic acid polymer compound as a main component may contain a solution or dispersion of water or an organic solvent.

  In addition, since the polycarboxylic acid polymer compound-containing liquid is usually an acidic liquid, an alkali such as sodium hydroxide, potassium hydroxide, or calcium hydroxide is added after adding a reducing inorganic compound and a reducing organic compound. It is preferable to adjust the pH to 7 to 9 by adding an aqueous solution of metal or alkaline earth metal. When the pH is not adjusted, the polymer compound in the mixture is easily hydrolyzed during the heating and drying treatment, or the COD value of water distilled off during drying is increased. When the polycarboxylic acid polymer compound-containing liquid has a pH of 7 to 9 from the beginning, it is not necessary to adjust by adding a pH adjuster.

The drying is not particularly limited as long as it is a convection type drying device such as a hot air type or a heat conduction type drying device. However, when the processed product is a solution of 5 to 40%, the former drying device is a spray dryer or flash jet dryer. Is suitable. In the case where the processed product is a high-concentration solution exceeding 40% or a material having high viscoelasticity, it is preferable to use a dryer such as the latter kneading and stirring dryer or a band type continuous vacuum dryer. However, since the polycarboxylic acid polymer compound having a polyalkylene glycol chain may become viscous in the concentration process, a means for dry powderization by kneading and stirring is particularly preferable from the viewpoint of powdering efficiency and the like. . The kneading / stirring temperature is preferably about 40 to 120 ° C, more preferably about 60 to 110 ° C. Kneading and stirring can be carried out in the air, but it is desirable to carry out under reduced pressure or an inert gas atmosphere such as nitrogen or argon from the viewpoint of preventing alteration. Further, it is preferable that the powder is concentrated to a hardness of 30 ° or more and then powdered while being kneaded and stirred with a horsepower of 0.5 kg / m ³ / rpm or more. By performing such a drying operation, a powdery dispersant can be obtained. In addition, although the powder after drying may be aggregated in the small lump shape, since this lump is fragile, it can be easily made into single particles with a slight crushing force.

(E) It is desirable that the powdered dispersant is adjusted to an average particle size of 5 to 2000 μm, more preferably 10 to 500 μm by an arbitrary pulverization / classification method for convenience in use. However, since the produced (E) powdered dispersant is relatively weak to heat, a pulverizer having low heat storage property is preferable, and specifically, a pin type mill is preferable. Further, although there is a pulverizer integrated with a screen for adjusting the particle size, it is preferable to perform pulverization and classification separately because the pulverization heat increases when the unpulverized material stays.
(E) As a powdery cement dispersant, the one described in the previous patent document 1 can be used, and as a commercial product, Coreflow NF-100 (Pacific Material Co., Ltd.) and the like can be mentioned.

  The amount of (E) powdered cement dispersant thus obtained added to the cement admixture of the present invention is not effective if it is too small, and if it is too large, it causes caking delay and strength reduction, so 100 parts by weight of calcium aluminates 0.5 to 5 parts by weight, particularly 1 to 4 parts by weight is preferred.

  The cement admixture of the present invention preferably further contains (F) a retarder. The retarder used in the cement admixture of the present invention functions to ensure working time by delaying the hydration reaction of fast-hardening cement. Any one can be used as long as it is usually used for a cement composition, but oxycarboxylic acid or oxycarboxylate is preferred from the viewpoint of short-time strength development. Examples of oxycarboxylic acid and oxycarboxylate include citric acid, citrate, gluconic acid, gluconate, tartaric acid, tartrate, heptonic acid, heptonic acid salt and the like. 0.5-20 weight part is preferable with respect to 100 weight part of calcium aluminates, and, as for the compounding quantity of a retarder, 1-15 weight part is especially preferable.

  In the cement admixture and fast-curing cement of the present invention, various additives usually used for cement and concrete may be further blended within a range that does not inhibit the curability of mortar and concrete. Such additives include alkali metal or alkaline earth metal sulfates, alkali metal or alkaline earth metal carbonates, dispersants, antifoaming agents, AE agents, thickeners, silica fume, limestone fine powder, Examples include blast furnace slag fine powder, fly ash, and quartzite powder.

  For the production of the cement admixture and fast-hardening cement of the present invention, any commonly used powder mixer can be used. For example, a Henschel mixer, a Laedige mixer, etc. are mentioned.

Any Portland cement can be used as the cement of the present invention, but early-strength Portland cement or ordinary Portland cement is preferred from the viewpoint of fast setting. With respect to these cements, it is more preferable to make the particle diameter finer in order to improve the strength for a single hour. The Blaine specific surface area, preferably at least 4000 cm ² / g, more preferably more than 7000 cm ² / g. Although the upper limit of the specific surface area is not particularly defined, it is industrially preferably 15000 cm ² / g or less from the viewpoint of cost.

  The content of the cement admixture in the quick-hardening cement composition of the present invention is preferably 15 to 60 parts by weight with respect to 100 parts by weight of the quick-hardening cement composition. Even if it is less than 15 parts by weight or more than 60 parts by weight, the strength may be reduced for a short time.

  The base mortar or the base concrete is not particularly limited and any one can be used.

  Examples of the fine aggregate include river sand, sea sand, mountain sand, crushed sand, and a mixture thereof. Examples of the coarse aggregate include river gravel, sea gravel, crushed stone, and a mixture thereof.

  The manufacturing method of mortar or concrete is not particularly limited, and each material may be mixed with a conventional mixer installed in a ready-mixed factory or a construction site.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

[Materials used]
(A) Calcium aluminates: Alumina cement (manufactured by Taiheiyo Materials Co., Ltd., Blaine specific surface area 5100 cm ² / g)
(B) Gypsum: Type ^II anhydrous gypsum (manufactured by Taiheiyo Materials, Blaine specific surface area 7500 cm ² /
g)
(C) Lithium carbonate: Reagent (manufactured by Kanto Chemical Co., Inc.)
(D) Sodium sulfate: Reagent (manufactured by Kanto Chemical Co., Inc.) and pulverized / classified product thereof (1) Anhydrous sodium sulfate (average particle size 150 μm)
(2) anhydrous sodium sulfate (average particle size 80 μm)
(3) anhydrous sodium sulfate (average particle size 50 μm)
(4) Anhydrous sodium sulfate (average particle size 15 μm)
(5) Sodium sulfate decahydrate (E) A polycarboxylic acid polymer compound having a polyalkylene glycol chain (the copolymer having the structural units (1) to (4)) is reduced to a main component. Powdered cement dispersant obtained by adding a neutral inorganic compound and a reducing organic compound and then drying to make powder: Coreflow NF-100 (manufactured by Taiheiyo Materials Co., Ltd.)
(F) retarder: sodium citrate (reagent, manufactured by Kanto Chemical Co., Inc.)
(G) Portland cement: ground Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) (Brain specific surface area 7500 cm ² / g)
(H) Fine aggregate: Crushed sand from Minami-Ogura-ku, Kitakyushu City (Specific gravity: 2.69): Sea sand off the coast of Noura, Iki-gun, Nagasaki Prefecture (Specific gravity: 2.59) = 3: 7 (Weight ratio) Mixed product (I) Water: tap water

[Manufacture of cement admixtures]
The above (A) to (F) were mixed with the composition shown in Table 1 using a Raedige mixer to obtain a cement admixture. Furthermore, the cement admixture and (G) were mixed in the formulation shown in Table 1 to obtain a fast-hardening cement.

[Production of cement composition]
Fast-hardening cement 10.0 kg, (H) 15.0 kg and (I) 4.6 kg were kneaded for 2 minutes in a constant temperature test chamber at 20 ° C. using a hand mixer to obtain a mortar sample.

[Evaluation of fast curing]
A cylindrical test body having a diameter of 5 cm and a height of 10 cm was molded, placed in a constant temperature test chamber at 20 ° C., and measured for compressive strength at 12 hours after kneading in accordance with JIS A 1108, and used as an index of fast hardening. .

[Evaluation of workability]
The J14 funnel flow time was measured according to the Japan Society of Civil Engineers standard JSCE-F541. In addition, the bleeding rate is measured according to JIS A 1108, and the presence or absence of bleeding is visually determined immediately after mixing is completed up to 2 hours later. It was. The case where even a small amount of bleeding is recognized is indicated as x, and the case where no bleeding is observed is indicated as ○. The results are shown in Table 1.

[Evaluation of long-term storage]
Regarding the level judged as good workability in the above, 25 kg of fast-hardening cement was left in a 20 ° C. constant temperature test chamber without sealing, and after 6 months, the above workability evaluation was performed again. When both the evaluation by the evaluation and the evaluation by the bleeding rate were good, it was judged that the long-term storage stability was good. The results are shown in Table 1.

As is apparent from Table 1, when the cement admixture and fast-curing cement of the present invention were used, the changes in compressive strength and J14 funnel flow time were small and no bleeding was observed even after storage for 6 months. As a result, it was found that the fast curing and workability can be maintained for a long time.
On the other hand, when sodium sulfate decahydrate is used or when sodium sulfate is not used, the J14 funnel flow time fluctuates greatly, and bleeding also occurs. It was found that a large change occurred in the dispersion performance of the dispersant due to storage. (Comparative Examples 1 and 2).

  Since the cement admixture of the present invention has a small change in quick-hardness and workability even after long-term storage, it is possible to extend the usable period of the manufactured product, and it must be discarded due to the expiration during the production and use. The amount of products can be greatly reduced. Therefore, the cement admixture of the present invention and the ultrafast cement are useful for reducing the environmental load.

Claims (4)

  (A) Calcium aluminate, (B) gypsum, (C) lithium carbonate, (D) anhydrous sodium sulfate, and (E) a polycarboxylic acid polymer compound having a polyalkylene glycol chain as a main component. A cement admixture containing a powdery cement dispersant obtained by adding a reducing inorganic compound and a reducing organic compound, and then powdered into a dry powder.   The cement admixture according to claim 1, further comprising (F) a retarder.   (D) The average particle diameter of anhydrous sodium sulfate is 100 μm or less, and the amount of anhydrous sodium sulfate is 2 parts by weight or more with respect to 100 parts by weight of calcium aluminates. Cement admixture.   A super-hard cement containing the cement admixture according to claim 1, 2, or 3 and (G) Portland cement.