Concrete admixture, concrete composition, method for placing concrete composition, and mass concrete

Abstract

To provide a concrete admixture which exhibits an excellent reducing effect on a structure strength correction value (S value) in a hardened body of concrete such as hot concrete and mass concrete, a concrete composition, a method for placing the concrete composition, and the mass concrete.SOLUTION: A concrete admixture comprises at least one component A selected from water-soluble vinyl copolymers comprising 50-99 mass% of a structural unit 1 and 1-50 mass% of a structural unit 2, and having a mass average molecular weight of 2000-500000, and at least one component B selected from lignin sulfonic acid and lignin sulfonate. The mass ratio of the component A / the component B is in the range of 40 / 60 to 5 / 95. The concrete admixture is added to a concrete composition to reduce an S-value, which is a structure strength correction value in a hardened body of the concrete composition. An S-value reduction amount, which is a difference between an S-value of the concrete composition and an S-value of a comparative concrete composition to which a comparative admixture having a mass ratio of the component A / the component B of 50 / 50 is added, is 1.5 N / mm2 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a concrete admixture, a concrete composition, a method for placing a concrete composition, and mass concrete. More specifically, the present invention relates to a concrete admixture, a concrete composition, a method for placing a concrete composition, and mass concrete that exhibit an excellent reduction effect on the structural strength correction value (S value) in hardened concrete such as summer concrete and mass concrete.

Background Art

[0002] Conventionally, concrete building structures and the like have been made using a concrete composition obtained by kneading a binder such as cement, water, fine aggregate, coarse aggregate, and a concrete admixture, etc. as materials, and this concrete composition is placed in a predetermined formwork at a construction site or the like and cured within the formwork. The operation of placing it in this formwork is called "placing".

[0003] Here, the concrete composition placed in the formwork cures under temperature conditions such as ambient environmental conditions and heat of hydration, and there are differences in the curing state depending on these environmental conditions and temperature conditions. For example, in the case of a concrete composition placed under conditions where the average daily temperature is high (for example, 25°C or higher) like in summer, the hardening of cement is promoted. As a result, the compressive strength at the initial age of the concrete (for example, after 1 to 3 days have passed since placing) increases, but the compressive strength at the long-term age of the concrete (for example, after 28 days have passed since placing) tends to decrease compared to concrete placed under normal conditions (for example, 20°C).

[0004] Concrete placed during a period when the daily average temperature exceeds 25°C as in the above example is called midsummer concrete. This midsummer concrete, particularly in the initial stage of hardening, undergoes a high temperature history due to ambient environmental conditions, heat of hydration, etc. Therefore, the strength of the hardened body of midsummer concrete (structural strength) tends to be lower than that of a concrete hardened body (specimen for strength control) whose temperature is controlled so as not to undergo a high temperature history. Thus, in the case of midsummer concrete, the mix proportion is determined in consideration of the fact that the structural strength of its hardened body is lower than that of the specimen for strength control.

[0005] Incidentally, the difference between the structural strength of the hardened body of midsummer concrete and the strength of the specimen for strength control is known as the structural strength correction value (S value).

[0006] In the case of concrete such as this midsummer concrete or mass concrete, which may undergo a high temperature history due to ambient environmental conditions, heat of hydration, etc. particularly in the initial stage of hardening, it is required to reduce the structural strength correction value (S value) (that is, reduction of the structural strength correction value (S value)). In other words, it is required to bring the structural strength of midsummer concrete, mass concrete, etc. closer to the strength of the specimen for strength control. Incidentally, mass concrete refers to concrete with a large cross-sectional dimension of the member (concrete with a large volume). Due to its large volume, this mass concrete tends to retain the heat of reaction such as heat of hydration generated during hardening inside and undergo a high temperature history.

[0007] As a means for reducing the structural strength correction value (S value), a concrete admixture containing a water-soluble vinyl copolymer and an aldehyde condensate having an aromatic ring, and a concrete admixture containing a water-soluble vinyl copolymer and saccharides have been reported (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

[0009] However, although the concrete admixtures described in Patent Documents 1 and 2 exhibit the effect of reducing the structural strength correction value (S value) for hardened concrete such as hot weather concrete and mass concrete (the effect of reducing the S value), there is still room for further improvement in the effect of reducing the S value.

[0010] In view of the above circumstances, an object of the present invention is to provide a concrete admixture, a concrete composition, a method for placing the concrete composition, and mass concrete that exhibit an excellent effect of reducing the structural strength correction value (S value) in hardened concrete (concrete hardened body) such as hot weather concrete and mass concrete. [Means for Solving the Problems]

[0011] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by containing a predetermined A component and a predetermined B component in a predetermined ratio. According to the present invention, the following concrete admixture, concrete composition, method for placing the concrete composition, and mass concrete are provided.

[0012] [1] At least one A component selected from water-soluble vinyl copolymers containing the following structural unit 1 in a proportion of 50 to 99% by mass and the following structural unit 2 in a proportion of 1 to 50% by mass, and having a mass average molecular weight of 2000 to 500000, and at least one B component selected from lignin sulfonic acid and lignin sulfonate, wherein the mass ratio of the A component to the B component is in the range of 40 / 60 to 5 / 95, It is added to a concrete composition and reduces the S value, which is the structural strength correction value in the hardened body of the concrete composition. The S value reduction amount, which is the difference between the S value of the concrete composition and the S value of a comparative concrete composition to which a comparative admixture with a mass ratio of the A component / the B component of 50 / 50 is added, is 1.5 N / mm 2 or more. The concrete admixture is characterized by this. Constituent unit 1: It is a constituent unit formed from a compound represented by the following general formula (1).

[0013] [Chemical formula] (However, in the general formula (1), R 1 is an alkenyl group having 2 to 5 carbon atoms or an unsaturated acyl group having 3 to 4 carbon atoms. A 1 O is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of such oxyalkylene groups are present, they can be of one kind alone or two or more kinds). R 2 is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. m is the average number of moles of addition of A 1 O and is a number from 1 to 300) Constituent unit 2: It is a constituent unit formed from at least one selected from (meth)acrylic acid, (meth)acrylate, (anhydrous)maleic acid, maleate, fumaric acid, and fumarate.

[0014] [2] The concrete admixture according to [1], wherein the mass ratio of the A component / the B component is in the range of 30 / 70 to 5 / 95.

[0015] [3] The concrete admixture according to [1], further containing at least one C component selected from saccharides.

[0016] [4] The concrete admixture according to [3], wherein the C component contains both sucrose and fructose.

[0017] [5] A concrete composition characterized by containing a concrete admixture according to any one of [1] to [4], cement, water, fine aggregate, and coarse aggregate.

[0018] [6] A method for placing a concrete composition, characterized by satisfying at least one of the following conditions (1) and (2) when placing the concrete composition according to [5] into a formwork. (1) The temperature of the concrete composition when placing it into the formwork is 25°C or higher. (2) The average daily temperature when placing it into the formwork is 25°C or higher.

[0019] [7] Mass concrete characterized by containing the concrete composition according to [5].

Advantages of the Invention

[0020] The concrete admixture of the present invention exhibits the effect of exerting an excellent reduction effect on the structural strength correction value (S value) in a concrete hardened body, which is a hardened body of the concrete composition, when added to the concrete composition.

[0021] The concrete composition of the present invention exhibits the effect of exerting an excellent reduction effect on the structural strength correction value (S value) in a concrete hardened body, which is a hardened body of the concrete composition, by containing the concrete admixture of the present invention.

[0022] According to the method for placing the concrete composition of the present invention, by adopting the concrete composition of the present invention under predetermined conditions, the effect of obtaining a concrete hardened body in which the structural strength correction value (S value) is effectively reduced can be achieved.

[0023] The mass concrete of the present invention exhibits the effect of exerting an excellent reduction effect on the structural strength correction value (S value) in a hardened body of this mass concrete (concrete hardened body) by using the concrete composition of the present invention.

Mode for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. Therefore, it should be understood that appropriate changes, improvements, etc. can be made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. In the following examples, etc., unless otherwise specified, % means mass%, and part means part by mass.

[0025] (1) Concrete admixture: The concrete admixture of the present invention contains at least one A component selected from water-soluble vinyl copolymers containing 50 to 99% by mass of the following structural unit 1 and 1 to 50% by mass of the following structural unit 2, and having a mass average molecular weight of 2,000 to 500,000, and at least one B component selected from lignin sulfonic acid and lignin sulfonate. And the mass ratio of A component / B component is in the range of 40 / 60 to 5 / 95. Further, the concrete admixture of the present invention is added to a concrete composition and reduces the S value which is the structural strength correction value in the cured body of the concrete composition. And the S value reduction amount which is the difference between the S value of the concrete composition and the S value of the comparative concrete composition which is the concrete composition to which "the comparative admixture which is a concrete admixture having a mass ratio of A component / B component of 50 / 50" is added is 1.5 N / mm 2 or more.

[0026] Structural unit 1: It is a structural unit formed from a compound represented by the following general formula (1).

[0027]

Chemical formula

[0028] Constituent unit 2: It is a constituent unit formed from at least one selected from (meth)acrylic acid, (meth)acrylate, (anhydrous)maleic acid, maleate, fumaric acid, and fumarate.

[0029] Such a concrete admixture exhibits an excellent reduction effect on the structural strength correction value (S value) in a concrete hardened body, which is a hardened body of a concrete composition, when added to the concrete composition.

[0030] Here, the method for calculating the S value will be described. That is, a specimen is prepared using the concrete composition, and then, the compressive strength of the concrete hardened body at 28 days of age (hereinafter referred to as the "standard curing strength") cured in water or in a wet state with temperature controlled at usually 20 ± 3°C is measured. Then, it can be obtained by subtracting the estimated value of the structural concrete strength obtained in accordance with the "Method for Estimating Structural Concrete Strength by Core Specimens (JASS5 T-605 (2022))" from this standard curing strength.

[0031] However, the above-described method for calculating the S value requires the production of a large-sized simulated member test body, etc., and the production work becomes large-scale, taking time and cost.

[0032] Therefore, a plurality of concrete specimens are accommodated in a heat-insulating container capable of inhibiting heat flow to the outside, and the estimated value of the strength of the structural concrete obtained in accordance with the "Method for Estimating Structural Concrete Strength by Simple Heat-Insulating Curing Specimens (JASS5 T-606 (2022))" that gives a temperature history close to the inside of the structural concrete is often used.

[0033] Using the compressive strength of the concrete in the simple heat-insulating curing obtained in this way (hereinafter sometimes referred to as "simple heat-insulating curing strength"), the S value can also be obtained by subtracting the simple heat-insulating curing strength from the standard curing strength. That is, the S value can be calculated by the formula: standard curing strength - simple heat-insulating curing strength.

[0034] The concrete admixture of the present invention can reduce the S value (structural strength correction value) calculated as described above, and the S value reduction amount is 1.5 N / mm 2 or more. This S value reduction amount is preferably a large value, and there is no particular upper limit, but the substantial upper limit value is about 10 N / mm 2 or so.

[0035] (1-1) Component A: Component A contains at least one selected from water-soluble vinyl copolymers containing 50 to 99% by mass of structural unit 1 and 1 to 50% by mass of structural unit 2, and having a mass average molecular weight of 2000 to 500000. By containing this component A and component B in a predetermined ratio, the concrete admixture of the present invention exhibits an excellent reduction effect on the structural strength correction value (S value) in the hardened concrete.

[0036] Note that structural unit 1 may be formed from one or more selected from the compounds represented by general formula (1). Further, structural unit 2 may be formed from one or more selected from (meth)acrylic acid, (meth)acrylate, (anhydrous)maleic acid, maleate, fumaric acid, and fumarate.

[0037] (1-1a) Structural unit 1: R in general formula (1) 1 is an alkenyl group having 2 to 5 carbon atoms or an unsaturated acyl group having 3 to 4 carbon atoms. Among these, an alkenyl group having 3 to 5 carbon atoms or an unsaturated acyl group having 4 carbon atoms is preferable.

[0038] A in general formula (1)1 O is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of such oxyalkylene groups are present, they can be of one kind alone or two or more kinds). Among these, an oxyalkylene group having 2 to 3 carbon atoms is preferred.

[0039] R in the general formula (1) 2 is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. Among these, a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms is preferred.

[0040] m in the general formula (1) is 1 the average number of moles of addition of O and is a number from 1 to 300. m is preferably a number from 5 to 150.

[0041] Examples of the compound represented by the general formula (1) specifically include α-allyl-ω-methoxy-(poly)oxyethylene, α-allyl-ω-methoxy-(poly)oxyethylene(poly)oxypropylene, α-allyl-ω-butoxy-(poly)oxyethylene, α-allyl-ω-butoxy-(poly)oxyethylene(poly)oxypropylene, α-allyl-ω-hydroxy-(poly)oxyethylene, α-allyl-ω-hydroxy-(poly)oxyethylene(poly)oxypropylene, α-vinyl-ω-hydroxy-(poly)oxybutylene-(poly)oxyethylene, α-vinyl-ω-methoxy-(poly)oxyethylene, α-vinyl-ω-methoxy-(poly)oxyethylene(poly)oxypropylene, α-vinyl-ω-hydroxy-(poly)oxyethylene, α-vinyl-ω-hydroxy-(poly)oxyethylene(poly)oxypropylene, α-methallyl-ω-methoxy-(poly)oxyethylene, α-methallyl-ω-methoxy-(poly)oxyethylene(poly)oxypropylene, α-methallyl-ω-hydroxy-(poly)oxyethylene, α-methallyl-ω-hydroxy-(poly)oxyethylene(poly)oxypropylene, α-(3-methyl-3-butenyl)-ω-methoxy-(poly)oxyethylene, α-(3-methyl-3-butenyl)-ω-methoxy-(poly)oxyethylene(poly)oxypropylene, α-(3-methyl-3-butenyl)-ω-hydroxy-(poly)oxyethylene, α-(3-methyl-3-butenyl)-ω-hydroxy-(poly)oxyethylene(poly)oxypropylene, α-acryloyl-ω-methoxy-(poly)oxyethylene, α-acryloyl-ω-methoxy-(poly)oxyethylene(poly)oxypropylene, α-acryloyl-ω-hydroxy-(poly)oxypropylene, α-acryloyl-ω-hydroxy-(poly)oxyethylene, α-acryloyl-ω-hydroxy-(poly)oxyethylene(poly)oxypropylene, α-methacryloyl-ω-methoxy-(poly)oxyethylene, α-methacryloyl-ω-methoxy-(poly)oxyethylene(poly)oxypropylene, α-methacryloyl-ω-hydroxy-(poly)oxyethylene, α-methacryloyl-ω-hydroxy-(poly)oxyethylene(poly)oxypropylene, and the like.

[0042] The content ratio of structural unit 1 is 50 to 99% by mass, preferably 60 to 95% by mass, and more preferably 65 to 92% by mass in all the structural units of the water-soluble vinyl copolymer.

[0043] (1-1b) Structural unit 2: Structural unit 2 is a structural unit formed from at least one selected from (meth)acrylic acid, (meth)acrylate, (anhydrous)maleic acid, maleate, fumaric acid, and fumarate. Among these, (anhydrous)maleic acid and fumaric acid, and maleate and fumarate can take the same form as the structural units in the copolymer when used as an aqueous solution.

[0044] The content ratio of structural unit 2 is 1 to 50% by mass, preferably 5 to 40% by mass, and more preferably 8 to 35% by mass in all the structural units of the water-soluble vinyl copolymer.

[0045] (1-1c) Other structural units: The water-soluble vinyl copolymer may contain other structural units in addition to structural unit 1 and structural unit 2. Examples of the compound (monomer) forming the other structural units include (meth)allylsulfonic acid and its salts, (meth)acrylamide, acrylonitrile, (meth)acrylic acid alkyl esters, etc. The other structural units may be employed alone or in combination of two or more.

[0046] The content ratio of the other structural units is preferably 20% by mass or less, and more preferably 10% by mass or less in all the structural units of the water-soluble vinyl copolymer.

[0047] The water-soluble vinyl copolymer can be produced by a known method.

[0048] Specifically, the water-soluble vinyl copolymer is synthesized, for example, by radical polymerization. A compound represented by the general formula (1), a compound forming the constitutional unit 2, and, if necessary, a compound forming other constitutional units are mixed (heated) with a radical initiator and polymerized to obtain the copolymer.

[0049] Examples of the radical initiator include peroxide compounds such as potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide; and azo compounds such as 2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobisisobutyronitrile. These can also be used as redox initiators in combination with reducing substances such as sulfites and ascorbic acid, and further with amines.

[0050] In addition, to make the mass average molecular weight of the obtained water-soluble vinyl copolymer fall within a desired range, a chain transfer agent such as 2-mercaptoethanol, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thioglycolic acid, or 3-mercapto-1,2-propanediol can be used. In the polymerization, water or an organic solvent may be used as the solvent, or it may be solvent-free.

[0051] The mass average molecular weight of the water-soluble vinyl copolymer is from 2,000 to 500,000, preferably from 5,000 to 100,000, and more preferably from 10,000 to 70,000. This mass average molecular weight is measured by gel permeation chromatography.

[0052] (1-2) Component B: Component B is at least one selected from lignin sulfonic acid and lignin sulfonate. The concrete admixture of the present invention exhibits an excellent reduction effect on the structural strength correction value (S value) in the hardened concrete body by containing this Component B and the above-described Component A in a predetermined ratio.

[0053] Lignosulfonic acid is a compound having a skeleton in which the carbon at the α-position of the side chain of the hydroxyphenylpropane structure of lignin is cleaved and a sulfo group is introduced. The structure of the above skeleton is shown in the following formula (a). Lignin is one of the main components constituting a plant body along with polysaccharides such as cellulose.

[0054]

Chemical formula

[0055] Lignosulfonate is a salt of lignosulfonic acid, and examples of the salt include monovalent metal salts, divalent metal salts, ammonium salts, organic ammonium salts, and the like. Specific examples of lignosulfonate include sodium lignosulfonate, calcium lignosulfonate, magnesium lignosulfonate, and the like.

[0056] The mass ratio of component A / component B is in the range of 40 / 60 to 5 / 95, and preferably in the range of 30 / 70 to 5 / 95. By satisfying such a range, an excellent reduction effect on the structural strength correction value (S value) in the hardened concrete body is exhibited.

[0057] (1-3) Saccharides (component C): The concrete admixture of the present invention preferably further contains at least one C component selected from saccharides. By further containing such a C component, an even more excellent reduction effect on the structural strength correction value (S value) in the hardened concrete body is exhibited. This C component may be employed alone or in combination of two or more.

[0058] Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (oligosaccharides), polysaccharides, sugar alcohols, and the like.

[0059] Examples of monosaccharides include pentoses such as ribose, arabinose, xylose, lyxose, ribulose, xylulose, and apiose; hexoses such as allose, altrose, glucose, mannose, gulose, idose, galactose, talose, psicose, fructose, sorbose, and tagatose; heptoses such as sedoheptulose and coliosose; and the like.

[0060] Examples of disaccharides include sucrose, lactulose, lactose, maltose, trehalose, cellobiose, kojibiose, nigerose, isomaltose, isotrehalose, sophorose, laminaribiose, gentiobiose, turanose, palatinose, melibiose, xylobiose, and the like.

[0061] Examples of oligosaccharides (low-molecular-weight sugars) include trisaccharides such as raffinose, maltotriose, and melezitose; tetrasaccharides such as stachyose; and oligosaccharides such as isomaltooligosaccharide, fructooligosaccharide, galactooligosaccharide, chitosan oligosaccharide, and gentiobiooligosaccharide.

[0062] Examples of polysaccharides include starch, amylose, amylopectin, glycogen, cellulose, chitin, agarose, carrageenan, heparin, glucomannan, cyclodextrin, and the like. These polysaccharides may contain monosaccharides, disaccharides, or oligosaccharides.

[0063] Examples of sugar alcohols include erythritol, arabinitol, xylitol, galactitol, sorbitol, mannitol, and the like.

[0064] The C component preferably contains both sucrose and fructose. By containing such specific saccharides, it exhibits an excellent reduction effect on the structural strength correction value (S value) in the hardened concrete.

[0065] (1-4) Other components (D component): Furthermore, in addition to the above-described Component A, Component B, and Component C, the concrete admixture of the present invention may contain a setting retardation component, a component having a dispersing action on the binder, etc. (excluding Components A to C) as long as the effects are not impaired. For example, oxycarboxylic acids such as gluconic acid, tartaric acid, and citric acid and their salts, setting retarders such as phosphates and zinc compounds (some of these may have a dispersing action on the binder), an AE regulator composed of an anionic surfactant, etc., an antifoaming agent such as an oxyalkylene-based one, a hardening accelerator composed of alkanolamine, etc., a drying shrinkage reducing agent composed of polyoxyalkylene alkyl ether, etc., a preservative composed of an isothiazoline-based compound, etc., a waterproof agent composed of a higher fatty acid derivative, etc., a rust preventive agent composed of nitrite, etc. can be mentioned.

[0066] Examples of the oxycarboxylic acid and oxycarboxylic acid salt include gluconic acid, glycolic acid, glyceric acid, tartaric acid, citric acid, malic acid, glucoheptonic acid, arabic acid, etc., and their salts. There is no particular limitation on this salt, and examples of the salt of the oxycarboxylic acid include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as magnesium and calcium, ammonium salts, amine salts, etc. These Component Ds may be used alone or in combination of two or more.

[0067] The content ratio of Component D in Components A to D (total 100% by mass) in the concrete admixture of the present invention is preferably in the range of, for example, 0 to 40% by mass.

[0068] In addition, other components include aldehyde condensates having an aromatic ring, but the concrete admixture of the present invention preferably does not contain an aldehyde condensate having an aromatic ring or contains only a small amount of an aldehyde condensate having an aromatic ring. Further, when an aldehyde condensate having an aromatic ring is contained, the mass ratio of the water-soluble vinyl copolymer (Component A) to the aldehyde condensate having an aromatic ring is preferably less than 30 / 1. That is, the aldehyde condensate having an aromatic ring is preferably contained in a proportion of less than 1 / 30 with respect to the water-soluble vinyl copolymer (Component A) (the value calculated by the formula: aldehyde condensate having an aromatic ring / water-soluble vinyl copolymer (Component A) is preferably less than 1 / 30). By doing so, a concrete admixture that does not contain (or hardly contains) an aldehyde condensate having an aromatic ring can be obtained. When the aldehyde condensate having an aromatic ring is not contained (or hardly contained), an increase in cost associated with an increase in the addition amount of the concrete admixture can be suppressed, and the storage stability when the admixture is made into a single liquid in an aqueous solution state can be improved. Further, since a trace amount of formaldehyde, which is a causative substance of sick house syndrome, may remain in the aldehyde condensate having an aromatic ring, it is preferably not contained (or hardly contained) in consideration of a stricter safety aspect.

[0069] The content ratio of each component in the concrete admixture of the present invention, that is, the content ratios of Component A to Component D (total 100% by mass) in the concrete admixture of the present invention can be, for example, as follows. The content ratio of Component A can be 1 to 35% by mass, and at this time, the content ratio of Component B can be 25 to 95% by mass. Preferably, the content ratio of Component A can be 2 to 35% by mass, and at this time, the content ratio of Component B can be 28 to 85% by mass. When the content ratios of Component A and Component B are within the above ranges, an excellent reduction effect on the structural strength correction value (S value) in the cured concrete can be exhibited. Further, a concrete admixture that does not contain (or hardly contains) an aldehyde condensate having an aromatic ring can be obtained.

[0070] In the components A to D (total 100% by mass) in the concrete admixture of the present invention, the total content ratio of component A and component B can be, for example, 26 to 100% by mass.

[0071] The concrete admixture of the present invention can be used in a form diluted with water or a solvent.

[0072] (2) Concrete composition: The concrete composition of the present invention contains the concrete admixture of the present invention, cement, water, fine aggregate, and coarse aggregate. Such a concrete composition can exhibit an excellent reduction effect on the structural strength correction value (S value) in the concrete hardened body, which is the hardened body, by containing the concrete admixture of the present invention.

[0073] The addition ratio of the concrete admixture (components A to D) of the present invention is not particularly limited, but it is preferably 0.02 to 1.0% by mass, and more preferably 0.1 to 0.5% by mass, based on the cement.

[0074] All of the concrete admixture may be added during the kneading of the concrete composition (that is, added in a state where the components constituting the concrete admixture are mixed), or the components constituting the concrete admixture may be added separately during the kneading of the concrete composition.

[0075] Examples of the cement include various Portland cements such as ordinary Portland cement, early-strength Portland cement, medium-heat Portland cement, and low-heat Portland cement, and various blended cements such as blast furnace cement, fly ash cement, and silica fume cement. Further, the constituent materials of the blended cement, such as blast furnace slag fine powder, fly ash, and silica fume, may be weighed separately from the Portland cement and used in combination (as part of the cement).

[0076] Examples of fine aggregates include river sand, mountain sand, land sand, silica sand, crushed sand, sea sand, blast furnace slag fine aggregate, etc.

[0077] Examples of coarse aggregates include river gravel, mountain gravel, land gravel, crushed stone, blast furnace slag coarse aggregate, etc.

[0078] Within the range where the effects are not impaired, the concrete composition of the present invention can be appropriately incorporated with an AE regulator composed of an anionic surfactant or the like, an antifoaming agent such as an oxyalkylene-based one, a hardening accelerator composed of an alkanolamine or the like, a drying shrinkage reducing agent composed of a polyoxyalkylene alkyl ether or the like, a preservative composed of an isothiazoline-based compound or the like, a waterproofing agent composed of a higher fatty acid derivative or the like, a rust preventive composed of nitrite or the like.

[0079] For the ratio of water to cement (water / cement ratio) of the concrete composition of the present invention, conventionally known ratios can be appropriately adopted. For example, it can be 25 to 70% by mass.

[0080] In the concrete composition of the present invention, the C component in the concrete admixture preferably has an addition ratio to cement in the range of 0.01 to 0.1% by mass. By adopting such an addition ratio range, it exhibits a particularly excellent reduction effect on the structural strength correction value (S value) in the hardened concrete body, and can moderately control the setting of cement, thereby enhancing the workability of the concrete composition during the hot season.

[0081] (3) Placing method of the concrete composition: The placing method of the concrete composition of the present invention is a method that satisfies at least one of the following conditions (1) and (2) when placing the concrete composition of the present invention into the formwork. (1) The temperature of the concrete composition when placing it into the formwork is 25°C or higher (2) The average daily temperature when placing it into the formwork is 25°C or higher

[0082] The method of placing this concrete composition is a method capable of obtaining a concrete hardened body with effectively reduced structural strength correction value (S value) by adopting the concrete composition of the present invention under predetermined conditions.

[0083] Regarding each temperature in conditions (1) and (2) of the method of placing the concrete composition of the present invention, the upper limit is not defined. However, when the concrete temperature or the air temperature is high, there is a possibility that the cement may flash set, so preferably any temperature is 45°C or lower.

[0084] (4) Mass concrete: The mass concrete of the present invention contains the concrete composition of the present invention. Since the mass concrete has a large volume, reaction heat such as hydration heat generated during hardening tends to remain inside and it tends to receive a high temperature history. However, by using the concrete composition of the present invention, an excellent reduction effect on the structural strength correction value (S value) in the hardened body of this mass concrete (concrete hardened body) will be exhibited.

[0085] Here, mass concrete is defined as concrete with a large cross-sectional dimension of the member. Specifically, the criteria described in the Architectural Construction Standard Specifications and Explanation (JASS5) Reinforced Concrete Work 2018 (Japan Architectural Society) can be adopted.

[0086] And as an example of mass concrete, there are wall-shaped members with a minimum cross-sectional dimension of 80 cm or more, mat-shaped members with a minimum cross-sectional dimension of 100 cm or more, or column-shaped members with a minimum cross-sectional dimension of 100 cm or more.

Examples

[0087] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0088] First, the components A (A-1 to A-6) used in the concrete admixtures of the examples and comparative examples are shown in Table 1 below.

[0089]

Table 1

[0090] L-1: α-Methacryloyl-ω-methoxy-poly(23 moles) oxyethylene L-2: α-Methacryloyl-ω-methoxy-poly(9 moles) oxyethylene L-3: α-Allyl-ω-methoxy-poly(33 moles) oxyethylene L-4: α-(3-Methyl-3-butenyl)-ω-hydroxy-poly(113 moles) oxyethylene L-5: α-Methallyl-ω-hydroxy-poly(53 moles) oxyethylene poly(2 moles) oxypropylene L-6: α-Vinyl-ω-hydroxy-oxybutylene poly(52 moles) oxyethylene

[0091] M-1: Methacrylic acid M-2: Maleic anhydride M-3: Acrylic acid

[0092] S-1: Sodium methallyl sulfonate S-2: Methyl acrylate

[0093] The production method of the water-soluble vinyl copolymer (Component A (A-1 to A-6)) is shown below.

[0094] (Production Example 1) Production of water-soluble vinyl copolymer A-1: 357.7 g of ion-exchanged water, 284.3 g of α-methacryloyl-ω-methoxy-poly(23 mol) oxyethylene, 68.4 g of methacrylic acid, 7.2 g of sodium methallyl sulfonate, 6.5 g of 3-mercaptopropionic acid, and 57.0 g of 30% aqueous sodium hydroxide solution were charged into a reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, and a nitrogen inlet tube, and uniformly dissolved while stirring. Then, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was set to 60 °C in a warm water bath. Next, 36.0 g of 20% aqueous sodium persulfate solution was added to initiate the polymerization reaction. After 2 hours, 18.0 g of 20% aqueous sodium persulfate solution was added and maintained at 60 °C for 2 hours to terminate the polymerization reaction. 30% aqueous sodium hydroxide solution was added thereto to adjust the pH to 7, and the concentration was adjusted to 40% with ion-exchanged water. The components of this reaction product were designated as A-1.

[0095] (Production Example 2) Production of water-soluble vinyl copolymer A-2: 393.9 g of ion-exchanged water, 272.4 g of α-methacryloyl-ω-methoxy-poly(9 mol) oxyethylene, 68.1 g of methacrylic acid, 17.9 g of methyl acrylate, and 7.9 g of 3-mercaptopropionic acid were charged into a reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, and a nitrogen inlet tube, and uniformly dissolved while stirring. Then, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was set to 60 °C in a warm water bath. Next, 35.8 g of 20% aqueous sodium persulfate solution was added to initiate the polymerization reaction. After 2 hours, 17.9 g of 20% aqueous sodium persulfate solution was added and maintained at 60 °C for 2 hours to terminate the polymerization reaction. 30% aqueous sodium hydroxide solution was added thereto to adjust the pH to 7, and the concentration was adjusted to 40% with ion-exchanged water. The components of this reaction product were designated as A-2.

[0096] (Production Example 3) Production of water-soluble vinyl copolymer A-3: 360.8 g of α-allyl-ω-methoxy-poly(33 mol) oxyethylene and 35.7 g of maleic anhydride were charged into a reaction vessel equipped with a thermometer, a stirrer, and a nitrogen inlet tube, and heated with stirring until uniformly dissolved. Then, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was set to 80 °C in a warm water bath. Next, 2.0 g of azobisisobutyronitrile was added and maintained at 80 °C for 1 hour to initiate the polymerization reaction. After 1 hour, 1.6 g of azobisisobutyronitrile was added and maintained at 80 °C for 3 hours to terminate the polymerization reaction. A 30% aqueous sodium hydroxide solution was added thereto to adjust the pH to 7, and the concentration was adjusted to 40% with ion-exchanged water. The components of this reaction product were designated as A-3.

[0097] (Production Example 4) Production of water-soluble vinyl copolymer A-4: 84.5 g of ion-exchanged water and 330.3 g of α-(3-methyl-3-butenyl)-ω-hydroxy-poly(113 mol) oxyethylene were charged into a reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, and a nitrogen inlet tube, and uniformly dissolved with stirring. Then, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was set to 60 °C in a warm water bath. Next, 19.2 g of a 10.0% aqueous hydrogen peroxide solution was added dropwise over 3.0 hours, and simultaneously, an aqueous solution prepared by dissolving 38.4 g of acrylic acid and 15.4 g of 2-hydroxyethyl acrylate in 268.8 g of ion-exchanged water was added dropwise over 3.0 hours. And simultaneously, an aqueous solution prepared by dissolving 1.9 g of 3-mercaptopropionic acid and 1.9 g of ascorbic acid in 15.4 g of ion-exchanged water was added dropwise over 4.0 hours. Then, it was maintained at 60 °C for 0.5 hour to terminate the polymerization reaction. A 30% aqueous sodium hydroxide solution was added thereto to adjust the pH to 7, and the concentration was adjusted to 40% with ion-exchanged water. The components of this reaction product were designated as A-4.

[0098] (Production Example 5) Production of water-soluble vinyl copolymer A-5: 350.0 g of ion-exchanged water and 700.0 g of α-methallyl-ω-hydroxy-poly(53 mol) oxyethylene poly(2 mol) oxypropylene were charged into a reaction vessel and uniformly dissolved with stirring. Then, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was set to 60 °C in a warm water bath. Next, 44.0 g of 3.5 mass% hydrogen peroxide solution was added dropwise over 3 hours, and an aqueous solution in which 77.8 g of acrylic acid was uniformly dissolved in 200.0 g of ion-exchanged water was added dropwise over 3 hours. And simultaneously, an aqueous solution in which 4.0 g of L-ascorbic acid and 3.2 g of 3-mercaptopropionic acid as a chain transfer agent were dissolved in 35.0 g of ion-exchanged water was added dropwise over 4 hours. Then, it was maintained at 60 °C for 2 hours to complete the polymerization reaction. To this, a 30% aqueous sodium hydroxide solution was added to adjust the pH to 7, and the concentration was adjusted to 40% with ion-exchanged water. The components of this reaction product were designated as A-5.

[0099] (Production Example 6) Production of water-soluble vinyl copolymer A-6: 330.1 g of ion-exchanged water and 447.9 g of α-vinyl-ω-hydroxy-oxybutylene poly(52 mol) oxyethylene were charged into a reaction vessel and uniformly dissolved with stirring. Then, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was maintained at 10 °C in an ice water bath. And after confirming that the inside of the reaction vessel was at 10 °C, 18.4 g of acrylic acid, 3.2 g of mercaptoethanol, 0.05 g of iron(II) sulfate heptahydrate, and 1.4 g of 35% aqueous hydrogen peroxide solution were charged into this reaction vessel. Next, an aqueous solution in which 16.4 g of acrylic acid, 15.0 g of 2-hydroxyethyl acrylate, and 2.8 g of mercaptoethanol were uniformly dissolved in 31.4 g of ion-exchanged water was added dropwise over 45 minutes. And simultaneously, an aqueous solution in which 1.0 g of sodium hydroxymethanesulfinate dihydrate was uniformly dissolved in 48.8 g of ion-exchanged water was added dropwise over 45 minutes. Then, it was maintained at 10 °C for 1 hour to complete the polymerization reaction. To this, a 30% aqueous sodium hydroxide solution was added to adjust the pH to 5, and the concentration was adjusted to 40% with ion-exchanged water. The components of this reaction product were designated as A-6.

[0100] (Measurement of mass average molecular weight) The mass average molecular weights of the water-soluble vinyl copolymers A-1 to A-6 were measured by gel permeation chromatography according to the measurement conditions shown below. <Measurement conditions> Apparatus: Shodex GPC-101 (manufactured by Showa Denko) Column: OHpak SB-806M HQ + SB-806M HQ (manufactured by Showa Denko) Detector: Differential refractometer (RI) Eluent: 50 mM aqueous sodium nitrate solution Flow rate: 0.7 mL / min Column temperature: 40 °C Sample concentration: An eluent solution with a sample concentration of 0.5 mass% Standard substance: PEG / PEO (manufactured by Agilent Technologies)

[0101] (Examples 1 to 21, 27, Comparative Examples 1 to 15) (1) Preparation of concrete admixture: The various components and their blending ratios of the prepared concrete admixture are shown in Table 2 below.

[0102] Note that the concrete admixture shown in Table 2 was prepared by mixing the various components (Components A to D) shown in Table 2 at the addition ratios shown in Table 2 and using ion-exchanged water so that the total mass% became 100 mass%.

[0103]

Table 2

[0104] The following specifically shows Components B to D in Table 2 that constitute the concrete admixture.

[0105] (Component B) B-1: Sodium lignosulfonate (reagent: Kishida Chemical)

[0106] (Component C) C-1: Sucrose (reagent: Kishida Chemical) C-2: Fructose (reagent: Kishida Chemical) C-3: Maltose (Reagent: Kishida Chemical) C-4: Sorbitol (Reagent: Kishida Chemical)

[0107] (Component D): D-1: Sodium gluconate (Reagent: FUJIFILM Wako Pure Chemical Corporation) D-2: Gluconic acid (Reagent: FUJIFILM Wako Pure Chemical Corporation)

[0108] (2) Preparation of concrete composition: Next, the concrete compositions of Examples 1 to 21, 27 and Comparative Examples 1 to 15 were prepared as follows.

[0109] Ordinary Portland cement (Taiheiyo Cement, density = 3.16 cm 3 ) and, as aggregates, fine aggregate (Oigawa River system land sand, density = 2.58 cm 3 ) and coarse aggregate (Okazaki crushed stone, density = 2.66 cm 3 ) were used with Mixing Nos. 1 to 3 shown in Table 3 below, respectively. Furthermore, concrete admixtures (d-1 to d-15, dr-1 to dr-5) were used in predetermined addition amounts to prepare the concrete compositions of Examples 1 to 21 and Comparative Examples 1 to 15 (see Tables 4 to 7). At that time, the concrete admixtures were used as part of the water. Note that the concrete composition of Example 27 was prepared as described later.

[0110] In the concrete compositions of each example and comparative example, commercially available AE agent AE-300 (manufactured by Takemoto Yushi) was appropriately used to adjust the target air content within the range of 4.5 ± 1.0%. Also, the target slump was set to 18.0 ± 1.5 cm, and the addition amount of the concrete admixture was adjusted so as to be within the range.

[0111] Note that the preparation of the concrete composition was carried out in an environment at a temperature of 35°C, and each material was stored in a 35°C environment for 1 day or more before preparation so that the kneading temperature of the concrete composition was within the range of 35 ± 2°C.

[0112]

Table 3

[0113] The evaluation results of the physical properties of each concrete composition prepared by adopting each of the mixtures No. 1 to No. 3 and the addition amounts of the admixtures are shown in Tables 4 to 6 below.

[0114] In addition, in Tables 4 to 6, the evaluation criteria for the addition amounts of the admixtures are shown below. S: When the ratio to cement (cement × mass%) is 1.5% or less A: When the ratio to cement (cement × mass%) exceeds 1.5% and is 2.0% or less C: When the ratio to cement (cement × mass%) exceeds 2.0%

[0115]

Table 4

[0116]

Table 5

[0117]

Table 6

[0118] Here, Tables 7 and 8 show another preparation method of the concrete composition. Specifically, a concrete composition (intermediate concrete composition) was prepared in the same manner as in Example 1 using the concrete admixture dr-6 during production. Then, before placing (i.e., 30 minutes after production), the concrete admixture dr-7 was added to the above intermediate concrete composition to prepare a concrete composition for placing (Example 27). In this Example 27, the mass ratio of Component A / Component B during production is 50 / 50 and does not satisfy the predetermined condition (in the range of 40 / 60 to 5 / 95). However, at the time of placing, Component A (total of Component A) and Component B (total of Component B) are 30 / 70 and satisfy the predetermined mass ratio (in the range of 40 / 60 to 5 / 95). In this way, the concrete admixture may be added step by step to obtain a concrete composition that satisfies the desired conditions at the final time of placing.

[0119] [Table 7]

[0120] [Table 8]

[0121] Regarding the slump, air content, and concrete temperature in the prepared concrete composition, they were measured as follows.

[0122] (Slump) For the concrete composition immediately after remixing, it was measured in accordance with JIS-A1101 (2020).

[0123] (Air content (volume %)) For the concrete composition immediately after remixing, it was measured in accordance with JIS-A1128 (2019).

[0124] (Concrete temperature (°C)) For the concrete composition immediately after remixing, it was measured in accordance with JIS-A1156 (2006).

[0125] (3) Preparation of hardened concrete: Each of the prepared concrete compositions was cured to obtain a hardened concrete body, and the physical properties (standard curing strength, simple heat-insulating curing strength, S value, and S value reduction amount) of this hardened concrete body were evaluated. The evaluation results are shown in Tables 9 to 11 below.

[0126] The standard curing strength and simple heat-insulating curing strength were measured as follows.

[0127] Standard curing strength (N / mm 2 ): Specimens were prepared using the concrete compositions of each of the prepared examples and comparative examples, and then stored in an environment of 20 ± 3°C so as not to dry until demolding. After 24 hours, demolding was carried out, and curing was performed in water at 20 ± 3°C. Then, in accordance with JIS-A1108 (2018), the compressive strength at 28 days of age was measured.

[0128] Simple heat-insulating curing strength (N / mm 2 ): For the concrete compositions of each of the prepared examples and comparative examples, in accordance with JASS5 T-606 (2018), the compressive strength in simple heat-insulating curing at 91 days of age was measured.

[0129]

Table 9

[0130] As shown in Table 9, the standard curing strength (α) was measured. Based on the standard curing strength of the hardened concrete body of Comparative Example 4, the increase amount was calculated, and furthermore, the following evaluation criteria were adopted. The hardened concrete body of Comparative Example 4 is a hardened concrete body obtained by curing a "comparative concrete composition to which a comparative admixture with a mass ratio of A component / B component of 50 / 50 is added". S: 1.5 N / mm 2 or more, when increased A: 0 N / mm 2 or more and less than 1.5 N / mm 2 when increased, B: 0 N / mm 2 Over 1.5 N / mm 2 When decreased below C: 1.5 N / mm 2 When decreased below and over

[0131] As shown in Table 9, the simple heat-insulating curing strength (β) was measured. Based on the standard curing strength of the concrete hardened body in Comparative Example 4, the increase amount was calculated, and furthermore, the following evaluation criteria were adopted. S: 6.0 N / mm 2 When increased above A: 3.0 N / mm 2 Above and below 6.0 N / mm 2 When increased but less than B: 0 N / mm 2 Above and below 3.0 N / mm 2 When increased but less than C: 0 N / mm 2 When decreased below and over

[0132] The evaluation of the S value reduction amount was calculated by the formula: S value of the comparative concrete (concrete hardened body in Comparative Example 4) - S value of the concrete hardened body in each test example, and the evaluation was carried out according to the following evaluation criteria. S: 3.5 N / mm 2 When reduced below and above A: 2.5 N / mm 2 Above and below 3.5 N / mm 2 When reduced but less than B: 1.5 N / mm 2 Above and below 2.5 N / mm 2 When reduced but less than C: 1.5 N / mm 2 When reduced but less than

[0133]

Table 10

[0134] As shown in Table 10, the standard curing strength was measured as (α). Based on the standard curing strength of the concrete hardened body of Comparative Example 9, the increase amount was calculated, and furthermore, the following evaluation criteria were adopted. Note that the concrete hardened body of Comparative Example 9 is a concrete hardened body obtained by curing a "comparative concrete composition to which a comparative admixture with a mass ratio of A component / B component of 50 / 50 was added". S: 1.0 N / mm 2 When increased above A: 0 N / mm 2 Above and 1.0 N / mm 2 When increased but less than B: 0 N / mm 2 Exceeding and 1.0 N / mm 2 When decreased below C: 1.0 N / mm 2 When decreased exceeding

[0135] As shown in Table 10, the simple heat insulation curing strength (β) was measured. Based on the standard curing strength of the concrete hardened body of Comparative Example 9, the increase amount was calculated, and furthermore, the following evaluation criteria were adopted. S: 4.0 N / mm 2 When increased above A: 2.0 N / mm 2 Above and 4.0 N / mm 2 When increased but less than B: 0 N / mm 2 Above and 2.0 N / mm 2 When increased but less than C: 0 N / mm 2 When decreased exceeding

[0136] The evaluation of the S value reduction amount was carried out by calculating the S value reduction amount according to the formula: S value of the comparative concrete (concrete hardened body of Comparative Example 9) - S value of the concrete hardened body of each test example, and evaluating with the following evaluation criteria. S: 2.5 N / mm 2 When reduced above A: 2.0 N / mm 2 Above and 2.5 N / mm 2 When reduced but less than B: 1.5 N / mm 2 Above and 2.0 N / mm 2When less or reduced C: 1.5 N / mm 2 When less or reduced

[0137]

Table 11

[0138] As shown in Table 11, the standard curing strength (α) was measured. Based on the standard curing strength of the concrete hardened body in Comparative Example 14, the increase amount was calculated, and furthermore, the following evaluation criteria were adopted. Note that the concrete hardened body in Comparative Example 14 is a concrete hardened body obtained by hardening a "comparative concrete composition to which a comparative admixture with a mass ratio of A component / B component of 50 / 50 is added". S: 2.0 N / mm 2 When increased above A: 0 N / mm 2 Above and 2.0 N / mm 2 When increased but less B: 0 N / mm 2 Exceeding and 2.0 N / mm 2 When decreased below C: 2.0 N / mm 2 When decreased and exceeding

[0139] As shown in Table 11, the simple heat-insulating curing strength (β) was measured. Based on the standard curing strength of the concrete hardened body in Comparative Example 14, the increase amount was calculated, and furthermore, the following evaluation criteria were adopted. S: 8.0 N / mm 2 When increased above A: 4.0 N / mm 2 Above and 8.0 N / mm 2 When increased but less B: 0 N / mm 2 Above and 4.0 N / mm 2 When increased but less C: 0 N / mm 2 When decreased and exceeding

[0140] The reduction amount of the S value was evaluated by calculating the reduction amount of the S value using the formula: S value of the comparative concrete (the hardened concrete of Comparative Example 14) - S value of the hardened concrete of each test example, and the evaluation was performed according to the following evaluation criteria. S: 4.5 N / mm 2 When reduced to the above A: 3.0 N / mm 2 When reduced to above and less than 4.5 N / mm 2 When reduced to less than the above B: 1.5 N / mm 2 When reduced to above and less than 3.0 N / mm 2 When reduced to less than the above C: 1.5 N / mm 2 When reduced to less than the above

[0141] Here, Table 12 shows the physical properties of the hardened concrete for Example 27. The evaluation criteria adopted were the same as those for Examples 1 to 15 described above.

[0142]

Table 12

[0143] (Examples 22 to 24, Comparative Example 16) For the concrete admixtures (d-1, dr-4), except that the environmental temperature shown in Table 13 was used, the concrete compositions of Examples 22 to 24 and Comparative Example 16 were prepared in the same manner as in Example 1 and Comparative Example 4. Before preparation, each material was stored in a predetermined environment for 1 day or more so that the kneading temperature of the concrete composition was within the range of ±2°C with respect to each environmental temperature. The temperature of the concrete composition (concrete temperature) prepared in the same manner as in Example 1 and Comparative Example 4 was measured, and the standard curing strength, simple heat insulation curing strength, and S value were measured. The measurement results are shown in Table 13.

[0144]

Table 13

[0145] In Examples 22 to 24 and Comparative Example 16, the "ambient temperature" was the daily average temperature at the time of placing into the formwork, and the "concrete temperature" was the concrete temperature at the time of placing into the formwork.

[0146] In Examples 22 to 24, the S value was sufficiently reduced as compared with Comparative Example 4 (ambient temperature: 35°C), and an effective S value reduction effect was shown regardless of the ambient temperature and the concrete temperature.

[0147] On the other hand, Comparative Example 16 is a concrete composition prepared using a concrete admixture (dr-4). The ambient temperature at which the concrete composition was prepared was 20°C, and the concrete temperature was 21°C. In this Comparative Example 16, when compared with Comparative Example 4 prepared at an ambient temperature of 35°C using the same concrete admixture (dr-4), the S value in Comparative Example 16 was a small value (5.3 N / mm 2 for Comparative Example 4, versus 2.9 N / mm 2 ). That is, when the ambient temperature is low (about 20°C), the S value is small even with the same formulation. Here, when taking the S value of the hardened concrete of Comparative Example 16 (ambient temperature 20°C) as a reference, the reduction amount of the S value of the hardened concrete of Example 24 (ambient temperature 19°C) prepared under the same "ambient temperature" and "concrete temperature" conditions was 2.5 N / mm 2 (formula: 2.9 N / mm 2 - 0.4 N / mm 2 ). This is a smaller value compared to the S value reduction amount of 4.4 N / mm 2 (formula: 5.3 N / mm 2 - 0.9 N / mm 2 ) of Example 1.

[0148] From such results, when the environmental temperature and the concrete temperature are about 20°C, even for a concrete composition using a conventional concrete admixture, since it does not exceed 25°C, the S value is small. Specifically, as shown in Comparative Example 4 and Comparative Example 16, in Comparative Example 16, the S value is smaller than that in Comparative Example 4. Conversely, in terms of this point, it can be seen that when the environmental temperature exceeds 25°C as in Comparative Example 4, the S value becomes larger. When using the concrete admixture of the examples, the S value becomes smaller regardless of the environmental temperature, but particularly when the environmental temperature is high (25°C or higher), the reduction amount of the S value can be increased. Thus, by adopting the concrete composition of the present invention under predetermined conditions, a concrete hardened body with the structural strength correction value (S value) effectively reduced can be obtained.

[0149] (Examples 25 - 26, Comparative Examples 17 - 18) Furthermore, Table 14 shows the results of preparing mass concrete using the concrete composition. The concrete composition was prepared for the concrete compositions of Examples 25, 26 and Comparative Examples 17, 18 using the same method as in Example 1 and Comparative Example 4, except that a forced two-shaft mixer of 3 m 3 was used and the environment was set to 21°C. Also, for the prepared concrete compositions, in accordance with JASS5 T-605 (2018), simulated members with the dimensions shown in Table 14 were fabricated, stored in an environment of 21°C, and then core specimens were taken, and the compressive strength of the core specimens at 91 days of age was measured. Each core specimen was fabricated by taking from the above-mentioned simulated members in accordance with JASS5 T-605 (2018). Specifically, two cylindrical bodies with a diameter of 100 mm were taken from the central part and the outer peripheral part of the simulated member in the longitudinal direction (the central axis direction of the simulated member) as core specimens.

[0150]

Table 14

[0151] Large-volume concrete (mass concrete) tends to retain reaction heat such as hydration heat generated during hardening inside it, and has a tendency to undergo a high temperature history, often resulting in a large structural strength correction value (S value). However, the concrete compositions (Examples 25 to 26) prepared using the concrete admixture (d-1) exhibited an effective S value reduction effect regardless of the member dimensions, and a sufficient S value reduction effect was also confirmed in the hardened concrete of Example 26, which is a 1000 mm square simulated member (mass concrete).

[0152] On the other hand, Comparative Examples 17 to 18 are concrete compositions prepared using the concrete admixture (dr-4). Particularly in Comparative Example 18, which is a 1000 mm square simulated member (mass concrete), despite the ambient temperature (21°C) and the concrete temperature (23°C) both being around 20°C, the S value showed a large value (5.6 N / mm 2 ). When taking the S value (5.6 N / mm 2 ) of the hardened concrete of Comparative Example 18 as a reference, the S value reduction amount of the hardened concrete of Example 26 prepared with the same member dimensions is 4.2 N / mm 2 (Formula: 5.6 N / mm 2 - 1.4 N / mm 2 ).

[0153] From such results, when the member dimensions to be applied are large, specifically, in the case of mass concrete such as a cube with a simulated member dimension of 1000 mm as shown in Comparative Example 18, as can be seen by comparing Comparative Examples 17 and 18, when the member dimensions are large, the S value is large. On the other hand, in Example 26 employing the concrete composition of the present invention, although the dimension of the simulated member is a 1000 mm cube, the S value is smaller than that in the case of Comparative Example 18. Therefore, by adopting the concrete composition of the present invention for mass concrete, the effect of exhibiting an excellent reduction effect on the structural strength correction value (S value) is achieved.

[0154] (Results) As shown in Tables 9 to 14, it was confirmed that by adding to the concrete admixture of this example, an excellent reduction effect was exhibited on the structural strength correction value (S value) in the hardened body of concrete (concrete hardened body) such as midsummer concrete and mass concrete.

Industrial Applicability

[0155] The concrete admixture of the present invention can be added to and used in concrete such as midsummer concrete and mass concrete. Further, the concrete composition of the present invention can be used to form a concrete hardened body such as a building structure. The driving method of the concrete composition of the present invention can be adopted as a driving method of the concrete composition for producing a building structure or the like. The mass concrete of the present invention can be used to form a concrete hardened body such as a building structure.

Claims

1. At least one A component selected from water-soluble vinyl copolymers containing 50 to 99% by mass of the following structural unit 1 and 1 to 50% by mass of the following structural unit 2, and having a mass average molecular weight of 2,000 to 500,000, and at least one B component selected from lignin sulfonic acid and lignin sulfonate, wherein the mass ratio of the A component / the B component is in the range of 40 / 60 to 5 / 95, which is added to a concrete composition and reduces the S value, which is the structural strength correction value in the cured body of the concrete composition, The reduction amount of the S value, which is the difference between the S value of the concrete composition and the S value of the comparative concrete composition to which a comparative admixture with a mass ratio of the A component / the B component of 50 / 50 is added, is 1.5 N / mm ２ or more. A concrete admixture characterized by the above. Structural unit 1: It is a structural unit formed from a compound represented by the following general formula (1). 【Chemical 1】 (However, in the general formula (1), R １ is an alkenyl group having 2 to 5 carbon atoms or an unsaturated acyl group having 3 to 4 carbon atoms. AO １ is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of such oxyalkylene groups are present, they may be of one kind alone or two or more kinds). R ２ is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. m is the average number of moles of addition of AO １ and is a number from 1 to 300) Structural unit 2: It is a structural unit formed from at least one selected from (meth) acrylic acid, (meth) acrylate, (anhydrous) maleic acid, maleate, fumaric acid, and fumarate.

2. The concrete admixture according to claim 1, wherein the mass ratio of the A component / the B component is in the range of 30 / 70 to 5 / 95.

3. The concrete admixture according to claim 1, further containing at least one C component selected from saccharides.

4. The concrete admixture according to claim 3, wherein the C component contains both sucrose and fructose.

5. A concrete composition comprising the concrete admixture according to any one of claims 1 to 4, cement, water, fine aggregate, and coarse aggregate.

6. A method for placing a concrete composition, characterized in that at least one of the following conditions (1) and (2) is satisfied when placing the concrete composition according to claim 5 into a formwork. (1) The temperature of the concrete composition at the time of placing into the formwork is 25 ° C or higher (2) The average daily temperature at the time of placing into the formwork is 25 ° C or higher

7. Mass concrete comprising the concrete composition according to claim 5.

Images