Dispersant composition for hydraulic powder

Abstract

To provide a dispersant composition for a hydraulic powder capable of imparting excellent freeze-thaw resistance to a hardened body of a hydraulic composition.SOLUTION: There is provided a dispersant composition for a hydraulic powder which comprises a copolymer (A) containing a constitutional unit (A1) represented the following formula (A1) and a constitutional unit (A2) represented by the following formula (A2) as constitutional units and having a weight average molecular weight of 40000 or more and 60000 or less, wherein in the copolymer (A), the ratio of the constitutional unit (A2) to the total of the constitutional unit (A1) and the constitutional unit (A2) is 20 mass% or more and 28 mass% or less and in the copolymer (A), the ratio of a compound having a molecular weight of 8000 or less is 5.0 mass% or more and 15.0 mass% or less. (A1):-[CH2-C(R1a)(COOM1)]-, (A2):-[CH2-C(R2a)(X1-O-(CH2CH2O)n1-R3a)]-.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a dispersant composition for hydraulic powder and a hydraulic composition.

Background Art

[0002] In the hardened body of a hydraulic composition such as concrete, there is a phenomenon in which the hardened body gradually deteriorates due to repeated freezing and thawing over the years. This is called freeze-thaw damage and is caused by the expansion of excess water in the hardened body or water that penetrates from the outside due to freezing. An air-entraining agent (hereinafter referred to as an AE agent) is used for the purpose of improving the freeze-thaw resistance of the hardened body of a hydraulic composition. For example, it is known that entraining about 4% of air bubbles in concrete is effective against freeze-thaw damage (Concrete Handbook, pages 87-95, edited by the Japan Concrete Institute, published in May 1976). Various highly foaming surfactants such as water-soluble salts of resin acids are used as the AE agents used for this purpose (Concrete Handbook, pages 228-233, edited by the Japan Concrete Institute, published in May 1976). However, with conventional AE agents, the amount of air bubbles in the initial stage of concrete preparation (mixing) can be set relatively accurately, but the amount of air bubbles may change over time. Also, when used in combination with a dispersant, the amount of air bubbles in the concrete may decrease.

[0003] Conventionally, it has been proposed to improve admixtures used in hydraulic compositions to improve the freeze-thaw resistance of the hardened body. For example, in Patent Document 1, there is disclosed an admixture for a hydraulic composition containing (A) a specific acrylic acid copolymer, (B) a specific acrylic acid ester copolymer, (C) polyethylene glycol having a weight average molecular weight of 9,000 or more and 18,000 or less, and (D) a polysaccharide derivative in which some or all of the hydrogen atoms of the hydroxyl groups of a polysaccharide or its alkylated derivative or hydroxyalkylated derivative are substituted with a specific hydrophobic substituent and a specific ionic hydrophilic group.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides a dispersant composition for hydraulic powder that can impart excellent freeze-thaw resistance to a hardened body of a hydraulic composition.

Means for Solving the Problems

[0006] The present invention is a dispersant composition for hydraulic powder containing a copolymer (A) having a weight average molecular weight of 40,000 or more and 60,000 or less and containing a structural unit (A1) represented by the following formula (A1) and a structural unit (A2) represented by the following formula (A2) as constituent units, In the copolymer (A), the ratio of the structural unit (A 1 ) is 20% by mass or more and 28% by mass or less based on the total of the structural unit (A1) and the structural unit (A2), In the copolymer (A), the ratio of a compound having a molecular weight of 8,000 or less is 5.0% by mass or more and 15.0% by mass or less, relates to a dispersant composition for hydraulic powder.

[0007]

Chemical Formula

[0008] [In the formula, R 1a and R 2a are the same or different and each represents a hydrogen atom or a methyl group, R 3a represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, M 1 represents a hydrogen atom or a counter ion that forms a salt, X 1 represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, and n1 represents the average number of added moles and is a number of 70 or more and 170 or less. ]

[0009] The present invention also relates to a hydraulic composition containing a hydraulic powder, water, and the dispersant composition for hydraulic powder of the present invention.

Advantages of the Invention

[0010] According to the present invention, there is provided a dispersant composition for hydraulic powder that can impart excellent freeze-thaw resistance to a hardened body of a hydraulic composition.

Embodiments for Carrying Out the Invention

[0011] <Dispersant Composition for Hydraulic Powder> In the present invention, by using the copolymer (A), it is possible to impart excellent freeze-thaw resistance to a hardened body of a hydraulic composition. The reason for this is not necessarily clear, but the present inventor speculates as follows. The copolymer (A) of the present invention contains a predetermined amount of a structural unit (A1) in the structural unit and also contains a compound in a predetermined low molecular weight region. Such a composition of the structural unit and the low molecular compound are excellent in air entrainment. On the other hand, the copolymer (A) also contains a certain amount of a compound in a molecular weight region with excellent dispersibility. As a result, while maintaining the function as a dispersant, it is considered that fine air can be entrained into the hydraulic composition, improving the freeze-thaw property. Considering the impact on the environment, cost, physical properties, etc., as a part of the hydraulic powder, alternative powders such as fly ash may be used, but in that case, the air entrainment tends to decrease. However, the copolymer (A) of the present invention does not reduce the air entrainment even when fly ash is used, so a hardened body with excellent freeze-thaw property can be obtained.

[0012] The copolymer (A) contains a structural unit (A1) represented by the following formula (A1) and a structural unit (A2) represented by the following formula (A2) as structural units, has a weight average molecular weight of 40,000 or more and 60,000 or less, and the proportion of the structural unit (A 1 ) with respect to the total of the structural unit (A1) and the structural unit (A2) is 20% by mass or more and 28% by mass or less, and the proportion of a compound with a molecular weight of 8,000 or less is 5.0% by mass or more and 15.0% by mass or less.

[0013] [Chemical formula]

[0014] [In the formula, R 1a and R 2a are the same or different and each represents a hydrogen atom or a methyl group, R 3a represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, M 1 represents a hydrogen atom or a counter ion forming a salt, X 1 represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, n1 represents the average number of moles added, and is a number between 70 and 170. ]

[0015] In formula (A1), R 1a represents a hydrogen atom or a methyl group, and a methyl group is preferred. In formula (A1), M 1 represents a hydrogen atom or a counter ion forming a salt. Examples of the counter ion forming a salt include alkali metal ions such as sodium ion and potassium ion, ammonium ion, alkanolammonium ion, and the like.

[0016] In formula (A2), R 2a represents a hydrogen atom or a methyl group, and a methyl group is preferred. In formula (A2), R 3a represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group is more preferred. In formula (A2), X 1 represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group (CO group), and a carbonyl group (CO group) is preferred. In formula (A2), n1 represents the average number of moles of addition of (CH2CH2O), which is 70 or more, preferably 80 or more, more preferably 90 or more, still more preferably 100 or more, preferably 115 or more, and 170 or less, preferably 160 or less, more preferably 150 or less, still more preferably 140 or less, even more preferably 130 or less, even more preferably 125 or less.

[0017] The copolymer (A) may optionally contain a structural unit other than the structural unit (A1) and the structural unit (A2). The optional structural unit may be, for example, a structural unit of a monomer such as methyl acrylate, hydroxyethyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxymethyl acrylate, hydroxyethyl methacrylate, and hydroxymethyl methacrylate, 2-(methacryloyloxy)ethyl phosphate (HEMA-P), allyl sulfonic acid, methallyl sulfonic acid, and salts thereof, such as alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts. Further, it may be a structural unit of a monomer such as (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-(meth)acrylamide-2-methanesulfonic acid, 2-(meth)acrylamide-2-ethanesulfonic acid, 2-(meth)acrylamide-2-propanesulfonic acid, styrene, styrene sulfonic acid, etc.

[0018] From the viewpoint of imparting workability to the hydraulic composition, the copolymer (A) has a proportion of the structural unit (A 1 ) of 20% by mass or more, preferably 22% by mass or more, and 28% by mass or less, preferably 26% by mass or less, based on the total of the structural unit (A1) and the structural unit (A2). In the present invention, the amount of the structural unit of the copolymer (A) may be calculated based on the charged amount of the monomer used for the synthesis of the copolymer (A).

[0019] Also, from the viewpoint of imparting dispersibility to the hydraulic composition, the proportion of the structural unit (A1) and the structural unit (A2) in all the structural units of the copolymer (A) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and 100% by mass or less, and may be 100% by mass.

[0020] The copolymer (A) has a weight average molecular weight of 40,000 or more, preferably 42,000 or more, and 60,000 or less, preferably 57,000 or less, from the viewpoint of imparting dispersibility. The weight average molecular weight of the copolymer (A) was measured by the GPC method under the conditions of a high-speed GPC apparatus (HLC-8320GPC), Tosoh Corporation, detector: RI, column: G4000PWXL + G2500PWXL (anion), mobile phase: 0.2M phosphate buffer / acetonitrile = 9 / 1, flow rate: 1.0 ml / min., column temperature: 40 °C, standard substance: polyethylene glycol).

[0021] From the viewpoint of fine air entrainment, the copolymer (A) has a proportion of a compound having a molecular weight of 8,000 or less (hereinafter also referred to as a low molecular ratio) of 5.0% by mass or more, preferably 6.0% by mass or more, and 15.0% by mass or less, preferably 14.0% by mass or less. The low molecular ratio of the copolymer (A) was measured by the ratio of the peak areas by the above GPC method.

[0022] The dispersant composition for hydraulic powder of the present invention preferably contains a copolymer (B) containing a structural unit (B1) represented by the following formula (B1) and a structural unit (B2) represented by the following formula (B2) as structural units, and the proportion of the structural unit (B1) in all the structural units is 5% by mass or more and less than 8% by mass.

[0023]

Chemical formula

[0024] [In the formula, R 1b and R 2b are the same or different and each represents a hydrogen atom or a methyl group, R 3b represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, M 2 represents a hydrogen atom or a counter ion that forms a salt, X 2 represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, n2 represents the average number of added moles, and is a number of 5 or more and 150 or less.]

[0025] In formula (B1), R 1b represents a hydrogen atom or a methyl group, and a methyl group is preferred. In formula (B1), M 2 represents a hydrogen atom or a counter ion that forms a salt. Examples of the counter ion that forms a salt include alkali metal ions such as sodium ion and potassium ion, ammonium ion, alkanolammonium ion, and the like.

[0026] In formula (B2), R 2b represents a hydrogen atom or a methyl group, and a methyl group is preferred. In formula (B2), R 3b represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group is more preferred. In formula (B2), X 2 represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond, or a carbonyl group (CO group), and a carbonyl group (CO group) is preferred. In formula (B2), n2 represents the average number of moles of addition of (CH2CH2O), and is a number of 5 or more, preferably 10 or more, more preferably 20 or more, and 150 or less, preferably 140 or less, more preferably 130 or less.

[0027] The copolymer (B) may optionally contain constitutional units other than the constitutional unit (B1) and the constitutional unit (B2). Optional constitutional units include, for example, methyl acrylate, hydroxyethyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxymethyl acrylate, hydroxyethyl methacrylate, and hydroxymethyl methacrylate, 2-(methacryloyloxy)ethyl phosphate (HEMA-P), allyl sulfonic acid, methallyl sulfonic acid, and salts thereof, such as alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts. Further, it may be a constitutional unit of a monomer such as (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-(meth)acrylamide-2-methanesulfonic acid, 2-(meth)acrylamide-2-ethanesulfonic acid, 2-(meth)acrylamide-2-propanesulfonic acid, styrene, styrene sulfonic acid. The copolymer (B) may contain a constitutional unit of a monomer selected from methyl acrylate and hydroxyethyl acrylate as a constitutional unit.

[0028] In the copolymer (B), the proportion of the constitutional unit (B1) in all the constitutional units is 5% by mass or more and less than 8% by mass. In the present invention, the amount of the constitutional unit of the copolymer (B) may be calculated based on the charged amount of the monomer used for the synthesis of the copolymer (B).

[0029] Also, from the viewpoint of dispersibility at a low addition amount in the hydraulic composition, the proportion of the constitutional unit (B2) with respect to the total of the constitutional unit (B1) and the constitutional unit (B2) in the copolymer (B) is preferably 70% by mass or more, more preferably 75% by mass or more, still more preferably 80% by mass or more, and preferably less than 98% by mass, more preferably 96% by mass or less, still more preferably 94% by mass or less, and even more preferably 92% by mass or less.

[0030] Further, in the copolymer (B), the proportion of the constitutional unit (B1) and the constitutional unit (B2) in all the constitutional units is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or less, and 100% by mass or less, and may be 100% by mass.

[0031] The copolymer (B) preferably has a weight average molecular weight of 30,000 or more, more preferably 40,000 or more, and preferably 100,000 or less, more preferably 80,000 or less. The weight average molecular weight of the copolymer (B) is measured by the same method as that of the copolymer (A).

[0032] When the dispersant composition for hydraulic powder of the present invention contains the copolymer (B), the mass ratio of the copolymer (A) / copolymer (B), which is the mass ratio of the content of the copolymer (A) to the content of the copolymer (B), is preferably 0.1 or more, more preferably 0.2 or more, and preferably 0.8 or less, more preferably 0.7 or less from the viewpoint of fine air entrainment.

[0033] The dispersant composition for hydraulic powder of the present invention can contain, as optional components other than the copolymer (B), components such as retarders, hardening accelerators, AE agents, swelling agents, foaming agents, thickeners, fluidizing agents, foaming agents, waterproof agents, antifoaming agents, etc.

[0034] The dispersant composition for hydraulic powder of the present invention can be used for hydraulic powder containing fly ash, and further for hydraulic powder containing 30% by mass or less of fly ash in the hydraulic powder. The fly ash includes, for example, fly ash having a Blaine value of less than 4,000 cm 2 / g.

[0035] <Hydraulic composition> The present invention relates to a hydraulic composition containing a hydraulic powder, water, and the dispersant composition for hydraulic powder of the present invention. The hydraulic composition of the present invention may be a hydraulic composition containing a hydraulic powder, water, a copolymer (A), and optionally a copolymer (B). The matters described in the dispersant composition for hydraulic powder of the present invention can be appropriately applied to the hydraulic composition of the present invention.

[0036] Hydraulic powder is powder having physical properties that harden by a hydration reaction, and examples thereof include cement and gypsum. Cement is preferred. Examples of cement include ordinary Portland cement, belite cement, medium heat cement, early strength cement, super early strength cement, sulfate resistant cement, and the like. Further, blast furnace slag cement, fly ash cement, silica fume cement, etc. to which powders having pozzolanic action and / or latent hydraulicity such as blast furnace slag, fly ash, and silica fume, and stone powder (calcium carbonate powder) are added may also be used.

[0037] The hydraulic powder may contain fly ash. In the hydraulic powder, the proportion of fly ash may be, for example, 40% by mass or less, further 30% by mass or less, further 25% by mass or less, and further 20% by mass or less. The Blaine value of fly ash is preferably less than 5000 cm 2 / g, more preferably 4500 cm 2 / g or less. The Blaine value is the specific surface area measured by the Blaine specific surface area measurement method. Specifically, the Blaine value of fly ash is measured using a Blaine air permeability apparatus defined in the physical test method for cement (JIS R5201). As the fly ash, for example, when pulverized coal is burned in a coal-fired power plant, by-products obtained by collecting fine particles in which molten ash is cooled and formed into spherical shapes with an electrostatic precipitator or the like can be used. The main components of fly ash are silica (SiO2) and alumina (Al2O3), and these two inorganic components typically account for, for example, 70 to 80% by mass of the whole. In addition, typically, it contains a small amount of ferric oxide (Fe2O3), magnesium oxide (MgO), calcium oxide (CaO), and the like. The chemical composition of fly ash, relative to the total mass of fly ash, preferably has SiO2 at 50 - 70% by mass, Al2O3 at 16 - 20% by mass, Fe2O3 at 5 - 6% by mass, and CaO at 1 - 3% by mass. The quality of fly ash may correspond to any of Class I, Class II, Class III, or Class IV fly ash specified in, for example, JIS A6201 - 2008 (Fly Ash for Concrete). Also, from the perspective of cost, fly ash with a SiO2 ratio of less than 50% by mass can also be used. The loss on ignition of fly ash is not particularly limited, but is preferably 5% or less, more preferably 3% or less. The loss on ignition of fly ash can be measured, for example, by the loss on ignition test method (heating fly ash at a high temperature of 950 - 1000°C, calculating the loss on ignition from the mass reduction rate, drying at 105°C for 3 hours, obtaining the moisture content from the mass reduction rate at constant temperature, and calculating the unburned carbon content by subtracting the moisture content from the loss on ignition of fly ash). The average particle size of fly ash is not particularly limited, but is preferably 15 - 25 μm. The average particle size of fly ash means the average particle size at the 50% integrated value in the particle size distribution determined by the laser diffraction / scattering method, that is, the median diameter (D 50 ).

[0038] The hydraulic composition of the present invention preferably has a water / hydraulic powder ratio of 40% by mass or more, more preferably 42% by mass or more, and preferably 50% by mass or less, more preferably 48% by mass or less. Here, the water / hydraulic powder ratio is the mass percentage (% by mass) of water and hydraulic powder in the hydraulic composition, and is calculated by (mass of water) / (mass of hydraulic powder) × 100. The water / hydraulic powder ratio is calculated based on the amount of water and the amount of powder having physical properties that harden by a hydration reaction. When the hydraulic powder contains a powder having a pozzolanic action, a powder having latent hydraulicity, and stone powder (calcium carbonate powder), in the present invention, their amounts are also included in the amount of the hydraulic powder. Further, when the powder having physical properties that harden by a hydration reaction contains a high-strength admixture, the amount of the high-strength admixture is also included in the amount of the hydraulic powder. This also applies to parts by mass and mass ratios in which the mass of the hydraulic powder is relevant.

[0039] The hydraulic composition of the present invention preferably contains an aggregate. Examples of the aggregate include aggregates selected from fine aggregates and coarse aggregates. Examples of the fine aggregate include those defined by No. 2311 in JIS A0203-2014. Examples of the fine aggregate include river sand, land sand, mountain sand, sea sand, lime sand, silica sand, and crushed sand thereof, blast furnace slag fine aggregate, ferronickel slag fine aggregate, lightweight fine aggregate (artificial and natural), and recycled fine aggregate. Examples of the coarse aggregate include those defined by No. 2312 in JIS A0203-2014. For example, examples of the coarse aggregate include river gravel, land gravel, mountain gravel, sea gravel, lime gravel, crushed stone thereof, blast furnace slag coarse aggregate, ferronickel slag coarse aggregate, lightweight coarse aggregate (artificial and natural), and recycled coarse aggregate. The fine aggregate and the coarse aggregate may be used as a mixture of different types or a single type may be used.

[0040] When the hydraulic composition of the present invention is concrete, from the viewpoints of expressing the strength of the hydraulic composition, reducing the amount of hydraulic powder such as cement, and improving the fillability into a formwork or the like, the bulk volume is preferably 50% or more, more preferably 55% or more, still more preferably 60% or more, and preferably 100% or less, more preferably 90% or less, still more preferably 80% or less. The bulk volume is the ratio of the volume (including voids) of the coarse aggregate in 1 m 3 of concrete. Also, when the hydraulic composition of the present invention is concrete, from the viewpoint of improving the fillability into a formwork or the like, the amount of fine aggregate used is preferably 500 kg / m 3 or more, more preferably 600 kg / m 3 or more, still more preferably 700 kg / m 3 or more, and preferably 1,000 kg / m 3 or less, more preferably 900 kg / m 3 or less. Also, when the hydraulic composition of the present invention is mortar, the amount of fine aggregate used is preferably 800 kg / m 3 or more, more preferably 900 kg / m 3 or more, still more preferably 1,000 kg / m 3 or more, and preferably 2,000 kg / m 3 or less, more preferably 1,800 kg / m 3 or less, still more preferably 1,700 kg / m 3 or less.

[0041] The hydraulic composition of the present invention can contain, as optional components, for example, components such as retarders, hardening accelerators, AE agents, swelling agents, foaming agents, thickeners, fluidizing agents, foaming agents, waterproof agents, defoaming agents, and the like.

[0042] 〔Method for producing hydraulic composition〕 The present invention provides a method for producing a hydraulic composition by mixing a hydraulic powder, water, and a dispersant composition for the hydraulic powder of the present invention. The method for producing a hydraulic composition of the present invention may be a method for producing a hydraulic composition by mixing a hydraulic powder, water, a copolymer (A), and optionally a copolymer (B). In the method for producing a hydraulic composition of the present invention, the matters described in the dispersant composition for the hydraulic powder and the hydraulic composition of the present invention can be appropriately applied. Note that the content of each component in the dispersant composition for the hydraulic powder and the hydraulic composition of the present invention can be applied to the method for producing a hydraulic composition of the present invention by reading it as a mixing amount. The mixing of the hydraulic powder, water, the copolymer (A), and the optional copolymer (B) can be performed using a mixer such as a mortar mixer or a forced biaxial mixer.

Examples

[0043] (1) Preparation of concrete Using the copolymers (A) and (B) shown in Table 1, concrete was produced with the formulation shown in Table 2. Specifically, after charging the coarse aggregate (G) into a forced biaxial mixer, the fine aggregate (S), the coarse aggregate (G), and the cement (C) were charged and stirring was started. The mixing water (W) obtained by mixing the copolymer (A), the copolymer (B), and water was charged simultaneously with the start of stirring of the mixer so that the addition amounts (parts by mass relative to 100 parts by mass of cement) of the copolymer (A) and the copolymer (B) were the values shown in Table 3. After 90 seconds from the start, the concrete was discharged from the mixer to obtain concrete.

[0044]

Table 1

[0045] The table shows the monomers of each structural unit. In the table, ME(120)E is ω-methoxypolyethylene glycol monomethacrylate [methanol ethylene oxide (average addition mole number 120) adduct · methacrylic acid ester] (in the general formula (A2), R 2a is a methyl group, X 1 is a carbonyl group, n1 is 120, and R 3a is a methyl group compound).

[0046]

Table 2

[0047] The components in the table are as follows. Also, W / P is the water / hydraulic powder ratio, and P is the total amount of C and FA. W: Tap water Cement (C): Ordinary Portland cement (two types mixed: Taiheiyo Cement / Sumitomo Osaka Cement = 1 / 1, mass ratio), density 3.16 g / cm 3 Fly ash (FA): Fly ash (two types mixed: Miike production / Kyotanabe production = 1 / 1 (mass ratio)), Blaine value 4026 cm 2 / g, loss on ignition 4.68%, average particle size 20 μm Fine aggregate (S): Shiroyama sand produced in Seongyang, density 2.55 g / cm 3 Coarse aggregate (G): Limestone crushed stone 2010 / Limestone crushed stone 1005 = 1 / 1, mass ratio), density 2.72 g / cm 3

[0048] (2) Evaluation of freeze-thaw resistance It was carried out in accordance with JIS A1148. The test method was Method A. The concrete produced in (1) was placed in a formwork of 10 cm × 10 cm × 40 cm and demolded 24 hours later. Thereafter, the specimens were cured in a water tank at 20 ± 2°C until the age of 28 days, which was the starting age of the test. After 28 days, the cured specimens were used in a freeze-thaw resistance test using a freeze-thaw testing machine (manufactured by Marui Co., Ltd., one-tank type brine circulation method). One cycle of freeze-thaw was defined as cooling from 5°C to -18°C and then heating from -18°C to 5°C. The maximum and minimum temperatures at the center of the specimen in each cycle were in the ranges of 5 ± 2°C and -18 ± 2°C, respectively. The time required for one cycle of freeze-thaw was 3 hours or more and 4 hours or less. The measurement items were the first resonance frequency and mass of the flexural vibration of each specimen according to JIS A1127, and the measurement times were before the start of the test after the end of water curing and at intervals not exceeding 36 cycles. The measurement was carried out with a target of 300 cycles or more. In this evaluation, when the relative dynamic elastic modulus is 80% or more after exceeding 300 cycles, it can be judged that the freeze-thaw resistance is excellent.

[0049]

Table 3

Claims

1. A dispersant composition for hydraulic powder, containing a copolymer (A) having a weight average molecular weight of 40,000 or more and 60,000 or less, which contains a structural unit (A1) represented by the following formula (A1) and a structural unit (A2) represented by the following formula (A2) as constituent units, in the copolymer (A), the ratio of the structural unit (A1) to the total of the structural unit (A1) and the structural unit (A2) is 20% by mass or more and 28% by mass or less, and the ratio of the compound having a molecular weight of 8,000 or less in the copolymer (A) is 5.0% by mass or more and 15.0% by mass or less. A dispersant composition for hydraulic powder. 【Chemical Formula 1】 [In the formula, R １ａ and R ２ａ are the same or different and each represents a hydrogen atom or a methyl group, R ３ａ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, M １ represents a hydrogen atom or a counter ion forming a salt, X １ represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, n1 represents the average number of added moles and is a number of 70 or more and 170 or less. ]

2. The dispersant for hydraulic powder according to claim 1, wherein the copolymer (A) has a ratio of the structural unit (A1) and the structural unit (A2) in all the constituent units of 80% by mass or more and 100% by mass or less.

3. Further, a copolymer (B) is contained, which contains a structural unit (B1) represented by the following formula (B1) and a structural unit (B2) represented by the following formula (B2) as constituent units, and the ratio of the structural unit (B1) in all the constituent units is 5% by mass or more and less than 8% by mass. The dispersant composition for hydraulic powder according to claim 1 or 2. 【Chemical Formula 2】 [In the formula, R １ｂ and R ２ｂ are the same or different and each represents a hydrogen atom or a methyl group, R ３ｂ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, M ２represents a hydrogen atom or a counter ion that forms a salt, and X ２ represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond, or a carbonyl group, n2 represents the average number of moles added, and is a number of 5 or more and 150 or less. ]]

4. The dispersant composition for hydraulic powder according to claim 3, wherein the copolymer (B) contains a structural unit of a monomer selected from methyl acrylate and hydroxyethyl acrylate as a structural unit.

5. The dispersant composition for hydraulic powder according to claim 3 or 4, wherein the mass ratio of the copolymer (A) to the copolymer (B), which is the mass ratio of the content of the copolymer (A) to the content of the copolymer (B), is 0.1 or more and 0.8 or less.

6. A hydraulic composition containing a hydraulic powder, water, and the dispersant composition for hydraulic powder according to any one of claims 1 to 5.

7. The hydraulic composition according to claim 6, wherein the water / hydraulic powder ratio is 40% by mass or more.

8. The hydraulic composition according to claim 6 or 7, wherein the hydraulic powder contains fly ash.

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