JP7693452B2 - Dispersant composition for hydraulic powder - Google Patents

Description

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

In the case of hardened hydraulic compositions such as concrete, repeated freezing and thawing over many years gradually deteriorates the hardened body. This is called frost damage, and occurs when excess water in the hardened body or water that has infiltrated from the outside expands due to freezing. Air entraining agents (hereinafter referred to as AE agents) are used to improve the freeze-thaw resistance of hardened hydraulic compositions. For example, it is known that entraining about 4% of air bubbles in concrete is effective against frost damage (Concrete Handbook, pp. 87-95, compiled by the Japan Concrete Institute, published May 1976). AE agents used for this purpose include various highly foaming surfactants, including water-soluble resin acid salts (Concrete Handbook, pp. 228-223, compiled by the Japan Concrete Institute, published May 1976). However, with conventional AE agents, the amount of air bubbles at the beginning of concrete preparation (mixing) can be set relatively accurately, but the amount of air bubbles can change over time. In addition, when used in combination with a dispersant, the amount of air bubbles in the concrete can decrease.

It has been proposed to improve the freeze-thaw resistance of a hardened body by improving the admixture used in a hydraulic composition. For example, Patent Document 1 discloses an admixture for a hydraulic composition that contains (A) a specific acrylic acid copolymer, (B) a specific acrylic acid ester copolymer, (C) a polyethylene glycol having a weight-average molecular weight of 9,000 to 18,000, and (D) a polysaccharide derivative in which some or all of the hydrogen atoms of the hydroxyl groups of a polysaccharide or its alkylated or hydroxyalkylated derivative are substituted with a specific hydrophobic substituent and a specific ionic hydrophilic group.

JP 2014-125397 A

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

The present invention provides a dispersant composition for hydraulic powder, which contains a copolymer (A) that includes, as structural units, a structural unit (A1) represented by the following formula (A1) and a structural unit (A2) represented by the following formula (A2) and has a weight average molecular weight of 40,000 or more and 60,000 or less,
The copolymer (A) has a proportion of the structural unit (A 1 ) of 20% by mass or more and 28% by mass or less with respect to the total of the structural unit (A1) and the structural unit (A2),
The copolymer (A) has a ratio of compounds having a molecular weight of 8,000 or less of 5.0% by mass or more and 15.0% by mass or less.
The present invention relates to a dispersant composition for hydraulic powder.

[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 becomes a salt, X ¹ represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, and n 1 represents the average number of moles added and is a number of 70 to 170.]

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

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

<Dispersant composition for hydraulic powder>
In the present invention, the use of the copolymer (A) can impart excellent freeze-thaw resistance to the set product of the hydraulic composition. The reason for this is not entirely clear, but the present inventors speculate as follows.
The copolymer (A) of the present invention contains a predetermined amount of the structural unit (A1) in the structural unit, and also contains a predetermined amount of a compound in the low molecular weight region. The low molecular weight compound in such a structural unit composition has excellent air entrainment. On the other hand, the copolymer (A) also contains a certain amount of a compound in the molecular weight region with excellent dispersibility. As a result, it is considered that fine air can be entrained in the hydraulic composition while maintaining the function as a dispersant, and the freeze-thaw property is improved. In consideration of the impact on the environment, costs, physical properties, etc., an alternative powder, such as fly ash, may be used as a part of the hydraulic powder, but in that case, the air entrainment property tends to decrease. However, the copolymer (A) of the present invention does not decrease the air entrainment property even when fly ash is used, so that a hardened body with excellent freeze-thaw property can be obtained.

Copolymer (A) contains as structural units a structural unit (A1) represented by the following formula (A1) and a structural unit (A2) represented by the following formula (A2), has a weight average molecular weight of 40,000 or more and 60,000 or less, the proportion of structural unit (A1) to the total of structural units (A1) and structural units ( A2 ) is 20% by mass or more and 28% by mass or less, and the proportion of compounds having a molecular weight of 8,000 or less is 5.0% by mass or more and 15.0% by mass or less.

[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 becomes a salt, X ¹ represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, and n 1 represents the average number of moles added and is a number of 70 to 170.]

In formula (A1), R ^1a represents a hydrogen atom or a methyl group, and a methyl group is preferable.
In formula (A1), M ¹ 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, and alkanol ammonium ion.

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

The copolymer (A) may optionally contain a structural unit other than the structural unit (A1) and the structural unit (A2). The arbitrary 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), allylsulfonic acid, methallylsulfonic acid, and salts thereof, for example, alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts. Furthermore, 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-methasulfonic acid, 2-(meth)acrylamide-2-ethanesulfonic acid, 2-(meth)acrylamide-2-propanesulfonic acid, styrene, or styrenesulfonic acid.

From the viewpoint of imparting kneading properties to the hydraulic composition, the proportion of the structural unit (A 1 ) in the total of the structural units (A1) and (A2) in the copolymer ( A ) is 20% by mass or more, preferably 22% by mass or more, and 28% by mass or less, preferably 26% by mass or less. In the present invention, the amount of the structural unit in the copolymer (A) may be calculated based on the charged amount of the monomer used in the synthesis of the copolymer (A).

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

From the viewpoint of providing dispersibility, 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. The weight average molecular weight of the copolymer (A) was measured by the GPC method under the following conditions: high-speed GPC device (HLC-8320GPC) Tosoh Corporation, detector: RI, column: G4000PWXL + G2500PWXL (anion), mobile phase: 0.2 M phosphate buffer / acetonitrile = 9/1, flow rate: 1.0 ml / min., column temperature: 40 ° C., standard substance: polyethylene glycol).

From the viewpoint of fine air entrainment, the proportion of compounds having a molecular weight of 8,000 or less (hereinafter also referred to as the low molecular weight ratio) of copolymer (A) is 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 weight ratio of copolymer (A) is measured as the ratio of peak areas by the above-mentioned GPC method.

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

[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 becomes a salt, X ² represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, and n2 represents the average number of moles added and is a number of 5 to 150.]

In formula (B1), R ^1b represents a hydrogen atom or a methyl group, and a methyl group is preferable.
In formula (B1), ^M2 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, and alkanol ammonium ion.

In formula (B2), R ^2b represents a hydrogen atom or a methyl group, and is preferably a methyl group.
In formula (B2), R ^3b represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.
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 is preferably a carbonyl group (CO group).
In formula (B2), n2 represents the average number of moles of (CH ₂ CH ₂ O) added and is 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.

Copolymer (B) may optionally contain a structural unit other than structural unit (B1) and structural unit (B2). Examples of the optional structural unit include methyl acrylate, hydroxyethyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxymethyl acrylate, hydroxyethyl methacrylate, and hydroxymethyl methacrylate, 2-(methacryloyloxy)ethyl phosphate (HEMA-P), allylsulfonic acid, methallylsulfonic acid, and salts thereof, such as alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts. In addition, the structural unit may be a monomeric structural unit such as (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-(meth)acrylamide-2-methasulfonic acid, 2-(meth)acrylamide-2-ethanesulfonic acid, 2-(meth)acrylamide-2-propanesulfonic acid, styrene, or styrenesulfonic acid. Copolymer (B) may contain, as a structural unit, a structural unit of a monomer selected from methyl acrylate and hydroxyethyl acrylate.

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

In addition, from the viewpoint of dispersibility in a low amount added in the hydraulic composition, the ratio of the structural unit (B2) to the total of the structural units (B1) and (B2) in the copolymer (B) is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and preferably less than 98% by mass, more preferably 96% by mass or less, even more preferably 94% by mass or less, and even more preferably 92% by mass or less.

In addition, the proportion of the structural unit (B1) and the structural unit (B2) in all structural units of the copolymer (B) is preferably 80% by mass or more, even more preferably 90% by mass or more, more preferably 95% by mass or less, and even 100% by mass or less, and may be 100% by mass.

The weight average molecular weight of copolymer (B) is preferably 30,000 or more, more preferably 40,000 or more, and preferably 10,0000 or less, more preferably 80,000 or less. The weight average molecular weight of copolymer (B) is measured by the same method as that of copolymer (A).

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

The hydraulic powder dispersant composition of the present invention may contain, as optional components other than the copolymer (B), components such as retarders, hardening accelerators, AE agents, expanding agents, foaming agents, thickeners, fluidizing agents, foaming agents, waterproofing agents, and defoamers.

The hydraulic powder dispersant composition of the present invention can be used for hydraulic powders containing fly ash, and further for hydraulic powders containing 30 mass % or less of fly ash in the hydraulic powder. For example, the fly ash has a Blaine value of less than 4,000 ^cm2 /g.

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

Hydraulic powders are powders that have the physical property of hardening through a hydration reaction, and examples of such powders include cement and gypsum. Cement is preferred. Examples of cement include ordinary Portland cement, belite cement, moderate heat cement, high-early strength cement, ultra-high-early strength cement, and sulfate-resistant cement. Powders that have pozzolanic properties and/or latent hydraulic properties, such as blast furnace slag, fly ash, and silica fume, and powdered stone (calcium carbonate powder) may also be added to cement, such as blast furnace slag cement, fly ash cement, and silica fume cement.

The hydraulic powder may include fly ash.
The proportion of fly ash in the hydraulic powder may be, for example, 40 mass% or less, further 30 mass% or less, further 25 mass% or less, and further 20 mass% or less.
The Blaine value of the fly ash is preferably less than 5000 ^cm2 /g, more preferably 4500 ^cm2 /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 the fly ash is measured using a Blaine air permeability device defined in the physical testing method for cement (JIS R5201).
As the fly ash, for example, a by-product obtained when pulverized coal is burned in a coal-fired power plant, in which molten ash is cooled and turned into spherical fine particles, is collected by an electric dust collector or the like, can be used.
The main components of fly ash are silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), and these two inorganic components account for, for example, 70 to 80 mass% of the total. In addition, it typically contains small amounts of ferric oxide (Fe ₂ O ₃ ), magnesium oxide (MgO), calcium oxide (CaO), etc.
The chemical components of the fly ash are preferably 50-70% by mass of SiO ₂ , 16-20% by mass of Al ₂ O ₃ , 5-6% by mass of Fe ₂ O ₃ , and 1-3% by mass of CaO, based on the total mass of the fly ash. The quality of the fly ash may be, for example, any of fly ash types I, II, III, and IV as specified in JIS A6201-2008 (fly ash for concrete). From the viewpoint of cost, fly ash with a ratio of SiO ₂ of less than 50% by mass may also be used.
The ignition loss of the fly ash is not particularly limited, but is preferably 5% or less, and more preferably 3% or less. The ignition loss of the fly ash can be measured, for example, by the ignition loss test method (JIS A6201 (fly ash is heated at a high temperature of 950 to 1000°C, and the ignition loss is calculated from the mass reduction rate, dried at 105°C for 3 hours, and the moisture content is calculated from the mass reduction rate at a constant temperature, and the amount of unburned carbon is calculated by subtracting the moisture content from the ignition loss of the fly ash).
The average particle size of the fly ash is not particularly limited, but is preferably 15 to 25 μm. The average particle size of the fly ash means the average particle size at an integrated value of 50% in the particle size distribution obtained by a laser diffraction/scattering method, that is, the median diameter (D ₅₀ ).

The hydraulic composition of the present invention has a water/hydraulic powder ratio of preferably 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 (mass%) of water and hydraulic powder in the hydraulic composition, and is calculated by mass of water/mass of hydraulic powder x 100. The water/hydraulic powder ratio is calculated based on the amount of water and the amount of powder having the physical property of hardening by hydration reaction. When the hydraulic powder contains a powder selected from a powder having a pozzolanic action, a powder having latent hydraulic properties, and stone powder (calcium carbonate powder), in the present invention, the amount of these powders is also included in the amount of hydraulic powder. In addition, when the powder having the physical property of hardening by hydration reaction contains a high-strength admixture, the amount of the high-strength admixture is also included in the amount of hydraulic powder. This is also true for parts by mass and mass ratios in which the mass of the hydraulic powder is related.

The hydraulic composition of the present invention preferably contains aggregate. Examples of aggregates include aggregates selected from fine aggregates and coarse aggregates. Examples of fine aggregates include those specified by number 2311 in JIS A0203-2014. Examples of fine aggregates include river sand, land sand, mountain sand, sea sand, lime sand, silica sand and crushed sands thereof, blast furnace slag fine aggregate, ferronickel slag fine aggregate, lightweight fine aggregate (artificial and natural), and recycled fine aggregate. Examples of coarse aggregates include those specified by number 2312 in JIS A0203-2014. For example, examples of coarse aggregates include river gravel, land gravel, mountain gravel, sea gravel, lime gravel, crushed stones thereof, blast furnace slag coarse aggregate, ferronickel slag coarse aggregate, lightweight coarse aggregate (artificial and natural), and recycled coarse aggregate. Fine aggregates and coarse aggregates of different types may be mixed and used, or a single type may be used.

When the hydraulic composition of the present invention is concrete, the amount of coarse aggregate used is preferably 50% or more, more preferably 55% or more, even more preferably 60% or more in terms of the expression of strength of the hydraulic composition, reducing the amount of hydraulic powder such as cement used, and improving the filling property into formwork, etc., and is preferably 100% or less, more preferably 90% or less, even more preferably 80% or less in terms of bulk volume. The bulk volume is the ratio of the volume (including voids) of the coarse aggregate in 1 ^m3 of concrete.
When the hydraulic composition of the present invention is concrete, the amount of fine aggregate used is, from the viewpoint of improving the filling property into a formwork or the like, preferably 500 kg/ ^m3 or more, more preferably 600 kg/ ^m3 or more, even more preferably 700 kg/ ^m3 or more, and is preferably 1,000 kg/ ^m3 or less, more preferably 900 kg/m3 or ^less .
When the hydraulic composition of the present invention is a mortar, the amount of fine aggregate used is preferably 800 kg/m3 or ^more , more preferably 900 kg/ ^m3 or more, even more preferably 1,000 kg/ ^m3 or more, and preferably 2,000 kg/ ^m3 or less, more preferably 1,800 kg/m3 or ^less , even more preferably 1,700 kg/ ^m3 or less.

The hydraulic composition of the present invention may contain optional components such as retarders, hardening accelerators, AE agents, expanding agents, foaming agents, thickeners, fluidizing agents, foaming agents, waterproofing agents, and defoamers.

[Method for producing hydraulic composition]
The present invention provides a method for producing a hydraulic composition, which comprises mixing hydraulic powder, water, and the hydraulic powder dispersant composition of the present invention. The method for producing a hydraulic composition of the present invention may comprise mixing hydraulic powder, water, copolymer (A), and optionally copolymer (B). The items described for the hydraulic powder dispersant composition and hydraulic composition of the present invention can be appropriately applied to the method for producing a hydraulic composition of the present invention. The contents of each component in the hydraulic powder dispersant composition and hydraulic composition of the present invention can be read as the mixing amount and applied to the method for producing a hydraulic composition of the present invention. The mixing of hydraulic powder, water, copolymer (A), and optional copolymer (B) can be performed using a mixer such as a mortar mixer or a forced twin-shaft mixer.

(1) Preparation of concrete Concrete was produced according to the mix ratio in Table 2 using the copolymer (A) and copolymer (B) shown in Table 1. Specifically, after the coarse aggregate (G) was charged into a forced twin-shaft mixer, the fine aggregate (S), the coarse aggregate (G), and the cement (C) were charged and stirring was started. Mixing water (W) obtained by mixing the copolymer (A), the copolymer (B), and water was charged at the same time as the mixing of the mixer started so that the amounts of the copolymer (A) and the copolymer (B) added (parts by mass relative to 100 parts by mass of cement) were the values shown in Table 3. After 90 seconds from the start of stirring, the concrete was discharged from the mixer to obtain the concrete.

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

The components in the table are as follows: 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-type mixture: Taiheiyo Cement/Sumitomo Osaka Cement = 1/1, mass ratio) Density 3.16 g/cm ³
Fly ash (FA): Fly ash (two-type mixture: Miike production/Hibiki-nada production = 1/1 (mass ratio)), Blaine value 4026 cm ² /g, ignition loss 4.68%, average particle size 20 μm
Fine aggregate (S): Joyo mountain sand density 2.55g/cm ³
Coarse aggregate (G): Crushed limestone 2010/crushed limestone 1005 = 1/1, mass ratio) Density 2.72g/cm ³

(2) Evaluation of freeze-thaw resistance The test was carried out in accordance with JIS A1148. The test method was Method A. The concrete produced in (1) was poured into a 10 cm x 10 cm x 40 cm formwork, and demolded after 24 hours. The specimen was then cured in a water tank at 20 ± 2 ° C until the 28th day, which was the test start age. After 28 days, the cured specimen was subjected to a freeze-thaw resistance test using a (device name: single-tank brine circulation type freeze-thaw tester, manufactured by Marui Co., Ltd.). One cycle of freeze-thawing was performed by lowering the temperature from 5 ° C to -18 ° C, and then raising the temperature from -18 ° C to 5 ° C, and the maximum and minimum temperatures of the center of the specimen in each cycle were in the range of 5 ± 2 ° C and -18 ± 2 ° C, respectively. The time required for one freeze-thaw cycle was 3 hours or more and 4 hours or less. The measurement items were the primary resonance frequency and mass of each specimen in flexural vibration according to JIS A1127, and the measurements were taken before the start of the test after the completion of underwater curing and at intervals not exceeding 36 cycles. Measurements were carried out after 300 cycles or more. In this evaluation, specimens with a relative dynamic modulus of elasticity of 80% or more at the time of exceeding 300 cycles can be judged to have excellent freeze-thaw resistance.

Claims (8)

A dispersant composition for hydraulic powder, comprising a copolymer (A) containing a structural unit (A1) represented by the following formula (A1) and a structural unit (A2) represented by the following formula (A2) as structural units and having a weight average molecular weight of 40,000 or more and 60,000 or less,
The copolymer (A) has a proportion of the structural unit (A 1 ) of 20% by mass or more and 28% by mass or less with respect to the total of the structural unit (A1) and the structural unit (A2),
The copolymer (A) has a ratio of compounds having a molecular weight of 8,000 or less of 5.0% by mass or more and 15.0% by mass or less.
Dispersant composition for hydraulic powder.

[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 becomes a salt, X ¹ represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, and n 1 represents the average number of moles added and is a number of 70 to 170.] The dispersant for hydraulic powder according to claim 1, wherein the proportion of the structural unit (A1) and the structural unit (A2) in the total structural units of the copolymer (A) is 80% by mass or more and 100% by mass or less. 3. The hydraulic powder dispersant composition according to claim 1 or 2, further comprising a copolymer (B) containing, as structural units, a structural unit (B1) represented by the following formula (B1) and a structural unit (B2) represented by the following formula (B2), and the proportion of the structural unit (B1) in all structural units is 5 mass% or more and less than 8 mass%.

[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 becomes a salt, X ² represents a divalent alkylene group having 1 to 6 carbon atoms, a direct bond or a carbonyl group, and n2 represents the average number of moles added and is a number of 5 to 150.] The hydraulic powder dispersant composition according to claim 3, wherein the copolymer (B) contains, as a constituent unit, a constituent unit of a monomer selected from methyl acrylate and hydroxyethyl acrylate. The dispersant composition for hydraulic powder according to claim 3 or 4, wherein the mass ratio of the content of copolymer (A) to the content of copolymer (B), copolymer (A)/copolymer (B), is 0.1 or more and 0.8 or less. A hydraulic composition comprising a hydraulic powder, water, and the hydraulic powder dispersant composition according to any one of claims 1 to 5. The hydraulic composition according to claim 6, wherein the water/hydraulic powder ratio is 40% by mass or more. The hydraulic composition according to claim 6 or 7, wherein the hydraulic powder contains fly ash.