JP5623847B2 - Method for producing thickened concrete - Google Patents

Description

  The present invention relates to a method for producing thickened concrete to which a thickener is added for the purpose of suppressing material separation.

As a method for improving the material separation suppressing performance of concrete, a method of adding and mixing a thickener into the concrete is often performed. A thickening agent is easily dispersed in a concrete kneaded material or the like, and since a blending effect appears easily by a slight kneading operation, a liquid one is used (for example, see Patent Document 1). Many liquid thickeners are obtained by dissolving a solid thickener in a solvent such as water. Since the solubility is generally low, it is difficult to obtain a high-concentration liquid. The management of the unit water volume in concrete becomes complicated with a large amount of solvent mixing. The use of a powdery thickener can be considered to solve this problem. However, when added to mortar or concrete kneaded material, the thickener powders stick together and do not disperse uniformly as a lump (ball shape), suppressing material separation. The effect was difficult to demonstrate. For this reason, it is known that the premixture of the water reducing agent powder and the thickener powder is added to the concrete kneaded material, and the presence of the water reducing agent in the vicinity of the thickener powder prevents the thickener powder from agglomerating. (For example, refer to Patent Document 2).
In addition, when the thickener powder is mixed with a fixed mixer such as a ready-mixed concrete plant, thickening components adhere to the inner wall and hopper of the mixer, which takes time for washing, and the effect on the concrete of the next batch tends to remain. Had problems. In order to avoid these problems, a method has been proposed in which a premixed mixture of water reducing agent powder and thickener powder is added to the concrete loaded in the agitator car and agitated and mixed in the drum of the agitator car. (For example, see Patent Document 3).

Japanese Patent Laid-Open No. 02-161015 Japanese Patent Laid-Open No. 06-55529 Japanese Patent Laid-Open No. 06-320528

However, when the premixture of water reducing agent powder and thickener powder is stirred and mixed in the drum of the agitator car, the air entrained during high-speed stirring of the drum is easily held in the concrete, and the amount of air contained in the concrete There is a problem in that the strength increases and the strength decreases after curing.
In order to prevent such an excessive amount of air entrainment, a means of adding an antifoaming agent to the concrete is also conceivable. In particular, an antifoaming component is often premixed in an underwater inseparable admixture (a kind of thickener) added during the production of underwater inseparable concrete.
In such concrete placed in water, there is little risk of freezing even in cold weather, so there is no need to improve frost resistance by securing an appropriate amount of air, but in general concrete JIS A 5308 “Ready mixed concrete” In order to improve the frost damage resistance, it is necessary to secure an air amount of about 4.5 to 5.0%. However, when an antifoaming agent is blended, there is a problem that the amount of air becomes too small and it becomes difficult to stably secure an air amount of about 5%.

  Therefore, the present invention is a method for producing a thickened concrete by stirring and mixing a premixture of a water reducing agent powder and a thickener powder in a drum type mixer, and it is possible to stably secure an appropriate amount of air. An object of the present invention is to provide a method for producing thickened concrete that can be used even in cold regions.

  Therefore, as a result of various studies, the present inventors have added the above-mentioned problem by adding and mixing a thickener and two kinds of water reducing agents having specific components in a specific procedure using a soluble bag. The present invention has been completed.

That is, the present invention mixes (a) a water reducing agent (A) having an air entrainment property containing a polycarboxylic acid compound or a lignin sulfonic acid compound as an active ingredient into base concrete, and (b) after mixing is completed. This structural unit (wherein represented by the following formula (1) and (2), R ^1, R ² and R ³ are the same or different and each represents a hydrogen atom or a methyl group, R ⁴ is 1 to carbon atoms 5 represents an alkyl group, M ¹ represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an organic amine, Y represents —CH ₂ O— or —COO—, and n represents a number of 20 to 50. A soluble bag (D) containing a mixture of a water reducing agent powder (B) having no air entrainment and a thickener powder (C) containing a (meth) acrylate compound having an active ingredient) Is mixed with a drum-type mixer There is provided a method for producing a thickening concrete.

According to the method for producing a thickened concrete of the present invention, a thickened concrete capable of stably securing an appropriate air amount of about 5% can be easily obtained even by stirring with a drum-type mixer such as a drum of a concrete agitator car. Can be obtained.
By securing an appropriate amount of air, it is possible to improve the frost damage resistance, and it is possible to use the thickened concrete in cold regions.

In the method of the present invention, first, (a) a water reducing agent (A) having an air entrainment property containing a polycarboxylic acid compound or a lignin sulfonic acid compound as an active ingredient is mixed into the base concrete (step a).
The water reducing agent (A) used in the step a is a water reducing agent (AE water reducing agent) having air entrainment properties, and contains a polycarboxylic acid compound or a lignin sulfonic acid compound. As polycarboxylic acid compounds, polyacrylic acid, polymethacrylic acid, polyoxyalkylene modified polyacrylic acid, polyoxyalkylene modified polymethacrylic acid or salts thereof, polyalkylene glycol and the like having 3 or more carboxyl groups as graft chains Examples thereof include those having a comb polymer compound as a main component. Examples of the lignin sulfonic acid compound include (modified) lignin sulfonic acid and (modified) lignin sulfonate.

  Base concrete is ordinary concrete, which is a mixture of cement, fine aggregate, coarse aggregate and water. As the cement, Portland cement, mixed cement, eco cement, or the like is used. As the fine aggregate and the coarse aggregate, both natural aggregate and artificial aggregate are used.

Moreover, the mixed production of the base concrete used for this invention can be performed using arbitrary apparatuses, such as a biaxial mixer, a pan-type mixer, a tilting cylinder mixer, for example.
The composition of the base concrete used in the production method of the present invention is not particularly limited, but it is 5 to 21 cm as a slump in that the thickener particles are easily dispersed quickly and the amount of air is easily stabilized. More preferably. When the slump of the base concrete is less than 5 cm, the entrainment of air when the thickener particles are added tends to increase, and the stabilization of the air amount may be hindered. Further, when the slump of the base concrete exceeds 21 cm, it is not preferable because the air amount tends to decrease after the additive of the present invention is mixed, and the stabilization of the air amount may be hindered.

  The mixing of the water reducing agent (A) into the base concrete is preferably performed by adding 0.002 to 0.05 parts by weight of the water reducing agent (A) in terms of solid content with respect to 100 parts by weight of the base concrete.

  (B) When the mixing of the water reducing agent (A) into the base concrete is sufficiently completed, the soluble bag (D) is mixed with a drum-type mixer (step b). Here, the time point when the mixing of the water reducing agent (A) into the base concrete is sufficiently completed is preferably after 10 minutes or more, further 20 minutes or more, particularly 30 minutes or more have passed since mixing. If the mixing time is short, the change in the hydration state of the cement in the base concrete due to the addition of the water reducing agent (A) acts on the water reducing agent (B), thereby reducing the air entrainment suppressing effect of the water reducing agent (B). This is not preferable because there is a fear.

The soluble bag-like material (D) used in the step b is a structural unit represented by the following formulas (1) and (2) (wherein R ¹ , R ² and R ³ are the same or different and are hydrogen atoms or methyl R ⁴ represents an alkyl group having 1 to 5 carbon atoms, M ¹ represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an organic amine, and Y represents —CH ₂ O— or —COO—. And n represents a number of 20 to 50.) A mixture of a water reducing agent powder (B) having no air entrainment and a thickener powder (C) containing a (meth) acrylate compound having an active ingredient It is a soluble bag-like product encapsulating.

  The water reducing agent (B) used here is a water reducing agent having no air entrainment.

The (meth) acrylate compound which is an active ingredient of the water reducing agent (B) contains the structural units of the above formulas (1) and (2), and the structural unit (1) is 40 to 80 mol%. In particular, it is preferably 45 to 75 mol%, and the structural unit (2) is preferably 1 to 45 mol%, particularly preferably 3 to 40 mol% in the case of one kind. Examples of M ¹ in the structural unit (1) include a hydrogen atom, an alkali metal such as lithium and sodium, an alkaline earth metal such as calcium and magnesium, an alkanolamine such as ammonium or ethanolamine, and the like. Moreover, although n in a structural unit (2) shows the number of 20-50, when n is less than 20, powdering will become difficult and it may become a gum shape. On the other hand, when n exceeds 50, the solubility is lowered, and the ability to disperse the thickener particles quickly is unfavorable. The particularly preferable range of n is 20 to 45. R ⁴ is not limited as long as it is an alkyl group having 1 to 5 carbon atoms, and preferably an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, or an i-propyl group.

In the structural unit (2), there are two types of Y, —CH ₂ O— and —COO—, and either or both of them may be present. When both are present, (2) where Y is —COO— is 1 to 30 mol%, (2) where Y is —COO— is 5 to 25 mol%, and Y is —CH 2 O—. Some (2) is preferably 3 to 25 mol%. Moreover, when (2) is mixed, n of any one structural unit should just be the range of 20-50. For those having no structural unit represented by the formulas (1) and (2) in the molecule, even if the mortar or concrete kneaded material exhibits an excellent water reducing action, When used in combination with an agent, air entrainment may not be controlled, and the ability to disperse thickener particles quickly may be reduced.

  The active ingredient (meth) acrylate compound of the water reducing agent (B) may further have one or more of the following structural units (3) and (4).

(In the formula, R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents an alkyl group having 1 to 5 carbon atoms, and X represents —SO ₃ M ² or —O—Ph—SO ₃ M ² (wherein M ² represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an organic amine, and Ph represents a phenylene group)

Examples of the alkyl group having 1 to 5 carbon atoms represented by R ⁶ in the structural units (3) and (4), a methyl group, an ethyl group, and a n- propyl or i- propyl group, a M ² is , Hydrogen atoms, alkali metals such as lithium and sodium, alkaline earth metals such as calcium and magnesium, alkanolamines such as ammonium and ethanolamine, and the like. The structural unit (3) is preferably 2 to 25 mol%, particularly preferably 5 to 20 mol%. The structural unit (4) is preferably from 3 to 20 mol%, particularly preferably from 5 to 15 mol%. In addition, mol% of a structural unit shows mol% of each structural unit when the sum total of all the structural units of (1)-(4) is 100 mol%.

In the structural units (1) to (4), R ^{1 to} R ⁶ are particularly preferably methyl groups, M ¹ and M ² are particularly preferably sodium, and X is preferably —SO ₃ Na. Moreover, as an active ingredient of a water reducing agent (B), what contains all the structural units (1)-(4) is preferable, and 1 type or 2 types may be sufficient as this structural unit (2). The number average molecular weight of the active ingredient (meth) acrylate compound used for the water reducing agent (B) is preferably in the range of 2000 to 50000, particularly preferably 3500 to 30000, in terms of polyethylene glycol by the GPC method.

  The water reducing agent (B) is used in a powder form. For powdering of the water reducing agent (B), for example, at least a mixture obtained by adding water to the above-mentioned (meth) acrylate-based compound is dried and powdered with a hot-air drying apparatus or a conductive electric heating drying apparatus or heated under reduced pressure. It is carried out by kneading and stirring. In addition, the water reducing agent powder (B) may contain components other than the (meth) acrylate compound as long as the effects of the present invention are not inhibited.

  The water reducing agent powder (B) is preferably subjected to a classification operation or the like to have a particle size of 300 μm or less because the water reducing agent can be sufficiently dissolved in the kneaded product before the adhesion between the thickening component powders proceeds.

  The thickener powder (C) used together with the water reducing agent powder (B) includes cellulose thickeners, acrylic thickeners, and other biopolymer polysaccharides (starch thickeners, various natural gums). Etc.). Examples of the cellulose-based thickener include carboxymethyl cellulose, alkyl cellulose, hydroxyalkyl cellulose, hydroxyalkylalkyl cellulose and the like. Examples of the acrylic thickener include carboxyvinyl polymer. Starch-based thickeners include starch and modified starch. Examples of natural gums include locust bean gum, xanthan gum and gellan gum.

  Further, the particle diameter of the thickener powder (C) is not particularly limited, but it is preferable to perform a classification operation or the like so that the particle diameter is 1000 μm or less because a material separation suppressing action can be easily obtained even in a short time mixing. .

  As the soluble bag-like product (D) for enclosing the mixture of the water reducing agent powder (B) and the thickener powder (C), a soluble bag-like product containing cellulose fibers as a main component, that is, a soluble paper bag is preferable. By using a soluble bag-like material, it is easily dispersed quickly by the effect of the water reducing agent (B), and the influence of air entrainment can be reduced.

  In the present invention, it is necessary to encapsulate a mixture of the water reducing agent powder (B) and the thickener powder (C) in advance in the soluble bag-like material (D).

Furthermore, in the present invention, the weight of the bag-shaped premixed composition obtained by premixing the water reducing agent powder (B) and the thickener powder (C) in the bag-shaped material (D) is 0.5 to 1.0 kg / More preferably, it is L.
Assuming mixing with the base concrete in the drum of the concrete agitator car, if the weight is less than 0.5 kg / L, the bag is formed on the surface of the base concrete by the air contained in the bag (D). Since the state (D) floats and it takes time to uniformly disperse the thickener, the possibility of excessive air entrainment increases, which is not preferable.
Further, when the weight exceeds 1.0 kg / L, the voids in the bag-like material (D) are too small, and it takes time for the moisture in the base concrete to penetrate into the bag. Since it takes time to disperse, there is a high possibility that air will be excessively involved.
If the weight is in the range of 0.5 to 1.0 kg / L, the thickener in the bag (D) is quickly and uniformly dispersed in the concrete, so there is little risk of excessive air entrainment. Therefore, it is preferable.

  Encapsulation of the mixture of the water reducing agent powder (B) and the thickener powder (C) in the bag-like product (D) is not particularly limited, but is preferably sealed.

  The soluble bag-like material (D) may be mixed with the mixed concrete in step a and performed with a drum mixer. However, in consideration of workability, it is preferably performed within the drum of a concrete agitator vehicle.

As the drum-type mixer used in the present invention, in particular, a concrete agitator wheel, any commonly used agitator wheel can be used.
Moreover, it is preferable that the load amount of the thickened concrete in the agitator vehicle is 30 to 60% by volume of the agitator vehicle drum capacity. If it is less than 30%, the total amount of concrete is too small compared to the stirring ability, and there is a possibility of air entrainment at the time of mixing the additives, which is not preferable. On the other hand, if it exceeds 60%, the ability to stir the thickened concrete is insufficient, and it takes too much stirring time for uniform mixing, which may cause air entrainment. It is more preferable that the load of the thickened concrete is 35 to 55% by volume of the agitator wheel drum capacity from the viewpoint of the stability of the air amount.

  Further, the mixing time of the mixed concrete and the soluble bag-like material (D) in the agitator wheel is preferably 40 seconds to 120 seconds by high speed stirring, and more preferably 60 seconds to 100 seconds. If it is less than 40 seconds, the thickener may not be uniformly dispersed in the concrete, which is not preferable. Further, if it exceeds 120 seconds, there is a possibility that excessive entrainment of air may occur.

  The method of the present invention uses two types of water reducing agents, a water reducing agent (A) having air entrainment property and a water reducing agent powder (B) having no air entraining property, and the water reducing agent (A) is previously mixed in the base concrete. In addition, the water reducing agent powder (B) is characterized in that it is mixed with the thickener powder (C) in the soluble bag (D) in advance.

  The water reducing agent (A) has an effect of stably entraining an appropriate amount of air into the concrete. Even when the water reducing agent (A) is used in combination with the water reducing agent (B) present in the soluble bag-like material (D), the air entraining effect does not change and a stable amount of air can be secured. . Moreover, the quick thickener powder dispersion | distribution effect of a water reducing agent (B) is not inhibited.

  On the other hand, the water reducing agent powder (B) used in the production method of the present invention is present in the vicinity of the thickener powder (C) to disperse the thickener powder particles so that the thickener powders adhere to each other. This has the effect of preventing the formation of lumps (balls). Furthermore, the water reducing agent (B) has an effect of suppressing excessive air entrainment even when used in combination with a thickener. The water reducing agent (B) is premixed with a thickener and encapsulated in a soluble bag, and then added to the concrete, thereby reducing the effect of the air entraining action of the water reducing agent (A) present outside the bag. Since the thickener can be dispersed in the concrete hardly receiving, the fluctuation of the air amount when the thickener is added can be minimized. In addition, since the powder of the water reducing agent (B) has high solubility, it quickly dissolves when a small amount of water penetrates into the bag when added to the concrete, and disperses the thickener powder in the concrete at an early stage. For this reason, an excessive stirring time is not required at the time of stirring in the mixer, and the effect of suppressing the entrainment of air is minimized.

  In the production method of the present invention, the weight ratio of the thickener (C) to the water reducing agent (B) is preferably (B) / (C) = 1 to 7 in terms of solid content, (B) / (C) = 2 to 6 is particularly preferable. If the weight ratio (B) / (C) is less than 1, the dispersion performance by the water reducing agent (B) is insufficient, and the thickener (C) is affected by the water reducing agent (A) at the time when it is not sufficiently dispersed. This is not preferable because excessive entrainment of air may occur. On the other hand, if the weight ratio (B) / (C) exceeds 7, the amount of the thickener (C) is relatively insufficient, and it is difficult to obtain a material separation inhibiting action, which is not appropriate.

  Moreover, in the manufacturing method of this invention, the weight ratio of the water reducing agent (A) with respect to the said water reducing agent (B) is (B) / (A) = 0.2-2.0 in conversion of solid content. Some are preferable, and (B) / (A) = 0.4 to 1.0 is particularly preferable. If the weight ratio (B) / (A) is less than 0.2, the effect of suppressing the entrainment of air by the water reducing agent (B) is insufficient, and the thickener (C) is affected by the water reducing agent (A), and the air This is not preferable because it may cause excessive entrainment. When the weight ratio (B) / (A) exceeds 2.0, the amount of the water reducing agent (A) is relatively insufficient, the air entrainment into the concrete is insufficient, and the amount of air is too small. It is not appropriate because there is a risk of becoming.

  The amount of additive added to the concrete in the production method of the present invention is the total amount of all of the above (A), (B) and (C), in terms of solid content, solids such as cement and aggregate in the concrete. A weight corresponding to about 0.005 to 0.1% of the total mass (excluding the present additive) is preferred. More preferably, it is 0.01 to 0.1% at a low temperature of about 5 ° C., and 0.005 to 0.08% at other normal and high temperatures. If it is less than about 0.005%, the effect of addition becomes difficult to be exhibited, and if it exceeds about 0.1%, the mixing resistance may increase, which is not suitable.

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples shown here.

<Experiment 1>
The water reducing agent and thickener used in this test are shown below.
(1) Water-reducing agent (water-reducing agents A2 and A3 are liquid, the rest are all powder)
Water reducing agent B1; trial product A (polycarboxylic acid, no air entrainment) (*)
Water reducing agent B2; Trial product B (polycarboxylic acid, no air entrainment) (*)
Water reducing agent A1; Mighty 100 (manufactured by Kao Corporation, naphthalenesulfonic acid type, no air entrainment)
Water reducing agent A2; Yamaso 09 NLR (manufactured by Yamaso Chemical Co., Ltd., polycarboxylic acid type, with air entrainment)
Water reducing agent A3; Pozzolith No. 78S (manufactured by BASF Pozzolith Co., Ltd., lignin sulfonic acid type, with air entrainment)

(*) Water reducing agent B1: What was obtained by trial manufacture by the method shown in the patent gazette corresponding to the composition of Table 1 in JP-A-2000-26145 (n = 23 in the formula (2)) ).
(*) Water reducing agent B2: a product obtained by trial production of a composition corresponding to the composition in Table 2 in JP-A-2000-26145 by the method shown in the patent publication (n ≧ 75 in formula (2)) ).

(2) Thickener powder Thickener C1; Metroles (manufactured by Shin-Etsu Chemical Co., Ltd., cellulose)
Thickener C2; TNS (manufactured by Taiheiyo Materials, acrylic)
Thickener C3; Casucol (Avebe, starch system)

(3) Soluble bag Water-soluble paper A6015 (manufactured by Nippon Paper Industries, Inc., main component: cellulosic fiber)

Using the materials (1) to (3), the mixture of the water reducing agent powder (B) and the thickener powder (C) was sealed in a soluble bag to 400 g / bag and sealed with staples. The blending ratio of the premix is shown in Table 1. The bag weight is sealed in two ways: when the premix is sealed in a soluble bag, with a table vibrator used to reduce the gap, and when packed without using the vibrator, The weight of the bag-like composition was controlled by changing the time during which the vibrator was used.
In addition, premixing of the water reducing agent powder and the thickener powder was carried out for 3 minutes at 50 kg / batch using a Redige mixer manufactured by Redige Co., to obtain a premixed product.

Using the following materials, 4 m ³ of base concrete having the composition shown in Table 2 was produced in a ready-mixed concrete factory. In addition, the water reducing agent (A) shown in Table 2 was premixed at the time of concrete manufacture.
The premixture of the produced water reducing agent (A) and the base concrete was loaded in a concrete agitator wheel (drum volume of about 8.7 m ³ ), and after 40 minutes, 1.6 kg of the bag-shaped premix of Table 1 was added thereto. (0.4 kg / m ³ ) was added and stirred at high speed for 90 seconds to produce thickened concrete. In Comparative Example 9 in Table 3 to be described later, immediately after the base concrete was produced, a bag-like premix was introduced and stirred at high speed for 90 seconds to produce a thickened concrete.
For the base concrete before the addition of the bag-like premix and the thickened concrete after the addition, the respective air amounts are measured according to JIS A 1128 “Test method using air pressure of fresh concrete—air chamber pressure method”. The variation in air volume was evaluated from the difference between
Moreover, about the produced thickened concrete, the whole quantity was discharged | emitted to the flexible container bag, and the presence or absence of the lump (ball) was observed visually. A sample in which a lump (ball) was recognized by visual inspection was rated as x, and a sample in which a block (ball) was not recognized at all was marked as ◯.

The above results are summarized in Table 3. Regarding the inventive products 1 to 6, it was confirmed that the difference in the air amount before and after the addition of the additive was small, and a stable air amount of about 5% was obtained. Moreover, although the presence or absence of the lump (ball) was observed visually, in this product 1-6, the lump (ball) was not recognized by any thickening concrete.
On the other hand, in Comparative Examples 1-4 and 8, it was difficult to secure an appropriate air amount of around 5%. Moreover, in Comparative Examples 5-7 and 9, the production | generation of the lump (ball) was recognized and it was confirmed that the uniform mixing of the thickener to the base concrete is not made.

(4) Concrete materials Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement)
Fine aggregate: Crushed lime sand (from Goro, Hokkaido)
Coarse aggregate: Limestone (from Goro, Hokkaido)
Water; tap water

<Experiment 2>
The thickened concrete of Example 4 and Comparative Example 1 shown in Table 3 was evaluated for frost damage resistance according to JIS A 1148 “Method for Freezing and Thawing Concrete”.
The specimen made of the thickened concrete of Example 4 has a relative dynamic elastic modulus of 60% or more even under conditions of freezing and thawing of 300 cycles, and is considered to have sufficient frost damage resistance.
On the other hand, in the test body made of the thickened concrete of Comparative Example 1, the relative dynamic elastic modulus was less than 60% before the freezing and thawing reached 300 cycles, the frost damage resistance was insufficient, It is considered difficult to apply on the ground.

Claims (3)

(A) A water reducing agent (A) having an air entrainment property containing a polycarboxylic acid compound or a lignin sulfonic acid compound as an active ingredient is mixed in the base concrete, and (b) 10 minutes or more after mixing, , Structural units represented by the following formulas (1) and (2) (wherein R ¹ , R ² and R ³ are the same or different and represent a hydrogen atom or a methyl group, and R ⁴ has 1 to 5 carbon atoms) Represents an alkyl group, M ¹ represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an organic amine, Y represents —CH ₂ O— or —COO—, and n represents a number of 20 to 50. A soluble bag-like material (D) enclosing a mixture of a water reducing agent powder (B) and a thickener powder (C) having an air entrainment property containing a (meth) acrylate compound having an active ingredient) Thickening, characterized by mixing with a drum-type mixer Method of manufacturing the concrete.
  The method for producing thickened concrete according to claim 1, wherein the soluble bag-like material (D) is obtained by packaging starch powder in a soluble paper bag mainly composed of cellulose fibers. The bag content weight / bag volume of the mixture in the soluble bag (D) containing the mixture of the water reducing agent powder (B) and the thickener powder (C) is 0.5 to 1.0 kg / L. The method for producing thickened concrete according to any one of claims 1 and 2.