JP5839658B2 - Preparation method of low shrinkage AE concrete - Google Patents

Description

  The present invention relates to a method for preparing low-shrinkage AE concrete, and more particularly to a method for preparing low-shrinkage AE concrete using a shrinkage reducing fluidizing agent. A fluidizing agent is an additive that is added to and mixed with a pre-kneaded base concrete to increase the fluidity of the base concrete. More specifically, a kneading agent with a small unit water amount that has been pre-kneaded. It is an additive that is used to obtain a concrete having a large slump by temporarily adding to the base concrete and mixing it, and temporarily increasing the fluidity of the base concrete. However, in recent years, most of the fluidizing agents have shifted to high-performance AE water reducing agents, and at present, the fluidizing agents are only used in some situations. On the other hand, demands for extending the life of concrete structures in civil engineering construction work have been increasing in recent years, and measures for improving the durability of cured concrete products have become important. Therefore, there is an increasing interest in drying shrinkage reducing agents that reduce the amount of drying shrinkage of concrete for the purpose of suppressing the occurrence of drying shrinkage cracks in the concrete structure. The dry shrinkage reducing agent is reduced in water as a shrinkage reducing component in advance from the viewpoint of workability and cost, compared to the method of adding and using the usual high performance AE water reducing agent or AE water reducing agent separately. Increasingly, it is used as a one-component shrinkage-reducing high-performance AE water reducing agent or a one-component shrinkage-reducing AE water reducing agent mixed with ingredients and conforming to JIS standards. However, when the shrinkage reducing component and water reducing component are mixed and used as a single component, the addition amount of the shrinkage reducing agent is fixed, and the addition level is inevitably lower than the required level. There is a limit to pursuing the reduction effect, and there is a problem that the amount of the drying shrinkage reducing agent cannot be adjusted and used. In addition, it has been attempted to use a dry shrinkage reducing agent alone and post-addition for a part of such a problem, but in fact, a dry shrinkage reducing agent whose JIS standard is not maintained is generally used. I have a problem that I can't. In view of such circumstances, a method using a one-component shrinkage reducing fluidizing agent that imparts shrinkage reduction performance is desired as one of the effective means, but there has been no such proposal so far.

  Conventionally, various drying shrinkage reducing agents are known for reducing the drying shrinkage of concrete (see, for example, Patent Documents 1 to 4). In addition, a shrinkage-reducing AE water reducing agent obtained by mixing a drying shrinkage reducing agent with a cement dispersant into a single solution, or a shrinkage-reducing high-performance AE water reducing agent (see, for example, Patent Documents 5 to 7) is also known. However, in general, when a drying shrinkage reducing agent is used, if the amount of the drying shrinkage reducing agent is increased, the shrinkage reducing effect is increased, but on the other hand, there is a problem that the freeze-thaw resistance is remarkably lowered. . In addition, many of the properties of AE concrete to which a drying shrinkage reducing agent has been added have a tendency that entrained air bubbles tend to be defoamed over time after kneading. In particular, the AE concrete is poured into a mold and tightened with a vibrator. When molding while solidifying, there is also a problem that unstable air bubbles are condensed on the upper surface of the concrete molded body and large voids are easily generated. Although a method of adding a fluidizing agent later (see, for example, Patent Document 8) has been known for a long time, this method is a technique for imparting fluidity exclusively, and shrinkage reduction performance using a fluidizing agent. There is no concrete proposal to give both high liquidity.

JP 56-37259 A JP 59-21557 A JP 59-152253 A JP 2010-58996 A JP 2004-2175 A JP 2009-161428 A JP 2010-1000047 Gazette JP 61-247653 A

  The problems to be solved by the present invention are as follows: 1) The entrained air of the concrete after mixing does not degas and keeps a stable amount of air over time; 2) The drying shrinkage of the resulting cured product is small 3) Suppression of cracking, 3) Excellent freeze-thaw resistance of the resulting cured product, 4) Little voiding on the surface of the resulting cured product, and beautiful surface appearance. The present invention is to provide a method for preparing low-shrinkage AE concrete using a shrinkage-reducing fluidizing agent capable of obtaining low-shrinkage AE concrete having the above-mentioned multiple functions 1) to 4).

  As a result of studies conducted by the present inventors to solve the above-mentioned problems, it is possible to prepare AE concrete by adding and mixing a predetermined proportion of a shrinkage reducing fluidizing agent to a pre-kneaded base concrete. It was found to be correct and suitable.

  That is, according to the present invention, a shrinkage reducing fluidizing agent is added to a pre-kneaded base concrete in a proportion of 0.1 to 8.0 parts by mass per 100 parts by mass of cement in the base concrete. And a method for preparing a low-shrinkage AE concrete characterized in that dry shrinkage-reducing properties and high fluidity are simultaneously imparted.

  A method for preparing low-shrinkage AE concrete according to the present invention (hereinafter simply referred to as the preparation method of the present invention) is performed by adding a shrinkage-reducing fluidizing agent to a hard-kneaded base concrete that has been mixed in advance. This is a method for preparing shrinkage AE concrete.

  In the preparation method of the present invention, the shrinkage-reducing fluidizing agent is in a ratio of 0.1 to 8.0 parts by mass per 100 parts by mass of cement in the base concrete that has been kneaded in advance. Add and mix.

  The shrinkage reducing fluidizing agent used in the preparation method of the present invention is a fluidizing agent having a function of reducing the drying shrinkage of the obtained cured product, and the following A component is 60 to 99.8% by mass and The component is composed of 0.2 to 40% by mass (a total of 100% by mass of component A and component B).

  Component A: Compound represented by the following chemical formula 1

In chemical formula 1,
p, q, r: all are 0 or a positive integer and satisfy p + q + r = 5-25

Component B: One or more selected from the following water-soluble vinyl copolymers Water-soluble vinyl copolymer: 45 to 85 mol% of the following structural units C in the molecule and 15 to 25 of the following structural units D Water-soluble vinyl copolymer having a mass average molecular weight of 3000 to 70000 having 55 mol% and the following structural unit E in a proportion of 0 to 5 mol% (total 100 mol% of structural unit C, structural unit D and structural unit E) Coalescence.

Structural unit C: One or more selected from a structural unit formed from methacrylic acid and a structural unit formed from methacrylate salt. Structural unit D: composed of 5 to 80 oxyethylene units in the molecule. Structural unit formed from methoxypolyethylene glycol methacrylate having a polyoxyethylene group Structural unit E: Structural unit formed from methallyl sulfonate

  The component A is a compound represented by Chemical Formula 1. Such a compound is a propylene oxide adduct of glycerin. In the chemical formula 1, p, q and r are all 0 or a positive integer and satisfy p + q + r = 5 to 25. Among them, it is preferable that p, q and r are all integers of 1 to 10 and satisfy p + q + r = 7 to 20. In Chemical Formula 1, p + q + r represents the number of moles of propylene oxide added per mole of glycerin. When p + q + r is too small, the resulting cured product has a large shrinkage on drying, and conversely, when p + q + r is too large, it is hardly soluble in water. This makes it difficult to adjust the amount of entrained air. Any of the compounds represented by Chemical Formula 1 of Component A can be synthesized by a known method.

  The water-soluble vinyl copolymer of component B was composed of 1) a water-soluble vinyl copolymer composed of structural unit C and structural unit D, and 2) composed of structural unit C, structural unit D and structural unit E. Examples of the water-soluble vinyl copolymer include the above 1), 2) and a mixture of 1) and 2).

  As the structural unit C, 1) a structural unit formed from methacrylic acid, 2) a structural unit formed from methacrylate, 3) a structural unit formed from methacrylic acid and a structural unit formed from methacrylate. Both are mentioned. Here, structural units formed from methacrylates are as follows: a) structural units formed from alkali metal salts such as lithium, sodium, and potassium methacrylic acid, and b) alkaline earths such as calcium and magnesium methacrylates. Examples include structural units formed from metal salts, and c) structural units formed from organic amine salts such as diethanolamine and triethanolamine of methacrylic acid. Especially, as the structural unit C, the structural unit formed from the methacrylate is preferable, and the structural unit formed from sodium methacrylate is more preferable.

  The structural unit D is a structural unit formed from methoxypolyethylene glycol methacrylate having a polyoxyethylene group composed of 5 to 80 oxyethylene units in the molecule. Especially, as the structural unit D, the structural unit formed from the methoxy polyethyleneglycol methacrylate which has the polyoxyethylene group comprised by 7-55 oxyethylene units in a molecule | numerator is preferable.

  The structural unit E is a structural unit formed from methallyl sulfonate. Examples of the salt include alkali metal salts such as lithium, sodium, and potassium, and a sodium salt is preferable.

  The water-soluble vinyl copolymer described above can be synthesized by a known method (for example, the method described in JP-A-58-74552 and JP-A-1-226757).

  When the water-soluble vinyl copolymer is composed of a water-soluble vinyl copolymer composed of the structural unit C and the structural unit D as described above, the water-soluble vinyl copolymer contains 45 structural units C in the molecule. ˜85 mol% and constitutional unit D in a proportion of 15 to 55 mol% (total of constitutional unit C and constitutional unit D is 100 mol%). In a ratio of 20 to 50 mol% (total of 100 mol% of the structural unit C and the structural unit D) is preferable. Further, when the water-soluble vinyl copolymer is composed of a water-soluble vinyl copolymer composed of the structural unit C, the structural unit D, and the structural unit E, the water-soluble vinyl copolymer has 45 structural units C in the molecule. ˜85 mol%, structural unit D is 15 to 55 mol%, and structural unit E is 5 mol% or less (total of 100 mol% of structural unit C and structural unit D + structural unit E). 49 to 80 mol% of unit C, 19 to 50 mol% of structural unit D, and 0.3 to 4.5 mol% of structural unit E (total 100 mol% of structural unit C, structural unit D, and structural unit E) It is preferable to have it in the ratio. In any case, the water-soluble vinyl copolymer described above has a mass average molecular weight of 3000 to 70000, preferably 6000 to 50000.

  The shrinkage-reducing fluidizing agent used in the preparation method of the present invention described above is composed of 60 to 99.8% by mass of component A and 0.2 to 40% by mass of component B (total 100% by mass of component A and component B) However, it is preferable that the component A has a ratio of 60 to 99.5% by mass and the component B has a ratio of 0.5 to 40% by mass (a total of 100% by mass of the component A and the component B). Of these, those having a ratio of 75 to 98% by mass of the A component and 2 to 25% by mass of the B component (a total of 100% by mass of the A component and the B component) are particularly preferable.

  Further, in the preparation method of the present invention, the shrinkage reducing fluidizing agent is used as a one-component mixed aqueous solution in which a mixture composed of a predetermined ratio of the above-described A component and B component is diluted with water and uniformly dissolved. Is preferred. Usually, the active ingredient concentration (the total concentration of the A component and the B component) is 10 to 80% by mass, but preferably the active ingredient concentration is 20 to 70% by mass. In the preparation method of the present invention, such a one-component mixed aqueous solution maintains a stable and uniform state over time. If the one-component mixed aqueous solution to be used is unstable over time and the solution is separated or a precipitate is generated, it may cause a trouble and cannot be used.

  In the preparation method of the present invention, the hard-mixed base concrete kneaded in advance has an air amount of 2 to 6% kneaded with cement, fine aggregate, coarse aggregate, AE water reducing agent, air amount adjusting agent, water and the like. Means a concrete with a slump value in the range of 8 to 15 cm. In the preparation method of the present invention, the shrinkage-reducing fluidizing agent as described above is added to the kneaded base concrete at a predetermined ratio and mixed.

  Examples of the cement used in the preparation method of the present invention include various mixed cements such as blast furnace cement, fly ash cement, and silica fume cement, in addition to various portland cements such as ordinary portland cement, early-strength portland cement, and moderately hot portland cement. . The cement to be used is not particularly limited, but among them, one selected from ordinary Portland cement and blast furnace cement is preferable, and B type is preferable for blast furnace cement. Examples of the fine aggregate used in the preparation method of the present invention include river sand, mountain sand, sea sand, and crushed sand. Examples of coarse aggregate include river gravel, crushed stone, and lightweight aggregate.

  The preparation method of the present invention reduces the drying shrinkage by about 10 to 30% as compared with ordinary AE concrete, so that the base concrete is kneaded in advance and is usually kneaded with a slump value of 8 to 15 cm. This is a preparation method in which a fluidizing agent for shrinkage reduction is added to and mixed with the base concrete to increase the fluidity so that the target slump value is 18 to 24 cm. The amount of shrinkage-reducing fluidizer added varies depending on the composition ratio of component A and component B of the shrinkage-reducing fluidizer, base concrete slump value, or target slump value. In terms of components (in terms of total amount of component A and component B), the ratio is 0.1 to 8.0 parts by weight, preferably 0.3 to 5.0 parts by weight per 100 parts by weight of cement. .

  In addition, in the preparation method of the present invention, in order to obtain a sufficient resistance to freezing and thawing of the resulting cured body, the amount of entrained air in the low-shrinkage AE concrete after preparation is 3 to 6 using an air amount regulator. The volume% is preferable, and 4 to 6 volume% is more preferable.

  The hardened body of low-shrinkage AE concrete obtained by the preparation method of the present invention was de-framed by filling the formwork with the entrained air of the low-shrinkage AE concrete after preparation in order to maintain a stable air amount over time. The feature is that the concrete surface after the concrete is beautiful and that the resulting cured product has a low drying shrinkage and at the same time exhibits excellent resistance to freezing and thawing. The reason is that the air entrainment of the component A itself is low, so that the desired high fluidity is provided while suppressing the generation of unstable entrained air (entrapped air), the AE agent and the AE water reducing agent. Since the minute air entrainment amount due to is stably maintained, the resistance to freezing and thawing of the obtained cured body is ensured, and high fluidity is imparted to facilitate filling into the mold, The voids on the surface of the resulting cured body are suppressed, the required amount of shrinkage reducing fluidizing agent is introduced into the concrete, and the drying shrinkage rate is reduced. The result is presumed to be obtained.

  In the preparation method of the present invention, in addition to the shrinkage reducing fluidizing agent described above, the air entraining agent, the setting accelerator, the waterproofing agent, the preservative, the rustproofing agent, etc., as long as the effects of the present invention are not impaired. These additives can also be used in combination.

  According to the present invention, not only the obtained cured body exhibits excellent compressive strength, but 1) the entrained air of the concrete after mixing does not degas and keeps a stable amount of air over time. 3) The dry shrinkage rate of the resulting cured body is small and the occurrence of cracks is suppressed, 3) the freeze-thaw resistance of the obtained cured body is excellent, and 4) the voids on the skin surface of the obtained cured body. There is an effect that the generation is small and the surface appearance is beautiful, and the above functions 1) to 4) are simultaneously satisfied.

  Hereinafter, in order to make the configuration and effects of the present invention more specific, examples and the like will be described. However, the present invention is not limited to the examples. In the following examples and the like, unless otherwise indicated,% means mass%, and part means mass part.

Test Category 1 (Synthesis of propylene oxide adduct of glycerin as component A)
Synthesis of propylene oxide adduct (a-1) of glycerin 184 g (2.0 mol) of glycerin was charged into an autoclave, and 1.8 g of potassium hydroxide was added as a catalyst, and then the inside of the autoclave was purged with nitrogen. While stirring, the reaction temperature was kept at 125 to 140 ° C., and 1160 g (20 mol) of propylene oxide was injected to carry out an addition reaction. After completion of the press-fitting, the reaction was terminated by aging at the same temperature for 2 hours to obtain a product. The residual catalyst of this product was subjected to adsorption treatment using an adsorbent, and then separated by filtration and purified. The obtained purified product was a liquid compound at room temperature, and was a 10-mol adduct (a-1) of glycerin propylene oxide according to the analysis results such as the hydroxyl value.

-Synthesis of propylene oxide adducts (a-2), (a-3) and (ar-1) to (ar-3) of glycerin In the same manner as the synthesis of propylene oxide adducts (a-1) of glycerin, Propylene oxide adducts (a-2), (a-3) and (ar-1) to (ar-3) of glycerin were synthesized. The contents of the A component and the like synthesized above are summarized in Table 1.

Test Category 2 (Synthesis of water-soluble vinyl copolymer as component B)
Synthesis of water-soluble vinyl copolymer (b-1) Reaction of 60 g of methacrylic acid, 310 g of methoxypoly (23 mol) ethylene glycol methacrylate, 3.5 g of sodium methallylsulfonate, 5.0 g of 3-mercaptopropionic acid and 540 g of water After charging into the container, 36 g of 48% aqueous sodium hydroxide was added, partially neutralized while stirring, and dissolved uniformly. Next, after the atmosphere was replaced with nitrogen, the temperature of the reaction system was kept at 60 ° C. in a warm water bath, 25 g of a 20% aqueous solution of sodium persulfate was added to start radical polymerization reaction, and the reaction was continued for 5 hours. Ended. Thereafter, 28 g of a 48% sodium hydroxide aqueous solution was added for complete neutralization to obtain a 40% aqueous solution of a water-soluble vinyl copolymer. When this water-soluble vinyl copolymer was analyzed, structural units formed from sodium methacrylate / structural units formed from methoxypoly (23 mol) ethylene glycol methacrylate / structural units formed from sodium methallylsulfonate = 70. It was a water-soluble vinyl copolymer (b-1) having a mass average molecular weight of 31200 (GPC method, converted to polystyrene, the same shall apply hereinafter) having a ratio of / 28/2 (mole% ratio).

Synthesis of water-soluble vinyl copolymers (b-2) to (b-4) and (br-1) to (br-4) In the same manner as the synthesis of the water-soluble vinyl copolymer (b-1), Water-soluble vinyl copolymers (b-2) to (b-4) and (br-1) to (br-4) were synthesized. The contents of each water-soluble vinyl copolymer synthesized as described above are shown in Table 2.

In Table 2,
M1: a structural unit formed from sodium methacrylate M2: a structural unit formed from methacrylic acid M3: a structural unit formed from methoxypoly (23 mol) ethylene glycol methacrylate M4: formed from methoxypoly (9 mol) ethylene glycol methacrylate Structural unit M5: Structural unit formed from methoxypoly (68 mol) ethylene glycol methacrylate M6: Structural unit formed from sodium methallylsulfonate

Test Category 3 (Preparation of fluidizer for shrinkage reduction)
-Preparation of shrinkage reducing fluidizing agent (p-1) 99 parts of glycerin propylene oxide adduct (a-1) as component A synthesized in test category 1 and component B synthesized in test category 2 27.5 parts of a 40% aqueous solution of water-soluble vinyl copolymer (b-1) and 73.5 parts of water were mixed and dissolved, and the active ingredient concentration of the shrinkage reducing fluidizing agent (p-1) (component A and 200 parts of an aqueous solution having a total concentration of component B) of 55% was prepared.

-Preparation of shrinkage reducing fluidizing agents (p-2) to (p-12) and (pr-1) to (pr-10) In the same manner as the shrinkage reducing fluidizing agent (p-1), Shrinkage reducing fluidizing agents (p-2) to (p-12) and (pr-1) to (pr-10) were prepared. The contents of each of the shrinkage reducing fluidizing agents prepared above are summarized in Table 3.

In Table 3,
Stability over time of aqueous solution with 55% active ingredient concentration of shrinkage reducing fluidizer: Putting 55% aqueous solution with active ingredient concentration of shrinkage reducing fluidizer into 100 ml capacity stoppered measuring cylinder and let stand at room temperature for 1 week. After that, the separation condition of the solution was evaluated according to the following criteria.
○: Uniform and transparent without separation.
X: The liquid phase was partly or completely separated, or a precipitate was observed.

Test category 4 (preparation of low shrinkage AE concrete, etc.)
Example 1
Formulation No. described in Table 4 In the condition of No. 1, ordinary Portland cement (density = 3.16 g / cm ³ , brain value = 3300 cm ² / g), fine aggregate (crushed sand from Iwase, density = 2.61 g / cm ³⁾ Coarse grain ratio = 2.83) and coarse aggregate (Iwase crushed stone, density = 2.63 g / cm ³ , coarse grain ratio = 6.74) were sequentially added and kneaded for 15 seconds. Next, so that the target slump is 8 ± 1 cm and the target air amount is in the range of 4.5 ± 1%, AE water reducing agent (trade name Tupol EX20 manufactured by Takemoto Yushi Co., Ltd.) and air amount adjusting agent (manufactured by Takemoto Yushi Co., Ltd.). A predetermined amount of each of the product names AE200) was mixed and diluted with water, and then added and mixed to prepare a hard-mixed base concrete. Then, a predetermined amount of a 55% active ingredient concentration aqueous solution of the shrinkage reducing fluidizing agent (p-1) prepared in Test Category 3 was added to this kneaded base concrete and mixed for 30 seconds, and the target slump was 18 ± 1 cm. A low-shrinkage AE concrete having a target air amount in the range of 4.5 ± 1% was prepared.

Examples 2-12 and Comparative Examples 1-10
In the same manner as in Example 1, a hard-kneaded base concrete was prepared, and a predetermined amount of a 55% active ingredient concentration aqueous solution of a shrinkage reducing fluidizing agent was kneaded with this base concrete, and the low-shrinkage AE concrete of each example, etc. Was prepared.

Examples 13 to 15 and Comparative Examples 13 and 14
Compound No. No. 1 is blended no. The same as in Example 1 except that the conditions were changed to 2 (Blast furnace slag cement B type: density = 3.04 g / cm ³ , brane value = 3500 cm ² / g), and a low-shrinkage AE concrete was prepared. did.

Comparative Example 11
Formulation No. described in Table 4 1. Prepare base concrete with a slump of 8 cm under the condition 1, add a predetermined amount of a commercially available fluidizing agent (trade name Hyflud made by Takemoto Yushi Co., Ltd.) to this base concrete and mix for 30 seconds. AE concrete having a range of 18 ± 1 cm and a target air amount of 4.5 ± 1% was prepared.

Comparative Example 12
Formulation No. described in Table 4 1. Using a commercially available high performance AE water reducing agent (trade name Tupole HP-11 manufactured by Takemoto Yushi Co., Ltd.) under the condition 1, the target slump is 18 ± 1 cm and the target air volume is 4.5 ± 1%. The following AE concrete was prepared.

Comparative Example 15
Formulation No. described in Table 4 Under the conditions of 2, prepare a base concrete with a slump of 8 cm, add a predetermined amount of a commercially available fluidizing agent (trade name Hyflud made by Takemoto Yushi Co., Ltd.) to this base concrete and mix for 30 seconds. AE concrete having a range of 18 ± 1 cm and a target air amount of 4.5 ± 1% was prepared.

Comparative Example 16
Formulation No. described in Table 4 Using a commercially available high-performance AE water reducing agent (trade name Tupole HP-11 manufactured by Takemoto Yushi Co., Ltd.) under the condition 2, the target slump is 18 ± 1 cm and the target air volume is 4.5 ± 1%. The following AE concrete was prepared.

Test Category 5 (Evaluation of prepared low shrinkage AE concrete, etc.)
For the low-shrinkage AE concrete of each example prepared in Test Category 4, the entrained air amount and slump are obtained as follows, and for the hardened body obtained from the low-shrinkage AE concrete of each example, the drying shrinkage rate, freeze-thaw Resistance and compressive strength were determined as follows. The results are shown in Table 5.

Entrained air amount (volume%): Low shrinkage AE concrete immediately after kneading and low shrinkage AE concrete left still for 60 minutes were measured according to JIS-A1128.
-Slump (cm): Measured according to JIS-A1101 simultaneously with the measurement of the air amount.
-Drying shrinkage: In accordance with JIS-A1129, dry shrinkage strain was measured by a comparator method for a 26-week-old specimen stored under conditions of 20 ° C x 60% RH using low shrinkage AE concrete of each example. Measured and determined the drying shrinkage. The smaller this value, the smaller the drying shrinkage.
-Freeze-thaw durability index (300 cycles): About the low-shrinkage AE concrete of each example, using the value measured according to JIS-A1148, the value calculated by the durability index of ASTM-C666-75 was shown. . This numerical value indicates that the maximum value is 100, and the closer to 100, the better the resistance to freezing and thawing.
-Compressive strength (N / mm < ² >): About the low shrinkage | contraction AE concrete of each example, based on JIS-A1108, it measured by material age 7 days and material age 28 days.

In Table 5,
p-1 to p-12, pr-1 to pr-10: fluidizing agent for shrinkage reduction described in Table 3, etc. * 1: Commercially available fluidizing agent (trade name Hyflud manufactured by Takemoto Yushi Co., Ltd.)
* 2: Commercially available high-performance AE water reducing agent (Brand name Tupol HP-11 manufactured by Takemoto Yushi Co., Ltd.)
Amount added: parts by mass in terms of active ingredients such as shrinkage reducing fluidizing agent per 100 parts by weight of cement Comparative Examples 3, 4 and 8: Measurement was not performed because an aqueous solution of shrinkage reducing fluidizing agent was separated.
Comparative examples 5, 6, 7 and 9: Since the target slump value was not obtained, it was not measured.

  Further, for the obtained cured bodies (cured bodies of Examples 1, 8, and 13 and Comparative Examples 11, 12, and 13), the surface finish was visually observed and evaluated by the following methods.

・ Surface finish: Low-shrinkage AE concrete immediately after preparation is poured into a wooden decorative form of length x width x height 0.15m x 1m x 1m, compacted with a rod-shaped vibrator, and removed after 3 days of age Framed. The number of bubbles with a bubble diameter of 3 mm or more present on the mold release surface of the cured product obtained (2 m ^{2 in} the total of two horizontal and height surfaces) was counted, and this was 0.3 m × 0.3 m = 0. The number of bubbles present in 0.09 m ² was converted, and the quality of the finished surface was evaluated based on the number of converted bubbles. The results are shown in Table 6.

  As is clear from the results of Tables 5 and 6, according to the low shrinkage AE concrete of each example, desired fluidity can be obtained and compared with AE concrete using a conventional high performance AE water reducing agent. The resulting cured product has a low drying shrinkage, and at the same time, excellent freeze-thaw durability and sufficient compressive strength are obtained, and the surface of the cured product has a small number of coarse bubbles and a smooth and beautiful appearance.

Claims (7)

The following shrinkage reducing fluidizing agent is added to and mixed in a pre-kneaded base concrete in a proportion of 0.1 to 8.0 parts by mass per 100 parts by mass of cement in the base concrete. And a method for preparing low-shrinkage AE concrete, wherein dry shrinkage-reducing properties and high fluidity are simultaneously imparted.
Shrinkage reducing fluidizing agent: 60 to 99.8% by mass of the following A component and 0.2 to 40% by mass of the following B component (total of 100% by mass of the A component and the B component) Consists of.
Component A: Compound represented by the following chemical formula 1

(In chemical formula 1,
p, q, r: all are 0 or a positive integer and satisfy p + q + r = 5 to 25)
Component B: One or more selected from the following water-soluble vinyl copolymers Water-soluble vinyl copolymer: 45 to 85 mol% of the following structural units C in the molecule and 15 to 25 of the following structural units D Water-soluble vinyl copolymer having a mass average molecular weight of 3000 to 70000 having 55 mol% and the following structural unit E in a proportion of 0 to 5 mol% (total 100 mol% of structural unit C, structural unit D and structural unit E) Coalescence.
Structural unit C: One or more selected from a structural unit formed from methacrylic acid and a structural unit formed from methacrylate salt. Structural unit D: composed of 5 to 80 oxyethylene units in the molecule. Structural unit formed from methoxypolyethylene glycol methacrylate having a polyoxyethylene group Structural unit E: Structural unit formed from methallyl sulfonate   The low-shrinkage AE concrete according to claim 1, wherein the component A is one in which p, q and r in Chemical Formula 1 are all integers of 1 to 10 and satisfy p + q + r = 7 to 20. Preparation method.   A water-soluble vinyl copolymer in which the component B is a structural unit formed from methoxypolyethylene glycol methacrylate having a polyoxyethylene group in which the structural unit D is composed of 7 to 55 oxyethylene units in the molecule. The method for preparing a low-shrinkage AE concrete according to claim 1 or 2, which is selected from water-soluble vinyl copolymers having a mass average molecular weight of 6000 to 50,000.   The shrinkage-reducing fluidizing agent contains 75 to 98% by mass of component A and 2 to 25% by mass of component B (100% by mass in total of component A and component B). The preparation method of the low shrinkage | contraction AE concrete of any one of -3.   Preparation of the low shrinkage | contraction AE concrete as described in any one of Claims 1-4 which uses the fluidizing agent for shrinkage | contraction as a one-pack type aqueous solution diluted with water so that an active ingredient density | concentration may be 20-70 mass%. Method.   The method for preparing low-shrinkage AE concrete according to any one of claims 1 to 5, wherein the cement of the base concrete is selected from ordinary Portland cement and blast furnace cement.   The method for preparing low-shrinkage AE concrete according to any one of claims 1 to 6, wherein the amount of entrained air is 3 to 6% by volume.