JP2013227179A - Freeze-thaw resistance low shrinkage ae concrete composition and hardened body thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a freeze-thaw resistance low shrinkage AE concrete composition capable of obtaining a hardened body having a dry shrinkage rate reduced to ≤400 micro, and having excellent freeze-thaw resistance; and to provide a hardened body obtained by hardening the composition.SOLUTION: In an AE concrete composition including high-early-strength portland cement, water, fine aggregate, coarse aggregate, a drying shrinkage reducing agent, a cement dispersant and an air amount adjusting agent, a specific drying shrinkage reducing agent is used at the rate of a unit amount of 7-30 kg/m, and the unit amount ratio determined from expression 1: unit amount ratio (%)=(unit amount of water+unit amount of drying shrinkage reducing agent)/(unit amount of early strength portland cement)×100 (%), is controlled in the range of 30-43%.

Description

The present invention relates to a freeze-thaw resistant low-shrinkage AE concrete composition capable of obtaining a cured product excellent in freeze-thaw resistance and drying shrinkage reduction property, and a cured product thereof. In recent years, from the viewpoint of extending the life and quality of a concrete structure, the concrete structure is required to suppress the occurrence of cracks due to drying shrinkage. For example, in order to suppress cracking due to drying shrinkage of a concrete structure, it is said that the drying shrinkage rate in general buildings needs to be about 600 × 10 ⁻⁶ (hereinafter 10 ^{−6 is referred} to as micro) or less. In particular, it is said that when the cross-section of the restraining member of the reinforcing bar is large, it is necessary to make the drying shrinkage rate about 400 micron or less. On the other hand, the concrete structure in a cold region is required to be particularly resistant to freezing and thawing because it is necessary to ensure frost damage resistance at the same time. The present invention suppresses the occurrence of cracks due to drying shrinkage by reducing the drying shrinkage ratio to 400 micron or less, and at the same time, a freeze-thaw resistant low-shrinkage AE concrete composition capable of obtaining a cured body having excellent freeze-thaw resistance. And a cured product thereof.

Conventionally, as a means for reducing the drying shrinkage of a cured body, it is known to use various drying shrinkage reducing agents during the preparation of AE concrete (for example, see Patent Document 1). Generally, the more the shrinkage reducing agent is added to the AE concrete composition, the more the shrinkage reducing effect tends to increase. Therefore, when a large effect is expected, it cannot be ignored as a part of the kneaded water. It will be used in an amount (such as concrete 1 m ³ per 5kg or more). However, reducing the drying shrinkage of the cured product and increasing the resistance to freezing and thawing is a trade-off phenomenon, so the more the drying shrinkage reducing agent is used, the more the freeze-thaw resistance of the resulting cured product is. There is a problem that decreases. For this reason, proposals for improving such problems have also been reported (see, for example, Patent Documents 2 to 6). However, the actual situation is that it has not yet reached a high-level stage in which a drying shrinkage rate is reduced to 400 μm or less, and at the same time, a cured product having excellent freeze-thaw resistance is obtained.

Japanese Patent Publication No.59-3430 JP 11-349367 A JP 2002-338315 A JP 2004-91259 A JP 2008-273766 A JP 2008-285336 A JP 2010-6626 A

  The problem to be solved by the present invention is to provide a freeze-thaw resistant low-shrinkage AE concrete composition capable of reducing the drying shrinkage rate to 400 micron or less and at the same time obtaining a cured product excellent in freeze-thaw resistance, and It exists in the place which provides the hardening body obtained by hardening.

  As a result, the present inventors have studied to solve the above-mentioned problems, and as a result, contain the early strong Portland cement, water, fine aggregate, coarse aggregate, dry shrinkage reducing agent, cement dispersant and air amount adjusting agent. It was found that an AE concrete composition comprising a specific component as a drying shrinkage reducing agent at a specific ratio and having a unit amount ratio within a specific range is suitable. .

That is, the present invention is an AE concrete composition comprising an early-strength Portland cement, water, fine aggregate, coarse aggregate, a drying shrinkage reducing agent, a cement dispersant, and an air amount adjusting agent, and the drying shrinkage reducing agent. The following shrinkage reducing agent is used at a rate of unit amount of 7 to ³⁰ kg / m ³ , and the unit amount rate obtained from the following formula 1 is set to 30 to 43%. Related low shrinkage AE concrete composition. The present invention also relates to a cured product obtained by curing the freeze-thaw resistant low-shrinkage AE concrete composition.

  Drying shrinkage reducing agent: one or two or more selected from diethylene glycol monobutyl ether and compounds represented by the following chemical formula 1

In chemical formula 1,
p, q, r: 0 or a positive integer that satisfies p + q + r = 5 to 25

  The freeze-thaw resistant low-shrinkage AE concrete composition according to the present invention (hereinafter referred to as the AE concrete composition of the present invention) is an early-strength Portland cement, water, fine aggregate, coarse aggregate, dry shrinkage reducing agent, cement dispersion And an air amount adjusting agent.

  The cement used in the AE concrete composition of the present invention is an early strength Portland cement. When other Portland cements such as ordinary Portland cement, medium-heated Portland cement, and low heat Portland cement are used, in the AE concrete composition containing a large amount of the drying shrinkage reducing agent as described above, excellent excellent freezing can be achieved. Melting resistance is not obtained.

In the AE concrete composition of the present invention, known river sand, sea sand, mountain sand, crushed sand and the like can be used as the fine aggregate. In the AE concrete composition of the present invention, it is preferable to use blast furnace slag fine aggregate as a part of these fine aggregates. Such blast furnace slag fine aggregate is described in JIS-A5011-1 and is preferably included in the classification according to the particle size of the blast furnace slag fine aggregate. Among them, as the blast furnace slag fine aggregate, the classification by particle size is preferably 5 mm blast furnace slag fine aggregate and / or 2.5 mm blast furnace slag fine aggregate, and the coarse particle ratio is in the range of 2.0 to 3.1. What was prepared is more preferable. In the AE concrete composition of the present invention, the drying shrinkage rate of a cured body obtained by using the blast furnace slag fine aggregate as a part of the fine aggregate in a unit amount of 50 to 249 kg / m ³ is further reduced. Preferred above.

  In the AE concrete composition of the present invention, as the coarse aggregate, known river gravel, crushed stone, lime crushed stone, lightweight aggregate and the like can be used. Among these, crushed limestone is preferable. Moreover, tap water can be used as water.

  In the AE concrete composition of the present invention, as the drying shrinkage reducing agent, one or more selected from diethylene glycol monobutyl ether and a compound represented by Chemical Formula 1 can be used. When using two or more, the mixing ratio is not particularly limited. Among these, as the drying shrinkage reducing agent, it is preferable to use diethylene glycol monobutyl ether alone or a mixture of diethylene glycol monobutyl ether and a compound represented by Chemical Formula 1.

The compound represented by Chemical formula 1 is a propylene oxide adduct of glycerin. In the compound represented by Chemical formula 1, p, q and r are all 0 or a positive integer, and p + q + r = 5 to 25. A satisfying integer. Especially, p, q, and r are all the integers of 1-10, and what satisfies p + q + r = 7-20 is preferable. When p + q + r is too small, and conversely, when p + q + r is too large, the target drying shrinkage reduction effect cannot be obtained. In the present invention, the drying shrinkage reducing agent is used in a unit amount of 7 to ³⁰ kg / m ³ , and preferably used in a unit amount of 9 to 27 kg / m ³ . Any of the compounds represented by Chemical Formula 1 can be synthesized by a known method.

  In the AE concrete composition of the present invention, known cement dispersants can be used. Among them, polycarboxylate-based ones are preferable, and polycarboxylate-based ones composed of water-soluble vinyl copolymers. Is more preferable. Examples thereof include those described in JP-A-58-74552 and JP-A-1-226757. Among them, the following constitutional unit A is contained in the molecule in an amount of 35 to 85 mol%, and the following constitution. A water-soluble vinyl copolymer having a mass average molecular weight of 5,000 to 100,000 and having 15 to 65 mol% of units B and 0 to 5 mol% (100 mol% in total) of the following structural units C is most preferable. The amount of the cement dispersant used is usually 0.05 to 2 parts by mass per 100 parts by mass of early strong Portland cement.

Structural unit A: One or more selected from a structural unit formed from methacrylic acid and a structural unit formed from methacrylate salt. Structural unit B: composed of 7 to 150 oxyethylene units in the molecule. Structural unit formed from methoxypolyethylene glycol methacrylate having a polyoxyethylene group Structural unit C: Structural unit formed from (meth) allyl sulfonate

  Furthermore, in the AE concrete composition of the present invention, known air amount adjusting agents can be used. For example, polyoxyalkylene alkyl ether sulfate, alkyl benzene sulfonate, polyoxyethylene alkyl benzene sulfonate, rosin soap, higher fatty acid soap, alkyl phosphate monoester salt, polyoxyalkylene alkyl ether phosphate salt, etc. Among them, an alkyl phosphate monoester salt is preferable in that the cured product obtained has excellent freeze-thaw resistance. The amount of the air amount regulator used is usually 0.001 to 0.01 parts by mass per 100 parts by mass of early strong Portland cement.

  In the AE concrete composition of the present invention, it is indispensable to adjust the air amount in order to secure the freeze-thaw resistance of the obtained cured product. The amount of air is usually 3 to 7% by volume, preferably 4 to 6% by volume. When the amount of air is small, the freeze-thaw resistance of the resulting cured body is weakened. Conversely, when the amount of air is large, the strength of the obtained cured body is reduced.

  Furthermore, in the AE concrete composition of the present invention, it is important that the unit amount ratio obtained from the above-mentioned formula 1 is 30 to 43%, preferably 34 to 41%. When the unit amount ratio exceeds 43%, the freeze-thaw resistance of the resulting cured body is lowered. Conversely, when the unit amount ratio is less than 30%, self-shrinkage of the obtained cured body is increased. However, if the unit amount ratio is out of the above numerical range, the desired effect of the present invention cannot be obtained sufficiently.

  As described above, the AE concrete composition of the present invention uses at least early-strength Portland cement, water, fine aggregate, coarse aggregate, dry shrinkage reducing agent, cement dispersant and air amount adjusting agent, and kneads them. Although it is prepared by mixing, the mixing procedure is not particularly limited.

  In addition, the AE concrete composition of the present invention is within the range that does not impair the effects of the present invention, and if necessary, an antifoaming agent, a rust inhibitor, a quick setting agent, a setting accelerator, a setting retarder, a waterproofing agent, and the like. These additives can be used in combination.

  According to the AE concrete composition of the present invention, it is possible to greatly reduce the drying shrinkage rate to about 150 to 400 micrometers, and at the same time, it is possible to obtain a cured body having excellent freeze-thaw resistance. Because the mechanism is complex, it is difficult to explain the reason, but it is presumed that the following 1) and 2) act mainly in cooperation. That is, 1) A predetermined amount can be mixed without limiting the addition amount of the drying shrinkage reducing agent, thereby greatly reducing the drying shrinkage rate of the obtained cured product. At the same time, 2) early strength Portland cement with a fast hydration reaction by densifying the structure of the hardened body obtained by blending early strength Portland cement, water and a drying shrinkage reducing agent so that the unit amount ratio falls within a predetermined range. The absolute amount of unreacted free water remaining in the hardened body of the solder is reduced, the destructive force of the volume expansion pressure at which the free water changes to ice when frozen at low temperature is suppressed, and the freeze-thaw resistance is increased.

The cured body according to the present invention is obtained by curing the AE concrete composition of the present invention described above. Among these hardened bodies, those having a drying shrinkage of 150 to 400 micro (150 × 10 ^{−6 to} 400 × 10 ⁻⁶ ) are preferable.

  The AE concrete composition of the present invention can be applied not only as an AE concrete composition placed at a construction site, but also as an AE concrete composition for a secondary product processed in a concrete product factory.

  According to the present invention, the obtained cured product not only exhibits excellent compressive strength, but also has an effect that the drying shrinkage rate is significantly small and resistance to freezing and thawing is strong.

  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 compounds represented by Chemical Formula 1 as a drying shrinkage reducing agent)
-Synthesis | combination of drying shrinkage reducing agent (g-1) 184g (2.0 mol) of glycerol was prepared to the autoclave, and after adding 1.8g of potassium hydroxide as a catalyst, the inside of an autoclave was nitrogen-substituted. 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. In order to remove the residual catalyst of this product, it was subjected to adsorption treatment using an adsorbent and then purified by filtration. The purified product was a propylene oxide 10 mol adduct of glycerin, which is a compound represented by Chemical Formula 1, according to the analysis result of the hydroxyl value and the like. This was designated as a drying shrinkage reducing agent (g-1).

-Synthesis of drying shrinkage reducing agents (g-2) and (g-3) In the same manner as in the case of the drying shrinkage reducing agent (g-1), a propylene oxide adduct of glycerin was synthesized, and these were dried shrinkage reducing agents. It was set as (g-2) and (g-3).

Synthesis of drying shrinkage reducing agents (gr-2) and (gr-3) In the same manner as in the case of the drying shrinkage reducing agent (g-1), a propylene oxide adduct of glycerin was synthesized, and these were dried shrinkage reducing agents. It was set as (gr-2) and (gr-3). Table 1 shows the contents of the drying shrinkage reducing agent synthesized above. The drying shrinkage reducing agent (gr-1) is glycerin.

Test Category 2 (Synthesis of water-soluble vinyl copolymer as cement dispersant)
Synthesis of cement dispersant (a-1) 60 g of methacrylic acid, methoxypoly (23 oxyethylene units, hereinafter referred to as n = 23) 300 g of ethylene glycol methacrylate, 5 g of sodium methallylsulfonate, 3 g of 3-mercaptopropionic acid and After 490 g of water was charged into the reaction vessel, 58 g of a 48% aqueous sodium hydroxide solution was added, and the mixture was partially neutralized with stirring and dissolved uniformly. After the atmosphere in the reaction vessel was replaced with nitrogen, the temperature of the reaction system was maintained 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. The reaction was terminated. Thereafter, 23 g of a 48% aqueous sodium hydroxide solution was added to completely neutralize the reaction product, thereby obtaining 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 (n = 23) ethylene glycol methacrylate / structural units formed from sodium methallylsulfonate = It was a water-soluble vinyl copolymer having a mass average molecular weight of 35500 (GPC method, converted to pullulan) having a ratio of 70/27/3 (mol%). This was designated as cement dispersant (a-1).

Synthesis of cement dispersants (a-2), (a-3) and (ar-1) to (ar-3) In the same manner as in the case of the cement dispersant (a-1), a water-soluble vinyl copolymer was prepared. These were synthesized and used as cement dispersants (a-2), (a-3) and (ar-1) to (ar-3). Table 2 summarizes the contents of the cement dispersant synthesized above.

In Table 2,
* 1: GPC method, pullulan conversion X-1: constitutional unit formed from sodium methacrylate X-2: constitutional unit formed from methacrylic acid Y-1: constitution formed from methoxypoly (23 mol) ethylene glycol methacrylate Unit Y-2: Structural unit formed from methoxypoly (68 mol) ethylene glycol methacrylate Z-1: Structural unit formed from sodium methallyl sulfonate Z-2: Structural unit formed from sodium allyl sulfonate

Test Category 3 (Preparation of AE concrete composition)
Example 1
Under the compounding conditions described in Example 1 of Table 3, a 50 L pan-type forced kneading mixer was subjected to early strong Portland cement (early strong Portland cement manufactured by Taiheiyo Cement, density = 3.14 g / cm ³ , brain value 4520), Mountain sand (Kimitsu mountain sand, density = 2.60 g / cm ³ ), cement dispersant (cement dispersant (a-1) in Table 2), air amount regulator (octyl phosphate monoester potassium salt) and drying shrinkage A predetermined amount of each of the reducing agents (diethylene glycol monobutyl ether (b-1)) was added together with kneaded water (tap water) and kneaded for 45 seconds. Next, a predetermined amount of coarse aggregate (Chichibu lime crushed stone, density = 2.70 g / cm ³ ) is added and kneaded for 60 seconds, the target slump is 18 ± 1 cm, and the target air amount is 4.5 ± 0. An AE concrete composition of Example 1 having a range of 5% was prepared. The contents of the prepared AE concrete composition are shown in Table 3.

Examples 2-18 and Comparative Examples 1-17
In the same manner as in Example 1, AE concrete compositions were prepared under the blending conditions described in Table 3, respectively. The contents of the prepared AE concrete composition are shown in Table 3.

In Table 3,
Unit weight: kg of AE concrete composition 1 m ³ per prepared
Fine aggregate: Kimitsu mountain sand, density = 2.60 g / cm ³
Coarse aggregate: lime crushed stone from Chichibu, density = 2.70 g / cm ³
Addition amount: parts by mass per 100 parts by mass of cement (parts by mass as solid content)
* 1: Blast furnace slag fine aggregate (classification by particle size = 5 mm, coarse particle ratio = 2.55, density = 2.76 g / cm ³ ), unit quantity 99 kg / m ³ and natural fine aggregate (Kimitsu mountain sand) Mixed sand used at a rate of 684 kg / m ³ * 2: The same blast furnace slag fine aggregate as above with a unit quantity of 206 kg / m ³ and fine aggregate (previously Kimitsu mountain sand) with a unit quantity of 583 kg / m ³ Mixed sand used in proportion c-1: Early strength Portland cement, density = 3.14 g / cm ³
c-2: Ordinary Portland cement, density = 3.16 g / cm ³
b-1: Diethylene glycol monobutyl ether g-1 to g-3, gr-1 to gr-3: dry shrinkage reducing agents described in Table 1 a-1 to a-3, ar-1 to ar-3: Table 2 M-1: Mixture of diethylene glycol monobutyl ether (b-1) / propylene oxide adduct of glycerin (g-1) = 75/25 (mass ratio) m-2: diethylene glycol monobutyl ether (b- 1) / Propylene oxide adduct of glycerin (g-1) = 50/50 (mass ratio) mixture d-1: Octyl phosphate monoester potassium salt d-2: Rosin soap

Test Category 4 (Evaluation of AE concrete composition)
About the AE concrete composition of each example prepared in Test Category 1, the air amount and slump were determined as follows, and the results are summarized in Table 4. Moreover, about the hardening body which hardened the AE concrete composition of each example, the freeze shrinkage durability index (300 cycles) and compressive strength as an index of dry shrinkage rate, freeze-thaw resistance were calculated | required as follows, and a result was represented. The results are summarized in FIG.

Air content (volume%): AE concrete composition immediately after kneading was measured according to JIS-A1128.
-Slump (cm): Measured according to JIS-A1101 simultaneously with the measurement of the air amount.

  -Drying shrinkage ratio: Based on JIS-A1129, the dry shrinkage strain was measured by a comparator method for a 26-week-old specimen in which the AE concrete composition of each example was stored at 20 ° C x 60% RH. Then, the drying shrinkage was determined. The smaller this value, the smaller the drying shrinkage.

-Freezing and thawing durability index (300 cycles): About the hardened | cured material of the AE concrete composition of each example, the value calculated by the durability index of ASTM-C666-75 was shown using the value measured based on JISA1148. . 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 hardened | cured material of the AE concrete composition of each example, based on JIS-A1108, it measured by material age 7 days and material age 28 days.

In Table 4,
* 1: Since the desired fluidity was not obtained, it was not measured.
○, ×: 400 × 10 ⁻⁶ or less in the case of drying shrinkage, and 80% or more in the case of the freeze-thaw durability index, and × when these could not be cleared.

As is clear from the results in Table 4, the AE concrete composition of each example has fluidity, and at the same time, the resulting cured product has a drying shrinkage of less than 400 × 10 ⁻⁶ and is frozen at the same time. The melt durability index is high, and the required compressive strength is obtained. On the other hand, in the AE concrete composition of the comparative example, when the unit amount of the drying shrinkage reducing agent deviates from the predetermined ratio, or when the unit amount ratio deviates from the predetermined range, the ordinary Portland cement other than the early strong Portland cement is used. In the case where the constituent requirements of the present invention are not satisfied, such as the case of using a low-shrinkage AE concrete composition excellent in freeze-thaw resistance, which is the object of the present invention, has not been obtained.

Claims (10)

AE concrete composition containing early strength Portland cement, water, fine aggregate, coarse aggregate, dry shrinkage reducing agent, cement dispersant and air amount adjusting agent, and the following dry shrinkage as a dry shrinkage reducing agent A freeze-thaw resistant low-shrinkage AE concrete characterized in that a reducing agent is used at a rate of a unit amount of 7 to ³⁰ kg / m ³ and a unit amount ratio obtained from the following formula 1 is 30 to 43%. Composition.

Drying shrinkage reducing agent: one or two or more selected from diethylene glycol monobutyl ether and compounds represented by the following chemical formula 1

(In chemical formula 1,
p, q, r: 0 or a positive integer and an integer satisfying p + q + r = 5 to 25)   The freeze-thaw resistant low-shrinkage AE concrete composition according to claim 1, wherein the unit amount ratio is 34 to 41%.   The freeze-thaw resistant low-shrinkage AE concrete composition according to claim 1 or 2, wherein the drying shrinkage reducing agent is diethylene glycol monobutyl ether or a mixture of diethylene glycol monobutyl ether and a compound represented by Chemical Formula 1. The freeze-thaw resistant low-shrinkage AE concrete composition according to any one of claims 1 to ³ , wherein a unit amount of the drying shrinkage reducing agent is 9 to 27 kg / m ³ . The cement dispersant has 35 to 85 mol% of the following structural unit A, 15 to 65 mol% of the following structural unit B, and 0 to 5 mol% of the following structural unit C (100 mol% in total) in the molecule. The freeze-thaw resistant low-shrinkage AE concrete composition according to any one of claims 1 to 4, which is a water-soluble vinyl copolymer having a mass average molecular weight of 5,000 to 100,000.
Structural unit A: One or more selected from a structural unit formed from methacrylic acid and a structural unit formed from methacrylate salt. Structural unit B: composed of 7 to 150 oxyethylene units in the molecule. Structural unit formed from methoxypolyethylene glycol methacrylate having a polyoxyethylene group Structural unit C: Structural unit formed from (meth) allyl sulfonate   The freeze-thaw resistant low-shrinkage AE concrete composition according to any one of claims 1 to 5, wherein the air amount adjusting agent is an alkyl phosphate monoester salt.   The freeze-thaw resistant low-shrinkage AE concrete composition according to any one of claims 1 to 6, which contains 3 to 7% by volume of air. The blast furnace slag fine aggregate contained in the classification according to the particle size of the blast furnace slag fine aggregate described in JIS-A5011-1 as a part of the fine aggregate is used in a unit amount of 50 to 249 kg / m ³ . 8. The freeze-thaw resistant low-shrinkage AE concrete composition according to any one of items 7 to 9.   A cured product obtained by curing the freeze-thaw resistant low-shrinkage AE concrete composition according to any one of claims 1 to 8. The cured product according to claim 9, which has a drying shrinkage ratio of 150 × 10 ^{−6 to} 400 × 10 ⁻⁶ .