JP6180273B2 - High fluidity concrete - Google Patents

Description

  The present invention relates to a high-fluidity concrete that has a good filling property even in a narrow place where reinforcing bars are arranged, and can be used for the next construction such as demolding at an early stage.

  In civil engineering and construction sites, high fluidity concrete with high fluidity is used in order to ensure workability, pumping performance, filling properties, etc. in deep places or narrow places where reinforcing bars are placed. Furthermore, in order to maintain the fluidity of concrete for a long time, it is known that it can be adjusted using a delay type dispersant or a setting retarder in general high-fluidity concrete (Patent Document 1, Patent Document 2). Etc.).

On the other hand, the ratio of the slump flow value after 120 minutes of kneading to the slump flow value after 120 minutes of kneading with respect to the slump flow value immediately after kneading for concrete containing a high-fluidity ultra-high strength admixture using general-purpose cement Has been proposed, and a high flow ultra-high strength concrete having a compression strength of 10 N / mm ² or more per day is proposed (see Patent Document 3). For this concrete, water-soluble cellulose, alkali sulfate and polycarboxylic acid-based water reducing agent are used.

JP 2009-23901 A JP 2011-20869 A Japanese Patent No. 5051579

However, even in the concrete of Patent Document 3, good fluidity can be maintained for about 120 minutes after mixing, and it is a place where deep rebar placement parts, places where deep pumping such as deep underground places need pumping, etc. In the construction, the maintenance time of the liquidity was not enough.
Accordingly, an object of the present invention is to provide a high fluidity concrete that maintains good fluidity for a long time of 4 hours (240 minutes) or longer after kneading and that has a sufficiently high compressive strength per day. is there.

  Therefore, the present inventor has made various studies to develop concrete that maintains fluidity for a long time, and increased the content of polycarboxylic acid-based water reducing agent, and the content of alkali metal sulfate and polycarboxylic acid-based water reducing agent. If the ratio is within a specific range and a specific amount of antifoaming agent is included, high fluidity concrete can be obtained that maintains good fluidity even after kneading 240 minutes and has a high compressive strength at the age of one day. As a result, the present invention has been completed.

That is, the present invention provides the following [1] to [5].
[1] Based on 100 parts by mass of cement, (A) 0.4 to 1.7 parts by mass of alkali metal sulfate, (B) 0.15 to 0.4 parts by mass of water-soluble celluloses, (C) polycarboxylic acid It contains 1.6 to 3.5 parts by mass of a water reducing agent and 0.01 to 0.4 parts by mass of (D) an antifoaming agent, and the mass ratio of component (A) to component (C) (C / A ) Is a high fluidity concrete of 1.5 to 5.0.
[2] The high fluidity concrete according to [1], wherein the content of the component (C) is 1.6 to 3.0 parts by mass with respect to 100 parts by mass of cement.
[3] The high fluidity concrete according to [1] or [2], wherein the content ratio (C / A) of the component (A) and the component (C) is 1.7 to 5.0.
[4] The ratio of the slump flow value after 240 minutes of kneading to the slump flow value immediately after kneading is 85% or more, and the compression strength per day of the age is 8 N / mm ² or more [1] to [ 3 ] The high fluidity concrete in any one of.

According to the present invention, the ratio of the slump flow value after 240 minutes of kneading to the slump flow value immediately after kneading is 85% or higher, and the compressive strength per day of the age is 8 N / mm ² or higher. Concrete is obtained. Using the high fluidity concrete of the present invention, it is possible to accurately fill a predetermined place, such as a deep reinforcing bar arrangement part or a deep underground place, where filling with a long pumping pump is necessary, and excellent strength at a material age of 1 day. The concrete can be formed. Therefore, if the high fluidity concrete of the present invention is used, the construction period can be shortened, the work can be reduced, and the construction cost can be reduced.

  The high fluid concrete of the present invention contains (A) an alkali metal sulfate, (B) a water-soluble cellulose, (C) a polycarboxylic acid-based water reducing agent and (D) an antifoaming agent.

  Examples of the alkali metal sulfate (A) used in the present invention include sodium sulfate, potassium sulfate, lithium sulfate and hydrates thereof. In particular, sodium sulfate and sodium sulfate hydrate are preferable.

The content of the alkali metal sulfate (A) in the high fluidity concrete of the present invention is 0.4 to 1.7 parts by mass with respect to 100 parts by mass of cement contained in the concrete. When the amount of the alkali metal sulfate used is within the above range, the compressive strength of the added concrete at the age of 1 day becomes high, and the decrease in the slump flow due to the elapsed time can be sufficiently suppressed. The alkali metal sulfate is preferably used in an amount of 0.45 to 1.5 parts by mass, more preferably 0.5 to 1.5 parts by mass with respect to 100 parts by mass of cement contained in the concrete. In this content range, the compressive strength of concrete at 1 day of age can be 8 N / mm ² and the compressive strength of 3 days of age can be 40 N / mm ² or more.

  Examples of the water-soluble cellulose (B) used in the present invention include nonionic water-soluble cellulose ethers selected from hydroxyalkyl cellulose and hydroxyalkylalkyl cellulose. Examples of the hydroxyalkyl cellulose include hydroxyethyl cellulose and hydroxypropyl cellulose. Examples of the hydroxyalkylalkylcellulose include hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylethylcellulose. These water-soluble celluloses may be used alone or in combination of two or more. Among these, one or more selected from hydroxypropylmethylcellulose and hydroxyethylcellulose are particularly preferable.

  The (B) water-soluble cellulose used in the present invention preferably has a viscosity of an aqueous solution at 20 ° C. of 2.0% by mass in a range of 30000 to 60000 Pa · s. Those in this viscosity range are preferred because they are easily dissolved in concrete mixing water at an early stage and hardly remain undissolved.

  Content of water-soluble celluloses in the high fluidity concrete of this invention is 0.15-0.4 mass part with respect to 100 mass parts of cement contained in concrete. When the amount of water-soluble cellulose used is in the above range, the slump flow can be sufficiently prevented from decreasing after 240 minutes of kneading. The content of preferable water-soluble celluloses is 0.16 parts by mass or more, more preferably 0.17 parts by mass or more with respect to 100 parts by mass of cement, from the viewpoint of not lowering the fluidity even after 240 minutes of kneading. Yes, more preferably 0.18 parts by mass or more. Moreover, 0.35 mass part or less is preferable, 0.32 mass part or less is more preferable, and 0.3 mass part or less is further more preferable. Specifically, 0.16-0.35 mass part is preferable, 0.17-0.32 mass part is more preferable, 0.18-0.32 mass part is further more preferable, 0.18-0.3 Part by mass is more preferable.

  Examples of (C) polycarboxylic acid-based water reducing agents used in the present invention include polycarboxylic acid-based water reducing agents, polycarboxylic acid-based AE water reducing agents, polycarboxylic acid-based high-performance AE water reducing agents, and polycarboxylic acid-based high-performance water reducing agents. Agents and the like. Of these, a polycarboxylic acid-based high-performance AE water reducing agent or a polycarboxylic acid-based high-performance water reducing agent is preferable, and a polycarboxylic acid-based high-performance AE water reducing agent mainly composed of a water-soluble methacrylic acid-based graft polymer, or polycarboxylic acid. Acid-based high performance water reducing agents are particularly preferred.

  Content of the (C) polycarboxylic acid-type water reducing agent in the high fluidity concrete of this invention is 1.0-3.5 mass parts with respect to 100 mass parts of cement contained in concrete. The compressive strength per day of the age of the concrete added in this usage amount range is increased, and the decrease in the slump flow after 240 minutes can be sufficiently suppressed. The content of the polycarboxylic acid-based water reducing agent is preferably 1.6 parts by mass or more, more preferably 1.8 parts by mass or more, and still more preferably 1.9 parts by mass with respect to 100 parts by mass of cement contained in the concrete. . Moreover, 2.9 mass parts or less are preferable, and 2.8 mass parts or less are more preferable. Specifically, 1.6 to 3.0 parts by mass is preferable, 1.8 to 2.9 parts by mass is more preferable, and 1.9 to 2.8 parts by mass is further preferable. In this content range, the decrease in the slump flow due to the elapsed time of the concrete is further suppressed, and the value of the slump flow immediately after mixing is 100, and after 240 minutes, it can be 85 or more, preferably 90 or more.

  The (D) antifoaming agent used in the present invention is not particularly limited as long as it is an antifoaming agent used for general concrete. For example, mineral oil-based antifoaming agent, ester-based antifoaming agent, amine-based antifoaming agent Agents, amide-based antifoaming agents, polyether-based antifoaming agents, silicon-based antifoaming agents and the like can be mentioned, but when mixed with an alkali metal sulfate metal salt powder in advance, the powder is preferable.

  Content of the (D) antifoamer in the high fluidity concrete of this invention is 0.01-0.4 mass part with respect to 100 mass parts of cement. By using in this range, sufficient compressive strength at a material age of 1 day can be obtained, and good fluidity can be secured. (D) The preferable content of the antifoaming agent is 0.015 parts by mass or more, more preferably 0.02 parts by mass or more, preferably 0.35 parts by mass or less, and more preferably 0.3 parts by mass or less. . Specifically, 0.015-0.35 mass part is preferable, and 0.02-0.3 mass part is more preferable.

In the high fluidity concrete of the present invention, the content ratio ( C / A ) of the component (A) and the component (C) is important in terms of securing fluidity after 240 minutes of kneading and early strength development. Yes, the ratio is 1.5 to 5.0. If this ratio is less than 1.5, the fluidity after 240 minutes of kneading is lowered, and if this ratio exceeds 5.0, the strength development is not sufficient. ( C / A ) is preferably 1.7 or more, more preferably 1.8 or more, and preferably 4.8 or less, more preferably 4.6 or less. Specifically, 1.7 to 5.0 is preferable, 1.7 to 4.8 is more preferable, and 1.8 to 4.6 is more preferable.

  The high fluidity concrete of the present invention contains aggregate and water in addition to cement and the above components.

  Examples of the cement used in the present invention include various portland cements such as normal, early strength, very early strength, low heat, and moderate heat, ecocement, and portland cement or ecocement, and fly ash, blast furnace slag, silica fume, or limestone. Examples include various mixed cements in which fine powders are mixed. One or a combination of two or more of these may be used. It should be noted that early strength Portland cement is preferred because of its high compressive strength at a material age of 1 day and easy availability.

The cement content of the high fluid concrete is preferably 300 to 700 kg / m ³ from the viewpoints of fluidity, prevention of material separation, and prevention of cracking. More preferably, it is 350-550 kg / m < ³ >.

  Examples of aggregates used in the concrete of the present invention include river sand, sea sand, mountain sand, crushed sand, artificial fine aggregate, slag fine aggregate, recycled fine aggregate, slag fine aggregate, quartz sand, stone powder, river gravel , Land gravel, crushed stone, artificial coarse aggregate, slag coarse aggregate, recycled coarse aggregate, slag coarse aggregate, and the like, and one or more of these can be used.

The aggregate content in the concrete is preferably 1200 to 1900 kg / m ³ from the viewpoints of fluidity, crack prevention and material separation prevention. More preferably, it is 1400-1700 kg / m < ³ >.

  The water used for the concrete of the present invention is not limited, but tap water is recommended. The content of water is preferably 30 to 65 parts by mass with respect to 100 parts by mass of cement from the viewpoint of fluidity and prevention of cracks. More preferably, it is 40-55 mass parts with respect to 100 mass parts of cement.

  One or two or more admixtures (materials) other than those described above can be used in combination in the high fluid concrete of the present invention as long as the effects of the present invention are not impaired. Examples of the admixture (material) material include cement polymer, foaming agent, foaming agent, waterproofing material, rust preventive agent, shrinkage reducing agent, thickener other than water-soluble cellulose, water retention agent, pigment, fiber, repellent. Water agent, anti-whitening agent, expansion agent (agent), quick setting agent (material), quick hardening agent (material), fine powder of blast furnace slag, fly ash, silica fume, volcanic ash, water repellent, surface hardener, water retention agent Etc.

  The high fluidity concrete of the present invention is produced by kneading using a mixer or the like. The apparatus and kneading apparatus used for kneading are not limited. It is preferable to use a mixer because a large amount can be kneaded. The mixer used may be a continuous mixer or a batch mixer. For example, a bread type concrete mixer, a pug mill type concrete mixer, a gravity concrete mixer, or the like is used. In addition, the materials may be put into a mixer at a time and kneaded, or the materials kneaded in two or more may be further kneaded and manufactured.

The high-fluidity concrete of the present invention supplies an admixture containing (A) an alkali metal sulfate and (D) an antifoaming agent from the viewpoints of workability, material uniformity during mixing, and ease of material measurement. It is preferable to manufacture the mixture by mixing cement, (B) water-soluble celluloses, and (C) a polycarboxylic acid-based water reducing agent.
Here, the admixture containing the component (A) and the component (D) preferably contains an inorganic powder as an additive.

  The content of the component (A) in the admixture is preferably 60 to 80% by mass. The component (D) is preferably a powder when used in an admixture, and the content of the component (D) in the admixture is preferably 2 to 10% by mass.

  The inorganic powder (additive) in the present invention is used to prevent the alkali metal sulfate metal salt powder from solidifying due to moisture absorption and to uniformly mix the alkali metal sulfate metal salt and the antifoaming agent. There is no particular limitation as long as it has a finer particle size than the alkali metal sulfate and does not adversely affect the properties of the high fluidity concrete in the present invention. For example, Portland cement, fly ash, blast furnace slag fine powder, calcium carbonate fine powder, silica stone fine powder, metakaolin, bentonite and the like can be mentioned. Of these, Portland cement is preferred from the viewpoint of economy. Content of the inorganic powder in the admixture of this invention is 10-40 mass%.

  The alkali metal sulfate, the antifoaming agent and the inorganic powder are mixed in advance and added to the concrete as an admixture before being added to the concrete in a predetermined blending amount. The mixing method is not particularly limited, and for example, a Henschel mixer, a Laedige mixer, or the like is used. The amount added to the concrete as an admixture is preferably 2 to 15% by mass.

The ratio of the slump flow value after 240 minutes of kneading to the slump flow value immediately after kneading is preferably 85% or more, more preferably 90% or more, and the high-fluidity concrete of the present invention is compressed at a material age of 1 day. The strength is preferably 8 N / mm ² or more, more preferably 9 N / mm ² or more.

[Example 1]
An admixture composed of the components shown in Table 2 was added to concrete having the blending conditions shown in Table 1 (mixing amount: 30 L), and the mixture was mixed in a forced-pan concrete mixer (capacity 55 L) to prepare concrete. The slump flow and compressive strength of the produced concrete were measured. The materials used, the kneading method, and the test method are shown below, and the test results are shown in Table 3.

<Materials used>
Cement: Early strong Portland cement (manufactured by Taiheiyo Cement, density: 3.14 g / cm ³ )
Fine aggregate: mountain sand from Kikugawa City, Shizuoka Prefecture (density: 2.61 g / cm ³ )
Coarse aggregate: Crushed stone 1305 (density; 2.64 g / cm ³ ) from Sakuragawa City, Ibaraki Prefecture
Water: Tap water Polycarboxylic acid-based water reducing agent: Powder-type high-performance water reducing agent based on water-soluble methacrylic graft polymer Alkali metal sulfate: Anhydrous sodium sulfate (commercially available powder)
Antifoam: SN deformer (San Nopco, powder)
Inorganic powder (additive): Ordinary Portland cement (manufactured by Taiheiyo Cement, density: 3.16 g / cm ³ )
Water-soluble celluloses: hydroxypropyl methylcellulose

<Kneading method>
First, alkali sulfate metal salt, antifoaming agent and inorganic powder (additive) are weighed so as to have the blending ratios shown in Table 2, and mixed for 1 minute with a Laedige mixer (Matsuzaka Giken Co., Ltd.). It was.
Next, coarse aggregate, about half amount of fine aggregate, cement, water-soluble cellulose and the above admixture, and the remaining about half amount of fine aggregate were put in the mixer and mixed for 15 seconds. Thereafter, an aqueous solution in which a polycarboxylic acid-based water reducing agent was dissolved in water was placed in a mixer and kneaded for 90 seconds to produce concrete. The kneading was performed in a constant temperature room at 20 ° C.

<Test method>
-Measurement of time-dependent change in slump flow The slump flow was measured 5 minutes after raising the slump cone in accordance with the standard [JIS A 1150 "Method for testing slump flow of concrete"]. The measurement was performed immediately after kneading, after 180 minutes and after 240 minutes. The value of the slump flow immediately after kneading was set to 100, and the ratio (flow ratio) of the slump flow at each measurement was obtained. The measurement of the change in slump flow with time was performed in a constant temperature room at 20 ° C.
In accordance with the compressive strength test standard [JIS A 1108 “Concrete compressive strength test method”], the compressive strength of the material at 1 day and 3 days was measured. The curing temperature was 20 ° C. until immediately before the test.

In all the examples of the present invention, the flow ratio after 180 minutes is 90 or more and the flow ratio after 240 minutes is 85 or more, and the fluidity is high even after 240 minutes. Further, in the examples of the present invention, the compressive strength per day of the age is 8 N / mm ² or more, and the material has a high age strength.
On the other hand, the comparative example in which the contents of components (A), (B) and (C) are outside the scope of the present invention and the comparative example in which ( C / A ) is outside the scope of the present invention have a flow ratio after 240 minutes. It was less than 85, or the compressive strength of the material age 1 day was low. Moreover, the comparative example (formulation No. 19) which does not contain an antifoamer had low compressive strength on the 1st day of age.

Claims (4)

(A) 0.4 to 1.7 parts by mass of alkali metal sulfate, (B) 0.15 to 0.4 parts by mass of water-soluble cellulose, (C) polycarboxylic acid-based water reducing agent with respect to 100 parts by mass of cement It contains 1.6 to 3.5 parts by mass, and (D) 0.01 to 0.4 parts by mass of an antifoaming agent, and the content ratio (C / A) of the component (A) to the component (C) is 1. High fluidity concrete which is .5 to 5.0.   The high fluidity concrete according to claim 1, wherein the content of the component (C) is 1.6 to 3.0 parts by mass with respect to 100 parts by mass of cement.   The high-fluidity concrete according to claim 1 or 2, wherein the content ratio (C / A) of the component (A) and the component (C) is 1.7 to 5.0. The ratio of the slump flow value of kneading 240 minutes after for slump flow value immediately after kneading is 85% or more, to any one of claims 1 to third compression strength of 1 day age of is 8N / mm ² or more Highly fluid concrete as described.