JP6955938B2 - High fluid concrete - Google Patents

Description

The present invention relates to high-fluidity concrete having good filling property and viscosity even in a narrow space and capable of early demolding.

At construction sites, high-fluidity concrete with high fluidity is used to ensure workability, pumping performance, filling performance, etc. in deep places and narrow places such as where reinforcing bars are placed. In general, high-fluidity concrete has an increase in admixture due to an increase in the amount of powder, and the use of a thickener system delays the setting time, making early demolding difficult.
On the other hand, concrete that uses general-purpose cement and has high fluidity and quick strength has been proposed, and early demolding is possible. Water-soluble cellulose, alkali sulfate and polycarboxylic acid-based water reducing agents are used in this concrete (Patent Documents 1 and 2).

JP-A-2009-155184 JP-A-2015-78084

However, high-fluidity concrete often has a large amount of unit water, and an increase in drying shrinkage is one of the problems of high-fluidity concrete when the amount of unit water is large, and the increase is remarkable especially in the case of early demolding.
Therefore, an object of the present invention is to provide a high-fluidity concrete which can maintain fluidity for about 4 hours, has good strength development thereafter, can be demolded at an early stage, and can suppress drying shrinkage.

Therefore, the present inventor made various studies to develop high-fluidity concrete that can maintain fluidity for a long time and can be quickly demolded. As a result, the content of alkali metal sulfate was increased, and alkali metal sulfate and polycarboxylic acid were increased. If the content-mass ratio of the acid-based water reducing agent is within a specific range and a defoaming agent is contained, good fluidity is maintained even after 240 minutes of kneading, and the compressive strength at 18 hours of age is high. We have found that a high-fluidity concrete that can suppress drying shrinkage can be obtained, and completed the present invention.

That is, the present invention provides the following [1] to [4].

[1] 1.7 to 2.5 parts by mass of (A) alkali metal sulfate, (B) 0.15 to 0.4 parts by mass of water-soluble celluloses, and (C) polycarboxylic acid with respect to 100 parts by mass of concrete. It contains 2.3 to 4.0 parts by mass of the water reducing agent and 0.01 to 0.4 parts by mass of the defoaming agent (D), and the content mass ratio (C / A) of the component (C) to the component (A). High fluidity concrete with a mass ratio of 1.35 to 1.75.
[2] High-fluidity concrete of [1] or [2] having a unit water amount of 200 to 250 kg / m ^3.
[3] 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 slump flow value 50 cm arrival time immediately after kneading and the slump flow value 50 cm after 240 minutes are reached. High-fluidity concrete of [1] or [2] having a ratio to time of 2.5 or less.
[4] High-fluidity concrete according to any one of [1] to [3], which has a compressive strength of 5 N / mm ^{2 or more at an age of 18 hours.}

According to the present invention, a high-fluidity concrete can be obtained in which good fluidity is maintained even after 240 minutes of kneading and the compressive strength at 18 hours of age is 5 N / mm ^{2 or more.} By using the high-fluidity concrete of the present invention, even in a site where filling with a long pumping pump is required, such as a deep reinforcing bar arrangement part or a deep underground place, it can be accurately filled in a predetermined place and has excellent strength capable of early demolding. Concrete can be formed. Therefore, if the high-fluidity concrete of the present invention is used, it is possible to shorten the construction period, reduce the work, and reduce the construction cost.

The high-fluidity concrete of the present invention contains (A) alkali metal sulfate, (B) water-soluble celluloses, (C) polycarboxylic acid-based water reducing agent, and (D) defoaming agent.

Examples of the (A) alkali metal sulfate 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 1.7 to 2.5 parts by mass with respect to 100 parts by mass of the cement contained in the concrete. When the amount of the alkali metal sulfate used is in the above range, the compressive strength of the added concrete becomes high, and the decrease in slump flow due to the elapsed time can be sufficiently suppressed. The content of the alkali metal sulfate is preferably 1.75 parts by mass or more, more preferably 1.80 parts by mass or more, and preferably 2.40 parts by mass or less with respect to 100 parts by mass of cement contained in concrete. 2.30 parts by mass or less is more preferable. Specifically, 1.75 to 2.40 parts by mass is preferable, and 1.80 to 2.30 parts by mass is more preferable. Within this content range, the compressive strength of concrete at 18 hours of age can be 5 ^{N / mm 2 or more.}

Examples of the (B) water-soluble cellulose used in the present invention include nonionic water-soluble cellulose ether selected from hydroxyalkyl cellulose and hydroxyalkyl alkyl cellulose. Examples of hydroxyalkyl cellulose include hydroxyethyl cellulose and hydroxypropyl cellulose. Examples of the hydroxyalkylalkyl cellulose include hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl ethyl cellulose and the like. One type of these water-soluble celluloses may be used, or two or more types may be used in combination. Among these, one or more selected from hydroxypropyl methylcellulose and hydroxyethyl cellulose are particularly preferable.

The water-soluble celluloses (B) used in the present invention preferably have a viscosity of an aqueous solution at a concentration of 2.0% by mass at 20 ° C. of 30,000 to 60,000 Pa · S. Those in this viscosity range are preferable because they are easily dissolved in the mixed water of concrete at an early stage and are hard to remain undissolved.

The content of (B) water-soluble cellulose in the high-fluidity concrete of the present invention is 0.15 to 0.4 parts by mass with respect to 100 parts by mass of cement contained in the concrete. When the amount of the water-soluble cellulose used is in the above range, the decrease in slump flow after 240 minutes of kneading can be sufficiently suppressed. The content of the water-soluble celluloses is preferably 0.16 parts by mass or more, more preferably 0.17 parts by mass or more with respect to 100 parts by mass of the 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. Further, 0.35 parts by mass or less is preferable, 0.32 parts by mass or less is more preferable, and 0.3 parts by mass or less is further preferable. Specifically, 0.16 to 0.35 parts by mass is preferable, 0.17 to 0.32 parts by mass is more preferable, 0.18 to 0.32 parts by mass is further preferable, and 0.18 to 0.3 parts by mass is preferable. Parts by mass are even more preferred.

Examples of the (C) polycarboxylic acid-based water reducing agent used in the present invention include a polycarboxylic acid-based water reducing agent, a polycarboxylic acid-based AE water reducing agent, a polycarboxylic acid-based high-performance AE water reducing agent, and a polycarboxylic acid-based high-performance water reducing agent. Examples include agents. Among 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 containing a water-soluble methacrylic acid-based graft polymer as a main component, or a polycarboxylic acid. Acid-based high-performance water reducing agents are particularly preferable.

The content of the (C) polycarboxylic acid-based water reducing agent in the high-fluidity concrete of the present invention is 2.3 to 4.0 parts by mass with respect to 100 parts by mass of the cement contained in the concrete. Within this range of usage, it is possible to sufficiently suppress a decrease in the slump flow of concrete after 240 minutes, and a high compressive strength at 18 hours of age can be obtained. The content of the polycarboxylic acid-based water reducing agent is preferably 2.4 to 3.5 parts by mass with respect to 100 parts by mass of cement contained in concrete.

In the high-fluidity concrete of the present invention, the content mass ratio (C / A) of the component (A) to the component (C) is important in terms of ensuring fluidity after 240 minutes of kneading and early strength development. Yes, the ratio is 1.35 to 1.75. If this ratio is less than 1.35, the fluidity after 240 minutes of kneading will decrease, and if this ratio exceeds 1.75, the early strength development will not be sufficient. (C / A) is preferably 1.38 or more, more preferably 1.40 or more, preferably 1.67 or less, and more preferably 1.65 or less. Specifically, 1.38 to 1.67 is preferable, and 1.48 to 1.65 is more preferable. In this range, the slump flow ratio after 240 minutes of kneading is 85% or more, the 50 cm arrival time ratio after 240 minutes is 2.5 or less, and the compression strength at 16 hours of age is 5 N / mm ² or more. be able to. In addition, the drying shrinkage strain at 6 months of age can be 8.0 × 10 ^-4 or less.

In the high-fluidity concrete of the present invention, the content mass ratio (B / A) of the component (B) to the component (A) is 0. 10 to 0.14 is preferable, 0.11 to 0.14 is more preferable, and 0.11 to 0.13 is further preferable.

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

The content of the (D) defoaming agent in the high-fluidity concrete of the present invention is 0.01 to 0.4 parts by mass with respect to 100 parts by mass of cement. By using it in this range, sufficient compressive strength can be obtained at a material age of 18 hours, and good fluidity can be ensured. The content of the defoaming agent (D) is more preferably 0.015 to 0.35 parts by mass, and even more preferably 0.02 to 0.3 parts by mass.

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

The cement used in the present invention includes various Portland cements such as ordinary, early-strength, ultra-fast-strength, low-heat, and moderate heat, eco-cement, and fly ash, blast furnace slag, silica fume, or limestone in these Portland cement or eco-cement. Examples thereof include various mixed cements in which fine powder and the like are mixed. These may be used alone or in combination of two or more. Early-strength Portland cement is preferable because it has excellent initial strength development and is easily available.

The content of the cement at high flow concrete, fluidity, prevention of segregation, in terms of crack prevention is preferably 300~700kg / m ^3, more preferably 350~550kg / m ^3.

Examples of the aggregate used for 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, silica sand, stone powder, and river gravel. , Land gravel, crushed stone, artificial coarse aggregate, slag coarse aggregate, regenerated coarse aggregate, slag coarse aggregate, etc., and one or more of these can be used.

The content of the aggregate of high fluidity in the concrete, the fluidity, preventing cracks from the viewpoint of segregation prevention, preferably 1200~1900kg / m ^3, more preferably 1400~1700kg / m ^3.

The water used for the concrete of the present invention is recommended, but not limited to, tap water. The water content (unit water amount) is preferably ^{190 to 260 kg / m 3} from the viewpoint of fluidity, strength development, and drying shrinkage performance. Further, 195 kg / m ³ or more is more preferable, 200 kg / m ³ or more is further preferable, 255 kg / m ³ or less is more preferable, and 250 kg / m ³ or less is further preferable. Specifically, more preferably ^{195~255kg / m 3, 200~250kg / m} 3 it is more preferred.

The amount of water with respect to 100 parts by mass of cement is preferably 30 to 65 parts by mass, more preferably 35 to 60 parts by mass, and even more preferably 38 to 55 parts by mass from the viewpoint of fluidity, strength development, and drying shrinkage performance.

One or more of the admixtures (materials) other than the above can be used in combination with the high-fluidity concrete of the present invention as long as the effects of the present invention are not impaired. Examples of such admixtures (materials) include cement polymers, foaming agents, foaming agents, waterproof materials, rust preventive agents, shrinkage reducing agents, thickeners other than water-soluble celluloses, water retention agents, pigments, and fibers. , Water repellent, anti-whitening agent, expansion material (agent), hardener (material), blast furnace slag fine powder, fly ash, silica fume and the like.

The high-fluidity concrete of the present invention is produced by kneading using a mixer or the like. The equipment and kneading equipment 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 pan-type concrete mixer, a pug mill-type concrete mixer, a gravity-type concrete mixer, or the like is used. Further, the materials may be put into a mixer at a time and kneaded, or the materials may be divided into two or more and kneaded, and the kneaded materials may be further kneaded and manufactured.

The high-fluidity concrete of the present invention prepares an admixture containing (A) alkali metal sulfate and (D) defoaming agent from the viewpoints of workability, material uniformity during kneading, and ease of material measurement. It can be produced by mixing cement, (B) water-soluble celluloses, and (C) a polycarboxylic acid-based water reducing agent.

It is preferable to add an inorganic powder as an additive to the admixture. Inorganic powder is used to prevent solidification of alkali metal sulfate powder due to moisture absorption and to uniformly mix alkali metal sulfate and antifoaming agent. It is not particularly limited as long as it has a finer particle size than the alkali metal sulfate and does not adversely affect the characteristics 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 preferable from the viewpoint of economy.

The content of the component (A) in the admixture is preferably 60 to 80% by mass. When the component (D) is used as an admixture, it is preferably powder, and the content of the component (D) in the admixture is preferably 2 to 10% by mass. Further, the content of the inorganic powder in the admixture is preferably 10 to 35% by mass.

The mixing method of the admixture is not particularly limited, but for example, a Henschel mixer, a Ladyge mixer, or the like is used. The amount added to concrete as an admixture is preferably 2 to 15% by mass with respect to cement.

In the high-fluidity concrete of the present invention, 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 slump flow immediately after kneading. The ratio of the time to reach the value of 50 cm to the time to reach the slump flow value of 50 cm after 240 minutes is preferably 2.5 or less, more preferably 2.3 or less. Further, the compressive strength at a material age of 18 hours is preferably 5 N / mm ² or more, and more preferably 6 N / mm ² or more.

[Example 1]
Concrete with the compounding conditions shown in Table 1 (mixing amount: 30 L) was kneaded with a forced pan-type concrete mixer (capacity 55 L) to prepare concrete. The slump flow and compressive strength of the prepared concrete were measured. The materials used, the kneading method, and the test method are shown below, and the test results are shown in Table 2.

<Material used>
Cement: Early-strength 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: 1305 crushed stone from Sakuragawa City, Ibaraki Prefecture (density; 2.64 g / cm ³ )
Water: Tap water Polycarboxylic acid-based water reducing agent: Powder-type high-performance water-reducing agent containing a water-soluble methacrylic graft polymer as the main component Alkali sulfate: Anhydrous glass (commercially available, powder)
Defoamer: SN deformer (manufactured by San Nopco Ltd., powdered)
Water-soluble cellulose: hydroxypropyl methylcellulose

<Kneading method>
The materials used excluding the water reducing agent were weighed so as to have the blending ratios shown in Table 1, placed in a concrete mixer, and mixed for 15 seconds. Then, an aqueous solution prepared by dissolving a polycarboxylic acid-based water reducing agent in water was placed in a mixer and kneaded for 90 seconds to produce concrete. The kneading was carried out in a constant temperature room at 20 ° C.

<Test method>
(1) Measurement of slump flow According to the standard [JIS A 1150 "Concrete slump flow test method"], the slump flow was measured 5 minutes after the slump cone was pulled up. The measurement was carried out immediately after kneading and 240 minutes later. The ratio of the slump flow at the time of measurement (flow ratio) was determined with the value of the slump flow immediately after kneading as 100. The slump flow was measured in a constant temperature room at 20 ° C.
(2) Viscosity increase test In the viscosity increase test of concrete, the slump flow 50 cm arrival time was measured according to JSCE-F516. The measurement was carried out immediately after kneading and 240 minutes later. The ratio of the slump flow 50 cm arrival time after 240 minutes to the value of the slump flow 50 cm arrival time immediately after kneading was determined. The measurement was performed in a constant temperature room at 20 ° C.
(3) Compressive strength test The compressive strength at 18 hours of age was measured according to the standard [JIS A 1108 “Concrete compressive strength test method”]. The curing temperature was 20 ° C. until just before the test.
(4) Measurement of drying shrinkage strain The drying shrinkage strain at 6 months of age was measured according to the standard [JIS A 1129 "Mortar and concrete length change measuring method"]. The concrete was demolded in 18 hours, the base length was measured, the strain amount at 6 months of age was measured, and the drying shrinkage strain was calculated. The concrete specimen was stored in a constant temperature room at 20 ° C. during the age period.

In each of the examples of the present invention, the slump flow ratio after 240 minutes is 85% or more and the 50 cm arrival time ratio after 240 minutes is 2.5 or less, and the fluidity is good even after 240 minutes. Further, in the examples of the present invention, the compressive strength at 18 hours of the material age is 5 N / mm ² or more, the strength is high from the early stage of the material age, and the mold can be removed within 24 hours.
On the other hand, in the comparative example, the slump flow ratio is less than 85%, or the 50 cm arrival time ratio is 2.5 or more, and the fluidity after 240 minutes is not sufficient. Further, in the comparative examples (No. 7 and 9) in which the fluidity after 240 minutes is ensured, the compressive strength at the age of 18 hours is significantly low.

Claims (4)

(A) Alkali sulfate metal salt 1.75 to 2.5 parts by mass, (B) Water-soluble celluloses 0.15 to 0.4 parts by mass, (C) Polycarboxylic acid-based water reducing agent with respect to 100 parts by mass of concrete. It contains 2.3 to 4.0 parts by mass and (D) 0.01 to 0.4 parts by mass of the defoaming agent, and the content mass ratio (C / A) of the component (C) to the component (A) is 1. High-fluidity concrete of 35 to 1.75. The high-fluidity concrete according to claim 1, wherein the unit water amount is 200 to 250 kg / m ^3. 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 slump flow value 50 cm arrival time immediately after kneading and the slump flow value 50 cm arrival time 240 minutes later The high-fluidity concrete according to claim 1 or 2, wherein the ratio is 2.5 or less. The high-fluidity concrete according to any one of claims 1 to 3, wherein the compression strength at a material age of 18 hours is 5 N / mm ^{2 or more.}