JP2017128489A - Preparation method and hardened body of early strength concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preparation method of a high-early-strength concrete promoting aggregation and curing at early time by stopping flowability quickly when filling of parts is completed sequentially while maintaining flowability during filling operation and a cured body thereof for overcoming problems that there is need for constructing a frame having a sufficient framework in a concrete construction for filling and installing concrete excellent in flowability and cost and labor are required for the operation and there is need for shortening construction period of the concrete construction.SOLUTION: There is provided a preparation method of a high-early-strength concrete, including mixing a concrete of a base blend and then adding, to the concrete slurry, a predetermined amount of an admixture composition containing, at a specific ratio, constitutional components containing A component:one or more selected from specific polyacrylamide and specific polyacrylic acid alkali metal salt, B component: silicate alkali metal salt, C component: specific polyalkylene glycol monoalkyl ether, D component: sodium phosphate, and E component: water.SELECTED DRAWING: None

Description

  The present invention relates to a method for preparing early-strength concrete and a hardened concrete body obtained by the preparation method.

  In the construction work and civil engineering work for placing concrete, the use of concrete having good workability and good fluidity in areas with many reinforcing bars has been increasing in recent years. In the new construction where concrete (hereinafter referred to as concrete including mortar) is cast, high fluidity is maintained for a long time after filling when a large amount of concrete with good fluidity is cast in the mold. The side pressure on the side of the mold is increased, and it is necessary to assemble a strong mold so that the concrete slurry after filling does not flow out of the gap between the molds. . That is, at the same time as reducing the work of assembling the mold, it is desired to realize a fast-strength concrete that quickly stops its fluidity after completion of sequential filling and quickly sets and hardens. Also, in concrete repair / reinforcement work, it is desired that the work for constructing wall members and top plate members be simplified and reduced as much as possible. In other words, in concrete repair / reinforcement work, it is desired to propose fast-strength concrete that maintains the fluidity of the concrete during filling work, but stops the fluidity immediately after successive filling and quickly sets and hardens. Yes. As conventional techniques related to such a problem, for example, Patent Documents 1 to 3 and the use of various rapid setting materials for promoting the setting and hardening of concrete particularly in tunnel blowing work are known. However, for example, the method of using a relatively inexpensive and highly safe silicate as a quick setting material has pointed out the problem that the shrinkage of the cured body is large (for example, Patent Documents 4 to 6). In the current situation, there are various problems that have not been fully solved.

  JP-A-11-35362   JP 2000-096820 A   JP 2011-184934 A   JP 2002-249360 A   JP 2011-84440 A   JP2015-120630A

  The problem to be solved by the present invention is that when filling concrete with good fluidity, it is necessary to assemble a formwork having a sufficient framework in consideration of a strong lateral pressure load, which requires labor and cost. There is a problem that it takes. In addition, in order to shorten the work period in concrete work, it is desired to have early-strength concrete that keeps the fluidity of the concrete during filling work and stops the fluidity quickly after completion of sequential filling, and quickly sets and hardens. There are challenges. As a result of diligent research to solve such problems, the present inventors have added a liquid admixture composition containing specific five constituent components in a specific ratio at a specific ratio to the base-mixed concrete slurry. It has been found that the method of inclusion is correct and suitable.

  That is, the present invention is based on the following admixture composition per 100 parts by mass of cement with respect to the concrete slurry after kneading the concrete containing the base containing cement, fine aggregate, coarse aggregate, water and cement dispersant. Is added at a ratio of 0.1 to 15 parts by mass, and relates to a method for preparing early strength concrete.

  Admixture composition: composed of the following A component, the following B component, the following C component, the following D component, and the following E component, and the A component is 0.05 to 3% by mass, and the B component is 15 to 48% by mass, C component 0.4-30% by mass, D component 0.05-3% by mass, and E component 16-84.5% by mass (total 100% by mass) Agent composition.

Component A: One or two or more selected from polyacrylamide having a molecular weight of 10 × 10 ^{4 to} 1500 × 10 ^{4 and} an alkali metal salt of polyacrylic acid having a molecular weight of 5 × 10 ^{4 to} 500 × 10 ⁴ .

Component B: alkali metal silicate

Component C: polyalkylene glycol monoalkyl ether represented by the following chemical formula 1

In chemical formula 1,
R ¹ : Alkyl group having 3 to 5 carbon atoms A ¹ : Excluding all hydroxyl groups from polyalkylene glycol having a polyoxyalkylene group composed of a total of 2 to 10 oxyethylene units and oxypropylene units in the molecule Residue.

D component: Sodium phosphate

E component: water

  The admixture composition according to the present invention (hereinafter referred to as the admixture of the present invention) will be described. The admixture of the present invention is a liquid admixture composition comprising an A component, a B component, a C component, a D component, and an E component.

As the component A, water-soluble polyacrylamide having a molecular weight of 10 × 10 ^{4 to} 1500 × 10 ⁴ can be used, and polyacrylamide having a molecular weight of 100 × 10 ^{4 to} 1000 × 10 ⁴ is preferable. When the molecular weight is smaller than this range, the aggregation effect for stopping the fluidity is weakened. Conversely, when the molecular weight is large, the viscosity of the aqueous solution is increased and handling is reduced. As the component A, the molecular weight of 5 × ^{10 4} ~500 × ¹⁰ 4 of can polyacrylic acid alkali metal salt is used, more polyacrylic acid alkali metal salt with a molecular weight ranging of ¹⁰ × 10 ⁴ ~200 × 10 4 Is preferred. When the molecular weight is smaller or larger than this range, it is not suitable for the same reason as described above. Examples of the alkali metal salt include sodium salt, potassium salt and lithium salt, and sodium salt is preferable. The water-soluble polymers of the high molecular weight polyacrylamide and polyacrylic acid alkali metal salt described above have a property that the aggregation effect is exhibited only after they are dissolved in water. Therefore, it is one of the important points of the admixture of the present invention to use an aqueous solution previously dissolved in water.

Component B is an alkali metal silicate. Examples of the alkali metal silicate include sodium silicate, potassium silicate, and lithium silicate. From the viewpoint of industrial availability, it is preferable to use water glass containing sodium silicate as a main component. The molecular formula of water glass is represented by Na ₂ O · nSiO ₂ and is not limited, but is a compound from No. 1 to No. 3 defined in JIS-K1408, in other words, silicon dioxide with respect to sodium oxide represented by the molecular formula The molar ratio (n) in the range of SiO ₂ / Na ₂ O = 1.8 to 3.5 can be advantageously used. Among these ranges, those having a high molar ratio are preferably used. In the present invention, the role of water glass is to stop the fluidity after filling while ensuring a certain work time, instead of causing instantaneous setting immediately after spraying like sprayed concrete when mixed with concrete slurry. Used as a role to accelerate the curing reaction by accelerating the setting.

  Component C is a polyalkylene glycol monoalkyl ether represented by the following chemical formula 1.

However, in chemical formula 1,
R ¹ : Alkyl group having 3 to 5 carbon atoms A ¹ : Excluding all hydroxyl groups from polyalkylene glycol having a polyoxyalkylene group composed of a total of 2 to 10 oxyethylene units and oxypropylene units in the molecule Those which are suitable for the conditions such as a compound composed of various residues can be used in the present invention.

Further, as the compound of Chemical Formula 1 in the component C, R ¹ is preferably a butyl group having 4 carbon atoms, and A ¹ is composed of a total of 3 to 8 oxyethylene units and oxypropylene units in the molecule. And compounds composed of residues obtained by removing all hydroxyl groups from a polyalkylene glycol having a polyoxyalkylene group. In the present invention, the compound composed of the component C is liquid at room temperature, the admixture composition is a uniform solution, the chemical stability of the product is excellent, and the role of suppressing shrinkage cracking of the hardened concrete after hardening Use as

  Component D is sodium phosphate. Examples of the sodium phosphate salt include trisodium phosphate, disodium phosphate, monosodium phosphate, etc. Among them, disodium phosphate or monosodium phosphate is preferable, and phosphorous is preferable from the viewpoint of good solubility in water. Acid monosodium is preferred. Further, in the admixture of the present invention, the role of sodium phosphate salt is to temporarily delay the rapid setting due to the rapid hydration reaction of cement when the alkali metal silicate B component is mixed with the concrete slurry. And used for securing the working time required for filling the slurry.

  The E component is water. There is no limitation on the type of water used, such as natural water, distilled water, and tap water, and it is usually preferable to use tap water. Moreover, it is because it is important for the role of water to use the admixture of this invention as a stable homogeneous solution without a precipitate and isolation | separation in the state of a solution.

  The admixture composition according to the present invention described above comprises an A component, a B component, a C component, a D component, and an E component, and the A component is 0.05 to 3% by mass, and the B component is 15 to 48 mass. %, C component is 0.4 to 30% by mass, D component is 0.05 to 3% by mass, and E component is 16 to 84.5% by mass (total 100% by mass). Yes, preferably 0.1 to 1.5% by weight of component A, 20 to 45% by weight of component B, 1 to 20% by weight of component C, 0.1 to 2% by weight of component D and 31 of component E 0.5 to 79.8% by mass (total 100% by mass) of the admixture composition.

  Next, a method for preparing early-strength concrete according to the present invention (hereinafter simply referred to as the method of the present invention) will be described. The method of the present invention comprises placing the admixture of the present invention in a concrete slurry having a slump value of 12 to 27 cm, preferably 15 to 25 cm of a base formulation containing cement, fine aggregate, coarse aggregate, water and cement dispersant. It is a method of preparing early-strength concrete by adding a fixed amount and stopping fluidity promptly after filling, and at the same time promoting setting and hardening. The timing of adding the admixture of the present invention to the concrete slurry after being kneaded with the base composition can be appropriately selected according to the circumstances of placing on site. For example, after transporting the concrete slurry kneaded in the ready-mixed factory to the setting site, the admixture of the present invention is added to the concrete slurry, mixed in a short time, and quickly filled into the mold and placed. be able to. As another method, for example, using a Y-shaped pipe, concrete slurry is transported by piping with compressed air or a piston pump on the one hand, and on the other hand, the admixture solution of the present invention is transported by another piping. Various predetermined amounts can be joined before the nozzle, mixed in a short time, and then extruded from the nozzle. In any case, the fluidity of the concrete slurry filled in the range of about 1 to 60 minutes after the addition and mixing is completely stopped, and thereafter, the setting starts and the curing gradually proceeds. The time during which the fluidity of the filled concrete slurry completely stops depends largely on the amount of the admixture of the present invention, and usually 0.1 to 15 of the admixture of the present invention per 100 parts by mass of cement contained in the concrete slurry. The composition ratio and amount of the admixture of the present invention are added in accordance with the target fluidity stop time and setting / curing time to be adjusted. Can be appropriately selected to add a predetermined amount.

  In the concrete containing the cement, fine aggregate, coarse aggregate, water, and cement dispersant, the ordinary cements include Portland cement, early-strength Portland cement, super-early-strength Portland cement, low heat Portland cement, and moderately hot Portland cement. It is also possible to use various Portland cements such as a cement, and mixed cements obtained by mixing these Portland cements with blast furnace slag fine powder, fly ash fine powder, or silica fume fine powder. Among them, in the present invention, ordinary Portland cement and early-strength Portland cement are preferable from the viewpoint of being generally available and easy to obtain, and it is more preferable to use early-strength Portland cement from the viewpoint of easily obtaining early strength.

  Examples of fine aggregates include river sand, mountain sand, and sea sand. Further, examples of the coarse aggregate include river gravel, crushed stone, and lightweight aggregate.

  The cement dispersing agent is not limited, and general cement dispersion such as polycarboxylic acid-based water-soluble vinyl copolymer, naphthalenesulfonic acid formalin high condensate, melamine naphthalenesulfonic acid formalin high condensate, lignin sulfonate, etc. In particular, in the method of the present invention, a polycarboxylic acid-based water-soluble vinyl copolymer having a polyethylene glycol chain as a side chain and having a strong dispersion force is preferable. For example, when a polycarboxylic acid cement dispersant (for example, Japanese Patent Application Laid-Open No. 2003-2720) mainly composed of a polycarboxylic acid water-soluble vinyl copolymer having a polyethylene glycol chain as a side chain is used, fluidity is imparted to concrete. When a large amount of fluidity is obtained with a small addition amount, and when the fluidity is strongly stopped, the interaction between the dispersant and the flocculant strongly acts, so that the specific dispersant and the specific component A The present inventors have found that by using a combination of the water-soluble polymer flocculant comprising the following, the fluidity is sharply stopped, and at the same time, a synergistic effect for promoting the setting / curing can be obtained.

  In the method of the present invention described above, after mixing concrete with a base, a predetermined amount of the admixture of the present invention is added to and contained in the concrete slurry. The slurry is characterized in that early fluidity can be obtained in a short period of time by reducing fluidity at an early stage to reduce the lateral pressure load and at the same time promoting setting and hardening.

In addition, when Portland cement is used, the hardened concrete obtained by the method of the present invention can remove the concrete slurry filling form at an early stage, and the compressive strength per day at room temperature is 20 N / mm ² or more. When steam curing is used, it can be applied not only to ready-mixed concrete but also to secondary concrete products.

Examples of the method of the present invention include the following 1) to 6).
1) 0.2% by mass of polyacrylamide having a molecular weight of 800 × 10 ⁴ and silicic acid based on a concrete slurry (CS-1) with a base / 40% water / cement ratio (hereinafter abbreviated as W / C). Sodium (SiO ₂ / Na ₂ O molar ratio = 3 to 3.3) 30% by mass, poly (n = 2 mol) ethylene glycol poly (n = 2 mol) propylene glycol monobutyl ether 8% by mass, phosphoric acid Additive composition (M-1) containing 0.8% by mass of 1 sodium and 61% by mass (total 100% by mass) of water at a rate of 2 parts by mass per 100 parts by mass of cement A method for preparing early strength concrete to be contained.

2) 0.2% by mass of polyacrylamide having a molecular weight of 800 × 10 ⁴ , 25% by mass of sodium silicate (the molar ratio = 3 to 3.3), and poly (n) with respect to the concrete slurry (CS-1). = 2 mol) ethylene glycol poly (n = 2 mol) propylene glycol monobutyl ether 15% by mass, monosodium phosphate 0.5% by mass and water 59.3% by mass (total 100% by mass) A method for preparing early-strength concrete containing the admixture composition (M-2) comprising 3 parts by weight per 100 parts by weight of cement.

3) 0.7% by mass of sodium polyacrylate having a molecular weight of 100 × 10 ⁴ , 30% by mass of sodium silicate (molar ratio = 3 to 3.3) with respect to the concrete slurry (CS-1), poly (N = 3 mol) 10% by mass of ethylene glycol poly (n = 3 mol) propylene glycol monobutyl ether, 0.3% by mass of monosodium phosphate and 59% by mass of water (total of 100% by mass) The admixture composition (M-3) formed as above is added and contained at a ratio of 2 parts by mass per 100 parts by mass of cement.

4) 0.5% by mass of sodium polyacrylate having a molecular weight of 100 × 10 ⁴ and sodium silicate (SiO ₂ / Na ₂ O molar ratio = _{2 to} 2.3) with respect to the concrete slurry (CS-1). 35 mass%, poly (n = 2 mol) ethylene glycol poly (n = 2 mol) propylene glycol monobutyl ether 15 mass%, disodium phosphate 0.2 mass% and water 49.3 mass% (total) A method for preparing early-strength concrete in which the admixture composition (M-4) contained at a rate of 100% by mass is added and contained at a rate of 3 parts by mass per 100 parts by mass of cement.

5) The admixture composition (M-1) is added at a ratio of 4 parts by mass per 100 parts by mass of cement to the concrete slurry (CS-2) containing 35% of W / C. A method for preparing early strength concrete.

6) A method for preparing early-strength concrete in which the admixture composition (M-3) is added to and contained in a proportion of 4 parts by mass per 100 parts by mass of cement with respect to the concrete slurry (CS-2).

Effect of the invention

  According to the present invention, since the method of the present invention can remove the formwork at an early stage when filling and placing concrete with good fluidity, the work of assembling a formwork having a sufficient framework considering the side pressure load This has the effect of reducing the labor and cost of the work, and at the same time, it accelerates the setting and hardening of the concrete, so that the work period in the concrete work can be shortened.

  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 (Preparation of admixture composition)
・ Reference Example 1
100 parts of polyacrylamide as a component A (molecular weight 800 × 10 ⁴ , product name: Takiflock AL-65, manufactured by Taki Chemical Co., Ltd.), 40% aqueous solution of sodium silicate as a component B : Water glass No. 3, molar ratio SiO ₂ / Na ₂ O = 3 to 3.3) 750 parts, poly (n = 2 mol) ethylene glycol poly (n = 2 mol) propylene glycol monobutyl ether as C component, 53 parts of 15% aqueous solution of monosodium phosphate as component D and 17 parts of tap water as component E are mixed and dissolved uniformly. A component / B component / C component / D component / E component = 0.2 / 30 An admixture composition (M-1) having an aqueous solution concentration of 39% by mass of /8/0.8/61 (mass ratio, total 100%) was prepared.

・ Reference Example 2
In the same manner as in Reference Example 1, polyacrylamide (AL-65) as component A, sodium silicate (water glass No. 3) as component B, poly (n = 2 mol) ethylene glycol poly (n = 2 mol) Propylene glycol monobutyl ether, monosodium phosphate as D component and tap water as E component are mixed and dissolved uniformly. A component / B component / C component / D component / E component = 0.2 / An admixture composition (M-2) having an aqueous solution concentration of 40.7% by mass at 25/15 / 0.5 / 59.3 (mass ratio, 100% in total) was prepared.

・ Reference Example 3
18 parts aqueous solution of sodium polyacrylate as the A component (molecular weight 100 × 10 ⁴ , trade name: Aron A-20L manufactured by Toa Gosei Co., Ltd.), 40 parts aqueous solution of sodium silicate as the B component (the water glass No. 3) 750 parts, 100 parts of poly (n = 3 mol) ethylene glycol poly (n = 3 mole) propylene glycol monobutyl ether as C component, and 20 parts of 15% aqueous solution of monosodium phosphate and 91 parts of tap water as D component And mixed uniformly with an aqueous solution concentration of 41% by mass of A component / B component / C component / D component / E component = 0.7 / 30/10 / 0.3 / 59 (mass ratio, total 100%) An agent composition (M-3) was prepared.

Reference example 4
39 parts of 18% aqueous solution of sodium polyacrylate (A-20L) as component A, 55% aqueous solution of sodium silicate as component B (water glass No. 1, molar ratio of SiO ₂ / Na ₂ O = 2-2. 3) 636 parts, poly (n = 3 mol) ethylene glycol poly (n = 3 mol) propylene glycol monobutyl ether as C component, and 67 parts of 3% aqueous solution of disodium phosphate and 108 parts of tap water as D component Mixing and dissolving uniformly, concentration of aqueous solution A component / B component / C component / D component / E component = 0.5 / 35/15 / 0.2 / 49.3 (mass ratio, total 100%) 50 A 7% by mass admixture composition (M-4) was prepared.

・ Comparative Reference Examples 1-4
(MR-1) to (MR-4) were prepared as Comparative Reference Examples 1 to 4 in the same manner as Reference Examples 1 to 4. The results of Reference Examples 1 to 4 {(M-1) to (M-4)} and Comparative Reference Examples 1 to 4 {(MR-1) to (MR-4)} prepared above are summarized in Table 1. Indicated.

In Table 1,
a-1: Polyacrylamide (molecular weight 800 × 10 ⁴ , Taki Chemical Co., Ltd. trade name: Takiflock AL-65)
a-2: Sodium polyacrylate (Molecular weight 100 × 10 ⁴ , Toa Gosei Co., Ltd. trade name: Aron A-20L)
b-1: Sodium silicate (Product name manufactured by Showa Chemical Co., Ltd .: Water glass No. 3, molar ratio SiO ₂ / Na ₂ O = 3 to 3.3)
b-2: Sodium silicate (Product name: Showa Chemical Co., Ltd .: Water glass No. 1, molar ratio SiO ₂ / Na ₂ O = _{2 to} 2.3)
c-1: poly (n = 2 mol) ethylene glycol poly (n = 2 mol) propylene glycol monobutyl ether c-2: poly (n = 3 mol) ethylene glycol poly (n = 3 mol) propylene glycol monobutyl ether d- 1: Phosphate monosodium d-2: Phosphate disodium e-1: Tap water ar-1: Polyacrylamide (molecular weight 1 × 10 ⁴ )
ar-2: sodium polyacrylate (molecular weight 1 × 10 ⁴ )

Test Category 2 (Preparation of base compounded concrete slurry)
Test example 1
Formulation No. described in Table 1 Under the conditions of 1, a 50-liter pan-type forced kneading mixer is mixed with early strong Portland cement, water, fine aggregate (river sand, density = 2.58 g / cm ³ ), coarse aggregate (crushed stone, density = 2.68 g / cm) ³ ), cement dispersant (Brand name manufactured by Takemoto Yushi Co., Ltd .: Tupole HP-11, a high-performance AE water reducing agent mainly composed of a polycarboxylic acid-based water-soluble vinyl copolymer having a polyethylene glycol chain as a side chain) and An air amount adjusting agent was added and kneaded for 90 seconds to obtain a base-blended concrete slurry (CS-1) having a slump value of 21 ± 2 cm and an air amount of 4 ± 1%.

Test example 2
Formulation No. described in Table 2 Under the conditions of 2, a base blend concrete slurry (CS-2) having a slump value of 21 ± 2 cm and an air amount of 4 ± 1% was obtained in the same manner as in Test Example 1 using ordinary Portland cement as the cement.

In Table 2,
* 1: Early strength Portland cement (density = 3.13 g / cm ³ )
* 2: Normal Portland cement (density = 3.16 / cm ³ )
* 3: Fine aggregate (river sand, density = 2.58 g / cm ³ )
* 4: Coarse aggregate (crushed stone, density = 2.68 g / cm ³ )

Test Category 3 (Preparation of early strength concrete)
Example 1
A predetermined amount of the admixture composition (M-1) of Reference Example 1 shown in Table 1 was added to the concrete slurry {(CS-1), slump 21.7 cm} prepared in Test Example 1, and a concrete mixer was added. Was mixed for 15 seconds to prepare a high strength concrete. The slump value of the slurry immediately after discharging from the mixer was 20.6 cm. In addition, the slump value of the concrete after 30 minutes from immediately after discharge was 0 cm (a state in which the side pressure was zero with no flow at all). In addition, concrete filled with a high-strength concrete slurry immediately after being discharged from the mixer in a steel cylindrical form with a diameter x height of 10 cm x 20 cm hardens after 3 hours have passed since the admixture composition was added. The mold was able to be removed. A hardened concrete body (HC-1) was obtained as a specimen of Example 1.

Examples 2-4
The high strength concrete of Examples 2-4 was prepared by the same method as Example 1. In the same manner as described above, the filled concrete was cured 3 hours after the admixture composition was added, and the formwork could be removed. Hardened concrete bodies (HC-2) to (HC-4) were obtained as specimens of Examples 2 to 4.

Example 5
A predetermined amount of the admixture composition (M-1) of Reference Example 1 shown in Table 1 was added to the concrete slurry {(CS-2) prepared in Test Example 2 and the slump value was 21.8 cm}. A high strength concrete was prepared by mixing for 15 seconds with a concrete mixer. The slump value of the slurry immediately after discharging from the mixer was 19.7 cm. Moreover, the slump value of the concrete after 30 minutes passed immediately after discharge was 0 cm. Concrete filled with concrete slurry immediately after being discharged from the mixer in a steel cylindrical form having a diameter x height of 10 cm x 20 cm is hardened after 3 hours have passed since the admixture composition was added, and the form is I was able to remove it. A hardened concrete body (HC-5) was obtained as a specimen of Example 5.

Example 6
The fast-strength concrete of Example 6 was prepared by the same method as Example 5. Similarly to the above, the filled concrete was hardened after 3 hours from immediately after the admixture composition was added, and the formwork could be removed. A hardened concrete body (HC-6) was obtained as a specimen of Example 6. The results of Examples 1 to 6 are summarized in Tables 3 and 4.

Comparative Examples 1-4
Using the admixture compositions (MR-1) to (MR-4) of Comparative Reference Examples shown in Table 3, concretes of Comparative Examples 1 to 4 were prepared in the same manner as in Examples. Concrete filled with concrete slurry immediately after being discharged from the mixer in a steel cylindrical form with a diameter x height of 10 cm x 20 cm is fluid even after 3 hours have passed since the admixture composition of the comparative reference example was added. It remained and could not keep its shape, and none of the molds could be removed.

Comparative Examples 5 and 6
Concretes of Comparative Examples 5 and 6 in the case where the admixture composition was not added were prepared in the same manner as in Examples. The concrete filled with the concrete slurry kneaded without adding the admixture composition is fluid and can not keep its shape after 3 hours, and both can be removed. There wasn't. The results of the above Comparative Examples 1 to 6 are summarized in Tables 3 and 4. In addition, it measured using the test body (HR-1)-(HR-6) which removed the formwork as 20-hour progress as a test body of Comparative Examples 1-6.

Test Category 4 (Concrete property evaluation)
-Evaluation of physical properties of concrete Slump, air content and setting / hardening properties of each concrete prepared in Test Category 3 were determined as follows. Moreover, the compressive strength and the drying shrinkage rate were calculated | required as follows about the concrete hardened | cured material (HC-1)-(HC-6) and (HR-1)-(HR-6) of each example.
-Slump (cm): Measured according to JIS-A1101.
Air amount (volume%): Measured according to JIS-A1128.
・ Possibility of early formwork removal: When concrete filled in a steel cylindrical form with a diameter x height of 10 cm x 20 cm is filled for 3 hours (stored at 20 ° C x 60% RH), the concrete hardens. The case where it was evaluated was evaluated as ◯, and the case where it was not cured was evaluated as ×.
-Compressive strength (N / mm < ² >): Based on JIS-A1108, the compressive strength of material age 3 hours, material age 1 day, and material age 28 days was measured. The concrete curing of the cylindrical specimen for measurement after removing the formwork was cured in water at 20 ° C.
-Drying shrinkage: According to JIS-A1132, a specimen was prepared by filling a steel rectangular mold with dimensions 10 cm x 10 cm x 40 cm, and dried at the age of 28 days by the comparator method according to JIS-A1129. Shrinkage was measured.

In Table 3,
* 1: Type of admixture composition shown in Table 1 of Test Category 1 * 2: Additive parts by mass of admixture composition per 100 parts by mass of cement in concrete * 3: Admixture of test examples in Test Category 2 Kind of concrete slurry before adding composition * 4: Whether or not the mold was removed when 3 hours passed after filling the concrete slurry into the cylindrical mold was evaluated. Evaluation was made as ○ for those that were cured and removable from the mold, and × for those that were not cured.

In Table 4,
* 1: Type of hardened concrete obtained by the method shown in Table 3 * 2: Not measured because it was not hardened.

  As is apparent from the results in Table 3, the method of the present invention can remove the mold at an early stage when filling and placing concrete with good fluidity, so that the mold having a sufficient framework considering the side pressure load. This has the effect of reducing the labor and cost of assembling the frame. At the same time, the method of the present invention has the function of accelerating the setting and hardening of concrete as is apparent from the results in Table 4, so that the work period in concrete work can be shortened, and a high-quality hardened body with low shrinkage can be obtained. There is an effect that it is obtained.

Claims (11)

Cement, fine aggregate, coarse aggregate, water and concrete containing a base dispersant containing a cement dispersant are kneaded and then mixed with 0.1 to 0.1 parts by mass of the following admixture composition per 100 parts by mass of cement. A method for preparing early-strength concrete, characterized by being added and contained at a ratio of 15 parts by mass.
Admixture composition: composed of the following A component, the following B component, the following C component, the following D component, and the following E component, and the A component is 0.05 to 3% by mass, and the B component is 15 to 48% by mass, C component 0.4-30% by mass, D component 0.05-3% by mass, and E component 16-84.5% by mass (total 100% by mass) Agent composition.
Component A: One or two or more selected from polyacrylamide having a molecular weight of 10 × 10 ^{4 to} 1500 × 10 ^{4 and} an alkali metal salt of polyacrylic acid having a molecular weight of 5 × 10 ^{4 to} 500 × 10 ⁴ .
B component: alkali metal silicate C component: polyalkylene glycol monoalkyl ether represented by the following chemical formula 1

(In chemical formula 1,
R ¹ : Alkyl group having 3 to 5 carbon atoms A ¹ : Excluding all hydroxyl groups from polyalkylene glycol having a polyoxyalkylene group composed of a total of 2 to 10 oxyethylene units and oxypropylene units in the molecule Residue)
D component: Sodium phosphate salt E component: Water   The method for preparing early-strength concrete according to claim 1, wherein the slump value of the concrete slurry containing the base is 15 to 25 cm. The method for preparing early-strength concrete according to claim 1 or 2, wherein the component A is polyacrylamide having a molecular weight of 100 x 10 ^{4 to} 1000 x 10 ⁴ . The method for preparing early-strength concrete according to claim 1 or 2, wherein the component A is a polyacrylic acid sodium salt having a molecular weight of 10 x 10 ⁴ to 200 x 10 ⁴ . The early strength according to any one of claims 1 to 4, wherein the B component is sodium silicate, and the molar ratio of SiO ₂ / Na ₂ O represented by the molecular formula is 1.8 to 3.5. Concrete preparation method. C component is in Chemical Formula 1, R ¹ is an alkyl group having 4 carbon atoms, and A ¹ has a polyoxyalkylene group composed of a total of 3 to 8 oxyethylene units and oxypropylene units in the molecule. The method for preparing early-strength concrete according to any one of claims 1 to 5, which is a residue obtained by removing all hydroxyl groups from polyalkylene glycol.   The method for preparing early-strength concrete according to any one of claims 1 to 6, wherein the component D is monosodium phosphate.   The admixture composition contains 0.1 to 1.5% by mass of component A, 20 to 45% by mass of component B, 1 to 20% by mass of component C, 0.1 to 2% by mass of component D, and E component. The method for preparing early-strength concrete according to any one of claims 1 to 7, wherein the composition is an admixture composition containing 31.5 to 79.8 mass% (total of 100 mass%).   9. The early-strength concrete according to claim 1, wherein the cement dispersant is a cement dispersant mainly composed of a polycarboxylic acid-based water-soluble vinyl copolymer having a polyethylene glycol chain as a side chain. Preparation method.   The method for preparing early-strength concrete according to any one of claims 1 to 9, wherein the admixture composition is added and contained at a ratio of 0.3 to 10 parts by mass per 100 parts by mass of cement. A hardened concrete body having a compressive strength of one day of age obtained by the preparation method according to claim 1 of 20 N / mm ² or more.