JP2021110163A - How to build a concrete building - Google Patents

Abstract

[Problem] To achieve both labor saving by omitting the compaction process and maintaining the quality of a concrete structure at a high level. [Solution] A method for constructing a concrete structure, comprising: a concrete transport and delivery process st1 in which ordinary concrete 1 is transported from a concrete production site S1 to a concrete pouring site S2 by an agitator truck 4; a compaction-free concrete production process st2 in which a water-soluble bag 2 containing a dispersant 21 and a thickener 22 is put into a mixing drum 41 of the agitator truck 4 at the concrete pouring site S2 and mixed to turn the ordinary concrete into compaction-free concrete with a slump flow of 500 mm or more; and a casting process st3 in which the compaction-free concrete is poured into a formwork, and after the casting process st3, a curing process st4 in which the compaction-free concrete is hardened without compaction is performed. [Selected drawing] Figure 1

Description

The present invention relates to a method for constructing a concrete building. More specifically, the present invention relates to a method for constructing a concrete structure that does not require a step of performing compaction work after casting.

In recent years, the labor shortage at construction sites has become more serious. As one of the options for labor saving to overcome this, the adoption of "concrete that does not require compaction" is being considered.

The above-mentioned "concrete that does not require compaction" means that concrete can be self-filled without compaction work after being placed in a formwork by providing a high level of fluidity and material separation resistance. It refers to a possible concrete material (see Patent Documents 1 and 2).

Here, in the case of using "other concrete" other than "concrete that does not require compaction" in the construction of a concrete building, for example, there is a shortage of the fluidity of the concrete to be cast within a certain range. Even so, the problems associated with it can be eliminated in the compaction process performed after placing.

However, when "compacting-free concrete" is selected, if a problem occurs due to variations in the quality of the concrete to be cast, it cannot be solved after the casting. For this reason, even a slight variation in quality, which is within a range that does not usually cause a problem in "other concrete" such as ordinary concrete, is a fatal defect in the building in "concrete that does not require compaction". May cause.

Therefore, in order to achieve both labor saving by using "concrete that does not require compaction" and maintenance of quality of concrete buildings, it is better than using other general concrete other than "concrete that does not require compaction". , It was necessary to control the quality of concrete for casting more strictly.

Japanese Unexamined Patent Publication No. 3-237049 Japanese Unexamined Patent Publication No. 10-146822

An object of the present invention is to achieve both labor saving by omitting a compaction step after concrete placing and maintenance of quality of a concrete building at a high level.

The present inventor carries general-purpose "ordinary concrete" into a construction site by an agitator truck, and just before placing the concrete, the necessary admixture is further added into the agitator truck and kneaded at the construction site. , The present invention has been completed by finding that the above-mentioned problems can be solved by a method of producing "concrete that does not require compaction" immediately before placing. Specifically, the present invention provides the following methods and the like.

(1) From the concrete manufacturing site to the concrete placing site with an agitator car, ordinary concrete containing water, cement, fine aggregate, and coarse aggregate is mixed so that the slump value is 5.5 cm or more and 24.0 cm or less. By putting a water-soluble bag containing a dispersant and a thickener into the mixing drum of the agitator car and kneading it in the concrete transport-carrying process and the concrete placing site. The ordinary concrete is made into concrete that does not require compaction and has a slump flow of 500 mm or more. A method for constructing a concrete building, in which a curing process is performed to harden the non-compacting concrete without compacting after performing the setting process.

(2) The dispersant is a lignin-based dispersant (also polycarboxylic acid-based or oxycarboxylic acid-based), and the thickener is an acrylic-based thickener, according to (1). How to build a concrete building.

According to the present invention, it is possible to achieve both labor saving by omitting the compaction step after concrete placing and maintenance of the quality of the concrete structure at a high level.

It is a work flow diagram which provides the explanation of the whole structure of the construction method of the concrete building of this invention. It is a schematic diagram provided for the explanation of the embodiment of the compaction-free concrete manufacturing process which is one process which constitutes the construction method of the concrete building of this invention.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

<Construction method of concrete building>
FIG. 1 is a work flow diagram for explaining the overall configuration of the “concrete building construction method” of the present invention. The "concrete building construction method" of the present invention is a total process for constructing a concrete building including a concrete transport-in process st1, a compaction-free concrete manufacturing process st2, a placing process st3, and a curing process st4. Is.

[Concrete transportation and delivery process]
In the concrete transport / carry-in step st1, in the “construction method of a concrete building” of the present invention, the ordinary concrete 1 is transported from the concrete manufacturing site S1 such as a ready-mixed concrete factory by, for example, an agitator truck 4 as shown in FIG. This is a process of carrying the concrete into the concrete casting site S2.

Conventionally, in the construction of concrete buildings, when the compaction process is to be omitted, a specific formulation is previously made in a concrete factory or the like in order to achieve both high fluidity that can eliminate the need for compaction and material separation resistance. An expensive premix type "concrete that does not require compaction" was used. On the other hand, in the method for constructing a concrete building of the present invention, first, in the concrete transport / carry-in process st1, relatively inexpensive ordinary concrete 1 is transported from the concrete manufacturing site S1 by the agitator truck 4 to the casting site. Will be delivered to.

Here, in the present specification, the above-mentioned ordinary concrete 1 specifically refers to water, cement, fine aggregate, coarse aggregate, and so as to have a slump value of 5.5 cm or more and 24.0 cm or less. It is a ready-mixed concrete that contains other admixtures as needed. Such ready-mixed concrete is easy to obtain from the market because of its high versatility and large distribution volume, and its price is lower than that of the above-mentioned premix type "compact-free concrete". The "slump value" in the present specification means the slump value (cm) according to JIS A 1101.

^{Ordinary concrete 1 has a cement amount of 300 kg / m 3} or more and 500 kg / m ³ or less per unit volume in order to maintain material separation resistance commensurate with high fluidity (slump flow) after making concrete that does not require compaction. It is preferably 320 kg / m ³ or more, and more ^{preferably 500 kg / m 3} or less. The water-cement ratio of the ordinary concrete 1 is preferably 35% or more and 60% or less, and more preferably 35% or more and 55% or less.

Incidentally, ordinary concrete 1, (JIS A 5308 2019) by nominal intensity is preferably 18N / mm ² or more 45N / mm ² or less. As long as the material separation resistance commensurate with the high fluidity (slump flow) after compaction-free concrete can be maintained and the above nominal strength can be ensured, the cement of ordinary concrete 1 can be maintained. The amount and water / cement ratio do not necessarily have to be within each of the above ranges.

Further, it is preferable to use ordinary Portland cement, which is inexpensive and easily available, as the binder of ordinary concrete 1, but a part of the cement material is a cement material other than the above, specifically, blast furnace cement, silica cement, fly ash. It can also be replaced with cement or the like.

Further, as the aggregate of the ordinary concrete 1, a conventionally known general aggregate can be appropriately used. The ratio of the fine aggregate in the aggregate is preferably about 40% or more and 55% or less in terms of volume ratio. As for the coarse aggregate, the amount of coarse aggregate per unit volume in ^{ready-mixed concrete is preferably 250 L / m 3} or more and 350 L / m ³ or less.

[Concrete manufacturing process that does not require compaction]
In the compaction-free concrete manufacturing process st2, the compaction-free concrete 3 is manufactured in the concrete placing site S2 by using the above-mentioned ordinary concrete 1 carried into the concrete placing site S2 in the concrete carrying-in step st1. It is a process.

The above-mentioned compaction-free concrete 3 produced in the compaction-free concrete manufacturing process st2 has a slump flow of 500 mm by additionally adding an appropriate amount of a dispersant and a thickener to the above-mentioned ordinary concrete 1. As mentioned above, it is preferable to refer to ready-mixed concrete having a size of 550 mm or more and 650 mm or less. Here, the slump flow means a slump flow value (mm) according to JIS A 1150.

Of the above-mentioned admixtures added to ordinary concrete 1 in the compaction-free concrete manufacturing process st2, the dispersant is not particularly limited, and known oxycarboxylic acid, polycarboxylic acid, lignin-based dispersant and the like are known. Various dispersants can be used. However, among them, a dispersant containing a lignin derivative, which is a reaction product of a lignin sulfonic acid-based compound and a water-soluble single-volume resistance having a polyalkylene oxide chain, which is particularly advantageous in maintaining the properties of fresh concrete. A lignin-based powdery dispersant of "" can be particularly preferably used.

Further, the amount of these dispersants added is preferably such that the content in the compaction-free concrete (ready-mixed concrete) is 0.01% or more and 2.0% or less in terms of the volume ratio with respect to the cement material, and is 0. More preferably, it is 0.05% or more and about 0.5% or less.

Thickener is a general term for additives that are mixed in to increase the viscosity of the liquid, but among the admixtures that are usually added to concrete 1, this thickener is also not particularly limited, and methyl cellulose (MC). , HEC (hydroxyethyl cellulose), or microbially fermented biopolymers such as welan gum, or acrylic thickeners such as polyacrylic acid, and various known thickeners can be used. However, among them, an acrylic thickener having a molecular weight of 5 million Mw or more can be particularly preferably used.

Further, in the compaction-free concrete manufacturing process st2, in addition to the above-mentioned dispersant 21 and thickener 22, other chemical admixtures such as a dispersant for powders containing polycarboxylic acid, oxycarboxylic acid and the like are required. Alternatively, it may be encapsulated in a water-soluble bag and added together.

In the production of the non-compacting concrete 3 in the compaction-free concrete manufacturing process st2, as shown in FIG. 2, the dispersant 21 and the thickener 22 are produced in the mixing drum 41 of the agitator truck 4 in which the ordinary concrete 1 is housed. This is carried out by a method in which the water-soluble bag body 2 containing the above is put in and kneaded.

By adopting the compaction-free concrete manufacturing process st2 by using the water-soluble bag body 2, the dispersant 21 and the thickener 22 are water-soluble in the mixing drum 41 of the agitator truck 4 in which ordinary concrete is housed. The entire sex bag body 2 can be put in.

In addition, a sufficient number of water-soluble bags 2 containing a specified amount of the dispersant 21 and the thickener 22 are prepared at the casting site, and the required number of water-soluble bags 2 are appropriately prepared. By putting it into the mixing drum 41, the compounding ratio of the material of the compaction-free concrete 3, which requires strict control of the compounding ratio of the dispersant 21 and the thickener 22, can be easily and accurately adjusted even at the casting site. It can be adjusted to the optimum ratio.

As the water-soluble bag body 2 used in the compaction-free concrete manufacturing process st2, one formed of water-dispersible paper can be used. Here, the water-dispersible paper in the present specification means a paper having a floc-like water dispersion time of 30 seconds or less and a fibrous water-dispersion time of 60 seconds or less. The floc-like water dispersion time is a time in which 300 ml of deionized water is placed in a 300 ml beaker, a 3 cm square test piece is thrown in while stirring at 650 rpm with a stirrer, and the test piece is cut into two or more pieces. The fibrous water dispersion time is the time during which the test piece is completely loosened into individual fibers.

Examples of the water-dispersible paper include water-dispersed paper containing 15% by weight or more and 95% by weight or less of purified pulp, water-dispersible paper impregnated or coated with a water-soluble polymer, or water-dispersible paper. A water-removable coated paper base paper containing fibers and a carboxyalkyl cellulose salt which is a water-soluble fiber can be used.

The surface pH of the water-dispersible paper is preferably 6.0 or more and 11.0 or less, and more preferably 6.2 or more and 10.0 or less. By adjusting the paper surface pH within this range, it is possible to prevent the acid and strong alkali in the paper from adversely affecting the inclusions. The method for adjusting the pH of the paper surface is not particularly limited, and for example, water-dispersible paper is made by using a material in the neutral region as a main component. Alternatively, the alkaline or acidic water-dispersible paper can be produced by neutralizing it with an acidic substance or an alkaline substance.

Table 1 below is an example of the compounding ratio of the non-compacting concrete in the compaction-free concrete manufacturing process st2. In this production example, ordinary Portland cement is used as the cement material for ordinary concrete to be carried into the casting site in the concrete transportation and carrying-in process st1. The dispersant 21 additionally added in the compaction-free concrete manufacturing process st2 is a lignin-based dispersant (lignin derivative (manufactured by Nippon Paper Industries)), and the thickener 22 is an acrylic thickener. (A-20P-X (manufactured by Toa Synthetic)) is used in an amount added so that the volume ratio (%) with respect to the cement material becomes the compounding ratio shown in Table 1.

As an example of manufacturing concrete that does not require compaction in the compaction-free concrete manufacturing process st2, for example, as shown in Table 1 above, an appropriate amount is added to ordinary concrete 1 in which each material is blended so that the slump value is 18 cm. An example can be mentioned in which compaction-free concrete 3 having a slump flow of 575 mm (slump value of 25 cm) can be obtained by additionally adding a dispersant and a thickener.

[Placement process]
In the casting process st3, in the compaction-free concrete manufacturing process st2, which is the previous process, the compaction-free concrete 3 manufactured immediately before casting is promptly placed in the formwork installed in the construction site. It is a process to do.

In the construction of a normal concrete building, following the placing step st3, a step of compacting the semi-hardened ready-mixed concrete placed in the formwork using a vibrator or the like is performed. However, in the method for constructing a concrete building of the present invention, this step is not required.
[Curing process]
In the curing step st4, compaction after casting is performed by keeping the compaction-free concrete 3 placed in the casting step st3, which is the previous step, under conditions under which the required hydration reaction can proceed for a certain period of time. It is a process of hardening concrete without going through.

By performing each of the above steps in the above manner, compaction-free concrete in which the quality of ready-mixed concrete necessary for maintaining the quality of the concrete structure is surely maintained is more economical than the equivalent concrete of the premix type. Can be obtained. Further, since the compaction step after placing can be omitted, it is possible to maintain the quality of the concrete building and the economic efficiency of the construction work at a high level.

1 Ordinary concrete 2 Water-soluble bag body 21 Dispersant 22 Thickener 3 No compaction required Concrete 4 Agitator truck 41 Mixing drum S1 Concrete manufacturing site S2 Concrete casting site st1 Concrete transportation and delivery process st2 No compaction required Concrete manufacturing process st3 Installation process st4 Curing process

Claims (2)

Ordinary concrete containing water, cement, fine aggregate, and coarse aggregate is transported from the concrete manufacturing site to the concrete casting site by an agitator truck so that the slump value is 5.5 cm or more and 24.0 cm or less. Concrete transport and carry-in process and
At the concrete casting site, a water-soluble bag containing a dispersant and a thickener is put into a mixing drum of the agitator truck and kneaded to knead the ordinary concrete with a slump flow of 500 mm. The above-mentioned compaction-free concrete manufacturing process and compaction-free concrete manufacturing process
The casting process of placing the compaction-free concrete into the formwork is performed.
After performing the casting step, a curing step of hardening the compaction-free concrete is performed without compaction.
How to build a concrete building. The dispersant is a lignin-based dispersant.
The thickener is an acrylic thickener.
The method for constructing a concrete building according to claim 1.

Images