JP6924646B2 - Cement composition for immediate demolding method and manufacturing method of precast concrete molded product using it - Google Patents

Description

The present invention relates to a cement composition for an immediate demolding method and a method for producing a precast concrete molded product using the same.

When constructing a concrete structure, concrete is placed at the construction site (on-site), or concrete products (precast concrete molded products) that have been made into parts are produced in advance at the factory, and this precast There is a case where a concrete molded product is transported from a factory to a construction site and carried in, and a concrete structure is constructed using this (see Patent Document 1).

On the other hand, there are roughly three types of methods for manufacturing a hardened concrete body: a pouring method, a centrifugal compaction method, and an immediate demolding method. The pouring method is a method of pouring relatively soft concrete into a mold and compacting it with a vibrator or pressurizer, and the centrifugal force compaction method is to apply centrifugal force to squeeze out the water inside the concrete. This is a method for producing concrete products with a lower water-cement ratio. Then, in the immediate demolding method, in general, hard-kneaded ready-mixed concrete having a water-cement ratio of about 30 to 40% is put into the formwork, and the concrete is made to stand on its own while applying strong vibration and pressure, and then placed. After that, it is a method of promptly removing the mold. This immediate demolding method is an extremely excellent method in terms of economy because a large amount of concrete molded products can be continuously molded using one formwork (see Patent Document 2).

However, in the production of concrete by the immediate demolding method, there is a restriction that it is necessary to use hard-kneaded ready-mixed concrete (cement composition) having a small water / cement ratio in material selection. Since such hard-kneaded ready-mixed concrete retains many voids inside, sufficient compaction is indispensable at the time of construction, and for that reason, strong vibration and pressurization can be applied. There was a restriction on manufacturing equipment that equipment was required. Due to these restrictions, concrete production by the conventional immediate demolding method is a process of transporting and carrying in to the construction site after being produced as a precast concrete molded product in a factory that can meet the above conditions in terms of manufacturing equipment. After that, it was a natural premise that it would be used.

On the other hand, it is known that by adding a water-retaining component such as a clay mineral, even a cement composition having a water / cement ratio increased to some extent can be immediately demolded (Patent Document 3). ). However, there is a technical trade-off between ensuring the independence of immediate demolding by increasing the viscosity due to the addition of clay minerals and preventing the surface of precast concrete molded products from becoming uneven and excessive voids during immediate demolding. In order to sufficiently prevent the above-mentioned non-landing and voids when the amount of clay mineral added is increased to the extent that it has an appropriate shape retention during immediate demolding. , Heavy equipment such as a large pressurizer for compacting the cast cement composition is indispensable. On-site, it is extremely difficult to introduce such equipment, and it is common that only the use of equipment that locally vibrates from the outside is allowed.

It is clear that if it becomes possible to manufacture precast concrete molded products by the on-site immediate demolding method in the construction of concrete buildings, it will contribute to the improvement of the economic efficiency of construction work. For the above reasons, the production of precast concrete molded products by the on-site immediate demolding method has not yet been implemented at any of the construction sites.

Japanese Unexamined Patent Publication No. 2015-206216 Japanese Unexamined Patent Publication No. 2002-53361 Japanese Unexamined Patent Publication No. 63-60139

The present invention provides a means capable of producing high-quality precast concrete molded products on-site by immediate demolding, thereby contributing to the improvement of the economic efficiency of construction work in the construction of concrete structures. With the goal.

The present inventors on-site by optimizing the water / cement ratio, the fine aggregate / mortar ratio, and the amount of clay mineral added to a specific range in the cement composition constituting the cement material. It has been found that a high-quality precast concrete molded product can be produced only by compaction with a simple vibrating device, which is easy to carry out, and the present invention has been completed. Specifically, the present invention provides the following.

(1) A cement composition for an immediate demolding method, which comprises water (W), cement material (C), fine aggregate (S), coarse aggregate (G), and clay mineral (CM). And, the water-cement ratio (W / C) is 30% or more and 80% or less, and the mortar (M) composed of water (W), cement material (C) and fine aggregate (S). ), The volume ratio (S / M) of the fine aggregate (S) is 30% by volume or more and 60% by volume or less, and the content of the clay mineral (CM) is 3% by mass with respect to water (W). A cement composition having a content of 10% by mass or less.

By using the invention of (1), a high-quality precast concrete molded product can be produced on-site and by immediate demolding. That is, according to the invention of (1), it is possible to produce a building material made of a precast concrete molded product on-site at a lower cost than before and with a significantly higher productivity than before. ..

(2) the content of the coarse aggregate is less than or equal to 400 L / ^{m 3} or more 550L / ^{m 3,} the cement composition according to (1).

In the invention of (2), the content of the coarse aggregate in the cement composition of (1) was optimized to a unique predetermined range higher than the content in a general cement composition. Thereby, the unevenness of the surface of the concrete molded product produced by using the cement composition of (1) can be suppressed with higher accuracy.

(3) A method for manufacturing a precast concrete molded product, which is a casting step of placing fresh cement in a formwork, a compaction step of compacting after placing the ready-mixed cement, and an immediate demolding method. A method for producing a precast concrete molded product, which comprises a demolding step and a curing step, wherein the ready-made cement is a kneaded product of the cement composition according to (1) or (2).

According to the invention of (3), while enjoying each of the above-mentioned effects by using the cement composition according to (1) or (2), a precast concrete molded product of excellent quality is produced by immediate demolding. Can be done.

(4) A manufacturing method for manufacturing the precast concrete molded product on-site, wherein the precast concrete molded product is used as a building material in all of the casting step, the compaction step, the demolding step, and the curing step. The method for manufacturing a precast concrete molded product according to (3), which is carried out at the construction site of a concrete building to be constructed by using the above.

According to the invention of (4), all the steps constituting the manufacturing method of (3) are performed on-site. According to this, it is possible to produce an excellent quality precast concrete molded product on-site by immediate demolding while enjoying each of the above effects by using the cement composition according to (1) or (2). can. This can significantly contribute to the reduction of the construction cost of the concrete building.

(5) In the compaction step, the entire surface of the cast ready-mixed cement is not pressed, but is cast only by a process of applying local vibration from the outside of the mold or a repetition of the process. The method for producing a precast concrete molded product according to claim (4), wherein the ready-mixed cement is compacted.

According to the invention of (5), high-quality precast concrete molded products can be manufactured on-site by a small compaction machine or the like that can be manually constructed even at a construction site where it is difficult to introduce a large press machine or the like. be able to. According to this, that is, the above effect of the implementation of the method for producing the precast concrete molded product (4) can be widely enjoyed at various construction sites under a wider range of conditions.

(6) The method for producing a precast concrete molded product according to (4) or (5), wherein the curing step is outdoor room temperature curing.

According to the invention of (6), a high-quality precast concrete molded product can be produced on-site in a short-term natural curing at room temperature outdoors at a construction site. According to this, that is, the above-mentioned effect of implementing the method for producing a precast concrete molded product according to (4) or (5) can be widely enjoyed at various construction sites under a wider range of conditions.

(7) A method for constructing a concrete structure in which a building is constructed using a building material made of a precast concrete molded product manufactured on-site by the manufacturing method according to any one of (3) to (6).

According to the invention of (7), the above-mentioned effect of the manufacturing method according to any one of (3) to (6) is enjoyed, and it contributes to the improvement of the economic efficiency of the construction work at the construction site of the concrete building. be able to.

According to the present invention, a means capable of producing a high-quality precast panel on-site by immediate demolding, that is, a cement composition for an immediate demolding method and a method for producing a precast concrete molded product using the same. Provided, which can contribute to the improvement of the economic efficiency of construction work in the construction of concrete structures.

It is a drawing which shows typically the embodiment of the construction method of the concrete building which constructs a building using the building material which consists of the precast concrete molded article manufactured on-site by the manufacturing method of this invention. It is a drawing which shows typically the embodiment of each process of the manufacturing method of the precast concrete molded article of this invention which can be formed by immediate demolding on-site.

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

<Construction method of concrete building>
The method for constructing a concrete building of the present invention (hereinafter referred to as "method for constructing a concrete structure") is a construction method for constructing a concrete structure using a building material made of a precast concrete molded product manufactured on-site. .. In this construction method, the cement composition for the immediate demolding method of the present invention (hereinafter referred to as "cement composition for the immediate demolding method") is used as the material of the precast concrete molded product, and the precast concrete is used. The molded product can be manufactured by the method for manufacturing a precast concrete molded product of the present invention (hereinafter, referred to as "method for manufacturing a precast concrete molded product"). Details of the cement composition and precast concrete molded product for the immediate demolding method and the manufacturing method thereof will be described later.

FIG. 1 schematically shows an example of an embodiment of the construction method of the present invention. "Manufacturing on-site" as used herein means, as illustrated in FIG. 1, a "single work area for performing construction work to construct a single or series of concrete structures 10. It means "manufacturing within a single or series of construction sites 100".

In the "construction method of a concrete building", a ready-made cement 1 made by kneading a cement composition for an immediate demolding method is placed in a formwork 2 installed in a construction site 100, and this is immediately applied. Molding is performed by the manufacturing method of precast concrete molded products by the demolding method. Then, the precast molded product such as the precast cement panel 1B thus obtained is used as the building material 1C for constructing the concrete building 10. The building material 1C can be used in various aspects as, for example, a residual formwork or various other building materials.

The above-mentioned residual formwork is a formwork for placing concrete, and is a formwork that constitutes the surface portion of the building as it is without being removed even after the placed concrete is solidified. Say that. For example, the mold disclosed in FIGS. 1 to 8 of JP-A-6-55522 can be mentioned as a specific example of the form of the residual mold. (Note that this formwork is also referred to as a waste formwork as another general name.)

Conventionally, a precast concrete molded product such as building material 1C is manufactured at a panel factory located in an area away from the construction site 100 and then transported to the construction site 100 by a truck or the like for use regardless of the usage mode. Was being done. On the other hand, the "construction method for concrete structures" of the present invention introduces "cement composition for immediate demolding method" and "manufacturing method for precast concrete molded products" to mold high-quality precast concrete on-site. It has made it possible to manufacture products by the immediate demolding method. According to the implementation of this construction method, the cost of transporting the precast concrete molded product to the construction site by the conventional factory production is not required, and the required amount of precast concrete molded product is removed at the required timing by immediate on-site demolding. The total productivity of the construction work of the concrete structure 10 is dramatically improved.

<Precast concrete molded product>
The precast concrete molded product according to the present invention is a building material developed on the premise of manufacturing by an on-site immediate demolding method. Here, a panel-shaped building material will be described as an example of the embodiment, but the building material is not limited to the panel-shaped building material, and is molded into various forms and shapes using the cement composition for the immediate demolding method of the present invention. be able to.

<Manufacturing method of precast concrete molded products>
In the method for producing a precast concrete molded product of the present invention, a ready-mixed cement 1 obtained by kneading a cement composition for an immediate demolding method is cured in a formwork 2 to immediately produce a precast concrete molded product used as a building material. This is a manufacturing method in which molding is performed on-site by a demolding method. This manufacturing method is a manufacturing method including a casting process, a compaction process, a mold removal process, and a curing process, but each of these processes is an excessive additional burden in a general construction site. It is a process different from the conventional method in that it can be carried out without any trouble. Hereinafter, the details of each step will be described with reference to FIGS. 1 and 2 as appropriate.

[Placement process]
In this step, as shown in FIGS. 1 and 2, the ready-made cement 1 obtained by kneading the cement composition is cast into the formwork 2 for the precast concrete molded product installed in the construction site 100. Is. As the cement composition, the cement composition for the immediate demolding method of the present invention is used.

[Compacting process]
As shown in FIG. 2, this step is a step of compacting the semi-cured raw cement 1A placed in the mold 2 by using a vibrator 3 or the like.

Normally, when the immediate demolding method is adopted in the production of precast concrete molded products by general factory production, the entire surface of semi-hardened ready-mixed cement cast by a large press such as a hydraulic system or a vacuum pump. The stability of molding is ensured by loading evenly. On the other hand, in the production method of the present invention, the surface of the semi-hardened raw cement 1 cast by using the raw cement 1 as a kneaded product of the cement composition for the immediate demolding method according to the present invention. The precast cement panel is molded by applying local vibration from the upper surface or side surface of the semi-hardened raw cement 1A that has been cast, or by compacting only by repeating the process, without performing the process of pressurizing the whole. Sufficient stability can be guaranteed.

Then, in this compaction process, for example, even under conditions where vibration from the upper surface is difficult to be applied, as shown in FIG. 2, a small rammer, a mold vibrator, or the like is used to pass through the side wall 22 of the mold 2. It can also be done only by applying vibration.

[Demolding process]
After compaction, as shown in FIG. 2, when the mold 2 can be removed from the mold, the side wall 22 of the mold 2 is promptly detached from the bottom surface 21 to remove the mold. The time from the completion of compaction to the removal of the mold is expected to be within 3 minutes. The formwork 2 may be demolded after the curing step described later, but by performing it before the curing step, the demolded formwork 2 can be immediately used for the production of another precast concrete molded product. Therefore, it is preferable to perform it before the curing process from the viewpoint of improving the production efficiency.

In the process up to this demolding step, it is not necessary to completely harden the fresh cement 1. For example, it may be cured to the extent that it can stand on its own while maintaining its shape within the required accuracy range. The ready-made cement made of the cement composition of the present invention has been enhanced to a necessary and sufficient accuracy in shape retention when immediately demolded on-site. The necessary and sufficient accuracy of shape retention at the time of immediate demolding may be within each range required for each site or application, but in general, it is immediately that the dimensions of the product are within ± 2 mm. This is a preferable range required as a quality control standard for cement molded products by demolding. According to the manufacturing method of the present invention, it is possible to sufficiently clear such a standard.

[Curing process]
After the demolding process, normal temperature curing is performed in an outdoor environment or a storage place that can be installed at a low cost in a construction site, such as a simple tent.

Normally, when the immediate demolding method is adopted in the production of precast concrete molded products by general factory production, the above-mentioned curing accompanied by carbonation treatment is performed on the semi-hardened cement by a large-scale curing device. By doing so, the strength of the precast concrete molded product after molding is guaranteed. On the other hand, in the production method of the present invention, a semi-hardened precast concrete molded product (demolded) is obtained by using the ready-made cement 1 as a kneaded product of the cement composition for the immediate demolding method according to the present invention. With respect to the precast cement panel 1B), the strength of the precast concrete molded product (precast cement panel) can be sufficiently ensured only by natural curing at room temperature for a short period of time outdoors.

<Cement composition for immediate demolding method>
The cement composition (hereinafter, also simply referred to as “cement composition”) used for producing the precast concrete molded product of the present invention includes water (W), a cement material (C), and a cement material (C), similarly to a general raw cement material. It is a composition containing a fine aggregate (S), a coarse aggregate (G), a damping material and the like. Then, in order to enable immediate on-site demolding, the fine aggregate (S) containing an appropriate amount of clay mineral (CM), the water-cement ratio (W / C), and the mortar (M) The ratio is optimized to a specific range different from the conventional product.

[Cement material (C)]
Portland cement can be preferably used as the cement material (C). In addition to ordinary Portland cement, there are various types of Portland cement such as early-strength, ultra-fast-strength, moderate heat, and low heat. In the cement composition, one or more of these various Portland cements can be blended. Among these, it is preferable to use one or two types of ordinary Portland cement and early-strength Portland cement.

Further, a part of the above-mentioned Portland cement used as the cement material (C) can be replaced with blast furnace slag. As a result, CO ₂ emissions at the cement manufacturing stage can be reduced.

The water-cement ratio (W / C) may be 30% or more and 80% or less. When the content of the coarse aggregate (G) is 400 L / m ³ or more, the water-cement ratio (W / C) is more preferably 40% or more and 55% or less.

[Fine aggregate (S)]
The fine aggregate is an aggregate defined by JIS A 5308, JIS A 5005, JIS A 5002 and JIS A 5011, and examples of the fine aggregate include crushed sand, sand, river sand, sea sand, lime crushed sand, and recycled sand. Examples include aggregates, lightweight aggregates, heavy aggregates and the like. The blending amount of the fine aggregate in the cement composition is the volume ratio (S / S) of the fine aggregate (S) to the mortar (M) composed of water (W), the cement material (C) and the fine aggregate (S). In M), it may be 30% by volume or more and 60% by volume or less. Further, it is more preferably 45% by volume or more and 60% by volume or less. By keeping the blending amount of fine aggregate in the cement composition to 60% by volume or less, in the molding of precast concrete molded products by on-site immediate demolding, which cannot use large vibrators, etc., molds It is possible to sufficiently suppress the generation of voids on the side surface of the precast concrete molded product, which is generated due to the mortar not being uniformly distributed throughout the frame.

[Coarse Aggregate (G)]
The coarse aggregate is an aggregate defined by JIS A 5308, JIS A 5005, JIS A 5002 and JIS A 5011 as described above, and is distinguished from fine aggregate by the size of grains, and is 5 mm. It is classified according to whether or not it passes through the sieve, but in practice, the fine aggregate is the one that passes through all the 10 mm sieves and 85% or more by weight through the 5 mm sieve, and the coarse aggregate is the one that stays at 85% or more by weight in the 5 mm sieve. .. The content of the coarse aggregate (G) in the cement composition may be 300 L / m ³ or more, preferably 400 L / m ³ or more. Further, the upper limit of the content is preferably ^{550 L / m 3} or less from the viewpoint of the actual volume ratio of the aggregate. By specifying the blending amount of the coarse aggregate (G) in the cement composition within the above range, in particular, the occurrence of non-landing on the surface of the precast concrete molded product formed by immediate demolding can be suppressed by a large-scale device, etc. It can be sufficiently suppressed regardless of the situation.

[Clay mineral (CM)]
The clay mineral is not particularly limited as long as it is a clay mineral having high swelling property, high water absorption and water retention, and various clay minerals can be used. However, the clay mineral used in the cement composition of the present invention. As (CM), formalite-based clay minerals are preferably used, and among them, sepiolite can be particularly preferably used. Sepiolite is a clay mineral whose main component is hydrous magnesium silicate, and its chemical structure is Mg ₈ Si ₁₂ O ₃₀ (OH ₂ ) ₄ (OH) ₄ 6 to 8H ₂ O, and it is dry-caking (in water). It has the property of hardening when kneaded and dried), and has excellent water absorption and water retention because it has fine continuous voids inside. In addition, the unit lattice of sepiolite is connected in a chain by repeating the arrangement shifted one by one. While kaolin and bentonite are called layered clays, sepiolite is classified as chain clay. In the cement composition, the content of such clay mineral (CM) may be 3% by mass or more and 10% by mass or less with respect to water (W), and should be 3% by mass or more and 7% by mass or less. Is preferable.

For the content of sepiolite in the precast concrete molded product after curing, 0.5 part of magnesium oxide was added to 4.5 parts of the cured product, and after sufficiently mixing in an agate mortar, powder X-ray diffraction measurement was performed. This can be specified by analyzing the measurement result with, for example, the quantitative software "SIROQUANT" manufactured by Sieronics.

[Other admixtures]
The cement composition may further contain other admixtures. As the other admixture, a known admixture may be used without particular limitation. The amount of the admixture is not particularly limited, and can be appropriately adjusted according to the application of the precast concrete molded product, the required characteristics, and the like. Examples of the admixture include γ-C2S, coal ash, fly ash, limestone fine powder and the like.

Further, the cement composition according to the present invention may contain various admixtures, if necessary, like a general cement composition. Examples of the admixture include a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, an AE agent, and a fluidizing agent. The blending amount of the admixture is preferably 0.001 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the cement component, for example.

Hereinafter, the precast concrete molded product and the method for producing the same according to the present invention will be described in detail with reference to examples. The present invention is not limited to the examples shown below.

In order to confirm the particular effect of the present invention, first, using each of the materials described below, each raw cement used for molding the precast concrete molded product specimens of Examples and Comparative Examples is shown in the table below. It was prepared using each material shown in 1. Table 2 shows the composition of each raw cement.

Table 3 shows "water-cement ratio (W / C) (%)", "water (W), cement material (C), and fine bones" in the ready-made cement used for molding the specimens of each example and comparative example. Volume ratio (S / M) (volume%) of fine aggregate (S) to mortar (M) composed of wood (S) and "content of clay mineral (sepiolite) (CM) with respect to water (W)" Amount (CM / W) (mass%) ”is shown respectively.

[Evaluation example 1: Shape retention during immediate demolding]
(Evaluation method)
For the raw cement of each example and comparative example, the inner glue is driven into a mold of 100 mm × 40 mm × 400 mm, and vibration is applied through the side wall of the mold by a small rammer to compact the cement only for about 5 seconds. Immediately after this, the side mold was demolded (immediate demolding) to obtain a semi-cured normal specimen. For the specimens of each Example and Comparative Example, the inner dimension of the mold and the difference between the length, width, and height of the specimen (hereinafter referred to as "deviation width") were measured. The evaluation criteria for this test are as follows, and the evaluation results are listed in Table 3 as "shape retention" (evaluation criteria).
◯: The length, width, and height deviation width of the specimen are all 2 mm or less.
Δ: The maximum value of the deviation width exceeds 2 mm and is 4 mm or less.
X: The maximum value of the deviation width exceeds 4 mm.

[Evaluation example 2: Void]
(Test method)
The side surfaces of each specimen in the semi-cured state of each Example and Comparative Example obtained by the above-mentioned immediate demolding were visually observed, and the degree of generation of voids was observed. The evaluation criteria in this test are as follows, and the evaluation results are shown in Table 3 as "voids".
(Evaluation criteria)
◯: The air gap on the side surface is less than 2% in area ratio.
Δ: The voids on the side surface are 2% or more and less than 10% in terms of area ratio.
X: The voids on the side surface have an area ratio of 10% or more.

[Evaluation example 3: Surface non-land]
(Test method)
The side surfaces of each specimen in the semi-cured state of each of the Examples and Comparative Examples obtained by the above-mentioned immediate demolding were visually observed, and the degree of surface unevenness was observed. The evaluation criteria in this test are as follows, and the evaluation results are listed in Table 3 as "surface unevenness".
(Evaluation criteria)
◯: Non-landing on the side surface is less than ± 5 mm.
Δ: Non-landing on the side surface is ± 5 mm or more and less than 20 mm.
X: Non-landing on the side surface is ± 20 mm or more.

[Evaluation example 4: Strength]
Each of the specimens in the semi-cured state of Examples 1 to 4 obtained by the above-mentioned immediate demolding was cured in an outdoor room temperature (25 ° C. to 27 ° C.) environment for 14 days to complete the curing. A precast concrete molded product specimen was obtained. Each of the specimens obtained in this manner was tested by loading in three equal points according to JSCE G 552, and the bending strength of each specimen was measured. As a result, the bending strength was 4 N / mm ^{2 in each case.} From the above, it was also confirmed that the precast concrete molded product according to the present invention has sufficient strength for practical use on the premise of on-site production.

From the above results, it can be seen that according to the present invention, a high-quality precast concrete molded product can be produced on-site by immediate demolding.

1, 1A raw cement 1B precast cement panel 1C building material 2 formwork 3 external vibrator 10 concrete building 100 construction site

Claims (5)

A cement composition for precast concrete molding by an on-site immediate demolding method.
It contains water (W), cement material (C), fine aggregate (S), coarse aggregate (G), and clay mineral (CM).
The water-cement ratio (W / C) is 40 % or more and 55 % or less.
The content of the coarse aggregate is, is at 400 L / ^{m 3} or more 550L / ^{m 3} or less,
The volume ratio (S / M) of the fine aggregate (S) to the mortar (M) composed of water (W), the cement material (C), and the fine aggregate (S) is 30% by volume or more and 60% by volume or less. And
A cement composition in which the content of the clay mineral (CM) is 3% by mass or more and 10% by mass or less with respect to water (W). It is a manufacturing method that manufactures precast concrete molded products on-site.
The casting process of placing fresh cement in the formwork and
A compaction process in which the ready-made cement is placed and then compacted,
Demolding process by immediate demolding method and
Including the curing process,
The ready-made cement is a kneaded product of the cement composition according to claim 1.
The casting step, the compaction step, the demolding step, and the curing step are all performed in the construction site of the concrete building constructed by using the precast concrete molded product as a building material.
Manufacturing method of precast concrete molded products. In the compaction step, the process of pressurizing the entire surface of the cast raw cement is not performed, but the process of applying local vibration from the outside of the mold or the process of placing the raw cement only by repeating the process. The method for producing a precast concrete molded product according to claim 2 , wherein the cement is compacted. The method for producing a precast concrete molded product according to claim 2 or 3 , wherein the curing step is room temperature curing. A method for constructing a concrete building in which a building is constructed using a building material made of a precast concrete molded product manufactured by the manufacturing method according to any one of claims 2 to 4.

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