Carbonation curing method for precast concrete components

Abstract

To provide a simple method for carbonating and curing a precast concrete member, which does not require large-scale construction or modification of a facility itself, and does not require occupancy of the entire facility until the end of carbonation curing.SOLUTION: A method of the present invention for carbonating and curing a precast concrete member includes: a precast concrete producing step of casting a fresh concrete into a formwork and curing the same to obtain one or more precast concrete members having a porosity of 5% or more and 45% or less; a drying step of drying the precast concrete members until the unit water content of the precast concrete members is reduced to 5.0% or more; and a carbonating-and-curing step of carbonating and curing the precast concrete member after drying, which is loaded on a pallet and enclosed by an enclosure member, by supplying a carbon dioxide-containing gas to the inside of the enclosure member.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for carbonation curing of precast concrete members. [Background technology]

[0002] The cement used in concrete emits large amounts of carbon dioxide (CO2) during production due to the decarbonation of raw materials and the fuel used during firing. In recent years, there has been growing interest in curbing climate change, and there is a demand for a significant reduction in carbon dioxide emissions during concrete production.

[0003] One method for reducing carbon dioxide emissions is to subject precast concrete members to carbonation curing, thereby immobilizing carbon dioxide in the precast concrete members through a carbonation reaction in the precast concrete members.

[0004] For example, Patent Document 1 describes a method for curing concrete products, although it is not intended to reduce carbon dioxide emissions. In the curing method of Patent Document 1, a surrounding frame is placed on a concrete product that has been stripped and placed on a pallet, and the pallets in this state are stacked in multiple layers, and atomized moisture and carbon dioxide are supplied into the surrounding frame. However, with a method in which unhardened concrete products are directly stacked in multiple layers via pallets, the concrete products in the lower layers are prone to deformation and damage, and rust and dirt from the pallets placed directly above the concrete products can fall and adhere to the top surfaces of the concrete products.

[0005] Furthermore, common methods for carbonation curing precast concrete members, including the method described in Patent Document 1, require large-scale construction or modification of the factory facilities to maintain a carbon dioxide atmosphere in the facility itself. Furthermore, because carbonation curing of precast concrete members requires a certain curing period, the entire facility must be occupied until the curing is complete. Thus, there is room for various improvements in carbonation curing methods for precast concrete members. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 01-145385 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a simple carbonation curing method for precast concrete members which does not require large-scale construction or modification of the facility itself and does not require the entire facility to be occupied until the carbonation curing is completed. [Means for solving the problem]

[0008] [1] A method for carbonation curing of precast concrete members, comprising: a precast concrete production step of pouring fresh concrete into a formwork and hardening it to obtain one or more precast concrete members having a void ratio of 5% to 45%; a drying step of drying the precast concrete members until the reduction rate of the unit water content of the precast concrete members is 5.0% or more; and a carbonation curing step of carbonation curing the dried precast concrete members that are loaded on a pallet and surrounded by an enclosing member by supplying a carbon dioxide-containing gas into the enclosing member. [2] The carbonation curing method for precast concrete elements described in [1] above, wherein the surrounding member is in the form of a film, and during the carbonation curing process, the precast concrete elements are carbonation cured while wrapped in the surrounding member, and after the carbonation curing process is completed, the precast concrete elements are shipped while maintaining the state in which they are wrapped in the surrounding member. [3] The precast concrete member after carbonation curing obtained in the carbonation curing process has a thickness of 40 mm or more and 500 mm or less and a hydraulic conductivity of 1 × 10 -4The carbonation curing method for precast concrete members according to [1] or [2] above, wherein the curing strength is m / s or more. [4] A carbonation curing method for precast concrete members described in any one of [1] to [3] above, wherein in the drying step, air whose temperature and / or humidity is controlled is blown onto the precast concrete members arranged at a predetermined distance from each other to dry the precast concrete members. [5] The carbonation curing method for precast concrete members according to any one of the above [1] to [4], wherein the pallet is air permeable. [Effects of the Invention]

[0009] The present invention provides a simple carbonation curing method for precast concrete members that does not require large-scale construction or modification of the facility itself and does not require the entire facility to be occupied until the carbonation curing is completed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flowchart showing an example of a carbonation curing method for a precast concrete member according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of the drying step. [Figure 3] FIG. 3 is a schematic diagram showing an example of the carbonation curing step. [Figure 4] FIG. 4 is a schematic diagram showing another example of the drying step. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a detailed description will be given based on an embodiment.

[0012] As a result of extensive research, the inventors have discovered a method in which precast concrete members that have been dried until the rate of reduction in unit water content falls within a specified range are subjected to carbonation curing, thereby enabling the precast concrete members to be carbonated efficiently as a whole, and as a result, it is not necessary to construct or remodel a large-scale facility for carbonation curing, and it is not necessary to occupy the entire facility until carbonation curing is complete.Based on this finding, they have completed the present invention.

[0013] The carbonation curing method for precast concrete members of the present invention comprises a precast concrete production step in which fresh concrete is poured into a formwork and hardened to obtain one or more precast concrete members having a void ratio of 5% to 45%; a drying step in which the precast concrete members are dried until the reduction rate of the unit water content of the precast concrete members is 5.0% or more; and a carbonation curing step in which the dried precast concrete members, which are loaded on a pallet and surrounded by an enclosing member, are carbonation cured by supplying carbon dioxide-containing gas into the enclosing member.

[0014] Fig. 1 is a flowchart showing an example of a carbonation curing method for precast concrete members according to an embodiment. As shown in Fig. 1, the carbonation curing method for precast concrete members includes a precast concrete producing step S1, a drying step S2, and a carbonation curing step S3.

[0015] In the precast concrete production step S1 of the carbonation curing method for precast concrete members, fresh concrete is poured into a formwork and hardened to obtain one or more precast concrete members. Hereinafter, the carbonation curing method for multiple precast concrete members will be described from the perspective of significantly demonstrating the effects of the carbonation curing method for precast concrete members, but the same effects can be achieved by carbonation curing a single precast concrete member.

[0016] The fresh concrete to be poured into the formwork is a hydraulic composition, and contains at least water, cement, and aggregate.

[0017] The cement contained in the fresh concrete is preferably Portland cement. Portland cement includes ordinary Portland cement as well as early-strength, ultra-early-strength, moderate-heat, and low-heat sulfate-resistant varieties, which are specified in JIS R 5210:2019. Fresh concrete can be made by blending one or more of these various Portland cements.

[0018] Alternatively, blast furnace cement (blended cement) containing ground granulated blast furnace slag and cement material may be used as the cement. The blast furnace cement specified in JIS R 5211:2009 can be used.

[0019] The aggregate contained in the fresh concrete includes at least one of fine aggregate and coarse aggregate.

[0020] The fine aggregate contained in fresh concrete is an aggregate defined in JIS A 5308, JIS A 5005, JIS A 5002, and JIS A 5011. Examples of fine aggregate include crushed sand, sand, river sand, sea sand, crushed lime sand, crushed stone, recycled aggregate, lightweight aggregate, and heavy aggregate.

[0021] Coarse aggregate contained in fresh concrete is defined in JIS A 5308, JIS A 5005, JIS A 5002, and JIS A 5011, and is distinguished from the above-mentioned fine aggregate by particle size, and by whether it passes through a 5mm sieve or not. In practice, fine aggregate is defined as aggregate that passes through a 10mm sieve in its entirety and 85% or more by weight passes through a 5mm sieve, and coarse aggregate is defined as aggregate that is retained by 85% or more by weight on a 5mm sieve.

[0022] In addition to the above components, the fresh concrete may contain admixtures such as γ-C2S, slaked lime, coal ash, fly ash, and limestone fine powder, as long as the effects of the present invention are achieved.

[0023] In the precast concrete production step S1, fresh concrete is poured into a formwork and allowed to harden to obtain a precast concrete member with a void ratio of 5% to 45%. The void ratio of the precast concrete member can be controlled, for example, by rolling the concrete or immediate demolding. Precast concrete members have a porous structure in which multiple pores are interconnected, giving them excellent air permeability and water permeability. Furthermore, the excellent air permeability and water permeability of the precast concrete member before drying obtained in the precast concrete production step S1 are maintained in the dried precast concrete member obtained in the drying step S2 described below.

[0024] When the porosity of a precast concrete member is within the above range, its air permeability and water permeability are improved, and the precast concrete member can be dried efficiently overall and at a faster drying rate in the drying process S2 described below, while the dried precast concrete member can be efficiently carbonated and cured overall and at a faster carbonation rate in the carbonation curing process S3 described below.

[0025] In the drying step S2 carried out after the precast concrete producing step S1, the precast concrete member obtained in the precast concrete producing step S1 is dried until the reduction rate of the unit water content of the precast concrete member is 5.0% or more.

[0026] The inventors have found that the carbonation rate of precast concrete members is related to their moisture content, and that carbonation proceeds efficiently in precast concrete members that have been dried until the reduction rate of their unit water content falls within a predetermined range. Furthermore, the inventors have found that by drying precast concrete members with a porosity within the above-mentioned predetermined range until the reduction rate of their unit water content falls within the predetermined range, the carbonation rate of the dried precast concrete members can be increased overall and carbonation cured efficiently in the carbonation curing step S3 described below. From this perspective, the reduction rate of the unit water content of the precast concrete members in the drying step S2 is 5.0% or more, preferably 15.0% or more, and more preferably 25.0% or more.

[0027] The unit water content of the precast concrete element before the drying process S2 is carried out (hereinafter also referred to as the precast concrete element before drying) and the precast concrete element after the drying process S2 is completed (hereinafter also referred to as the precast concrete element after drying) can be measured using a moisture meter such as an infrared moisture meter, and the value obtained by subtracting the unit water content of the precast concrete element before drying from the unit water content of the precast concrete element before drying is divided by the unit water content of the precast concrete element before drying and multiplied by 100 to determine the reduction rate (%) of the unit water content of the precast concrete element.

[0028] The rate of reduction in the unit water content of a precast concrete element can also be calculated from the rate of weight reduction of the precast concrete element before and after drying. The value obtained by subtracting the weight of the precast concrete element after drying from the weight of the precast concrete element before drying corresponds to the amount of water released from the precast concrete element in the drying step S2, and the rate of reduction in the unit water content of a precast concrete element is related to the rate of weight reduction of the precast concrete element.

[0029] Fig. 2 is a schematic diagram showing an example of the drying step S2. As shown in Fig. 2, in the drying step S2, a plurality of pre-dried precast concrete members 1 (pre-dried precast concrete members 1 are also simply referred to as precast concrete members 1) are aligned on a shelf member 10, and the precast concrete members 1 are dried.

[0030] As shown in Figure 2, by arranging multiple precast concrete members 1 at a specified interval, the multiple precast concrete members 1 can be dried evenly, and each precast concrete member 1 can be dried overall from the surface to the interior, and the rate of reduction of the unit water content of each precast concrete member 1 can be accelerated. However, since the precast concrete members 1 have a porosity within the above numerical range, even if multiple precast concrete members 1 are placed in contact with each other without any intervals, the drying state of the precast concrete members 1 will not be excessively uneven, and furthermore, the time required for the rate of reduction of the unit water content of the precast concrete members 1 to reach the specified range will not be excessively long.

[0031] In addition, in the drying process S2, air whose humidity and temperature are not controlled, or air whose temperature and / or humidity are controlled, is blown into the precast concrete member 1 to dry the precast concrete member 1, thereby increasing and controlling the drying rate of the precast concrete member 1, i.e., the rate at which the unit water content in the precast concrete member 1 decreases.

[0032] FIG. 3 is a schematic diagram showing an example of the carbonation curing step S3. As shown in FIG. 3, in the carbonation curing step S3, which is performed after the drying step S2, carbonation curing is performed on the dried precast concrete members 2 obtained in the drying step S2 (the dried precast concrete members 2 are also simply referred to as precast concrete members 2). In the carbonation curing step S3, the precast concrete members 2 are loaded on a pallet 20 and surrounded by an enclosing member 21. The precast concrete members 2 are placed inside the enclosing member 21. The bottom of the enclosing member 21 is open. In this state, a carbon dioxide-containing gas 22 is supplied into the inside of the enclosing member 21 to carbonation cure the precast concrete members 2. In this way, carbon dioxide can be fixed in the precast concrete members 2.

[0033] For example, as shown in Figure 3, carbon dioxide-containing gas 22 is supplied into the inside of enclosing member 21 from a carbon dioxide cylinder, which is a carbon dioxide-containing gas source 24, via piping 23 connected to gas injection hole 21a provided in the top of enclosing member 21. While Figure 3 shows an example in which one gas injection hole 21a is provided in enclosing member 21, multiple gas injection holes 21a may be provided in enclosing member 21. Additionally, multiple precast concrete members 2 may be fastened together or the precast concrete members 2 and pallet 20 may be fastened together with metal bands (not shown).

[0034] As described above, the precast concrete member 2 has a porosity within a predetermined range, and the multiple pores that make up the precast concrete member 2 are interconnected. Furthermore, the precast concrete member 2 is dried overall from the surface to the interior until the rate of reduction in unit water content falls within a predetermined range. The carbon dioxide-containing gas 22 supplied to the inside of the enclosing member 21 flows through the interior of the precast concrete member 2, which has a predetermined water content, via the multiple interconnected pores. As a result, the carbon dioxide contained in the carbon dioxide-containing gas 22 is immobilized throughout the entire interior of the precast concrete member 2.

[0035] In the carbonation curing step S3, carbon dioxide gas is forcibly fixed in the dried precast concrete member 2, and the precast concrete member 2 is thus forcibly carbonated.

[0036] The carbon dioxide-containing gas source 24 is preferably a carbon dioxide cylinder, separated and recovered carbon dioxide, exhaust gas from a thermal power plant, exhaust gas from a boiler, or any of a variety of exhaust gases containing carbon dioxide emitted in the manufacturing process of other products. The humidity and temperature of these exhaust gases may be adjusted.

[0037] The pallet 20 on which the precast concrete elements 2 are loaded is made of wood and is air- and water-permeable. Therefore, compared to loading the bottom of the precast concrete elements 2 on the floor of the facility or a support member with poor air permeability, placing the bottom of the precast concrete elements 2 in contact with the pallet 20 can improve the carbonation rate and uniformity of the precast concrete elements 2. Furthermore, because the pallet 20 is water-permeable, water generated during the carbonation curing of the precast concrete elements 2 passes from the bottom of the precast concrete elements 2 through the inside of the pallet 20 and is discharged outside the system.

[0038] The precast concrete members 2 have a porosity within a predetermined range. Therefore, even when multiple precast concrete members 2 are stacked vertically with no gaps between them, or when multiple precast concrete members 2 are arranged horizontally with no gaps between them, as shown in Figure 3, there are no practical problems with regard to slowing the carbonation rate or uneven carbonation in the precast concrete members 2. Arranging multiple precast concrete members 2 horizontally with a predetermined gap between them can improve the carbonation rate and uniformity of carbonation in the precast concrete members 2.

[0039] The enclosing member 21 surrounds at least the precast concrete member 2 except for its bottom surface, and the bottom of the enclosing member 21 is open. The enclosing member 21 may also surround the side of the pallet as shown in FIG. 3. The interior of the enclosing member 21 maintains a predetermined airtightness. The enclosing member 21, which surrounds the entire precast concrete member 2, prevents the carbon dioxide-containing gas 22 supplied inside the enclosing member 21 from leaking from anywhere other than the bottom of the enclosing member 21, and allows the carbon dioxide-containing gas 22 to circulate efficiently inside the precast concrete member 2.

[0040] The enclosing member 21 has low permeability to carbon dioxide gas. From the viewpoint of easily packaging the precast concrete members 2, the enclosing member 21 is preferably in the form of a film. When the enclosing member 21 is in the form of a film, the precast concrete members 2 can be enclosed by wrapping the enclosing member 21 around the precast concrete members 2 one or more times. For example, by aligning and stacking a plurality of precast concrete members 2 on a pallet 20 and then wrapping the plurality of precast concrete members 2 in the enclosing member 21, the precast concrete members 2 are ready to be installed for carbonation curing.

[0041] Furthermore, because carbon dioxide is heavier than air, when carbon dioxide-containing gas 22 is supplied from the top of enclosing member 21 as shown in Figure 3, the carbon dioxide-containing gas 22 flows through the interior of the precast concrete members 2 loaded on the upper pallet 20, then through the interior of the upper pallet 20, then through the interior of the precast concrete members 2 loaded on the lower pallet 20, then through the interior of the lower pallet 20, and then is released outside the system. In this way, the precast concrete members 2 can be efficiently carbonated and cured.

[0042] 3 corresponds to the way the precast concrete elements 2 are packed for shipping. Therefore, after the carbonation curing step S3 is completed, the precast concrete elements 2 can be shipped simply by keeping the precast concrete elements 2 wrapped in the enclosing element 21 and removing the piping 23 from the enclosing element 21. Therefore, the process from producing precast concrete elements from fresh concrete to carbonation curing and shipping can be carried out easily and quickly.

[0043] The precast concrete member after carbonation curing obtained in the carbonation curing step S3 has water permeability and air permeability. The water permeability coefficient of the precast concrete member after carbonation curing is 1×10 -4 The thickness of the precast concrete member after carbonation curing is preferably 40 mm to 500 mm. Such a precast concrete member is suitable for use as a water-permeable interlocking block.

[0044] In this way, the carbonation curing method for precast concrete members according to the embodiment can be implemented with almost no change to the conventional process from manufacturing to shipping of precast concrete members, which does not include a carbonation curing step, except for supplying a carbon dioxide-containing gas to the inside of the enclosing member. Therefore, the carbonation curing method for precast concrete members does not require large-scale construction or modification of the factory facilities themselves, and allows precast concrete members to be easily carbonated.

[0045] Furthermore, in the carbonation curing method for precast concrete members according to the embodiment, except for the carbon dioxide-containing gas source and piping required for carbonation curing, the materials required at the time of shipping the precast concrete members are basically used, so no new materials are required. Furthermore, because no new materials are required, large-scale construction or modification of the facility itself is not necessary. Furthermore, because the materials required at the time of shipping the precast concrete members are used, the entire facility does not need to be occupied until carbonation curing is complete.

[0046] In the above, an example has been described in which, in the drying step S2, multiple pre-dried precast concrete members 1 are lined up on shelf members 10 and dried, as shown in Figure 2. However, instead of using shelf members 10, multiple pre-dried precast concrete members 1 may be loaded onto a pallet 20 used in the carbonation curing step S3 and dried, as shown in Figure 4. In this case, the precast concrete members 1 may be surrounded by an enclosing member 21, but in order to increase the drying rate of the precast concrete members 1, it is preferable that the precast concrete members 1 are not surrounded by an enclosing member 21. If the drying step S2 is performed in the state shown in Figure 4, the carbonation curing step S3 can be performed quickly after the drying step S2 is completed, without changing the arrangement of the precast concrete members 2.

[0047] According to the embodiment described above, by carbonation curing precast concrete members that have been dried until the reduction rate of unit water content falls within a predetermined range, the precast concrete members can be carbonated efficiently throughout. As a result, the carbonation curing method for precast concrete members of the embodiment does not require large-scale construction or modification of the carbonation curing facility itself, and does not require the entire facility to be occupied until the carbonation curing is completed.

[0048] Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept and scope of the claims of the present disclosure, and can be modified in various ways within the scope of the present disclosure. [Example]

[0049] Next, examples and comparative examples will be described, but the present invention is not limited to these examples.

[0050] (Examples 1-1 to 1-3, Comparative Example 1-1) First, fresh concrete was prepared. Specifically, tap water 84 kg / m 3 , ordinary Portland cement 365 kg / m 3, crushed stone 1649 kg / m 3 The above was mixed to obtain fresh concrete. The fresh concrete was then poured into a formwork and allowed to harden, thereby obtaining precast concrete members having the void ratios shown in Table 1.

[0051] Next, while measuring the unit water content of the precast concrete elements with an infrared moisture meter, the precast concrete elements were dried until the reduction rate of the unit water content of the precast concrete elements reached the value in Table 1. After that, as shown in Figure 3, carbon dioxide gas was supplied inside the enclosing element, and the dried precast concrete elements, which were loaded on a pallet and surrounded by the enclosing element, were subjected to carbonation curing for three days. The thickness of the precast concrete elements after carbonation curing was 40 mm to 500 mm.

[0052] (Examples 2-1 to 2-3, Comparative Example 2-1) First, fresh concrete was prepared. Specifically, tap water 84 kg / m 3 , ordinary Portland cement 183 kg / m 3 , γ-C2S 183 kg / m 3 , crushed stone 1641 kg / m 3 The above was mixed to obtain fresh concrete. The fresh concrete was then poured into a formwork and allowed to harden, thereby obtaining precast concrete members having the void ratios shown in Table 2.

[0053] Next, while measuring the unit water content of the precast concrete elements with an infrared moisture meter, the precast concrete elements were dried until the reduction rate of the unit water content of the precast concrete elements reached the value shown in Table 2. After that, as shown in Figure 3, carbon dioxide gas was supplied inside the enclosing element, and the dried precast concrete elements, which were loaded on a pallet and surrounded by the enclosing element, were subjected to carbonation curing for three days. The thickness of the precast concrete elements after carbonation curing was between 40 mm and 500 mm.

[0054] (Examples 3-1 to 3-3, Comparative Example 3-1) First, fresh concrete was prepared. Specifically, tap water 84 kg / m3 , ordinary Portland cement 201 kg / m 3 , blast furnace slag powder 164 kg / m 3 , crushed stone 1636 kg / m 3 The above was mixed to obtain fresh concrete. The fresh concrete was then poured into a formwork and allowed to harden, thereby obtaining precast concrete members having the void ratios shown in Table 3.

[0055] Next, while measuring the unit water content of the precast concrete elements with an infrared moisture meter, the precast concrete elements were dried until the reduction rate of the unit water content of the precast concrete elements reached the values ​​shown in Table 3. After that, as shown in Figure 3, carbon dioxide gas was supplied inside the enclosing element, and the dried precast concrete elements, which were loaded on a pallet and surrounded by the enclosing element, were subjected to carbonation curing for three days. The thickness of the precast concrete elements after carbonation curing was between 40 mm and 500 mm.

[0056] The precast concrete members obtained in the above Examples and Comparative Examples after carbonation curing were subjected to the following measurements and evaluations.

[0057] [1] Carbonation rate After carbonation curing, the precast concrete members were cut to obtain cut samples. Next, phenolphthalein reagent was sprayed onto the entire cut surface of the cut sample. The areas that turned red with the phenolphthalein reagent were not carbonated and were alkaline. The areas that did not turn red were carbonated areas. The ratio of the area of ​​the areas that did not turn red on the cut surface to the area of ​​the cut surface sprayed with the phenolphthalein reagent was taken as the carbonation rate (%).

[0058] [2] Permeability coefficient The hydraulic conductivity of precast concrete members after carbonation curing was measured in accordance with JIS A 5371 (precast unreinforced concrete products).

[0059] [3] Evaluation The following ranking was performed: Ranks ◎, ◯, and △ are pass, and rank × is fail.

[0060] ◎: Carbonation rate was 80% or more. ○: Carbonation rate was 60% or more but less than 80%. △: Carbonation rate was 40% or more but less than 60%. ×: The carbonation rate was less than 40%.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] As shown in Tables 1 to 3, in the above examples, precast concrete members that had a porosity within a specified range and were dried until the rate of reduction in unit water content was within a specified range were subjected to carbonation curing, so the precast concrete members were able to be carbonated efficiently overall.On the other hand, in the above comparative examples, precast concrete members that had at least a rate of reduction in unit water content outside the specified range were subjected to carbonation curing, so the precast concrete members were not sufficiently carbonated. [Explanation of symbols]

[0065] 1 Precast concrete members before drying 2 Precast concrete members after drying 10 Shelf parts 20 palettes 21 Enclosure 21a Gas injection hole 22 Carbon dioxide-containing gas 23 Piping 24 Carbon dioxide-containing gas source

Claims

1. a precast concrete production step in which fresh concrete is poured into a formwork and hardened to obtain one or more precast concrete elements having a void ratio of 5% to 45%; a drying step of drying the precast concrete members until a reduction rate of the unit water content of the precast concrete members is 5.0% or more; a carbonation curing step of carbonating the dried precast concrete members loaded on the pallet and surrounded by an enclosing member by supplying a carbon dioxide-containing gas into the enclosing member; A carbonation curing method for precast concrete members, comprising:

2. the surrounding member is in the form of a film, In the carbonation curing step, the precast concrete member is carbonation cured while being wrapped in the enclosing member, After the carbonation curing step is completed, the precast concrete element is shipped while the precast concrete element is kept wrapped in the enclosing element.

2. The carbonation curing method for precast concrete members according to claim 1.

3. The precast concrete member after carbonation curing obtained in the carbonation curing step has a thickness of 40 mm or more and 500 mm or less and a water permeability coefficient of 1×10 －４ 2. The carbonation curing method for precast concrete members according to claim 1, wherein the carbonation curing rate is 1 / 2 m / s or more.

4. 2. The carbonation curing method for precast concrete members according to claim 1, wherein in the drying step, air whose temperature and / or humidity are controlled is blown onto the precast concrete members arranged at a predetermined distance from each other to dry the precast concrete members.

5. 2. The carbonation curing method for precast concrete members according to claim 1, wherein the pallet is air permeable.

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