Method for manufacturing precast piles, manufacturing apparatus for precast piles, and precast piles manufactured using the method

Abstract

To provide a method for manufacturing a precast pile and an apparatus for manufacturing a precast pile which suppress discharge of carbon dioxide from an existing pile manufacturing site, and a precast pile manufactured using the same.SOLUTION: A method for manufacturing a precast pile includes: curing steps S15 and S17 for arranging a mold of a pile formed by placing concrete in a curing tank, and heating the concrete while supplying water vapor into the curing tank; and an exhaust gas supply step S20 of supplying exhaust gas containing carbon dioxide into the concrete or raw material for the concrete.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing ready-made piles, a manufacturing apparatus for ready-made piles, and a ready-made pile manufactured using the method.

Background Art

[0002] Conventionally, technological developments have been carried out for suppressing emissions of carbon dioxide, which is a greenhouse gas. For example, in the civil engineering and construction field, as disclosed in Patent Document 1, technologies for absorbing carbon dioxide into concrete structures, and as disclosed in Patent Document 2, technologies for producing carbonated concrete by reacting carbon dioxide with γ - belite have been developed. The former absorbs carbon dioxide in the air into concrete structures, and the latter reacts carbon dioxide contained in the exhaust gas of thermal power plants with γ - belite.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, due to the social spread of SDGs (Sustainable Development Goals) adopted by the United Nations, the need to suppress carbon dioxide emissions has been increasing. In particular, in the civil engineering and construction field, since a large amount of carbon dioxide is emitted during the manufacturing process of clinker, which is a raw material for cement, the significance of technological development for suppressing carbon dioxide emissions is great. In view of the above circumstances, an object of the present invention is to provide a method for manufacturing ready-made piles in which carbon dioxide emissions from the ready-made pile manufacturing site are suppressed, a manufacturing apparatus for ready-made piles, and a ready-made pile manufactured using the method.

Means for Solving the Problem

[0005] (1) The method for manufacturing a precast pile according to at least one embodiment of the present invention comprises: placing a formwork of a pile in which concrete has been placed in a steam curing tank, heating the concrete while supplying steam into the steam curing tank, and After undergoing a centrifugal forming process, the concrete is compacted into a hollow cylindrical shape. a steam curing step of curing the concrete in the formwork to a predetermined strength; Compacted into a hollow cylindrical shape and an exhaust gas supply step of supplying exhaust gas containing carbon dioxide to the concrete in the formwork placed in the steam curing tank. Compacted into a hollow cylindrical shape There is an exhaust gas supply step in which the content of the exhaust gas changes stepwise in the radial direction of the concrete, and the exhaust gas is supplied such that the content of the exhaust gas is higher on the inner peripheral side than on the outer peripheral side. and is provided.

[0006] According to the above configuration (1), by supplying exhaust gas containing carbon dioxide, Inside the formwork arranged in the steam curing tank the carbon dioxide in the exhaust gas is dissolved, reacted, and absorbed by the concrete. Therefore, it is possible to suppress the absorption of carbon dioxide by the precast pile and the release of carbon dioxide in the exhaust gas into the atmosphere. To To

[0009] (2) The manufacturing apparatus for a precast pile according to at least one embodiment of the present invention comprises: a steam curing tank that can accommodate a formwork of a pile in which concrete has been placed and heat the formwork of the pile with steam, and cure the concrete in the formwork to a predetermined strength; After undergoing a centrifugal forming process, the concrete is compacted into a hollow cylindrical shape. Compacted into a hollow cylindrical shape exhaust gas supply means capable of supplying exhaust gas containing carbon dioxide to the steam curing tank in order to supply the exhaust gas containing carbon dioxide to the concrete in the formwork placed in the steam curing tank. There is exhaust gas supply means capable of supplying the exhaust gas such that the content of the exhaust gas changes stepwise in the radial direction of the concrete, and the content of the exhaust gas is higher on the inner peripheral side than on the outer peripheral side. and is characterized by comprising the above.

[0010] According to the above configuration ( 2) ), by supplying exhaust gas containing carbon dioxide, Inside the formwork arranged in the steam curing tank the carbon dioxide in the exhaust gas is dissolved, reacted, and absorbed by the concrete. To ​To The carbon dioxide is dissolved and reacted with the soil and absorbed. Therefore, the carbon dioxide is absorbed in the prefabricated piles, and the carbon dioxide in the exhaust gas can be prevented from being released into the atmosphere.

[0013] (3) The prefabricated pile according to at least one embodiment of the present invention is The prefabricated pile is manufactured using the manufacturing method for the prefabricated pile described in the above configuration (1). A precast pile which , Comprises a cylindrical concrete part constituted by the concrete, In the concrete part, the content of the exhaust gas changes stepwise in the radial direction, and the content of the exhaust gas is higher on the inner peripheral side than on the outer peripheral side.

[0014] The above configuration ( 3) According to the above, the prefabricated pile has the above configuration (1 ) To The precast piles are constructed using the described method of manufacturing, and the concrete absorbs carbon dioxide. The concrete thus carbonated by absorbing carbon dioxide is stronger than conventional non-carbonated concrete, improving the performance of the precast piles.

[0016] Also, The above configuration (3) According to the above configuration, since the inner periphery side of the concrete portion is carbonated and has high strength, the inner periphery side is prevented from collapsing when a bending moment is applied. (3) The precast piles have high bending strength. (4) The prefabricated pile according to at least one embodiment of the present invention comprises: a curing step of placing the formwork for the pile into which the concrete has been poured in a curing tank and heating the concrete while supplying steam into the curing tank; A prefabricated pile manufactured by a method for manufacturing a prefabricated pile, comprising: an exhaust gas supplying step of supplying exhaust gas containing carbon dioxide to the concrete or a raw material of the concrete, A cylindrical concrete portion formed of the concrete is provided, In the concrete portion, the amount of the exhaust gas contained varies stepwise in the radial direction, with the inner circumferential side containing a greater amount of the exhaust gas than the outer circumferential side. Effect of the Invention

[0017] According to the present invention, there are provided a method for manufacturing a precast pile in which carbon dioxide emissions from a precast pile manufacturing site are suppressed, a manufacturing apparatus for a precast pile, and a precast pile manufactured using the method.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0019] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

[0020] Figure 1 is a flowchart for explaining a schematic procedure of a method for manufacturing a ready-made pile according to an embodiment of the present invention (hereinafter, also simply referred to as a pile manufacturing method). As shown in Figure 1, the pile manufacturing method includes a weighing step S1, a mixing step S3, a reinforcing cage assembling step S5, a formwork arranging step S7, a concrete placing step S11, a tensioning step S12, a centrifugal forming step S13, a steam curing step S15, a demolding step S16, an autoclave curing step S17, and an exhaust gas supply step S20. In the weighing step S1, water, cement, and aggregate, which are raw materials of concrete, are weighed. Note that the raw materials may include admixtures and the like. In the mixing step S3, as shown in Figure 2, the raw materials of concrete are mixed using a mixer 1 to prepare concrete (fresh concrete).

[0021] On the other hand, in the reinforcing cage assembling step S5, a reinforcing cage is assembled using raw materials of the reinforcing cage, such as end plates, reinforcing bars, and PC steel bars. Note that the raw materials of the reinforcing cage may include deformed reinforcing bars, reinforcing cylinders, and the like. In the formwork arranging step S7, the assembled reinforcing cage is arranged inside the formwork.

[0022] In the concrete placing step S11, as shown in Figure 3, the concrete prepared in the mixing step S3 is placed into the formwork 5 in which the reinforcing cage 3 is arranged. In the tensioning step S12, the PC steel bars are stretched and tensioned by pulling the end plates of the reinforcing cage 3 into which the concrete has been placed, and the end plates are locked to the formwork in this state. In the centrifugal forming step S13, the formwork 5 that has undergone the concrete placing step S11 and the tensioning step S12 is rotated and compacted by centrifugal force. In the steam curing step S15, as shown in Figure 4, the formwork 5 that has undergone the centrifugal forming step S13 is arranged in a curing tank 7. Then, steam generated by a boiler 9 is supplied to the curing tank 7 to cure the concrete in the formwork 5 to a predetermined strength. The boiler 9 generates steam using heat generated by burning fuel, but the fuel is not particularly limited, and light oil, heavy oil, coal, and the like can be used. In the demolding step S16, after the steam curing step S15, it is confirmed whether the concrete has a predetermined strength, and the intermediate body of the precast pile is demolded from the formwork 5. At the same time, a compressive force is introduced into the intermediate body of the precast pile. The intermediate body of the precast pile is composed of the steel cage 3 and the concrete that have undergone the steam curing step S15, and is the inner part of the formwork 5 that has undergone the steam curing step S15.

[0023] In the autoclave curing step S17, as shown in FIG. 5, the intermediate body 13 of the precast pile is placed in the autoclave (pressure-resistant container) 11. Then, steam from the boiler 9 is supplied into the autoclave 11, and the intermediate body 13 of the precast pile is cured at a higher temperature and pressure than in the steam curing step S15. As a result, the concrete of the intermediate body 13 of the precast pile is cured to a predetermined strength, and the precast pile as the final product is obtained.

[0024] In the exhaust gas supply step S20, during the above-described metering step S1, mixing step S3, concrete placing step S11, tensioning step S12, centrifugal forming step S13, demolding step S16, steam curing step S15, and autoclave curing step S17, as shown in FIGS. 2 to 5, the exhaust gas of the boiler 9 is supplied to the concrete or the raw materials of the concrete that will constitute the precast pile.

[0025] According to the above configuration, by supplying the exhaust gas containing carbon dioxide discharged from the boiler 9 to the concrete or the raw materials of the concrete, the carbon dioxide in the exhaust gas is dissolved, reacted, and absorbed by the concrete or the raw materials of the concrete. Therefore, carbon dioxide can be absorbed by the precast pile, and the release of carbon dioxide in the exhaust gas into the atmosphere can be suppressed. In this embodiment, the case where the exhaust gas discharged from the boiler 9 is used has been described, but it is not limited to the boiler 9, and any device that discharges exhaust gas containing carbon dioxide may be used.

[0026] In some embodiments, in the exhaust gas supply step S20, before the mixing step S3, the exhaust gas of the boiler 9 is dissolved in water, which is a raw material of the concrete. According to the above configuration, by supplying the exhaust gas discharged from the boiler 9 to water, carbon dioxide in the exhaust gas is dissolved and reacted with water and absorbed. Here, the carbon dioxide dissolved and reacted with water also reacts with the cement when the water and cement are mixed, and is absorbed by the concrete. Therefore, the carbon dioxide in the exhaust gas mixed with water is dissolved, reacted, and absorbed by the concrete in the same manner as when mixed with the concrete. As a result, it is possible to suppress the release of carbon dioxide in the exhaust gas into the atmosphere.

[0027] Note that the absorption of carbon dioxide by concrete and the raw materials of concrete is considered to be represented by the following approximate reaction formula. However, xCaO·ySiO2 in the formula represents calcium silicates such as tricalcium silicate and dicalcium silicate (belite, γC2S), and the molar number consistency on both sides of the formula is ignored. As shown in the formula, calcium silicate, water, and carbon dioxide react to form calcium carbonate. xCaO·ySiO2 + H2O → vCaO·wSiO2·H2O + Ca(OH)2 Ca(OH)2 + CO2 → CaCO3 + H2O Also, the absorption of carbon dioxide by water is represented by the following approximate reaction formula. As shown in the formula, carbon dioxide and water react to form carbonic acid. CO2 + H2O → H2CO3

[0028] Hereinafter, a manufacturing apparatus for precast piles (hereinafter, also simply referred to as a pile manufacturing apparatus) according to an embodiment of the present invention will be described. The pile manufacturing apparatus includes a curing tank 7 and an exhaust gas supply means. As shown in FIG. 4, the curing tank 7 is configured to accommodate the formwork 5 of the pile in which the concrete is placed and heat the formwork 5 of the pile with the steam from the boiler 9. And the exhaust gas supply means is configured to supply the exhaust gas of the boiler 9 to the concrete or the raw materials of the concrete that will constitute the precast pile.

[0029] According to the above configuration, by supplying the exhaust gas discharged from the boiler 9 to concrete or the raw materials of concrete, carbon dioxide in the exhaust gas is dissolved, reacted, and absorbed by the concrete or the raw materials of concrete. Therefore, carbon dioxide can be absorbed by the precast piles, and the release of carbon dioxide in the exhaust gas into the atmosphere can be suppressed.

[0030] In some embodiments, as shown in FIG. 2, the exhaust gas supply means includes a pump 15 capable of supplying the exhaust gas of the boiler 9 to a mixer 1 for preparing concrete. In some embodiments, as shown in FIG. 3, the exhaust gas supply means includes a pump 19 for supplying the exhaust gas of the boiler 9 to a supply pipe 17 of the concrete placed in the formwork 5.

[0031] In some embodiments, as shown in FIG. 4, the exhaust gas supply means includes a pump 20 for supplying the exhaust gas of the boiler 9 into the curing tank 7. According to the above configuration, by supplying the exhaust gas into the curing tank 7, in addition to the heat of the steam, the heat of the exhaust gas and the reaction between the concrete and carbon dioxide, the concrete can be cured at a high temperature, and a predetermined strength can be obtained early. Furthermore, since the amount of carbon dioxide absorbed increases as the moisture content increases, if the exhaust gas is supplied to the curing tank 7 together with the steam, more carbon dioxide can be absorbed by the precast piles. In some embodiments, as shown by the dashed two-dot line in FIG. 4, it may be configured to supply the exhaust gas into the formwork 5 accommodated in the curing tank 7. In this case, the exhaust gas or carbon dioxide can be intensively absorbed by the concrete on the inner peripheral side of the precast pile having a hollow cylindrical shape.

[0032] In some embodiments, as shown in FIG. 5, the exhaust gas supply means includes a pump 21 for supplying the exhaust gas of the boiler 9 into the autoclave 11. According to the above configuration, by supplying exhaust gas into the autoclave 11, in addition to the heat and pressure of steam, the heat and pressure of the exhaust gas, and the reaction between concrete and carbon dioxide, the concrete can be cured at high temperature and high pressure, and a predetermined strength can be obtained at an early stage. Furthermore, since the amount of carbon dioxide absorbed increases as the moisture content increases, if exhaust gas is supplied to the autoclave 11 together with steam, more carbon dioxide can be absorbed by the precast piles. In some embodiments, as shown by the dashed two-dot line in FIG. 5, the exhaust gas may be configured to be supplied to the hollow portion of the intermediate body 13 of the precast pile accommodated in the autoclave 11. In this case, the exhaust gas or carbon dioxide can be intensively absorbed by the concrete on the inner peripheral side of the precast pile having a hollow cylindrical shape.

[0033] In some embodiments, the exhaust gas supply means is configured to dissolve the exhaust gas of the boiler 9 in the water for preparing concrete by mixing with cement and aggregates. According to the above configuration, by supplying the exhaust gas discharged from the boiler 9 to water, carbon dioxide is mixed with water, and the carbon dioxide in the exhaust gas is dissolved and reacted with water to be absorbed. Here, the carbon dioxide dissolved and reacted with water also reacts with the cement when the water and cement are mixed, and is absorbed by the concrete. Therefore, the carbon dioxide in the exhaust gas mixed with water is also dissolved, reacted and absorbed by the concrete in the same manner as when mixed with the concrete. As a result, it is possible to suppress the carbon dioxide in the exhaust gas from being released into the atmosphere.

[0034] FIG. 6 is a diagram schematically showing the configuration of the exhaust gas supply means according to an embodiment of the present invention. In some embodiments, as shown in FIG. 6, the exhaust gas supply means has an ultrasonic nozzle 23 having an ultrasonic vibrator, and supplies the exhaust gas to the supply pipe 17 of water or concrete via the ultrasonic nozzle 23. By using the ultrasonic nozzle 23, the exhaust gas can be supplied in the form of microbubbles, whereby the exhaust gas can be efficiently mixed and reacted with water or concrete.

[0035] FIG. 7 is a diagram schematically showing the configuration of an exhaust gas supply means according to an embodiment of the present invention. In some embodiments, as shown in FIG. 7, the exhaust gas supply means has an ultrasonic nozzle 25 having an ultrasonic vibrator, and supplies exhaust gas to a tank 27 in which water is stored via the ultrasonic nozzle 25. By using the ultrasonic nozzle 25, the exhaust gas can be supplied in the form of microbubbles, whereby the water and the exhaust gas can be efficiently mixed and reacted.

[0036] FIG. 8 is a diagram schematically showing the configuration of an exhaust gas supply means according to still another embodiment of the present invention. In some embodiments, as shown in FIG. 8, the exhaust gas supply means has a high-pressure tank 29 and a spray 31. In this case, water is sprayed into the high-pressure tank 29 filled with exhaust gas and having a pressure higher than the atmospheric pressure via the spray 31 to mix the water and the exhaust gas. By spraying water under a pressure higher than the atmospheric pressure, the water and the exhaust gas can be efficiently mixed and reacted.

[0037] The ready-made pile according to at least one embodiment of the present invention is manufactured using the pile manufacturing method having the above configuration. In this case, the ready-made pile is manufactured using the manufacturing method of the ready-made pile described above, and the concrete absorbs carbon dioxide. The concrete thus absorbed and carbonated carbon dioxide has higher strength than the conventional non-carbonated concrete, and the performance of the ready-made pile is improved. On the other hand, as the raw materials constituting the ready-made pile, for example, the end plate and the reinforcing bar, it is preferable to use those made of stainless steel having high oxidation resistance or those subjected to rust prevention treatment. This is because when the concrete carbonates, the alkalinity of the ready-made pile decreases and the oxidation resistance decreases. As the rust prevention treatment, resin coating such as epoxy or plating treatment such as zinc plating can be used.

[0038] FIG. 9 is a schematic cross-sectional view of a ready-made pile 32 according to an embodiment of the present invention. Referring to Fig. 9, the precast pile 32 is a PC pile, and includes a cylindrical concrete part 33, a PC steel bar 35 passing through the concrete part 33, steel bars (not shown) disposed within the concrete part 33, and end plates (not shown) disposed at both ends of the concrete part 33. The PC steel bar 35 is configured to compress the concrete part 33 via the end plates disposed at both ends of the precast pile 32.

[0039] And the concrete part 33 includes a cylindrical inner peripheral part 33a and a cylindrical outer peripheral part 33b provided so as to surround the inner peripheral part 33a. In the present embodiment, the inner peripheral part 33a is made of concrete containing exhaust gas or carbon dioxide, and the outer peripheral part 33b is made of concrete that does not contain exhaust gas or carbon dioxide, or has a lower carbon dioxide content than the inner peripheral part 33a. That is, in the concrete part 33, the content of exhaust gas or carbon dioxide changes stepwise in the radial direction, and the content of exhaust gas or carbon dioxide is higher on the inner peripheral side than on the outer peripheral side. And the PC steel bar 35 and the steel bars are disposed within the outer peripheral part 33b.

[0040] According to the above configuration, since the PC steel bar 35 and the steel bars are disposed within the outer peripheral part 33b made of concrete having a low content of exhaust gas or carbon dioxide, oxidation of the PC steel bar 35 and the steel bars can be prevented. On the other hand, the inner peripheral part 33a is made of concrete containing exhaust gas or carbon dioxide, and the inner peripheral part 33a is carbonated and has a higher strength than the outer peripheral part 33b. For this reason, even if a bending moment acts on the inner peripheral part 33a, it is difficult to be crushed, and the precast pile 32 has high bending strength. Note that the above-described precast pile 32 can be manufactured by placing concrete in two portions. On the other hand, as shown in Figs. 4 and 5, when curing the formwork 5 or the intermediate body 13 of the precast pile in the exhaust gas, the exhaust gas concentration on the inner peripheral side of the precast pile becomes high. In this case, the exhaust gas concentration changes continuously in the radial direction.

[0041] Finally, the present invention is not limited to the several embodiments described above, and also includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms. For example, the types of ready-made piles 32 are not limited to PC piles, and may be, for example, SC piles (concrete piles with outer shell steel plates), PHC piles (prestressed high-strength concrete piles), PRC piles (prestressed reinforced concrete piles), and the like.

Explanation of Signs

[0042] 1 Mixer 3 Steel bar cage 5 Formwork 7 Curing tank 9 Boiler 11 Autoclave 13 Intermediate body of ready-made pile 15, 19, 20, 21 Pump 17 Supply pipe 23, 25 Ultrasonic nozzle 27 Tank 29 High-pressure tank 31 Spray 32 Ready-made pile 33 Concrete part 33a Inner peripheral part 33b Outer peripheral part 35 PC steel bar

Claims

1. A method for manufacturing a precast pile, comprising: placing a formwork for a pile, in which concrete is compacted into a hollow cylindrical shape through a centrifugal forming process after the concrete is placed, in a steam curing tank, heating the concrete while supplying steam into the steam curing tank, and curing the concrete compacted into the hollow cylindrical shape in the formwork to a predetermined strength; an exhaust gas supply step of supplying an exhaust gas containing carbon dioxide to the concrete compacted into the hollow cylindrical shape in the formwork placed in the steam curing tank, wherein the content of the exhaust gas changes stepwise in the radial direction of the concrete, and the exhaust gas is supplied such that the content of the exhaust gas is higher on the inner peripheral side than on the outer peripheral side. The method for manufacturing a precast pile is characterized by comprising the above steps.

2. A manufacturing apparatus for a precast pile, comprising: a steam curing tank capable of heating a formwork for a pile, in which concrete is compacted into a hollow cylindrical shape through a centrifugal forming process after the concrete is placed, with steam, and curing the concrete compacted into the hollow cylindrical shape in the formwork to a predetermined strength; exhaust gas supply means capable of supplying an exhaust gas containing carbon dioxide to the concrete in the formwork placed in the steam curing tank, wherein the content of the exhaust gas changes stepwise in the radial direction of the concrete, and the exhaust gas can be supplied such that the content of the exhaust gas is higher on the inner peripheral side than on the outer peripheral side. The manufacturing apparatus for a precast pile is characterized by comprising the above means.

3. A precast pile manufactured by using the method for manufacturing a precast pile according to Claim 1, comprising a cylindrical concrete portion composed of the concrete, wherein in the concrete portion, the content of the exhaust gas changes stepwise in the radial direction, and the content of the exhaust gas is higher on the inner peripheral side than on the outer peripheral side. The precast pile is characterized by the above.

4. In a precast pile manufactured by a method for manufacturing a precast pile, comprising: a curing step of placing a formwork for a pile in which concrete is placed in a curing tank and heating the concrete while supplying steam into the curing tank; an exhaust gas supply step of supplying an exhaust gas containing carbon dioxide to the concrete or raw materials of the concrete, the precast pile comprises a cylindrical concrete portion composed of the concrete. In the concrete part, the content of the exhaust gas changes stepwise in the radial direction, and the content of the exhaust gas is higher on the inner peripheral side than on the outer peripheral side. A precast pile characterized by the above.

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