Demolition methods for concrete structures

Abstract

The objective is to efficiently fix carbon dioxide in concrete. [Solution] The concrete structure demolition method involves spraying water and carbon dioxide at the demolition site of the concrete structure 10, either at the demolition section 10R where the concrete structure 10 is demolished, or at the crushing section 20R where the demolished concrete 20 is crushed.

Description

[Technical Field]

[0001] This invention relates to a method for demolition of concrete structures. [Background technology]

[0002] A method is known in which alkaline construction sludge is neutralized using carbon dioxide, and the carbon dioxide is fixed to the construction sludge as calcium carbonate (see, for example, Patent Document 1).

[0003] Furthermore, a method is known for suppressing the generation of alkaline gases within concrete by neutralizing the surface layer of the concrete after it has been poured (see, for example, Patent Document 2).

[0004] Furthermore, a method is known in which carbon dioxide is fixed in waste concrete by contacting it with a carbon dioxide-containing gas (see Patent Document 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-074672 [Patent Document 2] Japanese Patent Publication No. 2010-100454 [Patent Document 3] Japanese Patent Publication No. 2022-126253 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, there has been a growing demand to reduce carbon dioxide emissions, and concrete has the property of fixing carbon dioxide through neutralization. Therefore, there is a need for methods to efficiently fix carbon dioxide in concrete.

[0007] Considering the above facts, the present invention aims to efficiently fix carbon dioxide in concrete. [Means for solving the problem]

[0008] The concrete structure demolition method described in claim 1 involves spraying water and carbon dioxide at the demolition site of the concrete structure, either at the demolition section where the concrete structure is demolished or at the crushing section where the demolished concrete is crushed.

[0009] According to the concrete structure demolition method of claim 1, at the concrete structure demolition site, water and carbon dioxide are sprayed onto the demolition section where the concrete structure is demolished, or onto the crushing section where the demolished concrete is crushed.

[0010] When water comes into contact with concrete, the calcium hydroxide in the concrete dissolves into the water as calcium ions and hydroxide ions. Additionally, carbon dioxide dissolves into the water as hydrogen ions and carbonate ions.

[0011] As a result, the calcium ions from the calcium hydroxide dissolved in the water react with carbonate ions to neutralize the water, forming calcium carbonate, thus fixing carbon dioxide. Therefore, carbon dioxide emissions are reduced.

[0012] Furthermore, in this invention, water and carbon dioxide are sprayed onto the demolished portion of the concrete structure or the crushed portion of the demolished concrete. In other words, in this invention, water and carbon dioxide are sprayed onto the demolished concrete, which has been broken down into smaller pieces, or onto the crushed concrete, which has been further broken down into smaller pieces.

[0013] By reducing the size of the demolished concrete or crushed concrete and increasing its specific surface area, carbon dioxide can be efficiently fixed into the demolished concrete or crushed concrete.

[0014] On the one hand, water in which hydroxide ions elute from calcium hydroxide in concrete becomes highly alkaline. Since such highly alkaline water requires water treatment according to the water quality standards of the discharge destination, etc., wastewater treatment is laborious and energy-consuming.

[0015] In contrast, in the present invention, since hydroxide ions react with hydrogen ions eluted into water from carbon dioxide to form water, the high alkalinity of the water is suppressed. Therefore, the labor and energy for wastewater treatment of the water sprayed on the dismantled part of the concrete structure or the crushed part of the dismantled concrete can be reduced.

[0016] Thus, in the present invention, while efficiently immobilizing carbon dioxide in concrete such as dismantled concrete or crushed concrete, the labor and energy for wastewater treatment of the sprayed water can be reduced.

[0017] The method for dismantling a concrete structure according to claim 2 is the method for dismantling a concrete structure according to claim 1, wherein carbon dioxide-containing water containing carbon dioxide is sprayed on the dismantled part or the crushed part as the water and the carbon dioxide.

[0018] According to the method for dismantling a concrete structure according to claim 2, carbon dioxide-containing water containing carbon dioxide is sprayed on the dismantled part of the concrete structure or the crushed part of the dismantled concrete as water and carbon dioxide.

[0019] Here, in carbon dioxide-containing water, carbon dioxide elutes into water as hydrogen ions and carbonate ions. When this carbon dioxide-containing water is sprayed on concrete, calcium hydroxide in the concrete elutes into the carbon dioxide-containing water as calcium ions and hydroxide ions. As a result, calcium ions become more likely to react with carbonate ions, and hydroxide ions become more likely to react with hydrogen ions.

[0020] Therefore, in the present invention, carbon dioxide can be efficiently fixed in the demolished concrete or crushed concrete compared to the case where water and carbon dioxide are sprayed separately on the demolished part of the concrete structure or the crushed part of the demolished concrete.

[0021] The demolition method of a concrete structure according to claim 3 is the demolition method of a concrete structure according to claim 1 or claim 2, wherein water and carbon dioxide are sprayed on the demolished part or the crushed part as water for suppressing dust scattering.

[0022] According to the demolition method of a concrete structure according to claim 3, water and carbon dioxide are sprayed on the demolished part of the concrete structure or the crushed part of the demolished concrete as water for suppressing dust scattering. Therefore, the dust in the demolished part of the concrete structure or the crushed part of the demolished concrete can be suppressed.

Effect of the Invention

[0023] As described above, according to the present invention, carbon dioxide can be efficiently fixed in concrete.

Brief Description of the Drawings

[0024] [Figure 1] It is a perspective view showing a demolition site of a concrete structure according to an embodiment. [Figure 2] It is a perspective view showing a placement area for demolished concrete at the demolition site of the concrete structure shown in FIG. 1.

Mode for Carrying Out the Invention

[0025] Hereinafter, an embodiment will be described with reference to the drawings.

[0026] (Demolition Site of Concrete Structure) First, the demolition site of the concrete structure will be described.

[0027] Figure 1 shows, as an example, a demolition site of a concrete structure 10 according to this embodiment. The concrete structure 10 is a structure (building) that includes concrete. This concrete structure 10 is, for example, made of reinforced concrete, steel-reinforced concrete, or a mixed structure of reinforced concrete, steel-reinforced concrete, and steel.

[0028] As shown in Figure 1, at the demolition site, the concrete structure 10 is demolished by heavy machinery 12 equipped with, for example, forks, cutters, crushers, etc. The part of the concrete structure 10 that is demolished by the heavy machinery 12 in this way is called the demolished section 10R of the concrete structure 10.

[0029] In the demolition section 10R of the concrete structure 10, dust is scattered due to vibrations during demolition and wind. Therefore, tap water is generally sprayed in the demolition section 10R of the concrete structure 10 using a sprinkler or the like to suppress the scattering of dust.

[0030] Furthermore, as shown in Figure 2, the concrete obtained by demolishing the concrete structure 10 (hereinafter referred to as "demolished concrete 20") is piled up, for example, at a demolition concrete storage area, and crushed (broken into smaller pieces) by the heavy machinery 12 mentioned above. The part of the demolition concrete 20 that is crushed by the heavy machinery 12 in this way is called the crushed section 20R of the demolition concrete 20. The crushed demolition concrete 20 is called crushed concrete 22.

[0031] In the crushed section 20R of the demolished concrete 20, similar to the demolished section 10R of the concrete structure 10 described above, tap water is generally sprayed using a sprinkler or the like to suppress the scattering of dust.

[0032] (Demolition methods for concrete structures) Next, the demolition method for concrete structures according to this embodiment will be described.

[0033] As shown in FIGS. 1 and 2, in the demolition method of the concrete structure according to the present embodiment, at the demolition site of the concrete structure 10, carbon dioxide-containing water 30 is sprayed onto the demolition part 10R that demolishes the concrete structure 10 or the crushing part 20R that crushes the demolished concrete 20, instead of or in addition to tap water.

[0034] The carbon dioxide-containing water 30 is water containing carbon dioxide (carbon dioxide gas), and examples thereof include carbonated water. This carbon dioxide-containing water 30 may be manufactured at the demolition site, or a pre-manufactured one may be brought to the demolition site.

[0035] Note that the carbon dioxide-containing water 30 may contain other gases or solids in addition to carbon dioxide. Also, the concentration of carbon dioxide in the carbon dioxide-containing water 30 can be appropriately changed, but a higher concentration is preferable.

[0036] (Actions and effects) Next, the actions and effects of the present embodiment will be described.

[0037] When the water in the carbon dioxide-containing water 30 touches the concrete, calcium hydroxide (Ca(OH)2) in the concrete elutes into the water as calcium ions (Ca 2― , 2― , 2+ , + ), and hydroxide ions (2OH ― ) (Ca(OH)2 = Ca 2+ + 2OH ― ).

[0038] Also, carbon dioxide (CO2) in the carbon dioxide-containing water 30 elutes into the water as hydrogen ions (2H + ) and carbonate ions (CO3 2― ) (CO2 + H2O = 2H + + CO3 2― ). As a result, the calcium ions of the calcium hydroxide eluted into the water react with the carbonate ions and are neutralized to form calcium carbonate (Ca 2+ + CO3 2― = CaCO3), and the carbon dioxide is fixed. Therefore, the amount of carbon dioxide emissions is reduced.

[0039] Furthermore, in this embodiment, as described above, carbon dioxide-containing water 30 is sprayed onto the demolition section 10R of the concrete structure 10, or the crushed section 20R of the demolished concrete 20. In other words, in this embodiment, the concrete structure 10 is demolished, and carbon dioxide-containing water 30 is sprayed onto the smaller demolished concrete 20, or the demolished concrete 20 is crushed, and the crushed concrete 22 is made even smaller.

[0040] By reducing the size of the demolition concrete 20 or crushed concrete 22 and increasing its specific surface area, carbon dioxide can be efficiently fixed into the demolition concrete 20 or crushed concrete 22.

[0041] On the other hand, hydroxide ions (2OH) are released from calcium hydroxide in concrete. ― Water from which (Ca(OH)2=Ca2) has dissolved becomes highly alkaline. + +2OH ― Such highly alkaline water requires water treatment (e.g., pH treatment) in accordance with the water quality standards of the discharge destination, which means that wastewater treatment is time-consuming and energy-intensive.

[0042] In contrast, in this embodiment, hydroxide ions (2OH ― ) is hydrogen ions (2H) that have leached from carbon dioxide into water. + (2OH) reacts with water to form water. ― +2H + (=2H2O), the high alkalinity of the water is suppressed. Therefore, the effort and energy required for draining the water sprayed on the demolition section 10R of the concrete structure 10, or the crushed section 20R of the demolished concrete 20, can be reduced.

[0043] In this embodiment, carbon dioxide can be efficiently fixed into concrete such as demolition concrete 20 and crushed concrete 22, while reducing the effort and energy required for wastewater treatment of the sprayed carbon dioxide-containing water 30.

[0044] Furthermore, as mentioned above, in carbon dioxide-containing water 30, carbon dioxide dissolves into the water as hydrogen ions and carbonate ions. When this carbon dioxide-containing water 30 is sprayed onto concrete, the calcium hydroxide in the concrete dissolves into the carbon dioxide-containing water 30 as calcium ions and hydroxide ions. As a result, calcium ions become more readily reactive with carbonate ions, and hydroxide ions become more readily reactive with hydrogen ions.

[0045] Therefore, in this embodiment, carbon dioxide can be efficiently fixed to concrete such as the demolished concrete 20 or crushed concrete 22, compared to the case where water and carbon dioxide are separately sprayed onto the demolished section 10R of the concrete structure 10 or the crushed section 20R of the demolished concrete 20.

[0046] Furthermore, in this embodiment, carbon dioxide-containing water 30 is sprayed onto the demolition section 10R of the concrete structure 10 or the crushing section 20R of the demolished concrete 20. This suppresses the scattering of dust in the demolition section 10R of the concrete structure 10 or the crushing section 20R of the demolished concrete 20.

[0047] In other words, in this embodiment, carbon dioxide-containing water 30 is sprayed as scattering suppression water onto the demolition section 10R of the concrete structure 10, or the crushed section 20R of the demolished concrete 20.

[0048] Therefore, in this embodiment, carbon dioxide can be fixed into concrete such as the demolished concrete 20 and crushed concrete 22 while suppressing dust in the demolished section 10R of the concrete structure 10 or the crushed section 20R of the demolished concrete 20.

[0049] (modified version) Next, a modified example of the above embodiment will be described.

[0050] In the above embodiment, carbon dioxide-containing water 30 was sprayed onto the demolition section 10R of the concrete structure 10 or the crushing section 20R of the demolished concrete 20. However, the demolition section 10R of the concrete structure 10 or the crushing section 20R of the demolished concrete 20 may be sprayed with carbon dioxide-containing water 30, or, for example, carbon dioxide (carbonic acid gas) and water separately. In this case, for example, a sprayer that sprays water and carbon dioxide (carbonic acid gas) simultaneously may be used.

[0051] Furthermore, in the above embodiment, carbon dioxide-containing water 30 was sprayed as dust dispersion suppression water onto the demolition section 10R of the concrete structure 10 or the crushing section 20R of the demolished concrete 20. However, the carbon dioxide-containing water 30 does not necessarily have to be sprayed as dust dispersion suppression water; it may also be sprayed for the purpose of fixing carbon dioxide to the concrete.

[0052] Although one embodiment of the present invention has been described above, the present invention is not limited to these embodiments, and various modifications may be used in appropriate combinations with one embodiment, and of course, the invention can be implemented in various forms without departing from the spirit of the present invention. [Explanation of Symbols]

[0053] 10 Concrete structures 10R Demolition Department 20 Demolition concrete 20R Crushing section 30 Carbon dioxide containing water

Claims

1. In a concrete structure demolition site, water and carbon dioxide are sprayed onto the demolition section where the concrete structure is demolished, or onto the crushing section where the demolished concrete is crushed. A method for demolishing concrete structures.

2. The dismantling section or the crushing section is sprayed with water and carbon dioxide-containing water, which contains carbon dioxide. The demolition method for concrete structures according to claim 1.

3. The water and carbon dioxide are sprayed on the dismantling section or the crushing section as a dust dispersion suppression solution. A method for demolishing a concrete structure according to claim 1 or claim 2.

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