How construction materials are manufactured

Abstract

To provide a manufacturing method of a construction material capable of solidifying carbon dioxide in a short time.SOLUTION: A method of manufacturing a construction material is a method of manufacturing a construction material containing cement. The manufacturing method of the construction material comprises a carbonation step S11 for applying a carbonation treatment to an alkaline solid containing calcium, and a kneading step S12 for kneading the mixture containing at least the carbonated alkaline solid material and the cement.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a construction material. [Background technology]

[0002] Materials containing cement are known as construction materials. During the production of cement, a large amount of carbon dioxide (CO2) is emitted. As a method for reducing the amount of carbon dioxide emitted during the production of construction materials, a technique for fixing carbon dioxide in hardened concrete is known. Patent Document 1 describes a carbonation curing method for densifying the surface layer of a concrete structure by bringing carbon dioxide into contact with concrete. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-054806 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, a long curing period is required to fix the carbon dioxide in the hardened concrete.

[0005] The present disclosure has been made in consideration of the above problems, and has an object to provide a manufacturing method for a construction material capable of fixing carbon dioxide in a short period of time. [Means for solving the problem]

[0006] In order to achieve the above object, a manufacturing method for a construction material according to one embodiment of the present disclosure is a manufacturing method for a construction material containing cement, and includes a carbonation step of subjecting an alkaline solid material containing calcium to a carbonation treatment, and a kneading step of kneading a mixture containing at least the carbonated alkaline solid material and cement.

[0007] In a preferred embodiment of the method for producing a construction material, the alkaline solid is an incineration residue.

[0008] In a preferred embodiment of the method for producing a construction material, the alkaline solid is a cement solidified material or lime-improved soil.

[0009] In a preferred embodiment of the method for producing a construction material, the alkaline solid is coal ash.

[0010] In a preferred embodiment of the method for producing a construction material, the alkaline solid is incineration ash.

[0011] In a preferred embodiment of the method for producing a construction material, the method includes a separation step of separating the incineration ash into large particle size ash and small particle size ash having a smaller maximum particle size than the large particle size ash, and the alkaline solid material is the small particle size ash.

[0012] In a preferred embodiment of the method for producing a construction material, in the carbonation step, the small particle size ash is carbonated in a portable container.

[0013] In a preferred embodiment of the method for producing a construction material, the small particle ash has a particle size of 5 mm or less. Effect of the Invention

[0014] According to the manufacturing method of the construction material of the present disclosure, carbon dioxide can be fixed in a short period of time. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a flow chart showing a method for manufacturing a construction material according to a first embodiment. [Diagram 2] FIG. 2 is a flow chart showing a method for manufacturing a construction material according to the second embodiment. [Diagram 3] Figure 3 is a schematic diagram of the experimental equipment used to examine the inorganic carbon concentration in carbonated incineration ash. [Figure 4]FIG. 4 is a graph showing the inorganic carbon concentration contained in carbonated incineration ash. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the form for carrying out the present invention (hereinafter, referred to as the embodiment). Furthermore, the components in the following embodiment include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiment can be appropriately combined.

[0017] (First embodiment) FIG. 1 is a flow chart showing a manufacturing method of a construction material according to a first embodiment. The manufacturing method of a construction material according to the first embodiment is a manufacturing method of a construction material containing cement. The construction material containing cement is, for example, concrete, mortar, paste, bricks, etc. According to the manufacturing method of a construction material according to the first embodiment, carbon dioxide (CO2) can be fixed in the construction material containing cement.

[0018] In the following, a case where the construction material containing cement is concrete will be described. As shown in Fig. 1, the manufacturing method of the construction material of the first embodiment includes a carbonation step S11, a first kneading step S12, and a second kneading step S13.

[0019] The carbonation step S11 is a step of subjecting an alkaline solid material containing calcium to a carbonation treatment. The alkaline solid material is a cement solidified material or an incineration residue. The alkaline solid material may also be soil mixed with lime (also called lime-improved soil). In the following, an incineration residue is used as the alkaline solid material for explanation. The incineration residue is, for example, coal ash discharged from a coal-fired power plant. Coal ash is ash collected by a dust collector installed downstream of a boiler in a coal-fired power plant. Coal ash is also called fly ash. According to an analysis using an X-ray diffraction method, an example of coal ash contains silicon dioxide (SiO2), aluminum oxide (Al2O3), iron oxide (FE2O3), calcium oxide (CaO), and magnesium oxide (MgO).

[0020] The carbonation process in the carbonation step S11 is a process in which the incineration residue is brought into contact with carbon dioxide gas (carbon dioxide (CO2) gas). For example, the carbon dioxide gas used in the carbonation step S11 is, for example, carbon dioxide gas discharged from a coal-fired power plant. In the carbonation step S11, the incineration residue is placed in a container (carbonation process tank). The container is, for example, a portable container having a substantially rectangular parallelepiped shape. The portable container can be placed on, for example, the bed of a vehicle. The container has a partition wall that divides the internal space vertically. The partition wall is a plate-shaped member parallel to the bottom surface of the container and has multiple vents. The incineration residue is placed on the partition wall. With the incineration residue placed on the partition wall, carbon dioxide gas is introduced into the space below the partition wall. The carbon dioxide gas comes into contact with the mixture through the vents in the partition wall. The incineration residue is carbonated by absorbing the carbon dioxide gas. Specifically, calcium components such as calcium oxide contained in the incineration residue are carbonated to generate calcium carbonate (CaCO3). Carbon dioxide is absorbed into the incineration residue by the carbonation step S11. Carbon dioxide is fixed in the incineration residue as carbonate. In addition, heavy metals such as lead (Pb) contained in the incineration residue become less soluble by the carbonation step S11.

[0021] The first kneading step S12 is a step of kneading a mixture containing carbonated incineration residue, cement, fine aggregate, and coarse aggregate. The first kneading step S12 is also called dry kneading. In the first kneading step S12, a part of the cement or fine aggregate is replaced with the incineration residue. The amount of cement or fine aggregate decreases by the amount of the incineration residue used. In the first kneading step S12, the incineration residue, cement, fine aggregate, and coarse aggregate are each weighed and then put into a mixer. The mixture put into the mixer is kneaded for, for example, 30 seconds or more.

[0022] The second mixing step S13 is a step of mixing the mixture mixed in the first mixing step S12, water, and admixtures. The second mixing step S13 is also called the main mixing. The admixtures are chemicals for adjusting the air content and fluidity of the concrete. In the second mixing step S13, the water and admixtures are each weighed and then poured into the mixer containing the mixture. The mixture, water, and admixtures are mixed for, for example, 90 seconds or more.

[0023] After the second kneading process S13, the manufactured construction material is discharged from the mixer. The construction material is then transported to the construction site by a vehicle or the like and cast into a formwork. The construction material hardens at the construction site and becomes a construction structural material or the like.

[0024] The incineration residue does not necessarily have to be coal ash. The incineration residue may be, for example, general waste, industrial waste, biomass, coal, incineration ash discharged from a waste incineration plant, etc. More specifically, the incineration ash is, for example, the main ash or fly ash of RPF (Refuse Paper and Plastic Fuel). According to an analysis using an X-ray diffraction method, an example of the incineration ash is calcite (CaCO3), gehlenite (Ca2(Mg 0.25 Al 0.75 )(Si 1.25 AL 0.75Other examples of incineration ashes, based on analysis using X-ray diffraction techniques, include calcite (CaCO3), portlandite (Ca(OH)2), hematite (Fe2O3), quicklime (CaO), quartz (SiO2), and anorthite ((Ca,Na)(Si,Al)4O8).

[0025] The carbon dioxide gas used in the carbonation step S11 does not necessarily have to be carbon dioxide gas discharged from a coal-fired power plant. The carbon dioxide gas may be, for example, carbon dioxide gas discharged from a factory such as a cement manufacturing plant, a chemical plant, an incineration facility, etc. The carbon dioxide gas may be gas generated for use in the carbonation step S11.

[0026] In the first kneading step S12, the mixture does not necessarily contain fine aggregate and coarse aggregate. For example, when the construction material is mortar, the mixture in the first kneading step S12 does not contain coarse aggregate. Also, when the construction material is paste, the mixture in the first kneading step S12 does not contain coarse aggregate and fine aggregate.

[0027] When the construction material is concrete, in the first kneading step S12, as described above, a mixture containing carbonated incineration residue, cement, fine aggregate, and coarse aggregate is kneaded. In other words, in the first kneading step S12, a part of the cement and fine aggregate is replaced with the carbonated incineration residue. For example, by replacing a part of the cement with the carbonated incineration residue, the amount of cement used can be reduced. This makes it possible to suppress the amount of carbon dioxide generated during the production of cement.

[0028] As described above, the manufacturing method of the construction material of the first embodiment is a manufacturing method of a construction material containing cement. The manufacturing method of the construction material of the first embodiment includes a carbonation step S11 in which an alkaline solid containing calcium is carbonated, and a kneading step (first kneading step S12) in which a mixture containing at least the carbonated alkaline solid and cement is kneaded.

[0029] In order to suppress global warming, it is desirable to suppress the emission of carbon dioxide (CO2) during the manufacture of construction materials. A large amount of carbon dioxide (CO2) is generated during the manufacture of cement. Therefore, one method of suppressing the emission of carbon dioxide (CO2) is to reduce the amount of cement used. For example, it is possible to reduce the amount of cement used by replacing cement with other admixtures. However, even if this method is used, there is a limit to the reduction in the amount of carbon dioxide emission. In response to this, as in the above-mentioned Patent Document 1, a technique for fixing carbon dioxide in hardened concrete is known. This makes it possible to further reduce the amount of carbon dioxide emission. However, in this method, carbon dioxide enters from the surface layer of the hardened concrete mass, and carbonation progresses gradually. A curing period is required to carbonate all of the concrete mass. Therefore, it takes a long time to fix carbon dioxide in the hardened concrete. In addition, there is a limit to the size of a tank that can accommodate a concrete mass, so carbon dioxide cannot be fixed in any concrete mass.

[0030] In contrast, in the manufacturing method of the construction material of the first embodiment, the alkaline solid is carbonated in the carbonation step S11. The alkaline solid containing calcium absorbs carbon dioxide. The alkaline solid that has absorbed carbon dioxide is mixed with cement to form a construction material, and carbon dioxide is fixed in the construction material. Since the alkaline solid is carbonated in the carbonation step S11, carbonation proceeds more quickly compared to the case in which carbon dioxide is brought into contact with hardened concrete as in Patent Document 1. Therefore, the manufacturing method of the construction material of the first embodiment can fix carbon dioxide in a short time. In addition, since the alkaline solid that has absorbed carbon dioxide is mixed with cement and then the construction material is formed, carbon dioxide can be fixed in the construction material regardless of the size of the construction material.

[0031] In the manufacturing method of the construction material of the first embodiment, the alkaline solid is an incineration residue.

[0032] Carbonation of the incineration residue in the carbonation step S11 allows the carbonation to proceed more quickly. Furthermore, heavy metals such as lead (Pb) contained in the incineration residue become less soluble in the carbonation step S11. Therefore, the manufacturing method of the construction material of the first embodiment can suppress the elution of heavy metals contained in the incineration residue.

[0033] In the manufacturing method of the construction material of the first embodiment, the alkaline solid is a cement solidified material or lime-improved soil.

[0034] By carbonating the cement solidified material or lime-improved soil in the carbonation step S11, the carbonation progresses more quickly.

[0035] In the manufacturing method of the construction material of the first embodiment, the alkaline solid is coal ash.

[0036] It is desirable for construction materials containing cement to have high workability. In addition, in order to increase the amount of carbon dioxide to be fixed, it is desirable to increase the proportion of alkaline solids in the mixture in the first kneading step S12. However, if the proportion of alkaline solids in the mixture is increased, the workability of the construction material may decrease. In contrast, when coal ash is used as the alkaline solid, the coal ash has a spherical particle size, so the workability of the construction material is likely to improve. Therefore, even if the amount of alkaline solids in the mixture is increased, the decrease in the workability of the construction material is suppressed. Therefore, the manufacturing method for the construction material of the first embodiment can achieve both the fixation of a large amount of carbon dioxide and the improvement of the workability of the construction material.

[0037] Second embodiment Fig. 2 is a flow chart showing a method for producing a construction material according to the second embodiment. As shown in Fig. 2, the method for producing a construction material according to the second embodiment includes a separation step S21, a carbonation step S22, a first kneading step S23, and a second kneading step S24. In the method for producing a construction material according to the second embodiment, the alkaline solid is an incineration residue, more specifically, an incineration ash.

[0038] The separation step S21 is a step of separating the incineration ash as the incineration residue into large-sized ash and small-sized ash. The incineration ash is ash discharged from an incineration facility. The incineration ash includes incineration bottom ash and incineration fly ash. The incineration bottom ash is the cinders discharged from the bottom of the incineration furnace when waste is incinerated in the incinerator. The incineration fly ash is soot that rises with the combustion gas. For example, the incineration ash used in the separation step S21 is incineration bottom ash. The maximum particle size of the small-sized ash is smaller than the minimum particle size of the large-sized ash. In other words, the small-sized ash is the group with the smaller maximum particle size of the two groups into which the incineration ash is divided. For example, the particle size of the small-sized ash is 5 mm or less. More specifically, the incineration ash that passes through a mesh with a mesh size of 5 mm is the small-sized ash. The incineration ash that does not pass through a mesh with a mesh size of 5 mm is the large-sized ash. The particle size of the small-sized ash does not necessarily have to be 5 mm or less, and is not particularly limited. The incineration ash is separated into large and small particle ash by, for example, a sieve. The incineration ash may also be separated into large and small particle ash by washing with water.

[0039] The carbonation process in the carbonation step S22 is a process in which the small ash is exposed to carbon dioxide gas (carbon dioxide (CO2) gas). In the carbonation step S22, the small ash is placed in a vessel (carbonation process tank). The vessel is, for example, a portable container. Water is added to the vessel so that the moisture content of the small ash is 10% or more and 20% or less. Carbon dioxide gas is then introduced into the vessel. Calcium components such as calcium oxide contained in the small ash are carbonated to produce calcium carbonate (CaCO3). Carbon dioxide is absorbed by the small ash in the carbonation step S22. Carbon dioxide is fixed in the small ash as carbonate salts. Furthermore, heavy metals such as lead (Pb) contained in the small ash become less soluble in the carbonation step S22.

[0040] The first kneading step S23 is a step of kneading a mixture containing carbonated small-particle ash, cement, fine aggregate, and coarse aggregate. The first kneading step S23 is also called dry kneading. In the first kneading step S23, a part of the cement or fine aggregate is replaced with small-particle ash. The amount of cement or fine aggregate decreases by the amount of small-particle ash used. In the first kneading step S23, the small-particle ash, cement, fine aggregate, and coarse aggregate are each weighed and then charged into a mixer. The mixture charged into the mixer is kneaded for, for example, 30 seconds or more.

[0041] The second kneading step S24 is a step of kneading the mixture kneaded in the first kneading step S23, water, and admixtures. The second kneading step S24 is also called the main kneading. In the second kneading step S24, the water and admixtures are each weighed and then added to the mixer containing the mixture. The mixture, water, and admixtures are kneaded for, for example, 90 seconds or more.

[0042] An experiment was conducted to investigate how much carbon dioxide can be fixed when incineration ash is carbonated. Specifically, the inorganic carbon concentration contained in the carbonated incineration ash was measured in the experiment. Figure 3 is a schematic diagram of the experimental equipment used to investigate the inorganic carbon concentration contained in the carbonated incineration ash. Figure 4 is a graph showing the inorganic carbon concentration contained in the carbonated incineration ash.

[0043] As shown in FIG. 3, the experimental equipment 90 includes a CO2 cylinder 91, a pressure regulator 92, a flowmeter 93, a drainage material 94, and a resin mesh 95. The experimental equipment 90 is also called a column test device. Carbon dioxide gas stored in the CO2 cylinder 91 passes through the pressure regulator 92, the flowmeter 93, the drainage material 94, and the resin mesh 95 and is introduced into the lower end of a container 96. The container 96 is cylindrical and is made of a resin such as polyvinyl chloride (PVC). The diameter of the container 96 is 104 mm. The height of the container 96 is 400 mm. The container 96 is filled with incineration bottom ash 97. Of the incineration bottom ash 97, the lower 1 / 3 of the container 96 is the lower layer, the upper 1 / 3 of the container 96 is the upper layer, and the portion between the lower layer and the upper layer is the middle layer. By introducing carbon dioxide gas from the lower end of the container 96, the incineration bottom ash 97 in the container 96 comes into contact with the carbon dioxide gas. After bubbling carbon dioxide gas into the vessel 96 for a predetermined period of time, inorganic carbon (IC) concentrations were measured for samples taken from each of the top, middle, and bottom layers.

[0044] The above-mentioned experiment was carried out on incineration bottom ash A and incineration bottom ash B collected from different incineration facilities. As shown in FIG. 7, the inorganic carbon concentration of carbonated incineration bottom ash is higher than that of untreated incineration bottom ash. In other words, the carbonated incineration bottom ash contains more carbon than the untreated incineration bottom ash. In this way, by carbonating the incineration bottom ash, a large amount of carbon dioxide can be fixed in the incineration bottom ash.

[0045] The above-mentioned experiment is an example of an experiment to investigate how much carbon dioxide can be fixed by carbonating an alkaline solid material containing calcium. The incineration bottom ash used in the experiment is merely one example of an alkaline solid material. Even when a similar experiment is performed using an alkaline solid material containing calcium other than incineration bottom ash, the carbonated alkaline solid material contains more carbon than the untreated alkaline solid material.

[0046] In the manufacturing method of the construction material of the second embodiment, when the incineration ash used in the separation step S21 contains moisture, the incineration ash is dried before the separation step S21. For example, the incineration ash is dried using exhaust heat from an incineration facility.

[0047] In addition, the manufacturing method of the construction material of the second embodiment may include an agitation washing step and a dehydration step instead of the separation step S21 when the incineration ash as an alkaline solid contains moisture. The agitation washing step is a step of agitating and washing the incineration ash (e.g., incineration bottom ash) in a cooling tank or a washing tank. The dehydration step is a step of producing dehydrated sludge by dehydrating the slurry-like incineration ash that has been subjected to the agitation washing step with a filter press machine. Thereafter, in the carbonation step S22, the dehydrated sludge as an alkaline solid is carbonated. Then, through the first kneading step S23 and the second kneading step S24, the construction material is manufactured.

[0048] The incineration ash separated into large and small particle ash in the separation step S21 does not necessarily have to be incineration bottom ash. The incineration ash separated into large and small particle ash in the separation step S21 may be incineration fly ash or a mixture of incineration bottom ash and incineration fly ash.

[0049] In addition, the manufacturing method of the construction material of the second embodiment may include a fly ash kneading step of kneading the small particle ash of the incineration bottom ash with the incineration fly ash after the separation step S21 and before the carbonation step S22. After the fly ash kneading step, the mixture of the small particle ash and the incineration fly ash is carbonated in the carbonation step S22. This can suppress the elution of heavy metals contained in the incineration fly ash.

[0050] As described above, in the manufacturing method for a construction material of the second embodiment, the alkaline solid is incineration ash.

[0051] By using incineration ash as the alkaline solid material, the surface area of ​​the alkaline solid material to be carbonated in the carbonation step S22 is increased. Therefore, the carbonation of the alkaline solid material is further promoted. Therefore, the manufacturing method of the construction material of the second embodiment can fix carbon dioxide in a short time. In addition, since incineration ash is generated in large quantities in incineration facilities, it can be easily procured. Therefore, the cost spent on procuring the alkaline solid material can be reduced.

[0052] The manufacturing method of the construction material of the second embodiment includes a separation step S21 in which the incineration ash is separated into large particle size ash and small particle size ash having a smaller maximum particle size than the large particle size ash. The alkaline solid matter is the small particle size ash.

[0053] By using small particle size ash as the alkaline solid, the surface area of ​​the alkaline solid to be carbonated in the carbonation step S22 is increased. Therefore, the carbonation of the alkaline solid is further promoted. Therefore, the manufacturing method of the construction material of the second embodiment can fix carbon dioxide in a short time. Furthermore, small particle size ash contains more heavy metals than large particle size ash. Since the heavy metals contained in the small particle size ash of the incineration ash are fixed in the construction material, the heavy metals contained in the large particle size ash are reduced. Therefore, the recycling of the incineration ash (large particle size ash) becomes easier. The incineration ash (large particle size ash) is recycled, for example, as a raw material for cement or a civil engineering material.

[0054] As described above, in the manufacturing method for a construction material according to the second embodiment, in the carbonation step S22, the small particle size ash is carbonated in a portable container.

[0055] This allows small-sized ash to be carbonated near the incineration facility, and therefore the method for producing a construction material according to the second embodiment allows alkaline solids to be carbonated more efficiently.

[0056] In the method for producing a construction material of the second embodiment, the small particle size ash has a particle size of 5 mm or less.

[0057] By using small particle size ash having a particle size of 5 mm or less as the alkaline solid matter, the surface area of ​​the alkaline solid matter to be carbonated in the carbonation step S22 becomes larger. Therefore, the carbonation of the alkaline solid matter is further promoted. Therefore, the manufacturing method of the construction material of the second embodiment can fix carbon dioxide in a shorter time. [Explanation of symbols]

[0058] 90 Laboratory Equipment 91 CO2 Cylinder 92 Pressure Regulator 93 Flow meter 94 Drainage material 95 Resin Net 96 Container 97 Bottom ash from incineration S11 Carbonation process S12 1st kneading process S13 2nd kneading process S21 Separation process S22 Carbonation process S23 1st kneading process S24 2nd kneading process

Claims

[Claim 1] A method for producing a cement-containing construction material, comprising the steps of: A carbonation step of subjecting incineration residue containing calcium, which is either coal ash or incineration ash, to a carbonation treatment without adding water; A first kneading process in which a mixture containing at least the carbonated incineration residue and cement is kneaded by dry kneading after the carbonation process; After the first kneading step, a second kneading step of kneading the mixture kneaded in the first kneading step, water, and an admixture in a main kneading step; A manufacturing method of a construction material comprising the steps of:

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