Base material and method for adsorbing and fixing carbon dioxide using base material

Abstract

To provide a base material and a method for adsorbing and fixing carbon dioxide using the base material which can semi-permanently adsorb and fix carbon dioxide onto the base material in the soil without using any thermal energy at all and solely through natural forces.SOLUTION: A base material 10 buried in the soil and used as a filler or backfill material to prevent clogging, the base material comprising a hard aggregate body 20, a wet coating layer 30 that coats the surface of the aggregate body 20 and is configured by a naturally derived wetting substance 31 having a function of adsorbing and fixing carbon dioxide, a function of capturing SS substances and an acidic functional group having at least a pH buffering action, and an adhesion promoting agent 32 exhibiting viscosity when wet and causing the wetting substance 31 to adhere to the surface of the aggregate body 20, and recycled concrete fine powder 33 that is adhered to the surface of the aggregate body 20 or the wet coating layer 30 and is a carrier for carbon dioxide.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide (CO2) adsorption technology using a base material that can be applied to sidewalks, parks, squares, roadways, etc., and in particular to a base material and a method for adsorbing and fixing carbon dioxide using the base material that can adsorb and fix carbon dioxide over a long period of time while maintaining a good vegetation environment. [Background technology]

[0002] As one of the recent countermeasures against global warming, it is known to adsorb carbon dioxide in the air onto various carriers as follows, with the aim of reducing carbon dioxide emissions.

[0003] (1) Biochar carrier Non-Patent Document 1 proposes that biochar produced by carbonizing trees at low temperatures be buried in the soil as a soil conditioner to fix carbon dioxide semi-permanently.

[0004] (2) Limestone carrier Non-Patent Document 2 proposes a system in which limestone is heated in a kiln to decompose it into calcium oxide and carbon dioxide, and the resulting calcium oxide is spread on a tray to adsorb carbon dioxide from the atmosphere.

[0005] On the other hand, it is known to reuse aggregate extracted from crushed waste concrete as recycled aggregate. If recycled aggregate with a large amount of concrete components attached to its surface is used as aggregate in a concrete structure, it can cause a decrease in strength, so it is necessary to remove as much of the concrete attached as possible. Patent Document 1 discloses that recycled aggregate raw material heated to 100° C. or higher is agitated and polished in a dry mixer to remove deposits on concrete.

[0006] Furthermore, high-quality natural aggregates such as crushed stone are used as base materials for the base directly under the sidewalk or for the vegetation base when constructing tree belts adjacent to sidewalks or roads (Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0007] [Non-Patent Document 1] https: / / jp-gx.com / credits / nT1pyXum [Non-patent document 2] https: / / www.orix.co.jp / grp / move_on / entry / 2022 / 07 / 13 / 100000 [Patent Document 1] Japanese Patent Publication No. 2023-182463 [Patent Document 2] Registered Utility Model No. 3065278 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-133458 Summary of the Invention [Problem to be solved by the invention]

[0008] Conventional techniques for immobilizing carbon dioxide by adsorbing it onto various carriers have the following problems. <1> The carbon dioxide fixation technology described in Non-Patent Document 1 is a match-and-pump technique because it emits a large amount of carbon dioxide when carbonizing the wood that serves as the carrier. <2> The carbon dioxide fixation technology described in Non-Patent Document 2 is also a match-and-pump technique, as it already emits a large amount of carbon dioxide during the heating stage, just like the cement manufacturing process. <3> Conventionally, a large amount of thermal energy is consumed when producing various carriers, which increases the production costs of the carriers. <4> In order to adsorb carbon dioxide onto the carrier, carbon dioxide must be continuously and forcibly supplied to the carrier, which increases the cost of carbon dioxide absorption.

[0009] Conventional techniques for using recycled aggregate or natural aggregate have the following problems. <1> It is technically difficult to completely remove the concrete components adhering to the surface of recycled aggregate, and trace amounts of concrete adhering to the surface of the recycled aggregate remain. Because the deposits on concrete are strongly alkaline, the use of recycled aggregate is limited to concrete aggregate, and new uses for recycled aggregate are desired. <2> Although the technology for crushing waste concrete and recovering recycled aggregate has been established, there has been no progress in recycling the fine concrete powder (concrete filler) generated during the production of recycled aggregate, and there is a need to propose new uses for the fine concrete powder.

[0010] The present invention has been made in view of the above points, and its object is to provide a base material and a method for adsorbing and fixing carbon dioxide using the base material, which can adsorb and fix carbon dioxide semi-permanently to the base material in the soil using only natural forces, without using any thermal energy whatsoever. [Means for solving the problem]

[0011] The present invention provides a base material that is buried in the soil and used as a filler or backfill material to prevent clogging, and that comprises a hard aggregate body, a wet coating layer that covers the surface of the aggregate body and is composed of a naturally occurring moist substance having an acidic functional group that has at least the function of capturing SS substances and a pH buffering action, and an adhesion aid that becomes viscous when wet and adheres the moist substance to the surface of the aggregate body, and recycled concrete fine powder that serves as a carbon dioxide carrier and is attached to the surface of the aggregate body or the wet coating layer. In another embodiment of the present invention, the recycled fine powder is untreated fine powder made from waste concrete. In another embodiment of the present invention, the recycled fine powder is adhered to the surface of the aggregate body or the wet coating layer by utilizing the wettability of the adhesion aid. In another embodiment of the invention, the moist material is allophane or humus. In another embodiment of the present invention, the adhesion aid is at least one of water, a highly water-absorbent resin, a polymeric absorbent, a vinyl acetate resin, and polyvinyl alcohol. In another embodiment of the present invention, the aggregate body is a recycled aggregate of single grain size produced from waste concrete material. In another embodiment of the present invention, the composition is used as a permeable base layer in a permeable roadbed structure. Furthermore, the present invention provides a method for adsorbing and fixing carbon dioxide using a base material, in which the base material described in claim 1 is buried in the soil as a filler or backfill material for preventing clogging, and when rainwater seeps into the soil, the concrete components of the base material react with the carbon dioxide contained in the rainwater as carbon dioxide to produce calcium carbonate, and the carbon dioxide is adsorbed and fixed on the surface of the base material in the form of calcium carbonate. [Effects of the Invention]

[0012] The present invention has at least one of the following advantages. <1> In the present invention, by attaching recycled fine powder to the base material, the base material that is buried in the soil and used as a filler or backfill material to prevent clogging can also be used as a carbon dioxide carrier. In particular, not only can carbon dioxide be efficiently adsorbed onto a base material buried in the soil without using any thermal energy, but the adsorbed carbon dioxide can also be effectively fixed (retained). <2> The present invention utilizes the natural phenomenon of atmospheric carbon dioxide being naturally absorbed into rainwater and the natural phenomenon of rainwater seeping into the soil under its own weight to cause a carbonation phenomenon in the soil due to a reaction between carbon dioxide and concrete components, thereby causing the carbon dioxide to be adsorbed and fixed in the base material. Therefore, the function of adsorbing and fixing carbon dioxide in the soil can be maintained semi-permanently. <3> In the present invention, recycled aggregate made from waste concrete is used for the aggregate body, which is a constituent material of the base material, and by using fine powder made from waste concrete that had been treated as industrial waste as the recycled fine powder, it is possible to make even more effective use of industrial waste. <4> In the present invention, the aggregate itself and recycled fine powder are used as they are without heat treatment, so that a base material that also acts as a carbon dioxide carrier is produced, eliminating the problems of mass consumption of fossil fuels and the generation of carbon dioxide due to heating. <5> Even if the base material contains concrete components, the naturally occurring moist substances contained in the wet coating layer act as a pH buffer, so the pH of the base material can be kept low. Therefore, even if vegetation or plants are grown on a permeable roadbed structure to which a base material is applied, the alkalinity caused by the concrete components can be alleviated, and the deterioration of the vegetation environment can be improved. <6> By using the base material as a filler or backfill material to prevent clogging, it is possible to not only achieve the single effect of increasing the amount of carbon dioxide adsorption, but also to make a significant contribution to the development of green infrastructure, such as by creating a landscape and improving the microclimate. [Brief explanation of the drawings]

[0013] [Figure 1] Model diagram of permeable roadbed structure using base material [Figure 2] An explanatory diagram of the manufacturing method of the base material. (a) is an explanatory diagram of the process of covering the surface of the aggregate body with a wet coating layer, and (b) is an explanatory diagram of the process of attaching recycled fine powder to the surface of the aggregate body and the wet coating layer. [Figure 3] Model of aggregate body with wet coating layer on the surface [Figure 4] Model diagram of a base material manufactured by adhering recycled fine powder to the surface DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below with reference to the drawings.

[0015] 1. Permeable roadbed structure <1> Overview of permeable roadbed structure A water-permeable roadbed structure to which the base material 10 illustrated in FIG. 1 is applied will be described. The permeable roadbed structure in this example is a structure stacked with a permeable base layer 41 mainly composed of base material 10 laid on a roadbed 40, a permeable roadbed layer 42 laid on the permeable base layer 41, and a permeable pavement layer 43 laid on the permeable roadbed layer 42. The base material 10 constituting the water-permeable base layer 41 will be described in detail later.

[0016] <2> Permeable base layer, permeable roadbed layer The permeable base layer 41 and the permeable roadbed layer 42 as a whole have continuous pores that allow water to move by capillary rise. The permeable base layer 41 also functions as a rainwater storage and infiltration facility. The thickness of the permeable base layer 41 and the permeable roadbed layer 42 is selected appropriately depending on the site conditions, etc.

[0017] The grain size of the permeable roadbed structure is larger in the lower permeable base layer 41 than in the upper permeable base layer 42, and the permeability of the lower permeable base layer 41 is also larger than that of the upper permeable base layer 42.

[0018] <3> Examples of permeable base layer materials The permeable base layer 42 is made of mineral particles or artificial particles that are not deteriorated by rainfall or the like and can maintain a certain gap for a long period of time, such as decomposed granite or red clay. More preferably, the permeable base layer 42 is made of decomposed granite.

[0019] Generally, paved roads are subjected to repeated foot traffic, and therefore, if ordinary soil or black soil is used as the permeable roadbed layer 42, a certain degree of permeability and capillary rise can be expected at the beginning of construction, but over time, the gaps between the soil particles decrease due to repeated loads, and the performance deteriorates. In contrast, since decomposed granite or red soil contains fewer clay particles than ordinary soil or black soil, the gaps between the soil particles are less likely to decrease even when subjected to repeated loads, and it is possible to maintain permeability and capillary rise function for a long period of time.

[0020] In this example, for ease of understanding, a form in which a permeable pavement layer 43 is formed on a permeable subgrade layer 42 is shown, but a known permeable base layer may also be provided between the permeable subgrade layer 42 and the permeable pavement layer 43.

[0021] <4> Permeable pavement layer The permeable pavement layer 43 is a permeable uppermost layer, and may be made of, for example, hard blocks or permeable asphalt (open grain asphalt) that are permeable and water-retentive.

[0022] 2. Base material <1> Base material composition The base material 10 is buried in the ground and used as a carrier for absorbing carbon dioxide, a filler or backfill material for preventing clogging, or the like.

[0023] The structure of the base material 10 will be described with reference to FIG. The base material 10 comprises an aggregate body 20 made of waste concrete, a wet coating layer 30 containing naturally occurring wet substances attached to the surface of the aggregate body 20, and recycled concrete fine powder 33 which serves as a carbon dioxide carrier attached to the surface of the aggregate body 20 or the wet coating layer 30.

[0024] In the present invention, it is assumed that 100% concrete recycled materials are used for the aggregate body 20 and recycled fine powder 33, so when manufacturing the base material 10, there are no problems such as mass consumption of fossil fuels or generation of carbon dioxide due to heating.

[0025] <2> Aggregate body The aggregate body 20 comprises, for example, hard recycled aggregate or natural aggregate. The particle size of the aggregate body 20 can be 10 mm to 20 mm, 20 mm to 30 mm, 30 mm to 40 mm, or 40 mm to 60 mm.

[0026] In this example, a form will be described in which recycled aggregate (recycled crushed stone) extracted from waste concrete is used as the aggregate body 20. When recycled aggregate is used for the aggregate body 20, for example, lumps of waste concrete are primarily crushed using a crushing device such as a jaw crusher, and the crushed concrete pieces are then further crushed using a crushing device such as a centrifugal crusher, after which they are classified into a predetermined particle size range. The aggregate body 20 may be of a single particle size or may have a predetermined particle size distribution.

[0027] <3> Wet Coating Layer The wetting coating layer 30 comprises a naturally occurring wetting substance 31 having acidic functional groups and an adhesion aid 32 having wetting properties.

[0028] <3.1> Naturally occurring moist materials The naturally occurring moist substance 31 is a naturally occurring substance having an acidic functional group, and for example, allophane, humic substances, etc. can be used. The naturally occurring moistening material 31 not only functions to capture SS substances but also significantly contributes to increasing the height of water uptake by capillary action.

[0029] <3.1.1> Allophane Allophane is a type of clay mineral, a porous, amorphous silica-alumina mineral formed by the long-term weathering of volcanic ash-derived soil, and its chemical composition is Al2O3·SiO2·nH2O. Because it contains many very fine pores, it has a large specific surface area and is prone to physical adsorption and moisture absorption.

[0030] <3.1.2>Humus Humus is a naturally occurring humic substance with acidic functional groups that is produced during the decomposition process in which the remains of plants and animals in the soil are broken down by the action of microorganisms.It becomes a colloidal organic polymer compound that is easily physically adsorbed and also has a neutralizing effect on the alkalinity of recycled aggregate.

[0031] <3.2> Adhesion aid (means for adhering wet material and recycled fine powder) It is difficult to make the wet material 31 and recycled fine powder 33 adhere to the aggregate body 20 in an inseparable manner. Therefore, by using an adhesion aid 32 having wettability, the wet substance 31 and recycled fine powder 33 are adhered to the surface of the aggregate body 20.

[0032] The adhesion aid 32 is a wettable aid that becomes viscous when wet, and examples of materials that can be used include water, highly absorbent resins, polymer absorbents (polyacrylic acid (salt)-based (sodium polyacrylate), starch graft polymerization-based, polyvinyl alcohol-based, and carboxymethyl cellulose (CMC)-based), vinyl acetate resin, and polyvinyl alcohol.

[0033] <4> recycled fine powder In the present invention, after the surface of the aggregate body 20 is covered with the wet coating layer 30, recycled concrete fine powder 33 is further sprinkled on the surface and adhered to it in the form of a thin film. The particle size of the recycled fine powder 33 is selected appropriately. The recycled fine powder 33 refers to untreated concrete fine powder obtained by crushing concrete rubble, etc. Untreated means that it has not been subjected to heat treatment.

[0034] <4.1> Purpose of use of recycled fine powder The recycled fine powder 33 is used for the following reasons: to utilize the carbonation phenomenon of concrete to continuously adsorb carbon dioxide, and to increase the surface area of ​​the aggregate body 20 to improve the function of capturing SS substances. "Sustainable" means that carbon dioxide can be adsorbed semi-permanently without consuming heat energy or the like.

[0035] When recycled aggregate is used as the aggregate body 20, the concrete components attached to the surface of the recycled aggregate can be used as a carrier of carbon dioxide, but since there is a large variation in the amount of concrete components attached, there is a limit to the stable adsorption of large amounts of carbon dioxide.

[0036] In the present invention, recycled concrete fine powder 33 is attached to the surface of the aggregate body 20 or the wet coating layer 30 in order to significantly increase the amount of concrete components attached to the base material 10 and the exposed area (surface area) of the concrete components, thereby stably adsorbing a large amount of carbon dioxide.

[0037] <4.2>Method of attaching recycled fine powder The recycled fine powder 33 is sprinkled and attached to the surface of the aggregate body 20 or the wet coating layer 30 using the adhesion aid 32 having the wettability described above.

[0038] <4.3> The amount of coating of naturally occurring moist materials and the amount of recycled fine powder attached The amount (adhesion area) of recycled fine powder 33 attached to the base material 10 affects the pH of the base material 10 and the amount of carbon dioxide adsorption. For example, if the amount of recycled fine powder 33 coated increases, the amount of carbon dioxide adsorption increases, while the pH of the base material 10 rises, deteriorating the planting environment. The amount (covered area) of the naturally occurring moist substance 31 applied to the base material 10 affects the pH of the base material 10; for example, increasing the amount of naturally occurring moist substance 31 applied decreases the pH of the base material 10, improving the planting environment. This is because the naturally occurring moist material 31 exhibits a pH buffering effect. Therefore, the amount of the naturally occurring moist substance 31 and the amount of the recycled fine powder 33 to be coated on the base material 10 should be appropriately selected taking into consideration the pH of the base material 10, the amount of carbon dioxide adsorption, and the like.

[0039] <5> Mixing method for base material In this example, a form of kneading using a kneading device 50 equipped with stirring blades in a storage tank will be described. There are no particular restrictions on the means for kneading the base material 10, and in addition to using the kneading device 50, kneading may also be carried out using construction machinery such as a backhoe.

[0040] 3. Manufacturing method of base material A method for manufacturing the base material 10 will be described with reference to FIG.

[0041] <1> Aggregate mixing process As shown in Fig. 2(a), the aggregate body 20 is first charged into the kneading device 50 and then kneaded. Dry kneading means that only the aggregate body 20 is kneaded. At this time, water is sprayed inside the kneading device 50 to wet the surfaces of the aggregate bodies 20. The dry mixing step of the aggregate body 20 is not essential and may be omitted.

[0042] <2> Coating process of wet coating layer onto aggregate body Next, specified amounts of the wetting material 31 and the adhesion aid 32 are put into the kneading device 50 and kneaded. By kneading the aggregate body 20, the wet substance 31 and the adhesion aid 32, a wet coating layer 30 is produced in the kneading device 50, and the wet coating layer 30 covers the surface of the aggregate body 20 (FIG. 3). The wet coating layer 30 is provided with adhesiveness (bonding properties) by the adhesive aid 32 and adheres to the surface of the aggregate body 20 . The coating form of the aggregate body 20 with the wet coating layer 30 may be either a coating form that covers the entire surface of the aggregate body 20 or a partial (patchy) coating form that covers the surface of the aggregate body 20 .

[0043] <3> Recycled fine powder adhesion process The coating layer 30 covering the aggregate body 20 contains a small amount of moisture, and thus has an appropriate viscosity (adhesion). In this state, the measured recycled fine powder 33 is added to the kneading device 50 and kneaded. By adding recycled fine powder 33 and kneading it, the recycled fine powder 33 adheres not only to the surface of the wet coating layer 30, which has wettability, but also to the exposed surface of the aggregate body 20 via the adhesion aid 32.

[0044] The recycled fine powder 33 is added and coated after the formation of the wet coating layer 30 in order to avoid the recycled fine powder 33 being buried deep in the wet coating layer 30, while allowing the recycled fine powder 33 to adhere to the surface of the wet coating layer 30 in an exposed state.

[0045] In this way, the base material 10 can be manufactured by a simple process of simply coating the surface of the aggregate body 20 with the wet coating layer 30 and the recycled fine powder 33.

[0046] It is also possible to manufacture the base material 10 by simultaneously adding the aggregate body 20, the wet substance 31, the adhesion aid 32 and the recycled fine powder 33.

[0047] <4> Heat energy required for manufacturing base materials As described above, the base material 10 according to the present invention uses 100% recycled concrete aggregate as the aggregate body 20, and further contains recycled fine powder 33 made of concrete filler that had been disposed of as industrial waste. Therefore, when manufacturing the base material 10, the concrete filler can be used as recycled fine powder 33 without being heat-treated, so there is no need to worry about the mass consumption of fossil fuels or the generation of carbon dioxide due to heating when manufacturing the base material 10 that also serves as a carrier.

[0048] [Function of permeable roadbed structure] The following describes the multiple functions of the permeable roadbed structure.

[0049] 1. Permeable roadbed structure provides rainwater storage and infiltration functions and atmospheric cooling functions

[0050] <1> Rainwater storage and infiltration function As shown in FIG. 1, each of the layers 41 to 43 that make up the permeable roadbed structure has continuous water permeability, so rainwater and the like permeates downward and is ultimately stored in the permeable base layer 41. The function of SS materials to capture rainwater as it seeps through will be described later.

[0051] <2> Atmospheric cooling function When the surface temperature of the permeable pavement layer 43 rises with the rise in summer temperature, the water stored in the permeable base layer 41 rises toward the permeable pavement layer 43 due to capillary action and evaporates into the atmosphere. When water evaporates into the atmosphere, it absorbs the heat of vaporization, thereby lowering the temperature around the permeable pavement layer 43 and effectively cooling it. Therefore, the cooling effect around the permeable pavement layer 43 can be maintained for a long period of time, which is extremely effective as a measure against the heat island effect in urban areas.

[0052] 2. Carbon dioxide fixation and storage function of the base material

[0053] <1> Dissolution of carbon dioxide into rainwater Carbon dioxide present in the atmosphere dissolves into rainwater as carbonic acid (H2CO3) during rainfall. Rainwater with dissolved carbonic acid is slightly acidic. H2O+CO2→H2CO3

[0054] <2> Carbonation phenomenon caused by concrete components and carbon dioxide The base material 10 is buried as a water-permeable base layer 41 in the ground in a state where it contains an aggregate body 20 made of waste concrete material and recycled fine powder 33 made of waste concrete material. Therefore, when rainwater containing carbon dioxide penetrates the permeable pavement layer 43, the concrete components of the base material 10 (aggregate body 20 and recycled fine powder 33) react with the carbon dioxide contained in the rainwater, causing carbonation.

[0055] Carbonation is a phenomenon in which calcium hydroxide (Ca(OH)2), a calcium compound in cement hydrate, reacts with carbon dioxide to form calcium carbonate.

[0056] That is, carbon dioxide (H2CO3) contained in rainwater reacts with the concrete components of the base material 10, causing calcium carbonate (CaCO3) to precipitate. Ca(OH)2+2H2CO3→CaCO3↓+2H2O

[0057] <2.1> Fixation and storage of carbon dioxide (calcium carbonate) In this way, carbon dioxide in the atmosphere permeates into the soil via rainwater, then carbonates in the permeation base layer 41 in the soil, and is finally fixed in the form of calcium carbonate (CaCO3) and accumulates on the surface of the base material 10.

[0058] The phenomenon of carbon dioxide absorption by concrete due to carbonation is well known, but the present invention does not simply involve the absorption of carbon dioxide. The base material 10 according to the present invention is designed to be able to continuously exhibit the function of adsorbing carbon dioxide to the base material 10 in the soil and the function of fixing (retaining) carbon dioxide.

[0059] <2.2> Carbon dioxide accumulation period The surface of the substrate 10 in the soil is always kept wet, and the substrate 10 remains alkaline, so that the substrate 10 can continue to adsorb carbon dioxide. The calcium carbonate (CaCO3) produced accumulates in the soil's permeable base layer 41 for approximately the period until the pH drops from around 12.6 to around 8.6, making it possible to continuously adsorb and fix carbon dioxide, albeit in small amounts, for several hundred years. That is, the carbonation phenomenon caused by the base material 10 that constitutes the permeation base layer 41 can continue for hundreds of years.

[0060] <2.3> Quantification of carbon dioxide As mentioned above, the permeable base layer 41 formed from the base material 10 functions as a carbon dioxide adsorption and fixation layer, so by selecting the thickness and volume of the permeable base layer 41, it is possible to quantify the fixation of carbon dioxide.

[0061] <2.4> Natural uptake of carbon dioxide As described above, the carbon dioxide adsorption function of the base material 10 is achieved naturally through the permeation phenomenon of rainwater containing carbon dioxide and the carbonation reaction. Therefore, in the present invention, no external energy such as thermal energy is used to adsorb carbon dioxide, and the adsorption and fixation of carbon dioxide can be continued semi-permanently using only natural forces.

[0062] 3. Other functions of the base material In addition to the functions already described, the base material 10 also performs the following functions.

[0063] <1> SS substance capture function and clogging prevention function For example, if the water-permeable base layer 41 is constructed using only ordinary aggregate bodies 20, the SS material that permeates along with rainwater will remain between the aggregate bodies 20 and cause clogging. Therefore, when a planting strip is provided adjacent to a sidewalk or road, it becomes difficult for the roots of plants and trees to extend between the aggregate body 20 serving as the base material, and there is room for improvement in terms of the growing environment.

[0064] In contrast, the base material 10 has a coating structure in which the entire surface of the aggregate body 20 is covered with a wet coating layer 30 containing naturally occurring wet substances 31, and the coating layer 30 has a moderate viscosity due to the small amount of moisture it contains. Therefore, when rainwater containing SS substances flows down along the wet coating layer 30 on the surface of the base material 10, the floating SS substances are easily attached and captured by simply coming into contact with the naturally occurring wet substance 31. The captured SS material is wet and has almost the same quality as the naturally occurring wet material 31, so new SS material is captured in the captured SS material. Since the infiltration rate of rainwater is extremely low, the captured SS substance does not separate from the base material 10 and flow out, and the captured state is maintained for a long period of time.

[0065] Focusing on the fact that allophane, humus, etc. that make up the naturally occurring wet material 31 have properties and compositions that are very similar to those of the kibushi clay, red soil, etc. that make up the SS material, the surface of the aggregate body 20 is coated with a wet coating layer 30 that contains the naturally occurring wet material 31 that is almost the same quality as the SS material, to form the base material 10.

[0066] In this way, by capturing SS substances on the surface of the base material 10, it is possible to effectively suppress the settling and deposition of SS substances, which are the cause of the formation of an impermeable layer at the bottom of the permeable base layer 41, which is an aggregate of base material 10. Therefore, the excellent clogging prevention effect of the base material 10 can be maintained for a long period of time.

[0067] <2> Buffering effect of naturally occurring moist materials The wet coating layer 30 covering the surface of the base material 10 contains a naturally occurring wet substance 31, which exhibits a pH buffering effect.

[0068] For example, if the naturally occurring wet substance 31 is humus, the reaction can be described as a deprotonation reaction of the acidic functional groups, carboxyl groups and phenolic hydroxyl groups, contained in humic acid (humic acid) and fulvic acid that constitute the humus (H + is called a proton). >COOH⇔>COO - +H + >OH⇔>O - +H + H dissociated from the acidic functional groups contained in humic acid and fulvic acid + is an alkaline component (OH - ) to form HO, lowering the pH.

[0069] The fact that the aggregate body 20 constituting the base material 10 is recycled aggregate made from concrete and that the recycled fine powder 33 coated on its surface is made from concrete are factors that increase the pH of the base material 10, but by utilizing the buffering action of the naturally occurring moist substance 31 contained in the moist coating layer 30, it is possible to keep the pH of the base material 10 at a low value. Therefore, even if vegetation or plants are grown on a water-permeable roadbed structure to which the base material 10 is applied, the alkalinity caused by the concrete components can be alleviated, and the vegetation environment can be improved. [Explanation of symbols]

[0070] 10. Base material 20 Aggregate body (recycled aggregate) 30 Wet coating layer 31. Wet substance 32. Adhesion aid 35...Recycled fine powder 40...Roadbed 41. Permeable base layer 42... Permeable channel bed layer 43. Permeable pavement 50...Kneading device

Claims

1. A base material to be buried in the ground and used as a filler or backfill material to prevent clogging, A hard aggregate body; a wet coating layer that covers the surface of the aggregate body and is composed of a naturally occurring wet substance having an acidic functional group that has at least a pH buffering function and a function of capturing SS substances, and an adhesion aid that exhibits viscosity when wet and causes the wet substance to adhere to the surface of the aggregate body; and recycled concrete fine powder, which is a carrier of carbon dioxide and is attached to the surface of the aggregate body or the wet coating layer. Base material.

2. 2. The base material according to claim 1, wherein the recycled fine powder is untreated fine powder made from waste concrete.

3. 3. The base material according to claim 1 or 2, wherein the recycled fine powder is adhered to the surface of the aggregate body or the wet coating layer by utilizing the wettability of the adhesion aid.

4. 2. The substrate of claim 1, wherein the moist material is allophane or humus.

5. 2. The base material according to claim 1, wherein the adhesion aid is at least one of water, a highly water-absorbent resin, a polymeric absorbent, a vinyl acetate resin, and polyvinyl alcohol.

6. 2. The base material according to claim 1, wherein the aggregate body is a single-grain recycled aggregate produced from waste concrete.

7. The base material according to claim 1, which is used as a permeable base layer of a permeable roadbed structure.

8. A method for adsorbing and fixing carbon dioxide using a base material, comprising: The base material according to claim 1 is buried in the soil as a filler or backfill material for preventing clogging, When rainwater seeps into the soil, the concrete components of the base material react with the carbon dioxide contained in the rainwater to produce calcium carbonate, Carbon dioxide is adsorbed and fixed on the surface of the base material in the form of calcium carbonate. A method for adsorbing and fixing carbon dioxide using base materials.

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