Neutrality modification method of soil and neutrality modification material

Abstract

To provide a neutrality modification method of soil capable of reducing environmental load and improving soil and a neutrality modification material.SOLUTION: A neutrality modification method of soil involves a mixing process 40 of soil 30 with a first component material 10, which contains biochar 11 and a gypsum-based solidifier 12, and a second component material 20, which contains a lime-based solidifier 21 and a coagulant 22. The mixing process 40 consists of adding to soil 30 the first component material 10, which contains biochar 11 and a gypsum-based solidifier 12, and the second component material 20, which contains a lime-based solidifier 21 and a coagulant 22, and then stirring the soil 30 for 30 to 180 seconds. After such a mixing process 40, improved soil 50 is obtained.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for neutrally modifying mud and a neutral modifier, and more particularly to a method for neutrally modifying mud and a neutral modifier for modifying mud to produce improved soil, for example. [Background technology]

[0002] Since it has been determined that global warming is caused by carbon dioxide emissions, there is growing interest in ways to reduce carbon dioxide emissions and in energy sources that do not come from fossil fuels. As a method for reducing carbon dioxide, "carbon dioxide fixation" is attracting attention. "Carbon dioxide fixation" refers to fixing carbon dioxide contained in the atmosphere, exhaust gases, etc. in some form.

[0003] The most familiar form of carbon dioxide fixation is photosynthesis, which occurs in nature. In photosynthesis, plants and microorganisms use light energy to split water, produce oxygen, and fix carbon dioxide into organic matter.

[0004] On the other hand, many technologies have been developed to achieve artificial carbon dioxide fixation. For example, Patent Document 1 describes a CO2 fixation method that includes the steps of injecting water into unused ready-mixed concrete, separating aggregate from the ready-mixed concrete, stirring the ready-mixed concrete from which the aggregate has been separated to reform the ready-mixed concrete into a slurry, and supplying carbon dioxide gas to the slurry-like ready-mixed concrete to fix the carbon dioxide gas in the ready-mixed concrete. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-143644 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, Japan's cement industry emits carbon dioxide equivalent to approximately 4% of total greenhouse gas emissions, making measures to reduce emissions an important issue.

[0007] In this context, it has been reported that carbonation treatment of improved soils made by mixing cement with sand or bentonite can increase their strength. By making good use of this technology, it is expected that a significant reduction in the environmental impact can be achieved through carbon dioxide fixation. Securing disposal sites for the mud has become an issue, and coupled with the need for effective use of the mud, a solidification process is being carried out in which the mud is solidified with cement.

[0008] However, when cement is used to solidify mud, the clay minerals and organic components in the mud may inhibit the formation of cement hydrate, which may result in the elution of chromium that is not fixed in the cement hydrate.

[0009] In addition, the pH of cement is 12 to 13, and since cement is very alkaline, improved soil that has been solidified with cement tends to become alkaline. When the soil becomes alkaline, trace elements such as iron, manganese, copper and zinc become insoluble, and plants are unable to absorb these elements, losing vitality and gradually worsening their condition, which may even lead to death. Furthermore, although humans ingest many trace elements from food, it is said that if they are completely unable to ingest trace elements, they will become ill.

[0010] For these reasons, there has been a demand for technology that can sufficiently fix carbon dioxide to reduce the environmental impact and can also modify mud without making it alkaline.

[0011] The present invention has been devised in consideration of the above points, and aims to provide a method for neutralizing mud and a neutral modifier that can reduce the environmental load and modify mud. [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, the method for neutral modification of mud of the present invention is a method for neutrally solidifying specified mud to turn the mud into improved soil, and includes a mixing step of mixing the mud with a solidification material capable of solidifying the mud and specified biochar.

[0013] Here, by mixing biochar into the mud, the carbon dioxide fixed as a carbon compound in the biochar can be stored in the improved soil.

[0014] In addition, mixing biochar into mud improves the strength of the improved soil. Therefore, a specified strength (e.g., cone index 200 kN / m 2 The amount of solidification material required to obtain the above-mentioned fourth-class improved soil can be reduced. In other words, the solidification material can be replaced with biochar.

[0015] Furthermore, in the present invention, by subjecting mud to neutral solidification treatment, it is possible to obtain a neutral solidified material (improved soil) that is also excellent for vegetation.

[0016] In addition, in the method for neutralizing muddy soil of the present invention, the mixing step can also include adding a solidification material and biochar to the muddy soil, and then stirring the muddy soil.

[0017] In this case, the strength of the improved soil is improved compared to when "a solidifying agent is added to the mud and stirred, then biochar is added and stirred" or when "biochar is added to the mud and stirred, then a solidifying agent is added and stirred." In other words, when adding solidification material and biochar to mud and then mixing it, the amount of solidification material required to achieve a specified strength can be further reduced.

[0018] In addition, in the method for neutralizing muddy soil of the present invention, the mixing step can also include adding a solidification material, biochar, and a water-absorbent flocculant to the muddy soil, and then stirring the muddy soil.

[0019] In this case, the flocculant can granulate the mud, increasing its specific surface area and speeding up the drying process, so even mud with a high water content can be easily modified.

[0020] In addition, in the method for neutralizing muddy soil of the present invention, the mixing step can also include adding a solidifying material to the muddy soil and stirring it, and then adding biochar and stirring it.

[0021] In addition, in the method for neutralizing mud soil of the present invention, the mixing process can also involve adding a second component material containing a water-absorbing flocculant to the mud and stirring it, and then adding a first component material containing a solidification material and biochar and stirring it.

[0022] In this case, the mud can be granulated using a flocculant, and then the granulated mud can be solidified using a solidification material. As mentioned above, because the mud can be granulated, even mud with a high water content can be easily modified.

[0023] In addition, in the method for neutralizing muddy soil of the present invention, the mixing step can also include adding biochar to the muddy soil and stirring it, and then adding a solidifying material and stirring it.

[0024] In the method for neutralizing mud soil of the present invention, the first constituent material may have a blending ratio of solidification material to biochar of 3:7 to 7:3.

[0025] In this case, even if the ratio of solidification material to biochar is changed to reduce the ratio of solidification material, in other words, even if the amount of solidification material (amount used) is reduced, improved soil with sufficient strength can be obtained.

[0026] Furthermore, in the method for neutralizing muddy soil of the present invention, a step of "adding a solidifying material and biochar to the muddy soil, and then stirring" can be adopted, and the stirring time can be set to 30 to 180 seconds.

[0027] In this case, the strength of the improved soil is further improved, and the amount of solidifying material required to obtain a predetermined strength can be further reduced.

[0028] In addition, in order to achieve the above-mentioned object, the neutral modifier of the present invention is a neutral modifier for neutrally solidifying specified mud to turn the mud into improved soil, and contains a solidification material capable of solidifying the mud and specified biochar.

[0029] Here, by containing biochar in the neutral modifier of the present invention, carbon dioxide fixed as a carbon compound in the biochar can be stored in the improved soil.

[0030] Furthermore, by including biochar in the neutral modifier of the present invention, the strength of the improved soil is improved. Therefore, the amount of solidification material required to obtain a certain strength can be reduced. In other words, the solidification material can be replaced with biochar.

[0031] Furthermore, in the present invention, by subjecting mud to neutral solidification treatment, it is possible to obtain a neutral solidified material (improved soil) that is also excellent for vegetation.

[0032] The neutral modifier of the present invention may also contain a flocculant having water-absorbing properties.

[0033] In this case, the flocculant can granulate the mud, increasing its specific surface area and speeding up the drying process, so even mud with a high water content can be easily modified.

[0034] Furthermore, the neutral modifier of the present invention may be configured so that the blending ratio of the solidification material to the biochar is 3:7 to 7:3.

[0035] In this case, even if the ratio of solidification material to biochar is changed to reduce the ratio of solidification material, in other words, even if the amount of solidification material (amount used) is reduced, improved soil with sufficient strength can be obtained. [Effects of the Invention]

[0036] The method for neutralizing mud according to the present invention can reduce the environmental load and can also modify the mud. The neutral modifier according to the present invention can reduce the environmental load and can also modify mud. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 4 is a schematic process diagram showing a method for neutralizing mud according to a second embodiment. [Figure 2] FIG. 10 is a schematic process diagram showing a method for neutralizing mud according to a third embodiment. [Figure 3] FIG. 10 is a schematic process diagram showing a method for neutralizing mud according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, modes for carrying out the invention (hereinafter referred to as "embodiments") will be described. The explanation will be given in the following order. 1. First embodiment (neutral modifier) 2. Second embodiment (neutral reforming method) 3. Third embodiment (neutral reforming method) 4. Fourth embodiment (neutral reforming method) 5. Variations 6. Working Example

[0039] <1. First embodiment> The neutral modifier of the first embodiment is intended to neutrally solidify mud to produce improved soil, and contains a solidification material capable of solidifying mud, a specified biochar, and a flocculant with water-absorbing properties.

[0040] [About the mud] "Mud" refers to soil with a high water content, such as "construction mud" generated at construction sites for tunnel construction (shield construction), excavation work (boring, pile installation), and building construction, "dredged mud" generated from lakes, rivers, harbors, etc., "sewage treatment mud," and "water purification plant mud."

[0041] [About solidification materials] The "solidification material" is, for example, a gypsum-based solidification material, a lime-based solidification material, or a magnesium oxide-based solidification material.

[0042] (Gypsum-based solidifying material) Common gypsum-based solidifying materials can be used, and specifically, they include materials that are mainly composed of gypsum hemihydrate (CaSO4·(1 / 2)H2O) and / or anhydrous gypsum (CaSO4) and are blended with components that promote strength and solidification (solidification-promoting components) such as Al2O3, MgO, Fe2O3, SiO2, and CaCO3, and the proportion of CaSO4 is preferably 20 to 80% by weight, and even more preferably 30 to 70% by mass.

[0043] The hemihydrate gypsum may be either α-type or β-type, and preferably has a particle size of 1 to 100 μm, more preferably 10 to 60 μm. Furthermore, the hemihydrate gypsum and anhydrous gypsum may be naturally occurring gypsum or by-product gypsum produced in the phosphoric acid production process by decomposing phosphate rock with sulfuric acid, and are not particularly limited.

[0044] Here, hemihydrate gypsum and anhydrous gypsum fix the moisture in the mud and coagulate and solidify the mud in the process of crystallizing into dihydrate (CaSO4·2H2O) in the presence of water.

[0045] Specific examples of solidification-promoting components include aluminum oxide, aluminum hydroxide, slag (blast furnace slag, converter slag, electric furnace slag), aluminum, silica sand, iron oxide, iron hydroxide, magnesium oxide, silica gel, and calcium aluminate.

[0046] (lime-based solidifying agent) As the lime-based solidifying material, a general material can be used, and specific examples include quicklime and calcium carbonate (calcium carbonate).

[0047] (Magnesium oxide solidification material) As the magnesium oxide-based solidifying material, a general material containing magnesium oxide as a main component can be used.

[0048] [About biochar] Biochar is a carbonized material obtained by pyrolyzing (carbonizing) biomass in a carbonization furnace or gasification furnace. Biomass is a reusable organic resource (excluding fossil fuels such as petroleum) derived from plants and animals.

[0049] Furthermore, any carbonized material obtained by pyrolyzing (carbonizing) biomass in a carbonization furnace or gasification furnace can be used as biochar.Specific examples include carbonized wood, carbonized bamboo, and carbonized plant shells (rice husks, soybean pods, etc.).

[0050] [About flocculants] The flocculant is preferably a water-soluble polymer compound having absorbency and / or water retention. Preferred examples include polyvinyl alcohol polymers, polyacrylic acid polymers and their sodium and potassium salts, polyacrylamide polymers and their sodium and potassium salts, polyoxyethylene polymers, poly N-vinylcarboxylic acid amide, alkaline hydrolysates of starch graft polymers (e.g., alkaline hydrolysates of starch / acrylonitrile graft polymers), sodium alginate, potassium alginate, chondroitin sulfate, agarose, etc. These may be blended alone or in combination of two or more. Depending on the moisture content of the mud, polyaluminum chloride, aluminum sulfate, aluminum sulfate, etc. may be further added as a supplementary flocculant.

[0051] [effect] The neutral modifier of the first embodiment contains biochar, so by adding it to mud, carbon storage can be achieved by trapping carbon dioxide fixed in the biochar as a carbon compound in the soil, thereby contributing to reducing carbon dioxide in the atmosphere.

[0052] Carbon dioxide from the atmosphere is absorbed by the leaves of plants, such as agricultural crops, and converted into sugars through photosynthesis, which then turn into various carbon compounds that make up plant biomass. Approximately half of the carbon that was in the biomass before carbonization remains in biochar. In addition, because the carbon bonds that make up biochar are strong, it is difficult for soil microorganisms to decompose, and it is expected to remain underground for a long period of time, perhaps more than 100 years. Therefore, the neutral reformer of the first embodiment makes it possible to achieve carbon storage as described above.

[0053] In addition, because biochar can improve the strength of improved soil, it is possible to reduce the amount of solidification material added to the mud (usage amount), and as a result, the desired strength can be achieved with a small amount of neutral modifier.

[0054] Furthermore, the pH of biochar is generally alkaline, between 9 and 11, but the pH of the carbon itself is neutral to begin with, and the alkalinity is due to metal oxides that adhere to the charcoal, so the pH can easily be lowered to the neutral side by adding water. Therefore, the improved soil obtained using the neutral improver of the first embodiment has a neutral pH and is extremely favorable for vegetation.

[0055] 2. Second embodiment FIG. 1 is a schematic process diagram showing the method for neutralizing mud according to the second embodiment. As shown in FIG. 1, in the method for neutral reforming mud according to the second embodiment, first, the neutral reforming material 1 according to the first embodiment is added to mud 30.

[0056] Here, the neutral modifier 1 contains biochar 11, a gypsum-based solidification material 12, a lime-based solidification material 21, and a flocculant 22, and the mixing ratio of the solidification materials (gypsum-based solidification material 12 and lime-based solidification material 21) to biochar 11 is 3:7 to 7:3.

[0057] Thereafter, a mixing process 40 is carried out in which the mud 30 to which the neutral modifier 1 has been added is stirred. Specifically, the mud 30 to which the neutral modifier 1 has been added is stirred for 30 to 180 seconds, whereby the modified soil 50 can be obtained.

[0058] [effect] The second embodiment of the neutral reforming method adds biochar to mud, thereby achieving carbon sequestration by trapping carbon dioxide fixed in the biochar as a carbon compound in the soil, thereby contributing to reducing carbon dioxide in the atmosphere.

[0059] Furthermore, since biochar can improve the strength of improved soil, the neutral reforming method of the second embodiment can achieve the desired strength with a small amount of solidification material.

[0060] Furthermore, the improved soil obtained by the neutral improvement method of the second embodiment has a neutral pH and is extremely favorable for vegetation.

[0061] 3. Third Embodiment FIG. 2 is a schematic process diagram showing a method for neutralizing mud according to the third embodiment. As shown in FIG. 2, in the method for neutralizing mud according to the third embodiment, first, a second constituent material 20 is added to mud 30.

[0062] Here, the second constituent material 20 contains a lime-based solidifying material 21 and a flocculant 22. The lime-based solidification material described in the first embodiment can be used as the lime-based solidification material 21. Similarly, the flocculant 22 can also be the flocculant described in the first embodiment.

[0063] Next, a first mixing process 41 is carried out in which the mud 30 to which the second constituent material 20 has been added is stirred. Specifically, the mud 30 to which the second constituent material 20 has been added is stirred for 30 to 180 seconds to obtain the intermediate improved soil 51.

[0064] Next, the first constituent material 10 is added to the intermediate improved soil 51.

[0065] Here, first constituent material 10 contains biochar 11 and gypsum-based solidifying material 12, and the mixing ratio of gypsum-based solidifying material 12 to biochar 11 is 3:7 to 7:3. The biochar described in the first embodiment can be used as the biochar 11. Similarly, the gypsum-based solidification material 12 can be the gypsum-based solidification material described in the first embodiment.

[0066] Thereafter, a second mixing process 42 is carried out in which the intermediate improved soil 51 to which the first constituent material 10 has been added is mixed. Specifically, the intermediate improved soil 51 to which the first constituent material 10 has been added is stirred for 30 to 180 seconds, thereby obtaining the improved soil 50.

[0067] [effect] The neutral improvement method of the third embodiment adds biochar to the intermediate improved soil 51, and similarly to the second embodiment described above, can achieve carbon storage by trapping carbon dioxide fixed in the biochar as a carbon compound in the soil, thereby contributing to reducing carbon dioxide in the atmosphere.

[0068] Furthermore, since biochar can improve the strength of improved soil, the neutral reforming method of the third embodiment can achieve the desired strength with a small amount of solidification material, as in the second embodiment described above.

[0069] Furthermore, the improved soil obtained by the neutral improvement method of the third embodiment has a neutral pH, similar to that of the second embodiment, and has excellent properties for vegetation.

[0070] 4. Fourth Embodiment FIG. 3 is a schematic process diagram showing a method for neutralizing mud according to the fourth embodiment. As shown in FIG. 3, in the method for neutralizing mud according to the fourth embodiment, first, the first constituent material 10 according to the third embodiment is added to mud 30.

[0071] Thereafter, a mixing process 40 is carried out in which the mud 30 to which the first constituent material 10 has been added is stirred. Specifically, the improved soil 50 can be obtained by stirring the mud 30 to which the first constituent material 10 has been added for 30 to 180 seconds.

[0072] [effect] The neutral reforming method of the fourth embodiment adds biochar to mud, and similarly to the second embodiment, carbon dioxide fixed as a carbon compound in the biochar can be trapped in the soil, thereby achieving carbon sequestration and contributing to reducing carbon dioxide in the atmosphere.

[0073] Furthermore, since biochar can improve the strength of improved soil, the neutral reforming method of the fourth embodiment can achieve the desired strength with a small amount of solidification material, as in the second embodiment described above.

[0074] Furthermore, the improved soil obtained by the neutral improvement method of the fourth embodiment has a neutral pH, similar to the second embodiment, and has excellent properties for vegetation.

[0075] <5. Variations> The second embodiment described above uses the example of "adding neutral modifiers (biochar, solidification material, and flocculant) to mud, and then stirring the mud," while the third embodiment described above uses the example of "adding solidification material and flocculant to mud, stirring it, and then adding biochar and solidification material, and stirring it." However, it is sufficient if the solidification material and biochar can be mixed with the mud, and a modification method such as "adding biochar to the mud and stirring, then adding the solidification material and stirring" is also acceptable.

[0076] 6. Examples Below, we will explain the tests conducted to demonstrate the effects of adding biochar to mud.

[0077] The test mud was taken from the cuttings of an earth pressure shield. The moisture content of the cutting mud was adjusted to obtain four types of sample mud (A, B, C, D). The mud was in a sludge-like state. The physical properties of sample mud A, sample mud B, sample mud C and sample mud D are shown in Table 1.

[0078] [Table 1]

[0079] In addition, in this example, carbonized rice husks (Examples 1 to 12, Examples 17 to 20, Comparative Examples 1 to 10), carbonized wood cutting chips (Example 13), and carbonized wood pellets (Examples 14 to 16) were used as biochar.

[0080] The carbonized wood cutting chips were obtained in a downdraft fixed-bed gasifier, and the carbonized wood pellets were obtained in an updraft fixed-bed gasifier.

[0081] The gypsum-based solidifying material used was composed mainly of gypsum hemihydrate, to which alumina, silica, iron oxide, and magnesium oxide were added. Furthermore, calcium carbonate (calcium carbonate) was used as a lime-based solidification material.

[0082] The flocculant used was a powdered acrylamide / sodium acrylate copolymer, which is an anionic polymer flocculant. Although an anionic polymer flocculant was used in this example, a cationic polymer flocculant may also be used.

[0083] Here, the first constituent material was prepared by mixing biochar and a gypsum-based solidification material (Examples 1 to 9, Examples 11 to 20) or biochar and a lime-based solidification material (Example 10) in the mixing ratios shown in Table 2. The second constituent material was prepared by mixing a flocculant and a lime-based solidification material in the mixing ratio shown in Table 2. The blending ratios shown in Table 2 are values ​​based on the total amount of the first constituent material and the total amount of the second constituent material.

[0084] [Table 2]

[0085] In this example, as shown in Table 3, "the first and second constituent materials were mixed with sample mud A to C" or "only the first constituent material was mixed with sample mud D." Specifically, 3000 g of sample mud was charged into a Hobart mixer, and the first and second constituent materials were then added to the sample mud and stirred.

[0086] Here, two types of mixing methods were carried out: a mixing method in which the number of stirring treatments was two (Examples 1 to 4) and a mixing method in which the number of stirring treatments was one (Examples 5 to 20).

[0087] The mixing method with two stirring steps involves putting the second component material into a Hobart mixer (i.e., adding the second component material to the sample mud) and stirring for 60 seconds (first stirring step), and then putting the first component material into the Hobart mixer (i.e., adding the first component material to the sample mud) and stirring for 30 seconds (second stirring step).

[0088] On the other hand, the mixing method with one stirring step (Examples 5 to 15) involves putting the first and second constituent materials together into a Hobart mixer (i.e., adding the first and second constituent materials to the sample mud) and stirring for 60 seconds. In addition, the mixing method with one stirring treatment (Examples 16 to 20) involves putting the first component material into a Hobart mixer (that is, adding the first component material to the sample mud) and stirring for 60 seconds. [Comparative Example] For comparison, a test was also conducted without adding biochar.

[0089] Here, the first constituent material was prepared by mixing a gypsum-based solidifying material and a lime-based solidifying material in the mixing ratio shown in Table 2. The second constituent material was prepared by mixing a flocculant and a lime-based solidification material in the mixing ratio shown in Table 2. The gypsum-based solidifying material, lime-based solidifying material, and flocculant used were the same as those used in the above-mentioned examples.

[0090] In the comparative examples, as shown in Table 3, "sample muds A and B were mixed with the first and second constituent materials" or "sample mud D was mixed with only the first constituent material."

[0091] [Table 3]

[0092] The improved soil obtained in this manner (improved soil of this example, improved soil of the comparative example) was discharged from the Hobart mixer and allowed to naturally cure, and the cone index of the improved soil was measured 1 day, 3 days, 7 days, and 28 days after mixing. The cone index was measured in accordance with the Geotechnical Society standard "Test method for cone index of compacted soil" (JGST716).

[0093] The pH of the improved soil was measured 28 days after mixing (7 days for Examples 10 to 16, and 3 days for Examples 17 to 20 and Comparative Examples 7 to 10). The pH was measured in accordance with the Geotechnical Society standard "pH test method for soil suspension" (JGS0211-2000). The Cohn Index and pH measurements are shown in Table 4.

[0094] [Table 4]

[0095] As can be seen from Table 4, when comparing "Examples 1 to 4" with "Comparative Examples 1 to 4," which were all under the same conditions, such as the amount of addition, and when comparing "Examples 17 to 20" with "Comparative Examples 7 to 10," the cone index of the improved soil mixed with biochar was higher than the cone index of the improved soil not mixed with biochar but in which the same amount of calcium carbonate was mixed instead of biochar.

[0096] Furthermore, since the amount of the first constituent material added is a ratio relative to 1000 kg of sample mud, in Example 1, for example, it can be seen that the mass of biochar added was 5 kg. Based on the total amount of improved soil, which is a mixture of the sample mud and the neutral modifier of the present invention, the proportion of added biochar is about 0.5 mass %. In addition, the cone index after 7 days in Example 1 was 1200 kN / m 2 From the above, it was found that adding only a small amount of biochar was sufficient to improve the quality of mud.

[0097] Furthermore, as can be seen from Table 4, the pH of the improved soil obtained by the improvement method of the present invention was within the neutral range of 6.5 to 8.5.

[0098] Furthermore, as can be seen from the comparison between "Examples 1-2" and "Examples 5-6", when the number of mixing treatments was two, i.e., when the first constituent material and the second constituent material were added separately with a mixing treatment in between, the cone index of the improved soil after three days was 600 kN / m 2 In contrast, when the number of mixing treatments was one, i.e., when the first and second constituent materials were added without any mixing treatments in between, the cone index of the improved soil after three days was 750 kN / m 2 That was all.

[0099] Furthermore, as can be seen from the comparison between Example 6 and Example 13, the cone index of the improved soil was 1200 kN / m at an earlier stage (after 3 days) when carbonized wood cutting chips (Example 13) were used as biochar than when carbonized rice husks (Example 6) were used. 2 That's all.

[0100] Furthermore, as can be seen from a comparison between Examples 13 and 14, which used carbonized wood-based materials, the cone index of the improved soil reached 1200 kN / m at an earlier stage (after 3 days) when carbonized wood cutting chips obtained in a downdraft fixed-bed gasifier (Example 13) were used than when carbonized wood pellets obtained in an updraft fixed-bed gasifier (Example 14). 2 That's all.

[0101] Furthermore, as can be seen from a comparison between "Examples 17 to 20" and "Comparative Examples 7 to 10," it was found that mud could be sufficiently modified even when only the first constituent material was added. [Explanation of symbols]

[0102] 1. Neutral modifier 10 First component material 11 Biochar 12 Gypsum-based solidifying material 20 Second component material 21 Lime-based solidifying agent 22 Flocculant 30 Mud 40 Mixing Treatment 41 First Mixing Treatment 42 Second Mixing Treatment 50 Improved soil 51 Intermediate improved soil

Claims

1. A method for neutralizing mud improvement, which comprises subjecting predetermined mud to a neutral solidification treatment to turn the mud into improved soil, The method includes a mixing step of mixing the mud with a solidification material capable of solidifying the mud and predetermined biochar. A method for neutralizing muddy soil.

2. The mixing step The solidification material and the biochar are added to the mud, and then the mud is stirred. The method for neutralizing mud according to claim 1.

3. The mixing step The solidification material, the biochar, and a water-absorbing flocculant are added to the mud, and then the mud is stirred. The method for neutralizing mud according to claim 1.

4. The mixing step The solidification material is added to the mud and stirred, and then the biochar is added and stirred. The method for neutralizing mud according to claim 1.

5. The mixing step A second component material containing a water-absorbent flocculant is added to the mud and stirred, and then the first component material containing the solidification material and biochar is added and stirred. The method for neutralizing mud according to claim 1.

6. The mixing step The biochar is added to the mud and stirred, and then the solidification material is added and stirred. The method for neutralizing mud according to claim 1.

7. The first constituent material is The blending ratio of the solidification material to the biochar is 3:7 to 7:

3. The method for neutralizing mud according to claim 5.

8. The stirring time is 30 to 180 seconds. The method for neutralizing mud according to claim 2 or 3.

9. The mixing step By mixing the biochar, it is possible to obtain improved soil with higher strength than when the same amount of the solidification material is mixed in place of the biochar. A method for neutralizing mud according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6.

10. By mixing the biochar, it is possible to obtain the improved soil in which carbon dioxide is stored as a carbon compound. A method for neutralizing mud according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6.

11. A neutral modifier for neutrally solidifying predetermined mud to turn the mud into improved soil, A solidification material capable of solidifying the mud; A predetermined biochar and a Neutral modifier.

12. Contains a flocculant with water absorption properties The neutral modifier of claim 11.

13. The blending ratio of the solidification material to the biochar is 3:7 to 7:

3. The neutral modifier of claim 11.

14. By including the biochar, it is possible to obtain improved soil with higher strength than when the same amount of the solidification material is included instead of the biochar. A neutral modifier according to claim 11, claim 12 or claim 13.

15. By including the biochar, the improved soil can be obtained in which carbon dioxide is stored as a carbon compound. A neutral modifier according to claim 11, claim 12 or claim 13.

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