JP7367487B2 - Solidification insolubilization neutral modifier for low fluidity mud and low fluidity mud modification method using the modifier - Google Patents

Description

The present invention relates to a solidified, insolubilized, neutral modifier for low-fluidization mud and a low-fluidization mud modification method using the modifier, and in particular to a method for converting mud such as high water content dredged soil and shield generated soil into organic polymers. By adding it to soil that has been made low fluidity with emulsion-type muddying agents or blowout prevention agents, it has the ability to insolubilize and adsorb heavy metals such as arsenic, thereby reducing elution and neutralizing soil pH. Consolidation, insolubilization, and neutral modifier for low-fluidization mud and low-fluidization using this modifier, which has soil modification performance that improves strength such as Cone index of compacted soil. Regarding mud reforming method.

Previously, muddy soil such as dredged soil and shield soil had high fluidity due to high water content and foaming agents, so it was difficult to transport it off-site unless it was dehydrated and dried and had a certain strength. Ta.
In addition, many of these muddy soils contain naturally occurring heavy metals such as arsenic and lead at low concentrations, and in order to effectively utilize these soils for embankments, etc., they must be modified to have the specified strength. In addition to improving soil quality, it is also necessary to insolubilize heavy metals and other substances to below the standard value for elution, and to maintain the amended soil in a neutral range to reduce the impact on vegetation and aquatic organisms.

In order to improve the handling of these highly hydrated muds such as dredged soil and shield generated soil in a short time and to reduce their fluidity, muddying materials mainly composed of emulsions containing organic polymers are generally used. May be added and processed. Note that the "mud material" is also referred to as a mud modifying material or a blowout prevention agent (hereinafter referred to as "mud material").
It is possible to use mud additives to agglomerate high water content mud and improve it so that it has a certain degree of strength, but if added in large quantities it may have an impact on aquatic organisms, Mud material has poor ability to insolubilize heavy metals, etc., and solidifying and insolubilizing agents had to be added to achieve solidification performance to develop strength and to insolubilize heavy metals.

Conventional solidifying materials include cement-based solidifying materials, MgO (magnesium oxide)-based solidifying materials, quicklime, and blast furnace slag-based materials. Because of this, strong alkaline groundwater flows into the surrounding environment due to rainfall, which is also undesirable as it may have an impact on vegetation. Furthermore, since the heavy metal insolubilization ability is low, there is a problem that heavy metals that have not been eluted in the neutral region are eluted.

Furthermore, as conventional insolubilizing materials, MgO-based insolubilizing materials, semi-baked dolomite-based insolubilizing materials, iron-based insolubilizing materials, and aluminum-based insolubilizing materials are known.
However, with MgO (magnesium oxide)-based insolubilizers, the pH of the soil after modification is strongly alkaline, with a pH of 10 or higher, and the pH of the insolubilized soil remains high for a long time, causing high-pH groundwater to flow into the surrounding environment. , there are concerns about the impact on vegetation.
Semi-calcined dolomite is alkaline with a pH of 9 to 10, iron-based insolubilizers are mainly in the form of iron salts and are acidic, and aluminum-based insolubilizers include polyaluminum chloride and aluminum sulfate and are acidic. It is something.

As a construction method using materials with solidification performance and insolubilization performance, JP 2017-051884A (Patent Document 1) describes (A) 100 parts by mass of an anionic polymer flocculant in mud generated by the bubble shield construction method. and a polymer flocculant containing 0.05 to 50 parts by mass of a cationic polymer flocculant, and the mud containing the polymer flocculant is crushed and mixed. a coagulant addition step for obtaining mud; and (B) a solidifying and insolubilizing material containing a magnesium component and a metal salt consisting of at least one selected from metal sulfates and metal chlorides to the mud containing the polymer flocculant. A method for treating mud generated in the bubble shield construction method is described, which includes a step of adding a solidified insolubilizing agent to form treated mud by adding and mixing.

In addition, JP 2018-015731 (Patent Document 2) discloses that an anionic polymer flocculant is added and mixed into mud generated by the bubble shield method without adding a cationic polymer flocculant. , a flocculant addition step to obtain mud containing a polymer flocculant, and a magnesium component and/or calcium component having a solidifying effect, and a metal sulfate and a metal chloride added to the mud containing the polymer flocculant. Mud generated by the bubble shield method, which includes a step of adding a solidifying insolubilizing agent containing at least one metal salt selected from the following, followed by pulverization and mixing to form treated mud. A bubble shield, characterized in that the pulverization in the step of adding the solidified insolubilizing agent is carried out until a 50% passing mass percentage of the mud containing the polymer flocculant and the solidified insolubilizing agent becomes 7 mm or less. It describes how to dispose of mud generated by the construction method.

Furthermore, JP 2019-177301A (Patent Document 3) states that the content of CaCO ₃ is 0≦x≦75.5 (mass%) and the content of CaO (calcium oxide) is 2.3≦x. A material for insolubilizing heavy metals, etc. is described, which is characterized in that it contains calcined dolomite of ≦75.5 (mass %) and a reducing agent in a mass ratio of 9:1 to 1:9.

The above conventional materials are alkaline MgO-based or CaO-based materials that improve strength and insolubilization performance through soil solidification, and are combined with acidic ferrous sulfate, aluminum sulfate, etc. at a predetermined mixing ratio to remove heavy metals such as arsenic. By making it insolubilized and further improving the solidification performance with other contained components and auxiliaries, it is possible to bring the soil pH into a neutral range and improve the solidification and insolubilization performance.

However, there is a concern that these conventional insolubilizing and solidifying materials may impede strength development performance when added to muddy soil that has been made low fluid by adding muddying materials whose main components are emulsions containing organic polymers. .
The main component of the muddy material is a polyacrylamide-based emulsion, and in order to avoid affecting aquatic toxicity, materials that are predominantly negatively charged and anionic are used. The polymer adsorbs to the positively charged soil particles contained in the mud, and cross-linking progresses, which aggregates while taking in pore water in the soil, making the mud less fluid. In such a state, if a large amount of iron-based or aluminum-based water-soluble materials from which polyvalent cations, especially trivalent cations, are eluted, they will react with the polymer, neutralizing the charge and creating a crosslinked structure. When disturbed, the pore water contained in the polymers flows out, causing the soil to re-sludge and reduce its strength.

JP2017-051884A Japanese Patent Application Publication No. 2018-015731 Japanese Patent Application Publication No. 2019-177301

The purpose of the present invention is to solve the above-mentioned problems by blending muddying material, which is an organic polymer emulsion, into muddy soil, such as dredged soil and shielding soil, which has high fluidity due to the influence of high water content and foaming agents. The low-fluidized mud can insolubilize heavy metals etc. leached from the soil without being re-sludged, and has solidification performance that improves and improves the strength of the treated soil, as well as neutralizing the pH of the improved soil. An object of the present invention is to provide a novel solidified and insolubilized neutral modification material that can be modified to a neutral region.

Another object of the present invention is to blend muddying material, which is an organic polymer emulsion, into dredged soil, shielded soil, and other muddy soil, which has high fluidity due to the influence of high water content and foaming agents, to reduce fluidity. Soil modification performance of insolubilizing heavy metals, etc. by applying the solidification insolubilization neutrality modifier of the present invention to low-fluidization muddy soil, as well as improving strength and neutralizing pH by solidification of the treated soil. An object of the present invention is to provide a solidification insolubilization neutral modification method using the solidification insolubilization neutral modification material of the present invention, which exhibits the following properties.

The present invention was achieved based on the discovery that the above-mentioned problems can be solved by including a specific material as an essential ingredient and including it in a specific blending ratio.

(1) The solidified and insolubilized neutral modifier of the present invention is a modifier for use in low-fluidization muddy soil that contains a muddying material whose main component is an organic polymer emulsion and has a cone index of 50 to 200 kN/m2 ^. and contains calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate as essential components, 5 to 15 % by mass of calcium oxide, 3 to 20% by mass of ferrous sulfate, and 50% by mass or more of calcium carbonate. A solidified and insolubilized material containing magnesium oxide in a proportion of 10 to 100 parts by mass and ferrous sulfate in a proportion of 20 to 200 parts by mass per 100 parts by mass of calcium oxide. It is a neutral modifying material.

(2) In the solidified and insolubilized neutral modifier of (1) above, a polymer flocculant is further added to the total amount of 100 parts by mass of calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate in an amount of 10 parts by mass. It is characterized by containing less than part by mass.
(3) In the solidified and insolubilized neutral modifier described in (2) above, the polymer flocculant has polyacrylamide as its main component and has a viscosity of 400 mPa·s or more when made into a 0.25% aqueous solution. Features.

(4) The solidified and insolubilized neutral modifier described in any one of (1) to (3) above is characterized in that it is in powder form.
(5) In the solidified insolubilized neutral modifying material according to any one of (1) to (4) above, the organic polymer emulsion that is the main component of the muddying material is a polyacrylamide emulsion. .

(6) The solidification insolubilization neutral modification method of the present invention uses the solidification insolubilization neutral modification material described in any of the above (1) to (5) as a muddying material whose main component is an organic polymer emulsion. This is a solidification, insolubilization, and neutral modification method that is characterized by its use in combination with low-fluidization mud containing soil.

(7) In the solidification insolubilization neutral modification method described in (6) above, the soil pH of the treated soil obtained by mixing the solidification insolubilization neutral modifier with the mud after 7 days of age is 5.8 to 8. 6, the elution amount of arsenic is 0.01 mg/L or less and the Cohn index is 200 kN/m ² or more.

In the present invention, "low-fluidization mud" refers to mud such as high water content dredged soil or shield generated soil, which is mixed with a known muddying agent such as an organic polymer emulsion to reduce the fluidity of the mud. Specifically, it refers to muddy soil with a cone index of approximately 50 to approximately 200 kN/ ^m2 , as specified in the Ministry of Land, Infrastructure, Transport and Tourism's ``Standards for Use of Generated Soil''. .

The solidification insolubilization neutral modifier of the present invention and the solidification insolubilization neutral modification method using the modifier add a muddying material containing an organic polymer emulsion as a main component to mud to reduce fluidity. It can effectively and long-term insolubilize heavy metals, etc. in the soil for low fluidization muddy soil, and has soil reforming performance such as improving the strength by solidifying the treated soil without re-silting. , the pH of the treated soil can be maintained in the neutral range. Therefore, it becomes possible to effectively perform the above-mentioned modification treatment on muddy soil such as high water content dredged soil and shield generated soil.
In the present invention, the term "neutral range" means a pH range of 5.8 to 8.6, which is the neutral range defined by the Uniform Effluent Standards of the Ministry of the Environment.

The present invention will be explained by the following preferred embodiments, but is not limited thereto.
The solidified and insolubilized neutral modifier of the present invention is a modifier used for low-fluidization mud containing a muddying material containing a mudding material whose main component is an organic polymer emulsion, and which includes calcium oxide, magnesium oxide, Contains ferrous sulfate and calcium carbonate as essential components, contains 3 to 30% by mass of calcium oxide, 1 to 20% by mass of ferrous sulfate, and 50% or more of calcium carbonate, and contains 100% by mass of calcium oxide. This solidified and insolubilized neutral modifier contains magnesium oxide in a proportion of 10 to 100 parts by mass and further contains ferrous sulfate in a proportion of 10 to 200 parts by mass.

The solidification and insolubilization neutral modifier of the present invention is applied to low-fluidization mud, which is obtained by adding a muddying agent to high-water content mud, such as dredged or shield soil, to reduce fluidization.
As the mudding material, any known mudding material can be used, and for example, mudding materials mainly composed of an organic polymer emulsion type, such as a polyacrylamide emulsion, are common. Although it is possible to improve the strength of highly water-containing mud to a certain degree by adding such muddying materials, the obtained low-fluidized mud is difficult to drive on such low-fluidized mud with heavy machinery such as trucks. is a low-fluidized mud with a cone index of about 50 to about 200 kN/ ^m2 , which is still not strong enough, and is to which the solidified insolubilized neutral modification material of the present invention is applied. The soil is such a low fluidization mud.
By applying the solidified and insolubilized neutral modifier of the present invention to such soil, it has the above-mentioned effects such as being able to maintain the pH in the neutral range.

The solidified and insolubilized neutral modifier of the present invention is preferably in powder form. Being in powder form makes it easier to handle and work at the construction site, and when mixed with low-fluidization mud, it can efficiently adsorb and insolubilize heavy metals dispersed in the soil. .
Furthermore, by making the solidified and insolubilized neutral modifier of the present invention in powder form, it comes into contact with water in the soil, precipitates hydrates, and makes it easier to aggregate the soil, thereby improving the strength of the soil. This makes it possible to improve soil efficiently.

Here, heavy metals etc. mean heavy metals and halogens, and examples of heavy metals include one or more of manganese, chromium, copper, cadmium, mercury, selenium, lead, arsenic, cadmium, etc. Examples include heavy metals and their compounds, and halogens include fluorine, chlorine, and their compounds. In addition to these, examples include elemental boron and its compounds, which are included in the Class 2 Specified Hazardous Substances stipulated in the Soil Contamination Countermeasures Act (Kansui Taidoho No. 1703313: Ministry of the Environment), but these heavy metals and halogen.

In the present invention, calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate are contained as essential materials of the solidified and insolubilized neutral modifier, and the content of each of these is within the above range. In addition to being able to effectively insolubilize heavy metals, etc., it also improves the strength of the treated soil for low fluidity mud and improves its solidification performance, thereby maintaining the pH of the treated soil in the neutral range. It becomes possible to achieve the above effects at the same time.

The solidified and insolubilized neutral modifier of the present invention contains calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate as essential components.
Calcium oxide contained in the solidified and insolubilized neutral modifier of the present invention mainly reacts with the water in the low-fluidization mud, lowering the water content ratio through water evaporation and hydration reaction due to heat generation, and reducing the hydration component. Calcium hydroxide is carbonated by carbon dioxide in the air and changes to calcium carbonate, which has the effect of quickly shifting the pH to a neutral range.

Calcium oxide is contained in the solidified and insolubilized neutral modifier in an amount of 3 to 30% by mass, preferably 3 to 20% by mass, and more preferably 5 to 15% by mass.
Within the above range, the solidification performance is excellent, the strength development is good, and the pH of the treated soil can be modified to a neutral range after 7 days of age. If it is less than 3% by mass, the solidification performance will be poor and the strength development will be reduced, while if it is more than 30% by mass, the pH of the treated soil will become strongly alkaline, and the pH of the treated soil will be reduced to a neutral range in a short period of 7 days. It becomes difficult to do so.

Further, the magnesium oxide contained in the solidified and insolubilized neutral modifier of the present invention mainly reacts with water in the low-fluidization mud to become magnesium hydroxide, which has an insolubilizing effect of adsorbing heavy metals and the like.
Magnesium oxide is contained in an amount of 10 to 100 parts by mass, preferably 30 to 100 parts by mass, and more preferably 30 to 50 parts by mass, based on 100 parts by mass of the calcium oxide contained in the solidified and insolubilized neutral modifier. Ru.

By keeping the content of magnesium oxide within the above range such that it does not exceed the content of calcium oxide, it is possible to maintain solidification performance while maintaining excellent performance for insolubilizing heavy metals and the like.
If it is less than 10 parts by mass based on 100 parts by mass of calcium oxide, the performance of insolubilizing heavy metals etc. will not be sufficient, while if it is more than 100 parts by mass, it will affect the solidification performance and pH neutralization of the treated soil, which is not preferable.

Furthermore, the solidified and insolubilized neutral modifier of the present invention contains ferrous sulfate as an essential material.
By containing ferrous sulfate, due to its high reducing action, arsenic is adsorbed to iron hydroxide precipitated by hydration against heavy metals such as arsenic and hexavalent chromium, and iron arsenate, which is sparingly soluble, etc. In addition to having an insolubilizing effect due to the precipitation of make it possible to
In addition, ferrous sulfate is presumed to have an effect as an inorganic flocculant, and is used in the solidification insolubilization neutral modifier of the present invention to electrically flocculate fine particles in the soil and make it easier to aggregate. It is also thought that its inclusion has the effect of making it easier to compact the soil.
In addition to ferrous sulfate, it is also possible to use acidic sulfates, such as, for example, aluminum sulfate, as alternative materials.

Ferrous sulfate is used in an amount of 10 to 200 parts by mass, preferably 30 to 100 parts by mass, more preferably 30 to 50 parts by mass, based on 100 parts by mass of the calcium oxide contained in the solidified and insolubilized neutral modifier. It is further contained in an amount of 1 to 20% by mass, preferably 3 to 10% by mass, and more preferably 5 to 10% by mass in the solidified and insolubilized neutral modifier.
The content range is a content range that does not hinder the strength development (solidification performance) of calcium oxide and can effectively insolubilize heavy metals such as arsenic under conditions where no change in strength occurs due to re-sludge of the treated soil.
If it is less than 1% by mass, the insolubilization performance of heavy metals etc. and the pH neutralization function of the treated soil will decrease, and if it exceeds 20% by mass, it will be affected by the reaction with the muddying agent contained in the low fluidization mud. The water trapped in the muddy material is released and becomes muddy again, reducing its strength.

Furthermore, the solidified and insolubilized neutral modifying material of the present invention contains calcium carbonate as an essential component, and has a pH buffering effect due to the carbonic acid-bicarbonate buffering effect, so that the pH of the treated soil remains neutral for a long period of time. becomes possible.
Calcium carbonate is contained in the solidified and insolubilized neutral modifier in an amount of 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more.
Within the above range, the solidification performance is excellent, the strength development is good, and the pH of the treated soil can be modified to a neutral range after 7 days of age.

More preferably, the solidified and insolubilized neutral modifier of the present invention can contain a polymer flocculant as an auxiliary agent. The polymer flocculant used as an adjuvant reacts with the moisture in the soil, promotes soil agglomeration, and makes it easier to compact the soil. In addition, because it has a high viscosity, it is difficult for the viscosity to decrease even when it reacts with iron ions, which helps maintain the strength of the soil.
The properties of the polymer flocculant include that it is easily soluble in cold water, that the pH of the aqueous solution is in the neutral range, and that the effective pH range covers the neutral range in order to correspond to various low fluidity soils. It is preferable that the viscosity becomes high when dissolved in water, and the preferable form is preferably a powder or a granular form with a maximum particle size of 1 mm or less.

As the polymer flocculant, an organic polymer flocculant that has the effect of reacting with moisture in the soil to agglomerate fine particles and make soil easier to compact can be suitably used. As for the type, at least one selected from the group consisting of anionic polymer flocculants, nonionic polymer flocculants, cationic polymer flocculants, and amphoteric polymer flocculants can be preferably used, and particularly preferred. It is an anionic polymer flocculant with a neutral solution pH and high viscosity.

As the organic polymer flocculant, at least one selected from the group consisting of polyacrylamide, polyacrylic ester, polyamidine, sodium polyacrylate, polyethylene oxide, and sodium acrylate-acrylamide copolymer can be used. Particularly preferable ones are polyacrylamide-based ones which have a high aqueous viscosity when dissolved in the same amount of water, for example, those having a viscosity of 400 mPa·s or more in a 0.25% aqueous solution are preferable.

The content of the polymer flocculant is 10 parts by mass or less based on 100 parts by mass of calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate, taking into account the pH of the treated soil. It is preferable. If the total amount exceeds 10 parts by mass, the cost will increase and it will not be economical, and there is a risk that the soil reforming performance will become too high due to excessive addition and the workability will deteriorate. Furthermore, adding large amounts of organic matter to soil is environmentally unfavorable.

The solidified and insolubilized neutral modifier of the present invention can be obtained by blending the above-mentioned essential containing materials of calcium oxide, magnesium oxide, ferrous sulfate and calcium carbonate in the above-mentioned proportions, and preferably further adding a polymer flocculant. By blending, the concentration of heavy metals such as arsenic in the test solution prepared in accordance with the Environment Agency Notification No. 46 (promulgated on August 23, 1991) can be determined in accordance with JIS K 0102 "Industrial Wastewater Test Method". The pH of the test solution was measured to be 0.01 mg/L or less, and the pH of the test solution was measured in accordance with JIS Z8802:2011 "pH measurement method" to be in the neutral range (the uniform wastewater standard of the Ministry of the Environment (5.8 ~ 8.6)), and without re-silting, the cone index can be increased to 200 kN/m, which is specified for type 4 construction generated soil in the soil classification standards of the Ministry of Land, Infrastructure, Transport and Tourism's ``Standards for Generated Soil Utilization.'' It becomes possible to set the number to ² or more.
In addition to the above-mentioned materials, any pH-adjusting materials such as slaked lime, soil-improving materials such as slag, etc. Any auxiliary materials may be added.

The solidified and insolubilized neutral modifier of the present invention can be obtained by uniformly mixing the above-mentioned essential ingredients of calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate, and a polymer flocculant contained as necessary. The materials can be mixed at once regardless of the order of mixing, or can be prepared by mixing these materials using any method.

The solidified and insolubilized neutral modifying material of the present invention prepared in this manner can be added to and mixed with low fluidization mud treated with a muddying material to effectively remove heavy metals, etc. in the soil over a long period of time. It has the ability to improve the soil by solidifying the treated soil to improve its strength without re-sludge, and it also maintains the pH of the treated soil in the neutral range. be.
Specifically, the pH of the soil eluate after 7 days of the treated soil obtained by mixing the solidified insolubilized neutral modifier of the present invention with the low fluidity mud is 5.8 to 8.6, and for example, the pH of the arsenic content is 5.8 to 8.6. It is possible to achieve an elution amount of 0.01 mg/L or less and a Cohn index of 200 kN/m ² .

Further, the solidification insolubilization neutral modification method of the present invention is a construction method in which the solidification insolubilization neutral modification material of the present invention and low fluidization mud are mixed, but the mixing method is not particularly limited, and for example, The solidified insolubilized neutral modifier of the present invention is sprinkled on the surface layer of the low-fluidization mud, and the same soil as that of conventional powdered insolubilized soil is improved by using heavy equipment that has surface modification mixing performance or by equipment for mixing with soil. Mixing equipment can be applied. As described above, by implementing the solidification insolubilization neutralization method of the present invention, the pH of the soil can be brought into the neutral range (5.8 to 8.6).

In addition, the solidified and insolubilized neutral modifier of the present invention is preferably used in powder form, and as a mixing device with the low fluidization soil, a backhoe, deep mixer, stationary mixer, power blender, etc. are used. The amount of the treatment material for preventing contamination, such as heavy metals, added to the treated soil varies depending on the moisture content of the soil, the required solidification strength of the treated soil, etc., and can be arbitrarily designed.

In this way, the solidified and insolubilized neutral modifier of the present invention is added to muddy soil, such as dredged soil and shield generated soil, which has high fluidity due to high water content and foaming agents, to remove heavy metals, etc. By contacting with low fluidity mud containing soil, heavy metals etc. are insolubilized without flowing out of the pore water captured by the muddying material in the soil, improving the solidification performance of the soil, and improving the solidification performance of the treated soil. It becomes possible to maintain the pH in the neutral range.
For example, all elution amounts of heavy metals, etc. in the soil measured based on the Soil Contamination Countermeasures Act are within the soil elution amount standards, and are compliant with the Environment Agency Notification No. 46 (promulgated on August 23, 1991). For example, after 7 days of age, the pH of the test solution prepared by this method can satisfy the environmental standard of 5.8 to 8.6 stipulated by the Ministry of the Environment's Uniform Effluent Standards. It is now possible to exceed 200kN/ ^m2 , which is stipulated for Type 4 construction generated soil in the soil classification standards of the Ministry of Land, Infrastructure, Transport and Tourism's ``Standards for the Use of Generated Soil'', making it possible to transport it by truck, etc. can be designed.

The present invention will be illustrated by the following examples and comparative examples.

(Test soil)
A muddying material containing polyacrylamide emulsion as a main component was added in an amount of 3 kg/ ^m3 to muddy soil having the physical properties shown in Table 1 below from which arsenic is eluted, mixed at low speed for 90 seconds with a soil mixer, and then After scraping off the soil adhering to the soil mixer container and paddle, the mixture was mixed again at low speed for 90 seconds to prepare test soil.

Regarding the water content ratio, wet density, fine particles with a particle size of less than 75 μm, arsenic elution amount and eluate pH of mud soil, and the Cone index of mud soil (before addition of mud addition) and test soil (after addition of mud addition), It is shown in Table 1.
The arsenic elution amount and Cohn index were measured according to the methods described in Test Examples 1 and 2 below.

(Raw materials used)
In preparing the solidified and insolubilized neutral modifier, the following materials were used.
・Calcium oxide: Powder (produced in Kudzu, Tochigi Prefecture)
・Magnesium oxide: Fine powder (produced in China)
・Calcium carbonate: Powder (Kudzu production in Tochigi Prefecture)
・Ferrous sulfate: Ferrous sulfate monohydrate fine powder (produced in China)
・Polymer flocculant: Anionic polymer flocculant (0.25% aqueous solution, viscosity 420 mPa/s)

(Solidified insolubilized neutral modifier)
Using each of the raw materials used above, each raw material was blended and mixed in the proportions shown in Table 2 below to prepare each solidified and insolubilized neutral modifier.
Although the mixing order of each raw material is not particularly limited, each raw material was mixed at the same time to prepare each solidified and insolubilized neutral modifier.
In addition, in Table 2, the polymer flocculant shows the blending ratio (mass %) based on the total amount of calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate.

(Test example)
Test example 1: Modification test (insolubilization test and neutralization confirmation test)
50 kg of each of the solidified and insolubilized neutral modifiers shown in Table 2 was added to 1 m ³ of the test soil in Table 1 above, and after mixing at low speed in a soil mixer for 90 seconds, it adhered to the container and paddle of the soil mixer. The soil was scraped off and mixed again at low speed for 90 seconds to prepare each treated soil.
After each treated soil was prepared, it was sealed and cured at 20°C until the age of 7 days, and then each treated soil of 7 days was treated in accordance with the Environment Agency Notification No. 46 (promulgated on August 23, 1991). Prepare a test solution (eluate), and measure the pH of the eluate (test solution) and the concentration of arsenic in the eluate (test solution) as the arsenic elution amount in accordance with JIS K 0102 "Factory wastewater test method". was measured.

For reference, the pH of the test solution and the amount of arsenic eluted were also measured in the same manner for the test soil in Table 1 to which the solidified and insolubilized neutral modifier was not added.
The results are shown in Table 2 above.

Test Example 2: Soil Solidification Test To 1 m ³ of the test soil in Table 1 above, 50 kg of each solidified insolubilized neutral modifier shown in Table 2 was added, and after mixing at low speed for 90 seconds with a soil mixer, The soil adhering to the container and paddle of the soil mixer was scraped off and mixed again at low speed for 90 seconds to prepare treated soil.
After each treated soil was prepared and hermetically cured at 20°C for up to 7 days, the treated soil was placed in three layers in a 10 cm mold as specified in JIS A 1210:2009 "Soil compaction test method by compaction". The materials were filled separately and the cone index at 7 days of age was measured in accordance with JIS A 1228 "Cone index test method for compacted soil".
The results are shown in Table 2 above.

It should be noted that the arsenic elution amount was considered to be passed if it was less than the soil elution amount standard 0.01 mg/L based on the Soil Contamination Countermeasures Law.
Furthermore, the pH of the eluate test solution was considered to be in the neutral range and passed if it fell within the range of 5.8 to 8.6 specified by the uniform wastewater standards of the Ministry of the Environment.
The cone index was passed if it was 200 kN/m ² or more, which is specified for type 4 construction generated soil in the soil classification standards of the Ministry of Land, Infrastructure, Transport and Tourism's ``Standards for Generated Soil Use''.

From Table 2 above, the solidified and insolubilized neutral modifiers of Examples (E1 to E8) containing calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate as essential components within the specified range of the present invention are as follows: Regarding soil that has been made to have low fluidity by blending muddying materials into highly water-containing fluidized mud, the amount of arsenic eluted in the 7-day-old treated soil is all within the soil leaching amount standard, and the amount of arsenic eluted from the soil The pH was uniformly within the wastewater standard range, and the cone index at 7 days of age was 200 kN/m ² or more, making it clear that the above-mentioned effects of the present invention could be effectively expressed.
Furthermore, by including a polymer flocculant (auxiliary agent) in a specific blending amount range in the neutral modifier, the amount of arsenic eluted in treated soil that is 7 days old is all within the standard for soil leached amount. The pH of the soil eluate was uniformly within the wastewater standard range, and the cone index at 7 days of age was 200 kN/ ^m2 or more, making it clear that the above effects of the present invention can be more effectively expressed. (E2-E6, E8).

Regarding the solidified insolubilized neutral modifier C1 of Comparative Example 1, which does not contain calcium oxide and has a low content of magnesium oxide, the arsenic elution amount standard is satisfied and the soil eluate pH is in the neutral range, but the Cohn index is It is lower than that of soil, and its solidification performance is inferior.
In addition, regarding the solidified insolubilized neutral modifier C2 that does not contain calcium oxide in Comparative Example 2, the arsenic elution amount standard is met, the soil eluate pH is also in the neutral range, and the Cone index is slightly increased compared to the test soil. However, the cone index was less than 200 kN/m ² and the solidification performance was not sufficient.

The solidified and insolubilized neutral modifier C3 of Comparative Example 3 has good solidification performance and satisfies the arsenic elution standard, but because the content of magnesium oxide is high relative to calcium oxide, the pH of the soil eluate becomes alkaline and falls within the neutral region. deviated from.
In addition, regarding the solidification and insolubilization neutral modifier C4 shown in Comparative Example 4, which does not contain ferrous sulfate and has a low content of magnesium oxide, the solidification performance is good, but the pH of the soil eluate becomes alkaline, and The amount of arsenic leached exceeded the soil leaching amount standard.

Regarding the solidified and insolubilized neutral modifier C5 shown in Comparative Example 5, the arsenic elution amount standard is satisfied and the pH of the soil eluate is also in the neutral range, but because the content of ferrous sulfate is high, the Cone index is lower than that of the original soil. The solidification performance is lower and the solidification performance is not sufficient.
Regarding the solidified insolubilized neutral modifying material C6 that does not contain calcium oxide and magnesium oxide in Comparative Example 6, the arsenic elution amount standard is met and the soil eluate pH is in the neutral range, but the Cohn index is lower than that of the test soil. This results in poor solidification performance.

Regarding the solidified and insolubilized neutral modifier C7 of Comparative Example 7, the solidification performance was good and the arsenic elution amount standard was satisfied, but the pH of the soil eluate became alkaline due to the high content of calcium oxide.
Regarding the solidified and insolubilized neutral modification material C8 shown in Comparative Example 8, the solidification performance is good, but because the content of ferrous sulfate is low, the pH of the soil eluate becomes alkaline, and the amount of arsenic eluted is lower than that of the soil. The elution amount standard was exceeded.

The solidification insolubilization neutral modifier of the present invention and the solidification insolubilization neutral modification method using the modifier can efficiently insolubilize heavy metals and halogens contained in mud that has been treated to have low fluidity with a muddying material. At the same time, it is possible to solidify the soil and improve its strength while maintaining the treated soil near the neutral region, so it can be effectively used for low fluidity soil containing muddying materials, for example, It can be effectively applied to the treatment of heavy metals, etc. in muddy soil with high water content and fluidity, which is generated in large quantities by excavation work and construction work of tunnels and dams, etc., and it is also easier to use modified soil effectively. It becomes possible to do so.

Claims (7)

A modifier used for low-fluid mud with a cone index of 50 to 200 kN/m2, including a muddying ^material whose main component is an organic polymer emulsion. Contains iron and calcium carbonate as essential components, contains 5 to 15 % by mass of calcium oxide, 3 to 20% by mass of ferrous sulfate, and 50% by mass or more of calcium carbonate, based on 100 parts by mass of calcium oxide. A solidified and insolubilized neutral modifier, characterized in that it contains magnesium oxide in a proportion of 10 to 100 parts by mass, and further contains ferrous sulfate in a proportion of 20 to 200 parts by mass. The solidified and insolubilized neutral modifier according to claim 1 further contains a polymer flocculant in an amount of 10 parts by mass or less based on 100 parts by mass of the total amount of calcium oxide, magnesium oxide, ferrous sulfate, and calcium carbonate. A solidified and insolubilized neutral modified material. The solidified and insolubilized neutral modifier according to claim 2, wherein the polymer flocculant is mainly composed of polyacrylamide and has a viscosity of 400 mPa·s or more when made into a 0.25% aqueous solution. Solidified and insolubilized neutral modification material. The solidified insolubilized neutral modifying material according to any one of claims 1 to 3 is in the form of a powder. The solidified insolubilized neutral modifying material according to any one of claims 1 to 4, wherein the organic polymer emulsion that is the main component of the muddying material is a polyacrylamide emulsion. Modified material. Solidification, characterized in that the solidification insolubilization neutral modifier according to any one of claims 1 to 5 is used in combination with low fluidity mud containing a muddying material whose main component is an organic polymer emulsion. Insolubilization neutral modification method. In the solidification insolubilization neutral modification method according to claim 6, the pH of the soil after 7 days of age of the treated soil obtained by mixing the solidification insolubilization neutral modification material with the mud soil is 5.8 to 8.6 and arsenic is present. A solidification insolubilization neutral modification method characterized by having an elution amount of 0.01 mg/L or less and a cone index of 200 kN/m ^{2 or} more.