JP7422071B2 - Heavy metal insolubilization solidification material and method for improving contaminated soil - Google Patents
Heavy metal insolubilization solidification material and method for improving contaminated soil Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims description 118
- 239000000463 material Substances 0.000 title claims description 79
- 229910001385 heavy metal Inorganic materials 0.000 title claims description 62
- 238000007711 solidification Methods 0.000 title claims description 51
- 230000008023 solidification Effects 0.000 title claims description 51
- 238000000034 method Methods 0.000 title claims description 26
- 239000004568 cement Substances 0.000 claims description 53
- 229910052785 arsenic Inorganic materials 0.000 claims description 44
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 claims description 44
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 41
- 239000000920 calcium hydroxide Substances 0.000 claims description 41
- 235000011116 calcium hydroxide Nutrition 0.000 claims description 41
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 41
- 238000010828 elution Methods 0.000 claims description 32
- 239000010802 sludge Substances 0.000 claims description 31
- 239000003795 chemical substances by application Substances 0.000 claims description 20
- 239000002893 slag Substances 0.000 claims description 18
- 239000010440 gypsum Substances 0.000 claims description 14
- 229910052602 gypsum Inorganic materials 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 8
- 229910052783 alkali metal Inorganic materials 0.000 claims description 3
- 150000001340 alkali metals Chemical class 0.000 claims description 3
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 3
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 3
- 150000001805 chlorine compounds Chemical class 0.000 claims description 3
- 150000003467 sulfuric acid derivatives Chemical class 0.000 claims description 3
- 229940037003 alum Drugs 0.000 claims 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 claims 1
- 239000004575 stone Substances 0.000 claims 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 18
- 239000010459 dolomite Substances 0.000 description 14
- 229910000514 dolomite Inorganic materials 0.000 description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 12
- 238000010276 construction Methods 0.000 description 10
- 239000000292 calcium oxide Substances 0.000 description 9
- 235000012255 calcium oxide Nutrition 0.000 description 9
- 239000004927 clay Substances 0.000 description 9
- 230000007613 environmental effect Effects 0.000 description 7
- 239000004576 sand Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000011398 Portland cement Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 4
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000011400 blast furnace cement Substances 0.000 description 3
- 239000011575 calcium Substances 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910000358 iron sulfate Inorganic materials 0.000 description 2
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 235000010893 Bischofia javanica Nutrition 0.000 description 1
- 240000005220 Bischofia javanica Species 0.000 description 1
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- -1 and conversely Substances 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- 239000002956 ash Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 235000011132 calcium sulphate Nutrition 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
- KOLXPEJIBITWIQ-UHFFFAOYSA-L disodium hydrogenarsenate heptahydrate Chemical compound O.O.O.O.O.O.O.[Na+].[Na+].O[As]([O-])([O-])=O KOLXPEJIBITWIQ-UHFFFAOYSA-L 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000010881 fly ash Substances 0.000 description 1
- 238000010413 gardening Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- RLJMLMKIBZAXJO-UHFFFAOYSA-N lead nitrate Chemical compound [O-][N+](=O)O[Pb]O[N+]([O-])=O RLJMLMKIBZAXJO-UHFFFAOYSA-N 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- 239000011505 plaster Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000012085 test solution Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K17/00—Soil-conditioning materials or soil-stabilising materials
- C09K17/02—Soil-conditioning materials or soil-stabilising materials containing inorganic compounds only
- C09K17/06—Calcium compounds, e.g. lime
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K17/00—Soil-conditioning materials or soil-stabilising materials
- C09K17/02—Soil-conditioning materials or soil-stabilising materials containing inorganic compounds only
- C09K17/10—Cements, e.g. Portland cement
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/12—Consolidating by placing solidifying or pore-filling substances in the soil
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Organic Chemistry (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Soil Sciences (AREA)
- Structural Engineering (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Environmental & Geological Engineering (AREA)
- Civil Engineering (AREA)
- Mining & Mineral Resources (AREA)
- Paleontology (AREA)
- Agronomy & Crop Science (AREA)
- General Engineering & Computer Science (AREA)
- Hydrology & Water Resources (AREA)
- Water Supply & Treatment (AREA)
- Processing Of Solid Wastes (AREA)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
- Treatment Of Sludge (AREA)
Description
本発明は、建設汚泥や浚渫土等の軟弱土壌に含まれる重金属の溶出を抑制でき、適切な強度の土壌に改良可能な重金属不溶化固化材、特にヒ素や鉛を含有する軟弱土壌の重金属溶出量を低減し得る不溶化固化材に関する。 The present invention provides a heavy metal insolubilization solidification material that can suppress the elution of heavy metals contained in soft soil such as construction sludge and dredged soil, and can improve the soil to an appropriate strength, especially the amount of heavy metal leached from soft soil containing arsenic and lead. The present invention relates to an insolubilized solidifying material that can reduce
現場工事において、建設汚泥や浚渫土等の軟弱土壌に、ヒ素や鉛等の重金属有害物質が含まれていることが報告されている。ヒ素や鉛等の重金属は、環境基準で規制された汚染物質であり、直接摂取することや溶出した水を摂取することで人体に影響を及ぼすおそれがあり、溶出基準値を上回ると、土壌の不溶化処理や吸着工法、遮蔽処理等の措置を行う必要がある。
加えて、建設汚泥や浚渫土等の軟弱土壌の場合、再生利用するために、固化処理によって所定強度の土壌に改良する必要がある。
It has been reported that during construction sites, soft soil such as construction sludge and dredged soil contains toxic heavy metals such as arsenic and lead. Heavy metals such as arsenic and lead are pollutants regulated by environmental standards, and can affect the human body if ingested directly or in the water they elute. It is necessary to take measures such as insolubilization treatment, adsorption methods, and shielding treatment.
In addition, in the case of soft soil such as construction sludge or dredged soil, it is necessary to improve the soil to a predetermined strength through solidification treatment in order to reuse it.
ヒ素や鉛に汚染された土壌の不溶化処理方法として、例えば、Ca/Mg系塩基性物質を添加した後、鉄の硫酸塩/塩酸塩を添加する方法(特許文献1)、焼石膏とAl化合物とCa/Mg含有化合物を混合使用する方法(特許文献2)によって、中性域で不溶化固化することが提案されている。
しかし、特許文献1,2に記載されている方法は、土壌からのヒ素や鉛の溶出を抑制することは可能であるものの、不溶化後における改良土壌の強度発現性が低く、軟弱土壌の再生利用には不十分である。
ヒ素含有汚泥の処理について、不溶化剤による不溶化処理工程、固化材による固化処理工程、及び乾燥剤による乾燥処理工程からなる三工程の処理方法(特許文献3)が提案されているが、工程が煩雑であり、現場施工に不向きである。また、ヒ素汚染土壌を200~700℃で加熱処理した後、Ca化合物と水を添加する処理方法(特許文献4)も提案されているが、こうした高温加熱処理も、現場での施工に適さない。
As an insolubilization treatment method for soil contaminated with arsenic or lead, for example, a method of adding a Ca/Mg-based basic substance and then adding iron sulfate/hydrochloride (Patent Document 1), a method of adding iron sulfate/hydrochloride, a method of adding calcined gypsum and an Al compound, etc. It has been proposed to insolubilize and solidify in the neutral region by a method (Patent Document 2) in which Ca/Mg-containing compounds are mixed and used.
However, although the methods described in Patent Documents 1 and 2 can suppress the elution of arsenic and lead from soil, the strength development of improved soil after insolubilization is low, and it is difficult to recycle soft soil. is insufficient.
Regarding the treatment of arsenic-containing sludge, a three-step treatment method has been proposed (Patent Document 3) consisting of an insolubilization treatment process using an insolubilizing agent, a solidification treatment process using a solidification agent, and a drying treatment process using a desiccant agent, but the process is complicated. Therefore, it is not suitable for on-site construction. Additionally, a treatment method has been proposed in which arsenic-contaminated soil is heat-treated at 200 to 700°C and then Ca compounds and water are added (Patent Document 4), but such high-temperature heat treatment is also not suitable for on-site construction. .
他方、セメントは、軟弱土壌のセメント系固化材として汎用されており、重金属の不溶化にも有効である。しかし、粘土分の多い土壌や重金属含有量の多い土壌に対しては、従来のセメント系固化材ではヒ素や鉛の不溶化には十分とはいえず、重金属の溶出環境基準を満たすためにセメント系固化材の添加量を多くすると、改良土壌の強度が過剰になり軟弱土壌の再生利用に支障を来す懸念がある。 On the other hand, cement is widely used as a cementitious solidifying agent for soft soil, and is also effective in insolubilizing heavy metals. However, for soils with a high clay content or heavy metal content, conventional cement-based solidifying agents are not sufficient to insolubilize arsenic and lead, and in order to meet the environmental standards for heavy metal elution, cement If the amount of solidification agent added is increased, there is a concern that the strength of the improved soil will become excessive, which will impede the recycling of soft soil.
特許文献5~9は、各種のセメント系固化材又は不溶化材を開示する。すなわち、特許文献5は、石膏と、生石灰又はセメントと、高炉スラグ微粉末とを混合した主材と、主材による土壌の強アルカリ化を抑制するpH調整剤とからなる汚染土壌の不溶化材を開示する。特許文献6は、土壌用セメント系固化材に、消石灰と軽焼ドロマイトとを所定比で配合してなるセメント系固化材用添加材、及び火山灰質土壌改良方法を開示する。特許文献7は、セメントクリンカ、石膏及び消石灰を含んでなる土壌固化材において、消石灰として粒子径30μm以上の粒子を5~40体積%含有する消石灰を用いることを開示する。特許文献8は、ポルトランドセメントと高炉スラグと石膏とを所定割合で含む重金属汚染土壌用セメント系処理材、及び重金属汚染土壌の固化不溶化処理方法を開示する。特許文献9は、セメント系固化材にセメント焼成炉プレヒーターから抽出されたセメント原料粉末(プレヒーター原料)を混合して用いる地盤改良工法を開示する。プレヒーター原料中には、セメント原料中の石灰石が熱分解して生成した生石灰が多く含まれる。 Patent Documents 5 to 9 disclose various cement-based solidifying materials or insolubilizing materials. That is, Patent Document 5 discloses a contaminated soil insolubilizing material consisting of a main material mixed with gypsum, quicklime or cement, and pulverized blast furnace slag, and a pH adjuster that suppresses strong alkalization of the soil by the main material. Disclose. Patent Document 6 discloses an additive for a cement-based solidifying material and a method for improving volcanic ash soil, which is made by blending slaked lime and lightly calcined dolomite in a predetermined ratio with a cement-based soil solidifying material. Patent Document 7 discloses the use of slaked lime containing 5 to 40% by volume of particles with a particle size of 30 μm or more as the slaked lime in a soil solidification material containing cement clinker, gypsum, and slaked lime. Patent Document 8 discloses a cement-based treatment material for heavy metal-contaminated soil containing Portland cement, blast furnace slag, and gypsum in a predetermined ratio, and a method for solidifying and insolubilizing heavy metal-contaminated soil. Patent Document 9 discloses a ground improvement method in which cement raw material powder (preheater raw material) extracted from a cement kiln preheater is mixed with a cement-based solidifying material. The preheater raw material contains a large amount of quicklime produced by thermal decomposition of limestone in the cement raw material.
本発明は、ヒ素及び鉛を含有する軟弱汚染土壌のヒ素及び鉛の溶出量を抑制し、かつ改良土壌として適切な強度発現性を示し得る重金属不溶化固化材、及び汚染土壌類の改良工法を提供することを目的とする。 The present invention provides a heavy metal insolubilization solidification material that can suppress the elution amount of arsenic and lead from soft contaminated soil containing arsenic and lead and exhibit appropriate strength development properties as improved soil, and a method for improving contaminated soil. The purpose is to
本発明者は、上記課題を解決するために、特定のセメント系固化材に消石灰を組み合わせることによって、上記課題を解決し得ることを見出した。 In order to solve the above-mentioned problem, the present inventor found that the above-mentioned problem could be solved by combining slaked lime with a specific cement-based solidifying material.
すなわち、本発明は、重金属としてヒ素及び鉛を含有する軟弱土壌又は汚泥を固化して改良土壌にする共に改良土壌からのヒ素及び鉛の溶出を抑制する重金属不溶化固化材であって、セメント、高炉スラグ及び石膏からなるセメント系固化材と、消石灰又は軽焼ドロマイトを含み、セメント系固化材と消石灰又は軽焼ドロマイトの合計に対し、消石灰の配合量が10~55質量%であることを特徴とする重金属不溶化固化材である。 That is, the present invention is a heavy metal insolubilization solidification material that solidifies soft soil or sludge containing arsenic and lead as heavy metals to make improved soil, and suppresses the elution of arsenic and lead from the improved soil. It is characterized by containing a cementitious solidifying material consisting of slag and gypsum, and slaked lime or lightly calcined dolomite, and the blending amount of slaked lime is 10 to 55% by mass based on the total of the cementitious solidifying material and slaked lime or lightly calcined dolomite. It is a heavy metal insolubilization solidification material.
上記消石灰としては、平均粒径が20μm以下であり、CaOを72.5質量%以上含有するものが適する。上記軽焼ドロマイトとしては、CaO・MgOを93.0質量%以上含有するものであり、粉末度は5000cm2/g~7000cm2/gが適する。また、上記セメント系固化材としては、セメントを25~90質量%、高炉スラグを5~50質量%、石膏を5~25質量%含有するものが適する。 As the above-mentioned slaked lime, one having an average particle size of 20 μm or less and containing 72.5% by mass or more of CaO is suitable. The above-mentioned light calcined dolomite contains 93.0% by mass or more of CaO/MgO, and suitably has a fineness of 5000 cm 2 /g to 7000 cm 2 /g. Further, as the above-mentioned cementitious solidifying material, one containing 25 to 90% by mass of cement, 5 to 50% by mass of blast furnace slag, and 5 to 25% by mass of gypsum is suitable.
上記重金属不溶化固化材は、上記セメント系固化材と消石灰又は軽焼ドロマイトの合計100質量部に対し、アルカリ金属及び/又はアルカリ土類金属の塩化物及び/又は硫酸塩を2~20質量部配合することができる。 The above-mentioned heavy metal insolubilization solidification material contains 2 to 20 parts by mass of chlorides and/or sulfates of alkali metals and/or alkaline earth metals to a total of 100 parts by mass of the cement-based solidification material and slaked lime or lightly calcined dolomite. can do.
上記重金属不溶化固化材は、軟弱土壌又は汚泥を、一軸圧縮強さ100~3000kN/m2の改良土壌にするために、ヒ素と鉛の溶出量を各0.01mg/L以下の改良土壌にするために好適に使用される。 The above-mentioned heavy metal insolubilization solidification material improves soft soil or sludge into improved soil with an unconfined compressive strength of 100 to 3000 kN/ m2 , and improves the elution amount of arsenic and lead to 0.01 mg/L or less each. It is suitably used for this purpose.
また、本発明は、ヒ素及び鉛を含有する軟弱土壌又は汚泥を改良して強度を高める共に上記重金属の溶出を抑制する軟弱土壌又は汚泥の改良工法であって、上記の重金属不溶化固化材を土壌又は汚泥に混合することを特徴とする軟弱土壌又は汚泥の改良工法である。
軟弱土壌又は汚泥を、一軸圧縮強さ100~3000kN/m2の改良土壌にしたり、ヒ素溶出量0.01mg/l以下、又は鉛溶出量0.01mg/l以下の改良土壌にする場合に好適な工法である。
The present invention also provides a method for improving soft soil or sludge containing arsenic and lead to increase its strength and suppress the elution of the heavy metals, wherein the heavy metal insolubilization solidification material is applied to the soil. Or, it is a method for improving soft soil or sludge, which is characterized by mixing it with sludge.
Suitable for converting soft soil or sludge into improved soil with unconfined compressive strength of 100 to 3000 kN/ m2 , improved soil with arsenic elution of 0.01 mg/l or less, or lead elution of 0.01 mg/l or less. It is a construction method.
本発明の重金属不溶化固化材によれば、簡易に、ヒ素及び鉛を含有する軟弱土壌又は汚泥類を適切な強度の改良土壌に固化でき、かつ、ヒ素及び鉛の溶出量を環境指定基準以下に抑制できる。 According to the heavy metal insolubilization solidification material of the present invention, soft soil or sludge containing arsenic and lead can be easily solidified into improved soil of appropriate strength, and the amount of arsenic and lead eluted can be reduced to below designated environmental standards. It can be suppressed.
本発明の重金属不溶化固化材は、重金属としてヒ素及び鉛を含有する軟弱土壌又は汚泥(以下、両者を軟弱土壌類又は土壌ともいう。)を固化して改良土壌にする共に、改良土壌からのヒ素と鉛の溶出を抑制する重金属不溶化固化材である。この重金属不溶化固化材は主成分としてセメント系固化材と消石灰又は軽焼ドロマイト(以下、消石灰類ともいう。)を含む。 The heavy metal insolubilization solidification material of the present invention solidifies soft soil or sludge containing arsenic and lead as heavy metals (hereinafter, both are also referred to as soft soils or soil) into improved soil, and also removes arsenic from the improved soil. It is a heavy metal insolubilization solidification material that suppresses lead elution. This heavy metal insolubilization solidification material contains a cement solidification material and slaked lime or light calcined dolomite (hereinafter also referred to as slaked lime) as main components.
セメント系固化材と消石灰類の配合割合は、両者の合計に対し、消石灰類の配合量が10~55質量%であり、好ましくは20~50質量%である。消石灰類が10質量%未満では、改良土壌の強度が過剰となり、ヒ素や鉛の不溶化も不十分となり易く、再生利用に支障を来す懸念がある。消石灰類の添加量が55質量%を超えると改良土壌の強度が不充分となるだけでなく、pHが高くなることから、鉛の溶出量が増加する。 The blending ratio of the cement-based solidifying agent and slaked lime is such that the blended amount of slaked lime is 10 to 55% by mass, preferably 20 to 50% by mass, based on the total of both. If the content of slaked lime is less than 10% by mass, the strength of the improved soil will be excessive, and the insolubilization of arsenic and lead will likely be insufficient, which may impede recycling. If the amount of slaked lime added exceeds 55% by mass, not only will the strength of the improved soil be insufficient, but also the pH will increase, leading to an increase in the amount of lead leached.
セメント系固化材は、セメントを母材とする固化性の材料であって、軟弱土壌類を効率良く安定化するために、セメントに高炉スラグや石膏を有効成分として添加したものである。セメント系固化材100質量%中に、セメントを25~90質量%、高炉スラグを5~50質量%、及び石膏を5~25質量%含有することがより好ましい。
セメントとしては、JIS規格品(JIS R 5210~5214)あるいは、ポルトランドセメントを製造する際の中間原料であるクリンカーを使用できる。すなわち、ポルトランドセメント、高炉セメント、シリカセメント、フライアッシュセメント、エコセメント及び混合セメントが挙げられるが、好ましくはポルトランドセメント、高炉セメントである。
高炉スラグとしては、徐冷スラグ、水砕スラグが挙げられるが、潜在水硬性を有する水砕スラグが適する。
石膏としては、無水石膏が適する。
なお、高炉セメントなどセメント中に高炉スラグや石膏を含むものも存在するが、本発明のセメント系固化材としてセメントに配合される高炉スラグや石膏は、これとは別に加える量であると理解される。
セメント系固化材の製造は、それぞれの粉末を混合、あるいは混合粉砕のいずれも使用できる。セメント系固化材の粒径は、ブレーン比表面積が4000cm2/g以上、好ましくは5000cm2/g以上である。
セメント系固化材に消石灰又は軽焼ドロマイトを配合した重金属不溶化固化材の粒径は、消石灰を配合する場合、ブレーン比表面積が7000cm2/g以上、好ましくは8000cm2/g以上である。軽焼ドロマイトを配合する場合、ブレーン比表面積が5000cm2/g以上、好ましくは6000cm2/g以上である。上限は特に限定されないが、粉砕限界の観点から、12000cm2/g程度である。
Cement-based solidifying materials are solidifying materials that use cement as a base material, and are made by adding blast furnace slag or gypsum to cement as active ingredients in order to efficiently stabilize soft soils. It is more preferable to contain 25 to 90 mass % of cement, 5 to 50 mass % of blast furnace slag, and 5 to 25 mass % of gypsum in 100 mass % of cement-based solidifying material.
As the cement, JIS standard products (JIS R 5210 to 5214) or clinker, which is an intermediate raw material when manufacturing Portland cement, can be used. That is, examples include Portland cement, blast furnace cement, silica cement, fly ash cement, ecocement, and mixed cement, with Portland cement and blast furnace cement being preferred.
Examples of blast furnace slag include slowly cooled slag and granulated slag, and granulated slag with latent hydraulic properties is suitable.
As the plaster, anhydrite is suitable.
Although there are cements such as blast furnace cement that contain blast furnace slag and gypsum, it is understood that the amount of blast furnace slag and gypsum that is mixed into cement as a cementitious solidifying agent of the present invention is added separately from this. Ru.
The cementitious solidifying material can be produced by mixing the respective powders or by pulverizing them. The particle size of the cement solidifying material has a Blaine specific surface area of 4000 cm 2 /g or more, preferably 5000 cm 2 /g or more.
The particle size of the heavy metal insolubilized solidifying material, which is a cement-based solidifying material blended with slaked lime or light calcined dolomite, has a Blaine specific surface area of 7000 cm 2 /g or more, preferably 8000 cm 2 /g or more when slaked lime is blended. When light calcined dolomite is blended, the Blaine specific surface area is 5000 cm 2 /g or more, preferably 6000 cm 2 /g or more. The upper limit is not particularly limited, but from the viewpoint of pulverization limit, it is about 12000 cm 2 /g.
消石灰又は軽焼ドロマイトの配合割合は、重金属不溶化固化材において10~55質量%の範囲とすることがよい。
消石灰としては、JIS規格品(JIS R 9001)を使用できる。好ましくは特号であり、CaO分を72.5質量%以上含有するものが適する。また、消石灰には、土壌と混合した際に消石灰となり得る化合物を含む。好ましくは生石灰である。
また、消石灰の平均粒径(d50)は、好ましくは20μm以下、より好ましくは10μm以下である。
軽焼ドロマイトとしては、JIS規格品(JIS R 9001)を使用できる。好ましくは特号であり、CaO・MgO分を93.0質量%以上、MgO分を30.0質量%以上含有するものが適する。
粉末度(比表面積)は、好ましくは5000~7000cm2/gである。ここで、粉末度は、軽焼ドロマイトをセメント固化材等と混合、粉砕した後の数値である。
The blending ratio of slaked lime or lightly calcined dolomite is preferably in the range of 10 to 55% by mass in the heavy metal insolubilization solidification material.
As the slaked lime, a JIS standard product (JIS R 9001) can be used. Preferably, it is a special issue, and one containing 72.5% by mass or more of CaO is suitable. Slaked lime also contains compounds that can become slaked lime when mixed with soil. Preferably it is quicklime.
Moreover, the average particle diameter (d50) of slaked lime is preferably 20 μm or less, more preferably 10 μm or less.
As the light calcined dolomite, JIS standard products (JIS R 9001) can be used. Preferably, it is a special issue, and one containing 93.0% by mass or more of CaO/MgO and 30.0% by mass or more of MgO is suitable.
The fineness (specific surface area) is preferably 5000 to 7000 cm 2 /g. Here, the fineness is a value obtained after mixing lightly calcined dolomite with a cement solidifying material and the like and pulverizing it.
本発明の重金属不溶化固化材は、ヒ素、鉛の溶出量を抑制するために、上記セメント系固化材と消石灰類に加えて、アルカリ金属及び/又はアルカリ土類金属の塩化物及び/又は硫酸塩を配合するとよい。
塩化物としては、好ましくは塩化カルシウム、又は塩化ナトリウムが挙げられ、硫酸塩としては、好ましくは硫酸マグネシウム、硫酸ナトリウム、又は硫酸カルシウムが挙げられ、これらを単独又は二種以上を混合して使用できる。
塩化物及び/又は硫酸塩は、上記セメント系固化材と消石灰類の合計100質量部に対し、2~20質量部を配合することがよく、好ましくは7~15質量部である。
In order to suppress the elution amount of arsenic and lead, the heavy metal insolubilizing solidifying material of the present invention contains, in addition to the above cementitious solidifying material and slaked lime, chlorides and/or sulfates of alkali metals and/or alkaline earth metals. It is recommended to mix.
The chloride preferably includes calcium chloride or sodium chloride, and the sulfate preferably includes magnesium sulfate, sodium sulfate, or calcium sulfate, and these can be used alone or in a mixture of two or more. .
The chloride and/or sulfate is preferably blended in an amount of 2 to 20 parts by mass, preferably 7 to 15 parts by mass, based on a total of 100 parts by mass of the cement solidifying agent and slaked lime.
本発明の重金属不溶化固化材には、必要によりコンクリート混和材や無機粉末などその他の成分を配合し得る。また、重金属不溶化固化材は配合成分を事前に混合してもよく、施工現場で同時に混合してもよいが、事前に混合しておけば、製品の品質安定性が優れる。 The heavy metal insolubilization solidification material of the present invention may contain other components such as concrete admixtures and inorganic powders, if necessary. In addition, the components of the heavy metal insolubilization solidification material may be mixed in advance or simultaneously at the construction site, but if they are mixed in advance, the quality stability of the product will be excellent.
本発明の重金属不溶化固化材は、軟弱土壌又は汚泥を処理して改良土壌とするために使用される。
軟弱土壌としては、一般に泥土と言われ、建設ないし浚渫等により発生する土壌のうち流動性を呈する状態のものであって、強度としては、コーン指数200kN/m2未満であるか、あるいは一軸圧縮強さが概ね50kN/m2以下の土壌がある。
汚泥としては水槽、川、池、湖沼、海底等に堆積したものがあるが、これらは水分量が多く、流動性が大きいので、陸地に放置してある程度乾燥させるか、水分量の少ない土壌と混合して事前処理して含水量を調整することがよい。
The heavy metal insolubilization solidification material of the present invention is used to treat soft soil or sludge to improve soil.
Soft soil is generally referred to as muddy soil, which is soil that is generated during construction or dredging and exhibits fluidity, and has a strength of less than 200 kN/ m2 in terms of Cone index, or uniaxial compression. There is soil with a strength of approximately 50kN/ m2 or less.
Sludge can be deposited in aquariums, rivers, ponds, lakes, ocean beds, etc., but since it has a high moisture content and is highly fluid, it must be left on land to dry out to some extent, or it can be removed from soil with low moisture content. It is advisable to mix and pre-treat to adjust the moisture content.
土壌の状態としては、含水比が10~200質量%、好ましくは20~50質量%の土壌であることがよい。重金属不溶化固化材が固化して強度を発現するためには適当な水分が必要であるが、過剰であると強度向上効果が劣る。
また、湿潤密度としては、1~3g/cm3、好ましくは1.5~2.50g/cm3の土壌に適する。
加えて、重金属としてヒ素と鉛を含む軟弱土壌類が対象である。ヒ素と鉛の含有量は特に限定されないが、土壌1kg当たり、各1.0mg以上、好ましくは10.0mg以上含むことがよい。上限には制限はないが、200mg程度以下であれば、固化後の改良土壌において、排出基準値(0.01以下)の溶出量に低減できる。
特に、粘土を多く含む軟弱土壌において、本発明の固化材や改良工法は有効である。土壌は通常、粘土と砂とから構成されるが、粘土が多い土壌は粘性土、逆に砂が多い土壌は砂質土と言われる。本発明は、粘土と砂の合計量に対して粘土を50質量%以上含む粘性土、又は粘土を30質量%以上含む砂質土を処理するのに有効である。
The soil preferably has a water content of 10 to 200% by mass, preferably 20 to 50% by mass. An appropriate amount of moisture is necessary for the heavy metal insolubilized solidification material to solidify and develop strength, but if it is in excess, the strength improvement effect will be poor.
Further, it is suitable for soil with a wet density of 1 to 3 g/cm 3 , preferably 1.5 to 2.50 g/cm 3 .
In addition, soft soils containing heavy metals such as arsenic and lead are targeted. The contents of arsenic and lead are not particularly limited, but each kg of soil preferably contains 1.0 mg or more, preferably 10.0 mg or more. There is no upper limit, but if it is about 200 mg or less, the elution amount can be reduced to the emission standard value (0.01 or less) in improved soil after solidification.
The solidification material and improved construction method of the present invention are particularly effective in soft soil containing a large amount of clay. Soil is usually composed of clay and sand, and soil with a lot of clay is called clayey soil, and conversely, soil with a lot of sand is called sandy soil. The present invention is effective in treating clay soil containing 50% by mass or more of clay or sandy soil containing 30% by mass or more of clay based on the total amount of clay and sand.
本発明の重金属不溶化固化材を使用して軟弱土壌類の不溶化固化処理する場合、処理対象の軟弱土壌類1m3に対し、重金属不溶化固化材を、10~300kg、好ましくは30~200kg、特に好ましくは50~150kg使用することがよい。また、重金属不溶化固化材に含まれる消石灰類の添加量としては、軟弱土壌類1m3に対し、5~55kgの範囲が好ましい。より好ましくは10~55kgの範囲である。 When insolubilizing and solidifying soft soil using the heavy metal insolubilizing solidifying material of the present invention, the heavy metal insolubilizing solidifying material is applied in an amount of 10 to 300 kg, preferably 30 to 200 kg, particularly preferably 1 m 3 of soft soil to be treated. It is recommended to use 50 to 150 kg. Further, the amount of slaked lime contained in the heavy metal insolubilization solidification material is preferably in the range of 5 to 55 kg per 1 m 3 of soft soil. More preferably, it is in the range of 10 to 55 kg.
本発明の重金属不溶化固化材は、軟弱土壌類を一軸圧縮強さ100~3000kN/m2の改良土壌にすることが可能となる。特に、一軸圧縮強さ300~2000kN/m2の改良土壌、さらに800~1800kN/m2の改良土壌にすることが可能となる。
本発明の重金属不溶化固化材は、上述のとおり軟弱土壌類を所定強度に固化できると共に、ヒ素と鉛の溶出量を低減できる。好ましくはヒ素又は鉛の溶出量の少なくともいずれかを環境基準値(0.01mg/L以下)にすることも可能となる。なお、溶出量の測定は実施例の条件に従う。
The heavy metal insolubilization and solidification material of the present invention makes it possible to transform soft soil into improved soil with an unconfined compressive strength of 100 to 3000 kN/m 2 . In particular, it becomes possible to make improved soil with an unconfined compressive strength of 300 to 2000 kN/m 2 , and further to 800 to 1800 kN/m 2 .
The heavy metal insolubilization solidification material of the present invention can solidify soft soil to a predetermined strength as described above, and can reduce the amount of arsenic and lead eluted. Preferably, it is also possible to reduce the elution amount of arsenic or lead to an environmental standard value (0.01 mg/L or less). Note that the measurement of the elution amount follows the conditions of the example.
以下、実施例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。なお、特に断りのない限り部は質量部であり、%は質量%である。 EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples. In addition, unless otherwise specified, parts are parts by mass, and % is mass %.
重金属不溶化固化材に使用した材料を次に示す。
普通ポルトランドセメント(OPC) 日鉄セメント社製、ブレーン比表面積3340 cm2/g
高炉スラグ 日本製鉄社製
無水石膏 タイ産
消石灰特特選 北海道石灰化工社製 (CaO:73.5%,平均粒径:4.8μm)
軽焼ドロマイト 黒崎播磨社製 (CaO・MgO:97.0%、MgO:39.5%、粉末度:6140 cm2/g)
The materials used for the heavy metal insolubilization solidification material are shown below.
Ordinary Portland Cement (OPC) Manufactured by Nippon Steel Cement Co., Ltd. Blaine specific surface area 3340 cm 2 /g
Blast furnace slag Made by Nippon Steel Anhydrous gypsum Made in Thailand Specially selected slaked lime Made by Hokkaido Lime Kako Co., Ltd. (CaO: 73.5%, average particle size: 4.8 μm)
Light calcined dolomite manufactured by Kurosaki Harima Co., Ltd. (CaO/MgO: 97.0%, MgO: 39.5%, fineness: 6140 cm 2 /g)
上記OPC単体をセメント系固化材(I)とした。セメント(I)とも言う。
上記OPC57.0質量部、高炉スラグ34.7部及び石膏8.3部を、混合、粉砕して、ブレーン比表面積6310cm2/gのセメント系固化材(II)とした。セメント(II)とも言う。
The above OPC alone was used as a cement solidifying material (I). Also called cement (I).
57.0 parts by mass of the above OPC, 34.7 parts of blast furnace slag, and 8.3 parts of gypsum were mixed and crushed to obtain a cement-based solidifying material (II) having a Blaine specific surface area of 6310 cm 2 /g. Also called cement (II).
下記の土壌材料及び重金属化合物(試薬)を使用し、温度50度で2日間乾燥させた土と蒸留水に重金属試薬を溶解させたものを、ソイルミキサーで3分間混合することで、含水比、重金属量を調整した模擬汚染土壌を作成した(土壌A~E)。
荒木田土 あかぎ園芸製
砕砂 白老産
8号珪砂 東北珪砂社製
ひ酸水素二ナトリウム七水和物(特級) 関東化学社製
硝酸鉛(II) 関東化学社製
Using the following soil materials and heavy metal compounds (reagents), mix soil that has been dried at a temperature of 50 degrees for 2 days and heavy metal reagents dissolved in distilled water for 3 minutes with a soil mixer to determine the water content ratio, Simulated contaminated soils with adjusted amounts of heavy metals were created (soils A to E).
Arakida Soil, Akagi Gardening, Crushed Sand, Shiraoi Product
No. 8 silica sand, Tohoku Silica Sand Co., Ltd. Disodium hydrogen arsenate heptahydrate (special grade), Kanto Kagaku Co., Ltd. Lead nitrate (II), Kanto Kagaku Co., Ltd.
土壌A~Eの配合組成、土質、含水比、密度及び重金属含有量を表1に示す。
表1において、湿潤密度の単位は(g/cm3)であり、ヒ素、鉛の含有量(上段)の単位は(mg/kg)であり、ヒ素、鉛の溶出量(下段)の単位は(mg/L)である。配合量は部である。
なお、溶出量の測定は、環境省告示46号に準拠して検液を作製し、ICP発光分光分析法によって測定した。
Table 1 shows the composition, soil quality, water content, density, and heavy metal content of soils A to E.
In Table 1, the unit of wet density is (g/cm 3 ), the unit of arsenic and lead content (upper row) is (mg/kg), and the unit of arsenic and lead elution amount (lower row) is (mg/L). The amount is in parts.
The elution amount was measured by preparing a test solution in accordance with Ministry of the Environment Notification No. 46 and using ICP emission spectrometry.
参考例1~4
土壌A~Dに、セメント系固化材(II)を100kg/m3となるように混合して、7日後及び28日後のヒ素溶出量と一軸圧縮強さを測定した。結果を表2に示す。
Reference examples 1 to 4
Cement solidification agent (II) was mixed into soils A to D at a concentration of 100 kg/m 3 , and the arsenic elution amount and unconfined compressive strength were measured after 7 and 28 days. The results are shown in Table 2.
表2から、土壌中の砂の量が増えるほどヒ素の溶出量は減少し、参考例4の土壌Dでは、セメント系固化材においても環境基準値以下までヒ素の不溶化が可能であることが分かる。しかし、粘土(荒木田土)が増えるほどヒ素溶出量が増加し、セメント系固化材では不溶化が困難であることが分かる。 From Table 2, it can be seen that as the amount of sand in the soil increases, the amount of arsenic eluted decreases, and in soil D of Reference Example 4, it is possible to insolubilize arsenic to below the environmental standard value even in cement-based solidification materials. . However, as the amount of clay (Arakita soil) increases, the amount of arsenic eluted increases, and it is clear that it is difficult to insolubilize it with cement-based solidifying agents.
実施例1~8、比較例1~5
上記土壌Eに対し、セメント系固化材(II)と消石灰を配合してなる重金属不溶化固化材を混合処理して、7日後の溶出量と一軸圧縮強さを測定した。結果を表3に示す。なお、表3には、重金属不溶化固化材のブレーン比表面積も示す。
Examples 1 to 8, Comparative Examples 1 to 5
The above soil E was mixed with a heavy metal insolubilizing solidifying material made by blending cement-based solidifying material (II) and slaked lime, and the elution amount and unconfined compressive strength were measured after 7 days. The results are shown in Table 3. Note that Table 3 also shows the Blaine specific surface area of the heavy metal insolubilization solidification material.
表3から、消石灰を配合しないと、ヒ素の不溶化が不十分となり、消石灰量が増えるとともに、ヒ素の溶出量も減少するが、鉛の溶出量が増加することが分かる。また、セメント系固化材(II)に代えて、OPC単独のセメント系固化材(I)を使用した場合は、鉛又はヒ素の不溶化が不十分となることが分かる。このことから、セメント系固化材(II)に含まれている高炉スラグが溶出量の抑制に有効であることが分かる。すなわち、OPC、高炉スラグ、石膏と消石灰(10~55質量%)とすることで、ヒ素と鉛の溶出量を環境基準値以下とすることができる。 Table 3 shows that if slaked lime is not added, insolubilization of arsenic is insufficient, and as the amount of slaked lime increases, the amount of arsenic eluted decreases, but the amount of lead eluted increases. Furthermore, it can be seen that when the cement-based solidifying material (I) containing OPC alone is used instead of the cement-based solidifying material (II), the insolubilization of lead or arsenic becomes insufficient. This shows that the blast furnace slag contained in the cement solidifying agent (II) is effective in suppressing the amount of elution. That is, by using OPC, blast furnace slag, gypsum, and slaked lime (10 to 55% by mass), the elution amount of arsenic and lead can be kept below the environmental standard value.
実施例9~14
上記模擬土壌Eに対し、セメント系固化材(II)と消石灰に加えて塩化物を配合してなる重金属不溶化固化材を混合処理して、7日後の溶出量と一軸圧縮強さを測定した。結果を表4に示す。なお、表4には、重金属不溶化固化材のブレーン比表面積も示す。
Examples 9-14
The simulated soil E was mixed with a cement-based solidifying agent (II) and a heavy metal insolubilizing solidifying agent containing chloride in addition to slaked lime, and the elution amount and unconfined compressive strength were measured after 7 days. The results are shown in Table 4. Table 4 also shows the Blaine specific surface area of the heavy metal insolubilization solidification material.
実施例15~20
上記模擬土壌Eに対し、セメント系固化材(II)と消石灰に加えて硫酸塩を配合してなる重金属不溶化固化材を混合処理して、7日後の溶出量と一軸圧縮強さを測定した。結果を表5に示す。なお、表5には、重金属不溶化固化材のブレーン比表面積も示す。
Examples 15-20
The simulated soil E was mixed with a cement-based solidifying agent (II) and a heavy metal insolubilizing solidifying agent containing sulfate in addition to slaked lime, and the elution amount and unconfined compressive strength were measured after 7 days. The results are shown in Table 5. Note that Table 5 also shows the Blaine specific surface area of the heavy metal insolubilization solidification material.
表4、5から、セメント系固化材(II)と消石灰に加えて塩化物又は硫酸塩を配合してなる重金属不溶化固化材を使用することにより、鉛溶出量を更に抑制できることが分かる。 From Tables 4 and 5, it can be seen that the amount of lead elution can be further suppressed by using a heavy metal insolubilization solidification material which is a mixture of cement-based solidification material (II) and slaked lime with chloride or sulfate.
実施例21~27
上記土壌E(表3と同条件の土壌)に対し、セメント系固化材(II)と軽焼ドロマイトを配合してなる重金属不溶化固化材を混合処理して、7日後の溶出量と一軸圧縮強さを測定した。結果を表6に示す。なお、表6には、重金属不溶化固化材のブレーン比表面積も示す。
Examples 21-27
The above soil E (soil under the same conditions as in Table 3) was mixed with a heavy metal insolubilization solidification material made by blending cement-based solidification material (II) and lightly calcined dolomite, and the elution amount and uniaxial compressive strength were measured after 7 days. We measured the The results are shown in Table 6. Note that Table 6 also shows the Blaine specific surface area of the heavy metal insolubilization solidification material.
表6から、軽焼ドロマイトにおいても消石灰と同様に、ヒ素、鉛の不溶化効果が認められ、ヒ素や鉛の溶出量を抑制することができる。 From Table 6, similarly to slaked lime, light calcined dolomite has the effect of insolubilizing arsenic and lead, and the amount of arsenic and lead eluted can be suppressed.
本発明によれば、簡易に、ヒ素及び鉛を含有する軟弱土壌又は汚泥類を適切な強度の改良土壌に固化でき、かつ、ヒ素及び鉛の溶出量を環境指定基準以下に抑制できる。よって、重金属で汚染された軟弱土壌類の強度を向上させると共に、ヒ素及び鉛の溶出量を抑制し得る重金属不溶化固化材、及び軟弱土壌又は汚泥の改良工法として、非常に有用である。 According to the present invention, soft soil or sludge containing arsenic and lead can be easily solidified into improved soil of appropriate strength, and the amount of arsenic and lead elution can be suppressed to below designated environmental standards. Therefore, it is very useful as a heavy metal insolubilization solidification material that can improve the strength of soft soils contaminated with heavy metals and suppress the amount of arsenic and lead elution, and as a method for improving soft soil or sludge.
Claims (10)
The method for improving soft soil or sludge according to claim 7 , wherein the soft soil or sludge is improved to have an arsenic elution amount of 0.01 mg/l or less, or a lead elution amount of 0.01 mg/l or less.
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