JP6997042B2 - Ground improvement material and ground improvement method - Google Patents
Ground improvement material and ground improvement method Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description
本発明は、地盤改良材及び地盤改良方法に関する。 The present invention relates to a ground improvement material and a ground improvement method.
セメントクリンカーは、石灰石、粘土、硅石、酸化鉄等を主原料として製造される。セメントクリンカーの製造には、これらの主原料のほか、各種産業副産物や産業廃棄物が原燃料として有効利用されている。このため、原材料の選択によっては、セメントクリンカー中に、各種原燃料に由来するカドミウム、クロム、鉛、モリブデン等の重金属類が少量混入することがある。 Cement clinker is manufactured using limestone, clay, silica stone, iron oxide and the like as main raw materials. In addition to these main raw materials, various industrial by-products and industrial wastes are effectively used as raw materials for the production of cement clinker. Therefore, depending on the selection of raw materials, heavy metals such as cadmium, chromium, lead, and molybdenum derived from various raw materials and fuels may be mixed in a small amount in the cement clinker.
このように重金属類を含むセメントクリンカーを用いたセメントをモルタル硬化体やコンクリート硬化体の原料として使用する場合、これらの硬化体からの重金属の溶出量は極めて少なく、問題となる可能性は低い。しかしながら、重金属類を含むセメントクリンカーを用いたセメントを地盤改良材（「固化材」、「セメント系固化材」又は「不溶化材」と称される場合もある。）の原料として使用する場合は、土の種類、配合条件及び地盤改良材の性状や種類によって、地盤改良土（「固化処理土」又は「不溶化処理土」と称される場合もある。）からの六価クロム等の重金属類の溶出量が多くなってしまうことがある。 When cement using a cement clinker containing heavy metals is used as a raw material for a hardened mortar or a hardened concrete, the amount of heavy metals eluted from these hardened bodies is extremely small and is unlikely to cause a problem. However, when cement using a cement clinker containing heavy metals is used as a raw material for a soil improving material (sometimes referred to as "solidifying material", "cement-based solidifying material" or "insolubilizing material"), Heavy metals such as hexavalent chromium from ground-improved soil (sometimes referred to as "solidified soil" or "insolubilized soil") depending on the type of soil, compounding conditions, and properties and types of ground-improving material. The amount of elution may increase.
重金属類の中でも、六価クロム［Ｃｒ（ＶＩ）］は、他の重金属類とは異なり、クロム酸イオン（ＣｒＯ４ ２－）等の安定なオキソ陰イオンの状態で存在し、高ｐＨ条件下であっても難溶性の水酸化物を形成しないため、その溶出対策が比較的難しいといえる。六価クロムの溶出量は、特に関東ローム等の火山灰質粘性土を地盤改良の対象とした場合に多くなることが知られている。 Among heavy metals, hexavalent chromium [Cr (VI)], unlike other heavy metals, exists in the state of stable oxo anions such as chromate ion (CrO 4-2 ), and under high pH conditions. However, since it does not form a sparingly soluble hydroxide, it can be said that it is relatively difficult to take measures against its elution. It is known that the elution amount of hexavalent chromium increases especially when volcanic ash cohesive soil such as Kanto Loam is targeted for ground improvement.
これまで、地盤改良土からの六価クロムの溶出対策としては、セメント系固化材に種々の還元性物質（第一鉄塩、高炉スラグ又は硫黄化合物等）を添加し、固化処理土から溶出しやすい六価クロムを三価クロムに還元して無害化する技術が提案されている（例えば、特許文献１）。その中でも、高炉スラグ微粉末を還元性物質として使用する方法は、高炉スラグ微粉末の入手が容易である点、高炉スラグ微粉末が比較的安価である点及び長期にわたって六価クロムの溶出を抑制する点で実用上優れている。 So far, as a countermeasure against the elution of hexavalent chromium from the ground-improved soil, various reducing substances (ferrous iron salt, blast furnace slag, sulfur compounds, etc.) have been added to the cement-based solidifying material and eluted from the solidified soil. A technique for reducing easy hexavalent chromium to trivalent chromium to make it harmless has been proposed (for example, Patent Document 1). Among them, the method of using the blast furnace slag fine powder as a reducing substance is that the blast furnace slag fine powder is easily available, the blast furnace slag fine powder is relatively inexpensive, and the elution of hexavalent chromium is suppressed for a long period of time. It is practically excellent in that it does.
本発明者らは、還元性物質として高炉スラグを含む地盤改良材の高性能化を鋭意検討した結果、地盤改良対象の土種によっては材齢初期における六価クロムの溶出量がこれ以降の材齢と比較すると多く、この点において改善の余地があることを見出した。 As a result of diligent studies on improving the performance of ground improvement materials containing blast furnace slag as a reducing substance, the present inventors have found that the amount of hexavalent chromium elution at the early stage of the material age is later depending on the soil species to be ground improvement. It was found that there is room for improvement in this respect, as it is more than age.
本発明は、セメントクリンカーのクロム含有率が比較的高く且つ六価クロムが溶出しやすい土種が地盤改良対象であっても、六価クロムの溶出量を材齢初期から長期にわたって十分に低いレベルに維持することができる地盤改良材及び地盤改良方法を提供することを目的とする。 In the present invention, even if the soil species having a relatively high chromium content of cement clinker and easily elution of hexavalent chromium is the target of ground improvement, the elution amount of hexavalent chromium is at a sufficiently low level from the early stage of the material age to a long period of time. It is an object of the present invention to provide a ground improvement material and a ground improvement method that can be maintained in the soil.
本発明に係る地盤改良材は、セメントクリンカーと、高炉スラグと、亜硫酸カルシウムと、石膏とを含む。地盤改良材が高炉スラグを含むことで、六価クロムを三価クロムに還元して無害化する作用が長期にわたって維持され、このため、長期にわたって六価クロムの溶出を抑制できる。しかし、本発明者らの検討によると、地盤改良対象の土種によっては、材齢が早いうちは高炉スラグのクロム還元効果が必ずしも十分ではない。これを改善するため、地盤改良材に亜硫酸カルシウムを更に配合した結果、材齢初期においても六価クロムの溶出量を十分に低減することができた。つまり、高炉スラグと亜硫酸カルシウムを併用することで、六価クロムの溶出量を材齢初期から長期にわたって十分に低いレベルに維持することができる。 The ground improvement material according to the present invention includes cement clinker, blast furnace slag, calcium sulfite, and gypsum. Since the ground improving material contains blast furnace slag, the action of reducing hexavalent chromium to trivalent chromium and detoxifying it is maintained for a long period of time, and therefore the elution of hexavalent chromium can be suppressed for a long period of time. However, according to the study by the present inventors, the chromium reducing effect of the blast furnace slag is not always sufficient depending on the soil species to be ground-improved, while the material age is early. In order to improve this, as a result of further adding calcium sulfite to the ground improvement material, the elution amount of hexavalent chromium could be sufficiently reduced even in the early stage of the material age. That is, by using blast furnace slag and calcium sulfite in combination, the elution amount of hexavalent chromium can be maintained at a sufficiently low level from the early stage of the age of the material to a long period of time.
本発明の地盤改良材の全質量基準で、亜硫酸カルシウムの含有率は、例えば、０．０１～２０質量％である。同基準で、高炉スラグの含有率は、例えば、１～８０質量％である。六価クロムの溶出量低減の観点から、本発明の地盤改良材の全質量基準で高炉スラグ及び亜硫酸カルシウムの合計量は２～８０質量％であることが好ましい。同様の観点から、本発明の地盤改良材における高炉スラグの含有量を１００質量部とすると、亜硫酸カルシウムの含有量は０．１～１００質量部であることが好ましい。 Based on the total mass of the ground improvement material of the present invention, the content of calcium sulfite is, for example, 0.01 to 20% by mass. According to the same standard, the content of blast furnace slag is, for example, 1 to 80% by mass. From the viewpoint of reducing the elution amount of hexavalent chromium, the total amount of blast furnace slag and calcium sulfite is preferably 2 to 80% by mass based on the total mass of the ground improvement material of the present invention. From the same viewpoint, assuming that the content of blast furnace slag in the ground improvement material of the present invention is 100 parts by mass, the content of calcium sulfite is preferably 0.1 to 100 parts by mass.
本発明の地盤改良材の全質量基準で、セメントクリンカーの含有率は、例えば、１０～９８質量％である。セメントクリンカーは、全クロム量が５０～２５０ｍｇ／ｋｇであってもよく、水溶性六価クロム量が３～４０ｍｇ／ｋｇであってもよい。なお、セメントクリンカーの全クロム量はＪＩＳ Ｒ５２０２：２０１０に記載の方法に準拠して測定され、水溶性六価クロム量はセメント協会標準試験方法Ｉ-５１－１９８１に記載の方法に準拠して測定される。 Based on the total mass of the ground improvement material of the present invention, the content of cement clinker is, for example, 10 to 98% by mass. The cement clinker may have a total chromium content of 50 to 250 mg / kg and a water-soluble hexavalent chromium content of 3 to 40 mg / kg. The total amount of chromium in the cement clinker was measured according to the method described in JIS R5202: 2010, and the amount of water-soluble hexavalent chromium was measured in accordance with the method described in the Cement Association Standard Test Method I-51-1981. Will be done.
本発明の地盤改良材の全質量基準で、石膏の含有率は、例えば、２～３０質量％である。石膏としては、無水石膏及び二水石膏の少なくとも一方を含むものであればよい。 Based on the total mass of the ground improvement material of the present invention, the gypsum content is, for example, 2 to 30% by mass. The gypsum may include at least one of anhydrous gypsum and dihydrate gypsum.
本発明に係る地盤改良方法は、地盤改良対象土と、セメントクリンカーと、高炉スラグと、亜硫酸カルシウムと、石膏とを混合する工程を含む。地盤改良対象土として、火山灰質粘性土（例えば、関東ローム）が挙げられる。 The ground improvement method according to the present invention includes a step of mixing a ground improvement target soil, a cement clinker, a blast furnace slag, calcium sulfite, and gypsum. Examples of soil for ground improvement include volcanic ash cohesive soil (for example, Kanto Loam).
本発明によれば、セメントクリンカーのクロム含有率が比較的高く且つ六価クロムが溶出しやすい土種が地盤改良対象であっても、六価クロムの溶出量を材齢初期から長期にわたって十分に低いレベルに維持することができる地盤改良材及び地盤改良方法が提供される。 According to the present invention, even if the soil species having a relatively high chromium content of cement clinker and easily elution of hexavalent chromium is the target of ground improvement, the elution amount of hexavalent chromium can be sufficiently increased from the early stage of the material age to a long period of time. Ground improvement materials and ground improvement methods that can be maintained at low levels are provided.
以下、本発明の実施形態について説明する。なお、本発明は以下の実施形態に限定されるものではない。 Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.
＜地盤改良材＞
本実施形態に係る地盤改良材は、セメントクリンカーと、高炉スラグと、亜硫酸カルシウムと、石膏とを含む。この地盤改良材は、高炉スラグ及び亜硫酸カルシウムの両方を含むことで、六価クロムの溶出量を材齢初期から長期にわたって十分に低いレベルに維持することができる。
<Ground improvement material>
The ground improvement material according to the present embodiment includes cement clinker, blast furnace slag, calcium sulfite, and gypsum. By containing both blast furnace slag and calcium sulfite, this ground improvement material can maintain the elution amount of hexavalent chromium at a sufficiently low level from the early stage of the material age to a long period of time.
（亜硫酸カルシウム）
亜硫酸カルシウムとして、化学合成された市販品又は天然に存在するもの、あるいは、排煙脱硫工程等で発生する石膏に含まれる亜硫酸カルシウム無水物及び／又は亜硫酸カルシウム半水和物等を使用することができる。亜硫酸カルシウムは粉状であることが好ましい。粉状の亜硫酸カルシウムは、レーザー回折式粒度分布計で測定されるメディアン径が０．１～２０μｍであることが好ましく、０．２～１０μｍであることがより好ましく、１～６μｍであることが更に好ましい。亜硫酸カルシウムの粒径がこの範囲にあることで、初期材齢で優れた六価クロムの還元効果を示す。
(Calcium sulfite)
As calcium sulfite, a chemically synthesized commercial product or a naturally occurring product, or calcium sulfite anhydride and / or calcium sulfite hemihydrate contained in gypsum generated in a flue gas desulfurization step may be used. can. Calcium sulfite is preferably in the form of powder. The powdery calcium sulfite preferably has a median diameter of 0.1 to 20 μm, more preferably 0.2 to 10 μm, and more preferably 1 to 6 μm, as measured by a laser diffraction type particle size distribution meter. More preferred. When the particle size of calcium sulfite is in this range, it exhibits an excellent reducing effect of hexavalent chromium at the initial age.
地盤改良材の全質量基準で、亜硫酸カルシウムの含有率は、例えば、０．０１～２０質量％であり、好ましくは０．０２～１５質量％であり、より好ましくは０．１０～１０質量％であり、更に好ましくは０．２５～１．００質量％である。亜硫酸カルシウムの含有率が上記範囲にあることで地盤改良土の初期材齢における六価クロムの溶出を十分に抑制できる。 Based on the total mass of the ground improvement material, the content of calcium sulfite is, for example, 0.01 to 20% by mass, preferably 0.02 to 15% by mass, and more preferably 0.10 to 10% by mass. It is more preferably 0.25 to 1.00% by mass. When the content of calcium sulfite is in the above range, the elution of hexavalent chromium at the initial age of the ground-improved soil can be sufficiently suppressed.
（高炉スラグ）
高炉スラグは高炉で発生するスラグを水冷したものである。高炉スラグは微粉末であることが好ましい。高炉スラグ微粉末の具体例として、市販されている高炉水砕スラグが挙げられる。高炉スラグ微粉末のブレーン比表面積は３０００ｃｍ２／ｇ以上であることが好ましく、３５００～６０００ｃｍ２／ｇであることがより好ましい。高炉スラグ微粉末のブレーン比表面積はＪＩＳ Ｒ５２０１：２０１５「セメントの物理試験方法」に記載の方法に準拠して測定される。
(Blast furnace slag)
Blast furnace slag is water-cooled slag generated in the blast furnace. The blast furnace slag is preferably a fine powder. Specific examples of the blast furnace slag fine powder include commercially available blast furnace granulated slag. The specific surface area of the brain of the blast furnace slag fine powder is preferably 3000 cm 2 / g or more, and more preferably 3500 to 6000 cm 2 / g. The brain specific surface area of the blast furnace slag fine powder is measured according to the method described in JIS R5201: 2015 “Physical test method for cement”.
高炉スラグ微粉末は、ＪＩＳ Ｒ５２０２：２０１０「セメントの化学分析方法」により規定される硫化物硫黄の含有量が０．５質量％以上であることが好ましく、０．６質量％以上であることがより好ましく、０．７５質量％以上であることが更に好ましい。高炉スラグ微粉末の硫化物硫黄の含有量がこの範囲であることで、高炉スラグ微粉末に含まれる硫化物硫黄の六価クロムの還元効果により、地盤改良土からの六価クロムの溶出を抑制できる。 The blast furnace slag fine powder preferably has a sulfur sulfide content of 0.5% by mass or more, preferably 0.6% by mass or more, as defined by JIS R5202: 2010 “Chemical analysis method for cement”. It is more preferably 0.75% by mass or more, and even more preferably 0.75% by mass or more. Since the content of sulfur sulfide in the blast furnace slag fine powder is within this range, the effect of reducing hexavalent chromium in the blast furnace slag fine powder suppresses the elution of hexavalent chromium from the ground-improved soil. can.
地盤改良材の全質量基準で、高炉スラグの含有率は、例えば、１～８０質量％であり、好ましくは２～７０質量％であり、より好ましくは５～６０質量％であり、更に好ましくは１０～３０質量％である。高炉スラグの含有率が上記範囲にあり且つ上記亜硫酸カルシウムを併用することで地盤改良土の初期材齢から長期材齢にわたって六価クロムの溶出を十分に抑制できる。 Based on the total mass of the ground improvement material, the content of the blast furnace slag is, for example, 1 to 80% by mass, preferably 2 to 70% by mass, more preferably 5 to 60% by mass, and further preferably. It is 10 to 30% by mass. By using the above-mentioned calcium sulfite in combination with the content of blast furnace slag, the elution of hexavalent chromium can be sufficiently suppressed from the initial age to the long-term age of the ground-improved soil.
上述のとおり、亜硫酸カルシウムと高炉スラグを併用することで、地盤改良土の初期材齢から長期材齢にわたって六価クロムの溶出を十分に抑制できる。六価クロムの溶出量の低減及び固化処理土の強度発現性の観点から、地盤改良材の全質量基準で高炉スラグ及び亜硫酸カルシウムの合計量は、好ましくは２～８０質量％であり、より好ましくは２～７０質量％であり、更に好ましくは５～３０質量％である。同様の観点から、地盤改良材における高炉スラグの含有量を１００質量部とすると、亜硫酸カルシウムの含有量は好ましくは０．１～１００質量部であり、より好ましくは０．５～７０質量部であり、更に好ましくは３～１０質量部である。 As described above, by using calcium sulfite and blast furnace slag together, the elution of hexavalent chromium can be sufficiently suppressed from the initial age to the long age of the ground-improved soil. From the viewpoint of reducing the elution amount of hexavalent chromium and developing the strength of the solidified treated soil, the total amount of blast furnace slag and calcium sulfite is preferably 2 to 80% by mass, more preferably, based on the total mass of the ground improvement material. Is 2 to 70% by mass, more preferably 5 to 30% by mass. From the same viewpoint, assuming that the content of blast furnace slag in the ground improvement material is 100 parts by mass, the content of calcium sulfite is preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 70 parts by mass. Yes, more preferably 3 to 10 parts by mass.
六価クロムの溶出量の低減をより一層高度に達成する観点から、亜硫酸カルシウム及び高炉スラグの含有率（地盤改良材の全質量基準、単位：質量％）は以下の不等式で表される条件を満たすことが好ましい。
亜硫酸カルシウムの含有率≧２．０－０．０５×高炉スラグの含有率
From the viewpoint of achieving a higher degree of reduction in the amount of hexavalent chromium elution, the content of calcium sulfite and blast furnace slag (based on the total mass of the ground improvement material, unit: mass%) is based on the conditions expressed by the following inequality. It is preferable to meet.
Calcium sulfite content ≧ 2.0-0.05 × Blast furnace slag content
（セメントクリンカー）
セメントクリンカーとして、ＪＩＳ Ｒ５２１０：２００３「ポルトランドセメント」に規定の各種ポルトランドセメントが好適に使用できる。その中でも、入手のしやすさや初期強度を考慮すると普通ポルトランドセメント又は早強ポルトランドセメントが好ましい。セメントクリンカーの全クロム量は、例えば、５０～２５０ｍｇ／ｋｇであり、１００～２００ｍｇ／ｋｇ又は１１０～１６０ｍｇ／ｋｇであってもよい。セメントクリンカーの水溶性六価クロム量は、例えば、３～４０ｍｇ／ｋｇであり、５～３０ｍｇ／ｋｇ又は１０～２０ｍｇ／ｋｇであってもよい。
(Cement clinker)
As the cement clinker, various Portland cements specified in JIS R5210: 2003 "Portland cement" can be preferably used. Among them, ordinary Portland cement or early-strength Portland cement is preferable in consideration of availability and initial strength. The total amount of chromium in the cement clinker is, for example, 50-250 mg / kg and may be 100-200 mg / kg or 110-160 mg / kg. The amount of water-soluble hexavalent chromium of the cement clinker is, for example, 3 to 40 mg / kg, and may be 5 to 30 mg / kg or 10 to 20 mg / kg.
地盤改良材の全質量基準で、セメントクリンカーの含有率は、例えば、１０～９８質量％であり、好ましくは２０～９０質量％であり、より好ましくは４０～８０質量％であり、更に好ましくは５０～７０質量％である。セメントクリンカーの含有率が１０質量％未満であると固化処理土の強度発現性が不十分となりやすく、他方、９８質量％を越えると六価クロムの溶出低減効果が不十分となりやすい。 Based on the total mass of the ground improvement material, the content of the cement clinker is, for example, 10 to 98% by mass, preferably 20 to 90% by mass, more preferably 40 to 80% by mass, and further preferably. It is 50 to 70% by mass. If the content of the cement clinker is less than 10% by mass, the strength development of the solidified soil tends to be insufficient, while if it exceeds 98% by mass, the effect of reducing the elution of hexavalent chromium tends to be insufficient.
石膏として、無水石膏、二水石膏、半水石膏のいずれの形態のものを使用してもよい。固化処理土の強度発現性の観点から二水石膏又は無水石膏を用いることが好ましく、二水石膏と無水石膏を混合した石膏も使用可能である。固化処理土の強度発現性の観点から、地盤改良材の全質量基準で石膏の含有率は、例えば、２～３０質量％であり、好ましくは３～２０質量％であり、より好ましくは５～１５質量％であり、更に好ましくは７～１１質量％である。 As the gypsum, any form of anhydrous gypsum, dihydrate gypsum, or semi-hydrated gypsum may be used. From the viewpoint of the strength development of the solidified treated soil, it is preferable to use dihydrate gypsum or anhydrous gypsum, and gypsum in which dihydrate gypsum and anhydrous gypsum are mixed can also be used. From the viewpoint of the strength development of the solidified soil, the gypsum content is, for example, 2 to 30% by mass, preferably 3 to 20% by mass, and more preferably 5 to 5 to 30% by mass based on the total mass of the ground improvement material. It is 15% by mass, more preferably 7 to 11% by mass.
＜地盤改良方法＞
本実施形態に係る地盤改良方法は、地盤改良対象土と、セメントクリンカーと、高炉スラグと、亜硫酸カルシウムと、石膏とを混合する工程を含む。例えば、上述の地盤改良材を準備し、地盤改良対象土と地盤改良材とを混合すればよい。地盤改良対象土１ｍ３に対して、地盤改良材の配合量は、例えば、２０～５００ｋｇであり、好ましくは５０～４５０ｋｇであり、より好ましくは５０～４００ｋｇであり、更に好ましくは１００～３５０ｋｇである。
<Ground improvement method>
The ground improvement method according to the present embodiment includes a step of mixing a soil to be improved, a cement clinker, a blast furnace slag, calcium sulfite, and gypsum. For example, the above-mentioned ground improvement material may be prepared, and the soil to be improved and the soil improvement material may be mixed. The blending amount of the ground improvement material is, for example, 20 to 500 kg, preferably 50 to 450 kg, more preferably 50 to 400 kg, and further preferably 100 to 350 kg with respect to 1 m 3 of the soil to be ground improvement. be.
地盤改良対象土としては、特に限定されないが、六価クロムの溶出抑制が比較的難しい火山灰質粘性土（例えば、関東ローム）が地盤改良対象土であっても、本実施形態に係る地盤改良方法によれば、六価クロムの溶出を十分に低いレベルとすることができる。 The soil for ground improvement is not particularly limited, but even if the volcanic ash cohesive soil (for example, Kanto Loam) for which it is relatively difficult to suppress the elution of hexavalent chromium is the soil for ground improvement, the ground improvement method according to the present embodiment. According to this, the elution of hexavalent chromium can be made at a sufficiently low level.
対象土に対する地盤改良材の配合量の調整及び地盤改良材の組成の調整をすることにより、地盤改良土の六価クロム溶出量は材齢７日及び材齢２８日において以下の範囲とすることが好ましい。すなわち、材齢７日の地盤改良土の六価クロム溶出量は０．０５ｍｇ／Ｌ以下であることが好ましく、０．０３ｍｇ／Ｌ以下であることがより好ましい。材齢２８日の地盤改良土の六価クロム溶出量は０．０５ｍｇ／Ｌ以下であることが好ましく、０．０３ｍｇ／Ｌ以下であることがより好ましい。 By adjusting the blending amount of the ground improvement material and the composition of the ground improvement material with respect to the target soil, the amount of hexavalent chromium elution of the ground improvement soil shall be within the following range at the age of 7 days and 28 days. Is preferable. That is, the amount of hexavalent chromium eluted from the ground-improved soil at the age of 7 days is preferably 0.05 mg / L or less, and more preferably 0.03 mg / L or less. The amount of hexavalent chromium eluted from the ground-improved soil at the age of 28 days is preferably 0.05 mg / L or less, and more preferably 0.03 mg / L or less.
対象土に対する地盤改良材の配合量の調整及び地盤改良材の組成の調整をすることにより、地盤改良土の一軸圧縮強さは材齢２８日において以下の範囲とすることが好ましい。すなわち、材齢２８日の地盤改良土の一軸圧縮強さは２００ｋＮ／ｍ２以上であることが好ましい。 By adjusting the blending amount of the ground improvement material and the composition of the ground improvement material with respect to the target soil, the uniaxial compressive strength of the ground improvement material is preferably in the following range at the age of 28 days. That is, the uniaxial compressive strength of the ground-improved soil at the age of 28 days is preferably 200 kN / m 2 or more.
以下、実施例、参考例及び比較例を挙げて本発明を詳細に説明するが、本発明は以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described in detail with reference to Examples , Reference Examples and Comparative Examples, but the present invention is not limited to the following Examples.
１．実験方法
[使用原材料]
（１）普通ポルトランドセメントクリンカーＡ：
・全クロム量＝１４９ｍｇ／ｋｇ
・水溶性六価クロム量＝１５．９ｍｇ／ｋｇ
（２）普通ポルトランドセメントクリンカーＢ：
・全クロム量＝１５６ｍｇ／ｋｇ
・水溶性六価クロム量＝１１．２ｍｇ／ｋｇ
（３）排脱二水石膏(宇部興産株式会社製)
（４）天然無水石膏：
・ブレーン比表面積＝３７９０ｃｍ２／ｇ
（５）高炉スラグ微粉末：
・ブレーン比表面積＝４７００ｃｍ２／ｇ
・硫化物硫黄量＝０．８３９％
（６）亜硫酸カルシウム半水和物（和光純薬工業株式会社、試薬）
1. 1. experimental method
[Raw materials used]
(1) Ordinary Portland cement clinker A:
・ Total amount of chromium = 149 mg / kg
・ Amount of water-soluble hexavalent chromium = 15.9 mg / kg
(2) Ordinary Portland cement clinker B:
・ Total amount of chromium = 156 mg / kg
・ Amount of water-soluble hexavalent chromium = 11.2 mg / kg
(3) Flue gas desulfurization gypsum (manufactured by Ube Industries, Ltd.)
(4) Natural anhydrous gypsum:
・ Brain specific surface area = 3790 cm 2 / g
(5) Blast furnace slag fine powder:
・ Brain specific surface area = 4700 cm 2 / g
・ Amount of sulfur sulfide = 0.839%
(6) Calcium sulfite hemihydrate (Wako Pure Chemical Industries, Ltd., reagent)
[地盤改良材の調製]
(参考例１及び比較例１～３)
表１に示す配合で、普通ポルトランドセメントクリンカーＡ、亜硫酸カルシウム半水和物、排脱二水石膏及び天然無水石膏をボールミルに投入した。ボールミルでブレーン比表面積が３２００±１５０ｃｍ２／ｇとなるように粉砕した後、高炉スラグ微粉末と混合し、参考例１及び比較例１～３の地盤改良材を調製した。
[Preparation of ground improvement material]
( Reference Example 1 and Comparative Examples 1 to 3)
Ordinary Portland cement clinker A, calcium sulfite hemihydrate, gypsum dehydrated gypsum and natural anhydrous gypsum were charged into a ball mill with the formulations shown in Table 1. After crushing with a ball mill so that the specific surface area of the brain was 3200 ± 150 cm 2 / g, it was mixed with blast furnace slag fine powder to prepare ground improvement materials of Reference Example 1 and Comparative Examples 1 to 3.
(実施例２，３、参考例４、比較例４，５)
表２及び表３に示す配合で、普通ポルトランドセメントクリンカーＢ、亜硫酸カルシウム半水和物及び排脱二水石膏をボールミルに投入した。ボールミルでブレーン比表面積が４０００±１５０ｃｍ２／ｇとなるように粉砕した後、高炉スラグ微粉末と混合し、実施例２，３、参考例４及び比較例４，５の地盤改良材を調製した。
(Examples 2 and 3, Reference Example 4, Comparative Examples 4 and 5)
Ordinary Portland cement clinker B, calcium sulfite hemihydrate and flue gas desulfuricated gypsum were charged into a ball mill with the formulations shown in Tables 2 and 3. After crushing with a ball mill so that the specific surface area of the brain was 4000 ± 150 cm 2 / g, it was mixed with blast furnace slag fine powder to prepare ground improvement materials of Examples 2 and 3, Reference Example 4 and Comparative Examples 4 and 5. ..
[地盤改良土からの六価クロム溶出試験及び一軸圧縮試験]
地盤改良材の配合量が対象土１ｍ３あたり２５０ｋｇ／ｍ３となるように対象土に対して実施例、参考例及び比較例の各地盤改良材を配合し、ホバートミキサーで５分間よく混合した。その後、直径５０ｍｍ×高さ１００ｍｍの円柱型枠にランマーを用いて三層詰めした後、２０℃で材齢７日、材齢２８日及び材齢９１日まで密封養生した。
[Hexavalent chromium elution test and uniaxial compression test from ground-improved soil]
The ground improvement materials of Examples , Reference Examples and Comparative Examples were mixed with the target soil so that the blending amount of the ground improvement material was 250 kg / m 3 per 1 m 3 of the target soil, and mixed well with a hovert mixer for 5 minutes. .. Then, three layers were packed in a cylindrical frame having a diameter of 50 mm and a height of 100 mm using a rammer, and then sealed and cured at 20 ° C. until the material age was 7 days, the material age was 28 days, and the material age was 91 days.
上記材齢の地盤改良土について、環境庁告示４６号(平成３年８月２３日)に則って溶出試験を行い、六価クロムの溶出量を求めた。六価クロムの溶出量は、浸とう後のろ液中の六価クロム濃度をジフェニルカルバジド吸光光度法にて定量することにより求めた。また、材齢２８日の地盤改良土の一軸圧縮強さをＪＩＳ Ａ１２１６「土の一軸圧縮試験方法」に準じて測定した。 An elution test was conducted on the ground-improved soil of the above-mentioned age in accordance with Notification No. 46 of the Environment Agency (August 23, 1991), and the elution amount of hexavalent chromium was determined. The elution amount of hexavalent chromium was determined by quantifying the concentration of hexavalent chromium in the filtrate after immersion by the diphenylcarbazide absorptiometry. In addition, the uniaxial compressive strength of the ground-improved soil at the age of 28 days was measured according to JIS A1216 "Soil uniaxial compressive test method".
（１）表１に示す評価結果について
高炉スラグ微粉末及び亜硫酸カルシウムを含む参考例１は、亜硫酸カルシウムを含まない比較例１に比べて、材齢７日(初期)における六価クロム(Ｃｒ(ＶＩ))の溶出量が少なく、六価クロムの土壌溶出量基準値（０．０５ｍｇ／Ｌ）よりも少なかった。これに加え、参考例１の六価クロム溶出量は材齢２８日においても土壌溶出量基準値より少なく、初期から長期において、優れた六価クロム低減効果を有することを確認した。なお、高炉スラグ微粉末及び亜硫酸カルシウムを含む比較例２の六価クロム溶出量は、土壌溶出量基準値よりも多かったが、亜硫酸カルシウムを含まない比較例３の材齢７日(初期)及び材齢２８日の溶出量よりも少なかった。
(1) Evaluation results shown in Table 1 Reference Example 1 containing blast furnace slag fine powder and calcium sulfite has hexavalent chromium (Cr (early) at 7 days of age (early stage) as compared with Comparative Example 1 containing no calcium sulfite. The elution amount of VI)) was small, and it was less than the soil elution amount standard value (0.05 mg / L) of hexavalent chromium. In addition to this, it was confirmed that the hexavalent chromium elution amount of Reference Example 1 was smaller than the soil elution amount standard value even at the age of 28 days, and that it had an excellent hexavalent chromium reducing effect from the initial stage to the long term. The amount of hexavalent chromium in Comparative Example 2 containing blast furnace slag fine powder and calcium sulfite was larger than the standard value of soil elution amount, but the material age of Comparative Example 3 containing calcium sulfite was 7 days (initial) and It was less than the elution amount at 28 days of age.
（２）表２，３に示す評価結果について
高炉スラグ微粉末及び亜硫酸カルシウムを含む実施例２，３及び参考例４は、亜硫酸カルシウムを含まない比較例５に比べて、材齢７日(初期)における六価クロム(Ｃｒ(ＶＩ))の溶出量が少なく、六価クロムの土壌溶出量基準値（０．０５ｍｇ／Ｌ）よりも少なかった。これに加え、実施例２，３及び参考例４の六価クロム溶出量は材齢２８日においても土壌溶出量基準値より少なく、初期から長期において、優れた六価クロム低減効果を有することを確認した。一方、比較例４の六価クロム溶出量は土壌溶出量基準値よりも多かった。
(2) Evaluation results shown in Tables 2 and 3 Examples 2 and 3 containing blast furnace slag fine powder and calcium sulfite and Reference Example 4 were 7 days old (initially) as compared with Comparative Example 5 not containing calcium sulfite. ), The amount of hexavalent chromium (Cr (VI)) eluted was less than the standard value of hexavalent chromium in soil (0.05 mg / L). In addition to this, the amount of hexavalent chromium elution in Examples 2 and 3 and Reference Example 4 is smaller than the soil elution amount standard value even at the age of 28 days, and it has an excellent hexavalent chromium reducing effect from the initial stage to the long term. confirmed. On the other hand, the amount of hexavalent chromium eluted in Comparative Example 4 was larger than the reference value for the amount of soil elution.
Claims (13)
高炉スラグと、
亜硫酸カルシウムと、
石膏と、
を含む地盤改良材であって、
当該地盤改良材の全質量基準で、高炉スラグの含有率が２～２０質量％であり、
当該地盤改良材の全質量基準で、亜硫酸カルシウムの含有率が１．０７～１０質量％であり、
当該地盤改良材の全質量基準で、セメントクリンカーの含有率が６７～９０質量％であり、
亜硫酸カルシウム及び高炉スラグの含有率（地盤改良材の全質量基準、単位：質量％）が以下の不等式で表される条件を満たす、地盤改良材。
亜硫酸カルシウムの含有率≧２．０－０．０５×高炉スラグの含有率 With cement clinker,
With blast furnace slag,
Calcium sulfite and
With plaster,
It is a ground improvement material including
Based on the total mass of the ground improvement material, the content of blast furnace slag is 2 to 20 % by mass.
The calcium sulfite content is 1.07 to 10% by mass based on the total mass of the ground improvement material.
Based on the total mass of the ground improvement material, the cement clinker content is 67 to 90% by mass.
A ground improvement material that satisfies the conditions expressed by the following inequality in the content of calcium sulfite and blast furnace slag (total mass standard of ground improvement material, unit: mass%).
Calcium sulfite content ≧ 2.0-0.05 × Blast furnace slag content
セメントクリンカー、高炉スラグ、亜硫酸カルシウム及び石膏の合計質量基準で、高炉スラグの含有率が２～２０質量％であり、
セメントクリンカー、高炉スラグ、亜硫酸カルシウム及び石膏の合計質量基準で、亜硫酸カルシウムの含有率が１．０７～１０質量％であり、
セメントクリンカー、高炉スラグ、亜硫酸カルシウム及び石膏の合計質量基準で、セメントクリンカーの含有率が６７～９０質量％であり、
亜硫酸カルシウム及び高炉スラグの含有率（セメントクリンカー、高炉スラグ、亜硫酸カルシウム及び石膏の合計質量基準、単位：質量％）が以下の不等式で表される条件を満たす、地盤改良方法。
亜硫酸カルシウムの含有率≧２．０－０．０５×高炉スラグの含有率 Including the step of mixing the soil to be ground improvement, cement clinker, blast furnace slag, calcium sulfite, and gypsum.
Based on the total mass of cement clinker, blast furnace slag, calcium sulfite and gypsum, the content of blast furnace slag is 2 to 20 % by mass.
Based on the total mass of cement clinker, blast furnace slag, calcium sulfite and gypsum, the calcium sulfite content is 1.07 to 10% by mass.
Based on the total mass of cement clinker, blast furnace slag, calcium sulfite and gypsum, the content of cement clinker is 67-90% by mass.
A ground improvement method in which the content of calcium sulfite and blast furnace slag (total mass standard of cement clinker, blast furnace slag, calcium sulfite and gypsum, unit: mass%) satisfies the condition expressed by the following inequality.
Calcium sulfite content ≧ 2.0-0.05 × Blast furnace slag content
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