JP5047745B2 - Ground improvement material - Google Patents
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- JP5047745B2 JP5047745B2 JP2007250317A JP2007250317A JP5047745B2 JP 5047745 B2 JP5047745 B2 JP 5047745B2 JP 2007250317 A JP2007250317 A JP 2007250317A JP 2007250317 A JP2007250317 A JP 2007250317A JP 5047745 B2 JP5047745 B2 JP 5047745B2
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- 239000000463 material Substances 0.000 title claims description 89
- 239000002893 slag Substances 0.000 claims description 84
- 239000002689 soil Substances 0.000 claims description 45
- 239000000843 powder Substances 0.000 claims description 44
- 239000011398 Portland cement Substances 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- 239000013078 crystal Substances 0.000 claims description 16
- 229910052602 gypsum Inorganic materials 0.000 claims description 16
- 239000010440 gypsum Substances 0.000 claims description 16
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 15
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 15
- 239000004571 lime Substances 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 4
- 239000010438 granite Substances 0.000 claims description 3
- 239000004576 sand Substances 0.000 claims description 3
- 238000004017 vitrification Methods 0.000 claims description 3
- 210000004556 brain Anatomy 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 239000011368 organic material Substances 0.000 claims 1
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 22
- 238000010828 elution Methods 0.000 description 19
- 239000004568 cement Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 15
- 238000002156 mixing Methods 0.000 description 14
- 238000007711 solidification Methods 0.000 description 13
- 230000008023 solidification Effects 0.000 description 13
- 238000006477 desulfuration reaction Methods 0.000 description 9
- 230000023556 desulfurization Effects 0.000 description 9
- 239000011575 calcium Substances 0.000 description 7
- 229910052791 calcium Inorganic materials 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 5
- 230000001603 reducing effect Effects 0.000 description 5
- 229910001653 ettringite Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- JGIATAMCQXIDNZ-UHFFFAOYSA-N calcium sulfide Chemical compound [Ca]=S JGIATAMCQXIDNZ-UHFFFAOYSA-N 0.000 description 3
- 238000010276 construction Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 238000006703 hydration reaction Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000009533 lab test Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 241000718541 Tetragastris balsamifera Species 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011400 blast furnace cement Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 239000003864 humus Substances 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000008239 natural water Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
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- Soil Conditioners And Soil-Stabilizing Materials (AREA)
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Description
本発明は、地盤改良に必要な固化性能を有するとともに、土壌の環境保全に適した地盤改良材に関するものである。 The present invention relates to a ground improvement material having solidification performance necessary for ground improvement and suitable for environmental conservation of soil.
従来、セメントや石灰を主材とした固化材が、主要な土木資材として広く認知され、広範囲に普及している。また、土木施工業者による施工技術の改善などにより、環境対策も進歩している。ここで言う環境対策とは、固化材中の高カルシウム含有物質（セメント、石灰）による改良土の高ｐＨ化および改良土からの高ｐＨ水漏出、セメント系固化材の使用時にみられる未固化時の６価クロムの溶出、などに対するものである。一般に、前者については適切な覆土と固化材使用量の削減などが、後者については高炉水砕スラグ微粉末の還元能の利用などが、広く行われている。 Conventionally, a solidified material mainly composed of cement or lime has been widely recognized as a major civil engineering material and has been widely spread. In addition, environmental measures have been improved due to improvements in construction technology by civil engineering contractors. The environmental measures mentioned here are high pH of the improved soil due to high calcium-containing materials (cement, lime) in the solidified material, high pH water leakage from the improved soil, and when unsolidified when using cement-based solidified material Of elution of hexavalent chromium. Generally, for the former, appropriate covering and reduction of the amount of solidification material used are widely used, and for the latter, the reducing ability of ground granulated blast furnace slag powder is widely used.
しかしながら、セメントや石灰を主材とした固化材を用い、例えば、一般の小規模宅地造成などで砂質シルト（地盤土質の分類）を改良する場合、固化材使用量が５０〜１５０ｋｇ／ｍ３程度であっても、改良土のｐＨは１２を超えてしまい、植生に適する状態とは言えなくなる。また、高有機質で高含水比地盤（例えば、高含水腐植土、高含水ローム土など）を改良する場合は、固化材使用量が３００ｋｇ/ｍ３を超え、さらに固化が遅いことも加わり、６価クロムやその他重金属類の溶出が懸念される。 However, when using a solidified material mainly composed of cement or lime and improving sandy silt (classification of ground soil), for example, in general small-scale residential land development, the amount of solidified material used is 50 to 150 kg / m 3. Even if it is a grade, the pH of improved soil will exceed 12, and it cannot be said that it is a state suitable for vegetation. In addition, when improving high organic and high water content grounds (for example, high water content humus soil, high water content loam soil, etc.), the amount of solidifying material used exceeds 300 kg / m 3 , and further solidification is added. There is concern about elution of valent chromium and other heavy metals.
したがって本発明の目的は、このような従来技術の課題を解決し、地盤改良に必要な固化性能を有するとともに、改良土のｐＨを低く抑えることができ、また、未固化時の６価クロムの溶出も確実に防止することができる地盤改良材を提供することにある。 Therefore, the object of the present invention is to solve such problems of the prior art, to have solidification performance necessary for ground improvement, to suppress the pH of the improved soil, and to reduce the hexavalent chromium in the unsolidified state. An object of the present invention is to provide a ground improvement material capable of reliably preventing elution.
上記課題を解決するため、本発明は以下を要旨とするものである。
［1］高炉スラグ微粉末：５０〜８０mass％、石膏：５〜２５mass％、ポルトランドセメントまたは／および石灰：１０〜３０mass％を含有し、
高炉スラグ微粉末はブレーン比表面積が３０００〜５０００ｃｍ ２ /ｇであり、
高炉スラグ微粉末の一部が結晶相からなるとともに、その結晶相量（ｘ）がポルトランドセメントまたは／および石灰量の１５〜２０mass％であり、
高炉スラグ微粉末は高炉水砕スラグと高炉徐冷スラグからなり、
高炉スラグ微粉末の結晶相は、（i）高炉徐冷スラグ、（ii）高炉水砕スラグの製造時に析出した結晶相と高炉徐冷スラグ、のいずれかからなることを特徴とする地盤改良材。
In order to solve the above problems, the present invention has the following gist.
[1] Blast furnace slag fine powder: 50-80 mass%, gypsum: 5-25 mass%, Portland cement or / and lime: 10-30 mass%,
The blast furnace slag fine powder has a brain specific surface area of 3000 to 5000 cm 2 / g,
Part of the blast furnace slag fine powder is composed of a crystalline phase, and the amount of the crystalline phase (x) is 15 to 20 mass% of the amount of Portland cement and / or lime ,
Blast furnace slag fine powder consists of blast furnace granulated slag and blast furnace slow-cooled slag,
Ground improvement material characterized in that the crystal phase of blast furnace slag fine powder consists of either (i) blast furnace slow-cooled slag, (ii) crystal phase precipitated during the production of blast furnace granulated slag and blast furnace slow-cooled slag .
［2］上記［1］の地盤改良材おいて、高炉スラグ微粉末のガラス化率が８０mass％以上であることを特徴とする地盤改良材。
［3］上記［1］又は［2］の地盤改良材を、山土または風化花崗岩からなる地盤の改良材として用いることを特徴とする地盤改良方法。
［4］上記［1］又は［2］の地盤改良材を、有機物質の比率が１０mass％以下、含水比が５０mass％以下であって、地盤土質の分類が粘土質シルト〜礫質砂である地盤の改良材として用いることを特徴とする地盤改良方法。
[2] The ground improvement material according to the above [1] , wherein the vitrification ratio of the blast furnace slag fine powder is 80 mass% or more.
[3] A ground improvement method using the ground improvement material according to [1] or [2] as a ground improvement material made of mountain soil or weathered granite.
[4] The ground improvement material according to the above [1] or [2] , the organic substance ratio is 10 mass% or less, the water content ratio is 50 mass% or less, and the soil classification is clayey silt to gravel sand. A ground improvement method characterized by being used as a ground improvement material.
本発明の地盤改良材は、既存のセメント系固化材と同等の優れた固化性能を有するとともに、改良土のｐＨを低く抑えることができ、また、未固化時の６価クロムの溶出も確実に防止することができる。 The ground improvement material of the present invention has excellent solidification performance equivalent to that of the existing cement-based solidification material, can suppress the pH of the improved soil, and reliably dissolves hexavalent chromium when not solidified. Can be prevented.
本発明の地盤改良材は、高炉スラグ微粉末を５０〜８０mass％、好ましくは６５〜８０mass％、石膏を５〜２５mass％、好ましくは１０〜２５mass％、ポルトランドセメントまたは／および石灰を１０〜３０mass％、好ましくは１０〜２０mass％含有する粉末状混合物である。
本発明の地盤改良材は、高炉スラグ微粉末と石膏を主成分とし、高カルシウム含有物質（ポルトランドセメントまたは／および石灰）の配合量を抑えることで、改良土の高ｐＨ化を防止している。高カルシウム含有物質（ポルトランドセメントまたは／および石灰）の配合量が３０mass％以下である本発明の地盤改良材を用い、砂質シルト改良時の平均的な使用量（１２０ｋｇ／ｍ３前後）で地盤改良を行い、一般的な改良目標である７日養生後の一軸圧縮強度（ＪＩＳ−Ａ−１２１６に準拠）が１．２〜１．５Ｎ／ｍｍ２となった改良土のｐＨ測定（ＪＧＳ−０２１１に準拠）を行い、既存のセメント系固化材を用いた場合と比較した結果、既存のセメント系固化材を用いた場合のｐＨが１２．１であったのに対し、本発明の地盤改良材を用いた場合のｐＨは１０．７であり、カルシウムイオン濃度を１／１０以下にできることが判った。
The ground improvement material of the present invention is 50 to 80 mass% of blast furnace slag fine powder, preferably 65 to 80 mass%, 5 to 25 mass% of gypsum, preferably 10 to 25 mass%, and 10 to 30 mass% of Portland cement or / and lime. Preferably, it is a powdery mixture containing 10 to 20 mass%.
The ground improvement material of the present invention is mainly composed of fine powder of blast furnace slag and gypsum, and suppresses the high calcium-containing material (Portland cement or / and lime) to prevent the pH of the improved soil from being increased. . Using the ground improvement material of the present invention in which the amount of high calcium-containing material (Portland cement and / or lime) is 30 mass% or less, the ground is used at an average use amount (around 120 kg / m 3 ) when sandy silt is improved. After the improvement, the uniaxial compressive strength (according to JIS-A-1216) after 7-day curing, which is a general improvement target, was measured at 1.2 to 1.5 N / mm 2 (JGS- As a result of comparison with the case of using an existing cement-based solidifying material, the pH when using an existing cement-based solidified material was 12.1, whereas the ground improvement of the present invention When the material was used, the pH was 10.7, and it was found that the calcium ion concentration could be reduced to 1/10 or less.
一方、高カルシウム含有物質（ポルトランドセメントまたは／および石灰）の配合量を抑えたことにより、対象土に対する脱水反応が少なくなり、ごく初期の固化性能の低下が懸念されるが、石膏を５mass％以上、好ましくは１０mass％以上配合し、且つポルトランドセメントや石灰よりも粒径の細かい高炉スラグ微粉末（通常、ブレーン比表面積３０００〜５０００ｃｍ２/ｇ程度）を５０mass％以上、好ましくは６５mass％以上配合することにより、十分な強度を確保できることが判った。特に、石膏を５mass％以上配合することで、膨張性水和物（エトリンガイト）の形成量が既存のセメント系固化材の５倍程度になることが、Ｘ線回折法による測定で明らかになった。エトリンガイトは結合水を多く持つ微細な針状物質であり、土粒子の空隙を埋めて緻密化させる効果と若干の脱水効果を有することが知られている。以上の点から、本発明の地盤改良材は、高カルシウム含有物質の配合量が抑えられているにもかかわらず、既存のセメント系固化材と同等の初期強度を発現できる。 On the other hand, by suppressing the amount of high calcium content (Portland cement or / and lime), the dehydration reaction to the target soil is reduced, and there is a concern that the initial solidification performance will be lowered. In addition, preferably 10 mass% or more, and blast furnace slag fine powder (usually about 3000 to 5000 cm 2 / g of Blaine specific surface area) finer than Portland cement or lime is blended in an amount of 50 mass% or more, preferably 65 mass% or more. It was found that sufficient strength can be secured. In particular, it became clear by the X-ray diffraction measurement that the amount of expansive hydrate (ettringite) formed by adding 5 mass% or more of gypsum is about five times that of the existing cement-based solidified material. . Ettringite is a fine needle-like substance with a large amount of bound water, and is known to have an effect of filling and densifying the voids of soil particles and a slight dehydrating effect. From the above points, the ground improvement material of the present invention can exhibit an initial strength equivalent to that of an existing cement-based solidified material, although the blending amount of the high calcium-containing substance is suppressed.
本発明の地盤改良材を用い、砂質シルト改良時の平均的な使用量（１２０ｋｇ／ｍ３前後）で地盤改良を行い、改良土の湿潤密度を測定した（ＪＩＳ−Ａ−１２２５に準拠）ところ、現土の湿潤密度が１．８９１ｇ／ｃｍ３であったのに対し、本発明の地盤改良材を使用した場合の湿潤密度は１．９８２ｇ／ｃｍ３、既存のセメント系固化材を使用した場合の湿潤密度は１．９２２ｇ／ｃｍ３となった。このように本発明の地盤改良材により高い湿潤密度が得られるのは、セメントよりも粒径の細かい高炉スラグ微粉末を５０mass％以上配合することで、セメントを多用した既存のセメント系固化材に比べて、砂質シルトに対する粒度改善効果が大きくなるためである。 Using the ground improvement material of the present invention, the ground was improved at an average use amount (around 120 kg / m 3 ) at the time of sandy silt improvement, and the wet density of the improved soil was measured (based on JIS-A-1225) However, the wet density of the present soil was 1.891 g / cm 3 , whereas the wet density when using the ground improvement material of the present invention was 1.982 g / cm 3 , and the existing cement-based solidified material was used. In this case, the wet density was 1.922 g / cm 3 . Thus, a high wet density can be obtained by the ground improvement material of the present invention by blending 50 mass% or more of blast furnace slag fine powder having a particle size smaller than that of cement into an existing cement-based solidified material that uses a lot of cement. This is because the particle size improvement effect on sandy silt is increased.
高炉スラグ微粉末は、ブレーン比表面積３０００〜５０００ｃｍ２/ｇ程度のものが好ましい。ブレーン比表面積が３０００ｃｍ２/ｇ未満では硬化不良を生じやすく、一方、５０００ｃｍ２/ｇを超えると経済的でない。また、高炉スラグ微粉末は、水和硬化性を確保するためガラス化率が８０mass％以上であることが好ましく、このためは、少なくとも高炉スラグ微粉末の主体は高炉水砕スラグであることが必要である。
地盤改良材中での高炉スラグ微粉末の配合量が５０mass％未満では、ポルトランドセメントの配合量を増やさざるを得なくなるため、強度向上以上に改良土のｐＨが高くなる問題を生じる。一方、高炉スラグ微粉末の配合量が８０mass％を超えると、他の成分の配合量が確保できなくなる。
The blast furnace slag fine powder preferably has a Blaine specific surface area of about 3000 to 5000 cm 2 / g. Prone to insufficient curing in Blaine specific surface area of 3000cm less than 2 / g, whereas, not economical exceeding 5000 cm 2 / g. Further, the blast furnace slag fine powder preferably has a vitrification rate of 80 mass% or more in order to ensure hydration curability. For this purpose, at least the main body of the blast furnace slag fine powder needs to be granulated blast furnace slag. It is.
If the blending amount of the blast furnace slag fine powder in the ground improvement material is less than 50 mass%, the blending amount of Portland cement must be increased, which causes a problem that the pH of the improved soil becomes higher than the strength improvement. On the other hand, if the amount of fine blast furnace slag powder exceeds 80 mass%, the amount of other components cannot be secured.
石膏の形態は、無水、半水、二水を問わない。地盤改良材中での石膏の配合量が５mass％未満ではエトリンガイト生成量が少なく、強度発現が十分でない。一方、石膏の配合量が２５mass％を超えても未水和の石膏が残るだけで、配合量に見合う強度向上効果は得られず、却って他の成分の配合量を減少させることにより、地盤改良材としての性能が低下する。
ポルトランドセメントまたは／および石灰は、強度発現に寄与することおよび潜在水硬性を有する高炉スラグ微粉末のアルカリ刺激剤として機能することを期待して配合される。地盤改良材中でのポルトランドセメントまたは／および石灰の配合量が１０mass％未満では強度の発現が不十分であり、一方、３０mass％を超えると改良土のｐＨが高くなる。
The form of gypsum does not ask | require anhydrous, half water, and two water. When the blending amount of gypsum in the ground improvement material is less than 5 mass%, the amount of ettringite produced is small and the strength expression is not sufficient. On the other hand, even if the blending amount of gypsum exceeds 25 mass%, only unhydrated gypsum remains, the strength improvement effect commensurate with the blending amount is not obtained, but the ground content is improved by reducing the blending amount of other components. The performance as a material is reduced.
Portland cement or / and lime are blended in the hope of contributing to strength development and functioning as an alkaline stimulant for ground granulated blast furnace slag. If the blending amount of Portland cement and / or lime in the ground improvement material is less than 10 mass%, the expression of strength is insufficient, while if it exceeds 30 mass%, the pH of the improved soil becomes high.
また、高炉スラグ微粉末には、ガラス質の高炉水砕スラグ微粉末よりも高い還元能を有する結晶相が含まれることが好ましく、これにより未固化時の６価クロムの溶出を確実に防止し、６価クロムをほぼ完全に無害化できることが判った。この結晶相は、（a）高炉水砕スラグ製造時に析出したもの、（b）高炉徐冷スラグ、のいずれか若しくは両方であってもよい。これらの結晶相は、抽出水中の未酸化硫黄による還元作用により６価クロムを還元し、無害化する。
高炉スラグ微粉末の一部として高炉徐冷スラグを用いる場合、反応性と経済性の面から、高炉徐冷スラグはブレーン比表面積２５００〜５５００ｃｍ２/ｇ程度のものが好ましい。
Further, it is preferable that the blast furnace slag fine powder contains a crystal phase having a higher reducing ability than the vitreous blast furnace granulated slag fine powder, thereby reliably preventing elution of hexavalent chromium when not solidified. It was found that hexavalent chromium can be almost completely detoxified. This crystal phase may be either or both of (a) precipitated during granulated blast furnace slag and (b) blast furnace slow-cooled slag. These crystalline phases reduce the hexavalent chromium by the reducing action of the unoxidized sulfur in the extraction water and render it harmless.
When blast furnace slag is used as part of the blast furnace slag fine powder, the blast furnace slow slag is preferably about a brane specific surface area of 2500 to 5500 cm 2 / g from the viewpoint of reactivity and economy.
また、本発明では高炉スラグ微粉末の結晶相と同様の効果を期待して、硫化カルシウム含有スラグである脱硫スラグを配合してもよい。この脱硫スラグは、溶銑予備処理の脱硫工程で発生するスラグであり、６価クロムの還元能を有する。反応性と経済性の面から、脱硫スラグはブレーン比表面積２５００〜５５００ｃｍ２/ｇ程度のものが好ましい。
脱硫スラグは、高炉スラグ微粉末の結晶相に代えて配合してもよいし、高炉スラグ微粉の結晶相と併存するように配合してもよい。
In the present invention, desulfurization slag, which is calcium sulfide-containing slag, may be blended with the expectation of the same effect as the crystal phase of blast furnace slag fine powder. This desulfurization slag is slag generated in the desulfurization step of the hot metal pretreatment, and has the ability to reduce hexavalent chromium. From the viewpoint of reactivity and economy, the desulfurization slag preferably has a Blaine specific surface area of about 2500 to 5500 cm 2 / g.
The desulfurized slag may be blended in place of the crystal phase of the blast furnace slag fine powder, or may be blended so as to coexist with the crystal phase of the blast furnace slag fine powder.
ポルトランドセメント量が１０〜３０mass％である本発明の地盤改良材において、６価クロムの溶出を防止するために必要な高炉スラグ微粉末中の結晶相量および脱硫スラグの配合量について検討した。その結果、まず、高炉スラグ微粉末中の結晶相量については、地盤改良材中での割合で１．５〜６mass％、すなわちポルトランドセメント量の１５〜２０mass％が好適であることが判った。一方、脱硫スラグについては、地盤改良材中での割合で０．７５〜３mass％（＝上記結晶相量の１／２の量）、すなわちポルトランドセメント量の７．５〜１０mass％が好適であることが判った。これは、高炉スラグ微粉末中の結晶相と脱硫スラグがそれぞれ含有する硫化カルシウム量が、約１：２の関係にあるためである。
したがって、本発明の地盤改良材は、下記（ａ）および／または（ｂ）を満足し、下記（ｂ）の脱硫スラグ量（ｙ）を２倍した値と下記（ａ）の結晶相量（ｘ）の合計［（ｘ）＋（ｙ）×２］がポルトランドセメント量の１５〜２０mass％であることが好ましい。
（ａ）高炉スラグ微粉末の一部が結晶相からなる。
（ｂ）地盤改良材が、さらに脱硫スラグを含有する。
In the ground improvement material of the present invention in which the amount of Portland cement is 10 to 30 mass%, the amount of crystal phase and the amount of desulfurized slag in the blast furnace slag fine powder necessary for preventing elution of hexavalent chromium were studied. As a result, first, it was found that the amount of crystal phase in the ground granulated blast furnace slag is suitably 1.5 to 6 mass%, that is, 15 to 20 mass% of the amount of Portland cement. On the other hand, about desulfurization slag, 0.75-3 mass% (= 1/2 quantity of the said crystal phase amount) in the ratio in a ground improvement material, ie, 7.5-10 mass% of the amount of Portland cement, is suitable. I found out. This is because the amount of calcium sulfide contained in the crystal phase in the blast furnace slag fine powder and the desulfurized slag has a relationship of about 1: 2.
Therefore, the ground improvement material of the present invention satisfies the following (a) and / or (b), the value obtained by doubling the desulfurization slag amount (y) of the following (b) and the crystal phase amount of the following (a) ( It is preferable that the total [(x) + (y) × 2] of x) is 15 to 20 mass% of the amount of Portland cement.
(A) Part of the blast furnace slag fine powder is composed of a crystalline phase.
(B) The ground improvement material further contains desulfurization slag.
高炉スラグ微粉末の一部として高炉徐冷スラグを配合する場合や、地盤改良材に脱硫スラグを配合する場合は、それらを個別に粉末状に粉砕した後に高炉水砕スラグ微粉末と混合してもよいし、高炉水砕スラグと混合した状態で粉末状に粉砕してもよい。
本発明の地盤改良材は、高炉スラグ微粉末（高炉水砕スラグ、さらに必要に応じて高炉徐冷スラグ）、石膏、ポルトランドセメントまたは／および石灰を含有し、さらに必要に応じて脱硫スラグを含有するものであるが、さらに、これら以外の成分を適量配合することができる。この添加成分としては、例えば、Ａｌ、Ｍｇ、Ｃａなどの硫酸塩などが挙げられ、通常、これらの添加成分の１種以上を合計で３mass％以下の範囲で配合してもよい。
When blending blast furnace slow-cooled slag as part of blast furnace slag fine powder, or when blending desulfurized slag into the ground improvement material, mix them with ground granulated blast furnace slag after individually grinding them into powder. Alternatively, it may be pulverized into a powder in a state of being mixed with blast furnace granulated slag.
The ground improvement material of the present invention contains blast furnace slag fine powder (blast furnace granulated slag, and optionally blast furnace slow-cooled slag), gypsum, Portland cement and / or lime, and further contains desulfurized slag as necessary. However, an appropriate amount of components other than these can be further blended. Examples of the additive component include sulfates such as Al, Mg, and Ca. Usually, one or more of these additive components may be blended in a range of 3 mass% or less in total.
次に、本発明の地盤改良材の好ましい使用形態について説明する。
地盤改良材は、その使用（施工）形態も性能を大きく左右するので、本発明の地盤改良材を施工する際の水／固化材（地盤改良材）比の影響を調査した。その結果、地盤改良材使用量が８０ｋｇ／ｍ３以下の場合、水／固化材比が１５０％を超えると初期の強度発現が低下すること、また、地盤改良材使用量が１２０ｋｇ／ｍ３以上の場合、水／固化材比が１００％未満では水和反応量が少なく、地盤改良材添加量を増加したことによる効果が十分に現れないことが判った。したがって、本発明の地盤改良材を施工する際は、水／固化材比を１００〜１５０％とすることが好ましい。
Next, the preferable usage form of the ground improvement material of this invention is demonstrated.
Since the use (construction) form of the ground improvement material greatly affects the performance, the influence of the water / solidification material (ground improvement material) ratio when the ground improvement material of the present invention was constructed was investigated. As a result, when the amount of ground improvement material used is 80 kg / m 3 or less, the initial strength expression decreases when the water / solidification material ratio exceeds 150%, and the amount of ground improvement material used is 120 kg / m 3 or more. In this case, it was found that when the water / solidification material ratio is less than 100%, the amount of hydration reaction is small, and the effect of increasing the amount of ground improvement material added is not sufficiently exhibited. Therefore, when constructing the ground improvement material of the present invention, the water / solidification material ratio is preferably 100 to 150%.
本発明の地盤改良材を適用する地盤としては、山土または風化花崗岩（いわゆるマサ土）からなる地盤が好ましい。これは、客土として宅地造成に用いられることが多く、ｐＨやクロム溶出などの点についての要求も厳しいためである。また、そのなかでも、有機物質の比率が１０mass％以下、含水比が５０mass％以下であって、地盤土質の分類が粘土質シルト〜礫質砂である地盤の改良材として好適である。セメント系高Ｃａ含有物の少ない本発明の地盤改良材は、このような地盤において特に有利に働く。 The ground to which the ground improvement material of the present invention is applied is preferably a ground made of mountain soil or weathered granite (so-called masa soil). This is because it is often used as residential land for residential land development, and demands on points such as pH and chromium elution are severe. Among them, the ratio of the organic substance is 10 mass% or less, the water content ratio is 50 mass% or less, and the ground soil classification is suitable as a soil improvement material having a clay silt to gravel sand. The ground improvement material of the present invention having a low cement-based high Ca content works particularly advantageously in such ground.
［実施例１］
表１に、参考例と比較例（既存のセメント系固化材に相当する比較例）の地盤改良材の原料配合割合を示す。なお、参考例では、結晶相の割合が３〜５mass％程度の高炉スラグ微粉末を用いた。室内試験において、これら地盤改良材（参考例、比較例）を水／固化材比＝１００％の条件で加水添加し、自然含水比１５mass％前後の標準的な砂質シルトを対象土として、一般的な改良目標である７日養生後の一軸圧縮強度（ＪＩＳ−Ａ−１２１６に準拠）が１．２〜１．５Ｎ／ｍｍ２となるように添加した。その地盤改良材添加量（試験土の湿潤体積に対する添加量）を表１に併せて示す。
[Example 1]
Table 1 shows the raw material blending ratio of the ground improvement material of the reference example and the comparative example (comparative example corresponding to the existing cement-based solidified material). In the reference example , blast furnace slag fine powder having a crystal phase ratio of about 3 to 5 mass% was used. In laboratory tests, these ground improvement materials ( reference examples and comparative examples) were added with water / solidified material ratio = 100%, and standard sandy silt with natural moisture content of around 15 mass% was used as the target soil. It was added so that the uniaxial compressive strength (according to JIS-A-1216) after 7-day curing, which is a typical improvement target, was 1.2 to 1.5 N / mm 2 . The ground improvement material addition amount (addition amount with respect to the wet volume of the test soil) is also shown in Table 1.
また、表２に、参考例と比較例の地盤改良材による改良土の特性として、７日養生後の改良土の一軸圧縮強度（ＪＩＳ−Ａ−１２１６に準拠して測定）、ｐＨ（ＪＧＳ−０２１１に準拠して測定）および６価クロム溶出量（環境庁告示４６号に準拠して測定）の各測定値を示す。図１に、改良土のｐＨと一軸圧縮強度の関係を示すが、参考例では強度の増加に伴うｐＨの上昇はみられない。これは、強度発現にエトリンガイト生成の水和反応を利用したことによるものである。
また、参考例は、比較例１〜７に比べて地盤改良材添加量が多いにもかかわらず、未固化時（養生７日後）の６価クロムの溶出はほぼ検出限界以下となった。
Moreover, in Table 2, as the characteristics of the improved soil by the ground improvement material of the reference example and the comparative example, the uniaxial compressive strength (measured according to JIS-A-1216) after 7 days curing, pH (JGS- Measured according to 0211) and hexavalent chromium elution amount (measured according to Environment Agency Notification No. 46). FIG. 1 shows the relationship between the pH of the improved soil and the uniaxial compressive strength. In the reference example , no increase in pH with increasing strength is observed. This is due to the use of the hydration reaction of ettringite formation for strength development.
Moreover, although the reference example had much ground improvement material addition amount compared with Comparative Examples 1-7, the elution of hexavalent chromium at the time of non-solidification (after 7 days of curing) was almost below the detection limit.
比較例１〜７は、既存のセメント系固化材相当の地盤改良材であり、ポルトランドセメント量が多すぎるため、改良土のｐＨが高く、また、土壌環境基準（≦０．０５ｍｇ／Ｌ）以下ではあるが、未固化時の６価クロムの溶出が認められる。また、比較例１５は、石膏量が少なすぎ且つポルトランドセメント量が多すぎるため、同様に改良土のｐＨが高く、且つ未固化時の６価クロムの溶出が認められる。
比較例８，９，１３は、石膏が配合されていないか若しくは石膏量が少なすぎる例であり、これらは強度確保のために地盤改良材添加量が多くなるが、ポルトランドセメント量に対する高炉スラグ微粉末量の相対的な割合の多寡により、比較例８，１３では改良土のｐＨが高く、且つ未固化時の６価クロムの溶出が認められ、一方、比較例９では改良土の一軸圧縮強度が低い。
Comparative Examples 1 to 7 are ground improvement materials equivalent to existing cement-based solidifying materials, and the amount of Portland cement is too large, so the pH of the improved soil is high, and the soil environment standard (≦ 0.05 mg / L) or less However, elution of hexavalent chromium when not solidified is observed. In Comparative Example 15, since the amount of gypsum is too small and the amount of Portland cement is too large, the pH of the improved soil is similarly high, and elution of hexavalent chromium when not solidified is observed.
Comparative Examples 8, 9, and 13 are examples in which gypsum is not blended or the amount of gypsum is too small. In order to secure strength, the amount of ground improvement material increases, but the amount of blast furnace slag with respect to the amount of Portland cement is small. Due to the relative proportion of the amount of powder, in Comparative Examples 8 and 13, the pH of the improved soil was high and elution of hexavalent chromium when not solidified was observed, whereas in Comparative Example 9, the uniaxial compressive strength of the improved soil Is low.
比較例１０，１１は、高炉スラグ微粉末量が多すぎ且つ石膏が配合されていない例であり、改良土の一軸圧縮強度がかなり低い。
比較例１２は、ポルトランドセメント量が少なすぎるため、改良土の一軸圧縮強度が低い。
比較例１４は、ポルトランドセメント量を下げてその分石膏量を多くした例であるが、ポルトランドセメント量に対する高炉スラグ微粉末量の相対的な割合が少ないこと、さらには強度確保のために地盤改良材添加量が多くなることにより、改良土のｐＨが高く、且つ未固化時の６価クロムの溶出が認められる。
Comparative Examples 10 and 11 are examples in which the amount of blast furnace slag fine powder is too large and no gypsum is blended, and the uniaxial compressive strength of the improved soil is considerably low.
In Comparative Example 12, since the amount of Portland cement is too small, the uniaxial compressive strength of the improved soil is low.
Comparative Example 14 is an example in which the amount of gypsum was increased by reducing the amount of Portland cement, but the relative proportion of the amount of fine powder of blast furnace slag to the amount of Portland cement was small, and further ground improvement was performed to ensure strength. By increasing the material addition amount, the pH of the improved soil is high, and elution of hexavalent chromium when not solidified is observed.
比較例１６は、高炉スラグ微粉末量が少なすぎる例であり、ポルトランドセメント量に対する高炉スラグ微粉末量の相対的な割合が少ないため、改良土のｐＨが高く、且つ未固化時の６価クロムの溶出が認められる。
比較例１７は、高炉スラグ微粉末量が多すぎる例であり、改良土の一軸圧縮強度が低い。
なお、詳細は省略するが、養生６３日ではいずれの供試体からも６価クロムは検出されなかった。
以上の試験結果から明らかなように、参考例の地盤改良材は、既存のセメント系固化材に較べて所定の強度を得るための添加量はやや増えるものの、ｐＨの上昇および６価クロムの溶出は見られない。
Comparative Example 16 is an example in which the amount of blast furnace slag fine powder is too small, and since the relative proportion of the amount of blast furnace slag fine powder to the amount of Portland cement is small, the pH of the improved soil is high, and the hexavalent chromium at the time of unsolidified Elution is observed.
Comparative Example 17 is an example in which the amount of blast furnace slag fine powder is too large, and the uniaxial compressive strength of the improved soil is low.
Although details are omitted, hexavalent chromium was not detected from any of the specimens on the 63rd day of curing.
As is clear from the above test results, the ground improvement material of the reference example has a slightly increased amount of addition for obtaining a predetermined strength as compared with the existing cement-based solidified material, but the increase in pH and elution of hexavalent chromium. Is not seen.
［実施例２］
地盤改良材を構成する高炉スラグ微粉末中の結晶相量（ここでは、高炉徐冷スラグの配合量）および脱硫スラグ（硫化カルシウム含有スラグ）の配合量と、６価クロムの溶出挙動について検討した。
表３に、本発明例と参考例の地盤改良材の原料配合割合を示す。なお、本発明例および参考例は、いずれも高炉スラグ微粉末と石膏を本発明範囲で含有している。
[Example 2]
The amount of crystal phase in the ground granulated blast furnace slag powder (in this case, the blending amount of blast furnace slow-cooled slag), the blending amount of desulfurized slag (calcium sulfide-containing slag), and the elution behavior of hexavalent chromium were examined. .
In Table 3, the raw material mixture ratio of the ground improvement material of this invention example and a reference example is shown. The examples of the present invention and the reference examples both contain blast furnace slag fine powder and gypsum within the scope of the present invention.
室内試験において、これら地盤改良材（本発明例、参考例）を水／固化材比＝１００％の条件で加水添加し、自然含水比１５mass％前後の標準的な砂質シルトを対象土として、一般的な改良目標である７日養生後の一軸圧縮強度（ＪＩＳ−Ａ−１２１６に準拠）が１．５Ｎ／ｍｍ２または６Ｎ／ｍｍ２となるように添加した。その改良土の７日養生後の６価クロム溶出量（環境庁告示４６号に準拠して測定）の測定値を、地盤改良材添加量（試験土の湿潤体積に対する添加量）などとともに表３に示す。 In laboratory tests, these ground improvement materials (examples of the present invention, reference examples) were added with water / solidification material ratio = 100%, and a standard sandy silt with a natural water content ratio of about 15 mass% was used as the target soil. general improvement goal is a 7 day unconfined compressive strength after curing (according to JIS-a-1216) was added to a 1.5 N / mm 2 or 6N / mm 2. Table 3 shows the measured value of hexavalent chromium elution after 7 days of curing of the improved soil (measured in accordance with Environment Agency Notification No. 46), along with the amount of ground improvement material added (added to the wet volume of the test soil) Shown in
表３によれば、高炉徐冷スラグ量（Ｂ）と脱硫スラグ量（Ｓ）による［（Ｓ）×２＋（Ｂ）］がポルトランドセメント量の１５〜２０mass％であれば、改良土の目標強度６Ｎ／ｍｍ２を達成するために地盤改良材を多量に添加した場合（地盤改良材目標添加量：３００ｋｇ／ｍ３）であっても、未固化時の６価クロムの溶出はほぼ検出限界以下であり、しかも、地盤改良材の目標添加量の範囲内で目標とする改良土の一軸圧縮強度が確保されている。これに対して、高炉徐冷スラグ量（Ｂ）と脱硫スラグ量（Ｓ）による［（Ｓ）×２＋（Ｂ）］がポルトランドセメント量の１５mass％未満であると（参考例１〜４，１０）、地盤改良材を多量に添加した場合（地盤改良材目標添加量：３００ｋｇ／ｍ３）には、未固化時の６価クロムの溶出が認められる。 According to Table 3, if [(S) × 2 + (B)] based on the blast furnace slow cooling slag amount (B) and desulfurization slag amount (S) is 15 to 20 mass% of the amount of Portland cement, the target strength of the improved soil Even when a large amount of ground improvement material is added to achieve 6 N / mm 2 (target addition amount of ground improvement material: 300 kg / m 3 ), elution of hexavalent chromium when not solidified is almost below the detection limit. Moreover, the target uniaxial compressive strength of the improved soil is ensured within the range of the target addition amount of the ground improvement material. On the other hand, when [(S) × 2 + (B)] based on the blast furnace slow cooling slag amount (B) and the desulfurization slag amount (S) is less than 15 mass% of the Portland cement amount (Reference Examples 1 to 4, 10) ), When a large amount of ground improvement material is added (target addition amount of ground improvement material: 300 kg / m 3 ), elution of hexavalent chromium when not solidified is observed.
表４に、参考例１１の地盤改良材、高炉セメント（Ｂ種）、普通ポルトランドセメントによる砂質シルト改良の施工結果を示す。改良土の特性として、７日養生後の改良土の一軸圧縮強度（ＪＩＳ−Ａ−１２１６に準拠して測定）、ｐＨ（ＪＧＳ−０２１１に準拠して測定）および６価クロム溶出量（環境庁告示４６号に準拠して測定）の各測定値を示した。 In Table 4, the construction result of the sandy silt improvement by the ground improvement material of the reference example 11 , a blast furnace cement (class B), and normal Portland cement is shown. As characteristics of the improved soil, uniaxial compressive strength after the 7-day curing (measured according to JIS-A-1216), pH (measured according to JIS-0211), and hexavalent chromium elution amount (Environment Agency) Each measured value was measured according to Notification No. 46.
Claims (4)
高炉スラグ微粉末はブレーン比表面積が３０００〜５０００ｃｍ ２ /ｇであり、
高炉スラグ微粉末の一部が結晶相からなるとともに、その結晶相量（ｘ）がポルトランドセメントまたは／および石灰量の１５〜２０mass％であり、
高炉スラグ微粉末は高炉水砕スラグと高炉徐冷スラグからなり、
高炉スラグ微粉末の結晶相は、（i）高炉徐冷スラグ、（ii）高炉水砕スラグの製造時に析出した結晶相と高炉徐冷スラグ、のいずれかからなることを特徴とする地盤改良材。 Blast furnace slag fine powder: 50-80 mass%, gypsum: 5-25 mass%, Portland cement or / and lime: 10-30 mass%,
The blast furnace slag fine powder has a brain specific surface area of 3000 to 5000 cm 2 / g,
Part of the blast furnace slag fine powder is composed of a crystalline phase, and the amount of the crystalline phase (x) is 15 to 20 mass% of the amount of Portland cement and / or lime ,
Blast furnace slag fine powder consists of blast furnace granulated slag and blast furnace slow-cooled slag,
Ground improvement material characterized in that the crystal phase of blast furnace slag fine powder consists of either (i) blast furnace slow-cooled slag, (ii) crystal phase precipitated during the production of blast furnace granulated slag and blast furnace slow-cooled slag .
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| WO2010143630A1 (en) * | 2009-06-09 | 2010-12-16 | 株式会社竹中工務店 | Slurry composition for soil improvement containing blast furnace slag cement and method for preparing soil cement slurry using same |
| JP5590702B2 (en) * | 2009-06-09 | 2014-09-17 | 株式会社竹中工務店 | Slurry composition for ground improvement using blast furnace slag composition and method for preparing soil cement slurry using the same |
| JP5685004B2 (en) * | 2010-05-10 | 2015-03-18 | 国立大学法人東京工業大学 | Soil improvement method |
| KR101482382B1 (en) | 2013-03-08 | 2015-01-14 | 주식회사 포스코 | Low-heat cement composition including desulfurization slag and blast furnace slag |
| JP2016044479A (en) * | 2014-08-25 | 2016-04-04 | ヒロセ株式会社 | Continuous underground wall structure |
| JP6023771B2 (en) * | 2014-10-09 | 2016-11-09 | 国立大学法人東京工業大学 | Cement composition and soil improvement method |
| JP7422071B2 (en) | 2018-06-22 | 2024-01-25 | 日鉄セメント株式会社 | Heavy metal insolubilization solidification material and method for improving contaminated soil |
| JP7193105B1 (en) * | 2022-10-03 | 2022-12-20 | 強化土エンジニヤリング株式会社 | Ground injection method using ground injection material and ground injection material |
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