JP4493159B2 - Method for manufacturing ground improvement material - Google Patents
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- JP4493159B2 JP4493159B2 JP2000162736A JP2000162736A JP4493159B2 JP 4493159 B2 JP4493159 B2 JP 4493159B2 JP 2000162736 A JP2000162736 A JP 2000162736A JP 2000162736 A JP2000162736 A JP 2000162736A JP 4493159 B2 JP4493159 B2 JP 4493159B2
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- calcium polysulfide
- ground improvement
- cement
- gypsum
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- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、有害重金属の安定化能力に優れた地盤改良材の製造方法に関するものである。詳しくは、軟弱地盤、建設廃棄物、各種汚泥の固化改良において、改良対象物に含まれる、あるいは産業廃棄物を多量使用したセメント又は該セメントを使用して製造された固化材に由来する有害重金属の溶出が抑制された地盤改良材の製法に関するものである。
【０００２】
【従来の技術】
軟弱地盤の改良や、廃棄物の埋め立て処理の際、処理対象物である土、廃棄物そのものに、環境上無視できない程度の有害重金属が含まれている場合がある。これ等処理対象物の処理には、通常、セメント系固化材が使用されるが、この場合、セメントの主成分であるカルシウム等のアルカリ成分が溶出することから、固化処理土のｐＨ値が１１を超えることが多々発生する。この様な高アルカリ環境下では、多くの重金属類は難溶解性の水酸化物を形成し固定化され、その溶出は抑制される。しかし、一部の両性重金属、例えば六価クロムは、高ｐＨ領域でイオン化した状態で存在するため、何等かの溶出防止策を講じないと、処理系外に溶出し、環境汚染を引き起こすことになる。更に、セメントが極微量の六価クロムを含むことから、セメント系固化材を使用すれば、固化材自体からの六価クロムの溶出も問題となる。
【０００３】
高ｐＨ域での六価クロムの固定化率を高め、その溶出を抑制する手段として種々の方法が提案されている。三価クロムの水酸化物は難溶性であるのを利用し、、固化材に、硫酸第一鉄、高炉スラグ等の還元剤又は含還元性物質材料を添加して、還元固定化する方法が公知である。この方法は、クロム溶出の抑制にはそれなりの効果があるが、単一材料のみの添加では、初期〜長期に亙って効果を維持するものがないのに加え、還元剤の添加はセメントの水和反応を遅延させる効果を有していることから、有害重金属の溶出抑制効果を確保する目的で多量添加（数％から数十％）すれば改良土の目的強度が得られ難くなる欠点を抱えたものであった。この様な事情を背景に、従来の固化特性を損なうことなく、初期から長期に亙り有害重金属を固定化しその溶出を抑制する地盤改良材の存在が望まれていた。
【０００４】
【発明が解決しようとする課題】
本発明の目的は、前記課題の解決された固化材の製造方法の提供、すなわち、改良処理土の強度の低下をもたらすことなく、有害重金属溶出を著しく抑制する機能を付加した地盤改良材の製造方法を提供することにある。
【０００５】
【課題を解決するための手段】
本発明者は、セメントおよびせっこうよりなる水硬性成分に、多硫化カルシウムを添加した固化材が上記目的とする固化材となることを見出し、本発明を完成した。すなわち本発明は、多硫化カルシウム水溶液に、該水溶液に含まれる水量のほぼ全量を吸水して全体が粉末状として扱える混合物を与える量の生石灰を加え混合物粉を調製する工程と、多硫化カルシウム水溶液と生石灰との混合物粉体をセメントおよびせっこうと混合する工程とを含む地盤改良材の製造方法であって、多硫化カルシウム水溶液の配合割合は、セメントとせっこうの合量１００重量部に対してＳ換算で０．０１５〜１．０重量部であり、せっこうの配合割合は、セメントとせっこうの合量１００重量部に対してＳＯ3基準で４〜２０重量部であることを特徴とする地盤改良材の製造方法に関する。以下に本発明を詳しく説明する。
【０００６】
【発明の実施の形態】
本発明の地盤改良材の製造方法は、ポルトランドセメントとせっこうを基本成分とする。せっこう量は、少なすぎると初期強度発現性が十分でなく、多すぎると長期強度発現性が低下することから、その添加量は、ＳＯ3基準で固化成分全体に対して４〜２０重量％とする。このように、せっこう分を富化した固化成分と多硫化カルシウムとの組合わせは、せっこう量がＳＯ3基準でが３重量％以下である一般構造用セメントを固化成分とする場合に対比して、本件発明の地盤改良材の示す優れた重金属溶出抑制効果及び強度付与効果の要因となっている。なお、使用するせっこうの形態は特に限定されるものではないが、２水塩、半水塩、II型無水塩の使用が好ましい。
【０００７】
地盤改良材中の多硫化カルシウム量は、少な過ぎると重金属溶出抑制効果が不十分であり、一方、多すぎると重金属溶出抑制効果は向上するものの、改良土の強度が低下するだけでなく経済性の面からも好ましくない。地盤改良材に存在する重金属量は、固化成分として使用されるセメントが由来する原料に依存して変動する。また、土自体が有する重金属固定化能力も処理対象土によって異なる。本発明では、多硫化カルシウム存在量を、セメントおよびせっこうよりなる固化成分１００重量部当たり、その成分として含まれる硫黄（Ｓ）換算で０．０１５〜１．０重量部とするが、一般的な土の改良処理に十分対応可能な地盤改良材を、一般的なセメントを使用して得ることが出来る。
【０００８】
多硫化カルシウムによる重金属の固定化能力（許容限界）は、多硫化カルシウムの濃度および形態、固化処理後の経過時間（材齢）等によって当然異なるが、例えば、Ｓ換算で０．３重量％の多硫化カルシウムを含む地盤改良材１ｋｇ当たりの六価クロム固定化能力は約３００ｍｇである。
【０００９】
多硫化カルシウムは、粉末および各種濃度の水溶液としたもののが知られている。特に、一般的な流通形態である各種濃度の水溶液は、入手が容易であるのに加え、優れた特性の地盤改良材を与えることから、好適に使用することが出来る。多硫化カルシウム水溶液を使用する場合には、２種の異なった方法を採ることが出来る。水溶液形状で他の構成成分に添加する方法では、後に混合処理が加わる状態に在る成分材料への添加例えば、ボールミルへの給材工程に在る材料への添加においては、添加方法を選ばないが、水溶液である材料の特性を活かした効果的な添加方法の一つは噴霧である。噴霧は、添加後に混合処理を加えない場合、例えば、ボールミリング後の、ベルトコンベア上を移送中の多硫化カルシウム以外の構成成分を含む原材料に水溶液を噴霧する方法でも、十分な重金属溶出抑制効果と固化強度を示す地盤改良材を得ることが出来る。
【００１０】
多硫化カルシウム含有固化材の製造において、この水溶液での添加は、余分な工程を必要としない長所が在るだけでなく、添加後にボールミリングを加える場合には、被粉砕物に対する高温処理と粉砕処理が同時に進行するため、水分の蒸発による多硫化カルシウムの固形化が微細化・分散と同時に進むと共に、粉砕処理を受けたセメント粒子表面への多硫化アルカリの融着が生じ、より高い添加効果を発現させることが可能となる。
【００１１】
本発明では、多硫化カルシウムを水溶液形状でセメント、せっこうに添加するのではなく、多硫化カルシウム水溶液に粉体状の固定化材を添加し、多硫化カルシウムがこれ等固定化材上に担持固定化されたと見做し得る状態で存在する粉体状物として添加する。粉状物は、貯蔵、運搬、秤量、他成分との混合等が容易で操作性に優れていることから、該方法による多硫化カルシウムの添加は、原料を混合して固化材の調製及び配送を行うステーションを複数箇所に設置して、事業を実施する場合には非常に好ましい方法である。
【００１２】
本発明において、多硫化カルシウム水溶液を粉体状に固定する固定化材は、生石灰である。固定化後すなわち多硫化カルシウム水溶液との混合後には、全体が実質的に粉体として扱える量の粉状固定化材を添加する。この状態にするための固定化材の添加量は、多硫化カルシウム水溶液濃度、吸水材、即ち固定化材の吸水容量更には固定化材比重に依存して変化するが、例えば、２７．５％の多硫化カルシウム水溶液の場合、硫黄換算多硫化カルシウムと固定化材との重量比を１：２とすれば、十分その目的を達成できる。
【００１３】
この生石灰は、軟焼した活性の高いものを使用するのが好ましい。
【００１４】
吸水材、即ち固定化材による多硫化カルシウム水溶液の粉体状への固定化は、多硫化カルシウム水溶液に固定化材粉末を添加する簡単な方法で実施できる。この工程では、混合処理を加えることは必ずしも必要でないが、固定化処理後の粉体をセメント等の構成他成分と混合して地盤改良材材に仕上げる際には、ボールミル等公知の混合手段で混合するのが好ましいことは言うまでもない。
【００１５】
多硫化カルシウムをその水溶液から固定化後添加する方法においては、その添加時期は、添加後に他の成分との混合処理が入る限り、特に限定はない。例えば、セメントクリンカーまたはセメントを、せっこうと混合するボールミルへの給材工程、ボールミル工程において添加することも出来るし、固定化した多硫化カルシウムを加えた後に、多硫化カルシウム分散のみを目的とした追加の混合処理を加えることも、当然、可能である。
【００１６】
本発明の地盤改良材の製造方法は、セメント、せっこうおよび多硫化カルシウムを必須成分とするものであるが、改良対象土の土性に合わせて、一般のセメント系固化材で使用されている生石灰、消石灰、高炉スラグ、石炭灰の１種以上の一般量を添加することが出来る。この中、前述した多硫化カルシウム水溶液の固定化材として使用可能なものについては、その形態での導入が出来るのは当然である。
【００１７】
本発明の地盤改良材は、一般的な地盤改良材同様、建設発生土、浚渫土等の処理対象土に添加・混合しての埋め戻し、埋め立ては勿論のこと、公知方法による浅層・深層地盤や表層軟弱土の現位置土改質にも適用出来る。
【００１８】
【実施例】
以下に具体例を挙げて、本発明を更に詳しく説明する。
（１）使用材料・セメント：ポルトランドセメントを使用したが、含有クロム量の異なるものを適宜使用した。
・せっこう：無水せっこうを使用した。
・多硫化カルシウム：２７．５％水溶液を出発原料として使用した。
（２）上記原材料からの地盤改良材調製方法については、添加形態、添加時期の異なる種々の方法で実施したが、調製法については各個所で適宜説明する。
（３）被試験土：火山灰質粘性土（関東ローム）
（４）被試験土１ｍ3に対し、地盤改良材１８０〜２００ｋｇを添加し、ホバートミキサーで３分間練り混ぜた後、直径５０ｍｍ×長さ１０ｍｍの円筒形型枠に入れ、材齢１日後に脱型した。成形体は、２０℃、湿度６０％で材齢７日まで密封養生して、供試体を得た。必要なものについては、１８０日の長期養生を実施した。
【００１９】
（５）供試体については、次の試験を行った。
・強度：ＪＩＳ Ａ １２１６に則って、一軸圧縮強度を測定した。
・溶出試験：環境庁告示第４６号に則って溶出試験を行い、振盪後のろ液をジフェニルカルバジド発色吸光度分析により、六価クロムの定量を行った。検出限界は、０．０２ｍｇ／リットルである。
【００２０】
参考例１、比較例１〜３ポルトランドセメント（ＳＯ3量：２．１重量％、総クロム濃度：７７ｍｇ／ｋｇ、水溶性６価クロム濃度：８．３ｍｇ／ｋｇ）に、無水せっこう及び／又は多硫化カルシウムを添加し、パン型混合機で３０分間混合し、地盤改良材を調製した。せっこう量は、（セメント＋せっこう）１００重量部に対しＳＯ3換算で９．５重量％であり、多硫化カルシウムは、同じく（セメント＋せっこう）量に対し硫黄（Ｓ）換算で０．３重量部となるように２７．５重量％水溶液で添加した。各地盤改良材について、地盤改良性能評価結果を表１に示す。セメント、せっこう及び多硫化カルシウムのすべてを構成成分として含む材料のみが、圧縮強度及び６価クロム溶出量抑制の両面で、顕著な効果を奏することが分かる。
【００２１】
【表１】
参考例２〜４、比較例４〜６ここでは、多硫化カルシウムの添加量を変えた例を示すが、検討は、地盤改良材構成成分に製鋼スラグを添加し、改良材自体に含まれる総クロム量を多くしたものについて行った。これは、セメント原料としてその使用量の増加が今後予想される産業廃棄物に伴って導入される重金属量増加への対応可能性を調べるためである。先ず、セメントの原料の一つに製鋼スラグを用い、混合焼成してクロム含有量の多いクリンカーを得、該クリンカーを粉砕した後無水せっこうを添加し、ＳＯ3換算で７．６重量％、総クロム濃度１７５ｍｇ／ｋｇ、水溶性６価クロム濃度２８．０ｍｇ／ｋｇの固化成分を調製した。次いで、該固化成分に所定量の多硫化カルシウムを添加し、参考例１と同様の方法で地盤改良材を調製し、参考例１と同様の方法でその評価を行った。結果を表２に示す。
【００２３】
【表２】
多硫化カルシウム添加量が少ないと、６価クロム溶出量を基準値である０．０５ｍｇ／リットル以下に抑制することが不可能であり、一方、多硫化カルシウム添加量が大であると、６価クロムの溶出は検出限界以下に抑制できるものの、強度が低下し、地盤改良材として持つべき本来の効果が十分に発現しないことが分かる。また、総クロム量の多いセメントに対しても、十分に対応可能なことを示している。
【００２５】
実施例１，２、参考例５，６ここでは、多硫化カルシウムの添加形態を変えた例として、その水溶液に生石灰、パーライト、活性炭を添加し粉状に固定化処理した後に添加した例を示す。２７．５％多硫化カルシウム水溶液に、所定量の吸水材、即ち固定化材を添加・混合し、粉状に改質された多硫化カルシウム固定化物を調製した。次いで、所定量のセメントおよびせっこうを混合し、地盤改良材を調製した。特性評価結果を表３に示す。
【００２６】
【表３】
表３には、対比を容易にするため多硫化カルシウムを水溶液状態で添加する参考例２を再掲しているが、多硫化カルシウム水溶液に粉状の固定化材を添加し、多硫化カルシウムを固体上に担持させる固定化処理を行った後に、地盤改良材を構成する他成分に添加しても、多硫化カルシウムを水溶液で添加したものと同等の効果を示す地盤改良材が得られることが分かる。
【００２８】
参考例７、比較例７ここでは、固化処理後における６価クロム溶出量の経時変化を調べた結果を示す。組成をせっこう９．５重量部、多硫化カルシウム０．１重量部にした以外は、参考例１の方法で地盤改良材を調製し、参考例１と同じ処理対象土に対して改良処理を行った。６価クロム溶出試験は、経時変化を追った以外は、実施例１と同じ方法で行った。結果を表４に示す。地盤改良材が、初期だけでなく長期に亙って６価クロム溶出抑制効果を維持していることが分かる。
【００２９】
【表４】
参考例８，９および比較例８ここでは、土と混合すること無く粉体状態の地盤改良材からの６価クロム溶出量を測定した。地盤改良材は、ボールミルへの給材工程におけるベルトコンベア上にあるセメントクリンカー及びせっこうに、多硫化カルシウム水溶液の所定量を滴下して調製した。セメントクリンカーおよびせっこう混合物から成る固化成分１ｋｇ当たりの水溶性６価クロム含有量は４．２３ｍｇであり、石こう量はＳＯ3換算で７．７重量％である。地盤改良材粉体からの６価クロムの溶出試験は、環境庁告示１３号に規定の方法で行った。結果を表５に示す。本発明の地盤改良材では、それ自身に含まれる６価クロムの溶出が基準値内に抑制されていることが分かる。
【００３１】
【表５】
【発明の効果】
本発明の製造方法で製造された地盤改良材は、十分な強度の改良土を与えるのは勿論のこと、初期から長期に亙って有害重金属の溶出抑制効果を発揮する。従って、今後要求される環境に配慮した地盤改良に、好適に使用できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a ground improvement material having an excellent ability to stabilize harmful heavy metals. Specifically, in the solidification improvement of soft ground, construction waste, and various sludges, hazardous heavy metals derived from solidification materials contained in the object to be improved, or using a large amount of industrial waste or manufactured using the cement It is related with the manufacturing method of the ground improvement material in which the elution of was suppressed.
[0002]
[Prior art]
When soft ground is improved or waste is landfilled, the soil, which is the object to be treated, and the waste itself may contain toxic heavy metals that cannot be ignored in the environment. A cement-based solidified material is usually used for the treatment of these treatment objects. In this case, since alkaline components such as calcium, which is the main component of cement, are eluted, the pH value of the solidified soil is 11. Often occurs. In such a highly alkaline environment, many heavy metals form a hardly soluble hydroxide and are immobilized, and their elution is suppressed. However, some amphoteric heavy metals, such as hexavalent chromium, exist in an ionized state in the high pH region, so if some kind of elution prevention measures are not taken, they will elute outside the processing system and cause environmental pollution. Become. Furthermore, since cement contains an extremely small amount of hexavalent chromium, if a cement-based solidifying material is used, elution of hexavalent chromium from the solidifying material itself becomes a problem.
[0003]
Various methods have been proposed as means for increasing the fixation ratio of hexavalent chromium in a high pH range and suppressing the elution. There is a method of reducing and fixing by adding a reducing agent such as ferrous sulfate and blast furnace slag to the solidified material or using a reducing substance material utilizing the fact that the hydroxide of trivalent chromium is hardly soluble. It is known. Although this method has a certain effect in suppressing chromium elution, in addition to the addition of a single material, there is nothing to maintain the effect from the beginning to the long term, and addition of a reducing agent is not necessary for cement. Since it has the effect of delaying the hydration reaction, it is difficult to obtain the target strength of the improved soil if it is added in a large amount (several percent to several tens of percent) in order to ensure the elution suppression effect of harmful heavy metals. It was what I had. Under such circumstances, there has been a demand for the presence of a ground improvement material that fixes harmful heavy metals and suppresses the elution from the initial stage for a long time without impairing the conventional solidification characteristics.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to provide a method for producing a solidified material in which the above-mentioned problems have been solved, that is, production of a ground improvement material to which a function of remarkably suppressing harmful heavy metal elution is added without reducing the strength of the improved treated soil. It is to provide a method .
[0005]
[Means for Solving the Problems]
The present inventor has found that a solidified material obtained by adding calcium polysulfide to a hydraulic component composed of cement and gypsum becomes the above-mentioned solidified material, and has completed the present invention. That is, the present invention includes a step of preparing a mixture powder by adding an amount of quick lime that absorbs almost the entire amount of water contained in the aqueous solution to give a mixture that can be handled as a powder as a whole. A ground improvement material comprising a step of mixing a mixture powder of lime and quicklime with cement and gypsum, wherein the mixing ratio of the calcium polysulfide aqueous solution is 100 parts by weight of the total amount of cement and gypsum characterized in that a 0.015 to 1.0 parts by weight S terms, the mixing ratio of gypsum is 4 to 20 parts by weight SO 3 criteria for the total amount 100 parts by weight of cement and gypsum Te The present invention relates to a method for manufacturing a ground improvement material. The present invention is described in detail below.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The ground improvement material production method of the present invention comprises Portland cement and gypsum as basic components. Zhejiang weight was too low initial strength development is not sufficient, too large since the long-term strength development is lowered, the addition amount is 4-20 wt% based on the total solidified component with SO 3 basis And Thus, the combination of the solidified component enriched with gypsum and calcium polysulfide is in contrast to the case where the amount of gypsum is 3% by weight or less based on SO 3 as the solidified component. And it becomes a factor of the outstanding heavy metal elution suppression effect and intensity | strength provision effect which the ground improvement material of this invention shows. The form of gypsum used is not particularly limited, but dihydrate, hemihydrate, and type II anhydrous salt are preferably used.
[0007]
If the amount of calcium polysulfide in the ground improvement material is too small, the effect of suppressing heavy metal elution is insufficient. On the other hand, if the amount of calcium polysulfide is too large, the effect of suppressing heavy metal elution is improved, but not only the strength of the improved soil is reduced but also economical. This is also not preferable. The amount of heavy metal present in the ground improvement material varies depending on the raw material from which the cement used as the solidifying component is derived. In addition, the heavy metal fixing ability of the soil itself varies depending on the soil to be treated. In the present invention, the amount of calcium polysulfide present is 0.015 to 1.0 part by weight in terms of sulfur (S) contained as a component per 100 parts by weight of a solidified component made of cement and gypsum. It is possible to obtain a ground improvement material that can sufficiently cope with the soil improvement treatment using ordinary cement.
[0008]
The ability to immobilize heavy metals with calcium polysulfide (allowable limit) naturally varies depending on the concentration and form of calcium polysulfide, the elapsed time after solidification (age), etc., for example, 0.3% by weight in terms of S The hexavalent chromium fixing capacity per 1 kg of ground improvement material containing calcium polysulfide is about 300 mg.
[0009]
Calcium polysulfide, despite an aqueous solution of the powder and various concentrations that have been known. In particular, aqueous solutions of various concentrations, which are general distribution forms, can be suitably used because they are easily available and provide ground improvement materials with excellent characteristics. When using a calcium polysulfide aqueous solution, two different methods can be employed. In the method of adding to other constituents in the form of an aqueous solution, addition to a component material that is in a state where a mixing process is added later, for example, in addition to a material in a feeding process to a ball mill, an addition method is not selected. However, one of the effective addition methods utilizing the characteristics of the material which is an aqueous solution is spraying. When spraying is not mixed after addition, for example, even when the aqueous solution is sprayed on the raw material containing components other than calcium polysulfide being transferred on the belt conveyor after ball milling, sufficient heavy metal elution suppression effect And a ground improvement material showing solidification strength can be obtained.
[0010]
In the production of calcium polysulfide-containing solidified material, the addition with this aqueous solution not only has the advantage of not requiring an extra step, but also when ball milling is added after the addition, high-temperature treatment and pulverization of the object to be crushed Since the treatment proceeds simultaneously, the solidification of calcium polysulfide due to moisture evaporation proceeds simultaneously with the refinement and dispersion, and the fusion of alkali polysulfide to the cement particle surface that has undergone pulverization occurs, resulting in a higher additive effect. Can be expressed.
[0011]
In the present invention, calcium polysulfide is not added to cement and gypsum in the form of an aqueous solution, but a powdery fixing material is added to the calcium polysulfide aqueous solution, and the calcium polysulfide is supported on these fixing materials. It added as powdery material which is present in a state capable considered to have been immobilized. Powdered materials are easy to store, transport, weigh, mix with other components, and have excellent operability, so adding calcium polysulfide by this method involves mixing raw materials and preparing and delivering a solidified material. This is a very preferable method when a plurality of stations are installed at a plurality of locations to conduct business.
[0012]
And have you the present invention, immobilized materials that the calcium polysulfide solution to fix the powder form, Ru quicklime der. After mixing with immobilization after namely calcium polysulfide solution, the addition of whole amount of powdered immobilized materials that can be handled as a substantially powder. The amount of the immobilizing material added to obtain this state varies depending on the concentration of the aqueous solution of calcium polysulfide, the water absorbing material , that is, the water absorbing capacity of the immobilizing material, and the specific gravity of the immobilizing material. For example, 27.5% In the case of the calcium polysulfide aqueous solution, the purpose can be sufficiently achieved if the weight ratio of sulfur-converted calcium polysulfide to the fixing material is 1: 2.
[0013]
The Oishi ash is preferably used having a high soft baking activity.
[0014]
Immobilization of the calcium polysulfide aqueous solution in the powder form by the water absorbing material , that is, the immobilization material can be performed by a simple method of adding the immobilization material powder to the calcium polysulfide aqueous solution. In this step, it is not always necessary to add a mixing treatment, but when finishing the ground improvement material by mixing the fixed powder with other components such as cement, a known mixing means such as a ball mill is used. Needless to say, mixing is preferable.
[0015]
In the method of adding calcium polysulfide after immobilization from the aqueous solution, the addition timing is not particularly limited as long as mixing treatment with other components is performed after the addition. For example, cement clinker or cement can be added to the ball mill mixing process with gypsum, in the ball mill process, or after the addition of immobilized calcium polysulfide, only for dispersion of calcium polysulfide It is of course possible to add additional mixing processes.
[0016]
The method for producing a ground improvement material of the present invention comprises cement, gypsum and calcium polysulfide as essential components, but is used in general cement-based solidification materials in accordance with the soil properties of the soil to be improved. One or more general amounts of quick lime, slaked lime, blast furnace slag, and coal ash can be added. Of these, those that can be used as the fixing material for the aqueous solution of calcium polysulfide described above can naturally be introduced in that form.
[0017]
The ground improvement material of the present invention, like a general ground improvement material, is added to and mixed with the soil to be treated such as construction generated soil and dredged soil, backfilling, landfilling, as well as shallow and deep layers by a known method. It can also be applied to in-situ soil improvement of ground and surface soft soil.
[0018]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples.
(1) Materials used / cement: Portland cement was used, but materials with different chromium contents were used as appropriate.
Gypsum: Anhydrous gypsum was used.
Calcium polysulfide: A 27.5% aqueous solution was used as a starting material.
(2) Although the ground improvement material preparation method from the said raw material was implemented by the various methods from which an addition form and the addition time differ, it explains suitably for each part about a preparation method.
(3) Soil under test: Volcanic ash clay (Kanto Loam)
(4) To 1 m 3 of the soil to be tested, add 180 to 200 kg of ground improvement material, knead with a Hobart mixer for 3 minutes, and then put into a cylindrical form with a diameter of 50 mm and a length of 10 mm. Demolded. The molded body was sealed and cured at 20 ° C. and a humidity of 60% up to a material age of 7 days to obtain a specimen. For necessary items, 180-day long-term curing was implemented.
[0019]
(5) For the specimen, the following test was performed.
Strength: Uniaxial compressive strength was measured according to JIS A 1216.
-Dissolution test: A dissolution test was conducted in accordance with Notification No. 46 of the Environment Agency, and hexavalent chromium was quantified by diphenylcarbazide color absorbance analysis of the filtrate after shaking. The detection limit is 0.02 mg / liter.
[0020]
Reference Example 1, Comparative Examples 1-3 Portland cement (SO 3 content: 2.1 wt%, total chromium concentration: 77 mg / kg, water-soluble hexavalent chromium concentration: 8.3 mg / kg), anhydrous gypsum and / or Or calcium polysulfide was added, and it mixed for 30 minutes with the bread type mixer, and prepared the ground improvement material. The amount of gypsum was 9.5% by weight in terms of SO 3 with respect to 100 parts by weight of (cement + gypsum), and calcium polysulfide was also 0 in terms of sulfur (S) with respect to the amount of (cement + gypsum). The solution was added in a 27.5% by weight aqueous solution so as to be 3 parts by weight. Table 1 shows the results of evaluating the ground improvement performance of the local ground improvement materials. It can be seen that only materials containing all of cement, gypsum and calcium polysulfide as constituents have remarkable effects both in terms of compressive strength and suppression of hexavalent chromium elution.
[0021]
[Table 1]
Reference Examples 2 to 4 and Comparative Examples 4 to 6 Here, an example in which the addition amount of calcium polysulfide is changed is shown. However, the study is performed by adding steelmaking slag to the ground improvement material component, and the total amount contained in the improvement material itself. The test was carried out for the chromium content increased. This is to investigate the possibility of dealing with an increase in the amount of heavy metals introduced along with industrial waste, which is expected to increase in the amount used as a cement raw material in the future. First, steelmaking slag is used as one of the raw materials for cement, mixed and fired to obtain a clinker with a high chromium content, crushed the clinker and then added anhydrous gypsum, 7.6% by weight in terms of SO 3 , A solidified component having a total chromium concentration of 175 mg / kg and a water-soluble hexavalent chromium concentration of 28.0 mg / kg was prepared. Then added calcium polysulfide predetermined amount of solid ingredients, the soil improvement material was prepared in the same manner as in Reference Example 1, the evaluation was conducted in the same manner as in Reference Example 1. The results are shown in Table 2.
[0023]
[Table 2]
When the amount of calcium polysulfide added is small, it is impossible to suppress the elution amount of hexavalent chromium to a reference value of 0.05 mg / liter or less, whereas when the amount of calcium polysulfide added is large, hexavalent Although elution of chromium can be suppressed below the detection limit, it can be seen that the strength is lowered and the original effect that should be possessed as a ground improvement material is not sufficiently developed. Moreover, it has shown that it can fully respond also to cement with much total chromium amount.
[0025]
Examples 1 and 2 and Reference Examples 5 and 6 Here, as an example of changing the addition form of calcium polysulfide, an example in which quick lime, pearlite, and activated carbon are added to the aqueous solution and fixed after being fixed in a powder form is shown. . A predetermined amount of a water-absorbing material , that is, an immobilizing material, was added to and mixed with a 27.5% calcium polysulfide aqueous solution to prepare a calcium polysulfide-immobilized product modified into a powder form. Next, a predetermined amount of cement and gypsum were mixed to prepare a ground improvement material. The characteristic evaluation results are shown in Table 3.
[0026]
[Table 3]
In Table 3, Reference Example 2 in which calcium polysulfide is added in an aqueous solution state is shown again for easy comparison. However, a powdery fixing material is added to the calcium polysulfide aqueous solution so that the calcium polysulfide is solidified. After performing the immobilization treatment to be supported on top, it can be seen that even if added to the other components constituting the ground improvement material, a ground improvement material showing the same effect as that obtained by adding calcium polysulfide in an aqueous solution can be obtained. .
[0028]
Reference Example 7 and Comparative Example 7 Here, the results of examining the temporal change in the elution amount of hexavalent chromium after the solidification treatment are shown. 9.5 parts by weight of the composition gypsum, except for using 0.1 part by weight of calcium polysulfide, a soil improvement material prepared in reference example 1 method, an improved process for the same processed soil as in Reference Example 1 went. The hexavalent chromium elution test was performed in the same manner as in Example 1 except that the change with time was followed. The results are shown in Table 4 . Land Release improvement material, it can be seen that maintain the elution of hexavalent chromium suppressing effect over a long but early only.
[0029]
[Table 4]
Reference Examples 8 and 9 and Comparative Example 8 Here, the elution amount of hexavalent chromium from the ground improvement material in a powder state was measured without mixing with soil. The ground improvement material was prepared by dropping a predetermined amount of the calcium polysulfide aqueous solution onto the cement clinker and the gypsum on the belt conveyor in the step of feeding the ball mill. The water-soluble hexavalent chromium content per kg solidified component consisting of a cement clinker and a gypsum mixture is 4.23 mg, and the amount of gypsum is 7.7% by weight in terms of SO 3 . The elution test for hexavalent chromium from the ground improvement material powder was carried out by the method prescribed in Notification No. 13 of the Environment Agency. The results are shown in Table 5. In the ground improvement material of this invention, it turns out that the elution of the hexavalent chromium contained in itself is suppressed within the standard value.
[0031]
[Table 5]
【The invention's effect】
The ground improvement material manufactured by the manufacturing method of the present invention not only provides improved soil with sufficient strength, but also exhibits an effect of suppressing the elution of harmful heavy metals from the beginning to the long term. Therefore, it can be suitably used for ground improvement considering the environment required in the future.
Claims (2)
前記多硫化カルシウム水溶液の配合割合は、前記セメントと前記せっこうの合量１００重量部に対してＳ換算で０．０１５〜１．０重量部であり、
前記せっこうの配合割合は、前記セメントと前記せっこうの合量１００重量部に対してＳＯ3基準で４〜２０重量部であることを特徴とする地盤改良材の製造方法。 A step of preparing a mixture powder by adding almost all the amount of water contained in the aqueous solution of calcium polysulfide to an amount of quick lime that gives a mixture that can be handled as a powder as a whole, and a mixture powder of the aqueous solution of calcium polysulfide and quick lime A method for producing a ground improvement material comprising a step of mixing a mixture powder with cement and gypsum,
The mixing ratio of the calcium polysulfide aqueous solution is 0.015 to 1.0 part by weight in terms of S with respect to 100 parts by weight of the total amount of the cement and the gypsum,
The mixing ratio of gypsum method for manufacturing a soil improvement material, characterized in that with respect to the total amount 100 parts by weight of the said cement gypsum is 4 to 20 parts by weight SO 3 basis.
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| JP4516780B2 (en) * | 2004-04-16 | 2010-08-04 | 三菱マテリアル株式会社 | Heavy metal fixing material, cement-based solidifying material, manufacturing method of heavy metal fixing material, manufacturing method of ground improvement material, and processing method of soil to be processed |
| JP6482877B2 (en) * | 2015-01-15 | 2019-03-13 | デンカ株式会社 | Quick setting agent and method for producing the same |
| JP2017128467A (en) * | 2016-01-19 | 2017-07-27 | デンカ株式会社 | Cement concrete and manufacturing method therefor |
| JPWO2017179121A1 (en) * | 2016-04-12 | 2019-02-21 | デンカ株式会社 | Cement additive and cement composition |
| CN106623379B (en) * | 2016-11-04 | 2020-04-07 | 甘肃天农一禾农业有限公司 | Resource recycling method of construction waste and heavy metal contaminated soil remediation agent |
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| JPS5339262A (en) * | 1976-09-21 | 1978-04-11 | Takenaka Komuten Co | Method of treating sludge containing heavy metals |
| JPH01231981A (en) * | 1988-03-11 | 1989-09-18 | Kubota Ltd | Treatment of waste |
| JPH06328063A (en) * | 1993-05-21 | 1994-11-29 | Poriyuushiyon Sci Kenkyusho:Kk | Waste stabilization agent and waste stabilization |
| JPH09136072A (en) * | 1995-11-10 | 1997-05-27 | Jgc Corp | Fly ash treatment method |
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| JP2503771B2 (en) * | 1987-04-28 | 1996-06-05 | 三菱マテリアル株式会社 | Solidifying material for cohesive soil of volcanic ash |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5339262A (en) * | 1976-09-21 | 1978-04-11 | Takenaka Komuten Co | Method of treating sludge containing heavy metals |
| JPH01231981A (en) * | 1988-03-11 | 1989-09-18 | Kubota Ltd | Treatment of waste |
| JPH06328063A (en) * | 1993-05-21 | 1994-11-29 | Poriyuushiyon Sci Kenkyusho:Kk | Waste stabilization agent and waste stabilization |
| JPH09136072A (en) * | 1995-11-10 | 1997-05-27 | Jgc Corp | Fly ash treatment method |
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| CN110591714A (en) * | 2019-09-26 | 2019-12-20 | 长沙凯天工研院环保服务有限公司 | Organic high-sulfur stabilizer, synthesis method thereof and application of organic high-sulfur stabilizer in heavy metal contaminated soil remediation |
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