JP4070982B2 - Neutral solidification material and neutral solidification treatment method - Google Patents
Neutral solidification material and neutral solidification treatment method Download PDFInfo
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- JP4070982B2 JP4070982B2 JP2001358883A JP2001358883A JP4070982B2 JP 4070982 B2 JP4070982 B2 JP 4070982B2 JP 2001358883 A JP2001358883 A JP 2001358883A JP 2001358883 A JP2001358883 A JP 2001358883A JP 4070982 B2 JP4070982 B2 JP 4070982B2
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00732—Uses not provided for elsewhere in C04B2111/00 for soil stabilisation
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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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
Description
【0001】
【発明の属する技術分野】
本発明は、中性固化材、特に含水土壌の固化処理に適した中性固化材、そして該中性固化材を用いる含水土壌の中性固化処理方法に関する。本発明は特に、粘性土や含水砂質土のような含水土壌を略中性条件にて固化処理を実施して、建設発生土利用技術マニュアルに規定されている第3種改良土および第2種改良土のような利用価値の高い改良土壌とすることを可能にする中性固化材と中性固化処理工法に関する。
【0002】
【従来の技術】
軟弱土壌の土質改良には通常、土壌固化材を使用する固化処理が施される。また、土木工事等に伴って発生する建設汚泥を搬出する際、該建設汚泥は、その流動性が高いことから、そのままでの搬送が困難な場合があり、予め固化材を使用して固化処理を施した後、搬出することがある。何れの場合でも、土壌固化材には、固化処理後の土壌が目的に合った十分な強度を有していること、適度の固化速度を有していること、固化材が化学的に安定であって、有害物質が溶出しないこと等の特性が要求されるが、これ等複数機能を要求される固化材として既に多くの技術が開示されている。
【0003】
この内、セメントを主成分とするセメント系固化材は高い強度は得られるものの、セメント自体が強アルカリであるため、固化処理後の土壌の高pH値が問題となる場合がある。一方、このアルカリ問題に対応して半水石膏等を主成分とする石膏系固化材がある。この石膏系固化材では、石膏自体が中性であるためpH値に関する問題の発生はないものの、改良後の土壌が十分な強度を示さないと云う問題がある。
【0004】
上記の問題を解決するために、セメント、石膏双方を成分とし、両系の長所を活かそうとする土壌固化材が幾つか提案されている。
例えば、特開平8−302346号公報および特開平8−311446号公報には、半水石膏、セメントおよび石灰、高炉スラグ等の混合材より成る土壌固化材が開示され、特開平6−220451号公報には石膏、ポルトランドセメントおよび硫酸アルミニウムより成る固化材が開示されている。
【0005】
特開平7−179854号公報には、無水または半水石膏、セメントおよび硫酸基を有する無機塩よりなる固化材が開示されている。さらに特開平10−273660号公報および特開平10−273663号公報には、半水石膏、アルミナセメント、またはアルミナセメントとポルトランドセメントの混合セメントと硫酸アルミニウムまたは硫酸鉄より成る固化材が開示されている。
【0006】
上記の各種の土壌固化材の作用効果については、各公報には記載があるが、固化処理対象の土壌、固化材添加量、評価方法等が夫々異なるため、土壌固化材としての厳密な比較評価はできない。ただし、一般に、これらのセメントと石膏を併用した土壌固化材は速硬性が強く、土壌との混合処理中に硬化反応が進行し、施工性が問題となる場合がある。また、混合時間によっては改良土の強度が低下する等の問題がある。
【0007】
【発明が解決しようとする課題】
本発明は、半水石膏とセメントを併用する固化材による固化処理において、所定の強度の改良土を与えることは勿論のこと、施工性に優れ、且つ処理コストが安い中性固化材を提供し、さらに該中性固化材を使用する中性固化処理工法の提供を目的とする。
【0008】
本発明は特に、pH値が、排水基準に相当する中性領域(5.8〜8.6)の範囲にあって、且つ、建設発生土利用技術マニュアルに規定されている、利用用途の広い、コーン指数が400kN/m2以上の第3種改良土、特にコーン指数800kN/m2以上の第2種改良土に変えることを可能にする中性固化材と中性固化処理工法の提供を目的とする。
【0009】
【課題を解決するための手段】
本発明者は、半水石膏に、それぞれ相対的に少量の高炉セメントと硫酸アルミニウムとを添加して製造した組成物において、半水石膏として特定の範囲のブレーン比表面積を持つ半水石膏を使用することにより、上記課題を解決する優れた中性固化材となることを見出し、本発明を完成した。
【0010】
本発明は、半水石膏70〜90質量%、高炉セメント5〜15質量%、そして硫酸アルミニウム5〜15質量%からなる中性固化材であって、該半水石膏のブレーン比表面積が500〜1500cm2/gの範囲にあることを特徴とする中性固化材にある。
【0011】
すなわち、本発明は、主成分の半水石膏に、高炉セメントと硫酸アルミニウムとを、それぞれ半水石膏に対して相対的に少ない量にて添加してなる中性固化材において、半水石膏としてブレーン比表面積が500〜1500cm2/gの範囲にある半水石膏を用いることを特徴とする。
【0012】
本発明はまた、粘性土に、本発明の中性固化材を添加、混合することを特徴とする中性固化処理工法にもある。この粘性土の中性固化処理工法は、液性指数が0〜1.65の範囲にある粘性土に、上記の中性固化材を該粘性土1m3当り50〜300kgの範囲の量にて添加、混合する方法で実施することが好ましい。あるいは、液性指数が0〜0.70の範囲にある粘性土に、上記の中性固化材を該粘性土1m3当り50〜100kgの範囲の量にて添加、混合する方法によって土壌の中性固化処理を行なうことも好ましい。
【0013】
本発明はまた、含水砂質土に、本発明の中性固化材を添加、混合することを特徴とする中性固化処理工法にもある。この含水砂質土の中性固化処理方法は、含まれる水分のpF値が1.5〜3.0の範囲にある含水砂質土に上記の中性固化材を該含水砂質土1m3当り50〜300kgの範囲の量にて添加、混合する方法で実施することが好ましい。あるいは、含まれる水分のpF値が2.0〜3.0の範囲にある含水砂質土に、上記の中性固化材を該含水砂質土1m3当り50〜100kgの範囲の量にて添加、混合する方法によって中性固化処理を行なうことも好ましい。
【0014】
【発明の実施の形態】
本発明の中性固化材は中性(略中性を含む)を示し、水硬性材料として高炉セメントと石膏との混合物を使用するものである。石膏は、それ自身が中性であるだけでなく、金属イオンの放出も極めて少なく、固化後土壌が二次公害を引き起こすおそれが全くないことから、化学的には望ましい材料であるが、強度的には固化材としての性能を十分に有しておらず、固化材として利用するには適当な固化助剤の存在が必要である。ただし、固化助剤としてのセメントと併用時には、前述のようにその速硬性が強すぎ施工性等に問題が生ずる。
【0015】
一方、セメントは、強度面では優れた固化改良土壌を与えるが、それ自身が強アルカリであり、セメントを固化材の成分として使用するに当っては、適正な添加量の検討やアルカリ中和剤の使用が必要となる。
【0016】
本発明者は、ブレーン比表面積が500〜1500cm2/gの半水石膏を主成分として用い、これに高炉セメントを少量添加し、さらに中和剤としての硫酸アルミニウムを少量添加した組成物を用いることを考え、これにより、上記課題を解決した。
【0017】
一般の市販半水石膏のブレーン比表面積は3000cm2/g以上であるが、本発明者の研究によると、本発明の用途に、このような微細な半水石膏を使用すると、混合直後にこわばりを生じ、施工性が悪くなるうえに、さらに練り殺しにより強度低下を引き起こす可能性があることが判明した。一方、ブレーン比表面積が500cm2/gより小さいと、反応速度が極端に遅くなると共に、強度の低下を招く恐れがあることも確認した。
【0018】
従って、本発明の固化材の主成分の一つである半水石膏は、ブレーン比表面積が500〜1500cm2/gの範囲に在る比較的粗粒の粒子成分を使用する。一般的な方法で焼成し、熟成して製造され、粉砕処理を施されていない脱硫石膏は、この範囲のブレーン比表面積を持つ半水石膏であり容易に入手できるものである。該石膏は、粒度が適度に粗いことから、反応速度が適度に制御され、含水土壌との混合中のこわばりの発生が少なく、そして、その後の強度はむしろ増加するため、従来の半水石膏系固化材より施工性が顕著に向上する。半水石膏の量は、セメント及び硫酸アルミニウム量に応じて、70〜90質量%の範囲内で選択することが好ましい。
【0019】
本発明の中性固化材においては、セメント成分として高炉セメントを使用するが、実際的量の固化材添加による固化処理後土壌の強度確保とpH値上昇を抑制するため、その添加量は、5〜15質量%の範囲にすることが好ましい。また、中和剤として用いる硫酸アルミニウムは、高炉セメントと略同等の量を添加することで中性を維持することが可能となるため、そのような量にて使用することが好ましい。
【0020】
硫酸アルミニウムは、高炉セメントの中和剤として作用するだけでなく、高炉セメントとの反応により二水石膏を生成し、該二水石膏はその後の半水石膏の水和による二水石膏生成時の種晶として作用し、二水石膏の形態を固化に有利なアスペクト比の大きなものとする。一般にこの種晶は石膏の反応を促進するため、前述したこわばりの問題を生ずるが、本発明においては、半水石膏の粒度を適正値に制御したことにより、この反応促進効果が逆にプラスに作用する。同時に、これらの反応で生成する非晶質のアルミニウムゲルやシリカゲルが二水石膏のバインダーとして作用するとともに二水石膏の溶解・再析出を抑制することで強度低下が抑制される。
【0021】
本発明の中性固化材の調製に必要な材料は何れも粉末状であること、そして固化材がそれら材料の単なる混合物であることから、その調製に当たっては特別な機器、手段を必要とせず、ミキサー等、公知の粉体混合用の機器を使った公知の粉体混合方法が適用できる。
【0022】
本発明の中性固化材を用いて含水土壌の中性固化処理を行なうに当たっては、土壌に余分な水を加えないことが好ましいことを考慮すると、粉末状態で混合するのが望ましい。その際、一般に行なわれている改良プラントを用いて混合するプラント混合法やバックホウやスタビライザー等を用いる方法が効果的に適用できる。
【0023】
本発明の中性固化材は、特に粘性土や含水砂質土の固化処理に特に有効に使用することができる。
【0024】
粘性土の固化処理に用いる場合には、液性指数が0〜1.65、特に0〜0.7の粘性土の固化処理に有効であって、液性指数が0〜1.65の粘性土に対しては、粘性土1m3当り、50〜300kgの使用量で、そして液性指数が0〜0.7の粘性土に対しては、粘性土1m3当り、50〜100kgの使用量で固化処理を行なうことが好ましい。液性指数は公知の指数であり、公知の液性・塑性限界試験を利用して測定算出することができる。
【0025】
含水砂質土の固化処理に用いる場合には、pFが1.5〜3.0、特に2.0〜3.0の含水砂質土の固化処理に有効であって、pFが1.5〜3.0の含水砂質土に対しては、含水砂質土1m3当り、50〜300kgの使用量で、そしてpFが2.0〜3.0の含水砂質土に対しては、含水砂質土1m3当り、50〜100kgの使用量で固化処理を行なうことが好ましい。砂質土のような殆どシルトや砂分で構成されている土については、液性・塑性限界試験の利用が困難であるため、pF(pF値)を用いて規定している。このpFは公知の指数であって、土の間隙に保持されている水分を取り出すのに必要な吸引力を水柱高さ(cm)の絶対値を常用対数で表わした値であり、この値が大きい程、水が土壌とより強く結合した状態にあることを示す。
【0026】
【実施例】
(1)固化材の調製
脱硫石膏を焼成・熟成した半水石膏粉末に所定量の高炉セメント、硫酸アルミニウムを添加したものを混合して固化材を調製した。原材料の配合比は表1及び表2に示す。
【0027】
(2)供試土壌の調製
対象とする粘性土が所定の液性指数を持つ様に、また、砂質土が所定のpFを持つ様に夫々加水し、ホバート型ミキサーで3分間混合したものを供試土壌とした。
【0028】
(3)土壌の固化処理
上記(1)で調製した固化材の所定量を上記(2)で調製した供試土壌に添加した後、ホバート型ミキサーで3分間混合した。混合後の土壌を、温度20℃、湿度96%の恒温恒湿槽内で1時間および7日間密封養生し、固化処理された改良土壌を得た。
【0029】
(4)改良土壌の評価:コーン指数測定
上記(3)で得られた改良土壌をときほぐし、9.5mmふるいを通した後、直径10cm、容量1リットルのモールドに締固め、JIS A 1228に則った方法でそのコーン指数を測定した。尚、コーン指数は、液性指数1.65以下の粘性土又は含まれる水分のpFが1.5以上の砂質土については対象土壌1m3当たり300kgの添加で第3種改良土に相当する400kN/m2以上、液性指数0.7以下の粘性土、または含まれる水分のpFが1.5以上の砂質土については、100kgの添加で第2種改良土に相当する800kN/m2以上を目標強度とした。
【0030】
(5)改良土壌の評価:pH測定
上記(3)で得られた成形前の土壌について、地盤工学会基準JGS0211−2000に則り、改良土壌のpHを測定した。pH値については、一般に中性の指標とされる排水基準5.8〜8.6の範囲を目標とした。
【0031】
[実施例1〜10、比較例1〜8]
半水石膏85質量%、高炉セメント7.5質量%および硫酸アルミニウム7.5質量%の固化材を調製し、含水比の異なる粘性土および砂質土を対象土壌とした場合の例を夫々表1、表2に示す。
【0032】
本発明の範囲に含まれる組成を有する固化材を用いた場合、固化改良後土壌のpH値は何れも中性領域に存在する。材齢1時間のコーン指数は、液性指数1.65以下の粘性土及び含まれる水分のpFが1.5以上の砂質土については対象土壌1m3当たり300kgの添加で第3種改良土に相当する400kN/m2以上を示し、土壌によっては第2種改良土に相当する800kN/m2以上の値を示す。また、液性指数0.7以下の粘性土及び含まれる水分のpFが1.5以上の砂質土については、100kgの添加で第2種改良土に相当する800kN/m2以上の値を示している。
【0033】
また、材齢の経過により強度は増大する。それに対して、半水石膏単独や本発明の範囲を外れる比表面積の半水石膏を用いた場合、固化改良後土壌のコーン指数は目標とした基準に達せず、さらに材齢の経過による強度低下が見られる。
【0034】
【表1】
【0035】
【表2】
【0036】
【発明の効果】
本発明の中性固化材は、中性領域において実用的な量の添加で、利用用途の広い強度を有する改良土の提供を可能にした。たとえば、本発明の中性固化材を用いて粘性土や含水砂質土を固化処理することによって、建設発生土利用技術マニュアルに規定されている、利用用途の広い、コーン指数が400kN/m2以上の第3種改良土、特にコーン指数800kN/m2以上の第2種改良土に変えることが可能になる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a neutral solidification material, particularly a neutral solidification material suitable for solidification treatment of hydrous soil, and a neutral solidification treatment method of hydrous soil using the neutral solidification material. In particular, the present invention performs a solidification treatment on a hydrous soil such as a cohesive soil or a hydrous sandy soil under a substantially neutral condition, and the third type improved soil and the second soil specified in the construction generated soil utilization technical manual. The present invention relates to a neutral solidification material and a neutral solidification treatment method that make it possible to provide improved soil such as seed improved soil.
[0002]
[Prior art]
In order to improve the soil quality of soft soil, a solidification process using a soil solidifying material is usually performed. In addition, when carrying out construction sludge generated in connection with civil engineering work, etc., the construction sludge has a high fluidity, so it may be difficult to carry it as it is. After carrying out, it may be carried out. In any case, the soil-solidifying material should have sufficient strength for the purpose after the solidification treatment, a suitable solidification rate, and the solidified material should be chemically stable. In addition, characteristics such as no leaching of harmful substances are required, but many techniques have already been disclosed as solidifying materials that require such multiple functions.
[0003]
Among them, a cement-based solidified material containing cement as a main component can obtain high strength, but the cement itself is a strong alkali, and therefore a high pH value of the soil after the solidification treatment may be a problem. On the other hand, there is a gypsum-based solidifying material mainly composed of hemihydrate gypsum corresponding to this alkali problem. This gypsum-based solidified material has a problem that although the gypsum itself is neutral, there is no problem with the pH value, but the improved soil does not exhibit sufficient strength.
[0004]
In order to solve the above-mentioned problems, some soil solidifying materials have been proposed which use both cement and gypsum as components and make use of the advantages of both systems.
For example, JP-A-8-302346 and JP-A-8-311446 disclose a soil-solidifying material composed of a mixture of hemihydrate gypsum, cement and lime, blast furnace slag, etc., and JP-A-6-220451. Discloses a solidifying material comprising gypsum, Portland cement and aluminum sulfate.
[0005]
Japanese Patent Application Laid-Open No. 7-179854 discloses a solidified material made of anhydrous or hemihydrate gypsum, cement, and an inorganic salt having a sulfate group. Further, JP-A-10-273660 and JP-A-10-273663 disclose a solidified material comprising hemihydrate gypsum, alumina cement, or a mixed cement of alumina cement and Portland cement, and aluminum sulfate or iron sulfate. .
[0006]
The effects of the above various soil solidification materials are described in each publication, but the soil to be solidified, the amount of solidification material added, the evaluation method, etc. are different, so a strict comparative evaluation as a soil solidification material I can't. However, in general, a soil-solidifying material using a combination of these cement and gypsum has high fast-curing properties, and a curing reaction proceeds during the mixing treatment with the soil, and workability may be a problem. Moreover, there exists a problem that the intensity | strength of improved soil falls depending on mixing time.
[0007]
[Problems to be solved by the invention]
The present invention provides a neutral solidified material that is excellent in workability and low in processing cost as well as giving improved soil of a predetermined strength in the solidification treatment using a solidified material that uses hemihydrate gypsum and cement in combination. Furthermore, it aims at provision of the neutral solidification processing construction method which uses this neutral solidification material.
[0008]
In particular, the present invention has a wide range of usage applications in which the pH value is in the neutral range (5.8 to 8.6) corresponding to the drainage standard and is defined in the Construction Soil Utilization Technical Manual. , Providing a neutral solidification material and a neutral solidification treatment method that make it possible to change to a third type improved soil having a corn index of 400 kN / m 2 or higher, particularly a second type improved soil having a corn index of 800 kN / m 2 or higher. Objective.
[0009]
[Means for Solving the Problems]
The present inventor uses hemihydrate gypsum having a specific range of Blaine specific surface area as hemihydrate gypsum in a composition produced by adding relatively small amounts of blast furnace cement and aluminum sulfate to hemihydrate gypsum , respectively. As a result, the present inventors have found that the present invention provides an excellent neutral solidifying material that solves the above-described problems, and has completed the present invention.
[0010]
The present invention is a neutral solidified material comprising hemihydrate gypsum 70 to 90% by mass, blast furnace cement 5 to 15% by mass, and aluminum sulfate 5 to 15% by mass. in neutral solidifying material being in the range of 1500 cm 2 / g.
[0011]
That is, the present invention provides a neutral solidified material obtained by adding blast furnace cement and aluminum sulfate to the main component hemihydrate gypsum in a relatively small amount with respect to the hemihydrate gypsum. A hemihydrate gypsum having a Blaine specific surface area in the range of 500 to 1500 cm 2 / g is used.
[0012]
The present invention also resides in a neutral solidification treatment method characterized by adding and mixing the neutral solidification material of the present invention to a viscous soil. The neutral solidification treatment method of this viscous soil is that the above-mentioned neutral solidification material is applied to the viscous soil having a liquidity index in the range of 0 to 1.65 in an amount in the range of 50 to 300 kg per 1 m 3 of the viscous soil. It is preferable to carry out by a method of adding and mixing. Alternatively, by adding and mixing the above-mentioned neutral solidifying material in an amount in the range of 50 to 100 kg per 1 m 3 of the viscous soil to the viscous soil having a liquidity index in the range of 0 to 0.70. It is also preferable to perform a property solidification treatment.
[0013]
The present invention also resides in a neutral solidification treatment method characterized by adding and mixing the neutral solidification material of the present invention to hydrous sandy soil. Neutral solidification method of the water-containing sandy soil, water-containing sandy soil 1 m 3 pF value of water above neutral solidifying material in water sandy soil in the range of 1.5 to 3.0 contained It is preferable to carry out by a method of adding and mixing in an amount in the range of 50 to 300 kg per unit. Alternatively, to the hydrous sandy soil in which the pF value of the contained water is in the range of 2.0 to 3.0, the neutral solidification material is added in an amount in the range of 50 to 100 kg per 1 m 3 of the hydrous sandy soil. It is also preferable to perform a neutral solidification treatment by a method of adding and mixing.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The neutral solidifying material of the present invention exhibits neutrality (including substantially neutrality), and uses a mixture of blast furnace cement and gypsum as a hydraulic material. Gypsum is a chemically desirable material because it is not only neutral in itself, but also emits very little metal ions and the soil after solidification has no risk of causing secondary pollution. Does not have sufficient performance as a solidifying material, and in order to be used as a solidifying material, the presence of a suitable solidifying aid is necessary. However, when used in combination with cement as a solidification aid, as described above, its fast-curing property is too strong, causing problems in workability and the like.
[0015]
On the other hand, cement provides a solidified and improved soil in terms of strength, but itself is a strong alkali. When using cement as a component of a solidifying material, an appropriate amount of addition or an alkali neutralizing agent is to be used. Need to be used.
[0016]
The present inventor uses a composition in which hemihydrate gypsum having a brain specific surface area of 500 to 1500 cm 2 / g is used as a main component, a small amount of blast furnace cement is added thereto, and a small amount of aluminum sulfate is added as a neutralizing agent. In view of this, the above-mentioned problems were solved.
[0017]
Although the Blaine specific surface area of general commercial hemihydrate gypsum is 3000 cm 2 / g or more, according to the study of the present inventor, if such fine hemihydrate gypsum is used for the present invention, it is stiff immediately after mixing. As a result, it was found that there is a possibility that the workability is deteriorated and the strength is further reduced by kneading. On the other hand, it was also confirmed that when the Blaine specific surface area is smaller than 500 cm 2 / g, the reaction rate becomes extremely slow and the strength may be lowered.
[0018]
Therefore, hemihydrate gypsum which is one of the main components of the solidifying material of the present invention uses a relatively coarse particle component having a Blaine specific surface area in the range of 500 to 1500 cm 2 / g. A desulfurized gypsum produced by firing and aging by a general method and not subjected to a pulverization treatment is a hemihydrate gypsum having a Blaine specific surface area in this range and can be easily obtained. Since the gypsum has a moderately coarse particle size, the reaction rate is moderately controlled, the occurrence of stiffness during mixing with the water-containing soil is small, and the strength after that increases rather, so the conventional hemihydrate gypsum system The workability is significantly improved compared to the solidified material. The amount of hemihydrate gypsum is preferably selected within the range of 70 to 90% by mass depending on the amount of cement and aluminum sulfate.
[0019]
In the neutral solidified material of the present invention, blast furnace cement is used as a cement component. However, in order to suppress the strength of the soil after the solidification treatment by adding a practical amount of the solidified material and suppress the increase in pH value, the amount added is 5 It is preferable to be in the range of ˜15% by mass. Moreover, since it becomes possible to maintain the neutrality of aluminum sulfate used as a neutralizing agent by adding an amount substantially equivalent to that of blast furnace cement, it is preferable to use such an amount.
[0020]
Aluminum sulfate not only acts as a neutralizing agent for blast furnace cement, but also produces dihydrate gypsum by reaction with blast furnace cement, and the dihydrate gypsum is produced at the time of dihydrate gypsum formation by subsequent hydration of hemihydrate gypsum. It acts as a seed crystal, and the dihydrate gypsum has a large aspect ratio advantageous for solidification. In general, this seed crystal promotes the reaction of gypsum, which causes the problem of stiffness described above. However, in the present invention, the reaction promoting effect is positively increased by controlling the particle size of hemihydrate gypsum to an appropriate value. Works. At the same time, the amorphous aluminum gel or silica gel produced by these reactions acts as a binder of dihydrate gypsum and suppresses dissolution and reprecipitation of dihydrate gypsum, thereby suppressing a decrease in strength.
[0021]
Since all the materials necessary for the preparation of the neutral solidifying material of the present invention are in the form of powder and the solidifying material is a simple mixture of these materials, no special equipment or means are required for the preparation. A known powder mixing method using a known powder mixing device such as a mixer can be applied.
[0022]
In carrying out the neutral solidification treatment of the hydrous soil using the neutral solidification material of the present invention, it is desirable to mix in a powder state considering that it is preferable not to add excess water to the soil. In that case, the plant mixing method and the method using a backhoe, a stabilizer, etc. which mix using the improved plant generally performed can be applied effectively.
[0023]
The neutral solidification material of the present invention can be used particularly effectively for the solidification treatment of viscous soil and hydrous sandy soil.
[0024]
When used for solidification treatment of clay soil, the liquidity index is 0 to 1.65, particularly effective for solidification treatment of clay soil having 0 to 0.7, and the viscosity index is 0 to 1.65. For soil, 50 to 300 kg used per 1 m 3 of viscous soil, and 50 to 100 kg used per 1 m 3 of viscous soil for viscous soil with a liquidity index of 0 to 0.7 It is preferable to perform a solidification process. The liquidity index is a known index and can be measured and calculated using a known liquidity / plasticity limit test.
[0025]
When used for the solidification treatment of hydrous sandy soil, it is effective for the solidification treatment of hydrous sandy soil having a pF of 1.5 to 3.0, particularly 2.0 to 3.0, and the pF is 1.5. for water sandy soil of 3.0, water sandy soil 1 m 3 per in usage 50~300Kg, and for pF hydrous sandy soil 2.0 to 3.0 are, It is preferable to perform the solidification treatment with a use amount of 50 to 100 kg per 1 m 3 of hydrous sandy soil. For soils that are mostly composed of silt or sand, such as sandy soil, it is difficult to use the liquid / plastic limit test, and therefore, pF (pF value) is used. This pF is a well-known index, and is a value representing the suction force necessary for taking out the water retained in the soil gap by expressing the absolute value of the water column height (cm) in common logarithm. Larger indicates that the water is more strongly bound to the soil.
[0026]
【Example】
(1) Preparation of solidified material A solidified material was prepared by mixing a half-water gypsum powder obtained by firing and aging desulfurized gypsum with a predetermined amount of blast furnace cement and aluminum sulfate added thereto. The mixing ratio of raw materials is shown in Tables 1 and 2.
[0027]
(2) Water that has been added so that the viscous soil to be prepared for the test soil has a predetermined liquidity index and that the sandy soil has a predetermined pF, and mixed for 3 minutes with a Hobart mixer Was used as test soil.
[0028]
(3) Solidification treatment of soil A predetermined amount of the solidification material prepared in (1) above was added to the test soil prepared in (2) above, and then mixed for 3 minutes with a Hobart mixer. The mixed soil was sealed and cured in a constant temperature and humidity chamber at a temperature of 20 ° C. and a humidity of 96% for 1 hour and 7 days to obtain a solidified improved soil.
[0029]
(4) Evaluation of improved soil: Cone index measurement The improved soil obtained in (3) above is loosened, passed through a 9.5 mm sieve, and then compacted into a mold having a diameter of 10 cm and a capacity of 1 liter, in accordance with JIS A 1228. The cone index was measured by the method described above. The corn index corresponds to the third type improved soil by adding 300 kg per 1 m 3 of the target soil for the viscous soil having a liquidity index of 1.65 or less or the sandy soil having a pF of water of 1.5 or more. For clay soil of 400 kN / m 2 or more and a liquidity index of 0.7 or less, or sandy soil having a water pF of 1.5 or more, 800 kN / m corresponding to the second type improved soil with the addition of 100 kg The target strength was 2 or more.
[0030]
(5) Evaluation of improved soil: pH measurement About the soil before shaping | molding obtained by said (3), pH of the improved soil was measured according to Geotechnical Society standard JGS0211-2000. About pH value, the range of the drainage standard 5.8-8.6 generally used as a neutral parameter | index was aimed.
[0031]
[Examples 1 to 10, Comparative Examples 1 to 8]
An example in which solidified material of 85% by weight of hemihydrate gypsum, 7.5% by weight of blast furnace cement and 7.5% by weight of aluminum sulfate is prepared, and viscous soils and sandy soils having different water content ratios are used as target soils is shown. 1 and Table 2 show.
[0032]
When a solidifying material having a composition included in the scope of the present invention is used, the pH value of the soil after solidification improvement is in the neutral region. The 1-hour corn index is 3rd modified soil by adding 300 kg per 1 m 3 of the target soil for viscous soil with a liquidity index of 1.65 or less and sandy soil with a pF of water of 1.5 or more. 400 kN / m 2 or more corresponding to the above, and depending on the soil, a value of 800 kN / m 2 or more corresponding to the second type improved soil. In addition, for clay soil with a liquidity index of 0.7 or less and sandy soil with a pF of water content of 1.5 or more, a value of 800 kN / m 2 or more corresponding to the second type improved soil is added by adding 100 kg. Show.
[0033]
In addition, the strength increases with age. On the other hand, when hemihydrate gypsum alone or hemihydrate gypsum with a specific surface area outside the scope of the present invention is used, the corn index of the soil after solidification does not reach the target standard, and further, the strength decreases due to the age of the material Is seen.
[0034]
[Table 1]
[0035]
[Table 2]
[0036]
【The invention's effect】
The neutral solidified material of the present invention can provide an improved soil having a wide range of usage applications by adding a practical amount in the neutral region. For example, by using a neutral solidifying material of the present invention to solidify viscous soil or hydrous sandy soil, the corn index is 400 kN / m 2, which is widely used, as defined in the Construction Soil Utilization Technical Manual. It becomes possible to change to the above-mentioned third type improved soil, in particular, the second type improved soil having a cone index of 800 kN / m 2 or more.
Claims (8)
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