JP7465115B2 - Ground improvement material and its manufacturing method - Google Patents
Ground improvement material and its manufacturing method Download PDFInfo
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- JP7465115B2 JP7465115B2 JP2020031679A JP2020031679A JP7465115B2 JP 7465115 B2 JP7465115 B2 JP 7465115B2 JP 2020031679 A JP2020031679 A JP 2020031679A JP 2020031679 A JP2020031679 A JP 2020031679A JP 7465115 B2 JP7465115 B2 JP 7465115B2
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- 239000000463 material Substances 0.000 title claims description 65
- 238000004519 manufacturing process Methods 0.000 title claims description 16
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 124
- 239000001569 carbon dioxide Substances 0.000 claims description 62
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 62
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 50
- 239000004568 cement Substances 0.000 claims description 32
- 239000002002 slurry Substances 0.000 claims description 17
- 238000002360 preparation method Methods 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 10
- 238000007664 blowing Methods 0.000 claims description 5
- 239000002689 soil Substances 0.000 description 25
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 12
- 239000007789 gas Substances 0.000 description 12
- 150000001875 compounds Chemical class 0.000 description 9
- 229910001385 heavy metal Inorganic materials 0.000 description 9
- 239000011398 Portland cement Substances 0.000 description 7
- 238000010828 elution Methods 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 3
- 229910052796 boron Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 239000010881 fly ash Substances 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 239000002075 main ingredient Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- 229910052661 anorthite Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 239000002956 ash Substances 0.000 description 1
- 239000011400 blast furnace cement Substances 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- GWWPLLOVYSCJIO-UHFFFAOYSA-N dialuminum;calcium;disilicate Chemical compound [Al+3].[Al+3].[Ca+2].[O-][Si]([O-])([O-])[O-].[O-][Si]([O-])([O-])[O-] GWWPLLOVYSCJIO-UHFFFAOYSA-N 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- -1 ecocement Substances 0.000 description 1
- 229910052602 gypsum Inorganic materials 0.000 description 1
- 239000010440 gypsum Substances 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- 229910021487 silica fume Inorganic materials 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
Landscapes
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
Description
本発明は、地盤改良材及びその製造方法に関する。 The present invention relates to a ground improvement material and its manufacturing method.
近年、地球温暖化の抑制のため、二酸化炭素の排出量の低減が重要な課題になっている。
例えば、特許文献１には、（Ａ）ムライトとアノーサイトのいずれか一方または両方を含むセメント混合用粉末、及び、ポルトランドセメントを含む粉末状セメント組成物、（Ｂ）水、及び、（Ｃ）骨材、を含むセメント混練物の硬化体を、炭酸化してなることを特徴とするセメント質硬化体が記載されている。該セメント質硬化体によれば、ポルトランドセメント以外の粉末材料を含むものの、常温（２０℃程度）で養生を行なった場合であっても、養生工程において多量の二酸化炭素を吸収することにより、排出される二酸化炭素の量を大幅に削減することができる。
In recent years, reducing carbon dioxide emissions has become an important issue in order to prevent global warming.
For example, Patent Document 1 describes a cementitious hardened body obtained by carbonating a hardened body of a cement kneaded product containing (A) a powder for mixing with cement containing either or both of mullite and anorthite, and a powdery cement composition containing Portland cement, (B) water, and (C) aggregate. Although the cementitious hardened body contains a powder material other than Portland cement, it is possible to significantly reduce the amount of carbon dioxide emitted by absorbing a large amount of carbon dioxide in the curing process, even when curing is performed at room temperature (about 20°C).
本発明の目的は、セメントの製造過程等において発生する二酸化炭素を有効利用することができ、地盤からの重金属類（例えば、六価クロム化合物）の溶出を抑制することができる地盤改良材、及び、該地盤改良材の製造方法を提供することである。 The object of the present invention is to provide a ground improvement material that can effectively utilize carbon dioxide generated during the cement manufacturing process and can suppress the leaching of heavy metals (e.g., hexavalent chromium compounds) from the ground, and a method for manufacturing the ground improvement material.
本発明者は、上記課題を解決するために鋭意検討した結果、セメント系材料及び炭酸ガス含有水を含むスラリーからなる地盤改良材によれば、上記目的を達成できることを見出し、本発明を完成した。
すなわち、本発明は、以下の［１］～［６］を提供するものである。
［１］ セメント系材料及び炭酸ガス含有水を含むスラリーからなることを特徴とする地盤改良材。
［２］ 上記炭酸ガス含有水の炭酸ガス濃度が１５０～８，０００ｍｇ／リットルである前記［１］に記載の地盤改良材。
［３］ 上記セメント系材料１００質量部に対する上記炭酸ガス含有水の量が５０～１５０質量部である前記［１］又は［２］に記載の地盤改良材。
［４］ 前記［１］～［３］のいずれかに記載の地盤改良材を製造するための方法であって、水に炭酸ガスを吹き込むことによって、上記炭酸ガス含有水を調製する炭酸ガス含有水調製工程と、上記セメント系材料と、上記炭酸ガス含有水を混合して、スラリーの形態を有する上記地盤改良材を調製するスラリー調製工程、を含む地盤改良材の製造方法。
［５］ 上記スラリー調製工程における上記地盤改良材の調製直後のｐＨが、１１．６～１３．０である前記［４］に記載の地盤改良材の製造方法。
［６］ 前記［４］又は［５］に記載の地盤改良材の製造方法によって、上記地盤改良材を得た後、上記地盤改良材を地盤中に注入して混合し、上記地盤改良材によって固化してなる改良地盤を形成させることを特徴とする地盤の改良方法。
As a result of intensive research into solving the above problems, the inventors discovered that the above object can be achieved by a ground improvement material consisting of a slurry containing a cement-based material and carbon dioxide-containing water, and thus completed the present invention.
That is, the present invention provides the following [1] to [6].
[1] A ground improvement material comprising a slurry containing a cement-based material and carbon dioxide-containing water.
[2] The ground improvement material according to [1], wherein the carbon dioxide concentration of the carbon dioxide-containing water is 150 to 8,000 mg/L.
[3] The ground improvement material according to [1] or [2], wherein the amount of the carbon dioxide-containing water is 50 to 150 parts by mass per 100 parts by mass of the cement-based material.
[4] A method for producing the ground improvement material according to any one of [1] to [3] above, comprising: a carbon dioxide-containing water preparation step of preparing the carbon dioxide-containing water by injecting carbon dioxide into water; and a slurry preparation step of mixing the cement-based material and the carbon dioxide-containing water to prepare the ground improvement material having the form of a slurry.
[5] The method for producing a ground improvement material according to [4], wherein the pH of the ground improvement material immediately after preparation in the slurry preparation step is 11.6 to 13.0.
[6] A method for improving ground, comprising the steps of: obtaining the ground improvement material by the method for producing the ground improvement material according to [4] or [5]; injecting and mixing the ground improvement material into the ground; and solidifying the ground improvement material to form an improved ground.
本発明の地盤改良材によれば、セメントの製造過程等において発生する二酸化炭素を有効利用することができ、地盤からの重金属類（例えば、六価クロム化合物）の溶出を抑制することができる。 The ground improvement material of the present invention can effectively utilize carbon dioxide generated during the cement manufacturing process, etc., and can suppress the leaching of heavy metals (e.g., hexavalent chromium compounds) from the ground.
本発明の地盤改良材は、セメント系材料及び炭酸ガス含有水を含むスラリーからなるものである。
本明細書中、セメント系材料とは、普通ポルトランドセメント、早強ポルトランドセメント、中庸熱ポルトランドセメント、低熱ポルトランドセメント等の各種ポルトランドセメントや、高炉セメント、フライアッシュセメント等の混合セメントや、エコセメント等のセメント、及び、これらのセメントを主な材料（通常、５０質量％以上、好ましくは７０質量％以上、より好ましくは８０質量％以上）として含み、かつ、任意に配合可能な混和材を含むものをいう。
混和材の例としては、高炉スラグ微粉末、石灰石粉末、フライアッシュ、シリカフューム、石膏粉末等が挙げられる。これらは１種を単独で用いてもよく、２種以上を組み合わせて用いてもよい。
セメントを主な材料として含むセメント系固化材の市販品の例としては、太平洋セメント社製の「ジオセット」（商品名）等が挙げられる。
The soil improvement material of the present invention comprises a slurry containing a cement-based material and carbon dioxide-containing water.
In this specification, the cement-based material refers to various Portland cements such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, and low-heat Portland cement, mixed cements such as blast-furnace cement and fly ash cement, and cements such as ecocement, as well as materials that contain these cements as the main ingredient (usually 50 mass % or more, preferably 70 mass % or more, and more preferably 80 mass % or more) and that contain admixtures that can be arbitrarily blended.
Examples of the admixture include ground granulated blast furnace slag, limestone powder, fly ash, silica fume, gypsum powder, etc. These may be used alone or in combination of two or more.
An example of a commercially available cement-based solidification material that contains cement as the main ingredient is "Geoset" (product name) manufactured by Taiheiyo Cement Corporation.
炭酸ガス含有水は、通常、水に炭酸ガス（二酸化炭素）を吹き込むことによって得られたものである。
炭酸ガス含有水の炭酸ガスの濃度は、好ましくは１５０～８，０００ｍｇ／リットル、より好ましくは５００～７，８００ｍｇ／リットル、より好ましくは１，０００～７，６００ｍｇ／リットル、さらに好ましくは１，５００～７，５００ｍｇ／リットル、さらに好ましくは３，０００～７，４００ｍｇ／リットル、特に好ましくは５，０００～７，３００ｍｇ／リットルである。該濃度が１５０ｍｇ／リットル以上であれば、重金属類の溶出抑制効果がより大きくなる。また、より多くの二酸化炭素を利用することができるため、二酸化炭素の排出量を低減する効果がより大きくなる。該量が８，０００ｍｇを超えるものは、製造が困難である。また、スラリー調製直後のｐＨが過度に低くなり（１１．６未満）、地盤と地盤改良材を混合した際の改良体の強度が大きく低下することがある。
Carbonated water is usually obtained by blowing carbon dioxide into water.
The carbon dioxide concentration of the carbon dioxide-containing water is preferably 150 to 8,000 mg/L, more preferably 500 to 7,800 mg/L, more preferably 1,000 to 7,600 mg/L, even more preferably 1,500 to 7,500 mg/L, even more preferably 3,000 to 7,400 mg/L, and particularly preferably 5,000 to 7,300 mg/L. If the concentration is 150 mg/L or more, the effect of suppressing the elution of heavy metals is greater. In addition, since more carbon dioxide can be used, the effect of reducing the amount of carbon dioxide emissions is greater. If the amount exceeds 8,000 mg, it is difficult to manufacture. In addition, the pH immediately after the slurry preparation is excessively low (less than 11.6), and the strength of the improved body when the ground and the ground improvement material are mixed may be greatly reduced.
セメント系材料１００質量部に対する炭酸ガス含有水の量は、好ましくは５０～１５０質量部、より好ましくは６０～１４０質量部、さらに好ましくは７０～１３０質量部、特に好ましくは８０～１２０質量部である。上記量が５０質量部以上であれば、地盤改良材を用いて地盤の改良を行う際の作業性が向上する。上記量が１５０質量部以下であれば、改良後の地盤の強度をより大きくすることができる。 The amount of carbon dioxide-containing water per 100 parts by mass of cement-based material is preferably 50 to 150 parts by mass, more preferably 60 to 140 parts by mass, even more preferably 70 to 130 parts by mass, and particularly preferably 80 to 120 parts by mass. If the amount is 50 parts by mass or more, the workability when improving the ground using the ground improvement material is improved. If the amount is 150 parts by mass or less, the strength of the improved ground can be increased.
本発明の地盤改良材を製造する方法の一例としては、水に炭酸ガスを吹き込むことによって、炭酸ガス含有水を調製する炭酸ガス含有水調製工程と、セメント系材料と、炭酸ガス含有水を混合して、スラリーの形態を有する地盤改良材を調製するスラリー調製工程、を含む方法が挙げられる。 One example of a method for producing the ground improvement material of the present invention is a method including a carbon dioxide-containing water preparation step in which carbon dioxide-containing water is prepared by injecting carbon dioxide into water, and a slurry preparation step in which a cement-based material and the carbon dioxide-containing water are mixed to prepare a ground improvement material in the form of a slurry.
炭酸ガス含有水調製工程において、水に炭酸ガスを吹き込む方法としては、例えば、水中に設置された炭酸ガス供給手段（例えば、炭酸ガスを含む気体を供給するための排気管等）を用いて、水中に炭酸ガスを含む気体を吹き込む方法等が挙げられる。炭酸ガス含有水中の炭酸ガスの濃度の向上や処理効率向上等の観点から、上記吹き込みは加圧下で行ってもよい。
炭酸ガスを含む気体は、炭酸ガスのみからなる気体であってもよいが、入手の容易性等の観点から、炭酸ガスを、好ましくは５体積％以上、より好ましくは１０体積％以上、さらに好ましくは１５体積％以上、さらに好ましくは２０体積％以上、さらに好ましくは４０体積％以上、さらに好ましくは６０体積％以上、特に好ましくは８０体積％以上の割合で含む気体である。該割合が５体積％以上であれば、より短時間で炭酸ガス含有水を得ることができる。
炭酸ガスを含む気体の例としては、セメント製造工程において発生した排ガス（炭酸ガス濃度：約２０体積％）、または、該排ガスからの分離回収ガス（炭酸ガス濃度：約１００体積％）等が挙げられる。
In the carbon dioxide-containing water preparation step, examples of the method for blowing carbon dioxide into water include a method for blowing a gas containing carbon dioxide into water using a carbon dioxide supply means (e.g., an exhaust pipe for supplying a gas containing carbon dioxide) installed in water. From the viewpoint of improving the concentration of carbon dioxide in the carbon dioxide-containing water and improving the treatment efficiency, the blowing may be performed under pressure.
The gas containing carbon dioxide may be a gas consisting of carbon dioxide only, but from the viewpoint of ease of availability, etc., the gas contains carbon dioxide at a ratio of preferably 5 vol% or more, more preferably 10 vol% or more, even more preferably 15 vol% or more, even more preferably 20 vol% or more, even more preferably 40 vol% or more, even more preferably 60 vol% or more, and particularly preferably 80 vol% or more. If the ratio is 5 vol% or more, carbon dioxide-containing water can be obtained in a shorter time.
Examples of gases containing carbon dioxide include exhaust gas (carbon dioxide concentration: about 20% by volume) generated in a cement manufacturing process, and gas separated and recovered from the exhaust gas (carbon dioxide concentration: about 100% by volume).
スラリー調整工程において、セメント系材料と炭酸ガス含有水を混合する方法は、特に限定されるものではなく、セメント系材料に炭酸ガス含有水を添加、混合してもよく、炭酸ガス含有水にセメント系材料を添加、混合してもよく、セメント系材料と炭酸ガス含有水を同時に混合槽に投入し、混合してもよい。
スラリー調製工程における地盤改良材の調製直後のｐＨは、好ましくは１１．６～１３．０、より好ましくは１１．７～１２．９、さらに好ましくは１１．８～１２．８、特に好ましくは１１．９～１２．７である。上記ｐＨが１１．６以上であれば、地盤と地盤改良材を混合した際の改良体の強度の低下を抑えることができる。スラリーのｐＨが１２．９以下であれば、重金属類の溶出抑制効果をより大きくすることができる。
In the slurry preparation step, the method of mixing the cement-based material and the carbon dioxide-containing water is not particularly limited, and the carbon dioxide-containing water may be added to the cement-based material and mixed, the cement-based material may be added to the carbon dioxide-containing water and mixed, or the cement-based material and the carbon dioxide-containing water may be simultaneously charged into a mixing tank and mixed.
The pH immediately after preparation of the soil improvement material in the slurry preparation step is preferably 11.6 to 13.0, more preferably 11.7 to 12.9, even more preferably 11.8 to 12.8, and particularly preferably 11.9 to 12.7. If the pH is 11.6 or more, the decrease in strength of the improved body when the soil and soil improvement material are mixed can be suppressed. If the pH of the slurry is 12.9 or less, the effect of suppressing the elution of heavy metals can be further increased.
本発明の地盤の改良方法は、上述した地盤改良材の製造方法によって、地盤改良材を得た後、地盤改良材を地盤中に注入して混合し、地盤改良材によって固化してなる改良地盤を形成させる方法である。
改良の対象となる地盤は、地盤からの重金属類の溶出を抑制するという本発明の目的から、重金属類を含むものが好適である。
重金属類とは、カドミウム及びその化合物、六価クロム化合物、シアン、水銀及びその化合物、セレン及びその化合物、鉛及びその化合物、ひ素及びその化合物、フッ素及びその化合物、及び、ホウ素及びその化合物（土壌汚染対策法（平成１５年）において第二種特定有害物質として挙げられているもの）のいずれかである。なお、フッ素及びホウ素は重金属ではないが、フッ素及びその化合物、及び、ホウ素及びその化合物は重金属類に含まれるものとする。中でも、溶出をより抑制することができる観点から、六価クロム化合物が好ましい。
The ground improvement method of the present invention is a method in which a ground improvement material is obtained by the above-mentioned manufacturing method of the ground improvement material, the ground improvement material is then injected and mixed into the ground, and improved ground is formed by solidification by the ground improvement material.
The ground to be improved is preferably one that contains heavy metals, since the object of the present invention is to suppress the elution of heavy metals from the ground.
Heavy metals are any of cadmium and its compounds, hexavalent chromium compounds, cyanide, mercury and its compounds, selenium and its compounds, lead and its compounds, arsenic and its compounds, fluorine and its compounds, and boron and its compounds (listed as Type 2 specified hazardous substances in the Soil Contamination Countermeasures Act (2003)). Although fluorine and boron are not heavy metals, fluorine and its compounds, and boron and its compounds are considered to be included in heavy metals. Among them, hexavalent chromium compounds are preferred from the viewpoint of further suppressing elution.
地盤への地盤改良材の添加量は、対象となる地盤の種類及び性状、施工条件、改良後の地盤に求められる強度等によっても異なるが、地盤改良材中のセメント系材料の量として、対象となる地盤１ｍ３当たり、好ましくは５０～５００ｋｇ、より好ましくは８０～４５０ｋｇ、特に好ましくは１００～４００ｋｇである。該量が５０ｋｇ以上であれば、改良後の地盤の強度（例えば、一軸圧縮強さ）をより大きくすることができる。該量が５００ｋｇ以下であれば、コストの増大を防ぐことができる。 The amount of the ground improvement material added to the ground varies depending on the type and properties of the target ground, construction conditions, and the strength required for the improved ground, but the amount of cement-based material in the ground improvement material is preferably 50 to 500 kg, more preferably 80 to 450 kg, and particularly preferably 100 to 400 kg per 1 m3 of the target ground. If the amount is 50 kg or more, the strength (e.g., uniaxial compressive strength) of the improved ground can be increased. If the amount is 500 kg or less, an increase in costs can be prevented.
以下、本発明を実施例により具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
［使用材料］
（１）炭酸ガス含有水Ａ（炭酸ガスの濃度：７，２００ｍｇ／リットル）；水に、炭酸ガス濃度が９９．９体積％である気体を吹き込んだもの
（２）炭酸ガス含有水Ｂ（炭酸ガスの濃度：４，３００ｍｇ／リットル）；水に、炭酸ガス濃度が９９．９体積％である気体を吹き込んだもの
（３）炭酸ガス含有水Ｃ（炭酸ガスの濃度：１，８００ｍｇ／リットル）；水に、炭酸ガス濃度が９９．９体積％である気体を吹き込んだもの
（４）土壌Ａ；粘性土
（５）土壌Ｂ；火山灰質粘性土に分類される関東ローム（表１中、「ローム」と示す。）
（６）水；上水道水
The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
[Materials used]
(1) Carbon dioxide-containing water A (carbon dioxide concentration: 7,200 mg/liter); water into which gas with a carbon dioxide concentration of 99.9% by volume has been blown. (2) Carbon dioxide-containing water B (carbon dioxide concentration: 4,300 mg/liter); water into which gas with a carbon dioxide concentration of 99.9% by volume has been blown. (3) Carbon dioxide-containing water C (carbon dioxide concentration: 1,800 mg/liter); water into which gas with a carbon dioxide concentration of 99.9% by volume has been blown. (4) Soil A; clayey soil. (5) Soil B; Kanto loam, classified as a volcanic ash clayey soil (shown as "loam" in Table 1).
(6) Water: tap water
［実施例１～３］
セメント系材料１００質量部と、表１に示す種類の炭酸ガス含有水１００質量部を、同時に混合槽内に投入し混合して、スラリー状の地盤改良材を得た。混合直後のスラリーのｐＨを表１に示す。
土壌Ａに該地盤改良材を、土壌１ｍ３に対して、セメント系材料が１５０ｋｇとなる量で添加し、ホバートミキサを用いて３分間混合して、改良土を得た。
改良土からの六価クロム化合物の溶出量を、環境省告示第１８号に準拠して測定した。
［比較例１］
炭酸ガス含有水の代わりに、水を用いる以外は実施例１と同様にして、改良土を得た後、改良土からの六価クロム化合物の溶出量等を実施例１と同様にして測定した。
また、実施例１～３の各々について、比較例１（水を使用したもの）に対する、六価クロム化合物の溶出量の低減率｛（比較例の六価クロム化合物の溶出量－実施例の六価クロム溶出量）÷比較例の六価クロム化合物の溶出量×１００（％）｝を算出した。
[Examples 1 to 3]
100 parts by mass of the cement-based material and 100 parts by mass of carbon dioxide-containing water of the type shown in Table 1 were simultaneously charged into a mixing tank and mixed to obtain a slurry-like ground improvement material. The pH of the slurry immediately after mixing is shown in Table 1.
The soil improvement material was added to soil A in an amount of 150 kg of cement-based material per 1 m3 of soil, and mixed for 3 minutes using a Hobart mixer to obtain improved soil.
The amount of hexavalent chromium compounds eluted from the improved soil was measured in accordance with Notification No. 18 of the Ministry of the Environment.
[Comparative Example 1]
Improved soil was obtained in the same manner as in Example 1, except that water was used instead of the carbon dioxide-containing water, and the amount of hexavalent chromium compounds eluted from the improved soil was measured in the same manner as in Example 1.
In addition, for each of Examples 1 to 3, the reduction rate of the amount of eluted hexavalent chromium compounds relative to Comparative Example 1 (using water) {(eluted amount of hexavalent chromium compounds in Comparative Example−eluted amount of hexavalent chromium compounds in Example)÷eluted amount of hexavalent chromium compounds in Comparative Example×100(%)} was calculated.
［実施例４～６］
土壌Ａの代わりに、土壌Ｂを使用し、土壌Ｂに該地盤改良材を、土壌１ｍ３に対して、セメント系材料が３００ｋｇとなる量で添加する以外は実施例１と同様にして、改良土を得た後、改良土からの六価クロム化合物の溶出量等を実施例１と同様にして測定した。
［比較例２］
炭酸ガス含有水の代わりに、水を用いる以外は実施例２と同様にして、改良土を得た後、改良土からの六価クロム化合物の溶出量等を実施例１と同様にして測定した。
また、実施例４～６の各々について、比較例２（水を使用したもの）に対する、六価クロム化合物の溶出量の低減率を実施例１と同様にして算出した。
結果を表１に示す。
[Examples 4 to 6]
Improved soil was obtained in the same manner as in Example 1, except that soil B was used instead of soil A and the soil improvement material was added to soil B in an amount such that the cement-based material was 300 kg per 1 m3 of soil. Then, the amount of hexavalent chromium compounds eluted from the improved soil was measured in the same manner as in Example 1.
[Comparative Example 2]
Improved soil was obtained in the same manner as in Example 2, except that water was used instead of the carbon dioxide-containing water, and the amount of hexavalent chromium compounds eluted from the improved soil was measured in the same manner as in Example 1.
In addition, for each of Examples 4 to 6, the reduction rate of the amount of eluted hexavalent chromium compounds relative to Comparative Example 2 (using water) was calculated in the same manner as in Example 1.
The results are shown in Table 1.
表１から、実施例１～３と比較例１を比較すると、実施例１～３における六価クロム溶出量（０．０２２～０．０２６ｍｇ／リットル）は、比較例１における六価クロム溶出量（０．０２８ｍｇ／リットル）よりも小さいことがわかる。
また、実施例１～３の、比較例１（水を使用したもの）に対する、六価クロム化合物の溶出量の低減率は、７．１～２１．４％であった。
また、実施例４～６と比較例２を比較すると、実施例２における六価クロム溶出量（０．０７１～０．０８４ｍｇ／リットル）は、比較例２における六価クロム溶出量（０．０９１ｍｇ／リットル）よりも小さいことがわかる。
また、実施例４～６の、比較例２（水を使用したもの）に対する、六価クロム化合物の溶出量の低減率は、７．７～２２．０％であった。
Comparing Examples 1 to 3 with Comparative Example 1 from Table 1, it can be seen that the amount of hexavalent chromium eluted in Examples 1 to 3 (0.022 to 0.026 mg/L) is smaller than the amount of hexavalent chromium eluted in Comparative Example 1 (0.028 mg/L).
Moreover, the reduction rates of the amount of eluted hexavalent chromium compounds in Examples 1 to 3 compared to Comparative Example 1 (using water) were 7.1 to 21.4%.
Furthermore, when Examples 4 to 6 are compared with Comparative Example 2, it is found that the amount of hexavalent chromium eluted in Example 2 (0.071 to 0.084 mg/L) is smaller than the amount of hexavalent chromium eluted in Comparative Example 2 (0.091 mg/L).
Moreover, the reduction rates of the amount of eluted hexavalent chromium compounds in Examples 4 to 6, compared to Comparative Example 2 (using water), were 7.7 to 22.0%.
Claims (3)
水に炭酸ガスを吹き込むことによって、上記炭酸ガス含有水を調製する炭酸ガス含有水調製工程と、
上記セメント系材料と、上記炭酸ガス含有水を混合して、スラリーの形態を有する上記地盤改良材を調製するスラリー調製工程、
を含み、
上記スラリー調製工程における上記地盤改良材の調製直後のｐＨが１１．６～１２．６であることを特徴とする地盤改良材の製造方法。 A method for producing a ground improvement material comprising a slurry containing a cement-based material and carbon dioxide-containing water having a carbon dioxide concentration of 3,000 to 8,000 mg/L,
a carbon dioxide gas-containing water preparation step of preparing the carbon dioxide gas-containing water by blowing carbon dioxide gas into water;
A slurry preparation step of mixing the cement-based material with the carbon dioxide-containing water to prepare the ground improvement material having a slurry form;
Including,
A method for producing a ground improvement material, characterized in that the pH of the ground improvement material immediately after preparation in the slurry preparation step is 11.6 to 12.6 .
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