JP7814985B2 - Cement-based solidification material - Google Patents
Cement-based solidification materialInfo
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- JP7814985B2 JP7814985B2 JP2022036130A JP2022036130A JP7814985B2 JP 7814985 B2 JP7814985 B2 JP 7814985B2 JP 2022036130 A JP2022036130 A JP 2022036130A JP 2022036130 A JP2022036130 A JP 2022036130A JP 7814985 B2 JP7814985 B2 JP 7814985B2
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Description
本発明は、セメント系固化材に関するものである。 The present invention relates to a cement-based solidification material.
下記特許文献１には、セメントクリンカ粉末と二水石膏粉末と無水石膏粉末と高炉スラグ微粉末とを含むセメント系固化材が記載されている。この文献によれば、セメントクリンカ粉末の水硬率を2.00～2.10、セメントクリンカ粉末のフリーライム量を0.1～1.0質量％、セメントクリンカ粉末における全クロム量を200ppm以上、全クロム量中の水溶性六価クロムの割合を３質量％以下、セメント系固化材中のSO3の割合を3.5～15質量％にすることにより、地盤改良土（セメント系固化材と水と地盤改良対象土との混合物）からの六価クロム溶出量を低減することができるとされている。 Patent Document 1 below describes a cement-based solidification material containing cement clinker powder, gypsum dihydrate powder, anhydrous gypsum powder, and ground granulated blast furnace slag. According to this document, the amount of hexavalent chromium eluted from ground improvement soil (a mixture of cement-based solidification material, water, and soil to be improved) can be reduced by setting the hydraulic ratio of the cement clinker powder to 2.00 to 2.10, the free lime content of the cement clinker powder to 0.1 to 1.0 mass%, the total chromium content in the cement clinker powder to 200 ppm or more, the proportion of water-soluble hexavalent chromium in the total chromium content to 3 mass% or less, and the proportion of SO3 in the cement-based solidification material to 3.5 to 15 mass%.
ところで、我が国では、近年、水道により供給される水（水道水）に含まれる六価クロムの基準量が0.05mg/Lから0.02mg/Lにまで引き下げられた。一方、地盤改良土から溶出した六価クロムは、地下水を経由して水道水に混入する可能性がある。すると、水道水に含まれる六価クロムの量を0.02mg/L以下にするためには、地盤改良土からの六価クロム溶出量を0.02mg/L以下にまで低減することが好ましいと考えられる。 In Japan, the standard amount of hexavalent chromium contained in water supplied by public waterworks (tap water) has recently been lowered from 0.05 mg/L to 0.02 mg/L. However, hexavalent chromium leached from ground improvement soil may be mixed into tap water via groundwater. Therefore, in order to keep the amount of hexavalent chromium contained in tap water at 0.02 mg/L or less, it is considered preferable to reduce the amount of hexavalent chromium leached from ground improvement soil to 0.02 mg/L or less.
下記特許文献１に記載の技術においては、上記のセメント系固化材を使用した六価クロム溶出試験（試験例４）において、セメントクリンカ粉末に含まれる水溶性六価クロム量が10.7ppmであり、地盤改良対象土１m3に対するセメント系固化材の混合量が70kgであり、地盤改良土からの六価クロム溶出量が0.02mg/Lとなっている。このため、セメントクリンカ粉末に含まれる水溶性六価クロム量が10.7ppmを超えている場合、あるいは、地盤改良対象土１m3に対するセメント系固化材の混合量が70kgを超えている場合には、上記の試験例４よりも多くの六価クロム（セメント系固化材に含まれていたもの）が地盤改良土に含まれることにより、地盤改良土からの六価クロム溶出量が0.02mg/Lを超えてしまうおそれがあると考えられる。 In the technology described in Patent Document 1 below, in a hexavalent chromium elution test (Test Example 4) using the above-mentioned cement-based solidification material, the amount of water-soluble hexavalent chromium contained in cement clinker powder was 10.7 ppm, the amount of cement-based solidification material mixed per 1 m3 of soil to be improved was 70 kg, and the amount of hexavalent chromium eluted from the ground improved soil was 0.02 mg/L. Therefore, if the amount of water-soluble hexavalent chromium contained in the cement clinker powder exceeds 10.7 ppm or if the amount of cement-based solidification material mixed per 1 m3 of soil to be improved exceeds 70 kg, it is considered that the amount of hexavalent chromium eluted from the ground improved soil may exceed 0.02 mg/L because the ground improved soil contains more hexavalent chromium (contained in the cement-based solidification material) than in Test Example 4.
そこで、本発明者は、上記の状況に鑑みて、六価クロムを溶出させにくい地盤改良土を作製可能なセメント系固化材について種々の研究を行った。その結果、セメント系固化材に含まれる高炉スラグ微粉末のＬ値又はｂ値を所定範囲内とすることにより、地盤改良土からの六価クロム溶出量を低減できるとの知見を得た。本発明は、この知見に基づき、六価クロムを溶出させにくい地盤改良土を作製可能なセメント系固化材を提供することを目的とする。 In light of the above situation, the present inventor conducted extensive research into cement-based solidification materials that can be used to produce ground improvement soil that is less likely to leach hexavalent chromium. As a result, the inventor discovered that the amount of hexavalent chromium leaching from ground improvement soil can be reduced by setting the L value or b value of the ground granulated blast furnace slag contained in the cement-based solidification material within a specified range. Based on this discovery, the present invention aims to provide a cement-based solidification material that can be used to produce ground improvement soil that is less likely to leach hexavalent chromium.
本発明の第１項目に係るセメント系固化材は、セメントクリンカ粉末と石膏粉末と高炉スラグ微粉末とを含んでいる。前記高炉スラグ微粉末のハンターＬａｂ色空間におけるＬ値は80.23以上86.29以下であり、あるいは／かつ、前記高炉スラグ微粉末のハンターＬａｂ色空間におけるｂ値は2.80以上4.89以下である。なお、以下において、ハンターＬａｂ色空間におけるＬ値、ａ値及びｂ値をそれぞれ単にＬ値、ａ値及びｂ値と表記する。前記石膏粉末としては、例えば、二水石膏粉末、半水石膏粉末及び無水石膏粉末のうちの、いずれか１つ、または、２つ以上の混合物を使用することができる。 The cement-based solidification material according to the first aspect of the present invention comprises cement clinker powder, gypsum powder, and ground granulated blast furnace slag. The ground granulated blast furnace slag has an L value of 80.23 or more and 86.29 or less in the Hunter Lab color space, and/or a b value of 2.80 or more and 4.89 or less in the Hunter Lab color space. Hereinafter, the L value, a value, and b value in the Hunter Lab color space will be referred to simply as the L value, a value, and b value, respectively. The gypsum powder can be, for example, any one of gypsum dihydrate powder, gypsum hemihydrate powder, and gypsum anhydrite powder, or a mixture of two or more thereof.
本発明の第２項目に係るセメント系固化材は、前記第１項目に係るセメント系固化材において、前記セメントクリンカ粉末の水溶性六価クロム含有率が27ppm以下であり、前記セメントクリンカ粉末の水硬率が2.26以上であり、前記高炉スラグ微粉末のSO3含有率が4.00質量％以下であり、前記セメント系固化材における前記高炉スラグ微粉末の含有率が25.0質量％以上45.0質量％以下であり、前記セメント系固化材のSO3含有率が4.5質量％以上8.0質量％以下であるものとされている。 The cement-based solidification material according to the second item of the present invention is the cement-based solidification material according to the first item, wherein the water-soluble hexavalent chromium content of the cement clinker powder is 27 ppm or less, the hydraulic coefficient of the cement clinker powder is 2.26 or more, the SO3 content of the ground granulated blast furnace slag is 4.00 mass% or less, the content of the ground granulated blast furnace slag in the cement-based solidification material is 25.0 mass% or more and 45.0 mass% or less, and the SO3 content of the cement-based solidification material is 4.5 mass% or more and 8.0 mass% or less.
本発明の第１項目によれば、六価クロムを溶出させにくい地盤改良土を作製することができる。本発明の第２項目によれば、六価クロムをさらに溶出させにくく、しかも高強度である地盤改良土を作製することができる。 According to the first aspect of the present invention, it is possible to produce ground improvement soil that is less likely to leach hexavalent chromium. According to the second aspect of the present invention, it is possible to produce ground improvement soil that is even more resistant to leaching of hexavalent chromium and has high strength.
本発明の一実施形態に係るセメント系固化材について説明する。本実施形態に係るセメント系固化材は、セメントクリンカ粉末と石膏粉末と高炉スラグ微粉末とを含んでいる。 This section describes a cement-based solidification material according to one embodiment of the present invention. The cement-based solidification material according to this embodiment contains cement clinker powder, gypsum powder, and ground granulated blast furnace slag.
本実施形態のセメントクリンカ粉末の鉱物組成としては、例えば、C3S含有率が64.9質量％以上73.8質量％以下、C2S含有率が5.4質量％以上12.9質量％以下、C3A含有率が8.8質量％以上9.6質量％以下、C4AF含有率が7.5質量％以上8.6質量％以下である。 The mineral composition of the cement clinker powder of this embodiment is, for example, a C3S content of 64.9 mass% or more and 73.8 mass% or less, a C2S content of 5.4 mass% or more and 12.9 mass% or less, a C3A content of 8.8 mass% or more and 9.6 mass% or less, and a C4AF content of 7.5 mass% or more and 8.6 mass% or less.
本実施形態に係るセメント系固化材を使用して作製した地盤改良土からの六価クロム溶出量（以下、単に「六価クロム溶出量」という。）を少なく抑えるためには、本実施形態のセメントクリンカ粉末の水硬率(HM)が2.26以上、水溶性六価クロム含有率が27ppm以下であると好ましい。本実施形態においては、例えば、この水硬率が2.26以上2.36以下、この水溶性六価クロム含有率が10ppm以上27ppm以下となっている。 In order to minimize the amount of hexavalent chromium leaching from ground improved soil prepared using the cement-based solidification material according to this embodiment (hereinafter simply referred to as "hexavalent chromium leaching amount"), it is preferable that the hydraulic modulus (HM) of the cement clinker powder according to this embodiment be 2.26 or more and the water-soluble hexavalent chromium content be 27 ppm or less. In this embodiment, for example, the hydraulic modulus is 2.26 or more and 2.36 or less, and the water-soluble hexavalent chromium content is 10 ppm or more and 27 ppm or less.
本実施形態の石膏粉末としては、例えば、二水石膏粉末、半水石膏粉末及び無水石膏粉末のうちの、いずれか１つ、または、２つ以上の混合物を使用することができる。 In this embodiment, the gypsum powder may be, for example, any one of gypsum dihydrate powder, gypsum hemihydrate powder, and anhydrous gypsum powder, or a mixture of two or more of these.
六価クロム溶出量を少なく抑えるために、本実施形態の高炉スラグ微粉末としては、次の（１）又は（２）の条件を満たすものを使用し、好ましくは、これらの条件を両方満たすものを使用する。
（１）高炉スラグ微粉末のＬ値が80.23以上86.29以下である。
（２）高炉スラグ微粉末のｂ値が2.80以上4.89以下である。
本実施形態の高炉スラグ微粉末のａ値は、例えば、-0.14以上0.38以下である。
In order to minimize the amount of hexavalent chromium eluted, the ground granulated blast furnace slag used in this embodiment satisfies the following condition (1) or (2), and preferably satisfies both of these conditions.
(1) The L value of the ground granulated blast furnace slag is 80.23 or more and 86.29 or less.
(2) The b value of the ground granulated blast furnace slag is 2.80 or more and 4.89 or less.
The a value of the ground granulated blast furnace slag of this embodiment is, for example, −0.14 or more and 0.38 or less.
六価クロム溶出量を少なく抑えるためには、本実施形態の高炉スラグ微粉末のSO3含有率が4.00質量％以下であると好ましく、本実施形態に係るセメント系固化材における高炉スラグ微粉末の割合が25質量％以上であると好ましい。本実施形態においては、例えば、このSO3含有率は0.08質量％以上4.00質量％以下になっている。また、本実施形態の地盤改良土の強度を高めるためには、本実施形態に係るセメント系固化材における高炉スラグ微粉末の割合が45質量％以下であると好ましい。 In order to minimize the amount of hexavalent chromium elution, the SO3 content of the ground granulated blast furnace slag of this embodiment is preferably 4.00% by mass or less, and the proportion of ground granulated blast furnace slag in the cement-based solidification material of this embodiment is preferably 25% by mass or more. In this embodiment, for example, the SO3 content is 0.08% by mass or more and 4.00% by mass or less. Furthermore, in order to increase the strength of the ground improvement soil of this embodiment, the proportion of ground granulated blast furnace slag in the cement-based solidification material of this embodiment is preferably 45% by mass or less.
本実施形態の高炉スラグ微粉末の比表面積は、例えば、3000cm2/g以上10000cm2/g以下である。なお、この明細書において、比表面積とは、ブレーン空気透過装置を用いて測定される比表面積を意味している。この比表面積の具体的な測定法は「JIS R 5201」に規定されている。 The specific surface area of the ground blast furnace slag of this embodiment is, for example, 3000 cm 2 /g or more and 10000 cm 2 /g or less. In this specification, the specific surface area means the specific surface area measured using a Blaine air permeation device. The specific method for measuring this specific surface area is specified in "JIS R 5201".
六価クロム溶出量を少なく抑えるためには、本実施形態に係るセメント系固化材の合計SO3含有率が4.5質量％以上8.0質量％以下であると好ましい。本実施形態に係るセメント系固化材の比表面積は、例えば、3000cm2/g以上10000cm2/g以下である。 In order to minimize the amount of hexavalent chromium leaching, the total SO3 content of the cement-based solidification material according to this embodiment is preferably 4.5% by mass or more and 8.0% by mass or less. The specific surface area of the cement-based solidification material according to this embodiment is, for example, 3000 cm2 /g or more and 10000 cm2 /g or less.
地盤改良対象土の体積〔m3〕に対する本実施形態に係るセメント系固化材の混合量〔kg〕は、例えば100kg/m3以上300kg/m3以下である。 The amount [kg] of the cement-based solidification material according to this embodiment to be mixed with respect to the volume [m 3 ] of the soil to be improved is, for example, 100 kg/m 3 or more and 300 kg/m 3 or less.
次に、本発明の一実施形態に係るセメント系固化材の性能を説明するための試験例について、表１～表４を参照しながら説明する。 Next, test examples to illustrate the performance of a cement-based solidification material according to one embodiment of the present invention will be described with reference to Tables 1 to 4.
１．各試験例における実験方法
（セメント系固化材の作製）
各試験例（表２に示す試験例Ａ１～Ａ４０、表３に示す試験例Ｂ１～Ｂ８、表４に示す試験例Ｃ１～Ｃ１０）において、セメントクリンカ粉末と石膏粉末と高炉スラグ微粉末とを混合してセメント系固化材を作製した。
1. Experimental methods for each test example (preparation of cement-based solidification materials)
In each test example (Test Examples A1 to A40 shown in Table 2, Test Examples B1 to B8 shown in Table 3, and Test Examples C1 to C10 shown in Table 4), cement clinker powder, gypsum powder, and ground granulated blast furnace slag were mixed to prepare a cement-based solidification material.
（セメント系固化材に用いる材料の分析）
ただし、セメント系固化材を作製する前に、使用するセメントクリンカ粉末の化学組成をJIS R 5204:2019に基づいて測定し、このセメントクリンカ粉末のモジュラス（下記の式1）を上記化学組成に基づいて算出し、このセメントクリンカ粉末の鉱物組成を上記化学組成に基づいてボーグ式（下記の式2）により算出した。また、使用する高炉スラグ微粉末のSO3含有率とＬ値とａ値とｂ値とを測定した。SO3含有率の測定についてはJIS R 5202:2010に基づいて行った。
（式1）
HM=CaO/(SiO2+Al2O3+Fe2O3)
SM=SiO2/(Al2O3+Fe2O3)
IM=Al2O3/Fe2O3
（式2）
C3S=(4.07×CaO)-((7.60×SiO2)+(6.72×Al2O3)+(1.43×Fe2O3)+(2.85×SO3))
C2S=(2.87×SiO2)-(0.754×C3S)
C3A=(2.65×Al2O3)-(1.69×Fe2O3)
C4AF=(3.04×Fe2O3)
(Analysis of materials used in cement-based solidification materials)
However, before preparing the cement-based solidification material, the chemical composition of the cement clinker powder to be used was measured in accordance with JIS R 5204:2019, the modulus of this cement clinker powder (Equation 1 below) was calculated based on the above chemical composition, and the mineral composition of this cement clinker powder was calculated using the Bogue formula (Equation 2 below) based on the above chemical composition. The SO3 content, L value, a value, and b value of the ground granulated blast furnace slag to be used were also measured. The SO3 content was measured in accordance with JIS R 5202:2010.
(Formula 1)
HM=CaO/(SiO 2 +Al 2 O 3 +Fe 2 O 3 )
SM = SiO2 /( Al2O3 + Fe2O3 )
IM = Al2O3 / Fe2O3
(Formula 2)
C 3 S=(4.07×CaO)-((7.60×SiO 2 )+(6.72×Al 2 O 3 )+(1.43×Fe 2 O 3 )+(2.85×SO 3 ))
C 2 S=(2.87×SiO 2 )-(0.754×C 3 S)
C3A =(2.65× Al2O3 ) -(1.69× Fe2O3 )
C4AF = (3.04 x Fe2O3 )
（セメント系固化材の分析）
また、作製したセメント系固化材のSO3含有率と比表面積とを測定した。SO3含有率の測定についてはJIS R 5204:2019に基づいて行った。
(Analysis of cement-based solidification materials)
The SO3 content and specific surface area of the prepared cement-based solidification material were also measured. The SO3 content was measured based on JIS R 5204:2019.
（セメント系固化材の第１実験）
（ステップ１：供試体の作製）
粉体状のセメント系固化材と試料土（地盤改良対象土に相当）と溶媒水とを混合することにより供試体（地盤改良土に相当）を作製した。ここで、供試体の作製方法は、「JCAS L-01:2006：セメント系固化材による改良体の強さ試験方法」に基づいた。供試体の作製においては、試料土の体積〔m3〕に対するセメント系固化材の混合量〔kg〕を100kg/m3にした。試料土としては、神奈川県川崎市の関東ロームを使用した。試料土の状態は、含水比102.1％、湿潤密度1.391g/cm3になっており、試料土の粒度組成は、礫分0.6％、砂分9.0％、細粒分90.4％になっていた。
(First experiment on cement-based solidification material)
(Step 1: Preparation of the specimen)
A test specimen (equivalent to the improved soil) was prepared by mixing powdered cement-based solidification material with sample soil (equivalent to the soil to be improved) and solvent water. The test specimen preparation method was based on "JCAS L-01:2006: Strength test method for improved bodies using cement-based solidification material." The amount of cement-based solidification material mixed per sample soil volume ( m3 ) was set at 100 kg/ m3 . Kanto loam from Kawasaki City, Kanagawa Prefecture was used as the sample soil. The sample soil had a water content of 102.1%, a wet density of 1.391 g/ cm3 , and a particle size composition of 0.6% gravel, 9.0% sand, and 90.4% fine particles.
（セメント系固化材の第１実験）
（ステップ２：供試体の性能測定）
供試体が材齢７日となった時、この供試体について、「JIS A 1216:2020：土の一軸圧縮試験方法」に基づく一軸圧縮強さ試験、「平成３年８月２３日環境庁告示第４６号：土壌の汚染に係る環境基準について」に基づく六価クロム溶出試験を行った。
(First experiment on cement-based solidification material)
(Step 2: Test piece performance measurement)
When the specimen was 7 days old, a uniaxial compressive strength test based on "JIS A 1216:2020: Uniaxial compression test method for soil" and a hexavalent chromium elution test based on "Environment Agency Notification No. 46 of August 23, 1991: Environmental Standards for Soil Contamination" were conducted on the specimen.
（セメント系固化材の第２実験）
第２実験は、以下の点において第１実験と異なっており、以下において明記していない点に関しては第１実験と同様である。
すなわち、第２実験においては、
セメント系固化材を土壌に粉体で添加するのではなく、セメント系固化材に水を加えてよく攪拌しスラリー状としたものを使用し、
試料土の体積〔m3〕に対するセメント系固化材の混合量〔kg〕を100kg/m3ではなく300kg/m3とし、
供試体の作製方法を「JCAS L-01:2006」ではなく「JGS 0821-2009：安定処理土の締固めをしない供試体作製方法」に基づくものとした。
ここで、スラリー状のセメント系固化材は、セメント系固化材１００質量％に対して水６０質量％を混合したものである。
(Second experiment on cement-based solidification material)
The second experiment differed from the first experiment in the following respects, and was similar to the first experiment in respects that are not specified below.
That is, in the second experiment,
Instead of adding cement-based solidification material to the soil in powder form, we use a slurry made by adding water to the cement-based solidification material and stirring it well.
The amount of cement-based solidification material mixed (kg) relative to the volume of sample soil (m 3 ) was set to 300 kg/m 3 instead of 100 kg/m 3 ,
The method for preparing the specimens was based on "JGS 0821-2009: Method for preparing specimens without compaction of stabilized soil" rather than "JCAS L-01:2006."
Here, the slurry cement-based solidification material is a mixture of 100 mass % of cement-based solidification material and 60 mass % of water.
２．各試験例における実験結果
表１は、各試験例において使用したセメントクリンカ粉末の組成を示している。各試験例においては、表１に示すCli-1～Cli-6のいずれか１種類のセメントクリンカ粉末を用いてセメント系固化材を作製した。表１において、「SiO2」～「MnO」の項目はセメントクリンカ粉末の化学組成（単位：質量％）を示しており、「Total」の項目は「SiO2」～「MnO」の項目における数値の合計値を示しており、「HM」～「IM」の項目はセメントクリンカ粉末のモジュラスを示しており、「C3S」～「C4AF」の項目はセメントクリンカ粉末の鉱物組成（単位：質量％）を示している。
2. Experimental results for each test example Table 1 shows the composition of the cement clinker powder used in each test example. In each test example, a cement-based solidification material was produced using one of the cement clinker powders Cli-1 to Cli-6 shown in Table 1. In Table 1, the items " SiO2 " to "MnO" indicate the chemical composition of the cement clinker powder (unit: mass%), the item "Total" indicates the total value of the values in the items " SiO2 " to "MnO", the items "HM" to "IM" indicate the modulus of the cement clinker powder, and the items " C3S " to " C4AF " indicate the mineral composition of the cement clinker powder (unit: mass%).
なお、表２～表４においては、各試験例において使用したセメントクリンカ粉末の種類（表１に示すCli-1～Cli-6のいずれか）を明記していないが、表１に示す「HM」と表２～表４に示す「HM」とを照合することにより、各試験例において使用したセメントクリンカ粉末の種類が分かるようになっている。 Note that Tables 2 to 4 do not specify the type of cement clinker powder used in each test example (any of Cli-1 to Cli-6 shown in Table 1), but by comparing the "HM" shown in Table 1 with the "HM" shown in Tables 2 to 4, the type of cement clinker powder used in each test example can be determined.
表２～表４における項目の意味は以下の通りである。
「HM」：セメントクリンカ粉末のHM(水硬率)
「Cr6+」：セメントクリンカ粉末の水溶性六価クロム含有率
「SO3」：高炉スラグ微粉末のSO3含有率
「Ｌ値」：高炉スラグ微粉末のＬ値
「ａ値」：高炉スラグ微粉末のａ値
「ｂ値」：高炉スラグ微粉末のｂ値
「割合」：セメント系固化材に対する高炉スラグ微粉末の質量百分率
「合計SO3」：セメント系固化材のSO3含有率
「比表面積」：セメント系固化材の比表面積
「一軸圧縮強さ（添加量100kg/m3）」：第１実験における一軸圧縮強さ試験の測定値
「一軸圧縮強さ（添加量300kg/m3）」：第２実験における一軸圧縮強さ試験の測定値
「六価クロム溶出量（添加量100kg/m3）」：第１実験における六価クロム溶出試験の測定値
「六価クロム溶出量（添加量300kg/m3）」：第２実験における六価クロム溶出試験の測定値
The meanings of the items in Tables 2 to 4 are as follows:
"HM": HM (hydraulic hardness) of cement clinker powder
"Cr 6+ ": Water-soluble hexavalent chromium content of cement clinker powder "SO 3 ": SO 3 content of ground granulated blast furnace slag "L value": L value of ground granulated blast furnace slag "a value": a value of ground granulated blast furnace slag "b value": b value of ground granulated blast furnace slag "Ratio": Mass percentage of ground granulated blast furnace slag to cement-based solidification material "Total SO 3 ": SO 3 content of cement-based solidification material "Specific surface area": Specific surface area of cement-based solidification material "Unconfined compressive strength (addition amount 100 kg/m 3 )": Measured value of unconfined compressive strength test in the first experiment "Unconfined compressive strength (addition amount 300 kg/m 3 )": Measured value of unconfined compressive strength test in the second experiment "Amount of eluted hexavalent chromium (addition amount 100 kg/m 3 )": Measured value of unconfined compressive strength test in the first experiment "Amount of eluted hexavalent chromium (addition amount 300 kg/m 3 )) : Measurement value of hexavalent chromium elution test in the second experiment
表２に示すように、試験例Ａ１～Ａ４０においては、「HM」が2.26以上2.36以下、「Cr6+」が10ppm以上27ppm以下、「SO3」が0.08質量％以上4.00質量％以下、「Ｌ値」が80.23以上86.29以下、「ａ値」が－0.14以上0.38以下、「ｂ値」が2.80以上4.89以下、「割合」が25質量％以上45質量％以下、「合計SO3」が4.5質量％以上8.0質量％以下、「比表面積」が3850cm2/g以上4200cm2/g以下になっている。なお、以下において、これらの項目をまとめて「条件項目」という。 As shown in Table 2, in Test Examples A1 to A40, "HM" was 2.26 to 2.36, "Cr 6+ " was 10 ppm to 27 ppm, "SO 3 " was 0.08 mass% to 4.00 mass%, "L value" was 80.23 to 86.29, "a value" was -0.14 to 0.38, "b value" was 2.80 to 4.89, "ratio" was 25 mass% to 45 mass%, "total SO 3 " was 4.5 mass% to 8.0 mass%, and "specific surface area" was 3850 cm 2 /g to 4200 cm 2 /g. These items are hereinafter collectively referred to as "condition items".
また、表２に示すように、試験例Ａ１～Ａ４０においては、「一軸圧縮強さ（添加量100kg/m3）」が269kN/m2以上370kN/m2以下、「一軸圧縮強さ（添加量300kg/m3）」が1880kN/m2以上2300kN/m2以下、「六価クロム溶出量（添加量100kg/m3）」及び「六価クロム溶出量（添加量300kg/m3）」が0.02mg/L以下になっている。 Furthermore, as shown in Table 2, in test examples A1 to A40, the "uniaxial compressive strength (addition amount 100 kg/m 3 )" is 269 kN/m 2 or more and 370 kN/m 2 or less, the "uniaxial compressive strength (addition amount 300 kg/m 3 )" is 1880 kN/m 2 or more and 2300 kN/m 2 or less, and the "hexavalent chromium leaching amount (addition amount 100 kg/m 3 )" and "hexavalent chromium leaching amount (addition amount 300 kg/m 3 )" are 0.02 mg/L or less.
表３に示すように、試験例Ｂ１～Ｂ４においては条件項目のうち「Ｌ値」のみが試験例Ａ１～Ａ４０の範囲外にあり、試験例Ｂ５～Ｂ８においては条件項目のうち「ｂ値」のみが試験例Ａ１～Ａ４０の範囲外にある。そして、試験例Ｂ１～Ｂ８においては、「一軸圧縮強さ（添加量100kg/m3）」及び「一軸圧縮強さ（添加量300kg/m3）」は試験例Ａ１～Ａ４０の範囲内にあるが、「六価クロム溶出量（添加量100kg/m3）」及び「六価クロム溶出量（添加量300kg/m3）」は試験例Ａ１～Ａ４０の範囲を超えている。 As shown in Table 3, in test examples B1 to B4, only the "L value" of the condition items is outside the range of test examples A1 to A40, and in test examples B5 to B8, only the "b value" of the condition items is outside the range of test examples A1 to A40. In test examples B1 to B8, the "uniaxial compressive strength (addition amount 100 kg/m 3 )" and "uniaxial compressive strength (addition amount 300 kg/m 3 )" are within the range of test examples A1 to A40, but the "hexavalent chromium elution amount (addition amount 100 kg/m 3 )" and "hexavalent chromium elution amount (addition amount 300 kg/m 3 )" exceed the range of test examples A1 to A40.
表４に示すように、試験例Ｃ１においては条件項目のうち「HM」のみが試験例Ａ１～Ａ４０の範囲外にあり、試験例Ｃ２、Ｃ３においては条件項目のうち「Cr6+」のみが試験例Ａ１～Ａ４０の範囲外にあり、試験例Ｃ４、Ｃ５においては条件項目のうち「SO3」のみが試験例Ａ１～Ａ４０の範囲外にあり、試験例Ｃ６、Ｃ７においては条件項目のうち「割合」のみが試験例Ａ１～Ａ４０の範囲外にあり、試験例Ｃ８～Ｃ１０においては条件項目のうち「合計SO3」のみが試験例Ａ１～Ａ４０の範囲外にある。そして、試験例Ｃ１～Ｃ６においては、「一軸圧縮強さ（添加量100kg/m3）」及び「一軸圧縮強さ（添加量300kg/m3）」は試験例Ａ１～Ａ４０の範囲内にあるが、「六価クロム溶出量（添加量100kg/m3）」及び「六価クロム溶出量（添加量300kg/m3）」は試験例Ａ１～Ａ４０の範囲を超えている。また、試験例Ｃ７～Ｃ１０においては、「六価クロム溶出量（添加量100kg/m3）」及び「六価クロム溶出量（添加量300kg/m3）」は試験例Ａ１～Ａ４０の範囲内にあるが、「一軸圧縮強さ（添加量100kg/m3）」及び「一軸圧縮強さ（添加量300kg/m3）」は試験例Ａ１～Ａ４０の範囲を下回っている。 As shown in Table 4, in test example C1, only "HM" among the condition items is outside the range of test examples A1 to A40; in test examples C2 and C3, only "Cr 6+ " among the condition items is outside the range of test examples A1 to A40; in test examples C4 and C5, only "SO 3 " among the condition items is outside the range of test examples A1 to A40; in test examples C6 and C7, only "ratio" among the condition items is outside the range of test examples A1 to A40; and in test examples C8 to C10, only "total SO 3 " among the condition items is outside the range of test examples A1 to A40. In test samples C1 to C6, the "uniaxial compressive strength (addition amount 100 kg/ m3 )" and "uniaxial compressive strength (addition amount 300 kg/ m3 )" are within the ranges of test samples A1 to A40, but the "hexavalent chromium elution amount (addition amount 100 kg/ m3 )" and "hexavalent chromium elution amount (addition amount 300 kg/ m3 )" are outside the ranges of test samples A1 to A40. In test samples C7 to C10, the "hexavalent chromium elution amount (addition amount 100 kg/ m3 )" and "hexavalent chromium elution amount (addition amount 300 kg/ m3 )" are within the ranges of test samples A1 to A40, but the "uniaxial compressive strength (addition amount 100 kg/ m3 )" and "uniaxial compressive strength (addition amount 300 kg/ m3 )" are below the ranges of test samples A1 to A40.
３．考察
上記の実験結果について以下のように考察することができる。
（１）セメント系固化材に含まれる高炉スラグ微粉末のＬ値が80.23以上86.29以下の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｂ１～Ｂ４）に比較して、このＬ値以外の条件が同程度であれば、地盤改良土からの六価クロム溶出量を低減することができる。
（２）セメント系固化材に含まれる高炉スラグ微粉末のｂ値が2.80以上4.89以下の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｂ５～Ｂ８）に比較して、このｂ値以外の条件が同程度であれば、地盤改良土からの六価クロム溶出量を低減することができる。
（３）セメント系固化材に含まれるセメントクリンカ粉末の水硬率が2.26以上の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｃ１）に比較して、この水硬率以外の条件が同程度であれば、地盤改良土からの六価クロム溶出量を低減することができる。
（４）セメント系固化材に含まれるセメントクリンカ粉末の水溶性六価クロム含有率が27ppm以下の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｃ２、Ｃ３）に比較して、この水溶性六価クロム含有率以外の条件が同程度であれば、地盤改良土からの六価クロム溶出量を低減することができる。
（５）セメント系固化材に含まれる高炉スラグ微粉末のSO3含有率が4.00質量％以下の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｃ４、Ｃ５）に比較して、このSO3含有率以外の条件が同程度であれば、地盤改良土からの六価クロム溶出量を低減することができる。
（６）セメント系固化材における高炉スラグ微粉末の含有率が25質量％以上の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｃ６）に比較して、この含有率以外の条件が同程度であれば、地盤改良土からの六価クロム溶出量を低減することができる。
（７）セメント系固化材における高炉スラグ微粉末の含有率が45質量％以下の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｃ７）に比較して、この含有率以外の条件が同程度であれば、地盤改良土の強度を高めることができる。
（８）セメント系固化材のSO3含有率が4.5質量％以上8.0質量％以下の範囲にある場合（試験例Ａ１～Ａ４０）、この範囲にない場合（試験例Ｃ８～Ｃ１０）に比較して、このSO3含有率以外の条件が同程度であれば、地盤改良土の強度を高めることができる。
3. Discussion The above experimental results can be considered as follows.
(1) When the L value of the ground granulated blast furnace slag contained in the cement-based solidification material is in the range of 80.23 to 86.29 (Test Examples A1 to A40), the amount of hexavalent chromium leaching from the ground improvement soil can be reduced compared to when the L value is not in this range (Test Examples B1 to B4), provided that all other conditions are similar.
(2) When the b value of the ground granulated blast furnace slag contained in the cement-based solidification material is in the range of 2.80 to 4.89 (Test Examples A1 to A40), the amount of hexavalent chromium leaching from the ground improvement soil can be reduced compared to when it is not in this range (Test Examples B5 to B8), provided that all other conditions are similar.
(3) When the hydraulic ratio of the cement clinker powder contained in the cement-based solidification material is in the range of 2.26 or more (Test Examples A1 to A40), the amount of hexavalent chromium leaching from the ground improvement soil can be reduced compared to when it is not in this range (Test Example C1), provided that the conditions other than the hydraulic ratio are similar.
(4) When the content of water-soluble hexavalent chromium in the cement clinker powder contained in the cement-based solidification material is in the range of 27 ppm or less (Test Examples A1 to A40), the amount of hexavalent chromium leaching from the ground improvement soil can be reduced compared to when it is not in this range (Test Examples C2 and C3), provided that all other conditions are similar.
(5) When the SO3 content of the ground granulated blast furnace slag contained in the cement-based solidification material is in the range of 4.00 mass% or less (Test Examples A1 to A40), the amount of hexavalent chromium leaching from the ground improvement soil can be reduced compared to when it is not in this range (Test Examples C4 and C5), provided that all conditions other than the SO3 content are similar.
(6) When the content of ground granulated blast furnace slag in the cement-based solidification material is in the range of 25 mass% or more (Test Examples A1 to A40), the amount of hexavalent chromium leaching from the ground improvement soil can be reduced compared to when it is not in this range (Test Example C6), provided that all other conditions are similar.
(7) When the content of blast furnace slag powder in the cement-based solidification material is in the range of 45 mass% or less (Test Examples A1 to A40), the strength of the ground improvement soil can be increased compared to when it is not in this range (Test Example C7), provided that all other conditions are the same.
(8) When the SO3 content of the cement-based solidification material is in the range of 4.5 mass% or more and 8.0 mass% or less (Test Examples A1 to A40), the strength of the ground improvement soil can be increased compared to when it is not in this range (Test Examples C8 to C10), provided that all conditions other than the SO3 content are similar.
Claims (2)
前記高炉スラグ微粉末のハンターＬａｂ色空間におけるＬ値が80.23以上86.29以下であり、あるいは／かつ、前記高炉スラグ微粉末のハンターＬａｂ色空間におけるｂ値が2.80以上4.89以下であり、
前記セメントクリンカ粉末の水溶性六価クロム含有率が27ppm以下であり、
前記セメントクリンカ粉末の水硬率が2.26以上であり、
前記高炉スラグ微粉末のSO 3 含有率が4.00質量％以下であり、
前記セメント系固化材における前記高炉スラグ微粉末の含有率が25.0質量％以上45.0質量％以下であり、
前記セメント系固化材のSO 3 含有率が4.5質量％以上8.0質量％以下であることを特徴とするセメント系固化材。 A cement-based solidification material containing cement clinker powder, gypsum powder, and ground granulated blast furnace slag,
the L value of the ground granulated blast furnace slag in the Hunter Lab color space is 80.23 or more and 86.29 or less, and/or the b value of the ground granulated blast furnace slag in the Hunter Lab color space is 2.80 or more and 4.89 or less,
The cement clinker powder has a water-soluble hexavalent chromium content of 27 ppm or less,
The hydraulic coefficient of the cement clinker powder is 2.26 or more,
The SO3 content of the ground granulated blast furnace slag is 4.00% by mass or less,
The content of the ground granulated blast furnace slag in the cement-based solidification material is 25.0% by mass or more and 45.0% by mass or less,
A cement-based solidification material characterized in that the SO3 content of the cement-based solidification material is 4.5 mass% or more and 8.0 mass% or less.
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| JP2010064905A (en) | 2008-09-09 | 2010-03-25 | Taiheiyo Cement Corp | Cement clinker and solidifying material using the same |
| JP2010202463A (en) | 2009-03-04 | 2010-09-16 | Ube Ind Ltd | Cement clinker, cement-based solidifying material, solidification treatment method for soil and method for producing cement clinker |
| JP2014058431A (en) | 2012-09-19 | 2014-04-03 | Taiheiyo Cement Corp | Method for preparing cement composition |
| JP2016074763A (en) | 2014-10-03 | 2016-05-12 | 宇部興産株式会社 | Method for producing cement-based solidifying material, method for solidifying soft soil, and method for reducing amount of hexavalent chromium to be eluted from solidified soil |
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| JP2010202463A (en) | 2009-03-04 | 2010-09-16 | Ube Ind Ltd | Cement clinker, cement-based solidifying material, solidification treatment method for soil and method for producing cement clinker |
| JP2014058431A (en) | 2012-09-19 | 2014-04-03 | Taiheiyo Cement Corp | Method for preparing cement composition |
| JP2016074763A (en) | 2014-10-03 | 2016-05-12 | 宇部興産株式会社 | Method for producing cement-based solidifying material, method for solidifying soft soil, and method for reducing amount of hexavalent chromium to be eluted from solidified soil |
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