JP5995992B2 - Method for producing cement-based solidified material - Google Patents

Description

  The present invention relates to a method for producing a cement-based solidified material excellent in strength development and an effect of suppressing elution of hexavalent chromium, and a cement-based solidified material produced by the production method.

Currently, there are a wide variety of types of solidification materials that are commercially available, their applications, and the soils that are subject to solidification treatment (hereinafter referred to as “target soils”). For example, there are various types of solidifying materials such as cement, gypsum, magnesia and lime, which contain cement, gypsum, magnesia and lime as main components. There are soil improvement, sludge solidification, deep layer improvement, generation soil improvement, etc., and these target soils include sandy soil, silt, clay, volcanic ash clay, organic soil, highly organic soil and the like. Moreover, even in the same type of target soil, the physical and chemical properties such as the content, particle size, and chemical composition of organic matter and water vary greatly depending on the place of origin and origin.
Therefore, in order to appropriately select the blending of the solidifying material according to the characteristics of the target soil, a blending test involving trial and error has to be performed, and the blending design of the solidifying material has been troublesome.

Furthermore, in the blended design of the cement-based solidifying material, it is necessary to cope with the elution of hexavalent chromium from the soil treated with the solidifying material (hereinafter referred to as “improved soil”). The source of the eluted hexavalent chromium is that contained in the Portland cement clinker in the cement-based solidified material, and was originally contained in the improved soil, and the dissolution was promoted in an alkaline environment due to the hydration of the cement-based solidified material. It is divided roughly into what was done.
Therefore, recently, by using a cement mixture having the effect of reducing hexavalent chromium, such as blast furnace slag, mixed with the solidified material, the Portland cement clinker contained in the solidified material is diluted and reduced. Many methods are used to suppress the amount of hexavalent chromium eluted due to the two effects of reducing the eluted chromium.
However, in general, the cement mixture having a reducing effect such as blast furnace slag decreases the strength of the improved soil as the amount of use increases.
Therefore, it is important for the blended design of the cement-based solidifying material to achieve both strength development and an effect of suppressing the elution of hexavalent chromium.

By the way, the mixing method of the cement-type solidification material according to object soil has been proposed from before.
For example, Patent Literature 1 proposes a cemented solidifying material blending method (claim 1) in which the amount of gypsum is determined according to the target soil and the amount of gypsum is blended. Further, based on the amount of aluminum eluted from the target soil into the alkaline aqueous solution, a blending method for calculating the blending amount of the gypsum using a specific formula (Claim 2), and further using another formula based on the aluminum amount Thus, a blending method (claim 3) for calculating the blending amount of cement has been proposed.
However, the property of the improved soil that is a problem of the blending method is only strength development, so that the blending adjustment components are only gypsum and cement, and blast furnace slag is not covered.
Non-Patent Document 1 describes soil components that affect the strength development of cement-based solidified materials. According to the literature, allophane in soil (volcanic ash clay) is said to reduce the strength development of cement-based solidified material.
However, even though allophane reduces the strength development of the solidified material, the No. in Table 2 below. 2 and No. As can be seen by comparing the strength of No. 3, the improved soil using the target soil having a low allophane content (in No. 2, P ₁ is 8.1 kN / m ² and P ₂ is 7.9 kN / m ² ). However, the strength may be lower than the improved soil using the target soil having a high content (No. 3, P ₁ is 954.5 kN / m ² , P ₂ is 1875.4 kN / m ² ). .
In Table 2, P ₁ is the strength of the improved soil using cement containing blast furnace slag (hereinafter referred to as “blast furnace slag containing cement”) as a solidified material, and P ₂ is ordinary Portland cement (reference cement). ) Is the strength of the improved soil using the solidified material, but the effect of the use of blast furnace slag on strength is not as simple as can be seen by comparing P ₁ and P ₂ .
As described above, since it is difficult to predict the strength development of the improved soil, the amount of blast furnace slag used in the solidification material is maximized in order to secure the predetermined strength development and suppress the elution amount of hexavalent chromium. The possible formulation design was difficult.

JP 2002-129158 A

“Examination on strength development in improved cement of volcanic ash clay”, published by Cement and Concrete, Cement Association, pages 3-8, No. 780, Feb. 2012

Therefore, the present invention provides a method for producing a cement-based solidified material (hereinafter referred to as “solidified material”) containing blast furnace slag and having high strength development and high hexavalent chromium elution suppression effect according to the target soil . For the purpose.

Therefore, the present inventor examined the relationship between the components of the target soil and the strength of the improved soil using cement. Based on the following findings (i) to (iii), etc. The present inventors have completed the present invention by finding a method for easily producing a solidified material having a high chromium elution suppressing effect.
(I) The content of allophane and amorphous inorganic components (hereinafter referred to as “allophanes”) in the target soil, the strength (P ₁ ) of the improved soil using cement containing blast furnace slag as a solidifying material, and the improved soil The following linear relational expression (1) is established between the strength ratio (P ₁ / P ₂ ) of the strength (P ₂ ) of the improved soil using the reference cement selected from the results regarding the strength (for example, (See FIG. 2 below). And
(Ii) If both sides of the linear relational expression (1) are multiplied by the content of the blast furnace slag in the blast furnace slag-containing cement, the content of allophanes in the target soil is the same as when using the reference cement Inclusion of blast furnace slag in a gypsum-determining base material (a mixture of cement and blast furnace slag used in the following step (C)) in which the strength of improved soil is obtained (that is, P ₁ / P ₂ = 1 is satisfied) A linear relational expression (2) indicating the relationship with the rate is obtained (for example, see FIG. 3 described later). Therefore,
(Iii) If the linear relational expression (2) is used, the gypsum amount determining base material capable of obtaining the strength of the predetermined improved soil (the strength of the improved soil with the reference cement) from the content of allophanes in the target soil The maximum content of blast furnace slag can be obtained, and the blending amounts of gypsum, blast furnace slag, and cement in the solidified material can be obtained through the following steps (D) and (E).

That is, the present invention is the preparation how the consolidated material characterized by a mix design below.
[1] A method for producing a solidified material, in which cement, blast furnace slag and gypsum of a blending amount determined through the following steps (A) to (E) are measured and mixed.
(A) Measure the following strengths P ₁ and P ₂ to obtain the following relational expression (1) between the content of allophanes in the soil and the strength ratio (P ₁ / P ₂ ): Induction step 1) P ₁ / P ₂ = ax + b (1)
Where P ₁ is the strength of the improved soil using the blast furnace slag-containing cement, P ₂ is the strength of the improved soil using the reference cement, x is the content (% by mass) of allophanes in the target soil, and a and b are Represents a constant.
(B) The following relational expression (2) is obtained by multiplying both sides of the relational expression (1) by the blast furnace slag content (s ₁ ) (mass%) in the blast furnace slag-containing cement. S ₂ = cx + d (2)
However, s ₂ is the content (mass%) of blast furnace slag in the base material for determining the amount of gypsum whose strength ratio is 1, x is the content (mass%) of allophanes in the target soil, and c is a × s. ₁ and d represent b × s ₁ .
(C) For target soil having a strength ratio of 1 or less, based on the content of allophanes in the target soil, the relational expression (2) is used to determine the amount of blast furnace slag in the base material for gypsum amount determination. On the other hand, the content ratio (s ₁ ) of the blast furnace slag in the cement containing the blast furnace slag is determined for the target soil having a strength ratio (same as s ₂ ) and the strength ratio exceeds 1. Gypsum, which is determined as the content of blast furnace slag (same as s ₁ ) and determines the content of cement in the base material for determining the amount of gypsum using the content of the blast furnace slag and the following equation (3) Step of determining the content of blast furnace slag and cement in the base material for determining the amount of cement (mass%) in the base material for determining the amount of gypsum = 100-Content of the blast furnace slag in the base material for determining the amount of gypsum (mass) %) ...... (3)
(D) Produced by mixing the target soil with a gypsum amount determining composition obtained by mixing a gypsum amount determining base material containing blast furnace slag and cement having the determined content and a plurality of levels of gypsum. Measure the strength of the improved soil, select the improved soil that exhibits the target strength, and determine the gypsum content (mass%) in the composition for determining the amount of gypsum used in the improved soil. The amount of gypsum in the solidified material determined in the step (D) is subtracted from the amount of gypsum in the solidified material (E) 100% by mass, which is determined as the amount of mass (% by mass). In addition, with respect to the remaining value, the content of blast furnace slag in the base material for determining the amount of gypsum determined in the step (C) (value of mass% × 0.01) and the content of cement (mass% × 0.01) Of the blast furnace slag in the solidified material. Step of determining the amount of blast furnace slag and cement in the solidified material determined as the amount (% by mass) and the amount of cement (% by mass)

According to the manufacturing method of the solidification material of this invention, the optimal compounding quantity of cement, blast furnace slag, and gypsum can be determined easily according to object soil. Moreover, the solidification material manufactured using the manufacturing method of the solidification material of this invention has high intensity | strength expression property and the elution inhibitory effect of hexavalent chromium.

It is a figure which shows the linear relationship of the compounding quantity of the blast furnace slag in a solidification material, and the uniaxial compressive strength of improved soil. It is a figure which shows the relationship between the content rate of allophanes in soil, and the strength ratio of improved soil. It is a figure which shows the relationship between the content rate of the allophanes in soil, and the content rate of the blast furnace slag in the base material for gypsum amount determination whose strength ratio of improved soil is 1.

Hereinafter, the method for producing a solidified material and the solidified material of the present invention will be described.
1. Method for producing solidified material As described above, the method includes (A) the induction step of relational expression (1), (B) the induction step of relational expression (2), and (C) blast furnace slag in the base material for determining the amount of gypsum. And cement content rate determining step, (D) cement amount of gypsum in solidified material determining step, and (E) cement amount of blast furnace slag and solid content of cement determined in the solidified material, blast furnace slag And a method for producing a solidified material in which gypsum is weighed and mixed. In the following, each process will be described separately.

(A) Induction step of relational expression (1) This step measures the following strengths P ₁ and P _2, and determines the content of allophanes in the soil and the following strength ratio (P ₁ / P ₂ ). It is the process of calculating | requiring the said relational expression (1) between. However, P ₁ is the intensity of the modified soil with blast furnace slag containing cement, P ₂ is the intensity of the modified soil with a reference cement selected from such results regarding strength of modified soil.
Here, the allophanes are a general term for allophane and amorphous inorganic components, and the amorphous inorganic components are allophane-like as described in the right column on lines 6 to 12 of page 3 of the following document (i). Silicate minerals such as aluminum and iron, weathered inorganic gels such as silicic acid, alumina and iron oxide that are amorphous to X-rays present in the soil, and more strictly, amorphous. Difficult but refers to minerals including iron minerals such as low crystalline goethite.

The allophanes can be quantified by, for example, an “acid-alkaline alternating dissolution method” described in the following document (i), a “200 ° C. heating dissolution loss method” described in the following document (ii), or the following document (iii) And “XRD-Rietbelt method” described in the following document (iv) and the like.
Also, relationship between the content of soil allophane compound and an intensity ratio _(P 1 _/ P ₂₎ can be determined by regression analysis using a least squares method.
[List of documents]
(I) Ikuo Kitagawa “Study on Quantification of Allophane and Amorphous Inorganic Components in Soil”, Agricultural Technology Research Institute Report No. 29, pp. 1-48 (1977)
(Ii) Kitagawa Ikuo, “Rapid Determination Method of Allophane and Amorphous Inorganic Components in Soil”, Japan Soil Fertilizer Science Journal, Vol. 48, No. 4, pp. 124-129 (1977)
(Iii) Ryosuke Okumura et al., “Improvement of Kanto loam with cement (Part 1: Simple determination of allophane and amorphous inorganic components in soil)”, 41st Geotechnical Research Conference, pp. 767-768 (2006) July)
(Iv) Seiichi Hoshino et al., “Application of X-ray diffraction / Rietbelt method in the determination of cement minerals containing amorphous admixtures”, Cement and concrete papers, No. 59, pp. 14-21 (2005)

  Any cement can be used as the reference cement, for example, Portland cement such as ordinary Portland cement, early-strength Portland cement, ultra-early strength Portland cement, medium heat Portland cement, low heat Portland cement, and sulfate-resistant Portland cement. , Blast furnace slag-containing cement (including blast furnace cement) and mixed cement such as silica cement, and one or more selected from eco-cement and the like.

(B) Induction step of relational expression (2) This step is performed by multiplying both sides of relational expression (1) by the content (% by mass) of blast furnace slag in the blast furnace slag-containing cement. It is the process of calculating | requiring.
As shown in FIG. 1 (drawing based on data of Comparative Examples 4, 6, and 7 and Example 11 in Table 4 described in Japanese Patent Laid-Open No. 2006-219312), empirically the blast furnace slag Since there is no problem that there is a linear relationship between the blending amount and the strength of the improved soil, the variable s _{2 in} the relational expression (2) indicates the content of the blast furnace slag in the base material for determining the amount of gypsum whose strength ratio is 1. Represent. 2 and FIG. 3 described later, both sides of the relational expression (1) in FIG. 2 are multiplied by 40 (mass%) which is the content of blast furnace slag in the used blast furnace slag-containing cement. Then, the variable P ₁ / P ₂ (strength ratio) in the relational expression (1) is converted into a variable s ₂ (content ratio of blast furnace slag in the gypsum amount determining base material in which the strength ratio becomes 1).

(C) Step of determining the content of blast furnace slag and cement in the base material for determining the amount of gypsum
(i) For the target soil having a strength ratio of 1 or less, based on the content of allophanes in the target soil, the relational expression (2) is used to determine the amount of blast furnace slag in the base material for gypsum amount determination. Determine the content (same as s ₂ ),
(ii) For the target soil having a strength ratio exceeding 1, the content of blast furnace slag in the blast furnace slag-containing cement (s ₁ ) is set to the content of blast furnace slag in the base material for determining the amount of plaster (s ₁ and The same),
(iii) A step of determining the cement content in the base material for determining the amount of gypsum using the content of the blast furnace slag and the formula (3).
Here, the base material for determining the amount of gypsum is a mixture composed of cement and blast furnace slag, and in the composition for determining the amount of gypsum described in (D) below, the composition in a state before mixing the gypsum. is there.

(D) Step of determining the amount of gypsum in the solidified material The step includes a gypsum amount determining composition formed by mixing the gypsum amount determining base material and a plurality of levels of gypsum, and the target soil. The strength of the improved soil prepared by mixing is measured, the improved soil that exhibits the target strength is selected, and the content (mass%) of gypsum in the composition for determining the amount of gypsum used in the improved soil is solidified. This is a step of determining the amount (mass%) of the gypsum inside.
Examples of the strength measurement method of the improved soil include JIS A 1216 “Soil uniaxial compression test method”.

(E) Blending amount determination step of blast furnace slag and cement in the solidified material The step is a remaining amount obtained by subtracting the blending amount (mass%) of gypsum in the solidified material determined in the step (D) from 100% by mass. The content of blast furnace slag in the gypsum-determining base material determined in the step (C) with respect to the value (mass% × 0.01 value) and cement content (mass% × 0.01 value) Are values determined by multiplying each of them as a blending amount (mass%) of blast furnace slag and a blending quantity (mass%) of cement in the solidified material, respectively.
That is, in the process, the content of blast furnace slag in the base material for determining the amount of gypsum (mass%) and the content of cement (mass%) displayed as the total amount of the two components of blast furnace slag and cement being 100 mass%. ) Is converted to the blending amount (mass%) of blast furnace slag in the solidified material and the blending amount (mass%) of cement, expressed as the total amount of three components of blast furnace slag, cement, and gypsum. Process.
In addition, the compounding quantity of the blast furnace slag in the solidified material needs to be at least an amount sufficient to suppress elution of hexavalent chromium, and this amount is empirically estimated to be 15% by mass or more.
By mixing, weighing more than the amount of gypsum as determined through the process, cement, and blast furnace slag, it is possible to produce a solid reduction material. The metering and mixing can be performed using a normal metering device and a mixing device.

2. Solidified material The solidified material produced by using the production method of the present invention contains cement, blast furnace slag and gypsum in the blending amounts determined by the production method as essential components as described above. Hereinafter, the components will be described separately.

(1) Cement The cement is not particularly limited. For example, normal Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderately hot Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement such as Portland cement, blast furnace One or more types selected from mixed cements such as cement and silica cement, eco-cement and the like can be mentioned.

(2) Blast Furnace Slag The blast furnace slag is obtained by pulverizing granulated slag obtained by quenching and crushing molten slag produced as a by-product when producing pig iron in a blast furnace with water, or by slowly cooling and crushing. An example of the pulverized product of the slowly cooled slag obtained. Among these, since it is excellent in latent hydraulic property, it is preferably a pulverized product of granulated slag, and more preferably blast furnace granulated slag as defined in JIS A 6206.
Blaine specific surface area of the blast furnace slag is preferably 3000 cm ² / g or more, more preferably 3500 cm ² / g or more, more preferably 4000 cm ² / g or more. When the value is less than 3000 cm ² / g, the initial strength development of the solidified material is low. The upper limit of the value is preferably 15000 cm ² / g from the viewpoint of grinding cost.
The basicity of the blast furnace slag powder is preferably 1.7 or more, more preferably 1.8 or more, and still more preferably 1.9 or more. If the value is less than 1.7, the strength development property of the solidified material may be lowered. Moreover, the upper limit of this value is 3.0 from the ease of acquisition. The basicity is calculated using the following formula (4).
Basicity = [(CaO + MgO + Al ₂ O ₃ ) / SiO ₂ ] (4)
However, the chemical formula in the formula represents the content (% by mass) of the compound represented by the chemical formula in the blast furnace slag powder.

(3) Gypsum The gypsum is not particularly limited. For example, one type selected from dihydrate gypsum, flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, hydrofluoric gypsum, refined gypsum, hemihydrate gypsum, and anhydrous gypsum. The above is mentioned. Among these, anhydrous gypsum is preferable in terms of high strength development, and anhydrous gypsum obtained by heating dihydrate gypsum recovered from gypsum waste material can also be used.
Moreover, the specific surface area of the plaster of the gypsum is preferably 2000 to 12000 cm ² / g, more preferably 3000 to 8000 cm ² / g, further preferably 4000 to 6000 cm ² / g, and particularly preferably 4500 to 5500 cm ² / g. . When the value is out of the range of 2000 to 12000 cm ² / g, the strength development property of the solidified material may be lowered.

(4) Other optional constituents, etc. The solidified material produced by using the production method of the present invention includes silica fume, silica powder, steelmaking slag powder, clinker dust, etc. as optional constituents, and the strength development of the solidified material. Or the hexavalent chromium elution inhibitory effect may be included within a range that is not impaired. Here, the clinker dust is dust generated by extracting a part of the combustion gas from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone, and cooling the extracted combustion gas. The dust includes chlorine bypass dust recovered from the combustion gas by a chlorine bypass device attached to the cement kiln. Clinker dust has the effect of improving the early strength development of the solidified material.
The fineness of the solidified material produced using the production method of the present invention is a Blaine specific surface area, preferably 2000 to 10000 cm ² / g, more preferably 2500 to 8000 cm ² / g, and even more preferably 3000 to 6000 cm ² / g. is there. If this value is in the range of 2000 to 10000 cm ² / g, the solidified material is excellent in strength development and workability.

Hereinafter, although an example of the compounding design of the solidifying material in the production method of the present invention will be described, the present invention is not limited to this example.
1. Materials used (1) Cement Normal Portland cement (reference cement) shown in Table 1 and blast furnace cement type B (cement containing blast furnace slag) containing 40% by mass of blast furnace slag were used. All the cements are manufactured by Taiheiyo Cement.

(2) Gypsum Anhydrous gypsum (natural product) having a density of 2.85 g / cm ³ was used.
(3) ground granulated blast furnace slag,
Blast furnace slag fine powder (manufactured by Sment Kanto Co., Ltd.) having a density of 2.89 g / cm ³ and a brain specific surface area of 4380 cm ² / g was used.
(4) Target soil No. shown in Table 2 1-5 target soils were used. Among these, No. The target soils 1 to 4 were used to obtain a linear relationship between the allophane content in the target soil and the strength ratio (P ₁ / P ₂ ) of the improved soil. No. The target soil 5 is a mixture of soils collected from three different points at the site of solidification treatment, and the composition of the solidification material used for the solidification treatment of the soil at the site is determined by the formulation design used in the present invention. Used for.
The moisture content of the target soil in Table 2 conforms to JIS A 1203 “Test method for moisture content of soil”, and the loss on ignition conforms to JIS A 1226 “Test method for loss on ignition of soil”. The density was measured in accordance with JIS A 1210 “Soil compaction test method by tamping”.

2. Example of solidification material blending design In accordance with the procedures of (1) to (5) below, a solidification material blending design having the same strength development as ordinary Portland cement and having a high hexavalent chromium elution suppression effect was performed. .
(1) Measurement of the content of allophanes in the target soil According to the “acid-alkaline alternating dissolution method” described in the literature (i), the inclusion of allophanes in the five types of target soil shown in Table 2 The rate was measured. The results are shown in Table 2.

(2) Measurement of strength of improved soil Normal Portland cement (reference cement) and blast furnace cement type B (cement containing blast furnace slag) shown in Table 1 were respectively No. 1 to ³ target soils 1 to 4 were mixed with 100 kg powder to prepare improved soil. Next, in accordance with JIS A 1216 “Soil uniaxial compression test method”, the uniaxial compressive strength (hereinafter referred to as “strength”) of the improved soil was measured, and the strength of the improved soil using ordinary Portland cement ( calculated intensity ratio of the intensity of the modified soil with blast furnace cement B type _{(P 1)} with respect to P ₂₎ and _(P 1 / P _2). Table 2 shows the measurement results of the strength of the improved soil at the age of 7 days.

(3) Derivation of relational expression (1) No. 2 shown in Table 2 The content (mass%) of allophanes in the target soils 1 to 4 is the explanatory variable (x), No. 1 shown in Table 2. Relational expression (1) shown in FIG. 1 was obtained by regression analysis using the strength ratio (P ₁ / P ₂ ) of _{1 to} 4 days of age 7 (P ₁ / P ₂ ) as an objective variable.
_{P 1 / P 2 = -0.05x +} 1.85 ... (1)
As shown in FIG. 1, a high linear relationship correlation (coefficient of determination R ² is 0.9669) between the content and the intensity ratio of allophane such is established.
Further, as shown in FIG. 1, since the linear relationship is established at the age of 28 days (black circle) as well as the age of 7 days (white circle), the linear relationship in the present invention is established regardless of the age of the material. I understand.

(4) Induction of relational expression (2) Since a linear relationship is established between the strength of the improved soil and the content of blast furnace slag, blast furnace slag in the used blast furnace cement type B is shown on both sides of relational expression (1). The value obtained by multiplying the content ratio of 40 (mass%) is the blend amount of the blast furnace slag in the solidified material having a strength ratio of 1. The following formula is a relational expression (2) obtained by multiplying the left side of the relational expression (1) by 40.
s ₂ = −2.0x + 74 (2)

(5) Determination of the content of blast furnace slag and cement in the base material for determining the amount of gypsum In addition, allophanes in the target soil (No. 5) mixed with soil collected from three different points at the site of solidification treatment When the content ratio (28.0 mass%) is substituted for x in the relational expression (1), the strength ratio (P ₁ / P ₂ ) is 0.45, which is 1 or less. Therefore, the content ratio (28.0 mass%) %) Was substituted for x in the relational expression (2), and the content of blast furnace slag in the base material for determining the amount of gypsum was determined to be 18% by mass. Accordingly, the cement content in the base material for determining the amount of gypsum was determined to be 82% by mass by subtracting 18 from 100.

(6) Determination of the amount of gypsum in the solidified material In accordance with the above determination, for determining the amount of gypsum containing 18% by mass of blast furnace slag and 82% by mass of ordinary Portland cement (the content of gypsum is 2% by mass in terms of SO ₃ ). A substrate was prepared. Next, the content of SO _{3 in} the gypsum amount determining composition, which is a mixture of the gypsum amount determining base material and gypsum, is 4% by mass and 6% by mass, respectively, where the total of the composition is 100% by mass. , 8% by mass, and 10% by mass to prepare the composition. Note that the amount of SO ₃ in the composition, the total amount of SO ₃ derived from gypsum to be mixed to produce gypsum is originally contained in the ordinary Portland cement, and a solidifying material.
Next, the composition was prepared as After preparing improved soil by mixing 100 kg powder with 1 m ^{3 of} 5 target soil, measure the strength of the improved soil 7 days in accordance with JIS A 1216 “Soil uniaxial compression test method” did. The results are shown in Table 3.
And considering the strength values and material costs shown in Table 3, the blending amount of gypsum in the solidified material is 6% by mass in terms of SO ₃ (from 6% by mass gypsum derived from ordinary Portland cement (in terms of SO ₃₎ ) Was subtracted from 2% by mass, the amount of anhydrous gypsum was 4% by mass in terms of SO ₃ , so the anhydrous gypsum itself was determined to be 7% by mass). Next, the compounding amount of the base material for determining the amount of gypsum in the solidified material is 93% by mass, by subtracting the compounding amount (7% by mass) of the anhydrous gypsum from 100% by mass.
Then, the blending amount (93% by mass) of the base material for determining the amount of gypsum is multiplied by 82% by mass (0.82) of the normal Portland cement content and 18% by mass (0.18) of the blast furnace slag content. Thus, the blending amount of cement in the solidified material was determined to be 76% by mass, and the content of blast furnace slag was determined to be 17% by mass.

(7) Determination of solidification material addition amount Based on the determined blending amount, ordinary Portland cement, blast furnace slag and anhydrous gypsum were weighed and mixed to produce a solidification material.
Next, no. 5 to 1 m ³ of the target soil, the solidified material is mixed with 50 kg, 100 kg, 150 kg and 200 kg powders respectively to prepare improved soil, and the improved soil of 7 days of age in accordance with the provisions of JIS A 1216 The strength of was measured. The results are shown in Table 4.

Further, based on Table 4, the following expression (5) is obtained by regression analysis using the solidified material addition amount (kg / m ³ ) as the explanatory variable (h) and the strength (kN / m ² ) of the improved soil as the objective variable (s). Asked.
s = 9.18h-267.6 (5)
And No. Since the required strength of the improved soil was 1000 kN / m ² at the site where 5 target soils were collected, the value was substituted for s in the equation (5), and the amount of solidification material added was 140 kg / m ³ was determined.

(8) Strength of the modified soil using the target soil at the age of 28 days and elution amount of hexavalent chromium Based on the above determination, ordinary Portland cement is 76 mass%, blast furnace slag is 17 mass%, and anhydrous gypsum A solidified material containing 7% by mass (Example 1) was produced. An improved soil was prepared by mixing with 1 kg ^{3 of} 5 target soil with 140 kg powder, and the strength of the improved soil at the age of 28 days was measured in accordance with the JIS regulations. Moreover, the elution amount of hexavalent chromium from the improved soil of the age was measured in accordance with Environment Agency Notification No. 46.
For comparison, a cement composition (comparative example 1) in which anhydrous gypsum was added to ordinary Portland cement so that the gypsum content was 6% by mass in the same manner as in Example 1 in terms of SO ₃ , and blast furnace slag Using blast furnace slag-containing cement (Comparative Example 2) in which anhydrous gypsum was added to blast furnace cement type B having a content of 40% by mass, and the gypsum content was 6% by mass in the same manner as Example 1 in terms of SO ₃ The improved soil was prepared in the same manner as described above, and the strength of the improved soil and the elution amount of hexavalent chromium from the improved soil were measured. The results are shown in Table 5.

As shown in Table 5, although Comparative Example 1 has high strength, elution of hexavalent chromium was observed, and Comparative Example 2 had no elution of hexavalent chromium, but the strength was low and below the target strength (1000 kN / m ² ). ing. On the other hand, in Example 1, the strength is high and exceeds the target strength, and there is no elution of hexavalent chromium.
In addition, based on the above favorable results, it can be concluded that the induction method of the relational expression (2) is appropriate.

  Therefore, according to the method for producing a solidified material of the present invention, a solidified material suitable for the target soil in the field can be easily produced. In addition, the solidified material produced by the production method of the present invention has both high strength development and hexavalent chromium elution suppression effect.

Claims (1)

The manufacturing method of the solidification material which measures and mixes the cement, blast furnace slag, and gypsum of the compounding quantity determined through the following (A)-(E) process.
(A) Measure the following strengths P ₁ and P ₂ to obtain the following relational expression (1) between the content of allophanes in the soil and the strength ratio (P ₁ / P ₂ ): Induction step 1) P ₁ / P ₂ = ax + b (1)
(Where P ₁ is the strength of the improved soil using the blast furnace slag-containing cement, P ₂ is the strength of the improved soil using the reference cement, x is the content (% by mass) of allophanes in the target soil, a and b Represents a constant.)
(B) The following relational expression (2) is obtained by multiplying both sides of the relational expression (1) by the blast furnace slag content (s ₁ ) (mass%) in the blast furnace slag-containing cement. S ₂ = cx + d (2)
(Where s ₂ is the content (mass%) of blast furnace slag in the base material for determining the amount of gypsum whose strength ratio is 1, x is the content (mass%) of allophanes in the target soil, and c is a × s ₁ and d represent b × s _1. )
(C) For target soil having a strength ratio of 1 or less, based on the content of allophanes in the target soil, the relational expression (2) is used to determine the amount of blast furnace slag in the base material for gypsum amount determination. On the other hand, the content ratio (s ₁ ) of the blast furnace slag in the cement containing the blast furnace slag is determined for the target soil having a strength ratio (same as s ₂ ) and the strength ratio exceeds 1. Gypsum, which is determined as the content of blast furnace slag (same as s ₁ ) and determines the content of cement in the base material for determining the amount of gypsum using the content of the blast furnace slag and the following equation (3) Step of determining the content of blast furnace slag and cement in the base material for determining the amount of cement (mass%) in the base material for determining the amount of gypsum = 100-Content of the blast furnace slag in the base material for determining the amount of gypsum (mass) %) ...... (3)
(D) Measure the strength of the improved soil prepared by mixing the gypsum amount determining composition formed by mixing the gypsum amount determining base material and a plurality of levels of gypsum, and the target soil, Select the improved soil that expresses the target strength, and determine the content (mass%) of gypsum in the gypsum content determining composition used in the improved soil as the amount of gypsum (mass%) in the solidified material. Step (E) for determining the amount of gypsum in the solidified material (E) From the remaining value obtained by subtracting the amount (% by mass) of gypsum in the solidified material determined in the step (D), (C ) Value obtained by multiplying the content of blast furnace slag (mass% × 0.01) and the content of cement (mass% × 0.01) in the base material for determining the amount of gypsum determined in the process Respectively, blending amount of blast furnace slag in the solidified material (mass%) and blending amount of cement (mass) %) Is determined as, higher amount determining Engineering of blast furnace slag and cement in the solidifying material

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