JP2001139948A - Ground improving agent and method for improving - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ground improving agent solidifying ground rigidly and economically preventing elution of hexavalent chromium from the solidified ground by a simple method. SOLUTION: This ground-improving agent is characterized by comprising a mixture of a cement-based solidifying agent and powder of coal or lignite. The coal is brown coal or anthracite. Blast-furnace slag, ferrous sulfate, quick lime or slaked lime can be included in the ground-improving agent. The method for its production comprises applying the cement-based solidifying agent including coal or lignite powder to soil or comprises adding the powder of coal or lignite to the cement-solidifying agent and mixing the resultant mixture with the soil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soil improvement method for mixing and solidifying a soil with a solidifying material containing cement.
In particular, while solidifying the ground,
The present invention relates to a soil improvement material and an improvement method for reducing the amount of elution of chromium (VI).

[0002]

2. Description of the Related Art Conventionally, when a road or a building is constructed on the ground composed of soft soil or dredged waste soil, these soils and the like are solidified with a solidifying material containing cement, and the necessary A ground improvement method has been implemented to secure the bearing capacity. Such a cement-based solidifying material contains cement such as Portland cement as one of its components. Normally, improved ground that has been solidified can be obtained by adding and mixing a cement-based solidifying agent to soil, but hexavalent chromium may be detected from such improved ground, albeit in a trace amount. If hexavalent chromium elutes, there is a concern about the problem of soil contamination. The cause of the detection of hexavalent chromium is that cement in the solidified material may contain a trace amount of hexavalent chromium, and it has been confirmed that some of the soil is eluted from the solidified treated soil.

[0003]

In view of the fact that the amount of hexavalent chromium eluted from the improved ground solidified in this way is extremely small, the present inventors attempted to prevent this elution. After various studies, the cement-based solidified material
It has been found that elution of hexavalent chromium from the solidified improved ground can be suppressed by adding coal or lignite powder to the soil, and the present invention has been accomplished. Therefore, a first problem to be solved by the present invention is to provide a ground improvement material that firmly solidifies the ground and prevents elution of hexavalent chromium from the improved ground. A second object of the present invention is to provide a ground improvement method that can economically prevent elution of hexavalent chromium from the improved ground with a simple method.

[0004]

The above object of the present invention is achieved by the following inventions.

[Claim 1] A ground improvement material comprising a mixture of a cement-based solidification material and a powder of coal or lignite. [2] The ground improvement material according to [1], wherein the coal is lignite or anthracite. [3] A ground improvement material according to claim 1 or 2, wherein the ground improvement material contains blast furnace slag powder, ferrous sulfate, quicklime or slaked lime. [Claim 4] In a soil improvement method for mixing and solidifying a cement-based solidifying material into soil, a cement-based solidifying material containing coal or lignite powder is used, or coal or lignite powder is added to the cement-based solidifying material. A ground improvement method characterized by using after mixing. [Claim 5] In claim 4, the cement-based solidifying material comprises:
Furthermore, a ground improvement method characterized by adding and mixing blast furnace slag powder, ferrous sulfate, quicklime or slaked lime. [6] The method for improving the ground according to [4] or [5], wherein the coal is lignite or anthracite.

The ground improvement material according to the first aspect comprises a mixture of a cement-based solidification material and a powder of coal or lignite, whereby sufficient solidification of the ground is maintained and hexavalent chromium from the improved ground is provided. Can be prevented from being eluted.

In the ground improvement material according to the second aspect, since the coal is lignite or anthracite, sufficient solidification of the ground can be maintained and elution of hexavalent chromium from the improved ground can be prevented. .

When the ground improvement material according to claim 1 or 2 contains blast furnace slag powder, ferrous sulfate, quick lime or slaked lime, sufficient strength of the ground can be obtained, and the ground from the improved ground can be obtained. Elution of hexavalent chromium can be further reduced.

In the ground improvement method according to the fourth aspect, wherein the cement-based solidifying material is mixed with the soil to solidify, the cement-based solidifying material containing coal or lignite powder is uniformly mixed because the cement-based solidifying material is mixed at the factory. Therefore, the construction can be carried out efficiently because it is only mixed with the soil on site. In addition, by adding and mixing coal or lignite powder to cement-based solidification material and using it, it is possible to directly mix coal or lignite powder with cement-based solidification material on site, so the mixing ratio can be changed depending on the type of soil etc. It has the effect of being able to do so.

[0010] According to a fifth aspect of the present invention, in the ground improvement method of the fourth aspect, the cement-based solidified material further comprises:
By adding and mixing the blast furnace slag powder, ferrous sulfate, quicklime or slaked lime, sufficient strength of the ground can be obtained during construction, and the elution of hexavalent chromium from the improved ground can be further reduced.

According to a sixth aspect of the present invention, in the ground improvement method according to the fourth or fifth aspect, since the coal is lignite or anthracite, sufficient solidification of the ground is maintained during construction. In addition, the elution of hexavalent chromium from the improved ground can be prevented.

[0012]

Embodiments of the present invention will be described below in detail. In the present invention, the cement-based solidifying material,
It is obtained by adding gypsum and other admixture materials to cement or cement, and is generally called a soil stabilizer.

The cement used in the present invention includes portland cement such as ordinary portland cement, early-strength portland cement and moderately heated portland cement, or mixed cement such as blast furnace cement, fly ash cement and silica cement. .

The cement-based solidifying material is gypsum,
When other admixtures are included, an alumina-based material is preferably used as the admixture. The ratio of gypsum and other admixtures is preferably 3 to 30% by weight based on the total amount of cement and cement.

In the present invention, lignite or anthracite is used as the coal, and the particle size of the coal or lignite powder used is preferably such that it can be sufficiently mixed with cement or cement-based solidifying material. 2000cm ² / g
As described above, it is particularly desirable to be 2,500 to 4000 cm / g.

In the present invention, the amount of coal or lignite used is not particularly limited, but the amount of coal or lignite is 10 parts by weight with respect to 100 parts by weight of the cement-based solidification material as described above.
It is desirable to use it in an amount of from 100 to 100 parts by weight, especially from 20 to 50 parts by weight. If this proportion is less than 5 parts by weight, the effect of preventing the dissolution of hexavalent chromium is small, and if it exceeds 100 parts by weight, the strength of the solidified material tends to decrease and the solidified material tends to be black, which is not preferable.

In the present invention, blast furnace slag powder, ferrous sulfate, quicklime or slaked lime may be used in combination with coal lignite. In this case, the amount of the blast furnace slag powder, ferrous sulfate, quicklime or slaked lime is not particularly limited, but the blast furnace slag powder is 5 to 150 parts by weight based on 100 parts by weight of the cement-based solidified material. And especially 20 to 1
00 parts by weight, and in the case of ferrous sulfate, 0.1 to
10 parts by weight, particularly preferably 1 to 5 parts by weight, and in the case of quicklime or slaked lime, 5 to 100 parts by weight, particularly preferably 20 to 80 parts by weight.

The blast furnace slag powder, ferrous sulfate and quick lime or slaked lime used in the present invention are added to the cement-based solidified material in the above-mentioned ranges, respectively. Elution of hexavalent chromium can be further reduced.

In order to carry out the method of the present invention, generally, a predetermined amount of coal, lignite or blast furnace slag powder, ferrous sulfate, quicklime, slaked lime is added to a commercially available cement-based solidified material and mixed. Or gypsum, if necessary for cement,
While mixing other admixtures, a predetermined amount of coal, lignite, lignite or blast furnace slag powder, ferrous sulfate, quicklime and slaked lime is added and mixed with the soft soil.
In this case, the mixing amount of soil improvement material including coal, lignite, lignite or blast furnace slag powder, ferrous sulfate, quicklime, slaked lime to the soil differs depending on the target soil and the method of adding the solidifying material or the mixing machine, but usually In this case, the range is 50 to 300 kg / m ³ .

(Function) In the soil improvement material of the present invention, solidification strength is developed by the formation of calcium silicate hydrate and calcium aluminate hydrate by cement, and hexavalent chromium is formed by adsorption by coal or lignite. Elution is prevented. In addition, by using the soil improvement material method of the present invention, on-site construction can be performed efficiently, and the compounding amount of the cement-based solidification material and coal or lignite can be changed according to the soil quality, and the soil can be optimally improved.

[0021]

The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Example] Ordinary Portland cement 90
Parts by weight and a mixture of 10 parts by weight of anhydrous gypsum powder, lignite (bashir coal, calorific value 5,820 kcal / k)
g), lignite (meal coal, from Thailand, calorific value 3,290 kca)
l / kg) and coal as anthracite (calorific value 8,500k
cal / kg) was pulverized so that the specific surface area became 3000 cm ² / g, and a mixture obtained at a ratio shown in Tables 1 and 2 was used as a solidifying material.

The test soil used was Kanto loam from Saitama Prefecture (wet density: 1.326 g / cm ³ , water content: 120.8%), which was mixed with the soil at a rate of 200 kg / m ³ and uniaxially compressed. Test specimen (diameter 50mm, height 100m
m) was molded and subjected to a 7-day-old uniaxial compression test. Further, a dissolution test of hexavalent chromium was performed in accordance with the Environment Agency Notification No. 46 method. The test results are shown in Tables 1 and 2.

[0024]

[Table 1] As is clear from Table 1, it can be seen that by mixing anthracite, lignite, and lignite, the elution amount of hexavalent chromium can be reduced to the environmental standard value (0.05 mg / L) or less without impairing the solidification strength.

[0025]

[Table 2] As is evident from Table 2, blast furnace slag powder, ferrous sulfate, quicklime or slaked lime can be added to lignite and used together.
The solidification strength is increased, and the solidification strength is not impaired.
It can be seen that the elution amount of valent chromium can be reduced to an environmental standard value (0.05 mg / L) or less.

[0026]

As described above, according to the present invention, the soil is solidified by the soil improvement material that is solidified by mixing the cement-based solidification material into the soil, and the elution of hexavalent chromium from the improved ground is achieved. Can be effectively prevented. Further, in the ground improvement material method of the present invention, by using a cement-based solidification material containing coal or lignite powder, the construction can be performed efficiently because it is only mixed with the soil on site. Also, after adding and mixing coal or lignite powder to cement-based solidification material, by using it, it is possible to perform on-site construction efficiently and change the compounding amount of cement-based solidification material and coal or lignite according to soil quality, Optimum soil improvement.

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Claims (6)

[Claims] 1. A ground improvement material comprising a mixture of a cement-based solidification material and coal or lignite powder. 2. The soil improvement material according to claim 1, wherein the coal is lignite or anthracite. 3. A ground improvement material according to claim 1 or 2, wherein the ground improvement material contains blast furnace slag powder, ferrous sulfate, quicklime or slaked lime. 4. A soil improvement method for mixing and solidifying a cement-based solidifying material in soil, wherein a cement-based solidifying material containing coal or lignite powder is used or coal or lignite powder is added to the cement-based solidifying material. A ground improvement method characterized by using after mixing. 5. The cement-based solidifying material according to claim 4,
Furthermore, a ground improvement method characterized by adding and mixing blast furnace slag powder, ferrous sulfate, quicklime or slaked lime. 6. The soil improvement method according to claim 4, wherein the coal is lignite or anthracite.