Stabilizer for absorbent polymer modified soil and stabilization method of absorbent polymer modified soil

Abstract

To provide: a stabilizer for an absorbent polymer modified soil with which the absorbent polymer modified soil can be stabilized to enhance strength in a short term; and a stabilization method of an absorbent polymer modified soil.SOLUTION: A stabilizer for an absorbent polymer modified soil contains quicklime and polysaccharide thickener.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an absorbent polymer-modified soil solidification material and a method for solidifying absorbent polymer-modified soil. [Background technology]

[0002] A technique for adding and mixing a superabsorbent polymer (commonly known as SAP) to absorb water in wet soil and improve the soil quality is known (see, for example, Patent Document 1). The superabsorbent polymer absorbs water in an amount 100 to 1000 times its own weight, swells, and gels. A large amount of muddy soil, which was industrial waste generated after the Great East Japan Earthquake, has been treated using this technique. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2974215 Summary of the Invention [Problem to be solved by the invention]

[0004] In soil to which water-absorbent polymers have been added, the apparent moisture content decreases as excess water is absorbed by the water-absorbent polymer. However, the water-absorbent polymer-modified soil obtained in this way is very difficult to solidify. Due to the gelation of the water-absorbent polymer, the water-absorbent polymer-modified soil becomes soft and cannot be solidified even by compaction. In the case of solidification materials such as cement, the soil is solidified using the moisture in the soil, but the water-absorbent polymer removes the moisture necessary for solidification, so sufficient strength cannot be achieved. As a result, the strength of the water-absorbent polymer-modified soil cannot be increased, and it must be disposed of as industrial waste. There is a need to solidify the water-absorbent polymer-modified soil to increase its strength.

[0005] Therefore, an object of the present invention is to provide a water-absorbent polymer-modified soil solidification material and a method for solidifying water-absorbent polymer-modified soil that can solidify water-absorbent polymer-modified soil and increase its strength in a short period of time. [Means for solving the problem]

[0006] In order to achieve the above-mentioned objectives, the inventors conducted extensive research and discovered that by blending quicklime and thickening polysaccharides, a solidification material can be obtained that can increase the strength of absorbent polymer-modified soil in a short period of time, and thus completed the present invention.

[0007] That is, the present invention relates to an absorbent polymer-modified soil solidification material containing quicklime and a thickening polysaccharide.

[0008] In addition, the present invention is a method for improving the soil by mixing the above-mentioned absorbent polymer-modified soil solidification material with absorbent polymer-modified soil, and then improving the soil by a cone index of 400 kN / m. 2 This invention relates to a method for solidifying absorbent polymer-modified soil, characterized in that the above solidified soil is obtained. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a water-absorbent polymer-modified soil solidification material and a method for solidifying water-absorbent polymer-modified soil, which can solidify water-absorbent polymer-modified soil and increase its strength in a short period of time. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail.

[0011] The subject of the present invention is water-absorbent polymer-modified soil, which has been modified with a water-absorbent polymer. Water-absorbent polymer-modified soil is soil containing a water-absorbent polymer, and the water-absorbent polymer content is preferably 0.02 to 10 mass%. The soil modified with a water-absorbent polymer has a moisture content of about 20 to 40 mass%.

[0012] Examples of water-absorbing polymers include polyacrylic acid polymers (e.g., sodium polyacrylate), polymethacrylic acid polymers, polyvinyl acetate polymers, and polyvinyl alcohol polymers. Of these, the preferred polymer is sodium polyacrylate.

[0013] Water-absorbent polymer-modified soil can be prepared by adding a water-absorbent polymer to soil and mechanically mixing it with a kneader. If necessary, inorganic minerals selected from calcium carbonate, zeolite, bentonite, etc., may be added to the water-absorbent polymer to form a mixture. These ingredients have the effect of enhancing the soil-modifying effect. The mixture can be prepared using, for example, a general vertical mixer or horizontal mixer. By adding the water-absorbent polymer, excess moisture in the soil is absorbed by the water-absorbent polymer, resulting in water-absorbent polymer-modified soil.

[0014] The water-absorbent polymer-modified soil solidification material of the present invention (hereinafter simply referred to as the solidification material) is used to solidify such water-absorbent polymer-modified soil and contains quicklime and a thickening polysaccharide. Each component will be explained below.

[0015] In water-absorbent polymer-modified soil, water molecules are trapped within the mesh of the water-absorbent polymer, which is a network-like polymer. By trapping water molecules, the water-absorbent polymer expands its mesh and swells. In order to solidify water-absorbent polymer-modified soil containing such water-absorbent polymer, it is necessary to remove water molecules from the water-absorbent polymer that has absorbed and swollen, thereby irreversibly losing the water-absorbing function of the water-absorbent polymer. The solidifying material of the present invention has the effect of causing the absorbent polymer to release water and then irreversibly losing the water-absorbing function of the absorbent polymer.

[0016] Quicklime acts as a water absorption inhibitor that inhibits the water absorption function of the water-absorbent polymer, and also contributes to soil solidification. As quicklime, industrially available quicklime can be used. For example, quicklime with a median diameter (D 50The content of quicklime is preferably 40 to 90 mass %, more preferably 50 to 80 mass %, of the solidifying material of the present invention.

[0017] The thickening polysaccharide acts as a water absorbent that absorbs water released by the water-absorbent polymer due to quicklime. It is preferably composed of at least one of pentose and hexose. Examples of pentose include gum arabic, and examples of hexose include xanthan gum. Among these, cellulose is preferred. The content of the thickening polysaccharide in the solidifying material of the present invention is preferably 10 to 60% by mass, more preferably 20 to 50% by mass.

[0018] In addition to the above components, the solidifying material of the present invention can contain at least one metal salt selected from divalent metal salts and trivalent metal salts. Examples of metal salts include magnesium oxide, ferrous sulfate, calcium chloride, and aluminum sulfate. The metal salt acts to inhibit the water absorption function of the water-absorbent polymer. The content of the metal salt is preferably 60% by mass or less of the solidifying material of the present invention, and more preferably 10 to 20% by mass.

[0019] Furthermore, water-soluble cellulose such as CMC, polymer flocculants such as anionic polymers and cationic polymers, and plant-derived polymers such as lignin may be contained. The content of such polymers is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, of the solidifying material.

[0020] The solidifying material of the present invention can be prepared by blending quicklime, thickening polysaccharides, and, if necessary, metal salts in predetermined proportions, and mixing them uniformly using a general vertical mixer, horizontal mixer, or the like.

[0021] The solidification material of the present invention is added to the water-absorbent polymer-modified soil at a mass ratio of 1 to 10%, mixed, and immediately compacted. The solidification material may be added in two separate batches. Compaction can be carried out using general construction machinery such as a backhoe or roller. The strength of the solidified soil obtained after compaction can be evaluated by the cone index. The method for measuring the cone index will be described in detail later.

[0022] By using the solidification material of the present invention, the strength remains at 400kN / m even immediately after aging. 2 It was possible to obtain solidified soil with a cone index of 400kN / m or more, making it possible to increase the strength in a short period of time. 2 It is preferable that this is equal to or greater than this. In this specification, "immediately after ageing" refers to the time immediately after adding a solidifying agent to the water-absorbent polymer-modified soil, stirring and mixing the soil, and then compacting the soil.

[0023] Furthermore, when a mixture containing quicklime and thickening polysaccharides and metal salts are added to the water-absorbent polymer-modified soil, the pH of the soil after treatment can be kept close to neutral. A neutral pH is advantageous in that it prevents organic matter in the soil from converting to ammonia, thereby reducing the environmental impact. [Example]

[0024] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0025] <Preparation of solidification material> Using cellulose as a thickening polysaccharide, the solidifying materials of Examples 1 and 2 were prepared according to the formulations (mass%) shown in Table 1 below. In addition, quicklime was prepared as the solidifying material of Comparative Example 1, and blast furnace cement type B was prepared as the solidifying material of Comparative Example 2.

[0026] [Table 1]

[0027] The materials used here are as follows: Quicklime: (Ube Material Industries, Ltd.) Cellulose: (hydroxypropyl methylcellulose) Blast-furnace cement type B: (manufactured by UBE Mitsubishi Cement Corporation)

[0028] <Preparation of sample soil> The sample soil was prepared by mixing equal amounts of commercially available black soil, No. 7 silica sand, and clay (Tochi clay and Kasaoka clay), and adding water to adjust the moisture content and water content shown below to 37.0% and 27.0%, respectively. Moisture content = amount of water added / dry weight of soil x 100 Moisture content = amount of water added / (dry weight of soil + amount of water added) x 100

[0029] On the other hand, the following sodium polyacrylate was used as the water-absorbing polymer, and predetermined components were blended to prepare a mixture with a water-absorbing polymer content of 5% by mass. Sodium polyacrylate (manufactured by Sanyo Chemical Industries, Ltd.) 5 parts by mass Calcium carbonate (Ube Material Industries, Ltd.) 84.2 parts by mass Zeolite (manufactured by Zieglite Co., Ltd.) 10 parts by mass Anionic polymer flocculant (manufactured by SNF Co., Ltd.) 0.8 parts by mass

[0030] 3% by mass of the mixture was added to the sample soil, and the mixture was mechanically stirred in a kneader to obtain water-absorbent polymer-modified soil. The cone index and wet density of the obtained water-absorbent polymer-modified soil were measured by the following methods.

[0031] Cone index: According to JIS A 1228 (Cone index test method for compacted soil) Wet density: According to JIS A 1210 (Soil compaction test method by tamping) The cone index of the water-absorbent polymer-modified soil is 36 kN / m 3 and the wet density is 1.738 g / m 3 It was.

[0032] The solidification materials of the examples and comparative examples were added to water-absorbent polymer-modified soil, and solidification tests were conducted. The amount of solidification material added was 5% by mass of the water-absorbent polymer-modified soil. For the test, a predetermined amount of solidification material was added to the water-absorbent polymer-modified soil to obtain solidified soil. The cone index and wet strength were measured immediately after aging and after 7 days of aging, and the results are shown in Table 2 below.

[0033] [Table 2] *2000kN / m 3 That's it, manual penetration is not possible

[0034] As shown in Table 2 above, when the material age is 7 days, the cone index is 2000 kN / m regardless of whether the solidification material of the Example or Comparative Example is used. 3 The above solidified soil was obtained, but the cone index was 400kN / m immediately after aging. 3 Only the solidification material of the embodiment can produce the above solidified soil.

[0035] It has been confirmed that by using the water-absorbent polymer-modified soil solidification material of the present invention, it is possible to solidify the water-absorbent polymer-modified soil and increase its strength in a short period of time.

Claims

1. An absorbent polymer-modified soil solidification material containing quicklime and thickening polysaccharides.

2. 2. The absorbent polymer-modified soil solidification material according to claim 1, further comprising at least one metal salt selected from divalent metal salts and trivalent metal salts.

3. The absorbent polymer-modified soil solidification material according to claim 1 or 2, wherein the content of quicklime is 40 to 90 mass%.

4. 3. The absorbent polymer-modified soil solidification material according to claim 1, wherein the content of the thickening polysaccharide is 10 to 60% by mass.

5. 3. The absorbent polymer-modified soil solidification material according to claim 2, wherein the metal salt is selected from the group consisting of magnesium oxide, ferrous sulfate, calcium chloride, and aluminum sulfate.

6. 3. The absorbent polymer-modified soil solidification material according to claim 2, wherein the content of the metal salt is 60% by mass or less.

7. The absorbent polymer modified soil solidification material according to claim 1 is mixed with the absorbent polymer modified soil, and the cone index is 400 kN / m. ２ A method for solidifying absorbent polymer-modified soil, characterized by obtaining the above solidified soil.

8. 8. The method for solidifying absorbent polymer-modified soil according to claim 7, wherein the absorbent polymer is a polyacrylic acid-based polymer.

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