JP4663999B2 - Soil neutral solidification material and soil neutral solidification improvement method - Google Patents

Description

  The present invention relates to a solidifying material for solidifying soil and an improved method for solidifying soil, and more particularly to a solidifying material for neutralizing and solidifying soil and an improved method for neutralizing and solidifying soil.

  Soft soil, such as construction mud and dredged mud from lakes and rivers, has been treated as industrial waste in the past, but in recent years it has been solidified using solidification materials from the viewpoint of environmental conservation and reduction of disposal costs. The improved soil is effectively used as paddy field raising, slope reinforcement, landfill soil, and the like. However, the improved soil produced from the lime-based solidified material or the cement-based solidified material has a strong alkalinity, and thus has a great limitation in use such as unsuitable for vegetation. Therefore, the improvement soil manufactured with the lime-based solidification material or the cement-type solidification material has been conventionally devised for neutralization. As such, a predetermined agent is added to the treated soil while stirring the treated soil in which the solidified material mainly composed of cement-based material or lime-based material is added to waste mud such as construction mud and dredged mud. Thus, there is a proposal of improved soil (refer to Patent Document 1) characterized in that a crystal coating is formed on the soil particles of the treated soil or the surface of the soil. On the other hand, there is a gypsum-based solidifying material that does not alkalinize soil. As such, when neutralized solidified material (see Patent Document 2) composed of 70 to 90% by weight of hemihydrate gypsum and 10 to 30% by weight of blast furnace slag, when the total solidified material is 100 parts by weight, 7 to 65 There is a proposal of a solidified material for hydrous soil (see Patent Document 3) in which the alumina cement is part by weight, 2 to 30 parts by weight of aluminum sulfate or iron sulfate, and the balance is gypsum, and the gypsum content is 20 parts by weight or more. is there.

However, the improved soil described in Patent Document 1 requires two steps of adding a solidifying material to the mud and once producing the treated soil, and then neutralizing the alkaline treated soil with the chemical, so work is required. There was a problem that it was cumbersome and burdensome in terms of human resources, cost, or construction period. Moreover, although the gypsum-based solidified material described in Patent Document 2 and Patent Document 3 has an advantage that the improved soil is not made alkaline, solidification with gypsum tends to cause a decrease in strength or re-mudging due to changes over time or rainwater. In addition, there is a problem that a large amount of addition is required so as to adversely affect the environment. Furthermore, as described in Patent Document 3, a solidifying material or cement-based solidifying material containing cement as a solidifying component has been used in recent years in consideration of the elution of hexavalent chromium of harmful substances into the soil, so that its use can be avoided. It has become. Therefore, a lime-based solidifying material that can neutralize and solidify the soil has been desired.
JP 2003-55948 A JP 09-263758 A Japanese Patent Laid-Open No. 10-273663

  This invention is made | formed in view of said situation, and makes it a subject to provide the lime type solidification material which neutralizes and solidifies soil by simple operation | work. Another object of the present invention is to provide a lime-based solidifying material that preferentially promotes soil solidification and neutralizes the soil. Furthermore, an object of the present invention is to provide an improved method for neutralizing and solidifying soil by a simple operation.

The present inventor has repeatedly studied to solve the above-described problems, and has completed the present invention.
That is, the present invention is quick lime, a solid neutralizing lime or heavy superphosphate lime that neutralizes the soil, dry soil, blast furnace slag, incinerated ash, silica gel, brick pulverized material, 1 and more solidifying auxiliaries selected from the group consisting of cement, Ri Do from the gypsum, in the combined weight of quicklime as neutralizing agent the whole weight of more than 50%, the balance is a solidification aid and gypsum The gist is neutral soil solidification material. Here, neutral includes substantially neutrality.

In the above invention, it may be 100 to 200 parts by weight with respect to the added amount of quicklime 100 parts by weight of medium flowable. A neutralizing agent such as this may be as granular. In here, and is solidified aid, silica (SiO ₂₎ and / or complement the setting reaction by quick lime by feeding the alumina _(Al 2 _{O 3),} it refers to a substance that promotes.

  The gist is a method for improving soil neutralization by treating soil with any of the above-mentioned soil neutralizing agents.

  The gist is a soil neutralization improving method in which soil is treated with any of the above-described soil neutralizing agents and the treated soil is brought into contact with air or carbon dioxide. In the present invention, the treated soil may be contacted with air or carbon dioxide while stirring.

  Since the soil neutral solidification material of the present invention can be neutralized and solidified by only a simple operation of adding to and mixing with the soil, it is advantageous in terms of personnel, cost, or construction period. Moreover, since the soil neutralization solidification material of this invention advances the solidification of soil preferentially and neutralizes soil, it can ensure the intensity | strength of improved soil enough and can neutralize. Furthermore, the soil neutralization improving method of the present invention can neutralize and solidify the soil only with a simple operation.

  Commercially available lime can be used without particular limitation, but to promote the solidification reaction of the soil contributed by the calcium hydroxide produced by the hydration reaction of quicklime, and to promote the neutralization reaction of the soil Is preferably in the form of fine powder, more preferably 100 mesh or less.

  Since the neutralizing agent is in a solid state, calcium hydroxide can be neutralized after being mixed with soil as a solidifying material. When neutralization reaction of calcium hydroxide proceeds simultaneously with mixing of neutralizer with quicklime, ettringite reaction in which calcium hydroxide reacts with alumina, gypsum and water in soil and calcium hydroxide reacts with silica and alumina in soil This is because the progress of the pozzolanic reaction is insufficient, and as a result, the consolidation of the soil particles of the improved soil is insufficient, and the strength development is reduced. Examples of such a neutralizing agent include a solid acid and a salt that becomes acidic in an aqueous solution. Of these, lime superphosphate, lime heavy superphosphate or aluminum sulfate is preferred, and any one or more of these can be used in combination. This is because superphosphate, heavy superphosphate, or aluminum sulfate undergoes a neutralization reaction over a period of one week to one month, and thus has little influence on the strength expression of the improved soil.

  The amount of superphosphate, heavy superphosphate or aluminum sulfate can be increased or decreased in consideration of the curing period of the improved soil solidified by the soil neutral solidifying material, but is usually 100 per 100 parts by weight of quicklime. -200 weight part is preferable. If the amount is less than 100 parts by weight, there is a possibility that a sufficient neutralization reaction cannot be performed. If the amount is more than 200 parts by weight, the load on the environment increases.

  The neutralizing agent is preferably controlled so as to delay the neutralization reaction until the described ettringite reaction or pozzolanic reaction proceeds to some extent after mixing with the soil. This is because the solidification of the soil with quicklime is performed by the ettringite reaction progressing early in the alkaline atmosphere and the pozzolanic reaction progressing with time, so that it is not preferable that the neutralization reaction proceed early. This neutralizer preferentially advances the solidification reaction of the soil, while neutralizing excess calcium hydroxide that does not contribute to the solidification reaction that causes the alkalinization of the soil. This is because the load on the environment can be reduced by reducing the amount added. As such a neutralizing agent, a granular neutralizing agent is preferable. While the powdery neutralizer has a large surface area and may neutralize calcium hydroxide that should contribute to the solidification reaction, the granular neutralizer has a smaller surface area than the powdery one, This is because the neutralization reaction proceeds gradually. The average particle diameter of the granular neutralizer is preferably 1 mm or more. This is because if the average particle size is smaller than 1 mm, the neutralization reaction cannot be sufficiently controlled. When there is no time for curing the improved soil, the use of a finer neutralizing agent makes it possible to neutralize the improved soil at an early stage, although the amount of solidifying material used is small and excessive.

  The soil neutral solidification material of the present invention can contain a solidification aid and gypsum. Examples of such a solidification aid include one or more selected from the group consisting of dry soil, blast furnace slag, incineration ash, silica gel, brick pulverized material, and cement. Dry soil is mined from common dry soil such as mackerel, dry clay (kaolinite, pyrophyllite, porcelain stone, sericite, shale, mudstone, Terrarossa, loam, etc.), Kira clay, limestone and crushed stone Fine clay (dried product of washed cake), pulverized pumice, etc. can be exemplified. Examples of the blast furnace slag include rapidly cooled slag, granulated slag, and slowly cooled slag. Examples of the incineration ash include sewage sludge incineration ash, incineration ash of soybean meal generated during oil production, paper sludge incineration ash, incineration ash of soot sludge and other waste, fly ash, clinker ash, and the like. Among these, dry clay, incineration ash, or blast furnace slag is preferable. Moreover, it is preferable to avoid using cement because it contains hexavalent chromium and has a risk of elution. The gypsum is preferably anhydrous gypsum. This is because the gypsum hydrate starts the hydration reaction of quicklime when it is mixed with other components of the soil neutral solidified material. The proportion of the solidification aid and gypsum is preferably the balance when the combined weight of quicklime and neutralizing agent is 50% or more of the total weight. This is because if the combined weight of quicklime and neutralizing agent is not 50% or more of the total weight, solidification and neutralization of the soil cannot be achieved in a good balance.

  The soil neutralized solidified material of the present invention can be prepared by uniformly mixing the quick lime, neutralizing agent, solidifying aid, gypsum and the like described above using a known mixing device such as a mixer.

  Next, the soil neutralization improving method of the present invention will be described. The soil neutral solidifying material of the present invention is added to mud such as dredged soil in lakes and rivers and mixed thoroughly. In that case, efficient mixing can be performed by using a known apparatus such as a backhoe or a stabilizer. After mixing, the soil is neutralized and solidified by curing for a predetermined period of time. As described above, the soil neutralization improving method of the present invention can be performed by a simple operation of only one step of adding and mixing the soil neutralization material to the mud. In addition, lime superphosphate, lime heavy superphosphate or aluminum sulfate tends to promote the carbonation reaction of calcium hydroxide, and when there is time to cure, the improved soil is brought into contact with air or carbon dioxide. The soil can be neutralized more efficiently by the carbonation of calcium oxide or calcium hydroxide. By using this neutralization by carbonation together, the blending amount of the neutralizing agent can be reduced and the material cost can be reduced. In addition, when the improved soil is brought into contact with air or carbon dioxide, the improved soil is preferably stirred. This is because neutralization can be performed evenly over the improved soil. The soil neutral solidification material of the present invention is particularly suitable for soft soil such as dredged soil and construction mud.

EXAMPLES Next, although an Example is given and this invention is demonstrated, this invention is not restrict | limited to a following example.

Examples 1 to 8 are soil neutralization solidified materials according to the present invention prepared by combining the components at the blending ratios shown in Table 1. Moreover, Comparative Example 1 and Comparative Example 2 are lime-based solidified materials with no neutralizer added, and Comparative Example 3 is a gypsum-based solidified material with no neutralizer added. These Examples and Comparative Examples were added to the mud, and the neutralization and solidification of the solidified material were evaluated by the presence of the pH test, the corn index test, and the re-mudification. In addition, the solidification auxiliary A in Table 1 is SiO ₂ 61%, Al ₂ O ₃ 29%, Fe ₂ O ₃ 4%, CaO ₃ %, SO ₃ 1%, ig.loss and a trace component 2% (weight%). Incinerated ash containing, solidified material B is SiO ₂ 30%, Al ₂ O ₃ 25%, Fe ₂ O ₃ 10%, CaO 25%, MgO 5%, SO ₃ 2%, ig.loss and trace component 3% (% by weight) ), Solidified material C is SiO ₂ 32%, Al ₂ O ₃ 19%, Fe ₂ O ₃ 1%, CaO 41%, MgO 5%, SO ₃ 1%, ig.loss and trace components 1% (weight) %) Blast furnace slag. Moreover, the compounding ratio of each component in Table 1 is parts by weight.

The properties of the tested mud are as follows.
Water content of 159% wet density: 1.27 g / cm ^3, dry density: 0.49 g / cm ³
pH: 5.2, uniaxial compressive strength: 12 kN / m ²

  The pH test was performed as follows. A mixed soil obtained by mixing 120 g of each of the solidification materials of Examples and Comparative Examples with respect to 1.27 kg of the above mud soil was put into a lump in a plastic bag so as to avoid contact with air (hereinafter, sealed) And soiled with a stainless bat (hereinafter referred to as an open system) for a predetermined period (1 week, 6 weeks) and used as sample soil. The pH measurement method is based on the Japan Geotechnical Society standard “pH test method for soil suspension” (JGS-0211-2000), and the moisture content of the sample soil is determined in advance by the Japanese Industrial Standard “Soil moisture content test method” ( JIS A 1203: 1999), the sample soil is collected based on the water content ratio so that the dry mass of the sample is 30 g, and the mass of water (including water in the sample) relative to the dry weight Water was added so that the ratio was 5 to prepare a suspension. This suspension is allowed to stand for 1 hour and stirred immediately before measurement to obtain a sample solution. The electrode of a glass electrode type hydrogen ion concentration meter (HM-12P, manufactured by Toa DDK) is immersed in this sample solution to adjust the pH. Was measured.

The cone index test was conducted as follows. 50 g, 100 g, and 150 g of each solidified material of Examples 3, 5, and 8 and Comparative Examples 1 to 3 per 1.27 kg of the mud were added and mixed to obtain sample soil. In accordance with JIS A1228, this sample soil was tamped into a mold having a diameter of 10 cm to prepare a specimen, which was cured in the air for 3 days, and the cone index was measured. The amount of solidification material added to obtain a cone index of 500 kN / m ² was calculated from the obtained data. In addition, the unit of the addition amount of a solidification material is kg / m < ³ >.

  The presence or absence of remudging was evaluated as follows. The mixed soil obtained by mixing 120 g of each of the solidification materials of Examples and Comparative Examples with respect to 1.27 kg of the above mud soil was filled in a mold having a diameter of 5 cm and a height of 10 cm, solidified, and then cured in the atmosphere for one week. A specimen was prepared. The obtained specimen was taken out of the mold, immersed in 2 L of water, and then whether or not it was re-mudged was evaluated according to whether the shape was maintained for 3 days or collapsed within 3 days.

As shown in Table 1, the pH of the soil was neutralized in all examples with a lower value than the comparative example. Further, in the examples, even when the pH was high in the sealed system, the pH was low in the open system, and all of the allowable limit pH 8.6 or less of the hydrogen ion concentration (pH) defined by the Water Pollution Control Law was satisfied. . In Examples using superphosphate lime as a neutralizing agent, the pH of the granular one was slightly lower than that of the powdered one (Example 1, Example 2 and Example 3 and Example). (See Example 5). In addition, a cone index of 500 kN / m ² could be obtained with a smaller amount of the granular material than that of the powdered material (see Example 3 and Example 5). Although the gypsum-based solidified material of Comparative Example 3 was added in a large amount to obtain a corn index of 500 kN / m ² , the soil strength was weak and re-mudification was observed.

Claims (6)

From the group consisting of quicklime, solid neutralizing lime or heavy superphosphate lime that neutralizes the soil, dry soil, blast furnace slag, incineration ash, silica gel, brick ground, cement 1 and more solidifying auxiliaries chosen, Ri Do from the gypsum, the combined weight of quicklime as neutralizing agent in the total weight of 50% or more, soil neutral solidifying material balance being solidified aid and gypsum. 2. The soil neutralized solidified material according to claim 1 , wherein the addition amount of the neutralizing agent is 100 to 200 parts by weight with respect to 100 parts by weight of quicklime. The neutralizing agent for soil according to claim 1 or 2 , wherein the neutralizing agent is granular. The soil neutralization improvement method which processes soil with the soil neutralization solidification material in any one of Claims 1-3 . The soil neutralization improvement method which processes soil with the soil neutral solidification material in any one of Claims 1-3 , and makes this treatment soil contact with air or a carbon dioxide. The method for improving soil neutralization according to claim 5 , wherein the treated soil is brought into contact with air or carbon dioxide while stirring.