Soil conditioner and method for treating mud

Abstract

To provide a soil improving material suppressing the discharge amount of carbon dioxide.SOLUTION: The soil improving material is composed of a blast furnace slag fine powder and quick lime, and the mass ratio of the quick lime is 30% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a soil improvement agent and a method for treating mud. [Background technology]

[0002] Surplus soil generated at construction and civil engineering work sites is often transported outside using dump trucks. Some surplus soil has high fluidity and cannot be loaded onto a dump truck in its current state. Patent Document 1 describes a solidification treatment material that can be added to such surplus soil to reduce its fluidity. An example of the solidification treatment material contains cement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-121016 Summary of the Invention [Problem to be solved by the invention]

[0004] Since cement emits carbon dioxide during its production, there is a demand for soil improvement materials that reduce carbon dioxide emissions. [Means for solving the problem]

[0005] The soil improvement material of the present invention comprises ground granulated blast furnace slag and quicklime, and the mass ratio of quicklime is 30% or more. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a soil improvement material that reduces carbon dioxide emissions. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a graph showing the relationship between the water-powder ratio and the moisture content in Examples and Comparative Examples. [Figure 2]1 is a graph showing the change in water content over time in an example and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention will be explained below with reference to examples and comparative examples. Table 1 shows an overview of the soil and soil improvement materials used in Examples 1-2 and Comparative Examples 1-2, and the blending ratios of the soil improvement materials in Examples 1-2 and Comparative Examples 1-2. Clayey soil was used as the soil. Soil improvement material A used in Comparative Example 1 is a commercially available product, containing quicklime as the main component and cement blended therein. Soil improvement material B was created by the inventors by mixing multiple materials, and in both cases, ground granulated blast furnace slag was used instead of cement as the material forming the skeleton of the solidified body. Comparative Example 2 further contains anhydrous gypsum and quicklime. Examples 1 and 2 further contain quicklime, and the mass ratio (blending ratio) of ground granulated blast furnace slag to quicklime differs between Examples 1 and 2.

[0009] [Table 1]

[0010] Water was added to natural clayey soil and mixed to create three soil samples with different initial moisture contents. The moisture content was adjusted to initial moisture contents of 110%, 150%, and 200%. The soil samples were then mixed with soil improvement agent A or B (see Table 1) to create the samples of Examples 1-2 and Comparative Examples 1-2. The amount of soil improvement agent A or B added was varied to create three samples with different water-to-powder ratios (W / B) for each of Examples 1-2 and Comparative Examples 1-2. W / B refers to the mass ratio of water to soil improvement agent A or B when adding the soil improvement agent. The mass of each sample, M1, immediately after mixing and the mass of each sample, M2, one hour after mixing were measured. The samples were then heated and dried until the mass remained constant, and the mass of each sample, M3, was measured. The initial moisture content was calculated as (M1 - M3) / M3, and the moisture content one hour after mixing was calculated as (M2 - M3) / M3.

[0011] FIG. 1 and Table 2 show the relationship between W / B and moisture content for Examples 1-2 and Comparative Examples 1-2. The initial moisture content was the same for Examples 1-2 and Comparative Examples 1-2. The moisture content after 1 hour of mixing differed between Examples 1-2 and Comparative Examples 1-2, but the difference was not significant. For samples with an initial moisture content of 200%, the moisture content after 1 hour of mixing was lower in Examples 1 and 2 than in Comparative Example 1. There was not a significant difference in the moisture content after 1 hour of mixing between Examples 1 and 2, but the decrease in moisture content was greater in Example 1, which had a higher mass ratio of quicklime.

[0012] [Table 2]

[0013] Figure 2 and Table 3 show the change in moisture content over time for samples with an initial moisture content of 110% for Examples 1-2 and Comparative Examples 1-2 up to 4 hours after mixing. There was no significant difference in the overall trends between Examples 1-2 and Comparative Examples 1-2. To facilitate the transport of mud using a dump truck, it is desirable for the fluidity to decrease to a level that allows for transport within a short time after mixing. Therefore, it is important for the moisture content to decrease quickly after mixing. The moisture content decreased rapidly 0.1 hours (6 minutes) after mixing. The moisture content of Example 2 decreased slightly less than that of Comparative Example 1, but still decreased by approximately 15% compared to the initial moisture content. This is thought to be due to the evaporation of surrounding moisture due to the heat generated when the quicklime absorbs moisture. Although the moisture content of Example 1 and Comparative Example 2 was not measured 0.1 hours after mixing, it is thought to show similar trends to those of Example 2 and Comparative Example 1.

[0014] [Table 3]

[0015] The present invention is not limited to the above-described Examples 1 and 2. The soil improvement material of the present invention is preferably composed of ground granulated blast furnace slag and quicklime, with the mass ratio of quicklime being 30% or more (i.e., the mass ratio of ground granulated blast furnace slag being 70% or less). As described above, the heat generated when quicklime absorbs moisture evaporates the surrounding moisture, so the higher the mass ratio of quicklime, the lower the moisture content. Therefore, the upper limit of the mass ratio of quicklime may be any value less than 100%. For example, the mass ratio of ground granulated blast furnace slag may be 50% or more and 70% or less, and the mass ratio of quicklime may be 30% or more and 50% or less. The soil improvement material of the examples does not contain any components other than ground granulated blast furnace slag and quicklime, but may contain trace amounts of additives (e.g., 5% or less by mass). The additives are not particularly limited as long as they do not affect the moisture content (transportability by dump truck). That is, the soil improvement agent may have a composition containing ground granulated blast furnace slag and quicklime as the main components (for example, a total mass ratio of 95% or more but less than 100%). In this case, too, it is preferable that the mass ratio of quicklime is 30% or more (i.e., the mass ratio of ground granulated blast furnace slag is 65% or less). In one example, the mass ratio of ground granulated blast furnace slag may be 50% or more but 65% or less, and the mass ratio of quicklime may be 30% or more but 50% or less. Although the present invention is directed to clayey soil, it is also effective for volcanic ash clayey soil and sandy soil.

[0016] The soil improvement material of the present invention can be suitably used for improving the soil quality of surplus soil generated at construction and civil engineering sites. Surplus soil is generated, for example, during pile construction. When constructing piles, pile holes are first excavated in the ground, and soil containing drilling water and groundwater is recovered, so the recovered soil is often muddy and contains a large amount of moisture. When treating mud as industrial waste, it must be transported from the site by dump truck. However, if the mud is highly fluid and cannot maintain its shape, it is likely to fall off the dump truck during transportation. For this reason, cement-based soil improvement materials have traditionally been added to the mud to reduce its fluidity before transporting it.

[0017] The soil improvement material of the present invention can be used in the same way as these conventional soil improvement materials. Moreover, since the soil improvement material of the present invention is composed of ground granulated blast furnace slag and quicklime and does not use cement, it is possible to reduce the carbon dioxide emissions generated during cement production. Although quicklime emits carbon dioxide during production, the amount of carbon dioxide emitted during the production of ground granulated blast furnace slag is much less than that of cement. Specifically, ground granulated blast furnace slag is a by-product generated during the production of pig iron in a blast furnace, and the carbon dioxide emitted from the blast furnace is emitted during the production of pig iron. Therefore, the amount of carbon dioxide emitted is reduced compared to conventional soil improvement materials whose main component is cement.

[0018] The present invention is not limited to soil improvement agents. A method for treating mud, which includes adding a soil improvement agent to mud, is also within the scope of the present invention. In the method for treating mud, the soil improvement agent is composed of ground granulated blast furnace slag and quicklime, with the mass ratio of quicklime being 30% or more. Alternatively, the soil improvement agent may contain ground granulated blast furnace slag and quicklime as main components (for example, a total mass ratio of 95% or more but less than 100%), with the mass ratio of quicklime being 30% or more and the mass ratio of ground granulated blast furnace slag being 65% or less.

Claims

1. A soil improvement material comprising ground granulated blast furnace slag and quicklime, the mass ratio of which is 30% or more.

2. A method for treating mud, comprising adding to the mud a soil improvement material comprising ground granulated blast furnace slag and quicklime, the mass ratio of said quicklime being 30% or more.

3. 3. The method according to claim 2, wherein the mud is surplus soil generated during construction of piles.

4. 4. The method according to claim 2 or 3, wherein the mud is clayey soil.

5. A soil improvement material containing ground granulated blast furnace slag and quicklime in a mass ratio of 95% or more, the mass ratio of the quicklime being 30% or more.

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