Soil improvement material

Abstract

To provide a soil improvement material that exhibits suppressed pH and superior permeability.SOLUTION: A soil improvement material characterized by comprising a compound containing amorphous calcium silicate and an alkali activator, wherein the alkali activator is generated from calcium chloride and an alkali metal hydroxide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a suspension-based ground improvement material. [Background technology]

[0002] Various ground improvement materials are used for ground improvement, but from the viewpoint of solidification strength, suspension-based ground improvement materials using cement, etc. tend to be preferred. Suspension-based ground improvement materials include fine particle cement that utilizes the hydration hardening of Portland cement, and compounds containing fine particle amorphous calcium silicate, such as granulated blast furnace slag, which are hydrolyzed by adding an alkaline stimulant, thereby revealing the latent hydraulic properties of the granulated blast furnace slag.

[0003] Conventionally, sodium hydroxide has been used as an alkaline irritant, but this method not only poses a risk to the work, but also raises the pH to around 14, which can lead to problems such as alkaline contamination around the injection area and metal corrosion.

[0004] Therefore, the use of slaked lime as an alkaline irritant has been proposed (see, for example, Patent Document 1). With this method, the pH can be kept at around 12. However, slaked lime has low solubility in water and a tendency to agglomerate due to its large specific surface area. While the hardening time for sodium hydroxide is around 0.5 to 5 hours, the hardening time for slaked lime, which has low solubility, is as long as 3 to 12 hours, raising concerns that the improvement material may be washed away by groundwater flow. Furthermore, the apparent particle size increases due to agglomeration, which poses a problem of poor permeability into the ground. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5398096 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a soil improvement material that has a controlled pH and excellent permeability. [Means for solving the problem]

[0007] The means for solving the above problems are as follows. (Means described in claim 1) A compound containing amorphous calcium silicate and an alkaline stimulant are blended, The alkaline irritant is made of calcium chloride and alkali metal hydroxide. A ground improvement material characterized by:

[0008] (Means described in claim 2) The amorphous calcium silicate compound is finely divided granulated blast furnace slag,

[0009] The amount of amorphous calcium silicate blended is 100 to 500 kg / m 3 The amount of calcium chloride blended is 1 to 80 kg / m 3 The amount of the alkali metal hydroxide is 10 to 60 kg / m 3 That is,

[0010] The ground improvement material according to claim 1. [Effects of the Invention]

[0011] According to the present invention, a soil improvement material having a controlled pH and excellent permeability is obtained. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described. Note that this embodiment is an example of the present invention, and the scope of the present invention is not limited to the scope of this embodiment.

[0013] The ground improvement material of this embodiment is a compound containing amorphous calcium silicate and an alkaline stimulant. The alkaline stimulant is produced from calcium chloride and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide. For example, calcium chloride and sodium hydroxide react to precipitate slaked lime as shown in the following formula: (Formula)CaCl2+ 2NaOH → Ca(OH)2+ 2NaCl

[0014] The precipitated slaked lime has a smaller proportion of large particles than conventional slaked lime (for example, Patent Document 1). Therefore, it penetrates into the ground well. Of course, the pH is kept at around 12 to 13.5.

[0015] Calcium chloride and alkali metal hydroxide may be mixed separately when preparing the soil improvement material, or may be reacted in advance to form slaked lime.

[0016] Examples of compounds containing amorphous calcium silicate include finely divided granulated blast furnace slag and blast furnace cement. However, the use of finely divided granulated blast furnace slag is preferred. The use of finely divided granulated blast furnace slag has the advantage that it is less susceptible to quality changes such as agglomeration caused by absorbing moisture from the air during storage.

[0017] The blending amount of each substance is 100 to 500 kg / m of amorphous calcium silicate. 3 , calcium chloride content is 1 to 80 kg / m 3 , the amount of alkali metal hydroxide is 10 to 60 kg / m 3 The amount of amorphous calcium silicate blended is preferably 100 to 400 kg / m 3 , calcium chloride content is 5 to 60 kg / m 3 , the amount of alkali metal hydroxide is 10 to 50 kg / m 3 , and the blending amount of amorphous calcium silicate is 150 to 300 kg / m 3 , calcium chloride content is 15 to 50 kg / m 3, the amount of alkali metal hydroxide is 20 to 50 kg / m 3 It is particularly preferable that the amount of amorphous calcium silicate is 100 kg / m 3 On the other hand, if the amount of amorphous calcium silicate blended is less than 500 kg / m, the strength cannot be expected to be developed. 3 If the calcium chloride content exceeds 1 kg / m, the viscosity will increase too much and the setting time will become too fast, hindering penetration. 3 If the amount of calcium chloride is less than 80 kg / m, the amount of slaked lime produced will be small, and the alkaline stimulation caused by slaked lime will not be expected, and the pH lowering effect will be lost. 3 If the amount of alkali metal hydroxide exceeds 10 kg / m, the pH will drop too low, the alkaline stimulation will be limited, and strength cannot be expected. 3 If the amount of alkali metal hydroxide is less than 60 kg / m, the amount of alkali is too small and slaked lime is not precipitated sufficiently. 3 Above this level, the alkalinity is high and the pH lowering effect is limited. 3 This shows the ratio to the total. [Example]

[0018] Next, an embodiment of the present invention will be described. (Grain size test) The soil improvement materials were prepared using the mix proportions shown in Tables 1 and 2. Mixing was carried out for 3 minutes using a paddle blade mixer, the same type as mixers normally used on-site. Table 2 shows the mix proportions for materials other than ultrafine slag. The ultrafine slag used had a D50 of 4-5 μm and a maximum particle size of 10-20 μm. The results are shown in Table 3.

[0019] [Table 1]

[0020] [Table 2]

[0021] [Table 3]

[0022] According to this embodiment (Test Example 3), it is clear that the amount of large particles that inhibit permeability is far less than that of conventional slaked lime (Test Examples 1 and 2).

[0023] (pH test) The soil improvement materials were prepared using the mixing ratios shown in Tables 1 and 4. The same ultrafine particle slag as used in the particle size test was used. The results are shown in Table 5.

[0024] [Table 4]

[0025] [Table 5]

[0026] It can be seen that the pH decreases when calcium chloride is added. However, if too much calcium chloride is added, the strength may become insufficient.

[0027] (particle size distribution) The particle size distribution of slaked lime was measured using IPA as the dispersion medium (particle size distribution measurement by ultrasonic dispersion). The results are shown in Table 6.

[0028] [Table 6]

[0029] Under the ideal conditions of IPA-ultrasonic dispersion, the ultrafine slaked lime of this form has a small average particle size and almost no large particles. On the other hand, when dispersed by mixing in water containing a dispersant, which is commonly used, the particles aggregate and the apparent particle size becomes large. [Industrial Applicability]

[0030] The present invention can be used as a ground improvement material.

Claims

1. A compound containing amorphous calcium silicate and an alkaline stimulant are blended, The alkaline irritant is made of calcium chloride and alkali metal hydroxide. A ground improvement material characterized by:

2. The amorphous calcium silicate compound is finely divided granulated blast furnace slag, The amount of amorphous calcium silicate blended is 100 to 500 kg / m ３ The amount of calcium chloride blended is 1 to 80 kg / m ３ , the amount of the alkali metal hydroxide is 10 to 60 kg / m ３ That is, The ground improvement material according to claim 1.

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