Soil cement and method for producing the same

Abstract

To provide soil cement and a method for producing the same, capable of suppressing deterioration of fluidity of the soil cement when dry ice is used.SOLUTION: A soil cement comprises a soil material, a cement-based solidifying material, water, and dry ice. The content of the dry ice is 5-10 mass% in terms of outer percentage based on the cement-based solidifying material. It is desirable that the soil material, the cement-based solidifying material, and the dry ice are mixed and dry-kneaded, and then water is added to the dry-kneaded material to perform main-kneading to produce the soil cement.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a soil cement and a method for producing the same. [Background technology]

[0002] Traditionally, earth retaining walls have been constructed on the ground as temporary structures for underground construction. In order to stop seepage in highly permeable ground, impermeable materials are sometimes used as the construction material for the earth retaining walls. Impermeable materials include steel sheet piles, steel pipe sheet piles, cast-in-place reinforced concrete, and soil cement. Soil cement is made up of soil, cement, and water, and is also used in ground improvement work and backfilling work.

[0003] On the other hand, cement compositions containing dry ice are known (see, for example, Patent Documents 1 and 2). By using dry ice, it is possible to fix a larger amount of carbon dioxide in the cement composition. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-18308 [Patent Document 2] Japanese Patent Publication No. 2022-131308 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when dry ice is used to immobilize more carbon dioxide in soil cement, the fluidity of the soil cement can decrease. For this reason, there has been a demand for technology that can suppress the decrease in fluidity of soil cement when dry ice is used.

[0006] The present invention has been made in consideration of the above, and aims to provide a soil cement and a method for manufacturing the same that can suppress the decrease in fluidity of soil cement when dry ice is used. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the soil cement of the present invention is a soil cement containing an earthen material, a cement-based solidification material, water, and dry ice, and is characterized in that the dry ice content is 5 to 10 mass% based on the cement-based solidification material.

[0008] Furthermore, the method for producing soil cement according to the present invention is a method for producing the above-mentioned soil cement, characterized in that the soil material, cement-based solidification material, and dry ice are mixed and dry-mixed, and then water is added to the dry-mixed material and the mixture is mixed to produce soil cement. [Effects of the Invention]

[0009] The soil cement of the present invention contains earthen material, cement-based solidification material, water, and dry ice, and the dry ice content is 5 to 10 mass% relative to the cement-based solidification material, thereby achieving the effect of suppressing the decrease in fluidity of the soil cement when dry ice is used.

[0010] Furthermore, according to the method for producing soil cement of the present invention, the soil cement described above is produced by mixing an earthen material, a cement-based solidification material, and dry ice and dry-mixing the mixture, and then adding water to the dry-mixed material and mixing it properly to produce soil cement, thereby achieving the effect of producing soil cement with reduced loss in fluidity. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic flow diagram showing an embodiment of the method for producing soil cement according to the present invention. [Figure 2] FIG. 2 is an explanatory diagram of the dry ice addition method. [Figure 3] FIG. 3 is a diagram showing the results of the slump flow test. [Figure 4] FIG. 4 shows the results of the bleeding test. [Figure 5] FIG. 5 shows the results of the compressive strength test. [Figure 6] FIG. 6 is a diagram showing an example of the relationship between the strength increase rate and the amount of dry ice added. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the soil cement and the method for producing the same according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments.

[0013] The soil cement according to the embodiment of the present invention contains a soil material, a cement-based solidification material, water, and dry ice. Examples of soil cement include fluidized soil, lean cement milk, cement-based ground improvement material, and cement-based earth retaining material.

[0014] The soil material may be a material containing sand and clay, or may be a material composed of either sand or clay. The cement-based solidification material is a solidification material composed of cement, and may be composed of, for example, ordinary Portland cement or blast furnace cement type B.

[0015] As described below, the dry ice content is preferably set at 5 to 10% by mass based on the cement-based solidification material. Furthermore, as described below, it is preferable to add dry ice in powder form with a particle size of 5 mm or less using the "pre-addition method (type a)." This prevents the fluidity of the soil cement from decreasing when dry ice is used.

[0016] Next, an example of the procedure for producing soil cement according to this embodiment will be described. As shown in FIG. 1, first, the target mix ratio for soil cement is set (Step S1). The mix ratio may be set to, for example, a basic mix (Base) such as that shown in Table 1 below, or another mix ratio is also acceptable. Next, the soil material, cement-based solidification material, and dry ice are mixed at the set mix ratio and dry-mixed (Step S2). Next, water is added to the dry-mixed material and the mixture is mixed properly to produce soil cement (Step S3). This allows for the production of soil cement with reduced fluidity.

[0017] (Verification of the effect of suppressing fluidity decline through blending tests) Next, we will explain the verification of the effect of suppressing the decrease in fluidity through a mix test using soil cement. In this verification, the slump flow (SF) was measured as an index of the fluidity of soil cement, and the change in SF over time was measured as an index of fluidity retention, to examine the effectiveness of suppressing the decline in fluidity.In addition, compressive strength (unconfined compressive strength) was measured as a property of soil cement.

[0018] The soil cement was prepared by mixing air-dried silica sand No. 7, clay (made by mixing Kibushi clay and kaolin clay in a mass ratio of 1:1), and water in a mass ratio of 4:1:2.15 with an adjusted muddy water, and a cement-based solidification material (addition amount of solidification material: 150 kg / m 3 The composition is composed of cement milk mixed with granular granular slag and water. Table 1 shows the basic mix (Base). The adjusting mud is a mixture of sand and clay (sample soil: soil material). Tap water was used for mixing. The cement-based solidification material was blast furnace cement type B (unit cement amount: 200 kg / m 3 The water content of the adjusted mud water and the water-cement ratio (W / C) of the cement milk were both set at 43%. The target strength of the soil-cement σ 28 (Compressive strength at 28 days) is 1.5N / mm 2 It was decided.

[0019] [Table 1]

[0020] Dry ice was used by placing dry ice plates in a plastic bag and crushing them with a wooden mallet to particles of 5 mm or less. The amount of dry ice added was determined based on the ratio of the cement addition amount C in the base mix in Table 1, and three cases were set: C x 5, 10, and 15 wt%, and the dry ice was mixed in proportion to the cement addition amount C.

[0021] As shown in Figure 2, two methods of adding dry ice were set: a "pre-addition method (type a)" and a "post-addition method (type b)." The pre-addition method (type a) corresponds to an embodiment of the present invention, in which soil, cement, and dry ice are dry-mixed, and then water is added for main mixing. The post-addition method (type b) is a method in which cement and water are mixed to make cement milk, while soil and water are mixed to make adjusted muddy water, and the cement milk, adjusted muddy water, and dry ice are then mixed.

[0022] Table 2 shows a list of mix conditions. The symbols in the mix names indicate the "dry ice addition method - base mix (Base) or dry ice addition amount." For example, the mix name "aC-10" for mix number 3 means that the dry ice addition method is Type a and the dry ice addition amount is 10 wt% relative to the cement addition amount C. Note that in the legends on the drawings, the symbols "C-number" are sometimes used, omitting the initial letters "a-" and "b-." For example, "C-10" means that the dry ice addition amount is 10 wt% relative to the cement addition amount C.

[0023] Tests were conducted on the soil cement mixes 1 to 8 in Table 2, and the test results are summarized in Figures 3 to 6. Test items included slump flow (SF), hydrogen ion concentration (pH), mixing temperature, slurry specific gravity, bleeding amount (1 day old), shear wave velocity (7 and 28 days old), and compressive strength (7 and 28 days old). Tests were conducted in accordance with JIS standards.

[0024] [Table 2]

[0025] Table 3 shows the physical properties immediately after mixing. Figure 3(1) shows the slump flow test results (average values). Figure 3(2) shows the relationship between the slump flow increase rate and the amount of dry ice added. Figure 4 shows the change in slump flow over time.

[0026] [Table 3]

[0027] As shown in Figure 3(2), when comparing the slump flow increase rate by dry ice addition method, it can be seen that the increase rate for Type A is greater than that for Type B. In particular, it can be seen that the increase rate is more significantly greater for Type A when the dry ice addition amount is 5 to 10 wt%. Therefore, to suppress the decrease in fluidity of soil cement, Type A is preferable, and it is even more preferable to add 5 to 10 wt% dry ice. In this way, the decrease in fluidity can be effectively suppressed and the fluidity can be improved.

[0028] As shown in Figure 4, when the amount of dry ice added is 5 to 10 wt%, the slump flow remains almost the same for the first 60 minutes after mixing as it was immediately after mixing. Therefore, with this type of mix, the fluidity of the soil cement can be maintained for about an hour.

[0029] Table 4 shows the test results for the amount of bleeding (1 day old).

[0030] [Table 4]

[0031] Table 5 shows the test results for compressive strength and shear wave velocity at 7 days old. Table 6 shows the test results for compressive strength and shear wave velocity at 28 days old. "No." in each table indicates the specimen number at the time of the compression test. Figure 5 shows the test results for compressive strength at 7 and 28 days old. Figure 6(1) shows the relationship between the strength increase rate and the amount of dry ice added.

[0032] [Table 5]

[0033] [Table 6]

[0034] As shown in Figure 5, when dry ice is added using Type A, the compressive strength is equal to or greater than that of the basic mix (Base) at each age. As shown in Figure 6 (1), the addition of dry ice results in a greater increase in compressive strength compared to when dry ice is not added.

[0035] As a result, this embodiment can prevent the decrease in fluidity of soil cement that occurs when dry ice is used. Furthermore, dry ice can improve fluidity without changing the water-cement ratio (W / C).

[0036] As described above, the soil cement of the present invention contains earthen material, cement-based solidification material, water, and dry ice, and the dry ice content is 5 to 10 mass% relative to the cement-based solidification material, thereby suppressing the decrease in fluidity of the soil cement that occurs when dry ice is used.

[0037] Furthermore, according to the method for producing soil cement of the present invention, the soil cement described above is produced by mixing earthen material, cement-based solidification material, and dry ice and dry-mixing them, and then adding water to the dry-mixed material and mixing it properly to produce soil cement, thereby producing soil cement with reduced reduction in fluidity.

[0038] The Sustainable Development Goals (SDGs) are 17 international goals adopted at the United Nations Summit in September 2015. The soil cement and its manufacturing method according to this embodiment can contribute to achieving one of the 17 SDGs, for example, goal 12, "Responsible Consumption and Production." [Industrial Applicability]

[0039] As described above, the soil cement and its manufacturing method according to the present invention are useful for soil cement used in retaining walls, etc., and are particularly suitable for suppressing the decrease in fluidity of soil cement when dry ice is used.

Claims

1. A soil cement containing a soil material, a cement-based solidification material, water, and dry ice, A soil cement characterized in that the dry ice content is 5 to 10 mass % relative to the cement-based solidification material.

2. A method for producing the soil cement of claim 1, This method for producing soil cement is characterized by mixing an earthen material, a cement-based solidifying material, and dry ice, dry-kneading the mixture, and then adding water to the dry-kneaded mixture and kneading it to produce soil cement.

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