Fluidized soil and method for producing fluidized soil

Abstract

To provide high-quality, high-strength fluidized soil that can reduce CO2 emissions. [Solution] A fluidized soil containing a special solidifying agent consisting of ordinary Portland cement and blast furnace slag, wherein when the total amount of ordinary Portland cement and blast furnace slag contained in the special solidifying agent is 100% by mass, the mixing ratio of ordinary Portland cement in the special solidifying agent is 20-30% by mass, and the mixing ratio of blast furnace slag is 70-80% by mass.

Description

[Technical Field]

[0001] The present invention relates to fluidized soil, which is prepared by adding a special solidifying agent consisting of ordinary Portland cement and blast furnace slag to a prepared slurry made from construction-generated soil or construction sludge, and to a method for producing the fluidized soil. [Background technology]

[0002] Fluidized soil is known as a fluidized backfill material obtained by treating construction by-products such as construction soil and construction sludge (see, for example, Patent Document 1). This fluidized soil can be used particularly well for backfilling in places where compaction is difficult.

[0003] Traditionally, fluidized soil has been produced by adding ordinary Portland cement or a cement-based solidifying agent to a prepared slurry made from raw materials such as construction waste soil or construction sludge. Specifically, blast furnace cement type B is primarily used as the cement-based solidifying agent. Figure 4 is a conceptual diagram showing the components of blast furnace cement type B, a solidifying agent used in conventional fluidized soil.

[0004] According to Figure 4, when the total amount of ordinary Portland cement and blast furnace slag contained in blast furnace cement type B is set to 100% by mass, the mixing ratio of ordinary Portland cement in blast furnace cement type B is 55-60% by mass, and the mixing ratio of blast furnace slag is 40-45% by mass. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-336145 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, if ordinary Portland cement or cement-based solidifying agents containing a large amount of ordinary Portland cement are added to the prepared slurry, as is done with conventional fluidized soil treatment, the amount of CO2 emissions generated during the production of ordinary Portland cement tends to increase, which is inconsistent with recent policies toward a decarbonized society.

[0007] Furthermore, there was a problem with the low strength of fluidized soil treated with ordinary Portland cement or cement-based solidifying agents containing a large amount of ordinary Portland cement. The objective of the present invention is to provide high-quality fluidized soil that can reduce CO2 emissions and has high strength. [Means for solving the problem]

[0008] The fluidized soil of the present invention A fluidized soil containing a special solidifying agent consisting of ordinary Portland cement and blast furnace slag, When the total amount of ordinary Portland cement and blast furnace slag contained in the special solidification material is set to 100% by mass, the mixing ratio of ordinary Portland cement in the special solidification material is 20 to 30% by mass, and the mixing ratio of blast furnace slag is 70 to 80% by mass.

[0009] In other words, by setting the mixing ratio of the special solidifying agent to 20-30% by mass of ordinary Portland cement and 70-80% by mass of blast furnace slag, it is possible to reduce CO2 emissions and provide high-quality, high-strength fluidized soil.

[0010] The method for producing fluidized soil according to the present invention is A mixing process for producing material soil by mixing raw materials consisting of construction excavated soil or construction sludge with water or muddy water and ordinary Portland cement. A screening step to obtain adjusted slurry by screening the material soil obtained in the above mixing step, A cement milk manufacturing process in which water and the above-mentioned special solidifying agent are mixed to produce cement milk. A stirring step of stirring the adjusted muddy water obtained by the screening step and the cement milk obtained by the cement milk production step characterized by including the above.

[0011] In this way, by going through the cement milk production step of mixing water and a special solidifying material to produce cement milk, the CO2 emissions can be reduced, and high-quality fluidized treated soil with high strength can be produced.

[0012] Moreover, the method for producing fluidized treated soil of the present invention the cement milk is a mixed composition in which 130 to 200 kg of ordinary Portland cement and 465 to 535 kg of blast furnace slag are mixed per 1 m , , ,

[0015] , , of water, characterized in that. That is, by setting the cement milk to such a mixing ratio, high-quality fluidized treated soil can be provided.

[0013] Moreover, the method for producing fluidized treated soil of the present invention in the mixing step, the water or muddy water mixed with the raw materials is 400 to 800 L per 1 m 3 of the raw materials, and the ordinary Portland cement mixed with the raw materials is 2 to 5 kg per 1 m 3 of the raw materials, characterized in that.

[0014] In this way, in the mixing step, by mixing an appropriate amount of water or muddy water, the moisture content of the material soil is adjusted. Also, by previously mixing ordinary Portland cement with the raw materials, the bleeding rate of the fluidized treated soil can be suppressed to less than 1%.

[0015] Moreover, the method for producing fluidized treated soil of the present invention the mixing time of water and the special solidifying material in the cement milk production step is 2 to 4 minutes, characterized in that. Thereby, bleeding of the cement milk can be suppressed, and the hardening efficiency of the blast furnace slag can be enhanced. [Effects of the Invention]

[0016] According to the invention of the present invention, it is possible to reduce CO2 emissions and provide high-quality fluidized soil with high strength. [Brief explanation of the drawing]

[0017] [Figure 1] This is a conceptual diagram showing the components of the special solidifying agent used in the fluidized soil according to the embodiment. [Figure 2] This is a flowchart showing the manufacturing process of fluidized soil according to the embodiment. [Figure 3] This table shows the results of uniaxial compression tests for fluidized soil according to the embodiment and conventional fluidized soil. [Figure 4] This is a conceptual diagram showing the components of blast furnace cement type B, which is used in conventional fluidized soil treatment. [Modes for carrying out the invention]

[0018] The fluidized soil according to an embodiment of the present invention will be described below with reference to the drawings. The fluidized soil according to the embodiment is manufactured by adding a special solidifying agent to a prepared slurry made from construction waste soil or construction sludge as raw materials. The special solidifying agent is a cement-based solidifying agent made by mixing ordinary Portland cement and blast furnace slag.

[0019] Figure 1 is a conceptual diagram showing the components of the special solidifying agent used in the fluidized soil according to the embodiment. According to Figure 1, when the total amount of ordinary Portland cement and blast furnace slag contained in the special solidifying agent is 100% by mass, the mixing ratio of ordinary Portland cement in the special solidifying agent is 20-30% by mass, and the mixing ratio of blast furnace slag is 70-80% by mass.

[0020] Thus, in the production of fluidized soil, the amount of ordinary Portland cement used can be reduced by using a special solidifying agent instead of blast furnace cement type B (see Figure 4).

[0021] Next, a method for producing fluidized soil according to the embodiment will be described. First, as shown in Figure 2, raw materials such as construction waste soil and construction sludge are collected by a transport vehicle and transported to a fluidized soil production plant (S1: transport process). Here, the construction sludge has a high water content, fine particles, and a muddy consistency, and its unconfined compressive strength at 28 days is approximately 5 N / cm². 2 The following applies. Furthermore, construction-generated soil refers to the soil and sand generated by construction work, and is a stable soil composed of a mixture of good quality sand, gravel, and clay.

[0022] The raw materials collected by the transport vehicle are sequentially fed into the receiving tank and stored in the receiving tank (S2: Receiving tank feeding process). Next, the required amount of raw materials is transferred from the receiving tank to the mixing tank, and a predetermined amount of water or slurry and ordinary Portland cement are supplied to the mixing tank. In this way, the water or slurry and ordinary Portland cement are mixed with the raw materials, and the material soil is produced (S3: Mixing process). Here, the amount of water or slurry mixed with the raw materials is 1 m of raw materials 3 The amount is 400-800L per unit, and the ordinary Portland cement mixed with the raw materials is 1m 3 Each unit contains 2-5 kg. Note that the water or muddy water used in the raw materials is 1 m of raw material. 3 A volume of 500-700L per unit is more preferable, and 550-650L is even more preferable. In addition, the ordinary Portland cement mixed into the raw materials is 1m 3 A weight of 3.0 to 4.5 kg per person is preferable.

[0023] In this way, the moisture content of the material soil is adjusted in the mixing process (S3) by mixing in an appropriate amount of water or mud. In addition, by mixing ordinary Portland cement with the raw materials in advance, the bleeding rate of the fluidized soil can be suppressed to less than 1%. Furthermore, in the mixing process (S3), the pH of the material soil being produced is controlled. Specifically, the pH of the material soil is controlled to be between pH 10 and 12.

[0024] Next, screening is performed to remove large-sized impurities such as gravel by passing the material soil stored in the mixing tank through a mud screen (S4: Screening Step). Note that, for example, a mud screen with a particle size of 10 mm or less is used.

[0025] As a result, adjusted muddy water from which impurities have been removed from the material soil is produced, and the produced adjusted muddy water is stored in a sludge storage tank (S5: Sludge Storage Step). Next, water and special solidifying materials (ordinary Portland cement, blast furnace slag) are mixed in a mixing plant to produce cement milk (S6: Cement Milk Production Step). The cement milk is a mixed composition obtained by mixing 130 - 200 kg of ordinary Portland cement and 465 - 535 kg of blast furnace slag per 1 m 3 of water. Here, the ordinary Portland cement mixed in the cement milk is more preferably 150 - 180 kg, and even more preferably 160 - 170 kg, per 1 m 3 of water. Also, the blast furnace slag mixed in the cement milk is more preferably 485 - 515 kg, and even more preferably 495 - 500 kg, per 1 m 3 of water. Note that the water content rate of the cement milk is adjusted according to the outside air temperature of the season.

[0026] Also, the mixing time of water and the special solidifying materials is 2 - 4 minutes, which is 1 - 2 minutes longer than the 1 - 2 minutes in the conventional production of fluidized treated soil, and about 3 minutes is more preferable. Thus, in the cement milk production step (S6), by mixing for about 1 - 2 minutes more than in the conventional fluidized treated soil, bleeding of the cement milk can be suppressed and the hardening efficiency of the blast furnace slag can be enhanced.

[0027] Note that, as described above, in the mixing step (S3), when producing the material soil, ordinary Portland cement is supplied to the mixing tank, and such ordinary Portland cement is particularly useful when increasing the blending ratio of blast furnace slag in the cement milk production step (S6).

[0028] Next, the adjusted slurry stored in the sludge tank and the cement grout produced in the mixing plant are mixed in a mixing tank (S7: mixing step). This yields the fluidized soil according to the embodiment. In addition, in the mixing step (S7), the addition of a certain amount of cement grout to the adjusted slurry suppresses bleeding of the fluidized soil.

[0029] The fluidized soil is loaded onto transport vehicles and delivered to the destination (S8: Delivery Process). The delivered fluidized soil is transported to its destination and used as construction material for backfilling, etc. According to this embodiment of fluidized soil, CO2 emissions during the manufacturing process can be reduced compared to conventional fluidized soil.

[0030] In other words, in the manufacturing process of conventional fluidized soil, ordinary Portland cement or blast furnace cement type B is added to the prepared slurry. The CO2 emissions when ordinary Portland cement is produced are 758 kg-CO2 / t (according to LCI data from the Cement Association), and the CO2 emissions when blast furnace slag is produced are 26.5 kg-CO2 / t (according to the Japan Society of Civil Engineers).

[0031] Assuming the CO2 emissions described above, in the fluidized soil according to the embodiment, for example, if the special solidifying agent consists of 25% by mass of ordinary Portland cement and 75% by mass of blast furnace slag, the CO2 emissions will be approximately 210 kg-CO2 / t.

[0032] Therefore, according to the embodiment of fluidized soil, CO2 emissions during the manufacturing process can be reduced by approximately 72% compared to conventional fluidized soil. In other words, by recycling construction waste soil and sludge, we can contribute to building a resource-recycling society and help achieve the national policy of carbon neutrality by 2050.

[0033] Furthermore, in the embodiment of fluidized soil, by setting the mixing ratio of blast furnace slag in the special solidification agent to 70% by mass or more, the unconfined compressive strength (7 days, 28 days) can be efficiently secured, thereby reducing the amount of solidification agent used.

[0034] Furthermore, even when the special solidifying agent is added in an amount approximately 25% less by mass than conventional cement-based solidifying agents such as blast furnace cement type B, it can achieve the same unconfined compressive strength as conventional fluidized soil. Therefore, the amount of solidifying agent added during the manufacturing process of fluidized soil can be reduced, thereby lowering the cost of fluidized soil.

[0035] Furthermore, in the fluidized soil according to the embodiment, the strength of the fluidized soil can be adjusted by changing the mixing ratio of ordinary Portland cement and blast furnace slag in the special solidifying agent.

[0036] Furthermore, in the fluidized soil according to this embodiment, by using construction sludge as the main material, a high calcium content is maintained, and an alkaline atmosphere is preserved, thereby increasing the hardening efficiency of blast furnace slag. In addition, the ordinary Portland cement contained in the special solidification agent functions as an alkaline stimulant, effectively promoting the strength development of blast furnace slag, thus strengthening the strength development of the fluidized soil to which the special solidification agent has been added.

[0037] Furthermore, conventionally, blast furnace cement concrete, which uses blast furnace cement type B as a component, has problems such as low initial strength and a tendency to crack. Therefore, it was not considered possible to manufacture fluidized soil with a higher proportion of blast furnace slag than that of blast furnace cement type B. However, by deliberately adding a special solidifying agent with a high proportion of blast furnace slag to the prepared slurry, it is possible to achieve high-strength fluidized soil.

[0038] Furthermore, according to the method for producing fluidized soil in this embodiment, since cement milk is obtained by mixing water, ordinary Portland cement, and blast furnace slag in a mixing plant, fluidized soil can be produced without installing any special additional equipment in an existing manufacturing plant.

[0039] Furthermore, simply increasing the proportion of blast furnace slag in the special solidifying agent compared to conventional cement-based solidifying agents is not enough to suppress the bleeding rate of the fluidized soil to less than 1% (the standard value in the Tokyo Metropolitan Government Bureau of Construction's Civil Engineering Materials Specifications). However, in the fluidized soil according to the embodiment, by mixing ordinary Portland cement with the raw materials in advance during the mixing process (S3) prior to the mixing process (S7) in which cement milk containing the special solidifying agent is added to the adjusted slurry and stirred, the bleeding rate of the fluidized soil can be suppressed to less than 1%. [Examples]

[0040] [Example 1] The table shown in Figure 3 shows the results of uniaxial compression tests for fluidized soil according to the embodiment and conventional fluidized soil.

[0041] In this test, four samples of fluidized soil were prepared: Sample 1, Sample 2, Sample 3, and Sample 4. Samples 1-3 are fluidized soil samples according to the embodiment, while Sample 4 is a sample of conventional fluidized soil.

[0042] In producing Sample 1, construction sludge was first mixed with water and ordinary Portland cement to create a modified slurry with a specific gravity of 1.42 and a slump flow of 330 mm x 330 mm. A special solidifying agent was added as a cement-based solidifying agent and mixed homogeneously in a mixer to produce fluidized soil.

[0043] The amount of special solidifying agent to be added is 1 m³ of adjusted slurry. 3 The volume was 60 kg per sample (test mixing with adjusted slurry), and the specific gravity of sample 1-2 was 1.43. The slump flow of the manufactured fluidized soil was 200 mm x 200 mm, and the bleeding rate was 0.3%. The uniaxial compressive strength (7 days) of cylindrical sample 1 using the fluidized soil was 12.64 N / cm². 2The uniaxial compressive strength (28 days) is 50.21 N / cm². 2 That was the case.

[0044] The following describes only the differences in the manufacturing process of Sample 2, Sample 3, and Sample 4 compared to Sample 1.

[0045] In manufacturing Sample 2, the amount of special solidifying agent added was 1 m³ of adjusted slurry. 3 The volume was 80 kg per sample (test mixing with adjusted slurry), and the specific gravity of sample 2 was 1.44. The slump flow of the manufactured fluidized soil was 220 mm x 220 mm, and the bleeding rate was 0.3%. The unconfined compressive strength (7 days) of cylindrical sample 2 using the fluidized soil was 15.83 N / cm². 2 The uniaxial compressive strength (28 days) is 68.71 N / cm². 2 That was the case.

[0046] In manufacturing Sample 3, the amount of special solidifying agent added was 1 m³ of adjusted slurry. 3 The sample size was 100 kg (test mix with adjusted slurry), and the specific gravity of sample 3 was 1.45. The slump flow of the manufactured fluidized soil was 230 mm x 230 mm, and the bleeding rate was 0.4%. The unconfined compressive strength (7 days) of cylindrical sample 3 using this fluidized soil was 21.89 N / cm². 2 The uniaxial compressive strength (28 days) is 89.70 N / cm². 2 That was the case.

[0047] In producing Sample 4, blast furnace cement type B was added to the prepared slurry and mixed homogeneously in a mixer to produce conventional fluidized soil.

[0048] The mixing ratio for blast furnace cement type B is 1 m³ of adjusted slurry. 3 The weight was 80 kg per sample (actual machine test), and the specific gravity of sample 4 was 1.43. The slump flow of the manufactured fluidized soil was 240 mm x 240 mm, and the bleeding rate was 0.8%. The uniaxial compressive strength (7 days) of cylindrical sample 4 using the fluidized soil was 8.52 N / cm². 2 The uniaxial compressive strength (28 days) is 34.45 N / cm². 2 That was the case.

[0049] According to the Tokyo Metropolitan Government Bureau of Construction's Civil Engineering Materials Specifications, the standard values ​​for fluidized soil are a specific gravity of 1.35 to 1.5, a slump flow value of 180 to 300 mm, and a bleeding rate of less than 1%. Therefore, all of the above samples 1 to 4 satisfy these standard values.

[0050] According to the above-described embodiment, it can be seen that Sample 1, Sample 2, and Sample 3, which are fluidized soils according to the embodiment, exhibit 1.45 to 2.6 times the uniaxial compressive strength (7 days, 28 days) compared to Sample 4, a conventional fluidized soil that uses a regular cement-based solidifying agent, by using a special solidifying agent.

[0051] Furthermore, the fluidized soil according to the embodiment using the special solidifying agent has a higher unconfined compressive strength (7 days, 28 days) than conventional fluidized soil using ordinary cement-based solidifying agents, thus reducing the amount of special solidifying agent used when manufacturing the fluidized soil.

[0052] [Example 2] Table 1 shows the measurement results for slump flow, bleeding rate, and unconfined compressive strength (28 days) when the amount of ordinary Portland cement, a special solidifying agent, was kept constant and the amount of blast furnace slag was increased in the fluidized soil according to the embodiment.

[0053] [Table 1]

[0054] Table 1 shows that as the amount of blast furnace slag contained in the special solidification material increases, the slump flow of the fluidized soil decreases, while the bleeding rate and unconfined compressive strength (28 days) of the fluidized soil increase.

[0055] In other words, in the fluidized soil according to the embodiment, the unconfined compressive strength (28 days) can be adjusted by adjusting the mixing ratio of ordinary Portland cement and blast furnace slag contained in the special solidifying agent.

[0056] According to the Tokyo Metropolitan Government Bureau of Construction's Civil Engineering Materials Specifications, the quality standards for fluidized soil are a slump flow value of 180-300 mm and a bleeding rate of less than 1%. As shown in Table 1, the fluidized soil according to the embodiment meets these quality standards.

Claims

1. A fluidized soil containing a special solidifying agent consisting of ordinary Portland cement and blast furnace slag, Fluidized soil, characterized in that, when the total amount of ordinary Portland cement and blast furnace slag contained in the special solidification material is 100% by mass, the mixing ratio of ordinary Portland cement in the special solidification material is 20 to 30% by mass, and the mixing ratio of blast furnace slag is 70 to 80% by mass.

2. A method for producing fluidized soil as described in claim 1, A mixing process for producing material soil by mixing raw materials consisting of construction excavated soil or construction sludge with water or muddy water and ordinary Portland cement. A screening step to obtain adjusted slurry by screening the material soil obtained in the above mixing step, A cement milk manufacturing process for producing cement milk by mixing water with the special solidifying agent, A stirring step in which the prepared slurry obtained in the screening step and the cement milk obtained in the cement milk manufacturing step are stirred together. A method for producing fluidized soil, characterized by including the following:

3. The aforementioned cement grout is mixed with 1 m of water. 3 The method for producing fluidized soil according to claim 2, characterized in that the mixed composition is a mixture of 130 to 200 kg of ordinary Portland cement and 465 to 535 kg of blast furnace slag per unit.

4. In the aforementioned blending process, the water or muddy water blended with the raw materials is 1 m of the raw materials 3 The amount is 400 to 800 liters per unit, and the ordinary Portland cement mixed with the raw materials is 1 m of the raw materials. 3 A method for producing fluidized soil according to claim 2, characterized in that the amount is 2 to 5 kg per unit.

5. The method for producing fluidized soil according to claim 2, characterized in that the mixing time of water and the special solidifying agent in the cement milk manufacturing process is 2 to 4 minutes.

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