Cement-based slurry composition and method for producing the same

Abstract

To provide a cement-based slurry composition containing calcium carbonate produced using carbon dioxide derived from exhaust gas as a raw material, and a method for producing the same, which can further enhance the contribution to reducing environmental impact. [Solution] A cement-based slurry composition used for ground improvement by mixing with soil, comprising at least a cement-based solidifying agent, light calcium carbonate F, and water W, without a dispersant, with a W / C (water-cement ratio) of 80% or more, and a light calcium carbonate F addition rate (ratio of the mass of light calcium carbonate F to the total mass of cement-based solidifying agent BB and light calcium carbonate F) in the range of 10 to 45%, with a bleeding rate of less than 5%.

Description

[Technical Field]

[0001] This invention relates to a cement-based slurry composition and a method for producing the same. [Background technology]

[0002] Conventionally, cement-based slurry compositions have been proposed and put into practical use for the purpose of ground improvement, which have sufficient fluidity during placement (when mixed with soil) and exhibit a predetermined strength (uniaxial compressive strength) after placement (see, for example, Patent Document 1).

[0003] However, the cement-based slurry compositions currently in practical use have the problem of having a large environmental impact because they use cement, which emits a large amount of carbon dioxide, a greenhouse gas, during manufacturing.

[0004] To address this problem, a cement-based slurry composition containing calcium carbonate produced using carbon dioxide derived from exhaust gas has been proposed (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 58-29374 [Patent Document 2] Japanese Patent Publication No. 2024-5883 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The cement-based slurry composition disclosed in Patent Document 2 contains calcium carbonate produced using carbon dioxide derived from exhaust gas as a raw material, and therefore contributes to reducing environmental impact, but it had the following problems. • It uses calcium carbonate and concrete waste as raw materials, resulting in a low carbon dioxide absorption rate per unit of raw material. • The large amount of by-products generated during the production of calcium carbonate places a significant environmental burden on the environment. In order for a cement-based slurry composition containing calcium carbonate to exhibit its intended performance, it is important to reliably disperse the calcium carbonate within the cement-based slurry composition, but a manufacturing method for achieving this has not yet been identified. • The resistance to material separation is unknown. • When the calcium carbonate addition rate exceeds 10%, the strength (uniaxial compressive strength) decreases.

[0007] The present invention aims to provide a cement-based slurry composition containing calcium carbonate produced using carbon dioxide derived from exhaust gas as a raw material, and a method for producing the same, which can further enhance the contribution to reducing environmental burden by resolving the problems of the above-mentioned cement-based slurry compositions for ground improvement. [Means for solving the problem]

[0008] To achieve the above objective, the cement-based slurry composition of the present invention is A cement-based slurry composition used by mixing with soil for ground improvement, It contains at least a cement-based solidifying agent, light calcium carbonate, and water, and does not contain a dispersant. The W / C ratio is 80% or higher, and the addition rate of light calcium carbonate (the ratio of the mass of light calcium carbonate to the total mass of cement-based solidifying agent and light calcium carbonate) is in the range of 10-45%. Within the enclosure, the breeding rate is less than 5%. It is characterized by the following:

[0009] In this case, the funnel viscosity flow time can be 50 s or less, and the viscosity measured by the vibrating viscometer can be 70 mPa·s.

[0010] Furthermore, the cement-based solidifying agent may be blast furnace cement type B or a hexavalent chromium elution-reducing cement-based solidifying agent with an SO3 content of 4.0 to 10.5%.

[0011] Further, the light calcium carbonate can be produced using carbide slurry and carbon dioxide derived from exhaust gas as raw materials.

[0012] Further, the amount of carbon dioxide fixation per 1 m of the cement-based slurry composition 3 can be 35 kg or more.

[0013] Further, the method for producing the cement-based slurry composition of the present invention is a method for producing a cement-based slurry composition that is used by being stirred with soil for ground improvement, contains at least a cement-based solidifying material, light calcium carbonate, and water, and does not contain a dispersant, using a turbine blade, while stirring water with the tip-side peripheral speed of the turbine blade being 2.9 m / s or more, adding the cement-based solidifying material and light calcium carbonate in this order, and stirring for 3 minutes or more characterized by this.

Advantages of the Invention

[0014] According to the cement-based slurry composition and the method for producing the same of the present invention, the problems of the cement-based slurry composition for the purpose of ground improvement can be solved, and the contribution degree to the reduction of the environmental load can be further enhanced.

Brief Description of the Drawings

[0015] [Figure 1] It is an explanatory diagram showing the production process of light calcium carbonate. [[ID=3,4]] [Figure 2] It is a graph showing the results of the funnel viscosity flow-down time test. [Figure 3] It is a photograph showing the results of the bleeding test of the cement-based slurry composition. [Figure 4] It is an explanatory diagram of the stirring blade used in the stirring test of the cement-based slurry composition. [Figure 5] It is the construction flow of the mechanical stirring method.

Embodiments for Carrying Out the Invention

[0016] The following describes embodiments of the cement-based slurry composition and its manufacturing method according to the present invention.

[0017] First, we will describe the cement-based solidifying agent and light calcium carbonate, which are constituent materials of the cement-based slurry composition of the present invention.

[0018] [Cement-based solidifying agent] For cement-based solidification materials, ordinary Portland cement, blast furnace cement, and cement-based solidification materials with reduced hexavalent chromium leaching (SO3 content: 4.0-10.5%) can be used. In the following examples, blast furnace cement type B (manufactured by Sumitomo Osaka Cement Co., Ltd., JIS R 5211), hexavalent chromium leaching reduction type cement-based general-purpose (for special soils) solidification agent (SO3 content: 4.0-9.5%, manufactured by Taiheiyo Cement Co., Ltd., "Geoset® 200" (product name)), and hexavalent chromium leaching reduction type cement-based solidification agent for high organic soils (SO3 content: 5.5-10.5%, manufactured by Taiheiyo Cement Co., Ltd., "Geoset® 225" (product name)) were used.

[0019] [Light Calcium Carbonate F] Light calcium carbonate F is based on CCU (Carbon Capture and Utilization) technology. Light calcium carbonate can be produced by reacting highly alkaline wastewater generated in concrete secondary product factories with carbon dioxide in boiler exhaust gas to fix carbon dioxide (for example, "Ecotancal" manufactured by Nippon Concrete Industry Co., Ltd.), by-products from acetylene gas production, by-products from steelmaking, and waste concrete as calcium sources. In the following examples, as shown in Table 1 and Figure 1, a by-product (carbide slurry) from acetylene gas production, which has a high carbon dioxide absorption rate per unit of raw material and generates a small amount of by-products associated with the production of calcium carbonate, was used as the calcium source, and the product was manufactured using this and carbon dioxide derived from exhaust gas (carbon dioxide produced at a quicklime production plant) as raw materials (https: / / www.konoike.co.jp / news / 2024 / 202403183319.html). The particle size of light calcium carbonate F can be controlled by changing the manufacturing conditions. In the following examples and comparative examples, two types of light calcium carbonate (K43: 18300 cm²) with different specific surface areas measured by the Blaine method are used. 2 / g, K19:25300cm 2 ( / g) was used.

[0020] [Table 1]

[0021] The cement-based slurry composition of the present invention is a cement-based slurry composition used by mixing with soil for ground improvement, and contains at least a cement-based solidifying agent, light calcium carbonate F, and water W, does not contain a dispersant, has a W / C (water-cement ratio) of 80% or more, and the addition rate of light calcium carbonate F (ratio of the mass of light calcium carbonate F to the total mass of cement-based solidifying agent and light calcium carbonate F) is in the range of 10 (preferably greater than 10) to 45%, and the bleeding rate is less than 5%.

[0022] Table 2 shows the CO2 emission intensity for each material.

[0023] [Table 2]

[0024] Tables 3-1 to 3-3 show examples and comparative examples of cement-based slurry compositions.

[0025] [Table 3-1]

[0026] [Table 3-2]

[0027] [Table 3-3]

[0028] As shown in Figure 2 and Table 4-1, the cement-based slurry compositions in Table 3-1 exhibit increased viscosity as the W / C (water-cement ratio) decreases and as the addition rate of light calcium carbonate F increases (the same applies to the cement-based slurry compositions in Tables 3-2 to 3-3, as shown in Tables 4-2 to 4-3). In this case, the funnel viscosity flow time of a cement-based slurry composition that can be cast (constructed) for the purpose of ground improvement is approximately 50 s or less, and as shown in Tables 4-2 to 4-3, the viscosity measured by a vibrating viscometer is considered to be approximately 70 mPa·s or less. Therefore, the examples of cement-based slurry compositions shown in Tables 3-1 to 3-3 (containing light calcium carbonate F and with a W / C ratio of 80-200%) can be said to be suitable for cast (construction) for the purpose of ground improvement. In this case, if the W / C ratio was 60% or less, the funnel viscosity flow time was 50 s or more, or the viscosity measured by a vibrating viscometer was 70 mPa·s or more, making it impossible to perform placement (construction) for the purpose of ground improvement.

[0029] Tables 4-1 to 4-3 and Figure 3 show the bleeding test results (test method: JSCE-F 522-2018, according to the polyethylene bag method), funnel viscosity flow time, and viscosity measurement results for the cement-based slurry compositions in Tables 3-1 to 3-3.

[0030] [Table 4-1]

[0031] [Table 4-2]

[0032] [Table 4-3]

[0033] From these results, it was confirmed that the example (containing light calcium carbonate F and with a W / C ratio of 80-200%) had a bleeding rate of less than 5%, while the comparative example (not containing light calcium carbonate F and with a W / C ratio of 80-200%) had a bleeding rate of 11.1-43.6%.

[0034] Here, instead of the light calcium carbonate F in the cement-based slurry composition shown in Table 3-1, a bleeding test was conducted using carbon dioxide fixed by reacting highly alkaline wastewater generated in a concrete secondary product factory with carbon dioxide in boiler exhaust gas (for example, "Ecotancal" manufactured by Nippon Concrete Industry Co., Ltd.). The bleeding rate was less than 1% in the W / C range of 80-180%, and the same effect as light calcium carbonate F using a by-product of acetylene gas production (carbide slurry) as the calcium source was obtained. However, since using a by-product of acetylene gas production (carbide slurry) as the calcium source has a high carbon dioxide absorption rate per unit of raw material and generates less by-product associated with calcium carbonate production, and thus contributes more to reducing environmental burden, it is desirable to use the light calcium carbonate F in the cement-based slurry composition shown in Table 3-1.

[0035] Tables 5-1 to 5-3 show the cement-based slurry compositions in 1 m³ of Tables 3-1 to 3-3. 3 Winner This shows the amount of carbon dioxide fixed and the amount of carbon dioxide released.

[0036] [Table 5-1]

[0037] [Table 5-2]

[0038] [Table 5-3]

[0039] Based on these results, the example (containing light calcium carbonate F and with a W / C ratio of 80-200%) uses light calcium carbonate F, which has a high carbon dioxide absorption rate per unit of raw material and is produced using a by-product of acetylene gas production as the calcium source, and allows for a high addition rate of light calcium carbonate F, resulting in a cement-based slurry composition of 1 m 3 We confirmed that it has a high carbon dioxide fixation rate per unit area, which can further enhance its contribution to reducing environmental impact.

[0040] By the way, in order for a cement-based slurry composition containing calcium carbonate to exhibit its full potential, it is important to ensure that the calcium carbonate is reliably dispersed within the cement-based slurry composition. Therefore, the method for producing the cement-based slurry composition of the present invention uses a turbine blade (shaped like a disc with blades attached, which has superior shear force compared to an inclined paddle blade), and while stirring water W at a peripheral speed of 2.9 m / s or more at the tip of the turbine blade, cement-based solidifying agent BB and light calcium carbonate F are added in succession, and stirring is continued for 3 minutes or more after the addition of light calcium carbonate is completed.

[0041] Table 6 shows the results of the stirring test using the impeller shown in Figure 4.

[0042] [Table 6]

[0043] These results confirm that it is important to use turbine blades and maintain a peripheral speed of 2.9 m / s or higher at the tip of the turbine blades when manufacturing cement-based slurry compositions.

[0044] Next, sandy soil sampled from a depth of 1 to 14 m at the site was mixed with the cement-based slurry composition of the present invention in a soil mixer for 5 minutes. After this, test specimens measuring φ50 mm × height 100 mm were prepared, and the results of a uniaxial compression test were performed 28 days after curing, as shown in Table 7. Here, the W / C ratio of the cement-based slurry composition was set to 80% and 120%. The amount of cement-based slurry composition added was the amount of cement-based solidifying agent BB added to the cement-based slurry composition for a target soil volume of 1 m³. 3 The weights were adjusted to be 50kg, 100kg, and 200kg per person. The specimen preparation method followed the Japanese Geotechnical Society standard for specimen preparation without compaction of stabilized soil (JGS0821). The uniaxial compression test was conducted in accordance with JIS A 1216.

[0045] [Table 7]

[0046] These results show that a W / C ratio of 80% results in increased unconfined compressive strength when using light calcium carbonate F, while a W / C ratio of 120% does not show a significant decrease in unconfined compressive strength even when using light calcium carbonate F, and the BB additive amount is 200 kg / m³. 3 Light calcium carbonate F We confirmed that using this method increases the uniaxial compressive strength.

[0047] Furthermore, in order to confirm the applicability of the cement-based slurry composition of the present invention to real-world applications, The uniaxial slurry-type mechanical agitation method (the construction process of the uniaxial slurry-type mechanical agitation method is shown in Fig. 5, and the construction specifications of the uniaxial slurry-type mechanical agitation method are shown in Table 8, respectively) was used to construct sandy soil at a depth of 1 to 14 m on-site. The W / C of the cement-based slurry composition was 80%. The discharge volume of the cement-based slurry composition was adjusted so that the BB addition amount was 150 kg per 1 m 3 of the improved target soil volume. The construction was carried out at F addition rates of 0% and 10.1% respectively.

[0048]

Table 8

[0049] Core boring was carried out on the improved soils with F addition rates of 0% and 10.1% respectively, 14 days after the completion of construction. The boring cores were cut so that the height of the core was twice the diameter, and a uniaxial compression test was carried out 28 days later. The uniaxial compression test conformed to JIS A 1216. The uniaxial compression strength is shown in Table 9.

[0050]

Table 9

[0051] From these results, the uniaxial compression strength of the case with an F addition rate of 0% was 2469 kN / m on average 2 , while the uniaxial compression strength of the case with an F addition rate of 10.1% was 2913 kN / m on average 2 . It was confirmed that even when the addition rate of light calcium carbonate F exceeded 10%, no strength reduction was observed, and rather, the strength increased by 18%.

[0052] The cement-based slurry composition and its manufacturing method of the present invention, as CCU technology, in addition to being able to further enhance the contribution degree to the reduction of environmental load, can exhibit the following effects . · It is possible to provide a cement-based slurry composition that can be suitably used for slurry-type mechanical agitation methods, high-pressure jet agitation methods, etc. When using slurry-type mechanical agitation methods or high-pressure jet agitation methods in highly permeable sandy ground, the leaching of alkali into groundwater can be reduced. • When using high-pressure jet agitation to protect against underpinning, the watertightness of the interface between the structure and the improved material can be improved.

[0053] The cement-based slurry composition and its manufacturing method of the present invention have been described above based on embodiments. However, the present invention is not limited to the configuration described in the above embodiments, and its configuration can be modified as appropriate without departing from the spirit of the invention. [Industrial applicability]

[0054] The present invention provides a cement-based slurry composition and a method for producing the same, which, by containing calcium carbonate produced using carbon dioxide derived from exhaust gas as a raw material, can further enhance the contribution to reducing environmental impact and can be widely used in various construction methods for the purpose of ground improvement.

Claims

1. A cement-based slurry composition used by mixing with soil for ground improvement, It contains at least a cement-based solidifying agent, light calcium carbonate, and water, and does not contain a dispersant. The W / C ratio is 80% or higher, and the addition rate of light calcium carbonate (the ratio of the mass of light calcium carbonate to the total mass of cement-based solidifying agent and light calcium carbonate) is in the range of 10-45%, with a bleeding rate of less than 5%. A cement-based slurry composition characterized by the following features.

2. The cement-based slurry composition according to claim 1, characterized in that the funnel viscosity flow time is 50 s or less, and the viscosity measured by a vibrating viscometer is 70 mPa·s.

3. The cement-based solidifying agent is blast furnace cement type B or SO ３ The cement-based slurry composition according to claim 1 or 2, characterized in that it is a cement-based solidifying agent with a hexavalent chromium elution reduction type having a content of 4.0 to 10.5%.

4. The cement-based slurry composition according to claim 1 or 2, characterized in that the light calcium carbonate is produced using carbide slurry and carbon dioxide derived from exhaust gas as raw materials.

5. The cement-based slurry composition 1 m ３ The cement-based slurry composition according to claim 4, characterized in that the amount of carbon dioxide fixed per unit is 35 kg or more.

6. A method for producing a cement-based slurry composition, which is used by mixing it with soil for ground improvement, and which contains at least a cement-based solidifying agent, light calcium carbonate, and water, but does not contain a dispersant, Using a turbine blade, while stirring water at a peripheral speed of 2.9 m / s or more at the tip of the turbine blade, cement-based solidifying agent and light calcium carbonate are added in succession, and stirring is continued for 3 minutes or more after the addition of the light calcium carbonate is completed. A method for producing a cement-based slurry composition characterized by the following:

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