Ground improvement cement slurry composition and method for preparing soil cement slurry

Abstract

Provided is a ground improvement cement slurry composition that has a reduced carbon dioxide balance, that has fluidity, that results in less precipitates, and that provides, after being implemented, a ground improvement body having strength. This ground improvement cement slurry composition is characterized by comprising water, an admixture, and a powder containing a binder and a CO2-fixed fine powder, and is characterized in that the mass ratio (water / powder) of the water and the powder is 0.3-0.8, the content proportion of the CO2-fixed fine powder in the total mass of the powder is 1-90 mass%, and the contained amount of the admixture is 0.01-5 parts by mass with respect to 100 parts by mass of the powder.

Description

Cement slurry composition for ground improvement and method for preparing soil cement slurry

[0001] The present invention relates to a cement slurry composition for ground improvement and a method for preparing a soil cement slurry, and more particularly to a cement slurry composition for ground improvement and a method for preparing a soil cement slurry, which have a reduced carbon dioxide balance, have fluidity, and provide a ground improvement body with strength after construction.

[0002] In recent years, efforts to achieve a carbon-neutral or carbon-negative society have been accelerating around the world. For example, Japan declared in 2020 that it would achieve carbon neutrality by 2050, and in 2021 set a target of reducing greenhouse gas emissions by 46% by fiscal 2030 (compared to fiscal 2013 levels).

[0003] For example, the construction industry is also working to reduce carbon dioxide (CO2) emissions.

[0004] Specifically, a ground improvement method has been reported that contributes to achieving carbon neutrality by fixing exhaust gases generated from plant facilities such as compressors and improvement machines, and by effectively utilizing the CO2 contained in the exhaust gases to create an improved body (see Patent Document 1). The ground improvement method described in Patent Document 1 is a method of creating an improved body using a solidification material that absorbs and solidifies carbon dioxide when it comes into contact with it.

[0005] Furthermore, since the cement used in concrete production emits a large amount of carbon dioxide during production, it is known to use ground granulated blast furnace slag or other CCU materials such as CO2 fixation fine powder in place of part of the cement used. CCU materials are an abbreviation for Carbon Capture and Utilization materials, and these CCU materials fix carbon dioxide to the calcium contained in concrete blocks.

[0006] Japanese Patent Application Laid-Open No. 2023-112322

[0007] However, although the use of CCU materials can reduce carbon dioxide balance, adding them to a ground improvement slurry (cement slurry composition) can cause a decrease in the fluidity of the slurry. Furthermore, there is a risk that the improved ground obtained after carrying out ground improvement work using this ground improvement slurry will not have sufficient strength.

[0008] Therefore, there is a need for the development of a cement slurry composition for ground improvement that reduces the carbon dioxide balance, has fluidity, produces little sediment, and provides a strong ground improvement body after construction.

[0009] It should be noted that "reducing the carbon dioxide balance" means reducing the total amount of carbon dioxide emissions derived from materials (i.e., the amount of carbon dioxide generated during the production of materials).

[0010] In view of the above circumstances, an object of the present invention is to provide a cement slurry composition for ground improvement and a method for preparing a soil cement slurry.

[0011] As a result of intensive research to solve the above problems, the present inventors have found that the above problems can be solved by including a predetermined powder and a predetermined admixture. According to the present invention, the following cement slurry composition for ground improvement and a method for preparing a soil cement slurry of the present invention are provided.

[0012] [1] A cement slurry composition for ground improvement, comprising: a powder containing the binder and the CO2-fixing fine powder; the admixture; and water; wherein the mass ratio of the water to the powder (water / powder) is 0.3 to 0.8; the content of the CO2-fixing fine powder in the total mass of the powder is 1 to 90 mass%; and the content of the admixture is 0.01 to 5 mass parts per 100 mass parts of the powder. Binder: A binder having a specific surface area of ​​2000 to 11000 cm3 relative to the total mass of the binder. 2 / g, 1 to 89% by mass of Portland cement, and 1 to 20% by mass of gypsum. CO2-fixing fine powder: The particle size is large enough to pass through a sieve with a mesh size of 1.7 mm, and the modified concrete powder is a reaction product of recycled concrete powder and carbon dioxide, and the modified concrete powder contains calcium carbonate and silicate. Admixture: A water-soluble vinyl copolymer containing a structural unit L formed from a compound represented by the following general formula (1), a structural unit M formed from at least one selected from (meth)acrylic acid, maleic acid (anhydride), fumaric acid, a (meth)acrylate, a maleate, and a fumarate, and a structural unit N formed from other polymerizable monomers, wherein, when the total proportion of the structural unit L, the structural unit M, and the structural unit N is taken as 100% by mass, the proportions of the structural unit L are 40 to 95% by mass, the structural unit M is 5 to 60% by mass, and the structural unit N is 0 to 5% by mass, and the weight average molecular weight is 1,000 to 1,000,000.

[0013] (In general formula (1), R 1 is an unsaturated acyl group having 3 to 4 carbon atoms or an alkenyl group having 2 to 5 carbon atoms. 2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. AO is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of oxyalkylene groups are present, one type may be used alone, or two or more types may be used). n is the average number of moles of AO added, and is a number from 1 to 500.

[0014] [2] The water-soluble vinyl copolymer in the admixture has a content of the structural unit L of 55 to 90% by mass, a content of the structural unit M of 10 to 45% by mass, and a content of the structural unit N of 0 to 5% by mass, wherein n is a number of 1 to 300, and the mass average molecular weight is 10,000 to 500,000. The ground improvement cement slurry composition according to [1].

[0015] [3] The ground improvement cement slurry composition according to [1], wherein the CO2 fixation fine powder in the powder is obtained by subjecting recycled concrete powder to at least one CO2 fixation treatment selected from wet treatment and dry treatment.

[0016] [4] The binder contains 32 to 90% by mass of ground granulated blast furnace slag, 8 to 66% by mass of Portland cement, and 2 to 15% by mass of gypsum. [1] The cement slurry composition for ground improvement according to [1].

[0017] [5] The mass ratio of the water to the powder (water / powder) is 0.3 to 0.6, [1] the cement slurry composition for ground improvement.

[0018] [6] A method for preparing a soil cement slurry, comprising injecting the soil improvement cement slurry composition according to any one of [1] to [5] into the ground.

[0019] The cement slurry composition for ground improvement of the present invention has the effects of reducing the carbon dioxide balance, having fluidity, producing little sediment, and providing a ground improvement body with strength after construction.

[0020] According to the method for preparing soil cement slurry of the present invention, the use of the cement slurry composition for ground improvement of the present invention reduces the carbon dioxide balance, the soil cement slurry has fluidity, there is little sediment, and the ground improvement body after construction has strength.

[0021] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. Therefore, it should be understood that appropriate changes, modifications, etc. can be made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. In the following examples, % means % by mass, and parts means parts by mass, unless otherwise specified.

[0022] (1) Ground improvement cement slurry composition: The ground improvement cement slurry composition of the present invention contains a powder containing the binder and CO2-fixing fine powder described below, the admixture described below, and water. Furthermore, the mass ratio of water to powder (water / powder) is 0.3 to 0.8. The content of the CO2-fixing fine powder in the total mass of the powder is 1 to 90 mass%. The content of the admixture is 0.01 to 5 mass parts per 100 mass parts of the powder.

[0023] Such a ground improvement cement slurry composition contains a predetermined CO2-fixing fine powder and a predetermined proportion of a predetermined admixture, thereby reducing the carbon dioxide balance, providing fluidity, and allowing the ground improvement body to have strength after construction. Having fluidity improves workability in ground improvement work. Furthermore, the strength of the ground improvement body after construction allows for a reduction in the amount of ground improvement cement slurry composition injected per unit volume of soil. The ground improvement cement slurry composition of the present invention produces little sediment after mixing, which is also a factor in ensuring the strength of the ground improvement body after construction.

[0024] Binder: A binder having a specific surface area of ​​2000 to 11000 cm of the total mass of the binder. 2 / g, 1 to 89% by mass of Portland cement, and 1 to 20% by mass of gypsum. CO2-fixing fine powder: The particle size is large enough to pass through a sieve with a mesh size of 1.7 mm, and the powder contains modified concrete powder, which is a reaction product of recycled concrete powder and carbon dioxide, and this modified concrete powder contains calcium carbonate and silicate. Admixture: A water-soluble vinyl copolymer containing a structural unit L formed from a compound represented by the following general formula (1), a structural unit M formed from at least one selected from (meth)acrylic acid, maleic acid (anhydride), fumaric acid, a (meth)acrylate, a maleate, and a fumarate, and a structural unit N formed from other polymerizable monomers, wherein when the total proportion of structural unit L, structural unit M, and structural unit N is taken as 100% by mass, the proportions of structural unit L are 40 to 95% by mass, the proportions of structural unit M are 5 to 60% by mass, and the proportion of structural unit N is 0 to 5% by mass, and the weight average molecular weight is 1,000 to 1,000,000.

[0025] (In general formula (1), R 1 is an unsaturated acyl group having 3 to 4 carbon atoms or an alkenyl group having 2 to 5 carbon atoms. 2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. AO is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of oxyalkylene groups are present, one type may be used alone, or two or more types may be used). n is the average number of moles of AO added, and is a number from 1 to 500.

[0026] (1-1) Powder: The powder contains a binder and a CO2-fixing fine powder. By containing a specific binder and a CO2-fixing fine powder in this way, the carbon dioxide balance can be reduced.

[0027] (1-1a) Binder: The binder has a specific surface area of ​​2000 to 11000 cm 3 of the total mass of the binder. 2The composition contains 10 to 98 mass% of ground granulated blast furnace slag with a porosity of 1000 to 10000 / g, 1 to 89 mass% of Portland cement, and 1 to 20 mass% of gypsum. By containing such binders, the carbon dioxide balance is reduced, the soil has fluidity, and the soil improvement body after construction has strength.

[0028] Ground granulated blast furnace slag has a specific surface area of ​​2000 to 11000 cm 2 / g, and the specific surface area is 3000 to 7000 cm 2 / g. This specific surface area can be expressed as a specific surface area measured in accordance with the specific surface area test specified in JIS R 5201. The specific surface area can generally be measured by a method such as the BET method, the permeation method, or the gas adsorption method.

[0029] Examples of Portland cement include ordinary Portland cement, moderate-heat Portland cement, low-heat Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, sulfate-resistant Portland cement, etc. These may be used alone or in combination of two or more.

[0030] Examples of gypsum include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum, and among these, it is preferable to use anhydrous gypsum.

[0031] Examples of anhydrous gypsum include natural anhydrous gypsum and by-product anhydrous gypsum, and it is preferable that the anhydrous gypsum contains either of them at a purity of 90% by mass or more. The specific surface area of ​​the anhydrous gypsum is 2500 to 8000 cm 2 / g is preferred, and 3000 to 6500 cm 2 / g is more preferred.

[0032] In addition to the above-mentioned ground granulated blast furnace slag, Portland cement, and gypsum, the binder may contain other conventionally known components, such as fly ash, silica fume, stone powder, limestone powder, and expansive agents.

[0033] The ground granulated blast furnace slag is contained in the binder at a ratio of 10 to 98 mass % as described above, and preferably at a ratio of 32 to 90 mass %.

[0034] As mentioned above, the Portland cement is contained in an amount of 1 to 89 mass % of the total mass of the binder, and preferably in an amount of 8 to 66 mass %.

[0035] As described above, the gypsum is contained in a proportion of 1 to 20 mass % of the total mass of the binder, and preferably in a proportion of 2 to 15 mass %.

[0036] The total amount of ground granulated blast furnace slag, Portland cement and gypsum in the total mass of the binder may be 50 to 100 mass %.

[0037] (1-1b) CO2-fixed fine powder: The CO2-fixed fine powder has a particle size that can pass through a sieve with a mesh size of 1.7 mm, and includes modified concrete powder, which is a reaction product of recycled concrete powder and carbon dioxide, and this modified concrete powder contains calcium carbonate and silicate.

[0038] The CO2-fixing fine powder is preferably produced by subjecting recycled concrete powder to at least one CO2 fixation treatment selected from wet treatment and dry treatment. By using such CO2-fixing fine powder, the carbon dioxide balance can be effectively reduced.

[0039] There are no particular restrictions on the particle size of the CO2 fixation fine powder, as long as it has a particle size that can pass through a 1.7 mm sieve. In other words, as long as it is a powder obtained by pulverizing hardened concrete and can pass through a 1.7 mm sieve (i.e., the maximum particle size is 1.7 mm or less), there are no particular restrictions on the particle size distribution, etc., that may be caused by differences in pulverization method, etc.

[0040] There are no particular restrictions on the average particle size of the CO2-fixing fine powder, but from the viewpoint of achieving a good balance between the amount of carbon dioxide fixed in the CO2-fixing fine powder (carbon dioxide fixation amount) and the strength of the resulting ground improvement body, it is preferably 1000 μm or less, and more preferably 100 μm or less.

[0041] Specifically, this CO2-fixing fine powder can be produced as follows.

[0042] First, concrete blocks (hardened concrete bodies) are crushed or ground to recover recycled concrete powder with a median diameter of 100 μm or less. The method for this crushing or grinding is not particularly limited, and known crushing or grinding devices, such as shot-blasting crushers, impact crushers, and grinding devices using mechanical grinding without heating, can be used. Next, the recovered recycled concrete powder is reacted with carbon dioxide at a volume concentration of 5% or more to fix CO2 to the cement-derived components contained in the recycled concrete powder. The reaction with carbon dioxide can be carried out either by a dry method in which gaseous carbon dioxide is brought into contact with the recycled concrete powder, or by a wet method in which the recycled concrete powder is immersed in a solution such as water and then carbon dioxide is blown into the liquid (dispersion) to contact the powder. In this manner, CO2-fixed fine powder can be produced.

[0043] The content of the CO2-fixing fine powder in the total mass of the powder is 1 to 90 mass%, preferably 10 to 90 mass%, and more preferably 20 to 80 mass%. By setting the content in this range, the carbon dioxide balance can be reduced.

[0044] (1-1c) Other Powders: The powder may contain other powders in addition to the binder and CO2-fixing fine powder. Examples of such other powders include non-hydraulic powders such as γ-CS (γ-2CaO.SiO2), bentonite, limestone fine powder, fly ash, and silica fume.

[0045] Examples of non-hydraulic powders include γ-2CaO.SiO2, 3CaO.2SiO2, α-CaO.SiO2, calcium magnesium silicate, and the like.

[0046] The non-hydraulic powder is a powder that does not have hydraulic properties and hardens by reacting with carbon dioxide. "Non-hydraulic powder" means "a powder that does not harden, or hardly hardens, when mixed with water alone."

[0047] The mass ratio of water to powder (water / powder) of the ground improvement cement slurry composition of the present invention is 0.3 to 0.8, preferably 0.3 to 0.6. By setting the mass ratio within this range, the carbon dioxide balance can be reduced, and the ground improvement body after construction can have fluidity and strength.

[0048] (1-2) Compatibility Agent: The compatibility agent contains a water-soluble vinyl copolymer having predetermined structural units L to N.

[0049] By including such a predetermined admixture, it is possible to reduce the carbon dioxide balance, and at the same time, it is possible to provide fluidity and ensure the strength of the ground improvement body after construction.

[0050] More specifically, in efforts to realize a decarbonized society, concrete products manufactured using carbon capture and utilization (CCU) materials such as CO2-fixing fine powder have been reported. However, the use of these CCU materials can change the physical properties (e.g., fluidity) of materials such as slurry compositions, resulting in reduced workability. Therefore, a material (slurry composition) that contains a CCU material is needed to achieve a reduction in carbon dioxide balance while maintaining or improving workability. Furthermore, it is important that the strength of the hardened concrete product (or ground improvement body, if the purpose is ground improvement) is not reduced. In this situation, the soil improvement cement slurry composition of the present invention, by incorporating a predetermined admixture in a predetermined ratio, can maintain fluidity (i.e., maintain or improve workability) and ensure the strength of the ground improvement body when the carbon dioxide balance is reduced using a CCU material.

[0051] (1-2-1) Water-soluble vinyl copolymer: The water-soluble vinyl copolymer contains a structural unit L formed from a compound represented by the following general formula (1), a structural unit M formed from at least one selected from (meth)acrylic acid, maleic acid (anhydride), fumaric acid, a (meth)acrylate, a maleate, and a fumarate, and a structural unit N formed from other polymerizable monomers. When the total content of structural units L to N is taken as 100% by mass, the structural unit L accounts for 40 to 95% by mass, the structural unit M for 5 to 60% by mass, and the structural unit N for 0 to 5% by mass. It is even more preferable that the content of structural unit L is 55 to 90% by mass, the content of structural unit M for 10 to 45% by mass, and the content of structural unit N for 0 to 5% by mass. It is particularly preferable that the content of the structural unit L is 70 to 85% by mass, the content of the structural unit M is 15 to 30% by mass, and the content of the structural unit N is 0 to 3% by mass.

[0052] (1-2-1a) Structural Unit L: The structural unit L is a structural unit formed from a compound represented by the following general formula (1).

[0053] (In general formula (1), R 1 is an unsaturated acyl group having 3 to 4 carbon atoms or an alkenyl group having 2 to 5 carbon atoms. 2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. AO is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of oxyalkylene groups are present, one type may be used alone, or two or more types may be used). n is the average number of moles of AO added, and is a number from 1 to 500.

[0054] R in general formula (1) 1 is an unsaturated acyl group having 3 to 4 carbon atoms or an alkenyl group having 2 to 5 carbon atoms.

[0055] R in general formula (1) 2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

[0056] In the general formula (1), AO is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of such oxyalkylene groups are present, one type may be used alone, or two or more types may be used).

[0057] In the general formula (1), n ​​is the average number of moles of AO added, and is a number from 1 to 500. n is preferably a number from 1 to 300, and more preferably a number from 1 to 150.

[0058] (1-2-1b) Structural unit M: The structural unit M is a structural unit formed from at least one selected from (meth)acrylic acid, maleic acid (anhydride), fumaric acid, (meth)acrylates, maleate salts, and fumarate salts. Among these, a structural unit formed from at least one selected from (meth)acrylic acid, maleic acid (anhydride), (meth)acrylates, and maleate salts is preferred.

[0059] (1-2-1c) Structural unit N: The structural unit N is a structural unit formed from another polymerizable monomer. In other words, it is a structural unit formed from a compound copolymerizable with the compound represented by general formula (1) that forms the structural unit L and the compound that forms the structural unit M.

[0060] Examples of compounds that form the structural unit N include sodium methallylsulfonate, methyl acrylate, sodium allylsulfonate, acrylamide, and N,N-dimethyl(meth)acrylamide.

[0061] The water-soluble vinyl copolymer has a mass average molecular weight of 1,000 to 1,000,000, preferably 10,000 to 500,000, and more preferably 30,000 to 100,000. By setting it in this range, it is possible to reduce the carbon dioxide balance, have fluidity, and ensure the strength of the ground improvement body after construction.

[0062] More specifically, the water-soluble vinyl copolymer has a content of the structural unit L of 55 to 90% by mass, a content of the structural unit M of 10 to 45% by mass, and a content of the structural unit N of 0 to 5% by mass, where n is a number from 1 to 300, and a mass average molecular weight of 10,000 to 500,000. Particularly specifically, the water-soluble vinyl copolymer has a content of the structural unit L of 70 to 85% by mass, a content of the structural unit M of 15 to 30% by mass, and a content of the structural unit N of 0 to 3% by mass, where n is a number from 1 to 150, and a mass average molecular weight of 30,000 to 100,000.

[0063] The water-soluble vinyl copolymer may be used alone or in combination.

[0064] The content (addition amount) of the admixture is 0.01 to 5 parts by mass, preferably 0.03 to 3 parts by mass, and more preferably 0.05 to 1 part by mass, relative to 100 parts by mass of the powder.

[0065] In addition to the water-soluble vinyl copolymer, the admixture may contain other components such as a dispersing component such as a polycarboxylate or a naphthalenesulfonic acid condensate, a setting retarding component such as an oxycarboxylate or a sugar, a hardening accelerating component such as an inorganic carbonate, an antifoaming component, and an antiseptic component.

[0066] (1-3) Water: There are no particular limitations on the water, and tap water, groundwater, or other water that does not adversely affect the hardening of the soil cement can be used as appropriate.

[0067] (1-4) Other additives: The cement slurry composition for ground improvement may further contain other additives as appropriate within the range that does not impair the effect. Examples of such other additives include antifoaming agents such as polyoxyalkylene alkyl ethers, setting retarders such as oxycarboxylates and sugars, hardening accelerators such as amines and inorganic carbonates, and fibers such as polypropylene fibers.

[0068] The content of the other additives may be, for example, 0 to 5% by mass relative to 100% by mass of the powder.

[0069] (2) Method for preparing the cement slurry composition for ground improvement: The cement slurry composition for ground improvement can be prepared by a conventionally known method, for example, by adding predetermined amounts of powder containing the binder and the CO2-fixing fine powder, admixtures, and water to a mixer and kneading them.

[0070] (3) Method for preparing soil cement slurry: The method for preparing soil cement slurry of the present invention is a method for injecting the soil improvement cement slurry composition of the present invention into the ground. According to the method for preparing soil cement slurry of the present invention, the soil improvement cement slurry composition of the present invention is used, so that the carbon dioxide balance is reduced, the soil cement slurry has fluidity, and the ground improvement body after construction has strength.

[0071] The method of injecting the cement slurry composition into the ground is not particularly limited, and any conventionally known method can be appropriately adopted. Examples include a CDM (Cement Deep Mixing) method in which the cement slurry composition for ground improvement of the present invention is directly injected into the ground while being mixed and stirred, and a high-pressure injection and stirring method.

[0072] 1m of ground 3 The amount of injection per unit can be selected appropriately depending on the fluidity required for the soil cement slurry, the strength required for the resulting hardened body (ground improvement body), and the properties of the ground to be mixed.

[0073] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0074] (Compatibilizer) The compatibilizer used was a water-soluble vinyl copolymer (aqueous solution of water-soluble vinyl copolymer) produced as follows: Compatibilizers P-1 to P-14 and rP-1 to rP-3 correspond to the aqueous solutions of water-soluble vinyl copolymers P-1 to P-14 and rP-1 to rP-3, respectively.

[0075] (Water-soluble vinyl copolymer) The water-soluble vinyl copolymers P-1 to P-14 and rP-1 to rP-3 contained in the admixture are shown in Table 1 below.

[0076]

[0077] In Table 1, the compounds forming the structural units L to N constituting the water-soluble vinyl copolymers P-1 to P-14 and rP-1 to rP-3 are as follows: L-1: methoxypoly(23 mol)ethylene glycol monomethacrylate L-2: poly(30 mol)ethylene glycol isoprenyl ether L-3: methoxypoly(68 mol)ethylene glycol monomethacrylate L-4: methoxypoly(9 mol)ethylene glycol monomethacrylate L-5: poly(2 mol)propylene glycol-poly(130 mol)ethylene glycol methallyl ether L-6: butoxypoly(45 mol)ethylene glycol monomethacrylate L-7: hydroxypropyl acrylate L-8: hydroxyethyl acrylate M-1: methacrylic acid M-2: acrylic acid M-3: maleic acid N-1: sodium methallyl sulfonate N-2: methyl acrylate N-3: sodium allyl sulfonate

[0078] The methods for producing the water-soluble vinyl copolymers P-1 to P-14 and rP-1 to rP-3 are described in the following Production Examples 1 to 17.

[0079] (Production Example 1) Synthesis of Water-Soluble Vinyl Copolymer P-1: 423.2 g of water, 314.6 g of methoxypoly(23 mol)ethylene glycol monomethacrylate, 66.1 g of methacrylic acid, and 1.9 g of 3-mercaptopropionic acid were charged into a reaction vessel, and the atmosphere inside the reaction vessel was replaced with nitrogen. The mixture was then gradually heated with stirring. The temperature of the reaction system was maintained at 65°C using a hot water bath, and 38.1 g of a 10% aqueous solution of sodium persulfate was added to initiate the radical polymerization reaction. After 2 hours, an additional 19.0 g of a 10% aqueous solution of sodium persulfate was added, and the radical polymerization reaction was continued for 2 hours. 82.9 g of a 30% aqueous solution of sodium hydroxide and 59.2 g of water were added to the resulting copolymer, yielding a 40% aqueous solution of water-soluble vinyl copolymer P-1.

[0080] When this water-soluble vinyl copolymer was analyzed by gel permeation chromatography (GPC), it was found to have a weight average molecular weight of 79,100.

[0081] (Production Example 2) Synthesis of Water-Soluble Vinyl Copolymer P-2: A 40% aqueous solution of water-soluble vinyl copolymer P-2 was obtained in the same manner as in Production Example 1, except that the types and amounts of each of the structural units L to N were changed as shown in Table 1, and the amount of 3-mercaptopropionic acid was changed so as to obtain a predetermined mass average molecular weight.

[0082] (Production Example 3) Synthesis of water-soluble vinyl copolymer P-3: 252.6 g of water, 361.6 g of poly(30 mol)ethylene glycol isoprenyl ether, and 10.4 g of acrylic acid were charged into a 1000 mL round-bottom flask equipped with a stirrer, a nitrogen inlet tube, and a dropping funnel. After uniform dissolution with stirring, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was maintained at 60°C in a warm water bath.

[0083] Next, 30.7 g of a 10% aqueous hydrogen peroxide solution was added dropwise over 3 hours, and simultaneously, an aqueous solution prepared by uniformly dissolving 3.1 g of 3-mercaptopropionic acid and 2.0 g of L-ascorbic acid in 20.4 g of water was added dropwise over 4 hours, and simultaneously, an aqueous solution prepared by dissolving 21.0 g of acrylic acid in 105.1 g of water was added dropwise over 3 hours. Thereafter, the temperature of the reaction system was maintained at 60°C for 1 hour, and the polymerization reaction was terminated. 30.6 g of a 30% aqueous sodium hydroxide solution and 180.5 g of water were added to the obtained copolymer, yielding a 40% aqueous solution of water-soluble vinyl copolymer P-3.

[0084] When this water-soluble vinyl copolymer was analyzed by gel permeation chromatography (GPC), it was found to have a weight average molecular weight of 68,100.

[0085] (Production Example 4) Synthesis of Water-Soluble Vinyl Copolymer P-4: A 40% aqueous solution of water-soluble vinyl copolymer P-4 was obtained in the same manner as in Production Example 1, except that the types and amounts of each of the structural units L to N were changed as shown in Table 1, and the amount of 3-mercaptopropionic acid was changed so as to obtain a predetermined mass average molecular weight.

[0086] (Production Example 5) Synthesis of Water-Soluble Vinyl Copolymer P-5: 422.5 g of water, 303.2 g of methoxypoly(9 mol)ethylene glycol monomethacrylate, 55.4 g of methacrylic acid, 11.1 g of acrylic acid, 8.3 g of maleic acid, and 3.8 g of 3-mercaptopropionic acid were charged into a reaction vessel. The atmosphere inside the reaction vessel was then replaced with nitrogen, and the mixture was gradually heated with stirring. The temperature of the reaction system was maintained at 65°C using a warm water bath, and 38.1 g of a 10% aqueous solution of sodium persulfate was added to initiate the radical polymerization reaction. After 2 hours, an additional 19.0 g of a 10% aqueous solution of sodium persulfate was added, and the radical polymerization reaction was continued for 2 hours. 88.2 g of a 30% aqueous solution of sodium hydroxide and 55.8 g of water were added to the resulting copolymer, yielding a 40% aqueous solution of water-soluble vinyl copolymer P-5.

[0087] When this water-soluble vinyl copolymer was analyzed by gel permeation chromatography (GPC), it was found to have a weight average molecular weight of 32,000.

[0088] (Production Example 6) Synthesis of Water-Soluble Vinyl Copolymer P-6: 212.2 g of water, 353.7 g of poly(2 mol)propylene glycol-poly(130 mol)ethylene glycol methallyl ether, 10.2 g of acrylic acid, and 7.9 g of methyl acrylate were charged into a 1000 mL round-bottom flask equipped with a stirrer, a nitrogen inlet tube, and a dropping funnel. After uniform dissolution with stirring, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was maintained at 60°C in a warm water bath. Next, 30.7 g of a 10% aqueous hydrogen peroxide solution was added dropwise over 3 hours. At the same time, an aqueous solution prepared by uniformly dissolving 3.1 g of 3-mercaptopropionic acid and 2.0 g of L-ascorbic acid in 20.4 g of water was added dropwise over 4 hours. At the same time, an aqueous solution prepared by dissolving 21.2 g of acrylic acid and 7.9 g of hydroxypropyl acrylate in 145.5 g of water was added dropwise over 3 hours. Thereafter, the temperature of the reaction system was maintained at 60°C for 1 hour to terminate the polymerization reaction. To the obtained copolymer, 30.6 g of a 30% aqueous solution of sodium hydroxide and 180.5 g of water were added to obtain a 40% aqueous solution of water-soluble vinyl copolymer P-6.

[0089] When this water-soluble vinyl copolymer was analyzed by gel permeation chromatography (GPC), it was found to have a weight average molecular weight of 40,000.

[0090] (Production Example 7) Synthesis of Water-Soluble Vinyl Copolymer P-7: 424.9 g of water, 306.0 g of butoxypoly(45 mol)ethylene glycol monomethacrylate, 68.0 g of methacrylic acid, 7.5 g of hydroxyethyl acrylate, and 1.9 g of 3-mercaptopropionic acid were charged into a reaction vessel. The atmosphere in the reaction vessel was then replaced with nitrogen, and the mixture was gradually heated with stirring. The temperature of the reaction system was maintained at 65°C using a warm water bath, and 37.4 g of a 10% aqueous solution of sodium persulfate was added to initiate the radical polymerization reaction. After 2 hours, an additional 18.7 g of a 10% aqueous solution of sodium persulfate was added, and the radical polymerization reaction was continued for 2 hours. 79.1 g of a 30% aqueous solution of sodium hydroxide and 61.6 g of water were added to the resulting copolymer, yielding a 40% aqueous solution of water-soluble vinyl copolymer P-7.

[0091] When this water-soluble vinyl copolymer was analyzed by gel permeation chromatography (GPC), it was found to have a weight average molecular weight of 76,500.

[0092] (Production Examples 8 to 14) Synthesis of Water-Soluble Vinyl Copolymers P-8 to P-14: 40% aqueous solutions of water-soluble vinyl copolymers P-8 to P-14 were obtained in the same manner as in Production Example 7, except that the type and amount of each structural unit L to N was changed as shown in Table 1, and the amount of 3-mercaptopropionic acid was changed so as to obtain a predetermined mass average molecular weight.

[0093] (Production Example 15) Synthesis of Water-Soluble Vinyl Copolymer rP-1: 26.6 g of water and 2.95 g of aqueous hydrogen peroxide were charged into a 1000 mL round-bottom flask equipped with a stirrer, a nitrogen inlet tube, and a dropping funnel. After uniform dissolution with stirring, the atmosphere was replaced with nitrogen, and the temperature of the reaction system was maintained at 60°C in a warm water bath. Next, an aqueous solution prepared by uniformly dissolving 6.8 g of 3-mercaptopropionic acid and 3.4 g of L-ascorbic acid in 50.6 g of water was added dropwise over 4 hours, and simultaneously, an aqueous solution prepared by dissolving 337.6 g of acrylic acid in 68.8 g of water was added dropwise over 3 hours. Thereafter, the temperature of the reaction system was maintained at 60°C for 1 hour, and the polymerization reaction was terminated. 316.6 g of a 30% aqueous sodium hydroxide solution and 186.6 g of water were added to the obtained copolymer, yielding a 40% aqueous solution of water-soluble vinyl copolymer rP-1.

[0094] When this water-soluble vinyl copolymer was analyzed by gel permeation chromatography (GPC), it was found to have a weight average molecular weight of 6,000.

[0095] (Production Examples 16 to 17) Synthesis of Water-Soluble Vinyl Copolymers rP-2 to rP-3: 40% aqueous solutions of water-soluble vinyl copolymers rP-2 to rP-3 were obtained in the same manner as in Production Example 7, except that the type and amount of each structural unit L to N was changed as shown in Table 1, and the amount of 3-mercaptopropionic acid was changed so as to obtain a predetermined mass average molecular weight.

[0096] (Weight-average molecular weight) The weight-average molecular weight of each of the water-soluble vinyl copolymers P-1 to P-14 and rP-1 to rP-3 was measured by gel permeation chromatography (GPC) under the following conditions. <Measurement conditions> Apparatus: Shodex GPC-101 (Showa Denko K.K.) Column: OHpak SB-G + SB-806M HQ + SB-806M HQ (Showa Denko K.K.) Detector: Differential refractometer (RI) Eluent: 50 mM aqueous sodium nitrate solution Flow rate: 0.7 mL / min Column temperature: 40°C Sample concentration: 0.5% by mass eluent solution Standard substance: PEG / PEO (Agilent Technologies)

[0097] (Powder) The powder was prepared by mixing the components so as to have the composition shown in Table 2 below.

[0098]

[0099] The components in Table 2 are as follows: sg-1: specific surface area of ​​4250 cm 2 / g of ground granulated blast furnace slag sg-2: specific surface area of ​​3200 cm 2 / g of ground granulated blast furnace slag sg-3: specific surface area of ​​6000 cm 2 / g of ground granulated blast furnace slag sg-4: specific surface area of ​​8500 cm 2 / g of blast furnace slag ground powder N: Ordinary Portland cement H: High-early-strength Portland cement gp-1: Specific surface area of ​​3920 cm 2 / g of anhydrous gypsum gp-2: specific surface area is 4050 cm 2 / g hemihydrate gypsum gp-3: specific surface area is 3480 cm 2 / g dihydrate gypsum C-1: CO2-fixed fine powder subjected to dry treatment (CO2 emission amount: -148.0 kg / t) C-2: CO2-fixed fine powder subjected to wet treatment (CO2 emission amount: -92.0 kg / t) C-3: CO2-fixed fine powder carbonated in the atmosphere (CO2 emission amount: -28.0 kg / t)

[0100] (Method for Measuring Specific Surface Area) The specific surface area was measured and calculated using a Blaine air permeation device in accordance with the specific surface area test specified in JIS R 5201.

[0101] The CO2 emissions (kg / t) in C-1 to C-3 above were calculated by calculating the amount of CO2 fixed using the following formula and then subtracting the amount of fixed CO2: (Amount of CaCO3 (%) x Molecular weight of CO2 / Molecular weight of CaCO3) x 1000 (kg / t)

[0102] For example, when the amount of CaCO3 is 10.0 (%), the amount of CO2 fixed (kg / t) is calculated from the above formula as (10% x 44.0 / 100.1) x 1000 = 44.0 (kg / t). However, the amount of CaCO3 (%) was calculated and quantified from the weight loss between 600 and 800°C by TG-DTA measurement. Note that if the decarboxylation reaction did not finish at the upper limit of 800°C, it was finished at 840°C.

[0103] (Method for Producing CO2 Fixation Fine Powder) Hereinafter, the methods for producing CO2 fixation fine powders C-1 to C-3 will be described.

[0104] CO2-fixing fine powder C-1: Dry-processed CO2-fixing fine powder. The CO2-fixing fine powder was specifically produced as follows. Specifically, concrete blocks were crushed and ground using a known grinder to obtain recycled concrete powder with a median diameter of 100 μm or less. The resulting recycled concrete powder was then evenly spread in a container of a specified capacity, and the container was placed in a carbonation accelerator at a temperature of 20°C, humidity of 60%, and a CO2 concentration of 10%, allowing the recycled concrete powder and CO2 to react (CO2 fixation treatment). This reaction was continued for seven days, and the sample was stirred every one to three days to ensure uniform distribution throughout the sample, ensuring contact of CO2 throughout the recycled concrete powder. After seven days, the resulting reaction product (CO2-fixing fine powder) was removed to obtain the CO2-fixing fine powder.

[0105] CO2-fixed fine powder C-2: CO2-fixed fine powder subjected to wet treatment. Recycled concrete powder was obtained in the same manner as CO2-fixed fine powder C-1. 3 1,800 kg of water and 200 kg of the resulting recycled concrete powder were sequentially added to the container and stirred. Carbon dioxide gas was then injected from the bottom of the container at a rate of 150 L / min to react the recycled concrete powder with CO (CO fixation treatment). The CO fixation treatment was continued until the pH of the dispersion reached 6.8 or less, after which a reaction product of the recycled concrete powder and CO was obtained. After the reaction was completed, the resulting reaction product was removed, excess water was removed using a polypropylene twill filter, and the mixture was air-dried to obtain a CO fixation fine powder.

[0106] CO2-fixed fine powder C-3: CO2-fixed fine powder carbonated in the atmosphere. Recycled concrete powder was obtained in the same manner as CO2-fixed fine powder C-1. Then, the recycled concrete powder was left in the atmosphere to react with CO2 (CO2 fixation treatment). The reaction was continued for three months, and the entire sample was stirred approximately every two weeks to ensure uniformity, so that CO2 came into contact with the entire recycled concrete powder. After three months, the resulting reaction product (CO2-fixed fine powder) was removed, and CO2-fixed fine powder was obtained.

[0107] In Table 2, "Total CO2 emissions from materials (kg / t)" was calculated using the formula: Total CO2 emissions = mass% of material × CO2 emissions from materials. Note that the values ​​in the "CO2 emissions (kg / t)" column in Table 3 were used for "CO2 emissions from materials."

[0108] For example, "B-1" is 34% by mass of ground granulated blast furnace slag, 16% by mass of Portland cement, 2% by mass of gypsum, and 48% by mass of CO2-fixed fine powder. Therefore, the total CO2 emissions (kg / t) is calculated from the above formula as ((34% x 26.5) + (16% x 764.3) + (2% x 16.1) + (48% x -148.0)) kg / t = 60.6 kg / t.

[0109]

[0110] C-1 to C-3 in Table 3 are the same as C-1 to C-3 shown in Table 2.

[0111] (Evaluation of CO2 emissions) Based on the "Total CO2 emissions from materials (kg / t)" shown in Table 2, CO2 emissions were evaluated according to the following evaluation criteria: S: 150 kg / t or less A: Over 150 kg / t and 200 kg / t or less B: Over 200 kg / t and 250 kg / t or less C: Over 250 kg / t and 500 kg / t or less D: Over 500 kg / t

[0112] Table 4 below shows the ratio (mass %) of each component (ground granulated blast furnace slag, cement, gypsum) to the binder for each powder.

[0113]

[0114] (Examples 1 to 33, Comparative Examples 1 to 12) (1) Cement Slurry Compositions: The components shown in Tables 5 and 6 were mixed in the proportions shown to prepare cement slurry compositions.

[0115] The prepared cement slurry compositions were measured for the flow time (seconds) through the P funnel and the settling volume (%), with the mixing time set to 0 minutes, and the flow time and settling volume were evaluated. The results are shown in Tables 5 and 6.

[0116] (Flow time evaluation (viscosity evaluation)) The flow time (seconds) through a P funnel was measured in accordance with the Japan Society of Civil Engineers' Standard Specifications for Concrete "Test method for fluidity of injection mortar for prepacked concrete (method using a P funnel)" (JSCE-F-5-521-1999). This P funnel flow time was measured immediately after mixing (0 minutes) and 30 minutes after mixing. The values ​​measured 30 minutes after mixing were then evaluated according to the following evaluation criteria. S: Less than 15.0 seconds A: 15.0 seconds or more but less than 17.5 seconds B: 17.5 seconds or more but less than 20.0 seconds C: 20.0 seconds or more

[0117] (Evaluation of Settling Rate) Using a polyethylene bag as used in the Japan Society of Civil Engineers' Standard Specifications for Concrete "Test Method for Bleeding Rate and Expansion Rate of Injection Mortar for Prepacked Concrete (Polyethylene Bag Method)" (JSCE-F-522-2013), the volumetric rate of viscous sediment observed at the bottom of the cement slurry composition was measured. The volumetric rate of this sediment was measured 60 minutes and 120 minutes after mixing. The volumetric rate (settling rate) (volume %) measured 120 minutes after mixing was then evaluated according to the following evaluation criteria. In Comparative Examples 2, 5, and 6, a large amount of bleeding water was generated. In Table 6, "*1" is attached. S: 0.0% or more and less than 3.0% A: 3.0% or more and less than 6.0% B: 6.0% or more and less than 12.0% C: 12.0% or more

[0118]

[0119]

[0120] (Examples 34 to 39, Comparative Examples 13 to 17) (Preparation of soil cement slurry) Using the cement slurry compositions (SL-1 to SL-33 and rSL-1 to rSL-12) shown in Tables 5 and 6, the injection amount of the cement slurry composition was set so that the powder amount per unit volume of soil cement was equivalent, and soil cement slurries were prepared.

[0121] Specifically, a predetermined amount of cement slurry composition was charged into a Hobart mixer, and then test soil (soil collected from the ground in Yokohama City, Kanagawa Prefecture) having the physical properties shown in Table 7 was added to the Hobart mixer and stirred and mixed. In this way, the soil cement slurries of Examples 34 to 39 and Comparative Examples 13 to 17 were prepared.

[0122] The contents of the prepared soil cement slurries of Examples 34 to 39 and Comparative Examples 13 to 17 are summarized in Table 8. The mixing, flow test, and uniaxial compression test were carried out under conditions of a material temperature of 20±3°C, a room temperature of 20±3°C, and a humidity of 60% or more.

[0123]

[0124] (Evaluation of physical properties of soil cement slurries) Next, the flow immediately after mixing (15-pile flow) and the unconfined compressive strength of the obtained hardened bodies were measured by the methods described below for the soil cement slurries of Examples 34 to 39 and Comparative Examples 13 to 17. The measured values ​​for Examples 34 to 39 were all within the allowable range.

[0125] (Evaluation of fluidity by flow) A flow test was carried out in accordance with JIS R 5201 immediately after mixing, and the flow after 15 drops (15 hit flow) was measured.

[0126] (Evaluation of Strength Development by Uniaxial Compression Test) In accordance with JIS A 1216, a test specimen (hardened specimen) having a diameter of 50 mm and a height of 100 mm was prepared, and the uniaxial compressive strength of this hardened specimen at an age of 7 days and an age of 28 days was measured.

[0127]

[0128] (Results) As shown in Tables 2, 5, and 6, the soil improvement cement slurry composition of this example reduces the carbon dioxide balance, has fluidity, produces little precipitate, and the ground improvement body after construction has strength. Also, as shown in Table 8, all of the measured values ​​in the examples were within the allowable range. According to the soil cement slurry preparation method of this example, by using the soil improvement cement slurry composition of this example, it can be seen that the carbon dioxide balance is reduced, the soil cement slurry has fluidity, and the ground improvement body after construction has strength.

[0129] The soil improvement cement slurry composition of the present invention can be used as a material for improving the ground. The method for preparing a soil cement slurry of the present invention can be employed as a method for improving the ground.

Claims

1. A cement slurry composition for ground improvement comprising a powder containing the binder and the CO2-fixing fine powder, the admixture, and water, wherein the mass ratio of the water to the powder (water / powder) is 0.3 to 0.8, the content of the CO2-fixing fine powder in the total mass of the powder is 1 to 90 mass%, and the content of the admixture is 0.01 to 5 mass parts per 100 mass parts of the powder. Binder: A binder having a specific surface area of ​​2000 to 11000 cm3 relative to the total mass of the binder. 2 / g, 1 to 89% by mass of Portland cement, and 1 to 20% by mass of gypsum. CO2-fixing fine powder: The particle size is large enough to pass through a sieve with a mesh size of 1.7 mm, and the modified concrete powder is a reaction product of recycled concrete powder and carbon dioxide, and the modified concrete powder contains calcium carbonate and silicate. Admixture: A water-soluble vinyl copolymer containing a structural unit L formed from a compound represented by the following general formula (1), a structural unit M formed from at least one selected from (meth)acrylic acid, maleic acid (anhydride), fumaric acid, a (meth)acrylate, a maleate, and a fumarate, and a structural unit N formed from other polymerizable monomers, wherein, when the total proportion of the structural unit L, the structural unit M, and the structural unit N is taken as 100% by mass, the proportions of the structural unit L are 40 to 95% by mass, the structural unit M is 5 to 60% by mass, and the structural unit N is 0 to 5% by mass, and the weight average molecular weight is 1,000 to 1,000,000. (In general formula (1), R 1 is an unsaturated acyl group having 3 to 4 carbon atoms or an alkenyl group having 2 to 5 carbon atoms. 2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. AO is an oxyalkylene group having 2 to 4 carbon atoms (however, when a plurality of oxyalkylene groups are present, one type may be used alone, or two or more types may be used). n is the average number of moles of AO added, and is a number from 1 to 500.

2. The ground improvement cement slurry composition according to claim 1, wherein the water-soluble vinyl copolymer in the admixture has a content of the structural unit L of 55 to 90% by mass, a content of the structural unit M of 10 to 45% by mass, and a content of the structural unit N of 0 to 5% by mass, wherein n is a number from 1 to 300, and wherein the mass average molecular weight is 10,000 to 500,000.

3. A cement slurry composition for ground improvement as described in claim 1, wherein the CO2-fixing fine powder in the powder is obtained by subjecting recycled concrete powder to at least one CO2 fixation treatment selected from wet treatment and dry treatment.

4. A cement slurry composition for ground improvement according to claim 1, wherein the binder contains 32 to 90 mass% of ground granulated blast furnace slag, 8 to 66 mass% of Portland cement, and 2 to 15 mass% of gypsum.

5. A cement slurry composition for ground improvement according to claim 1, wherein the mass ratio of the water to the powder (water / powder) is 0.3 to 0.

6.

6. A method for preparing a soil cement slurry, which comprises injecting the soil improvement cement slurry composition according to any one of claims 1 to 5 into the ground.

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