Cement-based solidifying material-containing composition and method for producing the same

Abstract

To provide a cement-based solidifying material-containing composition which is excellent in strength development, can suppress the elution amount of heavy metals, and can reduce CO2 discharge basic unit, and to provide a method for producing the cement-based solidifying material-containing composition.SOLUTION: A cement-based solidification-material-containing composition comprising a cement-based solidification material and a ready mixed concrete sludge carbonate powder, wherein the proportion of the ready mixed concrete sludge carbonate powder in the cement-based solidification-material-containing composition is 0.1 to 25.0% by mass. The method for producing a cement-based solidifying-material-containing composition includes a step of mixing ready-mixed concrete sludge with water to obtain a slurry, a step of bringing the slurry into contact with carbon dioxide gas to obtain a carbon dioxide fixing slurry, a step of subjecting the carbon dioxide fixing slurry to solid-liquid separation to obtain a ready-mixed concrete sludge carbonate powder, and a step of mixing a cement-based solidifying material with the ready-mixed concrete sludge carbonate powder to produce a cement-based solidifying-material-containing composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cement-based solidification material-containing composition and a method for producing a cement-based solidification material-containing composition. [Background technology]

[0002] In recent years, efforts to achieve carbon neutrality have been gaining momentum in the cement and ground improvement industries. As a ground improvement material that can effectively utilize carbon dioxide generated during the cement manufacturing process and has excellent strength development, for example, Patent Document 1 describes a ground improvement material that is characterized by being composed of a slurry containing cement-based materials and carbon dioxide-containing water. On the other hand, most of the ready-mix concrete sludge that remains after adding water to leftover concrete at concrete factories and construction sites and separating the aggregate is discarded, and it is becoming a problem that it is not being sufficiently recycled. Patent Document 2 describes a cement-based solidification material that effectively utilizes fresh concrete sludge, which, in thermogravimetric analysis (TG) measured in a nitrogen gas flow from 25°C to 1,000°C at a heating rate of 10°C / min, has a mass loss of 0.5 to 4.5% by mass at 400 to 500°C and a mass loss of 3.5 to 8.5% by mass at 600 to 800°C, contains 3 to 10% by mass of acid-insoluble residue (insol) and 45 to 60% by mass of calcium oxide, and has a Blaine specific surface area of ​​5,000 to 10,000 cm 2 The cement-based solidification material contains heat-dried powder of concrete sludge with a content of 1 / g. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-134282 [Patent Document 2] Patent No. 5683066 Summary of the Invention [Problem to be solved by the invention]

[0004] Cement-based solidification materials used in ground improvement are primarily made of cement and are composed of several other admixtures. Cement, the main ingredient of cement-based solidification materials, emits a large amount of CO2 during production, which has a significant impact on the CO2 emission intensity of cement-based solidification materials. However, since cement is an essential material for the strength development of cement-based solidification materials, simply reducing the cement proportion in the cement-based solidification material mix design in order to reduce the CO2 emission unit of the cement-based solidification material may result in a decrease in the strength development of the cement-based solidification material. The object of the present invention is to provide a cement-based solidification material-containing composition that has excellent strength development, can suppress the amount of heavy metals leaching from the ground after ground improvement to below environmental standard values, can effectively utilize ready-mixed concrete sludge, and can reduce CO2 emission unit, and a method for producing the cement-based solidification material-containing composition. [Means for solving the problem]

[0005] As a result of extensive research into solving the above problems, the present inventors have found that the above object can be achieved by a cement-based solidification material-containing composition containing a cement-based solidification material and a fresh concrete sludge carbonate powder, in which the proportion of the carbonate powder is 0.1 to 25.0 mass%, and have completed the present invention. That is, the present invention provides the following [1] to [4]. [1] A cement-based solidification material-containing composition comprising a cement-based solidification material and a fresh concrete sludge carbonate powder, characterized in that the ratio of the fresh concrete sludge carbonate powder in the cement-based solidification material-containing composition is 0.1 to 25.0 mass%. [2] The BET specific surface area of ​​the above-mentioned fresh concrete sludge carbonate powder is 20 to 100 m 2 / g of the cement-based solidification material-containing composition according to [1]. [3] A method for producing the cement-based solidification material-containing composition according to [1] or [2] above, comprising: a slurry preparation step of mixing fresh concrete sludge with water to obtain a slurry; a carbon dioxide gas supply step of bringing the slurry into contact with carbon dioxide gas to obtain a carbon dioxide fixation slurry; a solid-liquid separation step of subjecting the carbon dioxide fixation slurry to solid-liquid separation to obtain the fresh concrete sludge carbonate powder; and a composition preparation step of mixing the cement-based solidification material and the fresh concrete sludge carbonate powder to produce the cement-based solidification material-containing composition. [4] A method for improving ground using the cement-based solidification material-containing composition according to [1] or [2], characterized in that the cement-based solidification material-containing composition is added to the ground and mixed to obtain improved ground. [Effects of the Invention]

[0006] The cement-based solidification material-containing composition of the present invention has excellent strength development, can suppress the amount of heavy metals leaching from the ground after ground improvement to below environmental standard values, can effectively utilize ready-mixed concrete sludge, and can reduce CO2 emissions per unit of production. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a carbonation apparatus for producing fresh concrete sludge carbonate powder contained in the cement-based solidification material-containing composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] The cement-based solidification material-containing composition of the present invention is a cement-based solidification material-containing composition containing a cement-based solidification material and a fresh concrete sludge carbonate powder, and the proportion of the fresh concrete sludge carbonate powder (hereinafter sometimes simply abbreviated as "carbonate powder") in the cement-based solidification material-containing composition is 0.1 to 25.0 mass%. A detailed explanation is provided below. In this specification, the cement-based solidification material refers to a material that contains cement as the main material (usually 50% by mass or more) and also contains admixtures that can be optionally blended. Examples of cements used in cement-based solidification materials include various types of Portland cement such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement; blended cements such as blast-furnace cement, fly ash cement, and silica cement; ecocement; white cement; and ultra-rapid-hardening cement. Among these, various types of Portland cement are preferred from the viewpoint of ease of availability. Examples of optional admixtures include ground granulated blast furnace slag, fly ash, silica fume, and ground limestone, which may be used singly or in combination of two or more.

[0009] The proportion of cement in the cement-based solidification material is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more, from the viewpoint of improving the strength development of the cement-based solidification material-containing composition. In addition, when the cement is a mixed cement such as blast furnace cement, cement admixtures such as blast furnace slag powder contained in the mixed cement are not included in the cement ratio above, but are treated as admixtures contained in the cement-based solidification material.

[0010] The proportion of the cementitious solidification material in the cementitious solidification material-containing composition is preferably 75.0 to 99.9 mass%, more preferably 80.0 to 99.5 mass%, even more preferably 83.0 to 99.0 mass%, even more preferably 88.0 to 98.5 mass%, and particularly preferably 95.0 to 98.0 mass%. If the proportion is 75.0 mass% or more, the strength development of the cementitious solidification material-containing composition can be further improved. If the proportion is 99.9 mass% or less, the amount of carbonate powder used can be relatively increased, which can further promote the effective use of fresh concrete sludge and reduce the CO2 emission intensity of the cementitious solidification material-containing composition.

[0011] In this specification, the ready-mixed concrete sludge carbonate powder contains calcium carbonate (CaCO3) formed by the reaction of calcium contained in ready-mixed concrete sludge with carbon dioxide. Carbonate powder can be obtained by carbonating ready-mixed concrete sludge. "Carbonation" refers to the absorption and fixation of carbon dioxide in the target of carbonation. Carbonate powder is produced by absorbing and immobilizing carbon dioxide in industrial waste (ready-mixed concrete sludge), which has a CO2 emission unit of zero. Therefore, by including carbonate powder in a cement-based solidification material-containing composition, the CO2 emission unit of the cement-based solidification material-containing composition can be reduced.

[0012] The ready-mixed concrete sludge from which ready-mixed concrete sludge carbonate powder can be obtained is not particularly limited, and examples include: (i) a sludge containing fine powder components such as cement obtained by adding water to unused leftover concrete at a construction site or the like to form a slurry, and then separating coarse particles such as aggregate (coarse aggregate and fine aggregate) contained in the slurry; (ii) a sludge containing fine powder components such as cement obtained by separating coarse particles such as aggregate from residue containing concrete generated when cleaning an agitator truck or the like; and (iii) a sludge containing fine powder components such as cement obtained by separating coarse particles such as aggregate from concrete generated at a concrete product factory or the like. As a method for separating coarse particles such as aggregate, for example, a method is available in which coarse aggregate and fine aggregate are respectively separated from the slurry and residue using a plurality of vibrating sieves with different mesh sizes. The separated coarse aggregate and fine aggregate are reused as aggregate. The proportion of fine aggregate in the ready-mixed concrete sludge is preferably 10% by mass or less, more preferably 2 to 9% by mass, and even more preferably 4 to 8% by mass, from the viewpoints of ease of availability, strength development, etc. If the proportion is 10% by mass or less, the strength development of the cement-based solidification material-containing composition can be further improved. The proportion of coarse aggregate in the ready-mixed concrete sludge is usually 1% by mass or less, and preferably 0% by mass.

[0013] The ready-mixed concrete sludge may be diluted with water as needed, and then subjected to solid-liquid separation using a filter press, etc. From the standpoint of ease of handling, etc., the water content of the ready-mixed concrete sludge (mass of water / mass of ready-mixed concrete sludge × 100%) is preferably 150% or less, more preferably 120% or less, and particularly preferably 100% or less. Furthermore, the ready-mixed concrete sludge may be crushed, pulverized, and classified as necessary. By crushing the ready-mixed concrete sludge into powder form before carbonation, the ready-mixed concrete sludge can be more easily carbonated. Methods for carbonating fresh concrete sludge include a method of leaving the fresh concrete sludge in an atmosphere of gas containing carbon dioxide, and a method of bringing a slurry made by mixing fresh concrete sludge with water into contact with carbon dioxide (described below).

[0014] The proportion of carbonate powder in the cementitious solidification material-containing composition is preferably 0.1 to 25.0 mass%, more preferably 0.5 to 20.0 mass%, even more preferably 1.0 to 17.0 mass%, even more preferably 1.5 to 12.0 mass%, and particularly preferably 2.0 to 5.0 mass%. If the proportion is 0.1 mass% or more, the effective utilization of fresh concrete sludge can be further promoted, and the CO2 emission intensity of the cementitious solidification material-containing composition can be further reduced. If the proportion is 25.0 mass% or less, the strength development of the cementitious solidification material-containing composition can be further improved.

[0015] The BET specific surface area of ​​the carbonate powder is preferably 20 to 100 m 2 / g, more preferably 30 to 95m 2 / g, particularly preferably 35 to 90m 2 / g. The BET specific surface area is 20m 2 / g or more, the strength development of the cement-based solidification material-containing composition can be further improved. 2 / g or less, the fluidity of the cement-based solidifying material-containing composition can be further improved. The amount of CO2 fixed by the carbonate powder (mass (kg) of carbon dioxide absorbed and fixed per unit mass (1 ton) of carbonate powder) is preferably 100 to 250 kg / ton, more preferably 130 to 220 kg / ton, and particularly preferably 150 to 200 kg / ton. If the amount of CO2 fixed is 100 kg / ton or more, the CO2 emission intensity of the cement-based solidification material-containing composition can be further reduced. If the amount of CO2 fixed is 250 kg / ton or less, the labor required for carbonation of fresh concrete sludge can be further reduced.

[0016] An example of a method for producing the cement-based solidification material-containing composition of the present invention includes a production method including a slurry preparation step of mixing fresh concrete sludge with water to obtain a slurry, a carbon dioxide gas supply step of bringing the slurry into contact with carbon dioxide gas to obtain a carbon dioxide fixation slurry, a solid-liquid separation step of performing solid-liquid separation of the carbon dioxide fixation slurry to obtain a fresh concrete sludge carbonate powder, and a composition preparation step of mixing the cement-based solidification material and the fresh concrete sludge carbonate powder to produce a cement-based solidification material-containing composition. A detailed explanation is provided below.

[0017] [Slurry preparation process] This process involves mixing fresh concrete sludge with water to obtain a slurry. In this step, the mass ratio of water to fresh concrete sludge (water / fresh concrete sludge) is preferably 1.0 to 5.0, more preferably 1.5 to 4.5, even more preferably 2.0 to 4.0, and particularly preferably 2.5 to 3.5. If the ratio is 1.0 or more, the fluidity of the slurry is further improved, making it easier to uniformly supply carbon dioxide to the slurry in the carbon dioxide supply step described below. If the ratio is 5.0 or less, a greater amount of carbon dioxide is immobilized in the fresh concrete sludge contained in the slurry. The mass of the fresh concrete sludge in the above mass ratio is the mass converted to solid content. If the fresh concrete sludge before mixing with water contains water, the water contained in the fresh concrete sludge is included in the mass of water in the above mass ratio. In this step, the method for mixing the ready-mixed concrete sludge and water is not particularly limited. For example, water may be added to a mixing tank, and then the ready-mixed concrete sludge may be added thereto, and then they may be mixed; alternatively, water and the ready-mixed concrete sludge may be added to a mixing tank simultaneously, and then they may be mixed. The water to be mixed with the ready-mixed concrete sludge is not particularly limited, and examples thereof include tap water, treated sewage water, supernatant water from ready-mixed concrete, sludge water, and the like.

[0018] [Carbon dioxide gas supply process] This step is a step of contacting the slurry obtained in the slurry preparation step with carbon dioxide gas to obtain a carbon dioxide fixation slurry. Note that the carbon dioxide gas is gaseous carbon dioxide. In this step, from the viewpoint of uniformly carbonating the slurry, it is preferable to bring the slurry into contact with carbon dioxide gas while fluidizing it. An example of a method for contacting a slurry with carbon dioxide gas will be specifically described below with reference to FIG. FIG. 1 is a diagram schematically illustrating a carbon dioxide fixation slurry production apparatus 1 including a slurry preparation tank 2 and a carbon dioxide gas contact device 3. The ready-mixed concrete sludge and water are charged into the slurry preparation tank 2 and then mixed using a mixing means (not shown) such as a hand mixer to prepare a slurry 8 (this corresponds to the above-mentioned slurry preparation step). The slurry 8 is passed through a first slurry flow passage 4 for supplying the slurry into the carbon dioxide contactor 3 using a pump 6, and is then charged into the carbon dioxide contactor 3 from an opening formed in the top of the carbon dioxide contactor 3. Carbon dioxide gas is supplied into the carbon dioxide contactor 3 from a carbon dioxide gas supply device (not shown) through a carbon dioxide gas supply passage 9, and a gas phase containing carbon dioxide gas is formed. In the carbon dioxide contactor 3, the slurry is brought into contact with the gas phase, whereby the slurry is carbonated, and a carbon dioxide fixation slurry 7 can be obtained.

[0019] The carbon dioxide fixation slurry 7 is transferred to the slurry preparation tank 2 through a second slurry flow passage 5 for supplying the carbon dioxide fixation slurry 7 contained in the carbon dioxide gas contactor 3 into the slurry preparation tank 2. By circulating the slurry between the slurry preparation tank 2 and the carbon dioxide gas contactor 3 and carbonating the slurry, a sufficiently carbonated slurry (carbon dioxide fixation slurry) can be obtained. Another example of a method for bringing the slurry into contact with carbon dioxide gas is a method in which a carbon dioxide gas supply means for supplying carbon dioxide gas into the slurry is installed in a mixing tank for mixing the ready-mixed concrete sludge and water, and carbon dioxide gas is blown into a slurry obtained by mixing the ready-mixed concrete sludge and water, thereby bringing the slurry into contact with the carbon dioxide gas, thereby obtaining a carbon dioxide fixation slurry.

[0020] Carbon dioxide gas may be contacted with the slurry as a gas consisting of carbon dioxide gas alone, but from the viewpoint of ease of availability, etc., it may be contacted with the slurry as a gas containing carbon dioxide gas. The proportion of carbon dioxide gas in the carbon dioxide-containing gas is preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 20% by volume or more, even more preferably 50% by volume or more, still more preferably 80% by volume or more, and particularly preferably 90% by volume or more. If the proportion is 5% by volume or more, the amount of carbon dioxide immobilized in the carbon dioxide immobilization slurry can be further increased. In addition, the time required for supplying carbon dioxide gas can be shortened. Examples of gases containing carbon dioxide include exhaust gases generated in the cement manufacturing process (carbon dioxide concentration: approximately 20% by volume), exhaust gases generated in the steelmaking process (carbon dioxide concentration: approximately 20% by volume), exhaust gases generated in thermal power generation processes (carbon dioxide concentration: approximately 10% by volume), and gases separated and recovered from these exhaust gases (carbon dioxide concentration: approximately 100% by volume).

[0021] In this step, carbon dioxide gas is supplied so that the pH of the carbon dioxide fixation slurry is preferably 11.5 or less, more preferably 4.0 to 8.5, even more preferably 5.0 to 7.5, and particularly preferably 5.5 to 6.5. When carbon dioxide gas is supplied so that the pH is 4.0 or more, the strength development of the cement-based solidification material-containing composition is further improved. In addition, the time required for supplying carbon dioxide gas can be shortened. When carbon dioxide gas is supplied so that the pH is 11.5 or less, the amount of carbon dioxide fixed in the carbon dioxide fixation slurry (more specifically, the amount of carbon dioxide fixed in the solid content contained in the carbon dioxide fixation slurry) is increased. Note that the pH of the carbon dioxide fixation slurry decreases when carbon dioxide gas is supplied. The time for supplying carbon dioxide gas required to fix a sufficient amount of carbon dioxide in the slurry varies depending on the liquid-solid ratio of the slurry, the carbon dioxide gas supply means, the carbon dioxide gas concentration of the carbon dioxide-containing gas supplied using said means, etc. Therefore, in this step, it is preferable to determine the timing for ending the supply of carbon dioxide gas based on the actually measured pH value of the carbon dioxide fixation slurry.

[0022] [Solid-liquid separation process] This step is a step of obtaining carbonate powder by solid-liquid separation of the carbon dioxide fixation slurry obtained in the carbon dioxide gas supply step. The solid-liquid separation method is not particularly limited as long as it is a method that can separate the liquid contained in the carbon dioxide fixation slurry and recover the solid content (carbonates of the ready-mixed concrete sludge), and examples thereof include dehydration treatment using a filter press, a centrifuge, a belt filter, etc., sun drying, a dryer, an electric furnace, a hot air oven, etc. The moisture content of the carbonate powder varies depending on the target work efficiency, etc., but is preferably 10% by mass or less, more preferably 5.0% by mass or less, even more preferably 3.0% by mass or less, and particularly preferably 1.0% by mass or less. After drying, the carbonate powder may be pulverized so that the BET specific surface area falls within the above-mentioned preferred range, and may be classified as necessary.

[0023] [Composition preparation process] This step is a step of producing a cement-based solidification material-containing composition by mixing a cement-based solidification material with the fresh concrete sludge carbonate powder obtained in the solid-liquid separation step. A commercially available cement-based solidification material and carbonate powder may be added and mixed at the same time, or the cement and various admixtures constituting the cement-based solidification material and carbonate powder may be added and mixed at the same time.

[0024] According to the cement-based solidification material-containing composition of the present invention, the strength (e.g., uniaxial compressive strength) of the solidified improved soil obtained by mixing the cement-based solidification material-containing composition with the ground to be improved can be increased, and the leaching of heavy metals contained in the ground can be suppressed. Here, heavy metals are Type 2 specified hazardous substances as defined in the Soil Contamination Countermeasures Act (2003). Specifically, they are any of the following: cadmium and its compounds, cyanide compounds, hexavalent chromium compounds, mercury and its compounds, selenium and its compounds, lead and its compounds, arsenic and its compounds, fluorine and its compounds, and boron and its compounds. Note that although fluorine and boron are not heavy metals, fluorine and its compounds and boron and its compounds are considered to be heavy metals.

[0025] An example of a method for improving ground using the cement-based solidification material-containing composition of the present invention is a method in which the above-mentioned cement-based solidification material-containing composition is added to the ground (soil) to be improved and mixed to obtain improved ground. The ground to be improved is not particularly limited, and examples thereof include ground containing heavy metals. The amount of cement-based solidification material composition added to the ground varies depending on the properties of the ground, construction conditions, and the strength required for the improved ground obtained after solidification treatment, but it is recommended to use a composition containing cement-based solidification material for 1 m of the ground to be improved. 3The amount is preferably 10 to 400 kg, more preferably 25 to 300 kg, and particularly preferably 75 to 200 kg per unit weight. If the amount is 10 kg or more, the strength (e.g., unconfined compressive strength) of the solidified improved soil can be increased. If the amount is 300 kg or less, an increase in costs can be prevented.

[0026] Methods for adding and mixing the cement-based solidification material-containing composition to the ground include dry addition, in which the cement-based solidification material-containing composition is added as a powder to the target ground and mixed, and slurry addition, in which water is added to the cement-based solidification material-containing composition to form a slurry, and the slurry is added to the target ground and mixed. In the case of slurry addition, the mass ratio of water to cement-based solidification material-containing composition is preferably 0.6 to 1.5, more preferably 0.8 to 1.2. [Example]

[0027] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Cement-based solidification material: manufactured by Taiheiyo Cement Corporation, product name "Geoset", containing 50% or more by mass of ordinary Portland cement (2) Fresh concrete sludge A; BET specific surface area: 27.6 m 2 / g, fine aggregate content: 5.6% by mass, coarse aggregate content: 0% by mass, moisture content: 94%, density: 2.1 g / cm 3 (3) Fresh concrete sludge B; BET specific surface area: 19.6 m 2 / g, fine aggregate content: 7.3% by mass, coarse aggregate content: 0% by mass, moisture content: 98%, density: 2.3 g / cm 3 (4) Soil A: Sandy soil (5) Soil B: Toyoura sand

[0028] [Preparation of fresh concrete sludge carbonate powder A] A carbon dioxide fixation slurry containing carbonates of fresh concrete sludge A was prepared using the carbon dioxide fixation slurry production apparatus 1 shown in FIG. Specifically, water and fresh concrete sludge A were poured into a slurry preparation tank 2 in an amount such that the mass ratio of water to fresh concrete sludge A (water / fresh concrete sludge A) was 3.0, and the mixture was mixed using a hand mixer for 60 seconds to obtain a mixture (slurry, temperature: 23°C) (slurry preparation process). The mixture in the slurry preparation tank 2 was transferred through a first slurry flow path 4 to a carbon dioxide contactor 3 for supplying carbon dioxide to the mixture, and then gaseous carbon dioxide (carbon dioxide content: 99% by volume or more) was supplied into the carbon dioxide contactor 3 to form a gas phase containing carbon dioxide. Next, the mixture was repeatedly transferred into the slurry preparation tank 2 through a second slurry flow path 5 different from the first slurry flow path 4, and circulated until the pH of the slurry reached 8.5 or less, thereby obtaining a carbon dioxide fixation slurry containing ready-mixed concrete sludge carbonate powder (carbon dioxide supply step). Next, the carbon dioxide fixation slurry containing the fresh concrete sludge carbonate powder was subjected to solid-liquid separation, and then dried in an electric furnace at 105°C to obtain fresh concrete sludge carbonate powder A (referred to as "carbonate powder" in Tables 1 and 2) having a moisture content of 1.0 mass% or less.

[0029] The BET specific surface area of ​​the fresh concrete sludge carbonate powder A (shown as "specific surface area" in Table 1) was measured using an analytical measuring instrument manufactured by Shimadzu Corporation (product name "Flowsorb"). The amount of CO2 fixed by the fresh concrete sludge carbonate powder A was calculated by carrying out the following steps (a) to (i). (a) Thermogravimetry-differential thermal analysis (TG-DTA) was performed on each of the fresh concrete sludge A and the fresh concrete sludge carbonate powder A. From the measurement results, it was determined that the mass loss in the endothermic peak range between 550 and 850°C was due to the decarbonation of calcium carbonate contained in the fresh concrete sludge or the fresh concrete sludge carbonate powder, and the mass loss rate between 550 and 850°C (mass %; hereinafter also referred to as the "decarbonation rate") was calculated from the mass loss. (b) Each of the fresh concrete sludge A and the fresh concrete sludge carbonate powder A was heated to 1,000°C until it reached a constant weight, and the organic matter content (mass %; also referred to as "LOI") was calculated from the mass before and after heating. (c) For each of the fresh concrete sludge A and the fresh concrete sludge carbonate powder A, the decarbonation rate was subtracted from the organic matter content (LOI) to determine the HO content (mass%) in the fresh concrete sludge A or the fresh concrete sludge carbonate powder A. (d) For each of the fresh concrete sludge A and the fresh concrete sludge carbonate powder A, the organic matter content (LOI) was subtracted from the total mass (100% by mass) of the fresh concrete sludge A or the fresh concrete sludge carbonate powder A to determine the proportion of residue (% by mass) in the fresh concrete sludge A or the fresh concrete sludge carbonate powder A.

[0030] (e) The solid content (%) of the raw material in the ready-mixed concrete sludge carbonate powder A was calculated using the following formula (1). Solid content ratio (%) = Organic content of ready-mixed concrete sludge carbonate powder A (LOI) / Organic content of ready-mixed concrete sludge A (LOI) × 100 (1) (f) The CO2 content (mass%) derived from the fresh concrete sludge A in the fresh concrete sludge carbonate powder A was calculated using the following formula (2). CO2 content derived from fresh concrete sludge A = solid raw material ratio above × decarbonation rate of fresh concrete sludge A / 100 (2) (g) The content (mass%) of H2O derived from the fresh concrete sludge A in the fresh concrete sludge carbonate powder A was calculated using the following formula (3). HO content from fresh concrete sludge A = solid raw material ratio × organic matter content of fresh concrete sludge A (LOI) / 100 (3) (h) The CO2 content (mass%; excluding the CO2 content derived from fresh concrete sludge A) fixed by carbonation in fresh concrete sludge carbonate powder A was calculated using the following equation (4). CO2 content fixed by carbonation = decarbonation rate of fresh concrete sludge carbonate powder A - decarbonation rate of fresh concrete sludge A (4) (i) The amount of CO2 fixed (kg / ton) by the fresh concrete sludge carbonate powder A was calculated using the following formula (5). Amount of CO2 fixed = fixed CO2 content / solid content of raw material × 100 (5)

[0031] [Preparation of fresh concrete sludge carbonate powder B] Fresh concrete sludge carbonate powder B was prepared in the same manner as for preparing fresh concrete sludge carbonate powder A, except that fresh concrete sludge B was used instead of fresh concrete sludge A. In the same manner as for ready-mixed concrete sludge carbonate powder A, the BET specific surface area of ​​ready-mixed concrete sludge carbonate powder B was measured and the amount of CO2 fixed was calculated. The results are shown in Table 1.

[0032] [Table 1] TIFF2026019445000002.tif36152

[0033] [Examples 1 to 3] The types and amounts of fresh concrete sludge carbonate powder and cement-based solidification material shown in Table 2 were mixed using a Henschel mixer to prepare cement-based solidification material-containing compositions. 1m of soil 3The cement-based solidification material-containing composition was mixed in an amount of 50 kg to the soil, and then mixed at low speed for 1 minute using a Hobart mixer. After scraping off any adhering material from the mixer, the mixture was mixed at medium speed for 1 minute, and after scraping off any adhering material from the mixer again, the mixture was mixed at medium speed for 1 minute to obtain improved soil (improved ground). Also, 1 m of soil 3 Improved soil (improved ground) was obtained in the same manner as in the case of mixing 50 kg of cement-based solidification material-containing composition, except that the amount of cement-based solidification material-containing composition per 1 m of soil was changed to 100 kg or 150 kg. In Table 3, "50", "100", and "150" respectively represent the amount of cement-based solidification material-containing composition per 1 m of soil. 3 Addition amount of cement-based solidification material-containing composition (kg / m 3 ) means The improved soil thus obtained was evaluated according to the following method.

[0034] [CBR (California Bearing Ratio) Measurement] The CBR of the improved soil was measured 7 days after mixing in accordance with JIS A 1211:2020 (CBR test method). The higher the CBR, the better the strength of the improved soil. [Measurement of elution amount of hexavalent chromium] In accordance with Environment Agency Notification No. 46, the amount of hexavalent chromium eluted from the improved soil was measured 7 days after mixing.

[0035] [Comparative Example 1] Improved soil (improved ground) was obtained in the same manner as in Example 1, except that only a cement-based solidification material was used as the cement-based solidification material-containing composition. The CBR was measured in the same manner as in Example 1 using the improved soil obtained. Comparative Example 2 Improved soil (improved ground) was obtained in the same manner as in Example 1, except that only the ready-mixed concrete sludge carbonate powder A was used as the cement-based solidifying material-containing composition. The CBR was measured in the same manner as in Example 1 using the improved soil obtained.

[0036] [Example 4] In the same manner as in Example 1, improved soil (improved ground) was obtained. Using the obtained improved soil, the amount of hexavalent chromium eluted was measured in the same manner as in Example 1. In addition, the unconfined compressive strength of the improved soil 28 days after mixing was measured in accordance with JIS A 1216:2020 (Unconfined compression test method for soil).

[0037] Comparative Example 3 Improved soil (improved ground) was obtained in the same manner as in Example 4, except that only a cement-based solidification material was used as the cement-based solidification material-containing composition. The unconfined compressive strength of the improved soil was measured in the same manner as in Example 4. The results are shown in Table 3.

[0038] [Table 2]

[0039] [Table 3]

[0040] From Table 3, the CBR of Examples 1 to 3 is the same as that of Examples 1 to 3, except that the amount of cement-based solidification material-containing composition added is 50 kg / m 3 When the amount of the cement-based solidification material-containing composition added is 100 kg / m 3 or 150 kg / m 3 It can be seen that the value is larger than those of Comparative Examples 1 and 2. It is also apparent that the uniaxial compressive strength of Example 4 is greater than that of Comparative Example 3. Furthermore, it can be seen that in Examples 1 to 4, the amount of eluted hexavalent chromium satisfies the environmental standard value (0.05 mg / liter or less). Furthermore, the cement-based solidification material-containing compositions of Examples 1 to 4 have a smaller CO2 emission intensity than the cement-based solidification material-containing compositions of Comparative Examples 1 and 4 because they contain a ready-mixed concrete carbonate powder. [Explanation of symbols]

[0041] 1 Carbon dioxide fixation slurry manufacturing equipment 2. Slurry preparation tank 3 Carbon dioxide contact device 4. First slurry flow passage 5 Second slurry flow passage 6. Pump 7 Carbon dioxide fixation slurry 8. Slurry 9 Carbon dioxide supply line

Claims

1. A cement-based solidification material-containing composition containing a cement-based solidification material and a fresh concrete sludge carbonate powder, A cement-based solidification material-containing composition, characterized in that the ratio of the fresh concrete sludge carbonate powder in the cement-based solidification material-containing composition is 0.1 to 25.0 mass %.

2. The BET specific surface area of ​​the above-mentioned fresh concrete sludge carbonate powder is 20 to 100 m ２ The cement-based solidifying material-containing composition according to claim 1, wherein the hydroxyl group is 0.1 to 0.5g.

3. A method for producing the cement-based solidification material-containing composition according to claim 1 or 2, comprising: a slurry preparation step of mixing fresh concrete sludge with water to obtain a slurry; a carbon dioxide gas supplying step of contacting the slurry with carbon dioxide gas to obtain a carbon dioxide fixation slurry; a solid-liquid separation step of subjecting the carbon dioxide fixation slurry to solid-liquid separation to obtain the ready-mixed concrete sludge carbonate powder; a composition preparation step of mixing the cement-based solidification material and the fresh concrete sludge carbonate powder to produce the cement-based solidification material-containing composition; A method for producing a cement-based solidification material-containing composition, comprising:

4. A method for improving ground using the cement-based solidification material-containing composition according to claim 1 or 2, A ground improvement method characterized by adding the above cement-based solidifying material-containing composition to the ground and mixing it to obtain improved ground.

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