Method for manufacturing carbon dioxide-fixed concrete

Abstract

To provide a method for manufacturing carbon dioxide gas fixation concrete which can reduce an emission amount of carbon dioxide gas compared to conventional methods.SOLUTION: A method for manufacturing carbon dioxide gas fixation concrete includes: a slurry manufacturing step of supplying carbon dioxide gas to a sludge liquid obtained by solid-liquid separation of a concrete sludge, and manufacturing a light calcium carbonate-containing slurry containing a light calcium carbonate which is precipitated in the sludge liquid and where the carbon dioxide gas is immobilized; a water content adjustment step of measuring and adjusting a water content of the light calcium carbonate-containing slurry; a hydraulic fluidized material adjustment step of adjusting a hydraulic fluidized material which contains a water content-adjusted light calcium carbonate-containing slurry having an adjusted water content of the light calcium carbonate-containing slurry, cement, an aggregate, and a precipitation inhibitor for inhibiting precipitation of the light calcium carbonate, and has the water content within a predetermined range; and a curing step of placing and curing the hydraulic fluidized material, to obtain the carbon dioxide gas fixation concrete.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing carbon dioxide-fixed concrete.

Background Art

[0002] Cement used in concrete emits a large amount of carbon dioxide (carbon dioxide, CO2) from the decarbonation of raw materials during production and fuel during firing. In response to the increasing interest in suppressing climate change in recent years, it is required to significantly reduce the amount of carbon dioxide emissions during the production of concrete.

[0003] As one method of reducing carbon dioxide emissions, a blended cement in which blast furnace granulated slag (hereinafter simply referred to as blast furnace slag fine powder) is mixed with cement is widely used. However, when the amount of blast furnace slag fine powder is increased, the hardening becomes slow, the period until demolding becomes long, and long-term wet curing is required to obtain sufficient strength. Therefore, problems remain in terms of construction period and cost.

[0004] Further, Patent Document 1 describes a concrete sludge treatment apparatus including a sludge separation apparatus that separates concrete sludge generated in a centrifugal molding process of concrete into a sludge cake and a sludge liquid, a precipitation reaction apparatus that precipitates calcium carbonate from the sludge liquid separated by the sludge separation apparatus, and a calcium carbonate separation apparatus that separates calcium carbonate from the precipitation liquid in which calcium carbonate has precipitated. In the precipitation reaction apparatus, calcium carbonate is precipitated by supplying carbon dioxide to the sludge liquid. Therefore, by using the calcium carbonate obtained by the concrete sludge treatment apparatus of Patent Document 1 as a raw material for concrete, the amount of carbon dioxide emissions can be reduced.

[0005] However, in Patent Document 1, dehydration treatment and heat treatment are performed on the precipitation liquid in which calcium carbonate is precipitated, and by removing moisture, calcium carbonate powder is obtained. At this time, since heat treatment is performed, a considerable amount of carbon dioxide gas is discharged in order to obtain calcium carbonate. Therefore, although the amount of carbon dioxide gas discharged can be reduced by the technique of Patent Document 1, there is still room for further reducing the amount of carbon dioxide gas discharged.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a method for producing carbon dioxide gas-immobilized concrete capable of reducing the amount of carbon dioxide gas discharged as compared with the prior art.

Means for Solving the Problems

[0008] [1] A slurry production step of supplying carbon dioxide gas to a sludge liquid obtained by solid-liquid separation of concrete sludge, producing a light calcium carbonate-containing slurry containing light calcium carbonate precipitated in the sludge liquid and immobilizing the carbon dioxide gas, a water content adjustment step of measuring and adjusting the water content of the light calcium carbonate-containing slurry, a hydraulic fluid preparation step of preparing a hydraulic fluid containing the light calcium carbonate-containing slurry with adjusted water content, cement, aggregate, and a precipitation inhibitor for suppressing precipitation of the light calcium carbonate and having a water content within a predetermined range, and a hardening step of placing and hardening the hydraulic fluid to obtain carbon dioxide gas-immobilized concrete. A method for producing carbon dioxide gas-immobilized concrete. [2] The method for producing carbon dioxide-immobilized concrete according to [1] above, wherein the precipitation inhibitor is at least one selected from the group consisting of polyacrylate, thickener, AE agent, water reducer, and alkali. [3] The method for producing carbon dioxide-immobilized concrete according to [1] or [2] above, wherein the water content of the moisture-adjusted lightweight calcium carbonate-containing slurry is 39% or more and 98% or less. [4] The method for producing carbon dioxide-immobilized concrete according to any one of [1] to [3] above, wherein in the moisture adjustment step, the water content of the lightweight calcium carbonate-containing slurry is measured non-contactly.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a method for producing carbon dioxide-immobilized concrete that can reduce the amount of carbon dioxide emissions compared to the prior art.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0011] Hereinafter, a detailed description will be given based on the embodiments.

[0012] The method for manufacturing carbon dioxide-immobilized concrete of the present invention includes a slurry manufacturing step of supplying carbon dioxide gas to a slurry liquid obtained by solid-liquid separation of concrete sludge, depositing it in the slurry liquid, and manufacturing a lightweight calcium carbonate-containing slurry containing lightweight calcium carbonate that immobilizes the carbon dioxide gas; a water content adjustment step of measuring and adjusting the water content of the lightweight calcium carbonate-containing slurry; a hydraulic fluid preparation step of preparing a hydraulic fluid containing the lightweight calcium carbonate-containing slurry with adjusted water content, cement, aggregate, and a precipitation inhibitor for suppressing precipitation of the lightweight calcium carbonate, and having a water content within a predetermined range; and a hardening step of placing and hardening the hydraulic fluid to obtain carbon dioxide-immobilized concrete.

[0013] Figure 1 is a flowchart showing an example of the method for manufacturing carbon dioxide-immobilized concrete according to the embodiment. Figure 2 is a schematic diagram showing an example of an apparatus for manufacturing a lightweight calcium carbonate-containing slurry used in the slurry manufacturing step. As shown in Figure 1, the method for manufacturing carbon dioxide-immobilized concrete according to the embodiment includes a slurry manufacturing step S10, a water content adjustment step S20, a hydraulic fluid preparation step S30, and a hardening step S40.

[0014] In the slurry manufacturing step S10 of the method for manufacturing carbon dioxide-immobilized concrete, carbon dioxide gas (carbon dioxide, CO2) is supplied to a slurry liquid obtained by solid-liquid separation of concrete sludge to deposit lightweight calcium carbonate in the slurry liquid. The lightweight calcium carbonate deposited in the slurry liquid immobilizes the carbon dioxide gas supplied to the slurry liquid. Thus, a lightweight calcium carbonate-containing slurry containing lightweight calcium carbonate that has immobilized carbon dioxide gas is manufactured.

[0015] In the slurry manufacturing step S10, in order to manufacture a lightweight calcium carbonate-containing slurry, the lightweight calcium carbonate-containing slurry manufacturing apparatus 1 shown in Figure 2 is preferably used. The lightweight calcium carbonate-containing slurry manufacturing apparatus 1 mainly includes a solid-liquid separation unit 2, a precipitation reaction unit 3, and a carbon dioxide gas supply unit 4.

[0016] The solid-liquid separation unit 2 separates the concrete sludge, which is a concrete-based waste containing uncured cement fine particles, into a sludge cake, which is a solid content, and a sludge liquid, which is a liquid content containing uncured cement fine particles.

[0017] The concrete sludge is generated, for example, in the centrifugal molding of concrete products, in the manufacturing process of fresh concrete and concrete products, in the cleaning of concrete manufacturing facilities such as concrete mixers in fresh concrete factories and concrete factories, and in the cleaning of fresh concrete transport vehicles. It contains solids such as cement fine particles themselves and their hydration reaction products (calcium silicate hydrates and calcium hydroxide, etc.).

[0018] The solid-liquid separation unit 2 is generally used for dewatering (solid-liquid separation) of sludge and sewage. As the solid-liquid separation unit 2, for example, a pressure separation device that separates the solid content and the liquid content by using a filter and applying pressure or squeezing, a centrifugal separation device that separates the solid content and the liquid content by the action of centrifugal force, a sedimentation separation device that sediments the solid content by standing still, etc. are used.

[0019] The precipitation reaction unit 3 has a reaction tank 31 composed of an open-type normal pressure and normal temperature container. The reaction tank 31 is connected to the solid-liquid separation unit 2 via a pipe 32. A valve 33 is provided in the pipe 32. The sludge liquid separated by the solid-liquid separation unit 2 is supplied to the reaction tank 31 of the precipitation reaction unit 3 via the pipe 32. As will be described later, a dispersion member 34 for dispersing calcium carbonate precipitate formed in the sludge liquid is provided in the reaction tank 31. The dispersion member 34 is, for example, a stirrer.

[0020] The carbon dioxide supply unit 4 has a storage tank 41 for storing carbon dioxide or a carbon dioxide-containing gas. The storage tank 41 is connected to the reaction tank 31 of the precipitation reaction unit 3 via a pipe 42. A valve 43 is provided in the pipe 42. The carbon dioxide or the carbon dioxide-containing gas is supplied from the storage tank 41 to the reaction tank 31 of the precipitation reaction unit 3 via the pipe 42. From the viewpoint of improving environmental purification performance, the carbon dioxide-containing gas is preferably the exhaust gas of a thermal power plant, the exhaust gas from a boiler, the exhaust gas containing carbon dioxide discharged in the manufacturing process of other products, a high-concentration gas with an increased carbon dioxide concentration in the exhaust gas, or the like. Further, these gases may be adjusted in terms of humidity and temperature.

[0021] When carbon dioxide or a carbon dioxide-containing gas is supplied from the storage tank 41 to the reaction tank 31 storing the sludge liquid, the sludge liquid is bubbled with the carbon dioxide or the carbon dioxide-containing gas, and calcium in the cement fine particles in the sludge liquid reacts with carbon dioxide. By this reaction, calcium is carbonated, the carbon dioxide is immobilized, and crystallized calcium carbonate is precipitated in the sludge liquid. Thus, a calcium carbonate-containing slurry containing calcium carbonate obtained by immobilizing carbon dioxide can be produced in the reaction tank 31 of the precipitation reaction unit 3 using the sludge liquid as a raw material. At this point, the water content of the calcium carbonate-containing slurry produced is approximately 30 to 80%.

[0022] As shown in FIG. 1, in the water content adjustment step S20 carried out after the slurry production step S10, the water content of the calcium carbonate-containing slurry is measured and adjusted. The water content of the calcium carbonate-containing slurry is the ratio of the water contained in the calcium carbonate-containing slurry and is the weight water content. By measuring and adjusting the water content of the calcium carbonate-containing slurry in the water content adjustment step S20, it is possible to control the properties of the calcium carbonate-containing slurry so that the handling of the calcium carbonate-containing slurry becomes easy, to easily control the fresh properties of the hydraulic fluidized material in the hydraulic fluidized material preparation step S30 and the strength of the carbon dioxide-immobilized concrete in the hardening step S40, and to easily control the content of calcium carbonate contained in the carbon dioxide-immobilized concrete obtained in the hardening step S40, that is, the amount of CO2 immobilized.

[0023] In the water content adjustment step S20, the water content of the calcium carbonate-containing slurry can be measured using a water content measuring device. By using a non-contact type water content measuring device to measure the water content of the calcium carbonate-containing slurry without contacting the water content measuring device with the calcium carbonate-containing slurry, the measurement work becomes easy. As the non-contact type water content measuring device, a measuring device using infrared rays is suitable. Also, the water content of the calcium carbonate-containing slurry may be measured by bringing a contact type water content measuring device into contact with the calcium carbonate-containing slurry. For example, the amount of water in the calcium carbonate-containing slurry can be calculated from the amount of calcium carbonate obtained by heating a predetermined amount of the calcium carbonate-containing slurry to remove water from the calcium carbonate-containing slurry and the amount of the calcium carbonate-containing slurry, and based on these amounts, the water content of the calcium carbonate-containing slurry can be calculated. Also, the water content of the calcium carbonate-containing slurry can be calculated from the electrical resistivity of the calcium carbonate-containing slurry.

[0024] Measure the water content of the lightweight calcium carbonate-containing slurry, and adjust the water content of the lightweight calcium carbonate-containing slurry by adding moisture such as tap water to the lightweight calcium carbonate-containing slurry to obtain a lightweight calcium carbonate-containing slurry with adjusted water content. As a result of measuring the water content of the lightweight calcium carbonate-containing slurry, if the water content of the lightweight calcium carbonate-containing slurry is within a predetermined range, the adjustment of the water content of the lightweight calcium carbonate-containing slurry may not be performed. Hereinafter, for convenience, even when the adjustment of the water content of the lightweight calcium carbonate-containing slurry is not performed as a result of measuring the water content of the lightweight calcium carbonate-containing slurry, since the water content is within the predetermined range, the lightweight calcium carbonate-containing slurry is referred to as a lightweight calcium carbonate-containing slurry with adjusted water content.

[0025] Regarding the water content of the lightweight calcium carbonate-containing slurry with adjusted water content, the lower limit value is preferably 39% or more, more preferably 53% or more, and the upper limit value is preferably 98% or less, more preferably 70% or less. When the water content is 39% or more, it becomes slurry-like and is easy to handle. Also, when the water content is 98% or less, the amount of lightweight calcium carbonate contained in the slurry is sufficient, and the amount of CO2 fixed into the carbon dioxide-immobilized concrete can be increased.

[0026] Also, as shown in FIG. 1, in the hydraulic fluid preparation step S30 performed after the water content adjustment step S20, a hydraulic fluid is prepared. The hydraulic fluid contains a lightweight calcium carbonate-containing slurry with adjusted water content, cement, aggregate, and a precipitation inhibitor, and the content rate of the hydraulic fluid is within a predetermined range. The aggregate includes at least one of fine aggregate and coarse aggregate. The precipitation inhibitor suppresses the precipitation of lightweight calcium carbonate contained in the lightweight calcium carbonate-containing slurry with adjusted water content. Also, the hydraulic fluid immobilizes carbon dioxide gas.

[0027] The water content-adjusted lightweight calcium carbonate-containing slurry contained in the hydraulic fluidifying agent can be obtained without performing a treatment that emits a large amount of carbon dioxide gas such as heat treatment on the lightweight calcium carbonate-containing slurry obtained in the slurry production step S10. Therefore, the amount of carbon dioxide gas emissions can be reduced compared to the prior art.

[0028] Moreover, the cement contained in the hydraulic fluidifying agent is preferably a blended cement such as blast furnace cement containing blast furnace slag fine powder and a cementitious material, or fly ash cement containing fly ash and a cementitious material. As the blast furnace cement, those specified in JIS R 5211:2009 can be used.

[0029] Also, Portland cement may be used as the cement. Portland cement includes ordinary Portland cement, as well as types such as early strength, ultra-early strength, medium heat, and low heat sulfate-resistant, which are specified in JIS R 5210:2019. In the hydraulic fluidifying agent, those containing one or more of these various Portland cements can be used.

[0030] The fine aggregate contained in the hydraulic fluidifying agent is an aggregate defined in JIS A 5308, JIS A 5005, JIS A 5002, and JIS A 5011. Examples of the fine aggregate include crushed sand, sand, river sand, sea sand, lime crushed sand, recycled aggregate, lightweight aggregate, and heavyweight aggregate.

[0031] The coarse aggregate contained in the hydraulic fluidifying agent is an aggregate defined in JIS A 5308, JIS A 5005, JIS A 5002, and JIS A 5011, and is distinguished from the above-mentioned fine aggregate by the size of the particles, and is classified by whether it passes through a 5 mm sieve. In practical use, those that all pass through a 10 mm sieve and 85% or more by weight pass through a 5 mm sieve are regarded as fine aggregate, and those that remain at 85% or more by weight on a 5 mm sieve are regarded as coarse aggregate.

[0032] The precipitation inhibitor contained in the hydraulic fluidized product suppresses the precipitation of calcium carbonate in the hydraulic fluidized product. Therefore, even when the calcium carbonate contained in the moisture content-adjusted calcium carbonate-containing slurry is likely to precipitate in the hydraulic fluidized product due to the density difference with water, the precipitation inhibitor can suppress the precipitation of calcium carbonate. In this way, the uniformity of the hydraulic fluidized product is improved, and it becomes easier to control the fresh properties of the hydraulic fluidized product and the strength of the carbon dioxide-immobilized concrete.

[0033] The precipitation inhibitor is preferably at least one selected from the group consisting of polyacrylates such as sodium polyacrylate, cellulose-based and acrylic thickeners, AE agents (Air Entraining Agents), naphthalene-based, lignin-based, polycarboxylic acid-based water reducers, and alkalis. The precipitation inhibitor may be used alone or in combination of two or more. For example, polyacrylate is preferably used in elutriation treatment. The AE agent acts as a surfactant. The alkali is used to shift the pH of the hydraulic fluidized product from the isoelectric point.

[0034] The content ratio of the moisture content-adjusted calcium carbonate-containing slurry contained in the hydraulic fluidized product is preferably 0.5 vol% or more, more preferably 5.0 vol% or more, and still more preferably 10.0 vol% or more. When the content ratio of the moisture content-adjusted calcium carbonate-containing slurry contained in the hydraulic fluidized product is 0.5 vol% or more, the amount of carbon dioxide immobilized in the carbon dioxide-immobilized concrete is sufficient. Further, the content ratio of the moisture content-adjusted calcium carbonate-containing slurry contained in the hydraulic fluidized product is preferably 28.0 vol% or less, more preferably 23.0 vol% or less, and still more preferably 18.5 vol% or less. When the content ratio of the moisture content-adjusted calcium carbonate-containing slurry contained in the hydraulic fluidized product is 28.0 vol% or less, the fresh properties of the hydraulic fluidized product are good.

[0035] In addition to the above components, the hydraulic fluidifying agent may contain an expanding agent or a retarder. Also, within the scope where the effects of the present invention are achieved, other admixtures and the like may be further contained. Examples of other admixtures include carbonation admixtures such as γ - belite, glass fiber, coal ash, fly ash, fine limestone powder, water - reducing agent, fluidizing agent, and the like.

[0036] Further, depending on the state of the hydraulic fluidifying agent, the desired performance of the hydraulic fluidifying agent or the carbon dioxide - immobilized concrete obtained in the hardening step S40, water may be added to the hydraulic fluidifying agent in the hydraulic fluidifying agent preparation step S30.

[0037] Also, as shown in FIG. 1, in the hardening step S40 carried out after the hydraulic fluidifying agent preparation step S30, the hydraulic fluidifying agent obtained in the hydraulic fluidifying agent preparation step S30 is placed and hardened to obtain carbon dioxide - immobilized concrete. The carbon dioxide - immobilized concrete is a hardened product and immobilizes carbon dioxide.

[0038] In the hardening step S40, after placement, the hydraulic fluidifying agent that immobilizes carbon dioxide is cured in the air to harden, whereby carbon dioxide - immobilized concrete that immobilizes carbon dioxide can be obtained.

[0039] The carbon dioxide - immobilized concrete thus produced can significantly reduce the carbon dioxide emission compared with the conventional one. Also, since the carbon dioxide - immobilized concrete can maintain alkalinity, it can suppress the corrosion of steel materials in the carbon dioxide - immobilized concrete. Furthermore, the carbon dioxide - immobilized concrete obtained in the above process using the light calcium carbonate - containing slurry has many fine air bubbles introduced therein. Therefore, it is excellent in freeze - thaw resistance, fluidity, and material separation resistance.

[0040] In addition, the method for manufacturing carbon dioxide - fixed concrete according to the embodiment may further include a forced carbonation step. The forced carbonation step supplies a carbon dioxide source to at least one of the hydraulic fluidized material after placement and before hardening and the carbon dioxide - fixed concrete, and forcibly fixes carbon dioxide. The supply of the carbon dioxide source in the forced carbonation step forcibly supplies the carbon dioxide source to the hydraulic fluidized material or the carbon dioxide - fixed concrete.

[0041] The hydraulic fluidized material after placement and before hardening and the carbon dioxide - fixed concrete after hardening contain calcium of unreacted cement fine particles in the slurry production step S10. Therefore, when the unreacted calcium present on the surface of the hydraulic fluidized material or the carbon dioxide - fixed concrete reacts with the forcibly supplied carbon dioxide source, the carbon dioxide - fixed concrete can further fix carbon dioxide on the surface. Furthermore, as described above, the carbon dioxide - fixed concrete has many fine bubbles introduced therein. The supplied carbon dioxide can easily penetrate into the fine bubbles. Therefore, since the diffusion path of carbon dioxide due to the fine bubbles increases, the carbon dioxide fixation rate is improved.

[0042] As the carbon dioxide source in the forced carbonation step, any of gaseous, liquid, and solid carbon dioxide sources may be used. From the viewpoints of ease of handling, ease of supply, and ease of availability, the carbon dioxide source is preferably a gaseous carbon dioxide source, and more preferably carbon dioxide or a carbon dioxide - containing gas. Among them, from the viewpoint of improving environmental purification, the carbon dioxide - containing gas is preferably the exhaust gas from a thermal power plant, the exhaust gas from a boiler, or the exhaust gas containing carbon dioxide discharged in the manufacturing process of other products. Also, these exhaust gases may have their humidity and temperature adjusted.

[0043] As described above, the embodiments have been described, but the present invention is not limited to the above - described embodiments, and includes all aspects included in the concept of the present disclosure and the scope of the claims, and can be variously modified within the scope of the present disclosure.

Examples

[0044] Next, examples and comparative examples will be described, but the present invention is not limited to these examples.

[0045] (Examples A1 to A9) The properties of the light calcium carbonate-containing slurry obtained by supplying carbon dioxide gas to the sludge liquid obtained by solid-liquid separation of concrete sludge were investigated. Table 1 shows the mass M of the light calcium carbonate-containing slurry, the content P of residues such as light calcium carbonate contained in the light calcium carbonate-containing slurry, the water content W contained in the light calcium carbonate-containing slurry, the water content rate A of the light calcium carbonate-containing slurry, and the properties of the light calcium carbonate-containing slurry.

[0046] Regarding the content P of residues such as light calcium carbonate contained in the light calcium carbonate-containing slurry, the light calcium carbonate-containing slurry with the mass M shown in Table 1 was heated in a drying oven with the furnace temperature set at 105°C, and the residue obtained by removing moisture from the light calcium carbonate-containing slurry was measured. Also, the water content W and the water content rate A of the light calcium carbonate-containing slurry were calculated from the following formulas.

[0047] Water content W = M - P Water content rate A of light calcium carbonate-containing slurry = W / (W + P)

[0048]

Table 1

[0049] As shown in Table 1, when the water content rate of the light calcium carbonate-containing slurry is 39% or more, since it has the property of being in a slurry state, it was found that the light calcium carbonate-containing slurry can be used as a raw material for hydraulic fluidifying agents without adjusting the water content rate. Among them, it was found that the water content rate of the light calcium carbonate-containing slurry is preferably 53% or more and 70% or less.

[0050] Also, as in Example A9, when the water content rate of the light calcium carbonate-containing slurry was less than 39%, it was found to be in a paste state. In such a case, tap water or the like can be added to the light calcium carbonate-containing slurry to increase the water content rate of the light calcium carbonate-containing slurry, thereby imparting a slurry-like property. Then, the light calcium carbonate-containing slurry with the adjusted water content rate is used as a raw material for the hydraulic fluidifying agent.

[0051] (Examples B1 to B2 and Comparative Example B1) Using the materials shown in Table 2, a hydraulic fluidifying agent having the composition shown in Table 3 was prepared. Then, carbon dioxide gas-immobilized concrete was produced using the hydraulic fluidifying agent in Table 3. Table 4 shows the fresh properties of the hydraulic fluidifying agent, as well as the compressive strength and CO2 immobilization amount of the carbon dioxide gas-immobilized concrete. Regarding LSS, based on the results obtained from the above examples, a light calcium carbonate-containing slurry adjusted to a water content rate of 70 was adopted. Also, in Table 3, W / B is the water-binder ratio, s / a is the volume ratio (fine aggregate ratio) of fine aggregate among the aggregates, LSSw represents the water in the light calcium carbonate-containing slurry, and LSSp represents the light calcium carbonate in the light calcium carbonate-containing slurry. Further, the compressive strength shown in Table 4 was measured for the carbon dioxide gas-immobilized concrete 1 day, 7 days, and 28 days after placing the hydraulic fluidifying agent.

[0052]

Table 2

[0053]

Table 3

[0054]

Table 4

[0055] As shown in Table 4, the carbon dioxide - immobilized concrete obtained in Examples B1 to B2 was able to reduce the amount of carbon dioxide emissions compared to the conventional ones.

[0056] (Examples C1 to C2 and Comparative Example C1) Using the materials shown in Table 5, a hydraulic fluidized product with the composition shown in Table 6 was prepared. Then, carbon dioxide - immobilized concrete was produced using the hydraulic fluidized product in Table 6. Furthermore, forced carbonation was performed on the carbon dioxide - immobilized concrete. Table 7 shows the fresh properties of the hydraulic fluidized product, the compressive strength and CO2 fixation amount of the carbon dioxide - immobilized concrete, and the CO2 fixation amount after forced carbonation.

[0057]

Table 5

[0058]

Table 6

[0059]

Table 7

[0060] As shown in Table 7, the carbon dioxide - immobilized concrete obtained in Examples C1 to C2 was able to reduce the amount of carbon dioxide emissions compared to the conventional ones. Furthermore, by subjecting the carbon dioxide - immobilized concrete to forced carbonation, the amount of carbon dioxide fixation could be further increased.

Explanation of Symbols

[0061] 1 Light calcium carbonate - containing slurry production device 2 Solid - liquid separation section 3 Precipitation reaction section 4 Carbon dioxide supply section 31 Reaction tank 32 Pipe 33 Valve 34 Dispersion member 41 Storage tank 42 Pipe 43 Valve

Claims

1. A slurry production step of producing a calcium carbonate-containing slurry containing calcium carbonate precipitated in the sludge liquid and immobilizing the carbon dioxide gas by supplying carbon dioxide gas to the sludge liquid obtained by solid-liquid separation of concrete sludge; A water content adjustment step of measuring and adjusting the water content of the calcium carbonate-containing slurry; A hydraulic fluid preparation step of preparing a hydraulic fluid containing the water content-adjusted calcium carbonate-containing slurry with the adjusted water content, cement, aggregate, and a precipitation inhibitor for suppressing precipitation of the calcium carbonate, and having the water content within a predetermined range; A curing step of placing and curing the hydraulic fluid to obtain carbon dioxide gas-immobilized concrete and The precipitation inhibitor is one or more selected from the group consisting of polyacrylate, thickener, and alkali. A method for producing carbon dioxide gas-immobilized concrete.

2. A slurry production step of producing a calcium carbonate-containing slurry containing calcium carbonate precipitated in the sludge liquid and immobilizing the carbon dioxide gas by supplying carbon dioxide gas to the sludge liquid obtained by solid-liquid separation of concrete sludge; A water content adjustment step of measuring and adjusting the water content of the calcium carbonate-containing slurry; A hydraulic fluid preparation step of preparing a hydraulic fluid containing the water content-adjusted calcium carbonate-containing slurry with the adjusted water content, cement, aggregate, and a precipitation inhibitor for suppressing precipitation of the calcium carbonate, and having the water content within a predetermined range; A curing step of placing and curing the hydraulic fluid to obtain carbon dioxide gas-immobilized concrete and The precipitation inhibitor is one or more selected from the group consisting of polyacrylate, thickener, and alkali, and the water content of the water content-adjusted calcium carbonate-containing slurry is 39% or more and 82% or less. A method for producing carbon dioxide gas-immobilized concrete.

3. The water content of the water content-adjusted calcium carbonate-containing slurry is 39% or more and 98% or less. The method for producing carbon dioxide gas-immobilized concrete according to Claim 1.

4. The method for producing carbon dioxide gas-immobilized concrete according to any one of claims 1 to 3, wherein in the water content adjustment step, the water content of the calcium carbonate light-containing slurry is measured non-contact.

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