JP7713383B2 - Manufacturing method of carbon dioxide fixed concrete - Google Patents

Description

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

The cement used in concrete emits more carbon dioxide ( _CO2 ) during the decarbonation of the raw materials and the fuel used in the firing process than during production. In response to the growing interest in mitigating climate change in recent years, there is a demand to significantly reduce the amount of carbon dioxide emissions during the production of concrete.

As one method of reducing carbon dioxide emissions, blended cement, in which granulated blast furnace slag (hereinafter simply referred to as ground granulated blast furnace slag) is mixed into cement, is widely used. However, increasing the amount of ground granulated blast furnace slag slows down the hardening process, lengthening the time until demolding, and requires long periods of wet curing to obtain sufficient strength. As a result, issues remain in terms of construction time and cost.

Patent Document 1 also describes a concrete sludge treatment device that has a sludge separation device that separates concrete sludge generated in the centrifugal molding process into sludge cake and sludge liquid, a precipitation reaction device that precipitates calcium carbonate from the sludge liquid separated by the sludge separation device, and a calcium carbonate separation device that separates calcium carbonate from the precipitated liquid. In the precipitation reaction device, calcium carbonate is precipitated by supplying carbon dioxide to the sludge liquid. Therefore, by using the calcium carbonate obtained by the concrete sludge treatment device of Patent Document 1 as a raw material for concrete, it is possible to reduce carbon dioxide emissions.

However, in Patent Document 1, the precipitate liquid from which calcium carbonate has precipitated is subjected to a dehydration process and a heat treatment to remove water, thereby obtaining calcium carbonate powder. In this process, since a heat treatment is performed, a considerable amount of carbon dioxide gas is emitted in order to obtain calcium carbonate. Therefore, although the technology in Patent Document 1 can reduce the amount of carbon dioxide gas emitted, there is still room for further reduction in the amount of carbon dioxide gas emitted.

Patent No. 4892520

The object of the present invention is to provide a method for producing carbon dioxide-fixed concrete that can reduce carbon dioxide emissions compared to conventional methods.

[1] A method for producing carbon dioxide-immobilized concrete, comprising: a slurry production step of supplying carbon dioxide gas to a sludge liquid obtained by solid-liquid separation of concrete sludge, to produce a light calcium carbonate-containing slurry containing light calcium carbonate that has been precipitated in the sludge liquid and has the carbon dioxide gas immobilized therein; a moisture content adjustment step of measuring and adjusting the moisture content of the light calcium carbonate-containing slurry; a hydraulic fluidized material preparation step of preparing a moisture-adjusted light calcium carbonate-containing slurry obtained by adjusting the moisture content of the light calcium carbonate-containing slurry, the light calcium carbonate-containing slurry containing cement, aggregate, and a precipitation inhibitor for inhibiting precipitation of the light calcium carbonate, the moisture content of which is within a predetermined range; and a hardening step of pouring and hardening the hydraulic fluidized material to obtain carbon dioxide-immobilized concrete.
[2] The method for producing carbon dioxide fixed concrete according to the above [1], wherein the precipitation inhibitor is one or more selected from the group consisting of polyacrylates, thickeners, air entraining agents, water reducing agents and alkalis.
[3] The method for producing carbon dioxide fixed concrete according to the above [1] or [2], wherein the moisture content of the moisture-adjusted precipitated calcium carbonate-containing slurry is 39% or more and 98% or less.
[4] The method for producing carbon dioxide fixed concrete according to any one of the above-mentioned [1] to [3], wherein the moisture content of the precipitated calcium carbonate-containing slurry is measured in a non-contact manner in the moisture content adjusting step.

The present invention provides a method for producing carbon dioxide-fixed concrete that can reduce carbon dioxide emissions compared to conventional methods.

FIG. 1 is a flowchart showing an example of a method for producing carbon dioxide fixed concrete according to an embodiment. FIG. 2 is a schematic diagram showing an example of an apparatus for producing a precipitated calcium carbonate-containing slurry used in the slurry production step.

The following provides a detailed explanation based on the embodiment.

The method for producing carbon dioxide-immobilized concrete of the present invention includes a slurry production step of supplying carbon dioxide to a sludge liquid obtained by solid-liquid separation of concrete sludge, and producing a light calcium carbonate-containing slurry containing light calcium carbonate that is precipitated in the sludge liquid and has the carbon dioxide immobilized therein; a moisture content adjustment step of measuring and adjusting the moisture content of the light calcium carbonate-containing slurry; a hydraulic fluidized material preparation step of preparing a moisture-adjusted light calcium carbonate-containing slurry in which the moisture content of the light calcium carbonate-containing slurry has been adjusted, a hydraulic fluidized material that contains cement, aggregate, and a precipitation inhibitor for inhibiting the precipitation of the light calcium carbonate and has a moisture content within a predetermined range; and a hardening step of casting and hardening the hydraulic fluidized material to obtain carbon dioxide-immobilized concrete.

Figure 1 is a flow chart showing an example of a method for producing carbon dioxide-fixed concrete according to an embodiment. Figure 2 is a schematic diagram showing an example of a light calcium carbonate-containing slurry production apparatus used in the slurry production process. As shown in Figure 1, the method for producing carbon dioxide-fixed concrete according to an embodiment includes a slurry production process S10, a water content adjustment process S20, a hydraulic fluid preparation process S30, and a hardening process S40.

In the slurry production step S10 of the method for producing carbon dioxide gas fixed concrete, carbon dioxide gas (carbon dioxide, _CO2 ) is supplied to the sludge liquid obtained by solid-liquid separation of concrete sludge to precipitate light calcium carbonate in the sludge liquid. The light calcium carbonate precipitated in the sludge liquid fixes the carbon dioxide gas supplied to the sludge liquid. In this way, a light calcium carbonate-containing slurry containing light calcium carbonate with fixed carbon dioxide gas is produced.

In the slurry production step S10, a light calcium carbonate-containing slurry production apparatus 1 shown in FIG. 2 is preferably used to produce a light calcium carbonate-containing slurry. The light calcium carbonate-containing slurry production apparatus 1 mainly includes a solid-liquid separation section 2, a precipitation reaction section 3, and a carbon dioxide gas supply section 4.

The solid-liquid separation section 2 separates concrete sludge, which is concrete waste containing unsolidified cement particles, into a sludge cake, which is the solid content, and a sludge liquid, which is the liquid content containing unsolidified cement particles.

Concrete sludge is generated, for example, during the centrifugal molding of concrete products, during the manufacturing process of ready-mix concrete or concrete products, during the cleaning of concrete manufacturing equipment such as concrete mixers at ready-mix concrete plants or concrete factories, and during the cleaning of ready-mix concrete transport vehicles, and contains solids such as the fine cement particles themselves and their hydration reaction products (calcium silicate hydrates, calcium hydroxide, etc.).

The solid-liquid separation section 2 is generally used for dewatering sludge or wastewater (solid-liquid separation). Examples of the solid-liquid separation section 2 include a pressurized separation device that separates solids and liquids by applying pressure or squeezing using a filter, a centrifugal separation device that separates solids and liquids by centrifugal force, and a sedimentation separation device that allows solids to settle by leaving them to stand.

The precipitation reaction section 3 has a reaction tank 31 composed of an open-type normal pressure/normal temperature container. The reaction tank 31 is connected to the solid-liquid separation section 2 via a pipe 32. The pipe 32 is provided with a valve 33. The sludge liquid separated in the solid-liquid separation section 2 is supplied to the reaction tank 31 of the precipitation reaction section 3 via the pipe 32. The reaction tank 31 is provided with a dispersion member 34 that disperses the precipitated light calcium carbonate in the sludge liquid, as described below. The dispersion member 34 is, for example, an agitator.

The carbon dioxide gas supply unit 4 has a storage tank 41 for storing carbon dioxide gas 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 on the pipe 42. The carbon dioxide gas 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, the carbon dioxide-containing gas is preferably exhaust gas from a thermal power plant, exhaust gas from a boiler, exhaust gas containing carbon dioxide emitted in the manufacturing process of other products, or a high-concentration gas with an increased carbon dioxide concentration in the exhaust gas. In addition, the humidity and temperature of these gases may be adjusted.

When carbon dioxide gas or a gas containing carbon dioxide 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 gas or the gas containing carbon dioxide gas, and the calcium of the cement particles in the sludge liquid reacts with carbon dioxide. This reaction causes the calcium to be carbonated, the carbon dioxide gas to be immobilized, and crystallized light calcium carbonate is precipitated in the sludge liquid. In this way, a light calcium carbonate-containing slurry containing light calcium carbonate with immobilized carbon dioxide gas can be produced in the reaction tank 31 of the precipitation reaction section 3 using the sludge liquid as a raw material. The moisture content of the light calcium carbonate-containing slurry produced at this point is approximately 30 to 80%.

As shown in Fig. 1, in the moisture content adjusting step S20 performed after the slurry production step S10, the moisture content of the light calcium carbonate-containing slurry is measured and adjusted. The moisture content of the light calcium carbonate-containing slurry is the proportion of water contained in the light calcium carbonate-containing slurry, and is a weight moisture content. By measuring and adjusting the moisture content of the light calcium carbonate-containing slurry in the moisture content adjusting step S20, it is possible to control the properties of the light calcium carbonate-containing slurry so that the light calcium carbonate-containing slurry is easy to handle, 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-fixed concrete in the hardening step S40, and to easily control the content of light calcium carbonate contained in the carbon dioxide-fixed concrete obtained in the hardening step S40, i.e., the amount of _CO2 fixed.

In the moisture content adjustment step S20, the moisture content of the light calcium carbonate-containing slurry can be measured using a moisture content measuring device. If the moisture content of the light calcium carbonate-containing slurry is measured in a non-contact manner using a non-contact moisture content measuring device without contacting the light calcium carbonate-containing slurry, the measurement work becomes easier. As a non-contact moisture content measuring device, a measuring device using infrared rays is suitable. In addition, the moisture content of the light calcium carbonate-containing slurry may be measured by contacting a contact moisture content measuring device with the light calcium carbonate-containing slurry. For example, the moisture content of the light calcium carbonate-containing slurry can be calculated from the amount of light calcium carbonate obtained by heating a predetermined amount of the light calcium carbonate-containing slurry to remove moisture from the light calcium carbonate-containing slurry and the amount of the light calcium carbonate-containing slurry, and the moisture content of the light calcium carbonate-containing slurry can be calculated based on these amounts. In addition, the moisture content of the light calcium carbonate-containing slurry can be calculated from the electrical resistivity of the light calcium carbonate-containing slurry.

The moisture content of the light calcium carbonate-containing slurry is measured, and water such as tap water is added to the light calcium carbonate-containing slurry to adjust the moisture content of the light calcium carbonate-containing slurry, thereby obtaining a light calcium carbonate-containing slurry with an adjusted moisture content. If the moisture content of the light calcium carbonate-containing slurry is within a predetermined range as a result of measuring the moisture content of the light calcium carbonate-containing slurry, the moisture content of the light calcium carbonate-containing slurry does not need to be adjusted. Hereinafter, for convenience, the light calcium carbonate-containing slurry will be referred to as a light calcium carbonate-containing slurry with an adjusted moisture content, since the moisture content of the light calcium carbonate-containing slurry is within a predetermined range even if the moisture content of the light calcium carbonate-containing slurry is not adjusted as a result of measuring the moisture content of the light calcium carbonate-containing slurry.

The lower limit of the moisture content of the moisture-adjusted light calcium carbonate-containing slurry is preferably 39% or more, more preferably 53% or more, and the upper limit is preferably 98% or less, more preferably 70% or less. When the moisture content is 39% or more, the slurry becomes slurried and is easy to handle. When the moisture content is 98% or less, the amount of light calcium carbonate contained in the slurry is sufficient, and the amount of _CO2 fixed in the carbon dioxide gas-fixed concrete can be increased.

As shown in FIG. 1, in the hydraulic fluid preparation step S30 carried out after the moisture content adjustment step S20, a hydraulic fluid is prepared. The hydraulic fluid contains a moisture-adjusted light calcium carbonate-containing slurry, cement, aggregate, and a precipitation inhibitor, and the content of the hydraulic fluid is within a predetermined range. The aggregate contains at least one of fine aggregate and coarse aggregate. The precipitation inhibitor inhibits the precipitation of light calcium carbonate contained in the moisture-adjusted light calcium carbonate-containing slurry. The hydraulic fluid also immobilizes carbon dioxide gas.

The moisture content adjusted light calcium carbonate-containing slurry contained in the hydraulic fluid can be obtained without carrying out a process that emits a large amount of carbon dioxide, such as a heating process, on the light calcium carbonate-containing slurry obtained in the slurry production process S10. Therefore, the amount of carbon dioxide emitted can be reduced compared to the conventional method.

The cement contained in the hydraulic fluid is preferably a mixed cement such as blast furnace cement containing ground granulated blast furnace slag and cementing material, or fly ash cement containing fly ash and cementing material. The blast furnace cement specified in JIS R 5211:2009 can be used.

Portland cement may also be used as the cement. In addition to ordinary Portland cement, there are other types of Portland cement, such as early strength, super early strength, moderate heat, and low heat sulfate resistance, which are specified in JIS R 5210:2019. In hydraulic fluidized materials, one or more of these various Portland cements may be used.

The fine aggregate contained in the hydraulic fluidized material is an aggregate defined in JIS A 5308, JIS A 5005, JIS A 5002, and JIS A 5011. Examples of fine aggregate include crushed sand, sand, river sand, sea sand, crushed lime sand, recycled aggregate, lightweight aggregate, heavy aggregate, etc.

The coarse aggregate contained in hydraulic fluidized material is defined in JIS A 5308, JIS A 5005, JIS A 5002 and JIS A 5011, and is differentiated from the above fine aggregates by the size of the particles, and by whether or not it passes through a 5 mm sieve. In practice, fine aggregate is defined as aggregate that passes through a 10 mm sieve entirely, and at least 85% of the aggregate passes through a 5 mm sieve by weight, while coarse aggregate is defined as aggregate that is retained on a 5 mm sieve by 85% by weight.

The precipitation inhibitor contained in the hydraulic fluidized material inhibits the precipitation of light calcium carbonate in the hydraulic fluidized material. Therefore, even if the light calcium carbonate contained in the moisture-adjusted light calcium carbonate-containing slurry is prone to precipitate in the hydraulic fluidized material due to its density difference with water, the precipitation inhibitor can inhibit the precipitation of light calcium carbonate. In this way, the uniformity of the hydraulic fluidized material is improved, making it easier to control the fresh properties of the hydraulic fluidized material and the strength of carbon dioxide-fixed concrete.

The precipitation inhibitor is preferably one or more selected from the group consisting of polyacrylates such as sodium polyacrylate, cellulose-based or acrylic-based thickeners, AE agents (Air Entraining Agents), naphthalene-based, lignin-based, and polycarboxylic acid-based water reducers, and alkalis. The precipitation inhibitors may be used alone or in combination of two or more. For example, polyacrylates are preferably used in elutriation treatment. AE agents act as surfactants. Alkalis are used to shift the pH of the hydraulic fluid from the isoelectric point.

The content of the water-adjusted light calcium carbonate-containing slurry in the hydraulic fluid is preferably 0.5 vol% or more, more preferably 5.0 vol% or more, and even more preferably 10.0 vol% or more. When the content of the water-adjusted light calcium carbonate-containing slurry in the hydraulic fluid is 0.5 vol% or more, the amount of carbon dioxide fixed in the carbon dioxide gas fixed concrete is sufficient. In addition, the content of the water-adjusted light calcium carbonate-containing slurry in the hydraulic fluid is preferably 28.0 vol% or less, more preferably 23.0 vol% or less, and even more preferably 18.5 vol% or less. When the content of the water-adjusted light calcium carbonate-containing slurry in the hydraulic fluid is 28.0 vol% or less, the fresh properties of the hydraulic fluid are good.

The hydraulic fluid may contain an expansion agent and a retarder in addition to the above components. It may also contain other admixtures within the scope of the effects of the present invention. Examples of other admixtures include carbonate admixtures such as gamma belite, glass fiber, coal ash, fly ash, limestone fine powder, water reducing agents, and fluidizing agents.

In addition, water may be added to the hydraulic fluid in the hydraulic fluid preparation step S30 depending on the state of the hydraulic fluid and the desired performance of the hydraulic fluid and the carbon dioxide fixed concrete obtained in the hardening step S40.

As shown in FIG. 1, in the hardening step S40 carried out after the hydraulic fluid preparation step S30, the hydraulic fluid obtained in the hydraulic fluid preparation step S30 is poured and hardened to obtain carbon dioxide-fixed concrete. Carbon dioxide-fixed concrete is a hardened material in which carbon dioxide is fixed.

In the hardening step S40, after casting, the hydraulic fluid material in which the carbon dioxide gas has been fixed is cured in air to harden, thereby obtaining carbon dioxide-fixed concrete in which the carbon dioxide gas has been fixed.

The carbon dioxide-fixed concrete produced in this way can reduce carbon dioxide emissions significantly compared to conventional methods. In addition, because the carbon dioxide-fixed concrete can maintain its alkaline nature, corrosion of the steel material within the carbon dioxide-fixed concrete can be suppressed. Furthermore, the carbon dioxide-fixed concrete obtained in the above process using the above-mentioned light calcium carbonate-containing slurry has many fine air bubbles introduced into it. As a result, it has excellent freeze-thaw resistance, fluidity, and material separation resistance.

The manufacturing method of the carbon dioxide fixed concrete of the embodiment may further include a forced carbonation process. In the forced carbonation process, a carbon dioxide source is supplied to at least one of the hydraulic fluidized material and the carbon dioxide fixed concrete after casting and before hardening, to forcibly fix the carbon dioxide. The supply of the carbon dioxide source in the forced carbonation process is performed by forcibly supplying the carbon dioxide source to the hydraulic fluidized material and the carbon dioxide fixed concrete.

The hydraulic fluidized material after casting and before hardening, and the carbon dioxide fixed concrete after hardening, contain calcium from the cement particles that did not react in the slurry production process S10. Therefore, when the unreacted calcium present on the surface of the hydraulic fluidized material or the carbon dioxide fixed concrete reacts with the carbon dioxide source that is forcibly supplied, the carbon dioxide fixed concrete can further fix the carbon dioxide on the surface. Furthermore, as described above, many fine bubbles are introduced inside the carbon dioxide fixed concrete. The supplied carbon dioxide can easily penetrate into the fine bubbles. Therefore, the diffusion path of the carbon dioxide gas through the fine bubbles increases, and the fixation speed of the carbon dioxide gas is improved.

The carbon dioxide gas source in the forced carbonation process may be any of gaseous, liquid, and solid carbon dioxide gas sources. From the viewpoints of ease of handling, supply, and availability, the carbon dioxide gas source is preferably a gaseous carbon dioxide gas source, and more preferably carbon dioxide gas or a carbon dioxide gas-containing gas. Among these, from the viewpoint of improving environmental purification, the carbon dioxide gas-containing gas is preferably exhaust gas from a thermal power plant, exhaust gas from a boiler, or exhaust gas containing carbon dioxide emitted in the manufacturing process of other products. In addition, the humidity and temperature of these exhaust gases may be adjusted.

Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects included in the concept and claims of this disclosure, and can be modified in various ways within the scope of this disclosure.

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

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

The content P of residues such as light calcium carbonate contained in the light calcium carbonate-containing slurry was obtained by heating the light calcium carbonate-containing slurry having a mass M shown in Table 1 in an oven with an internal temperature set to 105°C, and measuring the residue obtained by removing water from the light calcium carbonate-containing slurry. The water content W and the water content A of the light calcium carbonate-containing slurry were calculated from the following formulas.

Water content W = M - P
Water content of the slurry containing precipitated calcium carbonate A=W/(W+P)

As shown in Table 1, when the moisture content of the slurry containing light calcium carbonate is 39% or more, it has slurry-like properties, and therefore it was found that the slurry containing light calcium carbonate can be used as a raw material for hydraulic fluidized materials without adjusting the moisture content. In particular, it was found that the moisture content of the slurry containing light calcium carbonate is preferably 53% or more and 70% or less.

In addition, as in Example A9, it was found that when the moisture content of the light calcium carbonate-containing slurry is less than 39%, it is in a paste-like state. In such a case, tap water or the like can be added to the light calcium carbonate-containing slurry to increase the moisture content of the light calcium carbonate-containing slurry, thereby imparting slurry-like properties. The light calcium carbonate-containing slurry with the moisture content adjusted is then used as a raw material for the hydraulic fluidized material.

(Examples B1 to B2 and Comparative Example B1)
Using the materials shown in Table 2, a hydraulic fluidized material having the composition shown in Table 3 was prepared. Carbon dioxide-fixed concrete was then produced using the hydraulic fluidized material shown in Table 3. Table 4 shows the fresh properties of the hydraulic fluidized material, as well as the compressive strength and _CO2 fixation amount of the carbon dioxide-fixed concrete. For the LSS, a light calcium carbonate-containing slurry prepared to a water content of 70 was used based on the results obtained from the above examples. In addition, in Table 3, W/B is the water-binder ratio, s/a is the volume ratio of fine aggregate to aggregate (fine aggregate ratio), LSSw indicates the water in the light calcium carbonate-containing slurry, and LSSp indicates the light calcium carbonate in the light calcium carbonate-containing slurry. In addition, the compressive strength shown in Table 4 was measured for the carbon dioxide-fixed concrete 1 day, 7 days, and 28 days after the hydraulic fluidized material was cast.

As shown in Table 4, the carbon dioxide fixed concrete obtained in Examples B1 and B2 was able to reduce the amount of carbon dioxide emissions compared to conventional methods.

(Examples C1 to C2 and Comparative Example C1)
A hydraulic fluidized material having the composition shown in Table 6 was prepared using the materials shown in Table 5. Carbon dioxide fixed concrete was then produced using the hydraulic fluidized material in Table 6. Furthermore, the carbon dioxide fixed concrete was subjected to forced carbonation. Table 7 shows the fresh properties of the hydraulic fluidized material, the compressive strength and _CO2 fixation amount of the carbon dioxide fixed concrete, and the _CO2 fixation amount after forced carbonation.

As shown in Table 7, the carbon dioxide fixed concrete obtained in Examples C1 and C2 was able to reduce the amount of carbon dioxide emissions compared to conventional concrete. Furthermore, the amount of carbon dioxide fixed could be further increased by forcibly carbonating the carbon dioxide fixed concrete.

REFERENCE SIGNS LIST 1 Precipitated calcium carbonate-containing slurry manufacturing apparatus 2 Solid-liquid separation section 3 Precipitation reaction section 4 Carbon dioxide gas supply section 31 Reaction tank 32 Pipe 33 Valve 34 Dispersion member 41 Storage tank 42 Pipe 43 Valve

Claims (4)

a slurry production step of supplying carbon dioxide gas to a sludge liquid obtained by solid-liquid separation of concrete sludge to produce a light calcium carbonate-containing slurry containing light calcium carbonate precipitated in the sludge liquid and having the carbon dioxide gas immobilized therein;
A moisture content adjusting step of measuring and adjusting the moisture content of the precipitated calcium carbonate-containing slurry;
a hydraulic fluidized material preparation step of preparing a hydraulic fluidized material containing a moisture-adjusted light calcium carbonate-containing slurry obtained by adjusting the moisture content of the light calcium carbonate-containing slurry, cement, aggregate, and a precipitation inhibitor for inhibiting precipitation of the light calcium carbonate, the hydraulic fluidized material having a moisture content within a predetermined range;
and a hardening step of casting and hardening the hydraulic fluid to obtain carbon dioxide-fixed concrete .
The method for producing carbon dioxide fixed concrete, wherein the precipitation inhibitor is one or more selected from the group consisting of polyacrylates, thickeners and alkalis . a slurry production step of supplying carbon dioxide gas to a sludge liquid obtained by solid-liquid separation of concrete sludge to produce a light calcium carbonate-containing slurry containing light calcium carbonate precipitated in the sludge liquid and having the carbon dioxide gas immobilized therein;
A moisture content adjusting step of measuring and adjusting the moisture content of the precipitated calcium carbonate-containing slurry;
a hydraulic fluidized material preparation step of preparing a hydraulic fluidized material containing a moisture-adjusted light calcium carbonate-containing slurry obtained by adjusting the moisture content of the light calcium carbonate-containing slurry, cement, aggregate, and a precipitation inhibitor for inhibiting precipitation of the light calcium carbonate, the hydraulic fluidized material having a moisture content within a predetermined range;
a hardening step of casting and hardening the hydraulic fluid to obtain carbon dioxide fixed concrete;
having
the precipitation inhibitor is at least one selected from the group consisting of polyacrylates, thickeners, and alkalis ;
The method for producing carbon dioxide fixed concrete , wherein the moisture content of the moisture content-adjusted precipitated calcium carbonate-containing slurry is 39% or more and 82% or less . 2. The method for producing carbon dioxide fixed concrete according to claim 1 , wherein the moisture content of the moisture content-adjusted precipitated calcium carbonate-containing slurry is 39% or more and 98% or less. The method for producing carbon dioxide fixed concrete according to any one of claims 1 to 3, wherein in the moisture content adjusting step, the moisture content of the precipitated calcium carbonate-containing slurry is measured in a non-contact manner.