Method for producing light-weight foam concrete

Abstract

To simultaneously achieve contribution to CO2 discharge amount reduction and holding of productivity and physical property of an ALC product in a production process of light-weight foam concrete (ALC).SOLUTION: A method for producing light-weight foam concrete comprises: a raw material slurry blending step of obtaining a carbon dioxide discharge suppression-type raw material slurry by adding and mixing calcium carbonate fine powder of an average particles diameter of 1.0 μm or more and 15.0 μm or less to a main raw material slurry containing a solidifying material including blast furnace slug fine powder as a main component, a solidification material, a calcareous raw material, a siliceous raw material, gypsum, and aluminum powder; a semi-curing step of obtaining a light-weight foam concrete raw cake by semi-curing the carbon dioxide discharge suppression-type raw material slurry in a mold; a cutting step of cutting the light-weight foam concrete raw cake to a prescribed dimension; and a curing step of obtaining the light-weight foam concrete by steam-curing the light-weight foam concrete raw cake cut to the prescribed dimension.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing lightweight aerated concrete (ALC). More specifically, the present invention relates to a method for producing ALC, which is used primarily as a panel-shaped building material for walls, roofs, floors, etc. of buildings, and which can contribute to reducing greenhouse gas (GHG) emissions while maintaining the quality of the ALC. [Background technology]

[0002] In recent years, with the rapid progress of global warming, reducing greenhouse gas (GHG) emissions, namely carbon dioxide (CO2), has become an urgent issue for the entire industrial sector, and there is a demand for ALC manufacturing to contribute to reducing CO2 emissions as well.

[0003] ALC is manufactured by a manufacturing method in which a raw material slurry is poured into a mold containing reinforcing steel bars, foams into a semi-hardened body (green cake), and then demolded. The demolded green cake is cut to a predetermined size and further subjected to high-temperature, high-pressure steam curing in an autoclave. The raw material slurry is a slurry-like raw material containing, as its main components, siliceous raw materials such as silica stone and silica sand, and calcareous raw materials such as cement and quicklime, as well as aluminum powder as a foaming agent, additives such as surfactants, and water (see Patent Document 1).

[0004] One way to contribute to reducing CO2 emissions at ALC manufacturing sites, which are carried out as described above, is to replace all or part of the cement used as a solidification agent in the raw slurry with ground granulated blast furnace slag, which has latent hydraulic properties and a low CO2 emission intensity. This would make it possible for ALC manufacturing sites to contribute to reducing the total CO2 emissions emitted by the entire industry.

[0005] Another possible measure to contribute to reducing CO2 emissions at ALC production sites is to replace a portion of the calcareous raw material contained in the raw slurry with various carbon dioxide fixation raw materials, such as calcium carbonate (CaCO3) produced by carbonate mineralization technology. Such CCSU (Carbon dioxide Capture, Utilization, and Storage) technology has attracted attention, for example, by reacting CO2 emitted from various industrial processes with minerals to fix the CO2 as carbonates such as calcium carbonate (CaCO3) (see Patent Document 2). This, too, is believed to contribute to reducing total CO2 emissions, as described above. In this specification, raw minerals made of minerals that have chemically fixed CO2 through industrial processes are generally referred to as "carbon dioxide fixation raw materials."

[0006] However, when introducing the above-mentioned measures that can contribute to reducing CO2 emissions in the production of ALC, the former measure of replacing all or part of the cement, which is the solidification agent in the raw slurry used for ALC production, with ground granulated blast furnace slag tends to delay the hardening of the slurry consisting of the above-mentioned components and reduce productivity, while the latter measure of increasing the proportion of calcium carbonate in the calcareous raw materials in the raw slurry used for ALC production tends to reduce the compressive strength of the ALC product after hardening. For this reason, it has not been easy to adopt each of the above measures at ALC manufacturing sites while maintaining desirable levels of productivity and product properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-199408 [Patent Document 2] Japanese Patent Application Publication No. 10-249153 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to contribute to reducing CO2 emissions while maintaining the productivity and physical properties of ALC products in the manufacturing process of lightweight aerated concrete (ALC). [Means for solving the problem]

[0009] The present inventors have discovered that by replacing all or part of the solidifying agent used as a raw material slurry in the production of ALC with ground granulated blast furnace slag and by using finely divided calcium carbonate powder finely pulverized to a specific particle size as the carbon dioxide fixation raw material to be added, it is possible to reduce CO2 emissions while maintaining the productivity and physical properties of the ALC product, and have completed the present invention. Specifically, the present invention provides the following.

[0010] (1) A method for producing lightweight aerated concrete, comprising: a raw material slurry preparation step of adding calcium carbonate to and mixing a main raw material slurry containing, as solid components, a solidifying agent whose main component is ground granulated blast furnace slag, a calcareous raw material, a siliceous raw material, gypsum, and aluminum powder to obtain a carbon dioxide emission-reducing raw material slurry; a semi-hardening step of semi-hardening the carbon dioxide emission-reducing raw material slurry in a formwork to obtain a lightweight aerated concrete green cake; a cutting step of cutting the lightweight aerated concrete green cake to a predetermined size; and a hardening step of steam-curing the lightweight aerated concrete green cake cut to a predetermined size to obtain lightweight aerated concrete, wherein the calcium carbonate is calcium carbonate fine powder having an average particle size of 1.0 μm or more and 15.0 μm or less.

[0011] According to the manufacturing method of lightweight aerated concrete (1), when all or part of the solidifying agent used as a material for the raw slurry is replaced with granulated blast furnace slag, which has latent hydraulic properties and a small CO2 emission unit, by limiting the calcium carbonate used as the "carbon dioxide fixation raw material" to a fine powder of a specified particle size, it is possible to contribute to the reduction of CO2 emissions in the ALC manufacturing process while maintaining the productivity and physical properties of the ALC product.

[0012] (2) A method for producing lightweight cellular concrete according to (1), wherein the proportion of ground granulated blast furnace slag in the solidifying agent is 90% by weight or more.

[0013] According to the manufacturing method of lightweight aerated concrete (2), even if the majority of the solidifying agent used as a material for the raw slurry in the manufacturing method of lightweight aerated concrete (1) is replaced with blast furnace slag powder, which has latent hydraulic properties and a low CO2 emission unit, the productivity and product properties of the ALC product can be maintained at a high level, and the contribution to reducing CO2 emissions by replacing the solidifying agent can be further increased.

[0014] (3) The method for producing lightweight cellular concrete according to (1), wherein the solidifying agent contains only ground granulated blast furnace slag.

[0015] According to the manufacturing method of lightweight aerated concrete (3), even if all of the solidifying agents used as ingredients in the raw slurry in the manufacturing method of lightweight aerated concrete (1) are replaced with blast furnace slag powder, which has latent hydraulic properties and a low CO2 emission unit, the productivity and product properties of the ALC product can be maintained at a high level, and the contribution to reducing CO2 emissions by replacing the solidifying agents can be maximized.

[0016] (4) A method for producing lightweight aerated concrete according to any one of (1) to (3), wherein the content of the calcium carbonate fine powder in the carbon dioxide emission reduction raw material slurry is 10% by weight or more and 50% by weight or less in terms of solid content ratio with respect to the total amount of solid content in the carbon dioxide emission reduction raw material slurry.

[0017] According to the method for manufacturing lightweight aerated concrete (4), the above-mentioned effects achieved by any of the methods for manufacturing lightweight aerated concrete (1) to (3) can be enjoyed in a more preferable manner and more stably.

[0018] (5) A carbon dioxide emission-reducing raw material slurry for the production of lightweight aerated concrete, which contains, as solid components, a solidifying agent mainly composed of blast furnace slag powder, a calcareous raw material, a siliceous raw material, gypsum, aluminum powder, and calcium carbonate, wherein the calcium carbonate is calcium carbonate powder having an average particle size of 1.0 μm or more and 15.0 μm or less.

[0019] According to (5) the carbon dioxide emission-reducing raw material slurry for the production of lightweight aerated concrete, when all or part of the solidifying agent used as an ingredient of the raw material slurry is replaced with granulated blast furnace slag, which has latent hydraulic properties and a small CO2 emission unit, by limiting the calcium carbonate used as the "carbon dioxide fixation raw material" to a fine powder of a specified particle size, it is possible to contribute to the reduction of CO2 emissions in the ALC production process while maintaining the productivity and physical properties of the ALC product.

[0020] (6) A carbon dioxide emission-reducing raw material slurry for producing lightweight aerated concrete according to (5), in which the proportion of ground granulated blast furnace slag in the solidifying agent is 90% by weight or more.

[0021] According to the carbon dioxide emission-reducing raw material slurry for the production of lightweight aerated concrete (6), even when the majority of the solidifying agent used as an ingredient in the raw material slurry for the production of lightweight aerated concrete (5) is replaced with blast furnace slag powder, which has latent hydraulic properties and a low CO2 emission unit, the productivity and product properties of the ALC product can be maintained at a high level, and the contribution to reducing CO2 emissions by replacing the solidifying agent can be further increased.

[0022] (7) A carbon dioxide emission-reducing raw material slurry for producing lightweight aerated concrete according to (5), in which the solidifying agent contains only ground granulated blast furnace slag.

[0023] According to the carbon dioxide emission-reducing raw material slurry for the production of lightweight aerated concrete (7), even if all of the solidifying agents used as ingredients in the carbon dioxide emission-reducing raw material slurry for the production of lightweight aerated concrete (5) are replaced with blast furnace slag powder, which has latent hydraulic properties and a low CO2 emission unit, the productivity and product properties of ALC products can be maintained at a high level, and the contribution to reducing CO2 emissions by replacing the solidifying agents can be maximized.

[0024] (8) A carbon dioxide emission reduction raw material slurry for producing lightweight aerated concrete according to any one of (5) to (7), wherein the content of the calcium carbonate fine powder is 10% by weight or more and 50% by weight or less in terms of solid content ratio relative to the total amount of solid content in the carbon dioxide emission reduction raw material slurry.

[0025] By using the carbon dioxide emission-reducing raw material slurry for producing lightweight aerated concrete (8), the above-mentioned effects of the carbon dioxide emission-reducing raw material slurry for producing lightweight aerated concrete (5) to (7) can be enjoyed in a more preferred manner and more stably. [Effects of the Invention]

[0026] According to the present invention, in the manufacturing process of lightweight aerated concrete (ALC), it is possible to contribute to reducing CO2 emissions while maintaining the productivity and physical properties of ALC products. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0028] <Method of manufacturing lightweight cellular concrete> The method for producing lightweight aerated concrete of the present invention comprises a "raw material slurry blending step" of obtaining a "carbon dioxide emission suppression raw material slurry" by a unique manufacturing method, a "semi-hardening step" of semi-hardening the carbon dioxide emission suppression raw material slurry in a formwork to obtain a lightweight aerated concrete green cake (ALC green cake), a "cutting step" of cutting the ALC green cake to a specified size, and a "hardening step" of steam-curing the ALC green cake cut to a specified size to obtain "lightweight aerated concrete (ALC)".

[0029] Of the above steps, except for the "raw material slurry blending step" which is a step unique to the present invention, the subsequent steps, i.e., the "semi-hardening step," "cutting step," and "hardening step," can be carried out in the same manner as in conventional manufacturing methods of lightweight aerated concrete. In other words, the manufacturing method of lightweight aerated concrete of the present invention is a manufacturing method mainly characterized by the fact that, prior to the above steps ("semi-hardening step," "cutting step," and "hardening step") which are also carried out in the same manner in conventional manufacturing methods, a "raw material slurry blending step" for obtaining a "carbon dioxide emission suppression raw material slurry," which is a raw material slurry for manufacturing ALC unique to the present invention, is carried out as a new and essential additional step.

[0030] [Raw material slurry blending process] The raw material slurry blending process is a process in which a "carbon dioxide emission suppression raw material slurry" is obtained by adding and mixing fine calcium carbonate powder of a specific particle size, which is also a carbon dioxide fixation raw material, to a "main raw material slurry" made from a solidification material whose main component is ground blast furnace slag.

[0031] (Main raw material slurry) In the "raw material slurry mixing process," which is a characteristic partial process in the manufacturing method of lightweight aerated concrete of the present invention, the "main raw material slurry" used as the main material can be a slurry containing the various solids and water described below, similar to the raw material slurries used in the conventional manufacturing of ALC.

[0032] The solid components contained in the "main raw material slurry" are a solidifying agent, a calcareous raw material, a siliceous raw material, gypsum, and a foaming agent (aluminum powder). The "main raw material slurry" may further contain, as a solid component, "ALC powder," an in-process recycled material made by pulverizing product scraps generated during the ALC production process. The "main raw material slurry" may also contain, as other components, various other additives (such as various surfactants) that are added as needed.

[0033] However, the "main raw material slurry" used in the manufacturing method of the present invention differs from conventional raw material slurries in that, among the above solid components, the solidifying agent must be "a solidifying agent whose main component is ground granulated blast furnace slag," and that calcium carbonate fine powder of a specific particle size, which is a carbon dioxide fixation raw material, must be added in a predetermined proportion.

[0034] In the present invention, the solidification agent refers to a solidification agent that semi-hardens the raw material slurry in a few hours in the semi-hardening step (described in detail below) to the point where it becomes a raw cake that can be cut with a piano wire or the like in the cutting step (described in detail below). Specific examples of solidification agents in the present invention include cement such as Portland cement, blended cement, and ecocement, as well as the below-mentioned ground granulated blast furnace slag, which has similar hardening properties.

[0035] Ground granulated blast furnace slag is a material formed when non-iron components such as silica (SiO2) and alumina (Al2O3) contained in iron ore, and the ash of coke used as a reducing agent in blast furnace operations at steelworks, combine with the raw material limestone (mainly CaCO3), and is known to have strong latent hydraulic properties due to its high-calcium aluminosilicate glassy nature.In addition, ground granulated blast furnace slag is a product made by drying and pulverizing granulated blast furnace slag, a by-product of the pig iron production process in the blast furnace mentioned above.As a result, there is no need to burn limestone (CaCO3) during the manufacturing process, as there is with ordinary Portland cement, and CO2 emissions during the manufacturing process can be kept to an extremely low level.

[0036] As mentioned above, the role of the solidifying agent in the ALC production process is to "semi-harden" the raw material slurry to the state of "ALC green cake." Therefore, in the production of ALC, it is not necessary for the solidifying agent to have the same hardening speed as that of general concrete products. Therefore, in the production of ALC, there is a greater potential for using a larger amount of ground granulated blast furnace slag as a solidifying agent other than cement, compared to the production of general concrete products. According to the present invention, this potential in the production of ALC can be realized while maintaining the productivity and physical properties of ALC products, thereby promoting the reduction of CO2 emissions by replacing various cements with ground granulated blast furnace slag.

[0037] The calcareous raw material refers to quicklime (CaO), slaked lime (Ca(OH)2), or raw materials containing these as the main component, while the siliceous raw material refers to silica stone, silica sand, or raw materials containing the SiO2 contained therein as the main component. Details of the calcium carbonate fine powder of a specific particle size that is added as a carbon dioxide fixation raw material will be described later.

[0038] A "solidification material primarily composed of ground granulated blast furnace slag" refers to a solidification material containing the largest proportion of ground granulated blast furnace slag among the various solidification materials mixed together in a "main raw material slurry." Furthermore, the proportion of ground granulated blast furnace slag in the solidification material is preferably 50% by weight or more, and more preferably 90% by weight or more. Alternatively, when CO2 emission reduction is particularly important, it is preferable that the proportion of ground granulated blast furnace slag in the solidification material be 100% by weight, i.e., the solidification material contains only ground granulated blast furnace slag. According to the manufacturing method of the present invention, by using such a composition for the "main raw material slurry," it is possible to maximize the contribution to CO2 emission reduction by replacing the solidification material.

[0039] As described above, the "main raw material slurry" contains, as solid components, a solidifying agent whose main component is ground blast furnace slag, calcareous raw materials such as quicklime, siliceous raw materials such as silica stone and silica sand, foaming agents such as gypsum and aluminum powder, and ALC powder, which is added as needed.The "main raw material slurry" can be prepared by adding an appropriate amount of water to materials that also contain various other additives, such as surfactants, which are added as needed, and kneading the mixture using various mixers.

[0040] (Carbon dioxide fixation raw material (fine calcium carbonate powder)) In the "raw material slurry blending step," calcium carbonate fine powder of a specific particle size can be used as the carbon dioxide fixation raw material added to the "main raw material slurry." Specifically, this calcium carbonate fine powder may have an average particle size of 1.0 μm to 15.0 μm, preferably 1.0 μm to 10.0 μm, more preferably 2.0 μm to 10.0 μm, and even more preferably 2.5 μm to 10 μm. By setting the average particle size of the calcium carbonate fine powder added to the "main raw material slurry" to 1.0 μm or more, the energy required for the physical process to finely powder the calcium carbonate can be reduced, thereby suppressing the increase in CO2 emissions associated with the fine powder process. Furthermore, by setting the average particle size of the calcium carbonate fine powder to 15.0 μm or less, a decrease in the hardening rate of the raw material slurry (carbon dioxide emission-reducing raw material slurry) and a decrease in the compressive strength of the hardened ALC product can be prevented in a balanced manner.

[0041] In this specification, the "average particle size" of the above-mentioned fine powder refers to the volume average diameter obtained by analyzing a slurry containing the powder to be measured or the powder using a particle size distribution measuring device (for example, the "SYNC particle size distribution analyzer manufactured by Microtrack Bell Corporation").

[0042] Although the above-mentioned calcium carbonate fine powder can be added to the main raw material slurry as a powder, it is preferable to mix the calcium carbonate fine powder with an appropriate amount of water to form a slurry before adding it to the main raw material slurry, in terms of ease of handling the raw material and dispersibility of calcium carbonate. Therefore, in the raw material slurry preparation step, in the treatment of further adding calcium carbonate to the main raw material slurry and mixing it, it is preferable to use a wet grinding method in which the material to be ground is mixed with water and ground.

[0043] (Carbon dioxide emission suppression raw material slurry) The "carbon dioxide emission-reduced raw material slurry (carbon dioxide emission-reduced raw material slurry for lightweight aerated concrete production)" produced in the "raw material slurry blending step" and usable as an ALC material in subsequent steps can be obtained by further adding and mixing a "carbon dioxide fixation raw material" consisting of calcium carbonate fine powder of a specific particle size, as described above, to a "main raw material slurry" whose main solidification material is ground granular blast furnace slag, as described above. The addition of "calcium carbonate fine powder" of a specific particle size to the "main raw material slurry" can be achieved by adding and mixing a slurry containing "calcium carbonate fine powder" or a pre-slurried slurry containing the above-described "calcium carbonate fine powder" to a pre-mixed main raw material slurry. Alternatively, the "carbon dioxide emission-reduced raw material slurry" can be obtained by adding "calcium carbonate fine powder" or a "pre-slurried slurry containing calcium carbonate fine powder" to a mixer when mixing the main raw material slurry in the mixer and mixing it with the ingredients of the main raw material slurry.

[0044] The content of the “fine calcium carbonate powder” having the specific particle size in the “carbon dioxide emission reduced raw material slurry” is preferably 10% by weight or more and 50% by weight or less, more preferably 25% by weight or more and 50% by weight or less, and even more preferably 30% by weight or more and 40% by weight or less, in terms of solid content ratio relative to the total amount of solid content in the “carbon dioxide emission reduced raw material slurry.” In the “raw material slurry preparation step,” the amount of “fine calcium carbonate powder” added may be appropriately adjusted so that the content ratio (solid content ratio) of the “fine calcium carbonate powder” having the specific particle size in the “carbon dioxide emission reduced raw material slurry” falls within the above content ratio range.

[0045] [Semi-curing process] The semi-hardening process is a process in which the "carbon dioxide emission reduction raw slurry" obtained in the "raw material slurry blending process" is semi-hardened in a formwork to obtain a semi-plastic lightweight aerated concrete green cake (ALC green cake). In this process, the "carbon dioxide emission reduction raw slurry" is poured into a formwork such as a mold in which reinforcing steel bars have been set. The injected "carbon dioxide emission reduction raw slurry" expands in volume as hydrogen gas reacts with the aluminum powder and is stabilized as spherical bubbles by the bubble stabilizer. The "carbon dioxide emission reduction raw slurry" then semi-hardens into a non-fluid, semi-plastic body, becoming the "ALC green cake." The solidification agent, whose main component is ground granulated blast furnace slag, absorbs the water in the raw material slurry and forms hydrates.

[0046] [Cutting process] The cutting process is a process of cutting the "ALC green cake" to a predetermined size with a piano wire. Specifically, this cutting is performed by removing the semi-hardened "ALC green cake" from the formwork and cutting it to a predetermined size with a wire such as a piano wire.

[0047] [Curing process] The hardening process involves hardening the "ALC raw cake" cut to the specified dimensions in the cutting process through steam curing at high temperature and pressure to obtain ALC. This high-temperature, high-pressure steam curing can be carried out in an autoclave at 180°C, 10 atmospheres, and for approximately six hours, just like in conventional ALC manufacturing methods. [Example]

[0048] The method for producing lightweight cellular concrete of the present invention will be described in detail below with reference to examples. However, the present invention is not limited to the embodiments of the examples shown below.

[0049] <Production of raw material slurry> In each Example and Comparative Example, a raw material slurry was produced by mixing the materials shown in Table 1 below with water in a mixer to prepare a main raw material slurry, and each carbon dioxide fixation raw material shown in Table 1.

[0050] In producing the main raw material slurry, "high-early-strength Portland cement manufactured by Sumitomo Osaka Cement Co., Ltd." was used as the cement solidification agent, and "ground granulated blast furnace slag powder manufactured by Nippon Steel Blast Furnace Cement Co., Ltd." (product name: Esment) was used as the granulated blast furnace slag. Furthermore, as the calcium carbonate used as the carbon dioxide fixation raw material, either pulverized calcium carbonate (corresponding to the calcium carbonate granulated powder in the present invention; referred to as "pulverized product" in Table 1 below) or untreated calcium carbonate (referred to as "unpulverized product" in Table 1 below) was used for each Example and Comparative Example. The average particle size of the pulverized calcium carbonate was 2.5 μm, and the average particle size of the untreated calcium carbonate was 20 μm. Furthermore, the content ratio of each calcium carbonate in terms of solid content relative to the total amount of the solidifying material, calcareous raw material, siliceous raw material, gypsum, ALC powder, aluminum powder, and calcium carbonate (i.e., the total amount of solid content) is shown as the "calcium carbonate substitution rate (%)" of the carbon dioxide fixation raw material in Table 1. The "water / solid ratio" of the raw material slurry in each of the Examples and Comparative Examples was 0.69 (weight ratio).

[0051] <Evaluation of CO₂ Emission Reduction> The evaluation of CO₂ emission reduction was carried out in accordance with the "Carbon Footprint Guidelines (March 2023, Ministry of Economy, Trade and Industry, https: / / www.env.go.jp / content / 000124385.pdf)". For the case of manufacturing ALC according to the manufacturing method of the present invention, except that different raw material slurries were used for each example and comparative example, the carbon footprint in each case was evaluated. Here, the "Cradle to Gate" scope was adopted, and the CO₂ emissions (kg-CO₂eq / m 3 -ALC) in the raw material procurement process and production process were calculated. The calculation results were as shown in Table 1. Then, taking the CO₂ emissions in the existing lightweight foamed concrete (Comparative Example 1) as the reference value of CO₂ emissions, the reduction amount of CO₂ emissions in each example and comparative example relative to this reference value was expressed as a percentage (%) relative to the reference value, and the value was calculated as the "CO₂ emission reduction rate (%)" and evaluated based on the following evaluation criteria. The calculation results and evaluation results were as shown in Table 1. (Evaluation Criteria) A: The CO₂ emission reduction rate (%) is 50% or more B: The CO₂ emission reduction rate (%) is 40% or more and less than 50% C: The CO₂ emission reduction rate (%) is 20% or more and less than 40% D: The CO₂ emission reduction rate (%) is less than 20%

[0052] <Evaluation of Hardening Rate> As an evaluation of the hardening rate, for each example and comparative example, a test (hardening rate determination test) comparing the semi-hardening rate (semi-hardening time) in the semi-hardening process was carried out as follows and evaluated based on the following evaluation criteria.

[0053] (Hardening Rate Determination Test) The raw material slurries of the examples and comparative examples were subjected to a hardening test in a 300 ml disposable cup at room temperature (20°C), and the hardness was measured 6 hours after the start of curing using a force gauge (Digital Force Gauge DST manufactured by Imada Co., Ltd.). The hardness was measured by attaching a 15 mm diameter (225 mm area) probe to the tip of the force gauge. 2 The stress value was calculated using the following formula (1) from the peak load (L(N)) when the jig was pressed against the hardened body and inserted 5 mm from the tip, and evaluated based on the following evaluation criteria. The calculation results and evaluation results are shown in Table 1. Hardness (N / mm 2 ) = L(N) / 225(mm 2 )···(1) (Evaluation criteria) A: Hardness (MPa) is 0.07 MPa or more B: Hardness (MPa) is 0.05 MPa or more and less than 0.07 MPa C: Hardness (MPa) is 0.03 MPa or more and less than 0.05 MPa D: Hardness (MPa) is less than 0.03 MPa

[0054] <Evaluation of compressive strength> To evaluate the compressive strength, a test (compressive strength evaluation test) was conducted for each example and comparative example to compare the compressive strength in the semi-hardening process as follows, and the compressive strength was evaluated based on the following evaluation criteria.

[0055] (Compression strength measurement test) Each ALC raw cake obtained by the semi-hardening process using the various raw material slurries of the Examples and Comparative Examples was further put into the hardening process and autoclaved to obtain lightweight aerated concrete blocks. From these blocks, rectangular parallelepipeds measuring 100 mm in length, 100 mm in width, and 100 mm in height were taken and tested using a universal testing machine (Shimadzu Corporation, Precision Universal Testing Machine Autograph AGX-V2). The compression test speed was 0.2 N / mm per second. 2 The compressive strength was calculated from the stress at the time of fracture and evaluated based on the following criteria. The measurement and evaluation results are shown in Table 1. (Evaluation criteria) A: Compressive strength (MPa) is 2.4 MPa or more B: Compressive strength (MPa) is 2.0 MPa or more but less than 2.4 MPa C: Compressive strength (MPa) is 1.6 MPa or more but less than 2.0 MPa D: Compressive strength (MPa) is less than 1.6 MPa

[0056] [Table 1]

[0057] As shown in Table 1, when the solidification agent used as an ingredient in the raw slurry is replaced with granulated blast furnace slag, which has latent hydraulic properties and a small CO2 emission intensity, it has been confirmed that by limiting the calcium carbonate used as the "carbon dioxide fixation raw material" to a fine powder of a specified particle size, it is possible to contribute to reducing CO2 emissions in the ALC manufacturing process while maintaining the productivity and physical properties of the ALC product.

Claims

1. A method for producing lightweight cellular concrete, comprising: a raw material slurry preparation step of further adding calcium carbonate to and mixing a main raw material slurry containing, as solid components, a solidifying material mainly composed of ground granulated blast furnace slag, a calcareous raw material, a siliceous raw material, gypsum, and aluminum powder, thereby obtaining a carbon dioxide emission suppression raw material slurry; a semi-hardening step of semi-hardening the carbon dioxide emission reduced raw material slurry in a formwork to obtain a lightweight aerated concrete fresh cake; A cutting step of cutting the lightweight aerated concrete fresh cake into predetermined dimensions; and a hardening step of steam-curing the lightweight aerated concrete green cake cut to a predetermined size to obtain lightweight aerated concrete, The calcium carbonate is a fine powder of calcium carbonate having an average particle size of 1.0 μm or more and 15.0 μm or less. A method for producing lightweight aerated concrete.

2. The proportion of ground granulated blast furnace slag in the solidifying material is 90% by weight or more. A method for producing lightweight cellular concrete according to claim 1.

3. The solidifying material contains only ground granulated blast furnace slag. A method for producing lightweight cellular concrete according to claim 1.

4. a content of the calcium carbonate fine powder in the carbon dioxide emission reduction raw material slurry is 10% by weight or more and 50% by weight or less in terms of solid content ratio with respect to a total amount of solid contents in the carbon dioxide emission reduction raw material slurry; A method for producing lightweight cellular concrete according to any one of claims 1 to 3.

5. A raw material slurry for producing lightweight aerated concrete, The solid content includes a solidifying material mainly composed of ground blast furnace slag, a calcareous raw material, a siliceous raw material, gypsum, aluminum powder, and calcium carbonate, The calcium carbonate is a fine powder of calcium carbonate having an average particle size of 1.0 μm or more and 15.0 μm or less. Carbon dioxide emission-reducing raw material slurry for the production of lightweight aerated concrete.

6. The proportion of ground granulated blast furnace slag in the solidifying material is 90% by weight or more. A carbon dioxide emission-reducing raw material slurry for producing lightweight aerated concrete according to claim 5.

7. The solidifying material contains only ground granulated blast furnace slag. A carbon dioxide emission-reducing raw material slurry for producing lightweight aerated concrete according to claim 5.

8. the content of the calcium carbonate fine powder is 10% by weight or more and 50% by weight or less in terms of solid content ratio with respect to the total amount of solid contents in the carbon dioxide emission reduction raw material slurry; A carbon dioxide emission reduction raw material slurry for producing lightweight aerated concrete according to any one of claims 5 to 7.

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