Method for producing hardened cementitious material

Abstract

To provide a method for producing a cementitious hardened body by which a larger amount of carbon dioxide is absorbed in a curing process, as a result, the total amount of discharged carbon dioxide can be reduced, and a cement composition having excellent strength developability can be obtained.SOLUTION: It is preferable that the hydraulic modulus (H. M.) is 1.1 to 2.0 (excluding 1.1 to 1.3). The silicate ratio (S. M.) is 1.5 to 3.5 (excluding 2.4 to 2.6). An iron ratio (I. M.) of 1.7 to 3.5 (excluding 2.0 to 2.3). A method for producing a hardened cementitious material, comprising a carbonation curing step of subjecting a cement composition to carbonation curing to obtain the hardened cementitious material, wherein the cement composition comprises gypsum, water, and a clinkers powder having a mineral composition in which the total content of aluminum oxides (Al2O3) and iron oxides (Fe2O3) is 9.0 to 14.0 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a hardened cementitious body. [Background technology]

[0002] Currently, reducing carbon dioxide emissions has become an important issue in order to curb global warming. As a method for reducing carbon dioxide emissions in the production of a cementitious hardened body, a method is known in which carbon dioxide is absorbed during the curing process of the cementitious hardened body, thereby reducing the total amount of carbon dioxide emitted until the hardened cementitious body is obtained. Patent Document 1 describes a cementitious hardened body that can significantly reduce the total amount of carbon dioxide emitted by absorbing a large amount of carbon dioxide during the curing process, and is characterized by being obtained by carbonating a hardened body of a cement mixture that includes (A) a powder for cement mixing containing either mullite or anorthite, or both, and a powdered cement composition containing Portland cement, (B) water, and (C) aggregate. Patent Document 2 also describes a cementitious hardened body obtained by carbonating a hardened body of a cement mixture containing (A) a powdered cement composition containing Portland cement, a pulverized product of a fired material containing 10 to 200 parts by mass of C2AS relative to 100 parts by mass of C2S and having a C3A content of 20 parts by mass or less, (B) water, and (C) aggregate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-153357 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-47788 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for producing a cementitious hardened body that can absorb a larger amount of carbon dioxide during the curing process, thereby reducing the total amount of carbon dioxide emitted, and that can produce a cement composition that is excellent in strength development. [Means for solving the problem]

[0005] As a result of intensive research into solving the above problems, the present inventors have found that the above objects can be achieved by a method for producing a cementitious hardened body, the method including the step of carbonation curing a cement composition containing clinker powder, gypsum, and water, the cement composition having a mineral composition in which the hydraulic modulus (HM) is 1.1 to 2.0 (excluding 1.1 to 1.3), the silicate modulus (SM) is 1.5 to 3.5 (excluding 2.4 to 2.6), the iron modulus (IM) is 1.7 to 3.5 (excluding 2.0 to 2.3), and the total content of aluminum oxide (Al2O3) and iron oxide (Fe2O3) is 9.0 to 14.0 mass%, to obtain the cementitious hardened body, and have completed the present invention. That is, the present invention provides the following [1] to [3]. [1] A method for producing a cementitious hardened body using a cement composition containing clinker powder, gypsum, and water, the mineral composition of which is a hydraulic modulus (HM) of 1.1 to 2.0 (excluding 1.1 to 1.3), a silicate modulus (SM) of 1.5 to 3.5 (excluding 2.4 to 2.6), an iron modulus (IM) of 1.7 to 3.5 (excluding 2.0 to 2.3), and a total content of aluminum oxide (Al2O3) and iron oxide (Fe2O3) of 9.0 to 14.0 mass%, the method comprising: a carbonation curing step of carbonating the cement composition to obtain the cementitious hardened body.

[0006] [2] The method for producing a cementitious hardened body according to [1], wherein the carbonation curing is carried out so that the carbonation depth from the surface of the cementitious hardened body becomes 2 mm or more in the carbonation curing step. [3] The cement composition according to [1] or [2], wherein the cement composition contains Portland cement clinker powder, and the amount of the clinker powder is 50 parts by mass or more per 100 parts by mass of the total amount of the clinker powder and the Portland cement clinker powder. [Effects of the Invention]

[0007] According to the present invention, a cement composition can be obtained which absorbs a larger amount of carbon dioxide during the curing process, thereby reducing the total amount of carbon dioxide emitted, and which is excellent in strength development. DETAILED DESCRIPTION OF THE INVENTION

[0008] The clinker powder of the present invention has a mineral composition in which the hydraulic modulus (HM) is 1.1 to 2.0, the silicate modulus (SM) is 1.5 to 3.5, the iron modulus (IM) is 1.7 to 3.5, and the total content of aluminum oxide (Al2O3) and iron oxide (Fe2O3) is 9.0 to 14.0 mass%. The hydraulic modulus (HM) of the clinker powder is 1.1 to 2.0, preferably 1.2 to 1.9, more preferably 1.3 to 1.8, even more preferably 1.3 to 1.7, even more preferably 1.3 to 1.6, and particularly preferably 1.3 to 1.5. If the hydraulic modulus is less than 1.1, the strength development of a cement composition containing the clinker powder will decrease. If the hydraulic modulus exceeds 2.0, the clinker will be less easily burnable, and free lime (f·CaO) will be more likely to remain, making it necessary to increase the burning temperature when producing the clinker.

[0009] The silicate ratio (SM) of the clinker powder is 1.5 to 3.5, preferably 1.6 to 3.3, more preferably 1.7 to 3.0, even more preferably 2.0 to 2.9, even more preferably 2.2 to 2.8, even more preferably 2.3 to 2.7, and particularly preferably 2.4 to 2.6. If the silicate ratio is less than 1.5, the fluidity of the cement composition containing the clinker powder decreases. If the silicate ratio exceeds 3.5, the clinker's burnability decreases, and unreacted silica (SiO2) tends to remain, making it necessary to increase the burning temperature when producing the clinker. The iron ratio (IM) of the clinker powder is 1.7 to 3.5, preferably 1.8 to 3.4, more preferably 1.9 to 3.3, still more preferably 2.0 to 2.4, and particularly preferably 2.0 to 2.3. If the iron ratio is less than 1.7, the strength development of the cement composition containing the clinker powder decreases. If the iron ratio exceeds 3.5, the fluidity of the cement composition containing the clinker powder decreases.

[0010] The total content of aluminum oxide (Al2O3) and iron oxide (Fe2O3) in 100% by mass of clinker powder is 9.0 to 14.0% by mass, preferably 9.5 to 13.0% by mass, more preferably 10.0 to 12.0% by mass, and particularly preferably 10.5 to 11.8% by mass. If the content is less than 9.0% by mass, carbonation does not progress easily to the interior of the cementitious hardened body, reducing the efficiency of carbon dioxide absorption. If the content exceeds 14.0% by mass, the amount of fixed carbon dioxide that can be absorbed by a cement composition containing clinker powder decreases.

[0011] An example of the method for producing the clinker powder of the present invention is a first production method including a firing step of firing a material mixture to be fired at 1,250 to 1,500°C to obtain clinker, and a crushing step of crushing the clinker to obtain clinker powder. Each step will be explained in detail below. [Firing process] In this step, the mixture of materials to be fired is fired at 1,250 to 1,500°C to obtain clinker. As the calcination material, it is possible to use common raw materials used in the production of cement clinker, such as calcium-containing raw materials (CaO sources) such as limestone, quicklime, and slaked lime, silicon-containing raw materials (SiO sources) such as silica stone and clay, aluminum-containing raw materials (AlO sources) such as clay, and iron-containing raw materials (FeO sources) such as iron slag and iron cake.

[0012] In addition to the above-mentioned raw materials, one or more materials selected from industrial waste, general waste, and construction waste soil can be used. Here, industrial waste refers to waste generated as a result of business activities (excluding "construction soil," which will be discussed later). Examples of industrial waste include raw concrete sludge, various sludges (e.g., sewage sludge, water purification sludge, steelmaking sludge, etc.), construction waste, concrete waste, various incineration ashes (e.g., coal ash, chicken manure ash, livestock manure ash, biomass ash, sludge incineration ash), foundry sand, rock wool, waste glass, secondary blast furnace ash, various by-products, and unused resources (unused remaining materials, etc.). Municipal waste refers to waste other than industrial waste (excluding "construction waste soil" described below). Examples of municipal waste include dried sewage sludge, municipal waste incineration ash, and seashells. Examples of construction waste soil include soil, earth and sand (such as waste soil from drilling the ground), surplus soil, waste soil, and sludge (construction sludge; for example, a mixture of cement milk and excavated soil generated during ground improvement work) that are generated secondarily at construction sites and other work sites. These raw materials can be mixed appropriately so that the hydraulic content, silica content, iron content, and total content of aluminum oxide and iron oxide of the resulting clinker powder are within the desired numerical ranges, thereby obtaining a material mixture for firing.

[0013] The firing temperature in the firing step is 1,250 to 1,500°C, preferably 1,260 to 1,400°C, and more preferably 1,280 to 1,350°C. If the temperature is below 1,260°C, the amount of free lime in the clinker powder increases, and the strength development of the cement composition containing the clinker powder decreases. If the temperature exceeds 1,500°C, the energy cost required for firing becomes excessive.

[0014] [Crushing process] This step is a step of pulverizing the clinker to obtain clinker powder. The method for pulverizing the clinker is not particularly limited, and may be a general method using, for example, a ball mill.

[0015] The clinker powder of the present invention may also be produced by mixing two or more types of clinker powder. Specifically, the second manufacturing method includes a firing step in which each of two or more types of mixtures of materials to be fired is fired at 1,250 to 1,500°C to obtain two or more types of clinker, a crushing step in which the two or more types of clinker are crushed to obtain two or more types of clinker powder to be mixed, and a mixing step in which the two or more types of clinker powder to be mixed are mixed to obtain clinker powder. Each of the two or more mixtures of firing materials used in the firing step can be obtained by appropriately mixing the above-mentioned firing materials so that the hydraulic content, silica content, iron content, and total content of aluminum oxide and iron oxide of the clinker powder obtained in the mixing step fall within the desired numerical ranges. The firing temperature is the same as the firing temperature in the firing step of the first production method described above (however, the above temperatures for each of the two or more types of material mixtures to be fired may be the same or different from each other).

[0016] Next, each of the two or more types of clinker obtained in the burning step is pulverized in a pulverization step to obtain two or more types of clinker powders for mixing, and then the two or more types of clinker powders for mixing are mixed in a mixing step to obtain the clinker powder of the present invention. The mixing ratio of the clinker powders for mixing can be appropriately determined so that the hydraulic ratio, silica ratio, iron ratio, and total content of aluminum oxide and iron oxide of the clinker powder obtained in the mixing step fall within desired numerical ranges.

[0017] The cement composition of the present invention contains the above-mentioned clinker powder, gypsum, and water. Examples of gypsum include anhydrous gypsum, dihydrate gypsum, hemihydrate gypsum, and mixtures thereof. The proportion of gypsum in the cement composition is preferably 0.1 to 5.0 mass%, more preferably 0.5 to 4.0 mass%, and particularly preferably 1.0 to 3.0 mass%, calculated as SO3. If the proportion is 0.1 mass% or more, the usable time before hardening of the cement composition (the time during which good fluidity can be maintained) increases. If the amount is 5.0 mass% or less, the strength development of the cement composition improves.

[0018] The water used in the present invention is not particularly limited, and examples thereof include tap water and sludge water. The amount of water to be blended is not particularly limited, and may be a general blending amount for paste, mortar, or concrete. For example, the amount of water to be blended is an amount such that the mass ratio of water to cement composition (water / cement composition) is preferably 0.20 to 0.60, more preferably 0.23 to 0.50, and particularly preferably 0.23 to 0.40. If the ratio is 0.20 or more, the workability is further improved. If the ratio is 0.60 or less, the strength development of the cement composition is further improved.

[0019] The cement composition may contain Portland cement clinker powder from the viewpoints of availability and improving strength development. The Portland cement clinker powder is not particularly limited, and various types of Portland cement clinker powder such as ordinary Portland cement clinker, high-early-strength Portland cement clinker, moderate-heat Portland cement clinker, and low-heat Portland cement clinker can be used. The amount of the clinker powder in 100 parts by mass of the total amount of the clinker powder and Portland cement clinker powder is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and particularly preferably 70 parts by mass or more. If the amount is 50 parts by mass or more, more carbon dioxide can be absorbed during the curing process.

[0020] The cement composition of the present invention may contain other materials as needed, such as (i) aggregates such as fine aggregate, coarse aggregate, and lightweight aggregate, (ii) various admixtures such as air-entraining agents, water-reducing agents, air-entraining water-reducing agents, high-performance water-reducing agents, and high-performance air-entraining water-reducing agents, (iii) various admixtures such as fly ash, silica fume, ground granulated blast furnace slag, and siliceous admixtures (excluding silica fume), and (iv) fibers such as organic fibers and glass fibers.

[0021] The method for producing a cementitious hardened body using the cement composition of the present invention is not particularly limited, and may be a general method for producing paste, mortar, or concrete. However, from the viewpoint of absorbing more carbon dioxide, a method including a carbonation curing step of carbonation curing the cement composition to obtain a cementitious hardened body is preferred. For example, before the carbonation curing step, the cement composition is prepared by mixing the materials constituting the cement composition using a conventional mixer, and then pouring the mixture into a formwork or the like. The concentration of carbon dioxide gas in the carbonation curing step is preferably 1% by volume or more, more preferably 10% by volume or more, even more preferably 50% by volume or more, and particularly preferably 60% by volume or more. If the concentration is 1% by volume or more, the amount of carbon dioxide absorbed in the carbonation curing step can be made larger. The upper limit of the carbon dioxide gas concentration is not particularly limited, and the higher the carbon dioxide gas concentration, the more carbon dioxide absorption can be achieved. However, from the viewpoint of reducing costs for curing equipment and the like, the upper limit is preferably 90% by volume or less, more preferably 85% by volume or less, and particularly preferably 80% by volume or less.

[0022] The temperature in the carbonation curing step is not particularly limited, but is preferably 5 to 100°C, more preferably 10 to 70°C, even more preferably 15 to 50°C, and particularly preferably 20 to 35°C. If the temperature is 5°C or higher, the productivity of the cementitious hardened body is further improved, and the strength of the cementitious hardened body is further increased. If the temperature exceeds 100°C, the energy cost for carbonation curing becomes excessively high. Furthermore, the relative humidity in the carbonation curing step is not particularly limited, but is preferably 20 to 90%, more preferably 30 to 80%, and particularly preferably 40 to 70%. If the relative humidity is 20% or higher, the productivity of the cementitious hardened body is further improved, and the strength of the cementitious hardened body is greater. It is difficult to increase the relative humidity above 90%, and the cost of equipment, etc. becomes excessive.

[0023] In the carbonation curing step, it is preferable to carry out carbonation curing so that the carbonation depth from the surface of the cementitious hardened body is preferably 2 mm or more, more preferably 3 mm or more, even more preferably 4 mm or more, and particularly preferably 5 mm or more. By carrying out carbonation curing so that the carbonation depth is 2 mm or more, a large amount of carbon dioxide can be absorbed by the cement composition. Specifically, the carbonation depth can be made 2 mm or more by appropriately adjusting the carbon dioxide gas concentration, temperature, and relative humidity values, as well as the curing time, in the carbonation curing step described above. From the viewpoint of absorbing carbon dioxide in a short time, it is preferable to carry out carbonation curing so that the carbonation depth is 2 mm or more, preferably at an age of 1 day, more preferably at an age of 3 days. The "carbonation depth from the surface of the cementitious hardened body" can be measured in accordance with "JIS A 1152:2018 (Method for measuring carbonation depth of concrete)". The obtained cementitious hardened body can be used as roadbed material, interlocking blocks, fish reef blocks, wave-dissipating blocks, side ditch blocks, planting concrete, manholes, pedestrian / vehicle boundary blocks, side ditches, high-strength external pressure pipes, etc. Furthermore, even after being installed as a roadbed material, etc., it can continue to absorb and fix carbon dioxide. [Example]

[0024] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Production of cement composition A] A mixture of materials for burning was prepared using a calcium-containing raw material, a silicon-containing raw material, an aluminum-containing raw material, and an iron-containing raw material, with the blending ratio determined so that the chemical composition of the clinker powder would be the values ​​shown in Table 1. The mixture of materials for burning was burned at 1,300°C for 30 minutes to obtain clinker, which was then crushed to produce clinker powder A. The Blaine specific surface area of ​​clinker powder A was 5,000 cm 2 / g. The obtained clinker powder A was designated as cement composition A. The content of SO3 in 100% by mass of cement composition A was 0.6% by mass.

[0025] [Production of cement composition B] Clinker was produced in the same manner as for clinker powder A, except that the chemical composition of the clinker powder was determined to be the values ​​shown in Table 1. The obtained clinker and gypsum dihydrate were mixed and ground to obtain cement composition B (a mixture of clinker powder B and gypsum) with an SO3 content of 2.0 mass%. The Blaine specific surface area of ​​the obtained cement composition B was 5,000 cm 2 / g. [Production of cement composition C] Clinker was produced in the same manner as for clinker powder A, except that the chemical composition of the clinker powder was determined to be the values ​​shown in Table 1. The obtained clinker and gypsum dihydrate were mixed and ground to obtain cement composition C (a mixture of clinker powder C and gypsum) with an SO3 content of 2.0 mass%. The Blaine specific surface area of ​​the obtained cement composition C was 3,000 cm 2 / g.

[0026] [Production of cement composition D] Cement composition A and cement composition C were mixed so that the content of cement composition A in cement composition D (a mixture of cement composition A and cement composition C) was 50 mass% and the content of cement composition C was 50 mass%, to produce cement composition D. The chemical composition of clinker powder D contained in cement composition D is shown in Table 1. The content of SO3 in cement composition D was 1.3 mass%. [Production of cement composition E] Cement composition A and cement composition C were mixed so that the content of cement composition A in cement composition E (a mixture of cement composition A and cement composition C) was 75 mass % and the content of cement composition C was 25 mass %, to produce cement composition E. The chemical composition of clinker powder E contained in cement composition E is shown in Table 1. The content of SO3 in cement composition E was 1.0 mass %.

[0027] [Production of cement composition F] Cement composition B and cement composition C were mixed so that the content of cement composition B in cement composition F (a mixture of cement composition B and cement composition C) was 75 mass% and the content of cement composition C was 25 mass%, to produce cement composition F. The chemical composition of clinker powder F contained in cement composition F is shown in Table 1. The content of SO3 in cement composition F was 2.0 mass%. [Production of cement composition G] Clinker was produced in the same manner as for clinker powder A, except that the chemical composition of the clinker powder was determined to be the values ​​shown in Table 1. The obtained clinker and gypsum dihydrate were mixed and ground to obtain cement composition G (a mixture of clinker powder G and gypsum) with an SO3 content of 2.0 mass%. The Blaine specific surface area of ​​the obtained cement composition G was 4,000 cm 2 / g.

[0028] [Production of Cement Composition H] A mixture of materials for burning was prepared using a calcium-containing raw material, a silicon-containing raw material, an aluminum-containing raw material, and an iron-containing raw material, with the blending ratio determined so that the chemical composition of the clinker powder would be the values ​​shown in Table 1. The mixture of materials for burning was burned at 1,450°C for 1 hour to obtain clinker. The obtained clinker was pulverized to produce clinker powder H. The Blaine specific surface area of ​​clinker powder H was 3,200 cm 2 / g. The obtained clinker powder H was used as cement composition H. The content of SO3 in 100% by mass of cement composition H was 2.0% by mass. Table 1 also shows the hydraulic ratio, silica ratio, and iron ratio of the clinker powders A to H contained in the cement compositions A to H.

[0029] [Table 1]

[0030] [Examples 1 to 7, Comparative Example 1] The cement composition, water, fine aggregate (mountain sand), and coarse aggregate (crushed stone No. 7) shown in Table 2 were charged into an Einrich mixer in the following order: coarse aggregate, fine aggregate (half the total amount of fine aggregate), cement composition, and the remaining fine aggregate, and dry mixing was performed. Next, while mixing each material, water premixed with a high-performance water-reducing agent (BASF Japan, product name "Masterglanium 8000SM") was added over 30 seconds, and the mixture was mixed for a further 60 seconds to prepare fresh concrete. The unit amounts of each material were determined as shown in Table 2. The resulting fresh concrete was placed in a high-vibration pressure molding machine (Gokosha, GK8-B model) and pressure molded to create a test specimen. The test specimen dimensions were 200 mm in length and 100 mm in width, with the target height after molding set at 80 mm. After molding, the specimen was placed together with the base plate in a thermostatic chamber at 30°C, relative humidity of 60%, and carbon dioxide concentration of 80% by volume, and carbonation curing was carried out for 7 days. The cured specimens (hardened cementitious bodies) were evaluated using the following methods. The results are shown in Table 3.

[0031] [Bending strength] The bending strength test was conducted in accordance with "JIS A 5371:2016 (Precast Unreinforced Concrete Products, Appendix B (Regulations) Pavement and Boundary Blocks, Recommended Specifications B-3 Interlocking Blocks)" and the bending strength of specimens aged 3 and 7 days was measured, starting from the day of molding. The loading span during the measurement was 160 mm, and the increase in edge stress was 0.8 to 1.0 N / mm per minute. 2 The loading rate was adjusted so that Three specimens were used for each age, and the average value was used as the measured value.

[0032] [Carbonation depth] For specimens aged 3 and 7 days after flexural strength measurements were completed, a 1% ethanol solution of phenolphthalein was sprayed onto the fracture cross section of the specimen in accordance with JIS A 1152:2018 (Method for measuring carbonation depth of concrete). After 4 hours or more, the carbonation depth on the pressure-molded surface side (the area colored by spraying the 1% ethanol solution of phenolphthalein) was measured using a vernier caliper, and this was taken as the carbonation depth value. Measurements were taken at five equally spaced points in an area excluding a range of approximately 10 mm from the corners of the specimen, and the average of the carbonation depths obtained was taken as the measured value. In Table 3, specimens in which the entire fracture cross section was colored are indicated as "completely carbonated."

[0033] [Amount of carbon dioxide fixed] After measuring the carbonation depth, each specimen was cut perpendicular to the long edge using a concrete cutter in a section relatively close to the fracture surface, and processed into plates approximately 10 mm thick. The plates were dried under atmospheric pressure until the surface was dry, then transferred to a vacuum dryer and dried under reduced pressure for at least 24 hours. The entire specimen was then finely pulverized using a vibrating disk mill and subjected to thermogravimetric analysis using a TG-DTA device. The weight loss observed within the 600-800°C temperature range was considered to be due to the decarbonation of CO2, and the amount of carbon dioxide fixation (shown as "CO2 fixation amount" in Table 3) was calculated by dividing this by the amount of binder used in the specimen.

[0034] [Table 2]

[0035] [Table 3]

[0036] From Table 3, the bending strength of the cementitious hardened materials of Examples 1 to 7 (material age 3 days: 3.4 to 5.3 N / mm 2 , material age 7 days: 3.7~5.6N / mm 2) is 3.0N / mm 2 This shows that the above cementitious hardened material has a bending strength (3.0 N / mm) of normal block N (mainly used for sidewalks) specified in "JIS A 5371:2010 (precast unreinforced concrete products) recommended specification B-3 interlocking block." 2 ) is found to be satisfied. Furthermore, the carbonation depth in Examples 1 to 7 (material age 3 days: 4.8 mm to complete neutralization, material age 7 days: 6.4 mm to complete neutralization) is greater than the carbonation depth in Comparative Example 1 (material age 3 days: 1.9 mm, material age 7 days: 3.3 mm), indicating that the carbonation of the hardened cement composition is more advanced. Furthermore, the amount of carbon dioxide fixed in Examples 1 to 7 at an age of 7 days (128 to 227 kg / ton) was greater than the amount of carbon dioxide fixed in Comparative Example 1 at an age of 7 days (120 kg / ton), indicating that the hardened body of the cement composition absorbed more carbon dioxide.

Claims

1. The hydraulic modulus (H.M.) is 1.1 to 2.0 (excluding 1.1 to 1.3), the silica modulus (S.M.) is 1.5 to 3.5 (excluding 2.4 to 2.6), the iron modulus (I.M.) is 1.7 to 3.5 (excluding 2.0 to 2.3), and the content of aluminum oxide (Al ２ O ３ ) and iron oxide (Fe ２ O ３ A method for producing a cementitious hardened body using a cement composition containing clinker powder having a mineral composition in which the total content of gypsum, gypsum, and water is 9.0 to 14.0 mass%, A method for producing a cementitious hardened body, comprising a carbonation curing step of carbonating the cement composition to obtain the cementitious hardened body.

2. 2. The method for producing a cementitious hardened body according to claim 1, wherein the carbonation curing is carried out so that the carbonation depth from the surface of the cementitious hardened body becomes 2 mm or more in the carbonation curing step.

3. the cement composition comprises Portland cement clinker powder; 3. The cement composition according to claim 1, wherein the amount of said clinker powder is 50 parts by mass or more per 100 parts by mass of the total amount of said clinker powder and said Portland cement clinker powder.

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