Fired products and powdered cement compositions

Abstract

The present invention provides a fired product with low CO2 emission intensity, excellent strength development during demolding and after carbonation curing, and excellent fluidity before hardening, as well as a powdered cement composition containing the fired product. [Solution] A fired product in which, as calculated using the Bogue formula, the value of C3S is -30 to 5 mass%, the value of C2S is 60 to 95 mass%, and the sum of the values ​​of C3A and C4AF is 15 to 40 mass%. A powdered cement composition containing the fired product and gypsum, wherein the proportion of gypsum in the powdered cement composition is 1.0 to 6.0 mass% in terms of SO3.

Description

Technical Field

[0001] The present invention relates to a fired product and a powdery cement composition containing the fired product.

Background Art

[0002] At present, reducing the amount of carbon dioxide emissions is an important issue for suppressing global warming. As a method for reducing the amount of carbon dioxide emissions in the production of cementitious hardened bodies, a method is known in which the total amount of carbon dioxide emitted until a cementitious hardened body is obtained is reduced by absorbing carbon dioxide in the curing process of the cementitious hardened body. As a cementitious hardened body that can significantly reduce the total amount of carbon dioxide emitted by absorbing a large amount of carbon dioxide in the curing process, Patent Document 1 discloses a powdery cement composition containing (A) a powder for cement mixing containing either or both of mullite and anorthite, and Portland cement, (B) water, and (C) an aggregate, wherein a hardened body of the cement kneaded material is carbonated. In addition, Patent Document 2 describes a cementitious hardened body characterized in that a hardened body of a cement kneaded material containing (A) a pulverized product of a fired product containing 10 to 200 parts by mass of C2AS with respect to 100 parts by mass of C2S and having a C3A content of 20 parts by mass or less, a powdery cement composition containing Portland cement, (B) water, and (C) an aggregate is carbonated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present invention is to provide a fired product and a powdered cement composition containing the fired product that have low CO2 emission intensity, excellent strength development during demolding and after carbonation curing, and excellent fluidity before hardening. [Means for solving the problem]

[0005] The inventors of the present invention conducted intensive studies to solve the above problems and found that the above objective can be achieved by firing a product in which the value of C3S is -30 to 5 mass%, the value of C2S is 60 to 95 mass%, and the sum of the values ​​of C3A and C4AF is 15 to 40 mass%, as calculated using the Bogue formula. Thus, the inventors of the present invention were completed. In other words, the present invention provides the following [1] to [8]. [1] A fired product characterized by having a C3S value of -30 to 5 mass%, a C2S value of 60 to 95 mass%, and a sum of C3A and C4AF values ​​of 15 to 40 mass%, as calculated using the Bogue formula. [2] The calcined product according to [1] further comprising wollastonite in a proportion of 0.1 to 10.0% by mass. [3] A powdered cement composition comprising the calcined product and gypsum described in [1] or [2] above, wherein the proportion of gypsum in the powdered cement composition is 0.5 to 6.0% by mass in terms of SO3. [4] The powdered cement composition according to [3], further comprising Portland cement clinker, wherein the proportion of the fired product in the powdered cement composition is 10 to 80% by mass. [5] The powdered cement composition according to [3] or [4] further comprising at least one selected from blast furnace slag powder, fly ash, silica fume, limestone powder, calcined clay, and volcanic glass powder. [6] A hydraulic composition comprising the powdered cement composition, aggregate, and water described in any of [3] to [4] above. [7] The hydraulic composition according to [6] further comprising a cement admixture. [8] The hydraulic composition according to [6] or [7], wherein the hydraulic composition is a carbonated hardened body. [Effects of the Invention]

[0006] The fired product and the powdered cement composition containing the fired product of the present invention have a low CO2 emission intensity, excellent strength development during demolding and after carbonation curing, and excellent fluidity before hardening.

[0007] The fired product of the present invention has a C3S value of -30 to 5% by mass, a C2S value of 60 to 95% by mass, and a sum of C3A and C4AF values ​​of 15 to 40% by mass, as calculated using the Bogue formula. In this specification, the values ​​of C3S (3CaO·SiO2: also called "alite"), C2S (2CaO·SiO2: also called "beelite"), C3A (3CaO·Al2O3: also called "aluminate phase"), and C4AF (4CaO·Al2O3·Fe2O3: also called "ferrite phase") are values ​​calculated using the following Bogue formula (Bogue's calculation formula) based on the chemical composition of the calcined raw material or calcined product (cement clinker). C3S(mass%)=(4.07×CaO(mass%))-(7.60×SiO2(mass%))-(6.72×Al2O3(mass%))-(1.43×Fe2O3(mass%)) C2S(mass%)=(2.87×SiO2(mass%))-(0.754×C3S(mass%)) C3A(mass%)=(2.65×Al2O3(mass%))-(1.69×Fe2O3(mass%)) C4AF(mass%)=3.04×Fe2O3(mass%) In this specification, the values ​​calculated using the Bogue formula are numerical values ​​calculated based on the chemical components (chemical composition) of the calcined raw materials or calcined product (cement clinker), and do not represent the actual content of C3S, etc., in the calcined product.

[0008] The C3S value calculated using the Bogue formula is -30 to 5% by mass, preferably -20 to 3% by mass, more preferably -15 to 2% by mass, even more preferably -10 to 0% by mass, and particularly preferably -5 to -3% by mass, from the viewpoint of strength development of the hydraulic composition (including the calcined product of the present invention, hereinafter the same). If the C3S value is 5% by mass or less, CO2 emissions during the production of the calcined product can be further reduced. The C2S value calculated using the Borg formula is 60-95% by mass, preferably 65-93% by mass, more preferably 70-90% by mass, and particularly preferably 75-88% by mass. If the C2S value is less than 60% by mass, the long-term strength development of the hydraulic composition decreases. If the C2S value exceeds 95% by mass, the initial strength development (strength development at demolding) of the hydraulic composition decreases.

[0009] The C3A value calculated using the Bogue formula is preferably 1 to 30% by mass, more preferably 5 to 25% by mass, even more preferably 10 to 20% by mass, and particularly preferably 12 to 17% by mass. If the C3A value is 1% by mass or more, the initial strength development (strength development at demolding) of the hydraulic composition is further improved. In addition, the amount of industrial waste used as raw material for the fired product can be increased, thereby increasing the waste unit cost in the production of the fired product. If the C3A value is 30% by mass or less, the fluidity of the hydraulic composition before hardening is further improved, and the heat of hydration can be reduced. The C4AF value calculated using the Bogue formula is preferably 4 to 25% by mass, more preferably 5 to 22% by mass, and particularly preferably 8 to 15% by mass, from the viewpoint of ease of manufacture. Furthermore, if the C4AF value is 4% by mass or more, the heat of hydration of the hydraulic composition can be reduced. In addition, the amount of industrial waste used as raw material for the calcined product can be increased, thereby increasing the waste unit cost in the manufacture of the calcined product. The sum of the C3A and C4AF values ​​calculated using the Bogue formula is 15-40% by mass, preferably 18-30% by mass, more preferably 20-28% by mass, even more preferably 22-26% by mass, and particularly preferably 23-25% by mass. If the sum of the C3A and C4AF values ​​is less than 15% by mass, the amount of industrial waste used as raw material for the calcined product decreases, and the waste unit cost in the production of the calcined product decreases. If the sum of the C3A and C4AF values ​​exceeds 40% by mass, the strength development and fluidity of the hydraulic composition decrease. In addition, when producing the calcined product, molten material tends to adhere to the inside of the kiln, making stable production difficult.

[0010] From the viewpoint of improving the strength development of the hydraulic composition, the calcined product may contain wollastonite (CaO·SiO2: also known as "CS"). The proportion of wollastonite in the calcined product is preferably 0.1 to 10.0 mass%, more preferably 0.4 to 8.0 mass%, even more preferably 0.5 to 7.0 mass%, even more preferably 2.0 to 6.0 mass%, and particularly preferably 3.0 to 5.0 mass%. Furthermore, the calcined product may contain görenite (2CaO·Al2O3·SiO2: also known as "C2AS") from the standpoint of promoting the utilization of waste and increasing the waste production rate in the manufacture of the calcined product. On the other hand, since gehlenite is not reactive to carbon dioxide, if a large amount of gehlenite is contained in the calcined product, the amount of carbon dioxide immobilized in the hydraulic composition during carbonation curing becomes relatively small, and the strength development of the hydraulic composition decreases. In addition, the initial strength development of the hydraulic composition (strength development at demolding) decreases. From this viewpoint, the proportion of C2AS in the calcined product is preferably 10.0% by mass or less, more preferably 8.0% by mass or less, even more preferably 6.0% by mass or less, and particularly preferably 3.0% by mass or less. The proportions of wollastonite and gheerenite in the calcined material can be quantified by performing X-ray diffraction (XRD) / Rietveld method on the calcined material.

[0011] The above-mentioned calcined product (cement clinker) can be produced by, for example, using one or more materials selected from industrial waste, general waste, and construction-generated soil as raw materials, preparing the raw materials so that the values ​​of C3S, mineral composition, and chemical composition of the calcined product, calculated using the Bogue formula, reach target values, and then calcining these raw materials at, for example, 1,000 to 1,550°C (preferably 1,200 to 1,500°C, and more preferably 1,300 to 1,450°C). Furthermore, if it is difficult to prepare the calcined product using only the above-mentioned raw materials so that the C3S values ​​calculated using the Bogue formula reach the target values, raw materials such as calcium (e.g., limestone), silicon, aluminum, and iron may also be used. The resulting calcined material is usually crushed as appropriate using a crushing machine such as a ball mill or rod mill. If the powdered cement composition contains gypsum, the calcined material and gypsum may be crushed and mixed together at the same time. Furthermore, when grinding the calcined material, grinding aids may be used to improve grinding efficiency. Examples of grinding aids include DEG (diethylene glycol), DEIPA (diethanolisopropanolamine), and TIPA (triisopropanolamine). These may be used individually or in combination of two or more.

[0012] The powdered cement composition of the present invention contains the above-mentioned calcined product and gypsum. Examples of gypsum types are not particularly limited and include, for example, natural dihydrate gypsum, flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, hydrofluoric acid gypsum, etc. These may be used individually or in combination of two or more types. Examples of gypsum forms (hydrate or not) include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum. These may consist of only one form or may include two or more forms. The proportion of gypsum in the powdery cement composition is preferably 0.5 to 6.0% by mass, more preferably 1.0 to 5.9% by mass, still more preferably 2.0 to 5.8% by mass, still more preferably 3.0 to 5.6% by mass, and particularly preferably 4.0 to 5.5% by mass in terms of SO3 conversion. If the above proportion is 1.0% by mass or more, the fluidity of the hydraulic composition before curing is further improved. If the above proportion is 6.0% by mass or less, the strength development property of the hydraulic composition is further improved.

[0013] From the viewpoint of ensuring sufficient strength at the time of demolding, the powdery cement composition of the present invention may contain Portland cement clinker. Examples of Portland cement clinker include various Portland cement clinkers such as ordinary Portland cement clinker, early strength Portland cement clinker, medium heat Portland cement clinker, low heat Portland cement clinker, sulfate resistant Portland cement clinker, etc. These may be used alone or in combination of two or more. Among them, ordinary Portland cement clinker is preferable from the viewpoints of strength development property and the like. The proportion of the fired product in the powdery cement composition is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 25% by mass or more, and particularly preferably 35% by mass or more from the viewpoints of increasing the waste unit in the production of the fired product and Portland cement clinker contained in the powdery cement composition and the CO2 emission unit of the powdery cement composition. The above proportion is preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 45% by mass or less, still more preferably 35% by mass or less, and particularly preferably 25% by mass or less from the viewpoints of further improving the strength development property and the fluidity before curing of the hydraulic composition. Particularly, from the viewpoint of ensuring sufficient fluidity before curing without adding a cement admixture, the above proportion is preferably 40% by mass or less, more preferably 35% by mass or less, and particularly preferably 25% by mass or less.

[0014] In addition, the powdery cement composition may contain, as necessary, other powder materials other than the above-mentioned fired product, gypsum, and Portland cement clinker, as long as the object of the present invention is not inhibited. Examples of other powder materials include finely ground blast furnace slag, fly ash, silica fume, limestone powder, calcined clay, finely ground volcanic glass, and the like. The proportion of other powder materials in the powdery cement composition is not particularly limited, but is usually 30% by mass or less, preferably 10% by mass or less. The content rate of total SO3 in the powdery cement composition (the total content rate of SO3 contained in the fired product, cement clinker, gypsum, etc.) is preferably 2.0 to 8.0% by mass, more preferably 2.5 to 7.5% by mass, still more preferably 3.0 to 7.0% by mass, and particularly preferably 4.0 to 6.0% by mass. If the above proportion is 2.0% by mass or more, the fluidity of the hydraulic composition before curing is further improved. If the above proportion is 8.0% by mass or less, the strength development property of the hydraulic composition is further improved.

[0015] The above-mentioned powdery cement composition can be cured by containing water. The hydraulic composition of the present invention contains the above-mentioned powdery cement composition, water, and aggregate. In this specification, the "hydraulic composition" includes a form having fluidity before curing and a form after curing. The water is not particularly limited, and examples include tap water, recovered water defined in "JIS A 5308:2019 (Ready-mixed Concrete)", and the like. The amount of water relative to 100 parts by mass of the powdery cement composition is preferably 25 to 75 parts by mass, more preferably 35 to 65 parts by mass, and particularly preferably 45 to 55 parts by mass. If the above amount is less than 25 parts by mass, the fluidity of the hydraulic composition before curing decreases. If the above amount exceeds 75 parts by mass, the strength of the hardened body of the hydraulic composition decreases.

[0016] Examples of the aggregate include only fine aggregate or a combination of fine aggregate and coarse aggregate. In addition, any of natural aggregate, artificial aggregate, and recycled aggregate can be used. The fine aggregate is not particularly limited and includes, for example, river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, limestone fine aggregate, slag fine aggregate, lightweight fine aggregate, clinker fine aggregate, glass aggregate, and CCU fine aggregate (fine aggregate with carbon dioxide fixed from one or more types selected from recycled aggregate, waste concrete, blast furnace slab, and steelmaking slag). These may be used individually or in combination of two or more types.

[0017] The coarse aggregate is not particularly limited and includes, for example, river gravel, mountain gravel, land gravel, sea gravel, crushed stone, limestone coarse aggregate, slag coarse aggregate, lightweight coarse aggregate, clinker coarse aggregate, glass aggregate, and CCU coarse aggregate (coarse aggregate with carbon dioxide fixed from one or more types selected from recycled aggregate, waste concrete, blast furnace slab, and steelmaking slag). These may be used individually or in combination of two or more types. When a hydraulic composition contains coarse aggregate, the fine aggregate ratio (the volume ratio of fine aggregate to (fine aggregate + coarse aggregate) expressed as a percentage) is preferably 5-70%, more preferably 10-60%, and particularly preferably 20-50%. If the fine aggregate ratio is within the above range, the workability and ease of molding of the hydraulic composition before hardening are improved. The aggregate content in the hydraulic composition (the total amount if fine aggregate and coarse aggregate are used in combination) is preferably 200 to 750 parts by mass, more preferably 250 to 600 parts by mass, per 100 parts by mass of the powdered cement composition. When the above content is within the above range, the strength of the hardened body of the hydraulic composition becomes greater, and the shrinkage rate of the hardened body becomes smaller.

[0018] The hydraulic composition may contain cement admixtures, from the viewpoint of further improving fluidity before hardening and strength development. Examples of cement admixtures include cement dispersants, air-entraining agents, air content regulators, setting retarders, and alkanolamines. Examples of cement dispersants include water-reducing agents, AE water-reducing agents, high-performance water-reducing agents, and high-performance AE water-reducing agents. Examples of alkanolamines include TIPA (triisopropanolamine), DEA (diethanolamine), MEA (monoethanolamine), MDEA (methyldiethanolamine), DEIPA (diethanolisopropanolamine), and HEPZ (hydroxyethylpiperazine). These may be used individually or in combination of two or more types. In particular, from the viewpoint of further improving fluidity before hardening, it is preferable to include an AE water-reducing agent, an air volume regulator, and a setting retarder.

[0019] The amount of cement admixture to be added (the total amount if multiple types of cement admixture are used) varies depending on the fluidity and strength development of the desired hydraulic composition, but is preferably 0.01 to 5.0 parts by mass, more preferably 0.1 to 4.0 parts by mass, even more preferably 0.5 to 3.0 parts by mass, and particularly preferably 1.0 to 2.0 parts by mass, per 100 parts by mass of the total of the calcined product, gypsum, and Portland cement clinker. If the amount is 0.01 parts by mass or more, the fluidity of the hydraulic composition can be further improved. If the amount is 5.0 parts by mass or less, the cost of the cement dispersant can be reduced.

[0020] Furthermore, the amount of cement dispersant added varies depending on the desired fluidity and strength development of the hydraulic composition, but is preferably 0.01 to 5.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, and particularly preferably 0.8 to 2.0 parts by mass, per 100 parts by mass of the total of the calcined product, gypsum, and Portland cement clinker. If the amount added is 0.01 parts by mass or more, the fluidity of the hydraulic composition can be further improved. If the amount added is 5.0 parts by mass or less, the cost of the cement dispersant can be reduced. The amount of air content adjusting agent to be added varies depending on the desired fluidity and strength development of the hydraulic composition, but is preferably 0.001 to 1.0 parts by mass, more preferably 0.005 to 0.5 parts by mass, and particularly preferably 0.008 to 0.1 parts by mass, per 100 parts by mass of the total of the calcined product, gypsum, and Portland cement clinker. If the amount is 0.001 parts by mass or more, the fluidity of the hydraulic composition can be further improved. If the amount is 1.0 part by mass or less, the cost of the air content adjusting agent can be reduced.

[0021] The amount of setting retarder to be added varies depending on the fluidity and strength development of the target hydraulic composition, but is preferably 0.01 to 2.0 parts by mass, more preferably 0.10 to 1.0 parts by mass, and particularly preferably 0.15 to 0.5 parts by mass, per 100 parts by mass of the total of the calcined product, gypsum, and Portland cement clinker. If the amount is 0.01 parts by mass or more, the fluidity of the hydraulic composition can be further improved. If the amount is 2.0 parts by mass or less, the cost of the setting retarder can be reduced. The amount of alkanolamine to be added varies depending on the desired strength development of the hydraulic composition, but is preferably 0.001 to 2.0 parts by mass, more preferably 0.005 to 1.0 parts by mass, even more preferably 0.01 to 0.5 parts by mass, and particularly preferably 0.015 to 0.05 parts by mass, per 100 parts by mass of the total of the calcined product, gypsum, and Portland cement clinker. If the amount is 0.001 parts by mass or more, the strength development of the hydraulic composition can be further improved. If the amount is 2.0 parts by mass or less, the cost of the alkanolamine can be reduced.

[0022] When the hydraulic composition of the present invention is a carbonated hardened body, the CO2 emission intensity of the hydraulic composition can be reduced. Carbonated hardened bodies are hardened bodies obtained by carbonating a hydraulic composition. Carbonated hardened bodies can be obtained, for example, by performing carbonation curing on a hydraulic composition. Carbonation curing fixes carbon dioxide in the hydraulic composition, thereby reducing the CO2 emission intensity of the hydraulic composition. In addition, the densification of the structure of the hydraulic composition increases its strength. The method of carbonation curing is not particularly limited, but examples include a method of carbonation curing by exposing the hydraulic composition to carbon dioxide, or a method of blowing carbon dioxide into the hydraulic composition during the mixing of the hydraulic composition (in this case, a larger amount of carbon dioxide can be absorbed). Furthermore, the carbonation of hydraulic compositions (other than carbonation curing) includes methods in which carbonation occurs naturally over a long period of time by absorbing carbon dioxide from the air in the form of concrete products, concrete structures, or concrete pavements.

[0023] An example of a method for producing a hardened body of a hydraulic composition obtained by carbonation curing is a method that includes a mixture preparation step of preparing a mixture using the materials constituting the powdered cement composition, water, and aggregate; a casting step of casting the mixture into a formwork; a demolding step of demolding the hardened mixture from the formwork after the mixture has hardened in the formwork; and a carbonation curing step of carbonizing the hardened mixture demolded from the formwork to obtain a carbonized hardened body. The following explains each step in detail.

[0024] [Preparation process for kneaded products] This process involves preparing a mixture of the various materials constituting the powdered cement composition, water, and aggregate. The method for preparing the above-mentioned mixture is not particularly limited, and examples include (a) a method of mixing a pre-prepared powdered cement composition with water and aggregate, and (b) a method of simultaneously mixing each component constituting the powdered cement composition with water and aggregate. The equipment used for mixing is not particularly limited; for example, conventional mixers such as omni mixers, pan mixers, twin-shaft mixers, and tilting drum mixers can be used.

[0025] [Concrete pouring process] This process involves pouring the mixture obtained in the previous process into a mold. The concrete placement method is not particularly limited, and conventional methods such as pour molding can be used. The curing method after pouring the mixed material into the formwork until demolding is not particularly limited, and general curing methods such as air curing, humid air curing, underwater curing, sealed curing, and steam curing can be employed. The curing temperature before demolding is preferably 5 to 100°C, more preferably 20 to 95°C, and particularly preferably 40 to 90°C. If the temperature is 5°C or higher, the time required for demolding can be shortened. If the temperature is 100°C or lower, the energy cost of curing can be reduced. The curing time until demolding is not particularly limited, but is preferably 12 to 48 hours, more preferably 24 to 36 hours. If the curing time is 12 hours or more, the strength of the cured body at demolding can be increased. If the curing time is 48 hours or less, manufacturing efficiency can be improved. [Demolding process] This process involves demolding the hardened hydraulic composition, which is formed from the hardened mixture inside the mold, from the mold after the mixture has hardened.

[0026] [Carbonation curing process] This process involves carbonizing the hardened hydraulic composition that has been demolded from the mold, in order to obtain a carbonated hardened body obtained by carbonizing the hardened hydraulic composition. Furthermore, from the viewpoint of maximizing carbon dioxide absorption during carbonation curing, the concentration of carbon dioxide gas is preferably 1 volume% or more, more preferably 10 volume% or more, even more preferably 50 volume% or more, and particularly preferably 60 volume% or more. Also, from the viewpoint of reducing costs related to curing equipment, etc., the concentration of carbon dioxide gas is preferably 95 volume% or less, more preferably 85 volume% or less, and even more preferably 80 volume% or less. The temperature for carbonation curing is preferably 5 to 120°C, more preferably 10 to 100°C, even more preferably 15 to 80°C, even more preferably 20 to 70°C, and particularly preferably 25 to 60°C. If the temperature is 5°C or higher, the efficiency of carbonation is further improved, and the strength of the cured product is increased. If the temperature is 120°C or lower, the energy cost of carbonation curing can be further reduced. Furthermore, the relative humidity during carbonation curing is preferably 20-90%, more preferably 30-80%, and particularly preferably 40-70%. If the relative humidity is 20% or higher, the efficiency of carbonation is further improved, and the strength of the cured material is increased. If the relative humidity is 90% or lower, the costs associated with curing equipment can be further reduced. [Examples]

[0027] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Calcined products A to F; Tables 1 to 3 show the chemical composition of the calcined products, the values ​​of mineral compositions such as C2S quantified using the Rietveld method, and the values ​​of C3S etc. calculated using the Bogue formula. Upon examination of calcined products A to F using an optical microscope, it was found that none of the calcined products contained C3S. (2) Ordinary Portland cement (indicated as "OPC" in Tables 5-6); manufactured by Taiheiyo Cement Corporation, gypsum content (SO3 equivalent: 1.16 mass%, dihydrate gypsum: 0.27 mass%, hemihydrate gypsum: 0.89 mass%), CO2 emission intensity of ordinary Portland cement clinker contained in ordinary Portland cement: 512.4 kg-CO2 / ton (3) Gypsum powder; Hemihydrate rate: 80% (4) Fine aggregate; standard sand (5) Cement admixture A; AE water-reducing agent, manufactured by Pozzolith Solutions, trade name "Master Polyheed 15S" (6) Cement admixture B; air content regulator, manufactured by Pozzolith Solutions, trade name "MasterAir 404" (7) Cement admixture C; setting retarder, citric acid

[0028] [Table 1]

[0029] [Table 2]

[0030] [Table 3]

[0031] [Examples 1-4, Comparative Example 1] Mixtures a to e (corresponding to the powdered cement composition of the present invention) were prepared by mixing the types of fired materials shown in Table 4 with the amounts of gypsum shown in Table 4. The Blaine specific surface area and total SO3 content of mixtures a to e are also shown in Table 4. 90g of the mixture (powdered cement composition), 270g of fine aggregate, and 45g of water were mixed in a mixing bowl with a capacity of approximately 1 liter in accordance with "JIS R 5201:1997 (Physical Test Methods for Cement)". More specifically, after adding 90g of the mixture and 45g of water to the mixing bowl, it was mixed at low speed for 30 seconds using a Hobart mixer, then 270g of fine aggregate was added to the mixing bowl and mixed at low speed for 30 seconds, and then mixed at high speed for another 30 seconds. Next, the mixture adhering to the inner wall of the mixing bowl was scraped off over 15 seconds, then it was left to stand for 75 seconds, and finally mixed at high speed for 60 seconds to obtain the final mixture. For Examples 1 to 3, cement admixture A, cement admixture B, and cement admixture C were added in amounts of 1.0 part by mass, 0.01 part by mass, and 0.21 part by mass, respectively, per 100 parts by mass of the total amount of fired material and gypsum. The resulting mixture was poured into two molds (2 x 2 x 3 cm, 6 sections) and then vibrated for 30 seconds using a table vibrator. Of the two formworks, one was placed in a curing tank, the temperature inside the tank was maintained at 20°C for 4 hours, then the temperature inside the tank was increased at a rate of 20°C / hour until it reached 65°C, the maximum temperature (65°C) was maintained for 4 hours, then the temperature inside the tank was decreased at a rate of 4.5°C until it reached 20°C, and then it was cured in the tank until it reached 24 hours of age before being demolded. The other mold was cured and demolded in the same manner as the first mold described above, except that the maximum temperature was 90°C and the cooling rate was 5.6°C / hour. For the demolded specimens, a special jig corresponding to 2 x 2 x 3 cm was set up so that both sides of the molded specimen would become the pressure surfaces. A load was then applied to the center of the specimen at a rate of 600 ± 50 N per second using a load-applying pressure plate, and the maximum load was measured. From the measured maximum load, the compressive strength of the specimen was calculated using the following formula. Compressive strength (N / mm 2 )=Maximum load (N) / 400(mm 2 ) The results for each are shown in Table 4. Furthermore, the specimen in Comparative Example 1 could not be demolded because it had not cured sufficiently.

[0032] [Table 4]

[0033] Table 4 shows that in Comparative Example 1, demolding was not possible (the material had not hardened), whereas in Examples 1 to 4, the compressive strength at demolding was sufficient to allow demolding.

[0034] [Examples 5-8, Comparative Examples 2-3] Mixture f was prepared by mixing the calcined material F with gypsum. The proportion of gypsum in mixture f, calculated as SO3, was 1.0% by mass. Powdered cement compositions were prepared by mixing ordinary Portland cement with the types and proportions shown in Table 5 (mixtures a to e prepared in Examples 1 to 4 and Comparative Example 1, and mixture f above). 90 g of the obtained powdered cement composition, 270 g of fine aggregate, and 45 g of water were mixed in a mixing bowl with a capacity of approximately 1 liter in accordance with "JIS R 5201:1997 (Physical Testing Methods for Cement)". The mixing method for each material was the same as in Example 1. For Examples 5 to 7, cement admixture A, cement admixture B, and cement admixture C were added in amounts of 1.0 part by mass, 0.01 part by mass, and 0.21 part by mass, respectively, per 100 parts by mass of the total mixture and ordinary Portland cement. The resulting mixture was poured into two molds (2 x 2 x 3 cm, 6 sections) and then vibrated for 30 seconds using a table vibrator. One of the two formworks was placed in a curing tank, then the temperature inside the tank was maintained at 20°C for 4 hours. After that, the temperature inside the tank was increased at a rate of 20°C / hour until it reached 65°C, and the maximum temperature (65°C) was maintained for 4 hours. After that, the temperature inside the tank was decreased at a rate of 4.5°C until it reached 20°C, and then cured in the tank until it reached an age of 24 hours. Subsequently, the formwork was demolded, and the demolded specimen was subjected to carbonation curing for 48 hours in a curing tank at 30°C, 60% relative humidity, and 80% by volume of carbon dioxide. Of the two formworks, the other formwork was left to stand in a curing tank, the temperature inside the tank was maintained at 20°C for 4 hours, then the temperature inside the tank was increased at a rate of 20°C / hour until it reached 90°C, the maximum temperature (90°C) was maintained for 4 hours, then the temperature inside the tank was decreased at a rate of 4.5°C until it reached 20°C, and then cured in the tank until it reached an age of 24 hours. Next, the formwork was demolded. The demolded specimens were then subjected to carbonation curing for 48 hours in a curing tank at 30°C, 60% relative humidity, and 80% by volume of carbon dioxide. For both steam-cured and carbonation-cured specimens, a special jig corresponding to 2 x 2 x 3 cm was set up so that both sides of the molded specimen would become the pressure surface. A load was then applied to the center of the specimen at a rate of 600 ± 50 N per second using a load-applying pressure plate, and the maximum load was measured. From the measured maximum load, the compressive strength of the specimen was calculated using the formula described above. Table 5 shows the proportion of gypsum contained in the powdered cement composition and the results for each. In Table 5, "-" indicates that the experiment was not conducted.

[0035] [Table 5]

[0036] Table 5 shows that the compressive strength of Examples 5-8 at demolding was greater than that of Comparative Examples 2-3, and that the compressive strength after carbonation curing was greater than that of Comparative Example 2.

[0037] [Examples 9-13] A powdered cement composition was prepared by mixing mixture a (prepared in Example 1) and ordinary Portland cement in the proportions shown in Table 6. 90 g of the obtained powdered cement composition, 270 g of fine aggregate, and 45 g of water were mixed in a mixing bowl with a capacity of approximately 1 liter in accordance with "JIS R 5201:1997 (Physical Testing Methods for Cement)". The mixing method for each material was the same as in Example 1. In Example 13, cement admixtures A, B, and C were added in amounts of 1.0 part by mass, 0.01 part by mass, and 0.21 part by mass, respectively, per 100 parts by mass of the total of the fired product and ordinary Portland cement. The resulting mixture was subjected to 15 drop tests in accordance with "JIS R 5201:2015 (Physical Testing Methods for Cement)," and the flow value was measured. The flow value was measured twice. The results are shown in Table 6.

[0038] [Table 6]

[0039] From the comparison of Examples 9-12 in Table 6, it can be seen that the flow value increases as the proportion of ordinary Portland cement in the mix increases. Furthermore, the results from Example 13 show that the flow value can be increased even when the proportion of ordinary Portland cement in the powdered cement composition is small, by including a cement admixture.

Claims

1. The value calculated using the Borg formula is C ３ The value of S is -30 to 5 mass%, and C ２ The value of S is 60-95% by mass, and C ３ The value of A and C ４ A fired product characterized by having a total AF value of 15 to 40% by mass.

2. Furthermore, the calcined product according to claim 1, further comprising wollastonite in a proportion of 0.1 to 10.0% by mass.

3. A powdered cement composition comprising the calcined product and gypsum described in claim 1 or 2, The proportion of the above gypsum in the above powdered cement composition is SO ３ A powdered cement composition having a concentration of 0.5 to 6.0% by mass.

4. Furthermore, it contains Portland cement clinker, The powdered cement composition according to claim 3, wherein the proportion of the calcined product in the powdered cement composition is 10 to 80% by mass.

5. Furthermore, the powdered cement composition according to claim 3 further comprises at least one selected from blast furnace slag powder, fly ash, silica fume, limestone powder, calcined clay, and volcanic glass powder.

6. A hydraulic composition comprising the powdered cement composition, aggregate, and water according to claim 3.

7. Furthermore, the hydraulic composition according to claim 6, further comprising a cement admixture.

8. The hydraulic composition according to claim 6, wherein the hydraulic composition is a carbonated hardened body.

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