Cement admixture and method for producing same

Abstract

Provided is a cement admixture containing gypsum and a γ-2CaO·SiO2-containing fired product which satisfies the following requirements (a) and (b), wherein SO3 / Al2O3 (mole ratio) is 0.10-2.00.　(a): C' / S' (mole ratio) represented by {[CaO]-2([Al2O3]+[Fe2O3])} / {[SiO2]-([Al2O3]-[Fe2O3])} is 1.90-2.10, and (b): Al2O3 is no greater than 25.00 mass%.

Description

Cement admixture and method for producing the same

[0001] The present invention relates to a cement admixture containing γ-2CaO·SiO ２ and a method for producing the same.

[0002] In recent years, the trend of decarbonization has been accelerating globally, and the movement is also active in the cement industry, which is a typical high-consumption industry. Among such circumstances, although it does not have hydraulicity, the γ-type of 2CaO·SiO ２ with high carbonation activity has attracted attention in recent years, and numerous studies have been conducted on its utilization. For example, it is known that by forcibly carbonating and curing concrete blended with γ-2CaO·SiO ２ as an admixture, concrete with a densified surface layer and high durability can be obtained, and its usefulness has been found in recent years (Patent Document 1).

[0003] On the other hand, in connection with recent global environmental problems, the effective utilization of waste has become an important issue. Making effective use of or treating waste as a raw material or heat energy source during the production of cement clinker, taking advantage of the characteristics of the cement industry and cement manufacturing facilities, is considered effective from the perspective of enabling safe and large-scale disposal.

[0004] Among wastes, fly ash, incineration ash of municipal waste, blast furnace slag, blast furnace slowly cooled slag, etc., especially fly ash, has a higher content of Al ２ O ３ compared to the normal cement clinker composition. Therefore, when the usage amount of such waste is increased, the content of 3CaO·Al ２ O ３ corresponding to the interstitial phase among the cement clinker components increases, which affects the physical properties of the cement. Therefore, the usage amount of waste in cement production is restricted by the amount of the Al ２ O ３ component and there is a problem that it cannot be used in large quantities. Along with this, there is a high possibility that the effective utilization of waste will also be required in the production of γ-2CaO·SiO ２ in the future.

[0005] However, in the production of γ-2CaO·SiO ２ Al２ O ３ If present, γ-2CaO·SiO ２ Instead, β-2CaO·SiO ２ It is known that this makes it easier to generate (see, for example, Patent Document 2).

[0006] Japanese Patent Publication No. 2006-182583, International Publication No. 2012 / 099254

[0007] Therefore, the present inventors have found that Al contained in waste ２ O ３ , and Fe2O that reacts with it ３ By using a new index that takes this into account, β-2CaO・SiO ２ The formation of γ-2CaO·SiO was suppressed. ２ We proposed a technique for obtaining calcined products containing the substance (Japanese Patent Application No. 2024-012017).

[0008] By the way, currently, such γ-2CaO·SiO ２ Environmentally friendly concrete (secondary) products are being manufactured using cement containing calcined materials. In the manufacture of these environmentally friendly concrete products, after concrete placement, steam curing is usually performed until the product reaches a specified strength, followed by carbonation curing. In this case, if the rate of strength development after concrete placement is slow (poor strength development at the initial age), the curing time will be prolonged, which may lead to increased costs. Therefore, it is desirable that the strength development at the initial age when the product is demolded is good.

[0009] The object of the present invention is to produce concrete products and the like with good strength development in the early stages of age, using γ-2CaO・SiO ２ The objective is to provide a cement admixture containing calcined material.

[0010] The present inventors propose the γ-2CaO・SiO₂ as described in the above-mentioned Japanese Patent Application No. 2024-012017. ２ Further research into the contained calcined material revealed that this γ-2CaO·SiO ２ The calcined product contains Al ２ O ３ Fe2O ３Although it allows for increased use of waste containing Al, when used as a cement admixture, Al is present in the manufactured concrete products, etc. ２ O ３ We found that the strength at the initial age of the material is lower than that of conventional materials with lower content.

[0011] The inventors of this invention conducted further intensive studies to solve the above problems and have now found that this γ-2CaO・SiO ２ Gypsum is added to the calcined product containing SO ３ / Al ２ O ３ We discovered that setting the molar ratio to 0.10 to 2.00 can improve the strength development of concrete products and the like in their initial stages of age, and thus completed the present invention.

[0012] In other words, the present invention is as follows: [1] γ-2CaO・SiO2 that satisfies the following requirements a) and b) ２ Contains calcined material and gypsum, SO ３ / Al ２ O ３ A cement admixture characterized by having a molar ratio of 0.10 to 2.00. a) {[CaO]-2([Al ２ O ３ ] + [Fe ２ O ３ ])} / {[SiO ２ ]-([Al ２ O ３ ]-[Fe ２ O ３ The C' / S' (molar ratio) shown in )} is 1.90 to 2.10 b) Al ２ O ３ However, less than 25.00% by mass.

[0013] [2] The requirement in b) above is, b) Al ２ O ３ The cement admixture according to [1] above, characterized in that it is more than 5.00% by mass and 25.00% by mass or less. [3] The γ-2CaO・SiO ２ γ-2CaO·SiO in calcined products containing ２A cement admixture according to [1] or [2] above, characterized in that the content of is 25.0% by mass or more. [4] A mortar molded product characterized in that it contains the cement admixture according to any one of [1] to [3] above, cement, and fine aggregate. [5] A concrete molded product characterized in that it contains the cement admixture according to any one of [1] to [3] above, cement, fine aggregate, and coarse aggregate.

[0014] [6] A method for producing a cement admixture according to any of [1] to [3] above, comprising CaO raw material, SiO ２ A raw material mixture including raw materials and waste is calcined at a calcination temperature of 1280°C to 1600°C to obtain γ-2CaO・SiO that satisfies the requirements of a) and b) above. ２ A process for manufacturing a calcined product containing the γ-2CaO·SiO ２ A method for producing a cement admixture, comprising the step of mixing a contained calcined product with gypsum. [7] The method for producing a cement admixture according to [6] above, characterized in that the waste is at least one waste selected from coal ash, blast furnace slag, steelmaking slag, concrete sludge, waste concrete, incineration fly ash and municipal solid waste incineration ash.

[0015] The cement admixture of the present invention can be used to produce concrete products and the like that exhibit good strength development in the early stages of aging.

[0016] The γ-2CaO・SiO used in this invention ２ This diagram illustrates the underlying concept for condition a) of the contained calcined product.

[0017] [Cement Admixture] The cement admixture of the present invention satisfies the following requirements a) and b): γ-2CaO・SiO ２ Contains calcined material and gypsum, SO ３ / Al ２ O ３ It is characterized by having a molar ratio of 0.10 to 2.00.

[0018] a) {[CaO]-2([Al ２ O ３ ] + [Fe ２ O ３ ])} / {[SiO ２ ]-([Al２ O ３ ]-[Fe ２ O ３ The C' / S' (molar ratio) shown in )} is 1.90 to 2.10 b) Al ２ O ３ However, less than 25.00% by mass.

[0019] The cement admixture of the present invention contains a predetermined amount of gypsum and SO ３ / Al ２ O ３ Since the molar ratio is adjusted to 0.10 to 2.00, concrete, mortar, etc., manufactured using this cement admixture exhibit good strength development in the early stages of maturation.

[0020] Concrete and mortar made using cement containing the cement admixture of the present invention become highly durable due to the densification of the surface layer through carbonation curing during manufacturing. Furthermore, in the manufacturing of this concrete, carbon dioxide is absorbed into the concrete during carbonation curing, which also reduces the amount of carbon dioxide emitted when obtaining concrete products.

[0021] <Gypsum> The cement admixture of the present invention contains gypsum. As for the gypsum, natural gypsum, chemical by-product gypsum such as flue gas desulfurization gypsum and phosphate gypsum, recycled gypsum from gypsum waste, etc. can be used without particular limitation.

[0022] The amount of gypsum used is the SO2 of the cement admixture of the present invention. ３ / Al ２ O ３ This is the amount that results in a molar ratio of 0.10 to 2.00. ３ / Al ２ O ３ From the viewpoint of early age strength development, the ratio is preferably 0.20 to 1.80, and more preferably 0.50 to 1.60. Furthermore, considering the fluidity of concrete and the like containing the cement admixture of the present invention, the ratio is even more preferably 0.50 to 1.40, and particularly preferably 0.50 to 1.20.

[0023] <γ-2CaO・SiO ２ Calcined product containing > (a) conditions) γ-2CaO・SiO２ The condition in the fired product of a) above is a new index proposed by the present inventors considering the influence of Al ２ O ３、 and Fe2O that reacts with it ３ . The meaning of the index shown in a) will be explained below.

[0024] First, when using raw materials containing CaO, SiO ２ , Al ２ O ３ and Fe ２ O ３ , generally, reactions are considered to occur in the order of (1) to (3) below. A schematic diagram thereof is shown in FIG. 1.

[0025] (1) Fe ２ O ３ reacts with Al ２ O ３ and CaO to form C ４ AF. (2) The remaining Al ４ O ２ after forming C ３ AF reacts with CaO and SiO ２ to form C ２ AS. (3) The remaining CaO after forming C ４ AF and C ２ AS reacts with SiO ２ to form 2CaO·SiO ２ (C ２ S).

[0026] The molar ratio (C / S) of CaO and SiO ２ in this (3) is adjusted to be about 2.00.

[0027] Specifically, CaO consumes 4 times the molar amount of the Fe ２ O ３ content in the reaction of (1), and in the reaction of (2), 2 times the molar amount of the unreacted Al ２ O ３ amount ([Al ２ O ３ - [Fe2O ３ ) is consumed. Also, SiO ２ in the reaction of (2) above is the unreacted Al ２ O３ Quantity ([Al ２ O ３ ]-[Fe2O ３ Equimolar amounts of ) are consumed. The CaO and SiO that remain after this consumption ２ The composition is designed so that the molar ratio of C' / S' is approximately 2.00 (1.90 to 2.10, preferably 1.93 to 2.07, more preferably 1.95 to 2.05). The balance of the above is shown in Table 1 below.

[0028]

[0029] Furthermore, applying the results of manufacturing example 5, which will be described later, to Table 1 yields the following:

[0030]

[0031] (Condition for (b)) γ-2CaO・SiO ２ In calcined products containing Al ２ O ３ However, it is 25.00% by mass or less. Al ２ O ３ If it exceeds 25.00 mass%, a large amount of C ２ AS and C ４ AF is generated, and γ-2CaO·SiO ２ It is not possible to obtain a calcined product that contains a sufficient amount of Al. ２ O ３ It is preferable that the amount is 22.00% by mass or less. Also, Al ２ O ３ There is no particular lower limit for the content, but for example, it should be 2.00% by mass or more, and even at high content levels exceeding 5.00% by mass, γ-2CaO·SiO ２ A calcined product containing a sufficient amount of [the substance] can be obtained.

[0032] (Other conditions) γ-2CaO・SiO used in this invention ２ In calcined products containing Fe ２ O ３ / Al ２ O ３ The molar ratio is preferably 0.05 to 1.10. Fe ２ O ３ / Al ２ O ３If it exceeds 1.10, depending on other requirements, a large amount of β-2CaO·SiO ２ This is generated, and γ-2CaO·SiO ２ In some cases, it may not be possible to obtain a calcined product that contains a sufficient amount of Fe. ２ O ３ / Al ２ O ３ The molar ratio is more preferably 0.05 to 0.90, and even more preferably 0.25 to 0.90. Fe ２ O ３ / Al ２ O ３ When the molar ratio is high, it is possible to lower the firing temperature by generating melt during firing.

[0033] The γ-2CaO・SiO used in this invention ２ The calcined product contains γ-2CaO・SiO ２ The content of is preferably 25.0% by mass or more, more preferably 30.0% by mass or more, even more preferably 40.0% by mass or more, and particularly preferably 50.0% by mass or more. Furthermore, β-2CaO・SiO ２ γ-2CaO・SiO ２ A high content of [this substance] is preferable.

[0034] (Raw material) γ-2CaO・SiO₂ used in this invention ２ The raw materials for obtaining the calcined product containing CaO, SiO ２ In addition to raw materials, Al ２ O ３ and Fe ２ O ３ Waste containing the following can be used.

[0035] In this invention, since waste can be used as a raw material, effective utilization of waste can be achieved. Furthermore, the γ-2CaO・SiO used in this invention ２ The calcined product containing it allows for the use of more waste as a raw material. The γ-2CaO・SiO used in this invention ２ The calcined product contains Al ２ O ３ Even when waste materials with a high content of β-2CaO・SiO are used as raw materials,２ Suppresses the formation of γ-2CaO·SiO ２ A fired product containing a high proportion of [the substance] can be obtained.

[0036] CaO raw materials and SiO ２ The raw materials include CaO raw materials and SiO, which are known as raw materials for cement clinker production. ２ The raw materials can be used without restriction, specifically CaO raw materials such as limestone, quicklime, and slaked lime, and SiO such as silica and silica fumes. ２ The raw materials are listed. Limestone (calcium carbonate), which is used as a CaO raw material, emits carbon dioxide during calcination. However, in this invention, by using waste materials such as concrete sludge and blast furnace slag containing calcium oxide, which can be used as a CaO raw material, the amount of limestone used, which is the cause of carbon dioxide emissions, is reduced, and γ-2CaO・SiO ２ This can reduce carbon dioxide emissions during manufacturing.

[0037] The waste used in this invention refers to waste and by-products used in cement manufacturing, etc. While there are no particular limitations on the types of waste that can be used, specific examples include blast furnace slag such as granulated blast furnace slag and slow-cooled blast furnace slag, steelmaking slag, non-ferrous metal slag, coal ash, concrete sludge (including returned concrete and residual concrete), waste concrete, sewage sludge, water treatment sludge, papermaking sludge, construction waste soil, foundry sand, fly ash, incinerator fly ash, molten fly ash, chlorine bypass dust, wood chips, waste clay, spoil, waste tires, seashells, municipal solid waste and its incinerator ash, etc. (Note that some of these can also serve as a source of thermal energy). Among these, in the production of cement clinker, Al ２ O ３ The amount of Al used is limited by its quantity. ２ O ３ Waste containing Al is preferable because it further promotes the effective utilization of waste. ２ O ３Typical waste materials containing Al include blast furnace slag, steelmaking slag, non-ferrous metal slag, coal ash, concrete sludge, waste concrete, sewage sludge, water treatment sludge, papermaking sludge, foundry sand, incinerator fly ash, molten fly ash, municipal solid waste and its incinerator ash. Among these, Al is particularly high compared to the composition of ordinary cement clinker. ２ O ３ It has a high content, and its main components are CaO and SiO ２ Al ２ O ３ From this perspective, the use of coal ash, blast furnace slag, steelmaking slag, concrete sludge, waste concrete, incinerator fly ash, and municipal solid waste incineration ash is preferable. These wastes may also be used in combination.

[0038] (Production method) γ-2CaO / SiO ２ The method for preparing and mixing the raw material mixture for producing the calcined product can be any known method as appropriate. For example, the raw materials may be prepared in advance using CaO raw materials such as limestone, quicklime, and slaked lime, and SiO2 such as silica. ２ The composition of the raw materials and waste can be measured, and the blending ratio of each raw material can be calculated from the proportion of each component in these raw materials to satisfy the requirements of a) and b) of the present invention, and the raw materials can be blended in that ratio.

[0039] CaO raw material, SiO ２ While a smaller particle size in the raw material mixture, including raw materials and waste, results in a faster calcination reaction rate, it also worsens the power consumption per unit of pulverization of each raw material and / or the raw material mixture. Therefore, it is sufficient to prepare the mixture so that the residue after sieving at 90 μm is 10-30%, with 20-26% being preferable. The pulverization method for each raw material and / or the raw material mixture is not particularly limited and can be done using known methods.

[0040] In the present invention, the firing temperature of the raw material mixture after preparation and mixing is preferably 1280 to 1600°C, and more preferably 1350 to 1500°C. Lower firing temperatures tend to result in a higher amount of free lime (f-CaO). The amount of free lime is preferably less than 3.0% by mass, and more preferably 1.5% by mass or less. Conversely, if the firing temperature is too high, the raw materials melt and vitrify, making operation difficult and undesirable from the viewpoint of heat energy consumption. The firing time depends on the firing temperature, but is generally 0.5 to 10 hours, preferably 1 to 5 hours.

[0041] The firing method is not particularly limited, and rotary kilns, shaft kilns, electric furnaces, tunnel furnaces, fluidized bed incinerators, etc., can be used. However, from the perspective of being able to use existing Portland cement manufacturing equipment, high-temperature heating equipment such as cement kilns represented by NSP kilns and SP kilns is preferably used. Furthermore, from the viewpoint of mass production, it is preferable to use such cement manufacturing equipment.

[0042] In this invention, a cooling operation is performed after firing, but the cooling conditions are not particularly limited. For example, in existing Portland cement manufacturing facilities, after firing in a rotary kiln, the material can be immediately cooled using a cooling device called a clinker cooler (a blower and a water sprayer).

[0043] [Molded Products] Mortar molded products of the present invention can be manufactured by blending the cement admixture of the present invention with cement and fine aggregate. Concrete molded products of the present invention can also be manufactured by blending the cement admixture of the present invention with cement, fine aggregate and coarse aggregate. Mortar molded products and concrete molded products manufactured using the cement admixture of the present invention exhibit good strength development in the initial stages. Therefore, the curing time for demolding in the manufacture of mortar and concrete products can be shortened, and mortar and concrete products can be manufactured efficiently.

[0044] The amount of cement admixture added to the cement is preferably 1 to 70% by mass, more preferably 10 to 50% by mass, and even more preferably 20 to 40% by mass, relative to the total amount of cement and cement admixture.

[0045] [Method for producing cement admixture] The method for producing cement admixture of the present invention involves a CaO raw material and SiO ２ A raw material mixture including raw materials and waste is calcined at a calcination temperature of 1280°C to 1600°C to obtain γ-2CaO・SiO that satisfies the requirements of a) and b) above. ２ The process for manufacturing the calcined product containing γ-2CaO・SiO ２ The process includes mixing the contained calcined material with gypsum, ３ / Al ２ O ３ The cement admixture of the present invention is manufactured having a molar ratio of 0.10 to 2.00.

[0046] γ-2CaO・SiO ２ The various conditions in the process of manufacturing the calcined product containing the substance are as described above. γ-2CaO・SiO ２ In the process of mixing the contained calcined material and gypsum, the cement admixture SO ３ / Al ２ O ３ (Molar ratio) is between 0.10 and 2.00, γ-2CaO·SiO ２ Mix the contained calcined material with gypsum. A known mixing method can be used as appropriate. For example, beforehand, γ-2CaO・SiO ２ The composition of the contained calcined material was measured, and the SO2 cement admixture was determined. ３ / Al ２ O ３ The amount of gypsum to be added should be calculated so that the molar ratio is between 0.10 and 2.00, and the mixture should be prepared according to that ratio. ３ / Al ２ O ３ The preferred range for the molar ratio is as described above.

[0047] The configuration and effects of the present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0048] Using industrial raw materials including waste and ready-mix concrete sludge, the raw materials are prepared and fired at 1400°C in a small rotary kiln to produce γ-2CaO・SiO ２ A calcined product containing [the specified substance] was obtained. Table 1 shows the chemical and mineral composition of the obtained calcined product.

[0049]

[0050] This γ-2CaO·SiO ２ For calcined products containing SO2, dihydrate gypsum (special grade reagent) is applied. ３ / Al ２ O ３ A cement admixture was obtained by dry mixing to achieve a predetermined molar ratio, and this was used. The cement mix with admixture conformed to JIS R 5201, and research cement (manufactured by the Japan Cement Association) was used as the binder: cement admixture (containing gypsum γ-2CaO・SiO ２ The mixture was formulated to have a ratio of 7:3 (mass ratio). Note that research cement (manufactured by the Japan Cement Association): cement admixture (γ-2CaO・SiO₂, which does not contain gypsum) ２ A sample formulation was used as a reference, with a ratio of 7:3 (by mass).

[0051] SO2 ３ / Al ２ O ３ Table 4 shows the results for (molar ratio), compressive strength at 1 day of age, and flow (fluidity).

[0052]

[0053] The various measurements were performed using the following method: γ-2CaO・SiO ２ The chemical composition of the contained calcined material was measured by X-ray fluorescence analysis in accordance with JIS R 5204. γ-2CaO・SiO ２ The mineral composition of the contained calcined material was determined by X-ray diffraction analysis of the obtained calcined material and subsequent Rietveld analysis. The compressive strength (at 1 day of age) of the admixture-mixed cement was measured according to the method compliant with JIS R 5201. The flow of the admixture-mixed cement was measured according to the method compliant with JIS R 5201.

[0054] As shown in Table 4, the admixture-containing cements of Examples 1 to 5 showed compressive strengths after one day that significantly exceeded those of the reference example, indicating improved strength development at the initial age. Furthermore, in terms of fluidity, the admixture-containing cements of Examples 1 to 5 were found to be equivalent to or superior to those of the reference example.

[0055] The following describes the various γ-2CaO·SiO used in the present invention. ２ Examples of the production of calcined products containing the following are shown. [Production Examples 1-6 and Comparative Production Examples 1-12] Limestone and SiO as CaO raw materials. ２ A raw material mixture is prepared using silica as the raw material and concrete sludge as waste, and then calcined in an electric furnace at 1450°C for 60 minutes to produce γ-2CaO·SiO of a predetermined composition. ２ A calcined product containing the raw materials was obtained. Table 5 shows the chemical composition of the raw materials, and Table 6 shows the chemical composition and mineral composition of the obtained calcined product.

[0056] Note that γ-2CaO・SiO ２ The measurement of the chemical and mineral composition of the contained calcined material is the same as described above.

[0057]

[0058]

[0059] (Sludge content: 30%) The compositions of Production Examples 1 to 3 (C' / S' = 1.90 to 2.10) are β-2CaO・SiO ２ It has a low content of γ-2CaO・SiO ２ The content of is high. On the other hand, the compositions of comparative manufacturing examples 1 to 4 (C' / S' less than 1.90 or greater than 2.10) contain β-2CaO・SiO ２ A large amount is produced, γ-2CaO·SiO ２ The content is low.

[0060] (Sludge content: 40%) The compositions of Production Examples 4-6 (C' / S' = 1.90-2.10) are β-2CaO・SiO ２ It has a low content of γ-2CaO・SiO ２ The content of is high. On the other hand, the compositions of comparative manufacturing examples 5 to 8 (C' / S' less than 1.90 or greater than 2.10) contain β-2CaO・SiO ２A large amount is produced, γ-2CaO·SiO ２ The content is low.

[0061] [Manufacturing Examples 7-18] Instead of concrete sludge, use special grade reagent Al ２ O ３ and Fe2O ３ A raw material mixture is prepared using [the specified method], and then calcined in an electric furnace at 1450°C for 60 minutes to obtain γ-2CaO・SiO of the predetermined composition. ２ A calcined product containing the active ingredient was obtained. Tables 7 and 8 show the chemical and mineral compositions of the obtained calcined product. Production examples 7 to 12 shown in Table 7 contain Al ２ O ３ These are variations in the content of Fe2O, and production examples 13 to 18 shown in Table 8 are Fe2O ３ / Al ２ O ３ This is a variation where the (molar ratio) is changed.

[0062]

[0063]

[0064] As shown in Table 7, the compositions of production examples 7 to 12 (C' / S' = 1.90 to 2.10) are Al ２ O ３ Even if the amount increases, β-2CaO·SiO ２ It has a low content of γ-2CaO・SiO ２ It has a high content of [ingredient].

[0065] As shown in Table 8, the compositions of Production Examples 13 to 18 (C' / S' = 1.90 to 2.10) are Fe2O ３ / Al ２ O ３ Even if the (molar ratio) increases, β-2CaO·SiO ２ It has a low content of γ-2CaO・SiO ２ It has a high content of [ingredient].

[0066] The cement admixture of the present invention is industrially useful because it can be used by being mixed with cement.

Claims

1. A cement admixture comprising a γ-2CaO·SiO sintered product satisfying the following requirements a) and b), and gypsum, wherein the SO / Al (molar ratio) is 0.10 to 2.

00. a) The C' / S' (molar ratio) represented by {[CaO] - 2([AlO] + [FeO])} / {[SiO] - ([AlO] - [FeO])} is 1.90 to 2.

10. b) AlO is 25.00% by mass or less ２ contains a sintered product and gypsum, and the SO ３ / Al ２ O ３ (molar ratio) is 0.10 to 2.

00. a) {[CaO] - 2([Al ２ O ３ + [Fe ２ O ３ )} / {[SiO ２ - ([Al ２ O ３ - [Fe ２ O ３ )} is 1.90 to 2.

10. b) Al ２ O ３ is 25.00% by mass or less 2. The requirement in b) above is, b) Al ２ O ３ The cement admixture according to claim 1, characterized in that the amount is greater than 5.00% by mass and less than or equal to 25.00% by mass.

3. The aforementioned γ-2CaO・SiO ２ γ-2CaO·SiO in calcined products containing ２ The cement admixture according to claim 1, characterized in that the content of is 25.0% by mass or more.

4. A mortar molded product characterized by comprising a cement admixture according to any one of claims 1 to 3, cement, and fine aggregate.

5. A concrete molded product characterized by comprising a cement admixture according to any one of claims 1 to 3, cement, fine aggregate, and coarse aggregate.

6. A method for producing a cement admixture according to any one of claims 1 to 3, comprising: CaO raw material, SiO ２ A raw material mixture including raw materials and waste is calcined at a calcination temperature of 1280°C to 1600°C to obtain γ-2CaO・SiO that satisfies the requirements of a) and b) above. ２ A process for manufacturing a calcined product containing the γ-2CaO·SiO ２ A method for producing a cement admixture, characterized by comprising the steps of mixing a contained calcined product with gypsum.

7. The method for producing a cement admixture according to claim 6, characterized in that the waste is at least one waste selected from coal ash, blast furnace slag, steelmaking slag, concrete sludge, waste concrete, incinerator fly ash, and municipal solid waste incineration ash.

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