γ-2CaO·SiO2-containing clinker, cement admixture, cement composition, and method for producing γ-2CaO·SiO2-containing clinker

Abstract

The present invention provides a γ-2CaO·SiO2-containing clinker with good workability even when it contains impurities, and a method for producing the same. [Solution] A γ-2CaO·SiO2-containing clinker and a method for producing the same, wherein the clinker contains at least one of Na2O and K2O and SO3 as chemical components, and the SO3 / (Na2O+K2O) (molar ratio) is 1.2 or more and 10.0 or less. Preferably, the γ-2CaO·SiO2-containing clinker contains 1% by mass or more and 20% by mass or less of Al2O3 as a chemical component.

Description

Technical Field

[0001] The present invention relates to a γ-2CaO·SiO2-containing clinker, a cement admixture, a cement composition, and a method for producing a γ-2CaO·SiO2-containing clinker.

Background Art

[0002] Since a large amount of cement is used as a raw material for concrete, it is regarded as a material with a large CO2 emission. This is mainly because, in the production process of cement, in addition to using a large amount of fossil fuel to obtain the combustion energy of the furnace, the decarbonation reaction of limestone (CaCO3→CaO+CO2) occurs. Reducing the CO2 emission as concrete has become an important theme as part of the countermeasures against global warming.

[0003] In order to reduce the total amount of CO2 emitted when manufacturing concrete products, it is effective to reduce the amount of cement used by using various wastes such as industrial wastes as cement substitutes, and various studies are being carried out.

[0004] In addition, by blending a non-hydraulic compound such as 2CaO·SiO2 (γ-C2S) into a cement composition as a cement or an admixture and bringing it into contact with CO2, γ-C2S absorbs CO2, and the total CO2 emission in obtaining a concrete product is reduced by this amount of CO2.

[0005] For example, Patent Document 1 below describes a γ-2CaO·SiO2-containing hydraulic clinker having a predetermined chemical composition and mineral composition, and describes using waste as a raw material.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] The γ-2CaO·SiO2-containing hydraulic clinker described in Patent Document 1 uses waste as a raw material, raising concerns that impurities in the waste may reduce the flow value of the manufactured cement composition, thereby decreasing workability. Furthermore, there are concerns that the impurities may prevent the formation of γ-C2S, leading to an increase in the production of β-2CaO·SiO2(β-C2S).

[0008] This invention has been made in view of these circumstances, and aims to provide a γ-2CaO·SiO2-containing clinker, cement admixture, cement composition, and a method for producing a γ-2CaO·SiO2-containing clinker, even when impurities are present, that exhibit good workability. [Means for solving the problem]

[0009] Through diligent research to solve the above problems, we discovered that the problems can be solved by setting the molar ratio of SO3 to alkali in the γ-2CaO·SiO2-containing clinker within a predetermined range, leading to the present invention. In other words, the present invention is as follows. [1] A γ-2CaO·SiO2-containing clinker containing at least one of Na2O and K2O, SO3, and having a molar ratio of SO3 / (Na2O+K2O) of 1.2 or more and 10.0 or less. [2] The γ-2CaO·SiO2-containing clinker described in [1], which contains 1% by mass or more and 20% by mass or less of Al2O3 as a chemical component. [3] The γ-2CaO·SiO2-containing clinker according to [1] or [2], wherein the amount passing through the 1.18 mm sieve is 50% by mass or more, and the γ-2CaO·SiO2 content of the amount passing through the 1.18 mm sieve is 40% by mass or more. [4] A γ-2CaO·SiO2-containing clinker as described in any of [1] to [3], wherein the angle of repose is 40 degrees or greater. A cement admixture containing γ-2CaO·SiO2-containing clinker as described in any of [5], [1], to [4]. A cement admixture containing the cement admixture described in [6] and [5]. [7] A method for producing γ-2CaO·SiO2-containing clinker according to any one of [1] to [4], comprising: a raw material mixing step of mixing at least a CaO raw material, an SiO2 raw material, and waste containing at least one of Na2O and K2O and SO3 as chemical components to produce a raw material mixture; and a calcination step of calcining the raw material mixture at a calcination temperature of 1350 to 1600°C. [8] The waste material contains Al2O3 as a chemical component, as described in [7] for the method of producing γ-2CaO·SiO2-containing clinker. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide γ-2CaO·SiO2-containing clinker, cement admixture, cement composition, and a method for producing γ-2CaO·SiO2-containing clinker, which have good workability even when impurities are present. [Modes for carrying out the invention]

[0011] The following describes in detail the γ-2CaO·SiO2-containing clinker, cement admixture, cement composition, and method for producing the γ-2CaO·SiO2-containing clinker according to the present invention, but the present invention is not limited to these embodiments. In this specification, "%" and "parts" refer to mass unless otherwise specified.

[0012] [γ-2CaO SiO2-containing clinker] The γ-2CaO·SiO2 (hereinafter also referred to as "γ-C2S")-containing clinker of this embodiment contains at least one of Na2O and K2O, and SO3 as chemical components, and the SO3 / (Na2O+K2O) (molar ratio) is 1.2 or more and 10.0 or less.

[0013] The γ-C2S-containing clinker of this embodiment contains, as chemical components, at least one of Na2O and K2O, and SO3. It is sufficient to contain at least one of Na2O and K2O, and it is preferable that Na2O is contained in the γ-C2S-containing clinker at a concentration of 1% by mass or less, more preferably 0.7% by mass or less, and even more preferably 0.5% by mass or less. Furthermore, it is preferable that Na2O is contained at a concentration of 0.05% by mass or more, and more preferably 0.1% by mass or more. The K2O content is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.75% by mass or less. Furthermore, the K2O content is preferably 0.8% by mass or more, and more preferably 0.15% by mass or more. Furthermore, the SO3 content is preferably 4% by mass or less, more preferably 2% by mass or less, and even more preferably 1.2% by mass or less. Additionally, the SO3 content is preferably 0.15% by mass or more, and more preferably 0.25% by mass or more.

[0014] The molar ratio of SO3 to alkali, SO3 / (Na2O+K2O) (molar ratio), is preferably 1.2 to 10.0, and more preferably 2.0 to 6.0. By setting SO3 / (Na2O+K2O) within the above range, the flow value of the cement composition containing γ-C2S-containing clinker can be improved, thereby improving workability. Furthermore, by setting the SO3 / (Na2O+K2O) ratio within the above range, it is possible to suppress the formation of β-C2S and increase the amount of γ-C2S produced in the mineral composition when manufacturing γ-C2S-containing clinker. Increasing the γ-C2S content can increase the amount of CO2 absorbed during curing.

[0015] Furthermore, the γ-C2S-containing clinker may contain 1% to 20% by mass of Al2O3 as a chemical component. The Al2O3 content is 3% to 15% by mass, more preferably 5% to 10% by mass. By including Al2O3 within the above range, the carbonation reaction rate of γ-C2S and β-C2S is improved without an excessive amount of C2AS, which does not have carbonation reactivity. In addition, even if the Al2O3 is within the above range, the amount of γ-C2S produced can be prevented from decreasing by setting the SO3 / (Na2O+K2O) value within the above range.

[0016] [Mineral composition] γ-C2S-containing clinkers have the following mineral compositions: γ-2CaO·SiO2(γ-C2S), β-2CaO·SiO2(β-C2S), and 2CaO·Al2O3·SiO2(C2AS). In this invention, by setting the molar ratio of SO3 to the alkali in the chemical composition to the predetermined range described above, a high content of γ-C2S can be produced. A high content of γ-C2S can increase the amount of CO2 absorbed when producing concrete from the cement composition. The mineral composition of the γ-C2S-containing clinker is preferably such that γ-C2S is 30% to 90% by mass, more preferably 40% to 85% by mass, and even more preferably 50% to 80% by mass. Furthermore, β-C2S is preferably 5% to 40% by mass, more preferably 10% to 20% by mass. C2AS is preferably 2% to 55% by mass, more preferably 8% to 40% by mass, and even more preferably 10% to 15% by mass. As other minerals, calcium silicates represented by 3CaO·SiO2, CaO·SiO2, 3CaO·2SiO2, calcium aluminoferrites represented by 4CaO·Al2O3·Fe2O3, 6CaO·2Al2O3·Fe2O3, 6CaO·Al2O3·Fe2O3, calcium ferrites such as 2CaO·Fe2O3, and calcium aluminates represented by CaO·Al2O3, 3CaO·Al2O3, CaO·2Al2O3, etc., may be included without particular limitation as long as they are commonly used in cement compositions.

[0017] The γ-C2S-containing clinker preferably has a fraction passing through a 1.18 mm sieve of 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. Further, the content of γ-C2S in the fraction passing through a 1.18 mm sieve is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. When the fraction passing through a 1.18 mm sieve of the γ-C2S-containing clinker is 50% by mass or more and the content of γ-C2S in the fraction passing through a 1.18 mm sieve is 40% by mass or more, it can be easily pulverized, and the reaction rate and absorption amount with C2O by the γ-C2S-containing clinker can be increased.

[0018] The γ-C2S-containing clinker preferably has an angle of repose of 40 degrees or more, more preferably 45 degrees or more. Also, the angle of repose is preferably 65 degrees or less, more preferably 55 degrees or less. By setting the angle of repose within the above range or more, it is difficult for the load to collapse, but there is an effect that it is easy to handle during bag opening. The adjustment of the angle of repose can be adjusted by the content and ratio of Na2O, K2O, SO3 and Al2O3.

[0019] The above γ-C2S-containing clinker can be suitably used as a cement admixture. When the γ-C2S-containing clinker is used as a cement admixture, it is preferably contained in the cement admixture at 20% by mass or more of the γ-C2S-containing clinker, more preferably 40% by mass or more.

[0020] In addition to the γ-C2S-containing clinker mentioned above, other admixtures can be used as cement admixtures. Other admixtures that can be used include known additives and admixtures commonly used in cement materials, such as blast furnace granulated slag powder, blast furnace slow-cooled slag powder, limestone powder, fly ash, and natural pozzolans such as silica fume and volcanic ash, as well as expansives, hardening agents, water-reducing agents, AE water-reducing agents, high-performance water-reducing agents, defoaming agents, thickeners, rust inhibitors, antifreezes, shrinkage-reducing agents, polymers, setting regulators, clay minerals such as bentonite, and anion exchangers such as hydrotalcite.

[0021] (Cement composition) The γ-C2S-containing clinker of the present invention can be used as a cement composition containing cement, other admixtures, and optionally aggregate. The cement used in the cement composition includes various types of Portland cement such as ordinary, rapid-hardening, ultra-rapid-hardening, low-heat, and moderate-heat cements, as well as various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica, with a Blaine specific surface area of ​​2000 cm². 2 Examples include filler cements mixed with limestone powder or blast furnace slow-cooled slag fine powder at a concentration of 1 / g or more, environmentally friendly cements (eco-cements) manufactured using municipal solid waste incineration ash or sewage sludge incineration ash as raw materials, and alumina cement used for refractory applications. One or more of these types can be used. The specific surface area of ​​the cement is 3000 cm². 2 A value of / g or more is preferable.

[0022] The content of γ-C2S-containing clinker in the cement composition of this embodiment is not particularly limited, but it is generally preferable that the amount of γ-C2S-containing clinker is 5% to 70% by mass, more preferably 10% to 50% by mass, and even more preferably 20% to 40% by mass, out of 100% by mass of the total of cement and γ-C2S-containing clinker.

[0023] (aggregate) The amount of aggregate used in the cement composition is preferably 80 to 1000 parts by mass per 100 parts by mass of cement. More preferably, it is 100 to 850 parts by mass, and even more preferably, 200 to 650 parts by mass. By using the above range for the amount of aggregate, the strength of the hardened cement can be increased to a certain level or higher. As for the aggregates used, fine aggregates such as river sand, mountain sand, sea sand, lime sand, and silica sand can be used, while coarse aggregates such as river gravel, mountain gravel, and lime gravel can be used.

[0024] (water) The cement composition is mixed with water, for example, in a pan-type concrete mixer. The amount of water used for mixing is not particularly limited, as it varies depending on the purpose, application, and content of each material. However, it is preferably 20 to 150 parts by mass per 100 parts by mass of cement, more preferably 30 to 100 parts by mass, and even more preferably 35 to 80 parts by mass. When the amount of water used for mixing is above the lower limit, fluidity is improved and workability is better. Also, when the amount of water used for mixing is below the upper limit, it becomes easier to ensure strength development.

[0025] [Method for producing clinker containing γ-2CaO·SiO2] The γ-C2S-containing clinker of the present invention can be produced, for example, by the following method. A method for producing γ-C2S-containing clinker comprises a raw material mixing step of mixing at least a CaO raw material, an SiO2 raw material, and waste containing at least one of Na2O and K2O and SO3 as chemical components to produce a raw material mixture, and a calcination step of calcining the raw material mixture at a calcination temperature of 1350 to 1600°C.

[0026] (Raw material mixing process) For the production of γ-C2S-containing clinker, calcium carbonate such as limestone and calcium hydroxide such as slaked lime can be used as CaO raw materials. Additionally, silica and clay can be used as SiO2 raw materials. Furthermore, examples of waste containing at least one of Na2O and K2O and SO3 as chemical components include by-product slaked lime such as acetylene by-product slaked lime, fine powder generated from waste concrete rubble, concrete sludge (dewatered cake) generated at ready-mixed concrete plants and concrete product plants, incineration ash (coal ash, woody biomass, municipal solid waste incineration ash, sewage sludge incineration ash, paper sludge, etc.), steel slag (converter slag, electric furnace slag, etc.), and various silicate dusts generated as industrial by-products such as silica fume and fly ash. Additionally, an Al2O3 raw material may be mixed in as needed. Bauxite or the like can be used as the Al2O3 raw material.

[0027] A raw material mixture is produced by mixing the above-mentioned CaO raw material, SiO2 raw material, and waste. For each raw material, the CaO raw material, SiO2 raw material, and waste are blended so that the SO3 / (Na2O+K2O) (molar ratio) of the γ-C2S-containing clinker is in the range of 1.2 to 10.0.

[0028] (Firing process) The firing process involves firing the raw material mixture obtained in the raw material mixing process at a firing temperature of 1350 to 1550°C. The firing process involves firing the raw material mixture in a rotary kiln or the like. The firing temperature is 1350 to 1600°C, with 1400 to 1550°C being preferred. By setting the firing temperature within this range, the desired properties can be obtained.

[0029] After the calcination process, the particle size of the γ-C2S-containing clinker produced may be appropriately adjusted by performing classification processes such as crushing, pulverization, and sieving as needed. For the pulverization process, for example, a pulverizer such as a roller mill, jet mill, tube mill, ball mill, or vibratory mill may be used.

[0030] According to the γ-C2S-containing clinker of the present invention, by adjusting the molar ratio of SO3 to alkali (total of Na2O and K2O) in the chemical composition, the fluidity of the cement composition containing the γ-C2S-containing clinker can be reduced, thereby improving workability. Furthermore, since the γ-C2S content in the γ-C2S-containing clinker can be increased, the amount of CO2 absorbed during curing can be increased. [Examples]

[0031] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0032] <Measurement Method and Evaluation Method> (Angle of repose) The angle of repose was measured using a powder tester (TP-X) manufactured by Hosokawa Micron Corporation. (flow) In accordance with JIS R 5201 "Physical Testing Methods for Cement 12. Flow Test," the flow of mortar mixed with γ-C2S-containing clinker was measured immediately after mixing.

[0033] (Method for producing γ-C2S-containing clinker) CaO and SiO2 raw materials were mixed to achieve the mineral composition shown in Table 1, and SO3, Na2O, K2O, and Al2O3 raw materials were mixed to achieve the chemical composition shown in Table 1. The mixture was then heat-treated in an electric furnace at 1450°C for 1 hour, slowly cooled to room temperature, and then milled using a ball mill to obtain a Blaine specific surface area of ​​3000 cm². 2 The material was ground to a concentration of / g to produce a clinker containing γ-C2S. The mineral composition of the manufactured γ-C2S-containing clinker was quantified by mineral composition analysis using powder XRD (SmartLab Studio II, Rigaku Corporation). Furthermore, the γ-C2S content of the sieved material, and the γ-C2S content of the sieved material, were measured using the manufactured γ-C2S-containing clinker before grinding. The angle of repose was also measured. The results are shown in Table 1.

[0034] (Preparation of cement composition) A cement composition was prepared by mixing 315 parts by mass of cement, 135 parts by mass of γ-C2S-containing clinker manufactured as a cement admixture, 1350 parts by mass of aggregate, and 225 parts by mass of water. The flow value was measured immediately after mixing. The results are shown in Table 1.

[0035] (Raw materials used) [γ-C2S-containing clinker] CaO raw material: Calcium carbonate (reagent) • SiO2 raw material: silicon dioxide (reagent) • SO3 raw material: Anhydrous calcium sulfate (reagent) • Na2O raw material: Sodium carbonate (reagent) • K2O raw material: Potassium carbonate (reagent) • Al2O3 raw material: Aluminum oxide (reagent) [Cement composition] • Cement: Research cement • Aggregate: ISO standard sand • Water: Tap water

[0036] [Table 1]

[0037] As shown in Table 1, by setting the molar ratio of SO3 to alkali within a predetermined range, the flow value can be made lower than that of the comparative example, confirming that the fluidity is suppressed. Furthermore, the mineral composition contains more γ-C2S than the comparative example, and it is thought that it can absorb more CO2 when used as a cement admixture.

[0038] (Experimental Example 2) The following raw materials were mixed in the proportions shown in Table 2. Subsequently, γ-C2S-containing clinker was produced using the same method as in Experimental Example 1. Using the manufactured γ-C2S-containing clinker, a cement composition was prepared in the same manner as in Example 1. Similar to Experimental Example 1, the mineral composition of the manufactured γ-C2S-containing clinker, the amount that passed through a sieve with a mesh size of 1.18 mm using the γ-C2S-containing clinker before grinding, the γ-C2S content of the sieved portion, and the angle of repose were measured. The flow value of the cement composition was also measured. The results are shown in Table 2.

[0039] (Raw materials used) ·CaO raw material: limestone (industrial raw material) ·SiO2 raw material: Silica stone (industrial raw material) • Waste: Concrete sludge

[0040] [Table 2]

[0041] As shown in Table 2, even when using waste materials, the angle of repose was similar to that of Experimental Example 1, in which impurities were adjusted with reagents. Furthermore, the flow value of the cement composition was also similar to that of the value adjusted with reagents. Based on the above, if the molar ratio of SO3 to alkali is within a predetermined range, the amount of γ-C2S can be increased even when using waste materials, and a good flow value can be obtained. [Industrial applicability]

[0042] The γ-2CaO·SiO2-containing clinker and the method for producing the γ-2CaO·SiO2-containing clinker of the present invention can contain γ-2CaO·SiO2 at a high concentration even when waste is used as a raw material, and has good fluidity, making it suitable for use as a concrete material in the civil engineering and construction fields.

Claims

1. As a chemical component, Na ２ O and K ２ At least one of O and SO ３ It contains and SO ３ / (Na ２ O+K ２ γ-2CaO·SiO₂ (molar ratio) is between 1.2 and 10.

0. ２ Contains clinker.

2. As a chemical component, Al ２ O ３ is contained in an amount of 1% by mass or more and 20% by mass or less, and the γ-2CaO·SiO ２ -containing clinker according to claim 1.

3. 1. The amount passing through the 1.18 mm sieve is 50% by mass or more, and the amount passing through the 1.18 mm sieve is γ-2CaO・SiO ２ The γ-2CaO・SiO2 according to claim 1 or 2, wherein the content is 40% by mass or more. ２ Contains clinker.

4. The γ-2CaO・SiO₂ according to claim 1 or 2, wherein the angle of repose is 40 degrees or more. ２ Contains clinker.

5. γ-2CaO・SiO2 according to claim 1 or 2 ２ A cement admixture containing clinker.

6. A cement composition comprising the cement admixture described in claim 5.

7. At least CaO raw material, SiO ２ Na as a raw material and chemical component. ２ O and K ２ At least one of O and SO ３ A raw material mixing process involves mixing waste containing and to produce a raw material mixture, The γ-2CaO・SiO₂ according to claim 1 or 2, comprising a firing step of firing the raw material mixture at a firing temperature of 1350 to 1600°C. ２ A method for producing clinker containing clinker.

8. The aforementioned waste has Al as a chemical component. ２ O ３ The γ-2CaO・SiO2 contained in claim 7 ２ A method for producing clinker containing clinker.

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