Cement clinker and method for estimating strength development of cement clinker

Abstract

To provide a cement clinker that can contain a large amount of water-soluble lithium while having excellent strength development properties.SOLUTION: The cement clinker contains the water-soluble lithium and water-soluble sulfur trioxide. A content of the water-soluble lithium is set to be 2 mg / kg or more and 300 mg / kg or less with respect to the cement clinker. An amount of the water-soluble sulfur trioxide is set to be 0.03 mass% or more and 0.15 mass% or less with respect to the cement clinker. A total amount of sulfur trioxide in the cement clinker is set to be 1.1 mass% or more and 1.6 mass% or less. A ratio of the amount of the water-soluble sulfur trioxide (mass%) to the total amount of sulfur trioxide (mass%) is set to be 0.020 or more and 0.120 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement clinker and a method for estimating the strength development of a cement clinker. [Background technology]

[0002] In order to achieve carbon neutrality in Japan, the number of gasoline-powered vehicles in use is expected to decrease and the number of hybrid and electric vehicles in use is expected to increase. This is expected to result in an increase in the amount of discarded lithium-ion batteries used as power sources for hybrid and electric vehicles.

[0003] Incidentally, cement manufacturing plants sometimes use waste materials received from local governments and other sources as raw materials for producing cement clinker. Furthermore, as the amount of used lithium-ion batteries processed (i.e., the amount of recycled batteries handled) increases, the amount of processing residue is expected to increase. Therefore, the amount of lithium derived from lithium-ion batteries and the proportion of water-soluble lithium in the raw materials for producing cement clinker may increase. This may also increase the amount of lithium and the content of water-soluble lithium in the produced cement clinker.

[0004] To date, various studies have been conducted on the relationship between the lithium content in cement clinker and the strength development when this cement clinker is used in a cement composition. It is generally believed that an excessively high amount of lithium in the clinker may inhibit strength development. For example, Patent Document 1 below describes that when the lithium content in cement clinker is 10 to 100 ppm, if the nickel content in this cement clinker is 20 to 200 ppm and the ratio of the nickel content to the lithium content is 1 or more, the strength development when the cement clinker is used in a cement composition is increased. However, there has not yet been sufficient research conducted on the relationship between the water-soluble lithium content in cement clinker and the strength development when this cement clinker is used in a cement composition. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-160168 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present inventors have conducted research into this relationship and have found that even if the content of water-soluble lithium in cement clinker exceeds 100 ppm, as long as the amount of water-soluble sulfur trioxide in the cement clinker is within a predetermined range, the strength development of a cement composition made from the cement clinker can be improved.

[0007] The present invention was made based on this finding, and has an object to provide a cement clinker that can contain a large amount of water-soluble lithium while having high strength development. Another object of the present invention is to provide a method for estimating the strength development of cement clinker containing water-soluble lithium. [Means for solving the problem]

[0008] The cement clinker according to the present invention contains water-soluble lithium and water-soluble sulfur trioxide. The content of the water-soluble lithium relative to the cement clinker is set to 2 mg / kg or more and 300 mg / kg or less, and the amount of the water-soluble sulfur trioxide relative to the cement clinker is set to 0.03 mass% or more and 0.15 mass% or less. Note that [mg / kg] is considered to be equivalent to [ppm].

[0009] The total amount of sulfur trioxide in the cement clinker is, for example, 1.1 mass % or more and 1.6 mass % or less, and the ratio of the amount of water-soluble sulfur trioxide (mass %) to the total amount of sulfur trioxide (mass %) is, for example, 0.020 or more and 0.120 or less.

[0010] A method for estimating strength development of cement clinker according to the present invention estimates the strength development of cement clinker containing water-soluble lithium and water-soluble sulfur trioxide. Specifically, the method includes the steps of: acquiring the content of the water-soluble lithium relative to the cement clinker; acquiring the amount of water-soluble sulfur trioxide relative to the cement clinker; determining whether the content of the water-soluble lithium is within a first range of 2 mg / kg to 300 mg / kg; determining whether the amount of water-soluble sulfur trioxide is within a second range of 0.03 mass% to 0.15 mass%; and estimating that the strength development of the cement clinker is high if the content of the water-soluble lithium is within the first range and the amount of water-soluble sulfur trioxide is within the second range; and estimating that the strength development of the cement clinker is low if the content of the water-soluble lithium is not within the first range or the amount of water-soluble sulfur trioxide is not within the second range. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a cement clinker that can contain a large amount of water-soluble lithium while having high strength development. This makes it possible to promote the reuse of lithium-ion battery waste as a raw material for producing cement clinker. Furthermore, according to the present invention, it is possible to provide a method for estimating the strength development of cement clinker containing water-soluble lithium. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram for explaining the procedure of a method for estimating strength development of cement clinker according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] First, the composition of the cement clinker according to one embodiment of the present invention will be described. This cement clinker contains water-soluble lithium and water-soluble sulfur trioxide. The content (mg) of water-soluble lithium in this cement clinker relative to the mass (kg) of this cement clinker is set to be 2 mg / kg or more and 300 mg / kg or less. The amount of water-soluble sulfur trioxide in this cement clinker relative to the mass of this cement clinker is set to be 0.03 mass% or more and 0.15 mass% or less.

[0014] Other chemical compositions of this cement clinker are, for example, as follows: Silicon dioxide amount: 21.60 mass% or more and 22.00 mass% or less Aluminum oxide content: 5.30% by mass or more and 5.60% by mass or less Ferric oxide amount: 3.00 mass% or more and 3.30 mass% or less Calcium oxide content: 65.00% by mass or more and 66.50% by mass or less Magnesium oxide content: 1.00% by mass or more and 1.25% by mass or less Total sulfur trioxide amount: 1.10 mass% or more and 1.60 mass% or less Sodium oxide content: 0.20% by mass or more and 0.35% by mass or less Potassium oxide content: 0.40% by mass or more and 0.60% by mass or less Titanium dioxide content: 0.20% by mass or more and 0.35% by mass or less Amount of diphosphorus pentoxide: 0.05% by mass or more and 0.10% by mass or less Manganese oxide content: 0.03% by mass or more and 0.07% by mass or less Ratio of water-soluble sulfur trioxide (mass%) to total sulfur trioxide (mass%): 0.020 or more and 0.120 or less

[0015] The mineral composition of this cement clinker is, for example, as follows: In this specification, the mineral composition of cement clinker refers to the one calculated from the chemical composition of the cement clinker using the Bogue formula. Alite amount: 55.0 mass% or more and 60.0 mass% or less Belite amount: 18.5% by mass or more and 21.0% by mass or less Aluminate phase amount: 8.5% by mass or more and 9.7% by mass or less Ferrite phase content: 9.0 mass% or more and 10.0 mass% or less

[0016] Next, tests for explaining the strength development of the cement clinker of this embodiment will be described based on the following Test Examples 1 to 6. The purpose of these tests is to clarify the relationship between the water-soluble lithium content and the water-soluble sulfur trioxide content in the cement clinker and the strength development of this cement clinker.

[0017] In this specification, the strength development of cement clinker refers to the strength development of cement clinker when gypsum is added to the cement clinker and the strength development of cement clinker is improved by adding gypsum to the cement clinker and improving the strength development of cement clinker when the Blaine specific surface area is 2500 cm 2 The compressive strength of a hardened cement product obtained by preparing a cement composition by finely pulverizing the mixture to a density of 1 / g or more, adding aggregate and water to the cement composition, and kneading the mixture is, for example, the compressive strength of a mortar measured in accordance with JIS R 5201 "Physical Testing Methods for Cement." Examples of hardened cement products include mortar or concrete that is 5 days or older (more specifically, 7 days or older and 28 days or younger).

[0018] The test procedures for Test Examples 1 to 6 were as follows. First, in Test Examples 1 to 6, a raw material refined flour containing calcium carbonate as a main component was mixed with a calcium carbonate reagent, a silicon dioxide reagent, an aluminum oxide reagent, a ferric oxide reagent, and anhydrous gypsum reagent, and in Test Examples 2 to 6, a lithium nitrate reagent was further added to prepare a raw material for producing cement clinker. Note that this raw material refined flour contains a trace amount of lithium. In the following description, the raw material for producing cement clinker in Test Examples 1 to 6 will be simply referred to as the "clinker raw material." Table 1 below shows the amount of lithium (mass%) in the clinker raw material and the amount of sulfur trioxide (mass%) in the clinker raw material for each of Test Examples 1 to 6.

[0019] [Table 1]

[0020] Specifically, the "lithium content (mass%)" in Table 1 refers to the percentage of the mass of lithium in the clinker raw materials relative to the mass of the cement clinker. The "sulfur trioxide content (mass%)" in Table 1 refers to the percentage of the mass of all sulfur trioxide in the clinker raw materials relative to the mass of the cement clinker. However, these masses of cement clinker are not the measured masses of cement clinker actually produced, but the calculated masses of cement clinker obtained when all calcium carbonate contained in the clinker raw materials is decarbonated. Furthermore, the mass of lithium here refers to the calculated mass of lithium oxide obtained when all lithium nitrate contained in the clinker raw materials is oxidized.

[0021] Table 2 below shows the target modulus values ​​common to the cement clinkers produced in Test Examples 1 to 6.

[0022] [Table 2]

[0023] Next, in each of Test Examples 1 to 6, the produced clinker raw material was pre-fired in an electric furnace at 1000°C for 90 minutes and then fired at 1450°C for 60 minutes. Subsequently, in each of Test Examples 1 to 6, the fired product removed from the electric furnace was air-cooled to obtain cement clinker. Furthermore, in each of Test Examples 1 to 6, a portion of the obtained cement clinker was sampled, and the main chemical composition of the sampled cement clinker was measured. Table 3 below shows the main chemical composition (mass%) of the sampled cement clinker for each of Test Examples 1 to 6.

[0024] [Table 3]

[0025] Furthermore, in each of Test Examples 1 to 6, a portion of the obtained cement clinker was sampled, and a sample solution was prepared from the sampled cement clinker in accordance with "4.2 Sample Solution Preparation Method" of "JCAS I-04:2004 Method for Analyzing Water-Soluble Components in Cement." Furthermore, using this sample solution, the water-soluble lithium content (mg / kg-Cli) in the cement clinker was measured by ICP-MS, and the amount of water-soluble sulfur trioxide (mass%) in the cement clinker was measured by ion chromatography. Table 4 below shows, for each of Test Examples 1 to 6, the water-soluble lithium content (mg / kg) in the cement clinker relative to the mass (kg) of the cement clinker, and the amount of water-soluble sulfur trioxide (mass%) in the cement clinker relative to the mass of the cement clinker.

[0026] [Table 4]

[0027] In each of Test Examples 1 to 6, the ratio of the amount of water-soluble sulfur trioxide (mass%) in the cement clinker to the total amount of sulfur trioxide (mass%) in the cement clinker was calculated. This ratio is the ratio of the "amount of water-soluble sulfur trioxide (mass%)" shown in Table 4 to the "SO3" value shown in Table 3. Table 5 below shows this ratio for each of Test Examples 1 to 6.

[0028] [Table 5]

[0029] In each of Test Examples 1 to 6, the mineral composition of the cement clinker was calculated by the Bogue formula based on the chemical composition shown in Table 3. Table 6 below shows the mineral composition (mass%) of the cement clinker for each of Test Examples 1 to 6.

[0030] [Table 6]

[0031] Furthermore, in each of Test Examples 1 to 6, the obtained cement clinker was mixed with pure gypsum dihydrate and the resulting mixture was pulverized to produce a test cement. The mixing was carried out so that the total amount of sulfur trioxide in the cement was 2.60 mass%.

[0032] In each of Test Examples 1 to 6, a portion of the test cement was sampled, and the specific surface area of ​​the sampled cement was measured using the specific surface area test specified in "JIS R 5201:2015." Table 7 below shows the specific surface area (cm) of the cement for each of Test Examples 1 to 6. 2 / g).

[0033] [Table 7]

[0034] In each of Test Examples 1 to 6, the test cement was used to prepare mortar in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement," and the compressive strength of the mortar was measured at ages of 3 days, 7 days, and 28 days. Table 8 below shows the compressive strength (N / mm) of the mortar for each of Test Examples 1 to 6. 2 ) is shown.

[0035] [Table 8]

[0036] As shown in Table 8, in Test Examples 1 to 4, the compressive strength of the mortar at 7 days old is higher, and the compressive strength of the mortar at 28 days old is higher, compared to Test Examples 5 and 6. In other words, if the content of water-soluble lithium in the cement clinker is in the range of 2 mg / kg or more and 300 mg / kg or less (the range of Test Examples 1 to 4), and the amount of water-soluble sulfur trioxide in this cement clinker is in the range of 0.03 mass % or more and 0.15 mass % or less (the range of Test Examples 1 to 4), the strength development of this cement clinker is high.

[0037] This principle can be explained as follows: If the content of water-soluble lithium in cement clinker is 2 mg / kg or more and the amount of water-soluble sulfur trioxide in this cement clinker is 0.03 mass% or more, when mixing cement containing this cement clinker, water-soluble lithium continues to gradually dissolve from the cement clinker into the liquid phase. This maintains the pH of the liquid phase in a highly alkaline range. This promotes the dissolution of water-soluble sulfur trioxide from the cement clinker into the liquid phase, and further promotes the hydration reaction between the water-soluble sulfur trioxide dissolved in the liquid phase and calcium ions in the liquid phase. As a result, hydrates such as ettringite and monosulfate are continuously produced in the liquid phase, increasing the compressive strength of mortar or concrete.

[0038] Furthermore, if the content of water-soluble lithium in the cement clinker is 300 mg / kg or less and the amount of water-soluble sulfur trioxide in the cement clinker is 0.15 mass% or less, the formation of an excessive amount of ettringite can be suppressed, thereby preventing a decrease in the compressive strength of mortar or concrete due to the expansion of ettringite.

[0039] Furthermore, in Test Example 4, as shown in Table 4, the content of water-soluble lithium in the cement clinker was 180 mg / kg, and the amount of water-soluble sulfur trioxide in the cement clinker was 0.14 mass%, and as shown in Table 8, the compressive strength of the mortar at 28 days was 60 N / mm 2 Therefore, even if a large amount of lithium ion battery waste is reused as part of the raw materials for manufacturing cement clinker, the strength development of this cement clinker can be increased by setting the content of water-soluble lithium in this cement clinker to about 180 mg / kg and the amount of water-soluble sulfur trioxide in this cement clinker to about 0.14 mass %.

[0040] To improve the strength development of the cement clinker, it is preferable that other components of the cement clinker also fall within the ranges of Test Examples 1 to 4. For example, the total amount of sulfur trioxide in the cement clinker is preferably 1.1 mass% or more and 1.6 mass% or less, as shown in "SO3" in Table 3. The amount of water-soluble sulfur trioxide (mass%) in the cement clinker relative to the total amount of sulfur trioxide (mass%) in the cement clinker is preferably 0.020 or more and 0.120 or less, as shown in Table 5.

[0041] Next, a method for estimating the strength development of cement clinker according to one embodiment of the present invention will be described. This method is for estimating the strength development of cement clinker containing water-soluble lithium and water-soluble sulfur trioxide.

[0042] As shown in Fig. 1, this estimation method includes a first acquisition step S1a, a first determination step S1b, a second acquisition step S2a, a second determination step S2b, and an estimation step S3. In the following description, the cement clinker for which strength development is estimated by the method of this embodiment is referred to as a "target clinker." An example of the target clinker is cement clinker produced using lithium-ion battery waste as part of the raw materials.

[0043] In the first acquisition step S1a, the content of water-soluble lithium in the target clinker relative to the mass of the target clinker is acquired. For example, an acquisition method includes performing ICP-MS using a sample solution in which a part of the target clinker is immersed.

[0044] In the first determination step S1b, it is determined whether the content of water-soluble lithium is within a first range of 2 mg / kg or more and 300 mg / kg or less. This determination can be made, for example, by an operator or a computer.

[0045] In the second acquisition step S2a, the amount of water-soluble sulfur trioxide in the target clinker relative to the mass of the target clinker is acquired. For example, an acquisition method may be performed by ion chromatography using a sample solution in which a part of the target clinker is immersed.

[0046] In the second determination step S2b, it is determined whether the amount of water-soluble sulfur trioxide is within a second range of 0.03% by mass or more and 0.15% by mass or less. This determination can be made, for example, by an operator or a computer.

[0047] In the estimation step S3, the strength development of the target clinker is estimated. Specifically, in the estimation step S3, if it is determined in the first determination step S1b that the water-soluble lithium content is within a first range and in the second determination step S2b that the water-soluble sulfur trioxide content is within a second range, it is estimated that the strength development of the target clinker is high. In addition, in the estimation step S3, if it is determined in the first determination step S1b that the water-soluble lithium content is not within the first range or if it is determined in the second determination step S2b that the water-soluble sulfur trioxide content is not within the second range, it is estimated that the strength development of the target clinker is low.

[0048] Next, an example of a method for operating a cement manufacturing plant using the method of this embodiment will be described. As a premise, the cement manufacturing plant receives lithium ion battery waste (for example, used lithium ion batteries themselves or residues generated by various treatments of used lithium ion batteries) from a local government or a treatment facility, and produces cement clinker using this waste as part of the raw materials for producing cement clinker.

[0049] First, in a cement manufacturing plant, the strength development of the produced cement clinker is periodically estimated using the method of this embodiment. If the strength development of the cement clinker is estimated to be high using the method of this embodiment, the amount of lithium-ion battery waste accepted from local governments, treatment facilities, etc. (e.g., approximately several tons per year) is maintained. If the strength development of the cement clinker is estimated to be low using the method of this embodiment, the amount of lithium-ion battery waste accepted from local governments, treatment facilities, etc. is limited.

[0050] This operating method can promote the reuse of lithium ion battery waste as a cement raw material while maintaining high strength development in the produced cement clinker.

Claims

1. A cement clinker containing water-soluble lithium and water-soluble sulfur trioxide, The content of the water-soluble lithium relative to the cement clinker is 2 mg / kg or more and 300 mg / kg or less, A cement clinker characterized in that the amount of water-soluble sulfur trioxide relative to the cement clinker is 0.03 mass% or more and 0.15 mass% or less.

2. The total amount of sulfur trioxide in the cement clinker is 1.1% by mass or more and 1.6% by mass or less, 2. The cement clinker according to claim 1, wherein the ratio of the amount of water-soluble sulfur trioxide (mass%) to the total amount of sulfur trioxide (mass%) is 0.020 or more and 0.120 or less.

3. A method for estimating the strength development of cement clinker containing water-soluble lithium and water-soluble sulfur trioxide, comprising: Obtaining the content of the water-soluble lithium relative to the cement clinker; Obtaining the amount of water-soluble sulfur trioxide relative to the cement clinker; determining whether the content of the water-soluble lithium is within a first range of 2 mg / kg or more and 300 mg / kg or less; determining whether the amount of water-soluble sulfur trioxide is within a second range of 0.03% by mass or more and 0.15% by mass or less; and estimating that the strength development of the cement clinker is high when the content of the water-soluble lithium is within the first range and the amount of the water-soluble sulfur trioxide is within the second range, and estimating that the strength development of the cement clinker is low when the content of the water-soluble lithium is not within the first range or the amount of the water-soluble sulfur trioxide is not within the second range.

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