Cement composition and method for manufacturing the cement composition

Abstract

To provide a cement composition which is a cement composition comprising a mixture containing cement clinker powder, gypsum powder, limestone powder and fly ash, and is enhanced in strength developability by gypsum powder and fly ash.SOLUTION: A cement composition comprises a mixture M containing cement clinker powder, gypsum powder, limestone powder L and fly ash A. The limestone powder L and the fly ash A are contained in a ratio of 10.0 mass% or less in total in the mixture M. The gypsum powder is contained in a ratio of 0.6 mass% or more and 2.4 mass% or less in terms of SO3 in the mixture M. It is preferable that the SO3 content of the cement clinker powder is 0.80 mass% or more, and the gypsum powder is contained in a ratio of 1.0 mass% or more in terms of SO3 in the mixture M.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cement composition comprising a mixture containing cement clinker powder, gypsum powder, limestone powder and fly ash, and a method for producing this cement composition.

Background Art

[0002] A cement composition generally consists of a mixture containing "cement clinker powder, gypsum powder and admixture powder". Patent Document 1 (Example 14) below discloses a cement composition using limestone powder and fly ash as this admixture powder.

[0003] By the way, in recent years, in order to reduce the amount of carbon dioxide emissions from the cement firing apparatus, the production amount of cement clinker in the cement firing apparatus is reduced, and the content of cement clinker powder in the cement composition is reduced to increase the content of gypsum powder or fly ash. However, when the content of gypsum powder or fly ash in the cement composition increases in this way, the strength development property of the cement composition may not be sufficiently high depending on the composition of the cement composition.

[0004] Therefore, in order to sufficiently increase the strength development property of the cement composition, it is conceivable to adjust the quality of the cement clinker (for example, the composition of each of a plurality of minerals in the cement clinker) in the cement firing process. However, when such adjustment is performed, it is necessary to input more fuel into the cement kiln, so even if the production amount of cement clinker in the cement firing apparatus is reduced, there is a risk that the amount of carbon dioxide emissions from the cement firing apparatus will increase.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] Therefore, the present invention aims to provide a cement composition comprising a mixture of cement clinker powder, gypsum powder, limestone powder, and fly ash, wherein the strength development is enhanced by the gypsum powder and fly ash. [Means for solving the problem]

[0007] The first item of the present invention relates to the following cement composition. This cement composition consists of a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash. The limestone powder and fly ash are included in the mixture in a total proportion of 10.0% by mass or less. The gypsum powder is included in the mixture in a proportion of 0.6% by mass or more and 2.4% by mass or less in terms of SO3.

[0008] According to the first item above, limestone powder and fly ash are included in the mixture in a total proportion of 10.0% by mass or less, and gypsum powder is included in the mixture in a proportion of 2.4% by mass or less in terms of SO3. Therefore, the mixture contains small amounts of gypsum powder and mixed material powder (limestone powder and fly ash). Furthermore, gypsum powder is included in the mixture in a proportion of 0.6% by mass or more in terms of SO3. For this reason, when this mixture is kneaded with water, the SO3 contained in the gypsum powder effectively promotes the hydration reaction of the fly ash, and a high-strength cement mixture can be produced. In other words, the cement composition according to the first item above has enhanced strength development due to the gypsum powder and fly ash contained in the mixture.

[0009] The second item of the present invention is that the first item above includes the following: The SO3 content of the cement clinker powder is 0.80% by mass or more (preferably 0.94% by mass or more). The gypsum powder is included in the mixture in a proportion of 1.0% by mass or more in terms of SO3.

[0010] According to the second point above, when the mixture is mixed with water, the rapid hydration (instantaneous setting) of the aluminate in the cement clinker powder is suppressed by the large amount of SO3 contained in the gypsum powder, causing the aluminate in the cement clinker powder to react with the limestone powder. As a result, a large amount of SO3 is leached from the cement clinker powder, and the hydration of the fly ash is promoted by the large amount of SO3 released from the cement clinker powder, producing a high-strength cement mixture. In other words, the cement composition according to the second point above has its strength development further enhanced by the gypsum powder and fly ash contained in the mixture.

[0011] Furthermore, item two does not specify the compositional range of each of the multiple minerals in the cement clinker powder, but rather specifies the content of a single chemical component (SO3) in the cement clinker powder. The cement clinker powder specified in item two (with an SO3 content of 0.80% by mass or more) can be easily manufactured by using waste with a high SO3 content as a cement raw material in a cement firing apparatus, and can be manufactured without adjusting the quality of the cement clinker by introducing a large amount of fuel into the cement kiln. Therefore, item two does not emit a large amount of carbon dioxide in the manufacturing process of the cement clinker powder.

[0012] The third item of the present invention includes the following in the second item described above: that is, the mixture of the third item does not contain cement clinker powder having an SO3 content of 0.56% by mass or less.

[0013] According to the third item above, since the mixture does not contain cement clinker powder with an SO3 content of 0.56% by mass or less, the proportion (content in the mixture) of cement clinker powder with an SO3 content of 0.80% by mass or more is relatively high. Here, cement clinker powder with an SO3 content of 0.56% by mass or less cannot dissolve enough SO3 to promote the hydration of fly ash even when mixed with water. Therefore, the cement composition according to the third item above has a high proportion of "cement clinker powder that promotes the hydration of fly ash" relative to the total amount of cement clinker powder, and the strength development of the mixture is further enhanced by the gypsum powder and fly ash contained in the mixture.

[0014] The fourth item of the present invention includes the following in any one of the first to third items described above. That is, when SO3 contained in the cement clinker powder is defined as clinker SO3, SO3 contained in the gypsum powder is defined as gypsum SO3, the ratio of clinker SO3 to the mixture is defined as S1 mass%, and the ratio of gypsum SO3 to the mixture is defined as S2 mass%, the sum of S1 mass% and S2 mass% is 1.90 mass% or more (preferably 2.05 mass% or more), and the ratio of S2 mass% to S1 mass% is 0.90 or more and 3.00 or less (preferably 0.998 or more and 2.837 or less).

[0015] According to the fourth item above, the mixture contains a balanced amount of clinker SO3 and gypsum SO3. Therefore, when this mixture is mixed with water, gypsum SO3 dissolves from the gypsum powder in the initial mixing stage, and clinker SO3 dissolves from the cement clinker powder after the initial mixing stage has passed. As a result, SO3 dissolves continuously from the gypsum powder and cement clinker powder without interruption during the mixing stage, and this SO3 continuously promotes the hydration of the fly ash without interruption. In other words, the cement composition according to the fourth item above has its strength development further enhanced by the gypsum powder and fly ash contained in the mixture.

[0016] The fifth item of the present invention includes the following in any one of the first to fourth items above: When the TiO2 content, MnO content, P2O5 content, Na2O content, and K2O content of the cement clinker powder are defined as T mass%, M mass%, P mass%, N mass%, and K mass%, respectively, the physical property value of the cement clinker powder "(T+M+P) / (N+0.658×K)" is 0.80 or more and 1.40 or less.

[0017] According to the fifth item above, when cement clinker powder is hydrated, promoting elements (Na2O and K2O) that promote the elution of SO3 contained in the cement clinker powder to the outside of the cement clinker powder and inhibiting elements (TiO2, MnO and P2O5) that inhibit this elution are evenly distributed in the cement clinker powder. Therefore, when the cement composition is mixed with water (when the cement clinker powder contained in this cement composition is hydrated), a large amount of SO3 is eluted from the cement clinker powder by the promoting elements, and the rate of elution of SO3 from the cement clinker powder is prevented from becoming excessively fast by the inhibiting elements. As a result, a large amount of SO3 contained in the cement clinker powder is gradually eluted from the cement clinker powder over a long period of time. In other words, when the cement composition is mixed with water, a large amount of SO3 eluted from the cement clinker powder can be gradually reacted with limestone powder and fly ash, making it possible to produce a cement mixture that exhibits high strength and high fluidity over a long period of time.

[0018] The sixth item of the present invention relates to a method for producing a cement composition as follows. This method comprises a finishing step and a mixing step. In the finishing step, cement clinker is crushed together with gypsum to produce a mixed powder. In the mixing step, the mixed powder, limestone powder, and fly ash are mixed to produce a cement composition. The limestone powder and fly ash are included in the cement composition in a total proportion of 10.0% by mass or less. The gypsum powder is included in the cement composition in a proportion of 0.6% by mass or more and 2.4% by mass or less in terms of SO3.

[0019] According to item six above, limestone powder and fly ash are included in the cement composition in a total proportion of 10.0% by mass or less, and gypsum powder is included in the cement composition in a proportion of 2.4% by mass or less in terms of SO3. Therefore, the cement composition contains small amounts of gypsum powder and mixed powder (limestone powder and fly ash). Furthermore, gypsum powder is included in the cement composition in a proportion of 0.6% by mass or more in terms of SO3. For this reason, when this cement composition is mixed with water, the SO3 contained in the gypsum powder effectively promotes the hydration reaction of the fly ash, and a high-strength cement mixture can be produced. In other words, according to item six above, a cement composition with enhanced strength development can be produced by gypsum powder and fly ash.

[0020] The seventh item of the present invention further comprises a firing step in the sixth item described above. In this firing step, the cement clinker is produced using waste gypsum board as a cement raw material.

[0021] According to item seven above, the SO3 contained in waste gypsum board can be used to enhance the strength development of the cement composition, and waste gypsum board can be effectively utilized as a raw material for the cement composition. [Effects of the Invention]

[0022] As described above, according to the present invention, there can be provided a cement composition comprising a mixture containing cement clinker powder, gypsum powder, limestone powder and fly ash, and having enhanced strength development due to the gypsum powder and fly ash.

Brief Description of the Drawings

[0023] [Figure 1] FIG. 8 is an overall configuration diagram showing a cement manufacturing apparatus for manufacturing a cement composition according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0024] FIG. 1 is an overall configuration diagram showing a cement manufacturing apparatus 1 for manufacturing a cement composition according to an embodiment of the present invention. As shown in FIG. 1, the cement manufacturing apparatus 1 includes a clinker silo 2, a finishing mill 3, a classification device 4, a mixing device 5, and a cement silo 6. The clinker silo 2 stores clinker (not shown) discharged from a cement firing apparatus (not shown). The finishing mill 3 pulverizes the clinker C discharged from the clinker silo 2 together with gypsum G to produce a pulverized product D (mixed powder). The classification device 4 classifies the pulverized product D discharged from the finishing mill 3 and separates it into coarse powder R and fine powder F. The mixing device 5 mixes the fine powder F discharged from the classification device 4 together with limestone powder L and fly ash A to produce a mixture M (cement composition). The cement silo 6 stores the mixture M discharged from the mixing device 5. Further, the classification device 4 returns the coarse powder R to the finishing mill 3. When the coarse powder R is returned from the classification device 4, the finishing mill 3 pulverizes the clinker C together with the gypsum G and the coarse powder R to produce a pulverized product D.

[0025] A cement composition according to one embodiment of the present invention comprises a mixture M containing clinker C powder, gypsum G powder, limestone powder L, and fly ash A. The limestone powder L and fly ash A are included in mixture M in a total proportion of 10.0% by mass or less. The gypsum G powder is included in mixture M in a proportion of 0.6% by mass or more and 2.4% by mass or less in terms of SO3. Preferably, the SO3 content of the clinker C powder is 0.80% by mass or more (preferably 0.94% by mass or more), and the gypsum G powder is included in mixture M in a proportion of 1.0% by mass or more in terms of SO3. More preferably, the mixture M does not contain cement clinker powder with an SO3 content of 0.56% by mass or less.

[0026] When the SO3 contained in the powder of clinker C is defined as clinker SO3, the SO3 contained in the powder of gypsum G is defined as gypsum SO3, the ratio of clinker SO3 to mixture M is defined as S1 by mass, and the ratio of gypsum SO3 to mixture M is defined as S2 by mass, in the cement composition according to one embodiment of the present invention, it is preferable that the total value of S1 by mass and S2 by mass is 1.90 by mass or more (preferably 2.05 by mass or more), and the ratio (percentage) of S2 by mass to S1 by mass is 0.90 or more and 3.00 or less (preferably 0.998 or more and 2.837 or less).

[0027] Preferably, when the TiO2 content, MnO content, P2O5 content, Na2O content, and K2O content of the clinker C powder (contained in the pulverized material D) are defined as T mass%, M mass%, P mass%, N mass%, and K mass%, respectively, the physical property value of the clinker C powder "(T+M+P) / (N+0.658×K)" is 0.80 or more and 1.40 or less.

[0028] As described above, the method for producing a cement composition according to one embodiment of the present invention comprises a finishing step (a grinding step using the finishing mill 3 shown in Figure 1) and a mixing step (a mixing step using the mixing apparatus 5 shown in Figure 1). In the finishing step, cement clinker (clinker C shown in Figure 1) is ground together with gypsum (gypsum G shown in Figure 1) to produce a mixed powder (a mixed powder of clinker C and gypsum G shown in Figure 1, which is contained in the ground material D). In the mixing step, the mixed powder (a mixed powder of clinker C and gypsum G shown in Figure 1, which is contained in the fine powder F), limestone powder (limestone powder L shown in Figure 1), and fly ash (fly ash A shown in Figure 1) are mixed to produce a cement composition (mixture M shown in Figure 1). Note that the method for producing a cement composition according to the present invention is not limited to the method using the cement manufacturing apparatus 1 shown in Figure 1.

[0029] Furthermore, the method for producing a cement composition according to one embodiment of the present invention may further include a firing step (a step in which clinker C shown in Figure 1 is produced in the preceding stage of the manufacturing apparatus 1 shown in Figure 1). In this case, in this firing step, cement clinker (clinker C shown in Figure 1) is produced using waste gypsum board (not shown) as a cement raw material.

[0030] Next, experimental examples of cement compositions according to the present invention will be described. In these experimental examples, various cement compositions were produced by mixing cement clinker powder (Cli1 to Cli6), gypsum powder, and mixed material powder (limestone powder, fly ash, and blast furnace slag powder) in various proportions, and the "compressive strength at 28 days" of the cement mixtures produced from each of these cement compositions was measured. Tables 1 to 4 show the composition or physical properties of the raw materials used in the cement compositions in these experimental examples, for each raw material. Tables 5 to 11 show the relationship between the composition and strength development of the cement compositions produced in these experimental examples, for each experimental example. Table 12 shows the physical properties of the cement compositions produced in these experimental examples, for each experimental example.

[0031] In Tables 1 to 12, "clinker" refers to cement clinker powder, "gypsum" refers to gypsum powder, "mixture" refers to mixture powder, "limestone" refers to limestone powder, and "blast furnace slag" refers to blast furnace slag powder.

[0032] Table 1 shows the content (mass %) of each compound in the cement clinker powder used in the above experimental example (corresponding to the clinker C powder shown in Figure 1). In Table 1, ig.loss (Ignition Loss) refers to the ignition raw material (volatile substance). Na2Oeq refers to the total alkali. The total alkali is the value calculated by the formula "Na2O + 0.658 × K2O". f.CaO refers to free calcium oxide. Free calcium oxide refers to the calcium oxide that remains after firing cement raw materials without reacting with silicon dioxide or aluminum oxide.

[0033] [Table 1]

[0034] Table 2 shows the modulus of the cement clinker powder used in the above experimental example. In Table 2, HM (Hydraulic Modulus) represents the hydraulic modulus, SM (Silica Modulus) represents the silica modulus, IM (Iron Modulus) represents the iron modulus, and AI (Activity Index) represents the activity index. HM is the ratio of CaO to (SiO2 + Al2O3 + Fe2O3). SM is the ratio of SiO2 to (Al2O3 + Fe2O3). IM is the ratio of Al2O3 to Fe2O3. AI is the ratio of SiO2 to Al2O3. As shown in Table 2, the modulus of the cement clinker powder used in the above experimental example is as follows: HM is between 2.15 and 2.21, SM is between 2.18 and 2.42, IM is between 1.87 and 2.18, and AI is between 3.19 and 3.70.

[0035] Table 2 also shows the mineral composition of the cement clinker powder used in the above experimental example. The mineral composition shown in Table 2 was calculated using the Bogue formula. In Table 2, C3S is tricalcium silicate (3CaO·SiO2), C2S is dicalcium silicate (2CaO·SiO2), C3A is tricalcium aluminate (3CaO·Al2O3), and C4AF is tetracalcium iron aluminate (4CaO·Al2O3·Fe2O3). As shown in Table 2, the mineral composition of the cement clinker powder used in the above experimental example is as follows: C3S is 55.2% by mass or more and 62.0% by mass or less, C2S is 12.7% by mass or more and 18.6% by mass or less, C3A is 10.1% by mass or more and 12.2% by mass or less, and C4AF is 9.1% by mass or more and 9.6% by mass or less.

[0036] Furthermore, Table 2 also shows the physical properties of the cement clinker powder used in the above experimental example. These physical properties represent the ratio of the strength development inhibition index to the strength development promotion index in the cement clinker powder. The strength development promotion index is the total alkali content in the cement clinker powder. The strength development inhibition index is the total content (mass%) of TiO2, MnO, and P2O5 in the cement clinker powder. As shown in Table 2, the above physical properties of the cement clinker powder used in this experimental example are between 0.853 and 1.326.

[0037] [Table 2]

[0038] Table 3 shows the chemical compositions of the limestone powder, fly ash, and blast furnace slag powder used in the above experimental example.

[0039] [Table 3]

[0040] Table 4 shows the specific surface area (Blaine specific surface area) and activity index of the limestone powder, blast furnace slag powder, and fly ash used in the above experimental example. Here, the activity index is as of 28 days of age.

[0041] [Table 4]

[0042] Tables 5 to 11 show the types of cement clinker powder used in the cement composition, the SO3 equivalent gypsum powder content (mass%), limestone powder content (mass%), fly ash content (mass%), total powder content of the mixed material (total content of limestone powder, fly ash, and blast furnace slag powder: mass%), and the compressive strength (N / mm²) of the cement mixture produced from the obtained cement composition at 28 days of age. 2 This shows the relationship between ")".

[0043] Table 5 shows that experimental examples A1 to A4 show the following: In a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash, if the gypsum powder content is between 0.6% by mass and 2.4% by mass in terms of SO3, the compressive strength of the cement mixture increases as the gypsum powder content of the cement composition increases. Experimental examples A5 to A8 show the following: That is, even when the total content of limestone powder and fly ash (total content of mixed powders) is increased from 7.5% by mass to 10.0% by mass in experimental examples A1 to A4, the compressive strength of the cement mixture increases as the gypsum powder content of the cement composition increases.

[0044] Table 5 shows that the sets of experimental examples A9-A12, A13-A16, A17-A20, and A21-A24 demonstrate the following: In sets A1-A4 and A5-A8, even when the type of clinker is changed, the compressive strength of the cement mixture increases as the gypsum powder content of the cement composition increases (or, even if the gypsum powder content of the cement composition increases, the compressive strength of the cement mixture is maintained without decreasing).

[0045] [Table 5]

[0046] Table 6 shows that the sets of experimental examples a1 to a24 demonstrate the following: In a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, and limestone powder, even if the gypsum powder content is between 1.2% and 2.4% by mass in terms of SO3, if fly ash is not included, the compressive strength of the cement mixture decreases as the gypsum powder content or limestone powder content of the cement composition increases.

[0047] [Table 6]

[0048] Based on the above, the following conclusions can be drawn from the experimental examples shown in Tables 5 and 6. That is, in a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash, if the total amount of limestone powder and fly ash is 10.0% by mass or less, and the amount of gypsum powder is 0.6% by mass or more and 2.4% by mass or less in terms of SO3, then when this cement composition is mixed with water, the SO3 contained in the gypsum powder effectively promotes the hydration reaction of the fly ash, and a high-strength cement mixture can be produced. In other words, such a cement composition has enhanced strength development due to the gypsum powder and fly ash contained in the mixture.

[0049] Table 7 is a rearrangement of Experimental Examples A1 to A24 shown in Table 5. The pair of Experimental Examples A1 and A5 shows the following: In a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash, if the gypsum powder content is 0.6% by mass in terms of SO3, the compressive strength of the cement mixture decreases as the fly ash content of the cement composition increases.

[0050] On the other hand, Table 7 shows that the pairs of experimental examples A2 and A6, A3 and A7, and A4 and A8 demonstrate the following: In experimental examples A1 and A5, when the gypsum powder content is 1.2% by mass, 1.8% by mass, or 2.4% by mass in terms of SO3, the compressive strength of the cement mixture increases as the fly ash content of the cement composition increases.

[0051] Table 7 shows that the pairs of experimental examples A9 and A13, A10 and A14, A11 and A15, A12 and A16, A17 and A21, A18 and A22, A19 and A23, and A20 and A24 demonstrate the following: In other words, even when the type of cement clinker powder is changed in pairs of experimental examples A1 and A5, if the gypsum powder content is 0.6% by mass in terms of SO3, the compressive strength of the cement mixture decreases as the fly ash content of the cement composition increases, and if the gypsum powder content is between 1.2% by mass and 2.4% by mass in terms of SO3, the compressive strength of the cement mixture increases as the fly ash content of the cement composition increases.

[0052] [Table 7]

[0053] Table 8 shows that experimental examples B1 and B2 are as follows: In experimental examples A1 and A5 shown in Table 7, even when the gypsum powder content in the cement composition is 1.0 mass% in terms of SO3, the compressive strength of the cement mixture increases as the fly ash content of the cement composition increases.

[0054] [Table 8]

[0055] Table 9 is a rearrangement of experimental examples a1 to a24 shown in Table 6. In Table 9, the sets of experimental examples a1 to a24 show the following: In a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, and limestone powder, even if the total content of the mixed powders is 10.0% by mass or less, and the gypsum powder content is 1.2% by mass or more and 2.4% by mass or less in terms of SO3, if fly ash is not included, the compressive strength of the cement mixture decreases as the content of the mixed powders in the cement composition increases.

[0056] [Table 9]

[0057] Table 10 shows that the combination of experimental examples C1 and C2 is as follows: In the combination of experimental examples A2 and A6 shown in Table 7, when Cli5 is used instead of Cli1, even if the gypsum powder content is 1.2% by mass in terms of SO3, and the total content of limestone powder and fly ash (total content of mixed powders) is 10.0% by mass or less, the compressive strength of the cement mixture decreases as the fly ash content of the cement composition increases. As shown in Table 1, the SO3 content of Cli1 to Cli4 (cement clinker powder used in experimental examples A1 to A24 and experimental examples B1 and B2) is 0.94% by mass or more, while the SO3 content of Cli5 used in experimental examples C1 and C2 is 0.56% by mass.

[0058] [Table 10]

[0059] Based on the above, the following conclusions can be drawn from the experimental examples shown in Tables 7 to 10. Specifically, in a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash, if the total amount of limestone powder and fly ash is 10.0% by mass or less, the amount of gypsum powder is 1.0% by mass or more and 2.4% by mass or less in terms of SO3, and the SO3 content of the cement clinker powder is 0.80% by mass or more (strictly speaking, 0.94% by mass or more), then when this cement composition is mixed with water, the rapid hydration (instantaneous setting) of the aluminate in the cement clinker powder is suppressed by the large amount of SO3 contained in the gypsum powder, and the aluminate contained in the cement clinker powder reacts with the limestone powder. As a result, a large amount of SO3 is leached from the cement clinker powder, and the hydration of the fly ash is promoted by the large amount of SO3 leached from the cement clinker powder, resulting in the production of a high-strength cement mixture. In other words, such cement compositions have their strength development further enhanced by the gypsum powder and fly ash contained in the mixture.

[0060] Furthermore, cement clinker powder with an SO3 content of 0.56% by mass or less cannot dissolve enough SO3 to promote the hydration of fly ash even when mixed with water. Therefore, if cement clinker powder with an SO3 content of 0.56% by mass or less is not included in the cement composition, the proportion of "cement clinker powder that promotes the hydration of fly ash" relative to the total amount of cement clinker powder in the cement composition will increase, and the strength development of the cement composition will be further enhanced by the gypsum powder and fly ash included in the cement composition.

[0061] Table 11 shows that the pairs of experimental examples D1 and D2, and D3 and D4, indicate the following: In a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash, if the total amount of limestone powder and fly ash is 10.0% by mass or less, and the amount of gypsum powder is 0.6% by mass or more and 2.4% by mass or less in terms of SO3, then even if blast furnace slag powder is also included, it is considered that the compressive strength of the cement mixture increases as the fly ash content of the cement composition increases.

[0062] [Table 11]

[0063] Next, we will explain Table 12, but before that, let's revisit Tables 5 and 10. Referring to the sets of experimental examples A1-A4, A5-A8, A9-A12, A13-A16, A17-A20, and A21-A24 in Table 5, we can see that when the gypsum powder content increases from 0.6 mass% to 1.2 mass% in terms of SO3, the compressive strength of the cement mixture increases sharply. However, even when the gypsum powder content increases from 1.2 mass% to 1.8 mass% and then to 2.4 mass% in terms of SO3, the compressive strength of the cement mixture increases only slightly.

[0064] In other words, among these experimental examples, the "experimental example with a gypsum powder content of 1.2 mass%, 1.8 mass%, or 2.4 mass% in terms of SO3" (hereinafter referred to as "Experimental Example Group X") maximizes the strength development of the cement composition through the gypsum powder contained in the cement composition. On the other hand, among these experimental examples, the "experimental example with a gypsum powder content of 0.6 mass% in terms of SO3" (hereinafter referred to as "Experimental Example Group Y1") enhances the strength development of the cement composition through the gypsum powder contained in the cement composition, but does not maximize it.

[0065] As explained above in the description of Table 7, in the experimental examples, specifically in the "experimental examples where the gypsum powder content is 1.2 mass%, 1.8 mass%, or 2.4 mass% in terms of SO3" (experimental example group X), the compressive strength of the cement mixture increases as the fly ash content of the cement composition increases. Furthermore, in the "experimental example where the gypsum powder content is 0.6 mass% in terms of SO3" (experimental example group Y1), the compressive strength of the cement mixture decreases as the fly ash content of the cement composition increases. On the other hand, in the pair of experimental examples C1 and C2 shown in Table 10 (hereinafter referred to as "experimental example group Y2"), even though the gypsum powder content is 1.2 mass in terms of SO3, the compressive strength of the cement mixture decreases as the fly ash content of the cement composition increases because the SO3 content of the cement clinker powder is low.

[0066] Table 12 shows "S1+S2" and "S2 / S1" for each of the experimental groups X, Y1, and Y2. Note that when SO3 contained in cement clinker powder is defined as clinker SO3, SO3 contained in gypsum powder is defined as gypsum SO3, the ratio of clinker SO3 to the cement composition is defined as S1 mass%, and the ratio of gypsum SO3 to the cement composition is defined as S2 mass%, then "S1+S2" is the sum of S1 mass% and S2 mass%, and "S2 / S1" is the ratio (percentage) of S2 mass% to S1 mass%.

[0067] In experimental example group X, "S1+S2" was between 2.05 and 3.60, and "S2 / S1" was between 0.998 and 2.837. In experimental examples Y1 and Y2, "S1+S2" was 1.80 or less, and "S2 / S1" was between 0.499 and 2.381. In other words, in the cement composition, when "S1+S2" is between 2.05 and 3.60 and "S2 / S1" is between 0.998 and 2.837, the strength development of the cement composition is maximized by the gypsum powder and fly ash contained in the cement composition.

[0068] Furthermore, considering that the "S1+S2" values ​​for experimental groups Y1 and Y2 are lower than those for experimental group X, it is considered that even if the "S1+S2" value exceeds 3.60 in the cement composition, as long as the "S2 / S1" value is between 0.998 and 2.837, the gypsum powder and fly ash contained in the cement composition will maximize the strength development of the cement composition.

[0069] [Table 12]

[0070] Based on the above, the following conclusion can be drawn from the experimental examples shown in Table 12. That is, in a cement composition consisting of a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash, if the total amount of limestone powder and fly ash is 10.0% by mass or less, the amount of gypsum powder is 0.6% by mass or more and 2.4% by mass or less in terms of SO3, the ratio of "S1 + S2" is 1.90 or more (strictly speaking, 2.05 or more), and the ratio of "S2 / S1" is 0.90 or more and 3.00 or less (strictly speaking, 0.998 or more and 2.837 or less), then the cement composition contains a balanced amount of clinker SO3 and gypsum SO3.

[0071] Therefore, when this cement composition is mixed with water, gypsum SO3 leaches from the gypsum powder in the initial mixing stage, and clinker SO3 leaches from the cement clinker powder after the initial mixing stage has passed. As a result, SO3 leaches continuously from the gypsum powder and cement clinker powder without interruption during the mixing stage, and this SO3 continuously promotes the hydration of the fly ash without interruption. Therefore, it is believed that such a cement composition will have its strength development further enhanced by the gypsum powder and fly ash contained in the mixture. [Explanation of symbols]

[0072] 1. Cement manufacturing equipment 2 Clinker Silo 3. Finishing mill 4 Classifier 5 Mixing device 6. Cement silo A Fly Ash C. Klinka D. Crushed material F Fine powder G plaster L limestone powder M mixture R Coarse powder

Claims

1. A cement composition comprising a mixture containing cement clinker powder, gypsum powder, limestone powder, and fly ash, The limestone powder and the fly ash are included in the mixture in a total proportion of 10.0% by mass or less. Here, the limestone powder is included in the mixture in a proportion of 5.0% by mass or more. The gypsum powder is SO in the mixture. 3 It is contained in a proportion of 0.6% by mass or more and 2.4% by mass or less, SO contained in the cement clinker powder 3 Clinker SO 3 Defined as SO contained in the gypsum powder, 3 gypsum SO 3 Defined as, and the clinker SO for the mixture 3 The ratio of S1 by mass is defined as the gypsum SO1 in the mixture. 3 When the proportion of is defined as S2 by mass%, The sum of the mass percentages of S1 and S2 is 1.90 mass or more, and the ratio of the mass percentage of S2 to the mass percentage of S1 is 0.90 or more and 3.00 or less. The SO4 of the cement clinker powder 3 The content is 0.80% by mass or more. The gypsum powder is contained in the mixture at a ratio of 1.0% by mass or more in terms of SO 3 conversion, and the cement composition is characterized by this.

2. In the above mixture, SO 3 The cement composition according to claim 1, characterized in that it does not contain cement clinker powder having a content of 0.56% by mass or less.

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