Manufacturing method of extruded cement board
By incorporating amorphous silica in the cement composition, the method addresses the challenge of achieving high-strength and stable cement panels at reduced curing temperatures, enhancing mechanical properties and energy efficiency.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- MITSUBISHI MATERIALS KENZAI CORP
- Filing Date
- 2024-12-27
- Publication Date
- 2026-07-09
Smart Images
Figure 2026115169000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing an extruded cement panel.
Background Art
[0002] Conventionally, an extruded cement panel containing silica sand mainly composed of quartz (crystalline silica) as a raw material has been known (see Patent Document 1). Since the extruded cement panel is lightweight and has high strength, it is widely used as an exterior wall or partition wall of a building.
[0003] In the process of manufacturing an extruded cement panel, autoclave curing is performed using high-temperature steam under a pressure higher than normal pressure in a high-temperature and high-humidity steam kiln. In autoclave curing, the silica component and calcium react to form a calcium silicate hardened body, so that the strength of the extruded cement panel increases and the dimensional change rate decreases. The curing temperature during autoclave curing is set, for example, at about 175°C.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] By the way, there are not a few needs to reduce the energy consumption by lowering the curing temperature during autoclave curing. However, when autoclave curing is performed at a low temperature, the silica component and calcium do not react sufficiently, the strength of the extruded cement panel cannot be ensured sufficiently, and the dimensional change is large, so there is a problem that cracks and warping are likely to occur in the extruded cement panel.
[0006] Therefore, even when autoclave curing is performed at a lower temperature than conventional methods, a technical challenge arises to obtain high-strength and stable extruded cement boards. The present invention aims to solve this problem. [Means for solving the problem]
[0007] In light of the above circumstances, the inventors conducted diligent research and, as a result, discovered that by using amorphous silica as a raw material for extruded cement boards, high-strength and stable materials can be obtained even when autoclave curing is performed at a lower temperature than conventional methods, thus completing the present invention.
[0008] To achieve the above objective, the method for manufacturing an extruded cement board according to the present invention comprises the steps of: mixing and kneading raw materials containing at least cement and amorphous silica to obtain a cement composition; and extruding the cement composition to obtain a molded body, which is then autoclaved at an autoclave temperature at which the amorphous silica can be dissolved.
[0009] Furthermore, in the method for manufacturing extruded cement boards according to the present invention, it is preferable that the amorphous silica is any of volcanic glass fine powder types I, II, or III as defined in JIS A 6209.
[0010] Furthermore, in the method for producing an extruded cement board according to the present invention, it is preferable that the molar ratio of calcium oxide to silicon dioxide (CaO / SiO2 molar ratio) in the cement composition is set to 1.3 or less in the step of obtaining the cement composition.
[0011] Furthermore, in the method for manufacturing extruded cement boards according to the present invention, it is preferable that the autoclave temperature is within the range of 80°C to less than 180°C. [Effects of the Invention]
[0012] According to the present invention, stable extruded cement boards can be obtained even when autoclave curing is performed at a lower temperature than conventional methods.
Brief Description of the Drawings
[0013] [Figure 1] Schematic diagram showing the manufacturing process of an extruded cement board according to an embodiment of the present invention. [Figure 2] (a) is a table showing the experimental conditions of Experimental Example 1, and (b) is a table showing the experimental results of Experimental Example 1. [Figure 3] Graph showing the flexural strengths of Comparative Examples 1-2 and Examples 1-6 of Experimental Example 1. [Figure 4] Graph showing the flexural change rate due to water absorption of Comparative Examples 1-2 and Examples 1-6 of Experimental Example 1. [Figure 5] (a) is a table showing the experimental conditions of Experimental Example 2, and (b) is a table showing the experimental results of Experimental Example 2. [Figure 6] Graph showing the flexural strengths of Comparative Examples 4-6 and Examples 7-17 of Experimental Example 2. [Figure 7] Graph showing the X-ray diffraction pattern of Comparative Example 3. [Figure 8] Graph showing the X-ray diffraction pattern of Comparative Example 4. [Figure 9] Graph showing the X-ray diffraction pattern of Experimental Example 8. [Figure 10] Graph showing the X-ray diffraction pattern of Experimental Example 11.
Embodiments for Carrying Out the Invention
[0014] An embodiment of the present invention will be described based on the drawings. In the following, when referring to the number of components, numerical values, amounts, ranges, etc., unless otherwise specified or limited to a specific number in principle, it is not limited to that specific number, and it may be more or less than the specific number.
[0015] Also, when referring to the shape, positional relationship of components, etc., unless otherwise specified or it is considered not to be so in principle, it includes those substantially approximate or similar to the shape, etc.
[0016] In addition, the drawings may be exaggerated, such as enlarging characteristic parts for easy understanding of the features, and the dimensional ratios of the components are not necessarily the same as the actual ones.
[0017] Hereinafter, a method for manufacturing the extruded cement board 1 according to the present embodiment will be described based on the drawings. FIG. 1 is a schematic diagram illustrating the process of manufacturing the extruded cement board 1.
[0018] In the method for manufacturing the extruded cement board 1 according to the present embodiment, cement (hydraulic material) is fed from the hopper 10, a siliceous raw material containing amorphous silica is fed from the hopper 11, organic fiber (reinforcing fiber) is fed from the hopper 12, an organic admixture is fed from the hopper 13, and water is fed from the hopper 14 in necessary amounts to the extrusion molding machine 15. The extrusion molding machine 15 extrudes a cement composition obtained by mixing and kneading them, thereby obtaining a molded body 2. After the molded body 2 is cured through primary curing and secondary curing (autoclave curing) and cut into predetermined dimensions, it is packed and stacked and shipped as the extruded cement board 1. Thus, in the method for manufacturing a general extruded cement board, silica sand, which is crystalline silica, is used as a raw material, whereas in the method for manufacturing the extruded cement board 1 according to the present embodiment, amorphous silica is used as a raw material. The bulk density of the extruded cement board 1 according to the present embodiment is preferably 1.7 g / cm 3 as described above, but by using lightweight aggregates or the like, it may be 1.4 g / cm 3 or more.
[0019] The amorphous silica is volcanic glass fine powder type I defined in JIS A 6209 (hereinafter simply referred to as "volcanic silica type I"), volcanic glass fine powder type II defined in JIS A 6209 (hereinafter simply referred to as "volcanic silica type II"), or volcanic glass fine powder type III defined in JIS A 6209 (hereinafter simply referred to as "volcanic silica type III"), etc.
[0020] Volcanic silica types I, II, and III are all fine powders mainly composed of volcanic glass, which is produced from volcanic ejecta through sorting, classification, and crushing. Volcanic silica type I is a relatively fine powder, volcanic silica type III is a relatively coarse powder, and volcanic silica type III refers to a fine powder with a particle size intermediate between volcanic silica type I and volcanic silica type III.
[0021] In the manufacturing method according to this embodiment, the curing temperature during autoclave curing (hereinafter simply referred to as "AC temperature") can be set to a lower temperature than conventional methods.
[0022] In autoclave curing, the molded body 2 is placed in a high-temperature, high-humidity steam oven 16, and the extruded cement board 1 is cured by supplying high-temperature steam to the steam oven at a pressure higher than atmospheric pressure. In autoclave curing, the silica and calcium components in the molded body 2 react to form a hardened calcium silicate body, increasing the strength and stability of the extruded cement board 1. Furthermore, it is believed that in autoclave curing, the silica component in amorphous silica dissolves and reacts with the calcium compounds in the cement in a pozzolanic reaction. The pozzolanic reaction densifies the hardened calcium silicate body, further increasing its strength. [Examples]
[0023] <Experimental Example 1> Comparative experiments were conducted on the mechanical properties (bending strength and length change rate) of extruded cement boards obtained from cement compositions containing crystalline silica (Comparative Examples 1-2) and extruded cement boards obtained from cement compositions containing amorphous silica (Examples 1-6). Except for the conditions described below, the same conditions were used to produce the extruded cement boards for Comparative Examples 1-2 and Experimental Examples 1-6.
[0024] First, Comparative Examples 1-2 and Examples 1-6 were prepared based on the AC temperature and formulation shown in Figure 2(a). In Figure 2(a), "crushed powder" refers to crushed scraps of extruded cement board, "pulp" refers to crushed newspaper waste, and "thickener" is "Metholose (registered trademark) SHV-WF" manufactured by Shin-Etsu Chemical Co., Ltd. Also, "C / S" in Figure 2(a) refers to the molar ratio (CaO / SiO2 molar ratio) of calcium oxide to silicon dioxide in the cement and crystalline silica and amorphous silica compositions.
[0025] The values for each raw material in Comparative Example 1 are the same as those for the raw materials of a typical extruded cement board. In Comparative Example 1, the AC temperature was set to 175°C. In Comparative Example 2, the AC temperature was set lower than in Comparative Example 1, to 105°C.
[0026] Examples 1 and 2 differ from Comparative Examples 1 and 2 in that they use volcanic silica type I as amorphous silica, whereas Comparative Examples 1 and 2 consist of crystalline silica; other raw materials are common to both. In Example 1, the AC temperature was set to 175°C, and in Example 2, the AC temperature was set to 105°C.
[0027] Examples 3 and 4 differ from Comparative Examples 1 and 2 in that they use volcanic silica type III as amorphous silica, whereas Comparative Examples 1 and 2 consist of crystalline silica; other raw materials are common to both. In Example 3, the AC temperature was set to 175°C, and in Example 4, the AC temperature was set to 105°C.
[0028] Examples 5 and 6 differ from Comparative Examples 1 and 2 in that they use silica fume as amorphous silica, whereas Comparative Examples 1 and 2 use crystalline silica; other raw materials are common to both. In Example 5, the AC temperature was set to 175°C, and in Example 6, the AC temperature was set to 105°C.
[0029] Furthermore, in extruded cement boards containing crystalline silica as a raw material, a C / S ratio of approximately 0.8 to 1 is preferable. If the C / S ratio falls outside the above-mentioned range, unreacted calcium oxide remains in the cement composition, and the desired strength cannot be obtained even after autoclave curing.
[0030] As shown in Figure 2(a), while the C / S values for Comparative Examples 1-2 are within the aforementioned numerical range, the C / S values for Examples 1-6 are outside the aforementioned numerical range, indicating that in Examples 1-6, the calcium component is excessively high relative to the silica component in the cement composition.
[0031] Next, the bending strength, bending modulus, material density, and length change rate due to water absorption were measured for Comparative Examples 1-2 and Examples 1-6. The bending strength was measured in accordance with JIS A 1408, Bending and Impact Test Methods for Building Boards. The bending modulus was calculated from the ratio of bending strength to strain by attaching strain gauges to the bending strength test specimen. The material density and length change rate due to water absorption were measured in accordance with JIS A 5441, Extruded Cement Boards, 7.4 Material Density and 7.7 Length Change Rate Test due to Water Absorption. Figure 2(b) shows the measured values of bending strength and length change rate, as well as the presence or absence of Ca(OH)2 detection by X-ray diffraction, for Comparative Examples 1-2 and Examples 1-6. Figure 3 shows graphs representing the bending strength of Comparative Examples 1-2 and Examples 1-6. In Figure 3, "Standard Value" is the lower limit of the bending strength required for extruded cement boards (17.6 N / mm2). Figure 4 shows graphs representing the length change rates for Comparative Examples 1-2 and Examples 1-6. The "Standard Value" in Figure 4 represents the upper limit (0.07%) of the length change rate due to water absorption required for extruded cement boards.
[0032] Figure 3 shows that Comparative Examples 1-2 and Examples 1-6 all exceeded the standard values for flexural strength. Furthermore, Comparative Example 2 showed a decrease in flexural strength compared to Comparative Example 1, likely due to a lower AC temperature. This is thought to be because, at low AC temperatures, the silica component in the cement composition did not dissolve sufficiently, resulting in poor reactivity of the pozzolanic reaction during autoclave curing.
[0033] On the other hand, Example 2 shows increased flexural strength compared to Example 1, despite a lower AC temperature. Similarly, Example 4 shows increased flexural strength compared to Example 3, which had a higher AC temperature, and Example 6 shows increased flexural strength compared to Example 5, which also had a higher AC temperature. This is thought to be because the amorphous silica in the cement composition dissolved even at a lower AC temperature than conventional methods, resulting in good reactivity of the pozzolanic reaction.
[0034] As shown in Figure 4, Comparative Example 4 falls below the standard value for the rate of change in length due to water absorption, while Comparative Example 5 exceeds the standard value for the rate of change in length due to water absorption. This is thought to be because, at low AC temperatures, the silica component in the cement composition did not dissolve sufficiently, and the pozzolanic reaction did not proceed sufficiently during autoclave curing, resulting in a deterioration of the rate of change in length due to water absorption.
[0035] On the other hand, it can be seen that all of Examples 1 to 6 are below the standard value for the rate of change in length due to water absorption. In particular, Example 2 shows a smaller rate of change in length due to water absorption than Example 1, despite a lower AC temperature. Similarly, Example 4 shows a smaller rate of change in length due to water absorption than Example 3, which has a higher AC temperature, and Example 6 shows a smaller rate of change in length due to water absorption than Example 5, which also has a higher AC temperature. This suggests that even at lower AC temperatures than before, amorphous silica in the cement composition dissolves, the reactivity of the pozzolanic reaction is good, and the rate of change in length due to water absorption improves.
[0036] As shown in Figures 3 and 4, it can be seen that in extruded cement boards containing crystalline silica as a raw material (Comparative Examples 1 and 2), sufficient mechanical properties cannot be obtained at an AC temperature of 105°C. On the other hand, in extruded cement boards containing amorphous silica as a raw material (Examples 1 to 6), sufficient mechanical properties can be obtained even at an AC temperature of 105°C.
[0037] Furthermore, Ca(OH)2 was detected in Comparative Example 2 and Example 4, whereas it was not detected in Comparative Example 1 and Examples 1-3, 5-6. Since Ca(OH)2 is produced when calcium components remain in the cement composition, it is possible that the autoclave curing was insufficient in Comparative Example 2 and Example 4, where Ca(OH)2 was detected.
[0038] In Comparative Example 1, the C / S ratio was within a generally considered appropriate range, and the AC temperature was high enough to allow the silica component in the cement composition to dissolve. Therefore, it is presumed that the calcium component in the cement composition did not react sufficiently and remained untreated.
[0039] On the other hand, in Comparative Example 2, although the C / S ratio was within the generally considered appropriate range, it is presumed that the calcium component in the cement composition remained unreacted because the AC temperature was low and below the dissolution temperature of crystalline silica.
[0040] Furthermore, in Examples 1-3 and 5-6, although the C / S ratio was outside the generally considered appropriate range, it is presumed that the calcium component in the cement composition did not react sufficiently and remained because the AC temperature was high enough to allow the silica component derived from amorphous silica in the cement composition to dissolve. However, in Examples 5-6, despite setting the amount of water to be lower than in Comparative Examples 1-2 and Examples 1-4, both the flexural modulus and material density were high, resulting in hard, heavy, and crack-prone physical properties.
[0041] On the other hand, in Example 4, although the C / S ratio was similar to that of Example 3, the particle size of the amorphous silica was coarser and the specific surface area was smaller compared to Example 3. Therefore, it is presumed that the silica component did not dissolve sufficiently, and the calcium component in the cement composition remained unreacted.
[0042] <Experimental Example 2> Next, comparative experiments were conducted on the mechanical properties (bending strength) of extruded cement boards obtained from cement compositions containing crystalline silica (Comparative Examples 3-5) and extruded products obtained from cement compositions containing amorphous silica (Examples 7-17). Except for the conditions described below, the same conditions were used to produce the extruded cement boards for Comparative Examples 3-5 and Experimental Examples 7-17.
[0043] First, Comparative Examples 3-5 and Examples 7-17 were prepared based on the AC temperature and formulation during autoclave curing shown in Figure 5(a). The various raw materials in Figure 5(a) are the same as those in Figure 2(a).
[0044] The various values of the raw materials in Comparative Example 3 correspond to the raw materials of conventional extruded cement boards. As shown in Figure 5(a), Comparative Example 3 was set to an AC temperature of 175°C. Comparative Example 4 was set to a lower AC temperature of 105°C than Comparative Example 3. Comparative Example 5 was set to a lower AC temperature of 80°C than Comparative Example 4.
[0045] Examples 7-9 differ from Comparative Examples 3-5 in that they use volcanic silica type I as amorphous silica, whereas Comparative Examples 3-5 consist of crystalline silica; other raw materials are common to all. In Example 7, the AC temperature was set to 175°C, in Example 8, it was set to 105°C, and in Example 9, it was set to 80°C.
[0046] Examples 10-14 differ from Comparative Examples 3-5 in that they use volcanic silica type III as amorphous silica, whereas Comparative Examples 3-5 consist of crystalline silica; other raw materials are common to both. In Example 10, the AC temperature was set to 175°C, in Examples 11 and 13 to 105°C, and in Examples 12 and 14 to 80°C. In Examples 13 and 14, the amount of cement was reduced and the amount of volcanic silica type III was increased compared to Examples 11 and 12 to adjust the C / S ratio to 1.
[0047] Examples 15-17 differ from Comparative Examples 3-5 in that they use silica fume as amorphous silica, whereas Comparative Examples 3-5 use crystalline silica; other raw materials are common to both. In Example 15, the AC temperature was set to 175°C, in Example 16, it was set to 105°C, and in Example 17, it was set to 80°C.
[0048] Next, the bending strength was measured for Comparative Examples 3-5 and Examples 7-17. The bending strength was measured in accordance with JIS A 1408, Bending and Impact Test Methods for Building Boards. Figure 5(b) shows the measured values of the bending strength for Comparative Examples 3-5 and Examples 7-17. Figure 6 shows graphs representing the bending strength for Comparative Examples 3-5 and Examples 7-17. In Figure 6, "Standard Value" refers to the lower limit of the bending strength required for extruded cement boards (17.6 N / mm2).
[0049] As shown in Figure 6, it can be seen that all of Comparative Examples 3-5 and Examples 7-17 exceeded the standard values for bending strength. However, Comparative Examples 3-5 showed approximately the same bending strength even when the AC temperature decreased.
[0050] On the other hand, in Examples 8 and 9, the bending strength increased compared to Example 7 despite the decrease in AC temperature. Similarly, in Examples 11-14, the bending strength increased compared to Example 10, which had a higher AC temperature, and in Examples 16 and 17, the bending strength increased compared to Example 15, which also had a higher AC temperature. This is thought to be because the amorphous silica in the cement composition dissolved even at a lower AC temperature than before, resulting in good reactivity of the pozzolanic reaction.
[0051] Furthermore, it can be seen that the bending strengths of Examples 8 and 9 were approximately the same. This is thought to be because, in Example 9, the reactivity of the pozzolanic reaction was good even when the AC temperature decreased, similar to Example 8.
[0052] On the other hand, it can be seen that the bending strength of Example 12 was lower than that of Example 11. This is thought to be because the pozzolanic reaction was less reactive in Example 12 than in Example 11. Also, it can be seen that the bending strength of Example 14 was lower than that of Example 13. This is thought to be because the pozzolanic reaction was less reactive in Example 14 than in Example 13. Furthermore, it can be seen that the bending strength of Example 17 was lower than that of Example 16. This is thought to be because the pozzolanic reaction was less reactive in Example 17 than in Example 16.
[0053] Here, Figure 7 shows the X-ray diffraction pattern of Comparative Example 3 (C / S: 1.01), Figure 8 shows the X-ray diffraction pattern of Comparative Example 4 (C / S: 1.01), Figure 9 shows the X-ray diffraction pattern of Example 8 (C / S: 1.22), and Figure 10 shows the X-ray diffraction pattern of Example 11 (C / S: 1.22).
[0054] Figure 7 shows that Comparative Example 3 did not contain slaked lime (Ca(OH)2). This means that no calcium components remained in the cement composition of Comparative Example 3. Therefore, it can be considered that the pozzolanic reaction during autoclave curing was highly reactive.
[0055] Figure 8 shows that Comparative Example 4 contained slaked lime (Ca(OH)2). This suggests that the calcium component was excessively high relative to the silica component in the cement composition, and the pozzolanic reaction was unresponsive at low AC temperatures. As a result, the calcium component in the cement composition remained, leading to the formation of slaked lime.
[0056] Figure 9 shows that Example 8 did not contain slaked lime Ca(OH)2. This suggests that although Example 8 had a higher calcium content relative to the silica content in the cement composition compared to Comparative Example 4, the fine particle size of volcanic silica type I resulted in good reactivity in the pozzolanic reaction, and no calcium content remained in the cement composition.
[0057] Figure 10 shows that Example 11 contained slaked lime Ca(OH)2. This suggests that, similar to Example 8, Example 11 had a higher calcium content relative to the silica content in the cement composition. However, because the particle size of volcanic silica type III was coarse, the pozzolanic reaction was poor, resulting in residual calcium in the cement composition and the formation of slaked lime.
[0058] As shown in Figure 6, Example 13 (C / S:1) exhibited increased flexural strength compared to Example 11 (C / S:1.2). This suggests that while the pozzolanic reaction was poor during autoclave curing in Example 11, the reduced proportion of calcium in the cement composition in Example 13 resulted in good pozzolanic reaction reactivity and high flexural strength, even with coarse-grained volcanic silica type III.
[0059] As shown in Figure 6, when autoclave curing was performed at a lower temperature of 105°C than conventional methods, Examples 8, 11, 13, and 16 showed higher bending strength than Comparative Example 4. Similarly, when autoclave curing was performed at a lower temperature of 80°C than conventional methods, Examples 9, 12, 14, and 17 showed higher bending strength than Comparative Example 5. In other words, when autoclave curing was performed at a lower AC temperature than conventional methods, extruded cement boards containing amorphous silica as a raw material (Examples 8, 9, 11-14, 16, 17) showed higher bending strength than extruded cement boards containing sand as a raw material (Comparative Examples 4-5).
[0060] Thus, the method for manufacturing an extruded cement board according to this embodiment includes the steps of: mixing and kneading raw materials containing at least cement and amorphous silica to obtain a cement composition; and extruding the cement composition to obtain a molded body, which is then autoclaved at an AC temperature at which amorphous silica can be eluted.
[0061] This makes it possible to obtain stable extruded cement boards even when autoclave curing is performed at a lower temperature than conventional methods.
[0062] Furthermore, the present invention can be modified in various ways as long as it does not deviate from the spirit of the invention, and it goes without saying that the present invention also applies to such modified versions. [Explanation of Symbols]
[0063] 1: Extruded cement board 2: Molded body 10-14: Hopper 15: Extrusion molding machine 16: Steam kiln
Claims
1. A step of obtaining a cement composition by mixing and kneading raw materials containing at least cement and amorphous silica, A step of extruding the cement composition to obtain a molded body and then curing it in an autoclave at an autoclave temperature at which the amorphous silica can be dissolved, A method for manufacturing an extruded cement board, characterized by including the following:
2. The method for manufacturing an extruded cement board according to claim 1, characterized in that the amorphous silica is any of volcanic glass fine powder type I, type II, or type III as defined in JIS A 6209.
3. The method for producing an extruded cement board according to claim 2, characterized in that, in the step of obtaining the cement composition, the molar ratio of calcium oxide to silicon dioxide (CaO / SiO2 molar ratio) in the cement composition is set to 1.3 or less.
4. The method for manufacturing an extruded cement board according to claim 1, characterized in that the autoclave temperature is within the range of 80°C or more and less than 180°C.