Damp-proof durable calcium silicate board and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to a damp-proof durable calcium silicate board and a preparation method thereof. The calcium silicate board is prepared from diatomite, quick lime, Portland cement, alkali-resistant glass fibers, modified montmorillonite and deionized water. The modified montmorillonite is obtained by carrying out ion exchange intercalation on sodium-based montmorillonite by adopting sodium 4-styrene sulfonate and grafting sodium styrene sulfonate, a silane coupling agent and a fluorine-containing monomer through free radical polymerization. Due to the introduction of the modified montmorillonite, the microstructure of the calcium silicate board is effectively improved, and the compactness and the water resistance of the calcium silicate board are enhanced. The calcium silicate board shows excellent breaking strength, moisture resistance and durability in a humid environment for a long time, and has important practical application value and popularization significance.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a moisture-proof and durable calcium silicate board and a preparation method thereof. Background Art

[0002] As an important building material, calcium silicate board is widely used in the fields of interior and exterior walls, ceilings, partitions, etc. of buildings due to its excellent fire prevention, heat insulation and mechanical properties. Calcium silicate board has the advantages of light weight, high strength, fire resistance, heat insulation, sound insulation, etc., and also has good environmental protection performance, so it has been widely recognized and promoted in modern buildings. However, with the continuous improvement of the requirements for material performance in the construction industry, some problems have also emerged in the actual application of calcium silicate board, especially its performance in high humidity or long-term humid environments, which has become an important factor restricting its application range.

[0003] Traditional calcium silicate board is prone to problems such as strength attenuation, high water absorption rate, and poor dimensional stability in humid environments. This is mainly determined by the internal microstructure characteristics of calcium silicate board. The main components of calcium silicate board are siliceous materials (such as quartz powder, silica fume, etc.) and calcareous materials (such as lime, cement, etc.), and they generate hydration products such as tobermorite through hydration reaction. These hydration products form a porous microstructure inside the material. Although this structure gives calcium silicate board better heat insulation performance, it also leads to a relatively high water absorption rate. Especially in a humid environment, water is easy to penetrate into the material through the pores, thus triggering a series of problems.

[0004] First of all, the infiltration of water will cause further hydration reaction or dissolution of the hydration products inside the calcium silicate board, damage the microstructure of the material, and reduce its mechanical strength. Secondly, the dimensional stability of the material will be affected after water absorption, and phenomena such as expansion and warping may occur, affecting its service life. In addition, long-term humid environment may also lead to problems such as mildew growth on the surface of calcium silicate board, further reducing its use performance and aesthetics. Therefore, how to improve the durability and moisture-proof performance of calcium silicate board in humid environments has become an important topic in current research and application. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a moisture-proof and durable calcium silicate board and a preparation method thereof to solve the problems of easy strength attenuation and high water absorption rate of existing calcium silicate board in humid environments.

[0006] Based on the above purpose, the present invention provides a moisture-proof and durable calcium silicate board, which is prepared from the following raw materials by weight: 400 - 450 parts of diatomite, 300 - 350 parts of quicklime, 160 - 200 parts of portland cement, 15 - 25 parts of alkali-resistant glass fiber, 5 - 15 parts of modified montmorillonite, and 300 - 350 parts of deionized water.

[0007] Preferably, the silica content of the diatomaceous earth is ≥ 85 wt%.

[0008] Preferably, the calcium oxide content in the quicklime is ≥ 89 wt%.

[0009] Preferably, the portland cement is P·II 52.5.

[0010] Preferably, the average length of the alkali-resistant glass fiber is 4 - 10 mm.

[0011] Furthermore, the preparation steps of the modified montmorillonite are as follows: S1: Sodium-based montmorillonite and 4-styrenesulfonic acid sodium are added into an ethanol / water mixed solution, ultrasonicated for 20 - 40 min, then subjected to ion exchange for 5 - 7 h under reflux conditions at 80 - 90 °C, centrifuged, washed, and vacuum dried to obtain intercalated montmorillonite; S2: Under nitrogen protection, the intercalated montmorillonite is added into a toluene solution, ultrasonicated for 20 - 40 min, then 4-styrenesulfonic acid sodium, γ-methacryloxypropyltrimethoxysilane, and perfluorooctylethyl acrylate are added, stirred for 20 - 40 min, then benzoyl peroxide is added, and stirred and reacted at 75 - 85 °C for 4 - 6 h, centrifuged, washed, and vacuum dried to obtain modified montmorillonite.

[0012] Preferably, the volume ratio of the ethanol / water mixed solution in step S1 is 3 - 5:1.

[0013] Preferably, the weight ratio of the sodium-based montmorillonite, 4-styrenesulfonic acid sodium, and the ethanol / water mixed solution in step S1 is 5 - 15:3 - 6:40 - 60.

[0014] Preferably, the weight ratio of the intercalated montmorillonite, toluene, 4-styrenesulfonic acid sodium, γ-methacryloxypropyltrimethoxysilane, perfluorooctylethyl acrylate, and benzoyl peroxide in step S2 is 5 - 15:50 - 200:2 - 6:6 - 18:1.2 - 3.6:0.2 - 0.5.

[0015] Furthermore, the present invention also provides a preparation method of a moisture-proof and durable calcium silicate board, including the following steps: (1) Mix the diatomaceous earth, quicklime, portland cement, alkali-resistant glass fiber, and modified montmorillonite and stir for 15 - 25 min, then add deionized water, and stir at 40 - 50 °C at a speed of 1000 - 1500 rpm for 10 - 20 min to obtain a slurry; (2) Inject the slurry into a mold, keep the pressure at 13 - 15 MPa for 15 - 25 min, and then seal and cure for 20 - 28 h to obtain a slab; (3) Transfer the slab into an autoclave, heat it up to 175 - 185°C at a rate of 8 - 12°C / min, maintain the treatment for 7 - 10 h under a saturated steam pressure of 1.2 - 1.5 MPa, then reduce the pressure to atmospheric pressure at a rate of 0.2 - 0.8 MPa / h, and dry it to obtain a moisture-proof and durable calcium silicate board.

[0016] Preferably, the drying step in the step (3) is: drying at 55 - 65°C for 3 - 5 h, drying at 80 - 90°C for 5 - 7 h, drying at 100 - 110°C for 1 - 3 h, and then cooling down.

[0017] The beneficial effects of the present invention: Through the modification treatment of montmorillonite and reasonable component ratio, the present invention significantly improves the flexural strength, moisture-proof performance and long-term durability of calcium silicate boards. The introduction of modified montmorillonite forms a more uniform dispersion structure inside the material, enhances its surface activity and interfacial compatibility, thus effectively improving the microstructure of calcium silicate boards, reducing the porosity and water absorption channels. The functional groups in the modified montmorillonite can chemically react or physically combine with Portland cement and other components, further improving the denseness and water resistance of the material.

[0018] Through the polymer on the surface of montmorillonite as a bridge, the present invention significantly enhances the interfacial bonding strength between the inorganic phase and the organic phase. The synergistic effect of this structural optimization and interfacial enhancement enables the calcium silicate board to maintain a high strength and a low strength attenuation rate in a long-term humid environment, showing excellent moisture-proof and durable properties, which has important practical significance and promotion value. Specific embodiments

[0019] To make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0020] In the specific embodiments of the present invention, the sodium-based montmorillonite comes from NANOCOR Company in the United States, with the model of PGW, the diatomite is purchased from Lingshou County Kunjian Mineral Products Processing Factory, and the silicon dioxide content is 85 wt%; the quicklime is purchased from Lingshou County Longde Mineral Products Sales Co., Ltd., and the calcium oxide content is ≥89 wt%, the Portland cement meets the P·II 52.5 standard in GB 175 - 2020, and the average length of the alkali-resistant glass fiber is 6 mm.

[0021] Example 1

[0022] (1) Add 5 g of sodium-based montmorillonite and 3 g of 4-styrenesulfonic acid sodium into 40 g of ethanol / water mixed solution (volume ratio 3:1), ultrasonicate for 20 min, then carry out ion exchange for 5 h under reflux conditions at 80°C, centrifuge, wash, and vacuum dry to obtain intercalated montmorillonite; (2) Under nitrogen protection, 5 g of intercalated montmorillonite was added to 50 g of toluene solution, and ultrasonicated for 20 min. Then, 2 g of sodium styrene sulfonate, 6 g of γ-methacryloxypropyltrimethoxysilane and 1.2 g of perfluorooctylethyl acrylate were added, and stirred for 20 min. Then, 0.2 g of benzoyl peroxide was added, and the mixture was stirred at 75 °C for 4 h. The mixture was centrifuged, washed, and vacuum dried to obtain modified montmorillonite. (3) 400 g of diatomaceous earth, 300 g of quicklime, 160 g of silicate cement, 15 g of alkali-resistant glass fiber and 5 g of modified montmorillonite were mixed and stirred for 15 min, and then 300 g of deionized water was added, and the mixture was stirred at 1000 rpm at 40° C. for 10 min to obtain a slurry; (4) The slurry is injected into the mold, maintained at a pressure of 13 MPa for 15 min, and then sealed and cured for 20 h to obtain a slab; (5) The slab was transferred into an autoclave, heated to 175°C at a rate of 8°C / min, maintained at a saturated steam pressure of 1.2 MPa for 7 h, then reduced to normal pressure at a rate of 0.2 MPa / h, dried at 55°C for 3 h, 80°C for 5 h, and 100°C for 1 h, and cooled to obtain a moisture-proof and durable calcium silicate board.

[0023] Example 2

[0024] (1) 10 g of sodium montmorillonite and 4.5 g of sodium 4-styrene sulfonate were added to 50 g of ethanol / water mixed solution (volume ratio 4:1), ultrasonicated for 30 min, and then ion exchanged at 85 °C reflux for 6 h, centrifuged, washed, and vacuum dried to obtain intercalated montmorillonite; (2) Under nitrogen protection, 10 g of intercalated montmorillonite was added to 100 g of toluene solution, and ultrasonicated for 30 min. Then, 4.1 g of sodium styrene sulfonate, 12.4 g of γ-methacryloxypropyltrimethoxysilane and 2.6 g of perfluorooctylethyl acrylate were added, and stirred for 30 min. Then, 0.3 g of benzoyl peroxide was added, and the mixture was stirred at 80 ° C for 5 h. The mixture was centrifuged, washed, and vacuum dried to obtain modified montmorillonite. (3) 420 g of diatomaceous earth, 330 g of quicklime, 180 g of silicate cement, 20 g of alkali-resistant glass fiber and 10 g of modified montmorillonite were mixed and stirred for 20 min, and then 330 g of deionized water was added, and the mixture was stirred at 45 ° C and 1200 rpm for 15 min to obtain a slurry; (4) The slurry is injected into the mold, maintained at a pressure of 14.5 MPa for 20 min, and then sealed and cured for 24 h to obtain a slab; (5) Transfer the slab into an autoclave, heat it up to 180 °C at a rate of 10 °C / min, maintain the treatment for 9 h under a saturated steam pressure of 1.35 MPa, then reduce the pressure to atmospheric pressure at a rate of 0.5 MPa / h, and then dry it at 60 °C for 4 h, 85 °C for 6 h, 105 °C for 2 h, and cool it down to obtain a moisture-proof and durable calcium silicate board.

[0025] Example 3

[0026] (1) Add 15 g of sodium-based montmorillonite and 6 g of sodium 4-styrenesulfonate to 60 g of an ethanol / water mixed solution (volume ratio 3 - 5:1), ultrasonicate for 40 min, and then carry out ion exchange under reflux conditions at 90 °C for 7 h, centrifuge, wash, and vacuum dry to obtain intercalated montmorillonite; (2) Under nitrogen protection, add 15 g of intercalated montmorillonite to 200 g of toluene solution, ultrasonicate for 40 min, then add 6 g of sodium styrenesulfonate, 18 g of γ-methacryloyloxypropyltrimethoxysilane, and 3.6 g of perfluorooctylethyl acrylate, stir for 40 min, then add 0.5 g of benzoyl peroxide, and stir and react at 85 °C for 6 h, centrifuge, wash, and vacuum dry to obtain modified montmorillonite; (3) Mix 450 g of diatomaceous earth, 350 g of quicklime, 200 g of portland cement, 25 g of alkali-resistant glass fiber, and 15 g of modified montmorillonite and stir for 25 min, then add 350 g of deionized water, and stir at 50 °C at a speed of 1500 rpm for 20 min to obtain a slurry; (4) Inject the slurry into a mold, keep the pressure at 15 MPa for 25 min, and then seal and cure for 28 h to obtain a slab; (5) Transfer the slab into an autoclave, heat it up to 185 °C at a rate of 12 °C / min, maintain the treatment for 10 h under a saturated steam pressure of 1.5 MPa, then reduce the pressure to atmospheric pressure at a rate of 0.8 MPa / h, and then dry it at 65 °C for 5 h, 90 °C for 7 h, 110 °C for 3 h, and cool it down to obtain a moisture-proof and durable calcium silicate board.

[0027] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that: sodium styrenesulfonate was not added in step (2); The specific steps are as follows: (1) Add 10 g of sodium-based montmorillonite and 4.5 g of sodium 4-styrenesulfonate to 50 g of an ethanol / water mixed solution (volume ratio 4:1), ultrasonicate for 30 min, and then carry out ion exchange under reflux conditions at 85 °C for 6 h, centrifuge, wash, and vacuum dry to obtain intercalated montmorillonite; (2) Under nitrogen protection, 10 g of intercalated montmorillonite was added to 100 g of toluene solution, ultrasonicated for 30 min, then 12.4 g of γ-methacryloxypropyltrimethoxysilane and 2.6 g of perfluorooctylethyl acrylate were added, stirred for 30 min, and then 0.3 g of benzoyl peroxide was added. The mixture was stirred and reacted at 80 °C for 5 h, centrifuged, washed, and dried under vacuum to obtain modified montmorillonite; (3) 420 g of diatomite, 330 g of quicklime, 180 g of portland cement, 20 g of alkali-resistant glass fiber, and 10 g of modified montmorillonite were mixed and stirred for 20 min, then 330 g of deionized water was added, and the mixture was stirred at 45 °C at a speed of 1200 rpm for 15 min to obtain a slurry; (4) The slurry was poured into a mold, kept under pressure at 14.5 MPa for 20 min, and then sealed and cured for 24 h to obtain a slab; (5) The slab was transferred into an autoclave, heated to 180 °C at a rate of 10 °C / min, treated under a saturated steam pressure of 1.35 MPa for 9 h, then depressurized to atmospheric pressure at a rate of 0.5 MPa / h, and then dried at 60 °C for 4 h, 85 °C for 6 h, and 105 °C for 2 h, and then cooled to obtain calcium silicate board.

[0028] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that: γ-methacryloxypropyltrimethoxysilane was not added in step (2); The specific steps are as follows: (1) 10 g of sodium montmorillonite and 4.5 g of 4-styrenesulfonic acid sodium were added to 50 g of ethanol / water mixed solution (volume ratio 4:1), ultrasonicated for 30 min, and then ion-exchanged under reflux conditions at 85 °C for 6 h, centrifuged, washed, and dried under vacuum to obtain intercalated montmorillonite; (2) Under nitrogen protection, 10 g of intercalated montmorillonite was added to 100 g of toluene solution, ultrasonicated for 30 min, then 4.1 g of 4-styrenesulfonic acid sodium and 2.6 g of perfluorooctylethyl acrylate were added, stirred for 30 min, and then 0.3 g of benzoyl peroxide was added. The mixture was stirred and reacted at 80 °C for 5 h, centrifuged, washed, and dried under vacuum to obtain modified montmorillonite; (3) 420 g of diatomite, 330 g of quicklime, 180 g of portland cement, 20 g of alkali-resistant glass fiber, and 10 g of modified montmorillonite were mixed and stirred for 20 min, then 330 g of deionized water was added, and the mixture was stirred at 45 °C at a speed of 1200 rpm for 15 min to obtain a slurry; (4) The slurry was poured into a mold, kept under pressure at 14.5 MPa for 20 min, and then sealed and cured for 24 h to obtain a slab; (5) Transfer the slab into an autoclave, heat it up to 180 °C at a rate of 10 °C / min, maintain the treatment for 9 h under a saturated steam pressure of 1.35 MPa, then reduce the pressure to atmospheric pressure at a rate of 0.5 MPa / h, and then dry it at 60 °C for 4 h, 85 °C for 6 h, and 105 °C for 2 h, and then cool down to obtain calcium silicate board.

[0029] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that: in step (2), perfluorooctylethyl acrylate was not added; The specific steps are as follows: (1) Add 10 g of sodium montmorillonite and 4.5 g of sodium 4-styrenesulfonate to 50 g of ethanol / water mixed solution (volume ratio 4:1), ultrasonicate for 30 min, then carry out ion exchange under reflux at 85 °C for 6 h, centrifuge, wash, and vacuum dry to obtain intercalated montmorillonite; (2) Under nitrogen protection, add 10 g of intercalated montmorillonite to 100 g of toluene solution, ultrasonicate for 30 min, then add 4.1 g of sodium 4-styrenesulfonate and 12.4 g of γ-methacryloxypropyltrimethoxysilane, stir for 30 min, then add 0.3 g of benzoyl peroxide, and stir and react at 80 °C for 5 h, centrifuge, wash, and vacuum dry to obtain modified montmorillonite; (3) Mix 420 g of diatomite, 330 g of quicklime, 180 g of portland cement, 20 g of alkali-resistant glass fiber, and 10 g of modified montmorillonite and stir for 20 min, then add 330 g of deionized water, and stir at 45 °C at a speed of 1200 rpm for 15 min to obtain a slurry; (4) Inject the slurry into a mold, keep the pressure at 14.5 MPa for 20 min, and then seal and cure for 24 h to obtain a slab; (5) Transfer the slab into an autoclave, heat it up to 180 °C at a rate of 10 °C / min, maintain the treatment for 9 h under a saturated steam pressure of 1.35 MPa, then reduce the pressure to atmospheric pressure at a rate of 0.5 MPa / h, and then dry it at 60 °C for 4 h, 85 °C for 6 h, and 105 °C for 2 h, and then cool down to obtain calcium silicate board.

[0030] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that: the modified montmorillonite in step (3) is replaced with intercalated montmorillonite; The specific steps are as follows: (1) Add 10 g of sodium montmorillonite and 4.5 g of sodium 4-styrenesulfonate to 50 g of ethanol / water mixed solution (volume ratio 4:1), ultrasonicate for 30 min, then carry out ion exchange under reflux at 85 °C for 6 h, centrifuge, wash, and vacuum dry to obtain intercalated montmorillonite; (2) Mix 420 g of diatomite, 330 g of quicklime, 180 g of portland cement, 20 g of alkali-resistant glass fiber, and 10 g of intercalated montmorillonite and stir for 20 min. Then add 330 g of deionized water and stir at a speed of 1200 rpm for 15 min at 45°C to obtain a slurry. (3) Inject the slurry into a mold, hold the pressure at 14.5 MPa for 20 min, and then seal and cure for 24 h to obtain a slab. (4) Transfer the slab into an autoclave, heat it to 180°C at a rate of 10°C / min, maintain the saturated steam pressure at 1.35 MPa for 9 h, then reduce the pressure to atmospheric pressure at a rate of 0.5 MPa / h, and then dry at 60°C for 4 h, 85°C for 6 h, and 105°C for 2 h, and then cool down to obtain calcium silicate board.

[0031] Performance test: Flexural strength: According to the standard of JC / T 564.1-2018, use a WDW-100 type microcomputer-controlled electronic universal testing machine to conduct a three-point bending test. Set the span to 100 mm and the loading rate to 2 mm / min. Record the maximum load when the specimen breaks and calculate the flexural strength. The results are shown in Table 1. Water absorption determination: Dry the specimen in an oven at 105°C until it reaches a constant weight (m0), completely immerse it in deionized water at 25°C for 24 h, then take it out, wipe off the surface moisture with a wet cloth and weigh it immediately (m1). Calculate the water absorption according to W=(m1 - m0) / m0×100%. The results are shown in Table 1. Long-term immersion strength attenuation: According to the standard of JC / T 564.1-2018, completely immerse the specimen in deionized water at 25°C, take it out and test the flexural strength at 0 d, 30 d, 90 d, and 180 d respectively, and calculate the strength attenuation rate relative to that at 0 d. The results are shown in Table 1.

[0032] Table 1 Performance test results

[0033] Data analysis: From the data of Examples 1-3 in Table 1, it can be seen that the moisture-proof and durable calcium silicate board prepared by the present invention has excellent flexural strength, low water absorption rate, and small long-term immersion strength attenuation rate. This indicates that through the modification treatment of montmorillonite and reasonable component ratios, the mechanical properties and durability of calcium silicate board can be significantly improved. The introduction of modified montmorillonite may form a more uniform dispersion structure inside the material. At the same time, its surface activity and interfacial compatibility are enhanced, thus effectively improving the microstructure of calcium silicate board, reducing porosity and water absorption channels. In addition, the functional groups in modified montmorillonite may undergo chemical reactions or physical bonding with portland cement and other components, further improving the denseness and water resistance of the material. The synergistic effect of this structural optimization and interfacial enhancement enables the calcium silicate board to maintain a high strength and a low strength attenuation rate under long-term immersion environment, showing excellent moisture-proof and durable properties.

[0034] From the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that the introduction of sodium styrene sulfonate plays an important role in improving the performance of calcium silicate board through two-stage functionalization. This is mainly because in the ion exchange stage, the replacement of sulfonic acid groups with interlayer cations of montmorillonite not only expands the layer spacing but also provides active sites for subsequent polymerization reactions. In the toluene-phase reaction, sodium styrene sulfonate participates in grafting as a comonomer. Its rigid benzene ring structure enhances the steric hindrance effect of montmorillonite sheets, effectively preventing the re-stacking of sheets. At the same time, the sulfonic acid groups form coordination bonds with Ca 2+ in the hydration products of cement, constructing an ion crosslinking network at the matrix-reinforcement phase interface. This dual action mechanism not only improves the dispersion stability of montmorillonite but also enhances the interfacial bonding strength between the inorganic and organic phases through chemical bond bridging, thus significantly improving the resistance of the material to hydration erosion.

[0035] From the data of Example 2 and Comparative Example 2 in Table 1, it can be seen that the introduction of γ-methacryloxypropyltrimethoxysilane significantly improves the flexural strength and moisture-proof durability of calcium silicate board. This is mainly because γ-methacryloxypropyltrimethoxysilane forms a reactive organic transition layer on the surface of montmorillonite, which not only improves the compatibility between the inorganic and polymer phases but also provides heterogeneous nucleation sites for the hydration products of cement, and forms an interpenetrating network structure that penetrates the inorganic and organic phases, significantly enhancing the flexural strength and moisture-proof durability of the material.

[0036] From the data of Example 2 and Comparative Example 3 in Table 1, it can be seen that the introduction of perfluorooctylethyl acrylate plays an important role in improving the moisture-proof durability of calcium silicate board and has little effect on the flexural strength. This is because perfluorooctylethyl acrylate, as a fluorine-containing functional monomer, contains strongly hydrophobic perfluorinated chain segments in its molecular structure, which can significantly improve the water resistance.

[0037] From the data of Example 2 and Comparative Example 4 in Table 1, it can be seen that the use of modified montmorillonite has a significant effect on improving the performance of calcium silicate board. This is because compared with the unmodified intercalated montmorillonite, the modified montmorillonite has been significantly improved in terms of dispersibility, activity and interfacial compatibility. During the modification process, by introducing functional monomers and coupling agents, a stable organic-inorganic composite structure may be formed on the surface of montmorillonite, thus significantly improving its bonding force with the matrix material. This composite structure can not only form a denser microstructure inside the material, but also effectively reduce the porosity and water absorption channels, thus significantly reducing the water absorption rate of the material.

[0038] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A moisture-proof and durable calcium silicate board, characterized in that: The invention is prepared from the following raw materials by weight: 400-450 parts of diatomaceous earth, 300-350 parts of quicklime, 160-200 parts of silicate cement, 15-25 parts of alkali-resistant glass fiber, 5-15 parts of modified montmorillonite and 300-350 parts of deionized water; The preparation steps of the modified montmorillonite are as follows: S1: sodium montmorillonite and sodium 4-styrene sulfonate are added to an ethanol / water mixed solution, ultrasonicated for 20-40 minutes, then ion exchanged at 80-90°C reflux for 5-7 hours, centrifuged, washed, and vacuum dried to obtain intercalated montmorillonite; S2: Under nitrogen protection, add the intercalated montmorillonite to the toluene solution, ultrasonicate for 20-40 minutes, then add sodium styrene sulfonate, γ-methacryloxypropyltrimethoxysilane and perfluorooctylethyl acrylate, stir for 20-40 minutes, then add benzoyl peroxide, stir and react at 75-85°C for 4-6 hours, centrifuge, wash, and vacuum dry to obtain modified montmorillonite; In the step S1, the weight ratio of sodium montmorillonite, sodium styrene sulfonate and ethanol / water mixed solution is 5-15:3-6:40-60; In the step S2, the weight ratio of intercalated montmorillonite, toluene, sodium styrene sulfonate, γ-methacryloxypropyltrimethoxysilane, perfluorooctylethyl acrylate and benzoyl peroxide is 5-15:50-200:2-6:6-18:1.2-3.6:0.2-0.

5.

2. The moisture-proof and durable calcium silicate board according to claim 1, characterized in that: The silicon dioxide content of the diatomaceous earth is ≥85wt%.

3. The moisture-proof and durable calcium silicate board according to claim 1, characterized in that: The calcium oxide content in the quicklime is ≥89wt%.

4. The moisture-proof and durable calcium silicate board according to claim 1, characterized in that: The silicate cement is P·II52.

5.

5. The moisture-proof and durable calcium silicate board according to claim 1, characterized in that: The average length of the alkali-resistant glass fiber is 4-10 mm.

6. The moisture-proof and durable calcium silicate board according to claim 1, characterized in that: The volume ratio of the ethanol / water mixed solution in step S1 is 3-5:

1.

7. A method for preparing a moisture-proof and durable calcium silicate board according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Mix diatomaceous earth, quicklime, silicate cement, alkali-resistant glass fiber and modified montmorillonite and stir for 15-25 minutes, then add deionized water, and stir at 40-50°C and 1000-1500 rpm for 10-20 minutes to obtain a slurry; (2) Inject the slurry into the mold, maintain the pressure at 13-15 MPa for 15-25 minutes, and then seal and cure for 20-28 hours to obtain a slab; (3) The slab is transferred into an autoclave, heated to 175-185°C at a rate of 8-12°C / min, and treated at a saturated steam pressure of 1.2-1.5 MPa for 7-10 hours. The pressure is then reduced to normal pressure at a rate of 0.2-0.8 MPa / h, and dried to obtain a moisture-proof and durable calcium silicate board.

8. The method for preparing the moisture-proof and durable calcium silicate board according to claim 7, characterized in that: The drying step in step (3) is as follows: drying at 55-65°C for 3-5h, drying at 80-90°C for 5-7h, drying at 100-110°C for 1-3h, and cooling.

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