A magnesium silicate composite board and a preparation method thereof

Abstract

The application discloses a magnesium silicate composite board and a preparation method thereof, and relates to the technical field of fireproof boards. The magnesium silicate composite board comprises the following raw materials in mass fractions: 10-40 parts of light-burned magnesium oxide, 2-6 parts of magnesium carbonate, 10-20 parts of calcined coal gangue powder, 5-30 parts of finely ground power plant furnace bottom slag, 20-30 parts of granulated blast furnace slag powder, 20-40 parts of limestone powder, 15-25 parts of water, 2.2-11 parts of reinforcing fiber and 0.01-0.5 parts of sodium phosphate. The magnesium silicate composite board is prepared by using the finely ground power plant furnace bottom slag and the granulated blast furnace slag powder to replace silica fume as a silicon source, so that the production cost is low, the preparation process is less harmful to human bodies, the prepared magnesium silicate composite board has the advantages of small dry shrinkage, strong anti-deformation capacity and good durability, and the problems of large dry shrinkage, easy deformation, poor durability and high production cost of the current magnesium silicate cement fireproof board are solved.

Description

Technical Field

[0001] This invention relates to the field of fireproof board technology, specifically to a magnesium silicate composite board and its preparation method. Background Technology

[0002] Magnesium silicate cement fireproof boards are fireproof boards made from magnesium silicate cement, and are an important decorative and functional composite material. Magnesium silicate cement is a low-alkali, high-strength, low-carbon, and highly water-resistant hydraulic cementitious material, usually prepared from active magnesium oxide and highly active siliceous raw materials.

[0003] Silica fume is a commonly used highly reactive siliceous raw material in the preparation of magnesium silicate cement. Although silica fume has high reactivity, its high price and limited availability lead to high production costs for magnesium silicate cement fireproof boards. Furthermore, the formation of magnesium silicate cement is limited by the reaction rate between magnesium oxide and siliceous raw materials. To increase the reaction rate, a large amount of silica fume with a high specific surface area is usually required in the formulation. The high proportion of silica fume in the formulation results in a large water requirement during the preparation of magnesium silicate cement fireproof boards, leading to significant shrinkage, easy deformation, and poor durability. Moreover, the silica fume used in traditional magnesium silicate cement fireproof boards is typically nano-sized, with extremely fine particles. The fine powder generated during the micro-reaction process in fireproof board production is harmful to human health. Therefore, these unfavorable factors limit the promotion and application of magnesium silicate cement fireproof boards. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to propose a magnesium silicate composite board, which uses finely ground power plant bottom slag and granulated blast furnace slag powder instead of silica fume as the silicon source to prepare the magnesium silicate composite board. This not only has low production cost and minimal harm to the human body during the preparation process, but also the magnesium silicate composite board obtained has the advantages of high shrinkage, strong resistance to deformation and good durability. This solves the problems of high shrinkage, easy deformation, poor durability and high production cost of current magnesium silicate cement fireproof boards.

[0005] Another objective of this invention is to provide a method for preparing a magnesium silicate composite board, which is used to prepare the aforementioned magnesium silicate composite board.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A magnesium silicate composite board comprises the following raw materials in parts by weight: 10-40 parts of lightly calcined magnesium oxide, 2-6 parts of magnesium carbonate, 10-20 parts of calcined coal gangue powder, 5-30 parts of finely ground power plant bottom slag, 20-30 parts of granulated blast furnace slag powder, 20-40 parts of limestone powder, 15-25 parts of water, 2.2-11 parts of reinforcing fiber, and 0.01-0.5 parts of sodium phosphate;

[0008] The particle size of the ground power plant bottom ash is 3-13 μm, and the median particle size of the ground power plant bottom ash is less than 5 μm.

[0009] The median particle size of the granulated blast furnace slag powder is 10–15 μm.

[0010] Preferably, the content of active magnesium oxide in the lightly calcined magnesium oxide is greater than 85% by mass percentage;

[0011] The fineness of the lightly calcined magnesium oxide is 325 mesh to 600 mesh.

[0012] Preferably, the total content of silica, alumina and iron oxide in the ground power plant bottom slag is >60% by mass percentage.

[0013] Preferably, the magnesium carbonate has a fineness of 325 mesh to 600 mesh, and the limestone powder has a fineness of 325 mesh to 2000 mesh.

[0014] Preferably, the reinforcing fibers, calculated by mass parts, comprise 2 to 6 parts of glass fiber mesh, 0.1 to 3 parts of calcium sulfate whiskers, and 0.1 to 2 parts of polypropylene fibers.

[0015] Preferably, the aspect ratio of the calcium sulfate whiskers is 30 to 60; the diameter of the polypropylene fiber is 30 to 50 μm and the length is 8 to 15 mm.

[0016] Preferably, the raw materials of the magnesium silicate composite board, calculated by mass parts, further include 2-6 parts of water-soluble resin, 120-180 parts of calcite sand, and 0.5-2 parts of polycarboxylate superplasticizer.

[0017] Preferably, the water-soluble resin includes any one or more combinations of polyvinyl alcohol, styrene-butadiene emulsion, polyacrylic acid emulsion, and polyurethane resin.

[0018] A method for preparing a magnesium silicate composite board, comprising the following steps: mixing lightly calcined magnesium oxide, magnesium carbonate, finely ground power plant bottom slag, granulated blast furnace slag powder, and calcined coal gangue powder evenly according to the specified ratio, adding water and reinforcing fibers for further mixing, placing the mixture in a mold, molding it under vacuum vibration and pressure, demolding it, and then curing it to obtain the magnesium silicate composite board.

[0019] Preferably, it includes the following steps:

[0020] (1) Weigh each raw material according to the proportion, dry mix the light calcined magnesium oxide, magnesium carbonate, ground power plant bottom slag, granulated blast furnace slag powder, calcined coal gangue powder, limestone powder and calcite sand evenly, and use a planetary mixer to mix evenly to obtain dry mix.

[0021] (2) Dissolve polycarboxylate superplasticizer, sodium phosphate and water-soluble resin in water, and add the dry mixture from step (1) into the solution in two batches, then gradually add calcium sulfate whiskers and polypropylene fibers, stir, and after stirring evenly, obtain a mixed slurry.

[0022] (3) Immerse the glass fiber mesh in the mixed slurry to obtain the composite material;

[0023] (4) Place the composite material in a steel mold, and then place the steel mold containing the composite material in a vibratory press with a vacuum function to apply pressure for molding. The vacuum degree in the mold cavity of the vibratory press shall not exceed 700 Pa, the vibration frequency shall be 20-60 Hz, and the pressure shall not be less than 100 N / mm². 2 The pressurization time shall not be less than 30 seconds;

[0024] (5) After demolding the molded board, place it in the curing room for curing to obtain magnesium silicate composite board; the temperature is controlled at 60℃~90℃, the ambient humidity is not lower than 95rh, and the curing time is 4~12h.

[0025] The technical solution provided in this application embodiment can include the following beneficial effects: The magnesium silicate composite board of this technical solution uses lightly calcined magnesium oxide, finely ground power plant bottom slag, granulated blast furnace slag powder and limestone powder as raw materials to prepare magnesium silicate cementitious materials, and fiber-reinforced magnesium silicate composite boards are prepared by adding reinforcing fibers. The resulting magnesium silicate composite board has the characteristics of being lightweight and high-strength, having strong resistance to deformation, high fire resistance and flame retardancy, good durability and good water resistance. As a result, the resulting magnesium silicate composite board is not easily deformed and has a longer service life, which expands the application prospects of magnesium silicate-based cement fireproof boards and solves the problems of easy deformation and poor durability of existing magnesium silicate cement fireproof boards. At the same time, based on the effective utilization of solid waste, it significantly improves the problems of poor water resistance, easy deformation and warping that are common in fireproof boards prepared with magnesium oxychloride and magnesium oxysulfide cement as cementitious materials. Furthermore, the magnesium silicate composite board of this technical solution uses finely ground power plant bottom slag and granulated blast furnace slag powder as siliceous raw materials, replacing the traditionally used siliceous raw material - silica fume. Finely ground power plant bottom slag and granulated blast furnace slag powder are both industrial solid wastes, which are inexpensive and can effectively reduce the production cost of magnesium silicate composite boards. Moreover, it can effectively utilize solid waste and has high potential application value in the field of fireproof boards. Detailed Implementation

[0026] To facilitate understanding of the present invention, a more complete description is provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0027] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0030] A magnesium silicate composite board comprises the following raw materials in parts by weight: 10-40 parts of lightly calcined magnesium oxide, 2-6 parts of magnesium carbonate, 10-20 parts of calcined coal gangue powder, 5-30 parts of finely ground power plant bottom slag, 20-30 parts of granulated blast furnace slag powder, 20-40 parts of limestone powder, 15-25 parts of water, 2.2-11 parts of reinforcing fiber, and 0.01-0.5 parts of sodium phosphate;

[0031] The particle size of the ground power plant bottom ash is 3-13 μm, and the median particle size of the ground power plant bottom ash is less than 5 μm.

[0032] The median particle size of the granulated blast furnace slag powder is 10–15 μm.

[0033] This technical solution utilizes lightly calcined magnesium oxide, finely ground power plant bottom slag, granulated blast furnace slag powder, and limestone powder as raw materials to prepare magnesium silicate cementitious materials. Fiber-reinforced magnesium silicate composite boards are then prepared by adding reinforcing fibers. This results in magnesium silicate composite boards that are lightweight and high-strength, with strong resistance to deformation, high fire retardancy, good durability, and good water resistance. Consequently, the resulting magnesium silicate composite boards are less prone to deformation and have a longer service life, expanding the application prospects of magnesium silicate-based cement fireproof boards. This solution addresses the problems of easy deformation and poor durability in existing magnesium silicate cement fireproof boards. Furthermore, by effectively utilizing solid waste, it significantly improves upon the common problems of poor water resistance, easy deformation, and warping found in fireproof boards prepared using magnesium oxychloride and magnesium oxysulfide cement as cementing materials. Furthermore, the magnesium silicate composite board of this technical solution uses finely ground power plant bottom slag and granulated blast furnace slag powder as siliceous raw materials, replacing the traditionally used siliceous raw material - silica fume. Finely ground power plant bottom slag and granulated blast furnace slag powder are both industrial solid wastes, which are inexpensive and can effectively reduce the production cost of magnesium silicate composite boards. Moreover, it can effectively utilize solid waste and has high potential application value in the field of fireproof boards.

[0034] Further explanation: This technical solution uses finely ground power plant bottom slag and granulated blast furnace slag powder instead of silica fume as the silicon source to prepare magnesium silicate cement. By reasonably adjusting the particle size distribution, the water requirement during board preparation is reduced to only 15-25 parts, thereby reducing drying shrinkage, making the boards less prone to deformation, and improving durability. Specifically, finely ground power plant bottom slag is a glassy substance with a high silicon content. After grinding, its surface has many broken bonds, resulting in high reactivity. Granulated blast furnace slag powder is a high-calcium glassy substance with high reactivity. The combination of the two optimizes the silicon-to-magnesium ratio, yielding more magnesium silicate product, thus resulting in magnesium silicate composite boards with better performance. Furthermore, in this technical solution, the particle size distribution of the ground power plant bottom ash is 3-13 μm, with a median particle size of less than 5 μm, and the median particle size of the granulated blast furnace slag powder is 10-15 μm. Compared with the traditional magnesium silicate-based cement fireproof board which uses nano-sized silica fume, this technical solution uses a combination of finer ground power plant bottom ash and slightly coarser granulated blast furnace slag powder, which can achieve dense particle packing, thereby reducing water demand and shrinkage. Macroscopically, it can maintain the flowability of the slurry under low water-ash ratio conditions. At the same time, since the magnesium silicate composite board of this technical solution does not require the use of nano-sized silica fume, the harm of fine powder to the human body during the production of composite boards can be reduced.

[0035] It is worth noting that this technical solution adds 10-40 parts of light-burned magnesium oxide, 2-6 parts of magnesium carbonate, 5-30 parts of ground power plant bottom slag, 20-30 parts of granulated blast furnace slag powder, and 10-20 parts of calcined coal gangue powder to the raw materials. With the assistance of phosphate (sodium phosphate), these raw materials react with light-burned magnesium oxide to produce aluminum magnesium hydrotalcite, magnesium hydroxide, and basic magnesium carbonate. The decomposition temperatures of aluminum magnesium hydrotalcite, magnesium hydroxide, and basic magnesium carbonate cover approximately 240℃-300℃, 360-420℃, and 550℃-600℃, respectively. The decomposition of aluminum magnesium hydrotalcite and magnesium hydroxide releases water vapor, while the decomposition of basic magnesium carbonate releases carbon dioxide. This gives the magnesium silicate composite board produced by this technical solution a strong fire-retardant effect. Meanwhile, the hydration of lightly burned magnesium oxide to form magnesium hydroxide causes volume expansion, which has shrinkage compensation ability and can further reduce the drying shrinkage of magnesium silicate composite boards.

[0036] Specifically, granulated blast furnace slag powder (hereinafter referred to as slag powder) is a powder made from granulated blast furnace slag through drying and grinding to achieve a sufficiently fine particle size and meet a suitable activity index. Granulated blast furnace slag powder is a standard industrial product and can be purchased commercially. Preferably, this technical solution uses granulated blast furnace slag powder of grade S95 or higher, which can ensure reactivity and product performance, and has the characteristics of fine particle size, suitable specific area, early strength and rapid hardening, freeze resistance, wear resistance and corrosion resistance.

[0037] Specifically, the finely ground coal-fired power plant bottom ash in this technical solution is also called finely ground coal-fired power plant bottom ash. It is a type of coal ash discharged from the bottom of the pulverized coal furnace in a coal-fired power plant, and its main components are silicon dioxide, alumina, iron oxide, and calcium oxide. The finely ground coal-fired power plant bottom ash in this technical solution is purchased from the market.

[0038] Specifically, the calcined coal gangue powder in this technical solution is selected from calcined high-alumina coal gangue powder. This powder is obtained by calcining high-alumina coal gangue containing boehmite at 600℃~700℃ for 30~50 minutes, followed by fine grinding. Its main components are Al2O3 (specifically γ-Al2O3) and SiO2. The Al2O3 in the calcined coal gangue powder can react with the Mg element in the formulation system to form magnesium aluminum hydrotalcite, which has flame-retardant properties. Furthermore, the active SiO2 contained in the calcined coal gangue powder can also react with the Mg element to form hydrated magnesium silicate, increasing the strength and durability of the slab. Specifically, the calcined high-alumina coal gangue powder in this technical solution is purchased commercially.

[0039] Specifically, light-calcined magnesia is produced by calcining magnesite, brucite, and magnesium hydroxide extracted from seawater or brine to decompose and release CO2 or H2O. Light-calcined magnesia is also known as light-calcined magnesia powder or simply magnesia powder. Light-calcined magnesia has a porous texture and high chemical reactivity. The light-calcined magnesia used in this technical solution is commercially available.

[0040] To further clarify, the content of active magnesium oxide in the lightly calcined magnesium oxide is greater than 85% by mass percentage;

[0041] The fineness of the lightly calcined magnesium oxide is 325 mesh to 600 mesh.

[0042] It should be noted that in the production process of magnesium silicate composite boards, only active magnesium oxide participates in the reaction; inactive magnesium oxide does not. This technical solution controls the silicon / magnesium ratio in the raw materials by controlling the active magnesium oxide content in the light-burned magnesium oxide, thereby improving the performance of the magnesium silicate composite boards. If the active magnesium oxide content in the light-burned magnesium oxide is less than 85%, it will result in a lower amount of magnesium silicate cement produced, leading to a lower strength in the resulting magnesium silicate composite boards. Furthermore, by controlling the fineness of the light-burned magnesium oxide to 325-600 mesh, this technical solution can further control the reactivity of the light-burned magnesium oxide, further enhancing the strength of the magnesium silicate composite boards.

[0043] To further clarify, the total content of silica, alumina, and iron oxide in the ground power plant bottom slag is >60% by mass percentage.

[0044] Specifically, the ground coal-fired power plant bottom ash in this technical solution is also called ground coal-fired power plant bottom ash. It is a type of coal slag discharged from the bottom of the pulverized coal furnace in a coal-fired power plant, and its main components are silica, alumina, iron oxide, and calcium oxide. Preferably, this technical solution uses a total content of silica, alumina, and iron oxide > 60%. The oxide content of the ground coal-fired power plant bottom ash determines the reactivity of the glassy particles within it; the higher the oxide content, the higher the reactivity of the glassy particles. Meanwhile, since finer particle size of the ground coal-fired power plant bottom ash results in higher reactivity, but also higher water demand, this technical solution uses ground coal-fired power plant bottom ash that has been ball-milled to a particle size distribution of 3–13 μm, with a median particle size of less than 5 μm. This results in high reactivity of the ground coal-fired power plant bottom ash while maintaining relatively low water demand.

[0045] In one embodiment of the present invention, the chemical composition of the ground power plant bottom slag used includes 52% SiO2, 6.5% Al2O3, 3.6% Fe2O3, and 9.5% CaO.

[0046] To further clarify, the magnesium carbonate has a fineness of 325-600 mesh, and the limestone powder has a fineness of 325-2000 mesh. By controlling the fineness of the magnesium carbonate to 325-600 mesh and the fineness of the limestone powder to 325-2000 mesh, the porosity of the composite board can be further reduced, thereby improving the strength and durability of the composite board.

[0047] Specifically, the magnesium carbonate added to the magnesium silicate composite board formulation system in this technical solution is magnesium carbonate powder, and the magnesium carbonate content in the magnesium carbonate powder is >90% (calculated by mass percentage).

[0048] Further explanation: Calculated by mass parts, the reinforcing fibers include 2-6 parts of glass fiber mesh, 0.1-3 parts of calcium sulfate whiskers, and 0.1-2 parts of polypropylene fibers.

[0049] This technical solution utilizes glass fiber mesh, calcium sulfate whiskers, and polypropylene fibers as reinforcing materials to prepare fiber-reinforced magnesium silicate-based fireproof boards, effectively improving the strength and toughness of the magnesium silicate composite boards. Because the formulation system of this magnesium silicate composite board is based on magnesium silicate cementitious material, which is a low-alkali cement, the low-alkali system has minimal corrosive effect on glass fibers, significantly enhancing the durability of the magnesium silicate composite board.

[0050] Specifically, the glass fiber mesh in this technical solution is a glass fiber mesh fabric, which is made of low-alkali glass fiber as the main material, through weaving, coating, and surface modification treatment with silane coupling agent. The tensile strength of the glass fiber mesh fabric is greater than 1500 N / 50 mm. By adding glass fiber mesh fabric to the magnesium silicate composite board, the strength and toughness of the magnesium silicate composite board can be effectively improved.

[0051] Further explanation: the aspect ratio of the calcium sulfate whiskers is 30 to 60; the diameter of the polypropylene fiber is 30 to 50 μm and the length is 8 to 15 mm.

[0052] Specifically, this technical solution uses calcium sulfate whiskers with an aspect ratio of 30 to 60 and polypropylene fibers with a diameter of 30 to 50 μm and a length of 8 to 15 mm (i.e., the aspect ratio of polypropylene fibers is 160 to 500), which is beneficial to increase the flexural strength of magnesium silicate composite boards. If the aspect ratio of calcium sulfate whiskers and polypropylene fibers exceeds the specified range, the reinforcing effect will decrease.

[0053] Preferably, this technical solution uses calcium sulfate whiskers with a diameter of 2-3 micrometers and polypropylene fibers with a diameter of 30-50 μm, a length of 8 mm-15 mm, and a tensile strength >600 MPa.

[0054] Further explanation: Based on mass percentages, the raw materials for the magnesium silicate composite board also include 2-6 parts water-soluble resin, 120-180 parts calcite sand, and 0.5-2 parts polycarboxylate superplasticizer. The water-soluble resin acts as a toughening agent in the formulation system, while the calcite sand, as aggregate, improves strength and reduces shrinkage. The addition of the polycarboxylate superplasticizer allows for the preparation of low water-cement ratio mortar, thereby improving the durability and strength of the composite board.

[0055] Further explanation: the water-soluble resin includes any one or more combinations of polyvinyl alcohol, styrene-butadiene emulsion, polyacrylic acid emulsion, and polyurethane resin.

[0056] A method for preparing a magnesium silicate composite board, comprising the following steps: mixing lightly calcined magnesium oxide, magnesium carbonate, finely ground power plant bottom slag, granulated blast furnace slag powder, and calcined coal gangue powder evenly according to the specified ratio, adding water and reinforcing fibers for further mixing, placing the mixture in a mold, molding it under vacuum vibration and pressure, demolding it, and then curing it to obtain the magnesium silicate composite board.

[0057] Further explanation includes the following steps:

[0058] (1) Weigh each raw material according to the proportion, dry mix the light calcined magnesium oxide, magnesium carbonate, ground power plant bottom slag, granulated blast furnace slag powder, calcined coal gangue powder, limestone powder and calcite sand evenly, and use a planetary mixer to mix evenly to obtain dry mix.

[0059] (2) Dissolve polycarboxylate superplasticizer, sodium phosphate and water-soluble resin in water, and add the dry mixture from step (1) into the solution in two batches, then gradually add calcium sulfate whiskers and polypropylene fibers, stir, and after stirring evenly, obtain a mixed slurry.

[0060] (3) Immerse the glass fiber mesh in the mixed slurry to obtain the composite material;

[0061] (4) Place the composite material in a steel mold, and place the steel mold containing the composite material in a vibratory press with a vacuum function for pressing. The vacuum degree in the mold cavity (i.e., the cavity used to place the mold) of the vibratory press is not greater than 700 Pa, the vibration frequency is 20-60 Hz, and the pressure is not less than 100 N / mm². 2 The pressurization time should be no less than 30 seconds. By controlling the vacuum level, vibration frequency, pressurization pressure and pressurization time, the density of magnesium silicate composite boards can be improved and the mechanical properties of the products can be increased.

[0062] (5) After demolding the molded board, place it in a curing room for curing to obtain magnesium silicate composite board; during the curing process, the temperature is controlled at 60℃~90℃, the ambient humidity is not lower than 95% h, and the curing time is 4~12h. By controlling the temperature and ambient humidity during the curing process, not only can the curing cycle be shortened, but the mechanical properties of magnesium silicate composite board can also be improved and the water absorption rate of magnesium silicate composite board can be reduced.

[0063] It is worth noting that this technical solution uses glass fiber mesh, calcium sulfate whiskers, and polypropylene fibers to reinforce magnesium silicate cement materials. Vacuum, vibration, and pressure molding processes are employed to improve the density of the board and obtain high-strength magnesium silicate. This technical solution uses lightly calcined magnesium oxide and industrial waste to replace silica fume in the preparation of magnesium silicate cementitious materials. Through precise combination of waste residue types, aluminum-magnesium hydrotalcite with ideal fire-resistant properties is generated. Furthermore, by combining glass fiber mesh, calcium sulfate whiskers, and polypropylene fibers, a high-strength, high-toughness, fire-resistant, and decorative integrated board is prepared. This effectively solves the problems of current fire-resistant boards being prone to deformation, warping, cracking, and poor weather resistance, effectively expanding the application scenarios of decorative fire-resistant integrated boards.

[0064] The technical solution of the present invention will be further described below with reference to the embodiments.

[0065] Examples 1-5

[0066] The magnesium silicate composite boards of Examples 1-5 are composed of the following raw materials in parts by weight: 10-40 parts of lightly calcined magnesium oxide, 2-6 parts of magnesium carbonate, 10-20 parts of calcined coal gangue powder, 5-30 parts of finely ground power plant bottom slag, 20-30 parts of granulated blast furnace slag powder, 20-40 parts of limestone powder, 15-25 parts of water, 2.2-11 parts of reinforcing fiber, 0.01-0.5 parts of sodium phosphate, 2-6 parts of water-soluble resin, 120-180 parts of calcite sand, and 0.5-2 parts of polycarboxylate superplasticizer; wherein, the reinforcing fiber includes 2-6 parts of glass fiber mesh, 0.1-3 parts of calcium sulfate whiskers, and 0.1-2 parts of polypropylene fiber; specifically, the formulations of the magnesium silicate composite boards of Examples 1-5 are shown in Table 1 below.

[0067] In the magnesium silicate composite plates of Examples 1-5, the particle size of the ground power plant bottom slag used was 3-13 μm, with a median particle size of 4.5 μm; the median particle size of the granulated blast furnace slag powder was 15 μm; the total content of silica, alumina, and iron oxide in the ground power plant bottom slag was 62.1%; the active magnesium oxide content in the light-burned magnesium oxide was 90%, and the fineness of the light-burned magnesium oxide was 325 mesh to 600 mesh (the light-burned magnesium oxide was first sieved using a 325 mesh sieve). Magnesium oxide is sieved, and the undersize is collected. The undersize is then passed through a 600-mesh sieve, and the oversize is collected. The oversize obtained is lightly calcined magnesium oxide with a fineness of 325-600 mesh (the same applies below). The fineness of magnesium carbonate is 325-600 mesh, and the fineness of limestone powder is 325-2000 mesh. The diameter of calcium sulfate whiskers is 2-3 micrometers, and the aspect ratio is 30-60. The diameter of polypropylene fibers is 30-50 μm, and the length is 8-15 mm.

[0068] In Example 1, the water-soluble resin used was polyvinyl alcohol; in Example 2, the water-soluble resin used was styrene-butadiene emulsion; in Example 3, the water-soluble resin used was polyacrylic acid emulsion; in Example 4, the water-soluble resin used was polyurethane resin; and in Example 5, the water-soluble resin used was polyacrylic acid emulsion.

[0069] Table 1 Formulations of Magnesium Silicate Composite Boards in Examples 1-5

[0070]

[0071] The preparation methods for the magnesium silicate composite boards in Examples 1-5 are the same, and the preparation methods include the following steps:

[0072] (1) Weigh each raw material according to the proportion, dry mix the light calcined magnesium oxide, magnesium carbonate, finely ground power plant bottom slag, granulated blast furnace slag powder, calcined coal gangue powder, limestone powder and calcite sand evenly, and use a planetary mixer to mix evenly to obtain dry mix.

[0073] (2) Dissolve polycarboxylate superplasticizer, sodium phosphate and water-soluble resin in water, and add the dry mixture from step (1) into the solution in two batches, then gradually add calcium sulfate whiskers and polypropylene fibers, stir, and after stirring evenly, obtain a mixed slurry.

[0074] (3) Immerse the glass fiber mesh in the mixed slurry to obtain the composite material;

[0075] (4) Place the composite material in a steel mold, and then place the steel mold containing the composite material in a vibratory press with a vacuum function to apply pressure. The vacuum degree in the mold cavity (i.e., the cavity used to place the mold) of the vibratory press is 600 Pa, the vibration frequency is 40 Hz, and the pressure is 120 N / mm². 2The pressurization time is 50 seconds;

[0076] (5) After demolding the molded board, place it in the curing room for curing to obtain magnesium silicate composite board; the temperature is controlled at 80℃, the ambient humidity is 100rh, and the curing time is 12h.

[0077] Specifically, the magnesium silicate composite boards prepared in Examples 1-5 were subjected to performance testing, and the test results are shown in Tables 2 and 3 below.

[0078] Table 2 Performance testing of magnesium silicate composite panels in Examples 1-5 (Part 1)

[0079]

[0080] Table 3 Performance testing of magnesium silicate composite panels in Examples 1-5 (Part 2)

[0081] Example Freeze resistance / weather resistance Fireproof and flame retardant 1 After 25 freeze-thaw cycles, there was no cracking or delamination, and the flexural strength ratio was 97.5%. Non-flammable Class A 2 After 25 freeze-thaw cycles, there was no cracking or delamination, and the flexural strength ratio was 96.3%. Non-flammable Class A 3 After 25 freeze-thaw cycles, there was no cracking or delamination, and the flexural strength ratio was 97.8%. Non-flammable Class A 4 After 25 freeze-thaw cycles, no cracking or delamination occurred, and the flexural strength ratio was 96.8%. Non-flammable Class A 5 After 25 freeze-thaw cycles, there was no cracking or delamination, and the flexural strength ratio was 97.0%. Non-flammable Class A Test Standards GB / T7019-2014 GB8624

[0082] As shown in Tables 1 and 2, the magnesium silicate composite boards prepared in Examples 1-5 all exhibit very low shrinkage rates, ranging from 0.03% to 0.07%. Furthermore, the flexural strength of these boards reaches 21-27 MPa, and the compressive strength reaches 116-127 MPa, demonstrating strong resistance to deformation. Additionally, none of the magnesium silicate composite boards prepared in Examples 1-5 showed cracking or delamination after 25 freeze-thaw cycles, and the flexural strength ratio remained above 96%, indicating good weather resistance. The fire retardant test results in Table 2 show that the magnesium silicate composite boards prepared in Examples 1-5 have high fire retardant ratings.

[0083] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A magnesium silicate composite board, characterized in that, The raw materials include the following parts by weight: 10-40 parts of lightly calcined magnesia, 2-6 parts of magnesium carbonate, 10-20 parts of calcined coal gangue powder, 5-30 parts of finely ground power plant bottom slag, 20-30 parts of granulated blast furnace slag powder, 20-40 parts of limestone powder, 15-25 parts of water, 2.2-11 parts of reinforcing fiber, and 0.01-0.5 parts of sodium phosphate, and the raw materials do not contain silica fume; The particle size of the ground power plant bottom ash is 3~13μm, and the median particle size of the ground power plant bottom ash is less than 5μm. The median particle size of the granulated blast furnace slag powder is 10~15μm; The reinforcing fibers, calculated by weight, comprise 2-6 parts glass fiber mesh, 0.1-3 parts calcium sulfate whiskers, and 0.1-2 parts polypropylene fibers.

2. The magnesium silicate composite board according to claim 1, characterized in that, The content of active magnesium oxide in the lightly calcined magnesium oxide is greater than 85% by mass percentage; The fineness of the lightly calcined magnesium oxide is 325 mesh to 600 mesh.

3. The magnesium silicate composite board according to claim 1, characterized in that, The total content of silica, alumina and iron oxide in the ground power plant bottom slag is >60% by mass percentage.

4. The magnesium silicate composite board according to claim 1, characterized in that, The magnesium carbonate has a fineness of 325 mesh to 600 mesh, and the limestone powder has a fineness of 325 mesh to 2000 mesh.

5. The magnesium silicate composite board according to claim 1, characterized in that, The calcium sulfate whiskers have an aspect ratio of 30 to 60; the polypropylene fibers have a diameter of 30 to 50 μm and a length of 8 to 15 mm.

6. The magnesium silicate composite board according to claim 1, characterized in that, The raw materials for the magnesium silicate composite board, calculated by mass, also include 2-6 parts of water-soluble resin, 120-180 parts of calcite sand, and 0.5-2 parts of polycarboxylate superplasticizer.

7. The magnesium silicate composite board according to claim 6, characterized in that, The water-soluble resin includes any one or more combinations of polyvinyl alcohol, styrene-butadiene emulsion, polyacrylic acid emulsion, and polyurethane resin.

8. A method for preparing a magnesium silicate composite board, characterized in that, The method for preparing the magnesium silicate composite board according to any one of claims 1 to 7 includes the following steps: after mixing lightly calcined magnesium oxide, magnesium carbonate, finely ground power plant bottom slag, granulated blast furnace slag powder, and calcined coal gangue powder evenly according to the formula, water and reinforcing fibers are added and further mixed evenly, and then the mixture is placed in a mold, formed by vacuum vibration and pressure, demolded and cured to obtain the magnesium silicate composite board.

9. The method for preparing the magnesium silicate composite board according to claim 8, characterized in that, Includes the following steps: (1) After weighing each raw material according to the proportion, dry mix the lightly calcined magnesium oxide, magnesium carbonate, finely ground power plant bottom slag, granulated blast furnace slag powder, calcined coal gangue powder, limestone powder and calcite sand evenly, and use a planetary mixer to mix evenly to obtain dry mix. (2) Dissolve polycarboxylate superplasticizer, sodium phosphate and water-soluble resin in water, and add the dry mixture from step (1) into the solution in two batches, then gradually add calcium sulfate whiskers and polypropylene fibers, stir, and after stirring evenly, obtain a mixed slurry. (3) Immerse the glass fiber mesh in the mixed slurry to obtain the composite material; (4) Place the composite material in a steel mold, and place the steel mold containing the composite material in a vibratory press with a vacuum function to apply pressure for molding. The vacuum degree in the mold cavity of the vibratory press shall not exceed 700 Pa, the vibration frequency shall be 20~60 Hz, and the pressure shall not be less than 100 N / mm. 2 The pressurization time shall not be less than 30 seconds; (5) After demolding the molded board, place it in the curing room for curing to obtain magnesium silicate composite board; the temperature is controlled at 60℃~90℃, the ambient humidity is not lower than 95%RH, and the curing time is 4~12h.

Images