A multi-layer structure magnesium-based light composite board and a preparation method thereof

Abstract

This invention discloses a multi-layered magnesium-based lightweight composite board and its preparation method. The composite board comprises a slurry layer, a reinforcing layer, and a lightweight layer, and is obtained through a multi-layered structure of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer. The reinforcing layer is a glass fiber mesh. The slurry layer is obtained by stirring a magnesium chloride solution and mixture A. The lightweight layer slurry is obtained by stirring a magnesium chloride solution, mixture B, and a foaming agent. The magnesium chloride solution is prepared by mixing magnesium chloride, citric acid, and water. Mixture A is obtained by dry-mixing bamboo fiber, lightly calcined magnesium oxide, and a thickener. Mixture B is obtained by dry-mixing bamboo fiber, lightly calcined magnesium oxide, a thickener, a foam stabilizer, an activator, and a foaming agent. Compared to ordinary lightweight composite boards, the lightweight composite board of this invention exhibits significantly enhanced flexural strength and possesses properties such as being environmentally friendly, lightweight, non-combustible, and energy-efficient, thus expanding the application of magnesium-based cement composite boards.

Description

Technical Field

[0001] This invention relates to the field of composite materials and environmentally friendly building materials, specifically to a multi-layered magnesium-based lightweight composite board and its preparation method. Background Technology

[0002] To improve building energy efficiency, reduce building energy consumption, and alleviate the load on roof beams and columns, lightweight building composite materials have emerged. In existing technologies, the preparation of lightweight composite materials typically involves adding foaming agents or mixing polystyrene foam, polyurethane foam, expanded perlite, etc., with cementitious materials. However, lightweight materials produced using this technology have low strength and are prone to cracking and collapse.

[0003] Magnesium cement is an air-hardening cementitious material. Due to its high strength, fast setting speed, and excellent flame retardant properties, it has become a widely used new building material in industries such as building materials, coatings, mining, and decoration. However, magnesium cement products have a relatively high density, typically 1.6–1.8 g / cm³. 3 It is not suitable for furniture-related applications. When using it for wall panels or ceilings, its weight and moisture absorption need to be considered. Moreover, its high density will increase the difficulty of transporting and installing the panels.

[0004] Chinese patent CN114656220A discloses a high-strength foamed cement lightweight soil and its preparation method. The method involves first mixing a mixture of cement, admixtures, and iron powder with a sodium alginate solution, then adding an aqueous solution of hydrogen peroxide, a foam stabilizer, and a water-reducing agent to prepare a foamed cement lightweight soil slurry. This slurry is then molded to obtain the foamed cement lightweight soil. This foamed cement lightweight soil not only has lower dry density and drying shrinkage but also higher compressive strength and impermeability. Chinese patent CN113800800A discloses a lightweight magnesium phosphate cement prepared by foaming and its preparation method. This method utilizes the hydration reaction of recalcined magnesium oxide and ammonium dihydrogen phosphate in an aqueous solution to generate a cementitious material with a certain strength. Simultaneously, foaming reduces the bulk density of the cement, resulting in lightweight magnesium phosphate cement boards with high mechanical properties and a uniform internal structure. Both methods employ a single structure and lack sufficient toughening measures, leading to poor flexural strength and limiting their application in ceilings and other applications. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings and defects mentioned in the background art above. By using a multi-layer structure paving method, a multi-layer structure magnesium-based lightweight composite board with advantages such as green environmental protection, lightweight, non-combustible, and high strength is provided. This solves the problem of low bending strength of magnesium-based lightweight composite boards and expands the application range of magnesium-based cement composite boards.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A multi-layer magnesium-based lightweight composite board is composed of a slurry layer, a reinforcing layer and a lightweight layer, and is obtained by a multi-layer structural laying method of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer;

[0008] The material of the rib layer is fiberglass mesh;

[0009] The slurry used in the slurry layer is obtained by stirring magnesium chloride solution I and mixture A;

[0010] The lightweight layer slurry used in the lightweight layer is obtained by stirring magnesium chloride solution II, mixture B and foaming agent;

[0011] Both magnesium chloride solution I and magnesium chloride solution II are independently prepared by mixing magnesium chloride, citric acid and water; mixture A is obtained by dry mixing bamboo fiber, lightly calcined magnesium oxide and thickener; mixture B is obtained by dry mixing bamboo fiber, lightly calcined magnesium oxide, thickener, foam stabilizer, activator, foaming agent and foam.

[0012] Furthermore, the amounts of each raw material added to the slurry layer are as follows, by weight:

[0013]

[0014] The amounts of each raw material added to the slurry in the lightweight layer are as follows, by weight:

[0015]

[0016] Furthermore, the active content of the lightly calcined magnesium oxide described in this invention is above 60%.

[0017] Furthermore, the bamboo fiber raw material described in this invention is bamboo yellow, and the bamboo fiber size is 20-30 mesh. The addition of bamboo fiber can improve the toughness of the composite board, reduce the micro-cracks generated under stress and prevent their propagation, thereby increasing crack resistance and toughness. In addition, the bamboo fiber is in a three-dimensional arbitrary distribution state in the matrix, and the load borne by the composite board is jointly borne by the matrix and the bamboo fiber. The traction effect of the bamboo fiber disperses the stress laterally, thereby improving its flexural strength.

[0018] Furthermore, the activator described in this invention is manganese dioxide, ensuring that it will not react with the components in the inorganic adhesive; the main function of selecting the activator is to stimulate the chemical reaction of the foaming agent and accelerate its gas release rate.

[0019] Furthermore, the foaming agent described in this invention is hydrogen peroxide, and the foaming agent (hydrogen peroxide) needs to generate bubbles under the catalysis of an activator.

[0020] Furthermore, the thickener described in this invention is selected from any one or more of polyacrylamide, sodium polyacrylate, and carboxypropyl methylcellulose.

[0021] Furthermore, the foam stabilizer described in this invention is calcium stearate.

[0022] Furthermore, the foam described in this invention is polystyrene foam.

[0023] The cement matrix used in this invention is magnesium oxychloride cement, which is composed of a ternary system of MgO-MgCl2-H2O. This cement differs from silicate cement in its hydration mechanism; its main hydration product is basic magnesium oxychloride crystals, namely xMg(OH)2·yMgCl2·zH2O, whose structural morphology is generally needle-like, rod-like, or fibrous. The interlocking and mechanical interpenetration of basic magnesium oxychloride crystals during hydration is the direct source of the strength of magnesium oxychloride cement.

[0024] This invention also provides a method for preparing the above-mentioned multilayer magnesium-based lightweight composite plate, comprising the following steps:

[0025] (1) Slurry preparation steps for the slurry layer:

[0026] S1. Mix magnesium chloride, citric acid and water to prepare magnesium chloride solution I;

[0027] S2. Dry-mix bamboo fiber, lightly calcined magnesium oxide, and thickener evenly to obtain mixture A;

[0028] S3. Add the mixture A from step S2 to the magnesium chloride solution I obtained in step S1, stir, and obtain the slurry layer;

[0029] (2) Slurry preparation steps for the lightweight layer:

[0030] S4. Mix magnesium chloride, citric acid and water to prepare magnesium chloride solution II;

[0031] S5. Mix bamboo fiber, lightly calcined magnesium oxide, thickener, foam stabilizer, activator, and foam dry-mix evenly to obtain mixture B;

[0032] S6. Add the mixture B from step S5 to the magnesium chloride solution II obtained in step S4, stir, and obtain slurry C;

[0033] S7. Add the foaming agent to the slurry C obtained in step S6 and stir to obtain a lightweight slurry.

[0034] The reinforcing layer, slurry layer, and lightweight layer slurry are sequentially laid in the mold in the order of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer, and then placed in a constant temperature and humidity chamber for static foaming and curing to obtain the multi-layer magnesium-based lightweight composite board of the present invention.

[0035] Furthermore, the reinforcing layer is made of fiberglass mesh, which serves as a toughening material. During installation, the fiberglass mesh is first soaked in water and then laid flat on the slurry. The water soaking improves its wettability and enhances its interfacial adhesion and hydrophilicity with the inorganic coating. The slurry is smoothed with a cement trowel to ensure the flatness of the installation surface before the fiberglass mesh is laid. The flatness of each layer effectively improves the stress and deformation performance of the fiberglass mesh-reinforced cement composite board, thereby increasing the strength of the matrix. The same operation is performed when laying the fiberglass mesh on the lightweight layer.

[0036] Furthermore, the conditions of the constant temperature and humidity chamber are: humidity 60-70% and temperature 22-27℃.

[0037] Furthermore, the maintenance time is 24–72 hours.

[0038] The magnesium-based lightweight composite board produced by the multi-layer paving method of slurry layer-reinforcement layer-lightweight layer-reinforcement layer-slurry layer in this invention exhibits superior performance compared to magnesium-based lightweight composite boards produced by a single paving method of lightweight layer-reinforcement layer-lightweight layer-reinforcement layer-lightweight layer. In this invention, no chemical foaming agent is added to the slurry layer, resulting in a significantly smaller number and size of pores compared to the lightweight layer. The addition of foam and hydrogen peroxide to the lightweight layer creates numerous tiny pores and voids in the cement matrix, reducing its density and consequently lowering its mechanical properties. The strength of cement depends on the density (porosity) of the cement matrix; higher density results in higher mechanical properties.

[0039] Compared with the prior art, the advantages of the present invention are as follows:

[0040] (1) The multi-layer structure paving method described in this invention reduces the porosity of the surface slurry and decreases the density of the slurry layer. Together with the reinforcement layer (fiberglass mesh), it enhances the mechanical properties. Compared with ordinary lightweight cement composite boards, the flexural strength is significantly enhanced, and it can be widely used in ceilings, decoration and other fields, expanding its application range.

[0041] (2) This invention uses a large amount of waste gas polystyrene foam particles, turning waste into treasure, reducing its impact on the environment, and has excellent social and economic benefits.

[0042] (3) The present invention uses bamboo fiber reinforcement, which is inexhaustible in nature. It is not only green and environmentally friendly, but also helps to reduce costs. At the same time, the bamboo fiber is mixed with inorganic adhesive, and the fiber distribution direction is multidimensional random arrangement, which has an improving and strengthening effect on the microstructure of inorganic adhesive. The strength of the composite material is enhanced by the entanglement bonding ability, and it can also prevent defects such as shrinkage, collapse and cracking of inorganic adhesive.

[0043] (4) The raw materials and products selected in this invention do not contain formaldehyde or other volatile organic compounds, and the manufacturing process does not require sintering and steam curing. It is a new type of green, environmentally friendly, and low-energy-consumption cementitious material. Attached Figure Description

[0044] Figure 1 This is a side view of the magnesium-based lightweight composite plate with a multilayer structure prepared in Example 1 of the present invention. Detailed Implementation

[0045] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0046] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0047] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0048] Example 1

[0049] A multi-layer magnesium-based lightweight composite board comprises a slurry layer, a reinforcing layer, and a lightweight layer, and is obtained through a multi-layer paving method of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer; the reinforcing layer is made of glass fiber mesh; the slurry used in the slurry layer is obtained by stirring magnesium chloride solution I and mixture A; the lightweight layer slurry is obtained by stirring magnesium chloride solution II, mixture B, and a foaming agent;

[0050] The specific preparation method includes the following steps:

[0051] (1) The slurry preparation steps of the slurry layer:

[0052] S1. Mix 200 parts magnesium chloride, 4 parts citric acid and 306 parts water to prepare magnesium chloride solution I;

[0053] S2. Mix 72 parts bamboo fiber, 395 parts lightly calcined magnesium oxide and 2 parts polyacrylamide evenly to obtain mixture A.

[0054] S3. Add the mixture A from step S2 to the magnesium chloride solution I obtained in step S1, stir, and obtain a slurry;

[0055] (2) The slurry preparation steps for the lightweight layer:

[0056] S4. Mix 200 parts magnesium chloride, 4 parts citric acid and 306 parts water to prepare magnesium chloride solution II;

[0057] S5. Mix 72 parts bamboo fiber, 395 parts lightly calcined magnesium oxide, 2 parts polyacrylamide, 1 part calcium stearate, 1.5 parts manganese dioxide, and 2 parts polystyrene foam evenly to obtain mixture B.

[0058] S6. Add the mixture B from step S5 to the magnesium chloride solution II obtained in step S4, stir, and obtain slurry C;

[0059] S7. Add 1 part of foaming agent hydrogen peroxide to the slurry C obtained in step 6, stir, and obtain a lightweight slurry.

[0060] The reinforcing layer, slurry, and lightweight slurry layer are sequentially laid in the mold in the order of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer, and then placed in a constant temperature and humidity chamber with a humidity of 65% and a temperature of 25°C for static foaming and curing for 24 hours to obtain the multi-layer magnesium-based lightweight composite board.

[0061] Example 2

[0062] A multi-layer magnesium-based lightweight composite board comprises a slurry layer, a reinforcing layer, and a lightweight layer, and is obtained through a multi-layer paving method of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer; the reinforcing layer is made of glass fiber mesh; the slurry used in the slurry layer is obtained by stirring magnesium chloride solution I and mixture A; the lightweight layer slurry is obtained by stirring magnesium chloride solution II, mixture B, and a foaming agent;

[0063] The specific preparation method includes the following steps:

[0064] (1) The slurry preparation steps of the slurry layer:

[0065] S1. Mix 200 parts magnesium chloride, 4 parts citric acid and 350 parts water to prepare magnesium chloride solution I;

[0066] S2. Mix 120 parts bamboo fiber, 450 parts lightly calcined magnesium oxide, and 3 parts polyacrylamide evenly to obtain mixture A;

[0067] S3. Add the mixture A from step S2 to the magnesium chloride solution I obtained in step S1, stir, and obtain a slurry;

[0068] (2) The slurry preparation steps for the lightweight layer:

[0069] S4. Mix 200 parts magnesium chloride, 4 parts citric acid and 350 parts water to prepare magnesium chloride solution II;

[0070] S5. Mix 120 parts bamboo fiber, 450 parts lightly calcined magnesium oxide, 3 parts sodium polyacrylate, 1 part calcium stearate, 1 part manganese dioxide, and 2 parts polystyrene foam evenly to obtain mixture B.

[0071] S6. Add the mixture B from step S5 to the magnesium chloride solution II obtained in step S4, stir, and obtain slurry C;

[0072] S7. Add 1 part of foaming agent hydrogen peroxide to the slurry C obtained in step 6, stir, and obtain a lightweight slurry.

[0073] The reinforcing layer, slurry, and lightweight slurry are sequentially laid in the mold in the order of slurry-reinforcing layer-lightweight slurry-reinforcing layer-slurry, and then placed in a constant temperature and humidity chamber with a humidity of 65% and a temperature of 25°C for static foaming and curing for 36 hours to obtain the multi-layer magnesium-based lightweight composite board.

[0074] Example 3

[0075] A multi-layer magnesium-based lightweight composite board comprises a slurry layer, a reinforcing layer, and a lightweight layer, and is obtained through a multi-layer paving method of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer; the reinforcing layer is made of glass fiber mesh; the slurry used in the slurry layer is obtained by stirring magnesium chloride solution I and mixture A; the lightweight layer slurry is obtained by stirring magnesium chloride solution II, mixture B, and a foaming agent;

[0076] The specific preparation method includes the following steps:

[0077] (1) The slurry preparation steps of the slurry layer:

[0078] S1. Mix 250 parts magnesium chloride, 5 parts citric acid and 250 parts water to prepare magnesium chloride solution I;

[0079] S2. Mix 50 parts bamboo fiber, 500 parts lightly calcined magnesium oxide, and 1 part sodium polyacrylate evenly to obtain mixture A;

[0080] S3. Add the mixture A from step S2 to the magnesium chloride solution I obtained in step S1, stir, and obtain a slurry;

[0081] (2) The slurry preparation steps for the lightweight layer:

[0082] S4. Mix 250 parts magnesium chloride, 5 parts citric acid and 250 parts water to prepare magnesium chloride solution II;

[0083] S5. Mix 50 parts bamboo fiber, 500 parts lightly calcined magnesium oxide, 1 part sodium polyacrylate, 0.5 parts calcium stearate, 0.5 parts manganese dioxide, and 3 parts polystyrene foam evenly to obtain mixture B.

[0084] S6. Add the mixture B from step S5 to the magnesium chloride solution II obtained in step S4, stir, and obtain slurry C;

[0085] S7. Add 0.5 parts of foaming agent hydrogen peroxide to the slurry C obtained in step 6, stir, and obtain a lightweight slurry.

[0086] The reinforcing layer, slurry, and lightweight slurry are sequentially laid in the mold in the order of slurry-reinforcing layer-lightweight slurry-reinforcing layer-slurry, and then placed in a constant temperature and humidity chamber with a humidity of 60% and a temperature of 27°C for static foaming and curing for 72 hours to obtain the multi-layer magnesium-based lightweight composite board.

[0087] Example 4

[0088] A multi-layer magnesium-based lightweight composite board comprises a slurry layer, a reinforcing layer, and a lightweight layer, and is obtained through a multi-layer paving method of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer; the reinforcing layer is made of glass fiber mesh; the slurry used in the slurry layer is obtained by stirring magnesium chloride solution I and mixture A; the lightweight layer slurry is obtained by stirring magnesium chloride solution II, mixture B, and a foaming agent;

[0089] The specific preparation method includes the following steps:

[0090] (1) The slurry preparation steps of the slurry layer:

[0091] S1. Mix 250 parts magnesium chloride, 2.5 parts citric acid and 252 parts water to prepare magnesium chloride solution I;

[0092] S2. Mix 120 parts bamboo fiber, 350 parts lightly calcined magnesium oxide, and 1.4 parts carboxypropyl methylcellulose evenly to obtain mixture A;

[0093] S3. Add the mixture A from step S2 to the magnesium chloride solution I obtained in step S1, stir, and obtain a slurry.

[0094] (2) The slurry preparation steps for the lightweight layer:

[0095] S4. Mix 203 parts magnesium chloride, 4 parts citric acid and 306 parts water to prepare magnesium chloride solution II;

[0096] S5. Mix 72 parts bamboo fiber, 395 parts lightly calcined magnesium oxide, 2 parts carboxypropyl methylcellulose, 1.5 parts calcium stearate, 1 part manganese dioxide, and 1 part polystyrene foam evenly to obtain mixture B.

[0097] S6. Add the mixture B from step S5 to the magnesium chloride solution II obtained in step S4, stir, and obtain slurry C;

[0098] S7. Add 1.5 parts of foaming agent hydrogen peroxide to the slurry C obtained in step 6, stir, and obtain a lightweight slurry.

[0099] The reinforcing layer, slurry, and lightweight slurry are sequentially laid in the mold in the order of slurry-reinforcing layer-lightweight slurry-reinforcing layer-slurry, and then placed in a constant temperature and humidity chamber with a humidity of 70% and a temperature of 22℃ for static foaming and curing for 72 hours to obtain the multi-layer magnesium-based lightweight composite board.

[0100] Comparative Example 1

[0101] A single-structure magnesium-based lightweight composite panel is composed of a reinforcing layer and a lightweight layer, and is obtained by laying the lightweight layer-reinforcing layer-lightweight layer-reinforcing layer-lightweight layer; the material of the reinforcing layer is glass fiber mesh.

[0102] The specific preparation method includes the following steps:

[0103] Lightweight slurry preparation steps:

[0104] S1. Mix 203 parts magnesium chloride, 4 parts citric acid and 306 parts water to prepare a magnesium chloride solution;

[0105] S2. Mix 72 parts bamboo fiber, 395 parts lightly calcined magnesium oxide, 2 parts polyacrylamide, 1 part calcium stearate, 1 part manganese dioxide, and 2 parts polystyrene foam evenly to obtain mixture A.

[0106] S3. Add the mixture B from step S2 to the magnesium chloride solution obtained in step S1, stir, and obtain slurry B;

[0107] S4. Add 1 part of foaming agent to slurry B obtained in step 6, stir, and obtain a lightweight slurry.

[0108] The reinforcing layer and lightweight layer slurry were laid in the mold in sequence as lightweight layer slurry-reinforcing layer-lightweight layer slurry-reinforcing layer-lightweight layer slurry, and then placed in a constant humidity chamber with a humidity of 65% and a temperature of 25℃ for static foaming and curing for 24 hours to obtain a magnesium-based lightweight composite board with a single structure.

[0109] Comparative Example 2

[0110] A single pure cement composite board, the specific preparation method includes the following steps:

[0111] S1. Mix 246 parts magnesium chloride, 2.4 parts citric acid and 252 parts water to prepare a magnesium chloride solution;

[0112] S2. Mix 96 parts bamboo fiber, 472 parts lightly calcined magnesium oxide, and 1.2 parts polyacrylamide evenly to obtain mixture A;

[0113] S3. Add the mixture A from step S2 to the magnesium chloride solution obtained in step S1, stir, and obtain a slurry.

[0114] The components are sequentially laid in the mold and placed in a temperature and humidity chamber for curing to obtain a single pure cement composite board.

[0115] Performance testing

[0116] The performance of the plates obtained in each embodiment and comparative example of the present invention was tested, and the results are shown in Table 1.

[0117] Table 1 Performance test results of magnesium-based lightweight composite panels

[0118]

[0119] As can be seen from Example 1 and Comparative Example 1 of the present invention, when the raw materials used to prepare magnesium-based lightweight composite panels are the same but the paving structure is different, the flexural strength of the resulting magnesium-based lightweight composite panels is also different. Compared with the magnesium-based lightweight composite panel prepared by a single structure in Comparative Example 1, the multi-layer magnesium-based lightweight composite panel prepared by Example 1 of the present invention has stronger flexural strength. The multi-layer paving method enhances the overall flexural strength of the composite panel by reducing the density of the slurry. Compared with the single pure cement composite panel in Comparative Example 2, the lightweight composite panel prepared by Example 1 of the present invention has lower density, reducing the difficulty of transporting and installing the panels and expanding the application scenarios.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A multi-layered magnesium-based lightweight composite plate, characterized in that: It consists of a slurry layer, a reinforcing layer, and a lightweight layer, and is constructed through a multi-layered paving method of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer; The material of the rib layer is fiberglass mesh; The slurry used in the slurry layer is obtained by stirring magnesium chloride solution I and mixture A; The lightweight layer slurry used in the lightweight layer is obtained by stirring magnesium chloride solution II, mixture B and foaming agent; Magnesium chloride solution I and magnesium chloride solution II are each independently prepared by mixing magnesium chloride, citric acid and water; mixture A is obtained by dry mixing bamboo fiber, lightly calcined magnesium oxide and thickener; mixture B is obtained by dry mixing bamboo fiber, lightly calcined magnesium oxide, thickener, foam stabilizer, activator, foaming agent and foam. The amounts of each raw material added to the slurry layer by weight are as follows: 200-250 parts magnesium chloride 250-350 parts water Bamboo fiber 50~120 parts, Lightly calcined magnesium oxide, 350-500 parts. Citric acid 2-5 parts, Thickener 1-3 parts; The amounts of each raw material added to the slurry in the lightweight layer are as follows, by weight: 200-250 parts magnesium chloride 250-350 parts water Bamboo fiber 50~120 parts, Lightly calcined magnesium oxide, 350-500 parts. Citric acid 2-5 parts, Foam stabilizer 0.5~1.5 parts, Thickener 1-3 parts, Activator 0.5~1.5 parts, 0.5-1.5 parts of foaming agent, 1-3 portions of foam.

2. The multi-layer magnesium-based lightweight composite plate according to claim 1, characterized in that, The active content of the lightly calcined magnesium oxide is above 60%.

3. The multi-layer magnesium-based lightweight composite plate according to claim 1, characterized in that, The bamboo fiber has a size of 20-30 mesh.

4. The multi-layer magnesium-based lightweight composite plate according to claim 1, characterized in that, The activator is manganese dioxide; The foaming agent is hydrogen peroxide.

5. A multi-layer magnesium-based lightweight composite plate according to claim 1, characterized in that, The thickener is selected from any one or a mixture of polyacrylamide, sodium polyacrylate, and carboxypropyl methylcellulose.

6. The multi-layer magnesium-based lightweight composite plate according to claim 1, characterized in that, The foam stabilizer is calcium stearate; The foam is polystyrene foam.

7. A method for preparing a multi-layered magnesium-based lightweight composite plate according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Slurry preparation steps for the slurry layer: S1. Mix magnesium chloride, citric acid and water to prepare magnesium chloride solution I; S2. Dry-mix bamboo fiber, lightly calcined magnesium oxide, and thickener evenly to obtain mixture A; S3. Add the mixture A from step S2 to the magnesium chloride solution I obtained in step S1, stir, and obtain the slurry layer; (2) Preparation steps of the slurry for the lightweight layer: S4. Mix magnesium chloride, citric acid and water to prepare magnesium chloride solution II; S5. Mix bamboo fiber, lightly calcined magnesium oxide, thickener, foam stabilizer, activator, and foam dry-mix evenly to obtain mixture B; S6. Add the mixture B from step S5 to the magnesium chloride solution II obtained in step S4, stir, and obtain slurry C; S7. Add the foaming agent to the slurry C obtained in step S6 and stir to obtain a lightweight slurry. The reinforcing layer, slurry layer, and lightweight layer slurry are sequentially laid in the mold in the order of slurry layer-reinforcing layer-lightweight layer-reinforcing layer-slurry layer, and then placed in a constant temperature and humidity chamber for static foaming and curing to obtain the multi-layer magnesium-based lightweight composite board.

8. The method for preparing a multi-layered magnesium-based lightweight composite plate according to claim 7, characterized in that, During installation, the fiberglass mesh is first soaked in water and then laid flat on the mortar. A cement trowel is then used to smooth the mortar, ensuring the flatness of the surface before installation.

9. The method for preparing a multi-layered magnesium-based lightweight composite plate according to claim 7, characterized in that, The conditions of the constant temperature and humidity chamber are: humidity 60~70% and temperature 22~27℃; The maintenance time is 24~72 hours.

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