High-insulation magnesium phosphate-based cement material and preparation method thereof

Abstract

The invention provides a high-insulation magnesium phosphate-based cement material and a preparation method, and belongs to the technical field of building materials, the high-insulation magnesium phosphate-based cement material comprises 250-400 parts of fused magnesia, 80-150 parts of potassium dihydrogen phosphate, 300-500 parts of quartz sand, 50-150 parts of insulation slag, 100-200 parts of water, 12-20 parts of a retarder, 2-4 parts of a water reducer, and 5-9 parts of an insulation additive. The preparation method comprises the steps of raw material dry mixing, reagent dissolving, solid-liquid mixing and mold casting and curing, and the method has the advantages that manufacturing is easy, raw materials are simple, and meanwhile it can be guaranteed that the insulativity and the comprehensive mechanical property are remarkably improved. After the high-insulation magnesium phosphate-based cement material is cured for 28 days, the breaking strength is greater than or equal to 14 MPa, and the compressive strength is greater than or equal to 70 MPa; and the resistivity is greater than or equal to 1000000 omega.cm under maintenance in an environment with the temperature of 20 + / -2 DEG C. The preparation method disclosed by the invention has low requirements on equipment, and the prepared high-insulation magnesium phosphate-based cement material has the advantages of good plasticity and machinability, easiness in construction and processing and the like.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-insulation magnesium phosphate-based cement material and its preparation method. Background Technology

[0002] With increasing societal awareness of safety and environmental protection, the requirements for materials used in construction and electrical engineering are also rising. Insulating cement materials possess excellent insulation, fire resistance, and environmental performance, effectively reducing the risk of electrical equipment accidents and minimizing energy waste, thus meeting modern society's demands for safety and environmental protection. In the construction industry, insulating cement materials are used for insulation treatment of building structures, such as the insulation protection of walls, floors, and roofs. Especially in special environments such as high-rise buildings, underground structures, and industrial plants, where insulation performance requirements are even more stringent, the application of insulating cement materials becomes particularly important.

[0003] Currently, patent application CN201911062924.3 discloses an ultra-high performance insulating cement-based material and its preparation method. By adding insulating additives and insulating minerals, the insulation properties of ordinary Portland cement are improved, resulting in an ultra-high performance insulating cement-based material with a 28-day resistivity of 100,000 Ω·cm or higher. This ultra-high performance insulating cement-based material not only possesses high strength, high toughness, and high resistivity, but also high impermeability and durability. However, this patent has many shortcomings; its raw materials are complex, and the manufacturing process is relatively cumbersome. In addition, patent application CN201810480171.7 discloses a surface-modified ultra-fine steel fiber high-resistance ultra-high performance concrete and its preparation method. The method for improving the surface of the ultra-fine steel fiber involves treating the surface of the ultra-fine steel fiber with SiO2 to increase its surface roughness. Simultaneously, the high flammability of nano-SiO2 volcanic ash is used to rehydrate the cement, improving weak areas at the interface. However, this method is complex to manufacture, and the resistivity after 28 days is only 20,000 Ω·cm, indicating that the insulation performance needs to be improved. Summary of the Invention

[0004] Based on the above-mentioned technical problems, the purpose of this invention is to provide a high-insulation magnesium phosphate-based cement material and its preparation method. This method is simple to produce and uses simple raw materials, while also ensuring significant improvement in insulation and comprehensive mechanical properties.

[0005] The specific technical solution is as follows: A high-insulation magnesium phosphate-based cement material is made from the following raw materials in parts by weight: 250-400 parts of fused magnesium oxide, 80-150 parts of potassium dihydrogen phosphate, 300-500 parts of quartz sand, 50-150 parts of insulating slag, 100-200 parts of water, 12-20 parts of retarder, 2-4 parts of water-reducing agent, and 5-9 parts of insulating additive.

[0006] In addition, the high-insulation magnesium phosphate-based cement material provided by the present invention may also have the following additional technical features: In the above technical solution, fused magnesia is produced by melting magnesite ore at a high temperature above 2800℃ in an electric arc furnace, finely grinding and pressing it into a billet, and then smelting it at a high temperature in an electric arc furnace. Its fineness is 150 mesh.

[0007] In the above technical solution, the quartz sand is composed of 60-90 mesh fine quartz sand and 30-70 mesh coarse quartz sand.

[0008] In the above technical solution, the insulating slag is a mixture of one or more of quartz powder, limestone, and mineral powder, and the particle size of the insulating slag is 30-90 mesh.

[0009] In the above technical solution, the insulating additive is made by using at least one of dimethylsiloxane and methylethylsiloxane as monomers, supplemented with crosslinking agents, catalysts and stabilizers, and then mechanically stirred until uniform.

[0010] A method for preparing a highly insulating magnesium phosphate-based cement material includes the following steps: S1: Dry mixing of raw materials: The specified amounts of fused magnesium oxide, potassium dihydrogen phosphate, quartz sand, insulating slag and insulating additives are dry mixed to obtain a uniformly mixed dry mixture. S2: Dissolve the reagents by adding the specified amounts of water-reducing agent and retarder to water and stirring until completely dissolved to obtain a mixed solution; S3: Solid-liquid mixing: Add the dry mixture obtained in step S1 to the mixed solution obtained in step S2, and mechanically stir for 3-4 minutes until it is evenly mixed to obtain cement slurry. S4: Molding and curing. The slurry obtained in step S3 is injected into a mold for molding, and then cured at 20±2℃ for 28 days to obtain a high-insulation magnesium phosphate-based cement material.

[0011] The present invention provides a high-insulation magnesium phosphate-based cement material and its preparation method, which, compared with the prior art, have the following advantages: 1. The high-insulation magnesium phosphate-based cement material prepared by this invention meets the following standards: 1) Mechanical properties: flexural strength ≥14MPa and compressive strength ≥70MPa after 28 days of curing; 2) Resistivity ≥1000000Ω.cm under curing at a temperature of 20±2℃.

[0012] 2. The manufacturing method of the present invention does not require high-end equipment, and the resulting high-insulation magnesium phosphate-based cement material has good plasticity and processability, is easy to construct and process, and can be cut, repaired, bonded and other treatments as needed, making the construction process more flexible and convenient.

[0013] 3. The high-insulation magnesium phosphate-based cement material prepared by this invention is suitable for power facilities and civil engineering projects with high requirements for insulation and durability. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the insulation mechanism of the high-insulation magnesium phosphate-based cement and the action mechanism of VAE in this invention. Detailed Implementation

[0015] The following are specific implementation cases and appendices. Figure 1 The present invention will be further described, but the present invention is not limited to these embodiments.

[0016] A high-insulation magnesium phosphate-based cement material is made from the following raw materials in parts by weight: 250-400 parts of fused magnesium oxide, 80-150 parts of potassium dihydrogen phosphate, 300-500 parts of quartz sand, 50-150 parts of insulating slag, 100-200 parts of water, 12-20 parts of retarder, 2-4 parts of water-reducing agent, and 5-9 parts of insulating additive.

[0017] In an embodiment of the present invention, fused magnesium oxide is obtained by melting natural magnesite ore at a high temperature above 2800°C in an electric arc furnace, finely grinding and pressing it into a billet, and then smelting it at a high temperature in an electric arc furnace. Its fineness is 150 mesh.

[0018] In an embodiment of the present invention, the quartz sand is composed of a mixture of 60-90 mesh fine quartz sand and 30-70 mesh coarse quartz sand.

[0019] In embodiments of the present invention, the insulating slag is a mixture of one or more of quartz powder, limestone, and mineral powder, and the particle size of the insulating slag is 30-90 mesh.

[0020] In embodiments of the present invention, the insulating additive is prepared by using at least one of dimethylsiloxane and methylethylsiloxane as monomers, supplemented with crosslinking agents, catalysts and stabilizers, and then mixing them evenly using mechanical stirring or mixing equipment.

[0021] A method for preparing a highly insulating magnesium phosphate-based cement material includes the following steps: S1: Dry mixing of raw materials: The specified amounts of fused magnesium oxide, potassium dihydrogen phosphate, quartz sand, insulating slag and insulating additives are dry mixed to obtain a uniformly mixed dry mixture. S2: Dissolve the reagents by adding the specified amounts of water-reducing agent and retarder to water and stirring until completely dissolved to obtain a mixed solution; S3: Solid-liquid mixing: Add the dry mixture obtained in step S1 to the mixed solution obtained in step S2, and mechanically stir for 3-4 minutes until it is evenly mixed to obtain cement slurry. S4: Molding and curing. The slurry obtained in step S3 is injected into a mold for molding, and then cured at 20±2℃ for 28 days to obtain a high-insulation magnesium phosphate-based cement material.

[0022] The raw material processing of this invention is simple, requiring no complex pretreatment. Furthermore, the core raw materials, such as fused magnesium oxide, quartz sand, and insulating slag, are all directly usable industrial-grade raw materials. Fused magnesium oxide itself already possesses the required high purity and fineness of 150 mesh; quartz sand only needs to be physically graded within a particle size range of 30-90 mesh; and insulating slag similarly only needs to be ground to 30-90 mesh before use. The entire formulation system eliminates the need for pretreatment steps such as surface modification, nano-processing, or complex chemical activation of the raw materials, significantly simplifying the raw material preparation process and reducing equipment investment and production energy consumption.

[0023] The preparation method of this invention comprises only three core steps: "dry mixing of raw materials—dissolving of reagents—solid-liquid mixing." All dry powder components, such as fused magnesium oxide, potassium dihydrogen phosphate, quartz sand, insulating slag, and insulating additives, can be added and dry mixed at once. All liquid agents, such as water-reducing agents and retarders, can be dissolved together in the mixing water. The dry and wet materials are then combined and stirred for 3-4 minutes to complete the slurry preparation. The entire process is clearly defined, requiring no staged or sequential addition of special components, and eliminating the need for prolonged aging or activation stirring, thus greatly improving production efficiency and placing no special requirements on the mixing equipment.

[0024] The high insulation performance of this invention is mainly achieved through physical gradation and chemical synergy, rather than relying on complex composite processes. Insulating additives such as organosilicones can be uniformly dispersed during mixing and spontaneously migrate to the pore interface to form an insulating film; insulating slag is directly mixed in as a functional filler. Compared with those technologies that require special processes to surface-coat fibers or construct multi-level complex insulation networks, the functionalization path of this invention is more direct, reliable, and easier to control in terms of quality.

[0025] This invention provides mild curing conditions, requiring no special environment: molded specimens only need to be cured at standard room temperature conditions, such as 20±2℃, to achieve the designed performance, without the need for steam curing, high-temperature and high-pressure curing, or specific humidity control environments. These mild curing conditions make on-site construction and large-scale production easier to implement, reducing energy consumption and production costs.

[0026] Specifically, the fused magnesium oxide used in this invention undergoes a high-temperature melting process exceeding 2800°C, resulting in a more complete crystal structure, larger grain size, relatively lower specific surface area, and moderate chemical reactivity. Compared to the more reactive recalcined magnesium oxide, its hydration reaction is less intense when encountering phosphate solutions, providing a favorable physical basis for controlling the setting time.

[0027] The retarder used in this invention is borax, which can form an adsorption film on the surface of fused magnesium oxide particles or form a complex with reactive ions, effectively slowing down the nucleation and growth rate of magnesium phosphate hydration products such as struvite phase, thereby significantly inhibiting the early hydration exothermic peak and delaying the solidification process.

[0028] In this invention, the moderate reactivity of fused magnesium oxide creates conditions for the effective action of the retarder, avoiding the risk of the retarder "failing" due to excessively rapid reaction; while the addition of the retarder further "tames" the hydration process of fused magnesium oxide. The two work synergistically to achieve precise control of the setting kinetics of the magnesium phosphate cement system, stabilizing the initial and final setting times at around 25 minutes, thus solving the technical problems of excessively rapid setting and rushed construction associated with traditional magnesium phosphate cement.

[0029] like Figure 1 As shown, Figure 1 (1) This is a diagram showing the relationship between the microstructure and properties of the high-insulation magnesium phosphate-based cement material of the present invention. The diagram illustrates that as the hydration reaction proceeds, some free water fills the pores, while some evaporates into the air, indicating that the porosity of the sample decreases with hydration. The decrease in porosity enhances the mechanical properties of the cement, while the reduction in free water in the pores also leads to an increase in the resistivity of the system. After 7 days, the hydration reaction is essentially complete. Since there are no large amounts of hydration products continuing to fill the pores, the porosity hardly changes. Therefore, the mechanism of increasing sample strength by reducing porosity is no longer effective. Thus, any increase in strength after 7 days is mainly provided by crystals generated within the system. Although the change in porosity is no longer significant, the water in the pores continues to evaporate, leading to a continuous and rapid increase in resistivity.

[0030] like Figure 1 As shown, Figure 1 (1) This represents the electron conduction process within the material, where the yellow spheres represent free electrons and the yellow curves indicate the electron transport path. Non-conductive materials present within the cement, such as quartz and magnesium oxide crystals, primarily confine electron conduction to the pore phase and water. To prevent electron conduction through the pore water, insulating additives added during sample preparation form a thin film on the pore walls, constituting an effective insulating barrier and blocking electron transport. Figure 1(2) The effective transmission path of the yellow electron sphere is blocked by the thin film, which explains the reason for the enhanced electrical insulation. Example 1:

[0031] A high-insulation magnesium phosphate-based cement material, with raw material proportions as shown in Table 1.

[0032]

[0033] In this embodiment, a method for producing a high-insulation magnesium phosphate-based cement material includes the following steps: S1: Dry mixing of raw materials: The specified amounts of light fused magnesium oxide powder, potassium dihydrogen phosphate, quartz sand, insulating slag and insulating additives are dry mixed to obtain a uniformly mixed dry mixture. S2: Dissolve the reagents by adding a measured amount of water-reducing agent and retarder to water and stirring until completely dissolved to obtain a mixed solution; S3: Solid-liquid mixing: Add the dry mixture obtained in step S1 to the mixed solution obtained in step S2, and stir mechanically for 3-4 minutes until it is evenly mixed to obtain magnesium phosphate-based cement slurry. S4: Molding and curing. The slurry obtained in step S3 is injected into the mold for molding, and then cured at 20±2℃ for 28 days to obtain a high-insulation magnesium phosphate-based cement material. The high-insulation magnesium phosphate-based cement material has a compressive strength of 75.8MPa and a resistivity of 13620000Ω.cm. Example 2:

[0034] A high-insulation magnesium phosphate-based cement material is prepared according to the raw material ratio in Table 2.

[0035]

[0036] In this embodiment, a method for producing a high-insulation magnesium phosphate-based cement material includes the following steps: S1: Dry mixing of raw materials: The specified amounts of light fused magnesium oxide powder, potassium dihydrogen phosphate, quartz sand, insulating slag and insulating additives are dry mixed to obtain a uniformly mixed dry mixture. S2: Dissolve the reagents by adding a measured amount of water-reducing agent and retarder to water and stirring until completely dissolved to obtain a mixed solution; S3: Solid-liquid mixing: Add the dry mixture obtained in step S1 to the mixed solution obtained in step S2, and stir mechanically for 3-4 minutes until it is evenly mixed to obtain magnesium phosphate-based cement slurry. S4: Molding and curing. The slurry obtained in step S3 is injected into the mold for molding, and then cured at 20±2℃ for 28 days to obtain a high-insulation magnesium phosphate-based cement material. The high-insulation magnesium phosphate-based cement material has a compressive strength of 82.1MPa and a resistivity of 8569420Ω.cm. Example 3:

[0037] A high-insulation magnesium phosphate-based cement material, with raw material proportions as shown in Table 3.

[0038]

[0039] In this embodiment, a method for producing a high-insulation magnesium phosphate-based cement material includes the following steps: S1: Dry mixing of raw materials: The specified amounts of light fused magnesium oxide powder, potassium dihydrogen phosphate, quartz sand, insulating slag and insulating additives are dry mixed to obtain a uniformly mixed dry mixture. S2: Dissolve the reagents by adding a measured amount of water-reducing agent and retarder to water and stirring until completely dissolved to obtain a mixed solution; S3: Solid-liquid mixing: Add the dry mixture obtained in step S1 to the mixed solution obtained in step S2, and stir mechanically for 3-4 minutes until it is evenly mixed to obtain magnesium phosphate-based cement slurry. S4: Molding and curing. The slurry obtained in step S3 is injected into a mold for molding, and then cured at 20±2℃ for 28 days to obtain a high-insulation magnesium phosphate-based cement material. The high-insulation magnesium phosphate-based cement material has a compressive strength of 87.5MPa and a resistivity of 5214500Ω.cm.

[0040] Comparative Example 1: Compared with Example 1, the difference in raw material ratio is that fused magnesium oxide is replaced with an equal amount of calcined magnesium oxide.

[0041]

[0042] In Comparative Example 1, the preparation method was the same as in Example 1, except that fused magnesium oxide was replaced with calcined magnesium oxide. As shown in Table 4, although the compressive strength increased to 78.3 MPa after 28 days, the resistivity decreased to 5046120 Ω·cm.

[0043] Comparative Example 2: Compared with Example 1, Comparative Example 2 differs in the raw material ratio by replacing fused magnesium oxide with calcined magnesium oxide, increasing the quartz sand ratio to 30 kg, and not adding insulating waste ore.

[0044]

[0045] In Comparative Example 2, the preparation method was the same as in Example 2, except that fused magnesium oxide was replaced with calcined magnesium oxide, the proportion of quartz sand was increased to 30 kg, and no insulating waste ore was added. As shown in Table 5, although the compressive strength increased to 84.5 MPa after 28 days, the resistivity decreased significantly to 4150690 Ω·cm.

[0046] Comparative Example 3: Compared with Example 1, Comparative Example 3 differs in the raw material ratio by replacing fused magnesium oxide with calcined magnesium oxide, increasing the quartz sand ratio to 30 kg, and not adding insulating additives or insulating waste ore.

[0047]

[0048] In Comparative Example 3, the preparation method was the same as in Example 1, except that fused magnesium oxide was replaced with calcined magnesium oxide, the proportion of quartz sand was increased to 30 kg, and no insulating additives or insulating waste ore were added. As shown in Table 6, although the compressive strength increased to 87.4 MPa after 28 days, the resistivity decreased significantly to 2584210 Ω·cm.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-insulation magnesium phosphate-based cement material, characterized in that, It is made from the following raw materials in parts by weight: 250-400 parts of fused magnesium oxide, 80-150 parts of potassium dihydrogen phosphate, 300-500 parts of quartz sand, 50-150 parts of insulating slag, 100-200 parts of water, 12-20 parts of retarder, 2-4 parts of water-reducing agent, and 5-9 parts of insulating additive.

2. The high-insulation magnesium phosphate-based cement material according to claim 1, characterized in that, The fused magnesia is produced by melting magnesite ore at a high temperature above 2800℃ in an electric arc furnace, followed by fine grinding, pressing, and then high-temperature smelting in an electric arc furnace. Its fineness is 150 mesh.

3. The high-insulation magnesium phosphate-based cement material according to claim 1, characterized in that, The quartz sand is composed of a mixture of 60-90 mesh fine quartz sand and 30-70 mesh coarse quartz sand.

4. The high-insulation magnesium phosphate-based cement material according to claim 1, characterized in that, The insulating slag is one or a mixture of several of the following: quartz powder, limestone, and mineral powder, and the particle size of the insulating slag is 30-90 mesh.

5. The high-insulation magnesium phosphate-based cement material according to claim 1, characterized in that, The insulating additive is prepared by using at least one of dimethylsiloxane and methylethylsiloxane as monomers, supplemented with crosslinking agents, catalysts and stabilizers, and then mechanically stirring until homogeneous.

6. A method for preparing a high-insulation magnesium phosphate-based cement material, based on the high-insulation magnesium phosphate-based cement material according to claims 1-5, characterized in that, Includes the following steps: S1: Dry mixing of raw materials: The specified amounts of fused magnesium oxide, potassium dihydrogen phosphate, quartz sand, insulating slag and insulating additives are dry mixed to obtain a uniformly mixed dry mixture. S2: Dissolve the reagents by adding the specified amounts of water-reducing agent and retarder to water and stirring until completely dissolved to obtain a mixed solution; S3: Solid-liquid mixing: Add the dry mixture obtained in step S1 to the mixed solution obtained in step S2, and mechanically stir for 3-4 minutes until it is evenly mixed to obtain cement slurry. S4: Molding and curing. The slurry obtained in step S3 is injected into a mold for molding, and then cured at 20±2℃ for 28 days to obtain a high-insulation magnesium phosphate-based cement material.

Images