Baking-free refractory brick and preparation method thereof

Abstract

The invention relates to the field of refractory bricks, and discloses a baking-free refractory brick and a preparation method thereof, the baking-free refractory brick comprises iron tailings, cement, fly ash, a functional additive, fine aggregate, quartz sand, a chromium-aluminum phosphate binder, a water reducing agent and water; the functional additive is prepared by using aluminum chloride hexahydrate and alkaline silica sol as raw materials and ammonium molybdate tetrahydrate as a catalyst, growing mullite whiskers on the surfaces of silicon carbide fibers by adopting a vacuum impregnation and heat treatment method, modifying the prepared composite silicon carbide fibers with 3-(methylacryloyloxy) propyltrimethoxysilane, and then adding the modified composite silicon carbide fibers into the functional additive, so as to obtain the composite silicon carbide fiber modified by 3-(methylacryloyloxy) propyltrimethoxysilane modified by 3-(methylacryloyloxy) propyltrimethoxysilane. And then carrying out copolymerization with acrylic acid and 4-hydroxybutyl vinyl ether. The chromium-aluminum phosphate binder is prepared by using aluminum hydroxide, phosphoric acid and chromium sesquioxide as raw materials and calcium hydroxide as a curing agent. The baking-free refractory brick with high compressive strength and breaking strength, small water absorption and good fire resistance and heat insulation performance is prepared through the synergistic effect of all the components.

Description

Technical Field

[0001] The present invention belongs to the technical field of refractory bricks, and in particular relates to a firing-free refractory brick and a preparation method thereof. Background Art

[0002] Refractory bricks can be broadly divided into fired bricks and unfired bricks, depending on whether the manufacturing process requires firing. Fired bricks are still widely used in many parts of my country due to their abundant raw materials and complex manufacturing process. However, the production process of fired bricks is associated with high energy consumption, significant pollution emissions, and secondary pollution caused by waste bricks after use. Unfired bricks, also known as chemically bonded bricks, are refractory materials that are used directly in masonry without firing, and their production process is relatively simple.

[0003] There are a large number of tailings and waste rocks in the existing resources that need to be properly handled, otherwise it will cause environmental pollution and waste of resources. Making them into building materials will help reduce the impact of solid waste on the environment and improve resource utilization efficiency. Refractory bricks, as a new type of green and environmentally friendly building material product, can solve the problem of hardening of urban surfaces and maintain the ecological balance of cities. Therefore, the use of iron tailings and waste rocks to prepare unburned bricks can help alleviate environmental pollution and resource problems while providing reliable technical support for urban construction. However, if industrial waste iron tailings are used as the main material to produce unburned bricks, their refractory properties cannot reach the level of using special raw materials. At the same time, there are defects such as cracks in their microstructure, which makes it difficult for their mechanical properties to reach an ideal height. Therefore, there is an urgent need for an unburned refractory brick and its preparation method, which can improve the utilization rate of industrial waste slag and reduce production costs while ensuring the excellent performance of the brick body itself. Summary of the Invention

[0004] In order to solve the deficiencies mentioned in the above background technology, the purpose of the present invention is to provide a fire-free refractory brick and a preparation method thereof, using iron tailings, cement, fly ash, functional additives, fine aggregate, quartz sand, and chromium aluminum phosphate binder as the main raw materials to prepare fire-free refractory bricks with high compressive strength and flexural strength, low water absorption, and good refractory and thermal insulation properties.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A fire-free refractory brick comprises the following components in parts by weight: 50-65 parts of iron ore tailings, 14-20 parts of cement, 10-15 parts of fly ash, 1.5-4.5 parts of functional additives, 5-10 parts of fine aggregate, 5-10 parts of quartz sand, 2-5 parts of chromium aluminum phosphate binder, 0.3-0.7 parts of water reducer, and 14-20 parts of water; The functional additive is prepared by using aluminum chloride hexahydrate and alkaline silica sol as raw materials, ammonium molybdate tetrahydrate as a catalyst, and adopting a vacuum impregnation and heat treatment method to grow mullite whiskers on the surface of silicon carbide fiber. The prepared composite silicon carbide fiber is modified with 3-(methacryloyloxy)propyltrimethoxysilane and then copolymerized with acrylic acid and 4-hydroxybutyl vinyl ether. The chromium aluminum phosphate binder is prepared by using aluminum hydroxide, phosphoric acid and chromium trioxide as raw materials and calcium hydroxide as a curing agent.

[0006] Preferably, the cement is P·O42.5 grade ordinary Portland cement; the fine aggregate is river sand with a fineness modulus between 2.4 and 2.8; the water reducer is a polycarboxylate water reducer; and the quartz sand has a particle size of 100 to 210 μm.

[0007] Preferably, the preparation method of the functional additive comprises the following steps: A. Place silicon carbide fiber in a mixed solution of hydrochloric acid and sulfuric acid with a pH value of 1, with a volume ratio of hydrochloric acid to sulfuric acid of 1:1, disperse evenly by ultrasonication, and heat in a water bath at 55-60°C for 0.5-1h. Then, take out, wash, and dry to prepare pretreated silicon carbide fiber. B. Ammonium molybdate tetrahydrate, aluminum chloride hexahydrate, alkaline silica sol and deionized water were stirred and mixed to obtain a modified solution, and the pretreated silicon carbide fiber was placed in the modified solution and vacuum impregnated for 0.5 to 1 hour, and then freeze-dried at -80 to -75°C for 10 to 12 hours, and then heated to 800 to 900°C for sintering, kept warm for 2 to 2.5 hours, and then naturally cooled to prepare a composite silicon carbide fiber; C. Take ethanol and deionized water in a reactor, then add glacial acetic acid, composite silicon carbide fiber, hydroquinone, and 3-(methacryloyloxy)propyltrimethoxysilane in sequence, disperse evenly by ultrasonication, place at 70-85°C for reaction for 20-24 hours, cool to room temperature after the reaction is completed, centrifuge, wash, and dry to prepare double-bonded composite silicon carbide fiber; D. Place double-bonded composite silicon carbide fiber, deionized water, and 4-hydroxybutyl vinyl ether in a reactor, disperse them uniformly by ultrasonication, then heat to 55-65°C, and simultaneously dropwise add an aqueous solution of acrylic acid and an aqueous solution of ammonium persulfate for 3.5-4 hours. After the addition is completed, place the mixture at 75-85°C for reaction for 4-5 hours. After the reaction is completed, centrifuge, wash, and dry to obtain a functional additive.

[0008] Preferably, the length of the silicon carbide fiber in step A is 4 to 8 mm.

[0009] Preferably, in step B, the addition ratio of ammonium molybdate tetrahydrate, aluminum chloride hexahydrate, alkaline silica sol and deionized water is 1.8-2 g: 6-6.2 g: 2-3.6 mL: 48-60 mL.

[0010] Preferably, the sintering procedure in step B is specifically as follows: increasing the temperature from room temperature to 800° C. at 5° C. / min, and then increasing the temperature to 900° C. at 1° C. / min.

[0011] Preferably, the volume percentage concentration of the acrylic acid aqueous solution in step D is 7.32%; the concentration of the ammonium persulfate aqueous solution is 0.025 g / mL; and the addition ratio of the double-bonded composite silicon carbide fiber, 4-hydroxybutyl vinyl ether, acrylic acid aqueous solution, and ammonium persulfate aqueous solution is 5 g:10-15 g:20-25 mL:18-22 mL.

[0012] Preferably, the preparation method of the chromium aluminum phosphate binder comprises the following steps: taking phosphoric acid and deionized water in a reactor, adding aluminum hydroxide in batches, stirring evenly and reacting at room temperature for 20 to 24 hours, then adding chromium trioxide, continuing to stir and react for 2 to 3 hours, then standing and reacting for 5 to 6 hours, and then adding calcium hydroxide with a mass fraction of 6.5 to 7.5%, mixing and stirring evenly to prepare the chromium aluminum phosphate binder.

[0013] Preferably, the molar ratio of the phosphorus element to the aluminum element is 3:1.55; the molar ratio of the aluminum element to the chromium element is 3:2.

[0014] A method for preparing unfired refractory bricks comprises the following steps: weighing each component by weight, dry-mixing iron tailings, cement, fly ash, fine aggregate, and quartz sand in a cement mortar mixer for 2 to 5 minutes, adding functional additives, a chromium aluminum phosphate binder, a water reducer, and water, mixing evenly, placing the mixture in a mold, pressing and forming the mixture, and naturally curing the mixture to prepare the unfired refractory bricks.

[0015] Beneficial effects of the present invention: The invention uses aluminum chloride hexahydrate and alkaline silica sol as raw materials, ammonium molybdate tetrahydrate as a catalyst, and adopts vacuum impregnation and heat treatment methods to grow mullite whiskers on the surface of silicon carbide fiber to prepare composite silicon carbide fiber. The mullite whiskers have the advantages of high strength, good thermal shock resistance, few internal defects, etc., and are relatively stable in high temperature environments. The grown mullite whiskers can not only enhance the interface bonding ability of the silicon carbide fiber, but the nano-scale whiskers can also synergize with other materials in the form of reinforcement. The composite silicon carbide fiber is treated with 3-( After modification with methacryloyloxy)propyltrimethoxysilane, it is copolymerized with acrylic acid and 4-hydroxybutyl vinyl ether to prepare a functional additive, thereby utilizing a chemical reaction to graft a polycarboxylate water-reducing agent onto the surface of the composite silicon carbide fiber. On the one hand, this can increase the dispersibility of the composite silicon carbide fiber, enabling it to be evenly filled in the pores of the matrix material. On the other hand, the macromolecular polymer on the surface of the composite silicon carbide fiber can entangle with the hydration products of the matrix, optimizing the internal structure of the matrix material, thereby enhancing the density, durability and mechanical strength of the brick.

[0016] The present invention uses aluminum hydroxide, phosphoric acid and chromium trioxide as raw materials to prepare a chromium aluminum phosphate binder, which has the advantages of high strength, high temperature resistance, small curing shrinkage, etc., and uses calcium hydroxide as a curing agent. The addition of calcium ions can reduce the water absorption of the binder, realize room temperature curing of the chromium aluminum phosphate binder, improve the performance of the chromium aluminum phosphate binder, improve the density of the matrix material, and enhance the ability of the matrix material to resist the invasion of water molecules. In addition, the mullite whiskers in the functional additive can absorb the stress and strain energy in the chromium aluminum phosphate binder in the system, ensuring that the brick structure is not damaged by high temperature, so that the structure can maintain structural stability for a long time under flame burning conditions, thereby improving the high temperature stability and mechanical strength of the brick body. The present invention uses iron tailings, cement, fly ash, functional additives, fine aggregate, quartz sand, and chromium aluminum phosphate binder as main raw materials, without high temperature calcination, and can produce unburned refractory bricks with high compressive strength and flexural strength, low water absorption, and good fire-resistant and heat-insulating properties. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0018] Example 1 A method for preparing a functional additive comprises the following steps: A. Silicon carbide fibers were placed in a mixed solution of hydrochloric acid and sulfuric acid with a pH value of 1, with a volume ratio of hydrochloric acid to sulfuric acid of 1:1. After being uniformly dispersed by ultrasonication, the fibers were heated in a water bath at 60°C for 1 hour. The fibers were then taken out, cleaned, and dried to prepare pretreated silicon carbide fibers. B. Take 1.85g of ammonium molybdate tetrahydrate, 6.04g of aluminum chloride hexahydrate, 2.5mL of alkaline silica sol and 50mL of deionized water and stir and mix them evenly to obtain a modified solution. The pretreated silicon carbide fiber is placed in the modified solution and vacuum impregnated for 0.5h, then freeze-dried at -80°C for 12h, and then placed in a high-temperature box furnace, raised from room temperature to 800°C at 5°C / min, and then raised to 900°C at 1°C / min. After keeping warm for 2h, it is naturally cooled to prepare a composite silicon carbide fiber; C. Take 90 mL of ethanol and 10 mL of deionized water in a reactor, then add 1.2 mL of glacial acetic acid, 5 g of composite silicon carbide fiber, 0.06 g of hydroquinone, and 2.8 mL of 3-(methacryloyloxy)propyltrimethoxysilane in sequence, disperse evenly by ultrasonication, place at 80 ° C for 24 h, and after the reaction is completed, cool to room temperature, centrifuge, wash, and dry to prepare double-bonded composite silicon carbide fiber; D. Take 5g of double-bonded composite silicon carbide fiber, 20mL of deionized water and 10g of 4-hydroxybutyl vinyl ether in a reactor, ultrasonically disperse them evenly, then heat to 60°C, and simultaneously add a mixed solution of 1.58mL of acrylic acid and 20mL of water and 20mL of 0.025g / mL ammonium persulfate aqueous solution dropwise for 4h. After the addition is completed, place the mixture at 80°C for reaction for 5h. After the reaction is completed, centrifuge, wash and dry to prepare a functional additive.

[0019] Example 2 A method for preparing a chromium aluminum phosphate binder comprises the following steps: 10 mL of phosphoric acid and 7 mL of deionized water were placed in a reactor, and 3.5 g of aluminum hydroxide was added in portions. After stirring evenly, the mixture was reacted at room temperature for 24 h. Then, 2.28 g of chromium trioxide was added, and the mixture was stirred and reacted for 2 h. The mixture was then allowed to stand and react for 6 h. Calcium hydroxide with a mass fraction of 7% was added, and the mixture was mixed and stirred evenly to prepare a chromium aluminum phosphate binder.

[0020] Example 3: A fire-free refractory brick comprises the following components, in parts by weight: 51 parts iron ore tailings, 15 parts PO4 2.5 grade ordinary Portland cement, 10 parts fly ash, 1.7 parts functional additive prepared in Example 1, 5.5 parts river sand, 5.5 parts quartz sand, 2.3 parts chromium aluminum phosphate binder prepared in Example 2, 0.4 parts polycarboxylate superplasticizer, and 15 parts water. The main chemical components (w / %) of the iron ore tailings are: SiO2: 49.72%, Al2O3: 12.73%, Fe2O3: 21.05%, MgO: 2.61%, CaO: 1.62%, K2O: 2.12%, Na2O: 0.96%, P2O5: 0.31%, and others: 5.65; the loss on ignition is 3.23%.

[0021] The preparation method of the above-mentioned unfired refractory bricks includes the following steps: weighing each component by weight, dry mixing iron tailings, P·O42.5 grade ordinary Portland cement, fly ash, fine aggregate, and quartz sand in a cement mortar mixer for 2 minutes, then adding functional additives, chromium aluminum phosphate binder, polycarboxylate water reducer and water, mixing evenly, placing in a mold, pressing and naturally curing for 28 days, and the molding pressure is 20MPa to prepare the unfired refractory bricks.

[0022] Example 4: A fire-free refractory brick comprises the following components, in parts by weight: 55 parts iron ore tailings, 17 parts PO4 2.5 grade ordinary Portland cement, 12 parts fly ash, 3.3 parts of the functional additive prepared in Example 1, 6.8 parts river sand, 7.5 parts quartz sand, 3.4 parts of the chromium aluminum phosphate binder prepared in Example 2, 0.5 parts of a polycarboxylate superplasticizer, and 17 parts of water. The main chemical components (w / %) of the iron ore tailings are: SiO2: 49.72%, Al2O3: 12.73%, Fe2O3: 21.05%, MgO: 2.61%, CaO: 1.62%, K2O: 2.12%, Na2O: 0.96%, P2O5: 0.31%, and others: 5.65; the loss on ignition is 3.23%.

[0023] The preparation method of the above-mentioned unfired refractory bricks is the same as that of Example 3.

[0024] Example 5: A fire-free refractory brick comprises the following components, in parts by weight: 62 parts iron ore tailings, 20 parts PO4 2.5 grade ordinary Portland cement, 14 parts fly ash, 4.3 parts of the functional additive prepared in Example 1, 9.5 parts river sand, 9.2 parts quartz sand, 4.6 parts of the chromium aluminum phosphate binder prepared in Example 2, 0.7 parts of a polycarboxylate superplasticizer, and 19 parts of water. The main chemical components (w / %) of the iron ore tailings are: SiO2: 49.72%, Al2O3: 12.73%, Fe2O3: 21.05%, MgO: 2.61%, CaO: 1.62%, K2O: 2.12%, Na2O: 0.96%, P2O5: 0.31%, and others: 5.65; the loss on ignition is 3.23%.

[0025] The preparation method of the above-mentioned unfired refractory bricks is the same as that of Example 3.

[0026] Comparative Example 1: A fire-free refractory brick comprises the following components, in parts by weight: 62 parts iron ore tailings, 20 parts PO4 2.5 grade ordinary Portland cement, 14 parts fly ash, 4.3 parts silicon carbide fiber, 9.5 parts river sand, 9.2 parts quartz sand, 4.6 parts chromium aluminum phosphate binder prepared in Example 2, 0.7 part polycarboxylate superplasticizer, and 19 parts water. The main chemical components (w / %) of the iron ore tailings are: SiO2: 49.72%, Al2O3: 12.73%, Fe2O3: 21.05%, MgO: 2.61%, CaO: 1.62%, K2O: 2.12%, Na2O: 0.96%, P2O5: 0.31%, and others: 5.65%. The loss on ignition is 3.23%.

[0027] The preparation method of the above-mentioned unfired refractory bricks is the same as that of Example 3.

[0028] Comparative Example 2: A fire-free refractory brick comprises the following components, in parts by weight: 62 parts iron ore tailings, 20 parts PO4 2.5 grade ordinary Portland cement, 14 parts fly ash, 4.3 parts composite silicon carbide fiber, 9.5 parts river sand, 9.2 parts quartz sand, 4.6 parts chromium aluminum phosphate binder prepared in Example 2, 0.7 parts polycarboxylate superplasticizer, and 19 parts water. The main chemical components (w / %) of the iron ore tailings are: SiO2: 49.72%, Al2O3: 12.73%, Fe2O3: 21.05%, MgO: 2.61%, CaO: 1.62%, K2O: 2.12%, Na2O: 0.96%, P2O5: 0.31%, and others: 5.65; the loss on ignition is 3.23%.

[0029] The preparation method of the above-mentioned unfired refractory bricks is the same as that of Example 3.

[0030] Comparative Example 3: A fire-free refractory brick comprises the following components, in parts by weight: 62 parts iron ore tailings, 20 parts PO4 2.5 grade ordinary Portland cement, 14 parts fly ash, 4.3 parts of the functional additive prepared in Example 1, 9.5 parts river sand, 9.2 parts quartz sand, 0.7 parts polycarboxylate superplasticizer, and 19 parts water. The main chemical components (w / %) of the iron ore tailings are: SiO2: 49.72%, Al2O3: 12.73%, Fe2O3: 21.05%, MgO: 2.61%, CaO: 1.62%, K2O: 2.12%, Na2O: 0.96%, P2O5: 0.31%, and others: 5.65%. The loss on ignition is 3.23%.

[0031] The preparation method of the above-mentioned unfired refractory bricks is the same as that of Example 3.

[0032] Performance testing The performance of the unburned refractory bricks prepared in Examples 3-5 and Comparative Examples 1-3 was tested: (1) Compression and flexural strength test: The compression and flexural strength tests were carried out using a YAW-300C cement compression and flexural integrated machine. The data results are shown in Table 1.

[0033] (2) Fire resistance test: According to GB / T 9978.1-2008, the initial back-fire surface temperature of the test sample is 26.4°C, the thickness of the test sample is 30 mm, the fire source temperature is 1300°C, and the position of the fire source and the test sample are adjusted so that they are placed on the same horizontal line. The temperature of the back-fire surface of the test sample after 120 minutes is measured. The data results are shown in Table 1.

[0034] (3) Water absorption test: After curing the sample for 28 days, take it out, dry it and weigh it. After curing the dried sample in water at a temperature of (20±2)℃ for 24 hours, take it out and wipe off the surface moisture and weigh it again. Calculate the water absorption rate and obtain the quantitative results as shown in Table 1.

[0035] Table 1 Test results of sample performance

[0036] From the data results in Table 1, it can be seen that the unfired refractory bricks prepared in Examples 3-5 of the present invention have high compressive strength and flexural strength, low water absorption, and good fire-resistant and heat-insulating properties. In Comparative Example 1, the functional additive is replaced by silicon carbide fiber in equal amounts, and in Comparative Example 2, the functional additive is replaced by composite silicon carbide fiber in equal amounts. In Comparative Example 3, no chromium aluminum phosphate binder is added. The compressive strength and flexural strength of Comparative Examples 1-3 are lower than those of Examples 3-5, and the water absorption is higher than that of Examples 3-5, indicating that the addition of functional additives and chromium aluminum phosphate binder both improves the mechanical strength and impermeability of the brick body to a certain extent. In addition, the back-fire surface temperature in Comparative Example 1 is measured to be higher than that of Examples 3-5 and Comparative Examples 2-3, indicating that the growth of mullite whiskers on the silicon carbide surface improves the fire-resistant and heat-insulating properties of the brick body to a certain extent.

[0037] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0038] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A fire-free refractory brick, characterized in that: The invention comprises the following components in parts by weight: 50-65 parts of iron ore tailings, 14-20 parts of cement, 10-15 parts of fly ash, 1.5-4.5 parts of functional additives, 5-10 parts of fine aggregate, 5-10 parts of quartz sand, 2-5 parts of chromium aluminum phosphate binder, 0.3-0.7 parts of water reducer, and 14-20 parts of water; The functional additive is prepared by using aluminum chloride hexahydrate and alkaline silica sol as raw materials, ammonium molybdate tetrahydrate as a catalyst, and adopting a vacuum impregnation and heat treatment method to grow mullite whiskers on the surface of silicon carbide fiber. The prepared composite silicon carbide fiber is modified with 3-(methacryloyloxy)propyltrimethoxysilane and then copolymerized with acrylic acid and 4-hydroxybutyl vinyl ether. The chromium aluminum phosphate binder is prepared by using aluminum hydroxide, phosphoric acid and chromium trioxide as raw materials and calcium hydroxide as a curing agent.

2. The unburned refractory brick according to claim 1, characterized in that: The cement is P·O42.5 grade ordinary Portland cement; the fine aggregate is river sand with a fineness modulus between 2.4 and 2.8; the water reducer is a polycarboxylate water reducer; and the quartz sand has a particle size of 100 to 210 μm.

3. The unburned refractory brick according to claim 1, characterized in that: The preparation method of the functional additive comprises the following steps: A. Place silicon carbide fiber in a mixed solution of hydrochloric acid and sulfuric acid with a pH value of 1, with a volume ratio of hydrochloric acid to sulfuric acid of 1:1, disperse evenly by ultrasonication, and heat in a water bath at 55-60°C for 0.5-1h. Then, take out, wash, and dry to prepare pretreated silicon carbide fiber. B. Ammonium molybdate tetrahydrate, aluminum chloride hexahydrate, alkaline silica sol and deionized water were stirred and mixed to obtain a modified solution, and the pretreated silicon carbide fiber was placed in the modified solution and vacuum impregnated for 0.5 to 1 hour, and then freeze-dried at -80 to -75°C for 10 to 12 hours, and then heated to 800 to 900°C for sintering, kept warm for 2 to 2.5 hours, and then naturally cooled to prepare a composite silicon carbide fiber; C. Take ethanol and deionized water in a reactor, then add glacial acetic acid, composite silicon carbide fiber, hydroquinone, and 3-(methacryloyloxy)propyltrimethoxysilane in sequence, disperse evenly by ultrasonication, place at 70-85°C for reaction for 20-24 hours, cool to room temperature after the reaction is completed, centrifuge, wash, and dry to prepare double-bonded composite silicon carbide fiber; D. Place double-bonded composite silicon carbide fiber, deionized water, and 4-hydroxybutyl vinyl ether in a reactor, disperse them uniformly by ultrasonication, then heat to 55-65°C, and simultaneously dropwise add an aqueous solution of acrylic acid and an aqueous solution of ammonium persulfate for 3.5-4 hours. After the addition is completed, place the mixture at 75-85°C for reaction for 4-5 hours. After the reaction is completed, centrifuge, wash, and dry to obtain a functional additive.

4. The unburned refractory brick according to claim 3, characterized in that: The length of the silicon carbide fiber in step A is 4-8 mm.

5. The unburned refractory brick according to claim 3, characterized in that: In the step B, the addition ratio of ammonium molybdate tetrahydrate, aluminum chloride hexahydrate, alkaline silica sol and deionized water is 1.8-2 g: 6-6.2 g: 2-3.6 mL: 48-60 mL.

6. The unburned refractory brick according to claim 3, characterized in that: The sintering procedure in step B is specifically as follows: increasing the temperature from room temperature to 800° C. at 5° C. / min, and then increasing the temperature to 900° C. at 1° C. / min.

7. The unburned refractory brick according to claim 3, characterized in that: The volume percentage concentration of the acrylic acid aqueous solution in step D is 7.32%; the concentration of the ammonium persulfate aqueous solution is 0.025 g / mL; and the addition ratio of the double-bonded composite silicon carbide fiber, 4-hydroxybutyl vinyl ether, acrylic acid aqueous solution, and ammonium persulfate aqueous solution is 5 g:10-15 g:20-25 mL:18-22 mL.

8. The unburned refractory brick according to claim 1, characterized in that: The preparation method of the aluminum chromium phosphate binder comprises the following steps: taking phosphoric acid and deionized water into a reactor, adding aluminum hydroxide in batches, stirring evenly, reacting at room temperature for 20 to 24 hours, then adding chromium trioxide, continuing to stir and react for 2 to 3 hours, then standing and reacting for 5 to 6 hours, and then adding calcium hydroxide with a mass fraction of 6.5 to 7.5%, mixing and stirring evenly to prepare the aluminum chromium phosphate binder.

9. The unburned refractory brick according to claim 8, characterized in that: The molar ratio of the phosphorus element to the aluminum element is 3:1.55; the molar ratio of the aluminum element to the chromium element is 3:

2.

10. A method for preparing unburned refractory bricks according to any one of claims 1 to 9, characterized in that: The following steps are involved: The components are weighed in parts by weight, and the iron tailings, cement, fly ash, fine aggregate, and quartz sand are dry-mixed in a cement mortar mixer for 2 to 5 minutes. Functional additives, chromium aluminum phosphate binder, water reducer, and water are then added. After mixing evenly, the mixture is placed in a mold for press molding and naturally cured to prepare the unfired refractory bricks.

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