High-strength building gypsum using by-product calcium sulfate as raw material and preparation method thereof

Abstract

The application belongs to the field of light building materials, and particularly relates to high-strength building gypsum with by-product calcium sulfate as raw material and a preparation method thereof. The preparation method comprises the following steps: S1, first, desulfurization gypsum is pretreated, then the pretreated desulfurization gypsum, concentrated sulfuric acid, glycerol and cetyltrimethylammonium bromide are mixed to prepare product A, and finally, the product A is surface treated by sodium oleate to obtain by-product calcium sulfate material; S2, the by-product calcium sulfate material, steel slag, initiator, sulphoaluminate cement, fly ash, methyl sodium silicate and water reducing agent are added into water and stirred and mixed, then injected into a mold, vibration formed, then subjected to ultraviolet light irradiation, and naturally cured at room temperature to obtain high-strength building gypsum with by-product calcium sulfate as raw material. The application can not only ensure low bulk density, but also effectively improve the bending strength and compressive strength, so that it can be effectively applied in the field of light building materials.

Description

Technical Field

[0001] This invention belongs to the field of lightweight building materials, specifically relating to a high-strength building gypsum made from by-product calcium sulfate and its preparation method. Background Technology

[0002] Gypsum is a hydrous sulfate mineral, primarily composed of calcium sulfate dihydrate. Widely distributed in nature, it is a common sedimentary mineral, mainly formed in evaporite depositional environments, typically in ancient oceans, lakes, or saline water environments. Due to water evaporation, dissolved calcium sulfate reaches a supersaturated state and precipitates, forming gypsum deposits. It is mainly distributed in sedimentary basins, arid regions, or ancient marine sedimentary areas. Gypsum can also be obtained as an industrial byproduct, but due to its high impurity content, further processing is required for waste utilization. Because of its good plasticity, setting and hardening properties, and refractoriness, gypsum has wide applications in building materials, medicine, agriculture, and chemical industries.

[0003] Desulfurized gypsum is mainly industrial solid waste generated during flue gas desulfurization in thermal power plants, heat production and metal smelting. The specific applications of desulfurized gypsum in the field of building materials include: (1) Gypsum board: The application of desulfurized gypsum in the production of gypsum board materials is a major direction for solving solid waste. Its waste cost is lower and less energy is consumed in the production of gypsum board; (2) Gypsum-based mortar: Gypsum mortar is a building material made by adding water and aggregates to gypsum as the main cementing material; (3) Gypsum blocks and wall panels: Lightweight gypsum wall products made by adding water, stirring, casting and drying industrial desulfurized gypsum as the main raw material are a new type of lightweight building material that is green, low-carbon, environmentally friendly and meets the development requirements of the new era.

[0004] Chinese patent (publication number CN118388204A) discloses a phase change phosphogypsum-based building insulation wall material and its preparation method. This invention uses phosphogypsum, calcium sulfate whiskers, fly ash, quicklime, cement, phase change microcapsules, water-reducing agent, and retarder as internal admixtures, mixed with water and foaming agents, to obtain the phase change phosphogypsum-based building insulation wall material. By replacing materials such as concrete with phosphogypsum in the production of insulation and energy storage enclosure materials, the production cost of enclosure materials can be reduced, the utilization rate of phosphogypsum can be improved, and it has advantages such as thermal insulation and energy storage. However, this patent lacks research on the by-product calcium sulfate material, and the strength of the material needs further improvement.

[0005] Therefore, there is an urgent need for a high-strength building gypsum made from by-product calcium sulfate. By using desulfurized gypsum as a raw material to prepare by-product calcium sulfate material, and adding functional modification components, the synergistic effect between the components can ensure that the material has a low bulk density while effectively improving its flexural strength and compressive strength, making it effective for application in the field of lightweight building materials. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-strength building gypsum made from by-product calcium sulfate and its preparation method. The invention first pre-treats desulfurized gypsum, then mixes it with concentrated sulfuric acid, glycerol, and hexadecyltrimethylammonium bromide for a hydrothermal reaction, followed by surface treatment with sodium oleate to obtain by-product calcium sulfate material. This material is then combined with sulfoaluminate cement, steel slag, fly ash, sodium methylsilicate, and other components to prepare building gypsum. This process achieves high strength while maintaining low bulk density, enabling its application in the field of lightweight building materials.

[0007] In a first aspect, the present invention provides a method for preparing high-strength building gypsum using by-product calcium sulfate as raw material, comprising the following steps: S1. First, the desulfurized gypsum is pretreated to obtain pretreated desulfurized gypsum; then, the pretreated desulfurized gypsum is mixed with concentrated sulfuric acid, glycerol, and hexadecyltrimethylammonium bromide to prepare product A; finally, product A is surface treated with sodium oleate to obtain by-product calcium sulfate material. S2. Add the by-product calcium sulfate material, steel slag, initiator, sulfoaluminate cement, fly ash, sodium methylsilicate and water-reducing agent to water and stir to mix. Then pour into a mold, vibrate to form, and then irradiate with ultraviolet light and cure naturally at room temperature to obtain high-strength building gypsum made from by-product calcium sulfate.

[0008] As a preferred technical solution of the present invention, the components in step S2 include, by weight, 90-100 parts of by-product calcium sulfate material, 10-20 parts of sulfoaluminate cement, 10-15 parts of steel slag, 6-10 parts of fly ash, 6-10 parts of sodium methylsilicate, 0.6-0.8 parts of initiator, 0.6-0.8 parts of water-reducing agent and 40-50 parts of water.

[0009] As a preferred technical solution of the present invention, the weight parts of the by-product calcium sulfate material can be 90 parts, 92 parts, 94 parts, 96 parts, 98 parts, or 100 parts, etc.

[0010] As a preferred embodiment of the present invention, the weight parts of the sulfoaluminate cement may be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, or 20 parts, etc.

[0011] As a preferred embodiment of the present invention, the weight parts of the steel slag may be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, or 15 parts, etc.

[0012] As a preferred technical solution of the present invention, the weight parts of the fly ash can be 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, etc.

[0013] As a preferred embodiment of the present invention, the sodium methylsilicate may be in the following weight proportions: 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts, etc.

[0014] As a preferred technical solution of the present invention, the pretreatment step is as follows: by weight, 500-600 parts of desulfurized gypsum are added to 900-1000 parts of deionized water and stirred for 50-60 minutes, then impurities are adsorbed using a magnet, filtered, and dried to obtain pretreated desulfurized gypsum.

[0015] In the pretreatment process of this invention, stirring with deionized water can remove soluble impurities remaining in desulfurized gypsum, and magnetic separation can remove iron filings or magnetic oxides from coal-fired boilers, thereby improving the purity of raw materials and avoiding affecting subsequent performance.

[0016] As a preferred technical solution of the present invention, the preparation steps of product A are as follows: by weight, 10-20 parts of pretreated desulfurized gypsum and 10-20 parts of concentrated sulfuric acid are mixed and stirred for 4-6 minutes, then 500-600 parts of glycerol, 4-6 parts of hexadecyltrimethylammonium bromide and 200-300 parts of deionized water are added, and the mixture is transferred to a homogeneous reactor and reacted at 130-140°C for 2-4 hours. After filtration, washing with boiling water, and drying, product A is obtained.

[0017] As a preferred technical solution of the present invention, the surface treatment steps are as follows: by weight, 2-4 parts of sodium oleate are added to 900-1000 parts of deionized water at 50-60°C and stirred to dissolve, then 200-300 parts of product A are added and stirred for 20-30 minutes, kept warm for 1-2 hours, filtered, washed with water, and dried to obtain by-product calcium sulfate material.

[0018] This invention first pretreats desulfurized gypsum to remove soluble and ferromagnetic impurities. Then, the pretreated desulfurized gypsum undergoes a hydrothermal reaction in a glycerol-water system. With the help of hexadecyltrimethylammonium bromide, product A with a two-dimensional nanosheet structure is prepared. Finally, sodium oleate is used for surface treatment to obtain sodium oleate-modified calcium sulfate by-product material.

[0019] As a preferred embodiment of the present invention, the steel slag is a mercapto-modified steel slag composite material; The preparation method of the mercapto-modified steel slag composite material is as follows: steel slag composite material is prepared using steel slag powder, melamine, nickel acetylacetonate and ascorbic acid as raw materials, and then the steel slag composite material is subjected to mercapto-modification treatment to obtain mercapto-modified steel slag composite material.

[0020] As a preferred technical solution of the present invention, the preparation steps of the steel slag composite material are as follows: by weight, 10-20 parts of melamine are added to 400-500 parts of anhydrous ethanol and ultrasonically dispersed for 4-6 hours, then 90-100 parts of 1mol / L hydrochloric acid solution are added and stirred for 100-120 minutes, left to stand overnight, and dried to obtain modified melamine; 50-60 parts of the modified melamine, 20-40 parts of nickel acetylacetonate and 8-10 parts of ascorbic acid are added to 900-1000 parts of deionized water and stirred for 100-120 minutes, then 50-60 parts of steel slag powder are added and stirred for 20-30 minutes, dried at 105-115℃ for 20-24 hours, and then transferred to a tube furnace for heat treatment to obtain the steel slag composite material.

[0021] As a preferred embodiment of the present invention, the heat treatment conditions are as follows: heating to 600~700℃ at a heating rate of 10℃ / min under an argon atmosphere, holding at that temperature for 120~140min, and then cooling to room temperature.

[0022] As a preferred technical solution of the present invention, the steps of the thiolation treatment are as follows: by weight, 20-30 parts of thiolation compound are added to 400-500 parts of N,N-dimethylformamide and stirred for 20-30 minutes, then 2-4 parts of the steel slag composite material are added and fully impregnated under light-protected conditions for 30-40 minutes, then transferred to an ultraviolet light environment for thiolation treatment for 50-60 minutes, washed with N,N-dimethylformamide, and vacuum dried.

[0023] As a preferred technical solution of the present invention, the preparation steps of the thiol compound are as follows: by weight, 4-6 parts of formaldehyde solution with a mass concentration of 30% and 100-120 parts of anhydrous ethanol are mixed, and then 6-8 parts of 2-aminothiophenol are added dropwise. The mixture is refluxed at 70-80°C for 4-6 hours, filtered, and dried to obtain the thiol compound.

[0024] This invention first uses anhydrous ethanol as a dispersant to protonate melamine with hydrochloric acid to introduce active sites, thus obtaining modified melamine. Then, using nickel acetylacetone as a catalyst, carbon nanotubes are grown in situ on the surface of steel slag with modified melamine and ascorbic acid to obtain steel slag composite material. Finally, a benzene ring-containing polythiol compound is used to thiolize the melamine to prepare a thiolized steel slag composite material.

[0025] As a preferred embodiment of the present invention, the initiator is benzophenone.

[0026] As a preferred embodiment of the present invention, the water-reducing agent is a polycarboxylate water-reducing agent.

[0027] A second aspect of the present invention provides a high-strength building gypsum prepared by the preparation method described in the first aspect, using by-product calcium sulfate as raw material.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) The by-product calcium sulfate material of the present invention has a two-dimensional nanosheet structure. This structure can act as a bridge at the tip of microcrack propagation or force the crack to deflect along the sheet interface, thereby consuming fracture energy and improving the strength of the material. At the same time, sodium oleate modification can reduce the water absorption rate of building gypsum and reduce the mechanical properties deterioration caused by water absorption. The two-dimensional nanosheet structure can inhibit the generation of excessively large interconnected pores during the hydration process of gypsum and promote the formation of closed micropores with uniform size and reasonable distribution. These pores can effectively reduce the material density and achieve the effect of lightweight.

[0029] (2) The carbon nanotubes grown in situ on the surface of the mercapto-modified steel slag composite material of the present invention serve as a high-strength reinforcing phase and can act as stress concentration points. When crack propagation encounters these hard particles, crack deflection or pinning effects occur, improving the mechanical properties of the material. At the same time, the benzene ring structure introduced by the mercapto compound has greater rigidity, and the rigid skeleton can effectively resist the slippage or deformation of molecular chains under external forces, synergistically increasing the flexural strength and compressive strength of building gypsum. In addition, the mercapto-modified steel slag composite material can reduce its own packing density by introducing carbon nanotubes and mercapto compounds. Meanwhile, the organic molecular chains will occupy a certain space and interfere with the dense packing of gypsum crystals during the growth process, thereby ensuring the material's lightweight and low density.

[0030] (3) The by-product calcium sulfate material of the present invention uses sodium oleate as a double bond donor and mercapto-modified steel slag composite material as a mercapto donor. Under the action of an initiator, a click reaction occurs, and the materials are tightly connected by covalent bonds to form a continuous rigid support skeleton in the building gypsum system. At the same time, the conjugated rigid structure of the benzene ring further enhances the strength of the composite material, thereby enabling the material to obtain good compressive strength and flexural strength. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0032] Figure 1 This is a schematic diagram illustrating the preparation of the thiol compound in Example 1 of the present invention.

[0033] Figure 2 This is the 1H NMR spectrum of the thiol compound in Example 1 of the present invention. Detailed Implementation

[0034] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0035] The sources of some components in the examples and comparative examples are as follows: Fly ash, product number A01085, purchased from Wuhan Jiyesheng Chemical Co., Ltd. Sodium methylsilicate, CAS No. 16589-43-8, was purchased from Shandong Longhui Chemical Co., Ltd. Benzophenone, CAS No. 119-61-9, was purchased from Sinopharm Chemical Reagent Co., Ltd. Polycarboxylate superplasticizer, model PCA-1, purchased from Jiangsu Subote New Material Co., Ltd. Glycerin, CAS No. 56-81-5, purchased from Sinopharm Chemical Reagent Co., Ltd. Hexadecyltrimethylammonium bromide, CAS No. 57-09-0, purchased from Sinopharm Chemical Reagent Co., Ltd. Sodium oleate, CAS No. 143-19-1, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Melamine, CAS No. 108-78-1, purchased from Sinopharm Chemical Reagent Co., Ltd. Nickel acetylacetonate, CAS No. 3264-82-2, was purchased from Sinopharm Chemical Reagent Co., Ltd. Ascorbic acid, CAS No. 50-81-7, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Formaldehyde, CAS No. 50-00-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. 2-Aminothiophenol, CAS No. 137-07-5, purchased from Sinopharm Chemical Reagent Co., Ltd. Example

[0036] This embodiment provides a method for preparing high-strength building gypsum using by-product calcium sulfate as raw material, including the following steps: S1. By weight, 600 parts of desulfurized gypsum were added to 1000 parts of deionized water and stirred for 60 minutes. Then, impurities were adsorbed using a magnet, filtered, and dried to obtain pretreated desulfurized gypsum. 20 parts of pretreated desulfurized gypsum and 120 parts of concentrated sulfuric acid were mixed and stirred for 6 minutes. Then, 600 parts of glycerol, 6 parts of hexadecyltrimethylammonium bromide, and 300 parts of deionized water were added. The mixture was transferred to a homogeneous reactor and reacted at 140°C for 2 hours. After filtration, washing with boiling water, and drying, product A was obtained. At 60°C, 4 parts of sodium oleate were added to 1000 parts of deionized water and stirred to dissolve. Then, 300 parts of product A were added and stirred for 30 minutes. The mixture was kept at this temperature for 2 hours, filtered, washed with water, and dried to obtain by-product calcium sulfate material.

[0037] S2. By weight, 100 parts of by-product calcium sulfate material, 15 parts of mercaptoized steel slag composite material, 0.8 parts of initiator benzophenone, 20 parts of sulfoaluminate cement, 10 parts of fly ash, 10 parts of sodium methylsilicate and 0.8 parts of polycarboxylate superplasticizer are added to 50 parts of water and stirred to mix. The mixture is then poured into a mold, vibrated to form, and then irradiated with ultraviolet light for 20 minutes and naturally cured at room temperature to obtain high-strength building gypsum made from by-product calcium sulfate.

[0038] Preparation of the mercapto-modified steel slag composite material: By weight, 20 parts of melamine were added to 500 parts of anhydrous ethanol and ultrasonically dispersed for 6 hours. Then, 100 parts of 1 mol / L hydrochloric acid solution were added and stirred for 120 minutes. The mixture was allowed to stand overnight and then dried to obtain modified melamine. 60 parts of the modified melamine, 40 parts of nickel acetylacetonate, and 10 parts of ascorbic acid were added to 1000 parts of deionized water and stirred for 120 minutes. Then, 60 parts of steel slag powder were added and stirred for 30 minutes. The mixture was first dried at 115°C for 20 hours, and then transferred to a tube furnace for heat treatment at a heating rate of 10°C / min under an argon atmosphere. The steel slag composite material was obtained by heating to 700℃, holding at that temperature for 120 min, and then cooling to room temperature. Six parts of a 30% formaldehyde solution and 120 parts of anhydrous ethanol were mixed, and then eight parts of 2-aminobenzylthiophenol were added dropwise. The mixture was refluxed at 80℃ for 4 h, filtered, and dried to obtain a mercapto compound. Thiamethoxam was added to 500 parts of N,N-dimethylformamide and stirred for 30 min. Then, four parts of the steel slag composite material were added and the mixture was fully impregnated under light-protected conditions for 40 min. The mixture was then transferred to an ultraviolet light environment for mercaptolation treatment for 60 min, washed with N,N-dimethylformamide, and vacuum dried. Example

[0039] This embodiment provides a method for preparing high-strength building gypsum using by-product calcium sulfate as raw material, including the following steps: S1. By weight, 500 parts of desulfurized gypsum were added to 900 parts of deionized water and stirred for 50 minutes. Then, impurities were adsorbed using a magnet, filtered, and dried to obtain pretreated desulfurized gypsum. 10 parts of pretreated desulfurized gypsum and 10 parts of concentrated sulfuric acid were mixed and stirred for 4 minutes. Then, 500 parts of glycerol, 4 parts of hexadecyltrimethylammonium bromide, and 200 parts of deionized water were added. The mixture was transferred to a homogeneous reactor and reacted at 130°C for 4 hours. After filtration, washing with boiling water, and drying, product A was obtained. 2 parts of sodium oleate were added to 900 parts of deionized water and stirred to dissolve. Then, 200 parts of product A were added and stirred for 20 minutes. The mixture was kept at this temperature for 1 hour, filtered, washed with water, and dried to obtain by-product calcium sulfate material.

[0040] S2. By weight, 90 parts of by-product calcium sulfate material, 10 parts of mercaptoized steel slag composite material, 0.6 parts of initiator benzophenone, 10 parts of sulfoaluminate cement, 6 parts of fly ash, 6 parts of sodium methylsilicate and 0.6 parts of polycarboxylate superplasticizer are added to 40 parts of water and stirred. The mixture is then poured into a mold, vibrated and molded, and then irradiated with ultraviolet light for 10 minutes and cured naturally at room temperature to obtain high-strength building gypsum made from by-product calcium sulfate.

[0041] Preparation of the mercapto-modified steel slag composite material: By weight, 10 parts of melamine were added to 400 parts of anhydrous ethanol and ultrasonically dispersed for 4 hours. Then, 90 parts of 1 mol / L hydrochloric acid solution were added and stirred for 100 minutes. The mixture was allowed to stand overnight and then dried to obtain modified melamine. 50 parts of the modified melamine, 20 parts of nickel acetylacetonate, and 8 parts of ascorbic acid were added to 900 parts of deionized water and stirred for 100 minutes. Then, 50 parts of steel slag powder were added and stirred for 20 minutes. The mixture was first dried at 105°C for 24 hours, and then transferred to a tube furnace for heat treatment. The mixture was heated at a heating rate of 10°C / min under an argon atmosphere. The mixture was heated to 600℃ and held for 140 min, then cooled to room temperature to obtain a steel slag composite material. Four parts of a 30% formaldehyde solution and 100 parts of anhydrous ethanol were mixed, and then six parts of 2-aminothiophenol were added dropwise. The mixture was refluxed at 70℃ for 6 h, filtered, and dried to obtain a mercapto compound. Twenty parts of the mercapto compound were added to 400 parts of N,N-dimethylformamide and stirred for 20 min. Then, two parts of the steel slag composite material were added and the mixture was fully impregnated for 30 min under light-protected conditions. The mixture was then transferred to an ultraviolet light environment for mercaptolation treatment for 50 min, washed with N,N-dimethylformamide, and vacuum dried. Example

[0042] This embodiment provides a method for preparing high-strength building gypsum using by-product calcium sulfate as raw material, including the following steps: S1. By weight, 550 parts of desulfurized gypsum were added to 950 parts of deionized water and stirred for 55 minutes. Then, impurities were adsorbed using a magnet, filtered, and dried to obtain pretreated desulfurized gypsum. 15 parts of pretreated desulfurized gypsum and 15 parts of concentrated sulfuric acid were mixed and stirred for 5 minutes. Then, 550 parts of glycerol, 5 parts of hexadecyltrimethylammonium bromide, and 250 parts of deionized water were added. The mixture was transferred to a homogeneous reactor and reacted at 135°C for 3 hours. After filtration, washing with boiling water, and drying, product A was obtained. 3 parts of sodium oleate were added to 950 parts of deionized water and stirred to dissolve. Then, 250 parts of product A were added and stirred for 25 minutes. The mixture was kept at this temperature for 1.5 hours, filtered, washed with water, and dried to obtain by-product calcium sulfate material.

[0043] S2. By weight, 95 parts of by-product calcium sulfate material, 12 parts of mercaptoized steel slag composite material, 0.7 parts of initiator benzophenone, 15 parts of sulfoaluminate cement, 8 parts of fly ash, 8 parts of sodium methylsilicate and 0.7 parts of polycarboxylate superplasticizer are added to 45 parts of water and stirred. The mixture is then poured into a mold, vibrated and molded, and then irradiated with ultraviolet light for 15 minutes and cured naturally at room temperature to obtain high-strength building gypsum made from by-product calcium sulfate.

[0044] Preparation of the mercapto-modified steel slag composite material: 15 parts by weight of melamine were added to 450 parts by weight of anhydrous ethanol and ultrasonically dispersed for 5 hours. Then, 95 parts by weight of 1 mol / L hydrochloric acid solution were added and stirred for 110 minutes. The mixture was allowed to stand overnight and then dried to obtain modified melamine. 55 parts by weight of the modified melamine, 30 parts by weight of nickel acetylacetonate, and 9 parts by weight of ascorbic acid were added to 950 parts by weight of deionized water and stirred for 110 minutes. Then, 55 parts by weight of steel slag powder were added and stirred for 25 minutes. The mixture was first dried at 110°C for 22 hours and then transferred to a tube furnace for heat treatment. The furnace was heated at a heating rate of 10°C / min under an argon atmosphere. The mixture was heated to 650℃ and held for 130 min, then cooled to room temperature to obtain a steel slag composite material. Five parts of a 30% (w / w) formaldehyde solution and 110 parts of anhydrous ethanol were mixed, and then seven parts of 2-aminobenzylthiophenol were added dropwise. The mixture was refluxed at 75℃ for 5 h, filtered, and dried to obtain a thiol compound. 25 parts of the thiol compound were added to 450 parts of N,N-dimethylformamide and stirred for 25 min. Then, three parts of the steel slag composite material were added and the mixture was fully impregnated for 35 min under light-protected conditions. The mixture was then transferred to an ultraviolet light environment for thiolization treatment for 55 min, washed with N,N-dimethylformamide, and vacuum dried.

[0045] Comparative Example 1 The difference between this comparative example and Example 1 is that desulfurized gypsum is used instead of by-product calcium sulfate material.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that no pretreatment is performed during the preparation of the by-product calcium sulfate material.

[0047] Comparative Example 3 The difference between this comparative example and Example 1 is that steel slag powder is used instead of mercaptoized steel slag composite material.

[0048] Comparative Example 4 The difference between this comparative example and Example 1 is that a steel slag composite material is used instead of a mercapto-modified steel slag composite material.

[0049] The performance of the above-mentioned embodiments and comparative examples was tested in accordance with the requirements of GB / T 9776-2022 Building Plaster.

[0050] The performance test data above are shown in Table 1.

[0051] Table 1 Performance Test Results Bulk density (kg / m³) Flexural strength (MPa) Compressive strength (MPa) Example 1 784 13.52 25.31 Example 2 791 13.38 25.16 Example 3 788 13.46 25.23 Comparative Example 1 833 9.67 18.95 Comparative Example 2 802 12.59 22.67 Comparative Example 3 820 10.25 20.04 Comparative Example 4 809 11.43 21.78 As can be seen from the above, the present invention first pre-treats the desulfurized gypsum, then mixes it with concentrated sulfuric acid, glycerol, and hexadecyltrimethylammonium bromide for a hydrothermal reaction, and then uses sodium oleate for surface treatment to obtain by-product calcium sulfate material. It is then combined with sulfoaluminate cement, mercaptoized steel slag composite material, fly ash, sodium methylsilicate and other components to prepare building gypsum (Examples 1 to 3), which has the best comprehensive performance.

[0052] Compared to Example 1, using desulfurized gypsum to replace the by-product calcium sulfate material resulted in a lack of the effect of the by-product calcium sulfate material, leading to an increase in the density and a decrease in the strength of the building gypsum (Comparative Example 1). Compared to Example 1, the by-product calcium sulfate material was not pretreated during preparation, resulting in impurities and a deterioration in performance, leading to an increase in the density and a decrease in the strength of the building gypsum (Comparative Example 2). Compared to Example 1, using steel slag powder to replace the mercapto-modified steel slag composite material resulted in a lack of the effect of the mercapto-modified steel slag composite material, leading to an increase in the density and a decrease in the strength of the building gypsum (Comparative Example 3). Compared to Example 1, using steel slag composite material to replace the mercapto-modified steel slag composite material resulted in a lack of mercapto-modification treatment, leading to an increase in the density and a decrease in the strength of the building gypsum (Comparative Example 4).

Claims

1. A method for preparing high-strength building gypsum using by-product calcium sulfate as raw material, characterized in that, Includes the following steps: S1. First, the desulfurized gypsum is pretreated to obtain pretreated desulfurized gypsum; then, the pretreated desulfurized gypsum is mixed with concentrated sulfuric acid, glycerol, and hexadecyltrimethylammonium bromide to prepare product A; finally, product A is surface treated with sodium oleate to obtain by-product calcium sulfate material. S2. Add the by-product calcium sulfate material, steel slag, initiator, sulfoaluminate cement, fly ash, sodium methylsilicate and water-reducing agent to water and stir to mix. Then pour into a mold, vibrate to form, and then irradiate with ultraviolet light and cure naturally at room temperature to obtain high-strength building gypsum made from by-product calcium sulfate.

2. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 1, characterized in that, The components in step S2, by weight, include: 90-100 parts of by-product calcium sulfate material, 10-20 parts of sulfoaluminate cement, 10-15 parts of steel slag, 6-10 parts of fly ash, 6-10 parts of sodium methylsilicate, 0.6-0.8 parts of initiator, 0.6-0.8 parts of water-reducing agent, and 40-50 parts of water.

3. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 1, characterized in that, The pretreatment steps are as follows: by weight, 500-600 parts of desulfurized gypsum are added to 900-1000 parts of deionized water and stirred for 50-60 minutes. Then, impurities are adsorbed using a magnet, filtered, and dried to obtain pretreated desulfurized gypsum.

4. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 1, characterized in that, The preparation steps of product A are as follows: by weight, 10-20 parts of pretreated desulfurized gypsum and 10-20 parts of concentrated sulfuric acid are mixed and stirred for 4-6 minutes, then 500-600 parts of glycerol, 4-6 parts of hexadecyltrimethylammonium bromide and 200-300 parts of deionized water are added, and the mixture is transferred to a homogeneous reactor and reacted at 130-140℃ for 2-4 hours. After filtration, the mixture is washed with boiling water and dried to obtain product A.

5. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 1, characterized in that, The surface treatment steps are as follows: by weight, 2-4 parts of sodium oleate are added to 900-1000 parts of deionized water at 50-60℃ and stirred to dissolve. Then, 200-300 parts of product A are added and stirred for 20-30 minutes, kept warm for 1-2 hours, filtered, washed with water, and dried to obtain by-product calcium sulfate material.

6. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 1, characterized in that, The steel slag is a mercapto-modified steel slag composite material; The preparation method of the mercapto-modified steel slag composite material is as follows: steel slag composite material is prepared using steel slag powder, melamine, nickel acetylacetonate and ascorbic acid as raw materials, and then the steel slag composite material is subjected to mercapto-modification treatment to obtain mercapto-modified steel slag composite material.

7. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 6, characterized in that, The preparation steps of the steel slag composite material are as follows: by weight, 10-20 parts of melamine are added to 400-500 parts of anhydrous ethanol and ultrasonically dispersed for 4-6 hours, then 90-100 parts of 1mol / L hydrochloric acid solution are added and stirred for 100-120 minutes, left to stand overnight, and dried to obtain modified melamine. Add 50-60 parts of the modified melamine, 20-40 parts of nickel acetylacetonate and 8-10 parts of ascorbic acid to 900-1000 parts of deionized water and stir for 100-120 minutes. Then add 50-60 parts of steel slag powder and stir for 20-30 minutes. First, dry at 105-115℃ for 20-24 hours, and then transfer to a tube furnace for heat treatment to obtain steel slag composite material.

8. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 6, characterized in that, The steps of the thiolation treatment are as follows: by weight, 20-30 parts of thiolation compound are added to 400-500 parts of N,N-dimethylformamide and stirred for 20-30 minutes. Then, 2-4 parts of the steel slag composite material are added and fully impregnated under light-protected conditions for 30-40 minutes. Then, the mixture is transferred to an ultraviolet light environment for thiolation treatment for 50-60 minutes, washed with N,N-dimethylformamide, and vacuum dried.

9. The method for preparing high-strength building gypsum using by-product calcium sulfate as raw material according to claim 8, characterized in that, The preparation steps of the thiol compound are as follows: by weight, 4-6 parts of a 30% formaldehyde solution and 100-120 parts of anhydrous ethanol are mixed, and then 6-8 parts of 2-aminothiophenol are added dropwise. The mixture is refluxed at 70-80°C for 4-6 hours, filtered, and dried to obtain the thiol compound.

10. A high-strength building gypsum made from by-product calcium sulfate, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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