A method for resource processing of desulfurization gypsum solid waste

Abstract

The application discloses a desulfurization gypsum solid waste resource treatment method, relates to the technical field of light building materials, and belongs to the patent publication C04B11 / 26. The method comprises the following steps: grinding desulfurization gypsum, calcined coal-series kaolin, calcium carbonate and triethanolamine together to obtain high-strength cementitious powder; mixing the high-strength cementitious powder with slag powder and silica fume to obtain a mixture; adding a composite alkali activator prepared by mixing water glass and NaOH solid into the mixture; and obtaining super-high-activity composite cementitious material after mechanical and chemical activation; stirring the super-high-activity composite cementitious material with deionized water to form slurry, and adding nano-SiO2, PVA fiber, basalt fiber and pre-hydrolyzed silane coupling agent KH-550; and after stirring, defoaming, pressing and forming and standard curing, a fiber-reinforced matrix building material is obtained. The application applies desulfurization gypsum to building materials to realize resource utilization of the desulfurization gypsum, and the obtained building material has excellent mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of lightweight building materials technology, and belongs to patent publication number C04B11 / 26, specifically a method for the resource utilization of desulfurized gypsum solid waste. Background Technology

[0002] With the continuous development of industrial production, the amount of desulfurized gypsum emitted during flue gas desulfurization processes in industrial enterprises such as coal-fired power plants and steel mills has been increasing year by year, becoming a typical type of bulk industrial solid waste. Statistics show that my country produces tens of millions of tons of desulfurized gypsum annually. A large amount of underutilized desulfurized gypsum needs to be disposed of through stockpiling, which not only occupies valuable land resources but also may cause dust dispersion due to open-air storage, impacting the surrounding air quality. Furthermore, if the seepage prevention measures at the stockpiling site are inadequate, the soluble salts it contains may seep into the soil under the leaching effect of rainwater, damaging the local soil structure and posing potential pressure on the ecological environment. Therefore, realizing the resource utilization of desulfurized gypsum has become an important issue in the field of industrial solid waste treatment.

[0003] Currently, applying desulfurized gypsum to the building materials field is one of the main ways to realize its resource utilization. For example, it is used as a retarder in cement production to regulate cement setting time, and as a main raw material in products such as paper-faced gypsum board, gypsum blocks, and plastering gypsum. However, desulfurized gypsum itself has problems such as loose crystal structure and high impurity content. When directly applied to building materials, it often leads to insufficient mechanical properties of the finished products, especially low flexural strength and compressive strength, making it difficult to meet the requirements of high-grade building components or load-bearing scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the resource-based treatment of desulfurized gypsum solid waste, thereby solving the technical problem mentioned in the background art where the mechanical strength of desulfurized gypsum directly applied to building materials is low. This invention enables the resource-based utilization of desulfurized gypsum, allowing it to be used in building materials with excellent mechanical strength, thus meeting the requirements of high-strength building components or load-bearing applications.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for the resource utilization of desulfurized gypsum solid waste includes the following steps:

[0007] a) Desulfurized gypsum, calcined coal-based kaolin, calcium carbonate and triethanolamine are ground together. The raw material is heated to 1300℃ in air and kept at that temperature before being rapidly cooled. Then it is ground again to obtain a high-strength cementitious powder with anhydrous calcium sulfoaluminate and dicalcium silicate as the main phases.

[0008] b) The high-strength cementitious powder is mixed with slag powder and silica fume to obtain a mixture. A composite alkali activator prepared with water glass and NaOH solid is added to the mixture. After mechanical and chemical activation, an ultra-high activity composite cementitious material is obtained.

[0009] c) The ultra-high activity composite cementitious material is mixed with deionized water to form a slurry, and nano-SiO2, PVA fiber, basalt fiber and pre-hydrolyzed silane coupling agent KH-550 are added. After stirring, degassing, pressing and molding and standard curing, fiber-reinforced matrix building material is obtained.

[0010] In the technical solution of this invention, firstly, desulfurized gypsum is mixed with calcined coal-based kaolin and calcium carbonate, and triethanolamine, a grinding aid, is introduced for co-milling to achieve uniform mixing of the materials at the molecular scale. Subsequently, a solid-phase reaction is carried out at a high temperature of 1300℃, causing the calcium sulfate component in the desulfurized gypsum to react with aluminum, silicon, and calcium sources, generating in situ a cementitious clinker with anhydrous calcium sulfoaluminate as the main crystalline phase and dicalcium silicate as the main crystalline phase, characterized by early-strength and rapid-hardening properties and excellent later-stage strength. The rapid cooling process effectively preserves the highly active form of dicalcium silicate, thus providing a foundation for high-strength building materials. Figure 1 The SEM image of the high-strength cementitious powder prepared in this invention shows that the microstructure of the high-strength cementitious powder exhibits an irregular morphology. Then, the obtained high-strength cementitious powder is compounded with ultrafine slag powder and silica fume, and a composite alkali activator made of water glass and NaOH is used to achieve mechanochemical activation through high-energy ball milling. On the one hand, mechanical force disrupts the surface lattice of the particles, increasing their surface energy and reactive sites; on the other hand, the alkali activator fully activates the pozzolanic effect of the slag and silica fume, causing them to react with Ca(OH)2 released during the hydration of the cementitious powder, generating a large amount of low-calcium-to-silicon ratio CSH gel, which efficiently fills capillary pores, optimizes the pore structure, and significantly improves the density and interfacial bonding strength of the system. Finally, reinforcements are introduced during the molding stage: nano-SiO2 further fills the nanoscale pores and enhances the matrix strength; PVA fibers and basalt fibers form a micron-scale three-dimensional network, which effectively prevents microcrack propagation through bridging and significantly improves the material's toughness and impact resistance; the pre-hydrolyzed silane coupling agent KH-550 greatly enhances the interfacial adhesion between the inorganic matrix and organic fibers through chemical bonding, ensuring efficient stress transfer. Harmful air bubbles are removed through vacuum degassing, and the structure is further densified using a high-pressure molding process, ultimately resulting in a fiber-reinforced building material with excellent mechanical properties.

[0011] Preferably, in step a), the mass ratio of desulfurized gypsum, calcined coal-based kaolin, and calcium carbonate is 50:30-35:10-15.

[0012] Preferably, in step b), the high-strength cementitious powder undergoes a modification treatment, including the following steps:

[0013] High-strength gelling powder was dispersed in an ethanol / water mixed solvent, then tetraethyl orthosilicate and a catalyst were added, and a hydrolysis-condensation reaction was carried out under stirring conditions. After filtration, washing and drying, a composite powder was obtained. The composite powder was then immersed in a saturated calcium hydroxide solution to pre-adsorb Ca in the shell layer. 2+ and OH - The ions are separated by filtration, washed and dried to obtain modified high-strength gel powder.

[0014] In the technical solution of this invention, the R&D team discovered through in-depth research that although the high-strength cementitious powder is mainly composed of anhydrous calcium sulfoaluminate and dicalcium silicate, possessing high activity, it differs from the subsequently incorporated auxiliary cementitious materials such as slag micropowder and silica fume in terms of physical morphology and chemical activity. Direct mixing easily leads to insufficient interfacial bonding between the powder and the high-strength cementitious powder, resulting in the failure to form the densest packing between particles. This creates weak links at the micro-interface, affecting the continuity and density of the hydration product network and limiting further improvement in the material's final mechanical strength. To solve this technical problem, this invention performs core-shell structure coating and surface activation pretreatment on the high-strength cementitious powder. The modification principle is as follows: an amorphous nano-SiO2 shell layer is constructed on the surface of the powder particles using the sol-gel method. This shell layer forms a gradual transition layer in chemical composition and structure between the core cementitious phase and the surrounding slag / silica fume, greatly improving interfacial compatibility. Subsequently, treatment with a saturated calcium hydroxide solution allows the nano-SiO2 shell layer to pre-adsorb Ca. 2+ and OH - The ions not only provide a direct calcium source and alkaline environment for the subsequent volcanic ash reaction of the slag, but also transform the shell itself into a highly active precursor that can preferentially react with slag and silica fume in the early stage of hydration to form CSH gel, "anchoring" the high-strength powder particles in the matrix, thereby realizing the transformation from physical mixing to chemical bonding. This significantly enhances the interfacial bonding strength and microstructure uniformity of the composite system, thereby further improving the mechanical strength of building materials.

[0015] Preferably, in step b), the mass ratio of high-strength cementitious powder, slag powder and silica fume is 100:15-20:8-12.

[0016] Preferably, in step b), the mass ratio of water glass to NaOH solid in the composite alkali activator is 6:2 to 4.

[0017] Preferably, in step b), the amount of the composite alkali activator added is 3-6 wt% of the mass of the mixture.

[0018] Preferably, in step c), the mass ratio of the ultra-high activity composite cementitious material, nano-SiO2, PVA fiber, and basalt fiber is 100:0.1~0.5:0.5~1:1~2.

[0019] Preferably, in step c), the degassing time is 10 to 20 minutes.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. Using desulfurized gypsum, a solid waste, as one of the main raw materials, it is mixed with calcined coal-based kaolin, calcium carbonate, etc., and processed through a series of processes to prepare fiber-reinforced matrix building materials. This realizes the resource-based reuse of desulfurized gypsum, reduces the emission of solid waste, and meets the requirements of environmental protection and sustainable development.

[0022] 2. By uniformly mixing desulfurized gypsum with other raw materials at the molecular scale, a cementitious clinker with anhydrous calcium sulfoaluminate and dicalcium silicate as the main crystalline phases is generated in situ through a high-temperature solid-phase reaction. The rapid cooling process preserves the highly active form of dicalcium silicate. Simultaneously, a composite alkali activator is used to activate the pozzolanic effect of slag and silica fume, generating a large amount of low-calcium-to-silicon ratio CSH gel, which fills capillary pores, optimizes the pore structure, and significantly improves the material's density and interfacial bonding strength, thus giving the material high strength.

[0023] 3. During the molding stage, nano-SiO2, PVA fibers, basalt fibers, and pre-hydrolyzed silane coupling agent KH-550 are introduced. Nano-SiO2 fills the nanoscale pores to enhance the matrix strength, PVA fibers and basalt fibers form a micron-scale three-dimensional network to prevent microcrack propagation, and the silane coupling agent enhances the interfacial adhesion between the inorganic matrix and organic fibers, ensuring efficient stress transfer, ultimately significantly improving the material's toughness and impact resistance. Attached Figure Description

[0024] Figure 1 This is a SEM image of the high-strength gelling powder prepared according to the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] A method for the resource utilization of desulfurized gypsum solid waste includes the following steps:

[0028] Step 1: Weigh 500g of desulfurized gypsum, 340g of calcined coal-based kaolin, and 145g of calcium carbonate. Mix them thoroughly, then add 0.95g of triethanolamine as a grinding aid. Place the above materials into a planetary ball mill for co-grinding, controlling the ball-to-material ratio at 5:1 and the rotation speed at 300 r / min, until the specific surface area of ​​the material reaches 420 m². 2 / kg. After grinding, the raw material is placed in a high-temperature sintering furnace and heated to 1300℃ at a rate of 8℃ / min in air atmosphere, and held at this temperature for 40 minutes. After the holding period, the furnace door is quickly opened and the material is removed. It is then immediately subjected to rapid cooling with a high-pressure airflow, causing the material to drop below 800℃ within 1 minute. After the material cools to room temperature, it is placed back into the ball mill and ground until the specific surface area reaches 480m². 2 / kg, to obtain high-strength cementitious powder with anhydrous calcium sulfoaluminate and dicalcium silicate as the main phases.

[0029] Step 2: Take 1000g of high-strength gelling powder and disperse it in a mixed solvent of 2000mL ethanol and water (volume ratio 1:1). Add 65g of tetraethyl orthosilicate and 0.8mL of concentrated hydrochloric acid (38wt%) as a catalyst to the dispersion system, adjust the pH of the system to 3.5, and react in a constant temperature water bath at 40℃ for 3 hours at a stirring rate of 400r / min. After the reaction is complete, filter with a Buchner funnel, wash three times alternately with deionized water and ethanol, and dry the resulting composite powder in an 85℃ oven for 5 hours. Then, immerse the dried composite powder in 2L of saturated calcium hydroxide solution for 1.5 hours, filter and separate, wash with deionized water until the pH of the filtrate is 7, and dry again in an 85℃ oven for 5 hours to obtain modified high-strength gelling powder.

[0030] Mix 1000g of modified high-strength cementitious powder, 190g of slag micro powder, and 110g of silica fume evenly to form a mixture. Prepare the composite alkali activator: Weigh 60g of water glass (modulus 1.2) and 35g of NaOH solid, add 100mL of deionized water, and stir until the NaOH is completely dissolved to obtain the composite alkali activator. Add the composite alkali activator (5wt% of the mixture's mass) to the mixture, and place them together in a high-energy ball mill. Control the ball-to-powder ratio at 8:1, the rotation speed at 400r / min, and perform mechanochemical activation for 2.5 hours until the powder specific surface area reaches 600m². 2 / kg, to obtain ultra-high activity composite cementitious material.

[0031] Step 3: Weigh 1000g of ultra-high activity composite cementitious material, 15g of polycarboxylate-based high-efficiency water-reducing agent, and 280mL of deionized water. Mix in a planetary mixer at 600r / min for 3 minutes to prepare a homogeneous slurry. Add 4g of nano-SiO2, 8g of PVA fiber, 18g of basalt fiber, and 8g of pre-hydrolyzed silane coupling agent KH-550 sequentially to the slurry (hydrolysis conditions: 8g KH-550 + 50mL deionized water + 0.5mL acetic acid, stirred for 30 minutes). Continue stirring at 800r / min for 5 minutes until uniformly mixed. Transfer the slurry to a vacuum mixer and degas for 15 minutes under a vacuum of -0.095MPa. Pour the degassed slurry into a standard mold measuring 40mm×40mm×160mm and press-mold at 20MPa for 2 minutes. After molding, the molded material is placed in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of ≥95% for 24 hours before demolding. After demolding, it continues to be cured under the same conditions for 28 days to obtain fiber-reinforced matrix building materials.

[0032] Example 2

[0033] A method for the resource utilization of desulfurized gypsum solid waste includes the following steps:

[0034] Step 1: Weigh 500g of desulfurized gypsum, 320g of calcined coal-based kaolin, and 115g of calcium carbonate. Mix them thoroughly, then add 0.95g of triethanolamine as a grinding aid. Place the above materials into a planetary ball mill for grinding, controlling the ball-to-material ratio at 5:1 and the rotation speed at 300 r / min, until the specific surface area of ​​the material reaches 420 m². 2 / kg. After grinding, the raw material is placed in a high-temperature sintering furnace and heated to 1300℃ at a rate of 8℃ / min in air atmosphere, and held at this temperature for 40 minutes. After the holding period, the furnace door is quickly opened and the material is removed. It is then immediately subjected to rapid cooling with a high-pressure airflow, causing the material to drop below 800℃ within 1 minute. After the material cools to room temperature, it is placed back into the ball mill and ground until the specific surface area reaches 480m². 2 / kg, to obtain high-strength cementitious powder with anhydrous calcium sulfoaluminate and dicalcium silicate as the main phases.

[0035] Step 2: Take 1000g of high-strength gelling powder and disperse it in a mixed solvent of 2000mL ethanol and water (volume ratio 1:1). Add 65g of tetraethyl orthosilicate and 0.8mL of concentrated hydrochloric acid (38wt%) as a catalyst to the dispersion system, adjust the pH of the system to 3.5, and react in a constant temperature water bath at 40℃ for 3 hours at a stirring rate of 400r / min. After the reaction is complete, filter with a Buchner funnel, wash three times alternately with deionized water and ethanol, and dry the resulting composite powder in an 85℃ oven for 5 hours. Then, immerse the dried composite powder in 2L of saturated calcium hydroxide solution for 1.5 hours, filter and separate, wash with deionized water until the pH of the filtrate is 7, and dry again in an 85℃ oven for 5 hours to obtain modified high-strength gelling powder.

[0036] Mix 1000g of modified high-strength cementitious powder, 165g of slag micro powder, and 90g of silica fume evenly to form a mixture. Prepare the composite alkali activator: Weigh 60g of water glass (modulus 1.2) and 25g of NaOH solid, add 100mL of deionized water, and stir until the NaOH is completely dissolved to obtain the composite alkali activator. Add the composite alkali activator (4wt% of the mixture mass) to the mixture, and place them together in a high-energy ball mill. Control the ball-to-powder ratio at 8:1, the rotation speed at 400r / min, and perform mechanochemical activation for 2.5 hours until the powder specific surface area reaches 600m². 2 / kg, to obtain ultra-high activity composite cementitious material.

[0037] Step 3: Weigh 1000g of ultra-high activity composite cementitious material, 15g of polycarboxylate-based high-efficiency water-reducing agent, and 280mL of deionized water. Mix in a planetary mixer at 600r / min for 3 minutes to prepare a homogeneous slurry. Add 2g of nano-SiO2, 6g of PVA fiber, 13.5g of basalt fiber, and 8g of pre-hydrolyzed silane coupling agent KH-550 sequentially to the slurry (hydrolysis conditions: 8g KH-550 + 50mL deionized water + 0.5mL acetic acid, stirred for 30 minutes). Continue stirring at 800r / min for 5 minutes until uniformly mixed. Transfer the slurry to a vacuum mixer and degas for 15 minutes under a vacuum of -0.095MPa. Pour the degassed slurry into a standard mold measuring 40mm×40mm×160mm and press-mold at 20MPa for 2 minutes. After molding, the molded material is placed in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of ≥95% for 24 hours before demolding. After demolding, it continues to be cured under the same conditions for 28 days to obtain fiber-reinforced matrix building materials.

[0038] Example 3

[0039] A method for the resource utilization of desulfurized gypsum solid waste includes the following steps:

[0040] Step 1: Weigh 500g of desulfurized gypsum, 330g of calcined coal-based kaolin, and 135g of calcium carbonate. Mix them thoroughly, then add 0.95g of triethanolamine as a grinding aid. Place the above materials into a planetary ball mill for grinding, controlling the ball-to-material ratio at 5:1 and the rotation speed at 300 r / min, until the specific surface area of ​​the material reaches 420 m². 2 / kg. After grinding, the raw material is placed in a high-temperature sintering furnace and heated to 1300℃ at a rate of 8℃ / min in air atmosphere, and held at this temperature for 40 minutes. After the holding period, the furnace door is quickly opened and the material is removed. It is then immediately subjected to rapid cooling with a high-pressure airflow, causing the material to drop below 800℃ within 1 minute. After the material cools to room temperature, it is placed back into the ball mill and ground until the specific surface area reaches 480m². 2 / kg, to obtain high-strength cementitious powder with anhydrous calcium sulfoaluminate and dicalcium silicate as the main phases.

[0041] Step 2: Take 1000g of high-strength gelling powder and disperse it in a mixed solvent of 2000mL ethanol and water (volume ratio 1:1). Add 65g of tetraethyl orthosilicate and 0.8mL of concentrated hydrochloric acid (38wt%) as a catalyst to the dispersion system, adjust the pH of the system to 3.5, and react in a constant temperature water bath at 40℃ for 3 hours at a stirring rate of 400r / min. After the reaction is complete, filter with a Buchner funnel, wash three times alternately with deionized water and ethanol, and dry the resulting composite powder in an 85℃ oven for 5 hours. Then, immerse the dried composite powder in 2L of saturated calcium hydroxide solution for 1.5 hours, filter and separate, wash with deionized water until the pH of the filtrate is 7, and dry again in an 85℃ oven for 5 hours to obtain modified high-strength gelling powder.

[0042] Mix 1000g of modified high-strength cementitious powder, 175g of slag micro powder, and 100g of silica fume evenly to form a mixture. Prepare the composite alkali activator: Weigh 60g of water glass (modulus 1.2) and 30g of NaOH solid, add 100mL of deionized water, and stir until the NaOH is completely dissolved to obtain the composite alkali activator. Add the composite alkali activator (4.5wt% of the mixture mass) to the mixture, and place them together in a high-energy ball mill. Control the ball-to-powder ratio at 8:1, the rotation speed at 400r / min, and perform mechanochemical activation for 2.5 hours until the powder specific surface area reaches 600m². 2 / kg, to obtain ultra-high activity composite cementitious material.

[0043] Step 3: Weigh 1000g of ultra-high activity composite cementitious material, 15g of polycarboxylate-based high-efficiency water-reducing agent, and 280mL of deionized water. Mix in a planetary mixer at 600r / min for 3 minutes to prepare a homogeneous slurry. Add 3g of nano-SiO2, 7.5g of PVA fiber, 15g of basalt fiber, and 8g of pre-hydrolyzed silane coupling agent KH-550 sequentially to the slurry (hydrolysis conditions: 8g KH-550 + 50mL deionized water + 0.5mL acetic acid, stirred for 30 minutes). Continue stirring at 800r / min for 5 minutes until uniformly mixed. Transfer the slurry to a vacuum mixer and degas for 15 minutes under a vacuum of -0.095MPa. Pour the degassed slurry into a standard mold measuring 40mm×40mm×160mm and press-mold at 20MPa for 2 minutes. After molding, the molded material is placed in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of ≥95% for 24 hours before demolding. After demolding, it continues to be cured under the same conditions for 28 days to obtain fiber-reinforced matrix building materials.

[0044] Example 4

[0045] A method for the resource utilization of desulfurized gypsum solid waste includes the following steps:

[0046] Step 1: Weigh 500g of desulfurized gypsum, 350g of calcined coal-based kaolin, and 150g of calcium carbonate. Mix them thoroughly, then add 0.95g of triethanolamine as a grinding aid. Place the above materials into a planetary ball mill for grinding, controlling the ball-to-material ratio at 5:1 and the rotation speed at 300 r / min, until the specific surface area of ​​the material reaches 420 m². 2 / kg. After grinding, the raw material is placed in a high-temperature sintering furnace and heated to 1300℃ at a rate of 8℃ / min in air atmosphere, and held at this temperature for 40 minutes. After the holding period, the furnace door is quickly opened and the material is removed. It is then immediately subjected to rapid cooling with a high-pressure airflow, causing the material to drop below 800℃ within 1 minute. After the material cools to room temperature, it is placed back into the ball mill and ground until the specific surface area reaches 480m². 2 / kg, to obtain high-strength cementitious powder with anhydrous calcium sulfoaluminate and dicalcium silicate as the main phases.

[0047] Step 2: Take 1000g of high-strength gelling powder and disperse it in a mixed solvent of 2000mL ethanol and water (volume ratio 1:1). Add 65g of tetraethyl orthosilicate and 0.8mL of concentrated hydrochloric acid (38wt%) as a catalyst to the dispersion system, adjust the pH of the system to 3.5, and react in a constant temperature water bath at 40℃ for 3 hours at a stirring rate of 400r / min. After the reaction is complete, filter with a Buchner funnel, wash three times alternately with deionized water and ethanol, and dry the resulting composite powder in an 85℃ oven for 5 hours. Then, immerse the dried composite powder in 2L of saturated calcium hydroxide solution for 1.5 hours, filter and separate, wash with deionized water until the pH of the filtrate is 7, and dry again in an 85℃ oven for 5 hours to obtain modified high-strength gelling powder.

[0048] Mix 1000g of modified high-strength cementitious powder, 200g of slag micro powder, and 120g of silica fume evenly to form a mixture. Prepare the composite alkali activator: Weigh 60g of water glass (modulus 1.2) and 40g of NaOH solid, add 100mL of deionized water, and stir until the NaOH is completely dissolved to obtain the composite alkali activator. Add the composite alkali activator (6wt% of the mixture's mass) to the mixture, and place them together in a high-energy ball mill. Control the ball-to-powder ratio at 8:1, the rotation speed at 400r / min, and perform mechanochemical activation for 2.5 hours until the powder specific surface area reaches 600m². 2 / kg, to obtain ultra-high activity composite cementitious material.

[0049] Step 3: Weigh 1000g of ultra-high activity composite cementitious material, 15g of polycarboxylate-based high-efficiency water-reducing agent, and 280mL of deionized water. Mix in a planetary mixer at 600r / min for 3 minutes to prepare a homogeneous slurry. Add 5g of nano-SiO2, 10g of PVA fiber, 20g of basalt fiber, and 8g of pre-hydrolyzed silane coupling agent KH-550 sequentially to the slurry (hydrolysis conditions: 8g KH-550 + 50mL deionized water + 0.5mL acetic acid, stirred for 30 minutes). Continue stirring at 800r / min for 5 minutes until uniformly mixed. Transfer the slurry to a vacuum mixer and degas for 15 minutes under a vacuum of -0.095MPa. Pour the degassed slurry into a standard mold measuring 40mm×40mm×160mm and press-mold at 20MPa for 2 minutes. After molding, the molded material is placed in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of ≥95% for 24 hours before demolding. After demolding, it continues to be cured under the same conditions for 28 days to obtain fiber-reinforced matrix building materials.

[0050] Example 5

[0051] A method for the resource utilization of desulfurized gypsum solid waste includes the following steps:

[0052] Step 1: Weigh 500g of desulfurized gypsum, 300g of calcined coal-based kaolin, and 100g of calcium carbonate. Mix them thoroughly, then add 0.95g of triethanolamine as a grinding aid. Place the above materials into a planetary ball mill for grinding, controlling the ball-to-material ratio at 5:1 and the rotation speed at 300 r / min, until the specific surface area of ​​the material reaches 420 m². 2 / kg. After grinding, the raw material is placed in a high-temperature sintering furnace and heated to 1300℃ at a rate of 8℃ / min in air atmosphere, and held at this temperature for 40 minutes. After the holding period, the furnace door is quickly opened and the material is removed. It is then immediately subjected to rapid cooling with a high-pressure airflow, causing the material to drop below 800℃ within 1 minute. After the material cools to room temperature, it is placed back into the ball mill and ground until the specific surface area reaches 480m². 2 / kg, to obtain high-strength cementitious powder with anhydrous calcium sulfoaluminate and dicalcium silicate as the main phases.

[0053] Step 2: Take 1000g of high-strength gelling powder and disperse it in a mixed solvent of 2000mL ethanol and water (volume ratio 1:1). Add 65g of tetraethyl orthosilicate and 0.8mL of concentrated hydrochloric acid (38wt%) as a catalyst to the dispersion system, adjust the pH of the system to 3.5, and react in a constant temperature water bath at 40℃ for 3 hours at a stirring rate of 400r / min. After the reaction is complete, filter with a Buchner funnel, wash three times alternately with deionized water and ethanol, and dry the resulting composite powder in an 85℃ oven for 5 hours. Then, immerse the dried composite powder in 2L of saturated calcium hydroxide solution for 1.5 hours, filter and separate, wash with deionized water until the pH of the filtrate is 7, and dry again in an 85℃ oven for 5 hours to obtain modified high-strength gelling powder.

[0054] Mix 1000g of modified high-strength cementitious powder, 150g of slag micro powder, and 80g of silica fume evenly to form a mixture. Prepare the composite alkali activator: Weigh 60g of water glass (modulus 1.2) and 20g of NaOH solid, add 100mL of deionized water, and stir until the NaOH is completely dissolved to obtain the composite alkali activator. Add the composite alkali activator (3wt% of the mixture mass) to the mixture, and place them together in a high-energy ball mill. Control the ball-to-powder ratio at 8:1, the rotation speed at 400r / min, and perform mechanochemical activation for 2.5 hours until the powder specific surface area reaches 600m². 2 / kg, to obtain ultra-high activity composite cementitious material.

[0055] Step 3: Weigh 1000g of ultra-high activity composite cementitious material, 15g of polycarboxylate-based high-efficiency water-reducing agent, and 280mL of deionized water. Mix in a planetary mixer at 600r / min for 3 minutes to prepare a homogeneous slurry. Add 1g of nano-SiO2, 5g of PVA fiber, 10g of basalt fiber, and 8g of pre-hydrolyzed silane coupling agent KH-550 sequentially to the slurry (hydrolysis conditions: 8g KH-550 + 50mL deionized water + 0.5mL acetic acid, stirred for 30 minutes). Continue stirring at 800r / min for 5 minutes until uniformly mixed. Transfer the slurry to a vacuum mixer and degas for 15 minutes under a vacuum of -0.095MPa. Pour the degassed slurry into a standard mold measuring 40mm×40mm×160mm and press-mold at 20MPa for 2 minutes. After molding, the molded material is placed in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of ≥95% for 24 hours before demolding. After demolding, it continues to be cured under the same conditions for 28 days to obtain fiber-reinforced matrix building materials.

[0056] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 1 is omitted, i.e., the desulfurized gypsum undergoes a solid-phase reaction.

[0057] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that step 2 is omitted.

[0058] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that in step 2, the high-strength gel powder is not modified.

[0059] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that in step 4, no nano-SiO2, PVA fiber, basalt fiber and pre-hydrolyzed silane coupling agent KH-550 are added.

[0060] Performance testing:

[0061] 1. Compressive Strength Test: The test shall be conducted in accordance with GB / T 17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". First, select standard specimens of 40mm × 40mm × 160mm cured to 28 days of age, preparing three parallel specimens for each age. Before testing, lightly sand the upper and lower surfaces of the specimen with sandpaper to ensure the surface is flat and perpendicular to the specimen axis. Measure the side length of the compression surface of the specimen with calipers, accurate to 0.1mm, and calculate the compression area. Place the specimen in the center of the lower platen of the hydraulic pressure testing machine. Adjust the machine so that the upper platen contacts the specimen surface but no pressure is applied. Set the loading rate of the testing machine to 2.4kN / s, start the machine, and load uniformly until the specimen fails. Record the maximum failure load (accurate to 0.1kN). The compressive strength is calculated using the formula: "Compressive Strength (MPa) = Maximum Failure Load (N) / Compression Area (mm²)". 2The arithmetic mean of the test results of three specimens at each age was used as the final result. If the result of a single specimen deviated from the average by more than ±10%, the data was removed and the average was recalculated. The test results are shown in Table 1.

[0062] 2. Flexural Strength Test: The three-point bending method was used according to GB / T 17671-1999 standard. The specimen specifications were the same as for the compressive strength test. Three parallel specimens were prepared after curing for 28 days. Before testing, surface impurities were cleaned from the specimens, and the width and height of the mid-section of the specimen were measured with calipers to an accuracy of 0.1 mm. The two support rollers and one pressure roller of the flexural testing machine were adjusted to the specified spacing (support roller spacing 100 mm, pressure roller positioned in the middle of the support rollers). The specimen was placed on the support rollers, ensuring that the length of the specimen was perpendicular to the support rollers, and the pressure surface was the side surface of the specimen during molding. The loading rate was set to 50 N / s, and the testing machine was started to apply the load uniformly downwards with the pressure roller until the specimen broke. The maximum breaking load was recorded (accurate to 0.1 N). The flexural strength was calculated using the formula: "Flexural Strength (MPa) = 3 × Maximum Breaking Load (N) × Support Roller Spacing (mm) / (Specimen Width (mm) × Specimen Height (mm))". 2 The calculation was performed, and the arithmetic mean of the test results of the three specimens was taken as the final result. The deviation handling rules were the same as those for the compressive strength test. The test results are shown in Table 1.

[0063] 3. Impact Resistance Test: The test was conducted according to GB / T 1843-2008 "Determination of Impact Strength of Plastic Cantilever Beams". 40mm×40mm×160mm specimens aged 28 days were cut into standard 80mm×10mm×4mm impact test specimens. Five parallel specimens were prepared for each group. Specimens were free of cracks, bubbles, and other defects. A simply supported beam impact testing machine was used, with a 2J pendulum selected. The pendulum pre-lift angle was adjusted to 150°. The anvil spacing was checked to be 60mm, ensuring the anvil and pendulum blade surfaces were smooth and undamaged. Before testing, the specimen surface was cleaned with alcohol. The specimen was placed horizontally on the anvil, with the midpoint aligned with the pendulum blade and the specimen length perpendicular to the anvil. The pendulum was released to impact the specimen, and the energy absorbed upon fracture (accurate to 0.01J) was recorded. If the specimen did not completely fracture, it was recorded as "not fractured" with a note; if the fracture surface deviated from the midpoint by more than 5mm, the data was invalid and the test needed to be repeated. Impact strength was calculated using the formula: "Impact Strength (kJ / m²) = 0". 2 = Absorbed energy (J) / Cross-sectional area of ​​the sample (m²) 2 The arithmetic mean of the valid test results is taken as the final result. The test results are shown in Table 1.

[0064] 4. Bulk Density Test: The density was determined according to GB / T 208-2014 "Method for Determination of Cement Density". Specimens aged 28 days were selected and dried in an oven at 105±5℃ until constant weight (the difference between two consecutive weighings should not exceed 0.1%). After drying, the specimens were removed and cooled to room temperature in a desiccator. The dried mass (m0) of the specimen was weighed using an electronic balance, accurate to 0.01g. The volume of the specimen was measured using the displacement method: A graduated cylinder containing an appropriate amount of distilled water was placed on the electronic balance. After zeroing the balance, the specimen was suspended by a thin thread and completely immersed in the water (the specimen should not touch the wall or bottom of the graduated cylinder). The mass displayed on the balance at this point was recorded (m1, accurate to 0.01g). The volume of the specimen, V, is calculated as V = m1 / ρ. 水 (ρ) 水 Take 1g / cm 3 Bulk density is calculated using the formula "Bulk density (g / cm³)". 3 The result was calculated as m0 / V. Three specimens were tested in each group, and the arithmetic mean was taken as the final result. The test results are shown in Table 1.

[0065] Table 1:

[0066]

[0067] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the resource-based treatment of desulfurized gypsum solid waste, characterized in that, Includes the following steps: a) Desulfurized gypsum, calcined coal-based kaolin, calcium carbonate and triethanolamine are ground together. The raw material is heated to 1300℃ in air and kept at that temperature before being rapidly cooled. Then it is ground again to obtain a high-strength cementitious powder with anhydrous calcium sulfoaluminate and dicalcium silicate as the main phases. b) High-strength gelling powder was dispersed in an ethanol / water mixed solvent, then tetraethyl orthosilicate and a catalyst were added, and a hydrolysis-condensation reaction was carried out under stirring. After filtration, washing and drying, a composite powder was obtained. The composite powder was then immersed in a saturated calcium hydroxide solution to pre-adsorb Ca in the shell layer. 2+ and OH - The ions are separated by filtration, washing and drying to obtain modified high-strength gel powder; Modified high-strength cementitious powder is mixed with slag powder and silica fume to obtain a mixture. A composite alkali activator prepared with water glass and NaOH solid is added to the mixture, and after mechanical and chemical activation, an ultra-high activity composite cementitious material is obtained. c) The ultra-high activity composite cementitious material is mixed with deionized water to form a slurry, and nano-SiO2, PVA fiber, basalt fiber and pre-hydrolyzed silane coupling agent KH-550 are added. After stirring, degassing, pressing and molding and standard curing, fiber-reinforced matrix building material is obtained.

2. The method for resource utilization treatment of desulfurized gypsum solid waste according to claim 1, characterized in that, In step a), the mass ratio of desulfurized gypsum, calcined coal-based kaolin, and calcium carbonate is 50:30-35:10-15.

3. The method for resource utilization treatment of desulfurized gypsum solid waste according to claim 1, characterized in that, In step b), the mass ratio of high-strength cementitious powder, slag powder and silica fume is 100:15~20:8~12.

4. The method for resource utilization treatment of desulfurized gypsum solid waste according to claim 1, characterized in that, In step b), the mass ratio of water glass to NaOH solid in the composite alkali activator is 6:2 to 4.

5. The method for resource utilization treatment of desulfurized gypsum solid waste according to claim 1, characterized in that, In step b), the amount of composite alkali activator added is 3-6 wt% of the mass of the mixture.

6. The method for resource utilization treatment of desulfurized gypsum solid waste according to claim 1, characterized in that, In step c), the mass ratio of ultra-high activity composite cementitious material, nano-SiO2, PVA fiber, and basalt fiber is 100:0.1~0.5:0.5~1:1~2.

7. The method for resource utilization treatment of desulfurized gypsum solid waste according to claim 1, characterized in that, In step c), the degassing time is 10-20 minutes.

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