Phosphogypsum-fly ash-slag multi-solid waste system high-performance concrete and preparation method thereof

Abstract

The application relates to a high-performance concrete of a phosphogypsum-fly ash-slag multi-solid waste system and a preparation method thereof, and relates to the technical field of solid waste resource preparation concrete. The high-performance concrete of the phosphogypsum-fly ash-slag multi-solid waste system comprises, in mass fraction, 45-55 parts of phosphogypsum, 60-95 parts of fly ash, 5-20 parts of slag, 0-20 parts of silica ash, 40-50 parts of alkali activator and 1-2% of steel fiber in volume fraction. The application makes full use of large solid wastes such as phosphogypsum, fly ash and slag, and does not use traditional raw materials such as cement and gravel when preparing the concrete, so that the prepared concrete has low cost, the defects of low strength development and poor performance of the solid waste are overcome, the concrete has high strength, the greenization and high performance development of the concrete material are promoted, and the application has important scientific significance and application value in the field of building materials.

Description

Technical Field

[0001] This application relates to the field of concrete preparation technology from solid waste resources, and in particular to a high-performance concrete based on a multi-component solid waste system of phosphogypsum-fly ash-slag and its preparation method. Background Technology

[0002] With the acceleration of global industrialization, the amount of industrial solid waste generated is increasing year by year, among which phosphogypsum, fly ash, and slag are typical industrial byproducts. Phosphogypsum is a solid waste produced in the wet-process phosphoric acid production process, its main component being calcium sulfate dihydrate. However, it contains impurities such as fluorides and organic matter, and direct discharge can cause serious pollution to soil and water bodies. Fly ash is a byproduct of coal-fired power plants and has potential pozzolanic activity, but its utilization rate is low. Large-scale accumulation not only occupies land resources but may also cause dust pollution. Slag is a high-temperature molten material produced during steel smelting. After water quenching, it has high activity, but its resource utilization still faces technical and economic challenges.

[0003] Traditional concrete materials use cement as the main binder, and its production process is energy-intensive and generates large amounts of carbon emissions, which contradicts the goal of green and low-carbon development. At the same time, the over-exploitation of natural sand and gravel, the main aggregate for concrete, has led to increasingly serious problems of ecological damage and resource depletion.

[0004] The relevant patents provide a method for preparing new concrete materials by combining solid wastes such as phosphogypsum, fly ash, and slag with traditional concrete, so as to realize the resource utilization of waste and reduce dependence on natural resources.

[0005] For example, CN112142428A discloses a method for preparing undisturbed phosphogypsum autoclaved aerated concrete. This method combines undisturbed phosphogypsum, fly ash, lime, and silicate cement to achieve resource utilization. However, the concrete prepared by this method has low strength, only 4 to 9 MPa.

[0006] Furthermore, CN115286348B discloses a synthetic concrete material made from coal mine / coal chemical solid waste and its preparation method. This method combines coal gangue, fly ash, slag, cement, and lime, and adds a large number of additives such as water glass, magnesium sulfate, industrial calcium chloride, and sodium hexametaphosphate. The resulting concrete has a 28-day strength between 39.9 and 44.8 MPa. Although this method improves strength, its strength is insufficient to meet current demands for building materials.

[0007] In addition, when solid wastes such as phosphogypsum, fly ash, and slag are used in concrete, they are combined with traditional materials such as lime and cement. Although solid waste materials are recycled to some extent, these methods still have a high dependence on natural resources.

[0008] In view of this, there is an urgent need to provide a method for preparing concrete with higher strength and a more environmentally friendly approach, which can produce concrete with high strength without the use of traditional materials such as lime and cement, so as to promote the greening and high-performance development of concrete materials. Summary of the Invention

[0009] The purpose of this application is to provide a high-performance concrete based on a multi-component solid waste system of phosphogypsum-fly ash-slag and its preparation method, so as to overcome the difficulty of existing single solid waste utilization technologies in meeting the strength, durability and economic requirements of high-performance concrete. Through the synergistic utilization of multiple solid wastes, the dual goals of solid waste resource utilization and high-performance concrete preparation can be achieved.

[0010] Firstly, the high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system and its preparation method provided in this application adopts the following technical solution:

[0011] A high-performance concrete based on a multi-element solid waste system of phosphogypsum-fly ash-slag, characterized in that it comprises, by mass fraction, 45-55 parts of phosphogypsum, 60-95 parts of fly ash, 5-20 parts of slag, 0-20 parts of silica fume, 40-50 parts of alkali activator; and by volume fraction, 1-2% of steel fiber.

[0012] Furthermore, the alkaline activator includes sodium silicate solution and sodium hydroxide solution.

[0013] Furthermore, the mass ratio of the sodium silicate solution to the sodium hydroxide solution is set to 1:2.25 to 2.75.

[0014] Furthermore, the modulus of the sodium silicate solution is set to 2 to 2.5.

[0015] Furthermore, the concentration of the sodium hydroxide solution is set to 11–13 mol / L.

[0016] Furthermore, the diameter of the steel fiber is set to 0.1-0.3 mm, and the length of the steel fiber is set to 10-15 mm.

[0017] Secondly, this application provides a method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system, employing the following technical solution:

[0018] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system includes the following steps:

[0019] Weigh each ingredient according to the proportions;

[0020] The fly ash, slag, and silica fume are thoroughly mixed to obtain the first mixture;

[0021] The phosphogypsum was thoroughly mixed with the first mixture, and an alkaline activator was added. After thorough mixing, the second mixture was obtained.

[0022] The second mixture is thoroughly mixed with steel fibers to obtain the third mixture;

[0023] The third mixture is then cured.

[0024] Furthermore, the phosphogypsum is pretreated before weighing. The pretreatment includes drying the phosphogypsum to a constant weight and then grinding it to 30-200 mesh using a ball mill.

[0025] Furthermore, before subjecting the third mixture to curing treatment, the third mixture is subjected to carbonation treatment; or

[0026] When performing curing treatment on the third mixture, the third mixture is carbonated.

[0027] Furthermore, when the third mixture is fully compacted into the mold and then cured, the curing temperature is 19–21°C and the relative humidity is 95–99%.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] In this application, bulk solid wastes such as phosphogypsum, fly ash, and slag are used as raw materials for concrete preparation. No cement or sand is used in the concrete preparation process, and the concrete preparation is carried out at room temperature. This reduces the requirements for equipment and makes the concrete preparation cost lower.

[0030] Meanwhile, this application overcomes the shortcomings of low strength development and poor performance of solid waste, enabling the prepared concrete to have high strength. This application effectively promotes the greening and high-performance development of concrete materials, and has significant scientific and application value for the building materials field. Attached Figure Description

[0031] Figure 1 This is a SEM microstructure image of Example 3.

[0032] Figure 2 This is a CT scan image from Example 3. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] Those skilled in the art will understand that, unless otherwise stated, the terms "the," "the," and "the foregoing" used in this application may also include plural forms. It should be further understood that the word "comprising" as used in the specification of this application means the presence of the stated features, steps, or operations, but does not exclude the presence or addition of one or more other features, integers, or steps.

[0035] Those skilled in the art will understand that, where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field; and where the manufacturers of the raw materials or instruments and equipment used are not specified, they are all conventional products that can be obtained commercially.

[0036] Those skilled in the art will understand that, unless otherwise stated in this application, when numerical ranges are given in the embodiments, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application, as well as the prior art known to those skilled in the art and the descriptions in this application, can be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made by means of methods, devices, and materials in the embodiments of this application.

[0037] A high-performance concrete based on a multi-element solid waste system of phosphogypsum-fly ash-slag comprises, by mass fraction, 45-55 parts of phosphogypsum, 60-95 parts of fly ash, 5-20 parts of slag, 0-20 parts of silica fume, 40-50 parts of alkali activator; and by volume fraction, 1-2% of steel fiber.

[0038] In some embodiments, the proportion of silica fume is preferably 5 to 20 parts.

[0039] Alkali activators are used to activate fly ash, phosphogypsum, slag, etc. in concrete to form a gel structure. In some embodiments, the alkali activator includes sodium silicate solution and sodium hydroxide solution.

[0040] Sodium hydroxide solution provides a strongly alkaline environment to rapidly dissolve the aluminosilicate glass in solid wastes such as fly ash and slag, releasing active SiO2 and Al2O3. Sodium silicate solution provides a soluble silicon source, which combines with the released active aluminum to form aluminosilicates, thereby effectively improving the strength of the final concrete.

[0041] It should be noted that other solid wastes containing large amounts of calcium, aluminum, and silicon can also be considered for addition or replacement in this scheme, such as: phosphorus tailings, steel slag, metakaolin, red mud, rice husk ash, etc.

[0042] In some embodiments, the mass ratio of sodium silicate solution to sodium hydroxide solution is set to 1:2.25–2.75. The ratio of sodium silicate solution to sodium hydroxide solution is adjusted according to the proportions of various solid wastes to ensure that the performance of the concrete remains at an excellent level.

[0043] Therefore, the concentrations of sodium silicate solution and sodium hydroxide solution can also be adjusted according to the solid waste.

[0044] In some embodiments, the modulus of the sodium silicate solution is set to 2 to 2.5. Taking a sodium silicate modulus of 2.25 as an example, in this case, the sodium silicate comprises 13.75% Na2O, 29.99% SiO2, and 56.26% H2O by mass ratio.

[0045] In some embodiments, the concentration of the sodium hydroxide solution is set to 11–13 mol / L.

[0046] When preparing the alkali activator, pour the sodium silicate solution and sodium hydroxide solution into a glass beaker, stir until the solution is evenly mixed, then seal the evenly mixed solution with plastic film and let it stand for 24 hours before use.

[0047] When sodium silicate solution is mixed with sodium hydroxide, a large amount of heat is generated, resulting in a high temperature for the prepared alkali activator. The high temperature causes excessive polymerization of sodium silicate solution, leading to uneven composition of the alkali activator. The alkali activator is cooled to room temperature by standing to ensure its uniformity and stability. In some specific embodiments, the alkali activator is prepared the day before concrete preparation.

[0048] In some embodiments, the diameter of the steel fibers is set to 0.1–0.3 mm, and the length of the steel fibers is set to 10–15 mm. The addition of steel fibers strengthens the concrete, and at the same time, steel fibers of appropriate length can form a bridging effect, inhibiting the development of cracks.

[0049] This application also provides a method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system, the preparation method specifically including the following steps:

[0050] S1. Weigh each raw material according to the proportion.

[0051] S2. Thoroughly mix fly ash, slag and silica fume to obtain the first mixture.

[0052] In some embodiments, the chemical composition of fly ash, slag, and silica fume is shown in Table 1.

[0053] Table 1

[0054]

[0055] S3. Mix the phosphogypsum with the first mixture thoroughly, add the alkali activator, and mix thoroughly to obtain the second mixture.

[0056] In some embodiments, after the phosphogypsum is thoroughly mixed with the first mixture, the mixing time with the alkali activator is set to 3 to 5 minutes.

[0057] In some embodiments, the phosphogypsum is pretreated before being thoroughly mixed with the first mixture. The pretreatment includes drying the phosphogypsum to constant weight and then grinding it to 30-200 mesh using a ball mill.

[0058] The chemical composition of phosphogypsum is shown in Table 2.

[0059] Table 2

[0060]

[0061] During the mixing process, the introduction of liquids is reduced, and fly ash, slag, silica fume and phosphogypsum are mixed in batches. Phosphogypsum is mainly composed of calcium sulfate dihydrate, and its moisture can be effectively removed by drying. After the above bulk solid wastes are fully mixed, an alkaline activator is added for further mixing, thereby reducing the uneven mixing caused by material adhesion during the mixing process.

[0062] S4. Mix the second mixture thoroughly with the steel fibers to obtain the third mixture.

[0063] In some embodiments, the mixing time of the second mixture with the steel fibers is set to 2 to 3 minutes.

[0064] In some embodiments, the diameter of the steel fiber is preferably 0.2 mm, and the length of the steel fiber is preferably 13 mm.

[0065] The specific parameters of the steel fiber are shown in Table 3.

[0066] Table 3

[0067]

[0068] S5. Perform curing treatment on the third mixture.

[0069] In some embodiments, S5 specifically includes the following steps:

[0070] S51. Pour the third mixture into a mold pre-coated with lubricant and compact it until it reaches a dense state to obtain the initial product.

[0071] S52. After sealing, the initial product and mold are placed in a curing box to complete standard curing.

[0072] In some embodiments, the curing temperature is 19–21°C, and the relative humidity is greater than 95%, preferably 95–99%.

[0073] S53. After curing for 24 hours, demold the initial product and continue to place it in the curing box for solidification and curing.

[0074] In addition, the third mixture can be carbonated, which effectively solidifies CO2 and has a good environmental optimization effect. At the same time, the carbon dioxide introduced during the carbonation process can react with the calcium hydroxide and calcium silicate (formed during the material mixing process) in the third mixture. The resulting calcium carbonate can enhance the strength of concrete and neutralize the acidity and alkalinity, making the concrete safer to use.

[0075] Based on this, considering that carbonation treatment may cause cracks in high-performance concrete during the preparation process, in some embodiments, nano-SiO2 can be added to the composition of high-performance concrete, or silica fume can be replaced in equal amounts with nano-SiO2. Nano-SiO2 has a finer particle size and can better bind with calcium carbonate, thereby improving the density of high-performance concrete.

[0076] In some embodiments, metakaolin can be further added to the original composition. As a solid waste with a smaller particle size, metakaolin can provide not only silicon but also aluminum compared to nano-SiO2.

[0077] Carbonation treatment is performed before or simultaneously with curing treatment.

[0078] In some embodiments, the third mixture is carbonated before curing. The concentration of CO2 introduced during carbonation is set to 85–95%, and the introduction time is set to 7–12 hours.

[0079] In some embodiments, the third mixture is carbonated during curing to optimize the progress of high-performance concrete production. The CO2 concentration introduced is set to 15–25%, and the relative humidity for curing is set to 75–85%.

[0080] The present application will be further described in detail below with reference to the embodiments.

[0081] Example 1:

[0082] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system includes the following steps:

[0083] S1. Weigh each raw material according to the proportion.

[0084] Specifically: 631.6g phosphogypsum, 1010.5g fly ash, 252.6g slag, 140.4g steel fiber, 144.3g NaOH solution, and 360.9g sodium silicate solution (Na2SiO3).

[0085] The alkali activator consists of a sodium silicate solution and a sodium hydroxide solution in a mass ratio of 1:2.5. The modulus of the sodium silicate solution is 2.25, and the concentration of the sodium hydroxide solution is 12 mol / L. The steel fiber accounts for 1.5% of the total volume, with a diameter of 0.2 mm and a length of 13 mm.

[0086] S2. Thoroughly mix fly ash, slag and silica fume to obtain the first mixture.

[0087] S3. Mix the phosphogypsum with the first mixture thoroughly, add the alkali activator, and mix thoroughly for 4 minutes to obtain the second mixture.

[0088] Before thoroughly mixing the phosphogypsum with the first mixture, the phosphogypsum is pretreated, including drying the phosphogypsum to constant weight and then grinding it to 100 mesh using a ball mill.

[0089] S4. Mix the second mixture with the steel fiber thoroughly for 2 minutes to obtain the third mixture.

[0090] In this embodiment, the diameter of the steel fiber is 0.2 mm and the length of the steel fiber is 13 mm.

[0091] S5. Compact the third mixture thoroughly into the mold, and then perform curing treatment.

[0092] In this embodiment, S5 specifically includes the following steps:

[0093] S51. Pour the third mixture into a mold pre-coated with lubricant and compact it until it reaches a dense state to obtain the initial product.

[0094] S52. After sealing, the initial product and mold are placed in a curing box to complete standard curing.

[0095] In some embodiments, the curing temperature is 19–21°C and the relative humidity is 95–99%.

[0096] S53. After curing for 24 hours, demold the initial product and continue to place it in the curing box for solidification and curing.

[0097] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-element solid waste system were tested. The results showed that the 7-day unconfined compressive strength of the block was 60.8 MPa, the 28-day unconfined compressive strength was 80.6 MPa, the 28-day splitting tensile strength was 5.3 MPa, and the elastic modulus was 17.1 MPa. All of these properties meet the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0098] Example 2:

[0099] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system includes the following steps:

[0100] S1. Weigh each raw material according to the proportion.

[0101] Specifically: 631.6g phosphogypsum, 884.2g fly ash, 252.6g slag, 126.3g silica fume, 140.4g steel fiber, 144.3kg NaOH solution, and 360.9g sodium silicate solution (Na2SiO3).

[0102] The alkali activator consists of a sodium silicate solution and a sodium hydroxide solution in a mass ratio of 1:2.5. The modulus of the sodium silicate solution is 2.25, and the concentration of the sodium hydroxide solution is 12 mol / L. The steel fiber accounts for 1.5% of the total volume, with a diameter of 0.2 mm and a length of 13 mm.

[0103] S2. Thoroughly mix fly ash, slag and silica fume to obtain the first mixture.

[0104] S3. Mix the phosphogypsum with the first mixture thoroughly, add the alkali activator, and mix thoroughly for 4 minutes to obtain the second mixture.

[0105] Before thoroughly mixing the phosphogypsum with the first mixture, the phosphogypsum is pretreated, including drying the phosphogypsum to constant weight and then grinding it to 100 mesh using a ball mill.

[0106] S4. Mix the second mixture with the steel fiber thoroughly for 2 minutes to obtain the third mixture.

[0107] In this embodiment, the diameter of the steel fiber is 0.2 mm and the length of the steel fiber is 13 mm.

[0108] S5. Compact the third mixture thoroughly into the mold, and then perform curing treatment.

[0109] In this embodiment, S5 specifically includes the following steps:

[0110] S51. Pour the third mixture into a mold pre-coated with lubricant and compact it until it reaches a dense state to obtain the initial product.

[0111] S52. After sealing, the initial product and mold are placed in a curing box to complete standard curing.

[0112] In some embodiments, the curing temperature is 19–21°C and the relative humidity is 95–99%.

[0113] S53. After curing for 24 hours, demold the initial product and continue to place it in the curing box for solidification and curing.

[0114] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-element solid waste system were tested. The results showed that the 7-day unconfined compressive strength of the block was 75.7 MPa, the 28-day unconfined compressive strength was 100.4 MPa, the 28-day splitting tensile strength was 7.9 MPa, and the elastic modulus was 20.3 MPa. All of these properties meet the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0115] Example 3:

[0116] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system includes the following steps:

[0117] S1. Weigh each raw material according to the proportion.

[0118] Specifically: 631.6g phosphogypsum, 757.9g fly ash, 252.6g slag, 252.6g silica fume, 140.4g steel fiber, 144.3kg NaOH solution, and 360.9g sodium silicate solution (Na2SiO3).

[0119] The alkali activator consists of a sodium silicate solution and a sodium hydroxide solution in a mass ratio of 1:2.5. The modulus of the sodium silicate solution is 2.25, and the concentration of the sodium hydroxide solution is 12 mol / L. The steel fiber accounts for 1.5% of the total volume, with a diameter of 0.2 mm and a length of 13 mm.

[0120] S2. Thoroughly mix fly ash, slag and silica fume to obtain the first mixture.

[0121] S3. Mix the phosphogypsum with the first mixture thoroughly, add the alkali activator, and mix thoroughly for 4 minutes to obtain the second mixture.

[0122] Before thoroughly mixing the phosphogypsum with the first mixture, the phosphogypsum is pretreated, including drying the phosphogypsum to constant weight and then grinding it to 100 mesh using a ball mill.

[0123] S4. Mix the second mixture with the steel fiber thoroughly for 2 minutes to obtain the third mixture.

[0124] In this embodiment, the diameter of the steel fiber is 0.2 mm and the length of the steel fiber is 13 mm.

[0125] S5. Compact the third mixture thoroughly into the mold, and then perform curing treatment.

[0126] In this embodiment, S5 specifically includes the following steps:

[0127] S51. Pour the third mixture into a mold pre-coated with lubricant and compact it until it reaches a dense state to obtain the initial product.

[0128] S52. After sealing, the initial product and mold are placed in a curing box to complete standard curing.

[0129] In some embodiments, the curing temperature is 19–21°C and the relative humidity is 95–99%.

[0130] S53. After curing for 24 hours, demold the initial product and continue to place it in the curing box for solidification and curing.

[0131] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-element solid waste system were tested. The results showed that the 7-day unconfined compressive strength of the block was 92.8 MPa, the 28-day unconfined compressive strength was 124.1 MPa, the 28-day splitting tensile strength was 9.2 MPa, and the elastic modulus was 26.4 MPa. All of these properties meet the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0132] Example 4:

[0133] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system is the same as that in Example 2, except that:

[0134] Before curing the third mixture, the third mixture is subjected to carbonation treatment. During carbonation treatment, the concentration of CO2 introduced is set to 85-95%, and the introduction time is set to 7-12 hours.

[0135] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-element solid waste system were tested. The results showed that the 7-day unconfined compressive strength of the block was 93.7 MPa, the 28-day unconfined compressive strength was 125.8 MPa, the 28-day splitting tensile strength was 8.8 MPa, and the elastic modulus was 24.9 MPa. All of these properties meet the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0136] Example 5:

[0137] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system is the same as that in Example 2, except that:

[0138] When curing the third mixture, it is carbonated to optimize the progress of high-performance concrete preparation. The CO2 concentration is set to 15-25%, the injection time is the same as the curing time (24 hours), and the relative humidity is set to 75-85%.

[0139] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-element solid waste system were tested. The results showed that the 7-day unconfined compressive strength of the block was 89.9 MPa, the 28-day unconfined compressive strength was 122.6 MPa, the 28-day splitting tensile strength was 7.9 MPa, and the elastic modulus was 22.4 MPa. All of these properties meet the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0140] Example 6:

[0141] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system is the same as that in Example 4, except that:

[0142] In S1, the specific components are as follows: 631.6g phosphogypsum, 884.2g fly ash, 252.6g slag, 126.3g nano-SiO2, 140.4g steel fiber, 144.3kg NaOH solution, and 360.9g sodium silicate solution (Na2SiO3).

[0143] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-element solid waste system were tested. The results showed that the 7-day unconfined compressive strength of the block was 95.7 MPa, the 28-day unconfined compressive strength was 126.9 MPa, the 28-day splitting tensile strength was 10.2 MPa, and the elastic modulus was 26.1 MPa. All of these properties meet the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0144] Example 7:

[0145] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system is the same as that in Example 4, except that:

[0146] In S1, the specific components are as follows: 631.6g phosphogypsum, 757.9g fly ash, 252.6g slag, 126.3g nano-SiO2, 126.3g metakaolin, 140.4g steel fiber, 144.3kg NaOH solution, and 360.9g sodium silicate solution (Na2SiO3).

[0147] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-element solid waste system were tested. The results showed that the 7-day unconfined compressive strength of the block was 98.7 MPa, the 28-day unconfined compressive strength was 132.9 MPa, the 28-day splitting tensile strength was 10.9 MPa, and the elastic modulus was 27.9 MPa. All of these properties meet the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0148] Example 8:

[0149] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system is the same as that in Example 1, except that:

[0150] In S1, the specific components are: 694.8g phosphogypsum, 1136.8g fly ash, 63.15g slag, 174.9g NaOH solution, and 393.5g sodium silicate solution (Na2SiO3).

[0151] The sodium silicate solution has a modulus of 2, and the sodium hydroxide solution has a concentration of 11 mol / L. The steel fiber accounts for 2% of the total volume, has a diameter of 0.3 mm, and a length of 11 mm.

[0152] In S3, when pretreating phosphogypsum, the phosphogypsum is dried to constant weight, and then ground to 30 mesh using a ball mill. The mixing time of the alkali activator with the phosphogypsum and the first mixture is 5 minutes.

[0153] In S4, the mixing time of the second mixture with the steel fiber is set to 3 minutes.

[0154] Example 9:

[0155] A method for preparing high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system is the same as that in Example 1, except that:

[0156] In S1, the specific components are as follows: 568.4g phosphogypsum, 757.9g fly ash, 252.6g slag, 63.15g silica fume, 119.8g NaOH solution, and 329.3g sodium silicate solution (Na2SiO3).

[0157] The sodium silicate solution has a modulus of 2.5, and the sodium hydroxide solution has a concentration of 13 mol / L. The steel fibers comprise 1% of the total volume, with a diameter of 0.1 mm and a length of 15 mm.

[0158] In S3, when pretreating phosphogypsum, the phosphogypsum is dried to constant weight, and then ground to 200 mesh using a ball mill. The mixing time of the alkali activator with the phosphogypsum and the first mixture is 3 minutes.

[0159] The mechanical property parameters of the high-performance concrete in Examples 1-3 are summarized in Table 3:

[0160] Table 3

[0161]

[0162] Comparing Examples 1-3, it can be seen that:

[0163] While keeping the total mass constant, increasing the silica fume content and decreasing the fly ash content can improve the strength of high-performance concrete. Furthermore, the higher the silica fume content, the higher the strength of the high-performance concrete.

[0164] This is because the Si in phosphogypsum, fly ash, and slag... 4+ The content of all these components is lower than that of silica ash; increasing the silica ash content can increase the Si content. 4+ Content, and Al dissolved from fly ash and slag 3+ The combination of these elements generates aluminosilicate gel, promoting strength generation and development. Furthermore, since silica fume is composed of spherical and fine amorphous silica particles, and concrete is a porous system, excess unreacted silica fume particles can enter the internal pores of the concrete, increasing the density of the structure. Therefore, the refinement of the microstructure contributes to improved compressive strength.

[0165] Comparing Example 2 and Example 4, it can be seen that:

[0166] Carbonation treatment of the third mixture further enhances the strength of high-performance concrete. This is because during carbonation, CO2 can penetrate effectively into the pores of the third mixture, reacting with the mixture to form substances such as calcium carbonate, thereby increasing the density of the structure. Simultaneously, the formation of calcium carbonate and other substances also further lowers the pH value of the high-performance concrete, making it safer.

[0167] Comparing Examples 4-5, we can see that:

[0168] Although the performance of simultaneously carbonating and curing the third mixture is slightly weaker than that of sequentially carbonating and curing the third mixture, its advantage of shorter preparation time makes it suitable for scenarios with high requirements for both concrete strength and preparation time.

[0169] By comparing Examples 4 and 6-7, it can be seen that:

[0170] Replacing silica fume with nano-SiO2 while keeping the total mass constant improves the performance of high-performance concrete. Compared to silica fume, nano-SiO2 has higher purity, smaller particle size, and higher surface activity, and can better fill pores and provide more Si. 4+ Elements that achieve the effect of refining the structure and increasing density.

[0171] While keeping the total amount constant, the addition of metakaolin further improves the performance of high-performance concrete. This is because metakaolin not only has a smaller particle size, but its aluminosilicate structure can also better adhere to other substances, such as calcium carbonate formed by carbonation, thereby improving strength and inhibiting crack formation.

[0172] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A high-performance concrete based on a phosphogypsum-fly ash-slag multi-element solid waste system, characterized in that, The composition by mass fraction includes 45-55 parts phosphogypsum, 60-95 parts fly ash, 5-20 parts slag, 0-20 parts silica fume, 40-50 parts alkali activator; and 1-2% steel fiber by volume fraction. The alkaline activator includes a sodium silicate solution and a sodium hydroxide solution, wherein the mass ratio of the sodium silicate solution to the sodium hydroxide solution is set to 1:2.25 to 2.75, the modulus of the sodium silicate solution is set to 2 to 2.5, and the concentration of the sodium hydroxide solution is set to 11 to 13 mol / L. High-performance concrete is formed through the following preparation methods: The fly ash, slag, and silica fume are thoroughly mixed to obtain the first mixture; The phosphogypsum was thoroughly mixed with the first mixture, and an alkaline activator was added. After thorough mixing, the second mixture was obtained. The second mixture is thoroughly mixed with steel fibers to obtain the third mixture; The third mixture is then cured.

2. The high-performance concrete based on the phosphogypsum-fly ash-slag multi-element solid waste system according to claim 1, characterized in that, The diameter of the steel fiber is set to 0.1-0.3 mm, and the length of the steel fiber is set to 10-15 mm.

3. The high-performance concrete based on the phosphogypsum-fly ash-slag multi-element solid waste system according to claim 1, characterized in that, Before curing the third mixture, the third mixture is carbonated; or When performing curing treatment on the third mixture, the third mixture is carbonated.

4. The high-performance concrete based on the phosphogypsum-fly ash-slag multi-element solid waste system according to claim 1, characterized in that, Before weighing the phosphogypsum, the phosphogypsum is pretreated, which includes drying the phosphogypsum to constant weight and then grinding it to 30-200 mesh using a ball mill.

5. The high-performance concrete based on the phosphogypsum-fly ash-slag multi-element solid waste system according to claim 1, characterized in that, When the third mixture is cured, the curing temperature is 19-21°C and the relative humidity is 95-99%.

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