High-performance concrete of phosphogypsum-fly ash-slag multi-element solid waste system and preparation method of high-performance concrete

Abstract

The invention relates to high-performance concrete of an ardealite-fly ash-slag multi-element solid waste system and a preparation method of the high-performance concrete, and relates to the technical field of preparation of concrete from solid waste resources, and the high-performance concrete of the ardealite-fly ash-slag multi-element solid waste system comprises the following components in parts by mass: 45-55 parts of ardealite, 60-95 parts of fly ash, 5-20 parts of slag and 0-20 parts of silica fume. 40-50 parts of an alkali activator; and the steel fiber accounts for 1-2% of the volume fraction. The ardealite, fly ash, slag and other bulk solid wastes are fully utilized, and cement, gravel and other traditional raw materials are not used during concrete preparation, so that the prepared concrete has low cost, the defects of low strength development and poor performance of the solid wastes are overcome, the concrete has high strength, and the application prospect is wide. The green and high-performance development of the concrete material is promoted, and the concrete has important scientific significance and application value in the field of building materials.

Description

Technical Field

[0001] This application relates to the technical field of preparing concrete from solid waste resources, and particularly to a high-performance concrete of a phosphogypsum-fly ash-slag multi-solid waste system and a preparation method thereof. Background Art

[0002] With the acceleration of the global industrialization process, the generation of industrial solid waste has increased year by year. Among them, phosphogypsum, fly ash and slag are typical industrial by-products. Phosphogypsum is a solid waste generated in the wet-process phosphoric acid process, and its main component is calcium sulfate dihydrate, but it contains impurities such as fluorides and organic matter, and direct discharge will cause serious pollution to soil and water bodies. Fly ash is a by-product of coal-fired power plants and has potential pozzolanic activity, but its utilization rate is low. A large amount of stacking not only occupies land resources, but may also cause dust pollution. Slag is a high-temperature melt generated during the steel smelting process and has high activity after water quenching treatment, but its resource utilization still faces technical and economic challenges.

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

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

[0005] For example, "CN112142428A" discloses a preparation method of autoclaved aerated concrete with original phosphogypsum. This method combines original phosphogypsum, fly ash with lime and portland cement to achieve resource utilization, but the concrete prepared by this method has low strength, only 4-9 MPa.

[0006] Furthermore, "CN115286348B" discloses a coal mine / coal chemical solid waste synthetic concrete material and a preparation method thereof. It combines coal gangue, fly ash, slag with cement and lime, and on this basis, a large amount of additives are added, such as: water glass, magnesium sulfate, industrial calcium chloride, sodium hexametaphosphate, etc. The 28d strength of the prepared concrete is between 39.9 and 44.8 MPa. Although this method improves the strength, with the increasing requirements for building materials, its strength is no longer sufficient to meet the current needs.

[0007] In addition, in the related art, when solid wastes such as phosphogypsum, fly ash, and slag are used in concrete, they are used in combination with traditional materials such as lime and cement. Although the solid waste materials have been recycled to a certain 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 more environmentally friendly, which can still have high strength without using traditional materials such as lime and cement, so as to promote the green and high-performance development of concrete materials. Summary of the Invention

[0009] The purpose of this application is to provide a high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system 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, and achieve the dual goals of solid waste resource utilization and high-performance concrete preparation through the collaborative utilization of multi-solid wastes.

[0010] In the first aspect, a high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system and its preparation method provided by this application adopt the following technical solutions:

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

[0012] Further, the alkali activator includes sodium silicate solution and sodium hydroxide solution.

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

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

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

[0016] Further, 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.

[0017] In the second aspect, a method for preparing a high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system provided by this application adopts the following technical solutions:

[0018] A preparation method of high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system, comprising the following steps:

[0019] Weigh each raw material according to the ratio;

[0020] Fully mix fly ash, slag and silica fume to obtain a first mixture;

[0021] Fully mix phosphogypsum with the first mixture, and add an alkali activator, and fully mix to obtain a second mixture;

[0022] Fully mix the second mixture with steel fibers to obtain a third mixture;

[0023] Carry out curing treatment on the third mixture.

[0024] Further, before weighing phosphogypsum, pre-treat phosphogypsum, and the pre-treatment includes: drying phosphogypsum to constant weight, and grinding it to 30-200 meshes with a ball mill after drying.

[0025] Further, before curing the third mixture, carbonize the third mixture; or

[0026] When curing the third mixture, carbonize the third mixture.

[0027] Further, when the third mixture is fully compacted in a mold and then cured, the curing temperature is 19-21 °C, and the relative humidity during curing 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 preparing concrete. Cement and sand and gravel are not used during the preparation of concrete, and the preparation of concrete is carried out at room temperature, which has lower requirements for equipment and makes the preparation of concrete have a lower cost.

[0030] At the same time, this application overcomes the defects of low strength development and poor performance of solid wastes, making the prepared concrete have higher strength. This application effectively promotes the green and high-performance development of concrete materials, and has important scientific significance and application value for the building materials field. Description of the Drawings

[0031] Figure 1 It is the SEM micrograph of Example 3.

[0032] Figure 2 It is the CT scan of Example 3. Detailed Description of the Invention

[0033] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0034] Those skilled in the art of the present technology can understand that unless specifically stated, the "said", "this", and "aforementioned" used in the text of the present application can also include plural forms. It should be further understood that the term "including" used in the specification of the present application means the presence of the described features, steps, and operations, but does not exclude the presence or addition of one or more other features, integers, and steps.

[0035] Those skilled in the art of the present technology can understand that for those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed; for the raw materials or instrument equipment whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0036] Those skilled in the art of the present technology can understand that unless otherwise specified in the present application, when an embodiment gives a numerical range, any value between the two endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application, based on the understanding of those skilled in the art of the present technology of the prior art and the description of the present application, any method, equipment, and material similar or equivalent to the methods, equipment, and materials described in the embodiments of the present application can also be used to implement the present application.

[0037] A high-performance concrete of a phosphogypsum-fly ash-slag multi-solid waste system includes, 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, and 40-50 parts of an alkali activator; and steel fibers accounting for 1-2% by volume fraction.

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

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

[0040] The sodium hydroxide solution provides a strong alkaline environment to quickly dissolve the silicon-aluminum glass bodies in solid wastes such as fly ash and slag, releasing active SiO2 and Al2O3. The sodium silicate solution provides a soluble silicon source, which combines with the released active aluminum to form aluminosilicate, thereby effectively improving the strength of the finally prepared and formed concrete.

[0041] It should be noted that other solid wastes containing large amounts of calcium, aluminum, and silicon elements may also be considered for addition or replacement into this solution, such as phosphate tailings, steel slag, kaolin, 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. According to the proportion of various solid wastes, the ratio of sodium silicate solution to sodium hydroxide solution is adjusted to ensure that the performance of concrete is always at an excellent level.

[0043] Based on this, 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 the modulus of sodium silicate as 2.25 as an example, in this case, the sodium silicate includes 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 alkaline activator, pour the sodium silicate solution and the sodium hydroxide solution into a glass beaker, stir until the solution is evenly mixed, and then seal the evenly mixed solution with a plastic film and let it stand for 24 hours before use.

[0047] When the sodium silicate solution is mixed with sodium hydroxide, a large amount of heat is generated, so that the prepared alkali activator has a higher temperature. The higher temperature causes the sodium silicate solution to over-polymerize, resulting in uneven composition of the alkali activator. The alkali activator is cooled to room temperature by standing to ensure the uniformity and stability of the alkali activator. In some specific embodiments, the alkali activator is prepared one day before preparing concrete.

[0048] In some embodiments, 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. The addition of steel fiber can strengthen the strength of concrete, and at the same time, steel fiber of appropriate length can form a bridging effect to inhibit the development of cracks.

[0049] The present application also provides a method for preparing high-performance concrete of a multi-solid waste system of phosphogypsum-fly ash-slag, and the preparation method specifically comprises the following steps:

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

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

[0052] In certain embodiments, the chemical compositions of fly ash, slag and silica fume are as shown in Table 1.

[0053] Table 1

[0054]

[0055] S3. Thoroughly mix the phosphogypsum with the first mixture, and add an alkali activator. After thorough mixing, a second mixture is obtained.

[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 - 5 min.

[0057] In some embodiments, before thoroughly mixing the phosphogypsum with the first mixture, the phosphogypsum is pretreated, and the pretreatment includes: drying the phosphogypsum to a constant weight, and after drying, grinding it to 30 - 200 mesh by a ball mill.

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

[0059] Table 2

[0060]

[0061] During the mixing process, the introduction of liquid substances is reduced, and fly ash, slag, silica fume, and phosphogypsum are mixed in batches. Among them, the phosphogypsum has calcium sulfate dihydrate as the main component, and its moisture can be better removed through drying. After the above-mentioned bulk solid wastes are thoroughly mixed, an alkali activator is added for mixing, thereby reducing the uneven mixing caused by material adhesion during the mixing process.

[0062] S4. Thoroughly mix the second mixture with steel fibers to obtain a third mixture.

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

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

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

[0066] Table 3

[0067]

[0068] S5. Carry out a 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 a lubricant and compact it until it reaches a dense state to obtain a preliminary product.

[0071] S52. Place the preliminary product and the mold in a curing box after sealing to complete standard curing.

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

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

[0074] In addition, the third mixture can also be carbonated. The carbonation treatment can effectively solidify CO2 and play a good role in optimizing the environment. At the same time, the CO2 introduced during the carbonation treatment can react with calcium hydroxide and calcium silicate (formed during the material mixing process) in the third mixture. The generated calcium carbonate can enhance the strength of the concrete and neutralize the pH value, making the use of the concrete safer.

[0075] On this basis, considering that the carbonation treatment may cause cracks in the preparation of high-performance concrete. In some embodiments, nano-SiO2 can be added to the composition of high-performance concrete, or silica fume can be equivalently replaced with nano-SiO2. It has a finer particle size and can better combine with calcium carbonate to improve the density of high-performance concrete.

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

[0077] The carbonation treatment is set before the curing treatment or carried out synchronously with the curing treatment.

[0078] In some embodiments, before the curing treatment of the third mixture, the third mixture is carbonated. When carbonating, the concentration of CO2 introduced is set to 85 - 95%, and the introduction time is set to 7 - 12 hours.

[0079] In some embodiments, when the third mixture is cured, the third mixture is carbonated to optimize the progress of preparing high-performance concrete. At this time, the concentration of CO2 introduced is set to 15 - 25%. The relative humidity during curing is set to 75 - 85%.

[0080] The following is a further detailed description of the present application in conjunction with embodiments.

[0081] Example 1:

[0082] A preparation method of high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system, comprising the following steps:

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

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

[0085] Among them, the alkali activator includes a sodium silicate solution and a sodium hydroxide solution with 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 volume ratio of the steel fibers accounts for 1.5% of the total volume. The diameter of the steel fibers is 0.2 mm, and the length of the steel fibers is 13 mm.

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

[0087] S3. Thoroughly mix phosphogypsum with the first mixture, and add the alkali activator. After thoroughly mixing for 4 min, obtain a second mixture.

[0088] Before thoroughly mixing phosphogypsum with the first mixture, pre-treat the phosphogypsum. The pre-treatment includes: drying the phosphogypsum to a constant weight, and after drying, grinding it to 100 mesh by a ball mill.

[0089] S4. Thoroughly mix the second mixture with the steel fibers for 2 min to obtain a third mixture.

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

[0091] S5. Thoroughly compact the third mixture in a mold, and then carry out a curing treatment.

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

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

[0094] S52. After sealing the preliminary product and the mold, place them in a curing box to complete standard curing.

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

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

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

[0098] Embodiment 2:

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

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

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

[0102] The alkaline activator includes 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 volume of the steel fiber accounts for 1.5% of the total volume, the diameter of the steel fiber is 0.2 mm, and the length of the steel fiber is 13 mm.

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

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

[0105] Before the phosphogypsum is fully mixed with the first mixture, the phosphogypsum is pretreated, and the pretreatment includes: drying the phosphogypsum to constant weight, and grinding the phosphogypsum to 100 meshes in a ball mill after drying.

[0106] S4. Fully mix the second mixture and the steel fiber for 2 minutes to obtain a 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. Fully compact the third mixture in a mold, and then perform a 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 a preliminary product.

[0111] S52. After sealing the preliminary product and the mold, place them in a curing box to complete standard curing.

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

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

[0114] For the high-performance concrete prepared from the phosphorus gypsum - fly ash - slag multi-solid waste system, mechanical property tests are carried out. The unconfined compressive strength of the block at 7 days is 75.7 MPa, the unconfined compressive strength at 28 days is 100.4 MPa, the splitting tensile strength at 28 days is 7.9 MPa, and the elastic modulus is 20.3 MPa, all of which meet the requirements of the Chinese specification "Technical Conditions for High-Performance Concrete" (GB / T 41054 - 2021).

[0115] Example 3:

[0116] A preparation method of high-performance concrete from a phosphorus gypsum - fly ash - slag multi-solid waste system, comprising the following steps:

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

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

[0119] Among them, the alkali activator includes a sodium silicate solution and a sodium hydroxide solution with 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 volume ratio of the steel fiber accounts for 1.5% of the total volume. The diameter of the steel fiber is 0.2 mm, and the length of the steel fiber is 13 mm.

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

[0121] S3. Thoroughly mix phosphorus gypsum and the first mixture, and add the alkali activator. After thoroughly mixing for 4 minutes, obtain a second mixture.

[0122] Before thoroughly mixing phosphorus gypsum and the first mixture, pre-treat the phosphorus gypsum. The pre-treatment includes: drying the phosphorus gypsum to constant weight, and grinding it to 100 meshes by a ball mill after drying.

[0123] S4. Thoroughly mix the second mixture with steel fibers for 2 min to obtain a third mixture.

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

[0125] S5. Thoroughly compact the third mixture in a mold and then carry out curing treatment.

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

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

[0128] S52. After sealing, place the preliminary product and the mold in a curing box to complete standard curing.

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

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

[0131] Perform mechanical property tests on the prepared high-performance concrete of the phosphogypsum-fly ash-slag multi-solid waste system. The unconfined compressive strength of the block at 7 d is 92.8 MPa, the unconfined compressive strength at 28 d is 124.1 MPa, the splitting tensile strength at 28 d is 9.2 MPa, and the elastic modulus is 26.4 MPa, all meeting the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T 41054 - 2021).

[0132] Example 4:

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

[0134] Before curing the third mixture, carbonize the third mixture. When carbonizing, the concentration of CO2 introduced is set to 85 - 95% and the introduction time is set to 7 - 12 h.

[0135] Perform mechanical property tests on the prepared high-performance concrete of the phosphogypsum-fly ash-slag multi-solid waste system. The unconfined compressive strength of the block at 7 d is 93.7 MPa, the unconfined compressive strength at 28 d is 125.8 MPa, the splitting tensile strength at 28 d is 8.8 MPa, and the elastic modulus is 24.9 MPa, all meeting the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T 41054 - 2021).

[0136] Example 5:

[0137] A preparation method of high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system is the same as that of Example 2, except that:

[0138] When curing the third mixture, carbonize the third mixture to optimize the progress of preparing high-performance concrete. At this time, the concentration of CO2 introduced is set to 15-25%, the introduction time is the same as the curing time, specifically set to 24h, and the curing relative humidity is set to 75-85%.

[0139] The mechanical properties of the prepared high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system were tested. The unconfined compressive strength of the block at 7d was 89.9MPa, the unconfined compressive strength at 28d was 122.6MPa, the splitting tensile strength at 28d was 7.9MPa, and the elastic modulus was 22.4MPa, all meeting the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0140] Example 6:

[0141] A preparation method of high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system is the same as that of Example 4, except that:

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

[0143] The mechanical properties of the prepared high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system were tested. The unconfined compressive strength of the block at 7d was 95.7MPa, the unconfined compressive strength at 28d was 126.9MPa, the splitting tensile strength at 28d was 10.2MPa, and the elastic modulus was 26.1MPa, all meeting the requirements of the Chinese standard "Technical Conditions for High-Performance Concrete" (GB / T41054-2021).

[0144] Example 7:

[0145] A preparation method of high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system is the same as that of Example 4, except that:

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

[0147] The mechanical properties of the high-performance concrete prepared from the phosphogypsum-fly ash-slag multi-solid waste system were tested, and the unconfined compressive strength of the block at 7 days was 98.7 MPa, the unconfined compressive strength at 28 days was 132.9 MPa, the splitting tensile strength at 28 days was 10.9 MPa, and the elastic modulus was 27.9 MPa, all of which meet the requirements of the "Technical Conditions for High-Performance Concrete" (GB / T 41054-2021) in China.

[0148] Example 8:

[0149] A preparation method of high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system is the same as that of Example 1, except that:

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

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

[0152] In S3, when pre-treating the phosphogypsum, the phosphogypsum is dried to a constant weight, and after drying, it is ground to 30 meshes by a ball mill. The mixing time of the alkali activator with the phosphogypsum and the first mixture is 5 min.

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

[0154] Example 9:

[0155] A preparation method of high-performance concrete with a phosphogypsum-fly ash-slag multi-solid waste system is the same as that of Example 1, except that:

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

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

[0158] In S3, when pre-treating phosphogypsum, the dried phosphogypsum is dried to a constant weight, and after drying, it is ground to 200 meshes by a ball mill. The mixing time of the alkali activator with phosphogypsum and the first mixture is 3 min.

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

[0160] Table 3

[0161]

[0162] Comparing Examples 1-3 shows that:

[0163] When the total mass remains unchanged, increasing the content of silica fume and decreasing the content of fly ash can improve the strength of high-performance concrete. Moreover, the higher the content of silica fume, the higher the strength of high-performance concrete.

[0164] This is because the Si 4+ contents in phosphogypsum, fly ash and slag are all lower than that of silica fume. The increase in the content of silica fume can increase the Si 4+ content, and combine with the Al 3+ dissolved from fly ash and slag to generate aluminosilicate gel, which promotes the generation and development of strength. At the same time, since silica fume is composed of spherical and fine amorphous silica particles, and concrete is a porous structure system, excessive unreacted silica fume particles will enter the internal pores of the concrete, increasing the density of the structure. Therefore, due to the contribution of the refinement of the microstructure, the compressive strength is improved.

[0165] Comparing Example 2 and Example 4 shows that:

[0166] Carbonating the third mixture further improves the strength of high-performance concrete. This is because during carbonation treatment, CO2 can enter the pores of the third mixture well and react with the third mixture in the pores to generate substances such as calcium carbonate, thereby further increasing the density of the structure. At the same time, the generation of substances such as calcium carbonate also further reduces the pH value of high-performance concrete, making the high-performance concrete safer.

[0167] Comparing Examples 4-5 shows that:

[0168] Although the simultaneous carbonation treatment and curing treatment of the third mixture are slightly inferior in performance to the sequential carbonation treatment and curing treatment of the third mixture, the advantage of its short preparation time makes it suitable for scenarios with high requirements for both the strength and preparation time of concrete.

[0169] Comparing Example 4 with Examples 6 - 7 shows that:

[0170] When the total mass remains unchanged, replacing silica fume with nano - SiO₂ improves the performance of high - performance concrete. Nano - SiO₂ has higher purity, smaller particle size and surface activity compared with silica fume, and can better fill pores and provide more Si 4+ elements, achieving the effect of refining the microstructure and increasing the density.

[0171] When the total amount remains unchanged, adding metakaolin further improves the performance of high - performance concrete. This is because metakaolin not only has a small particle size, but the aluminosilicate structure it provides can better adhere to other substances, such as substances like calcium carbonate formed by carbonation, achieving the effects of increasing strength and inhibiting crack formation.

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

Claims

1. A high-performance concrete of a phosphorus gypsum-fly ash-slag multi-solid waste system, characterized in that, By mass fraction, it includes 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 steel fibers accounting for 1 - 2% by volume fraction.

2. The high-performance concrete of a phosphorus gypsum-fly ash-slag multi-solid waste system according to claim 1, characterized in that, The alkali activator includes sodium silicate solution and sodium hydroxide solution.

3. The high-performance concrete of a phosphogypsum-fly ash-slag multi-solid waste system according to claim 2, characterized in that, The mass ratio of the sodium silicate solution to the sodium hydroxide solution is set to 1:2.25 - 2.

75.

4. The high-performance concrete of a phosphorus gypsum-fly ash-slag multi-solid waste system according to claim 2, wherein, The modulus of the sodium silicate solution is set to 2 - 2.

5.

5. The high-performance concrete of a phosphogypsum-fly ash-slag multi-solid waste system according to claim 2, characterized in that, The concentration of the sodium hydroxide solution is set to 11 - 13 mol / L.

6. The high-performance concrete of a phosphogypsum-fly ash-slag multi-solid waste system according to claim 1, characterized in that, 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.

7. A preparation method of high-performance concrete for a phosphogypsum-fly ash-slag multi-solid waste system, characterized in that, For forming the high-performance concrete according to any one of claims 1 - 6, the preparation method includes the following steps: Weigh each raw material according to the ratio. Fully mix fly ash, slag and silica fume to obtain a first mixture. Fully mix phosphogypsum with the first mixture, and add the alkali activator, and fully mix to obtain a second mixture. Fully mix the second mixture with the steel fibers to obtain a third mixture. Carry out curing treatment on the third mixture.

8. The preparation method according to claim 7, wherein Before carrying out curing treatment on the third mixture, carry out carbonation treatment on the third mixture; or When carrying out curing treatment on the third mixture, carry out carbonation treatment on the third mixture.

9. The preparation method according to claim 7, wherein Before weighing phosphogypsum, carry out pretreatment on phosphogypsum, and the pretreatment includes: drying phosphogypsum to constant weight, and grinding it to 30 - 200 meshes by a ball mill after drying.

10. The preparation method according to claim 7, characterized in that, When carrying out curing treatment on the third mixture, the curing temperature is 19 - 21 °C, and the curing relative humidity is 95 - 99%.

Images