Reinforced phosphogypsum aggregate, ultra-high performance concrete material and preparation method thereof

Abstract

The application provides a reinforced phosphogypsum aggregate, an ultra-high performance concrete material and a preparation method thereof, and belongs to the field of building materials. The preparation steps of the reinforced phosphogypsum aggregate are as follows: phosphogypsum, cement, primary aluminum ash, water and ettringite crystal form control agent are mixed to obtain a mixture; the mixture is extruded and molded and autoclaved to obtain the phosphogypsum aggregate; the phosphogypsum aggregate is immersed in a silicone emulsion, dried to obtain a hydrophobic phosphogypsum aggregate; and the hydrophobic phosphogypsum aggregate is placed in a strong alkali solution with continuous carbon dioxide to react, and dried to obtain the reinforced phosphogypsum aggregate. The application adopts the reaction of phosphogypsum and primary aluminum ash to generate ettringite and the reaction of phosphogypsum in a strong alkali solution and carbon dioxide to generate calcite to cooperatively improve the strength of the aggregate, and the reinforced phosphogypsum aggregate can be used to prepare an ultra-high performance concrete material with a compressive strength higher than 150 MPa, thereby solving the problem of the lack of natural quartz sand resources while consuming phosphogypsum resources and a large amount of accumulated primary aluminum ash resources.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a reinforced phosphogypsum aggregate, an ultra-high performance concrete material, and a method for preparing the same. Background Technology

[0002] High-performance concrete typically boasts a compressive strength of 50-120 MPa. However, for certain specialized structural applications, such as long-span bridges, critical components of high-rise buildings, and marine engineering structures, its strength still falls short of design requirements. Furthermore, traditional concrete exhibits significantly lower tensile strength, only 1 / 10 to 1 / 20 of its compressive strength. This makes concrete structures prone to cracking under bending, tensile, or shear loads, thereby impacting the structure's durability and safety.

[0003] On the other hand, ordinary concrete is susceptible to environmental erosion during long-term use, such as chloride ion corrosion, carbonation, and sulfate corrosion. In marine environments, chloride ions in seawater can penetrate into the concrete, causing steel reinforcement corrosion and leading to cracking, spalling, and other damage to the concrete structure. For some infrastructure projects, such as ports, wharves, and cross-sea bridges, the service life is required to be decades or even centuries, and the durability of traditional concrete is insufficient to meet such stringent requirements. Therefore, this patent proposes an ultra-high performance concrete material with high strength and high durability to overcome its technical limitations in the application of existing infrastructure projects.

[0004] Phosphogypsum is an industrial waste residue from the production of phosphoric acid. Currently, my country's phosphogypsum stockpile has reached approximately 700 million tons, and is increasing rapidly at a rate of 80 million tons per year. The utilization of phosphogypsum is urgently needed. This invention efficiently utilizes phosphogypsum, primary aluminum ash, and other solid waste to prepare reinforced phosphogypsum aggregate, and can provide a new approach to carbon sequestration. Using high-dosage reinforced phosphogypsum aggregate, ultra-high performance concrete with a compressive strength exceeding 150 MPa can be prepared. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a reinforced phosphogypsum aggregate, an ultra-high performance concrete material, and a method for preparing the same, addressing the above-mentioned shortcomings.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0007] In one aspect, the present invention provides a reinforced phosphogypsum aggregate. The reinforced phosphogypsum aggregate of the present invention is a synthetic aggregate with a particle size of 1.18-2.36 mm obtained by extruding and steam curing a paste prepared from phosphogypsum, cement, primary aluminum ash, water and ettringite crystal morphology control agent, continuously passing carbon dioxide through a strong alkaline solution, undergoing a series of chemical reactions, and then drying.

[0008] That is, the preparation method of the reinforced phosphogypsum aggregate includes:

[0009] A mixture is obtained by mixing raw materials including phosphogypsum, cement, primary aluminum ash, water and ettringite crystal form control agent;

[0010] The mixture is extruded and steam-cured to obtain phosphogypsum aggregate;

[0011] Hydrophobic phosphogypsum aggregate is obtained by impregnating phosphogypsum aggregate in an organosilicon emulsion and then drying it.

[0012] Hydrophobic phosphogypsum aggregate is placed in a strong alkaline solution containing sodium polyphosphate, and carbon dioxide is continuously bubbled into the strong alkaline solution to carry out the reaction. After the reaction is completed, the reinforced phosphogypsum aggregate is obtained by drying.

[0013] This invention utilizes the reaction of phosphogypsum with primary aluminum ash to generate ettringite, and the reaction of phosphogypsum with sodium hydroxide solution and carbon dioxide to generate calcium carbonate. During the preparation process, the proportions of ettringite crystals and calcite crystals are controlled to allow for better synergistic enhancement of aggregate strength. This invention's reinforced phosphogypsum aggregate can replace quartz sand in the preparation of ultra-high performance concrete materials with compressive strength exceeding 150 MPa.

[0014] Further, the mass ratio of phosphogypsum:aluminum ash:cement:water is (60-80):(10-30):(10-20):(10-20), and the main component of the ettringite crystal form control agent has a mass fraction of 0.5%-3% in the mixture. Preferably, the ettringite crystal form control agent is sodium sulfate solid powder, and after mixing with water, the mass fraction of sodium sulfate in the mixture is 0.5%-3%.

[0015] Furthermore, the preparation method of the reinforced phosphogypsum aggregate includes:

[0016] S1: Dry the raw phosphogypsum at 50-80 ℃ for 12-24 h and then put it into a ball mill for ball milling to obtain phosphogypsum powder;

[0017] S2: Dry the raw aluminum ash at 80-100 ℃ for 12-24 hours;

[0018] S3: Mix phosphogypsum powder, primary aluminum ash and cement, then add calcite crystal form control agent and water to obtain a mixture;

[0019] S4: The mixture is extruded into shape by machine with an extrusion pressure of 10-20MPa and an extrusion speed of 8-12mm / min, and the aggregate particle size is controlled at 1.18-2.36mm. Then, it is steam-cured for 1-3 days at a temperature of 60-80℃, a relative humidity of more than 90%, and a pressure of 0.8-1.5MPa to obtain phosphogypsum aggregate.

[0020] S5: The above-mentioned phosphogypsum aggregate is immersed in a 5%-20% organosilicon emulsion (the mass concentration of organosilicon in the emulsion is 5%-20%) for immersion treatment for 1-3 hours, immersion temperature 20-50 ℃, and stirring speed 50-200 r / min; then, the phosphogypsum aggregate is dried at 80-120 ℃ for 2-5 hours to obtain hydrophobic phosphogypsum aggregate.

[0021] S6: Add the hydrophobically treated phosphogypsum aggregate to a 1.5-3 mol / L sodium hydroxide solution. The mass ratio of phosphogypsum raw material to sodium hydroxide solid is (1-2):1 (the sodium hydroxide solid here refers to the content of sodium hydroxide solid added when preparing the sodium hydroxide solution). Add 0.5%-2% sodium polyphosphate to the sodium hydroxide solution (that is, after adding sodium polyphosphate to the sodium hydroxide solution, the mass concentration of sodium polyphosphate is 0.5%-2%) to adjust the crystal form of calcium carbonate to calcite crystal form. Control the reaction temperature at 20-60 ℃, maintain pH=11-13, and continuously introduce carbon dioxide at a flow rate of 1L / h-2L / h. The reaction time is 1-2h, and the solution is continuously stirred at a stirring rate of 50-200r / min.

[0022] S7: After the reaction is complete, the above phosphogypsum aggregate is dried at 50-80℃ for 24-48 hours to obtain reinforced phosphogypsum aggregate.

[0023] Furthermore, the phosphogypsum contains 70%-95% calcium sulfate, 0.5-8% phosphoric acid, 1%-8% phosphate, 0.1%-2% fluoride, less than 30 mg / kg arsenic, less than 100 mg / kg lead, less than 10 mg / kg cadmium, and less than 5 mg / kg mercury.

[0024] Furthermore, the primary aluminum ash contains 15%-70% aluminum, 1%-5% fluorine, 2%-10% silicon, and 0.5-3% sodium. The lead content is less than 0.1%, the cadmium content is less than 0.01%, and the chromium content is less than 0.1%.

[0025] In a second aspect, the present invention provides an ultra-high performance concrete material prepared using the above-mentioned reinforced phosphogypsum aggregate, comprising the following raw materials in parts by weight: 600-800 parts cement, 150-300 parts fly ash microspheres, 100-300 parts silica fume, 450-600 parts reinforced phosphogypsum aggregate, 100-200 parts quartz sand, 160-240 parts bent steel fiber, 30-40 parts water-reducing agent, and 150-200 parts water.

[0026] The cement mentioned is 52.5 grade ordinary Portland cement.

[0027] The fly ash is fly ash microspheres with a loss on ignition ≤5.5%, water requirement ≤90%, and spherical particle volume fraction ≥92%.

[0028] The silica fume contains ≥95% SiO2 by mass and has a specific surface area ≥14500 m². 2 / kg, 28d activity index ≥100%.

[0029] The reinforced phosphogypsum aggregate prepared by this invention has a compressive strength of 10-15 MPa and an apparent density of 2135-2492 kg / m³. 3 Water absorption rate: 5.2%-9.5%.

[0030] The hooked steel fiber has a nominal length of 25-40mm, a diameter of 0.25-0.60mm, and a tensile strength greater than 1600MPa.

[0031] The water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate greater than 30%.

[0032] This invention utilizes reinforced phosphogypsum aggregate to prepare ultra-high performance concrete, which can solve the problem of industrial solid waste treatment and is beneficial to environmental protection. Furthermore, it effectively addresses the current issues of scarce aggregate resources for ultra-high performance concrete, as well as the large-scale accumulation of phosphogypsum and primary aluminum ash, thus saving resources and energy. The use of polycarboxylate superplasticizer and fly ash microspheres and other mineral admixtures optimizes the workability of the concrete mixture, improves its density and homogeneity, and can reduce the shrinkage of ultra-high performance concrete to a certain extent. This invention, combining solid waste phosphogypsum and primary aluminum ash, effectively solves the problem of large-scale solid waste accumulation while simultaneously producing ultra-high performance concrete with high compressive strength and high durability.

[0033] A third aspect of the present invention also provides a method for preparing ultra-high performance concrete materials using reinforced phosphogypsum aggregate, comprising the following steps:

[0034] S1: Mix cement, silica fume, fly ash, quartz sand and reinforced phosphogypsum aggregate for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add bent steel fiber and continue mixing for 3 minutes.

[0035] S2: After molding, vibration and shaping, the surface is covered with a waterproof film for film curing. Then the mold is removed and the material is placed in a standard curing environment for 28 days to obtain the reinforced phosphogypsum aggregate ultra-high performance concrete material.

[0036] Compared with the prior art, the advantages of the present invention are:

[0037] (1) In this invention, phosphogypsum reacts with primary aluminum ash to generate ettringite and phosphogypsum reacts with carbon dioxide in sodium hydroxide solution to generate calcite crystals. By controlling the ratio of ettringite crystals to calcite crystals, the aggregate strength is improved in a synergistic manner. At the same time, the reaction process can provide a new way to fix carbon.

[0038] (2) The present invention uses reinforced phosphogypsum aggregate to prepare ultra-high performance concrete materials, which can greatly absorb phosphogypsum resources and a large amount of primary aluminum ash resources; on the other hand, the use of reinforced phosphogypsum aggregate as aggregate solves the problem of scarce natural quartz sand resources.

[0039] (3) Compared with the traditional method of using quartz sand to prepare ultra-high performance concrete materials, the present invention uses reinforced phosphogypsum aggregate to prepare ultra-high performance concrete with compressive strength higher than 150MPa. Detailed Implementation

[0040] The following further illustrates the application and preparation method of the reinforced phosphogypsum aggregate in UHPC materials using specific embodiments. This section further illustrates the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.

[0041] A reinforced phosphogypsum aggregate, the preparation method of which includes:

[0042] A mixture is obtained by mixing raw materials including phosphogypsum, cement, primary aluminum ash, water and ettringite crystal form control agent;

[0043] The mixture is extruded and steam-cured to obtain phosphogypsum aggregate;

[0044] Hydrophobic phosphogypsum aggregate is obtained by impregnating phosphogypsum aggregate in an organosilicon emulsion and then drying it.

[0045] Hydrophobic phosphogypsum aggregate is placed in a strong alkaline solution containing sodium polyphosphate, and carbon dioxide is continuously bubbled into the strong alkaline solution to carry out the reaction. After the reaction is completed, the reinforced phosphogypsum aggregate is obtained by drying.

[0046] In some examples, the ratio of phosphogypsum:aluminum ash:cement:water is (60-80):(10-30):(10-20):(10-20) (mass ratio), and the main component of the ettringite crystal form control agent has a mass fraction of 0.5%-3% in the mixture. Preferably, the ettringite crystal form control agent is sodium sulfate solid powder, and after mixing with water, the mass fraction of sodium sulfate in the mixture is 0.5%-3%.

[0047] In a specific example of the present invention, the method for preparing the reinforced phosphogypsum aggregate includes:

[0048] S1: Dry the raw phosphogypsum at 50-80 ℃ for 12-24 h and then put it into a ball mill for ball milling to obtain phosphogypsum powder;

[0049] S2: Dry the raw aluminum ash at 80-100 ℃ for 12-24 hours;

[0050] S3: Mix phosphogypsum powder, primary aluminum ash and cement, then add calcite crystal form control agent and water to obtain a mixture;

[0051] S4: The mixture is extruded into shape by machine with an extrusion pressure of 10-20MPa and an extrusion speed of 8-12mm / min, and the aggregate particle size is controlled at 1.18-2.36mm. Then, it is steam-cured for 1-3 days at a temperature of 60-80℃, a relative humidity of more than 90%, and a pressure of 0.8-1.5MPa to obtain phosphogypsum aggregate.

[0052] S5: The above phosphogypsum aggregate is immersed in 5%-20% organosilicon emulsion for 1-3 hours, 20-50 ℃, and 50-200 r / min; then, the phosphogypsum aggregate is dried at 80-120 ℃ for 2-5 hours to obtain hydrophobic phosphogypsum aggregate.

[0053] S6: Add the hydrophobically treated phosphogypsum aggregate to a 1.5-3 mol / L sodium hydroxide solution. The mass ratio of phosphogypsum raw material to sodium hydroxide solid is (1-2):1. Add 0.5%-2% sodium polyphosphate to the sodium hydroxide solution (that is, after adding sodium polyphosphate to the sodium hydroxide solution, the mass concentration of sodium polyphosphate is 0.5%-2%) to adjust the crystal form of calcium carbonate to calcite crystal form. Control the reaction temperature at 20-60 ℃, maintain pH=11-13, and continuously introduce carbon dioxide at a flow rate of 1L / h-2L / h. The reaction time is 1-2h, and the solution is continuously stirred at a stirring rate of 50-200r / min.

[0054] S7: After the reaction is complete, the above phosphogypsum aggregate is dried at 50-80℃ for 24-48 hours to obtain reinforced phosphogypsum aggregate.

[0055] In the following specific embodiments,

[0056] The phosphogypsum contains 70%-95% calcium sulfate, 0.5-8% phosphoric acid, 1%-8% phosphate, 0.1%-2% fluoride, less than 30 mg / kg arsenic, less than 100 mg / kg lead, less than 10 mg / kg cadmium, and less than 5 mg / kg mercury.

[0057] The primary aluminum ash contains 15%-70% aluminum, 1%-5% fluorine, 2%-10% silicon, and 0.5-3% sodium. The lead content is less than 0.1%, the cadmium content is less than 0.01%, and the chromium content is less than 0.1%.

[0058] The cement mentioned is 52.5 grade ordinary Portland cement.

[0059] The fly ash is fly ash microspheres with a loss on ignition ≤5.5%, water requirement ≤90%, and spherical particle volume fraction ≥92%.

[0060] The silica fume contains ≥95% SiO2 by mass and has a specific surface area ≥14500 m². 2 / kg, 28d activity index ≥100%.

[0061] The reinforced phosphogypsum aggregate obtained by this invention has a compressive strength of 10-15 MPa and an apparent density of 2135-2492 kg / m³. 3 Water absorption rate: 5.2%-9.5%.

[0062] The hooked steel fiber has a nominal length of 25-40mm, a diameter of 0.25-0.60mm, and a tensile strength greater than 1600MPa.

[0063] The water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate greater than 30%.

[0064] The water used is ordinary tap water, which meets the requirements of the "Standard for Water Used in Concrete" JGJ63.

[0065] The silicone emulsion used is a commercially available composite ionic hydroxyl silicone oil emulsion with a silicone mass concentration of 10%.

[0066] Example 1

[0067] A method for preparing UHPC material using reinforced phosphogypsum aggregate, comprising the following raw materials in parts by weight:

[0068] 780 parts cement, 200 parts fly ash microspheres, 150 parts silica fume, 450 parts reinforced phosphogypsum aggregate, 200 parts quartz sand, 240 parts bent steel fiber, 35 parts water-reducing agent, and 150 parts water.

[0069] The preparation method of reinforced phosphogypsum aggregate includes the following steps:

[0070] S1: After drying the raw phosphogypsum at 50 ℃ for 24 h, it is put into a ball mill and ball-milled to obtain phosphogypsum powder;

[0071] S2: Dry the raw aluminum ash at 90 ℃ for 12 hours;

[0072] S3: Mix phosphogypsum powder, primary aluminum ash, and cement, then add ettringite crystal form control agent and water to obtain a mixture. The ettringite crystal form control agent is sodium sulfate solid powder, and after mixing with water, the mass fraction of sodium sulfate is 3%. Phosphogypsum: Primary aluminum ash: Cement: Water = 60: 30: 10: 20 (mass ratio).

[0073] S4: The above mixture is extruded into shape by machine with an extrusion pressure of 10MPa and an extrusion speed of 8mm / min. The aggregate particle size is controlled between 1.18-2.36mm. Then, it is steam-cured at a temperature of 80℃, a relative humidity of more than 90%, and a pressure of 1.5MPa for 1 day to obtain phosphogypsum aggregate.

[0074] S5: The above-mentioned phosphogypsum aggregate is impregnated in a 5% organosilicon emulsion for 3 hours at a temperature of 50°C and a stirring speed of 50 r / min. Subsequently, the phosphogypsum aggregate is dried at 80°C for 2 hours to obtain hydrophobic phosphogypsum aggregate.

[0075] S6: Add the hydrophobically treated phosphogypsum aggregate to a 1.5 mol / L sodium hydroxide solution. The mass ratio of phosphogypsum raw material to sodium hydroxide solid is 1:1. Add 0.5% sodium polyphosphate to the sodium hydroxide solution to adjust the crystal form of calcium carbonate to calcite. Control the reaction temperature at 20℃, maintain pH=13, and continuously introduce carbon dioxide at a flow rate of 2L / h. The reaction time is 2h, and the solution is continuously stirred at a stirring rate of 50r / min.

[0076] S7: After the reaction is complete, the above phosphogypsum aggregate is dried at 50°C for 48 hours to obtain reinforced phosphogypsum aggregate.

[0077] The preparation method of ultra-high performance concrete material in this embodiment includes the following steps:

[0078] S1: Mix cement, silica fume, fly ash, quartz sand and reinforced phosphogypsum aggregate for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add bent steel fiber and continue mixing for 3 minutes.

[0079] S2: After molding, vibration and shaping, the surface is covered with a waterproof film for film curing. Then the mold is removed and the material is placed in a standard curing environment for 28 days to obtain the reinforced phosphogypsum aggregate ultra-high performance concrete material.

[0080] Example 2

[0081] A method for preparing UHPC material using reinforced phosphogypsum aggregate, comprising the following raw materials in parts by weight:

[0082] 600 parts cement, 230 parts fly ash microspheres, 300 parts silica fume, 600 parts reinforced phosphogypsum aggregate, 100 parts quartz sand, 210 parts bent steel fiber, 35 parts water-reducing agent, and 170 parts water.

[0083] The preparation method of reinforced phosphogypsum aggregate includes the following steps:

[0084] S1: After drying the raw phosphogypsum at 60 ℃ for 20 h, it is put into a ball mill and ball-milled to obtain phosphogypsum powder;

[0085] S2: Dry the raw aluminum ash at 80 ℃ for 24 hours;

[0086] S3: Mix phosphogypsum powder, primary aluminum ash, and cement, then add ettringite crystal form control agent and water to obtain a mixture. The ettringite crystal form control agent is sodium sulfate solid powder, and after mixing with water, the mass fraction of sodium sulfate is 2%. Phosphogypsum: Primary aluminum ash: Cement: Water = 70:25:15:15 (mass ratio).

[0087] S4: The above mixture is extruded into shape by machine at an extrusion pressure of 13MPa and an extrusion speed of 9mm / min, controlling the aggregate particle size to be 1.18-2.36mm. Then, it is steam-cured for 2 days at a temperature of 60℃, a relative humidity of more than 90%, and a pressure of 1.2MPa to obtain phosphogypsum aggregate.

[0088] S5: The above phosphogypsum aggregate is impregnated in a 10% organosilicon emulsion for 2 hours at a temperature of 40°C and a stirring speed of 100 r / min. Subsequently, the phosphogypsum aggregate is dried at 90°C for 3 hours to obtain hydrophobic phosphogypsum aggregate.

[0089] S6: Add the hydrophobically treated phosphogypsum aggregate to a 2 mol / L sodium hydroxide solution. The mass ratio of phosphogypsum raw material to sodium hydroxide solid is 1.4:1. Add 1% sodium polyphosphate to the sodium hydroxide solution to adjust the crystal form of calcium carbonate to calcite. Control the reaction temperature at 35 ℃, maintain pH=11, and continuously introduce carbon dioxide at a flow rate of 1.4 L / h. The reaction time is 2 h, and the solution is continuously stirred at a stirring rate of 100 r / min.

[0090] S7: After the reaction is complete, the above phosphogypsum aggregate is dried at 60°C for 36 hours to obtain reinforced phosphogypsum aggregate.

[0091] The preparation method of ultra-high performance concrete material in this embodiment includes the following steps:

[0092] S1: Mix cement, silica fume, fly ash, quartz sand and reinforced phosphogypsum aggregate for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add bent steel fiber and continue mixing for 3 minutes.

[0093] S2: After molding, vibration and shaping, the surface is covered with a waterproof film for film curing. Then the mold is removed and the material is placed in a standard curing environment for 28 days to obtain the reinforced phosphogypsum aggregate ultra-high performance concrete material.

[0094] Example 3

[0095] A method for preparing UHPC material using reinforced phosphogypsum aggregate, comprising the following raw materials in parts by weight:

[0096] 700 parts cement, 300 parts fly ash microspheres, 130 parts silica fume, 500 parts reinforced phosphogypsum aggregate, 150 parts quartz sand, 180 parts bent steel fiber, 40 parts water-reducing agent, and 180 parts water.

[0097] The preparation method of reinforced phosphogypsum aggregate includes the following steps:

[0098] S1: After drying the raw phosphogypsum at 70 ℃ for 16 h, it is put into a ball mill and ball-milled to obtain phosphogypsum powder;

[0099] S2: Dry the raw aluminum ash at 100 ℃ for 12 hours;

[0100] S3: Mix phosphogypsum powder, primary aluminum ash, and cement, then add ettringite crystal form control agent and water to obtain a mixture. The ettringite crystal form control agent is sodium sulfate solid powder, and after mixing with water, the mass fraction of sodium sulfate is 1%. Phosphogypsum: Primary aluminum ash: Cement: Water = 75:20:15:15 (mass ratio).

[0101] S4: The above mixture is extruded into shape by machine at an extrusion pressure of 16MPa and an extrusion speed of 10mm / min, controlling the aggregate particle size to be between 1.18-2.36mm. Then, it is steam-cured for 1 day at a temperature of 70℃, a relative humidity of more than 90%, and a pressure of 1.0MPa to obtain phosphogypsum aggregate.

[0102] S5: The above-mentioned phosphogypsum aggregate was impregnated in a 15% organosilicon emulsion for 1.5 hours at a temperature of 30°C and a stirring speed of 150 r / min. Subsequently, the phosphogypsum aggregate was dried at 100°C for 4 hours to obtain hydrophobic phosphogypsum aggregate.

[0103] S6: Add the hydrophobically treated phosphogypsum aggregate to a 2.5 mol / L sodium hydroxide solution. The mass ratio of phosphogypsum raw material to sodium hydroxide solid is 1.8:1. Add 1.5% sodium polyphosphate to the sodium hydroxide solution to adjust the crystal form of calcium carbonate to calcite. Control the reaction temperature at 50 ℃, maintain pH=12, and continuously introduce carbon dioxide at a flow rate of 1.8 L / h. The reaction time is 1.5 h, and the solution is continuously stirred at a stirring rate of 150 r / min.

[0104] S7: After the reaction is complete, the above phosphogypsum aggregate is dried at 70°C for 30 hours to obtain reinforced phosphogypsum aggregate.

[0105] The preparation method of ultra-high performance concrete material in this embodiment includes the following steps:

[0106] S1: Mix cement, silica fume, fly ash, quartz sand and reinforced phosphogypsum aggregate for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add bent steel fiber and continue mixing for 3 minutes.

[0107] S2: After molding, vibration and shaping, the surface is covered with a waterproof film for film curing. Then the mold is removed and the material is placed in a standard curing environment for 28 days to obtain the reinforced phosphogypsum aggregate ultra-high performance concrete material.

[0108] Example 4

[0109] A method for preparing UHPC material using reinforced phosphogypsum aggregate, comprising the following raw materials in parts by weight:

[0110] 800 parts cement, 150 parts fly ash microspheres, 180 parts silica fume, 600 parts reinforced phosphogypsum aggregate, 100 parts quartz sand, 160 parts bent steel fiber, 30 parts water-reducing agent, and 200 parts water.

[0111] The preparation method of reinforced phosphogypsum aggregate includes the following steps:

[0112] S1: After drying the raw phosphogypsum at 80 ℃ for 12 h, it is put into a ball mill and ball-milled to obtain phosphogypsum powder;

[0113] S2: Dry the raw aluminum ash at 85 ℃ for 24 hours;

[0114] S3: Mix phosphogypsum powder, primary aluminum ash, and cement, then add ettringite crystal form control agent and water to obtain a mixture. The ettringite crystal form control agent is sodium sulfate solid powder, and after mixing with water, the mass fraction of sodium sulfate is 0.5%; phosphogypsum: primary aluminum ash: cement: water = 80:10:20:10 (mass ratio).

[0115] S4: The above mixture is extruded into shape by machine with an extrusion pressure of 20MPa and an extrusion speed of 12mm / min. The aggregate particle size is controlled between 1.18-2.36mm. Then, it is steam-cured for 3 days at a temperature of 80℃, a relative humidity of more than 90%, and a pressure of 0.8MPa to obtain phosphogypsum aggregate.

[0116] S5: The above phosphogypsum aggregate is impregnated in a 20% organosilicon emulsion for 1 hour at a temperature of 20°C and a stirring speed of 200 r / min. Subsequently, the phosphogypsum aggregate is dried at 120°C for 2 hours to obtain hydrophobic phosphogypsum aggregate.

[0117] S6: Add the hydrophobically treated phosphogypsum aggregate to a 3 mol / L sodium hydroxide solution. The mass ratio of phosphogypsum raw material to sodium hydroxide solid is 2:1. Add 2% sodium polyphosphate to the sodium hydroxide solution to adjust the crystal form of calcium carbonate to calcite. Control the reaction temperature at 60 ℃, maintain pH=11, and continuously introduce carbon dioxide at a flow rate of 1L / h. The reaction time is 2h, and the solution is continuously stirred at a stirring rate of 200r / min.

[0118] S7: After the reaction is complete, the above phosphogypsum aggregate is dried at 80°C for 24 hours to obtain reinforced phosphogypsum aggregate.

[0119] The phosphogypsum has the following properties: calcium sulfate content 70%-95%, phosphoric acid content 0.5-8%, phosphate content 1%-8%, fluoride content 0.1%-2%, arsenic content less than 30 mg / kg, lead content less than 100 mg / kg, cadmium content less than 10 mg / kg, and mercury content less than 5 mg / kg.

[0120] The preparation method of ultra-high performance concrete material in this embodiment includes the following steps:

[0121] S1: Mix cement, silica fume, fly ash, quartz sand and reinforced phosphogypsum aggregate for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add bent steel fiber and continue mixing for 3 minutes.

[0122] S2: After molding, vibration and shaping, the surface is covered with a waterproof film for film curing. Then the mold is removed and the material is placed in a standard curing environment for 28 days to obtain the reinforced phosphogypsum aggregate ultra-high performance concrete material.

[0123] Comparative Example 1

[0124] This comparative example is basically the same as Example 1, except that the reinforced phosphogypsum aggregate is replaced with 1.18-2.36mm manufactured sand.

[0125] Comparative Example 2

[0126] This comparative example is basically the same as Example 1, except that the reinforced phosphogypsum aggregate is replaced with 1.18-2.36mm quartz sand.

[0127] Comparative Example 3

[0128] This comparative example is basically the same as Example 1, except that sodium sulfate and sodium polyphosphate are not added during the preparation of the reinforced phosphogypsum aggregate.

[0129] Comparative Example 4

[0130] This comparative example is basically the same as Example 1, except that sodium polyphosphate is not added during the preparation of the reinforced phosphogypsum aggregate.

[0131] Comparative Example 5

[0132] This comparative example is basically the same as Example 1, except that sodium sulfate is not added during the preparation of the reinforced phosphogypsum aggregate.

[0133] Comparative Example 6

[0134] This comparative example is basically the same as Example 1, except that the mass fraction of sodium sulfate is 8% in the preparation process of the reinforced phosphogypsum aggregate.

[0135] Comparative Example 7

[0136] This comparative example is basically the same as Example 1, except that 5% sodium polyphosphate is added during the preparation of the reinforced phosphogypsum aggregate.

[0137] Table 1 - Properties of the ultra-high performance concrete materials prepared in Examples 1-4 and Comparative Examples 1-7

[0138]

[0139] As can be seen from Table 1, compared with Comparative Examples 1-7, the ultra-high performance concrete material with reinforced phosphogypsum aggregate obtained by the present invention has high strength, with compressive strength comparable to traditional high-ductility cement-based materials and tensile strength twice that of traditional high-ductility cement-based materials. It can be applied to various large-scale projects, not only improving the strength of concrete itself, but also providing new ideas for phosphogypsum, primary aluminum ash and carbon dioxide curing, and has important economic and environmental benefits. The performance of the concrete materials in Comparative Examples 3-7 was far inferior to that in Example 1 of this invention. This was mainly due to the different ratios of ettringite and calcite crystals in the reinforced phosphogypsum aggregate. When the sodium sulfate content was too high, it caused the ettringite crystals in the cement stone structure to grow too quickly and disorderly. Excessive ettringite crystals were generated in large quantities in a short period of time, forming a thick coating layer on the surface of cement particles, which hindered the normal hydration reaction of cement. When there was an excessive amount of sodium polyphosphate, the calcium carbonate crystals could not grow normally into the expected calcite crystal form, but instead formed some irregular micro-particle agglomerates. All these reasons prevented the ettringite and calcite crystals in the reinforced phosphogypsum aggregate from exerting a better synergistic effect, thus leading to a decline in the performance of the concrete material.

[0140] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A reinforced phosphogypsum aggregate, characterized in that, The preparation method of the reinforced phosphogypsum aggregate includes the following steps: A mixture is obtained by mixing raw materials including phosphogypsum, cement, primary aluminum ash, water and ettringite crystal form control agent; The mixture is extruded and steam-cured to obtain phosphogypsum aggregate; Hydrophobic phosphogypsum aggregate is obtained by impregnating phosphogypsum aggregate in an organosilicon emulsion and then drying it. Hydrophobic phosphogypsum aggregate is placed in a strong alkaline solution containing sodium polyphosphate, and carbon dioxide is continuously bubbled into the strong alkaline solution to carry out the reaction. After the reaction is completed, it is dried to obtain reinforced phosphogypsum aggregate. The strong alkaline solution is a sodium hydroxide solution, and the mass concentration of sodium polyphosphate added to the sodium hydroxide solution is 0.5%-2%. The mass ratio of phosphogypsum, primary aluminum ash, cement, and water is (60-80):(10-30):(10-20):(10-20), and the main component of the ettringite crystal form control agent has a mass fraction of 0.5%-3% in the mixture; the ettringite crystal form control agent is sodium sulfate solid powder.

2. The reinforced phosphogypsum aggregate according to claim 1, characterized in that, The preparation method of the reinforced phosphogypsum aggregate includes: S1: Dry the raw phosphogypsum at 50-80 ℃ for 12-24 h and then put it into a ball mill for ball milling to obtain phosphogypsum powder; S2: Dry the raw aluminum ash at 80-100 ℃ for 12-24 hours; S3: Mix phosphogypsum powder, primary aluminum ash and cement, then add calcite crystal form control agent and water to obtain a mixture; S4: The mixture is extruded into shape by machine with an extrusion pressure of 10-20MPa and an extrusion speed of 8-12mm / min, and the aggregate particle size is controlled at 1.18-2.36mm. Then, it is steam-cured for 1-3 days at a temperature of 60-80℃, a relative humidity of more than 90%, and a pressure of 0.8-1.5MPa to obtain phosphogypsum aggregate. S5: Immerse the phosphogypsum aggregate in a 5%-20% silicone emulsion for 1-3 hours at a temperature of 20-50°C and a stirring speed of 50-200 r / min. Then, dry the phosphogypsum aggregate at 80-120°C for 2-5 hours to obtain hydrophobic phosphogypsum aggregate. S6: Add hydrophobic phosphogypsum aggregate to a 1.5-3 mol / L sodium hydroxide solution. The mass ratio of phosphogypsum raw material to sodium hydroxide solid is (1-2):

1. Add sodium polyphosphate to the sodium hydroxide solution to adjust the crystal form of calcium carbonate to calcite crystal form. Control the reaction temperature at 20-60 ℃, maintain pH=11-13, and continuously introduce carbon dioxide at a flow rate of 1L / h-2L / h. The reaction time is 1-2h, and the solution is continuously stirred at a stirring rate of 50-200r / min. S7: After the reaction is complete, the above phosphogypsum aggregate is dried at 50-80℃ for 24-48 hours to obtain reinforced phosphogypsum aggregate.

3. The reinforced phosphogypsum aggregate according to claim 1, characterized in that, The phosphogypsum contains 70%-95% calcium sulfate, 0.5-8% phosphoric acid, 1%-8% phosphate, 0.1%-2% fluoride, less than 30 mg / kg arsenic, less than 100 mg / kg lead, less than 10 mg / kg cadmium, and less than 5 mg / kg mercury.

4. The reinforced phosphogypsum aggregate according to claim 1, characterized in that, The primary aluminum ash contains 15%-70% aluminum, 1%-5% fluorine, 2%-10% silicon, and 0.5-3% sodium; lead content is less than 0.1%, cadmium content is less than 0.01%, and chromium content is less than 0.1%.

5. An ultra-high performance concrete material prepared using the reinforced phosphogypsum aggregate according to any one of claims 1-4, characterized in that, The raw materials include the following parts by weight: 600-800 parts cement, 150-300 parts fly ash microspheres, 100-300 parts silica fume, 450-600 parts reinforced phosphogypsum aggregate, 100-200 parts quartz sand, 160-240 parts bent steel fiber, 30-40 parts water-reducing agent, and 150-200 parts water.

6. The ultra-high performance concrete material according to claim 5, characterized in that, The reinforced phosphogypsum aggregate has a compressive strength of 10-15 MPa and an apparent density of 2135-2492 kg / m³. 3 Water absorption rate: 5.2%-9.5%.

7. The ultra-high performance concrete material according to claim 5, characterized in that, The particle size of the phosphogypsum aggregate is 1.18-2.36 mm.

8. A method for preparing the ultra-high performance concrete material according to claim 5, characterized in that, The steps include: mixing cement, silica fume, fly ash microspheres, quartz sand and reinforced phosphogypsum aggregate, adding water and water-reducing agent and mixing, adding bent steel fibers and continuing to mix; After the mixture is molded, vibrated, and shaped, the surface is covered with a waterproof film for film curing. After demolding, it is placed in a standard curing environment to obtain reinforced phosphogypsum aggregate ultra-high performance concrete material.

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