Non-calcined phosphogypsum foam light aggregate and preparation method and application thereof

Abstract

The application provides a non-calcined phosphogypsum foam light aggregate and a preparation method thereof, and belongs to the light aggregate field.The non-calcined phosphogypsum foam light aggregate provided by the application takes modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, kaolin and a foaming agent as the preparation raw materials of the foam inner core, takes phosphogypsum, fast-hard high-iron sulfoaluminate cement and building glue powder and water as the preparation raw materials of the fast-hard cementitious material shell layer, and the obtained non-calcined phosphogypsum foam light aggregate with a core-shell structure has a bulk density of <800 kg / m 3 The non-calcined phosphogypsum foam light aggregate has a small bulk density, and the fast-hard cementitious material shell layer improves the strength of the non-calcined phosphogypsum foam light aggregate, so that the non-calcined phosphogypsum foam light aggregate has a good application prospect in the ultra-light concrete field; the foam inner core and the fast-hard cementitious material shell layer are self-assembled into a core-shell structure, so that the pollutants are quickly encapsulated in the inner core by the shell layer material with good compactness, the leaching toxicity of the non-calcined phosphogypsum foam light aggregate is reduced, and the environmental protection performance is excellent.

Description

Technical Field

[0001] This invention belongs to the field of lightweight aggregate technology, specifically relating to a non-calcined phosphogypsum foam lightweight aggregate, its preparation method, and its application. Background Technology

[0002] Industrial by-product gypsum, also known as chemical gypsum, is a by-product generated during industrial production through chemical reactions, with calcium sulfate as its main component. It includes phosphogypsum, which is the primary component, followed by flue gas desulfurization gypsum and fluorogypsum, with smaller amounts of titanium gypsum, salt gypsum, and citric acid gypsum. Non-calcined phosphogypsum lightweight aggregate uses phosphogypsum as the main raw material, adding active mineral admixtures and alkaline activators, exhibiting gelling properties under the dual action of alkali and sulfur activation. It is prepared using disc or extrusion granulation processes. Non-calcined phosphogypsum lightweight aggregate has a compressive strength of 8–22 MPa and a selling price of over 120 yuan / ton, exhibiting high strength and low cost. However, the bulk density of existing non-calcined phosphogypsum lightweight aggregate is 900–1200 kg / m³. 3 Its high bulk density limits its application in the field of ultralight concrete. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a non-calcined phosphogypsum foam lightweight aggregate, its preparation method and application. The non-calcined phosphogypsum foam lightweight aggregate provided by this invention has a low bulk density.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention provides a non-calcined phosphogypsum foamed lightweight aggregate, comprising a foam core and a rapid-setting cementitious material shell located on the surface of the foam core; the bulk density of the non-calcined phosphogypsum foamed lightweight aggregate is <800 kg / m³. 3 ;

[0006] The foam core is obtained by curing and foaming a core mixture; by mass parts, the core mixture includes: 42-48 parts modified phosphogypsum, 22-30 parts mineral powder, 8-10 parts cement clinker, 6-10 parts bauxite, 5-8 parts silica fume, 5-8 parts kaolin, and 29.4-45.7 parts foaming agent; the modified phosphogypsum has a pH ≥ 7;

[0007] The raw materials for preparing the rapid-hardening cementitious material shell include a solid shell mixture and water. By mass, the solid shell mixture includes: 79-92 parts of phosphogypsum, 8-20 parts of rapid-hardening high-iron sulfoaluminate cement, and 1-2 parts of building adhesive powder.

[0008] Preferably, the mass ratio of the foam core to the solid shell mixture is 0.36 to 0.75:1.

[0009] Preferably, the mass ratio of solid shell mixture to water in the rapid-hardening cementitious material shell layer is 0.57–0.74:0.12–0.15.

[0010] Preferably, the foaming agent includes an aqueous solution of sodium bicarbonate or hydrogen peroxide;

[0011] The concentration of the sodium bicarbonate aqueous solution is 12-20 wt%.

[0012] The concentration of the hydrogen peroxide is 10–16 wt%.

[0013] Preferably, the method for preparing the modified phosphogypsum includes the following steps: mixing phosphogypsum, an alkaline substance and water, and aging the mixture to obtain modified phosphogypsum.

[0014] Preferably, the alkaline substance includes one or more of quicklime, hydrated lime, and carbide slag;

[0015] The mass ratio of the phosphogypsum to the alkaline substance is 1:0.06 to 0.15;

[0016] Preferably, the mass ratio of water to phosphogypsum in the raw materials for preparing the modified phosphogypsum is ≤0.15.

[0017] This invention provides a method for preparing the non-calcined phosphogypsum foamed lightweight aggregate described in the above technical solution, comprising the following steps:

[0018] Modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, kaolin, and foaming agent are mixed to obtain a core mixture; the core mixture is then cured and foamed to obtain a foam core.

[0019] Phosphogypsum, rapid-hardening high-iron sulfoaluminate cement and construction adhesive powder are mixed to obtain a solid shell mixture;

[0020] The foam core, the solid shell mixture, and water are mixed, self-assembled, and then cured to obtain non-calcined phosphogypsum foam lightweight aggregate.

[0021] Preferably, the curing foaming temperature is 50-70℃ and the time is 1-3 days.

[0022] Preferably, the maintenance time is 1 to 3 days.

[0023] The present invention provides the application of the non-calcined phosphogypsum foam lightweight aggregate described in the above technical solution or the non-calcined phosphogypsum foam lightweight aggregate obtained by the preparation method described in the above technical solution in thermal insulation materials, sound insulation materials or lightweight concrete.

[0024] This invention provides a non-calcined phosphogypsum foamed lightweight aggregate. The non-calcined phosphogypsum foamed lightweight aggregate of this invention uses modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, kaolin, and a foaming agent as raw materials for preparing the foam core. The foam core forms uniformly distributed pores, reducing the bulk density compared to a dense structure without foaming. The shell layer is prepared using phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, building adhesive powder, and water as raw materials. The resulting non-calcined phosphogypsum foamed lightweight aggregate with a core-shell structure has a bulk density of <800 kg / m³. 3 With its low bulk density, it has excellent application prospects in building materials, especially ultra-lightweight concrete. Furthermore, the modified phosphogypsum used in this invention complexes some soluble pollutants (water-soluble phosphorus and fluorine pollutants) with active anions and cations from other raw materials (mineral powder, cement clinker, bauxite, silica fume, and kaolin), forming a network structure interwoven with hydration products, pollutant solidification products, CSH gel, and calcium sulfate crystals. This solidifies the pollutants, reduces the leaching toxicity of the non-calcined phosphogypsum foam lightweight aggregate, and simultaneously forms a strong skeleton that encapsulates the unreacted phosphogypsum, giving the core sufficient strength for subsequent shell assembly. The foaming agent, at high temperatures... Under the action of decomposition, gas is generated and escapes, causing the foam core to form a porous structure. Phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and construction adhesive powder are used as raw materials for the preparation of the rapid-hardening cementitious material shell (i.e., solid shell mixture). The solid shell mixture forms a rapid-hardening cementitious material shell under the action of hydration, which improves the strength of the non-calcined phosphogypsum foam lightweight aggregate. The foam core and the rapid-hardening cementitious material shell self-assemble into a core-shell structure, so that pollutants are quickly encapsulated in the core by the shell material with better compactness, reducing the leaching toxicity of the non-calcined phosphogypsum foam lightweight aggregate, and exhibiting excellent environmental performance.

[0025] Furthermore, the present invention modifies phosphogypsum, transforming some water-soluble contaminants in phosphogypsum into insoluble contaminants. The modified phosphogypsum is then applied to the preparation of foam cores, giving some contaminants in the non-calcined phosphogypsum foam lightweight aggregate anti-leaching (dissolution) properties, thereby further reducing the leaching toxicity of the non-calcined phosphogypsum foam lightweight aggregate.

[0026] This invention provides a method for preparing non-calcined phosphogypsum foam lightweight aggregate as described in the above technical solution. The preparation method provided by this invention is simple to operate, low in cost, and suitable for industrial production. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The image shows the finished product of the non-calcined phosphogypsum foam lightweight aggregate in Example 2.

[0029] Figure 2 This is an enlarged cross-sectional view of the non-calcined phosphogypsum foam lightweight aggregate after artificial crushing in Example 2;

[0030] Figure 3 This is a magnified view of the surface of the uncrushed and screened foam core in Example 2;

[0031] Figure 4 This is an enlarged view of the core-shell structure of the non-calcined phosphogypsum foam lightweight aggregate in Example 2;

[0032] Figure 5 This is a SEM image of the non-calcined phosphogypsum foam lightweight aggregate shell in Example 2. Detailed Implementation

[0033] This invention provides a non-calcined phosphogypsum foamed lightweight aggregate, comprising a foam core and a rapid-setting cementitious material shell located on the surface of the foam core; the bulk density of the non-calcined phosphogypsum foamed lightweight aggregate is <800 kg / m³. 3 ;

[0034] The foam core is obtained by curing the core mixture; by mass parts, the core mixture includes: 42-48 parts modified phosphogypsum, 22-30 parts mineral powder, 8-10 parts cement clinker, 6-10 parts bauxite, 5-8 parts silica fume, 5-8 parts kaolin, and 29.4-45.7 parts foaming agent; the modified phosphogypsum has a pH ≥ 7;

[0035] The raw materials for preparing the rapid-hardening cementitious material shell include a solid shell mixture and water. By mass, the solid shell mixture includes: 79-92 parts of phosphogypsum, 8-20 parts of rapid-hardening high-iron sulfoaluminate cement, and 1-2 parts of building adhesive powder.

[0036] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0037] In this invention, the core mixture comprises 42-48 parts, preferably 43-47 parts, and more preferably 44-46 parts, of modified phosphogypsum by weight. In this invention, the particle size of the modified phosphogypsum is preferably ≤0.1 mm.

[0038] In this invention, the preparation method of the modified phosphogypsum preferably includes the following steps: mixing phosphogypsum, an alkaline substance, and water, and aging the mixture to obtain modified phosphogypsum. In this invention, the alkaline substance preferably includes one or more of quicklime, hydrated lime, and carbide slag. In this invention, the mass ratio of the phosphogypsum to the alkaline substance is preferably 1:0.07–0.13, more preferably 1:0.08–0.12, and most preferably 1:0.09–0.10. In this invention, the mass ratio of water to phosphogypsum in the raw materials for preparing the modified phosphogypsum is preferably ≤0.15, more preferably 0.12–0.15, and most preferably 0.13–0.14. In this invention, the aging temperature is preferably room temperature; the aging time is preferably 3–7 days, more preferably 4–6 days, and most preferably 5 days. This invention modifies phosphogypsum, neutralizes acidic residues in phosphogypsum, and converts water-soluble pollutants such as phosphorus and fluorine into inert water-insoluble salts, providing a good alkaline environment for subsequent hydration reactions. This improves the physical properties (such as cylinder compressive strength) and environmental performance (such as leaching toxicity) of non-calcined phosphogypsum foamed lightweight aggregate.

[0039] In this invention, the core mixture preferably comprises 22-30 parts by weight of mineral powder, more preferably 23-28 parts, and most preferably 25-26 parts. In this invention, the particle size of the mineral powder is preferably ≤0.1 mm.

[0040] In this invention, the core mixture preferably comprises 8 to 10 parts by weight of cement clinker, more preferably 9 parts. In this invention, the particle size of the cement clinker is preferably ≤0.1 mm.

[0041] In this invention, the core mixture preferably comprises 6 to 10 parts by weight of bauxite, more preferably 7 to 9 parts, and most preferably 8 parts. In this invention, the particle size of the bauxite is preferably ≤0.1 mm.

[0042] In this invention, the core mixture preferably comprises 5 to 8 parts by weight of silica fume, more preferably 6 to 7 parts. In this invention, the particle size of the silica fume is preferably ≤0.1 mm.

[0043] In this invention, the core mixture preferably comprises 5 to 8 parts by weight of kaolin, more preferably 6 to 7 parts. In this invention, the particle size of the kaolin is preferably ≤0.1 mm.

[0044] In this invention, the core mixture preferably comprises 29.4 to 45.7 parts by weight of a foaming agent, more preferably 30 to 40 parts, and most preferably 32 to 37 parts. In this invention, the foaming agent preferably comprises an aqueous solution of sodium bicarbonate or hydrogen peroxide. In this invention, the concentration of the aqueous solution of sodium bicarbonate is preferably 12 to 20 wt%, more preferably 13 to 17 wt%, and most preferably 14 to 16 wt%; the concentration of the hydrogen peroxide is preferably 10 to 16 wt%, more preferably 12 to 15 wt%, and most preferably 14 to 15 wt%. This invention uses an aqueous solution of sodium bicarbonate or hydrogen peroxide as a foaming agent. The foaming component in the foaming agent generates gas under the action of water and escapes, causing the foam core to form a porous structure.

[0045] In this invention, the shape of the foam core preferably includes cylindrical and / or irregular granular shapes. In this invention, the diameter of the cylindrical foam core is preferably 10-19 mm, more preferably 10-15 mm, and most preferably 10-14 mm; the length of the cylindrical foam core is preferably 10-20 mm, more preferably 12-18 mm, and most preferably 13-16 mm. In this invention, the particle size of the irregular granular foam core is preferably 4.75-19.5 mm, more preferably 6-15 mm, and most preferably 8-12 mm.

[0046] In this invention, the solid shell mixture comprises 79-92 parts by weight, more preferably 80-90 parts, and most preferably 85-88 parts of phosphogypsum. In this invention, the particle size of the phosphogypsum is preferably ≤0.05 mm.

[0047] In this invention, the solid shell mixture preferably includes 8 to 20 parts by weight of rapid-hardening high-speed iron sulfoaluminate cement, more preferably 10 to 18 parts, and most preferably 12 to 15 parts.

[0048] In this invention, the solid shell mixture preferably includes 1 to 2 parts of building adhesive powder by weight.

[0049] In this invention, the mass ratio of the solid shell mixture to water in the rapid-setting cementitious material shell layer is preferably 0.57–0.74:0.12–0.15, more preferably 0.6–0.7:0.12–0.15, and most preferably 0.65–0.67:0.12–0.15. In this invention, the mass ratio of the foam core to the solid shell mixture is preferably 0.36–0.75:1, more preferably 0.4–0.7:1, and most preferably 0.5–0.6:1.

[0050] This invention provides a method for preparing the non-calcined phosphogypsum foamed lightweight aggregate described in the above technical solution, comprising the following steps:

[0051] Modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, kaolin, and foaming agent are mixed to obtain a core mixture; the core mixture is then cured and foamed to obtain a foam core.

[0052] Phosphogypsum, rapid-hardening high-iron sulfoaluminate cement and construction adhesive powder are mixed to obtain a solid shell mixture;

[0053] The foam core, the solid shell mixture, and water are mixed, self-assembled, and then cured to obtain non-calcined phosphogypsum foam lightweight aggregate.

[0054] This invention mixes modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, kaolin and foaming agent to obtain a core mixture; the core mixture is then cured and foamed to obtain a foam core.

[0055] In this invention, the mixing is preferably achieved by stirring. The stirring speed and time are not specifically limited, as long as the raw materials are mixed evenly. In this invention, when the foaming agent is hydrogen peroxide, the mixing is preferably achieved by mixing modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, kaolin, and hydrogen peroxide to obtain a core mixture. In this invention, when the foaming agent is an aqueous sodium bicarbonate solution, the mixing is preferably achieved by mixing modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, and kaolin to obtain a solid core mixture; the solid core mixture is then mixed with sodium bicarbonate, and then water is added to obtain the core mixture.

[0056] In this invention, the curing and foaming temperature is preferably 50-70℃, more preferably 55-65℃, and most preferably 60-63℃; the curing and foaming time is preferably 1-3 days, and more preferably 2 days.

[0057] In this invention, when the foam core is cylindrical, curing and foaming the core mixture to obtain the foam core preferably includes: extruding the core mixture into strips, curing and foaming to obtain strip molding material; and cutting the strip molding material to obtain a cylindrical foam core.

[0058] In this invention, when the foam core is irregularly granular, curing and foaming the core mixture to obtain the foam core preferably includes: curing and foaming the core mixture to obtain a molding material; crushing and sieving the molding material to obtain an irregularly granular foam core.

[0059] This invention mixes phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0060] In this invention, the mixing is preferably agitated. This invention does not have any special limitations on the speed and time of agitation, as long as the raw materials are mixed evenly.

[0061] After obtaining the foam core and solid shell mixture, this invention mixes the foam core, the solid shell mixture, and water, performs self-assembly, and then cures it to obtain a non-calcined phosphogypsum foam lightweight aggregate with a foam core and a rapid-setting cementitious material shell. During the stirring process, the solid shell mixture (powder) is evenly coated on the surface of the core in an atmosphere moistened with a small amount of water, thereby forming a shell layer and thus forming the aggregate prototype. After curing, the non-calcined phosphogypsum foam lightweight aggregate is obtained.

[0062] In this invention, the mixing is preferably agitated mixing. This invention does not have a special limitation on the stirring speed, as long as the raw materials are mixed evenly. The stirring time is preferably 1.5 to 4 minutes, more preferably 2 to 3.5 minutes, and most preferably 2.5 to 3 minutes.

[0063] In this invention, the curing time is preferably 1 to 3 days, more preferably 2 days; the curing is preferably carried out at normal temperature and pressure.

[0064] This invention provides the application of the non-calcined phosphogypsum foam lightweight aggregate described in the above technical solution or the non-calcined phosphogypsum foam lightweight aggregate obtained by the preparation method described in the above technical solution in thermal insulation materials, sound insulation materials or lightweight concrete.

[0065] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes the non-calcined phosphogypsum foam lightweight aggregate, its preparation method, and its application, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0066] In all embodiments of the present invention, the modified phosphogypsum is prepared as follows: phosphogypsum, quicklime, and water are uniformly mixed and then aged at room temperature and pressure for 3 days to obtain modified phosphogypsum. The mass ratio of phosphogypsum, quicklime, and water is 100:4.5:15.

[0067] Example 1

[0068] The modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, and kaolin were mixed uniformly in a mass ratio of 44:26:10:7:8:5, with each material having a particle size below 0.1 mm, to obtain a solid core mixture. Sodium bicarbonate was added to the solid core mixture, along with water, and stirred until homogeneous, yielding the core mixture. The core mixture was extruded through a 20 mm conical nozzle. The extruded strips were placed in a curing pan, which was then placed in a 60°C high-temperature curing chamber for curing and foaming. After two days, the strips were removed and cut at 15 mm intervals to obtain cylindrical foam cores. The mass of sodium bicarbonate was 5% of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water was 1:0.29.

[0069] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 80:18:2 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0070] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.72:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 2 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 14% of the sum of the masses of the foam core and solid shell.

[0071] Example 2

[0072] Modified phosphogypsum: mineral powder: cement clinker: bauxite: silica fume: kaolin = 44:26:10:7:8:5 by mass. All materials are uniformly mixed, with a particle size below 0.1 mm, to obtain a solid core mixture. Sodium bicarbonate is added to the solid core mixture, followed by water and stirring until homogeneous, yielding the core mixture. Using a conventional mold, the core mixture is poured into the mold and placed in a 60℃ curing chamber for curing and foaming. After 2 days, it is demolded, crushed, and sieved to obtain irregular granular foam cores ranging from 4.75 mm to 19.5 mm. The mass of sodium bicarbonate is 5% of the mass of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water is 1:0.29.

[0073] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 80:18:2 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0074] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.72:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 2 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 14% of the sum of the mass of the foam core and solid shell mixture.

[0075] Figure 1 The image shows the finished product of the non-calcined phosphogypsum foam lightweight aggregate in Example 2.

[0076] Figure 2 This is an enlarged cross-sectional view of the artificially crushed lightweight aggregate of non-calcined phosphogypsum foam in Example 2. Figure 3 This is a magnified view of the surface of the uncrushed and screened foam core in Example 2. Figure 2 and Figure 3 It is known that the non-calcined phosphogypsum foam lightweight aggregate prepared by the present invention has a large number of pores inside, and the pores form a good network structure.

[0077] Figure 4 This is an enlarged view of the core-shell structure of the non-calcined phosphogypsum foam lightweight aggregate in Example 2. Figure 4 It is known that the non-calcined phosphogypsum foam lightweight aggregate prepared by the present invention has a core-shell structure, wherein the shell layer exhibits a relatively dense structure, while the core layer is full of pores.

[0078] Figure 5 This is a SEM image of the non-calcined phosphogypsum foam lightweight aggregate shell in Example 2. Figure 5 It can be seen that in the shell layer of the non-calcined phosphogypsum foam lightweight aggregate prepared by the present invention, the spaces between the phosphogypsum block particles are filled with fine needle-like hydration products, which connect the phosphogypsum block particles in different directions, so that the shell layer as a whole exhibits a dense structure.

[0079] Example 3

[0080] The modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, and kaolin were mixed uniformly in a mass ratio of 44:26:10:7:8:5, with each material having a particle size below 0.1 mm, to obtain a solid core mixture. Sodium bicarbonate was added to the solid core mixture, along with water, and stirred until homogeneous, yielding the core mixture. The core mixture was extruded through a 20 mm conical nozzle. The extruded strips were placed in a curing pan, which was then placed in a 60°C high-temperature curing chamber for curing and foaming. After two days, the strips were removed and cut at 15 mm intervals to obtain cylindrical foam cores. The mass of sodium bicarbonate was 5% of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water was 1:0.29.

[0081] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 90:9:1 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0082] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.72:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 3 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 15% of the sum of the mass of the foam core and solid shell mixture.

[0083] Example 4

[0084] Modified phosphogypsum: mineral powder: cement clinker: bauxite: silica fume: kaolin = 44:26:10:7:8:5 by mass. All materials are uniformly mixed, with a particle size below 0.1 mm, to obtain a solid core mixture. Sodium bicarbonate is added to the solid core mixture, followed by water and stirring until homogeneous, yielding the core mixture. Using a conventional mold, the core mixture is poured into the mold and placed in a 60℃ curing chamber for curing and foaming. After 2 days, it is demolded, crushed, and sieved to obtain irregular granular foam cores ranging from 4.75 mm to 19.5 mm. The mass of sodium bicarbonate is 5% of the mass of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water is 1:0.29.

[0085] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 90:9:1 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0086] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.72:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 3 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 15% of the sum of the mass of the foam core and solid shell mixture.

[0087] Example 5

[0088] Modified phosphogypsum: mineral powder: cement clinker: bauxite: silica fume: kaolin = 42:22:10:10:8:8 was mixed uniformly with all materials having a particle size below 0.1 mm to obtain a solid core mixture. Sodium bicarbonate was added to the solid core mixture, and water was added and stirred until uniformly mixed to obtain the core mixture. The core mixture was extruded through a 20 mm conical nozzle, and the extruded strip was placed in a curing tray. The curing tray was then sent to a high-temperature curing chamber at 60°C for curing and foaming. After 2 days, the strip was removed and cut at 15 mm intervals to obtain cylindrical foam cores. The mass of sodium bicarbonate was 5% of the mass of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water was 1:0.3.

[0089] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 80:18:2 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0090] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.55:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 2 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 15% of the sum of the mass of the foam core and solid shell mixture.

[0091] Example 6

[0092] Modified phosphogypsum: mineral powder: cement clinker: bauxite: silica fume: kaolin = 42:22:10:10:8:8 was mixed uniformly with each material having a particle size below 0.1 mm to obtain a solid core mixture. Sodium bicarbonate was added to the solid core mixture, and water was added and stirred until uniformly mixed to obtain the core mixture. Using a conventional mold, the core mixture was poured into the mold and placed in a curing chamber at 60℃ for curing and foaming. After 2 days, it was demolded, crushed, and sieved to obtain irregular granular foam cores ranging from 4.75 mm to 19.5 mm. The mass of sodium bicarbonate was 5% of the mass of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water was 1:0.3.

[0093] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 80:18:2 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0094] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.55:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 2 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 15% of the sum of the mass of the foam core and solid shell mixture.

[0095] Example 7

[0096] Modified phosphogypsum: mineral powder: cement clinker: bauxite: silica fume: kaolin = 42:22:10:10:8:8 was mixed uniformly with all materials having a particle size below 0.1 mm to obtain a solid core mixture. Sodium bicarbonate was added to the solid core mixture, and water was added and stirred until uniformly mixed to obtain the core mixture. The core mixture was extruded through a 20 mm conical nozzle, and the extruded strip was placed in a curing tray. The curing tray was then sent to a high-temperature curing chamber at 60°C for curing and foaming. After 2 days, the strip was removed and cut at 15 mm intervals to obtain cylindrical foam cores. The mass of sodium bicarbonate was 5% of the mass of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water was 1:0.3.

[0097] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 90:9:1 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0098] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.55:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 2 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 15% of the sum of the mass of the foam core and solid shell mixture.

[0099] Example 8

[0100] Modified phosphogypsum: mineral powder: cement clinker: bauxite: silica fume: kaolin = 42:22:10:10:8:8 was mixed uniformly with each material having a particle size below 0.1 mm to obtain a solid core mixture. Sodium bicarbonate was added to the solid core mixture, and water was added and stirred until uniformly mixed to obtain the core mixture. Using a conventional mold, the core mixture was poured into the mold and placed in a curing chamber at 60℃ for curing and foaming. After 2 days, it was demolded, crushed, and sieved to obtain irregular granular foam cores ranging from 4.75 mm to 19.5 mm. The mass of sodium bicarbonate was 5% of the mass of the solid core mixture, and the ratio of the sum of the masses of the solid core mixture and sodium bicarbonate to the mass of water was 1:0.3.

[0101] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then mixed in a high-speed mixer at a mass ratio of 90:9:1 with phosphogypsum, rapid-hardening high-iron sulfoaluminate cement, and building adhesive powder to obtain a solid shell mixture.

[0102] The foam core and solid shell mixture was added to a planetary mixer at a mass ratio of 0.55:1 and mixed while simultaneously spraying water evenly. The mixing speed was 120 rpm on its own rotation and 60 rpm on its revolution, and the mixing time was 2 minutes. After discharge, the mixture was cured at room temperature and pressure for 1 day to obtain non-calcined phosphogypsum foam lightweight aggregate. The mass of water was 15% of the sum of the mass of the foam core and solid shell mixture.

[0103] Comparative Example 1

[0104] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then combined with rapid-hardening high-iron sulfoaluminate cement and building adhesive powder in a mass ratio of 90:9:1 to obtain a solid mixture. The solid mixture was granulated using a conventional disc granulation method, cured, and sieved to obtain non-calcined phosphogypsum aggregates ranging from 4.75 to 19.5 mm.

[0105] Comparative Example 2

[0106] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then combined with rapid-hardening high-iron sulfoaluminate cement and building adhesive powder in a mass ratio of 80:18:2 to obtain a solid mixture. This solid mixture was granulated using a conventional disc granulation method, cured, and sieved to obtain 5–20 mm non-calcined phosphogypsum aggregate.

[0107] Comparative Example 3

[0108] Phosphogypsum was pulverized and ball-milled to below 0.05 mm. The mixture was then homogenized in a high-speed mixer at a mass ratio of 96:4 (phosphogypsum: rapid-hardening high-ferroaluminate sulfoaluminate cement) to obtain a solid mixture. Water was added to the solid mixture at 6% of its mass. The mixture was then extruded and granulated using a conventional roller extrusion molding machine, cured at room temperature and pressure for 3 days, and sieved to obtain 5–20 mm non-calcined phosphogypsum aggregate.

[0109] Comparative Example 4

[0110] Commercially available high-strength shale ceramsite for use in lightweight aggregate concrete.

[0111] Test case

[0112] The bulk density, compressive strength, water absorption, softening coefficient, and leaching toxicity of the aggregates prepared in Examples 1-8 and Comparative Examples 1-4 were tested. The test results are shown in Table 1.

[0113] The bulk density, compressive strength, water absorption rate, and softening coefficient of the aggregates prepared in Examples 1-8 and Comparative Examples 1-4 were determined sequentially according to the standard methods in GB / T 17431.2-2010 "Lightweight Aggregates and Their Test Methods".

[0114] Leachate was prepared according to HJ 557-2010 "Leaching Toxicity of Solid Waste - Horizontal Oscillation Method", and the total phosphorus and fluoride content in the leachate was determined. By comparing with the standard limits (total phosphorus 0.5 mg / L, fluoride 10 mg / L) in GB 5085.3-2007 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification", it was determined whether the aggregates prepared in Examples 1-8 and Comparative Examples 1-4 belong to hazardous waste with leaching toxicity characteristics.

[0115] Table 1. Performance test results of the aggregates prepared in Examples 1-8 and Comparative Examples 1-4

[0116]

[0117] Table 1 shows that by designing the configuration of the non-calcined phosphogypsum foam lightweight aggregate and controlling the proportion of each raw material, the bulk density of the obtained non-calcined phosphogypsum foam lightweight aggregate was increased from 1233 kg / m³.3 Reduced to 682-787 kg / m 3 Within the specified range, the compressive strength of the aggregate is 1.15 to 1.8 times that of the high-strength shale ceramsite within the same density range. Simultaneously, the leaching toxicity of the non-calcined phosphogypsum foam lightweight aggregate is effectively controlled. Compared to traditional extrusion molding methods, the environmental performance of the non-calcined phosphogypsum aggregate prepared by this invention is significantly improved.

[0118] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A non-calcined phosphogypsum foamed lightweight aggregate, characterized in that, The foam lightweight aggregate comprises a foam core and a shell layer of fast-hardening cementing material on the surface of the foam core; the bulk density of the non-calcined phosphogypsum foam lightweight aggregate is < 800 kg / m 3 ; The foam core is obtained by curing and foaming the core mixture; The core mixture comprises, in mass fraction, modified phosphogypsum 42-48 parts, mineral powder 22-30 parts, cement clinker 8-10 parts, bauxite 6-10 parts, silica fume 5-8 parts, kaolin 5-8 parts, and foaming agent 29.4-45.7 parts; the modified phosphogypsum has a pH≥7; The preparation raw material of the fast-hardening cementitious material shell layer comprises solid shell mixture and water, and the solid shell mixture comprises, in mass fraction, phosphogypsum 79-92 parts, fast-hardening high-iron sulfoaluminate cement 8-20 parts, and building glue powder 1-2 parts; The preparation method of the modified phosphogypsum comprises the following steps: mixing phosphogypsum, alkaline substance, and water, and aging to obtain modified phosphogypsum; The alkaline substance comprises one or more of quicklime, slaked lime, and carbide slag.

2. The non-calcined phosphogypsum foam lightweight aggregate according to claim 1, characterized in that, The mass ratio of the foam core and the solid shell mixture is 0.36-0.75:

1.

3. The non-calcined phosphogypsum foam lightweight aggregate according to claim 1, characterized in that, The mass ratio of the solid shell mixture and water in the fast-hardening cementitious material shell layer is 0.57-0.74:0.12-0.

15.

4. The non-calcined phosphogypsum foam lightweight aggregate according to claim 1 or 2, characterized in that, The foaming agent comprises sodium bicarbonate aqueous solution or hydrogen peroxide; The concentration of the sodium bicarbonate aqueous solution is 12-20 wt%; The concentration of the hydrogen peroxide is 10-16 wt%.

5. The non-calcined phosphogypsum foam lightweight aggregate according to claim 1, characterized in that, The alkaline substance comprises one or more of quicklime, slaked lime, and carbide slag. The mass ratio of the phosphogypsum and the alkaline substance is 1:0.06-0.15; The mass ratio of water and phosphogypsum in the preparation raw material of the modified phosphogypsum is ≤0.

15.

6. The process for the preparation of the non-calcined phosphogypsum foam lightweight aggregate according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: Mixing modified phosphogypsum, mineral powder, cement clinker, bauxite, silica fume, kaolin, and foaming agent to obtain a core mixture; Curing and foaming the core mixture to obtain a foam core; Mixing phosphogypsum, fast-hardening high-iron sulfoaluminate cement, and building glue powder to obtain a solid shell mixture; Mixing the foam core, the solid shell mixture, and water, and curing after self-assembly to obtain calcined-free phosphogypsum foam lightweight aggregate.

7. The production method according to claim 6, wherein The curing and foaming temperature is 50-70℃, and the time is 1-3 days.

8. The preparation method according to claim 6, characterized in that, The curing time is 1-3 days.

9. Application of the calcined-free phosphogypsum foam lightweight aggregate of any one of claims 1-5 or the calcined-free phosphogypsum foam lightweight aggregate obtained by the preparation method of any one of claims 6-8 in thermal insulation materials, sound insulation materials, or lightweight concrete.

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