A method for preparing weather-resistant flowerpots by using phosphogypsum-based composite cementing material

Abstract

The application relates to the technical field of phosphogypsum-based composite cementitious material application, and particularly discloses a method for preparing weather-resistant flowerpots by using phosphogypsum-based composite cementitious material. The method comprises the following steps: 1, uniformly mixing 60-80 parts of type II anhydrite, 15-35 parts of building gypsum powder, 2-8 parts of ordinary Portland cement, 0.5-2 parts of a sulfate-based activator, 0.05-0.3 parts of an organic-based retarder and 0.2-0.5 parts of a water reducing agent to obtain dry mixture; 2, mixing the dry mixture with water to obtain slurry; 3, casting forming: pouring the slurry obtained in the step 2 into a flowerpot mold and vibrating and compacting; 4, curing and demolding: demolding the slurry in the flowerpot mold after being left to stand and cured for 4-8 hours to obtain a flowerpot blank; and 5, natural curing: naturally curing the flowerpot blank until the embryo completely coagulates to obtain an outdoor weather-resistant flowerpot. The technical problem that phosphogypsum cannot be used for preparing flowerpots due to poor water resistance, softening and disintegration when meeting water, insufficient strength, easy surface pulverization and other characteristics in the prior art is solved.

Description

[0001] Technical Field

[0002] This application relates to the field of phosphogypsum-based composite cementitious materials, and specifically discloses a method for preparing weather-resistant flower pots using phosphogypsum-based composite cementitious materials. Background Technology

[0003] Phosphogypsum is an industrial byproduct generated during the wet-process phosphoric acid production. my country accumulates a huge amount of phosphogypsum annually, causing severe environmental problems. Current technologies mostly utilize calcination to produce building gypsum or type II anhydrous gypsum for the production of building materials (such as wall materials and mortar) to consume the stockpiled phosphogypsum. However, the consumption of phosphogypsum by building materials is still far from sufficient. Expanding the application scenarios of phosphogypsum would significantly increase its stockpiling and be of great importance to the development of the phosphate chemical industry.

[0004] Flower pots are common tools in gardening and indoor / outdoor decoration. Traditional flower pots are mostly made of ceramic, plastic, or cement. If phosphogypsum could be used to make flower pots for landscaping and greening, it would further expand the application scenarios of phosphogypsum and increase the consumption of phosphogypsum stockpiles. Therefore, there were early attempts in the industry to apply phosphogypsum to the field of flower pots. For example, patent document CN214338872U discloses an ecological water-retaining flower pot, the technical solution of which uses phosphogypsum, waste bricks, and other solid waste to mix and cast the flower pot body. However, in actual use, as the usage time increases, phosphogypsum flower pots reveal fatal quality defects: the surface of flower pots made with phosphogypsum is prone to powdering, the structure is extremely easy to collapse, the service life is short, and it is easy to disintegrate under sunlight after watering. Therefore, the industry concludes that phosphogypsum is difficult to apply in the field of flower pots, and the phenomenon of using phosphogypsum-based cementitious materials to make flower pots is rare in existing technology.

[0005] Therefore, the industry urgently needs a method to prepare phosphogypsum flowerpots that can overcome the problems of easy surface powdering, short service life, and easy disintegration under sunlight after watering. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing weather-resistant flower pots using phosphogypsum-based composite cementitious materials, in order to solve the technical problems mentioned above in the prior art where phosphogypsum is prone to surface powdering, has a short service life, and easily disintegrates under sunlight after watering when applied to flower pot products.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: A method for preparing weather-resistant flower pots using phosphogypsum-based composite cementitious materials, comprising the following steps: Step 1: Preparation of dry-mixed phosphogypsum-based composite cementitious material: By weight, add 60-80 parts of type II anhydrous gypsum, 15-35 parts of building gypsum powder, 2-8 parts of ordinary silicate cement, 0.5-2 parts of sulfate activator, 0.05-0.3 parts of organic retarder, and 0.2-0.5 parts of water-reducing agent to a mixing device and mix evenly to obtain the dry-mixed composite cementitious material; the type II anhydrous gypsum is obtained by pre-treatment of wet-process phosphoric acid by-product phosphogypsum through reverse flotation and then calcining at 700-850℃; Step 2, Add water and stir: Mix the dry mixture obtained in Step 1 with water until it is evenly mixed to obtain a slurry; Step 3, Casting and Molding: Pour the slurry obtained in Step 2 into the flowerpot mold and vibrate to compact it; Step 4, Curing and Demolding: After the slurry has been left to stand in the flowerpot mold for 4-8 hours to cure, demold to obtain the flowerpot blank; Step 5, Natural Curing: Allow the flowerpot blank to cure naturally until it is completely solidified, resulting in an outdoor weather-resistant flowerpot.

[0008] The beneficial effects of this implementation plan are as follows:

[0009] Because phosphogypsum-based flowerpots are prone to pulverization, structural collapse, and short lifespan in practical applications, and easily disintegrate under sunlight after watering, they are rarely used in existing technologies for making flowerpots. This application conducts in-depth research and analysis, finding that the pulverization of phosphogypsum flowerpots is mainly determined by the characteristics of phosphogypsum itself. Phosphogypsum is a byproduct of the wet-process phosphoric acid production, which results in residual soluble phosphate salts, fluoride salts, sodium salts, potassium salts, and other impurities in the phosphogypsum. During drying, these soluble impurities crystallize; when moist, the salts redissolve, repeatedly swelling and crystallizing, generating continuous expansion stress inside the phosphogypsum-based flowerpot, opening micropores and microcracks. Furthermore, the eutectic phosphorus in the phosphogypsum itself distorts the gypsum lattice, and impurities hinder hydration and crystallization, resulting in high porosity, poor crystal overlap, and a loose structure in the hardened phosphogypsum body. The loose structure and repeated cyclic expansion stress make phosphogypsum flowerpots prone to disintegration under sunlight after watering. Therefore, for phosphogypsum-based flowerpots, the wet-dry cycle results in continuous internal damage, while the application conditions of these pots inevitably involve this cycle (plants require regular watering and sufficient sunlight), severely limiting the use of phosphogypsum in flowerpots and planting containers. This application utilizes type II anhydrous phosphogypsum obtained by pre-treating wet-process phosphate byproducts through reverse flotation and calcining at 700-850℃. During the reverse flotation process, soluble salt impurities dissolve in the water, reducing the amount of soluble salt impurities in the phosphogypsum itself. This fundamentally reduces the repeated expansion stress of phosphogypsum-based flowerpots under wet-dry cycles, significantly improving their quality.

[0010] 2. The sulfate internal activator in this application can precipitate free soluble calcium salts, thereby strengthening the hardened phase of phosphogypsum. The organic retarder chelates / adsorbs the remaining soluble impurities in the phosphogypsum during reverse flotation. The chelate between the organic retarder and the soluble impurities is stable at low temperature / neutral conditions, making it perfectly suitable for the sunlight exposure of flowerpots, preventing precipitation, blooming, and powdering. The ternary composite system of these two components and ordinary silicate cement further improves the quality of flowerpots prepared with phosphogypsum. This successfully solves the problems of poor water resistance, low strength, and easy powdering of gypsum-based flowerpots, and successfully develops phosphogypsum-based flowerpots suitable for outdoor use.

[0011] Furthermore, the anhydrous gypsum of the type II anhydrous gypsum has an anhydrous gypsum content of ≥80%, a fineness of 200-400 mesh, a pH value of 8-10, and a total phosphorus content of ≤0.8%.

[0012] Furthermore, in step 1, the mass ratio of type II anhydrous gypsum, building gypsum powder, and ordinary Portland cement is 65-75:20-30:4-6. Preferably, the mass ratio of type II anhydrous gypsum, building gypsum powder, and ordinary Portland cement is 70:25:5. Furthermore, the sulfate activator is potassium sulfate, and the mass fraction of potassium sulfate is 0.8-1.2 parts.

[0013] Furthermore, the organic retarder is selected from protein-based retarders. Preferably, it is a protein-based gypsum-specific retarder.

[0014] Furthermore, the water-reducing agent is selected from powdered polycarboxylate water-reducing agents, with a mass fraction of 0.25-0.35 parts.

[0015] Furthermore, in step 2, when adding water and stirring, the water-cement ratio of the dry mixture to the water is 0.27-0.30.

[0016] Furthermore, the dry mix of the phosphogypsum-based composite cementitious material also contains 0.05-0.12 parts by weight of SAP dry powder.

[0017] Furthermore, the dry mix of phosphogypsum-based composite cementitious material added in step 1 also includes natural porous / layered inorganic mineral moisture-regulating and water-retaining material, the amount of which is 3-5% of the dry weight of phosphogypsum.

[0018] Furthermore, the natural porous / layered inorganic mineral moisture-regulating and water-retaining material is calcium-based bentonite. When flowerpots are placed in outdoor environments such as balconies, the large temperature difference between day and night in winter causes rapid evaporation of moisture during the day and potential freezing and expansion of residual moisture at night, further damaging the internal structure of the gypsum and exacerbating pulverization. Since the gypsum is already weak and lacks overall integrity, it is easily torn apart from the surface structure. This application utilizes a natural porous / layered inorganic mineral moisture-regulating and water-retaining material to absorb water that overflows from the soil onto the pot wall after watering, reducing the dissolution of soluble impurities and preventing the moisture from freezing and expanding, thus preventing damage to the internal structure of the gypsum. This allows the phosphogypsum-based flowerpots of this application to be used in colder northern regions during winter. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0020] The following detailed description illustrates the specific implementation method: Implementation, for example, attached Figure 1 As shown: General Methodology The raw materials used in the embodiments of this invention are as follows: Phosphogypsum: Phosphogypsum, a byproduct of wet-process phosphoric acid production, has a total phosphorus content of 0.6-0.8% after reverse flotation pretreatment. Type II anhydrous gypsum: The above phosphogypsum was calcined at 750℃ for 30 minutes, cooled naturally, and pulverized to 325 mesh. The anhydrous gypsum content was measured to be 83%, and the pH value was 9. Building gypsum powder: Commercially available β-type hemihydrate gypsum, fineness 200 mesh, initial setting time 6 minutes, final setting time 15 minutes; Ordinary Portland cement: PO 42.5 grade, conforming to GB 175-2007 standard; Potassium sulfate: Industrial grade, purity ≥98%; Protein-based retarder: Commercially available protein-based gypsum retarder, in powder form; Polycarboxylate superplasticizer: Powdered polycarboxylate superplasticizer with a water reduction rate of ≥25%.

[0021] Natural porous / layered inorganic mineral moisture-regulating and water-retaining materials: calcium-based bentonite, diatomaceous earth, zeolite, attapulgite / sepiolite.

[0022] A method for preparing weather-resistant flower pots using phosphogypsum-based composite cementitious materials includes the following steps: Step 1: Preparation of dry-mixed composite cementitious material based on phosphogypsum: By weight, add 60-80 parts of type II anhydrous gypsum, 15-35 parts of building gypsum powder, 2-8 parts of ordinary silicate cement, 0.5-2 parts of sulfate activator, 0.05-0.3 parts of organic retarder, 0.2-0.5 parts of water-reducing agent, 0.05-0.12 parts of SAP dry powder, and 1.8-4 parts of natural porous / layered inorganic mineral moisture-regulating and water-retaining material to a mixing device and mix evenly to obtain the dry-mixed composite cementitious material; the type II anhydrous gypsum is obtained by calcining phosphogypsum, a by-product of wet-process phosphoric acid production, after reverse flotation pretreatment at 700-850℃. Step 2, Add water and stir: Mix the dry mixture obtained in Step 1 with water until it is evenly mixed to obtain a slurry; Step 3, Casting and Molding: Pour the slurry obtained in Step 2 into the flowerpot mold and vibrate to compact it; Step 4, Curing and Demolding: After the slurry has been left to stand in the flowerpot mold for 4-8 hours to cure, demold to obtain the flowerpot blank; Step 5, Natural Curing: Allow the flowerpot blank to cure naturally until it is completely solidified, resulting in an outdoor weather-resistant flowerpot.

[0023] Test methods: The following test methods are used in the embodiments of the present invention: Setting time: Tested according to GB / T 17669.4-1999 "Determination of physical properties of building gypsum paste"; Compressive strength: Tested according to GB / T 17669.3-1999 "Determination of mechanical properties of building gypsum", specimen size 40mm×40mm×160mm; Softening coefficient: The ratio of the compressive strength of the specimen under saturated water absorption state to the compressive strength under dry state after 28 days of curing. Freeze-thaw cycles: The slow freezing method was carried out according to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". 25 freeze-thaw cycles were performed, and the appearance changes were observed and the strength loss was measured. Surface chalking evaluation: The degree of surface powder shedding is classified into poor (severe shedding), poor (significant shedding), fair (slight shedding), good (almost no shedding), and excellent (completely no shedding) based on the fingernail scratching method.

[0024] Example 1 (Standard Formulation) (1) Preparation of dry mix: Take 70 parts of type II anhydrous gypsum obtained after reverse flotation screening pretreatment and calcination, 25 parts of building gypsum powder, 5 parts of ordinary silicate cement, 1 part of potassium sulfate, 0.05 parts of protein retarder, 0.3 parts of polycarboxylate superplasticizer, and 0.12 parts of SAP dry powder, and dry mix for 5 minutes to obtain composite cementitious dry mix; (2) Add water and stir: Mix the dry mixture with water at a water-binder ratio of 0.28 and stir for 5 minutes to obtain the slurry; (3) Casting and molding: Pour the slurry into the flower pot mold (wall thickness 15mm) and vibrate to compact it; (4) Curing and demolding: Let it stand for curing. Demold in 4 hours in summer and 6 hours in winter to obtain the flower pot blank; (5) Natural maintenance: After 28 days of natural maintenance, outdoor weather-resistant flower pots are obtained.

[0025] Example 2 (Adjusted retarder - summer formulation) It is basically the same as Example 1, except that the protein retarder is 0.1 parts in step (1), and the other conditions are the same.

[0026] Example 3 (Adjusting the retarder - winter formulation) It is basically the same as Example 1, except that the protein retarder is 0.03 parts in step (1), and the other conditions are the same.

[0027] Example 4 (Adjusting Cement - Lower Limit) The method is basically the same as in Example 1, except that the amount of ordinary silicate cement is 2 parts and the amount of building gypsum powder is increased by 2 parts to 28 parts, while other conditions are the same.

[0028] Example 5 (Adjusting Cement - Upper Limit) The method is basically the same as in Example 1, except that the amount of ordinary silicate cement is 8 parts and the amount of building gypsum powder is reduced by 3 parts to 22 parts, while other conditions are the same.

[0029] Example 6 The method is basically the same as Example 1, except that calcium-based bentonite is added as a natural porous / layered inorganic mineral moisture-regulating and water-retaining material. The amount added is 2.1 parts, accounting for 3% of the dry weight of phosphogypsum.

[0030] Comparative Example 1 (without cement) The process is basically the same as in Example 1, except that in step (1), the type II anhydrous gypsum obtained by calcining ordinary phosphogypsum is used instead of the type II anhydrous gypsum obtained by calcining reverse flotation phosphogypsum. All other conditions are the same.

[0031] Comparative Example 2 (without potassium sulfate) It is basically the same as Example 1, except that potassium sulfate is not added in step (1), and the other conditions are the same.

[0032] Comparative Example 3 (without retarder) It is basically the same as Example 1, except that no protein retarder is added in step (1), and the other conditions are the same.

[0033] Comparative Example 4 (without water-reducing agent) It is basically the same as Example 1, except that polycarboxylate superplasticizer is not added in step (1), and the other conditions are the same.

[0034] Performance test results: The performance test results of the flowerpots (or standard specimens) prepared in each embodiment and comparative example are summarized in Table 1. It is worth noting that the powdering quality test in this application is based on a comprehensive consideration of the appearance and surface powdering evaluation after 25 freeze-thaw cycles. The surface powdering evaluation is carried out using the dry-wet cycle method, and the specific process includes: Step 1, Cycle: Soak in water for 4 hours (20±2℃) → Dry for 16 hours (60±5℃), for a total of 25 to 50 cycles.

[0035] Step 2, Evaluation: Rating: Visual inspection is used to determine the following grades: Excellent (smooth, powder-free surface, good hardness; scratches may appear when rubbed with a knife, but no powdering), Good (smooth, powder-free surface, good hardness; slight powdering may appear when rubbed with a knife), Average (smooth, powder-free surface; powder may appear when rubbed by hand), Poor (obvious powdering), and Very Poor (severely crumbly and peeling).

[0036] The appearance inspection after 25 freeze-thaw cycles includes the following steps: Step 1, Freezing: -18℃±2℃, 4h Step 2, Melting: In water at 20℃±5℃, for 4 hours. Step 3, Cycle: One cycle lasts 8 hours, for a total of 25 cycles.

[0037] Rating: Visual inspection is used to classify the following types of cracks: intact without cracks, surface micro-cracks (crack width < 0.2 mm), cracked (0.1 mm ≤ width < 0.2 mm), and severely cracked (width ≥ 0.2 mm).

[0038] Other tests, such as initial setting time, 6-hour compressive strength, 28-day compressive strength, and softening coefficient, shall be conducted in accordance with GB / T 9776-2022 and JCT698-2025.

[0039] Table 1: Performance Test Tables for Different Embodiments and Comparative Examples

[0040] The following conclusions can be drawn from the test results in Table 1: 1. Filling a technological gap, this invention marks the first application of phosphogypsum in the field of flowerpots. Example 1 of this invention is the first to use a phosphogypsum-based ternary composite cementitious material in flowerpot preparation, demonstrating excellent performance in terms of strength, weather resistance, and surface quality, successfully filling the technological gap in the application of phosphogypsum in the field of flowerpots.

[0041] 2. Addressing the presence of soluble phosphate, fluoride, sodium, and potassium salts as impurities in phosphogypsum is key to improving its weather resistance and anti-pulverization properties. A comparison of Example 1 and Comparative Example 1 shows that the formulation of type II anhydrous gypsum obtained by calcining ordinary phosphogypsum (Comparative Example 1) has a softening coefficient of only 0.82, exhibits micro-cracks after freeze-thaw cycles, and shows significant surface pulverization. In contrast, Example 1, which uses reverse flotation phosphogypsum calcined to produce type II anhydrous gypsum, achieves a softening coefficient of 0.91, remains intact without cracks after freeze-thaw cycles, and demonstrates good surface pulverization performance. This demonstrates that reducing soluble salt impurities in phosphogypsum significantly improves the water resistance and freeze-thaw resistance of flowerpots and solves the pulverization problem.

[0042] 3. Adjustable setting time: By adjusting the amount of retarder, the initial setting time of Examples 1-3 can be adjusted within the range of 35-55 minutes to adapt to different seasons and process requirements.

[0043] 4. The activator is indispensable: Comparative Example 2 (without potassium sulfate) sets very slowly and has very low early strength. The addition of sulfate activator causes some of the free calcium ions in phosphogypsum to react with sulfate to produce calcium sulfate precipitate. This reduces the soluble calcium salts in type II anhydrous gypsum and also strengthens the hardening phase of the gypsum itself. This shows that potassium sulfate plays a crucial role in activating anhydrous gypsum.

[0044] 5. The role of water-reducing agent: Comparative Example 4 (without water-reducing agent) showed a significant decrease in strength and a reduction in softening coefficient, indicating that the water-reducing agent can optimize the pore structure and improve density and durability.

[0045] 6. In the wet-dry cycle of watering and light exposure, the phosphogypsum matrix without calcium-based bentonite has loosely bonded crystals and well-developed interconnected pores. Residual soluble phosphorus, fluoride, and alkali metal salts migrate outwards with capillary water during wet-dry cycles, repeatedly dissolving and recrystallizing on the surface, generating crystalline expansion stress. Furthermore, residual acidic impurities continuously corrode the gypsum cement interface, leaving no buffer space for wet-dry deformation. Microcracks continuously emerge and expand, ultimately resulting in a loose structure and surface sanding, powdering, and peeling. However, in Example 6, after incorporating an appropriate amount of calcium-based bentonite, its layered fine particles effectively fill the voids in the gypsum matrix and refine the structure. The material reduces pore size and improves overall density. Relying on its reversible, mild water absorption and retention and slow water release characteristics, it significantly limits the rapid migration of free water and reduces the accumulation and crystallization of harmful soluble salts on the surface. At the same time, relying on the flexible deformation ability of the layered structure, it buffers the shrinkage and expansion stress caused by alternating wet and dry conditions, inhibits the generation of microcracks, and can also fix some residual acid and harmful impurities through surface adsorption, weakening long-term chemical corrosion. Moreover, the material itself does not contain soluble salts and will not cause secondary salt swelling damage. These multiple effects work together to effectively improve the stability of the phosphogypsum matrix and significantly alleviate the pulverization problem under wet and dry cycling conditions.

[0046] In summary, the method of this invention is the first to successfully apply phosphogypsum-based composite cementitious material to the preparation of flower pots. The product has high early strength, high late strength, excellent weather resistance and surface anti-powdering properties, filling a technological gap. It is suitable for long-term indoor or outdoor use and has good promotion and application value.

[0047] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials, characterized in that, Includes the following steps: Step 1: Preparation of dry-mixed phosphogypsum-based composite cementitious material: By weight, add 60-80 parts of type II anhydrous gypsum, 15-35 parts of building gypsum powder, 2-8 parts of ordinary silicate cement, 0.5-2 parts of sulfate activator, 0.05-0.3 parts of organic retarder, and 0.2-0.5 parts of water-reducing agent to a mixing device and mix evenly to obtain the dry-mixed composite cementitious material; the type II anhydrous gypsum is obtained by pre-treatment of wet-process phosphoric acid by-product phosphogypsum through reverse flotation and then calcining at 700-850℃; Step 2, Add water and stir: Mix the dry mixture obtained in Step 1 with water until it is evenly mixed to obtain a slurry; Step 3, Casting and Molding: Pour the slurry obtained in Step 2 into the flowerpot mold and vibrate to compact it; Step 4, Curing and Demolding: After the slurry has been left to stand in the flowerpot mold for 4-8 hours to cure, demold to obtain the flowerpot blank; Step 5, Natural Curing: Allow the flowerpot blank to cure naturally until it is completely solidified, resulting in an outdoor weather-resistant flowerpot.

2. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: The anhydrous gypsum of type II has an anhydrous gypsum content of ≥80%, a fineness of 200-400 mesh, a pH value of 8-10, and a total phosphorus content of ≤0.8%.

3. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: In step 1, the mass ratio of type II anhydrous gypsum, building gypsum powder, and ordinary silicate cement is 65-75:20-30:4-6.

4. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: The sulfate activator is potassium sulfate, with a mass fraction of 0.8-1.2 parts.

5. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: The organic retarder is a protein-based gypsum-specific retarder.

6. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: The water-reducing agent is selected from powdered polycarboxylate water-reducing agents, with a mass fraction of 0.25-0.35 parts.

7. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: When adding water and stirring in step 2, the water-cement ratio of the dry mixture to the water is 0.27-0.

30.

8. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: The dry mix of the phosphogypsum-based composite cementitious material also contains 0.05-0.12 parts by weight of SAP dry powder.

9. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 1, characterized in that: The dry mix of phosphogypsum-based composite cementitious material added in step 1 also includes natural porous / layered inorganic mineral moisture-regulating and water-retaining material, the amount of which is 3-5% of the dry weight of phosphogypsum.

10. The method for preparing weather-resistant flowerpots using phosphogypsum-based composite cementitious materials according to claim 9, characterized in that: The natural porous / layered inorganic mineral moisture-regulating and water-retaining material is calcium-based bentonite.

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