Phosphogypsum aggregate planting concrete and preparation method thereof

Abstract

The application relates to the technical field of building materials, and discloses a phosphogypsum aggregate vegetation concrete and a preparation method thereof. Raw phosphogypsum, solid waste admixture and an alkaline activator are mixed and proportioned to prepare cold-bonded artificial aggregates with single particle size and high sphericity, so as to prepare the phosphogypsum aggregate vegetation concrete. The application utilizes the acidity and soluble phosphorus elements of the phosphogypsum to perform alkali reduction treatment on the vegetation concrete and provide nutrients for plant growth; meanwhile, the hydration product can adsorb and solidify the soluble phosphorus, fluorine and heavy metal elements in the phosphogypsum, hinders the large-scale migration of the elements to the natural environment, eliminates the environmental risks caused by the direct utilization of the raw phosphogypsum, and provides high-quality raw materials for high-performance pervious concrete. In addition, according to the spherical dense packing and slurry wrapping theory, the mix proportion of the phosphogypsum aggregate vegetation concrete is optimized and designed, so that the connected porosity, the water permeability coefficient and the compressive strength of the pervious vegetation concrete can be adjusted and customized.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and discloses a phosphogypsum aggregate planted concrete and its preparation method. Background Technology

[0002] Vegetated concrete, as a novel slope protection material, combines slope protection and ecological restoration functions, and is currently widely used in roads, river embankments, parking lots, and urban greening. Compared to ordinary permeable concrete, vegetated concrete has higher porosity and permeability. Combined with concrete alkali reduction and plant growth substrate preparation technologies, it provides a stable environment for plant root growth. The interwoven plant root system forms a three-dimensional protective structure, not only reinforcing the slope and preventing soil erosion, but also conserving and purifying water quality and promoting biodiversity.

[0003] To achieve high porosity for plant rooting and growth, vegetated concrete is typically formulated with manufactured or recycled aggregates within a single particle size range. Theoretically, higher aggregate particle sphericity and better cement paste cohesion reduce the likelihood of pore blockage at the bottom of the vegetated concrete, resulting in higher pore connectivity. However, in reality, the sphericity of manufactured and recycled aggregates used is generally low (<0.7), and they often contain needle-like or flaky particles, leading to decreased porosity and connectivity in vegetated concrete. Furthermore, the pore structure and mechanical strength of concrete are contradictory factors. Summary of the Invention

[0004] The purpose of this invention is to provide a phosphogypsum aggregate planted concrete and its preparation method, which can realize the large-scale and harmless utilization of phosphogypsum resources and provide high-quality raw materials for high-performance permeable concrete.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows: A phosphogypsum aggregate-based planted concrete is made by sequentially mixing, vibrating, and curing raw material components including cement, phosphogypsum cold-bonding aggregate, silica fume, and water; the phosphogypsum cold-bonding aggregate is obtained by mixing, granulating, and curing a mixture containing undiluted phosphogypsum, solid waste admixture, and alkaline activator.

[0006] Further, by mass percentage, the phosphogypsum cold-bonded aggregate comprises 60%–80% unprocessed phosphogypsum, 20%–30% solid waste admixture, and 5%–10% alkaline activator; the unprocessed phosphogypsum is solid waste generated from the preparation of phosphoric acid from phosphate rock by reacting sulfuric acid with phosphate rock, and its mineral composition includes 90%–95% dihydrate gypsum, 5%–10% quartz, with the remainder being soluble phosphorus, fluorine, and trace heavy metals including Pb, Cr, Hg, Cu, Zn, and Cd; the solid waste admixture includes one or more combinations of granulated blast furnace slag, fly ash, silica fume, and steel slag; the alkaline activator includes one or more combinations of cement, lime, sodium hydroxide, and water glass.

[0007] Furthermore, the phosphogypsum cold-bonded aggregate has a particle size range of 10–20 mm, a cylinder compressive strength of 4–10 MPa, a water absorption rate of 5%–20% per hour, a particle sphericity ≥0.85, and a pH value of 7–9.

[0008] Furthermore, the curing regime of the planted concrete includes one or more combinations of natural curing, carbonation curing, or standard curing, and the curing regime of the phosphogypsum cold-bonded aggregate is natural curing, carbonation curing, or steam curing.

[0009] Furthermore, by weight, the raw material components also include 0.5 to 0.8 parts of polycarboxylate superplasticizer and 0.05 to 0.08 parts of hydroxypropyl methylcellulose ether water-retaining agent.

[0010] Furthermore, the cement is ordinary Portland cement of grade P·O 425R or higher, with a 3-day compressive strength ≥22MPa and a 28-day compressive strength ≥42.5MPa; the silica fume is SF85 grade or higher silica fume meeting national standards, with a specific surface area ≥15000 m². 2 / kg, with an activity index ≥105%; the water reduction rate of the polycarboxylate superplasticizer is ≥25%; the viscosity of the hydroxypropyl methylcellulose ether water-retaining agent is 80000~200000 mPa.s.

[0011] To achieve the above-mentioned technical effects, the present invention also provides a method for preparing phosphogypsum aggregate-grown concrete, which is used to prepare the aforementioned grown concrete, comprising: The amount of phosphogypsum cold-bonding aggregate used in vegetation concrete is determined based on the packing porosity of phosphogypsum cold-bonding aggregate. Based on the target permeability coefficient of the planted concrete, and the average particle size and packing void ratio of the phosphogypsum cold-bonded aggregate, the effective porosity of the phosphogypsum cold-bonded aggregate in the planted concrete was analyzed and obtained. Based on the target value of the 28-day compressive strength of the planted concrete, and the average particle size, packing void ratio and effective porosity of the phosphogypsum cold-bonded aggregate, the 28-day strength value of the cementitious slurry in the planted concrete was obtained by analysis. The water-cement ratio of the vegetation concrete was obtained based on the 28-day strength value of the cementitious slurry and the percentage of silica fume used. Based on the average particle size and packing void ratio of the phosphogypsum cold-bonded aggregate, as well as the percentage of silica fume used, the water-cement ratio of the vegetation concrete is obtained, and the amount of cementitious material and water used in the vegetation concrete is determined. Based on the determined amount of phosphogypsum cold-bonding aggregate, cementitious material, and water in the planted concrete, the corresponding raw material components are weighed and then mixed, vibrated, molded, and cured in sequence to obtain the final product.

[0012] Furthermore, the unit volume of phosphogypsum cold-bonding aggregate in vegetation concrete is based on... Analysis yielded, among which This refers to the unit dosage of phosphogypsum cold-bonding aggregate in vegetation concrete; The density of phosphogypsum cold-bonded aggregate; The porosity of phosphogypsum cold-bonded aggregate.

[0013] Furthermore, the effective porosity of the phosphogypsum cold-bonded aggregate in the planted concrete is based on... ,in, The target permeability coefficient for the vegetation concrete is given in the design based on construction requirements. The permeability coefficient is an empirical value corresponding to the unit interconnected porosity of permeable concrete, and is taken as (2.1~6.3)×10. -5 mm / s; This refers to the unit volume of the vegetation concrete. The average particle size of the phosphogypsum cold-bonded aggregate is... The porosity of phosphogypsum cold-bonded aggregate; The effective porosity of phosphogypsum cold-bonded aggregate; It is an exponent, with a value range of 0.8 to 4.6; The 28-day strength value of the cementitious slurry in the vegetated concrete is based on... ,in , For coefficients, The value ranges from 1 to 10. The value ranges from 0.01 to 0.1; The target value for the 28-day compressive strength of planted concrete; The water-cement ratio of the vegetation concrete is based on ,in The water-cement ratio for vegetation concrete; The standard strength of cement paste; For coefficients, The value is 1.68; It is a natural constant; This refers to the amount of silica fume added to the cementitious material.

[0014] Furthermore, the amount of cementitious material used in the vegetation concrete is based on... Water in the planted concrete ,in This refers to the unit volume of cementitious materials used in vegetation concrete, in kg / m³. 3 ; The density of the cementitious material is taken as 3000 kg / m³. 3 .

[0015] Compared with the prior art, the beneficial effects of this invention are: 1. This invention uses undisturbed phosphogypsum and solid waste admixtures to prepare phosphogypsum cold-bonded artificial aggregate, realizing the large-scale and harmless utilization of phosphogypsum resources. At the same time, the aggregate has a single particle size, high sphericity, and adjustable properties such as compressive strength and water absorption rate, providing high-quality raw materials for high-performance permeable vegetated concrete.

[0016] 2. Based on the theory of spherical close packing and slurry coating, this invention optimizes the mix design of phosphogypsum aggregate planted concrete, which can achieve adjustable and customizable interconnected porosity, permeability coefficient and compressive strength of permeable planted concrete.

[0017] 3. The phosphogypsum cold aggregate planted concrete prepared by this invention utilizes the acidity and soluble phosphorus element of phosphogypsum to reduce the alkali of the planted concrete and provide nutrients for plant growth, thereby effectively utilizing the valuable elements in phosphogypsum.

[0018] 4. The phosphogypsum cold aggregate planted concrete prepared by the present invention utilizes the alkaline hydration products and porous hydration products (CSH gel) of cement to adsorb and solidify soluble phosphorus, fluorine and heavy metal elements in phosphogypsum, preventing them from migrating to the natural environment on a large scale and eliminating the environmental risks caused by the direct use of undisturbed phosphogypsum. Attached Figure Description

[0019] Figure 1 The image shown is a SEM image of the surface of the phosphogypsum aggregate inside the planted concrete with phosphogypsum aggregate in the example during the carbonization curing process. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0021] Example 1. See also Figure 1 A phosphogypsum aggregate-based planted concrete, wherein the planted concrete is made by sequentially mixing, vibrating and molding, and curing raw material components including cement, phosphogypsum cold-bonding aggregate, silica fume and water; wherein the phosphogypsum cold-bonding aggregate is obtained by mixing, granulating and curing a mixture containing undiluted phosphogypsum, solid waste admixture and alkaline activator.

[0022] In this embodiment, undisturbed phosphogypsum is mixed with solid waste admixtures and an alkaline activator to prepare a cold-bonded artificial aggregate with a single particle size and high sphericity. Utilizing the acidity and soluble phosphorus of phosphogypsum, the alkali-reducing treatment of the vegetated concrete is carried out simultaneously, providing nutrients for plant growth and effectively utilizing valuable elements in the phosphogypsum. Meanwhile, the calcium ions dissolved from the hydration product calcium hydroxide can combine with soluble fluoride ions and some phosphate ions dissolved from the phosphogypsum to form insoluble CaF2 and slightly soluble Ca3(PO4)2, thereby inhibiting the leaching of soluble fluoride into the environment and allowing soluble phosphorus to be slowly released into the surrounding environment for plant growth, avoiding the risk of eutrophication caused by large-scale migration into the environment. Furthermore, the large specific surface area and nanoscale gel pores of the hydration product CSH gel can adsorb soluble heavy metal cations in the phosphogypsum, such as Zn. 2+ Cu 2+ Pb 2 + Cr 3+ / Cr 6+ As 3+ / As 5+ Hg 2+ These substances, such as cement hydration products, solidify and shield soluble phosphorus, fluorine, and heavy metals in phosphogypsum, preventing their migration and leaching into the environment. This eliminates the risk of environmental leaching of phosphogypsum, achieving multiple benefits and providing high-quality raw materials for high-performance permeable concrete.

[0023] In this embodiment, by mass percentage, the raw phosphogypsum in the phosphogypsum cold-bonding aggregate comprises 60%–80%, solid waste admixture comprises 20%–30%, and alkaline activator comprises 5%–10%. The raw phosphogypsum is solid waste generated from the preparation of phosphoric acid from phosphate rock by reacting sulfuric acid with phosphate rock. The mineral composition of the raw phosphogypsum includes 90%–95% dihydrate gypsum, 5%–10% quartz, and the balance being soluble phosphorus, fluorine, and trace heavy metals including Pb, Cr, Hg, Cu, Zn, and Cd. The solid waste admixture includes one or more combinations of granulated blast furnace slag, fly ash, silica fume, and steel slag. The alkaline activator includes one or more combinations of cement, lime, sodium hydroxide, and water glass.

[0024] Based on the same inventive concept, this embodiment also provides a method for preparing phosphogypsum aggregate-grown concrete, used to prepare the aforementioned grown concrete, comprising: The amount of phosphogypsum cold-bonding aggregate used in vegetation concrete is determined based on the packing porosity of phosphogypsum cold-bonding aggregate. Based on the target permeability coefficient of the planted concrete, and the average particle size and packing void ratio of the phosphogypsum cold-bonded aggregate, the effective porosity of the phosphogypsum cold-bonded aggregate in the planted concrete was analyzed and obtained. Based on the target value of the 28-day compressive strength of the planted concrete, and the average particle size, packing void ratio and effective porosity of the phosphogypsum cold-bonded aggregate, the 28-day strength value of the cementitious slurry in the planted concrete was obtained by analysis. The water-cement ratio of the vegetation concrete was obtained based on the 28-day strength value of the cementitious slurry and the percentage of silica fume used. Based on the average particle size and packing void ratio of the phosphogypsum cold-bonded aggregate, as well as the percentage of silica fume used, the water-cement ratio of the vegetation concrete is obtained, and the amount of cementitious material and water used in the vegetation concrete is determined. Based on the determined amount of phosphogypsum cold-bonding aggregate, cementitious material, and water in the planted concrete, the corresponding raw material components are weighed and then mixed, vibrated, molded, and cured in sequence to obtain the final product.

[0025] In this embodiment, by comprehensively considering the performance objectives of the planted concrete, such as permeability coefficient and compressive strength, as well as the average particle size, packing porosity, and cylinder compressive strength of the phosphogypsum cold-bonded aggregate, the mix design of the phosphogypsum aggregate planted concrete is optimized based on the theory of spherical close packing and slurry coating. The dosage of each raw material component of the planted concrete is accurately analyzed, thereby realizing the controllability and customization of the interconnected porosity, permeability coefficient, and compressive strength of the permeable planted concrete.

[0026] In this embodiment, the curing regime for the phosphogypsum cold-bonded aggregate is natural curing, carbonation curing, or steam curing. The curing regime for the vegetation concrete includes one or more combinations of natural curing, carbonation curing, or standard curing. For example, in some actual engineering projects, a combination of carbonation curing and standard curing can be used during the curing process of vegetation concrete. During standard curing with formwork, cement hydration produces alkaline (OH-) compounds. - In alkaline pore solutions, undisturbed phosphogypsum near the surface of cold-bonded aggregates dissolves in large quantities under the action of alkaline pore solutions, generating calcium ions (Ca). 2+ ) and sulfate (SO4) 2- During carbonization curing, CO2 gas diffuses into the vicinity of the surface of the cold-bonded phosphogypsum aggregate and dissolves to form carbonic acid (H2CO3), which further reacts with the calcium produced by the dissolution of phosphogypsum. 2+ and OH produced by hydration- The reaction forms insoluble calcium carbonate (CaCO3) precipitate and water. This process reduces the alkalinity of the concrete, which is beneficial for plant germination, growth, and root development. Furthermore, the calcium carbonate precipitate evenly coats the surface of the phosphogypsum aggregate, hindering subsequent contact and dissolution of the undisturbed phosphogypsum within the aggregate with external water, thus significantly improving the volume stability of the phosphogypsum aggregate-grown concrete. During subsequent standard curing, the SO4 produced by the dissolution of phosphogypsum... 2- SiO4 produced by the dissolution of silica fume 4- and Ca produced by hydration 2+ OH - Al(OH)4 - It will further react to generate ettringite (3CaO·Al2O3·CaSO4·32H2O) and hydrated calcium aluminosilicate (CASH) gel, improving the performance of the planted concrete.

[0027] In some other embodiments, the phosphogypsum cold-bonded aggregate has a particle size range of 10–20 mm, a compressive strength of 4–10 MPa, a 1-hour water absorption rate of 5%–20%, a particle sphericity ≥0.85, and a pH value of 7–9. The cement is ordinary Portland cement of grade P·O 425R or higher, with a 3-day compressive strength ≥22 MPa and a 28-day compressive strength ≥42.5 MPa; the silica fume is SF85 grade or higher meeting national standards, with a specific surface area ≥15000 m². 2 / kg, with an activity index ≥105%; the water reduction rate of the polycarboxylate superplasticizer is ≥25%; the viscosity of the hydroxypropyl methylcellulose ether water-retaining agent is 80000~200000 mPa.s.

[0028] In some other embodiments, the raw material components further include, by weight, 0.5–0.8 parts of polycarboxylate superplasticizer and 0.05–0.08 parts of hydroxypropyl methylcellulose ether water-retaining agent. By adding the superplasticizer and water-retaining agent, the flow spread (jump table test) of the cementitious material slurry is adjusted to 200–240 mm, resulting in good slurry cohesion and no obvious stratification or bleeding.

[0029] Example 2. A method for preparing phosphogypsum aggregate-based planted concrete, wherein the planted concrete is made by sequentially mixing, vibrating, and curing raw material components including cement, phosphogypsum cold-bonding aggregate, silica fume, and water; the phosphogypsum cold-bonding aggregate is obtained by mixing, granulating, and curing a mixture containing undiluted phosphogypsum, solid waste admixtures, and an alkaline activator. The preparation process of the planted concrete is as follows: 2.1 Determine the dosage of each raw material component 2.1.1 Determine the amount of phosphogypsum cold-bonding aggregate used in vegetation concrete based on the bulk porosity of the phosphogypsum cold-bonding aggregate. In this embodiment, the unit volume of phosphogypsum cold-bonding aggregate in the vegetation concrete is based on... Analysis yielded, among which This refers to the unit dosage of phosphogypsum cold-bonding aggregate in vegetation concrete. The density of phosphogypsum cold-bonded aggregate, The porosity of phosphogypsum cold-bonded aggregate. The method was obtained through experimental testing. The unit dosage of phosphogypsum cold-bonding aggregate in vegetation concrete was determined by the packing porosity of phosphogypsum cold-bonding aggregate, which achieved the compact packing of aggregate in vegetation concrete and ensured that vegetation concrete has good permeability and mechanical properties.

[0030] 2.1.2 Based on the target permeability coefficient of the planted concrete, and the average particle size and packing void ratio of the phosphogypsum cold-bonded aggregate, the effective porosity of the phosphogypsum cold-bonded aggregate in the planted concrete was analyzed and obtained. In this embodiment, the effective porosity of the phosphogypsum cold-bonding aggregate in the planted concrete is based on... ,in The target permeability coefficient for the vegetation concrete is specified in the design based on construction requirements. This refers to the empirical value of the permeability coefficient corresponding to the unit interconnected porosity of permeable concrete. The value ranges from (2.1 to 6.3) × 10 -5 mm / s, per unit volume The value is 1m 3 , The packing porosity of phosphogypsum cold-bonded aggregate, The effective porosity of phosphogypsum cold-bonded aggregate, The values ​​represent the average particle size of phosphogypsum cold-bonded aggregates, expressed in millimeters. The value is an exponent, ranging from 0.8 to 4.6. This analytical model fully considers the influence of structural parameters of the skeletal structure and pore structure of the phosphogypsum cold-bonded aggregate, such as particle size and cementitious material coating amount, on the permeability coefficient. While ensuring permeability, it accurately determines the effective porosity of the phosphogypsum cold-bonded aggregate in the phytochemical concrete, providing a theoretical basis for the mix design of phytochemical concrete.

[0031] 2.1.3 Based on the target value of the 28-day compressive strength of the planted concrete, and the average particle size, packing void ratio and effective porosity of the phosphogypsum cold-bonded aggregate, the 28-day strength value of the cementitious paste in the planted concrete was obtained by analysis. In this embodiment, the influence of the average particle size, packing void ratio, effective porosity of phosphogypsum cold-bonded aggregate, and the 28-day strength of the cementitious paste on the compressive strength of the planted concrete is fully considered. The 28-day strength value of the cementitious slurry in the planted concrete was determined, wherein... , For coefficients, The value ranges from 1 to 10. The value ranges from 0.01 to 0.1. The target value for the 28-day compressive strength of planted concrete.

[0032] 2.1.4 The water-cement ratio of the vegetation concrete was obtained based on the 28-day strength value of the cementitious slurry and the percentage of silica fume used. In this embodiment, the water-cement ratio of the vegetation concrete is based on ,in The water-cement ratio for vegetation concrete. This embodiment uses the standard strength of cement paste. By linearly extrapolating the relationship between the 28-day strength of cement paste and the water-cement ratio, the theoretical ultimate strength was obtained, which is 237.67 MPa. For coefficients, The value is 1.68. It is a natural constant. This refers to the silica fume content in the cementitious material. The determination of this water-cement ratio comprehensively considers the synergistic effect of the cementitious material paste strength and the silica fume content. It ensures that the vegetated concrete has sufficient strength to support plant growth and resist external environmental erosion, while also controlling the pore structure and permeability of the concrete through a reasonable water-cement ratio, providing favorable space and conditions for plant root growth. In particular, it allows for the accurate determination of the water-cement ratio of vegetated concrete based on different engineering requirements and raw material characteristics, thereby producing high-performance phosphogypsum aggregate vegetated concrete.

[0033] 2.1.5 Based on the average particle size and packing porosity of the phosphogypsum cold-bonded aggregate, as well as the percentage of silica fume used, the water-cement ratio of the vegetation concrete is obtained, and the amount of cementitious material and water used in the vegetation concrete is determined. In this embodiment, the amount of cementitious material in the vegetation concrete is based on The amount of water used in the vegetation concrete ,in This refers to the unit volume of cementitious materials used in vegetation concrete. The density of the cementitious material is taken as 3000 kg / m³ in this embodiment. 3Based on the specific parameters of phosphogypsum cold-bonded aggregate and silica fume, the amount of cementitious materials and water used in planted concrete can be accurately determined. This provides crucial raw material dosage data to support the subsequent preparation of stable and compliant phosphogypsum aggregate planted concrete, ensuring the scientific rigor and accuracy of the entire preparation process.

[0034] In this embodiment, through the analysis of steps S1 to S5, the relevant raw material components in the planted aggregate were determined as follows: 1221 parts of phosphogypsum cold-bonding aggregate, 307 parts of cement, 10 parts of silica fume, 70 parts of water, 0.58 parts of PCE water-reducing agent, and 0.07 parts of HPMC.

[0035] 2.2 Preparation of Vegetated Concrete Based on the above raw material components, the process for preparing phosphogypsum cold-bonded aggregate planted concrete is as follows: 2.2.1 Pre-absorption of aggregate: Weigh the phosphogypsum cold-bonding aggregate according to the mix proportion, let it stand in water to absorb water to saturation for about 1 hour, then take it out and put it on a sieve to turn it back and forth for about 1 minute before use. 2.2.2 Mixing: Put the weighed cement and silica fume into the concrete mixer and mix for about 2 minutes until they are evenly mixed. Then add water-reducing agent, water-retaining agent and water and mix for about 2 minutes to form a paste. Next, add pre-absorbent aggregate and continue mixing for about 2 minutes to make the paste evenly coat the surface of the aggregate. 2.2.3 Vibration molding: Pour the freshly mixed vegetated concrete into the mold and tamp the edges, then place it on the concrete vibration table and vibrate for 5-8 seconds. During the vibration molding process, use a trowel to flatten the surface of the specimen. 2.2.4 Curing with Formwork: Cover the surface of the planted concrete with plastic wrap and then place it in a standard curing room for curing with formwork for 24-36 hours. The temperature of the standard curing room is 20±1 ℃ and the humidity is ≥95 RH%. In this embodiment, after curing with formwork, all concrete specimens are divided into two test groups. Test group 1 is directly cured with standard curing to the specified age, while test group 2 is first carbonized and then cured with standard curing to the specified age.

[0036] The standard curing process is as follows: after carbonization curing, the planted concrete specimens or after demolding are moved to the standard curing room and cured for the specified age. The carbonation curing process involves demolding the planted concrete specimens after mold curing and then transferring them to a carbonation reactor for 3-5 hours. The pressure in the reactor is maintained at a constant 0.3-0.5 bar, and the CO2 volume concentration is 60-100%. Carbonation curing increases the degree of carbonization in the planted concrete, resulting in more CaCO3 products after hydration and a denser microstructure. This denser microstructure helps improve the strength of phosphogypsum cold-bonded aggregate planted concrete, lowers the pH, and reduces the risk of environmental pollution.

[0037] The microstructure and phase composition of the phosphogypsum cold-bonded aggregate planted concrete at 28 days of age in this example were analyzed using SEM. The relevant analysis results are as follows: Figure 1 As shown: The white dashed line represents the interface between the phosphogypsum cold-bonded aggregate and the hardened cement paste. The interior of the phosphogypsum cold-bonded aggregate consists of flaky, unprocessed phosphogypsum, covered by a large amount of needle-like ettringite and network-like hydrated calcium silicate gel products. These hydration products are mainly generated by the reaction of phosphogypsum, mineral admixtures, and alkaline activators. The outer layer of the phosphogypsum cold-bonded aggregate mainly consists of granular calcium carbonate and network-like hydrated calcium silicate gel, with a dense structure. These products are mainly generated by cement hydration and carbonation reactions. The multi-layered hydration and carbonation products encapsulate the unprocessed phosphogypsum, inhibiting its dissolution and the leaching of harmful elements, improving the long-term water resistance and environmental leaching toxicity of the planted concrete. Simultaneously, the products further fill and compact the aggregate-hardened cement paste interface, which is beneficial for improving the overall strength and performance of the planted concrete.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phosphogypsum aggregate-based planted concrete, characterized in that, The planted concrete is made by sequentially mixing, vibrating and molding, and curing raw material components including cement, phosphogypsum cold-bonding aggregate, silica fume and water; the phosphogypsum cold-bonding aggregate is obtained by mixing, granulating and curing a mixture containing undiluted phosphogypsum, solid waste admixture and alkaline activator.

2. The vegetation concrete according to claim 1, characterized in that, By mass percentage, the phosphogypsum cold-bonded aggregate comprises 60%–80% unprocessed phosphogypsum, 20%–30% solid waste admixture, and 5%–10% alkaline activator. The unprocessed phosphogypsum is solid waste generated from the preparation of phosphoric acid from phosphate rock using sulfuric acid reaction. The mineral composition of the unprocessed phosphogypsum includes 90%–95% dihydrate gypsum, 5%–10% quartz, and the balance being soluble phosphorus, fluorine, and trace heavy metals including Pb, Cr, Hg, Cu, Zn, and Cd. The solid waste admixture includes one or more combinations of granulated blast furnace slag, fly ash, silica fume, and steel slag. The alkaline activator includes one or more combinations of cement, lime, sodium hydroxide, and water glass.

3. The vegetation concrete according to claim 1, characterized in that, The phosphogypsum cold-bonded aggregate has a particle size range of 10–20 mm, a compressive strength of 4–10 MPa, a water absorption rate of 5%–20% per hour, a particle sphericity ≥0.85, and a pH value of 7–9.

4. The vegetation concrete according to claim 1, characterized in that, The curing regime of the planted concrete includes one or more combinations of natural curing, carbonation curing, or standard curing, and the curing regime of the phosphogypsum cold-bonded aggregate is natural curing, carbonation curing, or steam curing.

5. The vegetation concrete according to claim 1, characterized in that, By weight, the raw material components also include 0.5 to 0.8 parts of polycarboxylate superplasticizer and 0.05 to 0.08 parts of hydroxypropyl methylcellulose ether water-retaining agent.

6. The vegetation concrete according to claim 1, characterized in that, The cement is ordinary Portland cement of grade P·O 425R or higher, with a 3-day compressive strength ≥22MPa and a 28-day compressive strength ≥42.5MPa; the silica fume is SF85 grade or higher meeting national standards, with a specific surface area ≥15000 m². 2 / kg, with an activity index ≥105%; the water reduction rate of the polycarboxylate superplasticizer is ≥25%; the viscosity of the hydroxypropyl methylcellulose ether water-retaining agent is 80000~200000 mPa.s.

7. A method for preparing phosphogypsum aggregate-based planted concrete, used to prepare the planted concrete according to any one of claims 1 to 6, characterized in that, include: The amount of phosphogypsum cold-bonding aggregate used in vegetation concrete is determined based on the packing porosity of phosphogypsum cold-bonding aggregate. Based on the target permeability coefficient of the planted concrete, and the average particle size and packing void ratio of the phosphogypsum cold-bonded aggregate, the effective porosity of the phosphogypsum cold-bonded aggregate in the planted concrete was analyzed and obtained. Based on the target value of the 28-day compressive strength of the planted concrete, and the average particle size, packing void ratio and effective porosity of the phosphogypsum cold-bonded aggregate, the 28-day strength value of the cementitious slurry in the planted concrete was obtained by analysis. The water-cement ratio of the vegetation concrete was obtained based on the 28-day strength value of the cementitious slurry and the percentage of silica fume used. Based on the average particle size and packing void ratio of the phosphogypsum cold-bonded aggregate, as well as the percentage of silica fume used, the water-cement ratio of the vegetation concrete is obtained, and the amount of cementitious material and water used in the vegetation concrete is determined. Based on the determined amount of phosphogypsum cold-bonding aggregate, cementitious material, and water in the planted concrete, the corresponding raw material components are weighed and then mixed, vibrated, molded, and cured in sequence to obtain the final product.

8. The method for preparing phosphogypsum aggregate-grown concrete according to claim 7, characterized in that, The unit dosage of phosphogypsum cold-bonding aggregate in planted concrete is based on Analysis yielded, among which This refers to the unit dosage of phosphogypsum cold-bonding aggregate in vegetation concrete; The density of phosphogypsum cold-bonded aggregate; The porosity of phosphogypsum cold-bonded aggregate.

9. The method for preparing phosphogypsum aggregate-grown concrete according to claim 1, characterized in that: The effective porosity of the phosphogypsum cold-bonding aggregate in the planted concrete is based on... ,in, The target permeability coefficient for the vegetation concrete is given in the design based on construction requirements. The permeability coefficient is an empirical value corresponding to the unit interconnected porosity of permeable concrete, and is taken as (2.1~6.3)×10. -5 mm / s; This refers to the unit volume of the vegetation concrete. The average particle size of the phosphogypsum cold-bonded aggregate is... The porosity of phosphogypsum cold-bonded aggregate; The effective porosity of phosphogypsum cold-bonded aggregate; It is an exponent, with a value range of 0.8 to 4.6; The 28-day strength value of the cementitious slurry in the vegetated concrete is based on... ,in , For coefficients, The value ranges from 1 to 10. The value ranges from 0.01 to 0.1; The target value for the 28-day compressive strength of planted concrete; The water-cement ratio of the vegetation concrete is based on ,in The water-cement ratio for vegetation concrete; The standard strength of cement paste; For coefficients, The value is 1.68; It is a natural constant; This refers to the amount of silica fume added to the cementitious material.

10. The method for preparing phosphogypsum aggregate-grown concrete according to claim 9, characterized in that, The amount of cementitious material used in the vegetated concrete is based on Water in the planted concrete ,in This refers to the unit volume of cementitious materials used in vegetation concrete, in kg / m³. 3 ; The density of the cementitious material is taken as 3000 kg / m³. 3 .

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