Low-carbon coconut fiber modified ardealite vegetation concrete and preparation method thereof

Abstract

The invention discloses low-carbon coconut fiber modified ardealite vegetation concrete and a preparation method thereof. The ardealite vegetation concrete is prepared from the following components in parts by mass: 10 to 15 parts of anhydrous ardealite, 65 to 80 parts of natural aggregate, 0.5 to 2.5 parts of carbide slag, 3 to 9 parts of mineral powder, 0.07 to 0.5 part of alkali modified coconut fiber and 0.1 to 0.5 part of water reducing agent. The low-carbon coconut fiber modified ardealite vegetation concrete has excellent mechanical properties, ecological compatibility and durability, and the preparation method is simple, low in cost and suitable for industrial application.

Description

A low-carbon coconut fiber modified phosphogypsum planted concrete and its preparation method Technical Field

[0001] This invention relates to a plant-based concrete, specifically a low-carbon coconut fiber modified phosphogypsum plant-based concrete, and also to its preparation method, belonging to the technical field of industrial solid waste resource utilization and ecological building materials. Background Technology

[0002] Vegetated concrete is a porous concrete that combines structural load-bearing and vegetation growth functions. It is composed of cement or mineral admixtures, aggregates, additives, and other materials. After alkali reduction treatment, it can meet the needs of plant survival and growth, making it suitable for ecological projects such as slope protection, bank protection, and rooftop greening.

[0003] Vegetated concrete presents several key flaws and challenges. Regarding the balance between strength and porosity, there is a contradiction: increased porosity promotes root growth but reduces the concrete's strength and erosion resistance, making it difficult to meet engineering requirements. In terms of alkalinity control, cement hydration leads to excessively high pH levels in the pore solution, hindering plant survival. Regarding water retention, the high porosity and connectivity of vegetated concrete cause rapid water migration and evaporation, frequently stressing plant roots. Finally, relying on external fertilizers results in low utilization rates, mismatches between release patterns and plant needs, easy loss, and potential disruption of ecological balance.

[0004] Chinese patent CN119591361A discloses a low-alkali solid waste cementitious material-based vegetated concrete and its preparation method. The technology described in this patent achieves alkali reduction and vegetation through a composite method of low-alkali cement, aggregate pretreatment, and functional surface layer. However, this method has a limited capacity for phosphogypsum (admixture amount <5%), failing to fully utilize the resource value of solid waste. Its nutrient supply also mainly relies on fast-acting fertilizers in the surface layer, which has problems such as easy loss and a release pattern that does not match the long-term needs of plants.

[0005] Chinese patent CN120208625A discloses a phosphogypsum-based concrete and its preparation method. It prepares plant-grown concrete by introducing nanomaterials, complex artificial aggregates and various chemical admixtures. Although this can significantly improve the mechanical strength of phosphogypsum concrete, the technology is complex and costly, and it cannot meet the requirements of breathable and water-permeable space and alkaline environment required for plant root growth.

[0006] Chinese patent CN120622894A discloses a method for preparing low-alkali vegetated concrete with full-dosage phosphogypsum and recycled aggregate. It includes the fixed addition of electrolytic manganese slag. However, electrolytic manganese slag contains heavy metals, and long-term use in open-air environments poses a risk of soil and groundwater pollution. In terms of water retention, this patent relies entirely on chemical water-retaining agents and lacks physical mechanisms for active water absorption and slow water release, making it difficult to ensure plant survival under drought conditions.

[0007] Chinese patent CN120365026A discloses a method for preparing plant fiber modified and reinforced phosphogypsum-based mine filling material. In this patent, the material system relies on a high proportion of cement, forming a dense and highly alkaline structure that cannot meet the requirements for vegetation. At the same time, it utilizes corn / rice straw and jute fiber, which have a single fiber function and can only increase strength, while failing to solve the problem of fiber dispersion in the process.

[0008] Therefore, developing a phosphogypsum-based concrete that is simple to prepare, low in cost, and applicable to ecological restoration engineering protection is of great environmental significance. Summary of the Invention

[0009] To address the problems existing in the prior art, the first objective of this invention is to provide a low-carbon coconut fiber modified phosphogypsum planted concrete. This concrete possesses excellent mechanical properties, ecological compatibility, and durability.

[0010] The second objective of this invention is to provide a method for preparing low-carbon coconut fiber modified phosphogypsum planted concrete. This method is simple, inexpensive, and suitable for industrial application.

[0011] To achieve the above technical objectives, the present invention provides a low-carbon coconut fiber modified phosphogypsum planted concrete, which comprises the following components in parts by weight:

[0012] 10-15 parts of phosphogypsum

[0013] 65-80 parts natural aggregate,

[0014] 0.5-2.5 parts of calcium carbide slag.

[0015] 3-9 parts mineral powder

[0016] 0.07~0.5 parts of alkali-modified coconut fiber,

[0017] Water-reducing agent: 0.1-0.5 parts.

[0018] This invention utilizes alkali-modified coconut fiber as a water-retaining material and nutrient source. It can synergistically interact with natural microorganisms to comprehensively regulate the humidity and nutrient conditions of the plant microenvironment. Firstly, coconut fiber is a natural bundle-like long fiber with excellent length retention, high mechanical strength, and a unique internal porous structure. This structure allows it to form an effective three-dimensional reinforcing network and provide ample storage space for water, with its physical water retention capacity reaching several times its own weight. Secondly, coconut fiber is rich in lignin (content can reach over 40%), while having relatively low cellulose and hemicellulose content. The high lignin content reduces its degradation in the alkaline environment of concrete. The degradation process is extremely slow, which is beneficial for maintaining the morphology and functional integrity of the fibers over a long period of time. The organic matter released during the slow degradation process has little impact on the pH of the system and can even help neutralize some of the alkalinity. In addition, the present invention utilizes a surface-roughened three-dimensional network structure constructed from modified coconut fibers. By forming a strong mechanical interlocking interface with the hydration products of cementitious materials, it effectively bridges microcracks, transfers and disperses stress to significantly improve the tensile strength, flexural strength and fracture toughness of concrete. At the same time, its physical constraint effect can also inhibit the shrinkage deformation of concrete and reduce the width and number of macroscopic shrinkage cracks, thereby achieving a synergistic enhancement of the mechanical properties and volume stability of planted concrete.

[0019] This invention utilizes the acidity and phosphorus content of phosphogypsum to construct a low-alkali, high-porosity ecological matrix in synergy with carbide slag and mineral powder. Phosphogypsum, as the core cementitious component, primarily functions as a sulfate activator, pH regulator, and provider of phosphorus for plant growth. The inherent acidic components of phosphogypsum (mainly soluble phosphorus and a small amount of soluble fluorine) can rapidly neutralize the pore fluid (alkaline substance) in concrete, thus regulating the alkalinity within the concrete. Simultaneously, the introduced phosphorus is a macronutrient essential for plant growth. Through a rational composition ratio, this invention enables the pore fluid of hardened concrete to be maintained within a weakly alkaline range suitable for plant growth over a long period (pH range). The pH value is 7.5-8.5, which serves as a slow-release phosphorus source available to plants, promoting plant growth. Natural aggregates are mainly used to form the initial pore skeleton. Calcium carbide slag provides an alkaline activation environment. Mineral powder is activated under the dual activation of alkalinity and sulfate, reducing the alkalinity of the system and contributing to the later strength. The addition of coconut fiber not only achieves mechanical reinforcement while ensuring high porosity through its high toughness, but its excellent water retention also forms a "physical water storage-chemical nutrition" synergistic system together with the slow-release phosphorus source of phosphogypsum. At the same time, its slow degradation characteristics and dynamic matching with the acid and base components in the system jointly stabilize the pH value of the pore solution within a weakly alkaline range suitable for plant growth.

[0020] As a preferred embodiment, the low-carbon coconut fiber modified phosphogypsum planted concrete comprises the following components by weight:

[0021] 12-14 parts of phosphogypsum

[0022] Natural aggregates: 70.7-76.3 parts

[0023] 1-2 parts of calcium carbide slag

[0024] 5-7 parts mineral powder

[0025] 0.1-0.3 parts of alkali-modified coconut fiber,

[0026] 0.2 to 0.4 parts of water-reducing agent.

[0027] As a preferred embodiment, the alkali-modified coconut fiber is obtained by treating coconut fiber with an alkali solution. The alkali is preferably a weak alkali, such as calcium hydroxide. The preferred alkali concentration for alkali immersion is 0.1-0.2%. The alkali immersion conditions are: room temperature and 20-28 hours. After weak alkali immersion, the surface of the coconut fiber is purified and activated, eliminating the adverse effects of easily degradable impurities such as hemicellulose on the cementitious system and significantly enhancing the interfacial bonding strength between the fiber and the inorganic cementitious matrix. Simultaneously, the alkali treatment optimizes the porous hydrophilic structure of the fiber, effectively improving the water retention of the planted concrete, thereby increasing its ability to store water and nutrients. This allows the coconut fiber to degrade more slowly in the concrete environment, releasing organic matter and providing a long-term slow-release carbon source and nutrients for plant growth and microbial activity.

[0028] As a preferred method, coconut fiber is soaked in alkali, washed with water until the washing solution is neutral, and then dried.

[0029] As a preferred embodiment, the modified coconut fiber has an aspect ratio of 100 to 200:1 and a length preferably of 10 to 30 mm.

[0030] As a preferred embodiment, the anhydrous calcium sulfate content in the phosphogypsum is ≥85wt%, and the phosphorus pentoxide content is 0.8~1.0wt%.

[0031] As a preferred embodiment, the phosphogypsum has an average particle size D50 of 4~10μm and a pH value of 4~5.5.

[0032] As a preferred embodiment, the phosphogypsum is anhydrous phosphogypsum obtained by calcining and dehydrating phosphogypsum raw materials. The calcination temperature is 250~300℃, and the calcination time is 1~3h.

[0033] As a preferred embodiment, the particle size of the natural aggregate is 10~20mm.

[0034] As a preferred embodiment, the calcium hydroxide content in the carbide slag is not less than 60 wt%, the specific surface area is ≥400 m² / kg, and the moisture content is ≤3 wt%. The particle size D50 of the carbide slag is 10~50 μm.

[0035] As a preferred embodiment, the ore powder is granulated blast furnace slag powder of grade S95 or above, with a specific surface area ≥400m² / kg, and an activity index (7d) ≥75% and (28d) ≥95%.

[0036] As a preferred embodiment, the water-reducing agent is a lignin sulfonate. Lignosulfonates include at least one of calcium lignin sulfonate and sodium lignin sulfonate. Most preferably, calcium lignin sulfonate has a solid content ≥40% and a water reduction rate ≥10%.

[0037] This invention also provides a method for preparing low-carbon coconut fiber modified phosphogypsum planted concrete. The method is as follows: after wetting the natural aggregate with water, dry mix it with anhydrous phosphogypsum, carbide slag and mineral powder, then add alkali-modified coconut fiber and water-reducing agent solution in sequence, wet mix, and then pour and cure the concrete to obtain the final product.

[0038] This invention first wets the aggregate components to improve the uniformity of subsequent cementitious material adhesion. Simultaneously, it enhances fiber dispersibility by precisely controlling the timing of coconut fiber incorporation and adjusting the stirring rate. Incorporating the fiber at the optimal time—when the aggregate is wetted but the slurry has not yet formed—allows for initial dispersion of the coconut fiber through material friction, fundamentally avoiding the problem of fiber clumping upon contact with water. Further improving fiber dispersibility is achieved through a wet mixing method that progresses from low to high speed. Initially, a relatively low stirring rate ensures uniform dispersion of the coconut fiber with other dry materials, preventing clumping during subsequent wet mixing and thus performance degradation. Then, a relatively higher stirring rate ensures final uniform fiber dispersion and sufficient slurry coating of the aggregate, which facilitates the formation of a uniform reinforcing network and porous structure.

[0039] As a preferred embodiment, the total mass of water used in the preparation process of the low-carbon coconut fiber modified phosphogypsum planted concrete is 3 to 8 parts, of which the water used for wetting the natural aggregate accounts for 1 / 3 of the total water mass, and the water mass in the water-reducing agent solution accounts for 2 / 3 of the total water mass.

[0040] As a preferred embodiment, during the wet mixing process, the mixture is first stirred at a rate of 10-15 r / min for 1-2 min, and then stirred at a rate of 25-35 r / min for 3-5 min.

[0041] As a preferred embodiment, the maintenance conditions are: temperature 20±2℃, humidity ≥95%.

[0042] As a preferred approach, nutrient soil is laid on low-carbon coconut fiber modified phosphogypsum vegetation concrete, and plant seeds are sown, followed by watering for maintenance. The plants include herbaceous plants and / or shrubs.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] (1) The low-carbon coconut fiber modified phosphogypsum planted concrete of the present invention has excellent mechanical properties, ecological compatibility and durability. Through the synergistic effect between the components, a planted microenvironment with high porosity, suitable pH and water and fertilizer retention is constructed, realizing the leap from waste material landfill to ecological functional material. With planted material as the guide, the triple synergy of "structure-ecology-solid waste utilization" is realized.

[0045] (2) This invention utilizes alkali-modified coconut fiber to improve the compressive strength, toughness and water retention of concrete. It utilizes its three-dimensional network structure and hydrophilic properties to significantly enhance the water retention and soil particle retention capacity of the matrix, thereby effectively inhibiting soil erosion. At the same time, as a slow-release organic carbon source, it works synergistically with the inorganic phosphorus source provided by phosphogypsum to provide long-term and stable nutrient supply for plant growth.

[0046] (3) The preparation method is simple and the cost is low, making it suitable for industrial application. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0048] Figure 1 is a simplified process flow diagram of Embodiment 1 of the present invention. Detailed Implementation

[0049] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0050] The anhydrous phosphogypsum used in the following examples is a low-temperature dehydrated anhydrous phosphogypsum. Its preparation process is as follows: phosphogypsum is calcined at 250°C in air atmosphere for 2 hours, dehydrated, and then ground and sieved to obtain anhydrous phosphogypsum with an average particle size D50 of 4-10 μm. Its anhydrous calcium sulfate content is ≥85 wt.%, and its water-soluble P2O5 content is 0.9 wt.%. The anhydrous phosphogypsum has an average particle size D50 of 4-10 μm.

[0051] Natural aggregate is selected from single-size gravel with a particle size of 10-20mm and a compacted density of 1500kg / m³. 3 The apparent density is 2700 kg / m³. 3 The porosity is 45.6%.

[0052] The carbide slag is a dry powder with an effective calcium content of not less than 60% (calculated as Ca(OH)2), a particle size D50 of 15~30μm, a specific surface area ≥400m² / kg, a moisture content ≤3%, and an average particle size D50 of 10~50μm.

[0053] The ore powder is S95 grade granulated blast furnace slag powder with a specific surface area ≥400m² / kg, an activity index ≥75% after 7 days, and an activity index ≥95% after 28 days.

[0054] Example 1

[0055] The preparation method of alkali-modified coconut fiber is as follows: virgin coconut fiber is cut to a length of 20 mm and immersed in a 0.15% (w / w) calcium hydroxide solution. The solution is then soaked at a constant temperature of 25°C for 24 hours, with slow stirring during the treatment to ensure uniform action. The treated fiber is then removed and repeatedly washed with deionized water until the filtrate is neutral (pH≈7). Finally, it is dried at 60°C to a constant weight.

[0056] A low-carbon coconut fiber modified phosphogypsum planted concrete comprises the following components by weight percentage: 13% anhydrous phosphogypsum, 73.5% natural aggregate, 1.5% carbide slag, 6% mineral powder, 5.5% water, 0.2% alkali-modified coconut fiber, and 0.3% calcium lignosulfonate water-reducing agent.

[0057] A method for preparing low-carbon coconut fiber modified phosphogypsum planted concrete includes the following steps:

[0058] (1) Weigh each raw material according to the above component ratio.

[0059] (2) Pre-wetting of aggregates: Add part of the mixing water (accounting for 1 / 3 of the total water volume) to the mixer, then add all the natural aggregates, and mix at low speed (15r / min) for 50 seconds to make the surface of the aggregates evenly wet.

[0060] (3) Dry mixing of cementitious materials: Add anhydrous phosphogypsum, carbide slag and mineral powder to the moistened aggregate, and continue to stir at low speed for 2 minutes until the mixture is uniform.

[0061] (4) Fiber dispersion addition: Keep stirring at low speed, slowly and disperse the modified coconut fiber into the mixer, and continue to dry mix for 1 minute to initially disperse the fiber in the mixture.

[0062] (5) Preparation of water-reducing agent solution: Add the lignin sulfonate water-reducing agent to the remaining mixing water (accounting for 2 / 3 of the total water volume), stir until completely dissolved, and prepare water-reducing agent solution.

[0063] (6) Wet mixing and final mixing: Add the water-reducing agent solution into the mixer at a uniform speed. First, mix at a low speed of 15r / min for 2 minutes to initially wet and mix the materials; then switch to a high speed of 30r / min and mix for 3 minutes until the fibers are evenly distributed and the paste fully coats the aggregates to form a uniform concrete mixture with good workability.

[0064] (7) Casting and molding: The mixture is poured into the test mold in two layers. After each layer is poured, a steel tamping rod with a diameter of 16mm is used to tamp the mixture evenly 20-30 times along the perimeter and center of the test mold. The tamping should penetrate the height of the layer and avoid touching the bottom of the test mold.

[0065] (8) Curing: After pouring, cover with plastic film and then cure in an environment with a temperature of 20°C and a relative humidity of 65% for 2 days. After curing, remove the mold and place it in a standard curing room (temperature of 20°C and relative humidity of 95%) for 28 days. After demolding, the planted concrete is obtained.

[0066] Example 2

[0067] A low-carbon coconut fiber modified phosphogypsum planted concrete comprises the following components by weight percentage: 14% anhydrous phosphogypsum, 71.7% natural aggregate, 1% carbide slag, 7% mineral powder, 6% water, 0.1% alkali-modified coconut fiber, and 0.2% calcium lignosulfonate water-reducing agent. The concrete preparation method is the same as in Example 1.

[0068] Example 3

[0069] A low-carbon coconut fiber modified phosphogypsum planted concrete comprises the following components by weight percentage: 12% anhydrous phosphogypsum, 75.3% natural aggregate, 2% carbide slag, 5% mineral powder, 5% water, 0.3% alkali-modified coconut fiber, and 0.4% calcium lignosulfonate water-reducing agent. The concrete preparation method is the same as in Example 1.

[0070] Example 4

[0071] A low-carbon coconut fiber modified phosphogypsum planted concrete comprises the following components by weight percentage: 13.5% anhydrous phosphogypsum, 72.45% natural aggregate, 1.5% carbide slag, 6.5% mineral powder, 5.5% water, 0.25% alkali-modified coconut fiber, and 0.3% calcium lignosulfonate water-reducing agent. The concrete preparation method is the same as in Example 1.

[0072] Comparative Example 1

[0073] This comparative example provides a phosphogypsum-grown concrete without coconut fiber, comprising the following components by weight percentage: 13% anhydrous phosphogypsum, 73.6% natural aggregate, 1.5% carbide slag, 6% mineral powder, 5.5% water, 0.4% calcium lignosulfonate water-reducing agent, and 0% modified coconut fiber. The preparation method is the same as in Example 1.

[0074] Comparative Example 2

[0075] This comparative example provides a phosphogypsum-grown concrete, wherein the coconut fiber is not alkali-treated, and comprises the following components by weight percentage: 13% anhydrous phosphogypsum, 73.5% natural aggregate, 1.5% carbide slag, 6% mineral powder, 5.5% water, 0.2% untreated coconut fiber, and 0.3% calcium lignosulfonate water-reducing agent. The preparation method is the same as in Example 1.

[0076] Comparative Example 3

[0077] This comparative example provides a phosphogypsum-grown concrete, wherein the content of alkali-modified coconut fiber is increased, comprising the following components by weight percentage: anhydrous phosphogypsum 13%, natural aggregate 72.7%, carbide slag 1.5%, mineral powder 6%, water 5.5%, calcium lignosulfonate water-reducing agent 0.3%, and alkali-modified coconut fiber 1.0% (significantly higher than 0.3%). The preparation method is the same as in Example 1.

[0078] Comparative Example 4

[0079] This comparative example provides a phosphogypsum-grown concrete, using ordinary cement instead of carbide slag and mineral powder, comprising the following components by weight percentage: 13% anhydrous phosphogypsum, 73.5% natural aggregate, 7.5% ordinary cement (replacing carbide slag and mineral powder), 5.5% water, 0.3% calcium lignosulfonate water-reducing agent, and 0.2% alkali-modified coconut fiber. The preparation method is the same as in Example 1.

[0080] Comparative Example 5

[0081] This comparative example provides a phosphogypsum-grown concrete, in which modified coconut fiber is replaced with an equal amount of modified kapok fiber (modification method is the same as coconut fiber), comprising the following components by weight percentage: anhydrous phosphogypsum 13%, natural aggregate 73.5%, carbide slag 1.5%, mineral powder 6%, water 5.5%, alkali-modified kapok fiber 0.2%, and calcium lignosulfonate water-reducing agent 0.3%. The preparation method is the same as in Example 1.

[0082] Comparative Example 6

[0083] This comparative example provides a phosphogypsum-grown concrete, in which modified coconut fiber is replaced with an equal amount of modified jute fiber (modification method is the same as coconut fiber), comprising the following components by weight percentage: anhydrous phosphogypsum 13%, natural aggregate 73.5%, carbide slag 1.5%, mineral powder 6%, water 5.5%, alkali-modified jute fiber 0.2%, and calcium lignosulfonate water-reducing agent 0.3%. The preparation method is the same as in Example 1.

[0084] Comparative Example 7

[0085] This comparative example provides a phosphogypsum-grown concrete, wherein the content of alkali-modified coconut fiber is below the control range, and includes the following components by weight percentage: 13% anhydrous phosphogypsum, 73.65% natural aggregate, 1.5% carbide slag, 6% mineral powder, 5.5% water, 0.3% calcium lignosulfonate water-reducing agent, and 0.05% alkali-modified coconut fiber. The preparation method is the same as in Example 1.

[0086] The compressive strength, porosity, permeability coefficient, sand permeability, pH value and water retention of the phosphogypsum-grown concrete prepared in Examples 1-4 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0087] Among them, structural performance indicators:

[0088] (1) Compressive strength: The compressive strength was tested according to GB / T 50081-2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete, and the compressive strength at 28 days was measured.

[0089] (2) Porosity: After curing, the porosity of phosphogypsum-grown concrete was tested using the method of "JC / T 2557-2020 Test Method for Vegetation Performance of Vegetated Concrete".

[0090] (3) Permeability coefficient: Tested according to GB / T 36141-2018 Vegetated concrete.

[0091] (4) Sand permeability: Tested according to JC / T 2557-2020 Vegetated concrete.

[0092] Vegetation performance indicators:

[0093] (1) pH value: The pH value of phosphogypsum-grown concrete was tested using the "JC / T 2557-2020 Test Method for Vegetation Performance of Vegetated Concrete".

[0094] (2) Water retention performance: The test was conducted according to JC / T 2557-2020, mainly measuring its volume water retention rate.

[0095]

[0096] The table above shows that Comparative Example 1, without coconut fiber, has a certain strength. However, due to the lack of coconut fiber, there is no adsorption effect, resulting in a higher pH value and poor water retention, which is detrimental to plant growth. In Comparative Example 2, the coconut fiber was not modified, leading to a significant reduction in strength and poor water retention. Comparative Example 3, with a high coconut fiber content, experienced a decrease in strength and permeability due to excessive fiber aggregation. Comparative Example 4, using ordinary cement instead of carbide slag and mineral powder, achieved higher strength but excessive alkalinity and lower permeability, sand permeability, and water retention, which is also detrimental to plant growth. Comparative Example 5 shows that the addition of modified kapok fiber significantly reduced compressive strength and increased pH value, indicating that the degradation process of kapok fiber produces almost no organic acids to neutralize alkalinity. Although it has a high water retention rate, indicating strong physical water absorption, it lacks the function of slow nutrient release and cannot meet the synergistic requirements of strength and ecological pH balance in vegetated concrete. Comparative Example 6 shows that while alkali-modified jute fiber has high compressive strength, its porosity is too low, significantly reducing its water and sand permeability, which is detrimental to water penetration and root extension. It also has a low water retention rate and an excessively high pH value, indicating that jute fiber may release more alkaline ions in an alkaline environment, leading to increased system alkalinity, which contradicts the needs of plant growth. Comparative Example 7 shows that when the coconut fiber content is too low, its water retention rate (5.8%) and pH regulation ability (pH=11.7) are significantly worse than in Example 1 (water retention rate 8.0%, pH=10.5), proving that when the fiber content is below the range of this invention, it cannot fully exert its multiple ecological functions such as water retention and alkalinity regulation.

[0097] The above results show that the coconut fiber-modified phosphogypsum planted concrete prepared by the present invention through a specific raw material composition ratio has excellent comprehensive performance, which meets the needs of ecological engineering and realizes the synergistic effects of solid waste utilization, suitable pore structure, low alkalinity environment regulation for plant root growth, and water retention and nutrient supply.

[0098] Comparative Example 8

[0099] This comparative example involves the premature addition of alkali-modified coconut fiber during concrete mixing. The raw material composition ratio of the phosphogypsum-grown concrete in Example 1 is used. The preparation steps are as follows: After weighing the raw materials, all the mixing water and alkali-modified coconut fiber are pre-mixed to make a fiber suspension. Then, the suspension is added to the mixer along with the natural aggregate and stirred at a rate of 30 r / min for 1 min. Then, anhydrous phosphogypsum, carbide slag and mineral powder are added and stirred at a rate of 15 r / min for 2 min. Finally, water-reducing agent is added. In order to try to break up the formed fiber clumps, the wet mixing stage is adjusted to: first stir at 15 r / min for 3 min, and then increase to 30 r / min for 5 min to obtain the concrete mixture.

[0100] Comparative Example 9

[0101] This comparative example involves the late addition of alkali-modified coconut fiber during concrete mixing. The raw material composition ratio of the phosphogypsum-grown concrete in Example 1 is adopted. The preparation steps are as follows: After weighing the raw materials, a portion of the mixing water (accounting for 1 / 3 of the total water volume) is added to the mixer, followed by all the natural aggregates. The mixture is stirred at a low speed (15 r / min) for 50 seconds to uniformly wet the surface of the aggregates. Then, anhydrous phosphogypsum, carbide slag, mineral powder, and water-reducing agent solution (with water content equal to the remaining mixing water volume) are added to the wetted aggregates. The mixture is first stirred at a speed of 15 r / min for 2 minutes, then at 30 r / min for 3 minutes to form a uniform and viscous paste. Finally, alkali-modified coconut fiber is added, and the mixture is stirred at 30 r / min for 5 minutes to obtain the concrete mixture.

[0102] Comparative Example 10

[0103] This comparative example involves the disordered incorporation of alkali-modified coconut fiber during concrete mixing. The raw material composition ratio of the phosphogypsum-grown concrete in Example 1 is adopted. The preparation steps are as follows: After weighing the raw materials, a portion of the mixing water (accounting for 1 / 3 of the total water volume) is added to the mixer, followed by all the natural aggregates. The mixture is stirred at a low speed (15 r / min) for 50 seconds to uniformly wet the surface of the aggregates. Then, alkali-modified coconut fiber, anhydrous phosphogypsum, carbide slag, and mineral powder are added to the wetted aggregates and stirred at a rate of 15 r / min for 3 minutes. Next, a water-reducing agent solution (containing the remaining mixing water) is added, and the mixture is stirred at a rate of 15 r / min for 2 minutes, then at 30 r / min for 3 minutes to obtain the concrete mixture.

[0104] The states of the mixtures with premature, late, and disordered fiber incorporation in Comparative Example 1 and Comparative Examples 8-10 were observed, and the results are shown in Table 2.

[0105]

[0106] The table above clearly demonstrates that the timing of fiber incorporation is not simply a matter of process sequence; it directly affects the fiber dispersion and interfacial bonding, thus influencing the final product performance. The sequence established in this invention—"aggregate pre-wetting → fiber and cementitious material dry mixing and dispersion → water-reducing agent solution final mixing"—is an optimized process path. It utilizes changes in the physical state of the materials to solve the problems of coconut fiber's tendency to clump and its difficulty in dispersion. Furthermore, this invention employs a strategy of "partially pre-wetting the aggregate first, then introducing all remaining water with the water-reducing agent solution," which stabilizes the hydration of the high-solid-waste system and ensures the maximization of admixture effectiveness.

[0107] Example 5 (Ecological Restoration Application)

[0108] Three vegetated concrete specimens prepared in Example 1 were used as the experimental group. Simultaneously, ordinary porous cement concrete specimens of the same size (pH>12) and a plain soil control group were used for comparison. The ordinary porous cement concrete used P·O42.5 grade cement, and the plain soil was common local farmland soil (pH≈7.2, organic matter content 1.5%). A 2cm thick layer of nutrient soil was evenly spread on the surface of each specimen, and common slope protection grass species (such as Bermuda grass, sowing density 20g / m²) were sown. The specimens were placed in a greenhouse, and under controlled light and temperature, they underwent routine watering maintenance for 60 days. Plant growth was observed, and the results are shown in Table 3.

[0109]

[0110] As can be seen from the data in Table 3, the planted concrete of the present invention can provide an excellent growth environment for plants. While ensuring a high porosity structure, its low alkali, water retention and nutrient supply characteristics significantly promote the early establishment and long-term growth of plants. The roots can penetrate the interior of the material, achieving a true ecological integration and reinforcement effect.

[0111] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-carbon coconut fiber modified phosphogypsum planted concrete, characterized in that: It includes the following components by weight: 10-15 parts phosphogypsum, 65-80 parts natural aggregate, 0.5-2.5 parts carbide slag, 3-9 parts mineral powder, 0.07-0.5 parts alkali-modified coconut fiber, and 0.1-0.5 parts water-reducing agent.

2. The low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 1, characterized in that: It includes the following components by weight: 12-14 parts phosphogypsum, 70.7-76.3 parts natural aggregate, 1-2 parts carbide slag, 5-7 parts mineral powder, 0.1-0.3 parts alkali-modified coconut fiber, and 0.2-0.4 parts water-reducing agent.

3. A low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 1 or 2, characterized in that: The alkali-modified coconut fiber is obtained by treating coconut fiber with alkali soaking.

4. A low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 1 or 2, characterized in that: The modified coconut fiber has an aspect ratio of 100~200:

1.

5. The low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 1, characterized in that: The anhydrous calcium sulfate content in the phosphogypsum is ≥85wt%, and the phosphorus pentoxide content is 0.8~1.0wt%; the average particle size D50 of the phosphogypsum is 4~10μm, and the pH value is 4~5.

5.

6. A low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 1 or 5, characterized in that: The phosphogypsum is anhydrous phosphogypsum obtained by calcining and dehydrating phosphogypsum raw materials.

7. The low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 1, characterized in that: The natural aggregate has a particle size of 10-20 mm; the calcium hydroxide content in the carbide slag is not less than 60 wt%, the specific surface area of ​​the carbide slag is ≥400 m² / kg, and the moisture content is ≤3 wt%; the average particle size D50 of the carbide slag is 10-50 μm; the mineral powder is granulated blast furnace slag powder of grade S95 or above; and the water-reducing agent is lignin sulfonate.

8. A method for preparing a low-carbon coconut fiber modified phosphogypsum planted concrete according to any one of claims 1 to 7, characterized in that: After wetting the natural aggregate with water, dry mix it with anhydrous phosphogypsum, carbide slag and mineral powder. Then, add alkali-modified coconut fiber and water-reducing agent solution in sequence, wet mix, and then cast and cure.

9. The method for preparing a low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 8, characterized in that: The preparation process of the low-carbon coconut fiber modified phosphogypsum planted concrete uses 3 to 8 parts of water by mass, of which 1 / 3 of the water is used to wet the natural aggregates and 2 / 3 of the water is used in the water-reducing agent solution.

10. A method for preparing low-carbon coconut fiber modified phosphogypsum planted concrete according to claim 8 or 9, characterized in that: During the wet mixing process, the mixture is first stirred at a rate of 10-15 r / min for 1-2 min, and then stirred at a rate of 25-35 r / min for 3-5 min.

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