High-water-retention ecological slope-protection substrate based on rice hull biochar and preparation method thereof

Abstract

The application discloses a high-water-retention ecological slope protection substrate based on rice hull biochar, which comprises the following components in parts by weight: construction waste 40-60 parts, low-alkali sulfoaluminate cement 20-30 parts, rice hull biochar 10-15 parts, potassium polyacrylate water-retention agent 2-4 parts, organic fertilizer 5-8 parts, plant seeds 0.5-1.5 parts, soil conditioner 1-2 parts, and water-solid ratio 0.45-0.55. The preparation method comprises the following steps: raw material pretreatment, dry material mixing, water-retention agent pre-solution, wet material mixing and seed adding, so as to obtain the high-water-retention ecological slope protection substrate based on rice hull biochar. The high-water-retention ecological slope protection substrate based on rice hull biochar prepared by the application has the advantages of local waste resource utilization, adaptation to the climate characteristics of Sichuan, accurate pH value control, excellent anti-scouring performance and simple construction.

Description

Technical Field

[0001] This invention belongs to the field of ecological slope protection technology. Specifically, this invention relates to a high water retention ecological slope protection substrate based on rice husk biochar and its preparation method. Background Technology

[0002] Sichuan Province, located in the upper reaches of the Yangtze River, is predominantly mountainous and hilly, resulting in significant slope excavation during construction projects and prominent soil erosion issues. Urban development in the Chengdu Plain and surrounding areas generates substantial amounts of construction waste, while as a major rice-producing region, it also produces large quantities of agricultural waste such as rice husks annually. Therefore, the synergistic utilization of these two types of waste in ecological slope protection is of significant environmental and economic importance.

[0003] The existing ecological slope protection substrate has the following problems: (1) The source of river and lake bottom mud is limited and the transportation cost is high; (2) Ordinary cement has high alkalinity, which inhibits plant growth; (3) Insufficient water retention performance. Although the rainfall in Sichuan is abundant, the rainfall distribution is uneven. Summer rainstorms and winter droughts alternate, and the substrate is prone to water loss and cracking; (4) Existing technologies such as CN121488798A require special pyrolysis equipment for the sludge carbon used, which is costly. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0005] To achieve these objectives and other advantages of the present invention, a high water-retaining ecological slope protection substrate based on rice husk biochar is provided, comprising the following components by weight: 40-60 parts construction waste soil, 20-30 parts low-alkali sulfoaluminate cement, 10-15 parts rice husk biochar, 2-4 parts potassium polyacrylate water-retaining agent, 5-8 parts organic fertilizer, 0.5-1.5 parts plant seeds, 1-2 parts soil conditioner, water-solid ratio 0.45-0.55.

[0006] Preferably, the construction waste soil has a clay content of ≥20%, an organic matter content of ≥1.5%, and a pH value of 6.5~7.5; the low-alkali sulfoaluminate cement has a 28-day hydration pH value of 10~10.5.

[0007] Preferably, the method for preparing the rice husk biochar includes: pyrolyzing rice husks at 450-550℃ under anaerobic conditions for 2.5-3.5 hours, pulverizing the husks, and passing them through a 60-mesh sieve to obtain a specific surface area ≥220 m². 2 / g of rice husk biochar with a pH value of 8.5~9.5.

[0008] Preferably, the potassium polyacrylate water-retaining agent is a cross-linked potassium polyacrylate with a water absorption ratio of ≥600 times and a particle size of 60~80 mesh.

[0009] Preferably, the organic fertilizer is chicken manure organic fertilizer.

[0010] Preferably, the plant seeds are at least two of the following: Bermuda grass, tall fescue, Amorpha fruticosa, and Lespedeza bicolor.

[0011] Preferably, the soil conditioner is a mixture of citric acid and oxalic acid, with a mass ratio of citric acid to oxalic acid of 1 to 4:1.

[0012] A method for preparing a high water-retaining ecological slope protection substrate based on rice husk biochar as described above includes the following steps: Step 1: Raw material pretreatment: Air dry, crush, and pass through a 5mm sieve to obtain fine soil; Step 2: Dry material mixing: Weigh out fine soil, low-alkali sulfoaluminate cement, rice husk biochar, organic fertilizer, and soil conditioner according to the proportion, put them into a forced mixer, and dry mix for 3-5 minutes to obtain a dry material mixture. Step 3: Pre-dissolving the water-retaining agent: Add potassium polyacrylate water-retaining agent to 60 times its weight of water, stir to form a gel-like solution, let it stand and swell for 30-50 minutes to obtain the water-retaining agent gel solution; Step 4: Wet material mixing: Add the water-retaining agent gel solution to the dry material mixture, and add water to make the water-to-solid ratio 0.45~0.55. Wet mix in a forced mixer for 5~8 minutes to obtain the substrate; Step 5: Seed addition: After mixing the plant seeds with fine soil evenly, add them to the substrate and mix at a low speed of 20~40r / min for 1~2min in a forced mixer to obtain a high water retention ecological slope protection substrate based on rice husk biochar.

[0013] Preferably, in step four, the consistency of the wet-mixed substrate is controlled at 90~110 mm, and the bulk density is controlled at 1.1~1.3 g / cm³. 3 In step five, the mass ratio of plant seeds to fine soil is 1:3~7.

[0014] Application of a high water-retaining ecological slope protection substrate based on rice husk biochar as described above, or a high water-retaining ecological slope protection substrate based on rice husk biochar prepared by the preparation method described above, in slope protection.

[0015] The present invention has at least the following beneficial effects: 1. Local waste resource utilization: By utilizing the abundant construction waste soil and rice husk resources in Sichuan, the problem of waste disposal can be solved, reducing raw material costs by 35-45%, which is in line with the concept of circular economy.

[0016] 2. Adapted to the climate characteristics of Sichuan: The porous structure of rice husk biochar (specific surface area ≥ 220m²) 2 / g) combined with potassium polyacrylate with a high water absorption ratio (≥600 times) forms a dual water retention mechanism of "biochar water storage + water-retaining agent water locking". The saturated water holding rate can reach 75~85%, and it can still retain more than 60% moisture during the dry winter period in Sichuan (15 consecutive days without rain), with a vegetation survival rate of ≥75%.

[0017] 3. Precise pH control: The synergistic effect of low-alkali cement (pH≤10.5), weakly alkaline rice husk biochar (pH 8.5~9.5), and citric acid-oxalic acid regulator can stabilize the pH of the pore liquid after the substrate hardens at 7.0~7.8, which is suitable for the growth of slope protection plants such as bermudagrass and tall fescue in Sichuan.

[0018] 4. Excellent erosion resistance: 28-day compressive strength 10~14MPa, cohesion 12~16MPa, internal friction angle 33~38°. Under the conditions of summer heavy rain in Sichuan (simulated rainfall intensity 120mm / h), the substrate loss is ≤0.25kg / m³. 2 •h, which is much lower than that of ordinary topsoil substrate (0.6~0.8kg / m³). 2 ·h).

[0019] 5. Simple construction: It adopts conventional spraying equipment, requires no special process, and is suitable for mechanized construction in the complex terrain of Sichuan mountainous areas.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0021] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0022] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0023] In this invention, the construction waste soil was taken from the Shuangliu construction site in Chengdu, with a clay content of 26%, an organic matter content of 2.3%, and a pH value of 7.1; The low-alkali sulfoaluminate cement is a commercially available L·SAC42.5 grade cement with a 28-day hydration pH of 10.3. The preparation method of rice husk biochar is as follows: rice husks from Meishan rice are pyrolyzed at 500℃ under anaerobic conditions for 3 hours, then pulverized and passed through a 60-mesh sieve to obtain a specific surface area of ​​245 m². 2 / g, rice husk biochar with a pH of 9.0; The potassium polyacrylate water-retaining agent is a cross-linked potassium polyacrylate with a water absorption ratio of 620 times and a particle size of 70 mesh. The organic fertilizer is a locally produced Sichuan-made leafy chicken manure organic fertilizer; The soil conditioner is a mixture of citric acid and oxalic acid, with a mass ratio of citric acid:oxalic acid = 2:1; The plant seeds were Bermuda grass, tall fescue, and Amorpha fruticosa, with a mass ratio of Bermuda grass: tall fescue: Amorpha fruticosa = 5:3:2.

[0024] In this invention, the consistency and bulk density of the substrate are determined by the following method: Consistency determination: Refer to the consistency test method in the "Standard for Basic Performance Test Methods of Building Mortar" (JGJ / T 70-2009); fill the uniformly mixed substrate into the cone of the mortar consistency tester at a time, to about 10mm from the top of the cone, and tamp it 25 times from the center to the edge of the container with a tamping rod, and tap the container lightly 6 times to make the surface flat; contact the tip of the cone with the surface of the substrate, loosen the fixing screw to allow the cone to sink freely into the substrate, and read the sinking depth (unit: mm) after 10 seconds, which is the consistency of the substrate; Bulk density determination: The apparent density test method in the "Standard for Test Methods of Basic Performance of Building Mortar" (JGJ / T 70-2009) is followed. The uniformly mixed substrate is placed into a standard measuring cylinder of known mass, with a slight excess. The cylinder is tamped evenly 25 times with a tamping rod, and the outer wall of the container is lightly tapped to settle the substrate. Excess material is scraped off with a trowel to smooth the surface. The total mass of the measuring cylinder and substrate is weighed. The difference between the mass of the measuring cylinder and the volume of the measuring cylinder is the bulk density of the substrate (unit: g / cm³). 3 ).

[0025] Example 1 A high water-retaining ecological slope protection substrate based on rice husk biochar, comprising the following components by weight: 48 parts of construction waste soil, 25 parts of low-alkali sulfoaluminate cement, 12 parts of rice husk biochar, 3 parts of potassium polyacrylate water-retaining agent, 7 parts of organic fertilizer, 1.2 parts of plant seeds, 1.8 parts of soil conditioner, with a water-to-solid ratio of 0.5. A method for preparing a high water-retaining ecological slope protection substrate based on rice husk biochar includes the following steps: Step 1: Raw material pretreatment: Air dry, crush, and pass through a 5mm sieve to obtain fine soil; Step 2: Dry material mixing: Weigh 42 parts of fine soil, low-alkali sulfoaluminate cement, rice husk biochar, organic fertilizer, and soil conditioner according to the above ratio, put them into a forced mixer, and dry mix for 4 minutes to obtain a dry material mixture. Step 3: Pre-dissolving the water-retaining agent: Add potassium polyacrylate water-retaining agent to 60 times its weight of water, stir to form a gel-like solution, let it stand and swell for 40 minutes to obtain the water-retaining agent gel solution; Step 4: Wet Mixing: Add the water-retaining gel solution to the dry mixture, and simultaneously add water to a water-to-solid ratio of 0.5. Wet mix for 6 minutes in a forced mixer to obtain a consistency of 95 mm and a bulk density of 1.25 g / cm³. 3 The substrate; Step 5: Seed addition: Mix the plant seeds with 6 parts fine soil (the mass ratio of plant seeds to fine soil is 1:5) evenly, add it to the substrate, and mix at a low speed of 30r / min for 1.5min in a forced mixer to obtain a high water retention ecological slope protection substrate based on rice husk biochar.

[0026] Example 2 A high water-retaining ecological slope protection substrate based on rice husk biochar, comprising the following components by weight: 42 parts of construction waste soil, 22 parts of low-alkali sulfoaluminate cement, 15 parts of rice husk biochar, 4 parts of potassium polyacrylate water-retaining agent, 8 parts of organic fertilizer, 1 part of plant seeds, 2 parts of soil conditioner, with a water-to-solid ratio of 0.55. The preparation method of the high water retention ecological slope protection substrate based on rice husk biochar in this embodiment is basically the same as that in Example 1, except that: in step two, 42 parts of fine soil are replaced with 37 parts of fine soil; in step five, 6 parts of fine soil are replaced with 5 parts of fine soil (the mass ratio of plant seeds to fine soil is 1:5).

[0027] Example 3 A high water-retaining ecological slope protection substrate based on rice husk biochar, comprising the following components by weight: 55 parts of construction waste soil, 20 parts of low-alkali sulfoaluminate cement, 10 parts of rice husk biochar, 2.5 parts of potassium polyacrylate water-retaining agent, 6 parts of organic fertilizer, 1.5 parts of plant seeds, 1.5 parts of soil conditioner, with a water-to-solid ratio of 0.48. The preparation method of the high water retention ecological slope protection substrate based on rice husk biochar in this embodiment is basically the same as that in Example 1, except that: in step two, 42 parts of fine soil are replaced with 47.5 parts of fine soil; in step five, 6 parts of fine soil are replaced with 7.5 parts of fine soil (the mass ratio of plant seeds to fine soil is 1:5).

[0028] Comparative Example 1 This comparative example uses commercially available ordinary hydroseeding substrate (product of a landscaping company in Chengdu), whose main components are: planting soil, peat moss, and polyacrylamide binder.

[0029] Comparative Example 2 This comparative example uses a substrate prepared according to Example 1 of CN121488798A (50% river and lake sediment, 40% cement, 10% sludge, 2% humic acid solution, and 1% lignin sulfonate solution), wherein the river and lake sediment was taken from the Chengdu section of the river.

[0030] Comparative Example 3 An ecological slope protection substrate, by weight, is composed of the following components: 48 parts of construction waste soil, 25 parts of low-alkali sulfoaluminate cement, 3 parts of potassium polyacrylate water-retaining agent, 7 parts of organic fertilizer, 1.2 parts of plant seeds, 1.8 parts of soil conditioner, with a water-to-solid ratio of 0.5; The preparation method of the ecological slope protection substrate in this comparative example is basically the same as that in Example 1, except that rice husk biochar is not added in step two.

[0031] Comparative Example 4 An ecological slope protection substrate, by weight, is composed of the following components: 48 parts of construction waste soil, 25 parts of low-alkali sulfoaluminate cement, 12 parts of rice husks, 3 parts of potassium polyacrylate water-retaining agent, 7 parts of organic fertilizer, 1.2 parts of plant seeds, 1.8 parts of soil conditioner, with a water-to-solid ratio of 0.5. The preparation method of the ecological slope protection substrate in this comparative example is basically the same as that in Example 1, except that in step two, rice husk biochar is replaced with rice husk.

[0032] Comparative Example 5 An ecological slope protection substrate, by weight, is composed of the following components: 48 portions of construction waste soil, 25 portions of low-alkali sulfoaluminate cement, 12 portions of rice husk biochar, 3 portions of potassium polyacrylate water-retaining agent, 7 portions of organic fertilizer, 1.2 portions of plant seeds, and a water-to-solid ratio of 0.5. The preparation method of the ecological slope protection substrate in this comparative example is basically the same as that in Example 1, except that no soil conditioner is added in step two.

[0033] Comparative Example 6 An ecological slope protection substrate, by weight, is composed of the following components: 48 parts of construction waste soil, 25 parts of low-alkali sulfoaluminate cement, 12 parts of rice husk biochar, 3 parts of potassium polyacrylate water-retaining agent, 1.2 parts of plant seeds, 1.8 parts of soil conditioner, with a water-to-solid ratio of 0.5. The preparation method of the ecological slope protection substrate in this comparative example is basically the same as that in Example 1, except that no organic fertilizer is added in step two.

[0034] The substrates prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to performance tests, with the erosion resistance test simulating a rainfall intensity of 120 mm / h. The results are shown in Table 1 below: Table 1 Performance Test Comparison Table As shown in Table 1, the pH value of Examples 1-3 of the present invention was 7.0-7.4 after 28 days, which was significantly lower than that of Comparative Examples 1-2 of the prior art, making it more suitable for the growth of common slope protection plants in Sichuan. Water retention performance: Example 2 (for the arid western Sichuan region) showed the best water retention performance, with a water retention rate of 71.5% after 15 days, indicating that increasing the amount of water-retaining agent and biochar had a significant effect; Mechanical properties: The compressive strength of the embodiments of the present invention meets the requirements for slope protection, has excellent erosion resistance, and can withstand summer rainstorms in Sichuan; Vegetation effect: The germination rate of the embodiments of the present invention is over 90%, and the drought survival rate is over 75%, proving that the substrate of the present invention can adapt to the alternating dry and wet climate characteristics of Sichuan.

[0035] Compared with Example 1, Comparative Example 3 (without rice husk biochar) and Comparative Example 4 (with rice husk biochar replaced by rice husks) show that the present invention produces rice husk biochar by pyrolyzing rice husks, which increases the porosity of the rice husks to form a porous structure, significantly improving the specific surface area and saturated water holding capacity, which is more conducive to seed germination and survival. Comparative Example 5 shows that the pH of the substrate is lowered after adding soil conditioner, which is more suitable for the growth of slope protection plants such as bermudagrass and tall fescue in Sichuan. Comparative Example 6 shows that the seeds with added organic fertilizer have higher germination and survival rates and stronger erosion resistance.

[0036] The high water retention ecological slope protection substrate prepared in Example 1 of this invention is suitable for the hilly area of ​​the Sichuan Basin, the high water retention ecological slope protection substrate prepared in Example 2 is suitable for the dry and wet alternating area of ​​the western Sichuan plateau, and the high water retention ecological slope protection substrate prepared in Example 3 is suitable for the parallel ridge and valley area of ​​eastern Sichuan.

[0037] This invention, tailored to the climate characteristics and resource advantages of Sichuan Province, develops a high-water-retention ecological slope protection substrate based on rice husk biochar. By synergistically utilizing construction waste and rice husk biochar, resource recovery from waste is achieved. A dual mechanism of "biochar water storage + water-locking agent" solves the water retention problem under alternating wet and dry conditions. The combination of low-alkali cement and a composite regulator maintains the pH value within a suitable range of 7.0–7.8. Experimental results show that the substrate exhibits a saturated water holding capacity of 75–85%, a 15-day water retention rate of 62–72%, a 28-day compressive strength of 10–14 MPa, and a seed germination rate exceeding 90%, all performance characteristics superior to existing technologies. Engineering application verification demonstrates that this substrate is highly effective in slope protection in Sichuan Province, offering both ecological and economic benefits, and possesses significant value for widespread application.

[0038] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A high water-retention ecological slope protection substrate based on rice husk biochar, characterized in that, By weight, it includes the following components: 40-60 parts construction waste soil, 20-30 parts low-alkali sulfoaluminate cement, 10-15 parts rice husk biochar, 2-4 parts potassium polyacrylate water-retaining agent, 5-8 parts organic fertilizer, 0.5-1.5 parts plant seeds, 1-2 parts soil conditioner, water-solid ratio 0.45-0.

55.

2. The high water-retention ecological slope protection substrate based on rice husk biochar as described in claim 1, characterized in that, The construction waste soil has a clay content of ≥20%, an organic matter content of ≥1.5%, and a pH value of 6.5~7.5; the low-alkali sulfoaluminate cement has a 28-day hydration pH value of 10~10.

5.

3. The high water-retention ecological slope protection substrate based on rice husk biochar as described in claim 1, characterized in that, The method for preparing rice husk biochar includes: pyrolyzing rice husks at 450-550℃ under anaerobic conditions for 2.5-3.5 hours, pulverizing the husks, and passing them through a 60-mesh sieve to obtain a specific surface area ≥220 m². 2 / g of rice husk biochar with a pH value of 8.5~9.

5.

4. The high water-retention ecological slope protection substrate based on rice husk biochar as described in claim 1, characterized in that, The potassium polyacrylate water-retaining agent is a cross-linked potassium polyacrylate with a water absorption ratio of ≥600 times and a particle size of 60~80 mesh.

5. The high water-retention ecological slope protection substrate based on rice husk biochar as described in claim 1, characterized in that, The organic fertilizer mentioned is chicken manure organic fertilizer.

6. The high water-retention ecological slope protection substrate based on rice husk biochar as described in claim 1, characterized in that, The plant seeds are at least two of the following: Bermuda grass, tall fescue, Amorpha fruticosa, and Lespedeza bicolor.

7. The high water-retention ecological slope protection substrate based on rice husk biochar as described in claim 1, characterized in that, The soil conditioner is a mixture of citric acid and oxalic acid, with a mass ratio of citric acid to oxalic acid of 1 to 4:

1.

8. A method for preparing a high water-retaining ecological slope protection substrate based on rice husk biochar as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Air dry, crush, and pass through a 5mm sieve to obtain fine soil; Step 2: Dry material mixing: Weigh out fine soil, low-alkali sulfoaluminate cement, rice husk biochar, organic fertilizer, and soil conditioner according to the proportion, put them into a forced mixer, and dry mix for 3-5 minutes to obtain a dry material mixture. Step 3: Pre-dissolving the water-retaining agent: Add potassium polyacrylate water-retaining agent to 60 times its weight of water, stir to form a gel-like solution, let it stand and swell for 30-50 minutes to obtain the water-retaining agent gel solution; Step 4: Wet material mixing: Add the water-retaining agent gel solution to the dry material mixture, and add water to make the water-to-solid ratio 0.45~0.

55. Wet mix in a forced mixer for 5~8 minutes to obtain the substrate; Step 5: Seed addition: After mixing the plant seeds with fine soil evenly, add them to the substrate and mix at a low speed of 20~40r / min for 1~2min in a forced mixer to obtain a high water retention ecological slope protection substrate based on rice husk biochar.

9. The high water-retention ecological slope protection substrate based on rice husk biochar as described in claim 8, characterized in that, In step four, the consistency of the wet-mixed substrate is controlled at 90~110mm, and the bulk density is controlled at 1.1~1.3g / cm³. 3 In step five, the mass ratio of plant seeds to fine soil is 1:3~7.

10. The application of a high water-retaining ecological slope protection substrate based on rice husk biochar as described in any one of claims 1-7, or a high water-retaining ecological slope protection substrate based on rice husk biochar prepared by the preparation method as described in any one of claims 8-9, in slope protection.

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