Self-leveling underwater filling material and preparation method thereof

Abstract

The invention provides a self-leveling underwater filling material. The self-leveling underwater filling material is prepared from the following raw materials in parts by weight: 15-18 parts of a low-carbon cementing material, 8-10 parts of fly ash, 45-50 parts of engineering slurry, 0.2-0.4 part of biological glue, 3-5 parts of plant residue charcoal, 45-50 parts of recycled fine aggregate, 10-20 parts of recycled micro powder and 10-15 parts of water. The invention also provides a preparation method of the self-leveling underwater filling material. The self-leveling underwater filling material provided by the invention has relatively good strength and working performance, and is relatively low in cost.

Description

Technical Field

[0001] The invention relates to a filling material, in particular to a self-leveling underwater filling material and a preparation method thereof. Background Art

[0002] Karst geology is very common in my country, and karst is strongly developed in many engineering project sites. The geological structure in South China is complex, with large areas of soluble rocks, especially limestone. In addition, the climate in South China is humid and the rainfall is abundant, which makes the groundwater system developed. The groundwater will dissolve the soluble rocks during the flow, accelerating the formation of karst caves. The geological survey report of large-scale engineering projects shows that the karst geology in South China is mainly characterized by surface dissolution, poor distribution regularity, various shapes and sizes, poor filling of karst caves, mostly unfilled and semi-filled, and the filling in the filling state is weak in engineering properties and easily eroded by water flow. The local cave filling is mixed with gravel, which is a recent collapse. Most of them are unstable caves, which are very unfavorable to the stability of the engineering structure and have a great impact on the pile foundation construction. It may cause engineering accidents such as ground subsidence, water inrush, and shield machine collapse. The characteristics of karst development should be given full attention in project site selection, pile foundation construction and construction method selection.

[0003] Karst caves are commonly found in engineering project sites in South China. Before the construction of pile foundation, the side walls of the karst caves need to be reinforced or filled. The side wall reinforcement of the karst caves is mainly based on cement + water glass double liquid grouting technology. The fast setting characteristics of the technology are used to quickly close the channel between the karst caves around the pile hole and the outer karst caves to prevent the hole from collapsing during the pile foundation hole forming process. This method has a great pollution to the groundwater and is costly. It does not solve the problem of underground cavities from the root and is not suitable for friction pile foundations. For the karst caves in the bottom area of ​​the foundation pit, cement mortar filling treatment technology is mainly used. In the actual construction process, cement mortar is prone to segregation under high free pouring height and high pressure. After the slurry is separated, it can not only fail to achieve the backfilling effect, but also easily cause problems such as pipe blocking. If the karst cave cannot be effectively filled or there are cavities and gaps, it may cause the karst cave to collapse again or cause other geological disasters. This method has a great pollution to the groundwater, and the backfill volume is difficult to accurately estimate, and the engineering cost is high.

[0004] Low-intensity fluid filling materials are a type of engineering materials with diverse compositions and wide applications. They have excellent construction performance (can be pumped or vertically self-flowed for transportation), good homogeneity, and low economic costs, and are used in industries such as construction, municipal engineering, transportation, water conservancy, and mining. However, their construction and performance underwater may be severely affected, as groundwater can dilute the curing agent and affect the curing process of the materials. Using engineering muck as the main raw material and supplemented with a curing agent to prepare regenerated fluid filling materials with appropriate strength and high fluidity can not only reduce the costs of project karst treatment and muck removal at the same time, save engineering costs, but also complete the in-situ resource treatment of part of the muck, and then promote the construction of "waste-free construction sites" and realize the green and low-carbon development of engineering construction. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a self-leveling underwater filling material with good strength, working performance, and low cost.

[0006] To solve the above technical problem, the technical solution of the present invention is:

[0007] A self-leveling underwater filling material is made from the following raw materials in parts by weight: 15-18 parts of low-carbon cementitious material, 8-10 parts of fly ash, 45-50 parts of engineering slurry, 0.2-0.4 part of bio-glue, 3-5 parts of plant residue biochar, 45-50 parts of recycled fine aggregate, 10-20 parts of recycled micro-powder, and 10-15 parts of water.

[0008] Among them, the low-carbon cementitious material can generate hydration products through hydration reaction, providing adhesion and basic structural strength for the underwater filling material.

[0009] Fly ash is an industrial by-product with pozzolanic activity. It can react with calcium hydroxide Ca(OH)2 produced by cement hydration to form stable calcium silicate hydrate gel, which fills the pores, improving the compactness and strength of the material. In addition, most of the particles of fly ash are hollow microspheres, which can improve the particle gradation of the material, reduce the water consumption, and improve the fluidity.

[0010] The engineering slurry mainly provides the fluidity of the material, enabling it to self-level in the underwater environment. Its particles are fine, which can fill the voids between other aggregates, enhancing the overall compactness of the material. At the same time, the presence of the engineering slurry can also reduce the bleeding of the material, ensuring the stability of the material during underwater construction.

[0011] Bio-glue is a natural thickener and stabilizer, which can improve the adhesiveness and cohesion of the material. In the underwater environment, bio-glue can prevent the material from dispersing, ensuring its self-leveling and self-compacting properties underwater. In addition, bio-glue can also form an isolation layer on the surface of the material, preventing the rapid loss of water and extending the construction time of the material.

[0012] Plant residue biochar has good adsorption performance and microporous structure, which can absorb the excess water in the material and reduce the bleeding phenomenon. At the same time, the microporous structure of biochar can be filled in the pores of the material, improving the compactness and impermeability of the material. In addition, the addition of biochar can also improve the durability and corrosion resistance of the material.

[0013] Recycled fine aggregate mainly plays a skeletal role, providing sufficient volume stability for the material. Its particle gradation is reasonable, and it can cooperate with cement, fly ash and other cementitious materials to improve the overall strength of the material. At the same time, the use of recycled fine aggregate can also reduce the dependence on natural aggregate, meeting the environmental protection requirements.

[0014] Recycled micro powder is made of tiny particles from industrial waste residues or construction solid waste during the crushing process, with a relatively high specific surface area and activity. It can cooperate with cement and fly ash to further improve the strength and durability of the material. In addition, the addition of recycled micro powder can also improve the workability of the material and reduce the water consumption.

[0015] Water is mainly used to adjust the fluidity and hydration reaction of the material. An appropriate amount of water can ensure good fluidity of the material during construction, while ensuring the full hydration of cement and fly ash. In an underwater environment, reasonable water consumption can prevent the rapid loss and dispersion of the material.

[0016] Furthermore, the low-carbon cementitious material of the present invention is composed of steel slag, slag, desulfurized gypsum, and alkali activator in a weight ratio of (30 - 50):(20 - 40):(8 - 20):(1 - 3). The low-carbon cementitious material is compounded by steel slag, slag and desulfurized gypsum. Through the double salt effect and silicon tetracoordination isomorphization effect, C-S-H gel and ettringite are generated through potential active components (CaO, SiO2, Al2O3), providing bonding and strength.

[0017] Furthermore, the specific surface area of the steel slag in the present invention is 400 - 500m 2 / kg, the specific surface area of the slag is 350 - 450m 2 / kg, the specific surface area of the desulfurized gypsum is 150 - 350m 2 / kg, and the alkali activator is one or a mixture of two of sodium carbonate and sodium sulfate. Among them, the steel slag provides the main structural calcium source and participates in the double salt effect to generate ettringite and C-S-H gel; the slag provides the silicon-aluminum source and reacts with Ca 2 + in the steel slag to generate C-S-H and C-A-S-H gels; the desulfurized gypsum provides sulfate ions to stabilize the hydration products and avoid reaction instability in the alkali activation system; the alkali activator can fully activate the potential activity of the low-carbon cementitious material, thereby regulating the reaction environment.

[0018] Further, the particle size of the fly ash in the present invention is 0.5 - 75 μm.

[0019] Further, the engineering slurry in the present invention is the waste slurry generated during the construction of diaphragm wall trench excavation and pile foundation hole formation. The specific gravity of the engineering slurry is 1.03 - 1.5, the sand content is 5 - 20%, and the viscosity is 19 - 50 s.

[0020] Further, the bio - glue in the present invention is calcium alginate or chitosan. The bio - glue can be evenly dispersed in the self - leveling underwater filling material to enhance the stability of the filling material during pouring, and effectively control the air entrainment and segregation phenomena.

[0021] Further, the plant residue biochar in the present invention is one of bagasse biochar, corn straw biochar, coffee residue biochar or rice husk biochar. The specific surface area of the plant residue biochar is 80 - 110.12 m 2 / g.

[0022] Further, the recycled fine aggregate in the present invention is prepared by crushing and screening construction waste or engineering muck. The water absorption rate of the recycled fine aggregate is ≤0.2%, and the passing rate through a 4.75 mm square hole sieve is ≥90%.

[0023] Further, the preparation method of the recycled fine powder in the present invention is as follows:

[0024] Dry gangue, iron tailings or construction waste to a moisture content of <3%, then use a jaw crusher or a hammer crusher for coarse crushing to a particle size of ≤10 mm, then use a cone crusher or a counter - attack crusher for medium crushing to a particle size of ≤4.75 mm, and finally use a double - layer screen vibrating screen with screen hole diameters of 4.75 mm and 0.5 mm respectively for screening to obtain fine particles with a particle size of 75 μm - 0.5 mm and ultrafine particles with a particle size of <75 μm. Collect and mix the fine particles and ultrafine particles to obtain the recycled fine powder, and use a cyclone separator or a pneumatic separation device to separate the ultrafine particles and control their content to be 5 - 15 wt%, which can avoid the influence of excessive ultrafine particle content on grading imbalance and material fluidity; wherein, the construction waste is waste concrete or waste blocks.

[0025] Another technical problem to be solved by the present invention is to provide a preparation method of the above - mentioned self - leveling underwater filling material.

[0026] To solve the above - mentioned technical problems, the technical solution is:

[0027] A preparation method of a self - leveling underwater filling material, comprising the following steps:

[0028] S1. Weigh each raw material by weight parts. Add plant residue biochar, recycled fine aggregate, and recycled fine powder into a planetary mixer, and stir for 1 - 5 minutes at a rotation speed of 120 - 200 rpm to obtain mixture one.

[0029] S2. Add low - carbon cementitious material and fly ash into mixture one obtained in step S1, and stir for 1 - 5 minutes at a rotation speed of 120 - 200 rpm to obtain mixture two.

[0030] S3. Add bio - glue into mixture two obtained in step S2, and stir for 1 - 3 minutes at a rotation speed of 120 - 200 rpm to obtain mixture three.

[0031] S4. Add engineering slurry into mixture three obtained in step S3, and stir for 2 - 3 minutes at a rotation speed of 120 - 200 rpm to obtain mixture four.

[0032] S5. Add water into mixture four obtained in step S4, and stir for 2 - 3 minutes at a rotation speed of 120 - 200 rpm to obtain a self - leveling underwater filling material.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention significantly improves the strength and workability of the filling material, effectively reduces the phenomena of aggregate segregation and bleeding, and ensures the construction quality of the filling material under the condition of high - free fall.

[0035] (2) The present invention uses low - carbon cementitious material, fly ash, plant residue biochar, recycled fine aggregate, and recycled fine powder as the main components, significantly reducing the carbon footprint and environmental impact of the filling material.

[0036] (3) The material of the present invention has high strength, water stability, and low permeability after curing. These properties enable it to better resist the scouring of water flow and the erosion of groundwater, ensuring the long - term stability of the backfill project. In addition, it has good volume stability, small dry shrinkage, and good water stability, effectively reducing the quality problems caused by settlement.

[0037] (4) The material cost of the present invention is relatively low, which can reduce the overall project cost. In addition, the present invention can use local materials and dispose of waste, thus further reducing the costs of material transportation and treatment.

[0038] (5) During construction, the present invention can adopt centralized mixing. When pouring on - site, the material is in a liquid state, without generating dust pollution, which is more environmentally friendly and green. At the same time, the material formed after curing has low permeability, which can effectively prevent groundwater pollution. Detailed implementation mode

[0039] The present invention will be described in detail below in conjunction with specific embodiments. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0040] Example 1

[0041] The self-leveling underwater filling material is made from the following raw materials by weight: 16 parts of low-carbon cementitious material, 9 parts of fly ash, 48 parts of engineering slurry, 0.3 part of bio-glue, 4 parts of plant residue biochar, 48 parts of recycled fine aggregate, 15 parts of recycled micro-powder, and 12 parts of water. Among them, the low-carbon cementitious material is composed of steel slag, slag, desulfurized gypsum, and alkali activator with a weight ratio of 40:30:15:2. The specific surface area of the steel slag is 400 - 500 m 2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, the specific surface area of the desulfurized gypsum is 150 - 350 m 2 / kg, and the alkali activator is sodium carbonate; the particle size of the fly ash is 0.5 - 75 μm; the engineering slurry is the waste slurry generated during the construction of diaphragm wall trench excavation and pile foundation hole formation. The specific gravity of the engineering slurry is 1.03 - 1.5, the sand content is 5 - 20%, and the viscosity is 19 - 50 s; the bio-glue is calcium alginate; the plant residue biochar is bagasse biochar, and the specific surface area of the plant residue biochar is 80 - 110.12 m 2 / g; the recycled fine aggregate is obtained by crushing and screening construction waste, and the water absorption rate of the recycled fine aggregate ≤ 0.2%, and the passing rate through a 4.75 mm square hole sieve ≥ 90%.

[0042] The preparation method of the recycled micro-powder is as follows:

[0043] Dry the coal gangue until the moisture content < 3%, then use a jaw crusher or a hammer crusher for coarse crushing to a particle size ≤ 10 mm, then use a cone crusher or a counterattack crusher for medium crushing to a particle size ≤ 4.75 mm, and finally use a double-layer screen vibrating sieve with screen hole diameters of 4.75 mm and 0.5 mm respectively for screening to obtain fine particles with a particle size of 75 μm - 0.5 mm and ultra-fine particles with a particle size < 75 μm. Collect and mix the fine particles and ultra-fine particles to obtain the recycled micro-powder, and use a cyclone separator or a pneumatic separation device to separate the ultra-fine particles and control their content to be 10 wt%.

[0044] The preparation method of Example 1 includes the following steps:

[0045] S1. Weigh each raw material by weight, add the plant residue biochar, recycled fine aggregate, and recycled micro-powder into a planetary mixer, and stir at a speed of 160 rpm for 3 minutes to obtain mixture one;

[0046] S2. Add low-carbon cementitious materials and fly ash to the mixture one obtained in step S1, and stir at a speed of 160 rpm for 3 minutes to obtain mixture two;

[0047] S3. Add bio-glue to the mixture two obtained in step S2, and stir at a speed of 160 rpm for 2 minutes to obtain mixture three;

[0048] S4. Add engineering slurry to the mixture three obtained in step S3, and stir at a speed of 160 rpm for 2.5 minutes to obtain mixture four;

[0049] S5. Add water to the mixture four obtained in step S4, and stir at a speed of 160 rpm for 2.5 minutes to obtain a self-leveling underwater filling material.

[0050] Example 2

[0051] The self-leveling underwater filling material is made of the following raw materials in parts by weight: 15 parts of low-carbon cementitious materials, 8 parts of fly ash, 45 parts of engineering slurry, 0.2 part of bio-glue, 3 parts of plant residue biochar, 45 parts of recycled fine aggregate, 10 parts of recycled fine powder, and 10 parts of water. Among them, the low-carbon cementitious material is composed of steel slag, slag, desulfurized gypsum, and alkali activator in a weight ratio of 30:20:8:1. The specific surface area of the steel slag is 400 - 500 m 2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, the specific surface area of the desulfurized gypsum is 150 - 350 m 2 / kg, and the alkali activator is sodium sulfate; the particle size of the fly ash is 0.5 - 75 μm; the engineering slurry is the waste slurry generated during the construction of diaphragm wall trench excavation and pile foundation hole formation. The specific gravity of the engineering slurry is 1.03 - 1.5, the sand content is 5 - 20%, and the viscosity is 19 - 50 s; the bio-glue is chitosan; the plant residue biochar is corn straw biochar, and the specific surface area of the plant residue biochar is 80 - 110.12 m 2 / g; the recycled fine aggregate is prepared by crushing and screening engineering muck, and the water absorption rate of the recycled fine aggregate ≤ 0.2%, and the passing rate through a 4.75 mm square hole sieve ≥ 90%.

[0052] The preparation method of the recycled fine powder is:

[0053] Dry the iron tailings until the moisture content is < 3%, then use a jaw crusher or a hammer crusher for coarse crushing to a particle size ≤ 10 mm, then use a cone crusher or an impact crusher for medium crushing to a particle size ≤ 4.75 mm, and finally use a double-layer screen vibrating screen with screen hole diameters of 4.75 mm and 0.5 mm respectively for screening to obtain fine particles with a particle size of 75 μm - 0.5 mm and ultra-fine particles with a particle size < 75 μm. Collect and mix the fine particles and ultra-fine particles to obtain recycled micro-powder, and use a cyclone separator or a pneumatic separation device to separate the ultra-fine particles and control their content to 5 wt%.

[0054] The preparation method of Example 2 includes the following steps:

[0055] S1. Weigh each raw material by weight, add the plant residue biochar, recycled fine aggregate, and recycled micro-powder into a planetary mixer, and stir at a speed of 120 rpm for 5 minutes to obtain Mixing Material 1;

[0056] S2. Add the low-carbon cementitious material and fly ash into Mixing Material 1 obtained in Step S1, and stir at a speed of 120 rpm for 5 minutes to obtain Mixing Material 2;

[0057] S3. Add the bio-glue into Mixing Material 2 obtained in Step S2, and stir at a speed of 120 rpm for 3 minutes to obtain Mixing Material 3;

[0058] S4. Add the engineering slurry into Mixing Material 3 obtained in Step S3, and stir at a speed of 120 rpm for 3 minutes to obtain Mixing Material 4;

[0059] S5. Add water into Mixing Material 4 obtained in Step S4, and stir at a speed of 120 rpm for 3 minutes to obtain a self-leveling underwater filling material.

[0060] Example 3

[0061] The self-leveling underwater filling material is made of the following raw materials by weight: 18 parts of low-carbon cementitious material, 10 parts of fly ash, 50 parts of engineering slurry, 0.4 part of bio-glue, 5 parts of plant residue biochar, 50 parts of recycled fine aggregate, 20 parts of recycled micro-powder, and 15 parts of water. Among them, the low-carbon cementitious material is composed of steel slag, slag, desulfurized gypsum, and alkali activator with a weight ratio of 50:40:20:3. The specific surface area of the steel slag is 400 - 500 m 2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, and the specific surface area of the desulfurized gypsum is 150 - 350 m 2 / kg, the alkali activator is sodium carbonate; the particle size of fly ash is 0.5 - 75 μm; the engineering slurry is the waste slurry generated during the construction of the diaphragm wall trench and the pile foundation hole forming, the specific gravity of the engineering slurry is 1.03 - 1.5, the sand content is 5 - 20%, and the viscosity is 19 - 50 s; the bio - glue is calcium alginate; the plant residue biochar is coffee - residue biochar, and the specific surface area of the plant residue biochar is 80 - 110.12 m 2 / g; the recycled fine aggregate is obtained by crushing and screening construction waste, and the water absorption rate of the recycled fine aggregate ≤ 0.2% and the passing rate through the 4.75 mm square hole sieve ≥ 90%.

[0062] The preparation method of the recycled fine powder is as follows:

[0063] Dry the waste concrete until the moisture content < 3%, then use a jaw crusher or a hammer crusher for coarse crushing until the particle size ≤ 10 mm, then use a cone crusher or a counter - attack crusher for medium crushing until the particle size ≤ 4.75 mm, and finally use a double - layer screen vibrating screen with sieve hole diameters of 4.75 mm and 0.5 mm respectively for screening to obtain fine particles with a particle size of 75 μm - 0.5 mm and ultrafine particles with a particle size < 75 μm. Collect and mix the fine particles and ultrafine particles to obtain the recycled fine powder, and use a cyclone separator or a pneumatic separation device to separate the ultrafine particles and control their content to be 15 wt%.

[0064] The preparation method of Example 3 includes the following steps:

[0065] S1. Weigh each raw material by weight, add the plant residue biochar, recycled fine aggregate, and recycled fine powder into a planetary mixer, and stir at a speed of 200 rpm for 1 minute to obtain mixture one;

[0066] S2. Add the low - carbon cementitious material and fly ash into mixture one obtained in step S1, and stir at a speed of 200 rpm for 1 minute to obtain mixture two;

[0067] S3. Add the bio - glue into mixture two obtained in step S2, and stir at a speed of 200 rpm for 1 minute to obtain mixture three;

[0068] S4. Add the engineering slurry into mixture three obtained in step S3, and stir at a speed of 200 rpm for 2 minutes to obtain mixture four;

[0069] S5. Add water into mixture four obtained in step S4, and stir at a speed of 200 rpm for 2 minutes to obtain the self - leveling underwater filling material.

[0070] Example 4

[0071] Self-leveling underwater filling material is made from the following raw materials by weight: 17 parts of low-carbon cementitious material, 9.5 parts of fly ash, 49 parts of engineering slurry, 0.3 part of bio-glue, 4.5 parts of plant residue biochar, 49 parts of recycled fine aggregate, 18 parts of recycled fine powder, and 14 parts of water. Among them, the low-carbon cementitious material consists of steel slag, slag, desulfurized gypsum, and alkali activator with a weight ratio of 45:35:16:2.5. The specific surface area of the steel slag is 400 - 500 m 2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, the specific surface area of the desulfurized gypsum is 150 - 350 m 2 / kg, and the alkali activator is sodium sulfate; the particle size of the fly ash is 0.5 - 75 μm; the engineering slurry is the waste slurry generated during the construction of diaphragm walls and pile foundation hole formation. The specific gravity of the engineering slurry is 1.03 - 1.5, the sand content is 5 - 20%, and the viscosity is 19 - 50 s; the bio-glue is chitosan; the plant residue biochar is rice husk biochar, and the specific surface area of the plant residue biochar is 80 - 110.12 m 2 / g; the recycled fine aggregate is obtained by crushing and screening construction waste soil. The water absorption rate of the recycled fine aggregate is ≤0.2%, and the passing rate through a 4.75 mm square hole sieve is ≥90%.

[0072] The preparation method of the recycled fine powder is as follows:

[0073] Dry the waste blocks until the moisture content is <3%, then use a jaw crusher or a hammer crusher for coarse crushing until the particle size is ≤10 mm, then use a cone crusher or a counterattack crusher for medium crushing until the particle size is ≤4.75 mm, and finally use a double-layer screen vibrating sieve with screen hole diameters of 4.75 mm and 0.5 mm respectively for screening to obtain fine particles with a particle size of 75 μm - 0.5 mm and ultra-fine particles with a particle size <75 μm. Collect and mix the fine particles and ultra-fine particles to obtain the recycled fine powder, and use a cyclone separator or a pneumatic separation device to separate the ultra-fine particles and control their content to be 12 wt%.

[0074] The preparation method of Example 4 includes the following steps:

[0075] S1. Weigh each raw material by weight. Add the plant residue biochar, recycled fine aggregate, and recycled fine powder into a planetary mixer and stir at a speed of 150 rpm for 4 minutes to obtain mixture one;

[0076] S2. Add the low-carbon cementitious material and fly ash into mixture one obtained in step S1 and stir at a speed of 150 rpm for 4 minutes to obtain mixture two;

[0077] S3. Add the bio-glue into mixture two obtained in step S2 and stir at a speed of 150 rpm for 2.5 minutes to obtain mixture three;

[0078] S4. Add the engineering slurry to the mixture three obtained in step S3, and stir at a speed of 150 rpm for 3 minutes to obtain mixture four;

[0079] S5. Add water to the mixture four obtained in step S4, and stir at a speed of 150 rpm for 3 minutes to obtain the self-leveling underwater filling material.

[0080] Experimental example 1: Strength test

[0081] Refer to the "Code for Design of Cement Soil Mix Ratio" JGJ / T 233—2011 to test the 7-day compressive strength of the self-leveling underwater filling material prepared in Examples 1-4.

[0082] The test results are shown in Table 1:

[0083] 7d Compressive Strength (MPa) Example 1 1.5-1.6 Example 2 1.7-2.0 Example 3 2.1-2.2 Example 4 1.8-2.0

[0084] Table 1

[0085] It can be seen from Table 1 that the compressive strengths of Examples 1-4 of the present invention are all relatively high, indicating that the self-leveling underwater filling material prepared by the present invention has good strength.

[0086] Experimental example 2: Workability test

[0087] Refer to the "Standard Test Method for Properties of Ordinary Concrete Mixtures" GB / T 50080—2016 to test the final setting time of the self-leveling underwater filling material prepared in Examples 1-4.

[0088] The longer the final setting time, the better the workability. The test results are shown in Table 2:

[0089] Final Setting Time (minutes) Example 1 191-193 Example 2 188-190 Example 3 196-199 Example 4 192-195

[0090] Table 2

[0091] It can be seen from Table 2 that the final setting times of Examples 1-4 of the present invention are all relatively long, indicating that the self-leveling underwater filling material prepared by the present invention has good workability.

[0092] Experimental example 3: Impermeability performance test

[0093] Refer to the "Geotechnical Test Methods" GB / T 50123—2019 to test the 28-day permeability coefficient of the self-leveling underwater filling material prepared in Examples 1-4.

[0094] The lower the permeability coefficient, the better the impermeability performance. The test results are shown in Table 3:

[0095] <![CDATA[28d permeability coefficient (×10 -8 cm·s -1 )]]> Example 1 8.8-9.0 Example 2 9.2-9.4 Example 3 8.9-9.1 Example 4 9.1-9.2

[0096] Table 3

[0097] As can be seen from Table 3, the 28-day permeability coefficients of Examples 1-4 of the present invention are all relatively low, indicating that the self-leveling underwater filling material prepared by the present invention has good working performance.

[0098] Experimental Example 4: Fluidity Test

[0099] Place the self-leveling underwater filling materials prepared in Examples 1-4 in a slump cone, ensure that the surface is flush with the top of the cone, and then quickly pull out the slump cone to allow the self-leveling underwater filling material to flow freely under the action of gravity. After the flow stabilizes, use a steel ruler or tape measure to measure its maximum spread diameter and minimum spread diameter.

[0100] The larger the spread, the better the fluidity. The test results are shown in Table 4:

[0101] Slump Flow (mm) Example 1 510-520 Example 2 530-600 Example 3 490-500 Example 4 500-530

[0102] Table 4

[0103] As can be seen from Table 4, the spreads of Examples 1-4 of the present invention are all relatively large, indicating that the self-leveling underwater filling material prepared by the present invention has good fluidity.

[0104] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A self-leveling underwater filling material, characterized in that: The invention is made of the following raw materials in parts by weight: 15-18 parts of low-carbon cementitious materials, 8-10 parts of fly ash, 45-50 parts of engineering mud, 0.2-0.4 parts of biological glue, 3-5 parts of plant residue biochar, 45-50 parts of recycled fine aggregate, 10-20 parts of recycled micro powder and 10-15 parts of water.

2. The self-leveling underwater filling material according to claim 1, characterized in that: The low-carbon cementitious material is composed of steel slag, slag, desulfurized gypsum and alkali activator in a weight ratio of (30-50):(20-40):(8-20):(1-3).

3. The self-leveling underwater filling material according to claim 2, characterized in that: The specific surface area of ​​the steel slag is 400-500m 2 / kg, the specific surface area of ​​slag is 350-450m 2 / kg, the specific surface area of ​​desulfurized gypsum is 150-350m 2 / kg, the alkali activator is sodium carbonate, sodium sulfate or a mixture of the two.

4. The self-leveling underwater filling material according to claim 1, characterized in that: The particle size of the fly ash is 0.5-75 μm.

5. The self-leveling underwater filling material according to claim 1, characterized in that: The engineering mud is waste mud generated during the construction of underground continuous wall trenching and pile foundation hole forming. The engineering mud has a specific gravity of 1.03-1.5, a sand content of 5-20%, and a viscosity of 19-50s.

6. The self-leveling underwater filling material according to claim 1, characterized in that: The biological glue is calcium alginate or chitosan.

7. The self-leveling underwater filling material according to claim 1, characterized in that: The plant residue biochar is one of bagasse biochar, corn straw biochar, coffee grounds biochar or rice husk biochar, and the specific surface area of ​​the plant residue biochar is 80-110.12m 2 / g.

8. The self-leveling underwater filling material according to claim 1, characterized in that: The recycled fine aggregate is obtained by crushing and screening construction waste or engineering slag, the water absorption rate of the recycled fine aggregate is ≤0.2%, and the passing rate of the 4.75mm square hole sieve is ≥90%.

9. The self-leveling underwater filling material according to claim 1, characterized in that: The preparation method of the regenerated micropowder is: The gangue, iron tailings or construction solid waste are dried to a moisture content of <3%, and then coarsely crushed to a particle size of ≤10mm using a jaw crusher or a hammer crusher, and then medium crushed to a particle size of ≤4.75mm using a cone crusher or an impact crusher, and finally sieved using a double-layer mesh vibrating screen with sieve apertures of 4.75mm and 0.5mm to obtain fine particles with a particle size of 75μm-0.5mm and ultrafine particles with a particle size of <75μm, the fine particles and ultrafine particles are collected and mixed to obtain regenerated micropowder, and a cyclone separator or air separation equipment is used to separate the ultrafine particles and control their content to 5-15wt%; wherein the construction solid waste is waste concrete or waste blocks.

10. A method for preparing a self-leveling underwater filling material according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Weigh each raw material by weight, add plant residue biochar, recycled fine aggregate, recycled powder to a planetary mixer, and stir at 120-200rpm for 1-5 minutes to obtain a mixture; S2. The low-carbon cementitious material and fly ash are added to the mixture obtained in step S1, and stirred at a speed of 120-200rpm for 1-5 minutes to obtain a mixture II; S3. Add the bio-gum to the mixture obtained in step S2 and stir at 120-200 rpm for 1-3 minutes to obtain a mixture of three; S4. The engineering slurry was added to the mixture obtained in step S3 and stirred at a speed of 120-200rpm for 2-3 minutes to obtain a mixture of four; S5. Add water to the mixture obtained in step S4, and stir at a speed of 120-200 rpm for 2-3 minutes to obtain a self-leveling underwater filling material.