Marine anti-scour fluidized solidified soil material and its preparation method and application

Abstract

This invention discloses a marine anti-scour fluidized soil material, its preparation method, and its application, belonging to the technical field of marine engineering construction materials. The invention provides a marine anti-scour fluidized soil material comprising the following components: soil, an industrial solid waste composite, polyacrylamide (PAM), and an alkali activator. The addition of polyacrylamide (PAM) as a functional admixture helps improve the material's compressive strength and anti-scour efficiency when used as a marine anti-scour fluidized soil material.

Description

Technical Field

[0001] The present invention belongs to the technical field of marine engineering building materials, and in particular relates to a marine anti-scour fluidized solidified soil material and a preparation method and application thereof. Background Art

[0002] Fluidized solidified soil, a highly fluid filling material primarily composed of soil and a curing agent, is widely used in projects such as foundation pit backfill, pipeline backfill, trench backfill, and marine backfill. It holds unique potential for scour prevention. Compared to traditional scour prevention measures like riprap and concrete revetment, fluidized solidified soil, with its self-leveling properties, can cover complex underwater terrains and offers the advantages of in-situ hardening and ease of construction.

[0003] However, in the marine environment, chemicals such as chlorides and sulfates in seawater can easily corrode the solidified soil, thereby affecting its strength and durability. This poses a dual challenge to existing fluidized solidified soils: 1) Adaptability to underwater construction requires high fluidity: To overcome the effects of water flow disturbances, the material must maintain extremely high fluidity to ensure smooth underwater construction. 2) Harsh service environments require high performance: The marine environment places stringent demands on the scour resistance, corrosion resistance, and early strength of the anti-scour layer. In addition, conventional formulas often add excessive amounts of mixing water to improve fluidity, often leading to delayed hardening and loose structures. This makes the material susceptible to localized spalling and overall instability under tidal scouring. Summary of the Invention

[0004] In response to the technical difficulty in synergistically improving the fluidity and anti-scour performance of fluidized solidified soil in marine anti-scour projects, the present invention provides a marine anti-scour fluidized solidified soil material, a preparation method and application thereof. The present invention proposes a special anti-scour fluidized solidified soil system based on multi-component synergistic modification, which is suitable for anti-scour application scenarios of offshore wind power single pile foundations.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] In a first aspect, the present invention provides a marine anti-scour fluidized soil solidification material comprising the following components: soil, industrial solid waste composite material, polyacrylamide (PAM) and an alkali activator;

[0007] The mass ratio of soil and industrial solid waste composite material is (6-8):(2-4);

[0008] The industrial solid waste composite material includes blast furnace slag and fly ash, and the mass ratio of blast furnace slag to fly ash is (0.9-1.1):(0.9-1.1);

[0009] Polyacrylamide accounts for 0.05-0.2% of the total mass of the soil and industrial solid waste composite;

[0010] The mass of the alkali activator accounts for 28%-59% of the total mass of the soil and industrial solid waste composite material;

[0011] The alkaline activator is a mixed alkaline solution containing solid sodium hydroxide and water glass. The water glass modulus of the mixed alkaline solution is the molar ratio of silicon dioxide to sodium oxide, which is 1.0-1.4, and the sodium oxide content is 6%-10% (in mass percentage).

[0012] In addition, it should be noted that the mass of the alkaline activator includes solid sodium hydroxide and water glass, but does not include water.

[0013] In one or more embodiments, the percentage of polyacrylamide in the total mass of the soil and industrial solid waste composite material can be 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, etc., but is not limited to the above-listed point values. Other values ​​not listed but within the above-mentioned range are all within the scope to be protected by the present invention. Preferably, the polyacrylamide accounts for 0.08-0.12% of the total mass of the soil and industrial solid waste composite material. Adding an appropriate amount of anionic polyacrylamide (MW 8 million) can regulate the rheological properties of the slurry. PAM enhances the structural stability of the solidified soil through the adsorption effect of its polymer chain, improves the bonding force between particles, and thus increases the compressive strength of the solidified soil. At the same time, the addition of PAM can promote the formation of a more compact particle structure, reduce the erosion of the solidified soil by the fluid, and enhance the anti-scouring ability.

[0014] In one or more embodiments, the percentage of the mass of the alkali activator to the total mass of the soil and industrial solid waste composite material can be 28%, 30%, 32%, 35%, 40%, 52%, 45%, 50%, 51%, 52%, 55%, 56%, 58%, 59%, etc., but is not limited to the point values ​​listed above. Other values ​​not listed but within the above range are all within the scope to be protected by the present invention.

[0015] Alkali-activated fluidized soil materials have different water glass moduli and sodium oxide contents. Therefore, the mass fraction of the alkali activator (water glass and sodium hydroxide) varies with the modulus and sodium oxide content. For example, the water glass modulus of the mixed alkali solution can be 1.0, 1.1, 1.2, 1.3, 1.4, etc.; the sodium oxide content can be between 6% and 10%, such as 6%, 7%, 8%, 9%, 10%, etc. The combination of the water glass modulus and sodium oxide content in the mixed alkali solution can satisfy any of the following conditions: (a) the mixed alkali solution has a water glass modulus of 1.0 and a sodium oxide content of 6-10%; (b) the mixed alkali solution has a water glass modulus of 1.2 and a sodium oxide content of 6-10%; (c) the mixed alkali solution has a water glass modulus of 1.4 and a sodium oxide content of 6-10%. This combination of water glass modulus and sodium oxide content allows for optimal synergistic effects between the alkali activator and other components.

[0016] By adopting the technology of synergistic activation of industrial solid waste composites and soil, and through the dynamic ratio control of alkaline activators (water glass modulus and sodium hydroxide content), the reaction activity of geopolymers is significantly improved and the gel phase formation rate is accelerated.

[0017] In one or more embodiments, the water glass is an industrial-grade sodium silicate solution having a modulus of 3-3.5, a sodium oxide content of 5-10%, and a silicon dioxide content of 20-30%. For example, the modulus is 3.3, the sodium oxide content is 8.37%, and the silicon dioxide content is 26.09%. In the present invention, water glass is compounded with sodium hydroxide to adjust the water glass modulus in the final alkaline solution to 1.0-1.4 and the Na2O content to 6-10%, preferably 6-8%, to optimize the alkaline environment and activate the dissolution and polycondensation reactions of aluminosilicates in the solid waste.

[0018] In one or more embodiments, the soil is natural soil with a natural moisture content of approximately 40-60%. The soil is silty clay, primarily composed of SiO2 and Al2O3, with the combined SiO2 and Al2O3 content being ≥ 65%. The silt content (0.075-0.005 mm) accounts for ≥ 40%. For example, the soil can be derived from river silt, which is more conducive to resource utilization.

[0019] In one or more embodiments, the blast furnace slag is a product of a water quenching process, and its specific surface area is not less than 400m 2 / kg, 28d activity index ≥95%, its main components are CaO, SiO2, Al2O3 and MgO.

[0020] In one or more embodiments, the fly ash is Class I low-calcium fly ash, the loss on ignition of which does not exceed 5%, the residue on a 45 μm square sieve is ≤12%, and the main components of the fly ash are SiO 2 , CaO, and Al 2 O 3 .

[0021] The blast furnace slag and fly ash are configured in a certain proportion (for example, a mass ratio of 1:1), and the active ingredients of the two synergistically improve the efficiency of the gelling reaction.

[0022] In one or more embodiments, the sodium hydroxide is industrial grade caustic soda with a purity of ≥96%. - Content ≤0.1%.

[0023] In one or more embodiments, the polyacrylamide (PAM) is an anionic linear polymer with a molecular weight of 7-9 million, a degree of hydrolysis of 20-30%, and a residual monomer content of 0.05% or less. Anionic polyacrylamide, as a functional additive, improves the rheological properties of the slurry and the bond strength between particles through adsorption-bridging effects.

[0024] In a second aspect, the present invention provides a method for preparing a marine anti-scour fluidized solidified soil material, comprising the following steps:

[0025] Prepare an alkali activator using water, sodium hydroxide and water glass;

[0026] The pretreated soil and industrial solid waste composite material are mixed evenly, an alkali activator is added, polyacrylamide is added after fully mixing, and the mixture is stirred until uniform.

[0027] In one or more embodiments, the preparation method of the alkali activator is: according to the target parameters (water glass modulus and sodium oxide content in the mixed alkali solution), a mixed alkali solution is prepared using water glass, sodium hydroxide and water (for example, water glass with a modulus of 3.3 needs to be supplemented with NaOH to adjust to the target modulus of 1.0-1.4 and the sodium oxide content is 6%-10%, and water is supplemented to adjust the water-slag ratio to 0.1-0.5); stirring until there is no suspended particulate matter, sealing and standing at a constant temperature.

[0028] Specifically: Stir at 200-500 rpm for 5-20 minutes until no suspended particles are present. After sealing, place at a constant temperature of 20-30°C for 12-36 hours (preferably 20-26 hours). Only within the above parameters of speed, time, etc. can a transparent, homogeneous sol free of precipitates be formed.

[0029] The water in the water-slag ratio comes from three parts: sodium silicate solution, dissolved sodium hydroxide particles and added water; slag refers to the sum of soil and industrial solid waste composite materials.

[0030] In one or more embodiments, the pretreatment comprises drying the soil, crushing it, and then screening it. Furthermore, the specific steps of drying the soil, crushing it, and then screening it are as follows: drying the soil at 80-120°C for 10-36 hours (preferably 20-26 hours), crushing it after drying, and then passing it through a 1-3 mm square hole sieve. Only after the soil has been pretreated can it be fully mixed with the industrial solid waste composite material.

[0031] In one or more embodiments, after adding the alkali activator, stir at a low speed for 100-200 seconds (e.g., 120 seconds), pause for 10-20 seconds (e.g., 15 seconds), while scraping the slurry from the blades and the pot wall into the center of the pot. Then stir at a high speed for 100-200 seconds (e.g., 120 seconds), thoroughly mix, and then add the polyacrylamide. Stirring is then continued at a low speed and then at a high speed until uniform. The low speed is 100-600 rpm, and the high speed is 800-1500 rpm. This low-speed and high-speed stirring process allows for more complete reaction and mixing with the alkali activator.

[0032] In one or more embodiments, during the mixing process, the slurry temperature is controlled to be ≤35° C., and excessively high temperature is not suitable.

[0033] In a third aspect, the present invention provides an application of the above-mentioned marine anti-scour fluidized solidified soil material or the marine anti-scour fluidized solidified soil material obtained by the above-mentioned preparation method in marine anti-scour engineering. Furthermore, the application of the above-mentioned marine anti-scour fluidized solidified soil material in offshore wind power monopile foundation anti-scour engineering is provided.

[0034] One or more of the above technical solutions have the following advantages or beneficial effects:

[0035] (1) This invention constructs an "organic-inorganic composite gelling system" by integrating polyacrylamide (PAM), water glass, and alkali-activated materials in a multi-dimensional collaborative design, achieving systematic breakthroughs in material properties, reaction kinetics, and environmental benefits. In particular, the addition of anionic polyacrylamide (PAM) significantly improves the compressive strength and anti-scour rate of the solidified soil, although the fluidity is reduced. This indicates that the addition of PAM has a positive effect on material properties.

[0036] (2) The fluidized solidified soil material of the present invention is designed through a sol-powder gradient reaction mechanism, and 0.1% anionic PAM (MW8 million) is used to regulate the rheological properties of the slurry. PAM enhances the structural stability of the solidified soil through the adsorption of its polymer chains, improves the bonding force between particles, and thus increases the compressive strength of the solidified soil. At the same time, the addition of PAM can promote the formation of a more compact particle structure, reduce the erosion of the solidified soil by the fluid, and enhance the anti-scouring ability. This shows that PAM not only enhances the overall strength of the solidified soil through physical adsorption, but also reduces the scouring effect of water on the material surface by improving the microstructure of the material, thereby indirectly improving the anti-scouring effect.

[0037] (3) The fluidized solidified soil material prepared by the present invention has excellent self-compacting properties and underwater anti-dispersion properties. After hardening, it forms a continuous and dense anti-scour protective layer, which can effectively resist the wave-current coupled scour effect. When used for anti-scour of offshore wind power single pile foundations, it achieves both high fluidity and long-term anti-scour performance (anti-scour rate is greater than 97%).

[0038] (4) The present invention adopts the synergistic activation technology of industrial solid waste composite material (blast furnace slag / fly ash 1:1) and river silt. Through the dynamic ratio control of alkaline activator (water glass modulus in alkaline solution is 1.0-1.4, sodium hydroxide content is 6-10%), the reaction activity of geopolymer is significantly improved, the gel phase generation rate is accelerated, and the synergistic optimization of solidified soil compressive strength ≥6MPa (28d age) and fluidity ≥135mm is achieved.

[0039] (5) PAM captures suspended matter and dissolved organic matter through adsorption bridging, while the water glass and alkali-activated material gel network absorb heavy metal ions (such as Pb 2+ 、Cu 2+ ) has a chemical solidification rate of ≥99.5%, achieving "one dose, two effects"; compared with traditional cement-solidified soil, the mass of fly ash / blast furnace slag accounts for 30% of the total mass of soil and industrial solid waste composite materials, and the cost of raw materials is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0041] Figure 1 This is the anti-scour rate testing device of the present invention. DETAILED DESCRIPTION

[0042] In response to the problems of traditional concrete materials having insufficient anti-scouring performance in marine environments, high costs and poor environmental protection, the present invention has developed a green material with high fluidity, rapid hardening characteristics and long-term anti-scouring performance through the collaborative innovation of industrial solid waste resource utilization and alkali excitation technology.

[0043] In the specific plan, the soil used was taken from the river silt near the Dehui River in Wudi County, Binzhou City, Shandong Province; the blast furnace slag used was produced by a titanium oxide factory in Shandong Province; the fly ash (FA) was produced by a fly ash factory in Jinan; the water glass used was produced by Shanghai Aladdin Biochemical Technology Co., Ltd.; the sodium hydroxide particles and polyacrylamide powder were conventional commercial sources, such as those produced by Beijing Mairida Technology Co., Ltd.

[0044] The water glass has a Na2O content of 8.37%, a SiO2 content of 26.09%, a water content of 65.54%, and a modulus of 3.3.

[0045] The polyacrylamide (PAM) has a purity of MW: 8 million (anionic).

[0046] It should be noted that in the embodiments of the present invention, the amount of alkaline activator used in each group is different because the mixed alkaline solution is adjusted to the target modulus and sodium oxide content. Taking Table 1 as an example, the role of sodium silicate, sodium hydroxide, and water is to adjust the target modulus and sodium oxide content, so the mass of each group is different.

[0047] Table 1 Specific ratios of water glass modulus and sodium oxide content in sodium silicate, sodium hydroxide, water, slag and mixed alkali solution

[0048]

[0049] The “slag” in Table 1 refers to the sum of the soil and industrial solid waste composite. The “target modulus” refers to the modulus of water glass in the mixed alkaline solution.

[0050] In the present invention, unless otherwise specified, other experimental materials and instruments and equipment are conventional experimental materials in this field and can be purchased through commercial channels.

[0051] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0052] Example 1

[0053] For marine scour prevention, the fluidized solidification soil material is designed with a mass ratio of 7:3 between natural soil and industrial solid waste composites. The mass ratio of blast furnace slag to fly ash in the industrial solid waste composite is 1:1. The alkaline activator has a target modulus of 1.2 and a sodium oxide content of 8%. Anionic polyacrylamide (PAM, molecular weight 8 million) is added at a rate of 0.1% of the total mass of the natural soil and industrial solid waste composites. The components are thoroughly mixed in a blender to produce the fluidized solidification soil. The mass of the alkaline activator accounts for 28%-59% of the total mass of the soil and industrial solid waste composites.

[0054] The method for preparing the anti-scour fluidized solidified soil material used in the present invention specifically comprises the following steps:

[0055] (1) Taking the total mass of 500 g of soil and industrial solid waste composite as an example (the mass of soil is 350 g, and the mass of fly ash and blast furnace slag is 75 g respectively), 178.35 g of water glass, 125.82 g of deionized water and 32.36 g of sodium hydroxide particles were added to a borosilicate glass beaker in sequence through calculation, so that the target modulus of the mixed sol is 1.2 and the sodium oxide content is 8%.

[0056] (2) Stir with a magnetic stirrer (300 rpm) for 10 min until there is no suspended particle. Seal the mouth of the beaker with tin foil and place it in a constant temperature box at 25±1℃ for 24 h to form a transparent homogeneous sol without precipitates.

[0057] (3) At the same time, the riverbed silt is placed in an oven and dried at 105°C for 24 hours. After drying, the soil is crushed using a crusher and then passed through a 1mm square hole sieve.

[0058] (4) The prepared soil sample was mixed with the industrial solid waste composite material in a mass ratio of 7:3, wherein the ratio of blast furnace slag and fly ash in the industrial solid waste composite material was 1:1. The mixture was stirred continuously during the mixing process until the powdered materials were evenly mixed.

[0059] (5) Pour the prepared sol into the blender, add the mixed dry materials, stir at low speed for 120 seconds, stop for 15 seconds, and scrape the slurry on the blades and the pot wall into the middle of the pot. Stir at high speed for 120 seconds. After fully mixing, add polyacrylamide and stir at low and high speeds in turn until it is uniform.

[0060] Example 2

[0061] Different from Example 1, in the alkaline activator, the final target modulus is 1.2 and the sodium oxide content is 10%.

[0062] Example 3

[0063] Different from Example 1, in the alkaline activator, the final target modulus is 1.4 and the sodium oxide content is 8%.

[0064] Example 4

[0065] Different from Example 1, in the alkaline activator, the final target modulus is 1.4 and the sodium oxide content is 10%.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that anionic polyacrylamide (PAM, molecular weight 8 million) is not added.

[0068] Comparative Example 2

[0069] The difference from Example 2 is that anionic polyacrylamide (PAM, molecular weight 8 million) is not added.

[0070] Comparative Example 3

[0071] The difference from Example 3 is that anionic polyacrylamide (PAM, molecular weight 8 million) is not added.

[0072] Comparative Example 4

[0073] The difference from Example 4 is that anionic polyacrylamide (PAM, molecular weight 8 million) is not added.

[0074] When using pre-mixed curing agent to prepare fluidized solidified soil specimens, the mass ratio of industrial solid waste composite to soil is set to 3:7, and the water-slag ratio is controlled to 0.5 (the water comes from three parts: sodium silicate solution, dissolved sodium hydroxide particles and added deionized water; the slag refers to the sum of the soil and industrial solid waste composite).

[0075] The fluidity of the cured soil was tested with reference to GB / T 8077-2023 Test method for homogeneity of concrete admixtures; the setting time was tested with reference to GB / T 1346-2011 Test method for water consumption, setting time and stability of cement of standard consistency; the compressive strength was tested with reference to GB / T 17671-2021 Test method for strength of cement mortar (ISO method). The sample size selected for the test was 50mm×50mm×50mm.

[0076] Anti-scour rate test device such as Figure 1 As shown, the test method is as follows:

[0077] (1) First, weigh the mass of the circular culture dish and record it as m1;

[0078] (2) Place 50 g of fluidized solidified soil sample into a round Petri dish, and then place the Petri dish into a beaker filled with water;

[0079] (3) Place the beaker under the stirrer with the rotor 10 cm away from the bottom of the beaker and stir at 350 rpm for 5 min;

[0080] (4) After stirring, remove the culture dish and let it stand for a while, during which time, use a needle to extract excess water from the culture dish;

[0081] (5) Weigh the mass of the culture dish and the solidified soil, recorded as m2;

[0082] (6) Calculate the anti-scour rate using the formula: (50-m2-m1) / 50×100%.

[0083] The test results of the embodiments and comparative examples are shown in Table 2.

[0084] Table 2 Test results of examples and comparative examples

[0085]

[0086] As can be seen from the above table, compared with the comparative example, the fluidity (135-155 mm) of the solidified soil in the embodiment is reduced after adding PAM, but the effect is not significant; the 3d compressive strength is 4.5-7.5 MPa, the 28d compressive strength is 6.5-8.5 MPa, and the anti-scour rate is ≥97%, preferably ≥98%. In terms of compressive strength and anti-scour rate, the embodiment has obvious performance improvement, indicating that the addition of PAM has a positive effect on material properties.

[0087] In summary, the anti-scour fluidized solidified soil material provided by the present invention can achieve a good anti-scour effect while ensuring a certain fluidity.

[0088] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A marine anti-scour fluidized soil solidification material, characterized in that: The method comprises the following components: soil, industrial solid waste composite material, polyacrylamide and alkali activator; The mass ratio of soil and industrial solid waste composite material is (6-8):(2-4); The industrial solid waste composite material includes blast furnace slag and fly ash, and the mass ratio of blast furnace slag to fly ash is (0.9-1.1):(0.9-1.1); Polyacrylamide accounts for 0.05-0.2% of the total mass of the soil and industrial solid waste composite; The mass of the alkali activator accounts for 28%-59% of the total mass of the soil and industrial solid waste composite material; The alkaline activator is a mixed alkaline solution containing solid sodium hydroxide and water glass. The water glass modulus of the mixed alkaline solution is the molar ratio of silicon dioxide to sodium oxide, which is 1.0-1.4, and the sodium oxide content is 6%-10%. The polyacrylamide is an anionic linear high molecular polymer with a molecular weight of 7-9 million, a hydrolysis degree of 20-30%, and a residual monomer content of ≤0.05%.

2. The marine anti-scour fluidized soil solidification material according to claim 1, characterized in that: The combination of the water glass modulus and the sodium oxide content of the mixed alkali solution satisfies any one of the following: (a) the mixed alkali solution has a water glass modulus of 1.0 and a sodium oxide content of 6-10%; (b) the mixed alkali solution has a water glass modulus of 1.2 and a sodium oxide content of 6-10%; (c) The mixed alkali solution has a water glass modulus of 1.4 and a sodium oxide content of 6-10%.

3. The marine anti-scour fluidized solidified soil material according to claim 1 or 2, characterized in that: The water glass is an industrial grade sodium silicate solution with a modulus of 3-3.5, a sodium oxide content of 5-10%, and a silicon dioxide content of 20-30%.

4. The marine anti-scour fluidized solidified soil material according to claim 1, characterized in that: The soil is silty clay, the main components of which are SiO2 and Al2O3, the total amount of SiO2 and Al2O3 is ≥65%, and the content of 0.075-0.005mm powder particles accounts for ≥40%; The blast furnace slag is a product of water quenching and rapid cooling process, and its specific surface area is not less than 400m 2 / kg, activity index ≥95% at 28 days.

5. The marine anti-scour fluidized soil solidification material according to claim 1, characterized in that: The fly ash is Class I low-calcium fly ash, with a loss on ignition not exceeding 5% and a 45μm square hole sieve residue of ≤12%; The sodium hydroxide is industrial grade flake caustic soda with a purity of ≥96%. - Content ≤0.1%.

6. A method for preparing the marine anti-scour fluidized solidified soil material according to any one of claims 1 to 5, characterized in that: The following steps are involved: Prepare an alkali activator using water, sodium hydroxide and water glass; The pretreated soil and industrial solid waste composite material are mixed evenly, an alkali activator is added, polyacrylamide is added after fully mixing, and the mixture is stirred until uniform.

7. The preparation method according to claim 6, characterized in that Prepare a mixed alkaline solution using water glass, sodium hydroxide and water, stir until there is no suspended particulate matter, seal and let stand at a constant temperature.

8. The preparation method according to claim 6, characterized in that The pretreatment is to dry the soil, crush it and then sieve it.

9. Use of the marine anti-scour fluidized solidified soil material according to any one of claims 1 to 5 or the marine anti-scour fluidized solidified soil material obtained by the preparation method according to any one of claims 6 to 8 in marine anti-scour engineering.

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