Alkaline solid waste-based foam light soil suitable for high altitude areas and preparation method thereof

Abstract

The application discloses alkaline solid waste-based foam light soil suitable for high-altitude areas and a preparation method thereof. In view of technical bottlenecks such as bubble coarsening, foaming agent activity attenuation and foam rapid failure caused by the synergistic effect of low air pressure and high alkaline environment of a material system in high-altitude areas, the application takes solid wastes such as slag powder and desulfurization gypsum as main cementing raw materials, and forms a slurry under the activation of alkaline solid wastes such as red mud and carbide slag; a slow-release foaming agent is constructed by adopting a 'porous carrier (fly ash floating bead) loading + slow-release layer coating' strategy, controlled decomposition of hydrogen peroxide to produce gas under a high-alkali environment is realized by utilizing the pore channel confining effect, surface anchoring effect and slow-release effect of the slow-release coating; and hydrophobic / hydrophilic amphiphilic zeolite is used as a foam stabilizer to synergistically inhibit bubble merging and rupture under a low air pressure environment. The alkaline solid waste-based foam light soil has excellent performance and is suitable for roadbed backfill, thermal insulation cushion and slope protection engineering in high-altitude areas.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to an alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas and its preparation method. Background Technology

[0002] Alkaline solid waste-based foamed lightweight soil is currently the mainstream application form of solid waste-based solidified soil. It uses industrial solid waste such as fly ash, slag, and steel slag as main raw materials, forming a cementing system under the action of an alkaline activator, and then introducing a gas phase to prepare a porous lightweight material. This type of material typically has a density of 300-1000 kg / m³, and possesses multiple advantages such as lightweight, heat insulation, low carbon footprint, and solid waste disposal. In high-altitude areas such as the Qinghai-Tibet Plateau, where the climate is cold, air pressure is low, and the cost of transporting building materials is high, using local alkaline solid waste to prepare alkaline solid waste-based foamed lightweight soil for roadbed backfilling, thermal insulation layers, and slope protection can simultaneously solve the problems of engineering material needs and solid waste storage, possessing significant engineering value and ecological significance.

[0003] Currently, alkaline solid waste-based foamed lightweight soil mainly employs chemical foaming methods such as aluminum powder gas generation or hydrogen peroxide (i.e., decomposition) decomposition. In alkaline activation systems, the slurry pH value is typically above 12. The strongly alkaline environment significantly accelerates the decomposition rate of hydrogen peroxide, causing it to generate gas rapidly within seconds. Aluminum powder also rapidly undergoes a displacement reaction in strongly alkaline environments, releasing hydrogen gas. When the above foaming process takes place in a high-altitude, low-pressure environment, the problems are further exacerbated: on the one hand, low pressure significantly reduces gas solubility and bubble expansion resistance, causing bubbles to easily merge, break, and float to the surface; on the other hand, the excessively rapid gas generation rate caused by high alkalinity combined with the excessively rapid expansion under low pressure creates a superimposed effect, making the gas generation process even more difficult to control. Ultimately, this results in more prominent defects such as uneven material pore size, numerous interconnected pores, low strength, and high water absorption. Furthermore, the flammability and explosiveness risk of hydrogen generated by aluminum powder also increases significantly under low pressure. To improve foam stability, existing technologies mainly rely on passive protection by adding foam stabilizers, thickeners, or fibers. However, since these methods only protect the bubbles from the outside and fail to control the gas production rate from the source, the problems of excessively rapid gas production and uncontrolled bubbles remain prominent under the dual acceleration of high alkali and low gas pressure, making it difficult to fundamentally solve the problems of pore structure deterioration and performance degradation.

[0004] Therefore, there is an urgent need to develop a technology that can actively control the gas generation rate from the gas generation source and adapt the gas generation process to the slurry solidification process, so as to prepare alkaline solid waste-based foamed lightweight soil with uniform pore structure, light weight and high strength, suitable for high-altitude areas. Summary of the Invention

[0005] The purpose of this invention is to provide an alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas and its preparation method, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is: an alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas, wherein the raw materials include the following components by mass: 90 parts of alkaline solid waste-based cementitious material, 100 parts of soil, 6-10 parts of slow-release foaming agent, 0.2-0.5 parts of hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer, and 95-105 parts of water; The sustained-release foaming agent includes a porous carrier, hydrogen peroxide loaded in the porous carrier, and a sustained-release coating layer.

[0007] This invention achieves controlled release of the foaming agent (hydrogen peroxide) through a "porous carrier loading + slow-release layer coating," and achieves long-term foam stability through a hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer. The synergistic effect of these two components forms a uniform and stable porous structure during the preparation of alkaline solid waste-based foamed lightweight soil, significantly improving the pore structure and mechanical properties of the soil. The core technical principle of this invention includes: during the foaming process, hydrogen peroxide is slowly released from the porous carrier into the alkaline slurry and decomposes to produce oxygen, forming bubbles. Simultaneously, the porous carrier and the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer are adsorbed at the gas-liquid interface: the former provides a physical barrier, while the latter, with its amphiphilic structure, firmly adheres to the bubble surface, forming a dense particulate shell. The synergistic effect of these two components exerts steric hindrance and interfacial shielding, effectively inhibiting bubble aggregation and Ostwald curing, significantly extending the foam life, and ultimately resulting in a uniform and fine porous structure in the hardened body.

[0008] Furthermore, the alkaline solid waste-based cementitious material includes slag powder, red mud, desulfurized gypsum, and carbide slag.

[0009] In alkaline solid waste-based cementitious materials, carbide slag and red mud synergistically provide a strongly alkaline environment and Ca. 2+ The process disrupts the glassy network of slag powder, stimulating its potential hydraulic properties and releasing active SiO2 and Al2O3; desulfurization gypsum introduces SO4. 2- With active Al2O3 and Ca 2+ The reaction produces ettringite (AFt), which fills pores and enhances early strength. Slag powder hydration produces CSH and CAH gels, forming a strength framework, while the Fe and Al phases in red mud further participate in hydration or act as micro-aggregate fillers. Through multiple couplings of "alkali activation-sulfate activation-hydration hardening," these four components achieve chemical complementarity and physical filling synergy, forming a dense microstructure.

[0010] Furthermore, the mass ratio of the slag powder, red mud, desulfurized gypsum, and carbide slag is 40:30:15:5.

[0011] Furthermore, the soil includes natural soil or engineering waste soil; the soil has a plasticity index of 10-17, a liquid limit of 30-45%, a plastic limit of 18-25%, and a moisture content of 15-25%.

[0012] Further, the preparation steps of the sustained-release foaming agent include: mixing an aqueous hydrogen peroxide solution and a porous carrier, ultrasonically treating the mixture, and then filtering and drying it to obtain an intermediate; mixing the intermediate, polylactic acid-glycolic acid copolymer (PLGA), and an organic solvent, and ultrasonically emulsifying the mixture to obtain a primary emulsion; mixing the primary emulsion with an aqueous polyvinyl alcohol (PVA) solution and stirring to obtain a secondary emulsion; and subjecting the secondary emulsion to organic solvent evaporation, filtration, and drying to obtain the sustained-release foaming agent.

[0013] This invention first employs an ultrasonic-assisted loading process to load hydrogen peroxide into the pores of a porous carrier, ensuring sufficient permeation and preventing premature decomposition. Subsequently, an emulsion solvent evaporation method is used to coat the carrier with a sustained-release coating layer, further enhancing the stability and sustained-release properties of the hydrogen peroxide. The sustained-release coating layer is formed from PLGA and PVA. PLGA provides a hydrophobic framework for long-term sustained release, while PVA provides hydrophilic stability and surface modulation. Together, they form a dual barrier of "hydrophobic barrier - hydrophilic modulation," achieving controlled release of hydrogen peroxide and a stable coating structure.

[0014] Optionally, the molecular weight of the polylactic acid-glycolic acid copolymer is 30,000-50,000; and the molecular weight of the polyvinyl alcohol is 13,000-18,000.

[0015] Further, the porous carrier includes fly ash cenospheres; the concentration of the hydrogen peroxide aqueous solution is 30 wt%; the mass ratio of the hydrogen peroxide aqueous solution to the porous carrier is 10-15:1; the concentration of the polyvinyl alcohol aqueous solution is 1 wt%; the mass ratio of the intermediate, polylactic acid-glycolic acid copolymer, and organic solvent is 1:1-2:5-8; and the volume ratio of the primary emulsion to the polyvinyl alcohol aqueous solution is 1:18-22.

[0016] This invention uses fly ash cenospheres as a porous carrier. Fly ash cenospheres have a porous structure and a large specific surface area, providing ample adsorption sites for hydrogen peroxide. Furthermore, compared to traditional porous carriers such as diatomaceous earth, fly ash cenospheres have the following advantages: high compressive strength (70-140 MPa) ensures that its rigid shell is not easily broken under mechanical action; its regular spherical shape gives it excellent dispersibility, forming a continuous and stable barrier at the gas-liquid interface; its hollow structure also provides thermal insulation; and its chemical inertness (resistance to high alkali and high temperature) ensures the long-term effectiveness of the barrier.

[0017] Preferably, the specific surface area of ​​the fly ash cenospheres is greater than 1.5 m². 2 / g.

[0018] Furthermore, the ultrasonic treatment power is 100-300 W, and the time is 10-30 min.

[0019] Furthermore, the organic solvent includes dichloromethane.

[0020] Furthermore, the ultrasonic emulsification power is 100-200 W, and the time is 10-30 s.

[0021] Furthermore, when preparing the double emulsion, the stirring speed is 300-800 rpm and the time is 30-60 min.

[0022] Furthermore, the temperature at which organic solvents evaporate is 25-40℃.

[0023] Furthermore, the process of mixing the hydrogen peroxide aqueous solution and the porous support, ultrasonicating, filtering, and drying to obtain the intermediate specifically involves vacuum drying at room temperature for 1-3 hours.

[0024] Furthermore, the drying process of the compound emulsion, including organic solvent evaporation, filtration, and drying, specifically involves vacuum drying at room temperature for 1-3 hours.

[0025] Furthermore, the preparation steps of the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer include: placing zeolite in a closed reaction chamber, evacuating the chamber, introducing a gaseous hydrophobic precursor, and performing chemical vapor deposition at 200-400℃ to obtain the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer.

[0026] Zeolite surfaces naturally contain hydrophilic hydroxyl groups. This invention introduces hydrophobic groups onto the zeolite surface, which already contains hydrophilic hydroxyl groups, using chemical vapor deposition (CVD). These introduced hydrophobic groups, together with the hydrophilic hydroxyl groups originally present in the inner layer of zeolite, constitute an amphiphilic structure. Compared to other modification methods, introducing hydrophobic groups via CVD is more effective in maintaining the porous structure of zeolite while simultaneously introducing hydrophobic groups.

[0027] Furthermore, the gaseous hydrophobic precursor comprises trimethylchlorosilane; the flow rate of the gaseous hydrophobic precursor is 100 mL / min; and the chemical vapor deposition time is 1-3 h.

[0028] Furthermore, after the chemical vapor deposition is completed, a step of natural cooling to room temperature is also included.

[0029] The second technical solution of the present invention: a method for preparing the above-mentioned alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas, comprising the following steps: Alkaline solid waste-based cementitious materials, soil, and water are mixed to obtain an alkaline slurry; The slow-release foaming agent and the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer are added to the alkaline slurry and stirred to obtain a mixed slurry; The mixed slurry is foamed, expanded, statically stopped, and cured to obtain the alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas.

[0030] Furthermore, the stirring speed is 200-600 rpm, and the time is 3-10 min.

[0031] Furthermore, the foaming and expansion time is 8-25 minutes.

[0032] The third technical solution of the present invention: the application of the above-mentioned alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas in roadbed backfilling, thermal insulation cushion layer or slope protection in high-altitude areas.

[0033] Furthermore, the high-altitude areas specifically refer to areas with an altitude of ≥3000 m.

[0034] Furthermore, the air pressure in the high-altitude area is 0.60-0.70 atm.

[0035] Addressing the technical bottlenecks of bubble coarsening, foaming agent activity decay, and rapid foam failure caused by the synergistic effect of low air pressure and highly alkaline material systems in high-altitude areas, this invention uses solid wastes such as slag powder and desulfurized gypsum as the main cementing raw materials, forming a slurry under the activation of alkaline solid wastes such as red mud and carbide slag. A slow-release foaming agent is constructed using a "porous carrier loading + slow-release layer coating" strategy. The carrier's pore confinement effect, surface anchoring effect, and the slow-release effect of the coating layer enable the controllable decomposition and gas production of hydrogen peroxide in a highly alkaline environment. Furthermore, hydrophobic / hydrophilic amphiphilic zeolite is used as a foam stabilizer to synergistically inhibit bubble coalescence and collapse under low-pressure conditions. The alkaline solid waste-based foamed lightweight soil of this invention exhibits excellent performance and is suitable for roadbed backfilling, thermal insulation layers, and slope protection projects in high-altitude areas of 3000m and above.

[0036] The present invention discloses the following technical effects: (1) The gas generation process is actively controllable and the matching is significantly improved. This invention adopts the strategy of "porous carrier loading + slow-release layer coating" to construct a slow-release foaming agent. By utilizing the confinement effect of the porous carrier channels, the surface anchoring effect, and the slow-release effect of the slow-release coating layer, the decomposition and gas generation time of hydrogen peroxide in highly alkaline slurry is extended from less than 5 min to 10-25 min, overcoming the fundamental defect of explosive gas generation of existing materials in highly alkaline environments.

[0037] (2) The dual bubble-stabilizing mechanism enhances bubble stability significantly. This invention utilizes the rigid shell of fly ash cenospheres and the hydrophobic / hydrophilic amphiphilic zeolite particles adsorbed together at the gas-liquid interface: the former provides a physical barrier, while the latter, with its amphiphilic structure, firmly adheres to the bubble surface, forming a dense granular shell layer. The two work synergistically to exert steric hindrance and interfacial shielding effects, inhibiting bubble coalescence and Ostwald curing, significantly extending the foam lifespan, and resulting in a uniform and fine porous structure in the hardened body. The synergistic effect of the two effectively solves the problem of rapid merging, rupture, and escape of bubbles due to reduced expansion resistance at high altitudes and low air pressure.

[0038] (3) The pore structure quality is significantly improved, and the material properties are improved simultaneously. Due to the controllable gas generation rate and enhanced bubble stability, the pore size distribution of the foamed lightweight soil prepared by this invention is more uniform; under the same density level, the compressive strength of the product is significantly improved, realizing the synergistic optimization of lightweight and high strength.

[0039] (4) Outstanding process safety and environmental benefits. This invention uses hydrogen peroxide to produce oxygen instead of aluminum powder to produce hydrogen, which fundamentally eliminates the safety hazards of hydrogen being flammable and explosive in high-altitude and low-pressure environments; at the same time, it uses alkaline solid waste as the main raw material, realizing the high-value utilization of industrial solid waste, and has significant engineering economics and ecological benefits. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0046] Unless otherwise specified, the term "parts" in the following embodiments and comparative examples of the present invention refers to "parts by mass".

[0047] Unless otherwise specified, room temperature in the following embodiments, comparative examples and performance tests of this invention refers to 20-30°C.

[0048] Unless otherwise specified, all raw materials used in the following embodiments, comparative examples, and performance tests of this invention are commercially available products. The specific surface area of ​​slag powder is 432 m². 2 / kg, 28d activity index of 98%, moisture content ≤1%; The red mud has an average particle size of 13.82 μm and a specific surface area of ​​425 m². 2 / kg, moisture content ≤1%; The desulfurized gypsum has an average particle size of 43.26 μm and a moisture content of ≤1%. The average particle size of the carbide slag is 6.87 μm, the CaO content is 64 wt%, and the moisture content is ≤1%. The soil is clay (a type of natural soil), and its liquid limit (WL) 17 The content of the plasticity index was 32.1%, the plastic limit (WP) was 17.9%, the plasticity index was 14.2, and the moisture content was 16.5%. The specific surface area of ​​fly ash cenospheres is 1.65 m². 2 / g, average particle size 7.5μm, moisture content ≤1%; The concentration of the hydrogen peroxide aqueous solution is 30 wt%; The specific surface area of ​​zeolite is 450 m². 2 / g, moisture content ≤1%; The water is tap water.

[0049] Examples 1-4 In Examples 1-4, the types and amounts of raw materials for alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas are shown in Table 1.

[0050] In Examples 1-4, the specific preparation steps for alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas are as follows: (1) Preparation of sustained-release foaming agent: 1 kg of hydrogen peroxide aqueous solution and 100 g of fly ash cenospheres were mixed and ultrasonically treated at 250 W for 20 min, filtered, and vacuum dried at room temperature for 2 h to obtain an intermediate (the loading of hydrogen peroxide was calculated to be 0.25 g H2O2 / g fly ash cenospheres by the difference in mass before and after). All the obtained intermediates were mixed with polylactic acid-glycolic acid copolymer (molecular weight about 40000) and dichloromethane at a mass ratio of 1:2:6 and ultrasonically emulsified at 120 W for 30 s to obtain a primary emulsion. The primary emulsion was mixed with a 1 wt% aqueous solution of polyvinyl alcohol (molecular weight about 15000) at a volume ratio of 1:20 and stirred at 500 rpm for 30 min to obtain a secondary emulsion. The secondary emulsion was stirred at 35 ℃ at 100 rpm for 5 h to evaporate the organic solvent, then filtered and vacuum dried at room temperature for 2 h to obtain a sustained-release foaming agent.

[0051] (2) Preparation of hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer: Zeolite was placed in a closed reaction chamber, and gaseous trimethylchlorosilane was introduced after vacuuming at a flow rate of 100 mL / min. Chemical vapor deposition was carried out at 300℃ for 2 hours and then naturally cooled to obtain hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer.

[0052] (3) Preparation of alkaline solid waste-based foamed lightweight soil: Alkaline solid waste-based cementitious material, soil and water are mixed to obtain alkaline slurry; slow-release foaming agent and hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer are added to alkaline slurry and stirred at 500 rpm for 5 min to obtain mixed slurry; the mixed slurry is injected into a mold and placed in an air pressure environment of 0.60 atm (simulating high altitude low pressure environment, temperature of 20±2℃) for foaming and expansion until the mixed slurry expansion is stable (no significant change on the surface and no further increase in height), and the foaming duration is recorded; after the foaming and expansion is completed, the mixed slurry is statically stopped (temperature 20±2℃, air pressure 0.60 atm, time 1 h) and cured (temperature 20±2℃, relative humidity 60±5%, air pressure 0.60 atm, curing to 28 days) to obtain alkaline solid waste-based foamed lightweight soil specimens.

[0053] Table 1. Raw material composition of Examples 1-4 (by parts by mass) The performance of the mixed slurry in Examples 1-4 above or the finally obtained alkaline solid waste-based foamed lightweight soil (hereinafter referred to as foamed lightweight soil) was tested using the following methods: (1) Slurry expansion rate (λ): The test was conducted using a standard cylindrical mold (inner diameter 100 mm, height 200 mm). Fresh mixed slurry was poured into the mold until it was full, the surface was smoothed, and the initial slurry height H0 was recorded. Under the set environmental conditions (temperature 20±2℃, pressure 0.60 atm), the mixture was allowed to stand and generate gas. After the mixed slurry expansion stabilized (no significant change in the surface and no further increase in height), the final height H1 was recorded. The slurry expansion rate was calculated as λ=(H1-H0) / H0×100%. Each test group was conducted in parallel for 3 times, and the arithmetic mean was taken.

[0054] (2) Settling rate (η): After the slurry expansion rate test is completed, the sample and mold are left to stand for 1 h (temperature 20±2℃, pressure 0.60 atm), and the sample height H2 at this time is recorded (accurate to 1 mm). The settling rate is calculated as η=(H1-H2) / H1×100%, where H1 is the height after gas generation stabilizes. Each group of tests is conducted in parallel 3 times, and the arithmetic mean is taken.

[0055] (3) Dry density: The specimens cured to 28 days in each example were dried at (60±5)℃ to constant weight, cooled to room temperature, and weighed to an accuracy of 0.1 g. The dimensions of the specimens in all directions were measured using vernier calipers to an accuracy of 0.1 mm, and the volume was calculated. The dry density was calculated as the ratio of the dried mass to the volume, with the unit being kg / m³. 3 Three specimens were tested in each group, and the arithmetic mean was taken.

[0056] (4) Total porosity (P): The apparent density of the specimens was determined by the vacuum saturation method, and the total porosity was calculated as P = (1 - ρ0 / ρ1) × 100%, where ρ0 is the dry density of the specimen and ρ1 is the true density of the mixture of alkaline solid waste-based cementitious material and soil (determined by the specific gravity bottle method). Three specimens were tested in each group, and the arithmetic mean was taken.

[0057] (5) Compressive strength (f): According to JG / T 266, a 100 mm × 100 mm × 100 mm cube specimen cured for 28 days was used. The specimen was loaded at a rate of 2.0 kN / s until failure, and the load F was recorded (accurate to 0.1 kN). The compressive strength was calculated by f = F / A, where A is 10000 mm. 2 Three specimens were tested in each group, and the arithmetic mean was taken. If the difference between the maximum or minimum value and the median value exceeded 15% of the median value, the median value was taken.

[0058] (6) Specific strength: Calculated based on compressive strength and dry density, specific strength is the ratio of the two.

[0059] The test results are shown in Table 2: Table 2 Performance test results of Examples 1-4 As shown in Table 2, the foamed lightweight soil prepared in Examples 1-4 of this invention has a slurry expansion rate of more than 1.7 times, a settlement rate of less than 4%, a total porosity of more than 50%, a compressive strength of more than 1.2 MPa, and a specific strength of more than 1.73 kN⋅m / kg.

[0060] Comparative Example 1 Same as Example 3, except that the slow-release foaming agent is replaced with an aqueous solution of hydrogen peroxide, and the mass of hydrogen peroxide in the aqueous solution is the same as the content of hydrogen peroxide in 8 portions of slow-release foaming agent.

[0061] The performance tests conducted using the above method showed that the foaming duration in this comparative example was 3.5 min, the slurry expansion rate was 1.35 times, the settling rate was 11.23%, and the dry density was 1240 kg / m³. 3 The total porosity is 40.13%, the compressive strength is 1.38 MPa, and the specific strength is 1.11 kN⋅m / kg.

[0062] Comparative Example 2 Same as Example 3, except that the slow-release foaming agent is replaced by an intermediate (i.e., fly ash cenospheres loaded with hydrogen peroxide).

[0063] The performance tests conducted using the above method showed that the foaming duration in this comparative example was 9.3 min, the slurry expansion rate was 1.62 times, the settling rate was 5.53%, and the dry density was 935 kg / m³. 3 The total porosity is 48.12%, the compressive strength is 1.16 MPa, and the specific strength is 1.24 kN⋅m / kg.

[0064] Comparative Example 3 Same as Example 3, except that the use of hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer is omitted.

[0065] The performance tests conducted using the above method showed that the foaming duration in this comparative example was 17.8 min, the slurry expansion rate was 1.41 times, the settling rate was 12.53%, and the dry density was 1185 kg / m³. 3 The total porosity is 41.76%, the compressive strength is 1.39 MPa, and the specific strength is 1.17 kN⋅m / kg.

[0066] Comparative Example 4 Same as Example 3, except that in the preparation of the slow-release foaming agent, fly ash cenospheres were replaced by diatomaceous earth (with a specific surface area of ​​32 m²). 2 / g, moisture content ≤1%).

[0067] The performance tests conducted using the above method showed that the foaming duration in this comparative example was 10.5 min, the slurry expansion rate was 1.54 times, the settling rate was 7.65%, and the dry density was 965 kg / m³. 3 The total porosity is 46.23%, the compressive strength is 1.34 MPa, and the specific strength is 1.43 kN⋅m / kg.

[0068] Comparative Example 5 Same as Example 3, except that the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer is replaced by unmodified original zeolite.

[0069] The performance tests conducted using the above method showed that the foaming duration in this comparative example was 18.7 min, the slurry expansion rate was 1.57 times, the settling rate was 8.53%, and the dry density was 935 kg / m³. 3 The total porosity is 46.23%, the compressive strength is 1.34 MPa, and the specific strength is 1.43 kN⋅m / kg.

[0070] As can be seen from the above results, the foamed lightweight soil prepared in the embodiments of the present invention has good controllability of gas generation, bubble stability, volume retention, uniform pore structure, and lightweight and high-strength properties. Specifically, the gas generation process is slow and controllable, the slurry settlement rate is significantly reduced, the porosity is greatly increased and the pore size distribution is uniform. It effectively overcomes the problem of bubble rupture, merging and floating out caused by the explosive decomposition of hydrogen peroxide in high-altitude and low-pressure environments. It is suitable for roadbed backfilling, thermal insulation cushion layer or slope protection projects in high-altitude areas.

[0071] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A lightweight foamed soil based on alkaline solid waste suitable for high-altitude areas, characterized in that, The raw materials, by weight, include the following components: 90 parts alkaline solid waste-based cementitious material, 100 parts soil, 6-10 parts slow-release foaming agent, 0.2-0.5 parts hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer, and 95-105 parts water. The sustained-release foaming agent includes a porous carrier, hydrogen peroxide loaded in the porous carrier, and a sustained-release coating layer.

2. The alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in claim 1, characterized in that, The alkaline solid waste-based cementitious materials include slag powder, red mud, desulfurized gypsum, and carbide slag.

3. The alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in claim 2, characterized in that, The mass ratio of the slag powder, red mud, desulfurized gypsum, and carbide slag is 40:30:15:

5.

4. The alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in claim 1, characterized in that, The soil includes natural soil or engineering waste soil; the soil has a plasticity index of 10-17, a liquid limit of 30-45%, a plastic limit of 18-25%, and a moisture content of 15-25%.

5. The alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in claim 1, characterized in that, The preparation steps of the sustained-release foaming agent include: mixing an aqueous hydrogen peroxide solution and a porous carrier, ultrasonically treating the mixture, and then filtering and drying it to obtain an intermediate; mixing the intermediate, polylactic acid-glycolic acid copolymer, and an organic solvent, and ultrasonically emulsifying the mixture to obtain a primary emulsion; mixing the primary emulsion with an aqueous polyvinyl alcohol solution and stirring it to obtain a secondary emulsion; and subjecting the secondary emulsion to organic solvent evaporation, filtration, and drying to obtain the sustained-release foaming agent.

6. The alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in claim 5, characterized in that, The porous carrier includes fly ash cenospheres; the concentration of the hydrogen peroxide aqueous solution is 30 wt%; the mass ratio of the hydrogen peroxide aqueous solution to the porous carrier is 10-15:1; the concentration of the polyvinyl alcohol aqueous solution is 1 wt%; the mass ratio of the intermediate, polylactic acid-glycolic acid copolymer, and organic solvent is 1:1-2:5-8; and the volume ratio of the primary emulsion to the polyvinyl alcohol aqueous solution is 1:18-22.

7. The alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in claim 1, characterized in that, The preparation steps of the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer include: placing zeolite in a closed reaction chamber, evacuating the chamber, introducing a gaseous hydrophobic precursor, and performing chemical vapor deposition at 200-400℃ to obtain the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer.

8. The alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in claim 1, characterized in that, The gaseous hydrophobic precursor includes trimethylchlorosilane; the flow rate of the gaseous hydrophobic precursor is 100 mL / min; and the chemical vapor deposition time is 1-3 h.

9. A method for preparing alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas as described in any one of claims 1-8, characterized in that, Includes the following steps: Alkaline solid waste-based cementitious materials, soil, and water are mixed to obtain an alkaline slurry; The slow-release foaming agent and the hydrophobic / hydrophilic amphiphilic zeolite foam stabilizer are added to the alkaline slurry and stirred to obtain a mixed slurry; The mixed slurry is foamed, expanded, statically stopped, and cured to obtain the alkaline solid waste-based foamed lightweight soil suitable for high-altitude areas.

10. The application of alkaline solid waste-based foamed lightweight soil as described in any one of claims 1-8 in high-altitude areas for roadbed backfilling, thermal insulation layer or slope protection in high-altitude areas.

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