Carbon dioxide foamed lightweight solid waste-based soil and method of making same

Abstract

This invention relates to the field of solidified soil technology, and more particularly to a lightweight solid waste-based soil produced by carbon dioxide foaming and its preparation method. The raw materials for the aforementioned lightweight solid waste-based soil produced by carbon dioxide foaming, by weight, include: 40-65 parts of base soil, 15-25 parts of carbon dioxide foam, 15-25 parts of industrial solid waste, 5-8 parts of alkali activator, and 1-5 parts of water-retaining agent. The dry density of this invention is only 1.08-1.28 g / cm³. 3 Compared with traditional roadbed soil, it reduces the weight of the roadbed by 19-30%, effectively reducing the self-weight of the roadbed and lowering the risk of settlement and slippage; the 28-day compressive strength reaches 2.3-4.5MPa, combining high strength and good stability, meeting the engineering requirements of roadbed filling for high-grade highways, slope protection and other applications.

Description

Technical Field

[0001] This invention relates to the field of solidified soil technology, and in particular to a lightweight solid waste-based soil foamed with carbon dioxide and its preparation method. Background Technology

[0002] In the field of infrastructure construction, roadbed fill is a core basic material for road engineering, and its performance directly affects the stability, load-bearing capacity, and service life of the road structure. Traditional roadbed fill mostly uses natural soil, but the reserves of natural soil resources are limited, and traditional soil is heavy. When used in high-grade highways, slope backfilling, and other scenarios, it is prone to engineering hazards such as roadbed settlement and slope slippage due to excessive weight, increasing the cost of later maintenance.

[0003] Meanwhile, the large amount of high-moisture-content foundation soil generated during engineering construction (such as soil generated during foundation pit excavation and river dredging) generally has a moisture content as high as 60-80%, strong particle dispersion, and poor shaping stability, making it difficult to use directly as roadbed fill. Traditional disposal methods mostly involve off-site stockpiling or landfilling, which not only occupies a large amount of land resources but also easily causes ecological problems such as soil erosion and groundwater pollution, resulting in resource waste and environmental pressure.

[0004] With the deepening of the "dual-carbon" strategy, carbon capture, utilization, and storage (CCS) has become a key technological path for addressing global climate change. As a major greenhouse gas, carbon dioxide emissions from the industrial sector require resource utilization as a crucial direction for achieving carbon reduction targets. Currently, carbon dioxide storage and utilization technologies are mostly concentrated in areas such as chemical synthesis and geological storage, while their application in roadbed engineering materials remains in the exploratory stage.

[0005] While existing subgrade filling improvement technologies have attempted to achieve lightweighting using foaming agents, they mostly rely on chemical foaming agents (such as azo and sulfonyl hydrazide). These foaming agents are not only expensive, but also release harmful gases during preparation and use, polluting the environment. At the same time, existing lightweight filling technologies do not combine carbon capture with subgrade performance improvement, making it impossible to realize the resource utilization of carbon dioxide, which contradicts the concept of low-carbon and green construction.

[0006] On the other hand, the annual output of bulk solid waste (such as desulfurization gypsum and slag) generated in industrial production is enormous. If directly dumped, it will not only occupy land but also cause soil and water pollution due to leaching and weathering processes. Although some solid waste has been applied in the field of building materials, its high-value utilization in roadbed filling is still insufficient. Existing technologies are unable to achieve the coordinated development of solid waste resource utilization, soil improvement and carbon capture.

[0007] In summary, the current field of roadbed filling faces three core problems: First, high-moisture-content foundation soils are difficult to utilize directly, resulting in significant resource waste and environmental pressure; second, traditional roadbed fillings are heavy, lack stability, and have limited capacity for natural soil extraction; and third, carbon dioxide capture and industrial solid waste resource utilization have not yet been effectively integrated with roadbed filling technology, and there is a lack of new roadbed filling materials and preparation technologies that combine lightweight, high strength, and carbon sequestration functions.

[0008] Therefore, developing a lightweight roadbed fill material based on carbon capture and resource utilization to achieve resource utilization of high moisture content soil and industrial solid waste and carbon dioxide sequestration, while improving the engineering performance of roadbed fill, has become an urgent technical need to be addressed in this field. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing a lightweight solid waste-based soil with carbon dioxide foaming and its preparation method. Specifically, it aims to achieve the following objectives: (1) to efficiently utilize high-moisture-content basic soil with a moisture content of 60-80%, without additional dehydration treatment, thus solving the problems of its inability to be directly used as roadbed fill, environmental pollution from off-site dumping, and waste of resources; (2) to combine carbon capture and resource utilization technologies to stably seal carbon dioxide in lightweight soil, thereby realizing the carbon sequestration function of roadbed fill materials and contributing to the implementation of the "dual carbon" strategy; (3) to realize the high-value utilization of industrial solid wastes such as desulfurized gypsum and slag, reduce the ecological pollution caused by solid waste dumping, and lower the cost of roadbed fill raw materials; (4) to prepare lightweight fill material with low self-weight, high strength, and good stability, optimize the engineering performance of roadbed fill, and avoid the hidden dangers of settlement and slippage caused by the heavy self-weight of traditional roadbed fill.

[0010] A lightweight solid waste-based soil with carbon dioxide foaming, the raw materials of which include, by weight: 42-65 parts of basic soil, 15-25 parts of carbon dioxide foam, 15-25 parts of industrial solid waste, 5-8 parts of alkali activator, and 1-5 parts of water-retaining agent.

[0011] Preferably, the dry density of the carbon dioxide-foamed lightweight solid waste-based soil is 1.08-1.28 g / cm³. 3 The 28-day compressive strength is 2.3-4.5 MPa, and the carbon fixation rate is 50-60%.

[0012] Preferably, the industrial solid waste includes desulfurized gypsum and slag, with the mass ratio of desulfurized gypsum to slag being 30-50:50-70.

[0013] More preferably, the particle size of the desulfurized gypsum is 0.08 mm.

[0014] More preferably, the slag is S95 grade slag powder with a particle size of 46-100μm.

[0015] Preferably, the carbon dioxide foam is obtained by agitating a foaming solution in a closed carbon dioxide environment.

[0016] More preferably, the foaming solution comprises: dodecylamine polyoxyethylene ether and hydroxypropyl methylcellulose; the concentration of dodecylamine polyoxyethylene ether is 4-5 g / L, and the concentration of hydroxypropyl methylcellulose is 1-3 g / L.

[0017] Specifically, carbon dioxide foam is prepared by the following steps: injecting the foaming solution into a closed foaming machine, introducing carbon dioxide gas into the foaming machine to maintain the internal pressure at 0.25-0.30 MPa, and stirring at a stirring rate of 400-800 r / min for 20-30 minutes.

[0018] Specifically, the carbon dioxide foam has a foam half-life of ≥30 min and a pore size of 0.5-1.2 mm; preferably, the pore size is 0.9 mm.

[0019] Preferably, the base soil is waste soil from roadbed construction or waste mud from engineering projects, with a natural moisture content of 60-80% and a particle size ≤2mm.

[0020] More preferably, the water content of the engineering waste mud is 70%.

[0021] Preferably, the alkali activator is magnesium oxide with a particle size ≤ 0.1 mm; more preferably, the particle size is 0.08 mm.

[0022] Preferably, the water-retaining agent is anionic polyacrylamide with a molecular weight of 12-13 million and a water absorption rate of ≥300 times.

[0023] Preferably, the raw materials also include: synergist; the mass ratio of industrial solid waste to synergist is 15-20:0-3.

[0024] More preferably, the synergist is prepared by the following steps: polyaspartic acid and silica sol are added to water and stirred evenly. The pH of the system is adjusted to 2-3, the temperature is raised to 80-100℃, the reflux condenser is turned on, and nitrogen gas is bubbled through the system. The mixture is stirred for 2-4 hours, cooled to room temperature, cobalt phthalocyanine is added and ultrasonically treated at room temperature for 10-30 minutes, the temperature is raised to 60-70℃ under nitrogen protection, and sodium hydroxide solution is added dropwise while stirring to adjust the pH of the system to 9-10. The mixture is kept at a constant temperature and stirred for 2-3 hours, centrifuged, washed, freeze-dried, and pulverized.

[0025] The synergist uses a combination of polyaspartic acid and silica sol to support cobalt phthalocyanine, which can stably catalyze the reaction of CO2 and water to produce HCO3. - It promotes the reaction between the product and the alkali activator (MgO) to generate magnesium carbonate gel products, simultaneously achieving foam stabilization and CO2 mineralization and sequestration, and has high compressive strength while ensuring dry density.

[0026] More preferably, the molecular weight of polyaspartic acid is 5000-8000.

[0027] More preferably, the mass ratio of polyaspartic acid, silica sol, and cobalt phthalocyanine is 1-5:1-3:3-6.

[0028] The method for preparing the above-mentioned carbon dioxide foamed lightweight solid waste-based soil includes the following steps:

[0029] S1. Pour the basic soil, industrial solid waste powder, and alkali activator into a high-speed mixer and mix for 30-40 minutes. Adjust the mixing speed to 1100-1300 r / min to obtain a dry mixture.

[0030] S2. Inject the remaining raw materials into the dry mix to obtain lightweight soil premix;

[0031] S3. The lightweight soil pre-mixed material is laid out in layers, with each layer controlled to be 20-30cm thick. It is aged and matured for 12-24 hours, turning it over once every 4-6 hours, for a total of 2-3 times. The purpose of S3 is to release the internal air bubble stress of the mixture, balance the moisture distribution, and promote the initial reaction of carbon dioxide with the alkali activator and soil components, thereby improving the structural stability after subsequent construction and compaction.

[0032] S4. The aged and matured lightweight soil is delivered to the construction area, spread in layers, statically compacted 2-3 times, and naturally cured for 7-14 days (during the curing period, the surface is kept moist, and spraying can be used to keep it moist, avoiding water accumulation, and utilizing natural environmental conditions to complete the solidification reaction, ultimately forming lightweight soil that meets the requirements for roadbed use).

[0033] Preferably, in S1, the basic soil must be sieved through a 10-mesh sieve to remove impurities such as gravel, weeds, and roots, and then naturally piled up for later use.

[0034] Preferably, in step S1, the desulfurized gypsum, slag, and alkali activator are placed together in a forced-air drying oven and dried at a temperature of 105°C for 4 hours. After drying, the powder is removed and passed through a 200-mesh sieve, and the powder passing through the sieve is collected as a dry material component for later use.

[0035] Preferably, in S4, the thickness of each layer of the paving is 20cm.

[0036] Preferably, in S4, a light roller is used for static compaction, with a compaction degree of 93-95%, without the need for additional pressure molding.

[0037] The formula for calculating the carbon fixation rate is as follows: .

[0038] Where C is the carbon sequestration rate of lightweight soil, m1 is the mass lost by the obtained carbon dioxide foamed lightweight solid waste soil sample when heated from 560℃ to 800℃, and m2 is the mass of carbon dioxide absorbed by the foaming solution in the closed foaming machine.

[0039] The carbonation reaction process that occurs during the mixing of carbon dioxide foam and the mixed slurry is as follows:

[0040] MgO + H₂O → Mg(OH)₂

[0041] Mg(OH)2+CO2+2H2O→MgCO3•3H2O,

[0042] 5Mg(OH)2+4CO2+4H2O→Mg5(CO3)4(OH)2·4H2O,

[0043] 5Mg(OH)2+4CO2+5H2O→(Mg)5(CO3)4(OH)2·5H2O,

[0044] Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

[0045] 3CaO•2SiO2•3H2O+CO2→CaCO3+2CaO•2SiO2•3H2O

[0046] 3CaO•2SiO2•3H2O+2CO2→2CaCO3+CaO•2SiO2•3H2O

[0047] 3CaO•2SiO2•3H2O+3CO2→3CaCO3+2SiO2•3H2O.

[0048] Compared with existing technologies, the present invention has the following advantages:

[0049] (1) Resource utilization and environmental protection synergy: The high moisture content of the basic soil with a moisture content of 60-80% can be directly utilized without dehydration treatment, thus reducing energy consumption; at the same time, industrial solid waste such as desulfurized gypsum and slag can be digested to realize the resource utilization of solid waste and reduce the pollution of stockpiling; carbon dioxide can be stably sealed in the soil with a carbon sequestration rate of 50-60%, providing a new carbon sink path for the roadbed engineering field and helping to achieve the "dual carbon" goal.

[0050] like Figure 3 As shown, when treating waste foundation soil, the resource utilization method of roadbed filling has the lowest carbon emissions, highlighting the green and environmentally friendly nature of this invention.

[0051] (2) Significantly improved engineering performance: The dry density of the finished product is only 1.08-1.28 g / cm³. 3Compared with traditional roadbed soil, it reduces the weight of the roadbed by 19-30%, effectively reducing the self-weight of the roadbed and lowering the risk of settlement and slippage; the 28-day compressive strength reaches 1.9-4.5MPa, combining high strength and good stability, meeting the engineering requirements of roadbed filling for high-grade highways, slope protection and other applications.

[0052] (3) The process is adapted to the actual engineering: the preparation process is simplified, and after aging and maturation, it can be directly transported to the site for paving and compaction. It can be formed by natural curing without the need for special curing equipment. It is adapted to the needs of large-scale and continuous construction of roadbed engineering, and reduces production and construction costs. The foaming solution uses environmentally friendly components, with no release of harmful gases. Carbon dioxide foaming replaces traditional chemical foaming agents, avoiding environmental pollution and conforming to the concept of low-carbon and green construction.

[0053] (4) Wide range of applications: It is applicable to multiple engineering fields such as highway and railway subgrade backfilling, slope protection, and municipal road subgrade improvement. It is especially suitable for construction scenarios that are sensitive to the self-weight of the fill soil and have high environmental protection requirements. It provides technical support for the upgrading and iteration of subgrade fill soil materials and has extremely high promotion and application value. Attached Figure Description

[0054] Figure 1 This is a schematic flowchart of a method for preparing lightweight solid waste-based soil using carbon dioxide foaming, as proposed in this invention.

[0055] Figure 2 This is a performance comparison chart for different carbon dioxide foam dosages.

[0056] Figure 3 This is a comparison chart of carbon emissions under different methods of waste soil disposal. Detailed Implementation

[0057] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0058] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0059] The desulfurized gypsum used below was purchased from Hubei Puhui Building Materials Co., Ltd., with a particle size of 0.08 mm. The slag used below is S95 grade slag powder, purchased from Hebei Huishun Mining Co., Ltd., with a particle size of 50-100 μm. The alkali activator used below is magnesium oxide, with a particle size of 0.08 mm. The water-retaining agent used below is anionic polyacrylamide, with a molecular weight of 12-13 million and a water absorption rate ≥300 times. The polyaspartic acid used below was purchased from Hubei Xinghengye Technology Co., Ltd., with a density of 1.2 g / cm³. 3 The molecular weight is 1000-5000. The silica sol used below was purchased from Hubei Xingdongcheng Chemical Co., Ltd., and its density is 1.20±0.02 g / cm³. 3 The silica content is 20%. The cobalt phthalocyanine used below was purchased from Thermo Fisher Scientific.

[0060] like Figure 1 As shown, a method for preparing carbon dioxide foamed lightweight solid waste-based soil includes the following steps:

[0061] S1. Pour the basic soil, industrial solid waste powder, and alkali activator into a high-speed mixer and mix for 30-40 minutes. Adjust the mixing speed to 1100-1300 r / min to obtain a dry mixture.

[0062] S2. Inject the remaining raw materials into the dry mix to obtain lightweight soil premix;

[0063] S3. The lightweight soil raw material is laid out in layers, with each layer controlled at a thickness of 20-30cm. It is aged and matured for 12-24 hours, turning it over once every 4-6 hours, for a total of 2-3 times.

[0064] S4. After aging and maturing, the lightweight soil is delivered to the construction area, spread in layers, statically pressed 2-3 times, and naturally cured for 7-14 days.

[0065] All quantities used in the following examples are parts by weight.

[0066] Example 1

[0067] The raw materials and their quantities used in this embodiment are as follows: 45 parts of basic soil, 22 parts of carbon dioxide foam, 20 parts of industrial solid waste (8 parts of desulfurized gypsum + 12 parts of slag), 6 parts of alkali activator, and 3 parts of water-retaining agent.

[0068] Prepare a foaming solution (a mixed aqueous solution of 4.5 g / L dodecylamine polyoxyethylene ether and 2 g / L hydroxypropyl methylcellulose), inject it into a closed foaming machine, introduce carbon dioxide gas into the machine to maintain the internal pressure at 0.3 MPa, maintain a stirring speed of 600 r / min, and stir for 25 min to obtain carbon dioxide foam with a pore size of 0.8-1.0 mm.

[0069] The preparation process is as follows: The base soil is soil generated from the excavation of the foundation pit (moisture content 60%), which is passed through a 10-mesh sieve to remove impurities and naturally piled up for later use; Desulfurized gypsum, slag and alkali activator are placed together in a forced-air drying oven and dried at 105℃ for 4 hours. After being taken out, it is ground in a ball mill and passed through a 200-mesh sieve. The powder that passes through the sieve is collected as the dry material component for later use; The water-retaining agent is used directly; The pretreated base soil, industrial solid waste powder and alkali activator are weighed and poured into a high-speed mixer. The speed is adjusted to 1200r / min and mixed for 35 minutes to obtain a uniform dry mixture (no obvious lumps and uniform color); Carbon dioxide foam and water-retaining agent are slowly injected into the mixer containing the dry mixture and adjusted... Mix at 80 r / min for 10 minutes to ensure the foam is evenly dispersed in the mixture without stratification or bubble agglomeration, resulting in lightweight soil pre-mixed material. Transport the lightweight soil pre-mixed material to a temporary storage site, spread it in layers, with each layer controlled at a thickness of 25 cm, and age it for 18 hours, turning it over every 5 hours during this period, avoiding violent stirring. Transport the aged lightweight soil to the roadbed construction section, spread it in layers of 30 cm thickness, and use a 3t light roller to statically compact it twice, controlling the compaction degree at 94%. After spreading and compaction, spray it with moisture once a day to prevent the surface from drying and cracking, and allow it to cure naturally for 10 days to complete solidification.

[0070] After 28 days of curing, random samples were taken from the roadbed construction section for testing. The finished product performance indicators are as follows: dry density 1.15 g / cm³. 3 The 28-day compressive strength is 2.2 MPa, the carbon fixation rate is 58%, and there is no significant settlement after compaction, which meets the technical requirements for subgrade filling of secondary highways.

[0071] Example 2

[0072] The raw materials and their quantities used in this embodiment are as follows: 50 parts of basic soil, 20 parts of carbon dioxide foam, 18 parts of industrial solid waste (5.4 parts of desulfurized gypsum + 12.6 parts of slag), 7 parts of alkali activator, and 2.5 parts of water-retaining agent.

[0073] Prepare a foaming solution (a mixed aqueous solution of 4.5 g / L dodecylamine polyoxyethylene ether and 2 g / L hydroxypropyl methylcellulose), inject it into a closed foaming machine, introduce carbon dioxide gas into the machine to maintain the internal pressure at 0.28 MPa, maintain a stirring rate of 600 r / min, and stir for 30 min to obtain carbon dioxide foam with a pore size of 0.8-1.0 mm.

[0074] The preparation process is as follows: The base soil is high-moisture soil generated from the excavation of the foundation pit, with a natural moisture content of 65%, and is passed through a 10-mesh sieve to remove impurities before use; desulfurized gypsum, slag, and alkali activator are dried at 110℃ for 3.5 hours, ground, and passed through a 200-mesh sieve before use; each dry material component is weighed and put into a high-speed mixer and mixed at 1100 r / min for 40 minutes to obtain a uniform dry mixture; carbon dioxide foam and water-retaining agent are slowly injected into the mixer containing the dry mixture and mixed at 70 r / min for 12 minutes to ensure that the foam and materials are fully integrated; the mixture is laid in layers with a thickness of 20 cm and aged for 12 hours, turning it over once every 4 hours, for a total of 3 times; it is spread in layers of 25 cm and compacted three times with a 3t light roller to achieve a compaction degree of 95%; it is naturally cured for 10 days, during which time the surface is kept moist.

[0075] After 28 days of curing, the dry density of the finished product was measured to be 1.20 g / cm³. 3 With a 28-day compressive strength of 2.0 MPa and a carbon fixation rate of 52%, it is suitable for slope protection and subgrade backfilling projects on secondary highways.

[0076] Example 3

[0077] The raw materials and their quantities used in this embodiment are as follows: 42 parts of basic soil, 25 parts of carbon dioxide foam, 23 parts of industrial solid waste (11.5 parts of desulfurized gypsum + 11.5 parts of slag), 5 parts of alkali activator, and 4 parts of water-retaining agent.

[0078] Prepare a foaming solution (a mixed aqueous solution of 4.5 g / L dodecylamine polyoxyethylene ether and 2 g / L hydroxypropyl methylcellulose), inject it into a closed foaming machine, introduce carbon dioxide gas into the machine to maintain the internal pressure at 0.32 MPa, maintain a stirring rate of 600 r / min, and stir for 22 min to obtain carbon dioxide foam with a pore size of 0.9-1.2 mm.

[0079] The preparation process is as follows: The base soil is soil excavated from landscaping projects, with a natural moisture content of 75%, and impurities are removed by passing it through a 10-mesh sieve; industrial solid waste and alkali activator are dried at 100℃ for 5 hours, ground, and then passed through a 200-mesh sieve; each dry material component is mixed at 1300 r / min for 30 minutes to obtain a dry mixture; carbon dioxide foam and water-retaining agent are slowly injected into a mixer containing the dry mixture, and mixed at 90 r / min for 8 minutes to ensure uniform foam dispersion; the mixture is laid to a thickness of 30 cm and aged for 24 hours, turning it over once every 6 hours during this period; it is spread to the construction site in 40 cm / layers, and statically compacted twice with a 5t light roller, achieving a compaction degree of 93%; it is naturally cured for 14 days, with a spray moisturizing frequency of twice a day (once in the morning and once in the evening).

[0080] After 28 days of curing, the dry density of the finished product was measured to be 1.17 g / cm³. 3With a 28-day compressive strength of 1.9 MPa and a carbon fixation rate of 60%, it exhibits outstanding lightweight properties and is suitable for soft soil foundation roadbed improvement and backfilling projects.

[0081] This invention further uses carbon dioxide content as a variable, while keeping all other conditions constant. For example... Figure 2 As shown, with the increase of carbon dioxide content, the dry density and 28-day compressive strength of the finished product both decreased.

[0082] Example 4

[0083] The raw materials and their quantities used in this embodiment are as follows: 50 parts of basic soil, 20 parts of carbon dioxide foam, 18 parts of industrial solid waste (5.4 parts of desulfurized gypsum + 12.6 parts of slag), 7 parts of alkali activator, 2.5 parts of water-retaining agent, and 2.5 parts of synergist.

[0084] Prepare a foaming solution (a mixed aqueous solution of 4.5 g / L dodecylamine polyoxyethylene ether and 2 g / L hydroxypropyl methylcellulose), inject it into a closed foaming machine, introduce carbon dioxide gas into the machine to maintain the internal pressure at 0.28 MPa, maintain a stirring rate of 600 r / min, and stir for 30 min to obtain carbon dioxide foam with a pore size of 0.8-1.0 mm.

[0085] The synergist was prepared using the following steps: 2 parts polyaspartic acid and 2.5 parts silica sol were added to 50 parts deionized water and stirred until homogeneous. The pH of the system was adjusted to 2-3 using 2.5 mol / L hydrochloric acid. The temperature was raised to 95°C, and the reflux condenser was turned on while nitrogen was bubbled through. The mixture was stirred at 250 r / min for 3.5 h. After cooling to room temperature, 4 parts cobalt phthalocyanine were added and ultrasonically treated at room temperature for 25 min at a frequency of 55 kHz. The temperature was raised to 68°C under nitrogen protection. While stirring, 0.5 mol / L sodium hydroxide solution was added dropwise to adjust the pH of the system to 9-10. The mixture was stirred at a constant temperature for 2.2 h. After centrifugation, the precipitate was washed with deionized water, freeze-dried, and pulverized through a 100-mesh sieve.

[0086] The preparation process is as follows: The base soil is high-moisture soil generated from the excavation of the foundation pit, with a natural moisture content of 65%, and is passed through a 10-mesh sieve to remove impurities before use; desulfurized gypsum, slag, and alkali activator are dried at 110℃ for 3.5 hours, ground, and then passed through a 200-mesh sieve before use; each dry material component is weighed and placed in a high-speed mixer at 1100 r / min for 40 minutes to obtain a uniform dry mixture; carbon dioxide foam, water-retaining agent, and synergist are slowly injected into the mixer containing the dry mixture and mixed at 70 r / min for 12 minutes to ensure that the foam and materials are fully integrated; the mixture is laid in layers with a thickness of 20 cm and aged for 12 hours, turning it over once every 4 hours for a total of 3 times; it is spread in 25 cm layers and statically compacted 3 times with a 3t light roller to achieve a compaction degree of 95%; it is naturally cured for 10 days, during which time the surface is kept moist.

[0087] After 28 days of curing, the dry density of the finished product was measured to be 1.22 g / cm³. 3 28-day compressive strength is 3.1 MPa, and carbon fixation rate is 54%.

[0088] Example 5

[0089] The raw materials and their quantities used in this embodiment are as follows: 42 parts of basic soil, 25 parts of carbon dioxide foam, 23 parts of industrial solid waste (11.5 parts of desulfurized gypsum + 11.5 parts of slag), 5 parts of alkali activator, 4 parts of water-retaining agent, and 1 part of synergist.

[0090] Prepare a foaming solution (a mixed aqueous solution of 4.5 g / L dodecylamine polyoxyethylene ether and 2 g / L hydroxypropyl methylcellulose), inject it into a closed foaming machine, introduce carbon dioxide gas into the machine to maintain the internal pressure at 0.32 MPa, maintain a stirring rate of 600 r / min, and stir for 22 min to obtain carbon dioxide foam with a pore size of 0.9-1.2 mm.

[0091] The synergist was prepared using the following steps: 3 parts polyaspartic acid and 2 parts silica sol were added to 60 parts deionized water and stirred until homogeneous. The pH of the system was adjusted to 2-3 using 2.5 mol / L hydrochloric acid. The temperature was raised to 90°C, and the reflux condenser was turned on while nitrogen was bubbled through. The mixture was stirred at 300 r / min for 3 h. After cooling to room temperature, 4.5 parts cobalt phthalocyanine were added and ultrasonically treated at room temperature for 20 min at a frequency of 60 kHz. The temperature was raised to 65°C under nitrogen protection. While stirring, 0.5 mol / L sodium hydroxide solution was added dropwise to adjust the pH of the system to 9-10. The mixture was stirred at a constant temperature for 2.5 h. After centrifugation, the precipitate was washed with deionized water, freeze-dried, and pulverized through a 100-mesh sieve.

[0092] The preparation process is as follows: The base soil is soil excavated from landscaping projects, with a natural moisture content of 75%, and is sieved through a 10-mesh sieve to remove impurities; industrial solid waste and alkali activator are dried at 100℃ for 5 hours, ground, and then sieved through a 200-mesh sieve; each dry material component is mixed at 1300 r / min for 30 minutes to obtain a dry mixture; carbon dioxide foam, water-retaining agent, and synergist are slowly injected into a mixer containing the dry mixture, and mixed at 90 r / min for 8 minutes to ensure uniform foam dispersion; the mixture is laid to a thickness of 30 cm and aged for 24 hours, turning it over every 6 hours during this period; it is spread to the construction site in 40 cm / layers, and statically compacted twice with a 5t light roller, achieving a compaction degree of 93%; it is naturally cured for 14 days, with a spray moisturizing frequency of twice a day (once in the morning and once in the evening).

[0093] After 28 days of curing, the dry density of the finished product was measured to be 1.15 g / cm³. 3 It has a 28-day compressive strength of 3.6 MPa, a carbon fixation rate of 57%, and outstanding lightweight properties.

[0094] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A lightweight solid waste-based soil that is foamed with carbon dioxide, characterized in that, Its raw materials, by weight, include: 40-65 parts basic soil, 15-25 parts carbon dioxide foam, 15-25 parts industrial solid waste, 5-8 parts alkali activator, and 1-5 parts water-retaining agent.

2. The lightweight solid waste-based soil with carbon dioxide foaming according to claim 1, characterized in that, Industrial solid waste includes desulfurized gypsum and slag, with a mass ratio of 30-50:50-70 for desulfurized gypsum and slag.

3. The lightweight solid waste-based soil foamed with carbon dioxide according to claim 1, characterized in that, The desulfurized gypsum has a particle size of 0.05-0.1 mm; the slag is S95 grade slag powder with a particle size of 40-100 μm.

4. The lightweight solid waste-based soil foamed with carbon dioxide according to claim 1, characterized in that, Carbon dioxide foam is obtained by agitating a foaming solution in a closed carbon dioxide environment; The foaming solution includes: dodecylamine polyoxyethylene ether and hydroxypropyl methylcellulose; the concentration of dodecylamine polyoxyethylene ether is 4-5 g / L, and the concentration of hydroxypropyl methylcellulose is 1-3 g / L.

5. The lightweight solid waste-based soil foamed with carbon dioxide according to claim 1, characterized in that, The base soil is waste soil from roadbed construction or engineering waste mud, with a natural moisture content of 60-80% and a particle size of ≤2mm.

6. The lightweight solid waste-based soil foamed with carbon dioxide according to claim 1, characterized in that, The alkaline activator is magnesium oxide with a particle size ≤0.1mm.

7. The lightweight solid waste-based soil foamed with carbon dioxide according to claim 1, characterized in that, The water-retaining agent is anionic polyacrylamide with a molecular weight of 12-13 million and a water absorption rate of ≥300 times.

8. The lightweight solid waste-based soil foamed with carbon dioxide according to claim 1, characterized in that, Its raw materials also include: synergist; the mass ratio of industrial solid waste to synergist is 15-20:0-3; The synergist is prepared by the following steps: Polyaspartic acid and silica sol are added to water and stirred evenly. The pH of the system is adjusted to 2-3, the temperature is raised to 80-100℃, the reflux condenser is turned on, and nitrogen gas is bubbled through the system. The mixture is stirred for 2-4 hours, cooled to room temperature, cobalt phthalocyanine is added and ultrasonically treated at room temperature for 10-30 minutes, the temperature is raised to 60-70℃ under nitrogen protection, and sodium hydroxide solution is added dropwise while stirring to adjust the pH of the system to 9-10. The mixture is kept at a constant temperature and stirred for 2-3 hours, centrifuged, washed, freeze-dried, and pulverized.

9. The lightweight solid waste-based soil foamed with carbon dioxide according to claim 8, characterized in that, The molecular weight of polyaspartic acid is 5000-8000; the mass ratio of polyaspartic acid, silica sol, and cobalt phthalocyanine is 1-5:1-3:3-6.

10. The method for preparing carbon dioxide foamed lightweight solid waste-based soil according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Pour the basic soil, industrial solid waste powder, and alkali activator into a high-speed mixer and mix for 30-40 minutes. Adjust the mixing speed to 1100-1300 r / min to obtain a dry mixture. S2. Inject the remaining raw materials into the dry mix to obtain lightweight soil premix; S3. The lightweight soil raw material is laid out in layers, with each layer controlled at a thickness of 20-30cm. It is aged and matured for 12-24 hours, turning it over once every 4-6 hours, for a total of 2-3 times. S4. After aging and maturing, the lightweight soil is delivered to the construction area, spread in layers, statically pressed 2-3 times, and naturally cured for 7-14 days.

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