Coal-fired slag-based foam light soil roadbed and construction method thereof

Abstract

This application relates to the field of roadbed construction materials and methods, specifically disclosing a coal-fired slag-based foamed lightweight soil roadbed and its construction method. The coal-fired slag-based foamed lightweight soil roadbed is constructed by laying coal-fired slag-based foamed lightweight soil, which includes slag-based aggregates. The slag-based aggregates include slag-based microspheres. The preparation of the slag-based microspheres includes the following steps: adding a bio-carbon source and slag powder to a glacial acetic acid solution, stirring evenly, and then adding it dropwise to a sodium hydroxide solution to obtain granules; washing the granules until neutral, freeze-drying, and calcining under nitrogen protection to obtain slag-based aggregates. The roadbed construction method includes the following steps: S1, excavating the roadbed; S2, base treatment; S3, installing construction templates; S4, pouring coal-fired slag-based foamed lightweight soil; S5, laying galvanized wire mesh; S6, laying impermeable geotextile; S7, curing. This application has the effect of reducing the probability of roadbed cracking.

Description

Technical Field

[0001] This application relates to the field of roadbed construction materials and construction methods, and in particular to a coal-fired slag-based foamed lightweight soil roadbed and its construction method. Background Technology

[0002] Foamed lightweight soil is a lightweight fill material formed by thoroughly mixing foam, gelling materials, water, admixtures, and additives according to a certain mix ratio, and then solidifying it. Due to its advantages such as lightweight, adjustable strength and density, good fluidity, and vertical pouring, foamed lightweight soil can replace conventional earth fill for roadbed construction, effectively reducing foundation settlement and additional stress. This helps solve highway problems such as soft soil settlement, bridge approach slab settlement, slope stability of high embankment roadbeds, and frost heave in frozen soil roadbeds.

[0003] Coal ash, or simply coal ash, is the waste residue discharged from coal-fired power plants, industrial and domestic boilers, and other equipment after burning coal. Adding coal ash to foamed lightweight soil not only reduces costs, improves the workability of raw materials, and simplifies construction, but also promotes the recycling of coal ash, aligning with the concept of sustainable development.

[0004] Coal slag contains free magnesium oxide (f-MgO). Free magnesium oxide (f-MgO) reacts slowly with water. After the foamed lightweight soil solidifies, the free magnesium oxide (f-MgO) continues to react to produce magnesium hydroxide. The reaction is accompanied by volume expansion, which causes the foamed lightweight soil subgrade to crack under the effect of volume. In severe cases, the cracks extend to the road surface, affecting the service life of the highway and driving safety. Summary of the Invention

[0005] In order to improve the volume stability of foamed lightweight soil and thus reduce the probability of roadbed cracking, this application provides a coal-fired slag-based foamed lightweight soil roadbed and its construction method.

[0006] Firstly, the technical solution for a coal-fired slag-based foamed lightweight soil subgrade provided in this application is as follows:

[0007] A type of lightweight foamed soil roadbed based on coal slag is paved with lightweight foamed soil based on coal slag. The lightweight foamed soil based on coal slag comprises the following raw materials in parts by weight: 18-30 parts silicate cement; 30-50 parts coal slag-based aggregate; 10-18 parts mixing water; 2-4 parts foam; and 1.2-2 parts foam stabilizer.

[0008] The slag-based aggregate includes slag-based microspheres. The preparation of the slag-based microspheres includes the following steps: adding a bio-carbon source and slag powder to a glacial acetic acid solution, stirring evenly, and then adding it dropwise to a sodium hydroxide solution to obtain granules; washing the granules until neutral, freeze-drying them, and calcining them under nitrogen protection to obtain the slag-based aggregate.

[0009] By adopting the above technical solution, during the preparation of coal slag-based microspheres, coal slag powder is captured by a biological carbon source, thereby embedding the coal slag powder into the biological carbon source. The synthesized coal slag-based microspheres have a porous structure. Some of the magnesium oxide in the coal slag powder is encapsulated, making it difficult for it to contact water molecules. The remaining magnesium oxide reacts with water molecules in the sodium hydroxide solution to generate magnesium hydroxide. After freeze-drying and calcination, the magnesium hydroxide is pyrolyzed into magnesium oxide, releasing water vapor at the same time. This forms a porous structure with pore walls modified by nano-ions, which increases the specific surface area and pore volume of the coal slag-based microspheres. During the curing of foamed lightweight soil, the exposed free magnesium oxide hydrates and expands. The pore size of the coal slag-based microspheres provides expansion space for the free magnesium oxide, reducing the probability of cracking of the foamed lightweight soil subgrade under the effect of volume effect, improving the volume stability of the foamed lightweight soil, and thus reducing the probability of subgrade cracking.

[0010] Optionally, the bio-carbon source includes beer waste powder, and the preparation of the beer waste powder includes the following steps: allowing beer wastewater to stand, centrifuging, drying, and then grinding it to obtain beer waste powder.

[0011] By adopting the above technical solutions, the application of beer wastewater conforms to the concept of circular economy. The beer residue powder prepared from beer wastewater is rich in carbon source. The granules prepared from beer residue powder and coal slag powder are freeze-dried and calcined, resulting in improved compressive strength of the coal slag-based aggregate. During the preparation of coal slag-based aggregate, beer residue powder consumes oxygen, increasing the carbon dioxide concentration. Some magnesium oxide reacts with carbon dioxide to produce magnesium carbonate, improving the stability of the coal slag. This reduces the probability of cracking in foamed lightweight soil subgrade under the effect of volume effect, improves the volume stability of foamed lightweight soil, and thus reduces the probability of subgrade cracking.

[0012] Optionally, the ammonia nitrogen concentration in the beer wastewater is no more than 25%.

[0013] By adopting the above technical solutions, the ammonia nitrogen content in beer wastewater is controlled, thereby reducing the nitrogen content of beer waste residue powder, lowering the nitrogen content of coal slag-based aggregates, and improving chemical oxidation stability.

[0014] Optionally, the slag-based aggregate further includes low-melting-point glass powder, wherein the weight ratio of the low-melting-point glass powder to the slag-based microspheres is (6-8):(17-20).

[0015] By adopting the above technical solution, the low-melting-point glass powder is melted and then solidified into powdered coal slag-based microspheres. The resulting aggregate has high chemical stability and high mechanical strength, which improves the volume stability of foamed lightweight soil and thus reduces the probability of roadbed cracking.

[0016] Optionally, the preparation of the slag-based aggregate includes the following steps: after mixing and homogenizing slag-based microspheres and low-melting-point glass powder, stirring and heating to 380-400℃, stirring continuously for 20-30 minutes, allowing to stand and cool, and then granulating to obtain the slag-based aggregate.

[0017] By adopting the above technical solution, molten low-melting-point glass powder encapsulates or binds slag-based microspheres, increasing the particle size of the aggregate and improving the compressive strength of the slag-based aggregate.

[0018] Optionally, the slag-based aggregate further includes rubber powder and low-melting-point glass powder, wherein the weight ratio of the rubber powder, low-melting-point glass powder and slag-based microspheres is 2:(6-8):(17-20).

[0019] By adopting the above technical solution, the rubber powder provides elastic space for the volume change of the slag-based microspheres and cement, reducing the probability of cold shrinkage cracking of foamed lightweight soil and cracking due to volume effect after the roadbed is solidified.

[0020] Optionally, the preparation of the slag-based aggregate includes the following steps: slag-based microspheres, rubber powder and low-melting-point glass powder are mixed and homogenized, stirred and heated to 380-400℃, stirred continuously for 20-30 minutes, allowed to stand and cool, and then granulated to obtain the slag-based aggregate.

[0021] By adopting the above technical solution, the rubber powder and the coal slag-based microspheres are mixed evenly. Under the low melting point bonding effect, the rubber powder and the coal slag-based microspheres are not easily separated. After the free magnesium oxide in the coal slag-based microspheres reacts with water and expands in volume, the rubber powder is compressed, reducing the possibility of roadbed cracking under volume effect.

[0022] Optionally, the foam stabilizer comprises xanthan gum and ammonium stearate emulsion, wherein the weight ratio of xanthan gum to ammonium stearate emulsion is 1:(0.2-1).

[0023] By adopting the above technical solutions, the combination of xanthan gum and ammonium stearate emulsion improves the stability of the foam, thereby reducing the weight of the subgrade, decreasing subgrade settlement and additional stress, and effectively solving the problem of soft soil foundation settlement in highways. The ammonium stearate emulsion improves xanthan gum, enhancing the hydrophobicity of the foam stabilizer, thus reducing the moisture content of the foamed lightweight soil subgrade. The probability of volume expansion of the coal-fired slag-based foamed lightweight soil after subgrade stabilization is reduced, thereby reducing the probability of subgrade cracking. Xanthan gum improves the dispersion uniformity of the foam stabilizer, thereby improving the uniformity and stability of the foamed lightweight soil and reducing the probability of subgrade cracking.

[0024] Secondly, the construction method for a coal-fired slag-based foamed lightweight soil subgrade provided in this application adopts the following technical solution:

[0025] A construction method for a coal-fired furnace slag-based foamed lightweight soil subgrade includes the following steps:

[0026] S1. Excavation of the roadbed;

[0027] S2, substrate treatment;

[0028] S3. Install construction formwork;

[0029] S4. Pour the above-mentioned coal-fired slag-based foamed lightweight soil;

[0030] S5. Lay galvanized wire mesh;

[0031] S6. Lay impermeable geotextile;

[0032] S7. Maintenance.

[0033] By adopting the above technical solutions, the combination of coal slag-based foamed lightweight soil and galvanized wire mesh allows the coal slag-based microspheres to adsorb metal ions, thereby improving the bonding strength between the coal slag-based aggregate and the galvanized wire mesh and enhancing the stability of the roadbed. The combination of coal slag-based foamed lightweight soil and impermeable geotextile for immediate use reduces the water retention rate of the roadbed, decreases the probability of volume expansion and cracking of the foamed lightweight soil, and improves the stability of the roadbed.

[0034] In summary, this application includes at least one of the following beneficial technical effects:

[0035] 1. In the preparation process of cinder-based microspheres, cinder powder is captured by the carbon source of beer waste powder, thereby embedding the cinder powder into the carbon source of beer waste powder, and the synthesized cinder-based microspheres have a porous structure. After freeze-drying and calcination, magnesium hydroxide is pyrolyzed into magnesium oxide, and water vapor is released at the same time, forming a porous structure with the pore walls modified by nano-ions, which improves the specific surface area and pore volume of the cinder-based microspheres. The cinder-based microspheres, rubber powder and low melting point glass powder are combined to form aggregates. During the curing of foamed lightweight soil, the free magnesium oxide that is not embedded in the carbon source of beer waste powder hydrates and expands. The pore size of the cinder-based microspheres and the rubber powder provide expansion space for the free magnesium oxide, reducing the probability of cracking of the foamed lightweight soil subgrade under the action of volume effect, improving the volume stability of foamed lightweight soil, and thus reducing the probability of subgrade cracking.

[0036] 2. Ammonium stearate emulsion improves xanthan gum, enhancing the hydrophobicity of the foam stabilizer and thus reducing the water content of the foamed lightweight soil subgrade. The probability of volume expansion in the coal slag-based foamed lightweight soil after subgrade stabilization is reduced, thereby decreasing the probability of subgrade cracking. 3. Calcium oxide in the coal slag-based microspheres reacts with water molecules to form calcium hydroxide, increasing the alkalinity of the environment in which the microspheres are located. Cement and ammonium stearate emulsion exhibit improved stability in alkaline environments. The combined use of coal slag-based microspheres, cement, and ammonium stearate emulsion enhances the stability of the foamed lightweight soil subgrade. Detailed Implementation

[0037] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0038] Unless otherwise specified, the following examples were conducted under standard conditions or conditions recommended by the manufacturer. Unless otherwise specified, all raw materials used in these examples are commercially available. The silicate cement used is PO42.5R type ordinary silicate cement; the low-melting-point glass powder has a density of 2.3-2.5 g / cm³. 3 Melting point 390℃; rubber powder content ≥90%, tensile strength 4.5Mpa, particle size 800 mesh; ammonia nitrogen concentration in beer wastewater not greater than 25%; foam is made by diluting a composite foaming agent into a foaming liquid and then producing it by compressed air method, with a dilution ratio of 50 times, a foaming ratio of 35 times, a density of 45g / L, and a defoaming rate not greater than 7%; ammonium stearate emulsion solid content 25%.

[0039] Preparation Example

[0040] Preparation Example 1

[0041] S1. Grind the coal slag into powder and pass it through a 100-mesh sieve to obtain coal slag powder;

[0042] S2. Let the beer wastewater stand for 15 days, take the sediment, centrifuge and dry it, grind it in a grinding mill, and pass it through a 100-mesh sieve to obtain beer waste residue powder.

[0043] S3. Preparation of coal slag-based microspheres:

[0044] S31. Add 1.5 kg of beer waste powder to 30 L of 2% glacial acetic acid solution and stir vigorously until completely dissolved at a stirring speed of 1400 rpm to obtain the base solution.

[0045] S32. Add 28.5 kg of coal slag powder to the above base liquid and stir until completely dissolved to obtain a homogeneous liquid;

[0046] S33. Add uniform liquid droplets to a 0.5M sodium hydroxide solution to obtain condensed beads; keep the condensed beads in the sodium hydroxide solution for 12 hours, separate the particles, wash the particles until neutral, and obtain beads.

[0047] S34. Freeze-dry the beads to form porous aerogel beads; calcine the porous aerogel beads at 600℃ for 2 hours under nitrogen protection to obtain cinder-based microspheres.

[0048] S4. Take 30 kg of the coal slag-based microspheres prepared in S3, 3 kg of rubber powder and 12 kg of low melting point glass powder, heat to 400℃, stir at a constant temperature for 30 min, cool and cut into granules to obtain coal slag-based aggregate with a particle size of 5 mm.

[0049] Preparation Examples 2-11

[0050] The difference from Preparation Example 1 is that the amount of each material added is different. The amount of glacial acetic acid solution added is adjusted according to the amount of beer waste powder and coal slag powder, and is set in sufficient quantity, as detailed in Table 1.

[0051] Preparation Example 12

[0052] The difference from Preparation Example 2 is as follows: S4, take 40.5 kg of the coal slag-based microspheres prepared in S3 and 15 kg of low melting point glass powder, heat to 400℃, stir at a constant temperature for 30 min, cool and cut and granulate to obtain coal slag-based aggregate with a particle size of 5 mm.

[0053] Preparation Example 13

[0054] The difference from Preparation Example 2 is that 40.5 kg of coal slag-based microspheres prepared by S3 and 4.5 kg of rubber powder were taken, heated to 220°C, stirred at a constant temperature for 30 min, cooled, cut and granulated to obtain coal slag-based aggregate with a particle size of 5 mm.

[0055] Preparation Example 14

[0056] The difference from Preparation Example 2 is that 4.5 kg of rubber powder and 15 kg of low melting point glass powder were heated to 400°C, stirred at a constant temperature for 30 min, cooled, cut and granulated to obtain aggregate with a particle size of 5 mm.

[0057] Preparation Example 15

[0058] Take 40.5 kg of coal slag, 4.5 kg of rubber powder and 15 kg of low melting point glass powder, heat to 400℃, stir at a constant temperature for 30 min, cool and cut into granules to obtain coal slag-based aggregate with a particle size of 5 mm.

[0059] Preparation Example 16

[0060] S1. Grind the coal slag into powder and pass it through a 100-mesh sieve to obtain coal slag powder;

[0061] S2. Preparation of coal slag-based microspheres:

[0062] S21. Add 40.5 kg of coal slag powder to 50 L of 2% glacial acetic acid solution and stir vigorously until completely dissolved at a stirring speed of 1400 rpm to obtain a homogeneous liquid.

[0063] S22. Add uniform liquid droplets to a 0.5M sodium hydroxide solution to obtain condensed beads; keep the condensed beads in the sodium hydroxide solution for 12 hours, separate the particles, wash the particles until neutral, and obtain beads.

[0064] S23. Freeze-dry the beads to form porous aerogel beads; calcine the porous aerogel beads at 600℃ for 2 hours under nitrogen protection to obtain slag-based microspheres.

[0065] S3. Take 40.5 kg of coal slag-based microspheres prepared by S3, 4.5 kg of rubber powder and 15 kg of low melting point glass powder, heat to 400℃, stir at a constant temperature for 30 min, cool and cut into granules to obtain coal slag-based aggregate with a particle size of 5 mm.

[0066] Preparation Example 17

[0067] S1. Let the beer wastewater stand for 15 days, take the sediment, centrifuge and dry it, grind it in a grinding mill, and pass it through a 100-mesh sieve to obtain beer waste residue powder.

[0068] S2. Preparation of microbeads:

[0069] S21. Add 40.5 kg of beer waste powder to 50 L of 2% glacial acetic acid solution and stir vigorously until completely dissolved to obtain a homogeneous liquid.

[0070] S22. Add uniform liquid droplets to a 0.5M sodium hydroxide solution to obtain condensed beads; keep the condensed beads in the sodium hydroxide solution for 12 hours, separate the particles, wash the particles until neutral, and obtain beads.

[0071] S23. Freeze-dry the beads to form porous aerogel beads; calcine the porous aerogel beads at 600℃ for 2 hours under nitrogen protection to obtain microbeads.

[0072] S3. Take 40.5 kg of microspheres prepared by S3, 1.5 kg of rubber powder and 15 kg of low melting point glass powder, heat to 400℃, stir at a constant temperature for 30 min, cool and cut and granulate to obtain coal slag-based aggregate with a particle size of 5 mm.

[0073] Table 1. Raw material list for the preparation example (kg)

[0074]

[0075]

[0076] Example

[0077] Example 1

[0078] S1. Mix 1 kg of xanthan gum and 0.2 kg of ammonium stearate emulsion evenly as a foam stabilizer;

[0079] S2. Take 18 kg of silicate cement, 30 kg of cinder-based aggregate prepared in S1, 10 kg of mixing water and foam stabilizer prepared in S1, mix and stir evenly to obtain slurry;

[0080] S3. Use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0081] S4. Press 2 kg of foam into the slurry prepared in S2, mix and stir evenly to obtain foamed lightweight soil.

[0082] Examples 2-17

[0083] The difference from Example 1 is that the amount of each material added is different, as detailed in Table 2.

[0084] Example 18

[0085] S1. Measurement and layout of the roadbed edge line, excavation of the roadbed, and excavation into steps according to the set height and width;

[0086] S2. Subgrade treatment: Drainage ditches and collection wells are dug around the foundation pit of the roadbed for drainage. A 15cm thick crushed stone cushion layer is laid, leveled, and compacted.

[0087] S3. Install the construction formwork. The construction formwork is fixed by pre-embedded equilateral angle steel and concrete pouring.

[0088] S4. Pour the above-mentioned coal-fired slag-based foamed lightweight soil with a single layer thickness of 0.8m. Set a settlement joint every 10m with a settlement joint width of 2cm. Insert polystyrene board into the settlement joint, with the polystyrene board penetrating through the coal-fired slag-based foamed lightweight soil subgrade.

[0089] S5. Lay galvanized iron wire mesh 0.15 meters from the bottom of the coal-fired slag-based foamed lightweight soil subgrade, and 0m, 0.5m and 1m from the top of the subgrade respectively. The overlap length of the galvanized iron wire mesh is 20cm.

[0090] S6. Lay impermeable geotextile at a distance of 0.15 meters from the bottom and 0.5 meters from the top of the coal-fired slag-based foamed lightweight soil subgrade, with an overlap length of 5 cm.

[0091] S7. Curing: Cover with plastic film and cure for 7 days.

[0092] Comparative Example

[0093] Comparative Example 1

[0094] S1. Mix 1 kg of xanthan gum and 0.2 kg of ammonium stearate emulsion evenly as a foam stabilizer;

[0095] S2. Take 18 kg of silicate cement, 10 kg of mixing water and the foam stabilizer prepared in S1, mix them and stir evenly to obtain the slurry;

[0096] S3. Use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0097] S4. Press 2 kg of foam into the slurry prepared in S2, mix and stir evenly to obtain foamed lightweight soil.

[0098] Comparative Example 2

[0099] S1. Mix 1 kg of xanthan gum and 0.2 kg of ammonium stearate emulsion evenly as a foam stabilizer;

[0100] S2. Take 18 kg of silicate cement, 30 kg of coal slag with an average particle size of 5 mm, 10 kg of mixing water and the foam stabilizer prepared in S1, mix them and stir evenly to obtain the slurry;

[0101] S3. Use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0102] S4. Press 2 kg of foam into the slurry prepared in S2, mix and stir evenly to obtain foamed lightweight soil.

[0103] Comparative Examples 3-8

[0104] The difference from Example 2 is that the slag-based aggregates prepared in Preparation Examples 12 to 17 were added sequentially.

[0105] Comparative Example 9

[0106] The difference from Example 2 is that no foam stabilizer was added.

[0107] The raw material list for the examples and comparative examples is shown in Table 2:

[0108] Table 2. Raw material list (kg) for the examples and comparative examples.

[0109]

[0110]

[0111] Performance testing

[0112] Test methods

[0113] 1. Referring to "8 Shrinkage Test; 8.2 Contact Method" in GB / T50082-2009 Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete, prism specimens of 100mm×100mm×515mm were prepared by curing lightweight foamed soil based on coal-fired furnace slag for 7 days, and the gauge length L of the instrument was recorded. b The initial reading L0 (mm) of the length of the foamed lightweight soil specimen based on coal-fired boiler slag was measured. After immersing the specimen in water for 7 days, the length reading L1 (mm) of the foamed lightweight soil specimen based on coal-fired boiler slag was measured. The expansion rate (%) was calculated using the formula: Expansion rate (%) = (L1 - L0) / L b Ten groups of samples were tested, and the average expansion rate was included in the final addition. The test results are detailed in Table 3.

[0114] 2. The compressive strength (MPa) of the coal-fired slag-based foamed lightweight soil was tested using the method in "4 Mechanical Properties" of "GB / T11969-2008 Test Method for Performance of Autoclaved Aerated Concrete". The test results are detailed in Table 3.

[0115] Table 3. Test results data for each embodiment and comparative example.

[0116]

[0117]

[0118] Based on Examples 1, 2, and 3 and Table 3, it can be seen that by adjusting the amount and type of silicate cement, slag-based aggregate, mixing water, foam, and foam stabilizer, the volume stability of coal-fired slag-based foamed lightweight soil can be improved, thereby reducing the probability of roadbed cracking.

[0119] Comparative Example 1 is a conventional foamed lightweight concrete, prepared from silicate cement, mixing water and foam stabilizer. Combining Example 2 and Comparative Example 1 with Table 3, it can be seen that the addition of coal slag-based aggregates improves the compressive strength of coal-fired furnace slag-based foamed lightweight soil.

[0120] As can be seen from Example 2 and Comparative Example 2, and in conjunction with Table 3, compared to conventional coal slag, the addition of coal slag-based aggregates improved the compressive strength of the coal-fired boiler slag-based foamed lightweight soil and reduced its expansion rate. The coal slag-based aggregates include rubber powder, low-melting-point glass powder, and coal slag-based microspheres. The rubber powder and coal slag-based microspheres are bonded and fixed by the low-melting-point glass powder, thus improving the stability of the coal slag-based aggregates.

[0121] Based on Examples 2, 4, and 5 and Table 3, it can be seen that as the amount of coal slag-based aggregate added increases, the compressive strength of the coal slag-based foamed lightweight soil first increases and then decreases, while the expansion of the coal slag-based foamed lightweight soil first decreases and then increases.

[0122] As can be seen from Example 2 and Comparative Example 3 and Table 3, the addition of rubber powder to the coal slag-based aggregate improved the compressive strength of the coal slag-based foamed lightweight soil and reduced the expansion rate of the coal slag-based foamed lightweight soil.

[0123] Based on Examples 2, 6, and 7 and Table 3, it can be seen that as the amount of rubber powder added to the coal slag-based aggregate increases, the compressive strength of the coal slag-based foamed lightweight soil first increases and then decreases, while the expansion of the coal slag-based foamed lightweight soil first decreases and then increases.

[0124] As can be seen from Example 2 and Comparative Example 4, and Table 3, the addition of low-melting-point glass powder to the coal slag-based aggregate improves the compressive strength of the coal slag-based foamed lightweight soil and reduces the expansion rate of the coal slag-based foamed lightweight soil.

[0125] Based on Examples 2, 8, and 9 and Table 3, it can be seen that as the amount of low-melting-point glass powder added to the coal slag-based aggregate increases, the compressive strength of the coal slag-based foamed lightweight soil first increases and then decreases, while the expansion of the coal slag-based foamed lightweight soil first decreases and then increases.

[0126] As can be seen from Example 2 and Comparative Example 5, and Table 3, the addition of slag-based microspheres to the slag-based aggregate improves the compressive strength of the lightweight foamed soil based on coal-fired boiler slag. The raw materials for preparing the slag-based microspheres include brewer's waste powder and slag powder. The brewer's waste powder provides a bio-carbon source. The silica in the slag powder reacts with strong sodium oxide to form sodium silicate, which then precipitates silicic acid under the action of carbon dioxide. After freeze-drying, the precipitated silicic acid forms a colloid, improving the bonding strength between the slag powder and the brewer's waste powder. After freeze-drying and calcination, a porous structure with pore walls modified by nano-ions is formed, providing space for the volume expansion of free magnesium oxide.

[0127] Based on Example 2 and Comparative Example 6, and in conjunction with Table 3, it can be seen that, compared to the coal slag-based aggregate prepared by mixing rubber powder, low-melting-point glass powder, and coal slag powder, the addition of the coal slag-based aggregate prepared by mixing rubber powder, low-melting-point glass powder, and coal slag-based microspheres improves the compressive strength of the coal-fired furnace slag-based foamed lightweight soil and reduces the expansion rate of the coal-fired furnace slag-based foamed lightweight soil.

[0128] Based on Examples 2, 10, and 11 and Table 3, it can be seen that as the amount of coal slag-based microspheres added increases, the compressive strength of the coal slag-based foamed lightweight soil first increases and then decreases, while the expansion of the coal slag-based foamed lightweight soil first decreases and then increases.

[0129] Based on Example 2 and Comparative Example 7, and in conjunction with Table 3, it can be seen that the addition of beer waste powder to the coal slag-based microspheres reduces the expansion rate of the coal-fired furnace slag-based foamed lightweight soil.

[0130] As can be seen from Example 2 and Comparative Example 8, and Table 3, the addition of coal slag powder to the coal slag-based microspheres improves the compressive strength of the coal-fired furnace slag-based foamed lightweight soil.

[0131] Based on Examples 2, 12, and 13 and Table 3, it can be seen that as the ratio of beer waste powder to coal slag powder decreases, the compressive strength of the coal-fired slag-based foamed lightweight soil first increases and then decreases, while the expansion of the coal-fired slag-based foamed lightweight soil first decreases and then increases.

[0132] As can be seen from Example 2 and Comparative Example 9, and Table 3, the addition of the foam stabilizer improved the compressive strength of the coal-fired slag-based foamed lightweight soil and reduced its expansion rate. The foam stabilizer includes xanthan gum and ammonium stearate emulsion, which work together to improve the water repellency and dispersion uniformity of the foam stabilizer.

[0133] As can be seen from Examples 2 and 14 and Table 3, the addition of ammonium stearate emulsion to the foam stabilizer reduced the expansion rate of the coal-fired slag-based foamed lightweight soil.

[0134] As can be seen from Examples 2 and 14 and Table 3, the addition of xanthan gum to the foam stabilizer improves the compressive strength of coal-fired slag-based foamed lightweight soil.

[0135] Based on Examples 2, 16, and 17 and Table 3, it can be seen that as the ratio of xanthan gum to ammonium stearate emulsion decreases, the compressive strength of the coal-fired slag-based foamed lightweight soil first increases and then decreases, while the expansion of the coal-fired slag-based foamed lightweight soil first decreases and then increases.

[0136] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A lightweight foamed soil subgrade based on coal-fired furnace slag, characterized in that, It is made of lightweight foamed soil based on coal slag, which includes the following raw materials in parts by weight: 18-30 parts silicate cement; 30-50 parts coal slag-based aggregate; 10-18 parts mixing water; 2-4 parts foam; and 1.2-2 parts foam stabilizer. The slag-based aggregate includes slag-based microspheres, rubber powder, and low-melting-point glass powder; The preparation of the coal slag-based microspheres includes the following steps: adding a biochar source and coal slag powder to a glacial acetic acid solution, stirring evenly, and then adding it dropwise to a sodium hydroxide solution to obtain condensed beads; washing the condensed beads until neutral, freeze-drying them, and calcining them under nitrogen protection to obtain coal slag-based microspheres; the biochar source includes beer waste residue powder, and the preparation of the beer waste residue powder includes the following steps: allowing beer wastewater to stand, centrifuging, drying, and then grinding it to obtain beer waste residue powder; The preparation of the coal slag-based aggregate includes the following steps: coal slag-based microspheres, rubber powder and low melting point glass powder are mixed and homogenized, stirred and heated to 380-400℃, stirred continuously for 20-30 minutes, allowed to stand and cool, and then granulated to obtain coal slag-based aggregate; The foam stabilizer comprises xanthan gum and ammonium stearate emulsion, wherein the weight ratio of xanthan gum to ammonium stearate emulsion is 1:(0.2-1).

2. The lightweight foamed soil subgrade based on coal-fired furnace slag according to claim 1, characterized in that, The ammonia nitrogen concentration in the beer wastewater shall not exceed 25%.

3. The lightweight foamed soil subgrade based on coal-fired furnace slag according to claim 1, characterized in that, The weight ratio of the rubber powder, low melting point glass powder and slag-based microspheres is 2:(6-8):(17-20).

4. A construction method for a coal-fired furnace slag-based foamed lightweight soil subgrade, characterized in that, Includes the following steps: S1. Excavation of the roadbed; S2, substrate treatment; S3. Install construction formwork; S4. Pouring the coal-fired slag-based foamed lightweight soil as described in any one of claims 1-3; S5. Lay galvanized wire mesh; S6. Lay impermeable geotextile; S7. Maintenance.

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