A red mud-swelling soil combined microbial foam light soil and a preparation method thereof

Abstract

The application discloses a kind of red mud-expansive soil combined microbial foam light soil and its preparation method, including the following weight parts of component raw materials: red mud 150-200 parts;Expansive soil 400-500 parts;Indigenous urease bacteria culture fluid 20-50 parts;Foaming gas bubble group 30-50 parts;Water 200-300 parts.Indigenous urease bacteria culture fluid includes pH adjusting solution, indigenous urease bacteria inoculum and indigenous urease bacteria cementing fluid;Indigenous urease bacteria inoculum contains urea;Indigenous urease bacteria cementing fluid contains calcium ions.The application can effectively utilize indigenous urease bacteria in expansive soil, and play a synergistic role with solid waste red mud, so that it produces cementing material, improves the engineering performance of foam soil, can provide important technical support for safe, efficient resource utilization of solid waste red mud and expansive soil, and green, low-carbon civil engineering and building material research and development, has important engineering practice value and good social and economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of civil engineering materials, and particularly relates to a foamed lightweight soil of red mud-expansive soil combined microorganisms and a preparation method thereof. BACKGROUND

[0002] Red mud is a byproduct of industrial extraction of alumina. According to different aluminum production processes, there are mainly three types of red mud: sintered red mud, Bayer red mud and combined red mud. The existing aluminum production process has brought a serious burden to the healthy development of the industry, and it is urgent to explore new ideas for reasonable and rapid consumption of red mud.

[0003] Expansive soil, also known as "engineering cancer", is a high-plasticity clay with strong hydrophilicity and water saturation. It quickly expands when it comes into contact with water and shrinks easily when it loses water. Its engineering properties are closely related to water content. It is prone to cause various engineering accidents after coming into contact with water and is a typical disaster-causing special soil. In existing engineering construction, the "replacement method" is usually used to treat expansive soil foundations, that is, the expansive soil is removed and replaced with other soil with excellent engineering properties. This treatment method is labor-intensive and time-consuming, and the removed expansive soil needs to be transported and stored, which does not fundamentally achieve efficient, low-carbon and safe treatment of expansive soil. Civil engineering construction usually consumes a large amount of soil and stone building materials. These materials can meet the requirements of corresponding engineering design after being treated by specific scientific and technological means, thereby achieving safe and rapid treatment of solid waste and poor soil. In addition, the cost of engineering construction will be significantly reduced.

[0004] Existing scholars have proposed a technology for preparing foamed lightweight soil from red mud and expansive soil, which is applied to the infrastructure construction of various structures such as roads and bridges, and has achieved good economic and social benefits. It should be pointed out that in the current technology for preparing foamed lightweight soil from red mud, expansive soil or their mixture, a large amount of traditional cement material is still consumed to achieve cementation. Cement material consumes a large amount of natural clay and fossil energy in the production process, and emits greenhouse gases such as carbon dioxide, which is a high-energy-consumption and high-emission building material. Microbial-induced carbonate precipitation technology (MICP) based on urea hydrolysis reaction is a relatively efficient biological regulation technology. Its cementation process completely breaks through the limitations of traditional cement materials and truly realizes "green" and "low carbon", which is favored by scholars in many fields. Indigenous urease bacteria exist in natural expansive soil, which can be activated and cultured under specific conditions. Urease bacteria can secrete urease and hydrolyze urea to release carbonate ions. In a suitable alkaline environment, carbonate ions combine with calcium, magnesium and other cations to produce carbonate precipitates with cementation effect. Red mud contains rich calcium and aluminum ions, and has an alkaline pH, which can provide a necessary and good environment for the generation of carbonate cementation products.

[0005] Therefore, under the background of the "double carbon" goal and on the basis of the MICP technology, it is urgent to efficiently and safely stimulate indigenous urease bacteria in swelling soil, make full use of the good cementation and precipitation environment provided by red mud, break through the limitations of traditional cement materials, and develop completely green and low-carbon red mud-swelling soil foam lightweight soil materials. SUMMARY

[0006] The technical problem to be solved by the present application is to solve the above-mentioned problems of the prior art, and to provide a red mud-swelling soil combined microbial foam lightweight soil and a preparation method thereof, which can effectively utilize indigenous urease bacteria in swelling soil and play a synergistic role with solid waste red mud to produce cementing substances, improve the engineering performance of foam soil, provide important technical support for safe and efficient resource utilization of solid waste red mud and swelling soil, and green and low-carbon civil engineering building material research and development, and has important engineering practical value and good social and economic benefits.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is:

[0008] A red mud-swelling soil combined microbial foam lightweight soil, comprising the following components by weight:

[0009] Red mud 150-200 parts;

[0010] Swelling soil 400-500 parts;

[0011] Indigenous urease bacteria culture solution 20-50 parts;

[0012] Foaming gas bubble group 30-50 parts;

[0013] Water 200-300 parts;

[0014] The indigenous urease bacteria culture solution comprises an acid-base adjusting solution, an indigenous urease bacteria stimulating solution and an indigenous urease bacteria cementing solution.

[0015] The indigenous urease bacteria stimulating solution has urea with a concentration not less than 15 g / L.

[0016] The indigenous urease bacteria cementing solution has calcium ions with a concentration not less than 0.3 mol / L.

[0017] The mass fraction of calcium oxide in the red mud is not less than 10%, the mass fraction of silicon dioxide is not less than 10%, and the mass fraction of aluminum oxide is not less than 15%.

[0018] The free swelling rate of the swelling soil is not less than 50%.

[0019] The weight parts of the pH value adjusting liquid in the indigenous urease bacteria culture solution are 30-50 parts, the weight parts of the indigenous urease bacteria stimulating liquid are 300-400 parts, and the weight parts of the indigenous urease bacteria cementing liquid are 150-200 parts; wherein, the pH value adjusting liquid is 10 g / L ammonium sulfate; the indigenous urease bacteria stimulating liquid comprises 25-30 g / L nutrient broth and 15-20 g / L urea; and the indigenous urease bacteria cementing liquid comprises 35-40 g / L calcium chloride, 15-18 g / L urea, 5-10 g / L ammonium chloride and 0.5-1.0 g / L nutrient broth.

[0020] The foaming gas bubble group comprises the following component raw materials in weight parts: 10-30 parts of a foaming agent, 0.1-1 part of a foam stabilizer and 0.1-1 part of an active agent.

[0021] The foaming agent is one or a combination of rosin resins, synthetic surfactants, protein active substances and complex modified foaming agents; the foam stabilizer is one of macromolecular substances, silicone polyether emulsions, fatty alcohol and fatty acid foam stabilizers; and the active agent is sodium cocoyl glycinate.

[0022] A preparation method of a foamed lightweight soil of a red mud-swelling soil combined microorganism, comprising the following steps.

[0023] Step 1, mixing: stirring and mixing the red mud and the swelling soil according to a set ratio.

[0024] Step 2, adjusting pH value: adding the pH value adjusting liquid and water into the red mud-swelling soil mixture prepared in step 1-1 and stirring uniformly to obtain a red mud-swelling soil mixed slurry with a pH value of 8.0-9.0; the red mud-swelling soil mixed slurry contains active urease bacteria.

[0025] Step 3, generating carbonate ions: adding the indigenous urease bacteria stimulating liquid, which has been autoclaved and cooled to room temperature, into the red mud-swelling soil mixed slurry after adjusting the pH value; at this time, the urea in the indigenous urease bacteria stimulating liquid will be hydrolyzed under the action of the active urease bacteria to generate a slurry containing carbonate ions.

[0026] Step 4, generating cementing materials: adding the indigenous urease bacteria cementing liquid into the slurry containing carbonate ions in portions; the carbonate ions will generate cementing materials, including calcium carbonate cementing materials, silicate cementing materials and aluminate cementing materials, together with the calcium ions in the indigenous urease bacteria cementing liquid and the silicon ions and aluminum ions in the red mud.

[0027] Step 5, generating bubbles: adding the foaming gas bubble group into the slurry containing the cementing materials and stirring uniformly to obtain a slurry containing bubbles.

[0028] Step 6, preparation of foam lightweight soil: the slurry containing bubbles is cast into a set casting mold and cured at a constant temperature to a specified age to obtain the foam lightweight soil.

[0029] In step 5, the preparation method of the foaming gas bubble group comprises the following steps:

[0030] Step 5-1, preparation of foaming liquid: the foaming agent is diluted with water, and then the bubble stabilizer and the active agent are added and stirred to obtain the foaming liquid.

[0031] Step 5-2, foaming: the foaming liquid prepared in step 5-1 is added to the foaming machine; then, the air inlet valve of the foaming machine is opened to allow external gas to enter the foaming machine to generate foaming effect with the foaming liquid to form bubbles.

[0032] Step 5-3, bubble discharge: the bubbles formed in step 5-2 are discharged at a set pressure and a water pump speed ratio to obtain the foaming gas bubble group.

[0033] In step 5-1, the foaming agent is diluted with water by 70-80 times; in step 5-2, the external gas is one or a combination of air, carbon dioxide, nitrogen, hydrogen and helium; in step 5-3, when the set pressure is 200-500 kPa and the water pump speed ratio is 50-100, the foaming gas bubble group with a density of 48-55 kg / m 3 can be obtained.

[0034] In step 5, the foaming gas bubble group contains a foaming agent with a half-life period of γ; in step 6, the slurry containing bubbles must be cast into a set casting mold within the half-life period γ.

[0035] The present application has the following beneficial effects:

[0036] 1. The present application selects red mud, a solid waste material in the aluminum industry, as one of the raw materials for preparing foam lightweight soil, which can safely and quickly consume a large amount of red mud in the stockyard, promote the transformation of civil construction materials to green and low-carbon, and reduce the cost of engineering construction and energy consumption.

[0037] 2. The present application selects expansive soil, a poor soil body, as one of the raw materials for preparing foam lightweight soil, which utilizes indigenous urease bacteria in the expansive soil to decompose urea and ultimately induces the production of cementation products mainly composed of calcium carbonate to replace the cement component in traditional foam lightweight soil. In addition, the expansive soil has a strong water-swelling property, which can help improve the foaming quality of foam lightweight soil. The use of expansive soil to prepare foam lightweight soil can also solve the problem of storing excavated expansive soil and realize the recycling of natural resources.

[0038] 3. The alkaline environment of red mud is beneficial to the activation and function of indigenous urease bacteria in expansive soil. The main components of red mud, aluminum oxide, silicon dioxide and calcium oxide, can participate in the formation of cementation products in foam lightweight soil. Red mud and expansive soil play a synergistic cementation role, and improve the engineering performance of foam lightweight soil.

[0039] 4. The red mud-expansive soil combined microbial foam lightweight soil realizes "zero" cement addition, reduces energy consumption, greenhouse gas emissions and consumption of natural clay resources in the cement production process; provides a new way for green resource utilization of solid waste red mud; significantly improves the treatment level of "engineering cancer" expansive soil; the method of in-situ utilization of indigenous urease bacteria broadens the engineering application prospect of the foam lightweight soil; and meets the requirements of sustainable development and ecological civilization construction. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A flowchart of the preparation method of the red mud-expansive soil combined microbial foam lightweight soil of the present application is shown.

[0041] Figure 2 A schematic diagram of the appearance of the foam lightweight soil prepared in the specific embodiment of the present application is shown. DETAILED DESCRIPTION

[0042] The present application will be further described in detail below in combination with the drawings and specific preferred embodiments.

[0043] In the description of the present application, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and "first", "second" and the like do not represent the importance of the parts, so it cannot be understood as a limitation on the present application. The specific dimensions used in the present embodiment are only for the purpose of illustrating the technical solutions and do not limit the protection scope of the present application.

[0044] A red mud-expansive soil combined microbial foam lightweight soil, comprising the following components in parts by weight:

[0045] Red mud 150-200 parts.

[0046] Expansive soil 400-500 parts.

[0047] Indigenous urease bacteria culture solution 20-50 parts.

[0048] Foaming gas bubble group 30-50 parts.

[0049] Water 200-300 parts.

[0050] In the embodiment, the red mud is taken from a bayer process alumina production enterprise in Baise City, Guangxi Zhuang Autonomous Region, and preferably 150 parts by weight, the mass fraction of calcium oxide is not less than 10%, the mass fraction of silicon dioxide is not less than 10%, and the mass fraction of aluminum oxide is not less than 15%, and the specific chemical composition is shown in Table 1.

[0051] Table 1 Main chemical composition of red mud (mass fraction %)

[0052]

[0053] In the embodiment, the swelling soil is taken from a highway subgrade construction site in Baise City, Guangxi Zhuang Autonomous Region, and preferably 500 parts by weight, and the soil free swelling rate is not less than 50%, and the basic property index is shown in Table 2.

[0054] Table 2 Basic property index of swelling soil

[0055]

[0056] In addition, the active urease bacteria mainly exist in the swelling soil.

[0057] The indigenous urease bacteria culture solution is preferably 35 parts by weight, including pH adjusting solution, indigenous urease bacteria stimulating solution and indigenous urease bacteria cementation solution. Among them, the weight of the pH adjusting solution in the indigenous urease bacteria culture solution is preferably 30-50 parts, the weight of the indigenous urease bacteria stimulating solution is preferably 300-400 parts, and the weight of the indigenous urease bacteria cementation solution is preferably 150-200 parts.

[0058] The above-mentioned pH adjusting solution is preferably 10 g / L ammonium sulfate.

[0059] The above-mentioned indigenous urease bacteria stimulating solution has a urea concentration of not less than 15 g / L; preferably including 25-30 g / L nutrient broth and 15-20 g / L urea. In the embodiment, the indigenous urease bacteria stimulating solution preferably includes 26 g / L nutrient broth and 20 g / L urea.

[0060] The above-mentioned indigenous urease bacteria cementation solution has a calcium ion concentration of not less than 0.3 mol / L, and preferably includes 35-40 g / L calcium chloride, 15-18 g / L urea, 5-10 g / L ammonium chloride and 0.5-1.0 g / L nutrient broth. In the embodiment, the indigenous urease bacteria cementation solution preferably includes 35 g / L calcium chloride, 15 g / L urea, 8 g / L ammonium chloride and 1.0 g / L nutrient broth.

[0061] The foaming gas bubble group preferably has a weight of 50 parts, and includes the following components: a foaming agent 10-30 parts, a foam stabilizer 0.1-1 part, and an active agent 0.1-1 part.

[0062] The foaming agent is one or a combination of rosin resins, synthetic surfactants, protein active substances, and complex modified foaming agents; in this embodiment, the synthetic surfactants are preferred.

[0063] The foam stabilizer is one of macromolecular substances, silicone polyether emulsions, fatty alcohol and fatty acid foam stabilizers; in this embodiment, the silicone polyether emulsions are preferred.

[0064] The active agent is preferably sodium cocoyl glycinate.

[0065] A preparation method of a foamed light soil of a red mud-swelling soil combined microorganism, comprising the following steps.

[0066] Step 1, mixing: stirring and mixing red mud and swelling soil according to a set ratio (preferably 150 parts of red mud and 500 parts of swelling soil). The stirring device preferably stirs at a speed of 120 r / min for at least 3 minutes.

[0067] Step 2, adjusting pH: adding an acid-base adjusting liquid and water (preferably 200 parts) into the red mud-swelling soil mixture prepared in step 1-1 and stirring uniformly to obtain a red mud-swelling soil mixture with a pH value of 8.0-9.0 (preferably 8.5); the red mud-swelling soil mixture contains active urease bacteria.

[0068] The adding method of the acid-base adjusting liquid and water is preferably:

[0069] The acid-base adjusting liquid is added to the red mud-swelling soil mixture in portions, and then water is added to the red mud-swelling soil mixture in 5 portions, each time after adding water, stirring at a speed of 120 r / min for 2 minutes to ensure that there is no sediment, no agglomeration, and uniform mixing.

[0070] In the present application, the alkalinity of the red mud-swelling soil mixture is appropriately reduced by the acid-base adjusting liquid, and the alkaline environment with a pH value of 8.0-9.0 is suitable for activating the indigenous urease bacteria in the swelling soil.

[0071] Step 3, generating carbonate ions

[0072] The high-pressure sterilized and cooled to room temperature indigenous urease bacteria inoculum is preferably added to the pH-adjusted red mud-swelling soil mixture in two portions. After each addition of the indigenous urease bacteria inoculum, it is preferably stirred at a speed of 60 r / min for at least 3 minutes to ensure uniform mixing.

[0073] In the present application, the indigenous urease bacteria inoculum excites the activity and high survival rate of the indigenous urease bacteria in situ, and the indigenous urease bacteria cementing solution further improves the activity of the indigenous urease bacteria and provides necessary material conditions for generating carbonate cement.

[0074] The urea in the above-mentioned indigenous urease bacteria inoculum will be hydrolyzed under the action of active urease bacteria to generate carbonate ions:

[0075] CO(NH2)2+2H2O+active urease bacteria→2NH4 + +CO3 2-

[0076] Step 4, continuously generate cement: the indigenous urease bacteria cementing solution is preferably added to the slurry containing carbonate ions in two portions, and the carbonate ions will continuously generate cement-containing slurry with calcium ions in the indigenous urease bacteria cementing solution and silicon ions and aluminum ions in the red mud; the cement includes calcium carbonate cement, silicate cement and aluminate cement.

[0077] After each addition of the above-mentioned indigenous urease bacteria cementing solution, it is preferably stirred at a speed of 60 r / min for at least 2 minutes to ensure uniform mixing.

[0078] The chemical formula of the above-mentioned cement is preferably:

[0079] Ca 2+ +CO3 2- +SiO2+Al2O3+alkaline environment→CaCO3↓+silicate↓+aluminate↓

[0080] The above-mentioned cement begins to generate at the time of the addition of the cementing solution, but it is a continuous period of time, and there is also cement generation during the sample curing stage. As long as the urease bacteria reproduce and survive, and the cementing solution is not completely consumed, the cementing material will be continuously generated.

[0081] Step 5, generate bubbles: 50 parts of a foaming gas bubble group is added to the slurry containing the cement and stirred uniformly to obtain a slurry containing bubbles. At this time, the stirring rate is preferably 1000 r / min, and the stirring time is preferably not less than 15 minutes to ensure that the bubble group is uniformly distributed in the slurry, and the slurry has no sedimentation and no agglomeration, thereby obtaining a bubble group mixture.

[0082] The preparation method of the above-mentioned foaming gas bubble group preferably includes the following steps:

[0083] Step 5-1, preparation of foaming liquid: dilute the foaming agent preferably with water by 70-80 times, then add the foam stabilizer and active agent, and stir to mix, to obtain the foaming liquid. The half-life of the foaming agent is preferably gamma.

[0084] Step 5-2, foaming: the foaming liquid prepared in step 5-1 is preferably connected to the foaming machine through a pipeline; then, the air inlet valve of the foaming machine is opened, and external gas enters the foaming machine to generate foaming effect with the foaming liquid, to form bubbles.

[0085] The external gas is preferably one or a combination of air, carbon dioxide, nitrogen, hydrogen and helium, and in the embodiment, is preferably carbon dioxide.

[0086] Step 5-3, bubble discharge: the bubbles formed in step 5-2 are discharged at a set pressure of 200-500 kPa and a water pump speed ratio of 50-100, preferably to obtain a foaming gas bubble group with a density of 48-55 kg / m 3 .

[0087] Further, the bubbles are discharged at a set pressure of 350 kPa and a water pump speed ratio of 60, preferably to obtain a foaming gas bubble group with a density of 51 kg / m 3 .

[0088] Step 6, preparation of foamed lightweight soil: the slurry containing bubbles is poured into a set pouring mold within the half-life gamma to avoid the bubbles breaking and the gas escaping; then, the poured slurry is cured at a constant temperature (preferably at a temperature of 21 ˚C and a relative humidity of 97%) to a specified age (preferably for 7 days), to obtain the foamed lightweight soil. The inner wall of the set pouring mold is coated with a thin layer of lubricant and sealed.

[0089] In the embodiment, three cubic foamed lightweight soil test blocks with a side length of 100 mm and an average unconfined compressive strength of 0.62 MPa are selected after curing for 7 days. In order to compare the effect with the traditional cement foamed lightweight soil, the following components of the lightweight soil are prepared in parts by weight: red mud 150 parts, expanded soil 500 parts, portland cement 150 parts, foaming gas bubble group 50 parts, and water 300 parts. Three cubic foamed lightweight soil test blocks with a side length of 100 mm and an average unconfined compressive strength of 0.78 MPa are selected after curing for 7 days. The unconfined compressive strength of the red mud-expanded soil combined microbial foamed lightweight soil disclosed in the present application is basically the same as that of the traditional cement foamed lightweight soil, and meets the use requirements.

[0090] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, various equivalent transformations of the technical solutions of the present application can be made, and these equivalent transformations all belong to the protection scope of the present application.

Claims

1. A foamed lightweight soil composed of red mud and expansive soil combined with microorganisms, characterized in that: The raw materials include the following components in parts by weight: 150-200 parts red mud; 400-500 parts of expansive soil; 20-50 portions of indigenous urease-producing bacteria culture medium; 30-50 parts of foaming gas bubble clusters; 200-300 parts water; The indigenous urease bacteria culture medium includes pH adjustment medium, indigenous urease bacteria activation medium and indigenous urease bacteria cementing medium; The urea concentration in the indigenous urease-inducing solution was not less than 15 g / L; The cementitious solution of indigenous urease bacteria contains calcium ions at a concentration of not less than 0.3 mol / L.

2. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 1, characterized in that: The red mud contains no less than 10% calcium oxide, no less than 10% silicon dioxide, and no less than 15% aluminum oxide.

3. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 1, characterized in that: The free swelling rate of expansive soil shall not be less than 50%.

4. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 1, characterized in that: The indigenous urease bacteria culture medium contains 30-50 parts by weight of pH adjustment solution, 300-400 parts by weight of indigenous urease bacteria activation solution, and 150-200 parts by weight of indigenous urease bacteria gelling solution; wherein, the pH adjustment solution is 10 g / L ammonium sulfate; the indigenous urease bacteria activation solution includes 25-30 g / L nutrient broth and 15-20 g / L urea; the indigenous urease bacteria gelling solution includes 35-40 g / L calcium chloride, 15-18 g / L urea, 5-10 g / L ammonium chloride, and 0.5-1.0 g / L nutrient broth.

5. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 1, characterized in that: The foaming gas bubble cluster comprises the following components by weight: 10-30 parts foaming agent, 0.1-1 parts foam stabilizer, and 0.1-1 parts activator.

6. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 5, characterized in that: The foaming agent is one or a combination of rosin resin, synthetic surfactant, protein active agent, and composite modified foaming agent; the foam stabilizer is one of macromolecular substances, silicone resin polyether emulsion, fatty alcohol and fatty acid foam stabilizers; the activator is sodium cocoyl glycinate.

7. A method for preparing foamed lightweight soil composed of red mud and expansive soil combined with microorganisms, characterized in that: Includes the following steps: Step 1, Mixing: Mix the red mud and expanded soil evenly according to the set ratio; Step 2, pH adjustment: Add pH adjustment solution and water to the red mud-expanded soil mixture prepared in Step 1 and stir evenly to obtain a red mud-expanded soil mixture with a pH value of 8.0-9.0; the red mud-expanded soil mixture contains active urease bacteria; Step 3, generating carbonate ions: The indigenous urease bacteria activation solution, which has been autoclaved and cooled to room temperature, is added in portions to the red mud-expanded soil mixed slurry after the pH value has been adjusted; at this time, the urea in the indigenous urease bacteria activation solution will be hydrolyzed under the action of active urease bacteria to produce slurry containing carbonate ions. Step 4, Continuous generation of cementitious material: The indigenous urease bacteria cementing solution is added to the slurry containing carbonate ions in several batches. The carbonate ions will continuously generate cementitious material with the calcium ions in the indigenous urease bacteria cementing solution and the silicon and aluminum ions in the red mud. The cementitious material includes calcium carbonate cement, silicate cement and aluminate cement. Step 5: Generate bubbles: Add the foaming gas bubble group to the slurry containing the binder and stir evenly to obtain a slurry containing bubbles; Step 6: Prepare foamed lightweight soil: Pour the slurry containing air bubbles into the set casting mold and cure at a constant temperature to the specified age to obtain foamed lightweight soil.

8. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 7, characterized in that: Step 5, the method for preparing the foaming gas bubble cluster, includes the following steps: Step 5-1, Preparation of foaming liquid: Dilute the foaming agent with water, then add the foam stabilizer and activator, stir and mix well to obtain the foaming liquid; Step 5-2, Foaming: Add the foaming liquid prepared in step 5-1 to the foaming machine; then, open the air inlet valve of the foaming machine to allow external gas to enter the foaming machine and react with the foaming liquid to form bubbles. Step 5-3, Bubble Release: Release the bubbles formed in Step 5-2 at a set pressure and water pump speed ratio to obtain a group of foaming gas bubbles.

9. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 8, characterized in that: In step 5-1, the foaming agent is diluted with water 70-80 times; in step 5-2, the external gas is one or a combination of air, carbon dioxide, nitrogen, hydrogen, and helium; in step 5-3, when the set pressure is 200-500 kPa and the pump speed ratio is 50-100, a density of 48-55 kg / m³ can be obtained. 3 A cluster of foaming gas bubbles.

10. The foamed lightweight soil with red mud-expanding soil combined with microorganisms according to claim 7, characterized in that: In step 5, the foaming gas bubble cluster contains a foaming agent with a half-life of γ; in step 6, the slurry containing the bubbles must be poured into the designated casting mold within the half-life of γ.

Images