Red mud synergistically excited metallurgical slag solid waste foam light soil and preparation method thereof

Abstract

The invention discloses red mud synergistically excited metallurgical slag solid waste foam light soil and a preparation method thereof, and relates to the technical field of building materials. The building material comprises the following raw material components in parts by mass: 50-65 parts of red mud, 20-30 parts of metallurgical slag, 5-15 parts of steel slag, 10-15 parts of cement, 0.5-1 part of sodium silicate, 3-5 parts of calcium hydroxide, 0.3-0.4 part of a polycarboxylate superplasticizer, 5-8 parts of a composite foaming agent, 8-12 parts of modified nano bamboo charcoal powder and 0.1-0.15 part of graphene oxide nanosheets. By optimizing material components and a foaming process, the problems existing in traditional foam light soil are successfully solved, the product performance of the foam light soil is remarkably improved, meanwhile, efficient recycling of industrial solid waste is achieved, and important economic and social benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly to a red mud synergistic activation metallurgical slag solid waste foam lightweight soil and a preparation method thereof. Background Art

[0002] Foam lightweight soil is a new type of building material prepared by introducing foam into cement-based materials. In recent years, with the increasingly strict requirements for environmental protection and energy conservation, foam lightweight soil has been widely used in the fields of buildings, roads, bridges, etc.

[0003] Foam lightweight soil mainly has the following main technical advantages: (1) Low density: Due to the presence of a large number of uniformly distributed tiny air bubbles inside, its density is significantly lower than that of ordinary concrete or soil, usually between 300 - 1200 kg / m 3 ; (2) High strength: Although the density is low, after reasonable design and optimized proportioning, foam lightweight soil can still maintain a relatively high compressive strength, suitable for different engineering requirements; (3) Good heat insulation performance: Due to the existence of a large number of air pores inside, foam lightweight soil has excellent heat preservation and insulation effects, which can effectively reduce heat transfer; (4) High fluidity: Foam lightweight soil has good fluidity and self-compacting properties, and does not require vibration during construction, facilitating pumping and pouring, especially suitable for the application of complex-shaped structures or narrow spaces; (5) Good durability: Foam lightweight soil has good freeze-thaw resistance and chemical stability, and can be used for a long time in harsh environments.

[0004] However, traditional foam lightweight soil often relies on a large amount of high-energy-consuming materials such as cement during the preparation process, which not only increases the production cost but also causes greater pressure on the environment. In recent years, using solid waste to replace cement to prepare foam lightweight soil has become a current research hotspot.

[0005] Red mud is the waste residue generated during the extraction of alumina from bauxite, and the global annual output is huge. Due to its complex composition (containing various elements such as iron, silicon, and aluminum), the traditional disposal method is mainly stacking, which not only occupies a large amount of land resources but also may cause problems such as soil pollution and water pollution. In recent years, in order to effectively treat red mud, many studies have been committed to applying it to the field of building materials, such as making bricks, tiles, and producing cement additives, etc., but these application methods generally have problems such as low utilization rate and low added value.

[0006] Metallurgical slag is the solid waste generated during the steel smelting process, mainly including blast furnace slag, converter slag, electric furnace slag, etc. These waste slags contain rich silicate mineral phases and have relatively high potential activity. At present, most metallurgical slags have not been fully utilized and are still mainly stacked, which not only wastes resources but also brings environmental pollution risks.

[0007] Existing studies have preliminarily confirmed the feasibility of red mud-based foamed lightweight soil, but problems such as service performance and construction adaptability still need to be solved. For example, the activation of metallurgical slag activity is insufficient, the wet density control is difficult, which affects the lightweight effect; the solid waste particles vary greatly, the fluidity of the fresh mixture is poor, it is easy to stratify and segregate, and the pumping construction is difficult; the uneven pore structure leads to poor frost resistance and high risk of dry shrinkage cracking, resulting in poor durability, especially in cold regions or high humidity environments, etc.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The purpose of the present invention is to provide a red mud synergistically activated metallurgical slag solid waste foamed lightweight soil and its preparation method to solve the problems existing in the above-mentioned prior art and realize the resource utilization of solid waste on the basis of ensuring excellent service performance of the foamed lightweight soil.

[0010] To achieve the above object, the present invention provides the following solutions:

[0011] The present invention provides a red mud synergistically activated metallurgical slag solid waste foamed lightweight soil, which comprises the following raw material components in parts by mass:

[0012] 50 - 65 parts of red mud, 20 - 30 parts of metallurgical slag, 5 - 15 parts of steel slag, 10 - 15 parts of cement, 0.5 - 1 part of sodium silicate, 3 - 5 parts of calcium hydroxide, 0.3 - 0.4 part of polycarboxylate water reducer, 5 - 8 parts of composite foaming agent, 8 - 12 parts of modified nano bamboo charcoal powder, and 0.1 - 0.15 part of graphene oxide nanosheets.

[0013] Furthermore, the preparation method of the modified nano bamboo charcoal powder comprises the following steps:

[0014] Soak the bamboo charcoal powder in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, filter and then wash until neutral, dry and then soak in sodium hydroxide solution, filter and then wash until neutral, dry to obtain the modified nano bamboo charcoal powder;

[0015] Mechanically grind the obtained modified nano bamboo charcoal powder to obtain a nano-scale powder, which is the modified nano bamboo charcoal powder.

[0016] Furthermore, the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1; the soaking time in the mixed acid is 0.5 - 1 h.

[0017] More preferably, the mass concentration of the sodium hydroxide solution is 8 - 10%, and the soaking time in the sodium hydroxide solution is 0.5 - 1 h.

[0018] The more preferred steps of the preparation method of the modified nano bamboo charcoal powder are as follows:

[0019] Soak bamboo charcoal powder in a mixed acid solution with a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1 for 3 h, filter and wash it with deionized water multiple times until it is neutral to remove the residual acid solution; put the treated bamboo charcoal powder into an oven and dry it at 105 °C for 0.5 h; then add the dried bamboo charcoal powder into a 10% (mass concentration) NaOH solution and soak it for 3 h, filter and wash it with deionized water until it is neutral, and dry it again at 105 °C for 0.5 h.

[0020] As a raw material component, the modified nano bamboo charcoal powder has the following effects on the light soil raw materials:

[0021] The nanometer treatment and high specific surface area characteristics of the modified bamboo charcoal powder enable it to play a strengthening role in the cement matrix, significantly improving the compressive strength of the light soil; the treated bamboo charcoal powder with a porous structure can effectively reduce the thermal conductivity and improve the heat insulation performance of the light soil; the adsorption and protection effects of the modified bamboo charcoal powder can extend the service life of the light soil and improve its durability and stability.

[0022] The modified nano bamboo charcoal powder interacts with the composite foaming agent:

[0023] The abundant functional groups on the surface of the modified bamboo charcoal powder can adsorb the active components in the composite foaming agent, prevent the bubbles from bursting and merging, and at the same time, due to its small size and high specific surface area, it can effectively prevent the bubbles from contacting each other, further improving the foam stability.

[0024] Furthermore, the metallurgical slag is blast furnace slag, converter slag or electric furnace slag.

[0025] Furthermore, the composite foaming agent is prepared through the following steps:

[0026] (1) React saponin with lauric anhydride under the catalysis of lipase, and add a silane coupling agent to the reaction product to obtain modified saponin;

[0027] (2) Disperse bamboo charcoal powder and graphene oxide in water, then add the modified saponin, and react under the action of a microwave-ultrasound synergistic field to obtain a modified saponin@bamboo charcoal / GO composite;

[0028] (3) Mix the modified saponin@bamboo charcoal / GO composite with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and potassium carbonate in a solvent, disperse them by ultrasound, then react at 75-80 °C for 0.5-1 h under nitrogen protection, cool to room temperature after the reaction, wash and dry to obtain the composite foaming agent.

[0029] Furthermore, the molar ratio of saponin to lauric anhydride is 1:2-3.

[0030] Further, the reaction temperature of the lipase-catalyzed reaction in step (1) is 30 - 40 °C, the pH is 6.5 - 7.0, and the reaction time is 6 - 8 h; the reaction temperature for adding the silane coupling agent in step (1) is 55 - 60 °C, and the time is 0.5 - 1 h.

[0031] More preferably, the addition amount of the silane coupling agent is 3 - 5% of the total mass of the saponin and lauric anhydride.

[0032] Further, the mass ratio of the bamboo charcoal powder to the graphene oxide is 1 - 2:2; the addition amount of the modified saponin is 30 - 40 times the total mass of the bamboo charcoal powder and the graphene oxide.

[0033] Further, the microwave power of the microwave-ultrasonic synergistic field is 500 - 600 W, the ultrasonic frequency is 40 - 50 kHz; the action time of the microwave-ultrasonic synergistic field is 10 - 15 min.

[0034] Further, the mass ratio of the modified saponin@bamboo charcoal / GO composite, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and potassium carbonate is 8 - 10:4 - 5:2 - 3.

[0035] In the present invention, if the addition amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride is too high, the foaming activity will decrease.

[0036] Further, the saponin and lauric anhydride are added to a mixed system of acetonitrile and water (preferably acetonitrile:water volume ratio 7:3), and then lipase is added for catalytic reaction; more preferably, the concentration of saponin in the reaction system is 0.1 - 1 mol / L, and the concentration of lauric anhydride in the reaction system is 0.5 - 2 mol / L.

[0037] The present invention also provides a method for preparing the above-mentioned red mud synergistically activated metallurgical slag solid waste foam lightweight soil, comprising the following steps:

[0038] (1) Mix the heat-treated and activated red mud with the metallurgical slag, add calcium hydroxide and sodium silicate, and ball mill to obtain a synergistically activated material;

[0039] (2) Add the composite foaming agent to water, ultrasonically disperse to obtain a composite foaming agent solution, and then perform foaming treatment to obtain foamed foam;

[0040] (3) After mixing cement and steel slag, add the synergistically activated material and stir evenly, and then add graphene oxide nanosheets, polycarboxylate water reducer, modified nano bamboo charcoal powder, and water to the system and stir into a slurry;

[0041] (4) Inject the foamed foam into the slurry and mix to obtain the red mud synergistically activated metallurgical slag solid waste foam lightweight soil.

[0042] The present invention preferably uses a high-pressure air foaming machine to foam the foaming agent solution at 0.3 - 0.5 MPa. The gas-liquid ratio during the foaming process is 1:3 (foaming agent solution). High-speed shearing treatment is carried out during foaming, and the shearing rate is 10,000 - 15,000 rpm to obtain foamed foam.

[0043] Thermally activating red mud at 800 °C can effectively improve its activity. Research shows that red mud undergoes mineral phase transformation at high temperatures, increasing its specific surface area and reactivity, thus better combining with other materials. Calcium hydroxide and sodium silicate, as activators, can significantly improve the reactivity of red mud and metallurgical slag.

[0044] When using traditional single foaming agents to prepare foamed lightweight soil, there are often problems such as poor foam stability and uneven bubble distribution, resulting in unstable physical and mechanical properties of the final product. The composite material prepared by the present invention can adsorb gas and provide more nucleation sites, making bubbles easier to form and more evenly distributed, thereby endowing foamed concrete with excellent properties.

[0045] The present invention modifies saponin to prepare a composite foaming agent, such that the surface of the formed bubbles will be covered by a layer of surfactant molecules, thus greatly reducing the tendency of bubble coalescence. At the same time, the addition of bamboo charcoal powder and GO provides additional physical support, making the foam structure more stable. There are large interlayer spacings and abundant functional groups between the graphene oxide (GO) sheets, which can further enhance the mechanical strength and stability of the composite material, while improving the durability and compressive capacity of the foam.

[0046] The present invention introduces a quaternary ammonium salt group through 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTMAC) to ensure the stability of the composite foaming agent in an alkaline environment. Moreover, the hydroxyl group in the CHPTMAC molecular structure can form hydrogen bonds with the hydroxyl group of saponin or the surface hydroxyl group of bamboo charcoal, and the quaternary ammonium salt group provides alkali resistance protection. In practical applications, the foam after foaming the composite foaming agent can be mixed with the slurry, and air is introduced during the stirring process to form a large number of tiny bubbles. These bubbles not only reduce the weight of the material but also improve the thermal insulation performance and sound absorption effect of the material.

[0047] The present invention discloses the following technical effects:

[0048] The present invention provides a red mud synergistically activated metallurgical slag solid waste foamed lightweight soil. Under the condition of low cement dosage, by optimizing the material components and foaming process, the physical and mechanical properties and functionality of the product are significantly improved.

[0049] The present invention makes full use of industrial solid waste, realizes the efficient reuse of waste, reduces environmental pollution, and conforms to the concept of green development.

[0050] By optimizing the material components and foaming process, the present invention has successfully solved the problems existing in traditional foam lightweight soil, significantly improved the product performance of foam lightweight soil, and at the same time achieved the efficient reuse of industrial solid waste, having important economic and social benefits. Detailed Embodiments

[0051] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0052] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0053] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0054] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are merely exemplary.

[0055] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0056] It should be noted that the aspects not detailed in the present invention are all conventional operating means in the art and are not the focus of the present invention.

[0057] Example 1

[0058] The mass parts ratio of the raw materials in this example is as follows:

[0059] 55 parts of red mud, 28 parts of blast furnace slag, 12 parts of steel slag, 10 parts of P.O42.5 cement, 1 part of sodium silicate, 3 parts of calcium hydroxide, 0.3 part of polycarboxylate superplasticizer, 6 parts of composite foaming agent, 10 parts of modified nano bamboo charcoal powder and 0.1 part of graphene oxide nanosheets.

[0060] The preparation steps of the solid waste foam light soil are as follows:

[0061] Step 1: Prepare the modified nano bamboo charcoal powder

[0062] Add the bamboo charcoal powder into the mixed acid solution with the volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1 and soak for 0.5 h, filter and wash with deionized water for several times until neutral to remove the residual acid solution; put the treated bamboo charcoal powder into the oven and dry at 105 °C for 0.5 h; then add the dried bamboo charcoal powder into the NaOH solution with a mass concentration of 10% and soak for 1 h, filter and wash with deionized water until neutral, and dry again at 105 °C for 0.5 h.

[0063] Step 2: Prepare the synergistic activator:

[0064] (1) Activate the red mud at 800 °C to obtain activated red mud;

[0065] (2) Crush the blast furnace slag to a particle size of ≤2 mm, mix it with the activated red mud, add the activators (calcium hydroxide and sodium silicate), and perform wet ball milling for 30 min to obtain the synergistic activator.

[0066] Step 3: Preparation of the composite foaming agent:

[0067] (1) Add saponin and lauric anhydride into the mixed system of acetonitrile and water (volume ratio 7:3) according to the molar ratio of 1:3, so that the concentration of saponin is 0.5 mol / L and the concentration of lauric anhydride is 1.5 mol / L, and carry out the reaction under the catalysis of lipase (Novozym 435) (reaction temperature 37 °C, pH 6.5, reaction time 8 h); add silane coupling agent KH560 (3% of the total mass of saponin and lauric anhydride) to the reaction product, and stir at 60 °C for 0.5 h to obtain the modified saponin;

[0068] (2) Mix bamboo charcoal powder and graphene oxide (GO) according to the mass ratio of 1:2, ultrasonically disperse them in deionized water, and the total concentration of the two is 0.5 g / L. Then add the modified saponin (the addition amount is 30 times the total mass of bamboo charcoal powder and graphene oxide), and react for 15 min under the microwave-ultrasonic synergistic field (microwave power 600 W, ultrasonic frequency 40 kHz) to form the modified saponin@bamboo charcoal / GO composite;

[0069] (3) Mix the modified saponin@bamboo charcoal / GO composite, 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTMAC), and potassium carbonate in DMF at a mass ratio of 10:5:2, and ultrasonically disperse for 30 min (power 200 W, frequency 40 kHz). Then, heat to 80 °C and magnetically stir and react for 0.5 h under nitrogen protection. After the reaction, cool to room temperature, wash three times with ethanol and deionized water in sequence, and vacuum dry at 60 °C for 12 h to obtain the composite foaming agent.

[0070] Step Four: Form foamed foam:

[0071] (1) Mix the composite foaming agent with deionized water, ultrasonically disperse for 10 min (power 200 W, frequency 40 kHz), and stir for 30 min (rotation speed 800 rpm, temperature 25 °C) to obtain the composite foaming agent solution;

[0072] (2) Use a high-pressure air foaming machine to foam the foaming agent solution at 0.5 MPa. The gas-liquid ratio during the foaming process is 1:3 (foaming agent solution). Perform high-speed shearing treatment during foaming, with a shearing rate of 15,000 rpm, to obtain the foamed foam.

[0073] Step Five: Preparation of lightweight soil:

[0074] (1) After mixing cement and steel slag, add a synergistic activator and stir evenly. Then, add graphene oxide nanosheets, polycarboxylate superplasticizer, modified nano-bamboo charcoal powder, and water to the system and stir into a slurry;

[0075] (2) Inject the foamed foam obtained in Step Four into the slurry through a high-pressure pump, mix with a double-shaft screw mixer (rotation speed 300 r / min, 5 min), and adjust the wet density to 800 kg / m 3 to obtain foamed lightweight soil.

[0076] Pour and mold the lightweight soil prepared in the example, let it stand at room temperature for 24 h to achieve initial curing, then demold the test block and place it in a standard curing room, and cure it at 20 ± 2 °C and a relative humidity of more than 95% for 28 d.

[0077] Example 2

[0078] The raw material mass ratio in this example is as follows:

[0079] 60 parts of red mud, 25 parts of blast furnace slag, 10 parts of steel slag, 12 parts of PO42.5 cement, 0.8 part of sodium silicate, 3 parts of calcium hydroxide, 0.3 part of polycarboxylate superplasticizer, 5 parts of composite foaming agent, 8 parts of modified nano-bamboo charcoal powder, and 0.15 part of graphene oxide nanosheets.

[0080] The preparation steps of the solid waste foamed lightweight soil are as follows:

[0081] Step 1: Prepare modified nano bamboo charcoal powder

[0082] Soak the bamboo charcoal powder in a mixed acid solution with a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1 for 1 h, filter and wash it with deionized water multiple times until neutral to remove the residual acid solution; put the treated bamboo charcoal powder into an oven and dry it at 105 °C for 0.5 h; then add the dried bamboo charcoal powder to an 8% NaOH solution by mass concentration, soak it for 1 h, filter and wash it with deionized water until neutral, and dry it again at 105 °C for 0.5 h.

[0083] Step 2: Prepare a synergistic activator:

[0084] (1) Activate the red mud at 800 °C to obtain activated red mud;

[0085] (2) Crush the blast furnace slag to a particle size of ≤2 mm, mix it with the activated red mud, add activators (calcium hydroxide and sodium silicate), and perform wet ball milling for 30 min to obtain a synergistic activator.

[0086] Step 3: Preparation of a composite foaming agent:

[0087] (1) Add saponin and lauric anhydride to a mixed system of acetonitrile and water (volume ratio 7:3) according to a molar ratio of 1:2, so that the concentration of saponin is 0.5 mol / L and the concentration of lauric anhydride is 1.0 mol / L, and carry out a reaction under the catalysis of lipase (Novozym 435) (reaction temperature 38 °C, pH 7.0, reaction time 7 h); add silane coupling agent KH560 (3% of the total mass of saponin and lauric anhydride) to the reaction product, and stir at 60 °C for 0.5 h to obtain modified saponin;

[0088] (2) Mix bamboo charcoal powder and graphene oxide (GO) according to a mass ratio of 1:2, ultrasonically disperse it in deionized water, and their total concentration is 0.5 g / L. Then add modified saponin (the addition amount is 30 times the total mass of bamboo charcoal powder and graphene oxide), and react under a microwave-ultrasonic synergistic field (microwave power 550 W, ultrasonic frequency 40 kHz) for 15 min to form a modified saponin@bamboo charcoal / GO composite;

[0089] (3) Mix the modified saponin@bamboo charcoal / GO composite with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTMAC) and potassium carbonate in a mass ratio of 8:5:2 in DMF, ultrasonically disperse it for 30 min (power 200 W, frequency 40 kHz), then heat it up to 80 °C, stir magnetically under nitrogen protection for 0.5 h, cool it to room temperature after the reaction, wash it 3 times with ethanol and deionized water in turn, and dry it in vacuum at 60 °C for 12 h to obtain a composite foaming agent.

[0090] Step 4: Forming foamed foam

[0091] (1) Mix the composite foaming agent with deionized water, ultrasonically disperse for 10 min (power 200 W, frequency 40 kHz), and stir for 30 min (rotation speed 800 rpm, temperature 25 °C) to obtain a composite foaming agent solution;

[0092] (2) Use a high-pressure air foaming machine to foam the foaming agent solution at 0.5 MPa. The gas-liquid ratio during the foaming process is 1:3 (foaming agent solution). Perform high-speed shearing treatment while foaming, with a shearing rate of 15,000 rpm, to obtain foamed foam.

[0093] Step 5: Preparation of lightweight soil

[0094] (1) Mix cement and steel slag, add a synergistic activator and stir evenly. Then add graphene oxide nanosheets, polycarboxylate water reducer, modified nano bamboo charcoal powder and water to the system and stir into a slurry;

[0095] (2) Inject the foamed foam obtained in Step 4 into the slurry through a high-pressure pump, mix with a double-shaft screw mixer (rotation speed 300 r / min, 5 min), and adjust the wet density to 800 kg / m 3 to obtain foamed lightweight soil.

[0096] Cast and mold the lightweight soil prepared in the example, let it stand at room temperature for 24 h to achieve preliminary curing. Then demold the test block and place it in a standard curing room, cure it at 20 ± 2 °C and relative humidity above 95% for 28 d.

[0097] Example 3

[0098] The mass parts ratio of the raw materials in this example is as follows:

[0099] 50 parts of red mud, 30 parts of blast furnace slag, 13 parts of steel slag, 10 parts of PO42.5 cement, 0.5 part of sodium silicate, 4 parts of calcium hydroxide, 0.3 part of polycarboxylate water reducer, 5 parts of composite foaming agent, 12 parts of modified nano bamboo charcoal powder and 0.1 part of graphene oxide nanosheets.

[0100] The preparation steps of the solid waste foamed lightweight soil are as follows:

[0101] Step 1: Preparation of modified nano bamboo charcoal powder

[0102] Soak bamboo charcoal powder in a mixed acid solution with a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1 for 1 h, filter and wash it with deionized water multiple times until it is neutral to remove the residual acid solution; put the treated bamboo charcoal powder into an oven and dry it at 105 °C for 0.5 h; then add the dried bamboo charcoal powder to a 10% NaOH solution by mass and soak it for 0.5 h, filter and wash it with deionized water until it is neutral, and dry it again at 105 °C for 0.5 h.

[0103] Step 2: Prepare a synergistic activator:

[0104] (1) Activate red mud at 800 °C to obtain activated red mud;

[0105] (2) Crush blast furnace slag to a particle size of ≤2 mm, mix it with activated red mud, add activators (calcium hydroxide and sodium silicate), and perform wet ball milling for 30 min to obtain a synergistic activator.

[0106] Step 3: Preparation of a composite foaming agent:

[0107] (1) Add saponin and lauric anhydride to a mixed system of acetonitrile and water (volume ratio 7:3) according to a molar ratio of 1:3, so that the concentration of saponin is 0.5 mol / L and the concentration of lauric anhydride is 1.5 mol / L, and carry out a reaction under the catalysis of lipase (Novozym 435) (reaction temperature 37 °C, pH 6.8, reaction time 7 h); add silane coupling agent KH560 (5% of the total mass of saponin and lauric anhydride) to the reaction product and stir at 60 °C for 0.5 h to obtain modified saponin;

[0108] (2) Mix bamboo charcoal powder and graphene oxide (GO) according to a mass ratio of 1:2, ultrasonically disperse them in deionized water, and their total concentration is 0.5 g / L. Then add modified saponin (the addition amount is 35 times the total mass of bamboo charcoal powder and graphene oxide), and react for 15 min under a microwave-ultrasonic synergistic field (microwave power 550 W, ultrasonic frequency 40 kHz) to form a modified saponin@bamboo charcoal / GO composite;

[0109] (3) Mix the modified saponin@bamboo charcoal / GO composite, 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTMAC), and potassium carbonate in DMF according to a mass ratio of 10:5:2, ultrasonically disperse for 30 min (power 200 W, frequency 40 kHz), then heat up to 80 °C, stir magnetically under nitrogen protection for 0.5 h, cool to room temperature after the reaction, wash 3 times with ethanol and deionized water in sequence, and dry in vacuum at 60 °C for 12 h to obtain a composite foaming agent.

[0110] Step 4: Form a foamed foam:

[0111] (1) Mix the composite foaming agent with deionized water, disperse it ultrasonically for 10 min (power 200 W, frequency 40 kHz), and stir it for 30 min (rotation speed 800 rpm, temperature 25 °C) to obtain a composite foaming agent solution;

[0112] (2) Use a high-pressure air foaming machine to foam the foaming agent solution at 0.5 MPa. The gas-liquid ratio during the foaming process is 1:3 (foaming agent solution). Perform high-speed shearing treatment during foaming, with a shearing rate of 10,000 rpm, to obtain foamed foam.

[0113] Step Five: Preparation of lightweight soil:

[0114] (1) After mixing cement and steel slag, add a synergistic activator and stir evenly. Then, add graphene oxide nanosheets, polycarboxylate superplasticizer, modified nano-bamboo charcoal powder, and water to the system and stir into a slurry;

[0115] (2) Inject the foamed foam obtained in Step Four into the slurry through a high-pressure pump, mix it with a double-shaft screw mixer (rotation speed 300 r / min, 5 min), and adjust the wet density to 800 kg / m 3 , to obtain foamed lightweight soil.

[0116] Comparative Example 1

[0117] The difference from Example 1 is only that the foaming agent PFA-100 is used to replace the composite foaming agent.

[0118] Comparative Example 2

[0119] The difference from Example 1 is only that the modified bamboo charcoal powder is replaced with an equal amount of graphene oxide nanosheets.

[0120] Perform performance tests on the foamed lightweight soil prepared in the examples and comparative examples of the present invention:

[0121] 1. According to the GB / T 50081-2019 standard, use a compressive strength testing machine to conduct a compression test on the lightweight soil cube specimen (100 mm × 100 mm × 100 mm) to measure the compressive strength.

[0122] 2. According to the GB / T 50081-2019 standard, use a flexural strength testing machine to conduct a three-point bending test on the lightweight soil prism specimen (100 mm × 100 mm × 400 mm) to measure the flexural strength.

[0123] 3. According to the GB / T 50082-2009 standard, place the lightweight soil specimen at -15 °C for 4 hours, then melt it in water at 20 °C for 2 hours, and repeat this process 300 times to measure the freeze-thaw cycle durability of the foamed lightweight soil. The mass loss rate is shown in Table 1.

[0124] 4. According to the standard of GB / T 50082-2009, place the lightweight soil specimens in an environment with a carbon dioxide concentration of 20% and expose them for 28 days to measure the carbonation depth.

[0125] 5. Measure the thermal conductivity according to the standard of GB / T 10294-2008.

[0126] Table 1 shows the performance test results of the foam lightweight soil prepared in each example and comparative example.

[0127] Table 1

[0128]

[0129]

[0130] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A red mud synergistically stimulated metallurgical slag solid waste foam lightweight soil, characterized in that: The invention comprises the following raw material components in parts by weight: 50-65 parts of red mud, 20-30 parts of metallurgical slag, 5-15 parts of steel slag, 10-15 parts of cement, 0.5-1 parts of sodium silicate, 3-5 parts of calcium hydroxide, 0.3-0.4 parts of polycarboxylic acid water reducer, 5-8 parts of composite foaming agent, 8-12 parts of modified nano bamboo charcoal powder and 0.1-0.15 parts of graphene oxide nanosheets.

2. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 1, characterized in that: The preparation method of the modified nano bamboo charcoal powder comprises the following steps: The bamboo charcoal powder is soaked in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, filtered, washed to neutrality, dried, soaked in a sodium hydroxide solution, filtered, washed to neutrality, and dried to obtain modified nano bamboo charcoal powder; The obtained modified nano bamboo charcoal powder is mechanically ground to obtain nano-scale powder, which is the modified nano bamboo charcoal powder.

3. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 2, characterized in that: The volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1; the immersion time in the mixed acid is 0.5-1h; the mass concentration of the sodium hydroxide solution is 8-10%, and the immersion time in the sodium hydroxide solution is 0.5-1h.

4. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 1, characterized in that: The metallurgical slag is blast furnace slag, converter slag or electric furnace slag.

5. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 1, characterized in that: The composite foaming agent is prepared by the following steps: (1) reacting saponin with lauric anhydride under the catalysis of lipase, and adding a silane coupling agent to the product after the reaction to obtain modified saponin; (2) dispersing bamboo charcoal powder and graphene oxide in water, then adding the modified saponin, and reacting under the action of a microwave-ultrasound synergistic field to obtain a modified saponin@bamboo charcoal / GO composite; (3) The modified saponin@bamboo charcoal / GO composite is mixed with 3-chloro-2-hydroxypropyltrimethylammonium chloride and potassium carbonate in a solvent, ultrasonically dispersed, and then reacted at 80° C. for 0.5-1 h under nitrogen protection. After the reaction, the composite foaming agent is obtained after cooling to room temperature, washing and drying.

6. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 5, characterized in that: The molar ratio of the saponin to lauric anhydride is 1:2-3.

7. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 5, characterized in that: The reaction temperature of the lipase-catalyzed reaction in step (1) is 30-40° C., the pH is 6.5-7.0, and the reaction time is 6-8 hours; the reaction temperature of the silane coupling agent added in step (1) is 55-60° C., and the reaction time is 0.5-1 hour.

8. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 5, characterized in that: The mass ratio of the bamboo charcoal powder to the graphene oxide is 1-2:2; and the added amount of the modified saponin is 30-40 times the total mass of the bamboo charcoal powder and the graphene oxide.

9. The red mud synergistically activated metallurgical slag solid waste foam lightweight soil according to claim 5, characterized in that: The mass ratio of the modified saponin@bamboo charcoal / GO composite, 3-chloro-2-hydroxypropyltrimethylammonium chloride and potassium carbonate is 8-10:4-5:2-3.

10. The method for preparing light soil foamed by synergistic activation of metallurgical slag solid waste by red mud according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) mixing metallurgical slag with heat-treated activated red mud, adding calcium hydroxide and sodium silicate, and ball milling to obtain a synergistically activated material; (2) adding the composite foaming agent into water, dispersing by ultrasonication, obtaining a composite foaming agent solution, and then performing a foaming treatment to obtain a foamed foam; (3) After cement and steel slag are mixed, the synergistic excitation material is added and stirred evenly, and then graphene oxide nanosheets, polycarboxylic acid water reducer, modified nano bamboo charcoal powder and water are added to the system and stirred into a slurry; (4) Injecting the foamed foam into the slurry, and mixing to obtain the red mud synergistically stimulated metallurgical slag solid waste foam lightweight soil.

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