High-stability sludge-based foam light soil based on synergistic utilization of multi-source building solid waste and preparation method of high-stability sludge-based foam light soil

Abstract

The invention discloses high-stability sludge-based foam light soil based on synergistic utilization of multi-source building solid waste and a preparation method thereof. The foam light soil is prepared from the following components in parts by mass: 30 to 50 parts of cement, 20 to 30 parts of sludge, 10 to 20 parts of regenerated micro powder, 15 to 25 parts of regenerated fine aggregate, 20 to 30 parts of calcined muck, 5 to 10 parts of microbial bacterial liquid, 20 to 30 parts of seawater, 3 to 5 parts of water reducing agent, 10 to 25 parts of anti-cracking fiber and 5 to 10 parts of composite foaming agent. The preparation method comprises the following steps: adsorbing microbial bacteria liquid by the regenerated fine aggregate to obtain bioactive regenerated fine aggregate, stirring the cement, the sludge, the regenerated micro powder, the calcined muck and the bioactive regenerated fine aggregate together, adding the anti-crack fibers, and pouring the seawater and the water reducing agent; preparing foam from the composite foaming agent, adding, uniformly stirring, forming, demolding and curing. The mud-based foam light soil is good in durability and excellent in chlorine salt erosion resistance, and the problem that the strength is reduced due to dissolution of calcium ions in the mud-based foam light soil is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste resource utilization, and relates to a high-stability silt-based foam light soil based on multi-source building solid waste collaborative utilization and a preparation method thereof. BACKGROUND

[0002] Foam light soil, also known as bubble mixed light soil, as a new type of building material, is suitable for road engineering construction in the widely distributed coastal soft soil area in China due to its characteristics of light weight and high strength, adjustable density and strength, high flowability, convenient construction and excellent durability. The low density characteristics of foam light soil can effectively reduce the additional stress of the foundation and control the post-construction settlement, and its good flow performance is suitable for complex terrain construction.

[0003] Traditional foam light soil uses cement as the main cementitious material, and has problems of high carbon emission and high cost. Therefore, relevant research gradually turns to the preparation method of adding building solid waste-based admixture and inert material to replace cement, so as to realize the dual goals of solid waste resource utilization and economic cost control. At present, marine silt produced by channel dredging in coastal areas reaches hundreds of millions of tons per year, and this kind of silt has the characteristics of high water content (≥50%) and high organic matter content (10%-20%), and it is extremely difficult to directly utilize the resources. More importantly, when the existing technology is used to mix marine silt into cement foam light soil for solidification treatment, the humic acid produced by the degradation of organic matter in the silt will cause erosion and deterioration of the pore structure after cement solidification, resulting in a significant decrease in material performance, and it is difficult to guarantee the long-term stability of foam light soil. At the same time, the compatibility of ordinary water reducing agent and high-organic-matter silt is poor, and the water reducing performance is limited, which further restricts the improvement of the performance of foam light soil.

[0004] Based on the above-mentioned silt research background, the present invention proposes a method for preparing foamed lightweight soil by synergistically utilizing multi-source construction solid waste to improve silt utilization rate: dredged silt, recycled micropowder, recycled fine aggregate, calcined slag and ordinary Portland cement are used as the main raw materials, and microbial culture liquid, seawater, anti-cracking fiber and composite foaming agent are added to prepare high-stability silt-based foamed lightweight soil with both lightweight characteristics and excellent road performance. This technical solution achieves performance optimization through the following mechanisms: the incorporation of recycled micropowder removes bound water from the sludge, increasing the free water content of the system and improving material uniformity and workability. Recycled fine aggregate is used as a microbial carrier, and Bacillus pasteurianus is loaded into the pores of the recycled fine aggregate through a high-pressure adsorption process, forming a bioactive recycled fine aggregate that protects the microorganisms. During the hydration process, the microbial liquid degrades the organic matter in the sludge while generating additional calcium carbonate, which fills the gaps between the pore walls and the matrix, reducing initial defects and promoting structural densification. CASH gel, generated from calcined construction waste, effectively blocks the erosion of organic humic acid in the sludge, reduces the leaching of free calcium ions, and ensures the long-term stability of the material. This technology has important engineering practical value and academic innovation significance for promoting the green and sustainable development of road construction. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste. The soil has good durability and excellent resistance to chloride erosion, and effectively solves the problems of high water content, high organic matter content, continuous release of humic acid, and calcium ion dissolution in silt-based foamed lightweight soil, which lead to a decrease in the strength of the foamed lightweight soil.

[0006] Another object of the present invention is to provide a method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste.

[0007] The technical solution adopted by the present invention is a high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste, which includes the following components in parts by mass: 35-60 parts of cement, 20-30 parts of silt, 10-20 parts of recycled micropowder, 15-25 parts of recycled fine aggregate, 20-30 parts of calcined slag, 5-10 parts of microbial liquid, 20-30 parts of seawater, 3-5 parts of water reducer, 10-25 parts of anti-cracking fiber and 5-10 parts of composite foaming agent.

[0008] Furthermore, the cement is a mixture of ordinary Portland cement and sulphoaluminate cement in a mass ratio of 7-9:1-3.

[0009] Furthermore, the silt is coastal dredged silt with a moisture content of 50% to 60% and an organic matter content of 10% to 20%; the inorganic salt content of the seawater is ≤5%.

[0010] Furthermore, the recycled micro powder is obtained by crushing waste concrete and waste clay bricks, and has a particle size of ≤75 μm; the recycled fine aggregate is obtained by crushing waste concrete and waste clay bricks, and has a particle size of ≤2.36 mm.

[0011] Furthermore, the calcined slag is obtained by calcining kaolinite slag at 650-850° C. for 1.5-2 hours, and has a particle size of ≤75 μm.

[0012] Furthermore, the microbial culture liquid is Bacillus pasteurianus, and the number of viable bacteria is ≥1.2×10 8 CFU / g.

[0013] Furthermore, the water reducer is a mixture of a naphthalene-based water reducer and a melamine-based water reducer in a mass ratio of 3-6:1-3.

[0014] Furthermore, the anti-cracking fiber is glass fiber or polypropylene fiber, with a fiber diameter of 10 to 40 μm and a length of 10 to 20 mm.

[0015] Furthermore, the composite foaming agent is a mixture of alkylamidopropyl betaine, sodium lauryl sulfate, hydroxymethyl cellulose and water in a mass ratio of 2-5:1-3:0.1-0.4:30-70, and seawater is added to dilute the mixture 30-40 times based on the mass of the alkylamidopropyl betaine to obtain a uniform solution, which is then passed through a foaming machine to obtain foam.

[0016] A method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste comprises the following steps:

[0017] S1: Weigh 35-60 parts of cement, 20-30 parts of silt, 10-20 parts of recycled micropowder, 15-25 parts of recycled fine aggregate, 20-30 parts of calcined slag, 5-10 parts of microbial liquid, 20-30 parts of seawater, 3-5 parts of water reducer, 10-25 parts of anti-cracking fiber, and 5-10 parts of composite foaming agent, respectively, according to their mass proportions.

[0018] S2. First, take the microbial liquid and place it in a negative pressure vacuum pump. Then, add the recycled fine aggregate and shake it to make it evenly distributed. Adsorb it for 15 to 20 minutes under a vacuum pressure of 0.4 to 1 MPa to obtain bioactive recycled fine aggregate. Pour the weighed cement, calcined slag, silt, recycled micropowder and bioactive recycled fine aggregate into a mixing machine and stir at a speed of 9 to 12 r / min for 1 to 2 minutes. During the stirring process, slowly and evenly add the weighed anti-cracking fiber to ensure uniform mixing of various materials.

[0019] S3, pour the weighed seawater and water reducer into a mixing machine, and stir at a speed of 40-45 r / min for 1-2 minutes;

[0020] S4, diluting the weighed composite foaming agent with water, adding the obtained foam to a foaming machine to obtain the desired foam, adding the foam to the slurry in the mixer and stirring and mixing; after stirring evenly, forming and demolding, and curing the obtained foam. The curing conditions are: relative humidity ≥ 95%, temperature 18 ~ 22 ° C.

[0021] The beneficial effects of the present invention are:

[0022] Compared to existing technologies, this invention proposes a method for preparing highly stable silt-based foamed lightweight soil based on the synergistic utilization of multiple sources of construction solid waste. The highly stable silt-based foamed lightweight soil is prepared by combining cement, silt, recycled micropowder, recycled fine aggregate, calcined slag, microbial culture fluid, seawater, a composite foaming agent, and a water reducer. Recycled fine aggregate serves as a carrier for the microbial culture fluid. Four materials, cement, silt, recycled micropowder, and calcined slag, are mixed evenly with seawater to produce a fluid slurry. This is then mixed with a proportionately prepared foam to produce a foamed lightweight soil with adjustable density. Compared to traditional cement-based cementitious materials, the addition of calcined slag offers advantages such as higher strength, a dense slurry structure, and excellent resistance to humic acid erosion. Furthermore, the combination of recycled fine aggregate and microbial culture fluid effectively reduces the organic matter content and generates additional CaCO3, thereby enhancing the strength of the foamed lightweight soil. Its hydration products are primarily hydrated calcium silicate and hydrated calcium aluminosilicate. These gels can adsorb or solidify chloride ions in solution. The main function of the composite foaming agent is to improve the stability of the freshly mixed foam in an alkaline environment, and to obtain a foam with a large amount of foam and stable and unbreakable foam. This reduces or avoids the floating and bursting of bubbles during mixing, pouring and static periods, and ensures that the overall quality of the foamed lightweight soil is stable and uniform. The composite water reducer hinders the formation of flocculent particles in the cementitious material, releases internal free water, and improves the rheological properties of the slurry. In the present invention, the solid waste content accounts for more than 52%, and the foamed lightweight soil obtained by the preparation method of the present invention has good durability, adjustable and controllable bulk density, high road performance, and its 3d unconfined compressive strength is ≥0.5MPa, and its 28d unconfined compressive strength is ≥1.2MPa.

[0023] The main technical advantages of the high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste of the present invention are:

[0024] 1) Calcined slag and recycled micropowder are used to partially replace cement as the cementing material of foamed lightweight soil, which reduces carbon emissions and can better solidify chloride ions in sludge, resist the long-term erosion of subsequent humic acid, and effectively improve the durability of foamed lightweight soil; the recycled micropowder is used to physically adsorb the bound water in the sludge, increase the free water in the system by 15% to 20%, improve the fluidity of the slurry, and reduce the porosity after solidification; the microbial liquid adsorbed in the recycled fine aggregate can decompose organic matter and react with free Ca 2+The reaction generates calcium carbonate, which fills the gaps between the pore walls and the matrix, repairs microcracks, and further improves the long-term stability of the foamed lightweight soil.

[0025] 2) The use of composite foaming agents can improve the stability and foaming rate of foam in seawater environments, ensuring the formation of a good pore structure of foam lightweight soil materials; the use of composite water reducers can improve the fluidity of the material through adsorption, dispersion, wetting and lubrication, thereby reducing water consumption under the same ratio, improving the fluidity of foam lightweight soil, and reducing costs; the addition of anti-cracking fibers can effectively improve the crack resistance of foam lightweight soil through fiber bridging, reduce early shrinkage cracking, and improve road service performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a flow chart of the preparation of silt-based foamed lightweight soil according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] A high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste includes the following components in parts by mass: 30-60 parts of cement, 20-30 parts of calcined slag, 20-30 parts of silt, 10-20 parts of recycled micropowder, 15-25 parts of recycled fine aggregate, 5-10 parts of microbial liquid, 20-30 parts of seawater, 1-5 parts of water reducer, 10-30 parts of anti-cracking fiber and 5-10 parts of composite foaming agent.

[0030] The cement is a mixture of ordinary Portland cement and sulphoaluminate cement in a mass ratio of 7-9:1-3; the silt is coastal dredged silt with a moisture content of ≥50% and an organic matter content of 10%-20%. The composition of the silt is shown in Table 2; the calcined slag is kaolinite slag calcined at 650-850°C for 1.5-2h, with a particle size of ≤75μm; the seawater has an inorganic salt content of ≤5%. The composition of the kaolinite slag is shown in Table 1.

[0031] Recycled micropowder is obtained by crushing waste concrete, waste clay bricks and other construction waste, with a particle size of ≤75μm. Recycled fine aggregate is obtained by crushing waste concrete, waste clay bricks and other construction waste, with a particle size of ≤2.36mm. Components of waste concrete: quartz sand, limestone particles (CaCO3), CSH gel, Ca(OH)2, unhydrated cement. Components of waste clay bricks: porous structure, containing quartz, kaolinite and glass phase; the main components of recycled micropowder and recycled fine aggregate are CaO, SiO2, Al2O3 and Fe2O3. The difference between recycled micropowder and recycled fine aggregate is only the particle size. Recycled micropowder is added as a supplementary cementitious material, which can effectively promote cement hydration and capture water adsorbed in the sludge; the porous structure of recycled fine aggregate can provide a good carrier for microbial liquid.

[0032] The microbial culture liquid is Bacillus pasteurianus, with a viable cell count of ≥1.2×10 8 CFU / g, microbial culture liquid is used to degrade high organic matter in sludge and can generate CaCO3.

[0033] Table 1 Composition of kaolinite slag

[0034] chemical composition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO <![CDATA[K2O]]> SO3 other Quality score 55.01 29.95 10.25 0.07 2.26 0.13 2.33

[0035] Kaolinite-rich slag is converted into metakaolinite (Al2O3·2SiO2) by calcination at 800℃, which has high pozzolanic activity.

[0036] Table 2 Composition of sludge

[0037] chemical composition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> Fe2O3 CaO <![CDATA[K2O]]> <![CDATA[SO3]]> other Quality score 52.63 25.07 11.38 1.43 3.89 0.73 4.87

[0038] This embodiment of the invention effectively utilizes silt, addressing its high water content, organic matter, and chloride ion content, making it difficult to utilize. By combining multiple solid wastes, silt is effectively utilized for roadbed filling. The composite foaming agent is a 3:1 mixture of composite alkylamidopropyl betaine and sodium lauryl sulfate.

[0039] The composite foaming agent is a mixture of composite alkylamidopropyl betaine, sodium lauryl sulfate, hydroxymethyl cellulose, and water (seawater) in a mass ratio of 3-5:3-1:0.1-0.4:30-70. The solution is diluted 30-40 times with seawater, based on the mass of the composite alkylamidopropyl betaine before dilution, to form a uniform solution. The solution is then passed through a foaming machine to produce foam. Excessive addition of composite foaming agent can exacerbate defoaming and agglomeration, while too little can prevent the lightweight road fill from being achieved.

[0040] The anti-cracking fiber is glass fiber or polypropylene fiber, with a fiber diameter of 10 to 40 μm and a length of 10 to 20 mm.

[0041] The water-reducing agent is a mixture of naphthalene-based water-reducing agent and melamine-based water-reducing agent in a mass ratio of 3:1, which reduces the water-binder ratio to 0.4, the slurry fluidity reaches 180mm, and the strength is increased by 20%.

[0042] The dosage of water reducer is determined according to the final ratio of each component, and the specific dosage is adjusted according to the effective components of the water reducer and the rheological properties of the foam lightweight soil.

[0043] Example 1,

[0044] A method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste, such as Figure 1 As shown, the following steps are included:

[0045] S1. Select materials: Weigh, by mass, 40 parts cement, 25 parts calcined slag, 25 parts silt, 18 parts recycled micropowder, 22 parts recycled fine aggregate, 8 parts microbial solution, 25 parts seawater, 3 parts water reducer, 20 parts anti-cracking fiber, and 5 parts composite foaming agent. The silt moisture content must be measured in advance and calculated into the total mass of seawater required (60% in this example) to ensure that the required dry silt meets the design value. When calculating the total mass of seawater to be added, subtract the water content already in the silt.

[0046] Among them, cement is a mixture of ordinary Portland cement and sulfoaluminate cement in a mass ratio of 7:2; calcined slag is obtained by calcining kaolinite slag at 800℃ for 1.5h, with a particle size of ≤75μm; recycled micropowder and recycled fine aggregate are both obtained by crushing waste concrete and waste clay bricks (mixed in a mass ratio of 1:1), the particle size of recycled micropowder is ≤75μm, and the particle size of recycled fine aggregate is ≤2.36mm; the main components of recycled micropowder and recycled fine aggregate are CaO, SiO2, Al2O3 and Fe2O3.

[0047] The anti-cracking fiber is glass fiber with a fiber diameter of 10 μm and a length of 20 mm; the water reducer is a mixture of naphthalene-based water reducer and melamine-based water reducer in a mass ratio of 3:1; the composite foaming agent is a mixture of composite alkyl amidopropyl betaine, sodium lauryl sulfate, hydroxymethyl cellulose and water in a mass ratio of 3:1:0.2:60, and seawater is added to dilute it 30 times based on the mass of the composite alkyl amidopropyl betaine to obtain a uniform solution, which is then passed through a foaming machine to obtain foam.

[0048] In step S2, first place the bacterial solution in a negative pressure vacuum pump, then add the recycled fine aggregate and shake it to evenly distribute it. Adsorb it for 15 minutes under a vacuum pressure of 0.4 MPa to obtain the bioactive recycled fine aggregate. Pour the weighed cement, calcined slag, silt, recycled micropowder, and bioactive recycled fine aggregate into a mixer and stir at 10 r / min for 1 minute. During the stirring process, slowly and evenly add the weighed anti-cracking fiber to ensure uniform mixing of all materials.

[0049] S3, pour the weighed seawater and water reducer into the mixing machine and stir at a speed of 40 r / min for 1 minute;

[0050] S4, after diluting the composite foaming agent with water, add it into the foaming machine to prepare the required foam, add the foam into the slurry in the mixer and stir and mix; after stirring evenly, form and demould, and obtain solid waste-based sludge foam lightweight soil after curing; the curing process conditions are relative humidity ≥95% and temperature 20℃.

[0051] In Example 1, the Ca(OH)2 produced by cement hydration and the Al2O3 of the calcined slag form Friedel salt (3CaO·Al2O3·CaCl2·10H2O) in a seawater Cl- environment. The 28-day compressive strength reaches 2.48 MPa, a 40% increase compared to the single component, effectively eliminating the continuous release of organic humic acid. This is because metakaolin is rich in amorphous silicon and aluminum oxides, which have the ability to quickly capture calcium ions in calcium hydroxide solution, forming a stable cement, and is not easily corroded by humic acid. This proves that calcined slag can effectively improve the long-term strength of foamed lightweight soil, and the addition of microbial culture fluid can accelerate the decomposition of organic matter and reduce its impact. After 180 days of curing, the fulvic acid content in the cement-solidified sludge is reduced to 0.5%, accelerating the pozzolanic effect.

[0052] Example 1: A composite foaming agent is a complex of alkylamidopropyl betaine, sodium lauryl sulfate, hydroxymethyl cellulose, and water. Betaine is compounded with sodium lauryl sulfate (for foaming) and hydroxymethyl cellulose (for thickening). This composite foaming agent can be foamed using seawater, achieving a foaming expansion ratio of 38, a foam exudation of 5 g per 1 hour and a settling distance of 0.5 mm. The settling distance and exudation per 1 hour and 1 hour are determined by placing the fresh foam in a 1L beaker and observing the foam's settling distance (the distance between the foam and the beaker rim) and exudation within 1 hour. Existing animal protein foaming with seawater achieves a foaming expansion ratio of 12, a foam exudation of 91.9 g per 1 hour and a settling distance of 5.3 mm.

[0053] The sludge used in Example 1 (especially dredged sludge) typically has the following characteristics: a high organic matter content (10% to 20%), such as humic acid, which can hinder cement hydration and reduce the strength of the foamed lightweight soil. The organic matter coats the cementitious particles, inhibiting the formation of hydration products. Furthermore, the organic matter gradually degrades, releasing acidic substances (such as humic acid), which erode the hardened slurry over time, increasing free calcium ions in the matrix and leading to performance degradation.

[0054] Example 2,

[0055] A method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste comprises the following steps:

[0056] S1. Select materials: Weigh 35 parts of cement, 20 parts of calcined slag, 20 parts of silt, 18 parts of recycled micropowder, 15 parts of recycled fine aggregate, 5 parts of microbial liquid, 20 parts of seawater, 5 parts of water reducer, 10 parts of anti-cracking fiber and 6 parts of composite foaming agent according to their mass proportions; the silt moisture content is 50%.

[0057] The cement is a mixture of ordinary Portland cement and sulphoaluminate cement in a mass ratio of 8:3; the calcined slag is obtained by calcining kaolinite slag at 650°C for 2 hours, and the particle size is ≤75μm.

[0058] The anti-cracking fiber is polypropylene fiber with a fiber diameter of 10 μm and a length of 20 mm; the water reducer is a mixture of a naphthalene-based water reducer and a melamine-based water reducer in a mass ratio of 5:3; the composite foaming agent is a mixture of composite alkyl amidopropyl betaine, sodium lauryl sulfate, hydroxymethyl cellulose and water in a mass ratio of 2:2:0.2:45, and seawater is added to dilute the mixture 40 times based on the mass of the composite alkyl amidopropyl betaine to obtain a uniform solution, which is then passed through a foaming machine to obtain foam; the remaining raw materials are the same as those in Example 1.

[0059] In step S2, first place the bacterial solution in a negative pressure vacuum pump, then add the recycled fine aggregate and shake it evenly to ensure a relatively even distribution. Adsorb it under a negative pressure of 1 MPa for 20 minutes to obtain the bioactive recycled fine aggregate. Pour the weighed cement, calcined slag, silt, recycled micropowder, and bioactive recycled fine aggregate into a mixer and stir at a speed of 10 r / min for 1 minute. During the stirring process, slowly and evenly add the weighed anti-cracking fiber to ensure uniform mixing of all materials.

[0060] S3, pour the weighed seawater and water reducer into the mixing machine and stir at a speed of 43 r / min for 1 minute;

[0061] S4, the composite foaming agent is diluted with water, then added to the foaming machine to obtain the required foam, and the foam is added to the slurry in the mixer for stirring and mixing; after stirring and uniformity, shaping and demolding, and curing, the solid waste-based sludge foam lightweight soil is obtained; the curing process conditions are relative humidity ≥ 95%, and temperature 22℃.

[0062] Example 3,

[0063] A preparation method of high-stability sludge-based foam lightweight soil based on multi-source building solid waste collaborative utilization, comprising the following steps:

[0064] S1, selecting materials: taking cement 45 parts, calcined slag soil 20 parts, sludge 20 parts, recycled micro powder 15 parts, recycled fine aggregate 18 parts, microbial liquid 6 parts, seawater 30 parts, water reducing agent 5 parts, anti-cracking fiber 20 parts and composite foaming agent 10 parts according to mass fraction; the moisture content of sludge is 50%.

[0065] The cement is a mixture of ordinary portland cement and sulphoaluminate cement in a mass ratio of 9:1; the calcined slag soil is kaolinite slag soil calcined at 650℃ for 2h, with a particle size ≤75μm.

[0066] The anti-cracking fiber is polypropylene fiber with a fiber diameter of 10μm and a length of 20mm; the water reducing agent is a mixture of naphthalene-based water reducing agent and melamine-based water reducing agent in a mass ratio of 5:3; the composite foaming agent is a mixture of composite alkyl amide propyl betaine, sodium dodecyl sulfate, hydroxymethyl cellulose and water in a mass ratio of 5:3:0.4:30, which is diluted 40 times with seawater based on the mass of composite alkyl amide propyl betaine to obtain a uniform solution, and then foamed by a foaming machine to obtain foam; the remaining raw materials are the same as in Example 1.

[0067] S2, first, the microbial liquid is placed in a negative pressure vacuum pump, then the recycled fine aggregate is added and stirred to make it more evenly distributed, and under the condition of vacuum negative pressure of 0.4MPa, it is adsorbed for 15min to become bioactive calcined slag soil. The weighed cement, calcined slag soil, sludge, recycled micro powder and bioactive recycled fine aggregate are poured into the mixer at a speed of 12r / min for 2min; during stirring, the weighed anti-cracking fiber is slowly and evenly added to ensure uniform mixing of various materials;

[0068] S3, the weighed seawater and water reducing agent are poured into the mixer, and stirred at a speed of 43r / min for 2min;

[0069] S4, the composite foaming agent is diluted with water, then added to the foaming machine to obtain the required foam, and the foam is added to the slurry in the mixer for stirring and mixing; after stirring and uniformity, shaping and demolding, and curing, the solid waste-based sludge foam lightweight soil is obtained; the curing process conditions are relative humidity ≥ 95%, and temperature 22℃.

[0070] Example 4,

[0071] A method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste comprises the following steps:

[0072] S1. Select materials: Weigh 60 parts of cement, 30 parts of calcined slag, 30 parts of silt, 20 parts of recycled micropowder, 25 parts of recycled fine aggregate, 10 parts of microbial liquid, 30 parts of seawater, 3 parts of water reducer, 25 parts of anti-cracking fiber, and 8 parts of composite foaming agent according to the following mass proportions; the silt moisture content is 50%.

[0073] The calcined slag is obtained by calcining kaolinite slag at 850° C. for 1.5 hours, and the particle size is ≤75 μm.

[0074] The anti-cracking fiber is glass fiber with a fiber diameter of 40 μm and a length of 10 mm; the water reducer is a mixture of a naphthalene-based water reducer and a melamine-based water reducer in a mass ratio of 6:2.5; the composite foaming agent is a mixture of composite alkyl amidopropyl betaine, sodium lauryl sulfate, hydroxymethyl cellulose and water in a mass ratio of 4:2:0.1:70, and seawater is added to dilute the mixture 35 times based on the mass of the composite alkyl amidopropyl betaine to obtain a uniform solution, which is then passed through a foaming machine to obtain foam; the remaining raw materials are the same as those in Example 1.

[0075] In step S2, first place the bacterial solution in a negative pressure vacuum pump, then add the recycled fine aggregate and shake it to ensure a relatively even distribution. Adsorb it for 15 minutes under a vacuum pressure of 0.4 MPa to obtain the bioactive calcined slag. Pour the weighed cement, calcined slag, silt, recycled micropowder, and bioactive recycled fine aggregate into a mixer and stir at 9 rpm for 2 minutes. During the stirring process, slowly and evenly add the weighed anti-cracking fiber to ensure uniform mixing of all materials.

[0076] S3, pour the weighed seawater and water reducer into the mixing machine and stir at a speed of 45 r / min for 2 minutes;

[0077] S4, after diluting the composite foaming agent with water, add it into the foaming machine to prepare the required foam, add the foam into the slurry in the mixer and stir and mix; after stirring evenly, form and demould, and obtain solid waste-based sludge foam lightweight soil after curing; the curing process conditions are relative humidity ≥95% and temperature 18°C.

[0078] Example 5,

[0079] A method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste:

[0080] S1. Select materials: Weigh 35 parts cement, 20 parts calcined slag, 20 parts silt, 10 parts recycled micropowder, 15 parts recycled fine aggregate, 5 parts microbial culture fluid, 20 parts seawater, 5 parts water reducer, 10 parts anti-cracking fiber, and 5 parts composite foaming agent according to the following mass ratios. The remaining steps are the same as in Example 1.

[0081] The experimental data of Examples 1-5 are shown in Table 3.

[0082] Table 3 Experimental data of Examples 1-5

[0083]

[0084] Comparative Example 1,

[0085] A method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste:

[0086] S1, select materials: weigh 60 parts of cement, 20 parts of silt, 20 parts of seawater, 5 parts of water reducer, 10 parts of anti-cracking fiber, and 5 parts of composite foaming agent according to the following mass parts. The remaining steps are the same as in Example 1.

[0087] Comparative Example 2,

[0088] A method for preparing highly stable silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste:

[0089] S1. Select materials: Weigh 40 parts of cement, 20 parts of calcined slag, 20 parts of silt, 20 parts of seawater, 5 parts of water reducer, 10 parts of anti-cracking fiber, and 5 parts of composite foaming agent according to the following mass ratios. The remaining steps are the same as in Example 1.

[0090] The mechanical properties of Example 5 and Comparative Examples 1-2 are shown in Table 4, the chloride ion corrosion results of Examples 1-5 are shown in Table 5, and the sulfate corrosion durability test results of Examples 1-5 are shown in Table 6.

[0091] Table 4 Mechanical properties

[0092]

[0093] Table 5 Chloride ion corrosion results

[0094]

[0095] Table 6 Sulfate corrosion durability test results

[0096]

[0097]

[0098] The biggest difference between silt and other sludge is rich in organic matter, under natural conditions, the organic matter will slowly decompose, the humic acid produced will certainly neutralize the alkaline environment of cement and microbial bacteria liquid after hydration, affect the pozzolanic reaction process. In addition, humic acid may also erode the formed hydration silicate cementing material. It is found that when the curing period is more than 90d, the concentration of calcium ion increases, which shows that the calcium ion after solidification becomes free state again. According to this, it can be inferred that the hydration cementing material may be dissolved due to the erosion of humic acid. After the neutralization of alkaline solution and humic acid, the original acidic environment is broken, which will promote the organic matter to continue to decompose humic acid, and the content of humic acid gradually increases. The ionic state of humic acid will adhere to the surface of the sludge particles, on the one hand, due to the influence of fulvic acid in humic acid on the cementing between cement hydration products and silt, the cement hydration products cannot form a continuous network skeleton structure, so that the strength grows slowly, even shows a downward trend; on the other hand, the fulvic acid dissolves the cement, lime hydration products, Ca 2+ Gradually free from the cementing material, destroy the cementing structure. Because the silt has a large water demand, it will greatly reduce the fluidity of the foam lightweight soil and damage the pore structure.

[0099] During the initial hydration phase of the cement paste, the addition of calcined slag absorbs a significant amount of water from the system. The resulting vacuum pressure effect effectively reduces the distance between the cement paste and the recycled fine aggregate, improving the bond strength between the two. During the hydration process, the recycled fine aggregate slowly releases water, acting as a self-curing agent and facilitating cement hydration. During this process, microorganisms in the recycled fine aggregate degrade organic matter and generate CaCO₃, significantly reducing the humic acid content. Simultaneously, the CaCO₃ fills the pores of the foamed lightweight soil, strengthening the pore walls. The metakaolin in the calcined slag undergoes a secondary pozzolanic reaction with the hydration product, Ca(OH)2. The metakaolin in the calcined slag also undergoes a pozzolanic reaction with lime, further forming CSH gel. Changes in the Ca(OH)2 content of the hydration product reflect the extent of the metakaolin pozzolanic reaction. The addition of calcined slag increases the Al content in the hydrated CSH gel, resulting in significantly more CASH gel compared to samples without calcined slag. This is due to the large amount of Al2O3 present in the calcined slag. During the hydration process, some aluminum atoms dissolve into the CSH gel. During this dissolution process, Al atoms dissociate from the metakaolin glass and replace Si atoms in the CSH gel, forming aluminum oxide tetrahedra. Aluminum oxide tetrahedra act as bridges in the CSH gel. The greater the number of aluminum oxide tetrahedra, the higher the degree of polymerization of the CASH gel. These tetrahedra form an amorphous phase that bonds with the surrounding cement, forming a cohesive whole and enhancing the microstructure. Metakaolin has the ability to rapidly capture calcium ions, and its cement resists the erosion of humic acid. Therefore, the inherent porous nature of calcined slag makes it feasible as a carrier for cement-based microorganisms, thereby improving the various properties of foamed lightweight soil.

[0100] The embodiment of the present invention makes Cl in seawater – Combined with AFm, Friedel salt is formed. Friedel salt fills the pores of the hardened slurry to make the structure more compact. The metakaolin in the calcined clay promotes the hydration reaction, reduces the setting time, shortens the time that bubbles are exposed to an unstable state, limits the change in bubble volume, reduces bubble merging or rupture, and maintains independent and uniform distribution of foam. This is manifested in a decrease in pore size, a decrease in the proportion of connected pores, and a more regular pore shape with almost no large pores. The microbial culture provides an alkaline environment (pH>12), promotes the mineralization of organic matter, and accelerates the formation of CSH gel. The calcined slag provides active Al2O3, which reacts with Ca(OH)2 to form hydrated calcium aluminosilicate (CASH), enhancing corrosion resistance.

[0101] The embodiment of the present invention is based on the collaborative utilization of multi-source construction solid waste and is a high-stability silt-based foamed lightweight soil with a bulk density of 800-1200kg / m 3, 28d strength ≥1.2MPa, anti-Cl-erosion performance is 50% better than ordinary lightweight soil, effectively solving the problems of high organic matter content in silt, continuous release of humic acid, and decreased calcium ion dissolution strength; can be used in coastal soft foundation road filling and slope backfill.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste, characterized in that: The composition includes the following components in parts by mass: 35-60 parts of cement, 20-30 parts of silt, 10-20 parts of recycled micropowder, 15-25 parts of recycled fine aggregate, 20-30 parts of calcined slag, 5-10 parts of microbial liquid, 20-30 parts of seawater, 3-5 parts of water reducer, 10-25 parts of anti-cracking fiber and 5-10 parts of composite foaming agent.

2. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The cement is a mixture of ordinary Portland cement and sulphoaluminate cement in a mass ratio of 7-9:1-3.

3. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The silt is coastal dredged silt with a moisture content of 50% to 60% and an organic matter content of 10% to 20%. The inorganic salt content of the seawater is ≤5%.

4. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The recycled micro powder is obtained by crushing waste concrete and waste clay bricks, and has a particle size of ≤75 μm; the recycled fine aggregate is obtained by crushing waste concrete and waste clay bricks, and has a particle size of ≤2.36 mm.

5. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The calcined slag is obtained by calcining kaolinite slag at 650-850° C. for 1.5-2 hours, and has a particle size of ≤75 μm.

6. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The microbial liquid is Bacillus pasteurianus, and the number of viable bacteria is ≥1.2×10 8 CFU / g.

7. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The water reducer is a mixture of a naphthalene-based water reducer and a melamine-based water reducer in a mass ratio of 3-6:1-3.

8. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The anti-cracking fiber is glass fiber or polypropylene fiber, with a fiber diameter of 10 to 40 μm and a length of 10 to 20 mm.

9. The high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to claim 1, characterized in that: The composite foaming agent is prepared by mixing alkylamidopropyl betaine, sodium lauryl sulfate, hydroxymethyl cellulose and water in a mass ratio of 2-5:1-3:0.1-0.4:30-70, adding seawater to dilute the mixture 30-40 times based on the mass of the alkylamidopropyl betaine to obtain a uniform solution, and then passing the mixture through a foaming machine to obtain foam.

10. A method for preparing high-stability silt-based foamed lightweight soil based on the coordinated utilization of multi-source construction solid waste according to any one of claims 1 to 19, characterized in that: The following steps are involved: S1: Weigh 35-60 parts of cement, 20-30 parts of silt, 10-20 parts of recycled micropowder, 15-25 parts of recycled fine aggregate, 20-30 parts of calcined slag, 5-10 parts of microbial liquid, 20-30 parts of seawater, 3-5 parts of water reducer, 10-25 parts of anti-cracking fiber, and 5-10 parts of composite foaming agent, respectively, according to their mass proportions. S2. First, take the microbial liquid and place it in a negative pressure vacuum pump. Then, add the recycled fine aggregate and shake it to make it evenly distributed. Adsorb it for 15 to 20 minutes under a vacuum pressure of 0.4 to 1 MPa to obtain bioactive recycled fine aggregate. Pour the weighed cement, calcined slag, silt, recycled micropowder and bioactive recycled fine aggregate into a mixing machine and stir at a speed of 9 to 12 r / min for 1 to 2 minutes. During the stirring process, add the weighed anti-cracking fiber slowly and evenly to ensure uniform mixing of various materials; S3, pour the weighed seawater and water reducer into a mixing machine, and stir at a speed of 40-45 r / min for 1-2 minutes; S4, diluting the weighed composite foaming agent with water, adding the obtained foam to a foaming machine to obtain the desired foam, adding the foam to the slurry in the mixer and stirring and mixing; after stirring evenly, forming and demolding, and curing the obtained foam. The curing conditions are: relative humidity ≥ 95%, temperature 18 ~ 22 ° C.

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