In-situ foamed light-weight silt solidified soil, and preparation method and foaming agent thereof

Abstract

The application discloses in-situ foaming light-weight silt solidified soil and a preparation method and a foaming agent thereof, and belongs to the technical field of solidified soil materials.The light-weight silt solidified soil of the application uses an in-situ chemical foaming agent, and comprises metal aluminum powder and non-metal compound composite particles / powder.The aluminum powder particles are separated by the non-metal compound particles, and the median particle diameter of the metal aluminum powder and the non-metal compound particles is less than or equal to 5 microns.The application uses the metal aluminum powder and the non-metal compound composite particles / powder as the in-situ chemical foaming agent for the preparation of the light-weight silt solidified soil.The aluminum powder particles are fully separated by the non-metal compound through superfine grinding, and the separation of the non-metal compound particles ensures that smaller pores are generated through in-situ foaming and the uniformity of the pore size is ensured.Meanwhile, the agglomeration of the aluminum powder after being contacted with water can be effectively avoided, the pores are prevented from being connected to form large bubbles, and thus the strength of the obtained light-weight silt solidified soil is ensured.

Description

Technical Field

[0001] This invention belongs to the field of solidified soil materials technology, specifically relating to an in-situ foamed lightweight silt solidified soil material, its preparation method, and foaming agent. Background Technology

[0002] To meet construction needs while ensuring structural safety, engineering construction is gradually moving towards lightweight and cost-effective technologies. Lightweight silt soil is produced by creating a porous structure within the soil through physical or chemical means. This porous structure can consist of lightweight solid particles (EPS particles) or a gas (air, oxygen, hydrogen, etc.). The presence of these pores gives lightweight silt soil its excellent lightweight properties (density less than water). Furthermore, lightweight silt soil possesses self-compacting properties, adjustable density and strength, vibration reduction and noise reduction, and ease of construction. It is widely used in projects such as track engineering backfilling, roadbed widening, bridge backfilling, mine filling, and pipeline backfilling, aligning with the requirements of lightweight and cost-effective engineering construction.

[0003] The conventional foaming method for lightweight silt soil is physical foaming, which involves pre-expanding the foaming components into a foam using mechanical equipment, then mixing this foam with slurry and curing it to obtain lightweight silt soil. Representative patent applications related to physically foamed lightweight soil include:

[0004] Patent application CN 110128073 A discloses a microporous foamed lightweight soil and its preparation method. The method employs a physical foaming process, diluting the foaming components with water (mass ratio 1:50-100) and then placing the mixture in a foaming machine under a pressure of 0.6-0.8 MPa to obtain foamed foam (settlement distance 0-3 mm, water permeation 0-25 mL). This foamed lightweight soil is then mixed evenly with a cementitious slurry (a slurry formed by mixing PO42.5 cement, fly ash, molybdenum tailings powder, and water) to obtain the microporous foamed lightweight soil. This foamed lightweight soil has uniform and rounded pores, a high closed-cell rate, good closed-cell effect, high strength, and low permeability and water absorption. However, it requires foaming auxiliary equipment and is produced under high pressure.

[0005] Patent application CN 105801165A discloses a mixed foamed silt lightweight permeable composition and its preparation method for roadbed filling. The method involves mixing and stirring cement, fly ash, plasticizer, sand, water, and silt to form a slurry. Then, foaming foam (obtained by diluting the foaming component with water and then foaming it using a high-pressure air foaming machine) is added and mechanically stirred until homogeneous. The mixture is then molded, cured, demolded, and cured again to form foamed silt specimens. The foaming component is a mixture of animal protein foaming components and anionic foaming components. The lightweight silt soil prepared by this method has a high permeability coefficient and good water permeability. However, the foaming component requires mechanically assisted foaming, and the proportion of silt in the foamed soil must be less than 50%; otherwise, the strength of the lightweight soil will be significantly reduced.

[0006] As can be seen from the above representative patent applications, the foaming foam used in the existing physical foaming method for preparing lightweight silt mostly involves diluting the foaming components with water in a certain proportion beforehand, and then preparing it under high pressure using a foaming machine. This not only requires auxiliary mechanical equipment (foaming machine) but also high-pressure gas. Moreover, after the foaming foam is prepared, the storage time is short, and there will be some defoaming and water bleeding. When mixed with slurry, the foam will be consumed to a certain extent. More importantly, because the foam is unstable, foam stabilizing components need to be added, and the proportion of foaming foam added is relatively high, generally more than 70% of the volume of high water content slurry.

[0007] A search revealed Chinese patent CN113173769A, which discloses a chemically foamed lightweight silt soil and its production method. This application uses a chemical foaming process to prepare the lightweight silt soil. It selects a special foaming component—hydrogen peroxide—which, when added, does not pollute the soil. Furthermore, it requires no dilution or high-pressure foaming, has a long shelf life, and requires a low dosage of the foaming component. The chemically foamed lightweight silt soil prepared using this method has advantages such as low bulk density, high strength, low volume shrinkage, high silt utilization rate, good self-compacting properties, good water stability, significant environmental benefits, and low production cost. However, to make the sludge suitable for foaming and foam stabilization, this application requires the addition of various components such as inorganic composite binders, coagulants, thickeners, plasticizers, and hydrophobic components to the sludge before adding hydrogen peroxide, a foaming agent, to silt, clay, or silty clay-based sludge. This generates water and oxygen for in-situ foaming, forming a lightweight sludge structure. While this process avoids the defoaming effect of physical foaming, the unit dosage of the liquid foaming agent hydrogen peroxide is relatively large. Furthermore, without heating the sludge slurry and using a catalyst, the foaming process of hydrogen peroxide is difficult to control.

[0008] For example, Chinese patent CN116444250A discloses a method for preparing hierarchical porous ceramics by hydrolysis-self-foaming-gel integration, comprising: mixing pretreated secondary aluminum ash with other aluminosilicate raw materials, adding dispersant, binder, sintering aid and water, mixing evenly to obtain an aqueous suspension, heating the aqueous suspension to a certain temperature; dissolving an environmentally friendly gel material at a certain temperature, adding it to the heated aqueous suspension and stirring evenly to obtain a mixed suspension; then molding, foaming and curing, demolding, drying, debinding and sintering. In this application, the foaming component in the finely ground secondary aluminum ash undergoes a foaming reaction through heating and high temperature. The required foaming component can be fully dispersed in the aqueous suspension by stirring, and then in-situ chemical foaming is achieved by heating to form the final hierarchical porous ceramic structure. However, the proportion of the foaming component aluminum ash in the solid components of the ceramic ingredients is too high, ranging from 10% to 100%, and the foaming process of the metallic aluminum powder in the aluminum ash does not effectively play its role in forming the lightweight porous structure of the ceramic. When the aforementioned aluminum ash is directly used in the in-situ foaming reaction to form solidified sludge, it will lead to: 1) excessively high cost in preparing lightweight solidified sludge soil due to excessively high unit dosage of foaming agent; and 2) OH- ions released from the secondary aluminum ash, aluminum powder, and sludge solidifying agent. - When these two substances are mixed in silt, they react rapidly to produce H2, causing premature foaming and making it impossible to prepare in-situ foamed lightweight silt-stabilized soil. Summary of the Invention

[0009] The purpose of this invention is to provide an in-situ chemically foamed lightweight silt-stabilized soil, its preparation method, and a foaming agent. This invention can effectively solve the aforementioned technical problems existing in the preparation of lightweight silt-stabilized soil using existing physical foaming methods. It can also change the conventional hydrogen peroxide chemical foaming method and the method that requires heating the silt slurry to achieve in-situ foaming of aluminum ash in the slurry. This foaming process is easy to control and can ensure the strength of the obtained lightweight silt-stabilized soil.

[0010] To solve the above problems, the technical solution provided by the present invention is as follows:

[0011] This invention provides an in-situ chemical foaming agent for lightweight sludge solidification soil. The in-situ chemical foaming agent powder contains metallic aluminum powder and non-metallic compound composite particles / powder. The aluminum powder particles are separated by non-metallic compound particles, and the median particle size of the metallic aluminum powder and non-metallic compound particles is ≤5μm.

[0012] This invention utilizes a composite particle / powder of metallic aluminum powder and non-metallic compounds as an in-situ foaming component, adding it to a solidifiable sludge slurry to be foamed. The solidifiable sludge slurry is obtained by adding a sludge solidification cementitious material to the sludge slurry and mixing it evenly. The metallic aluminum powder releases OH- ions from the sludge solidification cementitious material. -Under the influence of the foaming process, numerous microbubbles are generated, forming a porous, lightweight mud structure. Due to the surface tension of the organic matter in the mud after the bubbles are generated, they form isolated, dome-shaped pores. After the in-situ foaming reaction is completed, the mud solidifies under the action of the solidifying cementitious material. The hydration products produced by the solidification process fix the pores in the mud into closed pores in situ, transforming the mud slurry into a honeycomb-like porous, lightweight structure. This honeycomb structure possesses the structural characteristics of a lightweight, high-strength structure, allowing it to be maintained for a long time in water-rich underground environments.

[0013] However, it should be noted that if aluminum powder is directly added as an in-situ foaming agent, on the one hand, its particle size is difficult to grind to a small size, resulting in larger bubbles and affecting the strength of the lightweight sludge-stabilized soil; on the other hand, aluminum powder is prone to agglomeration when it comes into contact with water, causing the generated pores to interconnect and form bubbles with uneven pore size distribution, especially prone to forming excessively large bubbles, which affects the strength of the resulting lightweight sludge-stabilized soil. Therefore, this invention uses aluminum powder and non-metallic compound composite particles / powder as an in-situ foaming agent, using non-metallic compound particles to separate aluminum powder particles, that is, using non-metallic compound particles to highly disperse aluminum powder, and controlling the median particle size of aluminum powder and non-metallic compound particles to be ≤5μm, thereby effectively controlling the pore size generated by foaming, ensuring the uniformity of pore size, and especially preventing the agglomeration of aluminum powder when it comes into contact with water, which would cause the pores to interconnect and form excessively large bubbles.

[0014] As a further improvement of the present invention, the non-metallic compound is one or more of alumina, aluminum carbide, silicon carbide, and silicon oxide, and the mass of the aluminum powder accounts for 10%-35% of the total mass of the aluminum powder and non-metallic compound composite particles / powder. By optimizing and controlling the composite ratio of aluminum powder and non-metallic compound, it is beneficial to further ensure the dispersion effect of aluminum powder.

[0015] As a further improvement of the present invention, the composite particles / powder of metallic aluminum powder and non-metallic compound are obtained by grinding and dispersing metallic aluminum powder and non-metallic compound together. Through ultrafine grinding, the particle size of metallic aluminum powder can be further reduced and fully separated by non-metallic compound.

[0016] As a further preferred embodiment of the present invention, the aluminum powder and non-metallic compound composite particles / powder are further mixed with an organic polymer solution / emulsion to form an in-situ chemical foaming agent slurry. Under the action of mixing and stirring, the rapid shearing action of the polymer solution can break down and further separate the aluminum powder, achieving a high degree of dispersion again; at the same time, the polymer can form a liquid film on the surface of the aluminum powder, which can affect the OH in the solidifiable sludge slurry. -It has a temporary blocking effect, allowing the aluminum powder to be further highly dispersed before foaming. More importantly, the encapsulation effect of the organic polymer emulsion delays the foaming reaction until after the solidifiable sludge slurry is poured into the filling location. This prevents premature foaming and premature hardening of the solidifiable sludge, and further prevents interconnected pores from forming uneven pore size distribution, especially excessively large bubbles. Furthermore, the polymer solution also acts as a foam stabilizer, thus eliminating the need for additional foam stabilizers.

[0017] As a further preferred embodiment of the present invention, the composite particles / powder of aluminum powder and non-metallic compound is composed of aluminum powder and aluminum ash, wherein the mass proportion of aluminum powder in the composite composition is 0-20% and the mass proportion of aluminum ash is 80-100%, thereby enabling efficient resource utilization of aluminum ash solid waste.

[0018] As a further preferred embodiment of the present invention, the organic polymer solution / emulsion is HPMC, MC, PVA, EG, polystyrene, polyacrylic acid, or waterborne epoxy resin emulsion / solution, more preferably HPMC, MC, or PVA solution, and the mass ratio of in-situ chemical foaming agent powder to polymer solution / emulsion in the in-situ chemical foaming agent slurry is 1:10-1:20, and the solid content of the organic polymer solution / emulsion is 0.1-5%.

[0019] The present invention also provides an in-situ chemically foamed lightweight sludge solidification soil, the raw material components of which include solidifiable sludge slurry and any of the above-mentioned in-situ chemical foaming agents.

[0020] Furthermore, the amount of in-situ chemical foaming agent powder added is 1 / 1000-1 / 100 of the mass of the solidifiable sludge slurry. The amount of in-situ chemical foaming agent powder added is small, and only a small amount is needed to directly convert high water content sludge slurry into high-performance (high strength-to-weight ratio) lightweight sludge solidification soil.

[0021] Furthermore, the solidifiable sludge slurry comprises sludge slurry and sludge solidification cementitious material, wherein the mass of the sludge solidification cementitious material accounts for 1 / 10 to 1 / 4 of the total mass of the solidifiable sludge slurry, and the water content of the sludge slurry is 80% to 200%.

[0022] Furthermore, the silt slurry can be: marine sedimentary silt slurry, lacustrine sedimentary silt slurry, channel dredging silt slurry, or pond dredging silt slurry, with a water content of 80% to 200%, and the solid composition of the silt slurry is mainly inorganic, consisting primarily of clay particles and silty soil particles, with an organic matter content of 2.5% to 20% and a pH value of 5 to 9; the above-mentioned silt slurry can also be made by mixing silty clay, silty silt, or peat soil with water to form silt slurry, with a water content of 80% to 150%, preferably 80% to 120%.

[0023] Furthermore, the sludge solidification cementitious material is composed of quick-setting cement, ordinary silicate cement, persulfate cement and artificial volcanic ash, wherein the quick-setting cement accounts for 0-20% by mass, ordinary silicate cement accounts for 10-40%, persulfate cement accounts for 30-90%, and artificial volcanic ash accounts for 0-20%.

[0024] The quick-setting cement is further preferably a composite of one or more of aluminate cement, sulfoaluminate cement, and ferroaluminate cement, and even more preferably aluminate cement or sulfoaluminate cement or a composite thereof, wherein the main mineral component of the aluminate cement is tricalcium aluminate. The sulfoaluminate cement is even more preferably a rapid-hardening sulfoaluminate cement with a specific surface area ≥400 m². 2 / kg.

[0025] The ordinary Portland cement is further preferably ordinary Portland cement with a grade ≥42.5 and a specific surface area ≥350m². 2 / kg.

[0026] The persulfate cement is further preferably made by finely grinding an alkaline component, sulfate, and blast furnace slag, wherein the alkaline component accounts for 5-10%, the sulfate accounts for 10-20%, the slag accounts for 70-85%, and the specific surface area is ≥400 m². 2 / kg.

[0027] Furthermore, the aforementioned alkaline component is at least one of alkali metal oxides, hydroxides, silicates, carbonates, alkaline earth metal oxides, hydroxides, silicates, and more preferably at least one of sodium silicate, sodium carbonate, calcium oxide, calcium hydroxide, and silicate cement clinker.

[0028] The sulfate in the above-mentioned persulfate cement is further preferably a composite of one or more of calcium sulfate dihydrate, calcium sulfate hemihydrate, anhydrous calcium sulfate, potassium sulfate, sodium sulfate, and lithium sulfate, or an industrial by-product sulfate containing the above-mentioned components as the main component. More preferably, it is a composite of one or more of calcium sulfate dihydrate, calcium sulfate hemihydrate, and anhydrous calcium sulfate, or a composite of one or more of by-product calcium sulfate containing calcium sulfate dihydrate, calcium sulfate hemihydrate, and anhydrous calcium sulfate in any proportion.

[0029] The aforementioned artificial volcanic ash is further preferably a composite of one or more of the following: slag powder, fly ash, circulating fluidized bed boiler ash, furnace slag powder, biomass incineration ash, and silica fume; even more preferably, a composite of one or more of the following: circulating fluidized bed boiler ash, biomass incineration ash, and silica fume, with a specific surface area ≥ 400 m². 2 / kg.

[0030] Furthermore, the in-situ chemically foamed lightweight sludge solidification soil has a honeycomb-like porous lightweight structure with pore sizes of 0.05–0.2 mm, and its solidified sludge body has a bulk density of 0.3–1.2 g / cm³ after 3 days of molding. 3 Unconfined compressive strength at 3 days: 0.2-0.8 MPa; Unconfined compressive strength at 28 days: 0.5-3 MPa; Softening coefficient: ≥0.7; Volume shrinkage rate: ≤5 / 1000.

[0031] The present invention also provides a method for preparing any of the above-mentioned in-situ chemically foamed lightweight sludge solidified soil, wherein an in-situ chemical foaming agent slurry is added to a solidifiable sludge slurry and stirred and mixed evenly, and after in-situ foaming and solidification reaction, the in-situ chemically foamed lightweight sludge solidified soil is obtained.

[0032] Furthermore, the specific preparation process of the in-situ chemical foaming agent includes:

[0033] A mixture of metallic aluminum powder and non-metallic compounds is subjected to ultrafine grinding to obtain in-situ chemical foaming agent powder with a median particle size ≤5μm.

[0034] The obtained metallic aluminum powder, non-metallic compound composite particles / powder, and organic polymer solution / emulsion are weighed according to the measurement and then mixed and stirred into a slurry, which yields the in-situ chemical foaming agent slurry.

[0035] Furthermore, the specific preparation process of the in-situ chemically foamed lightweight silt-stabilized soil includes:

[0036] After screening out the impurities in the sludge slurry, add sludge solidification cementitious material to the sludge slurry and stir thoroughly to form a solidifiable sludge slurry.

[0037] In-situ chemical foaming agent slurry is added to solidifiable sludge slurry and quickly mixed. The resulting slurry is then poured into the space to be filled. The metallic aluminum powder in the slurry reacts with the OH groups released by the sludge solidification cementitious material. - Under the action of the foaming agent, a large number of microbubbles are generated, forming a porous and lightweight mud structure. After the in-situ foaming reaction is completed within 0.5 hours, a large amount of hydration products such as ettringite, CSH (hydrated calcium silicate) gel, CAH (hydrated calcium aluminate) gel, and calcium hydroxide gel are produced in the sludge solidifying agent. This fixes the pores in the mud into closed pores, transforming the sludge into a honeycomb-like porous and lightweight structure with pore diameters of 0.05–0.2 mm. After 3 days, the bulk density of the solidified sludge is 0.3–1.2 g / cm³. 3 The 3-day unconfined compressive strength is 0.2–0.8 MPa, the 28-day unconfined compressive strength is 0.5–3 MPa, the softening coefficient is ≥0.7, and the volume shrinkage rate is ≤5 / 1000. The hydration reaction and pozzolanic reaction that occur within the silt-stabilized cementitious material itself, as well as the secondary pozzolanic reaction induced by silica and alumina in the silt, ensure that the long-term strength of the lightweight silt-stabilized body does not decrease. It can be used in various applications requiring lightweight replacement soil, especially at locations along coastal and river highways where bridge approach sags are likely to occur. After the subgrade is replaced with in-situ chemically foamed lightweight silt-stabilized soil, bridge approach sags will be less likely to occur, and various unstable subgrade and foundation collapse phenomena can be effectively avoided.

[0038] In summary, the technical solution provided by this invention has the following advantages compared with the prior art:

[0039] (1) This invention uses aluminum powder and non-metallic compound composite particles / powder as in-situ chemical foaming agents for the preparation of lightweight silt-stabilized soil. Through ultrafine grinding, the aluminum powder particles are fully separated by non-metallic compounds. With the help of the separation effect of non-metallic compound particles, on the one hand, the size of the foaming agent particles can be ground to a smaller size, thereby ensuring that small pores can be generated by in-situ foaming and ensuring the uniformity of pore size; on the other hand, it can effectively avoid the agglomeration of aluminum powder after it comes into contact with water, thereby avoiding the formation of excessively large air bubbles through the interconnection of pores, thus ensuring the strength of the obtained lightweight silt-stabilized soil.

[0040] (2) In this application, the median particle size of the composite particles / powder of metallic aluminum powder and non-metallic compound is ≤5μm after ultrafine grinding. Then, it is further mixed with organic polymer solution / emulsion to form a foaming agent slurry. On the one hand, the rapid shearing action of the polymer solution can break down and further separate the metallic aluminum powder, achieving a high degree of dispersion. On the other hand, after the polymer forms a liquid film on the surface of the metallic aluminum powder, it can inhibit the OH in the sludge slurry. -It has a temporary blocking effect, which delays the foaming reaction until the sludge is poured into the filling position. This makes it less likely for the pores to connect and form bubbles with uneven pore size distribution, especially less likely to form excessively large bubbles, thereby improving the strength of the lightweight porous structure.

[0041] (3) The foaming agent of this application can directly convert high-water-content sludge into high-performance (high strength-to-weight ratio) lightweight sludge-stabilized soil, and the amount of foaming agent added is small, and no additional foam stabilizer is required; at the same time, the bulk density and strength of the lightweight sludge-stabilized soil prepared by this invention are adjustable. In addition, the pores in the sludge-stabilized body are closed pores, and the bulk density of its lightweight structure will not increase when exposed to water.

[0042] (4) After bubbles are generated in the sludge slurry, they are subjected to the surface tension of organic matter in the sludge, forming isolated dome-shaped pores. After the pores are formed, the fast-setting cement in the sludge solidification cementitious material causes the high-moisture sludge (moisture content ≥100%) to solidify rapidly, fixing the bubbles in the in-situ foaming position. The resulting honeycomb structure has the structural characteristics of a lightweight and high-strength structure, which can be maintained for a long time in underground water-rich environments. After foaming, the volcanic ash component in the sludge solidification cementitious material continues to undergo volcanic ash reaction in the lightweight sludge solidified body. The resulting cementitious products cause the strength of the lightweight sludge solidified body to increase continuously over time, extending the life of its lightweight structure. The sludge solidification cementitious material can also create an alkaline environment that is conducive to promoting the foaming of aluminum powder while efficiently solidifying the sludge slurry. Attached Figure Description

[0043] Figure 1 These are photos of in-situ foamed lightweight solidified soil samples obtained in the examples, which can float on the water surface for a long time.

[0044] Figure 2 These are core photos of the in-situ foamed lightweight solidified soil obtained in the example in the backfill area. Detailed Implementation

[0045] This invention provides a lightweight sludge-stabilized soil, which comprises a solidifiable sludge slurry and an in-situ chemical foaming agent. The solidifiable sludge slurry includes sludge slurry and sludge-stabilizing cementitious material. The mass of the sludge-stabilizing cementitious material is 1 / 10 to 1 / 4 of the total mass of the sludge slurry and the sludge-stabilizing cementitious material. The mass of the in-situ chemical foaming agent powder is 1 / 1000 to 1 / 100 of the total mass of the sludge slurry and the sludge-stabilizing cementitious material.

[0046] Specifically, the in-situ chemical foaming agent powder of the present invention comprises composite particles / powder of metallic aluminum powder and non-metallic compounds. The aluminum powder particles are separated by the non-metallic compound particles, and the median particle size of the metallic aluminum powder and non-metallic compound particles is ≤5μm. In one embodiment of the present invention, the composite particles / powder of metallic aluminum powder and non-metallic compounds are obtained by grinding and dispersing the metallic aluminum powder and non-metallic compounds together. The ultrafine grinding effectively reduces the particle size of the metallic aluminum powder particles and fully separates them from the non-metallic compounds, ensuring that the median particle size of the composite particles / powder of metallic aluminum powder and non-metallic compounds is ≤5mm. Therefore, on the one hand, this is beneficial for improving the size and uniformity of the pores generated during foaming; on the other hand, when the in-situ chemical foaming agent is mixed with sludge slurry, it can effectively prevent the metallic aluminum powder from agglomerating upon contact with water, which would cause the pores generated during foaming to interconnect and form large pores, thus affecting the strength of the resulting lightweight sludge-stabilized soil.

[0047] The aforementioned non-metallic compound is further preferably a combination of one or more of alumina, aluminum carbide, silicon carbide, and silicon oxide, and the mass of the aluminum powder accounts for 10%-35% of the total mass of the aluminum powder and the non-metallic compound composite particles / powder.

[0048] As a further preferred embodiment of the present invention, the above-mentioned composite particles / powder of metallic aluminum powder and non-metallic compound is composed of metallic aluminum powder and aluminum ash. The mass proportion of metallic aluminum powder in the composite composition is 0-20%, and the proportion of aluminum ash is 80-100%, thereby achieving efficient resource utilization of aluminum ash solid waste, and the proportion of aluminum ash is relatively high. Specifically, the aluminum ash is primary aluminum ash, secondary aluminum ash, or a combination thereof, containing components such as metallic aluminum, alumina, aluminum carbide, silicon carbide, and silicon oxide, with a metallic aluminum content ≥5%. As one embodiment, after the aluminum powder and aluminum ash are mixed, they are ground in an ultrafine mill by grinding steel balls with a diameter ≤10mm and grinding steel segments with a diameter ≤10mm (or ceramic balls or ceramic segments of the above diameter), thereby reducing the median particle size to ≤5μm.

[0049] The in-situ chemical foaming agent powder is further preferably mixed with an organic polymer solution / emulsion to form an in-situ chemical foaming agent slurry. Under the action of non-metallic compounds, through ultrafine grinding, the particle size of the aluminum powder can be further reduced and separated from each other, and it will no longer agglomerate after encountering water, thereby increasing the amount of effective aluminum powder to obtain a lightweight structure. In addition, after the polymer forms a liquid film on the surface of the aluminum powder, it can inhibit the OH in the sludge slurry. -It has a temporary blocking effect, which allows the aluminum powder to be further dispersed before foaming. At the same time, the foaming reaction is delayed until the sludge is poured into the filling position. This makes it difficult for the pores to connect and form bubbles with uneven pore size distribution, especially making it difficult to form excessively large bubbles, thereby improving the strength of the lightweight porous structure.

[0050] The organic polymer solution / emulsion is preferably an HPMC, MC, PVA, EG, polystyrene, polyacrylic acid, or waterborne epoxy resin emulsion / solution, more preferably an HPMC, MC, or PVA solution, and the mass ratio of in-situ chemical foaming agent powder to polymer solution / emulsion in the in-situ chemical foaming agent slurry is 1:10-1:20, and the solid content of the organic polymer solution / emulsion is 0.1-5%.

[0051] Furthermore, the sludge slurry of the present invention can be marine sedimentary sludge slurry, lacustrine sedimentary sludge slurry, channel dredging sludge slurry, or pond dredging sludge slurry. The water content of the sludge slurry is 80%–200%, and the solid composition of the sludge slurry is mainly inorganic, consisting primarily of clay particles and silty soil particles. The organic matter content is 2.5%–20%, and the pH value is 5–9. The above-mentioned sludge slurry can also be made by mixing silty clay, silty silt, or peat soil with water to form sludge slurry. The water content of the sludge slurry is 80%–150%, more preferably 80%–120%.

[0052] Furthermore, the sludge solidification cementitious material of the present invention is preferably composed of quick-setting cement, ordinary silicate cement, persulfate cement and artificial volcanic ash, wherein the quick-setting cement accounts for 0-20%, the ordinary silicate cement accounts for 10-40%, the persulfate cement accounts for 30-90%, and the artificial volcanic ash accounts for 0-20%.

[0053] The quick-setting cement is further preferably a composite of one or more of aluminate cement, sulfoaluminate cement, and ferroaluminate cement; more preferably, it is aluminate cement or sulfoaluminate cement or a composite thereof; wherein: the main mineral component of the aluminate cement is tricalcium aluminate, and the sulfoaluminate cement is further preferably a rapid-hardening sulfoaluminate cement with a specific surface area ≥400 m². 2 / kg.

[0054] The ordinary Portland cement is further preferably ordinary Portland cement with a grade ≥42.5 and a specific surface area ≥350m². 2 / kg.

[0055] The persulfate cement is further preferably made by finely grinding an alkaline component, sulfate, and blast furnace slag, wherein the alkaline component accounts for 5-10%, the sulfate accounts for 10-20%, the slag accounts for 70-85%, and the specific surface area is ≥400 m².2 / kg.

[0056] Furthermore, the alkaline components in the persulfate cement are composed of one or more of alkali metal oxides, hydroxides, silicates, and carbonates, or alkaline earth metal oxides, hydroxides, and silicates in any proportion, preferably one or more of sodium silicate, sodium carbonate, calcium oxide, calcium hydroxide, and silicate cement clinker in any proportion. The sulfates in the persulfate cement are further preferably a combination of one or more of calcium sulfate dihydrate, calcium sulfate hemihydrate, anhydrous calcium sulfate, potassium sulfate, sodium sulfate, and lithium sulfate, or industrial by-product sulfates containing the above-mentioned components as the main components. More preferably, they are a combination of one or more of calcium sulfate dihydrate, calcium sulfate hemihydrate, and anhydrous calcium sulfate, or by-product calcium sulfate containing calcium sulfate dihydrate, calcium sulfate hemihydrate, and anhydrous calcium sulfate in any proportion.

[0057] The artificial volcanic ash is further preferably a composite of one or more of the following: slag powder, fly ash, circulating fluidized bed boiler ash, furnace slag powder, biomass incineration ash, and silica fume. More preferably, it is a composite of one or more of the following: circulating fluidized bed boiler ash, biomass incineration ash, and silica fume, with a specific surface area ≥ 400 m². 2 / kg.

[0058] This invention changes the conventional hydrogen peroxide chemical foaming method. It uses a highly dispersed aluminum powder foaming agent, which is further highly dispersed before being added to the sludge slurry mixed with the sludge solidification cementitious material. This dispersion is then stirred into the sludge slurry, delaying the reaction of the OH- ions generated by the reaction of the sludge solidification cementitious material with water. - The process generates hydrogen gas, and under the pressure of the gas, it forms honeycomb-shaped independent micropores that are fixed in situ. With the formation of a large number of hydration products in the pore walls, a lightweight silt-stabilized soil with a certain strength and a honeycomb-shaped pore structure is obtained.

[0059] To further understand the invention, it is now described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that, due to space limitations, the specific composition and proportions of the sludge slurry, solidifying cementitious material, and highly dispersed chemical foaming agent in the following embodiments only select some substances and values, but are not actually limited to the selection of the following specific embodiments. Furthermore, other substances can be added to the raw material composition of the lightweight sludge solidified soil in this invention according to actual needs; that is, its raw material composition is not limited to the embodiments of this invention. However, for the purposes of this application, only sludge slurry, sludge solidifying cementitious material, and highly dispersed in-situ chemical foaming agent need to be added. In addition, from the perspective of saving resources and realizing the recycling of solid waste resources, the highly dispersed in-situ chemical foaming agent of this invention is preferably composed of aluminum powder and aluminum ash. The following embodiments also use the aluminum powder and aluminum ash composite as a foaming agent for detailed explanation, wherein whether to additionally add aluminum powder and its compounding ratio can be determined according to the aluminum content in the aluminum ash.

[0060] Example 1

[0061] This embodiment describes an in-situ foamed lightweight sludge solidification soil, the raw material composition of which includes: sludge slurry, sludge solidification cementitious material, and highly dispersed in-situ chemical foaming agent. Among the above three components, the mass of the sludge solidification cementitious material is 1 / 4 of the total mass of the sludge slurry and the sludge solidification cementitious material, and the mass of the in-situ chemical foaming agent powder is 5 / 1000 of the total mass of the sludge solidification cementitious material and the sludge slurry.

[0062] Specifically, the sludge slurry in this embodiment is marine sedimentary sludge slurry from Yuhuan City, Taizhou, Zhejiang Province. The sludge slurry has a water content of 120%, an organic matter content of 5%, and a pH value of 9.

[0063] The sludge solidification cementitious material of this embodiment is composed of sulfoaluminate cement, ordinary silicate cement, persulfate cement, and biomass combustion ash (loss on ignition ≤ 5%), wherein sulfoaluminate cement accounts for 20% by mass, ordinary silicate cement accounts for 10%, persulfate cement accounts for 60%, and artificial volcanic ash accounts for 10%. Specifically, the sulfoaluminate cement is a rapid-hardening sulfoaluminate cement with a specific surface area of ​​400 m². 2 / kg; the ordinary Portland cement is a high-early strength type 42.5 ordinary Portland cement with a specific surface area of ​​400m². 2 / kg; the persulfate cement is made by finely grinding No. 52.5 silicate cement clinker, desulfurized gypsum and blast furnace slag, with a specific surface area of ​​400 m². 2 / kg, of which alkaline components account for 5%, sulfates account for 20%, and slag accounts for 75%; the specific surface area of ​​the biomass combustion ash is 600m². 2 / kg.

[0064] The highly dispersed chemical foaming agent powder of this embodiment is made by grinding aluminum powder and aluminum ash together. The aluminum powder accounts for 20% of the composite composition and the aluminum ash accounts for 80%. The aluminum ash is secondary aluminum ash, which contains components such as aluminum, alumina, aluminum carbide, silicon carbide, and silicon oxide, and the aluminum content in the aluminum ash is 5%.

[0065] Specifically, the preparation method of the in-situ foamed lightweight silt solidification soil in this embodiment is as follows: (1) After mixing aluminum powder and aluminum ash, the mixture is ground by grinding steel balls with a diameter of 10 mm in an ultrafine mill to obtain a median particle size of 2.5 μm in the in-situ chemical foaming agent powder; (2) Before use, the fully ground aluminum powder and aluminum ash composite powder is mixed with PVA solution and stirred into a slurry for 20 minutes at a speed of 60 rpm to obtain the in-situ chemical foaming agent slurry, so that the foaming agent components are highly dispersed again, and the in-situ chemical foaming agent slurry contains in-situ chemical foaming agent. The ratio of foaming agent powder to PVA is 1:10, and the concentration (solid content) of PVA solution is 2%; (3) After screening out the impurities in the sludge, add the sludge solidification cementitious material to the sludge according to the batching ratio, stir to form a solidifiable sludge slurry, stir for 10 minutes, and rotate at 60 rpm; (4) Then add the in-situ chemical foaming agent slurry to the solidifiable sludge slurry and stir quickly, stir for 10 minutes, and rotate at 60 rpm; (5) Pour the slurry obtained in step (4) into the space to be filled, and the aluminum powder in the slurry releases OH from the sludge solidification cementitious material. - Under the action of the process, a large number of microbubbles are generated, forming a porous and lightweight mud structure. After the reaction is completed within 0.5 hours, a large amount of hydration products such as ettringite, CSH gel, CAH gel, and calcium hydroxide gel are produced in the sludge solidifying agent. This fixes the pores in the mud into closed pores, transforming the sludge into a honeycomb-like porous and lightweight structure with a pore size of approximately 0.2 mm. After 3 days, the bulk density of the solidified sludge is 0.8 g / cm³. 3 The unconfined compressive strength at 3 days is 0.35 MPa, at 7 days it is 0.6 MPa, and at 28 days it is 1.2 MPa. The softening coefficient is 0.85, and the volume shrinkage rate is 3 / 1000. The hydration reaction and pozzolanic reaction occurring within the silt-stabilized cementitious material itself, as well as the secondary pozzolanic reaction induced in the silica and alumina in the silt, ensure that the long-term strength of the lightweight silt-stabilized body does not decrease. It can be used in various applications requiring lightweight replacement soil, especially at bridge approach points on coastal and riverside highways where bridge approach sags are likely to occur. After replacing the subgrade silt with in-situ foamed lightweight silt-stabilized soil, bridge approach sags are less likely to occur. The in-situ foamed lightweight stabilized soil sample prepared in this embodiment is as follows: Figure 1 As shown.

[0066] Example 2:

[0067] This embodiment describes an in-situ foamed lightweight sludge solidification soil, the raw material composition of which includes: sludge slurry, sludge solidification cementitious material, and highly dispersed in-situ chemical foaming agent. Among the above three components, the amount of sludge solidification cementitious material is 1 / 4 of the sum of the amounts of sludge slurry and sludge solidification cementitious material, and the amount of in-situ chemical foaming agent powder is 1.5 / 1000 of the sum of the amounts of sludge solidification cementitious material and sludge slurry.

[0068] The sludge slurry used in this embodiment is marine sedimentary sludge slurry from Shanghai, which is engineering waste slurry. The sludge slurry has a water content of 90%, an organic matter content of 7.5%, and a pH value of 6.5.

[0069] The sludge solidification cementitious material of this embodiment is composed of ordinary Portland cement and persulfate cement, wherein ordinary Portland cement accounts for 10% and persulfate cement accounts for 90%. Specifically, the ordinary Portland cement is grade 52.5 ordinary Portland cement with a specific surface area of ​​400 m². 2 / kg; the persulfate cement is made by finely grinding alkaline components, sulfates, and blast furnace slag, with a specific surface area of ​​420m². 2 / kg, of which the alkaline component is calcium hydroxide, accounting for 5%, the sulfate is anhydrous calcium sulfate, accounting for 20%, and the slag accounts for 75%.

[0070] The in-situ chemical foaming agent powder of this embodiment is made by grinding aluminum powder and aluminum ash together. The aluminum powder accounts for 10% and the aluminum ash accounts for 90% of the composite composition. The aluminum ash is primary aluminum ash, which contains metallic aluminum, aluminum oxide, aluminum carbide, silicon carbide, silicon oxide and other components. The metallic aluminum content in the aluminum ash is 10%.

[0071] The preparation method of the in-situ foamed lightweight sludge solidification soil in this embodiment is as follows: (1) After mixing aluminum powder and aluminum ash, the mixture is ground by grinding ceramic balls with a diameter of 5 mm in an ultrafine mill to obtain in-situ chemical foaming agent powder. The median particle size of the aluminum powder and aluminum ash particles in the obtained in-situ chemical foaming agent powder is 2.5 μm; (2) Before use, the in-situ chemical foaming agent powder and HPMC solution are mixed and stirred into a slurry. The stirring time is 10 minutes and the rotation speed is 120 rpm to obtain the in-situ chemical foaming agent slurry, so that the foaming agent components are highly dispersed again. The mass ratio of the in-situ chemical foaming agent powder to the HPMC solution in the in-situ chemical foaming agent slurry is 1:20, and the concentration (solid content) of the HPMC solution is 0.5%; (3) After screening out the impurities in the sludge, the sludge is added to the sludge according to the batching ratio. (3) Sterilize the cementitious material into a solidifiable sludge slurry and stir for 8 minutes at a speed of 60 rpm; (4) Then add the in-situ chemical foaming agent slurry to the solidifiable sludge slurry and stir quickly for 10 minutes at a speed of 60 rpm; (5) Pour the slurry obtained in step (4) into the space to be filled. Under the action of OH- released by the cementitious material, the aluminum powder in the slurry generates a large number of micro bubbles, forming a porous lightweight slurry structure. After the reaction is completed within 0.5 hours, a large number of hydration products such as ettringite, CSH gel, CAH gel, and calcium hydroxide gel are generated in the sludge solidifying agent, which fixes the pores in the slurry into closed pores. The sludge slurry is transformed into a honeycomb porous lightweight structure with a pore size of about 0.15 mm. The bulk density of the solidified sludge body after 3 days is 0.75 g / cm³. 3 The 3-day unconfined compressive strength is 0.8 MPa, the 7-day unconfined compressive strength is 2 MPa, and the 28-day unconfined compressive strength is 3 MPa. The softening coefficient is 0.9, and the volume shrinkage rate is 4.5 / 1000. The hydration reaction and pozzolanic reaction occurring within the silt-stabilized cementitious material itself, as well as the secondary pozzolanic reaction induced in the silica and alumina in the silt, ensure that the long-term strength of the lightweight silt-stabilized body does not decrease. It can be used in various applications requiring lightweight replacement soil, especially in soft soil foundations along coastlines and rivers where lightweight soil replacement is required, preventing foundation collapse. Figure 2 The image shown is a core photograph of the in-situ foamed lightweight solidified soil prepared in this embodiment in the backfill area.

[0072] Example 3:

[0073] This embodiment describes an in-situ foamed lightweight sludge solidification soil, the raw material composition of which includes: sludge slurry, sludge solidification cementitious material, and highly dispersed in-situ chemical foaming agent. Among the above three components, the amount of sludge solidification cementitious material is 1 / 10 of the sum of the amounts of sludge slurry and sludge solidification cementitious material, and the amount of in-situ chemical foaming agent powder is 1 / 1000 of the sum of the amounts of sludge solidification cementitious material and sludge slurry.

[0074] The sludge slurry used in this embodiment is marine sedimentary sludge slurry from Ningbo. The sludge slurry has a water content of 120%, an organic matter content of 20%, and a pH value of 5.6.

[0075] The sludge solidification cementitious material of this embodiment is composed of sulfoaluminate cement, ordinary silicate cement, persulfate cement, and biomass combustion ash (3% loss on ignition). The sulfoaluminate cement accounts for 10%, ordinary silicate cement for 10%, persulfate cement for 60%, and artificial volcanic ash for 20%. Specifically, the sulfoaluminate cement in this embodiment is a rapid-hardening sulfoaluminate cement with a specific surface area of ​​400 m². 2 / kg; the ordinary Portland cement is grade 52.5 ordinary Portland cement with a specific surface area of ​​400m². 2 / kg; Persulfate cement is made by finely grinding alkaline components, sulfates, and blast furnace slag, with a specific surface area of ​​410 m². 2 / kg, of which the alkaline component is calcium oxide, accounting for 10%; the sulfate is composed of anhydrous calcium sulfate and lithium sulfate (the ratio of anhydrous calcium sulfate to lithium sulfate is 100:1), accounting for 20%; slag accounts for 70%; the artificial volcanic ash is biomass combustion ash with a specific surface area of ​​600m². 2 / kg.

[0076] The in-situ chemical foaming agent powder of this embodiment is made by grinding aluminum powder and aluminum ash together. The aluminum powder accounts for 5% of the composite composition, and the aluminum ash accounts for 95%. The aluminum ash is primary aluminum ash, which contains aluminum, aluminum oxide, aluminum carbide, silicon carbide, silicon oxide and other components. The aluminum content in the aluminum ash is 15%.

[0077] The preparation method of the in-situ foamed lightweight silt solidification soil in this embodiment is as follows: (1) After mixing aluminum powder and aluminum ash, the mixture is ground by grinding ceramic balls with a diameter of 5 mm in an ultrafine mill to obtain in-situ chemical foaming agent powder. The median particle size of the aluminum powder and aluminum ash particles in the obtained in-situ chemical foaming agent powder is 1 μm; (2) Before use, the in-situ chemical foaming agent powder and MC solution are mixed and stirred into a slurry. The stirring time is 20 minutes and the rotation speed is 120 rpm to obtain the in-situ chemical foaming agent slurry, so that the foaming agent components are highly dispersed again. The in-situ chemical foaming agent slurry contains in-situ chemical foaming agent. The mass ratio of foaming agent powder to MC solution is 1:15, and the concentration (solid content) of MC solution is 1%; (3) After screening out the impurities in the sludge, add sludge solidification cementitious material to the sludge according to the batching ratio, stir to form solidifiable sludge slurry, stir for 5 minutes, and rotate at 60 rpm; (4) Then add the in-situ chemical foaming agent slurry to the solidifiable sludge slurry and stir quickly, stir for 10 minutes, and rotate at 60 rpm; (5) Pour the slurry obtained in step (4) into the space to be filled, and the metal aluminum powder in the slurry releases OH in the sludge solidification cementitious material.- Under the action of the process, a large number of microbubbles are generated, forming a porous and lightweight mud structure. After the reaction is completed within 0.5 hours, a large amount of hydration products such as ettringite, CSH gel, CAH gel, and calcium hydroxide gel are produced in the sludge solidifying agent. This fixes the pores in the mud into closed pores, transforming the sludge into a honeycomb-like porous and lightweight structure with a pore size of approximately 0.08 mm. After 3 days, the bulk density of the solidified sludge is 1.2 g / cm³. 3 3. Unconfined compressive strength 0.3 MPa, 28-day unconfined compressive strength 1.5 MPa, softening coefficient 0.75, volume shrinkage rate 3.5 / 1000.

[0078] Example 4:

[0079] This embodiment describes an in-situ foamed lightweight sludge solidification soil, which comprises: sludge slurry, sludge solidification cementitious material, and highly dispersed in-situ chemical foaming agent. The amount of sludge solidification cementitious material in the above three components is 1 / 8 of the sum of the amounts of sludge slurry and sludge solidification cementitious material, and the amount of in-situ chemical foaming agent powder is 2.5 / 1000 of the sum of the amounts of sludge solidification cementitious material and sludge slurry.

[0080] The sludge slurry in this embodiment is: lacustrine sedimentary sludge slurry from Chaohu Lake, with a water content of 120%, an organic matter content of 5%, and a pH value of 7.

[0081] The sludge solidification cementitious material of this embodiment is composed of aluminate cement, sulfoaluminate cement, ordinary silicate cement, persulfate cement, and artificial volcanic ash. The aluminate cement comprises 10%, the sulfoaluminate cement 10%, the ordinary silicate cement 10%, the persulfate cement 50%, and the artificial volcanic ash 20%. Specifically, the main component of the aluminate cement is tricalcium aluminate; the sulfoaluminate cement is a rapid-hardening sulfoaluminate cement with a specific surface area of ​​400 m². 2 / kg; the ordinary Portland cement is grade 42.5 ordinary Portland cement with a specific surface area of ​​400m². 2 / kg; the persulfate cement is made by compound grinding of cement clinker powder, industrial by-product phosphogypsum and blast furnace slag, with a specific surface area of ​​460m². 2 / kg; of which cement clinker powder accounts for 10%, industrial by-product phosphogypsum accounts for 10%, and slag accounts for 80%; the artificial volcanic ash is circulating fluidized bed boiler ash with a specific surface area of ​​600m². 2 / kg.

[0082] The in-situ chemical foaming agent powder of this embodiment is made by grinding aluminum powder and aluminum ash together. The aluminum powder accounts for 15% and the aluminum ash accounts for 85% of the composite composition. The aluminum ash is primary aluminum ash, which contains metallic aluminum, aluminum oxide, aluminum carbide, silicon carbide, silicon oxide and other components. The metallic aluminum content in the aluminum ash is 10%.

[0083] The preparation method of the in-situ foamed lightweight silt solidification soil is as follows: (1) After mixing aluminum powder and aluminum ash, the mixture is ground in an ultrafine mill by a grinding ceramic circle with a diameter of 5 mm to obtain in-situ chemical foaming agent powder. The median particle size of the particles in the obtained in-situ chemical foaming agent powder is 1 μm; (2) Before use, the in-situ chemical foaming agent powder is stirred with polyacrylic acid emulsion into a slurry for 20 minutes at a speed of 120 rpm to obtain the in-situ chemical foaming agent slurry, so that the foaming agent components are highly dispersed again. The in-situ chemical foaming agent powder and polyacrylic acid emulsion in the in-situ chemical foaming agent slurry are mixed. The ratio of acrylic emulsion is 1:20, and the concentration (solid content) of polyacrylic acid emulsion is 5%; (3) After screening out the impurities in the sludge slurry, add the sludge solidifying cementitious material to the sludge slurry according to the batching ratio, stir to form a solidifiable sludge slurry, stir for 5 minutes, and rotate at 60 rpm; (4) Then add the in-situ chemical foaming agent slurry to the solidifiable sludge slurry and stir quickly, stir for 10 minutes, and rotate at 60 rpm; (5) Pour the slurry obtained in step (4) into the space to be filled, and the metallic aluminum powder in the slurry reacts with the OH released by the sludge solidifying cementitious material. - Under the action of the process, a large number of microbubbles are generated, forming a porous and lightweight mud structure. After the reaction is completed within 0.5 hours, a large amount of hydration products such as ettringite, CSH gel, CAH gel, and calcium hydroxide gel are produced in the sludge solidifying agent. This fixes the pores in the mud into closed pores, transforming the sludge into a honeycomb-like porous and lightweight structure with a pore size of approximately 0.05 mm. The bulk density of the solidified sludge after 3 days is 0.6 g / cm³. 3 3-day unconfined compressive strength 0.3 MPa, 28-day unconfined compressive strength 0.8 MPa, softening coefficient 0.75, volume shrinkage rate 3 / 1000.

[0084] Example 5:

[0085] This embodiment of an in-situ foamed lightweight sludge solidification soil comprises: sludge slurry, sludge solidification cementitious material, and highly dispersed in-situ chemical foaming agent. The amount of sludge solidification cementitious material in the above three components is 1 / 4 of the sum of the amounts of sludge slurry and sludge solidification cementitious material, and the amount of in-situ chemical foaming agent powder is 2.5 / 1000 of the sum of the amounts of sludge solidification cementitious material and sludge slurry.

[0086] The sludge slurry used in this embodiment is river dredging sludge slurry with a water content of 200%, an organic matter content of 5%, and a pH value of 6.5.

[0087] The sludge solidification cementitious material of this embodiment is composed of sulfoaluminate cement, ordinary silicate cement, persulfate cement, and fly ash, wherein sulfoaluminate cement accounts for 20%, ordinary silicate cement accounts for 10%, persulfate cement accounts for 55%, and fly ash accounts for 15%. Specifically, the sulfoaluminate cement is a rapid-hardening sulfoaluminate cement with a specific surface area of ​​400 m². 2 / kg; the ordinary Portland cement is grade 52.5 ordinary Portland cement with a specific surface area of ​​400m². 2 / kg; the persulfate cement is made by finely grinding alkaline components, sulfates, and blast furnace slag, with a specific surface area of ​​450m². 2 / kg, of which the alkaline component is quicklime, accounting for 10%, the sulfate is calcium sulfate hemihydrate, accounting for 15%, and the slag accounts for 75%; the fly ash is Class I fly ash with a specific surface area of ​​550m². 2 / kg.

[0088] The highly dispersed in-situ chemical foaming agent powder of this embodiment is made by grinding aluminum ash; the aluminum ash is primary aluminum ash, which contains metallic aluminum, aluminum oxide, aluminum carbide, silicon carbide, silicon oxide and other components, and the metallic aluminum content in the aluminum ash is 20%.

[0089] The preparation method of the in-situ foamed lightweight silt solidification soil in this embodiment is as follows: (1) Aluminum ash is ground to a median particle size of 1μm in an ultrafine mill by the grinding action of a grinding ceramic circle with a diameter of 5mm to obtain in-situ chemical foaming agent powder; (2) The in-situ chemical foaming agent powder is stirred with polystyrene-acrylic emulsion into a slurry for 26 minutes at a speed of 110 rpm to obtain the in-situ chemical foaming agent slurry, so that the foaming agent components are highly dispersed again. The mass ratio of in-situ chemical foaming agent powder to polystyrene-acrylic emulsion in the in-situ chemical foaming agent slurry is 1:20, and the concentration (solid content) of polystyrene-acrylic emulsion is 2.5%. (3) After screening out the impurities in the sludge slurry, add the sludge solidification cementitious material to the sludge slurry according to the batching ratio, and stir to form a solidifiable sludge slurry. The stirring time is 10 minutes and the speed is 70 rpm. (4) Then add the in-situ chemical foaming agent slurry to the solidifiable sludge slurry and stir quickly. The stirring time is 15 minutes and the speed is 70 rpm. (5) Pour the slurry obtained in step (4) into the space to be filled. Under the action of OH- released by the sludge solidification cementitious material, the aluminum powder in the slurry generates a large number of micro bubbles, forming a porous lightweight slurry structure. After the reaction is completed within 0.5 hours, a large number of hydration products such as ettringite, CSH gel, CAH gel, and calcium hydroxide gel are generated in the sludge solidification agent, which fixes the pores in the slurry into closed pores. The sludge slurry is transformed into a honeycomb porous lightweight structure with a pore size of 0.1 mm. The bulk density of the sludge solidified body after 3 days is 0.7 g / cm³. 3The unconfined compressive strength at 3 days is 0.4 MPa, the unconfined compressive strength at 28 days is 1.5 MPa, the softening coefficient is 0.8, and the volume shrinkage rate is 2 / 1000.

[0090] Example 6:

[0091] This embodiment of an in-situ foamed lightweight sludge solidification soil comprises: sludge slurry, sludge solidification cementitious material, and highly dispersed in-situ chemical foaming agent. The amount of sludge solidification cementitious material in the above three components is 1 / 5 of the sum of the amounts of sludge slurry and sludge solidification cementitious material, and the amount of in-situ chemical foaming agent powder is 1 / 100 of the sum of the amounts of sludge solidification cementitious material and sludge slurry.

[0092] The sludge slurry used in this embodiment is sludge from the bottom of aquaculture ponds. The sludge has a water content of 150%, an organic matter content of 8%, and a pH value of 6.5.

[0093] The sludge solidification cementitious material of this embodiment is composed of sulfoaluminate cement, ordinary silicate cement, persulfate cement, and silica fume, wherein sulfoaluminate cement accounts for 20%, ordinary silicate cement accounts for 20%, persulfate cement accounts for 50%, and silica fume accounts for 10%. Specifically, the sulfoaluminate cement is a rapid-hardening sulfoaluminate cement with a specific surface area of ​​400 m². 2 / kg; the ordinary Portland cement is grade 52.5 ordinary Portland cement with a specific surface area of ​​400m². 2 / kg; the persulfate cement is made by finely grinding alkaline components, sulfates, and blast furnace slag, with a specific surface area of ​​500m². 2 / kg, of which the alkaline component is quicklime, accounting for 10%; sulfate is industrial by-product titanium gypsum, accounting for 10%; and slag accounts for 80%; the silica fume is semi-dense silica fume with a specific surface area of ​​20m². 2 / g.

[0094] The highly dispersed in-situ chemical foaming agent powder of this embodiment is made by grinding aluminum ash; the aluminum ash is primary aluminum ash, which mainly contains metallic aluminum, aluminum oxide, aluminum carbide, silicon carbide and silicon oxide, and the metallic aluminum content in the aluminum ash is 20%.

[0095] The preparation method of the in-situ foamed lightweight silt solidification soil in this embodiment is as follows:

[0096] (1) Aluminum ash is ground to a median particle size of 1μm by grinding ceramic segments with a diameter of 5mm in an ultrafine mill to obtain in-situ chemical foaming agent powder.

[0097] (2) Stir the in-situ chemical foaming agent powder and PVA solution into a slurry for 25 minutes at a speed of 120 rpm to obtain the in-situ chemical foaming agent slurry, so that the foaming agent components are highly dispersed again. The mass ratio of the in-situ chemical foaming agent powder to the PVA solution in the in-situ chemical foaming agent slurry is 1:20, and the concentration (solid content) of the PVA solution is 1%.

[0098] (3) After screening out the impurities in the sludge slurry, add the sludge solidification cementitious material to the sludge slurry according to the batching ratio, stir into a solidifiable sludge slurry, stir for 5 minutes, and rotate at 60 rpm.

[0099] (4) Then add the in-situ chemical foaming agent slurry to the solidifiable sludge slurry and mix quickly for 10 minutes at a speed of 60 rpm.

[0100] (5) The slurry obtained in step (4) is poured into the space to be filled. Under the action of OH- released by the sludge solidification cementitious material, the metallic aluminum powder in the slurry generates a large number of microbubbles, forming a porous lightweight slurry structure. After the reaction is completed within 0.5 hours, a large number of hydration products such as ettringite, CSH gel, CAH gel, and calcium hydroxide gel are generated in the sludge solidification agent, which fixes the pores in the slurry into closed pores. The sludge slurry is transformed into a honeycomb-like porous lightweight structure with a pore size of 0.2 mm. The bulk density of the sludge solidified body after 3 days is 0.5 g / cm³. 3 The 3-day unconfined compressive strength is 0.2 MPa, the 28-day unconfined compressive strength is 0.6 MPa, the softening coefficient is 0.8, and the volume shrinkage rate is 1 / 1000. The hydration reaction and pozzolanic reaction that occur in the silt solidification cementitious material itself, as well as the secondary pozzolanic reaction induced by the silica and alumina in the silt, ensure that the long-term strength of the lightweight silt solidified body does not decrease. It can be used in various applications of lightweight roadbed filling that require lightweight replacement soil.

[0101] Example 7:

[0102] This embodiment of an in-situ foamed lightweight sludge solidification soil comprises: sludge slurry, sludge solidification cementitious material, and highly dispersed in-situ chemical foaming agent. The amount of sludge solidification cementitious material in the above three components is 1 / 8 of the sum of the amounts of sludge slurry and sludge solidification cementitious material, and the amount of in-situ chemical foaming agent powder is 1 / 100 of the sum of the amounts of sludge solidification cementitious material and sludge slurry.

[0103] The sludge slurry in this embodiment uses peat soil from Kunming plateau lakes, which is mixed with water to form sludge slurry. The sludge slurry has a water content of 80%, an organic matter content of 10%, and a pH value of 6.5.

[0104] The sludge solidification cementitious material of this embodiment is composed of ordinary Portland cement and persulfate cement, wherein ordinary Portland cement accounts for 10% and persulfate cement accounts for 90%. Specifically, the ordinary Portland cement is grade 52.5 ordinary Portland cement with a specific surface area of ​​400 m². 2 / kg; the persulfate cement is made by finely grinding alkaline components, sulfates, and blast furnace slag, with a specific surface area of ​​500m². 2 / kg; of which the alkaline component is calcium hydroxide, accounting for 5%, the sulfate is anhydrous calcium sulfate, accounting for 20%, and the slag accounts for 75%.

[0105] The in-situ chemical foaming agent powder of this embodiment is made by grinding aluminum powder and aluminum ash together. The aluminum powder accounts for 10% and the aluminum ash accounts for 90% of the composite composition. The aluminum ash is primary aluminum ash, which contains metallic aluminum, aluminum oxide, aluminum carbide, silicon carbide, silicon oxide and other components. The metallic aluminum content in the aluminum ash is 10%.

[0106] The preparation method of the in-situ foamed lightweight silt solidification soil in this embodiment is as follows:

[0107] (1) The in-situ chemical foaming agent powder is obtained by mixing aluminum powder and aluminum ash, and then grinding it in an ultrafine mill using grinding ceramic balls with a diameter of 5 mm. The median particle size of the particles in the in-situ chemical foaming agent powder is 2.5 μm. (2) Before use, the in-situ chemical foaming agent powder is stirred with HPMC solution to form a slurry. The stirring time is 25 minutes and the rotation speed is 140 rpm. This results in the in-situ chemical foaming agent slurry, which further disperses the foaming agent components. The in-situ chemical foaming agent powder and HPMC solution in the in-situ chemical foaming agent slurry have a high mass. The ratio of the amounts is 1:20, and the concentration (solid content) of the HPMC solution is 1%; (3) After screening out the impurities in the sludge slurry, add the sludge solidifying cementitious material to the sludge slurry according to the batching ratio, stir to form a solidifiable sludge slurry, stir for 5 minutes, and rotate at 60 rpm; (4) Add the in-situ chemical foaming agent slurry to the solidifiable sludge slurry and stir quickly, stir for 20 minutes, and rotate at 50 rpm; (5) Pour the slurry obtained in step (4) into the space to be filled, and the aluminum powder in the slurry reacts with the OH released by the sludge solidifying cementitious material. - Under the action of the process, a large number of microbubbles are generated, forming a porous and lightweight mud structure. After the reaction is completed within 0.5 hours, a large amount of hydration products such as ettringite, CSH gel, CAH gel, and calcium hydroxide gel are produced in the sludge solidifying agent. This fixes the pores in the mud into closed pores, transforming the sludge into a honeycomb-like porous and lightweight structure with a pore size of 0.05 mm. After 3 days, the bulk density of the solidified sludge is 0.5 g / cm³. 3The unconfined compressive strength is 0.2 MPa after 3 days, 0.5 MPa after 7 days, and 0.8 MPa after 28 days. The softening coefficient is 0.85, and the volume shrinkage rate is 3 / 1000. The hydration reaction and volcanic ash reaction that occur in the silt solidification cementitious material itself, as well as the secondary volcanic ash reaction induced by silica and alumina in the silt, ensure that the long-term strength of the lightweight silt solidified body does not decrease. It can be used in various applications that require lightweight replacement soil, especially in soft soil foundations near Kunming plateau lakes that require lightweight soil replacement. After filling construction, the foundation will not easily collapse.

[0108] Comparative Example 1

[0109] This comparative example describes an in-situ foamed lightweight sludge solidification soil, the raw material composition of which includes: sludge slurry, sludge solidification cementitious material, and metallic aluminum powder paste. Among the above three components, the mass of the sludge solidification cementitious material is 1 / 4 of the total mass of the sludge slurry and the sludge solidification cementitious material, and the mass of the metallic aluminum powder paste is 1 / 1000 of the total mass of the sludge solidification cementitious material and the sludge slurry.

[0110] The sludge used in this comparative example was marine sedimentary sludge from Yuhuan City, Taizhou, Zhejiang Province. The sludge had a water content of 120%, an organic matter content of 5%, and a pH value of 9.

[0111] The sludge solidification cementitious material in this comparative example is composed of sulfoaluminate cement, ordinary silicate cement, persulfate cement, and biomass combustion ash (loss on ignition ≤ 5%), wherein sulfoaluminate cement accounts for 20% by mass, ordinary silicate cement 10%, persulfate cement 60%, and artificial volcanic ash 10%. Specifically, the sulfoaluminate cement is a rapid-hardening sulfoaluminate cement with a specific surface area of ​​400 m². 2 / kg; the ordinary Portland cement is a high-early strength type 42.5 ordinary Portland cement with a specific surface area of ​​400m². 2 / kg; the persulfate cement is made by finely grinding No. 52.5 silicate cement clinker, desulfurized gypsum and blast furnace slag, with a specific surface area of ​​400 m². 2 / kg, of which alkaline components account for 5%, sulfates account for 20%, and slag accounts for 75%; the specific surface area of ​​the biomass combustion ash is 600m². 2 / kg.

[0112] The preparation method of the in-situ foamed lightweight sludge solidification soil in this comparative example is as follows: (1) After screening out the impurities in the sludge, add the sludge solidification cementitious material to the sludge according to the batching ratio, stir to form a solidifiable sludge slurry, stir for 10 minutes, and rotate at 60 rpm; (2) Add the aluminum powder paste to the solidifiable sludge slurry and stir quickly, stir for 10 minutes, and rotate at 60 rpm; (3) Pour the slurry obtained in step (2) into the space to be filled. From the start of stirring in the aluminum powder paste, the aluminum powder in the slurry releases OH in the sludge solidification cementitious material. - Under the influence of this process, a large number of bubbles are generated and overflow, forming a sludge solidification structure with a small number of pores (≥2mm in diameter). After 3 days, the bulk density of the solidified sludge is 1.6g / cm³. 3 The unconfined compressive strength at 3 days is 0.8 MPa, at 7 days it is 2 MPa, and at 28 days it is 4.5 MPa. It does not exhibit the characteristics of lightweight solidified sludge, and its volume shrinkage rate is 1.5%.

[0113] Comparative Example 2

[0114] This comparative example describes an in-situ foamed lightweight sludge solidification soil using aluminum ash as a foaming agent. Its raw material composition includes: sludge slurry, sludge solidification cementitious material, and aluminum ash. The aluminum ash is finely ground aluminum ash. Among the above three components, the mass of the sludge solidification cementitious material is 1 / 4 of the total mass of the sludge slurry and the sludge solidification cementitious material, and the mass of the aluminum ash is 5 / 1000 of the total mass of the sludge solidification cementitious material and the sludge slurry.

[0115] The sludge used in this comparative example was marine sedimentary sludge from Yuhuan City, Taizhou, Zhejiang Province. The sludge had a water content of 120%, an organic matter content of 5%, and a pH value of 9.

[0116] The sludge solidification cementitious material in this comparative example is composed of sulfoaluminate cement, ordinary silicate cement, persulfate cement, and biomass combustion ash (loss on ignition ≤ 5%), wherein sulfoaluminate cement accounts for 20% by mass, ordinary silicate cement 10%, persulfate cement 60%, and artificial volcanic ash 10%. Specifically, the sulfoaluminate cement is a rapid-hardening sulfoaluminate cement with a specific surface area of ​​400 m². 2 / kg; the ordinary Portland cement is a high-early strength type 42.5 ordinary Portland cement with a specific surface area of ​​400m². 2 / kg; the persulfate cement is made by finely grinding No. 52.5 silicate cement clinker, desulfurized gypsum and blast furnace slag, with a specific surface area of ​​400 m². 2 / kg, of which alkaline components account for 5%, sulfates account for 20%, and slag accounts for 75%; the specific surface area of ​​the biomass combustion ash is 600m². 2 / kg.

[0117] The preparation method of the in-situ foamed lightweight sludge solidification soil of this comparative example is as follows: (1) After screening out the impurities in the sludge, add the sludge solidification cementitious material to the sludge according to the batching ratio, stir to form a solidifiable sludge slurry, stir for 10 minutes, and rotate at 60 rpm; (2) Then add aluminum ash to the solidifiable sludge slurry and stir quickly, stir for 20 minutes, and rotate at 60 rpm; (3) Pour the slurry obtained in step (2) into the space to be filled. From the moment aluminum ash is added to the sludge slurry, the metallic aluminum powder in the aluminum ash generates a large number of bubbles under the action of OH- released by the sludge solidification cementitious material, forming a sludge solidification structure with a small number of pores, the pore size is ≥1mm, and the bulk density of the sludge solidification body after 3 days is 1.7g / cm³. 3 The unconfined compressive strength at 3 days is 1.2 MPa, at 7 days it is 2.5 MPa, and at 28 days it is 5 MPa. It does not exhibit the characteristics of lightweight solidified sludge, and its volume shrinkage rate is 1.2%.

Claims

1. An in-situ chemical foaming agent for lightweight silt-stabilized soil, characterized in that, The in-situ chemical foaming agent is a slurry formed by mixing in-situ chemical foaming agent powder with organic polymer solution / emulsion. The in-situ chemical foaming agent powder contains metallic aluminum powder and non-metallic compound composite particles. The aluminum powder particles are separated by non-metallic compound particles, and the median particle size of the metallic aluminum powder and non-metallic compound particles is ≤5μm. The non-metallic compound is one or more of aluminum oxide, aluminum carbide, silicon carbide, and silicon oxide, and the mass of the aluminum powder accounts for 10%-35% of the total mass of the in-situ chemical foaming agent powder. The composite particles of metallic aluminum powder and non-metallic compound are obtained by grinding and dispersing metallic aluminum powder and non-metallic compound together; the organic polymer solution / emulsion is HPMC, MC, PVA, EG, polystyrene, polyacrylic acid or waterborne epoxy resin emulsion / solution.

2. The in-situ chemical foaming agent according to claim 1, characterized in that, The composite particles of metallic aluminum powder and non-metallic compound are composed of metallic aluminum powder and aluminum ash. In the composite composition, the proportion of metallic aluminum powder is >0 and ≤20%, and the proportion of aluminum ash is ≥80% and <100%. The mass ratio of in-situ chemical foaming agent powder to polymer solution / emulsion in the in-situ chemical foaming agent slurry is 1:10-1:20, and the solid content of organic polymer solution / emulsion is 0.1~5%.

3. An in-situ chemically foamed lightweight silt-stabilized soil, characterized in that, Its raw material components include solidifiable sludge slurry and the in-situ chemical foaming agent as described in claim 1 or 2.

4. The in-situ chemically foamed lightweight silt-stabilized soil according to claim 3, characterized in that, The mass of the in-situ chemical foaming agent powder is 1 / 1000-1 / 100 of the total mass of sludge slurry and sludge solidification cementitious material; the solidifiable sludge slurry includes sludge slurry and sludge solidification cementitious material, wherein the mass of the sludge solidification cementitious material accounts for 1 / 10-1 / 4 of the total mass of sludge slurry and sludge solidification cementitious material, and the water content of the sludge slurry is 80%~200%.

5. The in-situ chemically foamed lightweight silt-stabilized soil according to claim 4, characterized in that, The sludge solidification cementitious material is composed of quick-setting cement, ordinary Portland cement, persulfate cement and artificial volcanic ash, wherein the quick-setting cement accounts for 0-20% by mass, ordinary Portland cement accounts for 10-40%, persulfate cement accounts for 30-90%, and artificial volcanic ash accounts for 0-20%.

6. The in-situ chemically foamed lightweight silt-stabilized soil according to any one of claims 3-5, characterized in that, The in-situ chemically foamed lightweight sludge solidification soil has a honeycomb-like porous lightweight structure with a pore size ranging from 0.05 to 0.2 mm. After 3 days of curing, the bulk density of the solidified sludge body is 0.3 to 1.2 g / cm³. 3 Unconfined compressive strength at 3 days: 0.2-0.8 MPa; Unconfined compressive strength at 28 days: 0.5-3 MPa; Softening coefficient: ≥0.7; Volume shrinkage rate: ≤5 / 1000.

7. A method for preparing in-situ chemically foamed lightweight silt-stabilized soil as described in any one of claims 3-6, characterized in that, In-situ chemical foaming agent slurry is added to solidifiable sludge slurry and stirred until uniform. After in-situ foaming and solidification reaction, in-situ chemically foamed lightweight sludge solidified soil is obtained.

8. The method for preparing in-situ chemically foamed lightweight silt-stabilized soil according to claim 7, characterized in that, The specific preparation process of the in-situ chemical foaming agent includes: The mixed powder of metallic aluminum powder and non-metallic compound is subjected to ultrafine grinding to obtain composite particles of metallic aluminum powder and non-metallic compound with a median particle size ≤5μm, which is the in-situ chemical foaming agent powder. The obtained in-situ chemical foaming agent powder is mixed and stirred with an organic polymer solution / emulsion to form a slurry, thus obtaining the in-situ chemical foaming agent slurry.

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