A structural agent for lightweight solidified sludge, solidified soil and its preparation method

Abstract

This invention discloses a lightweight solidified sludge structural agent, solidified soil, and its preparation method, belonging to the technical field of solidified soil materials. The lightweight solidified sludge structural agent of this invention comprises sludge solidification cementitious materials, anti-over-dispersibility hydrogen peroxide emulsion / solution, a foaming catalyst, and expanded polystyrene particles. The anti-over-dispersibility hydrogen peroxide emulsion / solution is prepared by mixing hydrogen peroxide with a polymer solution / emulsion. The lightweight solidified sludge soil of this invention comprises sludge to be solidified and the lightweight solidified sludge structural agent of this invention. The technical solution of this invention can effectively solve the above-mentioned technical problems existing in the preparation of lightweight solidified sludge soil using existing physical foaming methods. It can also overcome the shortcomings of current hydrogen peroxide chemical foaming methods, such as the difficulty in controlling the process and the need to heat the sludge slurry to achieve in-situ foaming of hydrogen peroxide in the slurry.

Description

Technical Field

[0001] This invention belongs to the field of solidified soil materials technology, specifically relating to an in-situ foamed lightweight sludge solidifying agent, solidified soil materials and their preparation methods. Background Technology

[0002] To meet construction needs while ensuring structural safety, engineering construction is gradually moving towards lightweight and cost-effective methods. 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, carbon dioxide, etc.). This porosity 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 railway engineering for backfilling and load reduction, 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 obtaining it through a foaming mechanism under high pressure. 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, it is necessary to add foam stabilizing components, 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 chemical foaming to prepare the lightweight silt soil; the foaming component is hydrogen peroxide, which does not pollute the soil after addition, 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 by 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, in order to make the sludge suitable for foaming and foam stabilization, this application requires the addition of various components such as inorganic composite binder, coagulant, thickening component, plasticizer and hydrophobic component to the sludge. After being stirred evenly, the foaming component hydrogen peroxide is added to the sludge with silt, clay and silty clay as the base material. Water and oxygen are generated to foam in situ, forming a lightweight sludge structure. Although this process avoids the defoaming effect of physical foaming, adding hydrogen peroxide at the last stage of mud mixing makes it difficult to control the foaming process of hydrogen peroxide if the sludge is not heated and a catalyst is not used. In addition, the unit dosage of liquid foaming agent hydrogen peroxide is relatively large.

[0008] The first inventor of this application has been committed to the research of building materials such as foamed mortar and lightweight silt-stabilized soil, and has achieved a series of research results. Among them, the patent application with application number CN201410104347.0 proposed a method for controllable in-situ chemical foaming. By first loading hydrogen peroxide into expanded perlite microspheres, and then adding the expanded perlite microspheres into the mixed lightweight mortar, after the perlite microspheres are evenly distributed in the lightweight mortar, the hydrogen peroxide diffuses out from the expanded perlite and encounters the catalyst to produce a foaming reaction. This reaction can make the mortar lighter. However, in order to make the cement slurry set faster, a cement accelerator needs to be added to the mortar to prevent the segregation of expanded polystyrene particles. At the same time, if a certain amount of hydrogen peroxide encounters the increased viscosity of the cement slurry before leaving the carrier, then this part of hydrogen peroxide will not contribute to the lightening of the cement slurry structure. Summary of the Invention

[0009] The purpose of this invention is to provide a structural agent for lightweight solidified sludge, lightweight solidified sludge soil, and a method for preparing the same. This effectively solves the aforementioned technical problems associated with existing physical foaming methods for preparing lightweight solidified sludge soil. It also overcomes the shortcomings of current hydrogen peroxide chemical foaming methods, which are difficult to control and require heating of the sludge slurry to achieve in-situ foaming of hydrogen peroxide. The in-situ foaming process of this invention is controllable and effectively ensures the strength of the resulting lightweight solidified sludge soil.

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

[0011] This invention provides a structural agent for lightweight solidified sludge. The raw materials of the structural agent components include sludge solidification cementitious material, anti-over-dispersible hydrogen peroxide emulsion / solution, and foaming catalyst. The anti-over-dispersible hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0012] This invention utilizes hydrogen peroxide as a key component of the anti-over-dispersibility hydrogen peroxide emulsion / solution raw material in the structuring agent for in-situ chemical foaming. This allows for the formation of pores in the solidified silt, which helps reduce the bulk density of the resulting lightweight solidified silt. However, if hydrogen peroxide is added directly for chemical foaming, subsequent stirring and dilution of the hydrogen peroxide can affect the foaming effect, potentially preventing the formation of a lightweight porous structure or impacting the structural strength of the resulting solidified silt.

[0013] This invention creatively combines hydrogen peroxide with a polymer solution / emulsion through stirring to form an anti-over-dispersible hydrogen peroxide emulsion / solution. The viscous droplets formed by the polymer emulsion / solution and hydrogen peroxide can exist in a hydrogen peroxide-rich form during the stirring process into the sludge. This allows the foaming agent to be dispersed to a smaller size, thus ensuring that in-situ foaming produces smaller pores and guarantees the uniformity of pore size. On the other hand, it effectively avoids the hydrogen peroxide being highly dispersed by stirring after contact with water, which would result in an excessively low gas concentration, making it easily submerged in the sludge and unable to form a lightweight porous structure, or even failing to guarantee the strength of the resulting lightweight sludge-stabilized soil.

[0014] Furthermore, the polymer solution / emulsion is made of HPMC, CMC, MC, PVA, polystyrene-acrylic acid, polyacrylic acid, or waterborne epoxy resin solution / emulsion, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 2:1-5:1, with a solid content of 0.1-5%. By strictly controlling the mass ratio of the polymer solution / emulsion to hydrogen peroxide, the polymer emulsion / solution and hydrogen peroxide can be mixed and stirred to form viscous droplets, thereby ensuring the anti-dispersion, encapsulation, and protection of the hydrogen peroxide.

[0015] As a further preferred embodiment of the present invention, the sludge solidification cementitious material uses persulfate cement, and is further optimized to include sulfate activating components, alkaline activating components, active micro powder and citric acid. The sulfate activating component is calcium sulfate hemihydrate, such as building gypsum, and its mass accounts for 15-30% of the total mass of the sludge solidification cementitious material. The mass of citric acid is 1 / 1000-3 / 2000 of the mass of the sulfate activating component.

[0016] By using calcium sulfate hemihydrate as the sulfate activator and adding a certain amount of citric acid to the sludge solidification cementitious material, a controllable stepwise hydration effect is achieved. Specifically, the first step is the hydration of calcium sulfate hemihydrate to calcium sulfate dihydrate. This reaction is controlled by the citric acid component, preventing vigorous hydration before the hydrogen peroxide foaming reaction. After the hydrogen peroxide foaming reaction is complete, the hydration reaction becomes more vigorous, significantly increasing the viscosity of the foamed sludge slurry. The positions of air bubbles in the slurry are fixed, ensuring that air bubbles do not segregate or migrate within the lightweight structure. The honeycomb structure formed in this way possesses the structural characteristics of a lightweight, high-strength structure, which can be maintained for a long time in water-rich underground environments. After foaming, the volcanic ash component in the sludge solidification cementitious material continues to undergo a volcanic ash reaction within the lightweight sludge solidification body. The resulting cementitious products cause the strength of the lightweight sludge solidification body to continuously increase over time, thereby extending the lifespan of the lightweight structure. Furthermore, the sludge solidification cementitious material of the present invention can also efficiently solidify the sludge slurry while creating an alkaline environment that promotes the foaming of hydrogen peroxide.

[0017] Furthermore, the alkaline activating component is preferably at least one of silicate cement, aluminate cement, quicklime, and hydrated lime, and its mass accounts for 5-10% of the total amount of sludge solidification cementitious material; the active micro powder is preferably slag micro powder, and the mass of slag micro powder accounts for 60-80% of the total amount of sludge solidification cementitious material.

[0018] Furthermore, the raw materials of the structural agent component also include expanded polystyrene particles with a particle size of 3-10 mm. Based on the close-packed volume, the amount used is 1 / 4-2 / 3 of the volume of the slurry formed by the sludge to be solidified and the sludge solidification cementitious material. By adding a certain amount of expanded polystyrene particles as lightweight aggregate, it is beneficial to further reduce the bulk density of the resulting solidified sludge soil, thus preparing a lightweight solidified soil backfill material, while also solving the problem of white pollution.

[0019] However, it should be noted that due to the low density of expanded polystyrene particles, they are prone to segregation in slurry, which limits their application in lightweight sludge-stabilized soil. The technical solution of this invention, which utilizes the controllable stepwise hydration of the sludge-stabilizing cementitious material, allows the expanded polystyrene particles and air bubbles to be effectively fixed simultaneously when calcium sulfate hemihydrate is violently hydrated into calcium sulfate dihydrate. This effectively solves the problem of segregation of expanded polystyrene particles, enabling them to be effectively applied in lightweight sludge-stabilized soil.

[0020] Furthermore, the foaming catalyst uses expanded perlite particles as a carrier, and a catalyst solution made of catalytic components is loaded inside the expanded perlite particles. The catalytic components are any one of ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, and potassium permanganate, and the above-mentioned catalytic components account for 0.1% to 0.5% of the mass of the sludge solidification cementitious material.

[0021] The addition of a foaming catalyst can catalyze and control the in-situ chemical foaming process of hydrogen peroxide. As a further improvement of this invention, expanded perlite particles are used as the carrier of the catalytic component. By utilizing the convection and diffusion motion during the stirring process between expanded perlite particles and expanded polystyrene particles, they can be evenly distributed in the sludge between the expanded polystyrene particles at an extremely fast dispersion rate. At the same time, it will not have a negative impact on the fluidity of the obtained viscous body. Therefore, it can be ensured that the viscous body is smoothly pumped to the filling position before the in-situ chemical foaming reaction occurs.

[0022] Furthermore, the bulk density of the expanded perlite particles is ≤100kg / m³. 3 The particle size is 1-5 mm, and the dosage, based on the close packing volume, is 1 / 10-3 / 10 of the expanded polystyrene granules; the bulk density of the expanded polystyrene granules is ≤10 kg / m³. 3The specific surface area of ​​the sludge solidification cementitious material is ≥400m². 2 / kg, the dosage of which is 1 / 4 to 1 / 10 of the total amount of sludge and sludge solidification cementitious material; the hydrogen peroxide used is industrial grade hydrogen peroxide with a mass concentration of 30% to 50%, and the dosage of hydrogen peroxide is 0.2% to 2% of the total amount of sludge and sludge solidification cementitious material; the raw materials of the structural agent component further include water-reducing agent, and the amount of water-reducing agent added is 0 to 1 / 1000 of the amount of sludge slurry to be solidified.

[0023] The present invention also provides a lightweight sludge solidification soil, the raw materials of which include sludge slurry to be solidified and the structural agent component for lightweight sludge solidification of the present invention.

[0024] The present invention also provides a method for preparing the aforementioned lightweight silt-stabilized soil, comprising:

[0025] The sludge solidification cementitious material and the anti-over-dispersion hydrogen peroxide emulsion / solution in the structural agent components are stirred and mixed evenly with the sludge slurry to obtain a mixed slurry;

[0026] Adding the foaming catalyst from the structural agent component to the above-mentioned mixed slurry yields a solidifiable sludge slurry before in-situ foaming; and

[0027] The process involves pumping solidifiable sludge slurry into the space to be filled, and then solidifying it to form lightweight sludge-solidified soil.

[0028] It should be noted that the sludge slurry of the present invention can be marine sedimentary sludge slurry, lacustrine sedimentary sludge slurry, or pond bottom mud, and is more preferably 80% to 200% water content, and even more preferably 80% to 120% water content.

[0029] Furthermore, before adding the foaming catalyst from the structural agent component to the mixed slurry, the process includes adding expanded polystyrene particles from the structural agent component to the mixed slurry. This allows for full utilization of the diffusion motion between expanded perlite particles and expanded polystyrene particles, as well as the convection and shear motion between viscous fluids. After mixing for 3-5 minutes, the expanded perlite particles are uniformly dispersed in the expanded polystyrene particle-slurry mixture, obtaining a solidifiable sludge slurry before in-situ foaming. The solidifiable sludge slurry obtained after mixing is pumped and poured into the space to be filled. A large amount of catalyst ions from the expanded perlite particles are released into the slurry, and they react with the OH groups released by the sludge solidification cementitious material. -The combined effect of these factors causes hydrogen peroxide to decompose into water and oxygen, generating a large number of microbubbles and forming a porous, lightweight slurry structure. After the in-situ foaming reaction is completed within 0.5 hours, the hemihydrate calcium sulfate of the sludge solidification cementitious material is converted into dihydrate calcium sulfate. The large amount of products generated by this hydration reaction freezes the positions of pores and expanded polystyrene particles in the slurry. Later, the hydration products of the sludge solidification cementitious material, such as ettringite, CSH (hydrated calcium silicate) gel, CAH (hydrated calcium aluminate) gel, and calcium hydroxide gel, transform the sludge slurry into a honeycomb-like porous, lightweight solid structure with pore sizes of 0.1–0.5 mm. After 3 days, the bulk density of the solidified sludge is 0.3–1.0 g / cm³. 3 The 3-day unconfined compressive strength is 0.2–1 MPa, the 28-day unconfined compressive strength is 0.5–3 MPa, the softening coefficient is ≥0.7, and the volume shrinkage rate is ≤2 / 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 riverside 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.

[0030] In summary, by adopting the technical solution provided by this invention, the following beneficial effects can be achieved compared with the prior art:

[0031] (1) The structural agent of this application can directly convert high water content sludge slurry into high performance (high strength-to-weight ratio) lightweight sludge solidification soil. The encapsulation and protection of polymer solution / emulsion can prevent hydrogen peroxide from being too dispersed due to stirring and dilution, thus affecting its foaming effect.

[0032] (2) The addition of a large amount of expanded polystyrene particles in this invention helps to further reduce the bulk density of the sludge-stabilized soil and solve the white pollution problem caused by expanded polystyrene particles. At the same time, it also reduces the amount of foaming agent required and eliminates the need for additional foam stabilizers. Furthermore, through the stepwise hydration control of the sludge-stabilized cementitious material, this invention can effectively fix the position of the expanded polystyrene particles, allowing them to be evenly distributed in the slurry and avoiding segregation that could affect the strength of the sludge-stabilized body.

[0033] (3) The present invention further loads the foaming catalyst solution into the expanded perlite particles, thereby enabling it to be evenly distributed in the sludge between the expanded polystyrene particles at an extremely fast dispersion speed by means of the convection and diffusion motion between it and the expanded polystyrene particles during the stirring process. At the same time, it does not have a negative impact on the fluidity of the obtained viscous body, ensuring that the viscous body is smoothly pumped to the filling position before the in-situ chemical foaming reaction occurs. Attached Figure Description

[0034] Appendix Figure 1 This is a flowchart illustrating the preparation process of lightweight silt-stabilized soil according to one embodiment of the present invention.

[0035] Appendix Figure 2 A cross-sectional photograph of a 3-day sample (40mm×40mm×160mm) of lightweight silt-stabilized soil was obtained for Example 1.

[0036] Appendix Figure 3 A cross-sectional photograph of a 3-day sample (40mm×40mm×160mm) of lightweight solidified soil was obtained for Example 6. Detailed Implementation

[0037] This invention provides a structural agent for lightweight solidified sludge. The raw materials of the structural agent components include sludge solidification cementitious material, anti-over-dispersible hydrogen peroxide emulsion / solution, foaming catalyst, and expanded polystyrene particles. The anti-over-dispersible hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0038] In-situ chemical foaming is achieved by adding hydrogen peroxide, a structural agent component, to sludge, and foaming is controlled using a foaming catalyst. This process can be used to solidify sludge and create pores within the solidified sludge, resulting in lightweight solidified sludge soil. Furthermore, mixing hydrogen peroxide with a polymer solution / emulsion forms an anti-over-dispersible hydrogen peroxide emulsion / solution. This allows the polymer solution / emulsion to encapsulate and protect the hydrogen peroxide, forming the basic foaming units through stirring. This prevents the hydrogen peroxide from being diluted or reduced to excessively small sizes, which would negatively impact its foaming effect.

[0039] In some embodiments of the present invention, the polymer solution / emulsion is HPMC, CMC, MC, PVA, polystyrene-acrylic acid, polyacrylic acid, or waterborne epoxy resin solution / emulsion, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 2:1-5:1, and the solid content of the polymer solution / emulsion is 0.1-5%. In some embodiments, the hydrogen peroxide is industrial-grade hydrogen peroxide with a concentration of 30%-50%, and the amount of hydrogen peroxide used is 0.2% to 2% of the total amount of sludge and sludge solidification cementitious material, more preferably 0.5% to 1.5%.

[0040] As a further improvement of the present invention, expanded polystyrene particles are also added to the raw materials of the structural agent component, which can further reduce the bulk density of the sludge-stabilized soil and help solve the white pollution problem caused by expanded polystyrene particles. In some embodiments of the present invention, the expanded polystyrene particles have a bulk density ≤10kg / m³. 3 The expanded polystyrene particles are preferably waste expanded polystyrene particles obtained by crushing waste expanded polystyrene boards, with a particle size of 3 to 10 mm, more preferably 5 to 8 mm; the amount of expanded polystyrene particles used is 1 / 4 to 2 / 3 of the volume of the slurry formed by the sludge to be solidified and the sludge solidification cementitious material, more preferably 1 / 4 to 1 / 2, based on the close packing volume.

[0041] In a preferred embodiment of the sludge solidification cementitious material of the present invention, the sludge solidification cementitious material uses modified persulfate cement. More preferably, the sludge solidification cementitious material comprises a sulfate activating component, an alkaline activating component, active micro-powder, and citric acid, wherein the sulfate activating component is calcium sulfate hemihydrate, i.e., building gypsum, and its mass accounts for 15-30% of the total mass of the sludge solidification cementitious material, and the mass of citric acid is 1 / 1000-3 / 2000 of the mass of the sulfate activating component. Furthermore, the specific surface area of ​​the sludge solidification cementitious material is ≥400 m². 2 / kg, the amount of sludge solidification cementitious material used is 1 / 4 to 1 / 10 of the sum of the amount of sludge and the amount of sludge solidification cementitious material.

[0042] By using calcium sulfate hemihydrate as the activating component and adding a certain amount of citric acid, a controllable stepwise hydration effect can be achieved. This allows the first step of hydrating calcium sulfate hemihydrate to calcium sulfate dihydrate to occur vigorously only after the hydrogen peroxide foaming reaction has fully progressed. As a result, the positions of the bubbles generated by the hydrogen peroxide foaming reaction and the expanded polystyrene particles can be effectively fixed, preventing the segregation and cross-contamination of bubbles and expanded polystyrene particles. This helps to ensure the structural strength of the resulting silt-stabilized soil.

[0043] In some embodiments, the alkaline activating component is at least one of silicate cement, aluminate cement, quicklime, and hydrated lime, and its mass accounts for 5-10% of the total mass of the sludge solidification cementitious material; the active micro powder is slag micro powder, and the mass of the slag micro powder accounts for 60-80% of the total mass of the sludge solidification cementitious material.

[0044] As a further improvement of the present invention, the foaming catalyst in the structural agent component uses expanded perlite particles as a carrier, and a catalyst solution made of catalytic components is loaded within the expanded perlite particles. This fully utilizes the convection and diffusion motion during the stirring process between the expanded perlite particles and the expanded polystyrene particles, thereby enabling the expanded perlite particles to be evenly distributed in the sludge between the expanded polystyrene particles at an extremely rapid dispersion rate. Simultaneously, this does not negatively affect the flowability of the obtained viscous body, ensuring that the in-situ chemical foaming reaction only occurs after the viscous body is smoothly pumped to the filling location. More preferably, the bulk density of the expanded perlite particles is ≤100 kg / m³. 3 The particle size is 1-5mm, and the dosage is 1 / 10-3 / 10 of the expanded polystyrene particles based on the close packing volume.

[0045] In some embodiments of the present invention, the catalytic component is any one of ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, and potassium permanganate, and the above-mentioned catalytic component accounts for 0.1% to 0.5% of the mass of the sludge solidification cementitious material.

[0046] More preferably, the raw materials of the structural agent component also include a water-reducing agent, and the amount of water-reducing agent added is 0 to 1 / 1000 of the amount of sludge to be solidified.

[0047] This invention also provides a lightweight sludge-stabilized soil, the raw materials of which include sludge slurry to be stabilized and the structural agent component for lightweight sludge stabilization of this invention. The preparation method of the lightweight sludge-stabilized soil includes:

[0048] The sludge solidification cementitious material and the anti-over-dispersion hydrogen peroxide emulsion / solution in the structural agent components are stirred and mixed evenly with the sludge slurry to obtain a mixed slurry;

[0049] Adding the foaming catalyst from the structural agent component to the above-mentioned mixed slurry yields a solidifiable sludge slurry before in-situ foaming; and

[0050] The process involves pumping solidifiable sludge slurry into the space to be filled, and then solidifying it to form lightweight sludge-solidified soil.

[0051] As a further improvement of the present invention, the step of adding expanded polystyrene particles from the structural agent component to the mixed mud is included before adding the foaming catalyst to the mixed mud.

[0052] Specifically, a large amount of catalyst ions from expanded perlite particles are released into the mud, and these ions react with the OH groups released by the sludge solidification cementitious materials. -The combined effect of these factors causes hydrogen peroxide to decompose into water and oxygen, generating a large number of microbubbles and forming a porous, lightweight slurry structure. After the in-situ foaming reaction is completed within 0.5 hours, the hemihydrate calcium sulfate of the sludge solidification cementitious material is converted into dihydrate calcium sulfate. The large amount of products generated by this hydration reaction freezes the positions of pores and expanded polystyrene particles in the slurry. Later, the hydration products of the sludge solidification cementitious material, such as ettringite, CSH (hydrated calcium silicate) gel, CAH (hydrated calcium aluminate) gel, and calcium hydroxide gel, transform the sludge slurry into a honeycomb-like porous, lightweight solid structure with pore sizes of 0.1–0.5 mm. After 3 days, the bulk density of the solidified sludge is 0.3–1.0 g / cm³. 3 The 3-day unconfined compressive strength is 0.2–1 MPa, the 28-day unconfined compressive strength is 0.5–3 MPa, the softening coefficient is ≥0.7, and the volume shrinkage rate is ≤2 / 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 riverside 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 also be effectively avoided.

[0053] To further understand the content of this invention, it will now be described in detail with reference to the accompanying drawings and embodiments.

[0054] Example 1

[0055] This embodiment of a lightweight sludge solidification soil comprises sludge slurry to be solidified and a structural agent component for lightweight solidified sludge. The structural agent component comprises sludge solidification cementitious material, anti-over-dispersibility hydrogen peroxide emulsion / solution, expanded polystyrene particles, and a foaming catalyst. The anti-over-dispersibility hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0056] Specifically, in this embodiment, the sludge to be solidified is marine sedimentary sludge from Yuhuan, Taizhou, with a water content of 120%; the hydrogen peroxide in the anti-over-dispersion hydrogen peroxide emulsion / solution is 30% industrial-grade hydrogen peroxide, and the amount of hydrogen peroxide used is 0.5% of the total mass of the sludge and the sludge solidification cementitious material; the polymer in the polymer solution / emulsion is HPMC, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 2:1, and the solid content of the polymer solution / emulsion is 0.1%.

[0057] The sludge solidification cementitious material of this embodiment is a modified persulfate cement, composed of building gypsum (CaSO4·1 / 2H2O), 52.5PO cement, slag powder, and citric acid. The sulfate-activating component accounts for 15%, the alkaline-activating component accounts for 5%, the slag powder accounts for 80%, and the citric acid content is 1 / 1000 of the building gypsum component. The specific surface area of ​​the sludge solidification cementitious material is ≥400 m² / g. 2 / kg, the amount of sludge solidification cementitious material used is 1 / 10 of the sum of the sludge volume and the sludge solidification cementitious material volume. The expanded polystyrene particles have a bulk density of 8 kg / m³. 3 The expanded polystyrene granules are made from the crushing of waste expanded polystyrene boards, and the particle size is 5-8 mm. The amount of expanded polystyrene granules used (based on the close packing volume) is 1 / 2 of the volume of the slurry formed by the sludge and the sludge solidification cementitious material.

[0058] In this embodiment, the foaming catalyst uses expanded perlite particles as a carrier, with ferric sulfate solution as the catalytic component loaded within the expanded perlite particles. The mass of the ferric sulfate solution accounts for 0.1% of the total amount of the sludge solidification cementitious material, and the bulk density of the expanded perlite particles is 90 kg / m³. 3 The particle size is 2-3mm, and the particles can absorb 10 times their own weight in water; the amount of expanded perlite particles used is 1 / 10 of the amount of expanded polystyrene particles (based on the close packing volume).

[0059] Combination Figure 1 The specific steps for preparing lightweight silt-stabilized soil in this embodiment are as follows:

[0060] (1) First, the expanded perlite particles are saturated with the catalyst solution in the ingredients to obtain a foaming catalyst with expanded perlite as the carrier.

[0061] (2) Mix hydrogen peroxide and polymer solution (or emulsion) according to the metering ratio for 10 minutes to form an anti-over-dispersible hydrogen peroxide emulsion / solution.

[0062] (3) Add the obtained anti-dispersible hydrogen peroxide emulsion / solution and sludge solidification cementitious material to the sludge slurry weighed according to the mixing ratio and mix thoroughly for 2 minutes to obtain mixed slurry 1.

[0063] (4) Add the expanded polystyrene particles weighed according to the mixing ratio to the mixed mud 1, stir for 3 minutes to obtain mixed mud 2.

[0064] (5) Add the foaming catalyst obtained in step (1) to the mixed slurry 2 and continue stirring. Utilizing the diffusion motion between the expanded perlite particles and the expanded polystyrene particles, as well as the convection and shear motion between the viscous fluids, after mixing for 3 minutes, the expanded perlite particles are evenly distributed in the expanded polystyrene particle-slurry mixture, obtaining a solidifiable sludge slurry before in-situ foaming. The solidifiable sludge slurry obtained after mixing is poured into the space to be filled. A large amount of catalyst ions from the expanded perlite particles are released into the slurry, and they react with the OH groups released by the sludge solidification cementitious material. - The combined effect of these factors causes hydrogen peroxide to decompose into water and oxygen, generating a large number of microbubbles and forming a porous, lightweight slurry structure. After the in-situ foaming reaction is completed within 0.5 hours, the hemihydrate calcium sulfate of the sludge solidification cementitious material is converted into dihydrate calcium sulfate. The large amount of products generated by this hydration reaction freezes the positions of pores and expanded polystyrene particles in the slurry. Later, the hydration products of the sludge solidification cementitious material, such as ettringite, CSH (hydrated calcium silicate) gel, CAH (hydrated calcium aluminate) gel, and calcium hydroxide gel, transform the sludge slurry into a honeycomb-like porous, lightweight solid structure with pore sizes of 0.2–0.5 mm. The sludge solidified body after 3 days (see attached image) Figure 2 The white spherical objects in the picture are expanded polystyrene particles, and the larger annular pits are left after the expanded polystyrene particles were pulled out. The bulk density is 0.75 g / cm³. 3 The 3-day unconfined compressive strength is 0.35 MPa, the 28-day unconfined compressive strength is 0.9 MPa, the softening coefficient is 0.8, and the volume shrinkage rate is 1 / 1000. The hydration reaction and pozzolanic reaction that occur 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 locations on coastal 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 also be effectively avoided.

[0065] Example 2

[0066] This embodiment of a lightweight sludge solidification soil comprises sludge slurry to be solidified and a structural agent component for lightweight solidified sludge. The structural agent component comprises sludge solidification cementitious material, anti-over-dispersibility hydrogen peroxide emulsion / solution, expanded polystyrene particles, water-reducing agent, and foaming catalyst. The anti-over-dispersibility hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0067] Specifically, the sludge slurry in this embodiment is a sludge slurry made by mixing marine sedimentary silt from Yuhuan, Taizhou with water, and has a water content of 80%. The hydrogen peroxide in the above-mentioned anti-over-dispersibility hydrogen peroxide emulsion / solution is industrial-grade hydrogen peroxide with a concentration of 50%, and the amount of hydrogen peroxide used is 1% of the total amount of sludge and sludge solidification cementitious material. The polymer in the above-mentioned polymer solution / emulsion is PVA, and the mass ratio of polymer solution / emulsion to hydrogen peroxide is 3:1, and the solid content of polymer solution / emulsion is 1%.

[0068] The sludge solidification cementitious material of this embodiment is a modified persulfate cement, composed of building gypsum (CaSO4·1 / 2H2O), high-alumina cement, slag powder, and citric acid. The sulfate-activating component accounts for 25%, the alkaline-activating component (high-alumina cement) accounts for 10%, the slag powder accounts for 65%, and the citric acid is 1 / 1000 of the building gypsum component. The specific surface area of ​​the sludge solidification cementitious material is ≥400 m². 2 / kg, the amount of sludge solidification cementitious material used is 1 / 4 of the sum of the amount of sludge and the amount of sludge solidification cementitious material.

[0069] The expanded polystyrene particles in this embodiment have a bulk density of 8 kg / m³. 3 The expanded polystyrene granules are made from crushed waste expanded polystyrene boards, and the particle size is 5-8 mm; the amount of expanded polystyrene granules (based on the close packing volume) is 1 / 4 of the volume of the slurry formed by the sludge and the sludge solidification cementitious material; the amount of the powdered polycarboxylate superplasticizer added is 1 / 1000 of the sludge slurry.

[0070] In this embodiment, the foaming catalyst uses expanded perlite particles as a carrier, with ferric chloride solution as the catalytic component loaded within the expanded perlite particles. The mass of the ferric chloride solution accounts for 0.1% of the amount of sludge solidification cementitious material used. The bulk density of the expanded perlite particles is 90 kg / m³. 3 The particle size is 2-3mm, and the particles can absorb 10 times their own weight in water; the amount of expanded perlite particles used is 1 / 10 of the amount of expanded polystyrene particles (based on the close packing volume).

[0071] Combination Figure 1 The specific steps for preparing lightweight silt-stabilized soil in this embodiment are as follows:

[0072] (1) First, the expanded perlite particles are saturated with the catalyst solution in the ingredients to obtain a foaming catalyst with expanded perlite particles as the carrier.

[0073] (2) Next, the powder water-reducing agent in the ingredients is added to the sludge solidification cementitious material according to the proportion in the ingredients, and pre-stirred for 3 minutes to obtain a pre-stirred mixture.

[0074] (3) Mix hydrogen peroxide and polymer solution (or emulsion) according to the metering ratio for 10 minutes to form an anti-over-dispersible hydrogen peroxide emulsion / solution.

[0075] (4) Add the pre-stirred mixture obtained in step (2) and the anti-over-dispersible hydrogen peroxide emulsion / solution obtained in step (3) to the sludge slurry weighed according to the mixing ratio and mix thoroughly for 2 minutes to obtain mixed slurry 1.

[0076] (5) Add the weighed expanded polystyrene particles to the mixed mud 1 and stir for 3 minutes to obtain mixed mud 2.

[0077] (6) The catalyst carrier obtained in step (1) is added to the mixed slurry 2 and stirred for 3 minutes to obtain a solidifiable sludge slurry before in-situ foaming. The solidifiable sludge slurry obtained after mixing is poured into the space to be filled. Through foaming and solidification reactions, the sludge slurry is transformed into a honeycomb-shaped porous lightweight solid structure with a pore size of 0.1-0.2 mm. The bulk density of the solidified sludge body after 3 days is 0.6 g / cm³. 3 The unconfined compressive strength at 3 days is 0.3 MPa, the unconfined compressive strength at 28 days is 1.0 MPa, the softening coefficient is 0.7, and the volume shrinkage rate is 1 / 1000.

[0078] Example 3

[0079] This embodiment of a lightweight sludge solidification soil comprises sludge slurry to be solidified and a structural agent component for lightweight solidified sludge. The structural agent component comprises sludge solidification cementitious material, anti-over-dispersibility hydrogen peroxide emulsion / solution, polystyrene particles, water-reducing agent and foaming catalyst. The anti-over-dispersibility hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0080] Specifically, the sludge slurry in this embodiment is engineering waste sludge slurry from marine sedimentary silty soil in Jinshan, Shanghai, with a water content of 80%; the hydrogen peroxide in the anti-over-dispersibility hydrogen peroxide emulsion / solution is 30% industrial-grade hydrogen peroxide, and the amount of hydrogen peroxide used is 0.75% of the sum of the mass of sludge and sludge solidification cementitious material; the polymer in the polymer solution or emulsion is PVA, and the mass ratio of polymer solution / emulsion to hydrogen peroxide is 5:1, and the solid content of the polymer solution / emulsion is 5%; the water-reducing agent is powdered polycarboxylate water-reducing agent, and the amount added is 1 / 1000 of the sludge slurry.

[0081] The sludge solidification cementitious material of this embodiment is a modified persulfate cement, composed of building gypsum (CaSO4·1 / 2H2O), quicklime, slag powder, and citric acid. The sulfate-activated component, building gypsum, accounts for 30%, the alkaline-activated component, quicklime, accounts for 5%, and the slag powder accounts for 65%. Citric acid constitutes 1 / 1000 of the building gypsum component. The specific surface area of ​​the sludge solidification cementitious material is ≥400 m². 2 / kg, the amount of sludge solidification cementitious material used is 1 / 6 of the sum of the amount of sludge and the amount of sludge solidification cementitious material.

[0082] The expanded polystyrene particles in this embodiment have a bulk density of 9 kg / m³. 3 The expanded polystyrene granules are made from crushed waste expanded polystyrene boards, with a particle size of 5-8 mm. The amount of expanded polystyrene granules used (based on close packing volume) is 1 / 3 of the volume of the sludge plus the sludge solidification cementitious material. The foaming catalyst uses expanded perlite granules as a carrier and potassium permanganate solution as a catalytic component loaded within the expanded perlite granules. The mass of the potassium permanganate solution accounts for 0.1% of the amount of sludge solidification cementitious material used. The bulk density of the expanded perlite granules is 90 kg / m³. 3 The particle size is 2-3mm, and the particles can absorb more than 10 times their own weight in water; the amount of expanded perlite particles used is 1 / 10 of the amount of expanded polystyrene particles (based on the volume of close packing).

[0083] The specific steps for preparing the lightweight silt-stabilized soil in this embodiment are as follows:

[0084] (1) First, the expanded perlite particles are saturated with the catalyst solution in the ingredients to obtain the catalyst support;

[0085] (2) Next, add the powder water-reducing agent in the ingredients to the sludge solidification cementitious material according to the proportion in the ingredients, and pre-stir for 2 minutes to obtain a pre-stirred mixture.

[0086] (3) Mix hydrogen peroxide and polymer solution (or emulsion) according to the metering ratio for 8 minutes to form an anti-over-dispersible hydrogen peroxide emulsion / solution.

[0087] (4) Add the pre-stirred mixture obtained in step (2) and the anti-over-dispersible hydrogen peroxide emulsion / solution obtained in step (3) to the sludge slurry weighed according to the mixing ratio and mix thoroughly for 3 minutes to obtain mixed slurry 1.

[0088] (5) Add the measured expanded polystyrene particles to the mixed mud 1 and stir for 4 minutes to obtain mixed mud 2.

[0089] (6) The catalyst carrier obtained in step (1) is added to the mixed slurry 2 and stirred continuously. Utilizing the diffusion motion between expanded perlite particles and expanded polystyrene particles, and the convection and shear motion between viscous fluids, the mixing time is 3 minutes to obtain a solidifiable sludge slurry before in-situ foaming. The solidifiable sludge slurry obtained after mixing is poured into the space to be filled. Through foaming and solidification reactions, the sludge slurry is transformed into a honeycomb-like porous lightweight solid structure with pore diameters of 0.1–0.2 mm. The bulk density of the solidified sludge body after 3 days is 0.8 g / cm³. 3 The unconfined compressive strength at 3 days is 0.5 MPa, the unconfined compressive strength at 28 days is 1.5 MPa, the softening coefficient is 0.7, and the volume shrinkage rate is 2 / 1000.

[0090] Example 4

[0091] This embodiment provides a lightweight sludge solidification soil. The raw materials include sludge slurry to be solidified and a structural agent component for lightweight solidified sludge. The structural agent component includes sludge solidification cementitious material, anti-over-dispersibility hydrogen peroxide emulsion / solution, expanded polystyrene particles, water-reducing agent, and foaming catalyst. The anti-over-dispersibility hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0092] Specifically, the sludge slurry in this embodiment is engineering waste sludge slurry from Yixing Taihu silty soil, with a water content of 80%; the hydrogen peroxide in the anti-over-dispersibility hydrogen peroxide emulsion / solution is 30% industrial-grade hydrogen peroxide, and the amount of hydrogen peroxide used is 1.5% of the mass of the sludge plus the sludge solidification cementitious material; the polymer in the polymer solution or emulsion is CMC, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 5:1, and the solid content of the polymer solution / emulsion is 1%.

[0093] The sludge solidification cementitious material of this embodiment is a modified persulfate cement, composed of building gypsum (CaSO4·1 / 2H2O), alkaline activating components, mineral powder, and citric acid. The sulfate activating component (building gypsum) accounts for 20%, the alkaline activating component (quicklime and hydrated lime each account for 5%) accounts for 10%, the mineral powder accounts for 70%, and the citric acid is 1 / 1000 of the building gypsum component. The specific surface area of ​​the sludge solidification cementitious material is ≥400 m². 2 / kg, the amount of sludge solidification cementitious material is 1 / 8 of the sum of the amount of sludge and the amount of sludge solidification cementitious material; the water-reducing agent is a powdered polycarboxylate water-reducing agent, and its addition amount is 5 / 10000 of the sludge slurry.

[0094] The expanded polystyrene particles in this embodiment have a bulk density of 10 kg / m³. 3The expanded polystyrene granules are made from crushed waste expanded polystyrene boards, with a particle size of 5-8 mm. The amount of expanded polystyrene granules used (based on close packing volume) is half the volume of the sludge plus the sludge solidification cementitious material. The foaming catalyst uses expanded perlite granules as a carrier and ferrous chloride solution as a catalytic component loaded within the expanded perlite granules. The mass of the ferrous chloride solution accounts for 0.1% of the amount of sludge solidification cementitious material used. The bulk density of the expanded perlite granules is 100 kg / m³. 3 The particle size is 2-3 mm, and the amount of expanded perlite particles is 1 / 5 of the amount of expanded polystyrene particles (based on the close packing volume).

[0095] The specific steps for preparing lightweight silt-stabilized soil in this embodiment are as follows:

[0096] (1) First, the expanded perlite particles are saturated with the catalyst solution in the ingredients to obtain the foaming catalyst;

[0097] (2) Next, the powder water-reducing agent in the ingredients is added to the silt solidification cementitious material according to the proportion in the ingredients, and pre-stirred for 4 minutes to obtain a pre-stirred mixture.

[0098] (3) Mix hydrogen peroxide and polymer solution (or emulsion) according to the metering ratio for 9 minutes to form an anti-over-dispersible hydrogen peroxide emulsion / solution.

[0099] (4) Add the pre-stirred mixture obtained in step (2) and the anti-over-dispersible hydrogen peroxide emulsion / solution obtained in step (3) to the sludge slurry weighed according to the mixing ratio and mix thoroughly for 4 minutes to obtain mixed slurry 1.

[0100] (5) Add the measured expanded polystyrene particles to the mixed mud 1 and stir for 2 minutes to obtain mixed mud 2.

[0101] (6) The catalyst carrier obtained in step (1) is added to the mixed slurry 2 and stirred continuously. Utilizing the diffusion motion between expanded perlite particles and expanded polystyrene particles, and the convection and shear motion between viscous fluids, the mixing time is 4 minutes. The expanded perlite particles are then evenly dispersed again in the expanded polystyrene particle-slurry mixture, obtaining a solidifiable sludge slurry before in-situ foaming. The solidifiable sludge slurry obtained after mixing is poured into the space to be filled. Through foaming and solidification reactions, the sludge slurry is transformed into a honeycomb-shaped porous lightweight solid structure with pore diameters of 0.1–0.2 mm. The bulk density of the solidified sludge body after 3 days is 0.3 g / cm³. 3 The unconfined compressive strength at 3 days is 0.2 MPa, the unconfined compressive strength at 28 days is 0.5 MPa, the softening coefficient is 0.7, and the volume shrinkage rate is 1 / 1000.

[0102] Example 5

[0103] This embodiment of a lightweight sludge solidification soil comprises sludge slurry to be solidified and a structural agent component for lightweight solidified sludge. The structural agent component comprises sludge solidification cementitious material, anti-over-dispersibility hydrogen peroxide emulsion / solution, polystyrene particles and foaming catalyst. The anti-over-dispersibility hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0104] Specifically, in this embodiment, the sludge slurry is engineering waste sludge slurry from Yixing Taihu Lake silty soil, with a water content of 80%; the hydrogen peroxide in the anti-over-dispersibility hydrogen peroxide emulsion / solution is 50% industrial-grade hydrogen peroxide, and the amount of hydrogen peroxide used is 0.2% of the mass of the sludge plus the sludge solidification cementitious material; the polymer in the polymer solution or emulsion is CMC, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 5:1, and the solid content of the polymer solution / emulsion is 1%.

[0105] The sludge solidification cementitious material of this embodiment is a modified persulfate cement, composed of building gypsum (CaSO4·1 / 2H2O), 52.5PO cement, mineral powder, and citric acid. The sulfate-activating component, building gypsum, accounts for 30%, the alkaline-activating component, 52.5PO cement, accounts for 10%, and the mineral powder accounts for 60%. Citric acid constitutes 3 / 2000 of the building gypsum component. The specific surface area of ​​the sludge solidification cementitious material is ≥400 m². 2 / kg, the amount of sludge solidification cementitious material used is 1 / 5 of the sum of the amount of sludge and the amount of sludge solidification cementitious material.

[0106] The expanded polystyrene particles in this embodiment have a bulk density of 8 kg / m³. 3 The expanded polystyrene granules are made from crushed waste expanded polystyrene boards, with a particle size of 5-8 mm. The amount of expanded polystyrene granules used (based on close packing volume) is 1 / 4 of the volume of the sludge plus the sludge solidification cementitious material. In this embodiment, the foaming catalyst uses expanded perlite granules as a carrier, with ferric sulfate solution as the catalytic component loaded within the expanded perlite granules. The mass of the ferric sulfate solution accounts for 0.1% of the amount of sludge solidification cementitious material used, and the bulk density of the expanded perlite granules is 80 kg / m³. 3 The particle size is 1-3mm, and the amount of expanded perlite particles is 3 / 10 of the amount of expanded polystyrene particles (based on the close packing volume).

[0107] The specific steps for preparing the lightweight silt-stabilized soil in this embodiment are as follows:

[0108] (1) First, the expanded perlite particles are saturated with the catalyst solution in the ingredients to obtain the foaming catalyst;

[0109] (2) Mix hydrogen peroxide and polymer solution (or emulsion) according to the metering ratio for 9 minutes to form an anti-over-dispersible hydrogen peroxide emulsion / solution.

[0110] (3) Add the anti-over-dispersible hydrogen peroxide emulsion / solution obtained in step (2) to the sludge slurry weighed according to the mixing ratio and mix thoroughly for 3 minutes to obtain mixed slurry 1.

[0111] (4) Add the measured expanded polystyrene particles to the mixed mud 1 and stir for 2 minutes to obtain mixed mud 2.

[0112] (5) Add the foaming catalyst obtained in step (1) to the mixed slurry 2 and continue stirring. Utilize the diffusion motion between the expanded perlite particles and the expanded polystyrene particles, as well as the convection and shear motion between the viscous fluids. The mixing time is 4 minutes. The expanded perlite particles are once again evenly dispersed in the expanded polystyrene particle-slurry mixture, obtaining a solidifiable sludge slurry before in-situ foaming. The solidifiable sludge slurry obtained after mixing is poured into the space to be filled. Through foaming and solidification reactions, the sludge slurry is transformed into a honeycomb-shaped porous lightweight solid structure with pore diameters of 0.1–0.2 mm. The bulk density of the solidified sludge body after 3 days is 1 g / cm³. 3 The unconfined compressive strength at 3 days is 0.5 MPa, the unconfined compressive strength at 28 days is 3 MPa, the softening coefficient is 0.8, and the volume shrinkage rate is 1 / 1000.

[0113] Example 6

[0114] This embodiment provides a lightweight sludge solidification soil, the raw materials of which include sludge slurry to be solidified and a structural agent component for lightweight solidified sludge. The raw materials of the structural agent component include sludge solidification cementitious material, anti-over-dispersibility hydrogen peroxide emulsion / solution and foaming catalyst. The anti-over-dispersibility hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0115] Specifically, in this embodiment, the sludge to be solidified is marine sedimentary sludge from Yuhuan, Taizhou, with a water content of 120%; the hydrogen peroxide in the anti-over-dispersibility hydrogen peroxide emulsion / solution is 40% industrial-grade hydrogen peroxide, and the amount of hydrogen peroxide used is 2% of the total mass of the sludge and the sludge solidification cementitious material; the polymer in the polymer solution / emulsion is polystyrene-acrylic, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 3:1, and the solid content of the polymer solution / emulsion is 3%.

[0116] The sludge solidification cementitious material of this embodiment is a modified persulfate cement, composed of building gypsum (CaSO4·1 / 2H2O), 52.5PO cement, slag powder, and citric acid. The sulfate-activating component accounts for 25%, the alkaline-activating component accounts for 8%, the slag powder accounts for 67%, and the citric acid content is 3 / 2500 of the building gypsum component. The specific surface area of ​​the sludge solidification cementitious material is ≥400 m². 2 / kg, the amount of sludge solidification cementitious material used is 1 / 8 of the sum of the amount of sludge and the amount of sludge solidification cementitious material. In this embodiment, the foaming catalyst uses expanded perlite particles as a carrier, and ferrous sulfate solution is loaded into the expanded perlite particles as a catalytic component. The mass of ferrous sulfate solution accounts for 0.5% of the amount of sludge solidification cementitious material used, and the bulk density of the expanded perlite particles is 80 kg / m³. 3 The particle size is 1-3mm, and the amount of expanded perlite particles used (based on the close packing volume) is 1 / 40 of the volume of slurry formed by adding slurry solidification cementitious material.

[0117] The specific steps for preparing lightweight silt-stabilized soil in this embodiment are as follows:

[0118] (1) First, the expanded perlite particles are saturated with the catalyst solution in the ingredients to obtain the foaming catalyst;

[0119] (2) Mix hydrogen peroxide and polymer solution (or emulsion) according to the metering ratio for 10 minutes to form an anti-over-dispersible hydrogen peroxide emulsion / solution.

[0120] (3) Add the obtained anti-dispersible hydrogen peroxide emulsion / solution and sludge solidification cementitious material to the sludge slurry weighed according to the mixing ratio and mix thoroughly for 2 minutes to obtain mixed slurry.

[0121] (4) Add the foaming catalyst to the mixed slurry and continue stirring. After mixing for 3 minutes, a solidifiable sludge slurry is obtained. The solidifiable sludge slurry obtained after mixing is poured into the space to be filled. After foaming and solidification reactions, the lightweight sludge solidified soil of this embodiment is obtained. However, in this embodiment, the solidifiable sludge slurry undergoes in-situ foaming reaction and subsequent solidification reaction 0.5 hours after being poured into the space to be filled. The pore size of the obtained sludge solidified soil is 0.2-0.3 mm. The solidified sludge body after 3 days (see Appendix) Figure 3 The bulk density is 1.0 g / cm³. 3 The unconfined compressive strength at 3 days is 0.2 MPa, the unconfined compressive strength at 28 days is 0.5 MPa, the softening coefficient is 0.8, and the volume shrinkage rate is 2 / 1000.

[0122] Compared with Example 1, it can be seen that the amount of foaming agent H2O2 used in the structural agent component of Example 1 is only 0.5%, because its structural agent also contains expanded polystyrene particles. Example 1 obtained a sludge solidified body (see Appendix). Figure 2 The bulk density after 3 days is 0.75 g / cm³. 3 The 3-day unconfined compressive strength is 0.35 MPa, the 28-day unconfined compressive strength is 0.9 MPa, and the strength-to-density ratio is 1.2 MPa / (g / cm³). 3 In Example 6, the amount of foaming agent H2O2 used in the structural agent component was 2%, which is four times that of Example 1, but the bulk density of the cured body after 3 days was 1.0 g / cm³. 3 The 28-day unconfined compressive strength was only half that of Example 1, and the strength-to-weight ratio was 0.5 MPa / (g / cm). 3 It is only 0.4 times that of Example 1.

[0123] Example 7

[0124] This embodiment provides a lightweight sludge solidification soil, the raw materials of which include sludge slurry to be solidified and a structural agent component for lightweight solidified sludge. The raw materials of the structural agent component include sludge solidification cementitious material, expanded polystyrene particles, anti-over-dispersible hydrogen peroxide emulsion / solution and foaming catalyst. The anti-over-dispersible hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion.

[0125] Specifically, in this embodiment, the sludge to be solidified is marine sedimentary sludge from Yuhuan, Taizhou, with a water content of 120%; the hydrogen peroxide in the anti-over-dispersibility hydrogen peroxide emulsion / solution is 50% industrial-grade hydrogen peroxide, and the amount of hydrogen peroxide used is 1.0% of the total mass of the sludge and the sludge solidification cementitious material; the polymer in the polymer solution / emulsion is polyacrylic acid, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 4:1, and the solid content of the polymer solution / emulsion is 3%.

[0126] The sludge solidification cementitious material of this embodiment is a modified persulfate cement, composed of building gypsum (CaSO4·1 / 2H2O), quicklime, slag powder, and citric acid. The sulfate activating component accounts for 18%, the alkaline activating component for 10%, the slag powder for 72%, and the citric acid content is 1 / 1000 of the building gypsum component. The specific surface area of ​​the sludge solidification cementitious material is ≥400 m². 2 / kg, the amount of sludge solidification cementitious material used is 1 / 6 of the sum of the sludge amount and the amount of sludge solidification cementitious material. In this embodiment, the foaming catalyst is ferric sulfate solution, and the mass of the ferric sulfate solution accounts for 0.3% of the amount of sludge solidification cementitious material used, meaning that expanded perlite particles are not used as a carrier. The expanded polystyrene particles in this embodiment have a bulk density of 8 kg / m³. 3 The expanded polystyrene granules are made from the crushing of waste expanded polystyrene boards, and the particle size is 5-8mm. The amount of expanded polystyrene granules used (based on the close packing volume) is 1 / 4 of the volume of the sludge plus the sludge solidification cementitious material.

[0127] The specific steps for preparing lightweight silt-stabilized soil in this embodiment are as follows:

[0128] (1) Mix hydrogen peroxide and polymer solution (or emulsion) according to the metering ratio for 10 minutes to form an anti-over-dispersible hydrogen peroxide emulsion / solution.

[0129] (2) The obtained anti-dispersible hydrogen peroxide emulsion / solution and sludge solidification cementitious material are added to the sludge slurry weighed according to the mixing ratio and mixed thoroughly for 2 minutes to obtain mixed slurry 1.

[0130] (3) Add the expanded polystyrene particles weighed according to the mixing ratio to the mixed mud 1, stir for 3 minutes to obtain mixed mud 2.

[0131] (4) Add the foaming catalyst to the mixed slurry and continue stirring. Foaming occurs during stirring. After mixing for 3 minutes, a solidifiable sludge slurry is obtained. The solidifiable sludge slurry is poured into the space to be filled. After foaming and solidification reactions, the lightweight sludge-stabilized soil of this embodiment is obtained. The pore size of the sludge-stabilized soil obtained in this embodiment is 0.2-2 mm, and the bulk density of the sludge solidified body after 3 days is 1.2 g / cm³. 3 The unconfined compressive strength after 3 days was 0.2 MPa, after 28 days it was 0.5 MPa, the softening coefficient was 0.6, and the volume shrinkage rate was 2 / 1000. However, in this example, because the catalyst was not loaded into the expanded perlite particle carrier, the catalyst release process was uneven, resulting in an uncontrollable foaming process. The contribution of the foaming agent H2O2 to the reduction of the bulk density of the solidified body was relatively small. Compared with Example 2, with the same amount of expanded polystyrene particles and foaming agent H2O2 in the structural agent composition, this example, due to the lack of a slow-release effect of the expanded perlite particle carrier, made the foaming process of H2O2 uncontrollable, resulting in a strength-to-weight ratio of only 0.42 MPa / (g / cm³) of the solidified body. 3 The strength-to-weight ratio is much smaller than that of 1.7 MPa / (g / cm³) in Example 2. 3 ).

Claims

1. A structural agent for lightweight solidified sludge, characterized in that, The raw materials for this structural agent component include sludge solidification cementitious material, anti-over-dispersible hydrogen peroxide emulsion / solution, and foaming catalyst. The anti-over-dispersible hydrogen peroxide emulsion / solution is prepared by mixing and stirring hydrogen peroxide with a polymer solution / emulsion. The sludge solidification cementitious material contains sulfate-activated components, alkaline-activated components, active micro-powder, and citric acid. The sulfate-activated component is calcium sulfate hemihydrate, which accounts for 15-30% of the total mass of the sludge solidification cementitious material. The mass of citric acid is 1 / 1000-3 / 2000 of the mass of the sulfate-activated component.

2. The structural agent for lightweight solidified sludge according to claim 1, characterized in that, The polymer solution / emulsion is made of HPMC, CMC, MC, PVA, polystyrene, polyacrylic acid, or waterborne epoxy resin solution / emulsion, and the mass ratio of the polymer solution / emulsion to hydrogen peroxide is 2:1-5:1, and the solid content of the polymer solution / emulsion is 0.1-5%.

3. The structural agent for lightweight solidified sludge according to claim 1, characterized in that, The alkaline activating component is at least one of silicate cement, aluminate cement, quicklime, and hydrated lime, and its mass accounts for 5-10% of the total mass of the sludge solidification cementitious material; the active micro powder is slag micro powder, and the mass of the slag micro powder accounts for 60-80% of the total mass of the sludge solidification cementitious material.

4. The structural agent for lightweight solidified sludge according to any one of claims 1-3, characterized in that, The raw materials of the structural agent component also include expanded polystyrene particles with a particle size of 3-10 mm. Based on the close packing volume, the amount of expanded polystyrene particles is 1 / 4-2 / 3 of the volume of the slurry formed by the sludge to be solidified and the sludge solidification cementitious material.

5. The structural agent for lightweight solidified sludge according to claim 4, characterized in that, The foaming catalyst uses expanded perlite particles as a carrier, and a catalyst solution made of catalytic components is loaded into the expanded perlite particles. The catalytic components are any one of ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, and potassium permanganate, and the above-mentioned catalytic components account for 0.1% to 0.5% of the mass of the sludge solidification cementitious material.

6. The structural agent for lightweight solidified sludge according to claim 5, characterized in that, The bulk density of the expanded perlite particles is ≤100kg / m³. 3 The particle size is 1-5 mm, and the dosage, based on the close packing volume, is 1 / 10-3 / 10 of the expanded polystyrene particles; the bulk density of the expanded polystyrene particles is ≤10 kg / m³. 3 The specific surface area of ​​the sludge solidification cementitious material is ≥400m². 2 / kg, the dosage of which is 1 / 4 to 1 / 10 of the total amount of sludge and sludge solidification cementitious material; the hydrogen peroxide used is industrial grade hydrogen peroxide with a mass concentration of 30% to 50%, and the dosage of hydrogen peroxide is 0.2% to 2% of the total amount of sludge and sludge solidification cementitious material; the raw materials of the structural agent component further include water-reducing agent, and the amount of water-reducing agent added is 0 to 1 / 1000 of the amount of sludge slurry to be solidified.

7. A lightweight silt-stabilized soil, characterized in that, The raw materials for this solidified soil include sludge slurry to be solidified and a structural agent for lightweight solidified sludge as described in any one of claims 1-6.

8. A method for preparing lightweight silt-stabilized soil as described in claim 7, characterized in that, include: The sludge solidification cementitious material, the over-dispersed hydrogen peroxide emulsion / solution, and the sludge slurry are stirred and mixed evenly to obtain a mixed slurry; Add the foaming catalyst to the above mixed slurry to obtain solidifiable sludge slurry before in-situ foaming; as well as The process involves pumping solidifiable sludge slurry into the space to be filled, and then solidifying it to form lightweight sludge-solidified soil.

9. The method for preparing lightweight silt-stabilized soil according to claim 8, characterized in that, Before adding the foaming catalyst to the mixed slurry, the process also includes adding expanded polystyrene particles to the mixed slurry; the resulting lightweight sludge-stabilized soil has a honeycomb-like porous lightweight solid structure with pore sizes of 0.1–0.5 mm, and the bulk density of the sludge-stabilized body after 3 days is 0.3–1.0 g / cm³. 3 The unconfined compressive strength at 3 days is 0.2–1 MPa, the unconfined compressive strength at 28 days is 0.5–3 MPa, the softening coefficient is ≥0.7, and the volume shrinkage rate is ≤2 / 1000.

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