A modified dredged sludge-based composite solidified material and a method for preparing the same

Abstract

The application discloses a kind of based on modified dredged silt composite curing material and preparation method thereof. With mass fraction, the composite curing material includes 60~70 portions of modified dredged silt base material, 15~20 portions of composite curing agent, 3~6 portions of basalt fiber, 2~2.5 portions of modified carbon fiber, 3~6 portions of functional additive and 7~12 portions of water;The composite curing agent includes 40~45 portions of steel slag powder, 30~35 portions of slag powder, 10~15 portions of desulfurization ash, 8~12 portions of composite alkali activator and 2~3 portions of nano CaCO3;The functional additive includes 20~25 portions of chitosan-acrylamide copolymer, 5~8 portions of nano TiO2, 15~20 portions of modified montmorillonite and 5~10 portions of calcium lignosulfonate.The composite curing material provided by the application can improve the strength of high-organic soil and dredged silt, offset the inhibition of organic matter on gelation reaction;It can adsorb and degrade heavy metals and organic pollutants, reduce environmental risk;Improve the workability of high-moisture base material, reduce the shrinkage of cured body;It also realizes solid waste resource utilization, reduces engineering cost, and is suitable for multiple types of civil engineering scenarios.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geotechnics and water and soil conservation engineering materials, and particularly relates to a composite solidified material based on modified dredged silt and a preparation method thereof. BACKGROUND

[0002] In the field of soil solidification in civil engineering, the existing technology mostly takes plain soil as a base material, such as treating conventional plain soil with a soil solidification agent containing desulfurization slag and phosphogypsum, using granular solidification agent to improve the crack resistance of the road base, adding a composite active activator to improve the water stability of silt, using concrete waste slag to prepare a solidification agent to treat heavy metal contaminated soil, developing a special roadbed solidification agent to improve the impermeability, and optimizing the sand ratio of silt solidification mixture. However, these technologies have significant limitations and cannot meet the actual needs.

[0003] The current soil solidification and solid waste resource utilization technology system still has many problems. For example, when the organic matter content in the soil exceeds 5%, it will significantly interfere with the solidification reaction process, resulting in a significant decline in solidification effect, making it difficult to meet the engineering treatment needs of high-organic soil; different types of solid waste cannot form a synergistic effect, especially for dredged soil, the existing solid waste utilization scheme has poor treatment effect, and the resource potential of solid waste cannot be fully utilized; lack of environmental compatibility, unable to achieve adsorption treatment of heavy metals and other pollutants, and some solidification agents also have the problems of high cost and insufficient strength after solidification; the dredged silt treatment process is complex, and for high-organic silt, a tedious pretreatment process is required, and even after solidification, the solidified body still has the defect of high dry shrinkage rate, affecting the long-term stability of the engineering structure.

[0004] The current soil solidification and solid waste resource utilization in engineering application still cannot effectively solve various problems, and cannot meet the actual needs of road construction, silt treatment and other engineering for soil solidification effect, solid waste utilization efficiency, environmental compatibility and engineering economy, and a new technical solution that can break through the above technical bottlenecks is urgently needed. SUMMARY

[0005] The present application aims to overcome the problems of poor adaptability of existing solidified materials to high-organic matter, high organic matter content in the base material which seriously hinders the cementation reaction and causes a sharp drop in strength, and the function of adsorbing heavy metals, and provides a composite solidified material based on modified dredged silt and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] The application provides a modified dredged sludge-based composite curing material, which comprises 60-70 parts of a modified dredged sludge base material, 15-20 parts of a composite curing agent, 3-6 parts of basalt fibers, 2-2.5 parts of modified carbon fibers, 3-6 parts of functional additives and 7-12 parts of water in terms of mass fraction.

[0008] The composite curing agent comprises 40-45 parts of steel slag powder, 30-35 parts of slag powder, 10-15 parts of desulfurization ash, 8-12 parts of a composite alkali activator and 2-3 parts of nano CaCO3.

[0009] The functional additives comprise 20-25 parts of chitosan-acrylamide copolymer, 5-8 parts of nano TiO2, 15-20 parts of modified montmorillonite and 5-10 parts of calcium lignosulfonate.

[0010] The preparation method of the modified dredged sludge base material comprises the following steps:

[0011] Lime is added into the dredged sludge and uniformly mixed, and then the dredged sludge is left to obtain dewatered sludge; the water content of the dredged sludge is 65-75%, and the mass fraction of organic matter is 20-25%; the mass of the added lime is 3-5% of the mass of the dredged sludge;

[0012] The composite microbial agent is added into the dewatered sludge, and aerobic composting is carried out at 50-55 DEG C to obtain a compost product; the mass of the added composite microbial agent is 2-4% of the mass of the dewatered sludge; the composite microbial agent comprises Bacillus subtilis and actinomycetes in a mass ratio of 1:(1-2);

[0013] The compost product is ball milled to obtain the modified dredged sludge base material.

[0014] The mass fraction of CaO in the steel slag powder is 45-50%, and the mass fraction of SiO2 is 15-20%.

[0015] The mass fraction of Al2O3 in the slag powder is 15-20%.

[0016] The mass fraction of CaSO4 in the desulfurization ash is 40-50%.

[0017] The composite alkali activator comprises sodium hydroxide, water glass and magnesium fluosilicate, and the mass ratio of sodium hydroxide, water glass and magnesium fluosilicate is (3-5):(5-8):2.

[0018] The preparation method of the modified carbon fiber comprises the following steps:

[0019] The carbon fiber is soaked in an ethanol solution containing a silane coupling agent with a mass concentration of 3-5% and then dried at 80-90 DEG C to obtain the modified carbon fiber.

[0020] The preparation method of the chitosan-acrylamide copolymer comprises the following steps:

[0021] Chitosan and acrylamide are added into acetic acid solution according to a mass ratio of 1:(4-6), then ammonium persulfate is added, and after mixing, polymerization is initiated at 60-80 DEG C to obtain the chitosan-acrylamide copolymer; the mass of the ammonium persulfate is 0.8%-1% of the total mass of the chitosan and the acrylamide.

[0022] The preparation method of the modified montmorillonite comprises the following steps:

[0023] The montmorillonite is intercalated and modified by cetyltrimethylammonium bromide, and the mass of the cetyltrimethylammonium bromide is 3%-5% of the mass of the montmorillonite.

[0024] The application further provides a preparation process of the composite solidified material based on the modified dredged sludge.

[0025] The modified dredged sludge base material, the composite solidified agent, the basalt fiber and the modified carbon fiber are mixed to obtain dry materials;

[0026] The functional additives and water are added into the dry materials and mixed to obtain the composite solidified material.

[0027] Compared with the prior art, the application has the beneficial effects that:

[0028] The composite solidified material provided by the present application takes modified dredged sludge as a base material, can realize solid waste resource utilization, relieve environmental disposal pressure, can reduce the migration risk of pollutants and protect environmental safety; the added composite solidifying agent and functional additives can directly adapt to the high water content and high organic matter characteristics of dredged sludge, and there is no need to perform complex pre-removal treatment on high-organic dredged sludge as in traditional processes; the active ingredients contained in the steel slag powder and the mineral slag powder in the composite solidifying agent can supplement calcium-based and silicon-aluminum components in cooperation with the desulfurized ash, to make up for the defects of traditional solidifying agents due to the consumption of effective components by organic matter; the nano-CaCO3 can refine the microstructure of the solidified system, enhance the compactness of the gelled product, cooperate with the composite alkali activator to efficiently activate the activities of various solid wastes, break the hindrance of organic matter to the formation of C-S-H gel, effectively improve the solidified strength of the high-organic modified dredged sludge base material and avoid the problem of sudden strength reduction; reduce the porosity of the solidified body, effectively solve the problem of high drying shrinkage of the traditional sludge solidified body and improve the long-term stability; the basalt fiber and the modified carbon fiber can form a three-dimensional network support structure in the solidified system, enhance the crack resistance and toughness of the solidified body and make up for the defect that the traditional solidified body is prone to cracking; the calcium lignosulfonate in the functional additives can improve the workability of the mixture, cooperate with the reinforcing effect of the fiber and reduce the shrinkage stress in the solidification process; the chitosan-acrylamide copolymer in the functional additives has the ability to adsorb heavy metal ions, the nano-TiO2 can assist in degrading organic pollutants and the modified montmorillonite can further adsorb harmful substances, to make up for the defect that the traditional formula lacks environmental functions; in combination with the stabilizing effect of the composite solidifying agent on heavy metals, the material has both solidified strength and pollution control functions and can be applied to the treatment of sludge / soil in heavy metal pollution or organic pollution sites, breaks through the limitation that the traditional solidified material has a single function and expands the engineering application scenarios. In summary, the composite solidified material provided by the present application can improve the strength of high-organic soil and dredged sludge, offset the inhibition of organic matter on the cementation reaction, can adsorb and degrade heavy metals and organic pollutants to reduce environmental risks, can improve the workability of the high-water-content base material, reduce the drying shrinkage of the solidified body, can realize solid waste resource utilization, reduce engineering costs and adapt to various civil engineering scenarios.

[0029] The preparation of the composite solidified material of the present application is divided into two stages, first dry mixing to uniformly disperse the fiber and the composite solidifying agent in the base material to form a three-dimensional reinforced skeleton prototype, and then wet mixing, which needs to control the slump and spread of the composite solidified material to ensure that the fluidization performance meets the requirements of cast-in-place construction. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0032] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or the like refers to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0033] It should be understood that the size of the sequence number of the above-mentioned processes in various embodiments of the present application does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence. The execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0034] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0035] The mass of the related components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the mass ratio relationship between each component. Therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass mentioned in the specification of the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0036] The composite solidified material based on modified dredged sludge provided by the present application comprises, in mass fraction, 60-70 parts of modified dredged sludge base material, 15-20 parts of composite solidified agent, 3-6 parts of basalt fiber, 2-2.5 parts of modified carbon fiber, 3-6 parts of functional additive, and 7-12 parts of water.

[0037] The composite solidified agent comprises 40-45 parts of steel slag powder, 30-35 parts of slag powder, 10-15 parts of desulfurization ash, 8-12 parts of composite alkali activator, and 2-3 parts of nano-CaCO3.

[0038] The functional additives include 20-25 parts of chitosan-acrylamide copolymer, 5-8 parts of nano-TiO2, 15-20 parts of modified montmorillonite, and 5-10 parts of calcium lignosulfonate.

[0039] In some embodiments, the method for preparing the modified dredged sludge base material comprises:

[0040] The dredged sludge has an initial moisture content of 65%-75% and an organic matter mass fraction of 20%-25%, and a particle size of ≤50 mm; the dredged sludge is passed through a 10 mm sieve to remove impurity particles with a particle size greater than 10 mm, so as to ensure the uniformity of the base material.

[0041] Chemical pretreatment: after adding lime and stirring for 10 min, the dredged sludge is left to stand for 24 h to obtain dewatered sludge; wherein the mass of the added lime is 3%-5% of the mass of the dredged sludge, the mass fraction of CaO in the lime is ≥90%, the particle size of the lime is ≤0.15 mm, the lime is forced to react with water to generate calcium hydroxide and release heat, so that the moisture content is reduced to 45%-55%, and at the same time, the calcium ions complex with the carboxyl groups in the organic matter, reducing the interference of the organic matter on the subsequent cementation reaction.

[0042] Bio-thermal combined treatment: a composite microbial agent is added to the dewatered sludge, compressed air is passed at 50-55℃, the ventilation volume is 0.5 m 3 / (h kg), and aerobic composting is performed for 72-90 h to obtain a compost product; wherein the mass of the added composite microbial agent is 2%-4% of the mass of the dewatered sludge; the composite microbial agent includes Bacillus subtilis and actinomycetes, the viable bacterial count is ≥10 9 CFU / g, the mass ratio of Bacillus subtilis to actinomycetes is 1﹕(1-2), and the extracellular enzymes secreted by the microorganisms can efficiently degrade lignin, cellulose and other organic matters in the dewatered sludge, so that the organic matter content is reduced to below 5%.

[0043] Mechanical activation: the compost product is added to a planetary ball mill and ball milled for 15 min, and after ball milling, the product is passed through a 2 mm sieve, and the particle size of 0.075-2 mm is controlled to be ≥90%; during ball milling, agate ball milling media is used, the ball-to-material ratio is 5﹕1, and the rotation speed is 300 r / min; the ball milling treatment can destroy the particle agglomeration structure in the compost product by mechanical force, increase the specific surface area to above 35 m 2 / g, and enhance the reactivity with the composite solidifying agent.

[0044] It should be noted that the amount of quicklime is too low to reduce the moisture content of the system, and too high to cause the system to be too alkaline and inhibit microbial activity. If the amount of composite microbial inoculant is too low, it cannot fully decompose the organic matter in the dredged sludge, resulting in a high content of organic matter, and if it is too high, it will cause excessive decomposition of organic matter and cannot guarantee the effective components in the sludge. The compost temperature is strictly controlled at 50-55℃, which is the optimal activity range of the composite microbial inoculant. If it is lower than 50℃, the organic matter degradation efficiency will decrease, and if it is higher than 55℃, the microorganisms will be inactivated. The ventilation rate of the compost is maintained at 0.05m 3 / (h kg), insufficient ventilation will lead to an anaerobic environment, producing foul odor and reducing degradation efficiency; excessive ventilation will cause excessive evaporation of water, affecting the subsequent mechanical activation effect. The ball milling time is 15 min. Too short will not refine the particles enough, and too long will increase the energy consumption and possibly introduce too many impurities.

[0045] In some embodiments, the composite solidifying agent is compounded by a plurality of industrial solid wastes and functional components. The composite solidifying agent includes 40-45 parts of steel slag powder, 30-35 parts of slag powder, 10-15 parts of desulfurization ash, 8-12 parts of composite alkali activator, and 2-3 parts of nano-CaCO3 by mass fraction. The steel slag powder, slag powder, and desulfurization ash are added to a blender according to the ratio, stirred at 150 r / min for 5 min to ensure uniform mixing of solid particles; then the composite alkali activator and nano-CaCO3 are added, and stirring is continued at 200 r / min for 10 min to obtain the composite solidifying agent, so that the composite alkali activator is evenly coated on the surface of the solid particles, and the silicon-aluminum components in the steel slag and slag are activated.

[0046] In some embodiments, the steel slag powder is ground to a specific surface area of 400-450m 2 / kg after magnetic separation to remove iron from the converter steel slag. The mass fraction of CaO in the steel slag powder is 45%-50%, and the mass fraction of SiO2 is 15%-20%. The tricalcium silicate and dicalcium silicate components in the steel slag powder can provide cementitious activity, and the dense structure helps to inhibit the drying shrinkage of the solidified body.

[0047] In some embodiments, the raw material of the slag powder is S95 grade granulated blast furnace slag, and the 28-day activity index is ≥95%. The mass fraction of Al2O3 in the slag powder is 15%-20%, which can react with CaO in the steel slag powder to generate hydrated calcium aluminate, thereby strengthening the system strength.

[0048] In some embodiments, the raw material of the desulfurization ash is taken from the by-product of power plant desulfurization. The mass fraction of CaSO4 in the desulfurization ash is 40%-50%, and CaSO4 can react with CaO to generate ettringite, thereby improving the early strength and filling the pores.

[0049] In some embodiments, the composite alkali activator includes sodium hydroxide, water glass and magnesium fluosilicate, and the mass ratio of sodium hydroxide, water glass and magnesium fluosilicate is (3-5):(5-8):2. The composite alkali activator provides a strong alkaline environment, and can activate the depolymerization and reconstruction of siliceous and aluminous components in the strong alkaline environment (pH=12-13) to accelerate the hydration reaction. The modulus of the water glass is controlled to be 1.2-1.4; a too high modulus will reduce the solution fluidity, which is not conducive to uniform dispersion; and a too low modulus will affect the activation capacity and the development of the gel strength.

[0050] In some embodiments, the particle size of the nano-CaCO3 is about 50 nm; the nano-CaCO3 refines the pore structure through a filling effect to improve the compactness and compressive strength of the solidified body. A too low content of the nano-CaCO3 will not have a significant filling effect, and a too high content will cause particle agglomeration and increase the porosity.

[0051] The composite fiber system includes basalt fibers and modified carbon fibers.

[0052] In some embodiments, the length of the basalt fiber is 6 mm, the diameter is 13 μm, and the tensile strength is ≥3000 MPa. The basalt fiber is soaked in a NaOH solution with a mass concentration of 8% for 28 days, and the strength retention rate is ≥85%. The basalt fiber can effectively inhibit early plastic cracks of the solidified body.

[0053] In some embodiments, the length of the modified carbon fiber is 12 mm. The carbon fiber is soaked in an ethanol solution containing a silane coupling agent with a mass concentration of 3%-5% for 2 h, and then dried at 80-90°C to obtain the modified carbon fiber. The silane coupling agent is KH550, and a chemical bond is formed between the hydroxyl group of the silane coupling agent and the gel product to enhance the interfacial adhesion.

[0054] The basalt fibers and the modified carbon fibers form a three-dimensional network structure to synergistically improve the flexural strength and toughness of the solidified body, which is increased by more than 40% compared with a single fiber system. A too low amount of the composite fiber system will not have a sufficient reinforcing effect, and a too high amount will cause fiber entanglement and reduce the fluidity of the mixture.

[0055] In some embodiments, the functional additive is compounded from multiple functional components, and the functional additive includes 20-25 parts of chitosan-acrylamide copolymer, 5-8 parts of nano-TiO2, 15-20 parts of modified montmorillonite and 5-10 parts of calcium lignosulfonate in terms of mass fraction; the functional additive realizes water retention, environmental protection and construction property optimization.

[0056] In some embodiments, the preparation method of the chitosan-acrylamide copolymer includes:

[0057] The chitosan and acrylamide are added into acetic acid solution in a mass ratio of 1: (4-6), then ammonium persulfate is added and uniformly mixed, and then a polymerization reaction is initiated at 60-80 DEG C for 3h, and then chitosan-acrylamide copolymer is obtained by ethanol precipitation and drying. The molecular weight of the chitosan-acrylamide copolymer is 60000-80000, and the copolymer forms a viscous gel after being dissolved in water, and the water retention rate is greater than or equal to 80%, and the dry shrinkage cracking is reduced. The mass of the ammonium persulfate is 0.8-1% of the total mass of the chitosan and acrylamide; the degree of deacetylation of the chitosan is 90%, and the mass concentration of the acetic acid solution is 1%.

[0058] In some embodiments, the nano-TiO2 adopts an anatase type, and the particle size is 20nm. The nano-TiO2 can degrade organic pollutants such as formaldehyde and phenol through photocatalysis, and the degradation rate is greater than or equal to 30%.

[0059] In some embodiments, the modified montmorillonite is obtained by intercalation modification of montmorillonite with cetyltrimethylammonium bromide, and the mass of the cetyltrimethylammonium bromide is 3-5% of the mass of the montmorillonite. The interlayer spacing is increased from 1.2nm to 2.5nm, and the adsorption capacity of the modified montmorillonite for Pb 2+ , Cu 2+ is greater than or equal to 50mg / g, and the solidification rate is greater than or equal to 95%.

[0060] In some embodiments, the calcium lignosulfonate is of an industrial grade, and the water-reducing rate is greater than or equal to 10%. The calcium lignosulfonate can disperse cementitious particles and improve the fluidity of the mixture.

[0061] The preparation method of the modified dredged sludge-based composite solidification material comprises the following steps:

[0062] The modified dredged sludge base material, the composite solidification agent, the basalt fiber and the modified carbon fiber are mixed to obtain dry materials. The functional additives and water are added to the dry materials to obtain the composite solidification material.

[0063] In some embodiments, the modified dredged sludge base material, the composite solidification agent, the basalt fiber and the modified carbon fiber are stirred in a mixer at a speed of 200r / min for 3min to obtain the dry materials, so as to ensure that the fiber and the composite solidification agent are uniformly dispersed in the dredged sludge base material. The fiber and the composite solidification agent are uniformly dispersed in the base material to form a three-dimensional reinforced skeleton prototype. If the time is too short, the mixture is not uniform. If the time is too long, the fiber is broken or the functional additives are ineffective.

[0064] The water and the functional additives are added to the dry materials, and the mixture is stirred at a speed of 150r / min for 8min to obtain the composite solidification material. The slump is controlled to be 200-220mm, and the spread is controlled to be 550-600mm, so as to meet the requirements of cast-in-place construction. If the amount of the water is too low, the slump is insufficient, and the self-leveling cannot be achieved. If the amount of the water is too high, the stratification is caused, and the strength of the solidification body is reduced.

[0065] The composite solidified material obtained by the above method is applied to soil solidification.

[0066] After the composite solidified material is uniformly mixed with the substrate to be solidified, a mixture is obtained, the mixture is pumped to a mold or a construction site for pouring, and the mixture is filled and compacted by using its own flowability without vibration;

[0067] After pouring is completed, a film is covered for moisture retention, the mixture is cured at 18-22°C and humidity ≥ 95% for 7 days, then the film is removed and natural curing is performed for 28 days to ensure that the hydration reaction is fully performed and a stable gel structure is formed. The mixture is cured to ensure that the hydration reaction is fully performed, and the 28-day compressive strength can reach 8-10 MPa, and the permeability coefficient is ≤ 1 × 10 -7 cm / s.

[0068] Too low curing temperature will delay the hydration reaction, and too high temperature will cause the surface to lose water too quickly, resulting in dry shrinkage cracks. The curing humidity needs to be above 95%, and insufficient humidity will cause the cement hydration to be insufficient, affecting the strength development, especially reducing the early strength. The curing time is at least 28 days; the first 7 days are the key period of hydration reaction, and strict moisture retention is required; after 28 days, the gel structure tends to be stable, and the strength reaches the design requirement.

[0069] In the following examples, unless otherwise specified, each material used can be obtained through an ordinary channel; the test method used is a conventional method in the art. The modified dredged silt substrate is obtained from the silt produced in a channel dredging project.

[0070] Example 1

[0071] Substrate preparation:

[0072] The initial moisture content of the dredged silt is 65%, and the mass fraction of organic matter is 20%; the dredged silt is passed through a 10 mm sieve to remove impurity particles with a particle size greater than 10 mm, ensuring the uniformity of the substrate.

[0073] In the dredged silt, 3% of quicklime is added, and after stirring for 10 min, dehydrated silt is obtained by standing for 24 h.

[0074] 2% of the composite microbial agent is added to the dehydrated silt, and compressed air is passed at 50°C, with a ventilation amount of 0.5 m 3 / (h kg) to obtain a compost product after aerobic composting for 72 h, and the composite microbial agent is Bacillus subtilis and actinomycetes with a mass ratio of 1:1.

[0075] The compost product is added to a planetary ball mill and ball milled for 15 min, and after ball milling, it is passed through a 2 mm sieve, with a particle size of 0.075-2 mm accounting for 90%, to obtain a modified dredged silt substrate with a specific surface area of 35 m 2 / g.

[0076] The steel slag powder is obtained by grinding the converter steel slag after removing iron by magnetic separation, and the specific surface area of the steel slag powder is 400 m 2 / kg, the mass fraction of CaO in the steel slag powder is 45%, and the mass fraction of SiO2 is 20%.

[0077] The raw material of the slag powder is S95 grade granulated blast furnace slag, and the 28-day activity index of the slag powder is 95%, and the mass fraction of Al2O3 in the slag powder is 16.8%.

[0078] The raw material of the desulfurization ash slag is obtained from the desulfurization by-product of a power plant, and the mass fraction of CaSO4 in the desulfurization ash slag is 44.6%.

[0079] The composite alkali activator is composed of sodium hydroxide, water glass and magnesium fluorosilicate in a mass ratio of 4:6:2, and the modulus of the water glass is controlled at 1.2.

[0080] The particle size of the nano-CaCO3 is about 50 nm.

[0081] The composite solidifying agent includes 42.5 parts of steel slag powder, 30 parts of slag powder, 13.2 parts of desulfurization ash slag, 8 parts of composite alkali activator and 2 parts of nano-CaCO3 in mass fraction. The steel slag powder, the slag powder and the desulfurization ash slag are added into a forced mixer in a mass ratio, and stirred at 150 r / min for 5 min; then the composite alkali activator and the nano-CaCO3 are added, and continue to be stirred at 200 r / min for 10 min to obtain the composite solidifying agent.

[0082] The basalt fiber has a length of 6 mm, a diameter of 13 μm and a tensile strength of 3000 MPa.

[0083] The modified carbon fiber has a length of 12 mm, and the carbon fiber is soaked in an ethanol solution containing a silane coupling agent with a mass concentration of 3% for 2 h, and then dried at 80°C to obtain the modified carbon fiber.

[0084] The functional additive includes 20 parts of chitosan-acrylamide copolymer, 5 parts of nano-TiO2, 15 parts of modified montmorillonite and 5 parts of calcium lignosulfonate in mass fraction.

[0085] The chitosan and the acrylamide are added into an acetic acid solution with a mass concentration of 1% in a mass ratio of 1:4, and then ammonium persulfate is added and mixed uniformly, and the mass of the ammonium persulfate is 0.8% of the total mass of the chitosan and the acrylamide. A polymerization reaction is initiated at 60°C for 3 h, and then the chitosan-acrylamide copolymer is obtained by ethanol precipitation and drying.

[0086] The nano-TiO2 is in an anatase type, and the particle size is 20 nm.

[0087] The modified montmorillonite is obtained by intercalating modification of montmorillonite with cetyltrimethylammonium bromide, the mass of cetyltrimethylammonium bromide is 3% of the mass of montmorillonite, and the interlayer spacing is 2.5 nm.

[0088] The calcium lignosulfonate is of industrial grade, and the water-reducing rate is 10%.

[0089] In mass fraction, 63.2 parts of the modified dredged sludge base material, 18.5 parts of the composite curing agent, 3.8 parts of basalt fiber and 2.2 parts of modified carbon fiber are stirred at a speed of 200 r / min for 3 min to obtain a dry material.

[0090] 8.0 parts of water and 4.3 parts of functional additives are added to the dry material, and stirred at a speed of 150 r / min for 8 min to obtain a composite curing material, the slump is controlled at 204 mm, and the spread is 568 mm, which meets the requirements of cast-in-place construction.

[0091] The composite curing material of the present embodiment is mixed uniformly with the curing substrate to obtain a mixture, which is pumped to a mold or a construction site for pouring. After pouring, a film is covered for moisture retention, and the mixture is cured at 18°C and 95% humidity for 7 days, then the film is removed and then naturally cured for 28 days. After 28 days, the related performance is tested, and the test results are as follows: the compressive strength reaches 8.6 MPa, which can meet the basic strength requirements of most municipal backfill projects, and the mechanical properties are stable. The flexural strength is 1.8 MPa, which is 38% higher than that of the control group without fiber, and the crack resistance is significantly enhanced. The permeability coefficient is 3.5×10 -8 cm / s, which has good anti-seepage ability and is suitable for laying anti-seepage layers in shallow water conservancy projects. The heavy metal (Pb 2+ ) solidification rate is 95.8%, which meets the soil environmental safety utilization standard, and can be used for general construction land. The dry shrinkage rate is 0.31%, which is better than the traditional cement-soil curing material (usually >0.5%), reducing the maintenance cost in the later period.

[0092] Example 2

[0093] Preparation of the base material:

[0094] The initial moisture content of the dredged sludge is 68.4%, and the mass fraction of organic matter is 21.6%. The dredged sludge is passed through a 10 mm sieve to remove impurity particles with a particle size greater than 10 mm, ensuring the uniformity of the base material.

[0095] In mass percentage, 4.5% of quicklime is added to the dredged sludge, and after stirring for 10 min, the dehydrated sludge is obtained after standing for 24 h.

[0096] 4% of the composite microbial agent is added to the dehydrated sludge, and compressed air is passed at 55°C, with a ventilation rate of 0.5 m 3 / (h kg), and aerobic composting for 72 h to obtain a compost product, and the complex microbial inoculum was Bacillus subtilis and actinomycetes at a mass ratio of 1:1.8.

[0097] The compost product was added to a planetary ball mill and ball milled for 15 min, and then sieved through a 2 mm sieve, and the particle size of 0.075-2 mm accounted for 95%, to obtain a modified dredged sludge base material.

[0098] The steel slag powder was obtained by grinding the converter steel slag after magnetic separation to remove iron to a specific surface area of 400 m 2 / kg, and the mass fraction of CaO in the steel slag powder was 50%, and the mass fraction of SiO2 was 15%.

[0099] The slag powder was made of S95 grade granulated blast furnace slag, and the 28-day activity index was 95%, and the mass fraction of Al2O3 in the slag powder was 18.4%.

[0100] The desulfurization ash was obtained from the by-product of power plant desulfurization, and the mass fraction of CaSO4 in the desulfurization ash was 40%.

[0101] The composite alkali activator was composed of sodium hydroxide, water glass and magnesium fluorosilicate at a mass ratio of 5:8:2; and the modulus of the water glass was controlled at 1.2.

[0102] The particle size of the nano-CaCO3 was about 50 nm.

[0103] The composite solidifying agent included, in mass parts: 45 parts of steel slag powder, 31.5 parts of slag powder, 10 parts of desulfurization ash, 10.5 parts of composite alkali activator and 2.8 parts of nano-CaCO3. The steel slag powder, slag powder and desulfurization ash were added to a forced mixer and stirred at 150 r / min for 5 min; then the composite alkali activator and nano-CaCO3 were added and stirred at 200 r / min for 10 min to obtain the composite solidifying agent.

[0104] The basalt fiber had a length of 6 mm, a diameter of 13 μm and a tensile strength of 3000 MPa.

[0105] The modified carbon fiber had a length of 12 mm, and the carbon fiber was soaked in an ethanol solution containing a silane coupling agent at a mass concentration of 4% for 2 h and then dried at 80°C to obtain the modified carbon fiber.

[0106] The functional additive included, in mass parts: 22 parts of chitosan-acrylamide copolymer, 6 parts of nano-TiO2, 20 parts of modified montmorillonite and 7.8 parts of calcium lignosulfonate.

[0107] The chitosan and acrylamide are added into 1% acetic acid solution in a mass ratio of 1:5, then ammonium persulfate is added and mixed uniformly, the mass of ammonium persulfate is 0.9% of the total mass of chitosan and acrylamide, the polymerization reaction is initiated at 60℃ for 3h, and then chitosan-acrylamide copolymer is obtained by ethanol precipitation and drying.

[0108] The nano TiO2 adopts an anatase type, and the particle size is 20nm.

[0109] The modified montmorillonite is obtained by intercalation modification of montmorillonite with cetyltrimethylammonium bromide, the mass of cetyltrimethylammonium bromide is 5% of the mass of montmorillonite, and the interlayer spacing is 2.5nm.

[0110] The calcium lignosulfonate is of industrial grade, and the water-reducing rate is 10%.

[0111] In mass parts, 60 parts of modified dredged sludge base material, 20 parts of composite curing agent, 4.8 parts of basalt fiber and 2.4 parts of modified carbon fiber are stirred at a speed of 200r / min for 3min to obtain dry materials.

[0112] 7.0 parts of water and 5.0 parts of functional additives are added to the dry materials, and stirred at a speed of 150r / min for 8min to obtain a composite curing material, the slump is controlled at 200mm, and the spread is 550mm, which meets the requirements of cast-in-place construction.

[0113] The composite curing material of the present embodiment is mixed uniformly with the curing base material to obtain a mixture, which is pumped to a mold or a construction site for pouring. After pouring, a film is covered for moisture retention, and the mixture is cured at 21℃ and 96% humidity for 7 days, then the film is removed and natural curing is carried out for 28 days. After 28 days, the relevant performance tests are carried out, and the test results are as follows: the compressive strength is 11.2MPa, reaching the C10 concrete strength standard, and it can be used for light building foundation cushion. The flexural strength is 2.4MPa, the three-dimensional network structure formed by the fiber effectively disperses stress, and the flexural performance is improved by 45% compared with ordinary curing materials. The elastic modulus is 3.7×10 3 MPa, the structural stability can meet the bearing requirements of small structures. The strength loss after freeze-thaw cycle (25 times) is 6.1%, which can maintain good durability in outdoor engineering in cold regions.

[0114] Example 3

[0115] Preparation of base material:

[0116] The initial moisture content of the dredged sludge is 75%, and the mass fraction of organic matter is 25%. The dredged sludge is passed through a 10mm sieve to remove impurity particles with a particle size greater than 10mm, ensuring the uniformity of the base material.

[0117] 5% of quicklime was added into the dredged sludge, and after 10 min of stirring, the dewatered sludge was obtained by standing for 24 h.

[0118] 3.5% of the composite microbial agent was added into the dewatered sludge, and the aerobic composting was carried out for 90 h at 52°C under the condition of air compression with a ventilation rate of 0.5 m 3 / (h kg) to obtain the compost product, in which the content of organic matter was reduced to 4.3%, and the composite microbial agent was composed of Bacillus subtilis and actinomycetes with a mass ratio of 1:2.

[0119] The compost product was added into a planetary ball mill and ball milled for 15 min, and after ball milling, the product was sieved through a 2 mm sieve, and the particle size of 0.075-2 mm accounted for 92% to obtain the modified dredged sludge base material.

[0120] The steel slag powder was obtained by grinding the converter steel slag after magnetic separation to remove iron, and the specific surface area of the steel slag powder was 400 m 2 / kg, the mass fraction of CaO in the steel slag powder was 46.2%, and the mass fraction of SiO2 was 17.2%.

[0121] The slag powder was selected from S95 grade granulated blast furnace slag, and the 28-day activity index of the slag powder was 95%, and the mass fraction of Al2O3 in the slag powder was 20%.

[0122] The desulfurization ash was obtained from the by-product of desulfurization in a power plant, and the mass fraction of CaSO4 in the desulfurization ash was 47.5%.

[0123] The composite alkali activator was composed of sodium hydroxide, water glass and magnesium fluorosilicate with a mass ratio of 3:5:2, and the modulus of the water glass was controlled at 1.2.

[0124] The particle size of the nano-CaCO3 was about 50 nm.

[0125] The composite solidifying agent included, in parts by mass, 40 parts of steel slag powder, 35 parts of slag powder, 15 parts of desulfurization ash, 9 parts of composite alkali activator and 2.5 parts of nano-CaCO3. The steel slag powder, the slag powder and the desulfurization ash were added into a forced mixer, and stirred at 150 r / min for 5 min; then the composite alkali activator and the nano-CaCO3 were added, and stirred at 200 r / min for 10 min to obtain the composite solidifying agent.

[0126] The basalt fiber had a length of 6 mm and a diameter of 13 μm, and a tensile strength of 3000 MPa.

[0127] The modified carbon fiber had a length of 12 mm, and was obtained by immersing the carbon fiber in an ethanol solution containing a silane coupling agent with a mass concentration of 3% for 2 h and then drying at 80°C.

[0128] The functional additives include 25 parts of chitosan-acrylamide copolymer, 8 parts of nano-TiO2, 16.7 parts of modified montmorillonite, and 9 parts of calcium lignosulfonate, in terms of mass fraction.

[0129] The chitosan and acrylamide are added into an acetic acid solution with a mass concentration of 1% at a mass ratio of 1:4.5, and ammonium persulfate is added and uniformly mixed. The mass of ammonium persulfate is 0.8% of the total mass of chitosan and acrylamide. The polymerization reaction is initiated at 60°C for 3 hours, and then chitosan-acrylamide copolymer is obtained by ethanol precipitation and drying.

[0130] The nano-TiO2 is in an anatase type, and the particle size is 20 nm.

[0131] The modified montmorillonite is obtained by intercalation modification of montmorillonite with cetyltrimethylammonium bromide. The mass of cetyltrimethylammonium bromide is 4.3% of the mass of montmorillonite, and the interlayer spacing is 2.5 nm.

[0132] The calcium lignosulfonate is of industrial grade, and the water-reducing rate is 10%.

[0133] In terms of mass fraction, 67.5 parts of modified dredged sludge base material, 16 parts of composite curing agent, 3 parts of basalt fiber, and 2.5 parts of modified carbon fiber are stirred at a speed of 200 r / min for 3 min to obtain dry materials.

[0134] 10.0 parts of water and 6 parts of functional additives are added to the dry materials, and stirred at a speed of 150 r / min for 8 min to obtain a composite curing material. The slump is controlled at 212 mm, and the spread is 582 mm, meeting the requirements of cast-in-place construction.

[0135] The composite curing material of the present embodiment is mixed uniformly with the curing substrate to obtain a mixture, which is pumped to a mold or a construction site for pouring. After pouring, a film is covered for moisture retention. The mixture is cured at 22°C and 95% humidity for 7 days, after which the film is removed and then naturally cured for 28 days. After 28 days, the relevant performance is tested, and the test results are as follows: the compressive strength is 7.8 MPa, meeting the backfill strength requirements of ecological restoration areas. 2+ The curing rate is 98.8%, which is much lower than the hazardous waste leaching toxicity limit, and can be safely used in sensitive environmental areas. 2+ The adsorption capacity is 57.5 mg / g, and the capture capacity for heavy metal ions is increased by 18% compared with the basic formula. 2+ The measured value of leaching is 0.0048 mg / L, reaching the surface water class III standard, and being suitable for landscape water surrounding engineering. The composite curing material of the present embodiment is environmentally friendly, and can be used in areas requiring heavy metal repair.

[0136] Example 4

[0137] Preparation of base material

[0138] The water content of dredged sludge in initial state was 72.1%, and the mass fraction of organic matter was 23.8%. The dredged sludge was passed through a 10 mm sieve to remove impurity particles with a particle size greater than 10 mm, ensuring the uniformity of the base material.

[0139] 5% of quicklime was added to the dredged sludge, and after stirring for 10 min, dehydrated sludge was obtained by standing for 24 h.

[0140] 2.8% of the composite microbial agent was added to the dehydrated sludge, and compressed air was passed at 50°C, with a ventilation rate of 0.5 m 3 / (h kg), and aerobic composting was carried out for 90 h to obtain compost products. The composite microbial agent was composed of Bacillus subtilis and actinomycetes with a mass ratio of 1:1.5.

[0141] The compost product was added to a planetary ball mill and ball milled for 15 min. After ball milling, the product was passed through a 2 mm sieve, and the particle size of 0.075-2 mm accounted for 90%, obtaining modified dredged sludge base material.

[0142] The steel slag powder was obtained by removing iron from converter steel slag by magnetic separation and grinding to a specific surface area of 400 m 2 / kg. The mass fraction of CaO in the steel slag powder was 48.6%, and the mass fraction of SiO2 was 19%.

[0143] The raw material of the slag powder was S95 grade granulated blast furnace slag, with an activity index of 95 at 28 days. The mass fraction of Al2O3 in the slag powder was 15%.

[0144] The raw material of the desulfurization ash was obtained from the by-product of power plant desulfurization, and the mass fraction of CaSO4 in the desulfurization ash was 50%.

[0145] The composite alkali activator was composed of sodium hydroxide, water glass, and magnesium fluorosilicate with a mass ratio of 3:6:2. The modulus of the water glass was controlled at 1.2.

[0146] The particle size of the nano-CaCO3 was about 50 nm.

[0147] The composite curing agent included 44 parts of steel slag powder, 33 parts of slag powder, 12 parts of desulfurization ash, 12 parts of composite alkali activator, and 3 parts of nano-CaCO3 by mass fraction. The steel slag powder, slag powder, and desulfurization ash were added to a forced mixer and stirred at 150 r / min for 5 min; then the composite alkali activator and nano-CaCO3 were added and continued to be stirred at 200 r / min for 10 min to obtain the composite curing agent.

[0148] The basalt fiber had a length of 6 mm, a diameter of 13 μm, and a tensile strength of 3000 MPa.

[0149] The length of the modified carbon fiber is 12 mm. The carbon fiber is soaked in an ethanol solution containing a silane coupling agent with a mass concentration of 5% for 2 h and then dried at 80℃ to obtain the modified carbon fiber.

[0150] The functional additives include 23.5 parts of chitosan-acrylamide copolymer, 7 parts of nano-TiO2, 18.2 parts of modified montmorillonite, and 10 parts of calcium lignosulfonate, in terms of mass fraction.

[0151] The chitosan and acrylamide are added to an acetic acid solution with a mass concentration of 1% at a mass ratio of 1:6, and ammonium persulfate is then added and uniformly mixed. The mass of the ammonium persulfate is 1% of the total mass of the chitosan and acrylamide. The polymerization reaction is initiated at 60℃ for 3 h, and then the chitosan-acrylamide copolymer is obtained by ethanol precipitation and drying.

[0152] The nano-TiO2 is in an anatase type with a particle size of 20 nm.

[0153] The modified montmorillonite is obtained by intercalation modification of montmorillonite with cetyltrimethylammonium bromide. The mass of the cetyltrimethylammonium bromide is 3.5% of the mass of the montmorillonite, and the interlayer spacing is 2.5 nm.

[0154] The calcium lignosulfonate is of an industrial grade with a water-reducing rate of 10%.

[0155] In terms of mass fraction, 70 parts of the modified dredged sludge base material, 15 parts of the composite curing agent, 6 parts of basalt fiber, and 2 parts of the modified carbon fiber are stirred at a speed of 200 r / min for 3 min to obtain dry materials.

[0156] In the dry materials, 12 parts of water and 3 parts of the functional additives are added and stirred at a speed of 150 r / min for 8 min to obtain a composite curing material. The slump is controlled at 220 mm, and the spread is controlled at 600 mm, which meets the requirements of cast-in-place construction.

[0157] The composite curing material of the present embodiment is uniformly mixed with the curing substrate to obtain a mixture, which is pumped to a mold or a construction site for pouring. After pouring, a film is covered for moisture retention. The mixture is cured at 22℃ and a humidity of 95% for 7 days, after which the film is removed and then naturally cured for 28 days. After 28 days, the relevant performance is tested, and the test results are as follows: the compressive strength is 6.7 MPa, which meets the strength requirements of large-area site backfilling (compaction degree ≥ 92%). The material cost is reduced by 21% compared to Example 1, which is suitable for large-scale engineering applications such as municipal road subgrades. The pouring speed can reach 11.8 m 3The material's fluidity meets the requirements for self-leveling construction, eliminating the need for additional vibration. Its 28-day shrinkage rate is 0.44%, superior to similar economical curing materials (typically above 0.6%), reducing the risk of later cracking. This composite curing material is a low-energy, economical option suitable for areas requiring large-area backfilling.

[0158] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0159] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A composite solidification material based on modified dredged sludge, characterized in that, By weight, it comprises 60-70 parts modified dredged sludge substrate, 15-20 parts composite curing agent, 3-6 parts basalt fiber, 2-2.5 parts modified carbon fiber, 3-6 parts functional additives and 7-12 parts water; The composite curing agent comprises 40-45 parts steel slag powder, 30-35 parts slag powder, 10-15 parts desulfurization ash, 8-12 parts composite alkali activator, and 2-3 parts nano CaCO3; The functional additives include 20-25 parts chitosan-acrylamide copolymer, 5-8 parts nano-TiO2, 15-20 parts modified montmorillonite, and 5-10 parts calcium lignosulfonate. The method for preparing the modified dredged sludge substrate includes: Add quicklime to the dredged sludge, mix thoroughly, and let stand to obtain dewatered sludge; the mass of quicklime added is 3% to 5% of the mass of the dredged sludge. Add compound microbial agents to dehydrated sludge and perform aerobic composting at 50-55℃ to obtain compost products; the mass of the compound microbial agents added is 2%-4% of the mass of dehydrated sludge; the compound microbial agents include Bacillus subtilis and Actinomycetes in a mass ratio of 1:(1-2); The compost products were ball-milled to obtain a modified dredged sludge substrate; The method for preparing the modified carbon fiber includes: Modified carbon fibers are obtained by immersing carbon fibers in an ethanol solution containing silane coupling agent at a mass concentration of 3% to 5% and then drying them at 80 to 90°C.

2. The composite solidification material based on modified dredged sludge according to claim 1, characterized in that, The dredged silt has a water content of 65% to 75% and an organic matter content of 20% to 25%.

3. The composite solidification material based on modified dredged sludge according to claim 1, characterized in that, The steel slag powder contains 45%~50% CaO and 15%~20% SiO2 by mass.

4. The composite solidification material based on modified dredged sludge according to claim 1, characterized in that, The mass fraction of Al2O3 in the slag powder is 15%~20%.

5. The composite solidification material based on modified dredged sludge according to claim 1, characterized in that, The mass fraction of CaSO4 in the desulfurization ash is 40%~50%.

6. The composite solidification material based on modified dredged sludge according to claim 1, characterized in that, The composite alkali activator includes sodium hydroxide, water glass and magnesium fluorosilicate, with a mass ratio of (3~5):(5~8):

2.

7. The composite solidification material based on modified dredged sludge according to claim 1, characterized in that, The method for preparing the chitosan-acrylamide copolymer includes: Chitosan and acrylamide were added to an acetic acid solution at a mass ratio of 1:(4~6), and then ammonium persulfate was added and mixed. The mixture was then polymerized at 60~80℃ to obtain a chitosan-acrylamide copolymer. The mass of ammonium persulfate added was 0.8%~1% of the total mass of chitosan and acrylamide.

8. The composite solidification material based on modified dredged sludge according to claim 1, characterized in that, The method for preparing the modified montmorillonite includes: Montmorillonite was modified by intercalation with hexadecyltrimethylammonium bromide, wherein the mass of hexadecyltrimethylammonium bromide was 3% to 5% of the mass of montmorillonite.

9. A preparation process for a composite solidification material based on modified dredged sludge according to any one of claims 1-8, characterized in that, include: The modified dredged sludge substrate, composite curing agent, basalt fiber and modified carbon fiber are mixed to obtain dry material; Functional additives and water are added to dry materials to obtain composite curing materials.