Tunnel hole slag heavy metal solidification treatment and safe utilization method

Abstract

The invention discloses a tunnel hole slag heavy metal solidification treatment and safe utilization method. The method comprises the following steps: carrying out particle size regulation and control pretreatment on tunnel hole slag; uniformly mixing the pretreated tunnel hole slag with blast furnace slag, steel slag and a desulfurized gypsum curing agent which are compounded according to a preset mass ratio; adding water, stirring and forming, and performing standard curing to prepare the novel concrete material, and then performing environmental safety detection on the prepared concrete material. Through the double synergistic effect of physical coating and chemical fixation, efficient and long-acting curing of the heavy metal in the tunnel hole slag is achieved, the heavy metal leaching concentration of a cured body is far lower than the national standard limit value, a novel concrete material can be prepared, the environmental pollution risk of the tunnel hole slag is eliminated, and the service life of the tunnel hole slag is prolonged. And synergistic resource utilization of various bulk solid wastes such as tunnel hole slag, blast furnace slag, steel slag and desulfurized gypsum is realized.

Description

Technical Field

[0001] This invention relates to the field of solid waste pollution control and resource utilization technology, specifically to a method for the solidification treatment and safe utilization of heavy metals in tunnel slag. Background Technology

[0002] In recent years, my country's tunnel construction has progressed rapidly as transportation networks extend into the complex terrain of southwest China, generating massive amounts of tunnel debris. A rough estimate suggests that the construction of the Sichuan-Tibet Railway alone will produce approximately 240 million cubic meters of tunnel debris, leading to significant stockpiling issues. This debris has a complex composition; due to significant differences in lithology and composition across different regions, it may also contain heavy metals. Under natural processes such as rain leaching, heavy metal ions in the debris are easily leached out, entering surrounding soil and water bodies, potentially causing serious ecological and environmental problems and health risks. Therefore, tunnel debris is widely recognized as a representative type of solid waste and requires proper disposal.

[0003] To improve the resource utilization rate of tunnel muck, researchers have conducted studies on its use as roadbed material or concrete aggregate. However, the environmental leaching risk of heavy metals from direct use of tunnel muck has not been fundamentally resolved, limiting its application scenarios. To address the hazards of heavy metals in tunnel muck, traditional techniques often employ cement-based materials for solidification. While cement has a good solidification effect on most heavy metals, it is a building material with high cost and poor economic efficiency. Furthermore, its production process involves high energy consumption and large carbon emissions, which does not meet national requirements.

[0004] However, while existing research on the preparation of cementitious materials using bulk industrial solid wastes such as slag and steel slag is widespread, most studies are limited to the synergistic combination of specific solid wastes with good cementitious properties, and mainly focus on indicators such as mechanical properties. Research on technologies for treating heavy metal pollution using industrial solid waste is relatively scarce. Designing an efficient tunnel slag synergistic solidification system that utilizes the synergistic effects of multiple industrial solid wastes to achieve efficient and stable solidification of heavy metals, reducing environmental risks, and simultaneously yielding a series of new concrete materials could provide a technical reference for expanding the utilization of solid waste and improving its comprehensive utilization rate. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for the solidification treatment and safe utilization of heavy metals in tunnel slag. This method aims to solve the problems of difficult disposal and low utilization value of tunnel slag containing heavy metals, as well as the high cost and heavy environmental impact of traditional cementitious solidification methods. By synergistically utilizing various industrial solid wastes, it achieves efficient and stable solidification of heavy metals in tunnel slag and prepares new environmentally friendly concrete materials, achieving the dual goals of "treating waste with waste and turning waste into treasure."

[0006] This invention provides a method for the solidification treatment and safe utilization of heavy metals in tunnel slag, comprising the following steps: S1 Raw Material Pretreatment: Tunnel slag is crushed, washed, and screened; blast furnace slag, steel slag, and desulfurized gypsum are dried and ground respectively; S2 Mixing: The pretreated tunnel slag is mixed with a composite curing agent composed of blast furnace slag, steel slag and desulfurized gypsum. The components, on a dry basis by mass percentage, are as follows: tunnel slag accounts for 40% to 75% of the total mass, and composite curing agent accounts for 25% to 60% of the total mass. S3 Concrete Mixing: Add water to the mixture from step S2 and force-mix to form a homogeneous concrete mixture. S4 Molding and Curing: The concrete mixture is poured into a mold, vibrated and shaped, and then cured to obtain heavy metal-cured concrete material. S5 Concrete Environmental Safety Testing: The cured concrete material is subjected to heavy metal toxicity leaching to determine whether the heavy metal leaching concentration meets the requirements of national standards.

[0007] As an optional improvement, the raw material pretreatment in step S1 includes: Pretreatment of tunnel muck raw materials: After crushing, washing and screening, the maximum particle size of the screened material is controlled to be no more than 40mm. Blast furnace raw material pretreatment: Grind the blast furnace slag raw material to a specific surface area of ​​not less than 400 m² / kg; Steel slag raw material pretreatment: Grind the steel slag to a specific surface area of ​​not less than 350 m² / kg, and the content of free calcium oxide (f-CaO) in the ground particles is less than 4%; Pretreatment of desulfurized gypsum raw materials: Dry the desulfurized gypsum raw materials until the moisture content is less than 1%.

[0008] As an optional improvement, in the composite curing agent described in step S2, the components, by dry basis mass percentage, are: blast furnace slag accounting for 50% to 70% of the total mass of the composite curing agent, steel slag accounting for 15% to 35%, and desulfurized gypsum accounting for 5% to 20%.

[0009] As an optional improvement, the mixing in step S2 can be done by dry mixing, that is, all dry powder raw materials, tunnel slag, blast furnace slag, steel slag and desulfurization gypsum are placed in a mixer and dry mixed for 2 to 5 minutes before proceeding to step S3.

[0010] As an optional improvement, the ratio of the total mass of water to the total mass of the composite curing agent in step S3, i.e., the water-to-binder ratio, is controlled within the range of 0.30 to 0.50.

[0011] As an optional improvement, in step S2, the tunnel muck accounts for 40% to 75% of the total mass by dry basis weight, and the composite curing agent accounts for 25% to 60% of the total mass.

[0012] As an optional improvement, step S4 includes pouring the mixture into a 100mm×100mm×100mm cubic mold and compacting it on a vibrating table; then transferring the resulting test block with the mold into a curing room for curing for 24 hours before demolding, and continuing to cure in the curing room for at least 7 days; wherein the curing temperature is 20±2℃ and the relative humidity is not less than 95%.

[0013] As an optional improvement, step S5 includes testing the concentration of heavy metals after the maintenance is completed, and if the concentration of heavy metals is lower than the minimum limit of the national standard, it is considered qualified.

[0014] The present invention can achieve the following beneficial effects: Synergistic and efficient curing with high environmental safety: This invention innovatively constructs a ternary synergistic curing system of "steel slag-mineral slag-gypsum". Through the strong alkali activation of steel slag, the pozzolanic reaction of mineral slag generates CSH gel to achieve "physical coating", while gypsum participates in the formation of ettringite (AFt) crystals to achieve "chemical fixation". This dual physicochemical mechanism, especially the lattice fixation effect of ettringite on heavy metal ions, has higher curing efficiency and long-term stability than the simple physical coating and surface adsorption of traditional cement curing. It can effectively address the problem of heavy metal leaching and ensure the long-term environmental safety of the cured product.

[0015] The co-utilization of solid waste transforms waste into valuable resources by using four different types of bulk solid waste (tunnel slag, blast furnace slag, steel slag, and desulfurization gypsum) as raw materials, achieving full utilization of solid waste. This not only solves the pollution and disposal problems of tunnel slag but also provides a large-scale, high-value-added utilization pathway for by-products from the steel and thermal power industries, reducing the extraction of natural sand and gravel resources and realizing "waste treatment with waste" and "turning waste into valuable resources."

[0016] Low cost and significant economic benefits: The raw materials used in this invention—blast furnace slag, steel slag, and desulfurization gypsum—are all inexpensive, even negative-cost, industrial by-products. Compared to using expensive commercial cement or chemical agents, the material cost of this method is extremely low. The process is simple and can be carried out using existing concrete mixing plant equipment, requiring no large-scale new investment. The prepared concrete product has excellent performance and can replace traditional concrete in various engineering constructions, creating considerable economic value.

[0017] This invention replaces most, or even all, of the cement with industrial solid waste, significantly reducing carbon emissions during material production. The entire process generates no secondary pollution, making it a green, low-carbon, and circular advanced technology. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of a method for solidifying and safely utilizing heavy metals in tunnel slag according to some embodiments of the present invention. Figure 2 This is an overall block diagram of the method for solidifying and safely utilizing heavy metals in tunnel slag according to some embodiments of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Industries such as steel and power generate massive amounts of industrial solid waste annually, including blast furnace slag, steel slag, and desulfurization gypsum. The accumulation of these wastes places significant pressure on the surrounding environment. Research indicates that blast furnace slag is rich in glassy silica-alumina components, possessing potential pozzolanic and cementing activity; steel slag contains large amounts of cement minerals such as dicalcium silicate (C2S) and tricalcium silicate (C3S) and is strongly alkaline; and desulfurization gypsum's main component is calcium sulfate dihydrate, which can participate in hydration reactions to generate ettringite, a material with expansive and cementing properties. Combining these industrial solid wastes can form a novel low-carbon cementing material system.

[0022] Therefore, the present invention provides a method for solidification treatment and safe utilization of heavy metals in tunnel slag, the method comprising the following steps: S1 performs raw material pretreatment: the tunnel slag is crushed, washed and screened to control its maximum particle size to be no more than 40 mm; the blast furnace slag raw material is ground to a specific surface area of ​​no less than 400 m² / kg; the steel slag is ground to a specific surface area of ​​no less than 350 m² / kg; and the desulfurized gypsum raw material is dried to a moisture content of less than 1%.

[0023] S2 involves mixing and batching the pretreated tunnel slag with a composite curing agent composed of blast furnace slag, steel slag, and desulfurized gypsum. The components, by dry weight percentage, comprise 40%–75% of the total mass of the tunnel slag and 25%–60% of the total mass of the composite curing agent. Within the composite curing agent, the components, by dry weight percentage, comprise 50%–70% of the total mass of the composite curing agent, 15%–35% of the total mass of the steel slag, and 5%–20% of the total mass of the desulfurized gypsum.

[0024] S3 Concrete Mixing: Pour all the above dry materials into a forced concrete mixer and dry mix for 2-5 minutes. Then, slowly add water (water-cement ratio = water mass / composite curing agent mass) to make the water-cement ratio 0.3-0.5, and continue wet mixing for 2-5 minutes until a homogeneous concrete mixture is formed.

[0025] S4 Molding and Curing: Pour the mixture into a 100mm×100mm×100mm cubic mold and compact it on a vibrating table. Then, move the molded specimen into a standard curing room (temperature (20±2)℃, relative humidity ≥95%) and cure for 24 hours before demolding. Continue curing in the standard curing room for at least 7 days, such as 7 days, 14 days, 28 days, or 56 days.

[0026] S5 concrete environmental safety test: After curing for at least 7 days, the broken test blocks were subjected to leaching toxicity test. The heavy metal test values ​​were all lower than the limits in the national standard GB 5085.3-2007.

[0027] Therefore, this invention first proposes a complete process flow, which clarifies that the main steps of this invention include: S1 raw material pretreatment, S2 mixing and batching, S3 concrete mixing, and S4 molding and curing. This is the process for achieving the purpose of this invention. Step S1 ensures that each raw material has a suitable physical form to participate in subsequent reactions. Step S2 is one of the core steps of this invention. By mixing the main solid waste (tunnel muck) with functional solid waste (composite curing agent) in a specific range of proportions, the foundation of the cementitious material reaction system is formed. Tunnel muck, as aggregate, accounts for 40% to 75%, ensuring the main components and material properties of the final product; the composite curing agent accounts for 25% to 60%, ensuring sufficient cementitious materials and reactants to complete the curing of heavy metals. This proportion range takes into account the curing effect of different levels of heavy metal pollution and the performance requirements of the prepared materials, and has wide applicability. Steps S3 and S4 are conventional concrete preparation processes, but for the non-traditional cementitious system of this invention, the control of water volume and the selection of curing regime are also crucial to the performance of the final material.

[0028] The embodiments of the present invention further define the proportions of each component of the composite curing agent. This is the key to achieving the synergistic curing effect of the present invention.

[0029] This invention sets forth specific requirements for the physicochemical properties of the raw materials, which is an important prerequisite for ensuring the reactivity and the stability of the final product performance.

[0030] Specifically, step S1, the raw material processing of tunnel slag, involves screening the tunnel slag particles to ensure that the particle size is no greater than 40mm. The particle size is in accordance with the standards for "Construction Sand and Gravel" (GB / T 14684-2022) and "Construction Pebbles and Crushed Stone" (GB / T 14685-2022), which ensures the homogeneity and workability of the mixture, as well as the density and strength of the hardened concrete.

[0031] Step S1, blast furnace slag raw material processing, involves grinding the blast furnace slag until its specific surface area is not less than 400 m² / kg. A higher specific surface area means a larger reaction contact area, which can significantly improve its hydration rate and degree under alkaline activation conditions, thereby generating CSH gel more quickly and fully, which is particularly important for strength contribution and physical coating effect.

[0032] Step S1, the steel slag raw material processing, involves grinding the steel slag to a specific surface area of ​​not less than 350 m² / kg. Simultaneously, the content of free calcium oxide (f-CaO) in the steel slag must be controlled to not exceed 4%. A higher specific surface area also facilitates the rapid dissolution of alkaline substances, effectively activating the slag. Strictly controlling the free calcium oxide (f-CaO) content is crucial for controlling the volume stability of the steel slag product, preventing cracking of the solidified body due to subsequent hydration expansion of free calcium oxide (f-CaO), thus ensuring the long-term effectiveness and durability of the solidification effect.

[0033] The step S1, desulfurized gypsum raw material processing, involves reducing the moisture content of the desulfurized gypsum to below 1%. Controlling the moisture content is to ensure the accuracy of measurement, prevent the raw material from clumping, and ensure its uniform dispersion in the mixture.

[0034] In step S2, the composite curing agent contains 50%–70% blast furnace slag, which serves as the main component of the cementitious system. Its potential pozzolanic activity is the primary source of strength and the cured matrix (CSH gel). Its highest proportion ensures sufficient SiO2 and Al2O3 to participate in the hydration reaction.

[0035] The steel slag content in the composite curing agent of step S2 is 15%–35%. As an important component of the cementitious material in this embodiment of the invention, it can fulfill the roles of both an alkali activator and a calcium supplement. Steel slag contains a large amount of free calcium oxide (f-CaO), which rapidly hydrolyzes upon contact with water, quickly raising the pH of the system to a strongly alkaline level. This creates the necessary strongly alkaline environment for the rupture of the glassy network structure of blast furnace slag and the dissolution of active ions. Simultaneously, the steel slag itself also provides some cementing components and calcium, participating in the formation of CSH gel and ettringite. This ratio range ensures sufficient alkalinity to fully activate the slag while avoiding potential later-stage volume stability problems caused by excessive steel slag (especially when the free calcium oxide (f-CaO) content is too high).

[0036] The desulfurized gypsum content in the composite curing agent in step S2 is 5%–20%, serving as the sulfur source and speciation regulator of this invention. It provides sulfate ions (SO4²⁻). - Calcium ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O, AFt) is a key reactant in the formation of ettringite. The formation of ettringite not only consumes the calcium aluminate phase in the system that may lead to rapid setting, thus playing a role in retarding setting and improving workability, but more importantly, its unique needle-like crystal structure, large specific surface area, and ability to adsorb and isomorphically substitute cations during formation are the core mechanisms for achieving efficient "chemical fixation" of heavy metals. This ratio ensures the formation of sufficient ettringite to effectively fix heavy metals, while avoiding the risk of later strength reduction or "sulfate corrosion" that may result from excessive gypsum.

[0037] The scientific ratio of these three industrial solid wastes in the composite curing agent in step S2, and the coupling system of "steel slag alkali activation - slag volcanic ash reaction - gypsum sulfoaluminate reaction" in this embodiment of the invention, have a significant synergistic effect.

[0038] The preferred mixing process in step S3 involves pre-dry mixing of the raw materials followed by wet mixing. This "dry mixing followed by wet mixing" method ensures that the various powdery materials with different particle sizes and densities, such as tunnel slag, blast furnace slag, steel slag, and desulfurization gypsum, achieve a high degree of uniformity before adding water. This provides a foundation for the subsequent homogeneous hydration reaction and avoids problems such as uneven performance or incomplete solidification caused by local enrichment or the absence of a certain component.

[0039] The water-to-cement ratio (water-to-binder ratio) mentioned in step S3 is controlled within the range of 0.30 to 0.50. A ratio that is too low (<0.30) will result in poor flowability of the mixture, making it difficult to stir evenly and pour densely, and will also result in insufficient water for the reaction. A ratio that is too high (>0.50) will leave excessive capillary pores after hardening, leading to reduced strength and increased permeability of the cured body, thereby increasing the risk of heavy metal leaching. Experiments show that 0.30 to 0.50 is the optimal range that balances workability, strength, and durability.

[0040] The preferred formulation has a slag content of 40%–75% and a composite curing agent content of 25%–60%. The composite curing agent uses a ratio of medium-high content slag, medium content steel slag, and medium-low content gypsum to balance the rate and extent of the activation-hydration-sulfoaluminate reaction, forming a microstructure with the densest structure and the most suitable amount of ettringite formation.

[0041] The curing method described is standard curing. The curing method in step S4 is standard curing; the standard curing is curing for at least 7 days in an environment with a temperature of (20±2)℃ and a relative humidity of not less than 95%; standard curing is a general method for evaluating the basic properties of concrete materials.

[0042] Finally, the heavy metal-cured concrete material prepared by the method, after curing for at least 7 days and being tested according to the "Identification Standard for Hazardous Waste - Leaching Toxicity Identification" (GB 5085.3-2007), showed that the concentration of lead heavy metal in its leachate was lower than the standard limit. This fully demonstrates the effectiveness and safety of the method of the present invention in heavy metal curing, and ensures that no new environmental risks will be brought about during its resource utilization.

[0043] Example 1 Raw material pretreatment: Tunnel slag is crushed, washed, and screened to control its maximum particle size to no more than 40 mm; blast furnace slag is ground to a specific surface area of ​​400 m² / kg; steel slag is ground to a specific surface area of ​​350 m² / kg; desulfurized gypsum is dried to a moisture content of less than 1%.

[0044] Mixing and batching: The pretreated tunnel slag is mixed with a composite curing agent composed of blast furnace slag, steel slag and desulfurized gypsum. The components are as follows: by dry weight percentage, the tunnel slag accounts for 40% of the total mass and the composite curing agent accounts for 60% of the total mass. In the composite curing agent, the components are as follows: by dry weight percentage, the blast furnace slag accounts for 70% of the total mass of the composite curing agent, the steel slag accounts for 15% and the desulfurized gypsum accounts for 15%.

[0045] Concrete mixing: Pour all the above dry materials into a forced concrete mixer and dry mix for 2 minutes. Then, slowly add water (water-binder ratio = water mass / composite curing agent mass) to make the water-binder ratio 0.35, and continue wet mixing for 2 minutes until a homogeneous concrete mixture is formed.

[0046] Molding and curing: The mixture is poured into a 100mm×100mm×100mm cubic mold and compacted on a vibrating table. The molded specimens are then moved into a standard curing room (temperature (20±2)℃, relative humidity ≥95%) for 24 hours before demolding, and then cured in the standard curing room for 7 days, 28 days, and 56 days.

[0047] Concrete environmental safety testing: Leaching toxicity tests were conducted on concrete samples after they were broken at different ages. The heavy metal test results showed that the values ​​were all far below the limits in the national standard GB 5085.3-2007, indicating that the prepared concrete material can be used safely.

[0048] Table 1. Heavy metal leaching concentration (mg / L) during the solidification treatment of cave debris. Note: ND indicates not detected. Example 2 Raw material pretreatment: Tunnel slag is crushed, washed, and screened to control its maximum particle size to be no more than 40 mm; blast furnace slag is ground to a specific surface area of ​​no less than 400 m² / kg; steel slag is ground to a specific surface area of ​​no less than 350 m² / kg; and desulfurized gypsum is dried to a moisture content of less than 1%.

[0049] Mixing and batching: The pretreated tunnel slag is mixed with a composite curing agent composed of blast furnace slag, steel slag and desulfurized gypsum. The components are as follows: by dry weight percentage, tunnel slag accounts for 55% of the total mass and composite curing agent accounts for 45% of the total mass. In the composite curing agent, the components are as follows: by dry weight percentage, blast furnace slag accounts for 60% of the total mass of the composite curing agent, steel slag accounts for 25% and desulfurized gypsum accounts for 15%.

[0050] Concrete mixing: Pour all the above dry materials into a forced concrete mixer and dry mix for 2 minutes. Then, slowly add water (water-binder ratio = water mass / composite curing agent mass) to make the water-binder ratio 0.3-0.5, and continue wet mixing for 5 minutes until a homogeneous concrete mixture is formed.

[0051] Molding and curing: The mixture is poured into a 100mm×100mm×100mm cubic mold and compacted on a vibrating table. The molded specimens are then moved into a standard curing room (temperature (20±2)℃, relative humidity ≥95%) for 24 hours before demolding, and then cured in the standard curing room for 7 days, 28 days, and 56 days.

[0052] Concrete environmental safety testing: Leaching toxicity tests were conducted on concrete samples after they were broken at different ages. The heavy metal test results showed that the values ​​were all far below the limits in the national standard GB 5085.3-2007, indicating that the prepared concrete material can be used safely.

[0053] Table 2. Heavy metal leaching concentration (mg / L) during the solidification treatment of slag from the tunnel. Note: ND indicates not detected. Example 3 Raw material pretreatment: Tunnel slag is crushed, washed, and screened to control its maximum particle size to no more than 40 mm; blast furnace slag is ground to a specific surface area of ​​400 m² / kg; steel slag is ground to a specific surface area of ​​350 m² / kg; desulfurized gypsum is dried to a moisture content of less than 1%.

[0054] Mixing and batching: The pretreated tunnel slag is mixed with a composite curing agent composed of blast furnace slag, steel slag and desulfurized gypsum. The components are as follows: by dry weight percentage, tunnel slag accounts for 75% of the total mass and composite curing agent accounts for 25% of the total mass; in the composite curing agent, the components are as follows: by dry weight percentage, blast furnace slag accounts for 50% of the total mass of the composite curing agent, steel slag accounts for 35% and desulfurized gypsum accounts for 15%.

[0055] Concrete mixing: Pour all the above dry materials into a forced concrete mixer and dry mix for 2 minutes. Then, slowly add water (water-binder ratio = water mass / composite curing agent mass) to make the water-binder ratio 0.4, and continue wet mixing for 5 minutes until a homogeneous concrete mixture is formed.

[0056] Molding and curing: The mixture is poured into a 100mm×100mm×100mm cubic mold and compacted on a vibrating table. The molded specimens are then moved into a standard curing room (temperature (20±2)℃, relative humidity ≥95%) for 24 hours before demolding, and then cured in the standard curing room for 7 days, 28 days, and 56 days.

[0057] Concrete environmental safety testing: Leaching toxicity tests were conducted on concrete samples after they were broken at different ages. The heavy metal test results showed that the values ​​were all far below the limits in GB 5085.3-2007, indicating that the prepared concrete material can be used safely.

[0058] Table 3. Heavy metal leaching concentration (mg / L) during the solidification treatment of slag from the tunnel. Note: ND indicates not detected. The results of the above embodiments and comparative examples fully demonstrate the scientific validity, advanced nature, and practicality of the method proposed in this invention for synergistically solidifying heavy metals in tunnel slag using blast furnace slag, steel slag, and desulfurized gypsum. This method not only efficiently and stably solidifies heavy metals, eliminating their environmental risks, but also produces concrete materials with excellent mechanical properties, achieving the synergistic resource utilization of various bulk solid wastes and possessing significant value for widespread application.

[0059] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for the solidification treatment and safe utilization of heavy metals in tunnel slag, characterized in that, The steps include the following: S1 Raw Material Pretreatment: Tunnel slag is crushed, washed and screened; blast furnace slag, steel slag and desulfurized gypsum are dried and ground respectively; S2 Mixing: The pretreated tunnel slag is mixed with a composite curing agent composed of blast furnace slag, steel slag and desulfurized gypsum. The components, on a dry basis by mass percentage, are as follows: tunnel slag accounts for 40% to 75% of the total mass, and composite curing agent accounts for 25% to 60% of the total mass. S3 Concrete Mixing: Add water to the mixture from step S2 and force-mix to form a homogeneous concrete mixture. S4 Molding and Curing: The concrete mixture is poured into a mold, vibrated and shaped, and then cured to obtain heavy metal-cured concrete material. S5 Concrete Environmental Safety Testing: The cured concrete material is subjected to heavy metal toxicity leaching to determine whether the heavy metal leaching concentration meets the requirements of national standards.

2. The method for solidification treatment and safe utilization of heavy metals in tunnel slag according to claim 1, characterized in that, The raw material pretreatment in step S1 includes: Pretreatment of tunnel muck raw materials: After crushing, washing and screening, the maximum particle size of the screened material is controlled to be no more than 40mm. Blast furnace raw material pretreatment: Grind the blast furnace slag raw material to a specific surface area of ​​not less than 400 m² / kg; Steel slag raw material pretreatment: Grind the steel slag to a specific surface area of ​​not less than 350 m² / kg, and the free calcium oxide content of the ground particles is less than 4%; Pretreatment of desulfurized gypsum raw materials: Dry the desulfurized gypsum raw materials until the moisture content is less than 1%.

3. The method for solidification treatment and safe utilization of heavy metals in tunnel slag according to claim 1, characterized in that, In the composite curing agent described in step S2, the components, by dry basis mass percentage, are as follows: blast furnace slag accounts for 50% to 70% of the total mass of the composite curing agent, steel slag accounts for 15% to 35%, and desulfurized gypsum accounts for 5% to 20%.

4. The method for solidification treatment and safe utilization of heavy metals in tunnel slag according to claim 1, characterized in that, The mixing in step S2 is done by dry mixing, that is, the tunnel slag, blast furnace slag, steel slag and desulfurization gypsum are placed in a mixer and dry mixed for 2 to 5 minutes, and then step S3 is performed.

5. The method for solidification treatment and safe utilization of heavy metals in tunnel slag according to claim 1, characterized in that, In step S3, the total mass ratio of water to composite curing agent is controlled within the range of 0.30 to 0.

50.

6. The method for solidification treatment and safe utilization of heavy metals in tunnel slag according to claim 1, characterized in that, In step S2, the tunnel muck accounts for 40% to 75% of the total mass by dry basis weight percentage; the composite curing agent accounts for 25% to 60% of the total mass.

7. The method for solidification treatment and safe utilization of heavy metals in tunnel slag according to any one of claims 1-6, characterized in that, Step S4 includes pouring the mixture into a 100mm×100mm×100mm cubic mold and compacting it on a vibrating table; then transferring the resulting test block with the mold into a curing room for curing for 24 hours before demolding, and continuing to cure in the curing room for at least 7 days; wherein the temperature during curing is 20±2℃ and the relative humidity is not less than 95%.

8. The method for solidification treatment and safe utilization of heavy metals in tunnel slag according to any one of claims 1-6, characterized in that, Step S5 includes testing the concentration of heavy metals after the maintenance is completed. If the concentration of heavy metals is lower than the minimum limit of the national standard, it is considered qualified.

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