A heavy metal pollution isolation layer for waste fly ash-asphalt pavement and its performance evaluation method

Abstract

A heavy metal pollution isolation layer for waste fly ash-asphalt pavement and its evaluation method are disclosed. The heavy metal pollution isolation layer comprises a filter layer, a slow-release layer, a gel layer, a high-strength barrier layer, and an interactive shielding layer. These layers are sequentially laid from top to bottom to form the heavy metal pollution isolation layer. The beneficial effects of this invention are as follows: the synergistic effect of the different layers in the heavy metal pollution isolation layer effectively blocks and shields the dissolution and migration of heavy metal elements, ensuring the environmental friendliness and safety of waste fly ash resource utilization in road engineering. The performance evaluation method of this invention also defines four parameters, and the index "heavy metal element isolation rate G" enables accurate evaluation of the blocking effect of the heavy metal pollution isolation layer.

Description

Technical Field

[0001] This invention relates to the field of road materials technology, and in particular to a heavy metal pollution isolation layer for waste fly ash-asphalt pavement and a method for evaluating its performance. Background Technology

[0002] Waste fly ash is the precipitate collected in the flue gas purification system of municipal solid waste incineration plants and the bottom ash settling at the bottom of flues and chimneys. Its main components are CaO-SiO2-Al2O3-Fe2O3, similar to those of blast furnace slag and fly ash, making it suitable for use as a new type of building material. In my country, civil engineering construction faces the triple challenges of high carbon emissions, high resource consumption, and high energy consumption. Applying waste fly ash as a renewable resource in civil engineering can not only achieve large-scale, large-scale, and resource-based utilization of waste fly ash but also alleviate resource and energy shortages. Using it as filler or fine aggregate in asphalt pavement subgrades is one example of the resource-based application of waste fly ash.

[0003] Waste fly ash contains a certain amount of heavy metals, dioxins, and dissolved salts, while asphalt has good adhesion and chemical stability. Mixing fly ash with asphalt to prepare waste fly ash-asphalt mortar can effectively encapsulate soluble salts and toxic substances, inhibit their leakage, and to a certain extent improve the high-temperature stability, water stability, and other road performance properties of waste fly ash-asphalt mixture.

[0004] However, under the influence of external environmental factors such as high temperature and freeze-thaw cycles, the solidification and stabilization effect of asphalt on waste fly ash is easily reduced, leading to the leaching of heavy metals, soluble salts, and dioxins from the fly ash. Among these, the leached soluble salts react with rainwater or freeze-thawed snow in road surface cracks to form expansive substances such as CaSO4·2H2O and Na2SO4·10H2O, or react with water at low temperatures to form chloride crystals, causing expansion damage to the road surface and structural destruction, thus affecting road performance. On the other hand, toxic substances such as leached dioxins, furans, and heavy metals enter groundwater, surface water, and soil, causing environmental pollution, and then enter the human body through the ecosystem cycle. The accumulated heavy metal toxins further harm the skin, hematopoietic system, circulatory system, nervous system, and digestive system, causing irreversible damage.

[0005] Therefore, in view of the shortcomings of the existing technology, it is necessary to provide a heavy metal pollution isolation layer for garbage fly ash-asphalt pavement and its performance evaluation method to solve the shortcomings of the existing technology. Summary of the Invention

[0006] One objective of this invention is to overcome the shortcomings of existing technologies and provide a heavy metal pollution isolation layer for waste fly ash-asphalt pavements. This heavy metal pollution isolation layer for waste fly ash-asphalt pavements can effectively isolate heavy metal pollution, improving the environmental friendliness and safety of waste fly ash resource utilization in road engineering.

[0007] The above-mentioned objectives of the present invention are achieved through the following technical measures:

[0008] A heavy metal pollution isolation layer for waste fly ash-asphalt pavement is provided, comprising a filter layer, a slow-release layer, a gel layer, a strong barrier layer, and an interactive shielding layer, wherein the filter layer, the slow-release layer, the gel layer, the strong barrier layer, and the interactive shielding layer are laid sequentially from top to bottom to obtain the heavy metal pollution isolation layer.

[0009] Preferably, the gel layer is composed of multiple layers of gel units stacked together; the gel unit layer is composed of an adsorption structure and a gel carrier; the adsorption structure is composed of a heavy metal trapping agent and microporous ceramic spheres, and the heavy metal trapping agent is located inside the microporous ceramic spheres.

[0010] Preferably, the filter layer is made of geotextile.

[0011] Preferably, the sustained-release layer contains a gel, a controlled-release agent, component A polyurea, and component B polyurea; and the controlled-release agent is hydroxypropyl methylcellulose or methacrylic acid.

[0012] Preferably, the high-strength barrier layer contains hydroxyethyl cellulose, a chelating agent, and a gelling agent, wherein the chelating agent is ethylenediaminetetraacetic acid or diethyltriaminepentaacetic acid; and the gelling agent contains epoxy resin, polyamide resin, and a solvent.

[0013] Preferably, the aforementioned interactive shielding layer contains a binder and porous mineral particles.

[0014] Preferably, the above adsorption structure is prepared by the following steps:

[0015] A1. Two hollow hemispherical honeycomb ceramic pieces are bonded together to form a spherical structure, and the spherical structure is cooled and solidified at room temperature to obtain the microporous ceramic sphere.

[0016] A2. The adsorption structure is obtained by injecting a heavy metal trapping agent into the pores on the surface of the microporous ceramic spheres obtained in A1.

[0017] Preferably, the above-mentioned gel unit layer is prepared by the following steps:

[0018] B1. Apply release agent to the inside of the mold;

[0019] B2. Spray the gel carrier onto the mold, cool and solidify it, and then lay the adsorption structure flat on the surface of the gel carrier to obtain a layer of adsorption structure and a layer of gel carrier.

[0020] B3. Spray a gel carrier onto the upper layer of the previous layer, cool and solidify it, and then lay the adsorption structure on the upper surface of the gel carrier to obtain the lower layer.

[0021] B4. Repeat step B3 until N layers are obtained, where N ≥ 1 and is a positive integer;

[0022] B5. Spray a gel carrier onto the upper surface of the last layer, cool and solidify to obtain the gel unit layer.

[0023] Preferably, the preparation method of the gel layer is as follows: the gel unit layer is obtained by laminating the gel unit layer with an adhesive between adjacent gel unit layers, and finally the gel is directly laid on the upper surface of the strong barrier layer and compacted as a whole.

[0024] Preferably, the above-mentioned sustained-release layer is prepared by the following steps:

[0025] C1. Mix component A (polyurea), gel, and controlled-release agent according to the mass ratio to form component C;

[0026] C2. Using a high-pressure sprayer, component B (polyurea) and component C (obtained in C1) are simultaneously sprayed onto the upper surface of the gel layer to obtain the sustained-release layer.

[0027] Preferably, the above-mentioned strong barrier layer is prepared by the following steps:

[0028] D1. Mix epoxy resin, polyamide resin and solvent to obtain a gelling agent;

[0029] D2. Mix hydroxyethyl cellulose, chelating agent, and gelling agent;

[0030] D3. Transfer the mixture of D2 to a high-pressure sprayer and spray it onto the upper surface of the interactive shielding layer to obtain the strong barrier layer.

[0031] Preferably, the above-mentioned interactive shielding layer is prepared by the following steps:

[0032] E1. Mix the porous mineral particles and the binder, and then place the porous mineral particles and the binder under a shearing device to shear them.

[0033] E2. Transfer the material from E1 to a high-pressure sprayer and spray it onto the upper surface of the outer substrate to obtain the interactive shielding layer.

[0034] Preferably, B2 specifically involves spraying a 2mm-3mm thick gel carrier onto the mold, cooling and solidifying it, and then spreading the adsorption structure evenly on the surface of the gel carrier, with a spreading density of 11 structures / cm². 2 ~12 pieces / cm 2 This results in a layer of adsorption structure and a layer of gel carrier.

[0035] Preferably, B3 specifically involves spraying a 2mm to 3mm thick gel carrier onto the upper layer of the previous layer, cooling and curing it, and then spreading the adsorption structure on the upper surface of the gel carrier to obtain the lower layer.

[0036] Preferably, B5 specifically involves spraying a 2mm to 3mm thick gel carrier onto the upper surface of the last layer, cooling and curing it to obtain the gel unit layer.

[0037] Preferably, C1 is specifically formed by mixing component A (polyurea), gel, and controlled-release agent in a mass ratio of 2:1:1 to form component C.

[0038] Preferably, C2 is specifically obtained by simultaneously spraying component B (polyurea) and component C (C1) onto the upper surface of the gel layer using a high-pressure sprayer at a mass ratio of 1:1 and a pressure of 0.6-0.8 MPa to obtain the sustained-release layer.

[0039] Preferably, D1 is specifically obtained by mixing epoxy resin, polyamide resin and solvent in a mass ratio of 40:20:1 to obtain a gelling agent.

[0040] Preferably, D2 is specifically a mixture of hydroxyethyl cellulose, chelating agent, and gelling agent in a mass ratio of 1:5:25.

[0041] Preferably, D3 specifically involves transferring the mixture of D2 to a high-pressure sprayer and spraying it onto the upper surface of the interactive shielding layer at a pressure of 0.4 MPa to 0.6 MPa to obtain the strong barrier layer.

[0042] Preferably, E1 specifically involves mixing porous mineral particles and a binder, wherein the mass of the porous mineral particles is 20% to 30% of the mass of the binder, and placing the porous mineral particles and the binder in a shearing apparatus and shearing them at 160°C and 5000 rad / s for 20 to 30 minutes.

[0043] Preferably, E2 specifically involves transferring the material from E1 into a high-pressure sprayer and spraying it onto the upper surface of the external substrate at a pressure of 0.6MPa to 0.8MPa to obtain the interactive shielding layer.

[0044] Preferably, the binder is emulsified asphalt, and the content of evaporation residue is in the range of 58% to 65%.

[0045] Preferably, the porous mineral particles are zeolite or illite, and the fineness is 200 mesh to 300 mesh.

[0046] Preferably, the epoxy resin is a bisphenol A type epoxy resin, and the bisphenol A type epoxy resin is of type E52 (616), E51 (618) or E44 (6101).

[0047] Preferably, the polyamide resin is PA610, PA612, PA46 or PA650.

[0048] Preferably, the solvent is acetone.

[0049] Preferably, the heavy metal chelating agent is a dithiocarbamate derivative or a xanthate chelating agent.

[0050] Preferably, the microporous ceramic sphere is made of two hollow hemispherical honeycomb ceramic pieces joined together.

[0051] Preferably, the gel carrier is composed of liquid silica gel component A and liquid silica gel component B, with a mass ratio of 10:1.

[0052] Preferably, the geotextile is a polyester staple fiber geotextile, and its unit area mass ranges from 250 g / m². 2 The thickness is 2mm.

[0053] Preferably, the thickness of the aforementioned interactive shielding layer is 1mm to 3mm.

[0054] Preferably, the thickness of the aforementioned strong barrier layer is 1mm to 2mm.

[0055] Preferably, the gel layer is 12mm to 15mm thick.

[0056] Another objective of this invention is to overcome the shortcomings of existing technologies and provide a method for evaluating the performance of heavy metal contamination isolation layers. This method can quantitatively evaluate the isolation effect of heavy metal contamination isolation layers.

[0057] The above-mentioned objectives of the present invention are achieved through the following technical measures:

[0058] A method for evaluating the performance of heavy metal contamination isolation layers is provided, which involves the following steps:

[0059] S1. Prepare cement concrete slabs;

[0060] S2. Prepare the heavy metal pollution isolation layer as described above on the upper surface of the cement concrete slab obtained in S1.

[0061] S3. Cut out the cement concrete slab from S2 to obtain an intermediate specimen including a heavy metal pollution isolation layer and part of the cement concrete slab.

[0062] S4. Remove the cement concrete layer from the intermediate specimen and use the remaining heavy metal contamination isolation layer as the test specimen.

[0063] S5. Seal the four sides of the test specimen with wax, then place it in the middle of the test chamber and fix it with the positioning groove of the test chamber.

[0064] S6. Use wax to fill the gap between the test chamber wall above the positioning groove and the test specimen until the wax level is flush with the upper surface of the test specimen.

[0065] S7. Cover the upper chamber of the test chamber and close the output valve at the bottom of the test chamber. Open the exhaust valve at the top of the test chamber and inject heavy metal leaching solution through the input valve at the top of the test chamber until the liquid level reaches half the height of the upper chamber scale. Close the exhaust valve and then draw a vacuum through the input valve.

[0066] S8. Close the input valve, and then place the test chamber in a 60℃ constant temperature chamber for 12h~36h.

[0067] S9. Take 5ml of heavy metal leaching solution from the lower compartment into test tube A, and take 5ml of heavy metal leaching solution from the upper compartment into test tube B.

[0068] S10. Conduct a heavy metal leaching concentration test on the heavy metal leachates of test tube A and test tube B to obtain measurement data.

[0069] Preferably, the above measurement data are the initial concentration C2, the filtration concentration C1, the concentration gradient ΔC, and the heavy metal element isolation rate G.

[0070] Preferably, the initial concentration C2 is the relative concentration of heavy metals in the heavy metal leachate of test tube B, in μg / L.

[0071] Preferably, the above-mentioned filtration concentration C1 is the relative concentration of heavy metals in the heavy metal leachate of test tube A, in μg / L.

[0072] Preferably, the concentration gradient ΔC is the difference between the filtered concentration C2 and the initial concentration C1.

[0073] Preferably, the above-mentioned heavy metal element isolation rate G is the inhibitory effect of the heavy metal pollution isolation layer on the dissolution and infiltration of heavy metal elements.

[0074] Preferably, the isolation rate G of the above-mentioned heavy metal elements is the ratio of ΔC to C2.

[0075] Preferably, the dimensions of the above-mentioned cement concrete slab are 30cm×30cm×5cm.

[0076] Preferably, the above-mentioned cement concrete slab is prepared by mixing cement, sand, crushed stone and water in a mix ratio of 1:2:3:0.4.

[0077] Preferably, S3 specifically involves using the center of the bottom surface of the cement concrete slab in S2 as the center of a 15cm×15cm square, cutting the square to obtain an intermediate specimen including a heavy metal pollution isolation layer and part of the cement concrete slab.

[0078] Preferably, the preparation method of the above-mentioned heavy metal leachate is as follows: According to the "Solid Waste Leaching Toxicity Leaching Method Acetic Acid Buffer Solution Method" (HJ / T 300-2007), the fly ash-asphalt mortar and sulfuric acid-nitric acid mixed solution are mixed at a liquid-solid ratio of 10:1, and then placed in a horizontal shaker and shaken at an amplitude of 40 mm and a frequency of 110 times / minute for 8 hours. Finally, it is allowed to stand at room temperature for 16 hours to obtain the heavy metal leachate.

[0079] This invention provides a heavy metal pollution isolation layer for waste fly ash-asphalt pavement and its evaluation method. The heavy metal pollution isolation layer comprises a filter layer, a slow-release layer, a gel layer, a high-strength barrier layer, and an interactive shielding layer. These layers are sequentially laid from top to bottom to form the heavy metal pollution isolation layer. The beneficial effects of this invention are as follows: the synergistic effect of the different layers in the heavy metal pollution isolation layer effectively blocks and shields the dissolution and migration of heavy metal elements, ensuring the environmental friendliness and safety of waste fly ash resource utilization in road engineering. The performance evaluation method of this invention also defines four parameters, and the index "heavy metal element isolation rate G" enables accurate evaluation of the blocking effect of the heavy metal pollution isolation layer. Attached Figure Description

[0080] The invention will be further described with reference to the accompanying drawings, but the contents of the drawings do not constitute any limitation on the invention.

[0081] Figure 1 This is a schematic diagram of the structure of the heavy metal pollution isolation layer.

[0082] Figure 2 This is a schematic diagram of the adsorption structure.

[0083] Figure 3 The flowchart shows the cutting process for the test specimen.

[0084] Figure 4 This is a schematic diagram of the cross-section of the test specimen in the test chamber.

[0085] exist Figures 1 to 4 This includes:

[0086] Filter layer 1, sustained release layer 2, gel layer 3, strong barrier layer 4, interactive shielding layer 5, gel carrier 6, adsorption structure 7, exhaust valve 8, input valve 9, upper chamber 10, wax 11, positioning groove 12, middle chamber 13, lower chamber 14, output valve 15. Detailed Implementation

[0087] The technical solution of the present invention will be further described with reference to the following embodiments. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods. Unless otherwise specified, the raw materials and reagents used in the following embodiments can be purchased from conventional biochemical reagent stores or pharmaceutical companies.

[0088] Example 1

[0089] A heavy metal pollution isolation layer for waste fly ash-asphalt pavements, such as Figures 1 to 2 As shown, a filter layer 1, a slow-release layer 2, a gel layer 3, a strong barrier layer 4, and an interactive shielding layer 5 are provided. The filter layer 1, the slow-release layer 2, the gel layer 3, the strong barrier layer 4, and the interactive shielding layer 5 are laid sequentially from top to bottom to obtain the heavy metal pollution isolation layer.

[0090] The gel layer 3 is composed of multiple layers of gel units stacked together. The gel layer 3 is 12mm to 15mm thick.

[0091] The gel unit layer consists of an adsorption structure 7 and a gel carrier 6. The adsorption structure 7 consists of a heavy metal chelating agent and microporous ceramic spheres, with the heavy metal chelating agent located inside the microporous ceramic spheres. The heavy metal chelating agent is a dithiocarbamate derivative or a xanthate chelating agent. The dithiocarbamate derivative of this invention was purchased from Jiangmen Xinlingyu Co., Ltd., and the xanthate chelating agent was purchased from Suzhou Haonuo Industry & Trade Co., Ltd.

[0092] The microporous ceramic spheres are composed of two hollow hemispherical honeycomb ceramic pieces joined together. The honeycomb ceramics of this invention were purchased from Guangzhou Xinci Environmental Protection Materials Co., Ltd. The gel carrier 6 is composed of component A liquid silica gel and component B liquid silica gel. Component A and component B liquid silica gel of this invention are RX-E650 type AB two-component liquid silica gel from Shenzhen Sicheng Silica Gel Co., Ltd., with a mass ratio of 10:1.

[0093] The structure is composed of hollow hemispherical honeycomb ceramic pieces made of porous cordierite, with the following parameters: diameter 3 mm, thickness 100-120 μm, pore size 12-270 μm, porosity 32%-94%, and compressive strength 28-145 MPa. After curing, the gel carrier 6 of this invention has a density of 1.097 g / cm³. 3It has a viscosity of 11000 cps, tensile strength ≥6.0 MPa, tear strength ≥16.7 kN / m, tensile strength at break ≥180%, hardness of 50±2A, and average pore size of 1.8-3.2 nm.

[0094] The adsorption structure 7 is prepared through the following steps:

[0095] A1. Two hollow white spherical honeycomb ceramics are bonded together to form a spherical structure. The spherical structure is then cooled and cured at room temperature for 4 hours to obtain the microporous ceramic spheres. Specifically, the bonding is performed automatically using a micro-volume automatic dispensing machine. The parameters of the micro-volume automatic dispensing machine are as follows: power 400W, voltage 220V, dispensing frequency 100 times / min, minimum dispensing time 0.001s, and repeatability ±0.01mm. The precision injection device is a micro-gear pump with a flow rate of 0.0015-9ml / min, viscosity range of 0.3-25000mPa·s, precision CV<1% (coefficient of variation), speed range of 1-6000rpm, maximum input pressure of 5bar, operating temperature of -20℃~150℃, and displacement of 1.5μl.

[0096] A2. The adsorption structure 7 is obtained by injecting a heavy metal trapping agent into the pores on the surface of the microporous ceramic spheres obtained in A1. Specifically, this is done using a precision injection device for 84 seconds.

[0097] The gel unit layer is prepared through the following steps:

[0098] B1. Apply a release agent, specifically petrolatum, to the inside of the mold. The release agent has the following parameters: density 0.84 g / cm³. 3 It has a melting point of 45-60℃, an oil content of 99%, and a penetration of 165mm at 25℃.

[0099] B2. Spray gel carrier 6 onto the mold, cool and solidify, and then lay the adsorption structure 7 on the surface of the gel carrier 6 to obtain a layer of adsorption structure 7 and a layer of gel carrier 6.

[0100] B3. Spray the gel carrier 6 onto the upper layer of the previous layer, cool and solidify it, and then lay the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0101] B4. Repeat step B3 until N layers are obtained, where N ≥ 1 and is a positive integer;

[0102] B5. Spray gel carrier 6 onto the upper surface of the last layer, cool and solidify to obtain the gel unit layer.

[0103] Specifically, B2 involves spraying a 2mm-3mm thick layer of gel carrier 6 onto the mold, cooling and solidifying it, and then spreading the adsorption structure 7 evenly on the surface of the gel carrier 6, with a spreading density of 11 structures / cm². 2 ~12 pieces / cm 2 A layer of adsorption structure 7 and gel carrier 6 is obtained.

[0104] Specifically, B3 involves spraying a 2mm-3mm thick gel carrier 6 onto the upper layer of the previous layer, cooling and curing it, and then laying the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0105] Specifically, B5 involves spraying a 2mm-3mm thick gel carrier 6 onto the upper surface of the last layer, cooling and curing it to obtain the gel unit layer.

[0106] Specifically, the gel layer 3 is prepared by layering gel unit layers with an adhesive between adjacent gel unit layers to obtain the gel layer 3. Finally, the gel is directly laid on the upper surface of the strong barrier layer 4 and compacted as a whole.

[0107] Filter layer 1 is composed of geotextile. The geotextile is polyester staple fiber geotextile, and its unit area mass ranges from 250 g / m². 2 The thickness is 2mm. The parameters of the polyester staple fiber geotextile are as follows: tensile strength ≥ 8.0KN / m, elongation 25%-100%, CBR bursting strength ≥ 1.2KN, equivalent pore size (090) 0.07-0.2mm, tear strength ≥ 0.20KN, and vertical permeability coefficient K×(10 -9 ~10 -12 (cm / s), where K=1.0~9.9. When using polyester staple fiber geotextile, it is cut to the required size with a cutter according to the road paving dimensions, and then directly laid on the surface of the slow-release layer 2.

[0108] The sustained-release layer 2 contains a gel, a controlled-release agent, component A (polyurea), and component B (polyurea); and the controlled-release agent is hydroxypropyl methylcellulose or methacrylic acid. The thickness of the sustained-release layer 2 is 1 mm to 2 mm. The gel is type A fine-porous silica gel with a particle size of 0.2-2 mm, an average pore size of 2.0-3.0 nm, and a specific surface area of ​​650-800 m². 2 / g, pore volume is 0.35-0.40ml / g, and adsorption capacity is 8% (RH=20%), 20% (RH=50%), and 30% (RH=90%). Component A is a polyurethane prepolymer containing diisocyanate groups. Component B is a mixture of amino-terminated polyether, liquid amine chain extender, pigment, filler, and additives. The parameters of component B are as follows: tensile strength ≥16MPa, elongation at break ≥450%, tear strength ≥50N / mm, and low-temperature bending ≤-40℃. It should be noted that both component A and component B are commercially available products. The component A and component B polyurea used in this embodiment are AB two-component polyurea produced by Jinan Jiuxu Company.

[0109] The sustained-release layer 2 is prepared through the following steps:

[0110] C1. Mix component A (polyurea), gel, and controlled-release agent according to the mass ratio to form component C;

[0111] C2. Using a high-pressure sprayer, component B (polyurea) and component C (obtained from C1) are simultaneously sprayed onto the upper surface of the gel layer 3 to obtain the sustained-release layer 2.

[0112] Specifically, C1 is formed by mixing component A (polyurea), gel, and controlled-release agent in a mass ratio of 2:1:1. Specifically, C2 is formed by simultaneously spraying component B (polyurea) and component C obtained from C1 onto the upper surface of the gel layer 3 using a high-pressure sprayer at a mass ratio of 1:1 and a pressure of 0.6-0.8 MPa, thus obtaining the controlled-release layer 2.

[0113] The strong barrier layer 4 contains hydroxyethyl cellulose, a chelating agent, and a gelling agent, wherein the chelating agent is ethylenediaminetetraacetic acid or diethyltriaminepentaacetic acid. The thickness of the strong barrier layer 4 is 1 mm to 2 mm. The gelling agent contains epoxy resin, polyamide resin, and a solvent. The epoxy resin is a bisphenol A type epoxy resin, and the bisphenol A type epoxy resin is of type E52 (616), E51 (618), or E44 (6101); the polyamide resin is of type PA610, PA612, PA46, or PA650. The solvent is acetone. The material parameters of the hydroxyethyl cellulose are as follows: fineness 150-200 mesh, molar substitution ratio (MS) 1.8-2.0, pH value 6.0-8.5, viscosity 2 mPa·s. The density of acetone is 0.789 g / cm³. 3 (20℃), boiling range 1.0℃, acidity 0.003%, purity 99.0%, molar refractive index 15.97, molar volume 75.1 cm³ 3 / mol.

[0114] The strong barrier layer 4 is prepared through the following steps:

[0115] D1. Mix epoxy resin, polyamide resin and solvent to obtain a gelling agent;

[0116] D2. Mix hydroxyethyl cellulose, chelating agent, and gelling agent;

[0117] D3. Transfer the mixture of D2 to a high-pressure sprayer and spray it on the upper surface of the interactive shielding layer 5 to obtain the strong barrier layer 4. The high-pressure sprayer sprays 1-2 mm of the strong barrier layer 4 at a pressure of 0.4-0.6 MPa.

[0118] Specifically, D1 involves mixing epoxy resin, polyamide resin, and solvent in a mass ratio of 40:20:1 to obtain a gelling agent; D2 involves mixing hydroxyethyl cellulose, a chelating agent, and a gelling agent in a mass ratio of 1:5:25; and D3 involves transferring the mixture of D2 to a high-pressure sprayer and spraying it onto the upper surface of the interactive shielding layer 5 at a pressure of 0.4 MPa to 0.6 MPa to obtain the strong barrier layer 4.

[0119] The interactive shielding layer 5 contains a binder and porous mineral particles. The binder is emulsified asphalt, and the evaporation residue content ranges from 58% to 65%. The porous mineral particles are zeolite or illite, and the fineness is 200 mesh to 300 mesh. The thickness of the interactive shielding layer 5 of this invention is 1 mm to 3 mm.

[0120] The interactive shielding layer 5 is prepared through the following steps:

[0121] E1. Mix the porous mineral particles and the binder, and then place the porous mineral particles and the binder under a shearing apparatus for shearing. The parameters of the shearing apparatus are: shearing at 160℃ and 5000rad / s for 20-30 minutes.

[0122] E2. Transfer the material from E1 to a high-pressure sprayer and spray it onto the upper surface of the outer substrate to obtain the interactive shielding layer 5. The high-pressure sprayer parameters are 0.6-0.8MPa, and the spraying thickness is 1-3mm.

[0123] Specifically, E1 involves mixing porous mineral particles and a binder, with the porous mineral particles comprising 20%–30% of the binder mass. The porous mineral particles and binder are then placed in a shearing apparatus and sheared at 160°C and 5000 rad / s for 20–30 minutes. E2 involves transferring the material from E1 to a high-pressure sprayer and spraying it onto the upper surface of the external substrate at a pressure of 0.6 MPa–0.8 MPa to obtain the interactive shielding layer 5.

[0124] It should be noted that filter layer 1 prevents granular and cementitious materials in the upper base and surface layers from entering and damaging the contamination isolation layer. Simultaneously, after filling, it reduces the pore size of filter layer 1, decreasing the infiltration rate of heavy metal leachate and ensuring that heavy metal elements can slowly enter the slow-release layer 2. The slow-release layer 2, in turn, provides initial blockage and storage for heavy metal elements, slowing their migration rate and allowing them to enter the gel layer 3 uniformly and slowly. In this invention, filter layer 1 and slow-release layer 2 form the first barrier against heavy metal elements, primarily slowing their infiltration rate and ensuring uniform entry into the gel layer 3. When heavy metal elements enter the gel layer 3, the gel layer 3 adsorbs and encapsulates them. The embedded upper adsorption structure 7 adsorbs heavy metal elements within a certain range around it into the slow-release layer 2 inside, where they are then uniformly solidified and absorbed by the adsorption core. When the adsorption of the upper adsorption structure 7 reaches saturation, the supplementary adsorption of heavy metal elements by the lower adsorption structure 7 effectively ensures the durability and adsorption efficiency of the adsorption structure 7. The double protection of the upper and lower adsorption structures 7 forms a second barrier layer for heavy metal elements. When the concentration of heavy metal elements inside the gel layer 3 is too high and they seep downwards, the adsorption of the material inside the strong barrier layer 4 further prevents the migration of heavy metal elements, thus ensuring effective shielding against the dissolution and seepage of heavy metal elements, forming a third barrier layer. The interactive shielding layer 5 is mainly used to strengthen the interactive bonding between the heavy metal pollution isolation layer and the substrate, thereby ensuring the integrity and stability of the structural layer.

[0125] This heavy metal pollution isolation layer for waste fly ash-asphalt pavement can effectively block and shield the dissolution and migration of heavy metal elements through the synergistic effect of different layers in the heavy metal pollution isolation layer, ensuring the environmental protection and safety of waste fly ash in road engineering.

[0126] Example 2

[0127] A heavy metal pollution isolation layer for waste fly ash-asphalt pavements, such as Figures 1 to 2 As shown, a filter layer 1, a slow-release layer 2, a gel layer 3, a strong barrier layer 4, and an interactive shielding layer 5 are provided. The filter layer 1, the slow-release layer 2, the gel layer 3, the strong barrier layer 4, and the interactive shielding layer 5 are laid sequentially from top to bottom to obtain the heavy metal pollution isolation layer.

[0128] The gel layer 3 is composed of multiple layers of gel units stacked together. The gel layer 3 is 12 mm thick.

[0129] The gel unit layer consists of an adsorption structure 7 and a gel carrier 6. The adsorption structure 7 is composed of a heavy metal trapping agent and microporous ceramic spheres, with the heavy metal trapping agent located inside the microporous ceramic spheres. The heavy metal trapping agent is a dithiocarbamate derivative. The microporous ceramic spheres are composed of two hollow hemispherical honeycomb ceramic pieces, produced by Guangzhou Xinci Environmental Protection Materials Co., Ltd. The gel carrier 6 consists of component A liquid silica gel and component B liquid silica gel, both of which are RX-E650 type AB two-component liquid silica gel produced by Shenzhen Sicheng Silica Gel Co., Ltd., with a mass ratio of 10:1. The hollow hemispherical honeycomb ceramic pieces are made of porous cordierite, with parameters including a diameter of 3mm, a thickness of 100-120μm, a pore size of 12-270μm, a porosity of 32%-94%, and a compressive strength of 28-145MPa. After the gel carrier 6 of the present invention is cured, its density is 1.097 g / cm³. 3 It has a viscosity of 11000 cps, tensile strength ≥6.0 MPa, tear strength ≥16.7 kN / m, tensile strength at break ≥180%, hardness of 50±2A, and average pore size of 1.8-3.2 nm.

[0130] The adsorption structure 7 is prepared through the following steps:

[0131] A1. Two hollow hemispherical honeycomb ceramic pieces are bonded together to form a spherical structure. The spherical structure is then cooled and cured at room temperature for 4 hours to obtain the microporous ceramic spheres. Specifically, the bonding is performed automatically using a micro-volume automatic dispensing machine. The parameters of the micro-volume automatic dispensing machine are as follows: power 400W, voltage 220V, dispensing frequency 100 times / min, minimum dispensing time 0.001s, and repeatability ±0.01mm. The parameters of the precision injection equipment are: a micro-gear pump with a flow rate of 0.0015-9ml / min, viscosity range of 0.3-25000mPa·s, precision CV<1% (coefficient of variation), speed range of 1-6000rpm, maximum input pressure of 5bar, operating temperature of -20℃~150℃, and displacement of 1.5μl.

[0132] A2. The adsorption structure 7 is obtained by injecting a heavy metal trapping agent into the pores on the surface of the microporous ceramic spheres obtained in A1. Specifically, this is done using a precision injection device for 84 seconds.

[0133] The gel unit layer is prepared through the following steps:

[0134] B1. Apply a release agent, specifically petrolatum, to the inside of the mold. The release agent has the following parameters: density 0.84 g / cm³. 3 It has a melting point of 45-60℃, an oil content of 99%, and a penetration of 165mm at 25℃.

[0135] B2. Spray gel carrier 6 onto the mold, cool and solidify, and then lay the adsorption structure 7 on the surface of the gel carrier 6 to obtain a layer of adsorption structure 7 and a layer of gel carrier 6.

[0136] B3. Spray the gel carrier 6 onto the upper layer of the previous layer, cool and solidify it, and then lay the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0137] B4. Repeat step B3 until N layers are obtained, where N is 2 and is a positive integer;

[0138] B5. Spray gel carrier 6 onto the upper surface of the last layer, cool and solidify to obtain the gel unit layer.

[0139] B2 specifically involves spraying a 2mm thick layer of gel carrier 6 onto the mold, cooling and solidifying it, and then spreading the adsorption structure 7 evenly on the surface of the gel carrier 6, with a spreading density of 11 structures / cm². 2 A layer of adsorption structure 7 and gel carrier 6 is obtained.

[0140] Specifically, B3 involves spraying a 2mm thick gel carrier 6 onto the upper layer of the previous layer, cooling and curing it, and then laying the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0141] Specifically, B5 involves spraying a 2mm thick gel carrier 6 onto the upper surface of the last layer, cooling and curing it to obtain the gel unit layer.

[0142] Specifically, the gel layer 3 is prepared by layering gel unit layers with an adhesive between adjacent gel unit layers to obtain the gel layer 3. Finally, the gel is directly laid on the upper surface of the strong barrier layer 4 and compacted as a whole.

[0143] Filter layer 1 is composed of geotextile. The geotextile is polyester staple fiber geotextile, and its unit area mass ranges from 250 g / m². 2 The thickness is 2mm. The parameters of the polyester staple fiber geotextile are as follows: tensile strength ≥ 8.0KN / m, elongation 25%-100%, CBR bursting strength ≥ 1.2KN, equivalent pore size (090) 0.07-0.2mm, tear strength ≥ 0.20KN, and vertical permeability coefficient K×(10 -9 ~10 -12 (cm / s), where K=1.0~9.9. When using polyester staple fiber geotextile, it is cut to the required size with a cutter according to the road paving dimensions, and then directly laid on the surface of the slow-release layer 2.

[0144] The sustained-release layer 2 contains a gel, a controlled-release agent, component A (polyurea), and component B (polyurea); the controlled-release agent is hydroxypropyl methylcellulose or methacrylic acid. The thickness of the sustained-release layer 2 is 1 mm. The gel is type A fine-porous silica gel with a particle size of 0.2 mm, an average pore size of 2.0 nm, and a specific surface area of ​​650 m². 2 / g, pore volume is 0.35ml / g, and adsorption capacity is 8% (RH=20%), 20% (RH=50%), and 30% (RH=90%). Component A is a polyurethane prepolymer containing diisocyanate groups. Component B is a mixture of amino-terminated polyether, liquid amine chain extender, pigment, filler, and additives; the parameters of component B are as follows: tensile strength ≥16MPa, elongation at break ≥450%, tear strength ≥50N / mm, and low-temperature bending ≤-40℃. It should be noted that both component A and component B are commercially available products. The component A and component B polyurea used in this embodiment are AB two-component polyurea produced by Jinan Jiuxu Company.

[0145] The sustained-release layer 2 is prepared through the following steps:

[0146] C1. Mix component A (polyurea), gel, and controlled-release agent according to the mass ratio to form component C;

[0147] C2. Using a high-pressure sprayer, component B (polyurea) and component C (obtained from C1) are simultaneously sprayed onto the upper surface of the gel layer 3 to obtain the sustained-release layer 2.

[0148] Specifically, C1 is formed by mixing component A (polyurea), gel, and controlled-release agent in a mass ratio of 2:1:1. Specifically, C2 is formed by simultaneously spraying component B (polyurea) and component C obtained from C1 onto the upper surface of the gel layer 3 using a high-pressure sprayer at a mass ratio of 1:1 and a pressure of 0.6 MPa, to obtain the controlled-release layer 2.

[0149] The strong barrier layer 4 contains hydroxyethyl cellulose, a chelating agent, and a gelling agent, wherein the chelating agent is ethylenediaminetetraacetic acid (EDTA). The thickness of the strong barrier layer 4 is 1 mm. The gelling agent contains epoxy resin, polyamide resin, and a solvent. The epoxy resin is a bisphenol A type epoxy resin, and the type of the bisphenol A type epoxy resin is E52(616); the type of the polyamide resin is PA610. The solvent is acetone. The material parameters of the hydroxyethyl cellulose are as follows: fineness 150-200 mesh, molar substitution ratio (MS) 1.8-2.0, pH value 6.0-8.5, viscosity 2 mPa·s. The density of acetone is 0.789 g / cm³. 3 (20℃), boiling range 1.0℃, acidity 0.003%, purity 99.0%, molar refractive index 15.97, molar volume 75.1 cm³ 3 / mol.

[0150] The strong barrier layer 4 is prepared through the following steps:

[0151] D1. Mix epoxy resin, polyamide resin and solvent to obtain a gelling agent;

[0152] D2. Mix hydroxyethyl cellulose, chelating agent, and gelling agent;

[0153] D3. Transfer the mixture of D2 to a high-pressure sprayer and spray it on the upper surface of the interactive shielding layer 5 to obtain the strong barrier layer 4. The high-pressure sprayer sprays 1 mm of the strong barrier layer 4 at a pressure of 0.4 MPa.

[0154] Specifically, D1 involves mixing epoxy resin, polyamide resin, and solvent in a mass ratio of 40:20:1 to obtain a gelling agent; D2 involves mixing hydroxyethyl cellulose, a chelating agent, and a gelling agent in a mass ratio of 1:5:25; and D3 involves transferring the mixture from D2 to a high-pressure sprayer and spraying it onto the upper surface of the interactive shielding layer 5 at a pressure of 0.4 MPa to obtain the strong barrier layer 4.

[0155] The interactive shielding layer 5 contains a binder and porous mineral particles. The binder is emulsified asphalt, and the evaporation residue content ranges from 58% to 65%. The porous mineral particles are zeolite or illite, and the fineness is 200 mesh to 300 mesh. The thickness of the interactive shielding layer 5 of this invention is 1 mm.

[0156] The interactive shielding layer 5 is prepared through the following steps:

[0157] E1. Mix the porous mineral particles and the binder, and then place the porous mineral particles and the binder under a shearing apparatus for shearing. The parameters of the shearing apparatus are: shearing at 160℃ and 5000rad / s for 20 minutes.

[0158] E2. Transfer the material from E1 to a high-pressure sprayer and spray it onto the upper surface of the outer substrate to obtain the interactive shielding layer 5. The high-pressure sprayer parameters are 0.6MPa pressure and a thickness of 1mm.

[0159] Specifically, E1 involves mixing porous mineral particles and a binder, with the porous mineral particles accounting for 20% of the binder's mass. The porous mineral particles and binder are then placed in a shearing apparatus and sheared at 160°C and 5000 rad / s for 20 minutes. E2 involves transferring the material from E1 to a high-pressure sprayer and spraying it onto the upper surface of the external substrate at a pressure of 0.6 MPa to obtain the interactive shielding layer 5.

[0160] Example 3

[0161] A heavy metal pollution isolation layer for waste fly ash-asphalt pavements, such as Figures 1 to 2As shown, a filter layer 1, a slow-release layer 2, a gel layer 3, a strong barrier layer 4, and an interactive shielding layer 5 are provided. The filter layer 1, the slow-release layer 2, the gel layer 3, the strong barrier layer 4, and the interactive shielding layer 5 are laid sequentially from top to bottom to obtain the heavy metal pollution isolation layer.

[0162] The gel layer 3 is composed of multiple layers of gel units stacked together. The gel layer 3 is 15 mm thick.

[0163] The gel unit layer consists of an adsorption structure 7 and a gel carrier 6. The adsorption structure 7 comprises a heavy metal chelating agent and microporous ceramic spheres, with the heavy metal chelating agent located inside the microporous ceramic spheres. The heavy metal chelating agent is a xanthate chelating agent produced by Suzhou Haonuo Industry & Trade Co., Ltd. The microporous ceramic spheres are composed of two hollow hemispherical honeycomb ceramic pieces, produced by Guangzhou Xinci Environmental Protection Materials Co., Ltd. The gel carrier 6 consists of component A liquid silica gel and component B liquid silica gel, both of which are RX-E650 type AB two-component liquid silica gel produced by Shenzhen Sicheng Silica Gel Co., Ltd., with a mass ratio of 10:1. The hollow hemispherical honeycomb ceramic pieces are made of porous cordierite, with parameters including a diameter of 3mm, a thickness of 100-120μm, a pore size of 12-270μm, a porosity of 32%-94%, and a compressive strength of 28-145MPa. After the gel carrier 6 of the present invention is cured, its density is 1.097 g / cm³. 3 It has a viscosity of 11000 cps, tensile strength ≥6.0 MPa, tear strength ≥16.7 kN / m, tensile strength at break ≥180%, hardness of 50±2A, and average pore size of 1.8-3.2 nm.

[0164] The adsorption structure 7 is prepared through the following steps:

[0165] A1. Two hollow hemispherical honeycomb ceramic pieces are bonded together to form a spherical structure. The spherical structure is then cooled and cured at room temperature for 4 hours to obtain the microporous ceramic spheres. Specifically, the bonding is performed automatically using a micro-volume automatic dispensing machine. The parameters of the micro-volume automatic dispensing machine are as follows: power 400W, voltage 220V, dispensing frequency 100 times / min, minimum dispensing time 0.001s, and repeatability ±0.01mm. The parameters of the precision injection equipment are: a micro-gear pump with a flow rate of 0.0015-9ml / min, viscosity range of 0.3-25000mPa·s, precision CV<1% (coefficient of variation), speed range of 1-6000rpm, maximum input pressure of 5bar, operating temperature of -20℃~150℃, and displacement of 1.5μl.

[0166] A2. The adsorption structure 7 is obtained by injecting a heavy metal trapping agent into the pores on the surface of the microporous ceramic spheres obtained in A1. Specifically, this is done using a precision injection device for 84 seconds.

[0167] The gel unit layer is prepared through the following steps:

[0168] B1. Apply a release agent, specifically petrolatum, to the inside of the mold. The release agent has the following parameters: density 0.84 g / cm³. 3 It has a melting point of 45-60℃, an oil content of 99%, and a penetration of 165mm at 25℃.

[0169] B2. Spray gel carrier 6 onto the mold, cool and solidify, and then lay the adsorption structure 7 on the surface of the gel carrier 6 to obtain a layer of adsorption structure 7 and a layer of gel carrier 6.

[0170] B3. Spray the gel carrier 6 onto the upper layer of the previous layer, cool and solidify it, and then lay the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0171] B4. Repeat step B3 until N layers are obtained, where N is 1 and is a positive integer;

[0172] B5. Spray gel carrier 6 onto the upper surface of the last layer, cool and solidify to obtain the gel unit layer.

[0173] B2 specifically involves spraying a 3mm thick layer of gel carrier 6 onto the mold, cooling and solidifying it, and then spreading the adsorption structure 7 evenly on the surface of the gel carrier 6, with a spreading density of 12 structures / cm². 2 A layer of adsorption structure 7 and gel carrier 6 is obtained.

[0174] Specifically, B3 involves spraying a 3mm thick gel carrier 6 onto the upper layer of the previous layer, cooling and curing it, and then laying the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0175] Specifically, B5 involves spraying a 3mm thick gel carrier 6 onto the upper surface of the last layer, cooling and curing it to obtain the gel unit layer.

[0176] Specifically, the gel layer 3 is prepared by layering gel unit layers with an adhesive between adjacent gel unit layers to obtain the gel layer 3. Finally, the gel is directly laid on the upper surface of the strong barrier layer 4 and compacted as a whole.

[0177] Filter layer 1 is composed of geotextile. The geotextile is polyester staple fiber geotextile, and its unit area mass ranges from 250 g / m². 2The thickness is 2mm. The geotextile is made of polyester staple fiber geotextile, and the unit area mass range is 250g / m². 2 The thickness is 2mm. The parameters of the polyester staple fiber geotextile are as follows: tensile strength ≥ 8.0KN / m, elongation 25%-100%, CBR bursting strength ≥ 1.2KN, equivalent pore size (090) 0.07-0.2mm, tear strength ≥ 0.20KN, and vertical permeability coefficient K×(10 -9 ~10 -12 (cm / s), where K=1.0~9.9. When using polyester staple fiber geotextile, it is cut to the required size with a cutter according to the road paving dimensions, and then directly laid on the surface of the slow-release layer 2.

[0178] The sustained-release layer 2 contains a gel, a controlled-release agent, component A (polyurea), and component B (polyurea); and the controlled-release agent is hydroxypropyl methylcellulose or methacrylic acid. The sustained-release layer 2 has a thickness of 2 mm. The gel is type A fine-porous silica gel with a particle size of 2 mm, an average pore size of 3.0 nm, and a specific surface area of ​​800 m². 2 / g, pore volume is 0.40ml / g, and adsorption capacity is 8% (RH=20%), 20% (RH=50%), and 30% (RH=90%). Component A is a polyurethane prepolymer containing diisocyanate groups. Component B is a mixture of amino-terminated polyether, liquid amine chain extender, pigment, filler, and additives; the parameters of component B are as follows: tensile strength ≥16MPa, elongation at break ≥450%, tear strength ≥50N / mm, and low-temperature bending ≤-40℃. It should be noted that both component A and component B are commercially available products. The component A and component B polyurea used in this embodiment are AB two-component polyurea produced by Jinan Jiuxu Company.

[0179] The sustained-release layer 2 is prepared through the following steps:

[0180] C1. Mix component A (polyurea), gel, and controlled-release agent according to the mass ratio to form component C;

[0181] C2. Using a high-pressure sprayer, component B (polyurea) and component C (obtained from C1) are simultaneously sprayed onto the upper surface of the gel layer 3 to obtain the sustained-release layer 2.

[0182] Specifically, C1 is formed by mixing component A (polyurea), gel, and controlled-release agent in a mass ratio of 2:1:1. Specifically, C2 is formed by simultaneously spraying component B (polyurea) and component C obtained from C1 onto the upper surface of the gel layer 3 using a high-pressure sprayer at a mass ratio of 1:1 and a pressure of 0.8 MPa, thus obtaining the controlled-release layer 2.

[0183] The strong barrier layer 4 contains hydroxyethyl cellulose, a chelating agent, and a gelling agent, wherein the chelating agent is diethyltriaminepentaacetic acid. The thickness of the strong barrier layer 4 is 2 mm. The gelling agent contains epoxy resin, polyamide resin, and a solvent. The epoxy resin is a bisphenol A type epoxy resin, and the type of the bisphenol A type epoxy resin is E51(618); the type of the polyamide resin is PA612. The solvent is acetone. The material parameters of the hydroxyethyl cellulose are as follows: fineness 150-200 mesh, molar substitution ratio (MS) 1.8-2.0, pH value 6.0-8.5, viscosity 2 mPa·s. The density of acetone is 0.789 g / cm³. 3 (20℃), boiling range 1.0℃, acidity 0.003%, purity 99.0%, molar refractive index 15.97, molar volume 75.1 cm³ 3 / mol.

[0184] The strong barrier layer 4 is prepared through the following steps:

[0185] D1. Mix epoxy resin, polyamide resin and solvent to obtain a gelling agent;

[0186] D2. Mix hydroxyethyl cellulose, chelating agent, and gelling agent;

[0187] D3. Transfer the mixture of D2 to a high-pressure sprayer and spray it on the upper surface of the interactive shielding layer 5 to obtain the strong barrier layer 4. The high-pressure sprayer sprays 2mm of the strong barrier layer 4 at a pressure of 0.6MPa.

[0188] Specifically, D1 involves mixing epoxy resin, polyamide resin, and solvent in a mass ratio of 40:20:1 to obtain a gelling agent; D2 involves mixing hydroxyethyl cellulose, a chelating agent, and a gelling agent in a mass ratio of 1:5:25; and D3 involves transferring the mixture from D2 to a high-pressure sprayer and spraying it onto the upper surface of the interactive shielding layer 5 at a pressure of 0.6 MPa to obtain the strong barrier layer 4.

[0189] The interactive shielding layer 5 contains a binder and porous mineral particles. The binder is emulsified asphalt with an evaporation residue content ranging from 65%. The porous mineral particles are zeolite or illite with a fineness of 300 mesh. The thickness of the interactive shielding layer 5 of this invention is 3 mm.

[0190] The interactive shielding layer 5 is prepared through the following steps:

[0191] E1. Mix the porous mineral particles and the binder, and then place the porous mineral particles and the binder under a shearing apparatus for shearing. The parameters of the shearing apparatus are: shearing at 160℃ and 5000rad / s for 20-30 minutes.

[0192] E2. Transfer the material from E1 to a high-pressure sprayer and spray it onto the upper surface of the outer substrate to obtain the interactive shielding layer 5. The high-pressure sprayer is set to spray a thickness of 3 mm at a pressure of 0.8 MPa.

[0193] Specifically, E1 involves mixing porous mineral particles and a binder, with the porous mineral particles comprising 30% of the binder mass. The porous mineral particles and binder are then placed in a shearing apparatus and sheared at 160°C and 5000 rad / s for 30 minutes. E2 involves transferring the material from E1 to a high-pressure sprayer and spraying it onto the upper surface of the external substrate at a pressure of 0.8 MPa to obtain the interactive shielding layer 5.

[0194] This heavy metal pollution isolation layer for waste fly ash-asphalt pavement can effectively block and shield the dissolution and migration of heavy metal elements through the synergistic effect of different layers in the heavy metal pollution isolation layer, ensuring the environmental protection and safety of waste fly ash in road engineering.

[0195] Example 4

[0196] A heavy metal pollution isolation layer for waste fly ash-asphalt pavements, such as Figures 1 to 2 As shown, a filter layer 1, a slow-release layer 2, a gel layer 3, a strong barrier layer 4, and an interactive shielding layer 5 are provided. The filter layer 1, the slow-release layer 2, the gel layer 3, the strong barrier layer 4, and the interactive shielding layer 5 are laid sequentially from top to bottom to obtain the heavy metal pollution isolation layer.

[0197] The first step is to prepare the interactive shielding layer 5.

[0198] The interactive shielding layer 5 contains a binder and porous mineral particles. The binder is PCR-modified emulsified asphalt with an evaporation residue content ranging from 58% to 65%. The porous mineral particles are activated zeolite with a fineness of 200-300 mesh. The thickness of the interactive shielding layer 5 in this invention is 2 mm.

[0199] The interactive shielding layer 5 is prepared through the following steps:

[0200] E1. Mix the porous mineral particles and the binder, and then place the porous mineral particles and the binder under a shearing apparatus for shearing. The parameters of the shearing apparatus are: shearing at 160℃ and 5000rad / s for 30 minutes.

[0201] E2. Transfer the material from E1 to a high-pressure sprayer and spray it onto the upper surface of the outer substrate to obtain the interactive shielding layer 5. The high-pressure sprayer parameters are 0.6-0.8MPa pressure and a thickness of 2mm.

[0202] The evaporation residue indicators of PCR-modified emulsified asphalt are as follows: content ≥60%, penetration (25℃, 100g, 5g) 45-100 (0.1mm), ductility at 5℃ ≥20cm, softening point ≥57℃, solubility ≥97.5%, and storage stability (5d) ≤5%. The activated zeolite has a size of 0.8-1.5mm and a density of 1.8-2.2g / cm³. 3 The filtration rate is 4-12 m / h, and the bulk density is 1.4 g / cm³. 3 Wear rate <0.4%, porosity ≥50%, breakage rate <0.5%, specific surface area 500-1100 m² 2 / g, with an exchange capacity of 2.2-2.5mg / g.

[0203] The shearing machine is a high-speed shearing emulsifier with the following technical parameters: power of 500W, voltage of 220V, processing capacity of 3-30L, and rotation speed of 300-1100rp / min.

[0204] The high-pressure sprayer is a trolley-type, rapid, sealed sprayer with the following technical parameters: spray flow rate of 10L / min, power of 220V, working pressure of 0.8MPa, and spraying speed of 6m / min. 2 / min, air consumption is 55r / min, pressure ratio is 6:1, no-load displacement is 45r / min.

[0205] The coating thickness of the interactive shielding layer 5 is controlled by an ultrasonic coating thickness gauge. The technical parameters of the ultrasonic coating thickness gauge are as follows: measurement range is 50-7600μm, measurement error is ±(3%H+20)μm, and display resolution is 1μm.

[0206] The second step is to prepare a strong barrier layer 4.

[0207] The strong barrier layer 4 contains hydroxyethyl cellulose, a chelating agent, and a gelling agent, wherein the chelating agent is ethylenediaminetetraacetic acid (EDTA). The thickness of the strong barrier layer 4 is 2 mm. The gelling agent contains epoxy resin, polyamide resin, and a solvent. The epoxy resin is a bisphenol A type epoxy resin, and the bisphenol A type epoxy resin is type E-51 (618) bisphenol A type epoxy resin; the polyamide resin is type PA650 polyamide resin. The solvent is acetone.

[0208] The strong barrier layer 4 is prepared through the following steps:

[0209] D1. Mix epoxy resin, polyamide resin and solvent in a mass ratio of 40:20:1 to obtain a gelling agent;

[0210] D2. Mix hydroxyethyl cellulose, chelating agent, and gelling agent in a mass ratio of 1:5:25;

[0211] D3. The mixture of D2 is transferred to a high-pressure sprayer and sprayed onto the upper surface of the interactive shielding layer 5 at a pressure of 0.4MPa to 0.6MPa to obtain the strong barrier layer 4. The high-pressure sprayer sprays a 2mm strong barrier layer 4 at a pressure of 0.5MPa.

[0212] The material parameters of hydroxyethyl cellulose are as follows: fineness of 150-200 mesh, molar substitution rate (MS) of 1.8-2.0, pH value of 6.0-8.5, and viscosity of 2 mPa·s.

[0213] The technical specifications of E-51(618) bisphenol A type epoxy resin are as follows: epoxy value 0.48-0.54eq / 100g, epoxy equivalent 184-210g / eq, saponified chlorine ≤0.70%, inorganic chlorine ≤300ppm, and volatile matter ≤1.8%.

[0214] The technical specifications of PA650 polyamide resin are as follows: amine value 205-225 mgKOH / g, relative density 0.97-0.99, viscosity 6000-12000 mPa·s (25℃), and activity level 190.

[0215] The technical specifications of acetone solvent are as follows: density is 0.789 g / cm³. 3 (20℃), boiling range 1.0℃, acidity 0.003%, purity 99.0%, molar refractive index 15.97, molar volume 75.1 cm³ 3 / mol.

[0216] The high-pressure sprayer is a high-pressure airless sprayer with the following technical parameters: spray width of 300mm, air consumption of 2200r / min, air inlet pressure of 0.5MPa, pressure ratio of 36:1, and no-load displacement of 4r / min.

[0217] The third step is to prepare the gel layer 3.

[0218] The gel layer 3 is composed of multiple layers of gel units stacked together. The gel layer 3 is 12mm to 15mm thick.

[0219] The gel unit layer consists of an adsorption structure 7 and a gel carrier 6. The adsorption structure 7 comprises a heavy metal chelating agent and microporous ceramic spheres, with the heavy metal chelating agent located inside the microporous ceramic spheres. The heavy metal chelating agent is a xanthate chelating agent produced by Suzhou Haonuo Industry & Trade Co., Ltd., and the honeycomb ceramic is produced by Guangzhou Xinci Environmental Protection Materials Co., Ltd. The microporous ceramic spheres are composed of two hollow hemispherical honeycomb ceramic pieces joined together. The gel carrier 6 consists of component A liquid silica gel and component B liquid silica gel, which are RX-E650 type AB two-component liquid silica gel produced by Shenzhen Sicheng Silica Gel Co., Ltd., with a mass ratio of 10:1.

[0220] The adsorption structure 7 is prepared through the following steps:

[0221] A1. Two hollow white spherical honeycomb ceramics are bonded together to form a spherical structure. The spherical structure is cooled and solidified at room temperature for 4 hours to obtain the microporous ceramic sphere.

[0222] A2. Heavy metal trapping agent is injected into the pores of the microporous ceramic spheres obtained in A1 to obtain the adsorption structure 7. Specifically, this is achieved using a precision injection device, with an injection time of 84 seconds, completing the preparation of one adsorption structure 7. The above steps are followed to prepare 1.1 × 10⁻⁶ spheres. 6 -1.2×10 6 Preparation of adsorption structure 7.

[0223] The gel unit layer is prepared through the following steps:

[0224] B1. Apply petroleum jelly to the four sides and bottom of the square aluminum alloy container using a 2-inch wool brush and an 8-inch wool brush respectively.

[0225] B2. Spray gel carrier 6 onto the mold. During spraying, use an ultrasonic coating thickness gauge to control the thickness of any 7 points on the surface of the liquid silicone to be 2mm ± 0.1mm. Then cool and solidify at room temperature for 30 minutes to complete the first step. Then spread the adsorption structure 7 on the surface of the gel carrier 6 to obtain a layer of adsorption structure 7 and a layer of gel carrier 6.

[0226] B3. Spray the gel carrier 6 onto the upper layer of the previous layer, cool and solidify it, and then lay the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0227] B4. Repeat step B3 until N layers are obtained, where N ≥ 1 and is a positive integer;

[0228] B5. Spray gel carrier 6 onto the upper surface of the last layer, cool and solidify to obtain the gel unit layer.

[0229] Specifically, B2 involves spraying a 2mm-3mm thick layer of gel carrier 6 onto the mold, cooling and solidifying it, and then spreading the adsorption structure 7 evenly on the surface of the gel carrier 6, with a spreading density of 12 structures / cm². 2 A layer of adsorption structure 7 and gel carrier 6 is obtained.

[0230] Specifically, B3 involves spraying a 2mm-3mm thick gel carrier 6 onto the upper layer of the previous layer, cooling and curing it, and then laying the adsorption structure 7 on the upper surface of the gel carrier 6 to obtain the lower layer.

[0231] Specifically, B5 involves spraying a 2mm-3mm thick gel carrier 6 onto the upper surface of the last layer, cooling and curing it to obtain the gel unit layer. According to the planar dimensions of the test specimen, the gel layer 3 unit is cut into 30cm×30cm×1.2cm gel unit layer specimens using a cutting machine.

[0232] Specifically, the gel layer 3 is prepared by layering gel unit layers with an adhesive between adjacent gel unit layers to obtain the gel layer 3. Finally, the gel is directly laid on the upper surface of the strong barrier layer 4 and compacted by a hand-held road roller.

[0233] The technical parameters of the micro-volume automatic dispensing machine are as follows: power is 400W, voltage is 220V, dispensing frequency is 100 times / min, minimum dispensing time is 0.001s, and repeatability is ±0.01mm; the precision injection equipment is a micro-gear pump with a flow rate of 0.0015-9ml / min, viscosity range of 0.3-25000mPa·s, precision CV<1% (coefficient of variation), speed range of 1-6000rpm, maximum input pressure of 5bar, operating temperature of -20℃~150℃, and displacement of 1.5μl.

[0234] The technical specifications of the epoxy resin structural adhesive are as follows: Grade A, density 1.6 g / cm³. 3 The viscosity is 3200 mPa·s, the tensile strength is 30 MPa, the shear strength is 25 MPa, the permeability index is 1, the film-forming time is 2 h, and the curing time is 4 h (room temperature).

[0235] The technical specifications of the hollow hemispherical honeycomb ceramic are as follows: the material is porous cordierite, the diameter is 3mm, the thickness is 100-120μm, the pore size is 12-270μm, the porosity is 32%-94%, and the compressive strength is 28-145MPa.

[0236] The technical parameters of xanthate chelating agents are as follows: active ingredient content is 99%, and specific gravity is 1.15 g / cm³. 3 The pH value is 9.3 (1% solution), and the usable pH range is 8-12.5.

[0237] The technical parameters of the micro gear pump are as follows: flow rate 0.0015-9 ml / min, viscosity range 0.3-25000 mPa·s, precision CV<1% (coefficient of variation), speed range 1-6000 rpm, maximum input pressure 5 bar, operating temperature -20℃~150℃, and displacement 1.5 μl.

[0238] The square aluminum alloy container measures 5000mm × 1000mm × 12mm and is made of 5005 grade five-series aluminum alloy.

[0239] The technical specifications of gel carrier 6 are as follows: density is 1.097 g / cm³. 3 It has a viscosity of 11000cps, tensile strength ≥6.0MPa, tear strength ≥16.7kN / M, tensile strength at break ≥180%, hardness after curing 50±2A, and average pore size of 1.8-3.2nm.

[0240] The technical specifications of petroleum jelly are as follows: density is 0.84 g / cm³. 3 It has a melting point of 45-60℃, an oil content of 99%, and a penetration of 165mm at 25℃.

[0241] The technical parameters of the high-pressure airless sprayer are as follows: spray width is 300mm, air consumption is 2200r / min, air inlet pressure is 0.5MPa, pressure ratio is 36:1, and no-load displacement is 4r / min.

[0242] The cutting machine is a gantry-type CNC plasma cutting machine with the following technical parameters: guide rail span is 2m, length is 5m, running accuracy is ±0.2mm, cutting speed is 0-10000mm / min, and lifting stroke is 200mm.

[0243] The technical parameters of the handheld road roller are as follows: the width of the vibrating wheel is 600mm, the diameter of the vibrating wheel is 426mm, the working weight is 1.6t, the vibration frequency is 70Hz, and the rated power is 8.6kw.

[0244] The fourth step is to prepare the sustained-release layer 2.

[0245] The sustained-release layer 2 contains a gel, a controlled-release agent, component A (polyurea), and component B (polyurea); and the controlled-release agent is hydroxypropyl methylcellulose or methacrylic acid. The thickness of the sustained-release layer 2 is 1 mm to 2 mm.

[0246] The sustained-release layer 2 is prepared through the following steps:

[0247] C1. Mix component A (polyurea, gel, and controlled-release agent) in a mass ratio of 2:1:1 to form component C, and stir evenly using a stirrer.

[0248] C2. At a mass ratio of 1:1 and a pressure of 0.6 MPa, component B (polyurea) and component C (obtained from C1) are simultaneously sprayed onto the upper surface of the gel layer 3 using a high-pressure sprayer to obtain a 2 mm thick release layer.

[0249] The gel is type A fine-porous silica gel with a particle size of 0.2-2 mm, an average pore size of 2.0-3.0 nm, and a specific surface area of ​​650-800 m².2 / g, with a pore volume of 0.35-0.40ml / g, and an adsorption capacity of 8% (RH=20%), 20% (RH=50%) and 30% (RH=90%).

[0250] The technical specifications of hydroxypropyl methylcellulose are as follows: density is 1.39 g / cm³. 3 The carbonization temperature is 280-300℃, and the specific gravity is 1.26-1.31.

[0251] Component A is a polyurethane prepolymer containing diisocyanate groups.

[0252] Component B polyurea is a mixture of amino-terminated polyether, liquid amine chain extender, pigment, filler, and additives; its tensile strength is ≥16MPa, elongation at break is ≥450%, tear strength is ≥50N / mm, and low-temperature bending performance is ≤-40℃. It should be noted that both component A and component B polyurea are commercially available products. In this embodiment, the component A and component B polyurea used are AB two-component polyurea produced by Jinan Jiuxu Company.

[0253] The agitator is a top-entry three-blade impeller agitator with the following technical parameters: power 1.1-55kW, shaft diameter range 51-237mm, applicable temperature ≤100℃, applicable pH range 3-13, and applicable chloride ion concentration ≤60000ppm.

[0254] The high-pressure spraying machine is a polyurea spraying machine, with the following technical specifications: heating power of 22kW, output voltage of 36MPa, hydraulic pressure of 6-18MPa, raw material output of 3-12kg / min, and air source of 0.5-0.8MPa. The coating thickness of the slow-release layer 2 is controlled by an ultrasonic coating thickness gauge.

[0255] Step 5: Prepare filter layer 1.

[0256] According to the planar dimensions of the test specimen, the polyester staple fiber geotextile was cut into 30cm×30cm pieces using a cutter, and then directly laid on the surface of the slow-release layer 2 to complete the preparation of the filter layer 1.

[0257] The technical specifications of the polyester staple fiber geotextile are as follows: Mass per unit area range is 250g / m². 2 The thickness is 2mm, the tensile strength is ≥8.0KN / m, the elongation is 25%-100%, the burst strength of CBR is ≥1.2KN, the equivalent pore size (090) is 0.07-0.2mm, the tear strength is ≥0.20KN, and the vertical permeability coefficient is K×(10-9~10-12)(cm / s), where K=1.0~9.9.

[0258] Example 5

[0259] A method for evaluating the performance of heavy metal contamination isolation layers, such as Figures 3 to 4 As shown, the process is as follows:

[0260] S1. Prepare cement concrete slabs;

[0261] S2. Prepare a heavy metal pollution isolation layer as in Examples 1-4 on the upper surface of the cement concrete slab obtained in S1.

[0262] S3. Cut out the cement concrete slab from S2 to obtain an intermediate specimen including a heavy metal pollution isolation layer and part of the cement concrete slab.

[0263] S4. Remove the cement concrete layer from the intermediate specimen and use the remaining heavy metal contamination isolation layer as the test specimen.

[0264] S5. Seal the four sides of the test specimen with wax 11, then place it in the middle chamber 13 of the test chamber and fix it with the positioning groove 12 of the test chamber.

[0265] S6. Use wax 11 to fill the gap between the test chamber wall above the positioning groove 12 and the test specimen until the wax 11 liquid level is flush with the upper surface of the test specimen.

[0266] S7. Cover the upper chamber 10 of the test chamber and close the output valve 15 at the bottom of the test chamber. Open the exhaust valve 8 at the top of the test chamber and inject the heavy metal leaching solution through the input valve 9 at the top of the test chamber until the liquid level reaches half the height of the scale line of the upper chamber 10. Close the exhaust valve 8 and then draw a vacuum through the input valve 9.

[0267] S8. Close the input valve 9, and then place the test chamber in a 60℃ constant temperature chamber for 12h~36h.

[0268] S9. Take 5ml of heavy metal leaching solution from the lower chamber 14 into test tube A, and take 5ml of heavy metal leaching solution from the upper chamber 10 into test tube B.

[0269] S10. Conduct a heavy metal leaching concentration test on the heavy metal leachates of test tube A and test tube B to obtain measurement data.

[0270] The measurement data include initial concentration C2, post-filtration concentration C1, concentration gradient ΔC, and heavy metal element isolation rate G. Initial concentration C2 is the relative concentration of heavy metals in the heavy metal leachate from test tube B, in μg / L. Post-filtration concentration C1 is the relative concentration of heavy metals in the heavy metal leachate from test tube A, in μg / L. Concentration gradient ΔC is the difference between post-filtration concentration C2 and initial concentration C1. Heavy metal element isolation rate G is the inhibitory effect of the heavy metal contamination isolation layer on the dissolution and infiltration of heavy metal elements. Heavy metal element isolation rate G is the ratio of ΔC to C2.

[0271] The dimensions of the cement concrete slab of this invention are 30cm × 30cm × 5cm.

[0272] The cement concrete slab of the present invention is prepared by mixing cement, medium sand, crushed stone and water in a mix ratio of 1:2:3:0.4.

[0273] Specifically, S3 involves using the center of the bottom surface of the cement concrete slab of S2 as the center of a 15cm × 15cm square, cutting this square to obtain an intermediate specimen that includes a heavy metal pollution isolation layer and part of the cement concrete slab.

[0274] The preparation method of heavy metal leachate is as follows: According to the "Solid Waste Leaching Toxicity Leaching Method Acetic Acid Buffer Solution Method" (HJ / T 300-2007), the fly ash-asphalt mortar and sulfuric acid-nitric acid mixed solution are mixed at a liquid-solid ratio of 10:1. Then, the mixture is placed in a horizontal shaker and shaken at an amplitude of 40 mm and a frequency of 110 times / minute for 8 hours. Finally, it is allowed to stand at room temperature for 16 hours to obtain the heavy metal leachate.

[0275] The performance evaluation method of the present invention defines four parameters, and the "heavy metal element isolation rate G" index can be used to accurately evaluate the blocking effect of the heavy metal pollution isolation layer.

[0276] Example 6

[0277] A method for evaluating the performance of heavy metal contamination isolation layers, such as Figures 3 to 4 As shown, the process is as follows:

[0278] S1. Preparation of cement concrete slabs: Specifically, prepare a thermosetting plastic mold with dimensions of 30cm×30cm×5cm. Apply a 2mm thick layer of oil-based release agent to the inside of the mold using a 2-inch wool brush. Prepare appropriate amounts of 325 grade cement, medium sand, crushed stone, and water according to a mix ratio of 1:2:3:0.4. Turn on the mixer, add the crushed stone, sand, and cement in sequence, and dry mix for 3 minutes. Then, slowly add the water and mix for 8 minutes. Remove the mixing pot and use a tamping rod to transfer the mixture from the pot into the mold. Then, tamp the mixture evenly in a spiral motion from the edge to the center 25 times. Use a rubber mallet to tap the four sides of the mold to expel internal air. Use a trowel to smooth the surface of the mold from the center to the edge. Cover the surface of the mold with a damp cloth and cure for 3 days at 20℃±5℃ and relative humidity greater than 50%. Demold the cement concrete slab to complete the preparation of the cement concrete slab.

[0279] S2. Prepare a heavy metal pollution isolation layer according to Example 4 on the upper surface of the cement concrete slab obtained in S1.

[0280] S3. Cut out the cement concrete slab from S2 to obtain an intermediate specimen including a heavy metal pollution isolation layer and part of the cement concrete slab; specifically, draw a square with a side length of 15cm×15cm in the center of the bottom surface of the cement concrete slab with a white marker, and then cut along the marker mark with a stone cutting machine to obtain an intermediate specimen including a heavy metal pollution isolation layer and part of the cement concrete slab.

[0281] S4. Remove the cement concrete layer from the intermediate specimen, and use the remaining heavy metal pollution isolation layer as the test specimen; take out the intermediate specimen with dimensions of 15cm×15cm×7cm; use a stone cutting machine to cut along the boundary line between the side heavy metal pollution isolation layer and the cement concrete slab, and retain the heavy metal pollution isolation layer as the test specimen.

[0282] S5. Seal the four sides of the test specimen with wax 11, and then place it in the middle chamber 13 of the test chamber and fix it with the positioning groove 12 of the test chamber; specifically, use a 2-inch wool brush to apply a 2mm thick layer of wax 11 to the four sides of the heavy metal pollution isolation layer to complete the preparation of the heavy metal pollution isolation layer test specimen.

[0283] S6. Use wax 11 to fill the gap between the test chamber wall above the positioning groove 12 and the test specimen until the wax 11 liquid level is flush with the upper surface of the test specimen; heat the No. 80 vacuum sealing wax 11 to a softened state.

[0284] S7. Cool and solidify at room temperature for 20 minutes, cover the upper chamber 10 of the test chamber, close the output valve 15 at the bottom of the test chamber, open the exhaust valve 8 at the top of the test chamber, inject the heavy metal leaching solution through the input valve 9 at the top of the test chamber until the liquid level reaches half the height of the scale line of the upper chamber 10, close the exhaust valve 8, and then draw a vacuum through the input valve 9.

[0285] S8. Close the input valve 9, and then place the test chamber in a 60℃ constant temperature chamber for 24 hours;

[0286] S9. Take 5ml of heavy metal leaching solution from the lower chamber 14 into test tube A, and take 5ml of heavy metal leaching solution from the upper chamber 10 into test tube B.

[0287] S10. Perform heavy metal leaching concentration tests on the heavy metal leachates from test tubes A and B to obtain measurement data. The heavy metal leaching concentration test specifically involves inductively coupled plasma mass spectrometry (ICP-MS).

[0288] The parameters of the raw materials and machines in S1 are as follows: the viscosity of the oil-based release agent is 21000 mPa·s, and the pH value is 7-8. The fineness modulus of the medium sand is 2.3-3.0, and the average particle size is 0.5-0.35 mm; the particle size of the crushed stone is 10 mm; and the water is ordinary tap water. The mixer is a single-shaft concrete mixer with the following technical parameters: maximum feed capacity is 96 L, maximum discharge capacity is 66 L, mixing shaft speed is 45 rpm, motor power is 2.2 kW, and working voltage is 380 V. The rubber mallet is a fiber-reinforced fine-handled mallet, with a specification of 3 lbs and a weight of 920 g. The trowel is a stainless steel trowel, 195 mm long and 90-100 mm wide.

[0289] The parameters of the raw materials and machines in S3-S5 are as follows: The technical parameters of the stone cutting machine are as follows: material is diamond, voltage is 380V, power is 3000W, no-load speed is 2800rpm, and cutting thickness is 450mm. The size of the test specimen for the heavy metal pollution isolation layer is 15cm×15cm×2cm. Wax 11 is No. 80 vacuum sealing wax 11, and its technical indicators are as follows: saturated vapor pressure (20℃) <10-6Pa, softening point ≥95℃, penetration (25℃, 100g) = 5~15 (0.1mm).

[0290] The parameters of each device in S6-S10 are as follows: Input valve 9 and output valve 15 are stainless steel shut-off valves. The upper chamber 10 is made of borosilicate glass. The middle chamber 13 and lower chamber 14 are fixedly connected and non-removable, both made of rigid PVC. The external dimensions of the middle chamber 13 are 21cm × 21cm × 3cm. The bottom of the positioning groove 12 is fixedly connected to the lower chamber 14, and the side is fixedly connected to the middle chamber 13. It is made of stainless steel and has a square annular shape with an internal hollow cube. The internal plane dimensions are 15.5cm × 15.5cm, the external plane dimensions are 20.5cm × 20.5cm, and the height is 1cm. The technical parameters of the rotary vane oil-sealed single-stage vacuum pump are as follows: pumping speed is 0.5L / s, ultimate pressure is 6Pa, motor power is 120W, and inlet inner diameter is 11mm. The syringe is a 20ml plastic syringe. The test tube is a 5ml disposable upright plastic sample tube.

[0291] The heavy metal leachate of this invention is prepared according to the "Solid Waste Leaching Toxicity Leaching Method - Acetic Acid Buffer Solution Method" (HJ / T300-2007). First, appropriate amounts of nitric acid and sulfuric acid are weighed into two clean beakers using an electronic balance at a mass ratio of 2:1. Then, sulfuric acid is guided into the beaker containing nitric acid using a glass rod to bring the pH of the acidic mixed solution to 3.0. Next, an appropriate amount of waste fly ash-asphalt mortar is weighed at a liquid-to-solid ratio of 10:1 and cooled in a -5°C freezer for 2.5 hours. The waste fly ash-asphalt mortar is then removed and placed in a mortar, where it is crushed with a pestle into particles with a particle size of 3 mm. These particles are added to the acidic solution and initially stirred with a glass rod. The mixed solution is then placed in a horizontal vibrator and vibrated at an amplitude of 40 mm and a frequency of 110 times / minute for 8 hours. Finally, it is cooled and allowed to stand at room temperature for 16 hours to obtain the heavy metal leachate.

[0292] The parameters of the raw materials and equipment used in the preparation of heavy metal leachate are as follows: The technical parameters of the electronic balance are: maximum weighing capacity 1200g, scale division 0.01g. The technical specifications of nitric acid are as follows: density 1.5g / cm³. 3 It has a melting point of -42℃ and a boiling point of 83℃. The technical specifications of sulfuric acid are as follows: density 1.83 g / cm³. 3 The melting point is 10.37℃ and the boiling point is 338℃. The waste fly ash-asphalt mortar is prepared by mixing waste fly ash and base asphalt at a mass ratio of 1:2. Its technical specifications are as follows: ductility at 10℃ is 6.43cm, penetration at 25℃ is 3.65mm, and softening point is 60.2℃. The mortar and pestle are both made of stainless steel, with the mortar measuring 50mm × 50mm × 170mm and weighing 5kg. The technical parameters of the horizontal vibrator are as follows: rated power is 80W, oscillation frequency is 0-200rpm, oscillation amplitude is 40mm, and timing time is 0-9999h.

[0293] The measurement data in this embodiment are the initial concentration C2, the filtration concentration C1, the concentration gradient ΔC, and the heavy metal element isolation rate G.

[0294] The initial concentration C2 is the relative concentration of heavy metals in the heavy metal leachate from test tube B, in μg / L.

[0295] The filtration concentration C1 is the relative concentration of heavy metals in the heavy metal leachate from test tube A, expressed in μg / L.

[0296] The concentration gradient ΔC is the difference between the initial concentration C2 and the filtration concentration C1, i.e., ΔC = C2 - C1, with units of μg / L.

[0297] The heavy metal element isolation rate G is the effect of the heavy metal pollution isolation layer on the infiltration of heavy metal elements. Specifically, it is the ratio of ΔC to C2, i.e., G=ΔC / C2. The magnitude of the heavy metal element isolation rate G is related to the heavy metal element isolation effect of the isolation layer. The larger the G value, the better the isolation effect of the heavy metal pollution isolation layer.

[0298] Example 7

[0299] A method for evaluating the performance of a heavy metal contamination isolation layer, wherein the other steps are the same as in Example 6, except that:

[0300] In S2, the heavy metal trapping agent inside the adsorption structure 7 of the heavy metal pollution isolation layer is a dithiocarbamate derivative. The technical specifications of the dithiocarbamate derivative are as follows: 100% effective substance content, and a pH range of 4-9.

[0301] Example 8

[0302] A method for evaluating the performance of a heavy metal contamination isolation layer, wherein the other steps are the same as in Example 6, except that:

[0303] In S2, the slow-release layer 2 is in the heavy metal pollution isolation layer, and the coating thickness of the slow-release layer 2 is 1 mm.

[0304] Comparative Example 1

[0305] A method for evaluating the performance of a heavy metal contamination isolation layer, the other steps of which are the same as in Example 6, except that:

[0306] In S2, the gel layer 3 in the heavy metal pollution isolation layer only has a gel carrier 6 and no adsorption structure 7.

[0307] The specific method for gel unit layer is as follows:

[0308] Vaseline was applied to the four sides and bottom of a square aluminum alloy container using 2-inch and 8-inch wool brushes, respectively. Liquid silicone components A and B were mixed at a 10:1 mass ratio and placed in a high-pressure sprayer. A 12mm thick gel carrier 6 was sprayed using a high-pressure airless sprayer. During spraying, an ultrasonic coating thickness gauge was used to control the thickness of any 7 points on the liquid silicone surface to be 2mm ± 0.1mm. The mixture was then cooled and cured at room temperature for 30 minutes, completing the preparation of one gel layer unit (3 units).

[0309] Comparative Example 2

[0310] A method for evaluating the performance of a heavy metal pollution isolation layer, with other steps being the same as in Example 6, except that: in this comparative example, a cement concrete layer is directly used as the test specimen.

[0311] The test specimens were prepared as follows:

[0312] Prepare a thermosetting plastic mold measuring 15cm×15cm×2cm; apply a 2mm thick layer of oil-based release agent to the inside of the mold using a 2-inch wool brush; prepare appropriate amounts of 325 grade cement, medium sand, crushed stone, and water according to a mix ratio of 1:2:3:0.4; turn on the mixer, add the crushed stone, sand, and cement in sequence and dry mix for 3 minutes, then slowly add the water and mix for 8 minutes; remove the mixing pot, transfer the mixture from the mixing pot to the mold using a tamping rod, and then evenly insert and pump the tamping rod 20 times in a spiral motion from the edge to the center; tap the four sides of the mold with a rubber mallet to expel internal air; smooth the surface of the mold from the center to the edge with a trowel; cover the surface of the mold with a damp cloth and cure for 2 days at 20℃±5℃ and relative humidity greater than 50%; demold the cement concrete layer to complete the preparation of the cement concrete layer test specimen.

[0313] The oil-based release agent has a viscosity of 21000 mPa·s and a pH value of 7-8. The fineness modulus of the medium sand is 2.3-3.0, and the average particle size is 0.5-0.35 mm; the particle size of the crushed stone is 10 mm; and the water is ordinary tap water. The mixer is a single-shaft concrete mixer with the following technical parameters: maximum feed capacity of 96 L, maximum discharge capacity of 66 L, mixing shaft speed of 45 rpm, motor power of 2.2 kW, and working voltage of 380 V. The rubber mallet is a fiber-reinforced fine-handled mallet, with a specification of 3 lbs and a weight of 920 g. The trowel is a stainless steel trowel, 195 mm long and 90-100 mm wide.

[0314] Table 1. Results of heavy metal leaching concentration tests and performance evaluations in Examples 6-8 and Comparative Examples 1-2.

[0315]

[0316] The specific standard mentioned in Table 1 is the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB 5085.3-2007). Comparing the filtration concentration C1 with the standard limit in Table 1, it can be found that the Pb leaching concentration of Comparative Example 2 exceeds the standard limit, while all others meet the standard limits.

[0317] As shown in Table 1, the isolation rates G for the four heavy metal elements in Examples 6 and 7 were 88%-90%, the isolation rate G for the four heavy metal elements in Example 8 was 80%-85%, the isolation rate G for the four heavy metal elements in Comparative Example 1 was 75%-79%, and the isolation rate G for the four heavy metal elements in Comparative Example 2 was 29%-33%. The isolation effect of the five specimens on the leaching of heavy metal elements, from largest to smallest, is as follows: Example 6 ≈ Example 7 > Example 8 > Comparative Example 1 > Comparative Example 2.

[0318] Examples 6 and 7 showed similar isolation effects on heavy metal elements, indicating that both heavy metal trapping agents (xanthate chelating agents and dithiocarbamate derivatives) have a strong inhibitory effect on the leaching of heavy metal elements. The difference between Examples 6 and 8 lies in the thickness of the controlled-release layer 2. In Example 8, the thickness of the controlled-release layer 2 is 1 mm, while in Example 6 it is 2 mm. The inhibitory effect of Example 8 is slightly worse than that of Example 6, indicating that a greater thickness of the controlled-release layer 2 results in a better barrier effect against heavy metal contamination.

[0319] Comparing Example 6 and Comparative Example 1, the difference lies in whether the gel layer 3 has an adsorption structure 7. The gel layer 3 of Example 6 contains an adsorption structure 7, but Comparative Example 1 does not. Furthermore, the blocking effect of Comparative Example 1 is worse than that of Example 6, with a difference of 10%-15%. This indicates that the adsorption structure 7 has a significant inhibitory effect on the leaching of heavy metals.

[0320] Comparing Example 6 and Comparative Example 2, the difference lies in the test specimens used in the heavy metal leaching test. Example 6 uses a heavy metal pollution isolation layer, while Comparative Example 2 uses a cement concrete layer of the same thickness. The isolation effect of Comparative Example 2 is much lower than that of Example 6, indicating that the cement concrete layer has a weak inhibitory effect on heavy metal leaching.

[0321] In summary, this invention comprises a heavy metal pollution isolation layer consisting of a filter layer 1, a slow-release layer 2, a gel layer 3, a strong barrier layer 4, and an interactive shielding layer 5. Through the synergistic effect of multiple layers, it can effectively inhibit and shield the dissolution and migration of heavy metal elements from the road surface and upper base layer, thereby ensuring that fly ash from waste can be safely used as a renewable resource in road engineering. Furthermore, the performance evaluation method of this invention defines four parameters: initial concentration C2, post-filtration concentration C1, gradient concentration ΔC, and heavy metal element isolation rate G. The indicator "heavy metal element isolation rate G" enables an accurate evaluation of the heavy metal pollution isolation layer's blocking effect.

[0322] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A heavy metal pollution isolation layer for waste fly ash-asphalt pavement, characterized in that: The heavy metal pollution isolation layer is provided with a filter layer, a slow-release layer, a gel layer, a strong barrier layer and an interactive shielding layer, and the filter layer, the slow-release layer, the gel layer, the strong barrier layer and the interactive shielding layer are laid from top to bottom to obtain the heavy metal pollution isolation layer; The gel layer is composed of multiple layers of gel units stacked together; the gel unit layer is composed of an adsorption structure and a gel carrier; the adsorption structure is composed of a heavy metal catching agent and microporous ceramic spheres, and the heavy metal catching agent is located inside the microporous ceramic spheres. The filter layer is made of geotextile; The sustained-release layer contains a gel, a controlled-release agent, component A polyurea, and component B polyurea; and the controlled-release agent is hydroxypropyl methylcellulose or methacrylic acid. The high-strength barrier layer contains hydroxyethyl cellulose, a chelating agent, and a gelling agent, wherein the chelating agent is ethylenediaminetetraacetic acid or diethyltriaminepentaacetic acid; and the gelling agent contains epoxy resin, polyamide resin, and a solvent. The interactive shielding layer contains a binder and porous mineral particles.

2. The heavy metal pollution isolation layer for fly ash-asphalt pavement according to claim 1, characterized in that, The adsorption structure is prepared by the following steps: A1. Two hollow hemispherical honeycomb ceramic pieces are bonded together to form a spherical structure, and the spherical structure is cooled and solidified at room temperature to obtain the microporous ceramic sphere. A2. The adsorption structure is obtained by injecting a heavy metal trapping agent into the pores on the surface of the microporous ceramic spheres obtained in A1. The gel unit layer is prepared through the following steps: B1. Apply release agent to the inside of the mold; B2. Spray the gel carrier onto the mold, cool and solidify it, and then lay the adsorption structure flat on the surface of the gel carrier to obtain a layer of adsorption structure and a layer of gel carrier. B3. Spray a gel carrier onto the upper layer of the previous layer, cool and solidify it, and then lay the adsorption structure on the upper surface of the gel carrier to obtain the lower layer. B4. Repeat step B3 until N layers are obtained, where N ≥ 1 and is a positive integer; B5. Spray a gel carrier onto the upper surface of the last layer, cool and solidify to obtain the gel unit layer; The specific method for preparing the gel layer is as follows: the gel unit layer is stacked with an adhesive between adjacent gel unit layers to obtain the gel layer, and finally the gel layer is directly laid on the upper surface of the strong barrier layer and compacted as a whole.

3. The heavy metal pollution isolation layer for fly ash-asphalt pavement according to claim 2, characterized in that, The sustained-release layer is prepared by the following steps: C1. Mix component A (polyurea), gel, and controlled-release agent according to the mass ratio to form component C; C2. Using a high-pressure sprayer, component B (polyurea) and component C (obtained from C1) are simultaneously sprayed onto the upper surface of the gel layer to obtain the sustained-release layer. The high-strength barrier layer is prepared by the following steps: D1. Mix epoxy resin, polyamide resin and solvent to obtain a gelling agent; D2. Mix hydroxyethyl cellulose, chelating agent, and gelling agent; D3. Transfer the mixture of D2 to a high-pressure sprayer and spray it onto the upper surface of the interactive shielding layer to obtain the strong barrier layer; The interactive shielding layer is prepared through the following steps: E1. Mix the porous mineral particles and the binder, and then place the porous mineral particles and the binder under a shearing device to shear them. E2. Transfer the material from E1 to a high-pressure sprayer and spray it onto the upper surface of the outer substrate to obtain the interactive shielding layer.

4. The heavy metal pollution isolation layer for fly ash-asphalt pavement according to claim 3, characterized in that: Specifically, B2 involves spraying a 2mm-3mm thick gel carrier onto a mold, cooling and solidifying it, and then spreading the adsorption structure evenly on the surface of the gel carrier, with a spreading density of 11 adsorption structures / cm². 2 ~12 pieces / cm 2 This yields a layer of adsorption structure and a layer of gel carrier. Specifically, B3 involves spraying a 2mm-3mm thick gel carrier onto the upper layer of the previous layer, cooling and solidifying it, and then spreading the adsorption structure on the upper surface of the gel carrier to obtain the lower layer. Specifically, B5 involves spraying a 2mm-3mm thick gel carrier onto the upper surface of the last layer, cooling and solidifying it to obtain the gel unit layer. Specifically, component C1 is formed by mixing component A (polyurea), gel, and controlled-release agent in a mass ratio of 2:1:

1. Specifically, C2 is obtained by simultaneously spraying component B (polyurea) and component C (obtained from C1) onto the upper surface of the gel layer using a high-pressure sprayer at a mass ratio of 1:1 and a pressure of 0.6-0.8 MPa, to obtain the sustained-release layer. Specifically, D1 is a gelling agent obtained by mixing epoxy resin, polyamide resin and solvent in a mass ratio of 40:20:

1. Specifically, D2 is a mixture of hydroxyethyl cellulose, chelating agent, and gelling agent in a mass ratio of 1:5:

25. Specifically, D3 involves transferring the mixture of D2 to a high-pressure sprayer and spraying it onto the upper surface of the interactive shielding layer at a pressure of 0.4MPa to 0.6MPa to obtain the strong barrier layer. E1 specifically involves mixing porous mineral particles and cementitious material, with the mass of porous mineral particles being 20% ​​to 30% of the mass of cementitious material. The porous mineral particles and cementitious material are then placed in a shearing apparatus and sheared at 160°C and 5000 rad / s for 20 to 30 minutes. Specifically, E2 involves transferring the material from E1 into a high-pressure sprayer and spraying it onto the upper surface of the outer substrate at a pressure of 0.6MPa to 0.8MPa to obtain the interactive shielding layer.

5. The heavy metal pollution isolation layer for fly ash-asphalt pavement according to claim 4, characterized in that: The binder is emulsified asphalt, and the content of evaporation residue ranges from 58% to 65%. The porous mineral particles are zeolite or illite, and the fineness is 200 mesh to 300 mesh; The epoxy resin is a bisphenol A type epoxy resin, and the polyamide resin is of type PA610, PA612, PA46 or PA650. The solvent is acetone; The heavy metal chelating agent is a dithiocarbamate derivative or a xanthate chelating agent. The gel carrier is composed of liquid silica gel component A and liquid silica gel component B, with a mass ratio of 10:

1. The geotextile is a polyester staple fiber geotextile with a unit area mass range of 250 g / m². 2 The thickness is 2mm; The thickness of the interactive shielding layer is 1mm to 3mm; The thickness of the high-strength barrier layer is 1mm to 2mm; The thickness of the gel layer is 12mm to 15mm.

6. A method for evaluating the performance of a heavy metal contamination isolation layer, characterized in that, This can be done through the following steps: S1. Prepare cement concrete slabs; S2. Prepare a heavy metal pollution isolation layer as described in any one of claims 1 to 5 on the upper surface of the cement concrete slab obtained in S1; S3. Cut the cement concrete slab from S2 to obtain an intermediate specimen that includes a heavy metal pollution isolation layer and part of the cement concrete slab. S4. Remove the cement concrete layer from the intermediate specimen and use the remaining heavy metal contamination isolation layer as the test specimen. S5. Seal the four sides of the test specimen with wax, then place it in the middle of the test chamber and fix it with the positioning groove of the test chamber. S6. Use wax to fill the gap between the test chamber wall above the positioning groove and the test specimen until the wax level is flush with the upper surface of the test specimen. S7. Cover the upper chamber of the test chamber and close the output valve at the bottom of the test chamber. Open the exhaust valve at the top of the test chamber and inject heavy metal leaching solution through the input valve at the top of the test chamber until the liquid level reaches half the height of the upper chamber scale. Close the exhaust valve and then draw a vacuum through the input valve. S8. Close the input valve, and then place the test chamber in a 60℃ constant temperature chamber for 12h~36h. S9. Take 5ml of heavy metal leaching solution from the lower compartment into test tube A, and take 5ml of heavy metal leaching solution from the upper compartment into test tube B. S10. Conduct a heavy metal leaching concentration test on the heavy metal leachates of test tube A and test tube B, and obtain measurement data. The cement concrete slab is prepared by mixing cement, sand, gravel and water in a mix ratio of 1:2:3:0.

4.

7. The performance evaluation method for the heavy metal pollution isolation layer according to claim 6, characterized in that: The measurement data are the initial concentration C2, the filtered concentration C1, the concentration gradient ΔC, and the heavy metal element isolation rate G; The initial concentration C2 is the relative concentration of heavy metals in the heavy metal leachate of test tube B, in μg / L. The filtration concentration C1 is the relative concentration of heavy metals in the heavy metal leachate of test tube A, in μg / L. The concentration gradient ΔC is the difference between the initial concentration C2 and the filtered concentration C1; The heavy metal element isolation rate G is the effect of the heavy metal pollution isolation layer on the infiltration and dissolution of heavy metal elements. The isolation rate G of the heavy metal elements is the ratio of ΔC to C2.

8. The performance evaluation method for the heavy metal pollution isolation layer according to claim 7, characterized in that: The dimensions of the cement concrete slab are 30cm × 30cm × 5cm; Specifically, S3 involves using the center of the bottom surface of the cement concrete slab in S2 as the center of a 15cm × 15cm square, cutting the square to obtain an intermediate specimen including a heavy metal pollution isolation layer and part of the cement concrete slab. The preparation method of the heavy metal leachate is as follows: According to the "Solid Waste Leaching Toxicity Leaching Method Acetic Acid Buffer Solution Method" (HJ / T 300-2007), the fly ash-asphalt mortar and sulfuric acid-nitric acid mixed solution are mixed at a liquid-solid ratio of 10:1, and then placed in a horizontal shaker and shaken at an amplitude of 40 mm and a frequency of 110 times / minute for 8 hours. Finally, it is allowed to stand at room temperature for 16 hours to obtain the heavy metal leachate.

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