A method for studying migration and aggregation behavior of heavy metal elements in fly ash in asphalt binder

Abstract

This invention discloses a method for studying the migration and aggregation behavior of heavy metal elements in asphalt binders from waste fly ash. The method includes the following steps: preparing waste fly ash-asphalt characterization specimens; locating and delineating the micro-regions at the contact interface between fly ash and asphalt binder; analyzing the occurrence state of heavy metal elements in the micro-regions at the contact interface; defining and analyzing the migration distance and attenuation rate of heavy metal elements, and determining the key asphalt components based on the element migration inhibition effect; analyzing the migration distance and aggregation area of ​​heavy metal elements in composite materials of key components and ordinary components to clarify the synergistic inhibition effect of asphalt on the migration of heavy metal elements under multi-component fusion. This research method, based on microscopic analysis, accurately clarifies the migration law of heavy metal elements in waste fly ash within asphalt binders at the mechanistic level, providing a reference for the resource utilization of hazardous waste materials such as waste fly ash in asphalt pavements.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, specifically to a method for studying the migration and aggregation behavior of heavy metal elements in asphalt binders from waste fly ash. Background Technology

[0002] With the rapid urbanization in my country, the amount of waste generated has surged. This increase highlights the shortcomings of insufficient end-of-life treatment capacity, leaving many cities facing the predicament of being "besieged by garbage." In recent years, waste incineration, as an effective method for the harmless treatment of waste, has gradually become the main technological means in the field of waste management. Waste incineration can reduce the volume and harmlessly dispose of urban waste, but 20%-30% still remains in the slag and fly ash after incineration. The leaching of heavy metals such as Zn, Pb, Cr, and Cu contained in the fly ash can cause secondary pollution to the environment. Therefore, the proper disposal of waste incineration fly ash is of crucial significance for ecological and environmental protection.

[0003] Waste incineration fly ash possesses characteristics such as good thermal stability, large specific surface area, porosity, and strong alkalinity. Its fineness is similar to that of mineral powder, allowing for thorough interaction with asphalt binders and exhibiting excellent bonding effects, thus providing feasibility for its application as a filler in asphalt pavement materials. In road surface materials, asphalt, with its high viscosity and chemical stability, acts as a binder when mixed with waste incineration fly ash. Through selective adsorption, physical and chemical reactions, it achieves a coating and sealing effect on fly ash particles, effectively stabilizing and inhibiting the migration and dissolution of heavy metal elements in the fly ash. However, the influencing factors and mechanisms of the asphalt medium's inhibitory effect on heavy metal elements remain unclear, hindering the scientific basis for effectively improving and controlling its inhibitory efficiency. Therefore, proposing research methods for studying the migration and aggregation behavior of heavy metal elements in waste fly ash within asphalt binders is crucial for the resource utilization of waste fly ash in asphalt pavement materials. Summary of the Invention

[0004] The purpose of this invention is to provide a method for studying the migration and aggregation behavior of heavy metal elements in asphalt binders from waste fly ash, clarifying the migration patterns of heavy metal elements in waste fly ash within asphalt binders at the mechanistic level, so as to promote the resource utilization of hazardous waste materials such as waste fly ash in civil engineering materials. The specific scheme is as follows:

[0005] A method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash includes the following steps:

[0006] B1. Prepare characterization specimens of fly ash-asphalt binder and locate the micro-region of the contact interface between fly ash and asphalt binder;

[0007] B2. Delineate the micro-region range of the contact interface and analyze the occurrence state of heavy metal elements in the micro-region of the contact interface between waste fly ash and asphalt binder.

[0008] B3. Analyze the migration distance and attenuation rate of heavy metal elements in the micro-region of the contact interface to determine the key components of asphalt based on the element migration retardation effect;

[0009] B4. Based on the key component, analyze the migration distance and aggregation area of ​​heavy metal elements in the composite material of key component + ordinary component, and clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion.

[0010] In a method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash provided in an embodiment of the present invention, the preparation of waste fly ash-asphalt characterization specimens is specifically as follows:

[0011] Weigh 3-5g of waste fly ash and spread it evenly in a steel pan with dimensions of 100mm×100mm;

[0012] Apply hot melt black double-sided tape to the surface of a 76mm×26mm glass slide, and then insert the glass slide into a steel tray containing waste fly ash.

[0013] After removing the slide, brush away any unadheded fly ash from the surface. Then, use a magnifying glass to obtain individual fly ash particles in the marked field of view. Cut out the individual fly ash particles and a square area within a 5mm×5mm radius around them and save them for later use.

[0014] Heat the asphalt binder to a molten state and pour it evenly onto a pre-insulated glass slide measuring 76mm x 26mm. Then, place a black rubber strip with individual fly ash particles on the surface of the molten asphalt. After the hot-melt black rubber strip has completely melted into the asphalt, place it in a ventilated place to cool naturally.

[0015] The location of individual fly ash particles in the asphalt mortar specimen was marked with a white marker pen.

[0016] The thickness of the asphalt mastic specimen was controlled to be 30-50 μm using a thickness tester. Then, the asphalt mastic specimen was sliced ​​using a low-temperature cryostat with a planar size of 5 mm × 5 mm. The resulting asphalt mastic slice specimen was used as a characterization specimen of waste fly ash-asphalt mastic.

[0017] The asphalt binder can be a base asphalt or a modified asphalt, or other binding materials.

[0018] The aforementioned cryostat is a cryomicrotome with a diamond-tipped blade and a cutting speed of 1-3 mm / s.

[0019] The thickness tester is a laser thickness tester with a testing accuracy of ±0.4μm. The thickness test is limited to the difference between the thickness test results of any 10 measuring points being within 1μm, and the distance between any two of the 10 measuring points should be greater than 0.15mm.

[0020] In the method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder provided in this embodiment of the invention, the micro-region of the contact interface between fly ash and asphalt binder is located, specifically as follows:

[0021] Gold spraying treatment was applied to the characterization specimens of waste fly ash-asphalt mortar.

[0022] The approximate location of individual fly ash particles was dynamically scanned using a focused ion beam scanning electron microscope (FIB-SEM) to determine the precise location of the fly ash particles and the micro-regions at their interface with asphalt.

[0023] Next, a micro-EDXRF instrument was used to visualize and characterize the elemental composition at this location to verify the accuracy of the marking, thereby locating the micro-region at the interface between the fly ash and the asphalt binder.

[0024] The purpose of sputtering gold onto the asphalt mastic specimens is to improve their conductivity in order to ensure the quality of microscopic imaging.

[0025] In the method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder provided in this embodiment of the invention, the contact interface is characterized by dividing the micro-region range and analyzing the occurrence state of heavy metal elements in the micro-region of the contact interface between waste fly ash and asphalt binder. Specifically:

[0026] The range of 10μm-20μm between the inner and outer sides of the contact interface micro-region perpendicular to the vertical line of the contact interface micro-region is defined as the contact interface characterization micro-region range.

[0027] Micro-EDXRF was used to perform elemental mapping scans on the characterization areas of the waste fly ash-asphalt cementitious specimens. For the inner and outer sides of the micro-region of the contact interface, high-precision elemental mapping was used to quantify the elemental distribution of waste fly ash particles and asphalt binder. The relative content of heavy metal elements at 1μm intervals in the characterization micro-region of the contact interface was quantified by combining line scanning.

[0028] Based on the changing trends of the relative content of heavy metal elements, the migration distance L and migration attenuation rate V of heavy metals are determined to clarify the migration process of heavy metal elements in the process of changing attachment carriers.

[0029] The inner side of the contact interface micro-region faces the fly ash and is perpendicular to the vertical line of the contact interface micro-region, while the outer side of the contact interface micro-region faces the asphalt binder and is perpendicular to the vertical line of the contact interface micro-region.

[0030] The heavy metal migration distance L is defined as the distance between the point on the straight line where the relative content of heavy metal elements is less than 0.001% and the fly ash particles of the waste.

[0031] The migration decay rate V is defined as the slope of the regression line of the point where the relative content of heavy metal elements changes on the linear scan line.

[0032] In the method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash provided in this embodiment of the invention, the key asphalt components based on the element migration retardation effect are identified, specifically:

[0033] Preparation of specimens of key components in asphalt;

[0034] The contact interface micro-regions of the key components of asphalt specimens were located and marked.

[0035] Analysis of the occurrence state of heavy metal elements in the key components of asphalt specimens;

[0036] Based on the relative content variation trend of heavy metal elements, the migration distance L and migration attenuation rate V of heavy metals are determined. By comparing and analyzing the migration distance L and migration attenuation rate V of different components, the key components of asphalt based on the element migration hindrance effect are identified.

[0037] The method for preparing specimens of key components of asphalt is as follows: According to Chinese standard NB / SH / T 0509-2101, the four components of asphalt binder are separated using the SARA method to obtain asphaltene (At), saturated component (S), aromatic component (Ar), and resin (R); for solid At and R, At and R are prepared into a mixture of waste fly ash-At or waste fly ash-R using a dissolution-evaporation method, and then the micro-regions at the contact interface are located and marked; for viscous S and Ar, S or Ar is poured onto the surface of a glass slide, and then waste fly ash particles are sprinkled on the surface of S or Ar. After the waste fly ash particles are stably integrated into the interior of S or Ar, the micro-regions at the contact interface are located and marked.

[0038] The dissolution-evaporation method is as follows: At or R is added to CS2 to dissolve into a solution, and a certain amount of waste fly ash is added. Then, CS2 is removed by constant temperature evaporation to obtain waste fly ash-At or waste fly ash-R mixture specimens. The purpose of this method is to avoid the problem of asphalt thermal aging.

[0039] The method for locating and marking the micro-area of ​​the contact interface is the same as the method for locating the micro-area of ​​the contact interface between fly ash and asphalt binder described in step B1.

[0040] The method for analyzing the heavy metal occurrence state of the specimen is the same as the method for analyzing the heavy metal element occurrence state of the micro-region at the interface between waste fly ash and asphalt binder described in step B2.

[0041] In the method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder provided in this invention embodiment, based on the key component, the migration distance and aggregation area of ​​heavy metal elements in the composite material of key component + ordinary component are analyzed to clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion, specifically:

[0042] Based on the key components of asphalt determined in step B3, the key component (G) is used as the main component and mixed with the other three common components (F) in the combination of G+F and G+F+F respectively; then, waste fly ash is added to the mixture to obtain the corresponding composite material.

[0043] Locate and label the micro-regions at the contact interface of the composite material;

[0044] To compare the heavy metal occurrence states of composite materials under different combination methods, so as to clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion.

[0045] The method for locating and marking the micro-area of ​​the contact interface of the composite material is the same as the method for locating the micro-area of ​​the contact interface between fly ash and asphalt binder described in step B1.

[0046] The method for comparing the heavy metal occurrence state of composite materials under different combinations is the same as the method for analyzing the heavy metal element occurrence state of the micro-region at the interface between waste fly ash and asphalt binder described in step B2.

[0047] The above application methods have a strict order of preparation, detection and evaluation. Improper method steps will seriously affect the characterization results.

[0048] Compared with existing technologies, the advantages of this invention lie in the construction of research indicators and evaluation systems for the migration behavior of heavy metal elements in waste incineration fly ash within asphalt binders. This allows for accurate analysis of the migration behavior and distribution characteristics of heavy metal elements in waste fly ash within asphalt binders. Based on this, the inhibitory effects of different asphalt components on heavy metal elements in waste fly ash are clarified, further revealing the migration inhibition mechanism of heavy metal elements under the coupling effect of different components in asphalt. The evaluation indicators and methods of this approach can establish the correlation between microscopic indicators and macroscopic effects, thus providing a basis for evaluating the migration inhibition effects of different types of asphalt binders on heavy metal elements in waste fly ash, and providing theoretical basis and technical support for the resource utilization of waste fly ash in road engineering. Attached Figure Description

[0049] Figure 1 This is a flowchart of the technical solution of the present invention.

[0050] Figure 2 This is a schematic diagram illustrating the characterization range of heavy metals in the micro-region at the contact interface according to the present invention.

[0051] Figure 3 This is a schematic diagram illustrating the calculation of the migration micro-distance and migration attenuation rate of heavy metal elements in this invention. Detailed Implementation

[0052] The present invention will be further described below with reference to embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0053] Unless otherwise specified, the reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in this technical field.

[0054] Unless otherwise specified, all the following examples and the reagents and materials used are commercially available.

[0055] This invention provides a method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash, comprising the following steps:

[0056] B1. Prepare characterization specimens of fly ash-asphalt binder and locate the micro-region of the contact interface between fly ash and asphalt binder;

[0057] B2. Delineate the micro-region range of the contact interface and analyze the occurrence state of heavy metal elements in the micro-region of the contact interface between waste fly ash and asphalt binder.

[0058] B3. Analyze the migration distance and attenuation rate of heavy metal elements in the micro-region of the contact interface to determine the key components of asphalt based on the element migration retardation effect;

[0059] B4. Based on the key component, analyze the migration distance and aggregation area of ​​heavy metal elements in the composite material of key component + ordinary component, and clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion.

[0060] The method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder based on the present invention comprises the following steps:

[0061] Step B1. Prepare characterization specimens of waste fly ash-asphalt binder and locate the micro-region of the contact interface between fly ash and asphalt binder.

[0062] Weigh 3-5g of waste fly ash using a platform scale and spread it evenly in a steel pan with dimensions of 100mm×100mm;

[0063] Apply hot melt black double-sided tape to the surface of a 76mm×26mm glass slide, and then place the side of the glass slide with the hot melt black double-sided tape on it into a steel tray containing waste fly ash.

[0064] Remove the glass slide and brush away any unadheded fly ash from the surface. Then, use a magnifying glass to obtain individual fly ash particles in the marked field of view. Cut out the individual fly ash particles and a square area within a 5mm × 5mm radius around them and save them for later use.

[0065] The asphalt binder was heated to a molten state and poured evenly onto a pre-insulated glass slide measuring 76mm x 26mm. Then, a black adhesive strip with individual fly ash particles was placed flat on the surface of the molten asphalt. After the hot-melt black adhesive strip was completely melted into the asphalt, the specimen was placed in a ventilated place to cool naturally.

[0066] Use a white marker to mark the location of individual fly ash particles in the asphalt mortar specimen;

[0067] The thickness of the asphalt mastic specimen was controlled to be 35 μm using a thickness tester. Then, the asphalt mastic specimen was sliced ​​using a low-temperature cryostat with a planar size of 5 mm × 5 mm. The resulting asphalt mastic slice specimen was used as a characterization specimen of waste fly ash-asphalt mastic.

[0068] Gold spraying treatment was applied to the characterization specimens of waste fly ash-asphalt mortar.

[0069] The approximate location of individual fly ash particles was dynamically scanned using a focused ion beam scanning electron microscope (FIB-SEM) to determine the precise location of the fly ash particles and the micro-regions at their interface with asphalt.

[0070] Then, the elemental composition at this location was visualized using a micro-EDXRF analyzer to verify the accuracy of the marking, thereby locating the micro-region at the interface between the fly ash and the asphalt binder.

[0071] Specifically, the asphalt binder is 70# base asphalt, and the waste fly ash is incineration fly ash from a waste incineration plant in Guangzhou.

[0072] Specifically, the cryostat is a cryomicrotome with a diamond-tipped blade and a cutting speed of 3 mm / s.

[0073] Specifically, the thickness tester is a laser thickness tester with a testing accuracy of ±0.4μm; the thickness of the asphalt mortar specimen is controlled at 35μm; the thickness test is limited to the difference between the thickness test results of any 10 measuring points within 1μm, and the distance between any two of the 10 measuring points should be greater than 0.15mm.

[0074] Specifically, the purpose of sputtering gold onto asphalt mastic specimens is to improve their electrical conductivity in order to ensure the quality of microscopic imaging.

[0075] Step B2. Delineate the micro-region range of the contact interface and analyze the occurrence state of heavy metal elements in the micro-region of the contact interface between waste fly ash and asphalt binder.

[0076] The contact interface micro-region is defined as the area within 15 μm on the inner and outer sides of the micro-region, specifically the region within 15 μm of the intersection point on the vertical line of the contact interface micro-region. The micro-region range is characterized as follows: Figure 2 As shown;

[0077] Micro-EDXRF was used to perform elemental mapping scans on the characterization areas of the waste fly ash-asphalt cementitious specimens. For the inner and outer sides of the micro-regions at the contact interface, high-precision elemental mapping was used to quantify the elemental distribution of waste fly ash particles and asphalt binder. The results are shown in Table 1. At the same time, the relative content of heavy metal elements Zn, Cu, Cr and Pb at 1 μm intervals in the characterization micro-regions at the contact interface was quantified by line scanning. The results are shown in Table 2.

[0078] Based on the data in Table 2, an xy scatter plot was drawn and a linear regression curve was fitted. The results are as follows: Figure 3 As shown;

[0079] based on Figure 3 The scatter plot and linear regression curve were used to determine the migration micro-distance L and migration attenuation rate V of heavy metals. The results are shown in Figure 3.

[0080] Specifically, the inner side of the contact interface micro-region is the interface facing the fly ash and perpendicular to the vertical line of the contact interface micro-region, while the outer side of the contact interface micro-region is the interface facing the asphalt binder and perpendicular to the vertical line of the contact interface micro-region.

[0081] Specifically, the purpose of sputtering gold onto asphalt mastic specimens is to improve their electrical conductivity in order to ensure the quality of microscopic imaging.

[0082] Specifically, the heavy metal migration distance L is defined as the distance between the point on the straight line where the relative content of heavy metal elements is less than 0.001% and the fly ash particles in the waste.

[0083] Specifically, the migration decay rate V is defined as the slope of the regression line of the points where the relative content of heavy metal elements changes on the linear scan line.

[0084] Table 1. Surface scanning results of heavy metal elements on the inner and outer sides of the micro-region at the interface between fly ash and asphalt binder.

[0085]

[0086] Table 2. Linear scanning results of heavy metal elements in the micro-region of the interface between fly ash and asphalt binder.

[0087]

[0088] Table 3. Migration range and attenuation rate of heavy metal elements in the micro-region of the interface between fly ash and asphalt binder.

[0089] Specimen type Migration distance (μm) Migration attenuation rate (% / μm) 70# Base Asphalt Pb: 12 Cr: 13 Cu: 7 Zn: 7 Pb: 0.142 Cr: 0.195 Cu: 0.074 Zn: 0.098

[0090] Step B3. Analyze the migration distance and attenuation rate of heavy metal elements in the micro-region of the contact interface to determine the key components of asphalt based on the element migration hindrance effect.

[0091] Preparation of specimens of key components in asphalt;

[0092] The contact interface micro-regions of the key components of asphalt specimens were located and marked.

[0093] Analysis of the occurrence state of heavy metal elements in the key components of asphalt specimens;

[0094] The migration distance L and migration attenuation rate V of heavy metals were determined based on the relative content variation trend of heavy metal elements, and the results are shown in Table 4.

[0095] By comparing and analyzing the migration distance L and migration attenuation rate V of different components in Table 4, asphaltene was identified as the key component of asphalt based on the element migration retardation effect.

[0096] Specifically, the method for preparing specimens of key components of asphalt is as follows: According to my country's NB / SH / T 0509-2101, the SARA method is used to separate the four components of asphalt binder to obtain asphaltene (At), saturated component (S), aromatic component (Ar), and resin (R); for solid At and R, the dissolution-evaporation method is used to prepare At and R into a mixture of waste fly ash-At or waste fly ash-R, and then the micro-regions of the contact interface are located and marked; for viscous S and Ar, S or Ar is poured onto the surface of a glass slide, and then waste fly ash particles are sprinkled on the surface of S or Ar. After the waste fly ash particles are stably integrated into the interior of S or Ar, the micro-regions of the contact interface are located and marked.

[0097] Specifically, the dissolution-evaporation method involves dissolving At or R in CS2 to form a solution, adding a certain amount of waste fly ash, and then removing CS2 by constant-temperature evaporation to obtain waste fly ash-At or waste fly ash-R mixture specimens. The purpose of this method is to avoid the problem of asphalt thermal aging.

[0098] Specifically, the method for locating and marking the micro-area of ​​the contact interface is the same as the method for locating the micro-area of ​​the contact interface between fly ash and asphalt binder described in step B1.

[0099] Specifically, the method for analyzing the heavy metal occurrence state of the key components of asphalt specimens is the same as the method described in step B2 for analyzing the heavy metal element occurrence state in the micro-region of the interface between waste fly ash and asphalt binder.

[0100] Table 4. Test results of heavy metal element content in the micro-region of the contact interface of different components.

[0101]

[0102] Note: The locations of heavy metal elements on the inner and outer sides of the micro-region at the contact interface are as follows: Figure 2 As shown, the characterization region is L*W (8μm*10μm); schematic diagrams for migration macro calculation and migration attenuation rate calculation are shown below. Figure 3 As shown.

[0103] Step B4. Based on the key component, analyze the migration distance and aggregation area of ​​heavy metal elements in the composite material of key component + ordinary component, and clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion.

[0104] Asphalt (At) is used as the key component (G), and saturated components (S), aromatic components (Ar), and resins (R) are used as common components (F). The key component (G) and the three common components (F) are mixed in the combination of G+F and G+F+F respectively. Then, fly ash from waste is added to the mixture to obtain the corresponding composite material.

[0105] Preparation of composite material characterization specimens;

[0106] Locate and label the contact interface micro-regions of composite material characterization specimens;

[0107] The test results of different combinations of G+F and G+F+F were compared with the control group (G) to clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion. The results are shown in Tables 4 and 5.

[0108] Specifically, the preparation method of the composite material characterization specimen is the same as the preparation method of the waste fly ash-asphalt mortar characterization specimen described in step B1.

[0109] Specifically, the method for locating and marking the micro-regions of the contact interface of the composite material characterization specimen is the same as the method for locating the micro-regions of the contact interface between fly ash and asphalt binder described in step B1.

[0110] Specifically, the evaluation method for the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion is consistent with the method for determining the key asphalt components based on the element migration inhibitory effect described in step B3.

[0111] Table 5. Test results of heavy metal element content in the micro-region of the contact interface of different composite components (G+F)

[0112]

[0113] Note: The proportions of asphaltene, saturated components, aromatic components, and resins are all based on the proportions of the four components determined by the SARA method.

[0114] Table 6. Test results of heavy metal element content in the micro-region of the contact interface of different composite components (G+F+F).

[0115]

[0116] Note: The proportions of asphaltene, saturated components, aromatic components, and resins are all based on the proportions of the four components determined by the SARA method.

[0117] According to Tables 1 to 6 and Figure 2 , Figure 3Therefore, the method for studying the migration and aggregation behavior of heavy metal elements in asphalt binders caused by waste fly ash, as per this invention, enables quantitative analysis and research on the migration behavior of heavy metal elements in waste fly ash within asphalt and its components. Through quantitative analysis of the microscopic migration distance and migration attenuation rate of heavy metal elements in asphalt and its components, the migration behavior and characteristics of heavy metal elements in key asphalt components and composite components are clarified, providing a basis for the inhibition and control of heavy metal elements after waste fly ash is applied to asphalt pavement materials. This method uses microscopic analysis as the main technical means, and the analysis results are accurate and can clarify the migration law of heavy metal elements in waste fly ash within asphalt binders from a mechanistic perspective, demonstrating significant innovation.

[0118] The above description provides a detailed introduction to the method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash provided by this invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of this invention. Any simple modifications, alterations, and equivalent structural changes made to the above embodiments based on the technical essence of the invention shall still fall within the protection scope of this invention.

Claims

1. A method for studying the migration and aggregation behavior of heavy metal elements from waste fly ash in asphalt binder, characterized in that, Includes the following steps: B1. Prepare characterization specimens of fly ash-asphalt binder and locate the micro-region of the contact interface between fly ash and asphalt binder; B2. Delineate the micro-region range of the contact interface and analyze the occurrence state of heavy metal elements in the micro-region of the contact interface between waste fly ash and asphalt binder. B3. Analyze the migration distance and attenuation rate of heavy metal elements in the micro-region of the contact interface to determine the key components of asphalt based on the element migration retardation effect; B4. Based on the key component, analyze the migration distance and aggregation area of ​​heavy metal elements in the composite material of key component + ordinary component, and clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion.

2. The method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash according to claim 1, characterized in that, The preparation of the waste fly ash-asphalt cementitious mortar characterization specimen in step B1 is specifically as follows: Weigh 3-5g of waste fly ash and spread it evenly in a 100mm×100mm steel pan; stick hot-melt black double-sided adhesive tape on the surface of a 76mm×26mm glass slide, and then place the glass slide into the steel pan containing the waste fly ash; after removing the glass slide, brush off any unadheded waste fly ash from the surface, and then use a magnifying glass to obtain individual waste fly ash particles in the marked field of view. Cut out the individual waste fly ash particles and a square area within a 5mm×5mm radius around them for later use; heat the asphalt binder to a molten state. The asphalt was uniformly poured onto a pre-insulated glass slide measuring 76mm x 26mm. Then, a black adhesive strip containing individual fly ash particles was placed flat on the molten asphalt surface. After the hot-melt black adhesive strip completely melted into the asphalt, it was placed in a ventilated area to cool naturally. The locations of the individual fly ash particles in the asphalt mortar specimen were marked with a white marker. The thickness of the asphalt mortar specimen was controlled to be 30-50μm using a thickness gauge. Subsequently, the asphalt mortar specimen was sliced ​​using a cryostat with a 5mm x 5mm planar dimension. The resulting asphalt mortar slice specimen is the fly ash-asphalt mortar characterization specimen. The asphalt binder includes binders such as base asphalt or modified asphalt; The aforementioned cryostat is a cryomicrotome with a diamond-tipped blade and a cutting speed of 1-3 mm / s. The thickness tester is a laser thickness tester with a testing accuracy of ±0.4μm. The thickness test is limited to the difference between the thickness test results of any 10 measuring points being within 1μm, and the distance between any two of the 10 measuring points should be greater than 0.15mm.

3. The method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash according to claim 1, characterized in that, The process of locating the micro-region of the contact interface between fly ash and asphalt binder as described in step B1 is as follows: the fly ash-asphalt characterization specimen is sputtered with gold, and then the approximate position of the individual fly ash particles is dynamically scanned using a polyion beam scanning electron microscope (FIB-SEM) to determine the accurate position of the fly ash particles and the micro-region of the contact interface with asphalt. Then, a micro-EDXRF instrument is used to visualize and characterize the elemental composition at this position to verify the accuracy of the marking, thereby locating the micro-region of the contact interface between fly ash and asphalt binder. The purpose of sputtering gold onto asphalt mastic specimens is to improve their electrical conductivity in order to ensure the quality of microscopic imaging.

4. The method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash according to claim 1, characterized in that, Step B2, which involves dividing the contact interface characterization micro-region and analyzing the heavy metal element occurrence state of the contact interface micro-region between waste fly ash and asphalt binder, specifically involves: dividing the 10μm-20μm range between the inner and outer sides of the contact interface micro-region perpendicular to the vertical line of the contact interface micro-region as the contact interface characterization micro-region; then using Micro-EDXRF to perform element mapping scanning on the characterization area of ​​the waste fly ash-asphalt characterization specimen; further using high-precision element mapping to quantify the elemental distribution of waste fly ash particles and asphalt binder on the inner and outer sides of the contact interface micro-region, and combining this with line scanning to quantify the relative content composition of heavy metal elements at 1μm intervals within the contact interface characterization micro-region; and determining the heavy metal migration distance L and migration attenuation rate V based on the changing trend of the relative content of heavy metal elements to clarify the migration process of heavy metal elements in the process of changing their attachment to the carrier. The inner side of the contact interface micro-region is the interface facing the fly ash and perpendicular to the vertical line of the contact interface micro-region, and the outer side of the contact interface micro-region is the interface facing the asphalt binder and perpendicular to the vertical line of the contact interface micro-region. The heavy metal migration distance L is defined as the distance between the point on the straight line where the relative content of heavy metal elements is less than 0.001% and the fly ash particles of the waste. The migration decay rate V is defined as the slope of the regression line of the point where the relative content of heavy metal elements changes on the linear scan line.

5. The method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash according to claim 1, characterized in that, The determination of the key asphalt components based on the element migration retardation effect in step B3 specifically involves: preparing asphalt key component specimens, locating and marking the micro-regions of the contact interface of the asphalt key component specimens, analyzing the occurrence state of heavy metal elements in the specimens, and finally determining the heavy metal migration distance L and migration attenuation rate V based on the relative content change trend of heavy metal elements. The migration distance L and migration attenuation rate V of different components are compared and analyzed to determine the key asphalt components based on the element migration retardation effect. The method for preparing specimens of key components of asphalt is as follows: According to Chinese standard NB / SH / T 0509-2101, the SARA method is used to separate the four components of asphalt binder to obtain asphaltene (At), saturated component (S), aromatic component (Ar), and resin (R); for solid At and R, the dissolution-evaporation method is used to prepare At and R into a mixture of waste fly ash-At or waste fly ash-R, and then the micro-regions of the contact interface are located and marked; for viscous S and Ar, S or Ar is poured onto the surface of a glass slide, and then waste fly ash particles are sprinkled on the surface of S or Ar. After the waste fly ash particles are stably integrated into the interior of S or Ar, the micro-regions of the contact interface are located and marked. The dissolution-evaporation method is as follows: At or R is added to CS2 to dissolve into a solution, and a certain amount of waste fly ash is added. Then, CS2 is removed by constant temperature evaporation to obtain waste fly ash-At or waste fly ash-R mixture specimens. The purpose of this method is to avoid the problem of asphalt thermal aging. The method for locating and marking the micro-area of ​​the contact interface is the same as the method for locating the micro-area of ​​the contact interface between fly ash and asphalt binder described in step B1. The method for analyzing the heavy metal occurrence state of the specimen is the same as the method for analyzing the heavy metal element occurrence state of the micro-region at the interface between waste fly ash and asphalt binder described in step B2.

6. The method for studying the migration and aggregation behavior of heavy metal elements in asphalt binder from waste fly ash according to claim 1, characterized in that, Step B4 describes analyzing the migration distance and aggregation area of ​​heavy metal elements in composite materials containing key components and ordinary components, based on the key active components, to clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion. Specifically, based on the key active components of asphalt determined in step B3, the key component (G) is used as the main component and mixed with three other ordinary components (F) in G+F and G+F+F combinations, respectively. Then, fly ash is added to the mixture to obtain the corresponding composite material. The contact interface micro-regions of the composite material are located and marked. Finally, the heavy metal occurrence state of the composite material under different combinations is compared to clarify the synergistic inhibitory effect of asphalt on the migration of heavy metal elements under multi-component fusion. The method for locating and marking the micro-area of ​​the contact interface of the composite material is the same as the method for locating the micro-area of ​​the contact interface between fly ash and asphalt binder described in step B1. The method for comparing the heavy metal occurrence state of composite materials under different combinations is the same as the method for analyzing the heavy metal element occurrence state of the micro-region at the interface between waste fly ash and asphalt binder described in step B2.

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