Functional aggregate, preparation method thereof and self-purification asphalt pavement material

Abstract

The invention provides a functional aggregate, a preparation method thereof and a self-purification asphalt pavement material. The preparation method of the functional aggregate comprises the following steps: screening residual mud and residue soil, crushing and screening to obtain a raw material, or mixing low-iron-content residue soil and red mud to prepare the raw material; the preparation method comprises the following steps: heating raw materials to 400-550 DEG C, introducing CO2, carrying out heat preservation for 40-120 minutes, then heating to 750-850 DEG C, and carrying out heat preservation for 40-120 minutes, so as to obtain calcined aggregate; soaking the mixed material in a mixed solution containing 0.1-1mol / L FeCl3 for more than 10 hours, and then carrying out hydrothermal reaction at 100-150 DEG C for 4-8 hours to obtain aggregate; and dipping the aggregate in a bacterial liquid containing denitrifying bacteria, petroleum hydrocarbon degrading bacteria and a curing agent, and obtaining the functional aggregate by adopting a vacuum negative pressure dipping method. The material formed by compounding the functional aggregate and the asphalt modifier has the functions of adsorption, catalytic oxidation and biodegradation.

Description

Technical Field

[0001] The present invention relates to the technical field of environmentally functional building materials, and in particular to a functionalized aggregate and a preparation method thereof, and a self-purifying asphalt pavement material. Background Art

[0002] With the acceleration of urbanization, the negative environmental effects of traditional asphalt pavement are becoming increasingly prominent, with the following problems:

[0003] 1. Insufficient permeability causes urban flooding

[0004] According to authoritative statistics, over 60% of Chinese cities experience flooding three or more times annually, resulting in annual economic losses exceeding 30 billion yuan. Traditional dense-graded asphalt pavement has a permeability coefficient of only 0.01-0.05 mm / s (JTG E20-2011), resulting in surface runoff rates as high as 85% under heavy rain conditions. Typical field data shows that at rainfall intensities of 30 mm / h, runoff time on traditional pavement is shortened to 8-12 minutes, with peak runoff increasing 5-7 times compared to natural surface conditions (T / CECS 661-2020).

[0005] 2. Pollutant migration threatens groundwater safety

[0006] Groundwater monitoring data shows that petroleum hydrocarbons exceed standards at 34.6% of sites, and heavy metal levels exceed standards at 17.3%. Polycyclic aromatic hydrocarbon concentrations in road runoff exceed Class III groundwater standards by 750-2000 times. COD and NH3-N concentrations in rainwater seeping under traditional pavement exceed Class IV standards by 3.4 and 4.1 times, respectively, creating significant pollution pathways.

[0007] Current mainstream solutions have the following limitations:

[0008] Permeable asphalt concrete: Although the permeability coefficient is increased to 0.8×10 -2 cm / s, but the porosity is only 15% to 20%, and the water permeability decay rate under rainstorm conditions is greater than 40%. More seriously, it only relies on physical filtration and has no effect on dissolved pollutants (such as NO3 - -N, petroleum hydrocarbons) removal rate is less than 30%.

[0009] Adsorbent modified materials: Adding activated carbon can increase the COD removal rate to 55%, but the cost increases by 1,200 yuan / ton, and the clogging rate of the activated carbon pores exceeds 60% after 6-8 months of operation, resulting in a decrease in water permeability by more than 50%.

[0010] Bioretention facilities: For example, rain gardens can remove 65% of TN, but they require 10% to 15% of green space, making them difficult to apply on a large scale in road projects.

[0011] According to statistics, my country generated 1.87 billion tons of construction waste in 2022, with a comprehensive utilization rate of less than 35%. Traditional landfill disposal not only occupies 1.2 mu (approximately 1.2 acres) of land per 10,000 tons, but also increases the risk of landslides to 1.2 times per year when the pile height exceeds 10 meters. Although some studies have explored using waste in brickmaking, the added value is low (product price less than 80 yuan per ton), and the sintering energy consumption is as high as 0.8 tce per ton of product, which is inconsistent with carbon emission reduction goals.

[0012] The above analysis shows that there is a significant disconnect between the existing technologies in the multi-dimensional demands of “water permeability-purification-resource utilization”, and there is an urgent need to develop innovative solutions that combine engineering performance, environmental benefits and economic feasibility. Summary of the Invention

[0013] In response to the above technical problems, the present invention discloses a self-purifying asphalt pavement material and a preparation method thereof, which solves the problems of poor water permeability, lack of pollution interception capacity and resource utilization of residual mud and slag in traditional asphalt pavements.

[0014] To this end, the technical solution adopted in the present invention is:

[0015] A method for preparing a functionalized aggregate comprises the following steps:

[0016] Step S1, screening the residual mud and slag, crushing and screening it as raw material, or using low-iron content slag and red mud to mix to prepare raw material, the mass percentage of the components in the raw material meets the following requirements: SiO2+Al2O3≥65wt.%, Fe2O3≥wt.5%, organic matter≤3wt.%, and the mass percentage of Fe2O3 in the low-iron content slag is less than 5wt.%.

[0017] In step S2, the raw material is first heated to 400-550°C, CO2 is introduced, and the temperature is kept at 40-120 minutes, and then the temperature is raised to 750-850°C and the temperature is kept at 40-120 minutes to obtain a calcined aggregate; the calcined aggregate has a porous structure, and during this gradient calcination process, the differential expansion effect of Fe2O3 and aluminosilicate in the CO2 atmosphere forms directional micron-sized grooves on the surface of the calcined aggregate.

[0018] Step S3: immersing the calcined aggregate in a mixed solution containing 0.1-1 mol / LFeCl3 for more than 10 hours, and then performing a hydrothermal reaction at 100-150°C for 4-8 hours to obtain an aggregate with α-FeOOH heterojunction nanosheets generated in the pores; the Fe element mass proportion of the aggregate obtained in this step reaches 6.8wt.%-7.5wt.%.

[0019] Step S4: immersing the aggregate in a bacterial solution containing denitrifying bacteria, petroleum hydrocarbon degrading bacteria and a curing agent, wherein the concentration of the bacterial solution is 1 to 9×10 8CFU / g, and the denitrifying bacteria and petroleum hydrocarbon degrading bacteria are loaded into the pores of the aggregate by a vacuum negative pressure impregnation method to obtain a functionalized aggregate.

[0020] This technical solution uses urban construction waste as the main raw material, and through crushing and screening, high-temperature calcination to create pores, metal oxide loading and microbial immobilization, an ecological functional aggregate with a multi-level pore structure is formed. The porosity of the functional aggregate is ≥45%, and the specific surface area is ≥120m 2 / g, surface loading Fe 3+ / Fe 2+ Catalytic active sites and denitrifying bacteria. After being mixed with modified asphalt and used in pavement, it has a porous structure and can physically intercept suspended matter and heavy metals through the mesoporous-macroporous hierarchical structure of aggregates. The surface-loaded Fe 3+ / Fe 2+ Under alternating wet-dry conditions, a Fenton-like reaction is triggered, generating OH radicals that degrade organic matter. Immobilized microorganisms metabolize ammonia nitrogen and petroleum hydrocarbon pollutants, resulting in a COD removal rate exceeding 72%, demonstrating self-purification capabilities. This pavement utilizes residual mud and slag resources, exhibits excellent permeability, purifies rainwater, intercepts pollutants, and better protects groundwater resources.

[0021] As a further improvement of the present invention, in step S1, the step of preparing the raw material by mixing low-iron content slag and red mud comprises:

[0022] Step S11, measuring the mass percentage of Fe2O3 in the residual mud and slag, and calculating the mass proportion of red mud to be added based on the content, wherein the mass percentage of Fe2O3 in the red mud is ≥45%;

[0023] Step S12, weighing the residual mud and red mud, and stirring the residual mud and red mud to mix them evenly to obtain a mixture;

[0024] Step S13, adding water to the mixture to a moisture content of 12-18 wt.%, and aging for more than 20 hours to obtain a raw material.

[0025] As a further improvement of the present invention, the method for preparing the self-purifying asphalt pavement material further includes step S14, detecting the Fe / Si molar ratio of the raw material, with a target of 0.15-0.25, and adding red mud if it is insufficient.

[0026] As a further improvement of the present invention, in step S12, the stirring rate is 100-300 rpm, and the time is 20-40 min.

[0027] As a further improvement of the present invention, in step S13, water is added to the mixture to a water content of 15 wt.%.

[0028] As a further improvement of the present invention, in step S1, the residual mud and slag are crushed and screened to a particle size of ≤5 mm.

[0029] As a further improvement of the present invention, in step S2, the flow rate of CO2 is 2 to 4 L / min, and the temperature is kept at 400-550°C for 60 to 90 minutes.

[0030] As a further improvement of the present invention, in step S2, the raw material is first heated to 450-500°C.

[0031] As a further improvement of the present invention, in step S2, the heating rate to 750-850°C is 5-8°C / min, and the temperature is kept at this temperature for 60-90 minutes.

[0032] As a further improvement of the present invention, in step S3, the concentration of FeCl3 in the mixed solution is 0.5 mol / L.

[0033] As a further improvement of the present invention, the temperature of the hydrothermal reaction is 120° C. and the time is 6 hours.

[0034] As a further improvement of the present invention, in step S3, the thickness of the α-FeOOH heterojunction nanosheet is 20-50 nm.

[0035] As a further improvement of the present invention, the surface of the aggregate contains a micron-scale groove structure. Furthermore, the depth of the micron-scale groove structure is 50-100 μm and the spacing is 200-300 μm.

[0036] As a further improvement of the present invention, in step S4, the denitrifying bacteria is Pseudomonas denitrificans CGMCC 1.1785, and the petroleum hydrocarbon degrading bacteria is Rhodococcus erythropolis ATCC 4277.

[0037] As a further improvement of the present invention, the ratio of the number of denitrifying bacteria to the number of petroleum hydrocarbon degrading bacteria is 3:1.

[0038] As a further improvement of the present invention, the concentration of the bacterial solution is 1 to 5×10 8 CFU / g.

[0039] As a further improvement of the present invention, the vacuum degree of the vacuum negative pressure impregnation method is 0.05-0.1 MPa, and the pressure holding time is 20-40 minutes.

[0040] As a further improvement of the present invention, the curing agent includes sodium alginate and chitosan, wherein the concentration of the sodium alginate is 1.0-2.0 wt.%, and the concentration of the chitosan is 0.3-0.6 wt.%. Furthermore, the concentration of the sodium alginate is 1.5 wt.%, and the concentration of the chitosan is 0.5 wt.%.

[0041] The present invention also discloses a functionalized aggregate, which is prepared by using any one of the above methods for preparing the functionalized aggregate.

[0042] The present invention also discloses a self-purifying asphalt pavement material, which is obtained by shear mixing the functionalized aggregate described in any one of the above items with modified asphalt at 150-200° C., wherein the mass ratio of the functionalized aggregate to the modified asphalt is 1:1.2-2.

[0043] As a further improvement to the present invention, the functionalized aggregate is surface-grafted with a titanate and then shear-mixed with modified asphalt at 150-200°C. Furthermore, the titanate is NDZ-201. More preferably, the grafting rate is ≥85%. This technical solution increases the shear strength of the aggregate-asphalt interface to 2.8 MPa.

[0044] As a further improvement of the present invention, a titanate treatment process includes adding a titanate ethanol solution to a functionalized aggregate and performing a surface grafting treatment under ultrasonic conditions at a temperature of 70-90°C, an ultrasonic power of 150-250W, and a treatment time of 1-4 hours. The titanate is added in an amount of 2-3wt% of the weight of the functionalized aggregate. Furthermore, the titanate is added in an amount of 2.5wt% of the weight of the functionalized aggregate. Furthermore, the treatment temperature is 80°C, the ultrasonic power is 200W, and the treatment time is 2 hours.

[0045] As a further improvement of the present invention, the modified asphalt is SBS modified asphalt, and the shear mixing temperature is 160-180°C.

[0046] As a further improvement of the present invention, the porosity of the self-purifying asphalt pavement material is 45% to 55%, and the water permeability coefficient is 1.6 to 2.5×10 -2 cm / s.

[0047] As a further improvement of the present invention, the self-cleaning asphalt pavement material further comprises carbon nanotubes and basalt fibers. Furthermore, the carbon nanotubes comprise 1.5-2.5 wt.%, the basalt fibers comprise 3.5-4.5 wt.%, the functionalized aggregate comprises 34-38 wt.%, and the modified asphalt comprises 55-60 wt.%.

[0048] As a further improvement of the present invention, the gradation of the functionalized aggregate meets the requirements of the following Table 1:

[0049] Sieve hole size (mm) 9.5 4.75 2.36 1.18 0.6 Pass rate (%) 100 85-90 60-65 40-45 20-25

[0050] The present invention discloses a self-cleaning asphalt pavement comprising a gravel drainage layer having a gravel particle size of 10-20 mm and a thickness of 25-35 cm. The gravel drainage layer is paved with any of the self-cleaning asphalt pavement materials described above. This technical solution reduces the pore siltation rate to less than 15% per year.

[0051] As a further improvement to the present invention, a microencapsulated healing agent is added to the self-cleaning asphalt pavement material to provide self-repairing capabilities. Furthermore, the microencapsulated healing agent has a core material of methyl methacrylate, a wall thickness of 2-3 μm, and releases the healing agent when the crack width is greater than 0.3 mm, with a recovery rate greater than 82%.

[0052] The present invention also discloses the application of the self-purifying asphalt pavement material described above, which is used for asphalt pavement.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] First, the technical solution of the present invention uses residual mud and slag as the main raw material, and a multi-stage activation process is used to prepare a functional aggregate with a porous structure. This aggregate is then compounded with an asphalt modifier to form an ecological pavement material with adsorption, catalytic oxidation, and biodegradation functions. Its compressive strength is ≥35MPa, and its permeability coefficient is ≥1.5×10 -2 cm / s, organic matter (COD), heavy metals (Pb 2+ 、Zn 2+ ) removal rates reached 78.3%, 92.5%, and 87.6%, respectively. Compared to traditional asphalt pavement, this new system increases water permeability by 3-5 times and intercepts pollutants from initial rainwater by over 60%, effectively reducing the risk of urban flooding and ensuring groundwater safety. It also achieves a 95% resource utilization rate for residual mud, debris, and solid waste.

[0055] Second, the asphalt pavement of this invention boasts excellent water permeability and strong pollution retention capabilities, while also enabling the recycling of residual mud and debris. This meets the multi-dimensional requirements of "water permeability, purification, and resource utilization," achieving both engineering performance, environmental benefits, and economic feasibility. This reduces carbon emissions and lowers material production and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 3. This is a SEM comparison picture of the calcined aggregate and the original residual mud and slag according to the embodiment of the present invention; (a) is the original residual mud and slag, and (b) is the calcined aggregate.

[0057] Figure 2 It is a schematic structural diagram of the self-purifying asphalt pavement material according to an embodiment of the present invention.

[0058] Figure 3 It is a schematic diagram of the rainwater purification path of the self-purifying asphalt pavement according to an embodiment of the present invention. DETAILED DESCRIPTION

[0059] The preferred embodiments of the present invention are described in further detail below.

[0060] A self-purifying asphalt pavement material uses functionalized aggregate and is prepared using the following steps:

[0061] (1) Directional screening of the residual mud and slag to select raw materials that meet the following chemical indicators (mass fraction):

[0062] SiO2+Al2O3≥65wt.%,Fe2O3≥5wt.%,organic matter≤3wt.%

[0063] If the residual sludge has a low iron content, red mud (Fe2O3 content ≥ 45%) can be added to optimize the composition. The specific optimization steps are as follows:

[0064] ① Determine the Fe2O3 content in the residual mud and slag. If it is less than 5wt.%, add red mud in proportion (Fe2O3≥45wt.%);

[0065] ② Dry mix the residual sludge and red mud until uniform, stirring at a rate of 200 rpm for 30 minutes;

[0066] ③ Add water to a moisture content of 15 wt.%, and age for 24 hours to allow the iron element to migrate evenly;

[0067] ④ Check the Fe / Si molar ratio, the target range is 0.15-0.25, and add red mud if it is insufficient.

[0068] (2) Gradient calcination pore formation

[0069] Adopt two-stage temperature-controlled calcination process:

[0070] Low temperature section (400-550℃): organic matter decomposes to form mesopores (2-50nm), and CO2 is introduced to inhibit pore collapse;

[0071] High temperature stage (750-850°C): Aluminosilicate melts and reconstructs to form honeycomb-like macropores (1-5 μm). By adjusting the calcination rate (5-8°C / min) and holding time (60-90 min), a porosity of 45% to 55% and a penetration rate of >85% are achieved.

[0072] The calcined aggregate was obtained by the above steps. Figure 1As shown, compared with the original slag, it can be seen that the calcined aggregate in this embodiment has a porous structure.

[0073] (3) In-situ growth of nanocatalytic layer

[0074] The calcined aggregate was immersed in 0.5 mol / LFeCl3 solution for more than 10 h; then hydrothermal reaction was carried out at 120 ° C for 6 h to generate α-FeOOH heterojunction nanosheets in the pores with a thickness of 20-50 nm and a specific surface area of ​​320 m 2 / g, forming catalytic active sites.

[0075] (4) Directed immobilization of microorganisms

[0076] The denitrification bacteria (Pseudomonas denitrificans CGMCC 1.1785) and petroleum hydrocarbon degradation bacteria (Rhodococcus erythropolis ATCC 4277) were loaded into the pores of the aggregate at a ratio of 3:1 by vacuum impregnation method. The bacterial solution concentration reached 10 8 CFU / g. Immobilization process parameters:

[0077] Vacuum degree = 0.08 MPa, holding time = 30 min, curing agent = 1.5 wt.% sodium alginate + 0.5 wt.% chitosan.

[0078] The following describes the details in conjunction with specific embodiments.

[0079] Example 1

[0080] According to the preparation steps of the functionalized aggregate, including

[0081] (1) In this embodiment, the composition of the screened residual mud and slag is:

[0082] SiO2+Al2O3=68wt.%, Fe2O3=4.5wt.%

[0083] In this embodiment, the Fe2O3 content in the residual mud and slag is less than 5wt.%, and red mud is added in proportion, wherein the Fe2O3 content in the red mud is 46wt.%; the residual mud and slag are dry-mixed until uniform, with a stirring rate of 200rpm and a mixing time of 30min; water is added to a moisture content of 15wt.%, and the mixture is aged for 24h to allow uniform migration of the iron element; the Fe / Si molar ratio is detected and adjusted to 0.15.

[0084] (2) Calcination process: The raw materials were heated to a low temperature of 400°C, CO2 was introduced at a flow rate of 2 L / min, and the temperature was kept at this temperature for 60 minutes; then the temperature was raised to a high temperature of 750°C at a heating rate of 5°C / min and the temperature was kept at this temperature for 60 minutes. The calcined aggregate was obtained.

[0085] (3) The calcined aggregate was immersed in 0.5 mol / LFeCl3 solution for 12 h; then the hydrothermal reaction was carried out at 120 °C for 6 h to generate α-FeOOH heterojunction nanosheets in the pores with a thickness of 30 nm and a specific surface area of ​​320 m 2 / g, forming catalytic active sites.

[0086] (4) Directed immobilization of microorganisms

[0087] Denitrifying bacteria (Pseudomonas denitrificans CGMCC 1.1785) and petroleum hydrocarbon-degrading bacteria (Rhodococcus erythropolis ATCC 4277) were loaded into the pores of aggregate at a ratio of 3:1 using a vacuum impregnation method to obtain functionalized aggregate.

[0088] In this step, the bacterial solution concentration was 1×10 8 CFU / g. Immobilization process parameters:

[0089] Vacuum degree = 0.08 MPa, holding time = 30 min, curing agent = 1.5 wt.% sodium alginate + 0.5 wt.% chitosan

[0090] The obtained functionalized aggregate was tested and found to have a porosity of 45%, a COD removal rate of 72.5%, and a water permeability coefficient of 1.6×10 -2 cm / s.

[0091] Example 2

[0092] The preparation steps of this embodiment include:

[0093] (1) In this embodiment, the composition of the screened residual mud and slag is:

[0094] SiO2+Al2O3=72wt.%, Fe2O3=5.8wt.%, and can be used directly as raw material.

[0095] (2) Calcination process: The raw materials were heated to a low temperature of 500°C, CO2 was introduced at a flow rate of 3 L / min, and the temperature was kept at this temperature for 75 minutes; then the temperature was raised to a high temperature of 800°C at a heating rate of 6°C / min and the temperature was kept at this temperature for 75 minutes. The calcined aggregate was obtained.

[0096] (3) The calcined aggregate was immersed in 0.5 mol / LFeCl3 solution for 12 h; then the hydrothermal reaction was carried out at 120 °C for 6 h to generate α-FeOOH heterojunction nanosheets in the pores with a thickness of 30 nm and a specific surface area of ​​320 m 2 / g, forming catalytic active sites.

[0097] (4) Directed immobilization of microorganisms

[0098] Denitrifying bacteria (Pseudomonas denitrificans CGMCC 1.1785) and petroleum hydrocarbon-degrading bacteria (Rhodococcus erythropolis ATCC 4277) were loaded into the pores of aggregate at a ratio of 3:1 using a vacuum impregnation method to obtain functionalized aggregate.

[0099] In this step, the bacterial solution concentration was 5×10 8 CFU / g. Immobilization process parameters:

[0100] Vacuum degree = 0.09 MPa, holding time = 30 min, curing agent = 1.5 wt.% sodium alginate + 0.5 wt.% chitosan

[0101] The obtained functionalized aggregate was tested and found to have a porosity of 50%, a COD removal rate of 78.3%, and a water permeability coefficient of 2.1×10 -2 cm / s.

[0102] SEM examination of the functionalized aggregate prepared in this example showed that its surface had a micron-scale groove structure with a groove depth of 65 to 95 μm and a groove spacing of 220 to 280 μm. Fluorescence microscopy observation showed that the surface biofilm coverage was 78%.

[0103] The functionalized aggregate obtained in this example was subjected to an ammonia nitrogen degradation test:

[0104] Test conditions: Influent NH3-N concentration gradient is 2-15 mg / L, temperature gradient is 10-30℃.

[0105] Test method: Dynamic column test (HRT = 2h), tested according to HJ 536-2009, the results are shown in Table 1.

[0106] Table 1 Example 2 Ammonia nitrogen degradation test results

[0107]

[0108] Comparative Example 1

[0109] Based on Example 2, this comparative example differs in that CO2 is not introduced during the calcination stage in step (2), and the temperature is directly raised to 800°C and maintained. Other steps are the same as in Example 2.

[0110] The functionalized aggregate obtained in Comparative Example 1 was examined by SEM, and it was found that the surface of the aggregate was smooth and had no grooves. Observation under a fluorescence microscope showed that the biofilm coverage rate on the surface was 42%.

[0111] The ammonia nitrogen degradation test was carried out under the same conditions as in Example 2, and the results are shown in Table 2.

[0112] Table 2 Comparative Example 1 Ammonia Nitrogen Degradation Test Results

[0113]

[0114] A comparison of Example 2 and Comparative Example 1 shows that Example 2 has a higher surface biofilm coverage rate due to the grooves on the surface. Furthermore, the ammonia nitrogen degradation test results show that Example 2 achieves a removal rate of over 89% at 20°C and 30°C, while Comparative Example 1 achieves a maximum of only 62.4%. This demonstrates that the technical solution of Example 2 has a superior purification effect.

[0115] Example 3

[0116] According to the preparation steps of the functionalized aggregate, including

[0117] (1) In this embodiment, the composition of the screened residual mud and slag is:

[0118] SiO2+Al2O3=65wt.%, Fe2O3=3.8wt.%

[0119] In this embodiment, the Fe2O3 content in the residual mud and slag is less than 5wt.%, and red mud is added in proportion, wherein the Fe2O3 content in the red mud is 48wt.%; the residual mud and slag are dry-mixed until uniform, with a stirring rate of 200rpm and a time of 30min; water is added to a moisture content of 15%, and the mixture is aged for 24h to allow uniform migration of the iron element; the Fe / Si molar ratio is detected and adjusted to 0.25.

[0120] (2) Calcination process: The raw materials were heated to a low temperature range of 550°C, CO2 was introduced at a flow rate of 4 L / min, and the temperature was kept at this temperature for 90 minutes; then the temperature was raised to a high temperature range of 850°C at a heating rate of 8°C / min and the temperature was kept at this temperature for 90 minutes. The calcined aggregate was obtained.

[0121] (3) The calcined aggregate was immersed in 0.5 mol / LFeCl3 solution for 12 h; then the hydrothermal reaction was carried out at 120 °C for 6 h to generate α-FeOOH heterojunction nanosheets in the pores with a thickness of 30 nm and a specific surface area of ​​320 m 2 / g, forming catalytic active sites.

[0122] (4) Directed immobilization of microorganisms

[0123] Denitrifying bacteria (Pseudomonas denitrificans CGMCC 1.1785) and petroleum hydrocarbon-degrading bacteria (Rhodococcus erythropolis ATCC 4277) were loaded into the pores of aggregate at a ratio of 3:1 using a vacuum impregnation method to obtain functionalized aggregate.

[0124] In this step, the bacterial solution concentration was 1×10 9 CFU / g. Immobilization process parameters:

[0125] Vacuum degree = 0.10 MPa, holding time = 30 min, curing agent = 1.5 wt.% sodium alginate + 0.5 wt.% chitosan

[0126] The obtained functionalized aggregate was tested and found to have a porosity of 55%, a COD removal rate of 83.4%, and a water permeability coefficient of 2.5×10 -2 cm / s.

[0127] Analyze the above embodiments.

[0128] (1) Construct the pollutant migration equation in porous media:

[0129]

[0130] in:

[0131] k1=0.25h -1 (Fenton-like reaction rate constant, measured value);

[0132] k2=1.8×10 -3 L\cdotpmg-1\cdotph-1(Pb 2+ adsorption rate constant).

[0133] Verify the accuracy of the model through dynamic column experiments:

[0134] Experimental setup: filled with the material of Example 2, influent COD = 120 mg / L, flow rate = 0.5 m / d;

[0135] The COD removal rate predicted by the above model was 78.3%, and the actual measurement was 76.8%, with the COD removal rate error ≤5%.

[0136] Pb 2+ Adsorption dynamic fitting R 2 =0.96.

[0137] (2) Biofilm-mass transfer enhancement design

[0138] The micron-scale groove structure on the aggregate surface (depth 50-100μm, spacing 200-300μm) increases the biofilm attachment area, which increases the ammonia nitrogen degradation rate to:

[0139] r NH3-N =0.12×e 0.035T × C / (Ks+C) (T is temperature in °C, Ks = 2.3 mg / L)

[0140] (3) Dry-wet cycle electron transfer mechanism

[0141] Use Fe 3+ / Fe 2+ Valence state conversion produces reactive oxygen species:

[0142] Wet period: Fe 2+ +O2→FeO 2+ +H2O2

[0143] Drying period: Fe 3+ +H2O2→Fe 2+ +·OH+H +

[0144] Experiments show that the COD removal rate under alternating dry-wet (12h / 12h) conditions is 23.7% higher than that under single wet state.

[0145] The functionalized aggregates of Examples 1 to 3 were mixed with SBS modified asphalt at a mass ratio of 4:6 at 160-180° C. under high shearing conditions to obtain self-purifying asphalt pavement materials. The test results were as follows:

[0146] Marshall stability: 11.2-13.8kN (test method JTG E20-2011);

[0147] Freeze-thaw mass loss rate: 2.3% to 3.0% (GB / T 50082-2009);

[0148] Water permeability: 20~25L / (m 2 ·min)(ASTM C1701).

[0149] The performance of the self-purifying asphalt pavement material using the functionalized aggregate of Example 2 was compared with that of existing typical pavement materials. The results are shown in Table 1.

[0150] Table 3 Comparison of performance of typical pavement materials

[0151]

[0152] From the above comparison, it can be seen that the technical solution of the embodiment of the present invention has good water permeability, high COD removal rate, low cost, and better utilization of solid waste.

[0153] Example 4

[0154] A self-purifying asphalt pavement material is prepared by the following steps:

[0155] First, the functionalized aggregate of Example 1 was surface-grafted with NDZ-201 titanate, achieving a grafting efficiency of ≥85%. After grafting, the aggregate-asphalt interface shear strength increased to 2.8 MPa (tested according to ASTM D4541). In this embodiment, the titanate treatment process included adding an ethanol solution of NDZ-201 titanate to the functionalized aggregate of Example 1, with the titanate added in an amount of 2.5 wt % based on the functionalized aggregate. The surface grafting treatment was performed under ultrasonic conditions at a temperature of 80°C, an ultrasonic power of 200 W, and a treatment time of 2 hours. XPS surface elemental analysis determined a grafting efficiency of 87%.

[0156] Next, surface-grafted functionalized aggregate was shear-mixed with SBS-modified asphalt, carbon nanotubes, and basalt fibers at 180°C. The weight fractions were: 58% SBS-modified asphalt, 36% functionalized aggregate, 2% carbon nanotubes, and 4% basalt fibers. The SBS-modified asphalt, functionalized aggregate, carbon nanotubes, and basalt fibers acted as a binder, a structural framework and purification carrier, a conductive network (to prevent electrostatic breakdown), and crack resistance reinforcement, respectively.

[0157] The obtained material was tested and the interfacial shear strength was increased to 2.8MPa (55.6% increase compared to untreated); the water immersion peeling residue rate was increased to 93% (increased by 29.2%); the Marshall stability retention rate after freeze-thaw cycles was: 89% vs. 75% for untreated.

[0158] Comparative Example 2 (ungrafted)

[0159] Based on Example 4, the titanate surface treatment step was omitted, and other parameters remained unchanged: the functionalized aggregate was directly shear-mixed with the SBS modified asphalt at 180°C.

[0160] The aggregate-asphalt interface shear strength was measured to be 1.8 MPa (ASTM D4541); the water immersion stripping test residual rate was 72% (JTJ 052-2000T0616).

[0161] Example 4 and Comparative Example 2 were tested, and the test data are shown in Table 4. It can be seen that the material treated with titanate grafting has higher shear strength and fatigue life, and lower permeability coefficient attenuation rate.

[0162] As shown in Table 4, the experimental data of Example 4 and Comparative Example 2

[0163] Test items Ungrafted (Comparative Example 2) Grafting treatment (Example 4) Test standards Shear strength (MPa) 1.8 2.8 ASTM D4541 Residual rate (%) 72 93 JTJ 052-2000 Permeability attenuation rate 31％ 18％ ASTM C1701 Fatigue life (10,000 times) 12.5 19.8 AASHTO T321

[0164] Furthermore, the aggregate grading optimization shown in Table 5 was adopted to achieve a water permeability coefficient of > 2×10 -2 Compressive strength at cm / s ≥35MPa:

[0165] Table 5 Aggregate gradation

[0166] Sieve hole size (mm) 9.5 4.75 2.36 1.18 0.6 Pass rate (%) 100 85-90 60-65 40-45 20-25

[0167] Coarse aggregate (9.5-4.75mm): accounts for ≥85%, forming the main skeleton and permeable channels;

[0168] Medium aggregate (2.36-1.18 mm): accounts for 40%-45%, stabilizes the skeleton and prevents the loss of fine materials;

[0169] Fine aggregate (less than 0.6mm): accounts for ≤25%, fills micropores and enhances density.

[0170] Grading formula verification:

[0171] Theoretical verification is carried out using Talbot's continuous gradation formula:

[0172] P(d)=100×(D / d)n

[0173] Where: D = 9.5 mm, n = 0.45 (optimal permeability-strength balance index)

[0174] Example 5

[0175] Based on Example 4, in this example, the gradation of the functionalized aggregate is:

[0176] Table 6 Aggregate gradation of Example 5

[0177] Sieve hole size (mm) 9.5 4.75 2.36 1.18 0.6 Pass rate (%) 100 85 60 40 20

[0178] The coarse aggregate accounts for a high proportion (9.5mm passing rate 100%), forming through pores with a water permeability coefficient of 1.6×10 -2 cm / s; fine aggregate (0.6mm passing rate 20%) fills the skeleton gap, and the compressive strength is 35.2MPa.

[0179] Example 6

[0180] Based on Example 4, in this example, the gradation of the functionalized aggregate is:

[0181] Table 7 Aggregate gradation of Example 6

[0182] Sieve hole size (mm) 9.5 4.75 2.36 1.18 0.6 Pass rate (%) 100 88 63 43 23

[0183] 4.75mm sieve pass rate 88% balanced porosity and skeleton strength, water permeability coefficient 2.1×10 -2 cm / s; compressive strength 38.5MPa.

[0184] Example 7

[0185] Based on Example 4, in this example, the gradation of the functionalized aggregate is:

[0186] Table 8 Aggregate gradation of Example 7

[0187] Sieve hole size (mm) 9.5 4.75 2.36 1.18 0.6 Pass rate (%) 100 90 65 45 25

[0188] The proportion of fine aggregate is increased (0.6mm passing rate is 25%), the density is enhanced, the compressive strength is 41.7MPa; the permeability coefficient is 2.5×10 -2 cm / s (still higher than the standard 1.5×10 -2 cm / s).

[0189] The self-purifying asphalt pavement material of Example 5 was used to pave a road surface, and a rainfall intensity of 50 mm / h was simulated to test the pollutant purification efficiency. The results are shown in Table 9.

[0190] Table 9

[0191] pollutants Influent concentration Outlet concentration Removal rate Main mechanism of action COD 120mg / L 26.4mg / L 78.0％ Catalytic oxidation (62%) + biodegradation (38%) <![CDATA[NH3-N]]> 8.5mg / L 1.2mg / L 85.9％ Biological nitrification-denitrification <![CDATA[Pb 2+ ]]> 1.2mg / L 0.07mg / L 94.2％ Chemical adsorption + coprecipitation Petroleum hydrocarbons 35mg / L 3.8mg / L 89.1％ Biodegradation + Photocatalysis

[0192] The structural diagram of the self-purifying asphalt pavement material is as follows: Figure 2 As shown in the figure, the schematic diagram of the rainwater purification path of the paved road is as follows Figure 3 As shown, the self-purifying asphalt pavement material has many catalytic sites and a biofilm in the gaps. Under the action of rainwater, the self-purifying asphalt pavement intercepts pollutants and purifies rainwater through adsorption, catalysis, and biodegradation, better protecting groundwater.

[0193] The self-purifying asphalt pavement material of Example 5 was used to test Marshall stability according to JTG E20-2011, freeze-thaw strength loss rate according to GB / T 50082-2009, and permeability attenuation rate according to ASTM C1701. The results are as follows:

[0194] Marshall stability: 12.5kN (JTG E20-2011 requires ≥8kN);

[0195] Freeze-thaw strength loss rate: 2.3% (15 cycles, GB / T 50082-2009);

[0196] Water permeability reduction rate: 18% (after 5 years of service, ASTM C1701).

[0197] The purification effects of Examples 5 to 7 are shown in Table 10.

[0198] Table 10

[0199] Example COD removal rate <![CDATA[NH3-N removal rate]]> Permeability coefficient attenuation rate (5 years) 5 72.5％ 80.2％ 22％ 6 78.3％ 85.9％ 18％ 7 83.4％ 89.7％ 15％

[0200] In the above embodiment, the resource utilization of 1 ton of residual mud and slag can reduce CO2 emissions by 0.82 tons (compared with traditional fired bricks); cost savings: material production costs are reduced by 35% compared with permeable asphalt, and maintenance costs are reduced by 60%.

[0201] Furthermore, long-term performance guarantee improvements can be made based on Examples 5-7, specifically:

[0202] Anti-clogging design: A 30cm thick gravel drainage layer (10-20mm particle size) is set at the bottom of the pavement structure layer to keep the pore siltation rate less than 15% per year;

[0203] Self-repair function: Add microencapsulated healing agent (core material is methyl methacrylate, wall thickness 2-3μm), release the healing agent when the crack width is greater than 0.3mm, and the recovery rate is greater than 82%.

[0204] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a functionalized aggregate, characterized in that: The steps include: Step S1, screening the residual mud and slag, crushing and screening it as raw material, or using low-iron content slag and red mud to mix to prepare raw material, the mass percentage of the components in the raw material meeting the following requirements: SiO2+Al2O3≥65%, Fe2O3≥5%, organic matter≤3%, and the mass percentage of Fe2O3 in the low-iron content slag is less than 5%; Step S2, heating the raw material to 400-550°C, introducing CO2, and keeping the temperature for 40-120 minutes, then heating the raw material to 750-850°C, and keeping the temperature for 40-120 minutes to obtain calcined aggregate; Step S3, immersing the calcined aggregate in a mixed solution containing 0.1-1 mol / L FeCl3 for more than 10 hours, and then performing a hydrothermal reaction at 100-150°C for 4-8 hours to obtain an aggregate with α-FeOOH heterojunction nanosheets formed in the pores; Step S4: immersing the aggregate in a bacterial solution containing denitrifying bacteria, petroleum hydrocarbon degrading bacteria and a curing agent, wherein the concentration of the bacterial solution is 1 to 9×10 8 CFU / g, and the denitrifying bacteria and petroleum hydrocarbon degrading bacteria are loaded into the pores of the aggregate by a vacuum negative pressure impregnation method to obtain a functionalized aggregate.

2. The method for preparing the functionalized aggregate according to claim 1, wherein: In step S1, the preparation of raw materials by mixing low-iron content slag and red mud includes: Step S11, measuring the mass percentage of Fe2O3 in the residual mud and slag, and calculating the mass proportion of red mud to be added based on the content, wherein the mass percentage of Fe2O3 in the red mud is ≥45%; Step S12, weighing the residual mud and red mud, and stirring the residual mud and red mud to mix them evenly to obtain a mixture; Step S13, adding water to the mixture to a moisture content of 12-18 wt.%, and aging for more than 20 hours to obtain a raw material.

3. The method for preparing the functionalized aggregate according to claim 2, wherein: The step S14 is also included, wherein the Fe / Si molar ratio of the raw material is detected, with a target of 0.15 to 0.

25. If the molar ratio is insufficient, red mud is added; In step S12, the stirring rate is 100-300 rpm, and the time is 20-40 min; Step S13: adding water to the mixture to a water content of 15 wt.%.

4. The method for preparing the functionalized aggregate according to claim 1, wherein: In step S2, the flow rate of CO2 is 2-4 L / min, and the temperature is kept at 400-550°C for 60-90 min; the temperature is increased to 750-850°C at a rate of 5-8°C / min, and the temperature is kept for 60-90 min; In step S3, the concentration of FeCl3 in the mixed solution is 0.5 mol / L; the temperature of the hydrothermal reaction is 120°C and the time is 6 hours; In step S3, the thickness of the α-FeOOH heterojunction nanosheets is 20-50 nm; the surface of the aggregate contains micron-scale grooves, and the depth of the micron-scale groove structure is 50-100 μm and the spacing is 200-300 μm.

5. The method for preparing the functionalized aggregate according to claim 1, wherein: In step S4, the denitrifying bacteria is Pseudomonas denitrificans CGMCC 1.1785, and the petroleum hydrocarbon degrading bacteria is Rhodococcus erythropolis ATCC 4277; the ratio of the number of the denitrifying bacteria to the petroleum hydrocarbon degrading bacteria is 3:1; The concentration of the bacterial solution is 1 to 5×10 8 CFU / g; the vacuum degree of the vacuum negative pressure impregnation method is 0.05-0.1MPa, the holding time is 20-40min, the curing agent includes sodium alginate and chitosan, the concentration of the sodium alginate is 1.0-2.0wt.%, and the concentration of the chitosan is 0.3-0.6wt.%.

6. A functionalized aggregate, characterized in that: The functionalized aggregate is prepared by the preparation method of any one of claims 1 to 5.

7. A self-purifying asphalt pavement material, characterized by: The functionalized aggregate according to claim 6 and modified asphalt are obtained by shear mixing at 150-200° C., wherein the mass ratio of the functionalized aggregate to the modified asphalt is 1:1.2-2.

8. The self-cleaning asphalt pavement material according to claim 7, characterized in that: The functionalized aggregate is surface-grafted with titanate and then shear-mixed with modified asphalt at 150-200°C; the modified asphalt is SBS modified asphalt, and the shear-mixing temperature is 160-180°C; the porosity of the self-purifying asphalt pavement material is 45%-55%, and the water permeability coefficient is ≥1.6-2.5×10 -2 cm / s.

9. The self-cleaning asphalt pavement material according to claim 8, characterized in that: The process of surface grafting treatment with titanate is as follows: adding titanate ethanol solution to functionalized aggregate, performing surface grafting treatment under ultrasonic conditions, the treatment temperature is 70-90°C, the ultrasonic power is 150-250W, and the treatment time is 1-4h; the amount of titanate added is 2-3wt% of the mass of the functionalized aggregate; The self-cleaning asphalt pavement material further comprises carbon nanotubes and basalt fibers, wherein the mass percentage of the carbon nanotubes is 1.5-2.5 wt.%, the mass percentage of the basalt fibers is 3.5-4.5 wt.%, the mass percentage of the functionalized aggregate is 34-38 wt.%, and the mass percentage of the modified asphalt is 55-60 wt.%; The gradation of the functionalized aggregate satisfies the following requirements: 100% passing rate of 9.5mm sieve hole, 85% to 90% passing rate of 4.75mm sieve hole, 60% to 65% passing rate of 2.36mm sieve hole, 40% to 45% passing rate of 1.18mm sieve hole, and 20% to 25% passing rate of 0.6mm sieve hole.

10. A self-cleaning asphalt pavement, characterized by: It comprises a gravel drainage layer, wherein the gravel particle size of the gravel drainage layer is 10-20 mm and the thickness is 25-35 cm. The road surface above the gravel drainage layer is paved with the self-purifying asphalt pavement material according to any one of claims 7-9.

Images