Modified recycled asphalt mixture based on sewage sludge biochar, preparation method and application

Abstract

This invention provides a modified recycled asphalt mixture based on municipal sludge biochar, its preparation method, and its application. The preparation method includes the following steps: S1, taking new asphalt heated to 150-170℃, municipal sludge biochar heated to 180-200℃, coarse aggregate, fine aggregate, mineral powder, RAP heated to 110-130℃, and pine tar-based regenerator heated to 50-80℃; S2, mixing the RAP and pine tar-based regenerator at 180-200℃ to obtain a first mixture; S3, mixing the municipal sludge biochar, new asphalt, and the first mixture together at 180-200℃ to obtain a second mixture; S4, mixing the coarse aggregate, fine aggregate, mineral powder, and the second mixture together at 180-200℃ to obtain a modified recycled asphalt mixture. This invention can obtain a high-performance modified recycled asphalt mixture based on municipal sludge biochar, pine tar-based regenerator, and RAP.

Description

Technical Field

[0001] This invention relates to recycled asphalt mixtures, and more particularly to a modified recycled asphalt mixture based on sewage sludge biochar, its preparation method, and its application. Background Technology

[0002] As a byproduct of domestic sewage treatment, sewage sludge concentrates 30% to 50% of the pollutants in domestic sewage, possessing both "polluting" and "resource" attributes. The safe treatment, disposal, and resource utilization of sewage sludge have always been a hot research topic in the field of sewage treatment internationally. Sewage sludge carbonization technology is a new sewage sludge treatment technology developed in Japan and Europe in the 1990s. Since 2008, China has also gradually carried out research on sewage sludge carbonization technology. The carbonization process of sewage sludge produces a large amount of sewage sludge biochar, which urgently needs to be utilized as a resource.

[0003] Currently, for the recycling of modified old asphalt, the recycling agent cannot repair the broken C=C double bonds. The purpose of recycling is to adjust the proportion of the four components of the matrix asphalt in the modified old asphalt to the standard of new asphalt, which makes the resource utilization of SBS modified RAP difficult. Plant-mixed hot recycled asphalt mixtures are mainly used in the middle and lower layers of the road, and are rarely used in the upper layer.

[0004] Chinese invention patent application CN105017788A discloses a method for modifying asphalt and its mixtures using biochar. The method involves preparing a biochar modifier using plant carbon sources, then incorporating the biochar into the asphalt and its mixtures to produce biochar-modified asphalt and its mixtures. While this method improves the performance of ordinary asphalt and its mixtures, it does not yield modified recycled asphalt mixtures, nor does it explore regenerators for regenerated asphalt (RAP), thus failing to achieve the resource utilization of RAP. Furthermore, the biochar used is not municipal sewage sludge biochar. Therefore, it does not obtain high-performance recycled asphalt mixtures based on municipal sewage sludge biochar, regenerators, and RAP.

[0005] Therefore, it is necessary to provide a modified recycled asphalt mixture based on domestic sewage sludge biochar, its preparation method, and its application, in order to solve or at least alleviate the technical problem of how to obtain high-performance modified recycled asphalt mixtures based on domestic sewage sludge biochar, pine tar-based regenerators, and RAP. Summary of the Invention

[0006] The main objective of this invention is to provide a modified recycled asphalt mixture based on domestic sewage sludge biochar, its preparation method, and its application, aiming to solve the technical problem of how to obtain a high-performance modified recycled asphalt mixture based on domestic sewage sludge biochar, pine tar-based regenerator, and RAP.

[0007] To achieve the above objectives, this invention provides a method for preparing modified recycled asphalt mixture based on sewage sludge biochar, comprising the following steps:

[0008] S1, take new asphalt heated to 150-170℃; take domestic sewage sludge biochar, coarse aggregate, fine aggregate, and mineral powder heated to 180-200℃; take RAP heated to 110-130℃; take pine tar-based regenerator heated to 50-80℃;

[0009] The mass ratio of the new asphalt, the sewage sludge biochar, the coarse aggregate, the fine aggregate, the mineral powder, the RAP, and the pine tar-based regenerator is 3-3.2:0.7-0.9:40-41:18.5-20:1-1.2:34-36:0.09-0.11;

[0010] The pine tar-based regenerator comprises, by weight percentage: 60-80% pine tar, 10-15% plasticizer, 2-6% thickener, 1-5% softener, 2-6% pour point depressant, and 2-6% dispersant;

[0011] S2, the RAP and the pine tar-based regenerator are mixed at a temperature of 180-200°C to obtain the first mixture;

[0012] S3, the sewage sludge biochar, the new asphalt, and the first mixture are mixed together at a temperature of 180-200°C to obtain the second mixture;

[0013] S4, the coarse aggregate, the fine aggregate, the mineral powder and the second mixture are mixed together at a temperature of 180-200°C to obtain the modified recycled asphalt mixture.

[0014] Furthermore, the new asphalt is SBS modified asphalt, and the mass percentage of SBS in the SBS modified asphalt is 3.5% to 4.5%; the mass percentage of old asphalt in the RAP is 4% to 5%, and the RAP is derived from the surface layer of the road surface.

[0015] Furthermore, the biochar from the domestic sewage sludge is obtained by carbonization of domestic sewage sludge; the organic matter content in the domestic sewage sludge is 40-60% by mass; and the particle size of the biochar from the domestic sewage sludge is no larger than the pore size corresponding to a 100-mesh sieve.

[0016] Furthermore, the biochar from the sewage sludge contains carbon, oxygen, silicon, aluminum, iron, potassium, calcium, phosphorus, magnesium, nitrogen, hydrogen, titanium, sodium, sulfur, and manganese.

[0017] Furthermore, the plasticizer includes epoxidized soybean oil, the thickener includes C9 petroleum resin, the softener includes waste plastic oil, the pour point depressant includes polymethyl methacrylate, and the dispersant includes acrylamide.

[0018] Furthermore, the pine tar includes pyrolysis oil from pine roots and branches at 400–500°C.

[0019] Furthermore, the method of obtaining the pine tar-based regenerator includes:

[0020] S21, the pine tar, the softener, the pour point depressant, and the dispersant are sheared together at a temperature of 60-85°C to obtain the first processed product;

[0021] S22, the first processed material, the plasticizer, and the tackifier are sheared together at a temperature of 95-120°C to obtain the pine tar-based regenerator.

[0022] Furthermore, the coarse aggregate has two particle size ranges: the first range has a particle size of 9.5–13.2 mm, and the second range has a particle size of 4.75–9.5 mm. The mass ratio of the first range to the second range is 15–30:20–35. The fine aggregate has a particle size of less than 4.75 mm. The mineral powder includes limestone powder.

[0023] The present invention also provides a modified recycled asphalt mixture based on sewage sludge biochar, which is prepared by any of the modified recycled asphalt mixture preparation methods described above.

[0024] The present invention also provides an application of modified recycled asphalt mixture based on sewage sludge biochar as described above in roads.

[0025] Compared with the prior art, the present invention has at least the following advantages:

[0026] This invention yields a high-performance modified recycled asphalt mixture based on sewage sludge biochar, pine tar-based regenerator, and RAP. This invention enables large-scale utilization of sewage sludge biochar and RAP, conserving non-renewable resources, reducing the construction cost of asphalt pavement, realizing high-value and efficient resource utilization, and mitigating its environmental impact. This invention uses pine tar instead of extracted oil and combines it with epoxidized soybean oil, C9 petroleum resin, waste plastic oil, polymethyl methacrylate, and acrylamide to prepare a high-performance, environmentally friendly regenerator—a pine tar-based regenerator—that can fully regenerate heavy-duty asphalt in SBS-modified old asphalt. This invention also uses sewage sludge biochar as a modifier to modify the SBS-modified recycled asphalt, improving the performance of the SBS-modified recycled asphalt mixture and making it better suited for road surface layers. Furthermore, this invention optimizes the mixing process, adding sewage sludge biochar and SBS-modified asphalt to the mixing pot before the aggregate, ensuring thorough integration and regeneration of the pine tar-based regenerator, old asphalt, and SBS-modified asphalt, and ensuring sufficient mixing and modification of the SBS-modified recycled asphalt by the sewage sludge biochar.

[0027] In this invention, the biochar from municipal sewage sludge differs from conventional biochar primarily because it contains not only a large proportion of carbon (C) but also nutrients such as phosphorus (P), nitrogen (N), potassium (K), and calcium (Ca). Furthermore, it possesses porous and adsorbent properties, enabling it to specifically modify recycled asphalt. When this biochar is applied to regenerated asphalt (RAP) mixed with a pine tar-based regenerator, it effectively adsorbs the regenerated asphalt and improves its performance.

[0028] This invention tests the relevant indicators of municipal sludge biochar and SBS modified recycled asphalt mixture. Compared with the same type of SBS modified recycled asphalt mixture and new modified asphalt mixture, the residual stability, freeze-thaw splitting strength ratio, and dynamic stability of the municipal sludge biochar-based modified recycled asphalt mixture are better than those of SBS modified recycled asphalt mixture, and are basically close to those of new modified asphalt mixture. This indicates that municipal sludge biochar can effectively improve the water stability and rutting resistance of asphalt mixture. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0030] Figure 1 This is a gradation diagram for AC-13 asphalt mixture.

[0031] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0034] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0035] This invention provides a method for preparing modified recycled asphalt mixture based on sewage sludge biochar, comprising the following steps:

[0036] S1, take new asphalt heated to 150-170℃; take domestic sewage sludge biochar, coarse aggregate, fine aggregate, and mineral powder heated to 180-200℃; take RAP heated to 110-130℃; take pine tar-based regenerator heated to 50-80℃.

[0037] The mass ratio of the new asphalt, the domestic sewage sludge biochar, the coarse aggregate, the fine aggregate, the mineral powder, the RAP, and the pine tar-based regenerator is 3-3.2:0.7-0.9:40-41:18.5-20:1-1.2:34-36:0.09-0.11.

[0038] The new asphalt is SBS modified asphalt, and the mass percentage of SBS in the SBS modified asphalt is 3.5% to 4.5%; the RAP originates from the surface layer of the road surface; the RAP is SBS modified RAP; specifically, the RAP can be understood as: recycled material from SBS modified asphalt mixture recovered from old road surfaces; the proportion of aged asphalt (old asphalt) in the RAP is 4% to 5%. In this invention, the RAP has two grades: the first grade RAP has a particle size of 0 to 8 mm (less than 8 mm), and the second grade RAP has a particle size of 8 to 16 mm. The mass ratio of the first grade RAP to the second grade RAP can be 14-16:19-21.

[0039] The biochar from the municipal sludge is obtained by carbonizing municipal sludge. This invention uses municipal sludge as the carbon source and employs a pyrolysis method to prepare the biochar modifier, specifically using an integrated continuous sludge carbonization technology. In this invention, no oxygen is involved in the entire carbonization process, resulting in anaerobic carbonization, and no oxides are present in the product. The carbonization process of the municipal sludge biochar includes three parts: a pre-drying section, a drying section, and a carbonization section. In the pre-drying section, the municipal sludge with a high moisture content is directly contacted with a relatively low-temperature hot air for initial drying. In the drying section, the municipal sludge with a low moisture content is indirectly heated by high-temperature gas through the machine wall, continuously evaporating and drying. In the carbonization section, the municipal sludge is indirectly heated to 500-600°C through the machine wall by high-temperature gas, and the municipal sludge is pyrolyzed into biochar.

[0040] The domestic sewage sludge originates from a domestic wastewater treatment plant, and the organic matter content of the sludge is 40-60% by mass. The particle size of the domestic sewage sludge biochar is no larger than the aperture corresponding to a 100-mesh sieve. In this invention, the domestic sewage sludge biochar is ground into powder using a vertical planetary ball mill and sieved through a 100-mesh sieve. The undersize material is collected to obtain a domestic sewage sludge biochar modifier with the corresponding particle size. In this invention, the dosage of the domestic sewage sludge biochar is 10-20% of the mass of the blended asphalt (new asphalt + recycled asphalt), and the domestic sewage sludge biochar can replace part of the mineral aggregate as a filler in the mixture.

[0041] In this invention, the main component of the sewage sludge biochar is carbon (C), and it also contains small amounts of phosphorus (P), nitrogen (N), potassium (K), and calcium (Ca). All of these elements possess porous and adsorption properties, enabling them to effectively adsorb asphalt and improve its performance. Specifically, the sewage sludge biochar contains carbon, oxygen, silicon, aluminum, iron, potassium, calcium, phosphorus, magnesium, nitrogen, hydrogen, titanium, sodium, sulfur, and manganese.

[0042] The biochar from the sewage sludge contains, by mass fraction, 23-25% carbon, 22-25% oxygen, 17-20% silicon, 8-11% aluminum, 4-5% iron, 2.5-3.5% potassium, 1-2% calcium, 1-2% phosphorus, 0.5-1% magnesium, 0.5-1% nitrogen, 0.3-0.8% hydrogen, 0.2-0.6% titanium, 0.2-0.35% sodium, 0.2-0.35% sulfur, and 0.1-0.25% manganese.

[0043] In this invention, the pine tar-based regenerator, by mass fraction, comprises or consists of: 60-80% pine tar, 10-15% plasticizer, 2-6% thickener, 1-5% softener, 2-6% pour point depressant, and 2-6% dispersant; the total mass percentage of each component is 100%.

[0044] The pine tar is pyrolysis oil from pine roots and branches at 400–500°C; the plasticizer includes epoxidized soybean oil, the thickener includes C9 petroleum resin, the softener includes waste plastic oil, the pour point depressant includes polymethyl methacrylate, and the dispersant includes acrylamide. In this invention, the dosage of the pine tar-based regenerator is 6–10% of the mass of the aged asphalt (old asphalt) in the RAP.

[0045] The pine tar-based regenerator is obtained through the following methods:

[0046] S21, the pine tar, the softener, the pour point depressant, and the dispersant are sheared together at a temperature of 60-85°C or 60-80°C for 5-15 minutes to obtain the first processed product.

[0047] S22, the first processed material, the plasticizer, and the tackifier are sheared together at a temperature of 95-120°C or 100-120°C for 15-25 minutes, and then cooled to obtain the pine tar-based regenerator.

[0048] Currently, the majority of asphalt recycling agents are primarily composed of extracted oil, accounting for up to 80% or more by weight. However, extracted oil is a petroleum-based product and a non-renewable resource. Pine tar, on the other hand, is widely available, utilizes waste materials, and is environmentally friendly and renewable. As a renewable resource, it can effectively replenish the light components missing in aged asphalt, disperse the asphaltenes aggregated in aged asphalt, and reduce the viscosity of aged asphalt. Therefore, it can be used to replace extracted oil in the preparation of asphalt recycling agents.

[0049] In this invention, the coarse aggregate has two particle size ranges: the first range has a particle size of 9.5–13.2 mm, and the second range has a particle size of 4.75–9.5 mm. The mass ratio of the first and second ranges is 15–30:20–35 or 17.7–19.7:20.9–22.9. The fine aggregate has a particle size less than 4.75 mm, i.e., fine aggregate is a single grade with a size of 0–4.75 mm. The mineral powder includes limestone powder, and the mineral powder has a particle size greater than 75% below a 0.075 mm sieve (i.e., particles no larger than 0.075 mm account for more than 75% of the mineral powder).

[0050] In the research process of this invention, the main step is to determine the ratio of the RAP extraction and screening results to the oilstone ratio; then, the coarse aggregate, the fine aggregate, the mineral powder screening results and the RAP extraction and screening results are graded and combined to determine the proportion of each grade of aggregate.

[0051] S2, the RAP and the pine tar-based regenerator are mixed in a mixing pot at a temperature of 180-200°C for 50-70 seconds to obtain the first mixture.

[0052] S3, the sewage sludge biochar, the new asphalt, and the first mixture are mixed together in a mixing pot at a temperature of 180-200°C for 50-70 seconds to obtain the second mixture.

[0053] S4, the coarse aggregate, the fine aggregate, the mineral powder and the second mixture are mixed together in a mixing pot at 180-200°C for 100-140 seconds to obtain the modified recycled asphalt mixture.

[0054] In this invention, the sewage sludge biochar and the new asphalt are mixed before the mineral aggregate. The purpose is to fully integrate and regenerate the pine tar-based regenerator, the old asphalt in the RAP, and the new asphalt, and to fully mix and modify the SBS-modified regenerated asphalt with the sewage sludge biochar.

[0055] In this invention, the pine tar-based regenerator can fully regenerate the heavy-duty asphalt in SBS-modified old asphalt, and the sewage sludge biochar can improve the performance of SBS-modified recycled asphalt mixture, enabling it to be better applied to the road surface layer. This invention also enables large-scale utilization of sewage sludge biochar and SBS-modified RAP, saving non-renewable resources, reducing the construction cost of asphalt pavement, achieving high-value and efficient resource utilization, and mitigating its environmental impact.

[0056] The present invention also provides a recycled asphalt mixture based on sewage sludge biochar, which is prepared by any of the recycled asphalt mixture preparation methods described above.

[0057] The present invention also provides an application of recycled asphalt mixture based on sewage sludge biochar as described above in roads, especially in road surface layers.

[0058] The following are specific examples of the present invention:

[0059] In the following cases, the standards for each raw material are as follows:

[0060] 1. The mass percentage of SBS in the new asphalt (SBS modified asphalt) is 4%; the coarse aggregate has two particle size grades: the first grade has a particle size of 9.5-13.2 mm, and the second grade has a particle size of 4.75-9.5 mm; the fine aggregate has a particle size of less than 4.75 mm; the mineral powder is limestone mineral powder, and the particle size of the mineral powder is greater than 75% below a 0.075 mm sieve.

[0061] 2. RAP (modified RAP) is a recycled SBS modified asphalt mixture from old pavement, derived from the surface layer of the pavement. The mass ratio of aged asphalt (old asphalt) in RAP is 4.5%. RAP has two particle size grades: the first grade of RAP has a particle size of 0-8mm, and the second grade of RAP has a particle size of 8-16mm.

[0062] 3. The biochar from domestic sewage sludge is derived from domestic sewage sludge, which contains 52% organic matter by mass. The biochar from domestic sewage sludge in this invention is obtained by sampling from a domestic sewage sludge carbonization plant.

[0063] After obtaining the biochar from the domestic sewage sludge, it was ground into powder using a vertical planetary ball mill and sieved through a 100-mesh sieve. The material passing through the sieve was taken as the domestic sewage sludge biochar to be used as a modifier. The domestic sewage sludge biochar has a porous structure. The elemental analysis results of the domestic sewage sludge biochar are shown in Table 1.

[0064] Table 1. Elemental composition of sludge-based biochar

[0065]

[0066] 4. The method for obtaining pine tar-based regenerator is as follows:

[0067] Pine tar was heated to 80°C, and waste plastic oil, polymethyl methacrylate and acrylamide were added and sheared together at 80°C for 10 minutes. Then, the temperature of the sheared semi-finished product was raised to 100°C, and epoxidized soybean oil and C9 petroleum resin were added and sheared together at 100°C for 20 minutes. After cooling, pine tar-based regenerator was obtained. The pine tar was the cracked oil of pine roots and branches at about 450°C.

[0068] Of which, by mass fraction, the pine tar-based regenerator contains 75.0% pine tar, 11.3% epoxidized soybean oil, 3.8% C9 petroleum resin, 2.3% waste plastic oil, 3.8% polymethyl methacrylate, and 3.8% acrylamide.

[0069] Analysis example 1

[0070] 1. In this analysis, a performance test was conducted on a mixture of domestic sewage sludge biochar and AC-13 modified recycled asphalt; the mass percentage of asphalt in the mixture was 4.8%.

[0071] 2. In this analysis example, RAP (SBS modified RAP) accounts for 35% of the mass of the mixture; since the mass of old asphalt accounts for 4.5% of RAP, the old asphalt accounts for 1.6% of the asphalt content in the mixture; the indicators of old asphalt and new SBS modified asphalt are shown in Table 2.

[0072] 3. In this analysis example, the dosage of the rejuvenator (pine tar-based rejuvenator) is determined based on the requirement that the penetration index of the recycled asphalt meets the requirements of new asphalt. As shown in Table 2, the dosage of the rejuvenator is determined to be 8%. The dosage of the rejuvenator is the mass ratio of the rejuvenator to the old asphalt.

[0073] Table 2 Asphalt Test Results

[0074]

[0075] 4. In this analysis example, the mixture contains 1.7% recycled asphalt and 1.7% old asphalt, therefore, 3.1% new asphalt needs to be added.

[0076] Based on mass percentage, 10%, 13%, 16%, 19%, and 22% of domestic sewage sludge biochar were added to the blended recycled asphalt (calculated as recycled asphalt + new asphalt), respectively. The mixture was sheared for 20 minutes using a high-speed shearing machine. The indicators are shown in Table 3. The optimal dosage of domestic sewage sludge biochar under this RAP dosage is 16% of the mass of the blended recycled asphalt, accounting for 0.8% of the mass of the mixture.

[0077] Table 3 Asphalt Test Results

[0078]

[0079] Example 1

[0080] In this embodiment, the preparation method of the modified recycled asphalt mixture is as follows:

[0081] 1. Based on the analysis of Example 1, in the mixture of sewage sludge biochar and AC-13 modified recycled asphalt, the coarse aggregate... ( 9.5~13.2mm ) Coarse aggregate( 4.75~9.5mm ) The mass ratio of fine aggregate, RAP, mineral powder, sewage sludge biochar, new asphalt, and regenerator is 18.7:21.9:19.3:35:1.1:0.8:3.1:0.1. The RAP is available in two grades: the first grade has a particle size of 0-8mm, and the second grade has a particle size of 8-16mm. The mass ratio of the first grade RAP to the second grade RAP is 15:20.

[0082] Based on this, the recycled asphalt mixture in this embodiment is prepared according to the mass ratio of new asphalt, domestic sewage sludge biochar, coarse aggregate, fine aggregate, mineral powder, RAP, and pine tar-based regenerator as 3.1:0.8:40.6:19.3:1.1:35:0.1; wherein, the mass ratio of the first grade coarse aggregate to the second grade coarse aggregate is 18.7:21.9, and the mass ratio of the first grade RAP to the second grade RAP is 15:20.

[0083] 2. Heat the new asphalt to 160℃, heat the domestic sewage sludge biochar, coarse aggregate, fine aggregate and mineral powder to 190℃, heat the RAP to 120℃, and heat the pine tar-based regenerator to 60℃.

[0084] 3. First, add RAP and pine tar-based regenerator to a mixing pot at 180℃ and mix for 60 seconds (mixing temperature set at 180℃). Then, add domestic sewage sludge biochar and new asphalt to the mixing pot and mix for 60 seconds (mixing temperature set at 180℃). Finally, add coarse aggregate, fine aggregate and mineral powder to the mixing pot and mix for 120 seconds (mixing temperature set at 180℃) to obtain recycled asphalt mixture.

[0085] 4. The gradation curve for this embodiment is shown in [reference]. Figure 1 As shown; the test indicators for recycled asphalt mixtures are Marshall stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability, as detailed in Analysis Example 2.

[0086] Comparative Example 1

[0087] 1. SBS modified asphalt was used to conduct performance tests on AC-13 modified asphalt mixture.

[0088] 2. In AC-13 asphalt mixtures, coarse aggregate ( 9.5~13.2mm ) Coarse aggregate ( 4.75~9.5mm ) The gradation ratio of fine aggregate, mineral powder, and new asphalt is 26.7:30.5:34.2:3.8:4.8; the gradation curve for this comparative example is shown in [reference needed]. Figure 1 As shown, the gradation is basically similar to that of Example 1.

[0089] 3. Heat the new asphalt to 160℃; heat the coarse aggregate, fine aggregate and mineral powder to 190℃.

[0090] 4. Add coarse aggregate, fine aggregate and new asphalt to a mixing pot at 180℃ and mix for 60 seconds (mixing temperature set at 180℃). Then add mineral powder to the mixing pot and mix for 120 seconds (mixing temperature set at 180℃) to obtain asphalt mixture.

[0091] In this comparative example, the testing indicators for asphalt mixtures are Marshall stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability, as detailed in Analysis Example 2.

[0092] Comparative Example 2

[0093] Compared to Example 1, this comparative example omits the pine tar-based regenerator (adaptively adjusting the proportions of each component), while keeping other conditions unchanged; details are as follows:

[0094] 1. In this comparative example, the recycled asphalt mixture was prepared with the following mass ratios: new asphalt, domestic sewage sludge biochar, coarse aggregate, fine aggregate, mineral powder, and RAP: 3.2:0.8:40.6:19.3:1.1:35; wherein the mass ratio of the first grade coarse aggregate to the second grade coarse aggregate was 18.7:21.9, and the mass ratio of the first grade RAP to the second grade RAP was 15:20.

[0095] 2. Heat the new asphalt to 160℃, heat the domestic sewage sludge biochar, coarse aggregate, fine aggregate and mineral powder to 190℃, and heat the RAP to 120℃.

[0096] 3. Add RAP to a mixing pot at 180℃ and mix for 60 seconds (mixing temperature set to 180℃). Then add domestic sewage sludge biochar and new asphalt to the mixing pot and mix for 60 seconds (mixing temperature set to 180℃). Finally, add coarse aggregate, fine aggregate and mineral powder to the mixing pot and mix for 120 seconds (mixing temperature set to 180℃) to obtain recycled asphalt mixture.

[0097] 4. The testing indicators for recycled asphalt mixtures are Marshall stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability. For details, please refer to Analysis Example 2.

[0098] Comparative Example 3

[0099] Compared to Example 1, this comparative example omits the biochar from domestic sewage sludge (by adaptively adjusting the proportions of each component), while keeping other conditions unchanged; details are as follows:

[0100] 1. In this comparative example, the recycled asphalt mixture was prepared with a mass ratio of new asphalt, coarse aggregate, fine aggregate, mineral powder, RAP, and pine tar-based rejuvenator of 3.1:40.6:19.3:1.9:35:0.1; wherein the mass ratio of the first grade coarse aggregate to the second grade coarse aggregate was 18.7:21.9, and the mass ratio of the first grade RAP to the second grade RAP was 15:20. 。

[0101] 2. Heat the new asphalt to 160°C, the coarse aggregate, fine aggregate and mineral powder to 190°C, the RAP to 120°C, and the pine tar-based regenerator to 60°C.

[0102] 3. First, add RAP and pine tar-based recycler to a mixing pot at 180℃ and mix for 60 seconds (mixing temperature set at 180℃). Then, add new asphalt to the mixing pot and mix for 60 seconds (mixing temperature set at 180℃). Finally, add coarse aggregate, fine aggregate, and mineral powder to the mixing pot and mix for 120 seconds (mixing temperature set at 180℃) to obtain recycled asphalt mixture.

[0103] 4. The testing indicators for recycled asphalt mixtures are Marshall stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability. For details, please refer to Analysis Example 2.

[0104] Comparative Example 4

[0105] Compared to Example 1, this comparative example omits the pine tar-based regenerator and sewage sludge biochar, while keeping other conditions unchanged; details are as follows:

[0106] 1. In this comparative example, the recycled asphalt mixture was prepared with a mass ratio of new asphalt, coarse aggregate, fine aggregate, mineral powder, and RAP of 3.2:40.6:19.3:1.9:35; wherein the mass ratio of the first grade of coarse aggregate to the second grade of coarse aggregate was 18.7:21.9, and the mass ratio of the first grade of RAP to the second grade of RAP was 15:20. 。

[0107] 2. Heat the new asphalt to 160°C, the coarse aggregate, fine aggregate and mineral powder to 190°C, and the RAP to 120°C.

[0108] 3. Add RAP to a mixing pot at 180℃ and mix for 60 seconds (mixing temperature set to 180℃). Then add new asphalt to the mixing pot and mix for 60 seconds (mixing temperature set to 180℃). Finally, add coarse aggregate, fine aggregate and mineral powder to the mixing pot and mix for 120 seconds (mixing temperature set to 180℃) to obtain recycled asphalt mixture.

[0109] 4. The testing indicators for recycled asphalt mixtures are Marshall stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability. For details, please refer to Analysis Example 2.

[0110] Comparative Example 5

[0111] Compared to Example 1, this comparative example changes the preparation method of the recycled asphalt mixture while keeping other conditions unchanged; the details are as follows:

[0112] RAP and pine tar-based regenerator are first added to a mixing pot at 180°C and mixed for 60 seconds (mixing temperature set at 180°C). Then, coarse aggregate and fine aggregate are added to the mixing pot and mixed together for 60 seconds (mixing temperature set at 180°C). Next, new asphalt is added to the mixing pot and mixed together for 60 seconds (mixing temperature set at 180°C). Finally, domestic sewage sludge biochar and mineral powder are added to the mixing pot and mixed together for 60 seconds (mixing temperature set at 180°C) to obtain modified recycled asphalt mixture.

[0113] In this comparative example, the test indicators for recycled asphalt mixtures are Marshall stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability, as detailed in Analysis Example 2.

[0114] Analysis example 2

[0115] The asphalt mixtures in Example 1 and Comparative Examples 1-5 were tested according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). As shown in Table 4, the performance of the modified recycled asphalt mixture based on domestic sewage sludge biocarbon is basically close to that of the new AC-13 modified asphalt mixture.

[0116] Compared with Comparative Examples 2, 3, and 4, it was found that both pine tar-based regenerator and sewage sludge biochar play an important role in improving the performance of AC-13 modified recycled asphalt mixtures. The performance of the mixtures was significantly reduced when either of them was missing.

[0117] Compared with Comparative Example 5, the improved mixing process, in which sewage sludge biochar and SBS modified asphalt (new asphalt) are added to the mixing pot before the aggregate, resulted in better performance of the AC-13 modified recycled asphalt mixture. This indicates that the pine tar-based regenerator, old asphalt and SBS modified asphalt can be more fully integrated and regenerated during the mixing process, and that sewage sludge biochar can fully mix and modify the SBS modified recycled asphalt.

[0118] Table 4. Test Results of Asphalt Mixtures

[0119]

[0120]

[0121] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing modified recycled asphalt mixture based on sewage sludge biochar, characterized in that, Including the following steps: S1, take new asphalt heated to 150~170℃; take domestic sewage sludge biochar, coarse aggregate, fine aggregate, and mineral powder heated to 180~200℃; take RAP heated to 110~130℃; take pine tar-based regenerator heated to 50~80℃; The mass ratio of the new asphalt, the sewage sludge biochar, the coarse aggregate, the fine aggregate, the mineral powder, the RAP, and the pine tar-based regenerator is 3~3.2:0.7~0.9:40~41:18.5~20:1~1.2:34~36:0.09~0.11; By mass percentage, the pine tar-based regenerator comprises: 60-80% pine tar, 10-15% plasticizer, 2-6% thickener, 1-5% softener, 2-6% pour point depressant, and 2-6% dispersant, with the total mass percentage of each component being 100%. S2, the RAP and the pine tar-based regenerator are mixed at a temperature of 180~200°C to obtain the first mixture; S3, the sewage sludge biochar, the new asphalt, and the first mixture are mixed together at a temperature of 180~200℃ to obtain the second mixture; S4, the coarse aggregate, the fine aggregate, the mineral powder and the second mixture are mixed together at a temperature of 180~200℃ to obtain the modified recycled asphalt mixture.

2. The method for preparing modified recycled asphalt mixture according to claim 1, characterized in that, The new asphalt is SBS modified asphalt, and the mass percentage of SBS in the SBS modified asphalt is 3.5-4.5%; the mass percentage of old asphalt in the RAP is 4-5%, and the RAP is derived from the surface layer of the road.

3. The method for preparing modified recycled asphalt mixture according to claim 1, characterized in that, The biochar made from domestic sewage sludge is obtained by carbonization of domestic sewage sludge; the organic matter content in the domestic sewage sludge is 40-60% by mass; the particle size of the biochar made from domestic sewage sludge is no larger than the pore size corresponding to a 100-mesh sieve.

4. The method for preparing modified recycled asphalt mixture according to claim 1, characterized in that, The biochar from the sewage sludge contains carbon, oxygen, silicon, aluminum, iron, potassium, calcium, phosphorus, magnesium, nitrogen, hydrogen, titanium, sodium, sulfur, and manganese.

5. The method for preparing modified recycled asphalt mixture according to claim 1, characterized in that, The plasticizer includes epoxidized soybean oil, the thickener includes C9 petroleum resin, the softener includes waste plastic oil, the pour point depressant includes polymethyl methacrylate, and the dispersant includes acrylamide.

6. The method for preparing modified recycled asphalt mixture according to claim 1, characterized in that, The pine tar includes pyrolysis oil from pine roots and branches at 400-500°C.

7. The method for preparing modified recycled asphalt mixture according to claim 1, characterized in that, The pine tar-based regenerator is obtained through the following methods: S21, the pine tar, the softener, the pour point depressant, and the dispersant are sheared together at a temperature of 60~85°C to obtain the first processed product; S22, the first processed material, the plasticizer, and the tackifier are sheared together at a temperature of 95~120°C to obtain the pine tar-based regenerator.

8. The method for preparing modified recycled asphalt mixture according to claim 1, characterized in that, The coarse aggregate has two particle size ranges: the first range has a particle size of 9.5~13.2mm, and the second range has a particle size of 4.75~9.5mm. The mass ratio of the first range to the second range is 15~30:20~35. The fine aggregate has a particle size of less than 4.75mm. The mineral powder includes limestone powder.

9. A modified recycled asphalt mixture based on sewage sludge biochar, characterized in that, The modified recycled asphalt mixture is prepared using the preparation method described in any one of claims 1-8.

10. The application of a modified recycled asphalt mixture based on sewage sludge biochar as described in claim 9 in roads.

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