High-rap-content recycled stress absorbing layer mixture and preparation method thereof

Abstract

The application discloses a high-content RAP regenerated stress absorbing layer mixture and a preparation method thereof, and belongs to the technical field of road engineering regeneration. The mixture comprises, in terms of weight parts, RAP fine aggregate 50-70 parts, basalt new aggregate 24-32 parts, composite modified asphalt 5.0-6.8 parts, activated steel slag micro powder 3-6 parts and regenerator 0.5-1.0 parts; the activated steel slag micro powder is a filler obtained by surface treatment of steel slag micro powder with a silane coupling agent; the regenerator contains maleic anhydride grafted polyethylene. The application is used to solve the problems of insufficient fusion of new and old asphalts, insufficient adhesion of rubber powder and fillers to the asphalt interface in the high-content RAP system, and the activated steel slag micro powder, rubber powder and new and old asphalts are connected into one body by means of maleic anhydride grafted polyethylene, so that the obtained mixture has high-temperature stability, low-temperature anti-cracking performance and anti-fatigue performance, and can be used for road stress absorbing layers.

Description

Technical Field

[0001] This invention belongs to the field of road engineering recycling technology, specifically relating to a high-content RAP recycled stress-absorbing layer mixture and its preparation method. Background Technology

[0002] Every year, my country generates a large amount of recycled asphalt mixture (RAP) during highway reconstruction, expansion, and pavement maintenance projects. RAP contains aged asphalt and aggregates, possessing high resource utilization value. Using it in recycled asphalt mixtures can reduce the consumption of natural sand and asphalt, thus lowering project costs. Therefore, increasing the proportion of RAP added and realizing its large-scale, high-value utilization is an important development direction in the field of road engineering recycling.

[0003] Existing hot asphalt recycling technologies still face the following problems when achieving high RAP (Rich Acid Asphalt) content utilization. First, the RAP content is generally low, typically not exceeding 30% in conventional hot recycling processes, making high-content utilization difficult. Furthermore, the fine aggregates in RAP, due to their high degree of aging, surface coating by aged asphalt, and poor adhesion, have low utilization rates in recycled mixtures. Second, the aged asphalt in RAP hardens and becomes brittle after oxidation. Under high-content conditions, the aged asphalt film is not easily reactivated and fully integrates with the newly added binder. Insufficient compatibility and diffusion between old and new asphalt leads to poor water stability, low-temperature crack resistance, and fatigue resistance in the recycled mixture, making it difficult to meet the requirements of stress-absorbing layers for high elasticity, high adhesion, and crack resistance.

[0004] To improve the performance of binders used in stress-absorbing layers, recycled tire rubber powder is often used to modify the base asphalt. Although rubber powder-modified asphalt can improve the elasticity and bonding properties of the binder, the compatibility between rubber powder and asphalt is poor. It is unevenly dispersed in the asphalt matrix and prone to segregation. The modified asphalt also has insufficient storage stability, which affects the full realization of its modifying effect.

[0005] Steel slag is a major solid waste generated by the metallurgical industry. It is highly alkaline, has a rough surface, and a rich mineral composition, which is beneficial for improving the adhesion between asphalt and aggregates when used as a filler in asphalt mixtures. However, untreated steel slag powder has insufficient surface activity, limited interfacial compatibility and adhesion with asphalt, thus restricting its application in high-performance recycled asphalt mixtures.

[0006] There are existing public reports on recycled asphalt mixtures. For example, CN106904871A discloses a drainage recycled asphalt mixture and its mix design method, which uses milled recycled material as the aggregate source, limestone mineral powder as filler, and diluted polymer-modified asphalt as binder, and optimizes the blending ratio of recycled material; CN119977418A discloses a warm-mix high-proportion recycled asphalt mixture, which has a high content of waste asphalt and uses a regenerating agent made of aromatic oil and tung oil to regenerate aged asphalt. The above technologies have achieved certain results in improving the utilization rate of RAP, but the filler used is still conventional mineral powder without surface activation treatment. The filler and asphalt mainly rely on physical adhesion, and the regenerating agent does not have the function of forming a chemical bond with the filler surface. There is a lack of synergistic effect among the modified components. Therefore, under high RAP content conditions, it is still difficult to simultaneously take into account the high-temperature stability, low-temperature crack resistance and fatigue resistance of the mixture.

[0007] Therefore, how to further improve the utilization rate of fine aggregates, strengthen the interfacial adhesion between fillers and asphalt, and improve the comprehensive road performance of recycled mixtures such as crack resistance and fatigue resistance, while realizing the high-value utilization of steel slag solid waste in high-dosage RAP recycling technology, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the problems existing in current high-content RAP recycling technologies, such as insufficient integration of new and old asphalt, poor dispersibility of waste tire rubber powder in asphalt, and insufficient adhesion between inorganic fillers and asphalt, as well as the lack of synergy among the modified components and the difficulty in simultaneously achieving high-temperature stability, low-temperature crack resistance, and fatigue resistance in high-content RAP systems, this invention provides a high-content RAP recycled stress-absorbing layer mixture and its preparation method. The invention restores aged asphalt in RAP using a recycling agent, enhances the binder performance using composite modified asphalt, and activates the surface of steel slag powder using a silane coupling agent containing active groups. Then, maleic anhydride-grafted polyethylene in the recycling agent connects the activated steel slag powder, waste tire rubber powder, and new and old asphalt into a unified whole, constructing a synergistic modified system. This results in a recycled asphalt mixture suitable for road stress-absorbing layers, achieving high-value utilization of solid wastes such as RAP and steel slag.

[0009] To achieve the above objectives, the present invention adopts the following technical solution.

[0010] This invention provides a high-content RAP recycled stress-absorbing layer mixture, which, by weight, comprises 50-70 parts of RAP fine aggregate, 24-32 parts of basalt new aggregate, 5.0-6.8 parts of composite modified asphalt, 3-6 parts of activated steel slag powder, and 0.5-1.0 parts of recycling agent.

[0011] Preferably, the RAP fine aggregate is fine aggregate obtained by crushing and screening recycled asphalt pavement milling material. The particle size of both the RAP fine aggregate and the new basalt aggregate is 0-10 mm. The old asphalt content is 3.8%-5.6% as determined by centrifugal extraction. The aged asphalt obtained by extraction has a penetration of 24-25.5 (0.1 mm), a softening point of 66.8-67.5℃, and a ductility of 11.8-12.6 cm at 15℃ under the conditions of 25℃, 100g, and 5s. The moisture content of the RAP is less than 1%.

[0012] Preferably, the steel slag powder is a fine powder that has passed through a 0.075mm sieve.

[0013] Preferably, the activated steel slag powder is a filler obtained by surface treatment of steel slag powder with a silane coupling agent. The silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane. The amount of the silane coupling agent is 0.5% to 3.0% of the weight of the steel slag powder. The surface treatment method of the silane coupling agent is as follows: anhydrous ethanol and deionized water are mixed at a volume ratio of 95:5 to prepare an ethanol-water solution. The pH is adjusted to 4-5 with glacial acetic acid. The silane coupling agent is added and stirred for 30 minutes to prepare a treatment solution. The steel slag powder is added to the treatment solution at a liquid-solid ratio of 1:1 to 2:1 (mL:g) and stirred at room temperature. After drying, the activated steel slag powder is obtained. More preferably, the stirring time is 30 minutes, and the drying temperature is 105℃ for 4 hours.

[0014] Preferably, the composite modified asphalt comprises, by weight, 100 parts of 70# base asphalt, 10-18 parts of 60-mesh waste tire rubber powder, 2-5 parts of aromatic oil, and 0.5-1.5 parts of sulfur.

[0015] Preferably, the regenerant, by weight, comprises 35-50 parts waste edible oil methyl ester, 15-25 parts epoxidized soybean oil, 10-20 parts furfural extract oil, and 2-10 parts maleic anhydride-grafted polyethylene; more preferably, the maleic anhydride grafting rate of the maleic anhydride-grafted polyethylene is 0.8%-1.2%; more preferably, the melt index (190℃, 2.16kg) of the maleic anhydride-grafted polyethylene is 5-12 g / 10min. The regenerant is prepared by mechanically stirring the above components at 120℃ at 800-1200 r / min for 30 min.

[0016] This invention also provides a method for preparing the above-mentioned high-dosage RAP recycled stress-absorbing layer mixture, comprising the following steps: S1. Steel slag powder is surface-treated with silane coupling agent and dried to obtain activated steel slag powder. S2. 70# base asphalt, aromatic oil, waste tire rubber powder and sulfur are sheared and mixed to obtain composite modified asphalt; S3. Heat and keep warm the RAP fine aggregate, basalt new aggregate and activated steel slag powder separately; S4. First, mix the RAP fine aggregate with the recycling agent, then add the basalt new aggregate and activated steel slag powder and mix, and finally add the composite modified asphalt and mix to obtain the high-content RAP recycled stress-absorbing layer mixture.

[0017] Preferably, in step S1, the steel slag is naturally piled up and aged for no less than 3 months or treated with steam digestion to reduce its free calcium oxide content to below 3%, and then crushed and ground to obtain steel slag powder before being subjected to the silane coupling agent surface treatment.

[0018] Preferably, in step S2, the temperature of the shear mixing is 160°C, the rotation speed is 3000 r / min, and the time is 30 to 60 min.

[0019] Preferably, in step S3, the RAP fine aggregate is heated to 110-130°C, the new basalt aggregate is heated to 170-190°C, and the activated steel slag powder is heated to 160-180°C, with a holding time of not less than 4 hours.

[0020] Preferably, in step S4, the mixing temperature is 175°C. First, the RAP fine aggregate and the recycling agent are mixed for 90 seconds, then the new basalt aggregate and activated steel slag powder are added and mixed for 90 seconds, and finally the composite modified asphalt is added and mixed for 90 seconds.

[0021] The beneficial effects of this invention are: Compared with existing technologies, this invention restores aged asphalt in RAP through a regenerator, enhances the performance of the binder through composite modified asphalt, strengthens the interface between asphalt and filler by activating steel slag micropowder with a silane coupling agent containing active groups, and improves the interfacial compatibility and bonding state between activated steel slag micropowder, waste tire rubber powder and new and old asphalt by using maleic anhydride grafted with polyethylene in the regenerator. This constructs a synergistic modification system of new and old asphalt, binder and filler, thereby simultaneously improving the high-temperature stability, low-temperature crack resistance and fatigue resistance of the mixture under high RAP dosage conditions, which can meet the requirements for use in road stress absorption layers.

[0022] In this invention, the maleic anhydride-grafted polyethylene in the regenerator simultaneously plays multiple compatibility and interfacial bonding roles in the system. On one hand, the maleic anhydride groups on its molecular chain have a basis for reaction or interaction with the amino or epoxy groups introduced by the silane coupling agent on the surface of the activated steel slag powder, anchoring the steel slag powder in the asphalt matrix through interfacial chemical bonds and enhancing the interfacial adhesion between the filler and the asphalt. On the other hand, this long polyethylene chain can also act as a bridge and compatibility agent between aged asphalt and newly added asphalt in RAP, promoting the fusion of old and new asphalt. Thus, the originally independent filler, rubber powder, and old and new asphalt are linked into a whole, transforming the system from a simple physical blend into a structure with interfacial chemical bonds, thereby more fully utilizing the role of each component. Furthermore, due to the existence of the above-mentioned interfacial chemical bonds, the effects of filler activation and old and new asphalt regeneration mutually promote each other, and the improvement in the road performance of the mixture exceeds the simple superposition of their individual effects.

[0023] This invention employs silane coupling agents containing amino or epoxy groups to surface activate steel slag powder. One end of the silane coupling agent can bind to the surface of the steel slag powder, while the other end provides active groups that can participate in subsequent reactions. This not only improves the interfacial compatibility and adhesion between steel slag powder and asphalt, but also creates conditions for its connection with maleic anhydride-grafted polyethylene. This transforms steel slag powder from a common inert filler into an active filler that can synergize with the binder system, which is beneficial for improving the structural stability of recycled mixtures.

[0024] In this invention, the recycling agent reconstitutes and restores the aged asphalt in RAP, improving its hardened and brittle state caused by aging and increasing the utilization rate of RAP fine aggregates. The composite modified asphalt imparts higher elasticity and bonding properties to the binder, further meeting the performance requirements of the stress-absorbing layer. Furthermore, this invention uses RAP fine aggregates as the main aggregate source and also utilizes solid wastes such as steel slag and waste tire rubber powder. While increasing the amount of waste asphalt pavement materials disposed of, it achieves the synergistic high-value utilization of multiple solid wastes, which is beneficial for reducing engineering costs and has good prospects for widespread application. Detailed Implementation

[0025] The following examples are used to further illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, all raw materials used are conventionally available in the art, and all preparation processes and testing methods used are conventional methods in the art.

[0026] Example 1: A high-content RAP recycled stress-absorbing layer mixture and its preparation method: 1. Preparation of activated steel slag powder: Steel slag was naturally piled and aged for no less than 3 months, then crushed and ground, and passed through a 0.075 mm sieve to obtain steel slag powder. Anhydrous ethanol and deionized water were mixed at a volume ratio of 95:5, and the pH was adjusted to 4-5 with glacial acetic acid. KH-560 silane coupling agent was weighed at 1.5% of the weight of the steel slag powder and added to the mixture. The mixture was stirred and hydrolyzed for 30 min to prepare a treatment solution. The steel slag powder was added to the treatment solution at a liquid-to-solid ratio of 1.5:1 (mL:g), and stirred at room temperature for 30 min. Then, it was dried in a 105℃ oven for 4 h (without washing) to obtain activated steel slag powder.

[0027] 2. Preparation of Composite Modified Asphalt: Weigh the following components by weight: 100 parts of 70# base asphalt, 15 parts of 60-mesh waste tire rubber powder, 3 parts of aromatic oil, and 1 part of sulfur. Shear the above components at 160℃ and 3000 r / min for 45 min to obtain the composite modified asphalt.

[0028] 3. Preparation of the regenerant: Weigh the following components by weight: 42 parts waste edible oil methyl ester, 20 parts epoxidized soybean oil, 15 parts furfural extracted oil, and 5 parts maleic anhydride-grafted polyethylene. The maleic anhydride grafting rate used is 1.02%, and the melt index (190℃, 2.16kg) is 7.8g / 10min. Mechanically stir the above components at 1000r / min for 30min at 120℃ until the system is homogeneous and no undissolved particles are visually observed, thus obtaining the regenerant.

[0029] 4. The RAP fine aggregate was taken from milled material of the surface layer of AC-13 asphalt pavement that had been in service for 8 years. After crushing and screening, 0-10mm fine aggregate was obtained. Centrifugal extraction analysis showed that the old asphalt content was 5.20%; the extracted aged asphalt had a penetration of 24.6 (0.1mm), a softening point of 67.1℃, and a ductility of 12.4cm at 15℃ under the conditions of 25℃, 100g, and 5s; the RAP moisture content was 0.32%.

[0030] 5. Preparation of High-Concentration RAP Regenerated Stress Absorbing Layer Mixture: Weigh the following components by weight: 60 parts of 0-10mm RAP fine aggregate, 28 parts of 0-10mm basalt new aggregate, 6.0 parts of composite modified asphalt, 5 parts of activated steel slag powder, and 0.8 parts of recycling agent. Heat the RAP fine aggregate to 120℃, the basalt new aggregate to 180℃, and the activated steel slag powder to 170℃, holding for at least 4 hours. Place the RAP fine aggregate and recycling agent in a 175℃ mixing pot and mix for 90 seconds; then add the basalt new aggregate and activated steel slag powder, and mix for 90 seconds; finally, add the composite modified asphalt and mix for 90 seconds to obtain the high-concentration RAP recycled stress absorbing layer mixture.

[0031] Example 2: This example is basically the same as Example 1, except that the weight proportions of each component are as follows: 55 parts RAP fine aggregate, 32 parts basalt new aggregate, 5.8 parts composite modified asphalt, 4 parts activated steel slag powder, and 0.7 parts recycling agent.

[0032] The composite modified asphalt contains the following components by weight: 100 parts of 70# base asphalt, 12 parts of 60-mesh waste tire rubber powder, 4 parts of aromatic oil, and 0.8 parts of sulfur. The regenerator contains the following components by weight: 40 parts of waste edible oil methyl ester, 18 parts of epoxidized soybean oil, 12 parts of furfural extract oil, and 4 parts of maleic anhydride-grafted polyethylene. The remaining preparation steps are the same as in Example 1.

[0033] Example 3: This example is basically the same as Example 1, except that the weight proportions of each component are as follows: The mixture consists of 65 parts RAP fine aggregate, 24 parts basalt new aggregate, 6.5 parts composite modified asphalt, 3 parts activated steel slag powder, and 1.0 part recycling agent.

[0034] The composite modified asphalt contains the following components by weight: 100 parts of 70# base asphalt, 18 parts of 60-mesh waste tire rubber powder, 2 parts of aromatic oil, and 1.2 parts of sulfur. The regenerator contains the following components by weight: 45 parts of waste edible oil methyl ester, 22 parts of epoxidized soybean oil, 18 parts of furfural extract oil, and 6 parts of maleic anhydride-grafted polyethylene. The remaining preparation steps are the same as in Example 1.

[0035] Example 4: This example is basically the same as Example 1, except that in step 1, KH-560 silane coupling agent is replaced with an equal amount of KH-550 silane coupling agent, while the rest of the material composition and preparation process remain unchanged.

[0036] Comparative Example 1: This comparative example is basically the same as Example 1, except that the activated steel slag powder in Example 1 is replaced with steel slag powder that has not been surface treated with silane coupling agent, while the other material composition and preparation process remain unchanged.

[0037] Comparative Example 2: This comparative example is basically the same as Example 1, except that the activated steel slag powder in Example 1 is replaced with limestone mineral powder, and the amount of replacement is the same as the amount of activated steel slag powder in Example 1. The other material composition and preparation process remain unchanged.

[0038] Comparative Example 3: This comparative example is basically the same as Example 1, except that no recycling agent or composite modified asphalt is added, and 70# base asphalt is used as the binder, while the other components remain the same. The specific components and weight parts are as follows: 60 parts of RAP fine aggregate, 28 parts of basalt new aggregate, 6.0 parts of 70# base asphalt, and 5 parts of activated steel slag powder. The RAP fine aggregate, basalt new aggregate, and activated steel slag powder are preheated under the same conditions as in Example 1 and then mixed. Finally, 70# base asphalt is added and wet-mixed to obtain a recycled stress-absorbing layer mixture without any recycling agent or modifier.

[0039] Comparative Example 4: This comparative example is basically the same as Example 1, except that no recycling agent or composite modified asphalt is added, and 70# base asphalt is used as the binder, while the other components remain the same. The specific components and weight parts are as follows: 60 parts of RAP fine aggregate, 28 parts of basalt new aggregate, 6.0 parts of 70# base asphalt, and 5 parts of unactivated steel slag powder. The RAP fine aggregate, basalt new aggregate, and unactivated steel slag powder are preheated under the same conditions as in Example 1 and then mixed. Finally, 70# base asphalt is added and wet-mixed to obtain a recycled stress-absorbing layer mixture without any recycling agent or modifier.

[0040] Comparative Example 5: This comparative example is basically the same as Example 1, except that the KH-560 silane coupling agent in step 1 is replaced with an equal amount of KH-570 silane coupling agent, while the other material composition and preparation process remain unchanged.

[0041] Comparative Example 6: This comparative example is basically the same as Example 1, except that maleic anhydride-grafted polyethylene is not added in step 3 when preparing the regenerant. That is, the regenerant is composed of 42 parts of waste edible oil methyl ester, 20 parts of epoxidized soybean oil, and 15 parts of furfural extract oil. The composition of other materials and the preparation process remain unchanged.

[0042] The mixtures obtained in Examples 1-4 and Comparative Examples 1-6 were subjected to performance tests. Dynamic stability was determined using a rutting test, low-temperature bending failure strain was determined using a low-temperature small beam bending test, freeze-thaw splitting strength ratio was determined using a freeze-thaw splitting test, and fatigue life was determined using a four-point bending fatigue test. The test results are shown in Table 1.

[0043] Table 1. Asphalt mixture test results As shown in Table 1, the road performance of the mixtures obtained in Examples 1 to 4 is significantly better than that of the comparative examples, indicating that the synergistic system of the present invention, which "restores old asphalt with regenerator, strengthens binder with composite modified asphalt, strengthens asphalt-filler interface with activated steel slag micro powder, and connects the three into one with maleic anhydride-grafted polyethylene", has a significant effect.

[0044] Compared with Comparative Example 1, Example 1 showed that simply replacing the untreated steel slag powder with steel slag powder activated by a silane coupling agent significantly improved the various properties of the mixture, indicating that surface activation of steel slag powder with a silane coupling agent is beneficial to improving the interfacial compatibility and adhesion between steel slag powder and asphalt.

[0045] Compared to Comparative Example 5, although Comparative Example 5 also used a silane coupling agent to surface treat the steel slag powder, the organic end group of KH-570 is methacryloyloxy. Under the formulation and hot-mixing conditions of this application, it does not have the same functional group matching between the amino group introduced by KH-550 or the epoxy group introduced by KH-560 and the maleic anhydride-grafted polyethylene. Therefore, the interfacial synergistic effect is weaker, and the various properties of its mixture are significantly lower than those of Example 1 using KH-560, and only slightly higher than those of Comparative Example 1 without activation treatment. This indicates that the performance improvement of the present invention does not only come from the general coupling effect of the silane coupling agent, but mainly from the matching and binding between the active group provided by KH-560 and the maleic anhydride-grafted polyethylene.

[0046] Compared with Comparative Example 6, Example 6, which uses KH-560 to activate steel slag powder, does not contain maleic anhydride-grafted polyethylene in its regenerator. Therefore, the performance of its mixture is significantly lower than that of Example 1, but close to that of Comparative Example 5. This indicates that maleic anhydride-grafted polyethylene is an indispensable component in the system of this invention. Without this component, even after activation of the steel slag powder, it is difficult to obtain the comprehensive performance of Example 1.

[0047] The results of Comparative Examples 5 and 6 were similar, and their performance was significantly lower than that of Example 1 but higher than that of Comparative Example 1. This indicates that only when the active groups on the surface of the activated steel slag powder and maleic anhydride-grafted polyethylene coexist and match with each other (as in Example 1) can the best comprehensive road performance be obtained, further confirming the synergistic relationship between the two.

[0048] Example 4 shows similar performance to Example 1, indicating that activating steel slag powder with amino-containing KH-550 or epoxy-containing KH-560 can both be combined with maleic anhydride-grafted polyethylene and achieve good results.

[0049] Compared with Comparative Example 2, in Example 1, the performance of the mixture decreased significantly after replacing the activated steel slag powder with conventional limestone powder. This indicates that the activated steel slag powder is superior to conventional limestone powder in enhancing the interfacial bonding between asphalt and filler and improving the structural stability of the mixture.

[0050] Compared with Comparative Example 3, Example 1 showed an increase in dynamic stability from 4860 cycles / mm to 7120 cycles / mm, an increase in low-temperature bending failure strain from 2360 με to 3385 με, an increase in freeze-thaw splitting strength ratio from 75.8% to 90.8%, and an increase in fatigue life from 70200 cycles to 136500 cycles. This indicates that in a high-content RAP system, the restorative effect of the rejuvenator on aged asphalt and the reinforcing effect of the composite modified asphalt on the binder are equally indispensable.

[0051] To further illustrate the synergistic effect among the various technical means of this invention, using Comparative Example 4 (without activation treatment and containing no regenerator or composite modified asphalt) as a benchmark, the performance contributions of activated steel slag powder and the regeneration system (regenerator and composite modified asphalt) acting alone were calculated and compared with the expected value obtained by simply adding the two and the measured value of Example 1. The contribution of activated steel slag powder alone was the difference between Comparative Example 3 and Comparative Example 4, the contribution of the regeneration system alone was the difference between Comparative Example 1 and Comparative Example 4, and the expected value obtained by simply adding the two contributions was the sum of Comparative Example 4 and the above two contributions. The results are shown in Table 2.

[0052] Table 2. Analysis of the contribution and synergistic effect of each technical means As shown in Table 2, the measured values ​​of the four road performance indicators in Example 1 are all significantly higher than the simple sum of the contributions from each individual method, with the fatigue life exceeding the sum by 24.9%. This indicates that the relationship between activated steel slag powder and the regeneration system is not a simple linear superposition, but rather a significant synergistic effect. This synergistic effect is related to the interfacial compatibility and bonding between the silane-modified steel slag powder surface active groups, maleic anhydride-grafted polyethylene, and composite modified asphalt, thereby achieving technical effects that are difficult to predict using existing technologies alone.

[0053] In summary, this invention utilizes a silane coupling agent containing active groups to activate steel slag powder, and combines it with a regenerator containing maleic anhydride-grafted polyethylene and composite modified asphalt. This significantly improves the utilization rate of RAP fine aggregate and the comprehensive performance of recycled mixtures. The resulting mixture exhibits excellent high-temperature stability, low-temperature crack resistance, and fatigue resistance, meeting the requirements for use in road stress-absorbing layers.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the present invention.

Claims

1. A high-content RAP recycled stress-absorbing layer mixture, characterized in that, It includes the following components and their weight proportions: 50-70 parts of RAP fine aggregate, 24-32 parts of new basalt aggregate, 5.0-6.8 parts of composite modified asphalt, 3-6 parts of activated steel slag powder, and 0.5-1.0 parts of regenerator.

2. The high-dosage RAP recycled stress-absorbing layer mixture according to claim 1, characterized in that, The RAP fine aggregate is obtained by crushing and screening recycled asphalt pavement material. The mass content of old asphalt in the RAP fine aggregate is 3.8% to 5.6%. The particle size distribution of the RAP fine aggregate and the new basalt aggregate is 0 to 10 mm.

3. The high-dosage RAP recycled stress-absorbing layer mixture according to claim 1, characterized in that, The activated steel slag powder is a filler obtained by surface treatment of steel slag powder with a silane coupling agent; the silane coupling agent is at least one of γ-aminopropyltriethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane; the amount of the silane coupling agent is 0.5% to 3.0% of the weight of the steel slag powder.

4. The high-dosage RAP recycled stress-absorbing layer mixture according to claim 1, characterized in that, The composite modified asphalt comprises the following components in parts by weight: 100 parts of 70# base asphalt, 10-18 parts of 60-mesh waste tire rubber powder, 2-5 parts of aromatic oil, and 0.5-1.5 parts of sulfur.

5. The high-dosage RAP recycled stress-absorbing layer mixture according to claim 1, characterized in that, The regenerant comprises the following components in parts by weight: 35-50 parts waste edible oil methyl ester, 15-25 parts epoxidized soybean oil, 10-20 parts furfural extract oil, and 2-10 parts maleic anhydride-grafted polyethylene.

6. A method for preparing a high-dosage RAP regenerated stress-absorbing layer mixture as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Steel slag powder is surface-treated with silane coupling agent and dried to obtain activated steel slag powder. S2. The 70# base asphalt, aromatic oil, waste tire rubber powder and sulfur are sheared to obtain composite modified asphalt; S3. Heat and keep warm the RAP fine aggregate, basalt new aggregate and activated steel slag powder separately; S4. First, mix the RAP fine aggregate with the recycling agent, then add the basalt new aggregate and activated steel slag powder and mix, and finally add the composite modified asphalt and mix to obtain the high-content RAP recycled stress-absorbing layer mixture.

7. The preparation method according to claim 6, characterized in that, In step S1, the steel slag is successively aged, crushed, and ground to obtain steel slag powder; anhydrous ethanol and deionized water are mixed at a volume ratio of 95:5 to prepare an ethanol-water solution, the pH is adjusted to 4-5, a silane coupling agent is added and stirred for 30 minutes to obtain a treatment solution; the steel slag powder is added to the treatment solution at a liquid-solid ratio of 1:1 to 2:1 mL:g and then stirred and dried.

8. The preparation method according to claim 6, characterized in that, In step S2, the shearing temperature is 160℃, the shearing speed is 3000 r / min, and the shearing time is 30–60 min.

9. The preparation method according to claim 6, characterized in that, In step S3, the RAP fine aggregate is heated to 110-130℃, the new basalt aggregate is heated to 170-190℃, and the activated steel slag powder is heated to 160-180℃, with a holding time of not less than 4 hours.

10. The preparation method according to claim 6, characterized in that, In step S4, the mixing temperature is 175℃; the RAP fine aggregate is mixed with the recycling agent for 90s, then the new basalt aggregate and activated steel slag powder are added and mixed for 90s, and finally the composite modified asphalt is added and mixed for 90s.

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