A recycled asphalt mixture thin layer based on directional migration of aged asphalt and a preparation method thereof

Abstract

The application discloses a steel slag and recycled asphalt mixture thin layer based on directional migration of aged asphalt and a preparation method thereof, and belongs to the technical field of road engineering materials. The application also discloses a steel slag adaptive migration induction composite recycling agent. The steel slag adaptive migration induction composite recycling agent is used for permeating and activating the surface aged asphalt of RAP, cooperating with the porous adsorption and interface induction of pretreated steel slag, realizing directional migration and reconstruction distribution of the aged asphalt from the surface of RAP aggregate to the interface of steel slag, significantly reducing the harm of aged asphalt inferior phase, strengthening the dominant role of new asphalt, and synchronously reducing the risk brought by the volume stability of steel slag. The application prepares the recycled asphalt mixture thin layer through RAP preheating, primary permeation and activation regeneration, secondary migration induction regeneration and mixture molding, the thin layer is excellent in low-temperature crack resistance, water stability and durability, can greatly improve the utilization rate of RAP and steel slag solid waste, and is suitable for asphalt pavement preventive maintenance, thin layer overlay and micro-surfacing engineering.

Description

Technical Field

[0001] This invention belongs to the field of asphalt mixture technology, specifically relating to a recycled asphalt mixture thin layer based on the directional migration of aged asphalt and its preparation method. Background Technology

[0002] With the continuous increase in highway maintenance demands, the resource utilization of reclaimed asphalt pavement (RAP) has become a trend in road engineering development. However, during long-term service, the aged asphalt in RAP undergoes oxidation, condensation, and structural hardening, resulting in a significant increase in viscosity, a decrease in ductility, and an increase in brittleness. It also forms a dense film covering the surface of the original aggregate. During the mixing process, this aged asphalt is difficult to fully integrate with the new asphalt, easily forming local enrichment zones in the mixture. This leads to problems such as poor low-temperature crack resistance, insufficient water stability, and decreased durability of the recycled mixture.

[0003] Currently, existing recycling technologies mainly focus on softening and reducing viscosity with regenerators and supplementing lightweight components, lacking active control over the spatial distribution, interfacial behavior, and migration paths of aged asphalt, thus failing to fundamentally eliminate the adverse effects of the inferior phases in aged asphalt. Steel slag, as a byproduct of the metallurgical industry, possesses characteristics such as high strength, well-developed pores, rough surface, and strong alkaline interfacial activity, exhibiting good interfacial adsorption and interlocking capabilities. However, in existing technologies, steel slag is mostly used as a common substitute aggregate, and its porous structure and interfacial characteristics have not yet formed a synergistic mechanism with the RAP recycling system. For example, patent CN 119191761 A discloses an anti-aging and anti-skid asphalt concrete and its production process. This application solves the problem of insufficient long-term anti-aging performance of existing asphalt concrete by adding composite microspheres to the asphalt concrete, and by adding composite fibers, it compensates for the shortcomings in the performance of asphalt concrete, thereby improving the performance and quality of the asphalt concrete pavement to ensure that it maintains good anti-skid performance even after long-term use. However, the steel slag added to this concrete is still used as a common substitute aggregate, and it also suffers from problems such as difficulty in integrating aged asphalt and the failure to utilize the interfacial activity of steel slag.

[0004] More importantly, most existing regenerators are general-purpose designs and have not been optimized for the unique properties of steel slag, such as its porous structure, high adsorption capacity, strong alkaline interface, and easy hydration and expansion. This not only makes it impossible to effectively utilize the pore structure of steel slag as a migration target site for aged asphalt, but also fails to mitigate the negative impact of steel slag volume expansion on the stability of the mixture.

[0005] Therefore, there is an urgent need for a composite regenerator specifically designed for the characteristics of steel slag, which can synergistically regulate the "migration of aged asphalt - adsorption at the steel slag interface - reconstruction of the structure of new and old asphalt phases", thereby weakening the influence of the inferior phase of aged asphalt, enhancing the dominant role of the new continuous phase of asphalt, and simultaneously suppressing the risk of steel slag expansion, thus improving the overall service performance of recycled asphalt mixtures. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a recycled asphalt mixture thin layer based on the directional migration of aged asphalt and its preparation method. This recycled asphalt mixture achieves the directional migration and stable adsorption of aged asphalt in RAP from the original aggregate surface to the pores and interface region of steel slag, reconstructing the internal phase structure of the recycled system, weakening the influence of the inferior phase of aged asphalt, and strengthening the dominant role of the new asphalt continuous phase, thereby significantly improving the low-temperature crack resistance, water stability, durability, and interface stability of the recycled asphalt mixture thin layer.

[0007] This invention provides a steel slag-compatible migration-inducing composite regenerator, comprising a primary composite regenerator and a secondary composite regenerator. By weight, the primary composite regenerator comprises 30-60 parts of epoxidized soybean oil and 20-40 parts of heavy aromatic oil; the secondary composite regenerator comprises 5-10 parts of heavy aromatic oil, 25-30 parts of SBR latex, and 0.5-5 parts of an interface-inducing component. Targeting the porous and highly adsorbent characteristics of steel slag, epoxidized soybean oil and heavy aromatic oil are selected as the penetration and migration components. Both have moderate molecular weights and good fluidity, enabling them to fully penetrate the micropores on the steel slag surface and the aged RAP asphalt film, providing a migration carrier.

[0008] As a preferred embodiment of this application, the mass ratio of the primary composite regenerator to the secondary composite regenerator is 1:1 to 2:1.

[0009] As a further preferred embodiment of this application, the mass ratio of the primary composite regenerator to the secondary composite regenerator is 1.5:1.

[0010] As a preferred embodiment of this application, the total weight percentage of heavy aromatic oil in the primary composite regenerator and the secondary composite regenerator is 25 to 50 parts.

[0011] As a preferred embodiment of this application, the interface-inducing components, by weight, comprise: 1-3 parts of aminosilane coupling agent, 0.5-1.5 parts of amine adhesion promoter, and 0.5-2 parts of cationic interfacial activity promoter. Addressing the strongly alkaline interface characteristics of steel slag: adding aminosilane coupling agent, amine adhesion promoter, or cationic interfacial activity promoter as an interface compatibility component utilizes their chemical bonding and electrostatic adsorption under alkaline conditions to enhance the affinity of the steel slag surface for aged asphalt. Addressing the easy hydration and swelling characteristics of steel slag: this invention introduces SBR latex as a stabilizing synergistic component, which forms a flexible elastic film in the pore structure and surface of the steel slag, effectively buffering the stress generated during the hydration and swelling process. Simultaneously, SBR latex and new asphalt (rubber asphalt) jointly construct a continuous elastic network, enhancing the interfacial adhesion between the new asphalt and the steel slag and aged asphalt, thereby significantly reducing the risk of volume stability issues caused by water infiltration.

[0012] As a preferred embodiment of this application, the aminosilane coupling agent is γ-aminopropyltriethoxysilane and / or γ-aminopropyltrimethoxysilane.

[0013] As a further preferred embodiment of this application, the aminosilane coupling agent is γ-aminopropyltriethoxysilane.

[0014] As a preferred embodiment of this application, the amine adhesion promoter includes ethylenediamine and / or diethylenetriamine.

[0015] As a further preferred embodiment of this application, the amine adhesion promoter is ethylenediamine.

[0016] As a preferred embodiment of this application, the cationic interfacial activity promoter comprises hexadecyltrimethylammonium chloride and / or octadecyltrimethylammonium chloride.

[0017] As a further preferred embodiment of this application, the cationic interfacial activity promoter is hexadecyltrimethylammonium chloride.

[0018] As a preferred embodiment of this application, the mass ratio of the primary composite regenerator to the secondary composite regenerator is 1.5:1, and the primary composite regenerator comprises the following components: 40 parts of epoxidized soybean oil and 20 parts of heavy aromatic oil; the secondary composite regenerator comprises the following components: 10 parts of heavy aromatic oil, 27 parts of SBR latex, 1.5 parts of γ-aminopropyltriethoxysilane, 0.5 parts of ethylenediamine, and 1 part of hexadecyltrimethylammonium chloride.

[0019] This invention also provides a method for preparing recycled asphalt mixture based on the directional migration of aged asphalt, comprising the following steps:

[0020] Step 1: Preheating RAP milling material: Heat the RAP milling material to 120-160℃ to obtain preheated RAP milling material;

[0021] Step 2, Primary Penetration Activation Regeneration: Add primary composite regeneration agent to the preheated RAP milling material, mix for 2-4 minutes at a revolution speed of 20-30 r / min and a rotation speed of 55-65 r / min, and then keep warm for 5-15 minutes to allow the regeneration agent to preferentially penetrate into the aged asphalt film, reduce the surface viscosity, and enhance the molecular mobility to obtain the RAP system after penetration activation.

[0022] Step 3, Secondary migration-induced regeneration: Pretreated steel slag and the steel slag-compatible migration-induced composite regenerator are added to the activated RAP system to change the interfacial energy difference between RAP, aged asphalt and steel slag, and further drive the aged asphalt to migrate directionally to the steel slag interface. The mixture is then subjected to graded slow-down mixing and heat preservation treatment at 160~180℃ to obtain the recycled mixture.

[0023] Step 4: Mixture molding: Add new rubber asphalt, aggregates and stabilizers to the obtained recycled asphalt mixture, mix evenly at 170-200℃ and mold to obtain recycled asphalt mixture.

[0024] As a preferred embodiment of this application, in step 2, the amount of the primary composite regenerator added accounts for 3 to 6% of the mass of the RAP milling material.

[0025] As a preferred embodiment of this application, in step 3, the amount of the secondary composite regenerator added accounts for 2 to 4% of the mass of the RAP milling material.

[0026] As a preferred embodiment of this application, step 3, the steel slag pretreatment includes:

[0027] Steel slag is aged or subjected to wet heat treatment to reduce the free calcium oxide ((f-CaO) content to ≤3%;

[0028] The interface inducer is sprayed and impregnated with a treatment solution and dried at 60–120°C to form an asphalt-friendly active interface layer, which further improves the active adsorption capacity of steel slag for migrating and aging asphalt and seals some surface active sites to inhibit expansion. The amount of the interface inducer sprayed is 0.2–1.0% of the mass of steel slag, and it is pre-wetted for 2–5 minutes before impregnation.

[0029] This application achieves a dual transformation of the steel slag surface through "passivation followed by functionalization" by pre-treating the steel slag: aging / wet heat treatment eliminates the inherent expansion driving force of the steel slag; subsequently, an interface inducer treatment solution is used to perform surface engineering on the steel slag. The combination of spraying and impregnation processes with pre-wetting ensures effective loading and deep penetration of the inducer. During drying at 60–120℃, the inducer molecules chemically graft or physically deposit on the steel slag surface, forming an active interface layer with strong affinity for asphalt. This active layer plays a dual role: firstly, as a "molecular bridge," it actively "grabs" the migrating aged asphalt to the steel slag interface by increasing surface energy, promoting its uniform spreading and firm anchoring; secondly, as a "barrier layer," it physically / chemically seals the active sites such as CaO and MgO on the steel slag surface, cutting off the hydration reaction path and mechanistically inhibiting the later expansion of the steel slag. This "factor control-surface modification-efficiency enhancement" pre-treatment strategy fundamentally solves the technical bottleneck of steel slag's "difficulty in bonding and easy expansion" in asphalt mixtures.

[0030] As a preferred embodiment of this application, in step 3, the graded decreasing speed mixing and heat preservation treatment involves mixing for 3-5 minutes at a first mixing speed of 42-48 r / min (revolutionary speed) and 75-90 r / min (rotational speed), followed by mixing for 2-4 minutes at a second mixing speed of 20-30 r / min (revolutionary speed) and 55-65 r / min (rotational speed), and then heat preservation for 3-10 minutes. The core of the graded decreasing speed mixing process in this application lies in achieving the dual objectives of shear drive and structural protection through sequential speed switching. Specifically, the first mixing speed is high-speed mixing, which provides sufficient shear force to drive the desorption and migration of aged asphalt; subsequently, the mixing speed is switched to the second speed, which is low-speed mixing. By reducing the shear strength, excessive shearing can be avoided to prevent damage to the migrated asphalt film structure, promoting the uniform redistribution and stable anchoring of aged asphalt at the steel slag interface. Through graded decreasing speed mixing followed by high speed, a continuous induction process of "desorption-migration-redistribution-stabilization" of aged asphalt is achieved. After mixing, heat is applied to allow the molecular chains to rearrange fully, thereby enhancing the effect of the interfacial inducing components.

[0031] The present invention also provides a recycled asphalt mixture thin layer obtained according to the preparation method.

[0032] As a preferred embodiment of this application, the recycled asphalt mixture thin layer comprises the following components by weight: 10-20 parts of RAP milling material, 50-70 parts of steel slag, 8-30 parts of aggregate, 0.1-0.5 parts of stabilizer, and 5-6 parts of new rubber asphalt; the mixture also contains the steel slag-compatible migration-inducing composite recycling agent.

[0033] As a preferred embodiment of this application, the stabilizer is a fiber stabilizer. More preferably, it is an organic fiber, and most preferably, it is a lignin fiber.

[0034] As a preferred embodiment of this application, the steel slag-compatible synergistic recycled asphalt mixture thin layer adopts an SMA-10 discontinuous gradation design.

[0035] As a preferred embodiment of this application, the rubber powder content in the new rubber asphalt is 15%, which can fully compensate for the adsorption loss of steel slag pores and ensure the thickness and road performance of the SMA structure asphalt film.

[0036] As a preferred embodiment of this application, the RAP milling material is SBS modified bitumen milling material with a particle size of 0-9.5mm and steel slag with a particle size of 4.75-9.5mm.

[0037] As a preferred embodiment of this application, the RAP milling material is an SBS modified bitumen milling material with a particle size of 0-9.5 mm.

[0038] As a preferred embodiment of this application, the steel slag particle size is 4.75-9.5mm.

[0039] As a preferred embodiment of this application, the mineral material includes limestone of 2.36-4.75 mm, limestone of 0-2.36 mm, and mineral powder, with a mass ratio of 8:9:8.

[0040] As a preferred embodiment of this application, the recycled asphalt mixture thin layer comprises the following components by weight: 15 parts of RAP milling material, 60 parts of steel slag, 25 parts of aggregate, 0.3 parts of lignin fiber, and 5.03 parts of new rubber asphalt; wherein the aggregate contains 8 parts of limestone with a thickness of 2.36-4.75 mm, 9 parts of limestone with a thickness of 0-2.36 mm, and 8 parts of mineral powder.

[0041] The steel slag-compatible synergistic recycled asphalt mixture thin layer of the present invention adopts SMA-10 discontinuous gradation design. The mixture composition is 15 parts of 0-9.5mm RAP milling material, 60 parts of 4.75-9.5mm steel slag, 8 parts of 2.36-4.75mm limestone, 9 parts of 0-2.36mm limestone, 8 parts of mineral powder, 0.3 parts of lignin fiber, and 5.03 parts of new rubber asphalt.

[0042] Centrifugal extraction and combustion methods revealed that the old asphalt content in every 100 parts of RAP milling material was 5.8 parts, with 0.87 parts of old asphalt introduced by the RAP. Considering the high adsorption and porous characteristics of steel slag, the asphalt content was optimized, ultimately determining the optimal total asphalt content to be 5.9 parts, of which 5.03 parts were new rubber asphalt and 15 parts were rubber powder. This ratio effectively compensates for the adsorption loss due to the pores of the steel slag and ensures the thickness and road performance of the SMA structure asphalt film.

[0043] The mechanism of this invention is as follows: A steel slag-compatible migration-inducing composite regenerator first penetrates the aged asphalt film on the surface of the RAP, reducing local viscosity and restoring molecular mobility. Epoxidized soybean oil and heavy aromatic oil work synergistically to keep the aged asphalt in an activated state of "migratory but not unstable." Subsequently, the interface-inducing components (aminosilane coupling agents, amines, or cationic surfactants) form chemical bonds with the steel slag surface under alkaline conditions, significantly reducing the surface free energy of the steel slag and increasing its affinity for polar aged asphalt components. Under the effects of graded interface induction and segmented mixing and heat preservation, the aged asphalt actively desorbs from the original RAP aggregate surface driven by the interfacial energy difference, migrates directionally to the pores and surface areas of the steel slag, and is captured and enriched by the asphalt-inducing layer, thereby achieving spatial distribution reconstruction of the aged asphalt. Furthermore, the SBR latex forms a continuous elastic network on the steel slag surface, compensating for the loss of elastic components in the new asphalt phase after the migration of aged asphalt and enhancing the dominant role of the new continuous asphalt phase. On the other hand, the elastic film can buffer the expansion stress generated by the hydration of the steel slag, inhibiting the damage to the mixture structure caused by volume expansion. Meanwhile, after the aged asphalt migrates into the pores of the steel slag, it occupies the channels for moisture intrusion, further reducing the probability of hydration reactions and improving the volume stability of the steel slag from both physical and chemical perspectives. Ultimately, this achieves a synergistic regulatory mechanism of "penetration activation—directional migration—interfacial adsorption—phase structure reconstruction".

[0044] Compared with the prior art, the beneficial effects of this application are:

[0045] 1. This invention proposes a steel slag-adapted migration-inducing composite regenerator specifically designed for the characteristics of steel slag. Its composition clearly corresponds to the three inherent properties of steel slag: porous adsorption, strong alkaline interface, and easy volume expansion. It is not a simple softening agent of traditional regenerators.

[0046] 2. Epoxidized soybean oil, heavy aromatic oil, SBR latex and interface-inducing components form a synergistic mechanism of "penetration activation - colloidal stabilization - elastic compensation - interface induction", which realizes the transformation of aged asphalt from a high-viscosity hardened state to a stable activated state.

[0047] 3. Steel slag has the dual function of aggregate and adsorption carrier. Its porous structure actively adsorbs aged asphalt, transforming the "inferior phase" into a "stable phase". At the same time, SBR latex and interface inducer work together to inhibit the expansion of steel slag.

[0048] 4. This invention achieves the directional migration and spatial reconstruction of aged asphalt from the RAP surface to the steel slag interface through the synergistic effect of the graded regenerator program, the steel slag orifice pre-wetting program, and the segmented mixing and heat preservation program, thereby strengthening the dominant role of new asphalt and improving low-temperature crack resistance, water stability and durability.

[0049] 5. Achieving synergistic utilization of RAP and steel slag solid waste for high-value utilization results in significant economic and environmental benefits. Attached Figure Description

[0050] Figure 1 This is a process flow diagram of the present invention.

[0051] Figure 2 The results of atomic force microscopy testing of free bitumen in Example 1 of this invention are shown.

[0052] Figure 3 The results of atomic force microscopy testing of free bitumen in Comparative Example 2 of this invention are shown.

[0053] Figure 4 The results of atomic force microscopy testing of free bitumen in Example 4 of this invention are shown.

[0054] Figure 5 The results of atomic force microscopy testing of free bitumen in Example 6 of this invention are shown. Detailed Implementation

[0055] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0056] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0057] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0058] In the following embodiments of this application, the epoxidized soybean oil was purchased from Jinan Jinbang Environmental Protection Technology Co., Ltd.; the heavy aromatic oil was purchased from Hebei Wantai Chemical Co., Ltd.; the SBR latex was purchased from Shenzhen Yoshida Chemical Co., Ltd., product number F0603; the γ-aminopropyltriethoxysilane was purchased from Guangdong Luwei New Material Technology Co., Ltd., product number 919-30-2; the ethylenediamine was purchased from Guangdong Daxiao Chemical Co., Ltd., product number 107-15-3; and the hexadecyltrimethylammonium chloride was purchased from Jiangsu... The product is from Pulis Biotechnology Co., Ltd., product number 112-02-7; the steel slag was purchased from Donglu Jiaoke (Nanjing) Technology Co., Ltd., with a particle size of 4.75-9.5mm; the RAP milling material was from Zhejiang Huhangyong Maintenance Engineering Co., Ltd., with a particle size of 0-9.5mm; the new rubber asphalt was purchased from Beijing Juncheng Hengye Construction Engineering Co., Ltd.; the limestone was purchased from De'an Ruilong New Materials Co., Ltd., with a particle size of 0-2.36mm and 2.36-4.75mm; and the mineral powder was purchased from Changxing Shengwei Building Materials Co., Ltd.

[0059] Example 1

[0060] This embodiment provides a method for preparing a thin layer of recycled asphalt mixture based on the directional migration of aged asphalt, including the following steps:

[0061] Step 1: Preheating RAP milling material: Heat 15 parts of RAP milling material (specifically SBS modified bitumen milling material with a particle size of 0-9.5mm) to 140℃ to obtain preheated RAP milling material;

[0062] Step 2, Primary Penetration Activation and Regeneration: Add the primary composite regenerator to the preheated RAP milling material, mix for 3 minutes at 25 r / min revolution, 60 r / min rotation, and 140℃, and then keep warm for 10 minutes to obtain the RAP system after penetration activation; by weight, the primary composite regenerator includes the following components: 40 parts of epoxidized soybean oil and 20 parts of heavy aromatic oil.

[0063] Step 3, Secondary migration-induced regeneration:

[0064] (1) 60 parts of steel slag (particle size 4.75-9.5mm) are aged or wet-heat treated to make the free calcium oxide content ≤3%; then they are sprayed and impregnated with an interface inducer treatment liquid and dried at 80℃ to form an asphalt-friendly active interface layer on the surface of the steel slag; the amount of the interface inducer sprayed is 0.5% of the mass of the steel slag, and it is pre-wetted for 3 minutes before impregnation;

[0065] (2) Add pretreated steel slag and secondary composite regenerator to the activated RAP system, and perform graded slow-speed mixing and heat preservation treatment at 165℃ to obtain recycled mixture; wherein, the secondary composite regenerator includes the following components by weight: 10 parts heavy aromatic oil, 27 parts SBR latex, 1.5 parts γ-aminopropyltriethoxysilane, 0.5 parts ethylenediamine, and 1 part hexadecyltrimethylammonium chloride; the graded slow-speed mixing and heat preservation treatment is to first mix at a first stirring speed of 45 r / min and 80 r / min for 4 min, then mix at a second stirring speed of 25 r / min and 60 r / min for 3 min, and then keep warm for 5 min after completion;

[0066] Step 4, Mixture Molding: Add 5.03 parts of new rubber asphalt, 25 parts of aggregate (including 8 parts of 2.36-4.75mm limestone, 9 parts of 0-2.36mm limestone, and 8 parts of mineral powder) and 0.3 parts of lignin fiber to the obtained recycled mixture (the mass ratio of primary composite recycling agent to secondary composite recycling agent is 1.5:1). Continue to mix evenly at 180℃ and mold to obtain a thin layer of recycled asphalt mixture.

[0067] According to JTG 3410-2025 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" and JTG 3450-2019 "Field Test Procedures for Highway Subgrade and Pavement", the products were tested for dynamic stability, freeze-thaw splitting strength ratio, low-temperature beam bending test, 10-day immersion swelling rate (%) of steel slag asphalt mixture, and pendulum value test for skid resistance. The testing standards are shown in Table 1, and the specific data are shown in Table 2.

[0068] Table 1. Testing Indicators and Standards Dynamic stability JTG3410-2025 (T0719) Evaluation of high temperature rutting resistance Calculate the number of compaction cycles required to produce 1 mm of deformation by repeatedly rolling with a standard wheel at 60℃. Freeze-thaw splitting strength ratio JTG3410-2025 (T0729) Evaluation of water stability Compare the splitting tensile strength of specimens before and after freeze-thaw cycles to assess their resistance to water damage. Maximum bending tensile strain in low-temperature beam bending test JTG3410-2025 (T0715) Evaluation of low-temperature crack resistance A small beam specimen was bent to failure at -10℃, and its maximum flexural tensile strain was measured. Water swelling rate JTG3410-2025 (T0750) Evaluation of the volumetric stability of steel slag Measure the volume change of the specimens before and after immersion in water to control the risk of expansion of free calcium oxide in steel slag. Value of display JTG3450-2019 (T0964) Evaluation of road surface skid resistance The anti-slip performance of a simulated rubber slider sliding across a road surface is evaluated based on its pendulum value. .

[0069] Example 2

[0070] The difference between this embodiment and Embodiment 1 is that the proportion of the primary composite regenerator added in step 2 is different. In this embodiment, the primary composite regenerator consists of 45 parts of epoxidized soybean oil and 15 parts of heavy aromatic oil. The remaining processes are the same as in Embodiment 1.

[0071] Example 3

[0072] The difference between this embodiment and Embodiment 1 is that the proportion of the primary composite regenerator added in step 2 is different. In this embodiment, the primary composite regenerator consists of 35 parts epoxidized soybean oil and 25 parts heavy aromatic oil. The remaining processes are the same as in Embodiment 1.

[0073] Example 4

[0074] The difference between this embodiment and Embodiment 1 is that the proportions of the secondary composite regenerator are different. The secondary composite regenerator comprises the following components by weight: 10 parts heavy aromatic oil, 25 parts SBR latex, 2 parts γ-aminopropyltriethoxysilane, 1 part ethylenediamine, and 2 parts hexadecyltrimethylammonium chloride. The remaining processes are the same as in Embodiment 1.

[0075] Example 5

[0076] The difference between this embodiment and Example 1 is that the proportions of the secondary composite regenerator are different. The secondary composite regenerator comprises the following components by weight: 8 parts heavy aromatic oil, 30 parts SBR latex, 1 part γ-aminopropyltriethoxysilane, 0.5 parts ethylenediamine, and 0.5 parts hexadecyltrimethylammonium chloride. The remaining processes are the same as in Example 1.

[0077] Example 6

[0078] The difference between this embodiment and Embodiment 1 is that the mass ratio of the primary composite regenerator to the secondary composite regenerator is 1:1. The remaining processes are the same as in Embodiment 1.

[0079] Example 7

[0080] The difference between this embodiment and Embodiment 1 is that the mass ratio of the primary composite regenerator to the secondary composite regenerator is 2:1. The remaining processes are the same as in Embodiment 1.

[0081] Example 8

[0082] The difference between this embodiment and Embodiment 1 is that the mixing and heat preservation time in step 2 is 5 minutes. The rest of the process is the same as in Embodiment 1.

[0083] Example 9

[0084] The difference between this embodiment and Embodiment 1 is that the mixing and heat preservation time in step 2 is 15 minutes. The rest of the process is the same as in Embodiment 1.

[0085] Example 10

[0086] The difference between this embodiment and Embodiment 1 is that the mixing and heat preservation time in step 3 (2) is 3 minutes. The rest of the process is the same as in Embodiment 1.

[0087] Example 11

[0088] The difference between this embodiment and Embodiment 1 is that the mixing and heat preservation time in step 3 (2) is 10 minutes. The rest of the process is the same as in Embodiment 1.

[0089] Comparative Example 1

[0090] The difference between this comparative example and Example 1 is that the interface inducer is not applied to the steel slag in step 3(1). The rest of the process is the same as in Example 1.

[0091] Comparative Example 2

[0092] The difference between this comparative example and Example 1 is that heat preservation treatment is not performed in step 2. The rest of the process is the same as in Example 1.

[0093] Comparative Example 3

[0094] The difference between this comparative example and Example 1 is that the graded slow-down mixing in step 3 is replaced with high-speed mixing, with a mixing speed of 45 r / min for revolution and 80 r / min for rotation. The rest of the process is the same as in Example 1.

[0095] Comparative Example 4

[0096] The difference between this comparative example and Example 1 is that no graded regeneration treatment is performed. Instead, a steel slag-compatible migration-inducing composite regenerator is directly added to the preheated RAP milling material and mixed, followed by preparation and molding according to step 4. The remaining processes are the same as in Example 1.

[0097] Comparative Example 5

[0098] The difference between this comparative example and Example 1 is that no steel slag-compatible migration-inducing composite regenerator is added, and the steel slag is not treated with an interface-inducing agent spraying. The remaining processes are the same as in Example 1.

[0099] Comparative Example 6

[0100] The difference between this comparative example and Example 1 is that: no steel slag-compatible migration-inducing composite regenerator is added, no interface inducer is sprayed onto the steel slag, and the graded slow-motion mixing is replaced with high-speed mixing, with a mixing speed of 45 r / min revolution and 80 r / min rotation. Furthermore, no heat preservation treatment is performed after mixing. The remaining processes are the same as in Example 1.

[0101] Table 2. Performance test results of the products prepared in the examples and comparative examples. .

[0102] A comprehensive analysis of the test data from Examples 1-11 and Comparative Examples 1-6 in Table 2 shows that Example 1 represents the optimal formula and complete standard process combination of this invention, exhibiting the best performance in all road performance indicators: dynamic stability of 6484 cycles / mm, freeze-thaw splitting strength ratio of 92.1%, maximum bending tensile strain of the low-temperature beam of 2856 με, and a 10-day immersion swelling rate of only 0.18%. Examples 2-7 involve adjusting the proportions of the primary and secondary composite regenerator components and the mixing ratio of the two regenerators, respectively. Examples 8-11 involve changing the primary insulation time and the insulation time after secondary mixing, respectively. All of these examples fall within the formula and process parameter range defined by this invention, with only minor fluctuations in overall performance. The low-temperature crack resistance, water stability, and steel slag volume stability remained at a high level, verifying that the formulation system and process parameters of this invention have a wide range of applicability and stability. In contrast, Comparative Examples 1 to 6, by eliminating steel slag interface induction treatment, post-primary regeneration heat preservation, segmented slow-speed mixing, graded regeneration process, and completely removing the steel slag-compatible migration-inducing composite regenerator, or by removing multiple core processes, showed a continuous decrease in the freeze-thaw splitting strength ratio and low-temperature flexural strain of the mixture, and a continuous increase in the water immersion expansion rate of the steel slag, with Comparative Examples 5 and 6, which did not use the steel slag-compatible composite regenerator, exhibited the following characteristics. The most significant performance degradation was observed, with a substantial decrease in low-temperature crack resistance and a sharp increase in the risk of steel slag expansion. This fully demonstrates that the processes of graded recycling, interface modification, segmented mixing and insulation, as well as the specialized recycling agent, are the core elements for achieving directional migration of aged asphalt, inhibiting steel slag expansion, and improving the overall performance of the mixture. Simultaneously, the pendulum values ​​of the samples under dry and wet conditions showed relatively small fluctuations, with only the system without steel slag exhibiting a significant decrease in pendulum value. This further indicates that the type of composite recycling agent, graded mixing, and insulation process have a negligible impact on the anti-skid performance of the mixture, and that the anti-skid ability is primarily determined by the rough surface characteristics of the steel slag itself. The above data fully demonstrate that this invention, through a synergistic regulation mechanism of "penetration activation—directional migration—interfacial adsorption—phase structure reconstruction," can significantly improve the water stability, low-temperature crack resistance, and steel slag volume stability of the mixture under high solid waste utilization conditions of 60% steel slag and 15% RAP content. This achieves unexpected technical effects that are difficult to achieve with conventional recycling technologies, fully demonstrating the inventiveness and practicality of this invention.

[0103] To further verify the migration effect of steel slag-compatible migration-inducing composite regenerator and graded synergistic process on aged asphalt, atomic force microscopy tests were conducted on the free asphalt in the main embodiment and comparative examples. The results are shown in Table 3 below.

[0104] Table 3. Atomic force microscopy test results of free pitch in the main embodiments and comparative examples. <![CDATA[Arithmetic mean roughness R a > nm 22.6 28.1 29.0 133 <![CDATA[Root mean square roughness R q > nm 29.1 35.8 38.6 165 <![CDATA[Maximum height R max > nm 269 257 372 1138 <![CDATA[Ten - point average roughness R z > nm 26.5 34.0 38.3 166 <![CDATA[Average maximum height R pm > nm 12.9 14.9 18.3 81.1 Surface area difference rate % 15.2 11.6 9.63 45.0 .

[0105] As shown in Table 3 above, the arithmetic mean roughness R of the free asphalt in Example 1 is... a Only 22.6 nm, root mean square roughness R q 29.1nm, maximum height R max The surface roughness is 269 nm, and the average roughness at ten points is R. z The surface roughness was 26.5 nm, the lowest among the four groups, indicating the weakest surface undulation and microtexture, and a more uniform distribution of the asphalt continuous phase. Meanwhile, the surface area difference rate of Example 1 was only 15.2%, significantly lower than the 45.0% of Comparative Example 6, indicating that its surface had very few sharp protrusions formed by the agglomeration of aged asphalt hard phase, and a more stable phase structure distribution. In contrast, the R values ​​of Comparative Examples 2 and 4... a The corresponding wavelengths are 28.1 nm, 29.0 nm, and R. q The roughness indices were 35.8 nm and 38.6 nm, respectively, with Rz ranging from 34.0 to 38.3 nm. The roughness index was significantly higher than that of Example 1, indicating a higher enrichment of the hard phase. In contrast, Comparative Example 6, which did not employ the regeneration system and steel slag synergistic process of this invention, showed a higher Rz. a Up to 133nm, R q For 165nm, R max The surface area reaches 1138 nm, and the surface area difference rate rises to 45.0%, which is a typical characteristic of hard phase agglomeration and severe phase separation in aged asphaltene.

[0106] The essence of the above differences is as follows: In Example 1 of this invention, the aged asphalt hard phase is directionally migrated to the steel slag interface and adsorbed and fixed through a steel slag-compatible migration-induced composite regenerator and a graded synergistic process. Therefore, the free asphalt remaining in the system mainly consists of new asphalt and soft phase resins and oils activated by the regenerator, resulting in a significant reduction in surface roughness and a more uniform and stable phase structure. In contrast, Comparative Examples 2 and 4, lacking key process steps, did not have the aged asphalt hard phase effectively migrated and remained in the free asphalt, forming local enrichment and leading to increased surface roughness. In Comparative Example 6, without the introduction of steel slag and the regeneration system, the aged asphalt hard phase remained completely in the free asphalt, forming a severely inferior enriched phase, with the surface roughness index reaching its peak. These microscopic characterization results corroborate the improvement in the macroscopic road performance of the mixture (low-temperature crack resistance, water stability, and steel slag volume stability), indirectly confirming the core technical effect of this invention in achieving directional migration of aged asphalt and eliminating inferior enriched phases. This provides microscopic mechanism support for the performance optimization of recycled asphalt mixtures under high solid waste utilization.

[0107] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A steel slag-compatible migration-inducing composite regenerator, characterized in that, The product includes a primary composite regenerator and a secondary composite regenerator. By weight, the primary composite regenerator comprises the following components: 30-60 parts of epoxidized soybean oil and 20-40 parts of heavy aromatic oil; the secondary composite regenerator comprises the following components: 5-10 parts of heavy aromatic oil, 25-30 parts of SBR latex, and 0.5-5 parts of interface-inducing components.

2. The steel slag-compatible migration-inducing composite regenerator according to claim 1, characterized in that, The interface-inducing components, by weight, include: 1-3 parts of aminosilane coupling agent, 0.5-1.5 parts of amine adhesion promoter, and 0.5-2 parts of cationic interfacial activity promoter.

3. The steel slag-compatible migration-inducing composite regenerator according to claim 2, characterized in that, The aminosilane coupling agent is γ-aminopropyltriethoxysilane and / or γ-aminopropyltrimethoxysilane; the amine adhesion promoter includes ethylenediamine and / or diethylenetriamine; the cationic interfacial activity promoter includes hexadecyltrimethylammonium chloride and / or octadecyltrimethylammonium chloride.

4. The steel slag-compatible migration-inducing composite regenerator according to claim 3, characterized in that, The primary composite regenerator comprises, by weight, 40 parts of epoxidized soybean oil and 20 parts of heavy aromatic oil; the secondary composite regenerator comprises, by weight, 10 parts of heavy aromatic oil, 27 parts of SBR latex, 1.5 parts of γ-aminopropyltriethoxysilane, 0.5 parts of ethylenediamine and 1 part of hexadecyltrimethylammonium chloride.

5. A method for preparing a thin layer of recycled asphalt mixture based on the directional migration of aged asphalt, characterized in that, Includes the following steps: Step 1: Preheating RAP milling material: Heat the RAP milling material to 120-160℃ to obtain preheated RAP milling material; Step 2, Primary Permeation Activation Regeneration: Add the primary composite regenerator of the steel slag-compatible migration-inducing composite regenerator described in any one of claims 1-4 to the preheated RAP milling material, mix for 2-4 minutes at a revolution speed of 20-30 r / min and a rotation speed of 55-65 r / min, and then keep warm for 5-15 minutes to obtain the RAP system after permeation activation; Step 3, Secondary migration-induced regeneration: Add pretreated steel slag and secondary composite regenerator of any one of the steel slag-compatible migration-induced composite regenerators in claims 1-4 to the activated RAP system, and perform graded slow-down mixing and heat preservation treatment at 160~180℃ to obtain the regenerated mixture; Step 4: Mixture molding: Add new rubber asphalt, aggregates and stabilizers to the obtained recycled asphalt mixture, mix evenly at 170~200℃ and mold to obtain a thin layer of recycled asphalt mixture.

6. The preparation method according to claim 5, characterized in that, The steel slag pretreatment includes: Steel slag is aged or subjected to wet heat treatment to reduce the free calcium oxide content to ≤3%; The interface inducer is sprayed and impregnated with a treatment solution and dried at 60–120°C to form an asphalt-loving active interface layer on the surface of the steel slag. The amount of the interface inducer sprayed is 0.2–1.0% of the mass of the steel slag, and it is pre-wetted for 2–5 minutes before impregnation.

7. The preparation method according to claim 5, characterized in that, In step 3, the graded slow-down mixing and heat preservation treatment involves mixing for 3 to 5 minutes at a first mixing speed of 42 to 48 r / min revolution and 75 to 90 r / min rotation, followed by mixing for 2 to 4 minutes at a second mixing speed of 20 to 30 r / min revolution and 55 to 65 r / min rotation, and then heat preservation for 3 to 10 minutes.

8. A recycled asphalt mixture thin layer obtained by the preparation method according to any one of claims 5-7.

9. The recycled asphalt mixture thin layer according to claim 8, characterized in that, The recycled asphalt mixture thin layer comprises the following components by weight: 10-20 parts of RAP milling material, 50-70 parts of steel slag, 8-30 parts of aggregate, 0.1-0.5 parts of stabilizer, and 5-6 parts of new rubber asphalt; the mixture also contains a steel slag-compatible migration-inducing composite recycling agent.

10. The recycled asphalt mixture thin layer according to claim 9, characterized in that, RAP milling mix is ​​SBS modified bitumen milling mix with a particle size of 0-9.5mm, and steel slag with a particle size of 4.75-9.5mm; the aggregate includes limestone with a particle size of 2.36-4.75mm, limestone with a particle size of 0-2.36mm, and mineral powder.

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