Microwave-responsive molecular rotor mixture for emulsified asphalt cold recycling and construction method thereof

Abstract

The application provides a microwave response type molecular rotor mixture for emulsified asphalt cold regeneration and a construction method thereof, wherein raw materials of the microwave response type molecular rotor mixture comprise an A component and a B component, the A component comprises waste asphalt pavement material RAP, carbon black and molecular rotor powder, and the B component comprises emulsified asphalt; after the raw materials are mixed, microwave irradiation treatment is performed; wherein the molecular rotor powder is obtained by covalently connecting 4-(triphenylmethylamino)-4-oxobutyric acid to an aminated silicon dioxide carrier. The application realizes rapid and uniform heating inside the mixture, thereby greatly shortening maintenance time required for opening traffic intensity of the emulsified asphalt cold regeneration layer from traditional 3-7 days to within 24 hours, greatly improving construction efficiency, and improving long-term durability, fatigue resistance and other road performances of the regenerated material.

Description

Technical Field

[0001] This invention relates to the field of asphalt road materials technology, and in particular to a microwave-responsive molecular rotor mixture for cold recycling of emulsified asphalt and its construction method. Background Technology

[0002] Emulsified asphalt cold recycling technology is a sustainable pavement maintenance technology that involves milling, crushing, and screening waste asphalt pavement material (RAP), then mixing it with emulsified asphalt, water, and, if necessary, new aggregates and cement as active fillers at room temperature, followed by paving and compaction. This technology is widely recognized for its significant advantages in environmental protection, energy conservation, and economy because it can recycle RAP materials, significantly reducing the extraction of new materials and energy consumption, and lowering greenhouse gas emissions.

[0003] However, this technology faces a core bottleneck in practical engineering applications: its strength formation mechanism heavily relies on the demulsification and dehydration of emulsified asphalt, the evaporation of water, and the slow hydration reaction of active fillers such as cement. This complex multiphase physicochemical process leads to slow early strength development of the material, typically requiring a curing period of 3 to 7 days to reach the minimum strength required for opening to traffic. This excessively long curing time severely restricts the application of this technology in engineering scenarios such as highways and urban arterial roads where rapid traffic opening or emergency repairs are necessary. To address this challenge, the industry currently mainly adopts techniques such as adding inorganic salt chemical early-strength agents like calcium chloride and sodium sulfate, or increasing the amount of cement. However, these methods have significant limitations. First, while inorganic salt early-strength agents can accelerate the demulsification of emulsified asphalt by increasing the ionic strength of the system and promote early strength formation to some extent by lowering the freezing point of water, the introduced ions may competitively adsorb onto the aggregate surface, weakening the adhesion between asphalt and aggregate, thus leading to a decrease in the long-term water stability and durability of the mixture. Furthermore, these soluble salts pose a risk of precipitating onto the pavement surface with the migration of moisture, a phenomenon known as "salt blooming," which affects the pavement's appearance and skid resistance. Secondly, while simply increasing cement content can enhance early strength by increasing the amount of hydration products, excessively high cement content leads to a significant increase in the rigidity of recycled mixtures, while correspondingly weakening their flexibility and resistance to fatigue cracking. Their road performance tends to resemble brittle cement concrete, deviating from the excellent flexibility inherent in asphalt mixtures, and also increasing material costs.

[0004] More importantly, the existing early strength technology has a relatively simple mechanism of action, mainly focusing on accelerating cement hydration or promoting demulsification from a chemical perspective, while having limited intervention effect on the key physical processes driving moisture evaporation—heat transfer and moisture migration. The moisture evaporation rate under natural curing is constrained by environmental temperature and humidity, resulting in low efficiency. Summary of the Invention

[0005] In view of this, the present invention proposes a microwave-responsive molecular rotor mixture for cold recycling of emulsified asphalt and its construction method. By compounding molecular rotor powder with carbon black as an early-strength agent and implementing precise microwave treatment after paving, a macro-composite heating system synergistically combining "molecular frictional heat generation" and "dielectric loss heat generation" is constructed. This system can achieve rapid and uniform volumetric heating within the mixture, precisely controlling the temperature within a safe and efficient window of 60~80℃. On the one hand, this drastically accelerates the demulsification of emulsified asphalt, moisture migration and evaporation, and cement hydration, thereby significantly shortening the curing time required to achieve open traffic strength from the traditional 3-7 days to within 6~24 hours; on the other hand, the uniform thermal field avoids asphalt aging caused by local overheating, while the lower carbon black and cement content ensures excellent flexibility, water stability, and fatigue resistance of the recycled layer, achieving a balance between high efficiency, early strength, and long-term durability.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a microwave-responsive molecular rotor mixture for cold recycling of emulsified asphalt, the raw materials including component A and component B, wherein component A includes waste asphalt pavement material RAP, carbon black and molecular rotor powder, and component B includes emulsified asphalt, and the raw materials are mixed and then subjected to microwave irradiation treatment. The molecular rotor powder is obtained by covalently linking 4-(triphenylmethylamino)-4-oxobutyric acid to an aminated silica carrier.

[0007] The core of this invention lies in introducing a microwave-responsive molecular rotor mixture for the cold recycling of emulsified asphalt, applying microwave physical field intervention technology to the cold recycling process of emulsified asphalt. This invention achieves rapid and uniform volumetric heating within the material through the efficient coupling of the excellent dielectric loss characteristics of carbon black and microwave electromagnetic energy. Its mechanism can be analyzed through two synergistic pathways: First, when subjected to microwave radiation, the carbon black particles dispersed in the mixture act as numerous micro-absorbers and heating centers, converting microwave energy into heat energy, causing the system temperature to rise. This internal heat source directly acts on the continuous aqueous phase encapsulating the asphalt emulsion, accelerating the migration and evaporation of water, thereby promoting the demulsification of the emulsified asphalt and the aggregation of asphaltenes. Second, this thermal effect simultaneously acts on the cement components in the system, providing thermal activation power for their hydration reaction and accelerating the formation of cement hydration products.

[0008] To further improve heating uniformity and energy efficiency, and to avoid localized overheating, this invention introduces a microwave-driven "molecular rotor" microscopic mechanical energy conversion system. This system securely fixes the molecular rotor to a nanocarrier via covalent bonds to obtain molecular rotor powder. The molecular rotor powder undergoes directional rotation in a microwave field, and its mechanical energy is directly converted into heat energy through friction with the surrounding medium. This "molecular frictional heating" mechanism differs in principle from traditional dielectric loss heating, achieving a uniform distribution of the heat source at the molecular scale, thereby constructing a theoretically hotspot-free ideal thermal field within the material. This microscopic system can synergize with a macroscopic carbon black heating network to form a composite heating system spanning both macroscopic and microscopic scales.

[0009] The aforementioned molecular rotor mixture effectively overcomes the limitations of traditional technologies in addressing the physical bottleneck of moisture evaporation. By providing energy from within the material, this invention achieves simultaneous acceleration of the key processes of moisture evaporation and cement hydration, thereby enabling the cold recycled mixture to acquire early strength in a very short time. Simultaneously, it avoids the negative effects of increased mixture brittleness and decreased crack resistance caused by simply increasing cement content.

[0010] Based on the above technical solution, further, by weight, component A includes 90-120 parts of waste asphalt pavement material RAP, 0.5-2 parts of carbon black and 1-3 parts of molecular rotor powder, and component B includes 40-60 parts of emulsified asphalt.

[0011] The limitation on carbon black dosage is based on the microwave absorption characteristics of carbon black itself and its mechanism of action in the asphalt-aggregate system. The lower limit of 0.5 parts carbon black ensures a sufficient number of carbon black particles dispersed in the mixture, forming a continuous and effective three-dimensional heat absorption network. This allows for a significant and uniform volumetric heat effect under microwave radiation, providing the necessary energy for rapid demulsification and moisture evaporation. The upper limit of carbon black dosage aims to avoid negative effects caused by excessive carbon black: excessive carbon black content not only increases particle agglomeration, hindering dispersion uniformity, but also, due to its strong microwave absorption characteristics, may cause excessive reflection or absorption of microwave energy on the surface of the mixture, thus weakening the heating efficiency and uniformity of deeper materials. Furthermore, excessive carbon black can irreversibly adsorb too many lightweight asphalt components, potentially impairing the flexibility of the asphalt mastic and adversely affecting the long-term crack resistance of the mixture.

[0012] Based on the above technical solution, further, by weight, component A further includes 1 to 3 parts of cement, and component B further includes 10 to 20 parts of water.

[0013] Carbon black and cement form a synergistic system. In this system, cement acts as an active filler, and its dosage can be controlled at a low level.

[0014] The synergistic effect of the two lies in their clear division of labor and complementary enhancement: carbon black achieves rapid and uniform internal heating under microwave action, mainly breaking through the "thermodynamic bottleneck" of strength formation, and providing efficient energy for moisture evaporation and demulsification; after moisture evaporation, the stable bonding between aggregates still depends on cement hydration products. Low-dosage cement plays a key role in constructing the "chemically bonded skeleton"—its generated calcium silicate hydrate (CSH) gel, ettringite, and other products provide the main support for the final strength of the cooled mixture.

[0015] Thus, carbon black and cement form a complete early-strength system with interconnected functions and complementary stages: the former creates a high-temperature, low-moisture physical environment in a very short time, promoting rapid molding of the mixture and the formation of initial strength; the latter accelerates hydration in this optimized environment, ultimately endowing the material with long-term mechanical properties and durability. This division of labor and cooperation mechanism allows the amount of cement to be maintained at a low level, thereby avoiding problems such as increased rigidity, decreased flexibility, and increased risk of drying shrinkage cracks in the mixture caused by excessive cement, ensuring that the recycled layer has good resistance to fatigue cracking.

[0016] Based on the above technical solutions, furthermore, the power of the irradiation treatment is 2~5kW / m². 2 The time is 5 to 15 minutes.

[0017] This invention reveals and precisely defines two core control windows to ensure the successful operation of the system, thereby solving the industry problem of the inability to simultaneously achieve "high efficiency and early strength" and "long-term performance." The first window is the critical heating density window. It is defined as the distribution density of effective microwave heating points within a unit volume of the mixture. This parameter is determined by the carbon black content and its dispersion uniformity. Its function is to ensure uniform volume heating and avoid localized overheating only when the heating density is above a critical lower limit; simultaneously, the density also has an actual limit, as excessive density can lead to increased microwave reflection and asphalt adsorption problems. Establishing this window is a prerequisite for achieving uniform and efficient heating. The second window is the temperature-efficiency window. It is defined as the temperature range of 60℃ to 80℃ that must be strictly controlled within the mixture during the microwave treatment stage. Its function is that the lower limit of this window (≥60℃) ensures kinetic conditions that are sufficient to drastically accelerate the demulsification of emulsified asphalt, water evaporation, and cement hydration reaction; while its upper limit (≤80℃) is a key safety threshold, which is far below the rapid aging temperature of asphalt (about 150℃), thus ensuring the long-term durability and fatigue resistance of asphalt while pursuing high efficiency.

[0018] Based on the above technical solutions, the method for preparing the molecular rotor powder further includes: S1, dispersing nano-silica in a first organic solvent, adding 3-aminopropyltriethoxysilane, carrying out a silanization reaction under an inert atmosphere, centrifuging, washing, and obtaining an aminated silica carrier. S2. The 4-(triphenylmethylamino)-4-oxobutyric acid and condensing agent are dispersed in a second organic solvent, activated, and then the aminated silica carrier is added. The mixture is stirred and reacted, and after centrifugation, washing, and drying, the molecular rotor powder is obtained.

[0019] Based on the above technical solution, the mass ratio of the aminated silica carrier to 4-(triphenylmethylamino)-4-oxobutyric acid is (5~7):1.

[0020] Based on the above technical solution, the mass ratio of the nano-silica to 3-aminopropyltriethoxysilane is further (1~5):1.

[0021] Based on the above technical solution, the silanization reaction further includes: reflux reaction at 100℃~120℃ for 4~8 hours.

[0022] Based on the above technical solution, further, the stirring reaction in step S2 is carried out at a speed of 10-20 rpm for a time of 16-25 h.

[0023] Based on the above technical solutions, further, the first organic solvent includes toluene, and the second organic solvent includes N,N-dimethylformamide solution.

[0024] Secondly, the present invention also provides a construction method using the above-mentioned molecular rotor mixture, comprising the following steps: S1, dry mixing component A, then adding component B and wet mixing to obtain the mixture; S2. After spreading and initially compacting the mixture, microwave irradiation is applied, followed by secondary compaction, cooling, and curing.

[0025] The dry-mix process involves placing recycled asphalt pavement material (RAP), cement as an active filler, molecular rotor powder, and carbon black into a mixing plant for thorough dry mixing. Next, a specified amount of emulsified asphalt and water is added to the uniformly dry-mixed material, and wet mixing continues until all aggregate particles are evenly coated with emulsified asphalt, resulting in a cold recycled mixture with uniform color and suitable workability.

[0026] Next, paving and preliminary compaction are carried out. The mixed cold recycled material is transported to the construction site and paved. Then, a road roller is used to perform preliminary compaction to achieve the specified initial density and provide a relatively flat irradiated surface for subsequent microwave treatment.

[0027] Simultaneously, microwave activation treatment is performed. The specific process involves using industrial microwave emitting equipment to directionally irradiate the pre-compacted road surface. The preferred operating frequency for the microwave equipment is 915 MHz, which offers greater penetration depth. During irradiation, the power density is controlled within the range of 2-5 kW / m², and the irradiation time is controlled within 5-15 minutes based on the pavement thickness, environmental conditions, and target temperature rise.

[0028] Once the temperature of the mixture after microwave treatment has naturally dropped to a suitable temperature range for final compaction, a heavy-duty roller should be used immediately for final compaction to eliminate any tiny pores that may remain due to the evaporation of internal moisture after microwave treatment, ensuring that the mixture reaches the designed final density.

[0029] The purpose of the dry mixing process is to ensure that the micron-sized carbon black powder and cement can be evenly dispersed and adhered to the RAP and aggregate surface, forming the basis for subsequent efficient heat absorption.

[0030] The optimization objective of the microwave activation process parameters is to rapidly and uniformly raise the internal temperature of the mixture to the critical range of 60-80℃. Within this temperature range, carbon black efficiently absorbs microwave energy and converts it into heat energy, simultaneously achieving three major effects: rapidly accelerating the demulsification of emulsified asphalt, strongly driving the evaporation and migration of moisture, and providing thermal activation conditions for cement hydration.

[0031] After compaction, the mixture undergoes natural cooling and curing. Since microwave treatment has largely completed the dehydration and early structuring processes, the traditional curing cycle of several days is significantly shortened. Curing time can be reduced to 24 hours or less. Once the mixture has cooled to ambient temperature and its strength is confirmed to meet requirements, traffic can begin.

[0032] Compared with the prior art, the present invention has the following beneficial effects: (1) By introducing the synergistic mechanism of “molecular rotor friction heat generation” and “carbon black dielectric heat generation”, the present invention achieves rapid and uniform heating inside the mixture, thereby significantly reducing the curing time required for the cold recycled emulsified asphalt layer to reach the open traffic strength from the traditional 3-7 days to less than 24 hours, greatly improving construction efficiency.

[0033] (2) By precisely controlling the microwave processing temperature within a window of 60–80℃ and using a molecular-scale heat source to improve the uniformity of the thermal field, this invention effectively avoids the problem of asphalt aging caused by local overheating and ensures the long-term durability of recycled materials.

[0034] (3) By optimizing the amount of carbon black and cement, this invention achieves early strength while maintaining the good flexibility and fatigue resistance of the mixture. Its rebound modulus is closer to the requirements of flexible base layer, overcoming the defect of increased brittleness caused by traditional high cement content.

[0035] (4) The present invention fixes the molecular rotor on the nanocarrier by covalent bond, so that it can maintain structural and functional stability under the harsh mixing and compaction conditions of road engineering. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention is the first to introduce the physical mechanism of "microwave-driven molecular directional rotation and conversion into macroscopic thermal energy" into the field of macroscopic engineering materials with extreme heterogeneity, multiphase composite and stringent service requirements, namely "cold recycling of emulsified asphalt".

[0038] Existing research on molecular rotors largely focuses on homogeneous solutions, single-molecule devices, or precision nanotechnology, which involve controllable environments and microscopic scales. However, the emulsified asphalt cold-recycled mixture addressed in this invention is a solid, multiphase (aggregate, asphalt, water, cement), highly heterogeneous macroscopic engineering system that must withstand heavy machinery construction. Introducing molecular-scale functional units into this system and ensuring its structural stability and functional reliability during vigorous mixing, compaction, and long-term service, while simultaneously achieving effective energy transfer and macroscopic temperature rise, presents an unprecedented technical challenge in this field.

[0039] To address the aforementioned challenges, this invention provides a systematic technical solution encompassing molecular design, carrier immobilization, and engineering integration. First, 4-(triphenylmethylamino)-4-oxobutyric acid, possessing a well-defined nonpolar conjugated structure and capable of efficient coupling and rotational drive in an alternating microwave electromagnetic field, is selected as the core functional unit. Through organic synthesis, an alkyl chain with a carboxyl group at its end is grafted onto it as a "linker arm," providing an active site and the necessary spatial freedom for subsequent chemical immobilization.

[0040] Secondly, a two-step covalent grafting method is employed to ensure the durability of the functional units. First, an organic monolayer with amino groups is constructed on the surface of a nano-silica support using silane coupling agents such as 3-aminopropyltriethoxysilane (APTES). Subsequently, under the action of a condensing agent, the terminal carboxyl groups of the functionalized rotor molecules undergo an amidation reaction with the amino groups on the support surface, forming a strong covalent bond. This process ensures that the "molecular rotor" will not detach from the support or fail during subsequent high-speed shear mixing and use. Finally, the functionalized powder prepared above is added as a mixture during the dry mixing stage.

[0041] This invention can achieve an absolutely uniform distribution of heat sources at the molecular scale, thereby eliminating local overheating at any scale; and achieves safer intelligent temperature control through rotational motion and the self-limiting property of medium viscosity.

[0042] The construction method of the microwave-responsive molecular rotor mixture provided by the present invention includes the following steps: S1, after dry mixing of component A, component B is added and wet mixed to obtain the mixture; S2. After spreading and initially compacting the mixture, microwave irradiation is applied, followed by secondary compaction, cooling, and curing.

[0043] Component A was dry-mixed for 60 seconds, then component B was added and wet-mixed for 90 seconds. After the mixture was laid, it was initially compacted using a steel-drum roller with one pass of static compaction and two passes of vibratory compaction. Microwave activation treatment was then initiated, using an industrial microwave device with a working frequency of 915 MHz to irradiate the road surface. The microwave power density was precisely controlled at 3 kW / m², and the irradiation lasted for 10 minutes. After irradiation, the mixture was allowed to cool naturally to 50°C under ambient conditions. After final compaction, the mixture underwent a short curing period of only 6 hours. During this process, the material continued to cool, accompanied by the evaporation of residual moisture and subsequent cement hydration.

[0044] The preliminary compaction step aims to obtain a working surface with preliminary load-bearing capacity and a smooth surface, laying the foundation for subsequent efficient microwave energy coupling.

[0045] The microwave activation process ensures that microwave energy effectively penetrates into the material and is efficiently absorbed by the uniformly dispersed carbon black particles, converting it into heat energy. This achieves rapid and uniform heating, raising the core temperature of the mixture to the preset activation temperature range.

[0046] The 50°C final compaction temperature is based on the following considerations: at this temperature, most of the moisture has evaporated, the asphalt has fully demulsified and re-agglomerated, and its viscosity is in the optimal range for rolling, which can ensure further compaction effect and effectively avoid the sticking phenomenon that may occur when the rubber-tired roller is operating.

[0047] In the following specific embodiment, the preparation method of the acid-washed and activated nano-silica includes the following steps: Step 1: In a 1000 mL three-necked round-bottom flask, add 500 mL of deionized water and 100 mL of concentrated nitric acid to prepare a nitric acid solution with a concentration of approximately 2 mol / L. While stirring, slowly add 20.0 g of nano-silica powder to form a uniform suspension.

[0048] Step 2: Install the condenser and heat the reaction system to 80±5℃. At this temperature, continue stirring and reflux for 6 hours.

[0049] Step 3: After the reaction is complete, stop heating and allow the suspension to cool to room temperature. Filter using slow-speed quantitative filter paper and an acid-resistant filter membrane. Wash the filter cake repeatedly with 2 liters of deionized water until the pH of the filtrate reaches 5.0-7.0, ensuring complete removal of residual nitric acid and soluble impurities.

[0050] Step 4: Transfer the washed wet filter cake to a petri dish and place it in a vacuum drying oven at 80°C for 12 hours to completely remove physically adsorbed water, obtaining dry, acid-activated nano-silica powder. Store it in a desiccator for later use.

[0051] In the following specific embodiments, 4-(triphenylmethylamino)-4-oxobutyric acid may be simply referred to as triphenylmethyl-butyramic acid.

[0052] Trityl Chloride was purchased from Sigma-Aldrich (CAS: 76-83-5).

[0053] 4-Aminobutyric acid was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0054] Example 1 This embodiment provides a microwave-responsive molecular rotor mixture for cold recycling of emulsified asphalt and its construction method. The microwave-responsive molecular rotor mixture comprises components A and B. By weight, component A includes 100 parts of RAP material, 2 parts of cement, 1.5 parts of molecular rotor powder, and 1 part of carbon black. Component B includes 50 parts of emulsified asphalt and 15 parts of water. 1 part by weight is 1 kg.

[0055] Including: 1. Synthesis of 4-(triphenylmethylamino)-4-oxobutyric acid A1. In a dry 250 mL three-necked round-bottom flask, dissolve 20 mmol of 4-aminobutyric acid in 100 mL of anhydrous dichloromethane.

[0056] Under ice-water bath cooling and nitrogen protection, 21.5 mmol of triethylamine was slowly added dropwise to the system. Subsequently, 20 mmol of triphenylmethyl chloride was added in portions with stirring. The ice bath was removed, the reaction mixture was raised to 25°C, and the reaction was continued to be stirred under a nitrogen atmosphere for 12 hours.

[0057] A2: Post-treatment. After the reaction is complete, wash the reaction solution twice with 100 mL of deionized water. Dry the organic phase with anhydrous sodium sulfate and filter to remove the desiccant.

[0058] A3: Purification. The filtrate was concentrated under reduced pressure using a rotary evaporator to obtain the crude product. The crude product was purified by silica gel column chromatography with an eluent ratio of petroleum ether to ethyl acetate of 1:1 (volume ratio). The target fraction was collected, and the solvent was removed by rotary evaporation to obtain a white solid powder, which is the target product 4-(triphenylmethylamino)-4-oxobutyric acid.

[0059] 10. Preparation of molecular rotor powder S1. Weigh 10g of acid-washed and activated nano-silica and disperse it in 200mL of anhydrous toluene; Add 0.9 g of 3-aminopropyltriethoxysilane and reflux at 110 °C for 6 hours under nitrogen protection to carry out silanization reaction; After the reaction was completed, the mixture was centrifuged and washed repeatedly with toluene and ethanol to obtain the aminated silica support.

[0060] S2. 1.5 g of 4-(triphenylmethylamino)-4-oxobutyric acid, 1 g of condensing agent HOBt (hydroxybenzotriazole), and 1 g of EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride) were dissolved in 100 mL of anhydrous DMF and activated. Then, 9 g of the aminated silica support was added, and the mixture was stirred at 15 rpm for 24 hours at 25 °C. After centrifugation, washing, and vacuum drying, the molecular rotor powder was obtained.

[0061] 11. Construction method, including the following steps: Mix component A dry for 60 seconds, then add component B and mix wet for 90 seconds to obtain the mixture. After the mixture is spread, it is initially compacted by static compaction once and vibratory compaction twice with a steel wheel roller; Subsequently, microwave activation treatment was initiated, using industrial microwave equipment with a working frequency of 915 MHz to irradiate the road surface. The microwave power density was precisely controlled at 3 kW / m², and the irradiation was continued for 10 minutes.

[0062] After irradiation treatment, the mixture is allowed to cool naturally to 50°C under ambient conditions.

[0063] Example 2 This embodiment provides a microwave-responsive molecular rotor mixture for cold recycling of emulsified asphalt and its construction method. The microwave-responsive molecular rotor mixture comprises components A and B. By weight, component A includes 110 parts of RAP material, 1 part of cement, 1 part of molecular rotor powder, and 0.5 parts of carbon black. Component B includes 40 parts of emulsified asphalt and 10 parts of water. 1 part by weight is 1 kg.

[0064] Including: 1. Synthesis of 4-(triphenylmethylamino)-4-oxobutyric acid A1. In a dry 250 mL three-necked round-bottom flask, dissolve 20 mmol of 4-aminobutyric acid in 100 mL of anhydrous dichloromethane.

[0065] Under ice-water bath cooling and nitrogen protection, 21.5 mmol of triethylamine was slowly added dropwise to the system. Subsequently, 20 mmol of triphenylmethyl chloride was added in portions with stirring. The ice bath was removed, the reaction mixture was raised to 25°C, and the reaction was continued to be stirred under a nitrogen atmosphere for 12 hours.

[0066] A2. After the reaction is complete, wash the reaction solution twice with 100 mL of deionized water. Dry the organic phase with anhydrous sodium sulfate and filter to remove the desiccant.

[0067] A3. The filtrate was concentrated under reduced pressure using a rotary evaporator to obtain the crude product. The crude product was then purified by silica gel column chromatography with an eluent ratio of petroleum ether to ethyl acetate of 1:1 (volume ratio).

[0068] The target component fraction was collected, and the solvent was removed by rotary evaporation to obtain a white solid powder, which is the target product 4-(triphenylmethylamino)-4-oxobutyric acid.

[0069] 2. Preparation of molecular rotor powder S1. Weigh 10g of acid-washed and activated nano-silica and disperse it in 200mL of anhydrous toluene; Add 0.9 g of 3-aminopropyltriethoxysilane and reflux at 110 °C for 4 hours under nitrogen protection to carry out silanization reaction; After the reaction was completed, the mixture was centrifuged and washed repeatedly with toluene and ethanol to obtain the aminated silica support.

[0070] S2. Dissolve 1.5 g of 4-(triphenylmethylamino)-4-oxobutyric acid, 1 g of condensing agent HOBt, and 1 g of EDC in 100 mL of anhydrous DMF, activate the solution, and then add 7.5 g of the aminated silica support. Stir the mixture at 10 rpm for 25 hours at 25 °C. After centrifugation, washing, and vacuum drying, the molecular rotor powder is obtained.

[0071] 3. Construction method, including the following steps: Mix component A dry for 60 seconds, then add component B and mix wet for 90 seconds to obtain the mixture. After the mixture is spread, it is initially compacted by static compaction once and vibratory compaction twice with a steel wheel roller; Subsequently, microwave activation treatment was initiated, using industrial microwave equipment operating at a frequency of 915 MHz to irradiate the road surface, with the microwave power density precisely controlled at 2 kW / m². 2 Continue irradiation for 5 minutes.

[0072] After irradiation treatment, the mixture is allowed to cool naturally to 50°C under ambient conditions.

[0073] Example 3 This embodiment provides a microwave-responsive molecular rotor mixture for cold recycling of emulsified asphalt and its construction method. The microwave-responsive molecular rotor mixture comprises components A and B. By weight, component A includes 120 parts of RAP material, 3 parts of cement, 3 parts of molecular rotor powder, and 2 parts of carbon black. Component B includes 60 parts of emulsified asphalt and 20 parts of water. 1 part by weight is 1 kg.

[0074] Including: 1. Synthesis of 4-(triphenylmethylamino)-4-oxobutyric acid A1. In a dry 250 mL three-necked round-bottom flask, dissolve 20 mmol of 4-aminobutyric acid in 100 mL of anhydrous dichloromethane.

[0075] Under ice-water bath cooling and nitrogen protection, 21.5 mmol of triethylamine was slowly added dropwise to the system. Subsequently, 20 mmol of triphenylmethyl chloride was added in portions with stirring. The ice bath was removed, the reaction mixture was raised to 25°C, and the reaction was continued to be stirred under a nitrogen atmosphere for 12 hours.

[0076] A2. Post-treatment. After the reaction is complete, wash the reaction solution twice with 100 mL of deionized water. Dry the organic phase with anhydrous sodium sulfate and filter to remove the desiccant.

[0077] A3. Purification. The filtrate was concentrated under reduced pressure using a rotary evaporator to obtain the crude product. The crude product was purified by silica gel column chromatography with an eluent ratio of petroleum ether to ethyl acetate of 1:1 (volume ratio). The fraction containing the target component was collected, and the solvent was removed by rotary evaporation to obtain a white solid powder, which is the target product 4-(triphenylmethylamino)-4-oxobutyric acid.

[0078] 2. Preparation of molecular rotor powder S1. Weigh 10g of acid-washed and activated nano-silica and disperse it in 200mL of anhydrous toluene; Add 0.9 g of 3-aminopropyltriethoxysilane and reflux at 120 °C for 8 hours under nitrogen protection to carry out silanization reaction; After the reaction was completed, the mixture was centrifuged and washed repeatedly with toluene and ethanol to obtain the aminated silica support.

[0079] S2. Dissolve 1.5 g of 4-(triphenylmethylamino)-4-oxobutyric acid, 1 g of condensing agent HOBt, and 1 g of EDC in 100 mL of anhydrous DMF and activate. Then add 10.5 g of the aminated silica support and stir at 20 rpm for 16 hours at 25 °C. After centrifugation, washing, and vacuum drying, the molecular rotor powder is obtained.

[0080] 3. Construction method, including the following steps: Mix component A dry for 60 seconds, then add component B and mix wet for 90 seconds to obtain the mixture. After the mixture is spread, it is initially compacted by static compaction once and vibratory compaction twice with a steel wheel roller; Subsequently, microwave activation treatment was initiated, using industrial microwave equipment with a working frequency of 915 MHz to irradiate the road surface. The microwave power density was precisely controlled at 5 kW / m², and the irradiation was continued for 15 minutes.

[0081] After irradiation treatment, the mixture is allowed to cool naturally to 50°C under ambient conditions.

[0082] Comparative Example 1 The difference between this comparative example and Example 1 is that the steps S1 and S2 in preparing the molecular rotor powder in this comparative example do not contain an aminosilane support.

[0083] Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example does not contain molecular rotor powder.

[0084] Comparative Example 3 The difference between this comparative example and Example 1 is that step S2 in preparing the molecular rotor powder in this comparative example does not contain 4-(triphenylmethylamino)-4-oxobutyric acid.

[0085] Comparative Example 4 The difference between this comparative example and Example 1 is that this comparative example does not include microwave irradiation treatment.

[0086] Comparative Example 5 The difference between this comparative example and Example 1 is that this comparative example does not contain carbon black.

[0087] Comparative Example 6 The difference between this comparative example and Example 1 is that the molecular rotor powder in this comparative example is in excess, at 10 parts.

[0088] Comparative Example 7 The difference between this comparative example and Example 1 is that cement is used to replace molecular rotor powder and carbon black in this comparative example, and microwave treatment is not performed; instead, traditional curing methods are used.

[0089] Performance testing 1. The molecular rotor powder, aminated silica powder, and 4-(triphenylmethylamino)-4-oxobutyric acid prepared in Example 1 were respectively filled into the NMR rotor. Carbon-13 cross-polarized magic angle rotation spectra were acquired on the same solid-state NMR spectrometer under conditions of no microwave application and microwave irradiation with a specific power applied within the spectrometer cavity. The detection results are shown in Table 1 below.

[0090] Table 1. Detection results of molecular rotor powder, aminated silica carrier, and 4-(triphenylmethylamino)-4-oxobutyric acid in Example 1.

[0091] As shown in Table 1, the spectral peaks of the molecular rotor powder are significantly broadened and shifted under microwave conditions, indicating that the surface molecular rotors are rotating at high speed.

[0092] 2. Comparing the Marshall stability, flow value, unconfined compressive strength, and indirect tensile strength of Examples 1-3 after microwave treatment for 6 hours and Comparative Example 7 after curing for 3 and 7 days, the test results are shown in Table 2 below.

[0093] Table 2 Performance test results of Examples 1-3 and Comparative Example 7

[0094] As shown in Table 2, after 6 hours of curing, the stability of Examples 1-3 exceeded that of Comparative Example 7 after 3 days of curing and was close to that after 7 days of curing. The unconfined compressive strength reached 2.5 MPa after 6 hours, far exceeding the 1.2 MPa of the traditional 3-day curing. The indirect tensile strength was also significantly improved, indicating good early crack resistance.

[0095] 3. After 28 days of curing, the road performance of Examples 1-3 and Comparative Examples 1-7 was tested. The dry-wet splitting strength ratio, compressive resilience modulus and fatigue resistance were tested respectively. The test results are shown in Table 3 below.

[0096] Table 3. Road performance test results of Examples 1-3 and Comparative Examples 1-7

[0097] As shown in Table 3, the TSR values ​​of Examples 1-3 are higher than 90%, indicating excellent water stability and no salt efflorescence or adhesion problems. The compressive resilience modulus is between 850 MPa and 860 MPa, indicating good flexibility. The fatigue life is between 115 and 125 thousand cycles, indicating optimal long-term crack resistance.

[0098] 4. The water evaporation rate of Examples 1-3 and Comparative Examples 1-7 was tested, and the test results are shown in Table 4 below.

[0099] Table 4. Results of water evaporation rate detection in Examples 1-3 and Comparative Examples 1-7

[0100] As shown in Table 4, the use of molecular rotor powder, carbon black, and microwave radiation in Examples 1-3 can accelerate moisture evaporation.

[0101] 5. The internal temperature fields of Examples 1-3 and Comparative Examples 1-7 were tested, and the test results are shown in Table 5 below.

[0102] Table 5. Detection results of the internal temperature field of Examples 1-3 and Comparative Examples 1-7

[0103] As shown in Table 5, the internal temperature of Examples 1-3 is uniform and falls within the 60–80℃ range.

[0104] As can be seen from Tables 2-5, comparing Example 1 and Comparative Example 1, when the aminated carrier is missing, the molecular rotor is not firmly fixed, the heating uniformity decreases, the water evaporates slowly, and the long-term water stability and fatigue life decrease. A comparison of Example 1 and Comparative Example 2 shows that when molecular rotor powder is missing, heating with only carbon black results in slightly poorer temperature uniformity, slightly higher moisture retention, and decreased fatigue resistance. A comparison of Example 1 and Comparative Example 3 shows that when 4-(triphenylmethylamino)-4-oxobutyric acid is missing, the molecular rotor lacks a core rotating unit, resulting in reduced heating efficiency and weakened performance across the board. A comparison of Example 1 and Comparative Example 4 shows that without microwave treatment, there is almost no heating effect, moisture evaporates very slowly, early strength cannot be formed, and long-term performance deteriorates comprehensively. A comparison of Example 1 and Comparative Example 5 shows that without carbon black, the microwave absorption matrix is ​​missing, the heating temperature is insufficient, the moisture retention rate is high, and the early strength development is slow. A comparison of Example 1 and Comparative Example 6 shows that although the molecular rotor heats up slightly faster with excessive heat, the temperature distribution is uneven, posing a risk of local overheating, and the long-term fatigue life is slightly reduced. A comparison of Example 1 and Comparative Example 7 shows that although the traditional high-cement method has acceptable early strength, the material is brittle, has a low fatigue life, and slow moisture evaporation, resulting in overall road performance far inferior to that of the present invention.

[0105] In summary, this invention constructs a macro-composite heating system that synergistically combines "molecular frictional heat generation" and "dielectric loss heat generation" by compounding molecular rotor powder with carbon black as an early-strength agent and implementing precise microwave treatment after paving. This system enables rapid and uniform volumetric heating within the mixture, precisely controlling the core temperature within a safe and efficient window of 60-80℃. On the one hand, this drastically accelerates the demulsification of emulsified asphalt, moisture migration and evaporation, and cement hydration, thereby significantly reducing the curing time required to achieve open traffic strength from the traditional 3-7 days to within 6-24 hours. On the other hand, the uniform thermal field avoids asphalt aging caused by localized overheating, while the lower carbon black and cement content ensures the excellent flexibility, water stability, and fatigue resistance of the recycled layer, achieving a balance between high efficiency, early strength, and long-term durability.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microwave-responsive molecular rotor mixture for cold recycling of emulsified asphalt, characterized in that, The raw materials include component A and component B. Component A includes waste asphalt pavement material RAP, carbon black and molecular rotor powder, and component B includes emulsified asphalt. The raw materials are mixed and then treated with microwave irradiation. The molecular rotor powder is obtained by covalently linking 4-(triphenylmethylamino)-4-oxobutyric acid to an aminated silica carrier.

2. The microwave-responsive molecular rotor mixture as described in claim 1, characterized in that, By weight, component A comprises 90-120 parts of waste asphalt pavement material RAP, 0.5-2 parts of carbon black, and 1-3 parts of molecular rotor powder, and component B comprises 40-60 parts of emulsified asphalt.

3. The microwave-responsive molecular rotor mixture as described in claim 2, characterized in that, By weight, component A further includes 1 to 3 parts of cement, and component B further includes 10 to 20 parts of water.

4. The microwave-responsive molecular rotor mixture as described in claim 1, characterized in that, The power of the irradiation treatment is 2~5kW / m 2 The time is 5 to 15 minutes.

5. The microwave-responsive molecular rotor mixture as described in claim 1, characterized in that, The preparation method of the molecular rotor powder includes: S1, dispersing nano-silica in a first organic solvent, adding 3-aminopropyltriethoxysilane, carrying out a silanization reaction under an inert atmosphere, centrifuging, washing, and obtaining an aminated silica carrier. S2. The 4-(triphenylmethylamino)-4-oxobutyric acid and condensing agent are dispersed in a second organic solvent, activated, and then the aminated silica carrier is added. The mixture is stirred and reacted, and after centrifugation, washing, and drying, the molecular rotor powder is obtained.

6. The microwave-responsive molecular rotor mixture as described in claim 5, characterized in that, The mass ratio of the aminated silica carrier to 4-(triphenylmethylamino)-4-oxobutyric acid is (5~7):

1.

7. The microwave-responsive molecular rotor mixture as described in claim 5, characterized in that, The silanization reaction includes: reflux reaction at 100℃~120℃ for 4~8 hours.

8. The microwave-responsive molecular rotor mixture as described in claim 5, characterized in that, The stirring reaction in step S2 is carried out at a speed of 10-20 rpm for 16-25 hours.

9. The microwave-responsive molecular rotor mixture as described in claim 5, characterized in that, The first organic solvent includes toluene, and the second organic solvent includes an N,N-dimethylformamide solution.

10. A construction method using the microwave-responsive molecular rotor mixture as described in any one of claims 1 to 9, characterized in that, The process includes the following steps: S1. Dry-mix component A, then add component B and wet-mix to obtain a mixture; S2. After spreading and initially compacting the mixture, microwave irradiation is applied, followed by secondary compaction, cooling, and curing.

Images