A method for evaluating the diffusion behavior of regeneration agent in mixing and regenerating old asphalt based on non-equilibrium molecular dynamics simulation

Abstract

The present invention provides a method for evaluating the diffusion behavior of a regeneration agent when mixing and regenerating old asphalt based on non-equilibrium molecular dynamics simulation. Through stretching dynamics simulation, the dynamic process before the system reaches equilibrium during mixing and a period of time thereafter is more realistically simulated, and the non-equilibrium dynamic characteristics of the system are obtained. The gyration radius and diffusion coefficient of the regeneration agent calculated based on the obtained non-equilibrium dynamics trajectory can more objectively evaluate the diffusion behavior of the regeneration agent. The advantage of the present invention is that the mixing process is simulated more realistically by using non-equilibrium dynamics. In addition, after the mechanical mixing is completed, the mixed system is still in a non-equilibrium state, and the further diffusion of the regeneration agent is also described by NVT ensemble dynamics simulation. Therefore, these two steps of non-equilibrium dynamics simulation better achieve the reproduction of the fusion process of old asphalt and regeneration agent at the nanoscale on a macro scale, and can provide a more accurate and realistic characterization of the diffusion properties and behavior of the regeneration agent.

Description

Technical Field

[0001] The invention relates to the technical field of asphalt regeneration, and in particular to a method for evaluating the diffusion behavior of a regeneration agent when mixing and regenerating old asphalt based on non-equilibrium molecular dynamics simulation. Background Art

[0002] Under the current background of "dual carbon" goals and increasingly stringent environmental and resource protection regulations, the recycling and reuse of waste asphalt pavement materials has become a research hotspot for many years. Usually, in order to make up for the significantly deteriorated rheological properties of the binder in waste asphalt materials, when its dosage is not high (such as less than 20%), it can be achieved by adding low-grade matrix asphalt; if the recovery rate and dosage of old materials are to be further improved, the assistance of regeneration agents is usually required. Regeneration agents can be divided into two categories according to their sources: petroleum-based and bio-oil-based. The light components account for a large proportion in the molecular composition, which ensures that the regeneration agents have sufficient molecular mobility to diffuse into the old asphalt and replenish the oil lost in the asphalt during the aging process. Although some researchers have distinguished regeneration agents from ordinary softeners based on whether the regeneration agent molecules can effectively interact with asphaltene aggregates to depolymerize and disperse asphaltene, sufficient molecular mobility or diffusivity is essential as the primary prerequisite for regeneration.

[0003] In the field of intermolecular interactions and their visualization, molecular dynamics simulation has become an increasingly important technical means. Existing relevant literature basically uses the equilibrium molecular dynamics simulation method to study the diffusion behavior of regeneration agent molecules in old asphalt. The method is to randomly put the asphalt molecule model and the regeneration agent molecules into the simulation box at the beginning of the model establishment, and after a series of equilibrium treatments (energy minimization, annealing, NPT ensemble dynamics, etc.), obtain the equilibrium system at normal temperature (or mixing temperature) and normal pressure, analyze the mean square displacement of the regeneration agent molecules (Formula 1), and calculate the diffusion coefficient (i.e. 1 / 6 of the slope of the mean square displacement curve) according to the Einstein relationship.

[0004] (Formula 1)

[0005] In formula 1, MSD is the mean square displacement, N is the number of particles in the system, and represent the position vector of the i-th particle at time 0 and time t respectively.

[0006] However, the main limitation of the prior art method is that it uses equilibrium molecular dynamics, that is, it explores the dynamic behavior of the regeneration agent in the system after the mixing process of the regeneration agent and the old asphalt is completed. It should be emphasized that after reaching the equilibrium state, the molecules in the system only vibrate near their equilibrium position, and the main contribution to the numerical value of the mean square displacement of the regeneration agent molecules comes from this vibration. Therefore, the diffusion coefficient calculated based on the mean square displacement is difficult to reflect the true diffusion behavior of the regeneration agent molecules during the regeneration process. Moreover, the implicit premise of the prior art is that the regeneration agent will be randomly distributed in the system after mixing, and it is not possible to more realistically examine the diffusion of the regeneration agent in the old asphalt during the mixing process. The mixing process and the period before the system reaches equilibrium should be the most appropriate and critical stage for evaluating the diffusion properties of the regeneration agent, but the prior art method does not examine this stage.

[0007] The existing technology studies the diffusion of regeneration agent molecules in aged asphalt based on equilibrium kinetic simulation. A careful analysis of the trajectory files shows that in the equilibrium system, each molecule is vibrating near its equilibrium position and no substantial diffusion occurs. Therefore, the calculated diffusion coefficient cannot characterize the actual diffusion behavior of the regeneration agent molecules during the mixing process, and is therefore difficult to use to accurately compare the diffusion characteristics of different regeneration agents.

[0008] The diffusion rate of the regeneration agent in aged asphalt is a direct factor affecting its regeneration performance. From a thermodynamic point of view, the diffusion of the regeneration agent in the asphalt during the regeneration process is a non-equilibrium thermodynamic process. Therefore, how to reproduce this non-equilibrium process at the micro-nano level to objectively and accurately examine the diffusion characteristics of the regeneration agent has become the current research focus and difficulty. Summary of the invention

[0009] The purpose of the present invention is to provide a method for evaluating the diffusion behavior of a regeneration agent in a mixing process with old asphalt based on non-equilibrium molecular dynamics simulation, so as to solve the technical problem that the current research on the diffusion behavior of the regeneration agent in asphalt is not objective and accurate enough.

[0010] To achieve the above object, the present invention provides a method for evaluating the diffusion behavior of a regeneration agent in a mixing process with old asphalt based on non-equilibrium molecular dynamics simulation, and the specific steps are as follows:

[0011] (1) Placing the balanced aged asphalt molecular system and the regeneration agent molecular system in a vacuum container to construct a mixing model;

[0012] (2) The pull code in Gromacs was used to realize the stretching dynamics, so that the centers of mass of the two systems overlapped. The radius of gyration of the regenerant was calculated for the simulated trajectory, and the diffusion behavior of the regenerant clusters during the mixing process was investigated;

[0013] (3) Perform NVT ensemble dynamics simulation on the system after mixing, calculate the radius of gyration and diffusion coefficient of the regeneration agent based on the obtained trajectory, and investigate the diffusion behavior of the regeneration agent molecules in the aged asphalt before the system reaches equilibrium after mixing;

[0014] Preferably, in step (1), in the initial state of the mixing model, the distance between the aged asphalt molecular system and the regeneration agent molecular system after equilibrium is selected in accordance with the van der Waals cutoff radius, and the minimum distance between the atoms of the two systems is required to be greater than the van der Waals cutoff radius to avoid significant interaction.

[0015] Preferably, in step (1), the constructed mixing model is placed in a vacuum container, and the distance between the model boundary and the container boundary is required to be no less than 2 nm.

[0016] Preferably, in step (1), the method for obtaining the molecular equilibrium system of aged asphalt is as follows: the equilibrium system is obtained through a series of processes including energy minimization, annealing, and NPT ensemble dynamics, and the equilibrium conditions are a mixing temperature of 180°C and a normal pressure of 0.1 MPa.

[0017] Further preferred, the specific method is as follows: randomly mix the model molecules of each component of asphalt in proportion to establish an initial system; select the steepest descent method or the conjugate gradient method to minimize the energy of the system and eliminate the unreasonable spatial occupancy of the molecules; use a sawtooth temperature history between 200K and 800K to simulate annealing the system to enable the system to overcome local energy barriers and further effectively optimize the conformation; finally, perform conventional NPT ensemble dynamics simulation to obtain the equilibrium asphalt system, and the equilibrium conditions are mixing temperature (such as 180°C) and normal pressure (0.1MPa).

[0018] Preferably, in step (1), the method for obtaining the molecular equilibrium system of the regenerant is as follows: obtaining the equilibrium system through a series of processes including energy minimization, NPT ensemble dynamics, and NVT ensemble dynamics, wherein the equilibrium conditions are room temperature 25° C. and normal pressure 0.1 MPa.

[0019] Further preferred, the specific method is as follows: establish an initial system of regeneration agent molecules; select the steepest descent method or the conjugate gradient method to minimize the energy of the system and eliminate unreasonable spatial occupancy of molecules; perform conventional NPT ensemble dynamics simulation to obtain the balanced regeneration agent system, and the equilibrium conditions are room temperature (25°C) and normal pressure (0.1MPa). It should be noted that the size of the balanced regeneration agent system should be less than 1 / 3 of the size of the asphalt equilibrium system to avoid individual regeneration agent molecules flying out of the system during the mixing process, causing distortion in the calculation of subsequent parameters. Because the system is small, the simulated annealing step can be omitted during the equilibrium process. In addition, after the NPT dynamic equilibrium, the regeneration agent system is placed in a vacuum container for NVT ensemble dynamics simulation to reach a new equilibrium. The purpose of this step is to relax the configuration of the regeneration agent cluster to a spherical shape under the influence of surface tension, so as to avoid improper interference of configuration changes on the calculation results of the radius of gyration during subsequent tensile dynamics simulations.

[0020] Preferably, in step (2), stretching dynamics is used to make the aged asphalt molecular system and the regeneration agent molecular system approach and mix at a speed of 0.1 nm / ps. When the stretching is completed, the centers of mass of the two systems overlap.

[0021] Preferably, the specific method of step (2) is: using the pull code in Gromacs to realize the stretching dynamics under the NVT ensemble, so that the asphalt and the regeneration agent system are close to each other and merged along the center of mass line at a constant rate (such as 0.1nm / ps). The main parameters set for the simulation are: pull-coord1-type=constraint, pull-coord1-geometry=distance, and the initial center of mass distance is assigned to the parameter pull-coord1-init. During the simulation, the asphalt system is temperature-controlled at the mixing temperature, and the regeneration agent is not temperature-controlled (to avoid evaporation at high temperatures). For the trajectory obtained by the simulation, apply the gmx gyrate command and select the group where the regeneration agent is located to calculate the gyration radius. This parameter describes the change in the overall space occupied by the regeneration agent during the mixing process (expansion, contraction), which is used to examine the diffusion behavior of the regeneration agent clusters during the mechanical mixing process (under external force disturbance);

[0022] Preferably, in step (3), the starting condition of the NVT ensemble dynamics simulation is the final dynamic state of the stretching stage, and the checkpoint file generated in step (2) is required to generate the running file required for step (3) to ensure the accurate continuation of the dynamic state.

[0023] Preferably, the specific method of step (3) is: perform conventional NVT ensemble dynamics simulation on the system after the stretching dynamics is completed at the mixing temperature, and the parameter setting is similar to the previous step, only the pull code part needs to be removed, and the temperature control setting is completed because the mechanical mixing process has been completed, so the temperature of the entire model is controlled here, and the temperature is set to the mixing temperature; based on the obtained trajectory, the gyration radius (gmx gyrate command) and diffusion coefficient (gmx msd command) of the regeneration agent are calculated, and the diffusion behavior of the regeneration agent molecules in the aged asphalt before the system reaches thermodynamic equilibrium after mixing is examined.

[0024] The present invention has the following beneficial effects:

[0025] In order to more accurately evaluate the diffusion behavior of the regeneration agent when mixing and regenerating old asphalt, the present invention proposes a simulation method based on non-equilibrium tensile dynamics. Compared with the existing equilibrium dynamics simulation technology, the present invention simulates the mixing process more realistically through tensile dynamics simulation, and reproduces the dynamic characteristics of the system before it reaches equilibrium within a period of time after the mixing is completed, that is, the non-equilibrium dynamic characteristics. The calculation of the gyration radius and diffusion coefficient of the obtained non-equilibrium dynamic trajectory can more objectively evaluate the diffusion behavior of the regeneration agent in the mixing and regeneration process.

[0026] The advantage of the present invention is that it utilizes non-equilibrium dynamics to take into account the mixing process that is not considered in the prior art, that is, through stretching dynamics, the center of mass of the asphalt and the regeneration agent system is pulled to overlap to achieve mixing of the two, which simulates the mixing process more realistically. Aged asphalt is in equilibrium at common mixing temperatures (such as 180°C) and normal pressure. Due to its low boiling point and high volatility, the regeneration agent is usually mixed with the heated old asphalt at room temperature. Therefore, the regeneration agent system reaches a dynamic equilibrium state at room temperature and pressure. After mixing, the mixed system is still in a non-equilibrium state, and the further diffusion of the regeneration agent is also described by the NVT ensemble dynamics simulation after the mixing is completed. Therefore, these two steps of non-equilibrium dynamics simulation have better achieved the reproduction of the macroscopic fusion process of the old asphalt and the regeneration agent at the nanoscale. Compared with the existing equilibrium dynamics simulation technology, it can provide a more accurate and realistic characterization of the diffusion properties of the regeneration agent.

[0027] The present invention has been proved through simulation tests that it can reasonably describe the real diffusion behavior of the regeneration agent molecules in the process of regenerating old asphalt. The asphalt model used in the simulation is the famous 12-component model proposed by Li and Greenfield, and oxygen atoms are introduced on the benzyl carbon and thiophene sulfur to form carbonyl and sulfoxide groups to characterize the chemical effects of aging on asphalt molecules. The regeneration agent molecule used is the tetradecanoic acid amide reported previously. From the analysis of the principles behind the simulation process and the simulation results, it can be seen that the proposed non-equilibrium molecular dynamics method can more objectively and accurately describe the diffusion behavior of the regeneration agent when mixing and regenerating old asphalt. This method can provide strong support for the comparative selection and research and development of regeneration agents.

[0028] In summary, the present invention utilizes non-equilibrium molecular dynamics simulation to realize the mixing process of the regeneration agent and asphalt at the nanoscale, thereby examining the diffusion characteristics of the regeneration agent more objectively and accurately.

[0029] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 is a flow chart of the non-equilibrium molecular dynamics simulation method of the present invention;

[0032] Figure 2 It is the radius of gyration of the regeneration agent molecules during and after mixing;

[0033] Figure 3 To compare the relative changes in the gyration radius of the regeneration agent molecules obtained in the present invention and the prior art;

[0034] Figure 4 The distribution change of the rejuvenating agent molecules obtained by simulating the prior art in the old asphalt;

[0035] Figure 5 To compare the molecular mean square displacement of the regeneration agent obtained by the present invention and the prior art. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0037] In order to more realistically describe the diffusion behavior of the rejuvenating agent in the process of mixing with aged asphalt, the following simulation method based on non-equilibrium molecular dynamics is proposed (e.g. Figure 1 shown):

[0038] 1. Establish an aged asphalt molecular system, including 648 molecules and 49,266 atoms in total. A balanced cubic system (with a side length of 8 nm) is obtained through a series of processes including energy minimization, annealing, and NPT ensemble dynamics. The equilibrium conditions are a mixing temperature of 180°C and a normal pressure of 0.1 MPa. During the simulation, the temperature coupling method is set to the velocity rescale algorithm, the pressure coupling method is the Berendsen algorithm, and the cutoff radius for van der Waals force and real space Coulomb force calculation is set to 2.5 nm.

[0039] 2. Establish a tetradecanoic acid amide regeneration agent molecular system, including 30 molecules and a total of 1260 atoms. Obtain the equilibrium cubic system (side length is 2.5nm) through energy minimization and NPT ensemble dynamics, and the equilibrium conditions are normal temperature (25℃) and normal pressure (0.1MPa). Considering that in the next step of tensile dynamics simulation, the regeneration agent clusters will gradually transition from cubic to spherical due to surface tension in a vacuum (relatively speaking, the asphalt system does not change significantly), the equilibrium regeneration agent system needs to be placed in a vacuum container for NVT ensemble dynamics simulation to relax the regeneration agent clusters to a spherical system in advance.

[0040] 3. Combine the aged asphalt and the regeneration agent system and place them inside a larger vacuum container. The regeneration agent is outside the asphalt system. The center-of-mass distance between the two is set to 8nm. At this time, the closest distance between the atoms of the two parts is greater than the van der Waals cutoff radius. The mixing model constructed is as follows Figure 1 As shown in (a).

[0041] 4. Use the pull code in Gromacs to implement stretching dynamics. Specifically, the regeneration agent and asphalt are brought close to each other and mixed at a speed of 0.1 nm / ps. The simulation time is determined by the initial center of mass distance between the two parts (the initial distance of 8nm corresponds to a simulation time of 80ps). In this process, the asphalt temperature is controlled at the mixing temperature of 180℃, and the regeneration agent is not temperature controlled. For the simulated trajectory, the command gmx gyrate is used to calculate the gyration radius of the regeneration agent. Combined with the simulation trajectory, the diffusion behavior of the regeneration agent cluster during the mixing process (external disturbance) is investigated, such as Figure 1 As shown in (bc).

[0042] 5. Perform NVT ensemble dynamics simulation on the system after the tensile dynamics is completed, calculate the gyration radius (gmx gyrate) and diffusion coefficient (gmx msd) of the regeneration agent based on the obtained trajectory, and examine the non-equilibrium thermodynamic diffusion behavior of the regeneration agent molecules in the aged asphalt after the mechanical mixing is completed and before the system reaches equilibrium, such as Figure 1 As shown in (de).

[0043] From the above steps, it can be seen that compared with the existing equilibrium kinetics simulation technology, the proposed method can more realistically reproduce and examine the non-equilibrium kinetic characteristics of the system during the mechanical mixing process and a period of time thereafter through stretching kinetics simulation. The kinetic parameters calculated at this stage can provide a more accurate characterization of the diffusion behavior of the regeneration agent.

[0044] In order to further illustrate the advantages of the proposed method in describing the diffusion behavior of the regenerant, the radius of gyration of the regenerant molecules during the entire simulation process and their mean square displacement after the mixing are calculated and compared with the existing results based on equilibrium kinetic simulation, such as Figures 2 to 5 shown.

[0045] Figure 2 In the process, after the regeneration agent contacts the asphalt, the regeneration agent enters the asphalt ( Figure 1 bc), and then during the mixing process, due to the interaction with asphalt molecules, the gyration radius of the regenerant increases rapidly, and the regenerant clusters expand inside the asphalt, occupying more space, indicating that the regenerant has significant diffusion behavior during the mixing of the two-part system. After the mixing is completed, the gyration radius of the regenerant is continued to be investigated. During the 6ns simulation process, the space occupied by the regenerant clusters inside the asphalt continues to increase, showing significant diffusion behavior, and the gyration radius still does not show a balance trend at the simulation cutoff time, which means that the diffusion will continue. In specific applications, the slope of the gyration radius curve can be used as one of the parameters to characterize the diffusion rate.

[0046] In order to further highlight the characteristics and advantages of the proposed method, Figure 2 The gyration radius of the regenerator after the intermediate mixing is normalized based on the initial value and compared with the typical normalized gyration radius obtained based on the existing equilibrium molecular dynamics technology (the same molecular system is used in the simulation calculation). The results are as follows: Figure 3 As shown in Figure 2, the variation range of the gyration radius of the regenerant given by the existing method is very small, as shown in Figure 2. Figure 4 As shown in the figure, based on the prior art, in the system after equilibrium, the regenerant molecules only move in a very small spatial range near their respective equilibrium positions, and do not diffuse in the true sense, because the model state at this time corresponds to the situation after the diffusion is completely completed, and cannot simulate the diffusion behavior of the regenerant in the objective regeneration process. On the contrary, using the method proposed by the present invention, it can be seen that within the 6ns simulation period, the radius of gyration of the regenerant continues to increase relative to the initial value, and the space occupied continues to increase, as shown in FIG. Figure 1 As shown in (ce), it truly reflects the diffusion behavior of the regeneration agent during the mixing regeneration process.

[0047] To further support the above conclusions, based on the calculation results of the method proposed in the present invention, the mean square displacement history of the regeneration agent after the mixing is completed is determined and compared with the results obtained in the prior art. The results are as follows: Figure 5 As shown. It can be seen that the mean square displacement value given by the prior art is significantly smaller, and the corresponding diffusion coefficient is 0.26×10 -6 cm 2 / s, and Figure 4 The distribution changes of the regenerant in the system are consistent, that is, the regenerant has not substantially diffused, and the mean square displacement mainly comes from the contribution of the vibration of the molecules near their equilibrium position. In contrast, the mean square displacement of the regenerant calculated based on the method proposed in the present invention is significantly larger, and the corresponding diffusion coefficient is 1.04×10 -6 cm 2 / s, which is 5 times the result obtained by the existing technology. It is consistent with the conclusion based on the spatial distribution of regenerant molecules at different times and the history of gyration radius, and reasonably reflects the real diffusion behavior of the regenerant during the mixing process.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for evaluating the diffusion behavior of a regeneration agent when mixing and regenerating old asphalt based on non-equilibrium molecular dynamics simulation, characterized in that: The specific steps are as follows: (1) Placing the balanced aged asphalt molecular system and the rejuvenating agent molecular system in a vacuum container to construct a mixing model; The method for obtaining the molecular equilibrium system of aged asphalt is as follows: obtaining the equilibrium system through a series of processes including energy minimization, annealing, and NPT ensemble dynamics, wherein the equilibrium conditions are a mixing temperature of 180° C. and a normal pressure of 0.1 MPa; The model molecules of each component of asphalt are randomly mixed in proportion to establish an initial system; the steepest descent method or conjugate gradient method is selected to minimize the energy of the system and eliminate the unreasonable spatial occupation of molecules; the system is simulated annealed between 200K and 800K using a sawtooth temperature history to enable the system to overcome local energy barriers and further effectively optimize the conformation; finally, conventional NPT ensemble dynamics simulation is performed to obtain the equilibrium asphalt system, and the equilibrium conditions are a mixing temperature of 180°C and a normal pressure of 0.1MPa; The method for obtaining the molecular equilibrium system of the regenerant is as follows: obtaining the equilibrium system through a series of processes including energy minimization, NPT ensemble dynamics, and NVT ensemble dynamics, wherein the equilibrium conditions are normal temperature 25° C. and normal pressure 0.1 MPa; Establish the initial system of regeneration agent molecules; select the steepest descent method or conjugate gradient method to minimize the energy of the system and eliminate unreasonable spatial occupancy of molecules; Conduct conventional NPT ensemble dynamics simulation to obtain the regeneration agent system after equilibrium, and the equilibrium conditions are normal temperature and pressure; after the NPT dynamics equilibrium, the regeneration agent system is placed in a vacuum container for NVT ensemble dynamics simulation to reach a new equilibrium; (2) The pull code in Gromacs was used to realize the stretching dynamics, so that the center of mass of the two parts of the system overlapped. The radius of gyration of the regenerant was calculated for the simulated trajectory, and the diffusion behavior of the regenerant clusters during the mixing process was investigated. The stretching dynamics is used to make the aged asphalt molecular system and the rejuvenating agent molecular system approach and mix at a speed of 0.1nm / ps. At the end of the stretching, the center of mass of the two systems overlap. The pull code in Gromacs is used to realize the tensile dynamics under the NVT ensemble, so that the asphalt and regeneration agent system are close to each other and merged at a constant rate along the center of mass line. The main parameters set for the simulation are: pull-coord1-type = constraint, pull-coord1-geometry = distance, and the initial center of mass distance is assigned to the parameter pull-coord1-init; during the simulation, the temperature of the asphalt system is controlled at the mixing temperature, and the temperature of the regeneration agent is not controlled; for the trajectory obtained by the simulation, the gmx gyrate command is applied and the group where the regeneration agent is located is selected to calculate the gyration radius. This parameter describes the change of the overall space occupied by the regeneration agent during the mixing process, and is used to investigate the diffusion behavior of the regeneration agent clusters during the mechanical mixing process; (3) The NVT ensemble dynamics simulation of the system after mixing was performed. The radius of gyration and diffusion coefficient of the regeneration agent were calculated based on the obtained trajectory, and the diffusion behavior of the regeneration agent molecules in the aged asphalt before the system equilibrium after mixing was investigated.

2. The method according to claim 1, characterized in that In step (1), the constructed mixing model is placed in a vacuum container, and the model boundary is required to be no less than 2 nm away from the container boundary.

3. The method according to claim 1, characterized in that In step (3), the starting condition of the NVT ensemble dynamics simulation is the final dynamic state of the stretching stage. The checkpoint file generated in step (2) is required to generate the running file required for step (3) to ensure the accurate continuation of the dynamic state.

4. The method according to claim 1, characterized in that The specific method of step (3) is: after the stretching dynamics is completed, the system is subjected to conventional NVT ensemble dynamics simulation at the mixing temperature. The parameter settings are similar to the previous step, and only the pull code part needs to be removed. In the temperature control setting, since the mechanical mixing process has been completed, the temperature of the entire model is controlled here, and the temperature is set to the mixing temperature; based on the obtained trajectory, the gyration radius and diffusion coefficient of the regeneration agent are calculated, and the diffusion behavior of the regeneration agent molecules in the aged asphalt before the system reaches thermodynamic equilibrium after mixing is examined.

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