阅读说明：本技术 就地热再生中新旧沥青及再生剂混溶特性的评价方法 (Method for evaluating miscibility characteristics of new and old asphalt and regenerant in-situ thermal regeneration ) 是由 张伟光 范剑伟 朱雅婧 张一鸣 于 2021-06-03 设计创作，主要内容包括：本发明涉及就地热再生中新旧沥青及再生剂混溶特性的评价方法,属于道路工程领域。构建就地热再生中新沥青分子、旧沥青分子、再生剂混溶的三层分子动力学模型；绘制三层分子动力学模型中新沥青分子、旧沥青分子、再生剂分子相对浓度曲线；计算新沥青分子、旧沥青分子、再生剂分子的相对浓度曲线计算得到混溶后的新沥青分布区、旧沥青分布区、再生剂分布区；计算得到再生剂作用率、旧沥青激活率、新旧沥青混溶区比例；评价相同种类不同掺量的再生剂或不同种类相同掺量的再生剂与旧沥青激活率,该激活率越大指标越优；评价相同种类不同掺量的再生剂或不同种类相同掺量的再生剂与新旧沥青的混溶区比例,该激活率越大指标越优。(The invention relates to a method for evaluating the mixing and dissolving characteristics of new and old asphalt and a regenerant in-situ thermal regeneration, belonging to the field of road engineering. Constructing a three-layer molecular dynamics model of mixing and dissolving of new asphalt molecules, old asphalt molecules and a regenerant in-situ thermal regeneration; drawing relative concentration curves of new asphalt molecules, old asphalt molecules and regenerant molecules in the three-layer molecular dynamics model; calculating relative concentration curves of the new asphalt molecules, the old asphalt molecules and the regenerant molecules to obtain a new asphalt distribution area, an old asphalt distribution area and a regenerant distribution area after mixing and dissolving; calculating to obtain the action rate of the regenerant, the activation rate of the old asphalt and the proportion of the new asphalt and the old asphalt miscible region; evaluating the activation rates of the regenerants with the same type and different mixing amounts or the regenerants with the same type and different mixing amounts and the old asphalt, wherein the larger the activation rate is, the better the index is; the proportion of the regenerants with the same kind and different mixing amounts or the regenerants with the same kind and different mixing amounts to the miscible regions of the new asphalt and the old asphalt is evaluated, and the higher the activation rate is, the better the index is.)

1. The method for evaluating the miscibility characteristics of the new asphalt and the old asphalt and the regenerant in-situ hot recycling is characterized by comprising the following steps of:

s1: constructing a three-layer molecular dynamics model of mixing and dissolving of new asphalt molecules, old asphalt molecules and a regenerant in-situ thermal regeneration; in the three-layer molecular dynamics model, the regenerants are selected to be the same type and different doping amounts or different types and the same doping amounts;

s2: performing molecular dynamics simulation for the molecular dynamics simulation established in step S1;

s3: calculating the relative concentration of each molecular in the three-layer molecular dynamics model at each cross section in the model, and drawing a relative concentration curve of new asphalt molecules, old asphalt molecules and regenerant molecules in the three-layer molecular dynamics model;

s4: smoothing the relative concentration curves of the new asphalt molecules, the old asphalt molecules and the regenerant molecules in the step S3;

s5: calculating relative concentration curves of the new asphalt molecules, the old asphalt molecules and the regenerant molecules to obtain a new asphalt distribution area, an old asphalt distribution area and a regenerant distribution area after mixing and dissolving;

s6: calculating the acting rate of the regenerant, the activation rate of the old asphalt and the proportion of the mixing and dissolving area of the new asphalt and the old asphalt through the new asphalt distribution area, the old asphalt distribution area and the regenerant distribution area;

evaluating the activation rates of the regenerants with the same type and different mixing amounts or the regenerants with the same type and different mixing amounts and the old asphalt, wherein the larger the activation rate is, the better the index is;

the proportion of the regenerants with the same kind and different mixing amounts or the regenerants with the same kind and different mixing amounts to the miscible regions of the new asphalt and the old asphalt is evaluated, and the higher the activation rate is, the better the index is.

2. The method for evaluating the miscibility characteristics of new and old asphalt and recycling agent in hot-in-place recycling according to claim 1, wherein: the three-layer molecular dynamics model established in the step S1 is from the left horizontal axis to the right horizontal axis_leftTo l_right；

New asphalt molecules, a regenerant and old asphalt molecules are sequentially arranged in the horizontal axis from left to right; carrying out system geometric balance after modeling;

the new asphalt and the old asphalt and the regenerant are both composed of various molecules; the new asphalt molecules in the three-layer molecular dynamics model comprise 1 st to i th asphalt molecules_mSeed, old asphalt molecules include_m+1To the ith_nThe regenerant molecules include the ith_n+1To the ith_pAnd (4) seed preparation.

3. The method for evaluating the miscibility characteristics of new and old asphalt and recycling agent in hot-in-place recycling according to claim 1, wherein: in the step S2:

carrying out molecular dynamics simulation by using an NPT system aiming at the three-layer model established in S1, and determining the parameters of the pressure intensity and the force field in the simulation by referring to the parameters of the simulated actual in-situ heat regeneration engineering;

based on a temperature reduction curve of the paved asphalt mixture obtained by actual measurement or numerical simulation, the system temperature in the molecular dynamics simulation is determined through the following conditions:

if the actually measured or simulated temperature reduction curve time range is 0-t₁Then the total time of the NPT ensemble in the molecular dynamics simulation is 0-t₂(ii) a Will be 0-t₂Corresponds to 0-t₁The cooling process in the cooling curve divides the cooling curve and the NPT process into N sections (N is more than or equal to 20) according to time average, and the temperature corresponding to the time midpoint on each section of the cooling curve is taken as the temperature set in each section of NPT.

4. The method for evaluating the miscibility characteristics of new and old asphalt and regenerants in hot-in-place recycling according to claim 1 or 2, wherein: step S3 is specifically as follows: after the molecular dynamics simulation is finished, based on the output centroid position of each atom on each molecule; dividing the three-layer molecular dynamics model into a plurality of cross sections, and calculating the relative concentration of new asphalt molecules, old asphalt molecules and regenerant molecules in each cross section of the three-layer molecular dynamics model; to the abscissa in the model from_left-l_rightIn which l_leftFinger model left boundary position,/_rightThe right boundary position of the finger model is uniformly divided into the 1 st to Mth (M is more than or equal to 100) areas from left to right along the abscissa direction_pIn each cross section, i (1. ltoreq. i)_p) Relative concentration of the analogous molecule a (i, M)_p) The calculation method of (2) is as follows:

wherein a (x) is M_pThe total mass of the atoms belonging to the i-th class of molecules in the cross-section, b (x) being the centroid at M_pTotal mass of all atoms in each cross-section.

5. The method for evaluating the miscibility characteristics of new and old asphalt and recycling agent in hot-in-place recycling according to claim 4, wherein: m th_pRelative concentration of new bitumen molecules A (M) in one cross section_p) Relative concentration of old asphalt molecules B (M)_p) Relative concentration of regenerant molecules C (M)_p) The calculation method is as follows:

and calculating the relative concentrations of the new asphalt molecules, the old asphalt molecules and the regenerant molecules of the 1 st to Mth cross sections, drawing the relative concentrations in a plane rectangular coordinate system to obtain a relative concentration curve of the new asphalt molecules, the old asphalt molecules and the regenerant in the model, and smoothing the curve by applying a Gaussian filtering method to obtain a smoothed relative concentration curve of the new asphalt molecules, the old asphalt molecules and the regenerant.

6. The method for evaluating the miscibility characteristics of new and old asphalt and regenerants in hot-in-place recycling according to claim 1 or 5, wherein: step S5 is specifically as follows:

based on the smoothed relative concentration curve of the new asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the new asphalt after mixing, i.e. the abscissa is l_leftTo l₃A moiety of (a);

based on the smoothed relative concentration curve of the old asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the mixed old asphalt, i.e. the abscissa is l₂To l_rightA moiety of (a);

based on the smoothed relative concentration curve of the new asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the mixed regenerant, i.e. the abscissa is l₁To l₄A moiety of (a); l₂To l₃The part in between contains new and old asphalt molecules, which are defined as new and old asphalt miscible regions. Part of the reason for selecting more than 1% is to avoid the influence of the centroid position of atoms on individual molecules without statistical significance on the analysis result;

wherein l_leftAs the left boundary position coordinates of the model, l_rightAs the right boundary position coordinates of the model, l_midIs the median position of the modelSet coordinate,/₁And l₄The relative concentration curve of the regenerant in the model is 1 percent, and the corresponding left and right position coordinates are obtained; l₂And l₃And the position coordinates are respectively corresponding to the old asphalt and the new asphalt in the model when the relative concentration curve is 1%.

7. The method for evaluating the miscibility characteristics of new and old asphalt and recycling agent in hot-in-place recycling according to claim 1, wherein: step S6 is specifically as follows: the regenerant action rate Z is the mass ratio of the regenerant diffused into the old asphalt to the total regenerant, and the calculation method is as follows:

in the formula, c is the total mass of atoms belonging to the regenerant molecules in the regenerant distribution region with the centroid after mixing and dissolving, and d is the total mass of all atoms belonging to the regenerant molecules in the three-layer model.

The old asphalt activation rate J is the proportion of the old asphalt distribution area in which the regenerant molecules are diffused after mixing and dissolving to the old asphalt distribution area after mixing and dissolving, and the calculation method is as follows:

the ratio H of the new asphalt miscible region to the old asphalt miscible region refers to the ratio of the length of the new asphalt miscible region to the total length of the three-layer model, and the calculation method is as follows:

Technical Field

The invention relates to a method for evaluating the mixing and dissolving characteristics of new and old asphalt and a regenerant in-situ thermal regeneration, belonging to the field of road engineering.

Background

According to the regulations of technical Specification for regenerating asphalt pavement for roads (JTG T5521-2019) in the process of in-situ thermal regeneration, the milled old pavement asphalt mixture is heated to the temperature, a regenerant is added and mixed for 5-10 seconds, new asphalt and new aggregate are added and mixed, then the mixture is paved in situ, and the regenerated asphalt mixture is gradually cooled to the room temperature. In the existing research method, in order to find out the mixing degree of the new and old asphalt, indoor samples or field tests are required to be carried out, in molecular dynamics analysis, the mixing temperature is generally assumed to be a fixed value, the change of the mixing temperature of the new and old asphalt in the asphalt mixture in the actual in-situ thermal regeneration is ignored, and the mixing index of the new and old asphalt based on molecular dynamics simulation is lacked. Based on the situation, the invention provides an evaluation method for the miscibility characteristics of the new and old asphalt and the regenerant in hot in-place recycling, which is suitable for evaluating the miscibility characteristics of the new and old asphalt and the regenerant in the preparation of the recycled mixture in hot in-place recycling.

Disclosure of Invention

The invention provides a method for evaluating the miscibility characteristics of the new asphalt and the old asphalt and the regenerant in the hot in-place recycling according to the defects.

The invention adopts the following technical scheme:

the invention relates to a method for evaluating the miscibility characteristics of new and old asphalt and a regenerant in hot in-place regeneration, which comprises the following steps:

s1: constructing a three-layer molecular dynamics model of mixing and dissolving of new asphalt molecules, old asphalt molecules and a regenerant in-situ thermal regeneration; in the three-layer molecular dynamics model, the regenerants are selected to be the same type and different doping amounts or different types and the same doping amounts;

s2: performing molecular dynamics simulation for the molecular dynamics simulation established in step S1;

s3: calculating the relative concentration of each molecular in the three-layer molecular dynamics model at each cross section in the model, and drawing a relative concentration curve of new asphalt molecules, old asphalt molecules and regenerant molecules in the three-layer molecular dynamics model;

s4: smoothing the relative concentration curves of the new asphalt molecules, the old asphalt molecules and the regenerant molecules in the step S3;

s5: calculating relative concentration curves of the new asphalt molecules, the old asphalt molecules and the regenerant molecules to obtain a new asphalt distribution area, an old asphalt distribution area and a regenerant distribution area after mixing and dissolving;

s6: calculating the acting rate of the regenerant, the activation rate of the old asphalt and the proportion of the mixing and dissolving area of the new asphalt and the old asphalt through the new asphalt distribution area, the old asphalt distribution area and the regenerant distribution area;

evaluating the activation rates of the regenerants with the same type and different mixing amounts or the regenerants with the same type and different mixing amounts and the old asphalt, wherein the larger the activation rate is, the better the index is;

the proportion of the regenerants with the same kind and different mixing amounts or the regenerants with the same kind and different mixing amounts to the miscible regions of the new asphalt and the old asphalt is evaluated, and the higher the activation rate is, the better the index is.

The method for evaluating the mixing and dissolving characteristics of the new asphalt, the old asphalt and the regenerant in the hot in-place regeneration comprises the step S1 that a three-layer molecular dynamics model is established from the left horizontal axis to the right horizontal axis and is from l_leftTo l_right；

New asphalt molecules, a regenerant and old asphalt molecules are sequentially arranged in the horizontal axis from left to right; carrying out system geometric balance after modeling;

the new asphalt and the old asphalt and the regenerant are both composed of various molecules; the new asphalt molecules in the three-layer molecular dynamics model comprise 1 st to i th asphalt molecules_mSeed, old asphalt molecules include_m+1To the ith_nThe regenerant molecules include the ith_n+1To the ith_pAnd (4) seed preparation.

The invention relates to a method for evaluating the miscibility characteristics of new and old asphalt and a regenerant in hot in-place regeneration, which is characterized by comprising the following steps of: in the step S2:

carrying out molecular dynamics simulation by using an NPT system aiming at the three-layer model established in S1, and determining the parameters of the pressure intensity and the force field in the simulation by referring to the parameters of the simulated actual in-situ heat regeneration engineering;

based on a temperature reduction curve of the paved asphalt mixture obtained by actual measurement or numerical simulation, the system temperature in the molecular dynamics simulation is determined through the following conditions:

if the actually measured or simulated temperature reduction curve time range is 0-t₁NPT series in molecular dynamics simulationThe total time is 0-t₂(ii) a Since the temperature cannot be set to decrease continuously in NPT, 0-t is set₂Corresponds to 0-t₁The cooling process in the cooling curve divides the cooling curve and the NPT process into N sections (N is more than or equal to 20) according to time average, and the temperature corresponding to the time midpoint on each section of the cooling curve is taken as the temperature set in each section of NPT.

The invention relates to a method for evaluating the miscibility characteristics of new and old asphalt and a regenerant in hot in-place recycling, which comprises the following steps of S3: after the molecular dynamics simulation is finished, based on the output centroid position of each atom on each molecule; dividing the three-layer molecular dynamics model into a plurality of cross sections, and calculating the relative concentration of new asphalt molecules, old asphalt molecules and regenerant molecules in each cross section in the model; to the abscissa in the model from_left-l_rightIn which l_leftFinger model left boundary position,/_rightThe right boundary position of the finger model is uniformly divided into the 1 st to Mth (M is more than or equal to 100) areas from left to right along the abscissa direction_pIn each cross section, i (1. ltoreq. i)_p) Relative concentration of the analogous molecule a (i, M)_p) The calculation method of (2) is as follows:

wherein a (x) is M_pThe total mass of the atoms belonging to the i-th class of molecules in the cross-section, b (x) being the centroid at M_pTotal mass of all atoms in each cross-section.

The invention relates to a method for evaluating the mixing and dissolving characteristics of new and old asphalt and a regenerant in-situ thermal regeneration, Mth_pRelative concentration of new bitumen molecules A (M) in one cross section_p) Relative concentration of old asphalt molecules B (M)_p) Relative concentration of regenerant molecules C (M)_p) The calculation method is as follows:

and calculating the relative concentrations of the new asphalt molecules, the old asphalt molecules and the regenerant molecules of the 1 st to Mth cross sections, drawing the relative concentrations in a plane rectangular coordinate system to obtain a relative concentration curve of the new asphalt molecules, the old asphalt molecules and the regenerant in the model, and smoothing the curve by applying a Gaussian filtering method to obtain a smoothed relative concentration curve of the new asphalt molecules, the old asphalt molecules and the regenerant.

The invention relates to a method for evaluating the miscibility characteristics of new and old asphalt and a regenerant in hot in-place recycling, which comprises the following steps of S5:

based on the smoothed relative concentration curve of the new asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the new asphalt after mixing, i.e. the abscissa is l_leftTo l₃A moiety of (a);

based on the smoothed relative concentration curve of the old asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the mixed old asphalt, i.e. the abscissa is l₂To l_rightA moiety of (a);

based on the smoothed relative concentration curve of the new asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the mixed regenerant, i.e. the abscissa is l₁To l₄A moiety of (a); l₂To l₃The part in between contains new and old asphalt molecules, which are defined as new and old asphalt miscible regions. Part of the reason for selecting more than 1% is to avoid the influence of the centroid position of atoms on individual molecules without statistical significance on the analysis result;

wherein l_leftAs the left boundary position coordinates of the model, l_rightAs the right boundary position coordinates of the model, l_midIs the median position coordinate of the model, l₁And l₄The relative concentration curve of the regenerant in the model is 1 percent, and the corresponding left and right position coordinates are obtained; l₂And l₃And the position coordinates are respectively corresponding to the old asphalt and the new asphalt in the model when the relative concentration curve is 1%.

The invention relates to a method for evaluating the miscibility characteristics of new and old asphalt and a regenerant in hot in-place recycling, which comprises the following steps of S6: the regenerant action rate Z is the mass ratio of the regenerant diffused into the old asphalt to the total regenerant, and the calculation method is as follows:

in the formula, c is the total mass of atoms belonging to the regenerant molecules in the regenerant distribution region with the centroid after mixing and dissolving, and d is the total mass of all atoms belonging to the regenerant molecules in the three-layer model.

The old asphalt activation rate J is the proportion of the old asphalt distribution area in which the regenerant molecules are diffused after mixing and dissolving to the old asphalt distribution area after mixing and dissolving, and the calculation method is as follows:

the ratio H of the new asphalt miscible region to the old asphalt miscible region refers to the ratio of the length of the new asphalt miscible region to the total length of the three-layer model, and the calculation method is as follows:

advantageous effects

The invention provides an evaluation method for the miscibility characteristics of new and old asphalt and a regenerant in hot in-place recycling, and provides an evaluation method suitable for evaluating the miscibility characteristics of the new and old asphalt and the regenerant in preparation of a recycled mixture in hot in-place recycling from the perspective of molecular dynamics.

According to the method for evaluating the mixing and dissolving characteristics of the new and old asphalt and the regenerant in the hot in-place regeneration, when the conventional method is used for judging the permeation process of the new and old asphalt under the action of the regenerant, an indoor experiment is needed, the activation effect of the regenerant on the old asphalt, the acting proportion of the regenerant and the mixing and dissolving area range of the new and old asphalt are difficult to evaluate, and a simulation method for obtaining the three indexes is also lacked at present. Aiming at the three indexes, three indexes of the action rate of the regenerant, the activation rate of the old asphalt and the mixing and dissolving area ratio of the new asphalt and the old asphalt are respectively provided based on molecular dynamics simulation, so that the method can be used for comprehensively evaluating the action process of the new asphalt and the old asphalt under the action of the regenerant, and is convenient for optimizing the indexes such as the type, the mixing amount of the new asphalt and the like in the regeneration process based on the simulation result.

Drawings

Fig. 1(a) is a schematic diagram of the three-layer model created in step S1.

FIG. 1(b) is a schematic diagram of a model after completion of simulation

Fig. 1(c) is a graph showing the smoothed relative concentrations of the new asphalt molecules, the old asphalt molecules and the regenerant in step S4.

Fig. 2 is a cooling curve in the first embodiment.

FIG. 3 is a graph showing the effect rate Z of the regenerant and the activation rate J of old asphalt as a function of the amount of the regenerant added in the first example.

FIG. 4 is a graph showing the change of the ratio H of the miscibility gap between the new and old asphalts according to the mixing amount of the recycling agent in the first example.

Detailed Description

In order to make the purpose and technical solution of the embodiments of the present invention clearer, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

The method is suitable for evaluating the mixing and dissolving characteristics of the new and old asphalt and the regenerant in the in-situ thermal regeneration, and comprises the following 6 steps:

s1: constructing a three-layer molecular dynamics model of mixing and dissolving new and old asphalt and a regenerant in-situ thermal regeneration;

s2: carrying out molecular dynamics simulation;

s3: calculating the relative concentration of each molecular in each cross section of the model, and drawing a relative concentration curve of each molecular in the three-layer model;

s4: drawing a smoothing relative concentration curve of new asphalt, old asphalt and a regenerant;

s5: calculating a new asphalt distribution area, an old asphalt distribution area and a regenerant distribution area after mixing and dissolving;

s6: and calculating the action rate Z of the regenerant, the activation rate J of the old asphalt and the proportion H of the miscible region of the new asphalt and the old asphalt.

As shown in FIG. 1(a), the abscissa of the three-layer molecular dynamics model created in step S1 from left to right is from l_leftTo l_rightAnd from left to right, sequentially preparing new asphalt molecules, a regenerant and old asphalt molecules, determining the proportion of the new asphalt molecules, the regenerant and the old asphalt molecules according to the corresponding proportion in the simulated actual in-situ thermal regeneration engineering, and performing system geometric balance after modeling. The new and old asphalt and the regenerant are both composed of a plurality of molecules, wherein the new asphalt molecules in the model comprise 1 st to i th asphalt molecules_mSeed, old asphalt molecules include_m+1To the ith_nThe regenerant molecules include the ith_n+1To the ith_pAnd (4) seed preparation.

In step S2: and (4) carrying out molecular dynamics simulation based on the three-layer model established in S1, wherein parameters such as pressure, force field and the like in the simulation are actually determined by referring to the simulated actual in-situ heat regeneration engineering, and the scheme adopts an NPT ensemble. In particular, the system temperature in the molecular dynamics simulation can be determined based on the temperature reduction curve of the paved asphalt mixture obtained by actual measurement or numerical simulation. If the actually measured or simulated temperature reduction curve time range is 0-t₁The total time of the NPT ensemble in the molecular dynamics simulation is 0-t₂Since the temperature cannot be set to decrease continuously in NPT, 0-t is set₂Corresponds to 0-t₁The cooling process in the cooling curve divides the cooling curve and the NPT process according to the average timeN sections (N is more than or equal to 20), and the temperature corresponding to the time midpoint on each section of cooling curve is taken as the temperature set in each section of NPT.

As a preferred embodiment of the present invention, the details of step S3 are as follows: and after the molecular dynamics simulation is finished, based on the output centroid position of each atom on each molecule. The relative concentrations of each type of molecule in each cross-section of the model were calculated. For the abscissa of the model from 0-x_pThe total area of (2) is uniformly divided into 1 st to Mth (M is more than or equal to 100) areas from left to right along the abscissa direction, and the width of each area isM th_pIn each cross section, i (1. ltoreq. i)_p) Relative concentration of the analogous molecule a (i, M)_p) The calculation method of (2) is as follows:

a (x) is the M_pThe total mass of the atoms belonging to the i-th class of molecules in the cross-section, b (x) being the centroid at M_pTotal mass of all atoms in each cross-section. And calculating the relative concentration of each cross section, drawing in a plane rectangular coordinate system to obtain relative concentration curves of various molecules in the three-layer model, and smoothing the curves by applying a Gaussian filtering method to obtain the smoothed relative concentration curves of the new asphalt molecules, the old asphalt molecules and the regenerant.

As a preferred embodiment of the present invention, the details of step S4 are as follows: m th_pRelative concentration of new bitumen molecules A (M) in one cross section_p) Relative concentration of old asphalt molecules B (M)_p) Relative concentration of regenerant molecules C (M)_p) The calculation method is as follows:

and (3) calculating the relative concentrations of the new asphalt molecules, the old asphalt molecules and the regenerant molecules in the 1 st to M th cross sections, drawing the relative concentrations in a plane rectangular coordinate system to obtain a relative concentration curve of the new asphalt molecules, the old asphalt molecules and the regenerant in the model, and smoothing the curve by applying a Gaussian filtering method to obtain a smoothed relative concentration curve of the new asphalt molecules, the old asphalt molecules and the regenerant, as shown in fig. 1 (b).

As shown in fig. 1 (c): in step S5, based on the smoothed relative concentration curve of the new asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the new asphalt after mixing, i.e. the abscissa is l_leftTo l₃A moiety of (a); based on the smoothed relative concentration curve of the old asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the mixed old asphalt, i.e. the abscissa is l₂To l_rightA moiety of (a); based on the smoothed relative concentration curve of the new asphalt molecules obtained in S4, a part with a relative concentration greater than 1% is selected, and the corresponding range is defined as the distribution area of the mixed regenerant, i.e. the abscissa is l₁To l₄A moiety of (a); l₂To l₃The part in between contains new and old asphalt molecules, which are defined as new and old asphalt miscible regions. This is partly due to the fact that the influence of the position of the centroid of the atoms on the individual molecules, which is not statistically significant, on the analysis results is avoided.

As a preferred embodiment of the present invention, the details of step S6 are as follows: the regenerant action rate Z is the mass ratio of the regenerant diffused into the old asphalt to the total regenerant, and the calculation method is as follows:

in the formula, c is the total mass of atoms belonging to the regenerant molecules in the regenerant distribution region with the centroid after mixing and dissolving, and d is the total mass of all atoms belonging to the regenerant molecules in the three-layer model.

The old asphalt activation rate J is the proportion of the old asphalt distribution area in which the regenerant molecules are diffused after mixing and dissolving to the old asphalt distribution area after mixing and dissolving, and the calculation method is as follows:

the ratio H of the new asphalt miscible region to the old asphalt miscible region refers to the ratio of the length of the new asphalt miscible region to the total length of the three-layer model, and the calculation method is as follows:

the first embodiment is as follows:

and (3) carrying out hot recycling on a certain place, wherein the mixing temperature is 160 ℃ (433K), and the temperature of the recycled asphalt mixture layer after paving is reduced from 160 ℃ (433K) to 25 ℃ (298K). In the molecular dynamics simulation, a Compass-II force field and a period boundary condition are adopted, the temperature is controlled by a Nose-Hoover thermostat, the pressure is controlled to be 1atm by an Anderson barostat, and the time step is 1 fs. And the NVT ensemble of 30ps is adopted, so that the system reaches the temperature required by simulation under the condition of relatively stable volume, thereby stabilizing energy and preventing the generation of energy singularity. The NPT system trace of 5ns is adopted to keep the temperature and the pressure of the system at target values, and the diffusion and mixing processes of the regenerant, the raw asphalt and the aged asphalt are simulated.

The time parameter in molecular dynamics does not correspond to the actual time, and has relative significance. The temperature reduction curve of the in-situ hot in-place recycled asphalt mixture layer obtained based on finite element simulation is shown in figure 2, in order to reflect the influence of the temperature reduction curve, the NPT process of 0-5ns corresponds to the temperature reduction process of 0-2h, the temperature reduction curve is divided into 50 sections according to time, and the temperature corresponding to the time midpoint on each section of the temperature reduction curve is used as the temperature set in each section of the NPT. The effect rate Z of the regenerant and the activation rate J of the old asphalt are shown in FIG. 3, and the ratio H of the miscible region of the new asphalt to the old asphalt is shown in FIG. 4.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.