Method for improving anti-aging performance of graphene modified asphalt

Abstract

The application discloses an evaluation method for anti-aging performance of graphene modified asphalt, which comprises the following steps: constructing an asphalt molecular amorphous cell model, a graphene modified asphalt molecular amorphous cell model, an asphalt / oxygen mixed system amorphous cell model and a graphene modified asphalt / oxygen mixed system amorphous cell model by using a molecular dynamics simulation software, and respectively performing molecular dynamics simulation on the models, calculating the solubility parameter and interaction energy of graphene and asphalt, obtaining the mean square displacement curve MSD of each component and oxygen in the asphalt / oxygen mixed system and the graphene modified asphalt / oxygen mixed system and calculating the diffusion coefficient, and evaluating the anti-aging performance of the graphene modified asphalt material according to the compatibility degree and the diffusion coefficient index. The application has reliable theoretical basis and simple and clear results, overcomes the shortcomings of long time consumption and high cost of the existing evaluation method for anti-aging performance of graphene modified asphalt, and has important significance for improving the durability of asphalt pavement.

Description

Technical Field

[0001] This invention belongs to the technical field of evaluating the anti-aging properties of modified asphalt, and specifically relates to a method for evaluating the anti-aging properties of graphene-modified asphalt. Background Technology

[0002] Asphalt pavement, due to its advantages such as noise reduction, vibration damping, and wear resistance, is widely used in highways and airport runways. In my country, over 90% of the highway pavement is asphalt. However, in recent years, global climate change and increased traffic volume have led to problems such as rutting, cracking, and peeling appearing on some asphalt roads shortly after opening to traffic. This not only reduces the service life of asphalt pavement but also affects the normal traffic flow. Therefore, researching the anti-aging properties of asphalt pavement to improve pavement durability is of great significance.

[0003] Asphalt aging refers to the process by which asphalt undergoes a series of physicochemical changes during storage, processing, construction, and use, exposed to air for extended periods, including evaporation, deoxidation, condensation, and oxidation. These changes prevent the asphalt from maintaining its original properties, leading to hardening, brittleness, cracking, and other adverse phenomena. The aging process can be divided into two stages: thermal aging during construction, which may involve oxidation upon contact with air; and long-term aging during road use, a process that is lengthy and influenced by complex factors. From the perspective of the aging process, asphalt aging is caused by a combination of factors, including oxygen, sunlight, temperature, water, and mechanical damage and fatigue over time. Oxygen-induced oxidation is the most significant factor contributing to asphalt aging. Asphalt aging is unavoidable; therefore, efforts should focus on slowing down the aging rate to reduce the degree of aging and improve the aging performance of asphalt. Commonly used test methods for simulating asphalt aging include: short-term aging tests using a thin-film oven and rotating thin-film heating test; and long-term aging tests using a pressure aging chamber.

[0004] Adding nanomaterials as modifiers to asphalt or modified asphalt serves two purposes. First, the open pores on the filler surface can adsorb easily aging active lightweight components in the asphalt, thus preventing their rapid aging. Second, due to their excellent interfacial effects, nanomaterials increase the compatibility between the modifier and asphalt while also acting as gas barriers, effectively slowing down the aging rate of asphalt. Graphene, as an emerging nanomaterial, has attracted much attention due to its excellent mechanical properties and extremely high thermal conductivity. However, its application in road engineering is still in its early stages, and methods for improving the anti-aging properties of graphene-modified asphalt are not yet fully developed.

[0005] As a product of the rapid development of computers, molecular dynamics bridges the gap between macroscopic experiments and microscopic behavior. Its simulation methods fully consider the influence of the external environment on molecules when solving material performance problems at the molecular level. Because molecular models are at the atomic scale, the interactions between and within atoms in the system can be easily determined. This method, based on physical simulation, can simultaneously obtain the dynamic structure and thermodynamic properties of the system, exhibiting high accuracy and a wide range of applications. This method can be used in the research of asphalt, inheriting the advantages of component analysis while overcoming the shortcomings of static studies; it can be used to analyze the structure of asphalt molecules and predict the physical properties of asphalt.

[0006] In summary, current methods for studying the anti-aging properties of graphene-modified asphalt mainly involve conducting macroscopic tests using accelerated thermo-oxidative aging devices and evaluating the results. This method is time-consuming, costly, and wasteful of resources, and it cannot explore the root causes of the influence of graphene on the anti-aging properties of asphalt. Summary of the Invention

[0007] The purpose of this invention is to provide a method for improving the anti-aging properties of graphene-modified asphalt, in order to solve the problems of long macroscopic testing time, high cost, and waste of resources in current methods for improving the anti-aging properties of graphene-modified asphalt.

[0008] To achieve the above objectives, the present invention provides a method for improving the anti-aging properties of graphene-modified asphalt, comprising the following steps:

[0009] (1) Based on the sketch tool of Materials Studio software, construct the twelve molecular structure models of the four components of asphalt, the molecular structure model of graphene and the molecular structure model of oxygen, and optimize the geometric structure through the Forcite module;

[0010] (2) Based on the proportions of the four components of asphalt, the proportion of graphene material and the proportion of oxygen, the molecular structure model obtained in step (1) is used to construct the amorphous cell model of graphene molecule, the amorphous cell model of asphalt molecule, the amorphous cell model of graphene modified asphalt molecule, the amorphous cell model of asphalt / oxygen mixture system and the amorphous cell model of graphene modified asphalt / oxygen mixture system using the Amorphous Cell module in MS software.

[0011] (3) Perform molecular dynamics simulations on the five amorphous unit cell models obtained in step (2) to obtain the trajectory files of their stable configurations;

[0012] (4) Extract the last 100 frames of the trajectory file mentioned in step (3), calculate the solubility parameters and interaction energy of graphene molecules and asphalt molecules, obtain the mean square displacement curves (MSD) of each component and oxygen in the asphalt / oxygen mixture system and the graphene-modified asphalt / oxygen mixture system, and calculate the diffusion coefficient.

[0013] Furthermore, the four components of asphalt mentioned in step (1) are saturated components, aromatic components, resins, and asphaltenes; the geometric optimization mentioned in step (1) is as follows: select the Geometry Optimization function in the Forcite module, select the Smart algorithm, set the maximum number of iterations to at least 2000, select the precision as Medium, the cutoff radius as 12.5 Å, the force field as COMPASS II force field, and use the Atom based and Ewald methods to solve the van der Waals nonbonding interactions and electrostatic nonbonding interactions respectively, with the charge set by the force field.

[0014] Furthermore, the proportion of the four components of asphalt mentioned in step (2) can be determined according to the "Determination of Four Components of Petroleum Asphalt (NB / SH / T 0509-2010)"; the construction process mentioned in step (2) is as follows: select the Construction function in the Amorphous Cell module, select Medium precision, COMPASS II force field, and use the Atom-based and Ewald methods to solve the van der Waals nonbonding interactions and electrostatic nonbonding interactions respectively. The charge is set by the force field, and the density is set to 0.2-0.5 g / cm³. 3 .

[0015] Further, the molecular dynamics simulation operation in step (3) is as follows: First, the Geometry Optimization function in the Forcite module is used to iteratively optimize the amorphous unit cell model of asphalt molecules, the amorphous unit cell model of graphene-modified asphalt, the amorphous unit cell model of asphalt / oxygen mixture system, and the amorphous unit cell model of graphene-modified asphalt / oxygen mixture system for at least 20,000 steps, and iteratively optimize the amorphous unit cell model of graphene molecules for at least 2,000 steps; then, the Anneal function in the Forcite module is used to anneal the five amorphous unit cell models, and the ensemble is selected as the isothermal-isobaric ensemble (NPT), with the temperature set to 300-1000K. The annealing cycle was 2-5 times, with a time step of 1 fs, and a total time step of 100-200 ps. Finally, the Dynamic function in the Forcite module was used to perform isothermal and isochoric ensemble (NVT) simulations and isothermal and isobaric ensemble (NPT) simulations for 200-500 ps on five amorphous cell models. During the simulation, the pressure was set to 1 atm, the COMPASS II force field was selected, and the temperature control method and pressure control method were Nose and Berendsen, respectively. The van der Waals force and electrostatic force were calculated using the Atom-based and Ewald methods, respectively. Setting different temperatures can simulate the effect of graphene on the anti-aging properties of asphalt at different temperatures.

[0016] Furthermore, the trajectory file obtained in step (3) is as follows: during the isothermal and isobaric ensemble (NPT) molecular dynamics simulation of each amorphous unit cell model, one frame of configuration is output every 500 steps, resulting in 400-1000 frames of trajectory files for subsequent calculations.

[0017] Furthermore, the solubility parameter δ mentioned in step (4) is calculated using formula 1.

[0018] Formula 1: Solubility parameter

[0019] ,

[0020] In the formula, E is the total cohesive energy of the system, V is the total volume of the system, and CED is the cohesive energy density of the material.

[0021] The closer the solubility parameters of graphene molecules and asphalt molecules are, the better the compatibility between graphene and asphalt.

[0022] Furthermore, the interaction energy described in step (4) is calculated using Equation 2.

[0023] Formula 2: Interaction Energy

[0024] ,

[0025] ,

[0026] ,

[0027] In the formula, E P E represents the potential interaction energy between graphene molecules and asphalt molecules. V E represents the van der Waals interaction energy between graphene molecules and pitch molecules. ε E represents the electrostatic interaction energy between graphene molecules and asphalt molecules. abP E abV E abε These represent the potential energy, van der Waals energy, and electrostatic energy of graphene-modified asphalt molecules, respectively. aP E aV E aε These represent the potential energy, van der Waals energy, and electrostatic energy of a graphene molecule, respectively. bP E bV E bε These are the potential energy, van der Waals energy, and electrostatic energy of the asphalt molecule, respectively.

[0028] The larger the absolute value of the interaction energy, the more stable the graphene-asphalt blend system is, that is, the better the compatibility.

[0029] Furthermore, in step (4), the mean square displacement curves of saturated components, aromatic components, resins, asphaltenes, and oxygen in the asphalt / oxygen mixture and the graphene-modified asphalt / oxygen mixture are obtained, and their diffusion coefficients are calculated using formula 3.

[0030] Formula 3: Diffusion coefficient

[0031] ,

[0032] In the formula, D is the diffusion coefficient, N is the total number of particles to be averaged, and r i (t) is the position vector of particle i at time t, r i (0) is the position vector of particle i at the initial time, MSD is the mean square displacement, and a is the slope of the linear fitting line of MSD;

[0033] The higher the diffusion coefficient of the four components and oxygen in the asphalt / oxygen mixture system and the graphene-modified asphalt / oxygen mixture system, the worse the anti-aging performance of the asphalt.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention, based on molecular dynamics theory, utilizes Materials Studio software to construct amorphous unit cell models of asphalt molecules, graphene-modified asphalt molecules, asphalt / oxygen mixtures, and graphene-modified asphalt / oxygen mixtures. It calculates solubility parameters and interaction energies, obtains the mean square displacement (MSD) curves of each component and oxygen in the asphalt / oxygen mixture and graphene-modified asphalt / oxygen mixtures, and calculates the diffusion coefficient. The anti-aging performance of graphene-modified asphalt materials is evaluated based on compatibility and diffusion coefficient indices. This invention offers reliable theoretical basis and simple, clear results, overcoming the problems of time-consuming and costly macroscopic experimental processes and resource waste in current methods for assessing the anti-aging performance of graphene-modified asphalt. It is of great significance for improving the durability of asphalt pavements. Attached Figure Description

[0036] Figure 1 This is a model diagram of the amorphous unit cell of asphalt molecules in Example 1.

[0037] Figure 2 This is a model diagram of the amorphous unit cell of graphene-modified pitch molecules in Example 1.

[0038] Figure 3 This is an amorphous unit cell model diagram of the asphalt / oxygen mixture system in Example 1.

[0039] Figure 4 This is an amorphous unit cell model diagram of the graphene-modified bitumen / oxygen mixture system in Example 1. Detailed Implementation

[0040] To demonstrate the objectives, technical solutions, and benefits of this invention, the invention will be described in more detail below with reference to specific embodiments and accompanying drawings. Obviously, the specific embodiments used herein are only some, not all, embodiments of this invention, and are used merely to explain the invention and are not intended to limit it.

[0041] Example 1

[0042] A method for improving the anti-aging properties of graphene-modified asphalt, comprising the following steps:

[0043] (1) The twelve molecular structure models of the four components of asphalt, the molecular structure model of graphene, and the molecular structure model of oxygen were constructed using the sketch tool of MS software, and the geometric structure of each molecular structure model was optimized. The four components of asphalt include saturated components, aromatic components, resins, and asphaltenes; the relevant parameters for geometric structure optimization are as follows: select the Smart algorithm, set the maximum number of iterations to 2000, select the precision to Medium, the cutoff radius to 12.5 Å, the force field is the COMPASS II force field, and the van der Waals nonbonding interaction and electrostatic nonbonding interaction are solved using the Atombased and Ewald methods respectively, and the charge is set by the force field.

[0044] (2) Based on the determined proportions of the four components and the determined graphene content of 0.5% and oxygen content of 1%, the amorphous cell model of graphene and the amorphous cell model of pitch were constructed in the Amorphous Cell module of the software using the molecular structure model obtained in step (1) (see Figure 1 ), graphene-modified asphalt molecular amorphous unit cell model (see Figure 2 Amorphous unit cell model of asphalt / oxygen mixture (see...) Figure 3 ) and the amorphous unit cell model of the graphene-modified bitumen / oxygen mixture system (see Figure 4 The proportions of saturated components, aromatic components, resins, and asphaltenes in the four components of asphalt were determined according to the "Determination of Four Components of Petroleum Asphalt (NB / SH / T 0509-2010)". The relevant parameters for the Amorphous Cell module were: precision set to Medium, force field set to COMPASS II, van der Waals nonbonding interactions and electrostatic nonbonding interactions solved using Atom-based and Ewald methods respectively, charge set by the force field, and density set to 0.2 g / cm³. 3 .

[0045] (3) The five amorphous cell models constructed were subjected to a series of processes, including geometry optimization, annealing, and relaxation, through the Geometry Optimization, Anneal, and Dynamic functions of the Forcite module. Geometric structure optimization: 20,000 iterative optimization steps were performed on the amorphous cell models of asphalt molecules, graphene-modified asphalt, asphalt / oxygen mixtures, and graphene-modified asphalt / oxygen mixtures; 2,000 iterative optimization steps were performed on the graphene molecular amorphous cell model. Annealing: An isothermal-isobaric ensemble (NPT) was used, with temperatures set to 300-1000K, 5 annealing cycles, and time steps of 1fs and 100ps. Relaxation: The simulation temperature was set to 298K (25℃), and isothermal-isochoric ensemble (NVT) simulations were performed for 200ps and isothermal-isobaric ensemble (NPT) simulations for 500ps. During the simulation, the pressure was set to 1 atm, and the COMPASS II force field was used. The temperature-controlled method and pressure-controlled method were Nose and Berendsen, respectively, and van der Waals forces and electrostatic forces were calculated using the Atom-based and Ewald methods, respectively.

[0046] (4) In the process of performing a 500ps molecular dynamics simulation of each amorphous unit cell model isothermal and isobaric ensemble (NPT) in step (3), one frame of configuration is output every 500 steps, and finally 1000 frames of trajectory files are obtained. The last 100 frames of the 1000 frames of trajectory files are extracted to calculate solubility parameters, interaction energy and obtain the mean square displacement curves of each component and oxygen.

[0047] (5) Calculate the cohesive energy density of graphene and asphalt molecules using the Cohesive Energy Density function in the Forcite module, and calculate the solubility parameter according to Formula 1.

[0048] Formula 1: Solubility parameter

[0049] ,

[0050] In the formula, E is the total cohesive energy of the system, V is the total volume of the system, and CED is the cohesive energy density of the material.

[0051] (6) Calculate the energy of the graphene-modified pitch molecular system, as well as the energy of the system containing only graphene molecules and only pitch molecules, using the Energy function in the Forcite module. Calculate the interaction energy according to Formula 2.

[0052] Formula 2: Interaction Energy

[0053] ,

[0054] ,

[0055] ,

[0056] In the formula, E P E represents the potential interaction energy between graphene molecules and asphalt molecules. V E represents the van der Waals interaction energy between graphene molecules and pitch molecules. ε E represents the electrostatic interaction energy between graphene molecules and asphalt molecules. abP E abV E abε These represent the potential energy, van der Waals energy, and electrostatic energy of graphene-modified asphalt molecules, respectively. aP E aV E aε These represent the potential energy, van der Waals energy, and electrostatic energy of a graphene molecule, respectively. bP E bV E bε These are the potential energy, van der Waals energy, and electrostatic energy of the asphalt molecule, respectively.

[0057] (7) Using the Edit set tool, the saturated components, aromatic components, resins, asphaltenes, and oxygen molecules of the molecular dynamics simulation-derived asphalt / oxygen mixture and the graphene-modified asphalt / oxygen mixture are defined as A, B, C, D, and O. The Mean Square Displacement task within the Analysis function of the Forcite module is used to obtain the MSD curves of the four components and oxygen over time. Linear fitting is performed, and the diffusion coefficient is calculated according to Formula 3.

[0058] Formula 3: Diffusion coefficient

[0059] ,

[0060] In the formula, D is the diffusion coefficient, N is the total number of particles to be averaged, and r i (t) is the position vector of particle i at time t, r i (0) is the position vector of particle i at the initial time, MSD is the mean square displacement, and a is the slope of the linear fitting line of MSD.

[0061] The closer the solubility parameters of graphene molecules and asphalt molecules are, the larger the absolute value of their interaction energy, indicating better compatibility between graphene and asphalt. The smaller the diffusion coefficients of the four components and oxygen in a graphene-modified asphalt / oxygen mixture, the better the asphalt's anti-aging performance. Evaluating the anti-aging performance of graphene-modified asphalt materials based on compatibility and diffusion coefficient indices is theoretically reliable and yields simple and clear results. This overcomes the shortcomings of current methods for assessing the anti-aging performance of graphene-modified asphalt, such as time-consuming and costly macroscopic testing, and is of great significance for improving the durability of asphalt pavements.

[0062] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any modifications, substitutions, or improvements made under the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the anti-aging properties of graphene-modified asphalt, characterized in that, Includes the following steps: (1) Based on the sketch tool of Materials Studio software, construct the twelve molecular structure models of the four components of asphalt, the molecular structure model of graphene and the molecular structure model of oxygen, and optimize the geometric structure through the Forcite module; (2) Based on the proportions of the four components of asphalt, the proportion of graphene material and the proportion of oxygen, the molecular structure model obtained in step (1) is used to construct the amorphous cell model of graphene molecule, the amorphous cell model of asphalt molecule, the amorphous cell model of graphene modified asphalt molecule, the amorphous cell model of asphalt / oxygen mixture system and the amorphous cell model of graphene modified asphalt / oxygen mixture system using the Amorphous Cell module in MS software. (3) Perform molecular dynamics simulations on the five amorphous unit cell models obtained in step (2) to obtain the trajectory files of their stable configurations; (4) Extract the last 100 frames of the trajectory file mentioned in step (3), calculate the solubility parameters and interaction energy of graphene molecules and asphalt molecules, obtain the mean square displacement curves (MSD) of each component and oxygen in the asphalt / oxygen mixture system and the graphene-modified asphalt / oxygen mixture system, and calculate the diffusion coefficient.

2. The method according to claim 1, characterized in that, The asphalt four components mentioned in step (1) are saturated components, aromatic components, resins, and asphaltenes; the geometric optimization mentioned in step (1) is as follows: select the GeometryOptimization function in the Forcite module, select the Smart algorithm, set the maximum number of iterations to at least 2000, select the precision as Medium, the cutoff radius as 12.5 Å, the force field as COMPASS II force field, and use the Atom based and Ewald methods to solve the van der Waals nonbonding interaction and electrostatic nonbonding interaction respectively, and the charge is set by the force field.

3. The method according to claim 1, characterized in that, The construction process described in step (2) is as follows: Select the Construction function in the Amorphous Cell module, select Medium precision, and COMPASS II force field. Solve the van der Waals nonbonding interactions and electrostatic nonbonding interactions using the Atom-based and Ewald methods respectively. Set the charge to be determined by the force field and the density to 0.2-0.5 g / cm³. 3 .

4. The method according to claim 1, characterized in that, The molecular dynamics simulation in step (3) is as follows: First, the Geometry Optimization function in the Forcite module is used to iteratively optimize the amorphous unit cell model of asphalt molecules, the amorphous unit cell model of graphene-modified asphalt, the amorphous unit cell model of asphalt / oxygen mixture, and the amorphous unit cell model of graphene-modified asphalt / oxygen mixture for at least 20,000 steps, and iteratively optimize the amorphous unit cell model of graphene molecules for at least 2,000 steps; then, the Anneal function in the Forcite module is used to anneal the five amorphous unit cell models, and the ensemble is selected as the isothermal and isobaric ensemble NPT, with the temperature set to 300-1000 °C. K, annealing cycle 2-5 times, time step 1fs, total time step 100-200ps; finally, the Dynamic function in the Forcite module was used to perform isothermal and isochoric ensemble NVT simulation for 200-500ps and isothermal and isobaric ensemble NPT simulation for 200-500ps for five amorphous cell models; during the simulation, the pressure was set to 1atm, COMPASS II force field was selected, and the temperature control method and pressure control method were Nose and Berendsen respectively. Van der Waals force and electrostatic force were calculated using the Atom-based and Ewald methods respectively. Setting different temperatures can simulate the effect of graphene on the anti-aging properties of asphalt at different temperatures.

5. The method according to claim 1, characterized in that, The trajectory file obtained in step (3) is as follows: during the isothermal and isobaric ensemble NPT molecular dynamics simulation of each amorphous unit cell model, one frame of configuration is output every 500 steps, resulting in 400-1000 frames of trajectory file for subsequent calculations.

6. The method according to claim 1, characterized in that, The solubility parameter δ mentioned in step (4) is calculated using formula 1. Formula 1: Solubility parameter ， In the formula, E is the total cohesive energy of the system, V is the total volume of the system, and CED is the cohesive energy density of the material. The closer the solubility parameters of graphene molecules and asphalt molecules are, the better the compatibility between graphene and asphalt.

7. The method according to claim 1, characterized in that, The interaction energy mentioned in step (4) is calculated using Equation 2. Formula 2: Interaction Energy ， ， ， In the formula, E P E represents the potential interaction energy between graphene molecules and asphalt molecules. V E represents the van der Waals interaction energy between graphene molecules and pitch molecules. ε E represents the electrostatic interaction energy between graphene molecules and asphalt molecules. abP E abV E abε These represent the potential energy, van der Waals energy, and electrostatic energy of graphene-modified asphalt molecules, respectively. aP E aV E aε These represent the potential energy, van der Waals energy, and electrostatic energy of a graphene molecule, respectively. bP E bV E bε These are the potential energy, van der Waals energy, and electrostatic energy of the asphalt molecule, respectively. The larger the absolute value of the interaction energy, the more stable the graphene-asphalt blend system is, that is, the better the compatibility.

8. The method according to claim 1, characterized in that, In step (4), the mean square displacement curves of saturated components, aromatic components, resins, asphaltenes, and oxygen in the asphalt / oxygen mixture and the graphene-modified asphalt / oxygen mixture are obtained, and their diffusion coefficients are calculated using formula 3. Formula 3: Diffusion coefficient ， In the formula, D is the diffusion coefficient, N is the total number of particles to be averaged, and r i (t) is the position vector of particle i at time t, r i (0) is the position vector of particle i at the initial time, MSD is the mean square displacement, and a is the slope of the linear fitting line of MSD; The smaller the diffusion coefficient of the four components and oxygen in the asphalt / oxygen mixture system and the graphene-modified asphalt / oxygen mixture system, the better the anti-aging performance of the asphalt.

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