A method for modifying asphalt with graphene based on molecular dynamics simulation

Abstract

The application discloses a method for modifying asphalt with graphene based on molecular dynamics simulation, which comprises the following steps: constructing graphene molecular amorphous cell model, asphalt molecular amorphous cell model and graphene modified asphalt molecular amorphous cell model by using modeling software (Materials Studio), respectively performing molecular dynamics simulation on the models, calculating cohesive energy density and solubility parameter by using the Cohesive Energy Density function in the Forcite module, calculating interaction energy by using the Energy function in the Forcite module, calculating mechanical properties by using the Mechanical Properties function in the Forcite module, and analyzing the radial distribution function of each component in the asphalt molecular system and the graphene modified asphalt molecular system by using the Analysis function in the Forcite module. The application can more essentially explain the interaction between graphene material and matrix asphalt material from the molecular angle, can directly judge the performance of the graphene modified asphalt material, and provides a theoretical basis for the research and development of the graphene modified asphalt.

Description

Technical Field

[0001] This invention pertains to the evaluation of the performance of modified asphalt, specifically relating to a method for graphene-modified asphalt based on molecular dynamics simulation. Background Technology

[0002] Entering the 21st century, my country's total highway mileage began to grow rapidly. By the end of 2022, the total highway mileage in the country reached 5.3548 million kilometers, of which the mileage of expressways was 177,300 kilometers. Asphalt pavement has been widely used in my country's high-grade highways due to its advantages such as high driving comfort, convenient construction and maintenance, and good performance. Asphalt pavement will play a vital role in the future development of transportation.

[0003] Ordinary petroleum asphalt is a typical viscoelastic material with high temperature sensitivity, which makes asphalt pavements prone to damage. To reduce damage and extend the life of asphalt pavements, the most common method is to add modifiers (such as rubber or styrene-butadiene-styrene) to prepare modified asphalt. Microstructure is a decisive factor affecting macroscopic properties. Nanoparticles, due to their unique characteristics compared to large macroscopic particles and individual atoms and molecules, have attracted much attention for their ability to fundamentally and significantly improve material performance. Since its successful preparation, graphene has been widely used in various fields due to its excellent properties. Currently, research on graphene's application in road engineering is still in its early stages. Studies have shown that graphene has a significant effect on improving the high-temperature stability and anti-aging properties of asphalt. Currently, the method for judging the modification effect of graphene-modified asphalt is based on the data results of macroscopic tests conducted according to the requirements of JTG E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering".

[0004] With the development of computer technology, molecular simulation technology has become available for studying asphalt materials. Molecular simulation is based on molecular models, uses empirical potential functions to characterize intermolecular interactions, solves Newton's equations of motion to obtain molecular trajectories, and ultimately derives the objective function. Molecular dynamics is a type of molecular simulation that primarily uses intermolecular forces to drive changes in the molecular motion system. Its simulation process is always time-controlled; therefore, molecular dynamics simulation can obtain the dynamic information of asphalt molecular models changing over time, which helps in understanding the microscopic changes in asphalt materials.

[0005] In summary, the current evaluation of the performance of graphene-modified asphalt is mainly carried out through various macroscopic test methods required by the standards. Not only are the test processes cumbersome and complex, but the results obtained also have large errors and are greatly affected by human factors. Moreover, they cannot explain the interaction between graphene and asphalt from an essential perspective. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of conventional macroscopic tests in evaluating the performance of graphene-modified asphalt, such as cumbersome and complex testing processes, large errors in the results, and significant influence from human factors. This invention aims to fundamentally explain the dynamic interaction between graphene and asphalt from a molecular perspective, and to more directly determine the performance of graphene-modified asphalt.

[0007] To achieve the above objectives, the present invention provides a method for graphene-modified asphalt based on molecular dynamics simulations, comprising the following steps:

[0008] (1) Use MS software to construct amorphous unit cell models of pitch molecular system and graphene molecular system;

[0009] (2) Select the graphene content ratio in the graphene-modified asphalt material, and use the two amorphous cell models obtained in step (1) to construct the amorphous cell model of the graphene-modified asphalt molecular system through the Amorphous Cell module in the software.

[0010] (3) Molecular dynamics simulations were performed on the two stable amorphous unit cell models described in step (1) and the graphene-modified pitch amorphous unit cell model described in step (2);

[0011] (4) Calculate the cohesive energy density of the graphene molecular system and the asphalt molecular system, and then calculate their solubility parameters; calculate the energy of the graphene-modified asphalt molecular system and the system in which only the graphene molecular phase and only the asphalt molecular phase are retained, and then calculate the interaction energy.

[0012] (5) Calculate the bulk modulus, shear modulus and Young's modulus of the asphalt molecular system and the graphene-modified asphalt molecular system; use the analysis function to obtain the radial distribution function of each component in the asphalt molecular system and the graphene-modified asphalt molecular system.

[0013] Furthermore, the amorphous cell model of the asphalt molecular system mentioned in step (1) is constructed by optimizing the geometric structure of the twelve molecular model of the four asphalt components and then using the Amorphous Cell module; the amorphous cell model of the graphene molecular system mentioned in step (1) is constructed by drawing benzene ring phases connected into a single-layer structure using the sketch tool, optimizing the geometric structure, and then using the Amorphous Cell module.

[0014] Furthermore, the contents of saturated components, aromatic components, resins, and asphaltenes in the four components of asphalt can be determined according to the "Determination of Four Components of Petroleum Asphalt (NB / SH / T 0509-2010)".

[0015] Furthermore, the geometric structure optimization described in the construction of the amorphous unit cell models of the asphalt molecular system and the graphene molecular system is as follows: select the Geometry Optimization task in the Forcite module, use the COMPASS II force field, the charge is allocated by the force field setting, the accuracy is set to Medium, the electrostatic force is Ewald summation, the van der Waals force is Atom-based summation, the Smart algorithm is selected, and the maximum number of iterations is set to at least 2000.

[0016] Furthermore, the construction process described in step (2) is as follows: Select the Construction task in the Amorphous Cell module, use the COMPASS II force field, allocate the charge by setting the force field with a precision of Medium, use Ewald summation for electrostatic forces, use Atombased summation for van der Waals forces, and set the density to 0.2-0.5 g / cm³. 3 .

[0017] Furthermore, the molecular dynamics simulation operation in step (3) is as follows: First, the Geometry function in the Forcite module is used. The Optimization task iteratively optimized the amorphous cell model of the asphalt molecular system and the graphene-modified asphalt amorphous cell model for at least 20,000 steps, and the graphene molecular system amorphous cell model for at least 2,000 steps. Next, the Anneal task in the Forcite module was used to anneal the three amorphous cell models. The ensemble used was the isothermal-isobaric ensemble (NPT), with temperatures set to 300-1000 K, pressure set to 101 kPa, annealing cycles of 2-5, time steps of 1 fs, temperature controller set to Nose, and pressure controller set to Berendsen. Finally, the Dynamic task in the Forcite module was used to perform isothermal-isobaric ensemble (NVT) simulations and isothermal-isobaric ensemble (NPT) simulations for 200-500 ps on the three amorphous cell models. Setting different temperatures allowed for the simulation of the interaction between graphene and asphalt at different temperatures.

[0018] Furthermore, the solubility parameter δ mentioned in step (4) is calculated using formula 1.

[0019] Formula 1: Solubility parameter

[0020]

[0021] 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.

[0022] The closer the solubility parameters of the graphene molecular system and the asphalt molecular system are, the better the compatibility between graphene and asphalt.

[0023] Furthermore, the interaction energy described in step (4) is calculated using Equation 2.

[0024] Formula 2: Interaction Energy

[0025] E P =E abP -E aP -E bP ,

[0026] E V =E abV -E aV -E bV ,

[0027] E ε =E abε -E aε -E bε ,

[0028] In the formula, E P E represents the potential energy interaction energy between the graphene system and the asphalt system. abP E represents the potential energy of the graphene-modified asphalt system. aP E represents the potential energy of the graphene system. bP E represents the potential energy of the asphalt system. V E represents the van der Waals interaction energy between the graphene system and the pitch system. abV For van der Waals energy of graphene-modified bitumen systems, E aV For the van der Waals energy of the graphene system, E bV For van der Waals energy in bitumen systems, E ε E represents the electrostatic interaction energy between the graphene system and the asphalt system. abε E represents the electrostatic energy of the graphene-modified asphalt system. aε E represents the electrostatic energy of the graphene system. bε The electrostatic energy of the asphalt system;

[0029] A negative interaction energy indicates that the graphene system and the asphalt system attract each other. The larger the value, the greater the interaction energy, indicating that the graphene-asphalt blend system is more stable, i.e., the better the compatibility.

[0030] Furthermore, the bulk modulus, shear modulus, and Young's modulus mentioned in step (5) are calculated using Formula 3, Formula 3: Mechanical Properties

[0031]

[0032]

[0033]

[0034] In the formula, K is the bulk modulus, K V K is the approximate upper limit of the bulk modulus obtained by the Voigt method. R G is the approximate lower limit of the bulk modulus using the Reuss method, where G is the shear modulus. V G is the approximate upper limit of the shear modulus obtained by the Voigt method. R Here, E represents the approximate lower limit of the shear modulus using the Reuss method, and E is Young's modulus.

[0035] The larger the bulk modulus, shear modulus, and Young's modulus of the graphene-modified asphalt system, the better the modification effect of graphene on asphalt. Based on this method, the optimal graphene content in graphene-modified asphalt can be determined.

[0036] Furthermore, in step (5), the radial distribution functions of saturated components to saturated components, aromatic components to aromatic components, resins to resins, and asphaltenes to asphaltenes of the asphalt system and the graphene-modified asphalt system are obtained. When the distance between the peak intensities of the radial distribution functions of the four components is small, it indicates that graphene promotes the formation of a compact structure in the asphalt. Based on this method, the optimal graphene content of graphene-modified asphalt can be obtained.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] This invention, based on molecular dynamics simulations, uses Materials Studio software to construct amorphous unit cell models of graphene, asphalt, and graphene-modified asphalt molecular systems. It calculates solubility parameters, interaction energies, and mechanical properties, analyzes the radial distribution functions of the four components, and explains the interaction between graphene and asphalt from a molecular perspective. This overcomes the shortcomings of conventional macroscopic experiments, such as their cumbersome and complex processes, large errors in results, and significant influence from human factors. By setting different temperatures or graphene dosages, it provides a reference for the optimal mixing temperature and dosage of graphene-modified asphalt, offering a theoretical basis for the research and development of graphene-modified asphalt. Attached Figure Description

[0039] Figure 1 This is a model diagram of the amorphous unit cell of the graphene molecular system in Example 1;

[0040] Figure 2 This is a model diagram of the amorphous unit cell of the asphalt molecular system in Example 1;

[0041] Figure 3 This is an amorphous unit cell model of the graphene-modified pitch molecular system in Example 1. Detailed Implementation

[0042] 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. It should be noted that the specific embodiments used herein are merely illustrative of the invention and are not intended to limit the invention.

[0043] Example 1

[0044] A method for graphene-modified bitumen based on molecular dynamics simulations includes the following steps:

[0045] (1) The twelve molecular structures of the four components of asphalt were constructed using the sketch tool in MS software. The geometry of each molecular structure was optimized. Based on the measured content of the four components, an amorphous unit cell model of the asphalt molecular system was constructed using the Amorphous Cell module (see...). Figure 2 The asphalt consists of four components: saturated asphalt, aromatic asphalt, resins, and asphaltenes. The relevant parameters for geometric structure optimization are as follows: a COMPASS II force field is used, charge is distributed based on the force field, with a precision of Medium; electrostatic forces are summed using Ewald, and van der Waals forces are summed using Atom-based methods; the Smart algorithm is selected, with a maximum iteration count of 2000. The contents of saturated asphalt, aromatic asphalt, resins, and asphaltenes in the four components are determined according to the "Determination of Four Components of Petroleum Asphalt (NB / SH / T0509-2010)". The relevant parameters for the Amorphous Cell module are as follows: a COMPASS II force field is used, charge is distributed based on the force field, with a precision of Medium; electrostatic forces are summed using Ewald, and van der Waals forces are summed using Atom-based methods; the density is set to 0.2 g / cm³. 3 .

[0046] (2) The benzene rings were drawn using the Sketch tool in MS software, connected to form a single-layer structure, and after geometric optimization, an amorphous unit cell model of the graphene molecular system was constructed using the Amorphous Cell module (see...). Figure 1 The parameters for geometric structure optimization are as follows: COMPASS II force field is used; charge distribution is set by the force field with a precision of Medium; electrostatic forces are summed using Ewald; van der Waals forces are summed using Atombased; the Smart algorithm is selected; and the maximum number of iterations is set to 2000. The parameters for the Amorphous Cell module are as follows: COMPASS II force field is used; charge distribution is set by the force field with a precision of Medium; electrostatic forces are summed using Ewald; van der Waals forces are summed using Atombased; and the density is set to 0.2 g / cm³. 3 .

[0047] (3) After determining the graphene content to be 0.5%, the amorphous cell model of the graphene-modified pitch molecular system was constructed using the Amorphous Cell module in the software (see...). Figure 3 Select the Construction task in the Amorphous Cell module, use the COMPASS II force field, allocate the charge using the force field setting, set the precision to Medium, use Ewald summation for electrostatic forces, use Atom-based summation for van der Waals forces, and set the density to 0.2 g / cm³. 3 .

[0048] (4) The amorphous cell models of graphene molecular system, asphalt molecular system, and graphene-modified asphalt molecular system were subjected to a series of processes including geometric optimization, annealing, and relaxation using the Forcite module. Geometric optimization: The amorphous cell models of asphalt molecular system and graphene-modified asphalt were iteratively optimized for 20,000 steps, and the amorphous cell model of graphene molecular system was iteratively optimized for 2,000 steps; Annealing: The isothermal-isobaric ensemble (NPT) was selected, the temperature was set to 300-1000K, the pressure was set to 101kPa, the annealing cycle was 5 times, the time step was 1fs, the temperature controller was set to Nose, the pressure controller was set to Berendsen, and the annealing simulation time was 100ps; Relaxation: The simulation temperature was set to 298K (25℃), and the isothermal-isobaric ensemble (NVT) simulation calculation was performed for 200ps and the isothermal-isobaric ensemble (NPT) simulation calculation was performed for 500ps.

[0049] (5) Calculate the cohesive energy density of the graphene molecular system and the pitch molecular system using the Cohesive Energy Density function in the Forcite module, and calculate the solubility parameter according to Formula 1.

[0050] Formula 1: Solubility parameter

[0051]

[0052] 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.

[0053] (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.

[0054] Formula 2: Interaction Energy

[0055] E P =E abP -E aP -EbP ,

[0056] E V =E abV -E aV -E bV ,

[0057] E ε =E abε -E aε -E bε ,

[0058] In the formula, E P E represents the potential energy interaction energy between the graphene system and the asphalt system. abP E represents the potential energy of the graphene-modified asphalt system. aP E represents the potential energy of the graphene system. bP E represents the potential energy of the asphalt system. V E represents the van der Waals interaction energy between the graphene system and the pitch system. abV For van der Waals energy of graphene-modified bitumen systems, E aV For the van der Waals energy of the graphene system, E bV For van der Waals energy in bitumen systems, E ε E represents the electrostatic interaction energy between the graphene system and the asphalt system. abε E represents the electrostatic energy of the graphene-modified asphalt system. aε E represents the electrostatic energy of the graphene system. bε This refers to the electrostatic energy of the asphalt system.

[0059] (7) Calculate the approximate upper limit of the Voigt method bulk modulus / shear modulus and the approximate lower limit of the Reuss method bulk modulus / shear modulus for the asphalt molecular system and the graphene-modified asphalt molecular system using the Mechanical Properties function in the Forcite module. Calculate the bulk modulus, shear modulus, and Young's modulus according to Formula 3.

[0060] Formula 3: Mechanical Properties

[0061]

[0062]

[0063]

[0064] In the formula, K is the bulk modulus, K V K is the approximate upper limit of the bulk modulus obtained by the Voigt method. R G is the approximate lower limit of the bulk modulus using the Reuss method, where G is the shear modulus. V G is the approximate upper limit of the shear modulus obtained by the Voigt method.R Here, denoted by Reuss's method, the lower limit of the shear modulus is given, and E is Young's modulus.

[0065] (8) Using the Edit set tool, set the saturated components, aromatic components, resins and asphaltenes of the molecular dynamics simulation asphalt molecular system and the graphene modified asphalt molecular system to A, B, C and D, respectively. Use the Analysis function in the Forcite module to analyze the distance changes of the peak intensity of the radial distribution function of each component in the two molecular systems.

[0066] The closer the solubility parameters of the graphene system and the asphalt system are, the better the compatibility between graphene and asphalt. A negative interaction energy between the graphene system and the asphalt system indicates mutual attraction between the two systems; the larger the value, the more stable the graphene-asphalt blend, i.e., the better the compatibility. The compatibility between graphene and asphalt at different temperatures can be evaluated based on the solubility parameters and interaction energy.

[0067] The higher the bulk modulus, shear modulus, and Young's modulus of the graphene-modified asphalt system, the better the modification effect of graphene on asphalt. When the distance between the peak intensities of the radial distribution functions of the four components is small, it indicates that graphene promotes the formation of a compact structure in the asphalt. The modification effect of graphene-modified asphalt with different graphene dosages can be evaluated based on the mechanical properties and radial distribution functions.

[0068] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any changes, substitutions, optimizations, etc., made under the spirit and principle of the present invention are included within the protection scope of the present invention.

Claims

1. A method for graphene-modified bitumen based on molecular dynamics simulations, characterized in that, Includes the following steps: (1) Use MS software to construct amorphous unit cell models of pitch molecular system and graphene molecular system; (2) Select the graphene content ratio in the graphene-modified asphalt material, and use the two amorphous cell models obtained in step (1) to construct the amorphous cell model of the graphene-modified asphalt molecular system through the Amorphous Cell module in the software. (3) Molecular dynamics simulations were performed on the two stable amorphous unit cell models described in step (1) and the graphene-modified pitch amorphous unit cell model described in step (2); (4) Calculate the cohesive energy density of the graphene molecular system and the pitch molecular system, and then calculate their solubility parameters; The energies of the graphene-modified bitumen molecular system, as well as those of the system containing only graphene and bitumen molecules, are calculated, and then the interaction energies are calculated using Equation 2. Equation 2: Interaction Energy ， ， ， In the formula, E P E represents the potential energy interaction energy between the graphene system and the asphalt system. abP E represents the potential energy of the graphene-modified asphalt system. aP E represents the potential energy of the graphene system. bP E represents the potential energy of the asphalt system. V E represents the van der Waals interaction energy between the graphene system and the pitch system. abV For van der Waals energy of graphene-modified bitumen systems, E aV For the van der Waals energy of the graphene system, E bV For van der Waals energy in bitumen systems, E ε E represents the electrostatic interaction energy between the graphene system and the asphalt system. abε E represents the electrostatic energy of the graphene-modified asphalt system. aε E represents the electrostatic energy of the graphene system. bε The electrostatic energy of the asphalt system; (5) Calculate the bulk modulus, shear modulus, and Young's modulus of the asphalt molecular system and the graphene-modified asphalt molecular system; use the analysis function to obtain the radial distribution functions of each component in the asphalt molecular system and the graphene-modified asphalt molecular system, including the radial distribution functions of saturated components to saturated components, aromatic components to aromatic components, resins to resins, and asphaltenes to asphaltenes, so as to obtain the optimal graphene content of the graphene-modified asphalt; the bulk modulus, shear modulus, and Young's modulus are calculated by Formula 3, Formula 3: Mechanical Properties ， ， ， In the formula, K is the bulk modulus, K V K is the approximate upper limit of the bulk modulus obtained by the Voigt method. R G is the approximate lower limit of the bulk modulus using the Reuss method, where G is the shear modulus. V G is the approximate upper limit of the shear modulus obtained by the Voigt method. R Here, denoted by Reuss's method, the lower limit of the shear modulus is given, and E is Young's modulus.

2. The method according to claim 1, characterized in that, The amorphous cell model of the asphalt molecular system described in step (1) is constructed by optimizing the geometric structure of the twelve molecular model of the four components of asphalt and then using the Amorphous Cell module; the amorphous cell model of the graphene molecular system described in step (1) is constructed by drawing benzene ring phases connected into a single-layer structure using the sketch tool, optimizing the geometric structure, and then using the Amorphous Cell module.

3. The method according to claim 2, characterized in that, The contents of saturated components, aromatic components, resins, and asphaltenes in the four components of asphalt can be determined according to the "Determination of Four Components of Petroleum Asphalt (NB / SH / T 0509-2010)".

4. The method according to claim 2, characterized in that, The geometric optimization described in constructing the amorphous unit cell models of the asphalt molecular system and the graphene molecular system is as follows: the GeometryOptimization task in the Forcite module is selected, the COMPASS II force field is used, the charge is allocated by the force field setting, the accuracy is set to Medium, the electrostatic force is Ewald summation, the van der Waals force is Atombased summation, the Smart algorithm is selected, and the maximum number of iterations is set to at least 2000.

5. The method according to claim 1, characterized in that, The construction process described in step (2) is as follows: Select the Construction task in the Amorphous Cell module, use the COMPASS II force field, allocate the charge by setting the force field accuracy to Medium, use Ewald summation for electrostatic forces, use Atom-based summation for van der Waals forces, and set the density to 0.2-0.5 g / cm³. 3 .

6. The method according to claim 1, characterized in that, The molecular dynamics simulation in step (3) is performed as follows: First, the Geometry Optimization task in the Forcite module is used to iteratively optimize the amorphous cell model of the asphalt molecular system and the graphene-modified asphalt amorphous cell model for at least 20,000 steps, and the graphene molecular system amorphous cell model for at least 2,000 steps. Then, the Anneal task in the Forcite module is used to anneal the three amorphous cell models. The ensemble is selected as the isothermal and isobaric ensemble NPT, the temperature is set to 300-1000K, the pressure is set to 101kPa, the annealing cycle is 2-5 times, the time step is 1fs, the temperature controller is set to Nose, and the pressure controller is set to Berendsen. Finally, the Dynamic task in the Forcite module is used to perform isothermal and isobaric ensemble NVT simulation calculations for 200-500ps and isothermal and isobaric ensemble NPT simulation calculations for 200-500ps on the three amorphous cell models. Different temperatures are set to simulate the interaction between graphene and asphalt at different temperatures.

7. The method according to claim 1, characterized in that, The solubility parameter δ mentioned in step (4) is calculated by 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 the graphene molecular system and the asphalt molecular system are, the better the compatibility between graphene and asphalt.

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