Asphalt pavement microparticle generation simulation method based on molecular dynamics

Abstract

The invention provides an asphalt pavement microparticle generation simulation method based on molecular dynamics, belongs to the technical field of road traffic environments, and solves the problems that the interaction behavior of a tire and an asphalt pavement cannot be analyzed from the molecular level and a micromechanism generated by microparticles in the friction process cannot be revealed in the prior art. By means of a molecular dynamics simulation method, firstly, a modified asphalt molecule, tire rubber molecule and aggregate base model is built, and after the reasonability is verified, a three-layer interface contact model is built; after energy optimization, friction simulation is carried out through a Confined Shear task under a set working condition, and a micromechanism generated by microparticles is systematically revealed by analyzing conditions such as system energy change, atom motion trail and chemical bond fracture. The method breaks through the limitation of a traditional macroscopic test, reveals a microparticle generation mechanism from a microcosmic angle, and provides a theoretical basis for developing environment-friendly low-wear asphalt pavement materials and tires and controlling pavement microplastic pollution from the source.

Description

Technical Field

[0001] This invention is a method for simulating the generation of microparticles on asphalt pavement based on molecular dynamics, belonging to the field of road traffic environment technology. Background Technology

[0002] In recent years, road traffic pollution has become a severe challenge faced by countries worldwide, with studies indicating it accounts for more than a quarter of total environmental pollution. Road traffic pollution is divided into exhaust emission pollution and non-exhaust emission pollution. While exhaust emission pollution has been significantly reduced due to improved emission standards and purification technologies in various countries, as well as the widespread adoption of new energy vehicles, non-exhaust emission pollution remains serious. Microparticles formed from tire and road wear are a significant component of non-exhaust emissions. Asphalt pavement, currently the primary road paving material, is widely used due to its excellent construction, road performance, and maintenance characteristics. However, during long-term use, asphalt pavement is subjected to friction from vehicle tires, leading to wear on the asphalt film and tire surface, resulting in the formation of tiny asphalt and tire wear particles. Due to their material properties and small particle size, asphalt and tire wear particles perfectly meet the definition of microplastics and are one of the main sources of road microplastics.

[0003] After their formation, asphalt microparticles and tire wear microparticles are mainly deposited in and around roads. Some are carried into the soil or nearby water bodies by surface runoff, while other extremely fine particles can remain suspended in the atmosphere and migrate. Tire wear microparticles typically contain rubber additives, vulcanization accelerators, polycyclic aromatic hydrocarbons, and heavy metals such as zinc and cadmium. Asphalt, derived from petroleum refining residues, contains highly stable hydrocarbon compounds, sulfides, and various metal elements adsorbed on its surface. Due to their wide environmental distribution, complex chemical composition, and high persistence, these microparticles may enter the human body through inhalation or accumulate in the ecosystem via water migration, ultimately posing a potential threat to human health through the food chain.

[0004] Numerous studies have been conducted on tire wear particles, providing extensive information on their emission factors, particle size distribution, physicochemical properties, and impacts on biology and the environment. Some researchers have simulated tire wear particle generation in the laboratory by creating devices that mimic tire-road friction under simulated vehicle conditions. By obtaining the microscopic morphology of tire wear particles generated on simulated road surfaces at different vehicle speeds, tire pressures, and with different materials, the influence of various factors on tire wear particle generation has been determined. Furthermore, some researchers have collected tire wear particle samples from different road surfaces for particle size and chemical composition analysis. By combining the distribution of tire wear particles at different sampling points with road type and traffic flow information, emission factors for tire wear particles in certain regions have been calculated. However, research on asphalt particles generated from asphalt wear on asphalt pavements is relatively weak. Researchers have obtained road surface microparticle samples through field sampling, and then separated enriched tire wear microparticles and asphalt microparticles by density separation. They employed various modern analytical techniques, including scanning electron microscopy-energy dispersive spectroscopy and micro-Fourier transform infrared spectroscopy, to analyze the morphology and chemical composition of the microparticles. Currently, research on asphalt microparticles mostly focuses on macroscopic quantitative analysis or single-particle physicochemical property analysis; research on the formation mechanism of asphalt microparticles is almost nonexistent.

[0005] Currently, molecular dynamics simulation technology has been widely applied in research on asphalt pavement materials and rubber materials. Many scholars have used molecular dynamics simulations to study the compatibility of asphalt with modified materials, asphalt aging behavior, asphalt self-healing behavior, and water damage. Some researchers have applied molecular dynamics simulations to study tire-road friction. By establishing an interfacial contact model of the tire, asphalt layer, and aggregate substrate, they simulated the frictional behavior of the tire and aggregate under different environments, analyzing the influence of various environmental conditions, including road surface materials, vehicle speed, and road surface temperature, on the road surface friction coefficient.

[0006] Therefore, existing research mostly focuses on studying tire wear particles through macroscopic experimental methods such as simulation device tests and road surface sampling, concentrating on the effects of factors such as road surface type, vehicle speed, and tire pressure. Research on asphalt particles largely remains at the level of quantitative analysis and physicochemical property analysis. These macroscopic research methods struggle to reveal the mechanisms of particle generation during friction from a microscopic perspective, and cannot analyze the behavior of tire-road interaction at the molecular level. Existing molecular dynamics research largely focuses on the tribological behavior itself, paying insufficient attention to the generation mechanisms of particles during tire and asphalt pavement wear, and lacks a simulation method capable of revealing the generation of asphalt and tire wear particles at the microscopic level.

[0007] Therefore, this invention proposes a molecular dynamics-based simulation method for the generation of microparticles on asphalt pavements. By constructing a friction model of tire rubber and asphalt pavement, molecular dynamics simulation technology is used to analyze the energy changes, atomic motion trajectories, and chemical bond breaking of microparticles during the friction process. This systematically reveals the generation mechanism of asphalt microparticles and tire wear microparticles on asphalt pavements caused by friction between tires and asphalt pavement from a microscopic and molecular perspective. This is of great significance for fundamentally understanding road pollution and guiding the development of green road materials. Summary of the Invention

[0008] (1) Technical issues

[0009] The purpose of this invention is to provide a molecular dynamics-based simulation method for the generation of microparticles on asphalt pavements. This method uses molecular dynamics simulation technology to analyze the generation of microparticles and the corresponding energy changes, atomic motion trajectories, and chemical bond breaking during the friction between tires and asphalt pavements. It reveals the generation mechanism of asphalt microparticles and tire wear microparticles on asphalt pavements from a microscopic and molecular perspective. This solves the problems that existing macroscopic experiments or pavement sampling analysis techniques cannot analyze the interaction behavior between tires and pavements at the molecular level and are unable to reveal the microscopic mechanism of microparticle generation during the friction between tires and asphalt pavements.

[0010] (2) Technical solution

[0011] Given that current technologies cannot analyze the interaction behavior between tires and asphalt pavements at the molecular level, or reveal the microscopic mechanisms of asphalt microparticle and tire wear microparticle generation during tire-asphalt pavement friction, this invention primarily utilizes molecular dynamics simulation technology to analyze the generation of microparticles on asphalt pavements using a tire rubber and asphalt pavement friction model. This systematically reveals the generation mechanisms of asphalt microparticles and tire wear microparticles on asphalt pavements from a microscopic, molecular perspective. The technical solution of this invention is as follows: First, a modified asphalt molecular model, a tire rubber molecular model, and an aggregate substrate model are constructed, and the rationality of each model is verified. Then, using corresponding software modules, the tire rubber molecular model is used as the first layer, the modified asphalt molecular model as the second layer, and the aggregate substrate model as the third layer, thereby constructing an interface contact model for tire-asphalt pavement friction. Reasonable model dimensions, interface distances, and boundary conditions are set, and the interface model undergoes structural optimization and annealing. Finally, friction simulations are performed under set temperature, pressure, and velocity conditions in the interface model with the lowest energy. Based on the intermolecular interaction energy, atomic motion trajectories, and bond state changes during friction, the mechanisms of asphalt microparticle and tire wear microparticle generation on asphalt pavements are systematically revealed.

[0012] (3) Beneficial effects

[0013] Asphalt pavement is widely used due to its excellent properties. However, friction between the pavement and tires causes wear on the asphalt film and tire surface, resulting in the formation of tiny asphalt and tire wear particles. These particles are a major source of microplastics in asphalt pavement. These particles migrate to roadside soil and water bodies via surface runoff or diffuse into the atmosphere, posing a threat to human health and the environment. This invention utilizes molecular dynamics simulation technology to analyze the generation mechanism of microparticles during asphalt pavement-tire friction from a microscopic, molecular perspective. This method overcomes the limitations of traditional macroscopic experiments, which can only observe results but not reveal the underlying mechanisms. It accurately reveals the microscopic behavior of molecular chain breakage, interfacial peeling, and microparticle formation during friction, simultaneously analyzing the generation pathways of asphalt and tire wear particles within the same simulation system, establishing a unified and comparable analytical framework. Based on this, the present invention can provide a theoretical basis for the molecular design of low-wear asphalt pavement materials and environmentally friendly tires, promote the green development of transportation materials, and help identify the main links and key factors in the generation of microparticles, providing scientific support for controlling road microplastic pollution at the source and promoting the coordinated development of road traffic and the environment. Detailed Implementation

[0014] This invention provides a method for simulating the generation of microparticles on asphalt pavements based on molecular dynamics, and the specific implementation steps are as follows:

[0015] (1) Based on the selected typical road section pavement asphalt type, construct molecular models of asphalt, resin, aromatics, saturated components and modifiers in the Visualizer module of Materials Studio software. Use the Amorphous Cell module to mix the four asphalt component molecules and modifier molecules according to the actual mass ratio of the main components of modified asphalt, place them in the same cell, set a reasonable density, and construct the modified asphalt molecular model.

[0016] (2) The modified asphalt molecular model was structurally optimized and annealed at room temperature to minimize the model energy. Molecular dynamics simulation was performed on the model, and the simulated density value was compared with the density value measured by the modified asphalt test to verify the rationality of the modified asphalt molecular dynamics model.

[0017] (3) Based on the main components of the tire, a molecular chain model of polyisoprene and styrene-butadiene copolymer was constructed in the Visualizer module, with the degree of polymerization set to 60. Simultaneously, molecular models of disulfide and trisulfide were constructed. Using the AmorphousCell module, the two molecular chain models, disulfide and trisulfide molecular models were mixed according to the actual mass ratio of the main components of the tire and placed in the same unit cell. A reasonable density value was set. The chemical reaction between disulfide, trisulfide and the two molecular chains was simulated through the crosslinking script to form a crosslinking network structure. Then, the tire rubber molecular model was structurally optimized and annealed to ensure that the molecular system reached the lowest energy state. Finally, the rationality of the tire rubber molecular dynamics model was verified through molecular dynamics simulation.

[0018] (4) Import the SiO2 molecular model from the Materials Studio structure library, use the CleaveSurfaces tool in Build to cut out its crystal planes, use the Build Vacuum Slab tool to expand it into a plate-like model with a certain thickness, and set a sufficient vacuum layer to accommodate the modified asphalt molecule and tire rubber molecule model above to build the aggregate substrate model.

[0019] (5) In the Build Layers function, add a tire rubber molecular model as the first interface, a modified asphalt molecular model as the second interface, and an aggregate substrate model as the third interface to construct a tire and asphalt pavement interface contact model. Then, perform structural optimization and annealing on the interface model and select the interface model with the lowest energy as the initial model for molecular dynamics simulation.

[0020] (6) Using the Confined Shear task of the Forcite module, fix all atoms at the bottom of the aggregate substrate, and simulate the moving friction behavior of the tire on the asphalt road by applying a shear load and a moving speed along the x-axis to the first layer of tire rubber molecular model.

[0021] (7) The total energy, kinetic energy, potential energy and non-bonded interaction energy between modified asphalt molecules and tire rubber molecules in the simulation process are obtained by using the Analysis function of the Forcite module. The friction coefficient is calculated by the shear stress and normal stress of the system in the moving direction. The fracture and peeling process of modified asphalt molecules and tire rubber molecules and the formation of microparticles are directly observed according to the atomic motion trajectory on the interface. The number of chemical bonds broken during the friction process is counted by the analysis tool of Materials Studio. The atomic motion trajectory and molecular conformation changes are analyzed to determine the specific location and mode of interfacial contact wear and reveal the mechanism of microparticle generation on asphalt pavement.

Claims

1. A method for simulating the generation of microparticles on asphalt pavement based on molecular dynamics, characterized in that... The specific steps of this method are as follows: (1) Based on the selected typical road section pavement asphalt type, construct molecular models of asphalt, resin, aromatics, saturated components and modifiers in the Visualizer module of Materials Studio software. Use the Amorphous Cell module to mix the four asphalt component molecules and modifier molecules according to the actual mass ratio of the main components of modified asphalt, place them in the same cell, set a reasonable density, and construct the modified asphalt molecular model. (2) The modified asphalt molecular model was structurally optimized and annealed at room temperature to minimize the model energy. Molecular dynamics simulation was performed on the model, and the simulated density value was compared with the density value measured by the modified asphalt test to verify the rationality of the modified asphalt molecular dynamics model. (3) Based on the main components of the tire, a molecular chain model of polyisoprene and styrene-butadiene copolymer was constructed in the Visualizer module, with the degree of polymerization set to 60. Simultaneously, molecular models of disulfide and trisulfide were constructed. Using the AmorphousCell module, the two molecular chain models, disulfide and trisulfide molecular models were mixed according to the actual mass ratio of the main components of the tire and placed in the same unit cell. A reasonable density value was set. The chemical reaction between disulfide, trisulfide and the two molecular chains was simulated through the crosslinking script to form a crosslinking network structure. Then, the tire rubber molecular model was structurally optimized and annealed to ensure that the molecular system reached the lowest energy state. Finally, the rationality of the tire rubber molecular dynamics model was verified through molecular dynamics simulation. (4) Import the SiO2 molecular model from the Materials Studio structure library, use the Cleave Surfaces tool in Build to cut out its crystal planes, use the Build Vacuum Slab tool to expand it into a plate-like model with a certain thickness, and set a sufficient vacuum layer to accommodate the modified asphalt molecule and tire rubber molecule model above to build the aggregate substrate model. (5) In the Build Layers function, add a tire rubber molecular model as the first interface, a modified asphalt molecular model as the second interface, and an aggregate substrate model as the third interface to construct a tire and asphalt pavement interface contact model. Then, perform structural optimization and annealing on the interface model and select the interface model with the lowest energy as the initial model for molecular dynamics simulation. (6) Using the Confined Shear task of the Forcite module, fix all atoms at the bottom of the aggregate substrate, and simulate the moving friction behavior of the tire on the asphalt road by applying a shear load and a moving speed along the x-axis to the first layer of tire rubber molecular model. (7) The total energy, kinetic energy, potential energy and non-bonded interaction energy between modified asphalt molecules and tire rubber molecules in the simulation process are obtained by using the Analysis function of the Forcite module. The friction coefficient is calculated by the shear stress and normal stress of the system in the moving direction. The fracture and peeling process of modified asphalt molecules and tire rubber molecules and the formation of microparticles are directly observed according to the atomic motion trajectory on the interface. The number of chemical bonds broken during the friction process is counted by the analysis tool of Materials Studio. The atomic motion trajectory and molecular conformation changes are analyzed to determine the specific location and mode of interfacial contact wear and reveal the mechanism of microparticle generation on asphalt pavement.