Evaluation method for compatibility of gutta-percha modified asphalt based on molecular dynamics simulation

Abstract

The invention discloses a gutta-percha modified asphalt compatibility evaluation method based on molecular dynamics simulation, and belongs to the technical field of road modified asphalt compatibility. According to the method, an asphalt molecular model and a real gutta-percha molecular model are established, a gutta-percha modified asphalt molecular model is further obtained, a solubility parameter difference value and interaction energy are calculated, the compatibility of gutta-percha and asphalt of gutta-percha modified asphalt at different compatibility temperatures is evaluated, the modified asphalt compatibility evaluation method is enriched, and the evaluation accuracy is improved. The gap in the field of compatibility of the gutta-percha modified asphalt is filled, and the method has important significance in improving the stability of the gutta-percha modified asphalt.

Description

Technical Field

[0001] The invention belongs to the technical field of road modified asphalt compatibility, and in particular relates to a compatibility evaluation method for eucommia gum modified asphalt based on molecular dynamics simulation. Background Art

[0002] After nearly three decades of development in my country, asphalt pavement has become the main pavement structure in my country because of its good flatness, wear resistance, anti-skid and other properties. However, asphalt is also a temperature-sensitive composite material, and temperature changes directly affect its road performance. When the temperature is high in summer, the asphalt pavement begins to soften, and the road surface is prone to rutting, shifting, and congestion. When the temperature is low in winter, the road surface is prone to cracking, and the asphalt loses its ability to wrap the aggregate, causing the aggregate to fall off and form grooves. These diseases seriously affect driving comfort, increase maintenance costs, and endanger people's lives and property.

[0003] In recent years, in response to these problems, road workers at home and abroad have begun to develop modified asphalt, which can greatly enhance the ability of asphalt to resist various diseases and improve the performance of road surfaces. Currently, most common asphalt modifiers are polymer modifiers, such as styrene-butadiene-styrene (SBS) block copolymers, waste rubber powder (CR) Polyurethane (TPU), etc. Polymer modified asphalt is to improve the road performance of asphalt through physical blending, chemical blending or physical-chemical blending. No matter which blending method is used, it belongs to a two-phase blending system. The two-phase system can be divided into three types: one is a homogeneous system; the second is a "sea-island" structure, one phase is a continuous phase and the other phase is a dispersed phase; the third is a "sea-sea structure", both phases are continuous phases and penetrate each other. Polymer modified asphalt is mostly the latter two two-phase systems, so the compatibility of the two-phase system is the most important issue to consider. If the compatibility of asphalt and polymer is poor, segregation will occur, which seriously affects the performance of the modified asphalt.

[0004] At present, the evaluation methods for the compatibility of polymer modified asphalt are mainly through the separation softening point difference experiment and some microscopic microscopes to observe the phase structure, but both have certain limitations. Segregation softening point difference refers to the asphalt sample being divided into three parts after 48 hours of hot oxidation, and the difference between the upper and lower parts is taken to evaluate the compatibility of the modified asphalt. Although this method has some reference value, it cannot reflect the changes in the intrinsic properties of polymer modified asphalt; evaluating the compatibility of polymer modified asphalt by microscopic morphology is more intuitive, but it has high requirements for parts, and only morphology information can be obtained, so it is difficult to evaluate the compatibility of polymer modified asphalt by quantitative means.

[0005] In recent years, more and more scholars have begun to evaluate the compatibility of polymer modified asphalt from the molecular scale. Molecular dynamics (MD) simulation method is an effective method to determine material structure design and performance prediction from the molecular scale. MD simulation can fully consider the influence of temperature, potential energy, pressure and other conditions, making the simulation process more consistent with the actual process. Many scholars have used the MD principle to simulate the aging behavior, self-healing process and interface adhesion mechanism of polymer modified asphalt, which also provides a new research idea for evaluating the compatibility of polymer modified asphalt by using the MD principle.

[0006] The compatibility of polymer-modified asphalt has an important impact on road construction. The compatibility of different polymer-modified asphalts also varies greatly. The compatibility of modified asphalt is mostly caused by segregation due to the influence of high temperature. Therefore, temperature is a necessary key factor in exploring and evaluating the compatibility of modified asphalt. Chinese patent CN201910756241.1 provides an overview method for studying the compatibility of SBS and asphalt in SBS modified asphalt by molecular dynamics. The method does not further explore the actual working temperature, that is, it does not explore the changes in the compatibility of modified asphalt under different high temperatures. In summary, the current evaluation methods for the compatibility of polymer-modified asphalt all have certain limitations, and there is no related invention on the effect of temperature on the compatibility of eucommia gum and asphalt in eucommia gum modified asphalt. Summary of the invention

[0007] In view of the deficiencies in the above-mentioned prior art, the present invention provides a compatibility evaluation method for eucommia gum modified asphalt based on the principle of molecular dynamics, with the aim of enriching the evaluation means for the compatibility of polymer modified asphalt and filling the gap in the research field of compatibility of eucommia gum modified asphalt. The modeling process is standardized, the factors considered are reasonable, and the results are reliable.

[0008] In order to enrich the compatibility evaluation methods of polymer modified asphalt and fill the gaps in the compatibility research of eucommia gum modified asphalt, the present invention provides a molecular dynamics-based method for evaluating the compatibility of eucommia gum and asphalt in eucommia gum modified asphalt.

[0009] To achieve the above purpose, the present invention adopts the following technical solution: a method for evaluating the compatibility of eucommia gum modified asphalt based on molecular dynamics simulation, characterized in that it comprises the following specific steps: (1) According to the "Four-component Determination Method for Petroleum Asphalt (NB / SH / T-0509-2010)", the contents of saturated aromatics, aromatics, colloids and asphaltene in asphalt are obtained; (2) Use the Sketch function in Materials Studio software to draw representative molecules of each component of asphalt. The representative molecules of different asphalt components can be one or more; (3) Based on the molecular formula of the main components of Eucommia gum, a molecular model of Eucommia gum was constructed, and the number of repeating units of Eucommia gum when the solubility parameter calculated by cohesive energy density tended to be stable was used as the minimum molecular chain length of the actual Eucommia gum; (4) According to step (1) and step (2), the number of representative molecules in the asphalt is calculated respectively, and the molecular models of the base asphalt, aromatic component, asphaltenes, gum, and saturated component are constructed in sequence; according to step (3) and the proportion of eucommia gum, a molecular model of eucommia gum modified asphalt is constructed, which includes representative molecules of each component of asphalt and eucommia gum molecules with the smallest chain length; (5) Establish multiple conformations for each molecular model constructed in step (4), perform geometric optimization, select the conformation with the minimum energy for molecular dynamics annealing, and finally perform dynamic calculations under the NVT and NPT ensembles; (6) For the model processed in step (5), calculate the solubility parameters SP , molecular potential energy, to evaluate the compatibility of eucommia gum and asphalt; Solubility parameters ; ; ; ; In the formula, SP is the solubility parameter, CED is the cohesive energy density, J / cm 3 ; E abp , E abv , E abε Eucommia gum a 、 asphalt b Molecular potential energy, van der Waals potential energy, and electrostatic potential energy of the blend system, kJ / mol; E ap , E av , E aε Polymer Asphalt a Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; E bp , E bv , E bε Polymer Asphalt b Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; E p , E v , Eε Eucommia gum a , Asphalt b Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; (7) When the interaction energy is negative, it indicates that the eucommia gum system a , Asphalt system b Mutual attraction; (8) Changing the temperature in step (5) and repeating steps (4) to (6) respectively, the potential energy interaction energy at different compatibility temperatures can be obtained: E p , van der Waals interaction energy E v , electrostatic interaction energy E ε ; (9) Determine the optimal compatibility temperature of eucommia gum and asphalt; (10) Scanning electron microscopy tests were performed on eucommia gum modified asphalt at different compatibility temperatures to verify the above-mentioned optimal compatibility temperature point.

[0010] In step (3), the number of repeating units of the eucommia gum molecule is calculated every 5 in the range of 5-70, and it is determined that when the number of repeating units is 30-40, the solubility parameter tends to be stable.

[0011] In step (5), the number of geometry optimization conformations is 10, the force field is COMPASS, the number of iterations is 500,000, the van der Waals interaction is Atom based, and the electrostatic interaction is Ewald; the annealing temperature is 300-800K, and the number of iterations is 500,000; the temperature controller under NVT and NPT ensembles is Andersen, the pressure controller is Berendsen, the temperature range is between 373.15 and 453.15K, and the calculation time is 1000ps.

[0012] The temperatures selected in step (5) are 373.15K, 393.15K, 413.15K, 433.15K, and 453.15K, respectively.

[0013] In step (6), the SP The smaller the absolute value of the difference, the better the compatibility.

[0014] The larger the absolute value of the interaction energy in step (7), the stronger the interaction.

[0015] Based on the principle of molecular dynamics, the present invention constructs a molecular model of eucommia gum modified asphalt, separates the eucommia gum phase and the matrix asphalt phase, gives the compatibility of eucommia gum and asphalt under five different high temperature conditions, and combines scanning electron microscopy to verify the compatibility, which is more conducive to exploring the optimal compatibility temperature of eucommia gum and asphalt. The compatibility evaluation method of the present invention overcomes the shortcomings of existing experimental means, fills the gap in the compatibility evaluation of eucommia gum modified asphalt, provides a new idea for the compatibility evaluation system of eucommia gum modified asphalt, and is of great significance for clarifying the thermal storage stability of eucommia gum modified asphalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the solubility parameter of the molecular chain of Eucommia ulmoides with different numbers of repeating units; Figure 2 A true molecular chain of Eucommia ulmoides with 40 repeating units; Figure 3 Molecular model of eucommia gum modified asphalt; Figure 4 is the solubility parameter difference calculated in Example 1; Figure 5 is the interaction energy calculated in Example 1; Figure 6 The scanning electron microscope images of eucommia gum modified asphalt at different preparation temperatures are shown in the comparative example. DETAILED DESCRIPTION

[0017] In order to make the purpose, implementation scheme and technical advantages of the present invention clearer, the present invention is further described in detail in conjunction with the following examples. It should be understood that the following examples are only used to explain the present invention, but do not limit the present invention in any way. Example 1

[0018] The purpose of the present invention is to provide a method for simulating the compatibility of eucommia gum and asphalt in eucommia gum modified asphalt based on molecular dynamics. A 4-component 12-molecule asphalt model with high accuracy is selected. The process is standardized and rigorous, and has high reliability. The specific implementation steps are as follows: (1) According to the "Four-component Determination Method for Petroleum Asphalt (NB / SH / T-0509-2010)", the contents of saturated aromatics, aromatics, colloids and asphaltene in asphalt are obtained; (2) Use the Sketch function in Materials Studio software to draw molecular models representing each component of asphalt, and perform geometric optimization on each model to find reasonable bond lengths and bond angles in order to obtain stable molecular models of each component; the representative molecules of different asphalt components can be one or more; (3) Based on the molecular formula of the main components of Eucommia gum, molecular models of Eucommia gum with different numbers of repeating units were constructed, and the number of repeating units of Eucommia gum when the solubility parameter calculated by cohesive energy density tended to be stable was taken as the minimum molecular chain length of the actual Eucommia gum molecular chain, such as Figure 1 , 2 As shown in the figure, the number of repeating units of Eucommia ulmoides gum molecules was calculated every 5 units in the range of 5-70, and it was determined that when the number of repeating units was 30-40, the solubility parameter tended to be stable. (4) According to step (1) and step (2), the number of representative molecules in the asphalt is calculated respectively, and the molecular models of the base asphalt, aromatic component, asphaltenes, gum, and saturated component are constructed in sequence; according to step (3) and the proportion of eucommia gum, a molecular model of eucommia gum modified asphalt is constructed, which includes representative molecules of each component of asphalt and eucommia gum molecules with the smallest chain length; (5) Establish multiple conformations for each molecular model constructed in step (4) and perform geometry optimization with an initial density of 0.1 g / cm 3 , the number of conformations is 10, and the number of molecular models of each component is adjusted to make its proportion the same as the experimentally measured proportion of each component. Then, a 100,000-step structural optimization is performed. After the structural optimization is completed, annealing is performed under the NPT ensemble, and the annealing temperature is 300~800K. Finally, the annealed molecular model is subjected to dynamic NVT and NPT calculations. The ensemble temperature controller is Andersen, the pressure controller is Berendsen, the temperature is 373.15K, and the calculation time is 1000ps. Figure 3 As shown; (6) For the model processed in step (5), calculate the solubility parameters SP , molecular potential energy, to evaluate the compatibility of eucommia gum and asphalt; Solubility parameters ; ; ; ; In the formula, SP is the solubility parameter, CED is the cohesive energy density, J / cm 3 ; E abp , E abv , E abε Eucommia gum a 、 asphalt b Molecular potential energy, van der Waals potential energy, and electrostatic potential energy of the blend system, kJ / mol; E ap , E av, E aε Polymer Asphalt a Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; E bp , E bv , E bε Polymer Asphalt b Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; E p , E v , E ε Eucommia gum a , Asphalt b Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; (7) When the interaction energy is negative, it indicates that the eucommia gum system a , Asphalt system b Mutual attraction; (8) Change the temperature in step (5) to 393.15K, 413.15K, 433.15K, and 453.15K, and repeat steps (4) to (6) respectively to obtain the potential energy interaction energy at different compatible temperatures: E p , van der Waals interaction energy E v , electrostatic interaction energy E ε ,like Figure 5 As shown; (9) Determine the optimal compatibility temperature of eucommia gum and asphalt according to Figure 5 It can be judged that the optimal compatibility temperature of eucommia gum and asphalt is 433.15K; (10) To verify the accuracy of the results of the present invention, eucommia gum modified asphalt was prepared at 375.15K, 393.15K, 413.15K, 433.15K and 453.15K, respectively. The eucommia gum modified asphalt at different compatibility temperatures was tested by scanning electron microscopy. Figure 6 It can be seen that eucommia gum and asphalt have good compatibility at 433.15K, most of the eucommia gum particles are wrapped by asphalt, and the dispersion is more uniform, which is the same as the conclusion obtained in the above steps.

Claims

1. A method for evaluating the compatibility of eucommia gum modified asphalt based on molecular dynamics simulation, characterized in that: The following specific steps are included: (1) According to the "Four-component Determination Method for Petroleum Asphalt (NB / SH / T-0509-2010)", the contents of saturated aromatics, aromatics, colloids and asphaltene in asphalt are obtained; (2) Use the Sketch function in Materials Studio software to draw representative molecules of each component of asphalt. The representative molecules of different asphalt components can be one or more; (3) Based on the molecular formula of the main components of Eucommia gum, a molecular model of Eucommia gum was constructed, and the number of repeating units of Eucommia gum when the solubility parameter calculated by cohesive energy density tended to be stable was used as the minimum molecular chain length of the actual Eucommia gum; (4) According to step (1) and step (2), the number of representative molecules in the asphalt is calculated respectively, and the molecular models of the base asphalt, aromatic component, asphaltenes, gum, and saturated component are constructed in sequence; according to step (3) and the proportion of eucommia gum, a molecular model of eucommia gum modified asphalt is constructed, which includes representative molecules of each component of asphalt and eucommia gum molecules with the smallest chain length; (5) Establish multiple conformations for each molecular model constructed in step (4), perform geometric optimization, select the conformation with the minimum energy for molecular dynamics annealing, and finally perform dynamic calculations under the NVT and NPT ensembles; (6) For the model processed in step (5), calculate the solubility parameters SP , molecular potential energy, to evaluate the compatibility of eucommia gum and asphalt; Solubility parameters ; ； ； ； In the formula, SP is the solubility parameter, CED is the cohesive energy density, J / cm 3 ; E abp , E abv , E abε Eucommia gum a 、 asphalt b Molecular potential energy, van der Waals potential energy, and electrostatic potential energy of the blend system, kJ / mol; E ap , E av , E aε Polymer Asphalt a Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; E bp , E bv , E bε Polymer Asphalt b Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; E p , E v , E ε Eucommia gum a , Asphalt b Molecular potential energy, van der Waals potential energy, electrostatic potential energy, kJ / mol; (7) When the interaction energy is negative, it indicates that the eucommia gum system a , Asphalt system b Mutual attraction; (8) Changing the temperature in step (5) and repeating steps (4) to (6) respectively, the potential energy interaction energy at different compatibility temperatures can be obtained: E p , van der Waals interaction energy E v , electrostatic interaction energy E ε ; (9) Determine the optimal compatibility temperature of eucommia gum and asphalt; (10) Scanning electron microscopy tests were performed on eucommia gum modified asphalt at different compatibility temperatures to verify the above-mentioned optimal compatibility temperature point.

2. The method for evaluating the compatibility of eucommia gum modified asphalt based on molecular dynamics simulation according to claim 1, characterized in that: In step (3), the number of repeating units of the eucommia gum molecule is calculated every 5 in the range of 5-70, and it is determined that when the number of repeating units is 30-40, the solubility parameter tends to be stable.

3. The method for evaluating the compatibility of eucommia gum modified asphalt based on molecular dynamics simulation according to claim 1, characterized in that: In step (5), the number of geometry optimization conformations is 10, the force field is COMPASS, the number of iterations is 500,000, the van der Waals interaction is Atom based, and the electrostatic interaction is Ewald; the annealing temperature is 300-800K, and the number of iterations is 500,000; the temperature controller under NVT and NPT ensembles is Andersen, the pressure controller is Berendsen, the temperature range is between 373.15 and 453.15K, and the calculation time is 1000ps.

4. The method for evaluating the compatibility of eucommia gum modified asphalt based on molecular dynamics simulation according to claim 3, characterized in that: The temperatures selected in step (5) are 373.15K, 393.15K, 413.15K, 433.15K, and 453.15K, respectively.

5. The method for evaluating the compatibility of eucommia gum modified asphalt based on molecular dynamics simulation according to claim 1, characterized in that: In step (6), the SP The smaller the absolute value of the difference, the better the compatibility.

6. The method for evaluating the compatibility of eucommia gum modified asphalt based on molecular dynamics simulation according to claim 1, characterized in that: The larger the absolute value of the interaction energy in step (7), the stronger the interaction.

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