The asphalt-aggregate interface interaction plays a significant role in the overall performances of asphalt mixture. In order to analyze the chemical constitution of asphalt effects on the asphalt-aggregate interaction, the average structure C64H52S2 is selected to represent the asphalt, and the colloid, saturated phenol, and asphaltene are selected to represent the major constitutions in asphalt. The molecular models are established for the three compositions, respectively, and the Molecular Dynamics (MD) simulation was conducted for the three kinds of asphaltene-aggregate system at different presses. Comparing the
At present, scholars at home and abroad have more and more research perspectives on polymer materials [
In order to analyze the chemical constitution of asphalt on the AAI, the average structure C65H74N2S2 is selected in this paper to represent the asphalt and the colloid; saturated phenol and asphaltene are selected to represent the major constitution in asphalt. The molecular models are established for the three compositions, respectively, and the MD simulation was conducted for the three kinds of asphaltene-aggregate system at different presses.
When the force acts on the system and if the whole system is balanced, the external force suffered in the system will have an absolute balance with the internal force generated inside the system. Normally, stress can be expressed as a second-order tensor containing 9 components as shown in
In the process of molecular calculation, internal stress tensor can be expressed by the virial expression of
In formula (
Once stress acts on the molecular system, the position of internal particles of system will change relatively, where the change is expressed by the strain tensor of
For the parallel hexahedron structured in this paper, strain tensor is only determined by the column vectors
Elastic stiffness constant is associated with the different compositions of system stress and strain. With regard to small deformation, the relationship between stress and strain meets Hooke’s law, as shown in
Since stress tensor and strain tensor have some symmetry, stress formula (
Stain formula (
Suppose that the materials prepared are isotropic, and the stress and strain only depend on two independent coefficients. Stiffness matrix is shown as
In addition, with regard to isotropic materials, the Yong modulus
Long chain of colloid for the degree of polymerization at 15.
Forcite module was used to analyze geometry optimization for the long chain of colloid. Figure
Long chain of colloid after being geometrically optimized.
Afterwards, a cubic vacuum space in
Initial model of colloid at the density of 0.1.
The density of initial model is 0.1 g/cc, and the density was in the range of 0.99~1.1 g/cm3 at abnormal temperature; however, the low density system of Figure
Change graph of temperature with simulation time after NPT dynamics finished.
System temperature fluctuated
Partial enlarged detail of temperature change
Change of system energy with simulation time.
Change of (a) system density and (b) system length of side with time.
Change of (a) system density and (b) system length of side with time at 0.08 GPa.
It can be seen from Figure
It was obtained from Figure
It can be seen from Figure
Ultimately obtained colloid system.
Stiffness matrix obtained from colloid model (GPa).
|
1 | 2 | 3 | 4 | 5 | 6 |
---|---|---|---|---|---|---|
1 | 4.5089 | 2.8995 | 3.1170 | 0.1436 | 0.4446 | −0.3247 |
2 | 2.8995 | 6.6093 | 3.5637 | −0.0619 | −0.4925 | 0.2330 |
3 | 3.1170 | 3.5637 | 4.5407 | 0.9075 | 0.6968 | −0.1275 |
4 | 0.1436 | −0.0619 | 0.9075 | 1.5682 | 0.5402 | 0.2406 |
5 | 0.4446 | −0.4925 | 0.6968 | 0.5402 | 1.1374 | −0.0765 |
6 | −0.3247 | 0.2330 | −0.1275 | 0.2406 | −0.0765 | 0.0809 |
It can be seen from Table
After substituting
Initial model of saturated phenol at the density of 0.1.
Change of (a) system density and (b) system length of side with time at 0.01 GPa.
The true saturated density is 0.7944 g/cc, and thus the system should be compressed to increase the density and decrease the length of side. After optimizing the structure, NVT ensemble was conducted, and subsequently NPT ensemble was conducted stable again under 0.01 GPa and 298 K. The output temperature and energy curves tended to be stable and balanced with the changes of time after dynamics. The changes of density and the length of side of system can be seen in Figure
It can be seen from Figure
Change of system density with time at 0.02 GPa.
It can be seen from Figure
Ultimately saturated phenol model.
Stiffness matrix obtained for saturated phenol model.
|
1 | 2 | 3 | 4 | 5 | 6 |
---|---|---|---|---|---|---|
1 | 1.7170 | 1.3630 | 1.8868 | −0.2839 | 0.4201 | −0.4593 |
2 | 1.3630 | 2.0288 | 2.0845 | −0.3727 | 0.2747 | 0.0954 |
3 | 1.8868 | 2.0845 | 1.7931 | −0.1096 | 0.2204 | −0.0308 |
4 | −0.2829 | −0.3727 | −0.1096 | 0.1437 | −0.0936 | 0.1666 |
5 | 0.4201 | 0.2747 | 0.2204 | −0.0936 | 0.1250 | −0.1628 |
6 | −0.4593 | 0.0954 | −0.0308 | 0.1666 | −0.1628 | 0.2710 |
It can be seen from Table
Suppose the material is isotropic, and the calculation of lame constant can be seen in
After substituting
Initial model of asphaltene at the density of 0.1.
Under the temperature of 298 K, the true density of asphaltene was approximately 0.89 g/cm3 that the system must be compressed to increase the density and decrease the length of side. After optimizing the structure, NVT ensemble was conducted. Subsequently, NPT was conducted to stable system under 0.06 GPa and 298 K. The changes of system density and length of side are shown in Figure
Change of (a) system density and (b) system length of side with time at 0.06 GPa.
System density
System length of side
It can be seen from Figure
Ultimate model of asphaltene.
Stiffness matrix obtained for asphaltene model.
|
1 | 2 | 3 | 4 | 5 | 6 |
---|---|---|---|---|---|---|
1 | 7.8405 | 1.5765 | 1.9309 | −0.3414 | 1.3945 | −0.9280 |
2 | 1.5765 | 1.8645 | 0.6143 | −0.2868 | 0.4326 | −1.0948 |
3 | 1.9309 | 0.6143 | 2.5698 | −0.2413 | 0.1393 | −0.0903 |
4 | −0.3414 | −0.2868 | −0.2413 | 1.1054 | 0.0539 | 0.1551 |
5 | 1.3945 | 0.4326 | 0.1393 | 0.0539 | 1.2063 | −0.1860 |
6 | −0.9280 | −1.0948 | −0.0903 | 0.1551 | −0.1860 | 0.8541 |
Suppose the material is isotropic, and the calculation of lame constant is shown in
After substituting
The calculation of mechanical properties was conducted to the groups of colloid, saturated phenol, and asphaltene, respectively, and the parameters of stiffness and modulus of all the materials were obtained. Comparing the
The authors declare that there are no conflicts of interest regarding the publication of this paper.
The research was supported by the National Natural Science Foundation of China (Grant nos. 51378073 and 51408048), the Key Program for Science and Technology Projects of Shaanxi province (Grant no. 2017KCT-13), the science and technology projects of Shaanxi Provincial Transport Department (Grant no. 15-35T), and the Special Financial Grant from the China Postdoctoral Science Foundation (Grant no. 2016T90880).