Polymer Modified Asphalt Storage Stability Enhancing the Interfacial Adhesion
Carbon nanotubes (CNTs) can improve modified asphalt storage qualities by enhancing the interfacial adhesion of recycled polyethylene (RPE) and base asphalt.
polymer modified asphalt cement
In this study, the interaction of CNT/RPE asphalt was explored using molecular dynamics modeling factoring in the polymer stability.
A 12-component molecular model was used to analyze the base asphalt, and its validity was evaluated by evaluating its four-component content, elemental contents, radial distribution function (RDF), and glass transition temperature.
The adhesion characteristics of CNT/RPE-modified asphalt molecules were then studied using binding energy measurements.
A relative concentration distribution study was used to investigate the molecular structural stability of CNTs at the interface between RPE and asphalt molecules.
The mean square displacement (MSD) and diffusion coefficient were used to study the molecular mobility of modified asphalt.
CNTs boosted the binding energy between RPE and base asphalt, according to the findings.
CNTs inhibited RPE's attraction to asphaltenes and resins while increasing RPE interaction with light components, making RPE easier to mix with basic asphalt.
The interaction affected molecular motion, and the CNT/RPE-modified asphalt combination had a considerably lower molecular diffusion coefficient than RPE-modified asphalt.
Furthermore, CNTs aided in the distribution of the asphaltene component, improving the storage stability of RPE-modified asphalt.
Better viscoelastic properties were also reported, and CNTs greatly improved storage stability, according to the property indices.
Our findings lay the groundwork for the use of RPE in pavement engineering.
Humanity has currently created over 8.
3 billion tons of virgin plastics and over 6300 metric tons of plastic garbage, the most majority of which is dumped in nature and poses a huge environmental risk.
Plastic waste recycling is a global issue.
Because of its numerous advantages, including high consumption and low energy consumption, road engineering has emerged as a feasible method of consuming and recycling plastic debris.
High-density polyethylene (HPPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polyurethane resins are the most common materials used to make plastics.
PE has been proven to increase asphalt's high-temperature performance, low-temperature performance, and fatigue resistance as a modifier.
PE improves asphalt's thermodynamic, chemical, and physical qualities.
Furthermore, the molecular structure of PE has a significant impact on modified asphalt capabilities, with MDPE-modified asphalt having the best rutting resistance and highly branched PE-modified asphalt demonstrating superior low-temperature performance.
PE-modified asphalt also has better adhesion, elasticity, and hardness than matrix asphalt.
Because it can improve the functionality of the asphalt matrix and aid in the eradication of "white pollution," PE-modified asphalt has aroused a lot of attention.
However, because of insufficient interaction between PE and the asphalt matrix, severe stability difficulties arise while producing and storing PE-modified asphalt.
polymer modified asphalt emulsion
Numerous additives, the most common of which are carbon nanotubes (CNTs), have been used to improve the storage stability of asphalt treated with PE.
Carbon nanotubes (CNTs) are tubular one-dimensional (1D) carbon nanomaterials that have gotten a lot of attention.
It has favorable thermodynamic properties, mechanical strength, and surface area specificity.
When carbon nanotubes (CNTs) are added to the matrix of PE-modified asphalt, the weak interface between PE and asphalt is significantly strengthened, increasing the modified asphalt's high-temperature performance and storage stability.
Previous research has concentrated on the CNT-enhanced effect on PE-modified asphalt, but the microscopic mechanism behind this phenomenon is unknown, making designing the directional properties of modified asphalt difficult.
Several methodologies have been utilized to investigate the mechanics of asphalt alteration.
SEM can be used to investigate the properties of the interface between the modifier and the asphalt matrix; fluorescence microscopy can be used to observe the biphasic structure of modified asphalt, and Fourier infrared spectroscopy (FTIR) can be used to identify group changes in the modified asphalt system.
To some extent, these techniques can represent the microscopic state of asphalt, but the majority of them are phenomenological or qualitative descriptions, making it impossible to fully explain the microscopic mechanism generating macroscopic events.
The creation of molecular models is the foundation for the application of molecular dynamics simulation, which is a good tool for quantifying the micro-state of materials.
It is both impossible and unnecessary to create a realistic chemical model for immensely complex mixes like asphalt.
The assembly technique and the average molecular approach are both efficient methods for constructing a model based on the asphalt component method.
Numerous studies have used molecular dynamics simulations to investigate the quantitative relationship between the molecular composition and the macroscopic properties of asphalt.
Several asphalt properties were studied, including glass transition temperature, self-healing behavior, diffusion behavior, and aging behavior.
Modified asphalt has been investigated using molecular dynamics simulations, which include component interaction, contact angle, various mechanical properties, molecular aggregation and structure, and so on.
Modified asphalt is increasingly being used in road building.
As a result, molecular dynamics simulations may now be utilized to investigate the microscopic mechanisms that underpin macroscopic phenomena.
Asphalt Storage Stability
In this study, molecular dynamics simulations were used to evaluate the microscopic mechanisms underlying the enhanced storage stability of asphalt treated with CNT/RPE.
Asphalt samples were changed with CNT and RPE, and the properties before and after CNT addition were measured.
The models were validated using the four-component content, radial distribution function (RDF), elemental content, and molecular structure of virgin asphalt, RPE-modified asphalt, and CNT/RPE-modified asphalt.
The molecular structure, molecular mobility, and interfacial contact strength were defined using the relative concentration distribution, binding energy, and diffusion coefficient, respectively.
The amorphous cell (AC) package was used to generate a variety of asphalt systems, the visualizer package was utilized to map asphalt molecules, and Materials Studio was used for all molecular dynamics simulations in this study (MS).
Following the acquisition, the asphalt systems needed structural optimization.
Each asphalt molecule was optimized for geometry 100,000 times before being annealed at temperatures ranging from 300 to 500 K with a cycle number of 5 and a temperature interval of 20 K.
To imitate the actual situation, the annealing procedure was carried out in NPT with an air pressure of 1.01 104 Gpa.
Following that, each asphalt system was relaxed for the first time with a 50-second dynamic simulation using NVE ensemble synthesis.
The initial relaxation temperature was established at 400 K because low relaxation temperatures could result in very unbalanced asphalt systems.
Finally, for each asphalt system, molecular dynamics simulations were run at 100 ps in the NPT ensemble at 298 K, with a total step size of 100,000 and a model frame generated every 1000 steps.
To put it another way, the molecular dynamics simulation method provides a 100-frame trajectory trace, which is then used to compute a range of microscopic metrics.
Figure 6 shows the patterns in system parameter changes that occur during the molecular dynamics simulation.
polymer modified asphalt binder
It was obvious after 30 ps of simulation that the asphalt had essentially attained equilibrium.
The test ranks the binding energies between asphaltenes and the other asphalt constituents: Resins are first (232.26 kcal/mol), followed by saturates (701.76 kcal/mol), and finally aromatics (2700.93 kcal/mol).
All of the binding energies are greater than zero.
This means that asphaltenes and other components interact favorably, asphaltenes are most stable with aromatics and least stable with resins, while aromatics and resins bind to saturates first.
Asphalt is a dispersion system composed of asphaltenes and adsorbed resins dispersed in aromatics and saturates, according to the colloid theory.
In other words, resins are transient substances, but the interaction of asphaltenes with lighter components (aromatic and saturates) is important to the creation of an asphaltene colloidal system.
As a result, asphaltenes have significantly higher binding energy than saturates and aromatics-containing resins.
Despite the fact that the size trend remained constant, the binding energy of asphaltenes with each component of the RPE-modified asphalt system was substantially lower than that of virgin asphalt.
This implies that the addition of RPE decreased the interaction inside the asphalt rather than changing its colloidal structure.
Furthermore, asphaltenes (423.82 kcal/mol), resins (35.28 kcal/mol), saturates (118.01 kcal/mol), and aromatics (225.23 kcal/mol) were rated based on the strength of PE's binding energy.
It is worth mentioning that the negative binding energy of PE to asphaltenes and resins shows that PE and these compounds are antagonistic to one another.
RPE absorbs some of the light components when added to the base asphalt because the binding energy of PE with aromatics and saturates is positive, indicating that PE and these components are attracted to one another.
polymer modified asphalt shingles
RPE can only absorb a limited quantity of light components and cannot create a three-dimensional network structure like styrene-butadiene-styrene because the binding energy between PE and light components is substantially lower than that between asphaltene and light components (SBS).
Previous research has shown that PE has a proclivity to develop spherical "island constructions" in basal asphalt.
Because of the weaker interaction between PE and lighter components than asphaltenes, its mutual exclusion with asphaltenes and resins, and its very different molecular structure, polarity, and thermodynamic properties from asphalt, the binding energy results can explain the poor storage stability of RPE-modified asphalt.
When compared to RPE-modified asphalt, the CNT/RPE-modified asphalt system showed higher binding energy between asphaltenes and other components, showing that CNTs may improve the asphalt phase stability of the system.
The binding energy of PE with the four components also altered dramatically.
The improved asphalt system was more stable because the binding energy of PE with asphaltenes decreased (253.
17 kcal/mol), indicating that the repulsion between PE and asphaltenes was reduced.
PE's binding energy with resins shifted from negative to positive (10.
32 kcal/mol), showing that CNTs induce the link between PE and resins to shift from mutual repulsion to mutual attraction.
Furthermore, the binding energies of PE with aromatics (562.
84 kcal/mol) and saturates (326.
16 kcal/mol) in CNT/RPE-modified asphalt were much greater than in RPE-modified asphalt, indicating that CNTs facilitate PE adsorption of lighter compounds.
The positive qualities of RPE are imparted to the entire system during this process, increasing the high-temperature stability and low-temperature properties of CNT/RPE-modified asphalt above RPE-modified asphalt.
Furthermore, the addition of more lightweight components outside of RPE that are equivalent to the transition zone and improve RPE compatibility with the asphalt matrix improves CNT/RPE-modified asphalt storage stability.
Asphaltenes are equally dispersed throughout the system in new asphalt.
Asphaltenes, according to the asphalt colloid theory, are the primary source of system elasticity because they absorb resins to create colloids that are dispersed among aromatics and saturate.
polymer modified asphalt waterproofing
The homogeneous distribution of asphaltene in virgin asphalt implies a stable colloidal structure.
Asphaltenes are more cohesive in RPE-modified asphalt, and the PE molecular chains are distributed in strips across the asphaltenes.
According to the binding energy estimates, asphaltenes and PE resist each other.
Because the asphaltenes contain intermittent PE molecular chains, the RPE-modified asphalt system is unstable.
Furthermore, because the PE molecular chains are organized in strips, there is a larger contact surface between PE and asphaltenes, causing RPE-modified asphalt to be more unstable.
The asphaltene has a lot more room to spread out in CNT/RPE-modified asphalt, which promotes system stability.
Furthermore, the clustering of the PE molecule chains reduces the surface area in contact with asphaltene, lowering the repulsive reaction.
In other words, CNTs increase the stability of RPE-modified asphalt, which is compatible with the binding energy study's findings.
In this study, carbon nanotubes (CNTs) were utilized as a reinforcing agent to improve the storage stability and low-temperature properties of RPE-modified asphalt, and molecular dynamics modeling was performed to assess the reinforcing mechanism of CNTs on RPE-modified asphalt.
The following conclusions were reached as a result of the findings.
CNTs significantly improve RPE-modified asphalt's high-temperature rheological characteristics, low-temperature breaking resistance, and storage stability.
The glass transition temperature, elemental content, and four-component composition of virgin asphalt, RPE-modified asphalt, and CNT/RPE-modified asphalt all support the molecular models.
CNTs increased RPE by reducing the repulsion between RPE and asphaltene (resins) and diminishing the interaction between asphaltene and light components, as well as by improving RPE and light component adsorption.
As a result, RPE absorbed more light components, making RPE-based asphalt more compatible.
CNTs improve the storage stability of modified asphalt by increasing the distance between RPE and asphaltene and uniformizing the dispersion of asphaltene.
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