Carbon nanotube (CNT)–asphalt nanocomposites are
considered
to be the next generation of pavement materials; however, the interaction
between CNT and asphalt at the interface and the mechanisms of property
enhancement are not well understood, which limits the application
of CNT–asphalt nanocomposites. In this study, CNT is used as
a representative of one-dimensional nanomaterials, and the interfacial
multiscale interaction mechanism between CNT and asphalt molecules
is investigated by density functional theory (DFT), molecular dynamics
simulation, atomic force microscopy (AFM), gelation permeation chromatography
(GPC), Fourier transform infrared spectroscopy (FTIR), and performance
evaluation. It has been shown that CNT and asphalt substrates are
very compatible at the atomic scale, mainly due to π–π
stacking, mechanical entanglement, and van der Waals forces. The interfacial
energy barrier is −2.63 (kcal/mol)/Å2 and the
shear barriers are 52.70 MPa, with asphaltene and aromatic making
the greatest contribution to interfacial stress transfer. This research
provides a theoretical basis for the targeted tuning of properties
and establishes the basis for CNT–asphalt nanocomposites for
highway applications.
Carbon nanotubes (CNTs) can improve the storage properties of modified asphalt by enhancing the interfacial adhesion of recycled polyethylene (RPE) and base asphalt. In this study, the interaction of CNT/RPE asphalt was investigated using molecular dynamics simulation. The base asphalt was examined using a 12-component molecular model and verified by assessing the following properties: its four-component content, elemental contents, radial distribution function (RDF) and glass transition temperature. Then, the adhesion properties at the interface of the CNT/RPE-modified asphalt molecules were studied by measuring binding energy. The molecular structural stability of CNTs at the interface between RPE and asphalt molecules was analyzed through the relative concentration distribution. The motion of molecules in the modified asphalt was studied in terms of the mean square displacement (MSD) and diffusion coefficient. The results showed that CNTs improved the binding energy between RPE and base asphalt. CNTs not only weakened the repulsion of RPE with asphaltenes and resins, but also promoted the interaction of RPE with light components, which facilitated the compatibility of RPE with the base asphalt. The change in the interaction affected the molecular motion, and the molecular diffusion coefficient in the CNT/RPE-modified asphalt system was significantly smaller than that of RPE-modified asphalt. Moreover, the distribution of the asphaltene component was promoted by CNTs, resulting in the enhancement of the storage stability of RPE-modified asphalt. The property indexes indicated that the storage stability was significantly improved by CNTs, and better viscoelastic properties were also observed. Our research provides a foundation for the application of RPE in pavement engineering.
Interfacing and compatibility are the most challenging issues that affect the performance of polymer modified asphalt. Mechanisms of interfacial enhancement among four base asphalt components (asphaltenes, resins, aromatics, and saturate), styrene-butadiene-styrene (SBS), and carbon nanotubes (CNTs) were investigated by molecular dynamics simulation, with the aim of understanding the key parameters that control the compatibility of CNTs and interphase behavior on the molecular scale. The compatibility of SBS-modified asphalt (SBSMA) was simulated based on self-assembly theory using indexes of binding energy, mean square displacement, diffusion coefficient, and relative concentration distribution. The interphase behavior and microstructure were observed by fluorescence microscopy and scanning electron microscopy. In addition, a rutting experiment was used to verify the molecular dynamics simulation based on macroscopic performance. The results showed that after adding CNTs, the binding energy of the SBS and aromatics increased from 301.8343 to 327.1102 kcal/mol. The diffusion coefficient of the SBS and asphaltenes decreased more than 3.2×10 −11 m 2 /s, and the correlation coefficients between the diffusion coefficient and the molecular weight, surface area and volume were all lower than 0.3. Relative concentration distribution curves indicated that CNTs promote the ability of SBS to swell. Microscopic observations demonstrated that the swelling ability of SBS was increased by CNTs. Overall, the interphase of SBSMA was improved by the additional reinforcement, swelling, and diffusion provided by CNTs. Finally, the rutting experiment found that no matter what the temperature, the rutting factor of CNT/SBSMA is higher than that of SBSMA, which corroborates the findings from the molecular dynamics simulations.
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