Influence of Different Types of Emulsifiers on Properties of Emulsified Asphalt Binder and Its Evaporation Residue by Molecular Dynamics Simulation

There is an important role in the properties of emulsified asphalt binder and its evaporation residue about emulsifier, which has been confirmed by experiment and chemical tests. However, there is little research about the emulsifier at microperspective. Therefore, the influence of two kinds of emulsifiers, a typical cationic emulsifier (dodecyl benzene sulfonate) and a typical anionic emulsifier (dodecyl primary amine), on technical properties of emulsified asphalt binder and its evaporation residues such as store stability, workability, breaking behavior, and mechanical properties are investigated using a microapproach. Results show that there is an effective role in the storage stability, workability, and demulsification of emulsified asphalt binder about cationic emulsifier compared with anionic emulsifier. The anionic emulsifier makes the density of evaporation residue larger. However, the mechanical properties of anionic emulsified asphalt evaporation residue are conversely smaller compared with the cationic emulsified asphalt evaporation residue. The adhesion behavior results have confirmed that the anionic emulsified asphalt evaporation residue has a negative adhesion with aggregate due to its anion. The mechanism of the different emulsifiers on asphalt binders and their evaporation residue is explored at a microscale to help us to understand emulsified asphalt binder and its evaporation residue more in depth.

Modification Mechanism and Rheological Properties of Emulsified Asphalt Evaporative Residues Reinforced by Coupling-Modified Fiber

In order to solve the problems of the smooth surface of basalt fiber and its weak interfacial adhesion with emulsified asphalt cold recycled mixture, a silane coupling agent (KH550) was used to treat the surface of basalt fiber and the effects of treatment concentration and soaking time on fiber modification were studied. The influence of silane coupling-modified basalt fiber (MBF) on the rheological properties of emulsified asphalt evaporation residue was studied at high and low temperatures using three routine index tests: a dynamic shear rheological test (DSR), a bending beam rheological test (BBR), and a force ductility test. The elemental changes of the fiber before and after modification and the microstructure of the emulsified asphalt evaporation residue with the coupling-modified fiber were analyzed by Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS), which is used to study the modification mechanism of emulsified asphalt evaporation residue reinforced by coupling-modified fiber. The results indicate that the concentration and soaking time of the silane coupling agent have a great influence on the surface morphology and mechanical properties of the fiber, and that the optimal treatment concentration is 1.0% and the optimal soaking time is 60 min. The addition of coupling-modified fibers can reduce the phase angle and unrecoverable creep compliance of emulsified asphalt evaporation residue, increase the rutting factor and creep recovery rate, and improve the elastic recovery ability and permanent deformation resistance. However, excessive fiber will weaken the ductility of emulsified asphalt at low temperatures. The appropriate content of silane coupling-modified fiber (MBF) is 1.5%. After silane coupling modification, the fiber surface becomes rough and cohesion is enhanced between the fiber and the emulsified asphalt base. Silane coupling-modified basalt fiber (MBF) acts as reinforcement for stability and bridging cracks.