The Effects of Salt on Rheological Properties of Asphalt after Long-Term Aging
Limited studies in recent years have shown that asphalt pavement subject to seawater in coastal regions or deicing salt in cold regions may be seriously damaged after being soaked in saline water for a long time. However, there is limited research into the influence of salt on rheological properties of asphalt after long-term aging. In this study, rheological properties of unmodified and polymer-modified asphalt after long-term aging were tested after being soaked in different concentrations of salt (0.3%~5%) for different durations (1 day~30 days). Orthogonal array based on the Taguchi method was used for experimental design. The frequency sweep tests were performed on the specimens of aged asphalt after being soaked for complex modulus and phase angle master curves and ultimate fatigue temperature. BBR tests were performed for stiffness. The test results indicate that saline water appears to reduce low temperature properties and fatigue resistance properties and improved high temperature properties of aged asphalt, and it also affects the sensitivity of complex modulus and phase angles at low frequencies.
The effect of water solution erosion on rheological, cohesion and adhesion properties of asphalt
Abstract Asphalt pavement will be damaged under the action of asphalt aging and moisture damage. Water solution erosion degree is closely related to the aging of asphalt and degradation of the adhesive strength between asphalt and aggregate. In view of this, this paper investigated the effect of water solution erosion on rheological, cohesion and adhesion properties of virgin and aged asphalt. The experiment was performed by immersing asphalt into five different water solutions (includes distilled water, acid solution, alkali solution, sodium chloride solution and sodium sulfate solution) for different time, which was considered to be fully reflect the real service condition within an asphalt pavement in different areas. The rheological properties were evaluated by dynamic shear rheometer (DSR), the cohesion and adhesion properties based on the surface free energy test were got by sessile drop method. Meanwhile, the relationships between asphalt rheological, cohesion and adhesion properties with aqueous solute and water solution erosion time were studied. The effects of water solution erosion on virgin asphalt and its PAV aged asphalt were compared. It was observed that water solution erosion resulted in the increased of asphalt elastic component and stiffness, decreased of asphalt fatigue life and the cohesive force and adhesion to aggregates. This trend was reduced to some extent with the presence of acid, alkali, and salt solutes. Under the action of water solution erosion, PAV aged asphalt showed a worse resistance to water solution erosion. And unlike heat-aging and ultraviolet-aging, the development trends of rheological, cohesion and adhesion properties of asphalt were more complex and variable with the change of asphalt surface component.
Coupled hydro-mechanical wave propagation in road structures
The purpose of this paper is to simulate the water flow induced by the moving wheel pressure on wet asphalt road pavements, which may be a reason for a damage phenomenon in asphalt denoted stripping. The wet asphalt pavement is modeled as water saturated porous media. The interaction of the porous solid skeleton and the pore liquid leads to a coupled dynamic problem with the deformation of the solid and the relative velocity and pressure of the fluid as primary unknown fields. A FE program has been developed to perform simulations. The simulations clearly demonstrate the induced deformation and water flow in the asphalt. A water pumping phenomenon is obtained where water is squeezed out of the asphalt underneath the wheel load and then later sucked back when the wheel has moved away. The water velocity is however low.