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.
Impact of salt and freeze-thaw cycles on performance of asphalt mixtures in coastal frozen region of China
Abstract The impact of salt on asphalt binders was first studied through basal experiments of binders. The complex influence of freeze–thaw cycles and salt on strength, volume and weight of three types of asphalt mixtures was then investigated through freeze–thaw tests. Test results indicate that salt has a significant effect on the low temperature performance of asphalt binders; Freeze–thaw is a main influencing factor when the percentage of salt is less than 3%, and the erosion effect of salt accelerates the failure of asphalt mixtures when the percentage of salt is more than 3%. The damage of asphalt mixtures is initiated by ice expansion load and accelerated by the interfacial damage between asphalt and aggregate or fracture of asphalt mortar. It can therefore be concluded that different types of asphalt mixtures have fixed residual lives after a number of freeze–thaw cycles. Freeze–thaw cycles, salinity, percent air void, asphalt property and 4.75 mm percent passing are main factors having an influence on freeze–thaw strength.
POROUS ASPHALT AGAINST WATER NUISANCE
The various aspects of water nuisance problems was investigated and an attempt was made to answer questions relating to what constitutes a dangerous depth of water on the surface, how frequently and where does such a depth occur, and how can such occurrences be presented? The relation between water depth and the friction between tire and road surface has been determined at various speeds, and among others, the following types of surfacing: open-textured asphaltic concrete (texture depth 0.7 mm); synthetic resin surface dressing gritted with 5/8 mm crushed gravel (texture depth 2-3 mm), and porous asphalt. The main advantages of newly laid porous asphalt are its storage capacity and its coarse macrotexture. The report concludes that porous asphalt is a material that can be used to combat water nuisance on road surfaces, particularly in the newly laid condition and as yet uncontaminated. Depending on the extent of contamination of the material, a continuous film of water will not occur on its surface. Because of the open and coarse macro-texture, it will enable frictional forces of acceptable magnitude to be transmitted between tire and road surface.