| Asphalt mixture is widely applied in pavement engineering due to the excellent driving performance and low noise advantages.Servicing in the natural environment,asphalt pavement is often exposed to the water,and aqueous medium in the water is different in different areas such as acid rain area,seaboard,saline and alkaline land.This research result reveal the influence of different aqueous media on the composition and road performance of asphalt and asphalt mixtures.By analyzing the erosion of asphalt and asphalt mixtures under different aqueous media solutions,it provides a theoretical basis for scientifically evaluating and improving moisture corrosion resistance of asphalt pavement.In this paper,the influence of different aqueous solutions on the chemical composition and rheological properties of asphalt and the evolution of asphalt mixture road performance under the action of freeze-thaw cycles of different media were studied.In this paper,the 70#asphalt and SBS modified asphalt were used to moisture aging under different aqueous medium solutions?distilled water,acid,alkali,salt solutions?.Thin-layer chromatography with flame ionization detection?TLC-FID?test,Fourier transform infrared spectroscopy?FTIR?test and Dynamic shear rheometer?DSR?test were conducted to investigate the different media aqueous solution aging on chemical structure and composition and rheological properties of asphalt,and on this basis,analyzing the aging mechanism of different aqueous medium solutions.The70#asphalt and SBS modified asphalt were used to prepare asphalt mixtures samples.Air void test,Lottman test and Three-point Bending Fracture?TBF?test were conducted to investigate the effects of freeze-thaw cycles and different media aqueous solution erosion on mechanical and volume properties of asphalt mixtures.The objectives of this research were to evaluate the impact of distilled water,acid,alkali and salt solution on the road performance of asphalt mixtures.The main conclusions are as follows:?1?As the asphalt soaking in the aqueous solution,the surface of asphalt was not luster and became uneven,these phenomenon indicated asphalt aged under water.Some material of asphalt were dissolved into aqueous solutions,forming a layer of oil on aqueous solutions,the proportion of oil from big to small:pH 11 alkaline solution>pH 3 acid solution>10%Na2SO4 saline solution>distilled water.?2?Fourier transform infrared spectroscopy?FTIR?analysis revealed that the carbonyl and sulfoxide indices of asphalt increased and the Butadiene indices of SBS modified asphalt decreased after moisture aging.With the prolonging of soaking time,the aging degree of asphalt increased.Thin-layer chromatography with flame ionization detection?TLC-FID?analysis revealed that Saturates and Aromatics fraction became more and Resins and Asphaltenes fraction became more in earlier period of moisture aging?about 7days?,and less Resins and more Asphaltenes were observed with the extension of moisture aging time?after 7 days?.?3?The results of Dynamic Shear Rheometer tests showed that the immersion of water increased the complex modulus of asphalt and decreased the phase angle at the end.The change regular of the composite modulus and phase angle of 70#asphalt in the aging process is related to the change of its chemical composition.?4?The moisture aging of asphalt is different from ultra-violet aging,oxygen aging and heat aging,there are two actions during the moisture aging process,one is the oxidation reaction of aromatic and other light components of asphalt with oxygen in the water,result in the increasing of carbonyl,sulfoxide indices and Polar macromolecules,forming more Resins and Asphaltenes.The other hand,some hydrophilic groups and the polar molecules such as acidic esters,fatty amines and so on are more vulnerable dissolved and eroded by the aqueous solution,result in the reduction of shear resistance of asphalt,and the Saturates may also dissociate from the bituminous surface with the dissolution and migration,forming oil and float to the surface of the aqueous solution.Both of two effects affect the composition and rheological properties of moisture-aged asphalt.?5?The results indicated that freeze–thaw cycles influenced the road performance of asphalt mixtures significantly,increased the air void of asphalt mixtures,and reduced tensile strength ratio and failure strain of asphalt mixtures.Compared with the distilled water,the damage of acid,alkali and salt solution on the road performances of asphalt mixtures were more serious,especially alkali solution to tensile strength rate and failure strains in low temperature,and salt solution to VV.The moisture corrosion resistance of SBS modified asphalt mixtures is better than that of 70#asphalt mixtures. |
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