Research On The Interaction Between Chloride Salt And Asphalt And The Diffusion-migration In Mixture

With the continuous innovation and development of chloride salt snow melting de-icing agent,chloride salt snow melting de-icing agent is mixed into the asphalt mixture instead of mineral powder to make a salt-storing asphalt mixture,and the paved pavement is a saltstoring asphalt pavement.At present,the research on salt-stored asphalt pavement at home and abroad mainly focuses on the ice and snow melting performance and road performance,but lacks the research on the interaction between chloride salt and asphalt.Therefore,this paper studies the influence and mechanism of chloride salt on asphalt interaction,reveals the process of chloride precipitation-diffusion-migration,and provides theoretical support and technical guidance for the development of salt-stored asphalt pavement.(1)The viscoelastic parameters and surface physicochemical parameters of asphalt mortar in matrix asphalt,asphalt mortar and different salinities replacing limestone mineral powder were characterized by dynamic mechanical analysis and surface physicochemical methods.The rheological parameters were used to calculate the interaction level between asphalt and filler,and the C value of the interaction parameters and the evaluation index of complex shear modulus coefficient based on the Palierne theoretical model were optimized.The effect of salinate substitution mineral powder content on asphalt-filler interaction was evaluated by using the interaction attenuation percentage index,and the linear correlation between salinate substitution amount and interaction attenuation percentage was established.According to the surface free energy theory,the cohesion energy of asphalt mortar,the adhesion work and spalling work between asphalt mortar and aggregate are calculated.Based on this,the correlation between the two interaction evaluation indexes of rheology and surface physical chemistry was established.(2)A three-electrode electrochemical test system for asphalt membrane and asphalt slurry membrane was constructed,and the Tafel curve and electrochemical impedance spectrum were tested.The corrosion current density of Tafel curve was used to reflect the chloride diffusion performance of asphalt mortar,and the weakening ratio of chloride resistance was calculated based on the corrosion current density,and the effect of salt incorporation on chloride diffusion performance of asphalt mortar was analyzed,and a good linear correlation between the weakening ratio of chloride diffusion capacity and the percentage of interaction attenuation was obtained.(3)According to the Nyquist diagram and Bode diagram of electrochemical impedance spectroscopy,the diffusion behavior of chloride ions in asphalt mortar was analyzed,and the equivalent circuit was established to analyze the variation law of electrochemical elements in asphalt mortar.Based on the continuous diffusion model and Fick’s law,the chloride ion concentration is proportional to the 1/2 power of the diffusion time,and it is proved that the precipitation-diffusion migration process of chloride ions from asphalt mortar includes three processes: the process of water molecules infiltrating to form diffusion channels;chloride dissolution process;Steady-state diffusion process of chloride ions.(4)The improved steady-state electromigration test was used to accelerate the diffusion of chloride ions in the salt-storing asphalt mixture and the ordinary asphalt mixture.By testing the electrochemical impedance spectrum of asphalt mixture,the effects of mixture gradation,soaking time and applied voltage were explored,and the influence of mixture grade on chloride ion diffusion was small.Based on Fick’s law and Nernst’s equation,the chloride ion diffusion model was established,the apparent diffusion coefficient of chloride ions was obtained,the Poly2 D model of diffusion time and applied voltage was constructed,and the reliability of the model was verified by experimental data.(5)The asphalt-filler interaction interface,the surface morphology and chemical functional groups of asphalt-asphalt mortar before and after immersion in aqueous solution and salt solution,and salt-containing asphalt mortar before and after immersion in aqueous solution were characterized by microscopic techniques such as optical microscopy,SEM,FTIR and other microscopic techniques “Salt aging”.In this paper,the precipitation-diffusion law of salinity in asphalt mortar and asphalt mixture is quantified,and the correlation between the amount of salinate substitution and the interaction between asphalt and filler and precipitation-diffusion behavior is established,and the chloride ion diffusion model of salt-stored asphalt mixture is constructed,which provides a theoretical basis for the optimal design of salt-stored asphalt mixture.