Study On Compatibility Evaluation Of High Viscosity Modified Asphalt Colloid System Under Different Aging Conditions

In response to the national call to build a"sponge city",drainage asphalt pavement has become a research hotspot due to its excellent drainage,skid resistance,and noise reduction functions.As a bonding material for drainage asphalt pavement,high viscosity modified asphalt’s aging resistance is crucial to the structural stability and service life of drainage asphalt pavement.This thesis uses asphalt colloid theory and molecular dynamics simulation,combined with micro and macro experiments of high viscosity modified asphalt under different aging conditions,to study the compatibility of high viscosity modified asphalt colloid systems under different aging conditions,providing theoretical and methodological guidance for improving the aging resistance of high viscosity modified asphalt.The 70#base asphalt and SBS high viscosity modified asphalt were subjected to short-term aging,long-term aging,and ultraviolet aging using a rotating film oven,pressure aging oven,and ultraviolet aging oven.The basic properties of asphalt before and after aging were tested using penetration,softening point,and ductility tests.The results show that SBS high viscosity modified asphalt has better anti-aging performance than 70#base asphalt.The chemical composition and microscopic distribution characteristics of high viscosity modified asphalt under different aging conditions were studied using Fourier transform infrared spectroscopy（FTIR）and fluorescence microscopy（FM）.The FTIR test results show that short-term and long-term aging mainly involves thermal oxygen aging,generating a large number of polar oxidation functional groups such as carbonyl and sulfoxide groups,and the oxidation reaction is more significant during long-term aging,while the high viscosity agent undergoes partial degradation.UV aging occurs mainly in the form of degradation of high viscosity agents,with a significant decrease in the content of functional groups in polybutadiene and a small change in the content of carbonyl and sulfoxide groups.The FM test results show that short-term aging causes a large number of flocculent structures of high viscosity modified asphalt to decompose,resulting in the appearance of dot like structures;Due to long-term aging,the flocculent structure of high viscosity modified asphalt is greatly reduced,and the boundary is blurred;With the increase of irradiation time,the flocculent structure of the high adhesive distribution gradually destroyed,and the results of ultraviolet aging for 64hours were similar to those of long-term aging.The compatibility of high viscosity modified asphalt under different aging conditions was evaluated using four component method（SRAR）,spot test,and flocculation titration test.SRAR found that three types of aging increased the content of asphaltene and resin in asphalt,while decreased the content of saturated and aromatic hydrocarbons.The colloidal stability index IC was used to evaluate the colloidal compatibility of asphalt.During short-term and long-term aging,the degree of asphalt aging was positively correlated with the IC value;After long-term aging,the colloid compatibility is the worst;During UV aging,the increase of asphaltene content and the decrease of aromatic content are the main factors affecting the compatibility of asphalt colloids.The compatibility of high viscosity modified asphalt was quickly evaluated by spot test,which was consistent with SRAR results.The flocculation titration test quantitatively evaluates the compatibility of high viscosity modified asphalt through the solubility blending value S_BN,insoluble value I_N,and Heitaus parameter.The results show that both high viscosity agents and aging have no significant changes in the solubility of asphalt,but reduce the solubility of soluble matter and overall colloidal structure stability of asphalt.The compatibility of high viscosity modified asphalt under different aging conditions was evaluated based on molecular dynamics simulation.A four component（12 molecule）modeling method was used to construct a molecular model of aging asphalt.Parameters such as density,cohesive energy density,and solubility were used to jointly verify the rationality of the model.The compatibility of the blend model was evaluated by calculating the solubility difference,interaction energy,and radial distribution function（RDF）of the high viscosity molecular model and the matrix asphalt model.The simulation results were basically consistent with the macroscopic test.Analyzing the change of molecular potential energy in the model,it was found that the total molecular interaction energy of high viscosity modified asphalt increased,but the interaction energy decreased,and the compatibility became poor.The radial distribution function indicates that the main reason for the poor compatibility of asphalt is that the saturated fraction is wrapped with a high viscosity agent,resulting in the dispersion of asphaltene and the high viscosity agent.