Study On Properties And Regulation Mechanism Of Polyethylene/Rubber Compound Modified Asphalt

The accumulation of waste polyethylene plastics and rubber tires generated annually worldwide is astonishing,and traditional disposal methods have not solved the problem of polymer accumulation,posing a great threat to the environment.In recent years,researchers have recycled waste polyethylene plastics and rubber tires into asphalt pavement,an initiative that not only dissipates a large amount of waste polyethylene plastics and rubber tires,but also replaces natural polymer modifiers to achieve synergistic carbon reduction,with significant environmental benefits and engineering feasibility.However,it should not be ignored that the storage stability of polyethylene(PE)modified asphalt is insufficient and prone to separation,while the addition of rubber tires can compensate for the deficiency of a single modifier.At the same time,the traditional mechanical blending process has high energy consumption and unstable performance,while the melt blending process can improve this problem.Therefore,waste PE and rubber tires were processed for melt blending,and then incorporated this modifier to the virgin asphalt for preparing waste PE/rubber modified asphalt in this study.The interaction mechanism was explored based on macroscopic rheological tests,microscopic morphology detection and molecular dynamics simulations.Firstly,the effects of processing technology,rubber powder doping,rubber powder mesh and different types of recycled PE plastics on the basic properties of PE/rubber modified asphalt such as penetration,softening point,and ductility were studied.The results showed that the preparation method of PE/rubber modified asphalt with excellent performance was as follows: 40-mesh rubber and PE were selected for melt blending in a twin-screw extruder,in which the content of rubber powder was 15% and PE was 5%.Subsequently,PE/rubber blend was added to the virgin asphalt,and the shearing temperature was set at 170℃,the shear speed was set at 5000 rpm,and the time was set at 80 minutes.Secondly,the effects and mechanisms of different types of recycled polyethylene on the performance of asphalt were investigated.The reasonableness of the model was verified by density,radial distribution function(RDF),and glass transition temperature.And the interaction energy,molecular interaction morphology,and diffusion coefficient were used as evaluation indicators.Dynamic shear rheological(DSR)tests showed that slightly aged polyethylene(PE-D1)improved the rutting resistance of modified asphalt.Fluorescence microscopy revealed that PE-D1 was more uniformly dispersed in the asphalt phase and exhibited better compatibility.Molecular dynamics(MD)simulations indicated that the binding energy of PE-D1/saturates and PE-D1/aromatics was the highest,and the diffusion coefficient was decreased with increase of the interaction strength,which also validated the experimental results.Finally,the effects of different recycling types of PE/rubber blends on the performance and enhancement mechanism of asphalt were investigated.The high-temperature rutting resistance of the PE/rubber modified asphalt was characterized using dynamic shear rheological tests.The microstructure of the PE/rubber blends in asphalt was observed using fluorescence microscopy and scanning electron microscopy,and the compatibility was evaluated by storage stability tests.Furthermore,the mean square displacement(MSD)and aggregation behavior of the system trajectory were analyzed by calculating the diffusion coefficient and relative concentration distribution of molecules,so as to reveal the mechanism of the strengthening interaction between PE/rubber blends and asphalt molecules.The results showed that the melting blending of PE and rubber allowed for their maximum dispersion in asphalt,resulting in a fiber-reinforced mechanical effect.The difference in softening point was less than 3.5℃,indicating excellent compatibility.The addition of PE/rubber blends reduced the diffusion coefficient of the light component and made the concentration distribution more uniform,especially for PE-8/rubber modified asphalt.Based on the rheological properties and mechanism of modified asphalt prepared by polyethylene/rubber,the preliminary results show that the recycling of packaging plastics and rubber tires in pavement engineering has significant environmental benefits and technical feasibility,and can also improve the performance of modified asphalt for road use.This study provides a theoretical basis for the high value-added utilization of solid waste in road engineering.