| The developement and application of high-proformance polymer modified asphalt is an important tool to improve the ability of asphalt pavement disease resistance,prolong the pavement life and decrease the maintenance cost.However,the weak interface affect the performance of polymer modified asphalt.Therefore,in this paper,the effect of different factors on the interface of compoisited modified asphalt were investigated by numerical modeling.The objective of modeling was to find the suitable carbon nanotubes(CNTs)to modify asphalt and provide theoretical basis for materials preparation.Based on the principle of trans-scale enhancement,CNTs was selected as nanoscale,the most widely used linear type styrene-butadienestyrene(SBS)was selected as micrometer scale,and the composited polymer modified asphalt with carbon nanotubes were produced using blending technics.The effect of CNTs amount and adding CNTs methods on the micro-structures and rheological behaviors of composited modified asphalt was analyzed,the relationship between micro-structures and rheological behaviors were discussed,and finally the interface enhancement mechanism of composited polymer modified asphalt with carbon nanotubes were revealed.The molecular model of composited modified asphalt was built to obtain the effect of surface modification,wall numbers and pull-out behaviors of CNTs on the interface bonding characteristics of composited modified asphalt.The interface bonding characteristics were investigated using pull-out energy,shearing strength,snapshots of molecular dynamics,solubility parameters and radial distribution function.These parameters were used to capture the intermolecular interaction of the interphase,providing the theoretical foundation for materials production.Results showed that interfacial damage was relieved by pull-out behaviors of CNTs.Multiwalled carbon nanotube with hydroxyl performed better interphase bonding effect.The interphase in SBS modified asphalt was composed of SBS,aromatics,saturates and resins with small molecular size by adsorption,hightlighting a week interphase.However,in composited modified asphalt,CNTs improved the interphase by reinforcement.The benzene ring of CNTs and SBS had ?-? conjugation.SBS surrounded and intertwined with CNTs,the long alkane chains of asphaltenes were also wrapped around CNTs,giving large intermolecular interaction of interphase.Based on the principle of trans-scale enhancement of CNTs and surface modification,the preparation methods of composited polymer modified with carbon nanotubes were built.Preparation parameters were determined by key technical indicators of polymer modified asphalt.The differences between composited and individual modification for asphalt were investigated.Results showed that hydroxyl modified CNTs was the best for asphalt modification.For mechnics blending technics,the suitable mesh number of SBS polymer was 20;the best dispersion medium in the solution skill using ultrasound was furfural extract oil;the best temperature in melt skill was 180?.CNTs amount would heavily effect the properties of modified asphalt if CNTs amount below 0.5%.Composited modification had better anti-rutting properties and fatigue life than individual CNTs or SBS modification.Melting skill decreased low-performance,while mechnics blending methods and solution skill provided better anti-cracking properties than SBS modified asphalt.The micro-structures characteristics of composited modified asphalt were investigated.Raman spectrum was used to obtain the interaction between CNTs and other components,fluorescence microscope and atomic force microscope(AFM)were used to capture the characteristics of polymer-phases,and scanning electron microscope(SEM)as well as dynamic mechanical temperature spectra were used to reveal the interphase characters.Results showed that C=C of CNTs,aromatic hydrocarbons and alkanes of asphalt had interactions.There was also a coupling between SBS and CNTs in composited modified asphalt.Mechnics blending methods and solution skill had higher interaction than melting skill.Swelling degree,average particle size,distribution density,maximum particle size and mean height of polymerphases were used to qantize the characteristic of polymer-phases.Swelling degree of polymer-phases was increased as CNTs amount.CNTs linked the polymer-phases and asphalt-phases to improve swelling degree attributable to its hollow frictionless tubes.SBS orientated along CNTs diameter to make the polymer phase alignment.SBSphases particle size of mechnics skill was uniform distribution and embedded with each others,while the SBS networks of melting and solution skills were much denser.Moreover,CNTs adhered to the main frame of SBS,enriched at interface and enhanced the interface roughness of composited modified asphalt.The reinforcement and pull-out behaviors of CNTs were the main reason to improve the interphase bonding.The interfacial bond strength of mechnics skill was the best while melting skill was the worst when CNTs amount below 0.5%.In conclusion,the interphase of composited modified asphalt were improved by reinforcement,mechanical anchorage and pull-out behaviors of CNTs.The rheological behaviors of composited modified asphalt with different CNTs amount and adding methods were obtained by different methods.Flow characteristics at temperater above 100? were captured by viscosity-temperature curves and viscous resistance.The temperature dependency and time dependency at middle temperature on dynamic shear condition were tested and master curve were built using CAM model.The viscoelastic properties at middle temperature on small strain oscillation state were captured by black space diagram,Han curves and Cole-Cole diagram.The multiple stress creep and recovery test was used to obtain the repetition creep charateristics at middle temperatures.The bending beam rheometer was used to test creep properties at low-temperature.Also,the rheological properties at different aging condition was analyzed.Results showed that solution skill had the largest viscous resistance while mechnics and melting skill were similar.The flow barrier energy at high-temperare of SBS modified asphalt was decreased if adding CNTs among 0.02% and 0.5%.At middle temperature on dynamic shear condition,complex modulus of mechnics skill was the largest whill melting skill was the smallest.CNTs had little influence on the viscous modulus,but it had a great influence on the elasitic modulus in low frequency region.At middle temperature on small strain oscillation state,the enhancement of complex moduls at low frequency zone were attributable to the elastic deformation of polymer-phases particles,and solution skill showed larger elatic deformation than that of mechnics and melting skills.At middle temperatures on repetition creep condition,accumulative strain and nonrecoverable creep compliance of mechnics skill were the smallest but percent recovery was the largest,providing better anti-rutting properties than that of melting skill.The anti-rutting performance was increased if adding CNTs among 0.02% and 0.5%.For creep behaviors at low-temperature,the stiffness of solution skill was the smallest and m-value was the largest,while anti-cracking properties of melting skill was worst.The aging indexes of rheological parameters was decreased after adding CNTs attributable to the small oxygen amount absorbed to the system.The relationship between micro-structures and rheological parameters of composited modified asphalt was explored.The flow characteristics at high-temperture was depended on mean particle size and distribution density.R heological parameters at middle-temperature and creep properties at low-temperatures had a closed relationship with distribution density,mean particle size and swelling degree of polymer-phases.For road performance,the larger particle size of polymer-phases provided a better anti-rutting properties,larger swelling degree gave a better fatigue life,but smaller particle size obtained a good anti-cracking properties for composited modified asphalt.Therefore,the particle size and distribution density of polymer-phases had an optimal value. |
PDF Full Text Request