Study On The Preparation And Properties Of Multi-scale Nanomaterials/SBS Modified Asphalts

Styrene?S?-butadiene?B?-styrene?S?block copolymer?SBS?modified asphalt is widely used in asphalt pavement for its excellent high and low temperature performance.But in the process of road construction and operation,it is prone to be aged when suffering light,heat,oxygen and other natural external forces,which leads to the decline of service quality and reduction of service life of asphalt pavement.The present studies mainly make SBS modified asphalt as a unified whole to analyze,but in the actual process of aging,the aging of SBS modified asphalt is influenced by both the base asphalt and SBS modifier.So its aging mechanism needs further research.Most of the researches are conducted mainly by indoor accelerated aging tests,but laboratory conditions do not really reflect the impact of outdoor natural environment and climate change.At the same time,the research on the aging resistance of SBS modified asphalt is mainly focused on seeking a single solution for thermal oxygen aging resistance or photo oxidation aging resistance.Therefore,existing anti-aging additives are difficult to satisfy the requirements for both thermal oxygen and photo oxidation aging resistance.Besides indoor accelerated aging?short term aging TFOT,long term aging PAV and ultraviolet aging UV?in SBS modified asphalt,the natural weathering aging of matrix asphalt,SBS polymer and SBS modified asphalt is also introduced.A comprehensive analysis of its properties is carried out to analyze the aging of the natural environment in a comprehensive way.The aging analysis results are used as the theoretical basis to further investigate the aging resistance of SBS modified asphalt.For comprehensive improvement of thermal oxygen and photo oxidation aging resistance of SBS modified asphalt,two-dimensional layered silicate nanomaterials?organic vermiculite OEVMT,organic montmorillonite OMMT?compounded with zero dimensional nanometer inorganic nanoparticles?nano-ZnO,nano-SiO₂ and nano-TiO₂?are prepared to produce multiscale nanomaterials.By studying the composition of multiscale nanomaterials,the optimum volume of multi-scale nanomaterials is formulated by physical and rheological properties.Finally by the micro performance test methods?Fourier infrared spectroscopy?FTIR?,Gel permeation chromatography?GPC?and atomic force microscopy?AFM??,the interaction principle between multiscale nanomaterial and SBS modified asphalt is discussed and the mechanism of multiscale nanomaterials on improvement of thermal oxygen and photo oxidation aging resistance of SBS modified asphalt is revealed.The main conclusions are as follows:?1?The relative aging degree of the two kinds of matrix asphalt is in accordance with the relative aging degree of the SBS modified asphalt.UV aging has the most obvious effect on the chain breaking reaction of SBS modifier,and the degradation of SBS modifier after UV aging was the most complete.?2?Fluorescence microscopy shows that,with the deepening of aging,the distribution state of SBS modifier gradually changes from continuous network structure to dispersed dot distribution,and the particle size gradually decreases,and the outline of particles gradually become dim and dark.At the same time,topography after UV aging without any fluorescence reaction,means that the SBS modifier is almost completely degraded,which indicates UV aging and degradation effect of SBS modifier is more significant compared to the long-term aging.?3?At the initial stage of natural weathering aging,the high temperature stability and low temperature cracking resistance of SBS modified asphalt increased,and then the performance decreased.At the same time,grey relational analysis shows that the degradation rate of SBS modifier is most similar to the complex modulus of SBS modified asphalt at 30?.?4?The multiscale nanomaterial systems composed of organic vermiculite?OEVMT?,organic montmorillonite?OMMT?and inorganic nanomaterials?nano-ZnO,nano-SiO₂ and nano-TiO₂?were analyzed:in terms of physical properties,due to the multiscale nanomaterials,SBS modified asphalt ductility increase?with the exception of ZnO compound?,Brookfield viscosity increased;in terms of rheological properties,the complex modulus of multiscale nanomaterials/SBS modified asphalt increases,the phase angle decreases,while the rut factor is generally higher than the blank sample,and has better cracking resistance at low temperature and high temperature stability.The optimum ratio is OEVMT?1%?+TiO₂?3%?and OMMT?1%?+TiO₂?2%?by comprehensive evaluation of multi-scale nanomaterials.?5?The infrared spectrum of SBS modified asphalt is composed of several materials?SBS modified asphalt,OEVMT and nano-TiO₂?after OEVMT/TiO₂ and OMMT/TiO₂ combined,and there is a superposition of characteristic peaks,but no new characteristic peaks are generated.The GPC curve of multiscale nanomaterials/SBS modified asphalt shows that after the combination of OEVMT/TiO₂ and OMMT/TiO₂,the SBS modified asphalt curve shifts to the left as a whole?macromolecular direction?,indicating that the molecular weight of SBS modified asphalt increases after blending.At the same time,through the analysis of the proportion of asphalt molecular region,it is found that the content of large molecules increases and the content of middle molecules reduces after adding compounds.The average molecular weight of the asphalt system is increased.After mixing,the molecular force between bituminous materials is enhanced,and the relative displacement of molecular segments or the whole molecular motion is relatively difficult.The temperature sensitivity is reduced,which improves the high temperature stability.The trend of macromolecular ratio?LMS?of multiscale nanomaterials/SBS modified asphalt is analyzed.It is found that under the same aging condition,OEVMT/TiO₂ and OMMT/TiO₂ multiscale nanomaterials retard the increasing rate of LMS of SBS modified asphalt.The results show that the LMS increment of SBS modified asphalt decreases significantly with the addition of multi-scale nanomaterials,which effectively inhibites the rate of small molecules from transferring to macromolecules during aging.?6?The size of"bee-like structure"in multiscale nanomaterials/SBS modified asphalt increases significantly.Compared with blank samples,the number of"bee-like structure"in OEVMT/TiO₂ and OMMT/TiO₂ composite SBS modified asphalt increases.The addition of multi-scale nanomaterials makes the distribution more uniform and forms a more stable system.After aging,the surface roughness of the specimen shows a decreasing trend,and the difference of the surface phase height decreases gradually.The addition of multiscale nanomaterials makes the decrease rate of the microstructure roughness of SBS modified asphalt slow.