Investigation On The Influence Of The Asphalt Composition On The Microstructure And Properties Of The Epoxy Resin Applied To Modify Asphalt

As an engineering material with good performance,asphalt has been widely used in the pavement industry.Asphalt has complex chemical composition.According to the solubility characteristics,asphalt can be separated into asphaltene and maltene.In addition,maltene can further separated into saturates,aromatics and resins by chromatographic methods.Epoxy resin,as one of the most used reactive polymers,has been used to modify asphalt since late 1950s.Epoxy modified asphalt(epoxy asphalt)has been widely used for the steel deck pavement.It is known that the composition of asphalt influences the microstructure and properties of the epoxy asphalt.In this thesis,asphaltene and maltene were separated from the base asphalt.Asphaltene and maltene were added individually into epoxy resin to prepare the corresponding composites,and the microstructure and properties of the composites were investigated.Firstly,epoxy/asphaltene composites were prepared with asphaltene,epoxy oligomer and curing agent.The effect of asphaltene on the viscosity,dynamic mechanical behavior,thermostability,mechanical properties of the composites were evaluated by Brookfield rotational viscometer,dynamic mechanical analysis(DMA),thermogravimetric analysis(TGA)and universal testing machine.Scanning electron microscopy(SEM)observed that the size of pristine asphaltene powder varied around hundred microns.Interestingly,laser scanning confocal microscopy(LSCM)observed that the size of asphaltene in epoxy/asphaltene composites was much smaller than that of pristine asphaltene powder.In addition,the aggregation of asphaltene was observed and the size of the asphaltene aggregates increased with the increase of asphaltene loadings.It was found that asphaltene particles were initially dispersed in the epoxy resin,and gradually accumulated with the curing reaction.The addition of asphaltene slightly increased the viscosity of epoxy resin and had a marginal impact on the thermostability of the epoxy resin.Tensile tests revealed that the addition of asphaltene resulted in a sharp decrease in the mechanical properties of the epoxy resin.Dynamic mechanical analysis(DMA)showed that asphaltene had little effect on the damping properties of the epoxy resin.The addition of asphaltene increased the storage modulus of the epoxy resin at the rubbery stage.The glass transition temperature(T_g)of the epoxy/asphaltene composite slightly increased with the content of asphaltene.The epoxy composite with 5 wt%asphaltenes had higher T_g than the neat epoxy.Cole-Cole plots revealed that the heterogeneity of epoxy/asphaltene composites increased with the content of asphaltene.Then,the maltene was mixed with epoxy resin oligomers and curing agent to prepare epoxy maltene with different maltene loadings,and epoxy asphalts were prepared in the same way.The viscosity,phase separation,dynamic mechanical properties,thermal stability and mechanical performance of epoxy maltene were investigated and compared with epoxy asphalts.LSCM observed that epoxy maltene with 40 wt%maltene and epoxy asphalt with 40 wt%base asphalt had a similar microstructure.The particle size of the maltene phase in the epoxy maltene containing 50 wt%maltene was significantly smaller than that of the epoxy asphalt containing 50 wt%base asphalt.When the content of maltene was raised to 60 wt%,a complete phase inversion was observed.However,the epoxy asphalt containing 60 wt%base asphalt presented a complex microstructure including phase-inverted morphology.The viscosity of epoxy maltene decreased with the increase of maltene content.The viscosity of epoxy maltene was lower than that of epoxy asphalt at a specific loading.The thermal stability of the epoxy maltene was lower than the epoxy asphalt at a specific content and increased with maltene content.The epoxy maltene had a higher glass transition temperature(T_g)than the epoxy asphalt at a specific concentration.The T_g of epoxy maltenes increased with maltene content.The epoxy maltene with 60 wt%maltene had the best damping properties.The epoxy maltene with 40 wt%maltene had the best mechanical properties,while the phase inversion resulted in the epoxy maltene with 60 wt%maltene had the worst mechanical properties.