Investigation On Micro-properties Of Bio-rejuvenated Asphalt Mixture

With the depletion of nonrenewable materials,using renewable bio-materials to replace traditional petroleum-based products has gained great attentions nowadays.Asphalt,as a final residuum of crude oil distillation process,is a vital material in pavement engineering.Great engineering and social values can be achieved through the useof reclaimed asphalt pavement.Present researches have shown that using rejuvenator can enhance the efficiency of recycling asphalt pavement.However,most of the rejuvenators used today are derived from the crude oil which is unsustainable.Conversely,the cost of construction will be lowered and sustainable development can be achieved through the use of bio-materials.Thus,this research investigates the feasibility of using bio-rejuvenator in recycling asphalt concrete at both micro and macro scales.Firstly,three typical bio-oils(residue of bio-ethanol production,residue of bio-diesel production and epoxidized vegetable oil based bio-oil)were compared and epoxidized vegetable oil(EVO)based bio-oil was found to be suitable for fabricating bio-rejuvenator.Its rejuvenation efficiency was examined by conventional tests.Based on test results,plasticizer was added to enhance its rejuvenation ability.The rejuvenation effects were further evaluated using rheological tests and chemical methods.It was found the workability of long-term aged asphalt was improved and its stiffness was lowered while the recovery of anti-fatigue properties of aged asphalt was limited.Low temperature test results indicated that bio-rejuvenated asphalt was not suitable for regions with extreme low temperature.Chemical tests showed that the addition of bio-rejuvenator can lower the contents of oxidized functional groups and asphaltenes.The contents of low-and intermediate-molecule-weight molecules were also increased.Afterwards,bio-rejuvenation mechanism was proposed based on the analysis of the components-microstructure-performance relationship.It was found that the molecule diffusion ability was not enhanced though the viscosity of bio-rejuvenated asphalt decreased which may be due to the relatively high colloid content in bio-rejuvenator.For aged SBS modified asphalt,bio-rejuvenator can hence its molecule diffusion ability owing to the polymer in SBS asphalt.Then,bio-rejuvenator together with reclaimed asphalt pavement,virgin aggregate and virgin asphalt were used in preparation of recycled asphalt concrete.One commercial rejuvenator was also used for comparison.Wheel rutting test result showed that bio-rejuvenator exhibited best softening effect on reclaimed asphalt mixture.Low temperature bending test,freezing and thawing test and four point bending test results indicate that bio-rejuvenated asphalt mixture has best anti-thermal cracking,anti-moisture and anti-fatigue abilities.Dynamic modulus test verified that bio-rejuvenator exhibited better rejuvenation effect than commercial rejuvenator.Finally,nanoindentation test was used to characterize the micro properties of recycled asphalt concrete.It was found that bio-rejuvenator can significantly change the mechanical properties of mastic,transition zone and aggregate phase.Creep test analysis also showed that bio-rejuvenator had better rejuvenation effect than commercial rejuvenator in recycled asphalt mixture and can significantly improved the viscoelastic properties of asphalt materials.Micro test results proved that bio-rejuvenator can effectively enhance the pavement performance of recycled asphalt concrete.