Research On Performance Characteristics And Adhesion Evaluation Method Of Bio-oil Modified Asphalt Binder

As a traditional energy source,petroleum oil ensures the global economic development and industrialization process,while it belongs to the non-renewable resources.It is a major strategic plan to find alternative energy sources for petroleum oil.Biomass pyrolysis oil is a liquid product obtained by converting renewable biomass into a bio-oil based on rapid pyrolysis or high-pressure liquefaction technologies,and the flammability of bio-oil makes it possible to replace petroleum oil.At present,biomass heavy oil is mainly used as power fuel for marine engine,and the application of bio-oil as a modifier is also a new research focus in road material.In order to solve the difficulty of applying bio-oil in road asphalt,this research used different processes to mix bio-oil into asphalt based on the characteristics of bio-oil and the road performance requirements of road asphalt.Rapid pyrolysis oil deprived form waste plant,as a research material,was directly mixed with matrix asphalt to prepare bio-modified asphalt.The mechanical properties and modification mechanism of bio-asphalt and mastic were analyzed.The emulsified bio-asphalt was prepared by three kinds of emulsification techniques,and the method for obtaining the evaporation residue from asphalt emulsion was identified.The safety performance of emulsified bio-asphalt was evaluated based on corrosion test and combustion test.The composite modified asphalt was prepared by using bio-oil and rubber powder.The effects of bio-oil on the high-temperature performance of rubber modified asphalt were evaluated by rotational viscosity test and dynamic shear rheological test.Based on the‘Microwave Treatment’and‘Long-term Immersion’methods,bio-oil was used to pretreat the rubber powder prior to modification on matrix asphalt,and the effects of the preparation process on the high-temperature characteristics,fatigue characteristics and storage stability of the composite modified asphalt were studied.A modified blister test was proposed to evaluate the adhesion between asphalt and stone surface.The load from Universal Testing Machine(UTM)was used to drive the piston to produce pressure in blister.Digital image correlation,a non-contact measurement system,was selected to monitor the height of blister during burgling.The main contents and conclusions are as follows:(1)Bio-asphalt and mastic propertiesThe incorporation of bio-oil increased the penetration and ductility and reduced the softening point of the virgin asphalt binder.With the treatment of Rolling Thin-Film Oven Test,the effect of bio-oil on the above three performances of aged asphalt binder reversed in comparison with unaged asphalt binder.Based on the results of rotational viscosity test at different rotational speeds,the incorporation of bio-oil reduced the mechanical stability of the asphalt.At 25~oC,the 15%bio-oil enhanced the shear strength of the asphalt mastic,and the shear strength of the asphalt mastics with 0.8-1.4 filler-to-binder ratio increased by 73%to98%.Within a certain range,the shear strength of asphalt mastic increased with an increase in filler-to-rubber ratio.At 64~oC,the unrecoverable creep compliance of asphalt mastic decreased with an increase in filler-to-rubber ratio.Bio-oil affected the stress sensitivity of asphalt mastic at 64 ~oC.At-10 ~oC,bio-oil increased the strength of the asphalt mastic.(2)Preparation and properties of emulsified bio-asphaltThe‘Emulsification prior to Modification’preparation method was more suitable for preparing emulsified bio-asphalt in the laboratory.The method of‘Intermittent Heating’was suitable for obtaining asphalt residues from emulsified bio-asphalt.The moderate amount of bio-oil had a positive impact on improving the mechanical sensitivity of SBR emulsified asphalt residues.The emulsified asphalt residue with 6%bio-oil content was the most corrosive to metals.From the combustion test analysis,the incorporation of bio-oil prolonged the burning time of the emulsified asphalt mixture assisted by anhydrous ethanol,which also increased the maximum height of the flame so failed in controlling the spreading degree of a fire burning on asphalt pavement.After combustion,the appearance of the asphalt film exhibited many small micro-void structures.There was a good linear relationship between the bio-oil content and the mass loss rate after combustion.From the perspective of safety,a serious argument on project safety must be made before the construction operation if the practical application of bio-oil in road project involves the risk of corrosion of metal components or the situation of porous pavement structure.(3)Effect of bio-oil on high temperature performance of rubber modified asphaltThe viscosity of the 20-mesh rubber modified asphalt was higher than that of the80-mesh rubber modified asphalt.With the addition of pyrolysis bio-oil derived from straw,the viscosity of the rubber modified asphalt exhibited a tendency to decrease after increasing.Bio-oil can increase the viscosity characteristics of rubber asphalt,and the effect was related to the size of the rubber powder.The composite modified asphalt prepared by mixing bio-oil with large mesh rubber powder had good anti-fatigue potential.(4)Effect of microwave treatment on bio-oil-rubber composite modified asphaltThe preparation process affected the high temperature performance of the bio-oil-rubber composite modified asphalt.According the analysis of Multiple Stress Creep recovery(MSCR)test results,no obvious influence on the non-recoverable creep compliance of the composite modified asphalt under the stress level of 3.2 kPa was observed when bio-oil content was controlled at 6~15%,which meets the heavy traffic design requirements of AASHTO specification.The preparation process affected the storage stability of the bio-rubber composite modified asphalt.The‘Long-term Immersion’method ensured that the modification effect of the bio-oil on the rubber powder was milder,and the loss of volatilization of the bio-oil could be avoided,and the obtained composite modified asphalt had the lowest segregation index.The‘Microwave Treatment’method can complete the pretreatment of bio-oil on the rubber powder in a short time,and the segregation index of the rubber asphalt was reduced by half,which can effectively improve the storage stability of the rubber asphalt.Based on the observation of rubber powder by metallographic microscope,bio-oil changed the appearance of rubber particles under the action of‘Microwave Treatment’,which makes the spherical characteristics more obvious so improves the storage stability of asphalt.(5)Adhesion test method and evaluation indexThe micro-hole designed at the edge of the pressure chamber ensured the uniformity of the pressure medium and avoided the interference of the mixed air in the test.The connection between the micro-hole and the pressure medium collector enabled the recycling of the pressure medium.The test efficiency was improved by using a solenoid valve to control the flow direction of pressure medium.The Digital Image Correlation(DIC),non-contact measurement system,was used to monitor the appearance change of the blister spacemen during the loading process,which is more accurate than the traditional contact displacement sensor.A‘Dissolved Volatilization’process was proposed to control the thickness of the asphalt film.The film design ensured the debonding cracking of the asphalt on the surface of the stone to an adhesion failure.The incorporation of bio-oil had an adverse effect on the adhesion of asphalt on the granite surface.It’s believed that the incorporation of bio-oil increased the proportion of acid components in the asphalt,and the degree of chemical reaction of bio-asphalt on the granite surface was reduced.Granite,limestone and sandstone were used as base plate in this study.The results of the blister test were consistent with those of the traditional boiling method,but the blister test provided quantitative data,which is more valuable than the subjective evaluation from the boiling method.