Study On The Performance Of Waste Cooking Oil/Nano-SiO₂ Composite Recycled Asphalt

With the deployment of the national dual-carbon strategy,the research on recycling waste edible oil and applying it to asphalt pavement regeneration projects has emerged in an endless stream.Waste cooking oil（Waste Cooking Oil,WCO）can realize asphalt regeneration by supplementing oil.Relevant studies have shown that waste cooking oil can restore the physical properties of aged asphalt to 70%-80%of the original asphalt,but the improvement effect of high temperature deformation resistance,water damage resistance and anti-aging performance needs to be further improved.As an excellent asphalt modifier,nano-Si O₂（NS）can be uniformly dispersed in asphalt and significantly improve the aging resistance,high temperature performance,fatigue and water damage resistance of asphalt materials,which has broad application prospects.Therefore,this thesis proposes to improve the performance of waste edible oil recycled asphalt by organic nano-Si O₂ on the surface of KH-550 with lipophilic hydrophobicity,so as to improve the performance defects of WCO recycled asphalt and improve the comprehensive performance of recycled asphalt pavement.Firstly,through conventional physical performance test,anti-aging performance test,multi-stress creep（MSCR）test and adhesion performance test based on surface energy,the effect of different content of NS on the high temperature performance,anti-aging performance and water damage resistance of waste edible oil recycled asphalt was discussed,and the optimum content of WCO and NS was determined.The results show that nano-Si O₂ can improve the softening point and Brinell viscosity of WCO recycled asphalt,and reduce the ductility and penetration value.Under the content of 10%WCO+2%NS,its comprehensive performance is optimal and meets the requirements of the specification.Nano-Si O₂ can slow down the volatilization rate of light components in WCO and weaken the softening effect of WCO by absorbing the light components in WCO,thereby increasing the elastic properties of WCO recycled asphalt,reducing Jnr value and increasing R value.At the same time,it slows down the performance degradation of WCO recycled asphalt after aging,and significantly improves the high temperature deformation resistance and aging resistance of WCO recycled asphalt.WCO is weak in restoring the water damage resistance of aged asphalt.The addition of nano-Si O₂ can improve the surface free energy of WCO recycled asphalt and the adhesion work of asphalt-aggregate interface system,reduce the peeling work of asphalt-aggregate-water system,and significantly improve the water damage resistance of recycled asphalt,but the content should not be too high,2%is the best.Then,based on the surface free energy theory,the wetting effect of WCO/NS on the surface of asphalt with different aging degrees was explored by spreading and wetting thermodynamic parameters under the optimal dosage.Then,through the self-designed diffusion experiment,the asphalt after fusion was layered and peeled.The diffusion degree was qualitatively and quantitatively determined by infrared spectroscopy with WCO/NS characteristic functional groups and characteristic absorption peak area,and the diffusion depth was calculated to analyze the diffusion and fusion of WCO/NS in aged asphalt at different times and temperatures.The results show that WCO/NS is easier to infiltrate on the long-term aging surface,and the infiltration effect is better,which is more suitable for restoring the asphalt performance with deeper aging degree.The increase of temperature and the extension of time can improve the diffusion depth of WCO/NS in aged asphalt,but time is the biggest influencing factor in the process of diffusion to aged asphalt,followed by temperature.Excessive temperature will increase the carbonyl and sulfoxide index at the final fusion depth of WCO/NS and aged asphalt,which will aggravate the aging of asphalt and reduce the diffusion efficiency,so that the reoxidation of aged asphalt is more serious.Therefore,150°C is the best diffusion temperature of WCO/NS.Finally,the double-layer diffusion model of WCO（WCO/NS）-aging asphalt and the blending amorphous unit cell were established by molecular dynamics.The effects of NS on the diffusion characteristics and fusion degree of WCO and aging asphalt were evaluated by mean square displacement,diffusion coefficient and relative concentration.The solubility parameters and free volume fraction of WCO（WCO/NS）aging asphalt blending unit cell were calculated,and the aggregation changes of oxidized asphaltene molecules before and after regeneration were analyzed to explore the mechanism of NS enhanced diffusion and regeneration.The results show that NS improves the diffusion rate and diffusion depth of WCO-aged asphalt by increasing the free volume parameters of WCO recycled asphalt and activating macromolecular resins and asphaltenes,among which the diffusion coefficient of stearic acid with depolymerization function in WCO is the most obvious.NS can enhance the solubility parameter of WCO and enhance the compatibility between WCO and four components of aged asphalt through coupling effect.NS can effectively remove the asphaltene agglomeration in aged asphalt.In summary,NS is used to improve the performance of WCO recycled asphalt,which can enhance the compatibility between WCO and aged asphalt,accelerate the depolymerization of asphaltene,and slow down the volatilization of light components in WCO,thereby improving its high temperature deformation resistance,water damage resistance and aging resistance.Pavement performance effectively compensates for the performance defects of WCO recycled asphalt.It is of great practical significance to improve the road performance of recycled asphalt pavement,prolong the service life of pavement and increase the application value of WCO project.