Influence of macromolecular substances in waste cooking oil on rejuvenation properties of asphalt with different aging degrees

Abstract

Waste cooking oil (WCO) is generally regarded as one of components for the rejuvenators in recycled asphalt pavement (RAP). However, WCO has many kinds of substances and unstable characteristics due to its different sources, causing differences to the properties of rejuvenated asphalt. In this research, an innovative method of classification was adopted to transform WCO into small, middle and macromolecular substances according to the molecular weight. The thermogravimetric analysis revealed that macromolecular substances (Wmas) in WCO has better thermal stability. Combined with the results of separation test, Wmas has better compatibility with asphalt. Subsequently, the study of the physical, rheological and chemical properties was conducted for asphalt with three different aging degrees after regeneration by Wmas. The experimental results show that the adequate distribution of Wmas in the asphalt makes the aging asphalt soften effectively. Moreover, the rejuvenated asphalt exhibits superior high and low temperature rheological properties. However, the physical and rheological properties of the three aged asphalts differ in the rapidity of recovery and the dosage of Wmas. Meanwhile, the excessive dosing of Wmas will cause negative effects, such as a sharp decrease in viscosity and slow change in ductility of the asphalt. In addition, functional groups of rejuvenated asphalt show that Wmas does not react chemically with asphalt. The regeneration of aged asphalt by Wmas depends on its physical compatibility with asphalt and thermal stability. Overall, the properties of the aged asphalt can be restored to the level of virgin asphalt at the appropriate dosing of Wmas, but the sensitivity to the dosage of Wmas varies. The above study provides ideas for targeted restoring mechanisms between waste cooking oil components and aged asphalt.