Multi-scale study of compound modified asphalt materials by waste cooking oil and organic montmorillonite on high temperature performance

•The high temperature performance of WCO/OMMT modified asphalt materials was studied.•The multi-scale correlation of high temperature performance was analysed.•Bio-oil addition significantly reduces the rutting resistance of asphalt materials.•OMMT addition can make up for the loss of high-temperature performance.•The correlation of RTFO asphalt mortar Jnr3.2 index and flow number is good. Asphalt binder as a by-product of petroleum is a finite resource. Hence, finding an alternative material for asphalt binder is a potential topic in the road engineering. Performance of compound-modified asphalt material at high temperatures, by waste cooking oil (WCO) and organic montmorillonite (OMMT) was investigated in this study, and the multi-scale correlation evaluation was conducted. The findings revealed that the bio-oil significantly reduces the barrier to rutting of asphalt materials within multi-scales, and rutting resistance was reduced with increased content. High-temperature performance can be regained or even better than that of base asphalt materials when WCO Bio-oil: OMMT is 1:1, and OMMT can compensate for the loss of high-temperature performance. Besides, the multi-scale correlation analysis shows that the Jnr3.2 index of OMMT composite modified bio-asphalt mastic, asphalt mixtures' resistance to rutting at high temperatures can be predicted using their short-term aging condition.