Effect of Waste-Oil regenerant on diffusion and fusion behaviors of asphalt recycling using molecular dynamics simulation

In field asphalt hot recycling project, the diffusion and fusion of virgin and aged asphalt generates the weak interface under stress concentration. In this study, the representative components of waste cooking oil (WCO), waste vegetable oil (WVO) and waste engine oil (WEO) regenerant were simulated by molecular dynamics method. The influence of waste oil regenerant on the diffusion and fusion of virgin and aged bitumen was evaluated by calculating the diffusion rate, fusion amount, relative concentration in fusion area. The viscosity and solubility parameters were calculated to explore the driving mechanism of waste oil regenerant promoting fusion diffusion. The microstructure of asphalt was analyzed to determine the key components of waste oil to achieve regeneration effect. The results showed that the waste oil regenerant can promote the diffusion of virgin and aged bitumen by reducing the viscosity of aged bitumen. The promotion effect of WCO and WEO was better than WVO. When the content is higher than 6%, the promotion effect of WCO will be reduced. In terms of promoting fusion, the regeneration system containing WEO was the best. For chain molecules, the depolymerization effect of molecules (Oleic acid, Trilaurin, and Linoleic acid) with CIS structure was not as good as that of molecules (Palmitic acid, γ-Linolenic acid, N-Docosane, Eleostearic acid, and Stearic acid) with trans structure. Molecules with trans structure generally increased the binding distance between asphaltenes by 36%. The fat molecules in WCO will form new aggregates with asphaltene. Based on molecular dynamics models, the micro driving mechanism of waste-oil recycling agents on renewing the various properties of aged bitumen was demonstrated.