Using response surface methodology to optimize rubber and LDPE contents in bitumen at low-temperature performance

Abstract

Selecting the optimum amount of modifiers added to bitumen to modify its characteristics has always been one of the most important steps of such researches. In this study, the response surface method is used to design the experiments and to determine the optimal combination of different percentages of waste LDPE and crumb rubber. Waste LDPE in the amounts of 3%, 5%, and 7% and crumb rubber in the amounts of 1%, 3%, and 5% are used as the modifiers. In addition, the central composite design method is used to select the optimal combination of waste LDPE and crumb rubber. Polymer percentage is the most effective parameter in this research. The results show an optimum point of approximately 3% waste LDPE and 3% rubber powder. It can be the optimal point and has the best performance at low temperatures in this combination of modified bitumen percentages. However, the exact optimal point is obtained as 3% recycled plastic and 2.02% rubber powder after the optimization process.