Influence of Asphalt Grade and Content on the Properties of RAP Mixtures

In order to study the influence of new asphalt grade and content on the properties of RAP mixtures, 70# and 90# asphalt were selected to prepare the RAP mixtures with 0%, 20% and 40% RAP content. Based on the optimum asphalt content (OAC) of new binder, the OAC, OAC+0.5% and OAC-0.5% content of RAP mixtures were also fabricated. Dynamic modulus test, fatigue test and low temperature disc-shape tension test were conducted to analyze the properties of RAP mixtures. Then, for better understanding the crack resistance of RAP mixtures, the binders were extracted and recovered to study the cracking properties using G-R parameters. The mixtures results show that when using soft binder, hig-her binder content and lower RAP content, the RAP mixtures have better fatigue resistance and low temperature crack resistance. On the contrary, with harder binder and higher RAP content, the RAP mixtures have better rutting resistance. However, the low temperature results show that with 70# binder with OAC-0.5% and 40% RAP content, the RAP mixtures could not meet the requirement. The analysis of water stability shows that one time freeze-thaw cycle is limited to evaluate the water stability of RAP mixtures. After two time freeze-thaw cycles, the water stability of RAP mixtures is lower than that of new asphalt mixture. The G-R parameter results show that with higher RAP content and harder binder, the sextracted binders are more likely to crack. © 2021, Materials Review Magazine. All right reserved.