Effect of RAP's preheating temperature on the secondary aging and performance of recycled asphalt mixtures containing high RAP content

Abstract

Plant-mixed hot recycling technology is widely used. Due to concerns about the road performance of recycled asphalt mixtures with high RAP content, the content of RAP is strictly limited, which has negative impact on ecological and economic benefits. Low preheating temperature of RAP material is an important reason for reduced performance of recycled asphalt mixtures containing high RAP content. At the same time, excessive preheating temperature of RAP materials can cause secondary aging of asphalt in RAP. This study regarded the preheating temperature as a variable. Rheological and spectroscopic tests such as DSR and BBR, and FTIR tests were conducted to investigate the effect of RAP preheating temperature on the secondary aging of RAP. Afterwards, the influence of raising preheating temperature of RAP on the performance of recycled asphalt mixtures was explored synthetically. When the preheating temperature is below 160 ºC, there is no significant secondary aging of aged asphalt in RAP. However, when the preheating temperature increases to 180 ºC, the rheological properties of aged asphalt undergo certain changes. Increasing the preheating temperature of RAP can significantly improve the low-temperature crack resistance and fatigue performance of recycled asphalt mixtures by reason of maximally activating the aged asphalt. Increasing the preheating temperature of RAP does not weaken the high-temperature anti-rutting performance of recycled asphalt mixture. It is recommended to control the preheating temperature of RAP at 160 ºC in the design and production process of hot recycled asphalt mixtures.