Research on failure strength master curve and fatigue performance of asphalt mixture containing high-proportion reclaimed asphalt pavement

Reclaimed Asphalt Pavement (RAP) is a cleaner production widely used in road engineering. In order to investigate the failure strength and long-term performance of high-proportion RAP asphalt mixture, this research prepared two high-content RAP recycled asphalt mixtures (50% and 60% RAP-RAM) with the gradation of AC-20 based on Styreneic Methyl Copolymer (SMC) regenerant. Firstly, indirect tensile (IDT) strength tests were implemented on 50% and 60% RAP-RAM at four temperatures and six loading rates. Secondly, IDT fatigue tests at six stress levels were carried out. The relationships of strength and temperature, strength and loading rate were obtained based on strength test results. The master curve model of indirect tensile strength and loading rate of high-proportion RAP recycled asphalt mixture was established by linear and Sigmoidal functions. On the basis of the Sigmoidal strength master curve equation, the fatigue stress ratio was calculated. Finally, this paper established the fatigue equation of the high-content RAP recycled asphalt mixture based on the fatigue stress ratio. The analysis results show that 50% and 60% RAP-RAM based on SMC regenerant show favorable strength and fatigue properties. In addition, increasing the proportion of RAP improves the strength of the mix while reducing the loading rate sensitivity of strength. However, the fatigue performance of the mix reduces by increasing RAP content. The fatigue equation based on the fatigue stress ratio takes the factors of temperature and loading rate into account, reflecting the mix's fatigue performance more realistically. The strength and fatigue performance results verify the reliability of the high-content RAP recycled asphalt mixture based on SMC regenerant and provide a reference for the effective utilization of RAP which can generate environmental benefits of saving aggregate and asphalt and reducing energy consumption and carbon emissions.