Influences of Preheating Temperature of RAP on Properties of Hot-Mix Recycled Asphalt Mixture

This study analyzed the agglomerate characteristics of reclaimed asphalt pavement (RAP) material and evaluated the influences of the preheating temperature of RAP on the properties of recycled asphalt mixture. Specific surface-area analysis was conducted to reveal the agglomerate characteristics of RAP. A triaxial shear test was conducted for RAP with different preheating conditions to evaluate the dispersion characteristics of RAP and its influences on RAP property. Freeze–thaw splitting test, wheel tracking test, and low-temperature bending-beam test were conducted to evaluate the influences by preheating temperature of RAP on the properties of recycled asphalt mixture. It is found that, because of the agglomerates of RAP, the specific surface area of RAP is much lower than that of real aggregates. Sufficient preheating of RAP can promote the dispersion of RAP by activating the flowability of aged asphalt in RAP. The properties of recycled asphalt mixture keep improving with the increase of the preheating temperature of RAP. There is a minimum-temperature limit for RAP preheating to guarantee the properties of recycled asphalt mixture.