Performance evaluation of recycled asphalt mixtures with various percentages of RAP from the rotary decomposition process

This paper conducted an experimental study to evaluate the performance of recycled asphalt mixtures containing various percentages of reclaimed asphalt pavement (RAP). The variabilities and properties of RAP materials from the rotary decomposition process were determined first, through which the RAP materials were mainly decomposed in three stages including reclaimed stone aggregates barely containing asphalt, and asphalt-rich mortar sand. The results demonstrated that the mineral grading and asphalt percentage of decomposition products were stable. Then, the design aggregate gradation of AC - 20F was selected and its optimum asphalt content (OAC) was obtained using the Marshall mix design method. In addition, the laboratory performance, including the high-temperature performance, low-temperature crack resistance, moisture susceptibility and dynamic modulus tests, of recycled asphalt mixtures with varying RAP contents was conducted. The test results indicated that when the RAP content increased, the rutting resistance improved, but the crack resistance at low temperature and moisture damage susceptibility worsened. The RAP content had an effect on the dynamic modulus, especially at a lower loading frequency (high temperature). And the dynamic modulus of recycled asphalt mixtures increased with the loading frequency increasing and temperature decreasing. The dynamic modulus of the recycled asphalt mixture under standard conditions (20 degrees C and 10 Hz) was determined to be 11500-13000 MPa. The recycled asphalt mixture with higher percentages of RAP (more than 40%) was applicable to be used as a high modulus asphalt mixture (HMAM) in the future based on the results of the dynamic modulus test. Finally, an empirical predictive model of the dynamic modulus for recycled asphalt mixtures was established.