High-temperature creep and low-temperature relaxation of recycled asphalt mixtures: Evaluation and balanced mix design

In this study, high-temperature creep and low-temperature relaxation performance of recycled asphalt mixtures, with different contents of reclaimed asphalt pavement (RAP), rejuvenator, and virgin asphalt, were evaluated. The creep index (epsilon p/FN) and relaxation index (ts) were selected as evaluation indices of prepared samples. Based on the comparison of epsilon p/FN and ts of the recycled asphalt mixture and virgin asphalt mixture, a new balance design method was proposed. The results showed that epsilon p/FN increased gradually with the increase of rejuvenator and virgin asphalt when the RAP content was constant, while ts was decreased. It indicated that the hightemperature creep performance of the recycled asphalt mixture was improved, but the low-temperature relaxation performance became poor. The high-temperature creep and low-temperature relaxation evaluation indices could be directly compared, and the accuracy of the comparison results was improved. Therefore, the proposed balanced design was developed based on the comparison of the absolute value by mathematical formulas, which was not only simple or intuitive but also easy to operate. When the RAP content was less than 30 %, the optimum balance point of the high-and low-temperature performance was lmin. When the RAP content was 50 %, the best low-temperature relaxation performance point was the optimum balance point with the prerequisite of a good high-temperature creep performance. It is a new method to analyze the high-and low-temperature performance of recycled asphalt mixtures, which is of great significance to improve the durability of the recycled asphalt pavement.