Design Process of Asphalt Mixture Incorporating Compaction-Effort Variable

Abstract

The Superpave mix design is a process of repeatedly optimizing the aggregate gradation and asphalt content in accordance with specified limits. As one of the important design parameters, the number of design gyrations (Ndes) is adopted empirically to be a fixed number under a specific traffic level. Based on the concept of a performance-oriented approach, this study regarded Ndes as a variable design parameter and evaluated the influences of two design cases on the performance of asphalt mixture: Ndes variables and asphalt content (gradation unchanged) and Ndes variables and aggregate gradation (asphalt content unchanged). Two groups of experiments were designed. The first group used Ndes levels of 50, 75, and 100 gyrations, and less asphalt content was adopted with a higher Ndes. The second group used compaction levels of 50, 75, 100, and 125 gyrations, and coarser aggregate gradation was adopted with a higher Ndes. Both groups of experiments showed that with an increase in Ndes, rutting performance was increased and low-temperature performance was decreased. In addition, in the former group of experiments, fatigue performance was decreased with the increase of Ndes. Following these rules, this paper took Hainan province mix design as a case, and Ndes was optimized to meet requirements. It can be seen that regarding Ndes as design variable is necessary and can improve flexibility in the design.