Effect of load control mode on the fatigue performance of asphalt binder

Abstract

Fatigue cracking is one of the major distresses found in asphalt pavements. The ability of asphalt binder to resist the accumulation of fatigue damage can have a profound effect on the service life of asphalt pavements. However, different from other materials, the fatigue characteristics of asphalt binder depend heavily on the load control mode. That is the fatigue characteristics of asphalt binder under controlled-stress mode differ from those under controlled-strain mode. This discrepancy affects the analysis results of asphalt binder fatigue performance. Therefore, this study is aimed at analyzing the effects of the load control mode on the fatigue performance of asphalt binder through a comparison of the fatigue characteristics under two different load control modes. The effect range of the load control mode was confirmed, and the method to differentiate the region affected by load control modes from the region not affected by load control modes was put forward. The relationship between the fatigue performances of asphalt binder under different control modes was analysed. Based on the results, it is concluded that the fatigue process can be divided into two regions using the curve of normalized dynamic modulus versus normalized phase angle. And, if the controlled stress and the controlled strain are equivalent levels, the fatigue characteristics of asphalt binder are independent of load control modes in the first region. The accumulated dissipated energy at the division point of the two regions is independent of both control modes and load levels, and serves as the effect threshold of the load control mode. Besides, the curve of accumulated dissipated energy versus number of cycles under controlled-stress mode is symmetrical to that curve under controlled-strain mode.